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Frequently Asked Questions of Slope Maintenance



1.) Why is regular maintenance of slopes/retaining walls so important?

The lack of maintenance of slopes and retaining walls is the major contributory factor to many landslides in Hong Kong. Many landslides are triggered by water ingress into slopes and by soil erosion during heavy rain. Man-made slopes normally have drainage provisions and protective surfacing to prevent water ingress and soil erosion. These measures need regular maintenance to ensure their proper performance. Buried water-carrying services, if they leak, could increase the water pressure inside the slope and trigger landslides, and these services should therefore also be maintained.

 

2.) What will happen if I neglect to maintain my slope?

If a slope or retaining wall is not properly maintained, it will deteriorate and a landslide may occur causing injury to persons, damage to property and disruption of normal life. If this happens, suffering and hardship may result and great expense may be incurred to render the slope safe, to repair the property, and to compensate those injured.

 

3.) How do I know who is responsible for maintenance of a slope/retaining wall?

The responsibility for the maintenance of slopes and retaining walls rests with the owners or the party assigned such a responsibility. Ownership is conferred by lease documents issued by the Lands Department. The public can have access to lease documents and records of owners at the Land Registry. Private owners may also be liable under specific lease conditions for the maintenance of slopes and retaining walls adjoining the lots. Where appropriate, professional advice may need to be sought from lawyers or estate surveyors on the interpretation of the lease documents in respect of maintenance responsibilities. Private owners can browse the Website of the Lands Department to obtain information of maintenance responsibility of registered slopes ( http://www.slope.landsd.gov.hk/smris/ )

 

4.) How to maintain a slope/retaining wall to keep it in good condition?

Any slope or retaining wall for which an owner is responsible should be maintained in a state of good condition in accordance with "Geoguide 5 - Guide to Slope Maintenanc" published by the Geotechnical Engineering Office (GEO) of the Civil Engineering and Development Department. An abridged version entitled "Layman's Guide to Slope Maintenance" was also published by the GEO to aim at the general public, including property owners and agents for slope maintenance. Free copy of "Layman's Guide to Slope Maintenance" can be obtained from the GEO and District Offices, or downloaded from the Hong Kong Slope Safety Website ( http://hkss.cedd.gov.hk ) of the GEO. Slope owners should arrange maintenance inspections and works at frequency recommended in the Geoguide 5.


Layman guide

 

5.) What is Routine Maintenance Inspections?

The prime purpose of Routine Maintenance Inspections (RMI) is to establish the need for basic maintenance works. Such inspections can be carried out by a layman, including property management or maintenance staff. RMI should normally be carried out at least once every year. Any required maintenance works should be completed before the onset of the wet season in April. In addition, owners should arrange to inspect the drainage channels and clear any blockage after a heavy rainstorm or a typhoon. Typical routine maintenance shall include:

  1. clearance of accumulated debris from drainage channels and slope surface,
  2. repair of cracked or damaged drainage channels or pavement,
  3. repair or replacement of cracked or damaged slope surface cover,
  4. unblocking weepholes and outlet drain pipes,
  5. repair of missing or deteriorated pointing in masonry in masonry walls,
  6. removal of any vegetation causing severe cracking of slope surface cover and drainage channels,
  7. re-grassing bare slope surface areas,
  8. removal of loose rock debris and undesirable vegetation from rock slopes or around boulders,
  9. investigation and repair of buried water-carrying services where signs of possible leakage are observed,
  10. repair of leaky exposed water-carrying services,
  11. repair or replacement of rusted steel slope furniture, and
  12. maintenance of landscape items on the slope.
Routine maintenance works can be carried out by a building contractor. A list of Registered Contractors is available for inspection at District Offices and the Buildings Department (BD), or downloaded from the BD Website ( http://www.info.gov.hk/bd ).

 

6.) What is Engineer Inspections for Maintenance?

Although proper routine maintenance of a slope or retaining wall can greatly reduce the probability of a landslide, the slope may still not be sufficiently safe for various reasons, such as inherent design or construction deficiencies, or change that have taken place in the vicinity. Therefore, an Engineer Inspections for Maintenance should normally be carried out once every 5 years to look for all slope safety problems by a qualified Geotechnical Engineer. The Geotechnical Engineer will advise on the maintenance of the slope and any required improvement works. He will also advise on the need for a Stability Assessment to check the slope’s overall safety.

A list Registered Professional Engineers (Geotechnical) can be obtained from the Engineers Registration Board, c/o the Hong Kong Institution of Engineers, 9/F, Island Centre, 1 Great George Street, Causeway Bay, or downloaded from its Website ( http://www.erb.org.hk ).

 

7.) Why a Dangerous Hillside Order is needed when a slope/retaining wall was stable for more than 30 years?

Before the GEO was established in 1977, many man-made slopes and retaining walls might not have been designed or constructed to proper engineering standards. Slopes also deteriorate unless they are regularly and properly maintained. They may become dangerous or liable to become dangerous if inadequate or no maintenance is carried out. Past performance of slopes is not an indicator of adequate stability for the following reasons:

  1. deterioration of slope conditions with time,
  2. change in environmental factors which may give rise to concentration of surface water flow, and/or change in loading in surroundings,
  3. critical combination of duration and intensity of rainfall and antecedent rainfall may not have been previously experienced,
  4. deterioration and leakage or bursting of buried water-carrying services or services which act as conduits for water,
  5. progressive undetected movement, which may take place over a period of years.

 

8.) Under what circumstances, a Dangerous Hillside (DH) Order will be served to slope owners?

When a private slope or retaining wall is found to be dangerous or liable to become dangerous, the Buildings Department (BD) will serve a DH Order to require the slope owners to investigate and if necessary rectify the situation. DH Orders are usually issued in the following circumstances:

  1. a private slope is found to be dangerous or liable to become dangerous, in the Government “safety screening” studies under the ongoing Landslip Preventive Measures (LPM) Programme;
  2. a landslide has occurred or significant signs of distress are found in a private slope on which geotechnical study and/or extensive repair works are required to rectify its long term stability.
Recommendations for the service of a DH Order are made only after very careful consideration. All DH Order recommendations are reviewed by senior management of GEO before they are passed to the BD to ensure that DH Orders are issued only when there is a sound justification.

 

9.) How to handle a Dangerous Hillside Order?

Under section 27A of the Buildings Ordinance, a Dangerous Hillside (DH) Order may be served on the responsible slope owners requiring them to investigate and carry out necessary slope works to rectify the dangerous or liable to become dangerous situation. The owners should, within the stipulated period, appoint an Authorized Person to provide professional services such as (a) co-ordinates and supervises works as required under the Buildings Ordinance, (b) engages a registered geotechnical engineer to provide geotechnical consultancy service, and (c) monitors the stability of slope until completion of remedial works and gives warning of impending danger.

The GEO published a guide entitled “Simple Guide to Dangerous Hillside Orders” for private slope owners who receive a DH Order requiring investigation or repair of slopes. The guide provides a step by step approach to assist them in fulfilling the requirements of the DH Order promptly and effectively. Free copy of this guide can be obtained from the GEO and District Offices or downloaded from the Hong Kong Slope Safety Website ( http://hkss.cedd.gov.hk ) of the GEO.

If private owners encounter difficulties in dealing with a DH Order or require assistance and further information, they can contact the Community Advisory Unit (CAU) of the GEO at telephone no. 2760 5800.

 

10.) What will happen if owners fail to comply with a Dangerous Hillside Order?

If private owners do not carry out the investigation of their slopes by the date specified in the DH Order, the BD may carry out the investigation and any subsequent works as default works and will seek to recover the costs plus supervision charges from the owners, under sections 32A and 33 of the Buildings Ordinance. The Building Authority may also prosecute any person who fails to comply with the Order without a reasonable excuse under section 40 (1B) of the Buildings Ordinance. Such person shall be liable on conviction to a fine of $50,000, to imprisonment for one year and to a further fine of $5,000 for each subsequent day during which the failure to comply with the Order has continued.

 

11.) How do I know whether a building has received a Dangerous Hillside Order?

Under section 27A of the Buildings Ordinance, a Dangerous Hillside Order may be served on the responsible slope owners requiring them to investigate and carry out necessary slope works to rectify the dangerous or liable to become dangerous situation. Moreover, the BD will post a copy of the Order on a conspicuous part of the building on the date of issue, as well as arrange for registration by memorial in the Land Registry.

If the owners completed all the required works as stated in the DH Order to the satisfaction of the BD, the BD will issue a compliance letter to the owners for discharging the Order, and such letter will be registered in the Land Registry. Any person may check with the Land Registry that any Order has been served on the owners of the building, and whether the owners have fully complied with the Order. The Land Registry can be contacted at telephone no. 2867 2882.

 

12.) How to handle an Advisory Letter for Slope Maintenance?

On receipt of an Advisory Letter issued by Building Authority or the GEO recommending necessary maintenance works of slopes/retaining walls, the responsible owners should arrange as soon as possible to carry out all the recommended maintenance works. It should be stressed that the slopes/retaining walls is not currently regarded as being dangerous, however, if not properly maintained, it could deteriorate to a point where it would become dangerous. Slope maintenance works can be carried out by a building contractor. A list of registered contractors is available for inspection at District Offices and the BD, or downloaded from the BD Website ( http://www.info.gov.hk/bd ).

 

13.) Does Geotechnical Engineering Office provide any advisory services?

To enhance public understanding of slope safety, the GEO has set up a Community Advisory Unit (CAU) to assist private owners to discharge their slope maintenance responsibility through direct community outreach advisory and information services. The CAU has the following principal functions:

  1. organize slope safety and maintenance seminars and talks for private owners and bodies involved in slope maintenance;
  2. provide a meet-the-public service to answer queries and provide information on slope safety matters;
  3. meet private owners who have received DH Orders to advise them on how to proceed with the necessary slope upgrading works;
  4. meet Owners’ Corporations and Mutual Aid Committees to advise them on how to undertake slope maintenance works.

Advisory services       Advisory services       Advisory services

If private owners encounter difficulties in dealing with a DH Order or require assistance and further information, they can contact the CAU at telephone no. 2760 5800 or by electronic mail at cau@cedd.gov.hk.

 

14.) How to handle Dangerous Hillside Order or slope maintenance works if I have financial difficulty?

To encourage property owners to carry out slope maintenance works, the Urban Renewal Authority and the Hong Kong Housing Society have jointly rolled out a one-stop “Integrated Building Maintenance Assistance Scheme” (IBMAS) for providing financial assistance and technical support to property owners. Under the IBMAS, owners can submit one set of application forms for multiple financial assistance schemes, including the “Building Maintenance Grant Scheme for Elderly Owners” administered by the Hong Kong Housing Society and the “Building Safety Loan Scheme” administered by the Buildings Department. If owners have financial difficulty in carrying out slope maintenance works or upgrading works to comply with DH Orders, they may apply for a subsidy or loan under IBMAS. For further information or enquiry, please call Building Maintenance Assistance Schemes Hotline 3188 1188.

 

15.) Why do I need landscape works on slopes and how to carry out the works?

Landscape works on slopes and retaining walls can improve its appearance, create a greener environment and enhance the value of adjoining properties. A vegetated surface cover, as compared with shotcrete surface cover, is visually attractive, ecologically beneficial and less heat and light reflective. Where the use of a hard surface cover is unavoidable, owners should take measures to improve its appearance wherever practicable, e.g. retaining existing trees using tree rings and providing planters at slope toe.

The GEO published a "Layman's Guide to Landscape Treatment of Slopes ", which aims to help and encourage private slope owners to provide landscape treatment to their slopes when planning maintenance, upgrading works or new developments. Free copy of the Layman’s Guide can be obtained from the GEO and District Offices, or downloaded from the Hong Kong Slope Safety Website ( http://hkss.cedd.gov.hk ) of the GEO.