4.0 Marine Water Quality Monitoring

4.1 Monitoring Locations

The EIA conducted for the Project has identified a number of monitoring locations that may portentially be affected by construction and operational activities as summarized in Table 4.1 and shown in Figure TS 2031.

Table 4.1 Summary of Monitoring Locations

Station	Easting	Northing
M1	806244	827080
M2	806329	826408
M3	806235	826089
C1	806116	827618
C2	806034	825308

Control station C1 should be the upstream control station for all monitoring stations during mid-ebb and Control Station C2 should be the upstream control station for all monitoring stations during mid-flood.

4.2 Monitoring Parameters

Monitoring parameters for marine water quality monitoring have been set out in the Project are summarized as follow:

Table 4.2 Marine water quality monitoring parameters

Parameter	Duration	No. of Locations	Depth
Dissolved Oxygen, DO (mg/L)	2 tides/day, 3 days/week	5	3
Turbidity (NTU)
Suspended Solids (mg/L)

4.3 Environmental Quality Performance Limits

The marine water quality criteria, namely Action and Limit (A/L) levels, determined according to the baseline study carried out by ET are presented in the table below.

Table 4.3 Water Quality Action and Limit Levels

Parameter	Action Level	Limit Level
Dissolved Oxygen (DO), mg/L	Surface & Middle 4 mg/L Bottom 2.86 mg/L	Surface & Middle 4 mg/L Bottom 2 mg/L
Suspended Solids (SS), mg/L (Depth-averaged)	44 mg/L or 120% of the upstream control station’s SS at the same tide on the same day	49 mg/L or 130% of the upstream control station’s SS at the same tide on the same day
Turbidity, NTU (Depth-averaged)	37.4 NTU or 120% of the upstream control station’s turbidity at the same tide on the same day	46.2 NTU or 130% of the upstream control station’s turbidity at the same tide on the same day

4.4 Event-Action Plans

Event-Action Plans are presented in Appendix E.

4.5 Monitoring Results: Non-compliance against Action/Limit Levels

The results of DO, turbidity and SS are interpreted and present in terms of tidal depth average. The summary of marine water quality exceedances over the course of the Project is shown in Table 4.4.

Table 4.4 Summary of Marine Water Quality Exceedances over the course of the Project

Station	Exceedance Level	DO		Turbidity		SS
		Flood	Ebb	Flood	Ebb	Flood	Ebb
C1	Action	0	0	0	0	0	0
	Limit	0	0	1	0	1	0
M1	Action	0	0	0	1	0	0
	Limit	0	0	1	0	1	0
M2	Action	0	0	0	1	0	0
	Limit	0	0	1	0	1	0
M3	Action	0	0	0	0	0	0
	Limit	0	0	1	0	1	0
C2	Action	1	0	0	0	0	0
	Limit	0	0	1	0	1	0
Total	Action	1	0	0	2	0	0
	Limit	0	0	5	0	5	0

According to the summary of marine water monitoring results, thirteen exceedances of DO, Turbidity and SS were recorded during the Project.

4.6 Graphical Plots and Statistical Analysis of the trends of monitored parameters during the Project

The Graphical Plots shown in Appendix B represent the trends in DO (Surface & Middle and Bottom), Turbidity and SS during the course of the Project including the baseline monitoring and post-project monitoring.

According the graphical plots of the monitored parameters, it is found that a few exceedances of surface-middle DO, Turbidity and SS were recorded during the reporting period but they are not work-related. Since the trends of graphics of monitored parameters at baseline monitoring, impact monitoring and post-project monitoring are almost the same, this indicates that no adverse environmental impact was introduce to the surrounding environment from the construction works.

4.7 Explanation of Exceedances

Monitoring Date	Tide	Exceedance parameters	Locations	Explanation	Implementation of Event and Action Plan
13/06/03	Mid-ebb	Turbidity	M2	After ET’s investigation, it was found that no construction works were carried out. No visible foam, oil, grease, litter or other objectionable matter were observed near the construction site. Therefore, it has proved that the exceedance was not related to the construction work.	After discussing with the RE, the IE and the Contractor, it was concluded that no further mitigation measures should be taken since the exceedance was not works-related.
20/06/03	Mid-flood	Dissolved Oxygen	C2	After the ET’s investigation and discussion between the IE and ET, C2 was up-stream control station during mid-flood and the exceedance of dissolved oxygen (Surface and Middle) was not due to the construction works.	After discussing with the RE, the IE and the Contractor, it was concluded that no further mitigation measures should be taken since the exceedance was not works-related.
27/06/03	Mid-flood	Turbidity and Suspended Solids	C1, M1, M2, M3 and C2	After ET’s investigation, it was found that no construction works were carried out. No visible foam, oil, grease, litter or other objectionable matter were observed near the construction site. During the monitoring, ET found that the wave was so strong that settled solids were stirred up from the seabed to the water column. Therefore, the exceedance was not work-related.	After discussing with the RE, the IE and the Contractor, it was concluded that no further mitigation measures should be taken since the exceedance was not works-related.
03/11/03	Mid-Ebb	Turbidity	M1	During the marine water quality monitoring at 03/11/2003, ET found that the major construction works was demolishing existing pier. No visible foam, oil, grease, litter or other objectionable matter were observed near the monitoring stations. Comparing the monitoring results of the same tide, the turbidity at M1 was lower than 120% of upstream control station C1. Besides, the Turbidity result at monitoring station M2 which is closer to the existing pier was found lower than monitoring station M1 and within the Action and Limit Level, indicating that the water quality impact due the construction works was not significant and did not cause adversely effect on water quality near the site. Therefore, the exceedance was not work-related.	After discussing with the IEC and the Contractor, it was concluded that no further mitigation measures should be taken since the exceedance was not works-related.