Fulton Ditch Turnout Extension

Challenges

East Cooley Reservoir is a below-ground gravel pit reservoir in Adams County, Colorado and is used for raw water storage by the City of Thornton (Thornton).  Fulton Ditch is owned and operated by the Fulton Ditch Company and extends along the eastern edge of East Cooley Reservoir.  Thornton owns ditch shares and desired to install hydraulic facilities to convey water from Fulton Ditch into East Cooley Reservoir.

Thornton desired hydraulic facilities be designed for flow rates ranging from 5 to 150 cubic feet per second and measurement accuracies within 5 percent for the entire flow range.  Hydraulic facilities were required to cross Bull Seep, which is a low-lying swampy area with jurisdictional wetlands.

Solution

RJH performed conceptual through final designs, and provided construction phase services for the project.  An alternatives analysis was initially performed to evaluate potential options for the hydraulic facilities.  Concepts included combinations of buried pipelines and open channels, with measurement instrumentation ranging from flumes to flow meters.

Final design included dual buried steel pipelines with open channel, electromagnetic flow meters and a grouted riprap rundown along the slope of East Cooley Reservoir.  Slides gates were installed at each end of the conveyance pipelines to control flow through the pipes and provide acceptable hydraulic conditions for measurement of low flows.  The dual pipelines were constructed below Bull Seep and do not rely on siphon hydraulics, as originally requested by Thornton.  RJH and Thornton coordinated with an environmental permitting specialist to obtain a U.S. Army Corps of Engineers permit for disturbing wetlands in Bull Seep.