With a crumbling dam and hazardous spillway, the Homestake Arkansas River Diversion could no longer function as a reliable alternative to the primary intake at Twin Lakes Dam. The Homestake Project, a joint powers authority of Colorado Springs Utilities and Aurora Water in Colorado, retained the Boise, Idaho, office of Schnabel in 2016 to undertake the improvements.

The Homestake system provides about half of the annual water used by the two front-range cities by transmitting 180 cfs of water from the mountains of Colorado to Spinney Mountain and Rampart Reservoirs. However, due to sedimentation issues and a deteriorating condition, the existing facility needed to be replaced. Its spillway also presented significant hazards to river users in one of the most frequented recreational rivers in the world.

Our work consisted of replacing the existing diversion dam with a concrete dam crest and rockfill spillway channel set adjacent to a low-flow channel on the left bank for recreational use. The improvements also include a new fish ladder along the right bank, a 90-ft span Acrow Bridge across the river, and the replacement of the existing intake with a new cast-in-place concrete intake structure.

Over the course of design, we completed detailed geotechnical, geomorphologic, and hydraulic investigations of the existing facility. We summarized each stage of the design in a detailed technical memorandum that culminated with a final basis of design report. The project also included substantial permitting and stakeholder coordination including SHPO involvement, U.S. Army Corps of Engineers Section 404 permitting, Colorado 1041 permitting and environmental clearances, UPRR encroachment permitting, floodplain development permits, and land acquisition assistance.

Photo: Courtesy of Tom Hankins, Homestake Project

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