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Sent By: RWOCB SACRAMENTO; 916 255 3015; Feb-24.99 14:06; Page 216 <br /> California ejgo nal Water Quality Corol Board <br /> Central Valley Region <br /> wisaten H.IU&" Steven T.Butler:Acting Chair Gray tavb <br /> Secnrosryjar sammtwo Main 011166 Govst�eo. <br /> 6+�rirwnnornfa/ <br /> Protection tnteraet Addy=: lu pj1- r-vmb.-S-/-rwgcb3 <br /> 3443 Rvutiet Road.Seise A.Sacramento.Caiifoenia 95$V-3003 <br /> Phone(916)255-3000•FAX(916)25S-3415 <br /> TO: GLB FROM: Mark R.Ust <br /> WJM <br /> GMC <br /> DATE: 16 February 1999 SIGNATURE: <br /> SUBJECT: REVIEW OF DRAFT ORDER REGARDING PETITION BY UNOCAL <br /> CORPORATION FOR CLOSURE OF ITS LEAKING UNDERGROUND FUEL TANK <br /> CASE AT 1665 PACIFICA VENUE,.STOCJCTON, SAN-JOAQUIN COUNTY <br /> I reviewed the 25 January 1999 draft order regarding a closure petition proposed for the 3 March 1999 <br /> Workshop Session at the Division of Clean Water Programs. State Board staff recommend adoption of <br /> the petition and agree that the site should be closed. Based on my review of site information, <br /> discussions with Ms.Margaret Lagorio of San Joaquin County Underground Tank Program, and <br /> discussions with representatives of UNOCAL,the draft order is inappropriate and premature because it <br /> contains factual errors and does not consider watcr quality information from recently installed wells. <br /> A table located at the end of this document provides a comparison of State Board staff comments and <br /> my responses. <br /> High concentrations of petroleums constituents related to an underground storage tank release were <br /> identified in soil and groundwater below this site and up to 150 feet offsite. Over the past 9 years a <br /> network of monitoring wells was installed.limited overexcavation was completed and a vapor extraction <br /> system operated for a short time. Soil contamination is cohfrrmed to at least 54 feet below ground <br /> surface. County records document removal of 350 cubic yards of petroleum impacted soil from the.site; <br /> however,the petition claims 850 cubic yards of soil were removdA soil vapor extraction(SVE) <br /> VE) <br /> system operated at the site during 1996. SVE TPH influent concentrations were 3,800 pg/L during <br /> February 1996 and 3.000µg/L during November 19%. The SVE system was shut down 6 November <br /> 1996 when results of confirmation sampling showed the system was not satisfying the San Joaquin <br /> Valley Unified Air Pollution Control District permit requirements. <br /> During January 1999,at the request of San Joaquin County Environmental Health Division,UNOCAL <br /> ase <br /> installed deep monitoring wells to assess the vertical extent of dissolved ph groundwater <br /> contamination. One well is screened from 50 to 60 feet bis,and a second from 85 to 90 feet bgs. 'these <br /> wells were sampled on 3 February 1999. The results of deep plume assessment activities have not been <br /> submitted for regulatory review. Site closure should not be considered until all data are submitted and <br /> reviewed. Margaret Lagorio of San Joaquin County,who[was present during investigation activities, <br /> recalls preliminary onsite laboratory data showing groundwater contamination deeper than previously <br /> j documented(to approximately 70 feet bgs). i requested copies of the analytical results from decR plurrte <br /> I sampling activities and Mr.Robert$oust of UNOCAL indicated he will provide the data in a final report <br /> when the report is complete;however UNOCAL would not provide the preliminary data <br /> California Environmental Protection Agency <br /> k Rnrlcd Pq.,- <br />