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SAIC <br /> iHPP-BTR OVP MP#216.9 <br /> Surland Homes-Bridle Creek <br /> Reports <br /> ' Accession#06102.20120216.002 <br /> February 22, 2102 <br /> Michael Oliphant <br /> Chevron Environmental Project Manager <br /> t PO Box 6012 <br /> San Ramon,California 94583 <br /> ' Subject: Human Health Screening Evaluation Addendum <br /> Surland Homes-Bridle Creek <br /> Tracy, San Joaquin County,California <br /> ' Dear Mr. Oliphant: <br /> ' SAIC Energy, Environment& Infrastructure, LLC (SAIC)prepared this addendum on <br /> behalf of Chevron Environmental Management Company(CEMC) for your review. <br /> This addendum addresses issues raised in phone communications between the <br /> Department of Toxics Substances Control (DTSC) and SAIC regarding the February <br /> 2009 Human Health Screening Evaluation(HHSE)prepared for Surland Homes-Bridle <br /> Creek(the Site)'. <br /> BACKGROUND <br /> Geomatrix prepared and submitted a Health Risk Screening Evaluation(HRSE) for the <br /> ' Site in August 2002. The HRSE concluded that the theoretical lifetime excess cancer <br /> risk for an adult and child resident at the Site is 1 x 10-6, equal to the acceptable target <br /> risk of 1 x 10-6. The DTSC issued comments on the HRSE in a letter dated December <br /> ' 19, 2003, stating that there was insufficient data to reach a conclusion regarding the <br /> overall human health risk, and requesting additional analytical data from the Site. SAIC <br /> collected additional soil samples in 2007 to provide the additional data requested by the <br /> ' DTSC. <br /> Due to the construction of a residential development on the area of previous <br /> investigations, DTSC and SAIC agreed to collect the additional samples within the <br /> Union Pacific Railroad(UPRR) right of way(ROW) adjacent to the previous <br /> investigation area. The analytical data from this investigation as well as the historical <br /> analytical data were used by SAIC in developing the 2009 HHSE. Subsequent <br /> discussions between SAIC and DTSC resulted in the preparation of this HHSE <br /> addendum. DTSC requested that SAIC evaluate site data considering three additional <br /> scenarios utilizing only data from borings advanced in the UPRR ROW: <br /> 1. SAIC,2009. Human Health Screening Evaluation,Surland Homes-Bridle Creek, Tracy, California. February. <br /> SAIC Energy,Environment&Infrastructure,LLC <br /> 1000 Broadway I Suite#675 1 Oakland,CA 9460711 tel:(510)433-0635 1 fax:(510)446-7919 1 saic.com\eeandi <br />