Brier Creek comprises 264 apartments across four, five-story buildings on 14.43 acres. Given the density of the property, the most practical approach for the detention and treatment system was to place it underground.
After assessing various options, engineers at McAdams specified a corrugated metal pipe (CMP) system to meet the stormwater quantity regulations and a Stormwater Management StormFilter to meet water quality regulations.
The system is made from 603' of 138" diameter CMP providing 63,776 CF of storage. The system was installed at an depth of 28.95' from rim to invert at its deepest point to tie into the existing storm sewer lines. This allowed the engineers to use large diameter pipe and shrink the system's footprint. Contech provided customized structural designs to accommodate the deep burial. In addition, Contech Stormwater Design Engineers designed the system with an outlet control weir within the pipe. Doing so allowed the system to accommodate the water quality volume storage and main detention storage within one system, resulting in significant cost savings.
Additional treatment was needed as the development is in a nutrient-sensitive area. Two 8'X24' StormFilter vaults containing 58 media cartridges were installed downstream of the detention system. The filter media used in the cartridges was Phosphosorb, a media that has been field-tested in NC and approved for nutrient removal.. The StormFilter is an approved stormwater Control Measure by the North Carolina Department of Environmental Quality.
The installation was a resounding success. Despite the unique storm drainage design involving a challenging site and uncommon depth requirements, the contractor installed the detention and treatment systems in about one week.