Cascades Sedimentation Dam Design

Tyler, Texas

Looking to reclaim storage capacity, developer turns to TRC to redesign outdated dam structure.

Wanting to reclaim storage that had been lost upstream due to years of sediment collection, the client turned to TRC to design a replacement for the existing hydraulic fill dam structure. Because the dam location is situated within the backwaters of Bellwood Lake, there were a number of unique design challenges that had to be addressed during final design of the new dam structure:

• Lake Bellwood could not be lowered.
• Construction activity had to avoid the downstream reservoir.
• An old sewer line running through the center of the existing structure had to remain in service throughout construction.
• The new structure had to be designed hydraulically such that the existing flood levels upstream of the dam would not be exceeded by the dam modifications.
• The client wanted to construct the replacement dam as an earthen embankment.

Since there was no record of the original construction, another major concern involved the stability of the existing dam foundation. Since no work was allowed in Bellwood Lake, it was decided to use aluminum sheet piles to stabilize the foundation along both the upstream and downstream faces of the dam. The velocities across the earthen crest were then minimized through the construction of a concrete scour pad along the downstream face, while the crest was sloped downward toward the upstream face.

TRC initially performed project management, coordinated with the US Army Corps of Engineers for permitting and with the Texas Commission on Environmental Quality regarding water rights issues, performance of a spillway adequacy analysis, and preliminary dam modification design. As the project progressed, TRC performed additional services that encompassed stabilization of the existing dam structure, development of plans and specifications for the design, construction inspection services, construction coordination with the project’s various contractors and suppliers, and construction certification. In response to a partial failure of a section of the original dam during construction, TRC subsequently inspected the damage and developed repair specifications which required approval by the City of Tyler. The entire project was successfully completed while addressing all of the issues impacting the project.

• Client: Cascades of Tyler Joint Venture, LLP
• Project Location: Tyler, Texas