6.
WATER QUALITY
6.1 Water Quality Parameters
6.1.1 In
accordance with the recommendations of the EIA, construction phase water
quality EM&A is required.
Measurements of suspended solids (SS), turbidity in Nephelometric
Turbidity Units (NTU), dissolved oxygen (DO) in mg/L and pH shall be undertaken
by the Environmental Specialist (ES) (see Section 1 for a description of the ES
and duties) at strategic locations in the water courses and Tung Chung Bay
which are within the influence of construction works at least three times per
week to ensure that any deteriorating water quality could be readily detected
and timely action be taken to rectify the situation. The first parameter shall be determined in the laboratory with
latter three shall be measured in-situ.
In-situ measurements will also be undertaken at key locations on a daily
basis as requested by WSD in other to ensure protection of the water gathering
grounds.
6.1.2 Baseline
suspended solid measurements shall be used to prepare calibration curves that
convert NTU into approximate suspended solid concentrations. This is to be done
separately for each monitoring station. A statistically significant correlation
(p< 0.05) must be shown between the turbidity and total suspended solid data
before a calibration curve can be used to infer/interpolate suspended solid
concentrations from the NTU readings.
NTU to suspended solid interpolations shall be used on site to provide
an early warning of elevated suspended solid concentrations. The values
calculated shall be later verified by comparison with the water analysis
results obtained from the laboratory.
6.1.3 In
association with the water quality parameter measurements, relevant data shall
also be measured, including the monitoring location/position, time, water
depth, water temperature, salinity, DO saturation, weather conditions, sea
conditions and tidal stage if appropriate, and any special phenomena and work
underway at the construction site. Water
temperature and salinity shall be measured in-situ using direct reading
instrumentation. A sample monitoring
record sheet is shown in Figure 6.1.
6.1.4 Surveys
of the watercourses and Tung Chung Bay shall also be undertaken. The surveys shall include a description of
the stream course/bay, influencing factors, photographs and a map showing areas
of active project construction works and areas of stockpiled materials.
6.2 Monitoring Equipment
6.2.1 Dissolved
oxygen and temperature measuring equipment
6.2.1.1 The dissolved oxygen and temperature
measuring equipment will be as follows:
(a) The
instrument shall be a portable, weatherproof dissolved oxygen measuring
instrument complete with cable and use a DC power source. It shall be capable
of measuring:-
- a
dissolved oxygen level in the range of 0-20 mg/l and 0-200% saturation; and
-
a temperature of 0-45 degree Celsius.
(b) It shall have a membrane electrode with
automatic temperature compensation complete with a cable. Sufficient stocks of spare electrodes and
cables shall be available for replacement where necessary (e.g. YSI model 59
meter, YSI 5739 probe, YSI 5795A submersible stirrer with reel and cable or an
approved similar instrument).
(c) Should
salinity compensation not be integrated in the DO equipment, in-situ salinity
shall be measured to calibrate the DO equipment prior to each DO measurement.
6.2.2 Turbidity
Measurement Instrument
6.2.2.1 The instrument shall be a portable,
weatherproof turbidity-measuring instrument complete with comprehensive
operation manual. The equipment shall use a DC power source. It shall have a
photoelectric sensor capable of measuring turbidity between 0-1000 NTU and be
complete with a cable (e.g. Hach model 2100P or an approved similar
instrument).
6.2.3 Suspended
Solids
6.2.3.1 The equipment for measuring suspended solids
shall be as follows:
(a)
For
marine sampling in Tung Chung Bay, a water sampler comprises a transparent PVC
cylinder, with a capacity of not less than 2 litres and which can be
effectively sealed with latex cups at both ends. The sampler shall have a positive latching system to keep it open
and prevent premature closure until released by a messenger when the sampler is
at the selected water depth (e.g. Kahlsico Water Sampler or an approved similar
instrument).
(b)
For fresh water sampling within the water courses, a 500ml clean
plastic beaker shall be used.
(c) Water
samples for suspended solids measurement of both the marine and freshwater
environment shall be collected in high density polythene bottles, packed in ice
(cooled to 4oC without being frozen) and delivered to the laboratory
as soon as possible after collection.
6.2.4 Water Depth Detector
6.2.4.1 A portable, battery-operated echo sounder shall be used for the determination of water
depth at each designated monitoring station in Tung Chung Bay only. This unit can either be handheld or affixed
to the bottom of the work boat, if the same vessel is to be used throughout the
monitoring programme.
6.2.5 Salinity
6.2.5.1 A portable salinometer capable of measuring
salinity in the range of 0-40 ppt shall be provided for measuring salinity of the water at each monitoring location in
Tung Chung Bay only and setting salinity compensation on the Dissolved Oxygen
Meter.
6.2.6 pH Measuring
Equipment
6.2.6.1 A portable pH meter capable of measuring a
range between 0.0 and 14.0 shall be provided to measure pH under the specified
conditions (eg. Orion Model 250A or an approved similar instrument).
6.2.7 Location of the
Monitoring Sites
6.2.7.1 For the location of the monitoring locations
in the water courses a hand-held dGPS, together with a suitably scaled map
shall be used.
6.2.8 Calibration of
Equipment
6.2.8.1 All in-situ
monitoring instrument shall be checked, calibrated and certified by a
laboratory accredited under HOKLAS or any other international accreditation
scheme before use, and subsequently re-calibrated at 3 monthly intervals
throughout all stages of the water quality monitoring. Responses of sensors and
electrodes shall be checked with certified standard solutions before each use.
Wet bulb calibration for a DO meter shall be carried out before measurement at
each monitoring location.
6.2.8.2 For the on site calibration of field
equipment, the BS 1427:1993, "Guide to Field and on-site test methods for
the analysis of waters" shall be observed.
6.2.9 Back-up
Equipment
6.2.9.1 Sufficient stocks of spare parts shall be
maintained for replacements when necessary.
Back-up monitoring equipment shall also be available so that monitoring
can proceed uninterrupted even when some equipment is under maintenance,
calibration, etc.
6.3 Measurement and Analysis
6.3.1 Analysis of suspended solids shall be
carried out in a HOKLAS or other international accredited laboratory. Water
samples of about 500ml shall be collected at the monitoring stations for
carrying out the laboratory SS determination.
The SS determination work shall start within 24 hours after collection
of the water samples. The SS determination
shall follow TSS-SM25400 or equivalent methods subject to approval of the DEP.
6.3.2 The limits of detection for the in-situ
and laboratory measurements that shall be obtained are shown in Table 6.1.
Table 6.1: Detection Limits and Precision for
Water Quality Determinands
|
Determinand
|
Limit of Detection
|
Precision
|
|
Dissolved
Oxygen
|
0.1 mg/L
|
1%
|
|
Salinity
|
0.01 ppt
|
1%
|
|
Temperature
|
0.1
degree Celsius
|
1%
|
|
pH
|
0.01 units
|
1%
|
|
Turbidity
(NTU)
|
0.1 NTU
|
1%
|
|
Suspended
Solids
|
1 mg/L
|
2%
|
6.3.3 For the testing methods of other
parameters as recommended by the EIA or required by the Environmental
Protection Department (DEP), detailed testing methods, pre-treatment
procedures, instrument use, Quality Assurance / Quality Control (QA/QC) details
(such as blank, spike recovery, number of duplicate samples per batch, etc),
detection limits and accuracy shall be submitted to the DEP for approval prior
to the commencement of monitoring programme. It is recommended that a minimum
of 10% of the samples shall be collected and analysed in duplicate for QA/QC
purposes. The QA/QC shall be in
accordance with the requirement of HOKLAS or international accredited scheme.
The QA/QC results shall be reported.
The DEP may also request the laboratory to carry out analysis of known
standards provided by them for quality assurance. Additional duplicate samples may also be required by the DEP for
inter- laboratory calibration.
Remaining samples after analysis shall be kept by the laboratory for 3
months in case repeat analysis is required.
If in-house or non-standard methods are proposed, detailed of the method
verification may also be required to submit to the DEP. In any circumstance, the sample testing
shall have comprehensive quality assurance and quality control programmes. The laboratory shall be prepared to
demonstrate the programmes to the DEP or his representatives upon request.
6.4 Monitoring Locations
6.4.1 The water quality monitoring locations
are shown in Figure 6.2a-g and detailed in Tables 6.2 below. A schedule for water quality monitoring
shall be prepared by the ES and approved by the ER, the Independent Checker
(Environmental) (IC(E)), the DEP and Water Services Department (WSD) prior to
the commencement of the monitoring.
Table 6.2 Location
of Water Quality Monitoring Stations
|
Monitoring Station (Stream No.)
|
Structure
|
Type
|
Easting
|
Northing
|
|
Tung Chung Stream
|
No direct impacts
|
Reference
|
see Stream 15
|
see Stream 15
|
|
Impact
|
811735
|
813309
|
|
Cheung Sha Stream
|
No direct impacts
|
Reference
|
see Stream 26
|
see Stream 26
|
|
Impact
|
812445
|
811516
|
|
|
|
|
|
|
|
Stream 15
|
Widening existing bridge/culvert
|
Reference
|
811857
|
813287
|
|
Impact
|
811785
|
813296
|
|
Stream 18
|
Widening existing bridge/culvert
|
Reference
|
811893
|
813105
|
|
|
Impact
|
811840
|
813136
|
|
Stream 19
|
Widening existing bridge/culvert
|
Reference
|
811924
|
812925
|
|
|
Impact
|
811862
|
812984
|
|
Stream 21
|
New culvert
|
Reference
|
811998
|
812693
|
|
|
Impact
|
811877
|
812721
|
|
Stream 23
|
Widening existing bridge/culvert
|
Reference
|
811984
|
812586
|
|
|
Impact
|
811963
|
812621
|
|
Stream 25
|
Elevated structure
|
Reference
|
812357
|
812050
|
|
|
Impact
|
812328
|
812015
|
|
Stream 26
|
Elevated structure
|
Reference
|
812529
|
811978
|
|
|
Impact
|
812460
|
811893
|
|
Stream 27
|
Elevated structure
|
Reference
|
812602
|
811768
|
|
|
Impact
|
812608
|
811745
|
|
Stream 32
|
Elevated structure
|
Reference
|
812984
|
811408
|
|
|
Impact
|
812992
|
811325
|
|
Stream 35
|
Elevated structure
|
Reference
|
813235
|
811273
|
|
|
Impact
|
813222
|
811216
|
|
Stream 40
|
Elevated structure
|
Reference
|
813705
|
811245
|
|
|
|
Impact
|
813693
|
811210
|
|
Tung Chung Bay
|
N/A
|
Reference
|
810683
|
816036
|
|
|
Impact
|
810791
|
815734
|
6.4.2 The status and locations of water quality
sensitive receivers and the monitoring sites may change after issuing this
Manual. If such cases exist, the ES
shall propose updated monitoring locations and seek approval from the ER, the
IC(E), the DEP and WSD.
6.4.3 When alternative monitoring locations are
proposed, they shall be chosen based on the following criteria:
(a) at
locations close to and preferably at the boundary of the mixing zone of the
major site activities as indicated in the EIA final report, which are likely to
have water quality impacts;
(b) close
to the sensitive receptors which are directly or likely to be affected;
(c) for
monitoring locations located in the vicinity of the sensitive receptors, care
should be taken to cause minimal disturbance during monitoring; and
(d) reference
stations which are at locations representative of the project site in its
undisturbed condition.
6.4.4 Reference stations are necessary to
compare the water quality from potentially impacted sites with the ambient
water quality. Reference stations shall
be located within the same body of water as the impact monitoring stations but
shall be outside the area of influence of the works and, as far as practicable,
not affected by any other works. The
reference stations for the freshwater sampling are located at least 20m
upstream of the proposed construction area, a distance which is close enough to
represent the local aquatic area which may be affected but far enough not be
been influenced by the works.
6.4.5
The water depth in the streams will not be sufficient to take
samples at different depths and thus only one sample will be taken. However, in all cases duplicate water samples shall be
collected.
6.4.6
In
respect of the marine water quality monitoring in the Tung Chung Bay, all
measurements shall be taken at 3 water depths, namely, 1m below water surface,
mid-depth and 1m above sea bed except where the water depth less than 6m, the
mid-depth station may be omitted.
Should the water depth be less than 3m, only the mid-depth station will
be monitored. The water depth in the
streams will not be sufficient to take samples at different depths and thus
only one sample will be taken.
6.4.7
Replicates (that is, 2 samples) in-situ from each independent sampling event are required for all
parameters to ensure a robust statistically interpretable data set.
6.5 Baseline Monitoring
6.5.1 Baseline conditions for water quality
shall be established and agreed with the IC(E)
and the DEP prior to the commencement of works. The purpose of the
baseline monitoring is to establish ambient conditions prior to the commencement
of the works and to demonstrate the suitability of the proposed impact, control
and reference monitoring stations. The baseline conditions shall normally be
established by measuring the water quality parameters specified above.
6.5.2 The measurements shall be taken at all
designated monitoring stations including control stations, once per day for a
minimum of 4 days per week for 4 weeks prior to the commencement of an
influencing works. Measurements shall
be taken at each station at any time.
The interval between two sets of monitoring shall not be less than 36
hours. For ease of comparison and analysis, all samples should be taken at each
stations at approximately the same time.
6.5.3
Measurements
shall be taken at 3 water depths, namely, 1m below water surface, mid-depth and
1m above sea bed in Tung Chung Bay.
However, if the water depth is less than 6m, the mid-depth station may
be omitted and if the water depth is less than 3m, only the mid-depth station
shall be monitored. For the in-situ
parameters turbidity and DO, measurements shall be made during the descending
and ascending of the sensor. If the
difference between the measured values at any one depth is greater than 25%,
the measurements shall be repeated until an acceptable match is
made. If no match is achieved then the equipment shall be checked for
accurate calibration or malfunction. Only one sample will be
required for the stream monitoring, which shall be taken at mid depth. However,
in all cases duplicate water samples shall be collected.
6.5.4
Water samples for suspended solid analysis shall be collected at
all the designated monitoring stations and calibration curves produced as
described in Section 6.1.
6.5.5 No construction activities shall be
on-going in the vicinity of the stations during the baseline monitoring. The ES
shall be responsible for undertaking the baseline monitoring and submitting the
results within 10 working days from the completion of the baseline monitoring
work.
6.5.6 In exceptional cases when insufficient baseline
monitoring data or questionable results are obtained, the ES shall seek
approval from the IC(E) and the DEP on an appropriate set of data to be used as
baseline reference.
6.5.7 In addition, a baseline walkover survey
shall be conducted prior to the start of the construction works to note and
photograph the conditions of the water bodies.
6.6 Impact Monitoring
6.6.1
In-situ measurements shall be taken at all
designated monitoring stations which are under the influence of the works at
least three times per week during the course of the construction period. Measurements in Tung Chung
Bay shall be taken at 3 water depths, namely, 1m below water surface, mid-depth
and 1m above sea bed. However, if the
water depth is less than 6m, the mid-depth station may be omitted and if the
water depth is less than 3m, only the mid-depth station shall be
monitored. For in-situ parameters
turbidity and DO, measurements shall be made during the descending and
ascending of the sensor. If the
difference between the measured values at any one depth is greater than 25%,
the measurements shall be repeated until an acceptable match is
made. If no match is achieved then the
equipment shall be checked for accurate calibration or malfunction. Only one sample will be required for the streams, which shall be
collected at mid depth.
6.6.2
Replicates (2 samples) in-situ
from each independent sampling event are required for all parameters to ensure
a robust statistically interpretable data set.
In addition, daily monitoring of in-situ parameters at streams 15, 18,
19, 32, 35 and 40 is also recommended in order to provide an early warning
system for impacts that may affect the water gathering grounds.
6.6.2 In addition, water samples for suspended
solid analysis shall be collected at all the above stations and forwarded to
the laboratory for analysis. However, in all cases duplicate water samples shall be
collected. Results
for suspended solids shall be received back from the laboratory within 3 days
of the receipt of the samples.
6.6.3 Surveys of the watercourses shall also be
undertaken at least once every week.
The surveys shall include a description of the stream course/bay,
influencing factors, photographs and a map showing areas of project construction
works. As an integral part of the
surveys, the ES shall assess and report on the effectiveness of the proposed
mitigation measures as part of the construction phase EM&A works and
implement modifications and improvements as required.
6.7 Event and Action Plan
6.7.1 The water quality criteria, namely Action
and Limit levels, are shown in Table 6.3 below. Should the monitoring results of the water quality parameters at
any designated monitoring stations indicate that the water quality criteria are
exceeded, the actions in accordance with the Action Plan in Table 6.4 shall be
carried out.
6.7.2
Any noticeable change to water quality shall be recorded in the
survey reports and shall be investigated and remedial actions shall be
undertaken to reduce impacts. Particular attention shall be paid to the
Contractor’s implementation of the recommended mitigation measures.
Table 6.3 Action
and Limit Levels for Water Quality
|
Parameters
|
Action (mg/L)
|
Limit (mg/L)
|
|
DO in mg/L
(Surface,
Middle & Bottom)
|
Surface and
Middle
5%-ile of
baseline data for surface and middle layer
Bottom
5%-ile of
baseline data for bottom layers
|
Surface and
Middle
4mg/L
or
1%-ile of
baseline for surface and middle layer
Bottom
2mg/L or
1%-ile of
baseline data for bottom layer
|
|
Suspended
Solids
|
95%-ile of
baseline data or 120% of control
station's SS (at the same tide of the same day if appropriate)
|
99%-ile of
baseline or 130% of upstream control station's SS (at the same tide of the
same day, if appropriate)
|
|
Turbidity
(Tby) in NTU
(depth-averaged)
|
95%-ile of
baseline data or 120% of upstream control station's Tby (at the same tide of
the same day, if appropriate)
|
99%-ile of
baseline and 130% of upstream control station's Tby (at the same tide of the
same day, if appropriate)
|
|
pH
|
n/a
|
<6.5 or
>8.5
|
Notes:
- For DO, non-compliance of the water
quality limits occurs when monitoring result is lower than the limits.
- For SS, non-compliance of the water
quality limits occurs when monitoring
result is higher than the limits.
- All the figures given in the table are
used for reference only and the DEP may amend the figures whenever it is
considered necessary.
- ‘Depth Averaged’ is calculated by
taking the arithmetic mean of the in-situ parameters readings at all three
depths. For suspended solids ‘depth
averaged’ is calculated by combining all three samples into one mixed sample
which is analysed to produce a physical arithmetic mean.
6.7.3 The
Independent Checker (Environment) (IC(E)) shall be empowered to audit the
environmental performance of construction, all aspects of the EM&A
programme, validate and confirm the accuracy of monitoring results, monitoring
equipment, monitoring locations and procedures. If any exceedance occur, the IC(E) shall follow the actions
stated in the Event and Action Plan in Table 6.4.
6.8 Water Quality Mitigation Measures
6.8.1
The EIA report has recommended water quality mitigation measures.
The Contractor shall be responsible for implementation of the following
measures. The recommended mitigation measures are summarised in the Water
Quality Environmental Mitigation Implementation Schedule provided in Appendix
A.
¨
discharges to natural water
courses shall only take place when the effluent can be shown to comply with the
standards specified in the Technical Memorandum, Standards for Effluents
Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters.
Discharges in the water gathering grounds should meet Group A standards for
inland waters;
¨
the
drainage system capacity for the construction stage shall be designed for a
1:10 year storm event;
¨
for
the northern section, a drainage system shall be constructed ahead of the main
roadworks such that it may be used to discharge the construction site runoff,
thus avoid discharging construction site runoff into the streams;
¨
a
separate temporary drainage system will be provided for the control of the
construction site runoff in the southern area and shall be in place prior to
the main road works;
¨
the
southern alignment will be divided into small catchments for the provision of
the temporary drainage system in order to enhance the control of runoff;
¨
construction
of the off-line section of the road shall only commence when either the
pipeline trench or carrier pipe has been put in place up to Tai Tung Shan
Reservoir;
¨
during
excavation work for the drainage system itself, each stretch of dug channel
will be concrete lined before the end of each day to minimised run-off. Control
and proper disposal of excavated material in accordance with the Waste Management
Plan shall be undertaken;
¨
run-off
during the excavation of the drainage channel will be minimised by the
provision of a concrete lining to each stretch of dug channel before the end of
each day;
¨
all
temporary drainage channels shall be lined with concrete to prevent erosion;
¨
all
off-line sections of the haul road and associated slopes will be paved within 3
days of the individual sections having been completed;
¨
progress
of the construction phase drainage system shall be made in advance of the off-line
haul road formation;
¨
for
all haulage roads, temporary bridges shall be used to cross all streams with
spans of at least twice the stream width and no contact is to be made with the
stream or its riparian vegetation unless authorised by the Engineer;
¨
a
temporary barrier will be provided on the downhill side of the haul road to
prevent errant vehicles from crashing off the haul road;
¨
the
new bridge piers/abutments will be constructed at least 5m away from the
streams and excavation works for the columns will be protected by the drainage
works;
¨
all
culverts will be constructed separately prior to their connection with the
stream to avoid direct impacts on the streams during this period;
¨
during
bridge extension works, a dam shall be built across the stream, upstream from
the works and a temporary pipeline shall be used to divert the stream water
around the works area into the unaffected downstream area in order to prevent
contamination of the stream flow;
¨
areas
in which works have been completed shall be restored within 3 weeks of the
completion date in accordance with the Landscape Proposal detailed in Appendix
I;
¨
temporary
cut slopes shall be covered with tarpaulin during rainfall when not being
worked to prevent erosion;
¨
major stockpiles shall be sited outside the Country
Park and shall avoid being located near stream courses;
¨
spoil
heaps shall be covered at all times to minimise losses in the wet season and
reduce the dust emissions during the dry season to minimise impacts on air
quality;
¨
stock
piled materials shall be contained in a designated area down gradient from any
stream or up gradient with a suitably constructed barrier to reduce loss of
materials to the stream;
¨
hinterland
drainage shall be collected by the use of perimeter channels and diverted to
the nearest stream course to prevent external run off from crossing the site in
order to prevent it becoming contaminated and to minimise the amount of
polluted runoff to be controlled;
¨
sedimentation
tanks and oil interceptors shall be provided during the construction stage on the southern section
of the road above the catchwater for the treatment of all site runoff prior to
discharge into the streams;
¨
sedimentation
tanks shall be provided during the construction stage on the southern section
of the road below the catchwater for the treatment of all site runoff prior to
discharge into the streams or via the Pui O Wan outfall;
¨
where
settling tanks are close to the catchwater, the discharge from the tanks will
be diverted across the catchwater and discharged into adjacent streams to
reduce the amount of treated discharge flowing into the catchwater;
¨
where
the works area abuts the catchwater, the catchwater will be protected from
debris falling into the catchwater by
temporary decking;
¨
a
sedimentation tank shall be provided during the construction stage for the
treatment of all site runoff from the northern section of the road prior to
discharge into the Wong Lung Hang nullah;
¨
sedimentation
tank, oil interceptors and channels used during the construction phase should
be inspected every day rainfall is recorded and weekly thereafter. The sedimentation tanks and channels should
be cleaned out when the volume of settled sediments amounts to 10% of the total
volume of the tank and the oil interceptors should be cleaned when the volume
of oil amounts to 50% of the total volume of the oil interceptor;
¨
run
off from the roofs of site buildings shall be conveyed in closed drains to the
nearest surface water body to prevent the generation of excessive quantities of
surface water run off carrying suspended solids;
¨
wastewater
from the site offices and toilet facilities, if not connected to a sewerage
system, shall be discharged into an on-site chemical treatment and storage
facility with regular collection of the wastewater carried out by tanker. Where non-flush toilets are provided these
shall be chemical toilets and the holding tanks emptied by a licensed
contractor on a frequent basis;
¨
the
details of the chemical toilets shall be submitted to WSD prior to the
construction commencement;
¨
the wheels of all vehicles leaving and entering
the construction site shall be washed to minimise the carry over of mud onto
public roads and into the water gathering grounds. Wheel wash water shall be recycled and only
discharged following removal of silt by sand/silt removal traps;
¨
all
plant shall be in proper working order and maintained such that there is no
leakage of fuel or oil. Any waste oils
shall be collected in designated tanks prior to disposal off site;
¨
oils
and fuels shall be stored within lined and bunded containment areas which shall
have a capacity not less than 110% of the largest tank capacity and shall be
regularly drained of rain water;
¨
no
oil or fuel shall be stored within the Country Park or the water gathering
grounds;
¨
no
chemical wastes shall be stored in the water gathering grounds;
¨
The
Contractor will be required to prepare a response plan to the satisfaction of
FSD, HyD, Police, TD and WSD to define procedures for the control, containment
and clean-up of any spillage that could occur on the construction site;
¨
no
canteen facilities shall be located within the water gathering grounds;
¨
the
Contractor shall comply with WSD’s General Conditions for Working within Water
Gathering Grounds;
¨
no
maintenance activities which may generate chemical wastes shall be undertaken
in the water gathering grounds. Vehicle maintenance shall be confined to
designated paved areas only and any spillages shall be cleared up immediately
using absorbents and waste oils shall be collected in designated tanks prior to
disposal off site. All storm water
run-off from these areas shall be discharged via oil/petrol separators and
sand/silt removal traps.
¨
an
operational drainage system shall be provided for the northern which transfers
all road run off for discharge into the Wong Lung Hang nullah in Tung Chung;
¨
for
the southern section of the road, a carrier pipe will be designed to convey all
the road runoff south of the crest to the sea, avoiding discharge into the
streams crossed by the alignment. The
outfall shall be located on the foreshore of Pui O Wan and shall be over 1.0 km
away from the gazette boundary of Cheung Sha Beach to the west and over 1.2 km
away from the gazette boundary of Pui O Beach to the east;
¨
all
new bridges shall be provided with a special utilities trough to accommodate
the carrier pipe for operational road runoff; and
¨
an
oil interceptor shall be provided for the treatment of all road runoff from the
northern section of the road prior to discharge into the Wong Lung Hang
nullah. The largest standard Highways
Department oil interceptor should be used.
Recorded By :
Checked By :