6                                            Waste Management

6.1                                      Introduction

This section identifies and assesses the potential environmental impacts associated with waste management aspects of the construction and operation of the Designated and Potentially Designated Elements of the Project.

 

 

6.2                                      Relevant Legislation and Guidelines

The criteria and guidelines for evaluating potential waste management implications are laid out in Annexes 7 and 15 of the EIAO TM under the EIAO (Cap 499).

 

The following legislation covers, or has some bearing upon, the handling, treatment and disposal of wastes in the Hong Kong Special Administrative Region (HK SAR), and will also be considered in the assessment.

 

·       Waste Disposal Ordinance (Cap 354);

·       Waste Disposal (Chemical Waste) (General) Regulation (Cap 354);

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

·       Public Health and Municipal Services Ordinance (Cap 132) - Public Cleansing and Prevention of Nuisances (Urban Council) and (Regional Council) By-laws.

 

Waste Disposal Ordinance (Cap 354)

 

The Waste Disposal Ordinance (WDO) prohibits the unauthorised disposal of wastes, with waste defined as any substance or article which is abandoned.  Construction and demolition (C&D) waste is not directly defined in the WDO but is considered to fall within the category of "trade waste".  Trade waste is defined as waste from any trade, manufacturer or business, or any wasted building, or civil engineering materials, but does not include animal waste.

Under the WDO, wastes can only be disposed of at a licensed site.  A breach of these regulations can lead to the imposition of a fine and/or a prison sentence.  The WDO also provides for the issuing of licences for the collection and transport of wastes.  Licences are not, however, currently issued for the collection and transport of C&D waste or trade waste.

 

Waste Disposal (Chemical Waste) (General) Regulation

 

Chemical waste as defined under the Waste Disposal (Chemical Waste) (General) Regulation includes any substance being scrap material, or unwanted substances specified under Schedule 1 of the Regulation, if such a substance or chemical occurs in such a form, quantity or concentration so as to cause pollution or constitute a danger to health or risk of pollution to the environment.

A person should not produce, or cause to be produced, chemical wastes unless he is registered with the EPD.  Any person who contravenes this requirement commits an offence and is liable to fine and imprisonment.

Producers of chemical wastes must treat their wastes, utilising on-site plant licensed by the EPD or have a licensed collector take the wastes to a licensed facility.  For each consignment of wastes, the waste producer, collector and disposer of the wastes must sign all relevant parts of a computerised trip ticket.  The system is designed to allow the transfer of wastes to be traced from cradle-to-grave.

 

The Regulation prescribes the storage facilities to be provided on site including labelling and warning signs.  To minimise the risks of pollution and danger to human health or life, the waste producer is required to prepare and make available written procedures to be observed in the case of emergencies due to spillage, leakage or accidents arising from the storage of chemical wastes.  He/she must also provide employees with training in such procedures.

 

Land (Miscellaneous Provisions) Ordinance (Cap 28)

 

The inert portion of construction and demolition materials (C&DM)([1]) (also called public fill) may be taken to public filling facilities.  Public filling facilities usually form part of land reclamation schemes and are operated by the Civil Engineering Department (CED) and Territory Development Department (TDD).  The Land (Miscellaneous Provisions) Ordinance requires that Dumping Licences are obtained by individuals or companies who deliver public fill to the public filling facilities.  The licences are issued by the CED under delegated authority from the Director of Lands.

 

Individual licences and windscreen stickers are issued for each vehicle involved.  Under the licence conditions public filling facilities will accept only inert building debris, soil, rock and broken concrete.  There is no size limitation on the rock and broken concrete, and a small amount of timber mixed with inert material is permissible.  The material should, however, be free from marine mud, household refuse, plastic, metal, industrial and chemical wastes, animal and vegetable matters and any other materials considered unsuitable by the Filling Supervisor.

 

Public Cleansing and Prevention of Nuisances by-Laws

 

These by-laws provide a further control on the illegal tipping of wastes on unauthorised (unlicensed) sites.  The illegal dumping of wastes can lead to a fine and imprisonment.

 

 

Other Relevant Guidelines

 

Other 'guideline' documents which detail how the Contractor should comply with the regulations are as follows:

 

Waste Disposal Plan for Hong Kong (December 1989), Planning, Environment and Lands Branch Government Secretariat;

 

Environmental Guidelines for Planning In Hong Kong (1990), Hong Kong Planning and Standards Guidelines, Hong Kong Government;

 

New Disposal Arrangements for Construction Waste (1992), Environmental Protection Department & Civil Engineering Department;

 

Code of Practice on the Packaging, Labelling and Storage of Chemical Wastes (1992), Environmental Protection Department;

 

Works Branch Technical Circular, 32/92, The Use of Tropical Hard Wood on Construction Site; Works Branch, Hong Kong Government;

 

Works Branch Technical Circular Nos. 2/93, 2/93B, Public Dumps, Works Branch, Hong Kong Government;

 

Works Branch Technical Circular No. 16/96, Wet Soil in Public Dumps; Works Branch, Hong Kong Government;

 

Works Bureau Technical Circular Nos. 4/98,  4/98A, Use of Public Fill in Reclamation and Earth Filling Projects; Works Bureau, HK SAR Government;

 

Works Bureau Technical Circular No 5/98, On-site Sorting of Construction Waste on Demolition Site; Works Bureau, HK SAR Government;

 

Waste Reduction Framework Plan, 1998 to 2007, Planning, Environment and Lands Bureau, Government Secretariat, 5 November 1998;

 

Works Bureau Technical Circular Nos. 5/99, 5/99A Trip-ticket System for Disposal of Construction and Demolition Material; Works Bureau, HK SAR Government;

 

Works Bureau Technical Circular No 19/99,Metallic Site Hoardings and Signboards; Works Bureau, HK SAR Government;

 

Work Bureau Technical Circular Nos. 25/99, 25/99A, 25/99C Incorporation of Information on Construction and Demolition Material Management in Public Works Sub-committee Papers; Works Bureau, HK SAR Government;

 

Works Bureau Technical Circular No. 12/2000, Fill Management; Works Bureau, HK SAR Government;

 

Works Bureau Technical Circular No 29/2000, Waste Management Plan. Works Bureau, Hong Kong SAR Government; and

Works Bureau Technical Circular No 31/2000, Specification Allowing the Use of Recycled Inert Construction and Demolition Material. Works Bureau, Hong Kong SAR Government.

 

Landfill Disposal Criteria for Contaminated Soil

 

Excavated contaminated soil has to meet certain criteria before disposal to landfills is allowed.  The criteria presented in the EPD’s Guidance Notes for Investigation and Remediation of Contaminated Sites of: Petrol Filling Stations; Boatyards; and Car Repair/Dismantling Workshops issued by the EPD are set primarily in terms of Toxic Characteristic Leaching Procedure (TCLP) limits, as shown in Table 6.2a.

Table 6.2a       Landfill Disposal Criteria for Contaminated Soil

Parameter (a)

TCLP Limits (ppm)

Cadmium (Cd)

10

Chromium (Cr)

50

Copper (Cu)

250

Nickel (Ni)

250

Lead (Pb)

50

Zinc (Zn)

250

Mercury (Hg)

1

Tin (Sn)

250

Silver (Ag)

50

Antimony (Sb)

150

Arsenic (As)

50

Beryllium (Be)

10

Thallium (Tl)

50

Vanadium (V)

250

Selenium (Se)

1

Barium (Ba)

1,000

Note:

(a) In accordance with USEPA Method 1311

 

 

 

6.3                                      Assessment Methodology

The potential environmental impacts associated with the handling and disposal of waste arising from the construction and operation of sewers, rising mains and pumping stations was assessed in accordance with the criteria presented in Annexes 7 and 15 of the EIAO-TM, which are summarised as follows:

 

·       estimation of the types, timing and quantities of the wastes to be generated;

 

·       assessment of the secondary environmental impacts due to the management of waste with respect to potential hazards, air and odour emissions, noise, wastewater discharges and traffic; and

 

·       assessment of the potential impacts on the capacity of waste collection, transfer and disposal facilities.

 

6.4                                      Identification of Environmental Impacts

Construction Phase

 

During the construction phase, the main activities which will potentially result in waste generation involve site clearance, and construction of the sewers and pumping stations.

 

The typical waste types associated with these activities include:

 

·       site clearance waste;

·       excavated materials;

·       C&DM;

·       chemical wastes;

·       sewage; and

·       general refuse.

 

6.4.1                                Site Clearance Waste

Most of the sewers/rising mains will be laid under existing roads/pavement and hence minimal site clearance waste is expected.  The construction of the pumping stations may involve clearance of vegetation depending on the proposed location.  If not properly managed, the handling and disposal of the clearance waste may cause adverse environmental impacts.

 

6.4.2                                Construction and Demolition Materials (C&DM)

Excavated Materials

 

As most of the sewers/rising mains will be laid under existing roads/pavement, excavated materials will be generated from excavation of the pipe trenches and site formation activities for the proposed pumping stations.  These materials are expected to be mostly soil plus concrete/tarmac which are inert.  The anticipated quantities of excavated materials and backfilling materials are presented in Table 6.4a.  As the Designated and Potentially Designated Elements and the Non-Designated Elements are differentiated by virtue of their classification under the EIAO and not by the works packages, the estimated quantities also include the excavated materials from the Non-Designated Elements which will be constructed in the same period.

Table 6.4a       Estimated Quantities of Excavated Materials to be Generated from Laying of Sewers and Construction of Pumping Stations

Package

Excavation Volume (m3)

Backfilling Volume (m3)

Balance

(m3)

 

1A-1T (sewers/rising mains)

115,950

84,630

31,320

1B-1T (sewers/rising mains)

51,430

41,780

9,650

Pumping Stations

26,415

17,562

8,853

Total

193,795

143,972

49,823

 

The proposed sewers across the Yuen Long and Kam Tin MDC will be laid by the trenchless pipe jacking method.  Jacking pits and receiving pits will need to be constructed in the vicinity of the river embankments and the existing river embankment  will need to be demolished, removed and subsequently reinstated.  It should be noted that one of the risks inherent  to the trenchless pipe jacking method is that the lead shield may breakdown before it reaches the receiving pit.  In such an event, a rescue pit will be sunk to remove the studded shield and therefore some dredging works over the MDC may be required.  The proposed sewer/rising mains will also cross the MDC at three places.  In order to avoid dredging and excavation of river sediment, it is proposed to use the trenchless pipe jacking method to lay the twin rising mains.  The mains will be laid at 1 to 2 m below the bottom of the MDC.  It is estimated that approximately 2,900 m3 of inert materials will need to be excavated, of which about 2,000 m3 (about 69%) could be used for backfilling the launch and reception shafts.  Approximately 900 m3 of surplus excavated materials will need to be disposed of off-site.

 

In the event that the lead shield of the tunnelling machine is broken before it completes the whole length, a rescue pit will be sunk to remove it and therefore some dredging works over the river will be required.  It is estimated that about 50m3 of river sediment will be required to be excavated for the construction of the rescue pit.  Some of these sediments will be used for backfilling of the rescue pit.

 

C&DM from Construction of Pumping Stations

 

The construction of the proposed pumping stations will generate C&DM which includes packaging wastes, excess or damaged materials, hoarding etc.  The proposed pumping stations will typically consist of a superstructure and a substructure.   Most of the E&M equipment will be housed within the superstructure.  The best means to estimate the generation rate of C&DM will be to base the estimate on the floor area.  The typical floor areas of the proposed pumping stations are shown in Table 6.4b.

Table 6.4b       Typical Floor Areas of Proposed Pumping Stations

Pumping Stations

Dimensions

Ng Ka Tsuen PS (P5)

Sha Po PS (P2)

Kam Tin PS (P1)

 

~ 50 m x 35 m

 

~  Floor Area = 1,750 m2 each

Pang Ka Tsuen PS (P6)

Shui Tsan Tin PS (P4)

Leung Uk Tsuen PS (P7)

 

~ 27m x 23m

 

~ Floor Area = 620 m2 each

Nam Sang Wai PS (P3)

~ 50 m x 40 m

 

~ Floor Area = 2,000 m2

 

 

6.4.3                                Chemical Waste

Chemical waste, as defined under the Waste Disposal (Chemical Waste) (General) Regulation, includes any substance being scrap material, or unwanted substances specified under Schedule 1 of the Regulation.  A complete list of such substances is provided under the Regulation, however substances likely to be generated from the construction activities for the sewers construction will, for the most part, arise from the maintenance of equipment.  These may include, but need not be limited to the following:

 

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

·       used paint, engine oils, hydraulic fluids and waste fuel;

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

·       spent solvents / solutions, some of which may be halogenated, from equipment cleaning activities.

 

Chemical wastes may pose serious environmental, health and safety hazards if not stored and disposed of in an appropriate manner as outlined in the Waste Disposal (Chemical Waste) (General) Regulation and the Code of Practice on the Packaging, Labelling and Storage of Chemical Wastes.  These hazards may include:

 

·      toxic effect to workers;

·      adverse effect on air, water and land from spills; and

·      fire hazards.

 

6.4.4                                Sewage

Sewage will arise from the construction workforce, site office’s sanitary facilities and night soil from chemical toilets.  If not properly managed, these materials could cause odour and potential health risks to the workforce by attracting pests and other disease vectors. 

 

6.4.5                                General Refuse

The presence of a construction site with workers and site office will result in the generation of a variety of general refuse requiring disposal.  General refuse will mainly consist of food waste, aluminium cans and waste paper.

 

The storage of general refuse has the potential to give rise to adverse environmental impacts.  These include odour if the waste is not collected frequently (for example, daily), windblown litter, water quality impacts if waste enters water bodies, and visual impact.  The sites may also attract pests, vermin, and other disease vectors if the waste storage areas are not well maintained and cleaned regularly.  In addition, disposal of wastes at sites other than approved landfills, can also lead to similar adverse impacts at those sites.

 

Operation Phase

 

6.4.6                                Waste from Operation of Pumping Stations

During the operation phase,  the main waste types will include screenings and chemical waste generated from the operation of the pumping stations and the silt and debris from the maintenance of the sewers.  If not properly managed, these could have the potential to cause adverse environmental impacts.  These include odour if the waste is not collected frequently and water quality impacts if waste enters water bodies.  Based on records from existing pumping stations[2], it is estimated that the screenings which will arise at the seven proposed pumping stations will amount to approximately 46m3 per month.

 

 

6.5                                      Evaluation of Impacts

Construction Phase

 

6.5.1                                Site Clearance Waste

As most of the proposed pumping stations are located on developed land, the quantity of vegetation that needs to be cleared will be minimal.  Vegetation cleared from proposed pumping station sites can be disposed of as general refuse.   No adverse environmental impacts from the disposal of site clearance waste is expected.

 

6.5.2                                C&DM

Excavated Materials

 

As indicated in Table 6.4a, some of the excavated materials could be used

for backfilling the trenches.  The quantities of excavated materials which would need to be disposed of are shown in Table 6.5a.  It is expected that the majority of excavated material will be inert soil.


Table 6.5a       Disposal of Excavated Materials

Package

Excavation Volume

(m3)

Backfilling Volume

(m3)

Volume to be Disposed

(m3)

Construction Period

Disposal Rate

(Average/ Peak(a)) (m3day-1)

1A-1T (b)

115,950

84,630

31,320

08/03 - 02/06

(~912 days)

34/52

 

 

 

 

 

 

1B-1T (b)

51,430

41,780

9,650

06/04 - 11/06

(~912 days)

11/16

 

 

 

 

 

 

1A-2T(c)

12,970

8,700

4,200

08/04 - 02/08

(~1008 days)

4.2/6.3

P/Ss (d)

26,415

17,562

8,853

08/03 - 01/06

(~312 days)

24 /36

Pipe jacking under MDC

2,900

2,000

900

08/03 - 02/06

(~912 days)

1/1.5

 

 

 

 

 

 

Total

209,665

154,672

54,923

 

74.2/111.8

Notes:

(a)  Assume a peak generation rate of 1.5

(b)  Include Non-Designated Elements

(c)   From Non-Designated Elements

(d)  Assume the materials will be excavated in the first 12 months of construction.

 

It is estimated that approximately 210,000 m3 of materials will be excavated.  Due consideration was taken to reuse as much excavated material as possible (approximately 155,000 m3 (about 74%) of the excavated materials will be reused within the Project).  The volume of excavated materials which needs to be disposed of is approximately 55,000 m3.  The average and peak disposal rates for excavated materials are approximately 75 m3 day-1 and 112 m3 day-1, respectively.  Due to the relatively small volume of excavated materials which require disposal, it is not envisaged that this will have adverse impacts on the capacity of the available public filling facilities.  The final destinations of the excavated materials will be determined, subject to the availability of public filling facilities, by the Waste Management Plan to be submitted by the Contractors and agreed with the Engineer.    

 

A TIA has been conducted for this Project and the report indicated that the construction traffic generated by this project (including the traffic associated with the off-site disposal of the surplus excavated material) is insignificant and will not cause adverse traffic impacts, provided that the recommended temporary traffic measures are implemented.

 

As the proposed sewers/rising mains alignments pass close to potentially contaminated sites in some areas (eg car repair/dismantling works), there is the possibility that the excavated materials will be contaminated.  Section 7 addresses the land contamination issues.  The disposal of contaminated materials, if any, needs to comply with the Landfill Disposal Criteria for Contaminated Soil (see Table 6.2a).

 

The actual quantities of contaminated soil can only be estimated after conducting intrusive site investigation works after land resumption and hence cannot be estimated at this stage.  It is estimated that under the worse case scenario (ie assuming all the excavated materials from the trenches adjacent to potentially contaminated sites are found to be contaminated), the amount of contaminated soil to be treated and disposed of will be in the order of 14,000m3.  However, it should be noted that this is a very conservative estimate.   As discussed in Section 7, the potential for off-site migration of contaminants to the excavation area will be minimal.  It is expected that the actual quantity of contaminated soil, if any, to be excavated will be much less than that estimated under the worst case scenario.  If contaminated soils are found, their management will be addressed in the Remedial Action Plan, to be approved by the EPD.  A simplified procedure is shown in Figure 6.5a for reference.

 

Excavated river sediment (less than 50 m3) will be generated in the event that a rescue pit is required during pipe jacking across the MDC.   In view of the small quantities of surplus excavated sediment, it is envisaged that it will be more cost effective to dispose of these sediments to landfill.   The sediment should be dewatered and the disposal of the sediment should also comply with the Landfill Disposal Criteria for Contaminated Soil (see Table 6.2a). The final disposal arrangement should be agreed in advance with EPD (for landfill disposal) via the Waste Management Plan to be submitted by the Contractor.

 

Figure 6.5a     Simplified Procedure for Disposal of Contaminated Materials at Landfills

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


If excavated soil contains other contaminants in addition to the parameters in Table 6.2a, approval for disposal will be assessed on a case-by-case basis by the EPD.  Apart from landfill, another possible disposal outlet is the Chemical Waste Treatment Centre (CWTC) if volume is small and the concentration of contaminants is so high that the soil can be classified as chemical waste.

 

C&DM from Construction of Pumping Stations

 

As indicated in Section 6.4, the best means to estimate the generation of C&DM is based on the floor area.  Table 6.4b indicates that the total floor area to be constructed is approximately 9,110m2.  Based on a C&DM generation of 0.1 m3 per 1 m2 of gross floor area (GFA) constructed[3], it is estimated that approximately 911m3 of C&DM will be

 

generated from the construction of the pumping stations over a period of 17 months between August 2003 to January 2006.  This represents the average and peak C&DM generation of 2.2 m3day-1 and 3.3 m3day-1, respectively.  With proper segregation, the volume of C&DM that could be reused as public fill is approximately 730 m3 and the

volume to be disposed of to landfills (C&D waste) is approximately 181m3. The average

 

and peak generation of C&D waste which requires disposal at landfill is approximately 0.44 m3day-1 and 0.66 m3day-1, respectively  The public fills will be transported to public

filling areas at average and peak rates of 1.8 m3day-1 and 2.7 m3day-1, respectively. 

 

The generation of C&DM is considered to be small and is not envisaged to have an adverse impact on the capacity of landfills and public filling areas.

 

6.5.3                                Chemical Waste

It is difficult to quantify the amount of chemical waste which will arise from the construction activities as it will be highly dependent on the Contractor's on-site maintenance intention and the quantities of plant and vehicles utilised.  However, it is anticipated that the quantity of chemical waste, such as lubricating oil and solvent produced from plant maintenance will be small and in the order of a few hundred litres per month. The chemical waste to be generated from the construction activities will be readily accepted at the Chemical Waste Treatment Centre (CWTC) at Tsing Yi.

 

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 Waste published by the EPD.  Provided that this occurs, the potential environmental impacts arising from the handling, storage and disposal of a small amount of chemical waste generated from the construction activities will be negligible.

 


6.5.4                                Sewage

The number of construction workers to be employed on site is not available at this stage, however, is expected to be small.  As the workers will be scattered along the proposed sewers/rising mains alignment, the more cost-effective solution will be to provide adequate number of portable toilets along the alignment to ensure that domestic sewage from site staff is properly collected.  Depending on site conditions, land availability and site activities, the locations and number of portable toilets will be determined in the Waste Management Plan to be submitted by the Contractors and agreed by EPD.  No adverse waste impacts is envisaged provided that maintenance by licensed contractors is conducted regularly.

 

6.5.5                                General Refuse

The number of workers to be employed for the project is not available at this stage, however, it is expected to be small.  Provided that the mitigation measures recommended in Section 6.6 are adopted, the environmental impacts caused by the storage, handling, transport and disposal of general refuse are expected to be minimal.  It is recommended that the general refuse should be collected on a daily basis and be delivered to the WENT or NENT Landfill for disposal.  With respect to the anticipated small quantity of general refuse to be disposed of, adverse impacts to the operation of the landfills are not expected.

 

Operation Phase

 

6.5.6                                Waste from the Operation of the Pumping Stations

The screenings and silt, from the operation and maintenance of the proposed pumping stations and sewers/rising mains will be disposed of at the WENT or NENT landfill.  The relatively small quantity of these wastes (at total of 46m3 per month of screenings from seven proposed pumping stations) will have minimal impact on the operation of the landfills.

 

Small quantities of chemical wastes (mainly lubricant oil and paint) to be generated from the maintenance of the pumping stations could be readily accepted at the CWTC. Provided that this occurs, the potential environmental impacts arising from the handling, storage and disposal of a small amount of chemical waste generated from the construction activities will be negligible.

 

6.5.7                                Summary

Table 6.5b summarise impacts during the construction and operation of the Project.


Table 6.5b      Summary of Waste Management Impacts

Waste Type

General Evaluation

Construction Phase

 

Site Clearance Waste

Vegetation cleared from proposed pumping station sites can be disposed of as general refuse.  As most of the proposed pumping stations are located on developed land, the amount of site clearance waste will be minimal.

 

C&DM

Excavated Materials

 

It is estimated that approximately 210,000 m3 of excavated materials will be generated from the construction of the Project of which approximately 155,000 m3 (about 74%) will be reused on site.  The volume of excavated materials to be disposed off-site will be approximately 55,000 m3.  The average and peak disposal rate of excavated materials are 75 m3 day-1 and 112 m3 day-1, respectively.  Due to the relatively small volume of excavated materials which requires disposal, it is not envisaged that this will have adverse impacts on the capacity of the public filling facilities.  The final destinations of the excavated materials will be determined, subject to availability of public filling facilities, by the Waste Management Plan to be submitted by the Contractors and agreed with the Engineer. 

 

A Traffic Impact Assessment has been conducted for this Project and the concluded that the construction traffic generating from this project  (including the traffic associated with the off-site disposal of the surplus excavated material) will not cause adverse traffic impact provide that the temporary traffic measures as recommended are properly implemented.

 

The actual quantities of contaminated soil can only be estimated after conducting the intrusive site investigation after land resumption.  A rough estimation of worst case scenario  will be in the order of 14,000m3.  However, it should be noted that this is a very conservative assumption.   If contaminated soils are found, their management will be addressed in the Remedial Action Plan.

 

 

C&DM from Construction of Pumping Stations

 

Based on a C&DM generation of 0.1 m3 per 1 m2 of GFA constructed, it is estimated that approximately 911m3 of C&DM will be generated from the construction of the pumping stations over a 17 months period  between August 2003 to January 2006.  This represents the average and peak C&DM generation of 2.2 m3day-1 and 3.3 m3day-1, respectively.  With proper segregation, average and peak generation of C&D waste which requires disposal at landfill is approximately 0.44 m3day-1 and 0.66 m3day-1, respectively  The public fills will be transported to the public filling areas at average and peak rate of 1.8 m3day-1 and 2.7 m3day-1, respectively. 

 

With respect to the small quantity of C&DM to be generated from the Project, it is not envisaged that the disposal of which to landfill and public filling areas will affect the operations of these facilities.

 

Chemical Waste

It is difficult to quantify the amount of chemical waste which will arise from the construction activities as it will be highly dependent on the Contractor's on-site maintenance intention and the number of plant and vehicles utilised.  However, it is anticipated that the quantity of chemical waste produced will be small and in the order to a few hundred litres per month. The chemical waste to be generated from the construction activities will be readily accepted at the Chemical Waste Treatment Centre (CWTC) at Tsing Yi.

 

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 Waste published by the EPD.  Provided that this occurs, the potential environmental impacts arising from the handling, storage and disposal of a small amount of chemical waste generated from the construction activities will be negligible.

 

Sewage

The number of construction workers to be employed on site is not available at this stage, however, is expected to be small.  As the workers will be scattered along the proposed sewers/rising mains alignment, the most cost-effective solution will be to provide adequate number of portable toilets along the alignment.  No adverse waste impacts is envisaged provided that maintenance by licensed contractors is conducted regularly.

 

 

General Refuse

The number of workers to be employed for the project is not available at this stage, however, it is expected to be small.  Provided that the mitigation measures recommended in Section 6.6 are adopted, the potential environmental impacts caused by the storage, handling, transport and disposal of general refuse are expected to be minimal. With respect to the anticipated small quantity of general refuse to be disposed of, there will be no adverse impact to the operation of the strategic landfills.

Operational Phase

 

Screenings and Silt from Maintenance

The screenings and silt from the maintenance of the proposed facilities will be disposed of at the WENT or NENT landfill.  With respect to their relatively small quantity (a total of 46m3 per month of screenings), it is not anticipated that the disposal of these wastes will cause any adverse impacts to the operation of the landfills. 

Chemical Waste

It is anticipated that the quantity of chemical waste arising during operation, such as lubricating oil and paints will be small and no adverse environmental impacts are envisaged.

 

 

 

 

6.6                                      Mitigation Measures

6.6.1                                Introduction

This section recommends the mitigation measures to avoid or minimise potential adverse environmental impacts associated with handling, collection and disposal of waste arising from the Project.  The Contractors should incorporate these recommendations into a Waste Management Plan for the construction works.  The Contractors should submit the plan to the Engineer for approval prior to the commencement of the construction works.  Such a management plan should incorporate site specific factors, such as the designation of areas for the segregation and temporary storage of reusable and recyclable materials.

 

It is the Contractor’s (for the construction phase) and the Project Proponent’s (for the operational phase) responsibility to ensure that only reputable licensed waste collectors are used and that appropriate measures to minimise adverse impacts, including windblown litter and dust from the transportation of these wastes are employed.  In addition, the Contractor must ensure that all the necessary waste disposal permits are obtained throughout the construction and operation phases.

 

6.6.2                                Construction Phase

Excavated Material

Wherever practicable, excavated materials should be segregated from other wastes to avoid contamination thereby ensuring acceptability at public filling areas and avoiding the need for disposal at landfill.

 

Measures Taken in the Planning and Design Stages to Reduce the Generation of C&DM

 

The various waste management options can be categorised in terms of preference from an environmental viewpoint.  The options considered to be more preferable have the least impacts and are more sustainable in the long term.  Hence, the waste management hierarchy is as follows:

 

·       avoidance and minimisation, that is, not generating waste through changing or improving practices and design;

 

·       reuse of materials, thus avoiding disposal (generally with only limited reprocessing);

 

·       recovery and recycling, thus avoiding disposal (although reprocessing may be required); and

 

·       treatment and disposal, according to relevant law, guidelines and good practice.

 

This hierarchy should be used to evaluate the waste management options, thus allowing maximum waste reduction and often reducing costs.  For example, by reducing or eliminating over-ordering of construction materials, waste is avoided and costs are reduced both in terms the purchasing of raw materials and in disposing of wastes.  Records of quantities of wastes generated, recycled and disposed (locations) should be properly kept.

 

Standard formwork should be used as far as practicable in order to minimise the arisings of C&DM.  The use of more durable formwork or plastic facing for the construction works should be considered.

 

Any uncontaminated soil should be reused on site as far as possible, eg for landscape works, in order to minimise the amount of public fill to be disposed off-site.  The Project Proponent should liaise with the Public Fill Committee to identify as far as possible suitable reclamation or site formation projects near the project site to reuse the material.

 

The design of the foundation works will minimise the amount of excavated material to be generated.  Should piling be required, H-piling will be used as far as practical.

 

The purchasing of construction materials will be carefully planned in order to avoid over ordering and wastage.

 

Measures to be Taken in the Construction Stage to Reduce the Generation of C&DM

 

The Contractor should recycle as much of the C&DM as possible on-site.  Public fill and C&D waste should be segregated and stored in different containers or skips to enhance reuse or recycling of materials and their proper disposal.  Concrete and masonry, for examples, can be crushed and used as fill.  Steel reinforcing bar can be used by scrap steel mills.  Different areas of the sites should be designated for such segregation and storage.

 

The use of wooden hoardings shall not be allowed.  An alternative material, which can be reused or recycled, for example, metal (aluminium, alloy, etc) shall be used. 

 

Government has developed a charging policy for the disposal of waste to landfill.  When it is implemented, this will provide additional incentive to reduce the volume of waste generated and to ensure proper segregation to allow disposal of inert material to public filling areas.

 

Chemical Waste

 

Chemical waste producers should be registered with the EPD.  For those processes which generate chemical waste, it may be possible to find alternatives which generate reduced quantities or even no chemical waste, or less dangerous types of chemical waste.

 

Chemical waste that is produced, as defined by Schedule 1 of the Waste Disposal (Chemical Waste) (General) Regulation, should be handled in accordance with the Code of Practice on the Packaging, Handling and Storage of Chemical Wastes as follows.  Containers used for storage of chemical wastes should:

 

·       be suitable for the substance they are holding, resistant to corrosion, maintained in a good condition, and securely closed;

 

·       Have a capacity of less than 450 L unless the specifications have been approved by the EPD; and

 

·       display a label in English and Chinese in accordance with instructions prescribed in Schedule 2 of the Regulations.

 

The storage area for chemical wastes should:

 

·       be clearly labelled and used solely for the storage of chemical waste;

 

·       be enclosed on at least 3 sides;

 

·       have an impermeable floor and bunding, of capacity to accommodate 110% of the volume of the largest container or 20% by volume of the chemical waste stored in that area, whichever is the greatest;

 

·       have adequate ventilation;

 

·       be covered to prevent rainfall entering (water collected within the bund must be tested and disposed as chemical waste, if necessary); and

 

·       be arranged so that incompatible materials are adequately separated.

 

Disposal of chemical waste should:

 

·       be via a licensed waste collector; and

 

·       be to a facility licensed to receive chemical waste, such as the Chemical Waste Treatment Facility which also offers a chemical waste collection service and can supply the necessary storage containers; or

 

·       be to a re-user of the waste, under approval from the EPD.

 

Sewage

 

Adequate numbers of portable toilets should be provided for the number of workers along the proposed sewer alignment.  The portable toilets should be maintained in a state which will not deter the workers from utilizing these portable toilets.  Night soil should be collected by licensed collectors regularly.

 

Management of General Refuse

 

General refuse generated on-site should be stored in enclosed bins or compaction units separately from construction and chemical wastes.  A reputable waste collector should be employed by the Contractor to remove general refuse from the site, separately from construction and chemical wastes, on a daily basis to minimise odour, pest and litter impacts.  The burning of refuse on construction sites is prohibited by law.

 

Aluminium cans are often recovered from the waste stream by individual collectors if they are segregated and made easily accessible, so separate, labelled bins for their deposit should be provided if feasible.

 

Office wastes can be reduced through the recycling of paper if volumes are large enough to warrant collection.  Participation in a local collection scheme should be considered if one is available.  In addition, waste separation facilities for paper, aluminium cans, plastic bottles etc., should be provided.

 

Management of Waste Disposal

 

A trip-ticket system should be established in accordance with Works Bureau Technical Circular No. 5/99 to monitor the disposal of public fill and solid wastes at public filling facilities and landfills, and to control fly-tipping.  A trip-ticket system will be included as one of the contractual requirements and implemented by the Engineer.  The Engineer should audit the result of the system.

 

A recording system for the amount of waste generated, recycled and disposed of (including the disposal sites) should be established during the construction stage.

 

Staff Training

 

Training should be provided to workers on the concepts of site cleanliness and on appropriate waste management procedures, including waste reduction, reuse and recycling at the beginning of the Contract.

 

6.6.3                                Operational Phase

The main type of wastes generated during operation phase will be screenings from the proposed pumping stations and silt and similar materials removed during the maintenance of the sewers/rising mains which will be similar in nature to general refuse.  The waste generated at the proposed pumping stations and sewers/rising mains should be stored in enclosed bins or compaction units separately from chemical wastes.  A reputable waste collector should be employed by the operators to remove the screenings from the pumping stations, on a daily basis to minimise odour, pest and litter impacts.

 

For chemical wastes generated during the operation phases, the mitigation measures are same for those in Section 6.6.2 under Construction Phase.

 

 

6.7                                      Residual Environmental Impacts

With the implementation of recommended mitigation measures, in particular the establishment and implementation of a Waste Management Plan, minimal residual impacts are anticipated from either the construction or operation of the proposed Project.

 

 

6.8                                      Environmental Monitoring and Audit

It is recommended that audit of each waste stream should be periodically  carried out during the construction phase to determine if wastes are being managed in accordance with the Waste Management Plan.  The audits should look at all aspects of waste management including waste generation, storage, recycling, transport and disposal.  An appropriate audit programme would be to undertake a first audit at the commencement of the construction works and then quarterly audits, thereafter.

 

 

6.9                                      Conclusion

The following quantities of waste are expected to arise during the construction of the proposed sewers/rising mains: excavated material (average and peak disposal rates are 69 m3 day-1 and 104 m3 day-1, respectively); C&D waste (average and peak generation rates during construction are 0.44 and 0.66 m3 day-1, respectively); and chemical waste (a few cubic metres per month); and general refuse.

 

Screenings will arise from the operation of the proposed pumping stations.  Approximately 46m3 per month of screenings will be generated from the pumping stations.  The impact of its disposal at landfill will be minimal.  The generation of chemical wastes is expected to be very small and no adverse environmental impacts are envisaged.

 

Good waste management practices have been recommended to ensure that adverse environmental impacts from the handling and disposal of construction and operational wastes are prevented or minimised.   This EIA concludes that no unacceptable environmental impacts will result from the storage, handling, collection, transport, and disposal of wastes arising from the construction and operation of the Designated and Potentially Designated Elements of proposed Yuen Long and Kam Tin Sewerage and Sewage Disposal Stage 1 Sewers, Rising Mains and Ancillary Pumping Stations.

 

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(1)        “C&DM” refers to surplus materials arising from any land excavation or formation, civil/building construction, road works, building renovation or demolition activities.  It includes various types of reusable materials, building debris, rubble, earth, concrete, timber and mixed site clearance materials. When sorted properly, materials suitable for land reclamation and site formation (know as public fill) should be reused at public filling area whereas the remaining C&D waste are to be disposed of at landfills.

(1)        Feb 2001 at Ha Tsuen PS - average daily flow 60,000m3 day-1  generated approximately 17m3 screenings per month.

 (1) Hong Kong Polytechnic (1993).  Reduction of Construction Waste Final Report.  (Note:  Generation rate of C&DM from pipe lying activities is not available.)