Cardinal Fly Ash Reservoir 2 Dam Raising

Originally constructed as a zoned earth dam, the reservoir featured an inclined clay core and full height chimney drain. In 1997, the client raised the dam using roller compacted concrete (RCC) along with a downstream earth fill. In 2011, the owner desired to raise the dam again. A conventional downstream approach, however, would have required a half million cubic yards of engineered fill.

To satisfy unique site requirements and meet the need for increased storage capacity, S&ME designed a unique double-sided Mechanically Stabilized Earth (MSE) wall system.  The MSE increased the height of this large, on-stream, ash storage dam. In addition, it overcame site constraints and achieved the timely need for additional capacity. The unusual geometry of the existing dam crest allowed construction over the course of single season.

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.


  • 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