Hodgeman and Ness Counties, Kansas
Working within a joint venture holding a multiple award task order contracting vehicle with the Department of Agriculture, WRS is serving as the contract manager and project manager for this supplemental watershed project plan and environmental assessment to construct five new distributed flood-control dams in western Kansas.
Covering an area across 10 western Kansas counties almost the size of the entire state of Delaware, the Pawnee River Joint District No. 81 Watershed’s 1.6 million acres makes it purportedly the largest in the world. The local sponsor is considering implementing another five dams scheduled in its 1988 updated plan within two subwatersheds along the northern boundary of the district, impounding three creeks. NRCS requires a supplemental watershed plan and environmental assessment in support. WRS is managing the project currently performing the 580-day contract to complete preliminary designs of alternative solutions, inventory, survey, investigate, coordinate, and plan all necessary functions to complete a supplemental watershed plan and environmental assessment acceptable to Kansas NRCS under NRCS technical guidelines and criteria, regulations, policy, and conservation standards.
In addition to project management, WRS staff are also leading one of two hydrology and hydraulics teams, leading one of two geotechnical engineering teams, and providing design support to solution alternatives analysis, as well as public participation planning and execution. The H&H modeling for the five dams will be the first application of watershed-wide numerical modeling using the USACE HEC-RAS program to test the potential effectiveness of distributed flood control using smaller earthen dams in series to control downstream flooding. The H&H effort will also employ NRCS-Win TR20 and TR55; NRCS-SITES; HEC HMS Stream Hydraulics; US Army Corps of Engineers-HEC RAS Dam Breach Analysis modeling.
Some unique challenges in meeting the goals of the sponsor and NRCs included siting adjustments to accommodate individual property ownership concerns, modeling and planning adjustments required by existing upstream watershed dams, coordination with NRCS and Native American tribal authorities, and dam realignments to accommodate storage issues. In the past, the sponsor has identified strategic groundwater recharge for agricultural purposes as a significant benefit in its economic analysis.
The Plan-Environmental Document will describe alternatives and examine reasonable alternatives in detail and identify the preferred alternative as the most technically, economically, socially and environmentally defensible alternative as determined by NRCS in consultation with the Project Sponsor. Solutions design will incorporate structural design elements following the Kansas Dam Safety criteria and performance standards