4       Results and Observations

 

Monitoring Results

4.1         Baseline water quality monitoring was conducted on 22 November 2014, 13 December 2014 and 24 January 2015.  The monitoring schedule is provided in Appendix A. The monitoring results and the graphical presentation are provided in Appendices C and D.

4.2         The results of DO, turbidity levels and E. coli for all monitoring stations at the mid-ebb and mid-flood tides are summarized in Tables A and B, which show the averages and ranges of the readings recorded.

Table A          Baseline Water Quality Monitoring Results during Mid-Ebb Tide

Station

DO, surface & middle level (mg/L)

DO, bottom level (mg/L)

Turbidity, depth average (NTU)

E coli, depth average (cfu/100ml)

Average

Range

Average

Range

Average

Range

Geometric Mean

Range

B10

8.0

6.8-9.4

7.9

7-9.2

5.0

4.2-5.9

30

11-233

B11

7.9

6.6-9.7

-

0-0

4.3

3.5-5.3

5

1-16

B12

8.3

6.9-9.5

-

0-0

4.3

3-5.9

5

1-52

B13

7.8

6.7-9

7.6

6.5-9.1

5.7

2.4-7.8

8

3-40

B14

8.5

7.8-9.9

-

0-0

3.8

2.3-4.7

1

1-1

B24

7.4

6.2-8.1

7.3

6.3-8

3.4

1.1-5.7

1

1-2

B25

7.4

6.1-8.1

7.3

6.1-7.9

4.3

1-6.2

2

1-7

B26

7.5

6-8.2

7.7

6.7-8.2

5.2

0.8-8.8

1

1-2

B7

7.8

7.2-8.8

7.7

7-8.7

5.4

3.8-7

73

44-180

B8

7.9

7.2-9

7.9

7-9.1

5.9

4.1-7.1

76

8-865

B9

7.8

6.8-8.8

7.8

6.7-8.9

5.6

4.2-7

49

6-938

EM1

6.6

5.9-8

6.8

5.9-8.1

2.3

1-4.2

11

2-37

EM2

7.1

5.9-8.3

7.5

5.9-8.5

2.4

0.8-4.9

3

1-10

EM3

7.8

7-8.3

7.4

6.1-8.1

6.2

3.2-8.7

1

1-1

F1

7.3

6-8.1

7.2

5.8-8.2

3.3

1.3-5

1

1-2

F5

7.9

7.2-9.3

7.6

6.8-8.8

9.4

7.9-11.8

31

17-47

JM3

6.6

5.9-8

6.8

5.6-8.1

1.8

0.7-2.8

8

2-71

MM13

7.8

6.9-8.3

7.6

6.5-8.3

3.4

1-5.4

1

1-3

SM17

8.1

7.5-8.5

7.9

7.5-8.2

8.5

6.6-11.8

1

1-1

VM1

6.7

5.7-7.6

6.6

5.6-7.7

3.4

2.2-4.5

63

38-141

VM12

7.3

6.7-8.2

7.2

6.6-8.2

14.4

11.4-18.4

296

136-974

VM14

6.9

6.2-7.3

6.6

6.1-7.1

9.9

7.8-11.5

83

38-135

VM15

7.6

7.2-8.2

7.3

7-7.9

7.2

5.3-10

173

16-702

VM2

7.7

7.3-8.4

7.7

7.3-8.2

3.6

2.9-4.6

1425

544-4575

VM4

7.9

7.9-7.9

7.7

7.6-7.8

5.7

4.2-6.8

573

118-2240

VM5

7.3

6.9-7.6

7.1

6.7-7.4

6.1

3.5-8.7

559

185-1537

VM7

7.5

7-8

7.0

6.3-7.8

8.5

7.4-10.2

585

123-2109

VM8

7.8

7.1-8.3

7.8

7.4-8.1

6.5

6.5-6.6

254

130-478

WSD10

7.8

7.3-8.3

7.6

7.2-8

3.8

3-4.7

47

16-121

WSD11

6.8

6.3-7.3

6.7

6.2-7.4

3.6

2.6-4.5

54

10-163

WSD12

6.6

5.8-7.9

6.6

5.6-8.1

1.7

0.9-2.2

4

1-25

WSD13

7.2

6.1-7.9

7.3

5.9-8

3.0

0.8-5.4

81

37-156

WSD15

7.5

6.6-8.4

7.4

6.4-8.2

3.5

3.2-4.1

50

5-455

WSD17

7.2

6.7-7.9

7.4

7.2-7.8

4.6

4.2-4.9

305

114-891

WSD18

7.1

6.9-7.2

6.8

6.5-7

8.1

7-9.6

5178

3183-9117

WSD19

7.3

6.8-7.8

7.2

6.5-7.7

7.8

6.3-9.9

2134

1290-3905

WSD20

8.2

7.7-8.5

8.0

7.5-8.4

9.0

7.5-11.9

245

133-573

WSD22

6.9

6.7-7.2

6.8

6.5-7.3

7.2

3.7-10.4

608

141-1322

WSD5

7.3

6.2-8.3

7.1

6.1-8.1

10.5

9.7-11.3

34

4-124

WSD6

7.6

7-8.2

7.4

6.9-8.2

7.4

4.9-9.9

28

3-154

WSD7

7.4

7-8

7.2

6.8-7.9

6.4

6-7.3

121

81-206

WSD9

7.8

7.6-8

7.6

7.5-7.9

5.8

3.6-7.3

174

55-1087

 

Table B          Baseline Water Quality Monitoring Results during Mid-Flood Tide

Station

DO, surface & middle level (mg/L)

DO, bottom level (mg/L)

Turbidity, depth average (NTU)

E coli, depth average (cfu/100ml)

Average

Range

Average

Range

Average

Range

Geometric Mean

Range

B10

7.6

7.5-7.8

7.6

7.4-7.8

5.3

3.2-7.4

3

1-40

B11

7.4

7.1-7.5

-

0-0

5.2

4.1-7.2

3

1-42

B12

7.3

7-7.5

-

0-0

5.2

4.2-7

55

1-82000

B13

7.4

6.8-7.8

7.2

6.6-7.8

6.8

5.8-7.9

5

1-50

B14

7.9

7.5-8.2

-

0-0

6.1

5.5-7.2

1

1-1

B24

7.8

7.1-8.3

7.7

7-8.2

2.8

1.5-3.8

2

1-2

B25

7.6

6.7-8.3

7.5

6.7-8.2

5.2

2-7.8

4

1-24

B26

7.8

6.8-8.4

7.6

6.7-8.2

5.2

1.3-8.5

1

1-1

B7

7.3

7.2-7.4

7.3

7.1-7.4

6.1

5.4-6.9

2

1-15

B8

7.4

7.2-7.6

7.3

7.1-7.5

5.7

4.5-7.3

3

1-38

B9

7.4

7.4-7.5

7.3

7.2-7.4

5.4

3.9-7.7

3

1-19

EM1

7.7

6.9-8.6

7.7

6.8-8.5

3.3

1.7-5.5

14

4-91

EM2

6.8

5.3-8.2

6.7

5.2-8.2

3.5

1.6-6.1

3

1-6

EM3

7.8

6.9-8.2

7.8

7-8.2

5.9

1.9-9.2

1

1-1

F1

7.5

6.7-8.3

7.4

6.5-8.9

4.2

1.7-6.2

4

1-17

F5

7.5

7.2-7.8

7.5

7.2-8

9.3

7.4-11.7

5

1-24

JM3

7.1

7.1-7.2

7.2

7-7.4

2.9

2.2-3.3

17

2-255

MM13

7.7

6.8-8.3

7.6

6.7-8.1

5.1

1.7-7.9

1

1-1

SM17

8.1

7.9-8.3

7.8

7.6-8.2

7.2

3.6-12.1

1

1-2

VM1

7.8

7.2-8.2

7.7

7.3-8.1

3.5

2.5-4.6

129

102-197

VM12

7.7

7-8.6

7.7

6.9-8.5

9.9

8.7-11.4

23

5-86

VM14

7.7

7.2-8.4

7.5

7-8.3

10.8

8.8-12

4

1-24

VM15

7.9

7.3-8.5

7.6

7.1-7.9

6.3

5.3-7.7

134

60-281

VM2

7.5

7.1-8

7.2

6.6-7.7

4.3

2.8-5.9

260

100-816

VM4

7.4

6.8-8.2

7.2

6.7-7.8

5.2

3.7-6.7

1282

828-1629

VM5

7.4

6.8-8.2

7.3

6.7-7.9

5.3

3.6-6.4

4581

3022-6364

VM7

7.6

7-8.3

7.5

6.9-8.1

7.1

5.2-8.3

154

56-358

VM8

8.4

8-8.7

8.2

7.8-8.6

8.0

6.9-9.1

39

10-225

WSD10

7.6

6.9-8.5

7.6

7.1-8.4

4.4

3.5-5.9

180

93-275

WSD11

7.6

6.8-8.5

7.5

6.7-8.3

4.5

4-5.3

177

137-220

WSD12

7.0

6.9-7.1

7.3

7.2-7.3

3.7

2.6-5.3

16

1-561

WSD13

7.1

6.9-7.6

7.4

7-7.6

3.8

2.1-6.2

10

1-65

WSD15

7.4

6.9-8.3

7.3

6.7-8.1

4.0

3.3-5.4

275

70-612

WSD17

7.2

6.4-7.9

7.2

6.3-7.8

4.6

3.6-6.1

405

183-1086

WSD18

7.6

6.7-8.5

7.3

6.5-8

6.7

4.7-7.7

130

69-330

WSD19

7.7

7-8.4

7.5

6.8-8.3

6.6

5.2-7.8

304

163-624

WSD20

8.3

7.6-8.8

8.2

7.4-8.7

6.4

3.8-7.7

129

38-361

WSD22

7.2

6.7-7.4

7.0

6.4-7.3

5.2

3.3-7.6

296

110-1317

WSD5

7.6

6.9-8.5

7.4

6.8-8.2

8.8

7.7-10.6

12

4-36

WSD6

7.2

6.4-8.4

6.9

6.1-8.1

7.7

6.7-8.8

11

1-69

WSD7

7.5

7-8.3

7.2

6.8-8

7.8

6.4-10.5

33

17-71

WSD9

7.6

7.3-7.8

7.4

7.2-7.7

5.1

3.1-7.5

164

67-514

Observations

4.3         During the baseline water quality monitoring period, no observable pollution source was identified at all the designated monitoring stations during the baseline monitoring period.

4.4         Measurements and water sampling were conducted at various water depths at all Stations according to Table 3.4. Some of the water sample were taken near the proposed sampling locations due to inaccessibility of the area within shark net (B7, B9, B10, B11, B14 and B26), blockage of the ferry routes (WSD 19). While some of the proposed monitoring stations were marked on the shore (B11, B25, WSD7 and B24), in which reliable water samples could not be obtained. Note that these circumstances could not be accurately determined before the commencement of the baseline monitoring. Therefore, the monitoring teams on sampling boat had taken the water samples as close to the exact locations as possible to ensure the measured data would not deviated considerably from the proposed sampling point without compromising their own safety on the vehicles. As these adjusted locations are still within about 200m of the proposed stations, they are still considered to be representative to the original monitoring locations’ water samples.

4.5         Since no observable pollution activity was observed for all stations during sampling, the baseline monitoring results are considered to be representative of the ambient water quality levels.

Statistical Analysis

4.6         Normal Distribution (95% confidence interval) analysis was conducted to identify the outliers from the monitoring results. All identified outliers will be removed before the calculation of the Action and Limit Levels for Marine Water Quality.

4.7         One way Analysis of Variance (ANOVA) was applied to test the differences of the baseline monitoring data between the 27 water quality monitoring locations (the monitoring stations other than gradient stations and control stations). The purpose of the analysis was to test the following hypothesis:

H0: The data of the 27 monitoring stations would have no significant difference.

H1: The data of the 27 monitoring stations would have significant difference.

4.8         The analysis results are presented in Table 4.1 which show that there are no significant difference amongst the data of Dissolved Oxygen (for Surface/Middle and Bottom Depth).

Table 4.1          Summary of the Results of ANOVA (Dissolved Oxygen)

Monitoring locations

No. of Stations involved

Sample Size

Degree of Freedom

P-value

F-value

B10, B11, B12, B13, B14 B24, B25, B26, B7, B8, B9, F1, F5, WSD10, WSD11, WSD12, WSD13, WSD15, WSD17, WSD18, WSD19, WSD20, WSD22, WSD5, WSD6, WSD7, WSD9 (Surface & Middle depth)

27

159

26

0.5676

0.9294

B10, B13, B24, B25, B26, B7, B8, B9, F1, F5, WSD10, WSD11, WSD12, WSD13, WSD15, WSD17, WSD18, WSD19, WSD20, WSD22, WSD5, WSD6, WSD7, WSD9 (Bottom depth)

24

143

23

0.6808

0.8359

 

4.9         For the parameters of Turbidity, since the data of the 27 monitoring stations (the monitoring stations other than gradient stations and control stations) were found to have significant differences, a second hypothesis is proposed for the two parameters as follow:

H0: The data of the 27 monitoring stations would have no significant difference if they are divided into groups (Shown in Table 4.2).

H2: The data of the 27 monitoring stations would still have significant difference if they are divided into groups (Shown in Table 4.2).

4.10     The second ANOVA results shown that there are no significant differences among the data of the grouped monitoring stations. The analysis will be adopted to set the Action and Limit levels for E. coli (Non-WSD Intake’s locations), DO and Turbidity. The analysis results for Turbidity are shown in Table 4.2.  

Table 4.2          Summary of the Results of ANOVA (Turbidity)

The groups of Monitoring locations

No. of Stations involved

Sample Size

Degree of Freedom

P-value

F-value

B14, B10, B11, B12, B13, B7, B8, B9

8

48

7

0.6036

0.7852

WSD5, WSD20, WSD19, WSD18, WSD6, WSD7

6

35

5

0.0708

2.2997

WSD22, WSD9, WSD17, WSD10, WSD11, WSD15

6

36

5

0.0840

2.1702

WSD12, WSD13, F1, B24, B25, B26

6

36

5

0.4054

1.0532

Notes:

-  Based on the result of ANOVA, since the data of F5 is significantly different from its neighbouring monitoring locations, it was not included in any monitoring groups.  

 

4.11     For the E.coli parameter, the Action and Limit level will be established based on the result of the individual monitoring stations. The guideline for establishment of the E.coli’s Action/Limit level is shown in Table 4.4 and 4.5.

Action and Limit Levels

4.12     Formulated on the basis of the ANOVA results, the monitoring locations with no significant difference between their sampled parameters will be grouped together for the evaluation of the Action and Limit Levels. All outliers were removed before the calculation of the Action and Limit Levels for Marine Water Quality. An exceedance will be considered to be valid when either the monitoring results exceed the established Action/Limit levels which are derived from the baseline data, or exceed 20% (Action level) or 30% (Limit level) of the monitoring results from the control stations.

 

4.13     The Action and Limit levels guideline are established and shown in Tables 4.3 to 4.5. For reference, the Water Quality Objectives established for various Water Control Zones in the EIA study (CE 43/2005, Section 6.20) indicated that the target limit for E. coli, calculated as the geometric mean of all samples collected in one calendar year, was 610 cfu/100ml for Fish Culture Subzones and Secondary Contact Recreation Subzones. The level of 610 cfu/100ml is also the criteria value in which the gazetted beaches would be closed for poor water quality if exceeded. The Dissolved Oxygen levels were set at 4 mg/l for averaged depth and 2 mg/l for bottom depth. Also noted that the gradient station are used to assist in the identification of the source of potential impact at the sensitive receiver (e.g. beach locations) and was therefore excluded from the Action/Limit level Guidelines, along with the control stations.

 

Table 4.3        Guidelines for Establishment of Action and Limit Levels for In-situ Monitoring Parameters

Parameter (unit)

Water Depth

Action Level

Limit Level

DO

(mg/L)

Surface and Middle

5%-ile of baseline data

4 mg/L or 1%-ile of baseline data

Bottom

5%-ile of baseline data

2 mg/L or 1%-ile of baseline data

Turbidity (NTU)

Depth average

95%-ile of baseline data or 120% of upstream control station’s turbidity at the same tide of the same day

99%-ile of baseline data or 130% of turbidity at the upstream control station at the same tide of the same day

 

 

Table 4.4        Guidelines for Establishment of Limit Levels for E. coli for WSD Intakes

Parameter (unit)

Water Depth

Limit Level

E. coli

(cfu/100ml)

Depth average

20,000 cfu/100ml

Remark:

-       The limit level is based on Water Supplies Department’s criteria regarding the target limit of the flushing water.

 

 

Table 4.5        Guidelines for Establishment of Action and Limit Levels for Laboratory Testing Parameter for Monitoring Stations Other than WSD Intakes, Gradient Stations and Control Stations

Parameter (unit)

Water Depth

Action Level

Limit Level

E. coli

(cfu/100ml)

Depth average

E. coli of 95%-ile of baseline data

E. coli of 99%-ile of baseline data or

610 cfu/100ml

 

4.14     Following the criteria as shown in Table 4.3 to Table 4.5, the Action and Limit Levels for water quality impact monitoring have been established and shown in Tables 4.6 to 4.8.

 

Table 4.6        Calculated Action and Limit Levels for 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(1)

Bottom

6.2

5.8(1)

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(2) or 120% of upstream control station’s turbidity at the same tide of the same day

11.8(2) or 130% of upstream control station’s turbidity at the same tide of the same day

Notes:

1)   The 1 percentile of the DO baseline data for all water depths were selected as the limit levels, since the two quantities were much higher than the recommended limit level of 4 mg/L and 2 mg/L.

2)   The displayed quantities are rounded up from 11.775 and 11.795 respectively.

-       For DO, non-compliance of the water quality limits occurs when monitoring result is lower than the limit levels.

-       For turbidity, non-compliance of water quality limits occurs when monitoring result is higher than the limit levels.

 

Table 4.7        Limit Levels for E. coli for WSD Flushing Water Intakes

Parameter (unit)

Water Depth

Limit Level

E. coli

(cfu/100ml)

Depth average

20,000 cfu/100ml

Notes:

-       The limit level is based on the Water Supplies Department’s Criteria regarding the target limit of the flushing water.

-       For E. coli, non-compliance of water quality limits occurs when monitoring result is higher than the limit levels.

 

 

Table 4.8           Action and Limit Levels for E. coli at Monitoring Stations other than WSD Flushing Water Intakes, Gradient Stations and Control Stations

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

Notes:

-       For E. coli, non-compliance of water quality limits occurs when monitoring result is higher than the limit levels.

-       The Action and Limit Level were set as 95%-tile and 99%-tile of the baseline data if they were lower than the criteria value of 610cfu/100ml.

 

Action Plan

4.15     Actions prior to and during the Temporary Sewage Bypass will be carried out in accordance with the Action Plan as shown in Appendix F.