4 county-level rules, plus city-specific rules for 3 cities in Montgomery County, Maryland.
Verified from official government sources
Projects disturbing 5,000+ sq ft require a stormwater plan from MoCo DEP under Code Chapter 19. ESD techniques mandatory. Chesapeake Bay TMDL compliance required.
Montgomery County DEP - Stormwater Management Program
Polluted runoff (commonly called stormwater runoff) carries pollution and trash as it flows into our streams, lakes, ponds and rivers, making them unhealthy. Stormwater Management is the process where we slow, store, or allow stormwater to soak into the ground to help reduce the amount of pollution entering our waterways. Montgomery County uses above and below ground structures (we call them st...
Any land disturbance of 5,000+ sq ft requires an erosion and sediment control plan under MoCo Code Chapter 19. DPS is the MDE-delegated enforcement authority.
Montgomery County participates in FEMA's NFIP. County Code Chapter 19 and COMCOR §19.45.01.03 regulate floodplain development. Floodplain District Permits required for most land-disturbing activities within 100-year floodplain (30-acre drainage area or greater). New FEMA flood maps effective Spring 2026 following January 2025 appeal period.
DPS grading permits are required for 5,000+ sq ft disturbance or any work altering drainage. No adverse impact on neighbors allowed. Extra rules in floodplains and SPAs.
3 cities in Montgomery County have their own environmental rules rules. Each link goes to that city's dedicated page with code citations.
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