SITE INFORMATION AND CORRESPONDENCE_FILE 1

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Marci's Diesel Page 2 of 2 relates to the well survey and site hydrogeology. It may be necessary to re-survey MW heads to make an accurate gradient determination. PHS/EHD recommends collecting soil and groundwater samples fi-orn each significantly different lithological unit in the new-MW borings for analysis. Samples should be laboratory analyzed to determine permeability,porosity,bulk density,moisture and organic carbon content. This data would be helpful in calculating the rate at which contaminants could potentially migrate or be inhibited in this site's hydrogeologic setting. When the contaminant plume at this site has been defined vertically and laterally:and if continued quarterly monitoring information substantiates decreasing contaminant concentrations in groundwater, a complete closure document should be submitted to PHS/ EHD. This document should contain all pertinent information as outlined in the"Appendix B,Tri-Regional Board Staff Recommendations for Preliminary Investigation and Evaluation of Underground:Tank Sites,No Further Action Request". All relevant data should be tabulated and sources for the data should be clearly indicated. Mass balance calculations of the contaminant remaining in the soil and groundwater and fate-transport information which supports conclusions that the amount of contamination in soil and water is minimal, the contaminant plume will not expand in size and the contamination will not.reach sensitive receptors should be provided to PHS/EHD. Contact Carol Oz, Senior REHS, at(209 468-3440 at least 48 hrs. prior to inspection or if you have questions regarding this letter. Donna Heran, REHS, Director Environmental Health Division Carol Oz,,Senior REHS Margaret Lagorio;