The Maryland NPDES Stormwater Permit for construction—Maryland General Permit No. 20-CP—is the state permit that lets you discharge stormwater from a construction site that disturbs one or more acres of land. You apply for coverage by filing a Notice of Intent (NOI) with the Maryland Department of the Environment through its online ePermits system, and you cannot legally start earth-moving work until the state authorizes you.
Getting this wrong is costly. If you break ground without coverage, you discharge pollutants without authorization under the federal Clean Water Act, and that can lead to stop-work orders, fines, and personal liability. Maryland’s current permit, the 20-CP, took effect April 1, 2023 and runs through March 31, 2028, so always confirm you are working from the 20-CP-A version before you file.
Here is what you will learn in this guide:
- ✅ Who counts as an “operator” and must file the 20-CP NOI
- 📋 Every document and number you must gather before you open the ePermits form
- 🖊️ A line-by-line walkthrough of each NOI section with sample entries
- 🏗️ Three real-world filled-out examples from start to finish
- ⚠️ The field-level mistakes that get NOIs rejected or delayed
What the 20-CP Permit Is and Who Must File It
The 20-CP is Maryland’s general NPDES permit for stormwater discharges associated with construction activity. It is authorized under Clean Water Act Section 402 and the federal rules at 40 CFR 122.26 and 40 CFR 450, and at the state level it flows from Environment Article, Title 9, Subtitle 3 and COMAR 26.08.04. The Industrial Stormwater Permits Division inside MDE’s Water and Science Administration runs the program.
You must file if you are an operator of a site that will disturb one or more acres of land. Coverage is also required if your project disturbs less than one acre but is part of a common plan of development that eventually disturbs one acre or more. A common plan means a contiguous area where many separate construction activities happen under one overall plan, such as a subdivision built lot by lot.
An “operator” answers yes to at least one of these questions: Do you control the site plans and specifications? Do you have day-to-day operational control over permit compliance? Can you direct workers and halt work until violations are fixed? Most projects have two operators—often the owner/developer and the general contractor—and both may need coverage.
Subcontractors usually are not operators. If the general contractor directs your work on-site, you likely do not need your own coverage. The owner of land where a third party builds (like a homeowner having a house built for personal use) also may not be an operator, because the homebuilder controls the work.
Misreading the operator definition is the first big trap. If you assume “the owner files, so I don’t have to,” and you actually control daily compliance, you can be cited for discharging without a permit even though someone else filed. When in doubt, MDE publishes a Who Is an Operator Guide to help you decide.
Before You Start: Documents and Information You Need
The NOI asks for information that comes straight from your approved plans, so gather these items before you log in. A complete NOI with all supporting documents is what starts the 14-day public notice clock; an incomplete one just sits and delays you.
- Approved Erosion and Sediment Control (E&SC) plan. You must get E&SC and stormwater management approval from your local Soil Conservation District or other approval authority first; without it, MDE will not authorize coverage.
- Site name and exact location. Include the street address plus Maryland Grid Coordinates and latitude/longitude; a wrong coordinate sends inspectors to the wrong place.
- Watershed basin code and receiving waters. Name the stream, river, or storm sewer system that receives your runoff, because MDE checks it against impaired-water and Tier II lists.
- Total site area and disturbed area in acres. This number sets your fee tier and whether you need coverage at all.
- Estimated impervious surface area and runoff curve numbers. These come from your engineer’s drainage calculations.
- Stormwater BMPs and drainage area for each. List the management practices you will install and the area each one treats.
- Project type and end use. State whether the owner is public or private and whether the finished site is residential, commercial, or industrial, plus the SIC code if applicable.
- Stormwater Pollution Prevention Plan (SWPPP), if triggered. A SWPPP is required if you use chemical additives, disturb contaminated soils, have multiple operators under a common plan, or trigger dewatering turbidity monitoring.
- Tier II Antidegradation Checklist, if applicable. Sites discharging to a Tier II watershed must complete Appendix C before submitting.
- Subscriber Agreement Form. Federal rules require this form to validate that the person submitting can act for the responsible party.
If any item is missing, the practical consequence is delay: the public notice period will not start, and your project start date slips. Because the 20-CP has a roughly 45-day turnaround, a missing checklist can push your groundbreaking back by weeks.
Where to Get the Form and How to Access It
There is no paper NOI to download for the 20-CP. The Notice of Intent is submitted electronically through MDE’s ePermits website, and the same portal handles Notices of Termination and transfers of coverage. This is a change many longtime filers miss—mailing in a paper form will not get you coverage.
To access the system, create an ePermits account, then either prepare the NOI yourself or have an agent or consultant draft it. The portal lets agents and consultants fill in any part of the NOI and then route it to the responsible party for final electronic signature. The NOI must be electronically signed by a person in authority from the developer or builder.
Before you can sign on someone’s behalf, MDE requires a completed Subscriber Agreement Template Form so the agency can validate your authority. Technical problems with the portal go to the 24/7 Support link at the top of the system screen, or to mde.constructionswnoi@maryland.gov and mdhelp@egov.com.
You should also pull MDE’s helper documents from the same page before you start: the 20-CP Decision Tree (“Do I need a permit?”), the 20-CP Frequently Asked Questions, and the SWPPP Template. Reading the decision tree first can save you from filing when you do not need to, or from skipping a filing you do need.
Step-by-Step: How to Fill Out the 20-CP Notice of Intent Line by Line
The NOI is organized into five logical parts: Site Name and Location, Project Description, Permittee Identification, Certification, and Fees. Work through them in order, pulling answers from your approved plans. Each subsection below tells you what the field asks, how to answer it, a sample entry, an edge case, the common mistake, and the misconception to drop.
Part I — Site Name and Location
What it asks in plain English. This part wants to know what the project is called and exactly where on the map it sits.
How to answer it. Enter the project name as it appears on your approved E&SC plan, then the street address, county, Maryland Grid Coordinates, and the latitude and longitude of the site center. Add the watershed basin code for the receiving waters.
A specific example answer. Maria Lopez, a developer, enters Cedar Ridge Townhomes, 4400 Old Court Road, Baltimore County, and latitude 39.3812, longitude -76.7241.
A nuance or edge case. If your project has no street address yet because it is raw land, use the nearest road and a clear parcel description, then rely on the coordinates to fix the location.
A common mistake on this field and its direct consequence. Filers often copy latitude/longitude with a dropped minus sign or swapped values; this places the site outside Maryland in the mapping system and can flag your NOI for manual correction, delaying public notice.
A misconception people hold about this field. People think the address alone is enough. MDE’s e-Permits system maps the coordinates to check for Sensitive Species Project Review Areas and Tier II waters, so the coordinates do real work.
Part II — Project Description
What it asks in plain English. This section asks what you are building, how big it is, how much ground you will disturb, and where the runoff goes.
How to answer it. Enter total site area and disturbed area in acres, the estimated impervious surface area, the runoff curve numbers, the BMPs you will use with the drainage area each treats, the project type (public or private), the end use (residential, commercial, industrial), the SIC code if any, and the name of the receiving waters or storm sewer system.
A specific example answer. Maria enters total site area 12.5 acres, disturbed area 11.0 acres, end use residential, and receiving waters Gwynns Falls.
A nuance or edge case. For phased or staged construction under one common plan, use the total planned disturbance across all phases, not just the active phase, when deciding if you cross the one-acre line.
A common mistake on this field and its direct consequence. Filers understate disturbed acreage to drop into a lower fee tier; if MDE or an inspector finds the real number is higher, you face an enforcement issue and a corrected fee.
A misconception people hold about this field. Many think “disturbed area” means only where buildings go. It includes staging areas, access roads, and stockpiles, which often push the number past one acre.
Part III — Permittee Identification
What it asks in plain English. This part asks who is legally responsible for the permit and who to call about the site.
How to answer it. Enter the legal name of the permittee (company or person), the mailing address, and the name and phone number of the principal on-site contact. The permittee is the operator who will sign and be held accountable.
A specific example answer. Maria enters permittee Lopez Development LLC, contact Maria Lopez, phone (410) 555-0148.
A nuance or edge case. When an owner and a contractor are co-operators, each files its own NOI or they arrange co-permittee coverage; do not assume one filing covers both parties.
A common mistake on this field and its direct consequence. Listing a trade name that does not match the legal entity on file can cause the authorization letter to be issued to the wrong party, complicating later transfers and terminations.
A misconception people hold about this field. Owners think naming the contractor as permittee removes their own duty. If the owner still controls site plans, the owner remains an operator and shares liability.
Part IV — Certification and Electronic Signature
What it asks in plain English. This is the legal promise that everything you entered is true and that you will follow the permit.
How to answer it. A person in authority from the developer or builder reviews the NOI and applies the electronic signature in ePermits. Consultants may prepare the NOI, but only the responsible party can sign.
A specific example answer. Maria, as managing member of Lopez Development LLC, e-signs the certification on 04/15/2026.
A nuance or edge case. If a consultant signs for you, MDE must already have your Subscriber Agreement Form on file, or the signature will not be accepted as valid.
A common mistake on this field and its direct consequence. A consultant signs without authority and without a subscriber agreement; MDE treats the NOI as unsigned, and it is not processed, costing you the whole public notice window.
A misconception people hold about this field. People believe the certification is a formality. It is a sworn statement under penalty of law, and false information can lead to civil and criminal penalties.
Part V — Fees
What it asks in plain English. This part collects the application fee, which is set by how many acres you disturb.
How to answer it. The 20-CP fee structure lives in COMAR 26.08.04.09-1, section C. The historic NPDES construction fee schedule runs from exempt for the smallest sites up to $2,500 for the largest, scaling by disturbed acreage tier. Pay in ePermits by credit card or ACH.
A specific example answer. With 11 disturbed acres, Maria’s project falls in the 10-to-under-15-acre tier and she pays the matching tier fee plus the portal’s processing charge.
A nuance or edge case. Local and State government projects are exempt from fees, so a county public-works project enters its exempt status rather than paying.
A common mistake on this field and its direct consequence. Filers forget the portal adds a 3% credit-card fee or a $3 flat ACH fee; underpaying by the processing amount can leave the NOI marked unpaid and unprocessed.
A misconception people hold about this field. People assume the fee buys instant coverage. The fee only lets the NOI move into review and the 14-day public notice; authorization still has to be granted.
After the NOI: Public Notice and Authorization
Once you submit a complete NOI with all supporting documents, MDE starts a 14 calendar-day public notification period and posts the NOI on ePermits. Interested parties can review the E&SC plan and raise concerns with the approval authority and MDE.
For sites in Tier II watersheds, floodplains, or critical areas, Senate Bill 471 allows the notice period to extend up to a total of 60 days if MDE receives a written request for additional review. If site controls are challenged, you may have to revise the E&SC plan before the permit issues. After review, MDE grants 20-CP authorization and you may begin work.
Three Filled-Out Examples Using Real Scenarios
These three named filers show how different projects move through the NOI from start to finish. Each table covers the major sections you will complete.
Scenario 1: Maria Lopez — 11-acre residential subdivision (developer as permittee)
| Form Section | What Maria Enters |
|---|---|
| Site name | Cedar Ridge Townhomes |
| Location / coordinates | 4400 Old Court Road, Baltimore County; lat 39.3812, long -76.7241 |
| Total / disturbed area | 12.5 acres total, 11.0 acres disturbed |
| Receiving waters | Gwynns Falls |
| Project type / end use | Private / residential |
| BMPs | Sediment basin, silt fence, inlet protection |
| Permittee | Lopez Development LLC, contact Maria Lopez |
| SWPPP trigger | Yes — multiple operators under common plan |
| Fee tier | 10-to-under-15-acre tier |
| Signature | E-signed 04/15/2026 by managing member |
Scenario 2: Marcus Reed — 3-acre commercial pad site (contractor as sole permittee)
| Form Section | What Marcus Enters |
|---|---|
| Site name | Route 40 Retail Pad |
| Location / coordinates | 8800 Pulaski Highway, Baltimore County; lat 39.3105, long -76.4720 |
| Total / disturbed area | 3.4 acres total, 3.0 acres disturbed |
| Receiving waters | Back River (impaired for sediment) |
| Project type / end use | Private / commercial |
| BMPs | Silt fence, stabilized construction entrance, turbidity monitoring for dewatering |
| Permittee | Reed Site Contractors Inc., contact Marcus Reed |
| SWPPP trigger | Yes — dewatering to sediment-impaired water |
| Fee tier | Under-5-acre tier (exempt or lowest tier) |
| Signature | E-signed by company officer |
Scenario 3: Janet Cho — single-family home builder under a common plan
| Form Section | What Janet Enters |
|---|---|
| Site name | Willow Bend Lot 14 |
| Common plan number | MDRC12345 |
| Location / coordinates | Willow Bend Drive, Howard County; lat 39.2204, long -76.9011 |
| Total / disturbed area | 0.4 acres (part of 22-acre common plan) |
| Receiving waters | Little Patuxent River |
| Project type / end use | Private / residential |
| Permittee | Cho Custom Homes LLC, contact Janet Cho |
| Coverage basis | Single Family Home Builder under approved common plan |
| Fee | Tied to common-plan coverage |
| Signature | E-signed by owner |
Janet’s case uses the 20-CP’s Single Family Home Builder classification, which gives certain exemptions when detached homes are built on single lots inside a larger approved common plan. No townhomes or mixed construction qualify for that exception.
How to File the Completed Form
The 20-CP NOI has one filing channel: the MDE ePermits portal. There is no mail, fax, or in-person option for the NOI itself, which is why account setup is the first real step.
- Portal: Submit the NOI, attachments, and electronic signature through ePermits, linked from the 20-CP page.
- Fee and payment methods: Pay inside ePermits by credit card or ACH; credit cards add a 3% fee and ACH adds a $3 flat fee, with local and State government projects exempt.
- Processing time: Plan for about a 45-day turnaround, which includes the 14-day public notice and longer for Tier II sites.
- Proof of filing: Keep the email receipt from egov.com and your authorization letter, both retrievable in ePermits.
Separately, you must notify the Water and Science Administration Compliance Program two weeks before construction starts by calling (410) 537-3510. If your project dewaters more than 30 days or over 10,000 gallons per day on average, you also need a separate Water Appropriation and Use Permit under COMAR 26.17.06.
What Happens After You File
After you submit a complete NOI, MDE posts it for the 14-day public notice and the Industrial Stormwater Permits Division reviews it. If your site sits in a Tier II watershed with no assimilative capacity, MDE’s Tier II review staff must complete an antidegradation review before authorization, which adds time.
When review is complete, MDE grants 20-CP authorization, and only then may you begin earth disturbance. Throughout the project you must run self-monitoring inspections—generally weekly and after storm events, or every four business days—and keep records. Sites dewatering to Tier II or sediment-impaired waters must also perform daily turbidity benchmark monitoring against the 150 NTU daily-maximum benchmark and file quarterly turbidity reports.
When the work is done and the site reaches final stabilization, you close out coverage by filing a Notice of Termination in ePermits, which MDE Compliance must concur with. Termination requires established vegetative stabilization and removal of pollution controls and potential pollutants.
Mistakes to Avoid When Filling Out the Form
- Breaking ground before authorization. You discharge without a permit, which is a Clean Water Act violation exposing you to fines and stop-work orders.
- Filing a paper form. The NOI is electronic only, so a mailed form gets you no coverage and wastes time.
- Submitting an incomplete NOI. Without all supporting documents the 14-day notice never starts, stalling your project.
- Skipping E&SC plan approval first. MDE will not authorize coverage until your local approval authority signs off on the plan.
- Understating disturbed acreage. A low number triggers enforcement and a corrected fee when the true area is found.
- Wrong latitude/longitude. Bad coordinates misplace your site and flag the NOI for manual fixes and delay.
- Ignoring the common-plan rule. A sub-acre lot inside a one-acre-plus plan still needs coverage, and missing it means unauthorized discharge.
- Missing the SWPPP trigger. Using chemical additives or dewatering to impaired waters without a SWPPP is a compliance failure.
- Skipping the Tier II checklist. A Tier II site without the Appendix C antidegradation review cannot be authorized.
- No Subscriber Agreement on file. A consultant’s signature is rejected, leaving the NOI effectively unsigned.
- Forgetting the two-week start notice. Failing to call (410) 537-3510 before work starts is itself a permit condition violation.
- Underpaying the portal fee. Overlooking the 3% card or $3 ACH charge can leave the NOI marked unpaid.
Do’s and Don’ts
Do:
- Do confirm you are using the current 20-CP-A version, because filing under an expired permit is invalid.
- Do get E&SC approval first, since it is the gate to MDE authorization.
- Do check Tier II, impaired-water, and SSPRA status early, because they add review steps you cannot rush later.
- Do let your consultant prepare the NOI while you keep the signature, which speeds drafting without ceding legal control.
- Do save your egov.com receipt and authorization letter as your proof of coverage.
- Do call the Compliance Program two weeks before you start, as the permit requires it.
Don’t:
- Don’t start work before authorization, because that is an unpermitted discharge.
- Don’t understate acreage, since it triggers enforcement and fee corrections.
- Don’t assume one NOI covers every operator, because co-operators each carry duties.
- Don’t ignore staging areas and access roads when counting disturbed acres.
- Don’t use a chemical additive that is not on the pre-approved flocculant list without written MDE approval.
- Don’t forget to file a Notice of Termination, or you keep accruing compliance duties.
Pros and Cons of Filing on Your Own vs. With a Consultant
| Filing on Your Own | Filing With a Consultant |
|---|---|
| Saves consultant fees, good for simple sub-acre lots in an approved common plan | Costs more, but worth it on Tier II or impaired-water sites with extra reviews |
| You control timing directly in ePermits | Consultant drafts fast while you keep the signature, reducing errors |
| Builds your in-house knowledge for future projects | Brings expertise on SWPPP triggers and antidegradation checklists |
| Risk of missing field-level rules like coordinates or acreage | Lowers rejection risk by catching incomplete-NOI problems early |
| Fine when no SWPPP or Tier II review is triggered | Better when chemical additives, dewatering, or contaminated soils are involved |
The right choice depends on complexity. A single-family builder like Janet inside an approved common plan can reasonably self-file, while a developer like Maria with multiple operators and a SWPPP trigger benefits from professional help. The Industrial Stormwater Permits Division at (410) 537-3019 can answer questions either way.
FAQs
Do I need the 20-CP if my project disturbs less than one acre?
Yes. You still need it if your sub-acre work is part of a common plan of development that disturbs one acre or more overall. Stand-alone sub-acre sites generally do not.
Is there a paper version of the NOI I can mail in?
No. The 20-CP Notice of Intent is submitted only electronically through MDE’s ePermits portal, along with terminations and transfers.
Do staging areas and access roads count toward disturbed acreage in Part II?
Yes. Disturbed area includes staging areas, access roads, and stockpiles, not just building footprints, so include them in the acreage you enter.
Does naming the contractor as permittee remove the owner’s liability?
No. If the owner still controls site plans, the owner stays an operator and shares responsibility regardless of who signs.
Can my engineering consultant sign the NOI certification for me?
No. Only the responsible party signs, and a consultant may sign only if a Subscriber Agreement Form is on file with MDE.
Do I write total site area or only the graded area in the area fields?
Yes. Enter both—total site area and disturbed area are separate entries, and the disturbed figure sets your fee tier.
Are government projects charged the application fee?
No. Local and State government projects are exempt from the 20-CP fee, though they still file the NOI.
Do I need a SWPPP for every 20-CP project?
No. A SWPPP is required only when triggers apply, such as chemical additives, contaminated soils, multiple operators, or dewatering turbidity monitoring.
Does paying the fee mean I am covered and can start work?
No. The fee only moves your NOI into review and the 14-day public notice; you must wait for MDE authorization before breaking ground.
Can a Tier II site be authorized without the antidegradation checklist?
No. Operators discharging to a Tier II watershed must complete the Appendix C antidegradation review before submitting the NOI.
Do I have to tell MDE before I actually start construction?
Yes. You must notify the Compliance Program two weeks before starting by calling (410) 537-3510, separate from the NOI.
Does an over-150 NTU turbidity reading automatically mean a violation?
No. An exceedance of 150 NTUs requires corrective action, but only failing to take that action becomes a permit violation.
Do I need to file anything when the project is finished?
Yes. You file a Notice of Termination in ePermits after final stabilization, and MDE Compliance must concur before coverage ends.
Related reading
- How to Fill Out the Washington Ecology NPDES Industrial Stormwater Permit (NOI) + FAQs
- How to Fill Out the MassDEP NPDES Construction Stormwater Permit (With Examples) + FAQs
- How to Fill Out the Washington Ecology NPDES Construction Stormwater Permit (Notice of Intent) + FAQs
- How to Fill Out the North Carolina DEQ NPDES Construction Stormwater Permit (NCG01) + FAQs
- How to Fill Out the Maryland MDE Air Quality Permit to Construct (Form 5) + FAQs
- How to Fill Out the Maryland MDE Wetlands and Waterways Permit (Joint Federal/State Application) + FAQs
- How to Fill Out the Washington Ecology Water Quality Modification Permit + FAQs