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Enterprise Wastewater Treatment Facility

Enterprise Wastewater Treatment Facility

Facts that you need to know:

The City of Enterprise’s wastewater treatment facility was originally constructed in 1955. The 1955 treatment facility project consisted of construction of a preliminary treatment system including headwork’s, one 35 foot diameter primary clarifier, a 54 foot diameter rock-media trickling filter, one 35 foot diameter secondary clarifier, sludge pumping facilities, a control building, an 18.5 foot diameter anaerobic digester with external heat exchanger and mixing pump, sludge drying beds, a gas chlorinator system, and an outfall to the Wallowa River.

In 1986, the City received a Community Development Block Grant for $424,000 to complete limited improvements to the wastewater collection and treatment facilities. The limited improvements focused primarily on isolated repairs of the collection system to target reduction of the severe infiltration/inflow problem the City experiences in their collection system, a minor amount of work at the WWTF, and construction of an effluent polishing and dechlorination lagoon.

This 1955 WWTF was constructed to handle 750,000 gallons of wastewater per day. This treatment facility served the City well for 52 years, regulations over that 52 year period got more stringent over the years and the ageing facility was having problems staying in compliance with the DEQ’s regulations. At times flows would run into the 1,000,000 gallons/day at certain times of year because of the infiltration problems the City had in certain parts of their collection system. This facility was having problems meeting the DEQ’s permit limits for flows, biochemical oxygen demand, suspended solids and E-coli that were being discharged into the Wallowa River.

There have been some questions as to why the City over designed the new WWTF and that is not at all correct. The facility that was built in 1955 was designed for a population of 3,000 people, an average flow of .75 MGD, and an overall efficiency of 79%. Facility planning guidelines require that any treatment facilities be designed to handle flows for a 20 year period. Population records for Enterprise show that the population raised until 1960, at which time it began to decline for 10 years to a low of 1,680 in 1970, then began a steady increase to a certified population of 1,840 in December 1975. The current WWTF was designed from the certified estimated population of 1,940 in July 2004, for a 20 year projected design population of 2,650 people. This allows for a growth of 710 people over the next 20 years, a designed flow of .698 MGD and is currently achieving an overall efficiency 98 to 99% removal of all pollutants in the effluent before it is discharged into the Wallowa River. The City’s new wastewater treatment facility is producing such a good quality effluent that the Alpine Meadow Golf Course is utilizing it for irrigation to their course in the summer months instead of drawing it out of Trout Creek. This in turn is a benefit to the public and environment.