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Big Sky, Montana
Moonlight Basin Wastewater Treatment Plant
Designed to support sustainable resort growth near Big Sky, Montana, Moonlight Basin Wastewater Treatment Plant transforms wastewater into a high-quality reusable resource—expanding infrastructure capacity while protecting the surrounding environment.
The Challenge
Moonlight Basin is a premier mountain resort destination known for skiing, golf, lodging, dining, and other outdoor year-round recreation. As it grew, its owners faced a critical infrastructure challenge: how to expand wastewater capacity to support future development while aligning with Moonlight Basin’s long-term commitment to sustainability, environmental stewardship, and responsible water use.
Historically, treated effluent was managed through subsurface infiltration chambers and seasonal forest-land irrigation. While effective for earlier phases of development, that approach became less practical as the resort expanded. Varying flows from season to season and the need for greater operational flexibility made it clear that they needed a new strategy that would do more than keep up with demand. The new system also needed to protect the surrounding environment, prepare for future development options, and make beneficial use of water in a region with limited resources.
Services and Highlights
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Preliminary Engineering Report (PER) to determine service areas, effluent disposal, and treatment technology to meet the needs for future growth.
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This project is the second in a three-facility service area.
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This project utilizes a membrane bioreactor (MBR) plant capable of producing Class A-1 effluent, as permitted by the Montana Department of Environmental Quality.
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In addition to engineering design, this project required the pre-selection of a suitable MBR manufacturer and 3D modeling.
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Additional engineering services included construction administration and resident project representative (RPR) services.
The Solution
Morrison-Maierle helped Moonlight Basin define a path forward with a Preliminary Engineering Report that evaluated wastewater service areas, treatment alternatives, and disposal strategies to support future growth. As a result, the team recommended a three-plant concept that worked with the resort’s topography and phased development plans. For this facility, the second of the three-plant approach, Morrison-Maierle designed an ultrafiltration membrane bioreactor system with UV disinfection capable of producing Class A-1 reuse-quality effluent under Montana Department of Environmental Quality standards.
That decision was significant. As a result, this project became the first wastewater treatment plant in Montana designed to meet the state’s Class A-1 reuse standards, opening the door to unrestricted reuse applications. In the near term, treated water can be reused for golf course irrigation, reducing demand on potable and natural water sources. Over time, the same treatment standard can support additional beneficial uses, including groundwater recharge, landscape irrigation, and potentially snowmaking as regulatory pathways evolve.
The facility was also engineered for the realities of operating in a high-elevation resort environment. Seasonal occupancy creates major swings in flow, especially during Big Sky’s shoulder seasons, when resort activity drops sharply. To handle these seasonal ebbs and flows, Morrison-Maierle used process modeling to optimize basin sizing, equipment selection, and system phasing, enabling operators to maintain reliable performance under changing conditions. The treatment building was designed for cold-weather operation, with critical equipment housed indoors and controls integrated into a remote-access network that allows staff to monitor and adjust plant performance off-site.
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The project overlooks the Moonlight Basin Golf Course which is irrigated using treated Class A-1 effluent.
The design team buried the walls in the building to reduce the amount of energy needed to heat the building.
A fine screening system was incorporated to protect downstream equipment and the facility's ultrfiltration membranes.
The Impact
For Moonlight Basin, the benefits are both immediate and long-term. The project provides the wastewater capacity needed to support continued development while giving the resort far more flexibility in managing treated water. It reduces reliance on older disposal methods, helps avoid future land-use conflicts, and creates a more resilient infrastructure platform for expansion. Just as importantly, it supports the client’s vision of sustainable growth by turning wastewater into a reusable resource rather than a limitation.
The project also reflects Moonlight Basin’s broader stewardship goals within the Greater Yellowstone region. By enabling high-quality water reuse, the facility helps conserve groundwater and surface water resources, reduces the potential for pollution, and supports development practices that are more compatible with the surrounding landscape. Architectural and site design considerations further reinforced that goal by helping the facility blend with the resort environment and operate efficiently over time.
Ultimately, this plant is more than a utility project—it is a strategic investment in the resort’s future. By solving a pressing infrastructure need with an innovative reuse-based treatment approach, we delivered a solution that supports growth, protects natural resources, and creates lasting value for our client. The result is a facility that not only meets today’s needs but also positions Moonlight Basin for responsible, sustainable development for years to come.
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