Bristol, PA Environmental Rules: Flood Elevation Requirements (2026)

Section 8-502 sets the elevation rules for the Borough of Bristol floodplain. For a residential structure in AE, A1-30 and AH Zones, any new construction or substantial improvement needs the lowest floor, including the basement, elevated up to or above the regulatory flood elevation. Section 8-902 defines that term as the base flood elevation, or an estimated flood height from simplified methods, plus a freeboard safety factor of 1 1/2 feet. In A Zones where the FIRM shows no base flood elevation, the same standard applies using the elevation determined under § 8-402. In AO Zones the lowest floor must sit at or above the highest adjacent grade and at least as high as the depth number printed on the FIRM.

A nonresidential building in AE, A1-30 and AH Zones has a second option. Instead of elevating, the space below the regulatory flood elevation can be floodproofed so the structure is watertight, with walls substantially impermeable to water and components able to resist hydrostatic and hydrodynamic loads and buoyancy. Floodproofing follows the W1 or W2 classifications in the Army Corps of Engineers publication named in the code, and the plans carry a statement certified by a registered professional engineer or architect.

Fully enclosed space below the lowest floor, crawl spaces included, can be used only for parking, building access or incidental storage, and it needs openings that let floodwater in and out: at least two openings with a net total area of not less than one square inch for every square foot of enclosed space, the bottom of each no higher than one foot above grade. Accessory structures need not be elevated if floor area does not exceed 200 square feet, the structure is not used for habitation, and sanitary facilities and permanently affixed utility equipment are left out. A substantial improvement is one whose cost equals or exceeds 50% of the structure's market value before the start of construction. The Zoning Officer is the floodplain administrator, and § 8-302 requires a permit before any construction or development.