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Wright <br /> V <br /> Environmental <br /> Services, Inc. <br /> • May 21, 2001 <br /> Project No 4184 1 Construction • Engineering • Remediation <br /> City of Tracy <br /> 520 Tracy Boulevard <br /> Tracy, CA 95376 <br /> Attn Mr Paul Verma ~' <br /> Re: Addendum Letter-Request for Site Closure Report, <br /> Tracy Auto Stereo, 10 West Grant Line Road, Tracy, CA <br /> Wright Project No. 4184; PHS EHD Site Code 504834 <br /> Dear Mr Verma, <br /> NVnght Environmental Services has prepared this addendum letter for the above referenced <br /> Site Closure Report for your site A factor was inadvertently dropped from the calculations <br /> for contaminant mass estimates using the Lyman, Reidy and Levy (1992) formulas in our <br /> Site Closure Report dated May 9, 2001 Also the volume of residual estmate was nus- <br /> typed In order to provide comparable estimates for all parties to review, the contaminant <br /> mass estimates have been recalculated using a general formula of contaminant affected soil <br /> mass times soil density tunes average contaminant concentrations, and revised volume for <br /> residual soil The recalculated estimates are presented below <br /> • Soil-Contaminant Mass Estimated Removed 1993 <br /> TPHG Concentrations sum of October, 1993 data <br /> Area of 190 ft3 x average soil density 100 lb/ft3 x 0 002390 ppm = 45 4 ib <br /> 45 4 — 6 8 lb/gal petroleum product = 6 6 gallons TPH <br /> Benzene was not detected in that data set. <br /> MTBE was not analyzed for that data set <br /> Soil-Contaminant Mass Estimated Remaining <br /> TPHG <br /> Assumed about 1750 ft3, area of perimeter of excavated area 97 ft x 6 ft wide x 3 ft <br /> capillary fringe height <br /> Area of 1750 ft3 x average soil density 100 lb/ft3 x 0 000243 ppm= 42 5 lb <br /> 42 5 — 6 8 lb/gal petroleum product =6 3 gallons TPHG <br /> Benzene <br /> Area of 1750 ft3 x average soil density 100 lb/ft3 x 0 000003134 ppb = 0 54 lb <br /> 0 54 — 6 8 lb/gal petroleum product = 0 79 Ions Benzene <br /> MTBE was not detected in that data set. <br /> The calculations for water were recalculated as a check, and the following estimates <br /> . resulted <br /> 67 E 10th Street • Tracy,CA 95376 <br /> 209 833 0758 . Fax 209 832 5152 <br /> wright@znreach com Lic #651501 A-B HazMat page 1 <br /> webszt hup//home rnreach com/wrzght <br />