1.1
This Baseline Water Quality Monitoring Report was
prepared by Cinotech Consultants Ltd. for the Drainage Services Department’s (DSD)
Contract No. DC/2009/10
“HATS 2A –Upgrading works at Stonecutters Island Treatment Works – Main Pumping, Sedimentation Tanks and
Ancillary Facilities”. This report presents the baseline water quality
monitoring works performed for the Project on 22 November 2014, 13 December
2014 and 24 January 2015.
1.2
The
baseline water quality monitoring was conducted at 42 designated
monitoring stations, at
a frequency of one days per month during dry season prior to commencement of the
proposed temporary sewage bypass work under the Contract No. DC/2009/10. The monitoring was conducted for a total
of 3 days at mid-ebb
and mid-flood tides to monitor the parameters including temperature dissolved
oxygen, dissolved oxygen saturation, turbidity, salinity and E.
coli.
1.3
During
the baseline monitoring period, no marine construction works, temporary sewage
bypassing and other observable pollution source were identified in the vicinity
of the monitoring stations. The baseline water quality data established in this
report are considered to be representative of the baseline conditions.
1.4 The baseline data were processed, reviewed and analysed using One Way Analysis of Variance (ANOVA) wherever possible to categorise the sampled data. The Action and Limit Levels for dissolved oxygen, turbidity and E. coli are derived for impact monitoring (Tables I to III).
Table I Action and Limit Levels for Water Quality Monitoring (In-situ Monitoring Parameters)
|
Parameter (unit) |
Monitoring locations |
Water Depth |
Action Level |
Limit Level |
|
DO (mg/L) |
All locations |
Surface and Middle |
6.3 |
6.0 |
|
Bottom |
6.2 |
5.8 |
||
|
Turbidity (NTU) |
B14, B10, B11, B12, B13, B7,
B8, B9 |
Depth average |
7.6 or 120% of upstream control
station’s turbidity at the same tide of the same day |
7.9 or 130% of upstream control
station’s turbidity at the same tide of the same day |
|
WSD5, WSD20, WSD19, WSD18,
WSD6, WSD7 |
10.8 or 120% of upstream control
station’s turbidity at the same tide of the same day |
11.7 or 130% of upstream control
station’s turbidity at the same tide of the same day |
||
|
WSD22, WSD9, WSD17, WSD10,
WSD11, WSD15 |
7.5 or 120% of upstream control station’s turbidity at the same tide of
the same day |
9.4 or 130% of upstream control
station’s turbidity at the same tide of the same day |
||
|
WSD12, WSD13, F1, B24, B25, B26 |
8.0 or 120% of upstream control
station’s turbidity at the same tide of the same day |
8.7 or 130% of upstream control
station’s turbidity at the same tide of the same day |
||
|
F5 |
11.8 or 120% of upstream control
station’s turbidity at the same tide of the same day |
11.8 or 130% of upstream control
station’s turbidity at the same tide of the same day |
Table II Limit Levels for Water Quality Monitoring at WSD Intakes (E. coli)
|
Parameter (unit) |
Water Depth |
Limit Level |
|
E. coli (cfu/100ml) |
Depth average |
20,000 cfu/100ml |
Table III Action
and Limit Levels for Water Quality Monitoring at Monitoring Stations Other than WSD Intakes, Gradient Stations and Control Stations (E.
coli)
|
Parameter (unit) |
Monitoring locations |
Water Depth |
Action Level |
Limit Level |
|
E. coli (cfu/100ml) |
F1 |
Depth average (geometric mean) |
14 cfu/100ml |
16 cfu/100ml |
|
F5 |
44 cfu/100ml |
46 cfu/100ml |
||
|
B7 |
147 cfu/100ml |
173 cfu/100ml |
||
|
B8 |
59 cfu/100ml |
63 cfu/100ml |
||
|
B9 |
20 cfu/100ml |
21 cfu/100ml |
||
|
B10 |
34 cfu/100ml |
39 cfu/100ml |
||
|
B11 |
36 cfu/100ml |
41 cfu/100ml |
||
|
B12 |
42 cfu/100ml |
50 cfu/100ml |
||
|
B13 |
47 cfu/100ml |
50 cfu/100ml |
||
|
B14 |
1 cfu/100ml |
1 cfu/100ml |
||
|
B24 |
2 cfu/100ml |
2 cfu/100ml |
||
|
B25 |
20 cfu/100ml |
24 cfu/100ml |
||
|
B26 |
2 cfu/100ml |
2 cfu/100ml |