Precast stormwater system showcases speed and simplicity
By Mark Crawford
Scranton, Pa., is known for many things: being the home of fictional paper products company Dunder Mifflin, becoming the first city in the country to have streetcars powered only by electricity, and the sixth-largest city in Pennsylvania. As the area begins to attract more business, new offices are starting to pop up.
One such building, Richland 315, is a 53,000-square-foot building under development. With its large footprint and amount of impervious surface, stormwater detention is a key part of the project.
Thanks to a precast concrete system, residents and workers won’t have to worry.
Contech Engineered Solutions, headquartered in West Chester, Ohio, recently installed two Terre Arch 26 stormwater detention systems for the building located between Scranton and Wilkes-Barre.
Designed for underground installation, Terre Arch is a modular, multi-chambered, precast concrete stormwater storage system. Contech is the exclusive licensee for the system, originally designed by Terre Hill Concrete Products.
Precast concrete was selected for the project because of its strength and durability, providing a 100-year-plus lifespan. Once installed, the precast units are sturdy enough to handle heavy truck loading and also provide access to individual chambered rows to facilitate maintenance. The ease and speed of installation of precast components was another top consideration.
“The simplicity of the Terre Arch system allows for standardized fixed forms to be used for maximum efficiency through manufacturing,” said Kevin Tracy, director of stormwater sourcing and operations for Contech. “The strength of the concrete, combined with the loading benefits achieved from the arched shape, offers a significant benefit over non-precast chamber systems and makes this system a good choice for projects with minimal depth of cover.”
Speed of assembly was another important consideration for this project. Each precast unit installs quickly – a team can create several hundred cubic feet of storage within a matter of minutes.
With a properly excavated and prepared base, a Terre Arch unit can be set every five minutes. At this rate, up to 50,000 cubic feet of storage can be installed in one day, including cover and backfill.
For example, one of the basins consisting of 82 arches and 12 distribution manifolds was installed in just two days. This is an impressive feat considering it provides more than 31,000 cubic feet of storage capacity.
The system is a connected four-arch precast concrete structure providing 277 cubic feet of installed storage and 152 square feet of stone infiltration area. The Terre Arch 26 basin was an ideal solution when faced with the site restrictions such as high ground water tables and minimum separation between the top of the underground structure and the finished grade.
“This product is ideal for shallow burial applications and combines the strength and durability of precast concrete with the installation efficiency of chambered systems,” said Elaine Thomas, product manager for Contech.
Mark Crawford is a Madison, Wis.-based freelance writer who specializes in science, technology and manufacturing.