Investigation and Cleanup of Leaking Petroleum Sites

After there has been some initial indication that there may be petroleum contamination at a site, DWEE becomes involved in determining whether more investigation and cleanup are required. The agency determines whether parties who caused the contamination are still available and financially capable of assuming responsibility.

In the event these reports indicate a threat to health, safety, or the environment, DWEE requires a detailed study of the affected groundwater and soil to discover the severity of the contamination, direction of groundwater flow, and potential water supplies or points of exposure that may be impacted. Program staff review these reports to determine if cleanup requirements are needed and issue public notices with their decisions. Staff review remedial actions throughout the project and determine when sufficient cleanup has been accomplished.

Due in part to the recommendations of a technical advisory committee and legislative requirements, the program has developed risk-based corrective action (RBCA) regulations and accompanying guidance. The RBCA process allows evaluation of all petroleum release sites based on the risk they pose to human health and the environment. Those that pose no significant risk are closed; those that pose significant risk are prioritized for further work.

In recent years, the program has been initiating many new investigations to collect information needed for Tier 1, the first step in the RBCA process. The plan is to investigate additional sites each month until eventually the information necessary for a RBCA Tier 1 evaluation has been collected at all sites. Sites that fail Tier 1 are activated for Tier 2, which is a more detailed investigation and the next step in the RBCA process. If sites fail Tier 2, they are generally scheduled for cleanup.