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` California Regional Water Quality Control Board <br /> Central Valley Region <br /> Alan C.Lloyd,Ph.D. Robert Schneider,Chair 2005 NOV 28 PN 1: 17 Arnold <br /> Agency Secretary Sacramento Main OfficeJ, Schwarzenegger <br /> 11020 Sun Center Drive#200,Rancho Cordova,California 956'�d 1 'f 1`(I I-'I i-4 c OU N T Y Governor <br /> Phone(916)464-3291 •FAX(916)464-4645 "IRWNNENTAL <br /> E-(E A L T}{ p E p��R T�i E N T <br /> http://www.waterboards.ca.gov/centralvalley <br /> 22 November 2005 <br /> Ms. Kerry Heckman <br /> Connell Tire <br /> 2211 North Wilson Way <br /> Stockton, California 95205 <br /> REPORT REVIEW; FORMER RIVER CITYPET ROLEUM& FORMER CONNELL MOTOR <br /> LIFT TRUCK, 2211 NORTH WILSON WAY, STOCKTON,SAN JOAQUIN COUNTY <br /> I reviewed the 31 October 2005 Quarterly Report— Third Quarter 2005 (Report) submitted on your <br /> behalf by Advanced GeoEnvironmental, Inc. (AGE). The Report documents the operation of the Soil <br /> Vapor Extraction (SVE) system, the installation of new groundwater monitoring wells (MW-38 through <br /> MW-48) and the quarterly groundwater sampling conducted on 29 through 31 August 2005. The Report <br /> states: <br /> • The SVE system removed a total of 266 gallons of petroleum hydrocarbons this quarter from the <br /> vadose zone soil. <br /> • Depth to groundwater decreased over 7 feet since the previous quarterly sampling. <br /> • With the exception of the lateral extent of the deeper section of the 1,2-dichloroethane <br /> (1,2-DCA)plume,the monitoring well network delineates the vertical and lateral extent of the <br /> petroleum hydrocarbon plume. The new monitoring wells in the deepest zones (100 and 150 feet <br /> below ground surface or bgs)reveal a 1,2-DCA plume increasing in concentration with depth, <br /> down-gradient of the Underground Storage Tanks source area. AGE's Figures 6,7, and 8 <br /> (enclosed) iso-concentration maps show a 1,2-DCA plume that appears to be diving from the <br /> source area and expanding laterally into deeper hydrological units beyond the monitoring well <br /> network. <br /> • Maximum groundwater concentrations are: Total Petroleum Hydrocarbons as gasoline (TPHg, <br /> 39,000 µg/L), Benzene (11,000 µg/L), Toluene (7,000 µg/L), Ethylbenzene, (1,100 µg/L), <br /> Xylenes, (13,300 µg/L), Ethylene Dibromide(63 µg2), and 1,2-DCA(250 pg/L). <br /> • Monitoring wells MW-12, MW-15, and MW-16 were reported as not sampled due to "...vehicle <br /> parked over well or unaccessible (sic)for purging and sampling. " <br /> The Report recommends continued quarterly groundwater monitoring and SVE system operation. <br /> Comments: <br /> 1. Based on two years of quarterly groundwater monitoring, 1,2-DCA concentrations have declined <br /> by an order of magnitude (2,600 to 110 µg/L) in shallow source area well MW-1 while the <br /> 1,2-DCA plume appears to be spreading laterally in deeper zones beyond the deeper monitoring <br /> well network. It appears that interim groundwater remediation is necessary to reduce 1,2-DCA <br /> concentrations and protect nearby sensitive receptors. Additional groundwater monitoring wells <br /> California Environmental Protection Agency <br /> �a Recycled Paper <br />