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w 6 l�l I V G➢s <br /> 1 <br /> {J .� L()A1lltill(i. BRa\NN.II:. <br /> m �T <br /> ELHFAL7H M°„�E N ROORIOUF.: <br /> NVIRONMENTA <br /> Water Boards PERMIT/SERVICES <br /> 1fJl in[1Rtp[NTPI Pfiall("11111 <br /> Central Valley Regional Water Quality Control Board r <br /> 10 July 2012 <br /> Ben Terry <br /> Chevron Environmental Management <br /> 6111 Bollinger Canyon Road, Rm. 3652 <br /> San Ramon, CA 94583 <br /> DOCUMENTS REVIEW FOR COMMINGLED PLUME ACCOUNT CP0057 SITES AT <br /> 440 (TEXACO— SHELL, RB #390268)/441 (ARCO, RB #390657)/508 (CHEVRON, <br /> RB #390876) W. CHARTER WAY AND 1444 S. LINCOLN STREET, <br /> (COLUMBO/TOSCANA BAKERY, RB #390825) STOCKTON, SAN JOAQUIN COUNTY <br /> I reviewed the Corrective Action Plan (CAP) and the Semi-Annual Groundwater Monitoring <br /> Report, Second Quarter 2012 (Report), received 19 June 2012 from Stantec, the lead <br /> consultant. The Report provided the results of groundwater monitoring conducted from <br /> 9 April 2012 to 11 April 2012 at the four sites listed above. Maximum groundwater <br /> concentrations were total petroleum hydrocarbons as gasoline (TPHg), 120,000 micrograms per <br /> Liter (ug/L); benzene, 19,000 ug/L; toluene, 18,000 ug/L; ethylbenzene, 3,900 ug/L; xylenes, <br /> 20,000 ug/L; methyl tert butyl ether (MTBE), 20,000 ug/L; tert-butyl alcohol (TBA), 12,000 ug/L; <br /> and 1,2-dichloroethane (1,2-DCA), 66 ug/L. Depth to groundwater varied from 16 feet below <br /> ground surface (' bgs) to 19' bgs. Groundwater flow direction varied from northeast to south <br /> across four (4) aquifer zones (A through D), with the predominant flow towards the southeast. <br /> Groundwater gradient varied from 0.001 ft/ft to 0.006 ft/ft. <br /> The CAP proposed full scale expansion of the existing Soil Vapor Extraction (SVE) and Air <br /> Sparging (AS) system installed for the SVE/AS pilot test that was conducted from <br /> 12 December 2011 through 16 December 2011 at the Chevron facility. Currently one SVE well <br /> (VE-1), two AS wells (AS-1 and AS-2), and two piezometers (PZ-1 and PZ-2) are present. Five <br /> additional SVE wells (SVE-2 through SVE-6) and ten additional AS wells (AS-3 through AS-12) <br /> will be installed in November 2012. The SVE wells will be 4" diameter polyvinyl chloride (PVC) <br /> with 0.020-inch well screens placed from 11' bgs to 16' bgs above the water table. The AS <br /> wells will be 2” diameter PVC with 2 ft long 0.020-inch well screens set at varying depths, <br /> dependent upon lithology, from 25' bgs to 45' bgs. The SVE/AS system will be designed to fit <br /> within the spatial constraints of the Site and will address noise issues. A thermal-catalytic <br /> oxidizer will treat SVE vapor removed by an SVE blower, and a compressor will provide clean <br /> air for AS wells. The full scale SVE/AS system startup is scheduled for April 2013. <br /> The CAP states that SVE/AS will run until asymptotic levels are reached and a rebound test is <br /> completed. If rebound occurs, the SVE/AS will be restarted for a specific period of time and a <br /> Sc D. r1.E.. - iam I'gt,ALL-. C. CNLLLI :d r'l DGEE.LCL <br /> .. :nva,V00,RanOnO Gn[anva [,A 95670 Www wn*erttaalns ca 01 r Lalval:Py <br /> Cg^r.c:'­� n <br />