Table 5.8 Summary of Investigation on Water Quality Monitoring Exceedance Records in the Reporting Month

Date	Monitoring Stations	Parameters	Investigation Summary
2, 4 and 11 June 2021	SYR-IS1	DO	The exceedances are considered not due to the Contract due to the following reasons: 1) No pollution discharge from construction activity was observed; 2) DO value at control station were measured lower than the water quality criteria at SYR-IS1 (4 June 2021); 3) Water temperature recorded were relatively higher that that during baseline monitoring and led to low oxygen solubility in water.
4, 7 and 9 June 2021	SYR-IS1	Arsenic	No pollution discharge from construction activity was observed. The exceedances are considered due to the external factors rather than the contract works and non-project related.
4, 7 and 11 June 2021	NTR-IS1	DO	The exceedances are considered not due to the Contract due to the following reasons: 1) No pollution discharge from construction activity was observed; 2) DO value at control station were measured lower than the water quality criteria at NTR-IS1 (4 and 11 June 2021); 3) Water temperature recorded were relatively higher that that during baseline monitoring and led to low oxygen solubility in water.
9 June 2021	NTR-IS1	Turbidity and SS	An influx of muddy water from a tributary (out of Project boundary) to Ma Wat River and then to River Indus was observed which affect the water quality of River Indus during the monitoring day. No pollution discharge from construction activity under the Project was observed. Rainfall was recorded before monitoring which led to increased surface runoff and hence adverse water quality. The exceedances are considered due to the external factors rather than the contract works and non-project related.
2 and 7 June 2021	SHST-IS2	DO, turbidity and SS	No pollution discharge from construction activity was observed. Rainfall was recorded before monitoring which led to increased surface runoff and erosion from natural habitat along the Siu Hang San Tsuen Stream, and also may cause the dispersion of riverbed sediment to the monitoring station. (2 June 2021). DO value at control station were measured lower than the water quality criteria at SHST-IS2. The exceeded results were similar or within the ranges of baseline monitoring results. Water temperature recorded were relatively higher that that during baseline monitoring and led to low oxygen solubility in water. The exceedances are considered due to the external factors rather than the contract works and non-project related.
4, 9 and 11 June 2021	SHST-IS2	DO, turbidity and SS	Increased surface runoff from rainfall recorded before and during the water quality monitoring may lead to erosion from natural habitat along the stream, and also may cause the dispersion of riverbed sediment to the monitoring station. During monitoring, muddy surface runoff was observed between gaps of water barrier (under Contract No. ND/2019/04) near Station SHST-IS2 which was considered as a source of water pollution. In addition, DO value at control station were measured lower than the water quality criteria at SHST-IS2. Water temperature recorded were relatively higher that that during baseline monitoring and led to low oxygen solubility in water. Remedial works were observed in progress to clear the sediment trapped by desilting materials, provide concreting for exposed site area near Siu Hang San Tsuen Stream and provide surface channels for diverting storm water to wastewater treatment facilities. The following recommendations on remedial measures were given as below and shall be maintained to avoid further exceedances: 1) To regularly clear the slurry and sediment trapped by desilting materials; 2) To identify and minimise any source of surface runoff within site area near Siu Hang San Tsuen Stream; 3) To provide spare pumps for emergency use to pump muddy surface runoff to wastewater treatment facilities after rainstorm; 4) To minimise area of exposed soil surface by covering with impervious materials or clear loosen soil materials to reduce formation of muddy surface runoff; 5) To frequently check and ensure desilting materials for protection of Siu Hang San Tsuen Stream are intact and in good condition; 6) To provide channels, earth bunds or sand bag barriers to direct any muddy water to silt removal facilities and away from Siu Hang San Tsuen Stream; 7) Regular supervision and close monitoring on sediment control measures should be conducted by designated foreman to ensure normal operation; and 8) Proposal for mitigation measures on sediment control and contingency plan under Contract No. ND/2019/04 should be submitted to avoid further exceedances. The effectiveness of the remedial measures implemented should be closely reviewed The effectiveness of remedial measures implemented by the Contractor would be continuously checked and reviewed during water quality monitoring and weekly site inspection.
2, 4, 7, 9 and 11 June 2021	MWR-IS3	DO, Turbidity and SS	Influx of muddy water from a tributary (out of Project boundary) to Ma Wat River and then to the monitoring stations was observed which affect the water quality of Ma Wat River during the monitoring days. No pollution discharge from construction activity under the Project was observed. DO value at control station were measured lower than the water quality criteria at MWR-IS3 (2, 4, 9 and 11 June 2021). Water temperature recorded were relatively higher that that during baseline monitoring and led to low oxygen solubility in water. The exceedances are considered due to the external factors rather than the contract works and non-project related.