Habitat Area 2 Remedial Action Campus Bay Site

Part of the 86-acre Campus Bay Site in Richmond, CA, Habitat Area 2 (HA-2) is located adjacent to the East Stege Marsh, a tidal salt marsh influenced by daily tides from the San Francisco Bay. The area also serves as a nesting location for the California clapper rail (CCR).

Historically, the Campus Bay Site was occupied by former manufacturing plants and Stauffer Chemical Company’s Western Research Center. Under the oversight of the Department of Toxic Substances Control (DTSC), numerous investigations were performed within HA-2 to examine the impact of these historical operations on lagoon sediments and groundwater.

These investigations identified numerous constituents of concern (COCs), including arsenic, copper, nickel, lead, mercury, and zinc. Other contaminants included proprietary pesticides (PPs) in sediments, soils, and groundwater; polychlorinated biphenyls (PCBs) in sediment and soil; and organochlorine pesticides.

The site required intensive remediation to reduce or eliminate these contaminants and to reduce groundwater infiltration from HA-2 to the East Stege Marsh. The use of heavy machinery in this area was prohibited during the CCR breeding season (February 1 to August 31), creating a short window for construction activities with a strict deadline and posing a challenge to remediation efforts.

Assisting with remediation efforts, our team led excavation of sediments, in situ treatment, sediment cap, removal and reconstruction of berms, installation and removal of sheet piles, excavation and backfill of upland habitat areas, off-site disposal of non-RCRA and non-hazardous waste, and stormwater improvements. Our scope also included installation and operation of a water treatment system and two material handling pads.

To begin work, our team installed two Stormceptors replacing the existing drainage system and established a stormwater bypass to reroute stormwater into a public drainage inlet. This phase was crucial to begin sediment removal operations and subsequent tasks. During removal and reconstruction of the middle berm, we constructed a new headwall with two 28-inch stormwater pipes replacing the existing 36-inch pipe. The new 28-inch pipes were tied into the existing drainage system by installing a precast stormwater vault. The outfall of the 28-inch pipes was outfitted with a Tideflex system allowing water to exit into the East Stege Marsh while minimizing backflow of tidal water.

We disposed 60,900 tons of hazardous waste to Kettleman Hills Landfill and 9,100 tons of non-hazardous waste to the Potrero Hills Landfill. To streamline production, optimize waste handling, and minimize track out, our team designed and built two asphalt pads. These pads were located near the site entrance and away from intrusive activities allowing for a safe and clean loadout operation. Saturated soil or sediment was stockpiled in bays on the material handling pad, which were built to hold 100 cubic yards of material that would then be mixed with up to 5 percent by weight of Portland cement (PC) for stabilization. After passing a paint filter test, we transported the material with a Komatsu HM400 articulated haul truck to the loadout pad where it was stockpiled and loaded out by a Komatsu WA470 loader to its respective landfill for disposal. Due to the travel distance and quantity of material going to Kettleman Hills Landfill, trucks could only transport one load per day and needed to be loaded by 11:00 AM. We loaded out an average of 735 tons of non-RCRA waste daily throughout the duration of the project.

Our team installed sheet piles between the East Stege Marsh and the toe of the southern berm by a subcontractor in order for the berm to be completely removed. We built a stable work pad by partially degrading and compacting the berm so the sheet pile subcontractor could perform the installation with their crane. Berm removal and reconstruction occurred concurrently to reduce the potential for disturbance at the bottom of the excavation. To minimize the risk of cross-contamination, the 10,400 cubic yards of excavation material and 9,500 cubic yards of backfill were kept separate.

A third-party surveyor and geotechnician employed by the project owner’s representative were on site during operations to collect survey data and perform compaction testing. However, our team utilized new technology such as drone survey capabilities and VisionLink by Trimble to supplement surveying.

The lower lagoon was broken into three segments: sediment removal, in situ soil treatment, and capping-only. An isolation berm was constructed through the middle of the lower lagoon to provide heavy equipment access to perform 3,288 cubic yards of in situ treatment and 8,300 cubic yards of capping.

A Komatsu PC360 excavator fitted with GPS capabilities mixed in 1 percent by weight of activated carbon and 3 percent by weight of PC into 24 delineated cells in order to re-establish 100 psf to the agitated sediment. Anchor trenches were excavated around the perimeter of the lower lagoon to anchor in the geocell and geotextile. A geotextile layer was installed to separate the underlying sediments post removal from the clean backfill cap material and provide strength for placement of the cap. The geotextile was sewn in place by a subcontractor and pulled across the lagoon footprint with heavy equipment by utilizing cables sewn through the leading edge. Geotextile was then anchored into the trenches along with a geocell tendon system to provide lateral slope stability. Due to the soft sediment in the capping-only area and potential for mud wave, heavy equipment could not be utilized. In order to cap this area, a Telebelt was mobilized along with low ground pressure (LGP) equipment to spread 1 foot of clean backfill cap material.

Our team completed two lagoons and transitional habitat or habitat buffer area totaling approximately 9.2 acres. The lagoons act as a natural retention basin and contain water during the rainy season. During the summer months, the upper lagoon dries out and the lower lagoon water levels decrease from evapotranspiration. This work helped meet our client’s goal of reducing or eliminating COCs, PPs, and PCBs and reducing groundwater infiltration from HA-2 to the East Stege Marsh. While the project faced many adversities such as weather conditions, a restricted timeline, and permit restrictions, our team successfully completed the project and avoided extending construction into a second season. The project owner and their representative expressed appreciation for our ability to navigate a tight schedule and manage multiple delays.