Background
The Drainage Department of Hong Kong Government was building an under water sewage piping networks at Shum Tseng and there would be underwater blasting tasks to be performed associated with this civil project. However, there were fish farms in the vicinity and the owners of these farms were very concerned about the repeated blasting works, which might kill some of their fishes.
Objectives
DMSF acted as a consultant to China Construction Co. Ltd (main contractor of the HK Government) in monitoring the peak pressure generated from the blast to ensure that it was below the calculated risk level.
Technology
The measurement was done by using B&K 8103 hydrophones and charge conditioning amplifier. The hydrophone was lowered to a depth of around 7 meters below the sea surface. The change in water pressure at 15 minutes before and after the blast was measured at a sampling rate of 100KHz. Suitable software was written to extract the blast waveform from such recording.
Results
