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Emergency Pipe Bursting Project In Alaska Uses Chain-Drive System
Remote Pipe Bursting
Those in the lower 48 U.S. states know that winters in Alaska are very cold and that everyday life for the hardy souls who live there is different in many ways.
Constructing and maintaining utilities there also has special challenges. Many cities and towns are very remote and extreme cold limits construction through much of the year.
The Yukon-Kuskokwim Health Corporation (YKHC) Office of Environmental Health and Engineering has a Remote Maintenance Worker Program that provides training and technical assistance to community water systems in the Yukon-Kuskokwim Delta.
In this service area, the towns of Bethel, St. Mary’s and Pilot Station in Southwestern Alaska, are off the state’s road system and the only way to reach them in summer is by air. St. Mary’s and Pilot Station are on the Yukon River, making them also accessible by boat.
Pilot Station’s water system is owned by the town, and water for homes and businesses is provided through a buried four-inch chlorinated polyvinyl chloride (CPVC) water main inside a larger insulated pipe with water circulated through a loop to prevent freezing. The loop was installed more than 30 years ago.
In January 2012, approximately 1,000 feet of the return loop froze and cracked, clearly an emergency. The pipe was buried at depths ranging from five to 6 feet.
Pilot Point water plant operators immediately contacted YKHC’s lead remote maintenance worker, Alan Paukan, for assistance. The decision was made to cap the return loop and have customers on the last service lines on the supply side run their water so as to keep water moving through the main to prevent freezing while plans were initiated to repair the cracked segment of main.
Brian Lefferts, director of YKHC’s Office of Environmental Health and Engineering, contacted Utility Construction Management Company, (UCMC), Bellevue, WA, to discuss options for replacing the pipe. UCMC, distributor of TTS chain drive pipe bursting equipment, provides subcontractor, consultant and management services for pipe bursting projects.
Open-cut construction was considered and ruled out because of the logistics of getting equipment and materials to the remote location. It was estimated that the cost to install the pipe by excavation would be $250 per foot or $250,000.
There was interest in pipe bursting, but the broken pipe was enclosed inside a 12-inch diameter corrugated metal (CMP) pipe with the void between the water pipe and inside of the larger pipe filled with poly foam to protect the water line from freezing.