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Skip Navigation LinksDNREC : Division of Waste & Hazardous Substances : Site Investigation & Restoration : SIRS Risk Assessment and Cleanup Standards

 SIRS Risk Assessment and Cleanup Standards


The goal of risk assessment is to evaluate the risk to anyone who could come in contact with chemicals from a site under current and future conditions, and the risk to the environment. Site-specific risk assessment is used as a tool in deciding whether an environmental condition present at a site requires remediation.

Soil gas sampling at a site Human Health Risk Assessment

HSCA Human Health Risk Assessment Guidance - Effective April 1, 2015

Data collected at a site are screened to identify Contaminants of Potential Concern (COPC) in each media. Screening values approved by the Department are the Delaware Default Background Standards. Other screening values can be used with the DNREC's approval.

Exposure assessment is based on current and proposed specific future uses of the property (e.g., housing development, recreational space, office space, manufacturing facility). To determine the exposure point concentration, the Department recommends the use of EPA’s statistical program Pro UCL to calculate the 95 percent UCL of the mean.

For the human health risk calculation the Department recommends the use of the risk calculator available through the Risk Assessment Information System (RAIS). Other risk calculators can be used if approved by the Department.

The US EPA developed a set of standardized tables for use in risk assessment. For a detailed site specific risk assessment, the US EPA tables can be used. The tables provide a framework for performing the risk assessment and complement the site conceptual model.

Ecological Risk Assessment

Screening is performed for all sites for potential ecological concern using screening questions found in Attachment 2 of the DNREC’s Remediation Standards Guidance and the Hazardous Substance Cleanup Act. Additional evaluation is generally required if indicated by the initial screening.

Cleanup Standard

Site specific risk based cleanup standards shall be based on cumulative carcinogenic and non-carcinogenic risks of 1E-5 or a hazard index of one (1) respectively, except for lead and PCBs. Additional information on remediation standard is provided in DNREC’s Remediation Standards Guidance under the Hazardous Substance Cleanup Act. TheScreening Level Table ( Excel version) should be used in lieu of the URS values and the values established in the 2007 Policy Concerning the Default Background Concentration of Arsenic and the Revision to the Remediation Standards Guidance for all new sites (as of January 1, 2013) regulated under HSCA and for existing sites where a risk assessment has not yet been performed.

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