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Former Chevron Station 9-5775 -2 - 12 May 2009
<br />301 W Kettleman Lane, Lodi
<br />TPH-g, 85 mg/kg; benzene, 0.08 mg/kg; toluene, 0.7 mg/kg; ethylbenzene, 0.65 mg/kg;
<br />xylenes, 4.5 mg/kg: and MtBE, 77 mg/kg.
<br />Maximum groundwater concentrations from the monitoring well sampling in March 2000 were
<br />TPH-g, 51,000 ug/L; benzene, 39,000 ug/L; toluene, 1,000 ug/L; ethylbenzene, 1,800 ug/L;
<br />xylenes, 1,300 ug/L; MtBE, 720,000 ug/L; EtBE, 18,000 ug/L; and tertiary amyl methyl ether
<br />(TAME), 6,000 ug/L.
<br />In June 2000, ten additional groundwater monitoring wells (MW -5B, MW -8B, MW -10A and B,
<br />MW -11A and B, MW12A and B, MW -13, and MW -14) and one additional extraction well
<br />(EX -2) were installed. The 24 July 2000 Preliminary Assessment Report (PAR) reported the
<br />maximum groundwater analytical results for the new wells as: MtBE, 1.100 ug/L (MW -14);
<br />ethanol, 2,000 ug/L (MW -12B); and EtBE, 120 ug/L. The ethanol detected in groundwater in
<br />June 2000 disappeared within three quarters in all wells, and was attributed to, by the
<br />consultant with concurrence by the County and Regional Board staff, to ethanol -coated
<br />bentonite product used in the construction of the wells.
<br />Interim remediation for soil and groundwater was initiated in June 2000, to comply with
<br />Cleanup and Abatement order (CAO) No. 5-00-704 issued on 20 April 2000 by the Regional
<br />Water Quality Control Board, Central Valley Region Executive Officer. CAO No. 5-00-704
<br />required the installation and operation remedial measures, which for this site consisted of Soil
<br />Vapor Extraction (SVE) and Groundwater Pump and Treat (GWP&T) systems. The four SVE
<br />wells (VE -1 through VE -4) sustained an average vapor flow rate of 107 cubic feet per minute.
<br />Initially, groundwater was pumped from groundwater extraction wells EX -1 and EX -2 at a
<br />combined rate of six gallons per minute into an above ground storage tank at the Site, and
<br />then the water was hauled to an off site treatment facility. Three 2,000 pound carbon
<br />treatment units.. installed 3 July 2000, completed the GWP&T system, and treated
<br />groundwater was subsequently discharged to the City of Lodi sanitary sewer system.
<br />The 5 June 2001 Problem Assessment Report/Final Remediation Plan Addendum (PAR/FRP
<br />Add.) reported that between October 2000 and February 2001, nine groundwater -monitoring
<br />wells (MW -7B, MW -8S. MW -9B, MW -10C. MW -17B, MW -18B, MW -19C, MW -20A, MW -20B)
<br />and one additional groundwater extraction well (EX -3) were installed at the site (Figure 3). Soil
<br />samples analyses from boring MW -19C detected: TPHg, 2.38 mg/kg: benzene, 0.805 mg/kg:
<br />ethylbenzene, 0.049 mg/kg; MtBE, 17.2 mg/kg; EtBE, 0.647 mg/kg; and TAME. 0.229: at a
<br />depth of 58 feet bgs. The maximum MtBE groundwater concentration result was 0.99 pg/L
<br />from MW -19C.
<br />Quarterly groundwater monitoring has continued since January 1999, The SVE system and
<br />GWP&T system reached asymptotic contaminant levels, and were shut down in August 2003
<br />and in April 2005, respectively, with Regional Board staff approval. Post -remediation quarterly
<br />monitoring showed no rebound in groundwater concentrations, and the SVE and GWP&T
<br />system have remained offline. By January 2008, only the EX -3 sample reported petroleum
<br />hydrocarbons. specifically MtBE, 5 ug/L (Figure3).
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