Appendix I - Hazardous Materials Documentation - VTA

Contaminant Management Plan, SVRT/BART Extension
3.0 RISK-BASED EVALUATION OF CONTAMINANT LEVELS IN SOIL/BALLAST
This section presents an evaluation of the risks associated with exposure to site contamination during and
after construction of the SVRT project. The evaluation includes both the calculation of human health riskbased
levels and an assessment of ecological risk to determine appropriate soil and ballast management
procedures.
3.1 HUMAN HEALTH RISK-BASED LEVELS
The calculation of acceptable human health risk-based levels for the various exposure scenarios is presented
in Appendix B. The human health risk-based levels calculated in Appendix B are the Site-Specific Risk
Assessment (SSRA) results used in Section 4.2 to help determine criteria for appropriate material reuse. The
calculation of human health risk-based levels generally follows the guidance in Risk Assessment Guidance for
Superfund, Volume 1, Part A (U.S. EPA, 1989).
3.2 ASSESSMENT OF ECOLOGICAL RISK
A screening level assessment of ecological risk for the SVRT project is presented in Appendix C. The
screening level ecological risk assessment (ERA) generally follows the guidance in the Ecological Risk
Assessment Guidance for Superfund: Process for Designing and Conducting Ecological Risk Assessment -
Interim Final (U.S. EPA, 1997). The screening ERA integrates the detailed site-specific ecological evaluation
results presented in the Final EIR (VTA, 2004), including the selection of the identified special status species
(rare, threatened or endangered species as listed by state or federal agencies) potentially present within the
project area as the key ecological receptors.
The screening ERA presented in Appendix C concludes that additional measures to protect potential
ecological receptors are not needed in most areas covered by the project Migration Potential Zones (MPZ).
For surface water protection, MPZs are within 50 feet of surface water features (Section 4.2.1). Based on the
relatively flat land surface in these areas, this distance will provide a reasonable buffer between ecological
receptors and significant contaminant exposure.
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