Hydraulic & Hydrologic Evaluation

Hydraulic & Hydrologic Evaluation

Location: Mountainburg, Ark.

Client: City of Fort Smith Utility Department

Completion Date: Master plan: 1997; Design: 2002; Construction: 2006

Burns & McDonnell provided full planning and design phase services for the development of the enlarged Lake Fort Smith Water Supply Reservoir as part of continuing services to the City of Fort Smith, Ark. The project entailed the design of a single, enlarged dam and impoundment combining the existing Lake Fort Smith and Lake Shepherd Springs reservoirs. When constructed, the reservoir impounded approximately 84,000 acre-feet of conservation storage. The existing Lake Fort Smith dam was raised 101 feet to a structural height of approximately 200 feet spanning the Frog Bayou valley, over one-half mile in length. The dam is a zoned earth and rockfill structure with an impervious central core incorporating approximately 5 million cubic yards of fill. The project includes construction of a new spillway system, a new intake tower and outlet works as well as other appurtenant features.

Burns & McDonnell developed comprehensive hydrologic and hydraulic evaluations, analysis and design including development of the basin characterization, the water supply yield analyzes, the flood hydrology and the spillway and outlet works hydraulic design. Further, the U.S. Army Corps of Engineers, the Federal Emergency Management Agency, the Natural Resources Conservation Service and the U.S. Bureau of Reclamation standards for dam design and dam safety engineering were incorporated as general design methodology. The structure was designed as a single-purpose reservoir impounded by a high hazard dam.

  • Water supply and delivery plan formulation
  • Alternatives analyses
  • Hydraulic modeling and design
  • Water quality analyses
  • Water supply hydrology
  • Flood hydrology
  • 3-D design rendering
  • Physical hydraulic models
  • Spillway hydraulic design
  • Design plans and specifications
  • Construction services

Hydrologic and Hydraulic Design Analyses

  • Development of the water supply yield analysis
  • Basin characterization and hydrology
  • Flood hydrology for incremental floods from a five-year event up to and including a 100-year event
  • Hydraulic design
  • A study analysis of conservation pools and flood storage analysis
  • Reservoir and stream limnology
  • Downstream hydrology and flood analysis using HEC-RAS hydraulic analysis of the stream, flood inundation maps and Base Flood Elevation (BFE) data

Spillway System and Intake/Outlet Works Design

Burns & McDonnell engineers developed the concept, preliminary and detailed hydraulic design of:

  • The principal spillway system
  • The diversion works, as part of the intake/outlet works
  • An auxiliary spillway system to discharge and pass flood event flows for greater than the 100-year event