Ash Basin Clean Closure and Construction of Water Management Systems

SITUATION

With changing State and Federal regulations regarding ash basins and stormwater management, coal ash from within an existing ash basin was planned for Closure by Removal (CBR) to provide a suitable area for the rerouting, storing, treating and discharging of stormwater and process water created from the utilities’ power generation process. Charah® Solutions provided a plan to complete the multi-phased project without impacting daily operations and in accordance with prescribed regulatory deadlines.

INNOVATIVE SOLUTIONS

Stormwater/Groundwater Management:

The excavation of the ash basin was particularly challenging as the basin was situated between an active creek and a major river. This configuration contributed significantly to groundwater fluctuations during basin excavation and ash removal.  In response to these changing conditions, Charah Solutions engineered and implemented an automatic well-point system to control groundwater elevations throughout the ash removal process. Complementing the well-point system, Charah Solutions designed, constructed and continually modified over 1,500 lineal feet of rim ditches containing sumps with pump systems to ensure a safe work environment was maintained throughout the project.

Dam Modifications/Structural Fill:

Adjacent to the basin is an existing dam that separated the basin from the river. During basin construction, excavations exceeded depths of 40 feet and required the adjacent dam to be modified. The soil removed from the dam was utilized to create an engineered structural fill which ultimately provided the foundation for the onsite waste water treatment facility.

RESULTS

Once the structural fill was completed, the remaining portion was divided into two distinct basins that would be utilized for water storage and treatment. Both of the basins were lined with advanced engineered liner systems, over 1,200 cubic yards of reinforced concrete and multiple structures, electrical ductbank and piping. Additionally, an existing concrete ditch surrounding the coal pile was removed and replaced with reinforced concrete and a large bore carrier pipe installed 30 feet below the surface by jack-and-bore to carry stormwater and process water to the basins. Through years of water management experience and ingenuity, Charah Solutions completed the project prior to the facility’s committed regulatory deadline.