September 25, 2024 Engineering Criteria Review Board Meeting

Yerba Buena SX80: Science

Yerba Buena SX80: like to welcome everyone

Yerba Buena SX80: to this meeting of the San Francisco Bay Conservation and Development Commission’s Engineering Criteria Review Board. This meeting will be recorded.

Yerba Buena SX80: Okay, good afternoon. And welcome to to this hybrid in person and online

Yerba Buena SX80: Ecrb meeting. My name is Rod Iwashta.

Yerba Buena SX80: I am the chair of the ecrb and I have a few announcements.

Yerba Buena SX80: Our 1st order of business is to call the roll Board members. Please use the microphones on the table to respond.

Yerba Buena SX80: unmute yourselves to respond, then mute yourselves again. After responding. Jen, please call the role

Yerba Buena SX80: Rod Iwashta, chair of the board. Here.

Yerba Buena SX80: Jim French vice chair.

Yerba Buena SX80: Here.

Yerba Buena SX80: Bob Battaglio on the board is not present. He is recused from this meeting.

Yerba Buena SX80: Geema Casali.

Yerba Buena SX80: Yeah.

Yerba Buena SX80: Chris May.

Yerba Buena SX80: Chris May is also recused from this meeting.

Yerba Buena SX80: Ramin Golserki

Yerba Buena SX80: present

Yerba Buena SX80: Nick Sitar

Yerba Buena SX80: here.

Yerba Buena SX80: Gail Johnson.

Yerba Buena SX80: I know he is on vacation.

Yerba Buena SX80: Patrick Ryan

Yerba Buena SX80: here.

Yerba Buena SX80: Justin Vannever.

Yerba Buena SX80: here.

Yerba Buena SX80: Bill Tremaine

Yerba Buena SX80: here.

Yerba Buena SX80: and Dilip Trivetti.

Dilip Trivedi, Moffatt & Nichol: Here, but I will be there in person in 5 min.

Yerba Buena SX80: Okay, great. See you soon.

Yerba Buena SX80: Cherry watched it. We have a quorum of of 8, almost 9

Yerba Buena SX80: And so

Yerba Buena SX80: quorum is present. Okay, thank you, Jen. So if we have a quorum present, we’re duly constituted to conduct business.

Yerba Buena SX80: we may have some alternate board members who may be participating as members of the public.

Yerba Buena SX80: and it looks like Thalia is maybe one of those people.

Yerba Buena SX80: Do you know, Margie, do you know if Sally is on the line.

Yerba Buena SX80: Okay?

Yerba Buena SX80: Okay.

Yerba Buena SX80: okay, well, I I called the meeting to order.

Yerba Buena SX80: I want to start with some instructions on how we can best participate

Yerba Buena SX80: in this meeting, so that it runs as smoothly as possible. First, st

Yerba Buena SX80: everyone. When you are not involved in the active discussion, please make sure you have your microphones or phones muted

Yerba Buena SX80: to avoid background noise

Yerba Buena SX80: for board members. If you have a camera, please make sure

Yerba Buena SX80: that it is on during the meeting. So everyone online can see you

Yerba Buena SX80: also board members. If you would like to speak during the meeting, you may raise your actual hand or your virtual zoom hand, whichever you prefer.

Yerba Buena SX80: Every now and then I may refer to the meeting host, Margie, who is working behind the scenes to ensure that the technology moves

Yerba Buena SX80: the meeting forward smoothly and consistently.

Yerba Buena SX80: Please be patient with us if it’s needed.

Yerba Buena SX80: Ex parte communications as set forth in Bcdc’s regulations.

Yerba Buena SX80: A member of the Ecrb shall not have any oral or written communication

Yerba Buena SX80: regarding the proposed project or other matter that has been noticed to be considered at an Ecrb meeting with a project proponent permit applicant prospective applicant or member of the public, except on the record during an Ecrb meeting

Yerba Buena SX80: board members in case you have inadvertently forgotten to provide staff with

Yerba Buena SX80: a notice on any written or oral ex parte communications.

Yerba Buena SX80: I invite you to report on any such communications

Yerba Buena SX80: at this point by raising your hand and unmuting yourself.

Yerba Buena SX80: Okay, no raised hands.

Yerba Buena SX80: Okay. And now agenda. Item, 2 staff updates.

Yerba Buena SX80: Now, we will have a staff update from senior engineer and board. Secretary, Jen Hyman.

Yerba Buena SX80: Thank you. Chair Washta. I would like to provide an update on some upcoming Ecrb meetings.

Yerba Buena SX80: On October 15th

Yerba Buena SX80: the Ecrb will review and discuss the updated regional shoreline adaptation plan or Rsap guidelines.

Yerba Buena SX80: At the end of this meeting, Bcdc. Council, Michael Ng. Will give a legal training to Ecrb members on regulations and policies of the Ecrb

Yerba Buena SX80: and that meeting had was just moved from its original date on October 23.rd So I apologize for the last minute change of date on that.

Yerba Buena SX80: Now it’s going to be on October 15th

Yerba Buena SX80: the November meeting has also been changed from the 12th to the 19.th

Yerba Buena SX80: Currently there is nothing on that agenda.

Yerba Buena SX80: also board members, the building management like our last meeting. Needs this room at 5 o’clock sharp. And so if we can all try to wind up the meeting by around 4 30 building personnel would appreciate them.

Yerba Buena SX80: Lastly, I would like to ask board members when you speak today and applicant team.

Yerba Buena SX80: please move the microphones pretty close to your mouth.

Yerba Buena SX80: And speak loudly, so that everyone in the room and on zoom can hear you.

Yerba Buena SX80: And the mics are directional. So if it’s too much of a pain to turn them on and off. You can just keep them on

Yerba Buena SX80: if you’d like.

Yerba Buena SX80: Those are all my announcements.

Yerba Buena SX80: Okay, thank you. Jen. Before we move on to the presentation. Are there any announcement announcements from board members?

Yerba Buena SX80: Okay. Seeing none. Let’s move forward to agenda. Item, 3

Yerba Buena SX80: items of discussion. San Francisco International Airport Shoreline protection project.

Yerba Buena SX80: Now we will move on to the main agenda item related to the permit application

Yerba Buena SX80: for the San Francisco International Airport Shoreline Protection Project.

Yerba Buena SX80: Our discussion will focus on the stability

Yerba Buena SX80: of the proposed sheep steel sheet pile, flood wall that is approximately 7 miles long.

Yerba Buena SX80: and would surround the airport along its shoreline.

Yerba Buena SX80: Jen, the Board Secretary and Senior Engineer for Bcdc. Has a slide presentation for us

Yerba Buena SX80: with an introduction and a bit of background.

Yerba Buena SX80: Since this is the second meeting on the topic

Yerba Buena SX80: during the presentation. It is fine for board members to ask brief, clarifying questions.

Yerba Buena SX80: I would like to ask board members and presenters.

Yerba Buena SX80: so please turn on your cameras for any discussion during or after the presentation.

Yerba Buena SX80: and I would like now like to turn it over to Jen to begin her presentation.

Yerba Buena SX80: Okay, this is Jen Hyman, and I just have a few introductory slides regarding San Francisco International Airport Shoreline Protection Project.

Yerba Buena SX80: You’ll see it described as Sfo. Spp. That’s the shorthand for the project name.

Yerba Buena SX80: So Sfo. Has begun pre-application meetings with Bcdc. And submitted a draft permit application.

Yerba Buena SX80: The Ecrb review is focusing on the safety of the steel sheet pile flood wall, which is about 7 miles long.

Yerba Buena SX80: One of the reaches in the project reach 7 also includes 26 acres of fill and special geotechnical treatments.

Yerba Buena SX80: Sfo is pursuing Fema accreditation for the wall.

Yerba Buena SX80: And because of that, it’s being designed to Us. Army corps standards.

Yerba Buena SX80: Some of these design standards include looking at extreme

Yerba Buena SX80: wave loading and flood events.

Yerba Buena SX80: the the extreme scenario is a 750 year scenario.

Yerba Buena SX80: and they presented some of the results of that. In the last meeting, in 2023

Yerba Buena SX80: the project will be bid design build

Yerba Buena SX80: the project. Life is estimated to be about 60 years

Yerba Buena SX80: and hopefully get them about

Yerba Buena SX80: sea level rise adaptation out to about 2085.

Yerba Buena SX80: The airport is considered critical infrastructure.

Yerba Buena SX80: The 1st ecrb review of the project was on September 27, th in 2023.

Yerba Buena SX80: The presentations at that time included structural analysis, geotechnical analysis and sea level rise and flood hazards.

Yerba Buena SX80: In that meeting it was concluded that loads from flooding would govern over seismic loading.

Yerba Buena SX80: The Ecrb requested additional information regarding seismic stability.

Yerba Buena SX80: including a seismic and flooding scenario, some information on corrosion and corrosion, monitoring

Yerba Buena SX80: emergency operations and alternate designs.

Yerba Buena SX80: So this is the second Ecrb meeting for this meeting.

Yerba Buena SX80: San Francisco Airport provided

Yerba Buena SX80: some of the reports that have are required by Fema for accreditation of the flood wall.

Yerba Buena SX80: and also they presented information to be responsive to some requests from staff as well as the Ecrb comments already discussed.

Yerba Buena SX80: Some of the additional topics

Yerba Buena SX80: staff asked for information on include

Yerba Buena SX80: actually the ecrb requested seismic modeling at other reaches, then reach 6. To confirm that reach 6 was the most critical reach.

Yerba Buena SX80: Staff also asked if there were internal flood risks from deep wall construction or groundwater sea level rise.

Yerba Buena SX80: land subsidence.

Yerba Buena SX80: wave reflection.

Yerba Buena SX80: operation, maintenance plans and talking about the California seismic monitoring program

Yerba Buena SX80: were also topics that on Staff asked Sfo to report on today for the ecrb.

Yerba Buena SX80: So here are questions that Staff put together to help the Ecrb

Yerba Buena SX80: today and guide their discussion

Yerba Buena SX80: are the scenarios and design criteria. In the geotechnical stability analyses appropriate for the site, hazards, conditions, and site criticality.

Yerba Buena SX80: Our flooding concerns, IE from groundwater.

Yerba Buena SX80: coastal and rivering, flooding, flooding and sea level rise, addressed adequately.

Yerba Buena SX80: has the applicant demonstrated that adverse impacts to adjacent properties

Yerba Buena SX80: have been minimized in the design.

Yerba Buena SX80: What future plan reviews or monitoring programs would you recommend that the applicant submit to confirm future project? Safety as the floodwall ages?

Yerba Buena SX80: Some topics to consider are design, build, phase, submittals.

Yerba Buena SX80: corrosion, monitoring.

Yerba Buena SX80: interior drainage system function, monitoring.

Yerba Buena SX80: passive barrier function, testing

Yerba Buena SX80: storms, waves and sea level rise, monitoring

Yerba Buena SX80: emergency preparedness or response systems testing.

Yerba Buena SX80: And maybe there are others

Yerba Buena SX80: not mentioned here.

Yerba Buena SX80: And lastly, are there any other design or safety concerns that have not been addressed?

Yerba Buena SX80: And that’s my final slide.

Yerba Buena SX80: Okay, thank you, Jen.

Yerba Buena SX80: Now the San Francisco airport team will make their technical presentations

Yerba Buena SX80: and pause for some Ecrb discussion after each topic.

Yerba Buena SX80: We will take public comments at the conclusion of the presentations.

Yerba Buena SX80: Take it away.

Yerba Buena SX80: Good afternoon, Ecrb members. My name is David Kim. I’m the senior environmental planner for the San Francisco International Airport.

Yerba Buena SX80: I’m responsible for getting our project shoreline protection program through environmental review and permitting.

Yerba Buena SX80: I’m here today with my team of technical consultants to respond to questions from our 1st meeting last September on our project

Yerba Buena SX80: next slide.

Yerba Buena SX80: Here’s the agenda for our presentation today. We took your questions from the last meeting, and we’re here today to respond to each of them.

Yerba Buena SX80: The agenda here references each question.

Yerba Buena SX80: We’ll start with geotechnical analysis, then operations and maintenance, move on to groundwater and sea level rise

Yerba Buena SX80: subsidence, and then finally monitoring for seismic activity.

Yerba Buena SX80: Next slide

Yerba Buena SX80: I’m joined by consultants from Esa Coe, chair engineers and Geosyntech speakers will introduce themselves at the beginning of their presentations

Yerba Buena SX80: in the next few slides. I’m gonna go through very briefly since we’ve covered this last time and to maximize our time responding to your questions. We’re here because the airport is on the floodplain.

Yerba Buena SX80: and it’s at risk from flooding from sea level rise next slide.

Yerba Buena SX80: We have a number of excuse me

Yerba Buena SX80: so to address that we have a shoreline protection program which would consist of primarily steel sheet pile walls driven into the ground

Yerba Buena SX80: with some concrete walls. On the north side of reach one and south side reach 15,

Yerba Buena SX80: and also a new perimeter dike at the end of our runway, 19 End

Yerba Buena SX80: side.

Yerba Buena SX80: We have a number of project objectives, but they’re there primarily to protect our passengers, workers and airport operations. We want to get off the flood map and protect the airport against sea level rise

Yerba Buena SX80: and to do it in a way that meets Faa. Design standards and requirements

Yerba Buena SX80: next slide.

Yerba Buena SX80: This is a a.

Yerba Buena SX80: a summary of the project description. I’m not gonna go into this into too much detail. But they’re here for your

Yerba Buena SX80: for your review. Essentially, we’re going to be removing the existing shoreline protection that’s there. Now and then we will be installing new shoreline protection, mostly in the form of the steel sheet pile wall, with some concrete walls in the north and south end, establishing a new perimeter dike at the end of our runway. 19.

Yerba Buena SX80: It’s like

Yerba Buena SX80: we’ll have some associated improvements in addition to that, including shifting out our vehicle service roads to meet Faa design requirements

Yerba Buena SX80: retrofitting our existing infrastructure of storm drain, pump station outfalls.

Yerba Buena SX80: and the reconstruction of the lighting trestles at the end of runway 19 left

Yerba Buena SX80: anticipated fill is roughly 25 acres within BC. DC. Bay jurisdiction largely at the end of the runway, 19 ends.

Yerba Buena SX80: Here’s a conceptual schedule of what this project might look like, I just want to highlight. This is highly dependent on funding and budget authorizations. But we’re in the midst of going through Nepa right now. We cleared sequel last year.

Yerba Buena SX80: We’re also in the midst of securing permit approvals with the regulatory agencies and also securing compensatory mitigation for the fill for our project. We would anticipate that the projects would be constructed in phases based on

Yerba Buena SX80: the construction, methodology, and the location of the wall.

Yerba Buena SX80: We will be employing a design build process as a delivery method for the shoreline protection program.

Yerba Buena SX80: The again. As Jen mentioned the design, life is roughly 60 years. So we’re designing out about 2085.

Yerba Buena SX80: At this point I’d like to pause to see if there are any questions on the project description, for it passes along.

Yerba Buena SX80: David, real real quick. Yeah,

Yerba Buena SX80: so it’s gonna be design build

Yerba Buena SX80: So how far along is the design team here going to progress? The the design.

Yerba Buena SX80: So the team here was involved with the conceptual design. But we have yet to procure a design builder

Yerba Buena SX80: and that that can’t start until we get further along with our compensatory mitigation, our regulatory approvals. So we have to wait until that point.

Yerba Buena SX80: Question,

Yerba Buena SX80: when we say, design life of 60 years, are we? Are we really

Yerba Buena SX80: talking about performance life of 60 years

Yerba Buena SX80: beyond which there would be upkeep.

Yerba Buena SX80: and whatever maintenance retrofits might be needed to continue the useful life.

Yerba Buena SX80: Is that something that you can address. Right? We’ve we’ve targeted 2085, or basically 60 years establishing sort of like a sea level rise target and just general design life. The reality of is, we have an operation and maintenance plan which will touch on the corrosion question

Yerba Buena SX80: that with proper maintenance this spot can easily extend past 60 years.

Yerba Buena SX80: It’s just where we are with sea level rise in 60 years. Given the probabilities and the you know, the different scenarios. That’s why we’re not saying it’s gonna last much beyond that, with

Yerba Buena SX80: again, I’m really confident it will. But we have to see how sea level rise happens first, st

Yerba Buena SX80: and I’m assuming that there’s adaptive capacity built into this design. Yes, there would be.

Yerba Buena SX80: There are no other questions. I’m going to pass this on to Bob Kirby of Terra engineers to talk about the geotechnical analysis.

Yerba Buena SX80: Thank you, David. Yes, my name is Bob Kirby. I’m a principal with terra engineers.

Yerba Buena SX80: We’ve been working on the geotechnical design concepts for several years now.

Yerba Buena SX80: To my left is Juan Pastana, who’s been working with us for the last several years in a peer reviewed capacity on the

Yerba Buena SX80: on the geotechnical, particularly the dynamic analysis aspects of the project. I’m gonna make a brief summary of our presentation. But during the Q. And a. 1, i’m sure we’ll

Yerba Buena SX80: be available to to help me and help respond to your questions.

Yerba Buena SX80: And in terms of the supplemental geotechnical analysis. It’s really responding to an important question that the the Board raised during our meeting a year ago.

Yerba Buena SX80: we

Yerba Buena SX80: developed a and completed analyses for reach 6 reach 6 is A is the location where we have the

Yerba Buena SX80: the thickest amount of young bay mud.

Yerba Buena SX80: and our presumption was that, given this analysis of the section with the thickest amount of young Bay mud, that it would be a critical section for the for the seismic design.

Yerba Buena SX80: I think the the the board brought up the point that we need to be careful here, cautious because of the

Yerba Buena SX80: attenuation properties within the young bay mud. You know, it could lead to something less than the

Yerba Buena SX80: the maximum thickness being the the critical section. And you asked us to perform additional analysis, which we’ve done

Yerba Buena SX80: and will be presenting here this afternoon.

Yerba Buena SX80: Next slide, please.

Yerba Buena SX80: our goal is to move through this quickly. There’s a document that supports the presentation I’m giving. It’s footnoted at on this slide.

Yerba Buena SX80: It’s a supplemental report for for the one that we prepared last year.

Yerba Buena SX80: just to give you a preview of what? How we’ll be approaching this presentation.

Yerba Buena SX80: We’ll take a quick look at the at an overview of the shoreline protection program. The locations of the sections that we’ve analyzed.

Yerba Buena SX80: we’ll take a look at the average subsurface conditions and how they vary along by reach by reach.

Yerba Buena SX80: Then we’ll take a look at soil conditions at the sections that we’ve actually analyzed, which different

Yerba Buena SX80: usually somewhat from the average, because we were getting sections that were of most interest to us whether that’s maximum thickness or

Yerba Buena SX80: where we had available information.

Yerba Buena SX80: at at that time, too, I think it might be good at the beginning to give you a quick preview of what we found.

Yerba Buena SX80: and just kind of go over those results in a in a rather quick way, and having done that, we would then walk through the the models that we developed at 2 additional sections for the plexus

Yerba Buena SX80: in addition to plexus analysis, we did a number of sensitivity, studies, site, response analysis.

Yerba Buena SX80: using the deep soil approach if you will.

Yerba Buena SX80: and and that was also geared towards looking at the influence of the thickness of the young Bay mud on the, on the performance of the of the system.

Yerba Buena SX80: So after. So those are the additional studies that we’ve done, and then we’ll close with some summary and conclusions next slide, please.

Yerba Buena SX80: I think you’re probably familiar with this. And Jen showed something similar. These are the

Yerba Buena SX80: the shoreline protection program, nominally 7 miles long.

Yerba Buena SX80: 15 reaches the reaches we spoke about last year last time.

Yerba Buena SX80: or reach 6 and 7 reach 6 is typical of most of the program, and 7 is in this extended dike area.

Yerba Buena SX80: What we’ve added to that is plexus analysis at reach 5 and reach 14. And there there’s the locations of the

Yerba Buena SX80: analytical sections are shown on this slide.

Yerba Buena SX80: Next slide, please.

Yerba Buena SX80: Here are a couple of tables. They’re kind of bookends, if you will. From what we have in our report.

Yerba Buena SX80: Table one on the left. Indicates for the 15 reaches what are the the lengths of the reach and the average

Yerba Buena SX80: thickness of the existing fill the average thickness of the young bay mud. The depth to to rock, have to keep in mind that the variation within a reach, because the reaches are quite long can be pretty significant. So these are just the average values based on the

Yerba Buena SX80: borings that we have available. There’s lots of available information that we’ve summarized to to get these average values. We’ve shaded in the reaches where the analysis are being done just as shown on the previous slide.

Yerba Buena SX80: 5, 6, 7, and 14

Yerba Buena SX80: table, 8 s. 8 is shown to the right, and if we take a look at that, we see that for each 6, which is kind of our benchmark here our anchor for the analysis that we showed before what the conditions are. We had 20 feet of fill, and some of the data that are shown here. Thickness of fill was nominally 20 feet thickness of young bay mud, 61 feet

Yerba Buena SX80: and the analysis results that we got there are about 1.3 feet of lateral displacement

Yerba Buena SX80: for the for the top of the sheepah wall.

Yerba Buena SX80: and we had rather quite low and acceptable. Can I ask a question real quick? What level of earthquake is this?

Yerba Buena SX80: Thanks. It’s a 475 year return period.

Yerba Buena SX80: the earthquake.

Yerba Buena SX80: the

Yerba Buena SX80: So so we have. That’s some information about Route 6, Route 6, with the 475 year return earthquake

Yerba Buena SX80: and then, if we look at what we found out from our analysis of reach 5 and reach 14 just as a quick preview our reach 6 displacements of about 1.3 feet. Turned out to compare

Yerba Buena SX80: with we’ll see calculated displacement for reach 5 and reach 14 and point 8

Yerba Buena SX80: feet and point 9 feet.

Yerba Buena SX80: The

Yerba Buena SX80: the variation in properties that we looked at for reach 5 and reach 14 are summarized there. The thickness of the fill. It was 20 feet of reach, 6, and we went to 30 feet of reach, 5 and 7 feet at reach 14, and as far as the young bay mud is concerned. We had 61 feet at reach 6, and we went to 17 feet at reach 5 and 43 feet or so at reach 14

Yerba Buena SX80: with respect to the bending moments and stresses, they’re they’re summarized. They’re just in general comment. They they turn out to be

Yerba Buena SX80: really quite low, well within the elastic range from the soil structure, interaction perspective.

Yerba Buena SX80: and then the the PGA within the fill is a very important for the liquefaction assessment

Yerba Buena SX80: and the the values we had to reach 6.1 8

Yerba Buena SX80: at reach 5 and 14. We’re point 2. 0, and it’s actually point 2 3 at reach 5. That’s a typo in that table

Yerba Buena SX80: next slide. Please

Yerba Buena SX80: hang on, Bob. Sorry.

Yerba Buena SX80: real quick. Yeah.

Yerba Buena SX80: this. So the there are 3 new analyses that are being presented here today? 2, 2. And what was the selection? Criteria for the 2 reach these 2 new reaches? It was to

Yerba Buena SX80: give give a good representation of the variability in subsurface conditions. So we started with the maximum value of young bay mud at reach 6 at 60 feet. So we went to 40 feet and

Yerba Buena SX80: 17 feet, which which were the thicknesses that we’re looking. And if you look at the average values of the thickness of the young bay mud in that table to the left you’ll see that they tend to vary from 20 feet as the low at the low end to 60 feet at at the high end. So we’ve we’ve covered the range of thickness of the young bay mud, I think pretty well, and we are looking at

Yerba Buena SX80: some also some differences in thickness of the fill itself 20 feet at 6 went to 30 feet at 5, went to 7 feet at 14. This it looks like the new sections that got selected have

Yerba Buena SX80: higher maximum displacements.

Yerba Buena SX80: No, no, they no, they don’t. They have less.

Yerba Buena SX80: If if we look at the table. Essay.

Yerba Buena SX80: yeah. Essay. So reach 5 is, oh, and 14. Okay, I’m sorry. Yeah. Reach 5 and 14 are the new ones and reach 6. Is the the original. I was reading it wrong.

Yerba Buena SX80: Sorry? No problem.

Yerba Buena SX80: any any other

Yerba Buena SX80: next slide, please.

Yerba Buena SX80: I I have a question. Sure.

Yerba Buena SX80: Why is the 1st of all? Why are you? You have done a lot of work, and you call the report preliminary. And just

Yerba Buena SX80: what is the intent of this being a preliminary? Is it in the context of the design build?

Yerba Buena SX80: Yeah, yes, I think that’s a fair way to put it. And also it’s in the context of the geotechnical explorations that have been made. I mean, we. There’s a lot of data available, and we summarize the information available from borings.

Yerba Buena SX80: There was a huge study done in 2,001 on engineering properties, none. Nonetheless, there are a need for further geotechnical investigations. So with with that as a background, it it really supports the notion of preliminary, because there are additional

Yerba Buena SX80: investigations.

Yerba Buena SX80: And the next question, thank you. The next question, why is the bending moment, the maximum bending moment in reach? 14. So much

Yerba Buena SX80: less than everywhere else? It seems

Yerba Buena SX80: it’s it’s be and we’ll take a look at it, it’s because there’s much less fill. I I think the main reason is this, this, there’s considerably less fill, and I think the

Yerba Buena SX80: The bending moment in the in the sheep piles is driven by the interaction from from the fill. If you will. Yeah, thank you.

Yerba Buena SX80: Next slide, please.

Yerba Buena SX80: So reach 5.

Yerba Buena SX80: the. It’s it’s quite a. It’s quite a busy diagram. The cross section that you see there is one that was prepared in 2,001 by the Ada group.

Yerba Buena SX80: showing cpts. But it it. It shows how the general variation and

Yerba Buena SX80: the various young bay mud and fill, and the the much stronger layers beneath. Are.

Yerba Buena SX80: What we’re looking at is a boring at the edge of the

Yerba Buena SX80: the fill, if you will. There are 2 borings, one very deep boring that we we had to.

Yerba Buena SX80: I extend those that information above 700 feet to to get there, but it. It really provides good information on where the the top of the rock is.

Yerba Buena SX80: The the boring

Yerba Buena SX80: the other boring in that location gives us good delineation on the thickness of fill and young bay mud.

Yerba Buena SX80: And this was an unusual situation where there was quite a lot of fill and very little young Bay mud, comparatively speaking, but we decided to anchor on that and use that because we’re trying to get variability and judge the effects of having things that are really quite different. So that’s the reason we we selected that

Yerba Buena SX80: section for analysis. Next slide, please.

Yerba Buena SX80: So here’s the plexus model that was developed for

Yerba Buena SX80: for reach 5. The sheet pile is shown there.

Yerba Buena SX80: And that’s typical of what goes on and goes through the fill and penetrates into the young bay mud typically 10 feet.

Yerba Buena SX80: and what we’re looking at is the and this particular location of the

Yerba Buena SX80: quite, quite an additional thickness of fill because of the way it was construction. There are some mud waves that that were probably created during construction of the airport at a number of places

Yerba Buena SX80: next slide. Bob, can I back up to the previous slide for real quick question? Sure.

Yerba Buena SX80: Yeah, it’s pretty small. But, for instance, on the far left edge there, what? What’s the color coding mean on the Cpt

Yerba Buena SX80: you’ve got. If you zoom in yellow, red, and blue, I think, and green.

Yerba Buena SX80: wondering what those different color codes are. I’m not

Yerba Buena SX80: really sure. I I’m quite sure the the higher values, of course, are associated with, you know, cohesionless type, sandy materials, stronger standing materials.

Yerba Buena SX80: and I’m not

Yerba Buena SX80: really positive about the

Yerba Buena SX80: the I and and I think it may tie into the color code that’s used in the in the boring logs, for the.

Yerba Buena SX80: for the, for the different layers that have been interpreted.

Yerba Buena SX80: But but that is straight from the the the 2,001 Ada. Report.

Yerba Buena SX80: Okay.

Yerba Buena SX80: next slide, please, for going. After that I was just gonna add one more thing. If you, if you I can zoom in and see the the horizontal axis. Here is the tip resistance, if that helps with you tripping up.

Yerba Buena SX80: Yeah, but I’m curious. Why, there’s green, red, and blue on the the non yellow stuff

Yerba Buena SX80: it. It does look like tip resistance, but but the color is some sort of an interpretation. Yeah.

Yerba Buena SX80: So if we could move ahead

Yerba Buena SX80: and then next slide.

Yerba Buena SX80: So that was the model. And and and here are the results of the calculated lateral movements for for this, for this section.

Yerba Buena SX80: the the color coding

Yerba Buena SX80: shows the higher displacements in in red with the lower displacements in blue.

Yerba Buena SX80: The

Yerba Buena SX80: should point out and remind folks that

Yerba Buena SX80: we have 7 ground motions that were used for the analysis. So the analysis was repeated for 7 different ground motions that are associated with the 475 year event.

Yerba Buena SX80: They’re positive and reverse normal and reverse polarity. So there’s actually 14 cases that are that are analyzed.

Yerba Buena SX80: If we the displacement. The average displacement was 0 point 8 feet for the top of the sheepah wall, based on that analysis and the standard deviation was 0 point 3 feet

Yerba Buena SX80: next slide.

Yerba Buena SX80: This is information on the soil structure. Interaction for the sheet piles.

Yerba Buena SX80: What we’re looking at is the the maximum bending moment

Yerba Buena SX80: induced during shaking for each of the 7

Yerba Buena SX80: ground motions, and for both positive, our normal and reverse polarity.

Yerba Buena SX80: And

Yerba Buena SX80: the

Yerba Buena SX80: and in a general sense the maximum moment occurs at about the interface between the fill and the young bay. Mud.

Yerba Buena SX80: The maximum bending moment is about 27

Yerba Buena SX80: kip feet that compares to an allowable of 69 kip feet. And that’s just based on.

Yerba Buena SX80: you know, permanent loading. What? What kind of allowable bedding moments for a mild steel.

Yerba Buena SX80: So these these are really relatively

Yerba Buena SX80: low, and those red vertical lines are the allowables on either side. So you see that the the stresses and bending moments within the pile are actually quite small.

Yerba Buena SX80: And on the right are the the displaced position of of the pile for those 14 cases that were analyzed, and the lateral movement is exaggerated by a factor of 10,

Yerba Buena SX80: and in order to just

Yerba Buena SX80: allowed to see it if you will, but it’s really very straight. So so the the soil structure interaction is rather small and obvious. Yeah, quick question the so the at the piled the sheet pile tip. It looks like there is

Yerba Buena SX80: displacement. Yeah. And so

Yerba Buena SX80: they’re

Yerba Buena SX80: I guess maybe I’m getting out of my out of my lane here. But is there vertical settlements as well associated with all of this? With the

Yerba Buena SX80: with the the movement of a foot. Say.

Yerba Buena SX80: yeah, yes.

Yerba Buena SX80: Essentially, the the pile is translating with with the with the ground. We see that in the lateral movement. And then that is what’s plotted there on the right is the lateral movement. There, there will be some some vertical movement. That occurs. I think we’re

Yerba Buena SX80: but it’s

Yerba Buena SX80: and and when we look, if if we could back up a moment, Matt, to that

Yerba Buena SX80: deform mesh, so this on. These are typical lateral displacements.

Yerba Buena SX80: okay, yeah, no. These, these are just the lateral displacements. So so

Yerba Buena SX80: we in in the analysis, we’ve we’ve actually done a total stress analysis. And

Yerba Buena SX80: I, I think we’re we’re probably overstating a bit the the vertical movements that that are recurring. Okay, because it’s

Yerba Buena SX80: it’s going to be shared constant volume, you know, and and during the earthquake for the for the young Bay mud. That’s that’s going. But but it’s a permanent set, right. It’s a permanent okay, this is permanent. Thanks.

Yerba Buena SX80: I have a question about this

Yerba Buena SX80: figure also looks like the the dashed red line is the allowable moment capacity, and a couple of the cases.

Yerba Buena SX80: Ground motion one, both normal and reverse, exceed the allowable.

Yerba Buena SX80: I wonder if you can comment on that?

Yerba Buena SX80: No, no, let unless let’s review with this. So we are. Are we looking on the the left hand side, right, the left hand panel.

Yerba Buena SX80: So the the allowable bending moment of 69 foot kips is characterized by the

Yerba Buena SX80: the 2 vertical lines on either side. Oh, I see. There’s another dashed line. Dash, red line. Okay? I got it. Yeah.

Yerba Buena SX80: So that 69 on either side, plus or minus 69 compares to the width of the yeah, there’s there’s 2 dash red lines. Yeah. So when when you say reverse polarity, you mean you’re applying it as pushing the

Yerba Buena SX80: the mass in this case to the left.

Yerba Buena SX80: Is that what you mean by that? Yeah. And maybe Juan can help with this. But it’s it’s my understanding that you

Yerba Buena SX80: you you take the ground motions and on face value or normal, and you shake it.

Yerba Buena SX80: But it’s not symmetrical. And it’s and it’s a two-dimensional problem. That’s that’s asymmetrical itself. So depending on on which way the average movement is, you’ll get some different results, whether it’s normal polarity or reverse polarity.

Yerba Buena SX80: Yeah, I mean, that’s if it was level ground, the answer

Yerba Buena SX80: from the standard. So the the question is whether, there’s only one motion that we need to be applied, and if it’s level ground it doesn’t matter

Yerba Buena SX80: but if the ground is not level, if the geometry is not

Yerba Buena SX80: is symmetric in the sense we have to use.

Yerba Buena SX80: We have to apply the direction of the motion in the

Yerba Buena SX80: direction of the S. Axis, and then in the opposite direction, because we don’t know which direction it’s going to go.

Yerba Buena SX80: Yeah. So it’s the same. It’s the same motion. Yeah, it just reverse, because the geometry is not symmetric. Right

Yerba Buena SX80: on

Yerba Buena SX80: next slide. Matt hang on a second. I

Yerba Buena SX80: get a ton of zoom spam callers, and seems like they just temporarily cut us off

Yerba Buena SX80: back with you in a minute. Okay?

Yerba Buena SX80: Does the allowable bending moment for the steel sheet pile wall change with time during its 60 year life.

Yerba Buena SX80: Yeah, I can cover that. We actually trust that in the corrosion section. So we I don’t wanna get ahead of myself, but I’ll get ahead of myself. We have accounted for future corrosion loss.

Yerba Buena SX80: And so when we did our structural checks, we took some very conservative approaches on reduced wall thickness which in theory would reduce the capacity. But in that slide I’ll go into. Why, we believe that is an extremely conservative approach, and where the operation and maintenance manual airport will implement will actually result in likely vary to 0 to very little loss over the life of the project.

Yerba Buena SX80: But but 69 is the uncorroded

Yerba Buena SX80: allowable

Yerba Buena SX80: up?

Yerba Buena SX80: Yeah, that I mean, that was for for that section. Given the the properties. Yeah, I didn’t reduce it.

Yerba Buena SX80: We we did on our end. And again, based on, you know, just looking at that diagram. There’s plenty of room at the start. And we looked at a more conservative approach. If we lost this based on these values.

Yerba Buena SX80: and again, this is seismic bending. The the flood case actually ends up controlling from a structural perspective.

Yerba Buena SX80: And so that induced the actual maximum moments. But we’ll touch on that later. And again, there’s there’s quite a bit of reserve capacity on this. The wall thickness was actually selected

Yerba Buena SX80: primarily for installation. We didn’t want to go below 3 eighths inch wall thickness, just for driving purposes. So again, there’s there’s a lot of extra reserve structural capacity.

Yerba Buena SX80: But in 60 years this dash red line down the right edge would be shifted in theory. Yes, yes.

Yerba Buena SX80: James, did you also, while we have this plot up? Do you want to talk about where the corrosion would be more significant relative to where the maximum.

Yerba Buena SX80: Why don’t we table that up?

Yerba Buena SX80: Maybe if we wait to? A little later we could come back to the slide. If there’s further questions, because I do talk about corrosion rates, and where that corrosion will occur, you know, in ground atmospheric splash zone.

Yerba Buena SX80: And again, based on where this wall is relative to the actual water level, I have a graphic and some discussion there, I think, will help with this discussion.

Yerba Buena SX80: but the structural

Yerba Buena SX80: properties of these walls you provided to the geotechs correct. The sheet is a little small there, but the sheet pile the Az. 19700 was the basis of our structural design and Bob’s geotechnical analysis. We established a 36 inch, 36 ksi yield, which again

Yerba Buena SX80: the design build team may select 50 ksi if needed. We just picked a conservative value. And in this particular case the the stresses on the wall due to the seismic movement under the 475 is just not inducing a significant structural load. The sheet is essentially

Yerba Buena SX80: sort of sliding, moving with the mass of soil. There’s not a lot of differentials. It’s not retaining any soil in essence. But the shoreline does move as Bob has indicated.

Yerba Buena SX80: and I had a question, too. Here,

Yerba Buena SX80: and maybe you have slides that cover it. But my question was on slope stability.

Yerba Buena SX80: Primarily, because

Yerba Buena SX80: these are non tied back. These are cantilevered sheets right?

Yerba Buena SX80: And so they are relying on the passive

Yerba Buena SX80: pressure from the buttress in front of it.

Yerba Buena SX80: and so slope stability, analysis for existing case

Yerba Buena SX80: and post sheet pile construction case for the same design. Earthquakes that you have analyzed are those forthcoming in the slides that we’re going to see.

Yerba Buena SX80: They’re actually included.

Yerba Buena SX80: Mike. Sorry, I’m sorry. Thank you. The the plexus analysis is a is a nonlinear analysis. It it takes into account yielding, that goes on, and the and the movement associated with with that yielding

Yerba Buena SX80: So

Yerba Buena SX80: we and and what what it’s doing is the the movements aren’t taking the the system to failure, if you will. They’re they’re just analyzing the system as as it’s loaded by these inertial forces

Yerba Buena SX80: during shaking but but the the displacements that we see here include the yielding that that’s going on within the

Yerba Buena SX80: within the various soil layers

Yerba Buena SX80: understood. But for existing case all of the slopes

Yerba Buena SX80: meet

Yerba Buena SX80: the criteria of greater than 1.1 under seismic conditions, right? And and and of course they’ll they’ll there’ll be design criteria for the there’s going to be some regrading going on. And what have you that that’ll

Yerba Buena SX80: you know, in the final design? There’ll there’ll be minimal

Yerba Buena SX80: adjustment in geometry, because we?

Yerba Buena SX80: We? We have a situation that’s out there already, and we’re not trying trying to avoid new loads.

Yerba Buena SX80: But yeah, the current situation has is stable. Yes.

Yerba Buena SX80: So there is no rotational movement because of the imbalance in

Yerba Buena SX80: peace. Love.

Yerba Buena SX80: pre-previous slide, please.

Yerba Buena SX80: Yeah. And you can see the movement. Yeah.

Yerba Buena SX80: So one of the things you see there is that the sheet pile

Yerba Buena SX80: in the vicinity of the sheet pile? The ground level is is pretty much the same, so the the wall is not holding anything. So I, I understand your question about cantilever, but this is really not cantilever. This is

Yerba Buena SX80: this is essentially like an eye wall. It’s just providing flood protection is not retaining soil. That’s not the design criteria for the.

Yerba Buena SX80: So I have a question about how the movement was considered, and the analyses that you’ve been presenting are looking at out of plane response of the the wall and the different reaches, and I was interested to know if there’s any consideration given to

Yerba Buena SX80: in plane, the potential for any in plane differential movement to accumulate along the length of the wall. Given

Yerba Buena SX80: the preponderance of the movement appears to be in the soil.

Yerba Buena SX80: Obviously, there’s different conditions.

Yerba Buena SX80: As you work your way around the different reaches of the the seawall.

Yerba Buena SX80: Yeah. Well, again, I think there’s a specific question of the joint.

Yerba Buena SX80: Again, this is designed primarily as a flood protection element.

Yerba Buena SX80: There is seismic again, different. The 4 75 year event as Bob is presenting does create some movement.

Yerba Buena SX80: So we have some slides about how jointly

Yerba Buena SX80: that, like post seismic flood protection will be provided by Sfo. In this this structure we do make some rough assessments of where we think there could be some potential post 4, 75 year event damage.

Yerba Buena SX80: It’s a little hard to specify, particularly when we looked at kind of where discontinuities and alignment, where the wall makes a 90 degree turn. You know, these are generally movements trying to move towards the bay. So obviously, if you have 2 walls at angle each other, they’re going to want to move in different directions. The sheets are quite

Yerba Buena SX80: flexible. Accordion. Ask, but there still is limits. And so the expectation is there is potential

Yerba Buena SX80: for some interlock breakage. And then we discuss what new risk that induces from a flood protection standpoint back on the airport. And so I have a series of slides that I’ll go into that shortly.

Yerba Buena SX80: Yeah. And and I just might add that

Yerba Buena SX80: it. It is a 2 dimensional analysis.

Yerba Buena SX80: and so we have these estimated estimated movements from the 2D analysis. And we also

Yerba Buena SX80: took a look at the potential for differential movements along the along the the outer plane. Much the way you would looking at a

Yerba Buena SX80: a settlement of a building? Or what have you get? What’s the total settlement? What’s the differential settlement? And for this the analysis we use was the I estimated the differential settlement might be about half the total settlement, and then compare that to the kind of longitudinal strains that we would have along the alignment of the Shepa wall.

Yerba Buena SX80: And what kind of rotations these are? Zz! These aren’t flat sheet piles. These are Z shaped so they they have the ability to to handle some some longitudinal strains just just because of rotation, if you will. And and the

Yerba Buena SX80: James, that doesn’t look like there’s much much of a worry about breaking interlocks in for that mechanism. But but for when you have sharp ends, know that that where it’s it’s more

Yerba Buena SX80: correct, our our assumption right? Our analysis and evaluation is in alignment, like essentially one of the reaches. That’s a straight reach like reach 12 along that the general expectation is the movement will be towards the bay. It’s going to be fairly uniform across the alignment, obviously with variability in soil and so on. There could be some differential. But the differential isn’t significant enough where we’d expect a lot of breakages along those interlocks. Essentially, that whole wall is going to kind of move along.

Yerba Buena SX80: or when it reaches, reach 11 and reach 13 and makes a 90 degree turn.

Yerba Buena SX80: That’s going to induce significant, more stresses. And again, our theory is that there could be a gap there. Now we present where we think the gaps will happen. But our solution to that could apply. If there was a gap on a straight segment, because of unknown changes and stiffnesses and soils, it would still get addressed the exact same way at these other discontinuities. I would point out that our design purposely did not design a concrete cap initially for this project.

Yerba Buena SX80: We have a bent plates, and it’s because of the concrete caps rigidity. We felt that by binding all of the sheets together it would remove some of this kind of flexibility to accommodate these differential movements, and it would create sort of less predictability and more difficult repairs in the future.

Yerba Buena SX80: The steel sheets itself don’t need that cap from a structural standpoint to resist these loads from the flood wall, and the sheets themselves will act well in cantilever. However, we didn’t want to, also a rough looking sheet. So we provided a

Yerba Buena SX80: kind of a capping element.

Yerba Buena SX80: Bob, my question is, is the profile that you analyze and considered

Yerba Buena SX80: the most critical profile

Yerba Buena SX80: that you know you can think of. All could happen.

Yerba Buena SX80: Which means that anything that happens, you know, from natural phenomena

Yerba Buena SX80: will result more in accretion

Yerba Buena SX80: of flattest love.

Yerba Buena SX80: and there is no potential for removal of material which will change the slope.

Yerba Buena SX80: Something more critical than this. Yeah, and that. That’s a good question that what we’re looking at here are various sections now to to understand the impact of differing subsurface conditions on how the energy gets.

Yerba Buena SX80: You know, leads to seismic or influences seismic performance.

Yerba Buena SX80: So our presumption was that reach 6 because of its largest thickness of young Bay mud would be the critical location in terms of seismic performance. So this this is a case now, where there’s very little young bay mud. So we’re at the other end of the spectrum. We’re trying to understand

Yerba Buena SX80: how things behave for different soil profiles at this point.

Yerba Buena SX80: But

Yerba Buena SX80: yeah, the the basic idea, I think. And and I think it’s proven to be probably okay

Yerba Buena SX80: is that, you know. Reach 6 is a good

Yerba Buena SX80: good predictor of the the maximum movements that that we’re gonna encounter.

Yerba Buena SX80: Well, I guess the question is, I mean, do you foresee a potential that this profile.

Yerba Buena SX80: for example.

Yerba Buena SX80: could be

Yerba Buena SX80: the slope in front of the wall could be steeper

Yerba Buena SX80: due to

Yerba Buena SX80: coastal processes. Wow! I could take this one

Yerba Buena SX80: So in our cross section we do have riprap protection on the outboard side of all the reaches to provide that protection. So we’re not having soil loss or erosion.

Yerba Buena SX80: Thank you.

Yerba Buena SX80: Okay, Matt, why don’t we move?

Yerba Buena SX80: Okay, so that was reach 5. That. So we’ve covered that now.

Yerba Buena SX80: Similarly, we we analyze, analyzed reach 14

Yerba Buena SX80: the, this is

Yerba Buena SX80: along the mud flat. At at the airport. It’s on the on the on the eastern side.

Yerba Buena SX80: the

Yerba Buena SX80: the we. We have a deep boring at the location of our analytical section, the the one that’s normal to the to the shoreline. We we have information, then, on the on the depth to the rock, and and the the various layers

Yerba Buena SX80: beneath it. The the young bay mud is nominally in 40 feet or so thick. Here the the fill itself was was only 7 feet thick. So it’s it’s an intermediate thickness of young bay mud and a and a very nominal, a small thickness of fill for this analysis

Yerba Buena SX80: next slide.

Yerba Buena SX80: So this is the plexus model that that we developed for that

Yerba Buena SX80: the situation.

Yerba Buena SX80: And on the next slide we look at the

Yerba Buena SX80: the contours of lateral displacement and and the the average and the standard deviation of the

Yerba Buena SX80: of the movement of the sheep pile itself. And that’s the 0 point 9 feet on average.

Yerba Buena SX80: with a standard deviation of 0 point 4 feet.

Yerba Buena SX80: So so those are the the this, that’s the displacement information, and that we tried to capture in that table. We looked at at the beginning of the

Yerba Buena SX80: of the talk

Yerba Buena SX80: next slide, please.

Yerba Buena SX80: and and this is the the moment behavior. And, as as you noted earlier, they’re they’re smaller still at at reach 14 than they are at the others.

Yerba Buena SX80: And and I think again, that’s driven by the fact that there’s relatively little fill that that’s that’s that’s associated with with this particular section.

Yerba Buena SX80: So so that’s kind of a summary that is a summary of the the 2 new reaches that we’ve done, the plex analysis.

Yerba Buena SX80: We we also spent a fair amount of effort looking at site, response analysis, and how it varies with soil conditions. And that’s next next slide.

Yerba Buena SX80: you. You may recall from our last meeting that we looked at Reach 6. This is the site. Response analysis for reach 6

Yerba Buena SX80: 1. 1 of the interesting things and and a question that came up at our meeting.

Yerba Buena SX80: Last time was, boy that

Yerba Buena SX80: that very stiff layer beneath, right at the bottom of the young bay mud, I mean, what? How important is that in terms of the performance.

Yerba Buena SX80: So

Yerba Buena SX80: after our meeting, we we decided to take a a second look at that. On the next slide we can see

Yerba Buena SX80: the the peak ground acceleration panel that we had on the previous slide is shown again. That hasn’t changed. That’s the reach 6

Yerba Buena SX80: psa values and the panel just to the right of it is a an analysis where we said, Okay, assume that that stiff layer is in there, and that the engineering properties, the material underneath it extend through that.

Yerba Buena SX80: And what? What are the implications of that for the results of the analysis?

Yerba Buena SX80: So we we see that by removing that stiff layer we do get some increase in the PGA in the lower portions of the young bay mud.

Yerba Buena SX80: but as it works its way up

Yerba Buena SX80: and to towards the fill it. It winds up actually at at the same PGA within the fill, or not exactly the same, but 0 point 1 8 became 0 point 1 9 g. In terms of the the PGA with within the fill. So so we see that the PGA within the fill, which is

Yerba Buena SX80: but you know, the most important thing from a liquefaction. Assessment point of view is, is is pretty pretty stable.

Yerba Buena SX80: It’s it’s it’s not affected much by these kind of deep differences.

Yerba Buena SX80: And then we also looked at

Yerba Buena SX80: other sensitivities. We went to reach 5 where the rock is not as deep.

Yerba Buena SX80: You you see, the rock. Is higher up, and what we did there on on that reach. 5. We we looked at

Yerba Buena SX80: This happens to be a thickness of 40 feet

Yerba Buena SX80: of of young bay mud compared to the the 60 feet that we had at at reach 6. And what we see there is that the that the PGA

Yerba Buena SX80: within the fill is again

Yerba Buena SX80: 0 point 1 9. So so we see cutting that young vein thickness in half.

Yerba Buena SX80: really didn’t bother the it didn’t change anything within the

Yerba Buena SX80: the the fill. And 1 1 of the important things to

Yerba Buena SX80: that we have to keep in mind. We’ve kept the thickness of the fill the same across the sensitivity. Study. But but we see that the that

Yerba Buena SX80: that there’s really been hasn’t been a change in the in the PGA, and then we we reduced it even further in the final panel.

Yerba Buena SX80: And I guess that thickness there, I think it’s about 20.

Yerba Buena SX80: I’m not sure what. I don’t recall what that is. About 28 feet or so, and and there we have similar results. And the the the PGA in in that particular case, went to 0 point 2 0, as I recall. So so you know again, we’re we’re we’re seeing that we can

Yerba Buena SX80: turn the knobs in terms of the various thicknesses. And it’s not changing things in any substantial or material way.

Yerba Buena SX80: Sorry. Good question. Just

Yerba Buena SX80: when you remove that that stiff layer just below the bay mud

Yerba Buena SX80: did the displacement, profile, change of the

Yerba Buena SX80: of the soil column.

Yerba Buena SX80: I don’t have that in front of me. One, do you?

Yerba Buena SX80: I I don’t have that information in front of me, but I I don’t remember, it was very significant. So the results, the results were very, very similar.

Yerba Buena SX80: Just curious are these plexus results or deep soil results here. These are deep soil results. Yeah.

Yerba Buena SX80: Next next slide, please.

Yerba Buena SX80: This. This is a separate study that we made. It was actually, we reached out to on Gsntech

Yerba Buena SX80: to to do this for us.

Yerba Buena SX80: we most of our work is for the 475 year earthquake, but what we wanted to do was to take a look at.

Yerba Buena SX80: How does the magnitude of the earthquake change the the the PGA within the fill? So what this is? A plot showing the the PGA within, at the surface, within the fill, on the vertical axis and the horizontal is the PGA at at the input motion at the rock.

Yerba Buena SX80: And what we’re looking at here are return intervals of 72 years, 2, 25,

Yerba Buena SX80: 4, 75, and 9, 75. So we’re kind of looking at a full spectrum.

Yerba Buena SX80: and each of the diamonds that you see there represents a result, an analysis result for one of the ground motions.

Yerba Buena SX80: So there were 7 data points that that we analyzed for each of those return intervals.

Yerba Buena SX80: Now, this happens to be one where you don’t do the normal and reverse polarity. Because it’s a 1 dimensional problem. It’s not asymmetric. So

Yerba Buena SX80: then that’s that’s why there are only 7 of those diamonds. And and the the average values.

Yerba Buena SX80: For for those

Yerba Buena SX80: groups of 7 are captured with the red, the red circles, and the and the curve that goes through it.

Yerba Buena SX80: So what? What we, what we see is a a really, quite a well defined bend over curve, if you will,

Yerba Buena SX80: When we get to the design earthquake, which which has a PGA at the rock of about point 3 2 or so. We’re we’re at that 0 point 1 9 number

Yerba Buena SX80: that we saw before. And then when we get up to the 975 year event, it’s it’s

Yerba Buena SX80: leveled off asymptotically, it appears at about point 2.

Yerba Buena SX80: So it

Yerba Buena SX80: it. It just gives us a feel again for the the sensitivity of these results to the to the the intensity of of the ground, shaking.

Yerba Buena SX80: so the the next slide, please.

Yerba Buena SX80: So so here are the site. Response analysis, deep soil analysis for reach 5

Yerba Buena SX80: that really are a companion to the plexus analysis that we’ve done for reach 5

Yerba Buena SX80: and it and it shows actually, for for reach 5,

Yerba Buena SX80: the and and here the the thickness of the field is 30 feet rather than 20 feet, which is what we had it.

Yerba Buena SX80: reach 6

Yerba Buena SX80: and and we we do have a PGA of of about 0 point 2 3 is what we came up with here compared to the you know, the point 2 saturation number at

Yerba Buena SX80: at reach 6. Question. Yep.

Yerba Buena SX80: So if I look at this, obviously, you have the classic behavior between soft and stiff boundaries

Yerba Buena SX80: that could

Yerba Buena SX80: translate into issues of curvature on the sheet piles.

Yerba Buena SX80: and that that is additive to the.

Yerba Buena SX80: if you will, the inertial kind of demands on these. Okay.

Yerba Buena SX80: that’s that been looked at.

Yerba Buena SX80: Well, well, just to make sure I understand the.

Yerba Buena SX80: Of course the pox is modeled of

Yerba Buena SX80: that. We have

Yerba Buena SX80: has built into it those those various stiffnesses, and you know, soil properties. And and we are looking at the soil structure, interaction, which

Yerba Buena SX80: which reflects that so

Yerba Buena SX80: it the the displacement shapes, and the the moment diagrams that we looked at before. I mean they. They reflect the

Yerba Buena SX80: the difference in stiffness. Now, there are really only 2 materials that the pile is in. It’s in the fill, and it’s in the young bay. Mud.

Yerba Buena SX80: But but the the effect of differing stiffness is is captured by plexus.

Yerba Buena SX80: Okay, but

Yerba Buena SX80: it begs the question

Yerba Buena SX80: if these 2 analyses need to be kind of calibrated

Yerba Buena SX80: against each other, if you will.

Yerba Buena SX80: or how calibrated are they?

Yerba Buena SX80: So the deep soil analysis, the one dimensional analysis, was used to calibrate

Yerba Buena SX80: the plexus analysis. So plexus was.

Yerba Buena SX80: in a sense.

Yerba Buena SX80: was used to replicate the one dimensional assets we got from deep soil. So those are compatible. Okay, okay, they’re not identical because they’re 2 different tools, but they are. They are compatible regarding your questions.

Yerba Buena SX80: of the moment.

Yerba Buena SX80: the moments that we shown were the envelope of moments. So there was a maximum moment.

Yerba Buena SX80: It could have been at any given time, any given time or at the end.

Yerba Buena SX80: So it’s the envelope is not, is not necessarily capturing the inertial.

Yerba Buena SX80: I mean. I can tell you what the moment was at every point in time. But the those graphs show the envelope for all time, all depths. Instantaneous. Highest value. Yeah. Okay, thank you

Yerba Buena SX80: next slide. Oh, wait sorry, Bob.

Yerba Buena SX80: the the airport. I’m assuming that that the airport is classified as an essential facility, or is it? I I guess

Yerba Buena SX80: I’m curious about the 475 year versus, you know, 975 year

Yerba Buena SX80: selection, especially if you know from the previous

Yerba Buena SX80: slide that you know that there really isn’t a lot of

Yerba Buena SX80: additional ground acceleration occurring between those 2 events.

Yerba Buena SX80: and and I, miss and I apologize. I missed the the 1st meeting

Yerba Buena SX80: or last year’s meeting. I I just was curious. If there was

Yerba Buena SX80: an explanation or thought as to why 475 year return period

Yerba Buena SX80: was selected as the criteria rather than the 975 year return period.

Yerba Buena SX80: You know we we did a quite a quite a careful study on that. And have a tech memo that describes it.

Yerba Buena SX80: I think it’s included as an appendix within our original report

Yerba Buena SX80: and it has to do with the the kind, the potential for damage and loss of life, and the nature of the damage and and the return interval of the of the of the ground motion.

Yerba Buena SX80: We and we have to keep in mind that the

Yerba Buena SX80: the saturation that we saw in the PGA for the fill is

Yerba Buena SX80: I I think it’s it’s correct. It’s it’s for the fill. But but the

Yerba Buena SX80: the the increased magnitude of of shaking is is going to have an impact, not only on the fill, but on the on the young bay mud. And you know, so we? We want to choose an appropriate design level and I I wouldn’t

Yerba Buena SX80: necessarily.

Yerba Buena SX80: I wouldn’t.

Yerba Buena SX80: Conclude off the bat that that that this insensitivity to the level of shaking is is

Yerba Buena SX80: is is based on all failure mechanisms, if you will, I would add again, just the fundamental function of this is a flood wall. Yeah, and so, and we again, I’ll dress on it a little later, when we look at combined flooding and seismic. But essentially.

Yerba Buena SX80: we do not want it to fail during the flood. That is its design. There would be consequential impacts if you had the 100 Year Flood, especially when you start looking at sea level rise. If this wall failed at that moment, it’d be quite consequential to the airport.

Yerba Buena SX80: If there’s an earthquake and we’ll talk about it later. And gets damaged at these interconnections. There’s no

Yerba Buena SX80: the life safety risks. There’s no general risk. And obviously what the flood combined case

Yerba Buena SX80: which we’ll demonstrate in some slides. It doesn’t the airport. It’s not like a New Orleans situation where it’s retaining wall water continuously. If it fails, you have an instant flood. It’s quite the difference. 99% of this time over this life of this wall.

Yerba Buena SX80: we’ll see no load. It’s only during these few rare events.

Yerba Buena SX80: and at that point, obviously a combined seismic event hitting at that exact moment would be very bad. But again, we’re going to go into

Yerba Buena SX80: that kind of risk profile. Yeah, okay, thank you.

Yerba Buena SX80: What I mean.

Yerba Buena SX80: I just wanna comment that PGA is a very

Yerba Buena SX80: simple

Yerba Buena SX80: parameter. I don’t disagree about saturation, but it’s because of a lot of straining and nonlinear behavior that you’re not getting PGA to really be different for input levels that are

Yerba Buena SX80: higher necessarily. But a lot of other things can happen. So so I think

Yerba Buena SX80: the discussion about PGA being saturated and doesn’t matter.

Yerba Buena SX80: That’s not the whole picture.

Yerba Buena SX80: but

Yerba Buena SX80: to the point of of this being a critical lifeline facility. It’s an airport. It’s an international airport

Yerba Buena SX80: 10 miles south of here.

Yerba Buena SX80: while I understand the intent of this system.

Yerba Buena SX80: But

Yerba Buena SX80: if there is a higher level of shaking, and the intent of the system is compromised.

Yerba Buena SX80: is there some redundancy there? Against that? Again, we’re probably a few slides away to walking through our approach to this? Yeah.

Yerba Buena SX80: hopefully, one last question, or maybe a response is, Wait

Yerba Buena SX80: but these reaches all show the

Yerba Buena SX80: sheet pile through an existing perimeter.

Yerba Buena SX80: The new fill. The 26 acre of new fill is the cross section at the perimeter similar to these reaches. Ultimately it’ll be very similar. The wall we at the top of the slope with the Riprap. How we get there there’s, you know, it’s modern construction versus 19 thirties fill. So we’re going to accommodate for

Yerba Buena SX80: that, making sure we’re taking out initial settlements. But ultimately the cross section is very similar, Bob. Anything to add.

Yerba Buena SX80: So it is a. It is a. It is a new

Yerba Buena SX80: levee, right? Or a deck. Essentially, if you went out there after construction, it’ll look like everything else. Basically, we’re building out riprap on the shoreline. There’ll be a flood wall right at the edge of that.

Yerba Buena SX80: Okay? And so you have cross sections within the new fill area, so reach 7, which was previously presented, was at that particular reach. Yes, and and the

Yerba Buena SX80: The the analysis we did at Reach 7 was covered in our report from last year.

Yerba Buena SX80: Of of course, the requirements today are.

Yerba Buena SX80: you know, they tend to be more stringent than than they were 50 years ago, you know. So we’re we have preloading. We’re going to be installing wick drains to to allow this the settlement to occur more quickly.

Yerba Buena SX80: We’re we’re going to be

Yerba Buena SX80: treating the fill with with vibratory, deep, vibratory compaction to

Yerba Buena SX80: aggressively mitigate liquefaction. Potential.

Yerba Buena SX80: and yeah. So. So I I think that the

Yerba Buena SX80: the expectation is, and then the goal is, it’s going to be the the new construction is going to be better than than the old. The thing that the old construction has going for it, though, is old, I mean it’s good. I mean, it’s been there a long time, and then that that’s a good thing in terms of

Yerba Buena SX80: stability and and the like. So much much of the effort for the new construction is getting it to fully consolidate and strengthen. And what have you quickly? Which? Because we don’t have the the luxury of time

Yerba Buena SX80: in that regard? Yeah.

Yerba Buena SX80: yeah, and I think we’re some. Yeah. So the the next

Yerba Buena SX80: and yeah, reach reach 14 is essentially the same. There we we, we have about 40 feet of young bay mud, and the the PGA in that thinner is is 0 point 2 0 from from from this analysis, the deep soil analysis.

Yerba Buena SX80: So if we move on to the

Yerba Buena SX80: I think we can skip this because we’ve already looked at it. But just kind of the summary slide. Mark Matt next

Yerba Buena SX80: would be good.

Yerba Buena SX80: So I I think the

Yerba Buena SX80: the the 4 reaches analyzed. They. We think they bracket the most subsurface conditions along the shoreline prediction program.

Yerba Buena SX80: alignment

Yerba Buena SX80: on the additional plexus analysis and the and the site. Responsive analysis

Yerba Buena SX80: indicate that reach 6 provides a conservative estimate of the magnitude of lateral displacement of the Xipa wall.

Yerba Buena SX80: Where the reaches of the young bay mud is is less than at reach 6, and new fill is not added. That’s the case.

Yerba Buena SX80: the source structure. Interaction stressors are remarkably small, and it’s and that that’s what leads to kind of a counterintuitive conclusion that the calculated stresses

Yerba Buena SX80: for the flood walls under the flood loading are larger, and you know, in many ways controlling the design. I’ve just a general question.

Yerba Buena SX80: earlier on you gave us that tabulation of the 4 different cases that you had run with Reach 7

Yerba Buena SX80: being an a year old study result

Yerba Buena SX80: having

Yerba Buena SX80: twice as much deformation. I think it had higher

Yerba Buena SX80: moments also.

Yerba Buena SX80: But you didn’t present the plexus results on that is that coming up later in the presentation, we presented them last time

Yerba Buena SX80: the the reach, 7 analysis, were were summarized, so no no changes, no change in that, including the deep soil. And all right, right? There’s no changes.

Yerba Buena SX80: And and the

Yerba Buena SX80: right? And you’re you’re right. The the displacements every 7 are larger. We we had

Yerba Buena SX80: 1 1.3 feet at reach 6, and we have 2.1 feet, and I’ll get, and that’s something I cover in a in a wrap up, slide the next wrap up, slide

Yerba Buena SX80: So if we could get to the summary Matt

Yerba Buena SX80: and the the sensitivity studies.

Yerba Buena SX80: that varied the magnitude of the shaking we we looked at, and and show the maximum expected PGA within the fill is about

Yerba Buena SX80: 0 point 2 g.

Yerba Buena SX80: The the next slide.

Yerba Buena SX80: Th, this gets to the reach. 7 question that that you asked the

Yerba Buena SX80: The new fellow read 7.

Yerba Buena SX80: It. It’s gonna cause somewhat larger, estimated lateral displacements there.

Yerba Buena SX80: 2 2 feet versus 1.3 feet

Yerba Buena SX80: but the maximum transient bending stresses.

Yerba Buena SX80: and the she power wall at sixes and 7 at reach 6 and 7 would be less than 11 ksi.

Yerba Buena SX80: you know, really a very small stress. From a steel point of view.

Yerba Buena SX80: and far below the allowable bending stress on the for steel under permanent loading

Yerba Buena SX80: and and the final bullet here is in some ways a non sequiturge, but just to emphasize that

Yerba Buena SX80: as we discussed last time, we we really do need to do

Yerba Buena SX80: a very extensive program of of cone penetrometer tests to characterize the fill

Yerba Buena SX80: so that we get

Yerba Buena SX80: good good average properties within the field and are able to delineate areas that may require ground improvement.

Yerba Buena SX80: Of of the film.

Yerba Buena SX80: So that that’s that’s the last slide that I have.

Yerba Buena SX80: Okay, any other. Oh, Jim, you still got your mic on. Is there any other questions.

Yerba Buena SX80: I’m just looking through last year’s presentation for 6. Well, maybe I can. And and it’s probably non-technical. But in the reach 7 area, where there is a new

Yerba Buena SX80: containment levy being created.

Yerba Buena SX80: Is there a need to put in the cut off wall or a flood wall there, rather than just elevating the the levee to what it’s need to be.

Yerba Buena SX80: There was some reviews of different options, including our earthen levees, other structures. There was actually a cantilever cheap pile solution originally through kind of evaluation of each of those options. This was determined in the most cost, effective solution.

Yerba Buena SX80: but it also includes a sheep pile in the in the perimeter diet

Yerba Buena SX80: that goes into the young B. Martin.

Yerba Buena SX80: here’s the

Yerba Buena SX80: yeah.

Yerba Buena SX80: Yeah, that that is.

Yerba Buena SX80: it’s conceptual. But it’s showing the the dyke. The preload fills the the wick drains, and the

Yerba Buena SX80: and the sheepah wall, which would be installed last, you might say, once

Yerba Buena SX80: mo- movement, sir.

Yerba Buena SX80: are are done, then you would be yeah installing the sheet piles within that perimeter deck.

Yerba Buena SX80: Did did you want me to pull up the results from the last? The presentation last time, or are you okay checking it on your own?

Yerba Buena SX80: Gee!

Yerba Buena SX80: Do you? Do you have them? Do I have them? Do you want me to pull them up for all of us is what I’m asking. Would that be helpful?

Yerba Buena SX80: I wouldn’t mind looking at.

Yerba Buena SX80: Hang on.

Yerba Buena SX80: remember which 7 is new construction.

Yerba Buena SX80: Yeah. So that’s the difference between Reach 6 and reach 7 reach 7. We’re extending into the bay. So all that is new construction.

Yerba Buena SX80: I’m sorry, isn’t it. What? Oh, it is part of the project. Yeah, interested in the entire project, which?

Yerba Buena SX80: And so you’re presenting everything except everything today except for the worst case.

Yerba Buena SX80: And actually, I think those results are in appendix C

Yerba Buena SX80: of the turn your mic on.

Yerba Buena SX80: and I’m sorry. I think those results are an appendix C of last year’s report. I don’t think you have those with you. I do, do you? Okay? And I’ll add again, it looks like we’ll pull it up. But last year, when we met, we focused exclusively on Reach 6 and 7. And then the question basically was like, well, is that indicative of the entire report

Yerba Buena SX80: the exercise that we’ve been through is to demonstrate that we feel it’s representative. Again, given, this is a design build projects and trying to kind of fit that middle ground of going too far into design versus giving you assurances that we’ve captured a solution that’s representative. That’s where we’ve selected 2 additional reaches, but I think here we go. It’s pulled up so we can discuss about reach 7.

Yerba Buena SX80: There’s this one, and then I think

Yerba Buena SX80: there’s the envelopes

Yerba Buena SX80: the moment command envelopes. And and I think

Yerba Buena SX80: that’s Route 6.

Yerba Buena SX80: Yeah. I saw the deep 6 deep soil either reach 6 deep soil, but not reach 7.

Yerba Buena SX80: That might be in the report. Hang on a second.

Yerba Buena SX80: Okay? Well, well, Matt’s looking for

Yerba Buena SX80: the slide. Just do a quick time check. It’s almost 2 30.

Yerba Buena SX80: How how are we doing in in terms of your presentation?

Yerba Buena SX80: We’re about 20 min over where we said we were, gonna be we had left a

Yerba Buena SX80: about a half an hour allowance so that we’ve eaten up 2 thirds of our contingency.

Yerba Buena SX80: Okay.

Yerba Buena SX80: thank you.

Yerba Buena SX80: Do. I can keep looking for this in the background, and we come back to this one at maybe after James is done. Does that work for?

Yerba Buena SX80: Yeah, if it’s in last year’s presentation you give me some time notified. Yeah, I’m not all that worried about it just seems like if we’re comparing. Well, if you’re saying, all the new stuff is representative or last year’s was representative of what you’re showing now. It’d be nice to see the last year’s. It was included as a supplemental to the materials provided ahead of time.

Yerba Buena SX80: So there was an attachment to the geotech report that was focused on the new material was also provided was the old material well, so we didn’t focus it on this meeting, since it was repeat, but it was provided in the materials were provided, I think which appendixes I have all those attachments right now. Okay, let’s have James get started. Bob’s going to look through the ones, and and we can get you like the page numbers in those things. Okay.

Yerba Buena SX80: now, I gotta figure which version hang on a second.

Yerba Buena SX80: This

Yerba Buena SX80: actually, can I ask a question in the meantime, yeah.

Yerba Buena SX80: I have a question more about the process. You talk about design build.

Yerba Buena SX80: we’re looking at some very specific analyses. So how does the design come into this if if these analysis are not part of the design, so I could try. So I’m trying to understand who’s designing what? So again, it’s it’s with a design build approach. And we’ve been through this from some of our other clients generally. In order to

Yerba Buena SX80: get through a board like yourself. There has to be a certain level of analysis completed to establish the criteria and the general concept. So Sfo has asked us to take the analysis far enough to gain general acceptance of the approach that we’re taking here, and then this information will be established in the design criteria that will be used by the design build team.

Yerba Buena SX80: which we’re gonna help the airport which will be established by the airport. The design build team. Then ultimately, as the engineer of record will have to design, finalize the design to adhere to the criteria that we have established

Yerba Buena SX80: and provide additional analysis supporting all the reach designs. Our expectation is when they come to reach 6, 5, 7. Their results should essentially mirror or be very similar to what Bob and his team has presented.

Yerba Buena SX80: Again, it’s it’s in that process of design, build doing enough upfront to gain assurance of the criteria, but giving the contractor that kind of design, build advantages, especially in an airport project like this with a lot of the coordination

Yerba Buena SX80: that’s really going to be a challenge. And so they felt that models the best. So that’s generally how we see this project moving forward.

Yerba Buena SX80: And I’ll add a comment that

Yerba Buena SX80: Bcdc’s permit, which will be based on the conceptual design that you’re hearing about today. There will be a condition, special condition in the permit that

Yerba Buena SX80: the permitee will have to submit the final design documents and

Yerba Buena SX80: I’ll review them to make sure that they conform with. All the reports that they’ve already submitted.

Yerba Buena SX80: Okay, thank you. That’s what I was asking. At which stage do we make sure that actually, what was what was presented here

Yerba Buena SX80: is taken into account in the final design. Thank you.

Yerba Buena SX80: So Jen. Would. Does that mean that

Yerba Buena SX80: The engineer of record may not.

Yerba Buena SX80: or the Ecrb wouldn’t hear from the

Yerba Buena SX80: engineer of record with the final design.

Yerba Buena SX80: or would I? I think that’s where Nick’s going. Yeah.

Yerba Buena SX80: yeah.

Yerba Buena SX80: Well, I don’t want to speak for you guys. But design build packages. Typically have some. The design criteria written into them that have to be met right, and an example of a project that went through this full process is Redwood City wharfs one and 2 Koe. On that project was same position where the owners, engineer, preparing design build contract. We met with Bcdc. Went through this process, established the criteria, and then our job as the owner’s engineer kind of representing was to make sure that

Yerba Buena SX80: did final design adhered to the criteria that was agreed upon through this process it was submitted back through Bcdc. Again. I don’t know the how the wheels turn at Bcdc. But at that point it was they. There was enough checks completed that everyone agreed that this was in adherence with the permits.

Yerba Buena SX80: and I

Yerba Buena SX80: don’t recall it having to come back to Ecrb. But again, it’s somewhat up to your discretion. Okay, thank you. Yep, makes sense.

Yerba Buena SX80: I mean just one. So you guys will be 7 as peer reviewers. Then

Yerba Buena SX80: I cannot speak for Sfl.

Yerba Buena SX80: but we’ve been involved for this project for a while, and assuming they would like to keep us on, we would be.

Yerba Buena SX80: yeah.

Yerba Buena SX80: because that’s the only way you can assure that you know the criteria you’ve established.

Yerba Buena SX80: Right? So if you are not peer reviewing what they’ve done.

Yerba Buena SX80: there is no way of ensuring that the criteria be met.

Yerba Buena SX80: Understood. Yeah.

Yerba Buena SX80: should I jump on in?

Yerba Buena SX80: Okay. So I’ll try to talk fast, but feel free to stop me at any point. So this is related to operation and maintenance. In particular, you had a question

Yerba Buena SX80: you asked for a scenario of combining looking at both earthquake and flooding.

Yerba Buena SX80: So summary of our analysis to date is, we did evaluate both earthquake and flooding, but we looked at them initially as independent events. We looked at a hundred year flood event, which included a 3 and a half feet of sea level rise.

Yerba Buena SX80: And again, this is a flood wall. We designed it to remain completely elastic. No damage.

Yerba Buena SX80: We also looked at. Okay? And again, what we classified as medium hazard level. We call it 72 year. That’s terminology. We use for this. But it was a 72 year event

Yerba Buena SX80: again, that remains there’s no damage where they they’re the ground shaking is enough to create this lateral movement. The wall is essentially a sheet, pile.

Yerba Buena SX80: self weight. It can accommodate this. The loading on the wall is much less than the flood case

Yerba Buena SX80: is where we run into the 475 year event. As Bob just presented. There is some movement, so our expectation is there could be some localized, but we would assume, or we believe is repairable. Damage.

Yerba Buena SX80: A load case looking at specifically a flood case. So you have the 100 year Flood, and the seismic event happening at the exact same time given just the probabilities of the return periods of those is extremely

Yerba Buena SX80: improbable. Event very bad day for Sfo. I’m not saying could not happen. But just again, from a risk-based design standpoint, I think it wasn’t concern wasn’t happened at exactly the same time, which is an extremely rare event. But it’s a chance of what happens in the next 6 months. I’m glad you’re seeing that because that was a little worried you want at the same time. But so we focused our analysis is on that particular approach. Okay, you do have a seismic event. You do get the 475 damage occurs.

Yerba Buena SX80: What happens. Now, what risk have you reintroduced the airport from a flood perspective?

Yerba Buena SX80: So this analysis we present here is basically demonstrating what we believe is the post seismic behavior of the flood wall, the response for implementing temporary and permanent repairs. And generally, what is the risk the airport is looking at if you go to the next slide. And there’s a lot of kind of like moving targets in this. So we’ve had to make some key assumptions because there’s what’s occurring today, and I have a slide coming up. But what happens with civil level rise? So we do look at this at sort of 3 time horizons.

Yerba Buena SX80: 1st off. What is the expected post seismic behavior?

Yerba Buena SX80: Again, after the sizing event, some gaps are expected to form at discontinuities, and I have a figure that shows our estimate of where that might occur

Yerba Buena SX80: in this case. From 0 days to week, one after the seismic event, there is going to be gaps in the wall. That wall will not provide flood protection. At those particular gaps, however, the remaining portions will remain intact, providing a level of flood protection. So it’s not as if the entire wall collapses, just gaps will open.

Yerba Buena SX80: but it does reduce the flood protection, and we’ve made a conservative assumption that’ll get reduced down to the existing ground, level as it is, so that wall will split all the way down to the current ground level. We went through and looked at Lidar along the current proposed alignment and took basically the lowest elevation of each reach

Yerba Buena SX80: right at the wall, not behind the wall, because it does the wall. The land does dip down a little bit, but right in the alignment

Yerba Buena SX80: week, one to 6, the expectation is within one week the airport would be able to implement some level of temporary repairs, and we’re envisioning

Yerba Buena SX80: sandbags fill. They’ll be able to place and fill these gaps with a roughly up to about 3 feet, and again it will provide some level of flood protection. There might be some seepage through that gap, but it won’t be a free path of water.

Yerba Buena SX80: The airport will be responding to this event. You can imagine a 4, 75 year event

Yerba Buena SX80: is likely. Have other consequences at the airport. There’ll be a full response. So our expectation is they would have the the manpower and the personnel to inspect the wall and make these decisions within about a 1 week period. Let’s get some sandbags and close these gaps.

Yerba Buena SX80: Our expectation is the full, permanent repairs would take roughly about 6 months to implement, and that would generally consist of, probably, again, depends on what the exact damage, but probably pulling some sheets, driving some new sheets, welding in some interlocks, basically closing the gaps.

Yerba Buena SX80: So those are some just basic assumptions to set this analysis moving on to the next slide.

Yerba Buena SX80: we talk about where these gaps could form. And again, this is based on where we believe a discontinuity could create enough stress in those interlocks where you potentially could pop them. And you’d have a gap.

Yerba Buena SX80: We looked at each of the reaches, and you can see some of them have very distinct direction where it changes, and so we circle these at each of these discontinuity or changes in directions, and we roughly estimated 30 degrees. I’m not going to say here we analyze it to get exactly the 30 degrees. It was a engineering judgment on that. Just to get a order of magnitude, of potential gaps in this for this exercise. Next slide.

Yerba Buena SX80: Again we looked at 3 different timelines, the sea level rise. For this project we looked at a medium high risk aversion, so to add into the probability of all this that has a 1 in 200% chance of occurring

Yerba Buena SX80: of exceedance by the target date of 2085. So based on this, we’re saying, sea level rise by 2030, we just is it truly 0? No, it’s going to be a little bit more than 0 by 2030. But just for by the time this wall is built we just said 0 at that point 2050 would have 1.9 feet of sea level rise.

Yerba Buena SX80: and by the end of the project. Essentially, design life would be about 3 and a half feet of sea level rise is our target

Yerba Buena SX80: moving on the next slide.

Yerba Buena SX80: We looked at. Okay after the seismic event. When are we really vulnerable to flooding? Again, we assume the existing ground. Elevation at the wall would be essentially our lowest level of flood protection at that point, right after a seismic event. If the mean high high water exceeds that floods that elevation, the expectation is you could have some water pouring through

Yerba Buena SX80: could essentially create some flooding. Matt has some slides later, if in that scenario like, how much would then get sucked into the interior drainage. But for this purposes we’re assuming. If it reaches that level, we’re going to have some widespread flooding. It would be an area of concern.

Yerba Buena SX80: still water level. Now this requires a hundred year flood event to happen, or some lesser storm. That’s again the water raises to that full elevation. If that starts pouring through

Yerba Buena SX80: again, you could get some widespread flooding. The final one is total water elevation. Now, that’s sort of wave splashing over the top of your wall.

Yerba Buena SX80: That’s definitely more of a localized area. You wouldn’t, you know. It’s just a splash over the top. So our expectation, if that’s coming through your gaps of lesser concern, and it’s a little hard to see on the image on the right. But I do want to point out. I think this is a key point to this whole project

Yerba Buena SX80: is, if you stand out there currently on the shoreline, you are above mean high high water. You’re above the extreme atmospheric annual water elevation. The airport would only flood in this case if you had a storm event getting close to 100 year Flood, as it currently sits.

Yerba Buena SX80: When you start adding sea level rise only when we reach 2085 will the mean high water at any given day just barely get above our lowest point currently on ground elevation, which is elevation 10. So, and essentially, this wall is not under any load. It’s not under any flood

Yerba Buena SX80: cases. On every given normal tides. If you had earthquake and the storm hit, then yes, you would have some flooding. But you do need those combined events to occur

Yerba Buena SX80: next slide

Yerba Buena SX80: when you said on the last slide, 30 degrees of movement is that vertical? Oh, no, no sorry apologies. If you go back to it’s 30 in Plan View, where the wall direction makes a tangle change of more than 30 degrees. The most pronounced is at the end of the runways. You can almost see it like a 90 degree bend and the sheet direction changes. But we said anything over 30 degrees.

Yerba Buena SX80: And there’s been some questions like, Why don’t we just straighten out the wall? There’s a lot of stuff along 7 and a half miles. So we do have to accommodate existing infrastructure which does create some

Yerba Buena SX80: undulations of the wall alignment.

Yerba Buena SX80: Just a quick question. This long-term projection of levels does that include settlement of the of the airport itself? I mean, there’s a huge field that is slowly settling. We have some later slides on on settlements, I would say, to keep the variables down. One. I didn’t include the

Yerba Buena SX80: the, the expected settlement of the grade, the existing grade behind the wall. You’re correct over a long period of time, our elevation. I have some slides here, like our lowest elevation, is at reach 4. That’s at the Coast Guard. It’s about elevation 10 ish

Yerba Buena SX80: in theory. If there was subsidence now, 10 might turn into

Yerba Buena SX80: 9.5 9 point, you know some value, and we might have some slides later on that. But in the overall response post seismic I don’t believe it’ll change the results. Okay, I understand post seismic. But

Yerba Buena SX80: unfortunately, there, there are a couple of very modern airports that are becoming essentially unusable

Yerba Buena SX80: in situations like this because of the long term settlement, not because of other issues. We have a whole segment on subsidence that was looked at in detail, and it was about one to 4 inches, which would be about, you know, 0 point 1 to 0 point 3 feet. If you want to think of that in terms of these sea level rise amounts as a compensatory relative to seal rise.

Yerba Buena SX80: Thank you. Matt.

Yerba Buena SX80: Okay, so moving on past this slide again, these are a little hard to read here, but they’re presented in the report, but these are snapshots in time so essentially per reach. We establish what is the current design elevation of the wall.

Yerba Buena SX80: Again, that’s account for the sea level rise plus 2 free free boards. So it’s quite above the potential flood level.

Yerba Buena SX80: at the yeah post earthquake. Again, the existing minimum ground elevation per reach.

Yerba Buena SX80: The lowest is about 10. It goes up to around elevation 12 in some locations. So again, the risk at each reach varies, just depending on the existing grade. After you place the sandbags we’re assuming. Within a week you get 3 feet of flood protection back in there and then we looked at how many gaps within that area so potential spill points. And so if you start looking at 2030

Yerba Buena SX80: looking at just basically mean high high water again. You’re not going to get that every day, but you can get that several times a month. There’s no point as exceeding the existing ground elevation. So it’s essentially today

Yerba Buena SX80: at 1%. Still, water elevation. Even that is just barely above. So you’d have at reach for some very limited exposure. If you had the 100 year event within one week. But after the sandbags are placed, you’re essentially going to have protection from that event. Oh, sorry!

Yerba Buena SX80: Isn’t it correct that the titled items which you point out are from the

Yerba Buena SX80: a previous title epic.

Yerba Buena SX80: that when sea level rise is 0.

Yerba Buena SX80: Those

Yerba Buena SX80: elevations are really more closer to the year. Like 2,000, not 2030

Yerba Buena SX80: there could be some nuance in there. It might fluctuate these results a little bit. But again, for this purposes of trying to limited variables we assume that the Navd 88, the 0 out datum, as is currently published by the Noaa’s type charts and data would be representative of 2030. It’s not completely true, right? There will be some increase in the Navd 88, but not enough to significantly change the results.

Yerba Buena SX80: Thank you for bringing that up. I did have. You know. I don’t think it’s going to change the results, but sea level rise of 0,

Yerba Buena SX80: you know I would take. I would take objection to that.

Yerba Buena SX80: because, as Jen mentioned, all of these sea level rise numbers are based from 2,000, and we are already at 24,

Yerba Buena SX80: and I think the existing. We just did some of the recent NASA ultimatery data measurements we looked at as part of

Yerba Buena SX80: one of the other projects that we were responding to Vcdc for. And it’s about 4 inches has occurred to date right? And by 2030, yeah, it’s going to be about, you know, I’d say about 5 inches is baked into it. So you know 0 may not be, and I fully admit that is again, maybe my effort to keep things slightly simpler. I may have added this extra comment, but

Yerba Buena SX80: I think once we go to the next slides when we are, those were really, we’re targeting the sea level rise 1.9 feet 3.3 and a half feet. Those results in the future we’ll have those slides again, showing that there’s quite a bit of post seismic protection

Yerba Buena SX80: and immediate flooding is not expected. I was trying, I guess, in essence, with this current base case 2030 in essence. If you had this seismic event for about a 1 week period you’d have essentially the current flood risk potential that the airport has right now, as we sit here today.

Yerba Buena SX80: reach for has no protection. Currently, it’s the lowest point in the airport. It’s very vulnerable. So our goal is to get this wall built. Yes, there may be some damage after a seismic event. But the reintroducing risk is less than what you experience today.

Yerba Buena SX80: and you know the benefit of getting the flood protection in versus the cost of trying to mitigate all seismic damage.

Yerba Buena SX80: It’s just it’s the balance is just not there. The value to the airport isn’t significant enough to try and prevent all seismic damage.

Yerba Buena SX80: especially when you’re compared against how much benefit this provides from a flood protection standpoint.

Yerba Buena SX80: So so in conclusion, on this slide is is, you know, there’s very limited risk after the projects are initially constructed. Even in the short period of time, post seismic event of widespread flooding and essentially, at worst, you’re back to where you are sitting today for that week period.

Yerba Buena SX80: If you go to 2050 things start getting a little bit worse, but not much. Again in the week period after. You know, there’s no mean high water that’s above the existing ground elevation. Even when you add in the 1.9 feet of sea level rise to the mean high high water value.

Yerba Buena SX80: So again, our expectation is in a regular tide event. You shouldn’t have water pouring through. If you had the storm or event, the 1% yes, during the one week gap, you are vulnerable, for sure. But again, that would be very similar to where you’re sitting today. When you start looking at sandbags getting placed, you’re going to get that protection for that 6 month period, and eventually you’ll get your wall built back up, and again the protection will be placed there

Yerba Buena SX80: looking at 2085 things do start to get a little worse. But I would point out that this is at the very end of the project. It assumes a 1 in 200 chance of sea level rise, meeting 3 and a half feet, and the one reach that really has the biggest problem

Yerba Buena SX80: is reach 4, where, if you had a mean high high water elevation plus sea level rise, you could get a flood event coming across that one particular reach, and Matt will demonstrate later. Then, again, we believe the interior drainage can accommodate some of this spillage.

Yerba Buena SX80: I would say again, this also is a big assumption. The Coast Guard’s facility is

Yerba Buena SX80: 50 60 years old.

Yerba Buena SX80: The expectation that they will do no projects, no improvements to their airfield between now and 2085,

Yerba Buena SX80: and my opinion is very low, so our expectation is sometime between now and 2085,

Yerba Buena SX80: they will likely have reconstructed that there’ll be some benefits to their project to raise their existing elevation, and so we think this risk at the end of our project. Life is actually probably over pronounced here.

Yerba Buena SX80: but not to say it’s it’s it’s 0. Again. You do have more flood risk in 2085.

Yerba Buena SX80: If we had the large seismic event you would be looking at a little bit more flood risk. But again, is it worth the airport spending the money now

Yerba Buena SX80: to protect something at the end of your flood walls? Service life? And our opinion at this point is

Yerba Buena SX80: not necessarily.

Yerba Buena SX80: thanks, James. The question is the existing minimum ground elevation

Yerba Buena SX80: post project going to be raised at all? Or are we going to have an 8 foot stick up at reach

Yerba Buena SX80: 8 7 in general. Yes, if you go out there and go along the shoreline, the wall will basically be placed at the current top of shoreline. So where the Riprap meets the shore.

Yerba Buena SX80: there is some existing berms and other infrastructure. Some of that’s going to have to get cleaned off in order to install the new flood protection. So the last specific grade this is again, is going to be where the design build comes in. It’s probably varying a little bit, I’d say, plus minus a foot from the values I’ve had here. But again, the general conclusions I feel are fairly accurate.

Yerba Buena SX80: But the idea is, we’re not planning to use this as a retaining wall structure. We’re not going to pile up soil on the inside. The wall itself is the flood protection element.

Yerba Buena SX80: I think that’s it. I have a conclusion slide that I think I’ve more or less stated all of these.

Yerba Buena SX80: again, there is some exposure. I’m not going to sit here and say there’s 0 risk, but we feel it’s quite low.

Yerba Buena SX80: The site is not expected to be a risk of flooding due to daily tides until the very, very end of the project. And even that’s very limited. And that’s based on one and 200%, 200

Yerba Buena SX80: chance of exceedance and sea level rise. The expectation is, repairs can be placed within 7 days. Airport has a very robust group that can accommodate these these repairs, and we have an operation and maintenance plan in place that would work in this response.

Yerba Buena SX80: and essentially to prevent all of this damage that Bob had presented, or that movement. The cost of that just does not make a lot of economic sense, especially considering this is a flood protection project.

Yerba Buena SX80: And again, at no point. If there was an earthquake, it’s retaining a significant amount of water that would create a risk to the public

Yerba Buena SX80: unless we have a very, very unfortunate event of the flood a hundred year, Flood, and that seismic event occurring at the very same time.

Yerba Buena SX80: And that’s my presentation.

Yerba Buena SX80: Any more questions on that

Yerba Buena SX80: aspect of the combined event.

Yerba Buena SX80: just really quickly. You mentioned subsidence as well.

Yerba Buena SX80: Is that included in this?

Yerba Buena SX80: A. A. Again, I did not add that variable into those tables just because of the the amount as Matt had mentioned. It’s it’s minimal. And also just was one extra variable that’s trying to keep it simple.

Yerba Buena SX80: Okay, thank you. You could also think of it from 2050. The 1.9 value comes from some of the higher 2018 Opc. Values. Those have since been ratcheted down. So actually, now, 1.9 for 2050 is pretty high. So if you want to take your subsidence and park it into the sort of top end of that 1.9. It gets you there for 20. Yeah, yeah, thank you.

Yerba Buena SX80: I have a just a

Yerba Buena SX80: I. I have no issues with the analysis. I have more. You. You refer to operations and maintenance, and I think I mentioned it before.

Yerba Buena SX80: Does the does the airport stack a bunch of sandbags in ready made the idea after an earthquake looking for sandbags? That’s little too late. And again, this is part of the design process as it moves to design build. There’s been there’ll be agreements and requirements established with the maintenance group.

Yerba Buena SX80: we’ve had some on early ongoing discussions about the expectations of what we’d be looking for them to provide.

Yerba Buena SX80: We have one location. There’s a deployable barrier. We’ve walked through them like again. Nothing’s gonna get built there for a while. But we’ve already had those open, those discussions of a post Pre pre flood event.

Yerba Buena SX80: They may have to implement those post seismic event. This would be another thing that they would have to accommodate. Yes, and I think I asked this question

Yerba Buena SX80: in the previous meeting. Sandbags are low cost, low tech electrical supplies, and all of that.

Yerba Buena SX80: That’s not easily replaceable. If it gets flooded, I hope, and I assume that the airport is

Yerba Buena SX80: putting all of these things sufficiently high, that there is, however, incidental, flooding, electrical, you know, essential electrical services will not be flooded.

Yerba Buena SX80: That to me is this is what happened in Tokyo happened. You know, other places, I mean Japan. Those things you cannot repair in 3 days, and that’s something that really the airport should be looking at in terms of potential flooding

Yerba Buena SX80: send backs is not a problem. And again, I would say that the primary line of defense from flooding is this flood wall

Yerba Buena SX80: and the expectations. It will be intact

Yerba Buena SX80: in the unlikely event of a seismic event. There will be a 1 week. Vulnerability? So yes, there will be some vulnerability to that. Some of that equipment.

Yerba Buena SX80: But I would say it is at less risk in the future than it is as we sit here, currently

Yerba Buena SX80: lower risk in the future. I’m happy to hear that. But the point is, it’s still a risk. If you had gone to Japan the day before Tohoku earthquake and looked at those flood walls, you would have thought that the Japanese were crazy. All those flood walls were 4 meters too short.

Yerba Buena SX80: Okay, the day after. And the point is, if some of that equipment in the nuclear power plant had been elevated

Yerba Buena SX80: that power plant would still be there. So my point is that there are other ways of protecting yourself besides just putting the flood wall. I have no problems with the flood wall, I’m simply saying

Yerba Buena SX80: there is a there is value in looking at cumulative protection understood.

Yerba Buena SX80: Yeah, maybe what’s not not in here. And and that’s probably gonna happen at a later stage with the design builder is that you’re going to the airport is going to approach Fema for

Yerba Buena SX80: a Lomar application as part of that Lomar application.

Yerba Buena SX80: All of the electrical infrastructure will

Yerba Buena SX80: need

Yerba Buena SX80: backup systems, an alternative power system. So that’s all part of Fema’s requirements which will be baked into the design anyway, maybe not into the design. But to get the fema certification.

Yerba Buena SX80: And I can say we are actually right involved in the Clomar process right now we’re actually in. We’ve received our 90 day letter. We’re working through our last few comments. So you’re correct all those discussions through Fema, so the goal of the project will to have a Clomar in hand which

Yerba Buena SX80: then leads to the design build team, and ultimately a Lomar at the end.

Yerba Buena SX80: And and I would also say, I suppose, as part of a broader citywide program is working on its overall emergency response programs and responses that would probably envelope over top of this.

Yerba Buena SX80: I was wondering if you could go back to the slide that has the table with the results. Sure, you talked about the lateral displacement of the wall, but we didn’t really talk about the water side of the wall where the rock slope protection is. Presumably there would be some damage or displacement of the rock protection as well.

Yerba Buena SX80: And like, when I look at these ground elevations around the perimeter.

Yerba Buena SX80: I they’re kind of surprisingly high. I I didn’t really think that they would be that high, because the airport is kind of mostly lower than that, and I guess it sort of comes up around the perimeter.

Yerba Buena SX80: and I guess just my concern would be

Yerba Buena SX80: if the focus is on filling gaps and other activities in the airport to address damage, and you sort of have this exposed unarmored, you know.

Yerba Buena SX80: Earthen material it could erode there. So those elevations may not persist for very long.

Yerba Buena SX80: I was just wondering if that had been kind of considered sort of the waterside response. And I would say, Yeah, ultimately, our expectation post sizing event. Someone will go and inspect the entire wall, both the riprap, the sheet piles, and so on. The immediate concern will be the the gaps. The longer. A little bit further field. You’re absolutely right. We we do not want unprotected riprap

Yerba Buena SX80: like Riprap, that sloughed away. The way we assume is Riprap, in a certain sense as we get these movements as Bob had presented.

Yerba Buena SX80: the Riprap is going to go along for the ride and somewhat be self healing. It’s gonna fall back in. But it doesn’t mean there won’t be some exposed areas, and the expectation is after that those will be filled if we get widespread just like, wow! This rip out really slid in

Yerba Buena SX80: first, st it’s more moving than we are calculating, and then you would have to be looking at some other post media post seismic event to stabilize that area. So you don’t get erosion. But ultimately our most of our plan is most repairs will be implemented within 6 months.

Yerba Buena SX80: To be honest, there’s probably going to be a lot of other things of critical importance that are going to get damaged. The airport. We’re just trying to make sure the floodwaters don’t add to this problem.

Yerba Buena SX80: Yeah. And along those lines I would second the comment about looking at stockpiling materials nearby. And then, I guess, just in terms of like the one week and 6 month timeframe. I know that’s

Yerba Buena SX80: your assumption.

Yerba Buena SX80: But were those sort of vetted in in any way. Is that like a reasonable timeframe? So we’ve met with the maintenance group, and they confirmed the 7 days. They thought that was reasonable. The 6 months is a little bit more that’s based on our engineering like.

Yerba Buena SX80: how long is it gonna take permits? How long is the get a contractor on board. It’s a little hard to predict, but the level of damage we’re expecting within 6 months. If you could get a you know, a contractor out here with a driving rig, he should be able to fill that pretty quick.

Yerba Buena SX80: It’s hard to predict the permitting process in the future. And that response. But we felt 6 months is a reasonable estimate, especially

Yerba Buena SX80: being a critical infrastructure. We’re hoping they’ll have enough urgency to get.

Yerba Buena SX80: say, the front of the line. But get in the line pretty quick.

Yerba Buena SX80: Thanks.

Yerba Buena SX80: Do you think those passive gates will fail in an earthquake?

Yerba Buena SX80: There is some vulnerability to them, I would say, of those passive gates, especially once we start getting towards the later 2050, 2085,

Yerba Buena SX80: only one should remain operational. There are others assuming flood protection programs for South San Francisco, San Trans Island, Millbrae are implemented.

Yerba Buena SX80: These will all fall behind there.

Yerba Buena SX80: Flood protection will be sort of a uniform, so there’ll be less importance there. The one that would be required is at the Mr. Our expectation is there could be some vertical settlement. It’s a little hard to predict honestly, it might be something. We’ll look at a little bit further on a design perspective. If that’s where we have some localized ground improvement.

Yerba Buena SX80: Just to make sure that is less vulnerable, and that could be a good

Yerba Buena SX80: way to mitigate that risk.

Yerba Buena SX80: I have a related question to Justin’s, and taking the focus from the

Yerba Buena SX80: the water side to the land side.

Yerba Buena SX80: and looking at those gaps, I was curious. If there are always, wherever those gaps are expected to form. Is it always adjacent to hardscape? Or are there areas that may be more vulnerable to say

Yerba Buena SX80: erosion? If a flood were to occur and leak through those gaps, and perhaps scour out

Yerba Buena SX80: the material that’s otherwise stabilizing the the edges of the sheet pile where it’s damaged.

Yerba Buena SX80: And is that a consideration, perhaps, for the

Yerba Buena SX80: the maintenance operation plan, we would I’d have to go back and look at what’s behind each of those gaps. And again I would say, these are our best estimate of where the gaps ultimately, it’s going to be hard to predict exactly where all these reform. These are just a higher probability.

Yerba Buena SX80: I’d say majority of them have a roadway or some infrastructure right behind it. I wouldn’t say it’s all of them there may be somewhere. It’s sort of like we’re kind of our the Vsr. The roadway, and then you have like a berm or gravel gap.

Yerba Buena SX80: I’d say it’s probably a mixed match.

Yerba Buena SX80: I’d also say again, the the basic geometry

Yerba Buena SX80: of most of these is the interior ground surface is relatively flat. You saw that in Bob’s plots as well. So it’s not like. It’s coming over a levee, and you have the backside plunge that you might be thinking of in like a levee where you have really high free board over the backside of the levee. It’s coming out, and it’s mostly flat

Yerba Buena SX80: doesn’t extend that far here on this one. But if you take this figure here. But if you take this and Bob’s figures sort of from the cross sections, you could remember that. Yeah.

Yerba Buena SX80: I mean 20 to one slopes 50 to one slopes behind it. It’s not 3 to one, the back of a levee where it’s, you know, rushing back down the other side that you get the big erosion issues.

Yerba Buena SX80: Thanks, Matt.

Yerba Buena SX80: thank you.

Yerba Buena SX80: Anybody else.

Yerba Buena SX80: No, okay, let’s move. Move forward.

Yerba Buena SX80: Okay? Corrosion. So there was a question related to corrosion in particular

Yerba Buena SX80: discussion about providing a monitoring program to measure the actual corrosion rates as the site. So coding maintenance can be timed appropriately.

Yerba Buena SX80: So we’ll talk 1st about kind of our design assumptions. And then what is the current approach to inspection and monitoring corrosion? So again, the wall is designed with additional thickness, essentially sacrificial steel, and a coating system.

Yerba Buena SX80: The sheet piles have been selected as 3 8th inch minimum wall thickness. That’ll be part of the criteria, and the code is at least 10 feet below the mud line. The 3 eighths inch wall thickness, as we really mentioned, was selected for more drivability than pure structural capacity.

Yerba Buena SX80: We did assume. All this structural analysis was done with corrosion of the wall.

Yerba Buena SX80: and we followed the California Department of Transportation corrosion guidelines. Version 3.2

Yerba Buena SX80: these provide different corrosion rates. And essentially, we’ve assumed for the atmospheric zone

Yerba Buena SX80: which is the sheet pile above there. And again, as I previously said, I have one coming up. It’s going to be dry.

Yerba Buena SX80: 99.9% of the life of this structure. It’s not in the water, it’s not retaining water. So we feel the atmospheric zone is representative. So we use that. And in the fill and subsoil we use the values provided by Caltrans, we’ve assumed, the coating is good for 10 years. We’re made a conservative assumption. The airport is ignoring, coating and never going to maintain it. That’s not their plan, but from a structural analysis standpoint. We built that in

Yerba Buena SX80: so we have enough life with a 3 eighths inch wall. And as kind of Bob presented in our own structural calculations, we submitted. There’s plenty of capacity for all the load cases

Yerba Buena SX80: going on to the next slide talks about

Yerba Buena SX80: really, the operation and maintenance manual. So the plan is to the sheep piles will be visually inspected. Every 5 years is the current plan, and any damage will be documented and repairs will be implemented. The sheep piles will be accessible fully from land side and the waterside at the majority of tides.

Yerba Buena SX80: Again, in 2030, all tides in 2085. Again, you may not want to head out on a high to mean high high water day.

Yerba Buena SX80: The inspection program calls for the Asc. Waterfront facility. Inspection

Yerba Buena SX80: plan is a level one, general visual inspection on a 5 year basis. If corrosion is encountered, maintenance hasn’t been maintained, then we may trigger a level 3, which would be the ultrasonic testing at that point. And then we would check what the corrosion loss essentially, looking at the geotechnical results that we have. There’s no corrosive soils been identified to date, and that’ll be confirmed during the detailed design phase.

Yerba Buena SX80: You mean, even the Bmart is not corrosive.

Yerba Buena SX80: Bob.

Yerba Buena SX80: pay months corrosive not per our results correct.

Yerba Buena SX80: I guess I can’t speak to that again. From what we’re seeing and the corrosion rates we’re assuming, we feel that we’ve captured it. But again, this is assumption. So the final geotechnical investigation usually provides a report on the corrosive

Yerba Buena SX80: of the soils. And the if you had a higher corrosion rate, the final design would have to accommodate that, and we say 3 eighths inch minimum if they find that that case is higher corrosion rates, they would have to increase that for the final design.

Yerba Buena SX80: So that so so, not being corrosive, that really is a misstatement there, you don’t know. Well, I would say everything we have from all the existing borings that we went through. There’s been no reports or nothing mentioned in any of the geotechnical reports to date that have said it is corrosive soil so based on that, we feel it’s a valid conclusion. It’s something we feel needs to be validated.

Yerba Buena SX80: There is quite an extensive database borings. I would have thought it would have popped up at least one of them, but I could be wrong. And again, that’s where we feel the validated

Yerba Buena SX80: even if it admittedly my perspective, even if we did find we had some corrosive soils, feel the corrosion rates relative to the wall thickness, and then the demands on the wall.

Yerba Buena SX80: I feel like this design in essence would still work. We just may have to increase the wall thickness of the sheets

Yerba Buena SX80: when you say there’s no mention of corrosion. Are you saying that they tested? And and they say it’s non corrosive, or they just never tested it and never mentioned it

Yerba Buena SX80: could be either again. I’m not gonna swear on my kids.

Yerba Buena SX80: It’s not. Hence the final conclusion. This needs to be validated during the design build phase.

Yerba Buena SX80: But, Bob, I mean, you guys just some boring out there.

Yerba Buena SX80: Did you still saw corrosivity tests on the materials you encountered.

Yerba Buena SX80: Yeah. And

Yerba Buena SX80: I I think it’s something that James, that we can have.

Yerba Buena SX80: We we can look into and evaluate, you know, based on existing data. But I I just can’t speak to it this this afternoon. I I haven’t

Yerba Buena SX80: personally, you know, looked at that information.

Yerba Buena SX80: Now Rod Washita would probably have a good handle on corrosion, resistance and young bay mud for piles. But it

Yerba Buena SX80: yeah, I I would expect there to be some. But but you know these piles, I’m you’re I’m hearing that they’re coded.

Yerba Buena SX80: and the only the question that was kind of coming into my mind is the installation technique.

Yerba Buena SX80: I’ve noticed

Yerba Buena SX80: just anecdotally that you know driven pile

Yerba Buena SX80: especially in hard driving tends to affect the coding.

Yerba Buena SX80: And I’ve seen locations where the top you know the top section of pile piling

Yerba Buena SX80: the coding fails much sooner than

Yerba Buena SX80: you know anticipated, whereas the you know the lower sections are okay, and that’s correct. I’ve seen that also. Our approach here is these will be driven with a vibratory hammer. Yeah, we’re coating the top, 10 feet into the ground, and then everything to the top are the plan would be the design build contractor at the installation would have to repair any visibly damaged coating.

Yerba Buena SX80: And then at that point, Sfo’s operation and maintenance. 5 year annual inspection.

Yerba Buena SX80: Now you can’t really control what’s happening below ground. And again. Your point about corrosive soils is a good one. There is where we’d have to accommodate with a combination of sacrificial steel

Yerba Buena SX80: and then we put the coating at least 10 feet in even though some of it may get damaged, the bulk of it won’t, and that still adds some level of protections.

Yerba Buena SX80: and it is anaerobic at some point below. So you need you need that oxygen to make it grow. That’s usually where we pick about 10 feet. It’s kind of the general rule of thumb in the industry.

Yerba Buena SX80: Do we want to go back to that question we had with the bending moments, and how that affect corrosion. Because I think this relates to this point of where the maximum bending moments were were usually at those depths where you were starting to go anaerobic

Yerba Buena SX80: anybody.

Yerba Buena SX80: But I think that’s I think that’s the the kind of the conclusion of that. If

Yerba Buena SX80: the corrosion is expected at

Yerba Buena SX80: kind of in the upper exposed areas of the sheet pile.

Yerba Buena SX80: The maximum moments are not. It’s it’s further away from the maximum moments. Okay?

Yerba Buena SX80: I’m not an expert on coercion.

Yerba Buena SX80: but I assume you all are, and for the portions of the wall that are buried you mentioned something about there being this anaerobic environment.

Yerba Buena SX80: Wouldn’t the if the soils are corrosive

Yerba Buena SX80: and also if they’re if the young bay mud is corrosive, and also, if there are currents stray currents in the steel.

Yerba Buena SX80: Wouldn’t those corrode the buried steel? And you wouldn’t. You wouldn’t know about it? Or are you saying that there’s certain there’s going to be this anaerobic environment that’s gonna quash corrosion.

Yerba Buena SX80: Again, just just based on our design experience. Waterfront structures generally. Once you start getting below 10 feet, the expectation is, there’s not enough oxygen to create widespread. You do consider some corrosion, and that’s built in the corrosion allowance

Yerba Buena SX80: working with the geotech and ultimately establishing if it’s corrosive soils that then would factor into what corrosion rate you would use from that zone, from like the ground surface to that area where you’d feel the oxygen would drop off, and then you would have to reestablish your calculations on expected corrosion rate, and, if necessary, increase the wall thickness once it’s installed. It’s not really practical to inspect, and you have to pull out sheets. It seems pretty.

Yerba Buena SX80: Be destructive, and it’s usually not done. Again. My experience with waterfront structures in that zone. It’s not 0 concern, but it’s often.

Yerba Buena SX80: you know, you can mitigate it through design good design practices.

Yerba Buena SX80: Do people ever put in just a couple of extra sheet piles and then pull them out later

Yerba Buena SX80: to see what’s going on. No, okay.

Yerba Buena SX80: thank you.

Yerba Buena SX80: Here’s the figure with the maximum bending moment, which again, yeah, the maximum is down at like negative 10. And so the ground surface in this figure is at about 10 feet.

Yerba Buena SX80: because this is in Navd. So the maximum bending moments are about, you know, 20 feet below.

Yerba Buena SX80: This is where you would yeah expect to see that corrosion happening, though, is in the splash zone. So not at the top of the sheet. Right? Yeah, exactly. That’s what I was coming. But coming back to the point about where the corrosion would happen relative to the maximum bending moments. This is those zones don’t overlap. Yeah, and it’s more pronounced when you look at the flood case, which is the design event. Obviously you have your flood event. It’s cantilevered. Wall. Your maximum is in the ground.

Yerba Buena SX80: And it’s at depth. So we don’t expect a significant amount of corrosion. But we have accounted for in our design.

Yerba Buena SX80: and if you go back to our structural calculations. You’ll see the DC ratios are quite low, so there’s quite a belt and suspenders with a coating extra thickness. And again, we in theory, we could have picked a sheet thinner than 3 eighths, but from a drivability practicality of it, it’s not advisable we need to get these sheets in. So that ended up kind of dictating the wall thickness. Not so much the structural of the corrosion

Yerba Buena SX80: expectations. So we feel there’s a fairly robust solution. And again. Ultimately the design builder will

Yerba Buena SX80: validate all of this.

Yerba Buena SX80: So I mean, in looking at these results, I mean, the sheets are not very deep, right? These are 40 foot sheets, I think, is maximum. I saw, yeah, 30 to 40 feet sheets. We’re extending them deeper than they need to be, geotechnically or structurally to act as a potential help, as a cut off a little bit from and just allow the airport to mitigate it. If there’s any groundwater issues in the future, right? And and so.

Yerba Buena SX80: you know, and that’s being driven by very little loading. Right? I mean, there’s very little loading except

Yerba Buena SX80: hydrodynamic dynamic wave loading. That’s probably the largest loads, I guess, in this case, with sea level rise

Yerba Buena SX80: and largest wave heights there. That’s probably the largest loads.

Yerba Buena SX80: And so you’re

Yerba Buena SX80: it. It looks like you’re going to specify the thickness.

Yerba Buena SX80: Minimum 3 eights minimum.

Yerba Buena SX80: And you’re not specifying embedment depth. It’ll just be based on the analysis with us, or are you? I think we’ve we specified? And again, this will ultimately get in the design, build criteria. But I believe the goal right now is to have them seeded into the young bay muds.

Yerba Buena SX80: so they have to tow into that. And that is again, even if it’s not necessarily needed from a geotechnical standpoint, we want to at least tow it in there to provide again. Cut off a seepage path through the fills. If you ever had any sort of groundwater or seepage issues, especially when you start looking at

Yerba Buena SX80: future sea level rise, when the water in the bay could start getting higher than some elevations on land.

Yerba Buena SX80: Okay, yeah, it’d be good to specify that, as part of the criteria. And the reason I’m saying is, you know, a design builder would look at loading and say, You know my sheets could be just 25 feet deep.

Yerba Buena SX80: I concur, and that, I believe, is our plan. Yes, I’m pretty sure all the reaches and the design drawings show it towed in 10 feet into the young bay mud. Yeah.

Yerba Buena SX80: that was our design recommendation that it be 10 feet into the

Yerba Buena SX80: but but, as Dilip says, it might be good to put that as a design criteria rather than looking at design, build, their response is much more. It will be sorry. That’s too wishy-washy it will be.

Yerba Buena SX80: And to to that point I think it’s really critical not to let them drive it into the denser, stiffer material. So you want to make sure that that doesn’t happen. I mean, you could think that it’s better. But it’s not really better from a kinematic standpoint, understood. And I can speak from being a lot of design build teams. They don’t like to drive them any longer than they want to.

Yerba Buena SX80: So let’s say we have them in the yard, and we’re gonna use it.

Yerba Buena SX80: But no point taken we would be looking for, and we’re trying to reach the young Bay. MoD. But we don’t necessarily need to go beyond it.

Yerba Buena SX80: Yeah, they they should be floating files right?

Yerba Buena SX80: There is no connection at the top at all right. I know you’re going away from a pile cap, but even even a simple connection to just well again, there’ll be a bent plates which will be, have tabs attaching it to each of the individual sheets to hold it in place. But it’s not a structural element per se. So it’s not going to have it acts. Lock everything in together.

Yerba Buena SX80: We move towards Foster City. I don’t know if you’re familiar with that project. They do have a concrete cap along their seawall.

Yerba Buena SX80: It creates a lot of construction issues. And again, I haven’t seen their seismic design. But how do you manage this movement. Unless you have 0 movement on the wall, you’re going to get a lot of post cracking that you. It’s hard to predict, and it’s going to be difficult to repair.

Yerba Buena SX80: Given that, we don’t need that continuity from a structural standpoint. We felt this was the best approach.

Yerba Buena SX80: Yeah. And the reason I bring it up is, you know, depending on driving conditions, 7 miles of of sheets.

Yerba Buena SX80: It gives you some. Fluff gives the contractor some fluff to, you know to have some amount of

Yerba Buena SX80: inaccuracies in the top.

Yerba Buena SX80: you know, elevation of the sheets, and so pile cap sort of covers all of that, you know, and you could have joints in there. If you don’t want to transfer the load, the bend plate provides that similar behavior again. It’s gonna it’s like a cap. So from a visual perspective, it’ll flatten it out. There’s gonna be, you know, underneath that cap. The walls might be up and down a few inches right, and they’ll have a tab attaching, but it gives you that same visual look without all the kind of locked in concrete. But I agree I’ve seen concrete caps do that. It does look very nice.

Yerba Buena SX80: But I’ve also seen this detail used elsewhere. And we feel it’s effective

Yerba Buena SX80: in okay, great just one going back to the 3 eighths inch minimum thickness

Yerba Buena SX80: that’s been a rule of thumb for for us or for me

Yerba Buena SX80: forever. So Jen, just make sure. Put it in the conditions right that we’re we are gonna maintain that at least a minimum. 3 eights inch wall thickness.

Yerba Buena SX80: Yeah. And with the variability. Again. We’ve done checks, and you know

Yerba Buena SX80: the odds of them hitting something down there is pretty good at some point, you know. It’s all fill. It’s not a lot of rock fill. But we do expect. And being I have a 3 eighths inch, we feel that’ll improve the drivability and create less issues of them having to continuously go down and dig something out.

Yerba Buena SX80: I’m just gonna make a note on note on time. We’ve gone through the 30 min contingency. We had the end, and we’ve also gone through 5 min of the 10 min contingency of the break.

Yerba Buena SX80: So I wanted to check with you on the order which we’re presenting these things. So far, the order of questions that have come up that we’ve said is coming next. We’ve managed to hit all those

Yerba Buena SX80: because we got the geotech. Then we got the earthquake and flood. We got to corrosion. There were the gates and flood operations, which is next we touched on the groundwater one, which is the one after that. So we’ve hit all those, and then the ones we end in subsidence.

Yerba Buena SX80: and we have strong motion at the end. So I think we still relatively have them prioritized to the interest. But if there’s any particular need, or someone needs to go early, they’re sort of modular, and we can move them around.

Yerba Buena SX80: So again, those remaining topics are flood operations.

Yerba Buena SX80: groundwater subsidence and strong motion, monitoring

Yerba Buena SX80: any thoughts on changing those, or I, I I think what you guys have

Yerba Buena SX80: got organized is fine. It’s just

Yerba Buena SX80: talk faster. Everyone has to talk faster.

Yerba Buena SX80: Okay, so responding, this, this one on flood operations responds to a series of both Ecrb questions and also some Bcdc. Staff questions which are overlapping will be dealt with in the permit process. We sort of group them together because they have you know, sort of overlapping topics and the things that they touch.

Yerba Buena SX80: This 1st comment that we had here from Ecrb was talking about emergency events, and was one of the ones that we sort of roughly talked on is, how would emergency services and electrical

Yerba Buena SX80: things be provided in backup power. 1st on the flood case. What you see it in the lower left panel of this is the results of some of the modeling that was done for the fema Lomar application.

Yerba Buena SX80: That’s considered the extreme event for interior drainage assessment. That’s the 100 year precipitation event, and also, since some of the riverine channels, that sort of run behind and around the airport do not contain everything within the flood walls. It also includes inputs.

Yerba Buena SX80: In a few overtopping events from there. And in this situation you see that the this is the depth around.

Yerba Buena SX80: and some of the low lying parts of the area, and these blue shadings are all less than a foot and generally cursive there in the

Yerba Buena SX80: And the other thing I’ll point out is what’s overlaying on this as well is the storm drain system is the series of sort of purple lines there. It’s a little bit hard to read, but the red dots on the shoreline are the pump stations themselves. So you can see that the pump stations are not overlapping with where the low lying areas are, and the areas that would tend to pond even for this extreme case with the 100 year precipitation and the inflow from the adjoining cases.

Yerba Buena SX80: In the event that there is a power failure because of earthquakes or reasons to go down for other

Yerba Buena SX80: events. The airport plans to use portable electrical generators, such as those pictured in the lower right.

Yerba Buena SX80: and that would be in response to. There’s a they already have a standard operating plan that’s alluded to there. That’s sort of, you know, monitoring the pump stations, and when they’re needed, and that changes obviously between sort of a date, you know, once a day feature to when it’s raining more common, more recent updates. And so those cases, those portable generators, you know, basically have sort of an additional free board of a foot. So those 2 combinations of the pump stations are not in the areas where water would be expected to pool

Yerba Buena SX80: and the free board of the portable generators.

Yerba Buena SX80: Providing the capacity for backup power.

Yerba Buena SX80: The question also included considerations of earthquakes. We I’m going to refer back to the discussion we just had about this combined event of the 100. Well, the the 100 year Flood events.

Yerba Buena SX80: and the 475 year earthquake event occurring in the same year.

Yerba Buena SX80: being a relatively unlikely consideration. But in the event that it does happen, most of those 1st couple bullets have already been addressed by James. I’ll just point out, and we’ll get to a little bit later. That second to last bullet

Yerba Buena SX80: that that he touched on. We’ll go into a little bit more detail. The floodgates themselves are only anticipated to be need to block water rails for a few hours, so, in terms of like blocking access

Yerba Buena SX80: to the site that would only be like during the most extreme tide. So it’s not like the it’s not expected the floodgates would be up in such a way that they would be blocking the tide gate elevations.

Yerba Buena SX80: And then, also, there was a question about who would need to access the site. So just to follow up on that again with some of the discussion of the Sfo’s operations staff. You know the temporary repairs. If there’s not too many wall breaks. If there’s enough sandbags on hand, those sorts of things may involve just Sfo. Possibly an external contractor. Permanent repairs would likely include an outside contractor because of those things about driving additional walls.

Yerba Buena SX80: Where are the floodgates on the graphics? The floodgates will come up in a few slides. Oh, okay.

Yerba Buena SX80: so then another question that is, is a follow on. And again, sorry that we’ve we’ve changed over some of the Bcdc. Staff questions here a following was, how much water could pour in. So now we have sort of, you know, in combination of

Yerba Buena SX80: the

Yerba Buena SX80: 475 year earthquake event a week to repair to get those temporary structures up to about 3 feet high, and then, in that circumstance, what sort of inflow volumes would you have? So I followed for this sort of James’s designation of where they would happen by using this sort of green and orange. And if you remember from James’s, you really didn’t see anything significant happening until 3 and a half feet of seal rise. So just sort of skipped to that case

Yerba Buena SX80: and look for those conditions. I also took a worst case of assuming. There’s that column there that’s assumed number of gaps. Those are 56 of those at those junctions where the wall bends by at least 30 degrees, so I assumed all of those could possibly fail. You see, you know, it’s reach, for, as James alluded to before, is the one that even for mean higher high water starts, you know, earliest and sort of turn orange, although point of that case you only have 0 point 3 feet of free board.

Yerba Buena SX80: But in the event of if you had the 1% Stillwater case, you have 4 reaches where you have gaps in them. So I took for those 4 reaches and assumed all the gaps that could fail in those reach fails. I think you ended up with about

Yerba Buena SX80: sorry reach. 12 doesn’t have any assumed gaps. So you end up with 9 gaps. Think of them, each being 10 feet wide. Think of a maximum flow velocity! Think of a you know time that the tide would be at 100 year water level to get an estimated total still water inflow. And so I got that one on the upper right of about 24 million gallons, and then compare that to the overall stormwater pumping capacity again just at a very bulk level may not

Yerba Buena SX80: where it’s going to appear, and how it get routed to it didn’t cover at that point. But if you look at those you’re under an hour to, so the amount of water that could inflow during a hundred year tide happening after a 475 year earthquake.

Yerba Buena SX80: you still have the pumping capacity of only needing an hour to remove that amount of inflow. If you take a more extreme case of considering also the overwash from total water level and so wave splash as well, which would affect a few more reaches.

Yerba Buena SX80: You get a higher rate, maybe double. It’s about 2 h to remove the inflows.

Yerba Buena SX80: Oh, yeah.

Yerba Buena SX80: Chen.

Yerba Buena SX80: in this scenario, where there’s 3 and a half feet of sea level rise.

Yerba Buena SX80: I’m also envisioning that groundwater levels at the airport will be like close to ground level.

Yerba Buena SX80: and that the storm drain system, unless pumps are pumping continuously, the storm drains would be filled with groundwater.

Yerba Buena SX80: Is that have?

Yerba Buena SX80: What do you? What do you imagine is going on in the storm drain system and the shallow groundwater in this scenario?

Yerba Buena SX80: So we we didn’t envision that for the particular case in the groundwater study, which we’ll get to in a minute. We also compare those

Yerba Buena SX80: we looked at the maximum inflow rate from groundwater into the storm drain system was about

Yerba Buena SX80: 500 Gpm. And so that’s relative to the 500,000 Gpm. Capacity, the pump stations. So the pump stations may have

Yerba Buena SX80: a slight increase. If you were looking at the dry season pumping.

Yerba Buena SX80: you might have to turn on your sort of, you know low flow pump a little bit more often. But during the stormwater, heavy precipitation event it’s going to be really that precipitation event and the stormwater that’s coming that the stormwater system was designed for was really the surface water precipitation, and the groundwater is a minor part of that, either now or with seal for us. So it’s not the controlling factor.

Yerba Buena SX80: I’m not sure how you estimated that in the future

Yerba Buena SX80: high groundwater levels would only contribute 500 gallons a minute to the storm drain system. So we have a presentation coming that was detailed in the demo. So we and we have a presentation coming up. So maybe we should. Just yeah, we should work on that one that we do. They did a whole full groundwater model for that one. But are you? Are you envisioning in the future? Because I think in the last Ecrb meeting you did mention that

Yerba Buena SX80: the storm drain system is going to need upgrades in the future because of sea level rise. And I’m assuming that that’s because of groundwater rise, and the fact that groundwater will

Yerba Buena SX80: will continue to increase in how much it infiltrates into the stormwater system.

Yerba Buena SX80: And it’s my understanding that that actually the stormwater system currently operates like at high tide on a sunny day. Right?

Yerba Buena SX80: Is that not? Is that so? The the airport does want to meet, and some of the

Yerba Buena SX80: ways the airport would like to continue to maintain. Groundwater is to maintain it at roughly the same level.

Yerba Buena SX80: That’s why they’re willing to invest in the additional sheets getting driven down to the young Bay mud, because that provides part of their. It increases their capacity to manage the groundwater level, because there won’t be as much groundwater infiltrating from higher bay water levels into the site. So that’s part of the reason why that you know they’re willing. The additional depth of seats is going to cost more, and that’s 1 of the things that are trying to do is to cut that off

Yerba Buena SX80: and provide a cutoff wall.

Yerba Buena SX80: Previously, when we had talked about the storm drain systems need to be improved. We recognize that though we we I think we said something like it could.

Yerba Buena SX80: It may need to be improved, depending on how much infiltration rates there were into it.

Yerba Buena SX80: And so then that was one where we, as part of the groundwater study, tried to figure out sort of the overall water balance of like when we said it may need to be improved in the future, but we don’t know exactly when we just think it’s far as we wanted to, you know, be more specific about that response. And so that’s why we work with Geosyntech. They developed the whole groundwater model to provide at least a screening level approach for what those orders of magnitude would be that Julie’s going to present in a bit. And from that model results is where we’re getting the

Yerba Buena SX80: what seem to be the infiltration rates into the storm drain system of on the order of 500 Gpm, we don’t have. Maybe I’ll hold off my questions until that those slides. Okay.

Yerba Buena SX80: thank you. Yep.

Yerba Buena SX80: onto the floodgate locations. So there are 7 closures along the the edge.

Yerba Buena SX80: most of them are like sort of in reach, one and 15. Those are the reaches that you know have more crossings that come in because of roadways and things like that.

Yerba Buena SX80: So you know, that’s where you want to have this ability to have the gate down most of the time. But then deployed during the flood event.

Yerba Buena SX80: So this is what James was referring to before, where he thought, there’s a likely chance that, as other communities go forward with their their own flooding their own sea level rise. Prevention that these gates would maybe behind those, and that would be Gates one and 2 on the

Yerba Buena SX80: north side and reach one, and then gates 5, 6, and 7 on the other reach, and then at the end, I’ll show a little bit more detail on the 2 gates that are more exposed reaches 3 and 4

Yerba Buena SX80: so

Yerba Buena SX80: 4 with a gate. Elevations for that were shown in that previous table. Here’s a comparison of taking those and looking at how the gate, the the low point of where the gate lies

Yerba Buena SX80: along the reach compares to mean higher high water, so would the gate have to close about every day to as compared to the 100 year still water level. Like I said, most of these gates are inboard from the edge, and would probably be more exposed to the 100 year. Still water level rather than total water level, and looking at, you know under what conditions would they have to close? And so again, the apologies for using 0 feet of sea level rise rather than some small 0 point 3 or some amount to account for present day conditions relative to 2,000.

Yerba Buena SX80: You see that for both 0 feet of sail rise, and one and a half feet of sail rise for mean higher, high water. We don’t expect any of the gates to need to be closed on a daily basis. You will see with 1.5 gate 5 is the one that basically is these numbers. Here are the free board. So all these are positive free board means no cancel flooding.

Yerba Buena SX80: So gate 5 right at one and a half feet of silver rise gets to 0.

Yerba Buena SX80: The exact. As if that’s 1 of those gates that’s interior to the site and would likely be

Yerba Buena SX80: integrated as part of more of a regional flood protection program.

Yerba Buena SX80: The gates would need to be closed even present day, for the 1% floodwater levels for gates, 3 through 7 gates, one and 2 are the ones that are higher and the ones that are actually gate. One is basically from the north access road into like a maintenance yard

Yerba Buena SX80: gate 2 is the gate that’s really across the North access road. That would be the most impactful if it was closed for an extended period of time in terms of access to the site. And you see that gate 2, even for 3 and a half feet of Seville rise doesn’t need to be closed

Yerba Buena SX80: for mean high tides, and that’s also, again, if a project came regionally that sealed it off. It wouldn’t really need to be closed at all. So Gate 2, which is the one that had the biggest impact on access is really the gate that is least likely to ever be deployed. It is also the gate that would not is the only actively deployed gate as opposed to a passive gate, so

Yerba Buena SX80: you know, but presumably you’d have knowledge of forecasts. It would have to again probably be with fair amount of civil rights not likely to even be need to be deployed. Even for up to one and a half years civil rise. And so it’s really that last case of in the event that a regional shoreline planning doesn’t happen and you have the 100 year events. Then you might need to deploy. Gate. 2

Yerba Buena SX80: thanks, man for the information mean high high water, and 1%, you know, typically

Yerba Buena SX80: as engineers, we do like to know, just on an annual high tide, you know what? How is this going to function? And what I’m looking at here is that

Yerba Buena SX80: the closure number 5 is probably going to operate every year in December

Yerba Buena SX80: with a king tide.

Yerba Buena SX80: If you have one and a half, it would be at the edge if you could see. Well, we can go back and zoom where it is, but where it is. I it it’s currently there. And it’s currently exposed under present day conditions, and they don’t currently close it.

Yerba Buena SX80: So these assumptions are. Again, this is because it’s set back from the shoreline. There’s actually high ground between it and the thing. So this is also sort of the the fema approach of assuming the 100 year water level can get all the way up to where the gate is located.

Yerba Buena SX80: This current place they do not close every time it’s a it’s a there’s an extra access road where there’s like an emergency access on the the south part of the runway.

Yerba Buena SX80: Ye yeah. Because last year we had actually what a foot above King Tide. Right? So in that case, if

Yerba Buena SX80: you know, this would have operated, I’m not like, I said. It’s not changing the grade. There’s a current gap there, because it’s just the main reason why it’s there is. It’s emergency access like for vehicles to come in from the Millbrae side if they need to. And as far as I’m aware, it’s not a place that currently floods.

Yerba Buena SX80: Yeah.

Yerba Buena SX80: it’s right. At this bend

Yerba Buena SX80: As you go from along the shoreline I reach 14, and then, as you come in along like that’s where the uber waiting lot is

Yerba Buena SX80: gas station. There’s a few other things right there. So Gate 5 is inboard from that. And so it’s not actually right on the shoreline. It’s maybe 30 feet in from the shoreline. It’s actually

Yerba Buena SX80: it’s a little hard to see here, but they call it the fueling station entrance. There’s like a basically a parking lot. That’s not part of so those campus but so runs it. And so the plan is to provide flood protection around that. And so the 2 entrances

Yerba Buena SX80: get floodgates as part of this program, but, as as mentioned, the water has to get 1st get across their higher elevation and then dip back down is, if it ever did get in from the shore, it is a low spot, so the idea is to protect it.

Yerba Buena SX80: Where again, if mill great moves forward with their project. And again, they’re in that planning process.

Yerba Buena SX80: This, all will be behind theirs, and it becomes a moot point.

Yerba Buena SX80: any more questions on blood. What we can go back to?

Yerba Buena SX80: now to those 2 gates that would remain sort of, you know, not behind a regional flood protection.

Yerba Buena SX80: And we’re specifically asked about one was Sam. Trans Island. So that’s case. Reach 3 out here. So North access comes in just along reach one.

Yerba Buena SX80: and then Sam trends

Yerba Buena SX80: I think they’re the sole owner of the island. There might be one or 2 other sites that there’s a

Yerba Buena SX80: But San trench is the main user of the island. That’s where they store buses and things like that. So in this particular case, you know, they need access to move their equipment back and forth on a daily basis. So this would be one of the a passive floodgates sort of shown here in the conceptual cross section that deployed by buoyancy. Once there’s enough water

Yerba Buena SX80: approaching them. So while there would be issues for this, if this gate was up, it would impact access to Sam. Trans. The road that is outboard of that that is outside of the area. The airport’s control would be flooded as well, because it’s actually lower elevation by a foot or so.

Yerba Buena SX80: So. In this particular case the floodgate would be protecting the airport. But you wouldn’t have access, or you lose access previously for Samtrans, and to that point Sam trans. Is working on its own sea level, rise, protection, effort, and would address these sorts of things in the future. And again would be a case where likely the need to close the gate would decrease

Yerba Buena SX80: in the future. With Sam Trans’s efforts. I would just say there has been conversations between Sfo and Samtrans to coordinate their efforts. Again, we’re only showing this from a Clomar Fema perspective. Ultimately the goal would be to eliminate this from the project. If Sam, trans. And Sfo’s project align

Yerba Buena SX80: and from a timing perspective.

Yerba Buena SX80: additionally there’s reach 4 which includes the Murph, the marine emergency response facility. This is a place to store marine rescue vehicles that I think are primarily focused around, you know, emergency response to airplane issues out in the bay

Yerba Buena SX80: And so this is another case where, again, because of the desire to maintain access for all but the most extreme cases, there would be a passive floodgate. Basically, at the end of this pier, approaching the facility you can see here under present conditions. Sorry wouldn’t need to be closed for high tides until you’re starting to get to about 3 feet of seal rise

Yerba Buena SX80: again, that in that time period the mer facility itself might be would probably need to undergo its same sort of

Yerba Buena SX80: sea level rise protection, and this is also the reach for that James mentioned before is the Coast Guard reach, that they are also probably looking at raising the grade on the inboard side again as well, so that this again is a gate to

Yerba Buena SX80: you know, Dot, i’s and cross t’s from a clomar perspective under present day conditions. But you know we’ll change in the future and likely

Yerba Buena SX80: be less of a risk pathway in the future.

Yerba Buena SX80: The last part on the on the operation side was just the details of the operations maintenance for these gates. 6 of the gates were passive gates. So self activating don’t need any power, human intervention that one deployable gate that I talked about across North Access Road. But it’s also the one that’s highest and would least likely need to be deployed.

Yerba Buena SX80: All the gates would be managed by the Sfos facilities. Their paving and grounds group that manages basically everything that’s out there at the airport. They would be inspected, annually, repaired as they get needed. Follow vendor maintenance procedures, make sure that staff is trained. If they are deployed either for training purposes or in an actual event. Make sure they’re cleaned and restaged after that

Yerba Buena SX80: and in during an actual operational deployment. Of course, they would be sort of added into the things that would get checked to make sure that they’re not leaking

Yerba Buena SX80: what is the typical lifespan of a passive gate.

Yerba Buena SX80: I don’t know the answer. I mean, they’re built to be deployed outside, I from roughly looking at. I think they’re mostly made out of fiberglass, stainless steel and there’s I would guess the things they do have things like a few rubber gaskets in a few areas that I could guess would be something you might want to check every 10 years and maybe replace if they start to break down.

Yerba Buena SX80: a. Again. If you ask the manufacturer plenty long.

Yerba Buena SX80: But generally the idea with the maintenance program we would be replacing certain components and the idea we can extend that life through 50 years with our regular operation and maintenance, or sorry? 65 years.

Yerba Buena SX80: Okay, thanks.

Yerba Buena SX80: Any other questions about the flood operations.

Yerba Buena SX80: I had a couple of questions.

Yerba Buena SX80: can you go to the slide that has the flood map with the precipitation and riverine

Yerba Buena SX80: is is that showing

Yerba Buena SX80: flooding extents assuming the pump stations are operational like that. They don’t lose power.

Yerba Buena SX80: That’s assuming they’re operational. Yes. So if they did lose power.

Yerba Buena SX80: the flood extent could be greater than shown on the map. Yes, okay. And then I just I feel compelled to comment on the portable generator. Just it just doesn’t seem like the best solution. And maybe maybe there’s a reason

Yerba Buena SX80: why, like a kind of permanent installation of a generator co-located with the pump stations, just seems like something that might be worth considering.

Yerba Buena SX80: at least for ones that

Yerba Buena SX80: are critical or or vulnerable to flooding.

Yerba Buena SX80: So that would be one comment I have.

Yerba Buena SX80: Do you want to? Has there been any discussion with Fema about whether or not this meets their interior drainage criteria. Again, we’ve presented this, and they’ve accepted that again as far as redundant power. And they haven’t commented on that yet. I mean, your point is

Yerba Buena SX80: a good one, and I think we probably have to have some further discussion with Sfo about how this would be handled. How many portable generators does Sfo have? Could you supply all of the pump stations? Right? I can say again, the interior drainage system has been in place for a very long period of time. These rain events are probably what it sees. More than any of these flood. Events were occurring so, and we being a low line area, if the pumps were out, there would be

Yerba Buena SX80: some issues based on interior drainage. So

Yerba Buena SX80: I’m not sure we can quite give. I I think it’s a good point. I just can’t speak to what that supposed plans are for that.

Yerba Buena SX80: So for the for I’m sorry if it’s on that same topic, is it? Okay? Then, in that case I’ll I’ll maybe I’ll chime in. So I mean, Fema does require a backup system, anyway, right as part of the existing. So this would be a backup of a backup. Correct.

Yerba Buena SX80: I believe. Well, I’ll have to look back again what their requirements are. But we definitely have presented the operation and maintenance, and within the operations of that we outline exactly how Sfo is operating it currently and to date. We’re not fully through the process. But they have. That’s not been one of their comments or concerns. Yet.

Yerba Buena SX80: because, as far as I’m aware, I think the backup

Yerba Buena SX80: is an alternative grid which is still electric and not propane or natural gas.

Yerba Buena SX80: or any other backup. And so maybe that

Yerba Buena SX80: would be good to know at some point internally. Yeah, we’ll we’ll reach back, or I could reach back to H. And Tb. And suffl counterparts on that.

Yerba Buena SX80: Okay? And then the one actively deployed gate would just just curious the reason why that one alone is active as opposed to passive. So we did study this a lot, and it came down to the gap. It’s essentially crossing the roadway. There’s a spill point from our flood

Yerba Buena SX80: analysis. It’s a very as Matt presented at a higher point. But when you start looking at the future sea level rise and the Fema’s requirement of a 2 foot

Yerba Buena SX80: or one foot air gap it was below that point. So then we went through a whole series of concepts of

Yerba Buena SX80: how do we raise the grade here? Because we can’t put a flood wall across a permanent flood wall across the road. The road needs to remain open. We started looking at different options, raising grade. There’s a off ramp coming off the freeway. It started to snowball pretty rapidly into impacts.

Yerba Buena SX80: Then we started evaluating, and in conversations with Sam Trans. Island and some other South San Francisco, it became pretty apparent that they have flood protection programs that are going to tie in at essentially where our reach 2 ends right at Sam trans. Island.

Yerba Buena SX80: and this reach one will be behind all of that flood protection.

Yerba Buena SX80: So we felt that this solution, although it does require active deployment.

Yerba Buena SX80: it’s a stopgap until those future projects. Now, if we are sitting here having this conversation in 2070, and they never did anything in South San Francisco.

Yerba Buena SX80: you know that probably would have taken a different approach, and maybe looked at more permanent passive area that would open itself. But given that the likelihood they’ll never need to deploy this. We felt this was the the kind of the best path forward to be honest, to get through the Clomar Fema process.

Yerba Buena SX80: and and I assume that a requirement of that would be that there’s some kind of

Yerba Buena SX80: storm monitoring in place to identify those events in advance of when it has to be deployed as part of the Clomar package, we’re required to submit an operation and maintenance guidance, and we do have submitted that to fema how this would get deployed and what the process would be. And again they’re in review. I can’t say here they’ve accepted officially, but so far they haven’t commented on that.

Yerba Buena SX80: I just have a little question.

Yerba Buena SX80: Towards the end of the design. Life looks like

Yerba Buena SX80: half a dozen gates are gonna open and close every day. Right? I mean, that’s a couple 1,000 openings and closings, I would say. Most likely one.

Yerba Buena SX80: The Murph will be my suspicion in 2085. My expectation is, Millbury will have introduced a flood protection along their shoreline

Yerba Buena SX80: South San Francisco and Sam Trans. Will have also by 2085. Otherwise they’re going to be. Their entire towns will be flooding on a very regular basis. So it’s really the Murph will be the only location

Yerba Buena SX80: if we’re thinking at end of project life.

Yerba Buena SX80: I’m curious, are there gates like this that are currently opening and closing every day? Are they pretty darn reliable for so generally they’re not something you want opening and closing every day, but they have been Foster City. They have 2 of these gates as part of their flood protection, which has been built, we actually had a chance to tour it, and this gates have been used quite extensively now, being deployed in like back in New York.

Yerba Buena SX80: There’s a lot of different cities that have around hospitals, critical infrastructure. So it’s a.

Yerba Buena SX80: the technology is proven. So that’s why we selected that particular. It’s proven in the sense that they’re actually opening and closing on a semi somewhat regular basis. There are many openings and closings that have functioned properly correct under flood events again, I would not recommend this if we were in a case where you’re on a daily tide, and I understand in the future this is something that would be starting to creep in. If sea level rise at one and 200% chance.

Yerba Buena SX80: If that is the case, you know, I could imagine a future generation looking at that particular passive gate and looking at the vulnerability of its deployment

Yerba Buena SX80: on a regular basis. But as it stands right now, yes, this is a proven technology used at other projects. And again, you have a chance to visit Foster City. It’s they have 2 of them on that site.

Yerba Buena SX80: Jen.

Yerba Buena SX80: Sorry I missed this, if you already said it. Where are there already? Emergency generators on site for each of the storm drain, pump stations

Yerba Buena SX80: again. We’d have to get back to you on that one. I don’t know the exact appointment.

Yerba Buena SX80: We’re getting a head nod from Rinaldi behind us from Sfo. There we go. Yes, you can introduce yourself. So Rinaldi Project Manager Sfo. So the airport actually interconnects to the high voltage transmission at 2 locations.

Yerba Buena SX80: And then, as the power is fed into the airport, it actually is transformed from 1 15 kv. To 12 kv. And we operate a 12 Kv. System.

Yerba Buena SX80: and we have about 32 miles of cable. So that’s going away from the discussion here. But what I was gonna say was, each of the stations can be affected multiple locations. So there’s a redundancy built into the electrical distribution system. We that we manage as an airport

Yerba Buena SX80: in addition to the belt and suspenders of the electrical generators. Some of it’s mobile, but there are permanent ones, too. Yeah. But anyway, I think there is. There is a plan for resiliency and redundancy in the electrical system, especially for a critical facility like

Yerba Buena SX80: our assets, such as the outfalls and home stations which are primarily needed to

Yerba Buena SX80: collect and convey the storm water, especially during storm events.

Yerba Buena SX80: So cause I’m imagining that in in the large earthquake scenario also, the power will be out, and that you would have to deploy the emergency generators to keep the pump stations running. And so it sounds like you have emergency generates for each

Yerba Buena SX80: of your storm drain pump stations. Is that right?

Yerba Buena SX80: Okay?

Yerba Buena SX80: Also, I had a question, are there any

Yerba Buena SX80: you know, during the these time frames when

Yerba Buena SX80: in these emergency scenarios

Yerba Buena SX80: where the pond stations could be out. And there’s flooding. Are there any basements

Yerba Buena SX80: or subsurface areas on the airport

Yerba Buena SX80: that people are in that could be vulnerable to flooding.

Yerba Buena SX80: I’ll

Yerba Buena SX80: I can give it a 1st attempt. And, Ronaldo, you can correct anything. Say, but yeah, there is like at that central parking garage at the center of the airport. That is a low point. So in theory.

Yerba Buena SX80: if you had the flood event and it got through like right now, if you had the flood event 100 year flood event, the expectation is the water could get into those areas. Yeah. But there’s there’s no people in those spaces. It’s actually a bunch of chillers and boilers for the facilities. So it’s not a habitable space. So there’s nobody in there. I think, Rinaldi, you previously told me. It’s more of an operational impact than a life safety impact like you would lose critical infrastructure to run the airport.

Yerba Buena SX80: Oh, okay, so there are. There are components of critical infrastructure in below grade areas. Okay, thank you.

Yerba Buena SX80: Okay.

Yerba Buena SX80: How we doing with time, Matt.

Yerba Buena SX80: do you want it with the break or without the break?

Yerba Buena SX80: I don’t think we yeah, I don’t think we can take a break, and and our board members or folks. If you need to go, you need to go if we take the breakout then, and we’ve used our contingency. We’re we’re on track, but we gotta keep everything else to where

Yerba Buena SX80: we might make

Yerba Buena SX80: alright. I’m Judy Shaman from Geosyntech, and I’m gonna

Yerba Buena SX80: excuse me.

Yerba Buena SX80: Address common number A, that relates to

Yerba Buena SX80: the potential impact of the Spp on groundwater. And to address these comments we perform a quantitative assessment of potential changes in groundwater levels due to the Spp and Sea level rise, using a screening level groundwater model for Sfo and its immediate vicinity.

Yerba Buena SX80: This analysis really focused on evaluating the differences between current groundwater condition and future groundwater condition, taking into account sea level rise, and then looking at

Yerba Buena SX80: 2 scenario with and without the Spp. To really look at the impact that the Spp may have on groundwater.

Yerba Buena SX80: The evaluation was based on a screening level, steady state groundwater model using mud flow, and the area I evaluate is shown here on the figure, and it represents Sfo and its vicinity, including the San Francisco Bay to the east, and then we can see the proposed Spp as an orange line.

Yerba Buena SX80: The screening level model is

Yerba Buena SX80: is a simplified tool that can be used to evaluate the differences between current and future conditions, but because of the simplifications. It doesn’t necessarily accurately represent the current condition and the groundwater elevations at Sfo.

Yerba Buena SX80: If you look at the next slide

Yerba Buena SX80: cool.

Yerba Buena SX80: So this slide provide an overview of how the groundwater model is set up, and so for the model layering. It represents the observed geology with artificial field, with variable thickness that is overlying the young bay mud and the upper layered sediment that are below

Yerba Buena SX80: the bay area. The bay is represented with a specified head boundary condition, and that’s shown in purple on the figure.

Yerba Buena SX80: And the values that I use are based on the current water levels at 3.3 2 feet and then increase to 3.8 2 feet to account for sea level. Rise in 2085

Yerba Buena SX80: for the scenario with the proposed Spp. The subsurface barrier is represented with a hydraulic flow barrier that is

Yerba Buena SX80: along the reaches one through 15, and is shown on in orange. Here on the figure, and the barrier is specified in the field and 10 feet into the bay, which, as we heard previously from James, that’s a design future of the proposed Spp.

Yerba Buena SX80: The Sfo. White Storm drain system that we just talked about and is shown here. The actual drains are shown with green lines here on the figure. This is represented with a drain boundary condition in the model where groundwater can infiltrate into the drain. When the groundwater elevation is above the drain elevation.

Yerba Buena SX80: and the amount of water that infiltrates into the drain is controlled by the drain conductance that is basically representing how leaky the drain might be.

Yerba Buena SX80: And then we also represent an air recharge over the inland portion of the of the model.

Yerba Buena SX80: because we have some uncertainties in terms of how much recharge is occurring, and how leaky, or what is the conductance of the of the storm drain? We looked at 3 pairs of parameters, or 3 combination for the recharge and the conductance of the drains

Yerba Buena SX80: to account for this uncertainty. And look at how those parameters may impact the results. We selected those 3 pairs of parameters based on

Yerba Buena SX80: looking at the the simulated groundwater elevations with the model, and we wanted this to be consistent with what is currently observed at Sfo.

Yerba Buena SX80: Look at the next line.

Yerba Buena SX80: So we looked at 2 different metrics to evaluate the results. And this slide provide an overview of the results. For the 1st metric meaning the simulated granular level increase under future conditions as compared to current conditions.

Yerba Buena SX80: And here we see the results on the images for the 3 pairs of recharge conductance parameters, and then also for these 2 future conditions, which are

Yerba Buena SX80: for all of them silver rise. But then, without the subsurface barrier that’s on the left side, and with a subsurface barrier, and that’s on the right hand side.

Yerba Buena SX80: The colors indicate the simulated water level increase as compared again to future conditions from 0, which are shown in blue to 3 feet, which are shown in red.

Yerba Buena SX80: Based on these results, we can see that the extent of the serrated groundwater level increase from the shoreline depends on the drain conductance, and we can see it by comparing the different

Yerba Buena SX80: figures from top to bottom with a larger extent.

Yerba Buena SX80: for a smaller conductance, and then the proposed Spp translated to result in less increase to future groundwater levels at Sfo as compared to future conditions where we take into account sea level rise, but without the subsurface barrier, and this can be seen by comparing the 2 columns for the figures.

Yerba Buena SX80: and finally, more than half of the western portion of Sfo is not significantly influenced by silver Rise and the proposed Spp. And those are shown with the area in blue and light blue on the figures.

Yerba Buena SX80: If you look at the next line.

Yerba Buena SX80: The other metric that we looked at for this evaluation was a simulated

Yerba Buena SX80: flow rates, and here go back to the previous discussion.

Yerba Buena SX80: We looked at both the simulate inflows into the drainage system, and also the simulate flow from the bay into the field, and for both of those flows those are lower with the proposed Spp. As compared to future conditions, we still have arise, but without this subsurface barrier.

Yerba Buena SX80: and while we, it is anticipated that the ground that the groundwater infiltrating into the drainage system is going to increase

Yerba Buena SX80: the estimated increases which are shown here in highlighted in blue in the in the table for the case

Yerba Buena SX80: with with the Spp. Those values are less than 50 gallons per minute, and are really negligible as compared to the capacity of the storm drain system.

Yerba Buena SX80: If you look at the next line.

Yerba Buena SX80: and so to conclude, the proposed stp is anticipated to result in less increase to future groundwater levels as compared to without the Spp subsurface barrier which is really limiting groundwater intrusion from the bay.

Yerba Buena SX80: the increase in glomadar levels over more than half of the western portion of the airport, considered to be less than one foot.

Yerba Buena SX80: Then we can see that the influence of the sea level rise on groundwater is limited to westward, due to the attenuation from the bay, and also the existing storm drainage system that is providing some control

Yerba Buena SX80: the estimated water infiltration increase into the storm drainage system, which is estimated to be less than 50 Gpm. Is negligible compared to the capacity of this system that is really designed to handle to handle big storm events

Yerba Buena SX80: based on this evaluation, it is recommended that to monitor the groundwater elevation, and also the infiltration of groundwater into the storm drain system to refine the understanding and also detect changes that may warrant some adaptive measures.

Yerba Buena SX80: And I think that’s that.

Yerba Buena SX80: Did.

Yerba Buena SX80: I didn’t, really. I read this this report, and I didn’t really understand how

Yerba Buena SX80: the 50 gallons per minute, how the infiltration

Yerba Buena SX80: in current conditions in the storm drain was assumed. Is it? Is it assuming a certain amount of like cracks in the pipes, and a certain amount of head on the pipe based on its elevation. Or how does that work? Yeah. So how? How this is? If you go back to 3 slides before just to see the the drains.

Yerba Buena SX80: Yeah, so

Yerba Buena SX80: basically how this is set up. We don’t have a lot of detailed information on the on the condition of the storm drain system. So here it’s assumed that

Yerba Buena SX80: all of the trains have the same the same characteristics and the same conditions. And we assume, based on the information that we had, that the drains are 6 feet 6 feet below the ground surface, and then we assume that they have a certain conductance, or they have a certain

Yerba Buena SX80: leak ends, and it’s the same for all of the drains. What is probably the case, that some of them are more leaky, and some of them may be less leaky. But here it’s assumed that it’s an average condition, and then we are looking at when

Yerba Buena SX80: the groundwater is simulated to be above the elevation of the drain, then the water is infiltrating into the drain, and how much is infiltrating. Depend on how leaky this drain is. But this this process will occur everywhere where we have those green lines and where the groundwater elevation is above the bottom of the drain.

Yerba Buena SX80: Okay, thank you.

Yerba Buena SX80: Just out of curiosity.

Yerba Buena SX80: How?

Yerba Buena SX80: What area is subject to recharge from rainfall? I mean, you got a lot of pavement.

Yerba Buena SX80: and the way I see it is, the storm drains actually will feed the groundwater rather than the other way around in many situations. Isn’t that the case?

Yerba Buena SX80: Yeah. And here we applied research recharge kind of

Yerba Buena SX80: uniformly over the entire area, and this recharge would take into account both recharge from precipitation, and also any

Yerba Buena SX80: and any leakans from from the drain.

Yerba Buena SX80: And and here we that’s why we looked at 3 cases, the case where very, very low recharge only half an inch per year, and then a case with higher recharge, 3 and a half inches per per year, and that would that would account both for again precipitation and leakage.

Yerba Buena SX80: So you were looking at it on an annual basis. You didn’t consider a little storm in middle of winter where everything’s saturated. Yeah, that’s correct. This is looking at

Yerba Buena SX80: steady state conditions and then

Yerba Buena SX80: go ahead. I was just going to follow up on that. So the the calibration that was done for the combination of drain, conductance, and recharge shares was calibrated to like the Sfei Groundwater data set, which is based on like the highest observed water levels in a series of wells in that local area.

Yerba Buena SX80: The length varies, but it’s something like 20 ish years depending on which particular well record. So the the conditions that it was calibrated to was calibrated to the wet state conditions.

Yerba Buena SX80: I think that may answer, perhaps part of my question. I’m out of curiosity.

Yerba Buena SX80: You got so many borings, and and probably even monitoring wells. What is the elevation of the groundwater for summer and for wet weather out at the airport? Is it significantly below the pavement elevations, Bob, do you want to take this one? Or since you’ve been?

Yerba Buena SX80: Yeah, we. We have installed some odometers, and they’ve been monitored now for a couple of years.

Yerba Buena SX80: What what we find is that?

Yerba Buena SX80: typically, the groundwater levels are essentially at mean sea level.

Yerba Buena SX80: and

Yerba Buena SX80: on on in in the runways. And and what have you? However, we we do have good evidence of local conditions where you can have

Yerba Buena SX80: significant, particularly in areas that are not paved where you can have significant seasonal fluctuations in in groundwater level

Yerba Buena SX80: and

Yerba Buena SX80: and and we we have seen situations

Yerba Buena SX80: which are near the storm systems stormwater systems which really suggests that locally there, there is some

Yerba Buena SX80: connection and and infiltration into the stormwater system that’s lowering the

Yerba Buena SX80: the the water

Yerba Buena SX80: table. But

Yerba Buena SX80: I I guess the my general assessment is a feeling that

Yerba Buena SX80: it it it’s a the storm motor system is one that wasn’t designed to be a leaky system. It it happens to leak some in some places. And and you know. So

Yerba Buena SX80: it’s the the water balance that’s being done is is an interesting exercise, but it’s it’s it’s probably, you know, just in the long run, or in particular, quite quite more complicated than

Yerba Buena SX80: than that. And

Yerba Buena SX80: and maybe a quick

Yerba Buena SX80: assessment would be just how often are the strong drain pumps running?

Yerba Buena SX80: I mean, they’re probably not running all year round, right? I mean, probably just in the winters.

Yerba Buena SX80: And so that could be our answer.

Yerba Buena SX80: Again. They I’ve been out there. They do run occasionally in the summer dry season though. Maybe one of the 7 pumps together, one of them will go off and drain out a little bit, but they are running year round. Obviously they’re designed for the winter months.

Yerba Buena SX80: and that’s where you see the largest amount of use. So if they’re operating year round, there is groundwater infilled, so they are, they are draining. So the groundwater is pretty close to the

Yerba Buena SX80: pavement, elevations.

Yerba Buena SX80: to the, to the drain, to the drain elevation which, based on information that we had from the storm drains. It was around 6 feet below ground surface on on average

Yerba Buena SX80: and just wanted to add on the

Yerba Buena SX80: the depths to groundwater around Sfo. It’s and we have it in the memo. It’s between 4 4 and 14 feet below ground surface.

Yerba Buena SX80: January.

Yerba Buena SX80: but

Yerba Buena SX80: ultimately

Yerba Buena SX80: the groundwater level is going to be the bay level.

Yerba Buena SX80: right? I mean, this whole barrier business is just for instances where there’s a storm surge that yes, there is a you know. I mean, it’s it’s very much is low hydraulic contractivity. It’s not gonna react instantaneously on on the on the airport side.

Yerba Buena SX80: But ultimately your model considers the groundwater to be 3 feet higher than the sea level of today. Right?

Yerba Buena SX80: If we go back to the previous slide.

Yerba Buena SX80: yeah. So here, that’s where we we are seeing on the left hand side. If the subsurface barrier is not present, then you would expect the groundwater level to be

Yerba Buena SX80: 3 feet higher than today, really, along the in this red area, along the edge of the along the shoreline. And then this this value would decrease as you go westward towards the blue area, and that would be the

Yerba Buena SX80: increase in groundwater as compared to the groundwater elevation that we see today.

Yerba Buena SX80: and some of this

Yerba Buena SX80: some of the difference of why it doesn’t increase everywhere by 3 and a half feet, which is a increase in the along the bay is due to the presence of the storm drainage system that is controlling. How much water the storm drain is a sink. So it’s going to.

Yerba Buena SX80: Whatever your pump is.

Yerba Buena SX80: It’s going to be at that level. But ultimately it seems like that system needs to be working 24, 7

Yerba Buena SX80: to keep it at that level. So so this gets kind of the next point that Jen was referring to before about how much would it have to be referring. So this was this idea of quantifying the amounts.

Yerba Buena SX80: So you’ll see. The the 500 Gpm. That I was quoting before is from the case of sensitivity. 3. Which is the highest recharge and drain conductance. So I was rounding up the 460, so that the model is saying that

Yerba Buena SX80: for the highest cases of recharge that you need to reproduce observed groundwater levels.

Yerba Buena SX80: The recharge. The rate flowing through the storm drain system today

Yerba Buena SX80: with just due to groundwater is about 500 Gpm.

Yerba Buena SX80: And then it’s saying that these are the increases. Without the Spp it would increase up to about 620 to say, take that case, but if you build the Spp, then it’s only going to increase

Yerba Buena SX80: by about 10, because you have that cutoff wall.

Yerba Buena SX80: So yes, it would mean that the storm drain system is currently playing a role in the groundwater elevations there.

Yerba Buena SX80: The rates at which it’s inflowing all the time. In 24, 7, but the inflow rates are relatively low on the order of 500 Gpm. Per day for current conditions. If you build the Spp slightly higher. But this cutoff well is relatively effective. So the relative change in inflow to the system just due to groundwater and the higher bay water levels is pretty small in a time. Frame. Yes, in in like today. Versus tomorrow. Yes, but

Yerba Buena SX80: in 80 years, 50 years, 100 years, it’s going to be at the level of the bay. Yes, I’m not following this business of cutoff. It’s not a cut off.

Yerba Buena SX80: I mean. Well, if if you have a cutoff, but you have a very slow infiltration rate, and you’re removing it from the other side.

Yerba Buena SX80: Okay, that’s what I’m saying. So it wants to come up to the level that is going. It’s the increase that is being considered.

Yerba Buena SX80: And if your pump is at a level that this water reaches it, it has to pump 24, 7, basically, because you’re you’re not going to drain the San Francisco Bay, are you? No, you’re not. But right. But the they currently already they don’t pump 24, 7, because the wet well holds more than 500 gallons right between the accumulated wet wells of all of them.

Yerba Buena SX80: So the pumps don’t go on all the time. They go on to accommodate the present day in the extreme case, roughly, 500 Gpm. The pumps occasionally turn on, even throughout the dry period.

Yerba Buena SX80: If you build also the cutoff wall, the relative change of that, even with sea level, rise in the high rails, we relatively small, so the pumps may need to turn on somewhat more frequently

Yerba Buena SX80: to accommodate that additional inflow. But the amount is going is the increase with the Spp. Is only 10 Gpm. From 460 gpm, so they’re managing it now, with occasional pumping throughout the year

Yerba Buena SX80: by building the Spp. And by cutting off the inflow from the bay. They will have to manage slightly more, but only 10 gpm. More.

Yerba Buena SX80: I have a hard time.

Yerba Buena SX80: Well, I mean I I the way I’m understanding. Ramin’s point is that

Yerba Buena SX80: you are not fully cutting off the flow. Right? There is seepage around the embedment. You are reducing the energy that is pushing the water out, but the water is still going to come right. You’re just slowing it down.

Yerba Buena SX80: If you don’t have the

Yerba Buena SX80: the the wall

Yerba Buena SX80: right. I mean the flow rate into the storm drain system is going to be faster.

Yerba Buena SX80: right? But how much faster? Right? And not much. I mean, I don’t know. I think I think you need to think about this. The system we’re dealing with here is we’ve got bay mud underneath. You’ve got pavement on the top. You’ve got a cutoff through the fill that’s going in there, that yeah? Sure, the cutoff can be a little leaky.

Yerba Buena SX80: The indications from the modeling are that

Yerba Buena SX80: that the storm drain system is having an impact, whether it’s 10 Gpm. Or an order of magnitude higher or whatever there, there will be some additional need down the road, and we’ve recommended that there be monitoring of the system in order to see. But there doesn’t appear to be a critical.

Yerba Buena SX80: You know that that a critical thing where you need to go fix this right now or this, you know where the or the airport’s going to go underwater. We have a system that is carrying groundwater

Yerba Buena SX80: out of there right now. The change seems to be relatively mild.

Yerba Buena SX80: And so we’ve said, we think you need to monitor this system as we as we go along and adjust if you need to.

Yerba Buena SX80: if if it if you see something different. But yeah, so you’re going to need to to pump more sure. But how much more we got bay mud underneath, and we got. We’ve got sheet piles through the fill, and we’ve got pavement. We’ve got all these things. There’s it’s it’s a monitorable system, I think.

Yerba Buena SX80: Yeah, I mean, I think you know, maybe to Rameen’s point. There. You know just what is the elevation of the airport

Yerba Buena SX80: tarmac and most other places

Yerba Buena SX80: compared to the future ground level right compared to the future bay water level. And you said, it’s about mean sea level

Yerba Buena SX80: is about where the groundwater

Yerba Buena SX80: is that? Yeah? 3 feet to it. Are you above that? I think you are

Yerba Buena SX80: on the pavement elevations above plus 6 around the airport. Most places majority of them are. Yes, there’s a couple of low, lying, grassy areas. But yeah. And and again, I think in theory, if you turn the pumps off today and never had a pump, you’re correct. The groundwater will eventually reach a stable point.

Yerba Buena SX80: But the fact is, they’re gonna maintain the pumps. We’re gonna install the sheets, and it’s a way of managing

Yerba Buena SX80: that increasing ground or sea level rise and the increase in water elevation in the bay.

Yerba Buena SX80: It’s very similar to. Again, if you go to New Orleans they have pumps working all the time because they’re already below water. That’s how they often will manage this problem. It’s just eventually Sfo will have to be slightly similar. But they have an existing pump system that’s proven that

Yerba Buena SX80: it it seems to be pretty effective, but needs monitoring. Yeah. But you’ve gone through your fema studies, and the barrier is not

Yerba Buena SX80: a seepage barrier? Is it being designed as seepage control barrier with certain amounts of pumping?

Yerba Buena SX80: And is that

Yerba Buena SX80: baked into your design criteria? Again, the as you mentioned runways. The critical infrastructure is all above. Even when you start looking at sea level rise. But

Yerba Buena SX80: to assist with this, we’ve driven the sheets lower to act as an effective way to help mitigate this

Yerba Buena SX80: in the future.

Yerba Buena SX80: Because if we stop the sheets in the fill, the flow rates as presented are much higher. So that’s why the recommendation to go into the young bay months

Yerba Buena SX80: here, I just wanted to add on, why those flow are are much are very low is because groundwater flow is is very low. The gradient is very, very flat, and the hydraulic conductivity of both the field and

Yerba Buena SX80: really the young Bay mud, where groundwater from the bay, with the present of the of the subsurface by air, has to go through the young bay mud. And so that’s creating a very low, a very small inflow, and that’s it needs to be continuous. But those continuous pumping would be very, very low magnitude

Yerba Buena SX80: if I may, but your evaluation here?

Yerba Buena SX80: Does it have time element in it? Because ultimately, again.

Yerba Buena SX80: if you say the groundwater is mean, sea level, mean sea level is where the

Yerba Buena SX80: level of the bay is on average. So if in 50 years it’s going to be 3 feet higher, it’s going to be 3 feet higher on the on the everywhere.

Yerba Buena SX80: So I mean.

Yerba Buena SX80: that’s where I I’m not following the yeah, I think if yeah, go ahead.

Yerba Buena SX80: there are currently areas around the bay which are below mean sea level and are dry for a substantial portion of the year. A lot of those are either managed by local

Yerba Buena SX80: stormwater systems nearby, or they’re managed by. There’s enough evaporation that you don’t see groundwater building up, because you basically can remove the water faster than an inflows.

Yerba Buena SX80: And so this is just a large case like that of the other factors that are removing the water from the basin that is Sfo. And and the more depressed basin it will become relative with sea level rise

Yerba Buena SX80: is you’re able to remove the water faster than it accumulates. If if all the pumps went off and and you had an extended period, you would lose it. But

Yerba Buena SX80: I wasn’t. I’m not talking about that. All I’m saying is

Yerba Buena SX80: in your evaluation

Yerba Buena SX80: is, does it consider

Yerba Buena SX80: that the

Yerba Buena SX80: level of the groundwater

Yerba Buena SX80: at 50 years from now is 3 feet higher than what you consider today.

Yerba Buena SX80: So it is 3 feet higher at the along the show, and then there is a grade. There will be a gradient inward based on. So it’s

Yerba Buena SX80: it’s currently.

Yerba Buena SX80: let’s say it’s currently at

Yerba Buena SX80: 0 mean sea level. And then it’s gonna raise 3 feet along the floor. The show. And that’s gonna create a gradient. And that’s what we are seeing in this

Yerba Buena SX80: in this figure. And here I want to point. There is no time element, because all of those are steady state. So it’s really assuming that it’s

Yerba Buena SX80: it’s continuous, and it’s for an indefinite amount of time. And so that creates this gradient. And then this gradient is needs to be

Yerba Buena SX80: high enough so that water

Yerba Buena SX80: water would infiltrate into the into the Bay mode, and it would be at at steady state and at equilibrium.

Yerba Buena SX80: Was

Yerba Buena SX80: with the inland portion

Yerba Buena SX80: is that because the groundwater and ground surface elevation is higher on the land side.

Yerba Buena SX80: as you get farther away from the bay.

Yerba Buena SX80: because this is, if I understand this correctly. These are deaths, not elevation correct.

Yerba Buena SX80: So these are. These are water level increases.

Yerba Buena SX80: So it’s so level. So it but doesn’t

Yerba Buena SX80: connect to an elevation. There. There isn’t, I mean, there isn’t a groundwater set groundwater within the airport, right as a boundary condition for the model. It’s you’ve got the bay on the outside, which is set 3 and a half feet higher.

Yerba Buena SX80: and you’ve got

Yerba Buena SX80: a boundary condition on the on, you know, from the upland flow from west to east. I don’t know the specifics of that, but once you get into the airport, you have this pervasive train network

Yerba Buena SX80: right? And so that’s so. So it’s so. That’s so. What’s happening. I believe I’m not the modeler. But I talked to Julie a lot about this

Yerba Buena SX80: is that is, that when you’re coming from from west to east towards towards the airport.

Yerba Buena SX80: It doesn’t take much capacity in the drain system to handle that amount of flow right when you’re coming from east to west. You’ve got that 3 and a half foot higher at the bay.

Yerba Buena SX80: but is now, you know, is now flowing well, even without the the cutoff wall in there it dies down quickly, because it comes in at a certain rate through the permeability of the soil, and it gets into the drainage system.

Yerba Buena SX80: And that’s so, so the drainage system picks it up. But it doesn’t pick it up as quickly because you know. But but if you have the sheet file walls in there that limits, how much can come in from the bay? So that’s what you’re seeing is, that is is where the water is getting into the to the drainage system, and the drainage system has so much more capacity than the amount of flow that’s coming in.

Yerba Buena SX80: I have a problem with defining it as a flow.

Yerba Buena SX80: When your groundwater level is here and your drain is down here, it has to bring it down to that level continuously, because that’s the head

Yerba Buena SX80: that it’s not a flow. It’s not like a.

Yerba Buena SX80: you know. Damn cut off kind of a thing that you have a head, and you’re talking about flow. This is

Yerba Buena SX80: everything going up so it has to pump

Yerba Buena SX80: to get it down to whatever that the pump level is right.

Yerba Buena SX80: can I interject? Sure? I I think I I understand your point.

Yerba Buena SX80: and and I completely agree with you. If there were no drains whatsoever. Yeah.

Yerba Buena SX80: if the bay raises 3 feet.

Yerba Buena SX80: the ground everywhere was raised. There is no question.

Yerba Buena SX80: I think, what they’re what they’re saying, and please correct me if I’m wrong it was a they are including.

Yerba Buena SX80: They are not fixing a boundary condition

Yerba Buena SX80: on the west side. They’re not saying that the the elevation stays at 0.

Yerba Buena SX80: They are. They are mauling the entire basic.

Yerba Buena SX80: Okay. They are raising the water level. And with the current conditions. Which again, one of the things that you may ask is, are the recharges for the current conditions remain the same for these next 60 years? And that may not be the case. That’s a different story. But let’s assume that it is the case. They are not fixing the boundary condition with the West. They’re having the flow.

Yerba Buena SX80: They’re having this, and they have the drainage condition. They have the drainage and those strains. The existence of those drains is enough to keep that level at that elevation.

Yerba Buena SX80: That that’s what I understand. If those things were not there, I have to. If they were giving a different answer.

Yerba Buena SX80: you know I will strangle them myself. So the level will be completely the same.

Yerba Buena SX80: Yeah. And we are talking about flow, because basically, what is happening is that the drainage system is slightly decreasing. The groundwater elevation within the Sfo, and that creates a gradient between what is in the bay and what is in Sfo. And this gradient is equilibrating when the gradient is high is high enough so that the inflow into the bay correspond to how much, then, is

Yerba Buena SX80: coming out of the drainage system, and that’s where we reach this equilibrium between with the groundwater elevation

Yerba Buena SX80: within the Sfo.

Yerba Buena SX80: Okay, since I’m the modeler here, let me let me come back to this thing. I’m not worried about the Bay mud. I’m sorry that’s a red Herring Bay mud has low hydraulic conductivity. Yes, at steady state it’s gonna bring in certain amount of water. What I’m interested in is the boundary condition on the west. Okay from basically San Bruno.

Yerba Buena SX80: because, as was mentioned there, the water level is going to rise with the the base level basically will be the bay so 3 feet higher. So your recharge boundary is going to have 3 feet higher head at that point. How much water are you? Were you able to calibrate it for how much water you’re getting across that western boundary?

Yerba Buena SX80: I know we we didn’t change what was coming across the western boundary. Okay. But there, there, that water level has to respond to the sea level in all of Millbrae and San Bruno just to check. I think I brought the map with the I believe there is a fixed boundary condition along the west side, where the purple line is, and I think it was something on the order of like 10 feet based on local well data. So

Yerba Buena SX80: across the airport you have a rough gradient of 10 feet on the west to 3 feet at the bay, so that you already have a gradient. It has a gradient, and it has flow. So if you took every, you know, just a very simple model, you’d have it wedging out to the bay right? And the stormwater system currently pulls it down a little bit

Yerba Buena SX80: effectively, right? Right? And now you’re gonna raise the bay 6, you know, from about 3, 3 and a half feet to 6 feet.

Yerba Buena SX80: but you still keep the inland boundary at 10 feet, which is, that’s what I have a problem with, because the inland boundary will go up as well. That’s what people don’t understand your groundwater overall. The regional groundwater is going to go up as the bay goes up, and I think that’s probably where

Yerba Buena SX80: where Ramin was having a problem is that you know you’re raising the regional water table. You have to think about that. I’m not. I’m not worried that the strong drain is not strong enough, that I’m not worried.

Yerba Buena SX80: But if you’re thinking about modeling the original response, you also have to consider the regional response of the water. Yeah. So there has been. Regional work has been done. The beef is at all work. It’s part of the cosmos modeling. And we’ve looked at that, and that has been like a water-based scale that goes up to the watersheds. And we’ve looked at those in terms of differencing

Yerba Buena SX80: the amount of change that occurs, and what you see when you do the difference in those elevations, because I think there’s some issues with that groundwater model in terms of its absolute amounts. You see the same kind of pattern that we’re seeing here, that the ring of rise is very much constrained to, only like within a thousand feet or so of the bay.

Yerba Buena SX80: So raising. And so that’s a full Usgs, you know you could. So so it’s I think, if you’re upslope enough. Right? It doesn’t matter what the bay

Yerba Buena SX80: changes.

Yerba Buena SX80: Like, I understood, yeah, I understand. But here we are, Bayshore Freeway. We are not upslope. Okay? And so the point is that there the water level is going to be higher. Okay? I mean, Caltrans is having problems where the drains are blowing up in major storms, because wherever they have an underpass they don’t have enough capacity because nobody thought about it.

Yerba Buena SX80: So it is a standing problem. You know. We had orchards there. A long time ago people were using groundwater. We no longer use groundwater. All I’m saying is that when you do this I’m not worried from everything you say you have the capacity.

Yerba Buena SX80: But if you’re building a model like this, you do have to consider the regional response locally. You cannot use the Usgs. I’m sorry I love Usgs, but their regional models are just that they’re regional. They don’t really tell you what’s happening locally, Nick. It won’t go up 3 and a half feet, though. Right? Go up a foot 9 inches.

Yerba Buena SX80: Yeah. I mean, is there some number that you suggest that they increase the west boundary by. Well, I think it’s just matter. As I said, I think the capacity you have shown, because the hydraulic conductivity of the fill is not infinite, and you know you consider that. But I would certainly consider

Yerba Buena SX80: looking at what happens if the water level goes up on the you know, on the San Bruno, the you know, on the west side, and what it does to the overall. You say that there is a basically a 7 foot gradient right now.

Yerba Buena SX80: what if the gradient stays the same? What I gather is in that model? You? You assume that the gradient decreases because the sea level comes up. But actually, what if you just assume that the gradient stays the same?

Yerba Buena SX80: That’s that’s all I’m saying.

Yerba Buena SX80: And if there’s a gradient from the west towards this new wall, wouldn’t it pile up behind the wall as well it could conceptually, if there were no conceptually. But the drain is already doing its business. Yeah. So yes, it would if there is no drainage.

Yerba Buena SX80: The point is that there’s a huge network of French drains, essentially, that are keeping it from rising above the bottom of the French drains. Yeah, I mean, it’s big. I mean, the French drains are leaky storm drains which are not supposed to leak, but they do, and that I mean, that’s the assumption. And that’s

Yerba Buena SX80: observed, standard practice. It’s the way these pipes work.

Yerba Buena SX80: Yeah. And it’s just what I thought we can.

Yerba Buena SX80: that definitely can be a sensitivity case to to look at that, but wanted to point out that because the the gradient is very flat and that’s consistent with what is what is observed. The the flow from the west side is is also very, is very small, and and a lot of the

Yerba Buena SX80: the inflow, release from the assume arrow, recharge, and then from

Yerba Buena SX80: and then we still have arise from the flow from from the bay, so would it be a simple sensitivity. Analysis just to like Nick suggested. Raise the grade, keep the gradient the same. So you’re raising the west side 3 and a half feet.

Yerba Buena SX80: and instead of less than 50 gallons a minute, it’s gonna be less than 70 gallons a minute, or something like that.

Yerba Buena SX80: or still less than 50, probably. Still.

Yerba Buena SX80: I guess I would just note that

Yerba Buena SX80: based on what we’re seeing now, with the 3 and a half foot rise against on the on the base Bay side. If we if we raise things a little bit on the west side.

Yerba Buena SX80: we might see a little bit of an effect on the west side, but pretty far away from the wall.

Yerba Buena SX80: you know, and it’ll be picked up by those 1st drains, and it’s it’s gonna have a pretty minor effect on the overall. So

Yerba Buena SX80: oh, maybe I’ll just say that.

Yerba Buena SX80: When I was part of the what is it? The San Francisco sea level rise and flood Hazards committee

Yerba Buena SX80: groundwater inundation was a phenomenon that we were looking at, and I wish Chris May was here because she was leading that

Yerba Buena SX80: so I would.

Yerba Buena SX80: I, I think, recommend that you do look at this as a sensitivity study.

Yerba Buena SX80: and I don’t know what the con

Yerba Buena SX80: conductivity, or whatever that the the term is that brings the water in on the the west border or the boundary condition.

Yerba Buena SX80: But I but I think it is worth.

Yerba Buena SX80: you know, satisfying the the Board’s curiosity. Here

Yerba Buena SX80: 3 and a half foot rise on the West End would be an upper bound that one could have possibly imagined. I think right?

Yerba Buena SX80: And so it’s gonna be a 9 inches foot. I don’t know.

Yerba Buena SX80: I think you can do it on your iphone.

Yerba Buena SX80: Yeah.

Yerba Buena SX80: okay, we are at 4 30.

Yerba Buena SX80: And I don’t think there’s a plan B for for us

Yerba Buena SX80: and going past 5. Right? Jen.

Yerba Buena SX80: okay, can we? What do we have left?

Yerba Buena SX80: We? We have 2, we have subsidence. And the seismic monitoring.

Yerba Buena SX80: the presentation for both of those we think are relatively quick. 4 to 6 min.

Yerba Buena SX80: Okay, we. We still have to do public comment to make this a meeting. Right? So

Yerba Buena SX80: subscience is the one that’s come up the most.

Yerba Buena SX80: or has come up before the the

Yerba Buena SX80: I mean we can do it, whichever order you want if we are going to cut off. No, I think subsidence would be the the one to get to next.

Yerba Buena SX80: Okay, you get to hear from me again. This is Chris Hunt, Chris Hunt, with Geosyntech. I’m a principal geotechnical engineer in the Oakland in the Oakland office.

Yerba Buena SX80: so the question was, what is the expected amount of land subsidence that could cause the proposed wall to sink over the life of the project. The way the approach really took at this was just kind of what is the amount of subsidence that the that we are seeing at the airport.

Yerba Buena SX80: And what will be project out to this to 2085.

Yerba Buena SX80: We didn’t want to focus on Reach 7 where they’re doing new construction, new design. And they’re they’re handling all that. It’s it’s we just focused on. Kind of what do we project for the future settlement at the airport.

Yerba Buena SX80: You know, the fills are over 50 years old, and the last major fill was over 50 years old. So so there’s there’s there’s 3 sources of data. There’s some satellite. There’s 1. There’s a base station shown in blue on there which has satellite data.

Yerba Buena SX80: There are set. There’s a there’s a whole series of benchmarks around the airport, and we received data from a few different years. We focused in on

Yerba Buena SX80: the 2012 and 2015 sets of survey data and then towel. Recently did a ground validation survey at the end of 2023, with with points all over the airport.

Yerba Buena SX80: And we we use that data at the at those benchmark locations. So we have one base station with a good, a really good data set. And we have, we have a few years of data at the 5 red benchmark locations. So if you go to the next slide.

Yerba Buena SX80: so so all those those black circles on there, that’s the satellite kind of GPS data.

Yerba Buena SX80: And what it shows. This is a, this is a a linear timescale that that we’re showing here.

Yerba Buena SX80: But but between 2011, and the end of 2022. So right about the right, about right, about the start of 2023,

Yerba Buena SX80: we had about 3.3 and a quarter inches of settlement that occurred.

Yerba Buena SX80: We fit a a log linear.

Yerba Buena SX80: best fit line through that through that data, because this is, it’s 50 years since they’ve had any settlement, any any and any real fill placement. So this is secondary compression, which is an exponential decay

Yerba Buena SX80: process. So the if we look at that as a just as a linear. In the last few years, between between 2014 and 2220, 22. It’s been going about point 2 little over point 2 inches a year.

Yerba Buena SX80: But if we do that log linear fit to that, and we forecast it out to 2085, we get out to about 6 inches total, but that’s only about 2 and a half, 2.7 inches over. Then, you know, out to 2085. Chris, I have a quick question. Is that projection out 60 years

Yerba Buena SX80: just based on this curve? Fit

Yerba Buena SX80: log, linear line? Or is that based on? If you just extend the T in your secondary compression calculation, it’s it’s the it’s the fit. It’s the it’s the linear.

Yerba Buena SX80: It’s the linear extension out. So if you put T equals 60 more years.

Yerba Buena SX80: does it look about like this also?

Yerba Buena SX80: Oh, well, you’re going to get a look, you mean, am I gonna get more settlement, or or what do you? What do you mean

Yerba Buena SX80: if I have a different T.

Yerba Buena SX80: So this is based on a curve fit.

Yerba Buena SX80: I think you also at some point talked about using an alpha value, secondary compression value, and which I have, which I have in 2 slides.

Yerba Buena SX80: Okay, okay.

Yerba Buena SX80: so this is the one. This is the base station GPS data which we get. We get the A forecast of about about another 3 inches out to 2085. We go to the next slide. We have the survey data

Yerba Buena SX80: where we have measured settlement. From the 1st data point we had was 2012, and the last one was 2023.

Yerba Buena SX80: So we’ve had one to 3 and a half inches of settlement between those between those 2 dates. If we project each one of those out following that, you know, giving each one of them a log linear fit out there. We we get about

Yerba Buena SX80: another

Yerba Buena SX80: 3.1 1.4 to 3.7 inches between the different benchmarks over those next next 6 years I’ll just point out that the range. That linear fit over the last few years is 0 point 1 2 inches per year and point 3 2 inches 2.3 2 inches per year, with an average of 0 point 2 1 so very similar to what the satellite data was showing us, that point about 0 point 2 inches per year.

Yerba Buena SX80: but the exponential decay only gets us another 4 inches or so out another 60 years. If we look the next slide, we look at the kind of fundamental principles and some lab data, we, we turned each one of those forecasts into a strain rate based on the thickness of the bay mud. At each one of those benchmark locations.

Yerba Buena SX80: And what you see in that table. 2. So this C. Epsilon, Alpha number as geotechs all know. That’s basically a strain, a strain rate in in log time, space, but that range in in table, in table, 2 in the bottom, right corner of table 2 shows that

Yerba Buena SX80: that those strain rates are 0 point 0 0 4 to 0 point 0 0 1 with a mean of point 0 0 7. As those C. Epsilon alpha. If we go to that Adx study that Bob was talking about earlier, where they looked at soil properties, they did. They did a lot of lab tests. And if we look at the C alpha values that they measured in the lab from 0 point 0 1 to 0 point 0 3, and the equivalent void ratios from 1.1 to 1.8, all within the stress range of interest for the bay mud, we get a very similar answer. We get

Yerba Buena SX80: C. Epsilon, Alpha, 0 point 0 0 4 to 0 point 0 1 2. With a best estimate of 0 point 0 0 8, which gives us so we’re saying that the survey data and the geotechnical data lab data is telling us the same rates of strain out here. So we thought we thought that was good confirmation. So I think the last slide after that just kind of summing it up.

Yerba Buena SX80: We’ve got consistent between survey and and geotech tests. We’ve got recent rates of settlement going to be at the point 1 2 to 0 point 3 2, with a mean of 0 point 2 1 inches per year, but these are going to reduce over the long term. We forecast that out, and along the perimeter we see one and a half to 4 inches of settlement through 2085,

Yerba Buena SX80: you know. Obviously, this needs to be considered. That, there’s gonna be a few more inches of settlement out there, and in places where you’re actually gonna add new load, add, fill. Do other things like that. You need to. You need to do the actual analysis. And that would be part of that design build process.

Yerba Buena SX80: But it’s it’s pretty. It’s a pretty limited amount of settlement for a thick bay mud site, and it’s because we haven’t put any major fill out there for over 50 years.

Yerba Buena SX80: Okay.

Yerba Buena SX80: I understand there was some work along the perimeter

Yerba Buena SX80: of the airport, right? So going back. So could this be a relic of some of the construction work in terms of raising.

Yerba Buena SX80: you know, depending on how close your your base station is to the perimeter where work was done.

Yerba Buena SX80: It’s the I mean. So so the

Yerba Buena SX80: geotechnical settlement you have. Primary settlement and secondary settlement and primary is the kind of the it’s not always short term. It depends on how thick that layer of bay mud is, but you have more settlement early on in response to a load, and then you get this long, exponential decay, which is what we’re what we’re seeing here, and that that satellite data

Yerba Buena SX80: matched really nicely with this concept of kind of that, that exponential decay. So we just we think it’s just secondary compression. And it’s just going to go on. It’s just going to keep getting lower and lower and lower over over time. It’s just a log, linear.

Yerba Buena SX80: straight, straight relationship.

Yerba Buena SX80: Hi, Dilip, can you clarify the question about what work was done. I mean, I’m starting to see 3 inches of settlement that occurred between 2011 and 2022. There was no fill place in the airport at all. Yeah, I think the most recent set of work that was on our perimeter. Yeah, I don’t think there’s any work.

Yerba Buena SX80: The sheet piles were installed, probably in the nineties. That was it. The vinyl sheet piles that we have.

Yerba Buena SX80: Yeah, but I don’t think there’s any

Yerba Buena SX80: work on the perimeter. There were emergency repairs done. But you know that was at the edge of the the 19th

Yerba Buena SX80: runaways. That was it.

Yerba Buena SX80: Okay?

Yerba Buena SX80: Any other

Yerba Buena SX80: good source of science? I think we’re good to go. Okay.

Yerba Buena SX80: for this last one, can I? Maybe it’s a last, but not here.

Yerba Buena SX80: Satellite data. You know. I’m I’m separating subsidence from vertical land motion.

Yerba Buena SX80: You know there have been some studies, I think lately that we have seen where they’ve tried to

Yerba Buena SX80: isolate and understand what’s the vertical land motion

Yerba Buena SX80: separate from, you know.

Yerba Buena SX80: consolidation due to

Yerba Buena SX80: due to due to fill

Yerba Buena SX80: the satellite picks up all of that also. Right?

Yerba Buena SX80: Well, so I didn’t visit the site. But my understanding is that is a

Yerba Buena SX80: it’s. It’s a base station with elevation collected on a daily or at least weekly, I think, with every day. Same point. How’s that elevation changing based on?

Yerba Buena SX80: I think it’s Gnss. Which I think is also the same same, essentially a generic name for GPS in this case, probably. But I’m not. I’m not a surveyor, so it’s capturing the vertical settlement of that base at that base station location. At whatever the point where it’s measuring, it is right? So it’s ectonic activity plus secondary compression. Right? That’s what I was trying. Well, it’s whatever is called yeah. All vertical movement would be captured in that. Yes.

Yerba Buena SX80: I I would just like to throw one thing in, and we don’t need to discuss it at all. But

Yerba Buena SX80: you got 10 or 12 years of data and extrapolating it

Yerba Buena SX80: 60 more years.

Yerba Buena SX80: It’s a long extrapolation. If I look at the the your satellite data.

Yerba Buena SX80: I would be happier with a slightly

Yerba Buena SX80: do do a different logarithmic curve. That

Yerba Buena SX80: gives it more settlement, I think. Just

Yerba Buena SX80: eyeball curd fitting it.

Yerba Buena SX80: I’m not sure. I trust these numbers. I’m not sure that it matters much, but just

Yerba Buena SX80: the the memo has it in in in semi log space. You can see what the curve fit is. Sure you could. You could, I mean, if you went

Yerba Buena SX80: for the high end at the at the you know in in the, in the early stages, and a low end you could come up with a with a longer line, I guess.

Yerba Buena SX80: When we looked at the different benchmarks, and it all came into the same general area. It was still a matter of a few inches.

Yerba Buena SX80: So, Chris, do you have a plot where you superimpose your

Yerba Buena SX80: using the

Yerba Buena SX80: empirical approach to the secondary settlement.

Yerba Buena SX80: to the

Yerba Buena SX80: satellite data that

Yerba Buena SX80: well, so what I what I had was those tables, where I looked at the thickness of the bay mud at the base station, and used that to come up with the strain rate and the strain rates were about the same. I didn’t. I didn’t then try to plot that. Oh, yeah, okay.

Yerba Buena SX80: I’ll just say that I think the satellite data. There’s 2 sets. There’s the GPS satellite data, right? And I think people are also referring to some more recent insar satellite data that’s been used to detect elevations. And I’ll just say that

Yerba Buena SX80: that information, I think, is regional. I haven’t seen it locally validated at the airport, which you would do by ground truthing it with local elevation. So basically, instead of the satellite data, that’s regional data. If you wanted to ground truth that at the airport you would go find the base stations.

Yerba Buena SX80: the benchmarks, and those surveys like we’ve done here. And you’d find the GPS data. If you have that collected daily, and you’d compare that to the satellite data from the insar data. So you know, we know that there’s other data set out there. But this was to try to

Yerba Buena SX80: provide local

Yerba Buena SX80: measurements from what was collected locally. Not not sort of a regional, remote, sensing approach.

Yerba Buena SX80: it seems 3 inches in 11 years. That’s a lot for secondary, it seems to me

Yerba Buena SX80: any lights you can share shed on that. It.

Yerba Buena SX80: It was a it it as a geotechnical engineer. I thought this was an amazing data set to have. No, no, this is a great

Yerba Buena SX80: field level consolidation test. That’s good. But it seems, after 50 years. For 11 years, 3 inches. That’s if you if you go to table.

Yerba Buena SX80: so that last the table in there. So at the base station

Yerba Buena SX80: we estimated 35 feet of of young bay mud under there.

Yerba Buena SX80: So it’s a pretty small relative to the thickness of the bay mud. But yeah, I mean, it’s certainly not something that a normal structural engineer would want to design a new building on with 3 inches of.

Yerba Buena SX80: But that’s I mean.

Yerba Buena SX80: yeah.

Yerba Buena SX80: But but if this is, in fact, some residual primary consolidation or tail end of primary consolidation.

Yerba Buena SX80: It’s gonna the the rate will decay even faster than if this is actually secondary. So this is, I really don’t think it’s primary from what? From what we’re looking at, though.

Yerba Buena SX80: I mean.

Yerba Buena SX80: I just don’t know what the driver would be. I’m saying if it were, then your calculation becomes a conservative one. Yeah, yeah. Okay, yes, I would just say, going back fundamentally to the flood wall as a structure, these settlements are not a concern. There’s, and again, the vertical settlement. It should slide right by the sheet.

Yerba Buena SX80: We have plenty of extra height on it with the Fema fema free board. So ultimately.

Yerba Buena SX80: you know, additional settlements. Long term is not going to impact the flood protection of the project. Yeah, I was going to. Actually, when when did it. Final comment, I guess, on this. I think that the

Yerba Buena SX80: the subsidence

Yerba Buena SX80: report that you submitted

Yerba Buena SX80: alludes to, and Chris mentioned that you you were paying attention to everything except for 7, which is where new fill is going to be placed, which is where primary will be initiated.

Yerba Buena SX80: Just to make sure that you know, we think that

Yerba Buena SX80: primary needs to be looked at.

Yerba Buena SX80: And there we have a much different approach. Again, we’re gonna address the settlements directly in the construction.

Yerba Buena SX80: Yeah.

Yerba Buena SX80: and it will make a little bit of a difference in needing to over Bill. And you’re doing. I know you’re doing some surcharge, and I think wicking also

Yerba Buena SX80: correct cause. We identified that as a definitely an issue. So.

Yerba Buena SX80: James, just a clarification, since I’m not a geotechnical engineer on your comment?

Yerba Buena SX80: As the soil settles, does the wall height settle with it? Or is the soil settling again? We’d have to study again where in the soil column. If it’s going to have some down drag, or if the whole soil mass is settling, if the whole mass is going down the expectation, the wall might come down a little bit, but again given the wall height. Given the Freemore fema free board. Given some of these uncertainties on sea level rise, it’s all within

Yerba Buena SX80: kind of

Yerba Buena SX80: acceptable levels. If we’re losing a couple inches on top plus, there is some future adaptation.

Yerba Buena SX80: you know, extensions of the wall. Again, as much as I wouldn’t like to at the end of the service life. If you had to put a concrete cap on this, you could and gain another, you know easily a foot to 2 feet of wall height, if necessary, in the future.

Yerba Buena SX80: I again, from a structural capacity of putting a lollipop concrete block on there from a seismic.

Yerba Buena SX80: I will sleep very well. It’s not a problem. It’s not again. As long as you don’t pile up a bunch of soil and has become a retaining wall. Then that’d be a different story

Yerba Buena SX80: understood. But where we’re at on the DC ratios, I’m just not sweating it like it’s I’ve I’ve designed walls for retaining much larger loads than this. And you know there, this is pretty much holding back air most of the time. So

Yerba Buena SX80: okay, let let, can we do the seismic instrumentation in

Yerba Buena SX80: 5 min? I think so, Jackie, you ready.

Jackee Allmond (Geosyntec): Yes, I can. So hi everyone. My name is Jackie Almond. I’m a senior geotechnical engineer with Geosyntech.

Jackee Allmond (Geosyntec): I’m here to talk about the strong motion instrumentation, and specifically the Ecrb comment number 12, which is shown in the upper right hand. Here it’s really a 2 part comment. The 1st part is to check in with the California strong motion instrumentation program manager.

Jackee Allmond (Geosyntec): And the second part of the comment is to provide a draft seismic instrumentation plan, and that’s to provide a seismograph to be incorporated into the State seismic instrumentation network. So earlier this year in May, the project design team met with the Cgs Csnp program manager

Jackee Allmond (Geosyntec): and 2 other Cgs technical leads.

Jackee Allmond (Geosyntec): We started the meeting by providing and giving a brief description of the Sfo Spp. And then Cgs stepped through and summarized the instrumentation requirement itself and the process, and also provided Bcdc’s written steps for required instrumentation projects, and those written steps are shown over on on the right hand side there.

Jackee Allmond (Geosyntec): Really, the takeaway from this meeting is that the instrumentation planning process is a collaborative effort between the design team, Bcdc. Cgs, and also Cgs’s strong motion Instrumentation Advisory Council. There’s my Act subcommittee.

Jackee Allmond (Geosyntec): So if you go to the next slide, we’ll look at some things that we’ve done since that meeting.

Jackee Allmond (Geosyntec): Sfo. Provided Cgs with pertinent Spp design drawings and documents, and that’s really in support of Cgs’s review process

Jackee Allmond (Geosyntec): in response to comment number 12, we prepared a memorandum with recommendations for a strong motion instrumentation plan. It included the things that are bulleted here. I’ll really only have time to talk about the station location, but the memo also includes things like the foundation and enclosure layouts, equipment requirements, some power supply and communication needs. And then also some site specific information related to site access and points of contacts as well.

Jackee Allmond (Geosyntec): The recommendations in that memorandum were developed to meet the instrumentation requirement for the Sfo Spp.

Jackee Allmond (Geosyntec): And were built with consideration of the Bcdc. Instrumentation process that was shown on the previous slide. The State’s instrumentation specifications and state of practice guidelines for strong motion stations.

Jackee Allmond (Geosyntec): So if we move to the next slide, I’ll just briefly cover our strong motion station location, selection criteria. We’re trying to balance a lot of different things in selecting a location. Those are listed here in the memo. We’ve got the location identified shown on the right hand side as our the approximate station location between reaches 4 and 5.

Jackee Allmond (Geosyntec): The criteria that we’re that we’re trying to meet really are considering airport runway and operations activity. Thinking about site access and restricted entry access points wanting to avoid those those points for off site personnel, getting on to the site and accessing the strong motion station.

Jackee Allmond (Geosyntec): We also want a location that’s a distance away from existing buildings and existing infrastructure.

Jackee Allmond (Geosyntec): And then we also wanted to pick a location where not only we have subsurface geologic information, but the subsurface geology is in line with the goals of the Cgs season program.

Jackee Allmond (Geosyntec): So with all those things considered, we’ve laid out this proposed location.

Jackee Allmond (Geosyntec): So on to the next slide. We just have a few next steps and sort of our path forward in this process.

Jackee Allmond (Geosyntec): Cgs recently presented candidate locations via email and has requested review and feedback regarding their proposed locations. The design team will meet with Cgs to discuss those locations and also other elements of the strong motion instrumentation plan

Jackee Allmond (Geosyntec): and then the design team will continue our collaboration with Bcdc. Cgs and their Smiac Subcommittee in order to develop a strong motion instrumentation plan as part of the Sfo Spp.

Jackee Allmond (Geosyntec): And that’s it.

Yerba Buena SX80: Thank you.

Yerba Buena SX80: Any comments from from the board. Yep, I do have a comment. You had a red star there on the on the, on, the, on the drawing where you proposed to put it.

Yerba Buena SX80: You have a you have a boat ramp on one side, you have an approach to the Coast Guard facility, which at 1 point is going to be upgraded, which means piles are in the ground. That is a terrible location, and and I see it all the time that we put these strong motion stations

Yerba Buena SX80: in a place where there are adjacent structures that totally interfere with the ground response. Why couldn’t you pick anywhere along the whole thing where there is nothing adjacent except the wall that’s coming in?

Yerba Buena SX80: You know. I just like to raise it up there. I look at these stations. You know we have them in California all over the place where are in locations that are completely impossible to analyze after the earthquake because of the adjacent structures, and and we do it all the time. And with all the consultation with Usgs, Cgs, everybody sitting there, and we stick them into, you know.

Yerba Buena SX80: Yes, that is easily accessible. But these days, with satellite communication, and whatever else you don’t really need to be there in person to get the data, so I would strongly urge you. Please take a look at where you not next to adjacent infrastructure.

Yerba Buena SX80: anyway. Thank you.

Jackee Allmond (Geosyntec): I mean, I think you’d be. You’d be hard pressed to find a location at the airport that wasn’t next to existing infrastructure or existing activity, daily activity. So in the proposed area is shown sort of in the inset in the middle of the of the slide there. And there’s the kind of yellow dash area, really, that would probably come back some. We wouldn’t really want to put it quite close to the ramp, and also the the outfall pipes. So something quite farther away from that but again.

Yerba Buena SX80: I miss. Sorry I misunderstood. Okay, I saw your arrow and I thought it was, gonna Be right there. Okay, never mind.

Jackee Allmond (Geosyntec): Oh, no, sorry. Yeah, it’s it’s really that kind of area. It’ll be a collaborative process with Cgs. But we certainly want to pick a location that is far away from existing infrastructure.

Yerba Buena SX80: Thank you. Okay, sorry. I missed. As I said, I looked at the arrow, and I just couldn’t believe it. So thank you.

Yerba Buena SX80: Thank you, Nick?

Yerba Buena SX80: Okay.

Yerba Buena SX80: going to assume there are no more comments.

Yerba Buena SX80: So let’s

Yerba Buena SX80: Thank you very much for your presentations. It’s been really great.

Yerba Buena SX80: we have to go to public comment before conducting ecrb discussion.

Yerba Buena SX80: So for members of the public, if you would like to speak today, we request that you only provide comments or questions specific to the presentations given today.

Yerba Buena SX80: If you would like to speak, we will need you to do one in. Do so in one of 3 ways.

Yerba Buena SX80: If you are here in person.

Yerba Buena SX80: please raise your hand so we can call on you.

Yerba Buena SX80: and we’ll at which time will. You may come forward to the lectern.

Yerba Buena SX80: If you’re attending on the Zoom Platform on your computer, please raise your virtual hand in zoom.

Yerba Buena SX80: You may be you may do this by clicking on the hand at the bottom of your screen. If you are attending via phone, you must press Star 9

Yerba Buena SX80: on your keypad to raise your hand to make a comment, and star 6 to unmute or mute yourself.

Yerba Buena SX80: We will call on individuals who have raised their hands in order

Yerba Buena SX80: in the order they are raised during the public comment period. Starting with anyone present in person when called upon, you will be unmuted so that you can share your comments. Please state your name and affiliation at the beginning of your remarks.

Yerba Buena SX80: Normally, we give folks 3 min to make comments this time. I’m going to make it 1 min per speaker.

Yerba Buena SX80: For your comments as in any public meeting, please keep your comments respectful.

Yerba Buena SX80: We are here to listen to everyone who wishes to address the meeting.

Yerba Buena SX80: but, as always, we ask that everyone act in a civil manner. Hate speech, threats made directly or indirectly, and abusive. Language will not be tolerated, and anyone who fails to follow these guidelines or exceeds the established 1 min limit without permission will be muted.

Yerba Buena SX80: Margie, are there any hands

Yerba Buena SX80: raised.

Yerba Buena SX80: No, we have no public comments.

Yerba Buena SX80: Okay. Now, let’s return to board discussion.

Yerba Buena SX80: I think we’ve been pretty

Yerba Buena SX80: comprehensive in our comments during

Yerba Buena SX80: the presentations, but if somebody has a a concern

Yerba Buena SX80: that they would like to raise right now, I’d like I’d like to hear it.

Yerba Buena SX80: I made there. There is only 1 1 concern which I raised earlier, which was the issue of continuity

Yerba Buena SX80: in this design build process. And is it possible to put a condition that the current

Yerba Buena SX80: team that has done the analysis be then retained as a as a reviewer for future steps. So we we are assured that there is continuity in the in the thought process behind it. Is that something that we can do?

Yerba Buena SX80: I don’t think we’ve mandated. They hire.

Yerba Buena SX80: we can. I think we can mandate who they hire retainer, or when they get fed up with them and replace them, needs to be design continuity. In some matters, such as retaining the same team.

Yerba Buena SX80: Yeah, you don’t wanna shut out some of these other engineering firms that

Yerba Buena SX80: But yeah, I I agree, Nick, I think

Yerba Buena SX80: You know, the way I would approach it is that, you know. And like like this, you know, there’s a basis of design. There’s criteria that is very clearly

Yerba Buena SX80: delineated. And you know that that helps provide the continuity.

Yerba Buena SX80: But yeah, I don’t know. I don’t think we can. We can dictate.

Yerba Buena SX80: who who the applicant hires

Yerba Buena SX80: who is hired?

Yerba Buena SX80: Well, we would. So I think we suggest peer review of of

Yerba Buena SX80: engineer records. Design. Okay?

Yerba Buena SX80: For for consistency with the original analysis.

Yerba Buena SX80: So

Yerba Buena SX80: okay, just a quick comment. Well, I mean, I was trying to follow Jen’s. You know the advice on the questions that we, as the Ecrb should answer. So I’ve been listening to the presentations. The only thing that I haven’t heard much about is impact on adjacent

Yerba Buena SX80: existing structures

Yerba Buena SX80: are there any existing structures that

Yerba Buena SX80: the proposed construction the Svp is going to impact?

Yerba Buena SX80: And has that been

Yerba Buena SX80: sort of been incorporated into?

Yerba Buena SX80: You are thinking.

Yerba Buena SX80: not not directly. Again, we’ve we’ve established and selected a location for this alignment that would have least impacts to existing infrastructure as as possible. Again, the majority of it is within Sfo’s property.

Yerba Buena SX80: And I’ve attempted to limit the impacts, obviously from a cost perspective, if we have to take a lot of things out. Really, the biggest impacts is the existing flood protection systems there. Essentially, this is going to be replacing it.

Yerba Buena SX80: I’ll just add there was one

Yerba Buena SX80: we didn’t cover all the 12 ecrb questions before, partly, as you saw for time, we had to select some one of the ones that did come up that was related to the offsite impacts was the potential for wave reflection. So we referred to the coastal hydraulics report. So I’ll just briefly just

Yerba Buena SX80: and so there was a concern about way reflection. So again, I just wanted to

Yerba Buena SX80: show what was done for that. So a reminder again, as you saw the Cross section today is most of the time. The waves aren’t even reaching the sheet pile wall. And they’re basically just dissipating on the rock slope in front of it. And so we don’t really see that as a wave reflection issue as part of the coastal hydraulics assessment, we used Xpeach, which is a non hydrostatic model which allows you to understand the wave dynamics in more detail than a normal

Yerba Buena SX80: phase average model. So these are just some sample results here on the side. This is for reach 7. So that’s the case where you were, you know, you would be building out the perimeter dike. So that’s why you moved from the upper panel which is existing conditions to building out into the bay.

Yerba Buena SX80: And so for this case, this is for the 100 year water level

Yerba Buena SX80: under current conditions. And you can see. And in the this is the shear stresses, we’re basically using the bottom axis as the shear stresses. So as you would expect they’re occurring where the waves break at the shoreline. So they’re basically on the rock slope protection that doesn’t change.

Yerba Buena SX80: If you look in sort of a more detailed, you know, from the toe outward. And you consider what the changes. Again, this is using bed shear stress as a surrogate

Yerba Buena SX80: for that. That’s what we were looking at before was more focused on localized impacts to the bed. You can see between the existing, the sort of fainter, lighter weight red line versus the Width project line. You know, they change in variation because it’s non-hydrostatic models. They bounce off in different ways. But you know, didn’t really see any change in the mean in the sort of couple 100 feet in that area. So we don’t think that wave impacts are going to be an issue.

Yerba Buena SX80: Thank you.

Yerba Buena SX80: Thanks. Thanks. Geema. Jen.

Yerba Buena SX80: do you know, normally, I think we ask you to summarize questions and conditions. But you know, given our time constraints, I’m assuming you’re just

Yerba Buena SX80: gonna pass out to the board

Yerba Buena SX80: for review some of the major points or questions or further actions.

Yerba Buena SX80: Yes, I think you know, if there aren’t really any lingering

Yerba Buena SX80: questions about

Yerba Buena SX80: the stability of the wall. And it seems like

Yerba Buena SX80: there’s quite a lot of monitoring planned, and we can. Bcdc.

Yerba Buena SX80: We’ll be requesting information on that. There was the issue about the coercive of the soils, which I think we can request that in a sort of a plan review process as well.

Yerba Buena SX80: there’s 1 question about

Yerba Buena SX80: how much flooding would occur in a power outage

Yerba Buena SX80: and also sort of what’s the long term plan for the storm drain, pumping system?

Yerba Buena SX80: and if those aren’t urgent issues, those could also be handled in the future as permit conditions as well.

Yerba Buena SX80: do I? I see nodding heads here. Perhaps we

Yerba Buena SX80: just take a very quick boat

Yerba Buena SX80: on

Yerba Buena SX80: on those permit conditions.

Yerba Buena SX80: do I? And so I guess the motion is. And the big question is, should they come back for anything?

Yerba Buena SX80: thoughts I I we’re gonna I guess that’s something we have to discuss. Are there any thoughts about

Yerba Buena SX80: whether or not the airport comes back?

Yerba Buena SX80: It seems to me that we’ve expressed our

Yerba Buena SX80: engineering criteria concerns, and they’ve been responded to in a way that seems, I think, adequate

Yerba Buena SX80: to me, and there’s some ongoing responsibilities and work that needs to be done. And I think you know some of the corrosion thing things that you mentioned.

Yerba Buena SX80: We’d like to make sure there’s some continuity between

Yerba Buena SX80: the design team and the design build team

Yerba Buena SX80: to make sure that all these

Yerba Buena SX80: design criteria that we’ve been talking about get implemented on into the future.

Yerba Buena SX80: Otherwise I don’t think

Yerba Buena SX80: I don’t see a reason we need to have them come back to us again.

Yerba Buena SX80: plus things change a lot.

Yerba Buena SX80: Okay, I see nodding heads.

Yerba Buena SX80: so the motion is to not ask the airport to come back based on the presentation today.

Yerba Buena SX80: Second. Well, I think the motion is actually slightly different. The motion is that we don’t need to see them again. But we’ll we’d like to make sure that Jen continues to carry through. To be sure that

Yerba Buena SX80: design considerations that have been discussed here are carried through the design build process. Okay, thank you. Jim. Yeah. Second.

Yerba Buena SX80: all in favor.

Yerba Buena SX80: Okay, unanimous.

Yerba Buena SX80: Okay.

Yerba Buena SX80: I think that is.

Yerba Buena SX80: that’s

Yerba Buena SX80: So let’s have a. Is there a motion to adjourn?

Yerba Buena SX80: Okay, all right. All in favor. All right. Thank you.

Yerba Buena SX80: Thank you. Everybody.