8.2 Environmental Legislation, Standards and Guidelines
8.4 Water Quality Sensitive Receivers (WSRs)
8.7 Recommended Mitigation Measures
8.8 Environmental Monitoring and Audit
TABLES
Table 8.1 Water
Quality Objectives of Victoria Harbour WCZ
Table 8.2 WSD
Standards at Flushing Water Intakes
Table 8.3 Summary
of Marine Water Quality for Victoria Harbour WCZ in 2018
FIGURES
Figure
8.1 Location
of EPD’s Marine Water Quality Monitoring Stations
Figure
8.2 Location
of Water Sensitive Receivers
Figure
8.3 Schematic
Drawings of Foam System
8.1.1.1
This
section presents the water quality impact assessment for the Project,
identifying the water quality issues, assessing the potential impacts and
recommending mitigation measures where required. According to the EIA Study
Brief No. ESB- 311/2019, a general review of the potential effluent generated
from the Project has been carried out.
8.2.1
Environmental
Impact Assessment Ordinance (Cap. 499)
8.2.1.1
The
construction and operation of the rooftop helipad at New Acute Hospital is a
Designated Project under Item B.2 of Part I of Schedule 2 of the Environmental
Impact Assessment Ordinance (EIAO). The Technical Memorandum on Environmental
Impact Assessment Process (TM-EIAO) which specifies the assessment criteria,
guidelines, etc. for EIA studies has been issued under Section 16 of the EIAO. This study will follow the TM-EIAO to
assess the potential water quality impacts that may arise during the
construction and operational phases of the Project. Annexes 6 and 14 of the
TM-EIAO stipulate the “Criteria for Evaluating Water Pollution” and “Guidelines
for the Assessment of Water Pollution” respectively. In addition, the
requirements as stated in the EIA Study Brief No. ESB-311/2019 shall be
complied with.
8.2.2
Water
Pollution Control Ordinance (Cap. 358)
8.2.2.1
The
Water Pollution Control Ordinance (WPCO) is the principal legislation governing
water quality in Hong Kong. Under the provisions of this Ordinance and its
subsidiary legislation, Hong Kong’s waters have been divided into a series of
10 Water Control Zones (WCZs). In each WCZ, Water Quality Objectives (WQOs)
have been specified to protect the specific beneficial uses and conservation goals.
8.2.2.2
Given
that the Project is located on the rooftop of the New Acute Hospital, land
based activities are expected to be confined to the rooftop area only but with
any runoff passing through the local drainage system which may potentially
discharge to the nearby waters in the Victoria Harbour WCZ. Table 8.1 lists all the WQOs in the
marine environment for this WCZ.
Table 8.1 Water Quality
Objectives of Victoria Harbour WCZ
|
Parameters |
WQOs |
Sub-Zone |
|
Offensive odour, tints |
Not to be present |
Whole zone |
|
Visible foam, oil scum, litter |
Not to be present |
Whole zone |
|
Colour |
Not to exceed 50 Hazen units, due to human activity |
Inland waters |
|
E.
coli |
Not to exceed 1,000 count per 100
mL, calculated as the geometric mean of the most recent 5 consecutive samples
taken at intervals of between 7 and 21 days |
Inland waters |
|
Dissolved oxygen (DO) within 2 m of
the seabed |
Not less than 2.0 mg/L for 90% of
samples |
Marine waters |
|
Depth-averaged DO |
Not less than 4.0 mg/L for 90% of
samples |
Marine waters |
|
Not less than 4.0 mg/L |
Inland waters |
|
|
pH |
To be in the range of 6.5-8.5, change due to waste discharges not to exceed 0.2 |
Marine
waters |
|
To be in the range of 6.0-9.0 |
Inland
waters |
|
|
Salinity |
Change due to waste discharges not
to exceed 10% of ambient |
Whole
zone |
|
Temperature |
Change due to human activity not to
exceed 2°C |
Whole zone |
|
Suspended solids (SS) |
Not to raise the ambient level by
30% caused by waste discharges and shall not affect aquatic communities |
Marine waters |
|
Change due to waste discharges not
to exceed 25 mg/L of annual
median |
Inland waters |
|
|
Unionised ammonia (UIA) |
Annual mean not to exceed 0.021
mg/L as unionised form |
Whole zone |
|
Nutrients |
Shall not cause excessive algal
growth |
Marine waters |
|
Total inorganic nitrogen (TIN) |
Annual mean depth-averaged
inorganic nitrogen not to exceed 0.4 mg/L |
Marine waters |
|
5-day Biochemical Oxygen Demand
(BOD5) |
Change due to waste discharges not
to exceed 5 mg/L |
Inland waters |
|
Chemical Oxygen Demand (COD) |
Change due to waste discharges not
to exceed 30 mg/L |
Inland waters |
|
Toxic substances |
Should not attain such levels as to
produce significant toxic, carcinogenic, mutagenic or teratogenic effects in
humans, fish or any other aquatic organisms |
Whole zone |
|
Waste
discharges should not cause a risk to any beneficial use of the aquatic environment |
Whole zone |
8.2.3
Water
Supplies Department Water Quality Criteria
8.2.3.1
Besides the WQOs specified
under the WPCO, the Water Supplies Department (WSD) has also defined a set of
seawater quality objectives for water quality at their flushing water intakes as
detailed in Table 8.2 below.
Table 8.2 WSD
Standards at Flushing Water Intakes
|
Parameter (mg/L, unless
otherwise stated) |
WSD Target Limit |
|
Colour (Hazen Unit) |
<
20 |
|
Turbidity
(NTU) |
<
10 |
|
Threshold Odour Number
(odour unit) |
<
100 |
|
Ammoniacal Nitrogen |
<
1 |
|
Suspended
Solids |
<
10 |
|
Dissolved
Oxygen |
>
2 |
|
Biochemical Oxygen
Demand |
<
10 |
|
Synthetic Detergents |
<
5 |
|
E.coli (count/ 100 mL) |
<
20,000 |
8.2.4
Technical
Memorandum on Standards for Effluents Discharged into Drainage and Sewerage
Systems, Inland and Coastal Waters
8.2.4.1
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. Any effluent from the Project must
comply with the standards for effluents discharged into the foul sewers,
inshore water or marine waters of the Victoria Harbour WCZ.
8.2.5
Professional
Persons on Environmental Consultative Committee Practice Notes
8.2.5.1
The Professional Persons
Environmental Consultative Committee Practice Notes on Construction Site
Drainage (ProPECC PN 1/94) provides guidelines for the handling and disposal of
construction discharges. This note is applicable to the control of site runoff
and wastewater generated during the construction phase of the Project. The
types of discharges from construction sites outlined in the ProPECC PN 1/94
that could be relevant to this Project would include:
·
Surface run-off; and
·
Wastewater from construction activities and site facilities.
8.2.5.2
The ProPECC PN 5/93 on
Drainage Plans, subject to comments by EPD, provides guidelines and practices
for the 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 project area should follow the relevant guidelines and practices as given
in the ProPECC PN 5/93.
8.2.5.3
The ProPECC notes PN 1/94 and
PN 5/93 shall be followed as far as possible to minimise potential water
quality impacts during both the construction and operational phases.
8.3.1.1
The EPD’s marine water
quality monitoring stations VM1, VM2 in the Victoria Harbour WCZ and monitoring
station VT4 in the typhoon shelter are the closest to the Project Site.
Locations of these monitoring stations are shown in Figure
8.1 and the latest monitoring data at these stations are summarised in Table 8.3 below.
Table 8.3 Summary
of Marine Water Quality for Victoria Harbour WCZ in 2018
|
Parameters |
EPD Monitoring Station |
||
|
Victoria Harbour WCZ |
|||
|
VM1 |
VM2 |
VT4 |
|
|
Temperature (ºC) |
22.8 (16.1
– 26.6) |
23.2 (16.1 – 28.1) |
23.9 (18.0
– 27.5) |
|
Salinity (ppt) |
32.5 (31.2
– 33.5) |
31.9 (28.6 – 33.3) |
29.2 (24.5
– 31.0) |
|
Dissolved Oxygen – Depth average
(mg/L) |
5.9 (4.4
– 7.5) |
5.9 (4.4 – 7.4) |
5.9 (4.4
– 8.2) |
|
Dissolved Oxygen (Bottom) (mg/L) |
6.0 (3.2
-7.8) |
5.8 (3.8 – 7.5) |
5.6 (3.7
– 8.4) |
|
Dissolved Oxygen – Depth average (%
Saturation) |
83 (63
– 96) |
82 (63 – 92) |
82 (66
– 103) |
|
Dissolved Oxygen (Bottom) (%
Saturation) |
82 (47
– 102) |
81 (53 – 98) |
78 (55
– 107) |
|
pH value |
7.9 (7.6
– 8.1) |
7.9 (7.6 – 8.2) |
7.8 (7.5
– 8.2) |
|
Secchi Disc Depth (m) |
2.9 (2.0
– 3.8) |
2.9 (2.0 – 3.4) |
2.4 (1.8
– 3.0) |
|
Turbidity (NTU) |
3.2 (1.3
– 7.9) |
2.9 (1.3 – 7.0) |
1.7
(0.7
– 2.9) |
|
Suspended Solids (mg/L) |
8.0 (2.4
– 17.0) |
7.2 (33 – 12.0) |
7.2 (2.9
– 12.5) |
|
5-day Biochemical Oxygen Demand
(BOD5) (mg/L) |
0.6 (0.3
– 1.1) |
0.6 (0.3
– 1.7) |
0.9
(0.4
– 1.3) |
|
Ammonia Nitrogen (mg/L) |
0.060 (0.036
– 0.085) |
0.081 (0.043
– 0.123) |
0.351 (0.140
– 0.677) |
|
Unionised Ammonia (mg/L) (NH3 - N) |
0.002 (<0.001
– 0.004) |
0.003 (<0.001
– 0.007) |
0.009 (0.003
– 0.012) |
|
Nitrite Nitrogen (mg/L) (NO2-N) |
0.020 (<0.002
– 0.050) |
0.025
(<0.002
– 0.065) |
0.178 (0.048
– 0.447) |
|
Nitrate Nitrogen (mg/L) (NO3-N) |
0.094 (0.016
– 0.200) |
0.122 (0.037
– 0.231) |
0.716 (0.317
– 1.310) |
|
Total Inorganic Nitrogen (mg/L)
(TIN) |
0.17 (0.06
– 0.27) |
0.23 (0.09
– 0.36) |
1.24 (0.51
– 2.22) |
|
Total Kjeldahl Nitrogen (mg/L) |
0.34 (0.58
– 0.68) |
0.37 (0.20
– 0.77) |
0.78 (0.34
– 1.33) |
|
Total Nitrogen (mg/L) |
0.45 (0.20
– 0.87) |
0.52 (0.24
– 0.93) |
1.67 (0.70
– 2.69) |
|
Orthophosphate Phosphorus (mg/L) |
0.017 (0.004
– 0.031) |
0.021 (0.009
– 0.036) |
0.225 (0.066
– 0.460) |
|
Total Phosphorus (mg/L) (TP) |
0.03 (0.02
– 0.04) |
0.03
(0.02
– 0.05) |
0.26 (0.08
– 0.53) |
|
Silica (as SiO2) (mg/L) |
0.69 (0.13
– 1.53) |
0.71 (0.21
– 1.87) |
1.75 (1.13
– 2.87) |
|
Chlorophyll-a (mg/L) |
3.0 (0.3
– 10.8) |
3.9 (0.3
– 22.3) |
5.6 (1.9
– 10.5) |
|
E.
coli (cfu/100mL) |
100 (5
– 350) |
220 (23
– 1300) |
580 (90
– 1200) |
|
Faecal Coliforms (count/100L) |
210
(7
– 740) |
480
(35
– 2800) |
1600 (410 – 3000) |
8.3.1.2
According to the published
Marine Water Quality Report available on the EPD website, the overall WQO
compliance rate of Victoria Harbour WCZ in 2018 has increased to 97% as
compared to the 83% WQO compliance rate in 2017. Compliance rates of Dissolved
Oxygen (DO) and Unionised Ammonia Nitrogen (NH3-N) standard were
100%. The TIN level at VM1 and VM2 complied with the WQO standard.
8.3.1.3
The EPD’s marine water
quality monitoring data collected in the Victoria Harbour WCZ are shown in the
above table. The monitoring data shows that the water quality at the Victoria
Harbour WCZ comply with the DO level and NH3-N WQOs in 2018. The
overall percentage of WQO compliance for the WCZ was 97% in 2018. At the Kwun
Tong Typhoon Shelter monitoring station VT4, the NH3-N concentrations complied
with the WQO and the depth-average DO levels were observed in an improving
trend.
8.4.1.1 The assessment area for the water quality impact assessment is defined
within 300m from the site boundary. As the helipad will be located on the
rooftop of the New Acute Hospital in an urban area with no natural streams,
ecological valuable locations, country parks, beaches or water uses for
agriculture being present, only the Kwun Tong Typhoon Shelter (WSR 1) lies very
close to the assessment area, as shown in Figure
8.2. No wastewater will be
directly discharged or overflow into the Kwun Tong Typhoon Shelter. The other
potential WSR, the Seawater Intake for Kai Tak District Cooling System, is
quite remote from the subject site.
8.5.1.1
The assessment has been based
on the criteria and guidelines for assessing water quality impacts as stated in
Annexes 6 and 14 of the TM-EIAO.
8.5.1.2
A desktop study has been
conducted to identify the potential sources of water quality impacts during the
construction and operational phases. Analysis has then been undertaken to
assess the potential impacts on the identified representative sensitive
receivers from these potential sources of water pollutants and mitigation
measures recommended to minimise any potential impacts as necessary. The aim of
the assessment is to maintain the balance and integrity of the water bodies in
the assessment area as far as possible through prevention and minimisation of
impacts at sources in order to:
·
maintain the natural properties of the water body;
·
control any discharges to within the relevant Water Quality Objectives;
·
maintain the physical environment as far as practicable;
·
protect any aquatic ecology; and
·
protect any beneficial uses.
8.6.1
Construction
Phase
Background
8.6.1.1
Since the helipad will be
constructed on the roof of the Acute Block of the New Acute Hospital (NAH) (Figure 1.1),
only land-based activities would be undertaken during the construction of the
structure of the helipad. The project would not involve any soil excavation nor
marine works. Potential water pollution sources would include surface runoff
and effluent arising from the construction site activities including general
construction works, sewage from the construction workforce, storage of
construction materials and accidental spillage due to the use of the mechanical
plant.
Construction Runoff and Drainage
8.6.1.2
Construction run-off has the
potential to cause water quality impacts in terms of physical, biological and
chemical effects. The physical effects would include potential blockages of
drainage channels and increased suspended solids (SS) levels in the Victoria
Harbour WCZ. Local flooding may also occur in heavy rainfall situations. The
chemical and biological effects caused by construction runoff are highly dependent
upon its SS level and pH value. According to the preferred construction method
(Option C) (Refer to Section 2.5.17), the main structure of the proposed
helipad would be constructed by in-situ aluminium, steel and formworks and will be pre-fabricated off-site and assembled
on-site. The safety walkway and access ramp would be
formed by prefabricated steel members of a suitable size and weight and to be
assembled on site by welding or bolting. Therefore, there will be no concrete batching
on-site or concrete mixing activities. As such, there will be no direct
water quality impacts anticipated.
8.6.1.3
Since the proposed helipad
will be located on the roof deck of the new hospital building, no significant
impact of fugitive emissions from stockpiles or dusty surfaces are expected.
Therefore, erosion of site surfaces and associated wastewater from dust
suppression measures such as water spraying are not expected.
Sewage Effluent
8.6.1.4
Sewage effluent will arise
from the sanitary facilities provided for the on-site construction workforce.
The characteristics of sewage would include high levels of BOD5,
ammonia and E. coli counts. In respect of lavatory facilities for the
workforce, portable chemical toilets would be required if connection to a sewer
is not practicable. With the use of the available existing sewerage system
and/or chemical toilets being managed by a licenced Contractor, adverse water
quality impacts on the WSRs are not anticipated.
Accidental Spillages
8.6.1.5
The use of machinery during
construction may cause leakage of engine oil, lubricants or fuel. When spillage
occurs, the oil and chemicals can run off to the drainage system if not
controlled properly. According to the proposed plant inventory list, only a
small number of machinery will be expected to be placed on the rooftop
including air compressor and hand-held breaker etc.
8.6.1.6
In view of the potentially
small quantities of chemicals or oils involved in the construction works, any
potential leakage can be avoided/ controlled by good site practices, such as
provision of secondary containment during maintenance of the plants and storage
of the oils or chemicals.
8.6.2
Operational
Phase
8.6.2.1
During operational phase, the
helipad is intended to provide services for the emergency helicopter landing.
Such activities are not expected to give rise to any wastewater generation or
discharge. Moreover, fuelling facilities will not be provided on-site. As such,
no potential chemical or oil spillage is expected.
8.6.2.2
During the preparation of the
EIA report, fire fighting system either in the form of water system or foam
system is still under consideration for fire protection purposes at the helipad
for emergency situations and subject to confirmation from relevant parties.
8.6.2.3
In the worst-case scenario
from water quality assessment viewpoint, foam system is selected for assessment
purpose. The foam to be used will likely
consist of 97% water and 3% aqueous film forming foam concentrate (AFFF) and
the foam is biodegradable. The foam spraying system will be located within the
helicopter Touchdown and Lift-off (TLOF) area. A schematic drawing of the drainage
system is presented in Figure
8.3 which shows that under normal operating situations, the rainwater
collected on the rooftop and helipad will be discharged to the storm water
drainage system. A perimeter bund
will be installed to collect contaminated water and direct it to the foul
sewer.
8.6.2.4
According to Fire Services
Department (FSD) requirements, an annual inspection shall be conducted of the
fire service installations of the hospital and carried out by a Registered Fire
Service Installation Contractor (RFSIC). Fire drills will be conducted and the
frequency of these drills will be subject to the hospital’s operational
requirements. It is, also, subject to annual inspection procedures of the RFSIC
whether the foam in the helipad fire-fighting system is discharged or not
during the annual inspection. Hence, if there is fire drill or fire event, the
foam system will be activated and the valve position will be automatically
adjusted to direct the wastewater to the NAH foul water system. In such a fire
drill or fire event, the maximum discharge of this foam system (water and foam)
will only be 25m3, compared to the daily discharge of foul water
from Site A of the NAH of approximately 2000m3, thus, comprising
only around 1% of the total discharge per day. Hence, should such an emergency
or fire drill event occur, the effluent from the foam system will be discharged
to and combined with the daily sewage from the NAH and ultimately flow to the
sewage treatment plant for treatment. In case water is used for the fire
fighting system, water will be drawn from a water tank of the NAH for fire
fighting purposes only. A WPCO
effluent discharge licence for the above discharges to the public foul water
system will be obtained from EPD before commencement of operation, if required.
Therefore, no significant water
quality impacts caused to the environment are expected during the operational
phase.
8.7.1
Construction
Phase
8.7.1.1
In order to address the
potential surface runoff during the construction phase of the Project Site,
appropriate measures will be implemented in accordance with the guidelines as
stipulated in ProPECC PN 1/94 during the construction works to properly control
site runoff and drainage and to minimise potential water quality impacts. Major
relevant measures are highlighted below:
·
All drainage facilities and erosion and sediment control structures
should be regularly inspected and maintained to ensure their proper and
efficient operation at all times particularly following rainstorms.
·
Manholes (including newly constructed ones) should always be adequately
covered and temporarily sealed so as to prevent silt, construction materials or
debris being washed into the drainage system and storm runoff being directed
into foul sewers;
·
Precautions to be taken at any time of the year when rainstorms are
likely, actions to be taken when a rainstorm is imminent or forecasted and
during or after rainstorms, are summarised in Appendix A2 of ProPECC PN 1/94.
Particular attention should be paid to the control of silty surface runoff
during storm events, especially for areas located near steep slopes;
·
Oil interceptors should be provided in the drainage system downstream
of any oil/fuel pollution sources e.g. generators, equipment maintenance area.
Oil interceptors should be emptied and cleaned regularly to prevent the release
of oil and grease into the storm water drainage system after accidental
spillage. A bypass should be provided for oil interceptors to prevent flushing
during heavy rain;
·
The construction solid waste, debris and rubbish on-site should be
collected, handled and disposed of properly to avoid causing any water quality
impacts; and
·
Chemical waste should be handled in accordance with the Code of
Practice on the Packaging, Handling and Storage of Chemical Wastes.
8.7.1.2
By adopting the above mitigation
measures with best management practices it is anticipated that the impacts of
construction site runoff will be reduced to an acceptable level and there will
be no significant water quality impacts anticipated during construction phase.
8.7.2
Operational
Phase
8.7.2.1
If the foam system is used
for fire-fighting purpose, the foam to be used will be biodegradable. The
design of the operational phase mitigation measures should follow the ProPECC
PN 5/93, which provides useful non-statutory guidelines for pollution control
on different types of discharge to minimise water quality impacts from proposed
drainage systems. The design will incorporate the potential wastewater
generated from the foam system and automatically direct to the appropriate sewerage
system.
8.7.2.2
A WPCO effluent discharge
licence for discharging of the daily sewage from the NAH including the foam
water will be obtained from EPD before commencement of operation, if required.
No significant water quality impact is anticipated during operational phase and
hence no mitigation measure is required.
8.8.1.1
As no adverse water quality
impacts are anticipated due to the construction and operation of the proposed
helipad, environmental monitoring and audit in relation to water quality is not
required.
8.9.1.1
With the implementation of
good site practices throughout the construction of the proposed project, no
significant water quality impacts are anticipated and there shall be no adverse
residual impacts.
8.10.1.1
The potential water quality
impacts during the construction and operational phases of the Project have been
evaluated and no adverse impacts are anticipated with the adoption of the
mitigation measures during the construction phase and drainage design in
operational phase detailed in Section 8.7. Hence, water quality
monitoring and audit is not considered necessary during the construction and
operation of the Project.