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iyt <br /> R.M.B. Garage (Erardi Ventures) Page 2 of 2 <br /> 715 North Hunter Street 9/2/2008 <br /> Stockton, CA <br /> advancement of the borings, while the deep soil samples may have been cross- <br /> contaminated by shallower impacted groundwater. Since contaminant concentrations have <br /> been dropping and low levels of soil contamination exist at the deepest soil samples <br /> collected from the source area , including CPT-2 and CPT-3, the EHD believes that more <br /> quarterly groundwater data should be obtained from MW- 11 to determine if further vertical <br /> investigation is needed in the future. <br /> Additional investigation is needed to delineate the groundwater plume laterally away from <br /> the source area in the shallow zone between 20 to 40 feet bsg and in the first sandy <br /> interval between 50 and 65 feet bsg . In the source area , groundwater is significantly <br /> impacted in MW-10 and MW-11 . The less impacted MW-11 is screened in the second <br /> sandy interval between 90 and 103 feet bsg . There are no wells located laterally away <br /> from the source area that are screened in the first or second sandy intervals, which may <br /> be preferred migration pathways for contaminants. All remaining impacted monitoring <br /> wells are screened between 20 to 40 feet which is above the first sandy interval. EHD <br /> believes that further investigation is needed to delineate the plume in all directions in the <br /> shallow zone and first sandy interval . Based on the findings of this investigation and <br /> additional monitoring results from MW-11 , the need for further investigation of the second <br /> sandy interval , located between 90 feet to 103 feet bsg , can be evaluated . <br /> Submit a workplan to the EHD to complete the additional site investigation to define the <br /> lateral extent of the groundwater contamination plume in the shallow zone and in the first <br /> sandy interval by November 7, 2008. Please include an updated cross-section of the site <br /> in the workplan . <br /> The report for the first quarter 2008 monitoring event has not been submitted to <br /> Geotracker (State Water Resources Control Board internet database system). California <br /> Code of Regulations (CCR) Title 23, Section 2652 (d) requires responsible parties to <br /> submit reports to the local agency (EHD) every three months (quarterly) until investigation <br /> and clean-up of the site are complete. CCR Title 23 , Sections 3890 — 3895 requires that <br /> these quarterly reports be electronically submitted to Geotracker. Please submit the report <br /> for the first quarter 2008 monitoring event to EHD and Geotracker by September 29, <br /> 2008. <br /> If you have any 1questions, please contact Frank Girardi at (209)953-77868, <br /> Frank Girardi, REHS Nuel C. Henderson , Jr. , PG <br /> Senior Registered Environmental Health Specialist Engineering Geologist <br /> C : James Barton, RWQCB , 11020 Sun Center Dr. #200, Rancho Cordova , CA 95670 <br /> C: Tim Cuellar, AGE, 837 Shaw Road , Stockton , CA 95215 <br />