Sewer pipe installation.

A. Local utilities shall be contacted to verify construction plans and to make arrangements to disconnect all utility services, where required to undertake the construction work. The utility services shall later be reconnected. The work shall be scheduled so that there is minimum inconvenience to local residents. Residents shall be provided proper and timely notice regarding disconnection of utilities.B. The construction right-of-way shall be cleared only to the extent needed for construction. Clearing consists of removal of trees which interfere with construction, removal of underbrush, logs, and stumps, and other organic matter, removal of refuse, garbage, and trash, removal of ice and snow, and removal of telephone and power poles, and posts.

Any tree which will not hinder construction shall not be removed and shall be protected from damage by any construction equipment. Debris shall not be burned, but hauled for disposal in an approved manner.C. The public shall be protected from personal and property damage as a result of the construction work.D. Traffic shall be maintained at all times in accordance with applicable highway permits. Where no highway permits are required, at least 1/2 of a street shall be kept open for traffic flow.E. Erosion control shall be performed throughout the project to minimize the erosion of soils onto lands or into waters adjacent to or affected by the work.

Erosion control can be effected by limiting the amount of clearing and grubbing prior to trenching, proper scheduling of the pipe installation work, minimizing time of open trench, prompt grading and seeding, and filtration of drainage.F. The trench shall be excavated only wide enough for proper installation of sewer pipe, manhole, and appurtenances. Allowances may be made for sheeting, dewatering, and other similar actions to complete the work. Roads, sidewalks, and curbs shall be cut, by sawing or by other methods as approved by the Commissioner of Public Works and/or Chief Plant Operator and/or Superintendent of Sewers, before trench excavation is initiated.G.

Under ordinary conditions, excavation shall be by open cut from the ground surface. However, tunneling or boring under structures other than buildings may be permitted. Such structures include crosswalks, curbs, gutters, pavements, trees, driveways, and railroad tracks.H. Open trenches shall be protected at all hours of the day with barricades, as required.I. Trenches shall not be open for more than 30 feet in advance of pipe installation nor left unfilled for more than 30 feet in the rear of the installed pipe, when the work is in progress, without permission of the Commissioner of Public Works and/or Chief Plant Operator and/or Superintendent of Sewers.

When work is not in progress, including overnight, weekends, and holidays, the trench shall be backfilled to ground surface.J. The trench shall be excavated approximately six inches deeper than the final pipe grade. When unsuitable soils are encountered, these shall be excavated to a maximum depth of 2 1/2 feet below the final pipe invert grade and replaced with select materials.K. Ledge rock, boulders, and large stones shall be removed from the trench sides and bottom. The trench shall be over excavated at least 12 inches for five feet, at the transition from rock bottom to earth bottom, centered on the transition.L.

Maintenance of grade, elevation, and alignment shall be done by some suitable method or combination of methods.M. No structure shall be undercut unless specifically approved by the Commissioner of Public Works and/or Chief Plant Operator and/or Superintendent of Sewers.N. Proper devices shall be provided, and maintained operational at all times, to remove all water from the trench as it enters. At no time shall the sewer line be used for removal of water from the trench.O. To protect workers and to prevent caving, shoring and sheeting shall be used, as needed. Caving shall not be used to backfill the trench.

Sheeting shall not be removed but cut off no lower than one foot above the pipe crown nor no higher than one foot below final grade, and left in the trench, during backfill operations.P. The pipe barrel shall be supported, along its entire length, on a minimum of six inches of No. 1 stone or No. 1 and No. 2 mixed stone, free of organic material. This foundation shall be firmly tamped in the excavation.Q. Bell holes shall be hand excavated, as appropriate.R. Pipe shall be laid from low elevation to high elevation. The pipe bell shall be up-gradient; the pipe spigot shall be down gradient.S. Joint preparation and assembly shall be in accordance with the manufacturer's written instructions.T.

The grade and alignment shall be checked and made correct. The pipe shall be in straight alignment. Any negotiation of curves shall be at manholes, except when site conditions require alternative pipe-laying procedures. These alternative procedures, including bending the pipe barrel, deflecting the joint, and using special fittings, shall require prior written approval of the plans and also written confirmation approval of need by the Commissioner of Public Works and/or Chief Plant Operator and/or Superintendent of Sewers after examination of site conditions.U. When a smaller sewer joins a larger one, the invert of the larger sewer shall be lowered sufficiently to maintain the same hydraulic gradient.

An approximate method which may be used for securing this result is to place the 0.8 depth of both sewers at the same elevation.V. Crushed stone shall be placed over the laid pipe to a depth of at least six inches. The embedment of thermoplastic pipe shall be in accordance with ASTM D2321 using Class 1A or 1B backfill materials. Care shall be exercised so that stone is packed under the pipe haunches. Care shall be exercised so that the pipe is not moved during placement of the crushed stone.W. The migration of fines from surrounding backfill or native soils shall be restricted by gradation of embedment materials by use of suitable filter fabric.X.

The remaining portion of the trench above the pipe embedment shall be backfilled in foot lifts which shall be firmly compacted. Compaction near/under roadways, driveways, sidewalks, and other structures shall be 95% of the maximum moisture-density relationship, as determined by ASTM Specification D 698, Method D. Ice, snow, or frozen material shall not be used for backfill.