3 Construction Air Quality impact

3.2 Environmental Legislation, Policies, Plans, Standards and Criteria

3.2.1 The criteria for evaluating air quality impacts and the guidelines for air quality assessment are laid out in Annex 4 and Annex 12 of the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM) respectively.

3.2.2 The Air Pollution Control Ordinance (APCO) provides the statutory control on air pollutants from a variety of sources. The Hong Kong Air Quality Objectives (AQOs) should be satisfied in the Hong Kong Special Administrative Region (HKSAR). The AQOs stipulate the maximum allowable concentrations for typical pollutants. The relevant AQOs are listed in Table 3.1.

Table 3.1 Hong Kong Air Quality Objectives

	Maximum Concentration (µg m^-3) ⁽¹⁾
Pollutant	Averaging Time
	1 hour ⁽²⁾	8 hour ⁽³⁾	24 hour ⁽³⁾	Annual ⁽⁴⁾
Total Suspended Particulates (TSP)	^-	-	260	80
Respirable Suspended Particulates (RSP) ⁽⁵⁾	-	-	180	55
Sulphur Dioxide (SO₂₎	800	-	350	80
Nitrogen Dioxide (NO₂₎	300	-	150	80
Carbon Monoxide (CO)	30,000	10,000	-	-

(1) Measured at 298 K and 101.325 kPa.

(2) Not to be exceeded more than three times per year.

(3) Not to be exceeded more than once per year.

(4) Arithmetic mean.

(5) Suspended particulates in air with a nominal aerodynamic diameter of 10 mm or smaller.

3.2.3 The Annex 4 of the EIAO-TM stipulates that the hourly TSP level should not exceed 500 mgm^-3 (measured at 25^oC and one atmospheric pressure) for construction dust impact assessment. Mitigation measures for construction sites are specified in the Air Pollution Control (Construction Dust) Regulations. The EPD should be notified prior to the commencement of notifiable construction works.

3.2.4 The EIAO-TM also stipulates that the odour level at a sensitive receiver should not exceed 5 odour units based on an averaging time of 5 seconds for odour prediction assessment.

3.3 Description of the Environment

3.3.1 Sai Kung is a rural area of Hong Kong and air quality of the area is generally good. Vehicle exhaust emissions from Hiram’s Highway are the major pollutant sources of the area. Major industrial emissions are not identified within the Study Area.

3.3.2 The EPD’s Guideline on Assessing the ‘TOTAL’ Air Quality Impacts recommends that Sai Kung shall be classified as a rural/new development area. Background air quality of rural/ new development in Hong Kong has been estimated by EPD based on the annual average recorded at rural/new developments in Hong Kong. Table 3.2 shows the background air quality of rural/new development areas in Hong Kong.

Table 3.2 Background Air Quality (Rural/ New development Areas)

Pollutant	Annual Average Concentration (mg/m³) ⁽¹⁾
NO₂	39
SO₂	13
O₃	57
TSP	87

(1) Ref: Guidelines on assessing the ‘TOTAL’ Air Quality Impacts, EPD.

3.4 Air Sensitive Receivers

3.4.1 A total of twenty-two representative Air Sensitive Receivers (ASRs) have been identified for this assessment in accordance with the criteria set out in the EIAO-TM. Description of the representative ASRs and their horizontal distance from the Project are listed in Table 3.3. Locations of the representative ASRs are shown in Figures 3.1 – 3.3.

Table 3.3 Representative Air Sensitive Receivers

ASR	Description	Horizontal Separation from Site Boundary (m)
Sai Kung River
SK1	No 68, Sha Kok Mei	60
SK2	No 19, Village house adjacent to Hang Cho Shui	20
SK3	No 23, Muk Min Shan	40
SK4	No 21, Muk Min Shan	7
SK5	No 13, Muk Min Shan	20
SK6	No 1, Muk Min Shan	7
SK7	Mr & Mrs Jimmy Shaw	15
SK8	No 1, Burlingame Garden	30
Pak Kong River
PK1	Village House along Hiram’s Highway	15⁽¹⁾ /100⁽²⁾
PK2	No. 3, Village House along Hiram’s Highway	108⁽¹⁾ /4⁽²⁾
PK3	No. 14, Village House, Tai Chung Hau	106⁽¹⁾ /2⁽²⁾
PK4	No. 42, Village House, Tai Chung Hau	15⁽¹⁾ /110⁽²⁾
Ho Chung Channel
HC1	No 30, Ho Chung	12
HC2	No 27, Ho Chung First Lane	17
HC3	No 5B, Ho Chung	25
HC4	No 107, Ho Chung New Village	2
HC5	No 116, Ho Chung New Village	30
HC6	Rural Committee	8
HC7	Berkeley Bay Village House 18	30
HCT1	Che Kung Temple	15
HCSC1	Sai Kung Central Primary School	80
HCTV1	Asia Television Ltd	20

(1) The distance between the ASR and the site boundary of the BC1.

(2) The distance between the ASR and the site boundary of the BC2.

3.5 Identification of Environmental Impacts

Construction Phase

3.5.1 The Project includes drainage improvement of three river channels in Sai Kung. Major items of works are:

· Sai Kung River & Sha Ha Diversion Culvert: Construction of approximately 150m of channel using gabion lining with planting pit in Sai Kung River, approximately 280m of three cells 3.0mx 3.0m box culvert between Sai Kung River to Sha Ha and approximately 270m of access road.

· Pak Kong River: Removal of existing bottleneck by widening of approximately 100 m of channel. Construction of retaining wall along the channel and re-construction of one footbridge and one vehicular crossing.

· Ho Chung Channel: Construction of approximately 350 rectangular channel and 350m of channel using gabion walls with planting pits in Ho Chung River, construction of approximately 80m of access road and reconstruction of junction and weir arrangement adjacent to WSD’s Ho Chung Lowland Pumping Station.

3.5.2 The likely construction activities associated with the drainage improvement works are excavation and handling of excavated materials. The construction period for the Project is scheduled between December 2005 and April 2008 for duration of about 29 months.

3.5.3 Fugitive emissions would be generated through handling of spoils, excavation and movement of trucks over unpaved haul roads and work sites. The engineering estimates reveal that the volume of excavated spoils generated is expected to be about 20 m³ per hour from each work site. The excavated materials will be transported offsite by trucks, and number of trips generated per each site would be limited and is expected to be less than 8 trips per hour.

3.5.4 Odour may also be released when dredged and excavated mud or organic materials are lifted from the rivers.

Operation Phase

3.5.5 Potential air quality impacts such as dust and odour would not be expected from the operation of the proposed drainage works.

3.6 Assessment Methodology & Criteria

3.6.1 The major air quality impacts from construction activities are the dust emissions. Excavation, material handling and truck haulage are the major sources of dust emission for drainage improvement works. Emission factors for dusty activities were estimated based on USEPA Compilation of Air Pollution Emission Factors (AP42), 5^th Edition, and are presented in Table 3.4. Detailed calculations of emission factors are shown in Appendix 3.1.

Table 3.4 Emission Factors for Dusty Construction Activities

Activity	Emission Rate	Remarks
Materials handling	E = 4.09 x 10^-4 g/s	· Moisture content: 20% · Handling capacity: 20m³/hr · 50% reduction by watering the site area twice a day · AP42, Section 13.2.4
Excavation	E = 9.33 x 10^-4 g/s	· Capacity 20 m³/hr · AP42, Section 11.19.2
Truck haulage	E = 4.59 x 10^-4 g/s/m	· Moisture content: 20% · Silt content: 8.5% · Vehicle weight: 26 tonnes · Speed: 10 kph · Flow: 8 veh per hour · 50% reduction by watering the site area twice a day · AP42: Section 13.2.2

3.6.2 TSP concentrations at the ASRs were predicted using the model Fugitive Dust Model (FDM) recommended by EPD. Particle size distributions were determined based on AP42. The Air Pollution Control (Construction Dust) Regulation requires that dust suppression measures including watering should be applied for construction sites. According to AP42, watering the working area twice a day can reduce dust emissions by about 50 percent.

3.6.3 The USEPA’s screening data have been used for the model run. The meteorological conditions for screening procedures are listed in Table 3.5 below. The construction work shall be conducted during daytime only and daytime meteorological conditions are therefore assumed in the screening data.

Table 3.5 Meteorological Conditions for Model Run

Parameter	Meteorological Conditions
Stability and wind speed	A: 1,3 ms^-1 B: 1,3,5 ms^-1 C: 1,3,5, 8 ms^-1 D: 1,3,5,8,10 ms^-1
Mixing height	500 m
Temperature:	298 K

3.6.4 Hourly average and daily average TSP concentrations at various separation distances from a construction site with all the dusty activities (excavation, materials handling and truck haulage) conducted together have been predicted for this assessment. It is assumed that the length of haul road is 200m in the model. The daily average TSP concentrations is assumed to be 40% of the respectively hourly average, in accordance with the EPA’ Screening Procedures for Estimating the Air Quality Impact of Stationary Sources. The calculation of Daily TSP is present in Appendix 3.2.

3.7 Prediction and Evaluation of Impacts

3.7.1 Construction dust impacts were modelled using the FDM model. The hourly and daily TSP concentrations at different separations from a typical excavation, material handling and truck haulage have been predicted with the worst assessment height 1.5m above ground and are shown in Appendix 3.2. Predicted TSP concentrations at the ASRs are shown in Table 3.6. Dust mitigation measures, watering the work site twice a day, have been included in the prediction.

Table 3.6 Predicted TSP Concentration at Representative ASRs

ASR	Description	Hourly TSP Concentration (mg/m³) ^{(1) (2)(3)}	Daily TSP Concentration (mg/m³) ^{(1) (2)(3)}
Sai Kung River
SK1	No 68, Sha Kok Mei	142	109
SK2	No 19, Village house adjacent to Hang Cho Shui	237	147
SK3	No 23, Muk Min Shan	167	119
SK4	No 21, Muk Min Shan	402	213
SK5	No 13, Muk Min Shan	237	147
SK6	No 1, Muk Min Shan	402	213
SK7	Mr. & Mrs. Jimmy Shaw	282	165
SK8	No 1, Burlingame Garden	190	128
Pak Kong River⁽⁴⁾
PK1	Village House along Hiram’s Highway	218⁽⁵⁾ / 121⁽⁶⁾	165⁽⁵⁾ /101⁽⁶⁾
PK2	No. 3, Village House along Hiram’s Highway	119⁽⁵⁾ / 433⁽⁶⁾	100⁽⁵⁾ / 225 ⁽⁶⁾
PK3	No. 14, Village House, Tai Chung Hau	119⁽⁵⁾ / 524⁽⁶⁾	100⁽⁵⁾ / 262⁽⁶⁾
PK4	No. 42, Village House, Tai Chung Hau	282⁽⁵⁾ / 118⁽⁶⁾	165⁽⁵⁾ / 99⁽⁶⁾
Ho Chung Channel
HC1	No 30, Ho Chung	319	180
HC2	No 27, Ho Chung First Lane	262	157
HC3	No 5B, Ho Chung	206	135
HC4	No 107, Ho Chung New Village	524	262
HC5	No 116, Ho Chung New Village	190	128
HC6	Rural Committee	384	206
HC7	Berkeley Bay Village House 18	190	128
HCT1	Che Kung Temple	282	165
HCSC1	Sai Kung Central Primary School	129	104
HCTV1	Asia Television Ltd	237	147

(1) Background TSP included in the figure.

(2) Construction activity: material handling, excavation and truck haulage.

(3) Watering the site area twice a day (50% duct reduction for material handling and truck haulage).

(4) According to the construction programme, the construction works at BC1 and BC 2 will not be carried out at the same time. Thus, the dust impacts arising from these two work areas (i.e. BC1 and BC2) were assessed separately.

(5) The dust levels arising from the constriction works at BC1 were predicted based on the nearest distance between the ASR and the site boundary of BC1 working area.

(6) The dust levels arising from the constriction works at BC2 were predicted based on the nearest distance between the ASR and the site boundary of BC2 working area.

3.7.2 Dust levels at various distances from the construction site were predicted. With the small scale of construction works anticipated, the dust criteria would be satisfied at all identified receivers except PK3 and HC4 in the predictions. Figures 3.4 - 3.5 show the contour plots of hourly and daily TSP for Sai Kung River. As shown in Figures 3.4 –3.5, there is no air sensitive use within the areas with exceedance of AQOs outside the work site boundary of Sai Kung River.

3.7.3 Since the predicted TSP concentration would exceed the guideline and AQO at PK3 and HC 4, further mitigation measures are required for Pak Kong River and Ho Chung Channel.

3.7.4 The main source of odour from construction activities would be from the decomposing organic material trapped within river/stream sediments to be dredged or pond sediments. The rural river channels, though potentially eutrophic, are not the main dumping grounds for agricultural wastes. It is also not considered that the material within the ponds would be particularly malodorous. However, if the material is allowed to dry and decompose, especially under very hot weather conditions, odour may emanate from the breakdown of organic materials. As a result, caution and expedience should be used when dealing with excavated or any permitted stockpiled material to minimise the potential odour problem. Mitigation measures for minimizing odour emission from the drainage improvement works are described in Section 3.8.

3.8 Mitigation Measures

Construction Dust

3.8.1 As mentioned in Section 3.7.3, exceedance of both hourly and daily dust criteria was predicted at PK3 and HC4. In order to mitigate the construction dust impact arising from construction of Pak Kong River and Ho Chung Channel, extensive watering of the haul roads (at least every two hours daily) is recommended to maintain the haul roads in wet condition. Through the implementation of this mitigation measure, dust emissions from truck movement can be reduced by 70%, according to Control Techniques for Particulate Emissions from Stationary Sources, Volume 1, US Environmental Protection Agency 1992. Detailed calculations of emission factors are shown in Appendix 3.1.

3.8.2 With the implementation of the recommended mitigation measure, the predicted hourly and daily TSP concentrations are shown in Table 3.7. The hourly and daily dust levels at different separations from Pak Kong River and Ho Chung Channel have been predicted and the results are shown in Appendix 3.2. Figures 3.6-3.7 show the contour plots of hourly and daily TSP for Pak Kung River.

Table 3.7 Predicted TSP Concentration at Representative ASRs

ASR	Description	Hourly TSP Concentration (mg/m³) ^{(1) (2) (3)}	Daily TSP Concentration (mg/m³) ^{(1) (2)(3)}
Pak Kong River⁽⁴⁾
PK1	Village House along Hiram’s Highway	218⁽⁵⁾ / 108⁽⁶⁾	139⁽⁵⁾ / 95⁽⁶⁾
PK2	No. 3, Village House along Hiram’s Highway	107⁽⁵⁾ / 327⁽⁶⁾	95⁽⁵⁾ / 183⁽⁶⁾
PK3	No. 14, Village House, Tai Chung Hau	107⁽⁵⁾ / 377⁽⁶⁾	95⁽⁵⁾ / 203⁽⁶⁾
PK4	No. 42, Village House, Tai Chung Hau	218⁽⁵⁾ / 106⁽⁶⁾	139⁽⁵⁾ / 95⁽⁶⁾
Ho Chung Channel
HC1	No 30, Ho Chung	244	150
HC2	No 27, Ho Chung First Lane	203	134
HC3	No 5B, Ho Chung	165	118
HC4	No 107, Ho Chung New Village	377	203
HC5	No 116, Ho Chung New Village	153	114
HC6	Rural Committee	292	169
HC7	Berkeley Bay Village House 18	153	114
HCT1	Che Kung Temple	218	139
HCSC1	Sai Kung Central Primary School	113	97
HCTV1	Asia Television Ltd	186	127

(1) Background TSP included in the figure.

(2) Construction activity: material handling, excavation and truck haulage

(3) Watering the site area twice a day (50% duct reduction for material handling) and Frequency Watering for haul roads (70% dust reduction for truck haulage)

(5) The dust levels arsing from the construction works at BC1 were predicted based on the nearest distance between the ASR and the site boundary of BC1 working area.

(6) The dust levels arsing from the construction works at BC2 were predicted based on the nearest distance between the ASR and the site boundary of BC2 working area.

3.8.3 As shown in Table 3.7, the predicted dust levels at all air sensitive receivers would comply with the hourly and daily TSP criteria, with the adoption of the recommended mitigation measures.

3.8.4 The mitigation measures proposed for each work area are summarised in the Table 3.8.

Table 3.8 Mitigation Measures Proposed for Each River

Work Area	Recommended Mitigation Measures	Estimated Emission Reduction
Sai Kung River	Twice daily watering of the work site with active operations (material handling and haul roads) when the weather and the work site are dry.	50% ⁽¹⁾
Pak Kong River	Twice daily watering of the work site with active operations (material handling) when the weather and the work site are dry.	50% ⁽¹⁾
	Extensive watering of the haul roads (at least every two hours daily) to keep the haul roads in wet condition.	70% ⁽²⁾
Ho Chung Channel	Twice daily watering of the work site with active operations (material handling) when the weather and the work site are dry.	50% ⁽¹⁾
	Extensive watering of the haul roads (at least every two hours daily) to keep the haul roads in wet condition.	70% ⁽²⁾

Notes:

(1) US EPA’s AP42

(2) Control Techniques for Particulate Emissions from Stationary Sources, Volume1, US Environmental Protection Agency 1992

3.8.5 To further ensure compliance with the AQOs at the ASRs at all time, requirements of the Air Pollution Control (Construction Dust) Regulation shall be adhered to during the construction period. In addition, good site practices and a comprehensive audit programme are recommended to minimise cumulative dust impacts.

3.8.6 The dust mitigation measures stipulated in the Air Pollution Control (Construction Dust) Regulation should be implemented accordingly. The relevant dust control measures are listed below:

· skip hoist for material transport should be totally enclosed by impervious sheeting;

· every vehicle should be washed to remove any dusty materials from its body and wheels before leaving the construction site;

· the area where vehicle washing takes place and the section of the road between the washing facilities and the exit point should be paved with concrete, bituminous materials or hardcores;

· where a site boundary adjoins a road, streets or other accesses to the public, hoarding of not less than 2.4 m high from ground level should be provided along the entire length except for a site entrance or exit;

· all dusty materials should be sprayed with water prior to any loading, unloading or transfer operation so as to maintain the dusty materials wet;

· all stockpiles of aggregate or spoil should be covered and water applied;

· the height from which excavated materials are dropped should be controlled to a minimum practical height to limit fugitive dust generation from unloading; and

· the load of dusty materials carried by vehicle leaving a construction site should be covered entirely by clean impervious sheeting to ensure dust materials do not leak from the vehicle.

3.8.7 In addition, it is recommended that the speed of haul road traffic should be limited to 10 kph.

Odour

3.8.8 To minimise odour nuisance at nearby ASRs, it is recommended that:

· any odorous dredged material should be placed remote from air sensitive receivers;

· any odorous permitted stockpiled material should be removed within two days of work to reduce the amount of time available for decomposition; and

· any odorous permitted stockpiled material should be covered with plastic tarpaulin sheets.

3.9 Cumulative Impacts with Other Concurrent Projects

3.9.1 The project “Improvement of Ho Chung Road” by Highways Department would be undertaken between March 2005 and September 2006. Based on the latest available construction programme of “Improvement Work at Ho Chung Road”, the construction work (excavation, filling and road works from CH000 to CH450) would be undertaken concurrently with the proposed Project during the months of December 2005 to September 2006. Cumulative dust impacts from the project and the Drainage Improvement in Sai Kung may be experienced at sensitive receivers of Ho Chung.

3.9.2 The exact construction method and program of the Improvement of Ho Chung Road are not known at this stage. In order to assess the cumulative dust impact from the construction works, it is assumed that the Project will be constructed in phases and the typical size of works area is about 50m x 10m. The emission rate is assumed to be 2.69 Mg/hectare/month of activity in accordance with AP42, 13.2.3. Appendix 3.1 lists the dust emission factors adopted in this assessment. The construction works would comply with the Air Pollution Control (construction Dust) Regulation, and dust emission rate of the construction works could be reduced by 50%. The hourly and daily dust levels at different separations from the site have been predicted and the results are shown in Appendix 3.2 and the predicted cumulative dust levels are shown in Table 3.9 and Table 3.10.

Table 3.9 Cumulative Hourly TSP Level at Representative ASRs

		Hourly TSP Concentration (mg/m³)
ASR	Separation from Ho Chung Road⁽¹⁾(m)	Ho Chung Road	Sai Kung Drainage Improvement (Ho Chung Channel)	Background	Cumulative^{(2) (3)}
HC1	8	199	157	87	443
HC2	18	132	116	87	336
HC3	22	120	78	87	285
HC4	28	105	290	87	482
HC5	73	41	66	87	195
HC6	162	12	205	87	304
HC7	235	6	66	87	160
HCT1	130	17	131	87	235
HCSC1	295	4	26	87	117
HCTV1	18	132	99	87	319

Notes: Haul road located at more than 3 m from the receiver.

(1) The nearest distance from the construction work area (excavation, filling and road works from CH000 to CH450) to the ASRs.

(2) Background TSP included in the figure

(3) Cumulative = TSP from Ho Chung Road + TSP from Ho Chung Channel + Background

Table 3.10 Cumulative Daily TSP Level

		Daily TSP Concentration (mg/m³)
ASR	Separation from Ho Chung Road⁽¹⁾(m)	Ho Chung Road	Sai Kung Drainage Improvement (Ho Chung Channel)	Background	Cumulative^{(2) (3)}
HC1	8	80	63	87	230
HC2	18	53	47	87	187
HC3	22	48	31	87	166
HC4	28	42	116	87	245
HC5	73	17	27	87	130
HC6	162	5	82	87	174
HC7	235	2	27	87	116
HCT1	130	7	52	87	146
HCSC1	295	2	10	87	99
HCTV1	18	53	40	87	180