A redevelopment project for a medical clinic office building required a new stormwater management solution.
The engineer on the project, Lamont Engineers, had three major challenges to address when designing the stormwater management system. First, space at the site was very limited, so an underground solution was needed. Second, the site had shallow limestone bedrock, limiting the available depth of an underground system. Third, the project had to meet the redevelopment water quantity and quality requirements per theNew York State Department of Environmental Conservation (NYS DEC).
To meet these challenges, Lamont chose a Terre Arch underground detention system and a Vortechs hydrodynamic separator from Contech Engineered Solutions. Stormwater from the site is first directed to the Terre Arch underground detention system. Terre Arch is a modular, multi-chambered, precast concrete stormwater storage system that is engineered especially for underground installation and provides a load-bearing rating of HS-25, which is critical as the land above the Terre Arch system will be used as a parking lot. The system called for ten Terre Arch 26 units and two distribution manifolds, providing a total storage capacity of 5,064 cubic feet in a total footprint that was only 18’ -11½” x 88’- ¼”. The engineers included 12” of stone over the top of the Terre Arch system for frost heave, and the system was placed on an HDPE impervious liner for limestone erosion protection. Terre Arch also provides the advantage of simple, fast installation. The entire Terre Arch system was installed in less than two hours using a 485 excavator, dramatically reducing labor and installation costs.
“The system did allow us to use a much shallower installation than the plastic units, reducing blasting costs and time,” said Jodie Serowski, Design Engineer at Lamont Engineers. “The installation was accomplished in a few hours compared to several days or weeks for the plastic units.”