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t <br /> � w <br /> PUBLIC, HEALTH SERIfCES <br /> pUN <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Ernest M. Fujimoto, M.D., M.P.H., Actin; Health Officer - <br /> 304 E.Weber Ave., 3rd Floor • P. 0. Box 388 • Stockton, C�'�r9529I=g3gg—�; V— • c4 �P'• <br /> 209/468-3420 (; - J \ <<�E b'R r' <br /> CHAPIN BROS INC <br /> 1203 N CARLTON AVE MAILE AUG 1 81995 <br /> STOCKTON CA 95203 <br /> RE: 1766 MONTE DIABLO SITE CODE: 1190 <br /> STOCKTON CA <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS/E:-ID) 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 relaring 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 locarion of the proposed air marging well (northeast of MW-1) in the FRP <br /> should be reconsidered. Additional extraction/injecrion points maybe needed in the area of the former tank field <br /> (between MW-1 and MW4) in order to increase system influence and efficiency. <br /> The "Quarterly Ground Water Monitoring-ApriI 1995"sampling results indicate an increasing gasoline concentration <br /> trend in MW-3 located off site. Even though a zero concentration line was identified downgradient and in near <br /> proximity to MW-3 utiliring a hydropunch, a monitoring well will be required downgradient to supply reproducibie <br /> data. This point will identify any piume migration and guard against additional contamination spread 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 cleanupduring system operation and confirm remediation prior to site <br /> closure. <br /> If you have any nether questions regarding the matter, contact Harlin Knoll at (209) 468-3442. <br /> Donna Heran, REriS, Director <br /> Environmental Health Division <br /> Harlin Knoll, Senior REHS Diane M. Hinson, REHS <br /> Site Mirigation Unit Supervisor <br /> HK <br /> A Division of San Joaquin County Health Care Services <br />