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437 E. Miner Street, Stockton <br /> Page 2 <br /> collected and that soil samples would not be collected in the saturated zone. In a <br /> telephone conversation on December 18, 2007, Barbara Jakub from ENSR clarified that <br /> additional geoprobe locations would be used to collect the five soil samples to be <br /> submitted to a laboratory for analysis. The five sample locations will be determined by <br /> the results from the MIP detector (five highest detections). She also explained that a <br /> cone penetrometer testing (CPT) probe would be attached to five of the 17 MTP's to <br /> obtain continuous descriptions of soils in the selected borings. A map showing the five <br /> locations where the CPT probe will be attached to the MIP is to be submitted to EHD. <br /> The EHD approves this phase of investigation as adequate and necessary. Please <br /> note that depth to first groundwater at this site has been below 60 feet and there are <br /> results from soil samples collected in the southeast area of the site (former underground <br /> storage tank location) as deep as 45 feet bgs that had high concentrations of <br /> contamination. The level of contamination remaining in the soil at depths below the <br /> current vadose zone will have to be investigated at some time in the future. <br /> In the Proposal, ENSR recommended conducting a pilot test using the existing <br /> microsparge points to evaluate the integrity of the sparge points and collect design <br /> parameters for a biosparge system. In the December 18, 2007, telephone conversation <br /> Barbara Jakub clarified that the information from the MIP/CPT investigation would be <br /> used to determine where biosparge wells should be located and screened to conduct <br /> the pilot test and if the microsparge wells were located and screened appropriately then <br /> they would be used in the pilot test. The report on the proposed MIP/CPT work should <br /> include a detailed proposal for conducting a pilot test for a biosparge system. <br /> To conduct the MIP/CPT investigation an EHD well permit application and $89 permit <br /> fee must be submitted to EHD. Once the well permit has been approved, please notify <br /> the EHD of the proposed schedule for the work so that inspections of the work can be <br /> conducted. <br /> If you have any questions contact me at (209) 468-3449. <br /> Donna Heran, REHS, Director <br /> Environmental Health <br /> Department <br /> Margaret Lagorio, REHS <br /> Program Coordinator Unit IV <br /> C: Jim Barton — CVRWQCB <br /> David Irey — SJCADA <br /> Barbara Jakub - ENSR <br />