Feasibility study & master plan for water supply reservoir

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Courtesy of Burns & McDonnell

Client: North Central Missouri Regional Water Commission 
 
Completion Date: 2003 

Project Summary 

Burns & McDonnell completed the feasibility study and master plan for a new water supply reservoir in Sullivan County, Mo. Sullivan County and other surrounding counties experienced severe drought conditions for several years and existing water supplies were deemed insufficient to meet current and future water supply needs.

For the feasibility study, Burns & McDonnell performed an evaluation of the current and future water supply needs and then performed a detailed evaluation of alternatives to meet the needs. Water supply sources including groundwater, rivers and reservoirs were evaluated throughout a five-county region to determine which source could best meet the water supply needs. The alternatives evaluation resulted in selection of reservoirs as the best alternative and various reservoir sites were then evaluated to determine the optimum site. A reservoir site located on East Fork Locust Creek, near Milan, Mo., was determined to be the optimum site from both economic and environmental standpoints.

As part of the master plan, Burns & McDonnell performed comprehensive hydrologic and hydraulic evaluations, analysis and design including development of the basin characterization, the water supply yield, the flood hydrology, and the preliminary spillway and outlet works hydraulic design. A cursory geotechnical investigation was performed and the results were used to determine the preliminary configuration of the dam and measures required to minimize underseepage in the glacial deposits found below the dam site. U.S. Army Corps of Engineers, Federal Emergency Management Agency, Natural Resources Conservation Service (NRCS) and U.S. Bureau of Reclamation standards for dam design and dam safety engineering have been incorporated as general design methodology. The structure is designed as single purpose reservoir impounded by a high hazard earthfill dam (70 feet maximum height). The dam impounds 1,600 acres (30,000 acre-feet) at a conservation pool elevation of 910 feet, NGVD.

Computer models utilized in the hydrologic and hydraulic design development include the Corps of Engineers' HEC-1, HEC-RAS and HMR-52 software to analyze the flood hydrology and spillway hydraulics. Also utilized was Burns & McDonnell-developed software for yield and reservoir operations analysis — RESNET.

Key hydrologic and hydraulic design analysis featured:

  • Development of the water supply yield analysis for 2 percent probability yield and firm yield, including long-term reservoir simulations. Extensive statistical analyses were performed to determine yield by extrapolating regional gage data to the ungaged watershed.
  • Basin characterization and flood event hydrology for the 33-square-mile drainage basin was developed including infiltration and runoff analysis utilizing NRCS methodology.
  • Flood hydrology was developed for 100-year 24-hour, 100-year 10- day, spillway design flood (SDF) and probable maximum flood (PMF) events. The PMF was developed using HMR-52 software for the probable maximum precipitation (PMP) and the preferred storm orientation.
  • Hydraulic design was based on use of the PMF event for hydrologic adequacy of the dam and emergency spillway.
  • A study of varying conservation pools and flood storage was developed to determine an optimum conservation pool.

Burns & McDonnell also completed a preliminary evaluation of environmental impacts and impacts to existing infrastructure. Environmental impacts to wetlands, threatened and endangered species, and habitats were determined. Impacts to existing infrastructure such as housing, roads and utilities were determined and potential mitigation measures were evaluated.

Environmental permitting and design of the reservoir are scheduled to take place in 2004 and 2005 pending receipt of funding from the federal government sponsoring agency, the NRCS.

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