Basins 7 and 16 Sanitary Sewer Improvements
New Albany, IN
The objective of this project was to solve longstanding sanitary sewer overflow (SSO) problems in Basins 7 and 16 in the City of New Albany. The project included the installation of a 1.6 million gallon wet weather sanitary sewer equalization basin utilizing approximately 2,700 lineal feet of 120-inch diameter sanitary sewer pipe, a submersible dewatering pump station, approximately 6,900 feet of 15-inch to 24-inch sanitary relief sewers, road reconstruction, and site restoration. The project is the last in a series of more than $50 million in sanitary sewer and wastewater treatment improvements the City has undertaken to comply with a US EPA Consent Decree.
Clark Dietz carefully evaluated the existing site constraints, construction schedule, sewage characteristics, ease of installation, pipe joint integrity and other factors to select a large diameter pipe (120”) needed to provide the 1.6 million gallons of storage required to prevent SSOs. Key pipe performance requirements included a smooth interior wall and the ability to meet load, pipe deflection, and watertight joint criteria. After an extensive value engineering review, HDPE pipe was selected for this application. The selected pipe allowed the contractor to meet the aggressive construction schedule, minimize construction costs to the City of New Albany, and provide a long-term, sustainable solution to eliminate longstanding SSO occurrences. The project also included comprehensive sewer system modeling using XP-SWMM, which allowed us to optimize the sizing of the storage tank and relief sewers that convey excess flow to the facility. Downstream sewer system monitoring capability was also incorporated into the design, so the storage tank can be lowered/emptied whenever possible to reclaim storage quickly in the event of back to back storm events.
This project eliminates sanitary sewer overflows in an existing residential neighborhood and provides a very tangible benefit to area residents by eliminating raw sewage flowing down streets and into nearby waterways, thereby protecting public health and the environment, as well as complying with State and Federal mandates to eliminate SSOs. Secondary benefits include aesthetic improvements to the project area and a neighboring cemetery. Working with a local property owner to acquire the tank site allowed us to eliminate an unusable construction debris dump site and utilize excess spoil material to re-grade and flatten some steep slope areas in the adjacent St. Mary’s Cemetery. This allowed the cemetery to create additional burial plots, which was a significant benefit to the property owner and community. As part of the gravity relief sewer portion of the project, the City was able to reconstruct the streets and sidewalks in the neighborhood, significantly improving area drainage as well as general aesthetics and quality of life.
ACEC Engineering Excellence Merit Award Winner