Based on the type of application submitted, DOEE uses two methods for calculating discounts.. The Standard Application is used for projects that manage more than 2,000 square feet of impervious surface. The Simple Application is used for properties with green infrastructure (stormwater retention Best Management Practices or BMPs) that manages stormwater from 2,000 square feet of impervious surface or less. While both calculations are based on the amount of stormwater retained by green infrastructure, the Simple Application makes some assumptions in favor of the applicant.
The maximum RiverSmart Rewards discount is 55%. The maximum Clean Rivers Impervious Area Charge (IAC) discount is 20%. Applicants earn the maximum discount by using green infrastructure to retain the full volume of stormwater runoff from a property’s impervious surfaces in a 1.2-inch storm. Green infrastructure that retains the volume from smaller storms will produce a proportionally smaller discount. The calculations assume that 710.75 gallons of stormwater are produced from 1.2 inches of rain for each ERU. An ERU, or equivalent residential unit, is the unit of measurement DC Water uses to assess properties for impervious area. One ERU is equal to 1,000 square feet of impervious surface.