For Premier Power and Solar Power Partners
Richmond, California

Questa was retained to perform a geotechnical investigation and confirm the foundation design for siting of solar power panels at the West County Wastewater Treatment Plant site in Richmond/Western Contra Costa County, located adjacent to the levees of San Pablo Creek. The project involved construction of solar panel foundations in former wastewater treatment ponds and storm water retention ponds, and included evaluation of the potential for settlement of bay mud deposits from the loads imposed by the solar panels and foundations.

Consolidation testing of the bay mud and settlement calculations were completed for several conditions, including areas with alluvial deposits over bay mud, areas with compacted gravel road berms over bay mud, areas with asphalt concrete pavement and gravel over bay mud, and areas with recently placed fill over bay mud. Recommendations included a variety of stabilization measures for support of the concrete foundations and solar panel array.