The following question and answer document provides answers to general questions about U.S. Environmental Protection Agency (EPA) National Pollutant Discharge Elimination System (NPDES) construction stormwater permitting program, and specific questions about various requirements in EPA’s 2012 Construction General Permit (CGP). This document incorporates questions and answers from the 2012 EPA document, “The 2012 EPA CGP: Answers to Common Questions” which was most recently updated on December 16, 2014. It is intended for use by operators of construction sites who are eligible for coverage and/or who are permitted under EPA’s 2012 CGP, or by interested members of the general public.
The permit requires that sediment control practices (e.g., filter berms, silt fences, temporary diversion dikes) to be established on all down gradient perimeters and must be in place before any upgradient land‐disturbing activities begin. The Minnesota Pollution Control Agency recognizes that in some areas where land disturbance is minimal, perimeter controls may not be practicable or, alternatively, not necessary in order to minimize sediment from reaching surface waters or stormwater conveyance systems. When designing sediment control practices, the permit allows consideration for the nature of stormwater runoff and run-on at the site including factors such as slope and site drainage features. In these cases, permittees must document the site characteristics in the project’s Stormwater Pollution Prevention Plan (SWPPP) and may proceed with construction activity in those areas without installing perimeter controls.
It is important to remember, permittees are ultimately responsible for any off-site impacts from construction activity that result or may result in discharges to waters of the state (Minn. R. 7050.0210). For this reason, permittees are encouraged to provide a contingency plan in the SWPPP that addresses the procedures for correcting the site in the event that sediment has left those areas where sediment control practices were not installed and is causing or has the potential to cause off site impacts to waters of the state or other sensitive areas.
To clarify this concept, the sediment control requirement only applies to perimeter areas of the construction site that receive stormwater from the earth-disturbing activity. If a portion of the construction site’s perimeter area does not receive stormwater from earth-disturbing activities, perimeter controls would not be required in that portion of the site. Therefore, perimeter controls would not be necessary in the perimeter area surrounding construction activities in areas of sites where no new earth-disturbing activities occur, which could include:
Additionally, if stormwater does flow from small earth-disturbing activities associated with linear utility projects (e.g., utility pole setting) to perimeter areas of the site, but due to the nature of the site, sediment is prevented from leaving the site, then the perimeter control requirement will be satisfied. Site conditions that may prevent sediment from leaving the site include, but are not limited to, minimal scope of the disturbance, preservation of vegetation surrounding the disturbed area, implementation of controls that keep the ground stabilized (minimizing erosion and sedimentation) or minimal slopes. The following example illustrates site-specific conditions and practices that, should they occur in select areas of a small linear utility project, may make it unnecessary to install additional sediment controls along perimeter areas of the site because any discharge of construction-related pollutants will have been prevented:
While perimeter controls may be unnecessary or not practicable in the some circumstances, operators are reminded to continue all inspection requirements found in the permit. This includes all vehicle exit locations and surface waters or any other areas adjacent to the project for evidence of erosion and sediment deposition. Permittees must make amendments to the SWPPP as necessary anytime the SWPPP is found to be ineffective and is not achieving the general objectives of minimizing pollutants in stormwater discharges associated with construction activity.