5.1
Introduction
5.1.1
This
section presents an assessment of the potential water quality impacts
associated with the construction and operation phase of the
Project. The water quality impact assessment is conducted in
accordance with the requirements of Annex 6 and Annex 14 of the Technical
Memorandum on Environmental Impact Assessment Process (EIAO-TM) as well as the
requirements set out under Clause 3.4 of the EIA Study Brief (ESB-318/2019).
Appropriate mitigation measures were proposed to minimize the potential water
quality impacts.
5.2
Legislation, Standards and Guidelines
Environmental
Impact Assessment Ordinance (EIAO)
5.2.1
Technical Memorandum on
Environmental Impact Assessment Process (EIAO-TM) was issued by EPD under
Section 16 of the EIAO. The EIAO-TM specifies assessment methodologies
and criteria that are to be followed in an EIA Study. Sections in
the EIAO-TM relevant to water quality impact assessment comprise:
Annex 6 – Criteria for Evaluating Water
Pollution, and
Annex 14 – Guidelines for Assessment of Water
Pollution
These annexes provide the details of assessment
criteria and guidelines that are relevant to the water quality impact assessment.
Water
Pollution Control Ordinance -Water Quality Objectives
5.2.2
The Water Pollution Control
Ordinance (WPCO) (Cap. 358) provides the statutory framework for the protection
and control of water quality in Hong Kong. According to the WPCO and its
subsidiary legislations, Hong Kong waters are divided into 10 major Water
Control Zones (WCZs). Water Quality Objectives (WQOs) were established to
protect the beneficial uses of water quality in WCZs and specific WQOs are
applied to each WCZ. WQOs for the Deep Bay WCZ relevant to this assessment are
listed in Table 5-1.
Table 5‑1 Water Quality
Objectives for Deep Bay WCZ for Beas Subzone and Indus Subzone
|
Parameters
|
Objectives
|
Sub-Zone
|
|
Aesthetic Appearance
|
Waste discharges
shall cause no objectionable odours or discolouration of the water
|
Whole zone
|
|
Tarry residues,
floating wood, articles made of glass, plastic, rubber or of any other
substances should be absent.
|
Whole zone
|
|
Mineral oil should
not be visible on the surface. Surfactants should not give rise to a lasting
foam.
|
Whole zone
|
|
There should be no
recognisable sewage-derived debris.
|
Whole zone
|
|
Floating,
submerged and semi-submerged objects of a size likely to interfere with the
free movement of vessels, or cause damage to vessels, should be absent.
|
Whole zone
|
|
Waste discharges
shall not cause the water to contain substances which settle to form
objectionable deposits.
|
Whole zone
|
|
DO
|
Not less than
4.0mg/L
|
Yuen Long &
Kam Tin (Upper and Lower) Subzones, Beas Subzone, Indus Subzone, Ganges
Subzone, Water Gathering Ground Subzones and other inland waters of the Zone
|
|
5-Day Biochemical Oxygen Demand (BOD5)
|
Not to exceed
3mg/L
|
Yuen Long &
Kam Tin (Upper) Subzone, Beas Subzone, Indus Subzone, Ganges Subzone and
Water Gathering Ground Subzones
|
|
Chemical Oxygen Demand (COD)
|
Not to exceed
15mg/L
|
Yuen Long &
Kam Tin (Upper) Subzone, Beas Subzone, Indus Subzone, Ganges Subzone and
Water Gathering Ground Subzones
|
|
pH
|
To be in the range
of 6.5 – 8.5
|
Yuen Long &
Kam Tin (Upper and Lower) Subzones, Beas Subzone, Indus Subzone, Ganges
Subzone and Water Gathering Ground Subzones
|
|
Salinity
|
Change due to
waste discharges not to exceed 10% of ambient
|
Whole zone
|
|
Temperature
|
Change due to
waste discharges not to exceed 2°C
|
Whole zone
|
|
Suspended solids (SS)
|
Not to cause the
annual median to exceed 20mg/L
|
Yuen Long &
Kam Tin (Upper and Lower) Subzones, Beas Subzone, Ganges Subzone, Indus
Subzone, Water Gathering Ground Subzones and other inland waters
|
|
Unionized Ammonia (UIA)
|
Annual mean not to
exceed 0.021mg/L as unionized form
|
Whole zone
|
|
Bacteria
|
Should be zero per
100 ml, calculated as the running median of the most recent 5 consecutive
samples taken between 7 and 21 days.
|
Yuen Long &
Kam Tin (Upper) Subzone, Beas Subzone, Indus Subzone, Ganges Subzone and
Water Gathering Ground Subzones
|
|
Colour
|
Not to exceed 30
Hazen units
|
Yuen Long &
Kam Tin (Upper) Subzone, Beas Subzone, Indus Subzone, Ganges Subzone and
Water Gathering Ground Subzones
|
|
Toxins
|
Should not cause a
risk to any beneficial uses of the aquatic environment
|
Whole Zone
|
|
Should not attain
such levels as to produce toxic carcinogenic, mutagenic or teratogenic
effects in humans, fish or any other aquatic organisms.
|
Whole Zone
|
Requirement
of No Net Increase in Pollution Load to Deep Bay
5.2.3
The Potential Development
Area (PDA) is located in the catchment area of Beas Subzone and Indus Subzone
of Deep Bay Water Control Zone, there is a requirement for “No Net
Increase in Pollution Loading”. To provide protection to the inland and marine
water quality of the Deep Bay Water Control Zone, “No Net Increase in Pollution
Loading” requires the developments within the Deep Bay catchment areas do not
result in an increase in pollution loads to the inland and marine
waters.
Technical Memorandum
5.2.4
Discharges of effluents are
subject to control under the WPCO. The Technical Memorandum on Standards for
Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal
Waters (TM-DSS) sets limits for effluent discharges. Specific limits apply for
different areas and are different between surface waters and sewers. The limits
vary with the rate of effluent flow. Any sewage from the development should
comply with the standards for effluent discharged into the foul sewers, as
stipulated in the TM-DSS. Group B
and C inland water standards in TM-DSS are adopted and the effluent discharge
standards are presented in Table 5-2 and Table 5-3 respectively.
Table 5‑2 Standards for effluents
discharged into Group B inland waters
|
Parameter
|
Flow Rate(m³/day)
|
|
≤ 200
|
＞200 and
≤ 400
|
＞400
and
≤ 600
|
＞600
and
≤ 800
|
＞800
and
≤ 1000
|
＞1000
and
≤ 1500
|
＞1500
and
≤ 2000
|
＞2000
and
≤ 3000
|
|
pH (pH units)
|
6.5-8.5
|
6.5-8.5
|
6.5-8.5
|
6.5-8.5
|
6.5-8.5
|
6.5-8.5
|
6.5-8.5
|
6.5-8.5
|
|
Temperature (°C)
|
35
|
30
|
30
|
30
|
30
|
30
|
30
|
30
|
|
Colour (lovibond units)(25mm
cell length)
|
1
|
1
|
1
|
1
|
1
|
1
|
1
|
1
|
|
Suspended solids (mg/l)
|
30
|
30
|
30
|
30
|
30
|
30
|
30
|
30
|
|
BOD (mg/l)
|
20
|
20
|
20
|
20
|
20
|
20
|
20
|
20
|
|
COD (mg/l)
|
80
|
80
|
80
|
80
|
80
|
80
|
80
|
80
|
|
Oil & Grease (mg/l)
|
10
|
10
|
10
|
10
|
10
|
10
|
10
|
10
|
|
Iron (mg/l)
|
10
|
8
|
7
|
5
|
4
|
3
|
2
|
1
|
|
Boron (mg/l)
|
5
|
4
|
3
|
2.5
|
2
|
1.5
|
1
|
0.5
|
|
Barium (mg/l)
|
5
|
4
|
3
|
2.5
|
2
|
1.5
|
1
|
0.5
|
|
Mercury (mg/l)
|
0.001
|
0.001
|
0.001
|
0.001
|
0.001
|
0.001
|
0.001
|
0.001
|
|
Cadmium (mg/l)
|
0.001
|
0.001
|
0.001
|
0.001
|
0.001
|
0.001
|
0.001
|
0.001
|
|
Selenium (mg/l)
|
0.2
|
0.2
|
0.2
|
0.2
|
0.2
|
0.1
|
0.1
|
0.1
|
|
Other toxic metals
individually (mg/l)
|
0.5
|
0.5
|
0.2
|
0.2
|
0.2
|
0.1
|
0.1
|
0.1
|
|
Total Toxic metals (mg/l)
|
2
|
1.5
|
1
|
0.5
|
0.5
|
0.2
|
0.2
|
0.2
|
|
Cyanide (mg/l)
|
0.1
|
0.1
|
0.1
|
0.08
|
0.08
|
0.05
|
0.05
|
0.03
|
|
Phenols (mg/l)
|
0.1
|
0.1
|
0.1
|
0.1
|
0.1
|
0.1
|
0.1
|
0.1
|
|
Sulphide (mg/l)
|
0.2
|
0.2
|
0.2
|
0.2
|
0.2
|
0.2
|
0.2
|
0.2
|
|
Fluoride (mg/l)
|
10
|
10
|
8
|
8
|
8
|
5
|
5
|
3
|
|
Sulphate (mg/l)
|
800
|
800
|
600
|
600
|
600
|
400
|
400
|
400
|
|
Chloride (mg/l)
|
1000
|
1000
|
800
|
800
|
800
|
600
|
600
|
400
|
|
Total phosphorus (mg/l)
|
10
|
10
|
10
|
8
|
8
|
8
|
5
|
5
|
|
Ammonia nitrogen (mg/l)
|
5
|
5
|
5
|
5
|
5
|
5
|
5
|
5
|
|
Nitrate + nitrite nitrogen
(mg/l)
|
30
|
30
|
30
|
20
|
20
|
20
|
10
|
10
|
|
Surfactants (total) (mg/l)
|
5
|
5
|
5
|
5
|
5
|
5
|
5
|
5
|
|
E. coli (count/100ml)
|
100
|
100
|
100
|
100
|
100
|
100
|
100
|
100
|
Note:
1. All units in mg/L
unless otherwise stated
Table 5‑3 Standards
for effluents discharged into Group C inland waters
|
Parameter
|
Flow Rate (m3/day)
|
|
≤ 100
|
> 100 and ≤500
|
> 500 and ≤1000
|
> 1000 and ≤2000
|
|
pH (pH units)
|
6-9
|
6-9
|
6-9
|
6-9
|
|
Temperature (˚C)
|
30
|
30
|
30
|
30
|
|
Colour (lovibond units)
(25mm cell length)
|
1
|
1
|
1
|
1
|
|
Suspended solids (mg/l)
|
20
|
10
|
10
|
5
|
|
BOD (mg/l)
|
20
|
15
|
10
|
5
|
|
COD (mg/l)
|
80
|
60
|
40
|
20
|
|
Oil & Grease (mg/l)
|
1
|
1
|
1
|
1
|
|
Boron (mg/l)
|
10
|
5
|
4
|
2
|
|
Barium (mg/l)
|
1
|
1
|
1
|
0.5
|
|
Iron (mg/l)
|
0.5
|
0.4
|
0.3
|
0.2
|
|
Mercury (mg/l)
|
0.001
|
0.001
|
0.001
|
0.001
|
|
Cadmium (mg/l)
|
0.001
|
0.001
|
0.001
|
0.001
|
|
Silver (mg/l)
|
0.1
|
0.1
|
0.1
|
0.1
|
|
Copper (mg/l)
|
0.1
|
0.1
|
0.05
|
0.05
|
|
Selenium (mg/l)
|
0.1
|
0.1
|
0.05
|
0.05
|
|
Lead (mg/l)
|
0.2
|
0.2
|
0.2
|
0.1
|
|
Nickel (mg/l)
|
0.2
|
0.2
|
0.2
|
0.1
|
|
Other toxic metals
individually (mg/l)
|
0.5
|
0.4
|
0.3
|
0.2
|
|
Total toxic metals (mg/l)
|
0.5
|
0.4
|
0.3
|
0.2
|
|
Cyanide (mg/l)
|
0.05
|
0.05
|
0.05
|
0.01
|
|
Phenols (mg/l)
|
0.1
|
0.1
|
0.1
|
0.1
|
|
Sulphide (mg/l)
|
0.2
|
0.2
|
0.2
|
0.1
|
|
Fluoride (mg/l)
|
10
|
7
|
5
|
4
|
|
Sulphate (mg/l)
|
800
|
600
|
400
|
200
|
|
Chloride (mg/l)
|
1000
|
1000
|
1000
|
1000
|
|
Total phosphorus
|
10
|
10
|
8
|
8
|
|
Ammonia nitrogen (mg/l)
|
2
|
2
|
2
|
1
|
|
Nitrate + nitrite nitrogen
(mg/l)
|
30
|
30
|
20
|
20
|
|
Surfactants (total) (mg/l)
|
2
|
2
|
2
|
1
|
|
E. coli (count/100ml)
|
1000
|
1000
|
1000
|
1000
|
Note:
1. All units in mg/L
unless otherwise stated
Practice
Notes
5.2.5
A practice note for
professional persons was issued by the EPD to provide guidelines for handling
and disposal of construction site discharges. The Practice Note for
Professional Persons on Construction Site Drainage (ProPECC PN 1/94) provides
good practice guidelines for dealing with various types of discharge from a
construction site. Practices outlined in ProPECC PN 1/94 should be followed as
far as possible during construction to minimise the water quality impact due to
construction site drainage.
5.2.6
The ProPECC PN 5/93
"Drainage Plans subject to Comment by the Environmental Protection
Department – Building (Standards of Sanitary Fitments, Plumbing, Drainage Works
and Latrines) Regulations 40(1), 40(2), 41(1) and 90" provides guidelines
and practices for handling, treatment and disposal of various effluent
discharges to stormwater drains and foul sewers. The design of site
drainage and disposal of various site effluents generated within the new
development area should follow the relevant guidelines and practices as given
in the ProPECC PN 5/93.
Technical
Circular
5.2.7
Environment, Transport and
Works Bureau Technical Circular (ETWB TC) (Works) No. 5/2005 provides an
administrative framework to better protect all natural streams/rivers from the
impacts of construction works. The procedures promulgated under this Circular
aim to clarify and strengthen existing measures for protection of natural
streams/rivers from government projects and private
developments. The guidelines and precautionary mitigation measures
given in the ETWB TC (Works) No. 5/2005 should be followed as far as possible
to protect the inland watercourses at or near the Project area during the
construction phase.
5.2.8
For maintenance of
stormwater drainage system during operation phase, reference should be made to
ETWB TC (Works) No. 14/2004 “Maintenance of Stormwater Drainage Systems and
Natural Watercourses” where applicable. The circular sets out the
departmental responsibilities for the maintenance of stormwater drainage
systems and natural watercourses in government and private lands.
Technical
Specification
5.2.9
Technical Specifications on
Grey Water Reuse and Rainwater Harvesting issued by Water Supplies Department
state the grey water reuse and rainwater harvesting systems shall be designed
in a way that ensures the effluent is fit for purpose and presents no undue
risk to health.
Guidelines
5.2.10
Hong Kong Planning Standard
and Guidelines (HKPSG) Chapter 9 “Environment” listed out environmental requirements that need to be
considered in land use planning. The recommended guidelines, standards and
guidance cover the selection of suitable locations for the developments and
sensitive uses, provision of environmental facilities, and design, layout,
phasing and operational controls to minimise the adverse environmental impacts.
It also lists out environmental factors influencing land use planning and recommended
buffer distances for land uses.
Pesticides
Ordinance (Cap. 133)
5.2.11
The Pesticides Ordinance
Cap. 133 was introduced to regulate the import, manufacture, repackage,
storage, labeling and sale of all pesticides. Under the Pesticides Ordinance
Cap. 133, only registered pesticides may be imported into and freely
distributed for use in Hong Kong. Moreover, pesticides controlled under
Stockholm Convention and Rotterdam Convention are set out in two schedules to
the Ordinance (scheduled pesticides) - Schedule 1 lists pesticides under the
Stockholm Convention and Part 1 of Schedule 2 for pesticides under the
Rotterdam Convention. The import, export, manufacture, sale, supply,
possession, use or transhipment (except air transhipment cargo) of all
scheduled pesticides is prohibited except under a Pesticide Permit issued by
the Director of Agriculture, Fisheries and Conservation (DAFC).
Proposed
Assessment Criteria for Fungicides and Fertilizers
5.2.12
As the agrochemicals may
lead to potential water quality impacts and there are no statutory criteria for
assessing their concentration, their criteria have been established below for
further assessment in subsequent sections.
Fertilizers
5.2.13
Fertilizers will be applied
to the turf area in Sub-Area 2 to Sub-Area 4 in order to provide nutrients
(e.g. nitrogen, phosphorus, etc.) to turfgrass for healthy growth and
development. There are no numeric criteria for total inorganic nitrogen (TIN)
and total phosphorus (TP) in WQOs for Deep Bay WCZ. For EPD’s river water
quality monitoring stations, Station RB1 is the nearest monitoring station. The
river water quality monitoring data for Station RB1 in 2016-2020 is adopted as
criteria and is shown in Table
5-4 below.
Table 5‑4 Proposed
Criteria of Fertilizers in Surface Runoff
|
Nutrients
|
Criteria proposed (mg/L)
|
|
TIN
|
1.35
|
|
TP
|
0.312
|
Note: Total
inorganic nitrogen (TIN) is the sum of ammonia-nitrogen, nitrite-nitrogen and
nitrate-nitrogen.
Fungicides
5.2.14
As there are neither numeric
criteria under WQOs nor background measurement data for fungicides and
insecticides, the criteria of residual fungicides and insecticides are
determined with reference to the Manual for the Assessment of
Chemicals published by the Organization for Economic Co-operation and
Development (OECD) and the available ecotoxicity data in the corresponding
Material Safety Data Sheet (MSDS).
5.2.15
According to the manual
published by OECD, ecotoxicity test data (e.g.
fish, Daphnia or algae) could be used to determine the corresponding
Predicted No Effect Concentration (PNEC) which represents a concentration where
no unacceptable adverse effects on the aquatic ecosystem (e.g. coral,
fisheries, etc.) are expected. There are also examples of using PNEC as
assessment criteria in local studies. PNEC was adopted as the assessment
criteria for anti-scalant in the approved EIA study of Desalination Plant at
Tseung Kwan O (AEIAR – 192/2015) where numeric criteria and background
measurement data were not available. Also, the use of PNEC as assessment criteria
are also common for some local projects such as district cooling systems.
Therefore, it is proposed to adopt PNEC as the assessment criteria for this
study.
5.2.16
Based on current practice,
fungicides including Mancozeb, Heritage and Calvary would be used. The typical
MSDSs of these 3 agrochemicals have been extracted and reviewed. If there is
any change in the use of agrochemicals in the future operation, MSDSs and
monitoring parameters should be reviewed accordingly. According to the
corresponding MSDSs, information such as lethal concentration to 50% test
species (LC50) or half maximal effective concentration (EC50) and No Observable
Effective Concentration (NOEC) is available.
5.2.17
Either acute (e.g.
LC50 and EC50) or chronic (e.g. NOEC) toxicity data are eligible to
determine the criteria by applying an appropriate assessment factor to the
lowest acute or chronic toxicity data. The assessment factor ranges from 100 –
1000 for acute data and 10 – 100 for chronic data which depends on the
available toxicity test data from different trophic levels. If toxicity data is
available from species representing three trophic levels (i.e.
fish, Daphnia or algae), a lower assessment factor is applied. The
proposed criteria for fungicides are shown in Table 5-5
below.
Table 5‑5 Proposed Criteria for Fungicides in
Surface Runoff
|
Agrochemicals
|
Concentration
Limit (mg/L)
|
|
Mancozeb
|
1.00E-03
|
|
Heritage
|
1.06E-03
|
|
Calvary
|
7.00E-04
|
Herbicides and
Insecticides
5.2.18
There are also neither
numeric criteria under WQOs nor background measurement data for the herbicides.
While Mechanical methods (hand weeding) will be the primary means of control of
turfgrass weeds, it is still occasionally required to apply herbicides. However,
unlike fungicides which would be applied across the entire turf area, the
application of herbicides to the turf area is not on a regular basis and spot
spraying will be adopted in applying herbicides to selected areas. Therefore,
the amount of residual herbicides in runoff will be insignificant.
5.2.19
In similar, application of insecticide is not a
regular practice. It is anticipated that the amount of residual insecticides
in runoff will be insignificant.
5.3
Water Sensitive Receivers (WSRs)
5.3.1
Water Sensitive Receivers (WSRs) within the 500m
assessment area are indicated in Figure 5.1 and Table 5‑6. They include channelized
rivers, watercourses and a number of ponds.
Table
5‑6 Summary of Water
Sensitive Receivers
5.4
Description of Environment
5.4.1
Water courses in the vicinity of the PDA comprise the channelized River Beas (Sheung Yue
River), River Sutlej (Shek Sheung River), various ponds and a number of
channelized streams with unpolluted and polluted sections.
5.4.2
For those water courses near On Po and Ping
Kong, the direction of flow is towards north to the River Sutlej then to River
Indus and ultimately Inner Deep Bay via Shenzhen River, while for River Beas and
its tributaries, the direction of flow is towards north to the River Indus and
ultimately Inner Deep Bay via Shenzhen River also.
Baseline
River Water Quality
5.4.3
Water courses identified within the Assessment
Area (defined as 500 m from the project boundary) include the River Beas and
River Sutlej. The Assessment Area falls within the Deep Bay WCZ and
the WQOs designated for the whole zone are thus relevant
to this Project and are summarized on Table 5-6 above.
5.4.4
River water quality has been
regularly monitored by the EPD since 1986. Measurements and
laboratory tests of over 50 physico-chemical and biological parameters,
including organics, nutrients, metals and E. coli levels are
recorded on a monthly basis. In 2020, a total of 6 stations at River
Beas (RB) and River Indus (IN) were monitored, five of them were close to project.
5.4.5
Data of key water quality parameters
measured in 2020 at the five monitoring stations as reported in the Annual
River Water Quality Report are presented in Table 5‑7.
Table 5‑7 Summary of River Water
Quality Monitoring Data collected by EPD River Water Quality Monitoring
Programme for Stations in River Beas and River Indus (2020)
|
Parameter
|
Unit
|
RB1
|
RB2
|
RB3
|
IN1
|
IN2
|
|
Dissolved Oxygen
|
mg/L
|
9.9
(7.7-12.0)
|
7.2
(6.3-8.1)
|
7.4
(4.5-9.9)
|
6.0
(4.8-7.0)
|
6.1
(2.6-9.7)
|
|
pH
|
|
8.2
(7.3-9.5)
|
7.4
(7.2-7.8)
|
7.4
(7.2-8.0)
|
7.2
(7.0-7.4)
|
7.3
(7.2-7.6)
|
|
Suspended Solids
|
mg/L
|
5.4
(2.0-21.0)
|
7.7
(3.6-33.0)
|
24.0
(2.1-100.0)
|
16.0
(8.5-280.0)
|
6.1
(3.2-20.0)
|
|
5-Day Biochemical Oxygen Demand
|
mg/L
|
2.5
(1.3-4.8)
|
5.3
(3.7-7.4)
|
8.6
(2.0-16.0)
|
3.7
(1.3-12.0)
|
3.0
(1.0-6.0)
|
|
Chemical Oxygen Demand
|
mg/L
|
9
(5-14)
|
14
(9-21)
|
19
(12-33)
|
23
(12-46)
|
11
(5-17)
|
|
Oil & Grease
|
mg/L
|
<0.5
(<0.5-<0.5)
|
<0.5
(<0.5-<0.5)
|
<0.5
(<0.5-<0.5)
|
<0.5
(<0.5-<0.5)
|
<0.5
(<0.5-<0.5)
|
|
E. coli
|
counts/ 100mL
|
2300
(1400-6700)
|
3300
(570-12000)
|
16000
(7000-27000)
|
15000
(2200-140000)
|
4400
(800-17000)
|
|
Faecal Coliforms
|
counts/ 100mL
|
14000
(4400-75000)
|
13000
(990-84000)
|
58000
(10000-240000)
|
61000
(9300-300000)
|
20000
(4300-77000)
|
|
Ammonia-Nitrogen
|
mg/L
|
0.220
(0.110-0.730)
|
1.850
(0.180-4.600)
|
2.300
(0.180-5.200)
|
1.100
(0.280-5.400)
|
0.615
(0.090-1.800)
|
|
Nitrate-Nitrogen
|
mg/L
|
0.815
(0.480-1.200)
|
0.500
(0.140-1.200)
|
0.430
(0.200-1.400)
|
2.100
(0.480-3.300)
|
0.985
(0.530-1.300)
|
|
Total Kjeldahl Nitrogen
|
mg/L
|
0.61
(0.48-2.20)
|
2.60
(0.77-4.90)
|
4.30
(0.95-5.90)
|
2.20
(1.10-5.90)
|
1.25
(0.24-2.40)
|
|
Orthophosphate Phosphorus
|
mg/L
|
0.240
(0.120-0.370)
|
0.220
(0.110-0.290)
|
0.210
(0.095-0.390)
|
0.220
(0.120-0.490)
|
0.088
(0.017-0.130)
|
|
Total Phosphorus
|
mg/L
|
0.37
(0.16-0.48)
|
0.43
(0.14-0.59)
|
0.51
(0.22-0.72)
|
0.51
(0.26-1.10)
|
0.17
(0.10-0.24)
|
|
Sulphide
|
mg/L
|
<0.02
(<0.02-<0.02)
|
<0.02
(<0.02-<0.02)
|
<0.02
(<0.02-0.40)
|
<0.02
(<0.02-0.35)
|
<0.02
(<0.02-<0.02)
|
|
Aluminium
|
µg/L
|
<50
(<50-88)
|
<50
(<50-77)
|
<50
(<50-115)
|
58
(<50-348)
|
<50
(<50-151)
|
|
Cadmium
|
µg/L
|
(<0.1
(<0.1-<0.1)
|
<0.1
(<0.1-<0.1)
|
<0.1
(<0.1-<0.1)
|
<0.1
(<0.1-<0.1)
|
<0.1
(<0.1-<0.1)
|
|
Chromium
|
µg/L
|
<1
(<1-<1)
|
<1
(<1-<1)
|
<1
(<1-<1)
|
<1
(<1-1)
|
<1
(<1-<1)
|
|
Copper
|
µg/L
|
<1
(<1-2)
|
1
(<1-2)
|
2
(<1-2)
|
2
(2-2)
|
1
(1-3)
|
|
Lead
|
µg/L
|
<1
(<1-<1)
|
<1
(<1-<1)
|
<1
(<1-<1)
|
<1
(<1-1)
|
<1
(<1-<1)
|
|
Zinc
|
µg/L
|
<10
(<10-15)
|
<10
(<10-16)
|
<10
(<10-20)
|
12
(<10-30)
|
<10
(<10-23)
|
|
Flow
|
m3/s
|
0.301
(0.090-1.226)
|
0.149
(0.038-6.300)
|
NM
|
19.019
(2.680-75.460)
|
NM
|
Notes:
1.
Data source: EPD River Water Quality Report in Hong Kong in 2020
2.
cfu - colony
forming unit.
3.
Underlined figures =
non-compliance of WQO
4.
The WQO for Nitrogen under the WPCO refers to level of Un-ionized
Ammoniacal Nitrogen. As such, there is no applicable WQO to
Ammonia-Nitrogen.
5.
NM indicates no
measurement taken.
5.4.6
River Indus is a major river in the North
District. The overall WQO compliance rate was 85% in 2020, as compared with 26%
in 1990. The three monitoring stations (IN1, IN2 and IN3) situated along the
river maintained WQI gradings of “Good” to “Excellent” in 2020.
5.4.7
As a tributary of River Indus, River Beas
recorded an overall WQO compliance rate of 69% in 2020, as compared with 21% in
1990. Its three monitoring stations (RB1, RB2 and RB3) achieved “Fair” to
“Good” WQI in 2020.
5.4.8
Livestock farm discharges in
the district have been eliminated under the Livestock Waste Control Scheme
(LWCS). Under LWCS, most livestock farms in North District have ceased
operation. The WQI gradings for the downstream sections of River Indus, River
Beas and River Ganges improved from “Very Bad” in 1987 to “Fair” to “Good” in
2019, with over 90% reduction in E. coli level as compared with 1990.
Sewerage works for villages are being planned and progressively implemented.
The sewage treatment works at Shek Wu Hui and Sha Tau Kok will be expanded to
cater for projected population growth, and upgraded to produce higher quality
effluent.
Baseline
Water Quality Monitoring at Existing Watercourses
5.4.9
Other than the desktop
information as summarised above, in-situ water quality monitoring has been
conducted at selected watercourses. As construction works will be mainly
involved in Sub-Area 1, monitoring location is to be closed to this area. 2
channelised watercourses near Sub-Area 1 (BW1 and BW2) which currently do not
have baseline monitoring data are selected for monitoring. The project specific
water quality monitoring was conducted on 4, 6, 8, 11, 13 and 15 January
2021. Locations of the monitoring points are shown in Figure 5.1. The following Table 5‑8 summarises
the monitoring results.
Table
5‑8 Baseline Water Quality
Monitoring at Existing Watercourses under this Study
|
Parameter
|
Unit
|
BW1
|
BW2
|
|
pH
|
-
|
7.7
|
7.7
|
|
7.41
- 8.45
|
7.21
- 8.35
|
|
5-Day
Biochemical Oxygen Demand (BOD5)
|
mg/L
|
4.2
|
4.2
|
|
<3
- 8
|
<3
- 7
|
|
Chemical
Oxygen Demand (COD)
|
mg/L
|
<10
|
<10
|
|
<10-<10
|
<10-<10
|
|
Suspended
solids (SS)
|
mg/L
|
9.1
|
9.6
|
|
<3.1
- 36
|
4.9
- 18
|
|
Dissolved
oxygen (DO)
|
mg/L
|
7.8
|
8.1
|
|
6.5
- 8.96
|
6.5
- 10.1
|
|
Temperature
|
oC
|
15.1
|
13.1
|
|
12.1
- 17.7
|
9.2
- 16.9
|
|
Salinity
|
ppt
|
0.1
|
0.1
|
|
0.08
- 0.13
|
0.08
- 0.24
|
|
Ammonia-nitrogen
(NH3-N)
|
mg/L
|
2.1
|
1.2
|
|
1.47
- 3.05
|
0.17
- 1.97
|
|
Unionized
Ammonia
|
mg/L
|
0.05
|
0.03
|
|
<0.02
- 0.11
|
<0.02
- 0.09
|
|
Escherichia
coli (E.coli)
|
cfu/100mL
|
11180
|
8080
|
|
80
- 64000
|
80
- 47000
|
Notes:
1.
cfu - colony
forming unit.
2.
Underlined figures =
non-compliance of WQO
5.4.10
It is noted that high levels of E.
coli were observed at all monitoring stations, indicating
that the water quality there was likely affected by sewage discharged upstream
where scattered houses at On Po Village are not served by public
sewers. High levels of biological oxygen demand, ammonia-nitrogen
and unionized ammonia were also recorded suggesting high organic constituents
in the watercourse.
5.5
Assessment Methodology
5.5.1
The Assessment Area includes all areas within
500m distance away from the project boundary, and covers relevant Water
Sensitive Receivers that may have a bearing on the environmental acceptability
due to the Project within the Deep Bay WCZ. The assessment area should be extended to include other areas such
as stream courses and associated water systems, existing and planned drainage
system if they are found being impacted during the course of the EIA study and
have a bearing on the environmental acceptability of the Project.
5.5.2
The WSRs that may be affected by the
construction and operation of the Project were identified. Potential sources of
water quality impact that may arise during the land-based construction works
and operation of the Project are described. All the identified sources of
potential water quality impact were then evaluated, and their impact
significance were determined. Mitigation measures were also recommended to
reduce identified adverse impacts on water quality to acceptable levels.
5.6
Identification and Evaluation of Water Quality
Impacts - Construction Phase
5.6.1
The Project comprises the following works that
would impact water quality of the WSRs within and near the Project Site.
Sub-Area 1 (Potential Development Area)
·
Site formation, including removal / diversion of
watercourses;
·
Slope works, including construction of retaining
wall;
·
Road works and utilities;
·
Construction of waterworks, drainage and
sewerage infrastructural works;
·
Landscaping work; and
·
Construction of superstructures for residential,
commercial uses, community / institution, Public Transport Interchange and
supporting facilities.
Sub-Area 2 to Sub-Area 4 (Landscaping
Area)
·
Sub-Areas 2 to 4 are
proposed to be preserved with minimal works Sub-Areas 2 to 3 and no works in
Sub-Area 4
·
Land use such as public
park have been considered in Sub-Area 2. One storey visitor centre and toilet
will be provided.
·
Landscaping works, such as planting and minor
transplanting works that are
compatible with existing habitats.
· Site Run-off from General Construction
Activities;
·
Accidental Spillage;
·
Groundwater from Contaminated Areas;
·
Effects on Groundwater Table / Hydrology / Flow
Regime;
·
Sewage Effluent from Construction Workforce;
Impact on
Water Sensitive Receiver within Sub-Area 1
5.6.3
WSR8 is a ditch located within Sub-Area 1 of PDA
with approximate 85m long. Currently, it is solely to divert the surface
runoff of part of golf course to public drainage system.
5.6.4
During construction, site formation works will
be conducted in Sub-Area 1 and the above ditch will be demolished. Temporary
site drainage system will be provided and the site runoff will be properly
collected, treated and discharged. Adverse water quality impact to this
downstream is not anticipated.
Impact on
Water Sensitive Receiver within or in close proximity Sub-Area 2 to Sub-Area 4
5.6.5
WSR 10 is a marsh in Sub-Area 4. According to
current proposal, no work will be conducted in Sub-Area 4. This marsh may be
maintained but subject to future landscape design. Temporary site drainage
system will be provided in order to prevent site runoff divert to this WSR. WSR4
is Tai Long Experimental Farm, which is close to Sub-area 4. It is anticipated
that construction runoff from the Sub-Area 4 is limited. Meanwhile, with implementation
of measures, such as temporary site drainage and good
site management, adverse water quality impact to this
WSR is not anticipated.
5.6.6
WSR 9 is a pond which is located in Sub-Area 2.
This pond may be maintained but subject to future landscape design. Temporary
site drainage system will be provided in order to prevent site runoff divert to
this WSR. Adverse water quality impact to this WSR is not anticipated.
Site
Run-off from General Construction Activities
5.6.7
The land-based construction works, such as earth
working, excavation and stockpiles could have the potential to cause water
pollution. Besides,
various types of construction activities may generate wastewater. These
include general cleaning and polishing, wheel washing, dust suppression and
utility installation. These types of wastewater would contain high
concentrations of Suspended Solid (SS).
5.6.8
Effluent discharged from temporary site facilities should be controlled
to prevent direct discharge to the neighbouring storm drains. Such effluent
may include various types of wastewater generated from different construction
activities such as general cleaning and polishing, wheel washing, dust
suppression and utility installation. Adoption of the guidelines and good site
practices for handling and disposal of construction discharges as part of the
construction site management practices would minimize the potential impacts.
5.6.9
During rainstorms, site run-off would wash away
the soil particles on unpaved lands and areas with the topsoil exposed. The
run-off is generally characterized by high concentrations of SS. Release of
uncontrolled site run-off would increase the SS levels and turbidity in the
nearby water environment. Site run-off may also wash away contaminated soil
particles and therefore cause water pollution.
5.6.10
Windblown dust would be generated from exposed
soil surfaces in the works areas. It is possible that windblown dust would
fall directly onto the nearby water bodies when a strong wind occurs.
Dispersion of dust within the works areas may increase the SS levels in surface
run-off causing a potential impact to the nearby sensitive receivers. Potential pollution sources of site run-off may include:
·
Run-off and erosion of exposed bare soil and
earth, drainage channel, earth working area and stockpiles.
·
Wastewater from any dewatering associated with
any piling activities and excavation of wet material during construction.
·
Release of any bentonite slurries, concrete
washings and other grouting materials with construction run-off, storm water or
ground water dewatering process.
·
Wash water from dust suppression sprays and
wheel washing facilities.
·
Fuel, oil and lubricants from maintenance of
construction vehicles and equipment.
5.6.11
Construction site run-off and drainage may cause
local water quality impacts. Increase in SS arising from the construction
site could block the drainage channels. High concentrations of suspended
degradable organic material in inland water could lead to reduction in DO
levels in the water column.
5.6.12
It is important that proper site practice and
good site management be followed to prevent run-off with high level of SS from
entering the surrounding waters. With the implementation of appropriate
measures to control run-off and drainage from the construction site,
disturbance of water bodies would be avoided and deterioration in water quality
would be minimal. Thus, unacceptable impacts on the water quality are not
expected, provided that the recommended measures are properly implemented.
Accidental
Spillage
5.6.13
A large variety of chemicals may be used during
construction activities. These chemicals may include petroleum products,
surplus adhesives, spent lubrication oil, grease and mineral oil, spent acid
and alkaline solutions/solvent and other chemicals. Accidental spillage of
chemicals in the works areas may contaminate the surface soils. The
contaminated soil particles may be washed away by construction site run-off or
storm run-off causing water pollution.
5.6.14
The use of engine oil and lubricants, and their
storage as waste materials would have the potential to create impacts on the
water quality if spillage occurs and enters adjacent water environment. Waste
oil may infiltrate into the surface soil layer, or run-off into inland water
environment, increasing hydrocarbon levels. The potential impacts could however
be mitigated by practical mitigation measures and good site practices.
Groundwater from Contaminated area
5.6.15
Details of the land contamination assessment are
separately presented in Section 7. Any contaminated material disturbed, or
material which comes into contact with the contaminated material, has the
potential to be washed with site run-off into watercourses. Uncontrolled
discharge of the groundwater from contaminated areas may affect the surface or
groundwater quality. Mitigation measures should be implemented to control site
runoff from the contaminated areas, and to prevent runoff entering the adjacent
waters.
5.6.16
Groundwater pumped out or from dewatering
process during excavation works in these areas would be potentially
contaminated. Prior to the excavation works, the baseline groundwater quality
in these potentially contaminated areas should be reviewed with reference to
the relevant site investigation data and any additional groundwater quality
measurement results. The review results should be submitted to EPD for
examination.
5.6.17
If the review indicated that the groundwater to
be generated from the excavation works would be contaminated, this contaminated
groundwater will be either properly treated or properly recharged into the
ground in compliance with the requirements of the TM-DSS. If
wastewater treatment is to be deployed for treating the contaminated
groundwater, the wastewater treatment unit should deploy suitable treatment
processes to reduce the pollution level to an acceptable standard and remove
any prohibited substances to an undetectable range. All treated effluent from
the wastewater treatment unit should meet the requirements as stated in TM-DSS
and should be either discharged into the foul sewers or tankered away for
proper disposal. No direct discharge of contaminated groundwater will be
adopted.
5.6.18
If deployment of wastewater treatment is not
feasible for handling the contaminated groundwater, groundwater recharging
wells will be installed as appropriate for recharging the contaminated
groundwater back into the ground. The recharging wells will be selected at
places where the groundwater quality will not be affected by the recharge
operation as indicated in section 2.3 of the TM-DSS. Pollution
levels of groundwater to be recharged shall not be higher than pollutant levels
of groundwater at the recharge well. The Contractor
should apply for a discharge licence under the WPCO through the Regional Office
of EPD for groundwater recharge operation or discharge of treated groundwater.
Provided that all the mitigation measures and monitoring requirements as
recommended in Sections 5.9.4 and 5.9.5 are followed
properly, no adverse water quality impact would be envisaged.
Effects on
Groundwater Table / Hydrology / Flow Regime
5.6.19
Housing development is proposed in Sub-Area 1
and foundation works is involved. Impact from foundation work on water table
would be considered insignificant. Meanwhile, there would be no deep tunnel
due to the Project, adverse impact to groundwater table is not anticipated.
5.6.20
Major construction works are to be conducted in Sub-Area
1. Since the identified agricultural areas and mixed woodland at the On Po
Tsuen are located at the upstream, adverse impact due to the change of
infiltration rate in Sub-Area 1 is not anticipated.
5.6.21
Sub-area 2 to Sub-Area 4 are proposed to be preserved with landscaping works, such as planting
and minor transplanting works in Sub-Areas 2 to 3 and no works in Sub-Area 4.
Based on the works nature, change of unpaved area
would be minimal. Adverse impact to nearby receivers due to the change of
infiltration is not expected.
Sewage Effluent from Construction Workforce
5.6.22
Sewage effluents will arise from the sanitary
facilities provided for the on-site construction workforce. Based on Table T-2 of
the Guidelines for Estimating Sewage Flows for Sewage Infrastructure Planning Sewerage
Manual issued by EPD, the sewage production rate for construction workers is
estimated at 0.23 m3 per worker per day. Thus, for every 100
construction workers working simultaneously at the construction site, about 23
m3 of sewage would be generated per day. The characteristics of
sewage would include high levels of BOD5, Ammonia and E. coli
counts.
5.6.23
Portable chemical toilets would be provided for
handling the construction sewage generated by the workforce. The number of the
chemical toilets required for the construction sites would be subject to later
detailed design, the capacity of the chemical toilets, and contractor’s site
practices. A licensed contractor would be employed to provide appropriate and
adequate portable toilets and be responsible for appropriate disposal and
maintenance.
5.6.24
Notices would be posted at conspicuous locations
to remind the workers not to discharge any sewage or wastewater into the nearby
environment during the construction phase of the Project. Regular environmental
audit on the construction site would be conducted in order to provide an
effective control of any malpractices and achieve continual improvement of
environmental performance on site.
5.6.25
Provided that sewage is not discharged directly
into stormwater drains or inland waters, and temporary sanitary facilities are
used and properly maintained, no adverse water quality impact would be
anticipated. Mitigation measures and good site practices should be
implemented.
5.7
Identification and Evaluation of Water Quality
Impacts - Operation Phase
5.7.1
The identified potential sources of impact on
water quality during the operation phase of the Project would be:
· Hydrological change and surface run-off
·
Sewage and wastewater effluents from building
·
Usage of Agrochemicals in Sub-Area 2, 3 and 4
Hydrological change and surface run-off
5.7.2
In Sub-Area 1, surface runoff from roads, PTIs
and paved areas would contain pollutants and contaminants that impact the
downstream water quality. While in Sub-Area 2 and Sub-Area 4, runoff
may potentially be contaminated by agrochemicals. Pesticides or
fertilizers may be used in the maintenance of the landscaped area. Common good
practices would be applied to minimise potential water quality impact from
agrochemical application.
5.7.3
With reference to the current option, the
development is limited to Sub-Area 1 where the existing area is mainly unpaved.
There would be an increase in the total paved area, such change of pavement
around an addition of about 8ha will reduce the infiltration rate into the
ground.
5.7.4
Increasing flood risk as a result of extra
stormwater runoff may occur and this would be assessed in the Drainage Impact
Assessment Report under this study. In terms of water quality impact,
additional loading would be due to addition runoff (known as non-point source
pollution) from the reduction of infiltration rate from the development. Worst
scenario will be due to first flush under heavy rainstorm events.
5.7.5
According to “Stormwater Drainage Manual”,
annual rainfall in Hong Kong is around 2200mm. However, EPD’s report on
"Update on Cumulative Water Quality and Hydrological Effect of Coastal
Developments and Upgrading of Assessment Tool-Pollution Loading Inventory
Report" (Pollution Loading Report) indicates only rainfall events of
sufficient intensity and volume would give rise to runoff and that runoff
percentage for the wet season is about 82% while dry season is only 44%.
Therefore, only 1386mm of 2200mm annual rainfall would be effective rainfall to
generate additional runoff (i.e. 1386mm=2200mm×(82%+44%)/2).
5.7.6
For the Public Housing Development in the Sub-Area
1, the total surface area is around 8ha (paved) and 2ha (unpaved). It is assumed that 0.9 of runoff
coefficient is adopted for paved areas while 0.3 runoff coefficient for
unpaved/undeveloped area. Hence, the total additional average daily runoff from
Sub-Area 1 will be about 176 m3/day. As there are no
changes of paved/unpaved area in other Sub-Areas, no additional average daily
runoff from other Sub-Areas is expected.
5.7.7
It is expected that the
volume of surface runoff will increase in the developable area due to
increase in paved areas. The
total loading of non-point source pollution due to the Public Housing Development is compared with
that of existing condition in Appendix 5.1. Table 5‑9 summarises
the pollution loading from the existing and developed cases surface run-off by adopting 20% removal efficiency with the implementation of silt
traps.
Table 5‑9 Pollution Loading of
Surface Run-off
|
Parameters
|
Unit
|
Existing Case
|
Developed Case
|
Induced Loading
|
|
BOD5
|
kg/d
|
3.4
|
5.5
|
2.1
|
|
SS
|
kg/d
|
6.6
|
10.6
|
4.0
|
|
NH3-N
|
kg/d
|
0.03
|
0.05
|
0.02
|
|
OrgN
|
kg/d
|
0.18
|
0.29
|
0.11
|
|
TIN
|
kg/d
|
0.09
|
0.15
|
0.06
|
|
TN
|
kg/d
|
0.27
|
0.44
|
0.16
|
|
TP
|
kg/d
|
0.03
|
0.05
|
0.02
|
Note:
1.
BOD5
(5-day Biochemical Oxygen Demand); SS (Suspended Solid); NH3-N (Ammonia nitrogen); OrgN (Organic
Nitrogen); TIN (Total Inorganic Nitrogen); TN (Total Nitrogen); TP (Total
Phosphorus)
2.
In accordance with the “Stormwater Drainage Manual”, the runoff
coefficient for paved area is around 0.9 while for the unpaved area is around
0.3.
3.
20% removal efficiency of the silt traps is adopted.
5.7.8
Estimation on the potential
pollution loading due to the surface runoff from the developable area is
provided. To minimize the potential impact from the non-point source
pollution, the drainage system shall be referred to ProPECC PN 5/93 and
the capacities of drainage system shall be adequate to the target drainage
performance, subject to detailed design and requirement of relevant government
departments.
5.7.9
Prevention of “first
flush” pollution will be an effective way in controlling
pollution. This can be done by prevention of pollutants from
entering the drainage system and by removal of pollutants by installation of
appropriate devices as well as management measures.
5.7.10
The surface runoff could also be controlled by
best management practice. It could be intercepted by properly designed and
managed silt traps and petrol interceptor at appropriate spacings, so that
common roadside debris, refuse and fallen leaves etc. can be captured before
allowing the runoff to public drain. The operator should undertake the cleaning
at a frequent interval and the frequency should be increased to suit
actual site conditions. After removal of the pollutants, the pollution
levels from stormwater would be much reduced.
Sewage and Wastewater Effluents from Buildings
5.7.11
During operation phase,
sewage discharge will be the major water pollution source. All sewage flow will
be diverted to Shek Wu Hui Sewage Treatment Works for treatment.
5.7.12
There is wastewater
generated from municipal and commercial activities, e.g. refuse collection
points, restaurants etc, and may contain high levels of pollutants. The
design, construction and operation of refuse collection points should be
referred to Chapter 9 of HKPSG in order to minimum impact to nearby receivers.
In addition, each individual commercial tenant should apply for an effluent
discharge license under the WPCO and should comply with the standards for
effluent discharge into the public sewerage under the TM-DSS. And all
wastewater will be conveyed to the Shek Wu Hui Sewage Treatment Works for
treatment, no adverse water quality impact is anticipated.
5.7.13
There will be adequate
capacity for existing sewerage system and all the sewage will be diverted to
the existing sewerage system. No sewage overflow and emergency discharge is
anticipated and no additional mitigation measure is required. Details of sewage
and sewerage implication are presented in Chapter 6.
Usage of
Agrochemicals in Sub-Area 2, 3 and 4
5.7.14
In order to preserve the ecological value of the
Sub-Area 2, 3 and 4, major land use of Sub-Area 2, 3 and 4 will not be
altered. In addition, existing drainage system in Sub-Area 2, 3 and 4 will be maintained.
Residual Concentrations
of Fertilizers
5.7.15
Fertilizers proposed for the golf course mainly
contain nutrients including nitrogen, phosphorus, etc. and the residual
fertilizers will be washed away by surface runoff.
5.7.16
The residual Total Inorganic Nitrogen (TIN) and
Total Phosphorus (TP) concentration in surface runoff are calculated by using
the nutrient absorption rate in Kau Sai Chau case. Table 5-10 summarises
the results and the detailed calculation is presented in Appendix 5.2.
Table 5‑10 Concentrations
of Fertilizers in Surface Runoff
|
Nutrients
|
Residual
Percentage 1
|
Concentration in
Surface Runoff (mg/L)
|
Criteria proposed
(mg/L) 2
|
Compliance
|
|
TIN
|
1.6%
|
1.16
|
1.35
|
Yes
|
|
TP
|
0.6%
|
0.101
|
0.312
|
Yes
|
Note:
1.
With Reference to the EIA for Proposed Extension of Public Golf Course at Kau
Sai Chau Island, Sai Kung.
2.
Monthly mean of Total Inorganic Nitrogen and Total Phosphorus monitoring data
at River Water Quality Monitoring Station RB1 in Year 2016 to Year 2020 is
adopted as criteria.
5.7.17
It can be seen that the concentrations are
within the ranges of the monthly mean of TIN and TP in the monitoring data.
Adverse water quality impact is therefore not anticipated from the residual
fertilizers.
Residual Concentrations of
Fungicides
5.7.18
In the calculation, the runoff residual load is
calculated based on the application rate and application area. The residual
fungicide concentration is calculated by adopting the 2 years return period
rainfall in North District Area. Table 5-11 summarises the
results and the detailed calculation is presented in Appendix 5.2.
Table
5‑11 Concentrations
of Fungicides in Surface Runoff
|
Agrochemicals
|
Residual Percentage
1
|
Concentration in Runoff
(mg/L)
|
Criteria proposed (mg/L)
2
|
Compliance
|
|
Fungicides
|
|
Mancozeb
|
0.00072%
|
7.64E-06
|
1.00E-03
|
Yes
|
|
Heritage
|
0.00072%
|
5.82E-06
|
1.06E-03
|
Yes
|
|
Calvary
|
0.00072%
|
7.34E-06
|
7.00E-04
|
Yes
|
Note:
1. With Reference to the EIA for
Proposed Extension of Public Golf Course at Kau Sai Chau Island, Sai Kung.
2. Predicted No Effect
Concentration (PNEC) is adopted as the criteria, which is equal to toxicity
test data divided by assessment factor in accordance with Chapter 4 in the
Manual for the Assessment of Chemicals published by the OECD.
5.7.19
According to the calculated results, the
concentration of residual fungicides would comply with the proposed criteria.
Adverse water quality impact from the residual fungicides is therefore not
anticipated.
Residual Concentrations
of Herbicides and Insecticides
5.7.20
Mechanical methods (hand weeding) of removing
turfgrass weeds will be the primary means of control. The maintenance staff
will regularly inspect and to identify any noticeable weeds as early as
possible. Early identification can prevent expansive and persistent growth of
herbs and therefore minimize the use of herbicide.
5.7.21
With the practices as discussed above, the
application of herbicides is unlikely unless when expansive and persistent
weeds happen to appear in the site. However, it should be noted that the
application of herbicide is not a regular practice, and only spot spraying will
be adopted in the application. Hence, it is anticipated that the amount of
residual herbicides in runoff is not significant.
5.7.22
In similar, application of insecticide is not a
regular practice. It is anticipated that the amount of residual insecticides
in runoff is not significant.
Overall Impact from Agrochemicals
5.7.23
Based on the above evaluations, impacts from
residual agrochemicals are not significant.
5.7.24
The amount of agrochemicals will be stored in
specific on site and limited to small essential quantities at any one time.
Also, only staff that have expertise in handling the specific chemicals for
specific tasks are allowed to handle the agrochemicals. Therefore, the risk of
chemical spillage is insignificant.
5.7.25
Existing conditions of Sub-Area 2, 3 and 4 will
be maintained as far as possible. Application of agrochemicals to these Sub-Areas
would be similar as before. Therefore, water quality impact from agrochemicals to WSR 9 and 10 is
not anticipated.
5.8
Cumulative Impacts from Concurrent Projects
5.8.1
A number of concurrent land
base projects within the assessment area has been identified, including. Residential Development at Kwu Tung, Fanling, Lot 4076
(Year 2024 operation), Potential Housing Site at Ching Hiu Road (Construction
Program, 2022-2029), North District Hospital Extension (Construction Program,
2021-2030) and Residential Development at Tai Tau Leng (Construction Program,
2025-2030).
5.8.2
The public and private
housing developments, GIC facilities, and infrastructural works for roads and
drains would be constructed and operated simultaneously with the
Project. It is anticipated that general construction activities such
as site formation and superstructure works would be involved, and potential
impact from site run-off, accidental chemical spillage, sewage from
construction workforce, etc. would occur.
5.8.3
With proper implementation
of the mitigation measures recommended in Section 5.9 and ProPECC PN 1/94, it is anticipated
that site runoff and wastewater generated from the work sites would be properly
managed. With incorporation of the recommended
mitigation measures, no significant cumulative construction water quality impacts
would be expected.
5.8.4
Sewage flow from the PDA will
be diverted to Shek Wu Hui Sewage Treatment Works via gravity
sewers. The details of sewage impact assessment are discussed
in Chapter 6 in this report. Additional loading would be due to addition runoff (known as
non-point source pollution), with the implementation of recommended mitigation
measure in Section 5.10, no significant operation impact would be anticipated.
As such, unacceptable cumulative
water quality impact associated with sewage flow and non-point source pollution
from other concurrent projects is not anticipated during Project operation.
5.9
Recommended Mitigation Measures - Construction Phase
Site
Run-off from General Construction Activities
5.9.2
Proper site management measures should be
implemented to control site runoff and drainage, and thereby prevent high
sediment loadings from reaching downstream sections of the
river/stream. A storm
water pollution control plan is presented in Appendix 5.3. The
Contractor should follow the practices, and be responsible for the design,
construction, operation and maintenance of all the mitigation
measures. The design of the mitigation measures should be submitted
by the Contractor to the Engineer for approval. These mitigation
measures shall include the following practices to minimize site surface runoff
and the chance of erosion, and also to retain and reduce any suspended
solids prior to discharge:
·
Before commencing any work, all sewer and
drainage connections should be sealed to prevent debris, soil, sand etc. from
entering public sewers/drains.
·
Provision of perimeter channels to intercept
storm-runoff from outside the site. These should be constructed in
advance of the construction works.
·
Temporary ditches such as channels, earth bunds
or sand bag barriers should be included to facilitate runoff discharge into the
stormwater drain, via a sand/silt basin/trap.
·
Works programme should be designed to minimize
works areas at any one time, thus minimizing exposed soil areas and reducing
the potential for increased siltation and runoff.
·
Sand/silt removal facilities such as sand traps,
silt traps and sediment basins should be provided to remove the sand/silt
particles from run-off where necessary. These facilities should be
properly and regularly cleaned and maintained. These facilities
should be carefully planned to ensure that they would be installed at appropriate
locations to capture all surface water generated on site.
·
Careful programming of the works to avoid
excavation works during the rainy season.
·
Temporary access roads (if any) should be
protected by crushed gravel and exposed slope surfaces shall be protected when
rainstorms are likely; and
·
Open stockpiles of construction materials
on-site should be covered with tarpaulin or similar fabric during rainstorms to
prevent erosion.
Accidental Spillage
5.9.3
In the event that accidental spillage or
leakages of hazardous substances / chemical wastes occur, the response
procedures as listed below should be followed. It should be noted
that the procedures below are not exhaustive and the contractor
should propose other response procedures in the emergency contingency plan
based on the particular types and quantities of chemicals or hazardous
substances used, handled and stored on-site.
·
Oil leakage or spillage should be contained and
cleaned up immediately. Waste oil should be collected and stored for recycling
or disposal in accordance with the Waste Disposal Ordinance.
·
Instruct untrained personnel to keep at a safe
distance well away from the spillage area.
·
If the spillage /
leakage involve highly toxic, volatile or hazardous waste, initiate
emergency evacuation and call the emergency service.
·
Only trained persons equipped with suitable
protective clothing and equipment should be allowed to enter and clean up the
waste spillage / leakage area.
·
Where the spillage/ leakage is contained in the
enclosed storage area, the waste can be transferred back into suitable
containers by suitable handheld equipment, such as hand operated pumps, scoops
or shovels. If the spillage / leakage quantity is small, it can be
covered and mixed with suitable absorbing materials such as tissue paper, dry
soft sand or vermiculite. The resultant slurry should be treated as
chemical waste and transferred to suitable containers for disposal.
·
For spillage / leakage in other areas, immediate
action is required to contain the spillage / leakage. Suitable
liquid absorbing materials such as tissue paper, dry soft sand or vermiculite
should be used to cover the spill. The resultant slurry should be
treated as chemical waste and transferred to suitable containers for disposal.
·
Areas that have been contaminated by chemical waste
spillage / leakage should be cleaned. While water is a soluble
solvent for aqueous chemical wastes and water soluble organic waste,
kerosene or turpentine should be used for organic chemical wastes that are not
soluble in water. The waste from the cleanup operation
should be treated and disposed of as chemical waste.
·
In incidents where the spillage / leakage may
result in significant contamination of an area or risk of pollution, the EPD
should be informed immediately.
Groundwater
from Contaminated Areas
5.9.4
To avoid the water quality impact due to the
pumping and discharge of potentially contaminated water from contaminated area,
the following mitigation measures should be adopted.
·
Contaminated water should be treated by
wastewater treatment facility (WTF) to an acceptable level as indicated in
TM-DSS before disposal if the deployment of such WTF is
feasible. The need and detail requirement of the WTF cannot be
determined at this stage as the presence and type of contaminated groundwater
will only be made known after future land contamination site investigation
work; and
·
Recharging the contaminated groundwater back to
the aquifer should be sought if treatment of the contaminated groundwater by
WTF is not feasible, subject to the agreement with the EPD.
Effects on
Groundwater Table / Hydrology / Flow Regime
5.9.5
Compared to the whole stormwater catchments, the
overall hydrology regime will not be significantly changed with the
implementation of proper drainage system. Thus, the associated impact to water quality
regime is anticipated to be minimal and no specific mitigation measures are
required.
Sewage
Effluent from Construction Workforce
5.9.6
All discharges during the construction phase of
the Project are required to comply with the Technical Memorandum for Effluents
Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters (TM-DSS) issued
under Section 21 of the WPCO. Domestic
sewage/wastewater generated by workforce on-site should be collected in a
suitable storage facility such as portable chemical toilets. An
adequate number of portable toilets will be provided during the construction
phase. These toilets should be maintained in a state that will not
deter the workers from using them. The collected sewage/wastewater
will be discharged into the foul sewer or transferred to the Government sewage
treatment works by a licensed collector.
5.10
Recommended Mitigation Measures - Operation
Phase
Hydrological
Change and Surface Run-off
5.10.1
Runoff will be controlled by good design
practice and site management means. Runoff will be intercepted by properly
designed and managed silt traps at appropriate spacings so that common roadside
debris, refuse and fallen leaves etc can be captured before allowing the runoff
into drainage system.
5.10.2
The operation parties should manage the
road/open area cleaning prior to the occurrence of a storm. The operator
should undertake the cleaning at an interval of twice a week and the frequency
should be increased to suit actual site conditions. Moreover, it is recommended
each of the cleaning events should not be separated by more than four days and
should be carried out during low traffic flow period, preferably using either
manual methods or mechanical means such as vacuum sweeper/truck equipped
with side broom, which is to sweep road sludge and debris into the suction
nozzle to increase the removal efficiency of pollutants.
5.10.3
With implementation of mitigation measures, the
pollution levels from stormwater would be much reduced. A storm water pollution control plan is presented
in Appendix 5.3.
5.10.4
Given the intermittent nature of non-point
source pollution and adopting flexible management to suit site
conditions, the impact to the receiving water body is insignificant.
5.10.5
Compared to the whole stormwater catchments, the
change of overall hydrology regime will be limited with the implementation of
proper drainage system. Thus, the associated impact to water quality regime is
anticipated to be minimal and no specific mitigation measures are required.
Sewage and Wastewater Effluents from Buildings
5.10.6
The sewage from the Project will be connected to
public sewer. For individual municipal facilities and commercial tenants,
effluent discharge license under the WPCO will be required individually for
wastewater discharge. The discharge standards specified under the
TM-DSS should be observed and no specific mitigation measures are required.
Usage of
Agrochemicals in Sub-Area 2, 3 and 4
5.10.7
A management plan stating the details of
application of agrochemicals including the type, dosage, frequency, application
instructions shall be prepared.
5.10.8
The operator shall consider using organic
fertilizers and biological pesticides. The use and application of fertilizers
and pesticides shall follow normal practices in LCSD’s prevailing code of
practice and the Pesticides Ordinance (Cap. 133). Adverse water quality impact
associated with usage of fertilizers and pesticides is therefore minimized.
5.11
Environmental Monitoring and Audit
5.11.1
The Project is a land-based works. Construction
site runoff would be collected, treated and discharged to specified
location. Regular water quality monitoring should be carried out at
representative water discharge locations under WPCO license requirement. Regular
site audit should be carried out to check the implementation status of the
recommended water quality impact mitigation measures.
5.11.2
As no adverse water quality impact is
anticipated during operation of the Project, environmental monitoring and audit
during operation phase in relation to water quality is not required.
5.12
Evaluation of Residual Impacts
5.12.1
With the full implementation of the recommended
mitigation measures for the construction and operation phases of the Project,
no residual impacts on water quality are anticipated.
5.13
Conclusion
Construction
Phase
5.13.1
Minimization of water quality deterioration
could be achieved through implementing the appropriate mitigation measures.
Regular site inspections should be undertaken routinely to inspect the
construction activities and works areas in order to ensure the recommended
mitigation measures are properly implemented.
Operation
Phase
5.13.2
The key potential source of impact on water
quality during the operation phase of the Project would include the road
run-off, storm run-off from building, sewage and wastewater effluents and usage
of agrochemicals. Mitigation measures with adequate maintenance are
recommended to remove grits and grease from the runoff during operation. All
sewage and wastewater generated from these facilities would be properly
collected and diverted to public sewer. In addition, a management plan stating the details of application of
agrochemicals including the type, dosage, frequency, application instructions
shall be prepared. No adverse operation phase impact
is anticipated.