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California "egional Water Quality Con*-ol Board ,.
<br /> Central Valley RegionNE � � J
<br /> Karl E. Longle),Scl),P.F.,Chair ^
<br /> Linda S. Adams Arnold
<br /> Sacramento blain Office SchHarzenegger
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<br /> Phone(91bi 4(,4-;291 •FAX(1)16)464-464 Gorernor
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<br /> 29 January 2008
<br /> Ms. Kerry Heckman
<br /> Connell Tire FEB - 1 2008
<br /> 2211 North Wilson Way ENVIRO,'V;ti�E�IT yEALTH
<br /> Stockton, California 95205 PERMIT/SERVICES
<br /> DOCUMENT REVIEW, FORMER RIVER CITY PETROLEUM & FORMER CONNELL MOTOR
<br /> LIFT TRUCK, 2211 NORTH WILSON WAY, STOCKTON, SAN JOAQUIN COUNTY,
<br /> MONITORING AND REPORTING PROGRAM NO. R5-2005-0827
<br /> I reviewed the 31 December 2007 Corrective Action Plan (CAP) submitted on your behalf by
<br /> Advanced GeoEnvironmental, Inc. (AGE). The CAP provides a technical discussion of the
<br /> remedial investigation for a release of petroleum hydrocarbons, including total petroleum
<br /> hydrocarbons as gasoline (TPHg); benzene, ethylbenzene; toluene; xylenes; lead scavengers
<br /> 1 ,2-dichloroethane (1 ,2-DCA) and ethylene dibromide (EDB); and fuel oxygenates methyl tert-
<br /> butyl ether (MTBE), Di-isopropyl Ether (DIPE), t-amyl methyl ether (TAME), and t-butyl alcohol
<br /> (TBA) to soil and groundwater at your site. The CAP states the petroleum hydrocarbons
<br /> leaked from the dispensers of the underground storage tanks (USTs) system, and then
<br /> migrated downward through soil until reaching groundwater (enclosed Figure 3 cross section).
<br /> A localized Stoddard Solvent release to soil and groundwater on the opposite (west) side of
<br /> the property from the USTs does not appear to be related to the USTs release.
<br /> Current depth to water at the site is approximately 47 feet below ground surface (bgs),
<br /> however the water table has varied seasonably over the last two years from a high of 43 feet
<br /> bgs (rainy season) to a low of 56 feet bgs (dry season). During drought years prior to removal
<br /> of the USTs system, the depth to water reached approximately 70 feet bgs. Soil borings
<br /> samples indicate soil contaminants are present in a submerged source smear zone between
<br /> 50 and 70 feet bgs. Soils are mainly fine-grained silts and clays that are interfingered with
<br /> beds of coarse grained sands and gravels (preferential pathways) reported at 20 to 35 feet
<br /> bgs, 75 to 85 feet bgs, and 165 to 240 feet bgs (regional aquifer).
<br /> The maximum groundwater monitoring concentrations reported in shallow groundwater were
<br /> TPHg, 1,900,000 micrograms per Liter (ug/L); benzene, 16,000 ug/L; ethylbenzene,
<br /> 2,800 ug/L; toluene, 17,000 ug/L; xylenes, 83,000 ug/L; 1,2-DCA, 2,600 ug/L; EDB, 300 ug/L;
<br /> MTBE, 17 ug/L; DIPE, 21 ug/L; TAME, 220 ug/L; and TBA, 360 ug/L. Deeper groundwater
<br /> monitoring shows 1 ,2-DCA (up to 100 ug/L) dissolved plume impacts down to 150 feet bgs.
<br /> The data for the 1,2-DCA dissolved plume show a decreasing concentrations trend with
<br /> increasing depth and distance from the USTs. The 1,2-DCA (or EDB) was added as a lead
<br /> scavenger to leaded gasoline, until lead was banned in the 1970's and replaced by fuel
<br /> oxygenates (including MtBE).
<br /> California Environmental Protection Agency
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