The Tyndall Air Force Base (AFB) drainage system comprises two systems, generally divided by U.S. Highway 98 (US 98) and identified as the Flightline District drainage system and the Support District drainage system. The Florida Department of Transportation (FDOT) constructed and maintains the drainage system for US 98. This system ties into the existing base drainage systems along the highway. FDOT has developed an improvements plan for US 98 that will coincide with the reconstruction of Tyndall AFB.
The Flightline system includes a piped system and a few onsite treatment ponds in the upland areas, and a combination of piped and channelized drainage systems throughout the airfield. Wet ponds are generally not used in the Flightline areas because of Bird/Wildlife Aircraft Strike Hazard (BASH) risks. The Support District’s existing drainage infrastructure consists of an aging piped system that has been poorly maintained, linear surface channels, and scattered dry and wet detention ponds. Because the existing control structures were not studied in detail, the efficacy of the current ponds is unknown.
The onsite soils are highly permeable and the depth to the water table is generally shallow (approximately 2-5 feet below the ground). There are some areas that are more compacted and will require special treatments as described in this section. This creates challenges to designing and constructing dry stormwater elements (sometimes referred to as Integrated Management Practices [IMPs] or Best Management Practices [BMPs]) and will result in the base systems having large areas and shallow depths in order to provide at least 12 inches of separation to groundwater. In addition, there are known contaminant plumes in the ground that should be avoided for surface elements. Finally, there are several cultural heritage sites where grey stormwater infrastructure is not permitted.