Cardinal Fly Ash Reservoir 2 Dam Raising

To satisfy unique site requirements and meet a short term need for increased storage capacity, S&ME designed a unique double-sided Mechanically Stabilized Earth (MSE) wall system to increase the height of this large, on-stream, ash storage dam. The dam was originally constructed as a zoned earth dam in 1985 and featured an inclined clay core and full height chimney drain. In 1997, the dam was raised to a height of 237 feet through the use of an upstream block of roller compacted concrete (RCC) in conjunction with a downstream earth fill. In 2011, the owner desired to raise the dam again. Initially, a conventional downstream raising approach was assessed which would have required a half million cubic yards of engineered fill.

The double-sided MSE wall system developed by S&ME overcame site constraints and achieved the timely need for additional capacity. This innovative design resulted from the unusual geometry of the existing dam crest coupled with the owner’s desire to complete construction over the course of single season. To control seepage, a cement-bentonite slurry wall was constructed which penetrated into the existing clay core. A non-structural vinyl sheet pile wall was then inserted full depth through the slurry wall and extended to the top of the raised dam in between the MSE reinforced zones. The raised dam also includes a modified auxiliary spillway composed of mass concrete, and a precast service spillway extension. S&ME and the owner worked closely with state dam safety officials to permit this unique structure, including evaluating a variety of seepage and stability failure modes as well as the potential for corrosion of the reinforced concrete wall panels. S&ME served as the engineer of record for the design. During construction, S&ME provided all testing services and served as the certification engineer in accordance with Ohio dam safety rules.

Highlights

• Seepage control achieved through a cement-bentonite slurry wall which penetrated into the existing clay core
• A non-structural vinyl sheet pile wall was then inserted full depth through the slurry wall and extended to the top of the raised dam in between the MSE reinforced zones