Since 2011, McMillen has been focused on providing solutions to restore areas of Don Edwards NWR. From civil, hydraulic, structural, mechanical, and electrical to construction, our work ultimately safeguards the natural environment, wildlife, the local community, and critical infrastructure. Example projects include:
A16 & A17 Pond Rehabilitation.
McMillen was the design-build lead to restore 373 acres in two former salt ponds as part of the largest tidal wetland restoration on the West Coast. The project involved constructing water control structures, a large fish screen, outlet structures with slide gates and tide gates, and habitat nesting islands for Least Tern, waterbirds, and other sensitive bird species.
The scope of work included the demolition of existing intake structures and pipelines, breaching of a former salt pond levee, placement of new concrete intake and outlet structures, culverts, and intake pipes, installation of a fish screen, channel improvements, earthworks, sediment management plans, creation of access roads and levees, habitat restoration, NEPA process and permitting support, and environmental monitoring and compliance during construction.
Channel improvements involved demolishing the existing intake structure and shaping the intake channel to allow natural intrusion of the San Francisco Bay without causing rapid scour. The outlet channel was dredged to allow free-flowing water movement through the pond to the existing slough.
Earthwork and dredging activities included lowering levees, creating nesting islands, raising portions of the perimeter levee, and building earth plugs to divert water. A total of 50,000 cubic yards of material were excavated, moved, or placed. The work area in the pond was protected with sheet pile isolation walls.
Habitat restoration focused on creating nesting islands for resident and migratory birds, raising portions of the perimeter levee, and constructing water control structures. The island fill was mixed to prevent the loss of fledglings into cracks as the islands settled and cracked. The intake, fish screen, and pipe were sized to supply a large flow of water to improve water quality at the outlet structure discharge.
Environmental considerations were a priority throughout the project. McMillen coordinated construction around bird nesting surveys and adhered to buffer restrictions around active nests for endangered Snowy Plovers and Clapper Rails. Sediment management plans were implemented to control sediment deposition, and permitting support and environmental monitoring were provided to ensure compliance.
Water Control Structures (WCS) AB1 and AB2 and Levee Repairs.
McMillen rehabilitated AB1 and AB2 and their associated levees to restore the integrity of the pond system and protect wildlife habitat. We provided planning, evaluation, and design services, including a topographical survey and conceptual design analysis. The preferred alternatives from the conceptual phase were advanced to the final design. The project involved replacing the water control structures with new structures consisting of HDPE pipes, concrete slabs, wing walls, slide gates, and trash racks. The levees were repaired using re-vegetated soil and rip rap repairs, and gravel surfacing was added for improved conditions and access.
Alviso Pond Levee Rehabilitation (A10, A11, A9).
McMillen designed improvements to levees on ponds A10 and A11 and replaced the Alviso A9 WCS. The project was completed in two phases, with the first phase including design and construction initiated in September 2019. An additional 1,150 feet of deteriorated levee was repaired in November 2019. McMillen worked closely with USFWS project personnel to replace riprap material with a preferred substitute, resulting in significant cost savings to USFWS. The project was completed in collaboration with our 8a Mentor-Protégé firm, Water, Civil, and Environmental, Inc., as part of a design-build contract.
Alviso Pond Levee Rehabilitation Master Plan.
McMillen provided engineering services to prioritize improvements for over 40 miles of levee and WCS’s at the USFWS-managed ponds. The project included gathering history, stakeholder interests, system operations documentation, condition assessments, design criteria development, risk assessment, cost estimates, and repair prioritization. The work aimed to maintain coastal-marine ecosystems and habitats for various fish and wildlife species.
Alviso and Ravenswood Pond Levee Repair (A11) and A9 WCS Replacement:
To protect over 1,200 acres of pond habitat within the Alviso Pond system, McMillen repaired the 0.9-mile Alviso A11 levee segment. The deteriorating A9 WCS was replaced to support the management of the Alviso Pond system. As a cost-saving measure, Flexamat® was proposed for the A9 WCS and Pond A11. The Alviso levee segment required reshaping, repair, and erosion protection, considering hydraulics, slope stability, and compaction requirements. The existing A9 WCS was replaced with an upgraded cast-in-place reinforced concrete design due to deterioration. At the Ravenswood R1 Pond Levee, stabilization was achieved through earthwork activities and reusing existing riprap materials that had sloughed off into the San Francisco Bay.
Additional work at Don Edwards NWR included a wood bridge assessment at Pond 8 and a hydraulic model to replicate the tidal impact of the San Francisco Bay on the Moffett Pond System. The model incorporates intricate bathymetry, levees, and various water control structures that link the ponds. These simulations were utilized to devise a manual for operating the water control structures, enabling effective management of water surface elevation and detention times within the pond system.
