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Stoney Mountain Reservoir

Stoney Mountain Reservoir
Sheridan, Oregon

The City of Sheridan is constructing a 60-MG embankment reservoir with the option of expanding the reservoir to a capacity of 90-MG. The site is located approximately 8 miles north of Sheridan on the southwest flank of Stoney Mountain. The reservoir will be used to store untreated spring water, which is the City’s primary source of potable water. The design includes an embankment up to 100 ft high from toe to crest and about 900 ft long, constructed across a drainage ravine with a deep, active landslide. The embankment crosses the landslide and required construction of a cement-stabilized shear key for stability. The maximum height of cuts and fills required to construct the shear key and reservoir embankment will approach 80 ft. The geotechnical investigation included a review of available geologic information for the site, geologic mapping of surface features, subsurface explorations, geophysical testing, characterization of soil, rock, groundwater and landslide conditions, laboratory testing, and engineering analyses leading to design of the embankment. Geotechnical instrumentation installed and monitored on the site includes inclinometers, vibrating-wire inclinometers, and vibrating-wire and standpipe piezometers and dataloggers. GRI assisted with the preparation of construction drawings and specifications and has provided field engineering and observation services during construction.