Figure
Appendices
Appendix 6.1 Remediation Report
Appendix 6.2 Site Photos of STP Project Area
Appendix 6.3 Approval Letter of SSTP from EPD
Appendix 6.4 Chemical Testing Results
Appendix 6.5 Biological Testing Results
Appendix 6.6 Approval Letter of SQR from EPD
This section identifies the potential waste arising from the construction and operation activities of the Project and evaluates the potential environmental impacts that may result from waste generated. Mitigation measures on waste handling, transportation and disposal, are recommended with reference to applicable waste legislation and management guidelines to minimise potential waste management impacts.
The criteria and guidelines for assessing waste management implications are outlined respectively in Annexes 7 and 15 of the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM).
The following legislation relates to the handling, treatment and disposal of wastes in Hong Kong and has been used in assessing potential impacts:
● Waste Disposal Ordinance (Cap. 354)
● Waste Disposal (Chemical Waste) (General) Regulation (Cap. 354C)
● Waste Disposal (Charges for Disposal of Construction Waste) Regulation (Cap. 354N)
● Dumping at Sea Ordinance (Cap. 466)
● Public Health and Municipal Services Ordinance (Cap. 132) - Public Cleansing and Prevention of Nuisances Regulation
● Land (Miscellaneous Provisions) Ordinance (Cap. 28)
The Waste Disposal Ordinance (WDO) is the principal piece of legislation for management and control of waste disposal in Hong Kong. The WDO prohibits the unauthorised disposal of wastes. Construction waste is defined as any substance, matter or thing that is generated from construction work and abandoned, whether or not it has been processed or stockpiled before being abandoned, but does not include any sludge, screenings or matter removed in or generated from any desludging, desilting or dredging works. Under the WDO, waste can be disposed of only at designated waste disposal facilities.
Under the WDO, the Chemical Waste (General) Regulation provides regulations for chemical waste control, and administers the possession, storage, collection, transport and disposal of chemical wastes.
According to the Waste Disposal (Chemical Waste) (General) Regulation, all producers of chemical waste must register with Environmental Protection Department (EPD) and treat their wastes, either utilising on-site plant licensed by EPD, or arranging for a licensed collector to transport the wastes to a licensed facility. The Regulation also prescribes the storage facilities to be provided on site, including labelling and warning signs, and requires the preparation of written procedures and training to deal with emergencies such as spillages, leakages or accidents arising from the storage of chemical wastes.
The EPD has also issued a ‘guideline’ document, the Code of Practice on the Packaging, Labelling and Storage of Chemical Wastes (1992), which details how the Contractor should comply with the regulations on chemical wastes.
Under the Waste Disposal (Charges for Disposal of Construction Waste) Regulation, enacted in January 2006, construction waste delivered to a landfill for disposal must not contain more than 50% by weight of inert material. Construction waste delivered to a sorting facility for disposal must contain more than 50% by weight of inert material, and construction waste delivered to a public fill reception facility for disposal must consist entirely of inert material.
In accordance with the Dumping at Sea Ordinance (DASO), application for dumping permits from EPD is required for marine disposal of dredged materials.
The Practice Notes for Authorised Persons, Registered Structural Engineers and Registered Geotechnical Engineers ADV-21 (PNAP ADV-21) – Management Framework for Disposal of Dredged/ Excavated Sediment, set out the procedures for seeking approval to dredge/ excavate sediment and the management framework for marine disposal of such sediment. Applications for approval of dredging proposal and allocation of marine disposal shall be made to the Secretary of Marine Fill Committee (MFC). The aforementioned documents outline the requirements to be followed for assessing and classifying the sediment and explain the marine disposal arrangement for the classified material.
The Public Cleansing and Prevention of Nuisances Regulation provides control on illegal tipping of wastes on unauthorised (unlicensed) sites.
The Land (Miscellaneous Provisions) Ordinance requires that dumping licenses be obtained by individuals or companies who deliver public fill to public filling areas. The CEDD issues the licences under delegated powers from the Director of Lands. The current policy related to dumping of construction and demolition (C&D) materials is documented in the Works Branch Technical Circular No. 2/93 – Public Dumps. C&D materials that are wholly inert, namely public fill, should not be disposed of to landfill, but taken to fill banks or public filling areas.
Individual licences and windscreen stickers are issued for each vehicle involved. Under the licence conditions, public fill reception facilities will only accept soil, sand, rubble, brick, tile, rock, boulder, concrete, asphalt, masonry or used bentonite. In addition, in accordance with paragraph 12 of the Development Bureau (DEVB) Technical Circular (Works) TC(W) No.6/2010, Public Fill Committee (PFC) will advise on the acceptance criteria. The material will, however, be free from marine mud, household refuse, plastic, metal, industrial and chemical wastes, animal and vegetable matter and any other materials considered unsuitable by the public fill reception facility supervisor.
The criteria for assessing waste management implications are outlined in Annex 7 of the EIAO-TM. The methods for assessing potential waste management impacts during construction and operation phases of the Project follow those presented in Annex 15 of the EIAO-TM and include the following:
● Identify the quantity, quality and timing of waste arising as a result of the construction and operation activities of the Project;
● Adopt appropriate design, general layout, construction methods and programme to minimise the generation of inert C&D materials and maximise the use of inert C&D materials for other construction works.
● Prior to considering the disposal options for various types of wastes, opportunities for reducing waste generation, on-site or off-site re-use and recycling should be fully evaluated.
● Estimate the types and quantities of the wastes required to be disposed of.
● Identify the disposal methods / options for each type of waste.
● Identify the transportation routings and the frequency of the trucks / vessels involved.
● Assess the potential impacts from the management of solid waste with respect to potential hazards, air and odour emissions, noise, wastewater discharges, ecology and public transport.
● Identify and estimate excavated sediment transportation and disposal activities and requirements.
● Identify potential dumping ground to be involved.
● Identify and evaluate the best practicable methods to minimise excavation and dumping requirements.
The approved Environmental Impact Assessment (EIA) Report for the “Proposed Comprehensive Development at Wo Shang Wai, Yuen Long” (here after “approved EIA Report”) identified contaminated land at eight sampling locations within the proposed development area, containing a low-level exceedance of lead and or zinc (Dutch B levels) according to the Dutch Guidelines. An updated Contaminated Assessment Plan (CAP) based on the risk-based remediation goals (RBRGs) introduced by EPD for land contamination assessment since August 2007 to replace Dutch B levels was submitted to EPD in late 2009 for the adoption of criteria used for the Contamination Assessment Report (CAR) and Remediation Action Plan (RAP).
When the laboratory analytical results were compared with the relevant RBRGs, the nature of the contamination for the Comprehensive Development at Wo Shang Wai, Yuen Long (here after “WSW Development”) was narrowed down to only lead for heavy metals and none for hydrocarbons. Heavy metals concentration which have exceeded the respective RBRGs for “Rural Residential” criteria are found in boreholes BH-LC9 and BH-LC14 only at 1.25mbgl and 1.50mbgl respectively. It is noted that both BH-LC9 and BH-LC14 are located outside Project area of the on-site Sewage Treatment Plant (STP). The CAR and RAP were approved by EPD on 26 April 2010 and remediation has since been completed according to the procedures recommended in the approved RAP. The analytical results of soil samples had shown no exceedance of the respective RBRG “Rural Residential” criteria thus demonstrating successful completion of the remedial objectives. The remediation report (RR) was submitted to EPD on 27 January 2012 and it was approved by EPD on 12 March 2012. The treated soil was reused on site by backfilling as recommended in the RAP. The approved RR is presented in Appendix 6.1. No land contaminating activities have been carried out within the STP Project area after remediation works and the site photos of the STP Project area from 2013 to 2017 are presented in Appendix 6.2. The current land use of the STP project area is a vegetated land with temporary office building. Therefore, assessment of land contamination is considered not necessary.
The activities to be carried out for construction of the Project would generate a variety of wastes that can be divided into different key categories based on their composition and ultimate method of disposal. The identified waste types include:
● Construction and demolition (C&D) materials;
● Excavated sediment;
● Chemical waste; and
● General refuse.
Each type of the above waste arising is described below, together with an evaluation of the potential environmental impacts associated with the waste generation, handling, storage, transport and disposal.
Key Sources of C&D Materials
It is anticipated that the majority of C&D materials will be generated from the following key construction activities:
● Excavation works;
● Foundation works; and
● STP construction works.
It is estimated that the total amount of C&D materials to be generated would be mainly inert topsoil and approximately 14,000 m3. The amount of non-inert C&D materials generated during the construction phase of the Project is anticipated to be very minor as most site clearance and site formation works have been completed.
The inert materials should be segregated from the C&D materials on-site for reuse as far as practicable. In order to minimise the impact resulting from collection and transportation of C&D materials for off-site disposal, the inert C&D materials will be reused on-site as fill materials as far as practicable.
In case on-site reuse of all inert C&D materials is not applicable, the surplus inert C&D materials generated could be reused by the WSW Development or other concurrent projects in Hong Kong. During the detailed design stage, further alternative disposal arrangement (e.g. other potential projects that could receive inert C&D materials from the Project) will be continuously explored and identified. If no potential projects could receive the surplus inert C&D materials, the remaining inert C&D materials could be disposed of at the Government's Public Fill Reception Facilities (PFRFs) for beneficial use by any other projects in Hong Kong. Liaison with the CEDD Public Fill Committee (PFC) on the management of inert C&D materials will be required before the commencement of construction work. No construction work is allowed to proceed until all issues on management of C&D materials have been resolved and all relevant arrangements have been endorsed by the relevant authorities including PFC and EPD.
The Contractor should separate the non-inert C&D materials from the inert C&D materials on-site. Any recyclable materials (e.g., metal) should be segregated from the non-inert C&D materials for collection by reputable licensed recyclers. Only the remaining minor non-recyclable portion will be disposed of at designated landfill sites by dump trucks via Castle Peak Road – Mai Po using a reputable licensed waste collector. Therefore, the number of dump trucks required for delivery of the non-inert C&D materials would be minimal, which would not impose significant traffic loading on Castle Peak Road – Mai Po.
With careful planning for reuse of C&D materials on-site and proper implementation of good construction site practice and mitigation measures recommended, potential dust, noise and water quality impacts associated with on-site handling of C&D materials are not anticipated.
It is anticipated that approximately 800 m3 of sediment to be excavated from the Project. In the approved EIA Report, the sediment sampling work for WSW Development Project which covers the area of on-site STP was carried out in 2006. According to PNAP ADV-21, re-testing of sediment is required if the time lapse of sediment sampling and commencement of construction works is more than 3 years. Therefore, a Sediment Sampling and Testing Plan (SSTP) for WSW Development Project was submitted and approved by EPD on 23 October 2015. The approval letter of the SSTP is presented in Appendix 6.3. Site investigation (SI) works was carried out at the whole WSW Development Area from 10 December 2015 to 29 February 2016 to determine the properties of the excavated sediment. The location of relevant sampling point (BH04b) which covers the on-site STP is extracted and shown in Figure 6.1.
From the chemical testing results, all the sediment samples collected at BH04b exceeds the lower chemical exceedance level (LCEL) and/or the upper chemical exceedance level (UCEL) for arsenic, therefore belonging to either Category M or H. In accordance with the Geochemical Atlas of Hong Kong[1], high natural background levels of arsenic were recorded in the northern New Territories including the Project area. The details of the chemical testing results are presented in Appendix 6.4. Biological testing was further conducted on Category M sediment samples and the testing results showed that all the sediment samples collected at BH04b passed the biological tests. The details of the biological testing results are presented in Appendix 6.5. A Sediment Quality Report (SQR) was submitted and approved by EPD on 5 October 2016. The approval letter of the SQR is presented in Appendix 6.6.
The identified categories and the estimated quantities of sediment to be excavated from the Project is summarised in Table 6.1.
Table 6.1: Estimation of Sediment Quantities for Each Category
|
Sediment Category |
Estimated Sediment Quantity (m3) |
|
M |
480 |
|
H |
320 |
|
Total |
800 |
All the sediment will be treated and reused as backfilling material in the WSW Development. After exploring different possibilities of carrying out remediation on-site and reuse of treated sediment, it is proposed to mix sand/soil and cement with all the sediment generated from this Project to provide the treated sediment as construction material, which will be used as profiling and backfilling within the WSW Development. A minimum cement content of 5% is proposed for all categories (M and H) of contaminated sediment subject to corresponding tests.
The criteria for reuse of treated sediment are proposed with reference to the Universal Treatment Standards (UTS) and Unconfined Compressive Strength (UCS) Standard as shown in Table 6.2.
Table 6.2: Criteria for Reuse of Treated Sediment
|
Standard |
Parameters |
Criteria |
|
Universal Treatment Standards (1) |
Arsenic |
Toxicity Characteristics Leaching Procedure (TCLP) limit: 5 mg/L |
|
Unconfined Compressive Strength Standard |
Unconfined Compressive Strength |
Not less than 1 MPa |
Note: 1. Universal Treatment Standard – US 40 CFR 268.48
The methodology for mixing the sediment with sand/soil and cement involves drying the excavated sediment and mixing with sand/soil in batches using an excavator and/or backhoe. A cement and water mixture will then be added for the solidification process. The treated sediment will be placed at a temporary storage area covered by tarpaulin sheets, while samples are taken for laboratory testing. The testing frequency shall be one sample per 200 m3 for the first 10,000 m3 of treated sediment.
Chemical wastes arising during the construction phase may pose environmental, health and safety hazards if not stored and disposed of in an appropriate manner as stipulated in the Waste Disposal (Chemical Waste) (General) Regulations. The potential hazards include:
● Toxic effects to workers;
● Adverse impacts on water quality from spills; and
● Fire hazards.
The maintenance and servicing of construction plants and equipment may generate some chemical wastes such as used solvents, contaminated rags and waste lubricating oil. It is difficult to quantify the amount of chemical waste that will arise from the construction activities since it will be dependent on the Contractor’s on-site maintenance requirements. However, it is anticipated that the quantity of chemical waste, such as waste lubricating oil and solvents produced from plant maintenance, will be small and estimated to be less than a few litres per month. The amount of chemical waste to be generated will be quantified in the Waste Management Plan (WMP) to be prepared by the Contractor for the site.
Materials classified as chemical wastes will require special handling and storage arrangements before removal for off-site disposal at the approved Chemical Waste Treatment Facility (CWTF) or recycling by licensed facilities. Mitigation and control requirements for chemical wastes are detailed in Section 6.5.1.5. Provided that the handling, storage and disposal of chemical wastes are in accordance with these requirements, adverse environmental impacts are not expected.
The construction workforce will generate refuse comprising food scraps, waste paper and empty containers etc. The daily general refuse arising from the construction workforce can be estimated based on a generation rate of 0.65 kg per worker per day. It is estimated that about 30 construction workers would be employed during the construction phase. Therefore, approximately 20 kg/day of general refuse will be generated.
Such refuse will be properly managed so that intentional or accidental release to the surrounding environment will be avoided. Such refuse will be delivered to licensed landfill sites or refuse transfer stations. Disposal of refuse at sites other than approved waste transfer or disposal facilities will be prohibited. Effective collection of site wastes will be required to prevent waste materials being blown around by wind, flushed or leached into the drainage system, or creating an odour nuisance or pest/ vermin problem. Waste storage areas will be well maintained and cleaned regularly.
Corresponding to this maximum daily volume, up to around 1 vehicle-trip per day would be needed for delivery of the general refuse by dump trucks (each with a loading capacity of about 6 m3) to the designated landfill sites via Castle Peak Road – Mai Po. Given this small daily number of vehicle-trips, the extra traffic loading on the public roads would be negligible.
With the implementation of good waste management practices at the site, adverse environmental impacts are not expected to arise from the storage, handling and transportation of workforce wastes.
Table 6.3 presents a summary of all key types of waste arising during the construction phase of the Project.
Table 6.3: Summary of Waste Arising during Construction Phase
|
Waste Type |
Key Sources of Waste Generation |
Timing of Waste Generation |
Estimated Quantity of Waste Generation |
Waste Reuse or Disposal |
|
Inert C&D Materials |
Excavation works; foundation works; STP construction works |
Q3 2018 – 2021 |
About 14,000 m3 |
The inert C&D materials generated would be reused on-site as fill materials as far as practicable. In case on-site reuse of all inert C&D materials is not applicable, the surplus inert C&D materials generated could be reused by WSW Development or other concurrent projects in Hong Kong. |
|
Non-inert C&D materials |
Excavation works; foundation works; STP construction works* |
Q3 2018 – 2021 |
Anticipated as very minor |
Any recyclable materials (e.g., metal) will be segregated from the non-inert C&D materials for collection by reputable licensed recyclers. Only the remaining minor non-recyclable portion will be disposed of at designated landfill sites. |
|
Excavated Sediment |
Excavation works |
Q3 2018 – 2021 |
800 m3 |
The sediment will be treated and reused as backfilling material in WSW Development |
|
General Refuse |
Food scarps, waste paper, empty containers, etc. generated from the site workforce |
Q3 2018 – 2021 |
0.65kg per worker per day, the maximum daily arising of general refuse during the construction period would be approximately 20 kg
|
Encourage segregation of recyclable materials (e.g., paper, tin-cans, etc.) for collection by outside recyclers. The non-recyclable materials will be disposed of at refuse station or designated landfill sites. |
|
Chemical Waste |
Used cleansing fluids, solvents, lubricating oil, waste fuel, etc., from maintenance and servicing of construction plant and equipment |
Q3 2018 – 2021 |
Anticipated as small quantity To be quantified in the site Waste Management Plan to be prepared by the Contractor |
The chemical waste will be disposed of at the Chemical Waste Treatment Centre or other licensed recycling facilities. |
* Most site clearance and site formation works have been completed. Therefore, non-inert C&D materials are not anticipated to be generated from these works.
The on-site STP will temporarily handle the sewage generated by the WSW Development before the government sewerage network is available. The design capacity of the proposed treatment plant is 1,446 m3/day, which meets the design population of 1,245 persons based on the 400 residential units development.
The following types of wastes would be generated during operation of the on-site STP:
● Screening and grits;
● Sludge;
● General refuse; and
● Chemical waste.
Each type of the above waste arising is described below, together with an evaluation of the potential environmental impacts associated with the waste generation, handling, storage, transport and disposal.
Screening and grits would be generated at the inlet works of the proposed STP. The screening and grits will be properly stored in a fully enclosed container before disposal to designated landfill sites. The total quantity of screening and grits generated in the proposed STP is expected to be 0.075 m3/day. Considering the small amount of screening and grits generated, the number of containers required for disposal of screening and grits would be minimal. The transportation and disposal of the screening will be handled by a reputable licensed waste collector. No adverse environmental impact is anticipated given proper handling and disposal of the screening and grits generated.
The major solid waste types produced from the proposed STP would be the sludge associated with the sewage treatment process. The total quantity of sludge generated in the proposed STP is expected to be 13 m3/day. It is estimated that around 2 tankers per day would be required to transport the sludge for disposal via Castle Peak Road – Mai Po.
Sludge generated from the proposed sewage treatment plant will be mechanically dewatered, which will then be delivered to the designated landfill sites for final disposal. Another alternative to on-site dewatering of sludge, sludge could be transferred to government’s sewage treatment works for off-site treatment. Once the arrangement of disposal of sludge is finalised during the detailed design stage of the Project, agreement will be sought from relevant authorities.
The sludge will be properly stored in a fully enclosed container before delivery for disposal or off-site treatment in order to minimise odour emission and potential health risks to the workforce due to pests and other disease vectors. The transportation and disposal of the sludge will be handled by a reputable licensed waste collector. No adverse environmental impact is expected given proper handling and disposal during the operational phase of the Project.
General refuse (such as food scraps, waste paper, empty containers and packaging, etc.) from operation of the Project will mainly be generated from staff working within the Project. Such refuse will be properly managed by suitable waste collectors so that intentional or accidental release to the surrounding environment will not occur. The amounts of general refuse generation during the operation phase have been preliminarily estimated during the design stage of the Project, and are summarized in Table 6.4.
Table 6.4: Estimation of General Refuse Generation during Operation Phase
|
Number of Staff |
Waste Classification (1) |
Per capita disposal rate (2) |
Estimated Waste Generation |
|
10 |
Commercial waste |
0.35 kg/ person/ day* |
3.5 kg/day |
Source: (1) Appendix 1: Classification of Solid Waste and
Monitoring Methodology, in Monitoring of Solid Waste in Hong Kong – Waste
Statistic for 2014
(2) Plate 2.1 and Plate 2.7, Monitoring of Solid Waste in Hong Kong –
Waste Statistic for 2014
Note: *Calculated from percentage of commercial waste over total municipal solid waste, based on municipal solid waste disposal rate
Effective collection of general wastes will be implemented to prevent waste materials from creating odour nuisance or pest/ vermin problem. Waste storage areas will be well maintained and cleaned regularly. To reduce waste and improve recycling, it is expected that waste such as waste paper, plastics and aluminium can be segregated for off-site recycling.
Chemical waste will be generated from various routine maintenance and servicing activities for emergency generators and other electrical and mechanical equipment. Chemical waste such as waste lubricating oil, contaminated rags, waste paint, used solvents and spent chemicals are expected to be generated from these activities. It is difficult to quantify the amount of chemical waste that will arise from those activities at this stage since it will be dependent on the equipment maintenance requirements and the amount of equipment utilised.
Chemical wastes may pose environmental, health and safety hazards if not stored and disposed of in an appropriate manner as stipulated in the Waste Disposal (Chemical Waste) (General) Regulation. Chemical wastes will require special handling and storage arrangements in accordance with the relevant regulations before removal for off-site disposal at the approved CWTF or recycling by licensed facilities. Provided that the handling, storage and disposal of chemical wastes will be in accordance with these requirements, adverse environmental impacts will not be expected.
The on-site STP is proposed to temporary handle the sewage generated by the WSW Development before the government sewerage network is available. Once all the sewage is connected to the permanent government sewer, the on-site STP would be decommissioned but will not be demolished. Therefore, it is anticipated that no waste will be generated during decommissioning phase.
Adverse impacts related to waste management such as dust, odour, noise and wastewater discharge will not be expected to arise, provided that good site practices will be strictly followed. Recommendations for good site practices during the construction activities include:
● Nomination of an approved person, such as a site manager, to be responsible for good site practices, arrangements for collection and effective disposal to an appropriate facility, of all wastes generated at the site
● Training of site personnel in proper waste management and chemical handling procedures
● Provision of sufficient waste disposal points and regular collection of waste
● Appropriate measures to minimise windblown litter and dust/odour during transportation of waste by either covering trucks or by transporting wastes in enclosed containers
● Stockpiles of C&D materials should be kept covered by impervious sheets to avoid wind-blown dust.
● All dusty materials including C&D materials should be sprayed with water immediately prior to any loading transfer operation so as to keep the dusty material wet during material handling at the stockpile areas
● Provision of wheel washing facilities before the trucks leaving the works area so as to minimise dust introduction to public roads
● Well planned delivery programme for offsite disposal such that adverse environmental impact from transporting the inert or non-inert C&D materials is not anticipated
Good management and control can prevent the generation of a significant amount of waste. Waste reduction is best achieved at the planning and design stage, as well as by ensuring the implementation of good site practices. Recommendations to achieve waste reduction include:
● Sort non-inert C&D materials to recover any recyclable portions
● Segregation and storage of different types of waste in different containers or skips or stockpiles to enhance reuse or recycling of materials and their proper disposal
● Encourage collection of recyclable waste such as waste paper and aluminium cans by providing separate labelled bins to enable such waste to be segregated from other general refuse generated by the work force
● Proper site practices to minimise the potential for damage or contamination of inert C&D materials
● Plan the use of construction materials carefully to minimise amount of waste generated and avoid unnecessary generation of waste
In addition to the above measures, specific mitigation measures are recommended below for the identified waste arising to minimise environmental impacts during handling, transportation and disposal of these wastes.
In order to minimise impacts resulting from collection and transportation of inert C&D materials for off-site disposal, the inert C&D materials should be reused on-site as fill material as far as practicable. In addition, inert C&D materials generated from excavation works could be reused as fill materials in local projects that require public fill for reclamation.
The surplus inert C&D materials will be disposed of at the Government’s PFRFs for beneficial use by other projects in Hong Kong.
The C&D materials generated from general site clearance should be sorted on site to segregate any inert materials for reuse or disposal of at PFRFs whereas the non-inert materials will be disposed of at the designated landfill site.
In order to monitor the disposal of inert and non-inert C&D materials at respectively PFRFs and the designated landfill site, and to control fly-tipping, it is recommended that the Contractor should follow the DEVB Technical Circular (Works) No. 6/2010 for Trip Ticket System for Disposal of Construction & Demolition Materials issued by Development Bureau. In addition, it is also recommended that the Contractor should prepare and implement a Waste Management Plan detailing their various waste arising and waste management practices in accordance with the relevant requirements of the ETWB Technical Circular (Works) No. 19/2005 Environmental Management on Construction Site.
The following mitigation measures shall be implemented for excavation of sediment:
● The loading, unloading, handling, transfer or storage of treated and untreated sediment should be carried out in such a manner to prevent or minimise dust emissions;
● Temporary stockpiling shall be avoided as far as possible. In case temporary storage is needed, the untreated sediment should be placed at a designated area paved with either concrete or liner and covered properly with tarpaulins;
● Speed control shall be implemented for vehicles carrying untreated sediment within the site to minimise dust emission; and
● All necessary measures should be employed to prevent cross-contamination of untreated sediment with other excavated / fill materials.
General health and safety precautions shall also be employed for all personnel working on site, including:
● No food and drink allowed on site;
● Direct skin contact with excavated sediment should be avoided;
● Provide all necessary Personal Protective Equipment (PPE) to site workers;
● Bulk earth moving equipment shall be used for handling the sediment as much as possible;
● Minimise dust generation; and
● Provision of personal cleaning facilities.
The following mitigation measures shall be implemented for handling, collection, transportation and disposal of screening and grits:
● Screens should be cleaned regularly to remove any accumulated organic debris;
● Screening and grit transfer system should be flushed regularly with water to remove organic debris;
● Screening and grits generated should be transferred to closed containers before transportation and disposal at designated landfill sites.
The following mitigation measures shall be implemented for handling, collection, transportation and disposal of sludge:
● Frequent sludge withdrawal from tanks is necessary to prevent the production of gases;
● Sludge should be transferred to closed containers before transportation and disposal at designated landfill sites or public sewage treatment works by designated sewage tankers;
● Sludge tankers and containers should be flushed with water regularly;
● Sludge tankers should be washed thoroughly before leaving the proposed sewage treatment plant to avoid any odour nuisance during transportation;
● All wastewater, if any, generated from the sludge dewatering process should be diverted to the proposed sewage treatment plant for proper treatment.
General refuse should be collected on daily basis and delivered to the refuse collection point accordingly. A reputable waste collector should be employed to remove general refuse regularly to avoid odour nuisance or pest/vermin problem. Sufficient recycling containers are recommended to be provided at suitable locations of the Project to encourage recycling of such waste as aluminium cans, plastics and waste paper.
With the implementation of the recommended mitigation measures for the handling, transportation and disposal of the identified waste arising, residual impacts are not anticipated during both construction and operation phases of the Project.
It would be the Contractor’s responsibility to ensure that all wastes produced during the construction of the Project are handled, stored and disposed of in accordance with good waste management practices and EPD’s regulations and requirements. The recommended mitigation measures should form the basis of the WMP to be developed by the Contractor throughout the Project period. The WMP shall be prepared and implemented in accordance with ETWB TC (W) No. 19/2005 Environmental Management on Construction Site.
Throughout the construction phase of the Project, regular site inspections as part of the EM&A procedures should be carried out to determine if wastes are being managed in accordance with the WMP. Different aspects of waste management including waste generation, storage, recycling, treatment, transport and disposal would be included in the programme.
The major waste types generated by the construction activities will include C&D materials from excavation works, foundation works, STP construction works; sediment from excavation works; chemical waste from maintenance and servicing of construction plant and equipment and general refuse from the workforce. Provided that all these identified wastes are handled, transported and disposed of in accordance with the relevant legislative and recommended requirements and the recommended good site practices and mitigation measures are properly implemented, no adverse environmental impact is expected during the construction phase.
During the operation phase, the waste types generated will be screening and grits, sludge from the operation of the on-site STP, general refuse from staff, and chemical waste from regular maintenance activities. Provided that all these wastes are handled, transported and disposed of in accordance with the relevant legislative requirements and the recommended mitigation measures are properly implemented, no adverse environmental impact is expected during the operation phase.
[1] Sewell, R.J.. Geochemical Atlas of Hong Kong. Civil Engineering Department Geotechnical Engineering Office, 1999.