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Water Resources Department

Dam Design: Plans and Specifications

Oregon Statute 540.400 provides specific exemption for state design review of hydraulic structures with height less than 10 feet or storage less than 3 million gallons (9.2 acre-feet).  All other hydraulic structures that exceed both of these height and storage dimensions require design review and approval by the state dam safety program prior to construction.
 
Oregon does not have prescriptive standards for the design of dams, reservoirs or other hydraulic structures.  Oregon does require that the design must be prepared by a professional engineer who is registered with the state licensing board (OSBEELS) or designed by any other licensed professional engineer in the employment of the federal government.  The following items constitute the minimum design requirements for examination of design plans and technical specifications for construction of hydraulic structures: 
 
Owyhee Dam
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Vicinity Map
  • Location of dam and reservoir in relation to township, range and quarter-quarter section, together with a survey tie (bearing and distance) from a benchmark on the dam to an established government land corner.
  • Watershed map that delineates the contributing drainage area into the reservoir.
  • Access roads, significant land features, urban areas or downstream development.
  • Borrow areas, quarries, utilities and property lines within project boundaries.
 
Plan View of Dam and Appurtenances
  • Topographic contour map, maximum 2-foot interval.
  • Locate by station the primary outlet and auxiliary or emergency spillway;  if applicable, include toe drains, filters, log boom, or fish by-pass facilities.
  • Area/ Capacity Diagram or stage/ storage data tabulating hydraulic depth versus corresponding reservoir surface area and storage capacity.
  • Locations of field exploration or subsurface investigation including bore holes, test pits, excavations, trenches, monitoring wells and other invasive methods.
 
Longitudinal View Along Centerline Axis of Dam
  • Existing ground surface and thickness of stripping or grubbing.
  • Grade line for cutoff trench and/or excavation for foundation.
  • Bedrock or foundation material contacts.
  • Crest elevation of dam; include camber if applicable.
  • Locate by station the primary outlet and auxiliary or emergency spillway;  if applicable, include toe drains, filters, log boom, or fish bypass facilities.
 
Sectional View of Dam at Maximum Section
  • Upstream and downstream slopes, including erosion control or armoring.
  • Dam dimensions and elevations;  X (width) and Y (height) coordinates.
  • Emergency spillway crest elevation and spillway channel grade line(s).
  • Water surface elevations, including normal operating pool and flood maximum.
  • Interior material zones and/or internal filters.
  • Invert elevations of low-level outlet conduit, toe drains, and other internal piping.
  • Existing ground surface and thickness of stripping or grubbing.
  • Cutoff trench and/or excavation for foundation, with dimensions.
 
Emergency Spillway Detail Drawing
  • Both a sectional and profile view.
  • Elevations and dimensions at all stations where channel configuration or grade lines transition or otherwise change.
  • Dimensions and elevations for stilling basin or other flow and energy dissipaters, including both formed-in-place concrete or constructed channel armoring.
  • Elevations and dimensions of flow control mechanisms such as flash boards, stop logs, tainter gates, or channel splitters.
 
Outlet Conduit and/or Primary Spillway Detail Drawing
  • Cross section showing sizes, dimensions, and type(s) of material, including anti-seep collars and/or concrete encasement and/or pipe bedding.
  • Draw down curve, flow rating information, or discharge capacity data.
  • Longitudinal section (profile) illustrating configuration and position of anti-seep collars, joints, flanges or other connections.
 
Outlet Works Detail Drawing
  • Operating gates or valves, and guard gates or valves;  if manufactured, list the name, model number, supplier, etc.
  • Base block or anchor, pedestals, operating stem and/or lift mechanism.
  • Fish screen, trash rack, or other clog prevention device.
 
Technical Data
  • All elevations referenced to established benchmark, such as MSL or NGVD.
  • Hydrologic report or calculations verifying adequacy of emergency spillway at 100-year storm (1% flow) and minimum freeboard equal to two (2) feet.
  • Summary report of foundation investigation which may include site geology, groundwater hydrology, logs, laboratory test results and geotechnical stability analysis for rapid drawdown, flood loading and/or maximum credible earthquake.
  • Bid package, as appropriate, or a complete set of technical specifications for all materials, methods and manufacture.
 
Operation and Maintenance Manual - (Significant and High Hazard Dams)
  • Preventative maintenance schedule, contact information, storage/release schedule.
 
Emergency Action Plan - (High Hazard Dams)
  • Dam failure/ breach analysis for both sunny day and storm scenario.
  • Downstream inundation maps for sunny day and storm failure scenarios.
  • Monitoring and/or warning systems, notification charts, evacuation procedure(s).
 
 
 
Selected References:
  • Documentation for the 2002 Update of National Seismic Hazard Maps; USGS Open-File Report 02- 420.
  • Emergency Action Planning for Dam Owners; FEMA Mitigation Directorate 64; October 1998.
  • Estimation of Peak Discharges for Rural, Unregulated Streams in Western Oregon; USGS Scientific Investigations Report 2005-5116.
  • Probable Maximum Precipitation - Pacific Northwest States; NOAA Hydrometeorological Report No. 57; October 1994.
  • Seismic Design Mapping State of Oregon, Final Report; ODOT Personal Services Contract 11688; Geomatrix Consultants Project No. 2442; January 1995.