On August 7, the U.S. Army Corps of Engineers awarded a services contract to Adanta, Inc. of Napa to expand and enhance an existing wetland on the Veterans Affairs (VA) property at Alameda Point. The wetland project is being implemented to offset impacts to wetland areas elsewhere on the VA property where a health clinic, offices and a columbarium cemetery will be built.
“The four-year services contract, valued at up to $2,373,044, includes development, seed collection, propagation, restoration, and enhancement to ensure the wetland is completely established as a self-sustaining tidal marsh at the VA Alameda Point site,” states the Corps of Engineers August 14 news release. “In total, 8 acres of new tidal marsh will be installed and established, as will 3.3 acres of tidal transitional habitat; and 14.8 acres of existing tidal wetland will be enhanced.” Seed collection and preparation is scheduled to start this summer. The work is expected to be completed in 2025.
One-third of the wetland impacts of the VA project will not be offset at Alameda Point. The Corps of Engineers will purchase credits in the San Francisco Bay Wetland Mitigation Bank for 3.6 acres of impacts. The mitigation bank manages a wetland restoration project in Redwood City funded by Bay Area projects that impact wetlands. The credit purchase detail is not mentioned in the news release.
The Corps of Engineers and VA websites have not posted their 355-page “Final Wetland Mitigation and Monitoring Plan.” Details of the plan, including the mitigation credit purchase, were learned by obtaining a copy from the California Regional Water Quality Control Board, the state agency that approved the plan. No explanation was given for the credit purchase.
A key feature of the self-sustaining design is a tidal inlet in the adjacent rock seawall to allow Bay water to continually maintain a healthy marsh ecosystem. The tides flowing through the new inlet will enter a network of channels. “The pilot channel system is designed to emulate the structure and function of a well-developed slough channel system in a natural, mature tidal salt marsh of similar size,” according to the VA’s wetland plan prepared by H. T. Harvey & Associates, in collaboration with HDR Engineering, Inc.
Another key feature of the plan is a transition zone. “The created transition zone will provide the created tidal marsh with resilience to climate change by providing space for the tidal marsh to spread vertically upslope when sea level rises,” states the plan. The sea level rise zone will feature a complex mixture of vegetation that will include flowering and seeding plants that benefit birds and insects, as well as dense grasses, herbs, and subshrubs to provide long-term weed resistance.
Due to the poor amount of organic matter currently in the transition zone, the top 12 inches of soil will receive composted green waste to bring the soil to the optimal 2 percent of organic matter at the beginning. As the new vegetation matures, it will provide a self-sustaining amount of decaying plant matter. The soil for construction of the runway area was dredged from the Bay, and lack of organic matter in the sandy soil is the main reason the vegetation in the old runway area is sketchy.
As part of the project, the existing wetland comprising nearly 15 acres will see the removal of the invasive non-native ice plant and Algerian sea lavender. “In the restored condition, species such as gumplant, seaside arrow grass, alkali heath, and salt marsh sand spurry (Spergularia marina) will be established in patches within the marsh,” according to the plan.
Plants for the tidal marsh will be grown by a native plant nursery using parts, such as stems, gathered from existing Bay Area plants. But native plants in the historic sandy transition zones around the Bay’s tidal marshes are rare today. Therefore, the contractor will be seeking to acquire plants and seeds for the sea level rise transition zone from other parts of California from the northwest to the Central Valley.
Work was originally scheduled to begin in September 2019, but was delayed for unknown reasons. The wetland contract is the first construction contract to be awarded for the VA Alameda Point Project. On the other hand, no contracts for construction of the clinic and columbarium have been awarded yet, even though Congress has appropriated $113 million for the facilities. The 2021 budget request for another $152.8 million, if approved, will cover all of the funding necessary for the clinic, first phase of the cemetery and associated infrastructure.
Meanwhile, the City of Alameda is in the early planning stages for a shoreline wetland park, dubbed DePave Park, that will connect to the VA wetland.
Final Wetland Mitigation and Monitoring Plan – January 2019
Excerpts from Final Wetland Mitigation and Monitoring Plan, January 2019:
Section 3.2.1 Tidal Marsh Creation Area
The goals of the tidal marsh creation area are as follows:
- Create at least 7.3 acres of tidal marsh composed primarily of vegetated marsh plain with intertidal slough channels that meets the USACE [U.S. Army Corps of Engineers] definition of jurisdictional wetlands and other waters.
- Utilize design techniques that restore a self-sustainable tidal marsh ecosystem that will require minimal long-term maintenance.
- Restore a diverse mix of native tidal marsh species across the elevational range suitable for tidal marsh plants, including low-elevation marsh dominated by Pacific cordgrass (Spartina foliosa), mid-elevation and high-elevation marsh dominated by perennial pickleweed, and a transition zone with high-tide refuge cover.
- Create a gently sloping transition zone around the created tidal marsh to allow for marsh transgression toward higher elevations on the slope with sea level rise.
- Restore herbaceous vegetation (grasses and forbs) in the transition zone to provide high tide refuge habitat for resident tidal marsh animals, provide foraging habitat for bird and insect species, and increase native plant diversity.
- Design the restored habitats to minimize temporary impacts and avoid permanent impacts on the existing adjacent salina and wetland habitats.
- Allow the natural, inevitable formation of small unvegetated salinas and marsh ponds in the marsh creation area to enhance habitat diversity.
- Meet the RWQCB [Regional Water Quality Control Board]sediment contaminant screening guidelines for the protection of aquatic life.
- Avoid impacts on the California least tern colony during construction, post construction maintenance, and long-term management.
- Maintain the least tern viewshed by ensuring that vegetation height does not exceed 2 feet above the existing ground surface around the perimeter of the transition zone.
- Do not increase flood risk to the surrounding areas relative to the existing condition.
- Control invasive plants so that invasive plant cover is less than 5% in the created tidal marsh and transition zone.
- In the long-term (e.g., decades after installation), allow natural changes to the distribution of vegetated tidal marsh and un-vegetated tidal aquatic habitats. Sea level rise predictions in the San Francisco Estuary by the year 2100 vary from approximately 1.4 feet to 5.4 feet (NRC 2012). Sea level rise will likely result in temporal and spatial change to the distribution of wetland and aquatic habitats at the wetland mitigation site relative to the installed footprint of vegetated marsh and aquatic habitats. For example, sea level rise will likely drive the natural conversion of some vegetated marsh to marsh plain ponds and intertidal mudflat, as well as the landward transgression of vegetated marsh onto upland habitats in the transition zone. The site-specific temporal change in habitat distributions in response to sea level rise is unknown given the wide range of sea level rise predictions, the limited knowledge of tidal marsh responses to sea level rise, and potential future variability in sediment supply. Therefore, this mitigation plan allows for a natural, dynamic response of the spatial distribution of wetland and aquatic habitats to future sea level rise.
Section 3.2.2 Tidal Marsh Enhancement Area
The goals of the tidal marsh enhancement area are as follows:
- Increase the diversity of native plants relative to the current condition.
- Restore herbaceous vegetation (grasses and forbs) in the transition zone that enhance native plant community diversity and benefit wildlife and insect pollinators.
- Control invasive plants so that invasive plant cover is less than 5%.