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Credit: Photo: Advanced Drainage Systems

Crews installed a watertight drainage system using Nyloplast structures and N-12 corrugated high-density polyethylene pipe—both available from Advanced Drainage Systems Inc.—along Idaho's US 95.

The Pacific Northwest puts a high premium on sound environmental policy, and its drainage needs are specific. Factors include quantity and quality of water runoff, and the necessity of keeping runoff securely inside the drainage system. Those needs are leading to an underground revolution in Washington, Oregon, and Idaho that is paying off for these state DOTs.

Nyloplast drainage structures, from Hilliard, Ohio-based Advanced Drainage Systems Inc. (ADS), are constructed of heavy-duty PVC. They have been approved for use in three northwest states, proving grounds for the pairing of the company's N-12 corrugated high-density polyethylene (HDPE) pipe and Nyloplast structures with watertight joints, durability, and resistance to corrosion and abrasion.

The Washington State DOT (WSDOT) first gave “approval with limitations” for the structures, and the Hydraulic Office and New Products Committee have viewed the product favorably. Initial installations have been in heavy-traffic areas like ferry terminals, rest-area parking lots, and park-and-ride lots. In order to gain experience, WSDOT also recommends that local agencies engage in similar evaluation procedures.

“We have been encouraging this use and concurring with the local public directors,” said Matt Witecki, WSDOT supervisor of hydraulics. “That gives them an added comfort level, and gives us more projects to monitor.”

After installing and testing the structures and following up with check-ups, WSDOT officials like what they see. “We like the way in which the N-12 pipe is attached to the inlets so you're assured of a perfect watertight seal, the fact that the PVC makes it corrosion resistant, and that there is a considerable cost savings when it comes to installation,” said Witecki.

Lightweight Construction

In the city of North Powder, Ore., Crestline Construction decided to use Nyloplast structures for the drainage system along a newly constructed section of Second Street, a state highway project.

“It's such a simple idea, how the drainage structures are made specifically for the project and how everything fits together so easily,” said Ron Schmidt, manager of Crestline Construction.

Twenty-eight Nyloplast curb inlet drainage structures and four drain basins with standard H-25 rated ductile iron grates were installed along the edge of the street. Hank Keith, Crestline Construction superintendent, also calls it the easiest 5000-foot project he's ever been a part of, citing the structures' light weight, ease of handling, and interconnectivity with the pipe.

Idaho Installation

When Kevin Poole, project engineer and estimator for A&R Construction in Lewiston, Idaho, began work on a drainage system for the US 95 State of Idaho highway project, he turned to Nyloplast structures.

“We were raising and widening an existing highway from two lanes to five,” said Poole. “I knew the drainage structures and ADS N-12 pipe were perfect for the project because of their watertight joints and ability to easily handle the runoff from the heavy storms we have here.”

But before he could specify the structures, the Idaho DOT (IDT) had to approve them for statewide use. “Fortunately, they agreed to let us do the project as part of the research for their approval process,” he said. Once research and testing are complete, each person on the review team has to give a stamp of approval on a product before it can be approved for use on a project.

The highway reconstruction project called for three Nyloplast area drains, 48 type 2 Nyloplast drain basins, and two type 3 Nyloplast drain basins with ductile iron grates, as well as a total of 5075 feet of N-12 pipe in various diameters.

More than a year after its installation, IDT officials are using installed cameras to verify that the system on US 95 is working as designed. “That's the only true way to tell,” said Mike Dehlin, project development engineer for IDT. “And we couldn't be happier.”

Thanks to that successful highway installation, several other Idaho projects using Nyloplast structures are in the works.