I refer to the letter from David Cheng ('Rage over road works', South China Morning Post, February 2).

The sewer-laying work at Conduit Road is part of a Drainage Services Department contract to upgrade the existing sewerage system in Central, Western and Wan Chai West Districts. About 450 metres of sewer at Conduit Road between Glenealy Road and Castle Road will be enlarged to cater for future increase in sewage.

In order to maintain continuous traffic flow in Conduit Road, the works are being carried out in short sections from 9am to 5pm during weekdays. Outside these working hours, the trenches are covered by steel plates in order to give more space for traffic.

To reduce the impact on people's livelihoods caused by excavating roads, we have adopted a new contract management method such that the contractor is issued with works orders for opening trenches of up to 30 metres in length at a time. Subsequent sections of works are only allowed when the previous section has been completed. The engineer will only issue another works order to the contractor when their resources are readily available on site for carrying out the works expediently.