Wetland

Restoration

in the South

San Francisco Bay

Salt Ponds

GOLD GOLD

TurningSALT into

Environmental

TurningSALT into

Environmental

MA

P 1

.S

ou

th S

an

Fra

nc

isc

o B

ay

Sa

lt P

on

ds

Pro

po

sed

fo

r R

est

ora

tio

n

Car

gill

oper

ates

five

sal

t pro

duct

ion

plan

ts in

th

e So

uth

Bay

and

is p

ropo

sing

to s

ell t

hree

of

them

. Thi

s m

ap s

how

s th

e ar

ea a

vaila

ble

for

habi

tat r

esto

ratio

n, o

ther

miti

gatio

n an

d re

stor

atio

n pr

ojec

ts, a

nd e

xist

ing

mar

sh.

Alv

iso

Pla

nt (

8,28

0 ac

res)

Bau

mbe

rg P

lant

(4,

760

acre

s)

New

ark

#2 P

lant

(6,

380

acre

s)

New

ark

#1 P

lant

(3,

930

acre

s)

Red

woo

d C

ity P

lant

(2,

840

acre

s)

Reg

ion

al f

eatu

res

Po

nd

s av

aila

ble

fo

r h

abit

at r

esto

rati

on

an

d

enh

ance

men

t

Le

ge

nd

Mar

sh

Dee

p ba

y, d

epth

s gr

eate

r th

an 1

8 fe

et

belo

w m

ean

low

er lo

w w

ater

Sha

llow

bay

, dep

ths

0 to

18

feet

be

low

mea

n lo

wer

low

wat

er

Tid

al fl

ats,

dep

ths

rang

e fr

om lo

wes

t tid

e to

mea

n tid

e le

vel

City

bou

ndar

ies

Hig

hway

s

Rai

lroad

Ede

n La

ndin

g, H

ayw

ard;

Pon

d A

4,

Sun

nyva

le; a

nd B

air

Isla

nd, R

edw

ood

City

(2,

390

acre

s)

Po

nd

s re

mai

nin

g in

sal

t p

rod

uct

ion

Po

nd

s cu

rren

tly

pla

nn

ed f

or

rest

ora

tio

n a

nd

no

t co

nsi

der

ed in

th

is r

epo

rt

02,

000

4,00

000

0M

e

02

4

1,te

rs

1M

iles

Rep

rint

ed b

y pe

rmis

sion

of t

he C

alifo

rnia

Sta

te C

oast

al C

onse

rvan

cy©

Wetland

Restoration

in the South

San Francisco Bay

Salt Ponds

TurningSALT intoEnvironmentalGOLD

Save The Bay has been working for four decades to protect andrestore the San Francisco Bay and Sacramento-San Joaquin Delta andto improve public access to its shoreline. We are committed to keepingthe Bay healthy, alive, and beautiful for future generations.

Author

Cynthia Patton

Document Production

Paul Revier

Layout and Cover Design

Cutting Edge Graphics(202) 265-9028

Acknowledgements

Save The Bay’s Estuary Restoration Programreceives generous support from:

The Wallace Alexander Gerbode FoundationThe Richard and Rhoda Goldman FundThe David and Lucile Packard FoundationThe Smart Family Foundation

Our gratitude to others who contributed to this publication:Marilyn Kammelgarn, Eugenia Larson, Briggs Nisbet, Laurie Schuyler,GreenInfo Network

To order additional copies of this handbook, please contact:Save The Bay1600 Broadway, Suite 300Oakland, CA 94612(510) 452-9261

or visit www.savesfbay

Cover and back photo credits

Herb Lingl Aerial Photography(415) 771-2555

Copyright @ 2002 by the Save San Francisco Bay Association1600 Broadway, Suite 300, Oakland, CA 94612

All rights reserved.

Printed in the United States by Sequoyah Graphics.1535 34th Street, Oakland, CA 94608

Contents

3 Executive Summary

5 Introduction

9 Existing Conditions in theSouth Bay Salt Ponds

9 The Solar Salt Production Process

11 Biological Conditions

14 Physical Conditions

16 Environmental Chemistry

19 Restoration Feasibilityand Costs

19 Restoration Feasibility

20 Restoration Costs

23 Restoration Opportunities

25 Restoration Challenges

25 Subsidence and the Resulting

Sediment Deficit

28 Salt Pond Desalination

29 Bittern Disposal

31 Lessons Learned fromthe North Bay Salt Ponds

33 Issues to Consider duringAquisition Negotiations

35 Conclusion

Executive Summary

T idal wetland restoration is desperately needed in the

South San Francisco Bay, as it is throughout the

San Francisco Estuary. The Estuary has lost nearly 95

percent of its historic tidal and riparian wetlands, and

scientists estimate 100,000 acres of restored tidal marsh are

needed to preserve estuary health for future generations.

Acquisition and restoration of Cargill Salt’s solar salt pro-

duction ponds, located at the southern tip of San Francisco

Bay in the vicinity of San Jose, California, would provide a

significant portion of this acreage while preserving existing

wildlife resources.

Working to reverse a century of degradation to the Estu-

ary, Save The Bay analyzed the feasibility of restoring the

South Bay salt ponds to tidal wetlands and related habitats.

We found that all 26,190 acres of South Bay salt ponds are

potentially restorable to a mix of tidal marsh, open water,

and related habitats that will provide tremendous ecological

benefit to the Estuary’s fish, wildlife, and water quality. By

acquiring 15,500 to 18,000 acres of salt ponds, state and

federal resource agencies can dramatically increase the

amount of special status species habitat in the South Bay

and make cost-effective habitat decisions on a regional scale.

To provide the best ratio of habitats, our feasibility analysis

concurs with the Baylands Ecosystem Habitat Goals Report that

approximately two-thirds of the South Bay salt ponds

should be returned to tidal marsh. The remaining ponds

should be retained as managed open water ponds to

preserve existing waterfowl and shorebird habitat.

4

TU

RN

ING

SA

LT I

NT

O E

NV

IRO

NM

EN

TAL

GO

LD

To determine restoration options and priorities,resource agencies must understand existing pondconditions because they will affect not only restora-tion options, but also the cost and speed withwhich restoration can occur. Based on theseconditions, which are detailed in the report, weranked the salt ponds by their relative ease ofrestoration and determined rough costs for tidalwetland restoration. High feasibility ponds haverelatively few constraints and can be restored totidal marsh in a rapid, cost-effective manner.Estimates for restoring high feasibility ponds rangebetween $1,060 and $1,265 per acre. In contrast,low feasibility ponds exhibit a variety of con-straints and cannot be easily restored to tidalmarsh. Estimates for restoring low feasibility pondsto tidal marsh range between $4,900 and $90,445per acre. The use of clean dredged sediment toovercome severe pond subsidence and acceleratethe restoration process significantly increases coststoward the upper end of this range.

Because not every salt pond will be restored totidal marsh, resource agencies have the flexibilityto select restoration scenarios that optimize habitatbenefits while minimizing restoration costs. Giventhe difficulty and high cost of restoring lowfeasibility salt ponds to tidal marsh, these pondsmake excellent candidates for managed microtidallagoons, decreasing overall restoration costs andproviding valuable habitat for waterfowl andshorebirds. Crystallizer ponds can be quicklyconverted to habitat suitable for shorebirds,especially the threatened Western snowy plover,which will further reduce restoration costs for thesalt pond complex. Applying this rationale to theacquisition area, we developed rough total restora-tion costs. Based on an acquisition area of ap-proximately 15,500 acres, we estimate interimmanagement and restoration costs for the SouthBay ponds to be in the range of $148 to $228million over a 20-year timeframe. This figure doesnot include acquisition costs.

Restoration of the South Bay salt ponds pre-sents many opportunities and challenges. Thecomplex’s characteristics and substantial size offerunique benefits not found in many wetlandrestoration projects, such as creating large blocksof contiguous tidal marsh; accelerating restorationefforts through varied pond topography andantecedent channels; and reusing treated wastewa-ter for pond desalination. While challenges to such

large-scale restoration exist—including preserva-tion of existing wildlife habitat, pond subsidencecoupled with insufficient sediment supply, andpond desalination—our feasibility analysis findsthat each can be overcome with careful planning,sufficient funds, and patience.

Public acquisition of the North Bay salt pondsin 1994 teaches us that interim operations andmaintenance (O&M) costs will be significant andmust be factored into any successful acquisitionpackage. Problems that continue to troubleNorth Bay restoration efforts could have beenavoided with adequate O&M funding to coverwater management, levee maintenance,bittern removal, and other related costs.Creation of detailed hydrologic models should bethe first step in the restoration process. Thesemodels will provide important guidance on keyissues such as restoring tidal action to ponds;minimizing risks associated with levee breaches;predicting salt transport; and assessingsedimentation needs.

Several issues merit careful consideration duringacquisition negotiations. In particular,decisionmakers must evaluate the failure tocapture important restoration opportunities byallowing highly restorable ponds in the East Bay toremain in salt production, especially when doing sowill lower the ponds’ ecological value. Some of thebest ponds for short-term tidal marsh restorationlie within the Newark #2 Plant, where Cargillplans to continue salt production. (Others arelocated in the Redwood City Plant, near thewestern end of the Dumbarton Bridge.) In someof these ponds, intensified salt production willincrease salinity above current levels, eliminatinguseful habitat for birds and other species. A well-crafted acquisition agreement will address this andother management issues.

Save The Bay condenses two years ofexhaustive research into this report, providingdecisionmakers and the public with a clear yetconcise picture of the opportunities and challengesto wetland restoration in the South Bay. Moreinformation is provided at our website,www.savesfbay.org, including maps depictingexisting pond conditions. We believe this is the firsttime any organization has compiled and analyzedthis vast array of interrelated data, adding newperspective to the public debate over salt pondacquisition and restoration.

Introduction

W etlands play a vital and often overlooked role in

maintaining a healthy ecosystem. They improve

water quality, provide essential wildlife habitat, act as natu-

ral flood control, and prevent shoreline erosion. More

productive than all ecosystems but tropical rainforests,

wetlands feed and shelter countless species, support a di-

verse plant community, and form the foundation of the

food web. They also provide other beneficial functions such

as educational and recreational opportunities.

Unfortunately more than 90 percent of California’s

original wetlands have been destroyed by diking, draining,

and filling. Many remaining wetlands are threatened by

pollutant runoff and loss of freshwater flows caused by

diversion projects. Riparian areas have been lost as creeks

are routed underground or channelized for flood control

and urban development. The San Francisco Bay Area—

the nations’ fourth largest metropolitan region—has suf-

fered severe wetland losses due to urban development,

agricultural conversion, and salt production. As a result, the

Bay Area has lost nearly 95 percent of its historic tidal and

riparian wetlands, particularly in the San Francisco and

San Pablo Bays. Scientists estimate that a minimum of

100,000 acres must be restored to tidal marsh to keep the

San Francisco Estuary vital and self-sustaining.

Determined to improve the health of the Bay and its

inhabitants, many citizens, agencies, and organizations have

set their sights on a 26,190-acre complex of solar salt pro-

duction ponds located at the southern tip of San Francisco

6

TU

RN

ING

SA

LT I

NT

O E

NV

IRO

NM

EN

TAL

GO

LD

Bay in the vicinity of San Jose, California (seeMap 1 inside the front cover). The restorationpotential of these ponds is enormous, and creatinga combination of tidal marsh, managed ponds,and related habitats in this region will improve Baywater quality and greatly advance recovery ofendangered species. Although Cargill Salt (Cargill)currently operates these ponds, it owns only 56percent of the land (14,760 acres). Since 1974, theDon Edwards National Wildlife Refuge (Refuge) hasowned the remaining 44 percent (11,430 acres),with Cargill retaining mineral rights for salt produc-tion. (See Figure 1 for specific land ownership.) TheRefuge was established after the purchase of theselands from Leslie Salt, Cargill’s predecessor.

After years of salt production in the San Fran-cisco Bay Area, Cargill decided to consolidate itsoperations in October 2000. Negotiations withstate and federal resource agencies are underwayfor sale of Cargill’s mineral rights on lands ownedby the Refuge (approximately 25 percent of theproposed acquisition area) and outright sale ofother Cargill lands. The potential acquisition areatotals between 15,500 and 18,000 acres, including1,400 acres of former salt ponds north of SanPablo Bay along the Napa River and roughly 600acres of submerged South Bay tidelands. Afterpublic acquisition of these areas, Cargill’s saltproduction acreage will decrease to 10,310 acresand occur primarily on Refuge lands. Cargill willcontinue to own 2,800 acres of ponds along thesoutheastern shoreline near the City of Newark (seMap 1). This acreage represents 11 percent of theSouth Bay salt pond complex. Cargill’s annual saltproduction will remain close to current levelsbecause it plans to increase its per-acre yieldthrough improved operational efficiency andmodified salt harvest practices.

Regional Planning EffortsThe San Francisco Bay-Delta Estuary is anecological treasure that supports enormousbiodiversity. Approximately 120 fish species, 255bird species, 81 mammal species, 30 reptile species,and 14 amphibian species live in the Estuary,relying on riparian and tidal wetlands for food,shelter, and breeding habitat. Nearly half themigrating birds on the Pacific Flyway and two-thirds of California’s salmon pass through theEstuary each year.

Because of their biological importance, broadcommunity support exists for protecting existing

bayland restoration. The first such effort resultedin the Comprehensive Conservation and Management Plan

(CCMP). The CCMP identifies 145 actionsnecessary to return the San Francisco Estuary tohealth, and it requires creation of an estuary-wideplan to protect, enhance, restore, and create tidalwetlands. By 1994, resource agencies had begun todevelop a shared vision for Bay wildlife andwetlands. The San Francisco Estuary Institute(SFEI), the California Department of Fish andGame (CDFG), the National Marine FisheriesService (NMFS), the U.S. Fish and Wildlife Service(USFWS), and many others collaborated on theBaylands Ecosystem Habitat Goals Project—ablueprint for future estuary restoration based onecological principles.

The Baylands Ecosystem Habitat Goals Projectwas a four-year effort involving more than 100 BayArea participants from public, nonprofit, aca-demic, and private sectors. It focused on ecologicalrestoration of the San Francisco Estuary, resultingin the Baylands Ecosystem Habitat Goals Report. Thereport identifies key indicator species for baylandhabitats, evaluates those species’ habitat needs, andprovides recommendations for improving their

The Bay Area has lostnearly 95 percent of itshistoric tidal and riparianwetlands, particularly inthe San Francisco andSan Pablo Bays. Scientistsestimate that a minimumof 100,000 acres must berestored to tidal marsh tokeep the San FranciscoEstuary vital and self-sustaining.

Bay wetlands from destruction and restoringdegraded wetlands and diked, former tidal wet-lands (known as “baylands”) to productive ecosys-tems. Several regional efforts have addressed

RE

ST

OR

AT

ION

OF

TH

E S

OU

TH

SA

N F

RA

NC

ISC

O B

AY

SA

LT P

ON

DS

7

habitats. The report also discusses how to connectthese habitats with surrounding wetland-relatedhabitats, such as intertidal mudflats, seasonalwetlands, streams, and uplands.

Despite the desperate need for tidal wetlandsthroughout the Estuary, the Baylands Ecosystem

Habitat Goals Report notes the importance ofproviding a range of interconnected habitats in theSouth Bay, including tidal marsh, mudflats,seasonal wetlands, managed saline ponds, andbuffer and transitional zones. For this reason, thereport recommends restoring 16,000 to 21,000acres of South Bay salt ponds to tidal marsh andmanaging 10,000 to 15,000 acres as shallow pondsfor shorebird and waterfowl habitat. In otherwords, only 60 percent of the South Bay salt pondsshould be restored to tidal wetlands. It also recom-mends that restored tidal marsh and managed saltponds be interspersed and that wide corridors ofsimilar habitat connect these areas. Naturaltransitions from mudflat through tidal marsh toadjacent uplands should occur wherever possible.Restored areas should be linked to each other andto existing or restored riparian corridors. Addition-ally, uplands, transitional habitats, and exitingwildlife resources should be protected, and theentire South Bay ecosystem buffered from urbandevelopment.

Recently the USFWS began developing tworegional plans for the recovery of threatened andendangered species whose survival depends on theregion’s tidal wetlands. These are the Tidal Marsh

Ecosystem Recovery Plan and the Snowy Plover Recovery

Plan. When completed, the Tidal Marsh Ecosystem

Recovery Plan will incorporate recommendationsdeveloped in the Snowy Plover Recovery Plan, defineecological goals for South Bay salt pond restora-tion, and offer guidelines for achieving those goals.The plan will emphasize reestablishment ofdiverse wetland habitats within the South Bay,including the range of habitats that would bepresent under natural conditions. In addition, theplan is expected to recommend wetland restora-tion designs that minimize engineering andongoing maintenance.

The San Francisco Bay Joint Venture (SFBJV)is a partnership that brings together public andprivate agencies, conservation groups, develop-ment interests, and others to collaborate in restor-ing wetlands and wildlife habitat in the SanFrancisco Estuary. The SFBJV strives “to protect,restore, increase, and enhance all types of wet-lands, riparian habitat, and associated uplandsthroughout the San Francisco Bay region tobenefit waterfowl and other fish and wildlifepopulations.” The SFBJV recently preparedRestoring the Estuary: Implementation Strategy of the

San Francisco Bay Joint Venture. The report outlinesmeasures to achieve these goals, centering largelyon habitat protection, enhancement, and restora-tion. It recommends several strategies for salt pondrestoration, including: restoration of moderate andhigh salinity ponds to tidal marsh; preservation oflow salinity ponds for diving and dabbling duckhabitat; incorporation of large ponds into restora-tion design; and retention of some high salinityponds for production of brine shrimp andbrine flies.

8

TU

RN

ING

SA

LT I

NT

O E

NV

IRO

NM

EN

TAL

GO

LD

FIG

UR

E 1

.L

an

d O

wn

ers

hip

of

the

S

ou

th B

ay

Sa

lt P

on

ds

Car

gill

prod

uces

sal

t on

abou

t 11,

430

acre

s of

pub

licly

ow

ned

salt

pond

s. C

argi

ll re

tain

ed m

iner

al r

ight

s on

thes

e la

nds

unde

r th

e 19

79 p

urch

ase

agre

emen

t th

at h

elpe

d es

tabl

ish

the

Don

Edw

ards

Sa

n Fr

anci

sco

Bay

Nat

iona

l Wild

life

Ref

uge.

Pon

ds o

wne

d an

d op

erat

ed b

y C

argi

ll (1

4,76

0 ac

res)

Pon

ds o

wne

d by

Don

Edw

ards

S

an F

ranc

isco

Bay

Nat

iona

l Wild

life

Ref

uge,

op

erat

ed b

y C

argi

ll fo

r sa

lt pr

oduc

tion

(11,

430

acre

s)

City

bou

ndar

ies

Rai

lroad

Hig

hway

s

Le

ge

nd

02,

000

4,00

0 Met

ers

02

4M

iles

1,00

1

Rep

rint

ed b

y pe

rmis

sion

of t

he C

alifo

rnia

Sta

te C

oast

al C

onse

rvan

cy

©

Existing Conditions inthe South Bay Salt Ponds

T o develop effective wetland restoration strategies,

restoration planners must understand the salt produc-

tion process and Cargill’s system maintenance requirements.

In the period between salt pond acquisition and restoration

implementation, facilities such as channels, pumps, tide

gates, levees, siphons, and pipelines must be maintained and

operated to preserve system integrity and prevent problems

such as those encountered in the North Bay salt ponds.

(Lessons learned from the North Bay salt pond restoration

effort will be discussed later in the report.) Restoration

planners must also know the existing biological, physical,

and environmental chemistry conditions found in the ponds

to determine restoration options and priorities. These condi-

tions also will determine the cost and speed with which

restoration can occur.

The Solar Salt Production Process

Salt production in the San Francisco Estuary has occurred

since the 1860s. The current network of South Bay salt

production ponds has been operated for approximately 50

years, with Cargill acquiring the ponds from Leslie Salt in

the late-1980s. Although its collective capacity is over 1

million tons, Cargill currently produces only 650,000 tons of

salt per year on its 26,190-acre pond complex. Depending

on the water’s salinity during system intake, this requires

approximately 40 million tons of Bay water annually.

10

TU

RN

ING

SA

LT I

NT

O E

NV

IRO

NM

EN

TAL

GO

LD

In the South Bay, five discrete “plants”—Alviso,Baumberg, Newark #1, Newark #2, and RedwoodCity—produce salt through solar salt production(see Map 1). Each plant consists of a series of saltponds that concentrate and precipitate Bay waterthrough solar evaporation. Final-stage processingplants currently are located in Newark and Red-wood City. (The Redwood City Plant may be partof the acquisition.) Salt harvested from all fiveplants is processed at these two sites.

The solar salt production process begins whenBay water flows into eight intake ponds. The waterenters the ponds through pumps or automatic tidegates that open at high tide and close when theBay’s water level drops below the pond’s waterlevel. Bay water is typically less salty than seawaterbecause it is diluted by freshwater from the Sacra-mento and San Joaquin Rivers, local streams andcreeks, and wastewater treatment plant discharges.This is particularly true in winter and early springwhen rain and melting snow increase freshwaterflows into the Bay. Therefore, Cargill normallytakes Bay water into its pond system during drymonths when the Bay’s salinity is highest. Theintake period begins in April or May and contin-ues through the fall. Once in the salt pond system,Bay water is called “brine.” It moves through thesystem by a combination of gravity feed and

pumping. Prevailing summer winds also push thebrine between ponds.

Brine begins its journey through the salt pondsystem in the evaporator ponds. (See Figure 2.) InStage 1 ponds, the water volume is reduced byroughly 70 percent, brine salinity increases, andsuspended matter settles to the bottom of theponds. In Stage 2 ponds, salinity increases furtherand gypsum (calcium sulfate) precipitation begins.The final Stage 2 evaporator pond, called the“pickle pond,” distributes concentrated brine (nowcalled “pickle” due to its high salt content) to thecrystallizer ponds. By the time pickle leaves thepickle pond each spring, 95 percent of the intakepond’s original water volume has evaporated. Inthe crystallizer ponds, the pickle undergoes its finalevaporation; here sodium chloride (common salt)precipitates at a rate of approximately 40 tons peracre. By September, the salt bed is five to eightinches deep and is ready for harvest.

Salt harvesting begins in early October andcontinues 24 hours per day until the end ofDecember. The ponds are drained and harvestedone at a time to minimize the time the salt is leftuncovered. Mechanical harvesters break up thesalt bed with a rotating “pickroll,” scrape thepieces up with a blade, and deposit the salt intohopper cars. The harvester cuts a swath thirteen

FIGURE 2. The basic salt production process (based on the ten-pond model in Ver Planck 1958).

Stage 1 Evaporator Ponds

Stage 2 Evaporator Ponds

Abundant Brine Shrimp

Red Color

POND 1(intake pond)

POND 2 POND 3 POND 4 POND 5

POND 6POND 7POND 8POND 9(pickle pond)

POND 10(crystalizer

pond)

GypsumPrecipitation

Begins

BayWater

HarvestedSalt

BitternGoes toBitternPonds

RE

ST

OR

AT

ION

OF

TH

E S

OU

TH

SA

N F

RA

NC

ISC

O B

AY

SA

LT P

ON

DS

11

feet wide and four to six inches deep. Diesellocomotives pull the hopper cars along a tempo-rary track laid on the crystallizer pond floor. Eachhopper car holds approximately two tons of salt.The harvested salt is then washed and processedfor industrial and commercial use.

After harvesting ends in late December, thecrystallizer ponds are flooded with a weak brinesolution to dissolve any remaining sodium chloride.This brine solution is returned to intermediateevaporator ponds to reclaim the sodium chloride.In April when the rainy season ends, the crystal-lizer ponds are dried, leveled with scrapers, andpumped full of new pickle.

Bittern, the hypersaline byproduct of solar saltproduction, is stored in bittern ponds located nearthe processing plants in Newark and RedwoodCity. Salinity in these ponds can reach 447 partsper thousand, which is nearly 13 times more salinethan seawater. Bittern’s high salinity and ionicimbalance—due to precipitation of carbonates,calcium, sulfate, chloride, and sodium from thebrine—is toxic to aquatic species.

Once bittern is produced, few options exist forits disposal. Prior to 1970, bittern that was not soldwas discharged into San Francisco Bay. By theearly 1970s, the federal Clean Water Act (33 USC1251, et seq.) and the state Porter-Cologne WaterQuality Control Act (Cal. Water Resources Code13020, et seq.)—both implemented by the SanFrancisco Bay Regional Water Quality ControlBoard (RWQCB)—prohibited bittern discharge tothe Bay. This marked the beginning of long-term,onsite bittern storage in bittern ponds. While somebittern continues to be sold for use in dustsuppressants and de-icers, much of the bitternproduced since the 1970s is stored within theSouth Bay salt pond complex. Recent operationalchanges have reduced bittern production, but thebacklog of stored bittern remains. Bittern disposalis therefore an important consideration whenassessing the feasibility of salt pond restoration.

As part of its operations, Cargill conductsnumerous maintenance activities in the South Baysalt pond complex, but the most common is leveemaintenance. Throughout the pond complex,extensive levee maintenance is required due toerosion, subsidence, and soil compaction. Cargilluses a floating dredge and a system of accesschannels entered through dredge locks to maintainthe levees. Most of Cargill’s regulatory require-ments stem from levee maintenance and dredgelock use.

Biological ConditionsSalt ponds dramatically altered the South Bayecosystem. The creation of these shallow ponds in aregion characterized by broad stretches of tidalmarsh changed the Bay’s hydrology, degraded waterquality, and reduced wildlife habitat, resulting insevere impacts to many tidal-marsh-dependentspecies. But the shallow salt ponds, coupled with theBay’s abundant prey of fish and invertebrates,began providing valuable waterfowl habitat. SouthBay salt ponds now provide important habitat formany bird species, as well as other flora and fauna.

Successful salt pond restoration must accommo-date a range of biological conditions that willimpact restoration feasibility. The three mostsignificant biological conditions are: (1) specialstatus species, (2) preservation of existing biologicalresources, and (3) invasive non-native species.

Special Status Species

Numerous special status species reside in the SouthBay salt ponds, including 2 plants, 1 invertebrate,25 birds, 2 fish, and 3 mammals (see Table 1). Thepresence of these species will complicate restora-tion planning and probably increase restorationcosts. Federal and state laws protect these speciesand their habitats and will strongly influencerestoration design and implementation. Ponds thatsatisfy (or could satisfy) the specific requirementsof special status species should be identified andassigned a high priority for restoration.

Although salt pond restoration will benefit somespecial status species (e.g., salt marsh harvestmouse and California clapper rail), other species,such as the Western snowy plover, may be nega-tively impacted by a loss of salt pond habitat (seelast column in Table 1). The dependence of manyspecies on South Bay habitats, combined with thedramatic loss of historic tidal marsh, mandatescareful planning and a willingness to maketradeoffs between habitat types. Our primary goalmust be to benefit those species most at risk, whileminimizing impacts to other species that rely onexisting salt pond habitat.

Preservation of ExistingBiological Resources

Preservation of existing biological functions is aconstraint to salt pond restoration. The mostsignificant impact of reducing salt pond habitat is

12

TU

RN

ING

SA

LT I

NT

O E

NV

IRO

NM

EN

TAL

GO

LD

TABLE 1. Special status species found in the South Bay salt ponds.

Probable impactReproduces of tidal marsh

Common Name Scientific Name Status1 in salt ponds2 restoration3

PLANTS

California sea blite Suaeda californica FE, EX X +

Pt. Reyes bird’s beak Cordylanthus maritimus palustris FSC, EX X +

INVERTEBRATES

California brackish water snail Tryonia imitator FSC X -

BIRDS

Alameda song sparrow Melospiza melodia pusillula FSC, SSC X +

Aleutian Canada goose Branta canadensis leucopareia FT 0

American peregrine falcon Falco peregrinus anatum FD, SE 0

American white pelican Pelecanus erythrorhynchos SSC -

Barrow’s goldeneye Bucephala islandica SSC 0

Black skimmer Rynchops niger SSC X -

Black tern Chlidonias niger FSC, SSC -

Burrowing owl Athene cunicularia hypugea FSC, SSC X 0

California brown pelican Pelecanus occidentalis californicus FE, SE -

California clapper rail Rallus longirostris obsoletus FE, SE X +

California gull Larus californicus SSC X -

California horned lark Eremophila alpestris actia SSC X 0

California least tern Sterna antillarum browni FE, SE X -

Double-crested cormorant Phalacrocorax auritus SSC X 0

Elegant tern Sterna elegans FSC, SSC -

Long-billed curlew Numenius americanus SSC +

Northern harrier Circus cyaneus SSC X 0

Salt marsh common Geothlypis trichas sinuosa FSC, SSC X +yellow-throat

Short-eared owl Asio flammeus SSC X +

Tri-colored blackbird Aegelaius tricolor FSC, SSC X 0

Western least bittern Ixobrychus exilis hesperis FSC, SSC X +

Western snowy plover Charadrius alexandrinus nivosus FT, SSC X -

White-faced ibis Plegadis chihi FSC, SSC 0

White-tailed kite Elanus leucurus SSC X 0

Yellow warbler Dendroica petechia brewsteri SSC X 0

FISH

Coho salmon Oncorhynchus tshawytscha FT +

Steelhead Oncorhynchus mykiss irideus FT +

MAMMALS

Pacific harbor seal Phoca vitulina richardsi MMPA X 0

Salt marsh harvest mouse Reithrodontomys raviventris halicoetes FE, SE X +

Salt marsh wandering shrew Sorex vagrans halicoetes FSC,SSC X +

1 Acronyms: federal endangered species (FE), federal threatened species (FT), federal species of concern (FSC), federal delistedspecies (FD), state endangered species (SE), state threatened species (ST), state species of special concern (SSC), protected underMarine Mammal Protection Act (MMPA), and locally extinct (EX).

2 This includes species that currently reproduce, historically reproduced, or could potentially reproduce in the area.3 Symbols: positive impact (+), negative impact (-), and unknown or negligible impact (0).

RE

ST

OR

AT

ION

OF

TH

E S

OU

TH

SA

N F

RA

NC

ISC

O B

AY

SA

LT P

ON

DS

13

the potential reduction in migratory bird healthand population. Many species depend on the saltponds and adjacent tidal marsh for breeding,foraging, over-wintering, and migratory habitat.Some of these species were not historically abun-dant in San Francisco Bay, but because their historichabitats were greatly reduced (e.g., Central Valleywetlands), these species now rely on the salt ponds.

To balance the needs of various species andprovide the best ratio of habitats, the Baylands

Ecosystem Habitat Goals Report recommends return-ing roughly 60 percent of the South Bay salt pondcomplex to tidal marsh. Based on our analysis, weconcur with this finding. The remaining pondsshould be enhanced and managed as other wet-land-related habitats, particularly shallow openwater areas of varying salinity and depth.

Phasing salt pond restoration will optimizehabitat benefits for all species. Other restorationprojects have taught us that interim conditions—those existing from the time tides are reintroducedto the site until the emergence of tidal marsh—provide varied and significant ecological functions,especially for shorebirds and waterfowl. Forexample, a deeply subsided salt pond progressesfrom a tidal lagoon to a low intertidal mudflat to ahigh intertidal mudflat before becoming a veg-etated and fully channelized marsh. During thisevolution, the site provides dabbling and divingduck habitat that transforms into and coexists withwading bird and probing shorebird habitat. Fishuse also changes over time, especially as inverte-brates colonize these areas. These varied functionsare important to a variety of wildlife and should beenhanced through phased restoration.

Because restoration on this scale has never beenattempted in the Bay Area and wildlife use of thesalt ponds varies from year to year, we must adaptour plans as the restoration effort proceeds.Resource agencies must make ongoing adjustmentsto ensure adequate protection of all wildliferesources. In other words, adaptive managementwill be essential to the restoration process. This isparticularly true in the case of invasive plant andanimal species.

Invasive Non-Native Species

Salt pond restoration may provide new habitat forinvasive non-native species, which can be ex-tremely harmful to native species. The mostserious invaders in the South Bay are smoothcordgrass, Norway rat, and red fox.

Smooth cordgrass (Spartina alterniflora) is anaggressive non-native plant that poses a seriousthreat to the success of future tidal marsh restora-tion throughout the San Francisco Estuary. Theplant was introduced to the Estuary in the 1970s as

To balance the needs ofvarious species andprovide the best ratio ofhabitats, the BaylandsEcosystem Habitat GoalsReport recommendsreturning roughly 60percent of the South Baysalt pond complex to tidalmarsh.

part of a tidal marsh restoration project in Pond 3,located on Coyote Hills Slough near the AlamedaCreek flood control channel. Smooth cordgrass isnow well-established in the South San FranciscoBay, impacting about 1,000 acres located south ofthe Bay Bridge. The East Bay shoreline betweenthe San Mateo and Dumbarton Bridges is heavilyinfested with S. alterniflora.

Newly restored wetlands are especially vulner-able to invasion by smooth cordgrass. Seedsmigrating on tidal currents germinate easily inareas with disturbed soil and limited competitionfrom other vegetation. Three East Bay restorationsites—Cogswell Marsh, Oro Loma Marsh, and theMartin Luther King, Jr. Shoreline—were quicklycolonized by S. alterniflora in the initial stages ofrestoration.

Control of this highly invasive species is beingstudied by a multi-agency task force called theInvasive Spartina Project. Currently no satisfactorycontrol measure has been identified. Consequently,resource managers have suggested that tidal marshrestoration along the heavily infested East Bayshoreline occur later in the restoration process,allowing scientists more time to develop andimplement effective control measures for

14

TU

RN

ING

SA

LT I

NT

O E

NV

IRO

NM

EN

TAL

GO

LD

S. alterniflora. If control measures fail, resourceagencies must re-evaluate the ecological implica-tions of tidal restoration in this area.

The Norway rat (Rattus norvegicus) and red fox(Vulpes vulpes) are predators of ground nesting birds,

Antecedent Channels

Tidal marshes have channels that carry water,sediments, nutrients, and biological organisms intoand out of the marsh with the ebb and flow oftides. If a salt pond retains remnants of theoriginal tidal marsh channel network (calledantecedent channels), restoration feasibility isincreased because antecedent channels provide atemplate for reestablishing channel networks inthe restored marsh. The easier it is to restorethese networks, the simpler and less costly therestoration effort.

Antecedent channels are present in every SouthBay evaporator pond, but not in the crystallizerponds. Aerial photographs reveal that thesechannels are more intact in some evaporatorponds than in others. Typical antecedent channelscan be seen in an aerial photograph of AlvisoPonds A5 and A7 in Sunnyvale (see Figure 3).

Borrow Ditches

Sediment removed from borrow ditches wasoriginally used to construct the salt pond leveesystem, and levee maintenance activities overdecades have continued to mine sediment fromthese ditches. For this reason, borrow ditches up to200 feet wide run alongside most salt pond levees.Figure 2 shows typical borrow ditches adjacent tolevees in Alviso Ponds A5 and A7 in Sunnyvale.

Borrow ditches can affect the outcome ofrestoration efforts for two reasons. The mostsignificant concern is the decreasing ability ofborrow ditches to provide material for ongoinglevee maintenance. While this need will decline asmarsh restoration occurs, some ongoing leveemaintenance will always be needed, especially nearponds retained as open water areas. Nevertheless,the presence of borrow ditches may be beneficialbecause the variable water depth provides a rangeof forage opportunities.

FIGURE 3. Typical antecedent channels asshown in an aerial photograph.

including California clapper rail and Westernsnowy plover. They often gain access to nestingsites via salt pond levees, and restoration activitiesmay provide new predator corridors. Restorationefforts must strive to limit dispersal of predators.Existing levees can be breached in strategiclocations to limit predator access. Restoration oflarge tracts of tidal marsh will also hinder predatoraccess to the marsh interior.

Physical ConditionsSuccessful wetland restoration depends on ourunderstanding and accommodation of physicalconditions that directly affect the feasibility ofrestoring salt ponds to tidal marsh. Six physicalconditions will determine the ease with which eachpond can be restored to tidal marsh: (1) theabsence or presence of antecedent channels;(2) the absence or presence of borrow ditches;(3) the pond’s hydrologic connection to tidal waters(i.e., its remoteness from the Bay or slough chan-nels); (4) the sediment deficit created by subsid-ence; (5) the surrounding landscape’s topographyand its potential for flooding; and (6) variousinfrastructure impediments. These physicalconditions will influence, and to some extentdirect, restoration planning efforts. Ponds that areless feasible for tidal marsh restoration should bestrongly considered for preservation as managedopen water ponds or other habitats.

Ponds that are lessfeasible for tidal marshrestoration should bestrongly considered forpreservation as managedopen water ponds or otherhabitats.

RE

ST

OR

AT

ION

OF

TH

E S

OU

TH

SA

N F

RA

NC

ISC

O B

AY

SA

LT P

ON

DS

15

A second concern is the way borrow ditchesaffect a pond’s hydrology, sedimentation, andecology. Once a pond is returned to tidal action,borrow ditches will significantly alter the channelnetwork’s hydrology and sedimentation pattern byshort-circuiting the flow paths. This will not onlyimpact water velocity, but will transport sedimentin an atypical manner. A new technique mayprevent borrow ditches from capturing tidal flows.By constructing a series of “cutoff berms” atstrategic locations in the borrow ditch network,restoration scientists hope to prevent the ditchesfrom siphoning off flows in the restored marsh.

Hydrologic Connection to Tidal Waters

The character of each pond’s hydrologic connec-tion to the Bay fundamentally affects its ability tobe restored. Two factors determine how easily tidalaction can be restored: (1) the distance from orproximity to tidal waters, and (2) the existence orabsence of tidal marsh on the Bay or “outboard”side of pond levees. In the first factor, a pond’sdistance from tidal waters determines the ease withwhich tidal action can be brought to it. A pondcan have an open Bay edge, a tributary channeledge, or no tidal edge. A pond that fronts directlyonto the Bay provides the most effective tidalconnection and is often the easiest to restore. Apond that fronts a tidal channel, such as a creek orflood-control channel, might be more difficult torestore depending on the tributary channel’swidth, which can vary from a few to severalhundred feet. Narrow tributary channels reduce apond’s restoration feasibility because the channelsrequire enlargement to bring sufficient water to therestored pond. A pond with no tidal edge must becombined with other ponds in a multi-pondrestoration scenario. Approximately 20 percent ofthe salt pond acreage has no tidal edge. A case-by-case analysis is needed to determine how thisimpacts restoration feasibility.

In the second factor, the existence of tidalmarsh on the Bay side of salt pond levees (knownas “outboard marsh”) poses special problems forthe return of tidal action to that pond. Thesesmall, fragmented marshes must be preserved forthe endangered species that depend on them.Breaching levees in these areas is challengingbecause the breach may alter salinity or otherwisedisturb habitat in the outboard marsh. Thus, theexistence of outboard marsh significantly de-creases a pond’s restoration feasibility.

Based on this information, the optimal hydro-logic connection for tidal marsh restoration is anopen Bay edge without outboard marsh. Approxi-mately 11 percent of the South Bay salt pondacreage meets this criterion. The most challenginghydrologic connection for tidal marsh restoration isa tributary channel edge with outboard marsh.About half of the pond acreage falls into thiscategory.

Pond Subsidence

Existing pond bottom elevations are the result ofdecades of subsidence. Subsidence occurs for tworeasons: soil oxidation and groundwater with-drawal. Soil oxidation occurs when wetlands areisolated from tidal action and drained. As the soildries, oxidation results in soil compaction. Inponds drained as part of ongoing salt productionactivities, soil oxidation may cause limited subsid-ence. However, most South Bay salt ponds arecontinuously flooded, so oxidation is probably notsignificant. Groundwater withdrawal, on the otherhand, has caused considerable South Bay subsid-ence. Aquifer overdraft between 1912 and 1969resulted in as much as 13 feet of subsidence, withincreasing severity towards the south. The effecton salt ponds and adjacent land is readily visiblefrom Mountain View to San Jose. Consequently,many salt ponds require sedimentation to createbottom elevations suitable for tidal marsh.

The closer existing pond bottom elevations areto that at which marsh plants begin to colonize(mean tide level [MTL] to mean high water[MHW]), the more rapidly colonization will occurafter tidal action is restored. Where pond eleva-tions are substantially lower than MTL, it will takeconsiderable time for sedimentation to createsuitable elevations. If shorter timeframes aredesired, subsided ponds will need sediment aug-mentation with suitable fill, such as clean dredgedsediment.

Based on our review, approximately 60 percentof the complex’s pond bottom elevations arebetween MTL and MHW. In these ponds, plantcolonization should occur quickly during restora-tion, assuming other necessary factors are present.Approximately 20 percent of the salt ponds havemoderate subsidence and will take longer torestore to tidal marsh. The remaining 20 percentof the ponds have significantly subsided. Extend-ing from Mountain View to San Jose, most ofthese ponds have bottom elevations well below

16

TU

RN

ING

SA

LT I

NT

O E

NV

IRO

NM

EN

TAL

GO

LD

MTL. One pond—A3W in Sunnyvale—willrequire 7.9 feet of sediment to reach optimal tidalheight (mean higher high water [MHHW]). Forthese ponds, existing elevations are far too low tosupport intertidal marsh vegetation. If these areaswere opened to unrestricted tidal exchange, theywould function as open Bay water for decades.

Surrounding Topographyand Flood Control

Flooding from high tides is a fundamental risk formuch of the Bay Area. Salt pond levees providethe primary flood protection for large amounts ofSouth Bay property. Many (but not all) of theseareas have no other means of flood control.Therefore, an important consideration whenselecting which ponds to restore to tidal marsh willbe the extent and cost of levee reconstruction.

Public agencies currently maintain 17 miles offlood control levees within the salt pond complex. Incontrast, Cargill maintains 201 miles of levees, 21miles of which separate salt ponds from adjacentuplands. If the upland edge is sufficiently high,flooding is not a major concern, although erosionand related issues must still be addressed. If theupland edge is not high enough to protect adjacentland from flooding, a properly engineered floodcontrol levee must be strengthening or constructed.Salt pond levees, particularly the internal berms,were not designed for flood protection, so fullreconstruction often will be needed to meet currentseismic safety and flood control standards. Conver-sion of these levees entails more than raising leveeheight and will be costly.

Based on review of existing levees, about 21miles of interior pond levees must be converted toflood control levees. Ideally, the restoration planwill create the maximum acreage of restored tidalmarsh at a minimum cost for levee reconstruction.For example, Newark #2 Ponds 1, 2, and 3 (lo-cated between Mowry Slough and Coyote Creek)could be restored to tidal marsh by constructing asmall flood control levee between Ponds 3 and 6.In this instance, a single half-mile levee would yield1,500 acres of restored marsh. Additionally,techniques to better integrate these new levees intothe surrounding landscape—such as buildinglevees with gentler slopes and using native vegeta-tion for erosion control—should be adopted,rather than the traditional engineering approachof steep levee slopes with rock or concrete rubblerip rap for shoreline protection.

Infrastructure Impediments

Existing infrastructure can pose a barrier towetland restoration. Examples of infrastructureimpediments include overhead utilities, above- andbelow-ground pipelines, rail crossings, roads andbridges, structures, and flood control facilities. Todevelop cost-effective restoration strategies,comprehensive infrastructure information isneeded. Unfortunately, research on existinginfrastructure is complicated by the large numberof entities with potentially pertinent facilities, thevarious formats used to store relevant information,and the lack of a centralized database of suchinformation. While our research identified manyinfrastructure impediments, we also determinedthat a number of other facilities may exist, butwere not investigated. These facilities includestorm drain systems, petroleum pipelines, and fiberoptic cables.

Infrastructure impediments within the salt pondcomplex must be addressed during restorationplanning. Several types of structures could increaserestoration costs. Electrical towers generallyrequire vehicular access, concrete footings, andminimum line-sag clearance. As a result of restora-tion, some towers must be raised because theirconcrete footings lie below the increased waterlevel or they no longer provide minimum sag lineclearance from the ground or water surface. Thesolution in both cases is to increase the height ofthe tower’s concrete footings. Another type ofstructure that will increase restoration costs isunderground utilities that cannot be abandonedbut that lie at elevations that interfere with unre-stricted tidal exchange. Road and rail crossings, aswell as flood control facilities, can also limit orinterfere with tidal exchange. In addition, severalstructures that may qualify for historic preservationare located within the pond complex. For thesereasons, strategies to accommodate infrastructureimpediments can be difficult to design and costlyto build.

Environmental ChemistrySalt production over the past century has affectedwater quality and sediment chemistry within theSouth Bay salt ponds. Restoration efforts will beconstrained by these factors. For example, in theNorth Bay salt ponds, insufficient water inflowsdecreased sediment pH (i.e., acidified the sedi-ments) and made ponds inhospitable for plant

RE

ST

OR

AT

ION

OF

TH

E S

OU

TH

SA

N F

RA

NC

ISC

O B

AY

SA

LT P

ON

DS

17

colonization. Similar issues could pose a problemfor the South Bay salt ponds.

Water Quality

As brine passes through the salt pond system, itbecomes concentrated and increasingly saline.Exact salinity levels at a given pond vary seasonallyand annually due to climatic and operationalconditions, affecting pond water quality character-istics such as ionic imbalance, suspended solids,nutrient concentrations, temperature, dissolvedoxygen, and acidity. These characteristics affect theponds’ habitat value, but should be transitoryconditions once tidal flow resumes.

The water quality impacts most directly relatedto salt production are salinity and ionic imbalance.As brine evaporates, precipitation removes ionsfrom solution and alters the ionic balance. Theresulting ionic imbalance may be toxic to fish. Assalinity increases in subsequent ponds, differentbiotic communities establish themselves. Forinstance, water boatmen (Trichochorixa reticulata) arefound at low to moderate salinity levels, and brineshrimp (Artemia franciscana) are found in ponds withhigher salinity. Populations die off when salinityincreases above the suitable range. For instance,brine shrimp die-offs occur when salinity exceeds200 parts per thousand, resulting in potential odorproblems. In general, as salinity increases, habitatvalue decreases.

Pond Sediments and Gypsum

Salt production has also altered the chemistry ofpond sediments, although in some cases for thebetter. Contaminant levels in evaporator pondsediments are expected to be lower than thosefound in surrounding tidal marshes. While sus-pended sediments are a transport mechanism formany contaminants, including mercury, polychlori-nated biphenyls (PCBs), and dichloral diphenyldichloroethane (DDT), two factors suggest thatcontaminant accumulation within the salt ponds isless than that of surrounding marsh soils. First,detention times are relatively long in each pond(e.g., weeks or months). This water managementregime minimizes the import of suspended solidsinto the salt ponds. Second, biomass growth in theintake ponds can be relatively high. Macroalgaegrowth and subsequent settling may increase thesediment organic content and essentially dilute thecontaminants in these soils. For these reasons,

sediment contamination in the salt ponds ispresumably lower than in adjacent marshes.

Crystallizer pond sediments, in contrast, aretypically altered for the worse. In these ponds,approximately 95 percent of sodium ions and 80percent of chlorine ions precipitate from solution.Therefore, pond sediments will be hypersaline.Even after flushing, residual salts are left behind inthe sediments.

Another ramification of salt production is theformation of calcium sulfate (gypsum) on pondbottoms. The presence of gypsum may pose achallenge during restoration because it can form ahard, relatively insoluble layer on pond bottoms.This layer inhibits tidal channel formation, sedi-ment redistribution, and plant colonization.Gypsum impacts approximately 6,300 acres or 24percent of the salt pond complex. It will hinderestablishment of tidal marsh in one 310-acre pond(Baumberg 8A) and could hinder marsh establish-ment in another 2,140 acres of ponds scatteredthroughout the complex.

Before restoration can occur, ponds withhypersaline brines and sediments must be flushed.This flushing will also help dissolve accumulatedgypsum. In lower salinity ponds, dissolution is notgenerally an issue because gypsum remains insolution. In higher salinity ponds, gypsum precipi-tates from solution and dissolution probably willbe necessary. Gypsum dissolution depends on fivefactors: (1) the amount of gypsum in the sedi-ments; (2) the volume of water exchanged overtime; (3) the surface flow velocity; (4) the pond’swater chemistry, including salinity and tracemetal concentrations; and (5) the inundationperiod. Of the first four factors, salinity and watervelocity are the most important. Gypsum dissolvesrapidly at low salinity levels and high watervelocities (above 0.5 meters per second) if pondsare permanently inundated. Under these optimalconditions, gypsum in the pond complex could bedissolved in as little as four months. Intermittentinundation dramatically extends gypsum dissolu-tion time by a factor of ten. High salinity levelsand low water velocities further extend gypsumdissolution times.

The extent to which gypsum can impede tidalmarsh restoration is largely a function of pondelevation. In lower elevation ponds in whichsignificant accretion is needed (about 60 percent ofponds affected by gypsum) Bay sediment will burythe gypsum layer. In these ponds, the presence ofgypsum will have a negligible effect on restoration

18

TU

RN

ING

SA

LT I

NT

O E

NV

IRO

NM

EN

TAL

GO

LD

efforts. In mid- to high-elevation ponds whereelevations are closer to targeted levels, gypsummay persist for years, especially in ponds with aconsolidated gypsum layer. In these ponds (about40 percent of ponds affected by gypsum), gypsumcould hinder tidal channel formation, sediment

redistribution, and plant colonization, slowingmarsh restoration and recovery. For these ponds,rapid flushing with freshwater in a manner thatmaintains pond inundation will be imperative toquickly remove this constraint and enhance marshrestoration.

Restoration Feasibility and Costs

B ased on existing conditions found in the South Bay

salt ponds, we ranked ponds by their relative ease of

restoration and determined rough costs for tidal wetland

restoration. As shown on Map 2 (located inside the back

cover), we classified each South Bay salt pond into one of

three categories of tidal marsh restoration feasibility: high,

medium, and low. (We had insufficient data to classify 1,830

acres of ponds located primarily in the Newark #2 Plant.)

Our classifications reflect a cost-benefit analysis between the

money that must be spent to restore a given pond to tidal

action and the ecological gains achieved.

Restoration Feasibility

Restoration feasibility varies from pond to pond and de-

pends on many site-specific factors. Factors we considered

include the pond’s ecological characteristics, its restoration

constraints, and major structural elements. We also consid-

ered the ecological benefits and costs incurred by individu-

ally restoring ponds to tidal marsh or by combining contigu-

ous ponds for restoration as a large tract. (In cases where it is

easier to restore ponds in conjunction with adjacent ones,

our feasibility ranking is based on joint restoration.) Due to

the large number of feasibility criteria, ponds within a single

classification do not necessarily share identical reasons for

their classification.

20

TU

RN

ING

SA

LT I

NT

O E

NV

IRO

NM

EN

TAL

GO

LD

High Feasibility Ponds

A high feasibility pond requires minimal work torestore it to tidal marsh and provides considerableecological benefits. Because pond bottom eleva-

acres. Fifty-one percent of the salt pond pondswithin the South Bay complex fall into this cat-egory (see yellow ponds and green/yellow stripedponds on Map 2). These ponds can be restored totidal marsh, but require more time, effort, and costthan high feasibility ponds.

Low Feasibility PondsA low feasibility pond requires considerable workto restore it to tidal marsh. These ponds typicallyface one or more constraints: the need for newflood control levees; severe subsidence; infrastruc-ture that interferes with unrestricted tidal ex-change; and residual high salinities in pondsediments. Subsided ponds could be restored tointertidal elevations by natural sedimentation,which is time-consuming, or through the reuse ofdredged sediment, which would speed the processbut is very costly.

These criteria define a total of 40 evaporatorponds and all crystallizer ponds. Their total area is8,430 acres—32 percent of the salt pond complex(see blue ponds and yellow/blue striped ponds onMap 2). These ponds have the lowest likelihood ofmeeting ecological goals in a timely, sustainable,and cost-effective manner. Because these pondswill be difficult to restore to tidal marsh, werecommend using them for other types of habitatsuch as managed open water ponds and saltpannes (flat, unvegetated, hypersaline areas withseasonal ponds).

The Spartina alterniflora ConstraintSmooth cordgrass (Spartina alterniflora) presents amajor challenge to quick and cost-effective tidalmarsh restoration. Several ponds located on theEast Bay shoreline between the San Mateo andDumbarton Bridges are in close proximity toexisting tidal marshes that have been invaded by S.

alterniflora. For this reason, we downgraded therestoration feasibility classification for 3,420 acresof ponds. Of this total, 79 percent would havebeen classified as high feasibility if S. alterniflora

were not present. Absent this constraint, the highfeasibility acreage would increase by 2,690 acres (anadditional 10 percent of the salt pond complex).

Restoration CostsBecause not every salt pond will be restored totidal marsh, resource agencies have the flexibilityto select restoration scenarios that optimize habitat

Restoring low feasibilityponds to habitats otherthan tidal marsh willreduce overall restorationcosts and provide a rangeof interconnected habitats,optimizing benefits for allspecies. . .

tions are relatively high, marsh vegetation willquickly establish itself. A tidal source is readilyavailable, and antecedent channels remain intact.The pond also lies in proximity to existing marshand its restoration will aid endangered speciesrecovery efforts. All that is required for tidal marshrestoration in high feasibility ponds is modest leveealterations, closure of borrow ditches, and—ifoutboard marsh is present—excavation of a pilotchannel before breaching the levee. These pondshave the highest likelihood of meeting our ecologi-cal goals in a cost-effective and rapid manner.

Our application of these criteria to the SouthBay salt ponds yielded a total of eight pondsrepresenting 2,690 acres—only 10 percent of thesalt pond complex (see green ponds on Map 2).These ponds, due to their lack of restorationconstraints, will provide the quickest habitat.Acquisition of as many high feasibility ponds aspossible will reduce overall restoration costs byshrinking the average cost per acre for tidal marshrestoration and lowering interim maintenancecosts.

Medium Feasibility Ponds

A medium feasibility pond requires a moderateamount of work to restore it to tidal marsh.Restoration criteria for these ponds lie betweenthose for high feasibility and low feasibility pondsand yield a total of 49 ponds representing 13,240

RE

ST

OR

AT

ION

OF

TH

E S

OU

TH

SA

N F

RA

NC

ISC

O B

AY

SA

LT P

ON

DS

21

benefits while minimizing restoration costs.Restoring low feasibility ponds to habitats otherthan tidal marsh will reduce overall restorationcosts and provide a range of interconnectedhabitats, optimizing benefits for all species. Giventhe difficulty and high cost of restoring deeplysubsided evaporator ponds to tidal marsh, theseponds make excellent candidates for managedopen water ponds and microtidal lagoons, decreas-ing overall restoration costs and providing valuablehabitat for waterfowl and shorebirds. Crystallizerponds can be quickly converted to salt pannehabitat suitable for shorebirds, especially thethreatened Western snowy plover, which willfurther reduce restoration costs for the salt pondcomplex. Phasing restoration over time willoptimize habitat benefits for a variety of species.

Applying this rationale to the proposed acquisi-tion area, we developed a restoration framework aswell as rough costs associated with that framework.The South Bay salt ponds included in the acquisi-tion area total 13,610 acres. Because 4,696 acresof low feasibility ponds are scattered throughoutthis area, we determined that retention of theseponds for management as open water areas wasthe most cost-effective option. This left 1,170 acresof high feasibility ponds and 7,744 acres ofmedium feasibility ponds, for a total of 8,914acres, to restore to tidal marsh. Dividing theacquisition area in this manner complies with therecommendations of the Baylands Ecosystem Habitat

Goals Report to restore only 60 percent of the saltponds to tidal marsh and satisfies half of thereport’s restoration objectives for the South Bay.

Our next step was to develop rough restorationcosts for the South Bay salt pond acquisition areawithin the context of our restoration framework.The total cost of restoring all or a portion of thepond complex involves several components. Thesecomponents include: restoration planning, opera-tions and maintenance during the planning period,restoration construction, interim operations andmaintenance for ponds restored to tidal marsh,permanent operations and maintenance for pondsretained as open water, and monitoring. Based onour restoration classification for each pond, wedeveloped the rough cost estimates outlined below.

Restoration Planning Costs

We assumed a budget of $10 million for restora-tion planning activities, to be used over a five-yearplanning period.

Operations and Maintenance Costsduring the Planning Period

We calculated operation and maintenance (O&M)costs for the proposed acquisition area. We esti-

. . . Dividing theacquisition area in thismanner complies with therecommendations of theBaylands EcosystemHabitat Goals Report torestore only 60 percent ofthe salt ponds to tidalmarsh and satisfies half ofthe report’s restorationobjectives for the SouthBay.

mate it will require an annual O&M budgetranging between $3.8 and $9.1 million, or $278 to$670 per acre to desalinate the system, maintainlow salinity levels, and prevent degradation of thesystem’s ecological functions. These figures areconsistent with the California Department of Fishand Game’s estimated O&M costs of $286 peracre for the North Bay salt ponds. (See the“Lessons Learned” chapter for more details.) Forthe five-year planning period, total O&M costs willrange between $19 and $46 million.

Tidal Wetland Construction Costs

To help determine tidal wetland construction costs,we developed two marsh restoration case studies.The first case study involves a group of highfeasibility ponds. The second case study examinestidal marsh restoration of a group of deeplysubsided medium feasibility and low feasibilityponds.

Based on the case studies, we determined roughcosts for tidal wetland creation in the South Baysalt ponds. Estimates for restoring high feasibilityponds range between $1,060 and $1,265 per acre.

22

TU

RN

ING

SA

LT I

NT

O E

NV

IRO

NM

EN

TAL

GO

LD

In contrast, estimates for restoring mediumfeasibility and low feasibility ponds to tidal marshrange between $4,900 and $90,445 per acre.Subsided ponds at the low end of this cost rangerely on natural sedimentation (explained later inthis report) to raise pond bottoms to intertidalmarsh elevations suitable for plant colonization.While this approach is cheaper, it could take 100years to obtain a fully functioning tidal marsh. Theuse of clean dredged sediment to overcome pondsubsidence (explained later in this report) acceler-ates the restoration process, but significantlyincreases restoration costs toward the upper end ofthis range.

Interim Operations and Maintenancefor Ponds Restored to Tidal Marsh

High and medium feasibility ponds restored totidal marsh will require O&M funds for theinterim period prior to their restoration. Oncerestoration implementation begins, these pondswill incur decreasing O&M costs until marshvegetation is sufficiently established to preventlevee erosion. Because these costs will eventuallydecline to zero, we cut our estimated O&M costsin half. Therefore, we estimate it will cost $139 to$335 per acre each year to maintain these ponds.Assuming a 15-year restoration implementationperiod, this will result in a total cost rangingbetween $19 and 45 million.

Permanent Operations andMaintenance for Ponds Retainedas Open Water

Although low feasibility ponds retained as shallowopen water habitats do not require restorationconstruction funding, they will require permanentO&M funding to cover water control infrastruc-ture, salinity management, and levee maintenance.

These costs will remain steady over time at anannual rate of $278 to $670 per acre. For the15-year restoration implementation period, totalO&M costs for these ponds will range between$20 and $47 million.

Based on a 20-yeartimeline, we estimate totalrestoration costs for theproposed acquisition areato be in the range of $148 to$228 million.

Monitoring

We assumed an annual cost of $2 million formonitoring, to be used over the 5-year planningperiod as well as the 15-year restoration imple-mentation period. This will result in a total cost of$40 million spread out over 20 years.

Estimated Total Restoration Costsfor the Proposed Acquisition Area

Based on the rough cost estimates provided above,we calculated the total restoration costs for theproposed acquisition area. Based on a 20-yeartimeline, we estimate total restoration costs for theproposed acquisition area to be in the range of$148 to $228 million. This figure does not includea contingency fee or the acquisition costs ofapproximately $100 million.

Restoration Opportunities

A lthough numerous opportunities exist, the primary

opportunity in restoring the South Bay salt ponds is

the area’s large size. By acquiring an area ranging from

15,500 to 18,000 acres, resource agencies can evaluate the

“big picture” and make habitat decisions on a regional

rather than a local scale. This should ensure more cost-

effective restoration approaches. Additionally, tradeoffs

between habitat types should be easier to make because

there will be significantly more habitat for all species.

Another significant opportunity is the chance to dramati-

cally increase the amount of special status species habitat in

the South Bay. Increasing habitat for these species provides

the best chance for their recovery. Habitat features critical to

species survival during extreme high tides or other seasonal

fluctuations can also be created.

Additionally, creation of large blocks of tidal marsh

provides habitat continuity and facilitates species coloniza-

tion of what are now isolated habitat islands. Connecting

these areas to form contiguous habitat will result in larger

populations of special status species due to higher recruit-

ment among young adults seeking new territories. Contigu-

ous habitat also protects wildlife from upland-based preda-

tors such as the red fox. Combining ponds to create large

tracts of tidal marsh is also desirable because it reduces

construction costs and allows restoration of ponds that are

difficult to restore as stand-alone ponds.

24

TU

RN

ING

SA

LT I

NT

O E

NV

IRO

NM

EN

TAL

GO

LD

Other significant biological opportunitiesinclude:

• Enhancing existing salt pond habitat throughwater level management, predator and vegeta-tion control, and creation of artificial islandswithin the ponds. These enhancements willbenefit both special status wildlife and winteringbirds.

• Converting crystallizer ponds to salt pannessuitable for shorebird habitat, especially thethreatened Western snowy plover. Because theyneed relatively little modification, these pondsprovide quick and cost-effective habitat.

• Connecting tidal marsh to adjacent habitats tocreate ecologically valuable ecotones. Theability to provide a range of interconnectedhabitats is stressed in the Baylands Ecosystem

Habitat Goals Report.

• Buffering sensitive wildlife and plant popula-tions from urban development, human en-croachment, and predators. Larger blocks ofhabitat will help do this, as will creation ofbuffer and transitional zones along the uplandedge. Attention must be paid to this issue whenidentifying public access locations and restrictedareas for wildlife viewing.

• Upgrading existing infrastructure and mainte-nance access for facilities such as PG&E towers,roadways, and flood-control channels. Replac-ing traditional methods with more ecologicallysensitive practices will reduce wildlife distur-bance.

• Monitoring existing and restored habitats over along period of time to refine management goalsand further define species habitat requirements.Monitoring during early phases of restorationimplementation will identify the most successfulrestoration measures.

Since most baylands in the San FranciscoEstuary have been diked and drained, resource

agencies typically do not have the advantage ofutilizing antecedent channels when restoring tidalwetlands. In a restoration scenario that allowsnatural sedimentation to raise subsided ponds back

The primary opportunityin restoring the South Baysalt ponds is the area’slarge size.

to tidal marsh elevation, antecedent channels willexert a strong influence on channel networkformation. Even when several feet of sedimenta-tion are needed, channel networks persist as thepond bottom rises, imprinting themselves into therestored marsh’s geomorphology and enhancingwetland restoration. These benefits will not occurif fill is used to augment the sediment deficitbecause antecedent channels will be lost.

Lastly, the San Jose/Santa Clara Water Pollu-tion Control Plant (SCWPCP) pumps largequantities of effluent into the South San FranciscoBay. This daily source of freshwater did not existhistorically and has converted extensive tracts ofsalt marsh in the Bay’s southern reaches to tidalbrackish and tidal freshwater marsh.

Using SCWPCP effluent to desalinate decom-missioned ponds and dilute hypersaline brines andbittern will improve water quality, lower effluentlevels, and provide a ready source of freshwaterwithout tapping into municipal supplies. Wastewa-ter discharges also originate from the cities ofSunnyvale and Palo Alto. Although smaller involume than the SCWPCP discharge, these flowsalso could prove useful in pond desalination andbittern dilution along the western shoreline.

Restoration Challenges

R estoring the South Bay salt ponds to tidal marsh and

related habitats will be an enormous and compli-

cated undertaking requiring careful planning and adequate

funds. While the acquisition area’s large size presents an

enormous opportunity, it also presents a challenge: overlap-

ping governmental and regulatory jurisdictions, including

cities, counties, flood control districts, and state and federal

entities. Stakeholder involvement in the restoration process

will require long review periods and much compromise.

However, the opportunity to focus people’s attention on

South Bay ecology will clarify community needs and em-

phasize the value of our natural resources. By protecting

and enhancing these resources, the community helps ensure

the health of an ecologically rich and diverse region.

Several important constraints to salt pond restoration

exist: the dependence of shorebirds and waterfowl on exist-

ing salt pond habitat; subsidence and the resulting sediment

deficit; flood control issues; the presence of a gypsum layer

(particularly in higher elevation ponds); pond desalination;

the presence of freshwater discharges from wastewater

treatment plants; bittern disposal; and the proximity to sites

invaded by Spartina alterniflora. The following sections discuss

the most serious challenges to salt pond restoration and

various approaches to overcoming them.

Subsidence and the Resulting Sediment Deficit

A fully functioning tidal marsh typically occurs in the MHW

to MHHW elevation range. Yet subsidence below these

elevations is typical of South Bay salt ponds, hindering

26

TU

RN

ING

SA

LT I

NT

O E

NV

IRO

NM

EN

TAL

GO

LD

restoration because marsh plants cannot colonizeuntil pond elevations reach MTL. Successfulrestoration efforts will need to overcome thisconstraint without destroying existing biological

River supplies most of this sediment. Localwatersheds, including creeks and rivers, contributethe remaining 10 to 20 percent of the sedimentload. Most sediment enters the Estuary duringwinter and early spring, the periods of maximumfreshwater flows.

Despite the Delta’s prominent role in providingsediment to the Estuary as a whole, its role insediment supply to the South Bay is less certain.Studies suggest that the South Bay’s primarysediment supply is local watersheds, not the Delta.Whereas historic levels of sediment flow from theDelta have significantly decreased as a result ofupstream dam construction and other diversions,such structures are not prominent features in theSouth Bay watershed. For this reason, South Baysediment supply may not have decreased signifi-cantly from historic levels. Since 1955, South Baysediment has accumulated at an average rate of0.89 million cubic meters per year.

While a relatively small amount of new sedi-ment enters the South Bay annually, a greatvolume of sediment is continually resuspendedand redeposited. Resuspension of South Baysediment occurs when tidal flow velocities highenough to overcome the sediment’s resistance toerosion. Four mechanisms contribute to such flowvelocities: tidal currents, winds, freshwater inflows,and salinity-induced density differences. Tidalcurrents and winds contribute more to South Baysediment resuspension than the other two factors.

We estimated the sediment deficit for the SouthBay salt ponds based on marsh elevations ofMHHW. We found that roughly 88 million cubicyards (±10 to 20 percent) of sediment would beneeded to return ponds in the acquisition area tooptimal tidal height. If the entire pond complexwere raised to these elevations, over 100 millioncubic yards are needed. In general, the pondsCargill is offering to sell have the greatest sedimentdeficit. These ponds constitute 83 percent of thetotal sediment deficit even though they representonly 61 percent of the pond area.

Our sediment deficit estimate does not accountfor sea level rise, which has varied between 0.8 and2.1 millimeters per year along the Pacific Coast.Near San Francisco, current sea level rise isestimated at 1.3 millimeters per year, but a recentreview of global climate change has increasedpredicted sea level rise to 3.0 feet over the nextcentury, or roughly 10 millimeters per year. Ifthese predictions hold true, our estimated sedimentdeficit estimate is far too low.

Roughly 88 million cubicyards (±10 to 20 percent) ofsediment would be neededto return ponds in theacquisition area to optimaltidal height. . . .

resources. Of particular concern is the potentialdestruction of existing mudflats caused by regionalshifts in sediment deposition. The resulting de-crease in available habitat must be avoided if weare to achieve our ecological goals.

Estimating the Sediment Deficit

Restoring large areas of the South Bay to tidalaction will significantly alter local sedimentdynamics—the erosion, transport, and depositionof sediments. An understanding of these dynamicsis necessary to evaluate options for resolving thesediment deficit found in the South Bay salt pondsbecause these processes determine the size andelevation of deep-water channels, mudflats, andtidal wetlands. They also determine the amount ofsediment potentially available to restore subsidedbaylands. This in turn affects the timeframe inwhich natural processes can restore baylands to thecritical elevations for vegetative colonization.

The South Bay consists of shallow tidal flatswith a large deep-water channel (see Map 1).Sediment is deposited on these flats from externaland internal sources, known as the “sedimentsupply.” External inputs come from the Sacra-mento-San Joaquin Delta, San Pablo Bay, andlocal watersheds. Internal supply consists ofresuspended sediments.

The Sacramento-San Joaquin Delta provides 80to 90 percent of the Estuary’s total sediment load,transporting sediment from the Sacramento andSan Joaquin Valleys to the Bay. The Sacramento

RE

ST

OR

AT

ION

OF

TH

E S

OU

TH

SA

N F

RA

NC

ISC

O B

AY

SA

LT P

ON

DS

27

This sediment deficit represents the mostsignificant constraint to wetland restoration in theSouth Bay. Severely subsided ponds are some ofthe most difficult to restore. They also take thelongest time to restore. A comparison of thecurrent sediment deposit rate (0.89 million cubicmeters/year) with the estimated sediment deficit(88 million cubic yards) illustrates the magnitudeof the problem. It will take decades to rectify asediment deficit this large, and future sea level risewill exacerbate the problem. For this reason, werecommend that resource agencies retain many ofthe severely subsided ponds as managed ponds tosimplify the restoration process.

There are three possible approaches to restoringtidal marsh elevations: relying on natural sedimen-tation, importing dredged sediment, or retainingthe most subsided ponds as managed open waterhabitat. We discuss each approach in the followingthree sections.

Natural Sedimentation

The primary issue with natural sedimentation iswhether the approach will sustain mudflats at theircurrent elevation or cause them to erode. Tidalcurrents and the Bay’s bathymetry (depth andtopography) determine how sediment is trans-ported and distributed. These natural processescontinually resuspend and redistribute sediment onthe mudflats, but create a bathymetric equilibriumthat sustains mudflats at their current elevations.

If tidal marsh restoration in the South Bay saltponds were implemented too quickly (i.e., sedi-ment demand exceeded net sediment input),sediments would be transported and eventuallydeposited on the deeper areas awaiting restorationrather than on the shallower mudflats, effectivelydisrupting the equilibrium. The subsided saltponds would act as a “sink” for the suspendedsediments, preventing them from redepositing onthe mudflats. Over time, the existing mudflatswould erode.

If all South Bay salt ponds were opened to thetides immediately, the ponds would reach intertidalmarsh elevation in 15 to 50 years. However, amassive redistribution of sediments from existingmudflats to the salt ponds would occur, effectivelyscouring the mudflats of their sediment andcausing tremendous loss of mudflat habitat forshorebirds and waterfowl. This impact of thenatural sedimentation approach can be avoided byphasing restoration efforts over time. Phasing

restoration in this manner will balance sedimentdemand created by the restoration effort with theavailable South Bay sediment supply. Assumingthat sediment supply is adequate and restoration is

. . . This sediment deficitrepresents the mostsignificant constraint towetland restoration in theSouth Bay.

phased slowly enough to avoid mudflat scour, ourresearch indicates it will take 100 to 150 years toraise pond elevations to MHHW.

Dredged Sediment Importation

The second approach for restoring subsided saltponds to tidal marsh elevations is the use ofimported dredged sediment. Dredged sedimenthas been used in several Bay Area tidal marshrestoration projects: Pond 3 in Hayward, FaberTract in Palo Alto, Muzzi Marsh in Corte Madera,and Sonoma Baylands. Use of dredged sedimentshortens the restoration timeframe without causingmudflat erosion. When dredged sediment is usedto enhance salt pond restoration, the timeframedepends on two factors: the time needed to obtainand place the dredged sediment in the ponds, andthe time required for natural sedimentation toprovide the final one to two feet of tidal substrate.Assuming typical time periods for these twofactors, our research indicates use of dredgedsediment would shorten the salt pond restorationtimeframe to 45 to 60 years. Shorter restorationtimeframes will significantly reduce interim pondmaintenance costs.

The primary issues associated with the importedmaterial approach involve economics, logistics, andpracticality. Use of dredged sediment is contingenton several factors:

• Availability of sufficient quantities of suitablematerial.

• Loss of antecedent channels unless costlypreservation measures are taken.

28

TU

RN

ING

SA

LT I

NT

O E

NV

IRO

NM

EN

TAL

GO

LD

• Movement and placement of dredged sediment.

• Cost of obtaining dredged sediment whencompared to natural sedimentation.

Each of these factors presents significantdrawbacks to this approach. While import ofdredged sediment can accelerate the restorationprocess, there is a high price associated with thisspeed. Rough cost estimates for importing dredgedsediment to restore the entire salt pond complex tointertidal marsh elevations range from $660million to over $1 billion. For this reason, dredgedsediment reuse must be applied sparingly.

Retention as Managed Ponds

For many of the deeply subsided ponds in theSouth Bay complex, the best approach may notinvolve natural sedimentation or dredged sedimentimportation. It is possible to retain most or all ofthese ponds as managed open water areas. If theseponds are managed as non-tidal or micro-tidalwetlands with flexible water levels and salinity, theywill provide valuable habitat for salt marsh harvestmice, Western snowy plover and other shorebirds,and waterfowl.

Retaining most or all of the deeply subsidedponds as managed open water areas will signifi-cantly reduce the sediment deficit. While theseponds constitute 21 percent of the salt pondcomplex, they account for over half the estimatedsediment deficit. However, retaining subsidedponds as managed open water and wetland areaspresents two drawbacks. First, the flood controllevees and water control structures for these pondsmust be permanently maintained. Because theseponds are deeply subsided, their levees are pre-sumably the tallest, and therefore the most difficultand costly to maintain. These levees will also bemore prone to failure during catastrophic eventssuch as earthquakes and intense storms. Sufficientfunds must be allocated to cover these costs inperpetuity.

Second, the ecological goals stated in reportssuch as the Baylands Ecosystem Habitat Goals Report

envision a relatively uniform distribution of tidalmarsh and managed open water habitats through-out the South Bay. However, the deeply subsidedponds are clustered together from San Jose toMountain View. Furthermore, these ponds tend toborder the Bay, so retaining all of them as openwater ponds precludes creation of a continuousband of tidal marsh around the shoreline. This

problem can be remedied by dividing some of theponds to create narrow bands of bayfront tidalmarsh contiguous with the large, open water areas.

Resource managers must determine whichponds are most appropriate for natural sedimenta-tion, dredged sediment importation, or retentionas managed open water ponds. We believe utilizingall three approaches in a balanced and deliberatemanner will provide the most cost-effective andoptimal solution to the sediment deficit problem.

Salt Pond DesalinationDecommissioning South Bay salt ponds willrequire careful planning. Nearly every pond willneed water level and salinity management duringthe restoration planning and implementationperiod. Ponds retained as managed open waterareas will need permanent management. Inaddition, many ponds will require desalinationbefore restoration can occur.

Two questions are crucial to evaporator ponddesalination: Which ponds require desalination?Are additional actions needed to deal with ionicimbalance? Salinity levels determine which pondsrequire desalination; low salinity ponds requirelittle if any desalination. For moderate to highsalinity ponds, desalination may be required,depending on the salinity discharge level autho-rized by the San Francisco Bay Regional WaterQuality Control Board (RWQCB).

Ionic imbalance in the brine is caused by theprecipitation of non-commercial salts such asgypsum. Ionic imbalances can vary in intensity;those associated with bittern are known to be toxicto aquatic organisms. It is not known whether less-severe ionic imbalances will pose toxicity concerns.The RWQCB will consider this issue when permit-ting brine discharge into South San Francisco Bay.

At its most fundamental level, the desalinationprocess involves nothing more than repeatedlydiluting large quantities of hypersaline brine withlarge volumes of freshwater (also called “flushwater”). The greater the volume and speed of theflush water, the shorter the desalination period.Increasing desalination rates, however, may notincrease restoration speed because other factorsinfluence restoration rates. The most significantfactor identified in this report is the sedimentdeficit, which could hinder restoration rates farmore than pond desalination. For this reason,resource agencies must explore various approachesto overcome each restoration challenge and select

RE

ST

OR

AT

ION

OF

TH

E S

OU

TH

SA

N F

RA

NC

ISC

O B

AY

SA

LT P

ON

DS

29

solutions that work together to provide optimalresults.

There are four steps in the desalination andbrine disposal process for evaporator ponds: (1)removing high salinity brines from targeted ponds(desalination); (2) evaluating whether to use thebrines in Cargill’s salt production system ordischarge it into the Bay; (3) if discharge is se-lected, obtaining authorization for Bay discharge;and (4) diluting brines to meet the authorizedsalinity threshold. Three strategies exist for thisprocess: rapid desalination, desalination to opti-mize salt production, and desalination with Baydischarge. Each of these approaches will solve thedesalination issue, but involve varying degrees ofcooperation from and impacts to Cargill.

Rapid Desalination

This strategy flushes ponds rapidly to maximizedesalination rates. Cargill accepts all brine into itssalt production process, maximizing pond depthsat all salinity levels to increase its capacity. Thisresults in large decreases in salt production in theshort-term, but eventually unusually high saltproduction rates occur. Cargill’s interim operationand management responsibilities are minimized,placing a greater burden on the Refuge to manageponds during this period.

Desalination to Optimize Salt Production

This strategy involves conducting pond desalina-tion in conjunction with Cargill’s salt productioncycle. While Cargill continues to accept all brineinto its salt production process, ponds are flushedat a rate that maintains optimal salt production.Upstream pond depths may exceed normal levels,and production efficiencies are reduced slightly inthe short-term as less concentrated flush waters areintroduced into the system. Cargill’s interimoperation and management responsibilities arelikely to continue for two to five years, and its costsmay increase due to a more complicated watertransfer system. Ponds are also taken out ofproduction more gradually than under Strategy 1,reducing the Refuge’s burden for pond manage-ment during the interim period.

Desalination with Bay Discharge

This strategy is similar to the second strategyexcept that Cargill only accepts brine that exceeds

the salinity discharge threshold. This strategyutilizes Bay discharges to minimize the amount ofbrine Cargill must accept. Ponds are flushed at arate that maintains optimal salt production, andthe discharge threshold maximizes benefits toCargill while minimizing impacts to the Bay.Cargill’s interim operation and managementresponsibilities are likely to continue for two tofive years, and its costs may increase slightly.Ponds are taken out of production more graduallythan under Strategy 1, reducing the Refuge’sburden for pond management during theinterim period.

Bittern DisposalBittern, the hypersaline byproduct of solar saltproduction, occurs as both a liquid and a solid. Itis composed primarily of chloride, magnesium,sulfate, potassium, and bromide, plus any remain-ing sodium chloride that did not precipitate inthe crystallizer ponds. Although it is composed ofthe same minerals found in Bay water, at the timeit leaves the crystallizer ponds, bittern differsgreatly from the original brine. The brine volumeis reduced 97 to 98.4 percent, and salinity canreach 447 parts per thousand. Bittern’s highsalinity and ionic imbalance are toxic toaquatic species.

Because the byproduct has both a solid and aliquid phase, the term bittern is ambiguous andmay not mean the same thing to all stakeholders.Figure 4 shows a cross-section of a bittern pond.

Addressing the bittern problem for the SouthBay salt pond complex involves desalinating thebittern ponds so they can be restored, and dispos-ing of the bittern and all flush water. In the shortterm, Cargill plans to transfer all Redwood Citybittern to Newark, but it is not known where it willstockpile the additional bittern. In the long term,bittern disposal is more complex. Although Cargillestimates that the current bittern market equalsthe current bittern production rate, this estimateonly applies to liquid bittern. As stockpiles of bothliquid bittern and precipitated bittern salts accu-mulate in the bittern storage ponds, this excessmust be disposed of in some way. If Cargill ceasessalt production altogether in the Bay Area, theRefuge will be forced to deal with this problemunless Cargill has sold all the stockpiled bittern ordisposed of it.

Although bittern ponds are more difficult todesalinate than evaporator ponds because of the

30

TU

RN

ING

SA

LT I

NT

O E

NV

IRO

NM

EN

TAL

GO

LD

accumulation of precipitated bittern salts, it issubstantially the same process as the one describedin the previous section. There are two methods fordesalinating bittern ponds: the “push method” andthe “pull method.” Under both methods, bitternmust be diluted at a ratio of 100:1 to allow Baydischarge without harmful effects. The basicdifference between the two methods is the point inthe process at which the bulk of this dilution takesplace. In the push method, dilution occurs withinthe bittern pond as new water is pumped into thepond, and only limited dilution occurs in thedilution ponds. In the pull method, most dilutionoccurs in the dilution ponds; in later stages ofremoval, some dilution occurs in the bitternponds. The dilution pond must be at least twotimes the size of the bittern pond to allow forproper dilution.

Each method has it advantages and disadvan-tages, although both will desalinate bittern ponds.Selecting which method to use will depend on apond’s specific characteristics, such as levee heightand integrity, pump needs, and proximity to aslough channel or the Bay. It is important to notethat the presence of precipitated salts in bitternponds will greatly extend the desalination period,increase the water volume needed to flush theponds, and produce hypersaline outflow brines foran extended period. In the bittern storage ponds,approximately one-third of the salts have precipi-tated from solution. Thus, these ponds requiredesalination to remove both liquid bittern andbittern salts, increasing desalination time. Bitterndesalting ponds contain relatively small amountsof precipitated salts, minimizing their effect ondesalination time.

FIGURE 4. Cross section of a bittern storage pond.

Bittern Liquid

Precipitated Bittern Salts

Levee

Bay Mud

Levee

Lessons Learned fromthe North Bay Salt Ponds

I n 1994, the State of California purchased 10,000 acres

of Cargill’s North Bay salt pond complex on the north-

ern shores of San Pablo Bay for $10 million. A 7,500-acre

portion of the site contains ten salt evaporator and two

bittern storage ponds. The remaining 2,500 acres contain

tidal marsh and open water adjacent to the salt ponds. The

California Department of Fish and Game (CDFG) now

manages these lands and intends to restore them to a combi-

nation of tidal marsh and managed open water ponds.

The former North Bay salt ponds are similar to the South

Bay salt ponds in that both contain large expanses of con-

tiguous bayland habitat and both have a long history of salt

production. The tidal wetlands and diked ponds located in

the North Bay complex provide vital habitat for migrating

and wintering waterfowl and shorebirds, as well as for resi-

dent species.

Three significant problems have plagued restoration in the

North Bay salt ponds: (1) insufficient data and conflicting

ecological goals for the site’s restoration; (2) insufficient

funds for interim maintenance and management of levees,

water control structures, and salinity levels; and (3) presence

of hypersaline brines and bittern. These problems have

resulted in two serious consequences. First, the system’s

ecological functions have declined due to inadequate water

pumping and management. Second, serious deterioration of

the system’s levees has occurred due to inadequate mainte-

nance. These consequences have increased the risk of a

catastrophic release of hypersaline brines and bittern into

32

TU

RN

ING

SA

LT I

NT

O E

NV

IRO

NM

EN

TAL

GO

LD

the Napa River and San Pablo Bay. As time passes,the risk of such releases increases.

A multi-agency effort has been underway forseveral years to plan the North Bay salt pondrestoration. At the time of the purchase, insuffi-cient data existed to develop restoration alterna-tives because state resource agencies could notidentify antecedent channels, assess water qualityeffects, anticipate erosion, or quantify levee breachimpacts. There was also significant controversyover tradeoffs between restoration of historic, tidalmarsh habitats and preservation of existing saltpond habitats for shorebirds and waterfowl.Partially as a result of the Baylands Ecosystem Habitat

Goals Report, consensus now exists that increasedhabitat for all species is essential and that aneffective restoration strategy must be based on ahydrologic model. Efforts are underway to developsuch a model.

Due to the long delay in restoration planning,the transitional period continues for the North Baysalt ponds. To date, management efforts haveattempted to simply maintain the status quo. It hasbecome increasingly apparent that no provisionwas made for adequate operation and mainte-nance (O&M) funds. Prior to purchase, Cargill’sannual O&M budget for the North Bay salt pondswas approximately $500,000. In contrast, the stateallocates approximately $60,000 annually for thispurpose. This funding shortfall has criticallyhampered a broad range of O&M activities: waterpumping and management; repair and replace-ment of water control structures; levee repair andmaintenance; bittern management; and habitatenhancement. Although this problem has beenpartially mitigated by creative managementstrategies, alternative funding, and water manage-ment assistance from Cargill, it remains an issuethat must be resolved before wetland restorationcan occur.

After eight years of inadequate water manage-ment, the North Bay salt ponds have becomeincreasingly saline and have begun to dry out forthe first time since their construction. Approxi-mately two to four tons of residual salts remain inthe ponds, decreasing their habitat value forwaterfowl and other species. To further complicatethe situation, the acquisition agreement did notinclude a feasible bittern disposal or reuse plan.Unlike the proposed South Bay acquisition, Cargilldid not remove or dispose of this material. As a

result of these two issues, a large quantity ofhypersaline brines and bittern remains in theponds. The state resource agencies have developeda preliminary strategy to dilute these brines.Nonetheless, as the North Bay salt ponds continueto “make salt,” salt accumulation continues andintensifies the disposal problem.

Several lessons can be learned from restorationefforts at the North Bay salt ponds and are directlyapplicable to restoration of the South Bay saltponds. First—and most importantly—O&Mfunding must be made available immediately uponpurchase and it must be sufficient to cover leveemaintenance, water management, bittern removal,and other related costs. Tardy and inadequateO&M funding will compromise the short-termecological value of the salt ponds; increase therisks of uncontrolled hypersaline releases andother catastrophic events; allow salt production tocontinue; increase the cost of water management;and complicate future restoration efforts.

Second, creation of detailed hydrologic modelsshould be the first step in the restoration process.These models will provide important guidance onkey issues such as restoring tidal action to ponds;minimizing risks associated with levee breaches;predicting salt transport; and assessing sedimenta-tion needs.

Other lessons include:

• Consensus must exist among resource agenciesand stakeholders on the ecological goals and thetradeoffs between habitat types before restora-tion can proceed.

• Special status species complicate restorationplanning and increase restoration costs.

• The Reyes soils underlying most salt ponds areunsuitable for use as fill material because theyprovide poor conditions for upland vegetation.

• Per-acre restoration costs increase as salinitylevels increase.

• Hypersaline brines and bittern ponds will be themost difficult and time-consuming to restorebecause of high residual salt concentrations.

• Disposal of hypersaline brines and bittern is acritical restoration component that will impactlong-term restoration costs.

• Salt pond restoration is a complex and lengthyprocess requiring adaptive management.

Issues to Consider duringAquisition Negotiations

W hile it is critical that we publicly acquire a large

block of the South Bay salt ponds as quickly as

possible, it is also imperative that the public is protected by a

sound acquisition agreement. As discussed earlier, the Don

Edwards National Wildlife Refuge was established in 1979

after purchase of a block of salt ponds from Leslie Salt,

Cargill’s predecessor. Leslie retained mineral rights for salt

production on these ponds, and the purchase agreement has

not provided the level of resource protection desired by the

Refuge. We should not repeat past mistakes. To help craft a

sound acquisition agreement, decision makers must consider

several issues during acquisition negotiations.

Prioritize pond acquisition to capture the best marshrestoration opportunities.

Based on our feasibility analysis, some of the best ponds for

short-term tidal marsh restoration lie within the Newark #2

Plant, where Cargill plans to continue salt production.

Others are located in the Redwood City Plant, near the

western end of the Dumbarton Bridge (see Map 2). If state

and federal acquisition focuses on ponds where restoration is

most feasible, progress toward the goals stated in the Baylands

Ecosystem Habitat Goals Report will be greatly advanced. The

October 2000 acquisition proposal requires resource agen-

cies to focus their tidal marsh restoration efforts on ponds in

the Redwood City and Alviso Plants, where salinity, subsid-

ence, and sediment deficit issues are more challenging.

34

TU

RN

ING

SA

LT I

NT

O E

NV

IRO

NM

EN

TAL

GO

LD

Acquisition funding must beaccompanied by funds for restorationplanning as well as funds to maintainand operate the ponds whileplanning occurs.

Without restoration planning funds, restorationcannot take place. Given the size and complexityof the South Bay salt pond restoration effort,interim management of the ponds will be neces-sary. Detailed information on current operationand maintenance (O&M) costs—preferably fromCargill—is essential so that adequate funding canbe provided for these functions as part of theacquisition. Without sufficient funds, properinterim management will not be possible, andrestoration efforts will be hampered as they havebeen for the North Bay salt ponds. Adequate fundsfor restoration planning and O&M must beallocated if salt pond restoration is to succeed inthe South Bay. Additional funding for the lengthyrestoration effort must be available as well.

Agreement must be reached on howto dispose of hypersaline brines andbittern.

For ponds where salt production ceases, all concen-trated brines and bittern (both liquid and solid) aswell as other toxic contaminants must be removedas rapidly as possible. Wetland restoration cannotbegin until this occurs. Agreement on the best wayto capture and dilute hypersaline brines withoutcausing damage to the Bay ecosystem is crucial.

It is our understanding that recent pond realestate appraisals make numerous assumptionsregarding the level of cleanup required for habitatrestoration. However, fewer assumptions mean lesstaxpayer risk. Therefore Cargill should commit toas much site cleanup as possible to minimizeassumptions and potential taxpayer liability. Theacquisition agreement should include carefulevaluation of costs to remove toxic contaminationand who will pay them.

For salt ponds not acquired in theproposed acquisition, ecologicalfunctions must be protected to thedegree possible.

In many of the ponds Cargill intends to continueoperating for salt production, salinity will increaseabove useful habitat levels. This will adverselyaffect birds and other species that have growndependent on these ponds. Of particular concernis increased salinity in Mowry Ponds 1, 2, and 3 inthe Newark #2 Plant. These low salinity pondscurrently provide immense habitat value that willbe lost as Cargill alters its pond operations toincrease productivity. Additionally, increased pondwater levels will reduce available levee habitat fornesting and roosting birds. Since it is not contem-plated at this time to take the entire complex outof salt production, these adverse impacts towildlife should be minimized or mitigated to thegreatest extent possible.

Conclusion

After a century of degradation, tidal wetland

restoration is a top priority for improving the health

of San Francisco Bay, and one of the most promising

restoration sites is the South Bay salt ponds. Acquisition and

restoration of these ponds represents an important act of

land stewardship that will benefit not only the Bay and its

wildlife, but also future generations of Bay Area residents.

As we have shown in this report, all 26,190 acres of South

Bay salt ponds are potentially restorable to a mix of tidal

marsh, open water, and related habitats that will grant

tremendous ecological benefits to the Estuary’s fish, wildlife,

and water quality. Restoration of these ponds will provide a

significant portion of the minimum acreage scientists say the

Estuary’s fish and wildlife need. To reduce restoration costs

and optimize habitat benefits for all species, we recommend

restoring two-thirds of the pond complex to tidal marsh,

phased over time. All high feasibility ponds and many mod-

erate feasibility ponds can be restored to tidal marsh with

relative ease. Deeply subsided evaporator ponds should be

retained and managed as microtidal lagoons. Hypersaline

crystallizer ponds can be converted to salt pannes for quick,

cost-effective shorebird habitat. The challenges of compre-

hensive and integrated wetland restoration on a regional

scale can be overcome with careful planning, sufficient

resources, and patience.

Now is the time to turn salt into environmental gold for

the San Francisco Estuary. Acquisition and restoration of

the South Bay salt ponds is a unique, once-in-a-lifetime

36

TU

RN

ING

SA

LT I

NT

O E

NV

IRO

NM

EN

TAL

GO

LD

opportunity that is unparalleled in Bay Areahistory. In the midst of a densely urban area, wehave a chance to restore estuary health, perma-nently protect open space, and recreate thriving,

vital wildlife habitat. We need to seize this pricelessopportunity and run with it. Our estuary deservesnothing less.

Why are the salt ponds different colors?Salt pond colors reflect a complex interaction of plants, animals, and varying salinity.

• Low to mid-salinity ponds: Green algae creates the color.

• Moderate salinity ponds: Dunaliella algae proliferates and turns the ponds a lighter shade ofgreen.

• High salinity ponds: High salt concentrations cause the Dunaliella to produce a red pigment.Halophilic bacteria contribute to the red and purplish-red hues. Millions of tiny brine shrimp inmid-salinity ponds add an orange cast.

• In choppy conditions, the colors appear murkier. Heavy rain can even turn the water clear.

02,

000

4,00

0 Met

ers

02

41

Mile

s

1,00

0

Rep

rinte

d by

per

mis

sion

of t

he C

alifo

rnia

Sta

te C

oast

al C

onse

rvan

cy'

MA

P 2

. S

ou

th S

an

Fra

nc

isc

o B

ay

Sa

lt P

on

ds

Ra

nk

ed

by

Ea

se

of

Tid

al

Ma

rsh

Re

sto

rati

on

Insu

ffici

ent d

ata

to d

eter

min

e fe

asib

ility

(1

,830

acr

es)

City

bou

ndar

ies

Hig

hway

s

Rai

lroad

Le

ge

nd

Thi

s m

ap r

anks

sal

t pon

ds b

y th

eir

feas

ibili

ty

for

tidal

mar

sh r

esto

ratio

n ba

sed

on th

e fo

llow

ing

attr

ibut

es: s

ubsi

denc

e, ti

dal

conn

ectio

n, fl

ood

haza

rd, i

nfra

stru

ctur

e im

pedi

men

ts, s

alin

ity le

vels,

gyp

sum

, and

Spa

rtin

a al

tern

iflo

ra. P

onds

cla

ssifi

ed a

s lo

w

feas

ibili

ty fo

r tid

al m

arsh

res

tora

tion

shou

ld

be r

etai

ned

as m

anag

ed o

pen

wat

er p

onds

or

oth

er ty

pes

of h

abita

t.

Hig

h fe

asib

ility

for

tidal

mar

sh r

esto

ratio

n (2

,690

acr

es)

Med

ium

feas

ibili

ty fo

r tid

al m

arsh

res

tora

tion

(10,

550

acre

s)

Low

feas

ibili

ty fo

r tid

al m

arsh

res

tora

tion;

go

od c

andi

date

for

man

aged

pon

d or

oth

er

habi

tat (

7,70

0 ac

res)

Med

ium

feas

ibili

ty; i

ncre

ases

to h

igh

feas

ibili

ty w

ithou

t Spa

rtin

a al

tern

iflor

a co

nstr

aint

(2,

690

acre

s)

Low

feas

ibili

ty; i

ncre

ases

to m

ediu

m fe

asib

ility

w

ithou

t Spa

rtin

a al

tern

iflor

a co

nstr

aint

(7

30 a

cres

)

Save San Francisco Bay Association

1600 Broadway, Suite 300Oakland, CA 94612phone: 510.452.9161

fax: 510.452.9266email: savebay@savesfbay.org

www.savesfbay.org