The Bolsa Chica site is approximately 1,200 acres of degraded coastal wetland that has been affected by oil field activities for 80 years. After years of controversial development proposals, the site was purchased and set aside for restoration as an offset for construction activities in Los Angeles and Long Beach harbors. The California Coastal Conservancy, State Lands Commission, California Department of Fish and Wildlife, Regional Water Quality Control Board, Santa Ana Region and other agencies have oversight of the planning and design of the restoration at the Bolsa Chica Wetlands. Geosyntec has been the technical lead on several assessment and remediation efforts over the past two decades.
Geosyntec conducted detailed environmental, geotechnical, and hydrogeological field studies to assess the environmental impacts associated with historic land use, and to support the design of levees, tidal basins, culverts and a shallow groundwater control system as part of the overall design of the wetland restoration.
Since 1997, Geosyntec has conducted environmental site investigations of the Bolsa Chica, as well as remediation of the future full tidal, muted tidal, and seasonal ponds habitats for the Bolsa Chica Wetlands restoration. Geosyntec has also performed modeling studies of the shallow (perched) aquifer at the site to help understand and characterize the impacts of wetland restoration on groundwater levels beneath the adjacent neighborhood. The shallow groundwater database included monitoring of approximately 45 new and existing monitoring wells and piezometers throughout the site. Salinity concentration measurements were also taken to evaluate the hydraulic gradient with respect to the saltwater intrusion from the ocean. Using these data, Geosyntec helped to demonstrate the limited benefit of additional groundwater assessment that was proposed by the agency consortium. Geosyntec prepared geotechnical and hydrogeologic cross sections and a finite element model to design a 4,500-ft shallow groundwater barrier and saltwater intrusion dewatering system to protect the existing neighborhood from impacts of the wetland restoration.
Geosyntec has incorporated historical and new environmental, remediation, geotechnical, and groundwater databases in a GIS model in ArcView. The purpose of the GIS model is to provide a visually effective mechanism to relay remediation progress to project proponents and regulators, to facilitate project management and analyses, and to assist in three-dimensional visualization of the site conditions.
Geosyntec has also performed geotechnical analyses that were used to develop design recommendations for earthworks of levee profiles, nesting areas, and culverts for surface water control structures (culverts and tide gates). Additionally, the analyses included development of site-specific seismic parameters that were used to evaluate liquefaction, seismic settlement, and lateral spreading due to earthquake shaking.
Geosyntec designed a remediation strategy for a uniquely-impacted area of the oil field and facilitated a land deal between former site owners Hearthside and the state. Geosyntec provided technical and field oversight of the expeditious removal of this material via a streamlined permitting process using the state's contractor. Geosyntec monitored the excavation of approximately 12,000 tons of soil containing elevated concentrations of PCBs and submitted the necessary documentation for regulatory closure.
We assisted the client and regulatory team to streamline the constituents of concern list and helped negotiate cleanup criteria, saving the project millions of dollars and years of projected remediation effort, while still being protective of habitat. Geosyntec has overseen the bio-remediation of over 125,000 cubic yards of excavated impacted material at on-site soil handling areas, as well as the off-site hauling of impacted material above threshold cleanup levels. During this on-going multi-year/multi-stakeholder remediation effort, Geosyntec continues to provide technically-defensible cost-saving measures, as well as enhancements to the remediation approaches to individual areas and overall procedures. These efforts have resulted in a year-over-year reduction of cost per unit volume of treated soil, which allows more funding to remain for constructive site uses.
Geosyntec was successful in accomplishing a primary project objective of remediating (i.e., landfarming) the vast majority of impacted soil on-site and reusing this material on-site in other project locations. Geosyntec also had an integral part in implementing health and safety practices with the contractors that has resulted in over 150,000 hours worked without an incident.