XN000022-1997-03-27 — Page 15

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Phasing out noisy hammers in four stages

The Governor-in-Council has approved that legislative amendment be made to impose more stringent noise criteria on the noisy percussive hammers.

The Noise Control (Amendment) Bill 1997, gazetted today (Thursday), seeks to reduce noise level generated from percussive piling by phasing out the use of three types of noisy hammers -- diesel, pneumatic and steam in built-up areas and replace

them with quieter alternatives such as the hydraulic ones.

A spokesman for the Planning, Environment and Lands Branch said that percussive piling generates significant noise impact on its neighbourhood. Three types of hammers, namely diesel, pneumatic and steam hammers are the noisiest, of which diesel hammer accounts for over 80% of piling permits issued and produce noise levels up to 103 dB(A) at 10 metres. Pneumatic and steam hammer also produces noise level up to 106 dB(A) at 10 metres.

By comparison, hydraulic hammer is more environmentally friendly as it produces about two to nine dB(A) quieter than diesel, pneumatic and steam hammers under the same site conditions and will not emit filthy smoke. Moreover, mitigation measures such as acoustic shrouds may be applied to achieve further noise reduction.

In collaboration with government departments, the Hong Kong Construction Association has completed a series of piling tests which found that hydraulic hammers can achieve the required hammer efficiency. The results of the piling tests have been accepted by the Building Authority.

"To moderate the impact on the construction industry and to allow time for suppliers of hydraulic hammers to meet the demand, we propose to phase out noisy hammers in four stages at six-month intervals commencing in early 1998. Progressively, the noise criteria for issuing construction noise permits to percussive piling operations using those hammers will be tightened," the spokesman said.

During the final stage at around year 2000 the use of noisy hammers in built-up areas will practically be banned. Nonetheless, they can still be used in remote areas where they will not disturb anyone.

"From July 1, 1997, the Administration will take the lead in promoting the use of hydraulic hammers in public works and housing projects in advance of legislative controls," he added.