Miles of HDPE Pipe Used for Underground Stormwater Control System

To protect the environment of this area on the Pennsylvania/Maryland border, a new warehouse facility with a 1.5 million square foot building elected to use not one but five large underground stormwater storage units.  The need for the watertight system that would be under the loading and parking areas was due to karst topography and the created impervious area of some 83 acres.  One of the largest buildings and sites in Franklin County, the project used more than 17 miles of large diameter, corrugated high-density polyethylene (HDPE) pipe to construct the five large underground detention beds, one of which has 24,500 ft (4.64 miles) of 60-inch diameter pipe.  It was named Project of the Year by the Drainage Division of the Plastics Pipe Institute, Inc. (PPI), the major North American trade association representing the plastic pipe industry.

“The size and scope of the project along with the high visibility of using HDPE pipe and its features and benefits are among the many reasons that this earned the Project of the Year honor,” explained David M. Fink, PPI president.  “The project shows how the use of HDPE pipe can protect the environment, lower greenhouse gas emissions by reducing the number of truck loads as a

 result of nesting the light weight pipe.  Plus, the pipe can be installed quickly with minimum crew and without heavy machinery while providing the owner with a lower installed cost versus other types of pipe or structures.  There is also the fact that HDPE pipe can be made using a high amount of post-consumer recycled HDPE material, taking single use HDPE bottles, for example, and turning them into pipe that will last for generations”

The site civil engineer, Bohler, (Chalfont, PA) considered other materials, such as corrugated metal pipe (CMP) and precast chambers.  Even though CMP could handle the deep burial depths that could reach 22 feet, the Advanced Drainage Systems, Inc. (ADS) (NYSE: WMS) N-12® HDPE pipe from 36 to 60 inches in diameter with the proper backfill was selected by Bohler primarily for its long service life.  Depending on depth, the backfill consisted of Compacted Class I, Flowable Fill Concrete, or reinforced steel concrete encasement.

For the riser/inspection ports, 179 twelve-inch ADS Nyloplast® traffic-rated Inline Drain units were installed plus 119 ADS FlexStorm® 2×4 SS Pure FTC (full trash capture) units provided environmental water quality protection.

“We wanted to not only meet but exceed updated Pennsylvania Department of Environmental Protection specifications,” stated Will Jager, EIT, assistant project manager for Bohler.  “So, it was important that the system be watertight, and provide the ability to take care of total suspended solids.”

This project’s five large retention beds used more than 17 miles of ADS N-12 AASHTO pipe, as well as 862 fittings, gaskets.

“During just the past two years there has been a virtual explosion of new warehouse distribution centers being build,” said Daniel Currence, P.E., director of engineering for PPI’s Drainage Division.  “The common thread in all these projects is the desire by the building owners and developers to include stormwater management systems that protect the environment.  In Greencastle, the five retention beds can hold about 1.5 million gallons of water that will have a controlled output rate after being treated to remove total suspended solids and other pollutants.  As this is probably the largest single-project use of corrugated HDPE pipe for stormwater management – one bed had 24,500 ft (4.64 miles) of 60-inch diameter pipe – the solution of using the HDPE pipe with its cost and time benefits magnify the versatility, strength, flexibility and long-life of the pipe.The key was the HDPE pipe that could be deeply buried, provided a very favorable installed cost and is rated to last at least a hundred years.”  

The ADS N-12 dual-walled corrugated HDPE pipe is certified to meet CAN/CSA Standard B182.8, BNQ 3624-120 plus AASHTO Load Resistance Factor Design (LRFD) specifications  The ADS N-12 pipe has a smooth inner wall to provide optimum hydraulic flow.  Its structural strength from a corrugated outside will support H-25 live loads with 12 inches of minimum cover for most pipe diameters.  Sections are joined together using the pipe’s watertight integral bell and spigot with a factory-installed gasket.  The pipe requires no extra couplers to install.  The watertight connection between sections at 10.8 psi meets or exceeds the ASTM 3212 lab test and the ASTM F2487 infiltration/exfiltration field test, conforming to Environmental Protection Agency guidelines. 

ADS N-12 pipe meets the requirements for Type S pipe under the American Association of State Highway and Transportation Officials (AASHTO) specifications M 252 and M 294.  It can be specified for culverts, cross drains, storm sewers and other types of new and rehab projects. 

“This is a sustainable solution that not only takes care of runoff but also makes use of recycled plastic in the manufacturing of the HDPE pipe,” Currence continued.  “Corrugated HDPE pipe has the least environmental burden compared to other commonly used pipe for stormwater drainage and culvert applications.  This was the conclusion of a life-cycle assessment study conducted Franklin & Associates.  They investigated reinforced concrete, corrugated steel, PVC, and two types of corrugated HDPE pipe.  HDPE pipe made with virgin resin and HDPE pipe made with recycled content were found to have the best overall sustainability rating.”  

ADS is the largest plastic recycling company in North America using more than half a billion pounds of post-consumer plastic every year.

“The success of the project completed during the third quarter of 2021, shows the ability of HDPE pipe to provide a watertight retention system that is both cost effective and a superior, sustainable replacement for precast vaults, CMP and RCP systems,” Currence offered.

Additional information can be found at www.plasticpipe.org and www.plasticpipe.org/drainage.