The South Platte River in northeastern Colorado is characterized by high flows during the spring snowmelt runoff and relatively lower flows during the irrigation season.  This has created a need for reservoir storage to re-regulate the high surplus flows for later release to supplement direct flow diversion demands during the irrigation season.  Riverside Irrigation District and W. W. Wheeler and Associates, Inc. developed the Vancil Dam and Reservoir Project to create a new surface storage facility to regulate these seasonal fluctuations of flow.

The fundamental concept of the Vancil Project is to divert high rates of flow (up to 1,000 cfs) from the South Platte River during periods of surplus flow, using the existing diversion facilities of the Riverside Irrigation District.  The water is delivered to the new off-channel Vancil Reservoir where it can be released during the late summer months to provide supplemental irrigation supplies at the lower end of the Riverside system.  A portion of the stored water in the reservoir is released to the Riverside Service Canal for irrigation uses and a portion is allowed to recharge into the underlying alluvial aquifer in the recharge component of the Vancil Project.  Wheeler was the lead engineer for the dam and reservoir design project.

Vancil Reservoir is a 6,300 acre-foot storage facility located near the town of Snyder, Colorado.  The project includes a number of innovative and unique structural and hydraulic components.  Water delivery into the reservoir is by gravity feed from the Riverside Canal and delivery back into the canal is also by gravity release for the first several feet of reservoir storage, and then with a six-vertical turbine pump station for the lower storage levels.  The dam is designed with no outlet conduit extending through the embankment, but instead the outlet intake terminates at the pump wet well located near the dam crest.  The dam is also equipped with a 24-inch steel pipe operating as a pressurized outlet works at higher storage levels and operating as a true siphon at lower reservoir levels to provide for gravity release of storage water.  The entire probable maximum design flood can be stored in the reservoir surcharge pool and therefore the reservoir has no emergency spillway.  The earthfill embankment is designed at a 10 (horizontal) to 1.0 (vertical) upstream slope within the normal operating pool limits to take advantage of a natural wave dissipation and beaching action, thereby eliminating the need for riprap-type armoring of the upstream slope for wave erosion protection.

Wheeler prepared the engineering design including flood hydrology and hazard classification studies, hydraulic component design, and prepared the design plans and technical specifications for the construction of Vancil Dam and Reservoir.