- ENGINEERING INFO
- CASE STUDIES
With the existing 30" PCCP along Columbia Road in Grand Forks nearing the end of its useful life with crown corrosion becoming prevalent throughout the line, Webster Foster & Weston (WFW) was engaged to evaluate rehabilitation or replacement options. Columbia Road is a busy roadway with many businesses located near the campus of the University of North Dakota, a major economic hub in the area. WFW evaluated both conventional dig-and-replace and trenchless methods to solve the problem. Ultimately, sliplining was selected as it minimized disruption to traffic and businesses and importantly provided for a lower installed cost solution.
|Pipeline Details and Project Summary|
|Project:||Force Main Repair on Columbia Rd. from 10th Ave N. to Hwy 2|
|Owner:||City of Grand Forks, ND|
|Engineer:||Webster Foster and Weston; Grand Forks, ND|
|General Contractor:||Sellin Brothers Inc; Hawley, MN|
|Slipline Contractor:||North Core Bore; Fargo, ND|
|Distributor:||Fargo Water; Fargo, ND|
|Slipline Length:||1,440 LF 24" DR32.5 FPVC®|
WFW examined several materials for the project: cured-in-place (CIP), HDPE, rigid fiberglass (Hobas), and Fusible PVC® pipe. CIP was eliminated because it did not provide a long-term structural solution. Due to burial depth (exceeding 10' in locations) and the potential for the pipe to operate in a vacuum at a later date, wall thickness was required to accommodate a buckling capacity of one atmosphere. Required HDPE pipe wall thickness reduced the hydraulic capacity to an unworkable point. Both fiberglass pipe and FPVC® pipe met the hydraulic and structural requirements of the design, and contractors were allowed to select either material. Due to cost and ease of construction, the low contractor, Sellin, selected Fusible PVC® pipe. Patrick Hockett from Sellin Brothers stated, "Due to the tight time frame for the construction of this project, we needed to use a product that could be installed quickly and efficiently. Fusible PVC® pipe gave us the correct solution for this situation."
In less than a week the pipe was fused into two equal segments, to accommodate layout space limitations (driveways would have been blocked). Chris Schock from North Core Bore, the trenchless subcontractor that performed the pull-in stated, "Fusible PVC® pipe was chosen because we could use our 20-ton Hammerhead pipe pulling winch to install the 24" PVC in a single pull in a single day. The Hobas pipe would have required a direct push machine and installation of one stick at a time, taking four to five days. In addition, casing spacers were required, and the straight barrel of the Fusible PVC® pipe offered more clearance than the belled OD of the Hobas pipe. The condition of the host pipe was not known, so if there were issues the Fusible PVC® pipe could have been pulled back out. The Hobas pipe would have required the obstruction to be excavated."
Standard connections back to the existing PCCP pipe were made, and the pipe was successfully pressure tested to 60 psi. This project marked WFW's first use of large diameter Fusible PVC® pipe. Tom Hanson, design engineer, summed it up: "Fusible PVC® pipe was a great solution in this application."