A logging dam was typically built by making a square wooden crib, which was placed in the river and filled with rocks. Boards could be placed between two cribs to make a sluice gate. The dam would store up water for a few weeks, and then open to allow a slug of water and a group of logs to head down river. The slug of water would carry the logs over rapids and through shallow spots. To make the logs easy to handle, they would be pulled (or skidded) using teams of ox or horses. The animals would pull groups of logs onto the ice during the winter. In spring, the ice would melt, dumping the logs into the water ready to be sent downriver.
The bridge is built with steel girder beams strung between the abutments. A wood deck is then put down and attached to the girders. Every so often, a much longer deck board is installed. That longer deck board is used to cross-brace the railings giving them some side to side support.
It appears that the ATV bridge is relatively new. I suspect that the old logging dam supported a bigger bridge that allowed for vehicle traffic. Over time, that bridge would have rotted and became unsafe. At some recent time, the bridge and dam were removed, the rocks were used to build up the embankment, and this trail bridge was installed. If anyone knows more of this story, please let me know.
The photo above is looking east down the length of the bridge deck from the center of the ATV Trail. The photo below is a similar view looking east from the north side of the ATV trail. The trail is built on top of an old logging dam, resulting in the trail being well above the water level.
