As part of the U.S. Army Corps of Engineers regulatory program, NorthWestern Energy has participated in wetland and stream bank compensatory mitigation projects to ensure minimal cumulative adverse impacts to the nation’s wetlands and streams that may result from one of our projects. We have also secured mitigation for natural gas and electric transmission projects and for our hydro facilities.
Our construction projects that disturb one or more acres of land must have a permit to discharge storm water. This official permit requires implementation of best-management practices to prevent runoff of storm water from the construction area into streams, rivers and other surface waters. A permit also requires routine inspections and reporting by qualified personnel. In addition, NorthWestern Energy’s Environmental Permitting and Compliance Department has sponsored classes on storm water management for company managers and engineers.
We have been working for several years to address environmental impacts associated with the operation of former Manufactured Gas Plants. In Aberdeen, South Dakota, by using state-of-the-art technology, ingenuity and persistence, we eliminated the migration of coal tar into a nearby creek through the city’s storm sewer system. We also identified and resolved a problem with coal tar infiltrating the city’s sanitary sewer infrastructure and have installed a water treatment system. We have installed a massive underground collection pipe system to gather and recycle or dispose of drainable coal tar deep in the subsurface and we will continue for years to monitor the site closely.