2. Consideration of Alternatives

2.1 Introduction

2.1.1 Options and alternatives have been considered in this Project for refinement and selection of the preferred option for the Depot to be taken forward for the EIA and detailed design. Details of the options considered and constraints assessed in adopting the preferred scheme have been reviewed, including alternative site, designs and construction methodologies. The review has also taken into account engineering feasibility, site conditions, programme aspects and environmental considerations with a view to identifying the optimum arrangement.

2.1.2 This Section is prepared in accordance with Section 3.3.1 of the EIA Study Brief (No. ESB-245/2012).

2.2 Project Need

2.2.1 The existing Sai Yee Street Vehicle Depot in Mong Kok has to be demolished as the land of the Site is scheduled to be returned to Lands Department by March 2017. FEHD therefore requires a land piece for housing the existing facilities in Sai Yee Street Vehicle Depot.

2.2.2 The proposed offices-cum-vehicle depot building at Yen Ming Road aims to replace these facilities and to carry out vehicle washing and repairing services for the FEHD fleet in the district and their parking when they are not in operation.

2.3 Siting

2.3.1 As discussed in Section 1.2.1, the Project is located on an urbanised area at Yen Ming Road, which is a land piece zoned as “Government, Institution or Community” use, whilst commercial, residential and institutional uses are located in the proximity. The Site constitutes an area of previously developed reclaimed land which was recently occupied by CEDD as site offices and associated storage (being returned). The site location of this Project is shown in Figure 1-1.

2.3.2 In the early planning stage of the Project, site searching process was carried out and 2 potential sites in the district were identified by FEHD and shortlisted for evaluation, which are:

Site A – land piece at Yen Ming Road; and

Site B – land piece at Ngong Shung Road

and are indicated in Figure 2-1.

2.3.3 Compare to Site B, Site A is more accessible by the public and convenient to continue timely environmental hygiene services to the local districts, and thus preferred in view of providing public services. Also, Site B was occupied by Drainage Services Department for a sewage pumping station and therefore the site is now not available.

2.3.4 Furthermore, re-provision at the original Sai Yee Street site (eg. in form of basement) is screened out because of technical feasibility / preferences and lack of site for temporary reprovisioning to maintain the required services.

2.4 “Without Project” Alternative

2.4.1 A fundamental Project alternative is the option not to construct the new offices-cum-vehicle depot building at Yen Ming Road, which is referred to as the “Do-nothing” option in environmental terms. As spelt out in Section 2.2, the Site is scheduled to be returned to Lands Department by March 2017 whilst continuation of the vehicle repairing and maintenance services of the existing Sai Yee Street Vehicle Depot as well as the washing service of the new depot is crucial to ensure the vehicles are clean, hygienic and under normal and safe operation in the FEHD fleet of West Kowloon region including Sham Shui Po, Mongkok, Yau Ma Tei and Tsim Sha Tsui districts.

2.4.2 The existing depot in Sai Yee Street is the only depot currently for repairing and maintenance of the FEHD vehicle fleet in the region. In the absence of this proposed depot, the vehicle fleet of the said region would have to depend upon the services provided by other depot(s) in the surrounding region, which in turn demands longer travelling distance and time and, hence, lead to other off-site environmental impacts on the existing road networks, including traffic congestion, noise and vehicular emissions.

2.4.3 Taking the above reasons into accounts, the “Do-nothing” option is not preferred and not considered to be an environmentally preferred solution to cope with the current demand of the washing, repairing and maintenance of the FEHD vehicles fleet of the region.

2.5 Alternative Options

Design of the Depot

2.5.1 The following design options were considered and reviewed in order to optimise the operational and environmental benefits of the facility:

Form

2.5.2 The Project aims to reprovision of the existing facilities, including all offices, stores, workshop, etc, in Sai Yee Street Vehicle Depot at the new site. The form of Project was reviewed to examine whether separating offices from other facilities would be a preferred options.

2.5.3 Considering and taking a balance between various factors, including objectives, availability, convenience to the public, operability, etc, it is preferred for a combined option (ie. offices-cum-vehicle depot) rather than a separation form (ie. a site for offices whilst depot is at another location).

Building Design

2.5.4 To minimise the potential environmental impacts, in particular on noise and air quality perspectives, different forms of building have been considered and eventually non-open form was preferred for vehicle repairing and washing activities, which are now to be located at ground floor and refined and covered by the above floors.

Facilities Layout

2.5.5 Layout design was investigated in details in order to strike the balance between operational needs, as well as catering environmental considerations. Activities with potential environmental implication / nuisance were located in a confined manner as possible.

2.5.6 Vehicle repairing bays and workshop is proposed to be covered at ground floor, surrounded by storerooms for noise screening and buffering purpose as possible. In addition, solid partition wall is proposed to the manual vehicle washing bays to entirely isolate the pedestrian from potential nuisance.

2.5.7 Moreover, to enhance the visual quality of the Depot, substantial greenery features were considered, including vertical green walls and green roofing.

Ventilation and Local Exhaust Design

2.5.8 A vast amount of openings are proposed at the building façade to optimise the use of natural ventilation at the car parking area at lower floors. Mechanical ventilation is only designed for standby forced ventilation system. As a result of rare usage of the associated substantial mechanical ventilation system, potential noise nuisance from this fixed plant system could be minimised.

2.5.9 On the other hand, for those activities with potential environmental nuisance including vehicle repairing activities at the workshop and vehicle washing, controlled mechanical ventilation with sufficient forced air changes is desired, rather than merely relying on natural ventilation. In addition, ventilated exhaust is to be treated prior to discharging to the atmosphere. Various gas treatments were evaluated and the most appropriate technology with proven removal efficiency (eg. activated carbon filter, bio-oxygen generator, chemical scrubber) will be applied. Location and orientation of the local exhaust were carefully examined to ensure sufficient dispersion and to avoid direct impact to the nearby receivers.

Construction Method

2.5.10 Construction of the Depot would involve various typical work stages and conventional building services works. As such, consideration of alternative construction method is focused on the design of the foundation works. According to the ground condition of the Site, two foundation types, namely driven steel-H piling (percussive) and bored piling (non-percussive) are considered to be technically viable for the Project.

Steel-H Driven Piling

2.5.11 Steel-H driven piling is a percussive piling method and with the following advantages for the construction of the Project in term of engineering / economic features:

· Construction time required is relatively short;

· The system has been proof tested to work well;

· This technology is easily available;

· Driven H-pile has the supporting capacity more suitable for this kind of low rise buildings, higher flexibility in the pile arrangement, enabling higher load/capacity; and

· It is relatively the most cost effective pile system.

2.5.12 In terms of environmental issues, driven steel H-piling is anticipated to bring the following potential environmental benefits:

· Minimal waste is generated and fewer plants (e.g. sedimentation tank, grouting machines) are required; and

· With a shorter construction time, the potential environmental impacts during the construction phase, e.g. construction dust, noise, site effluent, C&D waste, etc would hence be reduced.

Bored Piling

2.5.13 Bored piling is a non-percussive piling method and with the following advantages for the construction of the Project in term of engineering features:

· Pile capacity is high. Suitable for medium to high rise buildings;

· Quality of pile can be controlled effectively; and

· Common pile type in Hong Kong and most specialist piling contractors are capable to install this pile type.

2.5.14 However, bored piling has the following disadvantages:

· Commonly end-bearing piles founded in rock. Hence, it needs to reach deep bedrock and with long pile length;

· Relatively more expensive compared to driven-H piling; and

· Construction time is long (especially in rock) in comparison to other pile types.

2.5.15 In terms of environmental issues, bored piling is anticipated to bring lower noise and vibration would be generated during construction.

2.5.16 Although less noise and vibration would be generated by bored piling during construction, as compared to steel-H driven piling, the pile borehole diameter is normally large in size. The excavation would hence be comparatively substantial and not cost effective when compared to driven steel H-pile with smaller diameter pile. In view of the above, driven steel H-pile would be considered to be more cost-effectiveness for the proposed development.

2.5.17 On the other hand, as the Project site is currently separated from noise sensitive receivers (including Sir Ellis Kadoorie Secondary School and Tai Kok Tsui Catholic Primary School located across Hoi Fan Road) by the existing CLP Tai Kok Tsui Substation, noise impact of percussive piling system is considered to be acceptable and it is anticipated that the noise criteria stipulated under the current noise regulation would be fulfilled even for the closest school, which is located over 80m away from the noise sources. With the implementation of the appropriate noise mitigation measures during piling operation, the noise level would further be reduced.

Traffic Routings

2.5.18 At the early stage of the Project, incoming and outbouding traffic routings were developed based on ease and need of operation. During project development and public engagement, local concerns on the proposed traffic routings were received and thus modification to the routings were considered necessary requiring substantial changes in order to address the concerns.

2.5.19 As a result of traffic assessment, alternative traffic routes as shown in Figure 2-2 were examined and proposed in order to avoid utilizing those concerned junctions and roads, as possible.

2.6 Preferred Option

2.6.1 Based on the above considerations of alternatives, a preferred option has been selected in the Scheme and Preliminary Design phases of this Project as summarised below, based on which the detailed design of this Project will be proceeded and this EIA study was carried out:

· Optimum design for building design, facilities layout, ventilation and local exhaust design; and

· Optimum construction method using steel-H driven piling.

2.6.2 This preferred option is determined upon the comparison of the feasibility in line with the environmental benefits and dis-benefits of the various options and alternatives. It was also selected on the principal of minimising the environmental impacts and optimizing overall environmental benefits and acceptability over the other options.