LW24A - EoP - MSEC

TAHMOOR COLLIERY

LONGWALL 24A

END OF PANEL

SUBSIDENCE MONITORING REPORT

FOR LONGWALL 24A

AT TAHMOOR COLLIERY

Mine Subsidence Engineering Consultants

Level 1, 228 Victoria Avenue - Chatswood – NSW 2103 PO Box 3047 – Willoughby North – NSW 2068

Tel. (02) 9413 3777 Fax. (02) 9413 3822 Email: [email protected]

www.minesubsidence.com

REPORT NO. MSEC335

January 2009

Mine Subsidence Engineering Consultants Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report

i

DOCUMENT REGISTER

Revision Description Author Checker Date

01 MJ DJK

Report produced for:-

Compliance with conditions attached to the SMP Approval by the Department of Primary Industries for Longwall 24A – 0m to 250m and Longwall 24A – 250m to End.

Acknowledgments

We would like to acknowledge the extensive contribution provided by various organisations to this report. These organisations have conducted most of the on-ground surveys and inspections. We would particularly like to acknowledge the close dialogue between Tahmoor Colliery and the Mine Subsidence Board, which has ensured a timely and accurate flow of information regarding impacts to structures.

We would like to acknowledge the following organisations:

Australian Rail Track Corporation

Department of Primary Industries

Geoterra

Hydrometric Consulting Services

Lean & Hayward Surveyors

Lutibo (Colin Dove)

Meadows Consulting

Mine Subsidence Board

Pidgeon Civil Engineering

Sunrise Building and Property Services

Sydney Water

Tahmoor Colliery

References

Mine Subsidence Engineering Consultants, (2004). Tahmoor Colliery Longwalls 24 to 26 Report on the Prediction of Subsidence Parameters and the Assessment of Subsidence Impacts on Surface and Sub-Surface Features due to Mining Longwalls 24 to 26 at Tahmoor Colliery in support of an SMP Application. Volume 1. Report No. MSEC157, Revision C, March 2006.

Geoterra, (2008). Xstrata Coal – Tahmoor Colliery End of Longwall 24A Surface Water, Dams & Groundwater Monitoring Report, Tahmoor NSW. GeoTerra Report No. TA8-R2, January 2009.

John Matheson & Associates Pty Ltd, August 2008. Tahmoor Town Centre - Report on column cracking at base of concrete columns in basement car park.

Pells Sullivan Meynink Pty Ltd, May 2008. Letter report entitled Assessment of Recent Rockfalls in the Bargo Gorge.


ii

TABLE OF CONTENTS

DOCUMENT REGISTER i

LIST OF DRAWINGS AND ILLUSTRATIONS iv

CHAPTER 1. INTRODUCTION 6

CHAPTER 2. COMPARISON BETWEEN OBSERVED AND PREDICTED SUBSIDENCE MOVEMENTS 7

2.1. Comparison between Predicted and Observed Systematic Subsidence Movements 8

2.2. Identification of Non-Systematic Subsidence Movements 11

2.3. Bargo River 13

2.3.1. Angle of Draw Surveys 15

2.4. Main Southern Railway 15

2.4.1. Strain Gauge and Switch Displacement Monitoring 15

2.4.2. Thirlmere Way Overbridge 16

2.4.3. Platform Clearance Surveys 16

2.5. Sewer Infrastructure 16

2.6. Power Pole Surveys 19

2.7. Tahmoor Town Centre 19

2.8. Inghams 19

2.8.1. Ground and Building Monitoring Results 19

2.8.2. Ammonia Pipes 19

2.8.3. Pipe Stress Transducers (PSTs) 20

2.8.4. Discussion 20

CHAPTER 3. SUMMARY OF SURVEYS AND INSPECTIONS 21

CHAPTER 4. IMPACTS TO SURFACE FEATURES 26

4.1. Summary of Impacts to Surface Features 26

4.2. Bargo River Gorge 29

4.2.1. Water Quality and Flow Impacts 29

4.2.2. Rockfalls 29

4.2.3. Exceedence of Defined Triggers 29

4.3. Main Southern Railway 29

4.3.1. Thirlmere Way Overbridge 30


4.4. Roads 30


4.5. Potable Water Infrastructure 32


4.6. Gas Infrastructure 32


iii


4.7. Sewer Infrastructure 32


4.8. Electrical Infrastructure 33


4.9. Telecommunication Infrastructure 33


4.10. Inghams Infrastructure 33

4.10.1. Processing Plant 33

4.10.2. Inghams Dams 34


4.11. Residential Structures and Public Amenities 34

4.11.1. Comparison in General 36

4.11.2. Comparison based on Predicted Impact Categories 37

4.11.3. Discussion of Results 37

4.11.4. Swimming Pools 42

4.11.5. Associated Structures 42

4.11.6. Fences 42


4.12. Public Amenities 42


4.13. Tahmoor Town Centre 42

4.13.1. Observations of Cracking 42

4.13.2. Possible Causes of Cracking 39

4.13.3. Conclusions 39


CHAPTER 5. SUMMARY OF RESULTS 44


iv

LIST OF DRAWINGS AND ILLUSTRATIONS

Drawings

Drawing No. Description

MSEC335-01 Longwall 24A Monitoring Lines

MSEC335-02 Longwall 24A Impacts

Figures

Figure No. Description

MSEC335-01 Total Subsidence Profiles along Bradbury Street Line

MSEC335-02 Total Subsidence Profiles along BC Line

MSEC335-03 Total Subsidence Profiles along Castlereagh Street Line

MSEC335-04 Total Subsidence Profiles along Chapman Street Line

MSEC335-05 Total Subsidence Profiles along Courtland Avenue Line

MSEC335-06 Total Subsidence Profiles along Emmett Street Line

MSEC335-07 Total Subsidence Profiles along Larkin Street Line

MSEC335-08 Total Subsidence Profiles along Lintina Street Line

MSEC335-09 Total Subsidence Profiles along LW24A Draw Line

MSEC335-10 Total Subsidence Profiles along LW25 Draw Line

MSEC335-11 Total Subsidence Profiles along LW26 Draw Line

MSEC335-12 Total Subsidence Profiles along the Main Southern Railway Corridor Line

MSEC335-13 Incremental Subsidence Profiles the Main Southern Railway Corridor Line

MSEC335-14 Total Subsidence Profiles along Mitchell Close Line

MSEC335-15 Total Subsidence Profiles along Pandora Place Line

MSEC335-16 Total Subsidence Profiles along Progress Street Line

MSEC335-17 Incremental Subsidence Profiles along Progress Street Line

MSEC335-18 Total Subsidence Profiles along Ralfe Street Line

MSEC335-19 Total Subsidence Profiles along Remembrance Drive Line

MSEC335-20 Incremental Subsidence Profiles along Remembrance Drive Line

MSEC335-21 Total Subsidence Profiles along Remembrance Drive Shopfronts Line

MSEC335-22 Total Subsidence Profiles along Tanya Place Line

MSEC335-23 Total Subsidence Profiles along Thirlmere Way Line

MSEC335-24 Incremental Subsidence Profiles along Thirlmere Way Line

MSEC335-25 Total Subsidence Profiles along Inghams Dam Line

MSEC335-26 Total Subsidence Profiles along Inghams East-West Line

MSEC335-27 Total Subsidence Profiles along Inghams High-Rise Freezer Line

MSEC335-28 Total Subsidence Profiles along Inghams North-South Line

MSEC335-29 Total Subsidence Profiles along Inghams Pipe Support Line (PS1-PS15)

MSEC335-30 Total Subsidence Profiles along Inghams Pipe Support Line (PS16-PS23)


v

MSEC335-31 Total Subsidence Profiles along Inghams Plant Line

MSEC335-32 Total Subsidence Profiles along Mermaid Pool Line

MSEC335-33 Total Subsidence Profiles along Bargo River X1 Line



MSEC335-36 Total Subsidence Profiles along Bargo River X3a Line


MSEC335-38 Total Subsidence Profiles along Bargo River X5a Line

MSEC335-39 Total Subsidence Profiles along Bargo River X5b Line

MSEC335-40 Total Subsidence Profiles along Bargo River X5c Line


Mine Subsidence Engineering Consultants 6 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report

CHAPTER 1. INTRODUCTION

This report has been prepared by Mine Subsidence Engineering Consultants Pty Ltd (MSEC) for Xstrata Coal Tahmoor Colliery to comply with conditions of the SMP Approval by the Department of Primary Industries, particularly Clause 23.

This report includes:

A summary of the subsidence and environmental monitoring results for Longwall 24A; An analysis of these results against the relevant impact assessment criteria, monitoring results

from previous panels and predictions provided in the SMP; The identification of any trends in the monitoring results; A description of actions that were taken to ensure adequate management of any potential

subsidence impacts

The location of Longwall 24A is shown in Drawing No. MSEC335-01, which together with all other drawings, is attached in Appendix A at the back of this report.

This report also includes many of the movements and impacts observed during the extraction of Longwalls 22 to 24A. Note that Longwall 24B was extracted prior to Longwall 24A. The dates of extraction for all longwalls are provided in Table 1-1.

Table 1-1 Start and Finish Dates for Longwalls 22 to 24A

Longwall Start Date Completion Date

Longwall 22 31 May 2004 27 July 2005

Longwall 23A 13 September 2005 21 February 06

Longwall 23B 22 March 2006 26 August 2006

Longwall 24B 14 October 2006 02 October 2007

Longwall 24A 15 November 2007 19 July 2008

The predicted movements and impacts resulting from the extraction of Longwalls 24 to 26 were provided in Report No. MSEC157 (Revision C), which was issued in March 2006.

Longwall 24A was approximately 991 metres long and 283 metres wide, rib to rib. The pillar width was approximately 34.5 metres wide, rib to rib. However, there is a coal barrier between Longwall 24A and the previously extracted 200 Panels of approximately 160 metres width. The depth of cover was relatively consistent over the panel, varying between 430 and 440 metres. While the seam thickness was approximately 2.1 metres, Tahmoor Colliery advised that the design cut was 2.15 metres and the shearer would never cut below 2.05 metres.

Chapter 2 of this report describes the monitoring lines and monitoring points at Tahmoor Colliery, and provides comparisons between the observed and predicted movements resulting from the extraction of Longwall 24A.

Chapter 3 of this report summarises the surveys and inspections undertaken during the mining of Longwall 24A.

Chapter 4 of this report describes the reported impacts on surface features resulting from the extraction of Longwall 24A, and compares these with the predicted impacts. The reported impacts on surface water and ecology are provided in other reports.

Appendix A includes all drawings and figures associated with this report.


CHAPTER 2. COMPARISON BETWEEN OBSERVED AND PREDICTED SUBSIDENCE MOVEMENTS

As set out in the Surface Safety and Serviceability Management Plan, for Tahmoor Colliery Longwalls 24 to 26, regular subsidence surveys have been conducted along monitoring lines that have been established in selected streets. The monitoring is being undertaken to compare observed movements against predicted movements, and to identify any anomalous movements that might potentially have an adverse effect on surface features. The locations of all of the monitoring lines near Longwall 24A are shown in Drawing No. MSEC335-01.

A number of these monitoring lines were installed prior to the commencement of Longwall 24A to measure subsidence movement at key surface features such as the Inghams Plant, Remembrance Drive and Main Southern Railway.

Additional monitoring lines were installed as mining progressed when it became apparent that the urban area may experience increased subsidence. Some subsidence had already developed at each of these additional survey marks prior to the initial survey. A summary of all monitoring lines, dates of initial survey and estimated subsidence prior to initial survey are provided in Table 2-1.

Table 2-1 Summary of Monitoring Lines directly above Longwall 24A

Monitoring Line Date of Initial

Survey Estimated subsidence due to LW 24A

prior to initial survey (mm)

LW24A Draw Line 15 November 2007 0

Dam Line 14 November 2007 0

East-West Line 14 November 2007 0

North-South Line 14 November 2007 0

High-Rise Freezer Line (HRF1 to HRF5)

14 November 2007 0

High-Rise Freezer Line (HRF6 to HRF18)

14 March 2008 30 to 130

Plant and Pipe Support Lines 04 December 2007 5

BC Line 22 April 2008 70 to 245

Ralfe Street Line 10 April 2008 20 to 25

Lintina Street Line 02 May 2008 25 to 70

Courtland Avenue Line 02 May 2008 15 to 55

Tanya Place Line 02 May 2008 30 to 50

Mitchell Close Line 02 May 2008 30 to 35

Pandora Place Line 02 May 2008 20 to 30

Progress Street Line 03 October 2006 0

Remembrance Drive Line 13 May 2005 0

Larkin Street Line 20 May 2008 10 to 30

York Street Line 20 May 2008 15 to 25

Emmett Street Line 20 May 2008 20 to 35

In addition to the monitoring lines, subsidence monitoring was conducted at survey stations located at and around the Tahmoor Town Centre, selected power poles and at the Bargo Gorge in accordance with the Surface Safety and Serviceability Management Plan.


Surveys were undertaken at regular intervals during the extraction of Longwall 24A and the End of Panel surveys were conducted during July and August 2008. The observed total and incremental subsidence profiles along the monitoring lines are provided in Figs. MSEC335-01 to MSEC335-41.

2.1. Comparison between Predicted and Observed Systematic Subsidence Movements

Observed subsidence, tilt and curvature due to the mining of Longwall 24A have substantially exceeded predictions. Maximum observed subsidence was 1169 mm, which was more than double the maximum predicted subsidence of 509 mm. While observed tilts and curvature were also substantially greater than predicted, observed ground strains were within the normal range.

The observation of increased subsidence was not observed at other nearby longwalls at Tahmoor Colliery, where there was a reasonable correlation between predicted and observed profiles over Longwalls 22, 23 and 24B.

Observed subsidence was greatest above the southern half of Longwall 24A, and gradually reduced in magnitude towards the northern half of the longwall, which was directly beneath the urban area of Tahmoor. These observations are shown graphically in Figure 2.1, which shows observed subsidence at survey pegs located along the centreline of Longwall 24A.

Figure 2.1 Observed Subsidence along Centreline of Longwall 24A

It can be seen from Figure 2.1 that while observed subsidence was substantially greater than predicted above the commencing end of the longwall, observed subsidence compared reasonably well with predictions towards the finishing end of Longwall 24A.

-350 -250 -150 -50 50 150 250 350 450 550 650 750 850 950 1050 1150 1250 1350Distance from goaf edge (m)

LW 24A LW 24B120011001000

900800700600500400300200100

0

Sub

side

nce

(mm

)

Peg 24-155.1 x prediction





Peg HRF102.3 x prediction

Peg RF191.9 x prediction

Peg LA91.2 x prediction

Peg R151 x prediction

Peg L11 x prediction

Observed subsidence atsurvey pegs during LW 24A

Observed Subsidence alongCentreline at end of LW 24A

Predicted Subsidence due toLW 24A (MSEC157)

250

255

260

265

270

275

280

285

Sur

face

Lev

el A

HD

(m

)

LW 24A15

-Nov

-07

11-D

ec-0

7

14-J

an-0

8

25-J

an-0

8 to

28-

Mar

-08

14-A

pr-0

8

21-A

pr-0

8

28-A

pr-0

8

8-M

ay-0

8

12-M

ay-0

8

19-M

ay-0

8

26-M

ay-0

8

2-Ju

n-08

11-J

un-0

8 to

19-

Jul-0

8

24-1 2

4-2

24-

324

-4 24-5 24

-624

-72

4-8

24-9

24-1

02

4-11

24-1

224

-13

24-

1424

-15

24-1

624

-17

24-1

82

4-19

HR

F10

RF

19

LA9

R15

L1

Y1

94.3

2T

71

LW 24B

I:\Projects\Tahmoor\SurveyData\LW24A Draw Line\LW24A Draw Line (EOP).grf


Maximum observed incremental and total subsidence parameters for all monitoring lines surveyed during Longwall 24A are summarised in Table 2-2. The maximum value for each parameter is highlighted.

Table 2-2 Summary of Maximum Subsidence along Monitoring Lines

Monitoring Line

Maximum Observed

Subsidence (mm)

Maximum Observed

Tilt (mm/m)

Maximum Observed Hogging

Curvature (km-1)

Maximum Observed Sagging

Curvature (km-1)

Maximum Observed

Tensile Strain

(mm/m)

Maximum Observed

CompressiveStrain

(mm/m)

Bradbury Street 47 0.8 0.05 -0.05 0.4 -0.3

BC Line 779 5.1 0.11 -0.18 0.1 -0.3

Castlereagh Street 17 0.2 0.01 -0.01 0.4 -0.2

Chapman Street 15 0.2 0.01 -0.01 0.2 -0.5

Courtland Avenue 730 6.0 0.14 -0.03 0.4 -0.6

Emmett Street 84 0.5 0.02 -0.01 0.1 -0.1

Larkin Street 110 1.2 0.03 -0.01 0.4 -0.2

Lintina Street 630 3.6 0.09 -0.13 0.1 -1.1

LW24A Draw Line 1091 10.2 0.15 -0.14 1.3 -0.4

LW25 Draw Line 12 0.3 0.01 -0.01 0.3 -0.3

LW26 Draw Line 20 0.4 0.02 -0.02 0.5 -0.5

Main Southern Railway

40 0.6 0.03 -0.06 0.3 -0.5

Mitchell Close 471 4.3 0.06 -0.23 0.3 -4.8

Pandora Place 120 1.1 0.02 -0.02 0.1 -0.1

Progress Street 26 0.3 0.08 -0.05 - -

Ralfe Street 937 8.4 0.1 -0.13 1.2 -3.2

Remembrance Drive 199 3.0 0.12 -0.11 0.8 -0.4

Remembrance Drive Shopfronts

127 1.4 0.10 -0.03 - -

Tanya Place 462 6.8 0.10 0.00 0.9 0.0

Thirlmere Way 36 1.5 0.12 -0.08 0.2 -0.2

Inghams

Dam Line 762 4.7 0.06 -0.14 0.5 -0.3

East-West Line 602 6.4 0.08 -0.03 1.0 -0.2

High-Rise Freezer Line

1169 12.7 0.29 -0.38 1.0 -2.5

North-South Line 174 0.5 0.01 -0.03 0.1 -0.2

Pipe Support Line 108 0.7 0.14 -0.10 0.7 -0.7

Plant Line 118 0.7 0.12 -0.08 2.8 -0.4


The distribution of subsidence transverse to the longwalls is illustrated by the results along the High-Rise Freezer Line (Figure 2.2). This shows that subsidence on the tailgate side (Inghams side) was greater than the subsidence on the maingate side (Progress Street side). The potential for increased subsidence on the tailgate side was anticipated as the tailgate side is located above mostly solid, unmined coal reserves that lie between a previously mined area (200 Panels) and the currently mined Longwall 24A. Observations of increased subsidence have been experienced in similar previous mining situations.

0 50 100 150 200 250 300 350 400 450Distance along High-Rise Freezer Line from Survey Mark NS7 (m)

LW 24A

-14-12-10

-8-6-4-202468

10

Tilt

(m

m/m

)

14001300120011001000

900800700600500400300200100

0

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

250

255

260

265

270

275

280

Sur

face

Lev

el A

HD

(m

)

LW 24A

NS

7

HR

F1

HR

F2

HR

F3

HR

F4

HR

F5

HR

F6

HR

F7

HR

F8

HR

F9

HR

F10

HR

F1

1

HR

F12

HR

F13

HR

F14

HR

F1

5

HR

F16

HR

F17

HR

F18

Note: It was predicted that up to 100mm of subsidence may occur in addition to predicted systematic subsidence between LW24A and 200 Panels

I:\Projects\Tahmoor\SurveyData\Inghams\High-Rise Freezer Line (LW24A EOP).grf

Estimated subsidence forPegs HRF6 to HRF17

Upsidence in creekCreek does not extend

to urban area

LW22

LW23A

LW24A

LW24B

Figure 2.2 Observed Subsidence along the High-Rise Freezer Line during Longwall 24A

While subsidence is greater on the tailgate side, tilts and curvatures on the tailgate side are comparatively less than on the maingate side as the shape of the subsidence profile is flatter. For example, maximum tilts on the tailgate side are approximately 8 mm/m, compared to over 10 mm/m on the maingate side along the High-Rise Freezer line.


The nature and magnitude of the increased subsidence is rare and the cause of the increased subsidence is currently not known. Tahmoor Colliery has commissioned a geotechnical study by Dr Winton Gale of Strata Control Technology to try to identify the cause or causes of the increased subsidence. Results of this study are not yet available as research is continuing. Once it became apparent that increased subsidence had developed, Tahmoor Colliery revised its management plans during extraction of LW24A to manage potential increased impacts to surface infrastructure before the longwall extracted beneath the urban area of Tahmoor.

2.2. Identification of Non-Systematic Subsidence Movements

A plan showing the locations of potential non-systematic movements observed at Tahmoor is shown in Figure 2.3. The locations were selected based on ground monitoring results or observed impacts that appear to have been caused by non-systematic movement. A total of approximately 30 locations (not including valleys) have been identified over the four extracted Longwalls 22 to 24, of which 3 locations are located above Longwall 24A.

Figure 2.3 Map of locations of potential non-systematic movement


Monitoring lines crossed the locations of non-systematic movement along two monitoring lines. A summary of non-systematic movements at these locations is provided below in Table 2-3.

Table 2-3 Location of New Identified Non-Systematic Movements during Longwall 24A

Monitoring Line or Location

Maximum Upsidence

(mm)

Maximum Strain

(mm/m)

Maximum Tilt(mm/m)

Type Impacts to Surface

Mitchell Close / Lintina Street

(Pegs ML1-LA8)

Not measured as end of

monitoring line -4.8 4.3 Anomaly

Road pavement cracking, adjustment to tension of aerial phone lines

Ralfe Street /Courtland Ave (Pegs RF19-20 and CL1-CL3)

35 (CL1 to CL3)

-3.2 (RF19-20)

5.9 (CL1 to CL3)

Anomaly

5 houses (3xCat 0, 1xCat 1 & 1xCat 4) and compression hump in pavement and kerbs

High-Rise Freezer

(Pegs HRF11-13) 82 -2.5 12.7

Valley upsidence & closure

None (in paddock)

In this table, “upsidence” is defined as the height of the local subsidence bump at the anomaly, as calculated or determined from an otherwise smooth systematic subsidence profile.

The most severe non-systematic movement observed during the mining of Longwall 24A occurred along Lintina Street. The road pavement experienced severe cracking. The movements developed gradually over time and the pavement was repaired on a number of occasions as mining progressed. Photographs of the impacts are shown in Figure 4.1.


2.3. Bargo River

The location of Longwall 24A relative to the Bargo River is shown in Figure 2.4.

Figure 2.4 Location of Longwall 24A in relation to the Bargo River

race

complete surface flow diversion

throughboulders

boulder

boulders

delaminating rock

race

complete surfaceflow diversion

boulders

flute holes

waterfall

race

boulders

waterfall

boulders

race

waterfall

waterfall

complete surfaceflow diversion flute holes

waterfall

boulder

cracks in cliff

waterfall

crackedtriangularwedge

joint inrockbar

crack inrock

ironprecipitation

and rapidsboulders

race rapids

and rapidsboulders

flute holes

waterfall

joint in rockbar

flute holes



weedscross bed

cross bed

joints

joint

joint

pond

rock shelf

Pencil Falls

rock shelf

rock pond

cliff wall

waterfall

joint in wall

efflorescencewaterfall

iron band

joint

waterfall

crack

rockfall

Walking Trail

GENERAL APPLICATIO

N AREA

RB F

Pool E

Pool F

Pool B

Pool D

RB C

RB E

RB G

Pool H

RB JPool J

Pool L

Pool Q

RB R

Pool N

Pool M

RB M

RB N

RB O

RB P

Pool V

Pool K

Pool O

Pool P

Pool R

Pool SRB S

Pool TRB T

RB U Pool U

RB V

Mermaids

RB K

Pool

RB L

RB Q

Pool W

Water quality sampling (not flow)

Water flow and quality sampling

HCS Bolt

HCS Bolt

HCS Bolt

HCS Bolt

HCS Bolt

HCS Bolt

HCS Bolt

HCS Bolt

HCS Bolt

HCS Bolt

HCS Bolt

HCS Bolt

HCS Bolt

HCS Bolt

HCS Bolt

HCS Logger

HCS Bolt

HCS Logger

HCS Logger

HCS Logger

HCS Logger

Pool A

RB B

RB D

RB H

Pool IRB I

RB APool C

HCS Logger





X3L

X2L

X4aL

X4aR

X3R

X1 Line

X6 Li

ne

X6L

X6R

X5c Line

X5b LineX5a Line

X5R

X5L

X4 Line

X4R

X4L

X1R

X1L

X3aR

X3aL

X3a Line

X2 Line

XMP Line

X2R

Dyke

Dyke

LW 25

LW 24A

X3 Line

623 m

Closest distance

of 200 panels to River

Closest distanceof LW24A to River

339 m

Closest distance

of LW25 to R

iver509 m

iron precipitation

iron precipitation

iron precipitation

LW24A Angle of D

raw Line

LW26 A

ngle of Draw

Line

LW25 A

ngle of Draw

Line

iron precipitation

iron precipitation

iron precipitation

Valley Connection Lines

Valley C

onnection Lines

295 m

NOTE:Where possible the valley closure pegs have been linked to the rockbar monitoring lines.Visual inspections fortnightly from Rockbar A to Pool W and Mermaids Pool.

Closure pegs on top of cliffs measured straight across gorge (monthly)

Rockbar monitoring points (end of each longwall)

HCS water level monitoring points (daily)Water flow and quality monitoring (monthly)

LEGEND

X Line

X1L X1R

HCS Logger

HCS water level monitoring points (monthly)HCS Bolt

387 m

Closest distance

to Rockbar I

Closest distance toWaterfall below Pool W

EP14-PEG

X4L-GPS

26-1 NAIL

Gate

ME3-GINSTUMP

ME5-GINSTUMP

25-2 PEG

SITE-GPS-BASE

Angle of Draw Lines

Valley Connection Lines


A summary of observed subsidence parameters is provided in Table 2-4.

Table 2-4 Summary of Observed Subsidence, Upsidence and Closure along Bargo Gorge Cross Lines

Monitoring Line

Maximum Observed

Subsidence at top of Gorge

(mm)

Maximum Observed

Subsidence at base of Gorge

(mm)

Upsidence (mm)

Closure (mm)

Survey Tolerance ± 5 mm

± 10 mm between top and bottom

of gorge

± 3 mm differential

vertical subsidence

± 3 mm for horizontal distance

across tops of Gorge

Mermaids Pool No pegs Not connected

to datum 0 0

X1 Cross Line Not connected

to datum Not connected

to datum 0 -2 (closure)



to datum 0 -2 (closure)

X3 Cross Line 9 15 0 0

X3a Cross Line 8 11 0 -2 (closure)

X4 Cross Line 8 12 0 -3 (closure)

X4a Cross Line 9 No pegs No pegs -2 (closure)

X5a Cross Line 11 12 0 0

X5b Cross Line 11 12 0 0

X5c Cross Line 11 11 0 0



to datum 0 0

The monitoring results indicate that no measureable upsidence or closure has occurred across any of the monitoring lines across the Bargo Gorge during the mining of Longwall 24A. All differential movements have been very small and close to or within stated survey tolerance.

The observed subsidence is less than 20 mm as predicted. The results indicate that the Gorge may be experiencing a small amount of vertical subsidence of approximately 11 mm or less, based on the more accurate surveys at the tops of the Gorge.

The current observed movements during the mining of Longwall 24A are less than the predicted Longwall 24A maximum incremental upsidence of 20 mm and maximum incremental closure of 50 mm. Given the incised nature of the Gorge and its significant valley height, it was considered possible that actual upsidence and closure movements might exceed predictions but this does not appear to have occurred.

The reason for the lack of valley bulging movement is not known. It is possible that the strata above Longwall 24A had already been stress-relieved by past geological activity. An unusually large amount of vertical subsidence has been observed directly above Longwall 24A. The combination of increased subsidence, tilt and curvature without increased ground strain directly above the goaf suggests that horizontal movements into the goaf have not been substantial, with the predominant direction of ground movement being vertical. The lack of significant differential horizontal movement suggests that mining, therefore, may not have significantly changed the stress environment in the overlying strata in the base of the valley.


The above comments only represent our considered opinion, which is based on limited facts. Tahmoor Colliery is currently undertaking a geotechnical investigation into the cause of the increased subsidence observed directly above Longwall 24A and the findings of the investigation may shed light on why no measureable upsidence or closure has occurred in the Bargo Gorge.

2.3.1. Angle of Draw Surveys

As shown in Drawing No. MSEC335-01, monitoring lines were installed off the commencing ends of Longwalls 24A, 25 and 26 to measure the extent of vertical subsidence that occurs between the extracted longwalls and the Bargo Gorge. The results of the survey in relation to Longwall 24A are attached to this report.

A summary of observed subsidence parameters along these three monitoring lines is shown in Table 2-5.

Table 2-5 Summary of Observed Subsidence Parameters along Angle of Draw Monitoring Lines

Monitoring Line

Maximum Observed

Subsidence (mm)

Maximum Observed Tilt

(mm/m)

Maximum Observed Tensile

Strain (mm/m)

Maximum Observed

Compressive Strain

(mm/m)

LW 24A Draw Line 1090 10.2 1.3 -0.4

LW 25 Draw Line 12 0.3 0.3 -0.3

LW 26 Draw Line 20 0.4 0.5 -0.5

2.4. Main Southern Railway

The Main Southern Railway was surveyed 17 times on a weekly, twice weekly and thrice weekly basis during the extraction of Longwall 24A. Details of the monitoring undertaken are provided in the monitoring reports prepared by MSEC on behalf of Tahmoor Colliery and these reports have been provided to ARTC throughout the mining period.

The Main Southern Railway experienced a maximum of 40 mm of subsidence during the mining of Longwall 24A. While observed subsidence was greater than predicted (less than 20 mm), the amount of subsidence is very small. Observed maximum incremental tilt was 0.6 mm/m. Observed maximum incremental strain was approximately 0.3 mm/m tensile and 0.5 mm/m compressive (excluding survey marks that have been obviously damaged).

Differential vertical and horizontal movements are relatively small and changes between each survey within survey tolerance. However, elevated ground strain of 0.45 mm/m was measured between 94.600 and 94.620 km. The ground strains represent a closure of 9 mm over a 20 metre bay. Increased ground strain was observed at this site during the mining of Longwall 23A but not during the mining of Longwall 24A. The movements are consistent with valley upsidence and closure movements, as their location coincides with a small watercourse. This watercourse continues beneath the Main Southern Railway through a ballast top bridge culvert at Ch. 94.576 km.

There are a number of locations where irregular subsidence has been observed including 94.260 km, 94.700 km and 95.160 km. These are considered to be due to disturbance of survey marks in the rail corridor in the period between October 2007 and May 2008. All of these bumps have been first observed at the time of first survey since the commencement of Longwall 24A, with nil or minimal change in differential movement for subsequent surveys.

2.4.1. Strain Gauge and Switch Displacement Monitoring

Monitoring in excess of the requirements of the Management Plan for Longwall 24A was conducted as part of the Trial Switch Management Plan. It included continuous rail stress gauge and switch displacement monitoring between 93.900 and 94.400 km.

Small reductions of between 4 and 5 degrees in Stress Free Temperatures (SFT) were observed on the Up and Down Tracks at 94.350 km and 94.400 km from the beginning of May 2008. It is considered that


these changes are related to mine subsidence. Some dissipation of tensile stress from fixed Continuously Welded Rail (CWR) track into the free rail on the Up Main was observed. Very little change in SFT was observed during the mining of the end of Longwall 24A, which correlates well with measured ground movements.

It is noted that no stress gauges are located near 94.600 km where maximum increases in compressive ground strains have been measured, though it is considered likely that some change in SFT has occurred. This section of track has since been re-stressed.

2.4.2. Thirlmere Way Overbridge

A total of 16 surveys and 38 visual inspections were undertaken of the Thirlmere Way Overbridge on a weekly basis in accordance with the agreed management plans with ARTC and Wollondilly Council.

Measured tilts and strain at the abutments are very small. The results indicate a fall of up to 1.0 mm/m between the bridge abutments from east to west, towards Longwall 24B. Changes in measurements between surveys have been within survey tolerance during the mining of Longwall 24A.

No impacts were observed to the Bridge during the mining of Longwall 24A, as expected following extensive strengthening works undertaken by Tahmoor Colliery prior to commencement of Longwall 24B.

2.4.3. Platform Clearance Surveys

A total of 14 platform clearance surveys were undertaken during the mining of Longwall 24A. All platform clearances are currently greater than minimum design clearances. Measured changes in clearances were within survey tolerance.

2.5. Sewer Infrastructure

One of the key items of infrastructure that had potential to experience impacts as a result of increased subsidence were the self-cleansing sewer pipes within the urban area. Subsidence monitoring was undertaken along the streets and at key sewer pit lids during mining.

Prior to Longwall 24A mining beneath the urban area, the potential changes in sewer grades were re-assessed based on observations along the High-Rise Freezer Line (refer Peg HRF10 in Figure 2.2) for all sewer pipes within the urban area. The reassessment indicated that the grades on the majority of the pipes were expected to remain greater than the minimum grades required for self-cleansing following the mining of Longwall 24A. However, the analysis identified three pipe sections where the projected grades were assessed to be only just greater than the minimum grade required for self-cleansing. The pipes identified were:

SMH30 to SMH31: A 17 metre long section of pipe with a pre-mining grade of 0.79%



A plot of projected changes in grade and projected grades during and after the mining of Longwall 24A is provided in Figure 2.5. The projected changes in grade are primarily based on observed monitoring results along the High-Rise Freezer Line. The projected values were compared with observations based on subsidence measured at nearby survey marks, which are also shown in Figure 2.5.

Relative height differences between the sewer pit lids for four identified pipe sections were measured three times a week in accordance with an agreed management plan with Sydney Water. A total of 29 surveys were conducted along the above pipe sections during the mining of Longwall 24A. A plot of observed height differences and changes in grade is provided in Figure 2.6. The results are compared with projected sewer grades, which were based on observations along the High-Rise Freezer line.

It can be seen from Figure 2.6 that changes in sewer grade have occurred and the changes in grade appear to be less than the grades that have been projected to develop based on observed monitoring results along the High-Rise Freezer Line.


It can be seen that the pipes between SMH30 and SMH31, and SMH31 to SMH32 had initially reduced as the longwall passed directly beneath it, but the grade has gradually improved as the longwall progressed away from the pipe. The pipe section is located near the centre of the longwall and is oriented almost parallel to the longitudinal direction of the longwall. The observed grades were expected as the pipe section was largely influenced by travelling tilts as the subsidence wave approached and passed the pipes. All grades remained positive and self-cleansing.

Figure 2.5 Projected & Observed Subsidence Profiles along selected Sewer Line during LW 24A

0 50 100 150 200 250 300 350 400 450 500 550 600 650Distance along Sewer Line from Survey Mark R23 (m)

-0.20.00.20.40.60.81.01.21.41.61.82.0

Gra

de (

%)

LW 24A

Initial Grade

-8

-6

-4

-2

0

2

4

6

8

10

Cha

nge

in G

rade

(m

m/m

)(P

ositi

ve =

incr

ease

in fa

ll)

120011001000

900800700600500400300200100

0

Sub

side

nce

(mm

) Projected Subsidenceusing HRF surveysup to 7 May 2008

(distances are lengthof LW 24A)

Proj @ 991m

Proj @ 950m

Proj @ 900m

Proj @ 850m

Proj @ 800m

Proj @ 750m

Proj @ 700m

Observed during LW24A

Latest Observedat 990.6m

REM

EMBR

ANC

E D

VE

LW N

o.24A

250

255

260

265

270

275

280

285

290

Sur

face

Lev

el A

HD

(m

)

LW 24A

R23 M

L6

ML5

ML4

ML3

ML2

ML1

LA8

LA7

LA6

LA5

LA4

LA3

RF

19

RF

20

RF

21

RF

22

RF

23

RF

24

RF

25

RF

26

RF

27

RF

28

RF

29

RF

30

1.38% 0.98% 1.20%1.64% 0.71% 0.79% 0.89%

0.96%SMH 26 SMH 25

SMH 32SMH 31

SMH 30 SMH 29SMH 28

I:\Projects\Tahmoor\SurveyData\Sewer Mains\Sewer Line Predicted.grf


Figure 2.6 Projected and Observed Changes in Grade between selected Sewer Pits

-300 -200 -100 0 100 200 300 400Distance between Longwall Face and Mid-Point between Sewer Pits (positive value when LW past Mid-pt) (m)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

Pip

e G

rad

ebe

twee

n S

ewer

Pits

(%

)

Average Grade for SewerPipe between Sewer Pits(includes pre-mining gradeand estimated change ingrade due to subsidenceat time of initial survey)

SMH29 to SMH30

Proj 29 to 30

SMH30 to SMH31

Proj 30 to 31

SMH31 to SMH32

Proj 31 to 32

SMH25 to SMH26

Proj 25 to 26

-300 -200 -100 0 100 200 300 400Distance between Longwall Face and Mid-Point between Sewer Pits (positive value when LW past Mid-pt) (m)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

He

ight

Diff

ere

nce

bet

wee

n S

ewer

Pits

(m

)

Measured Height Differencebetween Sewer Pits(raw survey data only)

SMH29 to SMH30

SMH30 to SMH31

SMH31 to SMH32

SMH26 to SMH25

-300 -200 -100 0 100 200 300 400Distance between Longwall Face and Survey Mark (positive value when LW past mark) (m)

900

800

700

600

500

400

300

200

100

0

Sub

side

nce

(mm

)

Subsidence at Survey Peg(including estimate of

subsidence prior to initial survey of each peg)

RF19

RF22

LA3

ML3

ML6

LW No.24A

RE

ME

MB

RA

NC

E D

VE

SMH26

SMH25

SMH32 SMH

30

SMH29

SMH31

ML6 LA3

ML3

RF19 RF22

0 50 100 150 200 250 300 350 400 450 500 550 600 650Distance along Sewer Line from Survey Mark R23 (m)

250

255

260

265

270

275

280

285

290S

urfa

ce L

evel

AH

D (

m)

LW 24A

R2

3 ML

6

ML

5

ML

4

ML

3

ML

2

ML

1

LA8

LA7

LA6

LA5

LA4

LA3

RF

19

RF

20

RF

21

RF

22

RF

23

RF

24

RF

25

RF

26

RF

27

RF

28

RF

29

RF

30

1.38% 0.98% 1.20%1.64% 0.71% 0.79% 0.89%

0.96%SMH 26 SMH 25

SMH 32SMH 31

SMH 30 SMH 29SMH 28

I:\Projects\Tahmoor\SurveyData\Sewer Mains\Key Sewer Grades LW24A.grf

SURVEY DATE: 28 JULY 08 Length of LW: 991.6 m - Complete


2.6. Power Pole Surveys

A total of 21 surveys of selected power poles were conducted in accordance with the agreed management plan with Integral Energy. No impacts were observed to any power pole during the mining of Longwall 24A as expected.

Of the poles that were surveyed, maximum subsidence of 489 mm was observed at Pole 240 on Lintina Street. A maximum horizontal movement of 109 mm was measured at the top of the same pole.

2.7. Tahmoor Town Centre

A total of 3 detailed surveys of the Tahmoor Town Centre and basement carpark were undertaken in accordance with the conditions of SMP Approval by the Department of Primary Industries. Maximum observed subsidence was 41 mm at the south-east corner of the complex.

2.8. Inghams

2.8.1. Ground and Building Monitoring Results

Ground and building surveys have been conducted in accordance with the Management Plan. The locations of monitoring lines relative to Longwall 24A and the Inghams infrastructure are shown in Drawing No. MSEC341-01 and a summary of maximum observed subsidence parameters for each monitoring line is provided in Table 2-6.

Table 2-6 Summary of Maximum Observed Subsidence Parameters

Monitoring Line

Maximum Observed

Subsidence (mm)

Maximum Observed

Tilt (mm/m)

Maximum Observed

Tensile Strain

(mm/m)

Maximum Observed

Compressive Strain

(mm/m)

Dam Line 762 4.7 0.5 -0.3

East-West Line 602 6.4 1.0 -0.2

North-South Line 174 0.5 0.1 -0.2

High-Rise Freezer Line

11692 12.7 1.03 -2.53

Plant Perimeter Line

1181 Please refer Table 2-7 for differential vertical and horizontal

movements.

Pipe Support Line 1081 Please refer Table 2-7 for differential vertical and horizontal

movements.

1 Observed subsidence along the Plant Perimeter Line and Pipe Support Line are less than other monitoring lines because they were installed just after the commencement of Longwall 24A. Based on surveys from the survey origin, it is estimated that 5 mm of subsidence occurred prior to the installation of these monitoring lines and it is recommended that this amount be added to the monitoring results. Pipe Support Marks 16 to 23 were installed as part of the Stage 2 Management Plan. Approximately 23 mm of subsidence had been measured near these pegs at this time. 2 High-Rise Freezer line was extended from HRF5 to HRF18 while Longwall 24A had stopped at 389 metres of extraction.

2.8.2. Ammonia Pipes

The Management Plan includes planned procedures that are triggered from results of monitoring in relation to ammonia pipes. The triggers for the blue trigger level are:

Ground survey: Differential vertical or horizontal movement of 10 mm between adjacent survey marks on the Plant Perimeter and Pipe Support Monitoring Lines

Displacement transducers: 10 mm movement since re-commencement of Longwall 24A


Pipe Stress Transducers: 82.8 MPa for low temp pipes and 112.5 MPa for high temp pipes

Ground survey

A summary of maximum observed differential vertical and horizontal movements along these monitoring lines are shown in Table 2-7.

Table 2-7 Summary of Maximum Observed Differential Movements along Plant Perimeter and Pipe Support Monitoring Lines

Monitoring Line

Maximum Observed

Subsidence (mm)

Maximum Observed

Differential Vertical

Movement (mm)

Maximum Observed

Differential Horizontal Movement

(mm)

Is BLUE trigger exceeded?

Plant Perimeter Line 1241 -10.7 to +9.4 -3.0 to +3.0 YES

Pipe Support Line 1131 -5.2 to +2.9 -1.0 to +6.0 NO 1 Please refer Note 1 for Table 2-6.

Differential vertical movements exceeded the blue trigger between survey marks Plant 11 and Plant 12, which are located on the southern side of the Carton Tunnel. The pegs are spaced approximately 21 metres apart and the corresponding ground tilt is therefore 0.5 mm/m. The measured differential horizontal movements were within survey tolerance.

Displacement transducers

The measured displacements for Sensors 2 and 3 exceeded the BLUE trigger on a number of occasions. However, the sensors were later found to be faulty. It is considered that the actual displacements did not exceed the trigger levels.

2.8.3. Pipe Stress Transducers (PSTs)

While some pipe stress transducers showed slight changes in stress, the majority of stress gauges did not reach the trigger level, except for intermittent spikes that were considered to be due to either electrical interference or influence of compressor operation. Only one gauge was observed to experience an increase in pipe stress. The pipe supports were adjusted during mining and the stresses were subsequently reduced.

2.8.4. Discussion

The subsidence associated with the Inghams Plant occurred in accordance with predictions. Increased subsidence above predictions obtained by the Incremental Profile Model was observed at the Plant during the mining of Longwall24A. However, this was predicted as the Plant was located above mostly solid, unmined coal reserves that lay between a previously mined area (200 Panels) and the currently mined Longwall 24A. Observations of increased subsidence had been experienced in similar previous mining situations and these are believed to be due to a regional relaxation of the insitu stresses in the overlying strata.

As discussed in the Management Plan, it was expected that this increased subsidence would be accompanied by low tilts and strains, and this was observed during the mining of Longwall 24A. It can be seen from the monitoring results that observed tilts and strains similar to or less than survey tolerance in the vicinity of the Inghams Plant and along nearby monitoring lines (North-South, High-Rise Freezer). A total variation of approximately 38 mm of subsidence was observed among all survey pegs along the Plant Perimeter and Pipe Support Monitoring Lines.

While subsidence developed as expected at the Plant, increased subsidence was observed at the dams. This was not predicted.


CHAPTER 3. SUMMARY OF SURVEYS AND INSPECTIONS

Many surveys and inspections were required to be conducted to meet the requirements of the Surface, Safety and Serviceability Management Plan. Due to the complexities involved, surveys and inspections were managed using a computer database on a weekly basis. A register was also kept, detailing when each survey and inspection had been completed. A timeline showing when each type of survey and inspection was conducted is shown in Fig. 3.1 and Fig. 3.2.

Fig. 3.1 Timeline and Surveys and Inspections during Longwall 24A (Part 1 of 2)

I:\Projects\Tahmoor\MSEC335 - Monitoring LW24A\LW24A - End of Panel Report\Survey and Inspection Timelines LW24A.grf

Nov-07 Dec-07 Jan-08 Feb-08 Mar-08 Apr-08 May-08 Jun-08 Jul-08 Aug-08 Sep-08


LW 24A

LW 24A

Thirlmere Way Overbridge Visual Inspections

Thirlmere Way Overbridge Surveys

Subsidence reports for Railway

Reports for Monitoring Results

Groundwater Water Quality Sampling - Lab

Groundwater Water Quality Sampling - Field

Groundwater Water Levels

Redbank Ck Water Quality Sampling - Lab

Redbank Ck Water Quality Sampling - Field

Redbank Ck Data Logger Downloads

Myrtle Ck Water Quality Sampling - Lab

Myrtle Ck Water Quality Sampling - Field

Myrtle Ck Data Logger Downloads

Bargo River Rockbar Monitoring Surveys

Bargo River Valley Closure Surveys

Bargo River Angle of Draw Surveys

Bargo River Visual Monitoring

Bargo River Water Quality Sampling

Bargo River Water Level Surveys

Bargo River Data Logger Downloads

Bargo River Flow Gauging

Tanya Pl

Remembrance Dve

Ralfe St

Progress St

Pandora Pl

Mitchell Cl

Lintina St

Larkin St

Emmett St

Courtland Ave

Bradbury St

Castlereagh St

Chapman St

Thirlmere Way

Main Southern Railway Corridor

Natural Features

Ground Monitoring Surveys

Main Southern Railway


Fig. 3.2 Timeline and Surveys and Inspections during Longwall 24A (Part 2 of 2)

I:\Projects\Tahmoor\MSEC335 - Monitoring LW24A\LW24A - End of Panel Report\Survey and Inspection Timelines LW24A - 2.grf



LW 24A

LW 24A

Visual Inspections

Building Surveys

Telstra Visual Inspections

Power Pole Surveys

Choke Report

Sewer Main Surveys

Dams

Pools and pool gates

Houses

Public Amenities / Commercial District

Dam Line

East-West Line

North-South Line

HIgh-Rise Freezer Line

Plant Line

Pipe Support Line

Weighbridge

BC Line

Visual Inspections

Wall & Column Tilt Surveys

Building Interface Surveys

Remembrance Drive Bridge Survey

Tahmoor Town Centre

Sydney Water - Sewer

Structure Inspections

Integral Energy - Electrical

Telstra - Telecommunications

Inghams

Agility - Gas


A count of surveys and inspections is provided in Table 3-1.

Table 3-1 Number of Surveys and Inspections conducted during Longwall 24A

Inspection / Survey Responsibility Number of Inspections / Surveys

Ground Monitoring Surveys

Main Southern Railway Corridor Meadows Consulting 17

Bradbury Street Lean & Hayward 1

BC Line Lean & Hayward 12

Castlereagh Street Lean & Hayward 1

Chapman Street Lean & Hayward 1

Courtland Avenue Lean & Hayward 11

Emmett Street Lean & Hayward 9

Larkin Street Lean & Hayward 9

Lintina Street Lean & Hayward 11

LW24A Draw Line Lean & Hayward 7

LW25 Draw Line Lean & Hayward 7

LW26 Draw Line Lean & Hayward 7

Mitchell Close Lean & Hayward 9

Pandora Place Lean & Hayward 9

Progress Street Lean & Hayward 8

Ralfe Street Lean & Hayward 14

Remembrance Drive Lean & Hayward 20

Remembrance Drive Shopfronts Lean & Hayward 1

Tanya Place Lean & Hayward 10

Thirlmere Way Lean & Hayward 12

Sub-Total 176

Natural Features

Bargo River flow gauging HCS 8

Bargo River data logger downloads HCS 8

Bargo River water level surveys HCS 9

Bargo River water quality sampling - field & lab

Geoterra 6

Bargo River visual inspections Tahmoor Colliery, Geoterra, HCS 32

Bargo River Angle of Draw Surveys Lean & Hayward 7

Bargo River Valley Closure Surveys Lean & Hayward 7

Bargo River Rockbar Monitoring Surveys

Lean & Hayward 4

Myrtle Creek - Download Level Data Loggers (bi-monthly)

Geoterra 3

Myrtle Creek - Water Quality Geoterra 3



sampling - Field (bi-monthly)

Myrtle Creek - Water Quality Sampling - Lab (quarterly)

Geoterra 3

Redbank Creek - Download Level Data Loggers (bi-monthly)

Geoterra 3

Redbank Creek - Water Quality sampling - Field (bi-monthly)

Geoterra 3

Redbank Creek - Water Quality Sampling - Lab (quarterly)

Geoterra 3

Groundwater - Water levels in piezometers (bi-monthly)

Geoterra 3

Groundwater - Water Quality sampling - Field (bi-monthly)

Geoterra 3

Groundwater - Water Quality Sampling - Lab (quarterly)

Geoterra 3

Sub-Total 109

Main Southern Railway (note Corridor survey above)

Reports for continuous discrete rail stress transducers monitoring results

Pidgeon Civil Engineering 13

Subsidence monitoring reports MSEC 6

Tahmoor Station Platform Clearance Surveys

Meadows Consulting 14

Thirlmere Way Overbridge surveys Meadows Consulting 16

Thirlmere Way Overbridge visual inspections

Sunrise 38

Sydney Water - Sewer

Sewer Main Surveys Lean & Hayward 28

Integral Energy - Electrical

Power Pole surveys Lean & Hayward 21

Telstra - Telecommunications

Visual inspections Lutibo (Colin Dove) 13

Tahmoor Town Centre

Building surveys Lean & Hayward 3

Structure Inspections

Public amenities / commercial district

Sunrise 3630

Houses, Units and Aged Care Villages

Sunrise 196

Pools and pool gates Sunrise 13

Dams Geoterra 18

Sub-Total 3856



Inghams

Dam Line Lean & Hayward 30

East-West Line Lean & Hayward 30

North-South Line Lean & Hayward 30

High-Rise Freezer Line Lean & Hayward 30

Plant Line Lean & Hayward 29

Pipe Support Line Lean & Hayward 28

Weighbridge Lean & Hayward 18

Wall & Column Tilt Surveys Sunrise 58

Building Interface Surveys Sunrise 105

Visual Inspections Sunrise 145

Sub-Total 503


CHAPTER 4. IMPACTS TO SURFACE FEATURES

4.1. Summary of Impacts to Surface Features

A comparison between predicted and observed impacts to surface features is summarised in Table 4-1 below. The predicted and observed impacts to surface features compare reasonably well, with the exception of locations where non-systematic movements have occurred.

Table 4-1 Summary of Predicted and Observed Impacts during Longwall 24A

SURFACE FEATURE PREDICTED IMPACTS OBSERVED IMPACTS

NATURAL FEATURES

Bargo River Potential cracking and uplift of river bed. Potential for observable loss of flow and pool level reduction Potential reduction in water quality Potential for transfer of water to shallow groundwater system Please refer report by Geoterra.

No cracks or uplift observed. No loss of stream flow or pool level reductions observed No observable reduction in quality No transfer of water to shallow groundwater observed Please refer report by Geoterra.

Aquifers or Known Groundwater Resources

Potential for enhanced groundwater seepage from the cliffs Temporary lowering of piezometric surface by up to 10m which may stay at that level until maximum subsidence develops Groundwater levels should recover with no permanent post mining reduction in water levels in bores on the plateau unless a new outflow path develops No permanent reduction in groundwater levels under the Bargo River Please refer report by Geoterra.

No change in cliff seepage flow or water quality observed Lowering of piezometric surface by up to 8.9m in piezometer P2 has been observed Groundwater levels in P2 have recovered by approximately 8.6m from their lowest point over approximately the last 12 months No reduction in groundwater levels under the Bargo River have been observed Please refer report by Geoterra.

Steep slopes and cliffs Potential soil slippage and cracking to slopes. Large-scale slope failures or cliff instabilities unlikely.

No impacts observed during Longwall 24A though 4 small natural rock falls occurred.

Natural Vegetation No impacts anticipated. No impacts observed during Longwall 24A.

PUBLIC UTILITIES

Railways No impact to track geometry likely if systematic movements occur.

Observed loss of rail stress free temperature of 4 to 5oC. Rail restressed. No impact to track geometry.

Roads (All Types) Minor cracking and buckling may occur in isolated locations.

Cracks and buckling in pavements on Lintina Street and Courtland Avenue. Cracks and buckling in kerbs and gutters along Remembrance Drive.

Water Pipelines Minor impacts possible to pipelines, particularly older cast iron pipes with lead joints.

No impacts observed during Longwall 24A.

Gas Pipelines Ground movements unlikely to adversely impact pipelines if





systematic movement occurs.

Sewerage Pipelines Mining induced tilt may reduce gradient of some pipes to less than that required for self-cleansing. Cracking to pipes and joints are unlikely if systematic movement occurs. Potential impacts at creek crossings where non-systematic movement is expected.


While grades for some pipes were reduced, none experienced a reversal of grade. Sydney Water advises that no pipes require re-levelling.

Electricity Transmission Lines or Associated Plants

Ground movements unlikely to adversely impact electrical infrastructure if systematic movement occurs.


Telecommunication Lines or Associated Plants

Ground movements unlikely to adversely impact telecommunications infrastructure if systematic movement occurs. Most vulnerable cables are older cables such as air pressurised lead sheathed cables. Strains may be higher where they connect to support structures or where affected by tree roots.

Retensioned consumer lines on Huen Pl, Pimelia St, Winpara Cl and Leiha Pl as precautionary measure.

PUBLIC AMENITIES Potential impacts to public amenities, particularly shops along Remembrance Drive. All public amenities expected to remain safe and serviceable due to the mining of Longwall 24A.

Separation of construction joint in one shop on Remembrance Drive. All structures remained safe and serviceable during mining.

FARMLAND AND FACILITIES

Farm Buildings or Sheds Negligible to slight impacts predicted for all farm buildings and sheds if systematic movement occurs.


Fences Potential for impacts to fences and gates. Gates are most vulnerable.

No impact on fences on farmland.

Farm Dams Potential adverse effects on dam walls and storage capacity. Please refer report by Geoterra.

No impacts observed to farm dams during Longwall 24A. Please refer report by Geoterra.

Wells or Bores No registered usage within SMP Area. Please refer report by Geoterra.

Water depressurisation observed in water bores. Please refer report by Geoterra.

INDUSTRIAL, COMMERCIAL & BUSINESS ESTABLISHMENTS

Negligible to slight impacts predicted for all business and commercial establishments.

Separation of construction joint in one shop on Remembrance Drive. Separation of floor slab joint and reversal of grade to connecting pipe between dams at Inghams Plant.

AREAS OF ARCHAEOLOGICAL OR HERITAGE SIGNIFICANCE

Negligible to very impacts predicted for items of heritage significance.


PERMANENT SURVEY Ground movement predicted at Ground movement occurred.




CONTROL MARKS identified survey marks.

RESIDENTIAL ESTABLISHMENTS

Houses, flats or units Status as at 24 August 2008 (two days after the start of Longwall 25).

Predictions and impact assessments provided for individual structures based on systematic subsidence movements. Of the 1,016 houses and public amenities within zone of influence of LWs 22 to 24A, 492 structures assessed to have Strain Category 1 or 2. Potential for impacts to occur as a result of non-systematic movement. Potential for some structures to experience minor impacts that may only be classified as Tilt Category A or Strain Category 1. All houses expected to remain safe, serviceable and repairable provided that they are in sound condition prior to mining.

No. of properties that have reported impacts after LW 24A = 160 (32 claims during LW 24A). No. of properties with impacts that relate to a residential structure = 147 (31 claims during LW 24A). No. of properties with impacts that only relate to associated structures = 13 (1 claim during LW 24A). Some structures are considered to have experienced impacts due to non-systematic movements. No structures have been identified as being either unsafe or unserviceable at this time. However, MSB have decided that cost of repair is greater than cost of replacement for four houses, one of which is located above LW 24A. Please refer details in this report.

Retirement or Aged Care Villages Longwall 24A will not Macquarie Grove Retirement Village

No impacts during mining of Longwall 24A.

Swimming Pools While predicted tilts are not expected to cause a loss in capacity, tilts are more readily noticeable in pools as the height of the freeboard will vary along the length of the pool. While predicted strains impacts are low, many of the pools are in-ground, which are more susceptible.

Impacts to 12 swimming pools during mining of LWs 22 to 24A. No impacts to pools due to mining of LW 24 A.

Associated Structures such as Workshops, Garages, On-Site Waste Water Systems, Water or Gas Tanks or Tennis Courts

Potential impact to pipes connected to in-ground septic tanks.

Negligible impacts predicted for non-residential domestic structures, including sheds and tanks.

Minor impacts to 23 structures during mining of LWs 22 to 24A. Impacts to 3 structures above Longwall 24A.

External Residential Pavements Cracking and buckling likely to occur, though majority minor.

Impacts to pavements observed on 61 properties during mining of Longwalls 22 to 24A. Impacts to 3 pavements above Longwall 24A.

Fences in Urban Area Some fences and gates could be slightly damaged. Most vulnerable are colorbond fences.

Impacts to gates and fences observed on 44 properties during mining of Longwalls 22 to 24A. Impacts to 3 properties above Longwall 24A.


4.2. Bargo River Gorge

4.2.1. Water Quality and Flow Impacts

Geoterra undertook an investigation into the effects of Longwall 24A on surface and ground waters in the area (Geoterra, 2008). Geoterra reported no cracks or riverbed uplift observed during mining and no observed impacts to pool levels, water flow or quality.

No adverse effect on stream water quality due to subsidence effects following extraction of Longwall 24A have been observed in the Bargo River for the monitored salinity, metals and nutrients. This is supported by the observation that the sulfate, as well as lithium, barium and strontium concentrations within the SMP Area also do not show any increase or decrease from changes in groundwater flow into or out of the river following extraction of Longwall 24A.

Field inspections, monitoring and laboratory analyses conducted to date have shown no increase the seepage volume, iron hydroxide precipitation or changes in other monitored water quality parameters within any pool containing a ferruginous groundwater seep within or outside the SMP area, either before or since Longwall 24A was extracted.

4.2.2. Rockfalls

Four very minor rockfalls have been observed during mining, though each of these has been observed following significant rainfall or wind events. The rock falls are referred to as RF-1, RF-A, B and C. Similar minor rockfalls were observed prior to mining.

A geotechnical inspection of the rockfalls was completed by Pells Sullivan Meynink (May 2008) and information below has been drawn from this report. No single factor can be identified as the cause of all the rock falls.

RF-1 lies below a relatively unstable portion of gorge wall and the morphology and condition of debris in the fall zone indicate that this has been and will continue to be an area of high rock fall potential. There is a strong correlation between rainfall intensity and RF-1.

RF-A, B and C represent single events that occurred in relatively stable regions of the gorge (plateau with thick vegetation). The presence of a water flow path down the cliff line in the location of RF-A suggests that a small rainfall event may have contributed to this rock fall.

The triggers of the four rock falls were assessed by PSM to be:

Increased rainfall and wind; and/or

Rapid changes in temperature and humidity.

There is no evidence to show that mining activity is directly responsible for any of the four rock falls and hence a mining associated trigger is considered unlikely. Given the unstable nature of cliffs, it is very difficult to know whether mine subsidence has contributed to these very minor rockfalls. However, given that no upsidence or closure is apparent across any of the monitoring lines, it is considered that any contribution from mining would be very small.

4.2.3. Exceedence of Defined Triggers

During the mining of Longwall 24A no triggers associated with the Tahmoor Colliery Longwall 24 to 26, Natural Features, Surface Safety Serviceability and Management Plan (Rev G, November 2007) have been reached or exceeded.

No remediation works have been required.

4.3. Main Southern Railway

No impacts were observed during the daily visual inspections.

As discussed in Section 2.34, small reductions in SFT between 4 and 5 degrees were observed during the mining of Longwall 24A. In accordance with the agreed management plan with ARTC, the rail was re-stressed and restored to pre-mining condition following cessation of subsidence from Longwall 24A.


4.3.1. Thirlmere Way Overbridge

No impacts were observed to the Bridge, as expected following extensive strengthening works undertaken by Tahmoor Colliery prior to commencement of Longwall 24B.


During the mining of Longwall 24A one of the triggers associated with the Tahmoor Colliery Longwall 24 to 26, Main Southern Railway Surface Safety Serviceability and Management Plan (Rev D, September 2006) was exceeded. The trigger was an observed incremental subsidence exceeding 10 mm, which is above predictions of systematic movement.

No remediation action was required in relation to this trigger exceedence. The extent of monitoring along the rail corridor was increased, in accordance with the Management Plan.

4.4. Roads

Approximately 10.3 kilometres of asphaltic pavement lie directly above the extracted longwalls and a total of 12 impacts have been observed. The observed rate of impact equates to an average of one impact for every 860 metres of pavement. The impacts were minor and did not present a public safety risk.

One of these impact sites, located on Lintina Street above Longwall 24A, was substantially greater than the other 11 impact sites. A selection of photographs is provided in Figure 4.1. The impacts on Lintina Street were repaired twice as the longwall progressed.

Cracks to kerbs and gutters were also observed in isolated locations on Courtland Avenue and Remembrance Drive.


During the mining of Longwall 24A one of the triggers associated with the Tahmoor Colliery Longwalls 24 to 26, Wollondilly Shire Council Roads, Bridges and Culverts, Surface Safety Serviceability and Management Plan (Rev B) was exceeded. The trigger exceeded was impacts to road pavements. The impacts have been recorded by the MSB and will be repaired. Temporary repairs have been conducted along Lintina Street.


Photographs courtesy of Tahmoor Colliery and Colin Dove

Figure 4.1 Photographs of impacts to road pavements and kerbs during Longwall 24A

Lintina Street Lintina Street

Remembrance Drive


4.5. Potable Water Infrastructure

Longwalls 22 to 24A have directly mined beneath approximately 960 metres of DICL pipe and 2.7 kilometres of CICL pipe, with only one noticeable impact recorded. This was a leak in a cast iron water main on Glenanne Place in June 2007. A very small number of minor leaks have been observed to consumer connection pipes on private properties

During the mining of Longwall 24A no impacts were observed to water mains above the longwall. No remediation was required.


During the mining of Longwall 24A no triggers associated with the Sydney Water Potable Water Infrastructure Surface Safety Serviceability and Management Plan (Rev E) were exceeded and no remediation was required.

4.6. Gas Infrastructure

It is noted that Longwalls 22 to 24A have directly mined beneath approximately 6.0 kilometres of gas pipes and no impacts have been recorded so far.

Subsidence monitoring and enhanced gas patrols were undertaken along the streets during mining. Increased subsidence has been observed above Longwall 24A with no impacts to gas infrastructure.


During the mining of Longwall 24A no triggers associated with the Tahmoor Colliery Longwalls 24 to 26 Alinta (now Jemena) Asset Management Surface Safety Serviceability and Management Plan (Rev E) were exceeded and no remediation was required.

4.7. Sewer Infrastructure

Longwalls 22 to 24A have directly mined beneath approximately 8.1 kilometres of sewer pipes. While changes in sewer grade have occurred as a result of mine subsidence, no noticeable impacts have been recorded so far. The observed frequency of incidences is similar to those in areas not affected by subsidence.

Subsidence monitoring was undertaken along the streets and at key sewer pit lids during mining as outlined in Section 2.5. Increased subsidence has been observed above Longwall 24A with no reported leakage, blockage or reversal of grade of the sewers.


During the mining of Longwall 24A one of the triggers associated with the Tahmoor Colliery Longwall 24 to 26, Sydney Water Sewer Infrastructure, Surface Safety Serviceability and Management Plan (Rev E, August 2008) was exceeded. The trigger exceeded was the minimum grade required for self cleansing of the sewer (i.e. less than 4 mm/m or 0.4%), and this occurred at SMH31-32.

On 23 May, the grade for SMH31 to SMH32 was measured to be 0.39%, which was less than the first trigger level of 0.4 % in the agreed management plan with Sydney Water. This trigger level was set as an early warning of potential impacts, where consideration would be given to tanker flush the affected sewer pipes. A teleconference was convened on 23 May, where Sydney Water recommended that tanker flushing not commence and to continue monitoring. It was agreed to re-set the trigger level to 0.3 % based on the observed gradual change in grade. On 27 May, it was apparent from the monitoring results that the grade would soon reduce below 0.3 % and it was agreed at a scheduled teleconference to re-set the trigger level to 0.2 % based on the observed gradual change in grade. The minimum grade at the end of Longwall 24A was 0.28 %.


4.8. Electrical Infrastructure

Longwalls 22 to 24A have directly mined beneath approximately 16.7 kilometres of electrical cables and 380 power poles and no noticeable impacts have been recorded so far.

Subsidence monitoring and daily visual inspections were undertaken along the streets during mining of Longwall 24A. While increased subsidence has been observed above Longwall 24A there were no reported impacts to electrical infrastructure.


During the mining of Longwall 24A no triggers associated with the Tahmoor Colliery Longwall 24 to 26, Integral Energy Surface Safety Serviceability and Management Plan (Rev C, August 2006) were exceeded and no remediation was required.

4.9. Telecommunication Infrastructure

Longwalls 22 to 24A have directly mined beneath approximately 19.1 kilometres of buried copper cable and 1.2 kilometres of buried optical fibre cable and 2.5 kilometres of aerial cable.

During the mining of Longwall 24A there was tilting of Telstra poles supporting the aerial cable network in the residential area of Tahmoor, around Courtland Avenue, Pandora Place, Tanya Place, Lintina Street and Mitchell Close. The movement of the poles created excess sag and tension within the aerial distribution network. Telstra, in consultation with the MSB, adjusted the cable tensions where necessary, to prevent loss of service, and where aerial cables crossed streets, hazard to traffic.

The areas requiring adjustment of the aerial cables were:

10 Pair second span east into Pandora Place, which were tight relative to other spans.

Lead-in to Nos 4 & 6 Tanya: No 4 was tight and required checking and No 6 ran through a tree in front yard.

Lead-in to No 9 Lintina was tight and required checking and adjustment.

2 x 10 Pair in Lintina, 3rd & 4th spans west from Courtland, 3rd span were loose and into two trees and 4th span cables were into one tree.

Lead-ins to No 8 & 10 Mitchell were tight and required checking and adjustment.

The major Inter Exchange Network optical fibre and main copper cables were not impacted by LW24A.


During the mining of Longwall 24A no triggers associated with the Management Plan for Longwall Mining (LW24 to LW25) Beneath Telstra Plant at Tahmoor and Thirlmere NSW were exceeded. Adjustments to aerial cables were carried out as required.

4.10. Inghams Infrastructure

4.10.1. Processing Plant

A joint between ground slabs within the Plant was observed to open up. The joint was sealed during mining and no further impacts were observed.

The Management Plan required a structural inspection and action plan to be developed if measured tilts of the High-Rise Freezer exceeded 2 mm/m tilt. This trigger level was not exceeded and no remediation work was necessary.

The most accurate measure of tilt is ground tilt between Plant Perimeter Marks 2 to 7. The survey results indicated a maximum tilt of approximately 0.69 mm/m after Longwall 24A, falling in an easterly direction towards the longwall face. This tilt contributed to correcting a tilt of approximately 0.5 mm/m which occurred in relation to previous mining in the area. This tilt is very small and is oriented in the expected direction.


4.10.2. Inghams Dams

Due to the increased subsidence at the Inghams dams, the grade on an overflow pipe between two treatment plants was reversed. This pipe has been re-laid and no further remediation work is required.


During the mining of Longwall 24A triggers associated with the Tahmoor Colliery Inghams Enterprises Pty Ltd Surface Safety Serviceability and Management Plan (Rev K, March 2008) were exceeded.

Differential vertical movements exceeded the Blue trigger between survey marks Plant 11 and Plant 12, which are located on the southern side of the Carton Tunnel. The pegs are spaced approximately 21 metres apart and the corresponding ground tilt is therefore 0.5 mm/m. No impacts were observed.

The displacement sensor 2 exceeded the Blue trigger on numerous occasions but was found to be faulty and in need of adjustment or replacement. These exceedences are therefore not related to mining.

4.11. Residential Structures and Public Amenities

A register of observed impacts is based on claims received from the Mine Subsidence Board (MSB). Information on the nature of the impacts was provided by the MSB and Sunrise Property Building Services, who inspect impacted structures on behalf Tahmoor Colliery. The register was updated on a weekly basis and the statistics provided in this report are based on impacts recorded up to the week starting 24 August 2008, two days after the commencement of Longwall 24A.

Information on the nature of impacts to each structure has been collected in the following manner:

1. Initial details of claim as supplied by the MSB on a weekly basis

2. Photographs taken during claim inspections by the MSB

3. Site visits to selected properties in company with MSB representatives

4. Inspection contained in claim files held by the MSB

A summary of reported impacts following the completion of Longwall 24A is provided in Table 4-2. The count of residential structures and public amenities includes only those structures that were predicted to experience more than 20 mm of subsidence due to the extraction of Longwalls 22 to 24A.

Table 4-2 Summary of Observed Impacts to Structures

Total after

LWs 22 to 24A Increment

during LW 24A

Number of Structures within zone of influence (predicted subsidence > 20 mm)

1016 183

Number of properties with reported impacts (not including refused claims)

160 32

Number of properties with reported impacts that relate to main structures (e.g. house or shop)

147 31

Number of properties with reported impacts that only relate to associated structures

13 1

The above information can be misleading as the majority of claims received during the mining of Longwall 24A were associated with the previous mining of Longwalls 22 to 24B. This is due to time lag between the actual impact and the claim of an impact by residents to the Mine Subsidence Board.

This is illustrated by a spatial plot of locations of impacts reported during the mining of Longwall 24A in Figure 4.2. A total of 18 of 32 claims related to the mining of Longwalls 22 to 24B, rather than the active Longwall 24A.


Figure 4.2 Locations of Impacts during the mining of Longwall 24A

Observed impacts have been classified in accordance with the impact classification tables provided in the SMP Report. Strain impacts are classified generally in accordance with Table C.1 of the Australian Standard AS2870 – 1996, although the classification was extended to include a Category 5, which corresponds to the Very Severe Damage Category of the UK National Coal Board Classification.

Australian Standards AS2870 advises that crack width is the main factor by which damage to walls is categorized. Predicted crack width was also the method by which impact assessments were conducted. Crack width has therefore been used for the purposes of classifying strain impacts to residential structures.

Predictions and impact assessments for residential structures and public amenities were provided in the SMP Report No. MSEC157. Predictions and assessments focussed on two separate types of subsidence movements: normal systematic subsidence movements and non-systematic movements. Detailed impact assessments were provided for each individual house on the basis that normal systematic movements would occur. The potential for impacts from non-systematic subsidence movements were discussed separately and no specific predictions were provided. Areas that are considered to have experienced non-systematic movements were identified in Section 2.2.


4.11.1. Comparison in General

A comparison between observed and predicted impacts is provided in Table 4-3.

Table 4-3 Comparison between Observed and Predicted Impacts in General

Predicted Total No. of

Structures Observed Total No. of

Structures

Tilt Impacts

No impact to house or civil structure 0 869

Tilt Impact Category A 1008 systematic

+/- unspecified non-systematic 142

Tilt Impact Category B 8 systematic


Tilt Impact Category C 0 systematic


Tilt Impact Category D 0 systematic


Total 1016 1016

Strain Impacts

No impact to house or civil structure 0 869

Strain Impact Category 0 524 systematic












Total 1016 1016

Notes: “Systematic” refers to impacts assessed based on predictions of systematic subsidence movements, as described in Section 3.17.1.1 of SMP Report No. MSEC157. “non-systematic” refers to the predicted potential for impacts to structures from non-systematic subsidence movements, as described in Section 3.17.1.4 of SMP Report No. MSEC157.

A discussion of the above comparison is provided in Section 4.11.3.


4.11.2. Comparison based on Predicted Impact Categories

A comparison has been made between observed and predicted impacts on a structure by structure basis for Strain Impacts only. The comparison is based on information up to 24 August 2008. A summary is provided in Table 4-4 below.

Table 4-4 Summary of Comparison between Observed and Predicted Impacts for each Structure

Strain Impact

Category

Total No. of Observed Impacts

for Structures predicted to be Strain Impact

Category 0

Total No. of Observed Impacts for Structures predicted to be Strain

Impact Category 1

Total No. of Observed Impacts for Structures predicted to be Strain

Impact Category 2

Total

No impact 476 373 20 869

Cat 0 28 68 5 101

Cat 1 7 8 1 16

Cat 2 6 10 1 17

Cat 3 2 2 0 4

Cat 4 3 2 0 5

Cat 5 2 2 0 4

Total 524 465 27 1016

% claim 9 % 20 % 26 % 14 %

% Obs > Pred

4 % 3 % 0 % -

% Obs <= Pred

96 % 97 % 100 % -

Note: Predicted impacts due to systematic subsidence only, as per Section 3.17.1.1 of SMP Report No. MSEC157.

4.11.3. Discussion of Results

Given that observed impacts are less than or equal to predicted impacts in 96 % of cases, it is considered that the current methods are generally conservative even though non-systematic movements were not taken into account in the predictions and assessments. However, when compared on a house by house basis, the predictions have been substantially exceeded in a small proportion of cases.

The majority, if not all, of the houses that have experienced Category 3, 4 or 5 impacts are considered to have experienced substantial non-systematic subsidence movements. The consideration is based on nearby ground survey results, where upsidence bumps are observed in subsidence profiles and high localised strain is observed. The potential for impact from non-systematic movements were discussed generally and not included in the specific impact assessments for each structure.

The inability to specify the number or probability of impacts due to the potential for non-systematic movements is a shortcoming of the current method. It is considered that there is significant room for improvement in this area and recommendations have been provided in a report following a review of predicted impacts on dwellings (Report No. MSEC361).

The comparison shows a favourable observation that the overall proportion of claims increased for increasing predicted impact categories. This suggests that the main parameters currently used to make impact assessments (namely predicted systematic curvature and maximum plan dimension of each structure) are credible.


The overall claim rate for main structures during the mining of Longwalls 22 to 24A was 14%. The claim rate for main structures affected by subsidence due to the mining of Longwall 24A was 8%. The result is surprising given that observed subsidence substantially exceeded predictions.

Importantly, all structures have remained safe and serviceable throughout the mining period.

4.11.4. Swimming Pools

No impacts have been observed to swimming pools due to the mining of Longwall 24A.

4.11.5. Associated Structures

Minor impacts have been observed for 3 structures due to the mining of Longwall 24A.

4.11.6. Fences

The potential for impacts to fences was raised in the SMP Report and a total of 3 properties have claimed impacts to gates and properties above Longwall 24A.


During the mining of Longwall 24A one of the triggers associated with the Tahmoor Colliery Longwall 24 to 26, Residential Establishments Surface Safety Serviceability and Management Plan (Rev C, May 2008) was exceeded. The trigger exceeded was a ground tilt which exceeded 7 mm/m along Ralfe St between Pegs RF21 and RF23.

In response to the identification of the exceedence of the above trigger, visual inspections of nearby houses on Tanya Place were undertaken and no structural issues were found.

Impacts to one house were observed to be Category 4. A structural inspection was undertaken and the house was found to be safe and serviceable.

4.12. Public Amenities

A number of public amenity structures experienced mine subsidence movements due to the mining of Longwall 24A. All of the structures were located along Remembrance Drive. The majority of the structures comprise of relatively small shopfronts. The large shopping centre, Tahmoor Town Centre, also experienced subsidence movements and discussion is provided separately in Section 4.13.

Only one structure experienced impacts during mining. A construction joint in one shop on Remembrance Drive was observed to open to Category 3 width during the mining of Longwall 24A. A structural inspection was undertaken and the house was found to be safe and serviceable.


During the mining of Longwall 24A one of the triggers associated with the Tahmoor Colliery Longwall 24 to 26, Public Amenities, Surface Safety Serviceability and Management Plan (Rev C, May 2008) was exceeded. One shop experienced an opening of a construction joint. A structural inspection was undertaken and the house was found to be safe and serviceable.

4.13. Tahmoor Town Centre

During the mining of Longwall 24A cracking at the base of some columns within the basement car park at the Tahmoor Town Centre development was reported. John Matheson & Associates Pty Ltd undertook an investigation of these, to observe the cracks and to report on the history of the observed cracks and the likely causes.

4.13.1. Observations of Cracking

Cracking was evident in the columns before the commencement of active subsidence as outlined in the pre-mining inspection report prepared by Mr John Schwarz.

Following mining, a number of columns were observed to have cracking around the column base, where the concrete has been poured so that it bears directly upon the ground floor slab. The report found that it was evident that the concrete ground slab was cast before the concrete column and that the ovoid recess


had been incorrectly located so that when casting the column, the cover concrete was cast directly onto the ground slab rather than wholly upon the underlying footing without any provision for differential movement between the ground slab and overlying column concrete. The intimate bearing of the column cover concrete on the ground slab has meant that restraint forces have been developed sufficient to cause slab cracking and surface spalling cracks at the base of the columns.

The connections between the concrete columns and the suspended concrete slab above were inspected and these connections appeared to be unchanged from earlier inspections and there was no discernable change in the condition of the structure in these locations.

4.13.2. Possible Causes of Cracking

The observed cracking appears to have been caused by restraint forces developed between the concrete column and the basement slab on ground. The restraint forces develop where the slab moves away from the column due to concrete shrinkage, significant slab shortening during extended periods of low temperature and tensile ground strains caused by mine subsidence.

From an analysis of crack size versus time overlaid with ambient temperature conditions and the progress of LW24A/B, the following was observed:

Prior to mining LW24B, 16 columns had pre-existing category 0 or 1 cracking.

During or after mining LW24B and prior to mining LW24A, 2 additional columns developed category 0/1 cracking and one column developed category 2 cracking.

During or after mining LW24A and prior to the extended cold period during winter 2008, 2 additional columns developed category 0/1 cracking and one column developed category 2 cracking.

Additional cracking appears not to have developed during the recent very cold period of weather.

4.13.3. Conclusions

It has been concluded that subsidence is the most likely cause of the additional 4 cracked columns and the growth in 2 columns from category 0/1 to category 2 although pre-existing ground slab shrinkage strains and poor column/ground slab construction detail may be contributing to the additional observed cracking.

The observed cracking appears to be localised within the column concrete cover zone and does not appear to propagate into the core of the column within the confinement of the column ties and longitudinal reinforcement. The columns were effectively designed as pinned at the base and therefore minor spalling cracking, whilst it is undesirable, is not considered to be seriously detrimental to the overall strength of the structure and that repairs may be carried out to control further cracking of category 1 cracking and epoxy concrete repairs to the small number of category 2 cracks observed.

Tahmoor Colliery has recently patched 20 columns within the TTC basement. The majority of the columns are located along Grid E. The patching works were undertaken to remove the existing spalling cracks from the reporting program so that the management plan can focus on the development of new structural cracking caused by subsidence. JMA reports that a number of construction defects were observed whilst making the repairs, which will improve concrete confinement, ductility and column shear strength.


During the mining of Longwall 24A no triggers associated with the Tahmoor Colliery Longwall 24 to 26, Tahmoor Town Centre, Surface Safety Serviceability and Management Plan (Rev D, August 2006) were exceeded.

No remediation works are required.


CHAPTER 5. SUMMARY OF RESULTS

Observed subsidence, tilt and curvature due to the mining of Longwall 24A have substantially exceeded predictions. Maximum observed subsidence was 1169 mm, which was more than double the maximum predicted subsidence of 509 mm. While observed tilts and curvature were also substantially greater than predicted, observed ground strains were within the normal range.

The observation of increased subsidence was not observed at other nearby longwalls at Tahmoor Colliery, where there was a reasonable correlation between predicted and observed profiles over Longwalls 22, 23 and 24B.

Observed subsidence was greatest above the southern half of Longwall 24A, and gradually reduced in magnitude towards the northern half of the longwall, which was directly beneath the urban area of Tahmoor.

The nature and magnitude of the increased subsidence is rare and the cause of the increased subsidence is currently not known. Tahmoor Colliery has commissioned a geotechnical study by Dr Winton Gale of Strata Control Technology to try to identify the cause or causes of the increased subsidence. Results of this study are not yet available as research is continuing. Once it became apparent that increased subsidence had developed, Tahmoor Colliery revised its management plans during extraction of LW24A to manage potential increased impacts to surface infrastructure before the longwall extracted beneath the urban area of Tahmoor.

While subsidence was substantially exceeded predictions in most locations, there remains a reasonable correlation between observed and predicted impacts, particularly in relation to public infrastructure such as sewer mains, water mains, gas mains, and electrical and telecommunications infrastructure. Impacts to road pavements were similar in frequency compared to those observed during the mining of previous longwalls. The impacts to the road pavement on Lintina Street were, however, more severe than had been observed previously.

In relation to structures, the overall claim rate for main structures during the mining of Longwalls 22 to 24A was 14%. The claim rate for main structures affected by subsidence due to the mining of Longwall 24A was 8%. The result is surprising given that observed subsidence substantially exceeded predictions.

Given that observed impacts to structures are less than or equal to predicted impacts in 96 % of cases, it is considered that the current methods are generally conservative even though non-systematic movements were not taken into account in the predictions and assessments. However, when compared on a house by house basis, the predictions have been substantially exceeded in a small proportion of cases.

Importantly, all structures have remained safe and serviceable throughout the mining period.

In relation to the Bargo Gorge, the monitoring results indicate that no measureable upsidence or closure has occurred across any of the monitoring lines across the Bargo Gorge during the mining of Longwall 24A. All differential movements have been very small and close to or within stated survey tolerance. The current observed movements during the mining of Longwall 24A are less than the predicted Longwall 24A maximum incremental upsidence of 20 mm and maximum incremental closure of 50 mm. Given the incised nature of the Gorge and its significant valley height, it was considered possible that actual upsidence and closure movements might exceed predictions but this does not appear to have occurred.

No physical, hydrological or water quality impacts were observed to the Bargo River. Four very minor rockfalls have been observed during mining, though each of these has been observed following significant rainfall or wind events. A geotechnical inspection of the rockfalls found no evidence to show that mining activity is directly responsible for any of the four rock falls and hence a mining associated trigger is considered unlikely. Given the unstable nature of cliffs, it is very difficult to know whether mine subsidence has contributed to these very minor rockfalls. However, given that no upsidence or closure is apparent across any of the monitoring lines, it is considered that any contribution from mining would be very small.


APPENDIX A. FIGURES AND DRAWINGS

Mine Subsidence Engineering Consultants Fig. MSEC335-01 Rev ?

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210Distance along Bradbury Street Line from Survey Mark BR1 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

-3

-2

-1

0

1

2

3

Tilt

(m

m/m

)

100908070605040302010

0-10

Sub

side

nce

(mm

)

During LW23

Latest Survey (End of LW24A)

Predicted Profiles

266

268

270

272

274

276

Sur

face

Lev

el A

HD

(m

)

BR1BR2

BR3BR4

BR5 BR6BR7

BR8BR9

BR10

Tahmoor Colliery - Total Subsidence Profilesalong Bradbury Street Line

Nominal Survey Toleranceof ± 0.25 mm/m

over 20 m bay lengths

I:\Projects\Tahmoor\SurveyData\Bradbury Street\Bradbury (LW24A EOP).grf

LW22

LW23A

LW24A

LW24B


0 50 100 150 200 250 300 350 400 450 500Distance along BC Line from Survey Mark Dam11 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

LW 24A

-6-5-4-3-2-10123456

Tilt

(m

m/m

)

1000

900

800

700

600

500

400

300

200

100

0

Sub

side

nce

(mm

)

During LW24A

Survey on 19-Mar-08

Survey on 22-Apr-08

Latest Survey

Predicted Profiles

250

255

260

265

270

275

280

285

Sur

face

Lev

el A

HD

(m

)

LW 24A

Dam

11

Dam

12

Da

m1

3

Da

m1

4

Dam

15

Dam

16

Dam

17

Dam

18

Dam

19

HR

F6

HR

F5

BC

1

BC

2

BC

3

BC

4

BC

5

BC

6

BC

7

RF

15

RF

16

RF

17

RF

18

RF

19

Tahmoor Colliery - Total Subsidence Profilesalong BC Line



I:\Projects\Tahmoor\SurveyData\Inghams\BC Line (LW24A EOP).grf

Monitoring line changesdirection at Pegs HRF5,RF15 and RF16

Estimate Peg HRF6 subsided80 mm at time of initial survey

Estimated subsidence for Pegs BC1 to BC7 at time of initial survey

LW22

LW23A

LW24A

LW24B


0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400Distance along Castlereagh Street Line from Survey Mark C1 (m)

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

Str

ain

(mm

/m)

LW 22 LW 23 LW 24B

-6-5-4-3-2-1012345

Tilt

(m

m/m

)

650600550500450400350300250200150100

500

Sub

side

nce

(mm

)

During LW22

During LW23

During LW24B


Predicted Profiles

264

266

268

270

272

274

276

278

280

282

284

Sur

face

Lev

el A

HD

(m

)

LW 22 LW 23 LW 24B

264.3

C1 C6

C11

C16 C21

C26 C31C36 C41

C46

C51

C56

C61

Pegs lost and replacedprior to start of LW24B

PotentialHidden Creek



Change inLine Direction

Reduced subsidenceafter LW22. Additionalsubsidence during LW23.

Break in Line acrossThirlmere Way


Survey discontinuity

Survey discontinuity

Tahmoor Colliery - Total Subsidence Profilesalong Castlereagh Street



Break in Line across

Thirlmere Way

Subsidencegreater thanpredicted

Systematic Compressive

Strain

MyrtleCreek

Anomaly


over 20m bay lengthsSystematic

CompressiveStrain

(Roadworks)

I:\Projects\Tahmoor\SurveyData\Castlereagh Street\Castlereagh (LW24A EOP).grf

LW22

LW23A

LW24A

LW24B

Tahmoor Colliery - Total Subsidence Profilesalong Chapman Street Line


0 50 100 150 200 250 300 350 400 450 500 550Distance along Chapman Street Line from Survey Mark CH1 (m)

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

Str

ain

(mm

/m)

LW 23 (not surveyed) LW 24B

-5

-4

-3

-2

-1

0

1

2

3

4

Tilt

(m

m/m

)

600

500

400

300

200

100

0

Sub

side

nce

(mm

)

During LW 24B


Predicted Profiles

270

272

274

276

278

280

282

284

286

288

Sur

face

Lev

el A

HD

(m

)

LW 23 (not surveyed) LW 24B

270.5

CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 CH9 CH10CH11

CH12CH13

CH14CH15

CH16CH17

CH18CH19

CH20

CH21CH22

CH23


over 20m bay lengths

I:\Projects\Tahmoor\SurveyData\Chapman Street\Chapman (LW24A EOP).grf

Closest peg to Railway

LW22

LW23A

LW24A

LW24B


0 50 100 150 200 250 300 350Distance along Line from Survey Mark RF21 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

LW 24A LW 25

-7

-6

-5

-4

-3

-2

-1

0

1

2

3

Tilt

(m

m/m

)

900

800

700

600

500

400

300

200

100

0

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

260

265

270

275

280

285

290

Sur

face

Lev

el A

HD

(m

)

LW 24A LW 25

RF

21

CL1 CL2 CL3 CL

4

CL

5

CL6

CL

7

CL8

CL9

CL

10

CL

11

CL1

2

CL1

3

CL

14

Tahmoor Colliery - Total Subsidence Profilesalong Courtland Avenue



I:\Projects\Tahmoor\SurveyData\Courtland Avenue\Courtland Ave (LW24A EOP).grf

Estimated subsidencefor Pegs CL1 to CL14

LW22

LW23A

LW24A

LW24B


0 10 20 30 40 50 60 70 80 90 100 110 120 130 140Distance along Line from Survey Mark R24 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

-3

-2

-1

0

1

2

3

Tilt

(m

m/m

)

140

120

100

80

60

40

20

0

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

255

260

265

270

275

280

285

Sur

face

Lev

el A

HD

(m

)

R24

ET

1

ET

2

ET

3

ET

4

ET

5

ET

6

Tahmoor Colliery - Total Subsidence Profilesalong Emmett Street



I:\Projects\Tahmoor\SurveyData\Emmett Street\Emmett St (LW24A EOP).grf

Estimated subsidencefor Pegs ET1 to ET6

LW22

LW23A

LW24A

LW24B


0 20 40 60 80 100 120 140 160 180 200 220 240 260Distance along Line from Survey Mark R14 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

LW 24A

-3

-2

-1

0

1

2

3

Tilt

(m

m/m

)

200

180

160

140

120

100

80

60

40

20

0

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

255

260

265

270

275

280

285

Sur

face

Lev

el A

HD

(m

)

LW 24A

R1

4

L1 L2 L3 L4

L5 L6

L7 L8

L9

L10

L11

L12

Tahmoor Colliery - Total Subsidence Profilesalong Larkin Street



I:\Projects\Tahmoor\SurveyData\Larkin Street\Larkin St (LW24A EOP).grf

Estimated subsidencefor Pegs L1 to L12

LW22

LW23A

LW24A

LW24B


0 20 40 60 80 100 120 140 160 180 200 220 240 260 280Distance along Line from Survey Mark LA1 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

LW 24A

-4

-3

-2

-1

0

1

2

3

4

Tilt

(m

m/m

)

800

700

600

500

400

300

200

100

0

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

260

265

270

275

280

285

290

Sur

face

Lev

el A

HD

(m

)

LW 24A

LA

1

LA

2

LA

3

LA4

LA5

LA

6

LA7

LA

8

LA

9

LA1

0

LA11

LA

12

LA13

Tahmoor Colliery - Total Subsidence Profilesalong Lintina Street



I:\Projects\Tahmoor\SurveyData\Lintina Street\Lintina Street (LW24A EOP).grf

Estimated subsidencefor Pegs LA1 to LA13

LW22

LW23A

LW24A

LW24B


0 50 100 150 200 250 300 350 400 450 500Distance along LW25 Draw Line from Survey Mark 24-1 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

LW 24A

-4

-2

0

2

4

6

8

10

12

Tilt

(m

m/m

)

11001000

900800700600500400300200100

0

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

250

255

260

265

270

275

280

285

Sur

face

Lev

el A

HD

(m

)

LW 24A

24-1 2

4-2

24-

3

24-

4 24-

5

24-

6

24-

7

24-8

24-

9

24-1

0

24-

11

24-1

2

24-1

3

24-1

4

24-1

5

24-1

6

24-

17

24-

18

24-

19

Tahmoor Colliery - Total Subsidence Profilesalong LW24A Draw Line



I:\Projects\Tahmoor\SurveyData\LW24A Draw Line\LW24A Draw Line (LW24A EOP).grf

LW22

LW23A

LW24A

LW24B


0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360Distance along LW25 Draw Line from Survey Mark 25-1 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

-3

-2

-1

0

1

2

3

Tilt

(m

m/m

)

50

40

30

20

10

0

-10

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

250

255

260

265

270

275

280

285

Sur

face

Lev

el A

HD

(m

)

25-

1 25-2 25

-3 25-4 25-

5

25-6

25-

7

25-8 25-

9 25-1

0

25-

11 25-

12 25-1

3

25-1

4

25-

15

25-1

6

Tahmoor Colliery - Total Subsidence Profilesalong LW25 Draw Line



I:\Projects\Tahmoor\SurveyData\LW25 Draw Line\LW25 Draw Line (LW24A EOP).grf

LW22

LW23A

LW24A

LW24B


0 50 100 150 200 250 300 350 400Distance along LW26 Draw Line from Survey Mark 26-1 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

LW26

-3

-2

-1

0

1

2

3

Tilt

(m

m/m

)

60

50

40

30

20

10

0

-10

-20

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

240

245

250

255

260

265

270

Sur

face

Lev

el A

HD

(m

)

LW26

26-1

26-2

26-3

26-426-5

26-6

26-7

26-826-9 26-10 26-11 26-12 26-13 26-14 26-15

26-1626-17 26-18

Tahmoor Colliery - Total Subsidence Profilesalong LW26 Draw Line



I:\Projects\Tahmoor\SurveyData\LW26 Draw Line\LW26 Draw Line (LW24A EOP).grf


93.6 93.7 93.8 93.9 94.0 94.1 94.2 94.3 94.4 94.5 94.6 94.7 94.8 94.9 95.0 95.1 95.2 95.3Chainage along Main Southern Railway (km)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

Str

ain

(mm

/m)

LW 25 LW 22LW 23LW 24BLW 25

-2

-1

0

1

2

Tilt

(m

m/m

)

140

120

100

80

60

40

20

0

Sub

side

nce

(mm

)

During LW 22

During LW 23

During LW 24B

During LW 24A

Latest Survey

Predicted Profiles

260

262

264

266

268

270

272

274

276

278

280

Sur

face

Lev

el A

HD

(m

)

LW 22LW 23LW 24BLW 25

Projectionof Dyke

93.600 93.700

93.800

93.90094.000 94.100

94.20094.300

94.400 94.500 94.600 94.700

94.80094.900 95.000

95.100 95.200 95.300

Thirlmere WayOverbridge Tahmoor

RailwayStation

Creek CreekCreek

MyrtleCreek

SewerSewer Water

Main

Gas

Gas

Culvert94.707

Culvert94.576

Culvert94.225

Culvert93.750

Pegs identified as disturbedby surveyor prior to start of LW24B

Survey discontinuity Reduced subsidenceduring LW22

Tahmoor Colliery - Total Subsidence Profilesalong Main Southern Railway Corridor Line

Upsidence

Upsidence

Valley ClosureIncreasing

during LW 24A

Bump

Pegs lost in week starting 7 Jan 2007 due to rail maintenance activities.Replaced 31 Oct 2007.

Datum check: extra 16mmfrom 21-Nov-06 to 30-Jan-07

Affected byvehicle loads



Bumped peg at entranceto rail corridor. No change.

Bumped peg at entranceto rail corridor

Bumped peg.No change since

first survey of LW24A.


first survey of LW24A.

Strains increasingduring LW24A.

I:\Projects\Tahmoor\SurveyData\Main Southern Railway\Railway Line\Main Southern Railway Total (LW24A EOP).grf

LW22

LW23A

LW23B

LW24A

LW24B

92.0 km

93.5 km

94.0 km

94.5 km

95.0 km

95.5 km

92.5 km

93.0 km

Overbridge

Culvert


93.6 93.7 93.8 93.9 94.0 94.1 94.2 94.3 94.4 94.5 94.6 94.7 94.8 94.9 95.0 95.1 95.2 95.3Chainage along Main Southern Railway (km)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

Str

ain

(mm

/m)

LW 25 LW 22LW 23LW 24BLW 25

-2

-1

0

1

2

Tilt

(m

m/m

)

100

80

60

40

20

0

Sub

side

nce

(mm

)

During LW 24A

Latest survey

Predicted Profiles

260

262

264

266

268

270

272

274

276

278

280

Sur

face

Lev

el A

HD

(m

)

LW 22LW 23LW 24BLW 25

Projectionof Dyke

93.600 93.700

93.800

93.90094.000 94.100

94.20094.300

94.400 94.500 94.600 94.700

94.80094.900 95.000

95.100 95.200 95.300

Thirlmere WayOverbridge Tahmoor

RailwayStation

Creek CreekCreek

MyrtleCreek

SewerSewer Water

Main

Gas

Culvert94.707

Culvert94.576

Culvert94.225

Culvert93.750

Tahmoor Colliery - Incremental Subsidence ProfilesMain Southern Railway Corridor Line during LW24A



Negligible change since first survey.Subsidence bumps likely to be due to

corridor activity October 2007.


first survey.

NOTE: Concrete sleepers installed on both Up and Dn Mainsbetween LW 24B and 24A. Expansion switch and free rail in operation as part of Tahmoor Switch Trial.


first survey.




Strain growth atcreek. This site haspreviously seencompressive strain.

Possible strain growth. This site has previouslyseen compressive strain.

LW22

LW23A

LW23B

LW24A

LW24B

92.0 km

93.5 km

94.0 km

94.5 km

95.0 km

95.5 km

92.5 km

93.0 km

Overbridge

Culvert

I:\Projects\Tahmoor\SurveyData\Main Southern Railway\Railway Line\Main Southern Railway Inc (LW24A EOP).grf


240 220 200 180 160 140 120 100 80 60 40 20 0Distance along Mitchell Cl Line from Survey Mark LA8 (m)

-5.0-4.5-4.0-3.5-3.0-2.5-2.0-1.5-1.0-0.50.00.51.0

Str

ain

(mm

/m)

LW 24A

-5

-4

-3

-2

-1

0

1

2

3

Tilt

(m

m/m

)

500

450

400

350

300

250

200

150

100

50

0

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

266

268

270

272

274

276

278

280

Sur

face

Lev

el A

HD

(m

)

LW 24A

LA8

ML

1

ML2

ML3

ML4

ML5

ML6

ML7

ML8

ML

9

ML1

0

ML1

1

Tahmoor Colliery - Total Subsidence Profilesalong Mitchell Close during LW24A



I:\Projects\Tahmoor\SurveyData\Mitchell Close\Mitchell Cl (LW24A EOP).grf

Estimated subsidencefor Pegs ML1 to ML11

Cracks in pavement atlocation of elevatedground strain.

LW22

LW23A

LW24A

LW24B


0 50 100 150 200 250Distance along Pandora Pl Line from Survey Mark PA1 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

LW 24A LW 25

-3

-2

-1

0

1

2

3

Tilt

(m

m/m

)

200

180

160

140

120

100

80

60

40

20

0

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

265

270

275

280

285

290

295

Sur

face

Lev

el A

HD

(m

)

LW 24A LW 25

PA

1 PA

2

PA

3

PA

4

PA

5

PA

6

PA

7

PA

8

PA

9

PA

10

PA

11

PG

16

Tahmoor Colliery - Total Subsidence Profilesalong Pandora Place



I:\Projects\Tahmoor\SurveyData\Pandora Place\Pandora Pl (LW24A EOP).grf

Estimated subsidencefor Pegs PA1 to PA11

LW22

LW23A

LW24A

LW24B


0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900Distance along Line from Survey Mark 25-17 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

LW 25

-3

-2

-1

0

1

2

3

Tilt

(m

m/m

)

150

100

50

0

-50

Sub

side

nce

(mm

)

During LW24B

During LW24A

Latest Survey

260

265

270

275

280

285

290

295

Sur

face

Lev

el A

HD

(m

)

LW 25

PG

1P

G2

PG

3

PG

4

PG

5

PG

6

PG

7 PG

8

PG

9

PG

10

PG

11P

G12

PG

13P

G14

PG

15

PG

16P

G17

PG

18P

G19

PG

20

PG

21

BO

LT

5

BO

LT

4

BO

LT

3

BO

LT2

BO

LT

1

GA

TE

Tahmoor Colliery - Total Subsidence Profilesalong Progress Street



I:\Projects\Tahmoor\SurveyData\Progress Street\Progress Total (LW24A EOP).grf

LW22

LW23A

LW24A

LW24B

Strain not measured beyond PG21

Tilts over 60m bays,not standard 20m bays

Connect to High-RiseFreezer Line

Connect toRalfe St Line

Connect toPandora Pl Line

Change inline direction

Suspect many PG pegs have been disturbed verticallyby vehicle loads since installation in October 2006.

Damaged peg, reinstated priorto start of LW 25.

Connect toAbelia St Line

Connect toCourtland Ave Line

Connect toRemembrance Dr Line


0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900Distance along Line from Survey Mark 25-17 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

LW 25

-4

-3

-2

-1

0

1

2

3

4

5

6

Tilt

(m

m/m

)

70

60

50

40

30

20

10

0

-10

Sub

side

nce

(mm

)

During LW24A

Latest Survey

260

265

270

275

280

285

290

295

Sur

face

Lev

el A

HD

(m

)

LW 25

PG

1P

G2

PG

3

PG

4

PG

5

PG

6

PG

7 PG

8

PG

9

PG

10

PG

11P

G12

PG

13P

G14

PG

15

PG

16P

G17

PG

18P

G19

PG

20

PG

21

BO

LT

5

BO

LT

4

BO

LT

3

BO

LT2

BO

LT

1

GA

TE

Tahmoor Colliery - Incremental Subsidence Profilesalong Progress Street during LW24A



I:\Projects\Tahmoor\SurveyData\Progress Street\Progress Inc (LW24A EOP).grf

LW22

LW23A

LW24A

LW24B

Strains not measured beyond PG21

Tilts over 60m bays,not standard 20m bays

Connect to High-RiseFreezer Line

Connect toRalfe St Line

Connect toPandora Pl Line


Damaged peg, reinstated priorto start of LW 25.

Connect toAbelia St Line

Connect toCourtland Ave Line

Connect toRemembrance Dr Line


0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750Distance along BC Line from Survey Mark Dam11 (m)

-3.5-3.0-2.5-2.0-1.5-1.0-0.50.00.51.01.52.0

Str

ain

(mm

/m)

LW 24A LW 25

-10

-8

-6

-4

-2

0

2

4

6

8

10

Tilt

(m

m/m

)

1000

900

800

700

600

500

400

300

200

100

0

Sub

side

nce

(mm

)

Survey on 10-Apr-08

During LW24A

Latest Survey

Predicted Profiles

260

265

270

275

280

285

290

Sur

face

Lev

el A

HD

(m

)

LW 24A LW 25

CP

12

RF

1

RF

2

RF

3

RF

4

RF

5

RF

6

RF

7

RF

8

RF

9

RF

10

RF

11

RF

12

RF

13

RF

14

RF

15

RF

16

RF

17

RF

18

RF

19

RF

20

RF

21

RF

22

RF

23

RF

24

RF

25

RF

26

RF

27

RF

28

RF

29

RF

30

PG

21

Tahmoor Colliery - Total Subsidence Profilesalong Ralfe Street



I:\Projects\Tahmoor\SurveyData\Ralfe Street\Ralfe Street (LW24A EOP).grf

Estimated subsidencefor Pegs RF1 to RF30

LW22

LW23A

LW24A

LW24B


0 100 200 300 400 500 600 700 800 900 1000Distance along Remembrance Drive Line from Survey Mark R36 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

LW 24A LW 25

-5

-4

-3

-2

-1

0

1

2

3

4

5

Tilt

(m

m/m

)

300

250

200

150

100

50

0

Sub

side

nce

(mm

)

During LW22

During LW23A&B

During LW24B

During LW24A

Latest Survey

Predicted Profiles

255

260

265

270

275

280

285

Sur

face

Lev

el A

HD

(m

)

LW 24A LW 25

R36

R34

R32 R30 R28

R26 R24 R22 R20 R18 R1

6

R14

R12

R10 R8 R6 R4

R2

RE

1

RE

3

RE

5

RE

7

RE

9

RE

11

Tahmoor Colliery - Total Subsidence Profilesalong Remembrance Drive Line



I:\Projects\Tahmoor\SurveyData\Remembrance Drive\Remembrance Total (LW24A EOP).grf

LW22

LW23A

LW24A

LW24B

Mine Subsidence Engineering Consultants Fig. MSEC335-20 Rev ?0 100 200 300 400 500 600 700 800 900 1000

Distance along Remembrance Drive Line from Survey Mark R36 (m)

-0.4

-0.2

0.0

0.2

0.4

Cur

vatu

re (

1/km

)

LW 24A LW 25

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

-8

-6

-4

-2

0

2

4

6

8

Tilt

(m

m/m

)

500

400

300

200

100

0

-100

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Projected Profiles based on High-Rise Freezer surveys

Predicted Profiles in SMP Report (MSEC157)

255

260

265

270

275

280

285

Sur

face

Lev

el A

HD

(m

)

LW 24A LW 25

R36

R34

R32 R30

R28

R26 R24 R22 R20

R18 R16

R14

R12

R10 R8 R6 R4

R2

RE

1

RE

3

RE

5

RE

7

RE

9

RE

11

Tahmoor Colliery - Incremental Subsidence Profilesalong Remembrance Drive due to LW24A

Irregularity in subsidence profileconsistent between surveys andnot increasing. Suspect damageto survey pegs. Check next survey.

Bump increased this survey.No noticeable increase inground strain. Bump in line with impacts on Lintina Street.Check next survey.

I:\Projects\Tahmoor\SurveyData\Remembrance Drive\Remembrance Inc (LW24A EOP).grf

LW22

LW23A

LW24A

LW24B


-20 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320Distance along line from Survey Mark SH13 (m)

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

Cur

vatu

re (

km-1)

LW 24A

-5

-4

-3

-2

-1

0

1

2

3

4

5

Tilt

(m

m/m

)

300

250

200

150

100

50

0

Sub

side

nce

(mm

)

Latest Survey

Observed LW24A profile pluspredicted normal LW25 (MSEC157)

Observed LW24A profile plusprojected LW25 (based on HRF LW24A)

260

265

270

275

280

285

290

Sur

face

Lev

el A

HD

(m

)

LW 24A

B03a B04 B05 B06a B06b B06c B07 B59a

B60a

B61a B62aB63a

B64a

B65aB66a Y01a Y02c

SH

13

SH

12

SH

11

SH

10

SH

9

SH

8

SH

7

SH

6

SH

5

SH

4

SH

3S

H2

SH

1

SH

14

SH

15

SH

16S

H1

7

SH

18

SH

19

SH

20

SH

21

Tahmoor Colliery - Total Subsidence Profilesalong Remembrance Drive Shopfronts

Tilt Trigger in Subsidence Management Plan

I:\Projects\Tahmoor\SurveyData\Remembrance Drive\Shopfronts\Shopfronts (LW24A EOP).grf

Estimated subsidence for PegsSH1 to SH13 at initial survey

Larkin St

Estimated subsidence for PegsSH14 to SH21 after LW24A

No.

155

No.

153

No.

151

No.

14

9

No.

14

7

No.

14

5

No.

14

3

No.

14

1

No.

13

9

No.

13

5-1

37

No.

13

1-1

33

No.

12

9

No.

12

5-1

27

No.

12

3

No.

12

1

No.

11

9

No.

11

9

Tilt Trigger in Subsidence Management Plan

Estimated tilt forPegs SH14 to SH21

after LW24A

Estimated curvature forPegs SH14 to SH21

after LW24A

LW22

LW23A

LW24A

LW24B


0 10 20 30 40 50 60 70 80 90 100 110Distance along Line from Survey Mark TA1 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

LW 24A LW 25

-7

-6

-5

-4

-3

-2

-1

0

1

2

Tilt

(m

m/m

)

600

500

400

300

200

100

0

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

250

255

260

265

270

275

280

285

290

Sur

face

Lev

el A

HD

(m

)

LW 24A LW 25

TA

1

TA

2

TA

3

TA

4

TA

5

TA

6

Tahmoor Colliery - Total Subsidence Profilesalong Tanya Place



I:\Projects\Tahmoor\SurveyData\Tanya Place\Tanya Pl (LW24A EOP).grf

Estimated subsidencefor Pegs TA1 to TA6

LW22

LW23A

LW24A

LW24B

LW25

LW26

18-Nov

559 m

Tahmoor Colliery - Total Subsidence Profilesalong Thirlmere Way Line


0 200 400 600 800 1000 1200 1400 1600 1800Distance along Thirlmere Way Line from Survey Mark T1 (m)

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

Str

ain

(mm

/m)

LW 22 LW 23A LW 24B LW 25

-4

-3

-2

-1

0

1

2

3

4

Tilt

(m

m/m

)

900

800

700

600

500

400

300

200

100

0

Sub

side

nce

(mm

)

During LW22

During LW23

During LW24B

During LW24A


Predicted Profiles

270

272

274

276

278

280

282

284

286

288

290

Sur

face

Lev

el A

HD

(m

)

LW 22 LW 23A LW 24B LW 25

Dyke

T1

T6T11

T16

T21

T26T31

T36

T41 T46T51

T56

T61

T66T71 T76

T81

T86

Cracks

Pegs lost and replacedprior to start of LW24B

Tributary ofMyrtle Creek

ValleyClosure

Tributary ofMyrtle Creek

Upsidence nearbottom of valley


Small bump in survey line

Survey line discontinuity

Thirlmere WayOverbridge

Systematiccompressivespike where

cracking and bumpobserved

in pavement

Fraser Stintersection

Changes inline direction



I:\Projects\Tahmoor\SurveyData\Thirlmere Way\Thirlmere Way Total (LW24A EOP).grf

(Roadworks)

Bumped peg(roadworks)

LW22

LW23A

LW24A

LW24B


1300 1350 1400 1450 1500 1550 1600 1650 1700 1750 1800Distance along Thirlmere Way from Survey Mark T1 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

LW 24B LW 25

-3

-2

-1

0

1

2

3

Tilt

(m

m/m

)

504540353025201510

50

-5-10-15

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

260

265

270

275

280

285

290

Sur

face

Lev

el A

HD

(m

)

LW 24B LW 25

T6

4

T66

T68

T7

0 T72 T

74

T76

T78

T80 T8

2

T8

4 T8

6

Tahmoor Colliery - Incremental Subsidence Profilesalong Thirlmere Way during LW24A



I:\Projects\Tahmoor\SurveyData\Thirlmere Way\Thirlmere Way Inc (LW24A EOP).grf

LW22

LW23A

LW24A

LW24B


0 50 100 150 200 250 300 350 400Distance along Dam Line from Survey Mark Dam1 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

LW 24A

-4

-3

-2

-1

0

1

2

3

4

5

6

Tilt

(m

m/m

)

800

700

600

500

400

300

200

100

0

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

250

255

260

265

270

275

280

Sur

face

Lev

el A

HD

(m

)

LW 24A

Dam

1

Dam

2

Dam

3

Da

m4

Da

m5

Da

m6

Dam

7

Da

m8

Dam

9

Da

m1

0

Da

m1

1

Dam

12

Da

m1

3

Dam

14

Dam

15

Dam

16

Da

m1

7

Da

m1

8

Dam

19

Tahmoor Colliery - Total Subsidence Profilesalong Inghams Dam Line




I:\Projects\Tahmoor\SurveyData\Inghams\Dam Line (LW24A EOP).grf

Monitoring line changesdirection at Peg Dam12

Monitoring line changesdirection at Peg Dam12

Small bump

Maximum compressive strainreduced from previous surveys

Elevated tensilestrain not repeatedin latest survey.

LW22

LW23A

LW24A

LW24B


0 50 100 150 200 250 300Distance along East-West Line from Survey Mark EW1 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

LW 24A

-1

0

1

2

3

4

5

6

7

Tilt

(m

m/m

)

700

600

500

400

300

200

100

0

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

250

255

260

265

270

275

280

Sur

face

Lev

el A

HD

(m

)

LW 24A

EW

1

EW

2

EW

3

EW

4

EW

5

EW

6

EW

7

EW

8

EW

9

EW

10

EW

11

EW

12

Dam

14

Tahmoor Colliery - Total Subsidence Profilesalong Inghams East-West




I:\Projects\Tahmoor\SurveyData\Inghams\East-West Line (LW24A EOP).grf

LW22

LW23A

LW24A

LW24B


0 50 100 150 200 250 300 350 400 450Distance along High-Rise Freezer Line from Survey Mark NS7 (m)

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

LW 24A

-14-12-10

-8-6-4-202468

10

Tilt

(m

m/m

)

14001300120011001000

900800700600500400300200100

0

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

250

255

260

265

270

275

280

Sur

face

Lev

el A

HD

(m

)

LW 24A

NS

7

HR

F1

HR

F2

HR

F3

HR

F4

HR

F5

HR

F6

HR

F7

HR

F8

HR

F9

HR

F1

0

HR

F1

1

HR

F1

2

HR

F1

3

HR

F14

HR

F15

HR

F16

HR

F1

7

HR

F18

Tahmoor Colliery - Total Subsidence Profilesalong Inghams High-Rise Freezer Line




I:\Projects\Tahmoor\SurveyData\Inghams\High-Rise Freezer Line (LW24A EOP).grf

Estimated subsidence forPegs HRF6 to HRF17

Upsidence in creekCreek does not extend

to urban area

Valley closure

LW22

LW23A

LW24A

LW24B


0 20 40 60 80 100 120 140 160 180 200Distance along North-South Line from Survey Mark EW7 (m)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Str

ain

(mm

/m)

-3

-2

-1

0

1

2

3

Tilt

(m

m/m

)

220200180160140120100

80604020

0

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

255

260

265

270

275

280

285

Sur

face

Lev

el A

HD

(m

)

EW

7

NS

1

NS

2

NS

3

NS

4

NS

5

NS

6

NS

7

NS

8

NS

9

Tahmoor Colliery - Total Subsidence Profilesalong Inghams North-South




I:\Projects\Tahmoor\SurveyData\Inghams\North-South Line (LW24A EOP).grf

Compressive strains reducedfrom previous surveys.

LW22

LW23A

LW24A

LW24B


0 5 10 15 20 25 30 35 40 45 50 55 60 65Distance from PS1 (m)

-10

-8

-6

-4

-2

0

2

4

6

8

10

Diff

ere

ntia

l Hor

izon

tal M

ovem

ent

betw

een

adja

cent

peg

s (m

m)

-10

-8

-6

-4

-2

0

2

4

6

8

10

Diff

eren

tial V

ert

ical

Mov

emen

tbe

twe

en a

djac

ent p

egs

(mm

)

220200180160140120100

80604020

0

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

255

260

265

270

275

280

285

Sur

face

Lev

el A

HD

(m

)

PS

1

PS

2

PS

3

PS

4

PS

5

PS

6

PS

7

PS

8

PS

9

PS

10

PS

11

PS

12

PS

13

PS

14

PS

15

Tahmoor Colliery - Total Subsidence Profilesalong Pipe Support Line (PS1 to PS15)



I:\Projects\Tahmoor\SurveyData\Inghams\Pipe Supports (LW24A EOP).grf

Recommend that an extra 5 mm of subsidencebe added to results to account for later initial survey.

Trigger for Blue Level

Ammonia pipes redundantin this area.

Triggers for Blue Level


Elevated closure notrepeated in latest survey.

LW22

LW23A

LW24A

LW24B


0 5 10 15 20 25 30 35 40Distance from PS16 (m)

-10

-8

-6

-4

-2

0

2

4

6

8

10

Diff

ere

ntia

l Hor

izon

tal M

ovem

ent

betw

een

adja

cent

peg

s (m

m)

-10

-8

-6

-4

-2

0

2

4

6

8

10

Diff

eren

tial V

ert

ical

Mov

emen

tbe

twe

en a

djac

ent p

egs

(mm

)

220200180160140120100

80604020

0

Sub

side

nce

(mm

)

During Lw24A

Latest Survey

Predicted Profiles

255

260

265

270

275

280

285

Sur

face

Lev

el A

HD

(m

)

PS

16

PS

17

PS

18

PS

19

PS

20

PS

21 12

PS

22

PS

23

Tahmoor Colliery - Total Subsidence Profilesalong Pipe Support Line (PS16 to PS23)


I:\Projects\Tahmoor\SurveyData\Inghams\Pipe Supports 16-23 (LW24A EOP).grf

Pipe Supports installed on 22nd February 2008.Approximately 28mm of subsidence had been

measured at Survey Mark 12 at this time.




LW22

LW23A

LW24A

LW24B


0 50 100 150 200 250 300 350 400 450Distance from Survey Mark 1 (m)

-10

-8

-6

-4

-2

0

2

4

6

8

10

Diff

ere

ntia

l Hor

izon

tal M

ovem

ent

betw

een

adja

cent

peg

s (m

m)

-12-10

-8-6-4-202468

1012

Diff

eren

tial V

ert

ical

Mov

emen

tbe

twe

en a

djac

ent p

egs

(mm

)

220200180160140120100

80604020

0

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Predicted Profiles

255

260

265

270

275

280

285

Sur

face

Lev

el A

HD

(m

)

12 3 4 5 6 7 89 10 11 12 13 14 15 16 17 18

19 20

21 22

23 24 25 26 27

28 29 30 31 32

33 34 35 36 37

38 3940

41 422

Tahmoor Colliery - Total Subsidence Profilesalong Inghams Plant Perimeter Line



Recommend that an extra 5 mm of subsidencebe added to results to account for later initial survey.

I:\Projects\Tahmoor\SurveyData\Inghams\Plant (LW24A EOP).grf

No access to pegs dueto construction activity



High-Rise(north side)

High-Rise(south side)

Carton tunnel(north side)

Carton tunnel(south side)

Note: All elevated differential vertical movementsrelate to relatively long bay lengths

Mark 32 replaced

LW22

LW23A

LW24A

LW24B

Nail at Peg 13 bumped duringconstruction activity


0 100 200 300 400 500 600 700 800 900 1000Longwall Chainage (m)

0

10

20

30

40

50

Ups

ide

nce

and

Clo

sure

(m

m)

Upsidence

Closure

-10 0 10 20 30 40 50 60 70 80Distance along Mermaids Pool Line from Survey Mark M00 (m)

-10

-8

-6

-4

-2

0

2

4

6

8

10

Diff

eren

tial H

oriz

onta

l Mov

emen

tbe

twe

en a

djac

ent p

egs

(mm

)

30

20

10

0

-10

-20

-30

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Nominal Survey Tolerance

0

10

20

30

40

50

Sur

face

Lev

el A

HD

(m

)

M00

M01

M02

M03

M04

M05

M06

M07

M08 M

09

M10 M11

M12

M13

Tahmoor Colliery - Total Subsidence Profilesalong Mermaids Pool Line across the Bargo River

I:\Projects\Tahmoor\SurveyData\Bargo River\Mermaid Pool\Mermaid (LW24A EOP).grf

LW24A



0

10

20

30

40

50

Ups

ide

nce

and

Clo

sure

(m

m)

Upsidence

Closure

-10 0 10 20 30 40 50Distance along X1 Line from Survey Mark X1-1 (m)

-10

-8

-6

-4

-2

0

2

4

6

8

10

Diff

eren

tial H

oriz

onta

l Mov

emen

tbe

twe

en a

djac

ent p

egs

(mm

)

30

20

10

0

-10

-20

-30

Sub

side

nce

(mm

)

During LW24A

Latest Survey

Nominal Survey Tolerance

45

46

47

48

49

50

51

52

53

54

55

Sur

face

Lev

el A

HD

(m

)

X1-

1

X1-

2

X1-

3

X1-

4

X1-

5

X1-

6 X1-

7

X1-

8

X1-

9

Tahmoor Colliery - Total Subsidence Profilesalong X1 Line across the Bargo River

X1 Line is not connected to datum.Subsidence is relative only.

I:\Projects\Tahmoor\SurveyData\Bargo River\Rockbars\X1 Line (LW24A EOP).grf

LW24A



0

10

20

30

40

50

Ups

ide

nce

and

Clo

sure

(m

m)

Upsidence

Closure

-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170Distance along X2 Line from Survey Mark X2-L (m)

-10-8-6-4-202468

1012

Diff

eren

tial H

oriz

onta

l Mov

emen

tbe

twe

en a

djac

ent p

egs

(mm

)

30

20

10

0

-10

-20

-30

Sub

side

nce

(mm

)

During LW24A

Latest Survey

180

190

200

210

220

230

240

250

260

270

Sur

face

Lev

el A

HD

(m

) X2-

L

X2-

1

X2-

2

X2-

3X

2-4

X2-

5X

2-6

X2-

7 X2-

8

X2-

R


Level connection betweenPeg X2-L and X2-6. Surveytolerance of level connectioninto gorge of ± 10 mm.

X2-L not connected todatum. Subsidence isrelative only.

Relative survey tolerance of levels inbase of gorge ± 3 mm.


LW24A



0

10

20

30

40

50

Ups

ide

nce

and

Clo

sure

(m

m)

Upsidence

Closure

-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170Distance along X3 Line from Survey Mark X3-L (m)

-10

-8

-6

-4

-2

0

2

4

6

8

10

Diff

eren

tial H

oriz

onta

l Mov

emen

t b

etw

een

adja

cent

peg

s (m

m)

30

20

10

0

-10

-20

-30

Sub

side

nce

(mm

)

During LW24A

Latest Survey

170

180

190

200

210

220

230

240

250

260

270

Sur

face

Lev

el A

HD

(m

)

X3-

L

X3-

1

X3-

2 X3-

3

X3-

R


Level connection betweenPeg X3a-L and X3-2. Surveytolerance of level connectioninto gorge of ± 10 mm.

Peg X3a-L destroyed and replaced on 15 Feb 08.Subsidence returned to zero for replaced X3a-L.Increased subsidence for X3a pegs in gorgemeasured since Peg X3a-L was replaced.Peg X3a-L destroyed again on 17-Apr 08.



LW24A



0

10

20

30

40

50

Ups

ide

nce

and

Clo

sure

(m

m)

Upsidence

Closure

-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180Distance along X3a Line from Survey Mark X3a-L (m)

-10

-5

0

5

10

15

20

Diff

eren

tial H

oriz

onta

l Mov

emen

tbe

ttwee

n ad

jace

nt p

egs

(mm

)

30

20

10

0

-10

-20

-30

Sub

side

nce

(mm

)

During LW24A

Latest Survey

160

170

180

190

200

210

220

230

240

250

260

270

Sur

face

Lev

el A

HD

(m

) X3a

-L

X3a

-1

X3a

-2

X3a

-3X

3a-4

X3a

-5

X3a

-6

X3a

-R

Tahmoor Colliery - Total Subsidence Profilesalong X3a Line across the Bargo River

Level connection betweenPeg X3a-L and X3a-6. Surveytolerance of level connectioninto gorge of ± 10 mm.

Peg X3a-L destroyed and replaced on 15 Feb 08.Subsidence returned to zero for replaced X3a-L.Increased subsidence for X3a pegs in gorgemeasured since Peg X3a-L was replaced.Peg X3a-L destroyed again on 17-Apr 08.Subsidence for this survey normalised basedon subsidence at nearby Peg 25-1.


Peg X3a5 destroyed and replacedon 17-Apr-08.Subsidence normalised to matchsubsidence of adjacent pegs.

I:\Projects\Tahmoor\SurveyData\Bargo River\Rockbars\X3a Line (LW24A EOP).grf

LW24A



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-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170Distance along X5a Line from Survey Mark X5-L (m)

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X5a

-7

X5-

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Tahmoor Colliery - Total Subsidence Profilesalong X5a Line across the Bargo River

Level connection betweenPeg X5-L and X5a-5. Surveytolerance of level connectioninto gorge of ± 10 mm.


I:\Projects\Tahmoor\SurveyData\Bargo River\Rockbars\X5a Line (LW24A EOP).grf

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-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170Distance along X5b Line from Survey Mark X5-L (m)

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Tahmoor Colliery - Total Subsidence Profilesalong X5b Line across the Bargo River

Level connection betweenPeg X5-L and X5b-7. Surveytolerance of level connectioninto gorge of ± 10 mm.


I:\Projects\Tahmoor\SurveyData\Bargo River\Rockbars\X5b Line (LW24A EOP).grf

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-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210Distance along X5c Line from Survey Mark X5-L (m)

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X5c

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Tahmoor Colliery - Total Subsidence Profilesalong X5c Line across the Bargo River

Level connection betweenPeg X5-L and X5c-7. Surveytolerance of level connectioninto gorge of ± 10 mm.

Tree has grown and restrictedline of sight from X5-L to X5c-7.Eccentric setup used for levelconnection for March survey.Level to X5c-7 now connectedby X5a and X5b base pegs.


I:\Projects\Tahmoor\SurveyData\Bargo River\Rockbars\X5c Line (LW24A EOP).grf

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-20 0 20 40 60 80 100 120 140 160 180 200 220 240 260Distance along X6 Line from Survey Mark X6-L (m)

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X6-L not connected todatum. Subsidence isrelative only.

Survey error, notrepeated in currentsurvey.



LW24A

LW24A - EoP - MSEC

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