Airport metro line: Eco assessment draws noise pollution limits

Finding noise pollution way beyond acceptable levels along the Outer Ring Road and Airport Road, an Environmental Impact Assessment (EIA) on the airport metro line has suggested a slew of measures to address the additional noise that would be generated by the project.

To control noise from active construction sites, the Bangalore Metro Rail Corporation Limited erects a three-metre temporary wall. This, the EIA report notes, is effective during pier construction but not during footing construction as the sound energy levels from vibro-hammers and backhoe pavement breakers are inherently high.

The EIA solution: Not taller noise walls, but alternative methods of pavement breaking that generate less noise. This means a shift from traditional excavator-mounted pavement breakers that typically generate noise between 95 and 105 deciBel dB(A) and handheld breakers (85-103 dB(A)) at a distance of 7 metres from the equipment.

The report cites a less noisy method suggested by the Hong Kong Environmental Protection Department: Saws and high-pressure water jetting to cut pavement. “This will reduce noise levels by about 20 dB(A) compared to excavated mounted breakers.”

Emphasising on good communication between the metro project contractor and the affected communities, the EIA notes: “The contractor should keep them well-informed of the work progress, when and where the noisiest activities will be taking place and how long they are expected to last.”

The contractor will be required to record, investigate and address all noise complaints, avoid night-time and weekend working, avoid working during prayer time, and to carry out noisy works near offices during holiday periods.

To minimise noise on the road, the EIA mandates that the project contractor employ modern, silenced and well-maintained plant and construction equipment. “All vehicles and the plant should be fitted with effective exhaust silencers, maintained in good and efficient working order.”

Besides, fitted acoustic covers should be kept in a good state of repair and closed when the plant is in use. “Vehicles should not wait or queue on the road with engines running, shut down when not in use or where this is impracticable, throttled down to a minimum.”

Concrete mixers should not be cleaned by hammering the drums. “When handling materials, care should be taken not to drop materials from excessive heights,” the EIA report notes.