Construction method: pipe bursting

King County’s contractor installed another pipeline in the existing pipe corridor using a method called pipe bursting. This method allows installation of a new pipe without losing design capacity in the existing pipe.

First, the contractor assembled a long pipe by fusing together shorter sections of pipe. A large drill rig located in Smith Cove Park pulled about 3,000 feet of pipe through the existing pipeline from the entry pit on 32nd Avenue West. To accomplish the pipe pull, a reamer on the front of the assembly cleared out dirt in the pipe. A cutter head and expander then followed to push the pipe outward to make room for the pipeline being pulled behind. The new pipe is made of polyethylene (HDPE), which works well for this method.

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The Magnolia project contractor used a reamer to clear dirt from the pipe, which was followed by a cutter head, an expander and about 3,000 feet of fused pipeline.