Long-term Effects of Decentralized Wastewater Treatment in Logan, Montana

In 1889, Logan, Montana, like many small communities across the west, was established to provide service to the expanding railroad industry. The community’s plat provided for the housing of railroad employees, townspeople and a commercial district. As with the railroad, the town flourished and at one point Logan even had its own school. 

The plat laid out multiple lots along several streets terraced on gently sloping topography running down into a river bottom. The lots ranged in size from 0.07 to 0.16 acres. While these lot sizes are common in towns platted during this era, they were usually meant to be served by public water and a centralized sewer. However, there is no indication that water and sewer infrastructure was ever planned for the community. Over the years, residents of Logan have had to make do with the outhouse, septic tank, cesspit, and drainfield for wastewater treatment and disposal, while relying on portable water containers or individual wells for potable water. Due to these small lot sizes, drinking water wells are in very close proximity to wastewater disposal. 

The problem is that treatment relies on percolation of wastewater through soils where  contaminants are broken down by biological and chemical actions as it is dispersed. This process requires the appropriate amount of distance from groundwater and potable well water before wastewater has a chance to interact with them. This distance is referred to as “separation.” Typically, 100 feet of separation is required between a well and treatment soils (drainfield). Also, four feet of vertical separation is also required between a drainfield and ground water depending on the soils. For planning, a minimum of a one-acre lot is required for an onsite well and a drainfield in order to achieve adequate separation between the two.   

Compounding the potential problems created by inadequate separation is the fact that the Ryell silt loam soil present on the lower slopes of the Logan area is prone to rapid percolation and is a poor filter media. This is complicated by the presence of a “karstic” limestone bedrock full of fissures, channels and chambers that have the ability to transport poorly treated wastewater into groundwater. Altogether, these issues increased the likelihood of treatment failure and thus contaminated well water.   

While it probably had been progressing for years, evidence of treatment failure surfaced in 2008 when multiple complaints of ponding sewage were filed with the local Environmental Health Services. The complaints led to the testing of 14 wells, with results demonstrating elevated nitrates in seven wells, six ranging from 2.12-7.20 mg/L and one at 33.6 mg/L.  Testing also found coliform bacteria (environmental contamination) in six wells with an additional well testing positive for E. coli (fecal contamination). These results and further complaints prompted a more formal study which found an additional five wells positive for E. coli and an additional ten positive for coliforms. 

Based on testing results, it was evident that wastewater-related contamination was finding its way into the groundwater supplying individual wells. Residents of Logan began to organize and look for solutions. In 2018, they contacted the Midwest Assistance Program (MAP) with the idea of forming a Water and Sewer District (WSD) with the goal of a wastewater treatment system to serve the community.   

MAP helped to organize an early community meeting to discuss the formation of a WSD but, due to aggressive push back from some in the community, the meeting concluded and the idea of a WSD was shelved. In 2022, MAP was contacted again with a request to facilitate a public meeting presenting the formation of a WSD and to answer questions. This time the pro-WSD community was larger and more organized and had petitioned the County Commission regarding the formation of a WSD and had it placed on an upcoming 2023 Ballot. Although the initial ballot measure failed, the measure was put on the ballot again the following year and, after a series of MAP-facilitated meetings and public outreach, the vote to create a WSD was ultimately successful. The community continues to work towards their goal of constructing a centralized wastewater treatment system to serve the community and alleviate the problems likely caused by the decentralized systems.   

This article was funded under RCAP’s EPA TW 4 2023 – 2026 grant.