PE Pipe Adapts to Storm Water Applications
Two years ago, the corrugated polyethylene (PE) pipe industry produced nearly one billion pounds of pipe. The specification and use of dual-wall corrugated PE pipe for storm water is skyrocketing based on factors such as total installed cost, enhanced hydraulic flow and unparalleled chemical and abrasion resistance when measured against other materials.
The evidence is mounting—forward-thinking municipalities are realizing the future of the storm water management industry will bring change.
Giving PE a chance
Public works officials in Akron, Ohio, south of Cleveland, discovered the benefits of using corrugated PE pipe last year. The city’s first storm water drainage project using corrugated, high-density PE (HDPE) pipe was completed in a residential neighborhood using more than 1,000 feet of 36-in. and 48-in. corrugated HDPE pipe to store the excess flow and prevent downstream flooding.
“We were able to save approximately two weeks worth of labor by using the HDPE (in Akron),” said Marv Hermes, an estimator for Spano Brothers Construction, Inc. “The same project using concrete would have cost approximately 40% more. We’ve done site visits to the Akron system several times since it’s been in the ground, and it’s working very well. We think HDPE is going to be used more and more for storm water projects in this area.”
In fact, it’s been well documented through research that merely writing alternative materials—such as PE—into the storm water pipe project specifications can significantly reduce an owner’s overall project cost due to the viability of more modern pipe materials.
Taking the lead and thinking long term
Research data from the New York State Department of Transportation shows that it used PE pipe for 56% of its roadway projects as of 2001.
These statistics help show that thinking ahead and considering the actual cost of a project over its useful life are beginning to receive much more consideration by owners and their engineers. Life-cycle costing is a well-documented process that calculates not only the initial installed cost of a pipeline or other system component, but also accounts for the other associated costs attributable to ongoing maintenance, repair and operations during its expected life.
“There is a billion-dollar pipeline rehabilitation industry out there that benefits from shortsighted thinking, where only the initial low dollar cost of a pipeline material is considered and not what additional costs may be required in the future,” said Mark Wallbom, senior vice president of the contracting firm Miller Pipeline Corp.
“Much of the pipeline rehabilitation work we do, using pipebursting, internal joint sealing, HDPE sliplining and/or cured in place lining is in failed concrete and corrugated metal pipelines,” Wallbom added.
“One very real example of this is where a client thought they would save around $300,000 by selecting a particular type of piping material when they initially constructed their project, but now 15 years later it is costing them millions to fix their problems,” Wallbom continued. “Material selection and installation methods are more complex than many realize so it behooves everyone involved in the process to not get caught in the trap of status quo thinking.”
PE in the game
The spring of 2002 marked the first full season for four brand new baseball fields in Everett, Wash., a city of 96,000 people near Seattle.
“We knew that field drainage would be a critical issue going into this project,” stated Ryan Sass, assistant park director for the Everett Parks and Recreation Department. “PE was our first choice. PVC pipe typically requires a greater depth of cover; corrugated metal would not give us the flow characteristics we needed. Concrete can be heavy and labor intensive. We chose corrugated polyethylene pipe because it is a cost-effective material.”
Rich Gottwald, president of the Plastics Pipe Institute (PPI) said corrugated polyethylene pipe is routinely chosen for a variety of projects because of the pipe’s structural design capabilities, service life and long-term performance.
“It says a lot about our product when public works engineers are increasingly choosing our product for such a wide range of applications,” said Gottwald.
Corrugated PE pipe has been successfully installed at depths as shallow as 12 in. with H-20 (vehicular) loads, as shallow as 24 in. with Cooper E-80 (railroad) loads and has been proven to handle burial depths routinely in excess of 20 ft. Flexible pipe can support deeper ground-covers because flexible pipe shifts the load to the soil—the soil becomes load-bearing instead of the pipe.
Specifically, instead of the pipe’s joints.
“Probably the leading cause of pipeline failure is leaking and broken joints,” said Jeffrey Hiott, applications engineer for PPI. “There are many reasons why joint failure is a much bigger issue for other pipe materials than for PE pipe.
“PPI has member companies that manufacture pipe to the most stringent soil-tight and silt-tight requirements,” Hiott explained. “PE pipe’s integral bell design resists distortion, chipping or cracking and spans several corrugations. The in-line design requires no bell hole, and factory installed rubber gaskets meet all requirements of ASTM F477.”
Besides soil-tight and silt-tight pipe, PPI member companies can manufacture corrugated PE pipe with watertight joining systems. These integral joints will meet the stringent standards mandated by the EPA in new legislation and comply with ASTM and AASHTO specifications. O-ring rubber or elastomeric gaskets, conforming to applicable ASTM standards, are used in both the silt-tight and watertight joining systems.
“High-density polyethylene is one of the most chemically inert of all plastics and therefore is extremely chemical-and corrosion-resistant,” Hiott said. “This gives corrugated polyethylene pipe a significant long-term strength advantage over concrete and metal pipe.”