Fort Worth, Texas — A project to upgrade the Eagle Mountain Spillway Dam in Fort Worth, Texas, received the 2014 National Rehabilitation Project of the Year Award from the Association of State Dam Safety Officials (ASDSO). ASDSO will present the award at its Annual Awards Banquet, to be held Tuesday, Sept. 23 during the Dam Safety 2014 conference in San Diego.
The annual ASDSO award recognizes a unique remedial design that advances the state-of-the-art in the field of dam safety and exemplifies the professional engineering and construction standards that dam safety requires. The Eagle Mountain Spillway Dam project was designed by Parsons Brinckerhoff on behalf of the Tarrant Regional Water District (TRWD).
Eagle Mountain Lake, located northwest of Fort Worth, is impounded by two large embankment dams: the Main Dam and the Spillway Dam. The Main Dam is approximately 85 feet high and 4,400 feet long. The Spillway Dam is a saddle dam that is 60 feet in height and 3,480 feet long. The dams were designed in the late 1920s and constructed in the early 1930s. The dams serve one of the largest raw water suppliers in the state of Texas; TRWD provides water to more than 1.7 million people in the North Central Texas area.
In 2007, TRWD engaged Parsons Brinckerhoff to perform a comprehensive seepage and stability assessment of both dams as part of a proactive management strategy for its existing infrastructure. The comprehensive assessment included a desktop study and analysis, investigation and testing program, detailed analysis and modeling study, and an assessment of upgrade measures. The findings of the assessment indicated that the existing cut-off under the Spillway Dam was not continuous, and that the safety of the dam could be improved by closing the gaps in the existing cut-off using a grout curtain.
The grout curtain, one of several alternatives considered, was ultimately chosen because it was technically feasible, cost effective, and made the best use of the existing features while minimizing impacts to the environment, the existing dam, and to the roadway on the crest. Parsons Brinckerhoff developed a test grout program that was instrumental in confirming the feasibility of the concept. The firm designed the grout curtain, completed the development of bid documents, and provided construction support for its implementation.
The project fulfills several environmental and aesthetic benefits by upgrading the dam without major disruptions to the public or changing the original 1930s appearance. The grouting program consisted of focused improvement measures that treated only the areas of concern and improved the in-situ characteristics. The entire construction project was efficient from several standpoints including costs, resources, environmental impacts, and minimized disruption to the public, yet produced an effective and conservative dam safety improvement.
The completed project provides TRWD with confidence that the dam will provide another 80 years of excellent service.