Soda Springs Dam is part of PacifiCorp’s North Umpqua hydroelectric project located about 60 miles east of Roseburg, Oregon. GRI assisted the contractor, Weekly Bros., with planning and design of the temporary cofferdam constructed in the North Umpqua River for construction of modifications to the existing tailrace, including installation of new fish screens. The cofferdam consisted of prefabricated steel bin structures filled with cobbles and gravel, designed to structurally support a large Komatsu 400 excavator that weighs about 110,000 lbs, which will be used to construct the cofferdam, and provide access for other construct equipment needed to construct the new tailrace barrier. GRI provided guidelines for estimating surcharge loads during construction; lateral earth pressures for the granular backfill; coefficient of friction for use in the sliding analysis; and addressed seepage, dewatering requirements, and erosion control for the project. The dewatering required pumping volumes up to 8,000 gpm to accomplish the required construction in the dry. GRI personnel provided on-site observation services and consultation during construction of the temporary cofferdam and dewatering phase of the project.