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    SECTION 02763

    GRAVITY SEWER REHABILITATION

   PART 1 - GENERAL

   1.01 SECTION INCLUDES

   A. Replace certain portions of the existing sewer system, including collection lines, service lines, and service connections, or else lay new lines, wherever the bidding instruments indicate that this is to be done. Control the existing flow in the line segment being replaced whenever necessary during replacement. The pipe used for replacement shall be either PVC pipe or ductile iron pipe, as set forth in the Bid Form and as specified below.

   B. Pipe and fitting material shall be PVC unless the Bid Form or drawings show otherwise, except that replacement pipe for any existing cast iron or ductile iron pipe shall be ductile iron.

   PART 2 - PRODUCTS

   2.01 STANDARDS

   A. All materials shall be in strict compliance with the required standards and specifications of ASTM, ANSI, and/or AWWA.

   2.02 PVC PIPE

   A. Pipe and fittings shall meet or exceed the requirements of ASTM D3034, SDR 35.

   B. All pipe shall be suitable for use as a gravity sewer conduit. Provisions must be made for contraction and expansion at each joint with a rubber ring. Standard lengths shall be 20' and 12.5' plus or minus 1".

   C. All fittings and accessories shall be manufactured and furnished by the pipe supplier, or approved equal, and have bell and/or spigot configurations identical to that of the pipe.

   D. Pipe shall be designed to pass all tests at 73 degrees F (plus or minus 3 degrees F).

   E. The minimum pipe stiffness at 5% deflection shall be 46 psi for all sizes when tested in accordance with ASTM D2412 regarding external loading properties of plastic pipe by parallel plate loading.

   F. There shall be no evidence of splitting, cracking, or breaking when the pipe is tested as follows:

   1. Flatten a specimen of pipe 6" long between parallel plates in a suitable press until the distance between the plates is 40% of the outside diameter of the pipe. The rate of loading shall be uniform and such that the compression is complete within 2 to 5 minutes.

   2. A 6" long section of pipe shall be subjected to impact from a free falling tup (20 pound Type A) in accordance with ASTM D2444. No shattering or splitting shall be evident; denting is not a failure.

   3. After 2 hours of immersion in a sealed container of anhydrous acetone (99.5% pure), a 1" long sample ring shall show no visible spalling or cracking when tested in accordance with ASTM D2152; swelling or softening is not a failure.

   4. PVC pipe shall have a minimum envelope of 6" of granular material around the pipe. All other bedding and backfill requirements remain the same as for other pipe material.

   2.03 DUCTILE IRON PIPE

   A. Ductile iron pipe shall conform to the specifications of ASTM A746. Unless otherwise shown by the drawings or the Bid Form, the wall thickness shall be Class 52 for all sizes of pipe.

   2.04 TEES, CLEANOUTS, AND STOPPERS OR PLUGS

   A. Unless otherwise specified or noted on the drawings, tees, cleanouts, and stoppers or plugs shall be of the same material used to repair the main sewer and have an inside diameter of the same size as the existing line, except that it shall in no case have a diameter smaller than 4". The stopper and installation shall be able to withstand all test pressures involved without leakage.

   2.05 JOINTS AND JOINTING MATERIALS

   A. PVC Pipe: Pipe shall be of the bell and spigot type with a rubber ring suitable to meet all test requirements of these specifications.

   B. Ductile Iron Pipe: Gasket type joints for bell and spigot ductile iron pipe shall be similar to U.S. Tyton, Clow Super Bell-Tite, or equal, and be designed to meet the infiltration requirements of these specifications.

   C. Jointing of Ductile Iron Pipe: Jointing of ductile iron shall comply with the applicable provisions of ANSI A21.11.

   2.06 COMPRESSION COUPLINGS

   A. When dissimilar pipe materials like PVC and concrete pipe are joined, use reinforced compression couplings as manufactured by Fernco or approved equal, that are resistant to the corrosive action of soils and sewage and that will provide a permanent watertight joint. The compression couplings shall meet the physical test and joint leak requirements specified by ASTM C594, and the bands for attaching the couplings to the dissimilar pipes shall be of stainless steel conforming to ASTM C594. Each coupling shall bear the manufacturer's identifying mark and an indication of its size.

   2.07 TESTING OF MATERIALS

   A. All testing of clay and concrete pipe and materials shall be made by a commercial testing laboratory. Before starting work, furnish the name of the pipe materials supplier to the Engineer. No pipe shall be delivered to the job site which does not bear the testing laboratory's stenciled or otherwise marked sign of acceptance. Furnish 2 certified copies of the testing laboratory's report of inspection, test, and acceptance on all pipe and specials to the Engineer.

   B. For PVC and ductile iron pipe, furnish a certificate from the pipe manufacturer indicating that the pipe meets all applicable requirements of these specifications.

   PART 3 - EXECUTION

   3.01 SEWER LINE REPLACEMENT AND/OR REPAIRS

   A. The Contractor shall locate all existing underground utilities before beginning excavation for line and service connection from the manhole of reference as shown in the drawings or elsewhere in these specifications.

   B. The Contractor shall provide for flow of sewage around the section or sections of pipe as specified in Section 02767 - Sewer Flow Control.

   C. Unless the construction of lines by tunneling, jacking, or boring is called for by the drawings or specifically authorized by the Engineer, make excavation for pipelines in open cut and true to the lines and grades of the existing pipeline being replaced or repaired shown on the drawings or established by the Engineer on the ground. Cut the banks of trenches between vertical parallel planes equidistant from the pipe centerline. The horizontal distance between the vertical planes (or, if sheeting is used, between the inside faces of that sheeting) shall vary with the size of the pipe to be installed, but shall not be more than the distance determined by the following formula: 4/3d + 15", where "d" represents the internal diameter of the pipe in inches. When approved in writing by the Engineer, the banks of trenches from the ground surface down to a depth not closer than 1' above the top of the pipe may be excavated to nonvertical and nonparallel planes, provided the excavation below that depth is made with vertical and parallel sides equidistant from the pipe centerline in accordance with the formula given above. Any cut made in excess of the formula 4/3d + 15" shall be at the expense of the Contractor and may be cause for the Engineer to require that stronger pipe and/or a higher class of bedding be used at no cost to the Owner.

   D. Take reasonable care during the initial excavation of the defective pipe so as not to disturb existing pipe that is still acceptable. Where the specifications require the material from excavation to be wasted and the trench backfilled with crushed stone, load this material directly into trucks during excavation; do not pile on the street. After defective pipe has been exposed, uncover as much additional pipe as is necessary to allow space for workmen and the installation of the new pipe. Cut out the defective pipe in such a way that the ends are straight and smooth and free of chips or cracks. Remove the defective pipe from the trench, and excavate the former bedding material of any nature of that pipe to 6" below the pipe grade. All excavation is to be done in accordance with applicable portions of Section 02220 - Excavation, Backfilling, Compaction. Then fill the bottom of the trench with 6" of 1/2" to 3/4" crushed stone.

   E. Lay no pipe except in the presence of an inspector representing the Engineer.

   F. Before placing sewer pipe in position in the trench, carefully prepare the bottom and sides of the trench, and install any necessary bracing and sheeting as specified in Section 02220 - Excavation, Backfilling, Compaction.

   G. Wherever necessary to provide a satisfactory bearing surface, place concrete cradles as shown on the drawings or as directed by the Engineer. Cradles shall be of concrete and shall conform to the dimensions shown on the drawings. Concrete placed outside the dimensions shown shall be at the Contractor's expense.

   H. Tightly stretch a mason's line or wire above ground level, parallel to and directly above the axis of the pipe to be installed. This line is to be supported at intervals not exceeding 50' on sewers being laid on a grade of 2% or more than not exceeding 25' on grades of less than 2%. Determine the exact line and grade for each section of pipe by measuring down this line to the invert of the pipe in place. Accurately place each pipe to the exact line and grade called for on the drawings. Furnish all labor and materials necessary for erecting batterboards.

   I. Lasers may be used after the type and procedures are approved by the Engineer. When lasers are used, set reference points for both line and grade at each manhole. Where grades are 0.6% or less, check the elevation of the beam each 100' with an offset point or engineer's level.

   J. Do not allow water to run or stand in the trench while pipe laying is in progress or before the trench has been backfilled. Do not at any time open up more trench than available pumping facilities are able to dewater.

   K. If trench bottoms are found to be unsuitable for foundations after pipe laying operations have started, correct and bring them to exact line and grade as required by Section 02220 - Excavation, Backfilling, Compaction.

   L. Carefully inspect each piece of pipe and special fitting before it is placed, and lay no defective pipe in the trench. Pipe laying shall proceed upgrade, starting at the lower end of the grade and with the bells upgrade. When pipe laying is not in progress, keep the ends of the pipe tightly closed with a temporary plug approved by the Engineer.

   M. Bell holes shall be large enough to allow ample room for pipe joints to be properly made. Cut out bell holes not more than 2 joints ahead of pipe laying. Carefully grade the bottom of the trench between bell holes so that each pipe barrel will rest on a solid foundation for its entire length. Lay each pipe joint to form a close concentric joint with adjoining pipe and so as to avoid sudden offsets or inequalities in the flow line. 

   N. Before constructing or placing any joints, complete at least one sample joint in order to demonstrate to the Engineer that the methods employed conform to the specifications and will provide a watertight joint, and further that the workmen intended for use on this phase of the work are thoroughly familiar and experienced with the type of joint proposed.

   O. Wherever pipe materials are joined, cut the replacement pipe to a length 1" less than the overall length of the section being replaced. Then place the pipe in the trench, thoroughly clean the ends of existing and replacement pipe, and install the compression couplings. After installation, check the work to ensure that the replacement pipe is vertically and horizontally aligned with the existing pipe and that the compression couplings are tight and evenly fitted.

   P. As the work progresses, thoroughly clean the interior of the pipe in place. After each line of pipe has been laid, carefully inspect and remove all earth, trash, rags, and other foreign matter from the interior.

   Q. After the joints have been completed, they shall be inspected before they are covered. The pipe shall meet the test requirements for watertightness; immediately repair any leak or defect discovered at any time after completion of the work. Take up any pipe that has been disturbed after joints were formed, clean and remake the joints, and relay the pipe; this shall be done at the Contractor's expense. Carefully protect all pipe in place from damage until backfill operations have been completed.

   R. Do not begin the backfilling of trenches until the pipe in place has been inspected and approved by the Engineer.

   3.02 DEFLECTION TESTING FOR PVC PIPE

   A. On new sewer or complete replacements of full line segments, test the deflection of the pipe by passing a vertical floating pin go/no-go mandrel sized to 95% of the pipe diameter of the actual pipe used with the pipe in place and covered. Make this acceptance test after backfill consolidation has occurred.

   3.03 SERVICE LINES

   A. If the work consists of constructing a new sewer to replace an existing sewer, renew all existing service lines to the new line and install an inspection tee at the property line or easement line.

   B. Replace service lines from the sewer line to the property line or easement line of the structure being served by the lines as shown in the drawings. If the entire service line is to be replaced, do so with PVC pipe of the same diameter as the existing line. Lay new service line in conformance with the standard drawings.

   C. When replacing service line and/or service connections to the main line, the replacement line and/or service connection shall be of the same size as the existing line and service connection.

   D. Install tee branches in any sanitary sewer lines designated by the Engineer. If such branches are not to be used immediately, close them with stoppers approved by the Engineer that are held in place to prevent infiltration and meet all test requirements.

   E. To repair or replace a service connection which, in the judgment of the Engineer, is the source of the leak, properly connect the service in conformance with the pipe manufacturer's recommendations and specifications and applicable ASTM specifications for the service connection and the installation of same. The material of the connection shall be similar to the sewer pipe it will connect to.

   3.04 CROSSING ABOVE WATER LINES

   A. Where sewers cross above water lines, encase the sewer pipe with concrete for a distance of 10' on each side of the crossing.

   3.05 CONNECTIONS

   A. Make connections to all existing sewer lines as shown on the drawings or as directed by the Engineer. Make connections by removing a section of the sewer from the existing line and inserting a tee branch of proper size into the space; adding a saddle; or by constructing a manhole, junction box, regulator chamber, or other structure as shown on the drawings.

   B. Make connections to existing manholes or inlets by cutting a hole in the wall of the existing structure, inserting a length of sewer pipe into the hole, filling around the pipe with non-shrink concrete or mortar, and troweling the inside and outside surfaces of the joint to a neat finish. Place a manhole coupling or gasket on the pipe before mortaring around the pipe. Shape or reshape the bottom of the manholes as necessary to fit the invert of the sewer pipe in the manner specified elsewhere.

   3.06 PIPE PROTECTION

   A. Provide sewers that, when completed, have less than 2-1/2' of cover, with concrete protection or concrete cap as shown on the drawings or as directed by the Engineer. When such pipe protection is not shown on the drawings, place it in accordance with the typical section shown on the standard drawings.

   3.07 EXISTING UTLITIES

   A. Carefully protect all existing sewers, water lines, gas lines, sidewalks, curbs, gutters, pavements, electric lines, or other utilities or structures in the vicinity of the work from damage at all times. Where it is necessary for the proper accomplishment of the work to repair, remove, and/or replace any such utility or structure, do so in accordance with the provisions set forth in the General and Special Conditions of these specifications. Any such work to be done at the Contractor's expense shall be considered incidental to the construction of sewers, and no additional payment will be allowed therefor.

   3.08 FIELD JUDGEMENT

   A. At any time during a repair, the Engineer may make field judgment that shall govern over the repair until such time that the specifications will again prevail.

   3.09 TESTING SEWER LINES THAT HAVE BEEN REPLACED

   A. All lines will be tested by air testing.

   B. Furnish all equipment and facilities and all personnel for conducting the test. The test shall be observed by a representative of the Owner.

   C. Make the air test after backfilling has been completed and compacted.

   D. Conduct the air test on entire sewer line replacements on new sewer lines, and on lined sewer lines.

   E. Plug all tees and ends of sewer services with flexible joint plugs, or securely fasten caps, to withstand the internal test pressures. Such plugs or caps shall be readily removable, and their removal shall provide an end suitable for making a flexibly jointed lateral connection or extension.

   F. Before testing, check the pipe to see that it is clean. If not, clean it by passing a full gauge squeegee through the pipe. It shall be the Contractor's responsibility to have the pipe clean and determine the ground water level.

   G. Immediately following this check or cleaning, test the pipe installation with low pressure air. Slowly supply air to the plugged pipe installation until the internal air pressure reaches 4.0 psi greater than the average back pressure of any ground water that may submerge the pipe. Allow at least 2 minutes for temperature stabilization.

   H. The pipeline shall be considered acceptable when tested at an average pressure of 3.0 psi greater than the average back pressure of the ground water that may submerge the pipe if (1) the test of air loss from any section tested in its entirety between manholes does not exceed 2.0 cfm, or (2) the section under test does not lose air at a rate greater than 0.0030 cfm per square foot of internal pipe surface.

   I. The pipeline shall be considered acceptable if the time required in seconds for the pressure to decrease from 3.5 to 2.5 psi greater than the average pressure of any ground water that may submerge the pipe is equal to or greater than that shown in the Allowable Time Table below.

    ALLOWABLE TIME TABLE

    Minimum Time/100 ft.

    Pipe Size Seconds

    8" 72

    10" 90

    12" 108

    15" 126

    18" 144

    21" 180

    24" 216

    27" 252

    30" 288

   J. If the pipe installation fails to meet these requirements, the Contractor shall determine at his own expense the source or sources of leakage and repair or replace all defective materials or workmanship. The completed pipe installation shall meet the requirements of this test before being considered acceptable.

   K. Recommended Procedures for Conducting Acceptance Test:

   1. Clean pipe that is to be tested.

   2. Plug all pipe outlets with suitable test plugs. Brace each plug securely.

   3. Increase gauge pressure by the amount of ground water pressure at the crown of the pipe being tested.

   4. Add air slowly to the portion of the pipe installation under test until the internal air pressure is raised to 4.0 psi greater than the average back pressure above the crown of the pipe.

   5. After the above internal pressure is obtained, allow at least 2 minutes for the air temperature to stabilize, adding only the amount of air required to maintain pressure.

   6. After the 2-minute period, disconnect air slowly.

   7. When the pressure decreases to 3.5 psig, start the stopwatch. Determine the time in seconds that is required for the internal air pressure to reach 2.5 psig. This time interval should then be compared with the time shown in the Allowable Time Table, above. If the time is more than that shown in the table, the test will be assumed to be acceptable.

   L. Safety Provisions: Securely brace the plugs used to close the sewer pipe for the air test in order to prevent the unintentional release of a plug, which can become a high velocity projectile. Locate gauges, air piping manifolds, and valves at the top of the ground. No one shall be permitted to enter a manhole where a plugged pipe is under pressure: 4 pounds (gauge) air pressure develops a force against the plug in a 12" diameter pipe of approximately 450 pounds. DO NOT air test pipes larger than 21" in diameter because of the difficulty of adequately blocking the plugs. Provide a safety release device set to release at 10 psi between the air supply and the sewer under test.

   M. Repairs: Regardless of outcome of any test, repair any noticeable leak.

   3.10 CLEANUP

   A. After completing each section of the sewer line, remove all debris and construction materials and equipment from the site of the work; grade and smooth over the surface on both sides of the line; and leave the entire construction area in a clean, neat, and serviceable condition.

    END OF SECTION

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