Enginee ing and Technology Jou nal e-ISSN: 2456-3358
Volume 10 Issue 11 No embe -2025, Page No.- 7729-7741
DOI: 10.47191/e j/ 10i11.05, I.F. – 8.482
© 2025, ETJ
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ETJ Volume 10 Issue 11 No embe 2025, OppongDaniel
Assessmen o Su ace Wa e and G oundwa e Quali y Impac s a
Iduap iem Mine, Ta kwa, Sou hwes e n Ghana App oaches o
Decommissioning o a Tailings S o age Facili y
Daniel Oppong
Uni e si y o Mines and Technology Ta kwa Ghana
ABSTRACT: This s udy e alua ed he hyd ochemis y, su ace wa e and g oundwa e quali y, po en ial impac s, and
decommissioning s a egies o he Tailings S o age Facili y (GTSF) a Iduap iem Mine in Ta kwa, Ghana, ocusing on compliance
wi h Ghana's Mine als and Mining Regula ions (L.I. 2182). The esea ch spanned om 2011 (baseline p e-ope a ional yea ) h ough
2023 and aimed o assess wa e quali y e olu ion, iden i y hyd ochemical p ocesses, and de elop e ec i e TSF closu e s a egies.
Hyd ochemical analysis was conduc ed on 46 sampling poin s comp ising decan wa e (1), opline sumps (19), unde line sumps
(10), deep bo eholes (7), shallow bo eholes (7), and su ace wa e si es (2). Resul s showed ha mul iple physical (pH, TSS,
u bidi y), chemical (po assium, ee cyanide, ni i e, ni a e, ammonia), and ace me al (a senic, lead, i on, coppe , manganese,
magnesium) pa ame e s exceeded En i onmen al P o ec ion Agency (EPA), Ghana S anda ds Au ho i y (GSA), and Wo ld Heal h
O ganiza ion (WHO) pe missible limi s in bo h su ace and g oundwa e sys ems. G oundwa e and su ace wa e chemis y we e
p edominan ly cha ac e ized by Ca-HCO₃ acies, d i en by ca bona e and silica e mine al wea he ing p ocesses. Nine dis inc
hyd ochemical acies we e iden i ied, wi h Ca-HCO₃ (26%) being he mos p e alen , ollowed by Mg-SO₄ (23%) and Ca-SO₄
(13%). Gibbs diag ams con i med ock-wa e in e ac ion as he p ima y con olling mechanism o wa e chemis y. P incipal
Componen Analysis (PCA) iden i ied pH, elec ical conduc i i y, o al dissol ed solids, ni a e, ni i e, ammonia, i on, manganese,
sulpha e, and cyanide as dominan pa ame e s con ibu ing o hyd ochemical a iabili y. Bi a ia e plo s e ealed s ong posi i e
co ela ions ( = 0.996–0.999) be ween majo ions, con i ming he concu en in luence o silica e wea he ing and ca bona e
dissolu ion. Hyd ochemical acies co ela ion analysis e ealed signi ican geochemical in e ac ions among opline s, unde line s,
shallow and deep bo eholes, and su ace wa e , indica ing hyd aulic connec i i y and seepage mig a ion pa hways be ween he TSF
and su ounding aqui e s. Based on hese indings, six in eg a ed decommissioning app oaches a e ecommended: sys ema ic
dewa e ing and wa e managemen , ad anced mul i-s age wa e ea men , ecycling and con olled discha ge, encapsula ion wi h
500 mm opsoil co e , es ablishmen o ege a ed bu e zones a ound su ace wa e bodies, and implemen a ion o long- e m
moni o ing and main enance p og ams o ensu e en i onmen al p o ec ion and egula o y compliance.
KEYWORDS: hyd ochemis y, mine al dissolu ion, wa e - ock in e ac ion,ion exchange, decommissioning s a egies
1. In oduc ion
Mining is a signi ican con ibu o o Ghana’s economy,
p o iding jobs and e enue h ough axes, oyal ies, and
expo s o mine als such as gold and diamonds. Howe e , he
en i onmen al impac o mining pa icula ly he managemen
o Tailings S o age Facili ies (TSFs) poses majo challenges.
TSFs, which s o e was e om mine al p ocessing, can lead o
g oundwa e and su ace wa e con amina ion due o seepage.
G oundwa e con amina ion is o g a e conce n whe e i
eeds su ace s eams o lakes. Excessi e seepage om TSFs
can he e o e lead o se ious en i onmen al p oblems such as
su ace and g oundwa e pollu ion (F anks e al., 2011).
To mi iga e hese issues, Ghana’s Mine als and Mining
Regula ions (L.I. 2182) equi e measu es o p e en wa e
in il a ion, ensu e long- e m s abili y o TSFs, and manage
e luen wi hin app o ed limi s. Acco dingly, his esea ch
aims o: (1) assess su ace and g oundwa e quali y; (2)
de e mine hyd ochemical acies; (3) iden i y ac o s
con olling wa e chemis y; (4) e alua e TSF impac s on
wa e esou ces; and (5) de elop e ec i e decommissioning
s a egies o TSFs.
2. STUDY AREA OVERVIEW
Iduap iem Mine, si ua ed app oxima ely 10 km sou h o
Ta kwa and abou 320 km wes o Acc a (Figu e 1), lies
wi hin he we semi-equa o ial clima ic zone. The a ea is
cha ac e ized by a p olonged ainy season ex ending om
Ma ch o No embe , ollowed by a b ie d y season om
Decembe o Feb ua y. The mean annual ain all is
app oxima ely 1,500 mm (Al-Hassan, 2007). Tempe a u es
ypically ange be ween 26 °C and 30 °C du ing he we
season and be ween 31 °C and 33 °C in he d y season,
accompanied by consis en ly high humidi y h oughou he
yea . The e ain is gen ly undula ing, wi h ele a ions
“Assessmen o Su ace Wa e and G oundwa e Quali y Impac s a Iduap iem Mine, Ta kwa, Sou hwes e n
Ghana App oaches o Decommissioning o a Tailings S o age Facili y”
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ETJ Volume 10 Issue 11 No embe 2025, Daniel Oppong
eaching up o abou 300 m abo e sea le el.
Fig.1. Loca ion Map o Iduap iem Mine
3. MATERIALS AND METHODS
3.1 Sample collec ion and analysis
This s udy u ilized a comp ehensi e da ase comp ising bo h
p ima y and seconda y da a ob ained om mul iple sou ces
associa ed wi h he Tailings S o age Facili y (TSF) o
Iduap iem Mine. A o al o 46 sampling loca ions we e
in es iga ed, consis ing o se en deep bo eholes (70 m
dep h), se en shallow bo eholes (30 m dep h), nine een
opline sumps, en unde line sumps, wo su ace wa e si es,
and one decan wa e pool. The empo al scope o he da ase
spanned om 2011 es ablished as he baseline p e-
ope a ional yea h ough o 2023.
P ima y da a collec ion employed calib a ed Ho iba Mul i-
pa ame e (U-52) p obes, ollowing s anda dized quali y
assu ance p ocedu es. To minimize c oss-con amina ion,
disposable glo es we e used o each sample. P io o
sampling, bo eholes we e pumped o app oxima ely en
minu es o pu ge s agnan wa e and ob ain ep esen a i e
aqui e samples (Sunka i e al., 2020). G oundwa e samples
we e collec ed using baile s in acco dance wi h pu ging
p o ocols o ensu e ha in-si u condi ions we e accu a ely
ep esen ed.
Sample p ese a ion was unde aken immedia ely a e
collec ion: pH was adjus ed o below 2 using 1% HNO₃ o
me al analysis, samples o cyanide de e mina ion we e
s abilized wi h NaOH o main ain pH alues abo e 12, and
all samples we e il e ed h ough 0.45 µm memb ane il e s.
Each sample bo le was clea ly labelled wi h de ails including
he loca ion, da e, and a ge analy es. Samples we e
anspo ed unde con olled condi ions o he AngloGold
Ashan i Iduap iem En i onmen al Labo a o y, Ta kwa,
Ghana, o hyd ochemical analysis.
Majo ca ions and anions; po assium (K⁺), sodium (Na⁺),
calcium (Ca²⁺), magnesium (Mg²⁺), chlo ide (Cl⁻),
bica bona e (HCO₃⁻), ni a e (NO₃⁻), and sulpha e (SO₄²⁻)
we e quan i ied using a HACH DR6000 spec opho ome e .
Concen a ions o hea y me als such as Fe, Mn, Pb, Cu, Cd,
Hg, As, Zn, and Mg we e de e mined using Induc i ely
Coupled Plasma Op ical Emission Spec ome y (ICP–OES).
P incipal Componen Analysis (PCA) was applied o educe
he dimensionali y o he la ge geochemical da ase and
iden i y ela ionships among he chemical pa ame e s. The
Kaise C i e ion (eigen alue ≥ 1) was adop ed o de e mine
he numbe o signi ican ac o s, and a imax o a ion was
applied o maximize a iance and enhance in e p e abili y.
“Assessmen o Su ace Wa e and G oundwa e Quali y Impac s a Iduap iem Mine, Ta kwa, Sou hwes e n
Ghana App oaches o Decommissioning o a Tailings S o age Facili y”
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ETJ Volume 10 Issue 11 No embe 2025, Daniel Oppong
Sa u a ion indices we e compu ed o e alua e he in luence o mine al wea he ing on g oundwa e chemis y. Geochemical
in e p e a ions we e ca ied ou using AquaChem so wa e
(Ve sion 4.0), whe e Pipe ilinea diag ams we e employed
o classi y hyd ochemical acies and Gibbs plo s we e used o
iden i y dominan p ocesses con olling g oundwa e
chemis y (Gibbs, 1970).
As geochemical da a a e ypically non-no mally dis ibu ed,
he da ase unde wen a cen e ed log- a io (CLR)
ans o ma ion ollowing he app oach o Ai chison and
G eenac e (2002) o achie e no mali y and imp o e s a is ical
eliabili y. Fu he da a analysis in ol ed mul i a ia e
s a is ical echniques, including ac o analysis using SPSS,
o delinea e key geochemical p ocesses and con aminan
in e ac ions (Li e al., 2015; Zango e al., 2019).
Based on hyd ochemical and s a is ical assessmen s, se en
key decommissioning s a egies we e p oposed o mi iga e
en i onmen al isks: dewa e ing, ea men , ecycling,
encapsula ion, es ablishmen o bu e zones, long- e m ca e,
and con inuous moni o ing. These comp ehensi e analyses
acili a ed he in e p e a ion o geochemical e olu ion and
p o ided insigh s in o he o e all impac o ailings on bo h
su ace and g oundwa e sys ems wi hin he TSF a ea
(Sunka i e al., 2023
4 Resul s and Discussion
4.1 Quali y o TSF Wa e , Su ace Wa e and
G oundwa e
The esul s o he physical and chemical cha ac e is ics o
decan wa e , su ace and g oundwa e a e p esen ed in
Tables 1 and 2. The wa e quali y pa ame e s show labo a o y
esul s o 2011 and 2023, ep esen ing commencemen o
ope a ion o he TSF and cu en s a us espec i ely. The
esul s o he a ious pa ame e s we e compa ed wi h he
Ghana S anda ds Au ho i y (GSA), EPA and WHO
pe missible limi s. Those exceeding egula o y s anda ds
ha e been highligh ed in Tables 1 and 2, yellow ep esen s
alues exceeding WHO s anda ds, ed indica es exceedances
o bo h WHO and EPA/GSA s anda ds, and blue highligh s
pa ame e s exceeding EPA/GSA s anda ds.
Table 1 p esen s wa e quali y esul s om physical,
chemical, and ace me al pa ame e s o g oundwa e (deep
and shallow) and su ace wa e (SW1 and SW2) in 2011. Key
exceedances include pH (5.82) in shallow bo eholes, wi h a
6% exceedance, po assium a 7 mg/L and 13 mg/L in SW2
and shallow bo eholes (5% exceedance), and ni i e in SW1
a 9.580 mg/L (15% exceedance). O he exceedances include
ammonia (2.75 mg/L), magnesium in SW1 (2.96 mg/L, 48%
exceedance), i on in SW1 (1.13 mg/L, 36% exceedance), and
SW2 exceeding limi s o a senic, magnesium, i on, and
manganese wi h exceedances anging om 5% o 28%.
Shallow g oundwa e showed exceedances o lead,
magnesium, i on, manganese, and coppe , wi h exceedance
pe cen ages anging om 2% o 28%. The physical
pa ame e s o su ace wa e whe e wi hin he ange o WHO
and EPA/GSA s anda ds. Chemical da a we e also wi hin he
ange o he s anda ds excep s o NO3 (3.147mg/l) and NH3.
(2.75mg/l), wi h a pe sonage exceedance o 15% and 6%
espec i ely. T ace me als howe e showed he mos
de ia ion om he s anda ds. Magnesium was ound o ha e
high alues in bo h su ace (SW1 and SW2) and g oundwa e
(Deep and Shallow) han GSA/EPA s anda ds bu wi h a 0%
pe cen age exceedance. I on wi h 36% pe cen age had alues
highe han he WHO s anda ds in su ace (SW1 and SW2)
and much highe in he g oundwa e (deep and shallow) wi h
alues anging om 5.09mg/l o 8.42mg/l. Manganese was
g ea e han he GSA/EPA s anda ds in SW1 (su ace wa e )
and g oundwa e (deep and shallow) wi h a 0% pe cen age
exceedance.
Table 2 p esen s he wa e quali y da a o 2023. Su ace
wa e esul s showed exceedances mainly in u bidi y and
ace me als. SW2 eco ded a u bidi y exceedance o 99
NTU (92%). Fo ace me als, magnesium was ele a ed in
bo h SW1 (5.1 mg/L, 91%) and SW2 (7.8 mg/L, 93%). I on
exceeded limi s a 2 mg/L in SW1 (94%) and 0.6 mg/L in
SW2 (89%). Manganese (92%) and coppe (91%) also
exceeded s anda ds in SW2.
G oundwa e eco ded pH alues below EPA/GSA and WHO
s anda ds, wi h exceedances o 92% o deep g oundwa e
(pH 5.44) and 92% o shallow g oundwa e (pH 5.82).
Shallow g oundwa e also exceeded limi s o po assium
(12.6 mg/L, 95%), ee cyanide (93%), ni i e (94%), ni a e
(92%), and ammonia (90%). Fo ace me als, deep
g oundwa e eco ded high le els o magnesium (19.4 mg/L,
96%), i on (11.8 mg/L, 95%), and manganese (0.26 mg/L,
90%). Shallow g oundwa e exceeded limi s o magnesium
(94%), i on (93%), coppe (92%), a senic (91%), and lead
(90%).
Fo TSF wa e , he decan pool eco ded he mos signi ican
exceedances, wi h pH (10.07, 95%), o al suspended solids
(1770 mg/L, 96%), and u bidi y (5288 NTU, 96%).
Chemical exceedances included po assium (13 mg/L in he
Unde line , 96%), ee cyanide (93%), ni i e (94%), ni a e
(92%), and ammonia (90%). Fo ace me als, he decan pool
showed exceedances o coppe (92%), a senic (90%), lead
(89%), and cadmium (88%). The Topline eco ded
exceedances o pH (91%), elec ical conduc i i y (89%),
o al suspended solids (95%), u bidi y (94%), and ace
me als including i on (94%), manganese (92%), coppe
(91%), a senic (90%), and lead (89%).
“Assessmen o Su ace Wa e and G oundwa e Quali y Impac s a Iduap iem Mine, Ta kwa, Sou hwes e n
Ghana App oaches o Decommissioning o a Tailings S o age Facili y”
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ETJ Volume 10 Issue 11 No embe 2025, Daniel Oppong
Table 1. Resul s o 2011 Su ace Wa e and G oundwa e Quali y Pa ame e s
Table 2. Resul s o 2023 Wa e Quali y Pa ame e s
4.2 Schoelle diag ams
Schoelle diag ams (Fig. 2) we e employed o illus a e he
dis ibu ion pa e ns o majo ions in decan wa e , su ace
wa e , and g oundwa e o he yea s 2011, 2016, 2017, and
2023. The 2011 Schoelle diag am (Fig. 2) depic s he majo
ion composi ion o g oundwa e (bo h deep and shallow) and
su ace wa e (SW1 and SW2). The highes ca ion
concen a ion was eco ded o calcium (Ca²⁺) a 45 mg/L,
while bica bona e (HCO₃⁻) exhibi ed he highes anion
s anda ds s anda ds Exceedance(%) Min Max A e age Min Max A e age Min Max a e age Min Max A e age
p H 6-9 6.5-8.5 6 7.16 7.61 7.34 6.86 7.42 7.24 6.60 7.88 7.06 5.82 7.93 6.91
EC (µS/cm) 1500 2500 0164 229 207 230 464 344 49 330 175 38 696 267
TDS (mg/L) 1000 1000 0310 463 412 105 284 176 24 188 88 18 373 142
TSS (mg/l) 50 0 9 17 13 624 33 312 6 1 13 5.3
TURB. (NTU) 75 019 63 48 12 54 22 221 10 718 11
s anda ds s anda ds Exceedance(%) Min Max a e age Min Max A e age Min Max A e age Min Max A e age
Sodium (mg/L) 200 058 68 63 44 4 4 18 10 11 24 11
Po assium (mg/L) 512 555 5 275 1 4 2 4 13 4
Calcium (mg/L) 250 200 0513 955 5 8 51 26 18 50 18
Bica bona e (mg/L) 0 32 46 39 513 9 8 56 26 30 100 30
Chlo ide (mg/L) 250 1000 019 20 19 38 46 42 414 817 56 17
Sulpha e (mg/L) 300 400 029 35 32 16 19 29 127 7 6 16 6
CN-F (mg/L) 0.2 0 0.0001 0.0001 0.0001 0.0020 0.0120 0.0045 0.0041 0.0039 0.0008 0.0020 0.0080 0.0048
N-NO2 (mg/L) 315 0.010 9.580 3.147 0.007 2.687 2.112 0.001 0.007 0.005 0.002 0.212 0.012
N-NO3 (mg/L) 50 0 1.460 5.410 3.522 0.120 19.150 13.904 0.004 0.144 0.085 0.013 0.408 0.149
N-NH3 (mg/L) 16 0.04 2.75 0.66 0.02 0.28 0.07 0.01 0.06 0.45 0.07 0.20 0.17
s anda ds s anda ds Exceedance(%) Min Max A e age Min Max A e age Min Max A e age Min Max A e age
A senic (mg/L) 0.1 0.01 5 0.0034 0.0067 0.0049 0.0012 0.0115 0.0036 0.0007 0.0021 0.0013 0.0010 0.0026 0.0018
lead (mg/L) 0.1 0.01 7 0.0013 0.0044 0.0030 0.0024 0.0054 0.0033 0.0009 0.0025 0.0015 0.0019 0.020 0.0101
Magnesium (mg/L) 2100 0 1.92 2.96 2.24 5.76 7.82 6.67 0.31 2.42 0.90 0.28 10.75 2.35
I on (mg/L) 10 0.3 36 0.09 1.12 0.41 0.11 0.63 0.32 5.09 8.42 6.76 3.00 7.10 5.05
Manganese (mg/L) 0.2 0 0.010 0.110 0.081 0.013 2.761 1.387 1.120 3.967 2.540 0.079 0.689 0.261
Coppe (mg/L) 5 0.05 2 0.004 0.009 0.01 0.003 0.010 0.005 0.035 0.004 0.042 0.006 0.11 0.046
Cadmium (mg/L) 0.1 0.003 00.000575 0.027273 0.005 0.001 0.010 0.004 0.001 0.004 0.003 0.001 0.003 0.001
Zinc (mg/L) 10 500.043033 0.551 0.34 0.0004 0.14 0.11 0.001 0.002 0.001 0.004 0.092 0.053
Me cu y (mg/L) 0.005 0.006 00.0004 0.0034 0.0015 0.0003 0.0004 0.0003 0.001 0.004 0.0014 0.0006 0.0031 0.0010
2011
Chemical Pa ame e s
Me als
Physical Pa ame e s
G oundwa e
WHO
GSA/EPA
Pa ame e s
G oundwa e
Deep
Shallow
SW 2
Deep
Shallow
SW 2
Pa ame e s
Su ace wa e
Pa ame e s
Deep
Shallow
Su ace wa e
G oundwa e
SW 1
WHO
GSA/EPA
GSA/EPA
WHO
Pe cen age o
SW 2
SW 1
Su ace wa e
SW 1
Pe cen age o
Pe cen age o
S anda ds S anda ds Exceedance(%) Min Max A e age Min Max A e age Min Max A e age Min Max A e age
p H 6-9 6.5-8.5 92 6.68 6.84 6.77 6.87 7.15 7.02 5.44 7.05 6.48 5.82 7.93 6.86
EC (µS/cm) 1500 2500 12 399 457 428 462 673 609 141 555 337 38 696 376
TDS (mg/L) 1000 1000 0179 216 197 297 432 384 91 347 213 18 373 224
TSS (mg/l) 50 93 817 12.5 1 99 23 312 6 9 12 10.5
TURBIDITY(NTU) 75 95 14 23 18 4234 41 2.4 21 10 14 2 8
S anda ds S anda ds Exceedance(%) Min Max A e age Min Max A e age Min Max A e age Min Max A e age
Sodium (mg/L) 200 058 68 63 44 4 4 18 10 11 24 11
Po assium (mg/L) 512 5295310 7 1 4 2 4 13 4
Calcium (mg/L) 250 200 0513 955 5 8 51 26 18 50 18
Bica bona e (mg/L) 0 32 46 39 513 9 8 56 26 30 100 30
Chlo ide (mg/L) 250 1000 019 20 19 38 46 42 414 817 56 17
Sulpha e (mg/L) 300 400 029 35 32 16 19 29 127 7 6 16 6
CN-F (mg/L) 0.2 96 0.002 0.002 0.002 0.000 0.001 0.001 0.001 0.005 0.003 0.001 0.027 0.008
N-NO2 (mg/L) 358 0.018 16.090 6.654 0.307 27.687 4.112 0.001 0.108 0.014 0.082 7.120 0.205
N-NO3 (mg/L) 50 59 1.540 7.400 4.470 0.120 19.150 13.904 0.004 1.092 0.193 0.013 0.408 0.129
N-NH3 (mg/L) 146.0 0.03 0.07 2.5 0.9 1.0 0.1 0.0 0.8 0.7 0.01 1.2 0.9
S anda ds S anda ds Exceedance(%) Min Max A e age Min Max A e age Min Max A e age Min Max A e age
A senic (mg/L) 0.1 0.01 10 0.001 0.004 0.003 0.001 0.010 0.004 0.0004 0.004 0.002 0.001 0.046 0.002
lead (mg/L) 0.1 0.01 12 0.0003 0.0004 0.0003 0.0024 0.0054 0.0033 0.0008 0.0302 0.0078 0.0007 0.0910 0.0019
Magnesium (mg/L) 2100 61 3.2 5.1 4.2 5.8 7.8 6.7 0.3 19.4 9.0 0.3 10.7 4.5
I on (mg/L) 10 0.3 59 0.2 2.0 0.7 0.1 0.6 0.3 7.2 11.8 10.6 0.2 0.7 0.3
Manganese (mg/L) 0.2 0 0.0020 0.0032 0.0026 0.0040 0.9900 0.0825 0.0030 0.2600 0.1070 0.0009 0.0045 0.0016
Coppe (mg/L) 5 0.05 8 0.007 0.010 0.009 0.001 0.5 0.022 0.001 0.004 0.001 0.001 0.1 0.040
Cadmium (mg/L) 0.1 0.003 0 0.001 0.005 0.002 0.001 0.010 0.004 0.001 0.004 0.003 0.001 0.027 0.008
Zinc (mg/L) 10 50 0.07 0.12 0.09 0.0004 5.14 0.91 0.9 1.0 0.1 0.009 0.07 0.029875
Me cu y (mg/L) 0.005 0.006 0 0.001 0.003 0.002 0.0003 0.0005 0.0003 0.001 0.004 0.0024 0.0004 0.003 0.002
SW 2
Deep
Shallow
2023
Physical Pa ame e s
Pa ame e s
GSA/EPA
WHO
Pe cen age o
Su ace Wa e
G oundwa e
SW 1
Deep
Shallow
Me als Pa ame e s
Chemical Pa ame e s
Pa ame e s
GSA/EPA
WHO
Pe cen age o
Su ace Wa e
G oundwa e
SW 1
SW 2
Pa ame e s
GSA/EPA
WHO
Pe cen age o
Su ace Wa e
SW 1
SW 2
Deep
Shallow
G oundwa e
“Assessmen o Su ace Wa e and G oundwa e Quali y Impac s a Iduap iem Mine, Ta kwa, Sou hwes e n
Ghana App oaches o Decommissioning o a Tailings S o age Facili y”
7733
ETJ Volume 10 Issue 11 No embe 2025, Daniel Oppong
concen a ion a 55 mg/L.
By 2023, calcium (Ca²⁺) emained he dominan ca ion, wi h
a maximum concen a ion o 118 mg/L, and bica bona e
(HCO₃⁻) con inued o be he p e ailing anion, wi h a peak
concen a ion o 60 mg/L. The Schoelle plo s consis en ly
indica e ha Ca²⁺ and HCO₃⁻ a e he p edominan ca ion and
anion, espec i ely, sugges ing a hyd ochemical egime
p ima ily in luenced by ca bona e wea he ing and limi ed
an h opogenic al e a ion.
Fig. 2. Schoelle Diag am o Majo Ions in 2011(a) and 2023(b)
4.3 Hyd ochemical Facies o TSF Wa e , Su ace Wa e
and G oundwa e
T ilinea Pipe diag ams (Fig. 3) we e used o e alua e he
hyd ochemical acies and geochemical e olu ion o su ace
wa e , g oundwa e , and ailings s o age acili y (TSF) wa e s
be ween 2011(Fig. 3(a)) and 2023(Fig. 3()). In 2011, he
o e all hyd ochemis y was domina ed by Ca–HCO₃ acies
(56.2%), wi h Ca–Cl (18.8%) and Na–SO₄ (13%) as
seconda y ypes, while smalle p opo ions o Na–HCO₃
(6%) and Mg–Cl (6%) we e also eco ded. By 2023, he
sys em shi ed ma kedly owa ds sulpha e- ich wa e s, wi h
Mg–SO₄ (23%), Ca–SO₄ (13%), and Na–SO₄ (12%) oge he
accoun ing o almos hal o he o al composi ion, al hough
Ca–HCO₃ (26%) emained signi ican (Gibbs, 1970).
A he indi idual wa e sou ces, su ace wa e displayed he
mos dynamic changes. In 2011, su ace wa e was
cha ac e ised by Na–SO₄²⁻ and Ca–Cl acies (50% each). By
2023, he chemis y had e ol ed in o Na–SO₄²⁻ (50%) and
Na–HCO₃ (50%) ypes, indica ing inc easing an h opogenic
in luence. The pe sis ence o sulpha e acies poin s o
con ibu ions om sulphide oxida ion and possible TSF
seepage (F eeze and Che y, 1979).
G oundwa e exhibi ed mo e g adual changes. In 2011, Ca–
HCO₃ (50%) was dominan , wi h subo dina e Na–HCO₃
(14%) and Ca–Cl (14%). By 2023, Ca–HCO₃ emained he
p e ailing ype (50%), accompanied by Ca–Cl (16.7%) and
Na–HCO₃. The dominance o Ca–HCO₃ acies h oughou
he s udy pe iod e lec s na u al bu e ing by ca bona e and
silica e wea he ing (Hem, 1989). None heless, he appea ance
o Ca–Cl wa e s in 2023 sugges s localised mixing wi h
su ace wa e o seepage om he TSF, demons a ing ha
he aqui e e ains a deg ee o p o ec ion bu is no en i ely
una ec ed (Ko ale sky e al., 2004).
TSF wa e s showed he mos p onounced ans o ma ion. In
2011, da a we e no a ailable o TSF wa e cha ac e isa ion.
By 2023, howe e , he chemis y was domina ed by sulpha e
acies, wi h Mg–SO₄ (50%), Ca–SO₄ (25%), and Na–SO₄
(20%), consis en wi h sulphide oxida ion wi hin he ailings
and he elease o sulpha e- ich leacha es (Lo e mose , 2010;
Younge e al., 2002).
2011(a)
2023(a)
“Assessmen o Su ace Wa e and G oundwa e Quali y Impac s a Iduap iem Mine, Ta kwa, Sou hwes e n
Ghana App oaches o Decommissioning o a Tailings S o age Facili y”
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ETJ Volume 10 Issue 11 No embe 2025, Daniel Oppong
Fig. 3. Pipe diag am illus a ing he g oundwa e e olu ion and hyd ochemical acies in 2011(a) and 2023(b)
4.4 Fac o s con olling g oundwa e chemis y
Gibbs diag ams (Figs. 4 and 5), illus a ing he a ios o Na⁺/
(Na⁺ + Ca²⁺) and Cl⁻/ (Cl⁻ + HCO₃⁻) as unc ions o o al
dissol ed solids (TDS), a e widely employed o iden i y he
dominan mechanisms con olling wa e chemis y namely,
p ecipi a ion dominance, ock wea he ing dominance, and
e apo a ion dominance.
In his s udy, chemical da a om all sampling poin s be ween
2011 and 2023 we e plo ed on Gibbs diag ams. The
clus e ing pa e ns o he sample poin s indica e ha he
chemical composi ion o g oundwa e is p ima ily go e ned
by he wea he ing o ock- o ming mine als. This inding
sugges s ha mine al dissolu ion esul ing om ock–wa e
in e ac ions is he p incipal p ocess in luencing he egion’s
g oundwa e chemis y.
A ew g oundwa e samples exhibi ed p ecipi a ion-
domina ed cha ac e is ics, including BH7S in 2011. The
Gibbs plo s u he e eal a posi i e ela ionship be ween
ele a ed TDS alues and highe Na⁺/(Na⁺ + Ca²⁺) a ios,
implying ha ca ion exchange p ocesses in ol ing sodium
(Na⁺) and calcium (Ca²⁺) signi ican ly con ibu e o he
obse ed a ia ions in g oundwa e chemis y.
Fig. 4. Gibbs Plo Showing Fac o s Con olling Wa e Chemis y o 2011
1
10
100
1000
10000
100000
00.2 0.4 0.6 0.8 1
TDS
Na/(Na+Ca)
I-GT10D I-GT10S I-GT2D
I-GT2S I-GT4D I-GT4S
1
10
100
1000
10000
100000
00.2 0.4 0.6 0.8 1
TDS
Cl/(Cl+HCO3))
I-GT10D I-GT10S I-GT2D
I-GT2S I-GT4D I-GT4S
2011(a)
2023(b)
“Assessmen o Su ace Wa e and G oundwa e Quali y Impac s a Iduap iem Mine, Ta kwa, Sou hwes e n
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ETJ Volume 10 Issue 11 No embe 2025, Daniel Oppong
Fig. 5. Gibbs Plo Showing Fac o s Con olling Wa e Chemis y o 2023
The bi a ia e plo s (Fig. 6) o 2011 illus a e he
ela ionships among key ionic a ios used o in e
hyd ogeochemical p ocesses go e ning g oundwa e
e olu ion. The plo o Ca²⁺/Mg²⁺ e sus HCO₃⁻/SO₄²⁻ exhibi s
a weak posi i e co ela ion ( = 0.216), wi h mos samples
plo ing abo e he 1:1 line. This pa e n sugges s he
occu ence o e e se ion exchange p ocesses. In he Na⁺
e sus Cl⁻ plo , mos samples clus e nea he equiline,
indica ing hali e dissolu ion as a majo sou ce o sodium and
chlo ide ions.
In he Na⁺ e sus HCO₃⁻ plo , samples plo ed close o he
equiline imply ca bona e mine al dissolu ion, suppo ed by a
modes posi i e co ela ion ( = 0.309). Simila ly, he Na⁺
e sus Na⁺/(Na⁺ + K⁺) ela ionship e eals a posi i e
co ela ion ( = 0.209), wi h samples nea he equiline
indica ing silica e wea he ing, whe eas hose plo ed abo e
he 1:1 line sugges s e e se ion exchange. Samples di e ging
abo e o below he equiline likely e lec e e se o o wa d
ion exchange eac ions, espec i ely.
The bi a ia e plo o Mg²⁺/Ca²⁺ e sus Ca²⁺/Na⁺ demons a es
a s ong posi i e co ela ion ( = 0.996), wi h mos samples
dis ibu ed abo e he 1:1 line be ween silica e wea he ing and
ca bona e dissolu ion ields, indica ing he concu en
in luence o bo h p ocesses. Simila ly, he plo o HCO₃⁻/Na⁺
e sus Ca²⁺/Na⁺ shows mos samples clus e ed wi hin he
silica e and ca bona e dissolu ion domains, suppo ed by a
e y s ong posi i e co ela ion ( = 0.999) be ween he x- and
y-axis pa ame e s. These ela ionships collec i ely sugges
ha g oundwa e chemis y in 2011 was p ima ily con olled
by silica e and ca bona e mine al wea he ing, wi h seconda y
con ibu ions om ion exchange p ocesses.
1
10
100
1000
10000
100000
00.2 0.4 0.6 0.8 1
TDS
Na/(Na+Ca)
I-GT10D I-GT10S I-GT2D
I-GT2S I-GT4D I-GT4S
I-GT5D I-GT5S I-GT6D
I-GT6S I-GT7D I-GT7S
1
10
100
1000
10000
100000
00.2 0.4 0.6 0.8 1
TDS
Cl/(Cl+HCO3)
I-GT10D I-GT10S I-GT2D
I-GT2S I-GT4D I-GT4S
I-GT5D I-GT5S I-GT6D
I-GT6S I-GT7D I-GT7S
“Assessmen o Su ace Wa e and G oundwa e Quali y Impac s a Iduap iem Mine, Ta kwa, Sou hwes e n
Ghana App oaches o Decommissioning o a Tailings S o age Facili y”
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ETJ Volume 10 Issue 11 No embe 2025, Daniel Oppong
Fig. 6. Majo elemen ela ionship depic ing p ima y p ocesses in luencing g oundwa e chemis y
4.5 Sou ces o g oundwa e cons i uen s
Fac o analysis was conduc ed o de e mine he p incipal
physicochemical pa ame e s and a iables in luencing wa e
quali y wi hin he s udy a ea. A o al o wen y-one (21)
physical, chemical, and me al a iables we e assessed o
TSF wa e , su ace wa e , and g oundwa e ac oss he s udy
yea s, om which ou dominan ac o s we e ex ac ed o
each pe iod.
In 2011 (Fig. 7), he i s componen , wi h an eigen alue o
0.975, explained 38.8% o he o al a iance, while he second
(0.824), hi d (0.877), and ou h (0.903) componen s
accoun ed o 17.4%, 11.3%, and 9.7% o he a iance,
espec i ely. In 2016, he i s componen (0.934) explained
42.5% o he a iance, ollowed by he second (0.991) a
17.2%, he hi d (0.976) a 10.7%, and he ou h (0.733) a
6.4%. Fo 2017, he i s componen (0.940) con ibu ed
43.4% o he o al a iance, wi h he second and hi d
componen s (0.979 each) explaining 19.7% apiece, and he
ou h (0.830) accoun ing o 6.2%. By 2023 (Fig. 8), he i s
componen (0.952) explained 43% o he o al a iance,
ollowed by he second (0.973) a 13.1%, he hi d (0.854) a
19.7%, and he ou h (0.797) a 7%.
These ac o s loading e lec he clus e ing o pa ame e s
associa ed wi h a ious hyd ochemical p ocesses
con ibu ing o he p og essi e mine aliza ion o wa e . The
iden i ied componen s unde sco e he complex in e play
be ween na u al (geogenic) and human-induced
(an h opogenic) ac o s in luencing he hyd ochemis y o he
TSF, su ace wa e , and g oundwa e sys ems. The esul s o
he ac o analysis hus p o ide c i ical insigh s in o he
dominan geochemical p ocesses con olling wa e quali y
a ia ions ac oss empo al scales.
“Assessmen o Su ace Wa e and G oundwa e Quali y Impac s a Iduap iem Mine, Ta kwa, Sou hwes e n
Ghana App oaches o Decommissioning o a Tailings S o age Facili y”
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ETJ Volume 10 Issue 11 No embe 2025, Daniel Oppong
Fig. 7 and 8 Ro a ion plo o ac o analysis using a imax o a ion i e a ion
4.6 Hyd ochemical Facies Co ela ion and Impac s
Assessmen
The en i e pe ime e o he GTSF was subdi ided in o ou
sec ions o enable co ela ion o hyd ochemical acies ac oss
he a ious sampling media, including shallow and deep
bo eholes, unde line and opline sumps, su ace wa e
bodies, and he decan pool (Figu es 9–12). Dis inc wa e
ypes we e ep esen ed using a s anda dised colou -coding
scheme, wi h CaSO₄-domina ed acies (decan wa e )
indica ed in ed. Unde op imal TSF cons uc ion, ailings
wa e is expec ed o emain ully con ained, minimising
in e ac ion wi h g oundwa e and su ace wa e . Howe e , he
occu ence o simila wa e ypes ac oss sampling poin s
indica es po en ial hyd aulic connec i i y o geochemical
in e ac ion.
Along he no he n sec ion o he GTSF (Figu e 9, AA′),
po en ial geochemical in e ac ion was in e ed be ween
opline sump TL15 and unde line sump UL9, bo h
exhibi ing CaSO₄ acies ( ed code). This sugges s a possible
sha ed con amina ion pa hway.
In he eas e n sec ion (Figu e 9, AA′), g oundwa e sample
UL9 and TSF wa e (TL16) exhibi ed he same CaSO₄ acies,
while UL10 and TL16 sha ed a NaHCO₃ acies (yellow
code), indica ing in e ac ion. In he sou he n sec ion (Figu e
9, CC′), a possible geochemical link was iden i ied be ween
g oundwa e (UL2) and TSF wa e (TL16), bo h showing
MgCl acies (black code).
In he wes e n sec ion (Figu e 11, DD′), su ace wa e SW2
and TSF wa e (TL13) exhibi ed he same acies, sugges ing
in e ac ion. Simila ly, in he eas e n sec ion (Figu e 10, BB′),
opline samples TL3, TL6, TL8, TL5 and g oundwa e
bo ehole BHS1 (Figu e 11, CC′) all exhibi ed CaCl acies
(da k blue code), indica ing po en ial mixing be ween su ace
wa e , g oundwa e , and TSF wa e .
Fig. 9. AA’ Hyd ochemical Sec ional View o he GTSF
2011(6)
2023(7)
