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0 4 <br /> TPHd IN SOIL SAMPLES FROM MW#1 <br /> 1600 <br /> 1400 _. <br /> 1200.... ... _ <br /> rn1000 .. - ......... ... .. .. ........... <br /> Y 800 <br /> E <br /> 600 .... . . <br /> 400 <br /> 200 <br /> p <br /> 5 10 15 20 25 30 35 40 45 50 55 <br /> DEPTH OF SAMPLE IN FEET <br /> Leaching Potential of This Site <br /> All ofthe soils encountered between 25'ofdepth to 45'ofdepth are low permeability clays and silts with <br /> an estimated permeability ofk= 1 x 10-5 to 1 x 10-6 cm/sec_ The finish grade ofthe surface of this site ;I <br /> can be modified to provide drainage away from the UST location. With the present water table depth <br /> of+/-46'the risk of diesel leaching to the water table is very low.Risk of the water table raising to the <br /> depth ofthe diesel contamination is higher,but still in the low range.A series of plus twenty-five year <br /> rain fall events would be required to raise the water table to contact the contaminated soil. The ever <br /> increasing draw-down ofthe water table due to the high demand of both domestic and irrigation wells <br /> will prevent the water table from rising into the contaminated soil. <br /> Recommendations for Closure <br /> It is recommended that this monitoring well be abandon as per the standards methods ofthe PHS/EHD. <br /> The surface of the area within fifty feet of the removed 12000 gallon diesel tank to be graded to drain <br /> from the tank area. The finish grade should slope between 1%and 2%to the southwest.The excavation <br /> ofthe 12000 gallon diesel tank should be backfilled with a one foot layer of selected low permeability <br /> soil in the bottom foot ofthe excavation.The remainder of the excavation can be backfill with any soil <br /> type from the site. All of the soil samples for the 8000 gallon UST excavation were non-detect. The <br /> excavation should be backfilled with any clean random fill found on the site. <br /> Please contact Ervin Rifenburg of this office (2091368-9381) if any questions arise concerning this <br /> request for closure and no further action on this former UST site. <br /> Respectfully submitted, <br /> t�QFf SS�p <br /> Foothill Engine C NF�pEf <br /> Ervin Rifenburg,, <br /> OFCI�L "' <br /> Enclosures: o <br /> 1.Site Map w/Monitoring We 1 ocation <br /> 2.Soi1 and Water Analysis Recap <br /> • 3.Del Tech water sample report <br /> 4.Soil and Water Analysis Lab Reports <br /> cc: Woodbridge Partners Inc. <br /> 3 <br />