Stormwater rate structures are typically based on impervious surface in some form; however, there is no standard and there are hundreds of variations in rate structures. Many utilities recognize that other surface types also contribute runoff and introduce flow factors for gravel surfaces. Some also consider land cover from compacted turf as well.
Residential and commercial rate structures balance the need to equitably charge customers with administrative simplicity. Many utilities choose to have one flat charge for each single-family residence. Other utilities recognize that not all single-family residences are the same, and develop rate structures with rate tiers for different property sizes or different footprints.
Rate credits are an important part of a stormwater rate structures. One of the most common types of rate credits are those for residential subdivisions that use retention and/or detention basins to remove or detain stormwater runoff. Other types of rate credits are those associated with on-site stormwater treatment facilities and direct discharge parcels where stormwater runoff is conveyed to a receiving water without entering a municipally-owned conveyance system.
