The U.S. Environmental Protection Agency (EPA) has published an updated calculator to help construction sites calculate their rainfall erosivity factor — the “R” in the Revised Universal Soil Loss Equation or RUSLE. The updated calculator uses data from the Natural Resources Conservation Service’s Revised Universal Soil Loss Equation, Version 2 (RUSLE2) database.

Many National Pollutant Discharge Elimination System (NPDES) permitting authorities waive stormwater permitting requirements for small construction sites with a low erosivity potential. If allowed by the NPDES permitting authority, this calculator can be used by small construction sites to determine their eligibility for a low erosivity waiver. Operators of small construction sites in areas where EPA is the NPDES permitting authority qualify for the waiver if the “R” factor is less than five during the period of construction activity. Read more.