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ES oath <br /> PUBLIC"' HEALTH SEROTIC P........ <br /> SAN JOAQUIN COUNTY r ;i <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Ernest M. Fujimoto, M.D., M.P.H., Acting Health Officer, e <br /> 304 E.Weber Ave., 3rd Floor a P. O. Box 388 is Stockton, CA 952 �;:P <br /> 209/468-3420 \1 F o R <br /> GORDON MARTS MAILED kU'Q 2 91995 <br /> CALTRANS <br /> PO BOX 2048 <br /> STOCKTON CA 95201 <br /> Re: Caltrans Shop 10 Site Code: 1018 <br /> 1603 South "B" Street <br /> Stockton CA 95205 <br /> San Joaquin County, Public Health Services, Environmental Health Division (PHS/EHD) has <br /> completed review of the "Site Assessment Workplan" dated June 21, 1995 and prepared by <br /> Geocon. PHSIEHD has the following comments for your consideration. <br /> The work plan included a proposal to restore monitoring wells which were temporarily lowered <br /> and to install three vapor extraction wells, VW-1, VM-1 and VM-2. PHSIEHD agrees with the <br /> proposal to retrofit monitoring wells, MW9, MW11, MW13, MW14, MW16, MW19, MW20, and <br /> MW24 to finished at grade completions. Once the wells have been repaired, samples should <br /> be collected and analytical results submitted to PHSIEHD for evaluation. <br /> PHSIEHD questions the effectiveness of the proposed design of the vapor extraction and <br /> monitoring wells. The design of vapor extraction wells are critical for evaluating performance. <br /> Significant heterogeneity exists in subsurface lithology which when transversed with 85-45 feet <br /> of screen will make it virtually impossible to determine where and how far vacuum influence is <br /> actually observed. PHSIEHD requests that the design of the proposed vapor extraction wells <br /> be reconsidered. PHSIEHD has discussed design concerns with Geocon and suggests that <br /> should the proposed design be implemented that a clear rationale and references be submitted <br /> to support the proposed design. PHS/EHD also suggests that at least one soil boring be drilled <br /> continuously to better characterize the subsurface lithology and that sufficient soil samples <br /> undergo analysis to determine the vertical extent of soil contamination. <br /> Enclosed is a copy of the permit #007094 to drill the vapor extraction wells. Please notify <br /> PHSIEHD at least 48 hour prior to initiating field activities. If you have any questions, please <br /> contact Mary Meays at (209) 468-0337. <br /> Donna Heran, REHS, Director <br /> Environmental Health Division <br /> Mary Meays, Senior REHS Diane M. Hinson, REHS <br /> Site Mitigation Unit Supervisor <br /> MM/16038 <br /> cc: Elizabeth Thayer, CVRWQCB <br /> CC' Saiyed Ali, Caltrans <br /> CC" Richard Walls, Geocon <br /> A Division of San Joaquin County Health Care Services <br />