PWP ITEM No. 4338DS -

IMPROVEMENT AND UPGRADING OF THE SEWERAGE SYSTEMS IN SHA TIN / MA ON SHAN NEW TOWN

MA ON SHAN AREA 108 PUMPING STATION

PROJECT PROFILE

Drainage Services Department

The Government of the Hong Kong Special Administrative Region

March 2006

Contents

		Page
1.	Basic Information	1

2.	Outline of Planning and Implementation Programme	2

3.	Possible Impacts on Environment	3

4.	Major Elements of the Surrounding Environment	6

5.	Environmental Protection Measures to be Incoporated in the Design and further Environmental Implications	6

6.	Summary of Potential Environmental Impacts and Mitigation Measures	11

1 Basic Information

1.1 Project Title

The title of this project is “Ma On Shan Area 108 Pumping Station” (hereinafter referred to as the “Project”).

1.2 Purpose and Nature of the Project

The Project aims at achieving an increase in sewage conveyance capacity from the residential area at Sai Sha [for catchment area, please refer to drawing no. DDN/338DS/1812 in Appendix A] and involves the construction of a new Ma On Shan Area 108 Pumping Station adjacent to the existing one. After completion of the new Pumping Station, the existing one will operate as a standby (hereinafter, the proposed Ma On Shan Area 108 Pumping Station is called the Pumping Station).

1.3 Name of Project Proponent

Drainage Services Department (DSD) is the works department while Environmental Protection Department is the client department.

1.4 Location and Scale of the Project

The existing Ma On Shan Area 108 Pumping Station is situated at the junction of Sha On Street and Sai Sha Road. The new Pumping Station will be constructed adjacent to the existing one, i.e. within GI/C zoning of the Ma On Shan Outline Zoning Plan No. S/MOS/13. The location and layout of the Pumping Station is shown on drawing no. DDN/338DS/1818C in Appendix A. Since the existing pumping station will be preserved, no demolition works is expected. The design average dry weather flow of the Pumping Station is approximately 14,500m³/day. The Pumping Station will be a single-storey building with the inlet chamber and the wet well being underground and enclosed with covers.

1.5 Rationale for Site Selection

The Pumping Station is situated adjacent to the existing Ma On Shan Area 108 Pumping Station and within the area reserved for the existing pumping station. By locating the new Pumping Station adjacent to the existing one, most of the existing sewers can be maintained and nuisance due to substantial modifications of existing sewerage system is avoided.

The Pumping Station will also make use of the by-pass route of the existing Ma On Shan Area 108 Pumping Station. Due to site constraints, laying a new by-pass pipe for overflow to another discharge point is impractical.

1.6 Number and Type of Designated Project

Since the nearest residential block (Lee Wing House of Lee On Estate) is about 75m away from the Pumping Station which has a proposed capacity of approximately 14,500m³/day, the Pumping Station is classified as a Designated Project under Schedule 2, Part I, F.3(b) of the Environmental Impact Assessment Ordinance (EIAO).

1.7 Contact Person

Mr. S. H. Leung

Engineer, Sewerage Projects Division, Drainage Services Department

44/F, Revenue Tower, 5 Glouces ter Road, Wanchai, Hong Kong

Tel: 2594 7364

Fax: 2827 8700

2 Outline of Planning and Implementation Programme

2.1 The Project is delivered by DSD using in-house resources. The Sewerage Projects Division and the Electrical and Mechanical Projects Divison of DSD are jointly responsible for the planning, design and construction supervision of the Project. The construction will be carried out by a qualified contractor. The Sewage Treatment Division 1 of DSD will be responsible for operating and maintaining the Pumping Station.

2.2 The Project is currently under the detailed design stage. The tentative implementation programme is as below: -

Design: Up to June 2006

Tender: July 2006 – October 2006

Construction & Commissioning: November 2006 – December 2010

Operation & Maintenance: January 2011

2.3 Interaction with Other Projects

There are no major projects in the vicinity of the Project with overlapping implementation programmes that will have significant environmental impacts due to cumulative effects. The construction of rising main across Sai Sha Road will not overlap with the construction of the Pumping Station.

3 Possible Impacts on the Environment

3.1 During Construction Stage

3.1.1 Air Quality

Dust may be generated from construction activities, mainly due to earthworks or handling and transportation of construction / demolition materials.

3.1.2 Noise

The major sources of construction noise are associated with the use of powered mechanical equipment (PME) such as air compressors, generators, hydraulic or pneumatic breakers, backhoes, etc. A detailed noise impact assessment is attached in Appendix C.

3.1.3 Water Quality

Muddy water may be generated from the construction activities such as dust suppression sprays, dewatering during excavation, washing of construction equipment, etc.

3.1.4 Landscape and Visual

The existing site of the Pumping Station is a concrete paved area with no existing trees or amenity planting within the proposed site boundary. The existing condition of the Project site is shown in the photos listed in Appendix E. At the Pumping Station, the appearance of a normal low-rise building construction site will be seen. The presence of construction plant and materials, site traffic and temporary lighting is expected.

3.1.5 Waste

Construction and demolition (C&D) material and waste such as excavated spoil (soil and rock), concrete and unusable cement/grouting mixes, wood/metal scraps, and packaging materials will be generated.

3.1.6 Ecology

Since the Pumping Station is located at an urbanized area and does not involve any reclamation or dredging activities, no impact on ecology is expected during the construction stage.

3.1.7 Cultural Heritage

No impact on historical monuments or buildings is expected during the construction stage.

3.1.8 Traffic

The Pumping Station does not involve excavation on public roads. Only a small amount of traffic will be generated by the construction of the designated project and the associated impact on traffic in the area will be minimal.

3.2 During Operation and Maintenance Stage

3.2.1 Odour

The inlet chamber and wet well of the Pumping Station may be sources of odour nuisance.

3.2.2 Water Quality

The Pumping Station is designed to convey sewage collected from residential areas near Sai Sha to Shatin Sewage Treatment Works for treatment and disposal. Implementation of the project will enhance the water quality of the surrounding environment, and will not cause any adverse impacts under normal operation. Under emergency situation such as prolonged power failure, sewage bypass into Tolo Harbour may occur. However, with the implementation of preventive measures described in paragraph 5.2.2, the probability of sewage bypass will be extremely remote.

3.2.3 Noise

The pumps and extraction fans of the deodourizer are potential noise sources during operation and maintenance of the Pumping Station. A detailed noise impact assessment is attached in Appendix C.

3.2.4 Waste

Mechanically raked bar screens will be installed at the inlet chamber to prevent large solid materials in sewage from entering the pumps and thus causing damage to them. A small quantity of screenings will thus be generated.

3.2.5 Landscape and Visual

No tree or amenity planting will be affected by the Project. The potential visual impact during operation and maintenance stage is the presence of a completed low-rise building.

3.2.6 Ecology

The Pumping Station is designed to expand the capacity of the existing Ma On Shan Area 108 Pumping Station. Implementation of the project will further minimize the chance of overflow along existing by-pass route to Starfish Bay and will not cause any additional adverse impact to ecology. The proposed preventive measures for minimizing the ecological impacts of the existing by-pass route during the operation and maintenance stage are detailed in paragraph 5.2.2.

3.2.7 Traffic

The delivery of materials and removal of screenings will be infrequent and will have insignificant impacts on traffic flow in the area.

3.2.8 Cultural Heritage

No impacts on historical monuments or buildings are expected during the operation stage.

4 Major Elements of the Surrounding Environment

This section is to outline the existing and planned sensitive receivers that might be affected by the Project. In addition, it also outlines the major elements of the surrounding environment that may affect the project.

4.1 Existing Sensitive Receivers and Sensitive Parts of Natural Environment

The locations of the sensitive receivers are shown in Appendix B.

There are three residential development near the Pumping Station, namely: (i) Lee On Estate (SR1 – approx. 75m away), (ii) Monte Vista (SR2 – approx. 130m away) and (iii) Wu Kai Sha Village (SR3 – approx. 130m away).

4.2 Planned Sensitive Receivers and Sensitive Parts

The locations of the sensitive receivers are shown in Appendix B.

The property development at Wu Kai Sha Station (SR4 – approx. 70m away) of Ma On Shan Railway is planned to have their population intake in mid 2008. As such, it is expected that the future residents will be some of the sensitive receivers of the Pumping Station.

4.3 Major Elements of the Surrounding Environment Affecting the Project

There are no major elements of the surrounding environment affecting the Project.

5 Environmental Protection Measures to be Incorporated in the Design and further Environmental Implications

5.1 During Construction Stage

5.1.1 Air Quality

The effect of dust generated from the construction works is expected to be insignificant with the implementation of proper mitigation measures. The impacts will be minimized by the adoption of proper working methods such as regular water spraying and providing wheel-washing facilities.

5.1.2 Water Quality

The construction activities of the Project will include excavation, earthworks, and general concrete building works. The contractor will be required to provide, where necessary, a silt removal facility so as to remove any silt before discharge of site runoff into the nearby stormwater drains. The mitigation measures should be provided prior to the commencement of excavation. The design of temporary on-site drainage and silt removal facilities will follow the guidelines stipulated in the EPD’s Practice Note for Professional Persons, Construction Site Drainage (ProPECC PN 1/94). With the above mitigation measures, no adverse impacts on water quality are expected during the course of construction.

5.1.3 Noise

Common construction plants including backhoes, concrete mixers, vibratory pokers, pneumatic breakers and the like will be used. Furthermore, temporary hoardings will be erected during construction of the pumping station to screen off any noise. The Contractor has to comply with the relevant regulations and the Noise Control Ordinance to limit the construction noise within the acceptable limit during the construction stage. Construction activities will be carried out in the daytime (0700 – 1900) and will avoid working on Sunday or public holidays. A quantitative noise assessment is provided in Appendix C. The use of quiet construction equipment and implementation of good site practices as mitigation measures are identified. Noise from the daytime construction shall comply with the relevant noise limit of 75dB(A) Leq(30 minutes) for domestic premises specified in the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM). A valid Construction Noise Permit is required under the Noise Control Ordinance in case the construction works to be carried out during nighttime (1900 – 0700), Sundays and public holidays.

5.1.4 Waste

The Contractor will be required to sort all C&D material and waste into different categories for reuse on site and disposal at public filling, landfills, or recycling facilities as appropriate. The total C&D material generated is estimated to be about 5,600m³ and approximately half of them can be reused on site. The rest will be disposed of to the Public Filling Facility at Tsuen Kwan O Area 137. No chemical waste is identified under this project.

5.1.5 Landscape and Visual

No endangered tree species are identified within the project site. Site hoardings will be erected around the site area as far as possible to minimize the potential impacts to nearby pedestrians.

5.2 During Operation Stage of Pumping Station

5.2.1 Odour

To minimize the potential odour problem, the inlet chamber, screen chamber, wet well, etc. will be located underground, and enclosed by a reinforced concrete superstructure. In addition, a deodourizer with a forced ventilation system will be installed to remove odour. As adopted in other similar sewage pumping stations, e.g. Nam San Wai Sewage Pumping Station, the removal efficiency of H₂S by the proposed deodourizer to be installed will be 99.5%. The exhaust of the proposed deodourizer shall be located in a direction away from the nearby sensitive receivers as far as practicable, i.e. facing north of the Pumping Station.

5.2.2 Water Quality & Ecology

The emergency by-pass of the sewage will make use of the by-pass routing currently in use by the existing Ma On Shan Area 108 Pumping Station. The by-pass discharge point is located at Starfish Bay of Tolo Harbour (please refer to Appendix D).

A sub-tidal diving survey at Starfish Bay was carried out on 20 February 2006. Marine organisms such as algae, mussels, bivalves, sea cucumber and sea anemones were observed during the inspection. As no coral or other uncommon species of marine organisms were found, the sub-tidal zone of Starfish Bay is considered to contain only common species as found in other Hong Kong waters. Nevertheless, according to the final report of Environment and Conservation Fund project 23/99 – “A study of soft shore habitats in Hong Kong for conservation and education purposes” carried out by City University of Hong Kong, the shores at Lok Wo Sha area are ranked as with important conservative potential. As such, this project will implement a series of measures to minimize the probability of sewage by-pass.

To minimize the probability of sewage by-pass, three duty and one standby pumps, one duty and one standby mechanical screens, as well as an approximate one-hour emergency storage will be provided to cater for breakdown and maintenance of the duty pumps and mechanical screens. Furthermore, the existing Ma On Shan Area 108 Pumping Station will be retained and it provides a standby backup capacity of 13,800 m³/day (approximately one-third of the peak flow capacity of the Pumping Station) when the equipment at the Pumping Station fails.

Over the past five years, there is only one by-pass incident for the existing Ma On Shan Area 108 Pumping Station due to power failure in March 2001. As such, in order to minimize the chance of power failure, a dual power supply will be provided for the Project by CLP. Furthermore, the existing Ma On Shan Area 108 Pumping Station is supported by an emergency generator, which can maintain the functioning of the duty pumps to provide a 13,800 m³/day flow capacity. In addition, a telemetry system will also be provided in order to transmit signals showing irregularity or any operational problem of the Pumping Station to the existing Shatin Sewage Treatment Works such that immediate actions can be taken. With these measures incorporated into the design of the pumping station, it is anticipated that the chance of emergency sewage bypass will be extremely remote. As a result, the impact of emergency by-pass on the ecology of Starfish Bay is considered minimal. An assessment for the scenarios of emergency is attached as Appendix G.

It is considered that with the implementation of this project and the above precautionary measures, the project will bring about environmental benefits as the chance of sewage by-pass will be greatly minimized when compared with the existing arrangement.

5.2.3 Noise

During the operation of the Pumping Station, all pumps will be enclosed inside the substructure of the Pumping Station and acoustic filters will be installed at the extraction fans of the deodourizers. According to the quantitative assessment attached in Appendix C, with the above design of the Pumping Station, no adverse noise impacts are anticipated and further mitigation measure are not required.

5.2.4 Waste

The screenings of sewage at the inlet works of the Pumping Station will be put in plastic bags or storage containers. This operation will be conducted inside the Pumping Station. The screenings would then be transported to landfills for disposal. As such, no adverse waste impacts are anticipated.

5.2.5 Landscape and Visual

The existing site of the Pumping Station is a concrete paved area with no existing trees or amenity planting within the proposed site boundary. The existing condition of the Project site is shown in the photos listed in Appendix E. It is anticipated that the parties most concerned with the visual impacts brought by the Pumping Station will be from Lee On Estate and the future property development of Wu Kai Sha Railway Station. As the existing Ma On Shan Area 108 Pumping Station is maintained as part of the emergency backup measures to minimize the chance of overflow by-pass (please refer to paragraph 5.2.2), its external finishes will be refurbished to match with those of the proposed Pumping Station. Elevations and plan showing the conceptual design of the appearance of the Pumping Station is shown in Appendix F. As the site is surrounded by retaining walls of Sai Sha Road and a nearby substation of CLP, the lower half of the proposed Pumping Station will be out of the sight of most residents. The external finishings and architectural features of the roof and upper half of the Pumping Station is designed with aesthetic consideration to allow the structure to blend with the surroundings. With the implementation of a green roof design (roof covered by green planting), the landscape of the site will be improved when compared with the current concrete paving appearance. Drawings showing the architectural and landscape proposal are attached in Appendix F. Advice on aesthetic aspect is also being sought from ArchSD according to ETWB Technical Circular No. 8/2005.

6 Summary of Potential Environmental Impacts and Mitigation Measures

6.1 The potential environmental impacts and proposed mitigation measures to be incorporated into the design and construction of the upgrading of Ma On Shan Area 108 Pumping Station are summarized in Table 1 below: -

Table 1

Project Stage	Potential Environmental Impact	Mitigation Measure	Relevant Section in the Project Profile
Construction	Minor dust nuisance	(1) Adopt proper working methods such as spray of water (2) Provide wheel washing facilities (3) Control by contract specification	5.1.1
Construction	Water quality impact	(1) Control of construction surface run-off according to ProPECC PN 1/94, EPD’s Practice Note for Professional Persons, Construction Site Drainage (2) Control by contract specification	5.1.2
Construction	Minor noise impact	(1) Erect Temporary hoarding (2) Construction activities will be carried out in daytime as far as possible (3) Comply with relevant regulations and Noise Control Ordinance (4) Use of quiet plant (5) Control by contract specification	5.1.3 / Appendix C
Construction	Minor waste impact	(1) C&D material and waste will be sorted as far as practicable (2) C&D material will be reused on site or disposed of to a designated public fill area (3) Control by contract specification	5.1.4
Construction	Minor landscape and visual impact	(1) Site hoardings will be erected (2) Control by contract specification	5.1.5
Operation	Odour nuisance	(1) All odour sources will be enclosed (2) Deodourizer will be installed to remove odour.	5.2.1
Operation	Water quality & ecology impact	No impact during normal operation. Measures to minimize abnormal situations and the possibility of sewage bypass to Tolo Harbour: (1) Standby pump and mechanical screen will be provided (2) Dual power supply will be provided (3) Emergency storage capacity will be provided (4) Existing pumping station with emergency power generator will serve as a backup (5) Telemetry system will be provided to send signals showing irregularities or any operation problem from the Pumping Station to Shatin Sewage Treatment Works	5.2.2
Operation	Noise impact	(1) Pumps will be enclosed inside the substructure of the Pumping Station (2) Acoustic filters will be installed at the extraction fans of the deodourizers	5.2.3
Operation	Waste generation	(1) Screenings will be enclosed and disposed of to NENT	5.2.4
Operation	Landscape and visual impact	(1) Architectural aspects of the superstructures, including color scheme, types of external finishing and layout of the pumping station is carefully designed taking into account of ArchSD’s advice and the surrounding features. A green roof design is adopted to replace the current concrete paving appearance. (2) The structure is proposed to be a single-storey building.	5.2.5

- END OF TEXT –

APPENDIX A

APPENDIX B

APPENDIX C

NOISE IMPACT ASSESSMENT

Introduction

This section presents an assessment of potential noise impact from the construction and operation of the Project to the nearby sensitive receivers near the proposed site. Appropriate mitigation measures have been recommended, where necessary, to alleviate the potential noise impacts to acceptable levels.

Environmental Legislation, Policies, Plans, Standards and Criteria

Noise impacts were assessed in accordance with the criteria and methodology given in the Technical Memoranda made under the Noise Control Ordinance (NCO).

The Noise Control Ordinance (NCO) provides the statutory framework for noise control. The NCO invokes the following four Technical Memoranda, which define the technical means for noise assessment:

s Technical Memorandum on Noise from Places other than Domestic Premises, Public Places or Construction Sites (IND-TM);

s Technical Memorandum on Noise from Construction Work in Designated Areas (DA-TM);

s Technical Memorandum on Noise from Construction Work other than Percussive Piling (GW-TM); and

s Technical Memorandum on Noise from Percussive Piling (PP-TM).

7 The NCO and the accompanying Technical Memoranda provide a mechanism for assessing noise levels and the statutory power to control noise.

With regard to the assessment of the operational noise impacts, the NCO designates acceptable noise levels for Noise Sensitive Receivers (NSRs) on the basis of an Area Sensitivity Rating (ASR), based on the characteristics of the area within which they are located such as rural, village, low-density residential, or urban. Within these areas, the presence of "influencing factors" (such as the presence of industrial activities or major roads) can further affect the ASR and therefore the acceptable noise level (see Table 1).

Table 1: Area Sensitivity Ratings

Type of Area Containing NSR	Degree to which NSR is affected by Influencing Factor
Type of Area Containing NSR	Not Affected	Indirectly Affected	Directly Affected
Rural Area	A	B	B
Urban Area	B	C	C
Low density residential area consisting of low-rise or isolated high-rise developments	A	B	C
Area other than those above	B	B	C

Construction Activities

Under the GW-TM, noise from construction activity is not restricted during the period 0700 - 1900 hours on weekdays, except Public Holidays. However, the EIAO-TM identifies a daytime general construction noise limit of 75 dB(A) _{Leq (30 minutes)} for domestic premises. This standard was used as an assessment criterion in the construction noise assessment.

Operation Activities

8 9 Operational noise emitted from the proposed pumping station is controlled under the IND-TM. According to the IND-TM, the acceptable Noise Levels (ANLs) for different Area Sensitivity Rating are given in Table 2. The ANL is a function of the type of area within which the NSR is located, and the degree of the effect on the NSR of influencing factors such as major roads and industrial areas. The ANLs for all ASRs are provided in Table 2.

Table 2 : Acceptable Noise Levels (ANLs) (dB(A))

Time Period	ASR A	ASR B	ASR C
Day (0700 to 1900 hours)	60	65	70
Evening (1900 to 2300 hours)	60	65	70
Night (2300 to 0700 hours)	50	55	60

10 The assessment area containing NSRs were regarded as urban area. As such, the study area is defined as ASR “B”. According to Table 2, the ANL for the sensitive receivers would be 65 dB(A) in the daytime/evening and 55 dB(A) at night, which would be used as the criteria for evaluation of the cumulative operational noise impact arising from all items of equipment including new equipment and existing equipment.

Noise Criteria arising from the New Proposed Equipment

11 The EIAO-TM states that all fixed noise sources should be so located and designed that when assessed in accordance with the IND-TM, the level of the intruding noise at the facade of the nearest sensitive use should be at least 5 dB(A) below the appropriate ANL shown in Table 2 of the IND-TM or, in the case of the background being 5 dB(A) lower than the ANL, the predicted noise level should not exceed the background.

Table 3: Noise Criteria for Operational Noise Levels (dB(A))

	ANL	Adopted Noise Criteria
Day (0700 to 1900 hours)	65	60
Evening (1900 to 2300 hours)	65	60
Night (2300 to 0700 hours)	55	50

12 In any event, the ASR assumed in this assessment is for indicative assessment only. It should be noted that fixed noise sources are controlled under section 13 of the NCO. Nothing in this assessment shall bind the Noise Control Authority in assessing noise from these sources upon the receipt of complaints. The Authority shall assess the noise impacts based on the contemporary conditions / situations.

Description of the Environment

The Project site is located at the intersection between Sai Sha Road and Sha On Street.

Assessment Methodology

Construction Phase

The assessment followed the procedures given in the GW-TM. For the assessment of noise from PME, the distance attenuation was estimated using the standard formula:

Distance Attenuation in dB(A) = 20 log D + 8 [where D is the distance in metres]

Sound Power Levels of the equipment were taken from BS5228:Part 1:1997 and Table 3 of the GW-TM. Groups of equipment likely to be employed for each construction task are shown in Annex 1A. The equipment lists are considered realistic and practicable.

Generally, all works would be carried out in the non-restricted hours (0700-1900 hours). In the event that the construction activities are undertaken during restricted hours, it would be the responsibility of the contractor to ensure compliance with the NCO and the relevant TMs. In such cases, the contractor will be required to submit CNP application to the Noise Control Authority and abide by any conditions stated in the CNP, should one be issued. Therefore, the potential noise impacts of construction works within restricted hours are not formally assessed in this assessment report. In order to avoid any potentially adverse noise impact, indicative assessment for representative NSRs have been undertaken.

As the E&M works are mainly installation work, limited number of PME would be used. Also most of the E&M works would be carried out indoors. Thus it is considered that the E&M works would not contribute to the cumulative impact at the NSRs.

Due to the limited space of the Project site, parallel construction tasks with grouping of PME as listed in Annex 1A is considered not practical. The construction tasks as listed in Annex 1A will only be carried out in sequence. The construction noise levels of civil works which are considered to be significant at the NSR has been assessed.

Noise impact was assessed on the basis of the following three conservative assumptions:

· All PME items required for a particular construction activity would be located at the notional source position, which was at a position mid-way between the appropriate geographical centre of the construction site and its boundary nearest to the NSR;

· A +3 dB(A) facade correction was added to the predicted noise levels to account for the facade effect at each NSR; and

· Noise impacts at the nearest sensitive facades of the residential buildings to the source positions were assessed.

Currently, there are no other construction activities proposed to be undertaken concurrently with this Project during construction period. Therefore, no cumulative construction noise impact was anticipated.

Operation Phase

The assessment followed the procedures given in the IND-TM. For the assessment of noise from equipment, the distance attenuation was estimated using the standard formula as mentioned above.

The estimated SWL of other equipment were taken with reference to the specifications of similar items of equipment provided by contractor/plant supplier and other similar projects.

Noise impact was assessed on the basis of the following three conservative assumptions:

· All items (including both duty and standby items) are in operation together;

· A +3 dB(A) facade correction was added to the predicted noise levels to account for the facade effect at each NSR; and

· Noise impacts at the nearest sensitive facades of the residential buildings to the source positions were assessed.

Identification of Environmental Impacts

Major potential noise impacts arising from the Project would be:

· Construction; and

· Operation noise.

Noise Sensitive Receivers (NSRs)

Potential noise sensitive receivers (NSRs) have been identified in accordance with the criteria set out in the EIAO TM and through site inspection. The representative sensitive receivers are shown in Table 5. Locations of the NSRs are shown in Annex 3.

Table 5: NSR identified under this Project

NSR	Description	Type of Use	Approx. Distance from Pumping Station Boundary (m)
SR1	Lee On Estate	Residential	75
SR2	Monte Vista	Residential	130
SR3	Wu Kai Sha Village	Residential	130
SR4	Wu Kai Sha Station Property Development	Residential	70

Since SR4 is nearest to the Project Site, it is considered as the most critical case and put into detailed assessment.

Prediction and Evaluation of Environmental Impacts

Construction Phase

13 As indicated in Annex 1A, the major noisy construction task would be Site Clearance and Set Up Site Office with total SWL of 120 dB(A).

14 15 With a plan distance of 70m, the Distance Attenuation is 45 dB(A). With an addition of 3 dB(A) façade effect, the predicted noise levels at SR4 were in the range of 77 to 78 dB(A). The cumulative noise level at SR4 would exceed the noise criteria of 75 dB(A). As a result, noise mitigation measures would be required.

Operation Phase

16 The plant inventory and the SWL are summarized in Annex 2. The plant inventory used for the prediction of operation noise impact is practical and realistic. To represent the worst-case scenario, all items of equipment were assumed to operate continuously 24 hours a day and the directivity was not included in the calculation.

17 18 Facilities that would be housed / enclosed in concrete structure were assumed to have a 20 dB(A) reduction of noise emitted from the sources due to transmission loss of the wall. Due to the facade effect, a positive 3 dB(A) has been added to predicted noise levels at the NSRs. For determining the distance correction factors, the distances between the probable source positions and the NSRs were considered.

19 The predicted noise level at SR4 is 39 dB(A), which would meet both the daytime and night-time criteria of 60 dB(A) and 55 dB(A) respectively. Thus no mitigation measures would be required for the new equipment. Details of the calculation are presented in Annex 2.

Mitigation of Potential Adverse Environmental Impacts

Construction Phase

Use of Quiet PME

To reduce construction noise impacts, silenced type of air compressor, which are in accordance with BS5228:Part 1:1997, is recommended. The total SWL of PME for each construction activities were calculated and are summarized in Annex 1B. The equipment lists are considered realistic and practicable.

A detailed calculation of construction noise impact for the mitigated scenario is presented in Annex 1B. The largest total SWL is 116 dB(A). With a Distance Attenuation of 45 dB(A) and addition of 3 dB(A) façade effect, the SPL will be 74 dB(A). The results indicate that the cumulative construction noise levels predicted at SR4 would comply with the daytime noise criterion of 75 dB(A).

Good Site Practice

In addition to quiet PME, good site practices listed below should be adopted to further abate any residual impacts during the construction phase of the Project and should be included in the contract:

· Only well-maintained plant should be operated on-site and plant should be serviced regularly during the construction phase;

· Silencers or mufflers on construction equipment should be utilised, if found necessary, to further reduce noise, and should be properly maintained during the construction phase;

· Mobile plant should be sited as far away from NSRs as possible;

· Machines and plant (such as trucks) that may be in intermittent use should be shut down between work periods or should be throttled down to a minimum;

· Plant known to emit noise strongly in one direction, should, where possible, be orientated so that the noise is directed away from nearby NSRs; and

· Material stockpiles and other structures should be effectively utilised, wherever practicable, in screening noise from on-site construction activities.

Operation Phase

The assessment results indicated that during operation phase of the Project, the predicted levels at SR4 would satisfy the requirement of the EIAO-TM and hence mitigation measures would not be required.

Conclusions

Construction Phase

With the adoption of quiet PME and good site practices, the predicted construction noise levels at representative NSRs would not exceed the relevant noise criteria.

Operation Phase

The noise impacts associated with the operation of the Project were also assessed. The assessment result indicated that the unmitigated operation noise levels predicated at representative NSRs would comply with both the daytime and nighttime criteria. Thus no adverse noise impact arising from the Project would be expected.

Annex 1A	Powered Mechanical Equipment (PME) for Different
	Construction Tasks during Normal Daytime Working Hours
	(Un-Mitigated Scenario)

Site Clearance and Set Up Site Office
Powered Mechanical Equipment	Reference	No. Items	SWL/Item	On-time	Barrier	Total SWL
(PME)			dB(A)	%	dB(A)	dB(A)
Breaker, excavator mounted	C2/11 #	1	115	100%	0	115
Excavator	C3/97#	1	105	100%	0	105
Dump Truck	C9/19#	1	102	100%	0	102
Air compressor	C7/40#	1	117	100%	0	117
Bulldozer	C9/2 #	1	104	100%	0	104
Generator	C7/45#	1	95	100%	0	95
					Total =	120

Excavation Work
Powered Mechanical Equipment	Reference	No. Items	SWL/Item	On-time	Barrier	Total SWL
(PME)			dB(A)	%	dB(A)	dB(A)
Dump truck	C9/19#	1	102	100%	0	102
Excavator	C3/97#	1	105	100%	0	105
Generator	C7/45#	1	95	100%	0	95
Air compressor	C7/40#	1	117	100%	0	117
Breaker, excavator mounted	C2/11#	1	115	100%	0	115
					Total =	119

Concreting Work
Powered Mechanical Equipment	Reference	No. Items	SWL/Item	On-time	Barrier	Total SWL
(PME)			dB(A)	%	dB(A)	dB(A)
Mobile Crane	C7/114 #	1	101	100%	0	101
Concrete Lorry Mixer	C6/23#	1	100	100%	0	100
Bar Bender and cutter	CNP 021@	1	90	100%	0	90
Concrete pump	C6/36#	1	106	100%	0	106
Poker (Power Rating limited to 2kW)	C6/32#	3	100	100%	0	105
Chipper, hand held	C6/45#	1	111	100%	0	111
Saw, circular, wood	C7/78#	1	106	100%	0	106
Generator	C7/45#	1	95	100%	0	95
Air Compressor	C7/40#	1	117	100%	0	117
					Total =	119
Miscellaneous Work
Powered Mechanical Equipment	Reference	No. Items	SWL/Item	On-time	Barrier	Total SWL
(PME)			dB(A)	%	dB(A)	dB(A)
Excavator	C3/97#	1	105	100%	0	105
Mobile Crane	C7/114#	1	101	100%	0	101
Lorry	C7/122#	1	112	100%	0	112
Compactor	C3/118#	1	108	100%	0	108
Generator	C7/45#	1	95	100%	0	95
Air Compressor	C7/40#	1	117	100%	0	117
Roller	C8/25#	1	96	100%	0	96
					Total =	119
Note:
# - BS 5228 Part 1 :1997
@ - Table 3 of PP-TM

Annex 2 : Calculation of Operational Noise Levels at NSR - Unmitigated

(1) Predicted Cumulative Noise Levels at SR4
Items^(#)	No.	Remark	Ref.	SWL	Total SWL dB(A)	Enclosed	Enclosure Reduction ^(*)	Distance	Distance Attenuation	facade correction	SPL at NSR
	of Items			/Item			dB(A)	(m)	d B(A)	d B(A)		10^(SPL/10)

Submersible Pump	4	3 duty + 1 standby	CNP283	85	91	enclosed	-20	70	-45	3	29	816.3265306

Exhaust Fan (with acoustic lourve)^(@)	4	2 CLP + 2 Deodourizer	Estimate	73	79			62	-44	3	38	6565.633137

Mechanically raked fine screen	2	1 duty + 1 standby	Estimate	89	92	enclosed	-20	70	-45	3	30	1025.259768
										Total SPL =	39	8407.219436

Remarks:
^(*): Enclosure Reduction is the reduction of SWL due to the enclosure for the equipment in reinforced concrete structure.
(@): The standard requirement in exhaust fan with acoustic lourve specified in previous delivered projects is max. 65 dB(A) measured 1m from the acoustic lourve.
Since the Pumping Station is of a size approximately 15m in width, a reduction of 8m in distance between sound source and receiver is assumed.
(#) : Only those noisy equipment are included in the table. Other equipment (e.g. monorail, CCTV, etc) which does not have significant noise impact are not included.