Improving the sewer system capacity and alleviating environmental impacts

Broad River Force Main Replacement and Sewer Capacity Improvements

When the City of Columbia was facing environmental challenges due to their sanitary sewer overflows, they worked with the Environmental Protection Agency (EPA) to create a consent decree that outlined the City’s required remedial actions. This included replacing existing sewers and other capacity improvements.

Our team was brought in to replace the Broad River force main with gravity sewers and force mains. Additionally, we completed a condition assessment of a 24-inch (61-centimetre) force main using PICA’s Recon+ sphere and Bracelet Probe. We also did extensive hydraulic modeling of the effects of projected flows on the existing 9,600 gallons per minute (43,600 litres per minute) Broad River pump station and force main, and we completed a condition assessment of the existing gravity sewers and force main, along with an analysis of options for crossing the Broad River, including horizontal directional drilling.

Our design ultimately considered multiple creek crossings, wetland impacts, SCE&G right-of-way crossing, and South Carolina Department of Transportation encroachments. Some other design challenges included surge protection (transient analysis), as well as complex bypass pumping at the Broad River Pump Station to connect the new force main and gravity sewer. With these sewer infrastructure upgrades and studies, the City of Columbia will be able to reduce sanitary sewer overflows and the resulting impacts to the local environment.