Congress enacted the Clean Water Act in 1972 with the expressed purpose of restoring and maintaining the quality of the waters of the United States. Later, in 1987, the Clean Water Act was amended by the Water Quality Act. The Water Quality Act added various provisions to the Clean Water Act, including provisions that authorized the United States Environmental Protection Agency (EPA) to regulate storm water discharges from construction sites. Pursuant to this authority, the EPA has set forth regulations that generally require construction operators to obtain storm water permits for construction activities that disturb land.
Large and Small Construction Activities
Under federal regulations enunciated by the EPA, certain construction activities with the potential to discharge storm water to domestic waters must either obtain a National Pollutant Discharge Elimination System (NPDES) permit or qualify for a waiver. Regulated storm water discharges can be generally grouped into two categories: "large" and "small."
- A "large" construction activity consists of an activity that will disturb, or is part of a "common plan of development or sale" that will collectively disturb, five or more acres of land
- A "small" construction activity consists of an activity that will disturb, or is part of a "common plan or development or sale" that will collectively disturb, between one and five acres of land
Only operators of small construction activities may obtain waivers from the ordinarily applicable permit requirements for storm water discharges. In other words, no waivers are available for large construction activity.
For small construction activities, three waivers are generally available, subject to the approval of the NPDES permitting authority in each state:
- Rainfall Erosivity Waiver: To qualify for this waiver, the construction activity basically must occur during a period of time where the volume of rainfall is predicted to be negligible. Specifically, the small construction project's rainfall erosivity factor calculation ("R" in the Revised Universal Soil Loss Equation) must be less than five during the period of construction activity. The construction operator must also submit certification to the NPDES permitting authority that construction activity will occur only when the rainfall erosivity factor is less than five.
- TMDL Waiver: This waiver may be available in situations where the EPA has set up or approved a total maximum daily load (TMDL) for the specific pollutants at issue. In construction projects, pollutants generally consist of sediment (e.g., total suspended solids or siltation) or other contaminants that are discharged as a result of the construction activity. If the EPA concludes, based on the TMDL, that storm water discharge controls are not necessary to protect water quality, the permit is likely applicable.
- Equivalent Analysis Waiver: This waiver is only available for non-impaired waters; it also rests on a determination that storm water controls for the small construction site are not necessary. Here, however, the construction operator is permitted to develop an equivalent analysis, (i.e., in lieu of a TMDL analysis), that establishes allocations for the site for the pollutants of concern. In the alternative, the analysis may ascertain that such allocations are not needed to protect water quality. The EPA requires the equivalent analysis to be developed based on the following factors:
- Existing in-stream concentrations
- Expected growth in pollutant concentrations from all sources
- Margin of safety
It should be noted that any discharge of storm water associated with small construction activity that is neither covered by a permit nor a waiver may be a considered a prohibited discharge under the Clean Water Act.
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