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2 - EovenxaRG Sxuwx Jx. <br /> 4 <br /> O.G LIIOPxI• <br /> MATTHEW <br /> ROOx10VEZ <br /> Water Boards <br /> iNVIPONM 6NLnL➢ROTGCLIOx <br /> �f. <br /> Central Valley Regional Water Quality Control Board <br /> 1 August 2013 <br /> Fassel & Amal Elder Aman Business Enterprises, Inc. <br /> 4880 Peach Avenue 801 North Granda Drive, No. 14A <br /> Manteca, CA 95337 Madera, CA 93637 <br /> Harjit Songh, et al Satinder Singh Dilawri <br /> 1675 Paseo Laguna Seco Vancity Inc. <br /> Livermore, CA 94550 420 W. Yosemite Ave <br /> Manteca, CA 95337 <br /> RAINWATER CAR WASH, 420 EAST YOSEMITE AVENUE, MANTECA, SAN JOAQUIN COUNTY <br /> (RB CASE#390835) <br /> I reviewed the Groundwater Monitoring Report, Second Quarter 2013 (Report) received 10 July 2013, <br /> and the MTBE Plume Travel Model(Fate and Transport Modeo, also received on 10 July 2013, prepared <br /> on your behalf by Ami Adini &Associates, Inc. (AA&AI). In the Report, AAAI provides the results of <br /> groundwater monitoring conducted on 15 May 2013. In the Model, AA&AI provided an estimate of the <br /> fate and transport of the groundwater pollutant plume. The Model results do not support closure under <br /> the State Water Resources Control Board Low Threat Closure Policy (LTCP), which does not allow <br /> petroleum releases to impact water supply wells. <br /> AA&AI reported that during the second quarter of 2013, depth to water varied from 15' below ground <br /> surface (bgs) to 19' bgs. Groundwater flow direction has historically varied from northwest (current) to <br /> east-northeast at a groundwater gradient of 0.0008 ft/ft. Maximum groundwater concentrations were <br /> total petroleum hydrocarbons as gasoline (TPHg), 16,500 micrograms per Liter (ug/L); benzene, <br /> 131 ug/L; toluene, 835 ug/L; ethylbenzene, 1,400 ug/L; xylenes, 6,130 ug/L; methyl tert butyl ether <br /> (MTBE), 131 ug/L; and tert butyl alcohol, 72.3 ug/L. <br /> A&AI provided plume maps in the Report that demonstrate a post-remediation declining trend in <br /> concentrations for TPHg, benzene, and MTBE in monitoring wells, and a shrinking aerial extent (laterally) <br /> of the groundwater plume since 2012. However, the lateral and vertical extent of the groundwater plume <br /> remains undefined downgradient of MW-11. The offsite shallow zone of wells MW-1 1-A through <br /> MW-13A are screened at least 15' below the current water table, which may result in the groundwater <br /> data not being representative of actual shallow groundwater conditions. An offsite groundwater <br /> investigation with new nested (shallow and intermediate zone) monitoring wells downgradient of MW-11 <br /> was approved in July 2012. <br /> AA&AI state in the Report that the seven (7) continuous multichamber tubing (CMT) wells (MW-7 A-F <br /> through MW-13 A-F) appear to have been compromised. AA&AI also recommended consideration for a <br /> Low Threat Closure and continued semi-annual groundwater monitoring in the Report. <br /> KARL E. LONCLEY SCD, P.E., CHAIR I PAMELA C. CREEDON P.E., SCEE, EXECUTIVE Orriom <br /> 11020 Sun Center Drive#200.Rancho Cordova,CA 95670 1 www.waterboards.ca.gov/centralvalley <br /> CWe RECYCLED PAPER <br />