On the light M3 ponton bridge, the main achorage was a shore to shore cable that the rafts were anchored to. In certain situations only 2 30-lb Danforth anchors were used, 1 on each hinge raft ( rafts closest to shore ).
An online copy of technical manual- TM 5-275, Pneumatic ponton bridge M3 dated April 19, 1943 can be found here:
http://digital.library.unt.edu/ark:/67531/metadc29951/m1/1/
The List of Equipment - Unit of Pneumatic Ponton Bridge M3
Anchor, Danforth, 30 -lb..... basic quantity: 2; spares: 0; Total: 2
Anchor, kedge, 100-lb........basic quantity: 14; spares: 4; Total: 18
Page 30, Note 2: If bridge is long and current is strong, upstream anchors ( one per hinge raft and float assembly ) are used instead of the upstream anchor cable, and are cast from the assault boat by the upstream anchor section.
http://digital.library.unt.edu/ark:/67531/metadc29951/m1/1/
