110kV TRANSMISSION LINE
HANGATIKI – TE AWAMUTU
ASSESSMENT OF NOISE EFFECTS
Report No 9886
Prepared for:
Waipa Networks Ltd
Te Awamutu
June 2014
Prepared by: …………………….
Nevil Hegley
MSc MICE CPEng IntPE, MIPENZ
2
CONTENTS
1 Introduction.................................................................... 4 2 Design Criteria ................................................................ 6 2.1
Waipa District Council ........................................................... 6
2.2
Otorohanga District Council .................................................... 8
2.3
Waitomo District Council........................................................ 9
2.4
Construction Standard ......................................................... 11
3 Existing Noise Environment ............................................ 13 4 Construction Work ........................................................ 22 5 Predicted Construction Noise .......................................... 26 6 7 5.1
Prediction Methodology ....................................................... 26
5.2
Predicted Noise Levels at Occupied Sites ............................... 26
5.3
Helicopter Noise .................................................................. 36
5.4
Summary of Results ............................................................ 38
Operation Noise ............................................................ 39 6.1
Corona Discharge ................................................................ 39
6.2
Surface Discharge ............................................................... 40
6.3
Wind Noise ......................................................................... 40
Conclusions.................................................................. 43 Appendix A .................................................................. 44 3
4
1
INTRODUCTION
Waipa Networks Limited is proposing to construct an 110kV single circuit
transmission line, entailing the construction of 177 pole support structures,
between the substations at Te Awamutu and Hangatiki, which will provide an
alternative electricity supply to Te Awamutu.
The transmission line connection between the two Transpower substations will
be achieved by constructing a new 32.29 km long transmission line as shown on
Figure 1.
Transmission line route
Figure 1.
Route of Proposed Transmission Line
5
The proposed line passes through the Waipa, Otorohanga and Waitomo District
Council areas and while the noise requirements in each District are similar there
are variations that need to be considered in the assessment.
This report considers the noise1 during the construction of the transmission line
and any subsequent operations noise, such as aeolian and corona discharge
noise, and how this noise will be controlled to within a reasonable level for any
neighbours as the line passes through the different districts.
1
See Appendix A for a Glossary of Noise Terms used in this report.
6
2
DESIGN CRITERIA
To determine what a reasonable noise level would be for the project guidance
has been taken from each of the three territorial authorities that the transmission
line passes through.
2.1
Waipa District Council
Although both the Operative and Proposed District Plans are available the
requirements of the Proposed District Plan have been adopted for the analysis, as
the controls are similar to the Operative Plan but reflect the use of the latest
acoustic Standards and approach to noise control. The relevant noise rules from
the Waipa Proposed District Plan are set out below.
In the Residential Zone Rule 2.4.2.18, Noise states:
Activities shall be conducted and buildings located, designed and used to ensure
they do not exceed the following noise limits at the boundary of the site:
(a) Monday to Saturday ‐ 7.00am to 10.00pm 50dBA (Leq)
(b) 50dBA (Leq)
(c) Sundays & Public Holidays ‐ 8.00am to 6.00pm,
50dBA (Leq) except in Character Area 4 in the
Cambridge Park Residential Zone where all
activities shall be conducted and buildings,
located, designed and used to ensure that noise
levels on any site zoned residential external to
Character Area 4 in the Cambridge Park
Residential Zone do not exceed this limits
between the hours of 8.00am and 8.00pm
Sundays ‐ 8.00am to 8.00pm (d) At all other times 40dBA (Leq) (e)
Night time 10.00pm to 7.00am single noise 70dBA (Lmax)
event
50dBA (Leq) 7
All noise levels shall be measured and assessed in accordance with the
requirements of NZS 6801:2008 – Acoustics – Environmental Sound
and assessed in accordance with NZS 6802:2008 – Acoustics –
Environmental Noise.
Rule 2.4.2.20, Construction noise sets the following criteria:
Construction noise emanating from a site shall meet the limits
recommended in and be measured and assessed in accordance with
New Zealand Standard NZS 6803:1999 Acoustics – Construction
Noise.
In the Rural Zone Rule 4.4.2.14, Noise states:
Noise generating activity other than that from farm animals including
farm dogs, agricultural vehicles (when not being used for recreational
purposes), agricultural machinery or equipment (including produce
packing facilities where the only produce packed is grown on site)
operated and maintained in accordance with the manufacturer’s
specifications and in accordance with accepted management practices
(e.g. for milking, spraying, harvesting, packing and the like, but not
including frost fans) and provided that the best practicable option is
adopted to ensure that the emission of noise does not exceed a
reasonable level; shall be conducted and buildings located, designed
and used to ensure that they do not exceed the following limits within
the notional boundary of any dwelling (excluding dwellings within
mineral extraction sites):
(a)
(b)
(c)
Day time ‐ 7.00am to 10.00pm
Night time ‐ 10.00pm to 7.00am
Night time single noise event
50dBA (Leq)
40dBA (Leq)
70dBA (Lmax)
The noise levels shall be measured and assessed in accordance with
the requirements of NZS 6801:2008 – Acoustics – Environmental
Sound and assessed in accordance with NZS 6802:2008 – Acoustics –
Environmental Noise.
8
Rule 4.4.2.16, Helicopter noise states:
Helicopter landings and take offs shall be in accordance with
NZS6807:1994 Noise Management and Landing Use Planning for
Helicopter Landing Areas where there are more than 10 landings per
annum.
Rule 4.4.2.18 sets the construction noise limits at the same limits as Rule
2.4.2.20 given above.
2.2
Otorohanga District Council
Rule 14, Noise in the Otorohanga District Plan sets the relevant noise
requirements within the district at:
Methods of Assessment
1.
All measurements shall be taken at the boundary of the site receiving
the noise except that in the Rural Effects Area the measurement shall
be taken at the notional boundary of any rural site receiving the noise
2.
NA
3.
NA
4.
Day shall be defined as:



5.
Monday to Friday 7am to 10pm.
Saturday 7am to 7pm.
Sunday and public holidays 8am to 5pm.
Night shall be defined as:

At all other times
6.
NA
7.
Sound levels will be measured in accordance with the provisions of
New Zealand Standard NZS 6801:2008 “Acoustics Measurement of
Environmental Sound” and will be assessed in accordance with the
provisions of New Zealand Standard NZS 6802:2008 “Acoustics
Environmental Noise”.
9
Standards
14A
Noise Measurements shall not exceed:
Effects Area
Rural Effects Area
(excluding Waipapa
Noise Control
Boundary)
Urban Services
Effects Area
Urban Limited Services
Effects Area
Renewable Electricity
Generation Policy Area
Waipapa Noise Control
Boundary – Well Drilling
and Testing within the
Renewable Energy
Generation Policy Area
Road
Order
1, 2 & 3
LAeq
(Day)
50dB
LAeq
(Night)
40dB
LAmax
(Night)
70dB
1&2
2A
3
55dB
70dB
50dB
55dB
45dB
60dB
40dB
45dB
75dB
75dB
70dB
75dB
1
2&3
1
50dB
40dB
70dB
55dB
40dB
75dB
1
70dB
60dB
75dB
14B
Within the Rural Effects Area, the noise being generated originates
from farm animals and/or agricultural vehicles (where not used for
recreational purposes), associated with the day to day operation of an
agricultural activity.
14.3
Any construction, maintenance or demolition activity which complies
with New Zealand Standard NZS: 6803:1999 “Acoustics
Construction Noise” is a permitted Activity.
2.3
Waitomo District Council
Rule 20.5 of the Waitomo District Plan sets the relevant noise levels to be
complied with in the district at:
20.5.1
Conditions for Permitted Activities (excluding Temporary Military
Training Activities covered by Rule 20.5.3)
10
All permitted activities shall be carried out such that the noise level
at the boundary of the site that the noise generating activity is
located on (or notional boundary in the rural zone – see definition in
section 28) in the relevant zone as set out in the following table is
not exceeded
Zone
Residential
Business
Rural
Special Industrial
Activities
Industrial
Conservation
Maximum Noise (dBA)
Day time L10
Night time L10
55
40
55
45
50
40
60
50
60
50
50
40
20.5.1.1
(a) Daytime means
7.00 am to 10.00 pm Monday to Saturday
and 8.00 am to 5.00 pm Sundays and Public
Holidays.
(b) Night-time means all other times.
(c) In any zone no single event noise shall exceed 70dBA Lmax at
night time.
20.5.1.4 All noise levels shall be measured and assessed in accordance with
the requirements of NZS 6801:1991 The Measurement of Sound
and NZS 6802:1991 Assessment of Environmental Sound. The
noise shall be measured with a sound level meter complying with
the International Standard IEC65I (1979): Sound Level Meters,
Type 1.
20.5.1.5 All construction shall be carried out so as to comply with New
Zealand Standard NZS 6803P:1984.
For this project the areas potentially influenced by the ongoing operation must
comply with a level of 40dBA as either a L10 or Leq value (the exact value being
dependent on the district) at night time plus a single event sound of 70dBA Lmax.
As the noise will be similar during both the daytime and night time compliance
with the noise criteria during the night time will give compliance during the
daytime.
11
2.4
Construction Standard
The Waipa and Otorohanga District Plans both adopt NZS 6803:1999 Acoustics
- Construction Noise and the Waitomo District Plan NZS 6803P:1984 The
Measurement and Assessment of Noise from Construction, Maintenance and
Demolition Work
Since this Waitomo District Plan was prepared NZS6803P:1984 has been
updated to NZS 6803:1999 Acoustics — Construction Noise.
The main
difference between the two Standards is that Leq is used in preference to L10 and
the ambiguities in the 1984 Provisional Standard have been removed.
As a
general rule, if the later Standard is complied with then the earlier Standard will
also be complied with. For this project it is recommended the 1999 version of
NZS6803 be adopted for construction work in the Waitomo District, which will
result in the same construction noise criteria being applicable along the total
route.
Tables 2 and 3 of NZS 6803:1999 Acoustics — Construction Noise adopts the
following noise limits for any construction activity:
Table 2 -
Recommended upper limits for construction noise received in
residential zones and dwellings in rural areas
Time of week
Time period
Weekdays
0630-0730
0730-1800
1800-2000
2000-0630
0630-0730
0730-1800
1800-2000
2000-0630
0630-0730
0730-1800
1800-2000
2000-0630
Saturdays
Sundays and
public
holidays
Typical duration
(dBA)
Lmax
Leq
60
75
75
90
70
85
45
75
45
75
75
90
45
75
45
75
45
75
55
80
45
75
45
75
Short term
duration
Lmax
Leq
65
80
80
95
75
90
45
75
45
75
80
95
45
75
45
75
45
75
55
85
45
75
45
75
Long term
duration
Lmax
Leq
55
75
70
85
65
80
45
75
45
75
70
85
45
75
45
75
45
75
55
85
45
75
45
75
12
Table 3 - Recommended upper limits for construction noise received in
industrial or commercial areas for all days of the year
Time period
Duration of work
Typical duration
0730-1800
1800-0730
Leq(dBA)
75
80
Short-term
duration
Leq(dBA)
80
85
Long-term duration
Leq(dBA)
70
75
Where:
"Short-term"
means construction work at any one location for up to 14
calendar days;
"Typical duration" means construction work at any one location for more than
14 calendar days but less than 20 weeks; and
"Long-term"
means construction work at any one location with a
duration exceeding 20 weeks.
For this project there is unlikely to be any site where the construction work
exceeds 14 calendar days so the short term duration noise levels in the above
tables are applicable for the construction work.
13
3
EXISTING NOISE ENVIRONMENT
To determine the noise effects of the proposed transmission line the existing
noise environment has been measured on two occasions at representative
houses along the route. Two sites were monitored over a full night and all other
sites were monitored over typically 15 minutes and excluded the effects of
passing traffic or any other transient noise in the area.
From these measurements the existing noise environment can be compared with
the proposed construction noise and the noise levels as predicted for the
operation of the transmission line. As a guide, if the predicted noise is below the
existing noise environment it is unlikely there will be any adverse noise effects
for the receiver.
However, it needs to be kept in mind that a noise with a
distinctive audible characteristic is able to be heard at levels below the
background sound (L95 or L90) so being below the existing noise environment
does not necessarily make a sound inaudible.
For a sound 10dB above the existing noise environment it will appear to be
approximately doubled the loudness of the original sound and an increase of
20dB four times as loud. An increase of noise will not necessarily result in an
unreasonable noise and an example of this is if the existing noise environment is
25dB at night time and the level is increased to 35dB there will be a clearly
noticeable increase to the noise. However, based on NZS 6802 a level of up to
45dB will allow undisturbed sleep so any increase in level up 45dB at night time
should be acceptable there will be undisturbed sleep. In the case of the District
Plans this project is subject to a level of 40dB is adopted at night time to provide
a factor of safety. The meaning of the noise terms used in this report are set out
in Appendix A.
All short term measurements were undertaken with a Brüel & Kjær 2250 Handheld Analyser Platform with Sound Level Meter Software BZ 7222, Frequency
Analysis Software BZ 7223, Logging Software BZ 7224.
The equipment has
been calibrated by the equipment manufacturer and the re-calibration is next due
14
in September 2015. The long term measurements were undertaken using ARL35
data loggers, which also have current calibration certificates from the
manufacturer. All equipment was field calibrated before and after measurements
using a Brüel & Kjær 4230 calibrator.
All measurements were undertaken in
accordance with the requirements of NZS 6801:2008 Acoustics - Measurement
of Environmental Sound.
As shown on Figure 2 the monitoring was undertaken at Colgan Street and
Station East Road in a Residential Zone in the Waipa District Plan where distant
traffic controlled the noise environment.
The existing noise levels at Colgan
Street between poles 11 and 13 are 47/35dBA L10/L95 during the daytime,
48/34dBA L10/L95 in the evening and 39/31dBA L10/L95 at night time.
In Station East Road, between poles 13 and 14A, the noise levels were
measured at 50/36dBA L10/L95 during the daytime, 43dBA/35BA L10/L95 in the
evening and 43/30dBA L10/L95 at night time.
Colgen Street
Station East Road Figure 2. Colgan Street and Station East Road, Te Awamutu
15
In Pokuru Road (Figure 3) near poles 25 and 26, the noise levels were measured
at 62/43dBA L10/L95 during the daytime, 57/35BA L10/L95 in the evening with a
background sound of 28dBA L95 at night time and the L10 varying between a low
of 35dBA and the typical high of 55dBA, the exact level being dependent on the
traffic flow.
Pokuru Road
Figure 3. Pokuru Road
Te Mawhai Road (Figure 4) is in a rural zone in the Waipa District Plan. Birds
controlled the noise level at this site at 45/34dBA L10/L95 during the daytime and
traffic controlled in the evening with a level of 39/32dBA L10/L95. At night time
the level was typically 36/27dBA L10/L95
Te Mawhai
Figure 4. Te Mawhai Road
16
Figure 5 shows the Te Kawa Road, Hinewai Road and Te Oro Road measurement
positions located in a rural zone near poles 71, 72, 72A and 75.
At the Te Kawa Road site near poles 72 and 72A the daytime level was
controlled by bird noise at 61/31dB LAeq /LA90, dropping to 33/24dB LAeq /LA90
during the evening and 31/23dB LAeq /LA90 at night time.
In Hinewai Road opposite pole 71 the daytime level was 41/37dB LAeq/LA90 and
37/24dB LAeq/LA90 in the evening. During the night time period the background
sound was measured as low as 23dB LA90. The LAeq level varied from a low of
24dB, 1dB above the background sound, to a typical upper level of 60dB from
passing traffic.
At the Te Oro Road position opposite pole 75 the daytime measurements were
41/37dB LAeq/LA90, 40/25dB LAeq/LA90 for the evening measurements dropping to
27/21dB LAeq/LA90 at night time.
Hinewai Road
Te Kawa Road Te Oro Road Figure 5. Hinewai, Te Kawa and Te Oro Roads
17
At Ormsby Road (which is in the Otorohanga District) the measurement position
is located in the Urban Services Effects area opposite pole 141 and as shown on
Figure 6 the site overlooks State Highway 3 (SH3). Daytime levels at this site
are 54/48dB LAeq/LA90 and evening levels were 54/43dB LAeq/LA90. The night time
levels were measured at 48/38dB LAeq/LA90.
Ormbsy Road
Figure 6. Ormsby Road, Otorohanga
The site on Fare Vue Lane opposite pole 151 is shown on Figure 7. Although
there is some screening from a bank between Fare Vue Lane and SH3, the noise
from traffic on SH3 controls the level at this location.
The daytime
measurements were 52/43dB LAeq/LA90, the evening levels 52/41dB LAeq/LA90 and
night time levels 48/40dB LAeq/LA90.
18
Fare Vue Lane
Figure 7. Fare Vue Lane, Otorohanga
As shown on Figure 8 the two monitoring sites were selected on Waitomo Caves
Road, which is in a Rural Zone in the Waitomo District Plan.
At site 1 the
daytime levels were 63/47dBA L10/L95. During the evening the levels dropped
slightly to 61/42dBA L10/L95 and at night time to 39/35dBA L10/L95. These levels
do not include any immediate traffic noise effects but are controlled by traffic on
SH3.
Waitomo Caves Rd Site 1 Waitomo Caves Rd Site 2
Figure 8. Waitomo Caves Road
19
At site 2 on Waitomo Caves Road the daytime levels were 66/48dBA L10/L95.
During the evening the levels dropped slightly to 58/43dBA L10/L95 and at night
time to 40/36dBA L10/L95. These levels are also controlled by traffic on SH3.
In addition to the above, unattended measurements were undertaken throughout
the night time at 15 minute intervals at Pokuru Road (Figure 3) and Hinewai
Road (Figure 5) to establish how the noise environment changes at night time.
As shown on Figure 9 the noise at Pokuru Road on a calm night had a
background sound (L95) of typically 28dBA with the L10 at a low of typically
35dBA. This level increased to typically 55dBA with the influence of passing
traffic. The single event sound (Lmax) was 86dBA from passing traffic and as low
as 43dBA without the influence from traffic.
Figure 9. Night Time Noise - Pokuru Road
At the Hinewai Road site the background sound (L95) is typically 23dBA with the
L10 being as low as 24dBA without any traffic in the area and up to 60dBA with
passing traffic. The single event sound (Lmax) was 80dBA from passing traffic
and as low as 38dBA without the influence from traffic as shown on Figure 10.
20
Figure 10. Night Time Noise - Hinewai Road
The existing noise at night time along the proposed transmission line route is
typical of that expected in any urban and rural environment. When near a busy
road the levels are controlled by traffic noise although as the traffic flow drop of
significantly in the early hours of the morning the background sound drops to 23
– 30dBA increasing to typically 38dBA near the busier roads.
During the
daytime the background increases to typically 40dBA and up to 44dBA where
there is a busy road nearby.
The L10/Leq level is typically 10dBA above the
background sound when clear of the busier roads. For the dwellings near a busy
road the L10/Leq levels increase to typically 60dBA during the daytime.
The only other significant noise in the environment is from trains passing through
a number of the sites.
passenger trains.
There are typically five daily freight trains and two
Figure 11 shows a freight train passing at 12m from the
measurement position.
21
%%Projec t 302 - F as t Logged in C alc ulat ions
Ev ent
Sound
dB
120
110
100
Locomotive
Wagons
90
80
70
60
50
40
09: 36: 00 PM
09: 36: 30 PM
LAeq
C urs or: 27-J ul-11 09: 35: 39 PM. 600 - 09: 35: 39 PM. 700
09: 37: 00 PM
09: 37: 30 PM
09: 38: 00 PM
LAeq=47. 8 dB
Figure 11. Freight Train at 12m
As shown on Figure 11 the duration of the train noise above 50dBA was just
under 2.5 minutes when at 12m from the train. It is noted that while the train
noise will be clearly heard by any neighbours near to the rail line Clause 1.2.1
NZS6802:2008 Acoustics - Environmental Noise states:
This Standard does not apply to the assessment of sound where the
source is within the scope of, and subject to, the application of other
New Zealand acoustical Standards, except as provided for in 1.2.3 and
1.2.4. In particular, assessment of specific sources of sound including
road or rail transport ... requires special techniques that generally are
outside the scope of this Standard.
However, in the same way traffic noise influences the existing noise environment
train noise also impacts on the existing noise environment.
22
4
CONSTRUCTION WORK
During the construction period the maximum hours expected to be worked are
between 7:00am – 6:00pm Monday to Saturday although all noisier work when
near a noise sensitive location will be restricted to 7:30am – 6:00pm when the
higher construction noise limits as set out in Section 2 of this report are
applicable. That is 75dBA Leq and 90dBA Lmax.
The following sets out the typical work to prepare the site, to install the poles
and to string the lines.
Some sites will need a farm type access track to be formed and this will be
undertaken where necessary using a 14 - 20t excavator and truck such as that
shown on Figure 12.
The sound power (LWA) of this machine operating was
measured at 104dB.
Figure 12. Komatsu PC150 15t Excavator
23
The other relatively noisy plant to be used would be a standard road truck
arriving and departing the construction sites. It has been assumed in the noise
predictions that a typical truck has a sound power (LWA) of 105dB.
Once the site has been leveled it is expected that for most of the sites reinforced
concrete piles will be used to support the poles. The holes will be drilled with a
hydraulically driven auger off a 4 x 4 drilling rig or tracked excavator such as
shown on Figure 13. The noise from the auger will be partly dependent on the
material being drilled and how the material will be cleared from the auger, but
this machine has the potential to generate a sound power level of 106dB LWA.
Figure 13. Example of an Auger to Drill Holes for the Foundations
During the construction of the foundations a concrete truck with a sound power
level of 112dB (such as shown on Figure 14) will used to place the concrete.
24
Figure 14. Concrete Truck
The poles need to be fitted together using hydraulic rams to squeeze the sections
together. The power pack will be driven off a small generator, which will have a
sound power of approximately 94dB LWA. Most of the poles will be able to be
erected with a Hiab but some of the larger ones will require a crane, possibly a
rough terrain crane of about 100 – 200kW such as shown on Figure 15. This
crane has a sound power level of typically 105dB LWA.
Figure 15. Typical Crane to place Poles
25
Stringing the lines will require running blocks to be installed on each pole using
bucket trucks and then ropes pulled out, then the wires pulled out under tension.
There will be a pulling winch (such as shown on Figure 16) at one end with a
tension machine approximately 2km away at the opposite end of the line. The
process for each major pull will take about a week.
The noise from these
winches is typically 104dB LWA.
Figure 16. Pulling Winch
To assist with construction work in difficult locations a helicopter is likely to be
used for some tasks. In the analysis an AS350 has been assumed.
26
5
PREDICTED CONSTRUCTION NOISE
5.1
Prediction Methodology
Based on the above the noise from construction has been predicted at the closer
houses and business activities along the route for the various stages of the
construction process. These predictions have been based on the noise levels as
set out above and taking into account the noise reduction due to the distance
between the plant operating and received and any localised screening effects
there is from the topography.
As the distance from the source (such as an excavator) increases so the level
received decreases.
The reduction in the noise is calculated based on the
equation 20 x log(R1/R2) where R1 is the distance to the source and R2 the
distance to the receiver position.
The reduction of noise from any screening effects is been based on the change
in path length the sound must travel over a barrier to arrive at the receiver
position, the greater the change in path length the greater the reduction due to
the barrier. As a guide, when just losing line of sight to the noise source there
will be a 5dBA sound reduction and as the screening effects of the barrier
increases the reduction will quickly increase to 10dBA.
However, to achieve
more than 12 – 14dBA reduction due to a barrier is generally impractical.
5.2
Predicted Noise Levels at Occupied Sites
The sites close to poles 1 – 10 (Figure 17) include commercial buildings with the
closest house being on the corner of Factory Road and Alexandra Street.
Assuming the building opposite pole 7 has an office at the front of the building
the noise levels at 1m from the façade of the office and the closest house, which
is at a similar distance, will be:
Prepare site Prepare foundations
Place pole
74dBA Leq
79dBA Leq
72dBA Leq
27
The other poles are all further from the buildings so the noise at those buildings
will be lower than given for pole 7.
Figure 17. Location of Poles 1 – 10
Figure 18 shows the location of poles 11 – 14A with the closest house to pole
13 being 78m and 19m to pole 14A.
The construction noise that will be
experienced at these houses is:
Pole 13
Prepare site Prepare foundations
Place pole
61dBA Leq
66dBA Leq
59dBA Leq
Pole 14A
Prepare site Prepare foundations
Place pole
73dBA Leq
78dBA Leq
71dBA Leq
72dBA
71dBA
67dBA
84dBA
83dBA
79dBA
Lmax
Lmax Lmax Lmax Lmax Lmax 28
Figure 18. Location of Poles 11 – 14A
Figure 19 shows the location of poles 24 and 25 with the closest house to pole
24 being 195m and 100m to pole 25.
The construction noise that will be
experienced at these houses is:
Pole 24
Prepare site Prepare foundations
Place pole
53dBA Leq
58dBA Leq
51dBA Leq
Pole 25
Prepare site Prepare foundations
Place pole
59dBA Leq
64dBA Leq
57dBA Leq
64dBA
63dBA
59dBA
70dBA
69dBA
65dBA
Lmax
Lmax Lmax Lmax Lmax Lmax 29
Figure 19. Location of Poles 24 – 25
Figure 20 shows the location of poles 34, 35 and 36 with the closest house to
pole 34 being 130m, 140m to pole 35 and 55m to pole 36. The construction
noise that will be experienced at these houses is:
Pole 34
Prepare site Prepare foundations
Place pole
57dBA Leq
62dBA Leq
55dBA Leq
Pole 35
Prepare site Prepare foundations
Place pole
56dBA Leq
61dBA Leq
54dBA Leq
Pole 36
Prepare site Prepare foundations
Place pole
64dBA Leq
69dBA Leq
62dBA Leq
68dBA
67dBA
63dBA
67dBA
66dBA
62dBA
75dBA
74dBA
70dBA
Lmax
Lmax Lmax Lmax Lmax Lmax Lmax Lmax Lmax 30
Figure 20. Location of Poles 34, 35 and 36
Figure 21 shows the location of poles 70, 71 and 72 with the closest house to
pole 70 being 153m, 44m to pole 71 and 45m to pole 72. The construction
noise that will be experienced at these houses is:
Pole 70
Prepare site Prepare foundations
Place pole
55dBA Leq
60dBA Leq
53dBA Leq
Pole 71
Prepare site Prepare foundations
Place pole
66dBA Leq
71dBA Leq
64dBA Leq
Pole 72
Prepare site Prepare foundations
Place pole
66dBA Leq
71dBA Leq
64dBA Leq
66dBA
65dBA
61dBA
77dBA
76dBA
72dBA
77dBA
76dBA
72dBA
Lmax
Lmax Lmax Lmax Lmax Lmax Lmax Lmax Lmax 31
Figure 21. Location of Poles 70 – 72
Figure 22 shows the location of poles 72A, 73 and 75 with the closest house to
pole 72A being 35m, 130m to pole 73 and 18m to pole 75. The construction
noise that will be experienced at these houses is:
Pole 72A Prepare site Prepare foundations
Place pole
68dBA Leq
73dBA Leq
66dBA Leq
Pole 73
Prepare site Prepare foundations
Place pole
57dBA Leq
62dBA Leq
55dBA Leq
Pole 75
Prepare site Prepare foundations
Place pole
74dBA Leq
79dBA Leq
72dBA Leq
79dBA
78dBA
74dBA
68dBA
67dBA
63dBA
85dBA
84dBA
80dBA
Lmax
Lmax Lmax Lmax Lmax Lmax Lmax Lmax Lmax 32
Figure 22. Location of Poles 72A, 73 and 75
Figure 23 shows the location of poles 140A, 140B and 141 with the closest
house to pole 140A being 120m, 135m to pole 140B and 55m to pole 141. The
construction noise that will be experienced at these houses is:
Pole 140A Prepare site Prepare foundations
Place pole
57dBA Leq
62dBA Leq
55dBA Leq
Pole 140B
Prepare site Prepare foundations
Place pole
56dBA Leq
61dBA Leq
54dBA Leq
Pole 141
Prepare site Prepare foundations
Place pole
64dBA Leq
69dBA Leq
62dBA Leq
68dBA
67dBA
63dBA
67dBA
66dBA
62dBA
75dBA
74dBA
70dBA
Lmax
Lmax Lmax Lmax Lmax Lmax Lmax Lmax Lmax 33
Figure 23. Location of Poles 140A, 140B and 141
Figure 24 shows the location of poles 142, 144, 145 and 146 with the closest
business buildings to pole 142 being 30m, 55m to pole 144, 60m to pole 145
and 78m to pole 146. The construction noise that will be experienced at these
businesses is:
Pole 142 Prepare site Prepare foundations
Place pole
69dBA Leq
74dBA Leq
67dBA Leq
Pole 144
Prepare site Prepare foundations
Place pole
64dBA Leq
69dBA Leq
62dBA Leq
Pole 145 Prepare site Prepare foundations
Place pole
63dBA Leq
68dBA Leq
61dBA Leq
34
Pole 146
Prepare site Prepare foundations
Place pole
61dBA Leq
66dBA Leq
59dBA Leq
Figure 24. Location of Poles 142 - 146
Figure 25 shows the location of poles 151 and 152 with the closest house to
pole 151 being 34m and 63m to pole 152. The construction noise that will be
experienced at these houses is:
Pole 151 Prepare site Prepare foundations
Place pole
68dBA Leq
73dBA Leq
66dBA Leq
Pole 152
Prepare site Prepare foundations
Place pole
63dBA Leq
68dBA Leq
61dBA Leq
79dBA
78dBA
74dBA
74dBA
73dBA
69dBA
Lmax
Lmax Lmax Lmax Lmax Lmax 35
Figure 25. Location of Poles 151 and 152
Figure 25 shows the location of poles 201, 202, 203 and 204 with the closest
house to pole 201 being 103m, 205m to pole 202, 170m to pole 203 and 95m
to pole 204. The construction noise that will be experienced at these houses is:
Pole 201 Prepare site Prepare foundations
Place pole
59dBA Leq
64dBA Leq
57dBA Leq
Pole 202
Prepare site Prepare foundations
Place pole
53dBA Leq
58dBA Leq
51dBA Leq
Pole 203 Prepare site Prepare foundations
Place pole
54dBA Leq
59dBA Leq
52dBA Leq
Pole 204
Prepare site Prepare foundations
Place pole
59dBA Leq
64dBA Leq
62dBA Leq
70dBA
69dBA
65dBA
64dBA
63dBA
59dBA
Lmax
Lmax Lmax 65dBA
64dBA
60dBA
70dBA
69dBA
65dBA
Lmax
Lmax Lmax Lmax Lmax Lmax Lmax Lmax Lmax 36
Figure 26. Location of Poles 201 – 204
5.3
Helicopter Noise
It is expected that a helicopter may be used in areas where access is difficult and
these areas are all well clear of residential developments. However, the effects
of helicopter use have been assessed in case the helicopters are used for
stringing the lines.
One of the noisier types of helicopter that are likely to be used is an AS350
helicopter such as shown on Figure 27.
Figure 27. AS350 Helicopter
37
Helicopter
noise
is
assessed
in
accordance
with
the
requirements
of
NZS6807:1994 Noise Management and Land Use Planning for Helicopter
Landing Areas and this Standard is adopted in the Waipa District Plan. Neither
the Otorohanga nor Waitomo District Plans reference NZS6807 so there is no
helicopter noise control in either of these Plans. It is noted that NZS 6802:1991
Assessment of Environmental Sound excludes its use to assess helicopter noise
as in clause 1.2 NZS6802 states:
Assessment of specific sources of transportation, construction, and
impulsive sound (such as gunfire, and blasting), requires special
measurement and assessment techniques that are generally outside the
scope of this Standard, but within the scope of others.
Clause 1.1 of NZS6807 states:
This Standard is intended to apply to helicopter landing areas used for
ten or more flight movements in any month, or where flight movements
are likely to result in a maximum sound level (Lmax) exceeding 70dBA at
night-time or 90dBA during day-time in any residential zone or within
the notional boundary of any rural dwelling.
The assessment of helicopter noise is based on the total noise energy from
helicopter movements over the 24 hour period with a 10dBA penalty included for
any night time flights (10:00pm – 7:00am). No night time flights are proposed
for any helicopter use at this site.
In order to understand the noise from helicopters Figure 28 shows the noise from
an AS350 helicopter measured at typically 50m from the helicopter taking off
then returning to land, idle for approximately 40 seconds before taking off again.
%Proj ec t 110 - Fas t Logged i n Cal c ul ati ons
Event
dB
100
idle Sound
Return, land, idle & take‐off
Take‐off 90
80
70
60
50
1 minute 40
30
10:21:00 a.m.
10:22:00 a.m.
10:23:00 a.m.
LAeq
Curs or: 14/02/2012 10:20:52 a.m..200 - 10:20:52 a.m..300
10:24:00 a.m.
10:25:00 a.m.
10:26:00 a.m.
LAeq=71.5 dB
Figure 28. AS350 Helicopter Noise at 50m
10:27:00 a.m.
38
From this information the noise of a helicopter operating at a given location can
be predicted.
As a guide, and taking the above as an example, a helicopter
operating at 100m from a house could be there for approximately 5 minutes of
hovering or 4 take-offs and 4 landings to give 50dBA Ldn. Inspection of the route
indicates there is unlikely to be any use of a helicopter within 100m of a dwelling
and more likely the minimum distance would be more than 500m. Similarly, it is
not proposed to locate a helipad near a dwelling.
5.4
Summary of Results
Based the equipment expected to be used to undertake the construction work
the predicted noise at all of the noise sensitive locations along the proposed
transmission line route will be within the requirements of NZS 6803:1999
Acoustics - Construction Noise.
This assumes all construction work near a
dwelling, or other occupied building, is undertaken within the time period when
the higher noise levels are permitted in NZS6803. That is, between 7:30 am –
6:00pm Monday to Saturday.
39
6
OPERATION NOISE
The electrical operation of the proposed line has the potential to create audible
noise from corona and surface discharging along the line insulation. In addition,
there is the potential of wind generated noise (Aeolian noise).
Each of these
phenomena is addressed below.
Under normal conditions the conductors themselves will be silent when in use.
However, there is the potential of wind generated noise and noise from corona
and surface discharging along the conductors insulation.
In order to address
these aspects of noise, field tests have been undertaken to determine the
potential noise effects.
However, as checking could only be undertaken in a
limited number of environmental conditions a search of technical literature
available on the effects of corona and surface electrical discharging has been
used to assist with the assessment of these phenomena.
6.1
Corona Discharge
Corona is generated when the electrical voltage stress in the air close to
energised components is so high that the air breaks down and becomes
conductive.
It causes electrical energy losses, and an audible 'hissing' or
'buzzing’ noise. Because of the energy loss associated with both these effects it
is in the interests of the line designer and owner of the line to minimise them.
Corona noise is generally only audible under wet conditions such as rain or fog.
The Electric Power Research Institute (EPRI) publication AC Transmission Line
Reference Book: 200 kV and Above, Third Edition, sets out formula to predict
noise from power lines, which give a level of approximately 25dBA at 20m from
the lines. However, these prediction techniques are for line voltages of at least
double that proposed for this line so calculations using this method need to be
treated with caution.
40
In order to check the noise from corona measurements were undertaken during
calm conditions and light rain at the base of a recently installed 110kV line in the
central Auckland area. When at the base of a pole at a quiet site there was no
audible noise from the insulators. A second check of a 110kV line at Te Papapa,
also in Auckland, gave similar results.
It is noted that in both cases the
background sound was between 28 – 30dBA, which would have masked any
noise below approximately 20dBA.
6.2
Surface Discharge
Surface discharging results when conducive pollutants deposited on the surface
of the insulators cause electricity to leak along the external surface.
The
accompanying noise is usually described as a ‘crackling’ or ‘frying’ sound.
The level of surface discharge is affected by the type of insulator used, the
insulator design, and contamination from the surrounding environment.
The insulation to be used on the overhead line is state-of-the-art composite
insulation consisting of a high strength fibreglass core rod, jacketed with weather
sheds of silicon rubber.
The silicone rubber material acts to suppress surface
discharging and results in an insulator that is very quiet.
The pollution level is critical to the operational noise level of the insulation. In
particular, any location near the sea coast and where the prevailing winds carry
sea salt inland can be expected to be noisier in operation, due to the increased
leakage current down the conductive layer of damp surface salt. The overhead
link is in a location in which little or no surface pollution is expected.
6.3
Wind Noise
Wind generated noise in the conductors is the other potential noise that
may be experienced. Potential problem areas of wind noise can come from
the insulators, conductors and components with hollow sections.
41
In the past, there have been problems with tones generated by porcelain
insulation. These problems have now been completely eliminated by new
designs which are wind tunnel tested prior to purchase to ensure they are
quiet at all wind speeds including severe storms. The insulators to be used
on this line are to be manufactured from modern composite materials.
These materials have the advantage that they are inherently resistant to
wind noise generation because of the soft flexible nature of the silicon
rubber outer covering.
Wind noise from the conductors, or moaning, is mainly associated with
large conductors of 30mm or more in diameter.
proposed for this line is 18.8mm in diameter.
The conductor that is
This same conductor has
been in use for many years in other locations and has proven to be
particularly quiet in the wind.
In addition to the above, site visits have been undertaken to a number of areas in
various wind conditions. Based on these visits it is apparent that wind generated
noise does not generally commence until the wind speed exceeds approximately
15m/s.
Monitoring of wind noise in the conductors of a 110kV transmission line was
undertaken at a site in Christchurch with the wind blowing at an estimated
20m/s and gusts as high as approximately 30m/s. As a guide, the wind was
sufficient to give the conductors a distinctive outward sway.
Noise is difficult to record in these conditions due to the wind effects on both
the measuring equipment and the noise in trees etc.
When the noise was
measured in these conditions, well clear of any large trees (there was a hedge
nearby) and on open flat terrain, the noise in the conductors was audible when
located directly beneath the line.
The main noise on this occasion was
considered to be from the general environment rather than the conductors.
42
By moving some distance along the line a measuring location was found adjacent
to a 4 - 5m high earth berm located 3 - 4m upwind of the transmission lines.
This enabled measurements to be carried out beneath the conductors at a
location sheltered from the wind although the lines themselves were in the same
relatively strong wind as set out above. From this measurement and after taking
into account the wind generated noise, the actual noise from the wind in the
conductors has been calculated at 43dBA directly under the conductors.
The
noise from the line could not be measured as the background sound (L95) was
42dBA in the sheltered location with the measured L10 value being 48dBA. In
the more exposed location the background sound measured 47dBA and the L10
measured 57dBA.
Assuming a similar wind speed, the noise around any adjacent house is expected
to be at least equal to the noise level in open conditions, and more likely to be
noisier due to the noise the wind would generate around the house itself.
When the effects of the background sound resulting from the wind are strong
enough to generate any noise in the conductors, the noise generated around
other features, such as trees and houses, is expected to control the overall noise
level.
In stronger winds the noise in the transmission lines will increase. However, the
background noise will also increase and as a result it is predicted that the relative
noise between the background sound and line generated noise will remain about
the same.
As set out above, noise from the conductors would be relatively low at any
residential / notional boundary of the houses along the route and below the
background sound as measured along the route when excluding any effects of
wind noise around the houses.
43
7
CONCLUSIONS
The existing noise environment has been measured in calm weather conditions at
a position representative of all of the closer houses to the proposed poles for a
15 minute period on two different days and one night plus throughout the night
at two sites.
The noise level during the construction of the proposed 110kV transmission line
has been predicted based on the noise from typical construction equipment plus
the effects of using a helicopter to assist with difficult construction sites and
possible stringing of the lines. Based on the predicted construction noise level
the requirements of NZS 6803:1999 Acoustics - Construction Noise will be
complied with at all sites along the route.
For the majority of the time there will not be any noise from the new
transmission line. However, in wet and/or windy conditions the operation noise
can include the effects of corona, surface discharging along the line and wind
generated noise. An analysis of this noise plus field measurements of existing
lines shows that while there may be some noise from these sources the effects
for the neighbours will be minimal and well within the requirements of the
relevant District Plan.
When taking into account the existing noise environment, the predicted noise
levels and the requirements of the District Plan, the noise effects of a proposal to
construct and operate an 110kV transmission line between the substations at Te
Awamutu and Hangatiki will be less than minor for the residents along the route.
*
*
*
44
APPENDIX A
Guide to Noise Terms
The following sets out an explanation of the acoustic terms that will be referred
to throughout this report.
The aim is not to necessarily provide technical
definitions, but to enable a basic understanding of what is meant.
The setting of specific noise levels to control any adverse effects does not
necessarily mean that noise will not be heard. Audibility depends on the level of
a sound, the loudness of the background sound and any special frequency
composition or characteristics that a sound may have.
Research suggests that a small number of people (approximately 10%) will find
any noise not of their own making unacceptable.
Conversely, there are
approximately 25% of the population that are essentially immune to any noise.
Neither of these two extremes is normally designed for.
In establishing the
appropriate noise levels the aim is to try and represent the typical expected
community reaction, this will generally be approximately 90% of the people.
In order to reflect community response to noise it is necessary to establish a
measure that reflects our attitude to the sounds that we hear.
Due to the
variability of many sounds (level, tone, duration, intrusiveness above the existing
sound, etc) no single descriptor will totally describe the potential community
reaction to a sound. For this reason there are a number of terms that need to be
understood.
dBA
The basic unit to quantify a sound is the decibel. The A-weighted sound level, or
dBA, is a good environmental noise descriptor because of the similarity between
A-weighting and the frequency response of the human ear at moderate sound
levels. It can also be measured easily. However, it provides no indication of
tonal frequency components or unusual frequency distributions of sound that
45
may be the cause of annoyance.
Where appropriate, this must be assessed
separately.
We can hear a change in sound pressure that varies from 1 (taken as the
threshold of hearing) through to 1,000,000,000,000 (taken as the threshold of
pain). In order to bring these numbers to a more manageable size a logarithmic
scale is normally adopted.
This reduces the above values to 0 and 12
respectively. The decibel is then described as 10 times the logarithm of the ratio
of the pressure level of interest, to a reference pressure level. Thus the scale
becomes 0 to 120dBA.
Some typical subjective changes in noise levels are:
A change of 3dBA is just perceptible
A change of 5dBA is clearly perceptible
A change of 10dBA is twice (or half) as loud
Because we use a logarithmic scale care must be taken when adding sound
levels. Two equal noise sources raise the level of one source by 3dBA. It takes
10 equal noise sources to raise the level of one source by 10dBA. ie 60dBA +
60dBA = 63dBA and 60dBA x 10 = 70dBA.
Maximum Sound Level (Lmax , LAmax)
This unit equates to the highest (maximum) sound level for a defined
measurement period.
It is adopted in NZS6802:1991 Assessment of
Environmental Sound, mainly as a method of protecting sleep.
L10
The sound level which is equalled or exceeded for 10% of the measurement
time.
This level is adopted in NZS6802:1991 Assessment of Environmental
Sound to measure intrusive sound. This level may be considered as the average
maximum sound level.
46
Background Sound L95 or L90
The sound level which is equalled or exceeded for 95% (or 90%) of the
measurement period.
This level may be considered as the average minimum
sound level and is the component of sound that subjectively is perceived as
continuously present.
Equivalent Sound Level (Leq, LAeq)
The Leq may be considered as the continuous steady noise level that would have
the same total A-weighted acoustic energy as a fluctuating noise over the same
time period.
Day Night Level, Ldn
The day/night level (Ldn) is defined as the time-average sound level in decibels (re
20µPa) over a 24 hour period from midnight to midnight) with the addition of
10dB to night time levels during the period from midnight to 07.00 hours and
from 22.00 hours to midnight, to take account of the increased annoyance
caused by noise at night.
Ambient Sound
The ambient sound is normally used to describe the total noise environment.
The ambient sound is often measured as the 24 hour Leq, which is an average
value over the 24 hour period.
Shorter times are often used, such as the
daytime period
Notional Boundary
The notional boundary is defined as a line 20 metres from the facade of any rural
dwelling or the legal boundary where this is closer to the dwelling.
Figure A1 shows a noise trace with the relationship of Lmax, L10, L95 and Leq
values when including all events over the 15 minute measurement period and
Figure A2 some typical noise levels.
Figure A1
Figure A2