The rearmoring of the Mud Mountain Dam’S 9-Foot tunnel was a highly collaborative and innovative project. The 432′ tall dam hosts two tunnels, each serving different functions. A 23′ wide, unarmored tunnel primarily handles water when pool elevation is high. A lower 9′ wide, 1,900′ long horseshoe shaped tunnel is used to flush sediment, known as bedload. The team was dedicated to the concepts and principals of design-build, integrated teamwork, collaboration, and continuous improvement, fostering an environment that allowed for innovation to thrive. One example is the team’s use of an alternative design lining the tunnel floor with granite block material instead of steel liner. This innovative approach would dramatically improve the service life and long-term life cycle cost of the tunnel while reducing safety risks and the overall cost of the project.
Thinking Outside the Box
Innovation is at the heart of this design-build team’s approach. The decision to use the granite block concept rather than the concrete liner provided durability, sustainability and cost-savings compared to using steel, while at the same producing the smallest carbon footprint of all options. This not only eliminated hazard but quadrupled the life span of a project that was previously having to be replaced every 10 years. At every step, the team continued to assess each decision, embrace unique solutions and adjust as needed. As a result, this project not only completed $400,000 under budget but also a year ahead of its original completion date.
Design-Build Team
| Client/Owner: | U.S. Army Corps of Engineers, Seattle District |
| Design-Build Firm: | Garney Federal, Inc. |
| General Contractor: | Garney Federal, Inc. |
| Engineer: | ILF Consultants, Inc. |
| Project Manager: | Garney Companies, Inc. |
| Construction Duration: | 22 Months |
| Project Cost: | $8,519,316.00 |
Photo Credit: Jay McQuillen