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Double-Diameter Upsizing With Pipe Reaming
Salina, KS, a city known as “The Best Place In Kansas To Raise Your Kids,” is in part managed by Utility Services personnel tasked with guarding the city treasury to help continue this style of community life. That led to the city exploring the various replacement methods and procedures to replace an aging 12-inch, vitrified clay pipe (VCP) gravity sewer with a 24-inch pipe line for needed increased capacity.
Design, plans and specifications were developed by Martha Tasker, Salina director of utilities, and Steve Palmer, utility engineer. The project was advertised in early November 2009, and bid on Dec. 8. The Notice to Proceed was dated Dec. 31 with work scheduled to begin Feb. 1, 2010. Due to inclement weather, work began on Feb. 15.
The existing line lay beneath a predominantly concrete street located near an old channel of the Smokey Hill River at a depth averaging more than 20 feet. With soil conditions being silt and sand, open cutting presented the likelihood of replacing the entire street, a disruptive situation at best. As an alternative, consideration was given to a trenchless process. The only process available to upsize and obtain the desired 400 percent increase in capacity and double the pipe diameter was through use of the InneReam pipe reaming system.
The pipe reaming process, an assemblage of the power and versatility of a horizontal directional drill and a modified backreamer, is the basis for the pipe reaming process. Procedurally simple, the drill is situated at one end of the replacement section, and then a drill rod is extended though the existing pipe and connected to the reamer. The unit, supplying high rotation speed and pull back force, cuts and pulverizes the existing pipe into small pieces as the reamer progresses. Drilling fluid, flowing from the pump on the drilling unit though the drill stem and numerous ports in the reamer, mixes with the ground up pipe particles and together flow through the existing pipe to a collection point where it is picked up by a vacuum truck for disposal. As the reamer progresses, grinding up the existing pipe, the replacement pipe connected to the rear of the reamer is simultaneously pulled into place.
The project consisted of 160 linear feet of 24-inch PVC to be installed by open cut because of a PI in the line and its location, 1,480 feet of 24-inch DIPS HDPE SDR 17 to be installed by pipe reaming, rehabilitation of three manholes and replacement of two manholes on the continuous line with three manholes removed and replaced away from the primary work site.