Table 3.2d Action and Limit Levels for Water Quality

Parameter (unit)	Water Depth	Action Level	Limit Level
Dissolved Oxygen (mg/L) (surface, middle, bottom)	Surface and Middle	*5.0*	*4.2* except 5 for FCZ
Dissolved Oxygen (mg/L) (surface, middle, bottom)	Bottom	*4.7*	*3.6*
Turbidity (NTU)	Depth average	Before 25 Mar 13: *27.5* or 120% of upstream control station’s turbidity at the same tide of the same day On or After 25 March 13: *27.5* and 120% of upstream control station’s turbidity at the same tide of the same day	Before 25 Mar 13: *47.0* or 130% of turbidity at the upstream control station at the same tide of same day On or After 25 March 13: *47.0* and 130% of turbidity at the upstream control station at the same tide of same day
Suspended Solids (mg/L)	Depth average	Before 25 Mar 13: *23.5* or 120% of upstream control station’s SS at the same tide of the same day On or After 25 March 13: *23.5* and 120% of upstream control station’s SS at the same tide of the same day	Before 25 Mar 13: *34.4* or 130% of SS at the upstream control station at the same tide of same day and 10mg/L for WSD Seawater Intakes On or After 25 March 13: *34.4* and 130% of SS at the upstream control station at the same tide of same day and 10mg/L for WSD Seawater Intakes

Note:

(1) Depth-averaged 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 that the limit.

(3) For SS & turbidity non-compliance of the water quality limits occur when monitoring result is higher than the limits.

(4) All the figures given in the table are used for reference only and the EPD may amend the figures whenever it is considered as necessary.

(5) The 1%-ile of baseline data for dissolved oxygen (surface and middle) and dissolved oxygen (bottom) are 4.2mg/L and 3.6mg/L respectively.

(6) The proposal for changing Action and Limit Levels for water quality monitoring was submitted to EPD on 15 March 2013. No objection was received from EPD according to the letter (ref. (10) in Ax(3) to EP2/G/A/129pt.4) dated 25 March 2013. Therefore, the updated Action and Limit Levels for water quality monitoring was used for comparison starting from 25 March 2013.