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t <br /> ENVIRONMENTAL EALTH DEPARTMENT <br /> SAN JOAQ IN COUNTY <br /> s.. P <br /> Unit Supervisors <br /> Donna K.Heran R.E.H.S. <br /> 304 East Weber Avenue Third Floor Carl Borgman,R.E.H.S. <br /> Director Mike Huggins,R.E.H.S.,R.13.I. <br /> Al Olsen,R.E.H.S. Stockton, California 95202-2708 <br /> Douglas W.Wilson,R.E.H.S. <br /> cQ.. �;w Program Manager Telephony (209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> O;E6R Laurie A.Cotulla,R.E.H.S. <br /> Fax: (2 9) 464-0138 Robert McClellon,R.E.H.S. <br /> Program Manager Mark Barcellos,R.E.H.S. <br /> ERNEST J POMBO JR JAN 2 7 2003 <br /> 1755 3_1Tx STREET <br /> TRACY CA 95376 <br /> RE: Pombo Ranch Property Site Code: #508110 <br /> 24100 Lammers Road <br /> Tracy CA 95376 <br /> kVORK PLAN: Excavation and Monitoring Well Installation <br /> DATED: December 10,2002 <br /> PREPARED BY: MJ Kloberdanz&Associates <br /> APPROVED: x-with conditions,see below <br /> DI APPROVED: <br /> ADDENDUM NEEDED: <br /> ADEQUATE AND NECESSARY ELEMENTS OF THE-WORK PLAN [H&S 25299.37,subd(c)(3)1: <br /> 1. Over-excavation and removal of contaminated soil near the source area. Soils will be kept segregated,clean/dirty, <br /> for appropriate treatment and/or disposal purposes. <br /> 2. The excavation will be backfilled with clean materials. <br /> 3. Prior to backfilling,oxygen--releasing compound will be introd ced to the over-excavation. <br /> 4. Installation of two monitoring wells down gradient of the sour a area;one screened from 5-20 feet below surface <br /> grade (bsg) and one screened from approximately 55-60 feet b g. Final construction of the deeper well and exact <br /> length of its screen interval will depend on the lithology encountered during the drilling of the borehole. <br /> 5. Soil samples will be collected during the drilling of the deeperboring;select samples will be submitted for analysis. <br /> 6. The well/sensitive receptor survey will be updated and the domestic well onsite will be sampled and analyzed for <br /> petroleum hydrocarbon constituents. <br /> COINMENT5 AND CONDITIONS: <br /> 1. The aerial extent of the proposed over-excavation must be in dified to include removal of the soil contamination <br /> detected in boring B-11 at 10 feet bsg. Exact dimensions oft the excavation may be determined in the field,with <br /> SJC/EHD concurrence. <br /> 2. Location of the monitoring wells must be moved closer to the source area. The work plan proposes to locate the <br /> wells approximately 70 feet down-gradient of boring B-3,which would defeat the purpose of installing them to <br /> monitor the groundwater contamination in the source area. I stallation of the wells following over-excavation would <br /> minimize the possibility of drawing the soil contamination down with the augers during drilling. <br /> 3. Groundwater flow direction has been determined at this site only once. The flow direction should be verified <br /> .immediately and again just before the well installations,ata um,to ensure proper placement of the wells. <br /> 4. SJC/EHD recommends continuous coring of the deeper boring in order to screen the monitoring well in an <br /> appropriate water bearing zone. <br /> 5. San Joaquin County Well Standards must be adhered to when building the wells. Appropriate grout mixture is neat <br /> N. cement;bentonite or concrete are not acceptable. Developm nt of the new wells may occur a minimum of 12 hours <br /> after they have been completed. <br />