All drains shall be laid in open trenches excavated to the proper depth, each pipe to be laid upon a firm foundation conforming to stakes set by the Engineer or Inspector assigned to the work, defining the true grade and proper alignment of the drain. All pipe to be laid complete in each section, or from stake to stake before the back filling shall commence. The stakes in each section to be set not less than eight feet (8') apart, pipe layer to use a line drawn from stake to stake in the same manner as public sewers are constructed in said Village.