ARCHIVED REPORTS_XR0012448 - Laserfiche WebLink

Home Browse Search

ERI 205513 QSR21 Tosca Service Station 5886 Stockton California July 30 2002 discontinued during third quarter 2000 pending clarification from the County regarding water sampling and data collection requirements Purging was resumed during January 2001, and continued through January 2002, when it was terminated following installation and operation of the microsparge remediation system Approximately 285,000 gallons of groundwater were purged from the UST cavity well and well MW3 and transported to the Tosco refinery for recycling during interim groundwater remediation efforts • During June 2001, Tracer Research Corporation (TRC) performed an enhanced leak detection test on underground storage systems to evaluate the system integrity According to Tosco, the results of the enhanced detection test indicated that the underground storage systems are functioning within acceptable parameters • During third quarter 2001, ERI submitted a CAP, dated September 25, 2001 The CAP included recommendations to install a micosparge system to remediate MTBE impacted groundwater beneath the site • During first quarter 2002, the micosparge remediation system was completed and ERI performed system startup and initiated monthly operation and maintenance (O&M) of the system Currently, there are ten on-site AS wells (ASI through ASS, AS7, ASS, and AS10, and nested wells AS6S/D and AS9S/D), three on-site, single-casing groundwater monitoring wells (MW1 through MW3), four on-site, dual-casing groundwater monitoring wells (MW4S/D through MW7S/D), one on- site UST cavity well, and nine off-site groundwater monitoring wells (MWBS/IID through MWIOS/I/D) consisting of three wells at each nested well location as shown on Plate 2 and the On-Site Well Locations (Plate 3) Based upon data collected during ongoing quarterly groundwater monitoring and sampling, dissolved hydrocarbons are effectively delineated both laterally and vertically in the vicinity of the site However, dissolved hydrocarbons continue to be detected in groundwater samples collected form on- site wells and are concentrated in the vicinity and downgradient of the UST cavity SECOND QUARTER ACTIVITIES Based upon previous work completed at the site, and in accordance with the correspondence and request from the County, the following tasks were performed during the second quarter 2002 • ERI performed monthly remediation system O&M and collected monthly groundwater samples from wells MWI through MW3 • Gettler-Ryan, Inc (GRI) of Dublin, California, under direct contract to Tosco, performed quarterly groundwater monitoring and sampling at the site on May 2 and 3, 2002 The GRI Second Quarter Event of May 2 and 3, 2002, Groundwater Monitoring and Sampling Report(GRI, June 12, 2002) is provided as Attachment A The results of the second quarter monitoring and sampling event indicate the following 3