Large-diameter pipes provide large amount of storage
La Quinta Inns & Suites in Portland, Maine, suffered from frequent flooding in its parking lot, which caused damage to the building and hindered service to customers. To alleviate this issue, it sought guidance from Acorn Eng. to design a solution to the problem.
Acorn suggested the construction of a storm water detention system under the parking lot. The addition of the subsurface infiltration would provide adequate storage for the design storm and minimize future impacts due to flooding.
The original specification called for plastic crates. Contech recommended a corrugated metal pipe (CMP) solution as an alternative to the crates. Fitting the volume of water in the small footprint made large-diameter—84- and 96-in.—CMP an attractive option. The use of the large-diameter pipe allowed for a smaller footprint, less excavation and backfill, and a faster installation. The plastic crate system’s installation was estimated at 40 days; the CMP system’s installation was estimated to take less than half that time. As a result, the contractor, CLH & Sons Inc., was able to save approximately $130,000 over the specified plastic crate system.
The detention system consists of 581 linear ft of 840-in. and 1,017 linear ft of 96-in., 14-gauge, perforated aluminized steel Type 2, providing 100,283 cu ft of storage. Twelve barrels of various lengths were fabricated to accommodate the footprint of the site.
The original design of the plastic crates had very small inspection ports that would allow for only minimal maintenance of the system. The CMP design provides three 36-in. risers for complete maintenance access, which will help to prolong the life of the system.
“Acorn appreciated partnering with Contech to develop a design alternative using large-diameter CMP compared to high-void stackable crates,” said Mark Arienti, senior environmental engineer with Acorn Eng. “The crates would have required onsite assembly by the contractor. Considering the design included 750,000 gal of detention, Contech’s CMP system required significantly less labor to install by utilizing the contractor’s onsite equipment.”
In the end, Contech reduced the cost of the originally designed system to meet financial requirements, provided a reliable system with ease of maintenance and supported the contractors throughout the entire installation process.