As officials from Miller Pipeline Corporation and Earth Tool Company considered bidding on a major mainline sewer replacement project in Plano, Texas, last February, they realized portions of it were bigger than anything either had tackled before. But, Mark Hallett, vice president of the Utility division for Miller, and Mark Randa, Earth Tool Company's director of pneumatics, believed a quadruple upsize — 24-inch reinforced concrete pipe (R.C.P.) to 32-inch outside-diameter (O.D.) HDPE — could be done. It was just going to be a matter of having suitable planning, teamwork, and the right primary tools and support equipment.
Left: The supersized bursting head is removed from the pipe in a right-of-way crowded with above ground obstacles.
The overall job called for updating 6,200 feet of a 30-year-old R.C.P. system deteriorating from H2S gas and significant amounts of rain by replacing current pipe capacities of 24, 27 and 30 inches with 32-inch O.D. The length of the job didn't particularly bother Hallett and his team — Miller has been known to do 50,000-foot projects before. But, as Hallett quickly points out, "Those jobs were 8-, 10-, 12-, or 18-inch pipe."
Miller Pipeline owns a 225-ton static bursting machine, which Hallett was confident could at least handle the size-on-size portions of the job.
"We weren't even too worried about the 30- to 32-inch bursts," he says. "We were a little conservative on the 27- to 32-inch runs, but we were very concerned about the 24-inch R.C.P. upsize."
As he became serious about bidding the project, Hallett called upon Randa and Earth Tool Company of Oconomowoc, Wisconsin, makers of the HammerHead Mole™ products, to bring in some engineering expertise and custom equipment to help get it done.
"Ninety-five percent of the equipment we own is HammerHead Mole," Hallett says. "I knew we didn't have a piece of machinery that could handle a job like this, so I asked them to develop a system that could perform under these conditions."
Randa was quite familiar with Hallett and his team, having worked with the group several times during his 14-year history with Earth Tool Company. But neither he nor Mike Walk, the ram and burst specialist from Earth Tool Company who later became involved with the project, had performed an upsize of this magnitude either. They echo Hallett, who says, "This is not the biggest job we've ever done in terms of length, but certainly the biggest that we've undertaken in terms of complexity."
On the "complexity" front, the upsize was just one of many challenges the team faced. Add to the list difficult proximity to above-ground obstacles, incredible bypass requirements, a right-of-way crowded with existing utilities, tough ground conditions, and brutal weather. They all came into play at one point or another. In fact, one irony was that the very thing that forced urgency on the job in the first place pushed its finish back a month before all was said and done ... rain. The time allowed for the job was 130 days. Originally, the target finish date was August 31, but it was moved back to September 31 as Texas was hammered with more rainfall in June alone than the state received during all of 2006.
Miller, with help from Godwin Pumps, configured a completely redundant system capable of handling 16 million gallons per day (mgd), taking out 8,000 feet of bypass. Hallett says that at one point, though, their system ended up pumping through more than 36 million gallons of water per day because of all the infiltration from rainfall. "At times, we were pumping and using the same line just to keep things from surcharging," he says.
The Bursting System
Earth Tool Company was primarily involved in just under 1,000 feet of the job, performed in four bursts — 230, 127, 272 and 188 feet — all of which involved upsizing from 24- to 32-inch O.D. HDPE. Previously, Randa and Walk's largest upsize went to 30 inches, so equipment brought to the site was truly customized:
Crews used a 36-inch bursting head.The head featured a long pilot on the front to keep the tool online and to keep material from collapsing in front of the pipe and impeding progress.It also had a cutting blade designed to cut through the old pipe's concrete and wire mesh.Traditional equipment included:A 20-inch pneumatic tool mounted on the tail of the pipe designed for a "burst-assist."Three compressors: two 900-cfm units to run the bursting head and a 1,300-cfm unit for the burst-assist.A 20-ton winch to pull the bursting head through.
Most of the custom concepts had been utilized before but on a much smaller scale. For example, Randa has added pilots to bursting heads before, but not for an upsize like this.
"We basically stepped up what had already been proven technology," he says.
The 20-inch tool utilized for burst-assist was an interesting component. It's an application that has been used many times before — but most often to save a bore on an HDD project.
"We just turned the hammer on, running very slowly to relieve the pipe drag and keep forward progress," Randa says. "We wanted to have as much energy downhole as possible to complete the job."
The 20-inch tool was also on-hand to back up Miller's static bursting unit in case burst progress slowed or stalled. To save the burst, the rod could be shuttled out of the burst head, through the back end of the pipe. The hammer could be attached, pulled into place and locked into the burst head. The burst could then resume using a combination of static and pneumatic forces.
"Although we didn't use it, it's good to have a contingency plan on jobs of this magnitude," Hallett says.
"The worst thing you can do is to rush through the preliminary planning," Randa says. "If you step back and take a few deep breaths, the problems can be anticipated. You have to think about everything that's going to be good and everything that's potentially going to be bad. Anticipate and create the right scenarios, and you'll end up being fully prepared."
Randa, Walk and team also employed a continuous "lube line" just behind the bursting head, pumping 15 to 20 gallons of polymer per minute, just to keep things moving.
"Frictional drag is a problem with length," Walk says. "If you have instances where you have a large amount of hose on the ground, you can get a larger compressor to make up for it. But you cannot make up for the ground conditions, so we compensated a little, just to be safe."
In the end, the upsize bursts went faster than expected. On the first pull, they intended to gather much of their data, and crews planned on about a foot per minute, according to Randa. But with the rear hammer (burst-assist) and lube, they ended up getting faster than a foot per minute.
Another challenge was being able to get the necessary HDPE pipe, especially within the relatively short timeframe as they were gathering permits and materials approvals. "It's typically very difficult to get a manufacturer to commit to a quoted price and then deliver that quantity of pipe on short notice," he says. "But Isco Pipe came through for us, and once the pipe was delivered, there was nothing stopping us."
"I am not aware of anything this size or this complex going on," Hallett says. "In fact, I cannot recall something this large in the past. The complexity of this job — with the upsize, traffic control, existing utilities, sense of urgency, bypassing, and rain events that we've had, I'm not sure there's been anything like it."
Hallett is particularly proud of his personnel — the superintendent managing the job day-to-day, Ray Gonzales, and the project manager, Brian Smith, working out of Indianapolis.
Mark Randa of Earth Tool Company believes the industry may see more collaboration, especially from Earth Tool Company, as large upsizes become even more common.
"It used to be that anything over 20 or 24 inches was unheard of," Randa says. "But cities are finally changing many of the larger dig-and-place jobs to bursting. And with each job, we become more experienced and our tools become more proven."
Provided by: Earth Tool Company LLC, Oconomowoc, Wisconsin, manufacturer of HammerHead Mole pneumatic piercing tools, pipe-bursting systems, pipe-ramming systems, and directional drilling accessories.