4. Waste Management Impact Assessment

4.1 Introduction

This section identifies the quantity, quality and timing of wastes arising during the construction and operation phases of the Project, in particular the dredged sediment, as a result of the construction activities and based on the sequence and duration of these activities to evaluate the potential environmental impacts that may result from these wastes. The major solid waste would be dredged marine sediment from the construction of the proposed submarine gas pipelines. Mitigation measures and good site practices, including waste handling, storage and disposal, are recommended with reference to the applicable waste legislation and guidelines.

4.2 Environmental Legislation, Standards, Guidelines and Criteria

4.2.1 General

The criteria and guidelines for assessing waste management implications are outlined in Annex 7 and Annex 15 of the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM), respectively.

The following legislation relates to the handling, treatment and disposal of wastes in the Hong Kong SAR and has been used in assessing potential impacts:

¡ Waste Disposal Ordinance (Cap. 354)

¡ Waste Disposal (Chemical Waste) (General) Regulation (Cap. 354)

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

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

¡ Dumping at Sea Ordinance (Cap. 466)

4.2.2 Waste Management

The Waste Disposal Ordinance (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, wastes can be disposed of only at designated waste disposal facilities.

Under the WDO, the Chemical Waste (General) Regulation 1992 provides regulations for chemical waste control, and administers the possession, storage, collection, transport and disposal of chemical wastes. The Environmental Protection Department (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.

The Public Cleansing and Prevention of Nuisances Regulation provides control on illegal tipping of wastes on unauthorised (unlicensed) sites.

4.2.3 Construction and Demolition (C&D) Materials

The current policy related to the dumping of C&D material is documented in the Works Branch Technical Circular No. 2/93, ‘Public Dumps’. Construction and demolition materials that are wholly inert, namely public fill, should not be disposed of to landfill, but taken to public filling areas, which usually form part of reclamation schemes. The Land (Miscellaneous Provisions) Ordinance requires that dumping licences be obtained by individuals or companies who deliver public fill to public filling areas. The Civil Engineering & Development Department (CEDD) issues the licences under delegated powers from the Director of Lands.

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.

Measures have been introduced under Environment, Transport and Works Bureau (ETWB) TCW No. 33/2002, “Management of Construction and Demolition Material Including Rock” to enhance the management of construction and demolition material, and to minimize its generation at source. The enhancement measures include: (i) drawing up a Construction and Demolition Material Management Plan (C&DMMP) at the feasibility study or preliminary design stage to minimize C&D material generation and encourage proper management of such material; and (ii) providing the contractor with information from the C&DMMP in order to facilitate him in the preparation of the Waste Management Plan (WMP) and to minimize C&D material generation during construction. Projects generating C&D material less than 50,000m³ or importing fill material less than 50,000m³ are exempt from the C&DMMP. The new ETWB TCW No. 19/2005 “Environmental Management on Construction Sites” includes procedures on waste management requiring contractors to reduce the C&D material to be disposed of during the course of construction. Under ETWB TCW No. 19/2005, the contractor is required to prepare and implement an Environmental Management Plan (EMP) and the Waste Management Plan (WMP) which becomes part of the EMP.

4.2.4 Marine Dredged Sediment

ETWB TCW No. 34/2002, “Management of Dredged/Excavated Sediment” sets out the procedures for seeking approval to dredge/excavate sediment and the management framework for marine disposal of such sediment. Dredged marine sediment arising from the Project will be managed in accordance with the requirements of ETWB TCW No. 34/2002. The sediment quality criteria for the classification of sediment are presented in Table 4.5.

In accordance with the Dumping at Sea Ordinance, application for dumping permits from EPD are required for marine disposal of dredged materials.

4.3 Assessment Methodology

4.3.1 General

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 the construction phase follow those presented in Annex 15 of the EIAO-TM and include the following:

Estimation of the types and quantities of the wastes generated.

¡ Assessment of potential impacts from the management of solid waste with respect to potential hazards, air and odour emissions, noise, wastewater discharges and public transport.

¡ Assessment of impacts on the capacity of waste collection, transfer and disposal facilities.

4.3.2 Marine Site Investigation

The Quaternary Geology of Hong Kong (CED, May 2000), 1:100 000 Seabed Sediments Map indicates that mud and sandy mud deposits are present over the proposed alignment. This is supported by the related 1:20 000 Hong Kong Geological Survey Geology Map (Sheet 11, Hong Kong & Kowloon, 1986) which identifies that the superficial geology along the proposed alignment comprises Holocene marine mud.

The Marine Water Quality in Hong Kong in 2007 (EPD 2008) indicated that there is only one EPD reference marine sampling point (VC3) in the vicinity of the alignment. The most recent available test results from recovered sediments from this location indicate that a number of heavy metals such as Copper, Silver and Zinc exceeded the Lower and Upper Chemical Exceedence Limits (LCEL & UCEL) as per PNAP 252. The high levels of Copper were attributed to discharges from printed circuit board, electroplating, metal and textile industries between the 1960’s and 1980’s, while the elevated Silver levels were stated to originate possibly from pollution due to electroplating industries, photo-processing business and dental clinics in the Harbour area. From the above quoted results, it is believed that a proportion of the proposed dredged marine clay volumes may be considered as Category M or H sediment that require chemical and biological screening.

Based on the results of the previous studies discussed above, the sediment of the Project Corridor could be contaminated with high levels of copper and possibly other heavy metals. In this respect and with reference to ETWB TCW No. 34/2002, the marine investigations consist of vibrocore sampling on a 100m by 100m grid spacing with 100mm subsamples taken at seabed, 0.9m down, 1.9m down, 2.9m down, 5.9m down and 8.9m down, where appropriate

A total of 30 vibrocore were taken at designated locations along the submarine gas pipelines alignment to determine the vertical profile of sediment quality. Coordinates, type and depth of the vibrocores are summarised in Table 4.1.

Table 4.1: Coordinates, Type and Depth of Vibrocores

Vibrocore	Coordinates		Material	Seabed level	Length
No.	Easting	Northing	Type	mPD	Recovered (m)
VC1A	837850.20	819314.60	Marine mud	-5.60	6.00
VC2A	837950.20	819309.10	Marine mud	-4.70	6.00
VC3	838032.20	819295.40	Marine mud	-7.10	6.00
VC4	838087.50	819210.20	Marine mud	-7.70	6.00
VC5	838141.60	819127.30	Marine mud	-7.80	6.00
VC7	838250.30	818960.10	Marine mud	-9.50	6.00
VC8	838316.80	818885.60	Marine mud	-9.20	6.00
VC9	838388.30	818817.20	Marine mud	-8.00	6.00
VC10	838464.30	818755.60	Marine mud	-9.20	6.00
VC11	838546.70	818702.60	Marine mud	-9.40	6.00
VC12	838632.50	818657.60	Marine mud	-12.10	6.00
VC13	838725.60	818619.30	Marine mud	-10.75	6.00
VC14	838821.10	818578.10	Marine mud	-11.00	6.00
VC15	838904.50	818533.20	Marine mud	-11.00	6.00
VC16	838981.50	818478.60	Marine mud	-11.00	6.00
VC17	839055.30	818420.20	Marine mud	-10.10	6.00
VC18	839122.20	818352.40	Marine mud	-11.00	6.00
VC19	839180.30	818281.60	Marine mud	-10.80	6.00
VC20	839233.10	818203.50	Marine mud	-10.20	6.00
VC21	839276.60	818123.50	Marine mud	-10.10	6.00
VC22	839313.00	818036.50	Marine mud	-10.20	9.00
VC23	839343.60	817948.40	Marine mud	-10.50	9.00
VC24	839372.00	817858.00	Marine mud	-10.70	9.00
VC31	839402.30	817760.10	Marine mud	-12.60	9.00
VC33	839462.70	817568.50	Marine mud	-12.60	4.00
VC33B	839447.30	817569.20	Marine mud	-16.40	5.00
VC34	839492.00	817473.00	Marine mud	-12.20	9.00
VC35	839523.40	817377.20	Marine mud	-12.40	9.00
VC36	839552.60	817281.30	Marine mud	-12.10	9.00
VC37	839582.20	817186.40	Marine mud	-12.00	9.00

4.3.3 Marine Dredged Sediment

4.3.3.1 General

Marine site investigation works of the Project were carried out in mid 2008. Vibrocore records are presented in Appendix C1. The records indicated that the material along the proposed alignment of the submarine gas pipelines consist mainly of marine deposits which are very soft, grey, sandy, silty clay with some gravel size shell fragments.

Laboratory testing of contaminants was included in the marine site investigation works to determine the level of contamination in the marine sediments at the existing seabed. The works included vibrocoring at 30 locations distributed along the proposed submarine gas pipelines alignment as detailed in Table 4.1. Locations of the vibrocore sampling points are presented in Figure 4.1.

4.3.3.2 Chemical Testing

Sample Arrangement

Tier II chemical screening was carried out to determine whether the sediment is suitable for open sea disposal without further testing in accordance with the requirements of ETWB TCW No. 34/2002. Sediment samples collected for chemical testing are presented in Table 4.2.

Table 4.2: Sample Arrangement for Chemical Testing

Vibrocore	Coordinates		Sampling Depth
No.	Easting	Northing	From (m) To (m)
VC1A	837850.20	819314.60	0.0 - 0.9 0.9 - 1.9 1.9 - 2.9 2.9 - 5.9
VC2A	837950.20	819309.10
VC3	838032.20	819295.40
VC4	838087.50	819210.20
VC5	838141.60	819127.30
VC7	838250.30	818960.10
VC8	838316.80	818885.60
VC9	838388.30	818817.20
VC10	838464.30	818755.60
VC11	838546.70	818702.60
VC12	838632.50	818657.60
VC13	838725.60	818619.30
VC14	838821.10	818578.10
VC15	838904.50	818533.20
VC16	838981.50	818478.60
VC17	839055.30	818420.20
VC18	839122.20	818352.40
VC19	839180.30	818281.60
VC20	839233.10	818203.50
VC21	839276.60	818123.50
VC22	839313.00	818036.50	0.0 - 0.9 0.9 - 1.9 1.9 - 2.9 2.9 - 5.9 & 5.9 - 8.9
VC23	839343.60	817948.40
VC24	839372.00	817858.00
VC31	839402.30	817760.10
VC33	839462.70	817568.50	0.0 - 0.9, 0.9 - 1.9 & 1.9 - 2.9
VC33B	839447.30	817569.20	2.9 - 5.9 & 5.9 - 8.9
VC34	839492.00	817473.00	0.0 - 0.9 0.9 - 1.9 1.9 - 2.9 2.9 - 5.9 & 5.9 - 8.9
VC35	839523.40	817377.20
VC36	839552.60	817281.30
VC37	839582.20	817186.40

Sample Preparation

Continuous samples were taken vertically from seabed down to the bottom of the proposed dredged layers. Vibrocoring was terminated in the alluvium layer below the marine mud deposit. On recovery, each vibrocore was cut into sub-samples. The top level of the sub-samples were at seabed, 0.9m below bed level, 1.9m below bed level, 2.9m below bed level, 5.9m below bed level and 8.9m below bed level, where appropriate.

Sections of vibrocore tube were cut, sealed and capped, labelled, stored in a dark environment in a cool box below 4⁰C immediately after collection on site. On transfer from site to laboratory, samples were kept at below 4⁰C, by regularly replacing the ice packs.

Determination Method and Reporting Limits

Chemical Testing was carried out for all vibrocores taken from the 30 locations. Each sub-sample recovered from vibrocoring was tested in the laboratory for the following parameters:

¡ Metals concentrations including cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), zinc (Zn), mercury (Hg), arsenic (As) and silver (Ag).

¡ Concentrations of organic compounds including total polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), and tributyltin (TBT).

Details of the determination methods and reporting limits are provided in Tables 4.3 and 4.4 respectively.

Table 4.3: Testing Methods and Reporting Limits for Metals and Metalloids Analysis

Code	Test Parameter	Preparation Method USEPA Method	Determination Method USEPA Method	Reporting limits (mg/kg)
Cd	Cadmium	3050B	6020A	0.20
Cr	Chromium	3050B	6010C	8.0
Cu	Copper	3050B	6010C	7.0
Ni	Nickel	3050B	6010C	4.0
Pb	Lead	3050B	6010C	8.0
Zn	Zinc	3050B	6010C	20
Hg
Mercury	7471A	7471A	0.05
As	Arsenic	3050B	6020A	1.0
Ag	Silver	3050B	6020A	0.10

Table 4.4: Testing Methods and Reporting Limits for TBT, PAHs and PCBs Analysis

Parameter	Method Reference	Reporting limits
Total PCB	USEPA 3550B & 8082	3 µg/kg
PAHs	USEPA 3550B, 3630C & 8270C	55 ug/kg for LMW PAHs 170 ug/kg for HMW PAHs
TBT in interstitial water	UNEP/IOC/IAEA	15 ng TBT/L

Sediment Classification

Dredged sediment destined for marine disposal are classified according to their level of contamination by 13 contaminants as detailed in Table 4.5:

Table 4.5: Sediment Quality Criteria for the Classification of Sediment

Contaminants	LCEL	UCEL
Heavy Metal (mg/kg dry weight)
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 weight)
Arsenic	12	42
Organic-PAHs (µg/kg dry weight)
PAHs (Low Molecular Weight)	550	3160
PAHs (High Molecular Weight)	1700	9600
Organic-non-PAHs (µg/kg dry weight)
Total PCBs	23	180
Organometallics (µg-TBT L-1 in interstitial water)
Tributyltin	0.15	0.15

Source: Appendix A of ETWB TCW No. 34/2002 Management of Dredged / Excavated Sediment

Note: LCEL – Lower Chemical Exceedance Level

UCEL – Upper Chemical Exceedance Level

Sediments are categorised with reference to the LCEL and UCEL, as follows:

Category L Sediment with all contaminant levels not exceeding the LCEL. The material must be dredged, transported and disposed of in a manner that minimises the loss of contaminants either into solution or by suspension.

Category M Sediment with any one or more contaminant levels exceeding the LCEL and none exceeding the 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.

In case of Category M and Category H contamination, the final determination of appropriate disposal options, routing and the allocation of a permit to dispose of material at a designated site will be made by EPD and the Marine Fill Committee (MFC) in accordance with the ETWB TCW No. 34/2002.

4.3.4 Biological Testing

For Category M sediment and Category H sediment with contaminant levels exceeding 10 times the LCEL, Tier III biological screening was carried out to determine the appropriate disposal methods in accordance with the requirements of ETWB TCW No. 34/2002.

Based on the results of the chemical testing and the estimated dredging depth of -8m for formation of the trench, the sediment samples presented in Table 4.6 were subjected to biological testing, with a total of seven test samples:

Table 4.6: Composite Sample Arrangement for Biological Testing

Composite Sample No.	Vibrocore No.	Coordinates		Sample Depth (m)
		Easting	Northing
1	VC-16	838981.50	818478.60	0.9-1.9
2	VC-36	839552.60	817281.30	1.9-2.9
3	VC-3	838032.20	819295.40	0.9-1.9
4	VC-2A	837950.20	819309.10	2.9-5.9
5	VC-1A	837850.20	819314.60	2.9-5.9
6	VC-1A	837850.20	819314.60	0.0-0.9
7	VC-1A	837850.20	819314.60	0.9-1.9

The following three toxicity tests (to be considered as one set) were conducted on each sample:

¡ a 10‑day burrowing amphipod toxicity test ; and

¡ a 20‑day burrowing polychaete toxicity test; and

¡ a 48‑96 hour larvae (bivalve or echinoderm) toxicity test.

The species used for each type of biological test and the test conditions are listed in Table 4.7 below.

Table 4.7: Test Species for Biological Testing

Test Types	Species	Reference Test Conditions*
10‑day burrowing amphipod toxicity test	Leptocheirus plumulosus	USEPA (1994)
20‑day burrowing polychaete toxicity test	Neanthes arenaceodentata	PSEP (1995)
48‑96 hour bivalve larvae toxicity test	Crassostrea gigas	PSEP (1995)

Notes:*

(1) U.S.EPA (U.S. Environmental Protection Agency) 1994. Methods for assessing the toxicity of sediment-associated contaminants with estuarine and marine amphipods. Office of Research and Development. U.S. Environmental Protection Agency, Cincinnati, OH. EPA/600/R94/025.

(2) PSEP (Puget Sound Estuary Program) 1995. Recommended guidelines for conducting laboratory bioassays on Puget Sound sediments.

Sediment samples were characterized by the testing laboratory for ancillary testing parameters such as porewater salinity, ammonia, TOC, grain size and moisture content. This provided necessary information on the general characteristics of the sediment.

The test endpoints and decision criteria are summarized in Table 4.8. The sediment was deemed to have failed the biological testing if it failed in any one of the three toxicity tests.

Table 4.8: Test endpoints and decision criteria for biological testing

Toxicity test	Endpoints measured	Failure criteria
10-day amphipod	Survival	Mean survival in test sediment is significantly different (p < 0.05)¹ from mean survival in reference sediment and mean survival in test sediment < 80% of mean survival in reference sediment.
20-day polychaete	Dry Weight²	Mean dry weight in test sediment is significantly different (p < 0.05)¹ from mean dry weight in reference sediment and mean dry weight in test sediment < 90% of mean dry weight in reference sediment.
48-96 hour bivalve larvae	Normality Survival³	Mean normality survival in test sediment is significantly different (p < 0.05)¹ from mean normality survival in reference sediment and mean normality survival in test sediment < 80% of mean normality survival in reference sediment.

¹ Statistically significant differences should be determined using appropriate two-sample comparisons (e.g., t-tests) at a probability of p£ 0.05.

²Dry weight means total dry weight after deducting dead and missing worms.

³ Normality survival integrates the normality and survival end points, and measures survival of only the normal larvae relative to the starting number.

4.4 Baseline Condition of Marine Dredged Sediment

4.4.1 Chemical Screening

The marine sediment quality analysis results of chemical screening from the marine site investigation works are included as Appendix C2, as compared with the sediment quality criteria for the classification of sediment, are presented in Table 4.9.

The sediment chemical testing results indicated that Category L sediments were found at all depths at vibrocores VC17, 19, 20, 21, 22, 23, 24, 31, 33, 33B and 34. Category M sediment was found at vibrocores VC1A, 2A, 3, 16 and 36 in terms of Cu, Ni, Pb, Hg, Ag and high molecular weight PAHs. Category H sediment was found at vibrocores VC1A, 4, 5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 18, 35 and 37. The contamination is high in terms of Cu, Ni, Zn, Hg, and Ag. Sediment samples at VC1A, 2A, 3, 16 and 36 were required to proceed to Tier III biological screening.

Chlorinated pesticides (including alpha-BHC, beta-BHC, gamma-BHC, delta-BHC, heptachlor, Aldrin, heptachlor epoxide, endososulfan, p,p’-DDT, p,p’-DDD, p,p’-DDE and endosulfan sulphate) were measured in sediment samples. The laboratory results showed that all the samples are below the detection limit which means pesticides were not detected in any of the sediment.

Table 4.9: Contaminant Levels of Vibrocore Samples and Their Categories

Vibrocore No.	From (m)	To (m)	Material	LMW	HMW	Total PCBs	Metals									TBT	Overall Category^#	Disposal Type
			Type	PAHs	PAHs	Total PCBs	mg/kg									ng/L
				ug/kg	ug/kg	ug/kg	Cd	Cr	Cu	Ni	Pb	Zn	Hg	As	Ag
VC-1A	0	0.9	Clay	1100	3700	<3	1.4	130	970	54	110	340	1.0	6.2	7.9	<0.015	H_f	3
VC-1A	0.9	1.9	Clay	950	6300	<3	1.5	110	660	45	110	420	1.5	6.5	14	<0.015	H_f	3
VC-1A	1.9	2.9	Clay	500	2400	<3	1.6	160	<7.0	69	58	380	1.2	5.7	7.8	<0.015	H	2
VC-1A	2.9	5.9	Clay/Silt	300	400	<3	<0.20	25	92	15	27	56	0.18	3.3	0.83	<0.015	M_f	2
VC-2A	0	0.9	Fill	<55	<170	<3	<0.20	17	55	7.2	52	140	0.15	4.0	0.44	<0.015	L	1
VC-2A	0.9	1.9	Clay/Silt	<55	<170	<3	<0.20	11	12	<4.0	30	<20	0.1	2.4	<0.10	<0.015	L	1
VC-2A	1.9	2.9	Clay/Silt	<55	<170	<3	<0.20	<8.0	17	<4.0	59	53	0.17	3.2	<0.10	<0.015	L	1
VC-2A	2.9	5.9	Clay/Silt	230	1800	<3	0.41	38	58	13	34	140	0.54	3.8	0.84	<0.015	M_f	2
VC-3	0	0.9	Fill	<55	<170	<3	<0.20	<8.0	19	<4.0	35	30	0.18	1.6	0.18	<0.015	L	1
VC-3	0.9	1.9	Clay	<55	<170	<3	0.42	47	82	16	83	120	0.81	4.4	1.3	<0.015	M_f	2
VC-3	1.9	2.9	Clay	<55	<170	<3	<0.20	21	<7.0	14	19	41	0.08	3.9	<0.10	<0.015	L	1
VC-3	2.9	5.9	Clay/Silt	<55	<170	<3	<0.20	15	<7.0	7.4	25	20	0.12	1.7	<0.10	<0.015	L	1
VC-4	0	0.9	Clay/Silt	<55	460	<3	1.2	96	420	34	78	260	0.71	7.0	9.8	<0.015	H	2
VC-4	0.9	1.9	Clay/Silt	260	1100	<3	1.1	110	560	33	93	210	0.87	6.2	3.2	<0.015	H	2
VC-4	1.9	2.9	Clay/Silt	380	4000	<3	0.97	65	110	28	95	230	1.1	6.4	1.4	*	H	2
VC-4	2.9	5.9	Alluvium	<55	<170	<3	0.24	17	23	9.2	34	57	0.35	3.3	0.76	<0.015	L	1
VC-5	0	0.9	Clay	<55	360	<3	1.1	94	530	33	76	170	0.59	6.4	4.30	<0.015	H	2
VC-5	0.9	1.9	Clay	<55	<170	<3	0.33	37	140	16	46	88	0.37	4.5	0.94	<0.015	H	2
VC-5	1.9	2.9	Silt	<55	<170	<3	<0.20	14	<7.0	11	11	30	0.10	2.4	0.11	<0.015	L	1
VC-5	2.9	5.9	Silt	<55	<170	<3	<0.20	13	14	5.8	13	21	0.09	3.3	0.23	<0.015	L	1
VC-7	0	0.9	Silt	240	3600	<3	0.56	56	160	18	78	170	1.0	6.6	1.7	<0.015	H	2
VC-7	0.9	1.9	Clay/Silt	<55	<170	<3	<0.20	21	<7.0	16	18	44	0.05	3.6	<0.10	<0.015	L	1
VC-7	1.9	2.9	Clay/Silt	<55	<170	<3	<0.20	35	13	33	61	71	0.06	3.7	<0.10	*	L	1
VC-7	2.9	5.9	Clay/Silt	<55	<170	<3	<0.20	45	11	38	14	85	0.05	5.7	<0.10	*	L	1
VC-8	0	0.9	Clay/Silt	<55	<170	<3	0.86	78	300	26	70	200	0.72	7.8	6.6	<0.015	H	2
VC-8	0.9	1.9	Clay/Silt	<55	<170	<3	1.1	82	370	28	68	180	0.77	6.8	3.5	<0.015	H	2
VC-8	1.9	2.9	Clay/Silt	<55	<170	<3	<0.20	24	<7.0	16	23	44	0.14	4.4	0.14	<0.015	L	1
VC-8	2.9	5.9	Clay/Silt	<55	<170	<3	0.45	40	15	36	38	74	0.11	3.2	0.12	<0.015	L	1
VC-9	0	0.9	Fill	<55	<170	<3	0.52	56	170	18	74	140	0.62	6.1	1.1	*	H	2
VC-9	0.9	1.9	Clay	<55	<170	<3	<0.20	28	8.1	20	22	61	0.13	4.1	0.11	*	L	1
VC-9	1.9	2.9	Clay	<55	<170	<3	<0.20	23	<7.0	17	18	45	0.08	4.0	<0.10	*	L	1
VC-9	2.9	5.9	Clay/Silt	<55	<170	<3	<0.20	18	<7.0	11	20	30	0.07	4.6	<0.10	*	L	1
VC-10	0	0.9	Clay/Silt	<55	<170	<3	1.4	98	520	28	76	200	1.3	6.6	3.0	<0.015	H	2
VC-10	0.9	1.9	Clay/Silt	<55	<170	<3	<0.20	52	110	17	68	120	1.3	5.4	1.4	<0.015	H	2
VC-10	1.9	2.9	Clay/Silt	<55	<170	<3	<0.20	19	<7.0	14	16	41	0.13	5.5	0.13	<0.015	L	1
VC-10	2.9	5.9	Clay/Silt	<55	<170	<3	<0.20	17	<7.0	11	18	31	0.10	4.0	<0.10	<0.015	L	1
VC-11	0	0.9	Silt	<55	<170	<3	1.1	70	320	20	77	130	0.65	5.4	2.0	<0.015	H	2
VC-11	0.9	1.9	Clay/Silt	<55	<170	<3	<0.20	13	<7.0	8.8	13	25	0.07	2.9	<0.10	<0.015	L	1
VC-11	1.9	2.9	Clay/Silt	<55	<170	<3	<0.20	11	<7.0	7.5	12	20	0.11	2.7	0.10	<0.015	L	1
VC-11	2.9	5.9	Clay/Silt	<55	<170	<3	<0.20	<8.0	<7.0	<4.0	9.4	<20	0.08	2.9	<0.10	<0.015	L	1
VC-12	0	0.9	Clay/Silt	<55	<170	<3	1.0	94	360	32	63	200	0.50	6.3	6.8	<0.015	H	2
VC-12	0.9	1.9	Alluvium	<55	<170	<3	0.49	34	140	13	120	81	0.40	4.2	1.1	<0.015	H	2
VC-12	1.9	2.9	Silt	<55	<170	<3	<0.20	9.5	<7.0	<4.0	24	12	0.08	2.6	<0.10	*	L	1
VC-12	2.9	5.9	Clay/Silt	<55	<170	<3	<0.20	<8.0	<7.0	<4.0	<8.0	<20	0.08	<1.0	<0.10	*	L	1
VC-13	0	0.9	Silt	<55	<170	<3	0.83	63	290	23	50	160	0.59	5.8	4.5	<0.015	H	2
VC-13	0.9	1.9	Clay/Silt	<55	<170	<3	<0.20	13	<7.0	11	12	32	0.06	2.2	0.11	<0.015	L	1
VC-13	1.9	2.9	Alluvium	<55	<170	<3	<0.20	<8.0	<7.0	<4.0	<8.0	<20	0.05	1.9	<0.10	<0.015	L	1
VC-13	2.9	5.9	Clay/Silt	<55	<170	<3	<0.20	<8.0	8.3	<4.0	12	<20	0.09	1.2	0.19	<0.015	L	1
VC-14	0	0.9	Clay/Silt	<55	<170	<3	0.93	87	360	29	62	220	0.58	6.2	8.0	<0.015	H	2
VC-14	0.9	1.9	Clay/Silt	<55	<170	<3	1.2	72	390	27	57	160	0.48	5.9	3.8	<0.015	H	2
VC-14	1.9	2.9	Clay/Silt	<55	<170	<3	0.46	30	140	12	32	60	0.25	3.5	1.0	<0.015	H	2
VC-14	2.9	5.9	Alluvium	<55	<170	<3	<0.20	13	15	<7.0	23	20	0.09	4.4	0.26	<0.015	L	1
VC-15	0	0.9	Clay/Silt	<55	<170	<3	0.66	42	220	16	36	81	0.26	3.7	1.5	<0.015	H	2
VC-15	0.9	1.9	Clay/Silt	<55	<170	<3	<0.20	14	17	9.8	14	31	0.07	3.6	0.19	<0.015	L	1
VC-15	1.9	2.9	Clay/Silt	<55	<170	<3	<0.20	<8.0	<7.0	<4.0	9.7	<20	0.05	2.5	<0.10	<0.015	L	1
VC-15	2.9	5.9	Alluvium	<55	<170	<3	<0.20	<8.0	<7.0	<4.0	8.5	<20	0.05	<1.0	<0.10	<0.015	L	1
VC-16	0	0.9	Clay/Silt	<55	<170	<3	0.37	36	120	14	52	110	1.5	5.3	1.1	<0.015	H	2
VC-16	0.9	1.9	Clay	<55	<170	<3	0.37	32	110	11	47	80	0.46	3.9	0.89	<0.015	M_f	2
VC-16	1.9	2.9	Clay/Silt	<55	<170	<3	<0.20	<8.0	<7.0	4.0	8.4	<20	0.06	3.5	<0.10	<0.015	L	1
VC-16	2.9	5.9	Clay/Silt	<55	<170	<3	<0.20	<8.0	<7.0	4.2	11	<20	0.06	3.0	0.18	<0.015	L	1
VC-17	0	0.9	Silt	<55	<170	<3	<0.20	12	31	6.1	18	31	0.11	2.5	0.41	<0.015	L	1
VC-17	0.9	1.9	Clay	<55	<170	<3	<0.20	19	<7.0	14	17	44	0.07	3.0	<0.10	<0.015	L	1
VC-17	1.9	2.9	Silt	<55	<170	<3	<0.20	8.3	<7.0	6.1	11	<20	0.06	3.3	<0.10	<0.015	L	1
VC-17	2.9	5.9	Silt	<55	<170	<3	<0.20	<8.0	<7.0	<4.0	9.5	<20	0.05	3.1	<0.10	<0.015	L	1
VC-18	0	0.9	Silt	<55	<170	<3	0.31	28	87	12	38	79	0.54	5.0	2.1	<0.015	H	2
VC-18	0.9	1.9	Clay	<55	<170	<3	<0.20	19	<7.0	14	18	41	0.06	3.4	<0.10	<0.015	L	1
VC-18	1.9	2.9	Clay	<55	<170	<3	<0.20	12	<7.0	8.8	13	23	<0.05	2.8	<0.10	<0.015	L	1
VC-18	2.9	5.9	Clay	<55	<170	<3	<0.20	9.4	<7.0	5.9	20	<20	0.06	3.8	<0.10	<0.015	L	1
VC-19	0	0.9	Silt	<55	<170	<3	<0.20	20	20	12	26	47	0.13	3.7	0.30	<0.015	L	1
VC-19	0.9	1.9	Silt	<55	<170	<3	<0.20	16	<7.0	12	14	34	<0.05	3.0	<0.10	<0.015	L	1
VC-19	1.9	2.9	Silt	<55	<170	<3	<0.20	13	<7.0	9.9	14	27	<0.05	3.0	<0.10	<0.015	L	1
VC-19	2.9	5.9	Clay/Silt	<55	<170	<3	<0.20	12	8.4	8.0	18	26	0.05	3.1	0.10	<0.015	L	1
VC-20	0	0.9	Silt	<55	<170	<3	<0.20	13	15	7.7	20	33	0.13	3.1	0.16	<0.015	L	1
VC-20	0.9	1.9	Silt	<55	<170	<3	<0.20	25	7.3	19	21	54	0.08	4.2	<0.10	<0.015	L	1
VC-20	1.9	2.9	Silt	<55	<170	<3	<0.20	12	<7.0	8.5	12	24	<0.05	2.8	<0.10	<0.015	L	1
VC-20	2.9	5.9	Clay	<55	<170	<3	<0.20	9.3	<7.0	6.0	15	<20	<0.05	3.7	<0.10	<0.015	L	1
VC-21	0	0.9	Silt	<55	<170	<3	<0.20	24	7.2	18	19	50	<0.05	3.5	<0.10	<0.015	L	1
VC-21	0.9	1.9	Clay/Silt	<55	<170	<3	<0.20	13	18	8.0	19	34	0.08	2.4	0.16	<0.015	L	1
VC-21	1.9	2.9	Clay/Silt	<55	<170	<3	<0.20	16	<7.0	11	14	30	<0.05	3.4	<0.10	<0.015	L	1
VC-21	2.9	5.9	Clay/Silt	<55	<170	<3	<0.20	11	<7.0	5.6	12	<20	<0.05	4.5	<0.10	<0.015	L	1
VC-22	0	0.9	Silt	<55	<170	<3	<0.20	<8.0	7.6	<4.0	23	25	0.21	2.2	0.13	*	L	1
VC-22	0.9	1.9	Silt	<55	<170	<3	<0.20	10	<7.0	7.5	22	36	0.11	2.8	<0.10	<0.015	L	1
VC-22	1.9	2.9	Silt	<55	<170	<3	<0.20	12	<7.0	8.5	14	25	0.08	3.4	<0.10	<0.015	L	1
VC-22	2.9	5.9	Clay/Silt	<55	<170	<3	0.24	13	<7.0	6.8	29	66	0.06	6.9	<0.10	<0.015	L	1
VC-22	5.9	8.9	Alluvium	<55	<170	<3	<0.20	<8.0	<7.0	<4.0	16	<20	0.06	2.0	<0.10	*	L	1
VC-23	0	0.9	Silt	<55	<170	<3	<0.20	13	<7.0	9.1	22	30	0.08	3.0	<0.10	<0.015	L	1
VC-23	0.9	1.9	Clay	<55	<170	<3	<0.20	11	<7.0	7.0	12	20	0.07	3.3	<0.10	<0.015	L	1
VC-23	1.9	2.9	Clay/Silt	<55	<170	<3	<0.20	13	<7.0	5.6	9.6	<20	0.07	3.4	<0.10	*	L	1
VC-23	2.9	5.9	Clay/Silt	<55	<170	<3	<0.20	33	7.3	13	25	35	0.06	5.3	<0.10	*	L	1
VC-23	5.9	8.9	Silt	<55	<170	<3	<0.20	<8.0	<7.0	<4.0	24	<20	0.11	2.0	<0.10	<0.015	L	1
VC-24	0	0.9	Silt	<55	<170	<3	<0.20	8.3	16	<4.0	58	52	0.18	2.4	0.16	*	L	1
VC-24	0.9	1.9	Silt	<55	<170	<3	<0.20	8.8	8.1	5.0	18	30	0.23	2.4	0.16	<0.015	L	1
VC-24	1.9	2.9	Clay/Silt	<55	<170	<3	<0.20	16	<7.0	8.6	14	24	0.09	2.7	<0.10	*	L	1
VC-24	2.9	5.9	Clay/Silt	<55	<170	<3	<0.20	9.0	<7.0	8.9	24	24	<0.05	1.9	<0.10	*	L	1
VC-24	5.9	8.9	Silt	<55	<170	<3	<0.20	12	<7.0	8.3	27	32	0.08	7.7	<0.10	*	L	1
VC-31	0	0.9	Silt	<55	<170	<3	<0.20	11	24	5.8	15	28	0.12	2.4	0.22	*	L	1
VC-31	0.9	1.9	Clay/Silt	<55	<170	<3	<0.20	<8.0	<7.0	5.9	9.5	<20	0.05	2.2	<0.10	*	L	1
VC-31	1.9	2.9	Clay/Silt	<55	<170	<3	<0.20	14	7.3	6.5	12	25	0.05	2.4	<0.10	*	L	1
VC-31	2.9	5.9	Clay/Silt	<55	<170	<3	<0.20	9.2	7.4	15	28	34	<0.05	3.4	<0.10	*	L	1
VC-31	5.9	8.9	Alluvium	<55	<170	<3	<0.20	<8.0	<7.0	4.6	15	<20	0.06	3.3	<0.10	*	L	1
VC-33	0	0.9	Silt	<55	<170	<3	<0.20	13	11	6.8	19	28	0.12	2.5	0.11	<0.015	L	1
VC-33	0.9	1.9	Clay/Silt	<55	<170	<3	<0.20	15	8.5	11	37	32	0.06	5.0	<0.10	*	L	1
VC-33	1.9	2.9	Clay/Silt	<55	<170	<3	<0.20	32	17	13	18	45	0.08	3.0	<0.10	*	L	1
VC-33B	2.9	5.9	Alluvium	<55	<170	<3	<0.20	20	<7.0	18	15	45	0.07	2.4	<0.10	*	L	1
VC-33B	5.9	8.9	Alluvium	<55	<170	<3	<0.20	<8.0	<7.0	5.0	<8.0	<20	<0.05	<1.0	<0.10	*	L	1
VC-34	0	0.9	Fill	<55	<170	<3	<0.20	11	20	6.9	41	42	0.19	3.2	0.19	<0.015	L	1
VC-34	0.9	1.9	Silt	<55	<170	<3	<0.20	11	<7.0	6.2	14	<20	0.10	2.7	0.11	<0.015	L	1
VC-34	1.9	2.9	Clay/Silt	<55	<170	<3	<0.20	20	8.1	14	20	44	0.08	4.8	<0.10	*	L	1
VC-34	2.9	5.9	Clay/Silt	<55	<170	<3	<0.20	17	8.1	16	19	46	0.06	5.6	0.11	*	L	1
VC-34	5.9	8.9	Alluvium	<55	<170	<3	0.23	22	13	19	16	48	0.08	1.9	0.12	*	L	1
VC-35	0	0.9	Silt	<55	<170	<3	<0.20	36	21	23	30	74	0.08	5.2	0.12	*	L	1
VC-35	0.9	1.9	Clay/Silt	<55	<170	<3	<0.20	37	15	41	25	83	0.08	2.9	<0.10	*	H	2
VC-35	1.9	2.9	Clay/Silt	<55	<170	<3	<0.20	38	13	34	18	78	<0.05	1.4	<0.10	*	L	1
VC-35	2.9	5.9	Clay/Silt	<55	<170	<3	<0.20	34	12	29	22	71	<0.05	3.3	<0.10	*	L	1
VC-35	5.9	8.9	Alluvium	<55	<170	<3	0.35	40	20	32	41	100	<0.05	2.0	<0.10	*	L	1
VC-36	0	0.9	Clay/Silt	<55	<170	<3	<0.20	19	25	11	22	40	0.11	3.9	0.23	<0.015	L	1
VC-36	0.9	1.9	Clay	<55	<170	<3	<0.20	17	15	7.3	21	32	0.10	2.7	0.17	*	L	1
VC-36	1.9	2.9	Clay/Silt	<55	<170	<3	<0.20	36	11	40	18	83	0.08	4.4	<0.10	*	M_f	2
VC-36	2.9	5.9	Clay/Silt	<55	<170	<3	<0.20	38	13	34	26	81	0.07	3.9	<0.10	*	L	1
VC-36	5.9	8.9	Clay/Silt	<55	<170	<3	<0.20	20	<7.0	8.5	16	46	0.06	<1.0	<0.10	*	L	1
VC-37	0	0.9	Clay	<55	<170	<3	0.70	58	180	28	54	180	0.59	6.6	6.4	<0.015	H	2
VC-37	0.9	1.9	Clay	<55	<170	<3	<0.20	23	38	14	28	58	0.26	4.6	0.57	<0.015	L	1
VC-37	1.9	2.9	Clay	<55	<170	<3	<0.20	26	8.6	22	18	54	0.11	3.0	0.11	<0.015	L	1
VC-37	2.9	5.9	Silt	<55	<170	<3	<0.20	42	17	49	45	94	<0.05	3.2	<0.10	*	H	2
VC-37	5.9	8.9	Silt	<55	<170	<3	<0.20	31	10	27	20	66	<0.05	3.3	<0.10	*	L	1

Notes:

(1) LMW = Low molecular weight PAHs, that is, acenaphthene, acenaphthylene, anthracene, fluorene, naphthalene and phenanthrene.

(2) HMW = High molecular weight PAHs, that is, benzo[a]anthracene, benzo[a]pyrene, chrysene, dibenzo[a,h]anthracene, fluoranthene, pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, indeno[1,2,3-c,d]pyrene and benzo[g,h,i]perylene.

(3) Values underlined indicate Category M sediment under ETWB TCW No. 34/2002.

(4) Values in bold indicate Category H sediment under ETWB TCW No. 34/2002.

(5) Values in bold and underlined indicate Category H sediment under ETWB TCW No. 34/2002 and that the contaminant level exceeded the LCEL by 10 times.

(6) “*” indicated insufficient porewater for testing

(7) Category and disposal option follows ETWB TCW No. 34/2002

(8) ^# In accordance with ETWBTC (Works) No. 34/2002, sediment with the following category:

L means Category L Material, ≤Lower Chemical Exceedance Level

M_f means Category M Material, >Lower & ≤Upper Chemical Exceedance Level and has failed biological screening test

H means Category H Material, >Upper Chemical Exceedance Level & <10 x Lower Chemical Exceedance Level and biological screening test is not required

H_f means Category H Material, >Upper Chemical Exceedance Level & >10 x Lower Chemical Exceedance Level and has failed biological screening test

A summary of classification of the vibrocore samples is provided in Table 4.10. The majority of the sediment samples (74%) were classified as Category L.

Table 4.10: Summary of Classification of Vibrocore Samples

Category	Number of Vibrocore Samples
Category L	93
Category M	5
Category H	25
Category H (10 x > LCEL)	2

4.4.2 Biological Screening

The marine sediment quality analysis results of biological screening from the site investigation works were presented in a comprehensive laboratory testing report and is provided in Appendix C3.

The general characteristic of the marine sediment is provided in the ancillary tests results summarised in Table 4.11.

Table 4.11: Summary of Ancillary Tests Results

Composite Sample No.	Vibrocore No.	Interstitial ammonia (mgNH3/L)	Interstitial salinity (ppt)	Grain Size < 63mm (%)	Mositure Content (%)	TOC (% Wet Weight)	TOC (% Dry Weight)
1	VC-16	0.11	32	21	29	0.33	0.43
2	VC-36	See Note 1	See Note 1	99	35	<0.05	<0.05
3	VC-3	0.92	33	55	41	0.42	0.59
4	VC-2A	0.03	31	48	50	1.7	2.55
5	VC-1A	0.17	33	45	28	0.29	0.37
6	VC-1A	<0.03	32	82	133	0.60	1.4
7	VC-1A	0.94	35	90	122	0.58	1.29

Note: 1. Analysis was not performed due to insufficient amount of porewater obtained.

The sediment biological screening results indicated that all composite samples had failed the toxicity tests. The sediment is deemed to have failed the biological test if it fails in any one of the three toxicity tests. A summary of toxicity tests failure is provided in Table 4.12.

Table 4.12: Summary of Toxicity Test Failure

Composite Sample No.	Vibrocore No.	Sample Depth (m)	Test			Biological Screening Results
Composite Sample No.	Vibrocore No.	Sample Depth (m)	Amphipod	Polychaete	Bivalve Larvae	Biological Screening Results
1	VC-16	0.9-1.9	Fail	Fail	Fail	Fail
2	VC-36	1.9-2.9	Pass	Fail	Pass	Fail
3	VC-3	0.9-1.9	Fail	Fail	Fail	Fail
4	VC-2A	2.9-5.9	Fail	Pass	Fail	Fail
5	VC-1A	2.9-5.9	Fail	Fail	Fail	Fail
6	VC-1A	0.0-0.9	Fail	Pass	Fail	Fail
7	VC-1A	0.9-1.9	Fail	Fail	Fail	Fail

4.5 Identification and Evaluation of Environmental Impacts

4.5.1 Construction Phase

The construction activities to be carried out for construction of the proposed submarine gas pipelines would generate a variety of wastes that can be divided into distinct categories based on their composition and ultimate method of disposal. The identified waste types include:

¡ Construction and demolition (C&D) materials

¡ General refuse;

¡ Chemical waste; and

¡ Marine dredged sediment

Each type of waste arising is described below, together with an evaluation of the potential environmental impacts associated with generation, handling, storage and transport of the waste.

4.5.1.1 Construction and Demolition (C&D) Materials

Excavated materials would arise from excavation works for construction of the landing points. It is anticipated that the volume of excavated material to be generated would be approximately 900 cubic metres. In order to minimise the impact resulting from collection and transportation of C&D material for off-site disposal, the excavated material which comprise of reclamation fill material that could be reused on-site as fill material should be reused on-site as backfilling material for the construction of the associated landmain gas pipelines as far as practicable. The amount of C&D material to be generated would be quantified in the site Waste Management Plan to be prepared by the Contractor.

4.5.1.2 General Refuse

The construction workforce will generate refuse comprising food scraps, waste paper, empty containers, etc. Such refuse should be properly managed so intentional or accidental release to the surrounding environment does not occur. Disposal of refuse at sites other than approved waste transfer or disposal facilities shall be prohibited. Effective collection of site wastes will be required to prevent waste materials being blown around by wind, flushed or leached into the marine environment, or creating an odour nuisance or pest and vermin problem. Waste storage areas shall be well maintained and cleaned regularly. 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. The maximum number of construction workers to be employed is estimated to be about 100 workers. Based on a generation rate of 0.65 kg per worker per day, the maximum daily arising of general refuse during the construction period would be approximately 65 kg and this waste can be effectively controlled by normal measures.

4.5.1.3 Chemical Waste

The maintenance and servicing of construction plant and equipment may generate some chemical wastes such as cleaning fluids, solvents, lubrication oil and fuel. Maintenance of vehicles may also involve the use of a variety of chemicals, oil and lubricants. 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 and the amount of plant utilised. However, it is anticipated that the quantity of chemical waste, such as lubricating oil and solvent produced from plant maintenance, would be small and in the order of a few cubic metres per month. The amount of chemical waste to be generated will be quantified in the site Waste Management Plan to be prepared by the Contractor.

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 associated adverse impacts on marine biota; and

¡ Fire hazards.

Materials classified as chemical wastes would require special handling and storage arrangements before removal for appropriate treatment at the approved Chemical Waste Treatment Facility. Wherever possible opportunities should be taken to reuse and recycle materials. Mitigation and control requirements for chemical wastes are detailed in Section 4.6.6. Provided that the handling, storage and disposal of chemical wastes are in accordance with these requirements, adverse environmental impacts are not expected.

4.5.1.4 Marine Dredged Sediment

In accordance with ETWB TC(W) No. 34/2002 - Management of Dredged/Excavated Sediment, review of existing information for site contamination assessment (Tier I), chemical screening (Tier II) and biological screening (Tier III) were conducted along the trench to be dredged for submarine gas pipelines installation to determine the sediment quality. Sediments were classified into Category L, M and H based on its contaminant levels identified from chemical screening. Sediment classified as Category M was then subjected to biological screening. The corresponding types of disposal required were thus identified and presented numerically in Table 4.9 and graphically in Figure 4.2.

The existing seabed area would be dredged to lay the submarine gas pipelines. According to Figure 4.2, the total volume of dredged sediment was estimated to be approximately 260,665 m³. The estimated volume of contaminated dredged sediment was approximately 81,669 m³. The potential environmental effects of the removal of these sediments on water quality have been assessed and presented in Section 3 of this Report.

To minimize any potential adverse impacts arising from the dredged marine sediment, the sediment shall be dredged, transported and disposed of in a manner that will minimise the loss of contaminants either into solution or by resuspension. Mitigation measures to minimise potential environmental impacts are described in Section 4.6.7. With the implementation of mitigation measures, no unacceptable impacts would be expected from the transportation and disposal of the dredged sediment.

4.5.2 Operation Phase

No solid wastes are anticipated to be generated during operation.

4.6 Mitigation of Adverse Environmental Impacts

4.6.1 Good Site Practices

Adverse impacts related to waste management such as air, odour, noise, wastewater discharge and public transport are not expected to arise, provided that good site practices are 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, separation of chemical wastes with appropriate treatment which is mentioned in Section 4.6.5

¡ Provision of sufficient waste disposal points and regular collection of waste

¡ Barges filled with dredged sediment shall be towed away immediately for disposal. In doing so, odour is not anticipated to be an issue to distant sensitive receivers

¡ Well planned delivery programme for offsite disposal such that adverse impact from transporting sediment material is not anticipated

¡ Well maintained PME should be operated on site

¡ Regular cleaning and maintenance of the drainage systems for construction of the landing points

¡ Appropriate measures to minimise windblown litter and dust during transportation of waste by either covering trucks or by transporting wastes in enclosed containers

4.6.2 Waste Reduction Measures

The total volume of dredged sediment is minimized in terms of the engineering design perspective, the gas pipelines are designed to achieve the minimum cover requirement of CEDD, Port Works. Based on this requirement, the proposed submarine gas pipelines is required to be laid at depths of at least 3m below seabed level. For the marine section crossing the fairway, 5m cover below Chart Datum -13mPD will be anticipated. In addition, rock armour should be provided to protect the gas pipelines, the pipelines and its associated protective layer should be laid below the maintenance dredged levels of the relevant marine facilities as practical as possible to avoid undermining of the protective layer due to the maintenance dredging works. The project involved removal of soft marine sediment in which the potential in reusing this material is very low but the minimum depth of trench required to lay the gas pipelines is minimized in accordance with the design requirement.

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 C&D material from demolition and decommissioning of the existing facilities to recover recyclable portions such as metals

¡ Segregation and storage of different types of waste in different containers, skips or stockpiles to enhance reuse or recycling of materials and their proper disposal

¡ Encourage collection of aluminium cans by providing separate labelled bins to enable this waste to be segregated from other general refuse generated by the work force

¡ Proper storage and site practices to minimise the potential for damage or contamination of construction materials

¡ Plan and stock 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.

4.6.3 C&D Material

In order to minimise impacts resulting from collection and transportation of C&D material for off-site disposal, the excavated materials should be reused on-site as backfilling material and for landscaping works for the associated land mains as far as practicable. Surplus C&D material generated from excavation works should be disposed of at public fill reception facilities for other beneficial uses. Other mitigation requirements are listed below:

¡ A Waste Management Plan should be prepared.

¡ A recording system for the amount of wastes generated, recycled and disposed (including the disposal sites) should be proposed.

¡ 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 (e.g. ETWB TCW No. 31/2004) should be included.

4.6.4 General Refuse

General refuse should be stored in enclosed bins or compaction units separate from C&D material. A reputable waste collector should be employed by the contractor to remove general refuse from the site, separately from C&D material. Preferably an enclosed and covered area should be provided to reduce the occurrence of 'wind blown' light material.

4.6.5 Chemical Waste

If chemical wastes are produced at the construction site, the Contractor would be required to register with the EPD as a chemical waste producer and to follow the guidelines stated in the Code of Practice on the Packaging, Labelling and Storage of Chemical Wastes. Good quality containers compatible with the chemical wastes should be used, and incompatible chemicals should be stored separately. Appropriate labels should be securely attached on each chemical waste container indicating the corresponding chemical characteristics of the chemical waste, such as explosive, flammable, oxidizing, irritant, toxic, harmful, corrosive, etc. The Contractor shall use a licensed collector to transport and dispose of the chemical wastes, to either the approved Chemical Waste Treatment Centre, or another licensed facility, in accordance with the Waste Disposal (Chemical Waste) (General) Regulation.

4.6.6 Marine Dredged Sediment

The basic requirements and procedures for dredged mud disposal are specified under the ETWB TCW No. 34/2002. The management of the dredging, use and disposal of marine mud is monitored by the MFC, while the licensing of marine dumping is the responsibility of the Director of Environmental Protection (DEP).

The dredged marine sediments would be loaded onto barges and transported to designated disposal sites depending on their level of contamination. Based on the chemical and biological screening results and subsequently the corresponding types of disposal required as presented in Table 4.9 and Figure 4.2, it was estimated that the volume of dredged sediment suitable for open sea disposal (Type 1) was estimated to be 187,179m³. The volume of contaminated sediment requiring confined marine disposal (Type 2) was estimated to be 76,936m³. The disposal site will be determined by the MFC and dumping licence should be obtained from EPD prior to the commencement of dredging works.

Based on the biological screening results, the volume of Type 3 contaminated sediment from the To Kwa Wan typhoon shelter would require special disposal arrangements. The volume of contaminated sediment requiring special treatment or disposal (Type 3) was estimated to be 3,488m³. The EIA report for “Wan Chai Development Phase II and Central-Wan Chai Bypass” proposed the use of geosynthetic container system for disposal of Type 3 sediment. Field trial test by using uncontaminated mud demonstrated its feasibility with negligible loss of contaminants for disposal of Type 3 sediments.

The proposed system is shown to be an effective system with negligible loss of contaminants to the environment during disposal. The arrangement of type 3 sediment encountered in this Project could possibly be followed by this method where the dredged sediments are sealed in geosynthetic containers and, at the disposal site, the containers should be dropped into the designated contaminated mud pit where they should be covered by further mud disposal and later by the mud pit capping, thereby meeting the requirements for fully confined mud disposal.

For the size and the specification of the geosynthetic container, reference is made with the study report from Wan Chai Development Phase II, Design and Construction (D&C) Consultancy (Agreement No. CE54/2001 (CE)) attached in Appendix 6.2 of the EIA Report for Wan Chai Development Phase II and Central-Wan Chai Bypass. The study report mentioned five type of geosynthetic containers and trial test was carried out to confirm the effectiveness of the disposal system, the report recommended the use of 300m³ geosynthetic container, with outer woven fabric tensile strength of 200 kN/m and seam strength of 140 kN/m would be the effective method for contained disposal which meets ETWB TCW No. 34/2002 requirements for assuring negligible loss of contaminants to marine environment during disposal. The detailed specification could be referred in Table 4.4 and Section 6.3.6 of the aforesaid Study Report.

The use of 300m³ geosynthetic containers system during the trial tests was demonstrated to be an effective method for contained disposal. Based on the quantity of the Type 3 contaminated sediment for this project, approximately 12 numbers of barge will be required.

Agreement from Marine Fill Committee for the dredging rationale and initial agreement on giving the disposal allocation for the project was obtained as presented in Appendix C4. Allocation of marine disposal sites and all necessary permits would be applied from relevant authorities for disposal of dredged sediment. Project Proponent would obtain confirmation from CEDD/Marine Fill Committee (MFC) on the disposal options before commencement of the Project.

In accordance with the ETWB TCW No. 34/2002, the contaminated material must be dredged and transported with great care, and the mitigation measures recommended in Section 3 of this Report should be strictly followed. Furthermore, the dredged contaminated sediment must be effectively isolated from the environment upon final disposal and shall be disposed of typically at the East Sha Chau Contaminated Mud Pits that is designated for the disposal of contaminated mud in Hong Kong.

During transportation and disposal of the dredged marine sediments for Type 1 and Type 2 disposal, the following measures should be taken to minimise potential impacts on water quality:

¡ Bottom opening of barges shall be fitted with tight fitting seals to prevent leakage of material. Excess material shall be cleaned from the decks and exposed fittings of barges and dredgers before the vessel is moved.

¡ Monitoring of the barge loading shall be conducted to ensure that loss of material does not take place during transportation. Transport barges or vessels shall be equipped with automatic self-monitoring devices as specified by the EPD.

¡ Barges or hopper barges shall not be filled to a level that would cause the overflow of materials or sediment laden water during loading or transportation.

Table 4.13 provides a summary of the various waste types likely to be generated during the construction activities for the proposed submarine gas pipelines, together with the recommended handling and disposal methods.

Waste Material Type*	Generated from works item	Timing to be Generated	Total Quantity Generated	Quantity to be disposed off-site	Disposal	Handling
Marine Dredged Sediment (Uncontaminated, Type 1), Category L	Trench excavation	April 2012 to Dec 2012	187,179 m³	187,179 m³	MFC gazetted marine disposal ground – open sea disposal site	Minimise resuspension by use of closed grab, controlled loading and transfer
Marine Dredged Sediment (Contaminated, Type 2), Category M_fand H	Trench excavation	April 2012 to Dec 2012	76,936 m³	76,936 m³	East Sha Chau contaminated mud pit	Minimise resuspension by use of closed grab, tight seal on barges, controlled loading and transfer
Marine Dredged Sediment (Contaminated, Type 3) Category H_f	Trench excavation	April 2012 to Dec 2012	3,488 m³	3,488 m³	By containment of the sediments in geosynthetic containers and disposal at East Sha Chau contaminated mud pit	Minimise resuspension by use of closed grab, tight seal on barges, controlled loading and transfer
C&D Material	Excavation works	Jan 2012 to April 2014	900 cubic meters (preliminary estimate)	Few hundred cubic meters (preliminary estimate)	To be reused on-site for construction of the associated landmain gas pipelines or To be disposed to public fill reception points for other beneficial uses or To be disposed to landfill	Segregate inert C&D material to avoid contamination from other waste arising
General Refuse	Waste paper, discarded containers, etc. generated from workforce	Jan 2012 to April 2014	65 kg per day (preliminary estimate based on workforce of 100)	65 kg per day	Refuse station for compaction and containerisation and then to landfill	Provide on-site refuse collection points
Chemical Waste	Cleansing fluids, solvent, lubrication oil and fuel from construction plant and equipment	2 Jan 2012 to April 2014	Few cubic metres per month (preliminary estimate)	Few cubic metres per month (preliminary estimate)	Chemical Waste Treatment Centre	Recycle on-site or by licensed companies. Stored on-site within suitably designed containers