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April 14, 2016
Reaping the benefits of a Low Erosivity Waiver
By Emily Remmel, JD, Legal Editor

If you are planning a small construction project now or in the future, did you know that you may qualify for a waiver from the U.S. Environmental Protection Agency (EPA) or your state permitting authority? Projects that qualify for the waiver are exempt from the Clean Water Act’s (CWA) National Pollution Discharge Elimination System (NPDES) construction stormwater permitting scheme.

During storm events, exposed soil and sediment at construction sites can run off-site and into water resources nearby. To protect water quality, the CWA requires certain construction projects to obtain a permit before breaking ground. Construction projects that disturb 1 or more acres of land or projects that disturb less than 1 acre but that are part of a common plan of development require a construction stormwater permit.

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However, certain small construction sites may qualify for a Low Erosivity Waiver (LEW) from their applicable NPDES permitting program. Erosivity is a method of describing the likelihood for soil to wash off disturbed, bare earth during a precipitation event. Several localized factors are at play when determining a site’s erosivity, such as soil type, geology, force of precipitation, and freeze/thaw cycles. Projects that qualify will save time and money by avoiding meandering through the NPDES permitting process.

Who qualifies for a LEW?

Small construction sites may qualify for LEWs, if:

  • The construction site disturbs less than 5 acres, and
  • The rainfall erosivity factor (the “R” factor) value is less than 5 during the period of construction activity.

Calculating the rainfall erosivity factor can be complicated using the United States Department of Agriculture’s Revised Universal Soil Loss Equation (RUSLE). To reduce error and minimize confusion, the EPA has developed an online calculator for construction projects to determine whether or not a site meets the eligibility requirements for the rainfall erosivity waiver.

To calculate the rainfall erosivity factor, operators will need the construction site’s longitude and latitude, or address, as well as the estimated start and end dates of construction. Often, construction projects that are flexible with start dates or that have the capability to expedite site stabilization may qualify for the waiver that others would not have.

How to apply for a LEW?

Operators of small construction sites must notify the EPA or state NPDES program authority of its intention to file for a waiver. The operator must submit a waiver certification before commencing construction activities. The EPA and many states allow prospective LEW projects to apply online.

Operators should check with their implementing NPDES permitting agency for more information.

Additional LEW tips to consider:

  • The NPDES permitting authority has broad discretion in determining where, when, and how to offer the waiver, including establishing an R factor less than 5.
  • Some states do not offer a waiver.
  • Other site-specific factors, such as proximity to water resources, sensitivity of receiving waters, and sedimentation may be considered.
  • If the site is not eligible for a waiver, the project must submit a Notice of Intent to obtain permit coverage.

Small construction sites should take advantage of the LEW because these sites usually do not have adverse water quality impacts. In doing so, the LEW can save construction project operators considerable time, money, and stress.

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