Car dealership expands lot, controls stormwater

Located south of the Twin Cities in Burnsville, Minnesota, Walser Honda was looking to expand the parking lot at their current dealership to maximize the usable area for both retail sales and customer parking. The site did not allow room for traditional storm water storage, requiring an underground system to be installed under the entire parking lot. Triton Stormwater Solutions in Brighton, Michigan was selected as the storm water provider.

Triton's proprietary design and patented construction offers larger-capacity, lighter-weight, easier-to-install stormwater chambers that are more than 50 percent stronger than traditional products. Triton stormwater chambers have 46 percent greater capacity per linear foot and withstand 16,000 more pounds of pressure than traditional chambers, according to independent tests.

Triton is also environmentally friendly, manufacturing materials from the same soy- based resin that has been in use for more than 50 years in the heavy equipment and automotive industries as well as achieving its carbon neutral certification. The products come with an industry leading lifetime system guarantee and provides up to 21 LEED credits.

Hoff explains that although Triton materials result in a stronger product with more storage capabilities because of its design.

"Ultimately when you consider the excavation savings and need for less rock, it beats the competition on cost," he says. "Once you add in the sustainable materials, the fact that there is less work involved to install the system plus you get more Leed credits, it is a smart choice all around."

A Triton retention system was chosen for its strength, design flexibility and for its ability to be serviced and maintained with the use of the patented main header row system The 106' long by 70' wide excavation uses 420 chambers that can retain over 135,500 gallons.

This particular site is very sandy and the local water shed district encourages infiltration to minimize the impact of development. "The district wants to keep run off conditions as close to existing conditions as possible and the only way to get rid of volume is to infiltrate," explains Hoff. "That's why systems like Triton are beneficial because you do get that infiltration component."

The installationFirst, 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 geo fabric. The site was backfilled with stones up to six inches past the crown of the chambers and the geo fabric was folded back down and backfilled with material to the desired elevation which left the Triton system under 12 feet of cover.

The depth of the installation required a lot of excavation work, including hauling dirt to another site. It took two days to dig the hole, two days to install and backfill the chamber system and another day to get it back to grade.

A key feature of the Triton chambers is that they weigh only 32 pounds apiece, enabling workers to carry two or three at a time.

A sediment pond on the site feeds the Triton system so the use of the Triton main header row system ensures the site's water infiltrating back into the ground is extremely clean and ensures that the infiltration rate for which the system was designed will not be reduced over time.

"The sediment pond is said to collect 65 to 70% of all sediments and the rest is collected into the Triton main header row," explains Joe Miskovich, president of Triton Stormwater Solutions. "Any water now in the Triton drainage field is virtually free of fines and or sediments."

Miskovich says that the infiltration rate used to determine the footprint size, amount of chambers and drainage rate ensures that the system should last a very long time as long as the pond and the system maintenance cycles are not neglected. "Even if the pond maintenance is delinquent, the Triton main header system serves as a secondary fail-safe backup system to help catch and reduce the sediment that is coming from the pond."

September 2008

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