An open cut method was used to install 8,500 feet of 72-inch centrifugally cast, fiberglass-reinforced, polymer mortar (CCFRPM) pipe.
An Earth Pressure Balance Machine exits the Cliff Avenue crossing in Sioux Falls, S.D.
The existing Outfall Trunk Sewer consists of two miles of 66-inch pipe. Built in the late 1970s, it is made of reinforced concrete pipe (RCP) with an asphalt/bituminous liner for corrosion protection. The Outfall Trunk Sewer conveys more than 90 percent of the city’s wastewater and has become structurally weakened from sewer gases. Hydrogen sulfide (H 2 S) gas typically is formed in wastewater collection systems that are conducive to creating septic conditions. The deterioration of the liner was resulting in significant corrosion of the pipe. Design considerations The City of Sioux Falls, along with its consultant, HDR Engineering, Inc.’s Sioux Falls office, investigated several options for replacement or rehabilitation of the line. Due to the conditions of the existing RCP pipe, extensive bypass pumping required, and the limited capacity for future development, relining with a cured-in-place pipe was not selected. “A thorough investigation of available sanitary sewer pipes was per- formed during the preliminary design of this project,” said Dustin Posten, P.E., project manager, City of Sioux Falls. “Considerations, amongst others, included life cycle costs, corrosion resistance, con- structability, operation and maintenance, compatibility with third-party products, and longevity.” The city’s consultant recommended fiberglass-reinforced pipe as the best overall material for this replacement project.
Sewer replacement increases capacity and reliability
Infrastructure and population grow side by side in Sioux Falls, S.D. By Erin Boudreaux
Sioux Falls is the largest city in South Dakota and growing larger each day. In 2016, the city’s population increased by 5,200 people to a cur- rent population of 178,500 residents. A growing, thriving community needs its infrastructure to grow as well. Since the first sewer was installed in the early 1890s, the Sioux Falls Water Reclamation Division has been investing in infrastructure with the most recent projects costing $35 million and involving reconstruc- tion of the main sanitary sewer system; replacement of the Outfall Trunk Sewer; and addition of the Main Pump Station Parallel Force Main. The Outfall Trunk Sewer carries wastewater to the Main Pump Station, which then pumps the wastewater to the city’s Water Reclama- tion facility.
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july 2018
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