Wastewater Treatment Plant and Combined Sewer Overflow Control

After completing the Town’s Long Term Combined Sewer Overflow Control Plan (LTCP), Chesterton, IN appointed DLZ to provide design, construction administration, and construction inspection services for the recommended plan. In addition to the LTCP projects, the Town included several other Wastewater Treatment Plant (WWTP) and Collection system projects. The WWTP had a capacity of 4.5 MGD average/10 MGD peak. The total project scope of work included the following elements:

Wastewater Treatment Plant Improvement Projects

Replacement of an existing blower with a 3,400 scfm high-efficiency Turbolex blower driven by a variable speed drive paced on new dissolved oxygen probes in the six aeration tanks.

• Replacement of the existing aeration diffusers in four aeration tanks with fine bubble membrane disc diffusers.
• The addition of aeration tank flow split valves in the influent of each aeration tank to control and equalize the flow through each tank.
• Replace and upgrade the sludge conveyor system from the sludge centrifuge to the sludge loading and storage area.
• Replace the existing generator along with the transfer switch and the current switchgear. The generator’s size served the loads provided by the existing generator plus the new load requirements of the headwork’s and storage basin.
• Replace the existing digester gas collection system with new piping, gas control system, and waste gas burner. Clean all three digesters and specify concrete crack repair.   
• Rotary Drum Thickener, with polymer feed, to dewater secondary sludge at a rate of 28 GPM before anaerobic digestion.
• Upgrade the existing SCADA control system.

Long Term Combined Sewer Overflow Plan Projects

• The wet weather headworks included grit, pumping, and screening facilities with a capacity of 26 MGD. The headworks pumped flows above the 10 MGD capacity of the WWTP to the 1.2 MGD storage tank. When the flows exceed the size of the storage tank and the pumping capacity of the headworks, the wet weather pumping station shuts down and flows discharge from CSO 101 to the Little Calumet River. Once the wet weather event has ceased, the contents of the storage tank are drained to the WWTP for full treatment.
• Collections System Improvements
• Upgrade the Dogwood and Golfview lift stations’ electrical power from single-phase to three-phase power.
• Installation of a backup natural power generator at Westwood lift station.
• Rehabilitation of approximately 3,700 feet of existing 15- and 42-inch diameter sanitary sewer with cured-in-place pipelining.
• Rehabilitation of five manholes with a protective coating to protect the manholes from hydrogen sulfide corrosion.

State Revolving Fund Loan

• To fund this project, the Town procured a State Revolving Fund Loan. DLZ assisted the Town and its financial consultant with the loan procurement. This work included the preparation of an application, preliminary engineering report, and evaluation of environmental impacts. To take advantage of surplus SRF funds and to take advantage of favorable interest rates, the Town split the project into two phases. The first phase included the WWTP Improvement Projects and Collections System Improvements. As several projects in this phase were eligible for the Green Project Reserve fund, the Town was eligible for a reduced interest rate. The savings over the life of the loan is estimated to be over $800,000.