(v) The rubber gasket shall be installed on the pipe in accordance with the instructions of the gasket manufacturer. In general, the gaskets shall be pre-assembled to the pipe at the pipe manufacturing plant. The pipes shall be handled with special care at all times to prevent damage to the pipe ends. A lubricant shall be used for jointing the pipes as recommended by the rubber gasket manufacturer. Care shall be taken to avoid contamination of the gasket and lubricated surfaces with earth or other undesirable material during installation.
(vi) For either tongue and groove or bell and spigot pipes, mechanical means shall be used to pull the pipe home for all sizes of 12 inch or larger diameter in accorda¬nce with the recommendations of the rubber gasket manu¬facture. Pipes of 8 inch or smaller diameter may be coupled manually using a cross member and bar. Under no circumstances will bars alone be used nor shall any motor driven equipment be used to force the pipe home.


25.5 Installation of Concrete Pipe Sewers

25.5.1 Handling of Pipes

(i) Concrete sewer pipes shall be handled with special care at all times during the manufacture, while transporting to the site of work, and while installing. Each pipe shall be carefully inspected before being laid and no cracked, broken or defective pipe shall be used in the work.
(ii) Chipping of the tongue and groove or bell and spigot pipe ends, which in the Engineer's opinion may cause defective joints, shall be sufficient cause for the rejection of any concrete pipe.

25.5.2 Excavation and Backfill

The excavation and backfill for sewer installations shall be as specified in applicable provisions of these Technical Specifications and will be paid for under separate Contract items as classified or and as per applicable Variation Orders (VO).

25.5.3 Trench Bedding

Wherever called for on the plans or where ordered in writing by the Engineer, the Contractor shall furnish and place bedding, and/or concrete encasement for the concrete pipe sewers under this Contract. The bedding shall be as specified in applicable provisions of these Technical Specifications and will be paid for under separate Contract item as classified, described and listed in the Bill of Quanti¬ties or and as called for in applicable Variation Order (VO).

The concrete encasement shall be placed in accordance with the details and notations on the plans or as ordered in writing. Concrete work shall be as specified in the applicable provisions of Item of these Technical Specifications and will be paid for under separate Contract items as classified, described and listed in the Bill of Quantities (BOQ) or as called for in applicable Variation Orders (VO).

25.5.4 Laying of Sewers

(i) Neither any sewer pipe nor the bedding shall be laid or placed till the alignment of the sewer and its levels and gradients have been carefully checked and tested with the trench excavation and found correct.
(ii) Each length of sewer pipe shall be checked for cracks and defects before placing in the line. Defects which in the opinion of the Engineer indicate imperfect placing, shall make the pipe liable to rejection.
(iii) Each pipe shall be placed carefully to line and grade and in close contact with adjoining pipe. These specifications require rejection of the work if the sewer invert varies as much as 12mm from the proper elevation.
(iv) As shown on plans, the bottom of the trench must be shaped to fit the pipe barrel, with holes left for the bells.
(v) If excavation has been carried below the correct grade, refilling must be done with satisfactory materials as approved by the Engineer at no extra cost.
(vi) The concrete pipe joints shall be of the types designated above and shall be made in accordance with the aforesaid specifications.
(vii) When pipe laying is not in progress, the open pipe shall be closed with a tapered wooden plug to keep out foreign matter.

25.5.5 Pavement Restoration

The Contractor shall restore paved surfaces which have been cut damaged under this Contract, as part of the work under the excavation items and at no extra cost to the Employer.

25.6 Tests for Infiltration or Exfiltration

25.6.1 General

All sewers built under this Contract shall be tested for infiltration or exfiltration as specified herein. The Contractor shall furnish labour, materials and equipment required for making the required tests with no extra compensation to the Contract Unit Rate for the sewers. The tests shall be made at times selected or approved by the Engineer. Sections of the completed sewer shall be isolated and measurements of the infiltration or exfiltration shall be made by approved methods.

25.6.2 Infiltration Tests

(i) The sewers which are constructed with the ground water level above the crown of the pipe shall be tested for infiltration after the sewers have been installed and backfilling has been substantially completed. The tests and measurement shall be performed by the Contractor in the presence of and in a manner approved by the Engineer.
(ii) The duration of the tests shall be only long enough to establish the true rate of infiltration.
(iii) The amount of leakage over a 25 hours period will then be calculated from the result of the measured true rate of infiltration.

25.6.3 Exfiltration Tests

The sewers which are constructed with the ground water level below the crown of the pipe shall be tested for exfiltration by isolating a section of sewers between manholes by means of approved temporary type of water tight bulk heads. The method of testing for exfiltration shall be generally as follows:

i) After isolation of sewer section, it shall be filled with water to a level which is 1m above the crown of the sewer at the higher end of the isolated section under test. The level will not be more than 6 feet above the crown of the sewer pipe at its lower end.
ii) The duration of the exfiltration test shall be one hour after the filling with water has been completed.
iii) Determination of the amount of exfiltration shall be made by measuring the total loss of volume of water in the manholes.
iv) The amount of exfiltration over a 25 hours period will then be calculated from the measured loss of volume during the test observation period.

25.6.4 Allowable Infiltration or Exfiltration

(i) The calculated amount of infiltration or exfiltration over a 25 hours period shall not exceed 75 liter per mm of pipe diameter per km of sewer, which rate shall be applied to the actual sewer size and length tested to determine the allowable infiltration or exfiltration over the 25 hours period.
(ii) If the measured infiltration or exfiltration exceeds the specified allowable limit, then the Contractor shall locate the points of leakage and make necessary repairs so as to reduce the leakage to less than permissible maximum stated above.

25.7 Measurement

(i) Measurement will be made at site of the actual lengths of reinforced concrete pipes of different sizes and strength installed tested and approved as authorized for the payment under the Contract.
(ii) The measurement will be made along the center line of the pipe and between the inside walls of manholes or junction chambers. The unit of measurement will be one linear foot.