Texas Municipality Finds In-House Pipe Bursting with Restrained-Joint PVC Pipe Efficient and Cost-Saving

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Ami Lamb
6 years ago
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Texas Municipality Finds In-House Pipe Bursting with Restrained-Joint PVC Pipe Efficient and Cost-Saving North American Pipe 's CertaFlo Greenline Helps Maryland Water and Wastewater Utility Minimize

1 Texas Municipality Finds In-House Pipe Bursting with Restrained-Joint PVC Pipe Efficient and Cost-Saving North American Pipe 's CertaFlo Greenline Helps Maryland Water and Wastewater Utility Minimize Disturbance in Congested Areas Greenline Offers Ideal Solution for Aging System Application: Water & Force Main Sewer Project Type: Static Pipe Bursting Owner: City of Brownwood Product Used: CertaFlo Greenline Equipment: TT Technologies Grundoburst 800 G Five years ago, David Harris, director of utilities for the City of Brownwood, Texas, was looking for a more practical, efficient way to update the city's aging wastewater collection system. Many of the clay gravity-fed sewer mains were getting close to 100 years old and had become severely cracked over the years by heavy clay soil that expands and contracts in response to varying moisture conditions. Over time, tree roots infiltrated these cracks and filled the sewer mains, leading to back-ups, overflows and the crumbling of pipe bells. These problems, combined with population growth on the outskirts of the original infrastructure, made apparent the need for the progressive replacement of several miles of pipe using the most efficient, budget-conscious means possible. After researching and evaluating a variety of different pipe materials and installation methods, Harris ultimately chose static pipe bursting to replace the clay sewer mains with restrained-joint polyvinyl chloride (PVC) pipe. In September 2007, the City of Brownwood rented a TT Technologies Grundoburst 800 G static pipe bursting system with 100,000 pounds of thrust and 200,000 pounds of pullback power and got ready to work. After only four days of training from TT Technologies, the Brownwood crew was ready to begin its first pipe bursting project. Within the timeframe of just a few weeks, static pipe bursting proved to be a fast, low-cost method for getting the job done. For Brownwood's municipal maintenance staff, which handles the bulk of the city's water and sewer system maintenance, it was also easy to learn, as they quickly became highly proficient in the process. At this point, five years later, Brownwood now owns the Grundoburst 800G and has used it in more than 80 projects to replace approximately 4 miles of clay sewer main, ranging in size from 6-inch to 10-inch, with 8-inch, 10-inch and 12-inch restrained-joint PVC pipe. The ongoing positive results of Brownwood's static pipe bursting sewer projects have made Harris an outspoken advocate for this pipe replacement method and the use of restrainedjoint PVC pipe. Serving nearly 1.8 million residents and maintaining more than 5,500 miles of fresh water pipeline and nearly 5,400 miles of sewer pipeline in the Maryland suburbs of Washington, D.C., Washington Suburban Sanitary Sewer Commission (WSSC) is the eighth largest water and wastewater utility in the nation. With the congested population and affluent neighborhoods in its service area, the WSSC is constantly looking for new ways to minimize disturbance to traffic and private residences during water and sewer main maintenance. The traditional open-trench method of replacing water and sewer pipe in urban and suburban areas often tears up landscaping, uproots trees, blocks driveway access and sometimes forces the closure of multiple traffic lanes on busy roads. It was factors like these that drew the WSSC to the less-invasive trenchless pipe replacement method of pipe bursting a few years ago. "We're currently under a mandate to take care of a lot of problems in our water and sewer systems before 2015, and part of that involves pipe replacement," says Mike Trail, construction manager for WSSC. "We have an abundance of 70-year-old clay pipe that has simply outlived its useful life. One of the biggest complaints we were getting about our water and sewer projects was the footprint that they were leaving on the community. Since we started using pipe bursting on our projects, it's helped minimize that footprint."

2 With pipe bursting, contractors can burst water and sewer mains under roads, sidewalks, back yards, creeks, groves of trees and other congested or sensitive areas without disturbing the surface, except for re-tapping services and excavating pits at the start and finish points. Pipe bursting is more cost-effective than an open-trench installation under asphalt or landscaped areas at any depth. And, it's inherently more affordable than open-trench any time the depth requires trench safety devices, regardless of surface materials or conditions. Pipe bursting also allows contractors to reduce their carbon footprint, since it doesn't require nearly as much excavation or disruption of landscaping as opentrench jobs and results in fewer loads of dirt and rock taken to dump sites. The pipe bursting installation method involves utilizing hydraulically powered machinery to split the existing pipe with a specially designed cutter head while simultaneously pulling new pipe back through the annular space previously occupied by the original pipe. In some cases, including many of the projects being undertaken by WSSC, an expander head is also added to the pull string directly behind the cutter and immediately ahead of the new pipe string. This allows the annular space to be increased during pull back forcing the original pipe fragments out into surrounding soil to make room for the larger diameter new pipe being pulled in behind it. WSSC started out using static pipe bursting to replace the old clay pipe with high-density polyethylene (HDPE) pipe, but this led to new "footprint" problems. Before each pipe pull, separate lengths of HDPE had to be fusion-welded together into one large 500-foot string of pipe, which got in the way and frustrated homeowners and businesses in the area. Last year, WSSC's trenchless contractor, Midas Utilities Inc., of College Park, Md., recommended using North American Pipe's CertaFlo Greenline, a restrained-joint polyvinyl chloride (PVC) sewer pipe. CertaFlo Greenline pipe is available in 10- foot lengths, as well as standard 20-foot lengths, to further decrease disturbance to surroundings. In addition to the shorter pipe lengths occupying less space, the restrained-joint PVC pipe can be quickly and easily assembled as pipe pullback continues. After observing Midas Utilities do a pipe bursting project with CertaFlo Greenline for another client, the WSSC was convinced that this combo would be a good fit for its own projects. "We had some areas where we simply couldn't string out a few hundred feet of HDPE pipe," Trail says. "For example, we had two project sites in downtown Silver Springs, Md., where that was not going to be possible, since the pipe would cross through a business district and a state highway. In order to string out the pipe, we'd have to go across the highway and you just can't do that. In areas like that, it's helpful for the contractor to have the option of shorter pipe lengths and be able to assemble them stick by stick. And, without the need for pipe fusion, the job moves along more quickly." So far, Midas Utilities has installed about 1,500 feet of restrained-joint PVC sewer pipe in three projects for WSSC, using a TT Technologies Grundoburst 800G Static Bursting System,n 80 metric-ton machine, with 176,000 pounds of pullback. The projects have all gone smoothly, and the WSSC has plans for more projects in the near future using pipe bursting with restrained-joint PVC sewer pipe. Most importantly, the feedback from homeowners is becoming much more positive. "We had one recent job, where we were going under people's yards, mature trees and a slate driveway and retaining wall that we would have had to tear out if we hadn't used pipe bursting," says David Ventresca, owner of Midas Utilities."The homeowners were all thrilled when we got the project done with a minimal amount of digging. It worked out great for everybody."

3 Serving nearly 1.8 million residents and maintaining more than 5,500 miles of fresh water pipeline and nearly 5,400 miles of sewer pipeline in the Maryland suburbs of Washington, D.C., Washington Suburban Sanitary Sewer Commission (WSSC) is the eighth largest water and wastewater utility in the nation. With the congested population and affluent neighborhoods in its service area, the WSSC is constantly looking for new ways to minimize disturbance to traffic and private residences during water and sewer main maintenance. The traditional open-trench method of replacing water and sewer pipe in urban and suburban areas often tears up landscaping, uproots trees, blocks driveway access and sometimes forces the closure of multiple traffic lanes on busy roads. It was factors like these that drew the WSSC to the less-invasive trenchless pipe replacement method of pipe bursting a few years ago. "We're currently under a mandate to take care of a lot of problems in our water and sewer systems before 2015, and part of that involves pipe replacement," says Mike Trail, construction manager for WSSC. "We have an abundance of 70-year-old clay pipe that has simply outlived its useful life. One of the biggest complaints we were getting about our water and sewer projects was the footprint that they were leaving on the community. Since we started using pipe bursting on our projects, it's helped minimize that footprint." With pipe bursting, contractors can burst water and sewer mains under roads, sidewalks, back yards, creeks, groves of trees and other congested or sensitive areas without disturbing the surface, except for re-tapping services and excavating pits at the start and finish points. Pipe bursting is more cost-effective than an open-trench installation under asphalt or landscaped areas at any depth. And, it's inherently more affordable than open-trench any time the depth requires trench safety devices, regardless of surface materials or conditions. Pipe bursting also allows contractors to reduce their carbon footprint, since it doesn't require nearly as much excavation or disruption of landscaping as opentrench jobs and results in fewer loads of dirt and rock taken to dump sites. The pipe bursting installation method involves utilizing hydraulically powered machinery to split the existing pipe with a specially designed cutter head while simultaneously pulling new pipe back through the annular space previously occupied by the original pipe. In some cases, including many of the projects being undertaken by WSSC, an expander head is also added to the pull string directly behind the cutter and immediately ahead of the new pipe string. This allows the annular space to be increased during pull back forcing the original pipe fragments out into surrounding soil to make room for the larger diameter new pipe being pulled in behind it. WSSC started out using static pipe bursting to replace the old clay pipe with high-density polyethylene (HDPE) pipe, but this led to new "footprint" problems. Before each pipe pull, separate lengths of HDPE had to be fusion-welded together into one large 500-foot string of pipe, which got in the way and frustrated homeowners and businesses in the area. Last year, WSSCâ s trenchless contractor, Midas Utilities Inc., of College Park, Md., recommended using North American Pipe's CertaFlo Greenline, a restrained-joint polyvinyl chloride (PVC) sewer pipe. CertaFlo Greenline pipe is available in 10- foot lengths, as well as standard 20-foot lengths, to further decrease disturbance to surroundings. In addition to the shorter pipe lengths occupying less space, the restrained-joint PVC pipe can be quickly and easily assembled as pipe pullback continues. After observing Midas Utilities do a pipe bursting project with CertaFlo Greenline for another client, the WSSC was convinced that this combo would be a good fit for its own projects.

4 "We had some areas where we simply couldn't string out a few hundred feet of HDPE pipe," Trail says. "For example, we had two project sites in downtown Silver Springs, Md., where that was not going to be possible, since the pipe would cross through a business district and a state highway. In order to string out the pipe, we'd have to go across the highway and you just can't do that. In areas like that, it's helpful for the contractor to have the option of shorter pipe lengths and be able to assemble them stick by stick. And, without the need for pipe fusion, the job moves along more quickly." So far, Midas Utilities has installed about 1,500 feet of restrained-joint PVC sewer pipe in three projects for WSSC, using a TT Technologies Grundoburst 800G Static Bursting System, an 80 metric-ton machine, with 176,000 pounds of pullback. The projects have all gone smoothly, and the WSSC has plans for more projects in the near future using pipe bursting with restrained-joint PVC sewer pipe. Most importantly, the feedback from homeowners is becoming much more positive. "We had one recent job, where we were going under people's yards, mature trees and a slate driveway and retaining wall that we would have had to tear out if we hadn't used pipe bursting," says David Ventresca, owner of Midas Utilities."The homeowners were all thrilled when we got the project done with a minimal amount of digging. It worked out great for everybody." Static pipe bursting has worked out very well for us, as it allows us to get a lot of work done in a short time," Harris says. "Plus, operating the equipment and assembling the pipe is not rocket science. That's one of the main reasons why we're doing pipe bursting, I don't have to send my staff to school to get certified before they can start on a job." The Method Static pipe bursting utilizes hydraulically powered machinery to fracture the existing sewer or water main, referred to as the "host pipe," with a cutting head specifically designed for cutting through the material of the host pipe. The cutting head is followed by an expander, which disperses host pipe fragments and increases the diameter of the hole. Attached to the rear of the expander is the new replacement pipe, which is pulled in simultaneously. This differs from pneumatic pipe bursting, a more common pipe bursting method where the bursting of the host pipe is done by a pneumatic soil displacement hammer connected to a hydraulic variable speed winch. Due to the force exerted by the pneumatic hammer, pneumatic bursting is only recommended for use with a more flexible pipe material. Static pipe bursting, however, is compatible with virtually any type of replacement pipe material, including restrained-joint PVC. The Pipe For its sewer bursting projects, Brownwood uses North American Pipe's CertaFlo Greenline restrained-joint PVC pipe, which is manufactured specifically for pipe bursting and other trenchless applications. Though somewhat new to the pipe bursting market, restrained-joint PVC offers several benefits over other thermoplastic pipe materials. For example, it provides improved mechanical properties, higher pressure ratings and better flow performance than high-density polyethylene (HDPE) pipe, and it allows municipalities to stick to a proven, long-lasting material that works seamlessly with existing infrastructure. And, equally as important, it makes pipe installation move faster with a simple assembly process. CertaFlo Greenline, for example, is assembled in 10- or 20-foot lengths with spline-locked integral bell ends as pullback continues, allowing pipe installation to continue at a steady pace. When Brownwood began its pipe bursting operations, the maintenance staff used a mix of 10-inch HDPE pipe and 8-inch and 10-inch CertaFlo Greenline to compare the two materials. The crew members largely preferred the

5 restrained-joint PVC pipe to HDPE, due to its ease of installation and ability to be assembled during pullback instead of before the pull. "With HDPE, we found that it takes three people about eight hours to fuse the pipe and then it has to have a cool-down period," Harris says. "Then, we had to have a place to put a 340-foot string of pipe. With restrained-joint PVC, however, we can actually put the pipe together as it's being pulled into the ground, and it only takes us about 45 minutes to get all the rods in," Harris says. "We don't have to assemble the pipe the day before or show up a few hours early to do it." Having the option of both 10- and 20-foot lengths with the CertaFlo Greenline pipe helps the Brownwood crew to have less waste on the jobsite, and the 10- foot lengths of pipe can also be assembled in a trench box in situations where less space is available. "If we have too much pipe left, we simply take the end piece off, put it back on the truck and use it next time," Harris says. We generally order a few 10-foot joints, either to start with or to finish with in those types of situations." Through the use of static pipe bursting, the Brownwood crew is not only able to replace 6-inch clay mains with 6-inch PVC, but also can increase the size of the main by two pipe sizes. Over the past five years, the 10-person crew has replaced 6-inch clay with both 8-inch and 10-inch pipe. The minimum grade for 6-inch pipe is.5 percent, or a 6-inch drop every 100 feet. For 8-inch pipe, minimum grade is.33 percent or a 4-inch drop per 100 feet, and minimum grade for 10-inch pipe is.25 percent or a 3-inch drop per 100 feet. So, by replacing a 6-inch main that is exceeding its designed capacity at minimum grade with a larger-diameter pipe at the same grade, the city gets a better pipe installed at a grade off of the minimum edge of the recommended slope and a significant increase in capacity. This increases capacity to accommodate past and future population growth. Pipe bursting pulls in Brownwood usually average around 300 feet, with the longest being close to 600 feet,the most allowed by the amount of rods the city owns. Each pull usually goes from one manhole to another, and the distance between manholes rarely exceeds 400 feet. No matter the length, CertaFlo Greenline pipe has always displayed excellent joint integrity during pulls, holding together very well. The Brownwood crew completed a 550-foot pull this past February with no problems whatsoever. Reaping the Benefits Through static pipe bursting with restrained-joint PVC pipe, the City of Brownwood has not only made sewer main replacements run more quickly and efficiently, but has also decreased disturbance to homes, businesses and roadways and significantly reduced costs. The amount of excavations needed is 84 percent less than an open-cut job, which leaves much of the landscaping unscathed and greatly reduces the need for backfilling and relandscaping after a project. Homeowners and business owners have been pleasantly surprised at how non-invasive the pipe bursting projects have been. "In every scenario, pipe bursting is less expensive and far less disruptive to our customers than open cut," Harris says. "We're able to burst under roads, flower gardens, fences, trees and other important landscaping, and people really appreciate that. It really shocks people when we finish and we haven't even been there that long. They're always asking how we could replace the pipe without leaving a hole in the street." The city also saves money by owning the pipe bursting equipment and supplying

6 the labor, which enables it to run on its own schedule and control the quality of installation. "We put one of our jobs out to bid and found that the contractor's price is $65 to $100 per foot of pipe installed," Harris says. "For us to take a 6-inch clay pipe and replace it with 8-inch, it costs us $25 a foot and that's for materials and labor. So, doing the sewer main bursts in-house saves us a considerable amount of money." Today, Harris continues to spread the word about the advantages of static pipe bursting with restrained-joint PVC pipe to other municipal sewer and water officials through occasional speaking engagements at industry conferences, where always offers an open invitation to visit Brownwood and observe one of his crew's ongoing sewer main bursts. Visitors are frequently impressed by the demonstration and use that experience to begin talking seriously about giving static pipe bursting a try in their own towns and municipalities. "We've had city engineers and municipal maintenance staff from all over Texas come out to observe our bursting projects and have their questions answered," Harris says. "They all want to know how it works, and the best way for them to learn is to watch an actual project take place and witness how efficiently it runs. It gives us a good opportunity to teach people how static pipe bursting works. When I tell them we can do a sewer burst for $25 a foot and put 400 feet of pipe together in an hour, they don't believe it. But, after you actually see it being done, there's no way you can't believe it. It's something you just have to see." For more information contact... Robert Eads North American Pipe Richardson, TX Mobile: Fax: reads@northamericanpipe.com

Garrett Richardson Mission Clay Products

Pipe Bursting with VCP - Addressing Space Constraints in Densely Populated Areas Garrett Richardson Mission Clay Products The 5 lengths of VCP were a critical asset in the tight working space. The City