Project Details

The area for this project extended from the main lift station at the south end of the City of Harrisburg, westward towards I-29, and northward to the Sioux Falls city limits, along three branches. While the city knew it would take years for the area to fully develop, they wanted to consider if it was more cost-effective to oversize downstream sewer interceptors for full basin build-out, or install smaller interceptors with future parallel interceptors to support flows, or use cross-connections to meet future demands. The city also requested information on when sewer flows will exceed the capacity of existing lift stations and interceptors within the project area and the timing of the recommended improvements to address these issues.

The study included detailed condition and capacity assessments of the aging Coyote, Honeysuckle, Tiger, and South Cliff Avenue lift stations within the study area, which required extensive maintenance for city staff. The remaining life of the lift station components was determined. The capacity of the lift station components was also evaluated, using the ANSI/Hydraulic Institute Standard 9.8 requirements to guide wetwell capacity evaluation.

The Facility Plan used LIDAR data to define the service area and develop the sewer basins and sub-basin boundaries. Lift station calibrations and pump runtime data provided information on existing sewer flows, while future land-use plans guided projections of future sewer flows. A sanitary sewer model was developed using SewerGEMS and was essential for evaluating sewer interceptor sizing and alignments, as well as cross-connections between the three branches, for the 15.3-square-mile area with elevations ranging from 1376 to 1550.

Probable cost estimates were prepared for the alternatives, and O&M cost impacts were also considered. Banner determined that two trunk sewer mains with a cross connection provided the most cost-effective solution to support future growth. The Phase I improvements were needed immediately due to capacity shortfalls in the existing system. The Phase I improvements included a 36"/30” Parallel Interceptor in Subbasin 1A from the Main Lift Station to Cliff Avenue, a 24" Interceptor in Subbasins 1A, 3A, and 3B from the 30" Interceptor to Creekside Avenue and Willow Street, and a 24” Interceptor from the southeast corner of Basin 3D to north of Tom Sawyer Trail. The Phase I improvements allowed for the decommissioning of three of the city’s lift stations, potentially saving them up to $263,500 over 10 years.

Phase II improvements in Subbasins 2C and 2D would be needed within 5-10 years to support the cross connection, depending on development rates. They included extending the 36"/30” Interceptor in Subbasins 1A and 1D from Cliff Avenue to Minnesota Avenue and a 21” Cross Connection from Subbasins 2C to 1D. To facilitate developers' sharing in the overall cost of the sewer interceptors, as allowed by codified law, per-acre cost recovery fees were developed.

This study was completed as a Facility Plan, including environmental review, allowing the City of Harrisburg to submit for State loan and grant funding to aid in financing the recommended improvements. After the study findings were presented to the City Council, Banner worked with the Southeastern Council of Governments (SECOG) to facilitate the public hearing and funding application documents.

Project goals:

Facility plan to assess current sewer system conditions throughout the west side of Harrisburg
Property Owner discussions for permanent easement acquisition
Cost analysis for multiple pipe routes
Analyze future arterial road alignments in conjunction with trunk sewer main alignments
Design of full roadway reconstruction
Bank stabilization of Harrisburg Tributary

Project features: