WATER PIPELINE TESTING AND DISINFECTION

WATER PIPELINE TESTING AND DISINFECTION


PART 1 - GENERAL

1.1      THE REQUIREMENT

A. The  Contractor  shall  furnish  all  tools,  equipment,  materials,  and  supplies  and  shall perform all labor required to complete the work as indicated in the Contract Documents.

B. The Contractor shall flush, clean and test all pipelines and appurtenant piping.   All potable city water pipelines and appurtenant piping shall be disinfected.  The Contractor shall be responsible for conveyance of test water from Owner-designated sources to point of use and all disposal thereof, in accordance with the requirements of the Contract Documents.

1.2      REFERENCE SPECIFICATIONS, CODES AND STANDARDS

A.         Comply  with  the  applicable  reference  specifications  as  specified  in  the  General
Conditions.

B.         Comply with the current provisions of the following Codes and Standards.

1.         Commercial Standards

ANSI/AWWA B300        Hypochlorites ANSI/AWWA B301        Liquid Chlorine ANSI/AWWA C651        Disinfecting Water Mains

1.3      SUBMITTALS

A.         Submittals shall be made in accordance with the General Conditions.

B.         The following submittals and specific information shall be provided:
1. A  testing  schedule,  including  proposed  plans  for  water  conveyance,  control, disposal, and disinfection, shall be submitted in writing for approval a minimum of
48 hours before testing is to start.

1.4      QUALITY ASSURANCE

A.         Comply with the applicable reference specifications of the General Conditions.

PART 2 - PRODUCTS

2.1      MATERIALS REQUIREMENTS

A. All test equipment, chemicals for disinfection, temporary valves, bulkheads, or other water control equipment and materials shall be determined and furnished by the Contractor and subject to the Engineer’s approval.   No materials shall be used which would be injurious to the construction or its future function.

B. Chlorine  for  disinfection  shall  be  in  the  form  of  liquid  chlorine, sodium  hypochlorite solution, or calcium hypochlorite granules or tablets.

C.         Liquid chlorine shall be in accordance with the requirements of ANSI/AWWA B301.
Liquid chlorine shall be used only:

1.         In combination with appropriate gas flow chlorinators and ejectors;

2.         Under the direct supervision of a certified testing laboratory;

3.         When appropriate safety practices are observed.

D. Sodium  hypochlorite  and  calcium  hypochlorite  shall  be  in  accordance  with  the requirements of ANSI/AWWA B300.

PART 3 - EXECUTION

3.1      GENERAL

A. All pressure pipelines shall be tested.  Unless otherwise provided herein, water for testing and disinfecting water pipelines inside the treatment plants will be furnished by the Owner; however, the Contractor shall make all necessary provisions for conveying the water from the Owner-designated source to the points of use.

B. Unless otherwise instructed by the Engineer, all pipeline trenches shall be backfilled and compacted per Section 02200, prior hydrostatic testing of pipe.

C. Disinfection shall be accomplished by chlorination.  All chlorinating and testing operations shall be performed by a certified laboratory in the presence of the Engineer.

D. Disinfection operations shall be scheduled by the Contractor as late as possible during the contract time period so as to assure the maximum degree of sterility of the facilities at the time the work is accepted by the Engineer.  Bacteriological testing shall be performed by a certified testing laboratory approved by the Engineer and at the expense of the Contractor.  Results of the bacteriological testing shall comply with the requirements of appropriate regulatory agencies.

3.2      HYDROSTATIC TESTING OF PIPELINES

A. Prior to hydrostatic testing, all pipelines shall be flushed or blown out at 6-8 feet per second or as approved by the Engineer.  The Contractor shall test all pipelines either in sections or as a unit.   No section of the pipeline shall be tested until all field-placed concrete or mortar has attained an age of 14 days.  The test shall be made by closing valves when available, or by placing temporary bulkheads in the pipe and filling the line slowly with water.   The Contractor shall be responsible for ascertaining that all test bulkheads are suitably restrained to resist the thrust of the test pressure without damage to, or movement of, the adjacent pipe.  Care shall be taken to see that all air vents are open during filling.

B. The pipeline shall be filled at a rate, which will not cause any surges or exceed the rate at which the air can be released through the air valves at a reasonable velocity and all the air within the pipeline shall be properly purged.  After the pipeline or section thereof has been filled, it shall be allowed to stand under a slight pressure for at least 24 hours to allow the concrete or mortar lining, as applicable, to absorb what water it will and to allow the escape of air from any air pockets.   During this period, bulkheads, valves, and connections shall be examined for leaks.   If leaks are found, corrective measures satisfactory to the Engineer shall be taken.

C. The hydrostatic test shall consist of holding the test pressure on the pipeline for a continuous period of 4 hours.  The test pressure for pipelines shall be 150 percent of the pipe pressure class shown or as specified in Section 15050, whichever is the highest. Test pressure shall be measured at the lowest point of the pipeline section being tested. All visible leaks shall be repaired in a manner acceptable to the Engineer.

D. The  maximum  allowable leakage  for  pipelines  shall  be  10 U.S. gallons  per  inch of diameter per mile of pipe per 24 hours for pipe with 40-ft or greater joint lengths and with rubber-gasketed joints, and 20 U.S. gallons per inch of diameter per mile of pipe per 24 hours for pipe with 20-ft or less joint lengths and with rubber-gasketed joints.  Pipe with welded joints shall have no leakage.   In the case of pipelines that fail to pass the prescribed leakage test, the Contractor shall determine the cause of the leakage, shall take corrective measures necessary to repair the leaks, and shall again test the pipelines.

3.3      DISINFECTING PIPELINES

A. General:   All water pipelines except those appurtenant to hydraulic structures shall be disinfected in accordance with the requirements of ANSI/AWWA C651 disinfection of water mains using the Continuous-Feed Method as modified herein.

B. Chlorination:  A chlorine-water mixture shall be uniformly introduced into the pipeline by means of a solution-feed chlorinating device.  The chlorine solution shall be introduced at one end of the pipeline through a tap in such a manner that as the pipeline is filled with water, the dosage applied to the water entering the pipe shall be approximately 50 mg/l. Care shall be taken to prevent the strong chlorine solution in the line being disinfected from flowing back into the line supplying the water.

C. Retention Period:   Chlorinated water shall be retained in the pipeline long enough to destroy all non-spore-forming bacteria.  This period shall be at least 24 hours.  After the chlorine-treated water has been retained for the required time, the free chlorine residual at the pipeline extremities and at other representative points shall be at least 25 mg/l.

D. Chlorinating Valves:  During the process of chlorinating the pipelines, all valves and other appurtenances shall be operated while the pipeline is filled with the heavily chlorinated water.

E. Final Flushing:  After the applicable retention period, the heavily chlorinated water shall be flushed from the pipeline until chlorine measurements show that the concentration in the water leaving the pipeline is no higher than that generally prevailing in the system or is acceptable for domestic use.  If there is any question that the chlorinated discharge will cause damage to the environment, a reducing agent shall be applied to the water to neutralize thoroughly the chlorine residual remaining in the water.

F. Bacteriological Testing:  After final flushing and before the pipeline is placed in service, a sample, or samples shall be collected from the end of the line, and shall be tested for bacteriological quality in accordance with the requirements of the Riverside County Department of Health Services or other appropriate regulatory agency.  For this purpose, the pipe shall be re-filled with fresh potable water and left for a period of 24 hours before any sample is collected.   Should the initial disinfection treatment fail to produce satisfactory bacteriological test results, the disinfection procedure shall be repeated until acceptable results are obtained.

3.4      CONNECTIONS TO EXISTING SYSTEM

A. Where connections are to be made to an existing potable water system, the interior surfaces of all pipe and fittings used in making the connections shall be swabbed or sprayed with a one percent hypochlorite solution before they are installed.   Thorough flushing shall be started as soon as the connection is completed and shall be continued until discolored water is eliminated.