shall be removed by the Contractor as soon as excavated, and the material subsequently excavated, if suitable for the purpose, shall be used to backfill the trenches in which the sewers have been built and neither the excavated material nor materials of construction shall be stored on the roadways or sidewalks. 10. Fence. Where required by the Engineer, suitable fences shall be placed along the sides of the trenches to keep the streets safe for traffic. 11. Temporary Bridges.-Crosswalks, where intersected by trenches, shall if required be temporarily replaced by substantial timber bridges not less than 3 feet wide, with side railings. Where required, suitable temporary bridges for vehicles shall be provided and maintained across trenches. 12. Disposal of Water from Trenches.-The Contractor shall at all times during the progress of the work keep the trenches and excavations free from water. Water from the trenches and excavations shall be disposed of in such a manner as will neither cause injury to the public health, nor to public or private property, nor to the work completed or in progress, nor to the surface of the streets, nor cause any interference with the use of the same by the public. 13. Cost to be Covered.-The cost of all labor required to be done and all materials required to be furnished in the performance of all of the work specified in paragraphs 1 to 12, inclusive, except as otherwise provided, shall be covered by all the contract prices for all the items for which there are contract prices. EARTH EXCAVATION. 14. Earth excavation shall include the removal of all material other than rock as defined in sections 21 and 22. 15. Width of Trench for Sewers, etc.-The minimum widths of trenches in earth for pipe sewers, basin connections, house connection and other drains not over 18 inches in diameter, shall be such as to give a clearance of 8 inches on each side of the barrel of the pipe, and for those of larger diameters, of 10 inches on each side of the barrel of the pipe, and all such trenches shall have a clear width equal to the maximum widths of the cradles of the sewers to be laid in them, when such cradles are wider than the minimum widths hereinbefore specified. The minimum clear widths of trenches in earth for other sewers shall be the greatest external width of the structures, including the necessary forms, to be built therein. 16. Excavation for Manholes, etc.-Where a riser, manhole or other appurtenance or the foundation therefor extends beyond the exterior lines of the sewer or its foundation, the minimum excavation in earth required for the same shall be that contained in a prism with vertical sides and a horizontal section equal to the smallest rectangle which will enclose such appurtenance and its foundation. 17. Excavation for Receiving Basins, etc.-The minimum dimensions of the excavation in earth for brick receiving basins, catchbasins and flush tanks shall be such as to give a clearance inside the sheeting of 1 foot on all sides above the foundation, but in all such cases the excavation shall be large enough to include the foundation for the structures shown on the plan. The excavation for concrete catchbasins and flush tanks shall be of such dimensions as to permit the proper placing and removal of the necessary forms. 18. Depth of Trenches.-Trenches shall be excavated to the depths required for the foundations of the sewers and appurtenances shown on the plan, and where conditions are such as to make it necessary, to such additional depths as may be directed. Where pipe is laid without a cradle, the bottoms of trenches shall be excavated to fit the lower third of the pipe, and excavations shall be made to receive the hubs. All irregularities in the bottoms of trenches shall be filled up to the required grade with suitable material. 19. (Same as paragraph 13, except paragraph numbers.) 20. Additional Earth Excavations.-When there is a contract price for additional earth excavation, it shall cover the cost of excavating all material (other than rock) ordered to be excavated beyond the lines and depths herein specified in sections 15 to 18, inclusive, and also the cost of excavating all material within the lines of the trenches above the surface of the ground as shown on the plan, when such material has not been placed there by the Contractor. This contract price shall also cover the cost of filling such excavations with approved material. Where no price is named in the contract for additional earth excavation, the cost of the several items enumerated above shall be covered by all the contract prices for all the items for which there are contract prices. ROCK EXCAVATION. 21. Definition.-Rock excavation shall include the excavation and removal of the following materials: a. Rock which shall be determined to be of such a character as to warrant its removal by blasting, in order to insure the prompt and proper prosecution of the work. b. Boulders and pieces of rock, masonry in mortar, and concrete, each of which contains one-third cubic yard or more, except the masonry and concrete of old sewers and their appurtenances. 22. Pieces of rock, masonry, concrete or boulders which fall or slide into the trench from beyond the lines thereof as herein defined, will not be measured, and the cost of the removal of the same shall be covered by all the contract prices for all the items for which there are contract prices. 23. Width of Trench.-The required width of trench in rock for pipe sewers, basin connections, house connections and other pipes will be such as to give a clearance of 1 foot on each side of the pipe, exclusive of spurs and hubs; the required width of trench in rock for other sewers and drains will be such as to give a clearance of one foot on each side of the structure to be built therein at its greatest external width. Where a riser, manhole or other appurtenance, or the foundation therefor, extends beyond the exterior lines of the sewer or its foundation, the excavation in rock required for the same will be that contained in a prism with vertical sides and a horizontal section 1 foot wider on each side than the smallest rectangle which will enclose such appurtenance and its foundation. The required dimensions of the excavation in rock for receiving basins, catch basins and flush tanks will be such as to give a clearance of I foot on all sides above their foundations. 24. Depth of Trench.-The rock shall be excavated to the depths required for the cradles and foundations of the structures as shown on the plan, and not less than 4 inches below the outside of the barrel for the pipe sewers. 25. Measurement.—The volume of rock to be paid for will be that contained in prisms with vertical sides and of such dimensions as to give the widths and clearances hereinbefore specified from the bottoms of the trenches, as specified and as shown on the plan, to the surface of the rock. 26. Rock Stripped.-Rock shall be stripped in sections, which, unless otherwise permitted, shall be not less than 50 feet in length, and the Engineer shall then be notified in order that he may measure the same. Rock excavated or blasted before such measurement is made will not be paid for. 27. Excavation for Branches.-Wherever a branch for a proposed sewer or extension of a sewer is built in the rock, the required trench shall be excavated for a distance of not less than 5 feet beyond the end of such branch, in the direction of the proposed sewer or extension. 28. Blasting. All blasting operations shall be conducted in strict accordance with existing ordinances and regulations relative to rock blasting and the storage and use of explosives. Any rock excavation within 5 feet of a water main less than 36 inches in diameter, and within 10 feet of a water main 36 inches or more in diameter, shall be done with very light charges of explosives, or, if directed, without blasting, and the utmost care shall be used to avoid breaking or disturbing the main. 29. Exposed Structure to be Protected. All exposed sewers, manholes, receiving basins and other structures shall be carefully protected from the effects of blasts. Any damage done to such structures shall be promptly repaired by the Contractor at his own expense. 30. Price to Cover.-The contract price for rock excavation shall cover the cost of all labor and materials required to excavate and remove all rock as specified, and without regard to its subsequent use. When there is no contract price for rock excavation the cost of excavating and removing rock shall be covered by all the contract prices for all the items for which there are contract prices. BACKFILLING. 31. Backfilling around Sewers, etc.-Unless otherwise specified or directed, all trenches and excavations shall be backfilled immediately after the structures are built therein. For a depth of at least 2 feet over the top of sewers, basins, basin connections, house connections and other drains, the material used for backfilling trenches as excavated shall be clean earth, sand or rock dust. It shall be carefully deposited in uniform layers not exceeding 6 inches in depth, and unless otherwise permitted each layer shall be carefully and solidly tamped with appropriate tools in such a manner as to avoid injuring or disturbing the completed work. 32. Backfilling for Remainder of Trench.-Backfilling for the remainder of the trenches as excavated shall be approved material free from organic matter and containing no stones over 10 inches in their largest dimensions. Stones which are used in backfilling shall be so distributed through the mass that all interstices are filled with fine material. Backfilling shall be deposited as directed, and unless otherwise permitted shall be spread in layers and solidly tamped. 33. Backfilling around Manholes, Receiving Basins, etc. - Backfilling within 2 feet of manholes, house connection drains, receiving basins, inlet basins, flush tanks and other structures shall be of the same quality as that specified in sections 31 and 32. It shall be uniformly deposited on all sides, and unless otherwise permitted solidly tamped in such a manner as to avoid injuring the structures or producing unequal pressures thereon. 34. Puddling. - Backfilling shall, if required, be flooded or puddled with water as the work progresses, instead of being tamped. 35. Cavities Filled. When sheeting is drawn, all cavities remaining in or adjoining the trench shall be solidly filled. When sheeting is left in place, all cavities behind such sheeting shall be solidly filled as directed. 36. Deficiency of Filling.-Unless otherwise shown on the plan, trenches shall be backfilled to the height of the surface of the ground as it existed at the commencement of the work. Should there be a deficiency of proper material for the purpose, the Contractor shall furnish and place such additional material as may be required. 37. Temporary Bulkheads. For retaining back filling only temporary bulkheads will be allowed. Such bulkheads shall not be of stone, and they shall be removed as the trenches are backfilled. 38. Curves, Branches, etc., not to be Covered.-Sewers built on curves, also drains, basin connections, house and sewer connections, and intersections, ends of sewers and branches shall not be covered until the Engineer shall have inspected, measured and located the same, and given permission to backfill the trenches over them. 39. Removal of Surplus Material.-As trenches are backfilled, the Contractor shall remove all surplus material and regrade and leave free, clear and in good order all roadways and sidewalks to within .... feet of the end of the completed work. During the progress of, and until the final payment for and acceptance of, the work, he shall maintain in good and safe condition the surface of the street over all trenches, and promptly fill all depressions over and adjacent to trenches caused by the settlement of backfilling. In case of failure or neglect on the part of the Contractor to comply with the requirements of this paragraph within 24 hours after the service upon him of a written notice so to do, the ... may furnish all materials and do all work required, and the cost thereof will be charged to the Contractor and deducted from any moneys due or to become due him under this contract. All surplus material or any part thereof shall, if required, be deposited as directed on the streets and avenues within the limits of this contract where surfaces are below grade, and in such a manner as to leave the surfaces of the filled material even. 40. (Same as paragraph 13, except paragraph numbers.) ART. 46. MASONRY AND MATERIALS THEREFOR CEMENT. 41. Quality. All cement used in the work shall be high-grade Portland cement of well-established and approved brands. 42. Specific Gravity; Weight. The cement shall have a specific gravity of not less than 3.10 after being thoroughly dried at 212° F. It shall weigh not less than 376 pounds net, to the barrel, 4 bags of 94 pounds each being considered equivalent to a barrel. For the purpose of measurement one bag shall be considered the equivalent of 1 cubic foot. I 43. Fineness.-The cement shall be dry, finely ground, of uniform color and free from lumps. It shall leave a residue of not more than 8 per cent by weight when passed through a No. 100 sieve, and not more than 25 per cent when passed through a No. 200 sieve. 44. Tensile Strength.-Standard briquettes shall develop, within the periods specified, tensile strength not less than that shown in the following table: 24 hours in moist air...... Neat Cement. 7 days (1 day in moist air, 6 days in water).. 28 days (1 day in moist air, 27 days in water).. Mortar consisting of 1 part cement and 3 parts standard Ottawa sand, by weight. 7 days (1 day in moist air, 6 days in water)...... 500 600 180 225 The average of the tensile strength developed at each age by the briquettes in any set from one sample will be considered the strength of the sample at that age, excluding any results that are manifestly faulty. The average strength of briquettes at 28 days shall be greater than the average strength at 7 days, and if tests are made after 28 days the strength shall be not less than that at 28 days. 45. Soundness.-Pats of neat cement, when tested for constancy of volume or soundness, shall remain firm and hard and show no sign of checking, cracking, distortion or disintegration. 46. Setting. Unless otherwise required, cement shall not develop initial set in less than 30 minutes, and shall develop final set in not less than one hour nor more than 10 hours. Quick-setting cement of an approved brand shall, |