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i Mr. Matt Gabris Page 2 of 2 Earth Grain/former Kilpatrick Bakery 18 March 2009 1717 S. Center Street, Stockton, California groundwater in the deeper well, MW-5A is impacted..The well-pair in the former UST pit area on your site, MW-2 (shallow) and MW-2A (deeper) are both impacted as one would normally expect in a source area. A common interpretation for a situation where the deeper well is impacted and an adjacent shallow well is not, is that the deeper impacted groundwater has migrated laterally from a more distant source, and without additional data or modeling available, that is the.EHD interpretation for the contaminants impacting monitoring well MW-5A. The EHD does not believe that the soil or ground water data supports your consultant's conclusions that your site has been impacted by a UST release on the adjacent parcel north of the subject site. t As elevated concentrations of various COCs are present in.the deepest monitoring wells for this site, the EHD concludes that the vertical and lateral extents of the impacted groundwater plume 'are not defined. Additional investigation is needed to delineate groundwater impacted by the unauthorized release from your,former UST system. ' Submit a work plan, in the context of the site conceptual model (SCM), to the EHD by 01 June 2009 to continue the assessment of the vertical and later extent of groundwater impacted by the unauthorized`release from the UST system formerly on the subject site; the EHD recommends the work plan include installation of a monitoring well midway between MW-2A and MW-5A, .screened in the same hydrogeological unit to further evaluate that relationship of COCs in MW-2A to those in MW-5A. include laboratory analysis for 1,2-dichloroethane (1,2-DCA) and ethylene dibromide (EDB) in groundwater samples from the new deep wells for two consecutive monitoring events. The'Report did not include either, iso-concentration maps for soil and ground water, or the calculations for the estimates of' the' residual mass,:of TPHg in the soil and groundwater; include these items in'the. work plan/SCM. The California State Water Resources Control Board Cleanup Fund has recommended in their annual 5-year review update letter that you be directed to reinitiate operation of the remediation system. In the report of findings for the additional assessment directed above, include a feasibility study for reinitiation of the soil vapor extraction and air sparging system or implementation of another more aggressive remediation technology. Thank you for your continued interest in cleaning up this site; the EHD appreciates your cooperation. Please continue to submit all reports, maps, wellhead survey data, work plans and laboratorydata to Geotracker. You may contact Michael infurna at (209) 468- 3454 if you have questions and to schedule the next ground water monitoring and sampling event. + Sincerely lltc,dat-t /4:/L JX4 Michael Infurna, Senior REHS Nuel Henderson, PG. LOP 1 Site Mitigation Unit IV Engineering Geologist cc: Paul Anderson— PSC Environmental, 210 West Sand Bank Rd. Columbia, Illinois 62236 Thomas Neely— ETIC, 2285 Morello Ave, Pleasant Hill, CA. 94523 Jerry Gregerson — P. O. Box 7385 Stockton CA 95267 Ismael & Magdalena Rivera — 1717 S. Center St. Stockton, CA. 95206 CVRWQCB —James Barton SWRCB-CUF— Mark Owens 1717 Center MWi report CML 3-18-09