Calculator determines if a construction site is eligible for an NPDES storm water permit waiver
The U.S. Environmental Protection Agency (EPA) released its updated Soil Erosivity Calculator for determining the soil erosivity (R) on construction sites. The EPA took the calculator down in 2012 to update its database and fix some problems. The erosivity calculator can be used to determine if a construction site meets the requirements for a waiver from a NPDES storm water permit. A construction site must have soil disturbance greater than 1 acre and less than 5 acres and have an R-value of less than five in order to qualify for the waiver. Typically this waiver is applicable to construction projects that have short durations and/or are very flat sites. Both of these characteristics result in low R-values. A waiver can save a construction project on consulting fees (less monitoring reports and sampling) and will reduce scheduling demands for inspections and reporting. The low erosivity waiver for California construction storm water projects is submitted through the SMARTS system prior to a project starting.