Pond A4 Resilient Habitat Restoration Project

Status

Design

Location

Sunnyvale, CA

Phase

Design

Schedule

Design and Permitting - June 2026 | Access Improvement Construction - June 2027

The Pond A4 Resilient Habitat Restoration Project reflects Valley Water’s commitment to environmental stewardship. The project aims to create mudflat habitat to benefit shoreline birds along Pond A4’s southern shoreline in Sunnyvale. By beneficially reusing sediment from Valley Water's Stream Maintenance Program and other sources that would otherwise be disposed of in landfills, the project intends to create a shallow-water shorebird foraging ecotone bench slightly below the existing ordinary high water mark.

Currently, Pond A4 provides limited foraging habitat for shorebirds, as water depths are suitable for use only in a very narrow band along the immediate shoreline and remnant internal berm features. As a result, this pond does not support large numbers of shorebirds. The project will beneficially reuse stream sediment to restore regionally scarce shorebird foraging habitat.

For more project information, please contact Judy Nam at [email protected] or 408) 630-2747.

The project is currently in the process of obtaining the necessary permits and finalizing the design. We anticipate completing both permitting and design by the end of 2026.

The Pond A4 Resilient Habitat Restoration Project offers a multitude of benefits that positively impact the environment and the community. These benefits include:

Restoration of approximately 45 acres of shorebird and salt marsh harvest mouse habitat
Enhancement of approximately 6,000 ft of existing Bay Trail by increasing the amount of biological activity adjacent to the existing Bay Trail, increasing the natural diversity of the viewshed, and providing interpretative signs.

The project’s ecotone bench will be designed to maximize habitat value given the existing water surface elevations of the Pond A4. Because the pond has limited hydraulic connectivity with nearby water bodies, it is insulated from the effects of sea level rise and water surface levels are not expected to change significantly during the project period.

Pond A4 is a roughly 300-acre former salt production pond nestled within Sunnyvale's southern San Francisco Bay shoreline. Owned by Valley Water, its boundaries are defined by Guadalupe Slough to the north and east, the Moffett Channel to the west (which converges with Guadalupe Slough), and to the south by the Sunnyvale Water Pollution Control Plant, Sunnyvale-Mountain View Recovery and Transfer Station, a closed sanitary landfill, and Sunnyvale Baylands Park. An earthen berm tracing a length of about 6,000 feet accommodates a segment of the Bay Trail at its southern edge.

Historically, the South San Francisco Bay, including Pond A4, was originally comprised of tidal marsh. Pond A4 underwent transformative shifts in the early 1900s when dredging and diking operations converted thousands of acres in the region to expansive ponds dedicated to salt production. In the year 2000, Valley Water acquired Pond A4 from the Cargill Corporation. Today, Pond A4 is a roughly 300-acre diked open water pond with limited hydrologic exchange with nearby Pond A3W. This results in a very muted tidal regime; water surface levels vary seasonally by about two feet. Pond bottom elevations are several feet below the water surface elevations. As a result, water depths are too deep for shorebird foraging and very little emergent vegetation grows in the pond. In its current condition, the Pond A4 has minimal biologic productivity. Against this backdrop, the Pond A4 Resilient Habitat Restoration RHR project emerges, envisioning a transformation with the creation of a shallow water ecotone bench spanning approximately 45 acres along the pond's southern margin.