The City’s existing treatment facilities were not able to satisfy pollutant limits established in their MPDES discharge permit. In response, the Montana Department of Environmental Quality issued an Administrative Order on Consent requiring the City of Three Forks to correct treatment deficiencies. Great West Engineering completed a detailed evaluation of the MPDES Permit, which included a mixing zone study in the Madison River utilizing a CORMIX model. Great West also prepared a Preliminary Engineering Report (PER) that evaluated a full range of wastewater treatment alternatives ranging from an advanced mechanical treatment plant to various lagoon technologies with reuse for crop irrigation.
The City selected the construction of an advanced covered lagoon system using a complete mix cell followed by two partial mix cells and a fixed film polishing reactor for ammonia removal. The project included design and construction of a lift station, headworks facility, covered aerated treatment lagoons, polishing reactor and an Ultraviolet (UV) disinfection system.