Union, NY Environmental Rules: Flood Elevation Requirements (2026)

Section 121-10.4 governs the flood-fringe, defined in subsection A as the part of the area of special flood hazard inside the one-hundred-year-flood (base flood) boundary and outside the regulatory floodway. Every use there other than the low-damage uses in § 121-10.1 is allowed only as a special permit use from the Planning Board, and the building standards below are conditions of that permit.

For residential buildings, § 121-10.4(B)(2)(a) sets the freeboard: the lowest floor, including basement, of all new residential construction, or substantial improvements to existing residential buildings, must be at least two feet higher than the base flood elevation. The definition of substantial improvement in § 121-4 reaches any repair, reconstruction or improvement costing 50% or more of the structure's market value, excluding land value.

For nonresidential buildings, subsection (b) requires the lowest floor, including basement, to be at least one foot higher than the base flood elevation, or the building and its attendant utility and sanitary facilities must be floodproofed up to one foot higher than the base flood elevation. Subsection (c) requires all uses in the flood-fringe to be floodproofed in the manner outlined in §§ 121-13 and 121-14.

Fill used to raise the lowest floor must extend at least 15 feet beyond the limits of any building built on it and must be protected against erosion by riprap, vegetation, bulkheading or other cover (subsection (d)). Any storage facility for chemicals, explosives or flammable liquids must sit at an elevation at least one foot higher than the base flood (subsection (e)).

Proving the number takes paperwork. Where the Planning Board deems it necessary in unnumbered A Zones, § 121-10.5 has the applicant establish the base flood elevation from federal or state data, such as the Army Corps of Engineers, the Soil Conservation Service or the New York State Department of Environmental Conservation, or from a certified determination by a New York State professional engineer and land surveyor. Under § 121-11 the application states the proposed lowest floor elevation in relation to mean sea level, and the permit holder files an as-built elevation certificate prepared by a licensed land surveyor or professional engineer. Further work before the certificate is approved is at the permit holder's risk.