J 01138R1 Environmental Noise Assessment: Anaerobic Digestion

72 Pages·2012·3.49 MB·English

Project: J 01138R1
Environmental Noise Assessment:
Anaerobic Digestion (AD) Plant

Consultants: Sound Planning Ltd
48 Windermere Way
Farnham
Surrey
GU9 0DE

Client: AcrEnergy Ltd

Prepared by: D. M. Thomas

Signed:

D. M. Thomas MSc A.M.I.O.A
Acoustic Consultant

Dated: Monday 26 November 2012

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CONTENTS

Section Page Number

1 BACKGROUND 3, 4

2 ASSESSMENT CRITERIA 5, 6

3 METHODOLOGY 7 - 9

4 RESULTS 9

5 DISCUSSION 10

6 NOISE LEVEL PREDICTIONS 10 - 13

7 NOISE MITIGATION 13 - 15

8 CONCLUSIONS 16 - 17

APPENDIX 1 – Glossary of Terms 18 - 21

APPENDIX 2 – Site Location 22, 23

APPENDIX 3 – Site Layout Plan 24 - 28

APPENDIX 4 – Photographs 29, 30

APPENDIX 5 – Background Levels – Deerleap 31 - 43

APPENDIX 6 – Background Levels – ‘Cedars’ 44 - 69

APPENDIX 7 – Noise Control Equipment 70 - 72

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1.0 BACKGROUND

1.1 The proposal is for the construction of an Anaerobic Digestion Biomass Plant to be
constructed on Coast Hill Farm, Damphurst Lane, Wotton, Dorking, Surrey RH5
6QH.

1.2 The site is located within the Rural Area and would constitute the provision of a
source of renewable energy.

1.3 The proposed site falls under the jurisdiction of Mole Valley District Council and
should be assessed against relevant standards and guidance, including PPS 22:

1.4 Planning Policy Statement 22: Renewable Energy1

1.4.1 For the purposes of this PPS, renewable energy covers those energy flows that
occur naturally and repeatedly in the environment – from the wind, the fall of
water, the movement of the oceans, from the sun and also from biomass.

1.4.2 Renewable technologies may generate small increases in noise levels (whether
from machinery such as aerodynamic noise from wind turbines, or from
associated sources – for example, traffic).

1.4.3 Local planning authorities should ensure that renewable energy developments
have been located and designed in such a way to minimise increases in
ambient noise levels. Plans may include criteria that set out the minimum
separation distances between different types of renewable energy projects and
existing developments.

1.5 PPS22 evaluates noise from traffic and plant operations as an ‘industrial
development’ and therefore considers BS 4142 an applicable standard2.

1.6 Noise Emissions from a Biogas Plant3:

1.6.1 Noise emissions can result mainly due the operation of the CHP (Combined
Heat and Power Unit) and other equipment/activities on an AD Plant site.

1 PPS 22 – Renewable Energy. Office of the Deputy Prime Minister (ODPM). Crown Copyright 2004.
2 Planning for Renewable Energy – A Companion Guide to PPS22. ODPM. Crown Copyright 2004.
3 Source: EnviTec Biogas.
3
1.6.2 CHP Primary Noise Sources:

 Air and Exhaust Fans
 Mixture Cooler
 Emergency Cooler
 Exhaust Stack

1.6.3 The operation of the biogas plant is a full-time, 24/7. The CHP unit will
operate over a full 24 hour period hence noise reduction is by mechanical
means.

1.7 The location of the proposed technical building (including CHP and ancillary plant) is
to the west of the proposed site; maximising the distance between plant and noise
sensitive receivers.

1.8 Sound Planning has been commissioned to evaluate noise emissions from the
Anaerobic Digestion Biomass Plant; conducting a noise assessment and evaluation in
accordance with appropriate standards and guidance.

1.9 Vehicular Movements4

1.9.1 Transportation of the feedstock (silage and farm yard manure) does not
increase existing traffic in the local area. The feedstock is now diverted to the
AD plant instead.

1.9.2 An internal roadway providing access to and from all areas of the site enters
the site from the west off the A25; the site entrance is over 400m away from
the nearest properties in The Rookery and Deerleap Bungalow.

1.9.3 Agricultural vehicles deliver silage to site over a period of four weeks, once a
year in September / October. Over the period from November to March
agricultural vehicles deliver farm yard manure (FYM) about twice a month.
The other half of the year agricultural vehicles deliver FYM about once every
two months.

1.9.4 The digestate from the plant (the highly nutritious fertiliser) is transported off
site and spread to surrounding agricultural land during the months February to
August period in line with current NVZ regulations.

1.9.5 Outside of these times access to site is used for operation and maintenance of
the plant by one passenger car per day.

4 Source: AcrEnergy.
4
2.0 ASSESSMENT CRITERIA

2.1 In order to evaluate potential noise disturbance for localised noise sensitive dwellings
the environmental noise assessment should adhere to BS 4142: 19975.

2.1.1 Noise from industrial sources radiated to residential areas is usually assessed
against British Standard BS 4142: 1997, `Method for rating industrial noise
affecting mixed residential and industrial areas’. This standard describes a
method for assessing whether the `specific noise’ from an industrial source is
likely to give rise to complaints from residents of the adjacent dwellings.

2.1.2 The `specific noise’ levels are determined outside dwellings. The specific
noise level is determined for reference time periods of 1 hour for the daytime
(07:00 to 23:00) and 5 minutes for the night time (23:00 to 07:00). Tonal or
impulsive characteristics of a noise are likely to increase the scope for
complaints and this taken into account by adding +5dB to the specific noise
source level to obtain the `Rating Level’. BS 4142: 1997 requires that the
Rating Level of a noise is compared with the existing background noise: (L
A90,
).
T

2.1.3 Guidance given in the standard states that if the difference between the Rating
Level and the background noise (L ) is +5dB, it would be considered as
A90, T
being of marginal significance. This is usually taken as being an acceptable
situation, as it is a reasonable compromise between the requirements of
commerce and the amenity of residents.

2.1.4 A difference of around +10dB or more indicates that complaints are likely.
Most Local Authorities use a difference of +10dB as the point at which they
will take action against the organisation producing the noise.

2.1.5 If the Rating Level is more than 10dB below the background noise this is a
positive indication that complaints are unlikely.

2.1.6 BS 4142: NOTE: “For the purpose of this standard, background noise levels
below about 30dB and rating levels below 35dB are considered to be very
low”.

5 British Standard 4142: 1997 – Method for rating industrial noise affecting mixed residential and industrial
areas. © BSI 1997. ISBN 0 580 28300 3.
5
2.2 Other relevant assessment criteria which could be considered:

2.2.1 World Health Organisation: Guidelines for Community Noise6

The W.H.O document covers a wide array of environmental noise issues and
appropriate assessment criteria in relation to acceptable noise levels in various
situations. The Guidelines look at appropriate assessment methodology and
statistical parameters which are most relevant when looking at particular noise
sources; whether they cause annoyance and to what degree.

Specific LAeq Time Base LAF max
Critical Health Effects
Environment (dB) (hours) (dB)
Serious annoyance,
55 16
Outdoor Living daytime evening

Area Moderate annoyance,
50 16
daytime evening

Speech intelligibility and
Dwelling,
moderate annoyance, 35 16
Indoors
daytime and evening
Sleep disturbance, night
Inside Bedrooms 30 8 45
time

Sleep disturbance,
Outside
window open (outdoor 45 8 60
Bedrooms
values)

2.2.2 British Standard 8233: 19997

BS 8233: 1999 is the Sound insulation and noise reduction for buildings –
Code of practice. The standard introduces its own internal and external design
standards, including a ‘Good’ and ‘Reasonable’ design range.

Design Range L
Aeq, T
Criterion Typical Situations dB
Good Reasonable
Reasonable
Living Rooms 30 40
resting/sleeping
Bedrooms 30 35
conditions
For a reasonable standard in bedrooms at night, individual noise events (measured with F
time-weighting) should not normally exceed 45dBL .
Amax

6 World Health Organisation – Guidelines for Community Noise 1999.
7 British Standard 8233: 1999 – Sound insulation and noise reduction for buildings – Code of practice.
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3.0 METHODOLOGY

3.1 Background Noise Assessments:

3.1.1 Background noise measurements have been conducted over extended time
periods at positions representative of the nearest noise sensitive residential
receivers.

3.1.2 Measurements were undertaken in accordance with BS 74458 and BS 41429.
The sound level meter was Type 1 – details provided in 3.4.1.

3.1.3 Microphones were located 1.5m above ground level and 3.5m away from any
reflective surfaces; contained within weatherproof housing and connected to
an external power source (battery kit). See APPENDIX 4 – Photographs.

3.1.4 The A-weighted L , L and L descriptors were measured using the Fast
90 eq max
(F) setting, and logged periodically every 5 minutes.

3.1.5 ‘Deerleap Bungalow’ (property on Coast Hill Lane, closest to Deerleap
Bungalow) measurements were taken over the period 11:25 hours Monday
29th October – 12:30 hours Wednesday 31st October 2012 and should be
considered representative of background levels at Deerleap Bungalow.

3.1.6 ‘Cedars’ measurements were taken over the period 15:40 hours Thursday 8th
November – 14:20 hours Monday 12th November 2012.

3.2 Noise Emissions10

3.2.1 The CHP is located in a sound proofed cabin within the CHP room of the
Technical Building. The technical building design may vary depending upon
the site, but generally would be of a steel framed construction, clad using a
combination of profiled steel sheeting, composite panels and concrete block
work to internal walls. The CHP runs at a sound level of 117 dB(A) within
the sound proofed cabin.

8 British Standard 7445-1: 2003 – Description and measurement of environmental noise. © BSI 1997. ISBN 0
580 19736 0.
9 British Standard 4142: 1997 – Method for rating industrial noise affecting mixed residential and industrial
areas. © BSI 1997. ISBN 0 580 28300 3. 
10 Source: EnviTec Biogas.
7
The construction of the sound proofed cabin is such that the noise from the
CHP is reduced to a level of 73 – 76 dB(A) at 1m from the sound cabin, within
the technical building.

3.2.2 The air management for supplying and removing air from the CHP room are
equipped with sound absorbers. Readings taken at site gave figures of
54dB(A) from the inlet grille and 59dB(A) from the exhaust grille at 1m.

3.2.3 On sites when the heated water is not to be used, a cooling and emergency
cooling system will be installed. These table radial cooling systems have a
rated sound level of 57dB(A) at a distance of 10m. The cooler is positioned
outside but adjacent to the technical building, measuring 1.12m to the top with
a clearance of 0.6m to the underside.

3.2.4 The exhaust air from the CHP is discharged through exhaust stack positioned
outside the technical building. The exhaust stack is fitted with a muffler
reducing the noise emission to a level of 65dB(A) at a distance of 10m.

3.3 Noise Calculations

BS 4142: 1997 – Evaluation of noise rating levels and the ‘likelihood of complaints’
in overall dB(A) levels.

3.4 Instrumentation

3.4.1 Sound Level Measurement Equipment

Serial UKAS
Equipment Make Model Class
Number Calibration
CEL 4640
Field Calibrator Casella 1 077948
110/1 (29/3/11)

3.4.2 The Sound Level Meter (SLM) was field calibrated before and after the on-site
noise assessments. A minor deviation of 0.1 dB was detected (1kHz) after the
Deerleap Bungalow assessment.

UKAS accredited calibration certificates are available on request.

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3.4.3 Other Equipment

Serial UKAS
Equipment Make Model Class
Number Calibration
Environmental

Tripod
Wind/Weather

Shield
Laser
Leica Disto A5 1073750838
Measurer
Digital
Samsung
Camera
Battery
Casella
Kit

4.0 RESULTS

4.1 Background Noise Levels

Lowest Background Level
dB L
A90, 5mins
Measurement
Location Daytime Night Time
07:00 – 23:00 23:00 – 07:00
Deerleap Bungalow 25.0 22.5
Cedars 33.0 32.5

4.2 BS 414211: NOTE: “For the purpose of this standard, background noise levels below
about 30dB and rating levels below 35dB are considered to be very low”.

4.3 The prevailing wind direction for both extended background noise assessments was
south westerly (although periods included alternative wind directions); assisting
propagation from the direction of the proposed AD plant.

11 British Standard 4142: 1997 – Method for rating industrial noise affecting mixed residential and industrial
areas.
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5.0 DISCUSSION

5.1 The BS 4142 calculation method of predicting industrial noise should be used for
predicting AD Plant noise. Equipment sound pressure levels are only available as
overall levels without frequency noise data.

5.2 Time corrections should not be applied as AD Plant could operate for continual 60
minute periods during the day and in excess of 5 minutes during the night time (23:00
– 07:00 hours).

5.3 Acoustic features can be defined as noise emitted which contains distinguishable,
discrete continuous notes (whine, hiss, screech, hums) and/or distinct impulses
(bangs, clicks, clatters, thumps)12. BS 4142 imposes a 5dB penalty (rating level) to
noise sources containing acoustic features.

5.4 The Exhaust Stack is constructed in double skin stainless steel with a thin mineral
layer between13.

5.5 Sound pressure levels provided by EnviTec do not posses directivity information.

5.6 Noise levels at the nearest Noise Sensitive Receivers (NSR’s) should be evaluated at
first floor level during the night time period i.e. 3.5m above ground level.

6.0 NOISE LEVEL PREDICTIONS

6.1 As discussed single (or one third) octave sound level data is not available, and
therefore attenuation through propagation will be based on overall levels in
accordance with BS 4142 methodology.

6.2 Distance Attenuation

6.2.1 EnviTec Biogas has provided sound pressure level noise data at distances from
individual components of which the AD Plant comprises.

6.2.2 In consideration of the distances to the nearest noise sensitive receivers, the
noise sources should be considered ‘point sources’ whereby distance
attenuation should be calculated by spherical divergence:

12 BS 4142 – Paragraph 8: ‘Rating Level’, Page 6.
13 Source: EnviTec Biogas.
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