The U.S. Army Corps of Engineers, Nashville District (Corps), is initiating scoping under the National Environmental Policy Act (NEPA) to evaluate potential impacts of the proposed revision of the 1998 Center Hill Dam and Reservoir Water Control Manual (WCM). The Center Hill WCM comprises pertinent project data, background information, the plan for day-to-day and emergency water management, and the effects of the plan on authorized project purposes.
Center Hill Dam is located at Mile 26.6 on the Caney Fork River in DeKalb County, Tennessee. Center Hill Reservoir spreads throughout Warren, White, and Putnam Counties (Figure 1). The Reservoir is one of four major flood risk management reservoirs for the Cumberland River; the others being J. Percy Priest Reservoir, Dale Hollow Reservoir, and Lake Cumberland. Center Hill Dam was completed for flood risk management operations in November 1948. The Dam is a concrete and earth structure with eight tainter gates and three hydro-electric power generating units (Figure 2). Subsequent to construction, Congress authorized additional project purposes including recreation, water supply, fish and wildlife conservation, and water quality. Visitors to Center Hill Dam and Reservoir have diverse interests such as camping, bird watching, sightseeing, fly fishing, and paddling. Center Hill Reservoir is consistently one of the top fifty most-visited Corps of Engineers reservoirs in the nation, receiving over one million visitors per year.
The WCM ensures unbiased operations and informs the public of mission priorities. The purpose of the proposed action is to update the Center Hill Dam and Reservoir WCM to include current project operations under the existing congressional authorizations. The WCM update would address factors such as basin hydrology, water usage and consumptive demands, new and rehabilitated structural features, and environmental considerations. The updated WCM would also contain records of institutional knowledge to prevent the loss of operational expertise and updates of Corps terms and definitions that have changed over the past couple decades.
Below are some current operations the Corps is considering updating:
- Hydropower Ramp Rates – This rate describes the number of generating units that could be turned on or off over a certain amount of time. The 1998 WCM allows for two units per hour up or down.
- Spillway Gate Operations – Spillway gates at Center Hill Dam are mechanical structures that regulate the rate of flow through the dam while the water level in the reservoir is within the Flood Control Pool. The 1998 WCM states that when spillway gates are being operated, they should maintain uniform openings of all gates as closely as possible with no more than one foot difference among the gate openings. The WCM also limits the maximum increase in discharge to 2,000 cubic feet per second (cfs) per hour and the maximum decrease in discharge to 4,000 cfs per hour.
- Minimum Flows –The 1998 WCM identifies the minimum water flow requirement, effective from June 1 through November 30, as the discharge resulting from one unit generation for one hour within any 48-hour period.
- Sluice and Orifice Gate Operation – The sluice and orifice gates release highly oxygenated water from the reservoir to the tailwater. The sluice gates sit at the base of the dam and the orifice gates are ported steel plates that are placed over the sluice gate openings. Both sluice and orifice gates can improve dissolved oxygen downstream when water quality is degraded due to warm summer temperatures.
On Thursday May 26, 2022, 5:00 – 7:30 pm, the Corps will host a public meeting at the Smith County Agricultural Center located at 159 Ag Center Ln, South Carthage, TN 37030. The Corps goal is to gather input from all stakeholders and best balance all the reservoir’s authorized project purposes. The Corps will evaluate input submitted to determine the proper level of analysis for NEPA review (categorical exclusion, environmental assessment, or environmental impact statement).
This letter serves to solicit scoping comments from the public, federal, state, local agencies and officials, Indian Tribes, and other interested parties in order to consider and evaluate the impacts of this proposed activity as part of the Corps’ planning process and in accordance with the NEPA process. We encourage comments not only about resources in the immediate project area, but also of plans or proposals for any other development that may impact or influence project resources. Comments are used to assess impacts on human environment. This letter also serves to initiate the public involvement requirements of Section 106 of the National Historic Preservation Act of 1966, as amended.
Comments must be submitted within 30 days of the date of this letter to the address listed above or electronically to Cody.A.Flatt@usace.army.mil. Comments will also be received at the public meeting. For additional information regarding the proposed project, please contact Cody Flatt at (615) 736-7954.
CRAIG D. CARRINGTON
Chief, Project Planning Branch