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749 E. Charter Way <br /> Page 2 <br /> In addition, site information does not support the report statements that methyl tertiary butyl ether (MtBE) <br /> is migrating to this site from the west. MtBE concentrations in BM-9 and BM-7 have remained less than <br /> 50 micrograms per liter since testing began whereas BM-3 and BM-4 have increased since July 1998 to <br /> concentrations as high as 3200 micrograms per liter. New underground storage tank (UST) systems that <br /> included pans beneath the dispensers were installed at 701 E. Charter Way in April 1998, PHS/EHD Unit <br /> HI reports that over-spill containers on the UST's installed in January 1990 at your site, 749 E. Charter <br /> Way were replaced prior to an October 2000 PHS/EHD inspection without notifying PHS/EHD and that <br /> there are no pans beneath the dispensers at 749 E. Charter Way. An unauthorized release may have <br /> occurred from the UST system at your site and the MTBE in the groundwater from BM3 and BM4 is from <br /> that release . <br /> i� PHS/EHD requires that groundwater from BM-6 and BM-8 continue to be sampled, along with all other <br /> wells, to monitor the deeper groundwater at this site. Review of previous work done on site also indicates <br /> that soil and groundwater contamination has not been defined south of VW-5. Soil sample results from B-2 <br /> appear to define the vertical extent of contamination in the soil on site, but the lateral extent of soil <br /> contamination has not been defined in all directions. In addition, there are no monitoring wells screened <br /> below 65 feet so the vertical extent of groundwater contamination has not been defined. Deeper monitoring <br /> wells with screen intervals below 65 feet must be installed. <br /> Lithological cross sections were prepared for your site early in the investigation. Additional work has been <br /> performed and new cross sections have not been prepared. In discussions with the CVRWQCB it was <br /> decided that prior to meeting with you to discuss your site you should prepare cross sections showing <br /> lithology and contaminant concentrations using all the site data gathered to date. Again, it is recommended <br /> you work with the responsible party and consultant for 701 E. Charter to better evaluate the lithology and <br /> contaminant concentrations on these sites. <br /> In conclusion, PHS/EHD directs you to continue quarterly monitoring of all monitoring wells and continue <br /> to operate the soil vapor extraction system. A work plan to define the lateral and vertical extent of soil and <br /> groundwater contamination, including the area south of VW-5 should be submitted by August 1, 2001 . <br /> Please contact Sam Savig, EHS at (209) 468-3453 if you have questions regarding this letter. <br /> Donna Heran, REHS, Director <br /> Environmental Health Division ` � <br /> SamSavi— g' EHS Margaret Lagor�HS' ` ``� <br /> Site Mitigation Unit IV Supervisor <br /> cc: Marty Hartzell-CVRWQCB <br /> California Geophysical Group <br /> �l <br />