Carroll Wastewater Treatment Facilities Improvements
Carroll, Iowa
Veenstra & Kimm, Inc. was retained by the City of Carroll to develop a facility plan for the City's sewerage facilities. The facility plan included both the wastewater treatment plant and the conveyance system.

The Carroll Wastewater Treatment Plant was a single stage trickling filter treatment plant. The City had expanded the capacity of the treatment facilities by constructing additional clarifiers. Although the treatment plant was adequate to meet secondary treatment standards the capacity of the treatment plant was inadequate under wet weather flow conditions. The treatment plant was not capable of producing an effluent to meet the ammonia nitrogen limitations established in the discharge permit.

The facility plan evaluated alternatives to upgrade or replace the treatment plant. The upgrade alternative included a phased upgrade or a single project.

The facility plan recommended a major renovation of the existing treatment plant and conversion of the treatment plant from a trickling filter plant to a vertical loop reactor activated sludge treatment process. To accommodate excess flow during wet weather periods a stormwater equalization basin was constructed adjacent to the treatment plant.

Veenstra & Kimm, Inc. was subsequently retained to design the improvements to the wastewater treatment plant and the collection system. The wastewater treatment plant improvements included construction of new facilities and renovation of existing facilities. Approximately 80% of the original treatment plant was replaced and the balance of the treatment facilities upgraded.

Construction of the wastewater treatment plant improvements started in the spring of 2004. The construction project was scheduled to extend over a 2 year period. The long construction period is a result of the extent of the improvements and the phasing necessary to maintain operations. The construction schedule included a specific phasing plan to complete key facilities by a compliance date established by the Iowa Department of Natural Resources.

The new activated sludge treatment facility was placed in service in the summer of 2005. The project was finally completed in the spring of 2006. The treatment facility has consistently met effluent limitations since the summer of 2005.