Safety and Skill Count When Closing a Coal Ash Impoundment
Location
Midwest
Industry
Utilities
Challenge
Close a large-scale wet ash impoundment with difficult access and site conditions in accordance with regulations on defined schedule
A Midwest utility needed to close a 140-acre wet fly ash impoundment − challenging work because of the difficult and unstable conditions involved. ENTACT’s experience and specialized construction skills helped to ensure a safe and successful closure for our utility client.
ENTACT Solution
ENTACT conducted a phased dewatering approach, planning water flow, drainage and the regrading of the exposed fly ash according to site elevation. The regrading process was difficult, setting an elevation that would ultimately direct the subgrade for the construction of a new spillway. This spillway allows stormwater to flow from the closed site to a nearby creek.
- Lowered main dam and removed saddle dam; constructed new spillway for both dams
- Drained surface water via pumping and/or temporary drainage channels
- Regraded exposed fly ash
- Installed cap system, including a geomembrane and protective soil layer, and seeded to establish vegetative cover
- Partially lowered dam and built new spillway for stormwater flow
The Results
- Managed 2.7 million cubic yards of ash, rock and soil
- Excavated and placed approximately 700,000 cubic yards of coal combustion residuals
- Lined and capped 136 acres
- Constructed 14,000 feet of stormwater channels
- Pumped and managed more than 7 billion gallons of water
