The scope of service under the Contract covers the provision of a ballast suction machine and ballast feeder system together with qualified machine operators and maintainers for an initial 4-week (tentatively in January 2021) on-site trial for the replacement of the top and bottom layers of ballast at turnout crossings and an optional scope to extend the service for the subsequent 48-week period (i.e. from February to December 2021) to complete the ballast replacement works of about 46 selected turnout crossings in East Rail Line (EAL). The service shall be mainly carried out during Non-Traffic Hours (NTH). The quantity of the ballast replacement is approximately 2,700 tons for 46 turnout crossings. The disposal of used ballast and the supply of new ballast are excluded from the scope of the Contract.