I would like to bridge a 80 foot corrugated pipe into an existing section.
While digging the ditch to for the 80 foot section. Is there any ditch \ trench techniques or tools to ensure that at any point the slope is either flat or downwards?
Update
For context, a bird's eye view is provided of the building. The above photo is snapped from the southeast corner of the building. Building is approximately 80' by 80'
Best Answer
For an even slope.
set-up profiles (frames, or stakes) at each end and run a sloping string line between them. Measure down to the floor of the ditch from the string line with a stick of appropriate length. You could possibly tie one and of the string to the downpipe. and the other to a stake
If you don't need an even slope just use a spirit level (repeatedly) to confirm that the floor of the trench is still sloping as you are digging it.