City Water, Light and Power lime pond 100% plans

Project Summary

Hanson provided engineering services for the relocation and replacement of the City Water, Light and Power (CWLP) Water Purification Plant’s three waste lime ponds in Springfield, Illinois. The ponds are constructed on top of fly ash fill at CWLP’s lakeside ash pond.

Because of impending coal combustion residual (CCR) and effluent limitation guidelines , the fly ash ponds will be closed eventually; therefore, the waste lime ponds needed to be replaced and relocated. Hanson confirmed process waste quantities and collaborated with the client on historical data regarding flows and solids concentrations for the various waste streams tributary to the lime waste ponds.

Hanson confirmed waste handling facility sizing information, sized the basins based on Ten States Standards and evaluated alternative sizing through coordination with the owner on an owner-defined level of comfort on storage volume coupled with the ability to dispose of the lime sludge year-round.

The report’s recommendations and conclusions were verified, including reviewing design assumptions and opinions of probable construction costs; evaluating present-worth costs based on actual operation and maintenance costs; and evaluating the feasibility of each alternative based on potential changes to the CCR rules that may disqualify several of the proposed alternatives.

The final design included self-supporting reinforced concrete walls for the settling tanks and a compacted clay liner and geomembrane composite liner system. Underground tile systems were installed to limit water surcharge issues and collect any water that could bypass the concrete and liner system. New pumps were added to the wet well to transport the water nearly half a mile to the new lime pond locations, with variable level discharge gates installed within each cell. The design of the system incorporated safety overflows in and between each cell.