SITE INFORMATION AND CORRESPONDENCE_FILE 2

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PUBLIC HIALTH SERVI&S OPQUIry SAN JOAQUIN COUNTY ENVIRONMENTAL HEALTH DIVISION Karen Furst, M.D., M.P.H., Health Officer 304 East Weber Avenue, Third Floor • Stockton, CA 95202 209/468-3420 KAREN PETRYNA FILE COPY EQUILON ENTERPRISES LLC P O BOX 6249 SEP 161999 CARSON CA 90749-6249 RE: Shell Service Station SITE CODE: 1223 6131 Pacific Ave. Stockton CA 95207 San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) has reviewed the"Quarterly Monitoring Report—Second Quarter 1999" (QMR), dated August 27, 1999, and the"Response Letter/Work Plan", dated February 28, 1998, that were prepared by Cambria Environmental Technology, Inc. for the above referenced site, and has the following comments. Significant groundwater contamination, up to 117,000 parts per billion (ppb) total petroleum hydrocarbons as gasoline (TPHg) and 3,130 ppb benzene, continues to be evidenced near the former tank pit in well VEW-2, and up to 41,800 ppb TPHg and 8,040 ppb benzene in the down- gradient well MW-4. Wells MW-1, MW-2, MW-3, MW4 and MW-7 all had detections of methyl tertiary butyl ether(MTBE) above the reportable limits. Wells MW-5, MW-6 and VEW-2 were reported as non-detect for MTBE, but the detection limits used in the analysis were elevated above acceptable limits. The acceptable limit for the detection of MTBE in water is .5-1.0 ppb. The up-gradient well, MW-5, is the only well which can be considered non-detect for all constituents. The QMR recommends discontinuing the analysis for methanol and ethanol, stating that these substances have not been detected in any of the site wells. The detection limits used in the EPA Method 8015m analysis for methanol have been generally consistent at 1,000-ppb. The detection limits for the ethanol analysis have been very inconsistent, ranging from 500-ppb to 150,000-ppb. The QMR also recommends reducing analysis for oxygenates by EPA Method 8260 to once a year, while continuing analysis for MTBE by EPA Method 8020. This change is agreeable to PHS/EHD, but positive results of MTBE by EPA Method 8020 should be confirmed by EPA Method 8260. Another cost effective alternative would be to use EPA Method 8260-B for all analyses. The work plan was written in response to a PHS/EHD correspondence dated January 6, 1998 in which a directive was made that a work plan be submitted that would propose sufficient soil borings and monitoring wells to define the vertical and lateral extent of contamination in soil and groundwater. The PHS/EHD correspondence also requested that the issue of feasibility studies be addressed with the proposal of additional vapor extraction and air sparge wells. The submitted work plan failed to adequately address each of these issues. A Division of San Joaquin County Health Care Services