Allegany County, MD Environmental Rules: Stormwater Management (2026)

Part 3 of Chapter 360 governs stormwater in unincorporated Allegany County, adopted under the Environment Article, Title 4, Subtitle 2 of the Annotated Code of Maryland and applying to development that had not received final erosion-and-sediment-control and stormwater approval by May 4, 2010 (§ 360-47B). Section 360-49's scope provision bars developing residential, commercial, industrial or institutional land without runoff-control measures, except where exempted, and ties design to the 2000 Maryland Stormwater Design Manual, incorporated by reference along with the USDA Pond Code 378 (§ 360-47C).

Section 360-50 sets the minimum control requirements: a developer must show that ESD techniques, such as preserving natural resources, minimizing impervious area and maintaining 100% of predevelopment groundwater recharge, have been implemented to the maximum extent practicable before any structural best-management practice like a pond or filtering system is used. The County can require stricter control than the minimum, including control of the ten-year storm event, where historical flooding or downstream conveyance problems exist. Culverts must safely carry at least the ten-year peak discharge, rising to the twenty-five-year peak flow along minor arterial roadways, with a minimum 12-inch diameter on private property and 15 inches where a culvert crosses a road (§ 360-50C).

No grading or building permit may issue until the County approves the final plan, and permits can require recorded easements, a maintenance agreement, and a performance bond under §§ 360-52 and 360-53. Section 360-56 allows an appeal within 30 days to an Appeals Board of the County Engineer, County Attorney and an outside stormwater expert, with further appeal to the Circuit Court for Allegany County.