February 19, 2010
Urban Redevelopment and Combined Sewer SystemsBy: Stuart Toraason
Urban infill and re-development projects require special means of minimizing increases in stormwater flow is to implement innovative sustainable design techniques to increase pervious area and improve rainwater retention. Projects like Timmons Group’s LEED® Gold certified 1050 K Street project in DC use green roofs, planter beds and rainwater harvesting to meet city code and minimize impact to the combined sewer system.
- Projects that involve large-scale infrastructure updates are often required to separate the storm and sanitary sewers as the project progresses. Rocketts Landing in Richmond, Virginia, is a good example of this. In this case, the existing combined sewer system was designated solely for stormwater runoff, and a separate sanitary sewer system was created by constructing new sanitary mains and connections. Stormwater runoff was treated on site and discharged directly to the James River, while the sanitary sewage was directed to the treatment plant.
- Combined sewer systems do have one benefit from a development standpoint, in that most local jurisdictions, as well as state and federal codes, do not require stormwater quality control since the stormwater runoff flows to a municipal treatment plant. In addition, for projects in localities that control stormwater quantity, previously mentioned sustainable design techniques may be implemented to eliminate any stormwater increases; thus, the end result can be that stormwater management is not required at all.