Through the City’s NPDES permit for wastewater discharges to the Wabash River, the Environmental Protection Agency (EPA) and the Indiana Department of Environmental Management (IDEM) required the City of Terre Haute and all CSO communities to solve their CSO problem to acceptable levels through a two-step process. First, the CSO Operational Plan was developed which prescribed operational measures in the wastewater utility which are focused on minimizing the volume of CSO flows. This document and its requirements has been completed and implemented by the City with annual updates completed on the methods and procedures required in the plan. The second step included the development of a Long Term Control Plan (LTCP) which evaluated alternatives for controlling CSO’s through modifications and improvements to the wastewater system which allow for CSO reduction over time to an acceptable level. The LTCP’s development and requirements are described separates and a copy of the document in its entirety is provided for reference in the Resources section.
What Solutions did the City consider?
As presented in the LTCP, the City considered a wide range of solutions to reduce the volume and frequency of CSO’s. These solutions included the following schemes which were evaluated and screened to only those methods which were deemed feasible for the Terre Haute system:
- Combined sewer separation (constructing new sanitary or storm sewers to eliminate introduction of storm water into the sanitary system)
- Storage Facilities – “in-line” storage utilizing existing oversized sewers, or “off-line” facilities including tanks, basins, etc. to hold CSO flows
- Relief sewers to convey CSO flows to points of treatment or storage
- Satellite treatment facilities to treat and discharge CSO flows at an outfall
- Expansion of treatment facilities
- Tunnels to store and convey CSO flows deep underground
After evaluation, these concepts were applied to develop comprehensive plans in the LTCP for review.
How will we achieve this goal?
The program combines the following strategies to achieve this goal:
- Miscellaneous "common" alternatives to consolidate outfalls, capture floatable material and allow for storage of combined flows in sewers.
- Revisions to CSO diversions to allow for increased CSO control and storage of comvined sewage flows in trunk sewers.
- Expanding the Wastewater Treatment Plant to treat more flow during wet weather .
- A 33 MGD high rate treatment facility for CSO flows at the former International Paper (IP) Brownfield site.
- A new main pump station to replace the existing facility constructed in 1965.
- A new large diameter CSO gravity sewer interceptor along the Wabash River between Fairbanks Park and the new main lift station to convey flows to the main lift station for transfer to the WWTF or the new high rate facility.
- Green infrastructure in selective basins to potentially reduce the size of or eliminate gray infrastructure at CSO 010.
- CSO storage facilities at the north end of the CSO system. (dependent upon success of green infrastructure initiatives.