13                                        ConclusionS

The EIA Report has assessed the potential environmental impacts associated with the construction and operation of the Designated and Potentially Designated Elements of the proposed Yuen Long and Kam Tin Sewerage and Sewage Disposal Stage 1 Sewers, Raising Mains and Ancillary Pumping Stations.  The findings of the assessments are summarised in the following sections.

 

 

13.1                                  Air Quality

The potential air quality impacts arising from the construction and operation of the sewers/rising mains and sewage pumping stations have been addressed.  With the implementation of the recommended mitigation measures and an effective monitoring and auditing programme, the potential construction dust and odour impacts will be minimised and kept within the relevant criteria.  In addition, cumulative construction dust impacts are expected to be within the dust criteria.

 

 

13.2                                  Noise

A construction noise assessment has been undertaken taking the cumulative impacts arising from projects proposed in the vicinity of the Study Area of this Project into consideration.  Unmitigated sources of construction noise associated with the proposed development would cause exceedances of the daytime construction noise criteria.  Mitigation measures such as quiet plant, moveable noise barriers and limiting the use of PME have been recommended. 

 

As the works area for the sewer laying works will be small, the use of mitigation measures such as movable noise barriers and/or enclosures are only considered practicable for the small size PME.  As road opening is the noisiest construction activity associated with the sewer laying works, the use of handheld breakers instead of excavator mounted breakers together with the use movable noise barriers and/or enclosures is recommended to further reduce the potential noise impacts at the nearby NSRs.  However, in view of the close proximity of some NSRs to the works site, noise exceedances are predicted even with the adoption of all practical mitigation measures.  It is anticipated that the sewers will be constructed in segments of up to 50m in length and noise exceedances of up to 6dB(A) may arise on isolated occasions during the three month maximum period required to construct each segment.  Exceedances of up to 12 dB(A) are predicted during reinstatement works; however, the period of such an exceedance is expected to last no more than 2 days.  It is recommended that regular monitoring of noise levels is undertaken as part of the EM&A programme.

 

Noise impacts due to the operation of the proposed sewage pumping stations would not be insurmountable, provided that the planning recommendations described in the EIA (DE) Study are followed.

 

 

13.3                                  Water Quality

Potential impacts to surface water quality due to land based construction activities would primarily occur due to surface run-off and wastewater generation from within the construction sites, including sewage effluent from the workforce.  The potential impacts may be readily controlled by on-site mitigation measures, which were specified in detail in Section 5.7.

 

Detailed water quality modelling was undertaken to determine the effects on marine water quality of decreasing the discharges of untreated sewage effluent to inland waterways.  This reduction will be achieved by the diversion of effluent to the Yuen Long STW and hence will result in an increase in the treated effluent flows from the STW.  The results of the water quality modelling determined that there would be improvements in marine water quality in the vicinity of the mouth of the Shan Pui River, via which the Yuen Long STW discharges to Deep Bay.  An assessment of the impacts of the Stage 1 works on inland water quality determined that there would be a 10% reduction in polluting discharges to the inland waterways and that there would thus be an improvement in water quality.

 

 

13.4                                  Waste Management

Good waste management practices have been recommended to ensure that adverse environmental impacts from the handling and disposal of construction and operational wastes are prevented or minimised.  No unacceptable environmental impacts were predicted from the storage, handling, collection, transport, and disposal of wastes arising from the construction and operation of this Project.

 

 

13.5                                  Land Contamination

Based on the available information and the findings of the site inspections, there is no evidence to suggest that the potentially contaminated sites identified in this study will be the source of significant off-site migration of contaminants to the proposed alignment of the sewers and locations of the pumping stations.  Should any of the excavated soils be found to be contaminated, they could be treated by standard methods prior to disposal.  It is therefore not considered that the presence of potentially contaminated sites adjacent to the proposed alignment of the sewer will cause an insurmountable impact.

 

A preliminary Contamination Assessment Plan (CAP) has been prepared.   The CAP will need to be reviewed and updated once site access is available.

 

13.6                                  Ecology

The ecological resources recorded within the Study Area included secondary woodland, grassland/shrubland, cultivated land, fishpond, marsh, stream/ channel & nullah and mangrove habitats, as well as the associated wildlife.  Of these habitats, grassland/shrubland, streams/channel & nullahs and urbanised areas have low ecological value.  Cultivated land, fishponds located outside the WCA and WBA and secondary woodland areas surveyed within the Study Area are of moderate ecological value.  Mangrove, marsh and fishponds within the WCA and WBA are of high ecological value. 

 

The proposed sewer alignment and pumping station sites are mainly located on existing roads/footpaths which are classified as urbanised/disturbed habitats of minimal ecological value.  The impact on the relatively low quality habitats is considered to be low, and no adverse residual impact is expected after the implementation of the recommended mitigation measures.  The most sensitive issue is the indirect impact within the WCA and WBA, in which scheduling of works and noisy activities outside of the winter period is expected to counteract any predicted impacts.  Mitigation measures in the form of good construction practice and use of quietened construction plant/ equipment and movable barriers are recommended to minimise potential disturbance to the surrounding environment.

 

 

13.7                                  Fisheries

Active fish ponds were identified within the Study Area with the majority concentrated to the north west.  Although fish ponds were observed in other areas, these appeared to be inactive and/or abandoned.  No active fish ponds are expected to be impacted by the construction and operation of the proposed sewerage system and pumping stations.

 

 

13.8                                  Cultural and Heritage

No direct impact to the identified historical buildings or features is expected. Appropriate mitigation measures have been recommended for indirect impacts where necessary.

 

Vibration monitoring has been recommended to ensure that the structural integrity of the historical compound at Ng Ka Tsuen (NKT) would not be affected by the construction of the NKTSPS.

 

No significant archaeological deposits would be impacted by the proposed sewerage facilities, except P4, P5 and P6.  A six month period at each site should be allowed for an archaeological field investigation to be undertaken once the land is resumed and access gained, but before any construction takes place.   Mitigation measures, agreed with the AMO, should be implemented to mitigate potential impacts, if any are identified during the archaeological field investigation.

 

13.9                                  Landscape and Visual

The Study Area is low-lying flat land forming of a series of broad alluvial valley floors draining into Deep Bay.  The main land uses are villages, industry and some agricultural activities.  The density of development is generally highest next to the main roads and major intersections in the east of the Study Area, giving way to agricultural land and fish ponds in the west.

 

The project elements likely to affect the landscape and visual baseline conditions during the construction phase will be the activity associated with the construction of the sewage pumping stations and underground sewers and rising mains.  The project elements likely to affect the landscape and visual baseline conditions during the operation phase will be the sewage pumping stations only. 

 

To mitigate these impacts, a number of on-site landscape mitigation measures have been recommended and outlined in the EM&A Manual for incorporation into the Project. With the implementation of the mitigation measures, the residual landscape and visual impacts are considered acceptable for the following reasons:

 

·         there will be some slight/moderate adverse effects on the baseline condition, but these can be eliminated, reduced or offset to a large extent by landscape mitigation measures;

·         The Project would result in the loss of 30 trees. Compensatory planting for each Pumping Station site has been recommended;

·         The introduction of the Project  into the study area will result in mainly negligible landscape impacts assuming mitigation measures are incorporated into the scheme;

·         The introduction of the Project  into the study area will result in mainly    negligible visual  impacts assuming mitigation measures are incorporated into the scheme;

·         there would be no significant adverse effect on the appearance of the Study Area; and

·         there would be no interference with key views.

 

 

13.10                              Summary of Environmental Assessments

No unacceptable residual impacts are predicted for the construction and operation of the Designated and Potentially Designated Elements of this Project.  Table 13.10a summarises the findings of the environmental assessments.


 

Table 13.10a  Summary of Environmental Assessments

 

Construction

Operation

Residual Impact

 

Project Description

·       Construction 10km of trunk sewers/rising mains and 7 sewage pumping stations

·       Operations of 7 SPSs

·       The expansion of sewers/rising mains networks under the Stage 1 works of this Project to deliver domestic sewage for treatment at Yuen Long Sewage Treatment Works will extend coverage of sewage collection and thus will allow 33% more sewage flow to be treated.  Untreated sewage would otherwise be discharged to inland waters.

n/a

 

Air Quality

With the implementation of mitigation measures, no adverse construction dust impacts are envisaged.

With the installation of odour removal systems at the SPSs, no adverse odour nuisance is envisaged.

No

 

Noise

The construction noise assessment indicated that unmitigated sources of construction noise associated with the proposed development and projects in the vicinity (ie the non designated elements of this project and Kam Tin Bypass; Yuen Long Bypass Floodway; Yuen Long, Kam Tin, Ngau Tam Mei and Tin Shui Wan Drainage Improvement Works Stage 1) would cause exceedances of the daytime construction noise criteria at the majority of the nearby NSRs.  Mitigation measures such as quiet plant, limiting the use of PME and movable noise barriers have been recommended where appropriate.  In view of the close proximity of some NSRs to the sewer laying works, exceedances are still predicted even allowing for all practical mitigation measures being implemented.

 

 

Noise impacts due to the proposed sewage pumping stations would not be insurmountable provided that the planning recommendations described in this report are followed.

 

Exceedances of the daytime construction noise criteria are predicted at the following NSRs:

 

·   Scattered House near Kam Tin Shi (D1)

·   Yuk Yat Garden Phases II (D4)

·   Scattered House in Nam Sang Wai (D12)

·   Kam Tin Shi North (D22)

·   Scattered House beside Kam Sheung Life Lutheran Church (D30)

·   Ng Ka Tsuen (D33)

·   Planned Residential Development beside Kam Tsin Wai (A-YL-KTS-174) (D36)

·   Kam Tsin Wai (D38)

·   Kam Kong Villa (D39)

·   Planned Residential Development near Shui Tsan Tin (DPA/YL-KTS/-YL-KTS-82) (D40)

Water Quality

With the implementation of mitigation measures, no adverse water quality impacts are envisaged.

Reductions in pollutant loads to the streams and watercourses adjacent to the areas to be connected to the new sewerage system are estimated as follows:

·       Suspended solids – 320 kg day-1;

·       BOD – 340 kg day-1;

·       COD – 730 kg day-1;

·       TKN – 70 kg day-1;

·       Ammonia – 40 kg day-1; and

·       E. coli – 3.5x1014 cfu day-1.

 

These loads represent approximately 10% of the total pollutant loads to the inland waterways.

No

 

Waste

With the implementation of good waste management practices, no adverse waste management impact is envisaged.

With the implementation of good waste management practices, no adverse waste management impact is envisaged.

No

 

Land Contamination

Based on the available information and the findings of the site inspections, there is no evidence to suggest that the potentially contaminated sites identified in this study will be the source of significant off-site migration of contaminants to the proposed alignment of the sewer and locations of the pumping stations.

No

No

 

Ecology

Direct habitat loss of approximately 0.26 ha cultivated lands of moderate ecological value, including the proposed location of pumping stations P4 (0.09 ha), P6 (0.07 ha) and P7 (0.10 ha), approximately 0.15 ha of abandoned fishpond (P2) and approximately 1.02 ha of urbanised/developed areas as a result of landtake for the construction and related temporary storage areas.

 

 

No operational impact is expected.

There will be the loss of 0.15 ha of abandoned fishpond with low to moderate impact and other low quality habitats including 0.26 ha of cultivated land and 1.02 ha of urbanised/disturbed area.  No adverse residual impact (direct or indirect) is expected due to the construction and operation of the sewerage system and pumping stations after the implementation of the proposed mitigation measures.

 

 

Direct impact to the bottom of the MDC channel (60 CD), as well as indirect impact to the associated fauna, in the section that the sewer crosses over.

 

 

 

 

Indirect impact to the birds inside WCA and WBA due to the increased noise impact, human activities and disturbance such as storage or dumping of construction material and construction site runoff.

 

 

 

 

Indirect impact to the surrounding habitats and associated wildlife arising from increased noise impact, human activities and disturbance such as storage or dumping of construction material and construction site runoff.

 

 

 

Fisheries

It is estimated that approximately 0.15 ha of the abandoned fish pond will be lost through construction of pumping station P2. This impact is not expected to be of concern as the fish pond is inactive and currently abandoned.

No operational impact is expected.

There are no residual impacts expected to occur to aquaculture fisheries resources and operations as a result of the construction and operation of the proposed sewerage system and pumping stations.

 

Cultural Heritage

No direct impact to the identified historical buildings or features is expected.

Vibration monitoring has been recommended to ensure that the structural integrity of the historical compound at Ng Ka Tsuen (NKT) would not be affected by the construction of the NKTSPS.

No significant archaeological deposits would be impacted by most of the proposed sewerage facilities except P4, P5 and p6.  A 6 month programme should be allowed for an archaeological field investigation to be undertaken at each of the proposed pumping stations, P4, P5 and P6, and once the land is resumed and access gained, but before any construction takes place.   Mitigation measures agreed with the AMO, would be implemented to mitigate the potential impacts, if any.

No operational impact is expected.

No residual impact is expected.

 

Landscape and Visual

“Significant” visual impact is predicted at the historic house at Ng Ka Tsuen (1C).  “Moderate adverse” landscape impact is predicted to the Village Development LCU during construction. “Slight/Moderate Adverse” visual impacts to viewer groups at Sensitive Visual Receivers (SVR) during construction, at the following locations.

·          Sha Po Tsuen Residential Development (1A);

·          Kam Tin Shi Residential Development (1B);

·          Residential Developments near Shui Tsan Tin SPS (1D);

·          Residential Developments near Pang Ka Tsuen SPS (1E);

·          Residential Development near Leung Uk Tsuen SPS (2A); and

·          Residential Developments west of Pang Ka Tsuen (3D).

“Significant” visual impact is predicted at  the historic house at Ng Ka Tsuen (SVR-1C) due to the close proximity to Ng Ka Tsuen SPS. 

“Slight/Moderate Adverse” visual impacts are predicted to those viewer groups at SVRs identified for the construction phase. The source of the visual impact is SPSs in proximity to residents during the operation phase of these SPSs.

The incorporation of mitigation measures into the Project will be effective in reducing “Moderate/Significant Adverse” construction impacts in the Village Development LCU to “Slight Adverse”.

The incorporation of mitigation measures into the Project will be effective in reducing “Significant” to “Moderate” visual impacts to SVR-1C during construction and from “Significant” to “Moderate” and “Negligible” visual impacts at “Day 1” and “Year 10”, respectively during operations.

The incorporation of mitigation measures into the Project will be effective in reducing “Slight/Moderate Adverse” to “Slight Adverse” visual impacts to SVRs-1A, 1B and 3D and to “Negligible” to SVRs- 1D, 1E and 2A during construction and from “Slight/Moderate Adverse” to “Slight adverse” and “Negligible” visual impacts at “Day 1” and “Year 10”, respectively during operations.

 

 

 

 

 

 

 

 

 

 

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