11. LANDSCAPE AND VISUAL IMPACT

11.1 Legislation and Standards

11.1.1.1 The landscape and visual impact assessments have been carried out in accordance with the guidelines contained in Annexes 10 and 18 of the Technical Memorandum on EIA Process. A general survey of the existing vegetation character and, in particular, the tree species within the proposed development 'footprint' has been carried out to assist with the landscape impact assessment. A detailed tree survey has not been carried out as part of the LVIA but would be a prerequisite to preparing detailed designs for the extension works and making formal application for tree felling or transplanting prior to construction work on site.

11.2 Assessment Methodology

11.2.1 Planning and Development Control Framework

11.2.1.1 A review of the relevant planning and development control framework has been carried out to ascertain the current and future committed development and associated sensitive receiver groups within the Study Area.

11.2.2 Landscape Impact Assessment Methodology

11.2.2.1 The assessment of the potential impacts of the proposed works on the existing landscape comprised two distinct sections as follows:
· Baseline survey; and
· Potential landscape impacts assessment.

11.2.2.2 A baseline survey of the existing landscape character and quality within a 500m radius of the proposed development has been undertaken by a combination of site inspections and desktop surveys. The impact assessment and associated mitigation works covers areas within permanent land take and temporary works / disturbed areas. The landscape elements considered include:

· Local topography
· Woodland and other vegetation types
· Built form, land use patterns of settlement
· Scenic spots
· Details of local materials, architectural styles and streetscapes
· Prominent watercourses
· Cultural and religious identity

11.2.2.3 In particular, an initial tree survey has been carried out to identify where the key woodland areas are located. This formed the basis of preliminary landscape design guidelines to assist the project team to fine-tune the alternative emergency bypass culvert alignments and STW expansion works away from the most sensitive areas, i.e. follow road alignments rather than crossing vegetated areas. Based on the refined / agreed alternative routes and works areas the data from the general tree survey have been used to quantify and indicate on plan the impact on the existing landscape resources. Where tree felling or transplanting is deemed necessary the report has included justification and compensatory planting proposals. The current government department jurisdiction for affected trees has been specified.

11.2.2.4 The landscape baseline survey formed the basis of the landscape context by describing broadly homogenous units of similar character (Landscape Character Units). These have been clearly indicated on plan. The landscape character has been rated into low, medium or high depending not only upon the quality of the landscape elements present but also according to their sensitivity to change and local or regional importance.

11.2.2.5 The assessment of the potential landscape impacts of the proposed development has resulted from:
· Identification of the sources and magnitude of impacts that would be generated during construction and operation.
· Identification of the principal landscape impacts, primarily in consideration of the degree of change to the baseline conditions.

11.2.2.6 Some common factors that have been considered in deriving the magnitude of change and sensitivity in assessing landscape impacts are as follows:
Factors affecting the magnitude of change:
· Compatibility of the project with the surrounding landscape
· Duration of impacts under construction and operation phases
· Scale of development
· Reversibility of change
Factors affecting the sensitivity:
· Quality of landscape character / resources
· Importance and rarity of special landscape elements
· Ability of the landscape to accommodate change
· Significance of the change in local and regional context
· Maturity of the landscape

11.2.2.7 The sensitivity / quality of the landscape has been assessed as follows:
· High: e.g. important components of a landscape of particularly distinctive character susceptible to relatively small changes
· Medium: e.g. a landscape of moderately valued characteristics reasonably tolerant to change
· Low: e.g. a relatively unimportant landscape able to absorb significant change

11.2.2.8 The magnitude of the change in the landscape has been classified as follows:
· Large: Notable change in the landscape characteristics over an extensive area ranging to very intensive change over a more limited area
· Intermediate: Moderate changes in a local area
· Small: Virtually imperceptible change in any components of the landscape
· Negligible: Indiscernible change to landscape characteristics

11.2.2.9 The degree of impact or significance threshold has been considered as follows:
Significant: adverse / beneficial impact where the proposal would cause significant deterioration or improvement in existing landscape quality
Moderate: adverse / beneficial impact where the proposal would cause a noticeable deterioration or improvement in existing landscape quality
Slight: adverse / beneficial impact where the proposal would cause a barely perceptible deterioration or improvement in the existing landscape quality
Negligible: no discernible change in the existing landscape quality

11.2.2.10 The analysis of the significance threshold for the landscape and visual impacts during construction and operation is presented in the following form of matrix:

Magnitude of Change Sensitivity / Quality
Low Medium High
Negligible Negligible Impact Negligible Impact Negligible Impact
Small Slight Impact Slight / Moderate Impact Moderate Impact
Intermediate Slight / Moderate Impact Moderate Impact Moderate / Significant Impact
Large Moderate Impact Moderate / Significant Impact Significant Impact

11.2.3 Visual Impact Assessment Methodology

11.2.3.1 Similar to the landscape impact assessment, the assessment of the potential visual impacts of the proposed works had two distinct stages as follows:
· Baseline survey
· Potential visual impact assessment

11.2.3.2 The baseline survey of views towards the proposed development has been carried out by identifying:
(1) The visual envelope (2km distance or defined by natural or manmade features) within which the proposed development may be contained whether wholly or partially within views, including indirect effects such as temporary contractor's works areas.
(2) The visually sensitive receivers (VSRs) within the visual envelope whose views will be affected by the scheme. The sensitivity of each VSR group is also influenced by the distance and direction of view to the proposed development. The potential receivers have been divided into three groups;
(a) Views from residences. This group is the most sensitive due to the high potential intrusion on the visual amenity and quality of life;
(b) Views from workplaces. This group including, e.g., schools, institutions and factories are less sensitive than (a) since visual amenity is less important within the work environment with less emphasis on external views.
(c) Views from public areas not included in (a) or (b). This group, e.g., public parks, footpaths, roads etc. Sensitivity of this group is relatively low and will depend on the transitory nature of the receiver with views being typically glimpsed rather than sustained for long periods.

11.2.3.3 The baseline survey describes and records by photograph typical views from within visual envelopes for low-level viewpoints (street level) and high level viewpoints (high-rise buildings or hillside vantage points). Both present and future VSRs have been considered, e.g. passengers on West Rail and users of the proposed Deep Bay Link.

11.2.3.4 The sensitivity of each receiver group and quality of views is based on the following:
· High: e.g. residential properties
· Medium: e.g. recreational facilities or partially screened views
· Low: e.g. workplaces, schools etc.

11.2.3.5 The assessment of potential visual impacts has resulted from the following:
· Identification of the sources of visual impacts and their magnitude that would be generated during construction and operation
· Identification of the principal visual impacts with particular consideration given to the degree of change to the baseline conditions

11.2.3.6 The impact assessment has compared the typical existing views identified in the baseline survey of the key receiver groups and the potential views after the proposed works are complete. Some typical factors affecting the magnitude of changes and sensitivity for assessing visual impacts included the following:
Factors affecting the magnitude of change:

· Compatibility of the project with the surrounding landscape
· Duration of impacts under construction and operation phases
· Scale of development
· Reversibility of change
· Viewing distance
· Potential blockage of view
Factors affecting the sensitivity of receivers:
· Value and quality of existing views
· Availability and amenity of alternative views
· Type and estimated number of receiver population
· Duration and frequency of view
· Degree of visibility

11.2.3.7 The magnitude of change to the views is classified as follows:
· Large: e.g. the majority of viewers affected / major changes in view
· Intermediate: e.g. many viewers affected / moderate change in view
· Small: e.g. few viewers affected / minor change in view
· Negligible: e.g. very few viewers affected / no discernible change in view

11.2.3.8 The degree of visual impact or significance threshold has been rated in a similar fashion to the landscape impact described above, i.e. significant, moderate, slight and negligible. The impacts may be beneficial or adverse.

11.2.4 Mitigation Measures

11.2.4.1 The identification of the landscape and visual impacts highlighted those sources of conflict requiring design solutions or modifications to reduce the impacts and, if possible, blend the development with the surrounding landscape. The proposed landscape mitigation measures are described and illustrated by means of site plans and simple photomontage and take into account factors including:
· Screen planting
· Transplanting of mature trees with good amenity value where appropriate
· Conservation of topsoil for reuse
· Sensitive alignment of box culverts to minimise disturbance to the surrounding vegetation
· Sensitive delineation of works areas to minimise impacts on surrounding vegetation
· Reinstatement of areas disturbed during construction
· The cumulative impacts of other development projects such as Deep Bay Link
· The design and finishes / colours of architectural features of the facilities in liaison with DSD
· Existing views, views with no mitigation, views with mitigation at day one of operation and 10 years after operation

11.2.5 Residual Impacts

11.2.5.1 Residual impacts are those impacts remaining after the proposed mitigation measures have been implemented. This is often 10 to 15 years after operation commences when the planting mitigation measures are deemed to have reached a level of maturity which allow them to perform their original design objectives.

11.2.5.2 The level of impact is derived from the magnitude of change which the proposals will cause to the view or landscape character which would have existed during this period if the proposed scheme had not been constructed and its ability to tolerate change, i.e. its quality and sensitivity taking into account the beneficial effects of the proposed mitigation. The significance threshold is derived from the matrix shown above.

11.2.5.3 The overall impact for the proposed works is defined as follows:

Beneficial Acceptable Acceptable with mitigation measures Unacceptable Undetermined
The impact is beneficial if the project will complement the landscape and visual character of its setting, will follow the relevant planning objectives and will improve overall and visual quality The impact is acceptable if the assessment indicates that there will be no significant effects on the landscape, no significant visual effects caused by the appearance of the project, or no interference with key views The impact is acceptable with mitigation measures if there will be some adverse effects, but these can be eliminated, reduced or offset to a large extent by specific measures The impact is unacceptable if the adverse effects are considered too excessive and are unable to mitigate practically The impact is undetermined if significant adverse effects are likely, but the extent to which they may occur or may be mitigated cannot be determined from the study. Further detailed study will be required for the specific effects in question

11.2.6 Funding, Implementation, Management and Maintenance

11.2.6.1 It is anticipated that initial funding and implementation will be by Drainage Services Department with LCSD responsible for the long-term management and maintenance of proposed transplanting and soft landscape works. An implementation programme for the landscape and visual mitigation measures shall be prepared as required by the TM of the EIAO.

11.2.6.2 The Works Bureau Technical Circular No. 14/2002 - Management and Maintenance of Natural Vegetation and Landscape Works, and Tree Preservation defines the management and maintenance responsibilities for natural vegetation and landscape works, including both softworks and hardworks, and the authorities for tree preservation and felling.

11.2.7 Photomontage Illustration

11.2.7.1 The existing conditions and effectiveness of the proposed impact mitigation proposals are illustrated by means of a set of photomontages comprising views of:
· The existing conditions
· Unmitigated impacts
· Partially mitigated impacts after implementation of the proposed mitigation measures at day one of the operation of the facility
· Residual impacts at year 10 of the facility operation

11.3 Review of Planning Development Control Framework

11.3.1.1 As indicated on the Draft Tin Shui Wai Outline Zoning Plan No. S/TSW/7, the proposed extension works at Ha Tsuen Pumping Station are contained within Area 3B zoned OU and allocated for waste water and sewerage treatment. As indicated on the Approved Ha Tsuen Outline Zoning Plan No. S/YL-HT/4 the proposed extension works at San Wai STW are contained within an area zoned 'Recreation' and 'G/IC'. Section 16 Planning Application is likely to be necessary for the expansion of San Wai STW. The expanded San Wai STW is included in the Recommended Outline Development Plan (RODP) of Hung Shui Kiu New Development Area (HSKNDA) that had brought to public consulation in late 1999 to early 2000.

11.3.1.2 Three key developments within the Study area have been noted regarding cumulative landscape and visual impacts and as a source of future VSRs, namely: West Rail which is currently under construction, the proposed Deep Bay Link currently under detailed design stage and the HSKNDA currently undergoing further study. For the HKSNDA reference has been made to the RODP of HSKNDA. To illustrate the cumulative impacts Figures 11.3 and 11.4 have incorporated these three developments for comparison with the proposed works at Ha Tsuen Pumping Station and San Wai STW Extension. The results are discussed in more detail in Section 11.5 below.

11.4 Assessment Results for Ha Tsuen Pumping Station

11.4.1 Existing Landscape and Visual Context

11.4.1.1 Figure 11.1 shows the general site context for the two sites at Ha Tsuen and San Wai by means of oblique aerial photographs. Figure 11.2 illustrates on plan the key landscape character units (LCUs) within 500m of the proposed extension works at the Pumping Station and Sewage Treatment Works. Figure 11.16 shows the dimensions of the above-ground structure of the proposed Ha Tsuen Pumping Station extension. Figure 11.3 maps the landscape impacts and includes the anticipated development 'footprint' of the HKSNDA. Figure 11.4 maps the visual envelope / key sensitive receivers including the DBL, HSKNDA and West Rail. Figure 11.5 includes photographs to illustrate the typical character of each of the LCUs throughout the Study Area which are described in more details below. As can be seen in the above noted figures, the majority of the Study area is dominated by extensive container storage yards with clusters of small factory buildings and village settlements on the western fringe of Tin Shui Wai New Town.

11.4.1.2 LCU1 comprises the high-rise housing estates bordering the nullah and includes the Ha Tsuen Pumping Station. The landscape resources in this LCU are a mix of recently planted common ornamental and amenity tree and shrub species associated with the open space facilities of the housing estates, roadside planting and within the grounds of the Pumping Station. No vegetation within the housing estates or roadside planting would be affected by the proposed extension of the Pumping Station. However, some loss of trees and grass cover within the grounds of the Pumping station would occur and this is quantified and described in more details in the following section.

11.4.1.3 LCU 2. This LCU comprises a cluster of village settlements with a mixture of old and new village houses. Scattered thinly throughout the village areas are small stands of mixed woodland, mainly fruit trees planted and maintained by the villagers. The majority of the LCU landscape is urbanised. No landscape resources in this LCU will be affected by the proposed development either at Ha Tsuen or San Wai.

11.4.1.4 LCU 3. This LCU comprises village settlements with predominantly older village houses amidst a patchwork of cultivated land, small orchards and wasteland. Similar to LCU 2 small stands of mixed woodland are scattered thinly throughout the area. No landscape resources in this LCU will be affected by the proposed development either at Ha Tsuen or San Wai.

11.4.1.5 LCU 4. This LCU was formerly farmland but is in transition, being levelled and cleared to accommodate industrial uses or container storage. There is no notable vegetation on the site.

11.4.1.6 LCU 5. This LCU comprises the San Wai Sewage Treatment Plant and the two adjacent ponds. The ecological assessment established that management of the ponds is limited and the plant species were common and of low diversity, i.e. in places the bunds were planted with trees such as Melia, Macaranga and Dimocarpus, the remainder being grass and weeds. Although not fully maintained the ponds do provide an important visual and landscape feature which is sensitive to change within the predominantly urbanised surroundings, see LCU 6 below.

11.4.1.7 LCU 6, LCU 7 and LCU 8. These LCUs comprise an extensive belt of container yards dominating the landscape and visual character of the study area. The landscape is totally urbanised with no notable vegetation and therefore none to be affected by the proposed development.

11.4.1.8 LCU 9. This LCU comprises a belt of small factory units which have urbanised and disturbed former farmland. There are still small stands of mixed woodland scattered throughout the area as remnants of village orchards or woodland. No vegetation within this LCU will be affected by the proposed development either at Ha Tsuen or San Wai.

11.4.1.9 LCU 10. This LCU is a small village settlement of new houses and school within the surrounding container yards of LCUs 6 and 7. There is a small belt of amenity roadside tree planting which would not be affected by the proposed development at either Ha Tsuen or San Wai.

11.4.1.10 LCU 11. This LCU comprises the mixed woodland and grass shrubland on the hillsides to the west of the Study Area. The woodland species are a mix of native and planted species, relatively young and open in structure. There are numerous graves in the lower slopes and the surrounding vegetation has been burned in a number of locations. Typical tree species include Acacia, Eucalyptus, Macarnaga, Celtis and Melia with Rhus and Sapium pioneering the burned areas. This LCU provides an important vegetated backdrop to the Yuen Long Valley as a whole and is sensitive to change. No vegetation will be affected by the proposed development at either Ha Tsuen or San Wai.

11.4.1.11 LCU 12. This LCU comprises the nullah which is concreted and has no vegetation.

11.4.2 Impacts

11.4.2.1 Immediately to the east of the Ha Tsuen Pumping Station is Tin Ying Road on an embankment with the high-rise blocks of Tin Shing Court beyond. To the south is Ping Ha Road with industrial / container storage areas beyond. To the west is the nullah with more industrial / container storage areas beyond. Recent amenity tree planting along Tin Ying Road and well-established boundary tree planting within the site provides a significant though partial screen to the pumping station from the street level.

11.4.2.2 Landscape: The proposed extension of the pumping station will be contained within the existing site boundary. The works comprise construction of a new pumping station building and laying of associated pipe mains. The northern portion of the site which is affected by the proposed extension works is currently under grass with a stand of semi-mature Acacia and Eucalyptus trees planted by DSD with some subsequent self-seeded Leucaena. Approximately 30 trees will need to be removed to accommodate the new building and driveway. Trees close to the boundary can be retained with careful alignment of the underground mains. The trees along the eastern boundary do not provide a continuous screen and would need to be supplemented with new tree planting to fill the gaps. Figures 11.6 and 11.7 indicate the existing and proposed Pumping Station site plan and general location of and impact on established trees. A detailed tree survey would be required of the area to be cleared to identify any trees suitable for transplanting to these peripheral locations. Acacia and Eucalyptus are both very common and fast growing species and it is often more effective to plant new trees which will establish quickly than to transplant larger trees which can take one or two seasons to recover from the shock of being transplanted. However, felling should be considered only as a last resort and the decision to transplant or fell would be subject to the results of the detailed tree survey. Figure 11.7 includes a summary of the estimated loss of vegetation as well as estimated new planting.

11.4.2.3 Visual: The visual envelope of the Ha Tsuen Pumping Station is relatively well contained for both low and high level visually sensitive receivers (VSRs). As noted above the perimeter tree planting screens the majority of the site from the adjacent roads and nullahside footpath and cyclepath. More distant village communities cannot see the site due to the intervening container storage areas. The only VSRs with a clear view of the new building are residents of upper floors in the high-rise blocks along the western perimeter of Tin Shing Court. Due to the close proximity of the high-rise blocks to the site the view from upper floors is an almost vertical 'bird's eye' view. The existing long distance views across the valley to the hills beyond are not obstructed by the new development. Since the Tin Shing Court blocks are close together they shield views from neighbouring blocks to the east. Similarly, blocks of neighbouring estates to the north have only an oblique view of the site. Passengers using West Rail which passes about 300m to the southeast of the site are unlikely to have a significant or prolonged view of the site due to the viaduct parapet and camber of that portion of the track.

11.4.3 Recommended mitigation measures during construction / operation

11.4.3.1 During construction: Prior to construction work the detailed tree survey should have been completed and, if appropriate, trees to be transplanted moved to their final positions. The transplants and existing trees to be retained should be properly protected from damage by stout hoarding positioned as directed by a qualified Landscape Architect. Hoarding will help screen the construction work from the view of passers by. Typically a minimum of 4 months should be allowed prior to construction to prepare trees for transplanting. During construction regular inspections of the retained and transplanted trees should be made to ensure the effectiveness of the hoarding. Any topsoil excavated in the course of the works shall be stored and protected on site for reuse for restoration and screen planting works.

11.4.3.2 During Operation: Upon completion the new building should be relatively unobtrusive by being of similar scale, height, mass and colour / finishes to the existing building complex. As many as possible of the trees along the site boundary will be retained and supplementary trees would be planted to fill gaps between existing trees and provide a continuous screen belt. All transplants and new planting would be maintained by the contractor for 12 months to ensure proper establishment. Figure 11.7 indicates the proposed supplementary planting design.

11.4.3.3 Summaries of the landscape and visual impact assessments, mitigation measures and residual impacts for the Ha Tsuen site are illustrated in Tables 11.1 to 11.4 below. Figures 11.6 and 11.7 indicate the existing and proposed Pumping Station site plan and general location of and impact on established trees, i.e. a net loss of 0.18 ha. of mixed woodland and 0.33 ha. of lawn and shrubs. The photomontages for Ha Tsuen Pumping Station are shown in Figures 11.8, 11.9 and 11.10.

11.5 Assessment Results for San Wai Sewage Treatment Works

11.5.1 Existing Landscape and Visual Context

11.5.1.1 Figures 11.1, 11.2, 11.3 and 11.4 noted above also illustrate and map the LCUs, and VSRs for the proposed San Wai STW extension. Figure 11.17 shows the dimensions of the above-ground structure of the proposed expanded San Wai STW. The surrounding landscape is highly fragmented in character comprising extensive container storage yards, semi-derelict ponds, clusters of factories and low hills with grass / shrubland and fragmented tree cover and numerous burial areas. Vegetation within the immediate environs is limited being mainly pockets of remnant woodland with scrub and grass cover to roadside and pond embankments. The heavy and noisy container yard traffic, in particular, has a large impact on what used to be a relatively quiet, remote part of the New Territories. Conversely, the high container stacks to the north and east effectively contain views of the existing sewage treatment works and proposed extension. Each of the key villages was visited and the views recorded to confirm that the containers do indeed screen low-level views. The villages visited were Tsueng Kong Wai, Sik Kong Tsuen, Sik Kong Wai, Ha Tsuen Shi, San Sang San Tsuen and San Sang Tsuen.

11.5.2 Impacts

11.5.2.1 Landscape: The proposed extension of the San Wai STW will encroach on the two ponds to the north of the site. The development footprint will require filling of the ponds and loss of the grasses and weeds vegetation along the pond embankments. The stand of trees to the north of the ponds which will be affected comprises common indigenous species found throughout Hong Kong, namely; Celtis sinensis, Mallotus paniculatus, Macaranga tanarius, Melia azedarach, Dimocarpus longan and Leucaena leucadendron. The trees are variable in size and are generally in fair to poor condition. Figures 11.11 and 11.12 indicate the existing and proposed STW site plan and general location and impact on established trees. A detailed tree survey would be required to assess precisely the quantity of trees affected by the development. However, a preliminary assessment indicates that approximately 50 trees would have to be removed to accommodate the new development. Figure 11.12 includes a summary of the estimated loss of vegetation as well as the estimated new planting to the boundary of the Sewage Treatment Works.

11.5.2.2 Visual: The extension works would be of a form similar to the existing STW. That is, low-rise and relatively unobtrusive in the surrounding clutter of container and light industrial buildings. Key VSRs would normally be residents the adjacent villages. However, as noted above, the extensive 'wall' of containers effectively blocks the views from all the surrounding village settlements. High-level VSRs include residents of the distant (1.5km to 2km) high-rise blocks in Tin Shui Wai to the east. The upland topography and likely alignment of the Deep Bay Link to the west forms the western boundary of the visual envelope. The most likely VSRs in the upland areas would be people visiting and tending family graves at Ching Ming and Cheung Yeung and would be relatively small in number. The visual impact for VSRs using the future Deep Bay Link would not be prolonged given the high design speed of the highway. The STW would be a relatively unobtrusive feature in the landscape with the more dominant mass of the container stacks backdrop. Moreover, if the DBL structure were elevated then the roadside parapet would likely screen the majority of the lower foreground view of the site. If the highway were at grade then the amenity planting associated with the Deep Bay Link in combination with boundary planting in the STW site would potentially provide a comprehensive screen for road users.

11.5.3 Recommended Mitigation Measures During Construction / Operation

11.5.3.1 During construction: Prior to construction work the detailed tree survey should have been completed and trees to be transplanted moved to their final positions clear of the construction site. Site hoarding will help screen the construction works from the view of passers by as well as protect adjacent vegetation from damage. Typically a minimum of 4 months should be allowed prior to construction to prepare trees for transplanting. During construction regular inspections of the transplanted trees should be made to ensure the effectiveness of the hoarding. Any topsoil excavated during the course of the works will be stored and protected on site for reuse for the restoration and screen planting works.

11.5.3.2 During operation: Upon completion the new building should be relatively unobtrusive by being of similar height, mass and colour / finishes to the existing low-rise building complex. A planting reserve around the site perimeter of approximately 5m width would be provided to allow a continuous belt of trees to be planted as a visual screen. This would complement the boundary planting to the existing sewage treatment works (refer Figure 11.12). All new planting would be maintained by the contractor for 12 months to ensure proper establishment.

11.5.3.3 A summary of the landscape and visual impact assessments, mitigation measures and residual impacts is illustrated in Tables 11.1 to 11.4 below. Figures 11.11 and 11.12 indicate the existing and proposed STW site plan and general location and impact on established trees, i.e. a net gain of 0.55 ha of mixed woodland, and net loss of 0.01ha. of grassland and 1.75 ha. of pond. The photomontages for the San Wai Sewage Treatment Works are illustrated in Figures 11.13, 11.14 and 11.15.

11.5.4 Emergency Bypass Culvert

11.5.4.1 The proposed emergency bypass culvert has been included in the impact assessment. The culvert will be aligned under the existing roads or proposed roads in the HSKNDA and connect to existing drainage channels. No loss of vegetation is anticipated and visual impacts will only be temporary during construction and generally screened from view by site hoarding. Notwithstanding there is no anticipated residual landscape or visual impacts it is recommended that the shortest alternative route, Alternative 4, is adopted to minimise disturbance to residents and road users during construction.

11.5.5 Cumulative Impacts

11.5.5.1 It is difficult to assess accurately the anticipated cumulative impacts of the Pumping Station and Sewage Treatment Works extensions in the context of other major developments, particularly Deep Bay Link and the future HSKNDA which cannot be defined in detail at this stage. However, Figures 11.3 and 11.4 have incorporated these different features as simply as possible into the mapping of landscape and visual impacts respectively. Figure 11.3 indicates that the scale of the landscape impacts from the Pumping Station and Sewage Treatment Works will be insignificant compared to the more massive combined development 'footprint' of the HSKNDA plan and DBL. The new road and land use patterns of the HSKDNA will have a far-reaching effect on the existing, albeit fragmented, landscape resources from the nullah in the east to the foothills in the west.

11.5.5.2 Figure 11.4 indicates the likely effect on the visual envelope by including the DBL and HSKNDA as future sources of visually sensitive receivers. As shown, the proposed residential development in Hung Shui Kiu North New Development Area (HSK North NDA) beside the nullah will encroach on the Ha Tsuen Pumping Station containing the high-level visual envelope close to the site. Similarly, the residential high-rise in HSKNDA will further contain the visual envelope around the San Wai Sewage Treatment Works although the views are still distant and have negligible impact on VSRs. Overall, compared with the extensive redevelopment associated with the HSKNDA and visual intrusion of the DBL, skirting the foothills to the west, the Pumping Station and Sewage Treatment Works represent an insignificant proportion of the overall visual impact.

11.6 Funding, implementation, management and maintenance

11.6.1.1 The proposed landscape and visual impact mitigation measures are all on-site. Any tree transplants will be accommodated within the existing or future site boundaries of San Wai Sewage Treatment Works and the Ha Tsuen Pumping Station. No off-site mitigation measures are proposed. Accordingly, the funding, implementation and management of the planted areas will be by Drainage Services Department and on-going maintenance by Leisure and Cultural Services Department.

Table 11.2  Analysis of Visually Sensitive Receivers and Impact Assessment

Table 11.3  Summary of Mitigation Measures and Residual Landscape Impacts

Table 11.4  Summary of Mitigation Measures and Residual Visual Impacts

11.7 Summary of Landscape Impacts

11.7.1 Ha Tsuen Pumping Station

11.7.1.1 Approximately 30 nos. trees comprising a mix of Acacia and Eucalyptus species planted by DSD as amenity planting in the Ha Tsuen Pumping Station compound will need to be removed to accommodate the new extension works. Subject to a detailed tree survey it may be possible to transplant some of the better specimens to the perimeter to reinforce the existing screen planting. Compensatory tree planting will be carried out upon completion of the building works to supplement the existing trees retained along the site boundary

11.7.2 San Wai Sewage Treatment Works

11.7.2.1 Approximately 50 nos. trees comprising a mix of Acacia, Celtis, Mallotus and Macaranga species established on pond bunds will need to be removed to accommodate the new extension works. Subject to a detailed tree survey it may be possible to transplant some of the better specimens to the perimeter of the existing STW works to reinforce the existing screen planting. Compensatory tree planting will be carried out upon completion of the building works to supplement the existing trees retained along the site boundary.

11.7.3 Summary Table of Net Landscape Impacts

11.8 Conclusions

11.8.1.1 In both the STW and Pumping Station sites the extension works are anticipated to result in a temporary loss of vegetation during construction. However, compensatory tree planting is expected to largely redress this loss by creating denser and more effective boundary screen planting. It is proposed that new planting comprise indigenous trees to enrich the variety of species, particularly in Ha Tsuen where the majority of the trees are exotic species (non-indigenous). The strategic location of the planting to the perimeter of each site will also effectively mitigate the potential visual impacts. In the case of San Wai STW this planting will create a beneficial impact by replacing a portion of the unsightly container yards adjacent to the site. It is unfortunate that the loss of the derelict ponds cannot be readily compensated as the local expertise and incentive to provide regular experienced management is no longer available. However, overall it is considered that the proposed works will be acceptable with the proposed mitigation.