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PUBLIC AEALTH SERNOTCES <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Ernest M. Fujimoto, M. D., M.P.H., Acting Health Officer <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 <br /> 209/468-3420 <br /> RICHARD BOKIDES JUN 0 3 '1997 <br /> 6421 W CAPITOL AVE <br /> LODI CA 95242 <br /> RE: Flag City Chevron SITE CODE: 1706 <br /> 6421 W. Capitol / Paddock PI. <br /> Lodi, CA., 95242 <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS- <br /> EHD), has reviewed the recently submitted Closure Summary Report and revisions <br /> submitted by your consultant, Advanced GeoEnvironmental, and has the following <br /> comments. <br /> Although the gasoline constituent's of TPH-G and BTEX have been defined laterally <br /> and vertically in previous investigations at this site, MTBE, which has been added to the <br /> list as a constituent that should be tested for at sites, has not been defined laterally or <br /> vertically. <br /> Groundwater sampling events on July 19, 1996, August 23, 1996, and most recently on <br /> May 9, 1997, have indicated a rising MTBE contamination concentration in all three <br /> monitoring wells currently located on site. With the most recent MTBE concentration in <br /> MW-1 at 440 ug/l, (up from 310 ug/I on July 19, 1996 and 380 ug/I on August 23, 1996), <br /> PHS-EHD has concluded that further groundwater investigation is warranted and <br /> cannot approve your request for closure at this time. <br /> In order to better evaluate the impact MTBE may have on the area around your site that <br /> has not been investigated, PHS-EHD will require you to delineate the groundwater <br /> MTBE plume in all historically known down-gradient directions. In addition, in the <br /> area between MW-1 and the off-site domestic drinking water well located at Rocky's <br /> Restaurant, a deeper groundwater investigation is required and the vertical extent of <br /> MTBE is to be determined. <br /> PHS-EHD recommends that push-point technology be utilized to gather as many data <br /> points as possible in one or two days of field work. You will need to evaluate and cost <br /> compare the effectiveness of over-night laboratory analyses versus an on-site mobile <br /> laboratory. If groundwater laboratory data indicate that MTBE is present above the <br /> current action level of 35 ug/I at a push point, it will be necessary to investigate by <br /> placing another push point further down-gradient. <br /> A Division of San Joaquin County Health Care Services <br />