5.6 Move along the length of the trench as each section is excavated to the required depth. Checking the depth with a builder's level where the grade is critical will ensure the finished trench does not require remedial work to make it usable.
5.7 Continue digging until the whole trench is complete.
Recheck the depth of the trench, check the embankments for stability, and do any smoothing or finished grading of the trench bottom necessary to allow installing the material the trench has been dug for.