Introduction

The Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended (Superfund), is a national program that establishes a means to respond to releases of hazardous substances. The National Oil and Hazardous Substance Pollution Contingency Plan (NCP) is the regulation that implements Superfund and establishes the general approach for remediation of hazardous waste sites. The objective of the program is to protect human health and the environment from the potential harm posed by the constituents present at these sites.

The U.S. Environmental Protection Agency (EPA), administrator of Superfund, has established a framework for assessing risks to human health that ultimately determines whether remedial action is necessary at a site. The risk assessment process, as set forth in EPA's Risk Assessment Guidance for Superfund, Volume I, Human Health Evaluation Manual (Part A) [1], provides an analysis of baseline risks, determines the need for remedial action, and establishes a basis for calculating cleanup levels. This process provides an alternative to meeting regulatory cleanup criteria and allows for the use of site-specific information to establish practical remedial alternatives.

Cleanup levels are being established for a pond that is adjacent to a former wood-treating facility that operated for 18 years. The facility used creosote as the preserving chemical. Of the 27 shallow sediment samples collected from the pond, cPAHs were detected in all samples with total concentrations ranging from 0.807 to 144.82 mg/kg (Table 1). In many cases, the high degree of contamination is limited to a small area and is not characteristic of the entire site. A frequency distribution of the cPAHs in the shallow pond sediments indicates that only four of the 27 samples had total cPAHs exceeding 30 mg/kg and seven had total cPAHs exceeding 10 mg/kg (Table 2).

A risk assessment was prepared in accordance with Superfund for this pond to establish baseline risks for all potential receptors and exposure scenarios. Based on the data, children wading in the pond and coming into direct contact with the cPAH-impacted sediments are those at the greatest potential risk. Therefore, development of cleanup levels for pond sediments is based on this most sensitive receptor.

The primary objective of establishing cleanup levels at this site is to be protective of human health, specifically the health of children wading in the pond. These children may come in contact with the cPAHs in the sediments through dermal contact and incidental ingestion. Baseline risks associated with exposure to the cPAH-contaminated sediments are based on the application of Chu and Chen's relative potency factor approach [2]. Using the site-specific data and the relative potency factors, a cleanup level can be calculated. Sediments with cPAH concentrations above a certain concentration would be removed, thus resulting in a reduced average concentration of cPAHs and a concomitant reduction in risk.

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