6.                       WASTE management

 

6.1                   Introduction

                                                          

6.1.1             This waste assessment examines the type, quantity, quality and timing of potential sources of waste that will arise during the construction and operation stages of the proposed secondary drainage channels. It identifies potential environmental impacts associated with their handling and disposal. Options for avoidance, minimization, reuse, recycling, treatment, storage, collection, transport and disposal of such wastes are examined.

 

6.1.2             Where unacceptable impacts are identified, appropriate mitigation measures and good site practices are recommended. Disposal options will be outlined for each type of waste, and the responsibilities for disposal or recycling discussed.

 

6.1.3             The main objectives of the waste assessment are to:

 

(i)             identify the sources, volumes, quality and timing of wastes arising from the construction activities;

 

(ii)           recommend construction waste management requirements in terms of minimisation through project design, construction method, and site location, identification of reuse and recycling opportunities and the responsible party for each step of the waste management process; and

 

(iii)          recommend disposal sites and routes for different types of wastes unsuitable for reuse or recycling.

 

6.1.4             The recommendations will be carried out in accordance with the current requirements for waste management.

 

6.2                   Relevant Legislation, Policies, Standards and Criteria

 

Legislation, Circulars, Guidelines related to Waste Management

 

6.2.1             The following legislation relates to the handling, treatment and disposal of wastes and will be used in assessing potential impacts:

 

·              Environmental Impact Assessment Ordinance (Cap.499)

·              Waste Disposal Ordinance (Cap.354)

·              Waste Disposal (Chemical Waste) (General) Regulation

·              Land (Miscellaneous Provisions) Ordinance (Cap.28)

·              Public Health and Municipal Services Ordinance (Cap.132) – Public Cleansing and Prevention of Nuisances Regulation

·              Dumping at Sea Ordinance (Cap.466)

 

6.2.2             The following documents, circulars and guidelines which relate to waste management and disposal will also be referred to during this study:

 

·              Technical Memorandum on Environmental Impact Assessment Process (TM-EIA) - Annex 7 - Criteria for Evaluating Waste Management Implications and Annex 15 - Guidelines for Assessment of Waste Management Implications

·              Code of Practice on the Packaging, Labelling and Storage of Chemical Wastes, EPD (1992)

·              WBTC No. 2/93 - Public Dumps

·              WBTC No. 2/93B - Public Filling Facilities

·              WBTC No. 16/96 - Wet Soil in Public Dumps

·              WBTC No. 4/98 & 4/98A - Use of Public Fill in Reclamation and Earth Filling Projects

·              WBTC No. 25/99, 25/99A & C - Incorporation of Information on Construction and Demolition Material Management in Public Works Subcommittee Papers

·              WBTC No. 12/2000 - Fill Management

·              WBTC No. 19/2001 - Metallic Site Hoardings and Signboards

·              WBTC No. 12/2002 - Specifications Facilitating the Use of Recycled Aggregates

·              ETWB TCW No. 33/2002 - Management of Construction and Demolition Material including Rock

·              ETWB TCW No. 34/2002 - Management of Dredged/Excavated Sediment

·              ETWB TCW No. 24/2004 - Specifications Facilitating the Use of Concrete Paving Units Made of Recycled Aggregates

·              ETWB TCW No. 31/2004 - Trip-ticket System for Disposal of Construction & Demolition Material

·              ETWB TCW No. 19/2005 - Environmental Management on Construction Sites

 

Sediment Quality

 

6.2.3             The procedures for assessing and classifying sediment and the management framework of disposing such sediment are outlined in the ETWB TCW No. 34/2002.  The sediment quality criteria for the classification of sediment are presented below in Table 6.1.

Table 6.1

Sediment Quality Criteria for the Classification of Sediment

 

Contaminants

Lower Chemical Exceedance Level (LCEL)

Upper Chemical Exceedance Level (UCEL)

Metal (mg/kg dry wt.)

Cadmium (Cd)

1.5

4

Chromium (Cr)

80

160

Copper (Cu)

65

110

Mercury (Hg)

0.5

1

Nickel (Ni)*

40

40

Lead (Pb)

75

110

Silver (Ag)

1

2

Zinc (Zn)

200

270

Metalloid (mg/kg dry wt.)

Arsenic (As)

12

42

Organic-PAHs (mg/kg dry wt.)

Low Molecular Weight PAHs

550

3160

Low Molecular Weight PAHs

1700

9600

Organic-non-PAHs (mg/kg dry wt.)

Total PCBs

23

180

Organometallics (mg TBT/L in Interstital water)

Tributyltin*

0.15

0.15

 

                    * The contaminant level is considered to have exceeded the UCEL if it is greater than the value shown.

                    PAH= polyaromatic hydrocarbon

                    PCB= polychlorinated biphenyl

 

6.2.4             The sediment is classified into 3 categories based on its contaminant levels:

 

§               Category L:   Sediment with all contaminant levels not exceeding the Lower Chemical Exceedance Level (LCEL). The material must be dredged, transported and disposed of in a manner which minimizes the loss of contaminants either into solution or by resuspension.

 

§               Category M:  Sediment with any one or more contaminant levels exceeding the LCEL and none exceeding the Upper Chemical Exceedance Level (UCEL). The material must be dredged and transported with care, and must be effectively isolated from the environment upon final disposal unless appropriate biological tests demonstrate that the material will not adversely affect the marine environment.

 

§               Category H:   Sediment with any one or more contaminant levels exceeding the UCEL. The material must be dredged and transported with great care, and must be effectively isolated from the environment upon final disposal.

 

6.2.5             Depending on the level of contamination, disposal options for the excavated sediments included the following:

 

§               Type 1 – Open Sea Disposal

§               Type 1 – Open Sea Disposal (Dedicated Sites)

§               Type 2 – Confined Marine Disposal

§               Type 3 – Special Treatment / Disposal

 

6.3                   Assessment Methodology

 

6.3.1             Reference has been made to the methodology laid out in the TM-EIA (Annexes 7 and 15). The principal legislation regulating waste is the Waste Disposal Ordinance (WDO) (Cap.354).

 

6.3.2             Procedures on the assessment and classification of sediment, the sampling and testing procedures and the disposal arrangements are listed out in the ETWB TCW No. 34/2002 – Management of Dredged/Excavated Sediment.

 

6.3.3             The land contamination assessment is investigated in accordance with ProPECC Note PN 3/94 – Contaminated Land Assessment and Remediation and EPD’s Guidance Notes for Investigation and Remediation of Contaminated Sites for Petrol Filling Stations, Boatyards, and Car Repair/Dismantling Workshops.

 

6.4                   Sources and Types of Waste arising from the Project

 

Introduction

 

6.4.1             The proposed drainage channel works include the following construction activities:

 

·              site clearance and demolition of temporary structures to form channels and works area;

·              excavation and formation of channel;

·              construction of channel by installing gabions, mattress linings, or pre-fabricated grasscrete panels;

·              construction of maintenance / access roads, footbridges, box culverts, installation of pipes and other ancillary structures; and

·              planting and landscaping works.

 

6.4.2             Construction activities will result in the generation of a variety of Construction and Demolition (C&D) materials. The C&D materials are usually mixed consisting of inert components (public fill) such as soil, rock, concrete, brick, and asphalt, etc and non-inert components (C&D waste) comprising metal, timber, paper, plastic and general garbage. Chemical and municipal wastes may also arise as a result of construction activities. The likely waste generated from the construction of the proposed drainage channels can be classified into the following categories:

 

·              site clearance / demolition materials;

·              excavated materials;

·              chemical waste; and

·              general works waste.

 

6.4.3             During operation period, only a small amount of excess silty material and vegetation will be generated from the maintenance of the channels during dry season.

 

6.4.4             Handling and disposal of the above mentioned wastes may cause environmental impacts and nuisance if it is not properly managed.

 

6.4.5             Alternative solutions to flooding problem at Lin Ma Hang instead of a bypass channel have been recommended under this Project to avoid impacts on the valuable ecological resources in the area. The revised works for Lin Ma Hang (LMH01) comprise the reconstruction of several access bridges, localised stream bank improvement, short section of gabion channel at downstream end as well as improvement to the existing security grille at the outlet of Lin Ma Hang stream. It also includes the installation of several flood alarm system in the village. As a consequence, construction activities are substantially scaled down. Given the small scale works, the amount of C&D materials generated from LMH01 is expected to be limited.

 

Site Clearance / Demolition Materials

 

6.4.6             Site clearance and demolition works will be required, thus generating unwanted material during construction.

 

6.4.7             The proposed drainage channels pass through village areas, agricultural land, bare ground, open storage and temporary structures. Site clearance / demolition works will involve the removal of vegetation (mainly grasses and shrubs) and some trees, demolition of structures (mostly temporary structures and a few village houses) and removal of a small portion of available topsoil.

 

6.4.8             Demolition of temporary structures and houses will generate concrete rubbles, plastics, metals, glasses, asphalts, wood and refuse. Potential for reuse of such materials on site is very limited.

 

6.4.9             Some good quality reusable topsoil is expected from site clearance works across agricultural land. This can be stockpiled and used later in final landscaping works, thus saving costs for such works and transportation and environmental impacts of disposal. Some suitable material may also be generated from excavation of the streams. This material can be mixed with the soil for landscaping use.

 

6.4.10         Estimated quantities of C&D materials generated during site clearance are tabulated in Table 6.2.

 

Table 6.2

Estimated Quantities of C&D Materials generated during Site Clearance

 

Channel

Amount of C&D Materials (m3)

Inert Soft C&D Material

Rock (Grade III or below)

C&D Waste

Total C&D Materials

MUP03

550

10

140

700

MUP04A&B

720

10

180

910

MUP05

5,500

50

1,410

6,960

Total

6,770

70

1,730

8,570

 

6.4.11         No land resumption is expected for the improvement works at LMH01. The reconstruction of the access bridges and localised stream bank improvement would generate a negligible amount of inert C&D material (approximately 40 m3) consisting mainly of broken concrete, rubbles, asphalt and the like. A very small quantity of non-inert C&D materials such as metal railings, vegetation will be generated. Potential for reuse of these materials on-site is also limited.

 

Excavated Materials

 

6.4.12         The majority of C&D materials generated from the Project will arise during the formation of the channels. It is expected that most of this material will be muddy deposits, top soil, sand, gravel and some underlying rock.

 

6.4.13         Some suitable material may be generated from excavation of the streams. This material can be mixed with topsoil and stockpiled for later landscaping use. Rocks, cobbles and other suitable material from existing stream beds should be stockpiled for later reused for backfilling or as stream bed materials subject to the size requirement.

 

6.4.14         A preliminary estimate of the C&D materials generated during channel excavation and construction and the breakdown is shown in Table 6.3.

 

Table 6.3

Estimated Quantities of C&D Materials generated during Channel Excavation and Construction

 

Channel

Amount of C&D Materials (m3)

Sediment

Inert Soft C&D Material

Rock (Grade III or below)

C&D Waste

Total C&D Materials

MUP03

0

3,200

60

10

3,270

MUP04A

150

5,800

100

50

6,100

MUP04B

0

1,200

30

10

1,240

MUP05

0

46,800

920

200

47,920

Total

150

57,000

1,110

270

58,530

 

6.4.15         The potential for reuse of suitable excavated materials should be explored at the early stage of the project.

 

Sediment Quality

 

6.4.16         A preliminary sediment quality characterisation survey was carried out in January 2005 as part of the Ground Investigation (GI) Study under this Project to characterise the level of contamination in the sediment of the existing stream course. The locations of the sample are shown in Figure 6.1.

 

6.4.17         The proposed sampling locations are chosen to verify the extent of contaminated sediment in the natural stream. The sampling locations are chosen in the natural stream bed, excluding all existing engineering channels within the site, assuming that any contaminated sediment beneath the existing engineering channels was removed during their construction. Based on the latest design, no sediment will be excavated from MUP03, MUP04B, MUP05 and LMH01.

 

6.4.18         All samples were tested for all contaminants (except Tributyltin) by a HOKLAS laboratory with analytical methods as stipulated in ETWB TCW No. 34/2002 or in-house methods approved by EPD.

 

6.4.19         The chemical testing results of the sediment samples are shown in Table 6.4 with the details presented in Appendix C. The results indicated that the sediments are considered as Category L material except for Arsenic (As), where Category M materials are found.

 

Table 6.4

Results of the Sediment Testing

 

Contaminants (mg/kg unless stated otherwise)

Sample Location ST13

Sample Location ST14

0 – 1m

Up to 2m

Up to 3m

0 – 1m

Up to 2m

Up to 3m

Cadmium (Cd)

< 0.1

0.5

0.3

< 0.1

0.2

< 0.1

Chromium (Cr)

2.2

< 1

2.3

3.6

1.3

< 1

Copper (Cu)

2.4

2.6

7.6

3.1

5.4

2.7

Nickel (Ni)

1.4

2.3

4.5

2.1

3.9

2.3

Lead (Pb)

14

69

53

21

7.8

4.4

Zinc (Zn)

25

38

45

130

68

46

Mercury (Hg)

< 0.05

< 0.05

0.07

< 0.05

< 0.05

< 0.05

Arsenic (As)

7.1

4.6

14

1.8

6.6

4.0

Silver (Ag)

< 0.1

< 0.1

0.1

< 0.1

0.2

< 0.1

LMW PAHs (mg/kg)

< 55

< 55

< 55

< 55

< 55

< 55

HMW PAHs (mg/kg)

< 170

< 170

< 170

< 170

< 170

< 170

Total PCBs (mg/kg)

< 2

< 2

< 2

< 2

< 2

< 2

Notes:

LMW PAHs: low molecular weight polyaromatic hydrocarbon

HMW PAHs: high molecular weight polyaromatic hydrocarbon

PCB: polychlorinated biphenyl

Values in BOLD indicate Category M sediment under ETWB TCW No. 34/2002

 

6.4.20         The reported level of Arsenic in one of the sample collected at sampling location ST13 is in MUP05 where excavation of stream bed was previously considered necessary. Subsequent to design review and changes, MUP05 is proposed to be a ‘two-stage’ channel where the stream bed will not be removed hence the sediment will be left in-situ. As such, the sediment testing result collected at MUP05 could only be used to broadly indicate the likely contamination level of the sediment. The results indicate that most of the contaminant levels are considered as Category L. In accordance with ETWB TCW No. 34/2002, Category L sediment should be disposed as Type 1 – Open Sea Disposal.

 

6.4.21         No sediment sample was collected at MUP04A as there are no evidence of contaminating sources from nearby land uses both current and historical which consist of active / inactive agricultural land.

 

6.4.22         Given the small quantity of sediment (about 150 m3) likely to be generated from MUP04A, it is proposed that the excavated sediment should be reuse on-site as backfilling material to minimize off-site disposal.

 

Chemical Waste

 

6.4.23         Wastes classified as chemical waste are listed in the Waste Disposal (Chemical Waste) (General) Regulation. Where the construction processes produce chemical waste, the contractor must register with EPD as a chemical waste producer. In general, chemical waste would mainly arise from maintenance of construction equipment. These may include the following items:

 

·              scarp batteries or spent acid/alkali from their maintenance;

·              used engine oils, hydraulic fluids and waste fuel;

·              spent mineral oils/cleaning fluids from mechanical machinery; and

·              spent solvents/solutions from equipment cleaning activities.

 

6.4.24         Chemical wastes pose serious environmental and health and safety hazards if not stored and disposed of in an appropriate manner as outlined in the Chemical Waste Regulation. These hazards include:

 

·              toxic effects to works;

·              adverse effects on water quality from spills; and

·              fire hazards.

 

6.4.25         The amount of chemical waste cannot be accurately predicted at this stage since it largely depends on the contractor’s housekeeping measure. The amount is anticipated to be small and it is recommended that the contractors should implement good housekeeping measures to minimise the amount of chemical waste generated.

 

General Works Waste

 

6.4.26         The following wastes will be generated during general construction activities:

 

·              concrete waste;

·              wooden materials; and

·              municipal waste.

 

Concrete Waste

 

6.4.27         As the channel structures and linings will be constructed mainly from gabions, mattress and/or pre-fabricated grasscrete panels as well as using natural stream bed, the use of concrete will be limited. Of the volume of concrete supplied, it is expected that only a very small percentage of the concrete used will be lost to waste.

 

Wooden Materials

 

6.4.28         Different kinds of wooden materials are essential to the construction project, such as wooden boards used as falsework and formwork for concrete structures, erection of site boundaries, as well as bamboo for scaffolding. Wooden materials are important and valuable resources.

 

6.4.29         Site fencing may be necessary to separate the construction works from the public and to reduce construction nuisance such as noise to nearby sensitive receivers. In this case metal fencing or building panels to provide site fencing should be used. Attention should be paid to WBTC No. 19/2001 – Metallic Site Hoardings and Signboards to reduce the amount of timber used on construction sites.

 

Municipal Waste

 

6.4.30         Municipal waste will be generated by the site staff and construction workers during the construction period. This includes food scraps, papers, plastic containers, packaging materials, etc. The amount of municipal waste that may be produced is dependent on size of workforce at site.

 

6.4.31         The storage of general refuse has the potential to give rise to a variety of adverse environmental impacts. These include odour if waste is not collected frequently, water quality impacts if waste enters water bodies and visual impact from windblown litters. The refuse may attract pests and vermin if the storage areas are not well maintained and cleaned regularly. In addition, disposal of waste at sites other than approved waste transfer or disposal facilities can also lead to environmental impacts.

 

6.4.32         Handling and disposal of general refuse should cope with the presence of peak workforce during the construction period. Provided that the refuse is stored and transported in accordance with proper practices and disposed at approved disposal facilities, potential environmental impact is not expected.

 

6.4.33         A summary of the main C&D materials and wastes expected to arise from the Project and the estimated quantities for each type of C&D materials is presented in Tables 6.5 and 6.6 respectively.

 

Table 6.5

Types of C&D Materials and Wastes Generated by the Proposed Works

 

Area

Major Activities

Waste Type

Temporary and permanent works area of all drainage channel

Site clearance and demolition of structures

Vegetation, garbage, topsoil, concrete and other inert materials

Permanent works area not part of existing streams

Excavation

 

Soil, rock and other inert materials

Permanent works area that are part of existing streams

Excavation

 

Soil, rock and other inert materials

Sediment

All

Construction of channel structures / general site activities

Chemical waste, concrete waste, scrap metal, wood and other non-inert waste

 

 

Table 6.6

Summary of the Quantities of C&D Materials and Wastes Arising from the Proposed Channels

 

Channel

Estimated Quantities* (m3)

Sediment
(see Note 1)

Inert Soft C&D Material
(see Note 2)

Rock (Grade III or below)
(see Note 3)

C&D Waste

Chemical Waste

General Works Waste

Total

MUP03

0

3,750

70

150

Minimum amount (see Note 4)

Minimum amount (see Note 5)

3,970

MUP04A

150

6,520

110

230

7,010

MUP04B

0

1,200

30

10

1,240

MUP05

0

52,300

970

1,610

54,880

Total

150

63,770

1,180

2,000

67,100

Approximate Timing*

end 2007 – mid 2011

 

Notes:

*      Tentative construction programme of end 2007 – mid 2011 will be subject to further changes. The estimated quantities are based on preliminary design of the proposed channel works and the available ground investigation data. The waste arising will largely depend on the contractor works programme and activities. The contractor will be required to provide detailed estimation of all the C&D materials and waste generated on-site using a Monthly / Yearly Waste Flow Table as required under ETWB TCW No. 19/2005.

1         Sediment should be reused on-site as backfilling material.

2         Topsoil and suitable materials should be stockpiled for later reuse in this or other projects subject to approval by relevant parties in accordance with the ETWB TCW No. 31/2004. The amount of materials that can be reuse in this Project will be examined further during the detailed design stage.

3         Suitable rock should be reused as backfilling materials, rip-rap linings or for filling of gabions.

4         The amount of chemical waste will be dependent on the contractor’s on-site maintenance programme and the number of equipment and vehicles used on-site. Chemical waste should be collected by licensed contractor and properly disposed of at approved chemical waste treatment facilities (e.g. the Chemical Waste Treatment Centre at Tsing Yi). Chemical waste will be generated throughout the construction period.

5         The amount of general works waste will dependent on the contractor’s operating procedures and housekeeping practices as well as the size of the workforce on-site. All such wastes should be sorted, reused and recycled before disposal at designated outlets. General works waste will be generated throughout the construction period.

 

6.5                   Mitigation Measures

 

General

 

6.5.1             The HKSAR Government's construction and demolition waste management policy follows the same hierarchy as for other wastes i.e. in order of desirability: avoidance, minimisation, recycling, treatment and safe disposal of waste. During the construction period the contractor, engineer and environmental assessors (Environmental Team, Independent Environmental Check) should work closely together with a view to reduce the volumes of materials requiring removal and final disposal.

 

6.5.2             Upon appointment, the main contractor of each construction contract should prepare and implement an Environmental Management Plan (EMP) in accordance with ETWB TCW No. 19/2005 – Environmental Management on Construction Sites which should describe the arrangements for avoidance, reuse, recovery, recycling, storage, collection, treatment and disposal of different categories of waste to be generated from the construction activities. Such a management plan should incorporate site specific factors, such as the designation of areas for segregation and temporary storage of reusable and recyclable materials. The EMP should be submitted to the Engineer for approval. The contractor should implement the waste management practices in the EMP throughout the construction stage of the Project. The EMP should be reviewed regularly and updated (preferably monthly) by the contractor. The EMP should take into account the recommended mitigation measures in the EIA Report.

 

6.5.3             The contractor also should refer to the Construction and Demolition Material Management Plan (C&DMMP) conducted for this Project (Appendix D1) to facilitate him in the preparation of the EMP of the contract. The C&DMMP provides the ways to minimize the generation and maximize the reuse of the C&D material at the early stage of the Project. The C&DMMP is to be endorsed by DSD’s Vetting Committee and approved by the Public Fill Committee (PFC). DSD’s Vetting Committee will monitor the implementation of the C&DMMP and report to Public Fill Committee in accordance with ETWB TCW No. 33/2002 during construction.

 

6.5.4             Training of construction staff should be undertaken by the contractor about the concept of site cleanliness and appropriate waste management procedures. The contractor should develop and provide toolbox talk for on-site sorting of C&D materials to enhance worker’s awareness in handling, sorting, reuse and recycling of C&D materials. Requirements for staff training should be included in the EMP.

 

6.5.5             Good planning and site management practice should be employed to eliminate over ordering or mixing of construction materials to reduce wastage. Proper storage and site practices will minimise the damage or contamination of construction materials.

 

6.5.6             Where waste generation is unavoidable, the potential for recycling or reuse should be rigorously explored. If waste cannot be recycled, disposal routes described in the EMP should be followed. A recording system for the amount of wastes generated, recycled and disposed (including the disposal sites) should be implemented. In order to monitor the disposal of C&D material and solid wastes at public filling facilities and landfills and to control fly-tipping, a trip-ticket system should be included. One may make reference to ETWB TCW No. 31/2004 for details.

 

6.5.7             Regular cleaning and maintenance of the waste storage area should be provided.

 

On-site Sorting, Reuse and Recycling

 

6.5.8             All waste materials should be segregated into categories covering:

 

·              excavated materials suitable for reuse on-site;

·              excavated materials suitable for public filling facilities;

·              remaining C&D waste for landfill;

·              chemical waste; and

·              general refuse for landfill.

 

6.5.9             Proper segregation and disposal of construction waste should be implemented. Separate containers should be provided for inert and non-inert wastes.

 

6.5.10         Sorting is important to recover materials for reuse and recycling. Specific area should be allocated for on-site sorting of C&D materials and to provide a temporary storage area for those sorted materials such as metals, concrete, timber, plastics, glass, excavated spoils, bricks / tiles and waste papers. If area is limited, all C&D materials should at least be sorted on-site into inert and non-inert components. Non-inert materials (C&D waste) such as bamboo, timber, vegetation, packaging waste and other organic materials should be reused and recycled wherever possible and disposed of to designated landfill only as a last resort. Inert materials (public fill) such as concrete, stone, clay, brick, soil, asphalt and the like should be separated and reused in this or other projects (subject to approval by the relevant parties in accordance with the ETWB TCW No. 31/2004) before disposed of at a public filling facility operated by Civil Engineering and Development Department (CEDD). Steel and other metals should be recovered from demolition waste stream and recycled.

 

6.5.11         The reuse of inert materials such as soil, rock and broken concrete should be maximised.  Waste should be separated into fine, soft and hard materials.  With the use of a crusher coarse material can be crushed to make it suitable for use as fill material where fill is required in the works.  This minimises the use of imported material and maximises use of the C&D material produced.

 

6.5.12         Prior to export of material from the site, the potential for it to be reused should be assessed.  With the exception of excavated clay most C&D material can easily be reused.  Waste separation methods should be followed to ensure that C&D waste is separated at source.  Suitable soft materials should be used for landscaping and grading of embankments. Fine material should be separated out and used as topsoil.

 

6.5.13         The feasibility of using recycled aggregates in lieu of virgin materials should be rigorously considered during the detailed design and construction stages as stipulated in WBTC No. 12/2002 and ETWB TCW No. 24/2004. In general, recycled aggregates are suitable for use as fill materials in earthworks, road sub-base formation, and drainage works. Recycled aggregates can also be used in concrete (up to Grade 35) for mass concrete walls and other minor structures such as planter boxes, toe wall planters and pavement, etc.

 

6.5.14         Recycled inert C&D material should be used in the works as sub-bases for access roads and footpaths of the proposed channels. Recycled aggregates should be considered for use in concrete as outlined in the above mentioned technical circulars.  Some recycled rock material can be reused in the gabions, as rock fill or as stream bed material. This is dependent on size of rock fragments but can be achieved by appropriate use of a crusher.

 

Site Clearance / Demolition Materials

Excavated Materials

 

6.5.15         All C&D materials should be sorted on-site into inert and non-inert components by the contractor. Non inert materials (C&D waste) such as wood, glass and plastic should be reuse and recycle before disposal to a designated landfill as a last resort (currently assume to be the nearby NENT Landfill). Inert materials (public fill) such as soil, rubble, sand, rock, brick and concrete should be separated and where appropriate broken down to size suitable for subsequent filling. Suitable C&D material should be use as pipe bedding or for backfilling of retaining walls, box culvert and formation of channel embankments. Excavated rocks from existing streams should be reuse for rip-rap lining and gabion lining. Inert materials should be reused on-site or in other projects approved by relevant parties in accordance with the ETWB TCW No. 31/2004 before disposed of at public filling facilities. Steel and other metals should be recovered from C&D materials and recycled.

 

6.5.16         Excavated sediment from existing stream should be reuse on-site as backfilling material.

 

6.5.17         Good quality reusable topsoil should be stockpiled for later landscaping works. Stockpiles should be less than 2 m in height, formed to a safe angle of repose and hydroseeded or covered with tarpaulin to prevent erosion during the rainy season and to minimise dust generation.

 

6.5.18         Control measures for temporary stockpiles on-site should be taken in order to minimize the noise, generation of dust, pollution of water and visual impact. These measures include:

 

·              surface of stockpiled soil should be regularly wetted with water especially during dry season;

·              disturbance of stockpiled soil should be minimized;

·              stockpiled soil should be properly covered with tarpaulin especially when heavy rain storms are predicted;

·              stockpiling areas should be enclosed where space is available;

·              stockpiling location should be away from the water bodies; and

·              an independent surface water drainage system equipped with silt traps should be installed at the stockpiling area.

 

6.5.19         The identification of final disposal sites for C&D materials generated by the construction works will be considered during the detailed design stage of the Project when the volume and types of C&D materials can be more accurately estimated. The Public Fill Committee of CEDD should be consulted on designated outlets (e.g. public filling area) for public fill, whilst EPD should be consulted on landfills for C&D waste. Marine Fill Committee of CEDD should be consulted on the marine disposal sites of the excavated sediment if needed. Disposal of C&D waste to landfill must not have more than 50% (by weight) inert material. The C&D waste delivered for landfill disposal should contain no free water and the liquid content should not exceed 70% by weight.

 

6.5.20         In order to avoid dust or odour impacts, any vehicle leaving a works area carrying C&D waste or public fill should have their load covered up before leaving the construction site.

 

6.5.21         C&D materials should be disposed of at designated public filling facilities or landfills. Disposal of these materials for use at other construction projects is subject to the approval of the EPD, Engineer and/or other relevant authorities, such as LandsD, PlanD, etc. Furthermore, unauthorized disposal of C&D materials in particular on private agricultural land is prohibited and may be subject to relevant enforcement and regulating actions. The disposal of public fill and C&D waste will be controlled through trip-ticket system in accordance with ETWB TCW No. 31/2004.

 

Chemical Waste

 

6.5.22         Where the construction processes produce chemical waste, the contractor must register with EPD as a chemical waste producer. Wastes classified as chemical wastes are listed in the Waste Disposal (Chemical Waste) (General) Regulation. These wastes are subject to stringent disposal routes. EPD requires information on the particulars of the waste generation processes including the types of waste produced, their location, quantities and generation rates. A nominated contact person must be registered with EPD. An updated list of licensed chemical waste collector can be obtained from EPD.

 

6.5.23         Storage, handling, transport and disposal of chemical waste should be arranged in accordance with the Code of Practice on the Packaging, Labelling and Storage of Chemical Wastes published by EPD, and should be collected by a licensed chemical waste collector.

 

6.5.24         Suitable containers should be used for specific types of chemical wastes, containers should be properly labelled (English and Chinese in accordance with instructions prescribed in Schedule 2 of the Regulations), resistance to corrosion, stored safely and closely secure. Stored volume should not be kept more than 450 liters unless the specification has been approved by the EPD. Storage area should be enclosed by three sides by a wall, partition of fence that is at least 2 m height or height of tallest container with adequate ventilation and space.

 

6.5.25         Hard standing, impermeable surfaces draining via oil interceptors should be provided in works area compounds. Interceptors should be regularly emptied to prevent release of oils and grease into the surface water drainage system after accidental spillages. The interceptor should have a bypass to prevent flushing during periods of heavy rain. Oil and fuel bunkers should be bunded and/or enclosed on three sides to prevent discharge due to accidental spillages or breaches of tanks. Bunding should be of sufficient capacity to accommodate 110% of the volume of the largest container or 20% of the total volume of waste, whichever is largest. Waste collected from any grease traps should be collected and disposed of by a licensed contractor.

 

6.5.26         Lubricants, waste oils and other chemical wastes are likely to be generated during the maintenance of vehicles and mechanical equipment. Used lubricants should be collected and stored in individual containers which are fully labelled in English and Chinese and stored in a designated secure place. If possible, such waste should be sent to oil recycling companies, and the empty oil drums collected by appropriate companies for reuse or refill.

 

6.5.27         The registered chemical waste producer (i.e. the contractor) has to arrange for the chemical waste to be collected by licensed collectors. The licensed collector should regularly take chemical waste to a licensed chemical waste treatment facility (such as the Chemical Waste Treatment Centre in Tsing Yi). A trip ticket system operates to control the movement of chemical wastes.

 

6.5.28         No lubricants, oils, solvents or paint products should be allowed to discharge into water courses, either by direct discharge, or as contaminants carried in surface water runoff from the construction site.

 

General Works Waste

 

Concrete Waste

 

6.5.29         Dry concrete waste (considered as public fill) should be sorted out from the other wastes and recycled for reuse or sorted out for disposal at designated public filling facilities.

 

Wooden Materials

 

6.5.30         All wooden materials used on-site should be kept separate from other wastes to avoid damage and to facilitate reuse. Timber which cannot be reused should be sorted out from other waste and stored separately from all inert waste before being disposed of to landfill.

 

6.5.31         Reusable steel or concrete panel shutters, fencing and hoarding and signboard should be used as a preferred alternative to items made of wood, to minimise wastage of wood. Attention should be paid to WBTC No. 19/2001 - Metallic Site Hoardings and Signboards to reduce the amount of timber used on construction sites. Metallic alternatives to timber are readily available and should be used rather than new timber. Precast concrete units should be adopted wherever feasible to minimize the use of timber formwork.

 

6.5.32         Only waste material need be taken to a landfill. It should be separated from recyclable wood and steel materials. As for all waste types these materials should be reused on-site or other approved sites before disposal is considered as an option.  Disposal to landfill should only be considered as a final option.  Contractors are responsible for storage of re-useable materials on-site.

 

Municipal Waste

 

6.5.33         General refuse generated on-site should be stored in enclosed bins or skips and collected separately from other construction and chemical wastes and disposed of at designated landfill. A temporary refuse collection point should be set up by the contractor to facilitate the collection of refuse by licensed contractors. The removal of waste from the site should be arranged on a daily or at least on every second day by the contractor to minimise any potential odour impacts, minimise the presence of pests, vermin and other scavengers and prevent unsightly accumulation of waste.

 

6.5.34         The recyclable component of the municipal waste generated by the workforce, such as aluminium cans, paper and cleansed plastic containers should be separated from other waste. Provision and collection of recycling bins for different types of recyclable waste should be set up by the contractor. The contractor should also be responsible for arranging recycling companies to collect these materials.

 

6.5.35         The burning of refuse on-site is prohibited under the Air Pollution Control Ordinance (APCO) (Cap.311).

 

6.5.36         A summary of the estimated C&D materials and waste and their disposal routes are tabulated in Table 6.7. The preliminary disposal programme breakdown is shown in Table 6.8.

 

Table 6.7

Summary of the Quantities and Disposal Routes of C&D Materials and Waste Arising from the Project

 

C&D Materials and Waste Types

Estimated Quantities*

Disposal Routes (see note 5)

Site Clearance / Demolition Materials

-          Public fill

-          C&D waste

8,570 m3 (see note 1)

-          6,840 m3

-          1,730 m3

Public Fill
Sort out recyclable materials, suitable material reuse on site or reuse at other approved projects, dispose to designated Public Filling Facilities (e.g. Fill Bank at Tuen Mun Area 38).

C&D waste
Sort out recyclable materials before disposal at NENT Landfill.

Excavated Materials

-          Sediment

-          Public fill

-          C&D waste

58,530 (see note 2)

-          150 m3

-          58,110 m3

-          270 m3

Sediment
To be reuse on-site as backfilling material.

Public Fill
Sort out recyclable materials, suitable material reuse on site or reuse at other approved projects, dispose to designated Public Filling Facilities (e.g. Fill Bank at Tuen Mun Area 38).

C&D waste
Sort out recyclable materials before disposal at NENT Landfill.

Chemical Waste

Minimum amount (see note 3)

Recycle, dispose to approved chemical waste treatment facilities.

General Works Waste

-          Concrete waste

-          Wooden waste

-          Municipal waste

Minimum amount (see note 4)

Concrete waste
Sort and recycle/reuse on site, recycle/reuse at other approved projects, dispose to designated Public Filling Facilities (e.g. Fill Bank at Tuen Mun Area 38).

Wooden waste
Sort and reuse on site, reuse at other approved projects, dispose to NENT Landfill.

Municipal waste
Sort out recyclable materials (e.g. paper, plastic, aluminium can), dispose to NENT Landfill.

 

Notes:

*      The estimated quantities are based on the preliminary design of the proposed channel works and the available ground investigation data. The waste arising will largely depends on the contractor works programme and activities. The contractor will be required to provide detailed estimation of all the C&D materials and waste generated on-site using a Monthly / Yearly Waste Flow Table as required under ETWB TCW No. 19/2005.

1         From clearance of vegetation, demolition of hard paved slab, temporary structures and small houses.

2         Topsoil and suitable materials including sediment will be stockpiled for later reuse in this or other projects subject to approval by the relevant parties in accordance with ETWB TCW No. 31/2004. The amount of materials that can be reuse in this Project will be examined further during the detailed design and construction stages.

3         The amount of chemical waste will be dependent on the contractor’s on-site maintenance programme and the number of equipment and vehicles used on-site. Chemical waste should be collected by licensed contractor and properly disposed of at approved chemical waste treatment facilities (e.g. the Chemical Waste Treatment Centre at Tsing Yi).

4         The amount of general works waste will depend on the contractor’s operating procedures and housekeeping practices as well as the size of the workforce on-site. All such wastes will be sorted, reused and recycled before disposal at designated outlets.

5         All suitable materials will be reuse and recycle before disposal. Reuse of C&D materials at other projects is subject to approval by the relevant parties in accordance with ETWB TCW No. 31/2004. Final disposal outlets subject to final agreement with Marine Fill Committee of CEDD for marine dumping grounds, Public Fill Committee of CEDD for Public Filling Facilities and EPD for landfills.

 

Table 6.8

Preliminary Disposal Programme of the C&D Materials

 

 

 

Quantity of C&D materials (m3)

2008

Reuse

9,240

Disposal of to public filling facilities

20,600

Disposal of to landfill

1,800

Reuse (sediment)

60

2009

Reuse

7,240

Disposal of to public filling facilities

16,100

Disposal of to landfill

100

Reuse (sediment)

60

2010

Reuse

2,170

Disposal of to public filling facilities

4,900

Disposal of to landfill

50

Reuse (sediment)

30

2011

Reuse

1,500

Disposal of to public filling facilities

3,200

Disposal of to landfill

50

Reuse (sediment)

0

 

Notes:

The exact programme and quantities of the disposal works will depend on the contractor’s programme after the contracts are awarded.

6.6                   Land Contamination

 

              Introduction

 

6.6.1             According to the EIA Study Brief, a land contamination assessment should be carried out if land lots/sites within the study area boundary, due to their past or present land uses, are assessed to be potentially contaminated.

 

6.6.2             Based on the current alignment, the proposed channels would not encroach on any land where there is presence of major polluting industries (e.g. electroplating factories, petrol filling station, vehicles repair/dismantling workshops). Majority of the proposed channels will be construction along existing stream alignment. The areas around the current streams are primarily riparian. A few of the channels will cross through grassland and/or agricultural land. However, a few works area will partly encroach upon storage areas and metal workshop which depending on its activities may give rise to potential concerns for land contamination.

 

6.6.3             This section aims to provide as a land contamination assessment as well as a preliminary Contamination Assessment Plan (CAP) which summarizes the identified historical and current land uses, possible contaminants, sampling requirements and testing parameters for further investigation if needed.

 

Assessment Methodology and Criteria

 

6.6.4             The land contamination assessment is investigated in accordance with ProPECC Note PN 3/94 – Contaminated Land Assessment and Remediation and EPD’s Guidance Notes for Investigation and Remediation of Contaminated Sites for Petrol Filling Stations, Boatyards, and Car Repair/Dismantling Workshops.

 

6.6.5             As indicated in the ProPECC Note PN 3/94, the “Dutch List” (Appendix IV of the ProPECC Note) could be used as the criteria for assessing whether the soil has been contaminated or not. It has been generally adopted that soil contamination is evident if Dutch B criteria has been exceeded.

 

Desk-top Appraisal

 

6.6.6             According to the Preliminary Report[1] for this Project, the Aerial Photograph Interpretation (API) of photographs taken between 1963 to 2002 indicates that all the sites were originally cultivated land and with very little changes throughout the last 40 years. Minor changes observed were formations of platforms for building construction and storage facilities. Details of the API are provided in Appendix D2.

 

Site Survey

 

6.6.7             Site surveys have been carried out to verify the desk-top appraisal and to identify current land use along the proposed works area. Surveys confirmed that majority of the alignment section are existing watercourses with riparian corridor, grassland, agricultural land and village areas. This applies to MUP03, MUP04A, MUP04B and LMH01.

 

6.6.8             The surveys also indicated that a works area at MUP05 will partly encroach upon a metal storage / workshop (Lot no. DD46 758 SB RP OSL) adjacent to Sha Tau Kok Road which due to its past and current activities may have potential of contaminated soil. Information on the current and past land uses of this lot was obtained from DLO of Lands Department.

 

6.6.9             The area to be resumed under the Project consists of an open area currently used for vehicle weighing and general open storage. No polluting activities were observed during several site inspections. Ground surface is generally clean and concrete paved. No cracks, visible oil or chemical stains were observed during the inspection.

 

6.6.10         No Dangerous Goods (D.G.) stores or underground fuel tanks were identified in the site inspections. Further information on D.G. storage, chemical waste producer, and chemical leakage/spillage incident were obtained from EPD and FSD. According to EPD and FSD, there are no current and past registration of D.G. within the premise and no records of spillage/leakage of chemicals. According to EPD, the premise at DD46 758 SB RP OSL is registered as a chemical waste producer with nature of business listed as trading company.

 

6.6.11         Based on the available information, land contamination is not expected for this Project. A summary of the assessment is presented in Table 6.9.

 

Table 6.9

Assessment of Potential Contaminated Sites

 

Proposed Channel

DD Lot No. (Land Status)

DLO Land Use Record

Site Inspection

Assessment of Potential Land Contamination

MUP05

DD46 758 SB RP OSL

Permitted use
No information available

§      Metal storage / workshop

§      Concrete paved surface

§      Clean surface, no cracks

§      No visible stained area

§      Presence of empty drums

§      No polluting activities observed

Not expected as the area to be resumed is an open area with concrete paving. The ground surface of the site looks clean and no visible oil or chemical stains were observed during site inspections.

 

6.7                   Operational Waste

 

6.7.1             As the quantity of the silt and vegetation removed from annual maintenance is limited, no adverse impact is expected during the operational phase of the proposed project.

 

6.7.2             Nonetheless, proper waste management procedures should be implemented. In general, desilting or maintenance works should be carried out during dry season where flow in the watercourse is low. Non-inert materials such as excess vegetation and garbage should be disposed of to landfill. Inert material such as excess silt should be dried and disposed of public filling facilities, or to landfill if the amount is negligible. The locations for the disposal of the above materials should be identified and agreement sought with the relevant departments before commencement of the maintenance works.

 

6.8                   Evaluation of Residual Impacts

 

6.8.1             With the implementation of mitigation measures and proper waste management practices for handling, transportations and disposal of identified waste arisings, no residual impacts are expected during the construction and operational of the Project.

 

6.9                   Environmental Audit

 

6.9.1             Auditing should be carried out periodically to determine if waste is being managed in accordance with prescribed waste management procedures and the EMP. The audits should examine all aspects of waste management including waste generation, storage, recycling, treatment, transportation, and disposal. The general site inspections including waste management issues will be undertaken weekly by the Environmental Team to check all construction activities for compliance with all appropriate environmental protection and pollution control measures, including those set up in the EMP. Meanwhile, waste management audit will also be carried out as part of the monthly audit by the Independent Environmental Checker.

 

6.10               Summary

 

6.10.1         Construction and demolition materials will inevitably be produced during the construction phase of the Project. Waste generated during construction works includes site clearance / demolition materials, excavated materials, chemical waste and general works waste. Waste types, quantities and timing have been estimated and mitigation measures have been proposed in terms of the avoidance-minimisation-reuse-recycling-disposal hierarchy.

 

6.10.2         Potential for reuse of inert construction & demolition material (public fill) within the Project will be rigorously explored throughout the course of the project in an effort to minimise off-site disposal.

 

6.10.3         A small quantity of sediment will be excavated from MUP04A and will be reused as backfilling material within the Project to minimize offsite marine disposal.

 

6.10.4         Provided that there is strict control of construction and demolition materials generated from construction works and that all arisings are stored, handled, transported and disposed of in accordance with the recommended mitigation measures, potential impact is not expected.

 

6.10.5         The recommended mitigation measures can be enforced by incorporating them into the waste management requirements as part of the Environmental Management Plan. Environmental audit would be necessary to ensure the implementation of proper waste management practices during construction.

 

6.10.6         Waste generated during operational maintenance is expected to be minimal. Proper waste management practices have been recommended.

 


[1]               Black & Veatch Hong Kong Limited (2004) Agreement No. CE 6/2002 (DS) Drainage Improvement in Northern New Territories Package C - Investigation, Design and Construction: Preliminary Report (report ref. 382486/27/Issue 1) dated August 2004.