Surface In-situ Stabilization of Saturated Ash for CCR Impoundment Closures

The operation of heavy equipment on the surface of saturated coal ash during the closure of impoundments containing CCR poses significant safety concerns. Saturated ash has little to no bearing strength and the depth of saturated ash in CCR impoundments can range up to hundreds of feet. In-Situ Stabilization (ISS) technology (treatment of the top 3 to 5 feet of saturated CCR material) may be used to quickly produce a stable work platform for subsequent CCR placement and compaction and capping activities within the impoundment. The plan area of the saturated ash is divided into a number of treatment cells, each sized to require a 25-ton truckload of Portland cement. Working from the edges of the treatment cells, the Portland cement is mixed into the saturated ash using long-reach excavators. Within 48 to 72 hours, the treated material develops sufficient bearing capacity to support the operation of long-reach excavators and treat the next row of treatment cells. With the stable work platform established, placement and compaction and capping activities can be conducted, operating safely on the ISS-treated CCR material.