Environmental and Design Challenges for a 1,500 mm Diameter Steel Pipeline River Crossing

The City of Saskatoon (City), with a population of 215,000, operates a water treatment plant on the west bank of the South Saskatchewan River (SSR) and a river pump station located across the river on the east bank. A 1,500-mm diameter pipeline river crossing connecting the pump station and the water treatment plant was required and subsequently constructed using an open-cut cofferdam method. This paper discusses the design team's challenges in formulating the final design in support of the cofferdam open-cut construction method. Interesting design elements included a river hydraulic assessment, the use of rock spur, articulated concrete mat to protect the earthen cofferdam, siltation curtains for aquatic habitat and water quality protection, river quality monitoring, and fish habitat compensation. The pipeline crossing was successfully completed within the specified nine months' timeline and allocated budget. Some of the lessons learned during the project include adjustment of the construction sequence and the importance of hydraulic analysis and robust cofferdam erosion control.