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r <br /> -6-1/17 '95 11:00 ID:PG2,E Sciences FAX:510-866-F PAGE 3 <br /> 04/17/86 10:00 $SIU 748 4232 CAS WC Q003 <br /> MEMORANDUM <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY REGION <br /> 3443 Rwur Road,Buts A Phom;(216)255.3000 <br /> Sacrarnanto, CA M274Ne CALNU:8-494-3000 <br /> TO: Wendy I- Cohen FROM: John D. Moody <br /> Seat"Engineer Pro glneet <br /> DATE: 10 April 1995 SiGNA'1URL <br /> SUBJECT: COMIIFIVTS ON WORK PLAN FOR PHASE III IAL RiVESTIGATIOW, <br /> PACWIC GAS AND ELECTRIC COMPANY,LATHROP GAS DEHYDRATOR <br /> STATION, SAN JOAQUIN COUNTY <br /> I have reviewed dw 10 March 1995 work plan emltlad-Wm*PLcar fa-Grc d-FK=ar-1nwsdg+adm <br /> Lathrop Gas Dehydrainr Ssarion, San Joaquin Cotin y, California,prepared by Technical and Ecological <br /> Services(TES), a division of PG&E. The work plan proposes activites for additional rermodial <br /> investigation ut?G&Vs Lathrop Gas Dehydrator Station. My comsTmtts on the work plan are included <br /> below. <br /> Background <br /> PG&Es Lathrop Gas Dehydrator Station is near the intersection of Undinc and Willow Gicn!toads about <br /> six miles northeast of Tracy in San Joaquin County. The site occupies approximately one-third of an=c <br /> and is surrounded by firmilanda and orchards_ The&cility odorizes and removes natural gas$uida, <br /> including wafer and petroleum hydrocarbons. Atter the discovery of petroleum-contaminated soil nto <br /> the facilitya former mboiler unit, PG&E conducted a site assessment and initial investigation of the <br /> sffoded area in 1988, and a second phase rctnedia)investigation in November 1992. The initial <br /> investigation included the removal of petrolcum-contaminated soil, collecting condensate sample from <br /> the rebeller unit, and the Installation of three soil borings near the reboiler unit, as shown in Attachment E <br /> Site Map, to funhot assasa the nature of the soil contamination_ In 1992,TES installed nine additional <br /> soil borings, also shown in Attach mer t 1 as part of the second phase investigation. The results of these <br /> previous investigations showed the presence of petroleum hydrocarbons In the soil and ground water,and <br /> glycol compounds in the reboilt r urdt condensate. These results are summarized, along with staff <br /> comments and a request fbr the subject third phase work plan,in a 5 Decanber 1994 staff memorandum <br /> entitled PacW Gas&Ekctrlc Company Lathrop Gas Dehydrator Station, San Joaquin County,wtuch <br /> is hereby incorporated by refereme. <br /> Scope of Work Plan <br /> The work plan proposes the installation of five new monitoring wells approximate to the locations shown <br /> in Attachment I. The soil bortrtgs for the wells will be drilled using a hollow stern augur and cores will be <br /> obtained using a split spoon sampler or other&alible means. TES proposes to select the well loeatioru <br /> based on the results of screening the borehole cuttings for hydrocarbons using a photoionization detector <br /> (PID). If hydrocarbons are detected in a boring, the boring would be abandoned and a new location <br /> selected approximately 50 feet outward from the abandoned boring. The well locations would be whom <br /> no hydrocarbons are detected in the borehole cuttings. The wells will be completed to depths nmgutg <br /> from 20 to 25 feet below ground surfhea(bgs)and screened over the top 10 to 15 feet of the watt table. <br /> Upon completion and development of the wdl3, TES plans to measure the ground water levels and <br />