As the end of the growing season approaches throughout much of the country, the focus at many construction sites may shift toward restoration activities. Goals could include implementing temporary stabilization controls or establishing cover crops to stabilize the site through winter and ultimately achieve permanent vegetative cover in the spring. Others may attempt to achieve final stabilization and terminate permit coverage prior to winter. Whichever scenario applies, some useful policies and exemptions exist that could relieve some of the regulatory burden for a site and even reduce the risk of permit violation.
The U.S. Environmental Protection Agency requires a National Pollutant Discharge Elimination System (NPDES) permit for stormwater discharges from construction activities that disturb 1 acre or more of land, or from smaller sites that are part of a larger, common plan of development that will disturb a cumulative total of 1 acre or more. For the purposes of the NPDES program, construction activities are defined as clearing, grubbing, grading and excavation. Although the EPA maintains jurisdiction over some states, federal facilities, and even oil and gas activities in Oklahoma, the majority of states have been delegated authority to authorize most construction projects under a state-specific permit.
Stabilizing the Site
While conducting construction activities, stabilization practices for disturbed soils are extremely important. The period in which soil areas are without a vegetative cover or an alternative cover must be minimized to the extent practicable. Stabilization measures must be initiated promptly whenever soil-disturbing activities have permanently ceased on any portion of the site, or when they have temporarily ceased and will not resume for more than 14 days.
To maintain compliance with the permit throughout construction, sites must temporarily be stabilized. To terminate authorization under the permit, sites must achieve permanent vegetative stabilization on areas not covered by permanent structures or permanent stabilization measures, such as gravel, gabions or riprap, and which otherwise must remain unvegetated, such as dirt access roads, utility pole pads or even the infield of a baseball diamond. (Yes, this is a real example.)
With some caveats for arid or semiarid areas, permanent vegetative stabilization is defined by the EPA and most states as a 70% or more uniform perennial vegetation that is evenly distributed across the site without large bare areas. Note that final stabilization criteria do not apply to disturbed areas on agricultural land that are restored to their preconstruction agricultural use.
Managing Inspection Cycles
At the commencement of soil-disturbing activities, routine and rain-event inspections must be initiated in compliance with the permit. Inspection frequencies vary but are generally required either:
- Once every 7 calendar days, or
- Once every 14 calendar days, and within 24 hours of a rain event producing 0.25 inch or more of rainfall within a 24-hour period.
Many permits allow for inspections at reduced frequencies under specific circumstances on a construction site, such as achieving temporary stabilization or encountering frozen conditions, based on the low potential for sediment discharges to occur. These conditions and frequencies can vary by state, so it is important to be familiar with your permit and the record-keeping requirements when adopting reduced inspection frequencies. The EPA outlines in detail the circumstances under which the number of inspections may be reduced, and the frequency at which they may be reduced, until coverage under the permit is terminated. A few conditions to note:
- Linear construction sites: Portions of the site that have undergone permanent stabilization may reduce inspection frequencies to twice per month for the first month as well as within 24 hours of a rain event as described above or following a snowmelt discharge producing 3.25 inches of snow within a 24-hour period. Where there is no evidence of stabilization problems, inspections may be suspended on that portion of the site. The remaining disturbed areas of the site must maintain the routine and rain-event inspection frequency.
- Arid, semiarid or drought-stricken areas: Inspection frequencies may be reduced to once per month and within 24 hours of a rain event or snowmelt as described above. The Stormwater Pollution Prevention Plan (SWPPP) must document that this reduced inspection frequency has been implemented, including the start and end dates of the seasonally dry period.
- Frozen conditions: If construction activities are being suspended because of frozen conditions, inspections may be temporarily suspended until thawing begins if discharges are unlikely because of continuous frozen conditions or if all disturbed areas of the site have been stabilized. If construction will continue during frozen ground conditions, inspections can be reduced to monthly, except for areas under active construction. These start and end dates must be documented in the SWPPP.
Leveraging Options to Minimize Frequency
Considering the level of effort needed to perform routine and rain-event inspections, sometimes in remote locations, the ability to reduce inspection frequencies can drive major cost savings. These savings can be compounded by a long winter with frozen ground conditions in some regions or by extended dry periods in other parts of the country.
The greatest cost savings, though, come through minimizing inspections altogether during these periods by achieving permanent stabilization on-site as quickly as possible and terminating permit coverage. In addition to producing cost savings, this also reduces the risk of noncompliance that comes with having an open permit on an idle site for months at a time. Achieving permanent vegetative stabilization by the end of the growing season and in advance of winter conditions can be challenging and takes some pre-planning. Project schedules are often focused on construction productivity and achieving substantial completion; they may overlook the pre-planning and restoration activities that should be performed to achieve permanent vegetative stabilization concurrent with construction completion.
Stabilization requirements and reductions in inspection frequencies vary, so it is critical to read and understand your permit. Some states, like Kansas, require a record of stabilization activities to be recorded on a Grading and Stabilization Activities Log as part of the SWPPP. Other states, like Michigan, have a specific Winter Construction Storm Water Inspection Policy in which the certified Storm Water Operator can certify the inspection report without performing an on-site inspection. Meanwhile, Arizona outlines a stabilization exemption for arid, semiarid and drought-stricken areas where stabilization is considered met when the site has been seeded or planted to establish 70% or more vegetative cover native to the local undisturbed area within three years.
With a thorough understanding of the permit regulations for a construction project, a strategic plan can be developed that alleviates the inspection burden and reduces the risk of noncompliance while providing adequate stabilization to minimize the potential for off-site sediment discharges and ultimately protect the natural environment.
SPCC plans are just as important during the construction phase as during operations. Incorporating them early can help reduce liability and schedule risks.