Tried to find this with watchingtheblur and Andi's Delight, not 100% sure but we did poke around in the brush for quite some time.

Not sure we found the right clump of trees and everything was very grown up along the trail, making it hard to determine.

If this box is still there, it would be best sought in late fall or early spring when the plants have not grown up. We searched around the bases of as many trees as we could, to no avail.

Nice plant. Log book soaked. Couldn’t stamp in.

Enjoyed getting this today with my daughter! Thanks!

You might wish to edit your clue to say that it is the concrete piers holding up the ramp, not the bridge. Thanks for the find!

Have ridden that trail on bikes a few times in the past but can't do that anymore but thanks for putting directions from parking at the bridge!