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Michael J. Infurn Jr., Senior R <br />LOP / Site Mitigation Unit IV <br />MI/ <br />Connell Motors/UST page 2 <br />2211 N. Wilson Way, Stockton. <br />MW-2 and MW-3 have consistently recorded very high concentrations of TPHg and <br />Benzene in the groundwater samples over the years. Although additional monitoring <br />wells were placed further out from the core of the plume in the last investigative phase, <br />the immediate area outward from MW-2 and MW-3 has not been adequately delineated. <br />With such high levels of petroleum in the groundwater, the plume cannot be considered <br />laterally defined. Additional shallow screened monitoring wells are needed outward of <br />MW-2 and MW-3, as well as west of MW-8. <br />QMRs are to contain groundwater iso-concentration maps that clearly reflect a pictorial <br />view of the extent of the petroleum contamination at the site. Of particular concern at <br />this UST site are TPHg and Benzene, as well as Lead, EDB, and 1,2-DCA. Separate <br />maps should be included for each constituent detected in the groundwater samples. <br />Since this site has deep-screened monitoring wells installed, additional iso-concentration <br />maps are required that show the contamination at this deep interval for each of these <br />constituents detected. These maps are to be included in each QMR submitted to EHD <br />for review. <br />Total Petroleum Hydrocarbon as Diesel (TPHd) has been detected in samples from <br />MW-1 and MW-2 in the past but has not been analyzed for since March 2001. On June <br />28, 2000, TPHd was detected in the MW-1 sample at 16,000 ug/I but was reported as <br />"non-detect" when the next sample collected on October 9, 2000 was analyzed. The <br />sample from MW-2 also detected TPHd at 4,700 ug/I on the June 2000 sampling event <br />and then was "non-detect" on the next sampling event, October 2000. With these <br />extreme fluctuations in the levels of TPHd in the groundwater at these two locations, <br />EHD feels that additional TPHd analysis is required. New monitoring wells installed at <br />this site are to have TPHd analyzed in soil and groundwater samples. Please resume <br />sampling the groundwater from MW-1 and MW-2 for TPHd on a quarterly basis. <br />A work plan that addresses the delineation concerns noted above should be submitted <br />to EHD in a timely manner. Additionally, quarterly sampling events should include <br />analyses for the additional constituents discussed above. Please call and confirm all <br />appointments for all fieldwork at this site with Michael lnfurna at (209) 468-3454. A forty- <br />eight (48) working hour notice for appointments is requested. <br />Donna Heran, REHS, Director <br />Environmental Health Division <br />( <br />Margare agorio, REHS <br />Supervisor <br />c: CVRWQCB — Marty Hartzell, Sacramento. <br />c: SWRCB-Technical — Mark Owens, Sacramento. <br />c: Foothill Eng - Erv Rifenburg, 12793 Paddy Creek, Lodi, 95240