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Dutch Slough Tidal Marsh Restoration

Dutch Slough Project Area

Dutch Slough Project Area



Project Description

The Dutch Slough Tidal Marsh Restoration Project, in an area formerly slated for urban development, will soon become 1,178 acres of critically needed habitat for fish and wildlife in the Sacramento-San Joaquin Delta. The project's location in the western Delta offers the opportunity, soil types, and lack of subsidence to create a large area of tidal marsh and complex intertidal channels favored by native Delta species. Shaded channels, native grasslands, and riparian forests will be restored in the upland portions of the site. The restored habitats are like those that historically dominated the Delta, and their restoration is considered a critical action to increase numbers of native sensitive species and improve general ecological health of the Delta.

This project will not only provide critical habitat for native plants, fish, and wildlife that are in rapid decline in the Delta, but will also provide outdoor recreation and resources for the residents of the Delta and Bay Area. The former landowners of the project area, once pursuing permits for developing the area with up to 6,000 houses, partnered with State, Federal, and private agencies to create a project to provide an island of habitats and open space in the rapidly urbanizing area of eastern Contra Costa County. The cooperative partnership between the Department of Water Resources, Department of Fish and Wildlife Ecosystem Restoration Program, State Coastal Conservancy, Reclamation Districts, Natural Heritage Institute, City of Oakley, Ironhouse Sanitary District, and private consultants has undertaken the long process of scoping, planning, preparing environmental documents, and securing funding. In 2013, after a decade of planning and preparation, the Dutch Slough Tidal Marsh Restoration Project will begin construction of the first of three phases of project implementation and begin to realize the Project's goals and objectives.

Project Goals

  1. Benefit native species by re-establishing natural ecological process and habitats.
  2. Contribute to scientific understanding of Delta habitat restoration.
  3. Provide shoreline access and educational and recreational opportunities.

In addition to restoring natural habitats, the Project has a significant recreational component. Fifty-five acres located in the south-central portion of the original land purchase will be deeded to the City of Oakley for a community park. To coordinate with the park, the Dutch Slough Project will include the following recreation features on the Emerson (westernmost) parcel: bike/pedestrian trails, shoreline access, fishing opportunities, and interpretive signs to facilitate educational visits to the site by school and community groups. Click on this link to access the City's Community Park and Public Access Conceptual Master Plan (PDF: 65.1 MB)

Background

The three parcels which make up the project site were originally leveed around the turn of the 20th century. For over a hundred years, the three parcels of the Dutch Slough property were used for grazing and dairy operations. During the past thirty years, eastern Contra Costa County has undergone a rapid urbanization, and, beginning in the 1990s, the former landowners began securing approvals for the eventual development of the property. In 1997, Contra Costa County approved a development agreement for this property that would have allowed for the construction of 4,500-6,100 housing units on the site. When the City of Oakley incorporated in 1999, this property was within the city limits, and the City accepted the County's development agreement.

In the fall of 2001, the Natural Heritage Institute (NHI) and the Department of Water Resources (DWR) identified the site as an important restoration opportunity and began working cooperatively with the landowners to obtain grant funding to acquire and restore the property. During 2002, the project partners worked with the Oakley City Council to build local support for the project. In 2002, CALFED's Ecosystem Restoration Program (now part of the Department of Fish and Wildlife) and the State Coastal Conservancy's San Francisco Bay Area Program awarded grants to fund the acquisition. In the fall of 2003, the Department of Water Resources completed the purchase of the restoration site.

Site Description

The Dutch Slough site is located in the City of Oakley, eastern Contra Costa County, in the western Delta. The site encompasses 1,178-acres, and is bounded by Dutch Slough on the north, Marsh Creek on the west, the Contra Costa Canal on the south and Jersey Island Road on the east. The site is comprised of three parcels, partially separated by Emerson Slough and Little Dutch Slough. Unlike much of the Delta, the site is not deeply subsided and still has topographic diversity.

East Bay Regional Park District's Big Break Regional Shoreline is adjacent to the northwestern edge of the site, and the Marsh Creek Regional Trail runs along the southwest side. The City of Oakley will own a 55-acre community park at the south end of the restoration site. The restoration project will re-route Marsh Creek onto the Emerson (westernmost) parcel, and once the restoration is complete, the Marsh Creek Trail will continue to the new mouth of Marsh Creek.

Project Construction

  1. Excavation and import of fill material
  2. The primary goal for the project is to create large expanses of intertidal tule and/or cattail marshes. These marshes develop in areas where the soil surface is exposed at low tide and flooded at high tide. To maximize the area that will become tidal marsh after the levees are breached, higher (southern) areas will be graded down and the excavated soil moved to areas of lower elevation. In addition, about 500,000 cubic yards of soil will be imported and placed in lower elevation areas. Because the northern portions of the site are the most subsided, it is not economically feasible to import the large quantities of material necessary to bring these areas to marsh elevations. These areas will be restored or enhanced as other habitats—open tidal water, managed marsh, or uplands.
  3. Grading
  4. After the soil is placed in areas that will be restored to tidal marsh, it must be graded to the correct elevations and slope, and tidal channels excavated. Proper grading is necessary to allow tidal waters to move freely, transporting nutrients, sediments, plant material, invertebrate organisms, and small fishes into and out of the marshes.
  5. Vegetation per-establishment
  6. In tidal marshes, tules germinate best in areas where the soil surface is exposed part of each day and water depths rarely exceed 1 foot. Once established, however, tules can withstand deeper and longer flooding. Therefore, to increase the area of vegetated marsh, a one or two-year period of tule pre-establishment will occur prior to levee breaching. Water levels will be controlled in new marsh areas to facilitate growth of large expanses of tules and cattails. These tules will also prevent soil erosion when the site is breached.
  7. Levee Breaching
  8. Once the tules are growing well, the levees will be breached, and project construction will be complete.

For more information, please contact Patty Finfrock, Project Manager at pfinfroc@water.ca.gov or (916) 651-0851.