Following is a question by the Hon Choy So-yuk and a written reply by the Secretary for the Environment, Transport and Works, Dr Sarah Liao, at the Legislative Council meeting today (February 28) :
The Government has indicated that landscaping works will be carried out in conjunction with slope stabilisation works. However, I am aware that when stabilisation works were carried out for three slopes by the Government recently, no tree was replanted in-situ after the removal of the original ones, and only concrete spraying was employed as finish for one of the slopes. One of them is situated at Old Peak Road (of slope number: 11SW-A/C211), and the other two are at Magazine Gap Road (the slope number of one of them is 11SW-D/CR1180 while the other is adjacent to Grenville House). In this connection, will the Government inform this Council:
(a) of the department responsible for the stabilisation works for the aforesaid slopes;
(b) whether tree-planting or other greening works will be carried out at such slopes; if such works will be carried out, of the details and timetable; if not, the reasons for that; and
(c) of the number of slopes for which stabilisation works were carried out by the Government last year and, among such slopes, the number of those at which greening works were not carried out and only concrete spraying was employed as finish, and the reasons for that?
(a) The three slopes mentioned in the question are situated at Old Peak Road (slope no. 11SW-A/C211), Magazine Gap Road (slope no. 11SW-D/CR1180) and the back of Grenville House adjacent to Magazine Gap Road (slope no. 11SW-D/CR330). The Highways Department (HyD) is responsible for the general routine maintenance of all three slopes. As part of the Landslip Preventive Measures Programme, the Civil Engineering and Development Department (CEDD) is responsible for carrying out some major slope stablization works. Under this programme, the CEDD has recently completed the stablization works of the two slopes situated respectively at Magazine Gap Road (slope no. 11SW-D/CR1180) and at the back of Grenville House adjacent to Magazine Gap Road (slope no. 11SW-D/CR330).
(b) (i) The Slope at Old Peak Road (Slope No. 11SW-A/C211)
During the passage of Typhoon Prapiroon in August last year, some trees on the slope were blown down and posed a road safety hazard. Hence, the HyD removed the fallen trees immediately. As the slope is too steep for replanting, the HyD plans to provide planters at the toe of the slope and to grow plants there as a greening measure. The greening works will commence in mid-2007 and is expected to complete by the end of 2007.
(ii) The Slope at Magazine Gap Road (Slope No. 11SW-D/CR1180)
In September 2006, the CEDD completed the stablization works of the slope. Owing to the loose rock debris on the slope surface and the largely steep slope gradient which rendered a vegetation cover unsuitable, the CEDD protected the slope with a shotcrete cover instead. To improve the appearance, planting holes have been provided on the slope cover and plants in the holes, when fully grown, will provide greening to most of the shotcrete cover of the slope.
(iii) The Slope at the Back of Grenville House (Slope No. 11SW-D/CR330)
The CEDD also completed the stabilisation works for the slope in February 2007. Some trees on the slope were found withered and had to be removed before the commencement of the works. As the largely steep slope gradient rendered a vegetation cover unsuitable, shotcrete cover was used instead and replanting has been carried out in suitable places, including tree planting at the top of the slope and provision of planting holes on the slope cover so that plants in the holes, when fully grown, will provide greening to most of the shotcrete cover of the slope.
(c) The Government regularly carries out routine maintenance, including drainage clearance and undergrowth cutting, on slopes and retaining walls. These kinds of work do not have any impact on the existing surfaces of the slopes concerned. Apart from the routine maintenance of slopes, the CEDD and other departments responsible for slope maintenance also carried out stabilisation and improvement works for a total of 601 slopes and retaining walls in 2006. Shotcrete covers were used on 196 of the above slopes and retaining walls which were not suitable for vegetation covers. However, landscape treatment, such as stone pitching, provision of toe wall planters and planting holes on the slope covers for growing plants, etc., was provided on the surfaces of these slopes and retaining walls.
The main reasons why vegetation covers cannot be used in slope stabilisation and improvement works include:
(i) slope safety reasons such as very steep slope gradient or slopes with loose rocks;
(ii) unsuitability for using vegetation covers on the surfaces of steep rock slopes or masonry retaining walls; and
(iii) nearby residents' objection to greening for fear of hill fires, mosquito nuisance, etc.
End/Wednesday, February 28, 2007