Appendix D. Surface water assessment report

Transcription

1 Appendix D Surface water assessment report

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3 Lake Ifould Surface Water Impact 11 September 2008 Iluka Resources Parsons Brinckerhoff Australia Pty Limited ABN PPK House 101 Pirie Street Adelaide SA 5000 GPO Box 398 Adelaide SA 5001 Australia Telephone Facsimile adelaide@pb.com.au A NCSI Certified Quality System ISO 9001

4 Parsons Brinckerhoff Australia Pty Limited (PB) [2008]. Copyright in the drawings, information and data recorded in this document (the information) is the property of PB. This document and the information are solely for the use of the authorised recipient and this document may not be used, copied or reproduced in whole or part for any purpose other than that for which it was supplied by PB. PB makes no representation, undertakes no duty and accepts no responsibility to any third party who may use or rely upon this document or the information. Author: M Schilling... Signed:... Reviewer: M Langmaid... Signed:... Approved by: M Langmaid... Signed:... Date: 11 September Distribution:... Please note that when viewed electronically this document may contain pages that have been intentionally left blank. These blank pages may occur because in consideration of the environment and for your convenience, this document has been set up so that it can be printed correctly in double-sided format. J:\A300-ADM\REPORTS\2008\ A.DOC

5 Lake Ifould Surface Water Impact Contents Page number Executive summary iii 1. Introduction 1 2. Site location and catchment Site Catchments Lake Ifould Jacinth mine Ambrosia mine 3 3. Rainfall 5 4. Design and modelling DRAINS Modelling parameters DRAINS models Rational method 8 5. Catchment analysis and stormwater runoff Mining period creek flow disruptions Modelling Results and analysis Results Analysis 10 List of tables Page number Table 2.1 Catchment areas 3 Table 5.1 Possible disruptions during mining periods 9 Table 5.2 Stormwater volumes draining to Lake Ifould A Page i

6 Lake Ifould Surface Water Impact List of figures Page Number Figure 4.1 Horton infiltration curves 7 Appendices Appendix A Appendix B Appendix C Site map Mine plans Gannt chart Page ii A

7 Lake Ifould Surface Water Impact Executive summary The surface water impact on Lake Ifould due to Jacinth Ambrosia mining operations is expected to be minimal. Six different mining periods with disruptions to the natural creek system have been modelled to determine the potential effects on the volume of stormwater travelling towards Lake Ifould, ranging in durations from 3 22 months. The maximum calculated volume of water that will be prevented from entering Lake Ifould due to the Jacinth-Ambrosia mines is 2.5%, occurring during a 100 year ARI event. This scenario is expected to have duration of only 15 months; hence there is a low probability of a 100 year event occurring during this period. During a 10 year ARI event, 1.9% of the stormwater is expected to be prevented from travelling towards Lake Ifould due to mining operations expected to last for approximately 15 months. The prevention of 1.9% of stormwater from travelling towards the lake is not considered significant considering the duration of the scenario. All other mining period scenarios are estimated to prevent less than 1% of stormwater from travelling towards Lake Ifould A Page iii

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9 Lake Ifould Surface Water Impact 1. Introduction This report outlines the concepts, processes, information and results of the investigation into the surface water impact of the Jacinth Ambrosia mining operations on Lake Ifould. Lake Ifould is located approximately 6 km to the west of the Jacinth Ambrosia mine site, north west of the village and airfield. Lake Ifould is a long and narrow waterbody, with a length of approximately 18 km, orientated north-east to south-west. The Jacinth-Ambrosia mine site is located within the Lake Ifould natural catchment boundary. This study has been undertaken to determine the potential impacts the mine may have on the lake A Page 1

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11 Lake Ifould Surface Water Impact 2. Site location and catchment 2.1 Site Lake Ifould lies approximately 6 km west of the Ambrosia mine area and is approximately 7 km north west of the Jacinth mine (Refer to Appendix A Site plan). The lake is narrow and approximately 18 km long, with both the Jacinth and Ambrosia mines being located within the lake s catchment. South of the Lake Ifould catchment, the land generally drains to in a south-westerly direction towards Lake Tallacootra. 2.2 Catchments Lake Ifould The topography of the eastern half of the Lake Ifould catchment would be defined as undulating and hilly. The land to the north and north west is relatively flat and has natural low lying areas. This makes defining the stormwater catchment in that area relatively difficult but the total catchment has been assessed as approximately 73,000 ha Jacinth mine The catchment area upstream of this mine site is in the undulating and hilly area with two clearly defined water courses. The north creek (Refer to Appendix B - Figure 1) has a catchment size of 530 ha. which is approximately 0.7% of the entire Lake Ifould catchment. (Refer to Table 2.1) The south creek s catchment is 960 ha. (1.3%) with their combined area 1,490 ha. (2.0%) Ambrosia mine The catchment of the mine is also in the undulating and hilly area with two clearly defined creeks and a third creek less defined. The north (Refer to Appendix B Figure 2) creek has a catchment size of 1,610 ha. (2.2% of the lake catchment), the central creek 250 ha (0.3%) and the less defined south creek 60 ha (0.1%). Table 2.1 Catchment areas Lake Ifould Jacinth Ambrosia North Creek South Creek North Creek Centre Creek South creek ha % 1 ha % 1 ha % 1 ha % 1 ha % 1 73, , Percentage of total Lake Ifould catchment area 2 Total catchment area upstream of mining area is approximately 4.8% of the total catchment area A Page 3

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13 Lake Ifould Surface Water Impact 3. Rainfall The rainfall events were created in the software (DRAINS) which uses the method from the Australian Rainfall and Runoff All durations for the 1 year, 2 year, 5 year, 10 year and 100 year ARI storms were used in the modelling. These events are based on generalised precipitation data developed by the Bureau of Meteorology for use in estimating rainfall. This method of estimating rainfall has been utilised due to no existing rainfall records being available A Page 5

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15 Lake Ifould Surface Water Impact 4. Design and modelling 4.1 DRAINS The stormwater modelling has been done using the DRAINS software package. DRAINS is a package that designs and analyses stormwater drainage systems and catchments. Hydrological modelling for this project has been done using an ILSAX model. This model uses time-area calculations and Horton infiltration procedures to calculate flow hydrographs from sub-catchments. The various sub-catchment flows are routed through a channel system. Calculations are performed at specific time intervals. 4.2 Modelling parameters DRAINS models An ILSAX model was developed for the sandy to sandy clay soils which would be classed as a medium infiltration soil, and has been classified as Soil Type B. As can be seen from the graph below for Soil Type B, the high initial infiltration rate of 200 mm/h quickly falls away to a final rate of 13 mm/h. The initial depression storage is set at 2 mm. FIGURE 4.1 Horton infiltration curves A Page 7

16 Lake Ifould Surface Water Impact Rational method The volume of stormwater draining to Lake Ifould from its catchment as a whole was calculated by modifying the Rational Method to calculate volumes instead of peak flows. A runoff coefficient of 0.25 has been used creating a reasonably conservative approach in comparison to the Prefeasibility Surface Water Assessment undertaken in August This coefficient was determined after discussions with the Senior Drainage Engineer at the Department for Transport, Energy and Infrastructure (DTEI) in South Australia. Values for runoff coefficients used by DTEI are the reflection of extensive experience in assessing cross road drainage in the remote areas of South Australia. Page A

17 Lake Ifould Surface Water Impact 5. Catchment analysis and stormwater runoff 5.1 Mining period creek flow disruptions The proposed method to be used for mining the mineral sands means that there will be disruption to the creek flows over the life of the mines. These disruptions are effectively blocking the creek flows by storing any stormwater flowing in the creeks within mine excavated areas and behind levee banks. There will be six different possible effects on the stormwater flows base upon the location and timing of the mine work. The first possible disruption is due to works proposed to start in March 2014 and that will be to the south creek running through the Jacinth mine. (Refer to Table 5.1 below and the Gannt Chart in Appendix C) Table 5.1 Possible disruptions during mining periods Mining Period Disruption start date Disruption finish date Time effected Creek affected 1 March 2014 August months Jacinth South Creek 2 Sept 2014 June months Jacinth North and South Creeks 3 July 2017 Dec months Ambrosia South Creek 4 Jan 2018 March months Ambrosia South and Centre Creeks 5 April 2018 Dec months Ambrosia Centre Creek 6 Jun 2019 Mar months Ambrosia North Creek 5.2 Modelling The modelling was done using the 1 year, 2 year, 5 year, 10 year and 100 year ARI storms. Only the areas upstream and within the mine sites were modelled using the DRAINS software. For the 100 year ARI event, it was assumed that none of the flows would exit the mine area for each of the creeks that were affected at the time of the storm. This is a worst case scenario because there may be some flow due to the proposed levee banks or the excavated mine areas not being able to contain the entire volume of stormwater. In which case overflows would result in small flows back into the existing creeks. The runoff volume from Lake Ifould catchment as a whole was calculated using the Rational method with a coefficient of Results and analysis Results The modelling shows that there was no stormwater running through the mine sites for the 1 year ARI storm and minimal volumes for the 2 year ARI events, as shown in Table 5.2 Stormwater Volumes. The minimal volumes during these events is attributable to the soils and creek beds absorbing the rainfall A Page 9

18 Lake Ifould Surface Water Impact Analysis From Table 5.2 Stormwater volumes, it can be seen that the worst case scenario would only stop 2.5% of the stormwater travelling towards Lake Ifould. The prevention of 2.5% of the stormwater reaching Lake Ifould occurs during a 100 year ARI event, for Mining period 6, which has an expected duration of 15 months. The probability of a 100 year ARI event over the 10 year life of the mine is 9.6%. However, the longest time of creek flow disruption is 3.25 years for mining period P1 and P2 at the Jacinth site, where the maximum total flow held back is 0.2% of the total runoff in a 100 year ARI event. The probability of this occurring is 3.2%. At the Ambrosia site, the longest period of diversion is mining period P5 (the centre creek), of one year. The amount of stormwater held back is 0.4% of the total catchment flow. The probability of this occurring is 1%. The diversion of the north creek at Ambrosia in mining period P6 is 9 months, with 2.5% of the total catchment flow held back. The probability of this occurring is 0.75%. The Tailings Storage Facility (TSF) at Jacinth will reduce the possible runoff during the first year. This represents approximately 0.8% of the total runoff. The TSF will be progressively rehabilitated so that within 3 years of mining commencement there will be no reduction in runoff in this area. There is only a 1% chance of a 100 year ARI event occurring during any one year period, therefore the probability of a 100 year ARI event within this 15 month period, mining period 6, is 1.25%. Page A

19 Lake Ifould Surface Water Impact Table 5.2 Stormwater volumes draining to Lake Ifould Stormwater volume ARI event Total yield of Mining Period catchment P1 P2 P3 P4 P5 P6 (m 3 ) (m 3 ) % (m 3 ) % (m 3 ) % (m 3 ) % (m 3 ) % (m 3 ) % 1 Year Minimal Nil Nil Nil Nil Nil Nil 2 Year 1,700, % % % % % % 5 Year 4,000,000 2, % 2, % 2, % 10, % 8, % 33, % 10 Year 4,900,000 5, % 10, % 4, % 23, % 18, % 94, % 100 Year 9,500,000 9, % 21, % 10, % 51, % 41, % 237, % Note: Different creeks have different critical storms. The worst case scenario (i.e. largest % calculated) has been used in this table A Page 11

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21 Appendix A Site map

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23 Lake Ifould MINE SITE AIRFIELD AND ACCOMODATION VILLAGE Contours 50m Drainage ML/MPL Boundary Former Catchment Boundary Waterbody :125,000 at A3 0 2,000 4,000 metres Source: Geoscience Australia, DEH, Iluka Coord.: GDA94 MGA Z53 Parsons Brinkerhoff Australia Pty Ltd ("PB") Copyright in the drawings, information and data recorded in this document ("the information") is the property of PB. This document and the information are solely for the use of the authorised recipient and this document may not be used, copied or reproduced in whole or part for any purpose other than that which it was supplied by PB. PB makes no representation, undertakes no duty and accepts no responsibility to any third party who may use or rely upon this document or the information. NCSI Certified Quality System to ISO 9001 APPROVED FOR AND ON BEHALF OF Parsons Brinkerhoff Australia Pty limited NOT REQUIRED SIGNED GIS File: J:\A302-ENG\PROJ\ A_DFS_JACINTHAMBROSIA_MINERAL_SANDS_PROJECT\10_GIS\Projects\Drawings_Figures_Sketches\ _GIS_F060_A.mxd DATE Drawing No.: Revision: Drawn By: Client Ref: A DF, RP _GIS_F060 Date: Checked by: 24/06/08 JACINTH-AMBROSIA PROJECT - Jacinth-Ambrosia Mineral Sands Project Lake Ifould Stormwater Impact Site Plan

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25 Appendix B Mine plans

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27 NORTH C REEK SOUTH CREEK 1:10,000 at A metres Source: Geoscience Australia, DEH, Iluka Coord.: GDA94 MGA Z53 Parsons Brinkerhoff Australia Pty Ltd ("PB") Copyright in the drawings, information and data recorded in this document ("the information") is the property of PB. This document and the information are solely for the use of the authorised recipient and this document may not be used, copied or reproduced in whole or part for any purpose other than that which it was supplied by PB. PB makes no representation, undertakes no duty and accepts no responsibility to any third party who may use or rely upon this document or the information. NCSI Certified Quality System to ISO 9001 APPROVED FOR AND ON BEHALF OF Parsons Brinkerhoff Australia Pty limited NOT REQUIRED SIGNED DATE Drawing No.: Revision: Drawn By: Client Ref: GIS File: J:\A302-ENG\PROJ\ A_DFS_JACINTHAMBROSIA_MINERAL_SANDS_PROJECT\10_GIS\Projects\Drawings_Figures_Sketches\ _GIS_F061_A.mxd A DF, RP _GIS_F061 Date: Checked by: 24/06/08 JACINTH-AMBROSIA PROJECT - Jacinth-Ambrosia Mineral Sands Project Jacinth Mine Figure 1

28 N O RTH CREE K CENTRE CREEK SO UTH CREEK 1:10,000 at A metres Source: Geoscience Australia, DEH, Iluka Coord.: GDA94 MGA Z53 Parsons Brinkerhoff Australia Pty Ltd ("PB") Copyright in the drawings, information and data recorded in this document ("the information") is the property of PB. This document and the information are solely for the use of the authorised recipient and this document may not be used, copied or reproduced in whole or part for any purpose other than that which it was supplied by PB. PB makes no representation, undertakes no duty and accepts no responsibility to any third party who may use or rely upon this document or the information. NCSI Certified Quality System to ISO 9001 APPROVED FOR AND ON BEHALF OF Parsons Brinkerhoff Australia Pty limited NOT REQUIRED SIGNED GIS File: J:\A302-ENG\PROJ\ A_DFS_JACINTHAMBROSIA_MINERAL_SANDS_PROJECT\10_GIS\Projects\Drawings_Figures_Sketches\ _GIS_F062_A.mxd DATE Drawing No.: Revision: Drawn By: DF, RP Client Ref: A _GIS_F062 Date: Checked by: 24/06/08 JACINTH-AMBROSIA PROJECT - Jacinth-Ambrosia Mineral Sands Project Ambrosia Mine Figure 2

29 Appendix C Gannt chart

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31 ID Task Name Start Finish 1 Jacinth Ambrosia Mine Proje 1/03/14 31/03/ Jacinth Mine 1/03/14 30/06/17 4 South Creek 1/03/14 30/06/17 5 North Creek 1/09/15 30/06/ Ambrosia Mine 1/07/17 31/03/20 8 South Creek 1/07/17 29/03/18 9 Centre Creek 1/01/18 31/12/18 10 North Creek 1/06/19 31/03/ Mining Period P1 P2 P3 P5 P6 P4 Project: Ck_Program lines.mpp Date: 10/09/08 Task Split Progress Milestone Summary Project Summary External Tasks External Milestone Deadline Page 1