In June 2002, First Independent Bank, began construction on its 15,000 square-foot First Investments Plaza office complex. The bank planned to use part of the space to relocate its banking and administrative services, and lease out most of the new complex.
Mackay & Sposito recognized that a bioinfiltration swale site took up about 2,750 square feet of buildable land. Trying to maximize available land usage and keep total costs down, they determined that replacing the swale with an underground system offered the most economical solution. It would also free more aboveground area and treat runoff from the site’s increased parking area.
The existing biofiltration swale and two underground systems, a sand filter and a cartridge filter, were on Vancouver’s approved best management practice (BMP) list. The city has specific restrictions for installation of stormwater treatment systems on private property, including a requirement that the installed system come with a long-term maintenance program.
The installation of a sand filter is complicated. Maintenance requires removing polluted sand manually to prevent clogging or decreasing its filtering effectiveness. No one currently offers maintenance services for sand filters. An alternative BMP that’s approved by Vancouver and nearly 400 other jurisdictions across the United States, the Stormwater Management StormFilter® provided a better solution. The passive filtration system features an underground concrete vault that houses rechargeable, media-filled filter cartridges with an integrated surface-cleaning mechanism.
Having already used this system at other sites, Mackay & Sposito engineers knew that integrating the system into the plaza site plans would be straightforward, and customizing the system for specific pollutants would provide the right level of treatment for parking lot runoff. Maintaining the system could also be managed through a long-term maintenance program with the manufacturer.