ARCHIVED REPORTS XR0009279 - Laserfiche WebLink

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RE CL* ENVIRONMENTAL HEALTH DEPARTMENT a�UfN SAN JOAQUIN COUNTY Ur:rtSupervrsars Donna K Heran,R E H S s < 304 East Weber Avenue, Third Floor Carl Borgman,R is H s Director Mike Huggins,R E H S ,R D 1 • Al Olsen,R.E H S Stockton, California 95202-2708 Douglas W Wilson,R E H S rq a�Q Pi ogram Manager Telephone (209)468-3420 Margaret Lagorio,R E H 5 i F°¢ Laurie A Cotulla,R E H S Program Manager Fax (209) 464-0138 Robert McCiellon,R E H 5 Mark Barcellos,R E H 5 APR 2 9 2002 STEPHEN VALENTINE 00 - STEVE & GENES SERVICE f 6232 HEMET AVE STOCKTON CA 95207 RE STEVE & GENES SERVICES SI TE CODE 2080 2315 N ELDORADO ST STOCKTON CA 95204 San Joaquin County Environmental Health Department (EHD) has reviewed 14ddztaonal Site Characterz:Zation (the report) dated November 30, 2001 and 4i6.Quarter 2001 Groundwater Monatonng Deport dated March 15, 2002 prepared by Geological Technics, Inc (GTl The newly installed deep monitoring well #201 (MW-201) is screened at 148 feet below surface grade (bsg) to 150 5 feet bsg Analytical results of the first quarterly groundwater sample from MW-201 were 13 8 micrograms per liter (µg/1) benzene and 1,140 µg/l total petroleum hydrocarbons as gasoline (IPH-g) Analytical results of the next deepest monitonngwell, 1`IW-101, screened at approximately 92 feet bsg to 97 feet bsg,were 19 µg/l benzene and 139 µg/l TPH-g The extent of the vertical contamination in groundwater has not been defined EHD agrees with GTI that cross-contamination may have occurred in MW-201 and contributed to the contamination detected in the groundwater samples EHD recommends an extended round of re-development of both GT-101 and GT-201 to remove potentially contarrunated silt from the casings and the filter packs to reduce the potential for cross-contamination in future quarterly samplings In a telephone conversation on April 18, 2002, GTI agreed to perforin this task before or during the upcoming second quarterly monitoring event of 2002 EHD requests that the investigation of both the vertical and horizontal extent of the contamination be combined under the same scope of work in order to minimize the number of mobilizations EHD requests submission of a workplan that would assess the vertical extent of the groundwater contamination first, and based on these results, establish the minimurn required depth for the borings or wells for the lateral investigation Submit the workplan to EHD by July 1, 2002 Please include a site conceptual model with geological cross-sections and a discussion of how the proposed work will test and refine the model Sufficient soil data should be • obtained to put GT-201 in a site conceptual model context EHD would also like to have an analysis and discussion in the next quarterly report on the apparent concentration switches between MW-4 and MW-5 between 12/97 and 9/99, could this be an effect of