4.1
In this section, the requirements, methodology, equipment, monitoring
locations, criteria and protocols for the monitoring and audit of ground-borne
noise impacts during the construction and operation phases of the Project are
presented.
4.2
The construction ground-borne noise level should be measured in terms of
the A-weighted equivalent continuous sound pressure level (Leq).
Leq (30 minutes) should be used as the monitoring parameter for the
time period between 0700 and 1900 hours on normal weekdays.
4.3
Supplementary
information for data auditing and statistical results such as L10
and L90 should also be obtained for reference. A sample data
record sheet is shown in Appendix B for reference.
4.4
With reference to
the Technical Memorandum for the
Assessment of Noise from Places Other Than Domestic Premises, Public Places or
Construction Sites (IND-TM) issued under the Noise Control Ordinance (NCO), the criteria for noise transmitted
primarily through the structural elements of a building or buildings should be
10dB(A) less than the relevant Acceptable Noise Level (ANL).
4.5
Between 1900 and
0700 hours and all day on Sundays and public holidays, activities involving the
use of powered mechanical equipment (PME) for the purpose of carrying out
construction work is prohibited unless a Construction Noise Permit (CNP) has
been obtained. A CNP may be granted
in cases of noise being contained within the ANL at the NSRs. ANLs are assigned depending upon the
Area Sensitivity Ratings (ASRs).
The criteria applicable to ground-borne noise are summarised in Table 4.1 below.
Table 4.1 Ground-borne Construction Noise Criteria
|
|
Ground-borne
Construction Noise Criteria, dB(A) |
||||||
GBNSR Description |
Daytime (0700-1900 hrs) |
Daytime during general
holidays and Sundays and all days during Evening |
Night-time |
||||
|
A |
B |
C |
A |
B |
C |
||
|
Education institutions |
60/55 [a] |
50 |
55 |
60 |
[b] |
||
|
Domestic premises, hotels |
65 |
50 |
55 |
60 |
35 |
40 |
45 |
|
Churches/temples, libraries,
courts, performing arts, clinics |
60 |
50 |
55 |
60 |
[b] |
||
Notes:
[a] A 5dB(A) reduction in the ground-borne noise criterion
is recommended for school during examination period.
[b]
No sensitive use during this period.
4.6
According to the
requirements of the Technical Memorandum (TM) issued under the NCO, sound level
meters in compliance with the International Electrotechnical Commission
Publications 651: 1979 (Type 1) and 804: 1985 (Type 1) specifications should be
used for carrying out the noise monitoring. Immediately prior to and
following each noise measurement the accuracy of the sound level meter should
be checked using an acoustic calibrator generating a known sound pressure level
at a known frequency. Measurements may be accepted as valid only if the
different between the calibration levels obtained before and after the noise
measurement is less than 1.0 dB.
4.7
Noise
measurements should not be made in the presence of wind with a steady speed
exceeding 5ms-1 or wind with gusts exceeding 10ms-1. The
wind speed should be checked with a portable wind speed meter capable of
measuring wind speeds in m/s.
4.8
The ET Leader is
responsible for the provision of the monitoring equipment. He should
ensure that sufficient noise measuring equipment and associated instrumentation
are available for carrying out the baseline monitoring, regular impact
monitoring and ad hoc monitoring. All the equipment and associated
instrumentation should be clearly labelled.
4.9
In the EIA, it is predicted that the
construction ground-borne noise will comply with the stipulated
noise criteria at all ground-borne noise
sensitive receivers (GBNSRs), except four GBNSRs in proximity to tunnel boring
machine (TBM) operation. The designated
construction ground-borne noise monitoring locations with predicted noise
levels equal to 65dB(A) or above are listed in Table 4.2 and their locations are shown
in Figure Nos. NOL/ERL/
Table 4.2 Construction Ground-borne Noise Monitoring Locations
|
GBNSR No. in EIA |
Monitoring Location* |
Uses |
|
GN3 |
|
Educational Institution |
|
GN5 |
Tower
5, |
Residential |
|
GN7 |
|
Residential |
|
GN8 |
|
Residential |
|
GN31 |
DD110
|
Residential |
Remark:
* The monitoring station should be at the lowest sensitive floor of
each designated monitoring location.
§
Monitoring at sensitive receivers
close to the major site activities that are likely to have noise impacts;
§
Monitoring close to the noise
sensitive receivers as defined in the Technical Memorandum; and
§
Assurance of minimal disturbance to
the occupants during monitoring in the vicinity of sensitive receivers.
4.11
The monitoring
station should be at the lowest sensitive floor of each designated monitoring
location and normally be at a position
4.12
Background
ground-borne noise should be measured inside the GBNSRs before the commencement
of operation of the TBM. The
baseline ground-borne noise levels should be measured for a continuous period
of at least 7 consecutive days at a minimum logging interval of 30 minutes for
daytime (between 0700 and 1900 hours of normal weekdays) and 15 minutes (as
three consecutive Leq, (5 minutes) readings) for evening time
(between 1900 and 2300 hours on normal weekdays), general holidays including
Sundays (between 0700 and 2300 hours) and night-time (between 2300 and 0700 of
all days). The Leq, L10 and L90 should be
recorded at the specified interval. A schedule for the baseline
monitoring should be submitted to the IEC for approval before the monitoring
starts.
4.13
There should not
be any construction activities in the vicinity of the monitoring stations
during the baseline monitoring. Any non-Project related construction
activities in the vicinity of the monitoring stations during the baseline
monitoring should be noted and the source and location of such activities
should be recorded.
4.14
In exceptional
cases, when insufficient baseline monitoring data or questionable results are
obtained, the ET Leader should liaise with the IEC and EPD to agree on an
appropriate set of data to be used as a baseline reference.
Construction Phase
4.15
Construction
ground-borne noise monitoring plan should be provided by the ET and submitted
to IEC and EPD for approval before the commencement of operation of the TBM. Continuous impact ground-borne noise
should be monitored at the GBNSRs when the TBM head is operating underneath the
designated monitoring locations to audit EIA findings and monitor the noise
impact.
4.16
To account for cases in which ambient noise levels, as identified
by the baseline monitoring, approach or exceed the stipulated Limit Levels presented
in Table 4.1 prior to commencement
of construction, a Maximum Acceptable Impact Level, which incorporates the
baseline noise levels and the identified construction noise Limit Level, may be
defined and agreed with EPD. The amended level will represent the maximum
acceptable noise level at a specific monitoring station.
4.17
Table 4.3 presents the proposed TBM operating hours in relation to
the measured ground-borne noise levels recorded at monitoring locations of
different uses.
Table 4.3 Proposed TBM Operating Time
|
Case |
Monitoring
Period |
Monitoring
Results |
Acceptable
Operating Time of TBM |
|
Domestic Premises |
|||
|
1 |
Daytime (Except general holidays and
Sundays) (0700 – 1900 hrs) only |
||
|
2 |
1900
– 2300 hours |
MNL < 50/55/60(3)
dB(A) |
Daytime and evening time including general
holidays and Sundays and all days during evening (0700-2300 hrs) only(4) |
|
3 |
2300
– 0700 hours |
MNL < 35/40/45(3)
dB(A) |
No restriction(4) |
|
Schools, |
|||
|
4 |
0700
– 1900 hours |
55 dB(A) < MNL < 60(2) dB(A) |
Daytime, evening and night-time period (including
general holidays and Sundays) (1900 – 0700 hrs) only(4) |
|
5 |
1900
– 2300 hours |
MNL < 55(2) dB(A) |
No restriction(4) |
Remark:
(1) MNL means Measured Noise Level.
If MNL is higher than the Limit level, the ET should inform the affected
NSRs the proposed working hour and period of TBM operation.
(2) Limit level subject to background noise measurement results. Highest noise level will be adopted as
the upper limit.
(3) Noise
criteria for Area Sensitive Rating “A”, “B” and “C” respectively.
(4) The operating
time of TBM only applies for those receivers without sensitive use during
restricted hours and subject to the granting of Construction Noise Permit and
usages of the sensitive receivers and nearby GBNSRs.
Operation Phase
4.18
With the predicted operation ground-borne noise levels complying with
the stipulated noise criteria at all GBNSRs, mitigation measures are not
required during the operation phase.
A noise commissioning test should be conducted by the ET prior to the
operation of the Project to confirm the compliance of the operational
ground-borne noise levels with the NCO noise criteria. The noise commissioning test
should be performed at selected key noise sensitive receivers including at
least but not limited to the GBNSRs listed in Table 4.2.
4.19
A summary of the operational ground-borne noise criteria for the ground-borne
GBNSRs is given in Table 4.4.
Table 4.4 Operational Ground-borne Noise Criteria
|
|
Ground-borne Railway Noise
Criteria, dB(A) |
|||||
GBNSRs Description |
Day and Evening (0900 to 2300 hrs) |
Night-time Period |
||||
|
A |
B |
C |
A |
B |
C |
|
|
Churches/temples, schools, medical clinics, libraries and courts |
50 |
55 |
60 |
[a] |
||
|
Domestic premises, hotels and
hospitals |
50 |
55 |
60 |
40 |
45 |
50 |
Note:
[a]
No sensitive use during this period.
Construction Phase
4.20
In
addition to the proposed ground-borne noise monitoring and proper scheduling of
works, close liaison with affected parties during the operation of the TBM is
proposed to minimise the noise impact to the GBNSRs. Prior to the commencement of the operation
of the TBM, the following information in relation to the Project should be
provided to nearby residents, schools and property owners:
§
the implementation programme of the tunnelling
works;
§
the planned construction activities
that will be involved;
§
the possible environmental impacts on
the affected communities;
§
the monitoring programme to check
the ground-borne noise construction noise levels; and
§
the communication channels between
the local communities and the Project’s community liaison office to enhance
communication with the public on the impacts and the necessity for enhancement
of the measures.
4.21
It is
considered that a close relation with local communities would
be instrumental in ensuring that the works are carried out in an environmentally acceptable manner and to the
satisfaction of the local communities environmental, and that environmental
non-compliance is promptly dealt with in a transparent manner during
construction. A 24-hour
hotline manned by the Contractor should be set up to maintain good
communications and provide immediate responses. All received enquiries or complaints should
be logged immediately and forwarded to the relevant project officers for follow-up.
4.22
Prior to the final design of the trackform and the extent of each type
of trackform, and after the proposed train in operation outside Hong Kong,
tests of the FDL of the train should be carried out to update the ground-borne
noise prediction and the recommendation on mitigation measures as necessary.
4.23
The vibration borehole testing should be carried out at two carefully
selected locations along the proposed tunnel alignment prior to the
commencement of construction works in order to determine the LSR values under
certain geological conditions. This
will also allow further update of the ground-borne noise predictions and the
recommendation on mitigation measures as necessary.
Operation Phase
4.24
With the
predicted operation ground-borne noise levels complying with the stipulated
noise criteria at all GBNSRs, mitigation measures are not required during
operation phase. Installation of low noise trackform is
recommended at several locations to further reduce the ground-borne noise
levels to account for uncertainty of FDL and LSR values.