Excavation shall be made to a point exactly six inches below the finish grade of the sidewalk.  After excavation is made, the surface shall be thoroughly tamped, with a tamper that shall weigh not less than 20 pounds and be not more than 12 inches square, to the satisfaction of the Engineer.  All excavated material not used in this work shall be the property of the city and shall be deposited in such a place and spread in such a manner as the Engineer may direct.  The maximum length of free haul shall not exceed 1,500 feet.  Excavated material not wanted by the city or property owner shall be disposed of by the contractor.  Upon the subgrade thus prepared shall be placed a concrete base three and one-half inches thick composed of one part portland cement, two parts clean, coarse, sharp sand, and four parts broken stone, no stone being more than two inches in its greatest dimensions, or one part best portland cement to five parts of mill-tailings.  The concrete deposited in the forms prepared to receive it and thoroughly tamped till free mortar flushes to the surface and the surface is exactly one-half inch below the finished grade of the walk.  No concrete or mortar that has been set will be permitted in the work.  No retem-pered concrete or concrete that has been mixed over 45 minutes shall be used.  Immediately after the surface has been prepared there shall be placed thereon the finished coat or wearing surface.  This will consist of a mortar composed of one part port-land cement and two parts clean, sharp, coarse sand, with sufficient water to make a good stiff mortar that can be easily worked with a trowel or afloat.  This shall be brought to a grade by a straight edge and then thoroughly compacted by trowling three times or more.  No patches or ragged edges will be allowed, and the whole must be finished in a neat, workman-like manner, leaving the walk cut in five- and six-foot sections with sand or open joints.  The finished walk shall be protected from the direct rays of the sun and shall be kept moist in hot, dry weather by sprinkling frequently during the first 24 hours.  Moistened sand, earth or straw may be used for this purpose.  The walk shall be protected from freezing during the cold weather.  The walk shall not be thrown open for travel for at least three days after completion, and it shall be the duty of the contractor to protect the walk from any injury until it has been accepted by the city.
(`83 Code, § 14-212)  Penalty, see § 101.99