Pipe Bursting in Bloomfield

Pre-chlorinated technique best suited for pipe replacement project in historic Michigan residential community.
Pipe Bursting in Bloomfield
Pipe bursting requires relatively small excavations such as this one to access the existing water main and valves instead of open cutting the entire run. Olivia Olsztyn-Budry, Bloomfield Township engineer, says prechlorinated pipe bursting was chosen for the water service upgrade project to minimize pavement demolition and reconstruction.

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Bloomfield Village, Michigan, is a 1,000-home section of Bloomfield Township, about a 30-minute drive northwest of Detroit. Gracefully winding, tree-lined residential streets branch off into carefully landscaped lanes and cul-de-sacs that provide access to homes maintained under guidance from the village’s homeowners association. Generations of residents here have worked hard to maintain the serenity and pleasing aesthetics of Bloomfield Village since its establishment in 1924.

Thanks to prechorinated pipe bursting, Bloomfield villagers were spared the property disfigurement and detouring traditionally associated with water main renovation.

Olivia Olsztyn-Budry, Bloomfield Township engineer, says almost from the beginning plans for the four- to five-year water service upgrade specified prechlorinated pipe bursting replacement. Open cut required pavement demolition and reconstruction, which Bloomfield Township preferred to avoid.

Olsztyn-Budry says other underground trenchless replacement methods were considered, such as horizontal drilling, but the pipe bursting technique was most conducive to the limited space available along the street right-of-ways in the village. With no rig to position as in the horizontal drilling technique, and working to and from comparatively small access pits, pipe bursting presented the least amount of disruption to traffic. Nor was residents’ water service interrupted except for the single day that work was performed in front of their homes.

Pipe bursting specialist

Pipe bursting specialist Bidigare Contractors of Northville, Michigan, was the low bidder for the multiphase project, expanding its workforce in a joint venture with D’Angelo Bros Utilities of Farmington Hills, Michigan.

For bursting operations Bidigare used its own hydraulic pipe bursting machine, a HammerHead Hydroburst HB100. Although the machine is capable of up to 100 tons of pulling force, John Bidigare, vice president of Bidigare Contractors, says the average burst required only about 20 tons.

Bidigare Contractors began replacing the 17,000 feet of Phase I pipe in October 2013, completing the first 3,000 feet as scheduled before shutting down for winter in November. Work resumed in March 2014.

Replacement specifications

The Bloomfield Village water system enhancement project launched with three primary objectives: replace aging and undersized water mains, replace and upgrade fire hydrants and improve coverage, and replace and add water system valves for more reliable water system operation. It was designed to take place in four phases, giving highest priority to sections that were most urgent. Phase triage considered three factors: age of pipe involved, water main breakage record, and potential conflicts with utilities.

Portions of Bloomfield Village’s legacy water system range in age from 47 to 90 years old. The newest sections of the 11 miles of ductile iron pipe, valves and hydrants were installed in 1968.

Most bursting in the Phase I stage of the project involved 8-on-8 replacement of ductile iron pipe with high-density polyethylene, with some sections of 6-inch ductile iron to be upgraded to 8-inch HDPE.

Prechlorinated pipe replacement

Originally a method devised in Europe, the prechlorinated pipe bursting technique was first introduced to the U.S. for a Florida municipal water main replacement in 2000. Fifteen years later the technique is commonly used throughout both the United States and Canada.

In his presentation to Bloomfield Village’s water main board, Bidigare explained in detail how prechlorinated pipe bursting would be conducted, property by property.

The process begins on the surface by fusing sticks of HDPE to the length required to complete a burst. The fused pipe is pressure tested, chlorinated and tested for bacteria by a state-certified lab. Then it is sealed at both ends, one with an 8-inch DIPS pulling head fused onto it and the other with a fused cap.

The prechlorination process can take up to two days. Once sealed, the sterilized pipe can remain this way for up to two weeks prior to use in the replacement process, which allows for staging pipe in advance of a series of bursts.

Installation process

Prior to each burst, Bloomfield Village utilities were located and flagged. Residents received 24 hours’ notification of when they would lose water service, which usually lasted eight to 12 hours. For many residents, the shut-off occurred at the time of day when they were away from home, minimizing disruption to their daily routines.

Each evening prior to the next day’s bursting operations, the crew prepared two 5-by-10-foot access pits, 5 to 6 feet deep. One would serve as a working pit with the pulling machine in it, and the other as the replacement pipe entry pit, where the bursting run would begin.

During a typical 10- to 12-hour shift that included a pipe bursting run, the burst itself generally took between two and three hours to perform.

Pull rod was paid out from the HB100 through the existing pipe to the entry pit. A flex joint connected the pull rod to a pulling head nestled inside a hollow body expander. The expander’s function is to fracture the existing pipe and press it away from the pipe path, leaving sufficient room for the pulling head and replacement pipe.

Expanders are typically 25 percent larger than a pipe’s nominal diameter. For the 8-inch HDPE in this application, the expander was 10 inches in diameter. The replacement pipe, which was fused directly to the pulling head, was drawn along behind the pulling head as the assembly progressed.

Once in place, crews flushed the pipe, reattached the residential service to the main and activated the water system. Other than the access pits, the only other landscape affected was a 3-by-3-foot pit to access the water service shut-off valve. Though pipes were believed to be sterile, residents were advised by the city to boil drinking water during the next day or two, until receiving confirmation by a certified laboratory that their water did indeed pass regulatory guidelines.   

Compression and ground memory

Ground material and pipe fragments compressed to the sides during a burst soon press back in around the replacement pipe after the run is complete. This tendency of ground conditions to restore themselves after bursting compression is referred to as soil memory.

The compression from the bursting head is actually confined to just a short radius in the ground immediately surrounding the pipe and does not affect the surface, which is several feet above the compression area. Nor does it impact nearby utilities.

Sensitive or rigid structures such as foundations, footings, brittle casings and manholes lying within the bursting run’s anticipated compression area may require precautionary measures but once identified are rarely obstacles that prevent a burst. The contractor didn’t encounter any such obstacles on this project.

Nate Hrabosky, a HammerHead bursting and ramming technician, says that when experienced contractors such as Bidigare discover such obstacles, the solution is to “shed daylight on them.” A small excavation is made to remove material at the point of interference, which eliminates the compression factor.

“Vacuum excavation is excellent for this, since it makes such a small hole and any fill sucked out is easily pumped right back in afterward,” Hrabosky says.

Bidigare Contractors replaced between 200 and 500 feet of pipe a day using this method. Olsztyn-Budry says the township is pleased with how well the pipe bursting process has been working. The number of lines included as part of Phase I was increased, and she says Bidigare Contractors is right on schedule.


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