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KLEINFELDE <br /> �� R <br /> 4 3 COMPARISON TO REGULATORY LIMITS <br /> The soil sampling analytical results were compared to the Total Threshold Limit Concentration <br /> (TTLC) and Soluble Threshold Limit Concentration (STLC) regulated levels as expressed in <br /> California Code of Regulations 22CCR§66261 24 and/or Residential and U S EPA Region IX <br /> Preliminary Remediation Goals (PRGs), dated October 1, 2002 <br /> ' PRGs for residential sites were selected because they are typically more stringent PRGs are <br /> contaminant concentrations in environmental media (i e soil, air, water), calculated by the U S <br /> EPA, that can be used as screening tools to evaluate a site for potential human health risks <br /> PRGs are calculated using standard assumptions and are specific for land use conditions (e g <br /> residential or industrial) The chemical concentrations calculated by the U S EPA typically - <br /> correspond to a fixed level of risk (usually 10-6, or 1 in 1,000,000 cancer risk, or a non-cancer <br /> hazard quotient of 1) for soil, air, and water The following exposure pathways were accounted <br /> for in the PRG calculation for soils assuming residential land use <br /> • Ingestion <br /> • Inhalation of particulates <br /> ' * Inhalation of volatiles <br /> • Dermal (skin) absorption <br /> M For the inhalation pathways, volatilization factors and particulate emission factors are used to <br /> estimate exposure due to emissions from soil to air For the dermal absorption pathway, a 10% <br /> skin absorption factor was used to calculate the PRGs for the constituents of concern at the <br /> ' subject site This factor assumes the dermal dose is equal to an adult's ingestion dose <br /> If contaminant concentrations at the subject site exceed the estimated FRG values and the <br /> ' exposure pathways used to calculate those PRGs are inappropriate for the site, additional site <br /> evaluations, such as an evaluation of background levels, supplementary sampling and <br /> calculations using site-specific data may be necessary <br /> rThe groundwater sampling results were compared to EPA California Regional Water Quality <br /> Control Board, Central Valley Regions document titled "A Compilation of Water Quality <br /> ' Goals", dated August 2000 and a City of Stockton, Department of Municipal Utilities Table <br /> titled "Self Monitoring Sample Program", summarizing acceptance criteria for discharge of <br /> water into the sanitary sewer system <br /> ' A summary discussion of the analytical results and comparisons to these hmits and goals are as <br /> follows <br /> 1 10 <br /> ' 28699 E01 /ST03R759 Page 10 of 17 <br /> Copyright 2003, Kleinfelder,Inc May 20,2003 <br />