hydrogeological investigations

7/30/2019 hydrogeological investigations

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1.0 INTRODUCTION

AngloGold Ashanti (Iduapriem) Limited engaged Geo-Systems Consulting Limited, aHydrogeological and Geo-environmental Engineers to provide hydrogeological services

leading to the construction of monitoring wells at the Greenfields Tailing Storage Facility.

The scope of work involves the finding of potential site (geological anomaly) for the

construction of the monitoring wells and also to identify places of higher resistivity where

groundwater flow is unlikely. The Geophysical investigations have since been carried out andthis report is on the results obtained.

Geo-Systems carried out the Hydrogeological studies (Siting) to ensure a smooth and

successful implementation of the project and also to achieve a high success rate for the

drilling works by applying the most scientific and appropriate approach to the site selection

activity. The ensuing pages elaborate on the studies carried out.

2.0 GEOPHYSICAL SETTING

A brief description of the physical setting of the project areas are presented in terms of

geological and hydrogeological conditions, topography, climate, vegetation, and drainage.


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Attitude measurement on indistinct relict bedding observed in the weathering representative

of the Banket Series Quartzite at the north western sector of the proposed site show dips of35

0to the north east.

Figure 2 1: Geological Map of Proposed TSF Site (Modified after SRK 1997)


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3.1 Initial studies

At the inception of the hydrogeological studies, a quick assessment of the terrain was carriedout. Information on the previous drilling activities in the areas was looked at, and other

relevant hydrogeological information was accessed.

3.2 Reconnaissance & Field Work

3.2.1 Field Reconnaissance and Terrain Evaluation

A Field reconnaissance survey was carried out in the project area to verify, confirm and

update results of the preliminary information at hand. The essential information gathered

in the area included; location of existing water supplies sources (boreholes, hand dug

wells, streams) if any, location of dry holes from previous drilling activities.

3.2.2 Geophysical profile measurements

Geophysical profile measurements were carried out at a station interval of 10 meters

along each traverse. The strategy for geophysical profiling was targeted at medium to

deeper zones. The main geophysical profiling method applied was the electrical resistivity

profiling using the Schlumberger array. On-site processing and interpretation of


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to delineate fractures and aquifer zones, and depth of drilling. Two sites were selected for

each borehole and prioritized as prime and alternate sites (ie.1st Choice and 2nd Choice).Accessibility of site for drilling machinery was also considered in the selection and

prioritization of sites.


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4.0 REPORTING

In the following section details of work carried out by Geo-Systems in the GreenfieldsTailing Storage Facility, covering background information collection, field reconnaissance

surveys, geophysical investigations, geophysical investigation results, geophysical data

analyses and interpretation with tables, graphs, etc. have been presented. Recommendations

on drilling sites and depths of drilling have also been outlined.

4.0 LINE 3A1-3A2

4.1 BackgroundThe line 3A1-3A2 is 300m in length and is located at southernmost part of the Greenfields

Tailing Storage Facility. The area is covered and underlain by Kawere Conglomerate.

4.2 Geophysical Investigation

4.2.1 Horizontal Profiling

The horizontal profiling was run along the line 3A1-3A2 with a total length of 300m as


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Table 4.2: VES results and their interpretation

Site No.

App. Resistivity

Range (Ohm-m)

Expected Aquifer

zone (m)

Average

weathering

depth (m)

Remarks

VES1 4021338 1050 20 Water may occur in

the weathered

zone.


the weathered

zone.

4.2.3 Recommendations

The investigated sites have been ranked as shown in Table 4.3. The recommended

maximum drilling depths for the various sites may not be exceeded. The decision to stop

drilling or to continue will be taken by the supervisor on site.


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SCHLUMBERGER HORIZONTAL PROFILING RESULTS

LOCATION : GTSF DATE : 16-03-2011

LINE :3A1-3A2

20 30 40 50 60 70 80 90 100 110 120 130 140

20 1291 2788 2031 2160 1899 1652 1909 1905 2174 1254 1464 922 1057

40 1862 1797 1630 2561 2343 1942 1937 1631 1983 2368 1950 1637 1520

150 160 170 180 190 200 210 220 230 240 250 260

20 1265 1613 906 610 473 435 649 701 468 614 476 493

40 1592 1809 1316 1112 940 1057 1368 1052 900 957 1061 1125

Figure 4.1: Horizontal profiling results and curves for Line3A1-3A2

50 100 150 200 250

100

1000

10000

100000

VES2

App.R

es(ohms-m

)

AB/2 (m)

20m

40m

LINE:3A1-3A2

VES1


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Project : GTSF Community : Tarkwa

Client : AGA IDUPRIEM District :

Survey No.:VES2 Date :16-03-2011

AB/2(m) MN/2(m) P(V) C(I) R(ohm)

Mult

factor App Res

(ohm)

1 0.2 7.54

1.5 0.2 17.36

2 0.2 31.11

3 0.2 70.40

5 0.2 25.03 18.24 1.372 196.11 269.120

7 0.5 33.41 15.09 2.214 153.21 339.224

10 0.5 25.42 19.11 1.330 313.50 417.016

15 0.5 7.71 9.62 0.801 706.36 566.114

20 0.5 8.02 14.36 0.558 1256.36 701.670

25 5.0 27.10 6.24 4.343 188.57 818.956

30 5.0 30.69 10.21 3.006 275.00 826.616

35 5.0 42.97 18.36 2.340 377.14 882.670

40 5.0 21.90 11.11 1.971 495.00 975.743

50 5.0 11.81 7.56 1.562 777.86 1215.145

58 5.0 15.56 12.45 1.250 1049.40 1311.539

70 5.0 16.80 16.47 1.020 1532.14 1562.842

80 10.0 9.94 6.06 1.640 990.00 1623.861

90 10.0 1257.14

100 10.0 1555.71

AB = distance between outer electrodes

MN=distance between inner electrodes Figure 4.2b: Vertical electric sounding curves for line3A1-3A2

P(V)= Potential R(ohm)= Resistance C(I)= Current

1 10 100

10

100

1000

10000

App.R

es.(

ohms-m

)

AB/2(m)

Schlumberger VES at Line 3A1 to 3A2 -VES2


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5.0 LINE 3B1-3B2

5.1 Background

The line 3B1-3B2 is 400m in length and is located at the southern part of the Greenfields




The horizontal profiling was run along the line 3B1-3B2 with a total length of 400m as

detailed in Table 5.1. Plots of apparent resistivity versus chainage (m) along the traverse

lines are presented in Figure 5.1. The anomalous points were picked based on both direct

observation and results of the resistivity readings.

Table 5.1: Results and interpretation of Horizontal Profiling

Line Bearing

(o

)

Length

( )

Anomalies Remarks


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Site No.

App. Resistivity

Range (Ohm-m)

Expected Aquifer

zone (m)

Average

weathering

depth (m)

Remarks


the weathered

zone.VES4 391689 10 - 70 25 Water may occur in

the weathered zone

VES5 656 - 1146 10 - 50 20 Water may occur in

the weathered zone

VES6 667

1286 10 - 40 20 Water may occur inthe weathered zone

VES7 608 - 1613 10 - 30 15 Water may occur in

the weathered zone


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SCHLUMBERGER HORIZONTAL PROFILING

RESULTS

LOCATION :GTSF DATE : 17-03-2011

LINE :3B1-3B2

20 30 40 50 60 70 80 90 100 110 120 130 140 150 160

20 676 377 457 598 982 626 1653 1984 1258 417 946 1135 489 405 549

40 647 532 717 1294 1980 1050 1352 1206 1103 1156 734 987 568 369 555

220 230 240 250 260 270 280 290 300 310 320 330 340 350 360

20 710 702 759 1081 1198 1911 1361 1674 2021 706 1365 1617 1670 865 2521

40 737 1201 959 1012 1171 1569 1578 1639 1655 1432 2263 2113 1866 1526 2572

Figure 5.1: Horizontal profiling results and curves for Line3B1-3B2

20 40 60 80 100 120 140 160 180

100

1000

10000

VES4

App.Res(ohms-m)

Chainage (m)

20m40m

LINE:3B1-3B2

VES3

220 240 260 280 300 320 340 360

100

1000

10000

100000

VES7VES6

App.Res(ohms-m)

Chainage (m)

20m40m

LINE:3B1-3B2

VES5


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AB/2(m) MN/2(m) P(V) C(I) R(ohm) Mult factor App Res

(ohm)

1 0.2 7.54

1.5 0.2 17.36

2 0.2 31.11

3 0.2 70.40

5 0.2 19.73 6.56 3.007 196.11 589.756

7 0.5 28.52 8.54 3.340 153.21 511.756

10 0.5 6.59 4.32 1.526 313.50 478.546

15 0.5 2.01 3.54 0.567 706.36 400.645

20 0.5 1.24 4.13 0.301 1256.36 377.546

25 5.0 15.89 6.56 2.422 188.57 456.756

30 5.0 9.69 5.45 1.779 275.00 489.089

35 5.0 9.02 6.65 1.357 377.14 511.634

40 5.0 5.60 5.21 1.075 495.00 532.132

50 5.0 3.64 4.87 0.747 777.86 581.312

58 5.0 3.59 6.12 0.587 1049.40 616.423

70 5.0 3.33 7.43 0.448 1532.14 686.756

80 10.0 2.70 3.76 0.717 990.00 709.809

90 10.0 4.36 7.650 0.570 1257.14 716.534100 10.0 2.42 4.76 0.509 1555.71 792.423


MN=distance between inner electrodes Figure 5.2a: Vertical electric sounding curves for line3B1-3B2

P(V) = Potential R (ohm) = Resistance C(I) = Current

1 10 100

10

100

1000

10000

App.Res.(ohms-m

)

AB/2(m)

Schlumberger VES at Line 3B1 to 3B2 -VES3


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Mult

factor App Res

(ohm)

1 0.2 7.54

1.5 0.2 17.36

2 0.2 31.11

3 0.2 70.40

5 0.2 26.24 7.32 3.585 196.11 702.980

7 0.5 21.08 4.77 4.422 153.21 677.508

10 0.5 12.42 6.13 2.025 313.50 634.870

15 0.5 1.56 2.07 0.754 706.36 532.756

20 0.5 2.56 6.89 0.372 1256.36 467.453

25 5.0 23.68 9.13 2.594 188.57 489.131

30 5.0 6.88 3.66 1.882 275.00 517.423

35 5.0 6.00 4.76 1.261 377.14 475.645

40 5.0 8.01 9.65 0.830 495.00 410.798

50 5.0 3.44 6.85 0.503 777.86 391.423

58 5.0 2.02 5.07 0.398 1049.40 417.645

70 5.0 1.30 4.13 0.314 1532.14 481.534

80 10.0 1.19 2.22 0.537 990.00 531.76890 10.0 3.59 7.31 0.491 1257.14 616.813

100 10.0 2.35 5.31 0.443 1555.71 689.067


MN=distance between inner electrodes Figure 5.2b: Vertical electric sounding curves for line3B1-3B2


1 10 100

10

100

1000

10000

App.Res.(ohms-m)

AB/2(m )



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(ohm)

1 0.2 7.54

1.5 0.2 17.36

2 0.2 31.11

3 0.2 70.40

5 0.2 18.91 5.65 3.347 196.11 656.481

7 0.5 31.38 6.45 4.865 153.21 745.323

10 0.5 19.37 7.68 2.523 313.50 791.112

15 0.5 4.43 4.08 1.086 706.36 767.418

20 0.5 1.94 3.43 0.566 1256.36 710.659

25 5.0 22.85 6.09 3.753 188.57 707.619

30 5.0 24.75 9.67 2.559 275.00 703.756

35 5.0 3.93 2.12 1.853 377.14 698.760

40 5.0 2.49 1.67 1.489 495.00 737.089

50 5.0 3.88 3.78 1.027 777.86 798.512

58 5.0 5.76 7.42 0.775 1049.40 813.660

70 5.0 2.50 4.21 0.593 1532.14 908.734

80 10.0 2.98 3.07 0.973 990.00 963.53190 10.0 6.08 7.560 0.805 1257.14 1011.834

100 10.0 2.85 3.86 0.737 1555.71 1146.712


MN=distance between inner electrodes Figure 5.2c: Vertical electric sounding curves for line3B1-3B2


1 10 100

10

100

1000

10000

App.Res.(o

hms-m

)

AB/2(m)



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(ohm)

1 0.2 7.54

1.5 0.2 17.36

2 0.2 31.11

3 0.2 70.40

5 0.2 10.45 3.07 3.403 196.11 667.320

7 0.5 22.05 4.53 4.867 153.21 745.630

10 0.5 12.48 4.87 2.563 313.50 803.408

15 0.5 3.58 3.23 1.107 706.36 781.787

20 0.5 3.28 5.43 0.604 1256.36 759.313

25 5.0 37.74 9.05 4.171 188.57 786.445

30 5.0 13.57 4.56 2.976 275.00 818.534

35 5.0 6.41 2.76 2.324 377.14 876.545

40 5.0 4.28 2.21 1.939 495.00 959.634

50 5.0 8.71 6.87 1.269 777.86 986.734

58 5.0 8.12 8.43 0.964 1049.40 1011.131

70 5.0 8.10 11.42 0.709 1532.14 1086.423

80 10.0 8.91 7.68 1.160 990.00 1148.645

90 10.0 10.33 10.67 0.968 1257.14 1216.534100 10.0 7.55 9.13 0.827 1555.71 1286.834


MN=distance between inner electrodes Figure 5.2d: Vertical electric sounding curves for line3B1-3B2


1 10 100

10

100

1000

10000

App.Res.(ohms-m

)

AB/2(m)



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Mult

factor App Res

(ohm)

1 0.2 7.54

1.5 0.2 17.36

2 0.2 31.11

3 0.2 70.40

5 0.2 9.57 2.65 3.612 196.11 708.340

7 0.5 20.05 4.76 4.212 153.21 645.320

10 0.5 13.54 6.98 1.940 313.50 608.121

15 0.5 4.30 4.56 0.942 706.36 665.32520 0.5 1.99 3.53 0.562 1256.36 706.534

25 5.0 35.28 7.89 4.471 188.57 843.132

30 5.0 31.43 9.43 3.333 275.00 916.560

35 5.0 42.92 14.00 3.066 377.14 1156.312

40 5.0 33.08 11.43 2.894 495.00 1432.657

50 5.0 16.89 8.68 1.946 777.86 1513.534

58 5.0 20.19 13.56 1.489 1049.40 1562.423

70 5.0 8.90 9.65 0.922 1532.14 1412.834

80 10.0 10.76 7.54 1.427 990.00 1412.52390 10.0 10.57 8.68 1.218 1257.14 1531.113

100 10.0 5.77 5.56 1.037 1555.71 1613.45


MN=distance between inner electrodes Figure 5.2e: Vertical electric sounding curves for line3B1-3B2


1 10 100

10

100

1000

10000

App.Res

.(ohms-m

)

AB/2(m)



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6.0 LINE 3A1-2A1

6.1 Background

The line 3A1-2A1 is 400m in length and is located at the southeastern part of the Greenfields




The horizontal profiling was run along the line 3A1-2A1 with a total length of 400m. The

line3A1-2A1 was subdivided in to line1 and line2, each of length 200m, as detailed in

Table 6.1. The subdivision was due to the presence of a stream at the midsection of the

line3A1-2A1 which hinders a continuous profiling. Plots of apparent resistivity versus

chainage (m) along the traverse lines are presented in Figure 6.1. The anomalous points

were picked based on both direct observation and results of the resistivity readings.

T bl 6 1 R l d i i f H i l P fili


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Site No.App. ResistivityRange (Ohm-m)

Expected Aquiferzone (m)

Averageweathering

depth (m)

Remarks


the weathered

zone.VES9 371606 10 - 70 25 Water may occur in

the weathered zone

VES10 386509 10 - 70 25 Water may occur in

the weathered zone

VES11 434

713 10 - 60 20 Water may occur inthe weathered zone

6.2.3 Recommendations

Th i i d i h b k d h i T bl 6 3 Th d d


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SCHLUMBERGER HORIZONTAL PROFILING

RESULTS

LOCATION :3A1-

2A1

DATE : 17-03-

2011

LINE :1

20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170

20 713 696 531 1001 868 701 616 519 631 541 546 686 713 589 413 518

40 891 801 721 997 961 816 713 691 806 631 601 738 869 608 384 686

LINE :2

20 30 40 50 60 70 80 90 100 110 120 130 140 150 160

20 486 416 410 536 616 510 498 486 716 813 1001 736 816 708 963

40 616 573 396 716 736 606 536 513 896 1001 1131 868 981 1001 1142

Figure6.1: Horizontal profiling results and curves for Line3A1-2A1

20 40 60 80 100 120 140 160 180

100

1000

10000

VES9

App.R

es(ohms-m

)

AB/2 (m)

20m

40m

LINE:1

VES8

20 40 60 80 100 120 140 160 180

100

1000

10000

VES11

App.R

es(ohms-m

)

AB/2 (m)

20m

40m

LINE:2

VES10


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(ohm)

1 0.2 7.54

1.5 0.2 17.36

2 0.2 31.11

3 0.2 70.40

5 0.2 9.56 3.76 2.543 196.11 498.634

7 0.5 7.40 2.08 3.561 153.21 545.613

10 0.5 7.80 4.76 1.638 313.50 513.534

15 0.5 4.34 5.76 0.754 706.36 532.756

20 0.5 3.19 7.34 0.435 1256.36 546.132

25 5.0 15.04 5.02 2.994 188.57 564.523

30 5.0 9.56 4.52 2.116 275.00 581.878

35 5.0 6.29 4.02 1.563 377.14 589.645

40 5.0 10.27 8.45 1.215 495.00 601.534

50 5.0 6.48 7.45 0.870 777.86 676.423

58 5.0 4.51 6.75 0.669 1049.40 701.634

70 5.0 2.61 5.45 0.480 1532.14 734.845

80 10.0 7.42 9.34 0.794 990.00 786.212

90 10.0 7.44 11.430 0.651 1257.14 818.476

100 10.0 3.72 6.83 0.544 1555.71 846.332AB = distance between outer electrodes

MN=distance between inner electrodes Figure 6.2a: Vertical electric sounding curves for line3A1-2A1


1 10 100 1000

10

100

1000

10000

App.R

es.(ohms-m

)

AB/2(m)

Schlumberger VES at Line1 -VES8


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Project : GTSF

Community :

Tarkwa

Client : AGA IDUPRIEM

District

:



Mult

factor App Res

(ohm)

1 0.2 7.54

1.5 0.2 17.36

2 0.2 31.11

3 0.2 70.40

5 0.2 12.69 4.56 2.782 196.11 545.623

7 0.5 21.90 6.61 3.313 153.21 507.650

10 0.5 4.58 2.95 1.552 313.50 486.53415 0.5 2.48 3.83 0.647 706.36 456.760

20 0.5 1.01 3.07 0.329 1256.36 413.034

25 5.0 14.46 6.70 2.158 188.57 407.008

30 5.0 8.33 5.70 1.461 275.00 401.767

35 5.0 4.06 3.86 1.051 377.14 396.383

40 5.0 2.16 2.78 0.777 495.00 384.565

50 5.0 2.33 4.87 0.478 777.86 371.723

58 5.0 2.30 5.87 0.392 1049.40 411.808

70 5.0 1.89 6.07 0.311 1532.14 476.423

80 10.0 2.77 5.45 0.509 990.00 503.823

90 10.0 3.98 8.670 0.459 1257.14 576.509

100 10.0 2.90 7.43 0.390 1555.71 606.322


MN=distance between inner electrodes Figure 6.2b: Vertical electric sounding curves for line3A1-2A1


1 10 100 1000

10

100

1000

10000

App.R

es.(o

hms-m

)

AB/2(m)



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Mult

factor App Res

(ohm)

1 0.2 7.54

1.5 0.2 17.36

2 0.2 31.11

3 0.2 70.40

5 0.2 9.13 3.43 2.661 196.11 521.767

7 0.5 14.74 4.53 3.255 153.21 498.657

10 0.5 7.92 5.21 1.520 313.50 476.513

15 0.5 2.36 3.67 0.642 706.36 453.323

20 0.5 0.68 2.07 0.327 1256.36 410.50825 5.0 8.61 3.87 2.225 188.57 419.645

30 5.0 9.46 6.45 1.466 275.00 403.138

35 5.0 4.61 4.34 1.062 377.14 400.645

40 5.0 1.85 2.31 0.802 495.00 396.745

50 5.0 3.20 6.45 0.497 777.86 386.434

58 5.0 1.93 5.03 0.384 1049.40 402.807

70 5.0 2.33 8.65 0.270 1532.14 413.323

80 10.0 1.86 4.53 0.411 990.00 406.867

90 10.0 1.43 3.77 0.381 1257.14 478.554

100 10.0 1.52 4.65 0.328 1555.71 509.665


MN=distance between inner electrodes Figure 6.2c: Vertical electric sounding curves for line3A1-2A1


1 10 100 1000

10

100

1000

10000

App.R

es.(

ohms-m

)

AB/2(m)



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hydrogeological investigations