PUBLIC NOTICE 
COCONINO COUNTY FORT TUTHILL QUAD WATER-SEWER REPLACEMENT
Pursuant to the National Environmental Policy Act of 1969, as amended (42 United States Code [U.S.C.] 4321, et seq.) (NEPA), the U.S. Army Corps of Engineers (Corps) is preparing an Environmental Assessment (EA) for the proposed Fort Tuthill Utility Line Project in Coconino County, Arizona. The purpose of the EA is to evaluate potential environmental impacts associated with the replacement of aging water and sewer infrastructure at Fort Tuthill County Park.
The proposed project would be funded in part by the Corps through the Section 595 Rural Infrastructure Program authorized under the Water Resources Development Act of 1999, Public Law 106-53, as amended (Section 595). Under Section 595, the Corps is authorized to provide design and construction assistance for water-related environmental infrastructure and resource protection and development projects in Arizona, including projects for wastewater treatment and related facilities, water supply and related facilities, and surface water resource protection and development.
The agreement between the Corps and Coconino County was entered into on June 10, 2024, for an initial increment of work consisting of the design and construction of the Fort Tuthill Utility Line Project. The Corps is partnering with Coconino County for this initial increment of work, which includes the replacement of approximately 2,700 feet of old sewer and water lines with modern infrastructure. The project will feature dual 8-inch PVC water lines—one for potable water and another for fire suppression—as well as an 8-inch PVC sewer line. The sewer system will include manholes, service cleanouts, and connections to the City of Flagstaff’s wastewater system, eliminating reliance on the existing septic system. The project also includes a looped fire suppression system to enhance fire protection within the park.
The project site is located within Fort Tuthill County Park, approximately 3.5 miles south of Flagstaff, Arizona. Fort Tuthill serves as a regional recreational hub and hosts various public events, including the annual Coconino County Fair. The park's infrastructure, originally constructed in 1929, has aged significantly, and its deterioration poses risks to public health, operational efficiency, and environmental integrity. The replacement of these outdated systems is necessary to support the park's long-term sustainability and ensure compliance with current environmental and safety standards.
The project site and all associated infrastructure improvements are located entirely within the boundaries of Fort Tuthill County Park. Construction activities will involve excavation, utility line installation, and restoration of disturbed areas. Best Management Practices (BMPs) will be implemented to minimize environmental impacts, including dust suppression, and erosion control. Additionally, coordination with the State Historic Preservation Office (SHPO) is ongoing to ensure cultural resource protection requirements are identified and included in the project and the project complies with the National Historic Preservation Act.
If the EA identifies significant impacts that cannot be mitigated to a level that is less than significant, an Environmental Impact Statement would be prepared. If no unmitigable, significant impacts are identified, then a Finding of No Significant Impact would be prepared. Preliminary environmental analysis anticipates that there would be no unmitigable, significant impacts on environmental resources.
Comments regarding the Proposed Action are invited and will be accepted through April 13, 2025. Feedback can be submitted electronically to Andrew.T.Gilham@usace.army.mil, or mailed to: U.S. Army Corps of Engineers, Coconino County Fort Tuthill Quad Water-Sewer Replacement, Attn: Andrew Gilham, Planning Division, 3636 N. Central Ave, STE 650, Phoenix, AZ 85012
Figure 1. Draft schematic of utility line locations for the Coconino County Fort Tuthill Quad