APPENDIX I GROUNDWATER IMPACT ASSESSMENT MODELLING
APPENDIX I
GROUNDWATER IMPACT ASSESSMENT MODELLING
March 2014
JEJEVO/ISABEL B PROJECT
Groundwater Impact Assessment Modelling
REPO
RT
Report Number. 137633001-3009-R-Rev0-2400
JEJEVO/ISABEL B PROJECT GROUNDWATER IMPACT ASSESSMENT MODELLING
March 2014 Report No. 137633001-3009-R-Rev0-2400 i
Table of Contents
1.0 INTRODUCTION ........................................................................................................................................................ 1
2.0 REGIONAL CLIMATE ............................................................................................................................................... 1
3.0 REGIONAL HYDROGEOLOGY ................................................................................................................................ 1
4.0 GROUNDWATER IMPACT MODELLING ................................................................................................................. 2
4.1 Mining Area................................................................................................................................................... 2
4.2 Modelling Approach ...................................................................................................................................... 4
4.3 Stochastic Rainfall ........................................................................................................................................ 5
4.4 Groundwater Level Response to Rainfall ..................................................................................................... 6
4.4.1 Rainfall-Recharge Relationship ............................................................................................................... 6
4.4.2 Recharge-Groundwater level response................................................................................................... 7
4.5 Mine Pit Effect on Groundwater .................................................................................................................... 8
4.5.1 Groundwater Inflow to Pits ...................................................................................................................... 8
4.5.2 Drawdown ............................................................................................................................................... 8
4.6 Simulation Scenarios .................................................................................................................................... 8
4.7 Simulation Results ........................................................................................................................................ 9
5.0 MODEL ASSUMPTIONS AND LIMITATIONS ........................................................................................................ 12
6.0 SUMMARY AND CONCLUSIONS .......................................................................................................................... 13
7.0 REFERENCES ......................................................................................................................................................... 14
TABLES Table 1: Summary of Estimated Groundwater Recharge .................................................................................................... 6
Table 2: Simulation Scenarios ............................................................................................................................................. 8
Table 3: Predicted Groundwater Inflow to Pit and Drawdown ........................................................................................... 12
FIGURES Figure 1: Groundwater Cross Section ................................................................................................................................. 3
Figure 2: Pre-Mine Conceptual Groundwater Model ........................................................................................................... 4
Figure 3: Mining Conceptual Groundwater Model ............................................................................................................... 5
Figure 4: Rainfall-Recharge Relationship for a Specific Yield of 0.5% ................................................................................ 6
Figure 5: Rainfall-Recharge Relationship for a Specific Yield of 1% ................................................................................... 7
Figure 6: Rai et al (2001) Conceptual Model ....................................................................................................................... 7
Figure 7: Scenario A - Computed Groundwater Level Variations and Recharge Profiles ................................................. 10
JEJEVO/ISABEL B PROJECT GROUNDWATER IMPACT ASSESSMENT MODELLING
March 2014 Report No. 137633001-3009-R-Rev0-2400 ii
Figure 8: Scenario B - Computed Groundwater Level Variations and Recharge Profiles ................................................. 10
Figure 9: Scenario C - Computed Groundwater Level Variations and Recharge Profiles ................................................. 11
Figure 10: Scenario D - Computed Groundwater Level Variations and Recharge Profiles ............................................... 11
Figure 11: Scenario E - Computed Groundwater Level Variations and Recharge Profiles ............................................... 12
JEJEVO/ISABEL B PROJECT GROUNDWATER IMPACT ASSESSMENT MODELLING
March 2014 Report No. 137633001-3009-R-Rev0-2400 1
1.0 INTRODUCTION
SMM Solomon Ltd. (SMM Solomon) is developing the Solomon Islands Nickel Project (SINP) on five tenements on two islands in Solomon Islands. The islands and tenements are:
Choiseul Island (Choiseul tenement)
Santa Isabel Island (Jejevo, Isabel B, D and E tenements)
Environmental and Social Impact Assessments (ESIA) were completed and approved by the Solomon Islands government for the Choiseul, and Isabel D and E tenements in 2012. SMM Solomon is now submitting an ESIA and supporting documents for the Jejevo/Isabel B (the Project).
The Project includes:
mining area
mine haul road
ore stockpile
jetty
accommodation camp
mine administration buildings
transhipment mooring
SMM Solomon will mine two ore types for the Project, limonite and saprolite. The limonite and saprolite will be mined and stockpiled separately, then limonite will be transported to elsewhere and saprolite will be shipped to Japan for further processing. The Project will have a production of about 0.685 Mt per year of ore and will operate for about 14 years.
This report provides a description and the results of the groundwater modelling undertaken to estimate the effects of the Project on groundwater levels, flow and volumes in the Local Study Area (LSA). It is based on available hydrologic, climatic, and soils information prepared in separate studies.
The Project will create a number of relatively small and shallow pits spread out across the mine area. These pits are a lowering of the topography of the ground surface and may intersect groundwater. If a mining pit intersects groundwater, groundwater will flow into the pit which may change groundwater flow directions and lower groundwater levels in the local vicinity of the pit (drawdown) which in turn could have an effect on vegetation and groundwater availability to springs and creeks. The purpose of the modelling in this study is to predict the frequency of groundwater interference and the spatial extent of incurred drawdown.
2.0 REGIONAL CLIMATE
The climate of the LSA, as at Santa Isabel Island and Solomon Islands, can be described as an equatorial monsoon climate. Rainfall in Solomon Islands in coastal (low elevation) stations ranges between 3,000 mm and 5,000 mm annually. Rainfall totals are higher at elevation than at coastal sites. On the southern side of larger islands such as Santa Isabel Island, and as is the case at the Project Area, there is little seasonal variation in rainfall. A detailed description of the local and regional climate is provided in the Climate Baseline Report (Appendix F).
3.0 REGIONAL HYDROGEOLOGY
The hydrogeological system is largely topographically and gravity-driven and experiences rapid recharge to groundwater from meteoric water. The water-bearing zones in the LSA appear to behave as one hydraulically connected, but aerially discontinuous, unconfined water table aquifer. A detailed description of the local and regional geology is provided in the Groundwater Baseline Report (Appendix A).
JEJEVO/ISABEL B PROJECT GROUNDWATER IMPACT ASSESSMENT MODELLING
March 2014 Report No. 137633001-3009-R-Rev0-2400 2
4.0 GROUNDWATER IMPACT MODELLING 4.1 Mining Area The mine area is shown in Figure 1 (the blue lines represent surface water courses, the brown shaded area represents the resource area to be mined). The resource area is 1.7 km2, with the exposed pit area at any one time being 0.42 km2.
Inform
ation
conta
ined o
n this
draw
ing is
the c
opyri
ght o
f Gold
er As
socia
tes P
ty. Lt
d. U
nauth
orise
d use
or re
produ
ction
of th
is pla
n eith
er wh
olly o
r in pa
rt with
out w
ritten
perm
ission
infrin
ges c
opyri
ght.
© G
older
Asso
ciates
Pty.
Ltd.
B
A
300
200
400
100
300
100
200
HUGHUKAPOTE
S IVOKO
NUHA
520,000
520,000
9,105
,000
9,105
,000
SOLOMON ISLANDS NICKEL PROJECTSMM SOLOMON LTD
GROUNDWATERCROSS SECTION
NOTES
±
137633001-008-F-Rev0-6100
SH
LEGENDCross Section A-BLogging RoadTrailContour - 100m IntervalWatercourse NamedWatercourse UnnamedWaterbodyJejevo TenementIsabel B TenementSSR Boundary
SCALE (at A3)DATUM WGS 84, PROJECTION UTM Zone 57 South
1:25,0000 200 400 600 800 1,000100 Metres
03 MAR 2014
File Location: R:\01 Client\Sumitomo\137633001\Programs\ArcMap\Aquatic\Hydrogeology\Rev0\137633001-008-F-Rev0-6100-Groundwater Cross Section.mxd
FIGURE 1
KolomolaBuala
SL
1. Tenement boundaries supplied by Client.2. Base data copyright © Solomon Islands Government, Ministry ofLand.3. Key Inset Bathymetry copyright © National Oceanic andAtmospheric Administration (NOAA), 2009.4. Key Inset Terrain copyright © Consultative Group onInternational Agricultural Research (CGIAR), 2013.
PROJECT:
CHECKED:
DATE:DRAWN:
REVIEWER: IGG
Project FootprintLinear InfrastructureDefined Resource AreaAccommodation CampJettyPotential Resource AreaStockpileOther Surface InfrastructureWeir Storage
ELEVATION750m
0
JEJEVO/ISABEL B PROJECT GROUNDWATER IMPACT ASSESSMENT MODELLING
March 2014 Report No. 137633001-3009-R-Rev0-2400 4
4.2 Modelling Approach A pre-mining hydrogeological conceptual model is presented in Figure 2. Recharge (blue arrows) is the proportion of rainfall that infiltrates through the ground surface and percolates to the groundwater table (the blue dashed line). The shape of the groundwater table generally follows topography. The level of the groundwater table rises in response to rainfall events and lowers as groundwater flows down gradient to the coast or discharges to surface water streams (Appendix A).
During mining (Figure 3), the overburden and ore are removed, creating up to 6 m deep pits. If the floor of the pit is below the groundwater table, groundwater will flow into the pit. It is assumed that any groundwater flowing into the pits will evaporate or be drained away and will not re-infiltrate into the ground. The effect of mining on groundwater will be to induce drawdown, where groundwater levels in the local vicinity of the pit are lower than they naturally would be. The groundwater modelling undertaken in this report is to estimate the magnitude of the drawdown (shown in green) and how far from the pit the drawdown extends (shown in red).
Figure 2: Pre-Mine Conceptual Groundwater Model
JEJEVO/ISABEL B PROJECT GROUNDWATER IMPACT ASSESSMENT MODELLING
March 2014 Report No. 137633001-3009-R-Rev0-2400 5
Figure 3: Mining Conceptual Groundwater Model
Groundwater modelling was undertaken using field data and analytical and stochastic methods. Effects of mining on groundwater were predicted by first estimating potential changes in groundwater recharge and discharge caused by strip mining and then computing the resultant groundwater level drawdown (if any). This was accomplished by
generating a rainfall pattern
estimating how much of the rainfall infiltrates the ground surface and reaches the groundwater table (recharge)
assessing how groundwater levels respond to that recharge
evaluate if (or how often) groundwater levels intersect the level of the pit floor
if groundwater levels intersect the pit floor:
compute how much groundwater flows into the pit (and is then lost from the groundwater system)
estimate the size of groundwater drawdown and how far from the pit the drawdown extends
Each of these steps is discussed in further detail below.
4.3 Stochastic Rainfall To enable a stochastic modelling approach, a synthetic 10-year rainfall profile was generated by the Surface Water Assessment Tool (SWAT) model (Arnold et al 1998; Arnold and Fohrer 2005). Details of the SWAT model are presented in the Water Balance and Sediment Transport Model report (Appendix G).
By using a 10-year rainfall profile, the groundwater system can be assessed under a wider range of rainfall conditions that can occur at the site, including periods of higher-than-average rainfall and periods of lower-than-average rainfall. Simulation results can then provide a statistical understanding of how the system may respond to strip mining.
JEJEVO/ISABEL B PROJECT GROUNDWATER IMPACT ASSESSMENT MODELLING
March 2014 Report No. 137633001-3009-R-Rev0-2400 6
4.4 Groundwater Level Response to Rainfall 4.4.1 Rainfall-Recharge Relationship An empirical rainfall-recharge relationship was developed from observed groundwater level measurements recorded at five groundwater bores and the rainfall recorded at station JRG02 (Table 1). The empirical rainfall-recharge relationships are shown in Figure 4 and Figure 5 for two specific yield values of the soils underlying the pit footprint. A log relationship is assumed for the range of data, displaying a general trend for recharge declining as a percentage of rainfall as rainfall increases (and levelling off at 5%). This trend is frequently due to short but heavy rainfall events with larger percentage runoff when compared to prolonged medium intense rainfalls. Outside the data range, the rainfall-recharge relationship may have a different characteristic with recharge decreasing to zero for low rainfall (foliage interception and capillary water storage in the shallow soil horizons responsible for negligible recharge at low intense, short rainfalls).
Table 1: Summary of Estimated Groundwater Recharge
Bore ID
Change in groundwater
level Time
period Rate of
groundwater change
Recharge [m/d]
Rainfall JRG02
Recharge [m/d]
[m] [d] [m/d] Sy = 0.5%
Sy = 1.0% [m/d] Sy =
0.5% Sy = 1.0%
JGW01 1.6 1.5 1.1 0.0053 0.011 0.032 16.8 33.6 JGW02 0.6 1.5 0.4 0.0022 0.004 0.055 3.9 7.8 JGW03 0.7 2.0 0.4 0.0018 0.004 0.026 6.6 13.2 JGW04 2.2 2.0 1.1 0.0055 0.011 0.026 20.8 41.5 JGW05 0.7 0.6 1.1 0.0057 0.011 0.068 8.4 16.7 Sy: Specific yield.
Figure 4: Rainfall-Recharge Relationship for a Specific Yield of 0.5%
JEJEVO/ISABEL B PROJECT GROUNDWATER IMPACT ASSESSMENT MODELLING
March 2014 Report No. 137633001-3009-R-Rev0-2400 7
Figure 5: Rainfall-Recharge Relationship for a Specific Yield of 1%
4.4.2 Recharge-Groundwater level response The groundwater response (i.e., the change in groundwater level) to rainfall is computed using the analytical methods of Rai et al (2001) and results from data analysis of field observations for hydrological parameters. The method of Rai et al (2001) estimates mounding water table fluctuations of an unconfined aquifer as a result of time-varying recharge. The unconfined aquifer is assumed to be discharging to two open waterbodies on either side of its boundaries. The resource area is 1.7 km2, with the exposed pit area at any one time being 0.42 km2.
In the conceptual model of Rai et al (2001), (Figure 6), the domain represents the hill on which mining occurs, with rivers forming the boundaries (the open waterbodies on either side). This is analogous to the cross-section illustrated by the line A-B shown in Figure 1.
Figure 6: Rai et al (2001) Conceptual Model
JEJEVO/ISABEL B PROJECT GROUNDWATER IMPACT ASSESSMENT MODELLING
March 2014 Report No. 137633001-3009-R-Rev0-2400 8
4.5 Mine Pit Effect on Groundwater 4.5.1 Groundwater Inflow to Pits If groundwater levels intersect the floor of the mining pit (assumed to be 6 m below ground surface) then groundwater inflow to the pits is estimated using the Theis (1935) equation. It is assumed that any groundwater flow into the pits is drained away immediately and does not infiltrate back to the groundwater table. The groundwater that flows into the pit is considered a loss to the groundwater system.
4.5.2 Drawdown If groundwater levels intersect the floor of the mining pit, drawdown is calculated as the vertical distance between the pit floor and the pre-mine groundwater level (i.e., the level to which groundwater would have risen to if the pit was not present, see the green arrow in Figure 3).
The drawdown radius is calculated as the horizontal distance from the pit wall to where the groundwater level has not been measurably affected by the pit (see the red arrow in Figure 3). This is accomplished by using the Theis (1935) equation and specifying a drawdown of less than 0.1 m as a threshold value. Drawdown of less than 0.1m is considered not being distinguishable from natural short term groundwater level fluctuations and long term groundwater level trends.
4.6 Simulation Scenarios During the baseline study, installation of five groundwater monitoring bores identified a range of hydraulic conditions within or adjacent to the resource area (Appendix A). Hydraulic conductivity varied by two orders of magnitude and the average depth to water below ground surface varied between 3 m and 14 m.
In order to capture the range of potential mining effects on groundwater, simulations of groundwater level responses to 10 years of rainfall have been performed for five scenarios. The parameters for those scenarios are based on the hydraulic conditions found at the groundwater monitoring bore sites (Figure 1). The details of the five scenarios are presented in Table 2.
Table 2: Simulation Scenarios
Scenario Conductivity K [m/d]
Average Water Level
[mbgl] Distance
[m] Specific Yield Sy
Saturated Thickness
[m]
Based on Bore
Site Location
Description
A 0.15 7.85 1.85 0.05 8.00 JGW01
Steep sloping ground, high elevation, approx. 500m from hilltop
B 0.15 7.85 1.85 0.1 8.00 JGW01
Steep sloping ground, high elevation, approx. 500m from hilltop
C 0.45 3.26 - 0.05 4.00 JGW02
Less sloping ground, high elevation approx. 200m from hilltop
D 0.31 13.63 7.63 0.05 6.12 JGW03
Steep sloping ground, lower elevation, approx. 800m from hilltop
JEJEVO/ISABEL B PROJECT GROUNDWATER IMPACT ASSESSMENT MODELLING
Table 2: Simulation Scenarios (continued)
March 2014 Report No. 137633001-3009-R-Rev0-2400 9
Scenario Conductivity K [m/d]
Average Water Level
[mbgl] Distance
[m] Specific Yield Sy
Saturated Thickness
[m]
Based on Bore
Site Location
Description
E 0.0053 8.22 2.22 0.05 5.13 JGW04
Less sloping ground, mid elevation, approx. 300m from hilltop
Notes: Distance: Distance from average water level to pit floor (m) mbgl = metres below ground level
4.7 Simulation Results The predicted rise in groundwater levels for both baseline and during mining are shown in Figure 7 to Figure 11 (for the first 100 days of simulation only). In each figure, the horizontal axis is time in days and:
the blue line is the predicted rise in groundwater levels before mining (Baseline Case)
the red line is the predicted rise in groundwater levels during mining
the horizontal black dashed line represents the distance from the average water level to the pit floor
the rainfall recharge is shown against the right vertical axis in black
Groundwater levels are predicted to rise above the level of the pit floor with various rates of occurrence in all scenarios with the exception of Scenario D which has the largest distance between average groundwater level and pit floor level.
Table 3 presents the simulation results of mining effects on groundwater, summarising modelling predictions of:
how frequent groundwater levels may intersect the pit floor
the maximum drawdown that was encountered during the 10-year simulation, (green arrow in Figure 3)
the maximum daily groundwater inflow to the pit (corresponding to the occurrence of maximum drawdown)
the maximum radius of drawdown (defined as drawdown of less than 0.1 m, red arrow in Figure 3)
In Scenario C, the average depth to groundwater is quite shallow and the pit floor is below the groundwater levels for almost the entire simulation. This scenario experiences the highest drawdown and highest rate of groundwater inflow to the exposed mining area. However, across all scenarios and variations in hydraulic parameters modelled, drawdown is computed not to exceed 0.1 m at a distance of 10 m from the pit.
JEJEVO/ISABEL B PROJECT GROUNDWATER IMPACT ASSESSMENT MODELLING
March 2014 Report No. 137633001-3009-R-Rev0-2400 10
Figure 7: Scenario A - Computed Groundwater Level Variations and Recharge Profiles
Figure 8: Scenario B - Computed Groundwater Level Variations and Recharge Profiles
0.00
0.01
0.02
0.03
0.040.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 10 20 30 40 50 60 70 80 90 100
Rain
fall R
echa
rge (
m/d
)
Chan
ge in
Gro
undw
ater
Leve
l (m
)
Days
Rainfall Recharge (m/d) Baseline Groundwater Level Response (m)Mining Groundwater Level Response (m) Pit Floor
0.00
0.01
0.02
0.03
0.040.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 10 20 30 40 50 60 70 80 90 100
Rain
fall R
echa
rge (
m/d
)
Chan
ge in
Gro
undw
ater
Leve
l (m
)
Days
Rainfall Recharge (m/d) Baseline Groundwater Level Response (m)
Mining Groundwater Level Response (m) Pit Floor
JEJEVO/ISABEL B PROJECT GROUNDWATER IMPACT ASSESSMENT MODELLING
March 2014 Report No. 137633001-3009-R-Rev0-2400 11
Figure 9: Scenario C - Computed Groundwater Level Variations and Recharge Profiles
Figure 10: Scenario D - Computed Groundwater Level Variations and Recharge Profiles
0.00
0.01
0.02
0.03
0.040.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 10 20 30 40 50 60 70 80 90 100
Rain
fall R
echa
rge (
m/d
)
Chan
ge in
Gro
undw
ater
Leve
l (m
)
Days
Rainfall Recharge (m/d) Baseline Groundwater Level Response (m)
Mining Groundwater Level Response (m) Pit Floor
0.00
0.01
0.02
0.03
0.040.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
0 10 20 30 40 50 60 70 80 90 100
Rain
fall R
echa
rge (
m/d
)
Chan
ge in
Gro
undw
ater
Leve
l (m
)
Days
Rainfall Recharge (m/d) Baseline Groundwater Level Response (m)
Mining Groundwater Level Response (m) Pit Floor
JEJEVO/ISABEL B PROJECT GROUNDWATER IMPACT ASSESSMENT MODELLING
March 2014 Report No. 137633001-3009-R-Rev0-2400 12
Figure 11: Scenario E - Computed Groundwater Level Variations and Recharge Profiles
Table 3: Predicted Groundwater Inflow to Pit and Drawdown
Scenario Duration of
Groundwater Inflow(a)
[days/year]
Maximum Drawdown
[m]
Maximum Groundwater
Inflow(b) [m3/d]
Maximum Radius of influence(c)
[m]
A 222 2.1 3.3 8 B 145 0.8 1.5 10 C 363 2.6 3.5 9 D 0 0 0 0 E 200 1.8 0.1 2
(a) Duration: Average number of days of groundwater flow into pit (days/year) (b) Inflow: Groundwater Inflow to Pit at maximum drawdown (m3/d) (c) Calculated using Theis (1935) and defined as the distance at which drawdown is less than 0.1 m.
5.0 MODEL ASSUMPTIONS AND LIMITATIONS The following assumptions and limitations apply to the groundwater effect modelling:
Resource area is 1.7 km2, exposed pit area is 0.42 km2, pits are 6 m deep.
Site rainfall record is less than a year in length and may not represent the full variation in rainfall patterns at the site.
Groundwater level records are less than two months in length, longer site rainfall and groundwater levels records would allow a more accurate rainfall-recharge relationship to be developed.
Rainfall is step-wise constant (i.e., rainfall varies from day-to-day but is assumed to be constant during a day).
0.00
0.01
0.02
0.03
0.040.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 10 20 30 40 50 60 70 80 90 100
Rain
fall R
echa
rge (
m/d
)
Chan
ge in
Gro
undw
ater
Leve
l (m
)
Days
Rainfall Recharge (m/d) Baseline Groundwater Level Response (m)Mining Groundwater Level Response (m) Pit Floor
JEJEVO/ISABEL B PROJECT GROUNDWATER IMPACT ASSESSMENT MODELLING
March 2014 Report No. 137633001-3009-R-Rev0-2400 13
Hydrological parameters obtained from analysis of field data are assumed to be representative of the hydrological variation across the site.
Groundwater response to rainfall occurs within a day.
Freshwater flow (from the surface) into the pits is not modelled nor included in calculations.
Any groundwater flow into the pits is diverted or drained out of the pits.
The Rai et al (2001) method assumes the unconfined aquifer is isotropic, homogeneous and rests on a horizontal impermeable base; the water level in the open bodies of water remains invariant with time; and the rate of recharge is small compared with the hydraulic conductivity so that the vertically added water flows almost horizontally after meeting the water table.
6.0 SUMMARY AND CONCLUSIONS An analytical and probabilistic approach has been used to estimate the likelihood and rate of groundwater flow intercepting the mine pits and the magnitude and extent of groundwater levels drawdown in areas adjacent to the pit.
Groundwater bore hydrographs were analysed in conjunction with rainfall records and bore lithology to identify a relationship between rainfall events and changes in groundwater levels. If groundwater levels do rise above the mining pit floors, analytical relationships from literature, using local parameters, are used to estimate the rate of groundwater inflow to the mining pits and the changes the mine dewatering has to groundwater levels adjacent to the mine pits.
Simulations of groundwater level response to rainfall and potential groundwater effect have been performed for various hydraulic conditions that cover the range of hydraulic conditions encountered at the site. The groundwater recharge likely occurs during rainfall events of all magnitudes. The hydraulic conductivity values of the water-bearing formations (the transition zone, weathered and fresh serpentinite bedrock) are relative low (K = 5.3×10-3 m/d to 6.9×10-1 m/d) (Appendix A). Results of the baseline groundwater recharge estimation indicate a recharge rate ranging from 4% to 42% (Appendix A).
In the areas where the mine pit floor is above the groundwater level, there will be no groundwater seepage into the mining areas. Where groundwater is shallow and is intercepted, the excavation during construction and mining has the potential to temporarily lower groundwater levels. Results of the predictive modelling are summarised as follows:
the estimated duration when groundwater flow into pits range from none to 363 days
the predicted groundwater inflow into the pit when water levels are above pit floor range from 0 to 3.5 m3/d
the maximum drawdown ranges from 0 m to 2.6 m
the maximum radius at which drawdown is less than 0.1 m extends to a maximum distance of 10 m from the mine area
The study indicated that mining will generate low volumes of groundwater seepage. The maximum groundwater inflow rate (across all scenarios) was estimated to be small (3.5 m3/d). The hydraulic conductivity values of the water-bearing formations are relatively low, thus greatly limiting the groundwater inflow rates and the spatial extent of effect (drawdown).
JEJEVO/ISABEL B PROJECT GROUNDWATER IMPACT ASSESSMENT MODELLING
March 2014 Report No. 137633001-3009-R-Rev0-2400 14
7.0 REFERENCES Arnold, J.G., R. Srinivasan, R.S. Muttiah, and J.R. Williams. 1998. Large area hydrologic modeling and assessment part I: Model development. J. Amer. Water Resour. Assoc. 34(1): 73-89. USA.
Arnold, J.G., and N. Fohrer. 2005. SWAT2000: Current capabilities and research opportunities in applied watershed modeling. Hydrol. Process. 19(3): 563-572. USA.
Rai, S.N., D.V. Ramana, S. Thiagarajan and A. Manglik. 2001. “Modelling of groundwater mound formation resulting from transient recharge”. Hydrol. Process. Vol 15: 1507-1514.
Theis, Charles V. 1935. "The relation between the lowering of the piezometric surface and the rate and duration of discharge of a well using ground-water storage". Transactions, American Geophysical Union 16: 519–524.
JEJEVO/ISABEL B PROJECT GROUNDWATER IMPACT ASSESSMENT MODELLING
March 2014 Report No. 137633001-3009-R-Rev0-2400
Report Signature Page
GOLDER ASSOCIATES PTY LTD
Scott Weeks Detlef Bringemeier Senior Numerical Modeller Principal Hydrogeologist
Ian Gilchrist Associate, Principal Environmental Consultant
SW/DB/IG/kg
A.B.N. 64 006 107 857 Golder, Golder Associates and the GA globe design are trademarks of Golder Associates Corporation.
\\bne1-s-file01\jobs\env\2013\137633001 sumitomo\2400 esia 1 documentation\12 - hold point (ready to finalise)\137633001-3009-r-rev0-2400-groundwater ia modelling (no
comments)\137633001-3009-r-rev0-2400-groundwater impact assessment modelling.docx