Underground modeling as a tool for impact
assessment of productive processes
A li ã ddo IImpacto
Avaliação
t ddos P
Processos P
Produtivos
d ti
e
Modelos do Ambiente Subterrâneo
Jorge Molinero
São Paulo. 15-18 Setembro de 2009
Outline
Modelingg underground
g
hydro-bio-geochemical
y
g
processes
Quantitative evaluation of impacts Æ Can we believe
in models?
Some examples of underground impact evaluation:
•
•
•
•
Mining activities
Deep geological repository for Radwaste
CO2 storage
t
Civil engineering facilities
Underground HBGQ processes
Can we believe in models?
All models are simplified versions of the reality and underground
models are necesarily over-simplified Æ UNCERTAINTY
•CONCEPTUAL UNCERTAINTY
Processes
I & B conditions
Time scale
•PARAMETER UNCERTAINTY
H
Heterogeneity
g n y
Time scale
Upscaling …
•MODEL RESULTS (IMPACT
ASSESSMENT)) must
acknowledge (and quantify if
possible) the uncertainty
One complex example…
Iberian
pyritic
belt
Sotiel
Riotinto
Tharsis
Aznalcóllar
Sevilla
Huelva
ESPANYA
Doñana
National
Park
50 km
One complex example…
Aznalcóllar
ESPANYA
50 km
One complex example…
Most sludge retired in 4
months.
But 0.1 to 5 % remained
representing a potential
environmental risk.
THE QUESTION:
THE PROBLEM:
Will the lake be affected?
Sludge
g
Unsaturated zone
Aquifer
Surface
water
One complex example…
• PROBLEM TREE
• PROBABILITY OF FAILURE
P[CA] = P[AN ] + P[AR] − P[AN I AR]
¿Can we evaluate these probabilities?
One complex example…
IF NATURAL ATTENUATION WORKS
Mine tailing
Unsaturated
zone
F S 2 ( s ) + O2 (aq) + 8 H 2O(l ) → Fe
FeS
F 2+ (aq) + 2SO42− (aq) + 16 H + (aq)
CaCO3 ( s ) + H + ( aqq) ↔ HCO3− (aqq ) + Ca 2+ (aq
q)
Calcite buffers pH
x>H2AsO4 + H2O ⇔ xO>H + AsO43- + 3 H+
x>HAsO4- + H2O ⇔ xO>H + AsO43- + 2 H+
xO>HAsO43- ⇔ xO>H + AsO43xO>Cu+ + H+ ⇔ xO>H + Cu2+
xO>Zn+ + H+ ⇔ xO>H + Zn2+
Aquifer
P it dissolves
Pyrite
di l
xO>Pb+ + H+ ⇔ xO>H + Pb2+
Contaminants adsorb
on ferrihydrite
One complex example…
IF NATURAL ATTENUATION FAILS
Mine tailing
10
F S 2 ( s ) + O2 (aq ) + 8 H 2O(l ) →9Fe
FeS
F 2+ (aq ) + 2 SO42− (aq ) + 16 H + (aq )
8
7
6
5
4
3
2
1
0
0
100
200
P it dissolves
Pyrite
di l
pH
pH drops to acidic values
Unsaturated
zone
Contaminants (such as Cu, Zn, Pb, As, etc.)
move freely through the unsaturated zone
Contaminants reach the aquifer
300
400
Time (days)
1.0E-02
1.0E-04
1.0E-05
1 0E-06
1.0E-06
2+
Aquifer
[Cu (a
aq)] (mol/L)
1.0E-03
1.0E-07
1.0E-08
1.0E-09
0
100
200
Time (days)
C. Domenech, 2002. Ph.D. Thesis
300
400
One complex example…
REMEDIATION ACTION
Limestone gravel
Porosity=0.4
Grain size= 1 cm
8
Q= 0,1 m/d
7
Q= 1 m/d
pH
p
6
5
Q= 10 m/d
4
0,0
0,2
0,4
0,6
0,8
( )
Barrier thickness (m)
YES! Models can help us to determine probabilities by
quantifying
f
uncertainties Æ PRA
Bolster et al. 2009. Probabilistic risk analysis of groundwater remediation strategies . Water
Resources Research,, 45
Trinchero et al. 2009. Probabilistic risk analysis of radioactive waste disposal – a case study,
Proceedings of American Geophysical Union, Fall Meeting, 2009
1,0
A second complex example…
Deep Geological Repository of RadWaste:
Canister & Chemical Barrier
Engineered Barrier
Natural or Geologic Barrier
The question:
Will the glaciar water reach the repository?
(at a given time T)
I Skandinavia
In
Sk di
i (S
(Sweden)
d ) the
th scenario
i off glaciation
l i ti mustt b
be evaluated
l t d
(m)
50
Glaciar
Ice Lake
Highly diluted water could
compromise the stability of
the bentonite
0
-800
-1000
Deep Brine > 1.5 Ma
20 Km
A second complex example…
100 equally probable streamlines crossing the repository
A second complex example…
100 equally probable streamlines crossing the repository
A second complex example…
100 equally probable streamlines crossing the repository
A second complex example…
100 equally probable streamlines crossing the repository
An application example…
> CDF at time T
More Examples…
U d
Underground
d storage
t
off CO2
Main risk related to deep storage
of
f CO2
LEAKAGE
Direct
emission of
CO2
Changes in shallow
aquifers
More Examples…
U d
Underground
d storage
t
off CO2
CO2 plays an important role in
solubility of metals.
metals Possible
leakage of CO2 could compromise
water resources quality Æ Study
and modeling of natural analogues
Testing with natural systems
EMPORDÀ
BASIN
1E-03
measured
Fe concentrattion (mol/l)
1E-04
LA SELVA BASIN
without Fe(OH)CO3(aq)
1E-05
1E-06
1E-07
1E-08
1E-09
0
10 km
with Fe(OH)CO3(aq)
More Examples…
G
Groundwater
d t and
d Tunnels
T
l
a) Potential hazard and control in advancement rate
b) U
Urban
b areas Æ geotechnical
t h i l iimpacts
t
c) Rural areas Æ water resources and environmental impacts
More Examples…
G
Groundwater
d t and
d Tunnels
T
l
Barcelona Subway (Línea 9) Æ Groundwater dewatering and ground settlement
A few insights for summary…
Numerical models provide powerful tools for quantitative
impact assessment in the subsurface environment
Nature
N
t is
i always
l
uncertain
t i ((subsurface
b f
nature
t even
more!). Uncertainty evaluation of model results is a must.
P b bili ti approaches
Probabilistic
h provide
id a soundd methodology
th d l
tto
account implicitly for the uncertainties
p of qquantitative assessment of
Some ppractical examples
subsurface environmental impact have been shown: (1)
Minigg activities, ((2)) Waste repositories
(3)
p
( ) Civil Engineering
g
g
works and (4) CO2 storage…
Muito
M it obrigado
obrigado…
bi d …