Elwood Dam Rehabilitation

Challenges

Elwood Reservoir is owned and operated by the Central Nebraska Public Power and Irrigation District (CNPPID), who began operating the reservoir at higher levels in response to requests from the Platte River Recovery Implementation Program to increase storage for environmental releases.  Significant seepage issues were observed when the reservoir was operated at higher storage levels.

Solution

CNPPID retained RJH to perform a dam safety inspection and evaluate the seepage issues at the dam.  Based on this evaluation, RJH recommended that CNPPID self-impose a storage restriction on the reservoir to avoid dam safety issues associated with increased seepage.

To address the seepage problems, RJH performed geotechnical explorations, performed geotechnical modeling and analyses, developed alternatives, selected a preferred alternative, and developed a final rehabilitation design.  The rehabilitation consisted of installing a new chimney filter and more than 7,000 linear feet of toe drain.  The result of the project was that CNPPID was able to remove the self-imposed reservoir restriction and increase the capacity of the reservoir from about 20,000 acre-feet to about 25,000 acre-feet.

RJH led the work from initial evaluation and assessment of the existing dam through geotechnical data collection, alternatives development, permitting, final design, and construction engineering.