The Kentucky Public Service Commission on Jan. 27 approved a June 2015 application from the Kentucky Power unit of American Electric Power (NYSE: AEP) for a Certificate of Public Convenience and Necessity (CPCN) to close in place the coal ash impoundment located at its Big Sandy Generating Station.
The Big Sandy plant is made up of two coal-fired units. In order to comply with the Mercury and Air Toxics Standards (MATS), Kentucky Power is converting Unit 1 to fire natural gas and it retired Unit 2 in May 2015. It has bought half of the Mitchell coal-fired plant in West Virginia to make up for the loss of the 800-MW Big Sandy Unit 2.
Because the Big Sandy station will no longer burn coal, the Big Sandy Ash Pond will no longer actively receive coal combustion residuals (CCRs) and, as a result, will lose its permit-by-rule status and will need to be closed. Kentucky Power asserted that closing the Big Sandy Ash Pond in place is the least-cost reasonable alternative to address the need for a long-term solution to dispose of the CCRs currently being stored in the Big Sandy Ash Pond.
The Big Sandy Ash Pond is an approximately 140-acre wet fly ash impoundment formed by the Horseford Creek Dam. The Saddle Dam, a 62-foot high embankment located at the southeast portion of the valley, also defines the impoundment. The Big Sandy Ash Pond was constructed and placed in service in 1969 and has a total storage capacity of 8,302 acre-feet (13.4 million cubic yards) when the surface of the impounded ash reaches an elevation of 705 feet above mean sea level. The impoundment is located in Lawrence County, Kentucky, and is approximately 0.75 miles northwest of the power plant, which is across U.S. 23 from the impoundment.
Since the Commonwealth of Kentucky does not have a specific ash pond closure permitting protocol, the closure of the Big Sandy Ash Pond is being pursued via the Kentucky Division of Waste Management’s (KDWM) Special Waste Landfill permitting process.
Kentucky Power retained consultant URS Corp. to examine and evaluate multiple aspects of the proposed project and the area impacted by it. Included in the scope of work performed by URS was the cap design and site drainage configuration needed for the closing in place of the Big Sandy Ash Pond.
The actual closure of the Big Sandy Ash Pond will be done in a stepwise fashion over five years from 2016 until 2020.
First, the impoundment will be drained of surface water by digging temporary drainage channels in the deposited fly ash. As the drainage occurs and as the accumulated dehydrated ash deposit is able to support earth-moving equipment, Kentucky Power will begin grading the exposed ash, establishing a subgrade that sets the elevations needed to channel storm water flow across the impoundment once it is closed. As the subgrade is established and additional fill is added to provide a positive grade, the area will be expanded to cover approximately 140 acres; this area will then be capped in order to prevent surface water from entering the underlying ash material. The capping system will include a flexible membrane liner, an 18-inch cover layer of protective earthen material, and six inches of topsoil to sustain vegetation and minimize surface erosion.
Lastly, a ground water monitoring network of wells will be installed to support the post-closure care and monitoring requirements for ensuring the integrity of the impoundment cap for a 30-year period following the completion of the closure construction. Once the Big Sandy Ash Pond is closed, the site will be regulated as a permitted Special Waste Landfill. The impoundment will also be subjected to the U.S. Environmental Protection Agency’s Disposal of Coal Combustion Residuals from Electric Utilities Final Rule (CCR Rule). Kentucky Power contends that the designed surface impoundment closure is consistent with the CCR Rule requirements.
Upon receipt of approval from the commission, Kentucky Power anticipates beginning construction in early 2016 and completing the project by the end of 2020. The project’s estimated total capital cost is $62.3 million, with the closure construction accounting for $59.1 million and the post-closure care and monitoring adding $3.2 million.