Remediation of soil and groundwater contamination caused by leaking underground storage tanks (LUSTs) in the state of Wisconsin is regulated by the Wisconsin Department of Natural Resources (DNR), in accordance with rules specified in Chapters NR 140 and NR 700-726 of the Wisconsin Administrative Code. By the end of 1995, nearly 12,500 LUST sites had been identified in Wisconsin of which over 8000 were still active. The investigation and remediation of these active LUST sites poses a significant economic liability.
To promote effective use of both public and private resources in the pursuit of environmental goals, the Wisconsin corrective action program has been evaluated with respect to the risk management objectives embodied in the ASTM E-1739 Standard for Risk-Based Corrective Action (RBCA) Applied at Petroleum Release Sites. The ASTM RBCA process is designed to facilitate the efficient allocation of corrective action resources based upon site-specific evaluation of human health and environmental risks. The ultimate endpoint of the RBCA planning process is the closure of sites in an expedient, protective, and cost-effective manner. State regulatory programs may achieve these same benefits by incorporating key risk management objectives in the existing regulatory framework or by customizing the RBCA process to meet local needs.
For the purpose of this planning effort, Groundwater Services, Inc. (GSI), has conducted a technical evaluation to: i) evaluate the risk management procedures of the Wisconsin regulatory program and ii) assess the implementability of the RBCA planning process under Wisconsin rules and statutes. Results of this evaluation support the following key findings:
Cost-Effective Risk Management: The ASTM RBCA process and the Wisconsin corrective action program share the objective of protecting public health and the environment in a cost-effective manner. The procedural steps specified under the Wisconsin NR 700 series regulations differ from those outlined in the ASTM RBCA standard. Nevertheless, the Wisconsin program does address the key risk management objectives of concern under RBCA, particularly in light of pending regulatory modifications. Regulatory amendments designed to encourage appropriate use of natural attenuation remedies are of particular importance with regard to cost-effective allocation of remedial action resources. Clear, streamlined guidelines for application of such remedial measures will be critical for successful implementation of the revised rules. Detailed discussion of the Wisconsin program is provided in Section 3.0 of this report.
Implementability of RBCA Procedures: On a case-by-case basis, the principal elements of the RBCA planning process are admissible under the Wisconsin corrective action program, as defined under current NR 140 and NR 700 series rules and proposed amendments. Guidelines for application of RBCA site classification procedures, tiered evaluation of risk-based cleanup standards, remedy selection criteria, and compliance monitoring procedures are provided in Section 4.0 of this report.
Potential Benefits of RBCA Program: Where applicable under Wisconsin rules, the planning procedures outlined in ASTM E-1739 and the associated Tier 1 and Tier 2 RBCA guidance manuals could facilitate streamlined preparation and review of site remediation/closure applications. In addition, the Partners in RBCA Implementation (PIRI) can provide technical and financial support for training of agency staff, responsible parties, and consultants.
Case Study Example: For purpose of illustration, a case study example has been completed to compare three alternate pathways to site remediation/closure, as allowed under Wisconsin rules:
Case 1: Generic Wisconsin Remediation Limits
Case 2: Wisconsin Remediation by Natural Attenuation (RNA) Option
Case 3: RBCA Tier 2 Performance Standard
For a given set of site conditions, Section 5.0 of this report reviews site remediation requirements and estimated costs associated with these various site management procedures. In this example, each of the three procedures provided effective response to human health and environmental risks. However, the RNA Option (Case 2) proved the least expensive site management approach in this example. The Tier 2 RBCA analysis (Case 3) also supported selection of remediation by natural attenuation for the affected groundwater plume, resulting in total remediation costs comparable to those of Case 2. Case 1, which involved active rather than passive site remediation, was significantly more costly than Case 2 but was predicted to achieve site closure in significantly less time. Of the three options addressed in this study, only Case 1, remediation to generic limits, involves no future restriction on land use. These findings suggest that the most cost-effective management option for a given site will depend on the nature and timing of future site development plans. Detailed discussion of this case study example is provided in Section 5.0 of this report.