6    Noise


6.1    Introduction


This Section provides an evaluation of the potential noise impacts associated with the activities at the proposed Contaminated Mud Disposal Facilities at the East of Sha Chau.  Mitigation measures will be recommended, if necessary, to ensure that the legislative criteria will be satisfied.


6.2    Identification of Sources of Noise Impacts


The principal noise sources associated with the disposal facility are dredging, backfilling and capping works within the Site.  The works programme presented in Section 1 indicates that concurrent undertaking of dredging, backfilling and capping are possible at several time intervals.


For dredging, it is assumed that two grab dredgers will be operating within the Site, but a barge will be only operated at any one time for either backfilling or capping operations.  The assumed construction plant list and the corresponding sound power levels are presented in

Table 6.1.


Table 6.1    Construction Plant List and Sound Power Levels (SWLs)






Sub-Total SWL


Dredger, Grab






Derrick barge






Derrick barge






6.3    Noise Assessment Methodology


The assessment of potential noise impacts has been undertaken in accordance with the Technical Memorandum On Noise From Construction Work Other Than Percussive Piling (GW-TM) and Annex 13 of the EIAO-TM.  The general methodology is summarised as follows:


·                identify the sequence and duration of noise generating activities (i.e. dredging, backfilling and capping) required for the implementation of the CMP Project;


·                identify the required type and number of Power Mechanical Equipment (PME) likely to be deployed for the dredging, backfilling and capping activities;


·                calculate the maximum total Sound Power Level (SWL) for each activity using the PME list and SWL data given for each plant in the GW-TM (as presented in Table 6.1);


·                identify representative NSRs with closest proximity to the CMP Site to represent the potential impact for the area (as identified in Table 6.2);


·                measure the distance and calculate the distance attenuation to the NSRs from worksite notional noise source point at each pit;


·                apply correction for façade reflection; and


·                predict noise levels at the NSRs in the absence of any mitigation measures.


As the distances between most of the NSRs and the Site are over 1 km, sound absorption by the atmosphere (assumed at 500 Hz, 20°C, RH 70%) has been accounted for in accordance with ISO 9613-1 Acoustics – Attenuation of Sound During

Propagation Outdoors – Part 1: Calculation of the Absorption of Sound by the Atmosphere.


If the noise assessment criteria are exceeded at the representative NSRs, mitigation measures will be explored.  A re-evaluation of the total SWL for each construction activity will be undertaken.


6.4    Assessment of Noise Impact


Noise assessments at the five representative NSRs were made based on the tentative construction program, PME list, distances attenuation, atmospheric absorption, façade reflection and corresponding Sound Power Level.  The results are summarised in Table 6.2 and detailed calculations are presented in Table 3 of Annex D.


Table 6.2    Noise Assessment Results



Area Sensitivity Rating

Noise Criteria (1)

Predicted Noise Levels


Regal Airport Hotel

C (2)

75 (3)/70 (4)/55 (4)

27 to 39 dB(A)


Seaview Crescent in Tung Chung

B (2)


12 to 23 dB(A)


Monterey Cove in Tung Chung

B (2)


13 to 24 dB(A)


Planned R(B)6 Residential Area at Area 77b (in Kei Tau Kok)

B (2)


16 to 28 dB(A)


Ho Yu School

B (2)

70/65 (5)

12 to 24 dB(A)


(1)                 Criteria for daytime/ all days during the evening (1900-2300) and general holidays including Sunday during the day and evening (0700-2300) / all days during the night-time (2300-0700)

(2)                 Area Sensitive Rating is assumed in accordance with the GW-TM

(3)                 Leq, 30min 75 dB(A) is the EIAO recommended daytime non-restricted hours criterion

(4)                 Noise criteria for restricted hours prescribed under the NCO in LAeq 5min

(5)                 Noise criteria for normal school days/examination period


As indicated in Table 6.2, the predicted noise levels at the representative NSRs would comply with the daytime (i.e. 0700 – 1900, non-restricted hours), evening hours (i.e. 1900 – 2300 restricted hours) and night-time hours (i.e. 2300 – 0700) noise criteria.  The highest noise level of 39 dB(A) has been predicted at NSR N1.


6.5    Mitigation of Adverse Noise Impact


As noise levels at all NSRs will comply with the daytime, evening and night-time criteria, no mitigation measure is required.


6.6    Residual Environmental Impacts


No residual environmental impacts, in terms of exceedances of applicable noise criteria, were predicted to occur during either the daytime, evening or at night-time.


6.7    Environmental Monitoring & Audit


Given the compliance with the noise criteria, noise monitoring is not required during the construction or operation of the East of Sha Chau facility. 


6.8    Conclusion


Noise impact associated with the dredging, backfilling and capping works at the East of Sha Chau Facility have been assessed.  It has assumed that 2 grab dredgers will be deployed on-site for dredging work and 1 barge for backfilling or capping activity.  Since restricted hours construction activities may be required, the prediction results were compared against the EIAO-TM daytime (non-restricted hours) and the evening (1900 – 2300) and night-time (2300 – 0700) restricted hours criteria.


The results indicated that the criteria for daytime, evening and night-time works will comply at all representative NSRs.  No mitigation measure is recommended.