Active Service Station, 3001 Jefferson Street, Napa

High levels of petroleum hydrocarbons and fuel oxygenates were previously reported at this service station located in downtown Napa. Free product was formerly measured on top of shallow groundwater at the site (groundwater levels measured at 7 to 11 feet bgs historically). Given the position of the fuel storage and delivery facilities, much of the dissolved petroleum hydrocarbon impact appeared to have migrated beneath an adjacent roadway. Dissolved GRO, benzene, and MTBE have been reported at maximum concentrations of 3,600,000 µg/L, 27,000 µg/L, and 60,000 µg/L, respectively. Given the contaminant concentrations observed at the site, this project received a high level of scrutiny from Napa County Department of Environmental Management (NCDEM) resulting in pressure on the RP to address the environmental concerns.

In order to remediate the subject property, Stratus selected remedial alternatives that would allow for extraction of contaminants that had migrated offsite beneath the adjacent roadway, as well as contaminants beneath the service station. This was achieved by using an SVE and GWE&T remedial approach. Following system construction, operation of the remedial equipment was initiated in 2002; SVE was performed until December 2007 and GWE&T was conducted until September 2008. At the time, that the remedial approaches were terminated, no petroleum hydrocarbons or fuel oxygenates were detected in vapor and groundwater influent samples into the treatment systems.

Post-remediation groundwater sampling has consistently indicated that no GRO or BTEX remain dissolved in the saturated interval. MTBE levels at most of the site wells have been reduced below MCL water quality objectives for the site (5 µg/L), although MTBE concentrations at a few wells remain above MCLs (less that 50 µg/L). Stratus is currently working with NCDEM in order to develop a site specific approach in order to achieve closure of the environmental case for the RP.

GRO Impact to Groundwater, June 2002

GRO Impact to Groundwater, July 2009