B09 Amendment 3 Yellowstone NE Entrance Project Report 0003.pdf
Posted: Sept. 2, 2026
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Summary
This Chapter 3 Permit to Construct Design Report, prepared by Stantec Consulting Services, Inc. for the National Park Service and Montana Department of Environmental Quality, addresses utility improvements for two new two-bedroom modular housing units at Yellowstone National Park’s Northeast Entrance Government Area in Park County, Montana. The project will replace existing water and sewer services formerly serving two demolished modular homes, install two approximately 150-foot combined 2-inch HDPE potable-water/fire-suppression services connected to the existing 4-inch water main along Meridian Road, and construct approximately 190 linear feet of new 6-inch PVC sanitary sewer main, two 48-inch manholes, and replacement 4-inch PVC sewer services connecting to the existing system.
Construction is anticipated to begin in summer 2026, and the improvements will be owned and maintained by Yellowstone National Park.
The water design assumes average daily demand of 500 gallons per day, maximum daily demand of 1,360 gallons per day, peak-hour demand of 3.8 gallons per minute, automatic fire-suppression demand of 150 gallons per minute, and a one-hour site fire-flow requirement of 1,000 gallons per minute. No new water mains, storage, pumping, treatment facilities, hydrants, valves, or water-treatment modifications are proposed.
The new services will use AWWA C901-certified, nonpermeable HDPE, be buried at least six feet, maintain required utility separations, and be individually metered in coordination with Yellowstone National Park operations. The existing water distribution system will remain in service.
The sanitary sewer improvements include a 6-inch SDR 26 bell-and-spigot PVC gravity main installed at a slope of 0.03 feet per foot, with a minimum six-foot cover and wye-connected services. The proposed main has a calculated full-flow capacity of 334 gallons per minute at 3.795 feet per second, while the downstream existing 6-inch vitrified-clay main has a capacity of 613 gallons per minute.
The existing septic system is rated for 3,000 gallons per day compared with calculated combined peak-day flows of 1,890 gallons per day. The report concludes that the existing septic and collection systems have adequate capacity because the two new units replace the former units in kind.
Design and construction will follow applicable Circular DEQ-1 and DEQ-2 requirements and the 2023 Wyoming Public Works Standard Specifications, with permit drawings, specifications, potable-water hydraulic analysis, and sewer-capacity calculations included as supporting appendices.
Construction is anticipated to begin in summer 2026, and the improvements will be owned and maintained by Yellowstone National Park.
The water design assumes average daily demand of 500 gallons per day, maximum daily demand of 1,360 gallons per day, peak-hour demand of 3.8 gallons per minute, automatic fire-suppression demand of 150 gallons per minute, and a one-hour site fire-flow requirement of 1,000 gallons per minute. No new water mains, storage, pumping, treatment facilities, hydrants, valves, or water-treatment modifications are proposed.
The new services will use AWWA C901-certified, nonpermeable HDPE, be buried at least six feet, maintain required utility separations, and be individually metered in coordination with Yellowstone National Park operations. The existing water distribution system will remain in service.
The sanitary sewer improvements include a 6-inch SDR 26 bell-and-spigot PVC gravity main installed at a slope of 0.03 feet per foot, with a minimum six-foot cover and wye-connected services. The proposed main has a calculated full-flow capacity of 334 gallons per minute at 3.795 feet per second, while the downstream existing 6-inch vitrified-clay main has a capacity of 613 gallons per minute.
The existing septic system is rated for 3,000 gallons per day compared with calculated combined peak-day flows of 1,890 gallons per day. The report concludes that the existing septic and collection systems have adequate capacity because the two new units replace the former units in kind.
Design and construction will follow applicable Circular DEQ-1 and DEQ-2 requirements and the 2023 Wyoming Public Works Standard Specifications, with permit drawings, specifications, potable-water hydraulic analysis, and sewer-capacity calculations included as supporting appendices.
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