A Risk-Based Screening Method for Evaluating Total Petroleum Hydrocarbons at Upstream Sites

Abstract

Abstract Regulators often require that Total Petroleum Hydrocarbons (TPH) be measured and set TPH clean-up criteria for soils impacted by crude oil. However, the lack of a standardized, scientifically defensible procedure for interpreting TPH has resulted in the establishment of arbitrary criteria ranging from 100 to 20,000 ppm (mg/kg) TPH in soil. In the past, TPH regulations and guidance have not considered a technical approach to addressing risk to human health. Recent efforts by the TPH Criteria Working Group (TPHCWG) have established human-health Risk-Based Screening Levels (RBSLs) for refined petroleum products. RBSLs for crude oils and exploration/ production wastes are being addressed by a joint industry effort through Petroleum Environmental Research Forum Project 97-08. The TPHCWG methodology was modified to include the high molecular weight compounds that are present in many crude oils. As part of the project, 48 crude oils were characterized for aliphatic and aromatic hydrocarbon content within equivalent carbon number ranges. Appropriate toxicity, fate, and transport values were determined for compounds greater than carbon number C35. Upon project completion, a risk-based screening method will be available for evaluating TPH at upstream sites. This method can be incorporated into an upstream version of a Risk-Based Corrective Action Plan (RBCA).