Emerald Valley Ranch Dam

Challenges

Emerald Valley Ranch is a luxury vacation ranch owned and operated by the Broadmoor Hotel.  Two original dams at the ranch were breached during a large flood event on Little Fountain Creek.  The dams were breached during the historic Colorado floods in September 2013 and the owner required rehabilitation to be completed by the following June for the summer vacation season.  The project schedule required the selection of materials that could be procured within a 6-week period.  Also, limited site access and a winter construction schedule required minimal use of cast-in-place concrete or grout.

The narrow, steep valley left very little space for traditional open channel spillways and required an embankment overtopping spillway to convey the design flood flows.  New facilities would need to be aesthetically pleasing and blend in with the surrounding natural features of the ranch.

Solution

The selected concept included construction of two new earthen embankment dams each with a low-level outlet works, pre-cast concrete principal spillway riser, and overtopping emergency spillways constructed with an articulating concrete block (ACB) lining system.  The ACB lining system is buried and covered with native grass to meet aesthetic requirements.  The native grass and fill above the ACB lining system were designed to erode relatively easily during a flood event so that the spillway has sufficient capacity to convey the inflow design flood.

RJH worked with the Colorado Office of the State Engineer to accommodate the very aggressive project schedule.  The Hazard Classification Report, Hydrology Report, and construction documents were all developed, submitted, and approved by the regulatory agencies within about a 3-month period, which is very streamlined compared to typical jurisdictional dam projects.

This project was featured on a History Channel special, which highlighted the damage caused to the dams during the historic flooding in Colorado.