Focus on: Stormwater

The installation of the stormwater detention system at Greyhound Plaza shopping center in Keyser, W.Va., took about six weeks and required 100,000 cubic ft. of storage.

In Keyser, W.Va., population 5,500, there isn’t much to do. And with the exception of the requisite Walmart and CVS drug store, the retail offerings are scarce.

So when locally based Greyhound Properties LLC decided to invest $7 million to erect a strip center on the outskirts of town, residents were understandably excited.

One of the first steps toward converting the 15-acre plot into viable retail was to specify and construct an underground storage system beneath the shopping center parking lot to capture water and release it slowly into a creek across the road without flooding it.

Because of the size and levelness of the site, a system that would contain about 100,000 cubic ft. of water would be required.

The team selected Triton Stormwater Solutions out of Brighton, Mich., which has developed an innovative underground stormwater management system comprised of chambers made from soy resin that are 50% lighter than competitive polymer products.

“The system is much lighter and stronger than what is on the market today,” said Joe Miskovich, president of Triton. “Because we use the soy component in our product, it is environmentally friendly.” Triton products provide up to 21 Leadership in Energy and Environmental Design (LEED) credits.

Installation on the Greyhound Plaza site took far longer than the typical Triton project. Because of the acreage involved and some inclement weather during the construction timeline in the fourth quarter of 2008, installation took about six weeks.

“Typical installation takes two days or less,” Miskovich said. Installed cost ranges from $2/cubic ft. of storage to $7/cubic ft. of storage.

To install the system at Greyhound Plaza, whose major tenant is Rent-A-Center, the crew first excavated down to elevation and laid a 6-in. base layer of stone. Next, the chambers were put in and the walls of the trench were lined with a class 2 non-woven geo fabric.

The site was backfilled with stones up to 6 ins. past the crown of the chambers, and the geo fabric was folded back down and backfilled with material to the desired elevation, with Triton chambers needing to be placed under just 16 ins. of cover.

“Because of the enormous size of the site, the team had to build and backfill in sections,” Miskovich explained. “The size of each section was limited by the reach of the excavation equipment.”

The fact that the Triton chambers are lightweight and stackable eased the installation. It took just one man to unload the chambers from the pallet and another to carry the chambers to the site. Roughly 2,550 stormwater chambers were used.

The larger the project, the greater the savings, Miskovich said.

“What we’re seeing on midrange jobs is a total install savings of between 20% to 30%,” he said. On larger jobs, such as Greyhound Plaza, “we’re seeing even greater cost savings than that.”

The system, in place since the end of 2008, not only has served to capture and control stormwater runoff, but also has improved water quality as it segregates debris, sediment and foreign objects in the system. The system, which is designed for service and maintenance with the use of bottom pieces and sumps in addition to chambers and end pieces for easy access, also is proving to be easy to clean and maintain, Miskovich said.

“Maintenance is the Achilles’ heel of any underground-detention system,” he said. “Anything buried isn’t as accessible to inspect and clean.”

© 2014