Fixing Geese at Goose Pasture Tarn

Goose Pasture Tarn Dam is a high hazard-potential dam constructed across the Blue River, two miles upstream of the Town of Breckenridge, Colorado. In 2004, continuous voids were discovered beneath the service spillway slab. Repairs made in 2006 included grouting the voids and anchoring the spillway slab using ground anchors to resist hydrostatic uplift pressures. However, voids were rediscovered in 2016, causing spillway damage that made the dam susceptible to breaching. Inundation analyses indicated that a dam-failure flood wave would pass through Breckenridge within 30 to 75 minutes after the dam breached, providing little warning for evacuation. In 2016, Colorado Dam Safety listed the dam as one of 24 requiring immediate repairs. This paper discusses the dam performance history, a $10 million Resilient Infrastructure Grant that the Federal Emergency Management Agency awarded for the rehabilitation, innovative spillway designs for resisting frost-heave uplift, and several construction challenges that were successfully overcome.