Approximately 70 tile long canal, 3 tiles wide to take the shortest route from these landlocked lakes to the open sea. Bridges will be about 20 tiles from the ends, 2 total. NE end at 1316, 1515 & SW end around 1246, 1585. I have already gotten permission from Gustl to dig through his deed (Pirate Bay). This link will show the planned Canal.
Try to dig a single hole and see when you hit rock. If corner has water in it, you can't build a tunnel.
If the hole does not have water, try to see how far you are from the waterbed. Lots of methods to do so from simply counting the tile elevation (the hard way) to using mods that will automatically count it for you (the easy way).
Once you have the idea how deep water goes you can subtract, say 20 dirts from your current point since the rock floor is never perfectly flat and there will be variation in elevation.
If you are high enough a boat tunnel is preferred.
Come back with the results and the GMs can approve the project.
When digging for dirt along the proposed route, I hit rock level at the following points: 1269, 1562 21 1285, 1546 38 1293, 1538 40
Each one was well over 50 sand dug before hitting rock. There are minor dips between each of these points in height as well, so do you still recommend/require that I do a tunnel? Or should I proceed as originally proposed?