CSO 6 and 7 (Storage Tank and Pump Station Renovation)

The Board of Public Works retained DLZ for the CSO 6 and 7 project. The project responsibilities included

  • Utility coordination
  • Survey
  • Land ownership confirmation
  • Geotechnical investigation
  • Basin SWMM modeling
  • Design
  • Bidding
  • Construction administration
  • Full-time inspection
  • Material testing
  • Startup services
  • Real-time controls

The City’s CSO Long Term Control Plan, approved in 2011, required building a 1.0 MG storage and pump facility. The CSO 6 and 7 facility is located where Jackson Boulevard crosses the Elkhart River. The CSO Storage Tank is of reinforced concrete, cast-in-place construction with flushing gates. The attenuation storage tank is located under the municipal parking lot at the southwest corner of Jackson Boulevard and Waterfall Drive. Construction of the CSO tank required complete reconstruction of the parking lot.   

The parking lot is designed per City ordinances for layout, storm drainage, landscape treatment, and recommended lighting levels, and accessible parking and connectivity standards. The staff chose porous concrete to make the project site environmentally friendly.

The Lift Station

The Jackson Boulevard Lift Station needed renovation to work in conjunction with the proposed CSO tank. DLZ team converted the station into a submersible lift station by converting the dry well into a wet well.  The combination of the new wet well and the existing wet well allowed for two independent pumping systems. One pump system pumps dry weather flows to the current force main, and the other pumps wet weather flows to the proposed CSO tank. The lift station will include a flo-minutor to grind up solids in the sewage.

To provide better access for maintenance crews, the design raised the lift station site to the walking path level. Also, the plan provided for the installation of a retaining wall and fall protection along the river bank. Design of the dry weather pumps included sizing the pump system for two separate applications: the existing force main to the intersection of Main Street and Jefferson Street, and a new force main to Harrison and 2nd Street to be constructed in the future.

The renovation included installing a new 18-inch sanitary sewer and 15-inch storm sewer along Waterfall Drive to separate the systems in the downtown area further. The City’s requirements needed the removal of the existing combined sewer system.

Water Main Replacement

Water Main replacement includes an existing 6-inch main along Lexington Avenue from Main Street to Waterfall Drive. DLZ installed a new 12-inch main in Lexington Avenue from Main Street along Lexington Avenue to Waterfall Drive then straight east under the Elkhart River across Kardzhali Park connecting to the 12-inch main along NIBCO Parkway. We evaluated the construction methods for the installation of the river crossing, including open cut and directional boring.

The project could have affected the soil and groundwater contamination near the intersection of Waterfall Drive and East High Street. The project included the research of existing IDEM files to define the contamination limits and the development of a strategy to avoid or effect that contamination. As historical use on the affected sites was industrial with railroad spur lines, the project included obtaining title and encumbrance reports for review and verification of existing ownership and encumbrances for the proposed CSO storage tank parking lot property.

Real Time Control (RTC) was a part of the system to maximize the CSO attenuation storage tank’s capacity by coordinating the operation with the rest of the collection system. RTC implements control logic improved the level of CSO control and reduces overflows by as much as 17% over the projected control identified in the LTCP.




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Elkhart, Indiana