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Donna Heran, REHS, Director <br />Environmental Health Division <br />Page 2 <br />3032 East Waterloo Road <br />The off-site water sampling depths should not be preselected in a mechanical <br />manner (i.e. 60, 100, 135, and 150 feet bgs) as proposed in the December 2, <br />2003 WP prepared by AGE. The zones to be sampled should be selected to <br />delineate the vertical extent of contamination on site in identified permeable <br />intervals that correlate with defined contaminated hydrogeologic units. Further <br />vertical definition must be performed on-site to better ensure establishing <br />appropriate target sampling depths before the proposed additional off-site <br />investigation can occur. <br />A site conceptual model (SCM) should be prepared for your site. The off-site <br />investigation to determine the lateral and vertical delineation of the plume will be <br />driven by the vertical extent of the on-site contamination. Additional phases of <br />investigation must be in agreement with the SCM that will be developed. <br />MW #8, which was located off-site, has been destroyed under EHD permit and <br />the supervision of AGE. This well was located on private property that has <br />recently changed ownership and the well interfered with land development. The <br />well has not been replaced as recommended in EHD letter dated May, 12, 2004. <br />The well must be replaced to properly investigate and monitor the groundwater <br />contamination in that direction. <br />Please prepare and submit a WP addendum to EHD for the vertical investigation <br />on site, soil feasibility testing, replacement of MW #8, and an SCM by December <br />2, 2004. <br />If you have any further questions regarding this matter, contact Harlin Knoll at <br />(209) 468-3442. <br />Harlin Knoll, Senior REHS <br />LOP/Site Mitigation Unit IV <br />Nuel C. Henderson, Jr.,RG <br />LOP/Site Mitigation Unit IV <br />Cc: SWRCB-Cleanup Fund <br />CVRWQCB-James Barton <br />AGE-Bill Little <br />4