air quality in construction

Agreement No. CE49/2002 (DS) Drainage Improvement in Southern Lantau Drainage Services Department Final EIA Report

P:\A02703\REPORTS\Final EIA\Sec 3-Air.doc 3-1 Maunsell

3 AIR QUALITY IMPACT

3.1 Introduction

3.1.1 This Section presents an assessment of the potential air quality impacts pertinent to the construction phase of the Project, and recommends appropriate mitigation measures, where necessary.

3.1.2 Air quality impacts during the construction phase would be mainly associated with dust and vehicle emissions from various construction activities. Appropriate mitigation measures have been recommended, where necessary, to alleviate the potential construction dust impacts to acceptable levels.

3.2 Environmental Legislation and Standards

3.2.1 The criteria for evaluating air quality impacts and the guidelines for air quality assessment are laid down in Annexes 4 and 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 authority for controlling air pollutants from a variety of sources. The Ordinance includes a number of Air Quality Objectives (AQOs) which stipulate maximum concentrations for a range of pollutants, of which total suspended particulates (TSP) are relevant to this study. The relevant AQO is listed in Table 3.1.

Table 3.1 Hong Kong Air Quality Objectives

Parameter Maximum Average Concentration (µgm-3)1 24-Hour2 Annual3

TSP 260 80 1. Measured at 298 K and 101.325 kPa. 2 Not to be exceeded more than once per year. 3. Arithmetic mean.

3.2.3 The EIAO-TM also stipulates that the hourly TSP level at sensitive receivers should not exceed 500 µgm-3 TSP (measured at 25°C and one atmosphere) Mitigation measures for construction sites have been specified in the Air Pollution Control (Construction Dust) Regulations.

3.3 Description of the Environment

3.3.1 The sites of the drainage improvement works are located in Mui Wo, Southern Lantau; an area rural in nature and occupied with mainly village houses. No major air pollutants source was found in the vicinity of the sites. In the absence of in-situ monitoring data, reference is made to the annual average concentration of major air pollutants measured at EPD’s nearest monitoring station (Tung Chung) for the last 4 years. The 4-year annual average TSP level at Tung Chung is 70 µgm-3 according to Hong Kong Air Quality 1999 – 20021.

1 Air monitoring at the Tung Chung station commenced in April 1999, i.e. only last 4 years data are available.



3.4 Air Sensitive Receivers

3.4.1 According to Annex 12 of the EIAO-TM, domestic premises, hotel, hostel, hospital, clinic, nursery, temporary housing accommodation, school, educational institution, office, factory, shop, shopping centre, place of public worship, library, court of law, sports stadium or performing arts centre are considered as air sensitive receivers (ASRs). Any other premises or places having similar sensitivity (in terms of duration or number of people affected) to the air pollutants may also be considered to be sensitive receivers.

3.4.2 Based on the criteria set out in the EIAO-TM, representative ASRs have been identified close to the Project site. A brief description of the representative ASRs is summarized in Table 3.2 and the corresponding locations are shown on Figure 3.1.

Table 3.2 Representative Air Sensitive Receivers

NSR Location Use Horizontal Nearest Distance to Works

Area (m) Pak Ngan Heung River APNH1 No. 22 Village House, Tai Tei Tong Residential 4

APNH2 No. 1 Village House adjacent to Pak Ngau Heung River

Residential 5

APNH3 No. 10 Village House adjacent to Pak Ngau Heung River

Residential 4

APNH4 Village House, Ling Tsui Tau Tsuen Residential 4

APNH5 No. 6 Village House adjacent to Pak Ngau Heung Outlet

Residential 6

APNH6 Village House, Ling Tsui Tau Tsuen Residential 2 ALT1 Village House, Ling Tsui Tau Tsuen Residential 17 ALT2 No. 75 Village House, Ling Tsui Tau Tsuen Residential 1 Tai Tei Tong River ATTT1 No. 25 Village House, Ma Po Tsuen Residential 27 ATTT2 No. 27 Village House, Ma Po Tsuen Residential 45

ATTT3 No. 23 Village House adjacent to Tai Tei Tong River

Residential 4

ATTT4 No. 10 Village House adjacent to Tai Tei Tong River Outlet

Residential 5

ASCH Mui Wo Shcool Education 17 Luk Tei Tong River and Luk Tei Tong By-pass Channel ALTT1 No. 135 Village House, Luk Tei Tong Residential 1 ALTT2 No. 19 Village House, Luk Tei Tong Residential 15 ALTT3 No. 36 Village House, Luk Tei Tong Residential 32 ALTT4 No. 4 Village House adjacent to Luk Tei Tong

River Outlet Residential 1

3.5 Identification of Environmental Impacts

3.5.1 Potential air quality impacts arising from the construction of the proposed drainage channels would include dust nuisance and gaseous emissions from the construction plant and vehicles. It is anticipated that dust would be generated from excavation, material handling and wind



erosion from the site during earthworks and backfilling for the box culvert, road and channel construction. The potential dust impacts arising from the drainage improvement works at Pak Ngan Heung River, Tai Tei Tong River, Luk Tei Tong River and Luk Tei Tong By-pass Channel are discussed in Section 3.6 below.

3.6 Prediction and Evaluation of Impacts

3.6.1 The sites of the proposed drainage improvement works at the Pak Ngan Heung River, Tai Tei Tong River, Luk Tei Tong River and Luk Tei Tong By-pass Channel would mainly lie on an area of inactive wet agricultural land. The proposed alignments would generally follow the existing river alignments. It is expected that the excavated materials would be mainly from the rivers and their surrounding inactive wet agricultural land and would have high moisture content. In addition, the construction materials used for the works would be mainly gabion, grasscrete and masonry, which are all non-dusty materials. As such, dust emission from materials handling would not be significant.

3.6.2 In view of the limited scale of the proposed works, construction dust emissions due to wind erosion and truck movement on unpaved roads would also be considered minor. Given the high moisture content of spoils, limited scale of works and implementation of appropriate mitigation measures and good site practices (as described in Section 3.7), no adverse dust impact would be expected.

3.6.3 As indicated in Section 2.10, construction of the Project would likely interface with the projects including “Outlying Sewerage Stage 2 – Mui Wo Village Sewerage (Package 1A)” (Late 05 to Mid 07) and “Construction of Emergency Vehicular Access (EVA) and Sewerage Works at Luk Tei Tong, Mui Wo” (late 04 to late 06). Although the construction of EVA and sewerage works at Luk Tei Tong would likely coincide with the proposed drainage improvement works under the Project during the period of mid 2006 to late 2006, it is expected that the major construction works of the EVA and sewerage works at Luk Tei Tong would have been finished substantially prior to the start of the Project and only minor construction works would remain during the coincidence period. As such, adverse cumulative dust impact from the construction works of this concurrent project would not be anticipated.

3.6.4 For the proposed sewerage works under the Mui Wo Village Sewerage, it would take place in the vicinity of the Pak Ngan Heung River and is expected to be small-scale. There would be limited potential for adverse cumulative dust impact from the minor construction activities of this concurrent project. Hence, adverse cumulative dust impact from the construction works of this concurrent project would not be anticipated.

3.7 Mitigation Measures

3.7.1 To ensure compliance with the guideline level and AQO at the ASRs, the Air Pollution Control (Construction Dust) Regulation should be implemented and good site practices should be incorporated in the contract clauses to minimize construction dust impact. A number of practical measures are listed below:

• Use of regular watering to reduce dust emissions from exposed site surfaces and unpaved

road, with complete coverage, particularly during dry weather;

• Use of frequent watering for particularly dusty static construction areas and areas close to ASRs;



• Tarpaulin covering of all dusty vehicle loads transported to, from and between site location;

• Establishment and use of vehicle wheel and body washing facilities at the exit points of the site; and

• Routing of vehicles and positioning of construction plant should be at the maximum possible distance from ASRs.

3.8 Residual Environmental Impact

3.8.1 With the implementation of the proposed dust suppression measures and good site practices, no adverse residual impact would be expected.

3.9 Environmental Monitoring and Audit Requirements

3.9.1 With the implementation of mitigation measures stipulated in the Air Pollution Control (Construction Dust) Regulation, no adverse air quality impact arising from construction works would be expected. Hence, no air quality monitoring would be required during construction of the Project. It is recommended that regular site inspections during construction phase be carried out to ensure that the mitigation measures are properly implemented.

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