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Advisory Note on Inspection & Maintenance of Buried Drainage & Water Services Affecting Slopes/Walls

This advisory note is intended to help property owners and their building managers to ensure that services within their lot are properly maintained and functioning.


Why is inspection & maintenance of buried water-carrying services important?

Persistent leakage of water from buried water-carrying services not only causes nuisance, but can also impose a serious risk to the stability of nearby slopes and retaining walls. Leakage may not produce visible signs on the surface. Accordingly, owners or parties responsible for maintaining water-carrying services that may affect slopes and retaining walls should arrange for regular checks of buried water-carrying services regardless of whether signs of suspected leakage have been observed. These services include sewers, stormwater drains and watermains. As a preventive measure, it is essential that the services are inspected and maintained regularly. Lack of maintenance may result in water leakage, which may affect the stability of slopes and retaining walls within or even away from the lot boundary. As a result, landslides can occur.


Identification of water-carrying services affecting slopes and retaining walls

As a first step, it is necessary to identify all the water-carrying services affecting slopes and retaining walls. Preliminary site reconnaissance can be carried out to locate manholes and valve pits, which will provide an indication of the existence of buried services and their alignments. Property owners or building managers can seek detailed information from building plans and records kept by them or by the respective Authorised Person or Developer of their properties. The following government departments may also assist in locating the missing details:


Buildings Department: Tel. No. 2135 2525
(for records of private drains)


Drainage Services Department: Tel. No. 2877 0660
(for records of public drains)


Water Supplies Department : Tel. No. 2824 5000
(for watermains records)


Regular Checks:

Owners or parties responsible for maintaining water-carrying services should appoint specialist leakage detection contractors to carry out regular checks of the services for signs of leakage. Sewers, stormwater drains and watermains should be inspected regularly for blockage and structural soundness.


Guidance on methods for checking buried water-carrying services is given in the "Code of Practice on Monitoring and Maintenance of Water-carrying Services Affecting Slopes" (Environment, Transport and Works Bureau, 2006). It can be downloaded from the website of the Development Bureau (http://www.devb.gov.hk). General guidance on slope maintenance is given in the "Layman's Guide to Slope Maintenance", which is available free of charge from District Offices. Alternatively, these publications can be downloaded from the Hong Kong Slope Safety Website given below.


Repair Immediately!

Any buried water-carrying services, which are found to be damaged or leaking should be repaired without delay. Where services owned by other private parties are found to affect slopes and retaining walls within the maintenance boundary, the services' owner should be asked to repair them. The case should also be referred to Buildings Department or Lands Department. If they are not repaired, persistent leakage may cause landslides, which may result in injuries or damage to property. If this happens, the services' owner may have to incur great expenses to remedy the slope or retaining wall and to compensate for the injuries and property damage.