The U.S. EPA’s original Coal Combustion Residuals Rule (published April 17, 2015) included an exemption clause from most Rule requirements for inactive CCR surface impoundments that closed by either capping or removal before April 17, 2018. This exemption clause was the incentive for Interstate Power and Light Company to expedite clean closure of the Fox Lake Generating Station surface impoundment. The station was converted to natural gas in 1998; however, the former ash impoundment contained nominal quantities of CCR from pre-1998 operations. Although the Rule revision, published August 5, 2016 (effective date of October 4, 2016), removed the exemptions for inactive impoundments, the CCR removal activities were completed and clean closure was independently certified on August 17, 2016. Final disposal and restoration activities were completed by the end of 2016.
The scope of the overall project included:
- Preliminary studies resulting in the decision to use hydraulic dredging, geotextile dewatering tube filtration, polymer addition, and discharge water filtration as necessary to achieve compliance;
- Plans and specification preparation;
- Bid evaluation; and
- Project execution, oversight, and certification.
Although the received bids included options of wet excavation, dewatering and excavation, and hydraulic dredging – options considered in the preliminary assessment -, re-evaluation of these options confirmed hydraulic dredging was the best option for successful clean closure.
This paper presents the success of the CCR impoundment closure including the planning, decision-making process, construction activities, and certification of the clean closure of a CCR surface impoundment.
Jason D. Fifarek – Sargent & Lundy
William Skalitzky – Alliant Energy Corporation