| ANNEX
A - ASSESSMENT OF NOISE FROM CONSTRUCTION WORK INVOLVING THE USE
OF SPECIFIED POWERED MECHANICAL EQUIPMENT (SPME) OTHER THAN PERCUSSIVE
PILING WITHIN A DESIGNATED AREA
| A.1. |
General
Introduction to the Procedures
For the purpose of assessing if a Construction
Noise Permit (CNP) may be issued for construction work involving
the use of SPME other than percussive piling within a designated
area during the restricted hours the Authority shall act in
accordance with the following general procedures which are
detailed in subsequent sections. The Authority shall:
| (a) |
identify the most affected Noise Sensitive Receiver (NSR),
determine the Area Sensitivity Rating (ASR) for the area
within which the NSR is located and hence determine the
relevant Acceptable Noise Level (ANL) (in accordance with
Sections A.2.1 to A.2.6); |
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| (b) |
calculate the Corrected Noise Level (CNL) which will be
generated by the construction work at the NSR (in accordance
with Sections A.2.7 to A.2.12); and |
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| (c)
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compare
the CNL with the ANL to determine if a CNP may be issued
(in accordance with Section A.2.13). |
If the CNL is equal to or less than the ANL
the CNP may be issued by the Authority in the prescribed form
and may include such conditions as the Authority considers
appropriate, such as the permissible items of SPME which may
be used on the construction site, the hours during which the
CNP is valid, the dates of commencement and expiry of the
CNP, any noise levels which may not be exceeded at specified
locations during specified times and any special noise control
measures that must be adopted. |
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| A.2. |
Calculation
Procedure
| A.2.1 |
Step 1 - Location of the Most Affected Noise Sensitive
Receiver (NSR)
The NSR which will be most affected
by noise from the construction work shall be identified.
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| A.2.2 |
Step
2 - Determination of the Area Sensitivity Rating
(ASR)
| A.2.2.1
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General
The ASR is a function of the type
of area within which the NSR is located and the
degree of the effect on the NSR of particular
Influencing Factors (IFs) as defined in Section
A.2.2.3. After a careful examination of the area
under consideration and the effect of any IFs,
the ASR may be determined from Table A.1.
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| A.2.2.2 |
Type of area within which the Noise Sensitive
Receiver (NSR) is located
The Authority shall have regard
to an area of adequate size when determining the
type of area within which the NSR is located in
accordance with the descriptions in Table A.1.
Typically, in urban areas an area of 100 m radius
around the NSR should be adequate whereas in sparsely
developed areas, such as rural districts, an area
of 500 m radius or even more should be considered,
depending upon the circumstances. Special factors
may dictate that other distances should be used
at the discretion of the Authority. |
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| A.2.2.3 |
Effect of Influencing Factors (IFs)
For the purpose of this Technical
Memorandum any industrial area, major road or
the area within the boundary of Hong Kong International
Airport shall be considered to be an IF. Industrial
areas and the Airport should be regarded as IFs
irrespective of the time of day.
The term "industrial area"
means an area which consists of a number of factories
or industrial undertakings located primarily in
purpose-built industrial buildings. It includes
any premises, buildings or activities which the
Authority deems, by virtue of their acoustical
characteristics, make an area industrial in nature.
The term "major road" means a road which
has a heavy and generally continuous flow of vehicular
traffic and, in normal circumstances, means a
road with an annual average daily traffic flow
in excess of 30,000. Where a major road has an
unusually low traffic flow rate (less than 300
vehicles per hour) at the time of day under consideration
it shall not be considered as an IF at that time.
In situations where more than
one IF affects the NSR to an equal degree only
one IF shall be considered.
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| A.2.2.4 |
Area Sensitivity Rating (ASR)
The
Authority shall determine the appropriate ASR
for the NSR under consideration from Table A.1.
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| A.2.3 |
Step 3 - Determination of the Basic Noise Level (BNL)
The appropriate BNL, in dB(A), for a
given NSR may be determined from Table A.2, having regard
to the appropriate ASR and the time period as specified
in the Construction Noise Permit application. |
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| A.2.4 |
Step 4 - Correction for the Duration of the Construction
Noise Permit (CNP)
If the duration of an initial CNP, or,
in the case of a renewal of a CNP, the combined duration
of the initial CNP and any renewal or renewals of a
CNP for associated construction work on substantially
the same construction site, will be less than or equal
to 14 days, a positive correction of 3 dB(A) shall be
applied to the BNL.
For the purposes of this Step a CNP
shall be considered to be a renewal of a CNP if its
date of commencement is less than or equal to 21 days
after the expiry date of any other CNP for associated
construction work on substantially the same construction
site. |
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| A.2.5 |
Step 5 - Correction for Multiple Permit Situations
If
in the opinion of the Authority the NSR will be materially
affected by noise from construction work associated
with more than one CNP, the Authority may make such
correction to the BNL as it considers appropriate having
regard to standard acoustical principles and practices.
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| A.2.6 |
Step 6 - Determination of the Acceptable Noise Level
(ANL)
The corrections obtained in Steps 4
and 5 shall be applied to the BNL obtained in Step 3
to give the ANL. |
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| A.2.7 |
Step 7 - Location of Items of Specified Powered Mechanical
Equipment (SPME)
All items of SPME should be considered
to be grouped at a position mid-way between the approximate
geographical centre of the construction site and its
boundary nearest to the NSR. This position is referred
to as the notional source position.
If the construction site is irregular
in shape the geographical centre may fall outside the
physical limits of the site. In such cases the notional
source position shall be taken to be the position on
the construction site boundary nearest to the geographical
centre of the site. If two such points exist, the point
nearest to the NSR shall be used.
If the construction site is linear in
shape (that is, long, thin and substantially uniform
in width, but not necessarily straight) with a length
to width ratio exceeding 5:1, only the dominant portion
of the site shall be considered for the purpose of determining
the notional source position. The dominant portion is
defined as the portion of the linear site closest to
the NSR and having a length to width ratio of 5:1. If
part of the construction site is linear in shape then
such part shall be subject to a separate assessment
for a separate CNP, at the discretion of the Authority.
If the construction site is large such
that the notional source position would be greater than
50 m from the point on the site boundary nearest to
the NSR the position shall be taken to be a point 50
m from that point on the site boundary measured along
the line between the approximate geographical centre
of the site and the point on the site boundary nearest
to the NSR.
If in the opinion of the Authority the
site is of such shape or dimensions that the procedure
outlined above cannot readily be applied or if such
application would lead to an inappropriate notional
source position the Authority may select such a notional
source position as it considers appropriate in the circumstances.
If the Authority is satisfied that any
item of SPME is to remain in substantially the same
position, and the particular item and its position has
been specified by the applicant, the actual position
may be used in conjunction with the notional source
position for all other items of SPME in the calculation
of distance attenuation in Step 9.
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| A.2.8 |
Step 8 - Sound Power Levels for Specified Powered
Mechanical Equipment (SPME)
The sound power levels in dB(A) of each
of the items of SPME intended for use on the construction
site shall be obtained from Table A.3.
If any item of SPME in Table A.3 intended
for use on the construction site is a prescribed product
under the Ordinance and is fitted with a valid noise
emission label, then the sound power level on the label
shall be used instead of the one in Table A.3 for the
calculation of CNL.
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| A.2.9 |
Step
9 - Distance Attenuation and Summation of Noise Levels
| A.2.9.1 |
General
In determining the distance from
the source position to the NSR blank facades shall
not be considered and the distance shall be determined
to the nearest NSR facade with windows, doors
or other openings. The plan distance or, where
appropriate, the slant distance shall be used.
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| A.2.9.2 |
Procedure for Use with a Single Notional Source
Position
If all items of SPME are assumed
to be located at a single notional source position,
the sound power levels obtained in Step 8 shall
be summed logarithmically in accordance with Table
A.4 to obtain a total sound power level.
The distance between the notional
source position and the NSR shall be determined
and the appropriate correction factor shall be
obtained from Table A.5. This correction factor
shall be subtracted from the total sound power
level to give the Predicted Noise Level (PNL)
at the NSR.
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| A.2.9.3 |
Procedure for Use with Actual Source Positions
or a Combination of Actual and Notional Source
Positions.
If in addition to a notional source
position a number of actual source positions are
being used, or if only actual source positions
are being used, the distances between the actual
source positions and the NSR shall be determined
and the appropriate correction factors shall be
obtained from Table A.5. These factors shall be
subtracted from the individual sound power levels
for each item of SPME to give the individual sound
pressure levels for each item of SPME at the NSR.
Any combined sound pressure level
from items of SPME assumed to be located at a
notional source position shall be determined in
accordance with Section A.2.9.2 and shall be added
logarithmically to the individual sound pressure
levels from items of SPME assumed to be at actual
source positions, in accordance with Table A.4,
to give the PNL at the NSR.
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| A.2.10 |
Step 10 - Corrections for the Effect of Barriers
In cases where the Authority considers
that all items of SPME to be used on the construction
site will be totally screened by a substantial barrier
such that none will be visible when viewed from any
window, door or other opening in any facade of the NSR,
a negative correction of 10 dB(A) shall be applied to
the PNL obtained in Step 9. In cases where the Authority
considers a higher negative correction should be applied,
the Authority shall use appropriate correction factors
having regard to standard acoustical principles and
practices.
Substantial barriers shall be taken
to be large solid objects, such as buildings or topographical
features, which will act as effective acoustic screens.
Barriers which are small, lightweight, incomplete or
temporary, such as site fences or hoardings, are not
to be considered. The effects of purpose-built acoustic
barriers may be taken into account in accordance with
Section 5.3.
In cases where the Authority considers
that all items of SPME to be used on the construction
site other than "quiet" items of SPME will
be totally screened when viewed from the NSR, a negative
correction of 5 dB(A) shall be applied to the PNL obtained
in Step 9. For the purpose of this section "quiet"
items of SPME shall be considered to be those whose
sound power level is more than 15 dB(A) below the total
sound power level being generated by all items of SPME.
In cases where the NSR is a building
directly adjacent to the construction site such that
none of the items of SPME to be used on the construction
site will be visible when viewed from any window, door
or other opening in any facade of the NSR, the NSR shall
be considered to be partially screened and a negative
correction of 5 dB(A) shall be applied to the PNL obtained
in Step 9.
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| A.2.11 |
Step 11 - Corrections for Acoustic Reflections
In cases
where the NSR is a building, a positive correction of
3 dB(A) shall be applied to the PNL obtained in Step
9.
An additional
positive correction of up to 3 dB(A) may be applied
to the PNL in cases where the Authority considers that
noise levels at the NSR will be increased due to the
confined or reverberant nature of the immediate locality
of the construction site or the NSR. |
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| A.2.12 |
Step 12 - Corrected Noise Level (CNL) at the Noise
Sensitive Receiver (NSR)
The corrections obtained in Steps 10
and 11 shall be applied to the PNL obtained in Step
9 to give the CNL at the NSR. |
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| A.2.13 |
Step 13 - Construction Noise Permit (CNP) Issuing
Procedure
The CNL at the NSR obtained in Step
12 shall be compared with the ANL obtained in Step 6.
If the CNL is equal to or less than the ANL the CNP
may be issued. If the CNL is greater than the ANL the
CNP shall not be issued unless the application is a
special case as defined in Section 5. The procedures
detailed in Section 5 shall then be followed.
| Table
A.1 Area Sensitivity Ratings (ASRs) |
| Type
of Area Containing NSR |
Degree
to which NSR is affected by IF |
|
Not
Affected |
Indirectly
Affected |
Directly
Affected |
| (i)
Rural area, including country parks or village type
developments |
A |
B |
B |
| (ii)
Low density residential area consisting of low-rise
or isolated high-rise developments |
A
|
B |
C |
| (iii)
Urban area |
B |
C |
C |
| (iv)
Area other than those above |
B |
B |
C |
For
the purpose of Table A.1, the following definitions
shall apply:
"country park" means an area
that is designated as a country park pursuant to section
14 of the Country Parks Ordinance;
"directly affected" means
that the NSR is at such a location that noise generated
by the IF is readily noticeable at the NSR and is a
dominant feature of the noise climate of the NSR;
"indirectly affected" means
that the NSR is at such a location that noise generated
by the IF, whilst noticeable at the NSR, is not a dominant
feature of the noise climate of the NSR;
"not affected" means that
the NSR is at such a location that noise generated by
the IF is not noticeable at the NSR; and
"urban area" means an area
of high density, diverse development including a mixture
of such elements as industrial activities, major trade
or commercial activities and residential premises.
| Table
A.2 Basic Noise Levels (BNLs) |
|
Time
Period |
ASR |
| A |
B |
C |
| All
days during the evening (1900 to 2300 hours), and
general holidays (including Sundays) during the
day-time and evening (0700 to 2300 hours) |
45 |
50 |
55 |
| All
days during the night-time (2300 to 0700 hours)
|
30 |
35 |
40 |
| Table
A.3
Sound Power Levels for Items of Specified Powered
Mechanical Equipment (SPME) |
| Identification
Code |
Description |
Sound
Power Level (dB(A)) |
| CNP
023 |
Breaker,
hand-held, mass <= 10kg |
108 |
| CNP
024 |
Breaker,
hand-held, mass > 10kg and < 20kg |
108 |
| CNP
025 |
Breaker,
hand-held, mass >= 20kg and <= 35kg |
111 |
| CNP
026 |
Breaker,
hand-held, mass > 35kg |
114 |
| CNP
030 |
Bulldozer |
115 |
| CNP
044 |
Concrete
lorry mixer |
109 |
| CNP
067 |
Dump
truck |
117 |
| CNP
170 |
Poker,
vibratory, hand-held |
113 |
| Table
A.4 Summation of Noise Levels |
| Difference
in dB(A) between two noise levels being summed |
Amount
in dB(A) to add to the higher noise level |
| 0
to 0.5
1.0 to 1.5
2.0 to 3.0
3.5 to 4.5
5.0 to 7.0
7.5 to 12.0
more than 12.0 |
3.0
2.5
2.0
1.5
1.0
0.5
0 |
When
using Table A.4 noise levels should be summed in a pairwise
fashion and the final total rounded to the nearest whole
dB(A), with values of 0.5 or more being rounded upwards.
| Table
A.5
Correction Factors to Obtain the Predicted Noise
Level (PNL) from Sound Power Levels at Given Distances
|
| Distance
(m) |
Correction
(dB(A)) |
Distance
(m) |
Correction
(dB(A)) |
| 0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15 to 16
17 to 18
19 to 21
22 to 23
24 to 26
27 to 29 |
8
8
14
18
20
22
24
25
26
27
28
29
30
30
31
32
33
34
35
36
37 |
30
to 33
34 to 37
38 to 41
42 to 47
48 to 52
53 to 59
60 to 66
67 to 74
75 to 83
84 to 93
94 to 105
106 to 118
119 to 132
133 to 148
149 to 166
167 to 187
188 to 210
211 to 235
236 to 264
265 to 300 |
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57 |
For the purpose
of determining the correction to be used for converting
from sound power level at the source to the PNL at the
NSR, the distance from the source position to the NSR
shall be determined to the nearest whole metre, with
values of 0.5 or more being rounded upwards.
This table
is only valid for distances of up to 300 m. For distances
greater than 300 m the Authority shall calculate appropriate
correction factors having regard to standard acoustical
principles and practices.
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