Developing Risk-Based Cleanup Standards for Soils in Nigeria

Abstract

Abstract Regulators outside of the United States either have not set cleanup goals for Total Petroleum Hydrocarbons (TPH) and other chemicals in soil, or they have proposed very low concentrations based on reviews of European and North American regulations. Soil TPH or oil and grease cleanup levels range from 50 to 10,000 ppm (mg/kg) in North America and Europe. This reflects that not all jurisdictions acknowledge differences between types of hydrocarbon mixtures (e.g., gasoline and crude oil), not all jurisdictions recognize that soil organic matter can report as TPH, and that not all jurisdictions utilize a risk analysis approach for evaluating human health and environmental impacts. In addition to these issues, there has been until recently no standardized, scientifically defensible procedure for interpreting risk associated with complex mixtures of hydrocarbons like TPH. However, recent efforts by the TPH Criteria Working Group (TPHCWG) and the Petroleum Environmental Research Forum (PERF) have established procedures to derive human-health Risk-Based Screening Levels (RBSLs) for refined petroleum products and crude oils. In 1999, the Nigeria Department of Petroleum Resources proposed using Intervention and Target Values established by the Dutch Ministry of Housing, Spatial Planning, and the Environment for soil remediation at oil impacted sites in Nigeria. They proposed using the Dutch Target Value for mineral oil of 50 mg/kg; however, since that time the Dutch have adopted an approach similar to that of the TPHCWG. This paper discusses the new approach being used by the Dutch, as well as the Risk-Based Corrective Action approach for TPH and other chemicals being used by many state regulators in the United States. A modified approach for developing Nigeria specific RBSLs for oil impacted soil is proposed.