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© Hunter Acoustics Ltd

Blast Vibration Monitoring

Bryn Quarry

Gelligaer

Independent Acoustic

Consultancy Practice

5100/VIB2


Project: Bryn Quarry

Site Address: Gelliargwellt Farm

Gelligaer

Caerphilly

CF82 8FY

HA Reference: 5100/VIB2

Date: 02/06/2020

Client: Bryn Aggregates

Gelliargwellt Farm

Gelligaer

Caerphilly

CF82 8FY

Contact: [email protected]


Project: Bryn Quarry, Gelligaer

HA Ref: 5100/VIB2 Page 2 of 21 02/06/2020

ISSUE / REVISION

DOCUMENT CONTROL

Hunter Acoustics has prepared this report for Bryn Aggregates (“the Client”), under the agreed

terms of appointment for acoustic consultancy services. This report is for the sole and specific

use of the Client, and Hunter Acoustics shall not be responsible for any use of this report or

its contents for any purpose other than that for which it was prepared and provided.

Should the Client wish to distribute copies of this report to other parties for information, the

whole report should be copied, however no professional liability or warranty shall be extended

to other parties by Hunter Acoustics in this connection without the explicit written agreement

thereto by Hunter Acoustics.

Rev Date

0 02 June 2020

Filename 20.5100_VIB2

Description First issue

Prepared by: Checked by:

Name Meirion Townsend

BSc(Hons) MIOA

Paul McGrath

BSc(Hons) MIOA

Signature



HA Ref: 5100/VIB2 Page 3 of 21 02/06/2020

TABLE OF CONTENTS

1. INTRODUCTION ................................................................................................... 4

2. PLANNING GUIDANCE & STANDARDS .............................................................. 5

MTAN1 ............................................................................................................... 5

British Standard 6472-2:2008 ............................................................................. 8

British Standard 5228-2:2009 ........................................................................... 10

British Standard 7385-2:1993 ........................................................................... 11

Planning Condition ........................................................................................... 11

3. BLAST VIBRATION MONITORING .................................................................... 12

Procedures ....................................................................................................... 12

Meteorological Conditions ................................................................................ 13

Measurement Equipment ................................................................................. 13

Results ............................................................................................................. 14

4. DISCUSSION ...................................................................................................... 15

Planning Limits ................................................................................................. 15

Damage to Buildings ........................................................................................ 15

- ACOUSTIC TERMINOLOGY ............................................................. 16

- DIAGRAMS, GRAPHS AND TABLES ............................................... 17

- DRAWING LISTS............................................................................... 21



HA Ref: 5100/VIB2 Page 4 of 21 02/06/2020

1. INTRODUCTION

An extension of quarrying operations is proposed at Bryn Quarry, Gelliargwellt Farm,

Gelligaer, Caerphilly, CF82 8FY.

Blasts at the quarry generally occur once or twice per calendar month and are always

during daytime hours.

The proposed extension would reduce the distance from blasts to the nearest residential

receptors from approximately 450m to 300m.

Previous monitoring at the nearest receptors indicates peak particle velocity (ppv) limits

in the planning conditions are easily met for the existing quarrying operations.

This report details results of blast monitoring at a representative distance of 300m for

the proposed quarry extension.

Results are compared against the current planning condition limits and the risk of

damage to property is assessed.

Appendix A explains acoustic terminology used in this report.



HA Ref: 5100/VIB2 Page 5 of 21 02/06/2020

2. PLANNING GUIDANCE & STANDARDS

MTAN1

Minerals Technical Advice Note (Wales) 1: Aggregates

The Welsh Government’s Minerals Planning Policy (Wales) – Minerals Technical Advice

Note (Wales) 1: Aggregates (MTAN1) contains the following guidance in relation to

quarry blasting;

“71. The objective of the buffer zone is to protect land uses that are most sensitive

to the impact of mineral operations by establishing a separation distance

between potentially conflicting land uses. Research44 has indicated that

people living close to mineral workings consider dust to be the main impact of

mineral extraction and any processing operations, followed by traffic, and noise

and vibration from blasting. After careful consideration, including consultation

with a number of interested and informed parties, the Welsh Assembly

Government takes the view that the following minimum distances should be

adopted unless there are clear and justifiable reasons for reducing the distance.

An example may be that, because of other means of control, there is very

limited impact from the mineral extraction site.

Mineral Extraction Type Minimum Distance

Sand and gravel (and others 100 metres

where no blasting is permitted)

Hard rock quarries 200 metres

The buffer zone should be defined from the outer edge of the area where

extraction and processing operations will take place, including site haul roads,

rather than the site boundary, as there may be land within site boundaries

where mineral activities are limited or no operations are proposed so that the

impact of the proximity of such land is negligible.

Where mobile plant is likely to be used it will usually be necessary to control by

planning conditions the location of the operational area where plant may

operate in order to maintain the buffer zone and thus protect amenity.”

“78. Production blasting can result in impacts that extend well beyond the extraction

site. This is likely to cause concern to neighbours and results from:

• ground vibration –these are stress waves generated within the ground by the

detonation of explosive charges. Sometimes these are reported by individuals

but usually the levels of vibration generated by mineral workings are well below

those required to cause structural damage to properties;



HA Ref: 5100/VIB2 Page 6 of 21 02/06/2020

• air overpressure –a pressure wave is formed in the atmosphere by the

detonation of explosives, this consists of energy manifested as audible (noise)

and inaudible (concussion);

• noise – audible noise is atmospheric pressure variations at frequencies

greater than 20Hz (hertz);

• dust; and,

• fly-rock – the projection of material from the blast site to any area beyond the

designated danger zone.”

“79. Ground vibration: It is often difficult to reconcile the needs of efficient and

economic mineral extraction with the comfort and amenity of neighbours,

particularly where quarries are located close to buildings that are sensitive to

vibration such as residential properties. Research50 has shown that the

vibration levels at which complaints are made varies significantly and that long

established sites with a good relationship with neighbouring communities are

far less likely to attract complaints from local residents.

Mineral planning authorities and site operators have accepted the need for

more definitive advice to ensure a more consistent approach to controlling

ground vibration and responding to complaints from neighbours. This is

therefore set out below.”

“80. Ground vibration is recorded in terms of particle velocity with the maximum or

peak value measured in 3 orthogonal directions at any one location – so-called

longitudinal, vertical and transverse. The measurement of peak particle velocity

(ppv) is the accepted standard for recording vibration levels together with

frequency content. The typical range of ground vibration frequency for surface

mineral workings is 5 to 40 Hz with values predominantly from 20 to 30 Hz for

hard rock quarries. Although sensitivity to vibration varies between individuals,

a person will generally become aware of blast induced vibration at around 1.5

mms-1 ppv (in some circumstances at levels as low as 0.5 mms-1 ppv). Public

concern often relates to the potential for vibration to cause damage to property.

British Standards51 specify guide values to preclude damage to various building

types from blast induced ground vibration. Cosmetic damage, or hairline cracks

in plaster or mortar joints, should not occur at vibration levels lower than 20

mms-1 ppv at a frequency of 15Hz and lower than 50 mms-1 ppv at 40Hz and

above. Vibration levels from production blasting measured at residential

properties rarely, if ever, approach the levels necessary to cause even cosmetic

damage but can have an impact on the amenity of the surrounding area. It is

important that proposals for new or extended aggregates extraction should

include an assessment of the impact of ground vibration in consultation with

the Health and Safety Executive and the operator.”



HA Ref: 5100/VIB2 Page 7 of 21 02/06/2020

“81. Air overpressure: Because air overpressure is transmitted through the

atmosphere, meteorological conditions such as wind speed and direction, cloud

cover and humidity will all affect the intensity of the impact. In view of this

unpredictability, planning conditions to control air overpressure are unlikely to

be enforceable. This is not a reason for doing nothing and careful blast design

should be able to resolve excessive levels of air overpressure. Such details are

controlled by quarry regulations52 which impose requirements relating to health

and safety at quarries.”

“83. Planning conditions relating to the control of blasting should only: relate to those

aspects of environmental management that are under the control of the

operator; should be directly relevant to environmental issues; and, should not

be in conflict with existing health and safety legislation. Consequently, planning

conditions should provide for the:

• acceptable days for blasting operations: unless there are exceptional

circumstances such as a safety emergency, blasting should take place at

regular times within the working week, that is, Mondays to Fridays. Blasting on

Saturday mornings should be a matter for negotiation between the operator

and the MPA taking into account the views of any nearby residents. No blasting

should take place at any other time, that is, Saturday afternoons, Sundays,

Bank or National holidays;

• acceptable times of blasting operations: blasting should only take place

between the hours of 10.00am and 16.00pm, except when there is an

emergency in the interests of safety;

• maximum level of ground vibration at vibration sensitive locations: ground

vibration as a result of blasting operations should not exceed a peak particle

velocity of 6 mms-1 ppv in 95% of all blasts measured over any 6 month period,

and no individual blast should exceed a peak particle velocity of 10 mms-1 ppv;

• approval of a scheme by which air overpressure is managed and mitigated

through careful design of blasting operations;

• approval of a scheme of vibration monitoring so that compliance within set

limits can be adequately demonstrated by the operator at any time.”

“84. Vibration from blasting may have an adverse impact on structures of historic

importance that may be of fragile construction, such as listed buildings or

ancient monuments. It may be necessary for developers to provide specialist

advice to demonstrate adequate protection for such structures prior to

development proposals involving blasting operations being approved.”



HA Ref: 5100/VIB2 Page 8 of 21 02/06/2020

50The Environmental Effects of Production Blasting from Surface Mineral Workings,

DETR, (Vibrock Ltd), 1998

51BS 7385: Evaluation and Measurement for Vibration in Buildings Part 2: 1993 Guide

to damage levels from groundborne vibration. British Standards Institute

52The Quarries Regulations 1999 SI No.1999/2024

British Standard 6472-2:2008

Guide to evaluation of human exposure to vibration in buildings Part 2: Blast-

induced vibration

Table 1 of BS 6472-2:2008 gives the following maximum satisfactory magnitudes of

vibration with respect to human response for up to three blasts events per day;

Air overpressure is also discussed in this standard. Section 5.1 states;



HA Ref: 5100/VIB2 Page 9 of 21 02/06/2020

“Whenever blasting is carried out energy is transmitted from the blast site in the form

of airborne pressure waves. These pressure waves comprise energy over a wide range

of frequencies, some of which are at frequencies higher than 20 Hz and are, therefore,

perceived as sound. The majority of the airborne energy is carried at frequencies below

20 Hz and hence is inaudible to the human ear, but can be sensed as concussion or

pressure. It is the combination of the sound and concussion that is known as air

overpressure.”

“Air overpressure can excite secondary vibrations at audible frequencies in buildings

and it is often this effect that gives rise to adverse comments from the occupiers. There

is no known evidence of structural damage occurring in the United Kingdom as a result

of air overpressure levels from blasting associated with mineral extraction. The highest

levels normally measured in the United Kingdom are generally less than 1% of the

levels known to cause structural damage [10].

The propagation velocity of air overpressure is at the speed of sound in air, i.e. about

340 m·s-1 and therefore it travels significantly slower than its associated ground-borne

vibration.

This results in the air overpressure always arriving after the ground vibration onset and

by several seconds if large distances are involved. Nevertheless, it is not readily

possible for an observer to differentiate between these two sources and their

respective effects and so any air overpressure significantly adds to the overall

subjective blast experience.”

Section 5.2 discusses the difficulty of measuring air overpressure “If measurements

include frequencies of less than 2 Hz they can be greatly distorted by even the slightest

pressure changes, which can be caused by the gentlest of wind or people walking past

the microphone”.

Section 5.3 states how “Accurate prediction of air overpressure is almost impossible

due to the variable effects of the prevailing weather conditions and the large distances

often involved.”

Section 6.1 goes on to say, “Vibration associated with blasting has the potential to

pose different problems from other sources of vibration, particularly since the vibration

event is often accompanied by air overpressure. Many of the complaints about

vibration from blasting might be due, either in part or entirely, to this air overpressure

exciting the elements of the building, rather than groundborne vibration. Subjective

separation of ground vibration and the effects of air overpressure is difficult.

NOTE Experience shows that the fear of property damage has a more significant effect

on human response than the effect of the vibration on the person directly, although

discussion of this matter is beyond the scope of this British Standard.



HA Ref: 5100/VIB2 Page 10 of 21 02/06/2020

In residential situations comments about vibration are often made when the

magnitudes are only slightly in excess of the perception levels. In the case of blasting,

adverse comments might be made even below perception thresholds due to the

influence of the air overpressure.”


Code of practice for noise and vibration control on construction and open sites

Part 2: Vibration

Line 2 in Table B.2 and Figure B.1 from BS5228-2 2009 shows Threshold Transient

Vibration Guidance Values for Cosmetic Damage of residential buildings.

“Minor damage is possible at vibration magnitudes which are greater than twice those

given in Table B.2, and major damage to a building structure can occur at values

greater than four times the tabulated values. Definitions of the damage categories are

presented in BS 7385-1:1990, 9.9.”



HA Ref: 5100/VIB2 Page 11 of 21 02/06/2020

It should be noted that the proposed limits (for cosmetic damage) are above the

threshold of perception; i.e. vibration levels below this could be felt by occupiers and

may still cause annoyance.

The standard advises: “...the threshold of perception being typically in the PPV range

of 0.14mm/s to 0.3mm/s…”

“..Vibration nuisance is frequently associated with the assumption that, if vibrations can

be felt, then damage is inevitable: however, considerably greater levels of vibration are

required to cause damage to buildings and structures.

Important buildings that are difficult to repair might require special consideration on a case by case basis. A building of historical value should not (unless it is structurally unsound), be assumed to be more sensitive.”


Evaluation and measurement for vibration in buildings Part 2: Guide to damage

levels from groundborne vibration

Much of the damage related information quoted in BS 5228-2:2009 referenced in section

2.3 above is taken from BS 7385-2:1993. Table B.2 and Figure B.1 quoted in BS 5228-

2:2009 are taken directly from Table 1 and Figure 1 of BS 7385-2:1993.

Planning Condition

Condition 9 of the planning consent for the quarry (12/0570/FULL dated 23/07/2012

granted by Caerphilly CBC) states;

“09. Blasting shall be designed so that the ground vibration measured as peak

particle velocity (PPV) in any one of three orthogonal planes shall not exceed

4mm per second in 95% of all blasts carried out over any six month period

and no individual blast shall exceed a PPV of 8mm per second as measured

at any sensitive receptor.

REASON: To safeguard amenity interests.”

The above planning condition limits are therefore tighter than those outlined in

paragraph 83 of MTAN1 and those in table 1 of BS 6472-2:2008.



HA Ref: 5100/VIB2 Page 12 of 21 02/06/2020

3. BLAST VIBRATION MONITORING

Procedures

Vibration was monitored from 1317hrs on Thursday, 28 May 2020, with the blast

occurring at 1331hrs.

Peak particle velocity (PPV) was logged in all three axis (radial, tangential & vertical) at

20ms intervals over the blast period.

Figure 3.1 – Site Plan Showing Monitoring Location

Site plan in Figure 3.1 above shows the quarry and monitoring position used, namely:

Table 3.1 – Continuous Monitoring Location Details

Position Description

B

Located on large, heavy concrete block, sunk a minimum of 300mm into

a stone track in the field, approximately 300m east of the blast.

Chosen as a representative location of likely ppv levels at nearest

receptors for the quarry extension.

A photograph of the monitoring set up can be seen in Figure B.2 of Appendix B.



HA Ref: 5100/VIB2 Page 13 of 21 02/06/2020

Meteorological Conditions

Approximate weather conditions are shown in time history graph in Figure B.1 of

Appendix B.

To summarise, the weather conditions during the monitoring period were dry and hot,

with an occasional breeze, in a north-easterly direction.

Measurement Equipment

The following measurement equipment was used during the surveys:

Table 3.2 – Vibration Monitoring Equipment List

Make Description Model Serial Number

Last Calibrated Certificate No.

Svantek Type 1 - Sound & Vibration Data Logger

SVAN 948

6962 20 August 2019 TCRT19/1656 / TCRT19/1653

Dytran Tri-axial Accelerometer

3233A 158 20 August 2019 TCRT19/1656

Dytran Cable 6483A09 - 20 August 2019 TCRT19/1656

Note: Copies of traceable calibration certificates for all equipment are available upon

request.



HA Ref: 5100/VIB2 Page 14 of 21 02/06/2020

Results

Time history graphs in Figure B.3 of Appendix B shows the peak particle velocity (PPV)

trace measured during monitoring of the blast. Results are summarised in the table

below;

Table 3.3 – Blast Monitoring Results at Position B

Blast Date

Maximum

Tangential

PPV (mm/s)

Maximum

Radial PPV

(mm/s)

Maximum

Vertical PPV

(mm/s)

Peak True

Resultant

Particle Velocity

(mm/s)

28/05/2020 2.9 3.1 1.9 4.2

Results therefore fall below both the 4mm/s 95% limit and the 8mm/s individual blast

limit in any of the three orthogonal planes set out in the planning condition (peak true

resultant particle velocity value included for information only).

Vibration was felt under foot with the blast audible in the distance.

RMS velocity spectra are included in Figure B.4 of Appendix B for the highest PPV

measured. The dominant third octave frequency band for the blast was 10Hz.



HA Ref: 5100/VIB2 Page 15 of 21 02/06/2020

4. DISCUSSION

Planning Limits

Groundborne vibration levels measured at approximately 300m away are shown to fall

below the limits in any of the three orthogonal planes outlined in the planning condition.

It should be noted that limits in the planning condition are tighter than those outlined in

paragraph 83 of MTAN1 and those in table 1 of BS 6472-2:2008.

Damage to Buildings

PPV results measured fall well below the 4mm/s limit for 95% of blasts in a 6 month

period and the 8mm/s limit for any individual blast. The dominant frequency measured

during this blast was in the 10Hz third octave band.

With the lowest PPV magnitudes likely to cause cosmetic damage according to BS 5228-

2 Table B.2 (mirrored in MTAN1) being 15mm/s at 4Hz rising to 20mm/s at 15Hz and

then 50mm/s at 40Hz, blasts at Bryn Quarry are not likely to cause any minor or major

damage to residential buildings based on monitoring undertaken to date.

“Minor damage is possible at vibration magnitudes which are greater than twice those

given in Table B.2, and major damage to a building structure can occur at values greater

than four times the tabulated values.”



HA Ref: 5100/VIB2 Page 16 of 21 02/06/2020

- ACOUSTIC TERMINOLOGY

Human response to noise depends on a number of factors including loudness, frequency

content and variations in level with time. Various frequency weightings and statistical indices

have been developed in order to objectively quantify ‘annoyance’.

The following units have been used in this report:

Air overpressure: A pressure wave in the atmosphere produced by a

detonation of explosives. Air overpressure consists of both

audible (noise) and inaudible (concussion) energy. It is

measured in pascals and usually reported in dB(lin).

ppv: The peak particle velocity (ppv) measured in mm/s.

Peak true resultant

particle velocity:

The true resultant particle velocity is obtained by vectorily

summing the three orthogonal components coincident with

time. The peak true resultant particle velocity is the

maximum value of the true vector sum obtained during a

given time interval.



HA Ref: 5100/VIB2 Page 17 of 21 02/06/2020

- DIAGRAMS, GRAPHS AND TABLES

Figure B.1 – Approximate Weather History for Thursday, 28 May 2020

Note: Taken from www.wunderground.com - weather station IHENGO1 located in Hengoed [Elev 794 ft, 51.666° N, 3.262° W]



HA Ref: 5100/VIB2 Page 18 of 21 02/06/2020

Figure B.2 – Photograph of Monitoring Setup



HA Ref: 5100/VIB2 Page 19 of 21 02/06/2020

Figure B.3 – Peak Particle Velocity Measured at Approximately 300m from Blast (Position B) on Thursday, 28 May 2020

0

0.5

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Pea

k P

arti

cle

Vel

oci

ty (

mm

/s)

Date | Time (hh:mm:ss:ms)

Tangential Radial Vertical



HA Ref: 5100/VIB2 Page 20 of 21 02/06/2020

Figure B.4 – RMS Velocity Spectra Measured for Highest PPV during Quarry Blast on Thursday, 28 May 2020 (13:31:38.000)

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4.00 Hz 5.00 Hz 6.30 Hz 8.00 Hz 10.0 Hz 12.5 Hz 16.0 Hz 20.0 Hz 25.0 Hz 31.5 Hz 40.0 Hz 50.0 Hz 63.0 Hz 80.0 Hz 100 Hz 125 Hz

RM

S V

elo

city

(m

m/s

)

Frequency

Tangential Radial Vertical



HA Ref: 5100/VIB2 Page 21 of 21 02/06/2020

- DRAWING LISTS

The following John Perkins Consulting Engineers drawings have been used in our

assessment;

Table C.1 – Drawing List

Drawing Title Drawing Number Rev Date

Distances between the quarry and

residential areas – 50m stand off

from the pylons

BAL-NQE-2017-50m-017 D 15/07.2019

Figure C.1 – Excerpt from JCPE Distances Drawing Referenced Above

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