Niver Creek Detention Dam is a high-hazard dam that is owned and maintained by the City of Thornton. The dam was constructed in the late 1970s to provide flood control along the Niver Creek drainageway. The dam is located in the Niver Creek Open Space, which consists of approximately 120 acres of open space and multi-use trails surrounded by commercial and residential developments.
The dam is regulated by the Colorado Office of the State Engineer – Dam Safety Division. The existing outlet works at the dam consists of a reinforced concrete riser structure with trashrack and a 36-inch-diameter reinforced concrete pipe extending through the dam. A 30-inch-diameter steel orifice plate is attached directly to the inlet of the reinforced concrete pipe to limit flows through the pipe.
Rehabilitation of the outlet works is required to address the following issues:
• The approach channel frequently collected trash, debris, and vegetation. Also, the approach channel is narrow and shallow, which makes maintenance difficult.
• The riser structure frequently collects trash, debris, and vegetation, which can reduce the capacity of the outlet works.
• The upstream segment of the outlet conduit has been damaged and rebar in the reinforced concrete pipe is exposed in places.
The project will include the following features:
• Widening the approach channel and installing a forebay with low-flow crossing and grasscrete pavers.
• Installing a new intake structure with sloping steel trashrack. A new orifice plate will be mounted to an interior wall 5-feet upstream of the outlet conduit to mitigate hydraulic issues that were previously causing damage.
• Demolishing and replacing damaged portions of outlet pipe.
The project is being funded by Mile High Flood District. RJH Consultants, Inc. is the design engineer. Stream Landscape Architecture provided landscape architecture services. The design has been approved by the Colorado Office of the State Engineer – Dam Safety Division.