Appendix 4.2 - Operational Noise Impact Assessment
NSR N1
	Potential Noise Sources	Sound Power Level for Each Equipment	No.	Total Sound Power Level	Distance to Sources	Distance Corrections	Façade Effect	Sight Line Effect	Acoustic Louvers	Correction by screening effect or/and silencer	Tonality Effect	Predicted Noise Level	SPL,dB(A)
1	Submersible Pump	88	3	92.8	121	-49.7	3			-20	6	32.1		1627.611
2	Mechanically raked screen	89	2	92.0	111	-48.9	3			-20		26.1		407.7407
3	Transformer	85	1	85.0	125	-49.9	3			-20	6	24.1		254.7886
4	Exhaust fan of Deodorization Unit	83	1	83.0	110	-48.8	3			-10	6	33.2		2075.939
	(5000 m3/hr)													1
												Total SPL =	36.4
NSR N2
	Potential Noise Sources	Sound Power Level for Each Equipment	No.	Total Sound Power Level	Distance to Sources	Distance Corrections	Façade Effect	Sight Line Effect	Acoustic Louvers	Correction by screening effect or/and silencer	Tonality Effect	Predicted Noise Level	SPL,dB(A)
1	Submersible Pump	88	3	92.8	85	-46.6	3			-20	6	35.2		3298.249
2	Mechanically raked screen	89	2	92.0	93	-47.4	3			-20		27.6		580.8501
3	Transformer	85	1	85.0	75	-45.5	3			-20	6	28.5		707.7461
4	Exhaust fan of Deodorization Unit	83	1	83.0	77	-45.7	3			-10	6	36.3		4236.611
	(5000 m3/hr)													1
												Total SPL =	39.5
NSR N4
	Potential Noise Sources	Sound Power Level for Each Equipment	No.	Total Sound Power Level	Distance to Sources	Distance Corrections	Façade Effect	Sight Line Effect	Acoustic Louvers	Correction by screening effect or/and silencer	Tonality Effect	Predicted Noise Level	SPL,dB(A)
1	Submersible Pump	88	3	92.8	37	-39.4	3			-20	6	42.4		17406.75
2	Mechanically raked screen	89	2	92.0	55	-42.8	3			-20		32.2		1660.751
3	Transformer	85	1	85.0	27	-36.6	3			-20	6	37.4		5461.004
4	Exhaust fan of Deodorization Unit	83	1	83.0	44	-40.9	3	-10		-10	6	31.1		1297.462
	(5000 m3/hr)													1
												Total SPL =	44.1
NSR N5
	Potential Noise Sources	Sound Power Level for Each Equipment	No.	Total Sound Power Level	Distance to Sources	Distance Corrections	Façade Effect	Sight Line Effect	Acoustic Louvers	Correction by screening effect or/and silencer	Tonality Effect	Predicted Noise Level	SPL,dB(A)
1	Submersible Pump	88	3	92.8	66	-44.4	3			-20	6	37.4		5470.58
2	Mechanically raked screen	89	2	92.0	64	-44.1	3			-20		30.9		1226.507
3	Transformer	85	1	85.0	76	-45.6	3			-20	6	28.4		689.2437
4	Exhaust fan of Deodorization Unit	83	1	83.0	76	-45.6	3	-10		-10	6	26.4		434.8834
	(5000 m3/hr)													1
												Total SPL =	38.9
NSR N6
	Potential Noise Sources	Sound Power Level for Each Equipment	No.	Total Sound Power Level	Distance to Sources	Distance Corrections	Façade Effect	Sight Line Effect	Acoustic Louvers	Correction by screening effect or/and silencer	Tonality Effect	Predicted Noise Level	SPL,dB(A)
1	Submersible Pump	88	3	92.8	65	-44.3	3			-20	6	37.5		5640.2
2	Mechanically raked screen	89	2	92.0	47	-41.4	3			-20		33.6		2274.229
3	Transformer	85	1	85.0	80	-46.1	3			-20	6	27.9		622.0425
4	Exhaust fan of Deodorization Unit	83	1	83.0	65	-44.3	3	-10		-10	6	27.7		594.5293
	(5000 m3/hr)													1
												Total SPL =	39.6
Remark:
(i)	SWL for the pump make reference to "Tuen Mun Sewerage - Eastern Coastal Sewerage Extension Final EIA Report (2000)".
(ii)	SWL for mechanically raked screen make reference to "Project Profile for Tai Po Tai Wo Road Sewage Pumping Station (2007)".
(iii)	SWL for transformer make reference to "San Wai STW and Ha Tsuen PS –EIA (2003)".
(iv)	The design flow rate of exhaust fan of deodorization unit is 5000 m3/hour.  The SWL make reference to the ventilation fan with 8600 m3/hr and 125 Pa stipulated in "Good Practices on Ventilation System Noise Control"
	published by EPD.
(v)	Overall noise reduction of 20 dB(A) is assumed for the pumps and mechanically raked screens which would locate underground and would be housed in a 200mm thick reinforced concrete structure with provision of silencers at the louvers.
	Noise reduction of 20 dB(A) is assumed for the transformer which is housed in an enclosed 200mm thick reinforced concrete structure with soundproof door.
	Noise reduction of 10 dB(A) is assumed for exhaust fan of deodourization unit with silencer.
(vi)	In accordance with NCO, 6 dB(A) for tonality correction was applied to exhaust fan of the deodourization unit, pump and transformer as a conservative approach.