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Agreement No. CE 67/98 Yuen Long, Kam Tin, Ngau Tam Mei & Tin Shui Wai Environmental Impact Assessment Drainage Improvement, Stage 1, Phase 2B – Kam Tin Final Report Secondary Drainage Channel KT13 382047/E/EIA/Issue 9 1. INTRODUCTION 1.1 Background 1.1.1 The Territorial Land Drainage and Flood Control Strategy Study – Phase II (TELAFLOCOSS 2), completed in August 1993, recommended as part of its findings that detailed studies were required to resolve secondary and local stormwater drainage problems in five drainage basins in the North and North West New Territories. Accordingly Drainage Services Department (DSD) commissioned the Yuen Long, Kam Tin, Ngau Tam Mei and Tin Shui Wai Drainage Master Plan (YLDMP) Study to investigate two of the five basins, namely the Yuen Long, Kam Tin and Ngau Tam Mei Basin and the Tin Shui Wai Basin. 1.1.2 The YLDMP started in January 1996 and was completed in December 1996. The Study was to examine and assess the secondary and local drainage systems, recommend prompt, short and long term improvement measures to resolve the identified problems, and develop a prioritized program for implementation of the recommended improvement works. 1.1.3 The YLDMP has identified problems in the existing drainage systems in the study area and has recommended drainage improvement proposals under a two- stage implementation program. The Stage 1 works (i.e. this Project - Yuen Long, Kam Tin, Ngau Tam Mei & Tin Shui Wai Drainage Improvement Stage 1) are to be implemented under this Assignment for mitigating major drainage problems requiring immediate attention. 1.1.4 Black & Veatch Hong Kong Limited (B&V HKL) (formerly Binnie Black & Veatch Hong Kong Limited) was commissioned on 26 July 1999 by the Employer, Drainage Services Department (DSD), to carry out the preliminary and detailed design and construction supervision of the Yuen Long, Kam Tin, Ngau Tam Mei & Tin Shui Wai Drainage Improvement, Stage 1 Project. This Stage 1 Assignment commenced on 9 August 1999. 1.2 Yuen Long, Kam Tin, Ngau Tam Mei & Tin Shui Wai Drainage Improvement, Stage 1 1.2.1 Stage 1 of Yuen Long, Kam Tin, Ngau Tam Mei and Tin Shui Wai Drainage Improvement comprises the construction of works as shown in Figure 1.1. In order to expedite the drainage improvement works in the urban areas, Stage 1 works are divided into two phases, namely Phase 1 and Phase 2, encompassing the following principal elements: May 2006 [g\report\ylkt-eia-kt13-6482] 1-1 B&V Agreement No. CE 67/98 Yuen Long, Kam Tin, Ngau Tam Mei & Tin Shui Wai Environmental Impact Assessment Drainage Improvement, Stage 1, Phase 2B – Kam Tin Final Report Secondary Drainage Channel KT13 382047/E/EIA/Issue 9 (a) Phase 1 – Bank Raising and Urban Drainage Improvements in Tin Shui Wai and Yuen Long Areas (i) Bank raising of about 2.5 km of primary channels (Ha Tsuen and Hung Shui Kiu Channels) and associated modification works including the replacement of railings by parapet wall, re- provision/modification of affected bridges and re-provision of local drains for affected areas in the Tin Shui Wai Basin. (ii) Construction of about 6.4 km of replacement/relief drains, associated manholes and lateral connections in Hung Shui Kiu, Ping Shan, and Yuen Long town areas. These works in Phase 1, under Contract No. DC/2000/06, are not Designated Projects (DP) as defined under the EIA Ordinance. The Environmental Study (ES) Report for Phase 1 works [Ref. 382047/E/ES/Issue 2, dated September 2001] was submitted to the Government. The PWSC paper for Phase 1 works was endorsed in June 2001, and the construction of Phase 1 works commenced on 31 December 2001. (b) Phase 2 – Construction of Secondary Drainage Channels (i) Construction of about 7.5 km of secondary channels and associated maintenance accesses including re-provision of vehicular and pedestrian crossings, drainage and utility diversion works, associated road furniture and lighting facilities, landscaping and other ancillary works at the following areas: (a) NTM1 – the total length of the proposed channel is about 400 m including a 90 m long box culvert. It comprises a rectangular concrete channel of 2.5 m width and 2 m height and a box culvert of 2.5 m width and 2 m height at downstream, connecting to an existing twin box culvert under San Tin Highway. (b) KT2 – the preliminary alignment generally follows the existing stream course. The total length of this channel is about 1320 m. The channel comprises three sections. The upstream section is a rectangular channel of 6m width May 2006 [g\report\ylkt-eia-kt13-6482] 1-2 B&V Agreement No. CE 67/98 Yuen Long, Kam Tin, Ngau Tam Mei & Tin Shui Wai Environmental Impact Assessment Drainage Improvement, Stage 1, Phase 2B – Kam Tin Final Report Secondary Drainage Channel KT13 382047/E/EIA/Issue 9 and 3m height. The middle section is a trapezoidal channel of 6 m width at the base and 3 m height. The downstream section, a rectangular channel of 8 m width and 3 m height, avoids affecting the Agriculture, Fisheries and Conservation Department’s Au Tau Fisheries Office. The downstream end of the channel will join the trained Kam Tin River Channel. (c) KT4 – the preliminary alignment generally follows the existing stream course. The total length of this channel is about 600 m. The preliminary design is a trapezoidal channel of 5 m width at the base and 2.5 m height. The downstream end of the channel will join the Kam Tin North River Channel to be constructed under Contract No. DC/98/04 – Construction of Main Drainage Channels for Yuen Long and Kam Tin, Stage II, Kam Tin San Tsuen to Wang Toi Shan Section (Contract D). (d) KT5 – the preliminary alignment generally follows the existing stream course. The total length of the channel is about 840 m. For 70 m upstream, the channel is rectangular, of 4 m width and 2 m height. The rest of the channel is trapezoidal, of 5m width at the base and 2.5 m height. The downstream end of the channel will join the Kam Tin North River Channel to be constructed under Contract No. DC/98/04 – Construction of Main Drainage Channels for Yuen Long and Kam Tin, Stage II, Kam Tin San Tsuen to Wang Toi Shan Section (Contract D). (e) KT6 – the preliminary alignment generally follows the existing stream course. The total length of the channel is about 600 m. The preliminary design is a trapezoidal channel of 5 m width at the base and 2 m height. The downstream end of the channel will join the Kam Tin North River Channel to be constructed under Contract No. DC/98/04 – Construction of Main Drainage Channels for Yuen Long and Kam Tin, Stage II, Kam Tin San Tsuen to Wang Toi Shan Section (Contract D). (f) KT7 – the preliminary alignment generally follows the existing stream course. The total length of the channel is about 730 m. The preliminary design is a trapezoidal May 2006 [g\report\ylkt-eia-kt13-6482] 1-3 B&V Agreement No. CE 67/98 Yuen Long, Kam Tin, Ngau Tam Mei & Tin Shui Wai Environmental Impact Assessment Drainage Improvement, Stage 1, Phase 2B – Kam Tin Final Report Secondary Drainage Channel KT13 382047/E/EIA/Issue 9 channel of 3.5 m width at the base and 2 m height. The downstream end of the channel will join the Kam Tin North River Channel to be constructed under Contract No. DC/98/04 – Construction of Main Drainage Channels for Yuen Long and Kam Tin, Stage II, Kam Tin San Tsuen to Wang Toi Shan Section (Contract D). (g) KT12 - the preliminary alignment generally follows the existing stream course. The total length of the channel is about 200 m. The preliminary design is a trapezoidal channel of 3.5 m width at the base and 2 m height. The downstream end will match with Box Culvert No. 4 constructed by the Kowloon and Canton Railway Corporation (KCRC) – West Rail. (h) KT13 - this is the Designated Project (DP) which is subject of this EIA. Section 2 gives a detailed description of the existing environmental elements of works proposal for secondary drainage channel KT13. (i) KT14 – the proposed channel comprises four local drainage channels with preliminary dimensions as below: Section A – 2.5 m width and 2.8 m height, 145 m Section B – 2.5 m width and 1.6 m height, 339 m Section C – 2.5 m width and 1.6 m height, 474 m Drain along Kam Sheung Road – 900 mm nominal size U-channel Bank raising along the existing toe channel of Pat Heung Road The downstream end of the channels will be connected to an open channel constructed by KCRC – West Rail. (j) KT15 - the preliminary alignment generally follows the existing stream course. The total length of the channel is about 796 m. The preliminary section design varies from a trapezoidal channel of 6.7 m – 9.9 m width at the base and 1.6 m height to a rectangular channel of 3.5 m width and 1.6 m height. May 2006 [g\report\ylkt-eia-kt13-6482] 1-4 B&V Agreement No. CE 67/98 Yuen Long, Kam Tin, Ngau Tam Mei & Tin Shui Wai Environmental Impact Assessment Drainage Improvement, Stage 1, Phase 2B – Kam Tin Final Report Secondary Drainage Channel KT13 382047/E/EIA/Issue 9 An Environmental Study has been carried out to review the potential impacts and environmental opportunities and requirements for those secondary channels.