Controlled release allows downstream configuration in compliance with local regulations
Mile High Apartments will bring 382 new apartment units to a location in Denver just minutes from the downtown area. The new development is located next to the Rodolfo “Corky” Gonzales Branch Library off of Colfax Ave., and kitty-corner to Sports Authority Field at Mile High.
The project had a number of challenges, including a limited footprint, corrosive soils and a high degree of treatment needed to meet water quality standards from the city of Denver.
To address these issues, engineers from Harris, Kocher & Smith designed a storm water detention system consisting of 388 linear ft of 120-ft polymer-coated corrugated metal pipe (CMP) in a double-manifold, three-barrel configuration. The system contains five 120-in. weir plates, two track racks, five 36-in. risers, 24 120-in. bands/gaskets and five stubs.
To meet the treatment requirements, an 8-by-11-ft Stormwater Management StormFilter vault with 24 27-in. cartridges was placed downstream of the detention system. The StormFilter cartridges are filled with ZPG media—a proprietary blend of zeolite, perlite and granulated activated carbon that target organics, soluble metals and other pollutants.
In this part of Colorado, storage and treatment typically is managed using aboveground ponds with biofiltration swales. The lack of space for such elements required engineers to manage these requirements belowground. Using a large-diameter pipe (120 in.) allowed for a large volume of storage in a small footprint.
Contech designed the detention system with a series of internal orifice plates and weirs to control targeted release rates and drain downtimes specified by local drainage requirements. Using the detention system to control release rates in this way allowed Contech to place the StormFilter in a downstream configuration, which provided the most economic treatment option.
The highly limited footprint was a unique element of this project. The detention system underwent multiple design iterations until the final layout was acceptable. Pipe material requirements also were an unusual element of this project, but having a poly-coated CMP option allowed Contech to provide an underground detention system in an area where soil conditions sometimes prohibit the use of aluminized pipe.
Contech also provided a long-term life-cycle analysis (25 years) for the StormFilter system to give the owner a better understanding of long-term maintenance cost of the system.
AGL Construction installed this system. A Contech representative was present for the preconstruction meeting and visited the site multiple times over the course of the four-week installation period. The installation was described as being “textbook.”