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4 <br /> 6.0 Closure Reguest <br /> The historical work performed by Beta Associates suggests that groundwater is <br /> encountered at 43 feet, (see section 4.1). Furthur stiff clayey low permeability soils are <br /> found from 29 to 43 feet. Our sampling informationsuggests that vertical extent of <br /> contamination is 26 to 28 feet. We believe that all source soils have been removed. <br /> All areas which have been excavated have been replaced with control density fill, which <br /> has a very low permeability. The entire site is capped with concrete or asphalt. It is <br /> extremely unlikely that groundwater could be impacted by any potential residual <br /> materials. <br /> Conservative estimates show a potential residual ' <br /> f approximately 10 gallons of <br /> gasoline hydrocarbon. This small amount of product is estimated to be distributed <br /> through some 3000 cubic feet of soil. Only one BTEX fraction was detected, <br /> ethylbenzene. The ethylbenzene was detected at a low level and in only one sample. <br /> The ethylbenzene level detected was 190 ppb. Drihking.water MCL for ehtylbenzene is <br /> 680 ppb. <br /> We believe that the potential residual material left in place represents little or no risk to <br /> the environment or the community, and that natural'biologicai processes will degrade <br /> and diminish the material. ' <br /> We respectfully request that the cleanup be deemeid complete and the site be closed. <br /> 7.0 Personnel Qualifications <br /> 1. Soil Excavation --Viking Drillers, Inc. of west Sacramento <br />' 2. Oversight -- The work was actively reviewed on-site by Tim McDonald under the <br /> direction of Ray Kablanow, Ph.D., Licensed California Geologist, of Geological <br /> Techniques. Mr. McDonald also performed on-site instrumental readings, OVM. <br /> 3. Soil Sampling was performed by Bob Bennett, REA hand Juan Quijano, REA, under the <br /> supervision of Tim McDonald. <br /> I 4. A copy of Geological Techniques Project Report is attached in the Appendix. <br /> t <br /> 8.0 Certification LN?�FtiT ' <br /> 4,1 �l <br /> i This plan was prepared by: <br /> f lk REA-1�13E1S <br /> .i <br /> Bob Bennett * pires: �� # <br /> Environm tar Services <br /> � <br /> Supervisor OF , •. <br /> p • <br /> Tri Valle <br /> ;yNuur*iµ+a► <br /> Y <br /> Growers <br /> Page 11 <br /> ij <br />