DEQ Approves Cleanup Plan for Petroleum Release at Former Helena Service Station

The Montana Department of Environmental Quality approved a Corrective Action Plan addressing a petroleum release at the former McGaffick Service property at 1020 N. Last Chance Gulch in Helena, the agency announced March 18.

The approved plan is classified as a Petroleum Mixing Zone Corrective Action Plan, a regulatory mechanism under §75-11-508, MCA, that evaluates whether a petroleum release can be resolved by establishing a defined contamination boundary rather than requiring active remediation across the entire affected area. Under state law, a release can be resolved with a PMZ only when all conditions set forth in law and rule have been met.

The cleanup plan will determine the extent and magnitude of contamination at the North Last Chance Gulch site, identifying which portions will rely solely on natural attenuation for further remediation. The approved report also evaluates the risk that residual contamination poses to human health, safety, and the environment and documents existing site conditions.

Several steps remain before the release can be officially closed. Following approval of the proposed institutional control language, a Montana-licensed surveyor must complete a metes and bounds survey of the proposed PMZ boundary, which is legally distinct from the property boundary. The PMZ boundary itself will be drawn at points where contaminant concentrations reach or fall below water quality standards, as determined under administrative rule ARM 17.56.604.

Once DEQ approves the institutional control language, the proposed control will be published for a minimum 30-day public comment period. DEQ will then work with the responsible party to amend the institutional control as necessary based on any concerns raised. The release will not be considered "Resolved with a PMZ" until all applicable institutional controls have been approved and duly recorded with both DEQ and the Lewis and Clark County registrar of deeds.

The identity of the current owner or responsible party who submitted the CAP was not disclosed in the DEQ announcement, nor were the specific petroleum contaminants, their concentrations, or the spatial extent of the contamination at the former service station site.