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• 101 S Wilson Way, Stockton Page 2 Tne faxed analytical results for MW6 and MW7 or the sampling event that tools place at this site on December 12, 2001, show MtBE as high as 21,000 ug/i in MW6A and BTEX and TPH-g in all the ground water samples collected The consultant for the ARCO at 130 S Wilson Way, Stockton, completed a well survey and reported the results in August 2001 There are three inactive and one active well operated by California Water Service down gradient and within 2000 feet of their site and your site According to Step 3 within the State Water Resources Control Board Guidelines for Investigation and Cleanup of MtSE and other Oxygenates (Guidelines) final draft dated 30 March 2000, es with persistent concentrations of MtBE over 10,000 ppb should perform interim remediation o reduce the concentrations and mass before the plume can spread MtSE nas been detec-led in groundwater samples from VINSB and MW6A at concentrations anove 10,000 ppb, so interim remediation should be proposed for this site_ Tne Quarterly Reports recommend performance of a ground water aquifer pumping test to predict general aquirer characteristics at the site in order to design an interim ground water pump and treat remediation system The pump test data along with the other site geologic data should also be used Dto the approximate travel time for the contaminant plume to reach nearby receptors. If the wca n�irit travel time to the nearest receptor is estimated to be less than 5 years, then a remedial action plan should be implemented in less than a year An eight hour vapor extraction test was performed on VW 1 S (screened interval 28 to 43 feet) in January 1996 when first groundwater was about 55 feet below surface grade A Corrective Action Plan —March 1996 was submitted to EHD in Apnl 1996, which recommended vapor extraction and air sparging In a letter dated October 22, 1956, EHD requested a specific design and cost estimate for a modified remediation system be suDmitted for review An August 13, 1997, Quarterly Report states that a Remedial Action Work Plan dated July 3, 1997, was submitted to EHD for this site EHD files do not contain that work plan Remedial options of vapor extraction, air sparging, groundwater extraction, and ozone inlection should all be evaluated for this site A work plan to install any wells necessary to evaluate these alternatives along with a pian for performing tests for these alternatives snould be submitted to EHD by March 4, 2002 In addition, the lateral and vertical extent of the soil and grouncwater contamination must continue to be investigated The work plan submitted should include installation of adtittienal -onitcring weirs thhat will define the extent of the contamination at and emanating from this site Please be advised that groundwater samples from monitoring wells MW3, MW4 and MW14 at 102 S Wilson Way, Stockton, which is across the street and down gradient from this site have increasing concentrations of MTBE that may be emanating from this site_ Please work with the responsible parties and consultants for the sites at 102 S Wilson Way and 130 S Wilson Way, Stockton, to determine current and previous groundwater flow direction and provide delineation of the contaminant plumes for each site If you have any questions or comments call Rebecca E Setliff at(299) 468-3440 Donna Heran, RENS, Director Pev6'ronme tal Health Departmenttecca E get:W-hHS Margaret l_agono, Supervising RENS LOP/Site Mitigation Unit IV LOP/Site Mitigation Unit 1V cc Marty Hartzell, CVRWQC8 ✓T smothy J Cuellar, Advanced Geo Erivironmental, Inc