XN000022-1990-06-27 — Page 35

WEDNESDAY, JUNE 27, 1990

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WATER MAINS BURSTS MOSTLY CAUSED BY EXTERNAL FACTORS

THE WATER SUPPLIES DEPARTMENT REGULARLY CARRIES OUT WASTE DETECTION TESTS ON WATER MAINS TO REDUCE THE NUMBER OF FAILURES, THE ACTING SECRETARY FOR PLANNING, ENVIRONMENT AND LANDS, THE HON CLIVE OXLEY, INFORMED THE LEGISLATIVE COUNCIL TODAY (WEDNESDAY).

IN A WRITTEN REPLY TO A QUESTION FROM THE HON POON CHI-FAI, MR OXLEY SAID THE DETECTION TESTS COULD ASSIST IN LOCATING LEAKAGES, SO THAT THEY MIGHT BE REPAIRED BEFORE DEVELOPING INTO SERIOUS BURSTS.

HE ADDED THAT DAMAGE OR DISTURBANCE TO WATER OTHER CONSTRUCTION ACTIVITIES COULD BE PREVENTED STEPPING UP VIGILANCE ON WORKS BEING CARRIED OUT.

"WHERE RESPONSIBILITY CAN BE ESTABLISHED, CONTRACTOR IS CHARGED WITH THE COST OF REPAIRS.

MAINS CAUSED BY OR MINIMISED BY

THE OFFENDING

"THE MATTER IS KEPT UNDER REVIEW BY THE WATER SUPPLIES DEPARTMENT IN CONJUNCTION WITH THE HIGHWAYS DEPARTMENT, THE UTILITY COMPANIES AND RELEVANT GOVERNMENT DEPARTMENTS WITH A VIEW TO ALLEVIATING THE PROBLEM," MR OXLEY SAID.

HE POINTED OUT THAT MOST MAINS BURSTS WERE CAUSED BY A VARIETY OF EXTERNAL FACTORS.

THESE INCLUDED ROAD CONSTRUCTION OR RECONSTRUCTION WHERE HEAVY PLANT MIGHT BE USED, TRENCH WORKS FOR OTHER UTILITIES AND DRAINAGE SERVICES, AND DEEP FOUNDATION EXCAVATIONS FOR BUILDING DEVELOPMENT AND FLYOVERS IN THE VICINITY OF THE WATER MAINS.

MR OXLEY SAID SOME OF THESE ACTIVITIES MIGHT DAMAGE THE WATER MAINS DIRECTLY OR DISTURB THEIR FOUNDATIONS.

"IT WOULD BE PROHIBITIVELY EXPENSIVE

STRONG ENOUGH TO RESIST SUCH EXTERNAL EFFECTS.

ΤΟ DESIGN WATER MAINS

"IT IS OFTEN IMPOSSIBLE TO ESTABLISH THE CAUSE AND LIABILITY AFTER A WATER MAIN BURST AS WATER GUSHING OUT UNDER PRESSURE REMOVES ALL THE EVIDENCE AND NATURALLY PRIORITY HAS TO BE GIVEN TO REPAIR WORK TO RESTORE THE WATER SUPPLY AND TRAFFIC FLOW, HE SAID.

MR OXLEY ADDED THAT THE WATER MAINS USED BY THE WATER SUPPLIES DEPARTMENT WERE TESTED AT THE MANUFACTURERS' WORKS TO TWICE THE DESIGNED WORKING PRESSURE AND WERE TESTED AFTER THEY WERE LAID IN POSITION TO ONE AND A HALF TIMES THE DESIGNED WORKING PRESSURE.

THE WATER MAINS WOULD HAVE A LONG SERVICEABLE LIFE, PROBABLY OF SEVERAL DECADES, IF UNDISTURBED AFTER THEY HAD BEEN LAID, HE SAID.

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