To help control costs and meet the requirements for the deep burial of a Chandler, Ariz. road expansion's new storm water drainage line, a highly engineered corrugated pipe from Advanced Drainage Systems Inc. (ADS) was used. ADS N-12 HP (high-performance) pipe is designed and manufactured to handle heavy loads and AASHTO-designated live loads without any additional bedding or special fill. More than 1,840 ft of the pipe was used in diameters ranging from 12 to 60 in. In one area, the 60-in.-diameter corrugated pipe is covered by 21 ft of fill.
The $4.5 million road project widened the intersection of Dobson Road and Chandler Boulevard, the main thoroughfare in the city, which has a weekday daily traffic load of more than 40,000 vehicles. Standard Construction Co. Inc. of Avondale, Ariz., was awarded the contract to reconstruct the intersection, which included dual left turn lanes, a third auxiliary through lane, right turn lanes, bike lanes, bus pullouts, the storm drain, water line, new traffic signals, streetlights and landscaping.
"This is the first public right-of-way project in the state of Arizona for the use of N-12 HP pipe," said Tori Durliat, director of marketing for ADS. "The independent engineering evaluation and discussion of this product was instrumental in achieving the approval for the HP pipe, which can now be specified for right-of-way road work in the City of Chandler. This project represents a savings of some $20,000 for the 1,840 ft of pipe required."
"Up until now, the city standards didn't typically allow HDPE [high-density polyethylene] pipe," saidSteve Sutton, president of Standard. "The Chandler road project was originally designed with [another product], but there was an interest in finding out more about the ADS pipe. We proposed it as a valued engineering product, which saved them about 10% of the cost of the pipe portion of this project."
The selection of the ADS pipe was reviewed by Engineering and Environmental Consultants of Tucson, Ariz., a civil and environmental engineering firm. According to Carrie Cote, P.E., project manager at the firm, "The ADS pipe was presented by the contractor as a different product that would serve in purpose and strength and capability. The contractor, Standard, presented it to the city as a viable alternative that would also save some money. The city wanted to make sure it satisfied their specifications, so we got involved, reviewed it and approved that type of pipe."
Known for its corrugated HDPE pipe, ADS manufactures N-12 HP corrugated pipe from an engineered grade of polypropylene resin. Designed and manufactured to be used in installations with less than ideal conditions, 12-in. through 24-in. diameters are made with dual wall construction. Larger diameters of 36- through 60-in. have triple wall construction and are also available in dual wall. The 30-in. diameter pipe is available in dual-wall and triple-wall, which was used for this project.
The ADS manufacturing process provides the pipe with a smooth interior and a corrugated exterior wall, supported by a honeycomb structural core for improved stiffness and greater beam strength, which minimizes deflection and enhances long-term performance. All N-12 HP sizes are watertight, exceeding the requirements of ASTM D3212 with dual gaskets and banded reinforced bell.
Burial depth for the pipe used at the Chandler Road project was specified at 18 ft for the retention basin to a minimum of 3 ft at collection points. At some points the bottom of the pipe was 26 ft deep. Backfill was aggregate base course and Class II backfill of sand and rock.
According to Sutton, "The pipe had to perform in deep and shallow depths. The N-12 HP is rated to meet AASHTO H-25 load requirements and the various ASTM standards, so there was total confidence in the long-term reliability."
"It was our first experience with the high performance pipe, but it’s virtually identical to their HDPE pipe, which we have used quite a bit," he said. "The HP installs the same as the ADS corrugated black HDPE pipe. The fittings just snap together and we didn't have to do anything special with the fittings. The ADS pipe is more forgiving as far as relocating it, because you could cut it and shorten the length or change the location of where you put the pipe and you don't have to use a crane."
