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PUBLIC HEALTH SERVICES <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION 2{ <br /> Ernest M. Fujimoto, M. D., M.P.H., Acting Health Officer <br /> 304 E. Weber Ave., Third Floor • P. O. Box 388 • Stockton, CA 95201-0388 <br /> 209/468-3420 <br /> CHAPIN BROS INC MAILED JAN 0 91990 <br /> 1203 N CARLTON AVE <br /> STOCKTON CA 95203 <br /> RE: 1766 MONTE DIABLO SITE CODE: 1190 <br /> STOCKTON CA <br /> This letter has been prepared at your request. It contains the same directive as previously outlined in <br /> correspondence sent to you on August 18, 1995. Our understanding is this newly dated directive is essential to your <br /> efforts in obtaining preapproval from the SWRCB Cleanup Fund for corrective action reimbursement. <br /> San Joaquin County Public Health Services, Environmental Health Division(PHS/EHD) has completed review of <br /> the "Final Remedial Plan" (FRP) and the "Quarterly Ground Water Monitoring - April 1995" for the above <br /> referenced site. <br /> The FRP prepared by Geological Audit Services, Inc. contains specific information relating to site history, geology, <br /> soil/ground water petroleum hydrocarbon plume delineation, and aquifer/soil vapor extraction testing. In addition, <br /> a feasibility study was presented which selected vapor extraction in conjunction with in-situ air sparging as the <br /> corrective action technology for site remediation. <br /> The conceptual design of the vapor extraction system (VES) appears appropriate for the site geology and the <br /> contaminant identified. The effectiveness of the VES will be dependent upon soil permeability and radius of <br /> influence between extraction points. The location of the proposed air sparging well(northeast of MW-1)in the FRP <br /> should be reconsidered. Additional extraction/injection points maybe needed in the area of the former tank field <br /> (between MW-1 and MW-4) in order to increase system influence and efficiency. <br /> The "Quarterly Ground Water Monitoring - April 1995" sampling results indicate an increasing gasoline <br /> concentration trend in MW-3 located off site. Even though a zero concentration line was identified downgradient <br /> and in near proximity to MW-3 utilizing a hydropunch, a monitoring well will be required downgradient to supply <br /> reproducible data. This point will identify any plume migration and guard against additional contamination spread <br /> downgradient. <br /> When budgeting for monitoring and cleanup, these additional required points should be included in cost estimates. <br /> Other points will also be required to evaluate cleanup during system operation and confirm remediation prior to site <br /> closure. <br /> If you have any further questions regarding the matter, contact Harlin Knoll at (209) 468-3442. <br /> Donna Heran, REHS, Director <br /> Environmental Health Division <br /> Harlin Knoll, Senior REHS Diane M. inson, REHS <br /> Site Mitigation Unit Supervisor <br /> A Division of San Joaquin County Health Care Services <br />