Doubling Down with HDPE
Springfield, Mo., utility uses butt fusion to create new water and gas lines
Atlantic Street in Springfield, Mo., is notorious for water line breaks. It has been torn up more times than locals can count to make repairs on a 1925 cast-iron water main that is buried three to four feet underneath it. All kinds of weather—heat waves, cold snaps, droughts and downpours—can cause the ancient pipe to burst or rip at the joint under the patched street. A recent polar blast that lasted roughly a week resulted in more than a dozen water main breaks, and every one of them occurred on the area’s oldest cast-iron lines.
It is a situation that City Utilities (CU) of Springfield wants to remedy, and it is why the community-owned utility—serving 110,000 customers in a city of more than 162,000—has started the slow process of replacing its crumbling infrastructure on a portion of Atlantic Street where some 126 water customers reside.
One of the most critical decisions CU had to make at their start of its first major renewal program was the type of pipe to use. It had to be durable, and it had to outperform cast-iron pipe.
High-density polyethylene (HDPE) pipe was the top pick because of its leak-free system. Not only is it designed to prevent water breaks, but it also eliminates the environmental waste and costly loss of water from leaking pipes—an ongoing and common occurrence in older lines. CU’s water loss is estimated to be no more than 10%, but that is still significant and not acceptable.
“It’s an extreme amount of money to waste on treating water that’s just going into the ground,” said Jobsite Superintendent James Medlin of Gillespie Excavating Co., the contractor for the project. “I believe HDPE is going to become more of a standard.”
“It costs a lot of money whenever (the main) breaks,” said Brad Marshall, CU’s contract inspector. “It’s an initial cost for CU to do this, but in the long run, it will be a savings to have this polyethylene system in place.”
Gillespie—based in Strafford, Mo.—is midway through the project to replace more than a mile of the 8-in. cast-iron pipe with 8-in. HDPE pipe.
“When we do a test, there’s no leakage,” said Medlin. “It has to be 100% no water leakage or it doesn’t pass.”
Because the cast iron is being left in place under the street and the new HDPE line is being buried in a much deeper 6-ft trench between the curb and the sidewalk, workers did not have to tear up the street.
CU is using the same trench to install a 4-in. medium-density PE pipe for gas service, which is being laid carefully 12 to 18 in. above the new water main.
An essential component of HDPE pipe’s leak-free system is the way it is joined together through the butt fusion process.
CU encouraged Gillespie to use McElroy’s fusion machines, which are engineered to apply the exact level of heat and pressure required to seal the ends of thermoplastic pipe together. When cooled and complete, these welds are as strong as or even stronger than the pipe itself.
Gillespie used McElroy’s TracStar 412 fusion machine to fuse the 40-ft lengths of 8-in. HDPE water line. The track-mounted vehicle is self-contained and self-propelled, so it glided easily from the box truck to the jobsite. Its hydraulic features allow the operator to easily handle the pipe.
For the 4-in. medium-density PE gas line, Gillespie used the Pit Bull 14, which is compact and lightweight, yet rugged enough to do the job.
Third-party industry research indicates that HDPE pipe and joints can have a lifespan of more than 100 years. The water main and gas line renewals are being funded by a three-year increase in utility rates.
Most water mains in the U.S. were unlined cast iron until the 1940s. Though replaced by ductile iron in the ’70s and ’80s, the EPA estimates that 40% of all water mains in the U.S. are still cast iron, which is susceptible to corrosion, breaks and leaks. The EPA estimates water infrastructure replacement needs nationwide at $325 billion over the next 20 years.
CU is very pleased with the progress Gillespie has made. The Atlantic Street water main renewal project sets the stage for future projects.
“I mean, from CU’s standpoint, all of our projects now are being designed with HDPE,” said Marshall.