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Missoula Measures - Sewer Connections


Why this topic?

As we grow, we hope to protect valuable resources as much as possible. Sewers directly protect the quality of both surface water and groundwater. Because sewer lines only exist within or closer to the urban area, the number of sewer connections is also an indirect indicator of how well we are containing sprawl. And if we contain sprawl, we are likely to be contending better with other issues such as air quality, the transportation system, budgets, taxes, schools, parks and recreation, police and fire services, and other infrastructure. The more we sprawl, the higher the cost and impact on all these resources.

How are we doing?

Since 1990 the number of new connections to public sewer has outpaced the number of new septic systems installed in the Missoula Valley. A significant number of the new sewer connections were made possible by federal grant-funded projects in the Wapikiya-Bellevue area. Because federal grants for sewer projects are no longer available, it is challenging to obtain affordable financing for sewer extension projects. Data reflects a trend toward infill development in areas served by public sewer. The initiation of a new project to sewer the area east of Reserve Street and south of the Clark Fork River in 1998 should allow new sewer connections to continue to outpace septic permits.

The Health Department's Environmental Health Division has more information on this topic.


Total numbers of hook-up and permits:

graph sewer and septic hookups, Missoula, 2000-2013

Source: Environmental Health, MCCHD and Missoula Public Works

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Brief Background

Why sewer?

About 30% of all homes and businesses in the Missoula Valley use septic systems such as drain fields, seepage pits, or cesspools to dispose of waste water, while 70% are connected to publicly owned treatment facilities in Missoula, Lolo, and El Mar Estates. Sewage disposed of through septic systems contributes pollutants, including nitrates, bacteria, viruses, and parasites, to groundwater, which can pose the threat of isolated waterborne disease outbreaks in areas vulnerable to pollution. Because all groundwater in the Missoula Valley eventually discharges to surface waters, pollutants such as nitrates from septic systems indirectly affect the quality of the Clark Fork and Bitterroot rivers. Waste water collection and treatment protects groundwater and drinking water and provides improved treatment for constituents such as nitrogen, which can cause surface water pollution. (Environmental Health, MCCHD)

542 million gallons of sewage

In the eight most densely populated areas of the valley, 7431 homes and businesses discharge approximately 542 million gallons of sewage per year to the groundwater. This effluent contains an estimated 52,378 pounds of nitrate per year. Groundwater in the Missoula Valley eventually discharges to the Bitterroot or Clark Fork rivers. For example, groundwater in the Orchard Homes/Target Range area drains into the Bitterroot, carrying a significant load of nitrogen. Connection of septic systems to public sewers in these areas would reduce the total nitrogen load to surface waters, because the treatment plant removes much nitrogen. Future plant improvements will allow improved nutrient removal. (Missoula Valley Water Quality District)

Priorities for sewer connection

In 1995, the Missoula Valley Water Quality District completed a study of eight high-density unsewered areas, and prioritized the areas for future connection to public sewer. The order of priority was based on the degree of water quality degradation and the potential health risks caused by septic systems in each area.

As of 2004, the following areas have been connected to the sewer:

Sewer connections still pending:


Related Websites

The Missoula Water Quality District has a wealth of information, including full reports, on aquifer related topics.


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