After September 11, 2001 the U.S. Pentagon
needed to relocate access drives further away from the Pentagon complex. This relocation created even more pressure on already tight parking resources. In addition, the U.S. Department of Defense wanted to adhere to local regulations for this retrofit construction, including proper stormwater quality treatment for the Potomac River watershed. High-level Pentagon officials were closely involved in all aspects of this project, and the Filterra Biofiltration System
was chosen as BMP for this application.
Parking for a large complex along with the high cost of real estate near Washington D.C. left minimal space for auxiliary systems such as stormwater treatment. In addition, the Potomac River and Chesapeake Bay watershed have stringent requirements for stormwater quality treatment.
Pentagon officials recognized the unique minimal space requirements for Filterra. Buildable space was maximized by positioning Filterra within curb easements. With Virginia Department of conservation and recreation allowing up to 74% total phosphorus removal, Filterra provided the most efficient proprietary BMP available and helped meet federal, state and local stormwater quality requirements.
11 Filterra units were installed in the roadways of the new Secure Bypass, with traditional curb inlet bypass. Predominantly cross-linear flow was established. Most rainfall is designated to run along the curb, first into the Filterra then to the bypass. Sizing was done to the standard Virginia ratio of 0.33% Filter area/Drainage Area (FA/DA). Grading placed the Filterra units slightly above their corresponding bypass structure.