4                   AIR QUALITY

 

4.1             Introduction

This section presents an assessment of the potential air quality impacts arising from the construction and operation of the proposed Wholesale Fish Market at Tuen Mun Area 44. Dust emission during the construction phase, odour emission, vehicular emission and marine traffic emission during the operational phase are the identified key issues associated with the proposed Wholesale Fish Market.

 

4.2             Background Air Quality

4.2.1    The assessment area, which lies within 500m from the boundary of the subject site, is shown in Figure 4.1. The land uses within the assessment area consists of residential/commercial development, industrial establishments as well as recreational facilities.  As the industrial, commercial and residential uses account for more than 50% of the area within 3km radius of the subject site, an urban land use classification is assigned for the assessment area.

 

4.2.2    Traffic emission from nearby roads is the major pollutant source within the area. Emission from the industrial establishments in the vicinity is also a potential source of air pollution of the assessment area. Besides, there are other potential sources of odour in the area, including the Tuen Mun Nullah and the Castle Peak Bay Typhoon Shelter.

 

4.2.3    The proposed Wholesale Fish Market (WFM) is located within the Tuen Mun Airshed. The nearest Environmental Protection Department (EPD) Air Quality Monitoring Station (AQMS) is located in Yuen Long. Air quality statistics in terms of annual averages recorded for the Yuen Long District1 during Year 1999 were used to represent the background air quality in the Tuen Mun Area. As the ambient concentration of Carbon Monoxide was not monitored at the Yuen Long AQMS, the air quality statistics recorded at the Tsuen Wan AQMS for Year 1999 were used. Table 4.1 shows the background pollutant concentration adopted in the study.

 

Table 4.1         Background Air Quality Levels

Pollutant

Background Concentration, mg/m3

SO2

22

NO2

60

TSP

102

RSP

62

CO

1177

 

There is no recorded data of the ambient odour concentrations at the Tuen Mun Area.

 

4.3             Identification of Potential Environmental Impacts

The potential air quality impacts associated with the construction and operational phases of the proposed WFM are identified and described in this section.

 

(i)         Construction Phase

4.3.1    Activities associated with the construction of the proposed WFM have the potential to cause dust impact on the surrounding environment by soiling properties close to the construction site.

4.3.2    The potential for dust emission during the construction phase of the WFM depends on the type of construction activities, the application of dust control measures to reduce emissions, and the weather conditions. Construction activities, which may cause dust impact on the nearby residents, include site excavation and concreting operations. However, there will be no concrete batching plant on the site. Other potential sources include dust blow-off and spillage from vehicles during the transport of materials as well as indirect transport of particles by vehicles accessing and leaving the site.

 

4.3.3    The construction work for the WFM can be divided into two phases, namely foundation and superstructure construction. The foundation construction is anticipated to last for 9 months and the superstructure construction for 17 months. Excavation will be carried out during construction of piles and pile-caps. In view of the fact that the subject site is an existing open space flat area, extensive demolition and excavation works will not be required. The construction activities that have the potential to generate dust will include material handling, wind erosion and truck haulage on unpaved roads. The potential air quality impact due to dust emission during the construction phase of the WFM was assessed quantitatively as detailed in Section 4.6.

 

(ii)        Operational Phase

Odour from the operation of the WFM

 

4.3.4        Odour arising from the operation of the WFM may impose air quality impact on the nearby residents. The potential sources of odour emissions include the various on-site and off-site activities involved in the daily operation of the WFM. Daily operations vary and can be divided into a) night time operations involving the wholesale activities associated with loose chilled fish and b) daytime operations involving the unloading and vehicular transportation of live and boxed fish.

4.3.5        Night time fish auction operations currently account for the major activities of the WFM and have the greatest potential for environmental impact as operations involve handling of loose chilled fish. The peak hours for fish auction and wholesale activities are from 3:00am to 6:30am and the on-site activities related to the fish wholesaling process are briefly described as follows. From the fishing vessels berthed at the WFM, fish will be unloaded, sorted and put into the buckets provided by the FMO. After passing through the weighing station, these buckets of fish will be arranged and displayed for auction. Fish bought by the fish traders will be transferred from FMO’s buckets to the fish traders’ containers and loaded onto parked lorries. Throughout the process, fish will be chilled with ice blocks and kept in open containers. These activities will be confined to the area within the WFM building. Upon completion of the night time auction and loading operations all remaining waste and organic matter will be sealed for removal and all areas thoroughly and hygienically cleaned before daytime activities commence.

4.3.6        The handling and temporary storing of fish at the WFM may contribute to the odour impact on the nearby sensitive receivers. Dead fish are potential sources of odour emission. They have a characteristic smell. Although the odour is not pungent or offensive generally, it may become a nuisance to some people when encountered at a relatively high concentration or where deterioration of quality takes place. The strength of the odour differs slightly for different types and storing conditions of the chilled fish. Night time operations deal with the sorting and loose handling of fish and as such have the greatest potential for generating odour and impacting on nearby sensitive receivers.

4.3.7        Daytime operations in addition to undertaking and updating paperwork associated with the night time auctions also account for the relatively simple and clean throughput of both live seafood and boxed fish. AFCD records currently confirm that unloading of some 660kg of live seafood and some 410kg of preboxed chilled fish (with a combined total of 1 ton per day representing a small fraction of the total of some 17 tonnes of chilled fish unloaded per day) take place between 7:00am to 2:30pm each day. Normally, the live seafood and boxed fish are unloaded and transferred directly to waiting vehicles for dispatch. Due to the method of containment, avoidance of sorting and handling of loose fish and lack of waste, the potential source of odour is greatly reduced.

4.3.8        After careful consideration of the above operations, the EIA identifies the peak hours for fish auction and wholesale activities from 3:00am to 6:30am as being the time when odour levels will be greatest and potential nuisance to sensitive receivers will be at its highest. It is considered that the potential for odour emission from other operations at the WFM, which mainly involves handling of live seafood and boxed fish, is greatly reduced since the concerned odour emission is normally associated with decay of organic matter when chilled fish is exposed to open air.

4.3.9        To meet community pressure to reduce potential noise pollution from the future market the WFM will be designed for all parking and loading of vehicles to be accommodated inside the building and with no openings (other than fixed windows and doors) on the sides of the building facing nearby premises (Wu Shan Road).  This is not customary practice in FMO markets and will require the extra operational expense of a mechanical ventilation system to exhaust engine fumes from FMO premises.  Such a system would also simultaneously exhaust potentially odorous air from fish handling areas and would vented from the waterfront side of the building. A quantitative assessment of the odour impact arising from these on-site activities is detailed in Section 4.6.

4.3.10    The off-site activities which may have the potential to generate odour impact is the transportation of the fish to and from the proposed WFM. During the operation period of the WFM for fish auction, the fish wholesalers will use marine/fish vessels to carry their fish stocks to the WFM. On the other hand, the fish traders will normally use lorries for the transport of the fishes. These offsite activities may contribute to the odour impact on the nearby residents.

4.3.11    Another potential source of odour impact is the refuse collection facilities. A Refuse Collection Point (RCP) and a Marine Refuse Collection Point (MRCP) have been proposed inside the WFM for the collection of general refuse and marine refuse respectively. The operation periods of the RCP and MRCP are 7:00am – 8:00pm and 8:00a.m. – 6:00pm respectively. The operation of these RCPs and the transportation of refuse to and from them may also pose odour impact on the nearby receivers. The concerns over the odour impact due to the off-site activities as well as the operation of the RCP and MRCP are addressed in Section 4.6.

 

Off-site marine traffic emission

4.3.6    During the night time operation hours of the WFM, fishing vessels will travel to and from the proposed WFM via Castle Peak Bay Typhoon Shelter.

4.3.12    Fishing vessels carrying the fish stocks to be sold at the WFM will approach the berthing area of the WFM. The vessels will be berthed at the sea frontage of the WFM while the fishes are unloaded for wholesaling at the WFM. According to the information provided by the AFCD, there are approximately 18 fishing vessels and 4 to 5 sampans landing fish at the WFM during 3:00am to 5:00am.  The 18 fishing vessels will be berthed in two layers along the sea frontage before 3:00am. Vessels in the second layer will be waiting behind for their turn to unload fish.  The vessels will leave the WFM when the trading activities between the fish wholesalers and the traders are completed but may remain alongside if they are not due to return to fishing. Vessels will remain berthed at the WFM or move to the Fishing Vessel mooring area if required to vacate the berth. It is likely that vessels will replenish supplies including ice from the ice plant currently located in Are 27 before proceeding to open water.

4.3.13    The emission from fishing vessels may impose air quality impact on the nearby residents. The major air pollutants indicative of marine traffic emissions are TSP, NO2 and CO. The SO2 emission from the fishing vessels and sampans is considered insignificant and therefore not included in this assessment.  This is in accord with the fact that there is no emission standard for SO2 stipulated in the USEPA Technical Highlights “Emission Standards for Marine Diesel Engines: Scope of Application”.  The potential impact due to the marine traffic emission is quantitatively assessed and addressed in Section 4.6.

 

Off-site vehicular emission

 

4.3.14    During the night time operating hours of the WFM, lorries will access the WFM for the loading of fish bought by fish traders and transport off-site.  The loaded lorries will leave the WFM when the trading activities between the fish wholesalers and the traders are completed.

4.3.15    According to the information provided by the AFCD, up to 40 vehicles will simultaneously access the WFM during its peak operation hours (3:00am to 6:30am).  Thus, an additional traffic flow of 40 lorries will be introduced to the road network in the vicinity of the WFM.

4.3.16    Vehicular emissions from off-site road traffic may have the potential to impose air quality impact on the nearby residents. The air pollutants indicative of vehicular emissions are NO2 and RSP. Although it is anticipated that the vehicular emissions from the additional traffic will not cause significant air quality impact on the nearby residents, a quantitative assessment of the air quality impact due to off-site road traffic was carried out and detailed in Section 4.6.

 

4.4             Determination of Air Sensitive Receivers

4.4.1    All the existing and planned Air Sensitive Receivers (ASRs) within 500m of the project site boundary have been identified in accordance with the criteria set out in the Technical Memorandum on Environmental Impact Assessment Process (TMEIA) and shown in Figure 4.1. These identified ASRs comprise domestic premises, schools and recreational areas located within the study area. The nearest sensitive receivers, A27 (Lawn Bowling Field) and A28 (Tennis Court), are less than 100m away from the subject site. Tuen Mun Wu Hong Clinic is located to the west at about 100m to the site boundary. Two secondary schools, namely Ka Chi Secondary School and South Tuen Mun Government Secondary School, are approximately 300m to the south of the site boundary.

4.4.2    Information on the representative ASRs identified are presented in Table 4.2. Location of the representative ASRs is illustrated in Figure 4.2.

Table 4.2         Representative Air Sensitive Receivers

ASR ID

Description

Sensitive Use

Horizontal separation distance from the proposed WFM (m)

Assessment Point and Elevation

A1

Wu Shan Recreation Playground

Recreational Facilities

270

G/F (6.7mPD)

A2

Siu Shan Court – Kwai King House

Domestic Premises

390

G/F (6.8mPD), 1/F (11.8mPD), 5/F (23.8mPD), 10/F (38.8mPD)

A3

School

Educational Institution

320

G/F (7.1mPD), 1/F (12.1mPD), 5/F (24.1mPD), 10/F (39.1mPD)

A4

Wu Hong Clinic

Clinic

90

G/F (6.8mPD)

A5

School

Educational Institution

340

G/F (7.1mPD), 1/F (12.1mPD), 5/F (24.1mPD), 10/F (39.1mPD)

A6

Po Leung Kok Leung Chau Shun Kam Primary School

Educational Institution

390

G/F (7.3mPD), 1/F (12.3mPD), 5/F (24.3mPD), 10/F (39.3mPD)

A7

Wu King Estate – Wu Tsui House

Domestic Premises

235

G/F (7.7mPD), 1/F (12.7mPD), 5/F (24.7mPD), 10/F (39.7mPD)

A8

Yan Tak Catholic Primary School

Educational Institution

450

G/F (7.9mPD), 1/F (12.9mPD), 5/F (24.9mPD), 10/F (39.9mPD)

A9

Playground

Recreational Facilities

300

G/F (7.7mPD)

A10

Possible Neighbourhood Community Centre

Community Centre

115

G/F (5.8mPD), 1/F (10.8mPD), 5/F (22.8mPD), 10/F (37.8mPD)

A11

Butterfly Estate Tip Yee House

Domestic Premises

420

G/F (8.4mPD), 1/F (13.4mPD), 5/F (25.4mPD), 10/F (40.4mPD)

A12

Police Station

Office

165

G/F (7.1mPD), 1/F (12.1mPD)

A13

Carmel Bunnam Tong Memorial Secondary School

Educational Institution

345

G/F (8.3mPD), 1/F (13.3mPD), 5/F (25.3mPD), 10/F (40.3mPD)

A14

Yuet Wu Villa – Block 15

Domestic Premises

90

G/F (6.8mPD), 1/F (11.8mPD), 5/F (23.8mPD), 10/F (38.8mPD)

A15

Wu King Road Garden

Recreational Facilities

240

G/F (10.9mPD)

A16

Tung Wa Group of Hospitals Sun Hoi Directors College

Educational Institution

340

G/F (8.0mPD), 1/F (13.0mPD), 5/F (25.0mPD), 10/F (40.0mPD)

A17

Yan Chai Hospital Law Chan Chor Si Primary School

Educational Institution

260

G/F (6.7mPD), 1/F (11.7mPD), 5/F (23.7mPD), 10/F (38.7mPD)

A18

Buddhist Wong Sewai Memorial School

Educational Institution

370

G/F (8.1mPD), 1/F (13.1mPD), 5/F (25.1mPD), 10/F (40.1mPD)

 

A19

Yuet Wu Villa – Block 3

Domestic Premises

160

G/F (6.6mPD), 1/F (11.6mPD), 5/F (23.6mPD), 10/F (38.6mPD)

A20

Siu Hei Court

Domestic Premises

250

G/F (6.7mPD), 1/F (11.7mPD), 5/F (23.7mPD), 10/F (38.7mPD)

A21

Wu King Estate  - Wu Boon House

Domestic Premises

425

G/F (8.0mPD), 1/F (13.0mPD), 5/F (25.0mPD), 10/F (40.0mPD)

A22

South Tuen Mun Government Secondary School

Educational Institution

300

G/F (6.6mPD), 1/F (11.6mPD), 5/F (23.6mPD), 10/F (38.6mPD)

A23

Ka Chi Secondary School

Educational Institution

300

G/F (6.6mPD), 1/F (11.6mPD), 5/F (23.6mPD), 10/F (38.6mPD)

A24

Lau Tak Yung Memorial Primary School

Educational Institution

335

G/F (6.7mPD), 1/F (11.7mPD), 5/F (23.7mPD), 10/F (38.7mPD)

A25

Pierhead Garden

Domestic Premises

435

G/F (7.0mPD), 1/F (12.0mPD), 5/F (24.0mPD), 10/F (39.0mPD)

A26

Miami Beach Towers

Domestic Premises

420

G/F (5.8mPD), 1/F (10.8mPD), 5/F (22.8mPD), 10/F (37.8mPD)

A27

Lawn Bowling Field1

Recreational Facilities

<100

G/F (6.3mPD)

A28

Tennis Court1

Recreational Facilities

<100

G/F (6.5mPD)

A29

Community Hall2

Amenities

--

15mPD

A30

Other Possible Community Uses2

Amenities

--

18.5mPD

Notes :

1The recreational facilities are inside the park located at the District Open Space Sites located adjacent to the proposed WFM. The park will be opened to the public 24 hours daily while the opening hours of these facilities will be from 7:00am to 11:00pm daily.

2Co-users of the proposed Joint User Complex and Wholesale Fish Market included for the odour assessment only.

 

4.4.3        For the other proposed facilities within the Joint User Complex and Wholesale Fish Market, namely community hall, marine park management office, spectator stand and other possible community uses, will be closed during the operation periods for fish auctioning of the WFM when odour levels will be at the highest (3:00 am and 6:30 am), they are unlikely to be affected by the air quality impact due to the operation of the WFM. Moreover, central air-conditioning system will generally be provided to the community hall, marine park management office and other possible community uses and these facilities will not rely on opened windows for ventilation. The air intake location for the central air-conditioning system should be suitably designed to ensure the fresh air supply to these facilities will not be affected by the localised air quality impact and odour removal systems (e.g. carbon filters) will be installed at the intakes if considered necessary. Notwithstanding, two representative air sensitive receivers have been identified within the WFM complex, namely the community hall and other possible community uses, and included in the odour assessment to evaluate the potential impact on the co-users and identify appropriate location for fresh air intake of the ventilation system provided to these facilities.

 

4.5       Assessment Methodology

 

(i)         Construction Phase

 

4.5.1    The potential impact of dust emission during the construction phase of the WFM depends on the quantity and drift potential of the dust particles emitted to the atmosphere. On the other hand, the quantity of dust emissions from the construction activities is dependent on the nature of activities and the extent of dust suppression measures applied.

4.5.2    The drift distance of dust particles can be expressed as a function of particle diameter and mean wind speed. For a mean wind speed of 4m/s, dust particles larger than about 100mm are likely to settle within 20 to 30 ft (6 to 9 m) from the point of emission. Particles that are 30 to 100mm in diameter are likely to undergo impeded settling and, depending on the extent of atmospheric turbulence, are likely to settle within a few hundred feet (100 ft = 30m) from the point of emission. Smaller particles have slower gravitational settling velocities and their settling rates are more likely to be retarded by atmospheric turbulence. At greater wind speeds, it is likely to cause more dust generation from dry exposed surfaces. The potential for dust emissions is substantially reduced during rainy periods.

 

4.5.3    In order to evaluate the potential air quality impacts on the neighbouring ASRs during the construction works, the dust emissions, measurable as Total Suspended Particulates (TSP) and Respirable Suspended Particulates (RSP), from various on-site construction activities are assessed under the worst-case scenario. The dust emission from unpaved area, bulk materials handling during excavation and wind erosion are estimated based on the emission factors compiled in the AP-422 and other available data. Detailed calculation of the emission factors adopted in the dust modelling is presented in Appendix 4.1. To enable the worst-case scenario prediction, conservative assumptions have been made in determining the emission rates of dust from the various construction activities based on the estimated emission factors.  Table 4.3 gives the dust emission rates adopted in the modelling and the assumptions made.

Table 4.3         Dust Emission Rates for Various Construction Activities

Construction Activities

Assumptions

Unmitigated Dust Emission Rates

Mitigated      Dust Emission Rates

Materials Handling

(an estimated total of 5000m3 of soil will be excavated)

-          The excavation area will cover the whole site area (8760m2);

-          A typical excavation rate of 367.2m3/day; and

-          The excavation works will last for 14 days (112 hours).

TSP – 1.11x10-6 g/m2/s

RSP – 5.23x10-7 g/m2/s

TSP – 5.53x10-7 g/m2/s

RSP – 2.62x10-7 g/m2/s

Unpaved Road

-          7m wide unpaved haul road along the site boundary;

-          2 trips of vehicle will travel around the site per hour; and

-          Distance travelled on unpaved road per hour is 0.808 km.

TSP – 1.23x10-4 g/m2/s

RSP – 2.51x10-5 g/m2/s

 

TSP – 6.14x10-5 g/m2/s

RSP – 1.26x10-5 g/m2/s

 

Wind Erosion

 

TSP – 2.695x10-6 g/m2/s

RSP – 1.347x10-6 g/m2/s

TSP – 1.35x10-6 g/m2/s

RSP – 6.74x10-7 g/m2/s

 

4.5.4    The assessment is carried out using the dispersion model Industrial Source Complex Short Term (ISCST3). The basis of the model is the linear, steady-state Gaussian plume equation. The ISCST area source model is used to simulate the effects of fugitive emission from sources such as unpaved haul roads, bulk material handling and storage piles.

 

4.5.5    The 1999 meteorological data (full year), as monitored by the Hong Kong Observatory at the Tuen Mun Weather Station, is used as model input parameter. These parameters include wind speed, wind direction, ambient temperature and stability class. Mixing heights are only monitored at the Hong Kong Observatory King's Park Weather Station and the mixing height data recorded for Year 1999 is used as model input.

 

4.5.6        The dust emission impact on the representative ASRs are predicted under the worst-case scenario with all the dust-generating activities concurrently taking place. The worst-case TSP and RSP concentrations are predicted at elevations of the ground floor, 1st floor, 5th floor and 10th floor levels of the representative ASRs. Sample output files of the ISCST3 model are given in Appendix 4.2.

 

(ii)        Operational Phase

Odour from the operation of the WFM

 

4.5.7    The potential odour impact arising from the operation of the proposed WFM upon the sensitive receivers in its vicinity was assessed under the worst-case scenario.

 

4.5.8    As the proposed WFM at Tuen Mun Area 44 is to replace the CPFM in Sam Shing Estate, the odour emission rate for the on-site activities at the proposed WFM is determined with reference to the operation of the CPFM. The odour concentration within the CPFM at Sam Shing Estate during its peak-hour operation was determined by means of odour sampling and testing. The rate of odour emission from the proposed WFM during its peak-hour operation is estimated based on odour testing results with due consideration to the building design of the proposed WFM. Appendix 4.3 details the derivation of odour emission rate. It was conservatively assumed that the proposed WFM will continuously emit odour at the worst-case emission rate during its peak hours of operation.

 

4.5.9    The proposed WFM will be mechanically ventilated. The air quality guidelines in the Environmental Protection Department Practice Note on Control of Air Pollution in Car Parks (ProPECC PN2/96) and the hourly AQOs for CO and NO2 are used as reference standards to determine the ventilation rate of 10 air changes per hour required for the lorry parking spaces inside the WFM (see Appendix 4.4). The major source of odour emission will be the ventilation exhaust discharge. The odour impact arising from the operation of the WFM has been predicted using the EPD accepted Gaussian dispersion computer model, “Industrial Source Complex Short Term Model 3” (ISCST3). Calculation of the emission factors adopted in the prediction model is detailed in Appendix 4.5.

 

4.5.10 The 1999 meteorological data (full year), as monitored by the Hong Kong Observatory at the Tuen Mun Weather Station, is used as model input parameter. These parameters include wind speed, wind direction, ambient temperature and stability class. Mixing heights are only monitored at the Hong Kong Observatory King's Park Weather Station and the mixing height data recorded for Year 1999 is used as model input. Sample output files of the ISCST3 model are given in Appendix 4.6.

 

4.5.11  The results of the ISCST3 dispersion model are the maximum odour units predicted at the ASRs based on an averaging time of 1 hour. For the assessment of odour impact on the ASRs, a shorter time-averaging period of 5 seconds is required due to the shorter exposure period tolerable by the receivers. The modelled hourly-average results are converted to 5-second average values to enable direct comparison against the odour assessment criterion. Appendix 4.7 details the conversion of ISCST3 dispersion model outputs to 5-second average concentration.

 

4.5.12    The worst-case concentrations of odour are predicted at elevations of the ground floor, 1st floor, 5th floor and 10th floor levels of the representative ASRs identified. It should be noted that the operation period for fish auctioning of the proposed WFM is 3:00am and 6:30am according to the information provided by the AFCD. Some of the representative ASRs, namely the educational institutions, district open space and clinic, would normally be closed during these hours and therefore, are not potentially affected by odour emission during the operation of the WFM.  The predicted odour levels at these ASRs are included for reference only.

 

Off-site marine traffic emission

 

4.5.13  The potential air quality impact due to off-site marine traffic emission upon the sensitive receivers in the vicinity of the proposed WFM was assessed under the worst-case scenario. The concentrations of air pollutants indicative of marine traffic emission, including TSP, NO2, and CO, were predicted at the representative ASRs to evaluate the potential air quality impact.

 

4.5.14  The marine traffic emission varies for different types of vessel and different modes of operation. The vessels involved in the off-site marine traffic relating to the operation of the proposed WFM will be mainly non-ocean going fishing vessels. The primary operating modes of the marine vessels would be slow cruise and manoeuvring within the typhoon shelter and hoteling (docking) at the sea frontage of the proposed WFM. According to a technical report on Commercial Marine Vessels Emissions published by the United States Environmental Protection Agency3, there is negligible emission from the non-ocean going vessels while they are in the hoteling mode. On the other hand, with a higher engine output associated with slow cruise mode, the emission from fishing vessels in slow cruise mode will be higher than that in manoeuvring mode. 

 

4.5.15    According to the information provided by AFCD, there will be approximately 18 fishing vessels and 4 to 5 sampans landing fish at the WFM during 3:00am to 5:00am. Moreover, there will be about 9 fishing vessels berthed at the sea frontage of the WFM and the remaining waiting within the typhoon shelter at any one time. It is considered that 9 fishing vessels and 2 sampans travelling in slow cruise mode within the typhoon shelter at the same time would represent the worst-case scenario of marine traffic emission.

 

4.5.16    Off-site marine traffic emission impact was predicted based on the assumed routes as shown in Figure 4.3. According to on-site observations, majority of the fishing vessels is using the eastern entrance of the typhoon shelter when approaching and leaving the existing temporary WFM at Sam Shing Estate. Therefore, Route 1 is considered to be a likely path the fishing vessels would take when travelling to and from the proposed WFM. On the other hand, in view of the fact that vessels calling at the proposed WFM from seaward may use a more direct route via the Western Fairway, Route 2 is included in the assessment to represent the worst-case scenario.

 

4.5.17  In determining the pollutant emission rates from the off-site marine traffic, reference was made to the emission standards for marine diesel engines4 published by the United States Environmental Protection Agency. The emission rates of the air pollutants depend on the horsepower of the vessels’ engines and the fractional load (the actual engine output divided by rated engine output).  Based on the engine data information of the fishing vessels provided by the Marine Department, the average horsepower of the fishing vessels and sampans was estimated to be 814hp and 203hp respectively.  The estimated emission rates of the air pollutants for fishing vessels and sampans are shown in Table 4.4.  Detailed calculation of the emission factors adopted in the dust modelling is presented in Appendix 4.8.

Table 4.4         Emission Rates of Marine Traffic

Pollutants

Types of vessels

Horsepower, hp

Fractional Load

Emission Rates, g/s

TSP

Fishing Vessel

814

0.4

0.0270

Sampan

203

0.4

0.0067

NO2

Fishing Vessel

814

0.4

0.1012

Sampan

203

0.4

0.0252

CO

Fishing Vessel

814

0.4

0.3372

Sampan

203

0.4

0.0841

 

4.5.18  The air quality prediction is carried out utilising the EPD accepted Gaussian dispersion computer model, “Industrial Source Complex Short Term Model 3” (ISCST3). The marine traffic emission for the primary operating modes of slow cruise and manoeuvring are modelled as line source, which was represented by separated volume sources in the ISCST3 model.

 

4.5.19  The 1999 meteorological data (full year), as monitored by the Hong Kong Observatory at the Tuen Mun Weather Station, is used as the model input parameter. These parameters include wind speed, wind direction, ambient temperature and stability class. Mixing heights are only monitored at the Hong Kong Observatory King's Park Weather Station and the mixing height data recorded for Year 1999 is used as model input. Sample output files of the ISCST3 model are given in Appendix 4.9.

 

4.5.20  The worst-case concentrations of TSP, NO2, and CO are predicted at elevations of the ground floor, 1st floor, 5th floor and 10th floor levels of the representative ASRs identified. It should be noted that the operation period of the proposed WFM for fish auction activities is from 3:00am to 6:30am according to the information provided by the AFCD. Some of the representative ASRs, namely the educational institutions and clinic, would normally be closed during these hours and therefore, are not potentially affected by marine traffic emission during the operation of the WFM. The predicted air quality levels at these ASRs are included for reference only.

 

Off-site vehicular emission

4.5.21  The potential air quality impact due to off-site vehicular emission on the sensitive receivers in the vicinity of the proposed WFM is assessed by modelling the concentrations of nitrogen dioxide (NO2) and respirable suspended particulates (RSP), which are indicative of the vehicular emissions, at the representative ASRs. Vehicular emission from roads located within 500m from the site boundary of the proposed WFM, namely Wu Shan Road, Hoi Wong Road, Wu Chui Road and Wu King Road, is included in the assessment. The vehicular emission rates are estimated based on the traffic flow data of the roads of concern.

 

4.5.22  According to the information provided by the AFCD, a maximum number of 40 lorries will access the proposed WFM during its night time operation period (3:00am to 6:30am). In the assessment, the following two scenarios are assessed:

-        vehicular emissions due to the existing traffic conditions; and

-        vehicular emissions due to the introduction of the 40 lorries approaching/leaving the proposed WFM.

 

4.5.23  In addition, the cumulative impacts due to the addition of 40 lorries to the traffic flow are evaluated by combining the results of the two scenarios. The published data of the Annual Average Daily Traffic5 (AADT) is adopted to represent the existing traffic conditions on the roads included in the assessment. With reference to the daily traffic flow statistic of the Tuen Mun and Yuen Long area, the night time traffic flow data is found to be 3.4% of the AADT. The composition of vehicles during night time is also taken from the daily flow statistic of the Tuen Mun and Yuen Long area. Table 4.5 gives the traffic flow data adopted in the assessment of the vehicular emissions due to the existing traffic conditions.

Table 4.5         Traffic Flow Data - Existing Traffic Conditions

Road

Section

AADT

Traffic Flow at Night Time

(veh/hr)

Wu Shan Road

Lung Mun Road to Wu King Road

9370

318

Wu Shan Road

Wu King Road to Wu Chui Road

9580

326

Wu Chui Road

Lung Mun Road to Wu Shan Road

9030

307

Hoi Wong Road

Hoi Chu Road to Wu Shan Road

24580

836

Wu King Road

Wu Shan Road to Wu Chui Road

9253*

314

*As there is no traffic flow data record for Wu King Road, the average traffic flow of Wu Shan Road and Wu Chui Road was adopted.

 

4.5.24  For assessing the potential air quality impact due to the increase of traffic flow during the operation of the WFM, it is assumed that the additional 40 lorries will be introduced to each of the roads included in the assessment to represent the worst-case scenario.

 

4.5.25    Vehicular emission rates of NO2 and RSP were derived from the traffic flow data using the Fleet Average Emission Factors for Year 1999 based on EURO III criteria provided by the EPD. Calculation of the vehicular emission rates adopted in the assessment is presented in Appendix 4.10.

 

4.5.26  The air quality prediction was performed using the California Line Source Dispersion Model (CALINE4), a Gaussian dispersion model accepted by the EPD. In order to evaluate the worst-case short-term air quality impact, the following meteorological conditions were adopted in the model :

-        Daytime : neutral atmospheric condition (class D); wind speed 1m/s (at 10m height); worst-case wind angle; mixing height 500m

-        Night time : stable atmospheric condition (class F); wind speed 1m/s (at 10m height); worst-case wind angle; mixing height 500m

 

4.5.27  The results of the CALINE4 dispersion model are the maximum hourly NO2 and RSP concentrations predicted at the ASRs. As the Air Quality Objectives for RSP have a longer time-averaging period of 24 hours, a daily RSP level is estimated to enable direct comparison against the RSP assessment criterion. To calculate the 24-hour RSP level, the day is divided into daytime and night time periods, representing two-thirds and one-third of a day, respectively. Given the above assumptions, both periods are modelled separately and a time-weighted 24-hour RSP level is then calculated by adding two-thirds of the daytime result and one-third of the night-time result. Sample output files of the CALINE4 model are given in Appendix 4.11.

 

4.5.28  The worst-case concentrations of NO2 and RSP are predicted at representative ASRs identified. It should be noted that the peak hours for fish auction and wholesale activities at the proposed WFM are from 3:00 am to 6:30 am according to the information provided by the AFCD. Some of the representative ASRs, namely the educational institutions and clinic, would normally be closed during these hours and therefore, are not potentially affected by road traffic emission during the operation of the WFM. The predicted air quality levels at these ASRs are included for reference only.

 

4.6       Prediction and Evaluation of Environmental Impacts

 

(i)         Construction Phase

 

4.6.1    The dust emission impact on the representative ASRs is predicted under the worst-case scenario with all the dust-generating activities concurrently taking place.

Isopleths of the maximum 1-hour and 24-hour average TSP concentration in the vicinity of the subject site at elevations of 6.5mPD, 11.5mPD, 23.5mPD and 38.5mPD are shown in Figures 4.4a-h. The maximum predicted suspended particulate concentrations at the representative ASRs due to dust emissions from unpaved area, loading/unloading and wind erosion are presented in Tables 4.6a & 4.6b. Background levels of 102mg/m3 for TSP and 62mg/m3 for RSP are incorporated into the modelled results. It should be noted that these results represent the worst-case TSP and RSP concentrations predicted to occur in a year and the concentrations at other times will be less than these values.

Table 4.6a       Maximum 1-hour and 24-hour Average TSP Concentrations – Without Mitigation

ASR ID

1- hour Average TSP Conc., mg/m3 

24-hour Average TSP Conc., mg/m3 

G/F

1/F

5/F

10/F

G/F

1/F

5/F

10/F

A1

212.0

-

-

-

118.1

-

-

-

A2

168.1

166.3

154.3

132.8

109.3

109.1

107.8

105.4

A3

181.7

178.8

160.1

130.3

111.2

110.9

108.9

105.6

A4

347.9

-

-

-

146.8

-

-

-

A5

173.5

171.0

155.1

129.1

111.0

110.7

108.8

105.6

A6

163.4

161.8

150.7

130.6

108.7

108.5

107.3

105.1

A7

195.2

189.3

156.0

131.2

112.7

112.0

108.5

104.6

A8

155.0

153.8

145.5

129.7

106.5

106.4

105.7

104.4

A9

179.1

-

-

-

109.2

-

-

-

A10

294.5

254.7

156.3

129.8

183.9

172.1

132.2

114.6

A11

158.3

156.9

147.2

129.3

106.1

106.0

105.3

104.1

A12

234.7

219.4

-

-

147.9

143.4

-

-

A13

170.4

168.0

152.2

126.8

108.2

108.0

106.6

104.4

A14

349.9

277.9

163.5

131.5

221.6

197.0

138.4

115.9

A15

193.0

-

-

-

118.6

-

-

-

A16

170.5

168.0

151.8

126.2

108.5

108.3

107.1

105.2

A17

187.7

183.1

156.1

129.2

130.4

129.1

121.2

111.9

A18

163.0

161.0

148.2

126.7

109.7

109.5

108.2

106.0

A19

272.8

258.1

183.9

142.6

179.6

173.5

142.2

120.8

A20

192.4

188.0

161.0

131.4

143.5

141.7

130.8

117.7

A21

158.0

156.6

147.1

129.4

109.0

108.9

107.9

106.0

A22

197.0

193.7

172.3

137.7

132.3

131.3

124.7

114.2

A23

199.1

195.6

173.5

138.0

124.7

123.9

118.8

110.9

A24

183.6

181.1

164.9

137.0

131.4

130.5

125.0

115.4

A25

152.6

151.5

144.0

129.5

125.0

124.6

121.3

115.0

A26

165.9

164.5

154.7

135.8

123.5

123.0

119.9

114.0

A27

485.3

-

-

-

360.4

-

-

-

A28

483.1

-

-

-

329.1

-

-

-

Remarks:

Results include annual TSP background level of 102mg/m3.

TSP – recommended 1-hour criterion (500mg/m3) and 24 hours AQO (260mg/m3)

 “ – “ represents no ASRs at the particular elevation

 

Table 4.6b       Maximum 24-hour Average RSP Concentrations  - Without Mitigation

ASR ID

24-hour Average RSP Conc., mg/m3 

G/F

1/F

5/F

10/F

A1

65.7

-

-

-

A2

63.7

63.7

63.4

62.8

A3

64.1

64.0

63.6

62.8

A4

72.2

-

-

-

A5

64.1

64.0

63.6

62.8

A6

63.5

63.5

63.2

62.7

A7

64.5

64.3

63.5

62.6

A8

63.1

63.0

62.9

62.6

A9

63.7

-

-

-

A10

81.0

78.2

69.0

64.9

A11

63.0

62.9

62.8

62.5

A12

72.4

71.4

-

-

A13

63.5

63.4

63.1

62.6

A14

90.1

84.3

70.6

65.3

A15

65.8

-

-

-

A16

63.5

63.4

63.2

62.7

A17

68.5

68.2

66.4

64.3

A18

63.8

63.7

63.4

62.9

A19

79.9

78.5

71.3

66.3

A20

71.7

71.3

68.7

65.7

A21

63.6

63.6

63.4

62.9

A22

69.0

68.8

67.2

64.8

A23

67.2

67.0

65.9

64.0

A24

68.8

68.6

67.3

65.1

A25

67.3

67.2

66.5

65.0

A26

67.0

66.9

66.1

64.8

A27

121.5

-

-

-

A28

113.6

-

-

-

Remarks:

Results include annual RSP background level of 62mg/m3.

RSP - 24 hours AQO (180mg/m3)

“ – “ represents no ASRs at the particular elevation

 

4.6.2    The assessment results indicate that the AQO for daily TSP will be exceeded at A27(Lawn Bowling Field) and A28(Tennis Court) while the recommended hourly TSP level and the AQO for daily RSP will not be exceeded at any of the representative ASRs under the worst-case scenario. The highest 1-hour TSP and daily RSP concentrations of 485.3µg/m3 and 121.5µg/m3 respectively are predicted at A27 (Lawn Bowling Field). The highest predicted 1-hour TSP and 24-hour RSP concentration represent 97% and 68% of the criteria for TSP and RSP respectively. On the other hand, the highest predicted 24-hour TSP concentration of 360.4 µg/m3 was predicted at A27 (Lawn Bowling Field) which exceeds the AQO for daily TSP. Thus, effective control measures will be required.

 

(ii)        Operational Phase

 

Odour from the operation of the WFM

 

4.6.3    The odour concentrations due to the operation of the WFM during its peak hours for auction and wholesale activities (from 3:00am to 6:30am) are predicted at representative Air Sensitive Receivers (ASRs) under the worst-case scenario. Isopleths of the maximum 5-second average odour concentrations in the vicinity of the subject site at elevations of 6.5mPD, 11.5mPD, 23.5mPD and 38.5mPD are illustrated in Figures 4.5a-d. The odour concentrations are predicted for ground floor level, 1st floor level, 5th floor level and 10th floor level. The maximum predicted 5-second average odour concentrations at the representative ASRs are presented at Table 4.7. It should be noted that these results represent the highest 5-second concentrations predicted to occur in a year and the concentrations at other times could be far less than these values.

Table 4.7         Maximum 5-second Average Odour Concentrations – With Enclosed WFM Design

ASR ID

Maximum 5-second Average Concentration (OU/m3)

With Mechanical Ventilation

G/F

1/F

5/F

10/F

A1

1.9

-

-

-

A2

1.3

1.2

1.0

0.7

A3

1.7

1.7

1.4

0.8

A4

4.8

-

-

-

A5

1.6

1.6

1.3

0.8

A6

1.1

1.1

0.9

0.6

A7

2.0

1.9

1.4

0.6

A8

1.2

1.2

1.0

0.7

A9

0.9

-

-

-

A10

4.1

3.8

2.0

0.9

A11

1.0

1.0

0.9

0.6

A12

3.4

3.2

-

-

A13

0.3

0.3

0.3

0.2

A14

4.9

4.4

2.2

1.0

A15

2.3

-

-

-

A16

0.8

0.8

0.7

0.4

A17

1.9

1.8

1.4

0.7

A18

1.4

1.3

1.1

0.7

A19

2.8

2.7

1.9

0.8

A20

2.1

2.0

1.6

0.8

A21

1.3

1.2

1.1

0.7

A22

1.5

1.5

1.2

0.7

A23

1.8

1.7

1.4

0.8

A24

1.3

1.2

1.0

0.7

A25

0.9

0.9

0.8

0.5

A26

1.2

1.2

1.0

0.7

A27

6.2

-

-

-

A28

6.1

-

-

-

A291

4.9 (15mPD)

-

-

-

A301

4.9 (18.5mPD)

-

-

-

Notes :

1Co-users of the proposed Joint User Complex and Wholesale Fish Market ;  fresh air intake points shall be located at levels above 15mPD and 18.5mPD for these co-users.

 

“ – “ represents no ASRs at the particular elevation

 

4.6.4        The predicted maximum 5-second average concentrations meet the stipulated assessment criterion of (less than) 5 odour units at the majority of the representative ASRs in the vicinity of the proposed WFM except for two. At most of the ASRs, the concentrations are well below the 5 odour units criterion. At A27 (Lawn Bowling Field) and A28 (Tennis Court), the worst-case odour concentration predicted at the ground floor was slightly above the odour criterion. As the opening hours of the Lawn Bowling Field and Tennis Court will be limited to 7:00am to 11:00pm daily, it is anticipated that these ASRs are unlikely to be adversely affected by the odour impact from the operation of WFM which peaks at 03:00 to 06:30.

 

4.6.5        As discussed in Section 4.3, the odour levels arising from the WFM operation will be at its highest during the night time auction period. Activities that have the potential to generate odour would cease after the auction period, thus insignificant odour impact on the nearby sensitive receivers, including A27 (Lawn Bowling Field) and A28 (Tennis Court), due to daytime operation of the WFM is anticipated. During the daytime, operation of the WFM involves handling of live seafood and preboxed fish which are not likely to generate odour levels experienced during the night time auction operations. Even if the odour emission during daytime is conservatively assumed to be 50% of its peak level during the night time auction period, it is unlikely to result in unacceptable odour impact on nearby sensitive receivers that open only during the day, including co-users of the WFM complex and Wu Hong Clinic, as indicated by the odour prediction results.

 

4.6.6        For the co-users of the WFM complex, namely community hall (A29) and Other Possible Community Uses (A30), further odour modelling was conducted to identify location for fresh air intake of the ventilation system that will not be subject to unacceptable odour levels due to the operation of the WFM. Modelling results indicate that at levels above 15mPD for the community hall (A29) and above 18.5mPD for the Other Possible Community Uses (A30), the maximum odour concentrations predicted under the worst-case scenario are below the 5 odour units criterion.

 

4.6.7        Apart from the daily operational activities of the proposed WFM, the RCP, marine RCP and public toilets within the complex represent another potential source of odour impact. In order to minimise the odour impact from these facilities, separate mechanical ventilation and odour treatment system will be provided for the RCP and marine RCP. Odour treatment will be provided to all exhaust air from the RCPs through water scrubber and deodorisers before discharge to outdoors and appropriate deodourisation system will be installed for the public toilets. With the incorporation of the deodourisation system, it is anticipated the odour emission from the RCPs and public toilets will be insignificant.

 

4.6.8        Since most activities related to the daily operation of the WFM will be taken place inside the WFM complex, off-site activities which have the potential to generate odour impact, notably the lorry parking which for the existing CPFM takes place on the road outside the market, will be eliminated. Nevertheless, measures should be taken to further minimize the potential odour impact during the transportation of fish or other odorous materials, including the use of properly covered containers. It is anticipated that the odour emission from lorries during the transportation of fish will be insignificant due to the short duration of travelling.

 

Off-site marine traffic emission

 

4.6.9        The off-site marine traffic emission impact on the representative ASRs is predicted under the worst-case scenario as mentioned in Section 4.5.13. Isopleths of the maximum 24-hour TSP, hourly NO2 and hourly CO concentrations in the vicinity of the subject site at elevations of 6.5mPD, 11.5mPD, 23.5mPD and 38.5mPD are shown in Figures 4.6a-l and 4.7a-l. The maximum predicted TSP, NO2 and CO concentrations at the representative ASRs due to Route 1 and Route 2 off-site marine traffic emissions are presented in Tables 4.8a-c and 4.9a-c respectively.  Background levels of 102mg/m3 for TSP, 60mg/m3 for NO2 and 1177mg/m3 for CO are incorporated to the modelled results.  It should be noted that these results represent the worst-case TSP, NO2 and CO concentrations predicted to occur in a year and the concentrations during other hours will be less than these values.

            Table 4.8a       Maximum 24-hour Average TSP Concentrations – Off-site Marine Traffic Emission (Route 1)

ASR ID

24-hour Average TSP Conc., mg/m3 

G/F

1/F

5/F

10/F

A1

104.1

-

-

-

A2

103.6

103.6

103.5

103.2

A3

103.9

103.9

103.7

103.3

A4

105.9

-

-

-

A5

103.8

103.7

103.6

103.2

A6

103.5

103.4

103.3

103.1

A7

103.9

103.9

103.6

103.1

A8

103.2

103.2

103.1

102.9

A9

103.4

-

-

-

A10

105.5

105.2

104.1

103.2

A11

103.2

103.2

103.1

102.9

A12

104.3

104.2

-

-

A13

103.2

103.1

103.0

102.8

A14

107.7

107.4

105.5

103.7

A15

103.7

-

-

-

A16

103.2

103.2

103.1

102.8

A17

103.8

103.7

103.4

103.0

A18

103.2

103.2

103.0

102.8

A19

108.0

107.8

106.4

104.3

A20

105.1

105.0

104.5

103.5

A21

103.0

103.0

102.9

102.8

A22

106.1

106.0

105.4

104.2

A23

107.0

106.9

106.0

104.5

A24

105.7

105.6

105.2

104.2

A25

104.6

104.6

104.3

103.7

A26

105.2

105.1

104.8

104.1

A27

110.6

-

-

-

A28

107.1

-

-

-

Remarks: Results include annual TSP background level of 102mg/m3.

TSP - 24 hours AQO (260mg/m3)

“ – “ represents no ASRs at the particular elevation

 

              Table 4.8b     Maximum 1-hour and 24-hour Average NO2 Concentrations – Off-site Marine Traffic Emission (Route 1)

ASR ID

1- hour Average NO2 Conc., mg/m3 

24-hour Average NO2 Conc., mg/m3 

G/F

1/F

5/F

10/F

G/F

1/F

5/F

10/F

A1

125.4

-

-

-

68.0

-

-

-

A2

107.4

106.8

102.6

93.6

66.1

66.0

65.5

64.3

A3

114.7

113.9

108.1

96.2

67.2

67.1

66.3

64.7

A4

151.9

-

-

-

74.6

-

-

-

A5

108.4

107.6

102.3

91.4

66.6

66.5

65.8

64.5

A6

103.9

103.3

99.3

90.6

65.5

65.4

64.9

63.9

A7

112.8

111.5

102.8

89.9

67.1

67.0

66.0

64.3

A8

94.2

93.8

91.2

85.5

64.5

64.4

64.1

63.3

A9

106.5

-

-

-

65.4

-

-

-

A10

123.1

120.0

103.8

84.8

73.0

72.1

67.9

64.5

A11

97.6

97.1

93.5

85.8

64.5

64.4

64.1

63.3

A12

113.8

111.9

-

-

68.5

68.2

-

-

A13

100.2

99.6

95.3

86.3

64.4

64.3

63.9

63.1

A14

117.9

114.6

98.8

82.6

81.4

80.1

72.9

66.4

A15

103.3

-

-

-

66.2

-

-

-

A16

97.3

96.7

92.1

82.8

64.6

64.5

64.0

63.0

A17

96.8

95.9

90.1

81.1

66.6

66.5

65.2

63.6

A18

92.9

92.4

89.0

81.8

64.4

64.3

63.9

63.0

A19

98.3

96.7

86.7

77.4

82.6

81.7

76.3

68.8

A20

93.4

92.5

86.9

78.4

71.7

71.3

69.3

65.7

A21

88.2

87.8

84.8

79.5

63.9

63.8

63.5

62.8

A22

87.6

86.8

82.0

74.8

75.5

75.1

72.6

68.3

A23

89.2

88.4

82.8

75.1

78.7

78.2

75.0

69.2

A24

85.6

85.1

81.2

74.5

73.9

73.7

71.8

68.2

A25

82.2

81.9

79.6

74.6

69.7

69.6

68.6

66.5

A26

81.7

81.4

78.7

73.9

71.9

71.7

70.5

67.8

A27

119.9

-

-

-

92.2

-

-

-

A28

162.3

-

-

-

79.1

-

-

-

Remarks:

Results include annual NO2 background level of 60mg/m3.

NO2 - hourly AQO (300mg/m3) and 24 hours AQO (150mg/m3)

“ – “ represents no ASRs at the particular elevation

 

Table 4.8c       Maximum 1-hour and 8-hour Average CO Concentrations – Off-site Marine Traffic Emission (Route 1)

ASR ID

1-hour Average CO Conc., mg/m3 

8-hour Average CO Conc., mg/m3 

G/F

1/F

5/F

10/F

G/F

1/F

5/F

10/F

A1

1394.9

-

-

-

1252.7

-

-

-

A2

1334.9

1332.9

1318.9

1289.1

1237.8

1237.0

1231.4

1219.5

A3

1359.4

1356.6

1337.2

1297.5

1248.4

1247.3

1239.3

1223.3

A4

1483.3