Virginia agencies would use climate-adjusted rainfall for public infrastructure

State agencies and local governments would use climate-adjusted rainfall values when setting design standards for public infrastructure. The standards would cover stormwater facilities, floodplain management, culverts, bridges, and other public infrastructure. The standards would also cover projects developed through public-private partnerships. Local governments could adopt stricter standards to address local or regional flood risks.

The State Water Control Board would set and maintain rainfall design standards using NOAA estimates and a climate projection period it selects. The Board's standards would guide public infrastructure design across Virginia. The standards would use the latest rainfall estimates in NOAA's national atlas to account for observed and projected changes in rainfall. The Board would review related state stormwater rules at least once a year and could adopt standards or guidance to speed implementation.

State agencies would update relevant manuals and standards, and the Board would issue interim rainfall guidance. The updates would cover relevant state agency manuals and design standards. Until NOAA Atlas 15 estimates are published and adopted by Virginia, the Board, working with the Department of Transportation, would require design values from NOAA Atlas 14 to be increased by at least 20 percent. Agencies would update manuals and standards by July 1, 2027. Interim standards would take effect no later than that date.