Attica, IN

CSO LTCP Phases 2/Wastewater Treatment Facility Renovation

HWC worked with Attica, Indiana to complete Phase 2 of the City’s mandated CSO LTCP project. 

The City’s CSO Long-Term Control Plan required a second and final phase, which included floatables screening of flows from the single remaining overflow outfall to remain operational and storage of approximately 750,000 gallons of combined sewer flows to meet IDEM’s design storm criteria. HWC was hired to develop a Preliminary Engineering Report for the CSO project and necessary improvements at the treatment facility to address depreciation and compliance needs. 

The plan developed included improvements at the treatment facility, including:

• New influent/CSO screening structure, which complied with the floatables control requirement of the CSO LTCP and fine screening for all influent flows
• New 750,000 gallon per day average flow/1.2 MGD peak flow oxidation ditch for biological treatment to replace the current trickling filter process
• Conversion of existing primary clarifiers to secondary clarifiers
• Conversion of the existing trickling filter tanks to CSO storage tanks, which will be filled by dedicated CSO pumps in the retrofitted influent wet well
• Chemical feed systems and piping for nutrient (phosphorus) control
• Implementation of a new plant-wide SCADA system for both biological and wet weather process control

Due to the re-utilization of existing structures and conversion to a new biological treatment process, significant construction sequencing considerations were required in the design of the project. HWC held working sessions with the plant staff during design and with both the contractor and staff during construction to ensure minimization of operational disruptions were realized through demolition and sequencing of construction activities.

The total project cost was approximately $5.5 million. HWC provided planning, design, construction engineering, and inspection services for the project.