Query whether some of these streams really cross under the track: I added tunnels (think it was me) prompted by iD error messages. But I suspect they may run in a ditch on the N side of the track and join together to cross in one place. 

On survey, the eastermost one (heading NNW) does go through a plastic culvert. I took water from the stream that heads directly North: I wasn't looking out for a culvert, but saw none. That stream was joined where it met the track by a v slow moving stream heading E along the ditch. Quite likely they both flowed to join the eastermost one before passing through its culvert.