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California Regional Water Quality Control Board ; 5 <br /> Central Valley Region „ <br /> Steven T.Butler,Chair <br /> Winston H.Hickox Gray Davis <br /> Secretary for' Sacramento Main Offi a Governor <br /> Environmental Internet Address: http://www.swrcb.c .govt—rwgcb5 <br /> Protection 3443 Routier Road,Suite A,Sacramento,Ca ifornia 95827-3003 <br /> Phone(916)255-3000•FAX(916)255-3015 <br /> TO: Gordon L. Boggs FROM: Marty Hartzell <br /> Underground Tank Program Manager .Associate Engineerg Geologist <br /> DATE: 27 December 2000 SIGNATURE <br /> REVIEW CORRECTIVE ACTION PLAN, POMBO RAN II PROPERTY, .24.100 SOUTH <br /> LAMMERS ROAD; TRACY,-SANJOAQUIN`COUNTY"- --'� <br /> At the request of San Joaquin County Environmental Health Division (County), I reviewed the <br /> 31 March 2000 Corrective Action Plan (CAP) submitted by M. J. Kloberdanz & Associates <br /> (Kloberdanz) for the Pombo Ranch Property. Kloberdanz completed an evaluation of four remedial <br /> alternatives for corrective action at this site. <br /> Site Background <br /> Prior to 1993, two USTs were reportedly removed from this site. In September 1998, under the direction <br /> of the County, Kloberdanz advanced eight geoprobe borings (B I through B8)near the former UST areas, <br /> and in July 1999, four additional geoprobe borings (B9 through B12) were advanced near the northern <br /> former UST areas (see attached Figure 4a from the CAP). Soil borings identified two medium sand units: <br /> the upper sand at 10 to 15 feet below ground surface (bgs), and the lower sand at 20 to 35 feet bgs. The <br /> upper sand is bound between two silty clay units, as shown n the attached Lithologic Cross Section <br /> Gasoline Concentration from Appendix 1 of the CAP. <br /> Soil contamination was only identified in the upper sand soil samples; however, groundwater <br /> contamination was identified in both sand units. The maximum groundwater contamination was found in <br /> the upper sand within the area of the former UST as shown in the following table. <br /> Sample Identification TPH /1 Benzene ( /l MtBE /l) <br /> B3 at 15 feet (Upper Sand) 56,000 3,700 3,400 <br /> B9 at 33 feet Lower Sand) 200 1.2 ND <br /> Grab groundwater sample results from outside the former U T area are significantly reduced, and water <br /> samples from three monitoring wells installed in July 1999 are non-detect for all analyzed constituents. <br /> The monitor wells are 80 to 140 feet from.the former UST, and screened from 5 to 25 feet bgs. There are <br /> no reports of testing for DIPE, TAME, EtBE, TBA, 1,2-DCA, or EDB. <br /> An on-site domestic water supply well is approximately 14C feet southwest of the former UST site, and <br /> two additional domestic wells are within 650 feet of the site. The on-site domestic well is upgradient <br /> from the former UST area as calculated from the July 1999 water levels from the three installed <br /> monitoring wells. Construction details and sample results have not been presented for these wells, and a <br /> sensitive receptor survey has not been submitted. <br /> California Environmental Protection Agency <br /> a Recycled Paper <br />