Georgia is inching toward joining a growing number of states permitting the use of larger-diameter corrugated high density polyethylene pipe products for municipal infrastructure.

The state is conducting its first pilot test of 60-inch diameter pipe in Fort Valley with an $8.5 million project to replace an old clay tile storm water drainage system running through the downtown.

That's two feet wider than the current pipe and a foot wider than the 48-inch diameter maximum size currently allowed for culverts and under-road pipes by the Georgia Department of Transportation (GDOT).

The project in the city of 9,700 just southeast of Macon is likely paving the way for GDOT to join more than half the nation's state DOTs that allow 60-inch, Daniel Currence, director of engineering for the corrugated plastic pipe division of the Plastics Pipe Institute (PPI), said in an email.

The trend toward tweaking state specifications to cover bigger pipes made of corrugated HDPE can be attributed to a couple reasons, according to PPI President Tony Radoszewski.

"This growing momentum in confidence is due to the numerous independent industry studies and the successful long-term use of HDPE," Radoszewski said in a statement.

"…During the past several years, the specification and use of dual-wall corrugated HDPE pipe for storm water drainage has increased dramatically based on factors such as the pipe's strength, durability, joint integrity and long-term cost effectiveness."

In typical drain applications, HDPE has a minimum service life of 100 years, and it is extremely resistant to chemicals and corrosion, Radoszewski said.

"The pipe's life-cycle savings over alternative drainage systems are significant," he added.

The Fort Valley drainage system was designed by Heath and Lineback Engineers, based in Marietta, Ga. Vice President Tom Barwick said replacement of the old system of 24-inch terra cotta pipe was badly needed.

"The existing pipes couldn't handle capacity and in some spots they were collapsing, undermining the streets," Barwick said in a statement.

Sixty-inch HDPE pipe was a good solution, he added, to handle additional flow criteria and fluid power.

"HDPE is a lot smoother and you can push more water through it than you could with concrete pipe," Barwick said. "It's wonderful that this is the first time that it's been used in a GDOT project. We've used the smaller diameters for a number of years."

To start off the project last fall, 1,180 linear feet of 60-inch NFlow corrugated HDPE pipe made by Southeast Culvert Inc. in Winder, Ga., was used. The product will be able to stand up to the wide range of pH values in the soil of central Georgia, Currence said.

"In this area of Georgia the soil pH has been recorded as low as 3.40," he said. "This extremely acidic soil would negatively affect other pipes materials, such as concrete and steel."

He also said corrugated HDPE makes flexible pipe systems that perform well at AASHTO HS-25 loads, which allows driveways, roads and parking lots to be built above it.

"Its unique ability to support and distribute live and dead load enables it to meet almost every installation condition," Currence said.

GDOT's inaugural project with larger diameter corrugated HDPE is expected to be completed in April.

"…GDOT is in the process of evaluating 60-inch diameter HDPE pipe for standard approval. Their process to reach that conclusion is to allow a series of five demonstration projects," Currence said.

Although in most cases, PVC can be used where HDPE pipe is used, Currence said once diameters exceed 12 inches, HDPE pipe is consistently less costly than PVC.

"By the time you get to large diameters greater than 24 inches, solid wall PVC becomes cost prohibitive," he added.

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