A.    The excavations for concrete alley paving shall be made parallel to the finished surface and after thorough hand tamping or rolling to a firm and solid bearing must be five inches below such finished surface. If soft places are found, they shall be removed and gravel tamped in until solid. In general, there shall be a drop of two inches from the sides of the alley to the center, the grade and line for the center being that established by the engineer. In case of unusual character of elevation in sidewalk, of alley crossing on sidewalk lines or alley ground surface, the contractor must receive and follow the special instructions as to grades and surfaces to be used from the engineer.

    B.    Upon the excavated foundation will be spread a layer of concrete which after thorough ramming and tamping shall be found inches thick, to be composed in the proportion of one sack of concrete to two and one-half cubic feet of sand and four and one-half cubic feet of screened gravel. By special written permission of the city engineer, providing the proper mixture is supplied, the concrete may be made in the proportion of one sack of concrete to six cubic feet of a natural mixture of clean river sand and gravel. This written permission will be revoked at any time if the resulting concrete is not equal to that first specified.

    C.    Upon the tamped concrete shall be placed at once, and before the concrete has set, the top wearing surface, one inch thick, composed of one sack of the same kind of concrete used in the concrete base and two cubic feet of sand or in the same proportion. After the wearing coat has been brought to the grade with a template or guide, it shall be finished with float and trowel to a sidewalk finish, not necessarily a smooth finish, but one free from depressions or inequalities of any kind and in perfect contact with the base. The concrete shall be laid in blocks approximately six by six feet, separated by a dry sand joint extending to the bottom of the concrete with the wearing surface out in blocks the same size and at the same places, to be creased over the sand joints with the jointer tool. The concrete paving shall be kept moist for three days and must be protected from the elements and travel until it has completely set and hardened. Travel shall not be permitted on the wearing surface for at least ten days after the same is laid. Concrete or mortar that fails to set or to show a proper bond, after in the opinion of the common council it has been allowed sufficient time, shall be taken up and replaced with new materials of the proper quality by the contractor.

    D.    As a basis for inspection, one barrel, four sacks, of concrete shall be used for each seventy square feet of four-inch one to two and one-half sand to four and one-half screened gravel concrete and 1.43 barrels of concrete for each one hundred square feet of such concrete. Also one barrel, four sacks, of concrete shall be used for each sixty square feet of four inch one to six concrete, or one and one-third barrels of concrete for each one hundred square feet of such concrete, being one to six natural mixture of sand and gravel. A barrel, four sacks, of concrete shall be used for each one hundred eight square feet of one inch of concrete to two of mortar for wearing surface, or .93 of a barrel of concrete for each one hundred square feet of such surface. (Prior code § 27-48)