With petroleum hydrocarbons leaking into soil and groundwater at the Coarsegold Maintenance Station, Caltrans needed a partner who could quickly assess the situation and remove the danger.
Underground storage tanks at the four acre site were leaking a number of contaminants, including gasoline and diesel, benzene, toluene, ethylbenzene, xylenes, and fuel oxygenates such as MTBE. To address the problem we constructed, installed, and operated a Soil Vapor Extraction (SVE) / Air-Sparging (AS) system.
We connected the SVE/AS system to granulated activated carbon filters to treat the extracted soil vapors and sampled the groundwater monitoring wells and the onsite domestic well, along with maintaining and operating the SVE/AS remediation system. After operating and monitoring the system from 2004 to 2010 and preventing the petroleum hydrocarbon plume from extending offsite, Stantec was able to prevent site closure from the Regional Water Quality Control Board in accordance with requirements of California’s Health and Safety Code.
We also saved Caltrans approximately $80,000 by operating the remediation system for an additional year on the existing funds in our contract.