Changes

'''Your end of the bridge is too close to the water level!'''

*raise both tiles of the one holding the range pole and dioptra by 10 slope higher for 5 tile-long bridge and 60 - 80 slope beyond it.

'''"The quality of the dioptra makes it too hard to work out the distance." or "You can't read the graduations on the range pole at this distance".'''

*Improve both materials. Note that the lowest ql of the two will determine the max length of bridge you can plan.

'''You notice that there is not enough clearance for a bridge to be built here.'''