Centennial Library

Sewer Department

The City of Grangeville owns and operates the municipal sanitary sewer system providing service to approximately 1400 residential, commercial, and industrial customers. The sewer system consists of approximately 30 miles of collection lines ranging in size from 4″ through 18″ in diameter. The original collection system in Grangeville was built in the early 1900’s using vitrified clay pipe and stacked brick manholes. Much of this 90+ year old system is still in use today. Projects in the 1960’s & 1970’s used asbestos cement pipe and concrete manholes. Later projects used PVC pipe and concrete manholes which is the current materials standard used today. In recent years the City has been able to budget funds to replace old and high maintenance lines, a trend which certainly needs to be continued if funds are available. The sanitary sewer system is operated and maintained by the Public Works Department employees.

The first treatment method for City wastewater was a large septic tank located along Three-mile Creek on the north edge of the City. In the early 1950’s the City built a mechanical wastewater treatment plant on the site of the current plant located along the airport road. The original plant has been upgraded twice; the last upgrade occurred in the late 1980’s. Minor modifications have been made to the current plant to improve its operation. The wastewater treatment plant is operated by two City employees licensed by the State of Idaho.

To view a diagram of the Wastewater Treatment Plant, Please click on the link below.

WWTP Process Schematic 2017


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