Most contractors know generally that if their construction work will disturb one acre or more of earth, they may need to obtain coverage under the applicable construction stormwater discharge general permit (“CGP”).  However, there are some instances where doesn’t hold true, as well as instances where CGP coverage is required even though the contractor’s work on site disturbs less than one acre.  There are also situations where federal or local permitting processes apply instead of the normal state CGP procedure.  This blog post covers some of these lesser-known exceptions where the typical CGP coverage surprisingly is, or is not, required.

Permits for less than one acre of disturbance

Most contractors are familiar with the “common plan of development” provision that is in every CGP, whether it be a state’s permit or EPA’s federal CGP.  This provision states that a permit must be obtained when your construction will disturb one or more acres of land or will disturb less than one acre but is part of a common plan of development or sale that will ultimately disturb one or more acres of land.  Definitions of “common plan of development” differ slightly from jurisdiction to jurisdiction, but contractors should always be alert if the owner is, has recently, or will soon be undertaking other construction nearby.  The different applications of this provision could take up a blog post by itself.

Contractors sometimes overlook the fact that, although on-site earth disturbance (including common plan) may be less than one acre, the earth disturbance acreage for permitting purposes can take into account disturbances occurring off the site.  If the project has a separate dedicated staging area, laydown yard, borrow pit, etc., then the disturbance resulting from that off-site activity will be added to the on-site disturbance when calculating whether one or more acres will be disturbed.  Note, however, that borrow pits that are not used solely by your project (e.g. commercial pits) do not count toward your project’s earth disturbance.

In some jurisdictions, CGP coverage may still be required even though the entire project (including common plan and off-site activities) disturbs less than one acre.  In Oregon, at least three cities require CGP coverage for disturbances less than one acre.  In coastal counties of South Carolina, CGP coverage is required for disturbances under one acre near state waters.  And in Miami, Florida, the City Code requires state CGP coverage for earth disturbances of ½ acre or more, and the Florida Department of Environmental Protection recognizes this as a valid requirement.  As always, it is important to know applicable state – and local – permitting rules.

Local Delegated Programs

In the states that have their own CGPs, that permitting authority was delegated to them from the U.S. EPA.  Some states have then further delegated permitting authority to certain local jurisdictions that have state-approved local programs.  Tennessee has a handful of counties or cities with Qualified Local Programs that have their own CGP approval processes.  In Colorado, three cities have Qualifying Local Programs, where projects of 1-5 acres qualified under the local regulations will be automatically permitted under the state CGP.  Wisconsin has a single Authorized Local Program in Waukesha County.  In the City of Chicago (except for O’Hare Airport), projects do not need state CGP coverage but must follow the stormwater discharge requirements of the City building permit.  Obviously, applying to the state for coverage when it should be done locally can lead to permitting delays.

Low-Erosivity Waivers

Many state CGPs have low-erosivity waiver provisions.  If conditions at the site location at the time of earth disturbance are such that negligible erosion is expected, the project may qualify for a waiver of the requirement to obtain CGP coverage.  Waivers often depend on fairly complex calculations, but if the project is in an arid location or performance is limited to a “dry” season, a waiver may be applicable.  This waiver doesn’t come into play often, but it is worth checking in certain areas of the country.

Combined Sewer

A fairly common, but still not universally known, exemption from CGP permitting is for discharges to a combined sewer system.  The goal of CGPs is to prevent sediment-laden stormwater from reaching public waters.  However, sediment in stormwater discharged to a combined sewer system (i.e. conveying both stormwater and sewage) that leads to a public treatment plant theoretically does not reach public waters because the sediment removed at the treatment plant.  Many older cities have combined sewer systems.

Therefore, the CGPs in some states expressly exempt stormwater discharges to combined sewers from the requirement to obtain permit coverage.  In other states, the combined sewer exemption is not clearly stated in the CGP, but the state permit authorities will clarify (in writing is best) that it applies.  Where the exemption is recognized, all stormwater discharges must be directly to a combined sewer to qualify.  For example, if stormwater leaves the site via a natural swale and only thereafter reaches a combined sewer inlet, the discharge is not exempt from permitting.  But in an urban setting where the site is surrounded by city streets and gutters, direct discharge to a combined sewer may be found.

Federal Facilities or Indian Lands

In some states, projects performed at federal facilities or on Indian Land must be permitted under the U.S. EPA CGP instead of the state CGP (even if the EPA has delegated permitting authority in general to the state).  Projects performed on federal facilities in Colorado, Delaware, Vermont, Washington State, and in Denali National Park in Alaska require federal EPA GCP coverage.  What counts as a federal facility (or work performed by a “federal operator”) varies somewhat from state to state.

In a little over half the states, earth disturbances on Indian Land must be permitted under the U.S. EPA CGP instead of the state CGP, in recognition of the unique legal status of Native American tribes.  What territory qualifies as Indian Land is defined in the applicable CGPs, but typically it means specifically designated reservations.

Oil and Gas Permitting

Permitting for stormwater discharge from construction work on oil and gas facilities varies from state to state.  In states where the U.S. EPA remains the permitting authority, uncontaminated discharges from construction activities relating to oil and natural gas exploration, production, process or treatment operations, or transmission facilities are exempt from permitting.  Among states with their own CGPs, some require permit coverage for such work and some don’t.  Texas and Oklahoma, however, are the true exceptions.  Due to a quirk in delegation of authority, oil and gas work in Texas or Oklahoma requires special U.S. EPA CGP coverage, in addition to the state CGP coverage for the rest of the project.  For example, a building under construction that requires a new gas service line can mean two Notices of Intent with separate permit coverage dates and two Notice of Termination with separate termination dates.


Stormwater permitting frequently is not as straightforward as it seems.  CGP coverage can be required, not required, or required under a different permit when you don’t expect it.  It is always best to carefully examine the issue to avoid obtaining permit coverage unnecessarily or, worse, undertaking work without obtaining the necessary permit coverage.

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