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Maryland Statewide Rule

Maryland Stormwater Management Act Statewide Standards

Heavy RestrictionsApplies statewide across Maryland (2026)

Key Facts

Statute
Environment 4-201 et seq.
Design Standard
ESD to MEP
Manual
MD Stormwater Design Manual
Permit
MS4 NPDES
Penalty
Up to $25,000/day
Last verified: August 20, 2026Source: Maryland General Assembly

Summary

The Maryland Stormwater Management Act of 2007, codified at Environment Article 4-201 through 4-215, mandates environmental site design and runoff treatment for new development statewide through MDE-approved local programs.

By July 1, 1984, each county and municipality shall adopt ordinances necessary to implement a stormwater management program. These stormwater management programs shall be consistent with flood management plans, if any, developed under Title 5, Subtitle 8 of this article for a particular watershed, shall meet the requirements established by the Department under § 4-203 of this subtitle, and shall be consistent with the purposes of this subtitle.

Source: Maryland General AssemblyView official code

Full Breakdown

Maryland Environment Article Title 4 Subtitle 2 requires every county and municipality to adopt stormwater ordinances meeting Maryland Department of the Environment minimum standards. Developers must implement Environmental Site Design (ESD) to the maximum extent practicable, treating runoff to recreate pre-development hydrology. The 2000 Maryland Stormwater Design Manual (updated periodically) prescribes practices like micro-bioretention, rain gardens, and permeable pavement. Phase II MS4 permits administered by MDE govern municipal separate storm sewer systems. Enforcement includes stop-work orders, restoration requirements, and penalties up to $25,000 per day.

Violations & Penalties

Stormwater violations may incur civil penalties up to $25,000 per day, criminal misdemeanor charges, mandatory restoration, and stop-work orders.

Frequently Asked Questions

What is ESD and when does it apply?
Environmental Site Design uses small-scale practices to mimic natural hydrology. It is required for new development and substantial redevelopment statewide under Environment 4-203.
Do counties enforce stormwater rules locally?
Yes. Each Maryland county and municipality administers stormwater plans under MDE oversight. Local ordinances must meet or exceed state standards in the Stormwater Design Manual.

Sources

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