- ENGINEERING INFO
- CASE STUDIES
Westminster, Colorado resides centrally between Denver and Boulder, placing residents within easy reach of major business centers, retail centers, and a variety of entertainment and recreational venues. Activities in Denver or Boulder are a 20-minute drive in either direction. The city covers 34 square miles and seemingly every area has an interesting history, including many landmarks which serve as examples of the historic development of the city since the 1870s.
Westminster has identified hundreds of miles of water transmission and distribution mains that are nearing the end of their useful lives. One high pressure waterline in particular was experiencing frequent and regular breaks. In 2011, the City recommended this 2,000 LF pipeline section for immediate replacement and designated it as a pilot test project for trenchless rehabilitation.
The City retained the Burns & McDonnell Engineering Company to engineer two phases of trenchless rehabilitation of the old, failing 12-inch cast iron water main. Burns & McDonnell staff evaluated four different rehabilitation/replacement methods, including: cured-in-place lining (CIPP), horizontal directional drilling, pipe bursting, and HDPE tight-fit swagelining. Based on historical experience and performance, City staff indicated that C900 PVC pipe was the plastic material of choice for the project. The City’s preference for PVC pipe is due to its resistance to the corrosive soils around the City of Westminster and its compatibility with standard mechanical joint fittings already in stock.
For Phase I, the City selected CIPP lining for roughly 1,700 LF of pipeline rehabilitation. Although the project was successful, the project team expressed concerns about the method and complexity required for connection, tapping, and service line activation. For the 1,760 LF slated for rehabilitation in Phase II, the team selected pipe bursting with Fusible PVC® pipe. City personnel were initially hesitant about pipe bursting, mostly due to negative experiences with pneumatic bursting in the past. Fusible PVC® pipe, however, may only be utilized with static bursting equipment; so anxiety dissipated and the decision to burst was approved. Static pipe bursting, when executed correctly, can eliminate most of the problematic pressure, noise, and vibration issues associated with pneumatic bursting methods.
American West was awarded the prime contract that included preparation for bursting operations and reconnection/testing of the pipeline. Global Underground, Inc. (Global), known primarily for horizontal directional drilling, was subcontracted to perform the pipe bursting installation. Global is also a licensed fusion contractor for Fusible PVC® pipe up to 16-inches in diameter. Global executed the bursting operations in three separate pulls, each taking approximately one day.
A portion of the water main alignment passed through an undeveloped field with no surface concerns. Proving that soil conditions have a significant impact on pipe bursting results, the ground surface showed slight surface heaving despite having an anticipated adequate amount of cover. When bursting under pavement and road sections, no surface heaving was evident.
Robert Meadows of Global Underground commented, “We saw some limited heave in the dry fields, but didn’t have any difficulties in the roadway where it mattered.” Project engineer, Mike Lehrburger, of Burns and McDonnell, added: “This project was a perfect candidate for pipe bursting for several reasons. First, the project area included only one service connection, so we were able to occupy the host pipe without designing and installing an extensive temporary water system. Second, pipe bursting allowed us to pull in a brand new PVC pipeline. An advantage of using Fusible PVC® pipe is what you’re left with when the project is complete; a PVC water main that everyone in the City is very comfortable with moving forward.”
|Pipeline Details and Project Summary|
|Project:||Lowell Boulevard Waterline Pipe Burst|
|Pipe Size:||12-inch DR14 Blue|
|Pressure Test:||150 psi|
|Owner:||City of Westminster|
|Engineer:||Burns & McDonnell Engineering Company, Inc.|
|Contractor:||American West / Global Underground, Inc.|