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1. 2nd International Workshop in “Geoenvironment and 1
Geotechnics”, September 2008, Milos island, Greece
Developing computational groundwater monitoring and management sys-
tem for Estonian oil shale deposit
H. Lind, K. Robam and I. Valgma
Tallinn University of Technology
K. Sokman
Estonian Oil Shale Company
ABSTRACT tive and prospective mining areas. The goal for
the model is to generate descriptive three and
Mining in Estonian oil shale deposit mainly
two dimensional dynamic water table maps de-
takes place in the Ordovician, Keila-Kukruse
picting hydrogeological conditions, in order to
aquifer. The aquifer is affected by mining and is
provide information regarding the changes of
fully dried out around the working mine areas
the water dynamics (i.e. from the graphical
(Perens and Savitski, 2008). The groundwater
maps of water flow directions), as well as dia-
level is decreased down to 30 m, to the mine
grams and reports of water in- and outflow.
floor elevation using about 30 pumping stations
Also information about the water exchange be-
(Lind, 2005). The pumping rate is very high -
tween mines is considered useful (Reinsalu and
depending on the season, ranging from 10 up to
Valgma, 2003; Reinsalu, 2005), as well as the
40 m3 per ton of produced oil shale (Reinsalu
water income rate into working mines. Today
et al., 2006). The Estonian oil Shale Company
the monitoring system used by Oil Shale Com-
mined 15.5 million tons of oil shale in 2007
pany is not very flexible to analyze the situation
(Source: Estonian Oil Shale Company). In order
and to create a dynamic model; a MS Excel
to predict the effects, and avoid the social and
worksheet with diagrams and a static model of
environmental impacts, there is a need to con-
groundwater level was created previously. The
tinuously monitor the situation and run software
research project presented here will create a sys-
simulations aiming at decreasing the pumping
tematic database for developing a computational
rate. This becomes even more important since
groundwater model of the oil shale deposit for
the environmental taxes on usage of groundwa-
sustainable management.
ter resources increase every year. Therefore, it is
necessary to monitor groundwater level and
quality, and develop a groundwater model for 2. INPUT DATA FOR MODELING
the overview of the situation during mine opera-
In order to build up the groundwater model it is
tions and also for a number of years after mine
necessary to have a lot of detailed input data in
closure.
a structured form. For a simplified model at
least information about the geological layers,
1. INTRODUCTION the hydraulic conductivity, observation wells,
pumping wells and boundary conditions is
The aim of the research is to develop and reor-
needed. For importing the data into the Visual
ganize monitored groundwater data by Estonian
ModFlow software some data processing is re-
Oil Shale Company and build a dynamic
quired. For the monitored water level data until
groundwater model in order to create a sustain-
today simple MS Excel worksheets were used.
able groundwater monitoring and management
Currently collected data did not allow analysis
system. The monitored data is used as input data
of the information and easy extraction of the
for the hydrogeological modeling using the Vis-
needed output for groundwater modeling.
ual ModFlow Professional software for the ac-
A MS Access database was created in order

2. 2 2nd International Workshop in “Geoenvironment and
Geotechnics”, September 2008, Milos island, Greece
to record continuously monitored observation
well data in a structured form. Also MapInfo
and its addition Vertical Mapper are used to
generate background information. For inserting
already existing data, a comfortable layout was
developed to copy the information from MS Ex-
cel worksheet into MS Access database. New
observed records for a certain observation well
will be added using a form, as there is no need
to insert well number, information of aquifer Figure 2: Groundwater model of Oil Shale deposit created
with Visual ModFlow.
and geography. Each observation well in the da-
tabase has a unique identification number to use
as a link in different query tables. Query tables
are used to extract only the needed information 3. BUILDING A GENERAL GROUNDWA-
from the main table; in addition, the monitored TER MODEL
information at certain time is added using que- Mathematical models have a key role in assess-
ries as filling the main database table with ob- ing the future behavior of a system to find effec-
served information at different time periods tive operating conditions for sustainable devel-
would be too complicated. Using query tables opment and management groundwater re-
the information needed for groundwater model- sources. Besides the importance of organizing
ing with Visual ModFlow software can be easily mining operations, advanced groundwater moni-
exported. Output can be given selectively by toring and modeling techniques are useful for
monitored time, by aquifer and by geographical environmental impact assessments, while differ-
well location. The database will be further de- ent infrastructure objects are planned to be build
veloped to give seasonal average water level per nearby closed and waterfilled underground
observation well as the groundwater level varies mines.
seasonally. The groundwater model of an oil shale de-
The MS Access database together with posit is under development using the Visual
linked geographic data by MapInfo Professional ModFlow software. The developed model will
software (Fig. 1) allows visualizing the well lo- be dynamic; the data obtained through monitor-
cation on a two dimensional map. All informa- ing can be used to rerun the model and obtain
tion added to the main table of the described da- results in real-time. As the software takes into
tabase can be presented. MapInfo is used to account different parameters, including geologi-
generate simple static groundwater level mod- cal, hydrological and hydrogeological data, it is
els, where the average water table elevations are necessary to restructure current databases and
generated from linked database as the Visual collect the additional input data necessary for
Modlow is rather inflexible to create simple the model. One of the difficulties when creating
static models. In addition, the user can not eas- the model is to collect and process the informa-
ily change interpolated data that Visual Mod- tion needed for building and running the model.
flow generates based on measured data. The area of the model is 127 x 55 ≈7000 km2
which includes mined out and prospective areas
of oil shale (Fig. 2). As the model area is large,
the accuracy of the results will be low and,
hence, the output will be used for a general
overview of groundwater dynamics.
The created model has a grid size 100x100 m
and has five main layers - on top is the ground,
below it a 1 m thick soil layer, then limestone
and an oil shale layer. The bottom of the model
is a water impermeable layer (mainly the Uhaku
Figure 1: Map of oil shale deposit with observation well geological bed) (Fig. 3). For the grid layer in-
database linked with Access database. formation, previous research information cre-

3. 2nd International Workshop in “Geoenvironment and 3
Geotechnics”, September 2008, Milos island, Greece
Figure 3: Visualisation of the model layers – ground layer
and layer of oil shale.
Figure 5: Part of mined out and prospective area (Aidu
opencast), observation wells can be seen.
ated with MapInfo Professional was utilized.
Today line information available in the
model includes rivers and streams, investigation
areas and mined out areas (properties and 4. WATER QUALITY MANAGEMENT
boundary conditions for these areas can be When the mine will be closed down, the
added later) (Fig. 4). groundwater level will increase within two to
Also, observation wells have been added as four years up to the level as it was before the
calibration data for the model (Fig. 5). While economic activities started (Reinsalu et al.,
adding the wells the following problem was en- 2006). Changing the groundwater regime during
countered: the interpolated model domain was and after mining will result in an increase in cer-
smaller than the actual observation well depth. tain chemical components of the groundwater.
Therefore not all wells are entered since the The 2004 data showed a higher rate of sulphate
software is rather inflexible to enlarge the model content, total Fe, total oil products and total
boundaries. phenol in the water sampled from the closed -
As the area of oil shale deposit is more than waterfilled - underground mine, which exceeded
2700 km2 the model can include only the basics the drinking water norm (Reinsalu et al., 2006;
for the general overview; when a detailed inves- Erg, 2005).
tigation is needed for a certain location a Therefore it is also necessary to monitor the
smaller model can be developed (extracted) water quality in the closed mine and of the
from the larger model. As there is lack of data pumped water from the mine which is settled in
for the area surrounding the oil shale deposit it settling basin before directing into nearby rivers
may be necessary to create inactive areas around or dikes. It is also necessary to monitor seasonal
the deposit. changes in the concentrations of chemicals in
the mine water. Hence, the groundwater quality
management program has been started in differ-
ent parts of the oil shale deposit. The model of
water dynamics will be developed further for
managing groundwater quality.
5. FURTHER DEVELOPMENT
Developing the management system the ob-
served data should be gathered in a structured
form to insert the specified input data into the
groundwater model. To create a simplified
model the following data should be collected:
Figure 4: Inserted line information - rivers, lakes, pro- geological layers, hydraulic conductivity, ob-
spective and mined out areas. Coloured background de- servation wells, pumping wells and boundary
scribes ground elevation. conditions. Further development of the model

4. 4 2nd International Workshop in “Geoenvironment and
Geotechnics”, September 2008, Milos island, Greece
foresees the creation of a database of pumping Computational mathematical models can be
wells to be inserted into the model. Pumping used to allocate the technical and environmental
wells will show the influence and changes on constraints.
the water level nearby the mine workings. Also To conclude it should be mentioned that the
the model will give information to optimize software package will be used to have a compu-
used pumping capacities and also reorganize the tational groundwater model to simulate condi-
location(s) of the pumping stations where it is tions at technogenic mining areas. Today is im-
technically possible. portant to predict the influence to the environ-
More detail information will be gathered re- ment before the mine starts working. The com-
garding the hydraulic conductivity at certain putational groundwater management system can
layers and areas and the parameters for some of be used while new mines are opened, current
the boundary conditions of the model like river, mining is progressed or to overview the situa-
lake, amount of precipitation and aquifer tion at closed down mines especially if nearby
groups. After specifying the input data the situa- building activity is needed. The output files
tion of model should be calibrated which re- from the software can be used to visualize the
quires the equal values of observed and calcu- current and also the future conditions after geo-
lated water table values. This requires running logical changes by mining development. The
the software and analyzing the results several output data can be used for economical calcula-
times before receiving any results. While the tions as well.
created model is very large and while it goes The current project is done as part of the re-
more and more detailed there can be limits on search “Conditions of sustainable mining”
capacity of regular computer. ETF7499, whose scope is to use computer mod-
eling to form the basics for sustainable, envi-
ronmentally friendly mining.
6. CONCLUSIONS
A groundwater management system in Estonian
REFERENCES
oil shale deposit is necessary to be developed
further in order to understand the groundwater Reinsalu, E. and I. Valgma, 2003. Geotechnical Processes
dynamics and the changes in the concentrations in Closed Oil Shale Mines, Oil Shale, Tallinn: Esto-
nian Academy Publishers, 398 - 403.
of potential pollutants (either primary or as a re- Reinsalu, E., 2005. Changes in Mine Dewatering After
sult of chemical reactions between water and the Closure of Exhausted Oil Shale Mines, Oil Shale,
minerals, i.e. pyrite) in order to decrease and/or Tallinn: Estonian Academy Publishers, 261 - 273.
avoid any negative impacts. Groundwater usage Erg, K., 2005. Changes in groundwater sulphate content
is sustainable today, but it can become even in Estonian oil shale mining area. Oil Shale, 22 (3),
more efficient by a) decreasing the influence of 275-289.
Lind, H., 2005. The modelling of hydrogeological condi-
mining to people living nearby active mine ar- tions. The case study of dewatering Tammiku Kose
eas whose drinking water wells could be dry or surface mine, Thesis, Estonian National Library.
polluted and b) avoiding any negative impacts Reinsalu, E., I. Valgma, H. Lind and K. Sokman, 2006.
on environmentally protected areas. As the de- Technogenic water in closed oil shale mines, Tallinn:
pression cone due to mining is very wide, influ- Oil Shale, Estonian Academy Publishers Vol. 23.
Perens, R. and L. Savitski, 2008. Põlevkivi kaevandamise
encing different environmentally protected ar- mõju põhjaveele (in English: Oil Shale mining influ-
eas, draining wells for drinking water etc, tech- ence on groundwater). Keskkonnatehnika, 3/08, 44-
nological solutions like impearmable walls, in- 47.
filtration dams, pumping water from mine back
to the area should be applied to keep the water
level. ModFlow helps to model this situation
and thus make the right decisions regarding the
application of these technological solutions.
Furthermore, it should be noted that if there
is a need to reach drinking water quality the
technical solutions are available, while the cost
and economical question should be considered.