Powerhouse Science CenterSacramento, California
Geocon is providing geoenvironmental consulting to the City of Sacramento and the project design team for the redevelopment of this historic former Pacific Gas & Electric (PG&E) powerplant. The former powerplant building will be the centerpiece of the new Powerhouse Science Center – a math and science discovery museum that will anchor the northern end of Sacramento’s “Mile of Museums” along the city’s old river waterfront. The project site presents unique environmental and geotechnical challenges in that 1) it is has significant remaining metals and petroleum soils contamination related to former site operations and 2) site soils consist of non-engineered fill that was placed behind a flood protection levee along the river overlying deep recent alluvium which is compressible and prone to seismic-induced liquefaction and dynamic instability. To address the soil contamination, Geocon is working closely with the City, the project design team, and the state Department of Toxic Substances Control (DTSC) to implement further cleanup that avoids an existing, approved cleanup remedy (a clay cap over contaminated soil), but that will remove other contaminated soils as part of construction. Contaminated soil beneath the historic building will be excavated, stockpiled, characterized, and transported to an approved waste disposal facility. The City is funding this effort under a USEPA Brownfields cleanup grant. To evaluate geotechnical conditions at the site, Geocon performed a targeted geotechnical investigation using conventional exploratory borings and in-situ cone penetration testing (CPT) and dilatometer testing (DMT). Geocon provided several deep foundation alternatives to provide structural support and to mitigate excessive static and seismic settlements for new structures and preservation of the existing historic powerplant building.