HISTORICAL RESEARCH REPORTResearch Report TM/75/01

1975

Pneumoconiosis Field Research: Environmental conditions at Coventry Mine 1973/74 Maynard RC, Annis R

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Pneumoconiosis Field Research: Environmental conditions at Coventry Mine 1973/74

Maynard RC, Annis R This document is a facsimile of an original copy of the report, which has been scanned as an image, with searchable text. Because the quality of this scanned image is determined by the clarity of the original text pages, there may be variations in the overall appearance of pages within the report. The scanning of this and the other historical reports in the Research Reports series was funded by a grant from the Wellcome Trust. The IOM’s research reports are freely available for download as PDF files from our web site: http://www.iom-world.org/research/libraryentry.php

HISTORICAL RESEARCH REPORTResearch Report TM/75/01

1975

ii Research Report TM/75/01

Report No. TM/75/1 Not for Publication

Pneumoconiosis Field

Research: Environmental

Conditions at Coventry

Mine, 1973/74

R. C. Maynard and

R. Annis

December 1975

Environmental Branch,Institute of Occupational Medicine,Roxburgh Place,Edinburgh, EH8 9SU(Tel. No. 031-667 5131)

Report No. TM/75/1

I N S T I T U T E O F O C C U P A T I O N A L M E D I C I N E

PNEUMOCONIOSIS FIELD RESEARCH

ENVIRONMENTAL CONDITIONS AT COVENTRY MINE, 1973/74

by

R. C. Maynard and R. Annis

CONTENTS

SUMMARY •

1. INTRODUCTION

2. COVENTRY MINE

2. 1 Mine details

2. 2 Ventilation and dust suppression

2. 3 Manpower and occupational groups

3. SAMPLING AND EVALUATION

3. 1 Sampling programme

3. 2 Sampling method and evaluation

4. RESULTS AND DISCUSSION

4. 1 Faceworkers

4. 2 Non- face workers

4. 3 Environmental summary

4.4 Relationship between control point and face concentrations

4. 5 Total dust measurements

5. RECOMMENDATIONS

REFERENCES

TABLE 6

^ Report No. TM/75/1

I N S T I T U T E O F O C C U P A T I O N A L M E D I C I N E

PNEUMOCONIOSIS FIELD RESEARCH

• ENVIRONMENTAL CONDITIONS AT COVENTRY MINE, 1973/74

byR. C. Maynard and R. Annis

SUMMARY

This report tabulates respirable dust concentrations and compositions atCoventry Mine for the period April, 1973 to March, 1974. Informationregarding methods of working, outputs and manpower is also given.

3The mine had a mean coalface respirable dust concentration of 3. 7mg/m .The mean ash content of the respirable dust was 40. 2 peg cent and the meanquartz content 4. 1 per cent (concentration of 0. 15 mg/m ).

Total dust concentrations are tabulated and, on average, for undergroundsamples were nine times higher than the respirable dust concentrations.

PNEUMOCONIOSIS FIELD RESEARCH ' . /-;-'V;vV/."

ENVIRONMENTAL CONDITIONS AT COVENTRY MINE, 1973/74 •"'"' /•

by

R. C. Maynard and R. Annis

1. INTRODUCTION

This report describes the environmental measurements made at CoventryMine from April, 1973 to March, 1974. Routine dust measurements weremade with the M.R.E. gravimetric dust sampler, Type 113A. Thestratification of manpower and method of sampling, mainly by volunteerinstrument carriers, were as previously described (Street, 1972). Sur-face group concentrations were sampled by P. F. R. Investigators.

3 *Dust concentrations, in mg/m , are presented in a series of face charts,showing the values for different sites and occupations. The compositionof the dust is also given.

The report gives general information about the mine, with additional noteson explosives and travelling times. The relationship between concentra-tions at control points and on faces is considered. The ratio of total torespirable dust concentrations is also noted.

2. COVENTRY MINE

2. 1 Mine details

2. 1. 1 Location Coventry Mine is situated at the southern extremity ofthe Warwickshire Coalfield, about three miles north of the centre of Coventry.

2.1. 2 Seams worked As previously, all the coal came from the Warwick-shire Thick Coal Seam, (16:350)*.

2. 1. 3 Quarterly Outputs April - June 1973: 116 880 ton

July - Sept. 1973: 70 938

Oct. - Dec. 1973: 73 625

Jan. - Mar. 1974: 33 838

Output was lower than for 1972, which averaged 130 000 tons per quarter.The Miners' strike took place in the last quarter, Jan. - Mar. 1974.

2. 1.4 Faces For the first seven months there were three productionfaces, in November 1973, South 84's face closed and for the remainingfive months the mine had only two faces. Full details of the faces aregiven in the face summary charts, Tables 1-3.

2. 1. 5 Explosives The type of explosive used at the faces was Dynagex(Type P5); during the course of a week approximately 4. 5kg was used atsites 1 and 7 on.each face. In coal headings, about 1. 5kg a week was used,mainly Dynagex but also a small proportion of Polar Ajax.

*National Seam Correlation Code

2. 2 Ventilation and dust suppression

Average air quantities, temperatures and relative humidities for thefaces are shown in Table 1-3.

Dust suppression measures, sprays, were applied to power loadersand conveyor systems.

vMartindale Type !U! respirators were available at the Mine and approx--imately 40 per cent of the faceworkers carried them.

' • .2. 3 Manpower and occupational groups

The mine population at the end of the dust year was approximately 1000, 'of whom 230 were classified as faceworkers, 520 as non-faceworkersunderground and 250 as surface workers.

The number of occupational groups at Coventry was as follows:

Face groups 12

Elsewhere underground groups 4 • .

Surface groups 4

During the period under review two occupational groups, face preparers(pre-production ) (E4l) and surface welders (S3) were opened.

3. SAMPLING AND EVALUATION

3. 1 Sampling programme

Most of the. underground sampling was carried out by volunteer instrumentcarriers. The surface samples were taken by P. F. R. investigators.Volunteer carriers took.instruments to their working places at fortnightlyintervals. Every shift was supervised but due to the distance betweendistricts it was not possible to inspect every instrument on all shifts.However, men not visited during the sampling period were questionedat the end of the shift to obtain the relevant working place details.

A check on the possible bias between the volunteer carrier and 'randomcollier1 sampling techniques was made, as in 1972/73, with the Haulageand Mineral Transport group, E39, (Maynard & Annis, 1974) but nobias was detected.

The total number of samples taken during the year was 571; 189 with face-workers, 344 with elsewhere underground workers and 38 with surfaceworkers. The high preponderance of samples taken with elsewhere under-ground groups reflects the difficulty of finding suitable volunteers amongstface workers.

3. 2 Sampling method and evaluation

The methods of sampling and evaluation of dust concentrations were aspreviously described (Street, 1972).

The compositional analyses of samples from each occupational groupwas undertaken at the Institute of Occupational Medicine as describedby Harrison, (1975).

RESULTS AND DISCUSSION

4. 1 Faceworkers

Tables 1-3 show the mean concentrations of respirable dust for faceoccupational groups for each quarter of the year, together with themean ash and quartz concentrations for the year. All groups wereadequately sampled except F247, Face-end men, S7l, for which onlyone sample was obtained. This is a long term group and has beenadequately covered in previous years.

4. 2 Non-faceworkers

Table 4 summarises the respirable dust, ash and quartz concentra-tions for non-faceworkers groups.

4. 2. 1 Development workers These 38 samples include 19 samplestaken with Coal Headers, and 19 samples taken with Haulagemen,Tradesmen and Officials in this type of location,

4. 2. 2 Elsewhere underground workers The five samples 'taken withthe newly opened group, E41, Face Preparers (pre-production) on newfaces., are included in this environment (Table 6). The details shownin Table 4 indicate that occasional very high concentrations were re-ported for these out bye groups, usually associated with conveyor transferpoints, bunkers and pit bottom operations.

TABLE 4

Mean Respirable Dust Concentrations - Non-faceworkers

Occupation

Coal Headers F83

Repairers E33

Haulage Workers E39

Tradesmen (Outbye) E40

Face Preparers „.,.( Pre-production)

Surface : Pit Top SO •

Coal Preparation 31

Boilermen 32

Surface Welders S3

Sample Mean Concentration (mg/n )

Respirnble Dust

Mean

3,8

2oTF

2«6

4.9

2.0

0.2

0.7

0.4

0.5

No. Obs.

19 .

169

165

6

16

7

12

14

4

Range

Oo7- 609

0.4-10.9

0.2-25.7

3.0- 603

0,5- 4o2

0.1- Oo3

0,3- 1.6

Oo2- 0.9

0.3- 0,8

Ash

U33

1.32

1.17

1.82

1.03

Quartz

OJ3

0.14

0.12

0.16

0.09

TABLE 1 FACE SUMMAHY

Scam N.C.R. Foco P.-co Typo of Face length Heighti Scam Corr. Coal IVir.k % Starting Finishing ~~ : 77 * ~

CcxJc Codis Carbon Date Date single umt- . — longwall U5n 1.97m

advancingWarwickshire Thick Coal 16:350 802 82 Dec. 1968 Nov. 1973

'. Sito

Method of Working

Machine Details

Oust Suppression

| Supports

l-—— —————— — ...- — .Site

j Occupation(Filllnc Shifts)

1 O.G.S.N.\ ' ^ > r - ' " "'" • -- • L

J Number of M:n In Occupation:.! Group

1 Mean Kcsplrabla ht Quarter

j Du,t 2nrJ Qucrtcr

| Concentration 3rd Quarter

1 for Occupation _ «h Quarter

I iTig/rn1 Yearii

; Mc.-.n fcrrij/lo Corcontntlon

far Sito rr>^/n>*

i A:h Coticcntratlon (np/ni*i} Quart* Concentration rag/en'

Situ,- . . " - ' - •- --. -•. •' — r __.

«

Occupationj (Prcpsrallon Shifts)j O.G.S.N.

1 Number of Men In Occujnliop.r.l Group

MC.VI f'.cspirablc Du5t Concentration

1 for Occupation mri/'T'9

' Moan Sample Concentrationij for Sito rn£/ms

As It Coi-.cc-ntnUon mg/rn'j

; Qu.'r'.Jt Concentration mj/m*

- INTAKE FACE-END '

Bored, fired, ripped, arched and packed.

2 Crawley conveyors.

.

3 section bolted arches: . 4.3n x 3.7uDovrty props and bars under rip.

1 . . . .Rippers

F237 .

8

3.0(8)

^

3.0 (8)1.3*3.0(8)

. 1.3* • . „ . . . . •1.Z3

0.09•

„

. :

1 ' """ {. Average sampling time on face was-6,61 hr.

(,-&(2. Average sampling time at control point was -8r30 hr.

3- .

( ) Murfib.:r cf Sa.'nplt

CHAivr SW 84's FACE

Shift Cydo Aycivtfo Koof Seam ' Floor . Averaro

filling, per Shift Coal Coal ' Coal Quantitypreparation "•" •"•" •" """"Filling . 230 ton . ^/s

FACE

Power loaded. .

Two 112kw disc shearers.

External sprays on machines.

Wild 50 goal post type chocks.

4Machine Operators Snakers, PackersGraders and Cablemen and Tinberers

F233 F236

10 12•

4.1 (6) 3.3(11)*•>

3.0 (3)

2.3(1) 2.6(1)

3.8(7) • 3.2(15)

1.3 0.833.4(22)

1.01.15

0.09

Snakers. Packersand Tinoerers

. F236

3.0 (1)

_,

3.0 (1)

1.01

0.08

RETURN FACE-END

Bored, fired, ripped, arched and packed.

Crawley conveyor.

3 section bolted arches: 4.3ra x 3.7nOowty props and bars under rip.

7Rippers and Packers Face Tradesmen

and Officials

F238 F251

8 8

4.7(2) 1.9(1)

, . . , . , , , , ™ --...,„,.- ...—..«-. . ^^

4.7(2) 1.9(1)

0.403.8 (3)

1.71.17

0.11

.

____________ :

Tcmpcraturv? C J

Dry 24 jWot 23(̂ .H.. 90? !

t

ii

ii

0

Control

Point

6.2 (4)

2.2(1)

Notel

5.4 (5)

2.61.88

0.12

t

Who!oi

Fc.-.c

ii

ii

3.5 +

Note 2 j

i;

\

Who!o

Fnco

3.0*

|

Note:s. . • • . . . •

6.

•" • 7.

• 0.

• Stsridsrd Deviation + Man-v/el£;ht«l Mci.i

*+ Sampled for time at face only TADLE 1

X

.> Sewn

} . . . ..' '.

Warwickshire Thick Coal

; Site

i

IABLE z FACE SUMMARY

Scam N.C.O. f.ir.o Frco Type of Face Length HeightCorr. Co,-.! Rank % St.'irilng flnlsliing "CoJe Code Carbon Date Dale oouble unit 92m

. . . . — „. _ ,_ _. _. . longwall . 95n 2m

retreating16:350 802 82- Sept. 72

Method of Working

Machine Details •

Oust Suppression

Supports

) Sito

i

Occupation(Filling Shifts)

O.G.S.N.! . . _ , _ . .

} Mui.itor cf t-loii In Occupation:;! Group

' Mean !<«-pirnl)lo

'< Dost

j Concentration

! for Occupation

iTip.ln\*\

1st Quarter

?.nd Quarter

3rd Quarter\

1th Quarter

Year

; K.can Ssniplu Concentration

I for Sito

i>. Quartz Concentration

Sit-:

Occupation

nv./'n*

rr.j/m*

rn,?/m*

(Preparation Shifts)O.G.S.N.

f-'umtior of Mtn in Occupations) Group

t-ic.Mi fxcspirable Dust Coo.centrcticn

for Occupation m,7/m*

l-lunn Sample Concentrationi

for Sito

ASM Coi\c«;ntr.ition

; Quartz Concentration

Motes:

mj;/m'

mg/m»

cnj/m*

INTAKE FACE - END •

Short Stable. Bored, fired, filled, dinted, packed.

' . Crawtey conveyor.

4.3ni x 3.1ra 3 -Section bolted arches.

0Other Face Work

F250

, 4

'

. , MO)6.8(1)

-*•6.8 (1)

' _t

2.91

0.38

.

1

Other Face Work Face Tradesmen andOfficials

F250 F251

i i T i i i i i . . - .*•

4.6 (1)

*

2.0 (1) S'

3.3 (2)3.8(3) 2.0(1)

0.823^ (4)

. ., . U ',_,..1.42

0.18•

Other Face Work

F250

64.3(2)

0.47*

4.3(2)

0.47*

1.87

0.24..

1. Average sampling time on face was 7.31 hr.

2. Average sampling time at control point was 5.40 hr. •., , *• ,•, ,

3. Concentration on face similar to control point.

*

r- '

( ) Number cf Samples

CHART

Shift Cycle

Filling•preparationfilling

. North 1/2- FACE

Avon<£Q Roof Seam Floor . AverseOutput ' ' . -i •• • -• •" i .• ' "• VorAiittionpar S.'iiti • Quantity

• "•"• Coal Coal Coal -— •310X0:1 . 5.2n,3/s

FACE

Power loaded.

Ranging drum shearer on each face.

External sprays on both machines.

F.S.H. 4 leg jtooT.Power advanced supports.

H/c Ops.and Graders

F249

8

8.1 (5)**

6.5 (6L

4.615]6.4(16)2.6

••

4O.F.H. Face Tradesmen

and Officials

F250 F251

16 4

9.9(12)

5.6 (9) 5.5 (1)

.5.M.1.3) ,.5.7(2),... , ,

4.4(201.6.1(54) 5.6 (3)5.0 1.16.1(73)

4.42.58

0.33

Notes:5.

6.

' 7.

n.

RETURN FACE-BIO

. Short stable. Dinted and packed.

Crawley conveyor.

•

4*3n x 3.1n 3 - Section bolted arches.

5Other Face Work

F250

6

... _ . . . , _ .

2.? (1)

2.2 (1).

2.2(1)

.

0.93

0.12

" 7 9O.F.W. Face Tradesmen and

Officials

F250 F251 F251

4 2

3.4(1) 10.4(1)

3.2(3)

1.9(1) . . . . : ,

, 4.3 (1)3.1 (2) 3.3 (4) 10.4 (1)

1.7 1.23.2(6) 10.4(1)

1.21.34 4.25

0.14 0.39

Temperature C_—

Dry 22.0Wet 18.0R.H.-. 71$

RtMA^KS

i

8

4-f

Control

Point

8.4 (2)

. 6.912).

4.2 (3)

Note 2

6.2 (7)

3.32.37

0.27

i|

Whole •facj

i4

— —,..—.

i.0 +

Note 3

J1

\Vho!o

Fito

4.3 +

.

:rd Davir.tio.i

Sampled for time at face onlyiOd Mr.:n

TABLE 2

TABLE 3 FACE SUMMARY

1 -" L- " " ' - ' T "~ r **•[ 7 1 ' " ' 1 -—•• - ' ' ' r— " • ~"~r •— *-— -.. — - i

Seam N.C.O. Faco Frco Typo of Face Lonfltd MciVhtScarn Corr. Co:.. IV.-.r.k % Starting l-'lnlshlng '•

Code Codo Carbon Dito Datu ~ . .., , , , , . . . . ., i._ , ... TT , „;„„, -_ ,.,,-..„„„...' Sinole unit

longwall 128m 1.97nHanwckshi re Thick Coal 16:350 802 82 May 1966 advancing

Site

Method of Working

Machine Details ' • ' '

Dust suppression '

i Supports

i Sito

Occupation(Filling Shifts)

O.G.S.N.i\

\ (lumber of t-iin In Occupational Group

i Mc?.n Kcspirabla 1st Quarter

! Dust 2ndQu=rtcr

' Concentration 3rd Quarter

mrrwurv..!™ <th Quarter

1 iriijym9 Year.t

! 1 !c.:n Gu.Ti.ola Concentration

fcr f.it'i m£/m*i A-.ii Cc-iiC'.'.iiiriMicn fn^/m*

) Quirtz CX'C.rcntriitlon mg/m*

Sili:

Occupation(Preparation Shifts)

O.G.S.N.

MumLvc of Mc-n In Occupati.'nsI Group

Moan Kcspirr.blc Dust Cor.cc;ntrr.licn

for Occupation rop/m*

Mean Sample Concentrationi

for Sito mc/m'

Asii Conctntrotion mg/m*

• Qu.irtz Concentration mj/m*

INTAKE FACE-BID '

Bored, fired, power loaded, packed and arched.

Eiraco scoop loader, Crawley conveyor.

4.3m X 3.7ra three - sectioned bolted arches.Dowty props and bars under rip.

1 -Face-end men Face Tradesmen and Officials

F247 F251

8 2

2.5(1).

1.4(1) /

1.4(1) , . 2.5(1)

-*

1.9 (2)

0.77*

' 0.84

0.08•

-

Notes:t. Average sampling time on the face was 7.03 hr. .

2. Average sampling tine at control point was 5.10 hr. ' • • -

| 3. Control point concentration much greater than on the face.•

( ) Number of Sample*

CHART S7l's fACE

Si'iIfiCyc'a Averse R°°' 5s-n Floor • Average-- — 1 O-l'-T-* -- --- . .. r , -in 1 ....... i._.n. ......... VCnti'l" ''Cl

/Filling (;GrtJi!Kt : . Quanlltypreparation Coal Coal Coalfilling 160 ton 6^3/s

FACE

Power loaded.

Two I50kn ranging drum shearers1.68 x 0.71m drums.

External sprays on machines.

F.S.W. 4-leg, 200 ton, supports.

4Machine Operators Packers, Snakers

and Tinberers

F226 F228

4 18

2.3 (6)

2.5 (4)

3,6(3) 3.9(2)

4.7(3) 4.2(1)

3.0(16) • 4.0(3)1.6 2.1

3.2(19)

1.7

1.21

0.11

: _

Notes:

RETURN FACE-BIO .

Bored, fired, power loaded, packed and arched.

Eiraco scoop loader, Crawley conveyor.

4.3m x 3.7m three-sectioned bolted arches.Dovfty props and bars under rip.

7 9Face-end men Face Tradesmen Face Tradesmen

and Officials and Officials

F248 F251 F251

8 2 2

3.1(7) 1.2(1) 1.7(1)

. .1 1 II ( - - - 1 I I . M J 1 -!_...•_.- •_. 1 1 1 1 1 - - - - ( .

2.8 (1)

3.1(8) . 1.2(1) 1.7(1)0.73

2.9(9) 1.7(1)

0.94

1.07 0.70

0.10 0.06

• •

Tcnipcrixturc! • C— - - — _.__.

Dry 21.5Wot 20.0 .R.H.. 87£

REMARKS

t

0

•H-Control

Point

7.6 (5)

5.9 (2)

.̂ JJ>M1

Note 2

6.8 (9)

3.5

2.72

0.19_

__

1

V.'holoi

F.r.co

i

j

i.

,

t2.8 +

Note 3

V/ho!o

Fr.co

5. .

•6. • ' ' . • • ' . . ' •

7. . . . • •

C. . ' ' .

Sampled for time at.face only TAr.LF.

4. 2. 3 Surface workers Reported concentrations are low, as in thepast.

4. 3 Environmental summary

Table 6 (at end of the report) gives a summary of the mean respirabledust concentration for faces, elsewhere underground and on surfacefor the years 1971, 1972 and 1973 and the compositional data for 1973.The lower concentrations for 1973 compared to the previous year'sis probably a reflection of the lower output of the mine.

4. 4 Relationship between control point and face concentrations

Table 6 shows for each face the ratio of mean respirable dust concentra-tion at the control point, (70m from the face in the return road) to meanface concentration. The value of the ratio varies from 1. 07 to 2. 29.For the mine^he ratio of the mean concentrations of all control pointsamples to th'e mean of all face samples (excluding development work)had a value of 1. 35. The value used by Jacob sen, Rae and Walton (1969)in the Interim Standard Study was 1. 4.

4. 5 Total dust measurements

The determination of 'total dust' concentrations for all groups at the minecontinued as previously described (Street, 1972).

TABLE 5

Total Dust Concentrations

Place ofWork

Intake Rip

Pace Line

Return Rip

ElsewhereUnderground

Surface

Site

1

4

7

No. ofSamples

4

52 .

5

25

2

Mean .TotalDustConccrng/m^

34.0

35.5

27.6

25.2

7.4

MeanResp.DustCone.mg/m^

2.9

4.3

3.9

2.8

0.3

Ratio Total Cone.Resp. Cone.

11.7

8.3

7.1

9.0

24.7

The results in Table 5 show that on coalfaces the total to respirabledust ratio was highest at the intake end. For underground samplesonly, the total to respirable ratio had a value of 9. 0 (c.f. 6. 8 for 1972).The two observations reported for the surface samples were unusuallyhigh.

Compositional analyses of the elutriator dust was carried out (Harrison,1975) and showed a lower content of ash and quartz than for the respirabledust on paired samples.

5. RECOMMENDATIONS

In view of the wide range of concentrations reported within some else-where underground groups, an investigation should be made into thesuitability of the occupational group structure to the present conditionsunderground.

REFERENCES

Harrison, G. E. (1975) Analysis of M. R. E. gravimetric dust samples

taken at Coventry Colliery during the 1973 dust year. Institute of

Occupational Medicine File No. BP 31004.

Jacobsen, M., Rae, S. & Walton, W. H. (1969) The relationship between

dust and pneumoconiosis as the basis of a gravimetric standard for air-

borne dust underground. N. C. B. Report No. ISM/P(69) 11.

Maynard, R. C. & Annis, R. (1974) Pneumoconiosis Field Research.

Environmental conditions at Coventry Mine, 1972/3. Institute of

Occupational Medicine Report No. TM/74/1.

Street, R. A. (1972) Pneumoconiosis Field Research. Environmental

conditions at Coventry Colliery, 1969. Institute of Occupational Medicine

Report No. TM/72/10.

TABLE 6

Summary of Dust Concentrations and Composition by Pace and General Environment for 1973/4

.i Mean Reap. Dust ! 1 Compositional Data for 1 9?3/4

• ' i I IConcentrations | control j Mean Cone. | Ash j Composition of Ash•• ! mg/nP | pace i 111 t i i f •

Class of Environment ' Seam Pace ^ i 1 Ash Quartz (Sample ' Quart ̂ Kaolin Micaj Ca..Mg. £ron

j 1 971 -j 19?2 j 1-973 : Ratio | mg/m5 rag/m3 ;„ j % \ % \ % \ % .."_ % ... "!

. Mechanised filling ^Q SW84 |2.7 1 4.0i '

! . ' N1 end d | 8.4

3.5 ! . (-, ! 1 o/i n mf-z-*V I o34 • 1.^4 U.1U133.;} i

t ' r \ \ " 1.24 : 2.09 0.26< • vooy • ;I . \ \ ' I: i ! P.R ' ! i 'i S 71 j 3..0 } 3.5

* ; ' *

: ' -f f

: Seam Mean ; 4.2 5.51 .

•

j ti ' » '1 : I

. ! j ': ; I

• - !

tI

• -- -- ' ' ' ' - - - •'- • •

Irex>aration All Seams | - -.. i

levelopment AH Seams 2.1 2.7

13AN COALFACE All Seams 3.6 5.0

! ._ ,.. - — — - - i.t-3 }• . 1 1gj j lit one drifting i All Seams

/* N| 2.42 ; 1.08 0.09(31;

3.8 i , 1.50 | 0.16i

• '• • • i',

:

' • : '

: i ;• • i

iii

. : .- 1^•-? . - i A CO t f\ 4 f\(-*\ i ; l •5o ; O»i9. \2 / .

j*>i - 1 •»_.!.. 9-1?.., 7 i 1.49 ; 0.155* i ' 1.83+ ! 0.19+

j -' i - •

j. A / j . — 4 . J . . . . . .

35.5 7.8' | j j

41.8 J12.5 i i: -

' I '38.5 s 8.8 | ;!

39.6 J10.6 \ 37.9 ; 14.6! • *

• '1 ij

' : ;j •

! i

! *i '

.

J '

[ : : -39.8 11.5 i 37.0 14.4

1 ' •42.6 I 9.7 J35.8 12.4

\ -;40.2 10.4 37.5 H.236.6+ 10.2+ 37.5+ 17.9+

-'+- : Hi:

i

8.8 7.9 !

1

.

l

* I

i !t ti

_ J. __m , ., .. ;

9.2 , 8.3— (

11.1 : 7.7

9.2 . 7.96.4+ 7.3+

\^_

Llsev/here undergroundj All Seams -3.2 3.6 j/|j?J I 1.30 | 0.13 I 46.6 J10.3 : 34.5 16. 5 j 11. 6 } 7.4

Surface - ! 0.9 0.8 : (^\ '• 0.15 j 0.01 I 31.4 J7.8 '29.6 13.9: 8.4 i 7.4

Number of samples Values for 1972

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