Ennis WWTP - Secondary Treatment Plant in Ennis, Montana

Ennis WWTP is a municipal wastewater treatment facility located in Ennis, Madison County, Montana, United States. The plant serves a small population of about 1,250 residents, reflecting the rural character of the surrounding area. Its location along US 287 places it within the Madison River watershed, a tributary of the Missouri River system. The plant provides secondary treatment, which is the standard level required under the U.S. Clean Water Act for municipal facilities of this scale. Secondary treatment typically involves biological processes to remove organic matter and suspended solids. The plant's designed capacity of 567.81 units and current discharge volume of 545.10 units indicate it operates near its capacity, serving the community's needs. Treated effluent from the plant ultimately drains into the Madison River, which flows north to join the Jefferson and Gallatin rivers, forming the Missouri River near Three Forks, Montana. The Missouri River then flows eastward across the Great Plains to the Mississippi River and eventually the Gulf of Mexico. The Madison River is a renowned blue-ribbon trout stream, making water quality protection critical for aquatic life and recreational fishing.

The plant discharges into the Madison River watershed, a headwater tributary of the Missouri River system. The Madison River supports a diverse aquatic ecosystem, including native trout species such as brown and rainbow trout, and is a popular destination for fly fishing. Downstream, the river joins the Missouri River, which flows through the Great Plains to the Mississippi River and the Gulf of Mexico. Protecting water quality in this headwater region is essential for maintaining downstream ecological health and recreational uses.