Reviving a Water System
For anyone in the public sector, keeping citizens happy while improving their lives is not always an easy task. In Miami-Dade County, Fla., an ongoing water revitalization project that might have required ripping up streets and destroying highly prized, decorated driveways could have provoked a civil uprising even though municipal water was dwindling to a trickle.
Fortunately, Miami-Dade’s water distribution chief, Luis Aguiar, determined that the old pipe system could be replaced and properties protected by using high-density polyethylene (HDPE) pipe. To ensure the delicate nature of the project was handled properly, Aguiar established an in-house crew to do the work.
With a potable water system approaching the halfway mark of its projected lifespan, Miami needed to start replacing the 2-in. galvanized line in 1999 to address the vast number of leaks in pipe joints and walls, and a system constricted due to tuberculation down to the size of a pencil. Completion of the pipe replacement will take at least another 20 years.
“What is being experienced in Miami is the same as the rest of the country,” said Tony Radoszewski, executive director of the Plastics Pipe Institute, Inc. (PPI). “The infrastructure is crumbling. Water is being wasted. Costs keep going up. Rate-payers pay more, and needlessly. There’s a ready solution at hand, just as Luis Aguiar found.”
“A leak-free system using HDPE pipe can be installed without a lot of property destruction and because it is corrosion-resistant, it will outlast any other type of system,” he added. “Plus, high-density polyethylene is a material that eliminates the problem of tuberculation because it does not support biological growth. And the need is critical. Just last year, the Miami-Dade district requested from the state more than $4.5 billion to fund capital improvement projects.”
“There are at least 500 miles of water pipe that need to be replaced,” Aguiar said. “In addition to the restricted flow, in many places the pipes have been disturbed and broken from the hurricanes; it’s the trees that have been pulled up and the roots taking the pipes. Plus, the very low water table eats into the metal pipes.”
Making Old Water Lines New
The Miami-Dade Water and Sewer Department (MDWASD) is one of the largest public utilities in the U.S. It provides service to more than 2.4 million customers. Approximately 330 million gal of water are drawn every day from the Biscayne Aquifer for consumer use. MDWASD has more than 7,000 miles of water lines.
Water pressure for the system should be between 58 and 60 psi. Because of the disintegration of the system, it is typical to find pressure in the low double digits; however, no one complains.
“People don’t realize they’re not getting enough water out of the shower because tuberculation gradually slows it down,” Aguiar said. “When we get a call, it’s usually because the flow is down to 1.5 cu ft a second and the pressure is below 20 psi. It’s like they have no water at all. Plus, the underground lines leak. So we go in and supply a brand new 2-in. HDPE line. Water pressure is immediately restored, and water is no longer being wasted from cracked pipes. For our customers, it’s like a brand new day and they’re seeing sunshine for the first time. And that’s a good feeling for us.”
Because the water department must maintain the water lines, which are mostly found in alleyways behind the houses, Aguiar had to find an efficient method that would bring in the new pipe and be effective without creating a nightmare for the residents of Miami-Dade County. In Miami, there are many art deco driveways. Homeowners decorate their driveways with poured, colored and tinted concrete, and they will not allow Miami-Dade to rip up it up—even to provide better water service.
For Aguiar’s crew, the process is pretty straightforward because the pipe replacement technique they use is nonevasive and moves quickly. Once the area for reclamation is determined, the smallest trench possible is dug and the galvanized pipe cut and split. Rods are inserted and pushed through the old pipe. At the end of the run, HDPE pipe is fed through and pulled back.
“Galvanized pipe is tough, and splitting it is really different from eliminating the newer cast iron,” Aguiar said. “Galvanized pipe reduces our efficiency, but we make it happen. Because we’re doing the work in house, our crews get inventive. We designed our own cutter head in the shop, and it is doing a great job.”
On a typical day, a three-person crew installs 300 to 500 ft of new HDPE pipe. “Our largest pull was 550 ft,” Aguiar said.
According to Frank Lopez, HDPE product manager for HD Supply Waterworks, Thomasville, Ga., who works closely with the water department, the pipe was selected because of convenience and performance. “Because the pipe is delivered in 500-ft coils, it’s easier to transport and unroll at the job site. Plus, it’s just more economical and flexible to work with.”
EndoTrace HDPE pipe by Endot Industries, Rockaway, N.J., was selected because of its high ultraviolet (UV) protection and tracer wire that makes it easy for a crew above ground to find the buried pipe. The average temperature in Miami is in the mid- to high 80s, and with the coils sitting out in the supply yard exposed to intense sunlight for long periods of time, it is important that the pipe have the proper UV stabilization package.
Both HD Supply Waterworks and Edot Industries are PPI member companies.
“One of the most important aspects that should not be overlooked is that we have a tremendous water shortage in south Florida,” said Aguiar. “And so we must have the most waste-proof system possible. Being able to split the old pipe and install a single pipeline down the narrow alley, in the long run, is going to help tremendously.”
“We believe that a great percentage of the water accountability problems we have are in those old lines,” he added. “Our water loss is below 8%, but that is a significant number, especially when you’re pumping 360 mgd (million gal per day), and the 500-plus miles of leaking alley mains are contributing.”
The cost of splitting an old line and inserting HDPE pipe can be 33% to 66% less than the traditional dig-and-replace method, according to PPI. Due to the longevity of the new HDPE pipe, the cost benefit can hit 300%.
“Replacing old pipe with a new line such as they’re doing in Miami can be accomplished only with HDPE pipe, and the benefits are numerous aside from low material and labor costs,” said Bruce Kuffer, P.E., manager of polyethylene market development for PPI. “Because there is significantly less road and environmental disturbance, a safer work area is promoted; there are about 50 people each year who die in trenching and excavation accidents. Plus, there is less disruption to the neighborhood and a much shorter construction time, which lowers liability exposure.”
Kuffer elaborated on the process of this HDPE pipe installation: “The pipe used by Miami-Dade, which they considered the main line at the time it was installed, was originally 2-in.-diameter,” he said. “And because it is being replaced by 2-in.-diameter HDPE pipe in 500-ft coils, it means that even long runs can be one, joint-free continuous piece. And when connections are made to homes or pipe sections added, these are literally melted together, which makes the system leak-free. This seamless, jointless system provides a longtime utility solution.”
Dan Mathews, Miami-Dade’s assistant superintendent for the Water Transmission and Distribution division, is a true fan of the operation, especially since it helps him solve a different puzzle nearly every day. “When the pipe was put in, there was no code enforcement or even a building code. That’s why there is no dedicated easement for the pipelines and it runs under alleyways,” he said. “If it weren’t for the trenchless method and the HDPE pipe, I think we’d have a pretty messy situation and very angry customers because we’d have no choice other than to do major excavation.”
“Even now, we run into gas and other utility lines crisscrossing our path,” Mathews continued. “But again, because we’re not in there with heavy equipment, we can control the path and the speed of the installation. That gives us a real advantage.”
The crew uses a compact, hydraulically operated, static pipe-splitting system that can fit in a small trench. It was selected also because it has the power to crack the older galvanized pipe, especially a coupling that doubles the thickness of the walls.
“In the trench, we feed the 1-meter-long rods through the old pipe and hook into the cutter with an expanding cone that splits the pipe and knocks down any sharp edges inside the pipe,” Mathews said. “Then the HDPE pipe is hooked up at the other end and pulled back.”
In Miami-Dade, service runs to the property line where the meter is placed. Connection to the main is done by electrofusing side-saddle tees from Central Plastics, Shawnee, Okla., also a PPI member company.
“We make the connection to the meter, and water is running typically within a few hours,” Mathews said. “We want our operation to be safe, reliable and efficient.”
“Miami-Dade is solving more than water loss and diminished water power,” Radoszewski said. “It is safely providing a system that will last and perform for generations, which is keeping today’s residents happy, improving their quality of life and protecting property. In light of what they are doing to save natural resources, protect the safety of their workers and deliver a value-enhanced pipeline, Luis Aguiar, Dan Mathews and the in-house crew are truly heroes in the community.”