1 INTRODUCTION

1.1 The Assignment Brief requires the Consultants to:

· refine the preliminary alignment presented in the Assignment Brief with a view to improving the road gradients, road bends and minimising the environmental impacts and impacts on the Country Park;

· produce at least six alignment options with different horizontal or vertical alignments within the “Broad Corridor for Alignment Options”, including at least two underpass/ short tunnel options (not exceeding 600 m in length);

· make a comprehensive comparison of all the alignments, taking into account all relevant factors, and recommend a preferred alignment option and road connection detail with South Lantau Road; and

· investigate all possible future usage of the existing sections of Tung Chung Road made obsolete by the construction of the new road.

1.2 This appendix presents the results of the assessment of the alignment options and the investigation of the future usage of the obsolete sections of the existing road.

1.3 The option assessment was carried out in the first half of the study period, with the purpose of selecting the preferred alignment option to complete the detailed studies required under the Assignment, including the environmental impact assessment, drainage impact assessment, geotechnical assessment, traffic impact assessment, etc.

2 DEVELOPMENT OF ALIGNMENT OPTIONS

2.1 Alignment Geometry

2.1.1 At present, Tung Chung Road is the only existing vehicular access between North and South Lantau. The road is about 7 km long, and connects Tung Chung in the north with South Lantau Road, near Cheung Sha, in the south.

2.1.2 The existing road is characterised by steep gradients and sharp bends. About 4 km of the road is steeper than 10% gradient, of which about 500 m is up to about 20% gradient. The road is also generally only 3.5 m wide, with about 40 passing-bays along its length, and as such, operates under single-lane two‑way traffic conditions over much of its length. The road has a total (two-way) maximum capacity of only about 100 vehicles per hour.

2.1.3 The alignment geometry of the existing road is grossly sub-standard. In fact, no other existing public road in the HKSAR has such long steep gradients. The reasons for the very poor geometry are the difficult topography and original intended function of the road.

2.1.4 The mountain ridge running along the spine of Lantau Island dominates the local topography. The route passes over the ridge at the saddle (334 mPD) between Lantau Peak (934 mPD) and Sunset Peak (869 mPD). The relatively short distances between the saddle and either end of the road, especially in South Lantau, give rise to the steep gradients along the road. This factor is compounded by the nature of the hillsides along the route, which are characterised by steep slopes and deeply incised stream courses.

2.1.5 When the existing road was built, Tung Chung was a relatively small village on the north shore of Lantau Island. The original intended function of the road was to serve the local communities and provide access for the construction of the nearby waterworks. Since there were no other uses for or demands on the road, traffic was very little, and the road was designed accordingly.

2.1.6 Improving the geometry of the existing road up to current standards, as stipulated in the Transport Planning and Design Manual, is now not favoured on consideration of the anticipated environmental impacts and impacts on the County Park. Such a scheme was considered in the “Widening of Tung Chung Road Feasibility Study” (Agreement No. CE 26/96). However, it was found that this scheme would affect about 20 ha of the County Park. When the scheme was presented to the Country Parks Committee (CPC) at its meeting on 20 March 1997, the CPC expressed its concern about the impacts on the County Park, and therefore the Steering Group for the study decided not to proceed with the scheme.

2.1.7 The only way to improve the geometry of the existing road, whilst minimising the environmental impacts, is to relax the design standards. Therefore, the Assignment Brief states that:

· the design standard of the road gradients may be relaxed at difficult locations, provided, in any case, the maximum gradient of the improved road does not exceed 15%;

· the provision of a continuous climbing lane will not be required, but that passing bays should be provided at suitable locations instead; and

· where there are practical site difficulties or severe environmental problems, all essential road design criteria such as design speed, vertical and horizontal curvatures, transition curves, visibility, footpath, etc might need to be reviewed, but that the prior agreement from the Director of Highways and the Commissioner for Transport shall be obtained for each case.

2.2 Alignment Design

2.2.1 The alignment options are shown on Drawings Nos. 90803/AO/KEY, 90803/AO/1, 2, 3A to 3D, 4A to 4G and 5A to 5D at the end of the appendix. The drawings were prepared at 1:2000 scale (A1 size), but have been reduced to 1:4000 scale (A3 size) for inclusion into this appendix. Longitudinal sections along the alignment options are also shown on Drawing Nos. 90803/LS/001 to 005.

2.2.2 The options were carefully designed to minimise the earthworks, and retaining walls and elevated structures were proposed to minimise the overall footprint of the works. However, traffic calming and safety enhancement measures that require land, such as central dividers at tight bends, were included, together with verges and footways.

2.2.3 Haul roads and working space were identified along each option, since these items would impact on the overall land requirements. However, works areas were not identified, since it was anticipated that the main works area would be located near Tung Chung, and would be common to each alignment option, and would therefore not affect the selection of the preferred option.

2.2.4 For the tunnel options, twin tubes with two lanes in each tube were considered, which are required for two-way tunnels for traffic safety and operational reasons to permit unimpeded access for emergency services in the event of accident or breakdown. The tunnel operational areas at the portals were also considered to better define the works limit for each tunnel option.

2.2.5 The junctions between the alignment options and South Lantau Road were also designed in outline to enable this important element of the Project to be included in the option assessment. The design of the junctions included the local improvements to South Lantau Road that would be required to satisfy safe sightline and turning movement requirements.

2.2.6 The bus-bus interchange options were also designed in outline to enable this element of the Project to be included in the option assessment as well. It was important that the operational aspects of this facility and its interface with the new road were considered as part of the option assessment.

2.3 Lung Tseng Tau to Tai Tung Shan Service Reservoir

2.3.1 All alignment options followed the existing road from Lung Tseng Tau to Tai Tung Shan Service Reservoir, as shown on the drawings, since sections of the existing road have already been widened to 6 m, and the existing geometry is within the acceptable standards for the Project. From Lung Tseng Tau, the gradient increases steadily from 1% to 13% by the reservoir, and the bends are relatively gentle. Improving the road on-line will have fewer impacts and be more economical than going off-line. Also, on consideration of the steep slopes above the existing road, there was no practical scope for an off-line option over this section of the route.

2.3.2 EPD and AFCD advised that the existing road should generally be widened on the eastern side of the road, such that during construction, the existing road can be used as a buffer zone to prevent any pollutants from entering into Tung Chung Stream. This should be feasible, except where the existing road is constrained by Burial Ground No. 18L and Tai Tung Shan Service Reservoir.

2.3.3 A dedicated haul road is not required along this on-line section of improvement works, since construction vehicles can make use of the existing road. However, working space is required along the road, and the works limit have been set back from the edge of the works accordingly, as shown on the drawings.

2.4 Tai Tung Shan Service Reservoir to Southside of Crest

2.4.1 Between the reservoir and the crest at Pak Kung Au (adjacent to Tai Tung Shan Header Tank), the existing road includes gradients above 15% and a number of hairpin bends, which places the existing geometry below the acceptable standards of the Project. Therefore, this section of road can only be improved by going off-line.

2.4.2 The existing road follows Tung Chung Stream up the valley, and then runs along the western fringe of a small plateau at the head of the valley. However, the plateau is only relatively level along its east-west axis. Along its north-south axis (ie, along the general direction of the road) the gradient of the plateau is greater than 15%. From a geometric point of view, this section of highway is probably the most difficult section to design. Only by winding the new road across the plateau can gradients of 15% or under be achieved.

2.4.3 Four off-line alignment options were developed for this northern section of the route. Options N1 and N2 involved overland routes, which connected to the existing road at the crest, since the road in this location has already been widened to 7.3 m in cutting, and Options N3 and N4 involved short tunnels under the crest. The options are described in further detail below:

(i) Option N1

This option was based on the alignment given in the Assignment Brief. The option goes off-line past the reservoir to the east of the existing road, cuts through the hillside on the eastside of the valley, then meanders up over the small plateau at the head of the valley, before connecting with the existing road at the crest. The alignment has been shifted slightly westward of that shown in the Brief to avoid a substantial double-cut just beyond the reservoir. The option includes relatively gentle bends, but the result is a shorter section of road, with a maximum gradient of 15%.

(ii) Option N2

This option was based on Option N1, but included larger meanders over the small plateau, which extend westward as far as the existing road in two locations. The eastward meanders require substantial cuttings into the hillside along the eastern fringe of the plateau. Furthermore, a very large double-cut is required through the hillside on the eastside of the valley just beyond the reservoir, which is avoided by Option N1. The larger meanders result in a longer section of road, with a maximum gradient of 13.1%.

(iii) Option N3

This option included a 560 m long tunnel under the crest to the west of the existing road. The northern portal is located in the hillside along the southwestern fringe of the small plateau, close behind the existing road. The alignment of the section of approach road between the reservoir and the portal is based on Option N1, and therefore has a maximum gradient of 15%. However, the gradient could be reduced slightly by increasing the size of the meanders. The gradient within the tunnel is limited to 3% to limit vehicle emissions. The southern portal is located in the hillside on the opposite side of Cheung Sha Valley to the existing road, as shown on the drawings. This is the only location south of the crest to the west of the existing road that suits the elevation and orientation of the tunnel. The resulting length of the tunnel is within the maximum length of 600 m stipulated in the Assignment Brief. The gradient of the southern approach road is 10.6%. The tunnel operational area is located in front of the northern portal on the small plateau at the head of Tung Chung Valley, which is the only relatively flat area outside the tunnel.

(iv) Option N4

This option included a 720 m long tunnel under the crest to the east of the existing road. The northern portal is located in the hillside along the southeastern fringe of the small plateau. As with Option N3, the alignment of the section of road between the reservoir and the portal is based on Option N1, and therefore has a maximum gradient of 15%, and the gradient within the tunnel is limited to 3% to limit vehicle emissions. The southern portal is located in the hillside above the existing road, as shown on the drawings. This is the only location south of the crest to the east of the existing road that suits the elevation and orientation of the tunnel. However, the resulting length of the tunnel exceeds the maximum length of 600 m stipulated in the Assignment Brief. As with Option N3, the gradient of the southern approach road is 10.6%, and the tunnel operational area is located in front of the northern portal on the small plateau at the head of Tung Chung Valley.

2.4.4 For this section of improvement works, access to the construction site will be made via the existing road at Tai Tung Shan Service Reservoir, the crest and at other suitable locations where the new road adjoins the existing road. The works limits for the northern options, including allowances for site accesses and working space, are shown on the drawings.

2.5 Southside of Crest to Cheung Sha (South Lantau Road)

2.5.1 Between the crest and South Lantau Road, the existing road includes gradients as steep as 20% and more hairpin bends, which also places the geometry of this section of existing road below the acceptable standards of the Project. Therefore, this section of road also can only be improved by going off-line as well.

2.5.2 Three off-line alignment options were developed for this southern section of the route. Options S1 and S2 can connect with any of the northern Options N1 to N4, but Option S3 is reliant on Option N3. The options are described below:

(i) Option S1

This option runs down along the hillside on the eastside of Cheung Sha Valley above the existing road, and continues eastward around the hillside at the mouth of the valley, before crossing the catchwater and connecting with South Lantau Road near the YWCA youth camp near Cheung Sha Sheung Tsuen. The road falls at a steady gradient of -10.6 to -12%, and comprises relatively gentle bends. The connection with South Lantau Road comprises a roundabout. The South Lantau Road approaches to the roundabout require local improvements to satisfy standard sightline requirements.

(ii) Option S2

This option was based on the alignment given in the Assignment Brief. The option runs down along the hillside on the eastside of Cheung Sha Valley above the existing road, similar to Option S1, but then loops back north of the catchwater and runs westwards, before connecting with the existing road where it crosses the catchwater. The loop in the road increases its length, and the road falls at a steady gradient of -10.6% between the crest and the catchwater. There are two alternative sub-options south of the catchwater, as follows:

(a) Option S2A

This option runs southwards at -11% gradient and then westward at ‑8% gradient along the hillside at the mouth of the valley, before connecting with South Lantau Road near LCSD’s beach facilities on Cheung Sha Beach. The connection with South Lantau Road comprises a T‑junction. The section of South Lantau Road at the junction requires local widening to include a dedicated right hand turn lane.

(b) Option S2B

This option runs southwestwards at ‑5.9% gradient higher up the same hillside, before looping back and running eastward at ‑6.5% gradient, before connecting with South Lantau Road in the same location as the existing junction between Tung Chung Road and South Lantau Road. Similar to Option S2A, the connection with South Lantau Road comprises a T‑junction with local widening of South Lantau Road to include a dedicated right hand turn lane.

(iii) Option S3

This option runs along the west side of Cheung Sha Valley and continues westward around the hillside at the mouth of the valley, before crossing the catchwater and looping back and connecting with South Lantau Road near the headland between Cheung Sha Beach and Tong Fuk Beach. The road falls at a steady gradient of -8 to -10%. Again, the connection with South Lantau Road comprises a T‑junction with local widening of South Lantau Road to include a dedicated right hand turn lane.

2.5.3 Since this section of improvement works is off-line, a dedicated haul road will be required along the route of the new road to gain access to the construction site. Access to the haul road in turn will be made via the new junction with South Lantau Road, the existing road at the crest and at other locations where the new road intersects the existing road. It may also be possible to gain limited access via the catchwater road, subject to agreement from Water Supplies Department (WSD), although generally not for construction traffic.

2.5.4 For this section of the route, the new road crosses a number of small side-valleys on elevated structure, and hence the haul road will need to deviate from the footprint of the new road to hug the side of these small valleys. At the locations of the loop-bends on Options S2A, S2B and S3, the haul road will also need to deviate from the new road to bypass the viaduct construction and climb up the hillside. The works limits for the southern options, including allowances for haul roads and working space, are shown on the drawings.

2.6 Possible Alignment Combinations

2.6.1 Based on the possible alignment options described above, the possible alignment combinations are summarised in Table 2.1 below.

Table 2.1: Possible Alignment Combinations

Northern Option	Southern Option
N1	S1, S2A, S2B
N2	S1, S2A, S2B
N3	S1, S2A, S2B, S3
N4	S1, S2A, S2B

2.6.2 For the purposes of the assessment of the alignment options, the point of demarcation between the northern options and the southern options was selected as follows:

(i) For Options S1, S2A & S2B

At the “common point” where the northern options converge and the southern options diverge on the south side of the crest, as shown on the drawings.

(ii) For Option S3

At a distance south of the southern portal of Option N3 equal to the distance between the southern portal of Option N3 and the “common point” for Options S1, S2A & S2B, as shown on the drawings.

2.6.3 Based on the above point of demarcation between the northern and southern alignment options, the lengths of the possible alignment combinations, including the on-line section between Lung Tseng Tau to Tai Tung Shan Service Reservoir, are summarised in Table 2.2 below.

Table 2.2: Lengths of Possible Alignment Combinations

On-Line Length (m)	Northern Option	Length (m)	Southern Option	Length (m)	Total Length (m)
2,250	N1	2,095	S1	1,860	6,205
			S2A	2,375	6,720
			S2B	2,920	7,265
	N2	2,270	S1	1,860	6,380
			S2A	2,375	6,895
			S2B	2,920	7,440
	N3	2,120	S1	1,860	6,230
			S2A	2,375	6,745
			S2B	2,920	7,290
			S3	2,405	6,775
	N4	2,030	S1	1,860	6,140
			S2A	2,375	6,655
			S2B	2,920	7,200

2.7 One-Way Traffic on Existing Tung Chung Road

2.7.1 It has been suggested that, where the new road goes off-line, the existing road could perhaps be used for one-way traffic in the uphill direction and the new road could be used for one-way traffic in the opposite downhill direction to minimise the width of the new road. This is only possible when the uphill section of the existing road is on the left hand side of the downhill section of the new road. This is to avoid traffic having to cross over where the roads merge/ diverge. The only location where this occurs is between the crest and the catchwater in Option S2A or S2B. This issue has been considered as part of the investigation of the future usage of the obsolete sections of the existing road, which is covered in Section 6 of the appendix.

2.7.2 The use of the existing road for one-way traffic in the downhill direction is considered far more dangerous than using the existing road in the uphill direction, and has therefore not been investigated.

2.8 Bus-Bus Interchange

2.8.1 Possible sites for the proposed bus-bus interchange included:

(i) Option S1

At the junction of Option S1 and South Lantau Road, on land which is currently earmarked as a future Government sale site, adjacent to the YWCA youth camp.

(ii) Options S2A, S2B and S3

At the existing bus lay-by adjacent to LCSD’s beach facilities on Cheung Sha Beach.

2.8.2 A third possible site for the bus-bus interchange, comprising the existing public transport facilities in Tong Fuk Village was dropped following a site visit with AC for T/NT, since the site mainly comprises the village car park, and it would not be possible to locate the bus-bus interchange on the site without relocating the car park. It was also considered that the site was too far from the junction between the new road and South Lantau Road, and would therefore not be able to serve its intended purpose.

3 ASSESSMENT METHODOLOGY

3.1 Assessment Stages

3.1.1 The alignment options were assessed in two stages as follows:

(i) Stage 1

The northern alignment options N1, N2, N3 and N4 were compared against each other.

(ii) Stage 2

The southern alignment options S1, S2A, S2B and S3 were compared against each other.

3.2 Broad Methodology

3.2.1 All relevant factors were taken into account in the comparison of the alignment options. The procedure was as follows:

(a) Sets of relevant criteria for comparison were developed, including:

· engineering criteria;

· environmental criteria;

· land use criteria; and

· costs and programme criteria.

(b) The alignment options were ranked for each criterion within each set of criteria, and assigned a score based on the ranking, as follows:

1st: 100 (maximum possible score)

2nd: 80

3rd: 60

4th: 40 (minimum possible score)

(c) The criterion within each set of criteria was weighted based on the relative importance of the criterion, and the sets of criteria were weighted based on the relative importance of the sets.

(d) The weighted score for each alignment option was calculated for each set of criteria as follows:

Weighted Score of Option_i = W_s x 3 (S_ic x W_c), where:

W_s = weight of particular set of criteria;

S_ic = score of Option_i against particular criterion; and

W_c = weight of particular criterion.

(e) The overall weighted score for each alignment option was calculated as follows:

Overall Weighted Score of Option_i = 3 (Weighted Score of Option_i).

(f) The overall weighted scores of the alignment options were compared, and the options were ranked accordingly.

(g) Sensitivity tests were carried out to determine the robustness of the ranking by adjusting the weighting for each set of criteria.

3.3 Comparison Criteria

3.3.1 Engineering Criteria

3.3.1.1 The engineering criteria that were used in the assessment of the alignment options are detailed in Table 3.1 below.

Table 3.1: Engineering Criteria

Engineering Criteria	Ranking Principle	Proposed Weighting (W_c)
Alignment Geometry	Options with better alignments, including lower gradients and gentler bends, were ranked higher	30
Junction with South Lantau Road	For the southern options, junctions which comprised roundabouts, as opposed to T‑junctions, were ranked higher	5
Traffic Considerations	For the southern options, alignments which better suit the predicted traffic patterns and terminated closer to the proposed site for the bus-bus interchange were ranked higher	5
Geotechnical Constraints	Options with fewer geotechnical constraints, including slope works and potential natural terrain hazards, were ranked higher	25
Highway Structures	Options with fewer elevated structures, particularly larger structures that would be difficult to construct given the site constraints, were ranked higher	20
Drainage Impacts	Options with fewer impacts on the natural drainage systems, requiring less mitigation, were ranked higher	10
Impacts on Utilities	Options with fewer impacts on the existing and planned utilities in the vicinity of the road were ranked higher	5

3.3.1.2 “Alignment Geometry” and “Geotechnical Constraints” were considered amongst the most important of the engineering criteria, and hence were weighted the highest. The difficult topography will complicate the design of the Project in terms of the slope works and protection from natural terrain hazards. Hence, there is a balance to be struck between good alignment design practice and good geotechnical design practice on this particular Project.

3.3.1.3 “Junction with South Lantau Road” and “Traffic Considerations” were only relevant to the assessment of the southern options. However, to delete these criteria from the assessment of the northern options would have created imbalance in the assessment, and therefore the northern options were scored 50 marks each for these criteria.

3.3.1.4 “Highway Structures” was weighted relatively high, since it was evident that the construction of elevated structures on this Project, particularly larger structures, would pose their own unique problems. The topography is very steep, and access to the foundation sites would be difficult. Transportation of materials and any bridge elements, including precast concrete or prefabricated steel beams, would also be difficult.

3.3.1.5 “Drainage Impacts” was weighted relatively low, since it was anticipated that any impacts on the existing drainage systems would be similar in nature and extent, and also relatively small, since it is anticipated that most stream courses would be bridged by elevated structures.

3.3.1.6 “Impacts on Utilities” was also weighted relatively low, since there are not many existing or planned services in the vicinity of the Project, and any impacts would therefore be relatively small.

3.3.2 Environmental Criteria

3.3.2.1 The environmental criteria that were used in the assessment of the alignment options are detailed in Table 3.2 below.

Table 3.2: Environmental Criteria

Environmental Criteria	Ranking Principle	Proposed Weighting (W_c)
Air Quality	Options with fewer air quality impacts were ranked higher	5
Noise	Options with fewer noise impacts were ranked higher	5
Water Quality	Options with fewer water quality impacts were ranked higher	20
Construction Waste	Options with fewer construction waste impacts were ranked higher	10
Ecology	Options with fewer ecological impacts were ranked higher	35
Landscape and Visual	Options with fewer landscape and visual impacts were ranked higher	15
Heritage	Options with fewer heritage impacts were ranked higher	5
Hazard to Life	Options with fewer hazard to life impacts were ranked higher	5

3.3.2.2 Of the eight environmental parameters, higher weighting was allocated to those issues that are of key importance to this particular Project. Tung Chung Road passes through an area of high ecological importance and sensitivity, as testified by the fact that much of the area is designated Country Park. Tung Chung Stream is considered to be the second most important stream in Hong Kong, after Tai Ho Stream, in terms of its ecological value. Cheung Sha Stream is also considered to have high ecological value. Much of the area is also water-gathering ground. The landscape, by virtue of the mountainous topography and rich vegetation is also highly valued. As such, “Ecology”, “Water Quality” and “Landscape and Visual” have been weighted the highest.

3.3.2.3 “Construction Waste” was given the next highest weighting, albeit relatively low in comparison, since all the options involve cutting but little fill, particularly the tunnel options, and therefore produce a surplus of excavated material to be disposed off site. This issue is exacerbated by the remoteness of the site and difficult access along the existing road for haulage vehicles.

3.3.2.4 “Air Quality” and “Noise” were weighted relatively low, since there are a relatively low number of sensitive receivers, and it is not anticipated that any of the alignment options will pose any particularly severe impacts, or at least impacts that cannot be readily mitigated. Similarly, “Hazard to Life” was weighted relatively low, since the existing and planned populations are relatively low and Cheung Sha Water Treatments Works is relatively small in comparison to other such facilities in South Lantau (ie, Silvermine Bay Water Treatment Works).

3.3.2.5 “Heritage” was also weighted relatively low, since none of the alignment options impact directly on any designated archaeological site.

3.3.3 Land Use Criteria

3.3.3.1 The land use criteria that were used in the assessment of the alignment options are detailed in Table 3.3 below.

Table 3.3: Land Use Criteria

Land Use Criteria	Ranking Principle	Proposed Weighting (W_c)
Impacts on Country Parks	Options with fewer impacts on the Country Park and Country Park recreational facilities were ranked higher.	60
Impacts on Private Land, etc	Options with fewer impacts on private land, sale sites, permanent and temporary government land allocations, short term tenancies and government land licenses were ranked higher	20
Impacts on Burial Grounds	Options with fewer impacts on burial grounds and graves were ranked higher	20

3.3.3.2 “Impacts on Country Park” was weighted the highest, since much of the “Broad Corridor for Alignment Options” comprises Country Park, which is by far the most significant land use on this Project. By comparison, “Impacts on Private Land, etc” and “Impacts on Burial Grounds” were weighted relatively low, since any such impacts will generally be confined to the north and south ends of the new road.

3.3.4 Costs and Programme Criteria

3.3.4.1 The costs and programme criteria that were used in the assessment of the alignment options are detailed in Table 3.4 below.

Table 3.4: Costs and Programme Criteria

Costs and Programme Criteria	Ranking Principle	Proposed Weighting (W_c)
Capital Costs	Options with lower capital costs were ranked higher	40
Recurrent Costs	Options with lower recurrent costs were ranked higher	20
Time for Construction	Options with shorter time for construction were ranked higher	40

Notes: (1) The cost and time required for land resumption and clearance are considered under Land Use Criteria.

3.3.4.2 “Capital Costs” and “Time for Construction” were weighted equally high. The Project is a very urgent and politically sensitive project. Therefore, any alignment options that offer savings in construction time were viewed favourably.

3.4 Sensitivity Testing

3.4.1 As discussed above, the sets of criteria were weighted based on their relative importance. The overall weighted scores for the alignment options were then calculated and compared with each other to determine the ranking of the options. The robustness of the ranking was then determined by adjusting the weighting of each set of criteria. The weighting of the sets of criteria and the adjustments to the weighting used in the sensitivity testing are detailed in Table 3.5 below.

Table 3.5: Sensitivity Testing

Criteria Set	Proposed Weighting (W_c)
	Base	Sensitivity Test
	A	B	C	D	E
Engineering	25	40	20	20	20
Environmental	45	40	60	40	40
Land Use	15	10	10	30	10
Costs and Programme	15	10	10	10	30
Totals	100	100	100	100	100

3.4.2 “Environmental” was weighted the highest in recognition of the high ecological value of the Country Park and also the Tung Chung and Cheung Sha streams.

3.4.3 At the Steering Group Meeting held on 18 September 2001, at which the option assessment was discussed, the relative importance of the “Landscape and Visual” environmental parameter was queried in respect of the assessment of the tunnel options. To answer this query, sensitivity testing was also carried out on the environmental criteria, as detailed in Table 3.6 below.

Table 3.6: Sensitivity Testing of Environmental Criteria

Environmental Criteria	Base Weighting (W_c)	Test I Weighting (W_c)	Test II Weighting (W_c)
Air Quality	5	5	5
Noise	5	5	5
Water Quality	20	10	15
Construction Waste	10	10	10
Ecology	35	30	20
Landscape and Visual	15	30	35
Heritage	5	5	5
Hazard to Life	5	5	5

3.4.4 In Test I, “Ecology” and “Landscape and Visual” were weighted the highest (30% each), followed by “Water Quality” and “Construction Waste” (10% each). In Test II, the weighting was adjusted even further, with “Landscape and Visual” weighted the highest (35%), followed by “Ecology” (20%), “Water Quality” (15%) and “Construction Waste” (10%).

4 ASSESSMENT OF ALIGNMENT OPTIONS IN THE NORTH

4.1 General

4.1.1 This section of the appendix covers the assessment of the northern alignment Options N1, N2, N3 and N4. Certain information on the on-line section of improvement works is also included for completeness.

4.2 Engineering Comparison

4.2.1 Alignment Geometry

4.2.1.1 The northern alignment options were all designed to satisfy the standards stipulated in the Assignment Brief. All four options proceed from Tai Tung Shan Service Reservoir at a gradient of 12.8%.

4.2.1.2 Option N1 meanders gently up Tung Chung Valley and across the small plateau at the head of the valley, before reaching the crest at Pak Kung Au. The alignment has radii no less than the “normal” minimum radius (R3) of 88 m, which makes for a relatively smooth alignment. However, the alignment has a maximum gradient of 15%, which is the “absolute” maximum gradient allowed in the Assignment Brief, but is 5% greater than the “absolute” maximum gradient allowed in the Transport Planning and Design Manual (TPDM) for bus routes. South of the crest, Option N1 runs down along the hillside on the eastside of Cheung Sha Valley. Again, the alignment is relatively smooth, with radii no less than the “normal” minimum radius (R3) of 88 m. The alignment also falls at a gentler gradient of –10.6%.

4.2.1.3 Option N2 follows the route of Option N1 up to the crest at Pak Kung Au, but meanders more extensively from east to west across the small plateau. As such, the alignment has radii as tight as the “recommended absolute” minimum radius (R2) of 63 m, which is the absolute minimum radius recommended for steep roads. However, the result is a reduction in the maximum gradient from 15% to 13.1%. South of the crest, Option N2 follows the alignment of Option N1.

4.2.1.4 Option N3 follows the same alignment as Option N1 for 700 m, before heading west towards the southwestern fringe of the small plateau and entering into tunnel, at which point the gradient falls from 15% to –3%. In the tunnel, the alignment gradually sweeps eastward, before exiting the hillside on the west side of Cheung Sha Valley. South of the crest, the alignment can follow two possible routes. It can either proceed across Cheung Sha Valley at a gradient –10.6% towards the eastside of the valley, or it can continue along the western side of the valley at a gradient of –10%.

4.2.1.5 Option N4 also follows the same alignment as Option N1 for 700 m, but then heads east towards the south-eastern fringe of the small plateau, before entering into tunnel, at which point the gradient falls from 15% to –3%, similar to Option N3. In the tunnel, the alignment sweeps southwards, before exiting the hillside on the eastside of Cheung Sha Valley. South of the crest, the alignment runs down along the hillside at a gradient of –10.6%.

4.2.1.6 The northern approach roads to the tunnel options have been based on Option N1, as discussed above. However, it would be possible to introduce larger meanders, similar to Option N2, and hence reduce the gradient to below 15%. From the vertical alignment perspective, the tunnel options were considered superior to the overland options, since they involve shorter sections of steep road, and Option N2 is considered superior to Option N1, since it involves gentler gradients. However, there is some concern here as to the appropriate balance between the gradient and the number and size of the bends. Notwithstanding this, the northern alignment options were ranked as follows:

1st = Option N4

1st = Option N3

2nd Option N2

3rd Option N1

4.2.2 Junction with South Lantau Road

4.2.2.1 This issue was only relevant to the assessment of the southern options, which is covered in Section 5 of the appendix. However, to avoid creating any imbalance in the assessment, the northern alignment options were awarded 50 marks each for this criterion, as discussed in Section 3 of the appendix.

4.2.3 Traffic Considerations

4.2.3.1 The main traffic-related issues, which affected the selection of the preferred alignment option, included:

· the traffic pattern (ie, the balance between traffic heading eastwards in the direction of Mui Wo or westwards in the direction of Ngong Ping) which may influence the location of the junction of the new road with South Lantau Road; and

· the location of the bus-bus interchange in relation to the junction of the new road with South Lantau Road.

4.2.3.2 The traffic pattern and the location of the bus-bus interchange were only relevant to the assessment of the southern options, which is covered in Section 5 of the appendix. However, to avoid creating any imbalance in the assessment, the northern alignment options were awarded 50 marks each for this criterion, as discussed in Section 3 of the appendix.

4.2.4 Geotechnical Constraints

4.2.4.1 All alignment options followed the existing road from Lung Tseng Tau to the Tai Tung Shan Service Reservoir, as discussed in Section 2 of the appendix. It is proposed to widen the existing road on the uphill (eastern) side along this section of the route. This will have the following geotechnical benefits:

· the existing features on the uphill side of the road will generally be replaced with new up-to-standard slopes; and

· the construction of fill slopes on the downhill side will be avoided as far as possible.

4.2.4.2 Areas prone to natural terrain land sliding have been identified on the slopes above this section of the road, particularly on the side slopes of incised drainage lines. Mitigation measures may be required depending on the degree of risk to the road, which will be determined during the geotechnical hazard assessment. Such measures may take the form of check dams on drainage lines to prevent channelised debris flows reaching the road, although the initial geotechnical assessment has not identified any records of a landslide or debris flow reaching this section of the road.

4.2.4.3 Beyond Tai Tung Shan Service Reservoir, the northern alignment options cross the small plateau at the head of Tung Chung Valley. The plateau lies at the foot of the steep slopes of Sunset Peak, where numerous previous landslides, identified in the initial geotechnical assessment, pose a significant risk. No ground investigation information is currently available for the plateau, although the published geological map indicates it to be covered extensively by colluvium. The geotechnical aspects of each option are further discussed below.

4.2.4.4 Option N1 involves the smallest amount of cutting amongst the overland options. Notwithstanding this, the new cut slopes would be up to about 18 m high in places. However, it is proposed to construct retaining walls to accommodate the lower 8 m of these slopes. This will help reduce the amount of earthworks and the size of the overall footprint of the works. Since this option runs close to the natural slopes below Sunset Peak, the road would be vulnerable to natural terrain hazards, and mitigation measures on drainage lines and the natural slopes above the road would be required, including the stabilisation of rock outcrops and boulders.

4.2.4.5 Option N2 involves the largest amount of cutting amongst the northern options, with one double-cut up to about 32 m high. Similar to Option N1, retaining walls would help reduce the amount of earthworks and the footprint of the works. Owing to the larger meanders, some parts of the road will be farther away from the slopes of Sunset Peak, and will therefore be at less risk from natural terrain hazards compared to Option N1. Conversely, some parts of the road will be closer to the slopes of Sunset Peak, and will hence be at greater risk. On balance, Option N1 is preferable to Option N2 in this respect, and more so on consideration of the amount of cutting involved.

4.2.4.6 Option N3 involves tunnelling under the crest to the west of the existing road. Existing ground investigation information (GIU Report No. 14303) in the northern portal area indicates the ground to comprise little or no colluvium and generally between 10 to 15 m of Grade IV to V decomposed tuff over rock. Such ground conditions would result in the tunnel portal and approximately the first 50 m of tunnel being located in “soft” ground. Similar conditions would likely be expected at the southern portal, with the ground in between consisting of Grade I to III tuff. However, there is a possibility that significant areas of deep weathering (possibly associated with the Tung Chung Fault) would necessitate technically difficult and expensive mixed ground tunnelling. Tunnel lining systems, such as pre-cast concrete segments for softer ground, to more hard rock systems, such as bolting and shotcrete, could be required to cope with the changes in ground conditions. Natural terrain hazards for the approach roads are likely to be less than for Option N1, since the approach roads are farther away from the slopes of Sunset Peak. In addition, the tunnel section would not require a natural terrain hazard assessment.

4.2.4.7 Option N4 involves tunnelling under the crest to the east of the existing road. No ground investigation information exists for this area, although rock exposures, identified during the initial geotechnical assessment, indicate the possibility of shallow bedrock. However, as with Option N3, the likelihood of zones of deep weathering must also be considered. Natural terrain hazards for the northern portal are likely to be greater than for Option N1, since the portal is located in the landslide prone slopes of Sunset Peak. However, as with Option N3, the tunnel itself would not require a natural terrain hazard assessment.

4.2.4.8 The natural terrain hazards and geotechnical works associated with the northern alignment options are summarised in Table 4.1 below.

Table 4.1: Northern Alignment Options – Natural Terrain Hazards and Geotechnical Works

Alignment Option	Natural Terrain Hazards ⁽¹⁾		Geotechnical Works
Alignment Option	Landslip Risk	Boulder Fall Risk	Approx. Length of Road (m)	Length of Slopes >8m High (m)	Length of Tunnelling (m)
N1	High	High	2,095	485	0
N2	High	High	2,270	805	0
N3	Medium	Medium	2,120	355 ⁽²⁾	560
N4	High	High	2,030	355 ⁽²⁾	720

Notes: (1) The terms used under “Natural Terrain Hazards” are qualitative and meant for comparison only.

(2) Excluding slopes associated with construction of tunnel portals.

4.2.4.9 Although the sections of tunnel are not prone to natural terrain hazards, the likely need for mixed ground tunnelling make tunnelling undesirable. Furthermore, the portals require relatively large slope works, and the natural slopes above the portals are prone to natural terrain hazards. The tunnel options were therefore considered inferior to the overland options from a geotechnical perspective. Of the overland routes, Option N1 was considered superior to Option N2, since on balance it would require less geotechnical works and would be subject to fewer natural terrain hazards. Based on the above, the northern alignment options were ranked as follows:

1st Option N1

2nd Option N2

3rd Option N3

4th Option N4

4.2.5 Highway Structures

4.2.5.1 Elevated structures were required where the alignment options traverse stream courses and side valleys. However, due to the steep topography, access to many of the bridge sites would be difficult, and therefore bridge works is an issue that should be included in the assessment. From a construction point of view, it will be preferable to limit the extent of bridge works on this Project. The number of elevated structures and the aggregate length and deck area of elevated structure for each northern alignment option are summarised in Table 4.2 below.

Table 4.2: Northern Alignment Options – Highway Structures

Alignment Option	No. of Structures	Aggregate Length (m)	Aggregate Deck Area (m²)
N1	4	150	1,760
N2	6	175	2,050
N3 ⁽¹⁾	6	185	2,120
N4	5	155	1,820

Notes: (1) Including new overbridge in front of the northern portal to carry the existing road over the new road.

4.2.5.2 Based on the above, the northern alignment options were ranked as follows:

1st Option N1

2nd Option N4

3rd Option N2

4th Option N3

4.2.6 Drainage Impacts

4.2.6.1 It is anticipated that the impacts of the Project on the existing drainage systems will be relatively small, as discussed in Section 3 of the appendix. The alignment options generally pass along side sloping ground and cross any stream course on elevated structure. Most of the streams comprise upper tributaries to the main streams below the Project, and as such their catchments are relatively small. It is therefore unlikely that the Project as a whole will have any significant impacts on the existing drainage regimes.

4.2.6.2 However, the northern alignment options do traverse the small plateau at the head of Tung Chung valley, as discussed above, over which a number of upper tributaries of Tung Chung Stream flow. Some of these streams will be intersected by sections of the road in cutting, and will hence require diverting down the cuttings and along the road. The number of stream crossings, culverts and diversions required for each northern alignment option is summarised in Table 4.3 below.

Table 4.3: Northern Alignment Options – Stream Crossings, Culverts and Diversions

Alignment Option	No. of Stream Crossings ⁽¹⁾	No. of Culverts	No. of Diversions
N1	4	6	6
N2	6	4	5
N3	4	6	6
N4	5	4	4

Notes: (1) Elevated highway structure

4.2.6.3 Based on the above, the northern alignment options were ranked as follows:

1st Option N4

2nd Option N2

3rd = Option N3

3rd = Option N1

4.2.7 Impacts on Utilities

4.2.7.1 In the vicinity of the northern alignment options, the existing services are generally confined to the existing road and WSD’s facilities, except for some CLP 11 kV and 33 kV overhead cables. Regarding any future services, it is proposed that these be laid under the obsolete section of the existing road, adjacent to the existing services.

4.2.7.2 CLP propose to replace the existing overhead lines and upgrade the power supply to South Lantau Road by installing new cables along the road in accordance with the above proposal. However, the existing overhead lines would remain operational until the new cables are commissioned, on completion of the Project. Therefore, the overhead lines will require temporary diversions where intersected by the Project, until the new supply is operational. This is considered to be the only significant diversionary work required. The number of diversions required for each northern alignment option is summarised in Table 4.4 below.

Table 4.4: Northern Alignment Options – CLP Overhead Cable Diversions

Alignment Option	No. of 11 kV Overhead Cable Crossing Locations	No. of 33 kV Overhead Cable Crossing Locations	Total No. of Overhead Cable Crossing Locations
N1	1	3	4
N2	1	4	5
N3	0	3	3
N4	0	3	3

4.2.7.3 In addition to the above, Option N3 includes an overbridge in front of the northern portal to carry the existing road over the new road. The construction of this bridge would be complicated by the presence of the existing services in the old road. The existing services would require diverting prior to the construction of the new overbridge. Similarly, any new services would require routing to avoid the bridge.

4.2.7.4 Based on the above, the northern alignment options were ranked as follows:

1st Option N4

2nd Option N1

3rd Option N2

4th Option N3

4.3 Environmental Comparison

4.3.1 Air Quality

4.3.1.1 Air quality impacts during both the construction and operational phases of the Project have the potential to affect sensitive receivers in the vicinity of the improvement works. Construction air quality impacts will be limited to dust nuisance from construction works, vehicular movement on unpaved haul roads and erosion of exposed surfaces. Construction impacts associated with plant emissions are not expected to exceed the Air Quality Objectives, since the amount of plant on site will be limited and the gaseous emissions minor.

4.3.1.2 Operational air quality impacts will be due to vehicular emissions, in the form of nitrogen oxides (NO_x) and respirable suspended particulates (RSP), from users of the proposed Project.

4.3.1.3 Representative air and noise sensitive receivers (SRs) have been identified in accordance with criteria set out in the Environmental Impact Assessment Ordinance (EIAO) and the Technical Memorandum on the Environmental Impact Assessment Process (TMEIA). SRs have been identified in an area 500 m either side of the proposed alignment options, and these are shown in Figures B4.1 and S4.2 and summarised in Table 4.5 below for North Lantau.

Table 4.5: North Lantau - Existing Representative Air and Noise Sensitive Receivers

Figure No.	SR Ref.	Address	No. of Floors	Distance from Road ⁽¹⁾ (m)	Description
B4.1	SR1	8, Ha Ling Pei	3	17	Residential
	SR2	7, Wong Ka Wai	3	15	Residential
	SR3	Village House	3	244	Residential
	SR4	8, Lung Tseng Tau	3	24	Residential
	SR5	Village House	3	210	Residential
	SR6	Village House	1	25	Residential
	SR7	41, Shek Lau Po	3	242	Residential
	SR8	Village House	3	194	Residential
	SR9	1, Shek Mun Kap	3	234	Residential
B4.2	SR10	Quarters of AFCD Management Office		150	Residential
B4.2	A1 ⁽²⁾	Sport Ground of Quarters	-	126	Recreation

Notes: (1) On-line section of improvement works between Lung Tseng Tau and Tai Tung Shan Service Reservoir.

(2) Air sensitive receiver only.

4.3.1.4 The SRs are concentrated in the village areas on the fringe of Tung Chung, at the north end of the alignment, and as such would only be affected by the on‑line section of improvement works between Lung Tseng Tau and Tai Tung Shan Service Reservoir. There are no permanent sensitive receivers in the upland areas. However, hikers and users of the Country Park will be sensitive to air quality impacts.

4.3.1.5 All four northern alignment options pass through an unpopulated area, and hence the only sensitive receivers that would be potentially affected by the construction and operation of the road would be visitors to the Country Park. Both Options N1 and N2 intersect the Lantau Trail, the major hiking route in this area, at the crest at Pak Kung Au, while Options N3 and N4 pass under the crest in tunnel.

4.3.1.6 Based upon the amount of earth works required, Option N2 has the potential to create more dust as its meandering alignment necessitates large cuttings on either side of the road. In respect of the tunnel Options N3 and N4, while the overland sections of the alignments both have minimal cut and fill requirements, the provision of the tunnel portals will require significant earthworks and removal of spoil. The portals are however some 200 m from the main walking area, and works within the tunnel sections will not give rise to dust.

4.3.1.7 Impacts during the construction phase would only be expected within about 10 m of the works, and dust levels could be reduced to acceptable levels by the application of standard dust suppression mitigation measures. Under the auspices of the Air Pollution Control Construction (Dust) Regulation, the Contractor will be required to ensure that construction dust levels are controlled to acceptable levels. The sensitive receivers are also transient in nature and will be close to the works for a short period of time only. Based on the above, no significant impacts to sensitive receivers are predicted for any of the options, and while all are acceptable, Option N1 would be slightly preferable based upon its limited earthworks.

4.3.1.8 Operationally, due to the limited number of sensitive receivers expected in the area and their transient nature, as discussed above, insignificant impacts are predicted from vehicular emissions. A concentration of air emissions can be expected at the tunnel portals for Options N3 and N4, which will increase the area of influence of the vehicular emissions, but levels would not be expected to be above the AQOs.

4.3.1.9 Based on the above, Option N2 has slight disadvantages associated with the magnitude of earthworks required, as do Options N3 and N4, due to the increased earthworks and the higher concentrations of emissions associated with the tunnel portals. The northern alignment options were thus ranked as follows:

1st Option N1

2nd = Option N3

2nd = Option N4

3rd Option N2

4.3.2 Noise

4.3.2.1 As for air quality, the only sensitive receivers in the vicinity of the northern alignment options will be visitors to the Country Park. During the construction phase, there will be numerous activities with potential to create noise impacts. The worst-case scenario will probably involve earthworks. Option N2 requires significant earthworks, and therefore has the potential to create higher noise levels for a longer time period than Option N1, which comprises notably smaller cuttings. It is anticipated that some blasting will be employed in the construction of the tunnels for Options N3 and N4, and while the noise will be screened once a certain depth of tunnel has been formed, noise will emanate from the tunnels.

4.3.2.2 Operationally, significant impacts would not be expected in all cases, due to the small number of sensitive receivers and their transient nature. However, the tunnels in Options N3 and N4 will effectively screen vehicular noise for approximately half the length of the options, and thus these options would be preferable from an operational noise perspective.

4.3.2.3 In all cases, the sensitive receivers to both construction and operational noise would be transient, and would be affected for a short time only. Based upon this, the alignments are relatively similar, with Option N2 marginally less preferred based upon the amount of earthworks. The northern alignment options were thus ranked as follows:

1st = Option N4

1st = Option N3

2nd Option N1

3rd Option N2

4.3.3 Water Quality

4.3.3.1 Tung Chung Stream is the main stream in the northern study area, and is fed by numerous steep upland streams, which have a high degree of naturalness. Tung Chung Stream has been identified as the second richest stream in Hong Kong for freshwater fish species, with 23 species being identified (Chong and Dudgeon, 1992), and has provided the first record of the fish Beijiang Thick-lipped Barb (Acrossocheilus wenchowensis beijiangensis), a species of locally restricted distribution. Recent surveys of the stream also identified the locally common Predaceous Chub (Parazacco spilurus), which is currently protected under international, Chinese and Hong Kong legislation. The lower reaches of the stream are however channelised, which reduces its ecological value due to the lack of suitable micro-habitat. Native fish species favour more natural environments comprising rocky streambeds, with cool, fast flowing, well-oxygenated water.

4.3.3.2 The existing Tung Chung Road runs parallel to the east of Tung Chung Stream, and bridges over numerous tributaries of the main stream as they descend the eastern hillside of the valley. The northern road alignment options all go off-line after Tai Tung Shan Service Reservoir, and traverse the eastern tributaries at the head of the valley, below Sun Set Peak.

4.3.3.3 There is the potential for impacts to water quality in these tributaries and Tung Chung Stream to arise during the construction. Key construction phase impacts will be associated with culverting and stream diversion works, which will cause direct impacts on the streams in questions, and construction site runoff containing elevated suspended solids and possibly oils due to erosion of exposed surfaces and stockpiles. Such impacts will be relevant to all alignment options. To comply with the Water Quality Objectives, the suspended solids concentrations due to site runoff must be reduced to such an extent that they do not exceed 25 mg/L in the surface waters.

4.3.3.4 In addition to the above, tunnel-dewatering effluent could also be an issue if either Options N3 or N4 are selected, since both northern portal portals are close to the upper tributaries of Tung Chung Stream and both southern portals are close to the upper tributaries of Cheung Sha Stream. Effluent from tunnel dewatering will contain suspended solids and adsorbed oils.

4.3.3.5 Between Tai Tung Shan Service Reservoir and the header tank at the Pak Kung Au, all four northern options follow approximately the same alignment. Options N1, N2 and N3 will cross the same nine tributaries in this area. Option N4 goes into tunnel before the header tank, and avoids the stream closer to this, but crosses the other eight streams as per the other options. On the southern side of the crest, Options N1, N2 and N4 pass to the eastern side of Cheung Sha Stream, whereas Option N3 comes out of tunnel on the western side, and crosses the valley on viaduct. None of the alignments will directly affect either Tung Chung Stream or Cheung Sha Stream.

4.3.3.6 Some construction works will be required on all tributaries crossed by the alignment options comprising either bridging over the stream, culverting the stream or diverting the stream (see Clause 4.2.6). In respect of potential impacts, bridging over the stream will yield the least direct impacts on the water body as all works will be confined to the areas either side of the stream as far as possible, although runoff from earthworks will need to be controlled. However, either culverting or diverting the stream will cause direct disturbance to the streambed, resulting in short-term elevation of suspended solids and the replacement of the natural streambed with a section of manmade structure. Options N1 and N3 both have the highest number of culverts and diversions, with six of each required along the length of their alignments (see Table 4.3). Option N2 is marginally better with four culverts and five diversions being required, and Option N4 has the least potential impacts on water quality with only four culverts and four diversions being required.

4.3.3.7 In addition to the direct impacts, the potential for construction site runoff also needs to be considered. The greatest potential will be associated with those schemes with the largest quantity of earthworks. The tunnel options require by far the largest quantity of earthworks, in so far as they generate about twice the amount of cut material than the overland options (see below). Tunnel construction generally requires large portal areas and platforms for tunnel facilities. This factor, combined with the anticipated large quantities of high suspended solids resulting from tunnel dewatering operations, mean that the tunnel options would have a greater potential for construction runoff, even though the tunnels would not be subject to overland runoff. This is particularly so south of the crest, where both portals are located very close to some of the upper tributaries of Cheung Sha Stream.

4.3.3.8 Option N2 also requires substantial cut slopes. Furthermore, the meandering alignment runs closer to Tung Chung Stream, and overlaps with the existing road in three locations, increasing the risk of construction site runoff discharging directly into Tung Chung Stream. As there is a general consensus that works should be confined to the eastern side of the existing road to provide a “barrier” to Tung Chung Stream, Option N2 would be less favoured as a result. Option N1 has the least amount of earthworks overall, and thus the amount of runoff is potentially the least and therefore more readily controlled.

4.3.3.9 In terms of operational water quality, impacts would be associated with the following:

· paved area runoff containing suspended solids into which may be adsorbed hydrocarbons and heavy metals;

· load spillages from accidents; and

· drainage of tunnel lining washing water.

4.3.3.10 As stated in Clause 6.1.4 of the Assignment Brief, Tung Chung Stream and Cheung Sha Stream are of very high ecological value, and this fact has been corroborated by the recent wet seasons surveys undertaken as part of this Assignment (see below). Based on this and in accordance with Clause 6.1.6 of the Assignment Brief, all possible means to avoid polluting the streams during the construction and operational phases of the Project should be investigated. In addition, WSD stated at the Environmental Study Management Group (ESMG) meeting held on 12 June 2001 that road runoff should not be discharged in water gathering ground during the operational phase. Furthermore, based on precedent set on previous highway projects, road runoff should also not be discharged into stream courses that outflow within 100 m of the boundary of a gazetted beach. Thus, it is proposed that a special pipeline be integrated into the new road to collect all road runoff and transport it to either end of the road for discharge either into the channelised section of Tung Chung stream or off shore at Cheung Sha. Based on this, there will be no discharge in the main streams or their tributaries during the operation phase of the Project.

4.3.3.11 Taking the above into account, the construction phase impacts are clearly the key in comparing the options. Option N3 would be the least favoured based on the large quantity of surplus excavated material, the need to cross Cheung Sha Stream and the larger number of culverts and diversions required. Option N1 would be most favoured, since, although it has a larger number of culverts and diversions than Option N2, the amount of earthworks required is significantly less and it passes Tung Chung Stream further to the east. Based on this, the northern alignment options were ranked as follows:

1st Option N1

2nd Option N2

3rd Option N4

4th Option N3

4.3.4 Construction Waste

4.3.4.1 Activities during the construction phase will result in the generation of a variety of wastes that can be broadly classified into distinct categories based on their nature and the options for their disposal. These include:

· excavated materials suitable for reclamation and fill;

· general construction waste;

· chemical waste;

· general refuse; and

· sewerage.

4.3.4.2 The quantities of the latter four categories of materials are expected to be relatively small, and based upon proper waste management practices, are not expected to give rise to any adverse environmental impacts. However, there will be larger quantities of excavated material involved in the construction of the road, and the amounts of cut and fill will vary for each option. Excavated material from earthworks and tunnelling, if applicable, will include soil and rock material, a large percentage of which is expected to be suitable for reuse. This material will therefore be used as fill on site, with any surplus material being disposed off site at public fill facilities. The storage and stockpiling of excavated material prior to utilisation on site or disposal off site could lead to the generation of dust and may be visually intrusive. The transport and disposal of excavated material also have the potential to result in additional noise impacts, possible congestion due to increased traffic loading, and dust and exhaust emissions from the haul vehicles.

4.3.4.3 Indicative waste quantities have been estimated, based on an assessment of the cut, fill and tunnelling activities for each alignment option, based in turn on the outline designs presented in the appendix. The amount of surplus excavated material for each northern alignment option is summarised in Table 4.6 below.

Table 4.6: Northern Alignment Options – Surplus Excavated Material

Alignment Option	Cut ⁽¹⁾ (m³)	Fill (m³)	Surplus (m³)
N1	117,384	13,000	104,384
N2	191,480	21,550	169,930
N3	256,002	11,480	244,522
N4	278,064	11,210	266,854

Notes: (1) Including excavated materials from inside tunnels.

4.3.4.4 The amount of surplus material generated by the tunnel options is about twice that of the overland options, of which Option N2 generates about 50% more surplus material than Option N1, due to the substantial size of its cuttings. The northern alignment options were thus ranked as follows:

1st Option N1

2nd Option N2

3rd Option N3

4th Option N4

4.3.5 Ecology

4.3.5.1 An initial ecological assessment of the Project was carried out as part of the overall assessment of the alignment options. The assessment covered the various northern and southern alignment options with the aim of assessing the ecological implications of each option. The assessment was made on the basis of field surveys backed up with a review of relevant literature.

4.3.5.2 Habitats within the northern study area are dominated at higher elevations by a mosaic of grass and shrubland, with plantation woodland, and dense shrubland in stream valleys.

4.3.5.3 The on-line section of the Project involves widening of the existing Tung Chung Road. This is not considered to present a significant impact to the ecology of the study area, since the habitats present in this northern section have been shown by the wet season surveys to be utilised less by many of the faunal groups that have been found in the southern study area. In addition, the construction phase and operational phase impacts are generally considered to be minor for all northern alignment options.

4.3.5.4 Conducting an assessment of the northern alignment options based on fauna present is not entirely recommended as many of these animals are highly mobile and may incur less impacts than habitat types as they can migrate from disturbed areas. Nonetheless, based on ecological sensitive receivers present that are the most susceptible to impacts (ie, the freshwater fish in Tung Chung Stream) options that have less potential impact on the stream and its tributaries are preferred. In this respect, the tunnel options have a large extent of earthworks and associated tunnel dewatering issues, and Option N2, while also having large amount of earthworks, also overlaps the existing Tung Chung Road, which could lead to runoff discharging directly into the Tung Chung Stream.

4.3.5.5 The least overall habitat area is lost to the tunnel Option N4, due to its longer length. However, tunnel Option N3 causes a slightly greater loss overall than Option N1, since its shorter section of tunnel does not compensate for the large portal area and platform. The overall habitat lost that is of any real value (ie, shrub, tall shrub and secondary woodland) is greatest for Option N3 (3.18 ha lost) and Option N2 (3.06 ha lost), and smallest for Option N4 (1.55 ha lost) and Option N1 (1.83 ha lost). However, Option N1 is considered marginally better in terms of ecology than Option N4, since it has less potential impact on the streams.

4.3.5.6 Based on the above, the northern alignment options were ranked as follows:

1st Option N1

2nd Option N4

3rd Option N2

4th Option N3

4.3.6 Landscape and Visual

4.3.6.1 There are a number of issues that influence the potential landscape and visual impacts, both at construction and operational stages. These issues, which form the basis of any comparative assessment from a landscape and visual perspective, are discussed below:

(i) Carriageway and Associated Structures

The carriageway and its associated structures, comprising lighting, barriers, etc, are a key source of landscape and visual impact. As a general rule, a shorter alignment can be perceived to have fewer landscape and visual impacts. However, this is not always the case, and factors, including the extent of slope works or numbers of visual receivers along the route, will contribute to the overall magnitude of impact.

In general, some variation in alignment is generally desirable. Roads that respond sympathetically to natural topographic variation, following natural contour patterns, sit better in the landscape than do roads that ignore these patterns by cutting through slopes or bridging valleys. Generally, following natural terrain where possible will also result in less need for slope or bridge engineering and therefore fewer landscape and visual impacts. Thus, where the new alignment remains close to the existing Tung Chung Road, impacts on landscape character will tend to be reduced by limiting the width of the new “transportation corridor”. Also, tunnelled alignments will overall result in fewer landscape and visual impacts than at-grade options.

(ii) Slope Works

Cut and fill slopes associated with the highway are a key source of landscape and visual impacts. This is particularly so in the study area where many slopes are likely to be rock cut slopes and where they will be very exposed, making vegetation establishment difficult. Where all other factors are equal, a route resulting in less slope works will always be preferable to one resulting in more.

(iii) Elevated Structures

Elevated structures, particularly long viaducts that run along hillside, are also a key source of landscape and visual impacts. Although viaducts may be preferable to extensive fill slopes in terms of landscape impact, retaining wall solutions are generally considered preferable to viaduct solutions in terms of visual impact. Hence, retaining wall solutions are generally preferable along hillside.

(iv) Other Associated Works

Other features, such as culverts and tunnel portals, may also result in landscape and visual impacts, although if sensitively designed, these impacts can be localised. Drainage works and construction of a bus-bus interchange on South Lantau Road may also result in landscape and visual impacts.

4.3.6.2 The landscape of the study area includes three discernibly different types of landscape, as described below:

(i) Lantau Peaks and Uplands

The landscape of Lantau Island, south of Tung Chung, lies on what is principally volcanic rock, forming a high mountainous ridge running along the length of the island. This mountainous ridge is here referred to as the Lantau Peaks and Uplands.

In western Lantau, pyroclastic rocks and lava are dominant, and a few of these occur as outcrops around Tung Chung Road. The peaks rise sharply from the sea to 869 mPD on Sunset Peak and 934 mPD on Lantau Peak, which lie to the east and west respectively of the Tung Chung Road. The uplands form rugged and dramatic ridges, peaks and spurs, angular in appearance and often given an undulating form by the numerous streams and gullies that run down them. Otherwise, the hilltops are large in scale, exposed and tranquil.

The lower slopes are characterised by scrub or woodland vegetation whilst the upper slopes are grass-covered with numerous rock outcrops and landslip scars. There are almost no human features in this landscape, except for occasional power lines, resulting in a landscape that is still highly sensitive to development. The high quality and sensitivity of this landscape are recognised by its designation as Country Park.

(ii) Upper Valleys

The alignment corridor follows two valleys that run approximately north and south across the island from a high point at Pak Kung Au, emanating at Tung Chung in the north and Cheung Sha in the south. The saddle of land between the two valleys is particularly sensitive in visual terms, as it defines the ridgeline in views from south and north. Though the more southerly of these two valleys is somewhat steeper, both are similar in character.

The upper valleys, lying generally above 100 mPD, are tightly contained, with steep, generally wooded or scrub-covered sides. Situated on colluvium, the valleys are characterised by small streams and watercourses, often lined with riparian scrub or woodland. The upper valleys possess few human features except Tung Chung Road itself, two power lines that run alongside the road and hiking paths and facilities associated with the Lantau Trail. These predominantly natural qualities mean it is a landscape that is still very sensitive to development. The high quality and sensitivity of this landscape is recognised by its designation as Country Park.

(iii) South Lantau Coast

South of the central Lantau uplands, between sea level and 100 mPD, lies the South Lantau Coast. This contrasts geologically with the uplands in that it lies on coarse tuff. Here the mountains fall steeply into the sea, leaving only a narrow strip of relatively flatter land along the coast. The South Lantau Road runs along the coast and much of this land has been exploited for scattered residential or public infrastructure development. A catchwater runs along the bottom of the mountains to the north, collecting run-off and directing it to Shek Pik Reservoir to the west.

Although very much maritime in character, the scale of the coastal landscape is surprisingly intimate, a quality provided by its covering of dense woodland, which helps to offset the impacts of existing development. The existing Tung Chung Road follows the steep contours of the coastal strip down to South Lantau Road. Only occasionally is human development intrusive, as in the case of new residential development around the former South Lantau Hospital. This is a landscape that still possesses its natural, intimate and unspoilt qualities largely intact. Though its woodland areas are capable of mitigating in part the impacts of development, this is still a landscape that is sensitive to human features.

4.3.6.3 The following groups of receptors may experience views of one or more of the proposed alignment options. It is notable that a large proportion of these are highly sensitive receivers.

(i) Residential Receivers (High Sensitivity), including:

· Residents in Tung Chung Development

· Residents in Cheung Sha Ha Tsuen

· Residents in Cheung Sha Sheung Tsuen

· Residents of Leyburn Villas

· Residents around the old South Lantau Hospital

· Residents in Tong Fuk

(ii) Recreational Receivers (High Sensitivity), including:

· Users of Cheung Sha Beach

· Hikers on Lantau Trail

· Hikers on South Lantau Catchwater

· Users of Cheung Sha YMCA Youth Camp

· Users of Lantau Country Parks facilities

(iii) Travelling Receivers (Medium Sensitivity), including:

· Travellers in aircraft

· Travellers on Macau Ferries

· Those in vessels off the South Lantau Coast

· Users of Tung Chung Road

· Users of South Lantau Road

4.3.6.4 Option N1 is moderately sensitive to existing topography, largely following the landform of the bottom of Tung Chung Valley. This results in only a moderate amount of cut/fill slope and/or elevated structure. Vegetation affected is largely tall shrub and plantation woodland and some secondary woodland. The alignment is reasonably sympathetic to landscape character, maintaining the meandering course of the existing road, whilst not appearing too imposing in terms of the scale of it associated structures. However, because the road goes some way off-line, it will widen the “transportation corridor” if the existing road is maintained. This will have resultant impacts on landscape character and on visual receivers. Cut slopes at the head of Cheung Sha Valley will also create landscape and visual impacts, being visible over a considerable distance on the south Lantau coast. Visual receivers potentially affected by this option will include:

· Residents in Tung Chung Development

· Residents around the old South Lantau Hospital

· Hikers on Lantau Trail

· Users of Cheung Sha Beach

· Users of Lantau Country Parks facilities

· Hikers on South Lantau Catchwater

· Travellers in Aircraft

· Travellers on Macau Ferries

· Those in vessels off the South Lantau Coast

· Users of Tung Chung Road

· Users of South Lantau Road

4.3.6.5 Because of its requirement for gentler gradients, Option N2 is not sensitive to surrounding topography, having to cut back and forth across the head of Tung Chung Valley, whilst creating extensive cut/fill slopes and/or elevated structure. Whilst some variation in alignment is often desirable, the cut and fill slopes associated with this alignment will create significant impacts on topography and cause greater loss of tall shrub and secondary woodland. Also, as the road goes farther off-line than Option N1, this alignment will further widen the “transportation corridor” if the existing road is maintained. This will have resultant impacts on landscape character and on visual receivers. Cut slopes at the head of Cheung Sha Valley will also create landscape and visual impacts, being visible over a considerable distance on the south Lantau coast. Visual receivers potentially affected by this option will include:

· Residents in Tung Chung Development

· Residents around the old South Lantau Hospital

· Hikers on Lantau Trail

· Users of Cheung Sha Beach

· Users of Lantau Country Parks facilities

· Hikers on South Lantau Catchwater

· Travellers in Aircraft

· Travellers on Macau Ferries

· Those in vessels off the South Lantau Coast

· Users of Tung Chung Road

· Users of South Lantau Road

4.3.6.6 Option N3 is sensitive to existing topography over the northern section of the alignment, closely following landforms across the floor of the head of Tung Chung Valley, before reaching the tunnel portal. This results in only limited cut/fill slopes and/or elevated structure. Although less plantation woodland is affected than the overland options, more secondary woodland is affected (near the northern portal). The alignment is sympathetic to landscape character, maintaining the meandering course of the existing road, going only a little distance off-line, and not appearing imposing in scale in terms of its associated structures. The proposed northern tunnel portal will however give rise to certain localised landscape and visual impacts.

4.3.6.7 Over the southern part of its alignment, because the route is tunnelled, it will not give rise to significant landscape or visual impacts on the saddle at Pak Kung Au. On leaving the southern portal, if combined with Options S1 or S2A/B, a linking section of alignment is required, which crosses Cheung Sha Valley. This is an intrusive alignment that will result in significant impact on landscape character and visual impact. Visual receivers affected by this option will include:

· Residents in Tung Chung Development

· Residents in Cheung Sha Ha Tsuen

· Residents of Leyburn Villas

· Residents around the old South Lantau Hospital

· Users of Cheung Sha Beach

· Hikers on Lantau Trail

· Hikers on South Lantau Catchwater

· Travellers on Aircraft

· Travellers on Macau Ferries

· Those in vessels off the South Lantau Coast

· Users of Tung Chung Road

· Users of South Lantau Road

4.3.6.8 Over the northern part of its alignment, Option N4 is sensitive to existing topography, closely following landforms across the floor of the head of Tung Chung Valley, before reaching the tunnel portal. This results in only a small amount of cut/fill slope and/or elevated structure. Option N4 affects least vegetation, including mainly tall shrub and plantation woodland. The alignment is sympathetic to landscape character maintaining the meandering course of the existing road, going only a little distance off-line (although further than Option N3), and not appearing imposing in scale. Resulting impacts in landscape character will be limited. The proposed northern tunnel portal will however give rise to certain limited landscape and visual impacts.

4.3.6.9 As with Option N3, no landscape or visual impacts on the saddle at Pak Kung Au will result as the alignment is in tunnel over this section. The southern tunnel portal is located on the eastern side of Cheung Sha Valley, meaning that the alignment does not have to cross the Cheung Sha Valley, unlike Option N3. Also, the southern tunnel portal is slightly less visible to visual receivers in South Lantau than is that of Option N3. Visual receivers affected by this option will include:

· Residents in Tung Chung Development

· Residents around the old South Lantau Hospital

· Users of Cheung Sha Beach

· Hikers on Lantau Trail

· Hikers on South Lantau Catchwater

· Travellers on Aircraft

· Travellers on Macau Ferries

· Those in vessels off the south Lantau Coast

· Users of Tung Chung Road

· Users of South Lantau Road

4.3.6.10 Of the at-grade alignments, Option N1 is preferable to Option N2 in terms of landscape and visual impact. Option N2 has more potential for significant impacts by virtue of its more meandering alignment, affecting both topography and vegetation, and resulting in significant cut/fill slopes and/or elevated structure. The significant engineering works associated with this alignment and its deviation from the alignment of the existing road mean that it will also result in more significant impacts on landscape character than Option N1.

4.3.6.11 Because the tunnel Options N3 and N4 do not have to pass over the saddle at Pak Kung Au, they are able to follow the topography of Tung Chung Valley floor and the existing road alignment more closely than the at-grade Options N1 and N2. This results in fewer cut/fill slopes in Tung Chung Valley and fewer resultant impacts on landscape resources, character or impacts on the visually important saddle at Pak Kung Au. The tunnel portals will be sources of impact that will not arise under Options N1 and N2, but these impacts are less significant than those resulting from the cut slopes at the head of Cheung Sha Valley under Options N1 and N2.

4.3.6.12 Option N4 has the significant advantage over N3 that it emerges on the eastern side of Cheung Sha Valley, meaning that it does not have to cross the head of the valley, thus avoiding significant visual impact. In addition, the southern portal of Option N4 is slightly less visible to sensitive visual receivers than that of Option N3.

4.3.6.13 In conclusion therefore, of the northern alignment options, Option N4 is the most favoured option in terms of landscape and visual impact. It avoids the creation of extensive cut/fill slopes and/or elevated structure required by the other options as well as avoiding impacts on the visually sensitive saddle at Pak Kung Au and on the head of Cheung Sha Valley. The next most favourable alignment option in terms of landscape and visual impact is Option N3, followed by Option N1 and Option N2 respectively. The northern alignment options were thus ranked as follows:

1st Option N4

2nd Option N3

3rd Option N1

4th Option N2

4.3.7 Heritage

4.3.7.1 There are a number of cultural heritage resources comprising both historic structures and areas of archaeological potential, within the overall study area for the widening of Tung Chung Road. The resources are largely concentrated at either end of the route corridor in Tung Chung and Cheung Sha, and there is potential for direct and indirect impacts on these as a result of the construction works for the Project. In addition, there is potential need to mitigate against any unacceptable indirect impacts of an aesthetic or visual nature on heritage resources, both during construction and operation.

4.3.7.2 Cultural heritage resources in Tung Chung and the lower Tung Chung valley include the villages of Ha Ling Pei, Wong Ka Wai, Sheung Ling Pei, Fui Yiu Ha and Shek Mun Kap and their associated Fung Shui woods, Tung Chung Fort and the local burial grounds. These features were not relevant to the assessment of the northern alignment options, and therefore potential impacts on these will be covered in the detailed assessment.

4.3.7.3 There are no villages containing historic buildings or woodland of Fung Shui significance in the vicinity of any of the northern alignment options. Furthermore, by virtue of the upland location of the options, no areas of archaeological potential or identified archaeological sites are present in this area. Thus, the only cultural heritage resource, which could be affected by these options, are pre‑war or clan graves inside and in close proximity to the alignments. There is potential for indirect impacts on any such grave, but the number of graves affected would be minimised by the tunnel sections associated with Options N3 and N4.

4.3.7.4 Based on the above, Options N3 or N4 would be slightly preferable in terms of potential indirect impacts (visual and/or aesthetic) on any historical clan grave that may be found in the area. However, since no graves have been found in the crest area, all of these options would be considered equally acceptable from a cultural heritage perspective. The northern alignment options were thus ranked as follows:

1st = Option N1

1st = Option N2

1st = Option N3

1st = Option N4

4.3.8 Hazard to Life

4.3.8.1 There are no designated Potentially Hazardous Installations (PHIs) within the study corridor. However, Cheung Sha Water Treatment Works, while not a PHI, uses and stores chlorine in 50 kg cylinders for the purpose of sterilisation of drinking water, and no maximum quantity of storage is specified for this facility other than the PHI threshold of 10 tonnes. Thus, the water treatment works presents a potential hazard to the potential population of the Project, specifically in terms of the handling and storing of chlorine, a highly toxic gas.

4.3.8.2 Cheung Sha Water Treatment Works is located just east of the point where the existing Tung Chung Road crosses the catchwater in Cheung Sha Valley, and is about 22 m below the catchwater. As areas beyond a radius of approximately 500 m have an insignificant likelihood of being exposed to chlorine hazards from the water treatment works, only two southern alignment options are relevant in terms of potential risk to the road population, as discussed in Section 5 of the appendix. The northern alignment options were thus ranked as follows:

1st = Option N1

1st = Option N2

1st = Option N3

1st = Option N4

4.4 Land Use Criteria

4.4.1 Impacts on Country Park

4.4.1.2 The impacts of the alignment options on the Country Park have been estimated in terms of the land requirements from the park and the impacts on the recreational facilities in the park of each option. The impacts are summarised in Table 4.7 below.

Table 4.7: Northern Alignment Options – Impacts on Country Park

Alignment Option	Area of Affected Country Park (ha)	Impacts on Country Park Recreational Facilities
N1	5.15	No perceived impacts on recreational facilities
N2	6.42	No perceived impacts on recreational facilities
N3	5.25	No perceived impacts on recreational facilities
N4	4.40	No perceived impacts on recreational facilities

4.4.1.3 Although, none of the alignment options avoid the Country Park completely, the tunnel options minimise the land required from the park. Option N2 requires most land, due to the substantial size of its cuttings. The northern alignment options were thus ranked as follows:

1st Option N4

2nd Option N1

3rd Option N3

4th Option N2

4.4.2 Impacts on Private Land, etc

4.4.2.1 The impacts of the alignment options on private land, sale sites, permanent and temporary government land allocations, short-term tenancies and government land licenses have been assessed in terms of the land requirements of each option. In North Lantau, most of these lands are located in the village areas on the fringe of Tung Chung, and as such would only be affected by the on‑line section of new road between Lung Tseng Tau and Tai Tung Shan Service Reservoir. The private land required for this section of the Project is summarised in Table 4.8 below.

Table 4.8: On-Line Section – Impacts on Private Land

Ref. No. ⁽¹⁾	Affected Area (m²)	Ref. No. ⁽¹⁾	Affected Area (m²)	Ref. No. ⁽¹⁾	Affected Area (m²)
1951 in DD 3TC	29	51 in DD 3TC	27	30 in DD 3TC	22
177 in DD 3TC	24	52 in DD 3TC	15	67 in DD 3TC	36
150 in DD 3TC	74	53 in DD 3TC	7	72 in DD 3TC	48
142 in DD 3TC	2	41 in DD 3TC	28	73 in DD 3TC	46
141 in DD 3TC	31	55 in DD 3TC	4	74 in DD 3TC	81
136 in DD 3TC	31	37 in DD 3TC	41	124 in DD 2	297
131 in DD 3TC	56	56 in DD 3TC	3	35 in DD 3TC	5
137 in DD 3TC	4	35 in DD 3TC	63	32 in DD 3TC	321
130 in DD 3TC	32	34 in DD 3TC	51	Total:	1,378

Notes: (1) Reference No. of private land lot affected by the Project, commencing at Lung Tseng Tau, and working south along the road.

4.4.2.2 No private land is affected by the northern alignment options between Tai Tung Shan Service Reservoir and the crest at Pak Kung Au. However, a number of temporary government land allocations, short-term tenancies and government land licences are affected, as summarised in Table 4.9 below. All the land in this area also comprises water-gathering ground.

Table 4.9: Northern Alignment Options – Impacts on Other Lands

Alignment Option	Summary of Impacts
N1	Temporary government land allocation: Nos. GLA-TIS-355 and GLA-TIS-251 Short term tenancy: No. STTCX144 Government land licence: No. W10410/1B
N2	Temporary government land allocation: Nos. GLA-TIS-355 and GLA-TIS-251 Short term tenancy: No. STTCX144 Government land licence: No. W10410/1B
N3	Government land licence: Nos. W10410/1 and W10410/1B
N4	Government land licence: Nos. W10410/1 and W10410/1B

4.4.2.3 The tunnel options only affect government land licences, whereas the overland options affect temporary government land allocations and short-term tenancies in addition to government land licences. On this basis, the northern alignment options were ranked as follows:

1st = Option N3

1st = Option N4

2nd = Option N1

2nd = Option N2

4.4.3 Impacts on Burial Grounds and Fung Shui

4.4.3.1 The impacts of the alignment options on burial grounds have been estimated in terms of the land requirements from the burial grounds shown on the Government digital 1:1,000 lot boundary mapping and also the impacts on the individual graves shown on the Government digital 1:1,000 scale survey mapping.

4.4.3.2 In North Lantau, the only burial ground of concern is No. 18L, but this lies adjacent to the on-line section of the new road between Lung Tseng Tau and Tai Tung Shan Service Reservoir. It should be possible to avoid the burial ground when designing the improvement works, except perhaps for Territory Development Department’s proposed extension to the burial ground, which comes very close to the existing road.

4.4.3.3 The northern alignment options affect neither any burial ground nor any individual graves. Furthermore, it is not anticipated that there would be any Fung Shui problems associated with the northern options. On this basis, the northern alignment options were ranked as follows:

1st = Option N1

1st = Option N2

1st = Option N3

1st = Option N4

4.5 Costs and Programme Criteria

4.5.1 Capital Costs

4.5.1.1 The capital cost base estimate has been calculated for each alignment option. The base estimates are current for August 2001, and are exclusive of preliminaries, design and related services and contract and project contingencies. It should be pointed out that the estimates are preliminary and for assessment purposes only at this stage. There has been significant reduction in tender prices over the last year due to increased competition in the market. The capital cost estimate for the Project will be thoroughly reviewed on selection of the preferred alignment option.

4.5.1.2 The base estimates for the northern alignment options, including the section of on‑line improvement works between Lung Tseng Tau and Tai Tung Shan Service Reservoir, are presented in Table 4.10 at the end of this section and summarised in Table 4.11 below.

Table 4.11: Northern Alignment Options – Summary of Capital Cost Base Estimates (August 2001)

On-Line Cost ($)	Alignment Option	Cost ($)	Total Cost ($)
109,197,400	N1	144,767,680	253,965,080
	N2	178,841,440	288,038,840
	N3	883,855,610	993,053,010
	N4	1,030,103,080	1,139,300,480

4.5.1.3 Based on a comparison of the capital cost base estimates, the northern alignment options were ranked as follows:

1st Option N1

2nd Option N2

3rd Option N3

4th Option N4

4.5.2 Recurrent Costs

4.5.2.1 The recurrent cost estimate has been calculated for each alignment option. It should be pointed out that the estimates are preliminary and for assessment purposes only at this stage. The recurrent cost estimate for the Project will be thoroughly reviewed on selection of the preferred alignment option.

4.5.2.2 The recurrent cost estimates for the northern alignment options, including the section of on‑line improvement works between Lung Tseng Tau and Tai Tung Shan Service Reservoir, are presented in Table 4.12 at the end of this section and summarised in Table 4.13 below.

Table 4.13: Northern Alignment Options – Summary of Annual Recurrent Cost Estimates

On-Line Cost ($)	Alignment Option	Cost ($)	Total Cost ($)
1,095,752	N1	1,308,095	2,403,847
	N2	1,706,912	2,802,664
	N3	22,713,942	23,809,694
	N4	28,641,447	29,737,199

4.5.2.3 Based on a comparison of the recurrent cost estimates, the northern alignment options were ranked as follows:

1st Option N1

2nd Option N2

3rd Option N3

4th Option N4

4.5.3 Time for Construction

4.5.3.1 As discussed in Section 3 of the appendix, the Project is a very urgent and politically sensitive project. Government has committed to complete:

· the on-line section of improvement works between Lung Tseng Tau and Tai Tung Shan Service Reservoir not later than December 2005;

· the off-line section of improvement works between Tai Tung Shan Service Reservoir and Pak Kung Au not later than June 2006; and

· the off-line section of improvement works between Pak Kung Au and South Lantau Road not later than December 2006.

4.5.3.2 It is clear that the tunnel options would take considerably longer to construct than the overland options. Indeed, it is anticipated that the tunnel options would require at least 12 months longer to construct to allow for portal construction and tunnel boring. Option N4 would require longer than Option N3, since its tunnel is 160 m longer than the latter’s. Option N2 would in turn require longer to construct than Option N1, due to the substantial size of its cuttings. On this basis, the northern alignment options were ranked as follows:

1st Option N1

2nd Option N2

3rd Option N3

4th Option N4

4.6 Option Assessment and Sensitivity Testing

4.6.1 The assessment of the alignment options and sensitivity testing of the results are presented in Tables 4.14 to 4.23 at the end of this section. Table 4.23, which summarises the assessment and sensitivity testing, is repeated below. The highest score per set is underlined.

Table 4.23: Northern Alignment Options – Summary of Assessment Results

Set	Option N1	Option N2	Option N3	Option N4
Base Set A	89.20	69.40	63.70	75.35
Test Set B	87.20	70.00	64.00	76.00
Test Set C	90.00	68.80	62.40	76.20
Test Set D	88.20	67.40	65.80	80.60
Test Set E	91.40	71.40	62.60	68.60

4.6.2 Based on the scores presented in Table 4.23, the options have been ranked as presented in Table 4.24 below.

Table 4.24: Northern Alignment Options – Overall Ranking

Set	Option N1	Option N2	Option N3	Option N4
Base Set A	1st	3rd	4th	2nd
Test Set B	1st	3rd	4th	2nd
Test Set C	1st	3rd	4th	2nd
Test Set D	1st	4th	3rd	2nd
Test Set E	1st	2nd	4th	3rd

4.6.3 Option N1 scored the highest marks for “Engineering”, “Environmental” and “Costs and Programme” and second highest for “Land Use”. Option N1 scored the highest marks overall in the base set and all test sets, and is therefore recommended as the preferred northern alignment option.

4.6.4 As discussed in Section 3 of the appendix, at the Steering Group Meeting held on 18 September 2001, the relative importance of the “Landscape and Visual” environmental parameter was queried in respect of the assessment of the tunnel options. To answer this query, two additional sensitivity tests were carried out on the environmental criteria. The test results are presented in Tables 4.25 to 4.34 and 4.35 to 4.44 at the end of this section. Tables 4.34 and 4.44, which summarise the additional test results, are repeated below. The highest score per additional base set and per additional test set is underlined.

Table 4.34: Additional Test I - Northern Alignment Options – Summary of Assessment Results

Set	Option N1	Option N2	Option N3	Option N4
Base Set A	86.50	67.15	66.40	77.60
Test Set B	84.80	68.00	66.40	78.00
Test Set C	86.40	65.80	66.00	79.20
Test Set D	85.80	64.50	68.20	82.60
Test Set E	89.00	69.40	65.00	70.60

Table 4.44: Additional Test II - Northern Alignment Options – Summary of Assessment Results

Set	Option N1	Option N2	Option N3	Option N4
Base Set A	85.60	67.15	67.30	77.60
Test Set B	84.00	68.00	67.20	78.00
Test Set C	85.20	65.80	67.20	79.20
Test Set D	85.00	65.40	69.00	82.60
Test Set E	88.20	69.40	65.80	70.60

4.6.5 Option N1 scored the highest marks overall in the additional base sets and all additional test sets. These additional tests demonstrated the robustness of the option assessment, and confirmed Option N1 as the recommended preferred northern alignment option.

5 ASSESSMENT OF ALIGNMENT OPTIONS IN THE SOUTH

5.1 General

5.1.1 This section of the appendix covers the assessment of the southern alignment Options S1, S2A, S2B and S3.

5.2 Engineering Comparison

5.2.1 Alignment Geometry

5.2.1.1 Options S1, S2A and S2B all proceed from the “common point” where the northern alignment options converge south of the crest on the east side of Cheung Sha Valley, and can connect with any of the northern options. Option S3 on the other hand can only proceed from the southern portal of the northern alignment Option N3.

5.2.1.2 Option S1 runs down along the eastern hillside of Cheung Sha Valley above the existing road and around the mouth of the valley above the catchwater at –10.6% gradient. As the alignment approaches the catchwater, the gradient increases to ‑12%, crossing at-grade with the catchwater access track. The alignment continues eastward along the hillside, before connecting with South Lantau Road just west of the YWCA youth camp near Cheung Sha Sheung Tsuen. The alignment is relatively smooth and straight, with radii no less than the “normal” minimum radius (R3) of 88 m.

5.2.1.3 Option S2A also runs down along the eastern hillside of Cheung Sha Valley above the existing road and around the mouth of the valley above the catchwater at –10.6% gradient. However, instead of continuing eastwards, like Option S1, the alignment loops back with an inside “recommended absolute” minimum radius (R2) of 63 m, before heading westwards at –10.6% gradient and connecting with the existing road where it crosses the catchwater. The alignment then runs southwards at –11% gradient and westwards at –8% gradient, before connecting with South Lantau Road just east of LCSD’s beach facilities on Cheung Sha Beach.

5.2.1.4 Option S2B follows the same alignment as Option S2A down to the catchwater. However, after the catchwater, the alignment runs south and westwards at -5.9% gradient, before looping back with an inside “recommended absolute” minimum radius (R2) of 63 m and running eastwards at –6.5% gradient, before connecting with South Lantau Road in the same location as the existing junction.

5.2.1.5 Option S3 runs down along the western hillside of Cheung Sha Valley and around the mouth of the valley above the catchwater at –10.6% gradient. The alignment then continues westwards towards Tong Fuk, crossing the catchwater at-grade with the catchwater access track, at a reduced gradient of –8%. It then loops back with an inside “recommended absolute” minimum radius (R2) of 63 m, and runs eastwards at –8% gradient, before connecting with South Lantau Road at the headland between Cheung Sha Beach and Tong Fuk Beach.

5.2.1.6 The loop-bends of Options S2A, S2B and S3, although within the “recommended absolute” minimum standard, would be best avoided on consideration of their relatively long length and the fact that they are located on alignments with relatively steep gradients. On this basis, Option S1 is considered the best alignment, since it is a smooth alignment with no loop‑bends, and Option S2B is considered the worst alignment, since it has two loop‑bends. Options S2A and S3 have one loop-bend each, but Option S3 is considered superior, since it has gentler gradients overall. Based on this, the southern alignment options were ranked as follows:

1st Option S1

2nd Option S3

3rd Option S2A

4th Option S2B

5.2.2 Junction with South Lantau Road

5.2.2.1 A roundabout solution is recommended for the junction between the improved Tung Chung Road and South Lantau Road, since it is anticipated that the flows will be relatively balanced, albeit with a preference to/from Mui Wo (see below). There will also be a high proportion of right turning vehicles from Mui Wo turning into Tung Chung Road. Both traffic situations favour a roundabout solution.

5.2.2.2 For Option S1, the junction location is set back from the coast, behind Cheung Sha Sheung Tsuen, where there is sufficient level land to accommodate a “normal” roundabout with a central island diameter of 4 m and a minimum inscribed circle diameter of 28 m. Although, some local improvement works would be required to South Lantau Road to improve the sight lines and gradients of the approaches, the propitious orientation of the approaches results in a favourable solution.

5.2.2.3 For Options S2A, S2B and S3, the junctions are located immediately behind the coast, where there is insufficient space between the beach and the hillside to accommodate a roundabout solution, without excessive encroachment either onto the beach or into the hillside. Only priority junctions can be accommodated in these locations.

5.2.2.4 For Option S2A, the junction is located opposite the proposed bus-bus interchange adjacent to LCSD’s beach facilities on Cheung Sha Beach. In this location, a priority crossroad junction with shadow islands is recommended. This provides a turning lane into the interchange for buses from the West, and also a turning lane into Tung Chung Road for traffic from the East. The crossroad junction will also allow buses to cross directly from Tung Chung Road into the interchange. The carriageway at the junction is 9.5 m wide to allow for a standard 3.5 m wide turning lane at the centre of the road and 3 m wide lanes for traffic either on side. An additional left-hand slip road off South Lantau Road into Tung Chung Road is provided to enable a more direct approach into Tung Chung Road for traffic from the West and for buses turning out of the interchange.

5.2.2.5 For Options S2B and S3, the junctions are located away from the proposed bus-bus interchange on Cheung Sha Beach. In these locations, priority T-junctions with shadow islands for right turning vehicles into Tung Chung Road are recommended. The carriageway at the junctions is 9.5 m wide with standard 3.5 m wide turning lanes at the centre of the road and 3 m wide lanes for traffic on either side. Unlike Option S2A, the locations of these two junctions do not directly affect the operation of the bus-bus interchange at Cheung Sha Beach.

5.2.2.6 Given that a roundabout solution is the favoured solution for the anticipated traffic conditions (see below), the Option S1 junction is considered superior to the other option junctions. The Option S3 junction is favoured least of all, since it is located on a bend in South Lantau Road, and hence has inferior sight lines, which are critical for a priority T-junction. On this basis, the southern alignment options were ranked as follows:

1st Option S1

2nd = Option S2A

2nd = Option S2B

3rd Option S3

5.2.3 Traffic Considerations

5.2.3.1 As discussed in Section 4 of the appendix, the main traffic-related issues, which affect the selection of the preferred alignment option include:

· the location of the bus-bus interchange in relation to the junction of the new road with South Lantau Road.

Traffic Pattern

5.2.3.2 The traffic pattern (ie, the balance between the traffic heading eastwards in the direction of Mui Wo, or westwards in the direction of Ngong Ping) is relevant to the assessment of the southern alignment options. The initial findings of the traffic impact assessment for this Assignment indicate that the dominant traffic flows on Tung Chung Road are towards Mui Wo during the weekdays, but are more even (with some preference towards Ngong Ping) on Sundays. This directional bias matches the landuse patterns, with more development at Mui Wo, but more recreational activity in the direction of Ngong Ping. Although the differences in the current observed flows are not large, current planning data indicates that future development will concentrate more at Mui Wo, and therefore the future heavier traffic flow is likely to be to and from Mui Wo. Furthermore, the construction of the Tung Chung Cable Car Project will likely give some relief to the future traffic flows to and from Ngong Ping.

5.2.3.3 Based on the above, the traffic pattern favours Option S1, since it is the closest alignment option to Mui Wo. The distance between the junction with South Lantau Road for Option S1 (the most eastern alignment option) and that for Option S3 (the most western alignment option) is about 3.1 km. Furthermore, Option S3 is about 0.6 km longer than Option S1, and therefore the distance in the actual trips between Tung Chung and Mui Wo would be about 3.7 km longer for Option S3 compared to Option S1.

Location of Bus-Bus Interchange

5.2.3.4 Bus services over Tung Chung Road are provided from Tung Chung to Mui Wo, Ngong Ping and Tai O. The provision of a bus-bus interchange on South Lantau Road, close to the junction with the improved Tung Chung Road, would enable some improvements in bus operation to be considered. These include improved levels of service to passengers and possible reductions in bus operating costs, which would benefit the bus operators and ultimately the bus passengers by reducing the need to increase fares.

5.2.3.5 The objective of the interchange would be to permit bus passengers to interchange between the services travelling over Tung Chung Road and the more frequent services along South Lantau Road. This could be implemented in a number of ways, but it would be most effective if there were only one route operating over Tung Chung Road from Tung Chung bus terminus, but at a frequency higher than currently provided by each individual route. Passengers would then have the benefit of less waiting time at Tung Chung. On reaching the interchange, passengers would then choose between the relatively frequent services, which use South Lantau Road. Although this would be the most effective operation, it would also be possible to continue with the current route structure, but permit passengers to interchange between services at the new interchange.

5.2.3.6 The interchange need only have a limited provision of facilities and bays. The number of bays would depend on operational concerns, but with one bay to Tung Chung, one bay for the Mui Wo direction, and one bay for the Ngong Ping/Tai O direction, a three to four bay interchange should be sufficient. The scope of facilities would depend on whether the interchange is located at a beach or close to potential bus users. At the simplest, the interchange would provide covered waiting areas for each bay, with some simple facility for a “dispatcher” if this is the terminus of the route to Tung Chung.

5.2.3.7 The current preferred arrangement of bus bays in interchanges in Hong Kong is the “saw-tooth” arrangement. Although this arrangement is primarily intended for large interchanges rather than much smaller ones, as required on this Project, suitable layouts for a four bay interchange would comprise either a “linear” (ie, all bays in a row) or “circular” (ie, bays arranged around the edge of a circular site) arrangement depending on the site constraints.

5.2.3.8 The location of the bus-bus interchange should be as close as possible to the junction between Tung Chung Road and South Lantau Road to avoid passengers having to “double-back” on their journeys. On this basis, Options S1 and S2A are preferable to Options S2B and S3.

5.2.3.9 On consideration of the above two main traffic-related issues, the southern alignment options were ranked as follows:

1st Option S1

2nd Option S2A

3rd Option S2B

4th Option S3

5.2.4 Geotechnical Constraints

5.2.4.1 Option S1 traverses the southwest and south facing slopes of Sunset Peak down to the catchwater. These slopes comprise some of the steepest and most landslide prone terrain in the study area. The initial geotechnical assessment identified several very large relict natural terrain landslides in drainage valleys above the route. Natural terrain landslide mitigation measures for this section of the road would therefore likely be required. However, the use of elevated structures to cross the drainage valleys may limit the need for large check dams/fences. It is likely that the foundations for the elevated structures would require socketing into bedrock to negate the potential for landslides to destabilise them. After crossing the catchwater, Option S1 continues across relatively gentle terrain down to South Lantau Road. Owing to the protection afforded by the catchwater above and the relatively gentle terrain, this section of the road would probably require fewer landslide mitigation measures and geotechnical works (the largest cut slope being less than 7 m high) than the other options.

5.2.4.2 Option S2A follows a similar alignment to Option S1 as far as the loop-bend, where it turns to the west on long elevated structure, the foundations for which would need to be socketed into bedrock for the same reasons given above. As the alignment loops back to the west it will be afforded some protection from natural terrain hazards by the section of road above and also the landslide mitigation measures constructed along that section. However, a cut slope over 40 m high would be required to construct the loop‑bend itself. After crossing the catchwater, Option S2A turns south and follows a similar course to the existing road. Over this section of the route, elevated structures will be required to carry the road across several deep incised valleys. The alignment then turns to the west and cuts along the hillside above South Lantau Road, before joining the road. Several cut slopes up to 20 m high would be required along this section. However, the risk from natural terrain hazards in this area is likely to be low, due to the protection afforded by the catchwater above the road.

5.2.4.3 Option S2B follows a similar alignment to Option S2A as far as the catchwater. South of the catchwater, Option S2B follows a different alignment down to South Lantau Road, although over similar terrain. Again, the risk from natural terrain hazards in this area is likely to be low, due to the protection afforded by the catchwater above. However, Option S2B does involve another loop-bend with a tall cut slope and long elevated structure above South Lantau Road.

5.2.4.4 Option S3 traverses the southeast and south facing slopes of Lantau Peak down to the catchwater. These slopes are generally less steep than those below Sunset Peak, and the initial geotechnical assessment identified relatively few natural terrain landslides in the area. However, it is most likely that there are some, and that some form of mitigation would be required, including the use of elevated structure to cross the drainage valleys. South of the catchwater, the risk from natural terrain hazards is likely to be low, due to the protection afforded by the catchwater above. However, similar to Option S2B, Option S3 involves a loop-bend with a tall cut slope and long elevated structure above South Lantau Road.

5.2.4.5 The natural terrain hazards and geotechnical works associated with the southern alignment options are summarised in Table 5.1 below.

Table 5.1: Southern Alignment Options – Natural Terrain Hazards and Geotechnical Works

Alignment Option	Natural Terrain Hazards ⁽¹⁾		Geotechnical Works
Alignment Option	Landslip Risk	Boulder Fall Risk	Approx. Length of Road (m)	Length of Slopes >8m High (m)
S1 Above Catchwater	High	High	1,175	70
S1 Below Catchwater	Low	Low	685	0
S2A/B Above Catchwater	Medium- High	Medium-High	1,275	130
S2A Below Catchwater	Low	Medium-High	1,100	80
S2B Below Catchwater	Low	Medium-High	1,645	240
S3 Above Catchwater	Medium-High	Medium-High	1,160	150
S3 Below Catchwater	Low	Medium-High	1,245	260

Notes: (1) The terms used under “Natural Terrain Hazards” are qualitative and meant for comparison only.

5.2.4.6 Table 5.1 shows that the hazards posed by the natural terrain lessen further south. This is due partly to the gentler topography and also because the catchwater offers some protection from landslips to the sections of road below the catchwater. Option S1 is considered to have the highest susceptibility to natural terrain hazards, but it is likely that these could be largely mitigated against if elevated structures are used to cross the stream courses. Option S1 also requires the least geotechnical works overall, due to the good fit of the alignment into the topography. Option S3, on the other hand, requires the most geotechnical works and is susceptible to natural terrain hazards from the slopes of Lantau Peak. Based on the above, the southern alignment options were ranked as follows:

1st Option S1

2nd Option S2A

3rd Option S2B

4th Option S3

5.2.5 Highway Structures

5.2.5.1 As discussed in Section 4 of the appendix, elevated structures are required where the alignment options traverse stream courses and side valleys. The number of elevated structures and the aggregate length of elevated structure for each southern alignment option are summarised in Table 5.2 below.

Table 5.2: Southern Alignment Options – Highway Structures

Alignment Option	No. of Structures	Aggregate Length (m)	Aggregate Area (m²)
S1	9	460	5,400
S2A	11	475	5,570
S2B	13	630	7,390
S3	10	515	6,040

5.2.5.2 The options with loop-bends, including Options S2A, S2B and S3, require both relatively long and tall structures where the alignment moves away from the hillside as it loops back on itself. These structures would be particularly difficult to construct on this Project given the restricted site access and working space. Based on the above, the southern alignment options were ranked as follows:

1st Option S1

2nd Option S2A

3rd Option S3

4th Option S2B

5.2.6 Drainage Impacts

5.2.6.1 As discussed in Section 4 of the appendix, it is anticipated that the impacts of the Project on the existing drainage systems will be relatively small. The alignment options generally pass along side sloping ground and cross any stream course on elevated structure. Most of the streams comprise upper tributaries to the main streams below the Project, and as such their catchments are relatively small. It is therefore unlikely that the Project as a whole will have any significant impacts on the existing drainage regimes. This is particularly so in South Lantau, where significantly fewer diversions will be required compared to the northern alignment options. The number of stream crossings, culverts and diversions required for each southern alignment option is summarised in Table 5.3 below.

Table 5.3: Southern Alignment Options – Stream Crossings, Culverts and Diversions

Alignment Option	No. of Stream Crossings ⁽¹⁾	No. of Culverts	No. of Diversions
S1	9	3	1
S2A	11	10	3
S2B	13	11	3
S3	10	4	2

Notes: (1) Elevated highway structure

5.2.6.2 Based on the above, the southern alignment options were ranked as follows:

1st Option S1

2nd Option S3

3rd Option S2A

4th Option S2B

5.2.7 Impacts on Utilities

5.2.7.1 In the vicinity of the southern alignment options, the existing services are generally confined to the existing road, WSD’s facilities, South Lantau Road and the various developments adjacent to South Lantau Road. The only services affected by the southern alignment options are the CLP 11 kV and 33 kV overhead cables. These are the same cables affected by the northern alignment options, and similarly will require temporary diversions where intersected by the Project. Again, this is considered to be the only significant diversionary work required. Option S2A also affects a low voltage overhead cable. The number of diversions required for each southern alignment option is summarised in Table 5.4 below.

Table 5.4: Southern Alignment Options – CLP Overhead Cable Diversions

Alignment Option	No. of LV Overhead Cable Crossing Locations	No. of 11 kV Overhead Cable Crossing Locations	No. of 33 kV Overhead Cable Crossing Locations	Total No. of Overhead Cable Crossing Locations
S1	0	0	1	1
S2A	1	1	2	4
S2B	0	1	2	3
S3	0	1	0	1

5.2.7.2 Based on the above, the southern alignment options were ranked as follows:

1st = Option S1

1st = Option S3

2nd Option S2B

3rd Option S2A

5.3 Environmental Comparison

5.3.1 Air Quality

5.3.1.1 As discussed in Section 4 of the appendix, representative air and noise sensitive receivers (SRs) have been identified in accordance with criteria set out in the Environmental Impact Assessment Ordinance (EIAO) and the Technical Memorandum on the Environmental Impact Assessment Process (TMEIA). SRs have been identified in an area 500 m either side of the proposed alignment options, and these are shown in Figures B5.1 to B5.4 and summarised in Table 5.5 below for South Lantau.

Table 5.5: South Lantau - Existing Representative Air and Noise Sensitive Receivers

Figure No.	SR Ref.	Address	No. of Floors	Distance From Road (m)	Description
Option S1
B5.1	SR11	74, Leyburn Villas	2	285	Residential
	SR12	12, Cheung Sha Sheung Tsuen	3	300	Residential
	SR13	32, Cheung Sha Sheung Tsuen	3	295	Residential
	SR14	31B, South Lantau Road	2	210	Residential
	SR15	Village House	2	170	Residential
	SR16	YWCA Youth Camp	1	96	Residential
	A2 ⁽¹⁾	Sport Ground of fire station	-	300	Recreation
Option S2A
B5.2	SR11	23, Tung Chung Road	1	30	Residential
	SR12	21, Butterfly Crest	2	140	Residential
	SR13	Former South Lantau Hospital Site	2	196	Residential
Option S2B
B5.3	SR11	23, Tung Chung Road	1	10	Residential
	SR12	21, Butterfly Crest	2	250	Residential
	SR13	Former South Lantau Hospital Site	2	180	Residential
	SR14	Village House	2	240	Residential
Option S3
B5.4	SR11	6J, Tong Fuk	3	90	Residential
	SR12	Village House	2	60	Residential
	SR13	Village House	2	80	Residential
	SR14	1, Tong Fuk	1	44	Residential
	SR15	Village House	1	20	Residential

Notes: (1) Air sensitive receiver only.

5.3.1.2 Options S1, S2A/B share the same alignment in the uplands above Cheung Sha Valley, and the only sensitive receivers that would be potentially affected by the construction and operation of the road in this area would be visitors to the Country Park. It is expected that the construction dust impacts would be localised around the works. Operational air quality impacts would also be expected to be insignificant. Walkers on the trails in the area will be the only sensitive receivers, and as they are transient in nature, significant impacts are not predicted from either alignment in this area.

5.3.1.3 Option S1 continues east and crosses the catchwater northeast of Leyburn Villas. This stretch of alignment down to South Lantau Road generally follows the topography and requires only minimal earthworks. Apart from the walkers along the catchwater, the majority of the other sensitive receivers, including Leyburn Villas and Cheung Sha Sheung Tsuen, are more than 300 m away from the alignment and also separated vertically by more than 100 m. The closest sensitive receiver will be the YWCA youth camp, which is about 100 m away from the point where Option S1 meets South Lantau Road. Given that the construction and operational impacts are expected to be local to within a few metres of the road and the overall distance of the sensitive receivers, significant impacts are not expected.

5.3.1.4 At the point where Options S1 and S2A/B split, Option S2A/B loops back in a substantial cutting to head west on a large elevated structure. Again, only transient sensitive receivers in the form of walkers along the catchwater have the potential to be affected in this area. Option S2A/B then splits into Options S2A and S2B, just after the alignment crosses the catchwater. Both of these alignments follow Chung Sha Valley, and the closest sensitive receivers are the residential properties around the former South Lantau Hospital. However, these are situated on the opposite side of the valley from the alignments, about 100 m away from Option S2A at its closest point. In both cases, the alignments are generally some distance from the sensitive receivers and significant impacts are not expected during either the construction or operational phase.

5.3.1.5 Option S3 passes down the western side of Cheung Sha Valley, and for the majority of its length does not pass close to any permanent sensitive receivers, although users of the trails in the area will be sensitive to short term impacts. As the alignment approaches South Lantau Road, it forms a large loop from west to east and passes within approximately 50 meters of the peripheral properties of Tong Fuk.

5.3.1.6 In all cases, proper site management and good construction practices should control any impacts from dust during the construction phase, and operational impacts are not expected to be significant. Thus, all southern options would be considered effectively equal from an air quality perspective, with Option S3 being marginally less preferred due to its proximity to Tong Fuk. Based on this the southern alignment options were ranked as follows:

1st = Option S1

1st = Option S2A

1st = Option S2B

2nd Option S3

5.3.2 Noise

5.3.2.1 Option S1 is largely located in the upland areas above Cheung Sha, and thus noise is only an issue for visitors to the trails in the area, particularly walkers along the catchwater. The closest sensitive receivers to this option are Leyburn Villas and Cheung Sha Sheung Tsuen, which are more than 300 m away from the alignment and also separated vertically by more than 100 m, and the YWCA youth camp, which is about 100 m away. Based on the horizontal and vertical distance from Option S1 to the majority of the sensitive receivers, significant impacts are not predicted during either the construction or operational phase. However, mitigation measures may be required to protect the youth camp.

5.3.2.2 Option S2A/B will only affect the transient visitors to the catchwater and trails much the same as Option S1. Once this alignment passes over the catchwater, however, Option S2A passes within 100 m of the residential properties around the former South Lantau Hospital. The properties, represented by SR15, are on the same level as the road on the other side of the valley, and would therefore have a direct view, from their upper floors particularly, of the road during both the construction and operational phases. This direct angle of view would increase the potential for noise impacts with no screening by the natural topography. Option S2B would be better in this respect, since it is farther than Option S2A.

5.3.2.3 Option S3 transects the western side of Cheung Sha Valley, and, besides visitors to the trails in the area, would not affect any sensitive receivers, until it passes close to the eastern side of Tong Fuk. Residential properties in this area are about 50 m from the alignment, with the alignment slightly up hill. Due to the relatively short distance from these properties, it is likely that they will be affected by noise during both the construction and operational phases of the Project.

5.3.2.4 The southern alignment options all affect visitors to the study area to about the same extent, but with the larger earthworks associated with Options S2A, S2B and S3 the construction impacts could be slightly longer term for these options. In respect of permanent sensitive receivers, Option S3 passes close to Tong Fuk, and has the greatest potential for noise impacts, and thus would be the least preferred. Option S1, on the other hand, affects the least number of sensitive receivers, with potentially only the YWCA youth camp requiring mitigation. Based on the above, the southern alignment options were ranked as follows:

1st = Option S1

1st = Option S2B

1st = Option S2A

2nd Option S3

5.3.3 Water Quality

5.3.3.1 The principal catchment in the study area drains naturally via the key watercourses of Cheung Sha Stream. However, much of the southern study area of hinterland forms part of the WSD water gathering ground, and water is collected in the catchwater, which runs east to west for much of the length of South Lantau and feeds Shek Pik Reservoir. This results in the majority of the watercourses below the catchwater having little or no flow, or in the case of Cheung Sha Stream, flow controlled via a weir at the junction of the existing Tung Chung Road.

5.3.3.2 Recent surveys of Cheung Sha Stream have also yielded some seven fish species, with two species of Regional Concern (Fellowes et al., in prep) being encountered. The Black-headed Thick-lipped Goby (Awaous melanocephalus) was first recorded in Hong Kong in 1999 (Chan, 1999) and has been recorded in only three other sites in Hong Kong. It is of high conservation value. The Philippine Neon Goby (Stiphodon atropurpureus) was only very recently discovered in Hong Kong (ibid.), and is known to occur in only one other site locally. In addition, the majority of tributary streams are steep in the upland reaches and remain natural and unpolluted due to the lack of pollution sources.

5.3.3.3 In the upper reaches of Options S1 and S2, where they share a common alignment, the road largely crosses streams, which feed into the catchwater. This is largely the case for the full length of Option S1, with only a couple of streams bypassing the catchwater. For Options S2A and S2B, however, after crossing Cheung Sha Stream at the existing road bridge, the alignments cross one of the major tributaries of Cheung Sha Stream. Option S3 continues from tunnel Option N3 and runs down the western side of Cheung Sha Valley, and also crosses tributaries of Cheung Sha Stream in the upper reaches after exiting the tunnel and lower down near the catchwater before the weir.

5.3.3.4 As with the northern options, the streams crossed will either be done so on elevated structure or will need to be culverted or diverted, depending on the level difference. The majority of streams crossed by Options S1 and S3 are traversed by bridge, with only three culverts and one diversion required for Option S1 and four culverts and two diversions required for Option S3. In contrast, Options S2A and S2B will need ten and eleven culverts respectively and also three diversions each. Thus, the direct impacts on the streams for Options S1 and S3 will be less than the other two options, although some of the streams affected by culverting or diversion works for Option S3 are tributaries of Cheung Sha Stream.

5.3.3.5 In terms of earthworks, Option S1 has notably the least requirement as the alignment largely follows the topography across the western hillside. As a result, not only is the potential for runoff much less than the other options, but the majority of the streams in this area drain into the catchwater, and thus no significant downstream effects will occur. In contrast, Options S2A, S2B and particularly Option S3 will require large cuttings largely associated with the large loop-bends incorporated into their alignments. In addition, these large earthworks are to be undertaken in steep terrain, which will exasperate the control of runoff, and within Cheung Sha Valley, which increases the potential for impacts on Cheung Sha Stream.

5.3.3.6 During the operational phase, a special pipeline will be integrated into the new road to carry all road runoff to an offshore discharge point, as discussed in Section 4 of the appendix. In respect of Options S2A, S2B and S3, discharge would be required in the vicinity of the gazetted Cheung Sha Beach. However, the precedent in other highway projects is that the authorities require that any discharge be made at least 100 m away from the boundary of any gazetted beach. In order to achieve this in this location, due to the constraint of only a 120 m area of non-restricted foreshore before the start of the next gazetted beach at Tong Fuk, it will be necessary to discharge the road run-off via a submarine outfall. During the construction phase this will cause disruption to the beach as the outfall is built.

5.3.3.7 In respect of Option S1, the carrier pipe will be extended, either as a pipe or open stepped channel approximately 200 m from South Lantau Road, down the slope to the coast, to discharge at the foreshore east of Cheung Sha Sheung Tsuen. Besides the required clearance a small swathe of woodland, the discharge would not impact on any gazetted beach.

5.3.3.8 Based on the above, Option S1 presents the most favoured option, benefiting from limited earthworks, few culverts and diversions and avoidance of both Cheung Sha Stream as far as possible as well as the gazetted Cheung Sha Beach. Option S2A is marginally preferable than Option S2B due to the slightly less earthworks quantities required and the fewer numbers of culverts required. However, the impacts associated with these options on Cheung Sha Stream and Cheung Sha Beach would be expected to be similar. Option S3 would be similar to Option S2B, as while this option has the largest amount of earthworks by far and therefore has the greatest potential for indirect effects on Cheung Sha Stream, the number of culverts required is minimal compared to Options S2A and S2B. Based on the above, the southern alignment options were ranked as follows:

1st Option S1

2nd Option S2A

3rd = Option S2B

3rd = Option S3

5.3.4 Construction Waste

5.3.4.1 As discussed in Section 4 of the appendix, the largest portion of construction waste on this Project will be surplus excavated material. The amount of surplus excavated material for each southern alignment option is summarised in Table 5.6 below.

Table 5.6: Southern Alignment Options – Surplus Excavated Material

Alignment Option	Cut (m³)	Fill (m³)	Surplus (m³)
S1	26,520	13,010	13,510
S2A	74,208	8,820	65,388
S2B	101,400	18,680	82,720
S3	160,800	11,930	148,870

5.3.4.2 Option S1 generally follows the topography down the hillside all the way to South Lantau Road, and this is reflected in the small quantities of both cut and fill required. The other three options all require significant earthworks associated with in part the large loop-bends in their alignments. The preferred option from a waste management perspective is the one that requires the minimal amount of material handling and has the smallest surplus for disposal. The southern alignment options were thus ranked as follows:

1st Option S1

2nd Option S2A

3rd Option S2B

4th Option S3

5.3.5 Ecology

5.3.5.1 Habitats in the southern study area comprise mainly plantation forest, dense tall shrubland and a mosaic of shrubland composed with fern, grass and dwarf shrub. In addition, several natural stream courses could also be potentially affected, including Cheung Sha Stream and its tributaries. Option S1 results in the least overall habitat loss (4.85 ha), followed by Option S2A (5.66 ha), Option S2B (7.76 ha) and Option S3 (9.23 ha). The overall habitat lost that is of any real value (ie, shrub, tall shrub and secondary woodland) is greatest for Option S3, with 6.74 ha of shrub, tall shrub and secondary woodland being affected. This habitat is also considered to be highly natural and of high value. This compares with 5.45 ha, 3.94 ha and 2.68 for Options S2B, S2A and S1 respectively.

5.3.5.2 Conducting an assessment of the preferred alignment option based on faunal characteristics is not entirely recommended as many of the fauna are mobile and may incur fewer impacts than habitat types as they can migrate. Nonetheless, based on faunal characters, Option S3 appears to hold some of the highest value habitat for birds, herpetofauna and dragonflies. Conversely, Options S2A and S2B provided the best habitat for fish species of high conservation interest. Option S1 was the poorest area for birds, fish and dragonflies. The preferred option based on overall faunal components present is similar to that of the habitat evaluation with S1 providing the most preferred option.

5.3.5.3 In respect of impacts on the streams in the area, Option S1 will be furthest away from Cheung Sha Stream and its tributaries. Construction runoff associated with this alignment will also be retained by the catchwater and can be prevented from entering the watercourses down stream from this. Also Option S1 has by far the least amount of earthworks and therefore the least potential for construction runoff. All the other options will have to cross the tributaries of the Cheung Sha Stream, and all works will be undertaken in the catchment of this stream. The earthworks are more significant also, particularly for S3 and this means that there is more potential to affect higher quality watercourses than for Option S1.

5.3.5.4 Thus, regarding the potential ecological impact resulting from the various alignment options from a habitat perspective, the preferred option based on the quality and size of the habitat types to be affected, would, therefore, be Option S1. In order of preference, the alignment option based on habitats would be Option S1, S2A, S2B and S3. The southern alignment options were thus ranked as follows:

1st Option S1

2nd Option S2A

3rd Option S2B

4th Option S3

5.3.6 Landscape and Visual

5.3.6.1 The issues that influence the potential landscape and visual impacts were discussed in Section 4 of the appendix, together with the landscape character and sensitive receptors in the vicinity of the Project.

5.3.6.2 Option S1 follows the eastern slopes of Cheung Sha Valley, and in this regard is very sensitive to topography, resulting in less cut/fill slopes than any of the southern alignment options. This is particularly the case over its southern section, where mitigation screen planting will be very effective. Despite this, the alignment will still result in landscape and visual impacts from cut slopes over its northern sections (as will all southern alignment options) and will require fill slopes or bridge structures over the central part of the alignment. The alignment mainly affects grassland, shrub and plantation woodland. Although Option S1 goes significantly “off-line” from the existing Tung Chung Road, the topographic sensitivity of the alignment and relatively limited extent of cut slopes mean that impacts on landscape character will be limited. A photomontage of the alignment along the southern flanks of Sunset Peak is presented in Figure B5.5. Option S1 may have limited visual impacts on users of the YWCA youth camp, which other options will not have, and will be more visible to residents of Cheung Sha Sheung Tsuen than other alignment options. Visual receivers affected by this option will include:

· Residents in Cheung Sha Ha Tsuen

· Residents of Cheung Sha Sheung Tsuen

· Residents of Leyburn Villas

· Residents around the old South Lantau Hospital

· Users of Cheung Sha Beach

· Users of Lantau Country Parks facilities

· Hikers on Lantau Trail

· Hikers on South Lantau Catchwater

· Cheung Sha YMCA Youth Camp

· Travellers on Aircraft

· Travellers on Macau Ferries

· Those in vessels off the South Lantau Coast

· Users of Tung Chung Road

· Users of South Lantau Road

5.3.6.3 Option S2A/B follows the eastern slopes of the upper Cheung Sha Valley, before turning abruptly to cut across the valley on tall, elevated structure. Impacts on topography and landscape character resulting from this change in direction and from the crossing of the valley are likely to be significant. Whilst impacts resulting from potential cut/fill slopes are significant over the northern part of the alignment, over the southern part, they will be much more limited. Option S2A/B will also result in impacts on grassland, shrub, plantation woodland and secondary woodland, the latter being of particularly high landscape sensitivity. A photomontage of the alignment along the southern flanks of Sunset Peak is presented in Figure B5.6. This option also crosses Cheung Sha Stream, with potentially significant landscape impacts on both stream course and riparian vegetation. The extensive slope works, tall, elevated structure and crossing of Cheung Sha Valley mean that impacts on landscape character and on visual receivers from this option are expected to be significant.

5.3.6.4 After crossing Cheung Sha Stream, Option S2A follows the existing Tung Chung Road, before turning west to join South Lantau Road. Option S2A follows the existing road and topography reasonably closely, avoiding the need for extensive cut/fill slopes and elevated structure, and limiting the extent of the new “transportation corridor”. This option passes through areas of grassland and shrub. It also crosses a major tributary of Cheung Sha Stream, with potential for impacts on the stream course and riparian vegetation. Option S2A passes very close to visual receivers living around the former South Lantau Hospital, as well as to users of Cheung Sha Beach, which would result in significant visual impacts.

5.3.6.5 Option S2B follows the lower slopes of Lantau Peak, just below the catchwater, before turning abruptly east on tall, elevated structure to join South Lantau Road. At the point at which it turns, the alignment creates very extensive cut slopes, which will result in significant landscape and visual impacts. Option S2B passes through areas of shrub and secondary woodland, and because of the length of the alignment, it is likely to have greater landscape impacts than Option S2A. It also crosses a major tributary of Cheung Sha Stream, with potential impacts on the stream course and riparian vegetation. Option S2B goes further “off-line” than Option S2A, with potentially greater impacts on landscape character. Although it does not pass as close to sensitive visual receivers as Option S2A, its cut slopes are more extensive and therefore more visible, resulting in greater visual impacts. Users of Cheung Sha Beach will be particularly affected by the tall, elevated structure required at the southern end of Option S2B. Visual receivers affected by Options S2A and S2B will include:

· Residents around the old South Lantau Hospital

· Residents in Cheung Sha Ha Tsuen

· Residents of Cheung Sha Sheung Tsuen

· Residents of Leyburn Villas

· Residents of Tong Fuk (Option S2B only)

· Users of Cheung Sha Beach

· Users of Lantau Country Parks facilities

· Hikers on Lantau Trail

· Hikers on South Lantau Catchwater

· Travellers on Aircraft

· Travellers on Macau Ferries

· Those in vessels off the south Lantau Coast

· Users of Tung Chung Road

· Users of South Lantau Road

5.3.6.6 Option S3 follows the lower slopes of Lantau Peak to the west, falling gently before turning abruptly to the east on tall, elevated structure to join South Lantau Road, just east of Tong Fuk. Although the alignment does not cross Cheung Sha Valley, it results in extensive cut/fill slopes, with significant impacts on the topography of the area. This option also passes through grassland, shrub, plantation woodland and secondary woodland, with potentially significant landscape impacts. Because the alignment goes very notably “off-line” from the existing Tung Chung Road and because of its significant engineering works, it will introduce an extensive new human element into the natural landscape of South Lantau, with significant impacts on landscape character. Also, this alignment remains high on the foothills of Lantau Peak for a considerable distance, and thus will be highly visible across the South Lantau coast. In particular, the alignment will pass very close to Tong Fuk with significant visual impacts on residents there. Visual receivers affected by this option will include:

· Residents around the old South Lantau Hospital

· Residents in Cheung Sha Ha Tsuen

· Residents of Cheung Sha Sheung Tsuen

· Residents of Leyburn Villas

· Residents of Tong Fuk

· Users of Cheung Sha Beach

· Users of Lantau Country Parks facilities

· Hikers on Lantau Trail

· Hikers on South Lantau Catchwater

· Travellers on Aircraft

· Travellers on Macau Ferries

· Those in vessels off the south Lantau Coast

· Users of Tung Chung Road

· Users of South Lantau Road

5.3.6.7 Option S1 includes a bus-bus interchange north east of Cheung Sha Sheung Tsuen, at its junction with South Lantau Road. This will result in certain limited impacts on landscape resources. However, given the limited scale of the works, there will be no significant impacts on landscape character or visual receivers.

5.3.6.8 Options S2A, S2B and S3 include a bus-bus interchange at the western end of Cheung Sha Beach. Because of their small scale, these works will not result in significant impacts on landscape resources or landscape character. The interchange will be visible to users of Cheung Sha Beach and South Lantau Road. However, given the limited scale of the works, this will result in very limited visual impacts.

5.3.6.9 Of the southern alignment options, Option S1 is the most sensitive in terms of topography, resulting in only limited cut/fill slopes and/or elevated structure and is also preferable in that it does not cross Cheung Sha Valley. Similarly, Option S3 avoids the need to cross the valley, unlike Option S2A/B. The most extensive cut slopes are associated with Options S2B and S3, which will give rise to very significant landscape and visual impacts.

5.3.6.10 In terms of impacts on landscape character, Option S2A follows most closely the existing Tung Chung Road, whilst Options S1 and S3 deviate most significantly from it. However, the extensive slope works required under Options S2A, S2B and S3 mean that Option S1 will in fact have the least impact on landscape character, as it involves the fewest engineered elements, and will therefore contrast least with the existing natural qualities of the landscape.

5.3.6.11 In terms of visual impact, the extensive cut slopes arising from Options S2B and S3 will generate very significant visual impacts on residents and recreational users of South Lantau, especially in the case of Option S3, on residents of Tong Fuk and users of Cheung Sha Beach. Option S2A passes closer to sensitive visual receivers living around the former South Lantau Hospital than any other alignment, resulting in significant visual impacts. Option S1 will pass closer to Cheung Sha Sheung Tsuen, though the limited scale of engineering work required on this alignment will mean that visual impacts may be mitigated more easily.

5.3.6.12 In conclusion, of the southern alignment options, Option S1 is the most favoured option in terms of landscape and visual impact. This option avoids the creation of extensive cut/fill slopes and/or elevated structure required by other options as well as avoiding the need to cross Cheung Sha Valley, with potential impacts on the stream course and sensitive riparian secondary woodland. The next most favourable southern alignment option in terms of landscape and visual impact is Option S2A, followed by Option S3 and Option S2B respectively. The southern alignment options were thus ranked as follows:

1st Option S1

2nd Option S2A

3rd Option S3

4th Option S2B

5.3.7 Heritage

5.3.7.1 In South Lantau, the Cheung Sha area is rich in cultural heritage, and includes the following resources:

· historical buildings in the Cheung Sha Ha Tsuen and Cheung Sha Sheung Tsuen traditional;

· Cheung Sha archaeological site; and

· areas of archaeological potential on lower slopes to west of Cheung Sha close to the YWCA youth camp and on lower slopes of Cheung Sha Valley.

5.3.7.2 All of the southern alignment options are some distance from the Cheung Sha archaeological site, and thus no impacts are predicted. In addition, the alignment options to not pass close to the historic villages of Cheung Sha Ha Tsuen, Cheung Sha Sheung Tsuen or San Shek Wan, and thus no direct or indirect impacts on these villages are predicted. However, there is potential for the other cultural heritage resources to be affected by the southern alignment options.

5.3.7.3 Option S1 does not affect any cultural heritage resources above and immediately below the catchwater. However, as the alignment descends to intersect with South Lantau Road, it transects an area of archaeological potential in the foothills, resulting in direct impacts on this area. However, undertaking an archaeological excavation and rescue excavation, as required, could mitigate any impacts.

5.3.7.4 Similarly, Option S2A/B does not affect any cultural heritage resources above and immediately below the catchwater. However, both Options S2A and S2B will directly affect an area of archaeological potential in the lower Cheung Sha Valley, but, as with Option S1, any impacts could be mitigated by undertaking an archaeological excavation and rescue excavation, as required

5.3.7.5 Option S3 winds down the west side of Cheung Sha Valley generally in an area devoid of cultural heritage features. In the foothills, the alignment passes within 50 m of the eastern properties of Tong Fuk, and the construction works could result in indirect impacts on the village in this location.

5.3.7.6 It can be concluded that all the southern alignment options will result in some impacts. However, undertaking a field-testing programme can mitigate the direct impacts on the areas of archaeological interest associated with Options S1, S2A and S2B, and any indirect impacts on Tong Fuk can also be mitigated. Based on this, all southern alignment options are considered to be effectively equal from a cultural heritage perspective. The southern alignment options were thus ranked as follows:

1st = Option S1

1st = Option S2A

1st = Option S2B

1st = Option S3

5.3.8 Hazard to Life

5.3.8.1 As discussed in Section 4 of the appendix, Cheung Sha Water Treatment Works (WTW) presents a potential hazard to the potential population of the Project, specifically in terms of the handling and storing of chlorine, a highly toxic gas. However, only Options S1 and S2/S2A lie within 500 m of the WTW, and are thus relevant in terms of potential risk to the road population.

5.3.8.2 Option S1 runs along the hillside on the eastside of Cheung Sha Valley, and continues eastwards across the catchwater, before connecting with South Lantau Road. About 800 m of the road falls within a 500 m radius of the WTW. This section of road extends from NNW to ENE of the WTW, and is located between 80 to 150 m higher than the WTW.

5.3.8.3 Option S2 runs down the eastern hillside of Cheung Sha Valley and loops back, north of the catchwater, and runs westwards, before connecting with the existing road where it crosses the catchwater west of the WTW. From here, Option S2A runs south and west along the hillside at the mouth of the valley, before connecting with South Lantau Road near LCSD’s beach facilities on Cheung Sha Beach. About 1,600 m of the road falls within a 500 m radius of the WTW. This section of road extends from NNW to NE of the WTW, before looping back and ending SW of the WTW. The upper section of the road is located up to 150 m above the WTW, but the lower section extends some 50 m below the WTW.

5.3.8.4 Chlorine is a toxic gas utilised for sterilisation of drinking water. At Cheung Sha Water Treatment Works, it is stored in 50 kg cylinders. On flat terrain, if loss of containment occurs, chlorine gas would be blown downwind, and would be potentially fatal if inhaled. The gas concentration reduces with distance, and the dispersion characteristics vary depending on the nature of the release, weather conditions, nature of the terrain, obstacles etc. The distance to “safe” concentrations for the small storage like this would most likely be in the range of 100 m to 500 m.

5.3.8.5 In this instance, the WTW and the roads are located on a hillside, and because chlorine gas is heavier than air, it is influenced by gravity, and will have a tendency to drift downhill. Only if the wind is strong enough to counteract this effect, could the gas be blown uphill.

5.3.8.6 In wind tunnel and Computational Fluid Dynamics (CFD) tests, there is significant influence from complex terrain and buildings on the downwind hazard range, and also the width and direction of the cloud. The effects observed are:

· diversion of dense clouds by slopes or large buildings;

· channelling of clouds along valleys or cuttings;

· entrapment of releases within the wake zone on the lee side of hills;

· preferential flow of dense gases down-slopes (including upwind flow); and

· lateral spreading of dense gas clouds at the foot of up-slopes.

5.3.8.7 From an experiment of two complex terrain sites, the lethal dose contours of 3% fatality (LD03), the maximum extent for continuous release of 1.4 kg/s (corresponding to a liquid release from full bore failure of a 50 kg cylinder draw-off line) varies from <125 m for wind tunnel tests and 265 m for CFD calculations.

5.3.8.8 Table 5.7 below presents a comparison of the two relevant route options relating to the key issues affecting the risk to road users from chlorine releases at the WTW.

Table 5.7: Southern Alignment Options - Comparison of Risk Factors

Factor	Option S1	Option S2/S2A	Comment
Length of route within the hazardous zone (500 m)	800 m	1,600 m	S1 2 times “safer”
Wind direction to blow gas towards road	90 degrees (25%)	180 degrees (50%)	i.e. there is a 25% chance of the wind blowing towards S1. S1 is 2 times “safer”
Proximity to WTW (leak source)	Typically 300-400 m from WTW	Much closer – 150 m to 300 m from WTW.	This will make a big difference in the risk, since many of the potential gas clouds might reach S2A, but would not be large enough to reach S1. S1 much “safer”.
Valley “channelling”	-	-	Not an issue with respect to this comparison.
Elevation	-	-	Not a key issue in terms of the comparison. Both routes are mainly above the WTW.

5.3.8.9 Based on the above assessment, it is clear that Option S1 is preferable on the basis of risk. The most significant issue is the relative proximity of Option S2/S2A. It is difficult to quantify the magnitude of the difference in risk, but it would be at least a factor of five and more likely an order of magnitude or more.

5.3.8.10 In the absence of a detailed quantitative risk assessment, which would provide an understanding of the magnitude of the risk, it is not possible to state whether the risk to Option S2/S2A is unacceptable, and should significantly influence the selection of this alignment. If the risk is very low, even for Option S2A, then the conclusion of increased risk over Option S1 might not be overly important, and the adoption of Option S2A may be perfectly acceptable, even though the risk is higher. Based on the above, the southern alignment options were ranked as follows:

1st Option S3

2nd Option S1

3rd Option S2B

4th Option S2A

5.4 Land Use Criteria

5.4.1 Impacts on Country Park

5.4.1.1 The impacts of the alignment options on the Country Park have been estimated in terms of the land requirements from the park and the impacts on the recreational facilities in the park of each option. The impacts are summarised in Table 5.8 below.

Table 5.8: Southern Alignment Options – Impacts on Country Park

Alignment Option	Area of Affected Country Park (ha)	Impacts on Country Park Recreational Facilities
S1	2.29	No perceived impacts on recreational facilities
S2A	3.60	Picnic site at catchwater affected
S2B	3.60	Picnic site at catchwater affected Pavilion at South Lantau Road affected
S3	5.09	No perceived impacts on recreational facilities

5.4.1.2 Based on the above, the southern alignment options were ranked as follows:

1st Option S1

2nd Option S2A

3rd Option S2B

4th Option S3

5.4.2 Impacts on Private Land, etc

5.4.2.1 As discussed in Section 4 of the appendix, the impacts of the alignment options on private land, sale sites, permanent and temporary government land allocations, short-term tenancies and government land licenses have been assessed in terms of the land requirements of each option. In South Lantau, most of these lands are located in the village areas and residential developments along South Lantau Road. The impacts are summarised in Table 5.9 below. All options also affect the water‑gathering grounds above the catchwater.

Table 5.9: Southern Alignment Options – Impacts on Private Land, etc

Alignment Option	Summary of Impacts
S1	Private land: 717 m² of Lot 727 in DD332L Sale site: 621 m² of Lots 711, 721, 724 & 726 in DD332 Government land licence: 5,724 m² of No. 0467GLL
S2A	Gazetted beach: 797 m² of Cheung Sha Beach No. NT86-DA Government land licence: Nos. W10411/1, W10411/2 and W10410/1B
S2B	Gazetted beach: 797 m² of Cheung Sha Beach No. NT86-DA Government land allocation: 1,179 m² of GLA-IS 241 2,028 m² of GLA-TIS 54/CGS/59 Government land licence: Nos. W10411/1, W10411/2 and W10410/1B Land feature: No. NT179
S3	Government land allocation: 559 m² of GLA-IS-259 No. DLO/IS 203/CMS/59 Government land licence: 983 m² of No. 5289GLL Nos. W10410/1B, W10411/1 and CX1174

5.4.2.2 Option S1 is the only southern option to impact on private land. It also impacts on a government sale site. Options S2A and S2B both impact on Cheung Sha Beach, in so far as the associated bus-bus interchange requires some land from the back of the beach between the beach and South Lantau Road. Option S3 apparently has the least impacts on private land, etc. On this basis, the southern alignment options were ranked as follows:

1st Option S3

2nd Option S2A

3rd Option S2B

4th Option S1

5.4.3 Impacts on Burial Grounds and Fung Shui

5.4.3.1 In South Lantau, only Burial Ground No. 48 is affected by Option S3, which requires about 3,000 m² of the ground. Options S1, S2A and S2B affect neither any burial ground nor any individual graves, based, on the fieldwork undertaken to date. Furthermore, it is not anticipated that there would be any Fung Shui problems associated with the southern alignments passing between the mountains and the village areas. Based on the above, the southern alignment options were ranked as follows:

1st = Option S1

1st = Option S2A

1st = Option S2B

2nd Option S3

5.5 Costs and Programme Criteria

5.5.1 Capital Costs

5.5.1.1 As discussed in Section 4 of the appendix, the capital cost base estimate has been calculated for each alignment option, based on August 2001 prices. The estimates are exclusive of preliminaries, design and related services and contract and project contingencies. The base estimates for the southern alignment options are presented in Table 5.10 at the end of this section and summarised in Table 5.11 below.

Table 5.11: Southern Alignment Options – Summary of Capital Cost Base Estimates (August 2001)

Alignment Option	Cost ($)
S1	167,709,600
S2A	201,194,480
S2B	255,292,140
S3	240,946,470

5.5.1.2 Based on a comparison of the capital cost base estimates, the southern alignment options were ranked as follows:

1st Option S1

2nd Option S2A

3rd Option S3

4th Option S2B

5.5.2 Recurrent Costs

5.5.2.1 The recurrent cost estimate has been calculated for each alignment option. It should be pointed out that the estimates are preliminary and for assessment purposes only at this stage. The recurrent cost estimate for the Project will be thoroughly reviewed on selection of the preferred alignment option. The recurrent cost estimates for the southern alignment options are presented in Table 5.12 at the end of this section and summarised in Table 5.13 below.

Table 5.13: Southern Alignment Options – Summary of Annual Recurrent Cost Estimates

Alignment Option	Cost ($)
S1	1,079,491
S2A	1,559,741
S2B	2,025,379
S3	2,030,624

5.5.2.2 Based on a comparison of the recurrent cost estimates, the southern alignment options were ranked as follows:

1st Option S1

2nd Option S2A

3rd Option S3

4th Option S2B

5.5.3 Time for Construction

5.5.2.3 The time required for the construction of the southern alignment options depends mainly on the amount of earthworks and bridge construction associated with each option. Option S1 has the least earthworks and aggregate length of bridge structure, and also avoids the relatively large structures associated with the loop-bends of the other options, and would therefore require the least time for construction. Option S3, on the other hand, has the most earthworks, and Option S2B has the most bridge works, including two large structures at its loop-bends. Based on this, the southern alignment options were ranked as follows:

1st Option S1

2nd Option S2A

3rd = Option S2B

3rd = Option S3

5.6 Option Assessment and Sensitivity Testing

5.6.1 The assessment of the alignment options and sensitivity testing of the results are presented in Tables 5.14 to 5.23 at the end of this section. Table 5.23, which summarises the assessment and sensitivity testing, is repeated below. The highest score per set is underlined.

Table 5.23: Southern Alignment Options – Summary of Assessment Results

Set	Option S1	Option S2A	Option S2B	Option S3
Base Set A	97.75	78.80	58.25	59.65
Test Set B	98.40	77.20	56.80	60.40
Test Set C	98.20	79.20	59.40	59.00
Test Set D	96.00	79.80	60.40	59.60
Test Set E	98.40	79.00	56.40	59.60

5.6.2 Based on the scores presented in Table 5.23, the options have been ranked as presented in Table 5.24 below.

Table 5.24: Southern Alignment Options – Overall Ranking

Set	Option S1	Option S2A	Option S2B	Option S3
Base Set A	1st	2nd	4th	3rd
Test Set B	1st	2nd	4th	3rd
Test Set C	1st	2nd	3rd	4th
Test Set D	1st	2nd	3rd	4th
Test Set E	1st	2nd	4th	3rd

5.6.3 Of the southern alignment options, Option S1 was the clear winner, scoring the highest marks for all criteria, and consequently the highest marks overall in the base set and all test sets, and was therefore recommended as the preferred southern alignment option.

6 INVESTIGATION OF THE OBSOLETE SECTIONS OF OLD ROAD

6.1 General

6.1.1 The Assignment Brief required the Consultants to investigate all possible future usage of the existing sections of Tung Chung Road that will be made obsolete by the construction of the new road. The possible future usage may include but not be limited to:

· using the obsolete sections for one-way traffic and the new road for the other way traffic;

· using the obsolete sections as an emergency vehicular access and emergency diversion route;

· using the obsolete sections as a walking trail or cycle track;

· using the obsolete sections to accommodate the utility services; and

· demolishing the obsolete sections and converting them to landscape areas.

6.1.2 In addition, the Brief states that any slope stabilisation works required to natural and manmade slopes, which would affect or be affected by the obsolete sections as well as the new road shall from part of the Project. The possible future usage of the obsolete sections is discussed below.

6.2 One-Way Traffic

6.2.1 As discussed in Section 2 of the appendix, it has been suggested that the obsolete sections of the old road could be used for one-way traffic in the uphill direction and the new road for one-way traffic in the opposite downhill direction to minimise the new roadworks and hence the construction cost and environmental impacts of the Project. This is only possible where the uphill section of the existing road is on the left-hand side of the downhill section of the new road to avoid traffic having to cross over where the roads merge/ diverge. The only location where this occurs is between the crest and the catchwater in Option S2A/B.

6.2.2 To investigate the possibility of using the old road in the uphill direction and the new road in the downhill direction, a number of scenarios have been developed based on Option S2A/B to allow a comparison to be made between the one-way and two-way modes of operation. The scenarios include the following possible alignment combinations:

· Option N1/2 combined with Option S2A/B, as shown on Drawing No. 90803/OW/001;

· Option N3 combined with Option S2A/B, as shown on Drawing Nos. 90803/OW/002 and 003; and

· Option N4 combined with Option S2A/B, as shown on Drawing Nos. 90803/OW/004 and 005.

6.2.3 The one-way traffic scenarios have been developed to the same level of detail as the two‑way traffic alignment options, in so far as they include retaining walls, elevated structures, verges, footways, haul roads and working space to better define the extent and impacts of the works.

6.2.4 On the surface, it might appear reasonable to expect that the one-way traffic scenarios would offer a saving in construction works of approximately half that required for the corresponding two-way traffic options. However, this is not the case for the overland scenarios, for which the minimum permissible one-way traffic carriageway width is as wide as 6 m, which is only 1.3 m less than the two-way traffic carriageway width of 7.3 m, to cater for vehicle breakdown and emergency vehicle access.

6.2.5 The difference in the widths of the carriageway for either scenario appears even smaller on consideration of the overall width of the highway, because the widths of the footways, verges, earthworks and working space are generally similar for either scenario. The relative smallness of the difference is demonstrated in Table 6.1 below.

Table 6.1: Comparison of Construction Widths for One-Way and Two-Way Traffic Scenarios

Scenario	Width (mm)
Scenario	Working Space	Footway	Carriageway	Verge	Working Space	Total ⁽¹⁾
Two-Way	3,000	1,600	7,300	1,250	3,000	16,150
One-Way	3,000	1,600	6,000	1,250	3,000	14,850

Notes: (1) Excluding width of earthworks, which vary along length of highway.

6.2.6 From Table 6.1, the actual saving in the overall construction width would only amount to about 8% for the one-way traffic overland scenarios, exclusive of any earthworks.

6.2.7 The situation is different though for the one-way traffic tunnel scenarios. For the two-way traffic tunnels, twin tubes with two lanes in each tube are required for traffic safety and operational reasons to permit unimpeded access for emergency services in the event of accident or breakdown. This is not the case for the one-way traffic tunnels, which only require a single tube with a 6.75 m wide carriageway. As such, the saving in construction works would not be insignificant for the one-way traffic tunnels compared to the two-way traffic tunnels.

6.2.8 To better understand the magnitude of the saving in construction works offered by the one-way traffic scenarios, the capital cost base estimates have been calculated for three of the possible alignment combinations given above. The base estimates are current for August 2001, and are exclusive of preliminaries design and related services and contract and project contingencies. The component base estimates for the one-way traffic scenarios based on Options N1, N3, N4 and S2A are presented in Table 6.2 at the end of this section, and the combined base estimates for the three possible combinations of these options are summarised in Table 6.3 below. Table 6.3 also includes the base estimates for the corresponding two-way traffic scenarios for comparison.

Table 6.3: Comparison of Capital Cost Base Estimates (August 2001) for One‑Way and Two-Way Traffic Scenarios

Alignment Combination	Cost ($)
Alignment Combination	Two-Way ⁽¹⁾	One-Way ⁽²⁾
N1/S2A	345,962,160	317,115,440
N3/S2A	1,085,050,090	755,178,410
N4/S2A	1,231,297,560	824,024,810

Notes: (1) Summation of estimates from Tables 4.10/11 and 5.10/11.

(2) Summation of estimates from Table 6.2.

6.2.9 From table 6.3, it is apparent that the one-way traffic tunnel scenarios would cost about 30% (N3/S2A) to 33% (N4/S2A) less than the equivalent two-way traffic tunnel scenarios. However, the one-way traffic overland scenarios would cost only about 8% (N1/S2A) less than the two-way traffic overland scenarios. Furthermore, when the section of on-line widening is taken into account, the overall cost saving to the Project would only amount to about 6%. It is thus evident that the one-way traffic scenario would offer no significant cost advantage to the preferred overland solution for the Project.

6.2.10 From an environmental perspective, the only real advantage of key significance would be the reduction in impacts on the adjacent habitats. Since the one-way traffic scenarios lie wholly within the Country Park, any reduction in impacts offered by the one-way traffic scenarios can be estimated by comparing the land requirements from the Country Park of both scenarios. The component land requirements for the one-way traffic scenarios based on Options N1, N3, N4 and S2A are presented in Table 6.4 below, and the combined land requirements for the three possible combinations of these options are summarised in Table 6.5 below. Table 6.5 also includes the land requirements for the corresponding two-way traffic scenarios for comparison.

Table 6.4: One-Way Traffic Scenarios – Impacts on Country Park

Alignment Option	Area of Affected Country Park (ha)
N1	5.10
N3	4.62
N4	3.91
S2A	3.02

Table 6.5: Comparison of Impacts on Country Park for One-Way and Two‑Way Traffic Scenarios

Alignment Combination	Area of Affected Country Park (ha)
Alignment Combination	Two-Way ⁽¹⁾	One Way ⁽²⁾
N1/S2A	8.75	8.12
N3/S2A	8.85	7.64
N4/S2A	8.00	6.93

Notes: (1) Summation of estimates from Tables 4.7 and 5.8.

(2) Summation of estimates from Table 6.4.

6.2.11 From Table 6.5, it is apparent that the one-way traffic tunnel scenarios would affect about 14% (N3/S2A) to 13 % (N4/S2A) less Country Park than the equivalent two‑way traffic tunnel scenarios. However, the one-way traffic overland scenarios would affect only about 7% (N1/S2A) less Country Park than the two-way traffic overland scenarios. It is thus evident that the one-way traffic scenario would not affect significantly less County Park, and thereby habitat, than the preferred two-way traffic overland solution for the Project.

6.2.12 Based on the above, it is clear that using the obsolete sections of the old road for one-way traffic in the uphill direction and the new road for one-way traffic in the downhill direction would offer no significant saving in either the construction costs or the environmental impacts.

6.2.13 Notwithstanding the above, the section of obsolete road between the crest and the catchwater comprises some of the most dangerous sections of the existing road, with gradients as steep as 20% and numerous hairpin bends, as discussed in Section 2 of the appendix. Even if this section of road were used for traffic in the uphill direction only, it would still comprise a hazard to motorists, and be especially dangerous for heavy goods vehicles and buses in the event of stalling or at worst brake failure. In this respect, it is most likely that Government would be criticised for not providing a “sensible” or “proper” solution. Thus, using the obsolete sections of the old road for one-way traffic is not recommended.

6.3 Emergency Vehicular Access and Emergency Diversion Route

6.3.1 Transport Department (TD) has requested that the obsolete sections of the old road be used as an emergency vehicular access and an emergency diversion route in the event of an accident on the new road. This request is fully supported, since the new road, although a significant improvement on the old road, is still relatively steep in sections. Furthermore, there are no alternative means of vehicular access along the new road, other than the obsolete sections of old road. This situation is exacerbated the relatively long length of the road, and its remote rural setting. Thus, using the obsolete sections of the old road as an emergency vehicular access and an emergency diversion route is supported.

6.3.2 To enable the old road to be used as an emergency vehicular access and an emergency diversion route, sections of drop kerb would need to be installed along the paved verge of the new road where it intersects the old road. Emergency crash gates or cantilevered barriers would also be required to prevent unauthorised vehicular access to the old road.

6.4 Walking Trail or Cycle Track

6.4.1 Use of the old road as an emergency vehicular access and an emergency diversion route would only be required in the event of a serious accident leading to closure of the new road. It is obviously hoped that such events on Tung Chung Road will be few and far between after the completion of the new road. As such, it is considered that the old road could be used for other purposes as well. One such suggestion, made by the Country and Marine Parks Board (CMPB), is to use the road as a walking trail, and this suggestion is fully supported and compatible with the above usage. Clearly, in the rare event that vehicles are directed to use the old road, then walkers can simply restrict themselves to the existing paved verges along the road, if indeed they choose to walk along the road in the first place when the road is open to traffic.

6.4.2 It has also been suggested that the old road be used as a cycle track. However, given the extremely steep gradients and hairpin bends, this usage is considered unsafe, and is therefore not recommended, particularly given that the road will be shared by walkers. It could be argued that the cyclists could be segregated from the walkers by say a drop kerb or barrier, but then the road could not be used as an emergency vehicular access and an emergency diversion route in this case. Thus, using the obsolete sections of the old road as a walking trail is supported, but using the old road as a cycle track is not recommended.

6.5 Accommodation for Utility Services

6.5.1 The existing services currently run under the western verge of the existing road. Many of these services are in a delicate state, and there is little room for any new services. Therefore, along the on-line section of improvement works, any new utility services and services required to operate the new road would need to be accommodated under the eastern verge. Based on the requests of the utility authorities and the anticipated service requirements of the new road, it has been assessed that a 1.6 m wide grassed verge in addition to a 2.0 m wide footway will be required to accommodate all the new services. The services required to operate the new road would be laid under the footway, and the utility authorities would share the ground under the grassed verge.

6.5.2 To be able to omit the additional 1.6 m wide grassed verge from the off‑line sections of the new road and also reduce the width of the footway to 1.6 m, and hence reduce the impacts of the off-line sections, it is proposed that the utility authorities lay their new services under the obsolete sections of the old road, adjacent to their existing services. It would be acceptable to lay the new services under the old carriageway in this case, since the old road would be generally closed to traffic, as discussed above. Therefore any future excavation of the old carriageway to repair any new services would not cause any disruption to traffic, since this would be generally confined to the new road.

6.5.3 If the obsolete sections of the old road are to be used to accommodate the existing and proposed utility services, then it would be reasonable to expect that the utility authorities would require vehicular access along the old road from time to time to carry out maintenance work and emergency repairs. Such access could be controlled by Government to avoid any abuse of the old road. In this case, it would perhaps be more sensible therefore to install lockable-cantilevered barriers, instead of emergency crash gates, at the intersections between the new and old roads. This issue would need further investigation and discussion amongst the relevant government departments.

6.5.4 Granting limited vehicular access to the utility authorities should not interfere with the safe usage of the old road as a walking trail. The odd maintenance vehicle should not pose any danger to walkers. In the event that a maintenance vehicle does need to use the old road, walkers can simply restrict themselves to the existing paved verges along the road. There should be plenty of room to pass safely by. Thus based on the above, using the obsolete sections of the old road to accommodate the existing and proposed utility services is recommended, and considered compatible with usage of the old road as an emergency vehicular access, emergency diversion route and walking trail.

6.6 Landscape Areas

6.6.1 One suggestion is to demolish the obsolete sections of the old road, and landscape the area. On the surface, this option has its attractions, in so far as the old road would be “returned to nature”. However, there are numerous drawbacks. Firstly, one would lose the usage of the old road as an emergency vehicular access, emergency diversion route and walking trail (although the latter could be incorporated into the landscape areas). Secondly, one would lose the usage of the old road to accommodate the existing and proposed utility services. In this respect, what might be gained in returning the old road to nature would likely be lost in the additional construction width required for the new road to accommodate the services. New landscape areas would likely be gained at the expense of existing habitats.

6.6.2 There are also construction impacts to be considered. Landscaping the old sections of road would require considerable amounts of fill material to bury the old cut slopes, with a view to “blending” the landscape areas into the existing landscape. The earthworks associated with this task would have potential to affect Cheung Sha Stream through construction site runoff. Owing to the steep topography, there is also potential for the fill material to be washed out under heavy rainfall before any planting has had the opportunity to bind the new soil.

6.6.3 There are also potential geotechnical problems associated with the proposal. As discussed above, any slope stabilisation works required to the existing manmade slopes along the old road should from part of the Project. It is anticipated that many of the existing slopes will not meet current safety standards, and will hence require upgrading. Placing fill material in front of existing cut slopes is one method of increasing the stability of the slope. However, this raises the issue of maintenance. If the old road were landscaped with fill material, as discussed above, the landscape areas would not be level, since they would generally fall from the crest of the existing cut slopes to the opposite verge. As such, the landscaped areas would still be considered manmade slope features, which would require maintenance, and the maintenance authority would likely require vehicular access, which would defeat the object of landscaping the old road in the first place.

6.6.4 Based on the above discussion, converting the obsolete sections of the old road to landscape areas is not recommended. However, “greening” the existing slopes to be upgrade under the Project is recommended, in accordance with GEO Publication No. 1/2000, “Technical Guidelines on Landscape Treatment and Bio-Engineering for Man-Made Slopes and Retaining walls”.

6.7 Summary

6.7.1 The recommended future usage of the obsolete sections of the old road is summarised in Table 6.6 Below.

Table 6.6: Summary of Recommended Future Usage of Obsolete Sections of Old Road

Usage	Recommended (4 for Yes – 8for No)
One-way traffic	8
Emergency vehicle access	4
Emergency diversion route	4
Walking trail	4
Cycle track	8
Accommodation for Utility Services	4
Landscape areas	8 ⁽¹⁾

Notes: (1) However, “greening” of existing slopes to be upgrade under the Project is recommended.

7 CONCLUSIONS AND RECOMMENDATIONS

7.1 Conclusions

7.1.1 This appendix presents the results of the assessment of the possible alignment options. The assessment has taken account of all relevant factors, including engineering, environmental, land use and costs and programme criteria, and recommends a preferred alignment option, including location for the proposed bus-bus interchange, for the Project.

7.1.2 The assessment has been carried out by ranking the options for each criteria and assigning a score based on the ranking. The criteria have been weighted based on the relative importance of the criteria, and the robustness of the assessment has been tested by adjusting the weighting of the criteria.

7.1.3 The assessment was split into two parts, commencing with the assessment of the northern alignment options between Tai Tung Shan Service Reservoir and the crest at Pak Kung Au, and culminating in the assessment of the southern alignment options between the crest and South Lantau Road.

7.1.4 In the assessment of the northern alignment options, Option N1 scored the highest marks in the base test and all sensitivity tests, and in the assessment of the southern alignment options, Option S1 scored the highest marks in the base test and all sensitivity tests.

7.2 Recommendations

7.2.1 Based on the results of the assessment of the alignment options presented in this appendix, Option N1/S1 was recommended as the preferred alignment option for the Project. The recommendation was endorsed by the Steering Group for the Assignment at its meeting on 18 September 2001. The main advantages of Option N1/S1, compared to the other alignment options, are as follows:

· shortest overland route between Tung Chung and South Lantau Road, with gentle bends and no loop-bends;

· least amount of bridgeworks, earthworks and retaining walls, resulting in least amount of “muck shifting” and surplus excavated material;

· least potential to impact Tung Chung Stream and Cheung Sha Stream (alignment avoids Cheung Sha Stream as far as possible);

· least ecological impacts;

· least landscape and visual impacts for overland route;

· least impacts on Country Park for overland route; and

· least construction cost and shortest construction programme.

7.2.2 Based on Option N1/S1 being the preferred alignment option for the Project, the recommended location for the proposed bus-bus interchange is adjacent to the junction of Option N1/S1 and South Lantau Road near the YWCA youth camp at Cheung Sha Sheung Tsuen.

7.2.3 The following future usage is recommended for the sections of the existing Tung Chung Road made obsolete by the new road:

· as an emergency vehicle access and an emergency diversion route in the event of an accident on the new road;

· as a walking trail; and

· as accommodation for the existing and planned utility services.

7.2.4 Finally, it is also recommended that the existing manmade slopes along the obsolete sections of the old road, which are to be upgraded under the Project, are “greened” as far as possible to reduce the visual impacts of the old road and improve the local environment for walkers and other users of the County Park.