Renewed General Permit for Stormwater Discharges Associated with Construction Activities in Maryland

The Maryland Department of the Environment (MDE) has issued the final renewal permit for the General Permit for Discharges ​of Stormwater Associated with Construction Activity (20-CP), effective April 1, 2023. Existing permittees (registered under the previous Maryland General Permit No. 14-GP [14-GP]) must submit a Notice of Intent (NOI) no later than September 30, 2023, to prevent a lapse in coverage. Maryland General Permit No. 20-CP replaces Maryland General Permit No. 14-GP, which expired on December 31, 2019.

The renewed permit incorporates significant changes over the prior permit. Per MDE’s notice, the significant changes between the prior 14-GP permit and the new 20-CP permit include:

1. The permit has been reorganized to consolidate similar requirements. Effluent limits are now organized into either technology-based (specific work practices related to erosion control, pollution control, and dewatering) or water quality-based requirements. The water quality-based requirements are established for projects in watersheds with High-Quality Waters (Tier II) or for watersheds with known impairments.
2. For projects in Tier II Watersheds, a completed checklist is required at the time an NOI is filed as proof of antidegradation review.
3. The permit clarifies that stormwater discharges from earth-disturbing activities associated with the construction of staging areas and the construction of access roads conducted prior to active mining are eligible for coverage under the 20-CP.
4. The permit language has been expanded with the goal of improved compliance by providing a clearer understanding of the requirements (e.g., requirements written directly into the permit).
5. The permit clarifies which non-stormwater discharges are prohibited and which are allowed.
6. A Stormwater Pollution Prevention Plan (SWPPP) is now required for each of the following: a) use of chemical additives or polymers, b) exposure of potential contaminants when disturbing soil or during demolition, c) activities where the permit requires implementation of specific pollution prevention controls (such as for vehicle fueling) and d) shared liability between and among operators on the same site, such as those that are part of a larger common plan of development.
7. If an SWPPP is required, it must be available on-site.
8. Technology-based limits have been updated to reflect the current federal Construction and Development Effluent Guidelines (40 CFR Part 450), which include managing dewatering activities, implementing pollution prevention measures, and providing and maintaining buffers around surface waters (referred to as Stream Protection Zones).
9. New Stream Protection Zone (SPZ) requirements require operators to avoid disturbances within 50 feet from the edge of Tier I streams or an average of 100 feet and not less than 50 feet at any point from Tier II streams. If disturbances are required within the SPZ, several controls must be considered for the project.
10. The permit includes one additional alternative and one additional requirement regarding inspection frequency. In addition to inspections once per week and 24 hours after a storm event, the permit allows more frequent inspections in lieu of the after-storm inspection. It also requires more frequent inspections for projects in Tier II watersheds.
11. A storm event is now defined as 0.25 inches of rain or more.
12. The permit will now address the use of chemical additives or polymers to reduce turbidity. The permit includes a pre-approved list of products to increase efficiency. For products not on the approved list, there is a required MDE review/approval method established to evaluate the potential toxicity of the product. Cationic polymers require an additional review with residual testing.
13. Sites with known contaminated soils or sites with demolition of buildings with paints or caulking containing polychlorinated biphenyls (PCBs) are subject to additional pollution prevention measures.
14. The permit clarifies when transfers of permit coverage are possible and when a new or separate NOI is required, to reduce ongoing confusion for larger common plans of development. In addition, there is a new classification of Single-Family Home Builder with certain exemptions when projects occur within a larger common plan of development.
15. The public notification period language was expanded to identify processes for addressing concerns regarding the Erosion and Sediment Control plan, how to request copies of plans, and how concerns may be provided to MDE even after the public notification period ends.
16. Other changes of note include updated definitions, minor updates to various permit conditions, a new table clarifying the various deadlines for coverage under the permit, additional requirements for the continuation of registration under an expired general permit, and prohibition of new registrations after permit expiration.

The General Permit for Discharges of Stormwater Associated with Construction Activity (20-CP) includes changes that should be reviewed carefully. MDE has reorganized the permit with the goal of creating a clearer understanding of permit requirements. Specific construction activities will now require a SWPPP and all NOI will be shown on the MDE e-Permits interface for 14 days. During this time, citizens may ask to review the available erosion and sediment control and stormwater management plans and submit concerns to the approval authority and MDE.

The full renewed permit and background documentation, including a fact sheet, frequently asked questions, NOI forms, and guidance documents, are available on MDE’s website.

If you would like to discuss Maryland’s revised General Permit for Discharges of Stormwater Associated with Construction Activity (20-CP), please contact Trinity’s Maryland office at 240.379.7490.