Usually, of course, water and wastewater utilities contract out such work.
Located on the southeast side of the Kansas City metropolitan area, City of Lee’s Summit, Mo., Water Utilities serves 93,000 customers. The department’s 580-mile system is mainly cast iron and ductile iron buried in clay soils, which is a recipe for corrosion.
Credit: David Reuter
PVC pipe can be mechanically joined or fused for trenchless applications. The former doesn’t require expensive butt-fusion equipment but has lower tensile strength, so is more common in gravity sewer pipeline projects than pressure pipelines like water and force mains.
In 2009, managers decided to replace mains that were being repaired most frequently: small-diameter lines in residential areas. To minimize inconvenience to residents, they focused on trenchless construction, particularly pipebursting because it would let them install a new line using the same path as the existing line with minimum excavation.
Potential contractors were allowed to choose between HDPE and Fusible C-900 PVC. The latter allowed the utility to maintain material continuity with other PVC pipe installed in its system, upsize lines with minimal increase in outside diameter, and use standard PVC and ductile iron fittings to reconnect the lines. Almost 13,000 linear feet of the PVC were installed by Wiedenmann and Godfrey, of Belton, Mo.
Three years later, in 2012, almost 25,000 linear feet were to be installed using two trenchless methods: 24,000 feet of 6-inch and 8-inch Fusible C-900 via pipebursting and 600 feet of 6-inch Fusible C-900 via HDD.
The project bid in March 2012 and was awarded to Lamke Construction of Marthasville, Mo., a first-time PVC fuser. The contractor began construction in May and by November had installed more than 9,000 feet via pipebursting.
“It worked well,” says Pat Dougherty of Lamke. “We’ve been pleased with the material’s overall performance. I wouldn’t hesitate to utilize the pipe on future projects.”
The remaining 10,000 feet were installed beginning in April 2013 when the weather warmed enough to eliminate concerns that the temporary system installed prior to the bursting process would freeze.
“We’re very pleased with the benefits this pipe has provided for these small main replacement projects,” says Lee’s Summit Senior Staff Engineer Kevin York.
UGSI’s brand names mirror American Water Works Association standards for the manufacture of PVC pipe in various lengths; i.e., Fusible C-900 (4- to 12-inch-diameter) and Fusible C-905 (12 inches and above). Until recently, no AWWA or ASTM standard specifically addressed installation and pressure-testing of fused PVC. However, AWWA C605-13 (Standard for Underground Installation of Polyvinyl Chloride (PVC) and Molecularly Oriented Polyvinyl Chloride (PVCO) Pressure Pipe and Fittings) has been updated to address “fused joints” (joining two pieces of plastic by heating or melting). The revised standard went into effect Feb. 1, 2014.