3. Project Description and key environmental issues identification

3.1 The Subject Site and its Environs

3.1.1 The proposed bus depot is planned to be constructed on an approximately 1 hectare site located in the Chai Wan East Industrial Area. The site selection process is described in Section 2. Figure 1-1 shows the location of the site.

3.1.2 A major portion of the site is currently unoccupied. Highways Department (HyD) is temporarily occupying a southern portion of the site for a work area until June 2001. A small area at the northern part of the site falls within the boundary of the NWFB temporary bus depot. Located at a minimum distance of about 80m to the North-west of the future bus depot is Hong Kong Institute of Vocational Education (IVE) (Chai Wan). Lying between the college and the bus depot site are the MTR railway tracks leading to the Chai Wan Station to the south and Shing Tai Road. To the immediate North of IVE is its associated Staff Quarters. Tsui Wan Estate is situated at more than 165m to the South-west of the site. The nearest residential blocks at Heng Fa Chuen is located at approximately 390m to the north of the site.

3.1.3 The site was reclaimed and is zoned for industrial use (“I”) similar to some other landuses in its vicinity as shown in the latest Draft Outline Zoning Plan (OZP) No. S/H20/11 gazetted on 20 April 2001. According to the Notes of the OZP, “Bus Depot” is a column 1 use that no planning permission from the Town Planning Board is required. Figure 3-1 presents an Extract of the OZP. Planning Department (PlanD) has advised that in addition to the proposed bus depot, the Chai Wan East Industrial Area is also planned to accommodate an Open Space, a Joint Government Departmental Depot, Lorry Park & Motor Vehicle Repair Workshop, New World First Bus Depot, LPG/ Petrol Filling Station and Hong Kong Post Super Centre.

3.1.4 The northern side of the site is planned by the Government for the provision of a LPG/ petrol filling station, while the Southern side of the site would be the HK Post Supercentre. At this stage, only the NWFB depot situated near Chong Fu Road and located at about 135m from the proposed bus depot is under active construction. The NWFB depot is expected to be completed by year 2002. All other proposed developments in the area are still at a planning stage without a concrete development programme.

3.1.5 The proposed Citybus depot will be bound by a future local road – Road 20/4 to the East and Shing Tai Road to the west. Other future new roads in the Chai Wan East Industrial Area include Road 20/6 and Road 20/10 as shown in Figure 1-1. Highways Department (HyD) has advised that the three new roads – 20/4, 20/6 and 20/10 would be completed in December 2002.

3.1.6 The planned bus routing plan agreed with TD is illustrated in Figure 3-2.The ingress point of the bus depot is planned at Road 20/4, which is a local road lying away from nearby sensitive receivers. Buses approaching the depot from Island Eastern Corridor (IEC) will travel via Shing Tai Road northbound, Road 20/6 and Road 20/4. There will only be one egress point each located at Shing Tai Road and Road 20/4 respectively. The egress point on Shing Tai Road will serve IEC bound buses which will go via Shing Tai Road southbound and Shun Tai Road. Buses leaving or returning to the depot will not pass through the section of Shing Tai Road further north of the site leading to Heng Fa Chuen.

3.1.7 The 20/4 Road egress point is planned for Siu Sai Wan bound buses. It is understood that Wing Tai Road currently carries high traffic flows during the peak hours. To avoid potential traffic noise impact attributed to the operation of the proposed bus depot, as agreed with the Authority, buses commuting between the bus depot and Siu Sai Wan area will be required to take the route through the future Sheung On Street Extension (connecting the existing Sheung On Street with the future Road 20/4) under normal operating conditions (i.e. except for emergency conditions), instead of allowed to use Wing Tai Road and Shing Tai Road at all time periods. Citybus will require its employees to strictly follow this requirement when entering/ leaving the bus depot.

3.2 Bus Depot Design

3.2.1 The proposed bus depot will be constructed in form of a low-rise building occupying a site area of approximately 1 hectare. The development will provide spaces for bus parking, maintenance and office areas. Architectural design of the development has been developed by the Project Architect – LCP, with input on the engineering, traffic and environmental aspects provided by the sub-consultants.

3.2.2 Figures 3-3 to 3-7 present the preliminary ground to fifth floor layout plans of the bus depot. A cross section of the building is shown in Figure 3-8. The bus depot will consist of three stories located at ground floor (G/F), first floor (1/F) and roof floor (3/F). As shown on the preliminary plans, the G/F will house approximately 2 refuelling bays, 2 washing bays, 29 sunken pits, 4 brake testers and 5 maintenance bays. The 1/F will provide some 46 maintenance bays for annual maintenance works. The 3/F (roof) floor will provide about 100 bus parking areas. The fourth floor (4/F) and fifth floor (5/F) that will be built at the southern portion of the site only will be used for office areas. The upper ground floor (U/G) and second floor (2/F) is a mezzanine floor provided at the southern part of the site near Road 20/4. Spare parts storage areas, chemical storage areas and scrap yards/ waste material stores will be provided on the G/F and 1/F. Taking into account the interface with the future developments located in its immediate proximity, including the LPG/ Petrol Filling Station and the Hong Kong Post Super Centre, the northern and southern sides of the bus depot building are planned to be constructed with a solid concrete facade.

3.2.3 At the ingress point at Road 20/4, the incoming buses will enter bays 1 and 2 for refuelling, coin collection, transfer of octopus data to databank, and vehicle washing. The whole process of the refuelling/ servicing and washing would normally take about 3 to 5 minutes. If maintenance is required, the buses will drive into one of the maintenance bays or sunken pits.

3.2.4 To facilitate the buses entering directly to the maintenance area, a passing lane will be provided in parallel to the refuelling/ washing bay lanes. The provision of a passing lane will also help to avoid the generation of a long queue length of buses waiting to be serviced and the associated potential traffic impact. The holding area within the bus depot was assessed to be sufficient to accommodate the bus queue, as confirmed in the approved TIA.

3.2.5 After the completion of washing procedure, buses will leave the depot for further servicing, or returning to parking areas located on 3/F of the bus depot or off-site. On the 1/F, normally a bus under annual maintenance check will have to station in a maintenance bay for about 5 to 7 days. Bus movements on the 1/F will therefore be very limited.

3.2.6 The number of staff working in the bus depot/ maintenance area and offices is estimated to be about 319 and 201 respectively during daytime (approx. 08:00 to 18:00). In the evening and night-time (approx. 18:00 to 08:00), some 50 workers are expected to be working at the bus depot.

3.3 Implementation Programme

3.3.1 Construction works are planned to start near end of 2001 to meet the urgent demand to have the depot ready for operation in mid-2003. Figure 3-9 shows a preliminary construction programme. The development is expected to be completed in mid-2003.

3.4 Identification of Key Environmental Issues

3.4.1 The key environmental issues during the construction and operational phases of the proposed development are identified to include the following:

During the Construction Phase

· Potential construction dust impact on the nearby air sensitive receivers;

· Potential construction noise impact from construction activities;

· Construction waste management and implications

During the Operational Phase

· Potential vehicular emission impact from buses moving within the depot and running at the adjacent roads;

· Potential traffic noise impact from buses running on the road carriageways in the vicinity of the depot;

· Potential fixed noise impact generated from activities at the bus depot;

· Undertaking of land contamination preventive measures;

· Proper chemical waste management;

· Provision of sewage treatment and disposal

3.4.2 The EIA Study Brief requires in general a study area of 300m and 500m from the boundary of the project site with respect to air quality impact assessment and noise impact assessment, respectively. Figure 2-10 shows the study area boundary for air quality and noise impact assessments.

3.4.3 In addition to the above key environmental issues, the EIA Study Brief requires an evaluation on the potential hazard impact arising from the operation of the future LPG/ Petrol Filling Station located on the northern side of the site (Section 8), Landscape and Visual Impacts associated with the implementation of the project (Section 9), and an illustration on the Sewage Treatment and Disposal Facilities (Section 10).

4. Air Quality Impact Assessment

4.1 Introduction

4.1.1 This section assesses the potential air quality impact associated with the construction and operational phase of the proposed bus depot. Air sensitive receivers (ASRs) have been identified and worst case impact on these receivers have been assessed quantitatively.

4.1.2 Dust generation from construction activities is identified to be of key interest during construction phase of the project. During the operational phase, vehicular emission from buses running within the bus depot and on the adjacent roads is the key focus of the study.

4.1.3 The assessment covers a study area of 500m from the development site boundary in accordance with the requirements of the EIA Study Brief.

4.2 Assessment Criteria

4.2.1 The principal legislation regulating air quality in Hong Kong is the Air Pollution Control Ordinance (APCO) (Cap. 311). Air Quality Objectives (AQOs) are set for the whole territory which specify statutory concentration limits for various criteria pollutants and the maximum numbers of times allowed to exceed over a specified period of time. The AQOs for Carbon Monoxide (CO), Nitrogen Dioxide (NO₂), Total Suspended Particulates (TSP) and Respirable Suspended Particulates (RSP), which are relevant to the assessments, are summarised in Table 4‑1.

Table 4‑1 Hong Kong Air Quality Objectives

Pollutant	Pollutants Concentration (mg/m³)
	Averaging Time
	1 hour (i)	8 hours (ii)	24 hours (ii)	1 year (iii)
CO	30,000	10,000	N.A.	N.A.
NO₂	300	N.A.	150	80
TSP	N.A.	N.A.	260	80
RSP	N.A.	N.A.	180	55

(i) Not to be exceeded more than 3 times per year;

(ii) Not to be exceeded more than once per year;

(iii) Arithmetic means;

N.B. Concentrations measured at 298 K and 101.325 kPa (one atmospheric pressure).

4.2.2 In addition to the AQOs, EPD requires under Annex 4 in the Technical Memorandum on EIA Process (EIAO-TM) issued under the EIA Ordinance an hourly TSP limit of 500mg/m³ for construction dust impact assessment.

4.2.3 The Air Pollution Control (Construction Dust) Regulation came into effect since 16 June 1997. Site formation, construction of the foundation and superstructure of buildings, road construction works, etc. are classified as “notifiable work” under the Regulation. Any work which involves stockpiling of dusty materials, loading, unloading or transfer of dusty materials, transfer of dusty materials using a belt conveyor system, use of vehicles, debris handling, excavation or earth moving, site clearance, etc. are regarded as “regulatory work”. A Schedule specifying the dust control requirements for a variety of construction activities is included in the Regulation. The contractor responsible for a construction site where a notifiable work and/ or regulatory work is being carried out have to ensure that the work is carried out in accordance with the Schedule with regard to dust control.

4.3 Air Sensitive Receivers (ASRs)

4.3.1 As stated in Annex 12 of the EIAO-TM, domestic premises and schools are defined as Air Sensitive Receivers (ASRs). The nearest ASRs situated in the vicinity of the proposed bus depot within the study area were identified for the air quality impact assessment. These ASRs include the IVE (Chai Wan) and its auxiliary Staff Quarters located to the north-west of the development site, Tsui Wan Estate located to the south of the development and Heng Fat Chuen situated to the north of the site.

4.3.2 Representative assessment points (A1 to A6) have been selected for the air quality impact assessment. The ASRs represented are described in Table 4‑2. Locations of the representative assessment points are shown in Figure 4-1.

Table 4‑2 Representative Assessment Points

Ref. No.	Location of ASR	Closest distance of ASR from bus depot boundary (m)
A1	Heng Fa Chuen	390
A2	Staff Quarters of Hong Kong Institute of Vocational Education (IVE) (Chai Wan)	135
A3	IVE (Chai Wan)	80
A4	IVE (Chai Wan)	85
A5	Tsui Hong House, Tsui Wan Estate	185
A6	Tsui Sau House, Tsui Wan Estate	165

4.4 Baseline Condition

4.4.1 The existing major air pollution sources in the study area are expected to be open road traffic emission from major road carriageways (e.g. Island East Corridor).

4.4.2 Annual average concentrations of nitrogen dioxide (NO₂) and respirable suspended particulate (RSP) recorded by EPD’s monitoring station in Eastern district for the year 1999 have been used as background pollutant concentrations in the study area. Although the number of monitoring records for NO₂ for Eastern monitoring station is below the minimum data required within a quarter, the concentration of 66mg/m³ was found to be comparable with the concentration at Tsuen Wan which have similar landuses.

4.4.3 For carbon monoxide (CO) and total suspended particulate (TSP) which has no published data available in the study area, EPD’s records from the Tsuen Wan monitoring station in 1999 has been adopted. Table 4‑3 summarises the background concentrations of CO, NO₂, and RSP adopted in the assessment for the purpose of evaluating the cumulative air quality impact.

Table 4‑3 Background Air Pollutant Levels Adopted in the Assessment

Air Pollutant	Annual Average Concentration (mg/m³)
CO	1177
NO₂	66
TSP	79
RSP	47

Note : Background concentrations of CO, NO₂ and RSP in the study area has been assumed based on reported data given in “Air Quality in Hong Kong, 1999” published by EPD.

4.5 Construction Dust Emission Impact Assessment

Introduction

4.5.1 The major air quality impact of concern during the construction phase will be potential dust emission impact on nearby ASRs. Unacceptable impacts from the criteria pollutants - nitrogen oxides (NO_x), sulphur dioxide (SO₂), and carbon monoxide (CO) are unlikely as significant emissions are not anticipated. Emission from diesel trucks for the haulage of materials and construction plants will contain high percentage of smoke particulate and unburned hydrocarbons in comparison with petrol driven vehicles. However, as the anticipated number of construction plants associated with the construction works will be limited, significant impact on the existing air quality is not envisaged.

Dust Emission Sources

4.5.2 Based on the nature of the construction, major dust emission sources associated with the construction activities are expected to arise from excavation, material handling and vehicle movement on unpaved haul roads during the foundation construction stage. The corresponding dust emission rates associated with these activities have been worked out by making reference to the typical emission factors reported in the Compilation of Air Pollutant Emission Factors (AP-42) 5^th Edition published by U.S. Environmental Protection Agency (USEPA).

à Excavation activities - dust emission from excavation has been estimated by making reference to the emission factor given in Section 13.2.4 of USEPA AP-42. Dust emissions have been estimated on a per excavator basis with consideration of typical excavation rate, number of excavator involved, etc. to simulate a representative scenario;

à Material handling - potential dust emission from loading/ unloading activities of excavated material have also been predicted by making reference to Section 13.2.4 of USEPA AP-42. Dust emissions from loading/ unloading have been estimated on a per truck basis with consideration of the capacity of each truck, and the estimated number of trucks to simulate a representative scenario.

à Vehicle movement on unpaved haul roads - dust emission from traffic movement on unpaved haul roads have been estimated by making reference to Section 13.2.2 of USEPA AP-42, with consideration of no. of trucks, typical vehicle speed, weight, number of wheels, etc.

4.5.3 A worksheet showing the calculation of dust emission rates from each activity is presented in Appendix 4-1 for reference.

4.5.4 Foundation works for the New World First Bus (NWFB) depot was completed. Concurrent superstructure construction activities at the NWFB depot is not expected to give rise to a significant cumulative dust impact. There are no known major planned construction activities in the vicinity of the site that may pose a potential significant cumulative impact. Besides, it is expected that even if there would be other construction activities planned in future, these works will also be required to implement sufficient dust control measures in accordance with the requirements of the Air Pollution Control (Construction Dust) Regulation.

Dust Emission Modelling

4.5.5 Construction dust impact arising from the key dust emission sources presented above during the foundation construction stage on the nearby existing ASRs has been predicted using the air quality model “Fugitive Dust Model” (FDM). The model was particularly developed to model fugitive dust emissions and is well accepted by HKEPD and USEPA for this purpose. The model was developed based on the widely used Gaussian plume formulae for estimation of pollutant concentrations but has been adapted to incorporate a gradient-transfer deposition algorithm which accounts for the settling out of dust particles, and to include the wind dependent factor on dust emission rates. The model is designed to predict fugitive dust dispersion from point, line, area and volume sources.

4.5.6 Based on information on general size distribution as reported in Guide to Rock and Soil Descriptions issued by the Geotechnical Control Office, Civil Engineering Services Department, Hong Kong (1988), it has been assumed in the dust dispersion model that 80% of particulates have size equal to 30µm, with the remaining 20% assumed to be respirable with a size of 10µm. An average dust density of 2,500 kg/m³ has been assumed in the study.

4.5.7 The following relevant meteorological data of the year 1998 were obtained from Hong Kong Observatory and used in the modeling study. Parameters used include:

à Hourly wind direction and speed, air temperature together with atmospheric Pasquill stability class obtained at King’s Park;

à Daily morning and maximum mixing heights based on the radiosonde ascent at King’s Park; and

à Hourly total sky cover, cloud amount and cloud based height of the 1^st - 4^th layers observed at the Hong Kong Observatory Headquarters in Tsim Sha Tsui.

4.5.8 Given the stringent noise limits that need to be satisfied before construction activities within the restricted hours will be allowed, it is expected that there will only be construction activities during daytime from 0700 to 1900 hours. Nevertheless, to be conservative in the study, dusty construction activities have been assumed to be in operation continuously over a 24-hour period to give a worst-case situation.

4.5.9 Maximum 1-hour and 24-hour TSP concentrations were predicted at each representative assessment points A1 through A6 identified above. Given the limited height of the dust emission sources, TSP concentrations were predicted at 1.5m, 5m and 10m above ground at the representative assessment points to simulate the worst-case situations. ASRs situated at higher levels are expected to be subject to lower dust impact. With account of the background TSP levels, the maximum 1-hour and 24-hour average TSP concentrations predicted were compared with the 1-hour and 24-hour TSP limits of 500mg/m³ and 260mg/m³, respectively. A typical FDM result file for construction dust impact assessment is enclosed in Appendix 4-2 for reference.

Assessment Results (Unmitigated Scenario)

4.5.10 The unmitigated maximum 1-hour and 24-hour average TSP concentrations predicted at the representative assessment points, with background concentration included, are presented in Table 4‑4 and Table 4‑5 below.

Table 4‑4 Maximum 1-hour TSP Concentrations predicted at the ASRs

(without Mitigation Measures)

Ref. No.	Location	Predicted TSP concentrations (mg/m³)
		1.5m above ground	5m above ground	10m above ground
A1	Heng Fa Chuen	115	110	100
A2	Staff Quarters of the IVE (Chai Wan)	190	157	136
A3	IVE (Chai Wan)	279	216	157
A4	IVE (Chai Wan)	504	378	212
A5	Tsui Hong House, Tsui Wan Estate	180	173	151
A6	Tsui Sau House, Tsui Wan Estate	227	217	184

Note: Background TSP concentration of 79mg/m³ has been included.

Table 4‑5 24-hour Average TSP Concentrations predicted at the ASRs

(without Mitigation Measures)

Ref. No.	Location	Predicted TSP concentration (mg/m³)
		1.5m above ground	5m above Ground	10m above Ground
A1	Heng Fa Chuen	89	89	88
A2	Staff Quarters of the IVE (Chai Wan)	112	108	100
A3	IVE (Chai Wan)	143	132	110
A4	IVE (Chai Wan)	352	247	147
A5	Tsui Hong House, Tsui Wan Estate	110	106	97
A6	Tsui Sau House, Tsui Wan Estate	150	144	126

Note: Background concentration of 79mg/m³ has been included.

4.5.11 The modelling results for the unmitigated scenario revealed that the nearby Air Sensitive Receivers will be subject to dust level at acceptable levels, except at A4. In accordance with the requirements set out in the Air Pollution Control (Construction Dust) Regulation, sufficient dust control/ mitigation measures shall be implemented to ensure full protection of the nearby ASRs.

Control Measures for mitigating Fugitive Dust Emissions

4.5.12 The following measures are specifically recommended for implementation together with those presented in the Air Pollution Control (Construction Dust) Regulation:

General Site Management

4.5.13 Appropriate working methods should be devised and arranged to minimise dust emissions and to ensure any installed air pollution control system and measures are operated and/or implemented in accordance with their design merits. In the event of malfunctioning of any control system or equipment, the relevant dusty activities shall stop until the relevant control system or equipment are restored to proper functioning.

4.5.14 Frequent mist spraying should be applied on dusty areas. The frequency of spraying required will depend upon local meteorological conditions such as rainfall, temperature, wind speed and humidity. The amount of mist spraying should be just enough to dampen the material without over-watering, which could result in unnecessary surface water runoff.

4.5.15 No free falling of construction debris shall be allowed at the site.

Vehicles and Site Haul Road

4.5.16 Dust emission from unpaved roads comes predominantly from travelling of vehicles. Areas within the site where there are regular vehicle movements should have an approved hard surface. Speed controls at an upper limit of 10 to 15 kph should be imposed and their movements should be confined to designed roadways within the site. All dusty vehicle loads should have side and tail boards and should be covered by tarpaulin extending at least 300 mm over the edges of the side and tail boards. Wheel-wash troughs and hoses should be provided at exit points of the site.

Material Stockpiling and Handling

4.5.17 The amount of stockpiling should be minimised as far as practicable. The surface of the stockpile should be kept wet by spraying with water. Dust emission during loading of fill material to dump trucks should be mitigated by spraying to sufficiently damp the material prior to any loading or unloading operation. Dusty construction debris should be covered or stored inside enclosed areas where practicable to avoid dust generation.

4.5.18 Watering is an effective dust control measure commonly employed in storage piles and handling operations and should be implemented where appropriate. Other control measures such as enclosed or semi-enclosed windboard should be used, where applicable, to minimise dust emission.

4.5.19 With the implementation of the above-mentioned dust mitigation measures together with those required in the Air Pollution Control (Construction Dust) Regulation, it is expected that a minimum dust control efficiency of at least 50% is achievable. Table 4-6 and 4-7 present the mitigated dust levels predicted at the ASRs based on 50% dust control efficiency. Implementation of dust control measures in accordance with the requirements under the Air Pollution Control (Construction Dust) Regulation will therefore ensure that unacceptable dust impact will not be generated.

Table 4‑6 Maximum 1-hour TSP Concentrations predicted at the ASRs

(with Mitigation Measures)

Ref. No.	Location	Predicted maximum 1-hr TSP concentrations (mg/m³)
		1.5m above ground	5m above ground	10m above ground
A1	Heng Fa Chuen	97	94	89
A2	Staff Quarters of the IVE (Chai Wan)	134	118	107
A3	IVE (Chai Wan)	179	147	118
A4	IVE (Chai Wan)	292	228	146
A5	Tsui Hong House, Tsui Wan Estate	130	126	115
A6	Tsui Sau House, Tsui Wan Estate	153	148	132

Note: Background TSP concentration of 79mg/m³ has been included.

Table 4‑7 24-hour Average TSP Concentrations predicted at the ASRs

(with Mitigation Measures)

Ref. No.	Location	Predicted 24-hour average TSP concentration (mg/m³)
		1.5m above ground	5m above Ground	10m above Ground
A1	Heng Fa Chuen	84	84	83
A2	Staff Quarters of the IVE (Chai Wan)	95	94	90
A3	IVE (Chai Wan)	111	105	95
A4	IVE (Chai Wan)	216	163	113
A5	Tsui Hong House, Tsui Wan Estate	94	93	88
A6	Tsui Sau House, Tsui Wan Estate	115	111	103

Note: Background concentration of 79mg/m³ has been included.

4.5.20 Contour maps presenting the predicted mitigated maximum 1-hour and 24-hour average TSP concentrations at 1.5m above ground are given in Figure 4-2 and Figure 4-3. Background TSP level has been included in the results. The results show that the fugitive dust impact arising from the construction works when dust mitigation measures required under the Air Pollution Control (Construction Dust) Regulation are implemented will be within the relevant dust assessment criteria. Implementation of the recommended Environmental Monitoring and Audit Program (EM&A) will further ensure full protection of the nearby ASRs. Details of the EM&A Programme are presented in the Environmental Management Plan (EMP).

4.6 Vehicular Emission Impact Assessment

4.6.1 During the operational phase of the bus depot, vehicular emission from buses running within the depot and commuting to and from the depot is the focus of the assessment. Emissions of the key criteria pollutants associated with vehicular traffic, including nitrogen dioxide (NO₂), carbon monoxide (CO), and respirable suspended particulate (RSP) have been studied.

4.6.2 Potential cumulative air quality impact from the concurrent operation of the NWFB depot in the area, as well as traffic emissions from the nearby road carriageways have been taken account of quantitatively in the study. Traffics generated from the future landuses within the Chai Wan East Industrial Area have been considered in the traffic forecast provided by the Project Traffic Consultant – LLA Consultancy Limited.

4.6.3 Air pollutants may also be generated from other depot operations including engine testing, brake testing and painting. However, the emission quantity and associated air pollution is expected to be insignificant.

Open Road Vehicular Emission

Traffic Forecast

4.6.4 Similar to other future developments, operation of the proposed bus depot will inevitably results in generation of some traffic flows on the nearby road carriageways. This section assesses the potential air quality impact associated with traffic movement in the study area, taking into account the additional traffic flows generated from the proposed bus depot. Effects of other possible future developments in the study area have also been taken into account through incorporation of traffic generation into the traffic forecast.

4.6.5 Traffic forecast for the year 2018 during the early morning (0530 to 0630) and mid-night (2300 to 0000) peak hour, when the highest traffic flow contribution is expected to be generated from the proposed bus depot, has been adopted in the study. Traffic generation from other possible future developments in the area, including the NWFB depot has been taken into consideration in the preparation of the traffic forecast. The traffic forecast data prepared by the Project Traffic Consultant has been endorsed by Transport Department for use in the EIA study (see Appendix 5-6). In the preparation of the traffic forecast, the Traffic Consultant has taken into account the data presented in the approved EIA reported carried out for NWFB Permanent Depot in Chai Wan to ensure that a consistent and conservative approach is being followed. Table 4-8 and Table 4‑9 present the 2018 Traffic Forecast during the early morning and nighttime peak hours when the highest bus flows will be generated from the bus depot. Alignment of the road carriageways studied is presented in Appendix 4-3.

Table 4‑8 Year 2018 Traffic Forecast during the early Morning Peak Leaving

Label	Traffic Volume (veh/hr)	% of Passenger Car	% of HGV	% of Bus
A	332	21.5	56.6	22.0
B	171	47.1	50.0	2.9
C	160	25.8	74.2	0.0
D	306	39.3	38.5	22.2
E	565	54.5	45.5	0.0
F	835	57.0	43.0	0.0
G	249	14.0	58.7	27.3
H	3086	71.1	26.6	2.4
I	114	15.0	85.0	0.0
J	162	24.2	72.7	3.1
K	47	25.0	28.2	46.8
L	212	24.3	75.7	0.0
M	232	24.3	75.7	0.0
N	3086	71.1	26.6	2.4
O	284	37.7	62.3	0.0
P	2694	70.1	29.9	0.0
Q	20	90.0	10.0	0.0
R	20	90.0	10.0	0.0

Table 4‑9 Year 2018 Traffic Forecast during the Nighttime Peak Return

Label	Traffic Volume (veh/hr)	% of Passenger Car	% of HGV	% of Bus
A	734	40.9	42.7	16.3
B	346	40.7	42.0	17.3
C	50	93.8	6.2	0.0
D	368	57.8	25.9	16.3
E	889	86.3	13.7	0.0
F	1325	77.6	22.4	0.0
G	368	44.9	38.8	16.3
H	2564	58.8	36.5	4.7
I	68	18.0	82.0	0.0
J	647	25.4	65.3	9.3
K	85	38.6	14.3	47.1
L	477	44.6	55.4	0.0
M	481	44.6	55.4	0.0
N	2564	58.8	36.5	4.7
O	433	55.8	44.2	0.0
P	1654	59.8	40.2	0.0
Q	20	90.0	10.0	0.0
R	20	90.0	10.0	0.0

Air Quality Modelling

4.6.6 Potential vehicular emission from open road traffic has been assessed with the air quality model CALINE4. The model is a line source model developed by the California Department of Transport. It was developed based on the Gaussian diffusion formulae and a mixing zone concept in predicting dispersion of pollutants emitted from road carriageways.

4.6.7 As the bus depot will commence operation in 2003, to be conservative in the assessment, emission factors for vehicular pollutants recommended by DEP in air quality study have been used with 2018 traffic forecast data in the modeling study. As pollutant emission factors are expected to be reduced as technology advance in reducing vehicular emissions, this approach to the study is considered very conservative. Table 4-10 presents the 2003 vehicular emission factors of CO, NO_x and RSP for passenger cars, buses and heavy diesel vehicles.

Table 4‑10 2003 Vehicular Emission Factors

*Vehicle Type*	*Emission Factor (mg/km)***
	CO	*NO_x*	*RSP*
Passenger Car (Petrol)	2.34	0.90	0.03
Franchised Bus Double Deck (FBDD)	9.22	10.53	1.17
Heavy Diesel Vehicle	8.53	6.21	1.05

The following assumptions were adopted throughout the study :

i. NO_x is a mixture of NO and NO₂;

ii. 20% of NO_x is assumed to be NO₂;

iii. NO was modelled as “Inert Gas”; with a molecular weight of 46g;

iv. The proportion of RSP in the vehicular emission is assumed to be 100% of the particulate matter which is, in general, less than 10 mm in the aerodynamic diameter.

4.6.8 Pasquill Stability Class F with a wind speed of 1m/s has been adopted in the CALINE4 modelling to simulate the worst-case meteorological conditions. The ambient temperature was assumed to be 25 degree Celsius. The average mixing height was taken as 500m according to monitoring data obtained from Kai Tak Weather Station. Wind direction standard deviation of 6 degree. The aerodynamic roughness coefficient was set at 100cm.

4.6.9 Concentrations of maximum 1-hour CO, NO₂ and RSP at the representative assessment points A1 through A6 presented in Figure 4-1 were predicted from the model. As there is currently no hourly AQO for RSP, the modeled peak hour RSP concentrations were converted to daily average concentration for checking compliance with the daily criteria of 180mg/m³. 24-hour NO₂concentrations at the assessment points were also predicted using the same approach. Assuming that the predicted maximum peak hour traffic flow would last for 10 hours and the wind would be blowing at the worst direction for 24 hours, a conversion factor of 0.4 has been applied to convert maximum 1-hour RSP and NO₂ concentrations to maximum 24-hour average for comparison with the relevant Air Quality Objectives.

Assessment Results

4.6.10 Table 4-11 presents the modeled maximum 1-hour NO₂, 1-hour CO and 24-hour average RSP and NO₂ concentrations at the representative assessment points for open road vehicular emission. Background pollutant concentrations have been added to the results. Typical CALINE4 result files are presented in Appendix 4-4.

4.6.11 It can be noted that all modeling results are falling well within the relevant AQOs.

4.6.21 The maximum 1-hour NO₂ concentration was predicted at A3 at 10m above ground from the modelling. In addition to the discrete representative assessment points, assessment points were selected based on a 50m x 50m grid covering the key air sensitive areas of interest, viz. Heng Fa Chuen, IVE (Chai Wan) and its associated Staff Quarters, and Tsui Wan Estate. Pollutant isopleths of maximum 1-hour NO₂, 1-hour CO and 24-hour RSP and NO₂ were generated from the ISCST3 and CALINE4 modelling results obtained at the worst affected level at 10m above ground. Background pollutant concentrations set out in Table 4‑3 were added to the modelling results for comparison with the relevant AQOs. The contour maps are presented in Figure 4-4 to Figure 4-7.

4.6.22 All predicted air pollutant concentrations at various levels of the ASRs are well within the AQOs. The assessment results reveal that vehicular emissions from open road traffic and emission from the two bus depots will unlikely pose an unacceptable air quality impact on the surrounding ASRs.

4.7 Environmental Monitoring & Audit (EM&A) Requirements

4.7.1 The quantitative construction dust impact assessment confirms that no unacceptable air quality impact affecting the nearby ASRs is anticipated when the required dust control/ mitigation measures required under the Air Pollution Control (Construction Dust) Regulation are implemented. Nevertheless, for checking the implementation of the dust mitigation measures required under the Air Pollution Control (Construction Dust) Regulation, implementation of a dust monitoring programme is recommended as part of the environmental monitoring and audit (EM&A) programme.

4.7.2 The detailed vehicular emission impact assessment indicates that vehicular emission from buses will not be a concern during the operational phase. The carrying out of air quality EM&A works in relation to air quality during the operational phase is not considered necessary.

4.8 Assessment Conclusions

Construction Phase

4.8.1 The dust impact assessment concluded that the dust impact during the construction phase of the development will be in compliance with the air quality criteria when dust control measures required under the Air Pollution Control (Construction Dust) Regulation are in place. Construction air quality impact should be minor and effective dust control can be achieved by implementation of the dust control measures required under the Air Pollution Control (Construction Dust) Regulation.

Operational Phase

4.8.2 Potential air quality impact arising from the operation of the proposed bus depot, including emission directly from the bus depot and from open road vehicular emission, has been assessed. Direct emission from the NWFB depot, as well as vehicular emission from traffic generated by the planned landuses including the NWFB depot in the area, has been considered. The cumulative pollutant concentrations predicted are all satisfying the relevant AQOs. The assessment results obtained with a conservative assessment approach indicate that the operation of the bus depot will not cause any unacceptable air quality impact on the surrounding air sensitive receivers.

5. Noise Impact Assessment

5.1 Introduction

5.1.1 This section presents an assessment of noise impact associated with the construction and operation of the project. During the construction phase, potential noise impact arising from the operation of powered mechanical equipment (PME) at the work sites is the key interest. Potential traffic noise impact from buses running on the road carriageways in the vicinity of the bus depot and that generated from fixed noise sources are the focus of the operational phase impact study. Where necessary, mitigation measures will be recommended to reduce the noise impact down to meet acceptable levels.

5.2 Study Area and Noise Sensitive Receivers (NSRs)

5.2.1 A study area of 300m from the boundary of the project site has been adopted in the study in accordance with the requirement stated in the EIA Study Brief.

5.2.2 As defined in Annex 13 of the EIAO-TM, domestic premises and schools are defined as noise sensitive receivers. In the current study, the nearest NSRs identified in the proximity of the proposed Bus depot are the residential developments to the north and south of the Bus Depot, namely Heng Fa Chuen and Tsui Wan Estate respectively, and the IVE (Chai Wan) and its associated Staff Quarters. Representative assessment points (RAPs) have been selected for each of these NSRs and their locations are shown in Figure 4-1. These RAPs are described in Table 5‑1. The separation distance between the RAPs and the bus depot is also shown in Table 5-1.

Table 5‑1 Representative Assessment Points selected for Noise Impact Assessment

RAPs	Description	Floors	Separation (Approx.) (m)
HF-1	Block 50, Heng Fa Chuen	G/F to 20/F	390
HF-2	Block 16, Heng Fa Chuen	G/F to 20/F	658
SH-1	Staff Quarters of the IVE (Chai Wan)	G/F to 25/F	200
SH-2	Staff Quarters of the IVE (Chai Wan)	G/F to 25/F	160
IV-1	IVE (Chai Wan)	G/F to 5/F	175
IV-2	IVE (Chai Wan)	G/F to 5/F	85
TW-1	Tsui Sau House, Tsui Wan Estate	G/F to 30/F	165
TW-2	Tsui Fuk House, Tsui Wan Estate	G/F to 30/F	235
TW-3	Tsui Ling House, Tsui Wan Estate	G/F to 30/F	305
TW-4	Tsui Hong House, Tsui Wan Estate	G/F to 30/F	205

5.2.3 Eastern facade of IVE (Chai Wan) Staff Quarters (SH-3 and SH-4 in Figure 4-1) is installed with fixed windows (i.e. does not rely on opened windows for ventilation) such that the relevant noise standards are not applicable. Therefore, RAPs were only selected on the western façade of the Staff Quarters for the assessment. Besides, it is identified that IVE (Chai Wan) is installed with air-conditioners such that the occupants in the teaching classrooms and laboratories will not rely on openable windows as the primary means for ventilation.

5.2.4 No planned NSRs are identified in the proximity of the bus depot that could be subject to a noise impact resulting from the project.

5.2.5 The existing dominant noise sources identified in the vicinity of these NSRs include traffic noise from the nearby major road carriageways (e.g. Island Eastern Corridor) and railway noise from the MTR tracks.

5.3 Construction Noise Impact Assessment

Legislation and Assessment Criteria

5.3.1 Construction noise is controlled under the Noise Control Ordinance (NCO) which prohibits the use of powered mechanical equipment (PME) during the restricted hours (7 p.m. to 7 a.m. on normal weekdays and any time on a public holiday, including Sunday) without a valid Construction Noise Permit (CNP) granted by the Authority. The criteria and procedures for issuing such a permit are specified in the “Technical Memorandum on Noise From Construction Works Other than Percussive Piling” (TM1).

5.3.2 For construction works other than percussive piling, although TM1 do not provide control over daytime construction activities, noise limits are set out in Table 1B of Annex 5 of the EIAO TM which have been adopted as the assessment criteria in this study. These noise standards are summarised in Table 5‑2 below:

Table 5‑2 Noise Limits for Daytime Construction Activities

NSR

0700 to 1900 hours on any day not being a Sunday or general holiday L_eq(30min.) dB (A)

All domestic premises including temporary housing accommodation

Educational institutions including kindergartens, nurseries.

65 (during examination)

N.B. (i) The above standards apply to uses which rely on opened windows for ventilation;

(ii) The above standards shall be viewed as the maximum permissible noise levels assessed at 1m from the external facade.

5.3.3 Construction works during the restricted hours are not required. However, if the Contractor finds that works during restricted hours are required, then, he should apply for a Construction Noise Permit (CNP). Despite any description or assessment made in this EIA Report on construction noise aspects, there is no guarantee that a CNP will be issued for the project construction. The Noise Control Authority will consider a well-justified CNP application, once filed, for construction works within restricted hours as guided by the relevant Technical Memoranda issued under the Noise Control Ordinance. The Noise Control Authority will take into account of contemporary conditions/ situations of adjoining land uses and ay previous complaints against construction activities at the site before making his decision in granting a CNP. Nothing in this EIA Report shall bind the Noise Control Authority in making his decision. If a CNP is to be issued, the Noise Control Authority shall include in it any condition he thinks fit. Failure to comply with any such conditions will lead to cancellation of the CNP and prosecution action under the NCO.

5.3.4 With effect from 1 November 96, the use of specified powered mechanical equipment (SPME) for carrying out construction work other than percussive piling and/ or the carrying out of prescribed construction work (PCW) within a designated area are also brought under control. The relevant technical details are provided in the “Technical Memorandum on Noise from Construction Work in Designated Areas” (TM2).

5.3.5 Percussive piling is controlled similarly by a noise permit system and described in the NCO and the “Technical Memorandum On Noise From Percussive Piling” (TM3) which restrict the number of hours during which piling can be conducted. No percussive piling may be carried out in the territory without a valid CNP issued by the Authority. Besides, a CNP will only be granted for percussive piling which is scheduled during normal working hours between 7 a.m. to 7 p.m. from Monday to Saturday. The carrying out percussive piling is prohibited at any time on Sundays and public holidays as well as during the weekday from 7 p.m. to 7 a.m. the next day.

Assessment Methodology

5.3.6 The approach used in the assessment of noise from construction works other than percussive piling is based on standard acoustic principles, and the guidelines given Para. 5.3 and 5.4 of Annex 13 of the EIAO TM. The methodology adopted is the same as that presented in TM1.

5.3.7 The methodology for assessing construction noise impact arising from the project has been developed based on the standard acoustic principles in TM1. In brief, this includes the following steps:

(i) based on the preliminary construction programme given in Figure 3-9, identify the most likely powered mechanical equipment (PME) to be used during foundation construction and superstructure construction;

(ii) identify the nearest representative assessment points of the NSRs to the work sites;

(iii) calculate the total Sound Power Level (SWL) of the equipment that would likely be used simultaneously at the notional source location of the site;

(iv) calculate the Predicted Noise Level (PNL) based on distance attenuation from the notional source positions to the NSRs;

(v) with consideration of the effect of façade reflection at the NSRs, calculate the Corrected Noise Level (CNL) at the NSRs; and

(vi) compare the CNL with the relevant daytime noise limits and identify situations and locations where the implementation of construction noise mitigation measures would be necessary.

Noise Sources

5.3.8 Exact details on the PME to be used during the construction phase would not be available before the appointment of the Contractor in future. Nevertheless, based on previous experience in similar construction projects, the Project Engineer, Wong Pak Lam & Associates Limited, has developed a preliminary PME inventory for the purpose of quantitative assessments in the study. Table 5-3 through Table 5-5 present the PME inventories for the foundation construction works; sheet piling and pile cap construction, and superstructure construction, respectively. The plant inventories listed in these tables have been confirmed by the Project Architect based on his experience in similar projects to be practical and practicable for completing the works within the planed construction programme, and demonstrated in practices through similar projects undertaken by contractors. Potential cumulative noise impact from concurrent use of different groups of PMEs has been assessed in the study for identification of the mitigation measures required under these situations.

5.3.9 The carrying out of a quantitative construction noise assessment based on the preliminary PME inventories established at this planning stage will allow the identification of potential construction noise problem and location of the potentially affected NSRs such that practicable and sufficient noise mitigation measures can be derived accordingly at this early stage and incorporated as contract requirements for the future Contractor to follow. Implementation of sufficient noise mitigation can be checked through Environmental Monitoring and Audit requirements.

Table 5‑3 PME Inventory for Foundation Construction Works

*PME*	*No. of Equipment*	*SWL, dB(A)*
Piling, large diameter bored, oscillator	10	115
Piling, large diameter bored, reverse circulation drill	7	100
Generator	4	108
Excavator	4	112
Lorry	2	112
Crawler crane	13	112
Concrete lorry mixer	4	109
Dump Truck	3	117

Table 5‑4 Inventory of PMEs during Sheet Piling and Pile Cap Construction

*Equipment Group*	*PME*	*No. of Equipment*	*SWL, dB(A)*
1	Compressor <10m³ /min	2	100
	Concrete pump	1	109
	Generator	2	108
	Compactor/ Concrete Vibrator	2	105
	Excavator	3	112
	Lorry	3	112
	Concrete Lorry Mixer	3	109

2	Tower Crane	2	95

3	Bar Bender	2	90
	Saw	2	108

4	Sheet Pile Vibrator	2	114

Table 5‑5 Inventory of PMEs during Superstructure Construction

*Equipment Group*	*PME*	*No. of Equipment*	*SWL, dB(A)*
1	Compressor <10m³ /min	2	100
	Concrete pump	2	109
	Generator	2	108
	Compactor/ Concrete Vibrator	5	105
	Excavator	3	112
	Lorry	3	112
	Concrete Lorry Mixer	6	109

2	Tower Crane	3	95
	Hoist, Material	2	95

3	Bar Bender	3	90
	Saw	4	108
	Planer	2	117

4	Poker	2	113

Representative Assessment Points

5.3.10 Three Representative Assessment Points (RAPs) including HF-1, IV-2 and TW-1 situated nearest to the development site were selected in the construction noise impact assessment. Locations of these RAPs are shown in Figure 5-1. As these RAPs are situated closest to the development site, compliance of the daytime construction noise limits at these RAPs will indicate that the standards will also be met at other Noise Sensitive Receivers located at further distance away from the site.

Assessment Results (Unmitigated Scenario)

5.3.11 Table 5‑6 presents the unmitigated noise levels predicted at the RAPs for the various construction stages and scenarios. For the sheeting piling and pile cap construction stage and superstructure construction stage, concurrent operation of different PME groups were considered under 6 scenarios (see notes under Table 5-6). Those predicted noise levels exceeding the noise criteria are highlighted in bold. Worksheets showing the calculation at IV-2, TW-1 and HF-1 are provided in Appendix 5-1 for reference.

Table 5‑6 Unmitigated Noise Levels predicted at the RAPs, L_eq(30min.)dB(A)

	Construction Stages
	Foundation	Sheet Piling and Pile Cap Construction			Superstructure Construction
RAPs	Construction	S1	S2	S3	S4	S5	S6
IV-2 (1/F)	82	75	76	76	78	77	79
IV-2 (3/F)	82	75	76	76	78	77	79
IV-2 (5/F)	82	75	76	76	78	77	79
TW-1 (1/F)	76	69	70	70	72	70	72
TW-1 (15/F)	76	69	70	70	72	70	72
TW-1 (30/F)	75	69	70	70	72	70	72
HF-1 (1/F)	71	64	65	65	67	66	68
HF-1 (10/F)	71	64	65	65	67	66	68
HF-1 (20/F)	71	64	65	65	67	66	68

S1 – scenario 1 : concurrent operation of Groups 1, 2 & 3 PMEs in Table 5-4;

S2 – scenario 2 : concurrent operation of Groups 1, 2 & 4 PMEs in Table 5-4;

S3 – scenario 3 : concurrent operation of Groups 1, 2, 3 & 4 PMEs in Table 5-4;

S4 – scenario 4 : concurrent operation of Groups 1, 2 & 3 PMEs in Table 5-5;

S5 – scenario 5 : concurrent operation of Groups 1, 2 & 4 PMEs in Table 5-5;

S6 – scenario 6 : concurrent operation of Groups 1, 2, 3 & 4 PMEs in Table 5-5

5.3.12 The assessment results from consideration of the unmitigated scenarios revealed that given the significant distance separation between the site and Tsui Wan Estate and Heng Fa Chuen, it is predicted that the daytime construction noise limit of L_eq(30min.) 75dB(A) will be fully satisfied at HF-1 and the NSRs represented at all floors. The noise standard will also be satisfied at TW-1 except for some units located at low and medium levels during the foundation construction stage which will be subject to a noise exceedance of 1dB(A).

5.3.13 Given the more stringent noise limit applied to educational institutions and the closer distance of IVE (Chai Wan) to the site, noise impact up to a maximum level of 82dB(A) exceeding the noise limit of 70dB(A) for 12dB(A) was predicted at IV-2 during the execution of foundation works. Noise mitigation measures will be required to mitigate the construction noise impact predicted at IV-2, as well as low and medium floors of TW-1.

5.3.14 It shall be noted that the assessment results predicted above only represent the worst-case construction scenarios i.e. when equipment adopted for different construction activities are in concurrent and continuous operation, and located at the same notional source position nearest to each RAP in question. In reality, the occurrence of these scenarios would be rare. Nevertheless, the assessment results revealed that particular attention should be placed to implement sufficient control/ mitigation measures to alleviate the noise impact during the execution of the construction works, especially for construction works carried out near the IVE (Chai Wan) and Tsui Wan Estate.

Recommended Construction Noise Mitigation Measures

5.3.15 Potential noise impacts from the foundation works, sheet piling and pile cap construction and superstructure construction can be minimised by adopting a combination of the following noise mitigation measures. These include:

· Use of quiet PME;

· Phasing of construction activities to minimise concurrent operation of PME; and

· Minimise number of PME working concurrently;

· Erect temporary noise barriers at required locations, and provision of acoustic enclosure for stationary emission sources;

· Good site practice and noise management

5.3.16 These standard noise mitigation measures have been proven to be practical and practicable in mitigating noise impact generated from PME. Local contractors have demonstrated through similar projects that the implementation of these standard noise mitigation measures in alleviating construction noise impact will not affect the completion of the works within scheduled timeframe.

Selecting Quiet PME

5.3.17 Silenced types of equipments are locally available for certain PMEs for use in construction activities. Based on the preliminary PME inventory, reduced SWL for a number of quieter plants were identified from TM1 or BS5228 (Part 1 : 1997) Noise and vibration control on construction and open sites (BS5228) for the purpose of the assessment. These quiet PME which are known to be locally available and adopted in the assessment are given below:

PME	Reference and SWL
Excavator	BS5228 Table C3/97 - 105dB(A) max;
Lorry	BS5228 Table C3/59 - 105dB(A) max;
Dump Truck	BS5228 Table C9/27 - 105dB(A) max;
Sheet Pile Vibrator	BS5228 Table C4/9 – 111dB(A) max;
Poker	BS5228 Table C6/43 – 105dB(A) max;
Saw	BS5228 Table C7/75 – 105dB(A) max;
Generator	TM CNP102 - 100 dB(A) max

5.3.18 Use of quiet plants in construction works have been demonstrated in many other construction projects requiring noise mitigation to be practical and practicable without affecting the target construction programmes. It is recommended that the future contractor appointed for the project should to be required to diligently seek equivalent models of silenced PMEs with a SWL similar to or less than that presented for the above PMEs, and quiet model of other PMEs as far as practicable.

5.3.19 Table 5‑7 sets out the mitigated noise levels predicted at the RAPs when silenced PME with the reduced SWL presented above are in use. Worksheets showing calculation of noise levels at the RAP are provided in Appendix 5-2 for reference.

5.3.20 It can be noted from Table 5‑7 that by adopting the available quiet PMEs, the noise levels at the NSRs will be reduced. Especially, noise levels radiated from the foundation works at TW-1 will also be alleviated to meet L_eq(30min.) 75dB(A) (i.e. the noise limit is satisfied at all nearby residential blocks). By comparison of Table 5-7 with Table 5-6, it can also be noted that noise impact at IV-2 can also be reduced for about 1 to 4dB(A) when the quiet PMEs are in use.

Table 5‑7 Mitigated Noise Level Predicted at the Representative NSRs (with silenced PMEs)

	Construction Stages
	Foundation	Sheet Piling and Pile Cap Construction			Superstructure Construction
RAPs	Construction	S1	S2	S3	S4	S5	S6
IV-2 (1/F)	81	72	73	73	77	74	77
IV-2 (3/F)	81	71	73	73	77	74	77
IV-2 (5/F)	81	71	73	73	77	74	77
TW-1 (1/F)	75	65	66	67	70	67	71
TW-1 (15/F)	75	65	66	67	70	67	71
TW-1 (30/F)	74	65	66	67	70	67	71
HF-1 (1/F)	70	61	62	62	66	63	66
HF-1 (10/F)	70	61	62	62	66	63	66
HF-1 (20/F)	70	61	62	62	66	63	66

S1 – scenario 1 : concurrent operation of Groups 1, 2 & 3 PMEs in Table 5-4;

S2 – scenario 2 : concurrent operation of Groups 1, 2 & 4 PMEs in Table 5-4;

S3 – scenario 3 : concurrent operation of Groups 1, 2, 3 & 4 PMEs in Table 5-4;

S4 – scenario 4 : concurrent operation of Groups 1, 2 & 3 PMEs in Table 5-5;

S5 – scenario 5 : concurrent operation of Groups 1, 2 & 4 PMEs in Table 5-5;

S6 – scenario 6 : concurrent operation of Groups 1, 2, 3 & 4 PMEs in Table 5-5

Phasing of Construction Activities & Reduce Number of Equipment working concurrently

5.3.21 Noise levels presented in Table 5-7 were obtained by assuming simultaneous operation of different groups of PMEs. In reality, this is unlikely as equipments serving different purpose are expected to be in use in sequence rather than operating concurrently. Taking into account the common work sequence in the assessment, as shown in Appendix 5-3, equipment involved in the foundation works can be sub-divided into the following two main groups:

· PME Group 1 - Bored piling (oscillator), piling (reverse circulation driller), generator, excavator and lorry.

· PME Group 2 – Crawler crane, concrete lorry mixer and dump truck.

5.3.22 Besides, with regard to the superstructure construction phase, it is expected that the equipment groups used concurrently can be sub-divided into the following two series: PME Groups 1, 2 and 3, or PME Groups 1, 2 and 4 after taking into consideration the nature of the construction activities involved.

5.3.23 In addition to phasing of construction activities, the number of similar PMEs operating simultaneously can be controlled to further alleviate the noise impact. Thus, during the foundation stage, it is expected that the noise levels at the RAPs can be further reduced when the number of concurrently working large diameter bored piles and crawler crane can be reduced for PME Groups 1 and 2; for the superstructure construction stage, the noise levels at the RAPs can be alleviated with reduction in number of concrete lorry mixer, saw and planer working simultaneously within a 30-minute period.

5.3.24 Table 5-8 presents the further mitigated noise levels when the above additional noise mitigation measures, including phasing of construction activities and reduce number of equipment operating simultaneously, are applied.

Table 5‑8 Predicted Noise Level at the Representative NSRs (with silenced PME, phasing of activities and reduction in number of PME operating simultaneously)

	Construction Stages
	Foundation Construction		Sheet Piling and Pile Cap Construction¹			Superstructure Construction
RAPs	P1	P2	S1	S2	S3	S4	S5
IV-2 (1/F)	75	75	72	73	73	75	73
IV-2 (3/F)	75	75	71	73	73	75	73
IV-2 (5/F)	75	75	71	73	73	75	72
TW-1 (1/F)	69	69	65	66	67	68	66
TW-1 (15/F)	69	69	65	66	67	68	66
TW-1 (30/F)	68	68	65	66	67	68	66
HF-1 (1/F)	65	64	61	62	62	64	62
HF-1 (10/F)	64	64	61	62	62	64	62
HF-1 (20/F)	64	64	61	62	62	64	62

P1 – cumulative noise levels when Group 1 PMEs presented in Paragraph 5.3.27 are in use;

P2 - cumulative noise levels when Group 1 PMEs presented in Paragraph 5.3.27 are in use;

S1 – scenario 1 : concurrent operation of Groups 1, 2 & 3 PMEs in Table 5-4;

S2 – scenario 2 : concurrent operation of Groups 1, 2 & 4 PMEs in Table 5-4;

S3 – scenario 3 : concurrent operation of Groups 1, 2, 3 & 4 PMEs in Table 5-4;

S4 – scenario 4 : concurrent operation of Groups 1, 2 & 3 PMEs in Table 5-5;

S5 – scenario 5 : concurrent operation of Groups 1, 2 & 4 PMEs in Table 5-5;

¹ Noise levels as presented in Table 5-7 i.e. mitigated noise levels when silenced PMEs only are in use.

5.3.25 The assessment results presented above demonstrated that with the consideration of phasing of construction activities and reduction in number of certain noisy equipment operating simultaneously under the planned construction programme, noise levels at IV-2 during the foundation stage can be reduced up to 6dB(A), while up to 2dB(A) can be reduced for the superstructure construction phase.

5.3.26 The provision of these additional noise mitigation measures will also benefit the NSRs represented by TW-1 and HF-1.

5.3.27 The mitigated noise levels indicated that IV-2 would still be affected, given its closer distance and the more stringent noise limit.

Use of Temporary Noise Barriers and Machinery Enclosures

5.3.28 The erection of noise barriers between major noise sources and affected NSRs at required locations will be effective in reducing the potential construction noise impact.

5.3.29 The minimum effective height of noise barriers should be as such that no part of the noise source should be visible from the target NSRs to be protected. The guidelines given in the Booklet entitled “A Practical Guide for the Reduction of Noise from Construction Works” issued by EPD is recommended to be referenced to in the detailed design of the temporary acoustic barriers by the contractor. Barriers should have no openings or gaps, and preferably have a superficial surface density of at least 7 kg/m². Where required, temporary barriers of sufficient height with skid footing and a cantilevered upper portion can be erected within a few meters from stationary plants, and at practicable distance from mobile plants operating over a small area or using a well defined route, to alleviate potential construction noise impact. In accordance with BS5228, proper use of barriers for PME can achieve a noise reduction of 10dB(A) when the noise screen completely hides the sources from the receiver; and of 5dB(A) when the top of the plant is just visible to the receiver over the noise barrier.

5.3.30 For protection of the low-rise IVE (Chai Wan) located at about 80m to the west of the site, a 6m high vertical noise barrier (or equivalent, if a cantilever type noise barrier is adopted) is recommended to be erected at the western site boundary along Shing Tai Road to shield the noise generated from noise activities generated behind the barrier. As confirmed with the Project Engineer, the required noise barrier can be incorporated into the design of the site hoarding along Shing Tai Road. For maintaining the acoustic shielding effectiveness of the temporary noise barrier proposed, vehicular access to the construction site shall not be positioned at Shing Tai Road as far as practicable. Figure 5-2 and Figure 5-3 show the location and preliminary design of the temporary noise barrier to be erected during the construction phase at the western site boundary along Shing Tai Road.

5.3.31 The erection of the fixed noise barrier at the western site boundary will allow a maximum noise reduction of 10dB(A) for those NSRs that are fully screened from the noise sources by the barriers located at ground level. To be conservative in the assessment, a noise reduction effect of -5dB(A) has only been applied in the calculation.

5.3.32 In addition to the temporary noise barriers, certain types of PME such as generators and compressors can be totally shielded by machinery enclosures. A transmission loss of 10dB(A) for noise enclosure has been conservatively applied in the study.

5.3.33 Table 5‑9 presents the further mitigated noise levels predicted at the RAPs when the noise reduction effect of the temporary noise barrier erected at the western site boundary and provision of machinery enclosures are considered in the calculation. Worksheets showing the calculation at the RAPs are provided in Appendix 5-4 for reference.

5.3.34 If required, additional movable noise barriers can be temporarily erected at specific locations within the site in the proximity of noisy work areas, when generation of high noise levels is expected to be associated with certain construction activities, or identified through the Environmental Monitoring and Audit (EM&A) progamme.

Table 5‑9 Mitigated Noise Levels at the RAPs (with silenced PME, phasing of activities and reduction in number of PME, fixed noise barrier and machinery enclosures)

	Construction Stages
	Foundation Construction²		Sheet Piling and Pile Cap Construction¹			Superstructure Construction³
RAPs	P1	P2	S1	S2	S3	S4	S5
IV-2 (1/F)	70	70	67	68	68	70	69
IV-2 (3/F)	70	70	67	68	68	70	69
IV-2 (5/F)	70	70	67	68	68	70	69
TW-1 (1/F)	69	69	65	66	67	68	66
TW-1 (15/F)	69	69	65	66	67	68	66
TW-1 (30/F)	68	68	65	66	67	68	66
HF-1 (1/F)	65	64	61	62	62	64	62
HF-1 (10/F)	64	64	61	62	62	64	62
HF-1 (20/F)	64	64	61	62	62	64	62

S1 – scenario 1 : concurrent operation of Groups 1, 2 & 3 PMEs in Table 5-4;

S2 – scenario 2 : concurrent operation of Groups 1, 2 & 4 PMEs in Table 5-4;

S3 – scenario 3 : concurrent operation of Groups 1, 2, 3 & 4 PMEs in Table 5-4;

S4 – scenario 4 : concurrent operation of Groups 1, 2 & 3 PMEs in Table 5-5;

S5 – scenario 5 : concurrent operation of Groups 1, 2 & 4 PMEs in Table 5-5.

¹ Noise levels as presented in Table 5-7 for TW-1 and HF-1 i.e. mitigated noise levels when silenced PMEs are in use;

² Noise levels as presented in Table 5-8 for TW-1 and HF-1 i.e. mitigated noise levels when silenced PMEs, phasing of activities and reduction in number of PME operating simultaneously are applied;

³ Noise levels as presented in Table 5-8 for TW-1 and HF-1 i.e. mitigated noise levels when silenced PMEs, phasing of activities and reduction in number of PME operating simultaneously are applied;

5.3.35 The results of the calculations revealed that with the combined application of quiet PMEs, implement phasing of construction activities, reduce number of the operating simultaneously, and use of temporary noise barrier and machinery enclosures, the construction noise levels at the RAPs can be alleviated to acceptable levels. The implementation of the recommended and sufficient noise mitigation measures by the contractor can be checked through the recommended Environmental Monitoring and Audit (EM&A) Programme.

5.3.36 As recommended in the EM&A programme presented in the Environmental Management Plan (EMP), the Environmental Team (ET) leader shall liaise with the representative of IVE (Chai Wan) and the Examination Authority to ascertain the exact time periods of all examination periods during the execution of construction works. During the examination periods, the Contractor shall liaise with the ET and the representative of IVE (Chai Wan) to ensure that sufficient/ additional noise mitigation measures are applied to further reduce the noise impact to meet the more stringent noise limit.

5.3.37 Other practicable noise mitigation measures are also identified and are recommended below for implementation to ensure full protection of the nearby NSRs.

Other Recommended Noise Mitigation Measures

5.3.38 To be prudent in the construction noise management, the following additional noise mitigation and good site practices are recommended for implementation.

· the Contractor shall comply with and observe the Noise Control Ordinance (NCO) and its current subsidiary regulations;

· before the commencement of any work, the Contractor shall submit to the Engineer for approval the method of working, equipment and sound-reducing measures intended to be used at the site;

· the Contractor shall devise and execute working methods that will minimise the noise impact on the surrounding environment; and shall provide experienced personnel with suitable training to ensure that these methods are implemented;

· only well-maintained plants should be operated on-site;

· plants should be serviced regularly during the construction programme;

· machines that may be in intermittent use should be shut down or throttled down to a minimum between work periods;

· silencer and mufflers on construction equipment should be utilised and should be properly maintained during the construction programme;

· noisy activities can be scheduled to minimise exposure of nearby NSRs to high levels of construction noise. For example, noisy activities can be scheduled for midday or at times coinciding with periods of high background noise (such as during peak traffic hours);

· noisy equipment such as emergency generators shall always be sited as far away as possible from noise sensitive receivers;

· mobile plants should be sited as far away from NSRs as possible; and

· material stockpiles and other structures should be effectively utilised as noise barrier, where practicable.

EM&A Requirements

5.3.39 Implementation of sufficient noise mitigation measures is identified to be required for the protection of certain NSRs located in the proximity of the development site. In order to check for the implementation of sufficient noise mitigation measures by the contractor, a construction phase noise monitoring and audit programme is recommended. Details on the noise monitoring and audit (EM&A) requirements, methodology and action plans are described in the Environmental Management Plan (EMP) submitted under a separate cover.

5.4 Operational Fixed Noise Impact Assessment

Legislation and Assessment Criteria

5.4.1 Noise standards required to be met at NSRs for noise generated from fixed noise sources are stated in the Technical Memorandum for the Assessment of Noise from Places other than Domestic Premises, Public Places or Construction Sites (TM4). In order to plan for a better environment, in accordance with the requirements under Table 1 in Annex 5 of the EIAO-TM, the maximum noise level arising from the noise sources, measured in terms of L_{eq(30 min)}at the NSRs shall be 5 dB(A) below the Acceptable Noise Level (ANL) as specified in TM4.

5.4.2 In determining the ANL, appropriate Area Sensitivity Rating (ASR) for a NSR have to be established first. Section 2.3.4 of the TM specifies that the Area Sensitivity Rating depends upon the characteristics of the area in which the NSRs are located. There are four types of areas described in the TM which are summarised in Table 5-9 below. An ASR “B” was assumed for residential blocks of Heng Fa Chuen assessed in this study. As the IVE (Chai Wan) is located in less than 100m from the boundary of the Chai Wan East Industrial Area, assuming an ASR “C” is considered appropriate. The annual average daily traffic flows on Wing Tai Road is over 30,000 veh/day based on the Annual Traffic Census issued by Transport Department in recent years. An ASR “C” was therefore also assumed at the facades of the blocks of Tsui Wan Estate directly facing Wing Tai Road in accordance with TM4.

5.4.3 In any event, the Area Sensitivity Rating assumed in this EIA Study is for indicative assessment only given that details on the design/ building layouts of the future developments at the Chai Wan East Industrial Area are not available at this early planning design. It should be noted that fixed noise sources are controlled under section 13 of the NCO. At the time of investigation, the Noise Control Authority shall determine noise impact from concerned fixed noise sources on the basis of prevailing legislation and practices being in force, and taking account of contemporary conditions / situations of adjoining land uses. Nothing in this EIA Report shall bind the Noise Control Authority in the context of law enforcement against all the fixed noise sources being assessed.

Table 5‑10 Area Sensitivity Ratings of NSRs

*Type of Area Containing NSR*	*Degree to which NSR is affected by Influencing Factors (Ifs)*
	*Not Affected*	*Indirectly Affected*	*Directly Affected*
(i) Rural area, including country parks, or village type developments	A	B	B
(ii) Low density residential area consisting of low-rise or isolated high-rise developments	A	B	C
(iii) Urban area	B	C	C
(iv) Area other than those above	B	B	C

5.4.4 For ASR “B”, the ANL for the daytime/ evening (0700-2300) and night-time (2300-0700 next day) periods measured at 1m in front of the building facade of the NSR shall be L_eq(30min.) 65 dB(A) and 55 dB(A), respectively. Taking into account the EIAO-TM requirements, a “5dB(A) margin has been applied to the noise limits stipulated in the TM. The noise assessment criteria, “Acceptable Noise Level (ANL) – 5 dB(A)” criteria, adopted in the study are therefore L_eq(30min.) 60dB(A) and 50dB(A) during the daytime/ evening and nighttime periods, respectively. For ASR “C” the applicable “ANL – 5dB(A)” criteria are L_eq(30min.) 65dB(A) and 55dB(A) during daytime/ evening and nighttime, respectively.

Assessment Approach

5.4.5 The assessment on fixed plant noise impact was conducted based on consideration of standard acoustics principles presented in TM4 and are summarized below:

(i) Based on the preliminary design layout plans and equipment inventory required to be provided at the new facility, identify the key noise sources of potential concern;

(ii) Estimate the sound power levels (SWL) associated with operation of each of these activities based on available measurement results obtained at an existing bus depot;

(iii) Calculate the Corrected Noise Level (CNL) at selected representative NSRs based on consideration of distance attenuation, noise shielding effect, and façade correction;

(iv) Compare the CNL with the relevant noise criteria and recommend noise mitigation measures if necessary.

Identified Noise Sources and Calculation

5.4.6 The consultants visited the existing, temporary bus depot of Citybus located at Aldrich Bay on 19 December 2001 in the morning, 15 February 2001 near mid-night and 12 June 2001 in the evening. The fixed noise sources that could be of concern during the operational phase of the proposed bus depot were identified to include:

· Brake testing;

· Bus parking/ leaving;

· Engine testing at maintenance bays;

· Bus washing bays

5.4.7 In addition to the above noise sources, potential noise impact from air charging before bus leaving has been taken into consideration in the study as a conservative approach, through it is understood that new models of bus currently in use normally do not require such operation as the old buses. The taking into consideration of air charging in the assessment therefore represents one conservative approach to the assessment.

5.4.8 Other operational activities such as bus refueling and general maintenance and repairing activities were not identified to be potential noise sources of concern as confirmed during the site visit to the existing bus depot.

5.4.9 Noise measurements were conducted by the consultants during the site visits using a calibrated Bruel & Kjaer Type 2236 Noise Meter. Noise levels were measured taking into consideration the acoustic principle as presented in the International Standard ISO 3766 : Acoustics – Determination of sound power levels of noise sources using sound pressure – survey method using an enveloping measurement surface over a reflecting plane. All measurement positions have been selected such that the radius of the hemispherical measurement surface is greater than twice the length of the noise sources. Repeated measurements were carried out and the highest noise levels measured or reported were adopted for the calculation.

5.4.10 Acoustic data associated with operation of bus washing bays, brake testing, and engine testing at maintenance bays were obtained by making reference to the approved EIA Report for NWFB permanent Depot at Chai Wan and tested to be conservative through noise measurement results. For air charging and bus parking/ leaving, sound exposure levels (SEL) were measured for prediction of the SEL associated with each of these activities and the cumulative noise levels at the assessment points. Appendix 5-5 presents a summary of the source terms considered in the assessment.

5.4.11 Table 5-10 summarises the acoustic characteristics of the identified noise sources that are expected to be associated with the future operation of the bus depot. Locations and numbers of noise sources were identified based on the number of facilities as presented in the preliminary design layout plans given in Figure 3-3 through Figure 3-8.

Table 5‑11 Identified Noise Sources associated with the Depot Operation

Activities	Noise Level, dB(A)⁽ⁱ⁾	Location	Max. no. of sources within a 30min. period⁽ⁱⁱ⁾
			Daytime/ Evening	Nighttime
Brake testing	98.6 (SWL)	G/F	4	4
Bus parking	83.2 (SEL)	3/F	33⁽ⁱⁱⁱ⁾	43^(iv)
Air charging	83.1 (SEL)	3/F	33⁽ⁱⁱⁱ⁾	43^(iv)
Maintenance area – engine testing	98.6 (SWL)	G/F	5	5
Maintenance area – engine testing	98.6 (SWL)	1/F	10	5
Bus washing bay	88.4 (SWL)	G/F	2	2
Bus washing bay	88.4 (SWL)	3/F	1	1

⁽ⁱ⁾SWL values based on the approved EIA report for NWFB Permanent Depot and tested through measurements. SEL values were based on repeated measurements at existing Citybus depot at Aldrich Bay;

⁽ⁱⁱ⁾ Conservatively estimated based on the number facilities provided as shown in the design layout and the nature of the activities in terms of likelihood of occurrence of concurrent noise sources;

⁽ⁱⁱⁱ⁾Based on the maximum number of buses entering the bus depot during the evening time period;

^(iv)Based on the maximum number of buses leaving the roof level bus parking space during early morning within a 30 minute period

Planned Shielding Structures

5.4.12 In the presence of the future LPG/ Petrol Filling Station and Hong Kong Post Super Centre on the northern and southern sides of the development site, these sides of the bus depot is planned to be constructed with a solid concrete façade without openings. A correction of –10dB(A) has therefore been applied to account for the noise shielding effect for noise sources located on G/F and 1/F in the prediction of the noise levels at TW1 and HF-1 as the sightline from these NSRs to the noise sources will be fully blocked. Besides, to account for the partial shielding effect provided by the parapet walls and other building structures along the northern façade of the development, a –5dB(A) correction has been applied to noise sources located on G/F and 1/F.

5.4.13 As a prudent approach in avoiding potential fixed noise impact, it is planned to erect a 3m high vertical wall along the northern, western and southern façades of the bus depot building at the roof level. Figure 5-4 shows the location of the planned 3m high noise barrier. The height of this barrier will be effective in providing full shielding to the top noise sensitive floor (i.e. 5/F) of IVE (Chai Wan) such as a noise reduction effect of 10dB(A) is achievable. To be prudent in the noise assessment, a noise reduction of 5dB(A) only was applied in the calculation.

5.4.14 NSRs located at low levels at Tsui Wan Estate and Heng Fa Chuen are also expected to be shielded by the proposed 3m high noise barriers erected at the roof level. As a conservative approach to the study, a - 5dB(A) correction has only been applied in the calculation of the noise level at the lowest floor studied. No correction was applied to those floors not directly shielded by the noise barriers.

Representative Assessment Points

5.4.15 The RAPs selected for the assessment include IV-2, TW-1 and HF-1 which represent the nearest NSRs. Locations of these RAPs can be found in Figure 5-1.

Assessment Results

5.4.16 Table 5-12 presents the highest noise levels predicted at the RAPs during daytime/ evening and the nighttime periods. Spreadsheets showing the calculations are presented in Appendix 5-5.

Table 5‑12 Predicted Noise Levels at the NSRs due to Depot Operation

RAPs	NSRs	Predicted noise level, L_eq(30min.)dB(A)		Noise Assessment Criteria
		Daytime/ evening (D/E)	Nighttime (N)	D/E	N
IV-2 (1/F)	IVE (Chai Wan)	59
IV-2 (3/F)	IVE (Chai Wan)	59	N/A	65	N/A
IV-2 (5/F)	IVE (Chai Wan)	59
TW-1 (4/F)	Tsui Sau House, Tsui Wan Estate	48	48
TW-1 (6/F)*	Tsui Sau House, Tsui Wan Estate	50	50	65	55
TW-1 (30/F)*	Tsui Sau House, Tsui Wan Estate	50	50
HF-1 (4/F)	Heng Fa Chuen	45	44
HF-1 (6/F)*	Heng Fa Chuen	46	46	60	50
HF-1 (20/F)*	Heng Fa Chuen	46	46

N/A – The Institute is not expected to be in operation during nighttime (2300 to 0700hrs);

* Predicted noise level when no noise reduction effect of the noise barriers (presented in Figure 5-4) has been applied.

5.4.17 As shown in Table 5‑12, the predicted noise levels are all in compliance with the relevant noise assessment criteria i.e. L_eq(30min.) 60dB(A) and 50dB(A) during daytime/evening and nighttime respectively for HF-1; L_eq(30min.) 65dB(A) and 55dB(A) during daytime/evening and nighttime respectively for HF-1; and the daytime/ evening noise limit of 65dB(A) applicable at IV-2. Noise impact on IV-2 during nighttime is not expected to be a concern as the Institute would not be in operation.

5.4.18 The northern and southern facades of the bus depot building will be constructed with solid concrete wall without openings. A 3m high vertical solid wall will also be erected at the northern, western and southern boundary at the roof bus parking level of the bus depot as a noise control measure. With these effective noise control measures in place, the assessment findings calculated based on a conservative approach has demonstrated that with the planned design of the bus depot, the nearby noise sensitive receivers will unlikely be subject to unacceptable fixed noise impact.

5.5 Operational Off-site Traffic Noise Impact Assessment

Bus Routing and Traffic Forecast

5.5.1 Operation of the proposed bus depot will inevitably generate some additional traffic (buses) on the adjacent road carriageways. This section presents an assessment on the potential noise contribution from the operation of the bus depot.

5.5.2 As a proactive approach in avoiding potential traffic and traffic noise impact, a bus routing plan has been agreed with the Government through the TIA. Based on the agreed plan, buses commuting between the depot and Siu Sai Wan area will be required to route through the future Sheung On Street Extesion (connecting Sheung On Street and Road 20/4) in leaving/ returning to the depot in normal operating conditions, instead of allowed to use Wing Tai Road and Shing Tai Road at all time periods. Citybus will require its employees to strictly follow this requirement agreed with TD. The agreed bus routing plan is as shown in Figure 3-2.

5.5.3 Bus ingress/ egress flows in the vicinity road carriageways during the early morning peak (0530 to 0630) and mid-night peak (2300 to 0000) were predicted by the Project Traffic Consultant. With the bus flow data and consideration of other future landuses in the area, including the NWFB depot, the 2003 and 2018 traffic forecast (traffic flows and percentage of heavy vehicles) at early morning peak (0530 to 0630) and mid-night peak (2300 to 0000) were projected by the Project Traffic Consultant and agreed with TD for two scenarios – “with proposed bus depot” and “without proposed bus depot”. These traffic forecast data are presented in Table 5‑13 and Table 5‑14. In the preparation of the traffic forecast, the Traffic Consultant has taken into account the data presented in the approved EIA reported carried out for NWFB Permanent Depot in Chai Wan to ensure that a consistent and conservative approach is being followed. Relevant correspondence showing the endorsement of the traffic forecast data by the Authority is presented in Appendix 5-6. Alignment of the road carriageways can be found in Appendix 4-3.

Table 5‑13 Year 2003 Traffic Forecast

Label	Morning Peak Leaving				Nighttime Peak Return
	All Traffic		Without Bus Depot		All Traffic		Without Bus Depot
	veh/hr	% of HV	veh/hr	% of HV	veh/hr	% of HV	veh/hr	% of HV
A	296	75.7	223	72.5	624	55.4	504	51.1
B	134	55.7	129	51.5	351	53.1	291	50.8
C	118	74.2	118	74.2	37	6.2	37	6.2
D	285	58.4	217	49.5	359	34.1	299	31.0
E	512	45.5	512	45.5	875	13.7	875	13.7
F	736	43.0	736	43.0	1262	22.4	1262	22.4
G	228	84.1	160	80.7	364	48.3	304	46.3
H	2584	30.2	2511	27.2	2342	41.3	2222	38.3
I	62	85.0	62	85.0	37	82.0	37	82.0
J	85	85.0	80	75.0	317	82.0	257	72.0
K	35	85.0	13	53.0	49	82.0	9	27.0
L	161	72.5	161	72.5	397	55.4	397	55.4
M	177	72.5	177	72.5	400	55.4	400	55.4
N	2584	30.2	2511	27.2	2342	41.3	2222	38.3
O	275	62.3	275	62.3	420	44.2	420	44.2
P	1999	29.9	1999	29.9	1347	41.1	1347	41.1
Q	20	10.0	20	10.0	20	10.0	20	10.0
R	20	10.0	20	10.0	20	10.0	20	10.0

Table 5‑14 Year2018 Traffic Forecast

Label	Morning Peak Leaving				Nighttime Peak Return
	All Traffic		Without Bus Depot		All Traffic		Without Bus Depot
	veh/hr	% of HV	veh/hr	% of HV	veh/hr	% of HV	veh/hr	% of HV
A	332	75.7	259	72.5	734	55.4	614	51.1
B	171	55.7	166	51.5	346	53.1	286	50.8
C	160	74.2	160	74.2	50	6.2	50	6.2
D	306	58.4	238	49.5	368	34.1	308	31.0
E	565	45.5	565	45.5	889	13.7	889	13.7
F	835	43.0	835	43.0	1325	22.4	1325	22.4
G	249	84.1	181	80.7	368	48.3	308	46.3
H	3086	30.2	3013	27.2	2564	41.3	2444	38.3
I	114	85.0	114	85.0	68	82.0	68	82.0
J	162	85.0	157	75.0	647	82.0	587	72.0
K	47	85.0	25	53.0	85	82.0	45	27.0
L	212	75.7	212	75.7	477	55.4	477	55.4
M	232	75.7	232	75.7	481	55.4	481	55.4
N	3086	30.2	3013	27.2	2564	41.3	2444	38.3
O	284	62.3	284	62.3	433	44.2	433	44.2
P	2694	29.9	2694	29.9	1654	40.2	1654	40.2
Q	20	10.0	20	10.0	20	10.0	20	10.0
R	20	10.0	20	10.0	20	10.0	20	10.0

Assessment Criteria and Methodology

5.5.4 A road traffic noise standard of L_10(1-hr)70dB(A) and L_10(1-hr)65dB(A) for domestic premises and educational institutions respectively is specified in Table 1 under Annex 5 of the EIAO-TM. These noise limits are meant for the hour having the overall peak traffic flows, and apply to uses which rely on opened windows for ventilation. They are therefore not directly applicable in the current study for the hours during which there will be maximum number of buses returning and/or leaving the bus depot.

5.5.5 In order to assess if the operation of the proposed bus depot would result in a significant increase in the overall noise levels on the nearby NSRs, a comparison of the traffic noise levels during early morning peak and mid-night peak for the “with bus depot” and “without bus depot” scenarios were considered with the 2003 and 2018 traffic forecast. Noise contribution from the bus depot is considered insignificant when the difference is less than 1.0dB(A) based on consideration of basis acoustic principle.

5.5.6 The methods described in the U.K. Department of Transport’s “Calculation of Road Traffic Noise (1988)” have been used in the prediction of traffic noise at the NSRs.

Representative Assessment Points

5.5.7 Locations of the representative assessment points (RAPs) selected for the traffic noise impact assessment are as shown in Figure 5-1. Although RAPs SH-3 and SH-4 located on the eastern façade of the IVE Staff Quarters are not of concern as fixed windows are installed, noise levels for the “with bus depot” and “without bus depot” scenarios have also been predicted at these RAPs for reference.

Assessment Results

5.5.8 Table 5‑15 to Table 5‑18 present a summary of the predicted 2003 and 2018 traffic noise levels at the RAPs for the “with bus depot” and “without bus depot” scenarios during the early morning peak hour (0530 to 0630) and mid-night peak hour (2300 to 0000). Detailed results (noise levels predicted at different floors) are given in Appendix 5-7.

Table 5‑15 Predicted Noise Levels for the “with bus depot” and “without bus depot”scenarios during early morning peak hour (0530 to 0630), L_10(1-hr)

		During Peak Hour Morning Leaving (dB(A))		Net Bus Noise Contribution (dB(A))
NSRs	Floors	All Traffic (year 2003)	No Buses (year 2003)	Year 2003
HF-1	1/F-20/F	66 – 67	65 – 67	0.1 – 0.2
HF-2	1/F-20/F	76 – 80	76 – 79	0.2 – 0.4
TW-1	1/F-30/F	71 – 77	71 – 77	0.1 – 0.2
TW-2	1/F-30/F	68 – 72	68 – 72	0.0 – 0.1
TW-3	1/F-30/F	69 – 72	69 – 72	0.1 – 0.2
TW-4	1/F-30/F	70 – 74	70 – 73	0.2 – 0.4
IV-1	1/F-5/F	75 – 78	74 – 78	0.4 – 0.5
IV-2	1/F-5/F	68 – 68	67 – 67	0.9 – 0.9
SH-1	1/F-25/F	71 – 72	70 – 72	0.4 – 0.4
SH-2	1/F-25/F	65 – 71	65 – 70	0.5 – 0.5
SH-3	1/F-25/F	64 – 66	64 – 65	0.2 – 0.3
SH-4	1/F-25/F	65 – 66	65 – 65	0.4 – 0.5

Table 5‑16 Predicted Noise Levels for the “with bus depot” and “without bus depot”scenarios during mid-night peak hour (2300 to 0000), L_10(1-hr)

		During Peak Hour Night-time Return (dB(A))		Net Bus Noise Contribution (dB(A))
NSRs	Floors	All Traffic (year 2003)	No Buses (year 2003)	Year 2003
HF-1	1/F-20/F	67 – 69	67 – 69	0.1 – 0.2
HF-2	1/F-20/F	76 – 80	76 – 80	0.5 – 0.5
TW-1	1/F-30/F	71 – 77	71 – 77	0.0 – 0.2
TW-2	1/F-30/F	69 – 72	69 – 72	0.1 – 0.2
TW-3	1/F-30/F	70 – 72	69 – 72	0.1 – 0.2
TW-4	1/F-30/F	70 – 74	70 – 73	0.2 – 0.4
IV-1	1/F-5/F	75 – 79	75 – 78	0.5 – 0.5
IV-2	1/F-5/F	70 – 70	69 – 69	0.9 – 0.9
SH-1	1/F-25/F	71 – 73	71 – 72	0.5 – 0.5
SH-2	1/F-25/F	66 – 72	65 – 71	0.5 – 0.6
SH-3	1/F-25/F	66 – 67	66 – 67	0.3 – 0.3
SH-4	1/F-25/F	67 – 68	67 – 68	0.4 –0.4

Table 5‑17 Predicted Noise Levels for the “with bus depot” and “without bus depot”scenarios during early morning peak hour (0530 to 0630), L_10(1-hr)

		During Peak Hour Morning Leaving (dB(A))		Net Bus Noise Contribution (dB(A))
NSRs	Floors	All Traffic (year 2018)	No Buses (year 2018)	Year 2018
HF-1	1/F-20/F	67 – 68	67 – 68	0.1 – 0.2
HF-2	1/F-20/F	77 – 80	76 – 80	0.4 – 0.4
TW-1	1/F-30/F	72 – 77	71 – 77	0.0 – 0.2
TW-2	1/F-30/F	69 – 73	69 – 72	0.1 – 0.1
TW-3	1/F-30/F	70 –73	70 – 73	0.0 – 0.2
TW-4	1/F-30/F	71 – 74	70 – 74	0.2 – 0.4
IV-1	1/F-5/F	75 – 79	75 – 78	0.4 – 0.4
IV-2	1/F-5/F	69 – 69	68 – 68	0.8 – 0.8
SH-1	1/F-25/F	71 – 73	71 – 73	0.4 – 0.5
SH-2	1/F-25/F	66 – 72	65 – 71	0.4 – 0.6
SH-3	1/F-25/F	65 – 67	65 – 67	0.2 – 0.3
SH-4	1/F-25/F	66 – 67	66 – 67	0.3 – 0.3

Table 5‑18 Predicted Noise Levels for the “with bus depot” and “without bus depot”scenarios during mid-night peak hour (2300 to 0000), L_10(1-hr)

		During Peak Hour Night-time Return (dB(A))		Net Bus Noise Contribution (dB(A))
NSRs	Floors	All Traffic (year 2018)	No Buses (year 2018)	Year 2018
HF-1	1/F-20/F	68 – 70	67 – 70	0.0 – 0.1
HF-2	1/F-20/F	77 – 81	76 – 80	0.4 – 0.5
TW-1	1/F-30/F	72 – 77	71 – 77	0.1 – 0.3
TW-2	1/F-30/F	69 – 73	69 – 72	0.1 – 0.2
TW-3	1/F-30/F	70 – 73	70 – 73	0.1 – 0.2
TW-4	1/F-30/F	70 – 74	70 – 74	0.2 – 0.4
IV-1	1/F-5/F	76 – 79	75 – 78	0.5 – 0.5
IV-2	1/F-5/F	71 – 71	70 – 70	0.8 – 0.8
SH-1	1/F-25/F	71 – 73	71 – 73	0.4 – 0.5
SH-2	1/F-25/F	66 – 72	66 – 71	0.5 – 0.6
SH-3	1/F-25/F	67 – 68	67 – 68	0.3 – 0.3
SH-4	1/F-25/F	68 – 69	68 – 69	0.4 – 0.4

5.5.9 A comparison of the noise levels for the “with bus depot” and “without bus depot” scenarios at the NSRs indicated that the noise contribution from buses is less than 1.0dB(A) under both year 2003 and 2018 scenarios. The assessment results therefore demonstrate that with the low level of traffic generation from the bus depot, operation of the bus depot will unlikely introduce any unacceptable traffic noise impact on the nearby NSRs for the short-term scenario and in the long run.

5.6 Conclusion

Construction Noise

5.6.1 The construction noise impact assessment has been undertaken based on the preliminary construction proramme and equipment inventory. Whilst the contractor appointed in future may prefer to use different types and numbers of equipment in the construction activities, the assessment has given information on individual and combined SWLs of Powered Mechanical Equipment (PME) that could be used and the noise mitigation measures required such that the overall noise levels at the NSRs can be controlled to meet the daytime construction noise limits.

5.6.2 The assessment results indicate that the implementation of a combination of noise mitigation measures will be necessary to alleviate the construction noise impact to acceptable levels. These measures include the use of quiet equipment, temporary noise barriers, noise enclosure, phasing of construction activities, reducing the numbers of equipment operating concurrently and good site practice as well as noise management.

5.6.3 Quantitative assessments indicated that the combined use of the recommended noise mitigation measures could alleviate the construction noise impact at all nearby NSRs to levels satisfying the noise standards. Sufficient mitigation measures shall be implemented to ensure that the noise levels at the NSRs are controlled within L_eq(30min.) 75dB(A).

5.6.4 Noise monitoring has been recommended as part of the Environmental Monitoring and Audit Programme and is described in the Environmental Management Plan (EMP).

Operational Phase Noise

5.6.5 Noise control measures have been incorporated into the design of the bus depot as a prudent approach. The northern and southern side of the bus depot building will have blank façade, and a 3m high solid wall will be erected alongside the northern, western and southern edge of the bus depot building at the roof level. The assessment on potential noise impact from fixed noise sources based on a conservative approach indicates that noise generated from the depot operation is not expected to be a concern. All predicted noise levels are satisfying the relevant daytime/evening and nighttime noise standards.

5.6.6 As a prudent approach, potential off-site traffic noise impact has been avoided by careful planning of the bus routing plan. Buses from Siu Sai Wan approaching the depot and Siu Sai Wan bound buses are required to route through the future Sheung On Street Extension and Road 20/4 at all time periods under normal operating conditions and use of Wing Tai Road and Shing Tai Road will not be allowed. Citybus will require its employees to strictly follow this requirement when entering or leaving the bus depot.

5.6.7 A comparison of the noise levels for the “with bus depot” and “without bus depot” scenarios predicted with 2003 and 2018 traffic forecast indicated that traffic noise contribution from buses generated from the depot on the background noise levels on the adjacent road carriageways will be insignificant. Therefore, operation of the bus depot will unlikely contribute any significant traffic noise impact on the nearby NSRs.

6. Waste Management

6.1 Introduction

6.1.1 This section identifies the types of waste likely to be generated during the construction and operation of the proposed bus depot, and assesses the waste management implications in accordance with the criteria and guidelines given in Annex 7 and Annex 15 of the EIAO TM.

6.1.2 Implementation of proper waste management during the construction phase is necessary. At this planning stage, appropriate disposal method for each type of waste was identified, along with consideration of opportunities for construction waste reduction, reuse or recycling. The potential impacts arising from the handling, collection, and disposal of construction wastes and the environmental mitigation measures required to mitigate these environmental impacts were identified and recommended.

6.1.3 The operation of the proposed bus depot is expected to generate limited and similar types of wastes as many other industrial undertakings. Significant environmental impact is not anticipated. Nevertheless, requirements on proper chemical waste management have been identified for future implementation.

6.2 Legislation and Guidelines

6.2.1 The principle legislation governing waste management in Hong Kong is the Waste Disposal Ordinance (Cap. 354) (WDO), and its subsidiary regulations. The Ordinance, enacted in 1980, generally encompasses all stages of waste management, from place of arising to final disposal point of waste. The Waste Disposal (Chemical Waste) (General) Regulation, enacted under the WDO in 1992, provides controls on all aspects of chemical waste disposal, including storage, collection, transport, treatment and final disposal.

6.2.2 In addition to the WDO and its subsidiary regulation, the following legislation have some bearing on the handling, treatment and disposal of wastes in Hong Kong, viz.,:

· Dumping at Sea Ordinance (1995);

· Crown Land Ordinance (Cap. 28);

· Public Health and Municipal Services Ordinance (Cap. 132) Public Cleansing and Prevention of Nuisances (Urban Council) and (Regional Council) By-laws; and

· Dangerous Goods Ordinance.

6.2.3 There are also various guidelines which are relevant to waste management in Hong Kong:

· Waste Disposal Plan for Hong Kong (December 1989), Planning, Environmental and Lands Branch Government Secretariat;

· New Disposal Arrangements for Construction Waste (1992), Environmental Protection Department & Civil Engineering Department;

· Code of Practice on the Packaging, Labelling and Storage of Chemical Wastes (1992), Environmental Protection Department;

· Works Branch Technical Circular No. 6/92, Fill Management;

· Works Branch Technical Circular 22/92, Hong Kong Government;

· Works Branch Technical Circular No. 2/93, Public Dumps;

· Work Branch Technical circular No. 16/93, Wet Soil in Public Dumps;

· Works Bureau Technical Circular No. 5/98, On Site Sorting of Construction Waste on Demolition Sites;

· Works Bureau Technical Circular No. 5/99, Trip-ticket System for Disposal of Construction and Demolition Material;

· Works Bureau Technical Circular No. 25/99, Incorporation of Information on Construction and Demolition Material Management in Public Works Subcommittee Papers;

· Technical Circular No. 11/92 Classification of Dredging Sediments for Marine Disposal, Environmental Protection Department

6.3 Construction Waste Impacts

Identification of Sources and Characteristics of Wastes

6.3.1 Construction of the proposed bus depot will involve the following key activities:

· Site clearance - the amount of works is expected to be minimal as the site will be vacated before handled over to the project proponent for the development;

· Foundation Works – the foundation works will involve piling and excavation activities;

· Superstructure Construction – this will involve construction of a 5 stories building (2 stories occupying the whole site and a 3-stories extension along Road 20/4).

6.3.2 The nature of these construction works is considered similar to other building construction works in the territory. The following waste categories are expected to be generated:

· Excavated Material;

· Construction and demolition waste;

· Chemical waste;

· General refuse.

6.3.3 The nature and likely quantity of each of these waste types arising from the construction phase of the Project are evaluated below. The potential environmental impacts, which may arise from the handling, storage, transport and disposal of each waste type, are then assessed. Prior to consideration of disposal options for each waste type, opportunities for waste reduction, reuse, or recycling have been identified.

Construction and Demolition (C&D) Material

6.3.4 A major portion of the subject site is currently unoccupied. It is also expected that when the site is handed over to the project proponent for the development of the bus depot, the existing structures occupying the site, including the work area temporary occupied by HyD, would be vacated. C&D Material generation during the site clearance is therefore expected to be very limited.

6.3.5 The major source of C&D Material is expected to arise from the excavation activities.

6.3.6 Excavated material will be generated from the foundation works from bored piling works and excavation activities for pile cap, manholes and other underground utilities and facilities, including underground fuel tanks and sunken pits. Detailed design of the foundation works is not available at this stage such that it is only possible to give a rough estimate on the amount of excavated material. A preliminary estimate is 28,000m³ for the bored piling works and 55,000m³ from other excavation activities, giving a total quantity of some 83,000m³.

6.3.7 Additional C&D material would also be generated from the building construction works. Based on the proposed GFA of the building and an assumed C&D generation rate of 0.1m³m^-2 (Ref.: Reduction of Construction Waste Final Report, Hong Kong Polytechnic, 1983), the quantity of C&D material is estimated to be about 2,900m³.

6.3.8 The total quantity of C&D material generated requiring offsite disposal to public filling areas is estimated to be 86000m³. The quantity of C&D waste is expected to be insignificant but should be disposed of proper if encountered as far as practicable. Wherever possible, the amount of C&D waste to be disposed of at landfill should be minimised.

6.3.9 Based on the preliminary construction programme, the daily quantity of excavation material to be handled is estimated to be some 900m³/day. Considering the nature of the project, it can be agreed that there is limited opportunity for reusing the excavated material onsite. It is estimated that approximately 20 truck load per hour is required to handle the daily quantity of excavated material for delivery to off-site public filling areas or other reclamation areas.

6.3.10 The key secondary environmental concern associated with the handling of the excavated material is expected to be potential fugitive dust emission and noise impact. With the implementation of the recommended dust and noise control/ mitigation measures presented in the air quality and noise sections, these secondary environmental factors are not expected to be a concern.

6.3.11 During the site clearance stage, it is recommended that the contractor should adopt a “selective demolition” approach if waste material are encountered as far as practicable such that reusable material such as wood, metal, and steel can be segregated for reuse or recycling. Inert demolition material such as soil, rock, concrete, brick, cement plaster/ mortar, inert building debris, aggregates and asphalt, etc. shall be reused by delivery to public filling area, public filling barging points or land formation sites. Only degradable waste shall be disposed of at landfill.

6.3.12 Beside, surplus construction material, which may arise from construction preparatory works and actual construction activities, shall be minimised, reused or recycled as far as practicable. These material may include:

· Wood from formwork;

· Surplus concrete or grouting mixes;

· Damaged or contaminated construction materials;

· Equipment and vehicle maintenance parts; and

· Materials and equipment wrappings, etc.

6.3.13 Wherever practicable, the production of construction waste should be minimised by the contractor through careful design, planning, good site management, control of ordering procedures, segregation and reuse of materials. These measures will also assist in minimising costs associated with the construction works. For examples, wooden boards can be reused on-site or off-site, though the reusability and quantity of final waste will depend on the quality, size and shape of the boards. Those timbers which cannot be reused again shall be sorted and stored separate from all inert waste before disposed of in landfill. Arrangement could be made for private contractors to collect used formwork materials for reuse. On-site incineration of wooden waste is prohibited.

6.3.14 If feasible, noise enclosure or barriers used on-site should be designed so that they are reusable after they have been dismantled and removed. Should construction site hoarding be erected, metal fencing or building panels, which are more durable than wooden panels, are recommended to be used where practicable. Opportunity shall also be sought to re-use any wooden boards used in site fencing on-site or off-site. Concrete and masonry can be crushed and used as fill material if practicable.

Chemical Waste

6.3.15 As defined under the Waste Disposal (Chemical Waste) (General) Regulation, chemical waste includes any substance being scrap material or unwanted substances specified under Schedule 1 of the Regulation. Chemical waste that would be generated from the construction of the bus depot is anticipated to arise from chemicals used in operation and maintenance of on-site equipment. These may include fuel, oil, lubricants, cleaning fluids, and solvents arising from leakage or maintenance of on-site equipment and vehicles. Chemicals generated from daily operation of the construction works shall be recycled/ reused on-site as far as practicable.

6.3.16 The amount of chemical waste that will be generated from the construction work will depend on the contractor’s on-site maintenance intention, age and number of plant and vehicles used. Chemical wastes such as lubricating oil or solvent generated by workers are not expected to be in large quantity, given the nature of the construction activities involved. The chemical waste types are expected to be readily accepted by licensed contractors in Hong Kong.

6.3.17 If off-site disposal of chemical waste is required, they should be collected and delivered by licensed contractors to Tsing Yi Chemical Waste Treatment Facility and be disposed of in strict accordance with the Waste Disposal (Chemical Waste) (General) Regulation. Contractors shall register with EPD as chemical waste producers when disposal of chemical waste is anticipated to be required. Chemical waste materials have to be stored on-site with suitable containers so that leakage or spillage is prevented during the handling, storage, and subsequent transportation.

6.3.18 Provided that the handling, storage and disposal of chemical wastes are in accordance with the Waste Disposal (Chemical Waste) (General) Regulation and the Code of Practice on the Packaging, Labelling and Storage of Chemical Wastes, it will not cause an unacceptable environmental impact.

General Refuse

6.3.19 Throughout the construction phase, the workforce on the construction site will generate a variety of general refuse requiring disposal. These refuse will mainly consist on food wastes, aluminium cans, and waste paper, etc. No information regarding the number of workers on-site is available at this feasibility study stage. Assuming that 100 workers are working together at any one time, and a waste generation rate of about 0.6 kg per person, it is estimated that the amount of general refuse that would be generated is in the order of 60 kg per day.

6.3.20 General refuse generated at the construction site shall be stored separated from construction and chemical wastes to avoid cross contamination. A reliable waste collector shall be employed by the Contractor to remove general refuse from the construction site on a daily basis where appropriate to minimise the potential odour, pest and litter impacts. The segregation of aluminum cans or other recyclable material for recycling should be considered as far as practicable.

Overall Waste Management

6.3.21 To ensure the appropriate handling of different construction waste types, it is recommended that the contractor shall be required to implement the recommended waste management measures through establishing a waste management plan. The WMP shall be submitted to the Project Engineer at the commencement of the project for approval on the advice of DEP.

6.3.22 The following additional control/ mitigation measures are recommended:

(i) Storage areas for different waste types - different types of waste should be segregated and stored in different containers, skips or stockpiles to enhance reuse or recycling of materials and their proper disposal. An on-site temporary storage area equipped with required control measures (e.g. dust) should be provided;

(ii) Trip-ticket system - in order to monitor the disposal of inert C&DM at public filling facilities and the remaining C&D waste to landfills, and control fly-topping, a trip-ticket system should be included as a contractual requirements and audited by the Environmental Team;

(iii) Records of Wastes - a recording system for the amount of wastes generated, recycled and disposed (including the disposal sites) should be proposed;

(iv) Training - training should be provided to workers in respect of site cleanliness and appropriate waste management procedure, including waste reduction, reuse and recycling, and avoid contamination of reusable C&DM.

6.4 Construction Waste EM&A Requirements

6.4.1 In order to ensure that each construction waste stream generated from the construction phase of the Project are managed in accordance with the procedures recommended in this EIA, it is recommended that regular auditing by an Environmental Team be carried out. The regular audit should look at all aspects of waste management including waste generation, storage, recycling, reuse, transport and disposal.

6.5 Operational Phase Waste Impact

6.5.1 The key waste type of potential concern with respect waste management during the operational phase would be chemical waste. The types and quantity of chemical waste material that would be generated from the operation of the bus depot has been preliminary estimated at this planning stage and is set out in Table 6‑1.

Table 6‑1 Likely Types and Estimated Quantity of Chemical Wastes to be produced from Depot Operation

Waste	Estimated Annual Quantity
Spent oil filters	18,000kg
Waste oil (including engine oil, transmission oil and rear axle oil)	360,000 litre
Waste Battery Cell	800 pcs.
Waste Electrolyte (i.e. diluted sulphuric acid)	13,000 litre
Spent Solvent	Insignificant
Spent Paint	Insignificant
Waste Diesel	Insignificant

6.5.2 Provided that chemical wastes generated during the operational phase are managed in accordance with the requirements under the Code of Practice on the Packaging, Labelling and Storage of Chemical Waste published by EPD, they should not cause any unacceptable impacts. Sludge generated from the water treatment system of the bus washing machines shall be regularly removed and transported away by licensed collectors for proper disposal. Oily sludge accumulated inside oil/petrol interceptors in the bus washing areas and grease traps in the kitchen areas should also be regularly removed and transported away by licensed collectors for proper disposal.

6.5.3 Proper chemical waste management and disposal is recommended to be checked through the impact-orientated EMS to be established during the detailed design stage and operational phase of the project, as recommended in the Environmental Management Plan.

6.6 Conclusion

6.6.1 The waste streams that would be generated during the construction phase of the proposed bus depot were identified and evaluated in terms of their quantity, type and nature, etc. Opportunities for reduction in waste generation through reuse or recycling are identified. The waste management implications and potential environmental impacts associated with the handling, transport, and disposal of the identified waste types are addressed. Mitigation measures based on good practices have been recommended for each waste type to address any potential environmental impacts.

6.6.2 The Contractor shall be required to implement the recommended waste management measures through establishing a Waste Management Plan (WMP) at an early stage before construction works commence. The WMP should be submitted to the Engineer for approval on the advice of the EPD. In addition, an audit programme is recommended to be in place during the construction phase to check that the waste generated from the construction site are being managed in accordance with the recommended procedures. Handling and disposal of waste generated from the project is not expected to give rise to any significant dust and noise in the presence of appropriate control/ mitigation measures recommended.

6.6.3 Provided that the recommendations set out in this section are implemented, no waste related regulatory non-compliance and unacceptable environmental impacts would be expected to arise from the handling, storage, transport and disposal of wastes during both the construction of the Project.

8. Hazard Impact

8.1 Introduction

8.1.1 According to the latest Draft Outline Zoning Plan (Plan No. S/H20/11), the “Other Specified Uses” (“OU”) Site on the northern side of the development is planned to be developed into a petrol filling cum liquefied petroleum gas (LPG) filling station.

8.1.2 Electrical and Mechanical Services Department (EMSD) requires a minimum separation distance of 15m between LPG filling station and industrial/ commercial buildings to minimise the potential hazard associated with operation of LPG filling station. Section 3.4.6 of the EIA Study Brief requires a review/ assessment of the planned population and the design layout of the bus depot project so as to ascertain the potential hazard impacts from the adjacent planned LPG filling station is acceptable if the 15m separation distance requirement cannot be provided.

8.1.3 Planning Department has advised that in identifying the LPG/ Petrol Filling Station, the requirement of providing a separation distance of 15m between LPG filling station and the bus depot has been observed. As shown in Figure 8-1, a width of about 35m has been reserved for the eastern part of the “OU” site to allow flexibility in the LPG filling station design so that the 15m separation between the future LPG filling station and the bus depot may be accommodated. However, required safety measures could only be worked out at detailed design stage by the developers of the sites in consultation with concerned Government departments.

8.1.4 Given the close proximity of the LPG/ Petrol Filling Station to the bus depot, to be prudent, a Quantitative Risk Assessment (QRA) was carried out to confirm whether there would be any potential hazard associated with the operation of the LPG/ Petrol Filling Station on the proposed bus depot. Precautionary measures have been identified and incorporated into the design of the bus depot as an at-receiver risk reduction measure.

8.1.5 A LPG filling station is classified as a Notifiable Gas Installation under the Gas Safety Ordinance. In accordance with EMSD’s guidelines, the future project proponent of the LPG filling station will be required by the Authority to carry out a Quantitative Risk Assessment (QRA) to ensure that its design and operation will not impose unacceptable individual risk and societal risk on the sensitive landuses in its proximity. There is currently no information on the design, servicing capacity, and development programme of the LPG/ Petrol Filling Station. The current assessment has therefore been carried out based on some reasonable and conservative assumptions.

8.2 Quantitative Risk Assessment

Assumptions on the Design of the Future LPG/ Petrol Filling Station

8.2.1 Design of the future LPG/ Petrol filling station is not available at this initial planning stage. In order to quantify the extent of potential hazard impact on the proposed bus depot, a typical LPG/ Petrol filling station design is assumed in this study. Figure 8-2 shows the layout plan of a typical Petrol cum LPG filling station.

8.2.2 Based on the typical design, both LPG and petrol/diesel storage vessels are expected to be installed underground, with all vessels covered with corrosion protection coating, stress relieved and have undergone 100% radiography. Two LPG storage vessels each with a maximum capacity of 12 tonnes are assumed to exist, giving a total storage capacity of 24 tonnes. It is also assumed that there are four sets of dispenser facilities (with 8 dispensing nozzles in total) for serving LPG-vehicles (taxis) for each vessel. LPG and Petrol/diesel vessels would be separated as a common design strategy so as to avoid any knock-on effect in case accident occurs. A bay area would be dedicated for the LPG filling tankers. Moreover, the station is assumed to be equipped with standard fire fighting apparatus, including fire extinguishers and boxes of sand. Solid radiation wall would be provided within the filling station at three sides along the station boundary. According to the location of the planned facility, access to the LPG/ Petrol filling station would be provided at Road 20/6.

8.2.3 It is assumed that the daily consumption of each LPG-vehicle is about 30kg. It is expected that about 60 LPG-vehicle would be served per day by each dispensing nozzle so that the daily consumption rate will be about 14.4 tonnes. LPG is expected to be delivered to the site by tanker trucks and pumped into the underground vessels. LPG is fed to the dispenser via a site pump installed with the storage vessels. Based on the daily consumption rate, the usual LPG stock maintained on-site is assumed to be ranging from about 5.5 to 20 tonnes with a maximum storage of about 85% of the maximum capacity. There would be a bay area for the parking of the delivery trucks. A LPG delivery truck normally has a maximum LPG capacity of about 9 tonnes. Truck-in frequency is therefore approximately 1.6 times a day. It is assumed that each loading process takes about 2 hours. Truck-in period is assumed at time of lower population in the vicinity, which is a usual operation practice of the station.

8.2.4 It is further assumed that the taxi trade would like to maintain the current practice for diesel taxis that each taxi would be refilled twice a day during the shift changes. Based on the above information, it can be estimated for the QRA study that:

Maximum no. of loading to LPG vehicle vessels per year (8x60x2x365) = 350,400

Maximum no. of loading to underground LPG vessel per year (1.6x365) = 584

Maximum total time spend in loading per year (2x1.6x365) = 1,168 hour

Fraction of loading time in a year (1168/24/365) = 0.133

8.2.5 Connection of safety valves associated with different types of pipelines of the LPG installation is assumed based on that provided at an existing facility observed as follows:

Table 8‑1 Safety Valves associated with Pipelines On-site

Pipeline	Approx. Pipe Length (m)	Safety valves
Liquid filling line leading to the storage vessel	2m	1 filler valve, 2 pressure relief valve, 3 shut off valve, 1 non-return valve
Liquid supply line leading to the dispensers	15m	3 shut off valve, 1 pressure relief valve
Vent Pipe connected to the storage vessel	3m	1 pressure relief valve
Vapour from dispenser to vessel	15m	1 excess flow valve, 1 shut off valve

The Study Area

8.2.6 Based on the normal storage quantity at a planned LPG/ Petrol filling station, the potentially affected area should a hazard event arises is expected to be limited. Nevertheless, a study area of 150m radius from the LPG installation is adopted in the study and is shown in Figure 8-1. Based on the latest Draft Outline Zoning Plan (Plan No. S/H20/11), existing and planned developments within the study area include:

· The proposed bus depot at the subject site;

· Open space area to the north of the filling station;

· Planned industrial area to the northeast of the filling station;

· Cargo handling area to the east of the filling station;

· A section of the railway track to the west of the filling station; and

· Local road carriageways.

8.3 Population Data

8.3.1 The QRA study has been carried out with population data reasonably assumed based on the planned landuses in the vicinity of the LPG/ Petrol filling station in accordance with the landuse zoning as shown in the Draft Outline Zoning Plan (OZP) and information provided by Planning Department.

Proposed bus depot

8.3.2 As described in Section 3, the proposed bus depot will be in the form of a low-rise building occupying a site area of approximately 1 hectare. The development will provide spaces for bus parking, maintenance and office areas. As a prudent approach in the design of the bus depot, the entire northern façade of the bus depot building will be constructed with a solid concrete wall without openings.

8.3.3 The number of staff working indoor in the bus depot and office area is estimated to be about 319 and 201 during daytime (approx. 08:00 to 18:00) respectively. In the evening and night-time (approx. 18:00 to 08:00), some 50 workers are expected to be working at the bus depot, and none in the office.

Open space area

8.3.4 The site bounded by Road 20/10 and located to the north of Road 20/6 is zoned as an Open Space Site (“O”) to serve the nearby working population in accordance with the Draft OZP (Plan No. S/H20/11). A population of 20 is assumed for this area based on observation of similar open space uses at other industrial areas.

Planned Industrial Site

8.3.5 According to information provided by Planning Department, the industrial site located to the immediate north of the LPG/ Petrol Filling Station is currently reserved for the construction of a Lorry Park & Motor Vehicle Repair Workshop. Based on the nature of use and the site area involved, an indoor working population of 300 is assumed at the facility.

Railway Track

8.3.6 The typical capacity of each cart will be about 280 person per compartment. A 12-cart train will have total passengers of 3360 at peak hour. A train speed of 50km/hr and a peak train frequency of about once per 1.5 minutes are assumed. Accordingly, the population can be estimated based on the following formula.

Population = No of person per train x No. of train per hour / Speed * Length of track fall within the study area

Road Carriageways

8.3.7 Road carriageways in the vicinity include Shing Tai Road, Sheung On Street, Road 20/4, Road 20/10 and Road 20/6. With the proposed bus depot, there will be additional flow of buses on these local road carriageways especially during the early morning and near mid-night return time period. The design capacity of these local roads, as shown in Table 8‑2, were adopted in the QRA study as a conservative approach.

Table 8‑2 Design Capacity of the Local Road Carriageways adopted in the QRA study

Road Carriageway	Peak Hour Traffic (veh/hr)	% of Heavy Vehicles
Shing Tai Road – south of Road 20/6	3200	22
Road 20/4 – north of Road 20/6	800	22
Road 20/6	800	22
Road 20/4 – south of Road 20/6	800	22
Shing Tai Road – north of Road 20/6	800	22
Road 20/10	800	22

Sources:

1 Design Capacity: TPDM Vol. 2 Table 2.4.1.1 and Guidelines on Traffic Impact Assessment & Day-time ban requirements for road works on traffic sensitive routes (Table 2);

2 % of Heavy Vehicles – ATC 1999 (Station 1009)

8.3.8 2 and 10 person/vehicle for passenger car and heavy vehicles is assumed in this study. The population along these roads is calculated as:

Population = No of person per vehicle x No. of vehicle per hour / Speed * Road Length

8.4 Meteorology

8.4.1 Local meteorology will influence the spreading of LPG. Hourly meteorological data of the Year 1998 from King’s Park Weather Station involving a matrix of weather class (speed/ stability combinations) and wind directions have been obtained from the Hong Kong Observatory for the QRA study. The three most dominant sets of wind speed-stability class combination during daytime and night-time are identified and summarised below in Table 8‑3.

Table 8‑3 Most Frequent Wind Speed-Stability Class Combination

	Meteorological Category
	Daytime			Night time
Direction	4D	3C	2B	1F	4D	2F	Total
0-30	0.38	0.83	0.56	2.80	0.43	1.75	6.75
30-60	0.32	0.32	0.19	1.35	0.73	1.10	4.01
60-90	2.15	1.67	1.21	4.06	4.74	3.23	17.06
90-120	11.03	3.15	2.02	5.17	12.64	2.85	36.86
120-150	0.00	0.32	0.35	1.67	0.16	0.35	2.85
150-180	0.08	0.62	0.27	1.21	0.24	0.59	3.01
180-210	0.27	0.89	0.48	1.21	0.54	0.97	4.36
210-240	0.19	1.59	1.24	2.58	0.24	0.94	6.78
240-270	0.03	0.30	2.64	5.97	0.16	1.72	10.82
270-300	0.03	0.03	0.19	0.75	0.05	0.13	1.18
300-330	0.00	0.05	0.08	0.40	0.00	0.11	0.65
330-360	0.19	0.86	0.73	1.99	0.62	1.29	5.68
Total	14.66	10.63	9.95	29.16	20.55	15.04	100.00

8.5 Local Topography

8.5.1 The site where the planned LPG/ Petrol filling station and the surrounding landuses are located is relatively flat. Gas dispersion has taken to affect up to a height of about 3 levels.

8.6 Ignition Source

8.6.1 Ignition source is an important parameter for determining the consequence due to delayed ignition. Source of ignition is identified to be associated with vehicles using the road carriageways. As a solid radiation wall will be provided along three sides of the planned LPG/ Petrol filling station, and the entire northern facade of the bus depot will be constructed with a solid concrete wall, dispersion is more likely spread to Road 20/6.

Hazard Events and Consequence

8.6.2 LPG release associated with the operation of the LPG filling station could occur as a result of spontaneous failure of pressurised LPG equipment such as storage vessel, tanker failure and pipework failure and loading failure such as hose misconnection and hose disconnection error.

8.6.3 Possible outcomes of LPG leakage leading to fatality include jet fire, flash fire and fireball. Pool fire is usually a localised hazard event and would not occur when LPG released is flashed to vapour so that flash fire, which can affect off-site area, is resulted. Occurrence of vapour cloud explosion (VCE) requires significant confinement of vapour which is expected to be unlikely for LPG vessels installed underground.

8.7 Hazard Events

8.7.1 An LPG release event could occur as a result of spontaneous failure of pressurised LPG equipment such as storage vessel, loading failure such as hose connection or disconnection error, and from external events such as earthquake. The various possible failure cases are summarised in Table 8‑4.

Table 8‑4 Identified Failure case of the LPG Installation

Failure category	Failure cases
Spontaneous	· Storage Vessel Failures · Tanker Failures · Pipework Failures · Dispenser Failures · Flexible Hose Failures · Flange Gasket Failures · Valve Leak Failures
Loading from Tanker to Vessel	· Vessel Filling Hose Misconnection · Vessel Filling Hose Disconnection Error · Disconnection with Valve Open · Tanker Drive Away · Tanker Impact · Tanker Collision during Unloading · Loading Pipework Over Pressurisation · Storage Vessel Overfilling
Loading from Dispenser to Vehicles	· Vessel Filling Hose Disconnection Error · Vehicle Drive Away · Vehicle Impact · Vehicle Collision during Unloading · Vehicle Storage Vessel Overfilling
External Event	· Earthquake · Aircraft Crash · Landslide · Severe Environmental Event · Subsidence · External Fire · Lightning Strike · Dropped Object

8.7.2 Generic failure rates associated with the various possible initiating events were adopted, where appropriate, to effect a conservative assessment. The significance of each failure case is thoroughly considered and incorporated in the assessment, where appropriate.

Spontaneous Failure

(i) Storage Vessel Failure

8.7.3 Storage vessel failure can be cold catastrophic, leading to instantaneous release of LPG, or cold partial failure resulting in continuous release of LPG to the atmosphere. The generic failure rate of 1.8 x 10^-7 has been adopted for cold spontaneous catastrophic failure. For partial failure, a generic value of 5.0 x 10^-6 has been adopted. The vessel is assumed stress relieved, 100% radiograph tested and covered with Chartek coating (a fire protective coating), which is typical of such kind of installation.

(ii) Tanker Failure

8.7.4 LPG delivery trucks in Hong Kong are covered with Chartek coating and equipped with many features so that they can be treated as a considerably well secured device. The definition of catastrophic and partial failure are similar to that of vessels. The catastrophic and partial failure rate of a road tanker for the study is 2.0 x 10^-6 and 5.0 x 10^-6 per year, respectively.

(iii)Pipework Failure

8.7.5 Failure of pipework can generally be classified into two types - guillotine (with complete severance of the pipe) and partial failure (pipe splits less than the pipe diameter). Risk from partial failure is considered negligible as the leakage is insignificant to the overall risk. This study will therefore only account for the consequence from guillotine failures. A generic guillotine failure rate of pipe of 1.0 x 10^-6 per metre per year has been adopted. However, it is noted that the effect of guillotine failure is significant only if leak(s) is failed to be isolated. In other words, it requires the failure of other safety systems to substantiate the event. Fault tree analysis technique will be adopted to account such “failure to isolate” risks.

(iv)Dispenser Failure

8.7.6 A dispenser is responsible for the supply of LPG fuel to vehicles (taxi in this case). The failure mode is regarded similar to that of pipework and storage vessels. That is, potential LPG release can be modelled as a guillotine failure of the liquid supply line at the dispenser. A frequency of 1.0 x 10^-6 was adopted for dispenser failure in the study.

(v) Flexible Hose Failure

8.7.7 The LPG delivery truck carries with it a flexible hose for LPG unloading to the underground vessel. On the other hand, there is also hose for dispenser facilities. Again, the effect of partial failure of the hose is anticipated to be negligible. Only guillotine failure is therefore considered. A generic guillotine failure rate of 1.8 x 10^-7 per transfer based on transfer duration of 2 hours is adopted. Each filling process for vehicles, on the other hand, takes about 1 minute. An Excess Flow Valve (EFV) is expected to be fitted immediately upstream of the hose reel.

(vi)Flange/ Gasket and Valve Leak Failures

8.7.8 It is considered that failures of gaskets would only tend to give relatively small scale of leakage and will not contribute significantly to the risk from the subject LPG installation. The results from gasket failure will not be considered further in the study. External leaks from valves is neither anticipated to contribute significantly to the risk from the LPG installation and hence were not considered in the study.

8.7.9 Table 8‑5 summarises the failure cases and the associated frequency of occurrences to be adopted in the QRA study.

Table 8‑5 Summary of Spontaneous Failure Cases and their Frequency of Occurrences

Failure case	Frequency
Storage vessel failure (assuming SR and 100% radiograph, with age of vessel < 20 years) · Catastrophic · Partial (25 mm equivalent diameter)	1.8 x 10^-7 per vessel year 5.0 x 10^-6 per vessel year
Road tanker failure · Catastrophic · Partial (25 mm equivalent diameter)	2.0 x 10^-6 per road tanker year 5.0 x 10^-6 per road tanker year
Guillotine failure of pipework	1.0 x 10^-6 per metre per year
Dispenser failure	1.0 x 10^-6 per year
Flexible hose guillotine failure · Filling to underground vessel · Filling to vehicles	9.0 x 10^-8 per hour; or 1.8 x 10^-7 per transfer 1.5 x 10^-9 per transfer

Loading from Tanker to Vessel Failure

(i) Hose Misconnection

8.7.10 This study only considers misconnection errors which results in hose coming completely apart, giving a full-bore release. It is anticipated that small leaks will be rectified instantaneously by the truck driver or his assistant, and hence are not considered. A failure rate of 3 x 10^-5 per operation resulting from human error which leads to misconnection is adopted.

(ii) Hose Disconnection Error

8.7.11 This is a gross human error event which require a complete disregard of normal operating procedure as well as the failure of assistant to prevent it from happening. A failure rate of 2 x 10^-6 per operation for an operator to disconnect a hose during loading operation has been used in the study.

(iii)Disconnection with Valve Open.

8.7.12 The event is significant only if the release is fed from the storage vessel and when the vessel is over-pressurised with failure of the associated safety valves (i.e. a Non-return Valve in the present case), as well as driver’s failure to shut down the Manual Valve.

(iv)Tanker Drive Away

8.7.13 A drive-away error could be resulted from (i) repositioning of truck during delivery and/ or (ii) inadvertent driver away before delivery completion. The outcome of this failure matches those of hose misconnection. A number of measures such as the use of wheel chocks, interlocks on shutters and parking brake have been implemented in Hong Kong. Moreover, there is a dedicated bay area for the parking of the truck so that repositioning during delivery is unlikely. Furthermore, the driver is also responsible for the unloading process. Therefore, driving away before completion is much unlikely. A failure rate of 4 x 10^-6 per operation has been adopted in the study.

(v) Tanker Impact

8.7.14 Tanker impact refers to the striking of part of the LPG installation by the LPG delivery truck, causing damage to the installation pipework, the tanker, the tanker fittings or the hose connection pipework. Given that the LPG vessel and pipework is situated underground, and there is a dedicated bay area of the parking of the tanker which is located apart from dispensers and other facilities, the probability of guillotine failure of pipework and dispensers is expected to be negligible.

(vi)Tanker Collision during Unloading

8.7.15 Although there is a dedicated area for the parking of the tanker, it is considered that the parked tanker can still be close to the path of the vehicle movement for vehicles utilising the inner dispenser systems. Mitigation measures can be proposed that loading process is carried out other than peak hours for vehicle refilling and control is taken to avoid vehicles using the inner dispenser system so as to avoid any occasion of collision.

(vii)Loading Pipework over Pressurisation.

8.7.16 It is possible that a LPG delivery truck driver makes an error when unloading from the truck to the underground storage vessel. Over pressurisation of the liquid filling line would be resulted should the operator forgets to open all relevant valves on the pipe/ hose. However, over-pressurisation protection system of the road tanker should fail and other failure to isolate leak system (e.g. possibility of the leak being isolating using manual valves) does not work. It is considered that the concerned scenario will have a much lower probability to happen than the “misconnection” error event (which will lead to a similar outcome) and hence is not considered to be a significant contributor to the overall risk.

(viii)Storage Tank Overfilling

8.7.17 The practice on-site in unloading LPG to the underground storage vessel is that it will only be filled to a maximum of lower than 85% of the maximum capacity, through monitoring with a level gauge during loading operation. It is considered that the probability of the driver overfilling the storage vessel is low. It is also an offence in Hong Kong for a person to overfill an LPG storage vessel. Even if overfilling does occur, the following failures are also required to occur for failure of the storage vessel as a result of the over pressurisation :

à failure of the truck pump overpressure protection system;

à failure of pressure relief valve on storage tank;

à failure of driver and his assistant to detect problem and to take effective mitigation action accordingly.

8.7.18 It is considered that the probability for occurrence of such combination of failures is extremely low. Such scenario is therefore neglected in the QRA study.

(ix) Human Error

8.7.19 Even failure of equipment occurs, it is possible for staff to rectify the problem before any hazard event occurs. There are two staffs responsible for the unloading process (i.e. the driver and one site staff). As the staff should have undergone training programme for the job, the probability that the problem cannot be rectified before hazard event occurs can be assumed to be lower than 0.5. In this study a probability of 0.2 is assumed for human error.

8.7.20 Table 8‑6 summarise the concerned loading failure cases and the associated frequency for occurrences for the QRA study.

Table 8‑6 Underground Vessel Loading Failure Cases and their Frequency of Occurrences

Concerned Loading Failure Case	Frequency of Occurrence
Hose Misconnection	3 x 10^-5 per operation
Hose Disconnection	2 x 10^-6 per operation
Tanker Drives Away	4 x 10^-6 per operation
Human Error	0.2 per demand

Loading from Dispenser to Vehicles Failure

(i) Hose Disconnection Error

8.7.21 Similar to the case of hose disconnection from tanker to vessel, a failure rate of 2 x 10^-6 per operation for an operator to disconnect a hose during loading operation has been adopted.

(ii) Vehicle Drives Away

8.7.22 In Hong Kong, vehicle engines should be off before the refilling process. The drives away accident is unlikely. Even a failure occurs, it is highly likely that the failure can be immediately rectified because there is a dedicated staff attending the filling process. A failure rate of 4 x 10^-6 per operation is assumed.

(iii)Vehicle Impact

8.7.23 Travelling speed when manoeuvring inside the station is usually very slow. Therefore, the impact is usually insignificant. There is no reported case in Hong Kong for dispenser failure due to vehicle impact for Petrol Filling Station in Hong Kong. In this study, the failure rate due to vehicle impact is assumed as 1 x 10^-9 per visit.

(iv)Vehicle Collision during Unloading

8.7.24 Vehicle may be crashed by coming vehicles during unloading. As the LPG quantity contained in the vessel of the vehicle is comparatively small, the leakage from taxi is negligible. On the other hand, if the safety devices fails, it is possible to have LPG leakage from dispenser. In this study, it is assumed that the failure rate due to vehicle impact is assumed as 1 x 10^-9 per visit.

(v) Vehicle Storage Vessel Overfilling

8.7.25 The overfilling of vehicle storage vessel may lead to the failure of storage vessel in the vehicle. Again, the event is not considered in this study due to the small quantity of storage.

Table 8‑7 Underground Vessel Loading Failure Cases and their Frequency of Occurrences

Concerned Loading Failure Case	Frequency of Occurrence
Hose Disconnection	2 x 10^-6 per operation
Vehicle Drives Away	4 x 10^-6 per operation
Vehicle Impact	1 x 10^-9 per visit
Vehicle Collision during Unloading	1 x 10^-9 per visit

External Event Failure

(i) Earthquake

8.7.26 It is estimated that earthquake of Modified Mercali Intensity (MMI) VII is required to provide sufficient intensity to result in damage to storage vessel or pipework. The probability of earthquake occurrence is assumed to be 1.0 x 10^-5 per year. The failure rate of pipework as well as partial failure of underground vessel due to earthquake is taken to be 0.01, whereas the other failure rate of road tanker and the underground vessel is considered to be zero.

(ii) Aircraft crash

8.7.27 The subject site is not under the existing airway and the distance between the subject site and the airfield (i.e. Chek Lap Kok International Airport) is over 5 miles which is the criteria for the consideration of airfield accident. Therefore, it is not considered in this study as the probability of crashing exactly onto the LPG installation is extremely small.

(iii)Landslide

8.7.28 As the vessel of the proposed LPG filling station is situated underground, only dispenser failure can result. Yet, the installation is not situated on hill side so that landslide leading to dispenser and landslide failure should not be accounted.

(iv)Severe environmental event

8.7.29 Loss of containment of LPG due to severe environmental event such as typhoon or tsunami (i.e. a tidal wave following an earthquake) is considered to be insignificant, especially for the proposed installation where LPG vessel is situated underground.

(v) Subsidence

8.7.30 Subsidence is usually slow in movement and such movement can be observed and remedial action can be taken in time. The probability of hazardous event due to subsidence is therefore considered negligible.

(vi)External fire

8.7.31 External fire means the occurrence of fire event which lead to the failure of tanker/vessel or other facilities. The key potential concern relates to the LPG road tanker shell being affected by an external fire. In Hong Kong, LPG delivery trucks are provided with safety features to prevent the spread of fire from an engine or cab fire to the LPG vessel and are shielded with Chartek coating, a fire-resisting material. Fire extinguishers are also provided. The regulations also require that the vessel be effectively screened with fire-resisting shields from the interior of the cab, fuel tank, electrical generator, engine, etc. Therefore, it can be assumed that such external fire will not lead to any significant event outcome.

(vii)Lightning strike

8.7.32 The frequency of a lightning strike on road tanker is extremely low. Risk resulting from lightning strike on the LPG vessel on-site is considered extremely low, as the vessel is located underground. Based on these analysis, no consideration is given for effect from lightning strike in this study.

(viii)Dropped object

8.7.33 As the LPG vessel and pipework system are situated underground, potential damage from dropped object is restricted to dispensers only. However, top shielding is provided such that damage by dropped object is unlikely.

Table 8‑8 External Event and their Frequency of Occurrences

Concerned Loading Failure Case	Frequency of Occurrence
Earthquake Modified Mercali Intensity (MMI) VII	1.0 x 10^-5 per year

8.8 Safety System and Fire Protection/Fighting System Failure

8.8.1 The previous section gives an analysis of all possible failure cases. For these failure cases to contribute a significant risk, these have to be accompanied with failure of the corresponding safety systems (valves) and/ or fire protection/ fighting system. The types and nature of safety systems and fire protection system present on site will be identified and taken into account in the study based on the associated failure rates presented below, where appropriate.

Safety System Failure

8.8.2 Typical safety systems involved in LPG installation include over-pressure protection system, pressure relief valve (PRV), excess flow valve (EFV), non-return valve (NRV), high pressure shut off valve (SOV), filler valve, emergency valve and breakaway coupling. These are responsible for the isolation of failure cases in order to avoid leakage, and risks incurred.

(i) Truck pump over-pressure protection system

8.8.3 It is used to terminate loading operation automatically in case over-pressure is detected. The failure rate is assumed to be 1.0 x 10^-4 per operation in this study.

(ii) Non-return valve

8.8.4 This type of valve is provided to avoid the back flow of LPG along liquid filling line. The failure rate is 0.013 per demand.

(iii)Emergency valve

8.8.5 This type of valve is provided for manual shut-off during emergency situation in order to isolate a leak. They are used in pipework of liquid inlet. The failure rate of emergency valve is determined to be 10^-4 per demand or 0.19 per year.

(iv)Pressure relief valve

8.8.6 Pressure relief valve (PRV) avoids pipework or vessels from being over pressurised. They are connected directly with vessels and at liquid inlet and outlet pipework, in order to relieve pressure in case it exceeds the desired level. In this study, the failure rate of PRV is assumed to be 0.01 per demand. Both PRV and over-pressure protection system aim at avoiding the occurrence of over-pressurisation. Added the fact that the practice of the existing LPG installation is to maintain a maximum LPG level of 85% of full capacity, failure of vessels due to overfilling is unlikely.

(v) Shut off valve

8.8.7 Shut off valves are connected in order to control the pressure of the output LPG vapour to avoid over-pressure. A failure rate of 0.01 per demand is adopted in this study.

(vi)Excess flow valve

8.8.8 The excess flow valve installed at the road tanker and the storage vessel are expected to be in operation when a guillotine failure of pipework or flexible filling hose occurs. Assuming a 10 year test interval as a conservative approach, a demand failure rate of 0.13 per demand was adopted in the study.

(vii)Breakaway coupling

8.8.9 A breakaway coupling is provided on the filling line to the storage tank, just downstream of the flexible hose connection in order to mitigate the effect of possible drive away incident The adopted failure rate is 0.013 per demand.

(viii)Filler valve

8.8.10 A filler valve is usually connected at the end of the liquid inlet position to avoid back flow of LPG. The adopted failure rate is 0.013 per demand.

8.8.11 Table 8‑9 sets out the adopted failure rates of various safety system.

Table 8‑9 Failure Rates of Various Safety Systems

Failure case	Frequency
Truck pump over-pressure protection system	1.0 x 10^-4 per demand
Non-return valve (NRV)	0.013 per demand
Emergency valve	0.19 per year or 10^-4 per demand
Pressure relief valve (PRV)	0.01 per demand
Shut off valve (SOV)	0.01 per demand
Excess flow valve (EFV)	0.13 per demand
Breakaway coupling	0.013 per demand
Filler valve	0.013 per demand

Fire Protection/Fighting System Failure

(i) Water Spray System Failure

8.8.12 The provision of a water spray system could put out a fire associated with a road tanker, since the tanker is covered with a fire protection coating called Chartek. It is considered that a water spray system can be effective against jet fire for a coated road tanker with a probability of 0.5.

(ii) Chartek Coating Failure

8.8.13 It was reported that a Chartek coating can give protection for at least 1 hour in case of jet fire. The coating ensured that the maximum wall temperature did not exceed 300°C where a temperature of 500°C is required for thermal weakening of vessel wall that leads to BLEVE (Boiling Liquid Evaporating Vapour Explosion). A failure rate of Chartek coating under jet fire is assumed to be 0.1 per demand under attack for over 1 hour.

(iii)Failure of Fire Service

8.8.14 In urban area, fire service will be available within a few minutes. It is considered unlikely that the Fire Service would not be active prior to the occurrence of a BLEVE. However, in this exercise, it is assumed that such failure rate is 0.5 per demand.

8.8.15 Table 8‑10 summarises the concerned fire fighting system failure cases and their associated frequency of occurrence.

Table 8‑10 Fire Fighting System Failure Cases and their Frequency of Occurrences

Failure case	Frequency
Water spray system failure	0.5 per demand
Chartek coating failure under jet fire	0.1 per demand
Fire service failure	0.5 per demand

8.9 Summary of Frequency of Failure Cases Adopted

8.9.1 Table 8‑11 gives a summary of the frequencies associated with the various failure cases as adopted in this study.

Table 8‑11 Summary of Frequency of Failure Cases

Failure case	Frequency
Storage vessel failure (SR and 100% radiography) · Catastrophic · Partial (25 mm equivalent diameter)	1.8 x 10^-7 per vessel year 5.0 x 10^-6 per vessel year
Road tanker failure · Catastrophic · Partial (25 mm equivalent diameter)	2.0 x 10^-6 per road tanker year 5.0 x 10^-6 per road tanker year
Guillotine failure of pipework	1.0 x 10^-6 per metre per year
Dispenser failure	1.0 x 10^-6 per year
Flexible hose guillotine failure · Filling to underground vessel · Filling to vehicles	9.0 x 10^-8 per hour 1.8 x 10^-7 per transfer 1.5 x 10^-9 per transfer
Hose misconnection	3 x 10^-5 per operation
Hose disconnection (underground vessel filling)	2 x 10^-6 per operation
Tanker drives away	4 x 10^-6 per operation
Human error	0.2 per demand
Hose disconnection (vehicle filling)	2 x 10^-6 per operation
Vehicle drives away	4 x 10^-6 per operation
Vehicle impact	1 x 10^-9 per visit
Vehicle collision during unloading	1 x 10^-9 per visit
Earthquake of Modified Mercali Intensity (MMI) VII	1.0 x 10^-5 per year
Truck pump over-pressure protection system	1.0 x 10^-4per demand
Non-return valve	0.013 per demand
Emergency shut-off valve	0.19 per year or 10^-4 per demand
Driver fails to close manual valve	0.5 per demand
Pressure relief valve	0.01 per demand
Excess flow valve	0.13 per demand
Breakaway coupling	0.013 per demand
Water spray system failure	0.5 per demand
Chartek coating failure under jet fire	0.1 per demand
Fire service failure	0.5 per demand

8.10 Hazard Occurrence

Hazard Event

8.10.1 There are various different events which could result in LPG release. Yet, based on the analysis given in Section 3, only the significant cases have been analysed in this study. Representative hazard initiating event of release cases are summarised below :

à Cold Catastrophic Failure of LPG Vessel;

à Cold Catastrophic Failure of Road Tanker;

à Cold Partial Failure of LPG Vessel;

à Cold Partial Failure of LPG Tanker;

à Failure of Filling Line to Vessel.

à Failure of Liquid Supply Line to Dispenser;

à Failure of Dispenser;

à Failure of Flexible Hose for Underground Vessel Loading;

à Failure of Flexible Hose for Vehicle Vessel Loading.

8.10.2 Fault tree analysis is taken based on the failure cases of the hazard events and significant event outcome as identified above. The fault tree diagram incorporates different types of failure cases, together with failure of safety equipment and other human errors which contribute to the release outcome as mentioned. It also addresses the failure to prevent occurrences of hazard event such as BLEVE (i.e. Boiling Liquid Evaporation Vapour Explosion) subsequently. The results as worked out using fault tree analysis are then applied to event tree analysis in order to relate failure cases with hazard events. A set of fault tree diagrams is shown in Appendix 8-1. The failure rate as estimated using the fault tree diagrams are summarised in Table 8‑12.

Table 8‑12 Estimated Failure Rates for Identified Representative Release Outcomes

Representative Release Outcome	Failure rate (per year)
Cold Catastrophic Failure of LPG Vessel	3.6 x 10^-7
Cold Catastrophic Failure of Road Tanker	2.7 x 10^-7
Cold Partial Failure of LPG Vessel	1.0 x 10^-5
Cold Partial Failure of LPG Tanker	6.7 x 10^-7
Failure of Liquid-Inlet Pipework	4.8 x 10^-8
Failure of Liquid Supply Line to Dispenser	1.0 x 10^-7
Failure of Dispenser	5.6 x 10^-6
Failure of Flexible Hose for Underground Vessel Loading	6.6 x 10^-10
Failure of Flexible Hose for Vehicle Loading	7.1 x 10^-8

8.11 Consequence of Hazard Occurrence

Hazard Consequence

8.11.1 With respect to LPG leakage, a fire or explosion event can be obtained. The possible outcomes include :

à Jet Fire;

à Flash Fire;

à Fireball;

à Vapour Cloud Explosion (VCE);

à BLEVE

8.11.2 It is assumed in this study that all LPG released will be flashed to vapour so that flash fire can be formed instead of pool fire. Actually, this assumption considers the worst scenario because pool fire is usually a localised hazard event while flash fire can affect off-site area as well. Beside the event mentioned above, thermal weakening of the pressure vessel can lead to the occurrences of BLEVE. Event tree diagrams will be used for event outcome analysis. The event tree describes the relationship between outcomes of release cases and hazard events as a result of such releases.

Frequency Analysis

8.11.3 The generic event tree diagrams take into account the following situations, which lead to possible outcome of fireball, BLEVE, jet fire and flash fire.

à immediate and delayed ignition;

à possible formation of VCE;

à progress of unloading process;

à possible flame impingement; and

à failure of safety equipment

8.11.4 In this study, WHAZAN II developed by DNV Technica Ltd. is used for consequence analysis. WHAZAN II contains a set of hazard analysis models (called consequence models) together with a physical properties database of up to one hundred chemicals for estimate of the effect of hazardous chemical releases. The release rate can be studied using WHAZAN II.

8.11.5 With respect to continuous release of LPG, the models: Liquid Discharge - Orifice and Liquid Discharge - Pipe in WHAZAN II will be used to determine the discharge rate for such continuous release from vessel/tanker and pipework. Table 8-13 shows the input and output for the release rate model.

Table 8‑13 Release Rate Model Input and Output

Model

Input

Output

Liquid Discharge - Orifice

Storage Temperature

Storage Pressure

Orifice Diameter

Discharge coefficient

Liquid Head

Discharge Rate

Flash Fraction

Exit Velocity

Liquid Discharge - Pipe

Storage Temperature

Storage Pressure

Pipe Diameter

Velocity Head Loss

Liquid Head

Discharge Rate

Flash Fraction

Exit Velocity

8.11.6 WHAZAN II uses the Bernoulli equation {eq 1} for incompressible flow of liquid through an orifice, which is as follows:

8.11.7 For the calculation of liquid outflow rates from pipers, WHAZAN II uses the Bernoulli equation for incompressible flow. The calculations assume that the pipe is horizontal and is connected, at the upstream end, to a vessel containing liquid with the surface of the liquid a height h above the level of the pipe. The mass flow rate (eq 2) is as follows:

8.11.8 Room temperature and saturated vapour pressure is assumed for liquid discharge modelling. This gives a storage temperature and pressure of 298K and 9.85 bar. The discharge rate of 9.5kg/s and 7kg/s respectively for vessel/tanker are resulted. On the other hand, LPG leakage from dispenser/flexible hose are affected by the submersible pump rate which is usually of about 100litre/min. By conversion, it is about 0.6kg/s. Based on the discharge rate, the time to empty the vessel and tanker for vessel/tanker partial failure and dispenser/flexible hose leakage should be about 15 minutes and 3 hours respectively.

8.11.9 It is known that BLEVE will result if the vessel/tanker is not empty when vessel failure due to thermal weakening by flame impingement occurs. Impingement is due to jet fire which attacks the vessel/tanker. And at the same time, safety equipment cannot effect to avoid the increase of temperature so that rupture occurs. The possibility of impingement on vessels/tankers is dependent upon the relative position of vessels/tankers and the orifice or pipe where leakage occurs. As the time to emptiness for partial failure of vessel/tanker is about 15 minutes, and the time for thermal weakening is about 1 hour, it is considered BLEVE is unlikely to occur for these failure case. In this exercise, it is assumed that the road tanker is not empty before failure only for guillotine failure of liquid inlet pipework, guillotine failure of liquid outlet pipework, failure of dispenser and failure of flexible hose.

8.11.10 Ignition probability is one of the determining factors of consequence of hazard outcome. Fireball will result in case immediate ignition upon catastrophic failure of vessels/ tankers occurs. Jet fire usually occurs as a result of partial failure of vessels/tankers or the breakaway of pipework, and is triggered by immediate ignition.

8.11.11 For delayed ignition, flash fire may occur and followed by jet fire if there is LPG fuel remained for continuous release. On the other hand, VCE can only occur in case a significant degree of confinement is available to generate the turbulence required, which is not anticipated in the current situation based on the “open” design of the LPG installation.

8.11.12 The ignition probability is dependent upon the time of release (e.g. ignition probability will be lower at night when fewer ignition sources are expected to be present), the scale of release, weather category/ wind direction and topography, which affects the dispersion distance to the lower flammable limit for LPG, and location of ignition sources. In case of catastrophic failure of vessel/ tanker, immediate ignition is more likely. On the other hand, there is a higher probability for delayed ignition with respect to continuous release due to partial failure, pipework failure, etc.

8.11.13 The probability of ignition would be determined for different directions, wind speed and stability class. With respect to the proposed LPG filling station, gas will more likely spread to Road 20/6 due to the use of solid wall on the other three sides.

8.11.14 Occurrence of VCE requires significant confinement of vapour, which is unlikely for such “open” design of the proposed LPG filling station. Therefore, the probability for VCE is occur is considered negligible in this study.

8.11.15 The proposed LPG filling station also provides facilities for the storage and supply of petrol and gasoline. It implies the necessity to consider knock-on effect due to LPG hazard outcome. With respect to the possible hazard outcomes, only fireball and BLEVE will result in significant impact leading to knock-on failure. Owing to the use of underground storage for petrol and gasoline, their vessels and pipework failure due to fireball and BLEVE are unlikely. However, failure of dispensers will be possible, which leads to jet fire occurrence. Yet, the effect and area covered by fireball or BLEVE will be much higher than that of jet fire. It is therefore concluded that such knock-on effect can be neglected in this study.

8.11.16 Event tree diagrams are developed for the study and are shown in Appendix 8-2. A summary of the result of event tree analysis is shown below in Table 8-14.

Table 8‑14 Hazard Event Outcome for Representative Release Event

Representative Release Event	Hazard Outcome and Probability of Occurrence
Cold Catastrophic Failure of LPG Vessel	Fireball (90%)
Cold Catastrophic Failure of Road Tanker	Flash fire (10%)
Cold Partial Failure of LPG Vessel	Jet fire (29%)
Cold Partial Failure of LPG Tanker	Flash fire (24%)
Failure of Filling Line to Flexible Hose	Jet fire (29%)
Failure of Liquid Supply Line to Dispenser	Flash fire (24%)
Failure of Dispenser	BLEVE (0.007%)
Failure of Flexible Hose for Underground Vessel Loading
Failure of Flexible Hose for Vehicle Loading

8.11.17 Based on the result in Table 8-14, there is an extremely low probability for BLEVE occurrence. By incorporating the failure rate and consequence of event, the probability of occurrences of each hazard outcome can be derived and summarised below in Table 8‑15.

Table 8‑15 Hazard Consequence Outcome Frequency

Frequency of Occurrence
Failure Case	Consequence
	Fire Ball	Flash Fire	Jet Fire	BLEVE
Cold Catastrophic Failure of LPG Vessel	3.2 x 10^-7	3.6 x 10^-8	0	0
Cold Catastrophic Failure of Road Tanker	2.4 x 10^-7	2.7 x 10^-8	0	0
Cold Partial Failure of LPG Vessel	0	2.4 x 10^-6	2.9 x 10^-6	0
Cold Partial Failure of LPG Tanker	0	1.6 x 10^-7	1.9 x 10^-7	0
Failure of Filling Line to Flexible Hose	0	1.2 x 10^-8	1.4 x 10^-8	3.4 x 10^-12
Failure of Liquid Supply Line to Dispenser	0	2.4 x 10^-8	2.9 x 10^-8	7 x 10^-12
Failure of Dispenser	0	1.3 x 10^-7	1.6 x 10^-7	3.9 x 10^-11
Failure of Flexible Hose for Underground Vessel Loading	0	1.6 x 10^-10	1.9 x 10^-10	4.6 x 10^-14
Failure of Flexible Hose for Vehicle Loading	0	1.7 x 10^-8	2.1 x 10^-8	5.0 x 10^-12

8.12 Consequence Analysis

8.12.1 Beside the release rate, spreading of fire and explosion events are also studied using WHAZAN II. The following models for propane are used to determine dispersion and affected distance of fire ball and jet fire event:

à Dense Cloud Dispersion;

à Jet Flame;

à Fireball/BLEVE.

8.12.2 Additionally, an in-house developed software, the QRA system 1.0 has been applied to predict the consequence of such hazard impacts and estimate the risk including societal and individual risks incurred based on the result generated by WHAZAN II.

Fatality Rate

8.12.3 The level of damage caused is a function of duration of exposure, as well as of heat flux. The variation of the effects on humans with changes in heat flux and in duration of exposure can be expressed in the form of a probit equation (Eisenberg, 1977) :

where Q is in Watts and t is in seconds.

8.12.4 Table 8‑16 presents time of exposure required for different fatality levels under various radiation levels.

Table 8‑16 Fatal Radiation Exposure Levels (From Probit)

	Seconds Exposure for % Fatality Levels
Radiation Level (kW/m²)	1%	50%	99%
1.6	500	1300	3200
4.0	150	370	930
12.5	30	80	200
37.5	8	20	50

8.12.5 It is assumed that it might be possible to “shelter” within half to one minute in general. Therefore, the radiation of 4.0 kW/m² or lower can be significant from the point of view of pain, but not of fatality as there should be sufficient time for escape.

8.12.6 Jet fire and flash fire are of longer duration and fireball is of limited duration between 2 to 30 seconds. Accordingly, radiation level of 4.0 kW/m² or lower for fireball will have a fatal rate of zero.

Fireball

8.12.7 Fireball is more likely to occur with respect to immediate ignition upon instantaneous release from vessels/tankers due to catastrophic failure. Instantaneous ignition of a certain mass of LPG results in explosion and fire of hemispherical shape. Heat is evolved by radiation. When the combustion has filled the fireball, the thermal radiation output of the fireball is at its maximum and the hemisphere forms a sphere and rises due to the buoyancy of the hot gases formed by the combustion to a height of about ¾ times of the diameter of the fireball. The principal hazard of an LPG fireball arises from thermal radiation. Due to its intensity, its effects are not significantly influenced by weather, wind direction or source of ignition. The effects can be expressed simply in terms of fatality rate at given distances and heights.

8.12.8 The radius of the fireball, radiation distance and duration is solely determined by the mass of LPG available. The mass for fireball calculation is assumed to be the total mass retained in the ruptured vessel. By adopting the Fireball model in Whazan II, the duration of the fireball and radiant heat level at particular distance can be obtained.

8.12.9 For the occurrences of fireball or BLEVE, empirical correlation in WHAZAN is used to calculate the size, duration and radiant intensity of fireballs of flammable liquid and/or vapour. Table 8‑17 shows the input and output of the fireball/BLEVE model.

Table 8‑17 Fireball/BLEVE Model Input and Output

Model

Input

Output

Fireball/ BLEVE

Flammable Mass

Efficiency Factor

Maximum fireball radius

Duration of fireball

Distances to the 1.6, 4.0, 12.5 and 37.5 kW/m² radiation levels

8.12.10 Using the correlation of Crossthwaite et al (1988) the maximum fireball radius is:

The duration for m<37,000 kg is: and for m>37,000 kg is:

The energy released by combustion at efficiency h is: Q = H_cmh and

Roberts (1982).

8.12.11 Accordingly, the fatality rate can be estimated using the probit formulae

Jet Fire

8.12.12 In case partial failure of the vessel/ tanker and failure of pipework, hose, etc. occur, a continuous release of LPG will be resulted. Vessel/tanker is usually pressurised so that the escape velocity of LPG is relatively high. WHAZAN II is used to determine the discharge rate and in turn the jet fire event for such continuous release from vessel/tanker and pipework. Table 8‑18 shows the escape velocity and discharge rate of LPG with respect to orifice and pipework discharge.

Table 8‑18 Release Rate for Liquid Discharge

Model	Mass Discharge (kg/s)	Release Rate (m/s)
Liquid Discharge - Orifice	9.5	32.7
Liquid Discharge - Pipe	7.0	24.3

8.12.13 The jet fire model in WHAZAN II is based upon that described in API RP521 (American Petroleum Institute, 1982). The size of the flame is dependent upon the flow rate and in turn the operating pressure and size of the break. Table 8‑19 shows the input and output of jet flame model where the length of the frame is given by:

Table 8‑19 Jet Flame Model Input and Output

Model

Input

Output

Jet Flame

Flare Diameter

Discharge Rate

Discharge Speed

Wind Speed

Efficiency Factor

Radiation Level Required

Downwind distance

Crosswind distance

Distances to 4.0, 12.5 and 37.5 kW/m² radiation levels

Flash Fire

8.12.14 With respect to continuous release, the dispersion distance of LPG should be found in order to determine the scale of influence geographically. Dense cloud dispersion model will be applied. Table 8‑20 shows the input and output for these dispersion models.

Table 8‑20 Dispersion Model Input and Output

Release

Model

Input

Output

Instantaneous

Dense Cloud Dispersion

(instantaneous release)

Mass Released

Release Temperature

Dilution Factor

Initial Cloud Radius

Wind Speed

Pasquill Stability Category

Surface Roughness Parameter

Ambient Temperature

Relative Humidity

Min Concentration of Interest

Maximum downwind effect distance

8.12.15 WHAZAN II uses the Cox and Carpenter (1980) model which is one of several “top-hat” or “box” models in existence for dense cloud dispersion modelling. An instantaneous release is represented as a cylindrical cloud. As the dense cloud disperses, it spreads laterally outwards due to density effects, and entrains air through its top and side surfaces. On the other hand, a continuous release is represented by a cloud of rectangular cross-section, which spreads laterally cross-wind because of gravity and moves with the wind.

8.12.16 Lateral spreading takes place at a rate:

where the constant k is obtained by comparison with experimental data and is found to have a value of approximately unity. In this equation, r is the radius of instantaneous clouds and the semi-width of continuous clouds. The ground level concentration at the cloud centreline in then modelled as:

for the instantaneous release case and as:

for the continuous release case

8.12.17 Humans who are encompassed outdoors by the flash fire will be fatally injured. A fatality rate of unity is assumed.

8.13 Risk Summation

Modelling of Consequences of Hazards

8.13.1 To calculate the risk of hazard occurrence including fireball, flash fire and jet fire, the in-house developed software QRA-LPG will be used. It is capable of integrating all contributing factors to produce an individual risk contour and societal risk in the form of F-N curve. These factors include failure frequencies, hazard ranges, weather parameters, population distribution (spacial and temporal) and appropriate impact factors.

Collection of Data

8.13.2 The collection of data as classified in QRA-LPG includes: topography, population, meteorology, risk source, event outcome probability, consequences and escape factor data. Additionally, protection factor is accounted by re-adjusting the population to emulate the effect of protection.

Topography

8.13.3 The topography is composed of objects called regions. A region can be defines as buildings, roads and other areas. Subsequently, population information can be related to the regions to calculate the impact.

Population and Ignition Source

8.13.4 Population data is defined with reference to the region of the topography information. Additionally, the variation of population is also specified here with respect to different period such as weekday/weekend or time of a day. Moreover, protection factor is applied here to take into account the difference between indoor (including population inside trains) and outdoor situation and the effect of thermal radiation wall. A protection factor of 0.8 is assumed for persons situated inside a structured building; a protection factor of 0.5 is adopted for vehicles. For population protected by the solid radiation wall (the northern façade) of the proposed bus depot, a higher protection factor has been applied to reflect further mitigation effect. Ignition source, on the other hand, is defined for calculating the extent of influence of flashfire event.

Meteorology

8.13.5 The frequency of occurrences of combination of wind speed and stability class in daytime and nighttime is also included for assessment.

Risk Event and Consequence

8.13.6 Each risk event consequence consists of information about the frequency of each consequence, consequence parameter, and time of occurrence.

Risk Source

8.13.7 This database includes information about the frequency of occurrence of each risk event and the location where it happens. As the LPG inventory level varies, it is assumed in this exercise that the consumption of LPG is in a linear manner, and 5 periods are sub-divided within which the inventory level will be different, such that the change of inventory level can be simulated.

8.14 Assessment Finding and Discussion

Assessment Criteria

8.14.1 Having considered every aspect ranging from initiating events, hazard occurrences, possible impact to quantified risk levels, the individual and societal risks obtained can be compared with the risk guidelines, which has been adopted by CCPHI to assess the off-site risk levels of PHIs. The maximum level of off-site individual risk associated with PHIs should not exceed 1 in 100,000 per year. On the other hand, the societal risk guidelines are expressed in terms of lines plotting the frequency (see Figure 8-3). Two Frequency of Fatalities (F) vs. Number of Fatalities (N) risk lines are used in the societal risk guidelines to determine “acceptable” or “unacceptable” societal risks. Moreover, there is a vertical cut-off line at the 1,000 fatality level extending down to a frequency of 1 in billion years. The intermediate region is incorporated in the societal risk guidelines in which the acceptability of societal risk is borderline and should be reduced to a level which is “as low as reasonably practicable” (ALARP). It seeks to ensure that all practicable and cost-effective measures which can reduce risks will be considered.

Control Measures

8.14.2 There are many practical methods for reducing risks associated with the operation of the LPG filling station. The application of a fireproof coating to tankers will greatly reduce the risk of BLEVE. The installation of safety devices such as EFV can reduce the frequency of failure events. The selection of safe site for the stationary installation and place for the parking of tanker is useful to reduce fatality and occurrence frequency of impact event. Moreover, the inventory should be kept as low as possible. Furthermore, proper training and safety practice can reduce the probability of incorrect action.

8.14.3 In this study, standard control measures has been assumed to be incorporated into the design of the LPG filling station such as the use of fireproof coating to tankers, the maintenance of low inventory (a maximum of about 85% of full capacity), installation of safety devices, the dedication of bay area for tanker parking and the avoidance of tanker collision during unloading by controlling the use of dispenser system, well-adopted training system and well-trained personnel. As a precautionary measure, the entire northern façade of the bus depot building will be constructed in form of a solid concrete wall without opening as an at-receiver risk-reduction measure.

Assessment Finding

8.14.4 The assessment result in the form of societal risk in form of F-N curve and individual risk contour are shown in Figures 8-3 and 8-4, respectively.

8.14.5 It can be observed that the societal risk is within the acceptable region as defined by the risk guidelines. The individual risk in the vicinity of the LPG installation expressed in terms of risk level contour line is shown in Figure 8-4. The individual risk level within the boundary of the bus depot site is also found to be within the acceptable level of 1 in 100,000 per year.

8.14.6 The Potential Loss of Life (PLL), which is calculated based upon the following equation, are equal to 2.5 x 10^-5. Moreover, significant events contributed to the PLL is listed in Table 8‑21.

Table 8‑21 Events contributed to PLL

Hazardous Event	Fatality	Frequency	F x N
Fireball	5 – 322	3.4E-07	2.3E-05
Flashfire	1 – 13	5.6E-07	9.9E-07
Jetfire	1 – 3	3.1E-07	5.9E-07
			2.5E-05

8.15 Conclusion

8.15.1 The findings of the QRA carried out based on the design of a typical LPG/ Petrol filling station indicated with the provision of standard risk control measures incorporated into the design of the LPG/ Petrol filling station, and the precautionary measure of providing a solid concrete wall for the entire northern façade of the bus depot building, the project based on the existing design will not be subjected to unacceptable risk from the operation of the LPG/ Petrol filling station and the overall societal risk impact will be within acceptable level. It is anticipated that the proposed project will not pose any unacceptable constraint on the future design of the LPG/Petrol filling station.

9. Landscape and Visual Impact Assessment

9.1 Introduction

9.1.1 The proposed building layout covers the entire site due to the need to accommodate the various provisions on site which is just over one hectare. These included driveway and ramp system with 15-m turning radius, 80 numbers of maintenance spaces, about 100 numbers of parking spaces and other supporting facilities. Consequently, there will be no space for plating after the building is completed.

9.2 Landscape Impact Assessment

9.2.1 A baseline study has been carried out to identify the existing landscape character of the site, according to the Guidelines for Landscape Impact Assessment of EIAO Technical Memorandum. The site is a flat vacant lot presenting no special landscape character and visual amenity in the area. The only landscape resource is the existing vegetation scattered throughout the study area.

9.2.2 As such, a comprehensive tree survey (See Appendix – 9-1 submitted under a separate cover) has been carried out to identify the baseline conditions of the existing landscape resources based on the survey parameters set out in WBTC 24/94. A total 111 numbers of trees, including 23 numbers of trees which are outside boundary, have been surveyed. The trees are mainly common species with trunk diameter varies from 0.1m to 0.4m. There is only one banyan tree (T51) which trunk diameter is over 0.5m.

9.2.3 According to the proposed architectural layout, all the existing trees within the site will be affected by the works and cannot be retained. In other words, a total 88 numbers of trees will be required to be removed from the site during the site clearance period.

Mitigation Measures

9.2.4 In order to mitigate the landscape impact, a detailed study on transplanting some of the high quality trees have been conducted (See Appendix 9-1) to formulate the transplanting strategies according to a set of established criteria.

9.2.5 In order to enhance the environmental quality of the area, the feasibility of transplanting T104 (Grevillea robusta), T105 (Bombax malabaricum) and T111 (Bombax malabaricum) to the nearby roundabouts on Road 20/4 (Annex 1) outside Citybus’ proposed depot has been explored. Given that Road 20/4 would only be completed in around July 2002 which could not match the time for transplanting of trees in December 2001, and the roundabouts on this road are quite small with a diameter of about 8 metres, Transport Department considered that it was not suitable to transplant the trees at such locations because these roundabouts were delineated by road markings only. Some long vehicles, particularly the container trucks observing the Superpost Centre on Road 20/4, might need to weave into the roundabout to make turnings. From road safety point of view, it is not appropriate to transplant these 3 trees at the roundabouts.

9.2.6 Discussions have been held with DAO of LCSD and Landscape Section of Highways Department on selecting suitable sites to accommodate all the transplanted trees. During the discussion, it was agreed that the trees should be transplanted to a large open space for better establishment and aesthetic reasons.

9.2.7 Effort is also being made through Lands Department to make enquiries from various government departments, including AFCD, etc., for an outlet for the trees.

9.2.8 In case no suitable site can be identified by government departments, it is recommended to transplant the trees to Chai Wan Park (Annex 2) Cape Collinson Chinese Permanent Cemetery (Annex 3), Yee Shing Lane Sitting Out Area (Annex 4) or the proposed Town Park at Aldrich Bay (Annex 5). Visit to the site and discussion with LCSC indicate that this option are feasible, subject to LCSD’s final agreement on the exact location of the transplanted trees.

9.2.9 If the trees cannot be transplanted to their permanent locations immediately due to various reasons, the transplanting contractor shall be required to form a holding nursery for the purpose of nursing the trees exclusively for this project. The maintenance of these trees shall be closely monitored by the landscape consultants until they are successfully transplanted to their permanent locations. The cost for the whole operation up to successful handover of trees to relevant departments shall be borne by the Applicant.

9.2.10 In addition, a planting proposal is included (Section 7 of Appendix 9-1) and is based on the proposed building layout with the intention to introduce greenery where possible to mitigate the landscape impact and further enhance the quality of the environment.

9.2.11 Since the existing vegetation mainly consists Ficus trees, as illustrated in the tree survey, a row of Ficus benjamina is proposed to be planted with understorey shrubs. The wall behind the planter will be covered by creepers and vines to form a green backdrop on the street level.

9.2.12 There are planters on the 1^st and 3^rd floor where Ficus benjamina will also be planted. In order to soften the hard edge and introduce more greenery to the building, hanging plants such as Allamanda cathartica and Scindapsus aureus will also be planted to improve the visual quality.

9.2.13 As the quality of streetscape is important to mitigate the landscape and visual impact, it is further recommended that a row of heavy standard Delonix regia should be planted along the proposed footpath along Road 20/4, and the footpath along Shing Tai Road where practicable. As the footpaths are outside site boundary, approval should be obtained form Highway’s Department.

Implementation

9.2.14 The transplanting works will be carried out strictly according to the Transplanting Specification (Appendix D of Tree Survey Report) under the close monitoring by ER who should be a qualified landscape architect or arboriculturist. The various responsible parties can be summarized as follows:

Table 9‑1 Summary of the Implementation for the Transplanting Works

Mitigation Measures	Funding	Implementation	Maintenance	Management
1. Transplanting 13 nos of trees to Chai Wan Park, Cape Collinson Chinese Permanent Cemetery, Yee Shing Lane Sitting Out Area or the proposed town park at Aldrich Bay	Citybus	Contractor	LCSD	Food and Environment Hygiene Department / LCSD
2. Compensatory Planting within site boundary	Citybus	Contractor	Citybus	Citybus
3. Tree Planting along Road 20/4 & Shing Tai Road	Citybus	Contractor	LCSD	Highways / Transport Department

9.3 Visual Impact

9.3.1 It is recognized that the two common side boundary walls could have an impact visually, particularly due to the requirements that they must be solid without openings. However, as the subject site to a class ‘A’ site, it is not normal to elaborately treat the side common walls. However, since it is anticipated that a petrol filling station, which traditionally is single-storey, will be erected on the site besides the northern boundary wall, special attention will be paid in its treatment. As no details are available on the petrol filling station to be built and therefore treatment of our external wall cannot take into consideration its location, building form, colour, etc., it is proposed that recessed grove lines be introduced to divide the wall into panels, so as to reduce its massive scale. Colours will also be used to further break down the scale by means of spray-painting on plaster. In addition to spray-painting, metal cladding, tiling will also be used for the main elevations facing Road 20/4 and Shing Tai Road, in order to add richness in texture and colour, so as to create an environmental in harmony with the surroundings.

9.3.2 The side and rear elevations of the building would be designed in line with the style of front elevation as shown in the perspective given in Appendix 9-2.

	Emission Factors
Bus activity	NO_x	CO	RSP
Traveling (g/km)	11.71	8.89	1.38
Idling (g/min/vehicle)	2.0	2.0	0.042

		Pollutant Emission Rate (g/s) Per Source
Floor	No. of Sources	NO₂	CO	RSP
G/F	80	0.00130	0.00032	0.000164
1/F	80	0.00062	0.00015	0.000059
Roof floor	70	0.00069	0.00016	0.000069

Location	Approximate Nearest Separation (m)
	Site B	Site C
Heng Fa Chuen	115	390
Staff Quarters of Hong Kong Institute of Vocational Education (IVE) (Chai Wan)	110	135
IVE (Chai Wan)	130	80
Tsui Wan Estate	490	165

Ref. No.	Location	Predicted pollutant concentrations (mg/m³) at discrete receptor
Ref. No.	Location
	Height above ground (m)	1-hr NO₂					24-hr NO₂					1-hr CO					24-hr RSP
		1.5	5	10	15	20	1.5	5	10	15	20	1.5	5	10	15	20	1.5	5	10	15	20
A1	Heng Fa Chuen	104	104	104	104	104	81	81	81	81	81	1635	1520	1520	1406	1406	63	62	59	56	55
A2	Staff Quarters of the IVE (Chai Wan)	179	141	141	141	141	111	96	96	96	96	1864	1864	1864	1749	1749	74	73	71	69	66
A3	IVE (Chai Wan)	179	179	179	141	141	111	111	111	96	96	1978	1978	1864	1864	1749	77	76	74	71	68
A4	IVE (Chai Wan)	141	141	141	141	141	96	96	96	96	96	1864	1864	1749	1749	1635	71	70	68	66	64
A5	Tsui Hong House, Tsui Wan Estate	141	141	141	104	104	96	96	96	81	81	1749	1749	1635	1520	1520	69	67	64	62	60
A6	Tsui Sau House, Tsui Wan Estate	141	141	141	104	104	96	96	96	81	81	1864	1749	1635	1635	1520	70	68	64	62	60
	Air Quality Objectives (AQO)	300					150					30,000					180

	Number of Buses/Hour¹
	During mid-night		During Early Morning
Floor Level	Entering	Leaving	Entering	Leaving
G/F	80	80	5	90
1/F²	80	80	0	85
Roof floor³	70	70	0	85

Environmentally Sensitive Areas	Estimated Population (approx.) protected during mid-night return or early morning leaving of buses
Heng Fa Chuen	350
Staff Quarters of Hong Kong Institute of Vocational Education (Chai Wan)	150
Institute of Vocational Education (Chai Wan)	N/A
Tsui Wan Estate	3,000

1. Introduction

1.1 Project Need

1.2 Project Design & Technical Assessments

1.2.5 This EIA report is prepared in accordance with the requirements stated in the Study Brief. An Environmental Permit will only be issued by DEP for the construction and operational of the project after the approval of the EIA Report.

1.3 Objectives of the Assessment

1.3.2 The objectives of this EIA study, as stated in Section 2.1 of the Study Brief, are as follows:

1.4 Public Inputs

1.4.2 Potential concern on these environmental factors has been taken into account in the study.

1.5 Structures of the EIA Report

1.5.2 The content in Sections 2 through 11 are listed below:

2. Site selection HistoRy

2.1 Identification of Alternative Development Sites

2.1.9 The site selection process confirmed that there are no available industrial sites in the Eastern District other than the industrial sites in Chai Wan East Industrial Area.

2.2 Selection of Preferred Site

2.2.4 Although the Hong Kong Institute of Vocational Education (IVE) (Chai Wan) is located closer to Site C, it is not expected to be in operation during the hours in the early morning and near mid-night when the bus depot would be most active.

2.3 Required Technical Assessments of Selected Site

3. Project Description and key environmental issues identification

3.1 The Subject Site and its Environs

3.1.1 The proposed bus depot is planned to be constructed on an approximately 1 hectare site located in the Chai Wan East Industrial Area. The site selection process is described in Section 2. Figure 1-1 shows the location of the site.

3.2 Bus Depot Design

3.2.6 The number of staff working in the bus depot/ maintenance area and offices is estimated to be about 319 and 201 respectively during daytime (approx. 08:00 to 18:00). In the evening and night-time (approx. 18:00 to 08:00), some 50 workers are expected to be working at the bus depot.

3.3 Implementation Programme

3.3.1 Construction works are planned to start near end of 2001 to meet the urgent demand to have the depot ready for operation in mid-2003. Figure 3-9 shows a preliminary construction programme. The development is expected to be completed in mid-2003.

3.4 Identification of Key Environmental Issues

3.4.1 The key environmental issues during the construction and operational phases of the proposed development are identified to include the following:

3.4.2 The EIA Study Brief requires in general a study area of 300m and 500m from the boundary of the project site with respect to air quality impact assessment and noise impact assessment, respectively. Figure 2-10 shows the study area boundary for air quality and noise impact assessments.

4. Air Quality Impact Assessment

4.1 Introduction

4.1.1 This section assesses the potential air quality impact associated with the construction and operational phase of the proposed bus depot. Air sensitive receivers (ASRs) have been identified and worst case impact on these receivers have been assessed quantitatively.

4.1.2 Dust generation from construction activities is identified to be of key interest during construction phase of the project. During the operational phase, vehicular emission from buses running within the bus depot and on the adjacent roads is the key focus of the study.

4.1.3 The assessment covers a study area of 500m from the development site boundary in accordance with the requirements of the EIA Study Brief.

4.2 Assessment Criteria

4.2.2 In addition to the AQOs, EPD requires under Annex 4 in the Technical Memorandum on EIA Process (EIAO-TM) issued under the EIA Ordinance an hourly TSP limit of 500mg/m3 for construction dust impact assessment.

4.3 Air Sensitive Receivers (ASRs)

4.3.2 Representative assessment points (A1 to A6) have been selected for the air quality impact assessment. The ASRs represented are described in Table 4‑2. Locations of the representative assessment points are shown in Figure 4-1.

4.4 Baseline Condition

4.4.1 The existing major air pollution sources in the study area are expected to be open road traffic emission from major road carriageways (e.g. Island East Corridor).

4.5 Construction Dust Emission Impact Assessment

4.5.3 A worksheet showing the calculation of dust emission rates from each activity is presented in Appendix 4-1 for reference.

4.5.7 The following relevant meteorological data of the year 1998 were obtained from Hong Kong Observatory and used in the modeling study. Parameters used include:

4.5.10 The unmitigated maximum 1-hour and 24-hour average TSP concentrations predicted at the representative assessment points, with background concentration included, are presented in Table 4‑4 and Table 4‑5 below.

4.5.12 The following measures are specifically recommended for implementation together with those presented in the Air Pollution Control (Construction Dust) Regulation:

4.5.15 No free falling of construction debris shall be allowed at the site.

4.5.18 Watering is an effective dust control measure commonly employed in storage piles and handling operations and should be implemented where appropriate. Other control measures such as enclosed or semi-enclosed windboard should be used, where applicable, to minimise dust emission.

4.6 Vehicular Emission Impact Assessment

4.6.3 Air pollutants may also be generated from other depot operations including engine testing, brake testing and painting. However, the emission quantity and associated air pollution is expected to be insignificant.

4.6.11 It can be noted that all modeling results are falling well within the relevant AQOs.

4.6.12 In addition to the off-site bus traffic, operation of the bus depot would also result in generation of some air pollutants directly from the depot.

4.6.18 The same set of meteorological data as presented in Section 4.5.7 has been adopted in the air quality modeling. Background pollutant concentrations as presented in Table 4‑3 were adopted.

4.6.22 All predicted air pollutant concentrations at various levels of the ASRs are well within the AQOs. The assessment results reveal that vehicular emissions from open road traffic and emission from the two bus depots will unlikely pose an unacceptable air quality impact on the surrounding ASRs.

4.7 Environmental Monitoring & Audit (EM&A) Requirements

4.7.2 The detailed vehicular emission impact assessment indicates that vehicular emission from buses will not be a concern during the operational phase. The carrying out of air quality EM&A works in relation to air quality during the operational phase is not considered necessary.

4.8 Assessment Conclusions

5. Noise Impact Assessment

5.1 Introduction

5.2 Study Area and Noise Sensitive Receivers (NSRs)

5.2.1 A study area of 300m from the boundary of the project site has been adopted in the study in accordance with the requirement stated in the EIA Study Brief.

5.2.4 No planned NSRs are identified in the proximity of the bus depot that could be subject to a noise impact resulting from the project.

5.2.5 The existing dominant noise sources identified in the vicinity of these NSRs include traffic noise from the nearby major road carriageways (e.g. Island Eastern Corridor) and railway noise from the MTR tracks.

5.3 Construction Noise Impact Assessment

5.3.6 The approach used in the assessment of noise from construction works other than percussive piling is based on standard acoustic principles, and the guidelines given Para. 5.3 and 5.4 of Annex 13 of the EIAO TM. The methodology adopted is the same as that presented in TM1.

5.3.7 The methodology for assessing construction noise impact arising from the project has been developed based on the standard acoustic principles in TM1. In brief, this includes the following steps:

4.2.2 In addition to the AQOs, EPD requires under Annex 4 in the Technical Memorandum on EIA Process (EIAO-TM) issued under the EIA Ordinance an hourly TSP limit of 500mg/m³ for construction dust impact assessment.