1. INTRODUCTION

1.1 Description of the Project

1.1.1.1 The Yuen Long and Kam Tin Sewerage Master Plan (YLKTSMP) was completed in early 1992. Subsequently, the Review of Yuen Long and Kam Tin Sewerage and Sewage Treatment Requirements (YLKTSMP Review) completed in early 1999 indicated that the original YLKTSMP needed to be revised to cater for the redistribution and increase of the future population in accordance with the latest Territorial Development Strategy Review (TDSR). The YLKTSMP Review recommended the Yuen Long and Kam Tin Sewerage and Sewage Disposal (YLKTSSD) scheme (Stage 1 and Stage 2) and the expansion and upgrading of the sewage treatment facilities at San Wai Sewage Treatment Works (STW) from preliminary treatment to chemically enhanced primary treatment (CEPT) with disinfection for the attainment of water quality objectives (WQO) on the aquatic environment in North West New Territories (NWNT).

1.1.1.2 Figure 1.1 shows the key elements recommended in the YLKTSMP Review and Figure 1.2 shows the locations of the existing NWNT effluent tunnel and Urmston Road outfall.

1.1.1.3 The YLKTSSD Stage 1 is to extend the existing sewerage network to the Au Tau and the Kam Tin / Shek Kong areas for the collection and conveyance of sewage generated therefrom. The current schedule for YLKTSSD Stage 1 is to commence the construction in 2003 for commissioning in 2006. The key items of YLKTSSD Stage 1 include:

1.1.1.4 The YLKTSSD Stage 2 aims at phased implementation of sewerage extension in the NWNT to cope with the existing and planned developments. The current schedule for YLKTSSD Stage 2 is to commence the construction in 2005 for commissioning in 2007. The key items of YLKTSSD Stage 2 include:

1.1.1.5 This project is to expand the sewage facilities at San Wai STW and Ha Tsuen Pumping Station to cater for the projected increase of population in NWNT and other planned developments in Yuen Long and Kam Tin areas and potential developments for Hung Shui Kiu whereas Hung Shui Kiu New Development Area (HSKNDA) is a proposed scheme, and upgrade the sewage treatment facilities at San Wai STW from preliminary treatment to CEPT with disinfection for the attainment of WQO on the aquatic environment in NWNT.

1.1.1.6 For the purpose of this EIA, a range of potential treatment options for the San Wai STW have been critical examined in terms of their associated water quality and ecological impacts on the aquatic environment with the findings presented in Sections 5 and 8 of this EIA Report. The potential treatment options considered are as follow:

1.1.1.7 Figure 1.3 shows the locations of the key items of this project. The current schedule for these key items is to commence the construction in mid 2004 for commissioning in late 2007.

1.1.1.8 The upgrading and expansion of San Wai STW includes the following key items of works:

1.1.1.9 The layout plan of the existing and the upgraded and expanded San Wai STW are shown in Figure 1.4.

1.1.1.10 The expansion of Ha Tsuen Pumping Station involves mainly expanding pumping capacity from 164,000 m3/d to 246,000 m3/d. The layout plan of the existing and the expanded Ha Tsuen Pumping Station are shown in Figure 1.5.

1.2 Enhancement Measures to Control Emergency Discharge

1.2.1.1 Figure 1.6 shows schematically the emergency discharge scenarios for the existing San Wai STW and Ha Tsuen Pumping Station. Under the current situation, in the emergency event when the NWNT effluent tunnel or the Urmston Road outfall is out of operation, raw sewage will be discharged directly from the Ha Tsuen Pumping Station into the Tin Shui Wai Drainage Channel and then to Deep Bay to avoid uncontrolled overflow of raw sewage in the catchment area.

1.2.1.2 In order to reduce the chance of discharging raw sewage into Tin Shui Wai Drainage Channel and hence Deep Bay, an emergency bypass culvert, in the form of box culvert, will be constructed from San Wai STW to nearby drainage channel as part of this project. Figure 1.7 shows schematically the emergency discharge scenarios for the future San Wai STW and Ha Tsuen Pumping Station. Under the emergency event when the NWNT effluent tunnel or the Urmston Road outfall is out of operation, raw sewage from the Ha Tsuen Pumping Station will be treated at the San Wai STW and then discharged via the proposed emergency bypass culvert to nearby drainage channel and then to Tin Shui Wai Drainage Channel and Deep Bay. With this enhancement measure, the effluent discharged to Deep Bay under the emergency event when the NWNT effluent tunnel or the Urmston Road outfall is out of operation will be treated effluent instead of raw sewage. The associated environmental impacts would certainly be lower when compared with the current arrangement.

1.2.1.3 Four alternative alignments of the emergency bypass culvert have been proposed and are shown in Figure 1.3. Some sections of the proposed emergency bypass culvert will cross over the proposed HSKNDA and will laid under the local roads of the proposed HSKNDA. The exact alignment of the proposed emergency bypass culvert will thus be subject to modifications as per the road alignment of the proposed HSKNDA. In order to minimise the impact associated with the construction of the emergency bypass culvert, the proposed emergency bypass culvert will be constructed at the same time as the infrastructure works of the proposed HSKNDA.

1.2.1.4 Comparing Figure 1.6 and 1.7, other than the scenario with the break down of the NWNT tunnel or the Urmston Road outfall, the other emergency discharge scenarios for the existing and the future arrangements are the same. Nonetheless, the chance of discharging raw sewage into the Tin Shui Wai Drainage Channel is in fact very remote and has not happened since the commissioning of the existing San Wai STW, the Ha Tsuen Pumping Station, and the NWNT effluent tunnel and Urmston Road outfall for more than 10 years. Besides routine monitoring, inspection, and maintenance to ensure satisfactory working condition of the system, the following have been and will be applied to the Ha Tsuen Pumping Station to further reduce the chance of system failure:

1.3 Concurrent Projects

1.3.1.1 Apart from the YLKTSSD Stage 1 and Stage 2 works, there are other planned projects in the vicinity of the study area that might have influence on this project and its surrounding receivers. Their respective construction programmes in relation to this project are as follows:

Project Anticipated Programme
San Wai STW Expansion and Upgradin 2004-2007
Ha Tsuen Pumping Station Expansion 2004-2007
YLKTSSD Stage 1 2003-2006
YLKTSSD Stage 2 2005-2007
Deep Bay Link* 2003-2006
Hung Shui Kiu New Development Area* 2004-2010
Hung Shui Kiu North New Development Area* No definite program

* The programme is tentative only and subject to review by the respective study.

1.3.1.2 The timetable indicated above is only for the purpose of evaluating any likely cumulative impacts with this project in this EIA Report. The actual implementation program will be subject to their individual study and government's decision.

Deep Bay Link (DBL)

1.3.1.3 The Deep Bay Link is a dual 3-lane trunk road. It starts at the shoreline of Deep Bay at Ngau Hom Shek and ends at Yuen Long Highway (YLH) at Lam Tei at the southern end. It connects the proposed Shenzhen Western Corridor (SWC) to both Yuen Long Highway and the proposed Route 10 (see Figure 1.8).

1.3.1.4 There are five ramps of some 2 km long forming the Lam Tei Interchange to connect the DBL and YLH in the east and west direction. There are four ramps at the Ha Tsuen Interchange, which will form the turn-around facility and future connection to the road system of the HSKNDA. Stub ends are provided at the Hung Shui Kiu Interchange to receive ramps connecting to HSKNDA.

1.3.1.5 Eighty percent of the mainline being on viaduct. There will be a span over Castle Peak Road and Light Rail Transit (LRT) and a span over KCRC West Rail and its emergency vehicular access. The project also includes the associated drainage, utilities, earthworks, environmental mitigation measures, landscape, weighting station, helipad, etc.

Hung Shui Kiu New Development Area (HSKNDA)

1.3.1.6 The Hung Shui Kiu New Development Area (formerly known as Hung Shui Kiu Strategic Growth Area) is located in the Tuen Mun -Yuen Long Corridor and centred on a newly proposed KCRC West Rail station. It is planned to accommodate residential developments and ancillary GIC facilities, education facilities, commercial developments, container back-up area, and other regional infrastructures.

1.3.1.7 The initial Recommended Outline Development Plan (RODP) of HSKNDA was brought to public consultation in late 1999 to early 2000. The assessment carried in this EIA is based on this RODP. Figure 1.9 shows the layout plan of HSKNDA RODP. A possible extension of the HSKNDA namely the HSK North NDA is also shown in the figure.

1.4 Objectives of Environment Impact Assessment

1.4.1.1 The objectives of this environmental impact assessment (EIA) as detailed in EIA Study Brief No. ESB-059/2000 issued by the Environmental Protection Department (EPD) under the Environmental Impact Assessment Ordinance (EIAO) are as follow:

(i) to describe the proposed project and associated works in detail together with the requirements for carrying out the proposed project;
(ii) to identify and describe the elements of the community and environment likely to be affected by the proposed project and/or likely to cause adverse impacts to the proposed project, including both the natural and man-made environment;
(iii) to identify and quantify emission sources and determine the significance of impacts on sensitive receivers and potential affected uses;
(iv) to identify and quantify any potential losses or damage to flora, fauna and wildlife habitats;
(v) to identify any negative impacts on sites of cultural heritage and to propose measures to mitigate these impacts;
(vi) to propose the provision of mitigation measures so as to minimise pollution, environmental disturbance and nuisance during construction and operation of the project;
(vii) to identify and quantify any potential landscape and visual impacts and to propose measures to mitigate these impacts;
(viii) to identify, predict and evaluate the residual (i.e. after practicable mitigation) environmental impacts and the cumulative effects expected to arise during the construction and operation phases of the project in relation to the sensitive receivers and potential affected uses;
(ix) to identify, assesses and specify methods, measures and standards, to be included in the detailed design, construction and operation of the project which are necessary to minimise any environmental impacts as far as practicable and reducing them to acceptable levels;
(x) to investigate the extent of side-effects of proposed mitigation measures that may lead to other forms of impacts;
(xi) to identify constraints associated with the mitigation measures recommended in the EIA study; and
(xii) to design and specify the environmental monitoring and audit requirements, if required, to ensure the implementation and the effectiveness of the environmental protection and pollution control measures adopted.

1.4.1.2 Figures 1.10, 1.11, and 1.12 shows respectively the study boundary around the proposed expanded and upgraded San Wai STW, the expanded Ha Tsuen Pumping Station, and the emergency bypass culvert.

1.5 Purpose of this EIA Report

1.5.1.1 The purpose of this EIA report is to provide information on the nature and extent of environmental impact arising from the construction and operation of the proposed scope of work as described in Sections 1.1 and 1.2 above and the other planned activities taking place concurrently as described in Section 1.3. This EIA report determines:

(i) the overall acceptability of any adverse environmental consequences that are likely to arise as a result of the proposed project;
(ii) the conditions and requirements for the detailed design, construction and operation of the proposed project to mitigate against adverse environmental consequences wherever practicable; and
(iii) the acceptability of residual impacts after the proposed mitigation measures are implemented.

1.5.1.2 Environmental aspects considered in this EIA Report include:

1.6 Structure of this EIA Report

1.6.1.1 This EIA Report contains 13 sections, including this introductory section.
Section 2 presents a review on different chemicals for the proposed CEPT at San Wai STW as well as a comparison of different potential disinfection options to be adopted for this project.

Section 3 is an assessment on Air Quality Impact (ref. EIA Study Brief S3.4.1).
Section 4 is an assessment on Noise Impact (ref. EIA Study Brief S3.4.2).
Section 5 is an assessment on Water Quality Impact (ref. EIA Study Brief S3.4.3).
Section 6 is an assessment on Waste Management Implications (ref. EIA Study Brief S3.4.4).
Section 7 is an assessment on Land Contamination Impact (ref. EIA Study Brief S3.4.5).
Section 8 is an assessment on Ecological Impact (ref. EIA Study Brief S3.4.6).
Section 9 is an assessment on Fisheries Impact (ref. EIA Study Brief S3.4.7).
Section 10 is an assessment on Cultural and Heritage Impact (ref. EIA Study Brief S3.4.8).
Section 11 is an assessment on Landscape and Visual Impact (ref. EIA Study Brief S3.4.9).
Section 12 refers to the environmental monitoring and audit requirements for this project (ref. EIA Study Brief S3.4.11 and S3.4.12).
Section 13 summarises the environmental outcome of this project on different aspects (ref. EIA Study Brief S3.4.10). This section also concludes the environmental benefits and disbenefits of different options on various issues including sewage treatment level, emergency bypass culvert alignment, and disinfection options examined under the relevant environmental aspects in the above sections.