Cornforth Consultants
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      • Port Westward Power Plant Seismic Design
    • Rock Slopes and Tunnels >
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      • Montana Rockfall Hazard Rating System
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      • Marmot Dam Removal
      • The Dalles Dam
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      • Bonneville Dam
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      • OTIA Cracked Bridge Geotechnical Baselines
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      • Navy CVN Drydock
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      • Fern Hill Water Treatment Plant
      • Tualatin Valley North Transmission Line
      • Evaluation of 28 Water Storage Facilities
      • City of Sandy Water Treatment Plant
      • Mt. Tabor Reservoir No. 5 Cap Study
      • Oakridge Water System Improvements
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Marmot Dam Removal

Sandy, Oregon
Marmot Dam was a diversion dam on the Sandy River and a major component of the Bull Run Hydroelectric Project. The project owner, Portland General Electric (PGE), decided to decommission the dam and other project structures and facilities. Cornforth Consultants (CCI) was retained by PGE to develop decommissioning plans.

​CCI prepared preliminary plans and details for cofferdams and river diversion structures to remove not only the dam but also the sediment that had accumulated upstream of the dam. Materials removed included 13,000 cy of an original timber crib dam; 12,000 cy of roller-compacted concrete; and 20,000 cy of sediment immediately upstream of the dam. The plan also included various regulatory and permitting tasks, project scheduling, and evaluation of options for removal of an additional 230,000 cy of sediment in the reservoir. In addition, CCI developed plans for decommissioning other components of the project, including tunnels, flume structures, and the powerhouse forebay reservoir.

Type 2 RHRS Slope on Highway 26
The Former Marmot Dam
Picture
Sandy River Following Marmot Dam Removal

​Services Provided:

  • Decommissioning Studies and Design
  • Hydrogeology​
  • Cofferdam Design
  • River Diversion
  • Home
  • Services
    • Earth & Rockfill Dams
    • Reservoirs, Canals, and Levees
    • Spillway Safety Inspections
    • Landslides and Rockfall
    • Earthquake Engineering
    • Geologic Hazards
    • Geotechnical Site Characterization
    • Hydrogeology
    • Expert Witness
    • Concrete Dams and Locks
    • Geotechnical Instrumentation
    • Deep and Shallow Foundations
    • Geotechnical Manuals
  • Industries
    • Water Resources
    • Energy
    • Natural Resources
    • Industrial
    • Transportation
    • Ports and Airports
    • Expert Witness
  • Projects
    • Earth and Rockfill Dams >
      • Barney Reservoir
      • Frog Lake Reservoir
      • Iron Gate Dam Raise
      • McGuire Dam Raise
      • Bonneville Cofferdam
      • Bull Run No. 2 Seismic Stability Analysis
    • Levees and Canals >
      • Libby Dike Rehab.
      • St. Johns Dike Stabilization
      • Cowlitz River Levees
      • Swift Canal Failure
    • Earthquake Engineering >
      • Barney Dam Seismic Analysis
      • Fern Hill WTP Liquefacation Study
      • Bull Run No. 2 Seismic Stability Analysis
      • Mt. Tabor Seismic Stability Analysis
      • Port Westward Power Plant Seismic Design
    • Rock Slopes and Tunnels >
      • Libby Rockfall Mitigation
      • Sandy River Pipeline Tunnels
      • Ketchikan Third Avenue Extension
      • Sain Creek Water Supply Tunnel
      • Montana Rockfall Hazard Rating System
    • Foundations >
      • Port Westward Power Plant
      • Cascade Locks Casino
      • Air National Guard Hangar
      • Biglow Canyon Windfarm
      • Oakridge Water System Improvements
    • Concrete Dams and Locks >
      • John Day Lock & Dam
      • Marmot Dam Removal
      • The Dalles Dam
      • Willamette Falls Dam
      • Bonneville Dam
    • Transportation >
      • OTIA Cracked Bridge Geotechnical Baselines
      • Newburg Dundee Bypass Design DEIS
      • I-84 Sandy River Bridge Investigation
      • Tanana River Bridge Foundation, Tok, Alaska
      • Montana RHRS Implementation
      • Ketchikan Third Avenue Extension
    • Ports and Airports >
      • Navy CVN Drydock
      • Depoe Bay Seawall Distress
      • Willamette Falls Flow Control Structure
      • Air National Guard Hangar
    • Water and Wastewater >
      • Fern Hill Water Treatment Plant
      • Tualatin Valley North Transmission Line
      • Evaluation of 28 Water Storage Facilities
      • City of Sandy Water Treatment Plant
      • Mt. Tabor Reservoir No. 5 Cap Study
      • Oakridge Water System Improvements
  • Staff
  • Resources
  • Careers
    • Geotechnical Engineer
  • Contact Us