Restaurant Upgrade Incorporates Underground Runoff Detention
An existing fast food restaurant, located within the fully developed St. Paul, MN, city limits, was greatly in need of an update.
by Joe Miskovich
An existing fast food restaurant, located within the fully developed St. Paul, MN, city limits, was greatly in need of an update. Not only did the store itself need a facelift but the property needed to be redeveloped to meet the new watershed requirements that had been put in place since the area was originally developed. Requirements dictated infiltration, filtration and rate of control of stormwater to be used on redevelopment projects within its watershed districts.
The site contained an aboveground detention holding pond that did not adequately meet current standards for water retention. Heavy rains would cause the pond to overflow and flood the local area.
High volume capacity was the driving factor in selecting the Triton stormwater system for the fast food restaurant renovation project.
The land itself was more valuable than the pond due to the small confines of the site, so the stormwater system needed to be underground in order to use the site of the pond as a parking lot.
Triton Stormwater Solution's underground detention system was selected for its high storage volume capacity.
The added benefit of a modular design allowed the contractor flexibility to assemble the systems as they had time in between other tasks.
“We worked closely with Royal Environmental Systems to determine which system holds the most volume at the best price,” said Eric Kellogg, design engineer with LandForm, who managed the project. “This is a good filtration system because of the volume it holds based on the price per square foot.”
The site is backfilled with stones up to six inches past the crown of the chambers and the geofabric is folded back down. The system will be under 12 feet of cover after the backfill process is complete.
When first developing the system, Joe Miskovich, president of Triton Stormwater Solutions, had the goal of creating a system with high volume capacity. Based on feedback he'd received from civil engineers, architects and contractors, it was clear that end users were looking for a system that offered a larger storage volume in a smaller footprint. “By listening to the feedback from those that actually work with the systems, I was able to implement that into my original design and deliver what the end user really wants,” said Miskovich.
The stormwater system allows the designer to target different goals: infiltration, filtration (as shown above), and/or storage for control of peak flow rates.
The tight confines of the site posed a challenge.
“The stormwater line that was discharging to the detention system runs very close between the property boundary and underground storage,” explained Lance Hoff, water resource engineer at Royal Environmental Systems.
Because the street had to be shut down, the team was only able to install the detention system in between working on the other utilities that were a priority in order to reopen the street to traffic.
“Luckily the contractor was able to multitask and assemble the system as they had time,” said Hoff. “It worked out well because the system is modular. They didn't have to have the hole open and shut in a certain timeframe; they could tackle it as time allowed.”
First, the crew dug down to elevation and put down a six-inch base layer of stone. Next, the chambers were put in and the walls of the trench were lined with a Class 2 non-woven geofabric. The site was backfilled with stones up to six inches past the crown of the chambers and the geofabric was folded back down and backfilled with material to the desired elevation, which left the system under 12 feet of cover.
The drainage area to the detention system is 1.02 acres at 85% impervious, which is the maximum allowed by city zoning. With 174 chambers, the system is designed with 7,732 cubic feet of storage.
The fact that this system requires less cover is another appealing feature to Kellogg. “When it makes sense, we try to design sites to only have 18 inches of cover, which is helpful when elevation and inverts are a concern.”
According to Kellogg, the installation proceeded smoothly and with no issues. “We had it all done within three or four days with the hole dug and backfilled,” said Kellogg.
The company's proprietary design and patented construction offer large-capacity, lightweight, easy-to-install stormwater chambers that are more than 50% stronger than traditional products. The chambers also have 46% greater capacity per linear foot and are able to withstand 16,000 more pounds of pressure than traditional chambers, according to independent tests.
Triton uses manufacturing materials from soy-based resin, helping the company to achieve its carbon neutral certification. The products come with a lifetime system guarantee and provide up to 21 LEED credits.
About the Author:
Joe Miskovich is president of Triton Stormwater Solutions. He oversees all corporate operations and is responsible for product design, engineering, marketing, sales and customer support for Triton's stormwater management chambers.