TM 5-820-1/AFM 88-5, Chap. 1
C-1. Design example.
The proposed layout
for the primary storm drainage system
for an airfield
C-1. This airfield is to be located in central Mississippi where the design storm index for a 2-year l-hour
rainfall intensity, according to figure 1, is 2.0 inches per hour. The duration of storm being considered is
60 minutes; thus, figure 2 (see main text) need not initially be used. Infiltration values for the paved and
turfed area are considered to be 0.0 and 0.5 inches per hour, respectively, according to paragraph 6 of
the main text. The supply curves applicable to this airfield are No. 2.0 for paved areas (2.00.0) and No.
1.5 for turfed areas (2.0--0.5). These supply curves are provided in figure 2. Coefficients of roughness
have been selected for the paved and turfed areas as 0.01 and 0.40, respectively, as suggested in table
b. In this example, two conditions are considered: where pending is permissible at inlets 4, 3, and 2,
and where no pending is allowed at these inlets. The purpose of these examples is to portray the
difference in pipe size requirements under these two imposing conditions. Tables C-1, C-2, and C-3
reflect the design where pending is permissible, and tables C-4, C-5, and C-6 reflect the design where
pending is not acceptable.