Rapid Drawdown Leads to Instability: Brush Hollow Dam

The Brush Hollow Dam and Reservoir is located approximately 3 miles northwest of the town of Penrose, Colorado. The reservoir impounds water which is primarily used for irrigation diverted horn Beaver Creek through a canal. Brush Hollow Dam is a 95-foot high earthfill dam that was constructed in 1922 and 1923 using horse drawn wagons. The dam has a crest width of about 12 f-, and was designed with embankment slopes of 3:1 (horizontal:vertical) upstream and 2:1 downstream. The core was a “puddle core,” with a top width of about 5 f~ 1:20 sideslopes down to natural ground, and a narrow core trench through the alluvium to bedrock. The core trench was “keyed” into bedrock and backfilled with select material. The upstream slope of the dam was covered by 9 inches of stone riprap paving salvaged from the spillway excavation north of the Ieft abutment. The outlet works is a concrete-en- 36-inch diameter welded steel conduit. Water stops were included in the concrete joints and anti-seepage collars were provided. The outlet pipe included a concrete support where it crossed the puddle core trench. A slide gate at the inlet is used to control release born the reservoir. Agate house at the downstream toe contains four Ludlow gate valves for discharge to the irrigation canal or stream channel.