EPA Stormwater Construction General Permit: Low Erosivity Waiver



For several years, property developers and the construction industry have been required to obtain EPA Stormwater Construction General Permits for their construction projects. If your project discharges to waters of the United States and meets either criteria listed below, your project is subject to NPDES permitting.

  1. Disturb one or more acres of land, or
  2. Disturb less than one acre of land but is part of a common plan of development or sale that will ultimately disturb one or more acres of land.

In February 2012, the EPA incorporated a waiver in SWPPP Appendix C for small construction activities that will impact less than five acres. Also incorporated was a rainfall erosivity waiver that evaluates the possibility of erosion in areas of the U.S. with an arid or semi-arid climate. EPA determined that areas with a rainfall erosivity factor (R) equal to, or lower than, 5 will not be required to apply for a stormwater permit.


In February 2017, the EPA issued a new general permit that made applying for this waiver more accessible. The waiver, now called Low Erosivity Waiver (LEW) Certification, may be completed using the newly approved form in conjunction with the updated EPA Rainfall Erosivity Factor Calculator, available here. This tool uses the property coordinates and proposed construction schedule to calculate the rainfall erosivity factor by using the Natural Resources Conservation Service’s (NRCS) Revised Universal Soil Loss Equation, Version 2 database. The applicability of this waiver in New Mexico is significant, especially in the low-rain months from November to March. During these months, the typical monthly precipitation is less than an inch. This waiver is available to the entire state of New Mexico with the exception of the Pueblo of Sandia.


For assistance in determining how this may affect your facility, contact Milton Rosado in the Albuquerque Office by calling (505) 266-6611 or the Trinity office nearest you by calling (800) 229-6655.