11. Construction Dust Impact Assessment

11.1 Introduction

This assessment has been based on the criteria and guidelines for evaluation and assessment of air quality impact stated in Annexes 4 and 12 of the EIAO-TM and covered the scope outlined in Section 3.4.9 of the EIA Study Brief.

11.2 Relevant Legislation, Standards & Guidelines

Hong Kong’s air quality is regulated through the Air Pollution Control Ordinance (Cap. 311) (“APCO”). The APCO specifies Air Quality Objectives (“AQOs”), which are the statutory limits for a number of pollutants and the maximum allowable number of times that these may be exceeded over specified periods – these pollutants are defined as Criteria Pollutants (“CP”). The AQOs defined for these criteria pollutants are given in the Table 11.1 below: -

Table 11.1: Hong Kong Air Quality Objectives

Pollutant	Concentration (mg/m³)⁽¹⁾ Averaging Period
Pollutant	1 Hour⁽²⁾	8 Hours⁽³⁾	24 Hours⁽³⁾	3 Months⁽⁴⁾	1 Year⁽⁴⁾
Sulphur Dioxide, SO₂	800	-	350	-	80
Total suspended Particulate, TSP	-	-	260	-	80
Respirable Suspended Particulates, RSP⁽⁵⁾	-	-	180	-	55
Nitrogen Dioxide, NO₂	300	-	150	-	80
Carbon Monoxide, CO	30,000	10,000	-	-	-
Photochemical Oxidants, (as ozone ⁽⁶⁾)	240	-	-	-	-
Lead	-	-	-	1.5	-

Notes:

(1) Measured at 298 K and 101.325 kPa (one atmosphere)

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

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

(4) Arithmetic means

(5) Respirable suspended particulates means suspended particles in air with a nominal aerodynamic diameter of 10mm or less

(6) Photochemical oxidants are determined by measurement of ozone only

For impacts during the construction stage, fugitive dust in particular, Section 1, Annex 4 of EIAO-TM stipulates the hourly average Total Suspended Particulate (“TSP”) concentration of 500 mg/m³ measured at 298 K (25°C) and 101.325 kPa (1 atmosphere) for construction dust impacts. Mitigation measures for construction sites specified in the Air Pollution Control (Construction Dust) Regulation should be followed.

The APCO’s subsidiary regulation Air Pollution Control (Construction Dust) Regulation defines notifiable and regulatory works activities that are subject to construction dust control.

Notifiable Works:

1. Site formation;

2. Reclamation;

3. Demolition of a building;

4. Work carried out in any part of a tunnel that is within 100 m of any exit to the open air;

5. Construction of the foundation of a building;

6. Construction of the superstructure of a building; or

7. Road construction work.

Regulatory Works:

1. Renovation carried out on the outer surface of the external wall or the upper surface of the roof of a building;

2. Road opening or resurfacing work;

3. Slope stabilisation work; or

4. Any work involving any of the following activities-

¡ Stockpiling of dusty materials;

¡ Loading, unloading or transfer of dusty materials;

¡ Transfer of dusty materials using a belt conveyor system;

¡ Use of vehicles;

¡ Pneumatic or power-driven drilling, cutting and polishing;

¡ Debris handling;

¡ Excavation or earth moving;

¡ Concrete production;

¡ Site clearance; or

¡ Blasting.

Notifiable works require that advance notice of activities be given to EPD. The Regulation also requires the works contractor to ensure that both notifiable works and regulatory works will be conducted in accordance with the Schedule of the Regulation, which provides dust control and suppression measures.

11.3 Study Area and Air Sensitive Uses

11.3.1 Study Area

Clause 3.4.9.2 of the EIA Study Brief prescribed a study area to be generally defined by a distance of 500m from boundary of the Project, or other project alignments as identified in the EIA. Figure 11.1 shows the study area (500m envelope) of the alignment and Figure 11.2 and Figure 11.3 show the identified representative ASRs of two landing locations, To Kwa Wan and North Point.

11.3.2 Air Sensitive Uses

Although the study area can be as wide as 500m from the work sites, the first tier of ASRs will usually be considered in planning the works in order to minimise the dust nuisances. Other ASRs further away from these first tier ones will be expected to be less affected.

There is a G/IC unit (planned schools) zoned in the vicinity of the proposed To Kwa Wan pigging station, however, based on the latest information obtained from Education Bureau (Appendix I1), the tentative school commencement year would be in 2014 academic year, which is beyond the construction programme of the proposed project, hence this G/IC unit is not identified as ASR.

The representative ASRs identified within the assessment area was tabulated in Table 11.2 below.

Table 11.2: Representative ASRs within the Assessment Area

ASRs	Location	Nature of Use	Distance to submarine gas main (m)	Distance to Pigging Station (m)
To Kwa Wan
A1	Wing Fai Mansion (Existing)	Residential	449	194
A2	Sunshine Villa (Existing)	Residential	427	230
A3	Po Leung Kuk Ngan Po Ling College (Existing)	Educational	370	122
A4	CCC Kei To Secondary School (Existing)	Educational	346	121
North Point
A5	ICAC Headquarters (Existing)	Office	332	364
A6	North Point Fire Station Fire Service Building and Married Quarters (Existing)	Office/ Residential	122	168
A7	North Point Government Office (Existing)	Office	39	76
A8	Eastern District Headquarters & North Point Division Police Station (Existing)	Office	12	53
A9	Healthy Garden (Existing)	Residential	497	519
A10	La Place de Victoria (Existing)	Residential	373	392
A11	Kut Cheong Mansion (Existing)	Residential	198	202
A12	Harbour Plaza, North Point (Existing)	Hotel	87	76
A13	Model Housing Estate (Existing)	Residential	159	144
A14	Lai King Building (Existing)	Commercial/ Residential	243	197
A15	Canossa College (Existing)	Institutional	338	289

11.4 Background Air Quality

There are currently 11 general and 3 roadside air quality monitoring stations operated by EPD and one of the purposes is to provide background air quality information. The proposed submarine gas pipelines starts from the To Kwa Wan and ends at North Point. The two air quality monitoring stations, viz., Kwun Tong and Eastern, are the nearest to the landmains respectively. The annual average air quality measured for the past 5 years (2004 to 2008) at the two stations are presented in Table 11.3.

Table 11.3: 5-year-averaged Background Air Quality of Kwun Tong and Eastern Air Quality Monitoring Stations

Pollutants	Kwun Tong, Annual average (µg/m³)	Eastern, Annual average (µg/m³)	HKAQO (µg/m³)
NO₂	61	57	80
RSP	54	49	55
TSP	78	N/A	80
SO₂	19	17	80

11.5 Construction Phase Impacts

11.5.1 Analysis of Construction Activities

The envisaged construction programme and activities have been presented in Appendix A.

The construction works will be separated into submarine and landmain works. The marine works starts with grab dredging and “Bottom Pull” method across the fairway, “Float and Sink” method near the landing point and either “Bottom Pull” or “Lay Barge” for other sections of the submarine gas pipelines followed by protection of the submarine gas pipelines by backfilling are the most practical construction method. The landmain works will start with site clearance, minimal excavation and finally the laying of land gas main.

11.5.2 Assessment Methodology

As the construction activities would be phased and are conducted mainly along the harbour, it is expected that, with implementation of dust suppression measures given in the Air Pollution Control (Construction Dust) Regulation and proposed mitigation measures mentioned in Section 11.5.4 below, no significant dust impact would be envisaged. A qualitative approach to evaluate the air quality impact induced by the construction of the Project is therefore adopted.

11.5.3 Identification of Potential Construction Dust Impact

The likely air quality impacts arising from the construction of the proposed submarine gas pipeline are dust nuisance and gaseous emission from construction plant, vehicles and barges. It is anticipated that dust would be generated from excavation, material handling and wind erosion from the site. A summary of construction activities and the potential emission sources is tabulated in Table 11.4 below.

Table 11.4 Construction Activities and Potential Emission Sources

Construction Activities		Potential Emission Sources	No. of Plant Used*
Marine Works	Trench Dredging	Gasesous emission from barges	1-3
	Pipe Laying (at sea)	Gasesous emission from barges	1-5
	Pipe Laying (on land)	Dust generated from site vehicles and gasesous emission from construction plant	1-2
	Backfilling	Gasesous emission from barges	1-3
Land Works	Mobilizations/ Site Preparation	Dust generated from site vehicles and gasesous emission from construction plant	1
	Seawall demolition	Dust generated from site vehicles and gasesous emission from construction plant	1-2
	Seawall reinstatement	Dust generated from site vehicles and gasesous emission from construction plant	1
	Construction of pigging station – Surface reinstatement	Dust generated from site vehicles and gasesous emission from construction plant	1
	Construction of pigging station – Facilities installation	Dust generated from site vehicles and gasesous emission from construction plant	1

Note:

[*] The no. of plant used is referred to Table 10.4 and Table 10.5 of this EIA report.

The submarine gas pipeline laying activities such as trench dredging and pipe pulling as detailed in the construction programme are not dust generating as the dredged mud is in high moisture content, fugitive dust is not anticipated. Given the separation distance between the barge and the sensitive receivers of both landing location is longer than 160m, the gaseous emissions of SO₂ and NO₂ from one barge at anytime on site is anticipated insignificant. Exceedance of AQOs from their operation is not anticipated.

The construction activities associated with the landing point would involve dust generating activities such as site clearance, minimal ground excavation, material handling and vehicle movements on haul roads. As the number of plant required on site would be limited each type of plant would be in the order of 1-2 as shown in the Table 11.4, dust impact and SO₂ and NO₂ emissions from plant and site vehicles would be minimal. With the implementation of appropriate dust suppression measures stipulated in the Air Pollution Control (Construction Dust) Regulation, together with proper maintenance of equipment, adverse air quality impacts are not anticipated.

The works may also involve the use of trucks/ lorries for material transport. The number of trucks/ lorries would be limited to 1-2 as shown in Table 11.4, emissions from the trucks/ lorries would be minimal. Moreover, use of vehicles is a regulatory work procedure and the required dust control measures shall ensure dust levels are controlled to an acceptable level.

11.5.4 Mitigation Measures for Fugitive Dust

To mitigate fugitive dust impact, all dust control measures recommended in the Air Pollution Control (Construction Dust) Regulation, where applicable, will be implemented. Relevant dust control measures include:

1. The works area for site clearance shall be sprayed with water before, during and after the operation so as to maintain the entire surface wet;

2. Restricting heights from which materials are to be dropped, as far as practicable to minimise the fugitive dust arising from unloading/ loading;

3. Immediately before leaving a construction site, all vehicles shall be washed to remove any dusty materials from the bodies and wheels. However, all spraying of materials and surfaces should avoid excessive water usage;

4. Where a vehicle leaving a construction site is carrying a load of dusty materials, the load shall be covered entirely by clean impervious sheeting to ensure that the dusty materials will not leak from the vehicle;

5. Any stockpile of dusty materials shall be covered entirely by impervious sheeting; and/or placed in an area sheltered on the top and 4 sides;

6. All dusty materials shall be sprayed with water immediately prior to any loading, unloading or transfer operation so as to maintain the dusty materials wet.

11.6 Potential Cumulative Impacts due to Concurrent Works

According to Section 2.11, there are potential concurrent projects identified which included the followings: -

¡ Dredging Works for Proposed Cruise Terminal at Kai Tak;

¡ Wan Chai Development Phase II and Central-Wan Chai Bypass (WCD II);

¡ Shatin Central Link (SCL);

¡ Trunk Road T2;

¡ Providing Sufficient Water Depth for Kwai Tsing Container Basin and its Approach Channel (KTCB); and

¡ Central Kowloon Route (CKR).

Although the Cruise Terminal project is located within the assessment area of this EIA project, the distance between the Cruise Terminal project and the air sensitive receivers at North Point and To Kwa Wan would be over 500m, hence the cumulative impacts from the Cruise Terminal project is predicted minimal.

While the WCD II, Trunk Road T2 and KTCB are located outside the assessment area of this EIA project, no cumulative impact assessment is considered necessary.

Based on the best information available in the websites, the tentative construction programe of the Shatin Central Link would be commenced in 2010 and end in 2015, but detailed construction programe is not available now. Moreover, based on the latest information obtained from MTRC website, the nearest Ma Tau Wai Station is out of 500m assessment area, no cumulative air quality impact is anticipated.

The CKR would be commenced in 2012 and end in 2016, but the CKR is all underground from Kai Tak Development to West Kowloon, hence, the potential cumulative project would unlikely to contribute significant impact to ASRs.

11.7 Operational Phase Impacts

There will not be any operational phase emissions.

11.8 Environmental Monitoring and Audit Requirements

It is necessary to ensure proper implementation of the dust control measures as required under the Air Pollution Control (Construction Dust) Regulation. As the dredged mud is in high moisture content during the dredging process and the number of plant operated on landmain site is limited, no significant dust impact is anticipated, hence no specific construction dust monitoring is recommended, although environmental audits during the construction stage will be desirable to ensure proper implementation of air quality control measures.

11.9 Summary

Potential air quality impacts arising from the construction and operation of the submarine and land gas pipelines have been evaluated.

As the number of construction plant involved in the submarine gas pipelines laying activities at anytime on site will be limited, exceedance of AQOs emissions of gaseous pollutants from these construction plant is not anticipated. The number of plant required on site for the construction of the landing points will also be limited. Dust impact and SO₂ and NO₂ emissions from plants and site vehicles will be minimal. With the implementation of appropriate dust suppression measures stipulated in the Air Pollution Control (Construction Dust) Regulation, together with proper maintenance of equipment, adverse air quality impact is not anticipated.

No air quality impact is anticipated at the operational phase since there will not have any operational phase emissions.