Located 35 miles southwest of Salt Lake City, Tooele bills itself as “the greatest city in Utah.” We’ve never been there, so we can neither confirm nor deny that. But we can tell you its infrastructure wins awards.
Most recently, a stormwater project in the main thoroughfare earned a national award for innovative material use. In 2015, the state DOT replaced 4.5 miles of gutter with a below-ground runoff-management system made of dual-wall corrugated HDPE. The N-12 pipe was manufactured by Advanced Drainage Systems Inc. of Hilliard, Ohio, in diameters ranging from 12 inches to 48 inches.
As always, speedy installation was important to minimize inconvenience to the driving public.
Plastic was used instead of reinforced concrete pipe (RCP) because its lighter weight enabled contracted crews to quickly rip up the old pavement, thread pipe sections under utility lines without using heavy equipment, and repave the street. Just-in-time (JIT) deliveries to where the crew was working on any given day eliminated the large staging area RCP would have required.
Another reason the pipe was chosen is strength. It meets American Railway Engineering and Maintenance-of-Way Association (AREMA) Cooper E80 loading requirements and American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specifications for Section 12 (buried structures).
"The use of dual-wall corrugated HDPE pipe for stormwater drainage has increased dramatically over the last several years,” says Daniel Currence, PE, engineering director at the Plastics Pipe Institute Inc. (PPI), which holds an annual Project of the Year awards program. The Utah DOT/ City of Tooele reconstruction project earned the Corrugated Plastic Pipe Division’s award.
"AASHTO’s Section 12 is a conservative, strain-based design procedure suitable for thermoplastic pipes such as HDPE, polypropylene, and PVC,” he says. “The code considers the actual failure modes, such as thrust, wall buckling, and combined strain. Deflection is considered as a service limit and serves as confirmation of the design and ensures suitable long-term performance.
“Utah’s been specifying HDPE pipe for at least 20 years. As one of the most chemically inert of all plastics, it’s extremely chemical- and corrosion-resistant. Users can expect a service life of 100 years in many typical drainage applications. Soil- and water-tight integral joints that meet t EPA standards as well as ASTM and AASHTO specifications prevent groundwater infiltration.”
Click here to learn how to design a similar system.