The monthly commercial stormwater rate is computed by multiplying the fixed rate ($16.73) times the number of impervious units applicable to the parcel times the rate adjustment as determined under Redmond Municipal Code (PDF) (RMC) Section 13.18.060. This formula is expressed mathematically as follows:
Fixed Rate times Impervious Units times Rate Adjustment equals Monthly Charge
An impervious surface refers to any hard surfaced area such as asphalt or concrete sidewalks, paving, parking lots, etc. which prevents the entry of water into the soil. One impervious unit is equivalent to 2,000 square feet of impervious surface area.
Generally, the rate adjustment used to compute the monthly service charge shall be determined by taking the coverage factors and adding or subtracting any applicable water quantity and quality factors.