Kokosing Construction Company, Inc.
AEP Cardinal Plant Fly Ash Reservoir Dam Raising
What makes it interesting?
MSE wall panels and VSP had to be installed across the dam at the same time, but since the crane required most of the dam width, crews alternated between 50-foot runs of VSP and then installing MSE panels on both sides for the same length. Every piece of piling and wall was kept in a storage yard and brought to the damn as needed due to limited room on the dam itself. Small loaders ferried materials from stockpiles to placement locations.
How HCSS Software assisted with this project
HeavyBid was used for all phases of the estimating and post-bid handoff process, including original cost estimates, budget generation, and post-bid alternative analysis. The notes features and ability to compare self-performed pricing to subcontracted pricing for the same work were invaluable during the post-bid handoff process to the field staff. Kokosing also heavily utilizes the import and export functions to generate specialty information for field engineers and superintendents that is tailored to their needs.
Kokosing constructed a very challenging dam-raising project for American Electric Power at the Cardinal Plant in Brilliant, Ohio. AEP’s existing fly ash reservoir dam was originally constructed in 1986 as a 180-foot tall arched earth embankment and later raised using embankment capped with 14 feet of roller-compacted concrete which brought the new height to 225 feet but reduced the crest width to only 30 feet. The entire 1600-foot-long dam sits on a little more than one acre.
To again increase reservoir capacity, the dam needed be raised an additional 13 feet on this very small footprint. The solution to building on this small surface was to construct back-to-back mechanically stabilized earth (MSE) walls on top of the existing 30-foot-wide crest with a run of Vinyl Sheet Piling (VSP) installed between the walls. Work on the project also included raising the primary and emergency spillway structures.
After constructing a new mile-long access road, safety cables were installed along the dam length to protect crews from the very steep side slopes. Kokosing then prepared the existing dam for VSP installation.
Kokosing trenched through 14 feet of the existing roller compacted concrete and then a subcontractor installed a 30-foot-deep cement-bentonite slurry wall across the entire length of the dam. The VSP were then installed to a depth of 30 feet through the slurry wall. Because the crest is only 30 feet wide, installation of the MSE wall panels and the VSP must proceed across the dam at the same time. The crane required most of the dam width so crews alternated between installing 50-foot runs of VSP and then installing MSE panels on both sides for the same length. Additionally, because of limited room to store materials on the dam itself, every piece of piling and wall was unloaded in a storage yard and brought to the dam as needed.
The VSP is similar to steel sheet piling but is only 3/8 inches thick and very flexible. To avoid damaging it during installation through the cement-bentonite slurry, Kokosing used a steel guide that penetrated ahead of the sheeting. Full-height, 10-foot-wide x 12.5-foot-tall MSE wall panels were utilized. Due to limited room for conventional panel support kickers, Kokosing designed and fabricated temporary steel support posts that were bolted to the roller compacted concrete just outside the wall. The MSE panel installation and backfill was the most challenging portion of the project due to the limited access. The distance between the VSP and the MSE panels was less than 10 feet on each side and all backfill material was brought in from one end of the dam.
The Service Spillway was designed to be constructed using poured concrete walls, however Kokosing offered an alternative precast concrete structure to the owner which increased safety and efficiency.
The Emergency Spillway work included mass concrete pours requiring thermal control monitoring and concrete cooling measures. The dam construction project was completed safely, on time, and to the owner’s satisfaction.