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California Regional Water Quality Control Board o <br /> Central Valley Region <br /> Robert Schneider,Chair <br /> Winston H.Hickox Gray Davis <br /> Secretary for Sacramento Main Office Governor <br /> Environmental Internet Address: httpJ/www,swTcb.ca.gov/—rwqcb5 <br /> Prolecuon 3443 Routier Road,Suite A,Sacramento,California 95$27-3003 <br /> Phone(916)255-3000-FAX(916)255-3164 ll <br /> MAR Z003 <br /> 20 March 2003 gNVIROM SERVICES I i <br /> . pERM <br /> Ms. Linda M. Gonsalves <br /> Pacific Gas and Electric Company , <br /> California Gas Transmission a <br /> 375 North Wiget Lane, Suite 200 <br /> Walnut Creek, California 94598-2412 3 s <br /> AUTHORIZATION TO ABANDON SELECT MONITORING WELLS, PACIFIC GAS AND <br /> ELECTRIC McMULLINDEHYDRATOR STATION, SAN JOA Q UIN CO UNTY <br /> We have reviewed the 6 January 2003 Remediation Completion Report(Report) submitted by � <br /> CH2MHill on behalf of the Pacific Gas and Electric Company(PG&E) for the McMullin ( �c <br /> Dehydrator Station (site). The site is an inactive PG&E facility that was used to dehydrate natural <br /> gas as part of its natural gas gathering system. The-site is at Airport Way and Perrin Road, about <br /> two miles south of Manteca in San Joaquin County, The Report details soil excavation and <br /> confirmation sampling results and contains a request to abandon Monitoring Wells MW-3 and <br /> MW-4. <br /> PG&E has sampled the monitoring wells at this site since March 1998, and continuous quarterly <br /> sampling has occurred since July 1998. During the continuous quarterly monitoring,benzene, <br /> ethylbenzene, total petroleum hydrocarbons as gasoline(TPHg) and total petroleum hydrocarbons as <br /> diesel(TPHd)were not detected in MW-3 and MW-4. Toluene and xylenes were detected during <br /> a single monitoring event in MW-3 at 4 gg/l and 3.1 gg/l, respectively. Toluene and xylenes were <br /> also detected during a single monitoring event in MW-4 at 2.3 gg/l and 2.2 gg/l, respectively. <br /> The toluene and xylene detections were an anomaly and are likely artifacts of sampling. The <br /> detected concentrations for toluene and xylenes are below the water quality objective for taste and <br /> odor, which are 40 gg/1 and 20 µg11,respectively. As part of Monitoring and Reporting Program <br /> No. 5-01-857 (MRP), PG&E will continue to sample PZ-3,which is an appropriate downgradient <br /> monitoring point for the former sump. PG&E may proceed to arrange with San Joaquin County <br /> Department of Environmental Management for the permitted abandonment of MW-3 and MW-4 <br /> only.- <br /> As part of the excavation work, PG&E abandoned five monitoring wells (MW-2, 5, 6, 7 and 8) <br /> and one piezometer(PZ-2) and reinstalled one monitoring well (MW-2R). Thus, revising the <br /> MRP is appropriate to require sampling at monitoring wells MW-1 and MW-2R and piezometers <br /> PZ-1, 3 and 4. Enclosed is a draft MRP for your comment that reflects these changes. <br /> California Environmental Protection Agency <br /> Vercycled Paper <br /> The energy challenge facing California is real. Every Californian needs to take immediate action to reduce energy consumption. For a list of �.� <br /> simple ways you can reduce demand and cut your energy costs,see our Web-site at http:l/www.swrcb.ca.govirwgcb5 <br />