August 21, 2024 Sand Studies Commissioner Working Group

Perfect.

There we go.

All right, here’s some.

See some more people.

Yesterday I was riding my back bike out to the Bay and I

noticed that there were all these trucks going back and

forth on the road on sort of on the other side of a of a little

slew and I realized it was trucking coming back and forth

to deliver dirt to pond A to West where we are restoring a

marsh.

You know, we’re, there’s a pond there and we’re filling it in

for a marsh.

So that was very exciting to see.

We, you know, we’re working with dirt brokers to get the money

for, I mean, to get the dirt for free.

And so it’s very much dependent on the construction cycle.

But the staff who were working on this project are making the

magic work.

It’s really exciting.

Anyway, I thought this group might care about that.

Yeah, we are definitely caring about that and working on making

it happen.

Yeah, that’s our other commissioner working group.

So looks like we have Andy.

People are still feeling filling in, so I think I’m gonna.

I’m wondering if I should unplug myself from the system or not.

You always wonder, right When you have multiple screens going,

should you be on three, two or one?

So do we see Pat yet?

Yeah.

I should be here.

I’m sorry.

I meant Barry.

You are here.

OK?

Yeah.

Brenda’s clearly losing her mind trying to keep it all together.

Oh, there’s Barry.

He’s right in the middle of my screen.

So I think we have all the commissioners.

We have Bill Butler, we have Aaron Holloway, we have

Christian Marsh.

And I don’t see Erica yet.

I’m here, Brenda.

OK, good.

Thank you, Erica.

So I think.

Oh, and Mike, so we have the sand miners and so we have the

commissioners, we have the sand miners, we have the independent

science panel members.

I’ve got Elias, one of our presenters I’m looking for.

Sorry, there’s a million of you on the screen.

Thank you all for joining.

I am looking for Lester and of course, he’s in New Zealand.

So always a little bit of a lag and I think it’s early in the

morning for him still, so we’ll give it another minute.

Anybody got any good jokes?

I think you just joined.

There’s Lester.

OK.

I think we have all of the people.

All of you are very important, but we have all the people we

need to make this rock’n’roll.

So Pat, I will turn it over to you.

Well, first, I want to welcome everyone for taking part in this

process.

It’s, it’s very important that we do this as just one of the

components that we need to do to make the the region of San

Francisco Bay more resilient to climate change, which I know we

were all very committed to.

And we’re of course, concentrating on being able to

build sea level rise, sea level rise protections, and also just

the, the, the, the functioning of the Bay as an economic and an

ecological engine in our community.

So with that, I’m going to start off with an informal roll call

of the commissioners and, and the staff.

So Catherine, could you help us with that?

Yes, Commissioner Nelson, I’m here.

Commissioner Gunther, Chair Showalter here.

And then BCDC staff who will be supporting this are Brenda

Gaiden here and Greg Scharf here.

We have everyone.

Thanks.

OK, thank you.

And Brenda, you’re going to go over some ground rules.

Yeah, I’m going to just quickly remind folks that we’re all here

in a collaborative effort to best understand the science of

sand and sand transport in the Bay, understanding that sand

mining is an actor in this realm.

When?

So we’re gonna have basically presentations, We’ll have a

moment or a period for the sand miners who are the principals on

this issue to provide comments and then we’ll open the

discussion for commissioner questions first.

But the audience is absolutely or the participants, not

audience participants of the commissioner working group are

welcome to raise their hand and join in.

You will call on folks in order.

We’re going to try to stick to a schedule, but we have, I think

ample time for discussion today hopefully.

And if you want to put questions in the chat, we’ll also try to

mind the chat and have that as a place where people can put

questions if they are thinking of something and don’t want to

forget before the time comes to chat.

There is a public comment period, the last part of the

meeting.

So if you want to make a public statement, that is the time to,

you know, make like a comment that’s overall versus discussion

about the studies.

I do want to note that the independent science panel

members, our esteem group who have been overseeing these

studies for now, gosh, it’s been four or five years.

Bob Battaglio, Dave Schulhammer and Craig Jones, I believe are

here with us today.

And then we also have Lester McKee who’s going to present

from SFEI and Edwin Elias from Del Terrace.

I’m gonna note that we these are both folks from the

international community.

Del Terrace is in Netherlands and Lester’s home base is New

Zealand.

So appreciate them spending weird times of the day.

It’s tomorrow for some of them with us.

I know it’s not necessarily the best time of day for you all,

but we appreciate you being here.

Are there any questions on that?

No.

OK, I’m going to quickly, quickly just do framing for the

group and I will.

You’ll probably all disappear, so hang tight.

Let me get my screen up and running.

OK, Can you all see this?

Someone has to say yes ’cause I can’t see you anymore.

Cannot see it.

OK, I’m gonna try to escape back out.

Try again.

A new dub.

Triple screens was a bad idea.

OK, how about now?

Can you see that?

Oh, here we go.

Sure.

I have to hit the button twice.

Of course we have to hit the button twice.

Now we can see it.

Brenda.

OK, excellent.

Thank you.

Thanks for pausing for my technical difficulties.

OK, so this is the BCDC stand Studies Commissioner working

group.

We’re focused here on the science that we have learned

over the last several years and I’m just going to give a high

level overview for those who may be joining for the first time.

So the process that we’ve been engaged in for the last several

years is BCDC along with the water Board, the EPA.

No, not the EPA.

They don’t issue a permit.

State Lands Commission leasing and the Army Corps of Engineers

permitted sand mining in 2015 as part of BCD CS requirements.

We required that the arm that the sand miners provide $1.2

million towards the study of sand transport and issues around

what it means to take sand out the sand system of the Bay.

We formed a technical advisory committee, which had a host of

the agencies that are involved, both regulatory and resource

agencies, as well as a few of the interested parties,

including the Coastal Commission because they’re interested in

the Outer Coast and Baykeeper.

The technical advisory committee formed management questions.

They helped develop study scopes, they developed and

requests for proposals, and they reviewed proposals as part of

their process.

We selected and we’re honored to have an independent science

panel of some very esteemed folks who’ve been working on

sediment for most of their career of many decades.

And so that includes, as I mentioned, Bob Battaglio, Dave

Schulhammer, Craig Jones, Paul Work, and also John Legere, two

of which are not here with us today due to other commitments.

But their job was to help us review the proposals.

They helped revise some of the scopes.

They helped us identify the science teams, identify and

select the science teams.

They worked with the science teams over a period of a couple

of years, two years to complete the studies and keep things

aligned.

There are multiple quarterly meetings and check insurance.

And then they developed a findings report that summarizes

the work of across the studies.

We are now in the commissioner working group phase.

So we are here to discuss the study findings.

We had a first meeting in July on July.

We have this one one coming up on in September and then

November.

And our process is leading to the next stages, which sequent

NEPA is ongoing with state lands right now.

I don’t know what’s happening with NEPA at the moment, but

we’ll be looking at permitting in 2025.

So these were the study questions that were asked.

There are multiple tiered questions below, but to not

overwhelm everybody with questions on a slide, the first

main question was, is mining at existing lease areas at

permitted levels having a measurable or demonstratable

impact on sediment transport and supply within San Francisco Bay?

There was questions about sustainability of this activity.

What were the anticipated physical effects of sand mining

at permitted levels on sand transport and supply within the

Bay and the outer coast?

What’s that connection?

And then the impacts to active sand and what’s feeding it,

whether or not the sand was old or if it’s new sand.

We heard a little bit about that last time.

And are there feasible alternatives or approaches to

mining sand in San Francisco Bay?

The studies admittedly could not address all of these questions.

We had limited funds and limited time.

The independent science panel was able to kind of sift through

the studies to help us identify what we could answer with the

information that we thought we could get through the studies

and help direct the studies to focus them.

So these were the questions we started with.

We did not answer all the questions.

We’re perfectly clear and honest, transparent about that.

We did what we could with the time and money that we had and

with the ability for us to understand this very large, very

complex system that is San Francisco Bay.

Just a quick, quick, quick overview.

So the lease areas here is the Central San Francisco Bay lease

areas.

The primary sand type is coarser grain material, which is the

left pile in the slide.

There is some sand along Crissy Field, the Presidio Shoal, which

is that finer grain sand that you see in the right part of the

the right pile in the slide.

Sassoon Channel lease area.

This is the lease area that we have up in the most eastern

extent of the Bay and the sand is fine sand.

Oops.

And then the last lease area that we have is middle ground

Shoal.

It is also fine grained sand, just as a reminder of where the

areas are that we’re talking about.

The equipment is hydraulic, so hydraulic mining, two different

drag head.

Well, one’s a drag head on the left, which is the Martin

Marionetta set up with a fish screen.

That silver tube that you see in both slides, both pictures is

the fish screen to exclude fish and then lens suction pipe which

is on the right.

And just as a reminder of the framing of the mining

activities, it is for construction aggregate.

It is not navigation dredging.

And because this is mine specifically for the aggregate

industry, it’s not really considered a beneficial reuse In

the LTMS lexicon.

Mining occurs year round.

There’s no work windows on mining.

There is a reduced period of time in which mining occurs in

the early, I guess it would be late winter to to reduce impacts

to our smelt lining.

Mining locations are based on the leases and the grain size.

So when the miners get an order for a particular type of sand

they reach, they go to that area of their lease to retrieve that

type of sand and mining happens often in the same area.

And you’ll see that in some of the meeting, in some of the

presentations that Edwin is going to provide today.

And why am I not moving?

OK, there we go.

Last.

I think this is my last slide.

We’ll get you in just a second, Jim.

So the questions that we looked at last meeting, well what we

did at last meeting was we had the independent science panel

members Dave Schulhamer and Bob Battaglio gave an overview of

the findings report, which is on BCD CS website under the Sand

Mining Commissioner Working Group and the UT Austin folks.

Zach Sickman presented the provenance and aging work that

they did and that study is in Appendix G along with all the

other studies.

And then lastly, the questions for today are listed in the

agenda.

But how does relic sand is?

How does how does mining affect relic sand or sand in transport?

And how much sand is there in the Bay?

And how does mining affect the budget?

Again, we cannot completely answer these questions, but

these studies presented today by Edwin and Lester will look at

volumetric change analysis and what that tells us about sand in

transport or sand in place.

And Lester will go over the sand budget.

And I think that is my last slide.

It is.

So I’m going to do my best to stop sharing.

And Jim, I saw that you had a hand up.

Did you want to quickly ask that question?

And you’re on mute.

I’m sorry, I just must have bumped that button.

I didn’t have a question.

Oh, good, thanks.

So that’s just a quick overview of where we are in case

anybody’s new or has forgotten anything.

And if there are any questions or thoughts at this time, we’re

happy to entertain them.

If not, we’ll turn the presentation over to Edwin.

OK, Edwin, I think you Brenda.

Yep, Sorry Brenda, this is Jen CU at EPA.

I do have a quick question and I’m haven’t really been involved

in this conversation on the mining side more.

I’m in the dredging world as you know why no work windows?

Well, the project proponents went through consultation with

US Fish and Wildlife Service, NOAA Fisheries, and they have an

incidental take permit from California Department of Fish

and Wildlife.

And the biological pinions did not recommend work windows.

They did recommend fish screening, but I think, yeah, I

think that’s that they did not find that it was necessary for

this activity and there is mitigation required of the

miners to cover the incidental take of the mining activity.

So they did note there would be take, but they did require

mitigation.

So I think that is the best and simplest answer for now.

Thank you.

We can talk more later if you’d like.

You’re welcome.

OK, Edwin, I think you are up.

OK, thank you.

And let me try to get everything going here.

OK, we can see your slides and that’s in presenter view.

Don’t know if you want to switch to full screen.

Oh, how did I do that one?

So on my screen, it’s full screen, unfortunately.

Hey, Edwin, on the three dots, the three dots on the right,

there’s hide presenter view.

There you go.

That’s the one, Marilyn.

Thank you.

So we always use Steam and not zoom in Europe.

So I guess that’s one of the differences between US and and

Europe.

I think you can all see the presentation now in, in full

screen.

Yes, thank you.

Well, let me first start with saying thank you for allowing us

this opportunity to present, maybe explain some of the

findings we have.

We understood the, the, it’s, it’s complex and we understand

and we, we also know that there are questions and hopefully we

can answer some.

So what I try to do is, is just do a very general overview of

the work we’ve done, the methods we used and also the reasoning

behind it because I think that’s the most important.

The work I’ve done is was done with a whole group of folks at

Deltares with floor to Ruwink and myself being the principal

investigators.

You may wonder why Deltares is involved because we are a Dutch

based well Research Foundation actually, but we have a very

strong ties with San Francisco Bay.

So I was actually stationed there with uses for almost 11

years doing a lot of work in the Bay Area and one of the first

assignments I had with the sand waves in the Golden Gate region

and it was maybe 15 years ago already.

So it’s a very interesting area and we’re very happy to

participate in the research and hopefully we could contribute

nicely to the cause.

So what I’ll present today is very briefly a our calls and

objectives.

And well, I’m not going to present the steady area, you all

know it all too well.

But I will show you a little bit of the available data and then

I’m going to jump to or I’m going to focus to the results

for West Central Bay.

And that’s where I’m going to really try to explain the

methods and the the reasoning behind our analysis.

And I’m going to run you through that for West Central Bay.

And I also have some slides prepared for Sassoon Bay.

But that’s really the the findings.

But to make things a little bit more digestible, because it’s a

lot of different data, a lot of different figures, I try to

focus on West Central Bay to provide you with most of the

insights.

So let me just go to the next one.

So Brand already showed the overarching questions that were

underlying the research with the questions we were tasked to do

were actually 4 diff, 4 different parts.

1st is a very detailed analysis of the mining areas, which we

call the ring analysis.

So I’m going to present the results of that one because I

think that will raise some questions from the descent

miners specifically.

So I’m going to focus on those results quite a bit.

Then we’re going to look into the bad forms, bad for mobility

because that allows us to tell to to maybe find relations

between mining areas and the surrounding areas.

The same codes for larger scale base scale morpho, morpho

dynamic change.

An additional task we’ve done together with USDS was, was from

sediment transport pathway modelling.

But that’s not part of this research or at least not what I

present today.

If you look at the available data, then we had, we focus on,

on basically two study sites.

We have West Central Bay and the Sassoon Bay and Middle Crown

Shoals.

And the data we have is, is actually five years of

bathymetric surveys for West Central Bay between 1997 and

2019.

And in the Sassoon Bay and Middle Crown we had slightly

less data.

So this is the data that we were able to work with.

And so all of our findings, all of our our real analysis is

based on this time frame.

And if you really want to talk about base wide morphodynamic

change, then of course this time frame is not long enough to

resolve that.

So we need to do a lot of interpretation, use expert

judgement, use other maybe other studies, user experience in

other systems to translate the findings from this from this

data to the overarching questions on what does this mean

for the overall settlement budget that Lester will present?

Or also what does this mean in, in the scope of sea level rise.

The data we have is is really, really beautiful data.

So I really have to compliment you for the poor site in

acquiring this data.

It’s not often that we have multi beam data available of

such high resolution and quality that we can work with.

And what you see on this screen is a is West Central Bay.

So the bathymetric maps based on that multi beam data that we

made in for the 1997 measurement that’s on the let me get a

pointer here.

That’s on the left panel.

This is the 1997 measurement.

What you see here is the sea floor.

If you would drain the entire West central Bay.

The blue areas are the really deep areas and the yellow areas

are the shallower areas, the Shoals or the the rock

pinnacles.

You can see this in the 1997 bathymetry.

You can see this for the most recent bathymetry we have on the

right.

That’s the 2019 bathymetry.

And if you kind of look from a very broadly, they look the

same.

It’s the same colour scheme.

It’s both blue, it’s both yellow.

It’s, but if you look in these maps, you can also already see

some differences.

One of the one of the things you actually notice are for example,

these really nice sand waves.

So that is the basis for our a platform analysis.

And you can see these sand wave fields in both maps.

So it’s not that mining changed that system completely that sand

waves are not in the maps.

But you can also see some effects of mining.

For example, if you look at these red dots, those are mining

lease areas, and you can see that the bathymetry changed

between 1997 and 2019.

So just looking, glancing at these maps, you can already see

that there is some effect of mining.

But what does this effect mean?

Well, to to really give you an answer, that’s where we need a

very detailed analysis and it’s not as straightforward as you

think.

It’s not because you see that things change that you cannot

can automatically say it’s negative or positive.

So we need to be very objective in that just because it changed,

it doesn’t mean it’s a very negative thing.

It it all depends on what you want or what you yeah, what you

expect from your from the mining effort.

So these maps are going to be, you’re going to see them

throughout the presentation.

So if there are questions, feel free to ask.

But I always use these colour schemes and kind of these

visualization techniques to show the data.

So Part 1 of the analysis that I’d like to explain is really

the local impact of mining.

So we’re going to focus on the lease areas and we’re going to

really try to quantify how much impact we have from mining on

the platform bathymetry.

And to do this, we use a method that was outlined by by E Track

in back in 2018.

They called it the ring analysis.

You kind of see the principle in this plot where you see these

little polygons around these bounding boxes, around the

different lease areas.

And in these bounding boxes you can compute the battimetric

change.

So based on the measurements, we can compute how much battimetric

change we have based on the dredge record.

We can also compute how much was actually removed from these

areas and the difference between the two.

So the ratio between the two, that’s what we call the recovery

factor and that recovery factor that becomes really important in

the interpretation of the results.

So here are the ring polygons for West Central Bay and here

you in the bottom plot, you can see that there is a similar

analysis for Sassoon Bay or for the Sassoon Channel.

If you look at the mind volumes within the lease areas in total

over the 2000, 8 to 2019 time frame, we have 5 and a half

million cubic cards of mining that takes place in the lease

areas.

But unfortunately the ring polygons that we have our

analysis based on the ring polygons.

In the ring polygons we only observe 4.4 million of mining.

So it means that still within the lease area there is mining

outside of the ring polygons.

That’s not a problem for in terms of the how do you call

that it’s, it’s not a problem in terms of the mining.

It is within the lease areas.

But we were, we were supposed or we were, we were hoping to use

the ring polygons to quantify the chains.

And we do this with two rings, an inner and an outer ring.

And that outer ring would help us define whether it’s a

diffusion effect where the mining will actually result in

changes outside the mined area.

But what we can see from these numbers is that the mining

tracks actually go through these ring polygons.

So that analysis we couldn’t fully do the way we intended to

do.

But so we have five and a half million mined of which 4.4

million in those in the lease area according to the dredging

records.

If you look at the mathematics, we can do a similar exercise

that we take and I’ve tried to outline how we do this analysis.

We take the two bathymetries, but this is for example the 1997

bathymetry, again, the 2019 bathymetry, and then the

difference between these two bathymetries that gives us the

volumetric change within each of these rings.

Volumetric change can be computed in two ways.

We can just look at the BET level difference between 2 maps

or we can do something slightly different which we call a

sediment thickness computation.

And what we do is we take the the the whole sequence of maps.

From these maps we create the minimum bathymetry, so that is

the minimum depth observed throughout the time frame.

And from that minimum depth, we compute how much sediment is

actually available in relation to that minimum bathymetry.

And that’s what you see here.

That’s a sediment thickness map.

This is kind of a difficult topic.

I think the most important thing to realize is that it does not

matter what method you use, whether you just compute full

metric change based on that level change or whether you use

the method we did with sediment thickness.

It doesn’t matter for the end result, the total change is

complete is the same.

The only, the only the reason why we use sediment thickness is

because it gives us a little bit of more information.

It helps us to define not only the change, but also how much

sediment is actually present during that timeframe and where

the mining is a big portion or a small portion of the sediment

that was active in the total system.

So it gives us a little bit more information, but it will not

change the findings of the volumetric analysis because of

that, that mining that takes place outside of the ring

polygons.

We used something we called an extended buffer analysis.

We use slightly larger areas to try to determine whether mining

also has a diffusive effect on the surroundings.

So if you do this analysis and now it’s a lot of numbers, but

there are only two numbers that are really important.

If we do this analysis, we can see that from the dredge records

there is 4.4 million mined in these different ring polygons.

And from the bathymetric observations we observe a BET

level change of 2.3 million.

So that means the BET lowered by 2.3 million, but there was 4.4

million removed.

So there is approximately almost 50% recovery over all the lease

areas.

So those holes that they dredge are filled in with sediments

either from the ocean or its relic sand or its sand that’s

already in the system.

But there is recovery of those dredge, the dredging of the

mining areas.

The one thing you notice is if you look carefully in this table

and over here you have the recovery rate.

This last column, the recovery rate varies greatly between the

different lease areas.

And what we observe is that there is a very different

response between the northern lease areas versus the southern

lease areas.

So the southern lease areas, the ones on the procedure shall have

a very high recovery rate while the northern lease areas have a

very low recovery rate.

And that becomes important in the interpretation of the

results.

And I’m going to try to explain that very simplistic because I,

I always find it that this is sometimes this is this difficult

concept to grasp.

So what I’ve done here is I’ve just draw, drew a box over San

Francisco Bay and I schematize that box into this vertical

column where I have water and where I have sediment.

And if you have an inflow, and this is a total hypothetical

case here, this is not the segment budget that Lester will

present.

But if you have an inflow of 10 million cubic yards or just 10

as a number and we have an outflow of 10, we can kind of

schematize this in this box.

And if there is an equilibrium state, so if the bed level is in

equilibrium to the water flow, then if 10 comes in, 10 will go

out.

That’s kind of what this segment budget will tell you.

So what if we include mining?

So we still have 10 coming in, but now we remove half of it

through mining.

Well, we can actually have two responses.

We can have a bat lowering or we can have a reduced flow because

the total sum always needs to be the same.

So if we have bat lowering with no recovery, so if the the

amount of mining results, if you mine 5,000,000 cubic yards, you

remove 5 million from the bed and the bed lowers by 5 million,

there is no recovery, then the total sediment budget remains

unchanged.

So there’s 10 coming in and there’s 10 going out.

So that’s important to realize.

So if you mine and there is no recovery, the overall sediment

budget of the entire thing, the amount of sediment moving to the

ocean in this case will not change.

But you have a local depth increase of the Bay.

So if you have high recovery, for example if you have 100%

recovery, you get the opposite response.

So there is still 10 coming in.

You remove 5.

But with 100% recovery the bet doesn’t lower.

Whatever you removed is filled in by the sediment supply that

came in.

So that means that you’re going to change the sediment budget so

less goes out.

So depending on the recovery, you have a local impact, you

lower the BET or you have a large scale impact on the

settlement budget.

So that’s two very different responses and that’s important

to realise whether and and you can base decisions on that.

What do you think is important?

Is this local depth increase?

Is that important?

That’s well, you can you can debate about that.

It’s not always the case.

Even just because you have a local increase, it doesn’t mean

that the system is negatively impacted.

I’m going to try to explain that a little bit better in the next

slides.

So if we zoom in on these protymetry, so these are the

exact same maps that I showed before, Blue is still deeper,

yellow is still shallower.

This is Polygon one that is just South of Angel Island.

This is that Polygon 3.

This Polygon 1 is right over here.

This is spring Polygon 3.

So this is Angel Island is is located right here.

But if you look, look in these two bathymetries where we have

very low recovery rates, you can actually see that through

because the mining and the spring Polygon, the local bed

decreased in depth and it did not recover with sediments.

So now the question is, is that important?

Well, if it’s not an important habitat, if no one, I don’t

think anyone will notice if you’re in -30 meters of water

depth, if that depth increases by 1 meter, is that a big impact

or not?

That’s something you have to decide.

It’s not by definition a negative.

If it’s in the middle of the Bay, you may say like OK, that’s

an acceptable loss or that’s an acceptable change.

So you have local bet loading, but no or very low impact on the

base scale set in budget.

If you go to show to the lease areas on procedures sold, for

example, we see a completely opposite behaviour over here.

We see that you mine, but you have a lot of recovery.

And what you can see in these ring areas here is sometimes

these are all different observations through the

different, different years.

You see that there is an impact of Miami.

You can see these little dredge holes, but the next year they’re

filled in again.

So in this area, the natural bat hardly is hardly affected.

If you kind of glance through your your eyes, you can see that

the bat forms kind of move on.

It’s the same structure.

There is very small local impact, but you did remove

sediment from the system.

So that has an impact on the sediment budget.

So it’s a totally opposite reaction to sand mining.

OK.

So that was the first part.

I was just looking at very much in depth into the mining areas.

And looking at how these mining areas respond differently with

low and high recovery rates, but we also try to do see whether

the mining areas had an impact on the larger scale sediment

budget.

And that’s where things become a little bit complicated because

the maps we have are really beautiful maps, but they only

cover a very small time span.

And if you look on more for dynamic scales on larger areas,

it takes a long time for change to happen.

So often you cannot get directly get those effects from short

term data.

But we can look at all kinds of different indicators to see if

we can see impacts.

One of the things we did was an extended ring analysis.

Another thing we did was to quantify platforms and mobility

and these platforms are really nicely illustrated here and we

try to understand the large scale settlement budget of West

Central Bay.

And I’m going to go through these results very quickly.

So if there are questions please ask him or after the ask him

after the presentation.

We have a lot of different, we performed a lot of different

ring analysis and we have lots and lots of plots.

So I’m only going to show one for and this is the one where we

had the most obvious results or the the result where we had the

most that we could analyse best.

And that’s for ring Polygon one.

So the extended buffer analysis, it basically just expands the

the ring Polycom that was drawn around the the mining area, it

expands it with all the rings up to a distance of a kilometre

almost.

And what you see in these colours, the red colours are

erosion.

So that’s bed loading and the green colours are accretion in

the bed.

And what you can see in these, in these maps and these are all

the different time intervals between the measurements, you

can see that there is more erosion around the mining area

some.

So some of that limited recovery is probably a result of sand

that came in from the adiation shore.

You can see that here in most areas you have some red more

redder colors around the the ring Polygon.

But we do have to state that the natural variability is probably

really large as well.

And that will become apparent in the bathymetric change analysis

that the Bay itself responds yearly or the bat level in this

in the Bay changes yearly depending on whether you had a

high flow year or low flow year, whether you had more wind or

less wind.

And there’s a lot of variability and you don’t fully capture that

with the six or the five parametric maps you had

available.

So we can say that there are indications that there is some

sand moving around from the Shoal into the the area and that

contributes to that recovery.

But you cannot contribute all of the erosion you see to the

mining activity.

That’s not a statement that we want to make.

Another aspect we we try to address is to see if platforms

can provide indications of of this larger scale effects.

And what you can see is that here are the lease areas again,

but you can see these really nice platform fields that are

located close to the lease areas, but close to a lease area

is not in the lease area.

So unfortunately we can detect lots of platforms and that’s in

the next slide.

We can detect a lot of platforms throughout West Central Bay, but

not exactly in the major lease areas.

And part of that that this discrepancy is just because in

these major lease areas here.

Let me just go back to this slide.

In this lease area you saw that the entire bed lowered because

of the the mining, there was less not a whole lot of

recovery.

So sand waves could not reform.

So we can get results for sand wave fields in the vicinity, but

not directly in these lease areas.

Over here we have a little bit more luck where the sand waves

are overlapping with the the mining areas.

So we did a lot of analysis to compute the transport and

migration rates.

And honestly the only real map that we can use to make

statistically meaningful correlations is the 2018

nineteen map because that’s the shortest interval between the

measurements.

If you really may want to make these statistical correlations,

even though the maps you have are, I know very costly to

acquire, it took a lot of effort to acquire, but you would have

to have a more frequent interval to really determine statistical

correlations in the platform fields.

But even with those limitations, we were able to derive the

sediment transport directions and rates for quite a

substantial portion of the Bay.

And based on these platforms, you can draw a couple of

conclusions.

Well, I’ve tried to make this one here is that over here, it

becomes quite difficult to link these platforms to these areas,

so I’m not going to do that.

And you have these rock pinnacles separating the two.

But over here, it becomes quite obvious that part of that high

recovery rate is probably because of these platform fields

that are from opposing directions, which also mean that

there is a convergence of sediment.

There is a lot of sediment that will actually travel to that

location and that explains why you have such high recovery in

this area.

OK, so in one last effort we try to do is to try to we try to

look at the larger scale segment budget based on these measures

between 1997 and 2019 and try to link larger scale batymetric

change in relation to the mining areas and what you see in this

plot.

All these little lines are artificial bounding boxes.

For each of these bounding boxes, we computed the vertical

change, and the vertical change is illustrated by these dots.

The larger dots show more vertical change.

Red is negative, that’s erosion, and green is accretion.

And what you can see that during a period of low mining

intensity, for example, 2008, 2014, there was actually a

positive, mostly positive feedback of the bed.

The beds are created during a period of high mining intensity.

And I’m, the way I phrase it now is, is I’m not suggesting

anything.

Let me, I’m, I’m going to come back to the words I’m going to

say now.

But during a period of high mining intensity, we also see

that the entire West Central Bay was negative.

There was a lot of erosion and we are not going to jump to the

conclusion that there is a link to the mining activity here.

The only thing we can say is that it’s very likely that

there’s a coincidence between this very high mining activity

and during this time frame, there was probably a very

negative balance of the Bay.

So maybe this was after major flood events or a dry period

that there was less sediment supply to the Bay, but it’s not.

We cannot make the correlation between mining activity and

overall response of the Bay.

That is just a coincidence that happens in these maps and we

cannot make that.

We cannot conclude that that that there is a relation between

the two.

I just wanted to make that clear because it’s very easy to

misread these figures in such a way.

OK, let me try to synthesize all of these results.

I know it’s probably goes really fast and it’s a lot of

information to digest.

One of the ways that I always use to try to, to explain

morphodynamic change is using this sort of stepped approach

where we, we call this the scale cascade, where we look at

different parts of the morphodynamics through time and

space.

So if we want to answer questions for the entire San

Francisco Bay, well, we cannot do that based on this study.

We need the settlement budget of lesser.

You need to do a full budget of the Bay and it’s going to take

decades to centuries to for the entire Bay to respond to morpho

dynamic change.

And what we’ve done is we analyzed mining events or a

couple of mining events.

So that’s completely on this spectrum of the Bay.

But through careful analysis and through expert judgment, you can

make links from the smallest scale, from the mining events to

the impacts on the large scale settlement budgets.

So one of the things we notice that on the smallest scale, you

can always see the impact of mining in the form of potholes.

Those always seem to appear and depending on the recovery those

fill in very quickly procedures show for example or they don’t

fill in at all.

And what happens then is then with the reoccurring mining then

the all of the potholes combined cause a depression in the

underlying show that on the time scale we looked at could not

recover fully.

So that show for example, in ring Polygon tree, this feature

over here that in our measurements that completely

disappeared because of the mining effects.

But maybe that’s not too bad that this Shoal is very far

offshore in the middle of the Bay.

So the impact of a disappearing Shoal is very low.

If you deepen the Bay in this part, maybe by half a meter, it

will not affect the waves near San Francisco.

If you really deepen Presidious Shoal where we actually saw that

there was very high recovery, then you would have an indirect

impact maybe on the shoreline.

If you deepen the shore the the Shoals, then the waves that can

propagate to the coast can actually become higher.

So the low versus high recovery is actually in a quite

convenient location in terms of indirect effects.

Deepening something that’s already really deep is less

cumbersome than deepening something that is shallow and

actually shelters the the shoreline that’s been needed.

So in that respect, the low versus high recovery seems to

work quite well.

Well, I think I covered most of the these these topics so on.

So depending on the recovery, you can have an impact locally

or you can have an impact on the larger scale.

If the recovery rates are low, as I mentioned before, then the

total settlement budget is less influenced and but that’s all

within reason.

So at some point, if you keep stretching, if you completely

deepen the entire Bay by meters and meters, so you have much

more tidal volume going in and out, then of course you’re going

to change the tides in San Francisco Bay.

So at some point you’re going to reach a tipping point that it

becomes too deep and then it becomes a problem what that

tipping point is.

Well, we can tell you you would need very careful modelling.

But I’m I can reassure you that the tipping point is probably

nowhere not reached right now.

And it’s very not even close to a tipping point because that’s

the the mining is too small scale for the the in relation to

the total sediment volume of the Bay to really have a major

impact on tidal propagation right now.

If you ask the same question in 100 years, I may give you a

different answer if you continue operations because then you

removed 100 times that 5 million or 20 times the 5 million

because it was a five year interval.

So, but at the moment that all seems that to me that did not

appear to be the biggest issue.

So if you remove sediments from an area that with high recovery

rates and obviously you do you do impact the sediment transport

systems and then you can can create the sediment difference

different deficit somewhere else in the Bay or you may reduce the

sediment supply to the to the outer coast.

This last point is maybe a little bit counterintuitive.

What I tried to say here is that if you remove sand, sometimes

it’s not completely apparent because you create a hole and

that hole can be filled in with silt.

So then the sand budget remains unchanged.

The sediment budget of course remains negative because it’s

filled in with mud, with a different material.

And as mud shows a very strong or fast response that can all

that can that that process can happen quickly, but you would

alter the Bay floor composition, which as a habitat may not be

the best or may may have and one wanted effect.

I think that were the main points I wanted to make at West

Central Bay.

Maybe maybe I should ask Brenda this one.

We can have a little pause for questions because I’m sure there

are questions about the method and the the results.

I also have some additional slides for the Sassoon channel

not displaying the method, but just showing the pure results in

terms of volume and butymetric change of the Sassoon channel.

So whatever you prefer.

Yeah, thank you so much, Edwin.

This was really helpful and I hope informative for everybody.

I think we should probably turn now to questions and discussion

for a few minutes because it is almost 11.

I think we got a little bit of a slow start this morning.

So I think I first need to do 2 things.

One, if everybody could please take a minute and just add your

name and affiliation in the chat because we do want to make sure

everybody who has joined is on the is on the interested parties

list, especially if you’re new to the group.

So please take a moment for that.

Sorry, I meant mentioned earlier, but in the meantime,

Erica and Bill and Aaron, did you have some comments you

wanted to share at this time?

And you’re all on mute.

So hi, Brenda, this is Erica.

Well, I guess Aaron, do you want to step in?

Well, yeah, I always think we’re just gonna say no, no comments

from us, but we would like to see the results on Sassoon Bay

presented because I think that’s important for Lynn Marine is

that the that’s where they do their mining.

So I think that’s where we’d like to see the the time spent.

OK, I think we do.

We have a fair amount of time for the the budget conversation.

So perhaps, Edwin, I don’t know how quickly you can do that

without turning all of our heads around in a circle.

But maybe if you could take 5 minutes or so and just run us

through so soon, that would be very helpful.

Thank you.

Sure, but the now I have to find the share button again.

Oh, sorry.

It should be at the bottom of your screen.

No, no, no, I I caught it.

I got it.

I caught it.

You can of course, we’re going to run into the issue of the

presenter mode, but I think we resolved that better button.

Three buttons again and then height.

Yep, there you go.

I should have left, I should have left this on screen, but my

apologies.

So this will be a very quick presentation because all the

methods and all the the techniques we did are the same.

One of the things you can clearly see in the Sassoon

channel is that is the the effect of mining you can see in

the we have we have less bathymetry.

See, well, what we’re looking at here is a 2014, 18 and 19

bathymetry.

Again, it’s the same colour scheme with blue with the deeper

channel, and yellow is the shallower part of the channel.

And you can also see these red lines or the outlines of where

you have the water versus dry land.

You can see that the multi beam doesn’t cover the entire reach

of the river, but what you can see in the mining area, that’s

the red dot.

Let me get the pointer.

You can see in 2014 it wasn’t mined a whole lot, but in 2018

and 19 you can see the cumulative effects of potholing.

Basically you can see all these little dots which are basically

individual mining events that create a depression in the bed.

And if you subtract the two bathymetry, so you do, if you do

a 2019 minus the 2014 bathymetry, you kind of get this

result where the light yellow colours are a small amount of

erosion.

And the darker it gets, the higher the erosion value

becomes.

So you can see this depression, you can clearly see it in the

the area.

So you see a deepening of the mining location, but what you

can also see is that the entire channel deepens and it deepens

on both sides.

So it’s not.

And from that observation alone, you can already tell that mining

is probably not the main factor in this overall deepening of the

entire channel.

It’s not that you capture all the sediment in the mining area

and that’s why the adjacent areas are depleted, because then

you would have a bias to the upstream or downstream side.

So apparently the entire system is just has lowered because of

the probably the, the, the, the amount of drainage from the

Sacramento River.

And that was also one of the underlying arguments why we say

that in West Central Bay that overall lowering of the Bay is

probably not due to mining because we also saw it in the

system channel.

So in the bathymetry’s you can kind of see that same response

with low recovery.

Sorry, I need to go do this a bit faster.

And that’s what was.

If you really zoom into that area, so now I’m just going and

I just went to the ring polygons, you can really see

that potholing.

You can also see that the mining volumes, which I summarized in

this table are a lot lower compared to the the volumes from

Central Bay.

But the vertical change in this ring Polygon was actually quite

substantially, almost 2 1/2 meters.

Unfortunately, in this area we could not identify bat forms

very close to the the mining area.

We did define some bat forms, but they were quite far away.

So any bat form analysis in relation to the mining areas, we

could not do in this.

In this area.

From the pics you can see that the recovery rates are quite

low, 1% actually between 2014 and 2019.

And if you look at mining impact on a slightly larger scale, we

did this extended ring analysis again.

Well, you can see that the ring Polygon itself, it’s dark red.

You see that in the channel there is overall erosion.

But as I mentioned before, the entire multi beam area actually

shows erosion.

So we, we can’t conclude that mining is the the main actor in

this erosional process.

I think that are the results that I wanted to present quickly

for Sasume.

Oh, actually I, I, I have one more slide.

I guess I did not prepare the additional slides as thorough as

thoroughly as I should have done.

But in this slide, it’s the same sediment budget analysis as we

did for Central Bay.

So we looked at the ring polygons, we identified other

similar polygons, computed the volumetric change and you can

see that everything is negative with the largest negative or the

largest vertical change in the mining areas.

The low recovery rates also suggest that, OK, it’s a large

local impact, but on the overall transport rates, it’s probably

it did not, probably didn’t change too much because whatever

you took out, that’s also the amount that bet lowered and you

did not.

So therefore you didn’t affect the overall settlement budget.

And I think that were the main conclusions here.

I hope that helps a little bit.

Thank you, Edwin.

OK.

So I think we can open it up to questions assuming Erin and

Erica and Bill that you don’t have anything further to say at

this time.

Yeah, nothing further, Brenda, thank you.

OK, So being commissioners, if you have questions, you’re up

first and the group beyond that will try to keep us moving just

because we are a little over time.

So Andy Gunther, it looks like you have your hand up first.

Thanks, Brenda.

Yeah, so I have two questions.

Thanks so much for this.

A lot of information crammed into a a, a, a elegant

presentation.

First question is on the Sassoon end.

So as I understood that we take sand out and we see the hole

that we left and we also see that there are changes in the

symmetry there that happened across the whole system.

So I am familiar with the old saying from the river

geomorphologists, which is that 5% of the flow carries 95% of

the sediment in the river.

And So what I’m wondering is in a major event like the 9798 San

Joaquin flood or something like that, could we theoretically,

from what you understand, kind of reform the whole bottom of of

that area so that in an essence the holes would fill in in one

episode of of or is that do we not move sand in that way

through the system?

I think your 5% is moved by the big storms analogy is quite

good.

So yeah, if you have a major flood event, you may be fill in

those holes.

There is, there’s a lot of material moving around the major

flood events, but the scale of such events should be, I don’t

know.

I don’t know if that’s a one in 100 year flood or whether that’s

a one in a 10 year flood or whether the time frame we looked

at because it’s a very limited time frame.

And yeah, I know your periods of drought and and maybe flooding

events are also on that same time scale.

So it’s possible that what we are looking at right now is just

a consequence of the five years of maybe low flow conditions and

not a whole lot of movement.

So I think your hypothesis could very well be be true, I think.

But I, I would say folks like Dave Schulheimer will probably

know a little bit better on how much how, how much sediment is

actually moved in suspension.

But yeah, I wouldn’t, I wouldn’t be surprised that during major

flood events a lot of infill would occur.

But it seems to me as we’re working here in preparation of

coming before the Commission with another permit, which

Brenda has a term of 10 years.

Yeah, it yes.

Well, the previous permit had a 10 year.

So, so I, I wanna be sure that we understand where we might be

just looking at, in our permit scale at, at, at A, at trying to

understand changes in the bed that actually happen on a

decadal, decadal scales.

And we shouldn’t just assume what we see is always gonna be

there.

So that, that’s what was one response to the Sassoon.

Andy, can I also have Dave speak to this?

Because I think Dave does have some expertise and there have

been some differences found from the river flow concept that I

think we’re looking forward deferring to Dave on questions

like this.

And I’m happy to do so again.

Yes, I think it’s important.

And also note that 19/8, the 2018 to 2019 bathymetry was

specifically done to try to capture those wet years because

we had a couple wet years.

And also note that we have bathymetry from 1997 to 2023.

So we’ve got 2 decades in there.

Dave, up to you.

OK.

The short answer, Commissioner Gunther, is that in Sassoon Bay,

looking at the total sediment supply, not just sand but for

all of sediment that the typical dry year or normal year, there’s

a slight bit of sediment accumulation in Sassoon Bay

being at the upper end of the estuary.

But during the really wet years, the 2000 sixes and I think it

was 2017, then we see a net export of sediment from Sassoon

Bay.

So it’s actually the large years move out the sediment

essentially as the soon Bay becomes fresh and potentially

even at Mallard Island anyway, more like the river, we lose

sediment.

So most years there’s a small amount of total accumulation.

And then in the really wet years, we see some erosion

taking place, Right, right.

But as we’re thinking about the impact of the area that’s mined

it, it seems to me like we have a situation where as we dig

these holes, those areas become much more hungry for sediment

and sand.

And you could have a situation with in a big year.

And I see Lester’s telling me 2017 was already was a big year.

And I, I, I, I would, I’m not exactly sure how the water flow

relates to the force that is coming through the Sassoon

region.

But we still could have a situation, couldn’t we, Dave?

Where you where these these holes we’ve dug fill in?

Even though the total transport situation is as you describe,

the velocity given that these holes question perhaps Edwin

could address is that given that these holes are in the channel,

there may be sufficient velocity there to prevent them, prevent

the finer sediments from filling in.

Most of these sediments coming in during the high flows are

gonna be very fine sediments, not the sand.

So, Edwin, I don’t know if you my, my, my gut feeling is that

the currents in in those holes are large enough where you’re

not going to fill them up with a bunch of mud.

They’re gonna remain as holes for the fines.

Indeed.

Yeah, Yeah.

And the and for the the core sands, I, I think if there’s

sand that can be moved around, then you create a large hole

that’s suitable for the position.

Theoretically it could fill in, but we did not see it in the

limited observations we had.

And if it fills in, of course, then it’s an additional deficit

to the Oval settlement budget.

And I think also one of the observations from your work

headwind that was really key was just the really very few bed 4,

but seemingly very little sand transport in Sassoon Bay, which

implies that those holes are not going to fill in with sand.

There just isn’t much sand moving there.

They’re not gonna fill in easily, not under the conditions

that we had during these measurements.

So I think that’s a very clear observation.

Am I correct then that this would be a hypothesis we could

test with ongoing monitoring during the period that we might

be conducting mining?

We know where these holes are now we can go look and see

what’s going on.

OK.

I want to move down to the Presidio Shoal where I have

another question, which as as you described, we have bed forms

coming in both directions and that seems to imply there’s

movement that fills up the holes we dig.

So as I understood what you said, that would be very, very

important with regards to the wave regime on the shoreline

there.

If we if we dug holes and it just got deeper and deeper, we

could influence the erosion.

OK.

So that’s an important thing for us to understand that happens

now as the way I’m seeing it, and this is, I’m glad we have

these.

I don’t have to do this kind of thing before the whole

Commission.

If we didn’t mine, the sand wouldn’t pile up there, right?

So, so in essence, we are taking sand from somewhere.

We just don’t know where it would have gone if we hadn’t

pulled it out ourselves.

OK, thanks.

Correct.

And if I can add a little bit to that 1, So it’s a very active

sediment regime over there, a lot of sand moving around.

You take out a little bit and we cannot see any observations.

We cannot see a clear correlation that well, we took

some out.

So now we see more erosion here.

And that’s where that remarks comes in that you created the

deficit, but it’s possible that that deficit is filled in by

fine sediments in shallower regions.

For example, if a lot of that sand was transported into South

Bay, you create a deficit in South Bay.

And then in South Bay is you have a very nice place where

fines can settle.

So then that accommodation space can be filled in with fines

deposition for the overall settlement budget.

That’s still negative, but you wouldn’t directly see it in the

sand budget, right?

But there’s right, but there we are even if we’re changing the

form of the Mass, we’re still conserving Mass here.

So, so it that there, there if we did a hole and there’s no

hole when we go back a year later, then then we have the

that material that deposited there would have gone somewhere

else because it won’t pile up.

Yeah, OK, thanks.

And I’ll just add that I think, and I would look to Mike Bishop

perhaps to give us a nod on this, that it’s these areas are

not filling up with fines because they keep going back to

get sand and they keep finding sand.

That’s why they keep going back to the same locations.

So we’re not to the best of my knowledge, and again, Mike,

correct me, we are not seeing it go from sand to fines at this

time.

That would be correct.

Thank you.

Mike, I understand what’s happening.

Pat, I see your hand up.

Thank you, Edward.

I really appreciated this, this presentation.

As Andrew said, it was very elegant and and really helpful.

There was one slide you went over much too fast for me,

actually several, but anyway, particularly one that showed it

had some black lines.

It was over kind of the whole Bay Area, the whole Bay sediment

it had had some black lines.

What do those black lines mean?

I think the arrow transport is what you’re referring to.

Yeah, I but I’m not sure what the arrow transport of what can

you go back to that?

Should should I just share my screen quickly?

Yes, please.

Yeah, I think this is the slide.

Do you figure you were referring to?

This is the one so, but you can see in this figure, I’m going to

try to blow it up a little bit.

So this is one of the figures you made to that in order to

conceptually understand the sediment transports that are

going on in relation to the platform fields and what these

black arrows mean.

These are the the high energetic tides that push in and out of

the Golden Cate and that are capable of transporting large

amounts of sediments if they are available.

So this whole area in the direct vicinity of the Golden Kate,

including this lease area, is probably fed by sediments that

push in and out of the Golden Kate.

But there isn’t a whole lot of sediment here.

So that may be one of the reasons why you don’t have a lot

of refill in this area.

What you can, what you can see here are these major platforms,

this entire Shoal area, these platforms are likely linked to

the flow acceleration around Angel Island and that kind of

creates these platforms.

But these platforms do not link up with these these areas

because they’re these are kind of linked to this process.

And that’s the other reason why this sediment won’t travel, at

least not in the time span of the observations to this area

within the in our reports, we try to conceptually describe

this.

And I just pulled one of the figures.

My apologies for not explaining it too well.

This is a very oh, no, no, that’s, that’s that’s very

helpful.

So in other words, in a, in this year, the transport was very

much from the Golden Gate into the Bay.

Well, it’s always like that.

You always have on these flood deltas, that’s the area we call

here that is directly influenced by the tides pushing in and out

of the Golden Gate.

That’s the flood delta that’s always influenced by the

sediment transport from the Golden Gate.

But apparently not.

There isn’t enough to refill this mining area completely.

So that part is on this these time scales, it’s apparently

limited.

And over here, it’s a completely different story because this is

has both sediment transports tides pushing in and out of the

Golden Gate.

You have the waves going along the along the coast.

So there’s a lot of littoral transport here.

There’s tides going back and forth into South Bay.

And all of these combined give a lot of energy to the sediment

transport.

So you have a lot of movement and high recovery in this area.

That’s our conception.

You, you can explain those differences.

Thank you.

That’s very helpful.

Right.

OK.

I have Jim’s hand up and I think this is going to be our last

question.

So we make sure we have time to get into the sand budget.

I think we’re still OK, but let’s try to wrap this piece up

and move on, please.

Thank you.

Thanks.

Fascinating stuff and I’ve been around this stuff for a while.

I hope you’ve all seen my letter of July 14th.

I did try to collect observations.

I’ve got 2 augmentations here which are based on direct

observation.

I, I used to race windsurfers at, at, at in front of the Saint

Francis every other Friday night in between races.

We would kind of hang out on the, on the submerged beach in

front of the seawall there.

There was sediment and, and transport, literal transport

cooking by us at a remarkable rate.

And there’s a, there’s a difference between the transport

mechanisms along the shoreline, which are literal and are one

way driven.

And you can get a budget for that from the the tip Shoal

dredging at the mouth of the Marina, the time it took to

refill the sub aerial deposition when they opened a an increase

in the tidal prism at the at, at at the Golden Gate National

Recreational Area, Presidio shallow.

Presidio Shoal is shallow enough and fed.

And I think there’s ample background information to know

that you’ve got sediment coming in from the ocean and, and it

goes in one, One Direction.

That’s very different transport mechanism than in the center of

the basin.

You have to have a Shoal which is shallow enough for wave

energy to, to disturb it and start it into the literal

process.

But a fascinating presentation.

The the the one point I wanted to make is that the redeposition

and refilling of the Presidio Shoal.

Doesn’t surprise me at all.

There’s a lot of literal way of energy.

Thank you.

Those observations are always the best.

The observations from the field and if they correspond with the

findings, that’s even better.

So thank you for your remarks.

OK, Thank you so much, Edwin.

So I just want to remind folks that if they want to read the

full study and you should because there’s a whole lot more

information on it.

It is in Appendix G of the sand findings report.

It is the second study in order of Appendix G And I think with

that, Edwin, thank you so very much.

We appreciate all the work you’ve done on this front and

coming to present today.

And I’m going to turn it over to Lester McKee.

And while Lester is warming up, I’ll just let folks know that

our next meeting, we will have Michael McWilliams presenting on

sand transport modeling, which will be even more information

and fun.

So get ready for that.

It’s coming up soon.

OK, Lester, we see your slides in presenter view.

Thank you.

And you’re on mute.

The little microphone button should be at the bottom of your

slides.

Got it.

You’re off.

Here you go.

So anyway, I got the same problem as Edwin that that

you’re seeing or are you seeing it in the in the appropriate

view?

It’s in the perfect view.

You’ve got it all straight.

Thanks, Lester.

OK, great.

Well, thanks everybody.

Again, my name is Lester McKee.

I’m a senior scientist with San Francisco SG Institute.

I’ve been studying sediments in the Bay and it’s watersheds now

since the year 2000.

And it’s a pleasure to assist you in this conversation about

how sand moves around in the Bay.

Let’s see, can we advance the slide?

How do we do that?

Here we go.

So just start off with a quick primer on what is a sediment

budget.

It’s a statement of the net quantity of sediment deposited

or eroded in a system balanced against the sum of sources and

external sinks.

Just to remind you that mass must be conserved, and I think

Edwin made this point very clearly.

That is, inflow minus outflow must equal the change in the

storage that we observe in the system.

So just repeating that again for a given control volume and

period of time, and we need to define both of those change in

the bed.

Functionally a change in elevation, but it could also be

a change in density or grain size or other things.

But functionally a change in elevation must equal inflow

minus outflow.

So it follows that if inflows are smaller than outflows, then

bed erosion must be observed in the system.

I want to make this last point loud and clear.

A sediment budget does not account for any sediment outside

the control volume.

That is all the sediment that’s stored in the Bay.

This is this other sediment is deemed permanently stored and

not dynamically in transport night, not dynamically part of

the sediment budget.

And I’ll make that point a few times more in the presentation.

So in our Bay, we set up a conceptual model to describe the

inflow terms, the way sediment is coming into the Bay and to

describe the way sediment is leaving the Bay, the outflow

terms, and these are the listed inflow and outflow terms you can

see that includes sand mining and dredging and wetland reuse

and wetland deposition and tidal flood control channel removal on

the outflows.

And for inflows, it’s the typical inflows we would see

into an estuary system inflow from our tributaries, in this

case the broader Central Valley tributaries as well as local

tributaries.

And then as being discussed already, this littoral transport

that occurs from what from wave forces along the beachfronts.

We also quantified the net change in the system that is the

baffinetric change and that was largely facilitated by work of

Bruce Jeff Jaffe and his team at USGS.

And then there is a a transport mechanism they of moving

sediment around by dredge materials disposal that is from

one pay part of the Bay to the other.

But in this case, it’s not a loss or a gain term, but rather

a just a movement of sediment from one place in inside the

control volume to another place inside the control volume.

Let’s see if I can move.

There we go.

So in our case, inflow and outflow and bed storage chains

change terms are all quantified such that we could rearrange the

conservation of mass equation to estimate the exchange for the

Pacific Ocean boundary.

We had no a priori assumption that it would be either in or

out, but rather the the budget would determine the net

transport direction.

So that that term is an unknown term in the budget and is done

by subtraction.

It’s the, it’s the balance of the inflows and the outflows.

I want to point out that there is very good certainty in the

sand mining numbers that we received from the sand mining

community and also the dredging numbers that we get from the

LTMS work.

So the disposal and beneficial youth numbers are all well

quantified.

However, the other terms are less certain, but we estimated

them using the best of, say, available science and the

methods and the results are well documented in the technical

reports that have been produced either through the study or in

past studies.

So I want to move now to just helping us to understand what a

settlement budget is lesser, Never mind, sorry, I was going

to say your slides weren’t moving, but they just did.

I apologize.

OK, so to help us understand how our Senate budget works, let’s

take a hypothetical example.

And this is actually similar to what Edwin described, but let’s

just run over it again.

Let’s assume that as there’s zero inflows from our tributary.

So in our diagram there you see zero input from the inflows and

let’s assume that there’s half a million metric tons of outflow

by sand mining or dredging.

From a simple sand budget standpoint, the Bay doesn’t

really care, but there was some outflow that was caused by

occurred from a removal.

So in our hypothetical example here, if we measured 0 metric, 0

million metric tons of sediment erosion from the bed, then since

mass must be conserved to develop to, to balance this

budget, there would need to be a half million metric tons flowing

out through the Golden Gate, sorry, flow in through the

Golden Gate from the Pacific Ocean.

And so you can see there a simple budget.

Now if we take the same hypothetical example and find

that in fact, there had been some bed lowering during that

same.

And let’s assume that it’s that it’s half a million as well,

since mass must be conserved to balance the budget.

Now there would need to be lesser amount flow in from the

ocean because that was accommodated by a bed reduction

and the bed elevation.

In this hypothetical case, the bed lowering balances the sand

out flow by dredging or mining.

And so there would be 0 in the exchange with the situation

through the Golden Gate Bridge.

And so that helps you perhaps to understand how the budget

conservation and mass concept works.

Now, if we take the same hypothetical example and find

that in fact there is some additional supply from the

tributaries, and let’s just pretend it’s 0.25 million metric

tons per year during that same period.

Since mass must be conserved to balance this budget, there would

need to be a greater amount flow to the ocean, in this

hypothetical case 0.25, to balance out the budget, and that

would flow out through the Golden Gate to the Pacific

Ocean.

So I hope these examples help you to understand how the

interim budget works.

Inflow or outflow through the Golden Gate from or to the

Pacific Coast as a result of the sum of all the inflow minus the

sum of all the outflows.

So you can think of the outflow term as a Ledger, an account of

the fate of the inflowing sediment in any sediment that is

eroded from the bed, that is the total mass that’s in transport

in this budget.

To note, because there is no change of stand storage in the

water column, that is we observed no trend in the

concentration during the budget period, there is no partitioning

of the changes in storage terms between the bed and the water

column.

So in our case, our budget is actually a bed sediment budget.

It’s an accounting of the fate.

That is what happens to the bed sediment and that additional

inflow from the watersheds during the budget period.

So now let’s talk about our assumptions for the budget.

We call this the control volume.

It’s the boundary contention and assumptions that set up the

construct of the mathematical budget.

So the spatial scale and extent that we included was everywhere

downstream from the Meladon cross section, essentially just

downstream from the the confluence of the Sacramento and

San Raquin River systems all the way through to the Golden Gate

Bridge.

Conceptually, the cross section that’s underneath the Golden

Gate Bridge, we included everything that is below head of

tide, that is everything that we think the tides are interacting

and moving sentiment around.

We assumed in this case that wetland deposition is

permanently stored and we are able to make that assumption

because we’re talking about a net process and our observations

in the Bay Area right now suggest that our wetlands are

still in the net depositional state.

In the future that could change.

But right now for this 20 year budget period, we assumed that

sentiment that moved into the wetlands is permanently stored.

And the accounting.

We chose was the period where there’s the most and best

quality data available which was 2001 to 2020.

That’s a 20 year.

And the active bid is any sediment that is exposed to

estrogen currents that is in transport at any time during the

accounting.

And so that’s what we call the active bid.

That is the part of the the bid landscape that is part of the

budget.

So now let’s move on to some results.

You can see now that we have different size arrows on this

diagram and those represent a relationship between the size of

transport for each of the different inflow and outflow

terms.

They’re not actually ranked on the basis of mass, they’re

ranked on the basis of order.

So don’t take this the actual areas of those areas to be

perfect indication of mass, but they give you a relative

relationship between the different inflow and outflow

terms.

What you can see from this diagram, this is the hull based

stand settlement budget is that the outflow is the the sand

mining is the largest outflow and it’s the second largest term

in the budget.

I need to wharfed a little bit by the change in and best metric

change.

It is roughly equivalent to the other slightly larger term best

metric change.

And so if we think about it, there’s a temptation to explore

what would happen to the budget if we were to turn off sand

mining by making it zero if one were to do this for the 20 year

accounting using the simple math, it wood forest an increase

in sediment outflow from the system.

But that assumes that there’s no other changes that would occur

if such a event if we were to turn off the send mining.

But this may or may not actually occur.

The system could also respond by less space metric change as

Edwin had discussed in the previous previous Pres Pres

presentation.

In this case, if we accounted for it all in a change change in

the bathymetric change, then it would be just .13 million, the

difference between 1.33 and 1.2.

Or it may cause a requirement for navigational dredging

somewhere else.

Or it might change the literal sand transport into the system

from the Pacific Coast.

Or it may also increase the sand supply to beaches.

But one cannot say from the budget, but what one can say is

as a large term and most certainly has an influence on

the system.

In contrast, if we were to turn off one of the smaller terms,

for example, stop issuing permits with the flood control

agencies to dredge their settlement locally, we’d like to

see a net gain in elevation in the flood control channels.

We could see local flooding as a result.

We could see some supply to the changing supply to the mud flats

locally or to the wetlands locally, but except at that very

local temporal and spatial scale, this would likely be

difficult to measure.

But mass must be conserved and so we would know that it would

be there somewhere.

We would rightly conclude that sediment removal by flood

control agencies has virtually no influence on the system wide

or the large scale budget, in stark contrast to the larger

budget term of sand mining, which we can say most certainly

has a large influence from the budget.

But from a budget standpoint we can’t say exactly what that

influence would be.

So now if we look at the sand mining, sorry, the sand

settlement budget for the Sun Bay, we see a similar

conclusion.

Sand mining is the largest term in the budget.

We can say it has a large effect but had not occurred during the

budget period.

There are a variety of options for the fate of that segment

that may have allowed bid gain to the bed to gain elevation.

It may have caused the need for more navigational dredging, or

it may have caused an increase in flux out to some Pablo Bay,

for example.

That other very large arrow in this diagram we cannot say, but

we can say it has a large influence in the budget, unlike

the other smaller terms in the budget.

Now if we look at the sand sediment budget that stands

Central Bay, we we have a similar situation.

Sand mining is also the largest term in this budget.

We can say it has a large effect at the scale, at the local scale

of the mining leases where there were in some cases only partial

replenishment, the bid level lowered by meters over the

decade with large morphologic, morphologic disruption.

So that’s what Edwin described, but if it had not occurred

during the budget, there are a variety of options for the fate

of that sediment.

It may have allowed the bed to gain meters of elevation in the

lease areas or if averaged across the House of abatement

and about 1.8mm of bed elevation gain could have occurred.

Or it may have caused the need for more navigational dredging

or may have caused a reduction in flux from San Pablo Bay or

from the South Bay.

You can see there’s some large arrows on the top left hand side

of this diagram that that potentially could have changed

or it may have caused an increase in flux towards the

Pacific Ocean.

We cannot say from the budget, but we can say it has a large

influence on the budget, unlike the smaller terms.

So now to the the questions that were asked in the primary for

this meeting.

How much sand is there in the Bay?

During the 2001 to 2020 budget, we can say that .545 million

metric tons per year of sediment came into the Bay from the

tributaries and from littoral sand transport along the

beachfront in the Presidio, and 1.33 million metric tons of sand

was sourced from the bed of the Bay.

The sum of the amount of sand that was in the Bay during this

2001 period from the budget standpoint was the sum of those

two terms .45 + 1.33 or 1.78 million metric tons.

So that is the that is the the sediment amount per year that

then needed to be accounted for that needed to be.

We need to determine what the fate of it was during the budget

period.

And all those arrows on the on the outflow terms on this

diagram show that the fate of that sediment, this of course is

this slide here is talking about the whole Bay.

That last slide was just giving the central Bay example.

I want to emphasize that we did not report legacy sediment that

is outside of our control volume.

That is the sediment below the active bed stored in wetlands or

in beach and dune deposits around the Bay.

These pools are in permanent storage from a budget

standpoint, as we define the control volumes and not actively

contributing to the same transport in the budget.

The volumes in these pools are massive compared to the budget.

I want to give an example of just how massive.

If we think about the surface area of the bed of the Bay, it’s

about 1200 square kilometers, square kilometers in that 1200

square kilometers in the 1m top 1 meter of that sediment,

there’s about 300 million metric tons of sand and permanent

storage.

From the standpoint of this budget, if we assume an average

bulk density of about 820 kilograms per meter cubed and

average sand content of about 30%.

So I want to if says again, we did not include this and S&S

and budget, these volumes are massive compared to the amount

of sand that’s in, in movement in in the control volume.

So how does mining affect the budget?

It was the second question in the in the in the outline for

this discussion.

Today, sand mining is the largest term in the meta scale

whole Bay sand budget and in the macro scale the soon and central

paid Bay budgets.

Mining undoubtedly has an influence on the Bay morpho

dynamics at these scales.

If sand mining were to be turned off, or maybe just a change, a

change in the volumes either increase or decrease.

Since sand mining is a large term, there would be large

changes to other elements in the budget, but which other elements

would change and the amount of change for each individual

element are unknown.

But mass must be conserved, and so there would be.

A concomitant amount of change in the other budget elements

that must add up to the change that we would would see from

either turning off or changing the thin mining volumes.

So thanks very much.

That’s the summary of the SAN budget for the Bay.

With that I’m willing to take questions.

Thank you, Lester.

So I guess at this point, we will again open up the

presentation to the sand miners.

And Erica.

Aaron, Bill, Mike, did you have comments you wanted to provide?

This is Bill.

Yeah, I think Aaron, Aaron has some comments that that he would

like to provide on behalf of the miners.

Thank you.

Sure.

I’m going to go ahead and share my screen.

Could you stop sharing Lester, please?

It says I can’t share while someone else is sharing.

Thank you.

Yep, there we go.

OK, I’m going to cover.

Let me just click through a couple slides.

We just want to cover a few main points, one of them Lester made.

But the important part we want to emphasize is that the sand

budget is really a balance of the sand that’s moving in and

out of the system, but it doesn’t include that large

reservoir sand.

So you know you wouldn’t apply it like you would a a financial

budget and how much you’re going to spend this year and next year

etcetera.

So that for that exercise, you need to take into account this

size of the large sand reservoir.

And then the next key point we want to make has to do with the

uncertainty.

So there is a lot of parameters that go into that sand budget

and the conversation of mass and all those different inputs and

outputs have their uncertainties.

And so because of the methods applied and assuming it’s all a

connected system, those uncertainties accumulate

throughout the Bay until you end up at that Golden Gate boundary

flux.

And so the the results at that Golden Gate boundary end up

having, you know, a significant uncertainty between the upper

and lower values.

So the lower, lower end of the values is actually a flux into

the Bay of 0.66 million metric tons per year.

The upper estimate is 1.1 million metric tons out of the

Bay with the best estimate at 0.25.

So that’s an uncertainty of, you know, over 300%.

So the things that make up that uncertainty are described in

Lesser’s report.

So bathymetric change is the big one.

So there’s a lot of uncertainty and all the different surveys

that were used with different methods over different time

periods.

So we understand that in the methods applied, the sand budget

variation or variability accounts for a 50% uncertainty

in that bathymetric change.

But the USGS reports that, oh, it could be up to 100%.

So that’s the largest and most uncertain term in the budget and

has A and significantly influences the the results

including the flux at the Bay.

Dry bulk density is another one.

I think it was assumed that sand was a, a single dry bulk density

for all the sand in the Bay, which we think there’s, it’s,

it’s probably more complicated than that.

And then the other important point we want to make is that if

there’s a lot of sand moving in and out of the Bay, you know,

it’s, it was described in the strategic stratigraphy report in

the last working group that there’s a, a large sand

reservoir that extends, you know, on either side of the

Golden Gate Bridge.

And, you know, in Lesser’s report, he highlights that

bidirectional fluxes are 10 times greater than the net flux.

So we’re talking about a large amount of sand moving both ways.

And what’s reported in the sand budget is kind of the net.

So the net is a fraction of what’s moving in and out of the

Bay.

And given that uncertainty, we don’t really know which way it’s

going.

So on in, you know, the span of, you know, years to decades, you

know, that could fluctuate one way or the other given the

uncertainties.

And then the last point we want to make, we appreciate the time

we got to spend with the researchers in the ISP

understanding the methods a little better.

But one of the issues we have is that the bathymetric change and

the mining, you know, are are are linked and the studies point

to, you know, both the Deltares maps we’re looking at here and

the USGS maps we’re looking at is that mining significantly

affects the bathymetric change at the local scale.

So it’s not as simple as if you turned off mining, you’d have

all this extra sand, you know, going out elsewhere throughout

the Bay.

You know, what would happen is that you’d have a lot less

bathymetric change.

So it’s important that to highlight that a lot of this

mining happens at at a depth that that sand would not

otherwise be mobilized.

You know, a lot of that active sediment and change occurs, you

know, in the in the upper layers as you see throughout the Bay,

you know, plus or minus a meter, whereas the mining areas are

going down several meters deep into that layer of sand below

the active bed.

So we, we think that’s an important point when you’re

starting to pick and choose which variables you’re adjusting

in the sand budget.

So that wraps up our our comments on this study.

OK, maybe I don’t know, Lester, before we go to Commissioner

questions, Lester, if you wanted to respond to any of that or if

Bob or Dave wanted to respond or Craig, we also have Craig here

this morning.

So if you’d like to respond, feel free.

And I see Lester, your hand is up.

Yeah, just quickly, Aaron, nothing you just said bothered

me.

I, I don’t find any, any, any inaccuracies in what you just

said.

I do acknowledge that there is an uncertainty in the flux at

the Golden Gate.

And what we did in our report was we gave a worst case

scenario.

And so I do agree that the air bands are very, very large for

the worst case scenario.

But that was done through a sensitivity analysis, not

through an air analysis.

And so the sensitivity analysis gives the worst case scenario.

It it assumes that all the inflow terms were maximized and

all the outflow terms were minimized to give a worst case

scenario.

And then you do the opposite and you go through that process

iteratively determined that the potential range of the of the

flux into and out of the system at that unknown term.

I would submit that the uncertainty in that number is

probably a lot smaller than that, but we just can’t quantify

it because a classic error analysis could not be done.

So the .25 at is our best judgment of the of the of of the

central tendency of the data.

The the best estimate that I do acknowledge that there is

uncertainty that probably includes the potential for flux

into the system.

But it’s it’s it’s all well documented what we did.

And and I and I do acknowledge that that’s the term that has

all the uncertainty piled into it.

Thank you, Lester.

Craig, did you want to comment?

And yeah, and maybe I just want to punt this a little bit to set

Edwin up to answer this.

You made a statement there at the end, Edwin or I’m sorry,

Aaron, that without mining we simply wouldn’t have a change,

which seems to suggest that you believe that definitively if

there was no mining, It’s all relic sand and that control

volume.

I think what we’re seeing is actually that that that mining

of sand is on the order of what Lester is seeing for other

sediment inflows.

So I, you know, I feel like that that final statement is a little

bit of a definitive statement that might mischaracterize what

we know.

We don’t know if we stopped the mining, what would happen to

that bathymetric change in the Bay.

And we don’t know that without that mining, it wouldn’t have

any effect on the overall budget.

I, I think that’s a bit of an oversimplification.

And Edwin, I think you, you touched on that a bit of what we

do and don’t know regarding bathymetric change.

So I might unto you for that.

I’m not sure if I can give you the right answer.

I, I, I did like, actually like, I appreciated the comments of

the descent miners actually, because we’re trying to, to, to,

maybe to, to, to give an analysis that also kind of

confirms what they’re saying as well.

So if you just look at the mathematical settlement budget,

whatever you take out is always negative.

But the mining also has a lot of positives.

There’s an economic value, there’s the sand is a resource

and you cannot just look at the negative and the sentiment

budget alone.

You also have to look at what is the impact maybe locally.

So locally mining has an impact.

If there’s no recovery, it deepens the bed.

But as Aaron, I think really nicely mentioned is that there

is a huge amount of sediment available.

And is that deepening of the bed such a negative effect that you

actually think it’s a negative or is it just taking out a

little bit of sediment that was already there?

And it’s substantial if you look at the total bathymetric change

because the, the the Bay is relatively in equilibrium.

So whatever you take out, you it stands out, but it doesn’t mean

that you’re distorting the entire system.

It’s, it’s in the amount that moves.

It’s substantial, but it’s a huge reservoir of sand

available.

And that’s also what we’re trying to or at least try to

address that depending on the location, whether you have high

or low recovery, you have a slightly different impact that

you may or may not feel is important.

And that that’s kind of the the reasoning I tried to outline in

my presentation.

I’m not sure if that really helped answer Craig’s question.

Thanks, Edwin.

And I’m going to go to Bob and then Andy and Barry.

So I do see your hands.

But I’m gonna let the independent science panel

respond again first.

Bob.

Yeah.

Thanks, Brenda.

Hopefully you can’t hear this rock’n’roll music at the coffee

shop that I’m at.

Nope.

Yeah.

I just wanted to say I put some comments in the chat.

I wanted to point out that the ring analysis would be useful to

identify the local changes in the sand mining areas that

Commissioner Gunther mentioned and I think if that can that was

extended into the future that could help look at this question

about large slugs of deposition etcetera.

So I think that’s a good tool.

Secondly, Commissioner Schollwalter mentioned, you know

the question about the big black arrows and I appreciated the

clarification that we were only looking at part of the littoral

cell the there.

The literature indicates that the sand that the Central Bay

Shoals and the mining areas occupy are part of a system that

includes the Ed bars outside of the Golden Gate and San

Francisco Bay all the way down to Pacifica.

So that’s if they’re all LinkedIn in a sense.

Third, we did correlate changes out at the San Francisco Bar in

Ocean Beach with changes at Chrissy Field indicating

somewhere around a 30 year lag in terms of a large slug input

and accretion at Chrissy Field.

And I, I put in the chat a couple of papers that I’ve

written on that topic.

Thank you.

Thanks, Bob And I as I turn it over to Andy for his question.

I also just want to remind folks that one of the reasons we did

multiple studies is to get multiple lines of evidence that

help us understand what this all means, right?

One study doesn’t answer at all.

And so we are literally pulling information from different

studies to kind of get an understanding of the system.

And if you think back to our meeting in July, the provenance

work helped us understand that the Sassoon sand is separate

from the Central Bay sand, right?

It’s no longer connected.

And so that speaks to some of what Bob just mentioned about

the outer coast connection to Central Bay because there is a

strong connection shown there in the Providence work and the

Providence work talked about Sassoon Bay having some

different origins at this point in time and age.

And with that, Andy, thanks Brenda.

One question for Lester, and it’s about the use of the word

sand and the word sediment and the the OR and then sand

sediment.

And I verify that there was you were like when you refer to

terms such as the material dredged by the flood control

agencies, you’re doing some kind of grain size correction there

or something to just figure out the sand.

They’re taking that total sediment, Yes.

OK, great.

Thanks.

And I just want to thank everybody for the the

particularly the our our independent science panel

members.

The there’s a lot of trying to make sense out of this is a

challenge.

This is a regular been a regular occurrence in my career.

Every time anyone studies anything at the Golden Gate,

whether it’s the any movement of any particles there is

overwhelmed by the, the, the daily versus the net transport.

And it’s a very challenging topic.

And I hope as we go forward here we can, it seems to me we’re

already framing the, the, there are both short term impacts.

Then there’s also things we have to watch for in maybe a two or

three permit frame at in order to make sure that we’re not

creating some kind of cumulative impact.

And then also this idea that there are certain episodes might

reset the system in, in, in a way.

And that we, these are their, their, I would like the staff to

really think about this as we go forward, is that there are

things that we’re, we’re identifying that we’re, we’re

really not going to be able to make any kind of definitive

statements about.

And, and so, so, but we that doesn’t mean we will never know

about these things.

And, and any kind of work, any kind of permit work permitting

going forward should really try and hone in on how we can use

ongoing monitoring to, to work on particular issues and not

lose these questions, you know, 10 years hand.

So that we’re really refining our understanding as we go

forward.

Thanks.

Thank you, Andy.

Just in response to that, a brief response.

So on the big reset to the system, there are other studies

that can help us understand that, that are not in this

collection of the five to seven studies we did.

So if you were to look at Bruce Jaffe’s work on Babe Athemetery

from 1850 to today, right before he retired and left me, I’m so

sad You don’t see a big reset of the system.

You do see net erosional and net deposition, but what you don’t

see is a big reset to the system.

What he was able to tract was sediment moving out of the

system from the gold rush.

And so I think, you know, we need to be cognizant of other

information that’s available.

What we’re presenting in this set of series is the recent work

that was done, which is the best and latest technology and

ability to study this work.

I mean, one of the reasons why Middle Ground Shoal only has two

surveys is because the technology had to catch up with

being able to do bathymetry in shallow water at an affordable

rate.

We can now do that.

We couldn’t do that before 2014 or so.

So but we will be looking to other lines of evidence as well

to help us understand the context and what’s all which

these studies fit you citing Bruce’s work did did was he

differentiating sediment and silt and mud and clay.

It’s, it’s bathymetric change overall, but you can see whether

the set the system is resetting through flooding.

We, we know the areas where the sand is so we can, we can look

to those to help us understand if in, you know, those time

frames we’re seeing resets of the system.

Is it time to have the public comment?

Oh, Pat, you’re keeping track.

Thank you.

Yes.

Is there any public comment?

Wait, didn’t Barry have a comment?

Did you guys hand down?

I think you may be answered his question.

Oh, actually I’m not sure how my hand dropped down.

I just, I don’t know.

Thank.

Thanks, Brenda.

I wanted to follow up on the exchange between Aaron and I

think it was Bob who responded about the, the, the, the, the

effect of bathymity with regard to dredging.

And I want to tie it.

I want to tie it back to what we heard at our last meeting where

we learned that one of the the one of the things that’s clear

about the majority of the sand we’re dredging out of the system

is that it’s relic sand.

I assumed that that that reinforced Aaron’s conclusion

that most of the net effect of dredging is deepening of

bathymetry.

Bob, I think it was you who said that that wasn’t entirely clear

from the, the work we’re discussing today.

And I just wanted to ask if you could tie those two threads of

evidence together.

Was that for me?

I’m yeah, it, it was, it was, I think it was you who had that

exchange with Aaron.

Well, actually I’m not sure, but I’ll just say that we did have

a, a discussion ISP sand miners and, and lesser and GHD.

And I think we addressed the question about the double

counting.

And I don’t think that’s a question anymore, although I

think it was a good question.

And, and I’m not sure what could, could you repeat the

other two questions that you had?

Oh, I, you know, I, I my one of the conclusion I, I our

conclusions I reached from our last meeting was that if most of

what we’re dredging is relics, and that that the net effect of

dredging is gonna be deepening of bathymetry.

And perhaps it wasn’t you, Bob, I apologize, but someone said

that it wasn’t entirely clear that was the case.

Yeah, I could address that and I’ll let someone else.

There is relic sand in the mining areas based on available

information and the the certigraphy fingerprinting

study, but that there is also relic sand in motion through the

golden gates.

So one of the confusing aspects is that we have relic sand

that’s moving now.

And so it’s not, they’re not exclusive relic.

And and in transport almost all the sand is relic essentially.

But I think the question is if you excavate sand from below the

bed, do you have no effect on the surface sands that are being

in transport?

And I think that’s a really good question.

However, where they’re sand mining, we do see the bed

lowering and changing.

So in our view, the surface is being changed and I’ll just

leave it at that that that and I don’t if anyone else wants to

jump in, Edwin, go ahead.

Sorry, I couldn’t find the hand in the in the system.

So actually I do, I do think that you have a point about

relic sand in terms of the lease number of lease areas.

It’s probably not evenly distributed.

You have number of lease areas where it’s very active, but the

the etching volumes are quite a lot lower in those areas.

The areas with hydrates volume are probably in the areas with

less sediment activity.

So you’re more likely to mine relic sand.

So in terms of the total volume, you’re probably right.

Yeah.

And Edwin, just for your background with the provenance

work, what the University of Texas, Texas at Austin found was

is that the age of the sand and its origins basically say that

the sand was laid down at the last Ice Age in Central Bay and

is a pool between the ocean and Central Bay, and it’s all that

very old sand.

And then Sassoon has slightly newer but also very old sand and

there doesn’t seem to be recent sand being deposited.

And I’m not gonna define recent off the top of my head, but I

think the general conclusion was is that all of the sand is truly

considered relic sand.

And so we should probably step away from those terms and talk

about sand in transport versus sand in place, movement versus

not movement, I think would be a better way to think about it in

our framing for the conversation now, because I think we have

pretty fairly definitive information that says this is

all very old sand.

And I’m happy to hear disagreement with that.

But I think that’s what the study tells us at large.

Thanks, Brenda.

Yep.

OK, public comment if any.

I think we’ve stunned everybody into silence.

OK, so last call, I don’t see any hands.

So thank you.

Yes, sorry, I just had a quick question actually for Lester and

I’m I’m one of the permanent council for the sand miners and

really appreciate the presentation.

This has all been fantastic.

It’s, you know, a lot of information and, and, and solid

analysis.

But I did want to ask there seem to be, and I think this is

getting to some of the questions from Barry and others last year.

There’s a slightly different statement that I thought I heard

from, from your presentation and from Edwin’s that Edwin was

seemed to be saying that if you’re removing sand from the

bed, but it’s not an act of transport that it’s possible

that you’re really not affecting the budget.

And then I’m hearing you instead say that that it has a, it

could, it would have a significant impact on the

budget.

But I’m wondering if you would comment on what does that mean

to the to when you say significant impact on other

terms of the budget, I’m assuming that that means that

for example, you could just simply have a change in

bathymetry.

It doesn’t necessarily mean an adverse change elsewhere in the

system.

And I want wanted to just confirm that that’s what what

you mean by significant impact or significant effect on other

terms.

And I think you’re muted.

Yeah, you’re muted.

You gotta unmute bottom left corner of your screen just it

just depends on where.

Yeah.

So thanks for that question.

I think it’s a question of scale and time.

But remember the settlement budget is a blunt tool, it’s an

average annual tool and it’s a miss balance tool.

So it demands that if you change one term, some other terms, one

or two terms must change.

So I think what we’re trying to say is that if you do change the

the volume or mass removed by one of the terms, for example

sand mining, then it’s going to demand in the budget that some

other terms change in the mass balance.

I think it’s more likely that if you, for example, were to mine

less sentiment from a, from a mining lease area, it’s more

likely that the, that the immediate impact would be a

change in the symmetry in that lease area.

But over a 20 year.

Or a 40 year.

Or some other longer time period, you could get a cascade

of a six.

That is that you could initially have a change in one element

that then might translate into a change in another element.

And the budget, the the toolbox that’s called the budget is is

too blunt to predict which other terms would change and when and

by what magnitude.

But the budget does suggest that they would change, but we can’t

say when and by how much and which terms exactly.

So does that, does that help help to answer?

You would use other tools to to get those questions.

The type of tools that Edwin described or modeling tools are

examples.

The budget could also be refined to be a more, to be a less blunt

tool.

For example, we could do if we had more detailed information,

we could do budgets for shorter time periods or smaller spatial

scales.

And as Edwin described, you know, you can do a budget right

down to the to the the footprint of a mining event.

So, so you could use a budget tool to to get down to some of

those more nuanced answers to the to the question, how would

the system change?

But this annual average 20 year budget at a whole system scale

doesn’t tell you can’t tell you exactly what the changes would

be and when and how they would temporally and spatially

arrange.

That’s helpful.

Thank you.

Pat, you’ve got your hand back up.

Yes, I do.

I just one thing I think might make it a little easier for us

to understand sort of the magnitude of everything is for

you to put a number in that box of the approximate amount of

sand that’s in the Bay total.

Because when we look at that, we don’t really have a feel for

we’re just talking about the change, right?

We’re not talking about how big the system is that that change

is on.

So I think that’s another thing to fit for us to think about in

the future is, you know, how big is the the sediment storage box

of the Bay total?

And you mentioned that it was massive and you and you gave a

figure, but I think making that a little more prominent would be

useful anyway.

So that’s, that’s just a comment.

May I, may I respond to that just by saying we would have to

then decide what we include.

Do we include all the wetlands?

Do we include all the same beaches?

Do we include just the 1m depth of the Bay or is it 10

centimeters depth of the Bay or is it 10 meters depth of the

Bay?

And so you get into the OR, or the whole earth because actually

the reality is that the, the sediment and storage is, is

essentially the lithos lithosphere of the Earth.

You know, how, how do you have, you know, and I’m perhaps being

a little bit silly to point out that, you know, the, the, the,

the, the geologic substrate of the Bay is a big, big volume

number.

And, and I can’t remember that off the top of my head.

How much stand is deposited in the Bay?

But I think it’s, I think there’s evidence that in some

areas it’s literally 100 meters of, of, of, of, of mud, sandy

mud sitting underneath the Bay.

So, so I couldn’t put a number on this figure without a lot of

input from the independent science panel panel and from the

broader sediment community.

So while I gave an example of 300 million, it was just to show

you that it’s a big, big, big number.

Well, that’s great.

And Lester, I think that my question sort of as a policy

maker here and your answer as a scientist is really that really

demonstrates the difficulty of converting this information and

making it honest and to information that we can use.

And so that was one of the things I wanted to talk about as

to close this meeting.

What is being done here is actually very difficult

intellectually and conceptually.

And I really appreciate all of the effort that has gone into

not only collecting this information, but massaging it

and, and analysing it and organizing it in ways that you

can explain it to people who are not part of your field because

that’s when it becomes, you know, so useful.

And so anyway, I appreciate you doing that.

And, and it’s good to find out why.

Well, that simple suggestion I had turns out to not be a good

idea.

OK, good to know.

But I, I didn’t say it wasn’t a good idea.

Rather, I just said it’s a difficult number to give you

without.

That’s that’s what I mean.

But it’s not, it’s not something you can just, you can just add,

you know, it’s a, it’s a hard thing and it’s, it’s probably

outside of the scope of what we’re doing right now.

So that’s OK.

I I mean, it’s good for me to know that.

So for all I really need to know is it’s a massive amount.

That’s the answer really.

I need to know it’s a massive amount.

OK, yeah.

I don’t need to put a number on it.

And, and we did try to, we looked at the concept of doing

deep sediment cores in the area of the sand mining activity to

figure out how deep it was and if it was sand layers or sand

and mud layers.

And that would have taken our entire $1.2 million budget just

to get the cores.

Not a good idea, but we couldn’t do it.

Maybe we’ll do it next time, who knows?

But I also will just say Edwin and Lester and Bob and Dave and

Craig, they all make it look so easy, right?

They do.

And we all know that’s not true.

That’s not true.

So anyway, with that, I think we can, I want to thank everybody

again for their contributions to this science and this and, and

answering these real life questions for us.

And we’ll look forward to our next meeting.

Do we have a date for that, Brenda?

Yeah, it’s coming up really soon.

We have two close together.

So I believe it’s September 4th.

Is it Kat is.

Thank you, Kat, for nodding your head.

I believe it is also from 11:50.

OK.

So we’ll see you back here in a matter of a couple of weeks

after Labor Day.

And upcoming is if you think this was fun, just wait for

Michael McWilliams and sediment transport modeling.

It’s a, it’s a what Evan Edwin did and more so, so we can talk

about flow now.

Well, from my point of view, this was both fascinating and

fun because I was learning so much.

So thank you to everybody.

And with that, I think the meeting’s adjourned.