(A) General. All work shall conform to the requirements of all local, state and federal agencies having jurisdiction and the requirements of these specifications.
(B) General trenching.
(1) Not more than 300 feet of trench shall be opened at any time with not more than 100 feet opened in advance of the completed pipe laying operation.
(2) Surface encumbrances, located so as to create a hazard to employees involved in excavation work or in the vicinity thereof at any time during operations, shall be removed or made safe before excavating is begun.
(3) During excavation, material satisfactory for backfilling shall be stockpiled in an orderly manner at a distance from the banks of the trench sufficient to avoid overloading and to prevent slides and cave-ins. Adequate drainage shall be provided for the stockpiles and surrounding areas by means of ditches, dikes or other suitable methods. The stockpiles shall also be protected from contamination with unsatisfactory excavated material or other material that may destroy the quality and fitness of the suitable stockpiled material.
(4) Grading shall be done as may be necessary to prevent surface water from flowing into the excavation, and any water accumulating therein shall be removed so that the stability of the bottom and sides of the excavation is maintained. In wet trenches, dewatering equipment shall be operated ahead of pipe laying and the water level kept below the pipe invert.
(5) Excavation work shall be performed in accordance with all applicable provisions of the OSHA standards for trench and excavation safety and as recommended by the pipe manufacturer.
(6) Excavation for manholes or similar structures shall be sufficient to leave at least 12 inches clear between the outer structure surfaces and the face of the excavation or support members and be of sufficient size to permit the placement and removal of forms for the full length and width of structure footings and foundations. When concrete is to be placed in an excavated area, special care shall be taken not to disturb the bottom of the excavation. Excavation to the final grade level shall not be made until just before the concrete is to be placed.
(7) Dust conditions shall be kept to a minimum by the use of water. The use of salt or calcium chloride will not be permitted.
(C) Removal of excavated material. As trenches are backfilled, the contractor shall remove all surplus material, regrade and leave clear, free and in good order all roadways and sidewalks affected by the construction. During the progress of and until the expiration of the guarantee period, he or she shall maintain in good and safe conditions the surface or any street over the trenches and promptly fill all depressions over and adjacent to trenches caused by settlement of backfilling.
(D) Pavement removal. Where necessary, the contractor shall remove existing street pavements, driveways, curbs and sidewalks to the minimum width necessary to accommodate the sewer construction work. Asphalt and concrete surfaces shall be cut and removed to straight lines parallel to the trench.
(E) Protection and care of existing facilities. All poles and overhead utility wires, fences, sidewalks, curbs, signal lights, mail boxes, road or street signs, culverts, building and other surface structures shall be protected and preserved by the contractor and shall be repaired, replaced or otherwise restored to a condition equal to or better than they were before the work was started. All water and gas mains and services: sewers and sewer services; drains, petroleum pipes, buried electric, telephone, television, telegraph and signal cables and conduits; manholes, storm water inlets, foundations and other subsurface structures shall be properly supported and protected during construction and left in a condition equal to or better than they were before the work started. Fire hydrants shall remain accessible to Fire Department personnel at all times.
(F) Structures encountered.
(1) The contractor shall contact the owners of the various utilities or facilities in the project area prior to the start of construction for the location of the various utilities or facilities. The contractor shall take the necessary steps and actions to determine the exact location of underground utilities and facilities, and shall exercise sufficient care during construction to prevent damage to said utilities and facilities.
(2) If, during the course of construction, it becomes necessary to relocate any water main, gas main, telephone cable or conduit, cable television or electric line, it shall be the responsibility of the utility company involved to make the necessary relocation. However, the contractor shall assume all risk and liability for any inconvenience, delay or damage sustained by him or her due to any interference from the said underground utility or the operations of moving them.
(3) Where existing sanitary and storm sewers exist which are in conflict with the construction of the proposed pipe, the contractor shall relocate, or temporarily remove and reconnect said conflicting sewers. The contractor shall be responsible for properly handling any flow in said sanitary or storm sewers during his or her work. In either case, sewer shall be returned to a condition equal to or better than the condition at the start of construction.
(4) All culverts, which are in conflict with the construction, shall be relocated or temporarily removed and relocated. The contractor shall be responsible for properly handling any flow through said culverts during his or her construction.
(G) Covering ends. Before leaving the work for the night, during a storm, or for any other reason, care must be taken that the unfinished end of any pipe is securely closed with a tightly-fitting cover or plug. Any earth or other material that may find entrance into the pipe, through any such open end of an unplugged pipe shall be removed at the contractor’s expense.
(H) Stabilization. If portions of the bottom of trenches or excavations consist of material unstable to such a degree that it cannot adequately support the pipe or structure, the bottom shall be over excavated and stabilized with granular material in compliance with Art. 211.02 and 211.04 of the INDOT Standard Specifications.
(I) Sheeting and bracing.
(1) Sheeting and bracing shall be placed in the trench, as may be necessary for the safety of the work and public, for the protection of the workers, adjacent properties, and for the proper installation of the work in accordance with all applicable provisions of the OSHA standards.
(2) Sheeting and/or bracing shall be progressively removed as the backfill is placed in such a manner as to prevent the caving in of the sides of the trench or excavation and to prevent damage to the work.
(3) Sheeting which is placed for the protection of the public, adjacent properties or structures shall not be removed until the backfill has been placed and thoroughly compacted. While being removed, all vacancies left by this sheeting shall be carefully filled with sand free from silt, rammed into place, puddled or otherwise firmly compacted.
(J) Pipe bedding.
(1) Rigid pipe and conduit. All rigid conduit and pipe shall be laid to the lines and grades shown on the plans, unless otherwise directed by the Engineer. All rigid conduit and pipe shall be bedded in compacted Class I or II material, placed on a flat trench bottom. The bedding shall have a minimum thickness of four inches or one-fourth the outside pipe diameter below the pipe and shall extend halfway up the pipe barrel at the sides. All material shall be placed in the trench in approximately six-inch layers. Each layer, shall be leveled and evenly distributed on both sides of the pipe so as not to disturb, displace or damage the pipe and shall be thoroughly compacted. When Class I or II materials are used, compaction may be accomplished by hand or mechanical tamping or by “walking” the material in. Bedding from the halfway point on the pipe to a point six inches above the top of the pipe shall be a Class I, II, III or IV material placed in six-inch layers and thoroughly compacted to prevent settlement. Class III and IV material shall not be used when the trench is located in an area subject to vehicular traffic.
(2) Flexible and semirigid conduit. All flexible and semirigid pipe shall be laid to the lines and grades shown on the plans, unless otherwise directed by the Engineer. All flexible and semirigid conduit shall be bedded in compacted Class I or Class II material, placed on a flat trench bottom. The bedding shall have a minimum four-inch thickness or one-fourth the outside pipe diameter below the pipe and shall extend to six inches above the top of the pipe level the full width of the trench. All material shall be placed in the trench in a maximum of six-inch layers (before compaction). Each layer shall be leveled and evenly distributed on both sides of the pipe so as not to disturb, displace or damage the pipe and shall be adequately compacted. When Class I materials are used, compaction may be accomplished by hand or mechanical tamping or by “walking” the material in. When Class II materials are used, compaction shall be accomplished only by hand or mechanical tamping to a minimum 85% Standard Proctor Density.
(K) Backfilling.
(1) Areas not subject to vehicle traffic.
(a) For purposes of this specification, trenches shall be considered subject to vehicular traffic if any portion of the excavation is located within four feet of a roadway or alley.
(b) The trench between a level six inches above the top of the pipe and the ground surface shall be backfilled with Class I, II, III or IV materials. The contractor shall consolidate the backfill by the back and forth travel of a suitable roller, wheeled device or other similar heavy equipment until no further settlement is obtained. Heavy equipment shall not be used until there is a cover of not less than three feet over the pipes. To assist in promoting maximum settlement, the surface of the trench shall be left in a slightly rounded condition. Periodical dressing of the backfill in the trench to promote the drainage and safety conditions shall be made during the course of the contract as required or ordered by the Engineer.
(2) Areas subject to vehicle traffic.
(a) The trench between a level of six inches above the top of the pipe and the surface, which are located in areas subject to vehicular traffic, shall be backfilled with granular backfill materials, deposited in maximum lifts of 12 inches. Each layer shall be thoroughly compacted by mechanical tamping to not less than 95% density as determined by the Proctor Test (ASTM D-698).
(b) Granular backfill materials shall terminate at a point below finished grade sufficient to allow placement of the permanent surface materials. Where the permanent surface is asphalt or concrete, the aggregate base thickness shall be the specified thickness of the pavement material plus six inches.
(c) For portions of the trench surface not subject to traffic, the backfill material shall end six inches below the finished grade. This six-inch depth shall be filled with good top soil and seeded in accordance with these specifications.
(3) Placement.
(a) No fill shall be placed against any manhole or other structure until placed concrete has been allowed to cure for at least three days. Backfill shall be placed in such a manner that the structure will not be damaged by shock from falling earth.
(b) The backfill material shall be deposited and compacted as specified for final backfill, and shall be placed in such a manner as to prevent eccentric loading and excessive stress on the structure.
(L) Compaction testing.
(1) Sampling and testing shall be the responsibility of the contractor. Tests shall be performed by an approved commercial testing laboratory or may be tested with approved facilities furnished by the contractor.
(2) Laboratory tests for moisture-density relations shall be determined in accordance with ASTM D-698. A minimum of one test shall be performed on each different type of material used for backfill.
(3) Field in-place density tests:
(a) Shall be performed in sufficient numbers to ensure that the specified compaction is being obtained. A minimum of one test per lift of backfill for every 500 feet of installation shall be performed; and
(b) Shall be determined in accordance with ASTM D-1556, ASTM D-2167 or ASTM D-2922. When ASTM D-2922 is used, the calibration curves shall be checked and adjusted using only the sand cone method as per ASTM D-1556. ASTM D-2922 results in a wet unit weight of soil and when using this method, ASTM D-3017 shall be used to determine the moisture content of the soil. The calibration curves furnished with the moisture gauges shall be checked along with density calibration checks as described in ASTM-D3017. The calibration checks of both the density and moisture gauges shall be made at the beginning of a job and on each different type of material encountered.
(4) All test results shall be submitted to the town.
(5) Trenches improperly compacted shall be reopened and then refilled and compacted to the density specified. Field in-place density tests shall also be repeated for improperly compacted trenches that are reopened, refilled and recompacted.
(2004 Code, Art. I, § B, part 3)