Ameren Hutsonville ash pond closures

Project Summary

Hanson completed construction and permitting documents, including a detailed closure plan for capping the inactive Ash Pond D at Ameren’s Hutsonville Power Station in Hutsonville, Illinois. The closure was complicated by site-specific environmental regulations (Title 35, Illinois Administrative Code, Part 840), groundwater impacts, the adjoining Wabash River and limited construction space. Illinois Environmental Protection Agency and Illinois Department of Natural Resources permitting was required for the project, which represented the first ash pond in the country closed in accordance with regulatory requirements.

Hanson also provided hydrogeologic and engineering services to design a cutoff/collection trench to intercept and collect groundwater along a half mile of the plant’s property boundary. The closure included short- and long-term groundwater monitoring to determine equilibrium time estimates, background water quality evaluations, groundwater statistical trend analyses and contingency plans for unplanned constituent spikes.

In addition, Hanson designed a cap for the 22-acre pond. The design included site regrading, the installation of a high-density polyethylene (HDPE) geomembrane and 3 feet of soil cover. The design also incorporated appropriate runoff controls for long-term stability, as well as National Pollutant Discharge Elimination System compliance, and it restricts surface water infiltration into the ash.

Following the successful closure of Ash Pond D, Hanson was retained to prepare construction and permitting documents for the closure of the power station’s ash ponds A, B and C, as well as the bottom ash pond. Detailed closure plans for Ash Pond A included site regrading, the installation of a HDPE geomembrane and 3 feet of soil cover. The closure design also incorporated substantial runoff controls for long-term stability. The remaining three ash ponds were clean-closed with removal of all ash and liner products, limiting long-term monitoring to just two ash ponds.

The closures were complicated by pending environmental regulations, groundwater impacts and the adjoining Wabash River.