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Code Update: Construction Stormwater Permitting and Regulations

Lily Montesano on October 26, 2020 - in Articles, Column

LILY MONTESANO, CISEC


Construction sites can generate substantial amounts of pollutants during a relatively short period of time. From exposed soils to concrete, trash and solvents, pollutants present at construction sites, if uncontrolled, can easily be conveyed offsite and into waterways, degrading water quality and damaging delicate ecosystems. To limit such degradation, the discharge of stormwater from construction sites is regulated at several levels: federally by the U.S. Environmental Protection Agency (EPA), by some state governments, and locally, generally by the holders of Municipal Separate Storm Sewer System (MS4) permits.

ANDREW EARLES, PH.D., P.E.

The Clean Water Act and Construction General Permit

The authority to regulate construction stormwater discharges ultimately lies in the Clean Water Act (CWA), which is enforced by the EPA. The CWA is the United States’ primary legal framework for regulating the discharge of pollutants into waters of the United States (WOTUS).

Section 402 of the CWA establishes the National Pollutant Discharge Elimination System (NPDES). This permitting system regulates discharges into WOTUS—including discharges of stormwater from construction sites—to protect water quality.

In some states, the discharge of stormwater from construction sites is authorized directly by the Construction General Permit (CGP) under the NPDES. However, Section 402.5 authorizes the EPA to delegate to state governments the authority to issue and enforce NPDES permits as long as those governments can demonstrate the capacity to administer such a program. It’s important to note, however, that the EPA retains the authority to directly regulate all construction sites subject to the CWA; the EPA can still visit, review and enforce codes upon construction sites that are operating under a state-based construction stormwater discharge permit.

JENNIFER KEYES, CPESC

From a permitting perspective, a typical construction project would be subject to either a certification under the national CGP or a certification under the state’s own permitting system, but not both unless the project is straddling jurisdictional boundaries between state and federal authority (i.e., a linear project that crosses a portion of a federal facility as well as a delegated MS4 jurisdiction). The EPA provides a helpful tool at www.epa.gov/npdes-permits to determine which permits are issued directly by the EPA and which permits are issued by a state agency.

Municipal Separate StormSewer Systems

An MS4 is a system of conveyances owned by a government or other publicly owned entity that serves to transport storm flows to WOTUS. Because MS4s discharge into WOTUS, their activities also are generally regulated by the CWA and permitted under the NPDES or a state program with delegated authority from the EPA.

MS4 permits contain several requirements designed to reduce the discharge of pollutants from sources feeding into the MS4, including that the MS4 develop and implement a program to regulate stormwater discharges from construction sites. From a permitting perspective, this means a typical construction project located within a permitted MS4 would be subject to the local stormwater construction site program, which may require a local permit authorized by the MS4.

The best way to determine if a construction project is subject to local permitting is to check the municipality’s website. If the website can’t be found or the requirements are still unclear, reach out directly to the municipality.

Locating Construction Stormwater Discharge Requirements

A key to attaining and maintaining compliance with all applicable construction stormwater discharge permits at a given site is knowing where to look for the regulations. Because authority over construction stormwater discharge permits and MS4 permits is delegated to some state governments by the EPA, permitting requirements aren’t standardized across the United States. The information that follows can be used as a good starting point to figure out which permits do and do not apply to a given project.

A photograph shows evidence of an overwhelmed perimeter control measure and resulting offsite discharge of sediment-laden water.(Drew Maraglia)

The CGP and state-administered equivalent permits apply to construction sites that disturb 1 acre or more as well as sites that will disturb less than 1 acre but are part of a larger common plan of development or sale that will disturb 1 acre or more. For states where the EPA has delegated authority to a state agency, the EPA provides a hyperlink to the issuing agency’s website at www.epa.gov/npdes-permits. The text of the CGP can be found at bit.ly/32kqO5l.

The typical threshold for MS4 regulation of construction sites is disturbance of 1 acre or more, or disturbances of less than 1 acre that are part of a larger common plan of development or sale disturbing 1 acre or more, as mandated by the NPDES or state-equivalent permit. However, MS4s can choose to set their own thresholds, which may be lower than 1 acre of disturbance or triggered by the specific risks of the project. Many MS4s have created websites to assist permittees in locating and understanding permit requirements. Stormwater regulations also are typically found within land-development codes, municipal ordinances, and/or storm drainage criteria manuals. If still in doubt, contact the municipality directly.

There also are many professionals who specialize in construction stormwater permitting and can help evaluate the construction stormwater permitting requirements for your project. Such professionals have experience navigating the multi-tiered construction stormwater discharge permitting process and can offer comprehensive services to assist with compliance, ranging from drafting permit-mandated documents to performing required site inspections. Organizations such as the International Erosion Control Association (IECA) provide resources to members that can help with locating consulting specialists with the necessary experience for your project. 


Lily Montesano, CISEC, is a water resources specialist for Wright Water Engineers Inc.; email: lmontesano@wrightwater.com; Andrew Earles, Ph.D., P.E., CPESC, is vice president of water resources at Wright Water Engineers Inc.; email: aearles@wrightwater.com; and Jennifer Keyes, CPESC, is a water resources specialist for Wright Water Engineers Inc.; email: jkeyes@wrightwater.com.

About Lily Montesano

Lily Montesano, CISEC, is a water resources specialist for Wright Water Engineers Inc.; email: lmontesano@wrightwater.com; Andrew Earles, Ph.D., P.E., CPESC, is vice president of water resources at Wright Water Engineers Inc.; email: aearles@wrightwater.com; and Jennifer Keyes, CPESC, is a water resources specialist for Wright Water Engineers Inc.; email: jkeyes@wrightwater.com.

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