Laserfiche WebLink
PUBLIC HEALTH StRVICE <br /> SAN JOAQUIN COUNTY F. a <br /> ENVIRONMENTAL HEALTH DIVISION ` <br /> Karen Furst, M.D., M.P.H., Health Officer , <br /> 304 East Weber Avenue, Third Floor• Stockton, CA 95202 <br /> 209/468-3420 <br /> BRETT HUNTER DEC 0 3 1997 <br /> CHEVRON USA <br /> PO BOX 6004 <br /> SAN RAMON CA 94583-0904 <br /> Re: Ron's Chevron Site Code: 1039 <br /> 139 South Center <br /> Stockton CA 95202 <br /> San Joaquin County Public Health Services, Environmental Health Division(PHS/EHD)has reviewed the <br /> Pacific Environmental Group's"Soil and Groundwater Investigation Report and Work Plan"dated <br /> November 24, 1997. PHS/EHD has prepared the following comments for your consideration. <br /> The report included the results of the October 6, 1997 off site and on site investigation,with the drilling and <br /> sampling of two monitoring wells MW8 and MW9. Significant soil contamination was evidenced during <br /> the installation of the on site MW9 to the maximum depth sampled which was 75 feet below ground surface <br /> (bgs). Groundwater was reportedly encountered at approximately 28 feet bgs. MW9 was constructed as a <br /> depth discrete well with screened intervals between 52 and 57 feet bgs. Soil contamination was not detected <br /> during the installation of off site MW8. The lateral extent of the vertical soil contamination that has been <br /> evidenced remains undefined. <br /> Extremely high concentrations of petroleum hydrocarbons were detected in the groundwater sample <br /> collected on November 3, 1997 from MW9 of 130,000 ppb TPH-gas and 20,000 ppb benzene; however,the <br /> concentrations which were detected from MW8, located 360 feet from the former tanks location, were <br /> significantly less with concentrations of 370 ppb TPH-gas and 19 ppb benzene. The lateral and vertical <br /> extent of the groundwater contamination remains undefined. Please note that PHS/EHD must question the <br /> reliability of the current monitoring well configuration to characterize the groundwater plume. As you are <br /> aware, significant fluctuations of the depth to groundwater have been documented at this site, resulting in <br /> monitoring wells with 25 feet of screened interval which is approximately 10 feet below the groundwater <br /> table. <br /> While PHS/EHD appreciates your effort to comply with the submittal due dates which were established, it is <br /> important that information submitted within reports accurately portray site conditions and activities. <br /> Please note once again,that the notation "ND"provides little meaning without the reference to the detection <br /> limit. For example,the detection limit for the"ND"noted for the benzene results from the sample collected <br /> at 15 feet during the installation of MW9, was elevated from the typical <5 ppb to<1250 ppb. Also, Table 2 <br /> indicated that groundwater samples were collected from MW8 and MW9 on October 6, 1997 when the chain <br /> of custodv and laboratory report indicate that the samples were collected on November 4, 1997 after well <br /> development. Finally, PHS/EHD questions why methyl tertiary butyl ether(MTBE)analysis was not <br /> conducted on all samples using EPA Method 8020, especially since the reporting limits were so elevated <br /> using EPA Method 8260. The reporting limits were up to 1000 ppm for MTBE and <br /> A Division of San Joaquin County Health Care Services <br />