All house drains and private sewers shall be constructed in open trenches, carefully excavated in the proper direction, and to such width and depth as may be necessary to secure the correct alignment, and faithful execution of the work, which latter must be vigorously prosecuted, so as to cause the least possible inconvenience to the traveling public. If the sides of the trenches will not maintain their vertical position they shall be sheeted, shored and strongly braced. Prior to commencing the excavation, all the materials composing the sidewalks, roadway, paving and other similar improvements, shall be carefully removed, and piled in some convenient place, and in such position there as will insure their safety, and where they will be out of the way of street traffic, and of the material taken from the trenches, which latter must likewise be so disposed of as not to seriously interfere with the legitimate use of sidewalks and roadways.