end of panel report longwall 14 - centennial...

End of Panel Report

Longwall 14

Mandalong Mine

December 2013

Mandalong Mine LW14 End of Panel Report – December 2013

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Table of Contents

1 INTRODUCTION ....................................................................................................................................... 1

2 SUBSIDENCE RESULTS ............................................................................................................................. 1

2.1 BACKGROUND ............................................................................................................................................... 1 2.2 DESCRIPTION OF IMPACT ................................................................................................................................. 1 2.3 MONITORING RESULTS ................................................................................................................................... 2

2.3.1 Monitoring Data .............................................................................................................................. 2 2.4 PERFORMANCE AGAINST PREDICTION ................................................................................................................ 2

2.4.1 Longwall Summary .......................................................................................................................... 9 2.4.2 Dwellings ....................................................................................................................................... 10

3 SUBSIDENCE MANAGEMENT ................................................................................................................. 10

3.1 NOTIFICATIONS ........................................................................................................................................... 10 3.2 SUBSIDENCE MANAGEMENT PLAN TRIGGERS .................................................................................................... 10 3.3 REMEDIAL ACTIONS...................................................................................................................................... 10 3.4 SUBSIDENCE MANAGEMENT STATUS REPORTS .................................................................................................. 10

4 ENVIRONMENTAL CONSIDERATIONS .................................................................................................... 10

4.1 GROUNDWATER .......................................................................................................................................... 10 4.2 SURFACE HYDROLOGY .................................................................................................................................. 13

4.2.1 Stream Channel and Floodpaths ................................................................................................... 13 4.2.2 Wetland Monitoring ...................................................................................................................... 14 4.2.3 Surface Water Monitoring Mandalong ......................................................................................... 16

5 COMMUNITY CONSULTATION ............................................................................................................... 18

5.1 COMPLAINTS .............................................................................................................................................. 18 5.2 INQUIRES ................................................................................................................................................... 18 5.3 MANDALONG MINE COMMUNITY CONSULTATIVE COMMITTEE ............................................................................ 18

6 BIBLIOGRAPHY ...................................................................................................................................... 19

List of Figures

FIGURE 1 - TOPOGRAPHY AND SUBSIDENCE LINES MEASURED FOR LW14 ............................................................................... 2 FIGURE 2 - DEPTH OF COVER OVER LW1 TO LW14 ........................................................................................................... 3 FIGURE 3 - VISUALISATION OF SUBSIDENCE TO LW14 ......................................................................................................... 4 FIGURE 4 - VISUALISATION OF SUBSIDENCE TO THE END OF LW14 ON THE TOPOGRAPHY .......................................................... 4 FIGURE 5 - GEOPHYSICAL LOGS SHOWING CONGLOMERATE BEAM THICKNESS ALONG LW14 ..................................................... 5 FIGURE 6 - DIFFERENCE BETWEEN PREDICTED AND ACTUAL SUBSIDENCE ................................................................................ 6 FIGURE 7 - LW14 TILT HISTOGRAM ................................................................................................................................ 7 FIGURE 8 - LW14 COMPRESSIVE STRAIN HISTOGRAM ........................................................................................................ 8 FIGURE 9 - LW14 TENSILE STRAIN HISTOGRAM ................................................................................................................. 8 FIGURE 10 - HYDROGRAPH OF BH08 LOCATED OVER LW11 .............................................................................................. 11 FIGURE 11 - GROUNDWATER MONITORING BORES AND MINE PLAN ................................................................................... 12 FIGURE 12 - WETLAND MONITORING LOCATIONS AND UNDERGROUND WORKINGS ............................................................... 15

List of Tables

TABLE 1 - LONGWALL 14 MINING PARAMETERS ................................................................................................................ 1 TABLE 2 - FREQUENCY HISTOGRAM SUMMARY LONGWALLS 6 TO 14 ..................................................................................... 9 TABLE 3 - SUMMARY OF MONITORING LOCATIONS WITH RESPECT TO POSITION WITHIN THE CATCHMENTS ................................... 16 TABLE 4 - AVERAGE SURFACE WATER QUALITY FOR THE MANDALONG VALLEY FOR THE 12 MONTH PERIOD FROM NOVEMBER 2012 TO

OCTOBER 2013 (‘ANNUAL’) AND THE LONG-TERM AVERAGE (‘LTA’).......................................................................... 17


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Document Control Details DOCUMENT DETAILS

Name: Longwall 14 End of Panel Report

Author: Phil Enright

Reference: LW14 End of Panel Report.docx

Revision No.: 1

Document Status Final

APPROVAL DETAILS

Revision No.

Date Sent Details of Approval Approved By Approval Date

0 9/12/13 Draft for comment J Dunwoodie 9/12/13

1 9/12/13 Approved for Submission

C Macdonald 9/12/13

Director of Environmental Sustainability

NSW Department of Trade and Investment, Regional Infrastructure and Services

1

Principal Subsidence Engineer

NSW Department of Trade and Investment, Regional Infrastructure and Services - Resources & Energy

1

Director General Department of Planning & Infrastructure

1

Regional Hydrologist NSW Office of Water 1

Manager, Mining & Extractive Industries

Environment Protection Authority

1

Chairman Mandalong Community Consultative Committee

1

Chairman Mine Subsidence Board 1

Technical Services Superintendent

Mandalong Mine Technical Services

1


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1 Introduction The Subsidence Management Plan Approval for Longwalls 11 to 14, condition 18, requires an end of panel report to be submitted to the Director, Environmental Sustainability of NSW Trade and Investment, Regional Infrastructure & Services (TIRIS) within six months of the extraction being completed of each longwall panel. This report aims to fulfil this condition and encompasses all environmental and subsidence monitoring, including a comparison of actual subsidence impacts with predicted subsidence impacts, subsidence trends and management actions. Development Consent condition 18 also requires an end of panel report to be provided within 4 months of panel completion to the Director General of the Department of Planning & Infrastructure (DOP) and submitted to the Mandalong Community Consultative Committee (CCC), TIRIS, Environment Protection Authority (EPA), NSW Office of Water (NOW) and any other relevant agency.

2 Subsidence Results

2.1 Background

The extraction of Longwall 14 occurred over a period of six months, commencing on the 16 February 2013 and finishing on the 5 August 2013. Longwall 14 had an extraction width of 160m and chain pillars 46m wide, the same as the previous nine panels. The depth of cover was approximately 280m at the commencement of the panel, decreasing to around 230m at the end of the panel. Table 1 provides a summary of Longwall 14 mining parameters.

Table 1 - Longwall 14 Mining Parameters Longwall 13 Parameters

Length 2900m Face Width 150m Void 160m Extraction Height 3.4m to 4.8m Chain Pillar Width 46m Cover Range 230m to 280m Commenced 16 February 2013 Completed 5 August 2013 Coal Extracted 2.9 million tonnes

A variation to the SMP was sought and approved by the Director-General (DRE) on 24 December 2012 to reduce the approved length of the longwall block by a total 79m due to the presence of a hard silica rich dyke and reduced seam thickness at the installation roadway location.

2.2 Description of Impact

Similar to the previous longwall panels, the area affected by Longwall 14 covered properties both above and within the Mandalong floodplain. This area includes a total of 12 properties and three dwellings. Surface features include Stockton Creek, Sauls Rd, Mandalong Rd, Browns Rd, Telstra communications network and the Ausgrid network. The Subsidence Management Plan predicted low impact across the area influenced by the extraction of Longwall 14. Two private and one Centennial owned dwelling were impacted directly from the extraction of Longwall 14. All dwellings were predicted to and remained safe, serviceable and repairable. Two inquiries were made to the MSB for minor subsidence impacts to both private dwellings following


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the extraction of Longwall 14. There have been no observed or reported of damage to infrastructure during the extraction of Longwall 14.

2.3 Monitoring Results

2.3.1 Monitoring Data

Subsidence monitoring was completed in accordance with the approved subsidence monitoring programme. Following the completion of Longwall 14, Seedsman Geotechnics (2013) reviewed the data and provided a report on the measured subsidence and subsidence performance. Subsidence surveys were completed on all or part of 11 subsidence lines and a number of dwellings. Figure 1 shows the topography and subsidence lines occupied during Longwall 14 extraction. The largest vertical subsidence recorded during the retreat of Longwall 14 was 0.53m measured on Crossline 9 at the intersection of Sauls Rd and Walls Lane, near the commencement end of the panel and the greatest depth of cover. Maximum subsidence over the majority of the panel was between 0.25m and 0.35m.

Figure 1 - Topography and Subsidence Lines measured for LW14

2.4 Performance against Prediction

The depth of cover was approximately 280m at the commencement of the panel, decreasing to around 230m at the end of the panel. The variation in depth of cover is primarily driven by the surface topography over Longwall 14. Figure 1 above and Figure 2 below illustrate the topography and depth of cover.


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Figure 2 - Depth of Cover over LW1 to LW14

Figure 3 presents a visualisation of the vertical subsidence over the whole area based on interpolation of the survey data. Figure 4 shows the subsidence visualisation overlayed on the topography. This figure illustrates the association of the greatest subsidence with the most elevated topography which provides greater the depth of cover. In addition, the sag above the extraction panels and general trend for increasing subsidence with depth can be seen.


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Figure 3 - Visualisation of Subsidence to LW14

Figure 4 - Visualisation of Subsidence to the End of LW14 on the Topography


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The subsidence results above Longwall 14 were generally within anticipated levels, with maximum vertical subsidence over the majority of the panel typically ranging between 0.25m and 0.35m, consistent with less variation in the depth of cover and conglomerate beam 35m to 40m thick as shown in Figure 5.

Figure 5 - Geophysical Logs showing Conglomerate Beam Thickness along LW14 Figure 6 below, shows the difference between actual and predicted subsidence, where green shading is where actual subsidence is less than predicted and red shading is where actual subsidence greater than predicted. Apart from the slight increase in subsidence at the commencement of the panel (0.53m), maximum subsidence was within the predicted range.


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Figure 6 - Difference between Predicted and Actual Subsidence

Based on the results of 2100m of subsidence line monitoring data located over Longwall 14 and all points judged to be impacted by subsidence from Longwall 14, frequency histograms for tilt, tensile strain and compressive strain have been produced. The histograms compare the subsidence results against the Safe Serviceable and Repairable (SSR) criteria for dwellings, being less than 5mm/m for tensile and compressive strains and less than 7mm/m of tilt.


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Figure 7 indicates that all of measured tilts over Longwall 14 were below SSR criteria of 7mm/m. Similarly, all compressive strain and tensile strain measurements recorded were below 5mm/m as shown in Figure 8 and Figure 9. A summary of the histogram results for Longwalls 6 to 14 confirms the high level of confidence in the mine design achieving low levels of subsidence. Table 2 summarises these results compared to SSR criteria for dwellings.

Figure 7 - LW14 Tilt Histogram

1 2 3 4 5 6 7Greaterthan 7

Frequency 162 42 27 4 4 0 0 0

Cumulative % 67.8% 85.4% 96.7% 98.3% 100.0% 100.0% 100.0% 100.0%

67.8%

85.4%

96.7% 98.3% 100.0% 100.0% 100.0% 100.0%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0

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100

120

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160

180

Fre

qu

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cy

Tilt less than mm/m

LW14 Tilt Histogram


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Figure 8 - LW14 Compressive Strain Histogram

Figure 9 - LW14 Tensile Strain Histogram

1 2 3 4 5Greaterthan 5

Frequency 57 6 4 1 0 0

Cumulative % 83.8% 92.6% 98.5% 100.0% 100.0% 100.0%

83.8%

92.6%

98.5% 100.0% 100.0% 100.0%

75%

80%

85%

90%

95%

100%

0

10

20

30

40

50

60Fr

eq

ue

ncy

Compressive Strain less than mm/m

LW14 Compressive Strain Histogram

1 2 3 4 5Greaterthan 5

Frequency 126 8 1 0 0 0

Cumulative % 93.3% 99.3% 100.0% 100.0% 100.0% 100.0%

93.3%

99.3%

100.0% 100.0% 100.0% 100.0%

90%

91%

92%

93%

94%

95%

96%

97%

98%

99%

100%

0

20

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60

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Fre

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Tensile Strain less than mm/m

LW14 Tensile Strain Histogram


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Frequency Histogram Summary for Longwalls 6 to 14 Compared Against SSR Criteria for Dwellings

Longwall Panel Tilt

Less that 7mm/m Tensile Strain

Less than 5mm/m Compressive Strain Less than 5mm/m

LW6 97.7% 99.8% 97.4%

LW7 97.6% 100% 97.8%

LW8 100% 100% 99.4%

LW9 100% 100% 100%

LW10 98.8% 100% 98.5%

LW11 96.5% 100% 100%

LW12 96.4% 100% 93.3%

LW13 95.6% 100% 95.6%

LW14 100% 100% 100%

Average 98.0% 99.9% 97.7%

Table 2 - Frequency Histogram Summary Longwalls 6 to 14

2.4.1 Longwall Summary

Longwalls 1 to 11 Subsidence monitoring over the major crosslines including annual surveys has shown that subsidence has remained stable. Longwall 12 Following the extraction of Longwall 14, there has been minimal movement observed over Longwall 12, typically less than 40mm. Longwall 13 Consistent with previous longwalls, the settlement of Longwall 13 has occurred as expected with the extraction of Longwall 14, providing an additional 0.1m to 0.2m subsidence over the chain pillars and maximum subsidence at the centre of the panel. Longwall 13 Consistent with previous longwalls, the settlement of Longwall 13 has occurred as expected with the extraction of Longwall 14, providing an additional 0.1m to 0.2m subsidence over the chain pillars and maximum subsidence at the centre of the panel. Longwall 14 The largest vertical subsidence recorded during the retreat of Longwall 14 was 0.53m measured on Crossline 9 at the intersection of Sauls Rd and Walls Lane, near the commencement end of the panel and the greatest depth of cover. Maximum subsidence over the majority of the panel was between


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0.25m and 0.35m. All measured tilts and strains over the longwall panel were low and below SSR criteria for dwellings.

2.4.2 Dwellings

Two private and one Centennial owned dwelling were impacted directly by subsidence from Longwall 13. All properties were predicted to and remained Safe Service Repairable. Some minor cosmetic repairs were required on both private dwellings and facilitated by the MSB.

3 Subsidence Management

3.1 Notifications

All one month mining notifications were issued to landowners, tenants and infrastructure owners affected by Longwalls 14.

3.2 Subsidence Management Plan Triggers

There were inquiries to the MSB for impacts to two private dwellings following the extraction of Longwall 14. There have been no observed or reported of damage to infrastructure including public roads and Telstra network during the extraction of Longwall 14.

3.3 Remedial Actions

MSB has completed some minor cosmetic repairs to one dwelling and is currently in progress providing cosmetic repairs to the second dwelling.

3.4 Subsidence Management Status Reports

Fortnightly Subsidence Management Status reports were prepared in accordance with SMP LW11-14 approval. Sixteen reports were prepared during the extraction of Longwall 14. There were two Subsidence Management Status Reports (four monthly) produced during the extraction of Longwall 14. Subsidence Management Status Report #28 for 1 January 2013 to 30 April 2013 and # 29 was for the period 1 May 2013 to 31 August 2013. The reports were provided to all relevant agencies and stakeholders and made available on the Centennial Coal website.

4 Environmental Considerations

4.1 Groundwater

An extensive groundwater monitoring network has been established and monitoring program implemented at Mandalong Mine. This program has been established to provide timely warnings of deviations from natural or background levels, so that if necessary, remedial measures and/or management strategies can be put in place. The current monitoring network consists of 51 bores; 22 alluvial monitoring bores, 27 overburden monitoring bores and 2 coal seam monitoring bores. The bores consist of 14 nests of 2 or 3 bores monitoring strata at increasing depth at the same site and 13 single bore sites (refer Figure 11 for location of bores). The bores are monitored every month with the water level, EC and pH being measured. At Mandalong, the alluvium forms an unconfined shallow aquifer with a water table typically ranging in depth from less than 1m and up to about 3m below ground level and aquifer thickness less than 20m. Monitoring within the alluvium has indicated that there is regular seasonal fluctuation in water level around 0.5m in the lower catchment and fluctuations between 1.5m to 2.0m in the middle to upper catchment areas. The alluvial groundwater is moderately acidic to slightly alkaline, brackish to


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saline, extremely hard and of sodium chloride type. Reported groundwater electrical conductivity (EC) throughout the Mandalong Mine approval area exceeds 10,000 μS/cm at some locations. Due to the relatively high silt and clay content of the alluvium, the groundwater yields are relatively low (typically less than 1 L/s). As a result of the low yield and relatively poor water quality, there are very few registered private alluvial groundwater bores. The environmental value of the alluvial groundwater is considered to be ‘primary industry’ (specifically stock watering), with the saline groundwater only suitable for stock watering. The most recent review of the monitoring network was undertaken in July 2013 by GHD (2013) in preparation of the SMP application for Longwalls 18 to 21. As part of the review, groundwater hydrographs were plotted for each of the alluvium bores and compared to the CRD (Cumulative Rainfall Departure) curve for the rainfall dataset to establish the relationship between groundwater levels and rainfall and to identify whether other natural or anthropocentric factors have been influencing these groundwater levels. Where possible, a statistical comparison was undertaken using the HARTT (Hydrograph Analysis: Rainfall and Time Trends) statistical methodology, to reduce the uncertainty inherent with visual interpretation of time series graphs. The CRD curve is shown in blue in each hydrograph. HARTT analysis has been undertaken for each alluvial dataset to establish the relationship between groundwater levels and rainfall and to detect underlying trends in groundwater level that are independent of rainfall. The best fit HARTT regression line is shown in red. Figure 10 shows the hydrograph for BH08 located over the LW11 that was extracted during 2011.

Figure 10 - Hydrograph of BH08 located over LW11

GHD (2013) concluded that the HARTT statistical analysis, on bores over existing longwalls confirms there has not been a loss of alluvial groundwater into the workings, long term reductions in alluvial groundwater levels or deterioration in groundwater quality. All statistically significant trends in alluvial groundwater levels (in mm/month) were below the limit of reading of groundwater


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measurements. Therefore, there does not appear to have been impacts on Groundwater Dependent Ecosystems or other alluvial groundwater users.

Figure 11 - Groundwater Monitoring Bores and Mine Plan


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4.2 Surface Hydrology

4.2.1 Stream Channel and Floodpaths

The Mine’s development consent requires the condition of major floodpaths be inspected every six months or following a flood event in an area subject to a Subsidence Management Plan (SMP) application. The Floodpath Condition Report for 2012 has been developed to compile survey and photographic records of subsidence induced changes to Stockton Creek as per assessment methodology in Section 1.2 of the report. The full report is contained within the Annual Environmental Management Report (AEMR) for 2012. The Floodpath Condition Report for 2013 will be included in the 2013 AEMR which will be prepared in March 2013. The Floodpath Condition Report assesses the changes to the condition of floodpaths along stream reaches mined beneath by Longwalls 14 and 15 extracted in 2013 and previously subsided Longwalls 1 to 13, identifying the effects of subsidence on the floodpaths. The pre-mining condition of the floodpaths above Longwall 14 and 15 is also documented in this report. On the basis of the information obtained from field surveys the pre mining characteristics of Stockton Creek and the associated tributary in the mining area are described as having a deep bed broad stream section with some pre mining erosion on bank areas above Longwalls 4 and 5. Pre-mining stream condition above Longwalls 7 to 10 has stream widths broadening to some 7 to 20 m wide and low bank heights of 0.5m to 2 m. Surveys in June and December 2013 recorded some further minor erosion of stream banks along these stream sections likely to be caused by a combination of stock access exposing soils and concentrated flows scouring the banks. Areas of subsidence induced remnant ponding were also identified. The subsidence levels above Longwalls 3 to 6 remained unchanged in 2013. The stream condition in 2013 above Longwall 1 to 3 and 6, where stock have been excluded, were in a similar condition to that recorded pre mining. No change to the well-established riparian vegetation was found on stream banks and with no further bank erosion. The bank widening and erosion process above Longwalls 4 and 5 in Stockton Creek has been occurring prior to mining and for a considerable length of time prior to mining given the large difference in stream widths compared to other stream sections. This erosion process is unlikely to have been caused by subsidence as the areas of erosion identified prior to mining were observed in June 2008 to be a result of the concentrated flows on the opposing bank causing further erosion. In addition to areas identified in previous reports, remnant ponding was evident on a Centennial property above Longwall 11 in 2012 and 2013. The ponding is located on an area of Redgum Rough-bark Apple Forest and pasture. To date only minor dieback of the vegetation community has occurred and an ecologist is monitoring the area to assess the effects of ponding on this vegetation community. At present due to limited impact, remediation works are being assessed and may be considered if recommended by the external ecologist. The maximum subsidence levels recorded in 2013 on Longwall panels 11 to 14 are within the predicted range, with the changes in stream grade above these panels similar to pre-existing grades occurring on Stockton creek. All subsidence and stream grade changes are below the anomalous results triggers in the UMEMP therefore, further stream impact assessment or remedial works are not required. Given the unchanged stream condition recorded following mining and the low subsidence levels on Stockton Creek, it is likely that recent subsidence above Longwalls 13 and 14 has had minimal adverse impacts to the stream flow conveyance.


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4.2.2 Wetland Monitoring

Condition 74 of Development Consent for the Mine requires monitoring and management of wetlands in the mining area. The wetlands management and monitoring plan (WMP) approved by LMCC was prepared by Hunter Eco (Centennial Mandalong, 2009), identifying eight (8) wetlands for monitoring as shown in Figure 12. Wetlands 1, 2, and 3 are located outside of the subsidence zone and are control sites while the remaining five wetlands are within the proposed mining area. In April 2009 a baseline report was prepared (Hunter Eco, 2009) which described the status of the wetlands prior to any subsidence having occurred. In 2013 Hunter Eco conducted two monitoring rounds in April and November. The following is a summary monitoring results from the current report “Mandalong Wetlands Monitoring Report April 2013” (Hunter Eco, 2013) and will be provided in the 2013 AEMR. The purpose of this monitoring program, as prescribed in the Conditions of Consent, is to determine what, if any, changes in the monitored wetlands in the Mandalong floodplain can be attributed to subsidence. Monitoring of eight wetlands commenced in April 2009 so as at April 2013 the total monitoring period has been four years, nine monitoring occasions. All wetlands started out with water then began to dry until May 2010 when only Wetlands 1 and 3 had water. There has been an increasing rainfall trend up to May 2012 falling to November 2012 after which it has risen to the highest level since the start of monitoring. Clearly these wetlands are dynamic ecosystems with species composition and diversity varying with the amount of available water and seasons. Variable land-use activities also have an influence on the state of the wetlands. Water analysis results continue to be highly variable, showing no trends over time or within or among wetlands. Wetland 6 is located over a pillar between panels 11 and 12, both panels having been subsided. The most noticeable change at this wetland is the change from dry to margin habitat at the beginning of the transect. This change appears to now be a feature of this transect. Wetland 8 has been subject to subsidence for over three years and there is no change in the wetland vegetation and water levels that can clearly be assigned to being an impact of subsidence. Around the middle of 2012, Longwall 13 was subsided beside Wetland 7 which is located over a pillar between Longwalls 13 and 14. There is no subsidence monitoring through this wetland and it is too soon to detect any impact on the structure of this wetland.


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Figure 12 - Wetland Monitoring Locations and Underground Workings


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4.2.3 Surface Water Monitoring Mandalong

There is an established surface water quality monitoring program for the Mandalong catchment conducted by the Mine. Periodic sampling commenced in 1996, with the program established on a regular monthly frequency since August 1999. Three surface water monitoring points (SW13-15) above the Licenced Discharge Points 1 and 2 (LDP001 & LDP002) and two monitoring points (SW16-17) in the receiving waters below the LDP’s were added in late 2011 at the Cooranbong Services Site, remote from the current mining area. The monitoring locations are summarised below in Table 3.

Table 3 - Summary of monitoring locations with respect to position within the catchments

Location Reference Creek Sub-catchment Position along Creek Sub-catchment

SW008 Stockton Creek Upper

SW004 Stockton Creek Mid

SW012 Stockton Creek Lower

SW011 Moran’s Creek Upper

SW003 Moran’s Creek Mid

SW006 Moran’s Creek Lower

SW002 Stockton and Moran’s At Confluence

SW001 Stockton Creek Downstream Confluence

SW009 Pourmalong Creek South

SW010 Pourmalong Creek North

SW13 Muddy Lake (Unnamed tributary upstream LDP001).

Upper


Upper


Upper

SW16 Muddy Lake (Unnamed water body 1km downstream Simpson Rd Causeway Crossing)

Mid

SW17 Muddy Lake (North Dora Creek Village) Lower

Surface water quality is monitored at 15 locations on a monthly or quarterly basis. These locations encompass four different catchment areas. The water is tested for pH, Total Suspended Solids (TSS) and Specific Conductance/Electrical Conductivity (EC). The annual and long-term average (LTA) results are summarised in Table 4.


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Table 4 - Average surface water quality for the Mandalong Valley for the 12 month period from November 2012 to October 2013 (‘annual’) and the long-term average (‘LTA’)

Site Location Catchment

pH TSS Specific Conductance

uS/cm

Average LTA Average LTA Average LTA

SW008 Stockton 7.1 6.9 5.35 37.3 982.2 952

SW004 7.0 6.8 21.2 17.2 747.4 672

SW012 6.0 6.1 20.1 27.8 2667 1558

SW011 Moran’s 6.6 6.6 18.6 47.5 662 574

SW006 6.6 6.5 30.3 21.4 465 535

SW003 6.5 6.4 10.2 15 459.5 488

SW002

Stockton and Moran’s Creek (Confluence) 7 6.9 9.9 18.1 13135 12595

SW001 7 7.1 7 15 25259 27913

SW009 Pourmalong 6.8 6.5 14.2 20.3 394.7 281

SW010 5.9 6.1 9.5 18.6 885.7 399

SW013 5.6 6.4 8 21.9 2674 1302

SW014 6.9 7.1 7.7 20.6 385 479.5

SW015 Muddy Lake 5.9 5.9 80.1 83.7 87.8 90.9

SW016 8.3 8.1 21 17.7 2762.4 2141.5

SW017 8.1 8.1 578 1843.8 2861 2914

The results presented in Table 4 are characteristic of the natural conditions of the area, particularly Stockton and Moran’s Creek. Both Stockton and Moran’s creek are the main drainage systems for the Mandalong area. Stockton Creek is located within the longwall mining area, while Moran’s Creek is situated outside the current longwall mining area to the south east of the longwall panels. SW013 to SW017 are located in the Muddy Lake catchment, near the Cooranbong Services Site.

Surface waters are tested for pH, Total Suspended Solids (TSS) and Specific Conductance/Electrical Conductivity (EC) and the annual and long-term average (LTA) results will be summarised in the AEMR 2013 and will contain graphs of EC, pH and TSS for each of the surface water monitoring points sampled in 2013. The monitoring sites are sampled each month at SW001, SW002, SW003, SW004, SW006, SW008 SW011, SW012, SW013, SW014, SW015, SW016 and SW017 and quarterly for SW009 & SW010 during this period.


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The EC (salt content) for the November 2012 to October 2013 period shows a relatively consistent level compared to the long-term average. The average EC recorded for sites SW01, SW03, SW06, SW014, SW015 and SW017 this period is lower than the long-term average. The average total suspended solids (TSS) for the November 2012 to October 2013 are relatively low and are characteristic of natural surface water conditions in creeks. At sites SW01, SW02, SW03, SW08, SW09, SW010, SW011, SW012, SW013, SW014, SW015 and SW017 the 2013 average was lower than the LTA. At the majority of monitoring points, the results showed an annual average pH similar to the long-term average. SW013 had the lowest pH average of 5.6. The highest pH average recorded during the period was 8.3 recorded at SW016 which is located outside the mining area.

5 Community Consultation

5.1 Complaints

There were no community complaints relating to subsidence management during the extraction of Longwall 14.

5.2 Inquires

During the extraction of Longwall 14, a number of inquiries were made by the public regarding potential purchase of properties located over the Mandalong mining area. Publically available documents, management plans and environmental reporting are available on the Centennial Coal website.

5.3 Mandalong Mine Community Consultative Committee

During the extraction of Longwall 14, two meetings of the Mandalong Mine Community Consultative Committee (MMCCC) were held on the 19 February 2013 and 22 October 2013. Representatives of the Mandalong Community Association, appointed local representatives, relevant government organisations and company representatives attended the two other meetings. Detailed presentations were provided to attendees at each MMCCC meeting on the progress of mining activities, geological and exploration update, results of subsidence and environmental monitoring, Centennial projects, stakeholder consultation, SMP approvals status and land management. A copy of the meeting minutes and presentation material is available on the Centennial Coal website.


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6 Bibliography

AGE. (2013). Mandalong Mine Groundwater Monitoring Review for AEMR 2012, Project No. G1455/I. Australasian Groundwater & Environmental Constultants Pty Ltd.

Centennial Mandalong. (2009). Weltand Management Plan.

Centennial Mandalong. (2013). Annual Environmental Management Report 2012, Mandalong Mine.

GHD. (2013). Centennial Mandalong Subsidence Management Plan LW18-21 Groundwater Impact Assessment, 22/16883.

Hunter Eco. (2009). Centennial Coal Mandalong Underground Coalmine Wetlands Monitoring Baseline Report April 2009.

Hunter Eco. (2013). Monitoring the Impact of Subsidence on Wetlands of the Mandalong Floodplain - Wetland Monitoring Report April 2013.

Seedsman Geotechnics. (2013). Review of Subsidence LW14 – MAND13-07.

Centennial Coal Company Limited P O Box 1000 Toronto NSW 2283 www.centennialcoal.com.au

end of panel report longwall 14 - centennial...

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