ARMY TM 5-5420-212-10-1 MARINE CORPS TM 08676A-10/1-1 (2) Double story bridges (2E + 1 thru 2E + 12 bay ).  The bank height above flowing water or obstructions in the gap should be a minimum of 2 ft (0.6 m). (3) Link reinforced bridges.  The bank heights above flowing water or obstructions in the gap should be a minimum of 12.0 ft (3.7 m).  In addition, there must be no obstacle intruding above a plane inclined 20 degrees downward in the gap for a distance of 15 ft (4.6 m) from each AR Peg as shown below (fig.  3-4). FIGURE 3-4.  Bank clearance-link reinforced bridges If the bank height is less than 12.0 ft (3.7 m) the rules in (a) and (b) below apply. (a) For  bridges  2E  +  14  bays  and  below  there  is  no  limit  on  bank  height  as  long  as  the  current  does  not exceed 5 fps (1.5 m/s) in which the reinforcing links can be immersed during launching and before tensioning. (b) For  bridges  2E  +  15  bays  and  above  there  is  no  limit  on  bank  height  as  long  as  the  current  does  not exceed either: 1 3.5  fps  (1.0  m/s)  in  which  case  the  reinforcement  can  be  immersed  only  during  launching  and before tensioning. 2 The current speed is shown in Table 3-4. TABLE 3-4 Maximum current velocity v bridge length 2E + No. 22 21 20 19 18 17 16 15 14 13 of Bays Bridge ft 162 156 150 144 138 132 126 120 114 108 Length m 49.4 47.6 45.7 43.9 42.1 40.2 38.4 36.6 34.8 32.9 Current on fps 1.64 1.64 3.08 3.67 3.93 4.29 6.95 7.67 8.43 8.43 immersed links m/s 0.5 0.5 0.94 1.12 1.2 1.31 2.12 2.34 2.57 2.57 3-13