- Forensic evaluation
- Alternatives evaluation
- Geotechnical engineering
- Hydraulic engineering
- Spillway design
- Construction documents
- Resident engineering
- Construction administration services
The West Cooley Reservoir complex is located along the west bank of the South Platte River in Adams County, Colorado and is used for raw water storage by the City of Thornton (Thornton). West Cooley consists of three lined, below grade reservoir cells (South Cell, Central Cell, and North Cell).
Historic flooding in the South Platte River resulted in river flows overtopping the reservoir cells and causing moderate to severe damage including erosion of reservoir berms and other damage. Several years later and just prior to beginning construction for the previous flood repairs, another flood in the river resulted in flows completely breaching the berm between the river and the South Cell. As part of this flood event, much of the river was diverted through the South Cell and Central Cell, leaving a portion of the main river channel nearly dry and depositing a significant volume of sediment in the South Cell.
A major component of the repair project involved installing spillways at each reservoir cell to mitigate future flooding damage. RJH evaluated flood conditions in the river to select invert elevations and widths for the spillways. A key takeaway was that the spillways would need to operate as a system to be effective and could not be designed individually.
Another significant component of the project included repairing the damaged soil-bentonite barrier walls. A traditional repair of the soil-bentonite wall was not desirable because it would require specialized construction equipment and would be technically challenging to establish a connection to the remaining portions of the existing barrier wall. RJH developed an innovative repair approach that included amending existing stockpiled earthfill materials (from previous Thornton projects) with bentonite to form a low-permeable material.
Other site work included repairing damaged trails and fences, restoring wetland areas, and reconstructing access roads. RJH performed conceptual through final designs, and provided construction phase services for the project.