Introduction
1.
This Baseline Environmental
Monitoring and Audit (EM&A) Report is prepared by Cinotech Consultants
Limited (ET-Cinotech) for the post-trenching works for the project “Lamma
Project Station Extension – Supply and Installation of Submarine Gas Pipeline”
(the Project). This report presents the
baseline environmental monitoring works performed at the sensitive receivers
including Ping
Chau, southern Po Toi and Lamma
between 31st May and 2nd
June 2005.
Water Quality
2.
The baseline water quality monitoring was conducted at fourteen
designated monitoring stations at the three sensitive zones which are
identified in the EIA Report, including Ping Chau, southern Po Toi and Lamma three days per week for a period of one week between 31st May and 2nd
June 2005. Salinity, dissolved oxygen
(DO), turbidity and suspended solids (SS) were
monitored in accordance with the Work Procedure.
3.
Data collected was reviewed and analyzed. Details of the
methodology, locations and results are presented in the report. The monitoring results show that the water quality
in the concerned water body is good. No major pollution sources were identified during the
baseline monitoring. However, the
baseline water quality data may not be representative to present the ambient
conditions due to the small sample size (only three days of water samples) and limitation in tidal range selection (tidal range
less than 0.5 m on one of the sampling events).
4.
As a result, the EPD long-term monitoring
data were used to establish the Action
and Limit Levels (Table I) for the relevant parameters during impact monitoring
throughout post-trenching period.
Table
I Action and Limit Levels for
Water Quality
|
Parameter (unit)
|
Water Depth
|
Action Level
|
Limit Level
|
|
Lamma Island – L-I1 and L-I2
|
|
|
|
|
DO
(mg/L)
|
Surface
and Middle
|
4.7
|
4
|
|
Bottom
|
4.1
|
2
|
|
Turbidity
(NTU)
|
Depth
average
|
17.2
|
18.4
|
|
SS
(mg/L)
|
Depth
average
|
10.2
|
10.7
|
|
|
|
|
|
|
Po Toi – PT-I1, PT-I2 and PT-I3
|
|
|
|
|
DO
(mg/L)
|
Surface
and Middle
|
5.0
|
5
|
|
Bottom
|
3.3
|
2
|
|
Turbidity
(NTU)
|
Depth
average
|
14.0
|
21.9
|
|
SS
(mg/L)
|
Depth
average
|
6.7
|
7.2
|
|
Ping Chau – PC-I1,
PC-I2 and PC-I3
|
|
|
|
|
DO
(mg/L)
|
Surface
and Middle
|
4.8
|
4
|
|
Bottom
|
2.9
|
2
|
|
Turbidity
(NTU)
|
Depth
average
|
11.2
|
13.0
|
|
SS
(mg/L)
|
Depth
average
|
5.7
|
7.6
|
Notes:
-
For DO, non-compliance of the water quality limits
occurs when monitoring result is lower than the limits.
-
For turbidity and SS, non-compliance of water quality
limits occurs when monitoring result is higher than the limits.
1.1
Hong Kong Electric
Holdings Ltd. (HEC) intends to develop a 1,800 MW power station in Hong Kong
Special Administrative Region (HKSAR) to meet the forecast increase in
electricity demand to cope with the social and economical growth of the HKSAR.
The proposed power station will be located at reclaimed land in the south of
the existing Lamma Power Station at the western edge of Lamma
Island, termed Lamma Power Station
Extension.
1.2
The proposed Power
Station will use natural gas as fuel to generate electricity. The natural gas
will be supplied from Guandong Liquefied Natural Gas (GD LNG) Terminal located
at Cheng Tou Jiao of Shenzen PRC via a 20 inches diameter gas submarine
pipeline.
1.3
HEC awarded Saipem Asia
Sdn. Bhd. (hereafter called “the Contractor) for the design, engineering,
supply of materials, fabrication, testing at works, delivery to site, complete
erection including pre-trenching, pipe laying, rock dumping, testing and
pre-commissioning at site, preservation during the Defects Liability Period of
Submarine Gas Pipeline under to Project titled “Lamma Power Station Extension –
Supply and Installation of Submarine Gas Pipeline” (hereinafter called “the
Project”). Cinotech Consultants Limited was subsequently commissioned by the
Contractor as the Environmental Team (ET-Cinotech) to provide environmental
consultancy services and to undertake the Environmental Monitoring and Audit
(EM&A) works for the Project.
1.4
The Project works
include Pre-Trenching works, Pipe-Lay installation, Post-Lay Trenching
(Jetting) and Rock Dumping works related to the installation of 92 km of 20
inches diameter Submarine Gas Pipeline between Guandong Liquefied Natural Gas
Terminal (GD LNG) and the receiving point at Gas Receiving Station (GRS) at
South-West of Lamma Extension on Lamma Island of Hong Kong – SAR. An
Environmental Permit (EP) has been issued for the Lamma Power Station Extension
project. Variations to the EP
requirements have been proposed recently for the Project works and the VEP no.
EP-071/2000/C was issued on 18th
May 2005.
1.5
In accordance with the
requirements of the EM&A Manual, water quality monitoring should be carried
out for the jetting operations for
the first two weeks of the construction programme. Further monitoring after the
initial two weeks should be carried out if unacceptable impacts are
revealed. In addition, monitoring
should be carried out at Ping Chau, southern Po Toi and southern Lamma when
jetting operation is conducted in the vicinity of these ecological sensitive
areas identified in the EIA report. The original water quality monitoring
programme stipulated in the EM&A Manual has been reviewed and updated to
cater for the proposed variations of the EP requirements. The updates include a 3-day intensive water
quality programme, which supersedes the original two-week programme. Baseline and impact monitoring will also be undertaken at the said
three sensitive zones defined in the EIA report.
1.6
A Work Procedure
outlining the monitoring and audit programme to be undertaken for the post-trenching
works was submitted. The baseline water quality monitoring was
conducted at the three sensitive zones prior to the commencement of the
post-trenching works.
1.7
The purpose of this Baseline Environmental Monitoring Report is to set
out baseline levels for the water quality at the sensitive receivers in
accordance with the Work Procedure.
These baseline levels will be used as the basis for the impact
monitoring during the post-trenching stage of the Project. This report presents the monitoring
locations, equipment, period, methodology, results and observations for the water
quality measurements during the baseline period.
1.8
Different parties with
different levels of involvement in the project organization include:
· Project Proponent –Hong Kong Electric Holdings Ltd.
(HEC)
· Contractor – Saipem Asia Sdn. Bhd.
· Environmental Team (ET-Cinotech) – Cinotech
Consultants Limited
1.9
The responsibilities of
respective parties are detailed in Section 3 of the EM&A Requirements
Review (Review) and the project organization chart is presented in Figure 3.1
of the Review. The key contacts of the ET- Cinotech are shown in Table 1.1.
Table 1.1 Key Project Contacts
|
Party
|
Name
|
Role
|
Phone No.
|
Fax No.
|
|
ET-Cinotech
|
Dr. Priscilla Choy
|
Project Manager
|
2151 2089
|
3107 1388
|
|
Ms. Winniss Kong
|
Coordinator
|
2151 2068
|
3107 1388
|
|
Mr. Henry Leung
|
Monitoring Team Leader
|
2151 2087
|
3107 1388
|
2.1
Baseline conditions for water quality should
be established 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 and control monitoring stations. The
baseline conditions should be established by measuring all the water quality
parameters for salinity, dissolved oxygen (DO), turbidity and suspended
solids (SS) in accordance with the work procedure.
2.2
The following water quality parameters were included in the monitoring
programme.
Table 2.1 Water Quality
Monitoring Parameters
|
Phase
|
Water
Quality Parameters
|
|
Construction
|
· Salinity (ppt)
· Turbidity (NTU)
· Dissolved oxygen (DO) (mg/L and % of saturation)
· Suspended solids (SS) (mg/L)
|
2.3
The water samplers used for water quality monitoring were Kahlsico
Water-Bottle Model 135DW150. The
samplers with associated equipment complied with the specifications stipulated
in the work procedure.
2.4
Table 2.2 summarizes the equipment used in the water quality monitoring
program. All the monitoring equipment
complied with the specifications stipulated in the work procedure. Copies of the calibration certificates of
are attached in Appendix A.
Table 2.2 Water Quality Monitoring Equipment
|
Equipment
|
Model and Make
|
Qty.
|
|
Water Sampler
|
Kahlsico Water-Bottle Model 135DW 150
|
2
|
|
Multi-parameter Water Quality System
|
YSI 6820
|
2
|
2.5
A total of fourteen water quality monitoring locations were
selected. Table 2.3 describes the
locations of these monitoring stations. The locations of the control and impact monitoring
stations are shown in Figures 2.1 and
2.2.
Table 2.3 Locations of Water Quality Monitoring Stations
|
ID
|
Location / Corresponding Sensitive Zone
|
Type of Monitoring Station
|
Co-ordinates
|
|
|
|
|
L-C1
|
Lamma Island
|
Control Station
|
|
|
|
L-C2
|
Control Station
|
|
|
|
L-I1
|
Impact Station
|
|
|
|
L-I2
|
Impact Station
|
|
|
|
PT-C1
|
Po Toi
|
Control Station
|
|
|
|
PT-C2
|
Control Station
|
|
|
|
PT-I1
|
Impact Station
|
|
|
|
PT-I2
|
Impact Station
|
|
|
|
PT-I3
|
Impact Station
|
|
|
|
PC-C1
|
Ping Chau
|
Control Station
|
|
|
|
PC-C2
|
Control Station
|
|
|
|
PC-I1
|
Impact Station
|
|
|
|
PC-I2
|
Impact Station
|
|
|
|
PC-I3
|
Impact Station
|
|
|
2.6
Table 2.4 summarizes the monitoring period and frequencies of water
quality monitoring.
Table 2.4 Frequency and Parameters of Water Quality Monitoring
|
Station
|
Parameters
|
Frequency
|
No. of depth
|
|
L-C1, L-C2, L-I1, L-I2,
PT-C1, PT-C2, PT-I1, PT-I2, PT-I3, PC-C1, PC-C2, PC-I1, PC-I2, PC-I3
|
SS, turbidity, DO and
in-situ parameters*
|
3 times a week for a
period of one week in both mid-ebb and mid-flood tides
|
3 (1m below water
surface, mid-depth and 1m above channel bed.)
|
Notes:
* In-situ parameters
included temperature, salinity and DO saturation.
Instrumentation
2.7
A multi-parameter meter (Model YSI 6820 CE-C-M-Y) was used to measure
DO, turbidity, salinity, and temperature.
Digital
Global Positioning Systems (DGPS) were used to ensure that the correction
locations were arrived prior to measurement and sample collection.
Operating/Analytical
Procedures
2.8
At each measurement, two consecutive measurements of in-situ parameters
were taken. The probes were retrieved out
of the water after the first measurement and then re-deployed for the second
measurement. Where the difference in
the value between the first and second readings of each set was more than 25%
of the value of the first reading, the reading was discarded and further
readings were taken.
2.9
For SS measurement, grab samples were collected. Water samples of about 1,000 ml were
collected and stored in polyethylene bottles.
The sample bottles were packed into an ice-box and delivered to a HOKLAS
Laboratory, WELLAB Ltd., for the analysis within 24 hours.
Maintenance
and Calibration
2.10 Before each round of
monitoring, a zero check in distilled water was performed with the turbidity
probe of YSI 6820. The probe was kept
in wet condition and then calibrated with a solution of known NTU.
2.11 Verifications of the DGPS were carried out at a
known fixed reference point (survey nail obtained from the Survey and Mapping
office of Lands Department). The
position was monitored over a period of 5 minutes. Deviations of smaller than +/- 5 metres were demonstrated
and recorded.
2.12 QA/QC procedures for the suspended solids analyzed in
the HOKLAS-accredited laboratory, Wellab Limited are attached in Appendix C.
Results and Details on Influencing Factors
2.13 Baseline water quality monitoring was conducted
between 31st May 2005
and 2nd June 2005 in both mid-ebb and
mid-flood tides. The monitoring results and the graphical
presentation are shown in Appendix B.
Note that in Appendix B, the “sea condition” is given as indicative
information and does not necessarily adhere to any standard sea state
descriptions. In general, “calm” means
small or no waves were observed; “rough” includes white-capped sea or rougher;
and “moderate” means all conditions in between “calm” and “rough”.
2.14 The results are summarized in Tables 2.5 and 2.6,
which show the averages and the ranges of readings recorded during mid-ebb and
mid flood tides.
Table 2.5 Water Quality
Baseline Monitoring Results during Mid-Ebb
|
Sensitive Zones
|
Stations
|
Average DO at S&M*,
mg/L
(Range)
|
Average DO at Bottom,
mg/L
(Range)
|
Average Turbidity, NTU
(Range)
|
Average SS, mg/L
(Range)
|
|
Lamma Island
|
L-C1
|
7.5
(6.3 – 9.3)
|
5.6
(5.0 – 6.1)
|
3.8
(3.5 – 4.2)
|
4.7
(2.8 – 5.9)
|
|
L-C2
|
7.1
(6.7 – 7.9)
|
6.1
(6.0 – 6.1)
|
3.6
(2.0 – 5.1)
|
3.4
(2.2 – 4.1)
|
|
L-I1
|
7.5
(6.4 – 9.4)
|
5.7
(5.7 – 5.8)
|
4.1
(3.1 – 5.0)
|
5.0
(2.5 – 7.1)
|
|
L-I2
|
7.1
(6.6 – 8.1)
|
5.8
(5.6 – 6.0)
|
4.4
(3.6 – 5.3)
|
3.9
(2.3 – 4.8)
|
|
Po Toi
|
PT-C1
|
6.8
(6.5 – 7.2)
|
6.6
(5.5 – 7.3)
|
1.9
(1.2 – 2.4)
|
2.9
(2.5 – 3.6)
|
|
PT-C2
|
6.7
(6.1 – 7.2)
|
5.9
(5.1 – 7.0)
|
1.4
(1.1 – 1.6)
|
2.8
(2.1 – 4.2)
|
|
PT-I1
|
7.2
(7.1 – 7.2)
|
6.4
(5.1 – 7.0)
|
2.5
(1.3 – 3.7)
|
4.1
(3.5 – 4.5)
|
|
PT-I2
|
6.7
(6.4 – 7.1)
|
5.9
(4.7 – 7.1)
|
2.5
(1.3 – 4.5)
|
2.6
(1.2 – 3.4)
|
|
PT-I3
|
6.7
(6.4 – 7.1)
|
6.4
(6.1 – 7.1)
|
2.1
(1.8 – 2.6)
|
3.2
(2.7 – 4.0)
|
|
Ping Chau
|
PC-C1
|
7.1
(6.6 – 7.9)
|
6.2
(6.1 – 6.4)
|
2.9
(1.8 – 4.6)
|
3.2
(2.0 – 4.5)
|
|
PC-C2
|
7.0
(6.8 – 7.3)
|
6.3
(6.0 – 6.5)
|
1.5
(1.2 – 1.7)
|
2.9
(1.9 – 3.6)
|
|
PC-I1
|
7.6
(6.8 – 9.2)
|
7.2
(6.6 – 8.3)
|
1.7
(1.2 – 2.1)
|
3.0
(2.2 – 4.3)
|
|
PC-I2
|
7.1
(6.7 – 7.8)
|
6.2
(5.8 – 6.4)
|
3.9
(2.6 – 5.4)
|
4.0
(2.0 – 6.3)
|
|
PC-I3
|
6.9
(6.6 – 7.6)
|
6.0
(5.4 – 6.4)
|
3.1
(2.4 – 4.0)
|
4.3
(2.7 – 7.2)
|
* Surface and middle depths
Table 2.6 Water Quality
Baseline Monitoring Results during Mid-Flood
|
Sensitive Zones
|
Stations
|
Average DO at S&M*,
mg/L
(Range)
|
Average DO at Bottom, mg/L
(Range)
|
Average Turbidity, NTU
(Range)
|
Average SS, mg/L
(Range)
|
|
Lamma Island
|
L-C1
|
7.0
(6.1 – 7.8)
|
5.4
(4.7 – 5.8)
|
5.1
(4.6 – 6.0)
|
6.7
(5.5 – 7.7)
|
|
L-C2
|
7.4
(6.6 – 8.0)
|
5.8
(5.2 – 6.1)
|
3.3
(2.4 – 4.3)
|
3.2
(3.0 – 3.5)
|
|
L-I1
|
7.3
(6.5 – 8.2)
|
5.6
(5.2 – 5.9)
|
4.5
(3.4 –5.4)
|
6.0
(4.8 – 7.4)
|
|
L-I2
|
6.8
(6.1 – 7.3)
|
5.4
(4.5 – 6.0)
|
4.8
(4.3 – 5.1)
|
4.9
(3.3 – 6.6)
|
|
Po Toi
|
PT-C1
|
6.5
(6.2 – 7.2)
|
6.0
(5.1 – 7.2)
|
2.7
(1.2 – 5.0)
|
2.5
(1.9 – 2.9)
|
|
PT-C2
|
6.7
(6.2 – 7.1)
|
6.2
(4.9 – 6.9)
|
2.0
(1.3 –3.2)
|
2.5
(1.7 – 3.0)
|
|
PT-I1
|
6.8
(6.4 – 7.1)
|
5.8
(4.7 – 7.1)
|
2.5
(1.6 – 3.1)
|
2.9
(2.3 – 3.8)
|
|
PT-I2
|
6.5
(6.2 – 6.8)
|
5.7
(4.9 – 6.5)
|
2.0
(1.4 – 2.9)
|
2.4
(1.5 – 3.0)
|
|
PT-I3
|
6.5
(5.7 – 7.2)
|
6.0
(5.2 – 6.6)
|
2.4
(1.7 – 2.8)
|
2.6
(1.4 – 3.6)
|
|
Ping Chau
|
PC-C1
|
6.9
(6.8 – 6.9)
|
6.2
(6.0 – 6.4)
|
2.8
(2.3 – 3.6)
|
3.7
(2.9 – 4.1)
|
|
PC-C2
|
6.3
(5.8 – 6.8)
|
5.7
(4.5 – 6.6)
|
1.3
(1.2 – 1.5)
|
2.8
(1.7 – 3.4)
|
|
PC-I1
|
7.5
(6.5 – 9.3)
|
7.0
(6.5 – 7.8)
|
1.2
(0.7 – 1.8)
|
3.2
(2.0 – 5.1)
|
|
PC-I2
|
7.1
(6.7 – 7.8)
|
6.2
(6.0 – 6.5)
|
3.3
(2.0 – 4.0)
|
4.4
(2.3 – 7.0)
|
|
PC-I3
|
7.2
(6.7 – 7.9)
|
6.1
(5.5 – 6.5)
|
2.4
(2.0 – 3.2)
|
3.6
(2.7 – 5.0)
|
* Surface and
middle depths
2.15
No major pollution
source and influencing factor was observed during the baseline monitoring
period. However, the baseline water
quality data may not be representative to present the ambient conditions due to
the small sample size (only three days of water samples) and limitation in tidal range selection (tidal range
less than 0.5 m on one of the sampling events).
2.16
Guidelines for
establishment of the Action and Limit levels for the impact monitoring during
the post-trenching works of the Project were provided in the work procedure, as
presented in Table 2.7.
Table 2.7 Guidelines for
Establishment of Action and Limit Levels proposed in the Work Procedure
|
Parameter (unit)
|
Action
|
Limit
|
|
Dissolved Oxygen (mg/L)
(surface, middle, bottom)
|
Surface and middle
80% of upstream control station at the same tide of the
same day
Bottom
80% of upstream control station at the same tide of the
same day
|
Surface and middle
4 mg/L except 5mg/L for FCZ
Bottom
2 mg/L
|
|
SS (mg/L)
(depth average)
|
120% of upstream control station’s SS at the same tide of
the same day
|
130% of SS readings at the upstream control station at the
same tide of same day and specific sensitive receiver water quality
requirements
|
|
Turbidity (NTU)
(depth average)
|
120 % of upstream control station’s turbidity at the same
tide of the same day
|
130% of turbidity at the upstream control station at the
same tide of same day
|
Notes:
1.
“Depth-average” is calculated by
taking the arithmetic means of reading of all three depths.
2.
For DO, non-compliance of the water
quality limit occurs when monitoring result is lower than the limit.
3.
For SS and turbidity, non-compliance
of the water quality limits occur when monitoring result is higher than the
limits.
2.17
For determination of
Action / Limit Levels of DO, turbidity and SS, the control station approach was
proposed in the work procedure.
However, based on the baseline water quality monitoring results, the
water quality of the control stations, especially that at the Po Toi (PT-C1 and
PT-C1) and Ping Chau (PC-C1 and PC-C2) were considered good (with low turbidity
and SS levels). In order to avoid false
alarm of the impact of the post-trenching works, it is proposed to adopt the
percentile approach of baseline water quality data at the three sensitive
receivers including Ping Chau, southern Po Toi and southern Lamma for
establishment of Action / Limit Levels.
The proposed Action / Limit Levels for water quality are provided in
Table 2.8.
2.18
Given the limitation of
the baseline monitoring data as identified in Section 2.15, the EPD long-term
monitoring results (DO, turbidity and SS) collected in the years from 1998 to
2003 at Stations SM5, SM19 and MM5 were adopted for the establishment of Action
/ Limit Levels for the stations at Lamma, Po Toi and Ping Chau
respectively.
2.19
Also, the Action /
Limit Levels were computed based on two categories, dry season and wet season. Since the pipeline jetting works would be
carried out in the wet season only, only the Action / Limit Levels for wet
season are derived. The EPD long-term
monitoring results collected from May to October in the years of 1998 to 2003
are adopted for the computation for wet season.
Table 2.8 Proposed Action and
Limit Levels for Water Quality
|
Parameter (unit)
|
Action
|
Limit
|
|
Dissolved Oxygen (mg/L)
(surface, middle, bottom)
|
Surface and middle
5%-ile of baseline data
Bottom
5%-ile of baseline data
|
Surface and middle
4 mg/L except 5mg/L for
FCZ
Bottom
2 mg/L
|
|
SS (mg/L)
(depth average)
|
95%-ile
of baseline data
|
99%-ile
of baseline data
|
|
Turbidity (NTU)
(depth average)
|
95%-ile
of baseline data
|
99%-ile
of baseline data
|
Notes:
1. “Depth-average”
is calculated by taking the arithmetic means of reading of all three depths.
2.
For DO, non-compliance of the water
quality limit occurs when monitoring result is lower than the limit.
3.
For SS and turbidity, non-compliance
of the water quality limits occur when monitoring result is higher than the
limits.
2.20
A summary of the past
data of 1998-2003 at station SM5, SM19 and MM5 is provided in Table 2.9.
Given that major marine works (including the HEC Navigation Channel Improvement
and Lamma Power Station Extension Reclamation) were carried out in the vicinity
of SM5 since April 2001 until end of 2004, the wet season data at station SM5
between 1998 and 2000 is presented for better illustration of the natural
ambient levels.
Table 2.9 Past Wet Season Data at EPD’s Monitoring Stations
SM5, SM19 and MM5
|
Year
|
1998-2000
|
1998-2003
|
|
Stations
|
SM5 (Lamma)
|
SM5 (Lamma)
|
SM19
(Po Toi)
|
MM5
(Ping Chau)
|
|
DO at S&M*, mg/L
|
Average
|
6.8
|
7.0
|
6.2
|
6.1
|
|
Maximum
|
10.6
|
11.9
|
8.0
|
8.0
|
|
Minimum
|
4.5
|
4.2
|
4.6
|
4.0
|
|
5%-ile
|
4.7
|
4.7
|
5.0
|
4.8
|
|
1%-ile
|
4.5
|
4.3
|
4.7
|
4.2
|
|
DO at Bottom, mg/L
|
Average
|
5.8
|
5.9
|
4.9
|
5.0
|
|
Maximum
|
7.0
|
9.1
|
7.4
|
7.9
|
|
Minimum
|
3.5
|
3.5
|
2.8
|
1.6
|
|
5%-ile
|
4.1
|
4.2
|
3.3
|
2.9
|
|
1%-ile
|
3.6
|
3.7
|
2.8
|
2.0
|
|
Turbidity, NTU
|
Average
|
7.8
|
8.3
|
8.4
|
6.3
|
|
Maximum
|
18.7
|
18.7
|
23.6
|
13.2
|
|
Minimum
|
1.2
|
1.2
|
1.1
|
2.6
|
|
95%-ile
|
17.2
|
15.1
|
14.0
|
11.2
|
|
99%-ile
|
18.4
|
18.0
|
21.9
|
13.0
|
|
SS, mg/L
|
Average
|
4.9
|
5.8
|
4.1
|
2.3
|
|
Maximum
|
10.9
|
20.7
|
7.3
|
7.9
|
|
Minimum
|
0.8
|
0.8
|
1.1
|
0.5
|
|
95%-ile
|
10.2
|
12.2
|
6.7
|
5.7
|
|
99%-ile
|
10.7
|
18.6
|
7.2
|
7.6
|
* Surface
and middle depths
2.21
Following the criteria
set out in Table 2.8, the Action and Limit Levels for water quality impact
monitoring have been established as Table 2.10. In addition, based on the data summarized in Table 2.9, elevated
SS levels at SM5 are observed between 2001 and 2003. The elevated SS levels may be related to the said marine
projects. As a result, the data at SM5
between 1998 and 2000 is adopted for deriving Action and Limit Levels at
sensitive receivers at Lamma. For the
sensitive receivers at Po Toi and Ping Chau, the data between 1998 and 2003 are
adopted.
Table 2.10 Calculated Action
and Limit Levels for Water Quality (Wet Season)
|
Parameter (unit)
|
Water Depth
|
Action Level
|
Limit Level
|
|
Lamma Island – L-I1 and L-I2
|
|
|
|
|
DO
(mg/L)
|
Surface
and Middle
|
4.7
|
4
|
|
Bottom
|
4.1
|
2
|
|
Turbidity
(NTU)
|
Depth
average
|
17.2
|
18.4
|
|
SS
(mg/L)
|
Depth
average
|
10.2
|
10.7
|
|
|
|
|
|
|
Po Toi – PT-I1, PT-I2 and PT-I3
|
|
|
|
|
DO
(mg/L)
|
Surface
and Middle
|
5.0
|
5
|
|
Bottom
|
3.3
|
2
|
|
Turbidity
(NTU)
|
Depth
average
|
14.0
|
21.9
|
|
SS
(mg/L)
|
Depth
average
|
6.7
|
7.2
|
|
Ping Chau – PC-I1, PC-I2 and PC-I3
|
|
|
|
|
DO
(mg/L)
|
Surface
and Middle
|
4.8
|
4
|
|
Bottom
|
2.9
|
2
|
|
Turbidity
(NTU)
|
Depth
average
|
11.2
|
13.0
|
|
SS
(mg/L)
|
Depth
average
|
5.7
|
7.6
|
Notes:
-
For DO, non-compliance of the water quality limits occurs
when monitoring result is lower than the limits.
-
For turbidity and SS, non-compliance of water
quality limits occurs when monitoring result is higher than the limits.
3.1
Environmental monitoring works were performed on 31st May, 1st
and 2nd June 2005
in accordance with the work procedure.
3.2
During the baseline water quality monitoring period, no observable
pollution source was identified in the vicinity of the monitoring stations. However, the baseline water quality data may not be representative to
present the ambient conditions due to the small sample size (only three days of
water samples) and
limitation in tidal range selection (tidal range less than 0.5 m on one of the sampling
events).
3.3
The EPD long-term monitoring
data were used
to establish the Action and Limit Levels for the relevant parameters during
impact monitoring at sensitive receivers throughout post-trenching period.
