07-09-18 Drainage and Flooding Committee Meeting

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IML of runoff on runway and taxiway pavements. The center 50-percent of runways and taxiways is to be kept free of stormwater ponding resulting from the 10-year storm event. FAA AC 150/5200-3313, Hazardous Wildlife Attractants on or Near Airports, requires storm water detention ponds to allow a maximum 48-hour detention period for the design storm and recommends avoidance or removal of retention ponds and detention ponds featuring dead storage to eliminate standing water. 2.4. CRITERIA FOR THIS PROJECT During the project kick-off meeting for this project, the subject of the airport classification versus the criteria for airfield geometrics was discussed. Civil PEs noted that the standards were not going to be met if the airport design group was maintained and that since the ALP "design aircraft" were both B-1 (small aircraft), that the standard could be changed and would bring the airport geometry to standards. TxDOT Aviation Division staff reviewed the observation and directed Civil PEs to proceed with the project but not change the airport classification. Aviation Division noted that future projects involving the taxiways could then consider the geometry and relocation of the parallel taxiways. Taxiway Design Group The Taxiway Design Group (TDG) is also based on the two listed aircraft from the ALP — the Cessna 421 and the King Air 100. The Cessna has a Main Gear Width (MGW) of 14'-811 4. The King Air 100 has a MGW of 13'-0"5. The Cockpit to Main Gear (CMG) dimension is not listed in the advisory circulars, but a conservative estimate is that the cockpit to main gear reference is half the distance from the nose wheel to main gear. For the Cessna 421, the wheel base is 1 T-8116, and the King Air 100 has a wheel base of 14'-11117. Therefore, the Cessna has an estimated CMG of 5'-10" and the King Air 100 has an estimated CMG of 7'-6". The results of these determinations are shown in Figure 1 and indicates the appropriate TDG is 1A. During the several site trips to the airport, the aircraft seen using the airport did not indicate a need to change the TDG based on observed traffic. 4 FAA Advisory Circular150/5300-13: Airport Design, Appendix 12 — Airplane Data, Figure Al2-7, dimension F, September 1989. 5 Ibid Figure Al2-20, dimension F. 6 Ibid Figure Al2-7, dimension D. Ibid Figure Al2-20, dimension D. Page 15