Senate Select Committee on Baylands Acquisition
Thursday, June 20, 2002

Prepared by the California Research Bureau, California State Library

History of the Salt Pond Lands

Before Europeans arrived in the San Francisco Bay, Native Americans harvested salt from natural salt ponds in the South Bay. These natural ponds were located in the vicinity of Hayward, in the marshlands scattered along the shoreline (see attached map of the historical extent of wetlands in San Francisco Bay). ìThe Yrgin Ohlone apparently used the salt ponds for salt production. They collected salt crystals from willow sticks placed in the briney waters. The Spanish missionaries adopted the native salt harvest practice and used the Ohlone to harvest the salt.[1]

Commercial production of salt began in 1854, when Captain John Johnson settled at Mount Eden and established the first commercial solar evaporationn the Bay.[2] Other settlers also laid out salt ponds in the tidal marsh and went into production. By 1868, there were 18 salt companies on the Bay. By the Great Depression, the 18 companies had merged into one ñ Leslie Salt.

By the 1930s, almost half of the South Bayís historical tidal marshes had been converted into salt ponds. In the 1950s, Leslie Salt expanded salt production into the North Bay, creating 10,000 acres of salt ponds in the tidal marsh near the mouth of the Napa River. At peak levels of production, salt ponds covered about 36,000 acres throughout the Bay.[3] Today, about 26,000 acres of salt ponds exist in the South Bay.

Salt Pond OwnershipSalt Pond Ownership

In mid-1970s, the U.S. Fish and Wildlife Service acquired approximately 13,000 acres of salt ponds in the South Bay from Leslie Salt. These salt ponds became part of the San Francisco Bay National Wildlife Refuge. In 1978, the Cargill Corporation purchased Leslie Salt. Although Cargill does not own the Refuge salt ponds, it retains the mineral rights on the salt ponds and continues to produce salt on Refuge lands.

The Department of Fish and Game acquired 9,000 acres of North Bay salt ponds on the west side of the Napa River in 1994. These ponds are now known as the Napa Sonoma Marsh State Wildlife Area. Cargill retained ownership of 1,400 acres, which are the site of the former production plant on the east side of the river.

Salt Production

Currently, Cargill produces annually about one million tons of common salt. Depending on the salinity of the Bay water when the salt-making process begins, this requires about 40 million tons of Bay water.

In the South Bay, five ìplantsî produce salt through solar evaporation, a process that takes several years. Bay water enters the ponds through intake pumps or tide gates. Once in the system, the water is called ìbrine.î The brine moves through the ponds by a combination of gravity flows and pumping. In a series of eight evaporator ponds, the volume of brine reduces nearly 70 percent, and salinity increases. In the ninth evaporator pond, known as the ìpickleî pond due to the high salt content of the brine, 95 percent of the intake pondís original water volume has evaporated. In the last stage of production, the ìcrystallizerî pond, the common salt (sodium chloride) precipitates out of the pickle at a rate of approximately 40 tons per acre. [4]

Salt harvest begins in the autumn, when Cargill drains the crystallizer ponds and uses machinery to harvest the salt. Temporary railroad tracks are laid in the ponds, and the salt is deposited into hopper cars. The salt is washed and processed for commercial and industrial uses.

The extremely saline liquid by-product of salt production is known as ìbittern.î Bittern is stored in bittern ponds located near the processing plants in Newark and Redwood City. Because of its high salinity, bittern is toxic to aquatic wildlife and cannot be discharged into the Bay. In addition, there has been no viable commercial market for bittern since 1972. As a result, Cargill has stored bittern on-site. There are about 1,600 acres of bittern storage and desalting ponds in the South Bay.

Habitat Values of Salt Ponds

Although salt ponds are dramatically different than the historical tidal marshes and mudflats that preceded them, they provide important habitat for birds, fish, plants, and invertebrates. The amount of shallow pond habitats is greater than it was before European settlement and development of the Bayís shoreline.[5]

More than 30 ìspecial status speciesî occur in the vicinity of the salt ponds. These species are listed by the federal or state government as ìthreatenedî or ìendangered,î are considered candidates for listing, or are protected under federal legislation. Special status bird species found near salt ponds include the Western snowy plover, California brown pelican, California least tern, and the California clapper rail, all of which are threatened or endangered.

Many animals depend particularly on salt ponds for breeding, migration stopover, or wintering habitat. These include shorebirds such as American avocet, Black-necked stilt, and Long-billed curlews. Waterfowl such as Northern pintail, Northern shoveler, Canvasback, Bufflehead, and Ruddy duck spend the entire winter on the salt ponds, feeding on invertebrates or vegetation. Wading birds, songbirds, and raptors all rely on the salt ponds for foraging, nesting habitat, or resting during migration. Pacific Harbor seals, which are protected by federal law, have several haul-out sites in the margins of salt ponds. The largest pupping site in San Francisco Bay is on Mowry Slough in the South Bay salt ponds.

The Loss of Tidal Marshes and Mudflats in the San Francisco Bay

Pre-1850s Extent of Wetlands

When Europeans first arrived in the San Francisco Bay region, there were about 50,000 acres of mud flats at low tide. There were sandy beaches in the Central Bay and on the eastern shore of the North Bay, totaling about 23 miles in length. These beaches and mud flats were fringed with marshes and tidal lagoons. There were nearly 200,000 acres of tidal marshes in vast expanses around the Bay. The marshes were mainly concentrated in 3 areas: South Bay, North Bay, and Susuin, with each region containing about 50,000 acres of tidal marsh. Large tidal channels connected the marshes to the bays and created complex networks of smaller channels throughout the marshes. Altogether, there were about 6,000 miles of channels.

Beginning in the mid-1800s, large portions of the San Francisco Bay Estuaryís tidal marshes and mudflats were filled, diked, or drained to create farms, ports, salt ponds, rail lines, and roads. Eventually, whole cities were built on fill, such as the cities of Alameda and Emeryville, and large portions of Berkeley and Oakland.

Current Extent of Wetlands[6]

The San Francisco Estuary Institute has published maps showing the historical extent of tidal marsh and mudflats, and the current extent of wetlands in San Francisco Bay (attached to this report). As the maps show, development of the Bay shoreline has altered the extent, location, and nature of wetlands habitats:

  • There are now 40,000 acres of tidal marsh, reduced from about 200,000, with about 1,000 miles of channels, formerly about 6,000 miles.
  • The tidal mud flats have been reduced to 29,000 acres from bay fill, erosion, and tidal marsh evolution. Formerly, there were about 50,000 acres.
  • There are now about 7 miles of sandy beaches, down from 23 miles. Most of the current beaches occur in different places than the historic beaches.
  • The total amount of shallow ponds in the baylands and adjacent grasslands used to range from about 16,000 to 22,000 acres, depending on rainfall. Now, there are between 63,000 and 92,000 acres, depending on rainfall and water management. The increase is due to the conversion of tidal marsh to salt ponds and diked baylands.

The Importance of Restoring San Francisco Bay Wetlands

The San Francisco Bay Estuary is of great importance to migratory shorebirds and waterfowl. More than one million shorebirds use Bay wetlands each winter, leading to the designation of the Bay as a Western Hemisphere Shorebird Reserve Network site of international importance. San Francisco Bay is also an important wintering area for waterfowl, with more than 50 percent of the diving ducks in the Pacific Flyway wintering on the Bay.[7]

The Bayís wetlands are also important for a variety of fish and shellfish, some of which support large commercial or recreational fisheries. Invertebrates, amphibians, and reptiles also require wetlands and shallow water habitats that have dwindled substantially from their historical extent.

The Need for Restoration Efforts

The Estuaryís problems, and the need for restoration of wetlands and other habitats, are well documented:

  • The National Estuary Program identified valuable estuaries nationwide that needed work to restore their natural resources, especially wetlands, fisheries, and water quality. In 1987, the National Estuary Program initiated a study of San Francisco Bay Estuary, a collaborative effort involving federal, state and local governments, business interests, and environmental organizations. After more than 5 years of research, in 1994 the San Francisco Estuary Project published the Comprehensive Conservation and Management Plan (CCMP) for the San Francisco Bay Estuary. The CCMP called for 145 actions necessary to return the Estuary to health. Among the recommendations was the restoration of vast tracts of tidal marsh.
  • Another recommendation of the CCMP was to develop habitat restoration goals. The Baylands Ecosystem Habitat Goals Report, published in 1999, recommended a species-based approach to restoring a mosaic of different types of habitats throughout the Estuary, including tidal flats, tidal salt marsh, tidal brackish marsh, lagoons, diked wetlands, riparian forest, grassland/vernal pool complexes, coastal prairie, oak woodland, and salt ponds of a range of salinities. The Goals Report also recommended creating connections between the wetlands and upland habitats. The Habitat Goals Project was a four-year effort involving participants from Bay Area government agencies, non-profits, and private sector organizations.
  • The San Francisco Bay Joint Venture recently prepared report entitled Restoring the Estuary: Implementation Strategy of the San Francisco Bay Joint Venture.  The Joint Venture is a coalition of more than 60 agencies, conservation groups, development interests, and others whose goal is to restore the Estuary through a program of habitat restoration, enhancement, and protection.

Water Quality

Development of the Bayís shoreline, as well as the upper reaches of the watersheds abutting the Estuary, has taken its toll on the Bayís water quality. San Francisco Bay does not meet state water quality standards for a variety of pollutants, including pesticides and metals.

Urban areas have high proportions of impervious surfaces such as asphalt and concrete. Instead of percolating down into the ground, where pollutants remain and some eventually decompose, rainwater and irrigation water carry pollutants and sediment across the impervious surfaces and into storm drains, which lead to the Bay or its tributaries. Wetlands and riparian areas that formerly filtered impurities and assisted with percolation have been filled.

Restoration of tidal marsh and seasonal wetlands in the South Bay can help to improve water quality.

Endangered Species

Over the past 150 years, the Bay and Estuaryís populations of fish and wildlife have changed dramatically. This is a result of natural and human-induced factors, including introduced species, pollutants, habitat loss and degradation, over-harvest, and changed freshwater flows into the Bay.

As discussed above, more than 30 special status species are associated with the salt ponds. Restoration of large tracts of habitat will assist in the species recovery efforts currently underway at both the state and federal levels. .

Restoration Issues

Once the Cargill property has been acquired, a great deal of planning must be done before restoration can begin. Restoration of tidal marsh may take several decades. Some of the major issues that must be addressed during the planning process are highlighted below.

  1. Determine the mix of tidal marsh and managed ponds, and protect existing resources while restoring tidal marsh.  The Habitat Goals Report recommended restoring tidal marsh, muted marsh, and buffer zones in the South Bay as well as maintaining 10,000 to 15,000 acres of managed salt ponds as habitat for shorebirds and waterfowl.[*] Many species depend on the salt ponds in their current state. For example, black-necked stilts, western snowy plovers, and Caspian terns nest on partly dry salt ponds, on levees, and on salt pond islands.[8] Some species occur in much higher densities in the salt ponds than in the adjacent open water, and some use the salt ponds almost exclusively. In some cases, the species were not historically abundant in the Estuary, but are so today because their habitats elsewhere are greatly reduced. [9] Historically, tidal marsh species were more abundant.

    The planning process will need to determine which ponds remain as managed salt pond habitat, and which areas are restored to tidal marsh. Conversion of salt ponds to tidal marsh could significantly reduce or even extirpate some resident species. Any changes to habitats of listed species will require careful consideration and will involve regulatory agency oversight.
  2. Raise salt pond bottom elevations to salt marsh elevations.  Currently, the elevations of the salt pond bottoms are well below the level at which tidal marsh plants will colonize. This is a result of soil compaction and groundwater withdrawal. To raise bottom elevations to allow tidal marsh vegetation to become established, sediment must settle into the salt ponds. Planning for the restoration must consider all of the physical conditions that will affect the rate at which sediment accumulates in the salt ponds. Such conditions include: the surrounding topography, hydrologic connections to tidal waters of the Bay, and the amount of sediment available (from tributary streams, tidal action, and possibly dredging activity.) 
  3. Control invasive species.  Restoration of the salt ponds creates opportunities for the spread of invasive non-native species. Some invasive species can harm native species by out-competing natives, altering their environment, or preying upon them. The two most serious problems with invasive species in the South Bay are smooth cordgrass and non-native predators (primarily red fox and Norway rat).[10]

    Smooth cordgrass (spartina alterniflora) is an aggressive, non-native plant that was introduced to the Estuary in the 1970s in a tidal marsh restoration project in the South Bay. Spartina is now established, with about 1,000 acres south of the Bay Bridge. Spartina displaces and interbreeds with the native Pacific cordgrass. Unlike the native cordgrass, spartina grows in very dense stands, eliminating small tidal channels, reducing tidal flow, and possibly impairing the ecological functions of the tidal marsh. These effects may harm the endangered California clapper rail, which uses small channels for foraging and protection. Spartina colonizes a wider range of habitats than the native cordgrass, and can take over pickleweed habitat, harming the endangered Salt marsh harvest mouse and other species that rely on this habitat.

    Newly restored wetlands are vulnerable to invasion by spartina alterniflora, which prefers disturbed sites with few competitors. Once established, it grows quickly, interbreeds with native cordgrass, and is almost impossible to eradicate.

    The Norway rat (rattus norvegicus) and the red fox (vulpes vulpes) are non-native mammals that have become established in the South Bay. Red foxes prey on a wide variety of food sources, including small mammals, birds, reptiles, amphibians, and insects. Declines in the population of federally listed California clapper rail and Western snowy plover have been linked to the establishment of red fox populations in coastal California. Norway rats are known to prey on California clapper rail nests.

    Restoration activities in the salt ponds could provide new corridors that would allow the red fox and Norway rat to disperse further. Trapping efforts are underway, and will need to be continued.
  4. Maintain levees.  The bayward levees of most South Bay salt ponds provide the primary flood protection for many South Bay communities. Other levees on the upland side of the salt ponds will have to be reinforced if the bayward levees are breached to restore tidal marsh. Breeching the levees transfers the flood protection function inland to an internal salt pond berm or to the upland edge of the pond. If the upland edge of the pond is sufficiently high, there is little concern about flooding. If the upland edge is not high enough, adjacent land uses will require additional protection from flooding. This usually involves building a flood control levee. Currently, there are 80 miles of external salt pond levees, 76 miles of internal levees, and 21 miles of upland levees that control flooding in South Bay communities.[11]

    As discussed above, the levees themselves are important nesting areas for some birds. Maintenance and reinforcement of the levees will need to be done in a manner that maintains or improves the levees as habitat. Recently, conservation organizations and flood control agencies have made efforts to incorporate flood control levees into the landscape. This involves building levees with gentler slopes and using native vegetation to control erosion, rather than rock or concrete rubble rip rap. Levee maintenance will be one of the major costs of the salt pond restoration efforts.
  5. Manage water to avoid creating salt. To avoid producing salt in the ponds, water will need to circulate. Water and salt management will be needed in perpetuity for those ponds not restored to tidal marsh. Preparing decommissioned salt ponds for restoration to tidal marsh will require desalinating those ponds and managing water levels and salt concentrations up to the time that each pond is restored to tidal marsh. This will require operation and maintenance of a complex series of pumps and tide gates, as well as dredging. Adequate and steady funding will be necessary to ensure that water management occurs on an ongoing basis, and protects the existing habitat values of the salt ponds.
  6. Desalinate evaporator ponds.  The evaporator ponds used to make salt contain brine with various salinity levels. The ponds range from bay water concentrations at the intakes to hypersaline brine at the pickle pond ñ a salinity range of 21 ñ 356 parts per thousand (sea water is 35 parts per thousand). Once the salt ponds are no longer in production, the brines that remain must be reduced in salinity so that they can be discharged into the Bay without harming aquatic life.[12]

    Disposal and decontamination of the salt ponds will involve regulatory and logistical considerations. For example, the San Francisco Bay Regional Water Quality Control Board (RWQCB) will have to establish salinity limits for any discharge resulting from pond desalinization. Many factors will be incorporated into the limits, including the sensitivity of various species to variations in salinity, the area affected by the discharge, the mixing of fresh water from rain, storm water, or treated waste water, and the time of year that the discharge occurs.

    As a result of the constraints involved in discharging saline brines into the Bay, desalination of salt ponds will need to occur in a piecemeal fashion over several years. Decisions will need to be made regarding who should pay for desalination, the method and timing, which ponds should remain in production during this period, and what maintenance or restoration activities should also occur. 

[*]  See attached excerpt from the Habitat Goals report showing potential project locations and recommendations for restoration projects in the South Bay. 

[1] Goals Project, 1999. Baylands Ecosystem Habitat Goals. A report of habitat recommendations prepared by the San Francisco Bay Area Wetlands Ecosystem Goals Project. U.S. Environmental Protection Agency, San Francisco, California/ San Francisco Regional Water quality Control Board, Oakland, California.

[2] Cargill Salt, The Bayís Edge. Volume 8 Number 1, June 1997. pp 1-2.

[3] Goals Project, 1999. p 26.

[4] Cynthia Patton, Turning Salt Into Environmental Gold:  Wetland Restoration in the South San Francisco Bay Salt Ponds. Save San Francisco Bay Association, Oakland, California, 2002. pp 10-11.

[5] Goals Project, 1999. p. 36.

[6] Goals Project, 1999. Inside front cover.

[7] Stuart Siegel, Philip Bachand. Feasibility Analysis of South Bay Salt Pond Restoration. Wetlands and Water Resources, San Rafael, California, 2002. p. 25.

[8] Goals Project, 1999. p. 85

[9] Siegel and Bachman, 2002, p 20.

[10] The following discussion of invasive species is an excerpt from Siegel and Bachman, 2002, pp 31-32.

[11] Siegel and Bachman, 2002, pp 41, 54.

[12] The following discussion of desalination is an excerpt from Siegel and Bachman, 2002, pp 77-88.