Washington DC has just revised its stormwater management regulations as of July 2013 [GAI22]. The new rule is another demonstration of the move of American cities towards green stormwater infrastructure, and this rule harnesses the private sector much like Philadelphia. Some highlights include
· The new regulations affect large construction projects that disturbs 5,000 square feet or more of soil. Property owners must retain the volume of water generated from a 1.2 inch storm. The 1.2-inch storm retention standard refers to a storm that falls within the current 90th percentile rainfall event for D.C., meaning that 90 percent of storms are smaller than 1.2 inches.
· The new rule also now includes renovations to structures of 5,000 square feet or more in size and which cost more than 50 percent of the pre-project value of the structure. For a major improvement, the retention volume is the volume of water generated from a 0.8 inch storm. The 0.8 inch storm is the current 80th percentile rainfall event for the District. This is new and quite unique.
· A trading program in the context of the retention program that is the first in the US. Property owners can retain up to one half of the required amount through the purchase of credits in the new market or payment of an in-lieu fee to the D.C. Department of Environment.
The citys revised stormwater rule is even more stringent than Philadelphias, and illustrates several concepts: the value of federal regulation to drive the process, the importance of local implementation with citizen input, the emphasis that a city places on sustainability and, ultimately, the need to harness the private sector as a partner.