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Jerry Lile March 3, 2014 Page 2 of 13 surface (bgs), extending below the current water table elevation which is 9.5— 12 ft bgs. Groundwater flows generally to the north-northwest. Petroleum sheen has been reported in grab groundwater samples. Currently, installation of private water supply wells is prohibited by a City of Tracy Ordinance. Previously, HERD reviewed the August 2002, "Health Risk Screening Evaluation, Surland Homes Property, Tracy, California" and the August 1998 "Soil and Groundwater Investigation and Site Status Report, Surland Homes Property, Tracy, California" prepared for Chevron by Geomatrix Consultants, Inc. in Oakland, CA and San Francisco, CA, respectively. Our written comments were provided in a December 10, 2003 memorandum. DOCUMENTS REVIEWED HERO reviewed the February 12, 2009 "Human Health Screening Evaluation, Surland Homes—Bridle Creek, Tracy, California" prepared for Chevron by Science Applications international Corporation (SAIC) in Oakland, California. HERO also reviewed the January 1999 "Supplemental Groundwater Investigation and Recommendation for Site Closure, Surland Homes Property, Tracy, California" and the'August 1998, "Soil and Groundwater Investigation and Site Status Report, Surland Homes Property, Tracy, California" both prepared for Chevron by Geomatrix in San Francisco, California. HERO also reviewed the February 22, 2012 "Human Health Screening Evaluation, Addendum, Surland Homes—Bridle Creek, Tracy, San Joaquin County, California" prepared for Chevron by SAIC in Oakland, California. This document was prepared after a 6/15/2011 teleconference discussing inadequacies of the 2009 Human Health Screening Evaluation. SCOPE OF REVIEW HERO's review and comments below focus on the 2009 Human Health Screening Evaluation (HHSE) and the February 2012 Human Health Screening Evaluation Addendum (HHSE Addendum). The 1998 and 1999 Investigation Reports cited above were reviewed to a limited extent, to determine adequacy of the data for use in a screening-level human health risk appraisal. The documents were reviewed for consistency with DTSC and USEPA guidance as well as technical accuracy and validity of the human health screening-level risk evaluation for releases from the OVP onto the Surland Homes property. Neither the screening-level risk assessment, nor HERO's review, is reflective of the potential risks from any other potential or actual sources of release on the Surland Homes property. Furthermore, releases from the OVP that may have migrated off the Surland Homes property, particularly via groundwater, were not included in the scope of the screening-level risk appraisal or HERO's review of the document. file:20140303JL.doc