Wastewater Treatment Plant in Construction

In 2017, the local sanitarian stated in a letter to the City small lot sizes resulted in a “serious challenge for 2 of every three systems” with an estimated 400 of the 619 systems needing replacement.

The City’s wastewater treatment system was a three-celled aerated lagoon system discharging into the Clark Fork River.  The system received seasonal E. coli violations, had duck weed blooms and did not have capacity to handle any more than 300 sewer connections which was further reduced due to excessive I/I from the Clark Fork River.

The City responded by beginning to evaluate various configurations expanding the sewer collection system, rehabilitating existing sewer mains to lower I&I, and wastewater treatment alternatives for upgrading the treatment system to handle a fully constructed collection system that allowed all City parcels to have the ability to connect to the system.

The final designed and constructed project included the installation and relocation of new gravity collection mains and force mains, three new lift stations, connecting new users to the sewer system, abandoning existing septic systems, and upgrading the treatment systems capacity.  Low pressure grinder pump services and systems were used to account for steep grades and large boulders present throughout the project area.

The treatment system was upgraded to a two celled complete/partial mix aerated lagoon with insulated covers.  A stairscreen was added as pretreatment, a fixed film nitrifying/polishing reactor was added after the lagoons for future ammonia limits, and a UV disinfection was added before final effluent disposal.

The new wastewater system and collection system improvements project began construction in March of 2021 and was substantially completed in November of 2023.  These improvements improved service to existing users, added new users, removed non-compliant septic systems, and expanded the treatment capacity for future development.  The wastewater system is now operating within permit limits and has future capacity for additional phases of collection system expansion.  This project represents Phases 1 & 2 for a 4 phased approach to expanding sewer service to all residences in the community.