Pipe bursting is a proven, reliable method for replacing deteriorated and undersized pipe lines. Although many North American utility system owners and operators, consulting engineers, suppliers and contractors have years of overall experience, a substantial number still have not had their first experience with the technology. This article will detail some of the perspectives surrounding users “first time” application of pipe bursting.
As a utility owner, there are many benefits that merit consideration of pipe bursting for your next utility renewal project. However, in today’s ever-growing marketplace, there seems to be a never-ending supply of new methods that are touted as the next best thing.
Pipe bursting is often considered to be a rehabilitation technique and frequently compared to CIPP lining. However, in reality, pipe bursting is a renewal process as it installs a new pipe in place of the old one. With that said, pipe bursting can be looked at in terms of feasibility vs. open-cut construction, slip lining and/or CIPP. For an owner, research is important to gain a general understanding of the technology and its applications. Like many technologies, lingo and terminology can be hard to understand (this subject was the focus of an article in the May 2011 issue of Underground Construction) which leaves an owner somewhat confused through the feasibility, design, bid and construction stages of a project. There are many sources for learning the basics as well as more advanced means and methods considerations including trade shows such as UCT or No-Dig, a NASTT good practices course, or studying the IPBA guideline and case studies.
A system owner recently had his first experience bidding and awarding a pipe bursting job. Although the project was successful, there were some stressful moments through the process which were unnecessary. The owner had a 24-inch VCP gravity sewer line that ran cross country approximately 400-feet through a number of private utility easements. The pipe was shown during a CCTV inspection to be partially collapsed and had a number of sinkholes developing above the pipe on private property. In considering open-cut construction, the damage caused to the private property and mature trees would have been significant and costly. CIPP would have limited success and require a costly excavation to repair the partial collapse that measured almost 50-feet in length. In considering pipe bursting, the owner liked the process and the benefits but was simply unfamiliar with how to best bid, award and make sure the project was executed correctly.
In the design stages, the owner called an IPBA contractor and asked simply “How can this be done by pipe bursting, what are the considerations, and what could go wrong?” This was a very straight forward question and one that deserved a comprehensive review of the project and burst plan. In the site evaluation, it was clear to the contractor that pneumatic pipe bursting would be the preferred method and using the IPBA guideline was able to show in detail the process and considerations that would be part of the planning of a Class C pneumatic pipe burst. The 24-inch pipe required a new 24-inch HDPE pipe be put installed and the owner had not installed HDPE pipe before in a continuous application. Therefore, it was very important to review the area needed for fusing and staging of the pipe as well as insertion into the pit which would be located in a way to minimize disruption to the site.
Through the preliminary design and planning, the owner began to get a picture of what the project would look and feel like and what benefits and challenges he would need to be prepared to deal with. Contingency plans were discussed and risk properly allocated in the contract documents.
On day one of the project the owner began to gain a sense of reality as 50-foot pieces of 24-inch HDPE pipe was unloaded and fused into a continuous 400-foot pipe alongside the roadway. The winch and hammer was delivered to a small receiving pit being excavated on one end of the jobsite and another machine excavated a 20-foot pipe insertion pit at the other end. Set-up was completed and the next day would be important for the owner and project team.
Early the following morning final preparation included pulling the pipe into place, attaching the hammer, setting the final configuration of the winch and support equipment such as an air compressor and mud system. The owner was amazed that the 24-pipe pipe could be maneuvered in a way to enter the insertion pit and make a 90 degree turn out to the city street. Neighbors started asking many questions and at this point the owner was easily able to explain the process and why the city chose it. As the pipe was inserted, the hammer and winch started and the pipe burst was officially underway. At this point, the owner was anxious to see the pipe successfully exit almost 400-feet away. The pull, which ran under four properties, was completed in about one hour and 20 minutes. Once in place, the owner’s crew was able to make final connections back to the existing structures and sewer flow restored early on the third day.
In summary, the owner had a choice to make and in considering and constructing a project with a method that was considered alternative in his area. There were some unknowns and comfort building that was assuaged with the successful install.
FOR MORE INFORMATION:
IPBA (NASSCO), (410) 486-3500, www.nassco.org