Below-Grade Parking Requirements for Buildings Located in Special Flood Hazard Areas in Accordance with the National Flood Insurance Program [open pdf - 56KB]
"The purpose of this bulletin is to provide technical guidance on the National Flood Insurance Program (NFIP) floodplain management requirements for below-grade parking garages for nonresidential buildings in Special Flood Hazard Areas (SFHAS) shown on Flood Insurance Rate Maps (FIRMs). Below-grade parking garages are commonly found in large engineered commercial buildings and are used for parking and access to the above-grade floors of the building. Flooding of these enclosed areas may result in significant damage to the building and any mechanical, electrical, or other utility equipment located there, such as ventilation equipment, lighting, elevator equipment, and drainage pumps. The garage walls, which often are major structural components of the building's foundation, are also susceptible to flood damage. The potential for injury to anyone in the garage, the potential for damage to parked cars, and the safety issue of removing parked cars when flooding threatens are important design considerations."
Technical Bulletin 6-93
Federal Emergency Management Agency: http://www.fema.gov/