The Cat Reservoir is a 1,500 acre-ft below grade, lined, water storage reservoir being constructed in conjunction with aggregate mining activities. It is a design build project and is located near the confluence of Clear Creek and the South Platte River in Adams County, Colorado.
Initial compacted embankment slope liner construction along the mine highwall.
The reservoir liner is a 7,700-foot long compacted earthen embankment slope liner constructed from on-site soils. Design challenges include coordinating the aggregate mining/highwall design and reservoir construction along existing utilities, including a 42-inch diameter PCCP force sewer main. Highwall and compacted embankment slope liner stability challenges were compounded by the presence of a relatively thick and soft mud lens.
Final riprap placement on embankment.
The site is underlain by fractured permeable claystone bedrock. Complicated and expensive construction methods had been previously proposed to “seal” the reservoir from infiltration. Under guidance from Deere & Ault, and to help minimize the project construction costs, the liner was constructed in two phases using an observational approach.
Phase I work generally consisted of standard construction methods to minimize infiltration and, as required, localized seepage areas were addressed. A leakage test was completed after Phase I. The lined reservoir passed the State Engineer criteria, thus allowing the reservoir construction to be completed with a simplified Phase II.
Client: Cat Construction and Denver Water Board