Na-ijlende gevolgen steenkolenwinning
Zuid-Limburg
Final report
on the results of the working groups
5.2.4 - groundwater quality
5.2.5 - groundwater quantity
by
Projectgroup
"Na-ijlende gevolgen van de steenkolenwinning in Zuid-Limburg"
(projectgroup GS-ZL)

on behalf of
Ministerie van Economische Zaken - The Netherlands

Aachen (D), Deventer (NL), 31. August 2016
(Rev. a: 02. December 2016)

This report consists of 131 pages, 5 appendices and 1 plan.
Y:\Daten\projekt\SODM\Bericht\WG_524_525\Rev_a\WG_524_525_Final_report_v13_Rev_a_V2.docx

Na-ijlende gevolgen steenkolenwinning Zuid-Limburg
WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

This report is edited by

Ingenieursbureau Witteveen+Bos
Van Twickelostraat 2
7400 AE Deventer
The Netherlands
Telephone:
+31 (570) 697911
E-mail:
info@witteveenbos.com
Authors:

ir. Jaap H. Spaans
Dipl.-Geol. Nancy Sevriens-Visser
Drs. Arie Biesheuvel

Ingenieurbüro ahu AG
Kirberichshofer Weg 6
52066 Aachen
Germany
Telephone:
+49 (241) 900011-0
E-mail:
info@ahu.de
Author:

Dr. Michael Denneborg

Ingenieurbüro Heitfeld Schetelig GmbH
Jean-Bremen-Straße 1-3
52080 Aachen
Germany
Telephone:
+49 (241) 70516 -0
E-mail:
info@ihs-online.de
Authors:

Dr.-Ing. Michael Heitfeld
Dr. Peter Rosner

with contributions by

Van Rooijen Adviezen
Grubenweg 20A
6343 CC Klimmen
The Netherlands
Telephone:
+31 (45) 4053257
E-mail:
p-van-rooijen@hotmail.com

Author:

Dr. Pieter van Rooijen

Na-ijlende gevolgen steenkolenwinning Zuid-Limburg
WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

page I

Contents
1

Objectives ............................................................................................... 1

2

Methodology ........................................................................................... 4

2.1

Introduction............................................................................................... 4

2.2

Problem statement ................................................................................... 6

2.3

Risk assessment ...................................................................................... 7

2.3.1
2.3.2

General approach..................................................................................... 7
Determination potential wetting ................................................................ 8

2.3.3
2.3.4

Determination potential change of groundwater quality ............................ 9
Bow-Tie-Analysis .................................................................................... 10

3

Hydrogeological system of the basement.......................................... 11

3.1

Introduction............................................................................................. 11

3.2

Hydrogeological structure of the basement ............................................ 13

3.3

Top Carboniferous (TC) ......................................................................... 16

3.3.1

Database ................................................................................................ 16

3.3.2

Structure and covering strata ................................................................. 19

3.4

Hydraulic situation in the mining areas ................................................... 20

3.4.1
3.4.2
3.4.3

Hydraulic connections between mine workings in South Limburg .......... 25
Hydraulic connections between German and Dutch mines .................... 27
Hydraulic connections between Dutch and Belgian mines ..................... 28

3.5

Hydrochemical characteristics of the mine water ................................... 28

3.6

Hydraulic system in the operation period ............................................... 30

3.7

Mine water level rise until the present day ............................................. 32

3.8

Present mine water flow system ............................................................. 36

4

Hydrogeological system of the overburden ....................................... 38

4.1

Hydrogeological structure of the overburden .......................................... 38

4.1.1
4.1.2
4.1.3

Aachen and Vaals formation .................................................................. 39
Maastricht/Houthem formation ............................................................... 41
Tongeren/Rupel and Breda formation .................................................... 42

4.2

Discussion differences REGIS-II v2.1 and REGIS-II v2.2 ...................... 42

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4.3

Groundwater levels in the overburden.................................................... 45

4.3.1
4.3.2
4.3.3
4.3.4
4.3.5

Phreatic groundwater and 1st aquifer ..................................................... 45
Second aquifer ....................................................................................... 46
Development of groundwater levels ....................................................... 46
Groundwater extractions ........................................................................ 51
Development of groundwater quality ...................................................... 52

5

Hypothesis ............................................................................................ 54

5.1

Groundwater flow 2015 .......................................................................... 54

5.2

The future steady-state situation ............................................................ 56

5.3

Land use and protection of drinking water extractions ........................... 57

5.3.1
5.3.2
5.3.3

Land use ................................................................................................ 58
Nature .................................................................................................... 58
Protection zones drinking water and industrial extractions ..................... 60

6

Groundwater model ............................................................................. 61

6.1

Description ............................................................................................. 61

6.2

Model structure....................................................................................... 61

6.3

Elaboration of the groundwater model .................................................... 64

6.4

Modelling scenarios................................................................................ 67

6.4.1
6.4.2

Present state/Reference scenario .......................................................... 69
Final state ............................................................................................... 70

7

Assessment of the impact potential ................................................... 77

7.1

Introduction............................................................................................. 77

7.2

Potential Impact Areas ........................................................................... 77

7.2.1
7.2.2

Wetting ................................................................................................... 77
Groundwater quality ............................................................................... 80

7.3

Potential impacts on groundwater quality ............................................... 83

7.3.1
7.3.2
7.3.3
7.3.4
7.3.5

Approach ................................................................................................ 83
Analysis of possible effects on groundwater quality ............................... 85
Water balance analysis of effect on groundwater quality ....................... 88
Transport model analysis of effect on groundwater quality .................... 90
Hydrogeochemical simulations ............................................................... 92

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WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

page III

7.3.6

Three dimensional chloride transport simulation .................................. 105

8

Discussion .......................................................................................... 106

8.1

Verification............................................................................................ 106

8.2

Plausibility of the parameters and assumptions made ......................... 110

8.2.1
8.2.2
8.2.3

The conductivity of the Carboniferous .................................................. 111
Boundary conditions at the river Maas ................................................. 112
Model structure..................................................................................... 112

8.2.4

Accuracy............................................................................................... 113

9

Bow-Tie-Analysis ............................................................................... 115

9.1

Top Event: Change quality of deep groundwater (WG 5.2.4) ............... 115

9.1.1
9.1.2
9.1.3

Threats, Consequences ....................................................................... 115
Prevention Controls .............................................................................. 116
Recovery Controls ................................................................................ 117

9.2

Top Event: wetting of stream valleys (WG 5.2.5) ................................. 118

9.2.1
9.2.2

Threats, Consequences ....................................................................... 118
Prevention Controls .............................................................................. 118

9.2.3

Recovery and Escalation Controls ....................................................... 118

10

Monitoring ........................................................................................... 120

11

Summary and conclusions ................................................................ 123

11.1

Groundwater quality ............................................................................. 123

11.2

Wetting ................................................................................................. 126

11.3

Bow-Tie-Analysis and monitoring ......................................................... 127

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WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

page IV

Figures
Fig. 1:

Mines in South Limburg and adjacent areas of Belgium and
Germany.............................................................................................................. 2

Fig. 2:

Water in mine Oranje Nassau IV (www.RHCL.nl) ................................................ 5

Fig. 3:

Schematic representation of a Bow-Tie-Analysis ............................................... 10

Fig. 4:

Main tectonic structures of the Carboniferous basement ................................... 11

Fig. 5:

Main fault zones and hydrogeological units ....................................................... 12

Fig. 6:

Stratigraphy of the basement in the South Limburg mining district
(ROSNER, 2011) ................................................................................................. 13

Fig. 7:

NW-SE cross-section profile 1 ........................................................................... 15

Fig. 8:

NW-SE cross-section profile 3 ........................................................................... 15

Fig. 9:

SW-NNE cross-section profile 2......................................................................... 16

Fig. 10:

Top of Carboniferous formation (TC) according to PATIJN (1961)....................... 18

Fig. 11:

Top Carboniferous/hydrogeological basis according to TNO (2015) .................. 19

Fig. 12:

Aachen formation on top of Carboniferous (REGIS-II v2.1)................................ 21

Fig. 13:

Vaals formation on top of Carboniferous (REGIS-II v2.1) ................................... 22

Fig. 14:

Maastricht formation on top of Carboniferous (REGIS-II v2.1);
northwest of the anticline of Puth the Maastricht formation is
underlain by Triassic sediments ......................................................................... 23

Fig. 15:

Tongeren formation on top of Carboniferous (REGIS-II v2.1) ............................ 24

Fig. 16:

Gallery between the Emma and Maurits concessions ........................................ 25

Fig. 17:

Hydraulic structure of the South Limburg mining district .................................... 26

Fig. 18:

Average chloride-concentrations in the different mine waters (ROSNER,
2011)

Fig. 19:

29

Groundwater inflow and average mine water salinity during
operation time (shown schematically) ................................................................ 31

Fig. 20:

Flooded areas in the Dutch mines in 1994 and 2014 ......................................... 33

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Fig. 21:

Rising mine water levels in the South Limburg hard coal district ........................ 33

Fig. 22:

Ground-/mine water inflow and average ground-/mine water quality
today (shown schematically) .............................................................................. 36

Fig. 23:

Geological structure of the overburden according to REGIS-II v2.1 ................... 38

Fig. 24:

Aachen formation: thickness and presence (REGIS-II v2.1) .............................. 39

Fig. 25:

Vaals formation: Thickness and presence (REGIS-II v2.1) ................................ 40

Fig. 26:

Maastricht Houthem formation: Thickness and presence (REGIS-II v2.1)

Fig. 27:

Tongeren-Sands: Thickness and presence (REGIS-II v2.1)............................... 43

Fig. 28:

Phreatic heads in the IBRAHYM model ............................................................. 45

Fig. 29:

Groundwater monitoring wells and former mine shafts used for

41

monitoring the mine water level ......................................................................... 47
Fig. 30:

Monitoring well B60C0860 (Maurits concession) ............................................... 48

Fig. 31:

Monitoring well B60C0839 (Emma concession) ................................................. 48

Fig. 32:

Monitoring well B62B0837 near Hoensbroek (Emma concession) ..................... 49

Fig. 33:

Monitoring well B62B0838 near Voerendaal (Emma concession) ...................... 49

Fig. 34:

Shallow and deep groundwater extractions ....................................................... 51

Fig. 35:

Schematic representation of the current status of the ground-/mine
water flow system .............................................................................................. 54

Fig. 36:

Schematic representation of the hypothetical final situation of the
confined ground-/mine water flow system (average case) ................................. 56

Fig. 37:

Areas with thickness of the unsaturated zone < 3,5 m ....................................... 57

Fig. 38:

Location of nature reserves with high groundwater level and
groundwater protection zones ............................................................................ 59

Fig. 39:

Cross-section REGIS-II v2.1 .............................................................................. 62

Fig. 40:

Cross-section of the model layers in IBRAHYM ................................................. 62

Fig. 41:

Areas with a large amount of water from overburden documented in
the mine maps (SHGM, 1975) ........................................................................... 66

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WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

page VI

Fig. 42:

Calculated heads in aquifer 1 (near-surface) - reference Scenario .................... 69

Fig. 43:

Calculated heads in aquifer 2 (limestone) - reference Scenario ......................... 70

Fig. 44:

Mine water pressure in the Carboniferous - average case scenario ................... 72

Fig. 45:

Difference in phreatic groundwater table - average case scenario ..................... 73

Fig. 46:

Increase of groundwater head in second aquifer - average case
scenario ............................................................................................................. 74

Fig. 47:

Potential impact areas “wetting” ......................................................................... 79

Fig. 48:

Potential impact areas for change of groundwater quality .................................. 81

Fig. 49:

Potential impact area near profile 1 (shown schematically) ................................ 82

Fig. 50:

Potential impact area near profile 2 (shown schematically) ................................ 82

Fig. 51:

Bow-Tie-Analysis - Threats triggering quality change and wetting ..................... 84

Fig. 52:

Mine-/Groundwater flow paths in potential impact area I .................................... 85

Fig. 53:

Schematic presentation mixing of mine water with groundwater ........................ 88

Fig. 54:

Percentage mine water at wellfields in area Ia and Ib ........................................ 90

Fig. 55:

Development groundwater quality between coal seams and
wellfield, scenario 1 ......................................................................................... 103

Fig. 56:

Development groundwater quality between coal seams and
wellfield, scenario 2 ......................................................................................... 104

Fig. 57:

Development groundwater quality between coal seams and
wellfield, scenario 3 ......................................................................................... 104

Fig. 58:

Calculated chloride concentrations in area Ia and Ib ........................................ 105

Fig. 59:

Measured and calculated heads B60C0860 .................................................... 107

Fig. 60:

Measured and calculated heads B60C0839 .................................................... 107

Fig. 61:

Measured and calculated heads B62B0837 ..................................................... 108

Fig. 62:

Measured and calculated heads B62B0838 ..................................................... 109

Fig. 63:

Rising mine water and groundwater heads in the chalk aquifer ....................... 110

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WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

page VII

Tables
Tab. 1:

Overview of the average mineral content of mine water ..................................... 29

Tab. 2:

Groundwater extractions (for location see Fig. 34) ............................................. 52

Tab. 3:

Groundwater analysis in the “Zoutwachters” ...................................................... 53

Tab. 4:

Model layers IBRAHYM ..................................................................................... 63

Tab. 5:

Characteristics flow path Carboniferous-Aachen/VaalsMaastricht/Gulpen ............................................................................................. 86

Tab. 6:

Head difference between top Carboniferous and bottom Maastricht
(limestone aquifer) ............................................................................................. 87

Tab. 7:

Calculated travel times ...................................................................................... 87

Tab. 8:

Summary of results ............................................................................................ 89

Tab. 9:

Mixing scenarios abstraction wells ..................................................................... 91

Tab. 10:

Generated quality mine water ............................................................................ 93

Tab. 11:

Water samples of the Emma Mine waste rock tip (water samples
from 2006, WITTEVEEN+BOS, 2011) ............................................................... 94

Tab. 12:

Expected water quality at top Carboniferous ...................................................... 95

Tab. 13:

Calculated mixed water Carboniferous-Vaals .................................................... 97

Tab. 14:

Expected water quality top Vaals ....................................................................... 98

Tab. 15:

Expected water quality Maastricht/Vaals............................................................ 99

Tab. 16:

Measured water quality abstraction Wells Craubeek........................................ 100

Tab. 17:

Characteristic shallow groundwater quality ...................................................... 100

Tab. 18:

Results scenarios water quality change at wells Craubeek .............................. 102

Tab. 19:

Monitoring - proposed observation wells .......................................................... 122

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page VIII

Appendix
Appendix 1:

Diepteligging van het Carboon oppervlak in het model Na-ijl effecten
Mijnbouw Zuid-Limburg by VAN ROOIJEN ADVIEZEN, 2015

Appendix 2:

Comments on REGIS-II v2.1 and REGIS-II v2.2 by VAN ROOIJEN
ADVIEZEN, 2015

Appendix 3:

Model scenarios - calculated heads for worst case and best case
scenarios

Appendix 4:

Bow-Tie-diagram change groundwater quality

Appendix 5:

Bow-Tie-diagram wetting

Plans
Plan 1:

Potential impact areas, overview; scale 1:125.000
(Drawing No. 107-17-001b)

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WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

1

page 1

Objectives

Between 1967 and 1975 the mines in the western and eastern mining regions of
South Limburg were closed, starting with the Maurits mine in Geleen, and
ending with the Julia mine in Eygelshoven (Fig. 1). This marked the end of a
once highly productive and profitable 150-year period for the mining industry. At
its peak, there were nine privately owned mines (Neu Prick, Dominiale, Willem
Sophia, Laura, Julia, and Oranje Nassau I, II, III and IV) and four state-owned
mines (Wilhelmina, Hendrik, Emma, and Maurits)
Due to the closing of the mines there was no longer any reason to continue
pumping water to keep the mines dry. Step by step, the extraction of water in the
mines was reduced. Most of the mines were interconnected, which meant that the
reduction in extraction had to be carefully executed in order to not flood the
remainder of the operating mines.
The mines that were still operational between 1967 and 1974 were protected
from flooding by the construction of dams in mine corridors, which allowed a
careful and controlled rise of the mine water. The German company EBV GmbH
continued the extraction of mine water from the Beerenbosch II shaft on the
Limburg side of the border and the Von-Goerschen Schacht, Gouley-Laurweg in
Würselen (D), until 1994. The pumping was necessary to protect the German
mines east of the Feldbiß fault from flooding.
In Flanders the mines continued operating for 13 years after the last mine in the
Netherlands was closed. But, in the period 1987 to 1992, these mines were also
shut down (Watershei and Eisden in 1987, Winterslag in 1988, Beringen in 1989,
and, finally, Zolder in 1992).

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Fig. 1:

page 2

Mines in South Limburg and adjacent areas of Belgium and Germany

In 1987 the pumping of mine water was stopped in the Belgian mine closest to
the Dutch border (the Eisden mine in Maasmechelen). In 1994 pumping was also
stopped in the Beerenbosch II shaft. This caused the water level in the mines to
rise gradually in large parts of Germany, South Limburg and Flanders.

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It is important to know how far the water in the mines will rise, and what the
consequences will be for the groundwater level in South Limburg. Furthermore,
it is necessary to assess whether the rising mine water will infiltrate into the
overburden, and to what extent this affects the quality of the groundwater in the
overburden.
The effects of rising mine water levels have been studied before. In 1975 the
Limburg province established a study group called “Hydrological consequences
of the mine closures”. Based on the recommendations of this group, piezometers
were drilled to monitor the rise of the mine water level and to track the water
quality of shallow groundwater. In 1998 the state of affairs was reported and an
initial prognosis was given about the expected effects of rising mine water levels.
More recently, research was done on the effects of rising mine water levels in the
Netherlands. In 2011 Peter Rosner published his dissertation in which a lot of
fundamental data was collected and analysed about the mining region and water
in the mines (ROSNER, 2011). In 2007, the company Heitfeld-Schetelig (IHS),
commissioned by the Ministry of Economic affairs, carried out a preliminary
study on the effects of rising mine water.

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2

Methodology

2.1

Introduction

page 4

In several preliminary studies it was found that the geohydrological system is
highly complex; the coal deposits in the Carboniferous formation are present at
the surface near the German border and drop down to greater depth in
northwestern direction. In northwestern direction, on top of the Carboniferous
formation there is a layer of increasing thickness consisting of sand, clay deposits
and limestone (the overburden).
The faults present in the region and historic tectonic movement have caused the
subsurface to differ greatly between locations. In some places permeable layers
lie directly on top of the Carboniferous formation allowing water levels to rise in
the overlying aquifers, by rising mine water. These locations will be referred to
as “Hydraulic Windows” in this report. Hydraulic Windows sometimes occur
naturally: some mines, such as the Maurits, were known as “wet mines”, because
of the considerable volume of water which was seeping into the mine from the
overburden (Fig. 2). In other places there are semi-permeable aquitards between
the Carboniferous formation and the overlying aquifers. At these locations the
rising mine water levels cause an increase in groundwater head (higher pressures)
in the overlying aquifers, but no considerable upward flow of mine water.
Additionally, in areas where many upward and downward drillings were carried
out, near faults, or where only a thin Carboniferous layer was left between mine
works and the overburden, upwards flow of water may take place in the future.
Previous research also showed that predicting the effects of rising mine water
was hampered by the lack of data on the mine water level in the Carboniferous
formation. The mine water level is only measured in the eastern mining region

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page 5

(the Beerenbosch II and Willem II shafts in the Domaniale mine, shaft I
Wilhelmina, shaft II Oranje Nassau I and shaft II in the Julia mine). In the mines
from the Emma concession, in the Maurits mine, and in Belgium mines water
levels are not measured.

Fig. 2:

Water in mine Oranje Nassau IV (www.RHCL.nl)

In four locations however, the groundwater level is measured in the permeable
limestone deposits in the overburden. Based on these measurements it is possible
to get an indication of the effect of rising mine water levels on the overlying
geological layers.
The lack of data is one of the reasons that previous research was mostly
qualitative in nature. Additionally, in this period, no state-of-the-art 3D computer
models were available which could quantify the effects of rising mine water and
test different hypotheses concerning future developments as a result of rising
mine water.

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2.2

page 6

Problem statement

According to preliminary studies the following aspects were considered to be the
most important effects of rising mine water and had to be investigated by
WG 5.2.4 and WG 5.2.5:
- Wetting
Rising mine water can lead to an increase in groundwater level in the overburden.
In regions with relatively high groundwater tables, such as the valleys in South
Limburg, an increase of the shallow groundwater level could lead to water
nuisance. If, and to what extent, this effect occurs is highly dependent on the
magnitude of the interaction between rising mine water levels and the head in the
deep aquifers, as well as the interaction between the deep aquifers and shallow
groundwater.
- Change in groundwater quality
The composition of mine water is very different, compared to groundwater in
shallow aquifers nearby. Mine water can have a high salt content and can contain
heavy metals or additives used in the mining industry. Mine water can be very
acidic and deoxidised. If mine water flows through covering layers and shallow
aquifers and is mixed with water from shallow aquifers, several hydrochemical
reactions will take place, such as dissolution and precipitation of minerals. These
reactions will influence groundwater quality. The dissolution of minerals can
cause contamination with heavy metals like arsenic.
The occurrence of an upward flow of mine water, besides being dependent on the
possible existence of hydraulic connections between the Carboniferous formation
and the overburden, is also determined by the head of the shallow groundwater.
As long as the shallow groundwater level is higher than the mine water level in

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the Carboniferous layer, no mine water will infiltrate into the upper aquifers.
Conversely, when the head in the Carboniferous formation is higher than the
shallow groundwater head, groundwater quality in the overburden may be
affected.

2.3

Risk assessment

2.3.1 General approach
With respect to the above described major effects expected due to rising mine
water, a scenario analysis was carried out in order to obtain insight into the
effects of the rising mine water levels. The analysis is engineered to show the
scope of the possible effects: a “worst case” scenario describes how high the
maximum mine water level rises. Hence, the fundamental assumptions for this
scenario are worst case assumptions. For best “case scenarios” best case
assumptions are made. Hence these best case scenarios yield lower calculated
values for future mine- and groundwater levels. In the same manner an “average
case” scenario was created which lies between these extremes. The average case
scenario is also the “most likely” scenario.
The three scenarios are based upon a large amount of data which was gathered
for this study by TNO and IHS and supplemented with literature reviews. Based
on these data the system analysis was carried out. The analysis describes the
complex stratification of the Carboniferous and its overlying layers.
After determining the three scenarios the conditions for the occurrence of each
scenario was investigated. This analysis was carried out with the three
dimensional subsurface model IBRAHYM. The model was used to review the
following matters:

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page 8

- under what conditions the described scenarios/after-effects can occur;
- identification of the “potential impact areas”;
- evaluation of the possible “consequences”.
Finally, the measures that can be taken to reduce or stop changing the quality of
the groundwater and the increase in its level were investigated, and a proposal for
appropriate monitoring is presented.

2.3.2 Determination potential wetting
Due to mine water rise, groundwater levels nearby mining areas can also rise.
Areas were the groundwater levels were already high are most vulnerable for the
rise of the mine water. Based on the surface level and the groundwater levels in
the first aquifer, maps with the thickness of the unsaturated zone are elaborated.
These maps are extended with land use areas like nature, urban areas,
infrastructure and agriculture.
A groundwater model is used to estimate the effect of mine water rise on phreatic
groundwater levels. Assumptions have to be made about the amount of mine
water exfiltrating from the Carboniferous towards the shallow aquifers. These
assumptions will be made upon measurements of mine water level over the past
decades, since the mine water pumps stopped. The IBRAHYM-groundwater
model is used to calculate the effects. First of all the current situation is
calculated and evaluated. Subsequently, the estimated effect of rise of
groundwater levels, due to mine water rise is evaluated.
Based upon the calculated groundwater level a risk map was prepared of areas
where groundwater levels are already shallow and will rise due to mine water
rise. These areas are identified as potential impact areas for wetting.

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page 9

2.3.3 Determination potential change of groundwater quality
As indicated before hydro-geochemical reactions can occur along flow paths.
Determining the location of hydraulic contacts in mining areas is important, both
in the current situation, as in the future, under rising mine water conditions. To
identify these contacts and their impact, several soil survey maps will be studied,
such as maps with the top level of the Carboniferous formation, thickness and
characteristics of covering layers, contact with shallow aquifers nearby, and
characteristics of these shallow aquifers (permeability etc.). Furthermore,
information is collected about the situation during mining activities. Were there
specific circumstances during mining, which affected this hydraulic contact?
Subsequently, the effect of mine water rise on the occurrence of these contacts is
estimated.
Data considering the quality of mine water was collected. This was done for both
the water from covering layers and the water from shallow aquifers nearby.
Furthermore, information about possible reactive components in these aquifers is
collected. Based on this information, a characteristic hydro geochemical situation
is defined. The reactive transport model PHREEQC was used to calculate the
effects of mine water entering the covering layers and on the groundwater quality
of the aquifers in the overburden.
Based on the maps of expected groundwater quality and the recharge areas for
groundwater extractions, the expected influence on the groundwater extracted by
the Waterleiding Maatschappij Limburg or industry is estimated. Extent and
nature of these risks are identified.

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2.3.4 Bow-Tie-Analysis
In this study the Bow-Tie-Analysis is used as the method to analyse the risks per
after-effect, to create possible impact maps, define mitigation and prevention
measures.
Bow-Tie-Analysis is a strong tool to visually clarify the risks and map measures
associated with the effects or hazards. The power of a BowtieXP diagram is that
it gives an overview of multiple plausible scenarios in a single picture.
Fig. 3 shows a schematic representation of a Bow-Tie-Analysis. The knot of the
Bow-Tie, i.e., the centre of the diagram, is formed by the incident, or Top Event,
which is connected to a certain Hazard. On the left side, the various causes that
may trigger the incident are summarised, i.e. the Threats. On the right side, the
potential impacts from the Top Event are listed, i.e., the Consequences.

Fig. 3:

Schematic representation of a Bow-Tie-Analysis

Subsequently, Controls can be added in between the Threats, Consequences, and
the Top Event. These can be either preventive, i.e. prevent the cause from
escalating into a top Event, or mitigating, i.e., reduce the consequences once the
Top Event occurred. Also, monitoring controls can be added to detect a Top
Event or to direct preventive and/or mitigating controls.

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3

Hydrogeological system of the basement

3.1

Introduction

page 11

The mining district of South Limburg is located on the northwestern flank of the
great tectonic unit Venn Anticline. Due to the tectonic compression numerous
SW-NE striking anticlines and over thrusts occur (from NW to SE: anticline of
Puth, 70 m fault, anticline of Waubach/Oranje fault, Willem fault), which are of
importance for the structure of the Carboniferous bedrock and the distribution of
mine workings (Fig. 4).

Fig. 4:

Main tectonic structures of the Carboniferous basement

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Almost perpendicular to these old tectonic structures, there is a system of three
main NW-SE orientated faults: the Benzenrade fault, the Heerlerheide fault, and
the Feldbiß fault (Fig. 5). These faults run through the overburden to the surface
and

divide

the

study

area

into

three

main

(HYI/HYII/HYIII, HYIVb in Fig. 5).

Fig. 5:

Main fault zones and hydrogeological units

hydrogeological

units

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3.2

page 13

Hydrogeological structure of the basement

The relevant part of the basement for this study consists of the coal-seam-bearing
part of the Upper Carboniferous (Westphalian A to C, Jabeek, Wilhelmina,
Hendrik and Maurits Groep). The overall thickness is about 2.000 m. Fig. 6
shows the stratigraphy of the basement in the study area.

Fig. 6:
2011)

Stratigraphy of the basement in the South Limburg mining district (ROSNER,

It is a cyclic sequence of predominantly shale, claystones and sandstones with
coal seams. The layers of Namur and Westphalian as a whole are classified as
groundwater aquitards, if they are not fractured by the mining activities.
Although there is an increased permeability within well fissured sandstones,
these sandstones do not have a connection to a regional groundwater flow
system.
The coal-seam-bearing Upper Carboniferous ends with an extended eroded layer.
The formations overlying the Carboniferous (Cretaceous, Tertiary, Quaternary)

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consist of various layers with varying thickness, distribution and hydrogeological
characteristics.
Below the coal-seam-bearing Upper Carboniferous lies a 600 to 700 m thick
formation known as the Namurian. This formation forms a hydrological barrier
between the upper layers and the deeper layers of the Kohlenkalk (Lower
Carboniferous) and the Massenkalk (middle Devonian). These limestone
formations form a deep saline aquifer.
The surface of the Carboniferous formation and the oldest layers of the
overburden slope gently downwards, generally at about 1° to 2°, in a
northwestern direction. Near the German border the Carboniferous formation is
covered by less than 40 m of young sediments. In the western part of the Maurits
mine the Carboniferous formation is covered by up to 400 m of younger deposits.
The sloping surface of the Carboniferous formation and the overburden in
northwestern direction are shown in Fig. 7 and Fig. 8. The offset of the top of the
Carboniferous bedrock at the main tectonical fault to the NE is shown by
profile 2 in Fig. 9.

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Fig. 7:

NW-SE cross-section profile 1

Fig. 8:

NW-SE cross-section profile 3

page 15

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Fig. 9:

3.3

page 16

SW-NNE cross-section profile 2

Top Carboniferous (TC)

3.3.1 Database
There are several sources of data from which the depth of the surface of the
Carboniferous formation can be estimated:
- a well-documented map by PATIJN (1961),
- the Regional Geohydrological Information System REGIS-II v2.1 and the
subsequent update in 2015 performed by TNO for the project (REGIS-II v2.2),

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- maps of mine shafts and corridors, and analysis of drillings, both downward
drillings (used in the period that mines were operational to determine the depth
of the Carboniferous layer) as well as upward drillings. The drillings were
performed to determine where the Carboniferous should not be excavated as a
safety precaution to prevent the collapse of mining corridors,
- a map of the Top Carboniferous (TNO, 2015).
Analysis of the data shows that there are significant local differences in the
presumed elevation of the Top Carboniferous. Especially where the
Carboniferous formation is found at a larger depth (generally between faults), the
maps produced by PATIJN (Fig. 10) show different elevations than REGIS-II v2.1
and REGIS-II v2.2, or the more recent map by TNO (Fig. 11). Furthermore it has
to be considered that the REGIS model shows the “hydrogeological basis”,
which is not equivalent to Top Carboniferous in the places where the Triassic
formation occurs (Fig. 8).
VAN ROOIJEN (2015) performed a detailed analysis of the differences in

interpretation of the Top Carboniferous and identified local differences of the
Top Carboniferous according to PATIJN and REGIS (Appendix 1).
In

this

investigation

it

was

decided

not

to

elaborate

the

REGIS

model/groundwater model IBRAHYM according to the remarks of VAN
ROOIJEN, because the relevance for the groundwater modelling itself was limited.
However, it is advised to take notice of the remarks delivered by VAN ROOIJEN,
when the groundwater model IBRAHYM, which is based on the REGIS-II v2.1
model, is updated in the near future.
The remarks from VAN ROOIJEN (2015) to the REGIS-II v2.1 model are
presented in Appendix 2.

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Fig. 10:

Top of Carboniferous formation (TC) according to PATIJN (1961)

page 18

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Fig. 11:

page 19

Top Carboniferous/hydrogeological basis according to TNO (2015)

3.3.2 Structure and covering strata
The calculation of the effects of rising mine water was performed using the
IBRAHYM groundwater model. For the calculations it was important to
determine the elevation of the Carboniferous formation, the thickness of the
remaining coal deposits and the aquitards lying directly on top of the

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Carboniferous formation. This was especially important because IBRAHYM is
based on the REGIS-II v2.1 and not on the updated REGIS-II v2.2.
In the figures below the geohydrological layers overlaying the Top
Carboniferous are shown on the basis of REGIS-II v2.1.
Southwest of the Heerlerheide fault, the Top Carboniferous is overlaid by the
Aachen formation and/or the Vaals formation (Fig. 12, Fig. 13). There are only a
few small “windows” in this cover where limestones from the Maastricht
formation directly overlie the Carboniferous (Fig.14).
Northeast of the Heerlerheide fault the Maastricht formation, consisting mostly
of limestones and marls, overlies the Top Carboniferous in the central part of the
project area (Fig. 14). In the southeastern part of the investigation area, near
Heerlen, a complex of sand, silt and clay belonging to the Tongeren formation, is
found on top of the Carboniferous bedrock (Fig. 15). In the northwestern part,
northwest of the anticline of Puth and outside the mined area, Triassic sediments
form the basis of the overburden (Fig. 8).

3.4

Hydraulic situation in the mining areas

The South Limburg mining district builds the central part of the coal mine region
that reaches from the Aachen area in Germany in SE to the Hasselt/Beringen area
in Belgium to the NW (Fig. 1). Along the borderlines (Maas river and Wurm
river valley) hydraulic interactions have to be considered. Within the South
Limburg mining district a complex hydraulic system has developed after closure
of the mines.

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Fig. 12:

Aachen formation on top of Carboniferous (REGIS-II v2.1)

page 21

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Fig. 13:

Vaals formation on top of Carboniferous (REGIS-II v2.1)

page 22

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Fig. 14:
Maastricht formation on top of Carboniferous (REGIS-II v2.1); northwest of
the anticline of Puth the Maastricht formation is underlain by Triassic sediments

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Fig. 15:

Tongeren formation on top of Carboniferous (REGIS-II v2.1)

page 24

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page 25

3.4.1 Hydraulic connections between mine workings in South Limburg
All the Dutch mining areas were more or less connected by underground works.
It is assumed that the mined layers have a permanently higher hydraulic
conductivity than the unmined bedrock.
Due to the tectonical structure of the Carboniferous only parts of the concessions
were mined. Especially in the area of the anticline of Puth between the Maurits
and Emma mines there is a mining gap (Fig. 4). As a result, this area has a lower
hydraulic conductivity than the mined area, and can be regarded as a hydraulic
barrier within the South Limburg mining district.
During the closure of the mines the hydraulic connections between the mines
have been closed especially in the deeper levels. In particular the connecting
gallery between Emma and Maurits and the galleries across the Feldbiß fault to
the mine workings of Hendrik mine northeast of the Feldbiß fault were closed.
Therefore these mining areas are now hydraulically isolated basins in the level of
the Carboniferous.
Fig. 16 shows that the Maurits and Emma mines once were connected to each
other by an approximately 11,5 km long gallery at a depth of 390 m. After the
closure of Maurits mine this gallery was sealed by a “dam door”.

Fig. 16:

Gallery between the Emma and Maurits concessions

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All the other mines of the South Limburg mining district are still connected to
each other at different levels. There are some main galleries that connect the
former mines and create a system of several main basins that interact
hydraulically with one another (Fig. 17).

Fig. 17:

Hydraulic structure of the South Limburg mining district

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3.4.2 Hydraulic connections between German and Dutch mines
Due to the historical development the Dutch mines are quite close hydraulically
connected via galleries and mine workings to the German Gouley-Laurweg mine,
which is located along the Wurm river valley in the Southwest of the Feldbiß
fault. Therefore mine Gouley-Laurweg together with the mines in South Limburg
form a hydraulically connected “western mine water province”. The further
German mines, which are all located northeast of the Feldbiß fault (“eastern mine
water province”), have no direct connection to the Dutch mines or the GouleyLaurweg mine.
But there are some locations where a hydraulic connection could theoretically
exist between Dutch and German mines northeast of the Feldbiß fault. These are
three known locations at a depth of -123, -207 and -162 mNAP where the
distance of single mine workings or galleries of Dutch and German mines is
reduced to a few metres only.
However, since the water level in the German mines northeast of the Feldbiß
fault in the year 2009 was approximately 100 to 110 m lower than that in the
Dutch mines, it seems quite evident that there is almost no mine water flow
across the Feldbiß fault into the German mines. This is not expected to change in
the future. However, a flow of mine water across the border and the Feldbiß fault
in the overburden via the Tongeren formation has to be considered.
On the German side of the Wurm three former dewatering galleries to the Wurm
river were reopened to drain future mine water into the Wurm. According to the
mine water concept of the responsible German mining company further former
mining galleries will be opened if the mine water should reach the Wurm level to
restrict the rise of the mine water level to the level of the Wurm river. Therefore,
the rise of mine water in the German mining district will be limited to about

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110 mNAP along the Dutch-German borderline. That is also the lowest level of
the river Wurm in the area where the Carboniferous reaches the surface.

3.4.3 Hydraulic connections between Dutch and Belgian mines
On the west side of the river Maas Belgium also mined coal till 1992. According
to the information acquired within this project there is no hydraulic connection
between the Maurits concession and the adjacent Belgian mine Eisden on the
other side of the river Maas. Nevertheless the hydraulic interactions in the level
of the overburden (limestone) have to be considered.

3.5

Hydrochemical characteristics of the mine water

Deep groundwater is characterised by a higher mineral content than near-surface
groundwater. The main reason for the high mineral content is the high NaClcontent, which can reach up to 300 g/l through dissolution of salt deposits. Lower
mineral contents of up to 30 g/l NaCl often occur due to fossil seawater
inclusions (connate water). Highly mineralised water typically rises along
specific flow paths in thermal water springs (e.g. the thermal springs in Aachen)
or along faults.
The groundwater in the study area is characterised by an increasing degree of
NaCl mineralisation at increasing depths. KIMPE (1963) and ROSNER (2011)
described five different types of groundwater mineralisation with smooth
transitions. Tab. 1 shows the average mineral content in 1992, 1993 and 2009 in
the basement of the South Limburg mining district (ROSNER, 2011).
The differences in inflow from the overburden led to different degrees of the
“sweetening” of mine water in the concessions (see Fig 19).

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Tab. 1:

page 29

Overview of the average mineral content of mine water

Concession
(shaft)

Year
time

Electr.
conductivity
[µS/cm]

Chloride
[mg/l]

Maurits

operation

3.000

Oranje Nassau I

operation

7.660*

operation

510

Domaniale
(Beerenbosch II)

Iron
[mg/l]

Calcium
[mg/l]

12

400

1992/93

9.000

2.700*

300

2009

1.750

200

300

operation
Gouley-Laurweg
(Von-Goerschen)

Sulphate
[mg/l]

10

90-150

1992/93

1.700

100

80

2009

1.900

200

300**

0,5

1750
70

* Inflow from deep thermal water, probably along faults
** increasing FeS weathering

Fig. 18:

Average chloride-concentrations in the different mine waters

(ROSNER, 2011)

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There is a trend towards a lower mineral content in the southeast of the study
area, where the overburden is thinner and sometimes missing completely.
Contrary to this trend, the mining concessions Oranje Nassau I North (and
probably also the more south-east mining concession Oranje Nassau I South) had
an average chloride content of 7.660 mg/l due to the inflow of thermal water.
This inflow of thermal water occurred in the Oranje Nassau I South mine at a
depth of about 250 m below the surface (KIMPE, 1963). Initially, the outflow of
saline thermal water (50º C) was up to 7 m3/min but later dropped to 2 m3/min. In
1960 the flow path was sealed off. The rise probably occurred along one of the
NW-SE faults. The inflow was 4 to 15 % of the total inflow.
The NaCl concentration of the thermal water was about 35 g/l. The water
probably rose from a depth of 1.300 to 2.800 m from the Kohlenkalk (Lower
Carboniferous). KIMPE (1963) described this occurrence near Benzenrade along
the Grondgalerij Laag VI fault as a local upward inflow of saline water from
greater depths. Further occurrences of ascending thermal water are also reported
from Wilhelmina (16 g/l NaCl at a depth of 700 m) and Oranje Nassau IV
(12 g/l NaCl at a depth of a 420 m).

3.6

Hydraulic system in the operation period

The total inflow during the active mining period was estimated with the historic
data gathered by ROSNER (2011) and reached up to 48 m3/min. Groundwater
flow towards the mining area is the result of three “driving forces” (Fig. 19):
- direct groundwater recharge in zones without overburden (four blue arrows);
- groundwater leakage through the overburden while there is still a downward
gradient (blue arrow);
- rising of thermal water (red arrow).

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If the inflow of thermal water (max. 7 m3/min) in Oranje Nassau I is subtracted
from the total inflow, there is still an inflow of approximately 40 m3/min, which
originates from the overburden.
In the southeast the inflow was and still is significant. Consequently, the
concentration of minerals is low (90 mg/l chloride (Willem Sophia) up to
510 mg/l chloride (Domaniale)). The main cause is the thin and locally absent
overburden. The area with only thin cover or absence of overburden in the
southeast is about 14 km2. There is also an additional flux from infiltrating water
from the Wurm and the floodplains of the Wurm, which cannot be quantified.

Fig. 19:
Groundwater inflow and average mine water salinity during operation time
(shown schematically)

In the northwest, where the overburden is quite thick, the inflow was about half
of the average groundwater recharge. In summary, the level of groundwater
recharge can be used to subdivide the area into three general groups, with high
levels in the southeast and low levels in the northwest (ROSNER, 2011):

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- Wilhelmina/Laura:

6,0 - 6,3 l/s/km2

- Oranje Nassau II, III, IV, Emma/Hendrik:

2,7 - 4,8 l/s/km2

- Maurits:

1,4 l/s/km2.

The general development of mine water quality is influenced by several major
processes:
- decrease of the mineral content by push back of deep thermal water,
- increase of sulphate weathering,
- decrease of the mineral content by inflow of fresh groundwater from the
overburden,
- future leaching of salt in the submerged mines.
Based upon the mechanisms above, it can be expected that - due to the oxygenrich groundwater supply from the overburden - the oxidation of pyrite will
increase. As a consequence the pH-value will decrease and the sulphate level and
the solubility of heavy metals will increase. Overall, the mineral content of water
in subsequent decades is expected to be significantly lower than the mineral
content during the mining period. It is likely the recognisable trend of
hydrochemical stratification will continue in the future with heavy salt water
settling at the greatest depths.

3.7

Mine water level rise until the present day

The rise of mine water in the “western mine water province” (South Limburg
mines with Gouley-Laurweg) occurred in two distinct phases (Fig. 20, Fig. 21):
- The shutting down of the mines between 1967 and 1974 and the subsequent
rise of mine water with the exception of the mine areas Domaniale and
Gouley-Laurweg (D).

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Fig. 20:

Flooded areas in the Dutch mines in 1994 and 2014

Fig. 21:

Rising mine water levels in the South Limburg hard coal district

page 33

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In these mines the mine water was kept at a low level until 1994 to protect the
German mines east of the Feldbiß fault (“eastern mine water province”) from
flooding.
Since November 1987, when the mine water level exceeded -63 mNAP in
Emma and Hendrik mine, all Dutch mine water basins (besides Maurits (1)
and Hendrik NE (4); Fig. 17) were hydraulically connected.
In this period three main basins developed with different mine water levels
according to the level of the respective connecting gallery to the pumping
station in Domaniale:
- a northern main basin with a hydraulic head at -63 mNAP
(Emma, Hendrik, Oranje Nassau I, III, IV)
- a central main basin with a hydraulic head at about -120 mNAP
(Oranje Nassau II, Wilhelmina, Laura)
- a southern main basin with a hydraulic head at -214 mNAP (-167 mNAP in
Gouley-Laurweg)
(Willem, Domaniale, Gouley-Laurweg).
The galleries from Laura to Julia were closed by dams; nevertheless there is a
significant hydraulic connection between these two mines due to water
creeping around the dams. The mine water level in Julia corresponds to the
level in Laura at a somewhat deeper level.
In January 1994 this protective pumping of mine water in Domaniale and
Gouley-Laurweg (D) ended. Since then the mine water level rises in the whole
region.
The pumping equipment in the Von-Goerschen-Schacht (Gouley-Laurweg, D)
was preserved, which allowed for future regulation of the mine water levels.
The pumping station in Von-Goerschen-Schacht was used for a number of
pumping tests during the rising phase to investigate the hydraulic connections in

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the subsurface between the individual mines. It was shown that there is a high
hydraulic conductivity between the different mining zones and that the inflow
from the southeast can be assumed to about 6,5 m3/min in 2007 at a mine water
level of about 25 mNAP in Gouley-Laurweg (ROSNER, 2011).
The rise of mine water can be observed in six shafts: Von-Goerschen-Schacht
(Gouley-Laurweg, D), the Beerenbosch II and Willem II shafts (Domaniale),
shaft I Wilhelmina, shaft II Julia, and shaft II Oranje Nassau I (Fig. 20, Fig. 21).
When the mining activities were brought to an end the other shafts were filled up.
In the five remaining shafts in South Limburg measuring devices were installed
to monitor the mine water levels.
Five additional deep monitoring wells in the basement (HH1, HH2, HLN1,
HLN2, HLN3) were installed during the mine water project in Heerlen. For these
wells only selected measurements are available from 2007, 2008 and 2014. The
heads measured in these wells show more or less the same levels as the
measurements in shaft II, Oranje Nassau I, with additional influences from the
local pumping for the mine water project.
Fig. 21 shows that mine water rise was more or less uniform in the whole
western mine water province after the mine water levels in the three main basins
reached a more or less uniform level in 1995. The speed of the rise of mine water
is determined by the volume (mine workings, pore and joint volume) and by the
flow (groundwater recharge) from Germany.
Surface outflows from the Dutch mines do not occur yet. Until December 2014
the mine water reaches a level between about 50 mNAP in Gouley-Laurweg and
about 21 mNAP in Oranje Nassau I; Julia still is at a slightly deeper level of
about 11 mNAP. The average speed of the mine water rise from the year 2003 on
is about 2,5 m/a, respective about 4,9 m/a for Julia.

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3.8

page 36

Present mine water flow system

The present mine water flow system is schematically shown in Fig. 22. The
inflow towards the mines decreased from 48 m3/min (operation period) to about
6,5 m3/min in 2007. ROSNER (2011) calculated this by analysing pumping tests
performed in the Von-Goerschen-Schacht and the rise of mine water levels over
certain time periods. For the final state, when the mine water level might reach
the level of the Wurm river valley ROSNER (2011) assumed a total inflow of
about 3 to 4 m3/min. This inflow from the southeast was used to calibrate the
groundwater model.

Fig. 22:
Ground-/mine water inflow and average ground-/mine water quality today
(shown schematically)

The amount of ascending thermal water is not known. Due to the sealing of the
outflow paths and the higher water levels in the mines the amount of rising
thermal water should now be much lower than in the period of active mining.

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After the pumping of mine water stopped, an equilibrium was formed between
fresh and salt water at the base of the overburden/top of basement. The electric
conductivity is here about 1.000 µS/cm (based on measurements in the deep
monitoring wells from the Mine water Project in Heerlen). During a pumping test
it rose to 4.000 µS/cm after 20 days, which indicates that the mineralisation in
the deeper parts of the basement is still high (ROSNER, 2011).
In the mining concessions such as Oranje Nassau I North, where the mine water
level in 2015 had not yet reached the top of the basement the electric
conductivity is higher (approximately 6.000 µS/cm)1. It shows that there still is
an influence from the inflow of thermal water.
The following conclusions, derived from the analysis of the groundwater flow
system in the basement, were used to construct the groundwater model:
- The general flow direction was and still is from the Wurm Valley towards the
river Maas. The total flux dropped to 5 to 10 % relative to the flux at the
operational time of the mines and is expected to drop further in the future.
- The unmined basement between Emma and Maurits is a major flow barrier at
which significant drops of the hydraulic heads are expected. Due to the lack of
monitoring wells, the real groundwater levels cannot be measured.
- The hydraulic connections between the basement and the overburden can be
identified only on a regional level (concessions). There is a trend showing a
higher recharge in the southeast due to a thinner or missing overburden.
- In 2015 there is still a downward flow from the upper aquifer towards the
basement.
- There are strong indications that the deep saline groundwater is stratified.

1

Sea water with approximately 30 g/l NaCl has an electric conductivity of approximately 50.000 µS/cm.

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4

Hydrogeological system of the overburden

4.1

Hydrogeological structure of the overburden

page 38

The hydrogeological system of the overburden is characterised by a complex
layering of several aquifers and aquitards from the Cretaceous to the Quaternary
formations.
The layers are slope downwards towards the northwest as shown in Fig. 23.
Therefore the thickness increases from the southeast towards the Northwest near
the Maas (approximately 400 m). In the southeast - near the Wurm - the
overburden is very thin or missing in an area of approximately 14 km2 and the
basement locally crops out.

Fig. 23:

Geological structure of the overburden according to REGIS-II v2.1

In the following chapters, the overburden is described starting with the oldest
Cretaceous layers, which lie directly on top of the Carboniferous, and end with
the youngest Quaternary deposits.

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4.1.1 Aachen and Vaals formation
The oldest geologic formation is the Aachen formation. This formation is present
at only a few locations south of the Heerlerheide fault. It consists of a layer of
fine sands with a thickness between 20 to 50 metres. These sands often contain
heavy clays with lignite and pyrite. In Fig. 24 the presence and thickness of the
Aachen formation (according to REGIS-II v2.1.) is shown.

Fig. 24:

Aachen formation: thickness and presence (REGIS-II v2.1)

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On top of the Aachen formation lies the Vaals formation. This layer is present
almost everywhere south of the Heerlerheide fault (Fig. 25).

Fig. 25:

Vaals formation: Thickness and presence (REGIS-II v2.1)

On a few locations, where the sandy part is higher, groundwater extraction from
this layer is possible, for example in the southeast corner of the Oranje Nassau I,
III, IV concession. The thickness of the layer fluctuates strongly between 50 and
100 m.

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4.1.2 Maastricht/Houthem formation
Next in line are the chalk deposits from the Cretaceous (Fig. 26). They consist of
the Gulpen, Maastricht, and Houthem formations. The Gulpen formation is not
present in the project area.

Fig. 26:

Maastricht Houthem formation: Thickness and presence (REGIS-II v2.1)

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The upper parts of the chalk formations are weathered as a result of their karstic
characteristics. Therefore, the Maastricht and Houthem formations are the main
aquifers for the production of drinking water companies and the extraction of
groundwater by industries. These formations consist of chalk deposits with a
thickness between 30 and 90 m (Maastricht) and 20 to 40 m (Houthem).
South of the Heerlerheide fault both layers are present. The Houthem formation
only exists in the northwest part of the project area. North of the Heerlerheide
fault (in the SE part of the investigation area) the Maastricht formation locally
lies directly on top of the Carboniferous.

4.1.3 Tongeren/Rupel and Breda formation
The Tongeren formation is younger than the chalk deposits and is present over a
large area; the Tongeren formation (Fig. 27) consists of clay and sand. North of
the Heerlerheide fault it lies partly direct on top of the Carboniferous. The lowest
parts of this formation contain clay layers which cause the overall layer to be
characterised by a low permeability.
The youngest deposits are the Rupel formation (clayey sands and clays) and the
layers that form the upper aquifer, known as the Breda formation. Maas deposits
contain gravel, sand and clay. The top layer, deposited in the Quaternary,
consists of silty sediments (Löss).

4.2

Discussion differences REGIS-II v2.1 and REGIS-II v2.2

Model calculations were performed using the groundwater model IBRAHYM
version 2015. This model is based on the geohydrological schematisation of the
subsurface in REGIS-II v2.1. During the period in which this research was done

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TNO updated REGIS-II v2.1. In order to determine the relevance of this update
for IBRAHYM and the modelling results an analysis was performed to determine
where REGIS-II v2.2 differed from REGIS-II v2.1. Subsequently, it was
determined whether IBRAHYM could still be used unchanged, or whether an
update of the schematisation of the subsurface was required. A brief summary of
the results is shown below. This summary is based on a more detailed analysis in
(WITTEVEEN+BOS, 2015).

Fig. 27:

Tongeren-Sands: Thickness and presence (REGIS-II v2.1)

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For each of the geological formations shown in chap. 4.1, maps were created
showing the difference in thickness between REGIS-II v2.1 and REGIS-II v2.2.
In total, about 20 locations were identified where significant differences were
found. For each of these points the cause of the difference was determined and
what the consequences were for the modelling process. This analysis was partly
based on input by TNO 2015.
The analysis shows that the biggest differences were caused by a new
interpretation of drilling data. Samples that were initially classified as limestone
belonging to the Maastricht formation were now classified as belonging to the
Houthem formation. Additionally, the thickness of several layers was adjusted
according to new data.
In WITTEVEEN+BOS (2015) a detailed analysis is provided on the differences
between the two REGIS models. For now, it suffices to conclude that there are
differences, but these differences occur locally, at the edges of the research area,
or near faults, where the elevations at which geological layers are found already
show large variations over short distances. The quantification and visualisation of
the differences was deemed to be an important step considering future updates
for the models. It was also concluded that it was not necessary to update
IBRAHYM before performing the calculations. The current version of
IBRAHYM was deemed sufficiently accurate as a regional groundwater model
for this research.

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4.3

page 45

Groundwater levels in the overburden

4.3.1 Phreatic groundwater and 1st aquifer
The IBRAHYM model is used to perform steady-state and transient calculations
of the groundwater level in the research area. Fig. 28 shows the calculated
phreatic groundwater level.

Fig. 28:

Phreatic heads in the IBRAHYM model

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The inset shows a zoomed portion of the map, in which the more elevated
regions in Heerlen/Kerkrade can be identified. This region is also known as the
plateau of Schimmert and is characterised by a radial flow of groundwater
towards the surrounding stream valleys. The low groundwater levels near the
Maas (at around 40 mNAP) can also be identified.

4.3.2 Second aquifer
The Maastricht and Houthem formations are often referred to as the second
aquifer within the investigation area. There are only few available groundwater
monitoring wells. In the 1980s four monitoring wells were installed to measure
the effects of rising mine water. The filters were installed in the overburden
directly above the basement with several filter sections to monitor the possible
effects of rising mine water.
The location of groundwater monitoring wells is shown in Fig. 29:
Stein

B60C0860 (4 Filters), Maurits concession;

Schinnen

B60C0839 (3 Filters), Emma concession;

Hoensbroek

B62B0837 (4 Filters), Emma concession;

Voerendaal

B62B0838 (4 Filters), Emma concession.

4.3.3 Development of groundwater levels
Generally, the groundwater heads in the deep aquifer are influenced by several
factors including long-term fluctuations, deep groundwater extractions and the
effect of rising mine water. In Fig. 30 to Fig. 33 the groundwater levels are
shown in the four mine water monitoring wells. All of the wells show an
increasing groundwater table in the second aquifer since the 1990s.

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Fig. 29:
Groundwater monitoring wells and former mine shafts used for monitoring
the mine water level

The measurements in monitoring well B60C0860 (Stein) show the most
significant reactions on rising mine water:
- No significant change in shallow groundwater levels (filter 1)
- Rise of groundwater head in the second aquifer (Maastricht and Houthem
formations) since the early nineties, with approximately 20 to 25 m;
- The parallel development of the groundwater levels in filters 3 and 4 indicates
that there is a hydraulic connection between the different layers.
In all layers a rise of the groundwater head is shown.

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50

B60C0860
45

40

Groundwater level (m NAP)

35

30

25

20

15

10

5

filter 1-Beegden

Fig. 30:

filter 2-Houthem

filter 3-Maastricht

filter 4-Vaals

Monitoring well B60C0860 (Maurits concession)

80

B60C0839
75

Groundwater level (m NAP)

70

65

60

55

50

45

filter 1-Breda

Fig. 31:

filter 2-Houthem-Maastricht

filter 3-Maastricht

Monitoring well B60C0839 (Emma concession)

page 48

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80

B62B0837
75

Groundwater level (m NAP)

70

65

60

55

50

45

filter 1-Rupel-zand

Fig. 32:

filter 2-Maastricht

filter 3-Maastricht

filter 4-Vaals

Monitoring well B62B0837 near Hoensbroek (Emma concession)

B62B0838
84

82

Groundwater level (m NAP)

80

78

76

74

72

70

filter 1-Tongeren-zand

Fig. 33:

filter 2-Maastricht

filter 3-Vaals

filter 4-Vaals

Monitoring well B62B0838 near Voerendaal (Emma concession)

page 49

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The observed increase in well B60C0839 (Schinnen) is from 46 mNAP to
58 mNAP over a period of more than 30 years. Measurements in filter 1 show a
more or less continuous groundwater level.
Measuring point B62B0837 (Hoensbroek) shows a decreasing groundwater level
from 1983 to approximately 1997 in the level of the Vaals formation followed by
a continuous increase of the groundwater level until the present. Measurements
from the deep filter in the Maastricht formation are only available at the
beginning of the 1980s; the development of the heads with time seems to be
correspondent to the situation in the Vaals formation.
The filter in the upper level of the Maastricht formation does not show the
intermediate decrease of the piezometric heads in the 1990s. In this level two
phases of constant increase of the groundwater level in the 1980s and in the
1990s with a short phase of decrease in 1989 to 1991 can be observed. In the
beginning of the 2000s an equilibrium is reached with the groundwater level in
the 1st aquifer. Since then groundwater level in the upper Maastricht formation is
more or less constant depart from the seasonal influence from rainfall.
These measurements show the combined effect of rising mine water and a
decreasing withdrawal of groundwater by the water company in Limburg, which
shows the most influence in the deeper levels of the overburden.
The southeastern most located well B62B0838 (Voerendaal) shows a similar
development of the groundwater levels as the well B62B0837 with less
significant undulations.
In chap. 8 these measurements are discussed more in detail.

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4.3.4 Groundwater extractions
The current locations of groundwater extractions are shown in Fig. 34. The
colour of the dots indicates the stratigraphic level of the extraction.

Fig. 34:

Shallow and deep groundwater extractions

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Tab. 2 summarises the relevant groundwater extractions in the main aquifer
(Maastricht) and in the overburden.
Tab. 2:

Groundwater extractions (for location see Fig. 34)
Depth

No.

Groundwater extraction

Aquifer

[m below
surface]

Permit
Purpose

3

[m /a]

1

P.S. CRAUBEEK

Maastricht

55

Drinking water

3.500.000

2

HOENSHUIS GOLF

Maastricht

78

Irrigation

18.000

3

ZIEKENHUIS SITTARDGELEEN

Maastricht

180

Thermal storage
system

900.000

4

REFRESCO BENELUX BV
LOCATIE HOENSBROEK

Maastricht

140

Process and
product water for
nutrition

600.000

5

ALFA BROUWERIJ

Maastricht

151

Process and
product water for
nutrition

200.000

6

PROEF KWO
PARKEERTERREIN IKEA
TERHOEVENERWEG
HEERLERHEIDE

Carboniferous

700

Thermal storage
system

2.200.000

7

TROMPENBURGSTRAAT
TERHOEVENDERWEG

Carboniferous

230

Thermal storage
system

499.900

8

DSM ONTTR MAASGRINDEN

Beegden

-

Process water

1.800.000

9

P.S. SCHINVELD

Rur valley graben

200

Drinking water

5.000.000

Most of these are situated in the upper aquifer (Quaternary deposits) and in the
limestone. One extraction lies north of the Feldbiß fault and extracts groundwater
from the Rur Valley Graben. All these extractions are points of interest with
respect to the effects of mine water rise.

4.3.5 Development of groundwater quality
The influence of mine water on groundwater quality should be noticeable
through a higher chloride and sulphate content of the groundwater. In the
samples from the mine water project in Heerlen the chloride concentration
reaches 6.000 mg/l sulphate, formed through the oxidation of pyrite (FeS2), is

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page 53

also a typical indicator for mine water. Until now, there has been no mine water
flow from the basement to the overlying aquifers in the overburden due to the
higher potential in the overburden. Therefore, the chloride content in the
overburden still is comparatively low (Tab. 3).
Tab. 3:

Groundwater analysis in the “Zoutwachters”
Measuring
point /

[mg/l]

09.1979

12.1982

11.1983

01.1986

03.1998

Filter
B60C860
Stein /

Cl

-

3

2

<1

7

SO4

-

5

2

5

10

Cl

-

2

3

4

57

SO4

-

4

10

6

<0,4

Cl

25

6

2

4

5

SO4

30

7

4

9

9

Cl

7

8

5

6

6

3

SO4

10

9

6

12

10

B62B0837
Hoensbroek /

Cl

17

17

15

14

11

4

SO4

39

44

58

52

35

B62B838
Voerendaal/

Cl

12

15

18

15

19

3

SO4

34

54

48

55

61

3
B60C860
Stein /
4
B60C0839
Schinnen /
2
B60C0839
Schinnen /

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5

Hypothesis

5.1

Groundwater flow 2015

page 54

The current knowledge about the groundwater flow system - before groundwater
modelling was performed - is presented in Fig. 35. This is a transient situation as
the mine water levels are still rising. The characteristics of the actual flow regime
can be described as follows (Fig. 35):

Fig. 35:
Schematic representation of the current status of the ground-/mine water
flow system

(1) The highest groundwater recharge occurs in the area where the overburden is
missing (14 km2), and in the southeast where the overburden is thin. Water
infiltrates from the Wurm, the floodplain of the Wurm and its smaller tributaries,
but the magnitude of this infiltration cannot be quantified.

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(2a) The mine water level in the southeast in 12.2014 was 50 mNAP (VonGoerschen-Schacht, Gouley-Laurweg).
(2b) The groundwater gradient is oriented to the northwest. The mine water level
in the Oranje Nassau I (South) mine in 12.2014 was 28 mNAP. The
Carboniferous was not yet fully submerged.
(2c) In this area the Carboniferous bedrock was completely flooded. The
confined water level was about 21 mNAP in 12.2014.
(2d) The mine water level near the Maurits mine (without a measured mine water
level) is assumed to be at a similar level as in the Emma mine.
(2e) The groundwater level in the main aquifer (Maastricht) drops from
130 mNAP to 30 mNAP near the Maas. The groundwater is highly confined. The
flow direction in 2015 was still downward.
(3) The current inflow to the basement and the mines is approximately
6,5 m3/min (evaluation of pump tests in the Von-Goerschen-Schacht). In the
future the inflow will be lower as the gradient gets smaller (about 3 to 4 m3/min).
(4a) According to the measurements, the electric conductivity in Oranje Nassau I
and III increases with depth from 4.000 µS/cm up to 7.400 µS/cm.
(4b) This indicates that the mineral inflow of deep thermal water is still active to
a small degree. As the mine water level rises further, the inflow will become
lower.
(4c) In the main aquifer (Maastricht) the electric conductivity is about 600 800 µS/cm.
(4d) The mine water near the top of the Carboniferous has an electric
conductivity of about 1.000 µS/cm.

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5.2

page 56

The future steady-state situation

Based on the knowledge of the hydrogeological system, the hypothesis for the
final steady-state situation is proposed. The final situation is defined as the
situation in which the mine water has reached its highest level and the
groundwater system is in equilibrium again (Fig. 36).

Fig. 36:
Schematic representation of the hypothetical final situation of the confined
ground-/mine water flow system (average case)

The main recharge is delivered from the southeast (Wurm river valley); the
recharge rate is assumed to be 3 to 4 m³/min (ROSNER, 2011). This situation
supposes that the mine water level in the Carboniferous will end up higher than
the near-surface groundwater level in the central part of the South Limburg
mining district but will not exceed the surface level. Due to the hydraulic barrier
between the Emma and the Maurits mines, the upflow of mine water might
concentrate in the Emma area.

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5.3

page 57

Land use and protection of drinking water extractions

Areas with high groundwater levels are the most vulnerable to the rise of mine
water because of the risk of wetting. Fig. 37 shows the areas where groundwater
is found less than 3,5 m below the surface level. In these areas an increase of
groundwater level could (theoretically) cause the wetting of cellars, change of
agriculture production (both positive or negative), or damage to nature.

Fig. 37:

Areas with thickness of the unsaturated zone < 3,5 m

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A large part of the area of interest has a groundwater table deeper than 3,5 m
below the surface level (white colour). This is caused by the high surface levels
of the different plateaus in South Limburg. Areas of interest with high
groundwater tables are mostly located in the river valleys, both the smaller
valleys like the Geleenbeek valley and the larger valleys like the Maas river
valley (on the western border of the area of interest).
Some smaller river valleys (Rode Beek and Anselderbeek) are also areas with a
thinner unsaturated zone. A large area with high groundwater tables lies north of
the area of interest. This area has a lower surface level due to erosion by the river
Maas. Therefore, groundwater tables are higher there.

5.3.1 Land use
Main townships and villages are situated mostly on top of the plateaus. In several
areas, buildings are also situated in river valleys or areas with a higher
groundwater table: for example, in the towns of Hoensbroek, Schinveld,
Nieuwstadt, and parts of the city of Sittard. Some main roads are also situated in
zones with a high groundwater table, especially in the north of the area of interest
and parallel to the valley of the Geleenbeek.

5.3.2 Nature
The Province of Limburg has defined several types of nature reserves. These
nature reserves are often situated in the river valleys which means they are often
located in areas with a higher groundwater table. Areas with both a high
groundwater table and an area of high natural value are therefore areas of interest
regarding groundwater quantity. These areas are (Fig. 38):

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-

Valley of the river Maas;

-

Valley of the river Geleenbeek and tributaries;

-

Valley of the river Anselderbeek;

-

Nature reserve Brunssummerheide;

-

Valley of the river Rode Beek;

-

Several forested areas in the north of the area of interest and near Schinveld.

Fig. 38:
Location of nature reserves with high groundwater level and groundwater
protection zones

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5.3.3 Protection zones drinking water and industrial extractions
In the investigation area the drinking water extraction Craubeek is protected by a
“groundwater protection zone” (Fig. 38). Craubeek is situated in the Emma
concession (extraction on both sides of the Kunrader fault).
In the research area there are two (deep) industrial groundwater extractions, both
situated in the area of the Emma concession. Vulnerable industrial and drinking
water extractions are protected against potential pollution by the Water
Framework Directive and the Groundwater Directive.
In the “gebiedsdossiers” a number of measures are listed for the protection of the
groundwater extractions. These measures range from monitoring to the
implementation of controlling measures, etc. It must be noted that the industrial
pumping wells are not regionally protected. Contrary to the approach for
drinking water extractions, no protection zones or well capture zones are defined.

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6

Groundwater model

6.1

Description

page 61

The groundwater model IBRAHYM is a regional hydrological model. It
describes the groundwater system of the Province of Limburg. It has been
developed by TNO/Deltares, Alterra, and Royal Haskoning.
The construction of the model was commissioned by the Waterboards Peel en
Maasvallei and Roer en Overmaas, the Province of Limburg and the drinking
water company WML. In 2015, Deltares updated the model by adding the area of
South Limburg to the model and recalibrating it.

6.2

Model structure

The layers in IBRAHYM are based on REGIS-II v2.1 (Fig. 39). As mentioned
before in chap. 3, REGIS-II v2.1 contains all geological formations between the
surface and the Top Carboniferous.
The REGIS layers have been converted into 19 model layers. In Fig. 41 an
example is given for how the REGIS layers are divided into the model layers.
The IBRAHYM model contains the geological formations from Holocene to the
Aachen formation.
Tab. 4 contains an overview of the geological formations and their corresponding
model layers in IBRAHYM. Within the systematic of the IBRAHIM model it has
to be regarded, that the numbers of the layers are different for each main
hydrogeological unit/tectonic block (Hydrogeological homogeneous areas in
Fig. 5). Therefore the same stratigraphic layer may have a different number in the
different hydrogeological homogeneous areas.

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Fig. 39:

Cross-section REGIS-II v2.1

Fig. 40:

Cross-section of the model layers in IBRAHYM

page 62

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Tab. 4:

page 63

Model layers IBRAHYM

Formation
name

Aquifer or
Aquitard

Holocene
Boxtel

Aquifer

Model layer
Model layer
between the
south of the
Heerlerheide fault
Heerlerheide fault and the Feldbiß
fault

Model layer
north of the
Feldbiß fault

1

1

1

1

1

1

Beegden

Aquifer

2

2

4

Kiezelooliet clay 1

Aquitard

not present

not present

12

Kiezelooliet clay 2

Aquitard

not present

not present

13

Kiezelooliet clay 3

Aquitard

not present

not present

14

Kiezelooliet clay 4

Aquitard

not present

not present

15

Kiezelooliet clay 5

Aquitard

not present

not present

16

Frimmersdorf

Aquitard

not present

15

17

Morken

Aquitard

3

16

18

Rupel clay 1

Aquitard

4

not present

not present

Rupel clay 2

Aquitard

5

17

18

Tongeren

Aquifer /
Aquitard

6

18

not present

Landen

Aquitard

7

not present

not present

Houthem

Aquifer

8

*

not present

Maastricht

Aquifer

9

*

not present

Gulpen

Aquifer

10

not present

not present

* These layers are present north of the Heerlerheide fault, but not integrated in the IBRAHYM model
because of their limited thickness

The layers 1-2 (phreatic groundwater) and 9 (limestone aquifer) represent the
main aquifers of the hydrogeological system.

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6.3

page 64

Elaboration of the groundwater model

- Carboniferous
IBRAHYM contains the overburden, divided into 19 model layers, based on
REGIS-II v2.1. The Aachen formation forms the bottom of the original
IBRAHYM model. In order to model mine water rise, the Carboniferous has to
be added to the model. Two layers have been added to the model to include the
Carboniferous:
- Basement above the mining zone (thickness 20 m, model layer 20);
- Mining zone (thickness 900 m, model layer 21).
The mining was mainly carried out up to approximately 20 m below the
overburden. In some parts upward drilling took place to explore the distance
between the basement and the overburden. Both layers, the basement above the
mining zone and the mining zone, have been given a conductivity of 1∙10-3 m/d.
- Integration of the mine workings
A large part of the concessions was mined. The conductivity in the Carboniferous
has to be adjusted according to the hydrogeological conditions. The areas with
mining works are located in model layer 21.
Different literature shows different values for the hydraulic conductivity of the
unmined Carboniferous (PAAS, 1997, GD NRW, 2011, WALLBRAUN, 1992,
DE MAN, 1988, JÄGER et al., 1990). In the groundwater model IwanH, which has
been developed especially for South Limburg, the Carboniferous has been given
a conductivity of 1∙10-3 m/d. Values given in literature indicate a conductivity
between 10-8 and 10-10 m/d.

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There is very little data on the hydraulic conductivity of the mined Carboniferous
formation, but based on literature and the pumping tests that were carried out for
the mine water project in Heerlen, it is assumed that the conductivity is relatively
high because of the galleries and the loosened rock. In the model the calculations
were carried out with a conductivity of 250 m/d. Sensitivity analysis
demonstrated that the hydraulic conductivity of the mined Carboniferous is not a
major influencing factor on the heads in the Carboniferous.
- Hydraulic windows
During the active mining period, areas with a large inflow of groundwater from
above were known, like the Douvergenhout event (DE MAN, 1988). This event
describes a situation in 1930 where groundwater from the overburden flowed
toward the Emma mining district (discharges starting at 2,5 m3/min). According
to DE MAN (1988) the reason was the existence of a hydraulic connection
between Devonian sandstone, the sandy Tongeren layer and the Maastricht layer
(limestone). Areas with large inflow from the overburden documented in the
mine maps (“hydraulic windows”, Fig. 41) are taken into account in the model.
These areas are assigned to model layer 20 with a conductivity of 5 m/d.

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page 66

Fig. 41:
Areas with a large amount of water from overburden documented in the
mine maps (SHGM, 1975)

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6.4

page 67

Modelling scenarios

All scenarios are steady-state calculations. The outcome of the calculations
represents the future equilibrium situation of groundwater heads, after the rise of
mine water has ended.
A sensitivity analysis was performed with the groundwater model to define the
three scenarios. The goal of the analysis was to determine which factors mostly
strongly influence the mine water levels. It was determined that the hydraulic
conductivity of the Carboniferous and the amount of future recharge to the
Carboniferous formation were highly influential.
Due to the strong spatial variations in the hydraulic conductivity of the
Carboniferous formation, the effects of a high and low hydraulic conductivity
were investigated. Additionally, the effect of a lower and higher recharge rate
was investigated. A high recharge rate occurs when there is a large amount of
groundwater flow under the Wurm, originating from the German mining area,
that feeds the Carboniferous formation. A low recharge rate occurs when it is
assumed that only the Dutch regions contribute to the total recharge to the
Carboniferous.
This analysis has led to the definition of three scenarios for the final state when
the mine water rise finishes, and a reference scenario:
- Reference model/scenario: This is the current situation, in which groundwater
levels are calculated in the layers overlying the Carboniferous (overburden).
The reference scenario is calculated with the current version of the
IBRAHYM model and is calibrated using long term average groundwater
levels.

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- Worst case scenario: Mine water will rise to its highest level. The maximum
level is determined by the discharge/drainage capacity of the Wurm river in
the eastern part of the research area. The Wurm river has a reference elevation
of about 110 mNAP. The presence of the Wurm and the rebuilt mine galleries
in the Wurm river valley prevent groundwater levels from rising beyond this
elevation.
It was investigated under which conditions (i.e. for which hydraulic
parameters of the Carboniferous formation) such a rise in groundwater levels
was possible, and how much water must infiltrate from overlying formations
and from precipitation in the regions where the Carboniferous reaches the
surface. Additionally, it was tested whether this was a realistic scenario.
- Best case scenario: In this scenario, it was investigated what the amount of
mine water level rise would be assuming a relatively high hydraulic
conductivity for the Carboniferous formation. The recharge to the
Carboniferous only originates from a narrow zone around the Wurm, yielding
a relatively low amount of recharge. The combination of a narrow zone in
which recharge occurs and a high hydraulic conductivity results in relatively
low mine water level in the future. It was tested whether this was a realistic
scenario.
- Average case scenario: In this scenario, the level of mine water rise was
determined assuming a low hydraulic conductivity of the Carboniferous
formation and a large amount of recharge. The area in which recharge to the
Carboniferous takes place was assumed to include parts of the German mining
area.

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6.4.1 Present state/Reference scenario
The reference scenario is a steady-state calculation of the reference model. The
reference model is the 2015 IBRAHYM model provided by the water boards and
water company. In this model/scenario, also referred to as scenario 0, the
Carboniferous has not been added to the model yet. The results of the
calculations are shown in Fig. 42 and Fig. 43.

Fig. 42:

Calculated heads in aquifer 1 (near-surface) - reference Scenario

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Fig. 43:

page 70

Calculated heads in aquifer 2 (limestone) - reference Scenario

6.4.2 Final state
With the stationary groundwater model the final state is investigated. For all
three scenarios it was investigated whether the scenario is likely to happen.

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page 71

In the worst case scenario it was approximated that the rising mine water near the
Wurm river would reach a maximum of 110 mNAP. Above this level, the water
will be discharged/drained by the Wurm river. Only to the west of the Wurm
there are small areas in which higher hydraulic heads can occur. Under which
conditions this situation could occur was studied with the IBRAHYM model.
Calculations show this situation can only take place when the hydraulic
conductivity of the Carboniferous is low, and the recharge rates in the
contributing area are high. The requisite recharge to the Carboniferous in this
situation was calculated to be a factor 50 higher than is expected considering the
characteristics of the subsurface and the size of the recharge area. Therefore the
probability of the worst case scenario to happen can be considered to be very
small.
In the best case scenario it was approximated that the recharge to the
Carboniferous is very limited and that the conductivity of the Carboniferous is
relatively high. The recharge is defined by a specific amount of inflow into the
Carboniferous in the Wurm Valley. This situation was studied with the
IBRAHYM model. Calculations show this situation results in relatively low
pressures compared to other scenarios. Therefore the probability of the best case
scenario to occur can be considered to be very small.
In the average case scenario a realistic recharge is assumed. Therefore the
conductivity of the mined Carboniferous is assumed to be lower than in the
worst- and best case scenario, i.e. 50 m/d. In this scenario, a no flow boundary
was modelled. The maximum head at the boundary is calculated and not defined
in the model like the worst and best case scenario.
As a result the model calculates a more realistic recharge into the Carboniferous.
The average case scenario is assumed to be the most realistic scenario.

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- results average case scenario
In this scenario, the head in the Carboniferous in the eastern concessions will rise
to a maximum of about 80 mNAP. Between the Emma and Maurits concessions
lies an unmined zone which operates as a hydraulic barrier. Therefore, the
hydraulic gradient between Emma and Maurits is very large. In the Maurits
concession, the calculated heads in the Maurits concession are about 40 to
50 mNAP.
The results of the average case scenario calculations are shown in Fig. 44, Fig. 45
and Fig. 46 below.

Fig. 44:

Mine water pressure in the Carboniferous - average case scenario

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The rise of the mine water results in an increase of the groundwater level in the
near-surface groundwater reservoir. There is hardly any effect visible in the
eastern mine concessions (Julia, Hendrik, Laura, Domaniale and Neu Prick). In
these regions, an increase of between 0 and 0,10 m of the groundwater table is
calculated with respect to the reference scenario (see Fig. 45). In the Maurits
concession, increases of 0,25 to 0,5 m are calculated.

Fig. 45:

Difference in phreatic groundwater table - average case scenario

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The calculated rise of the (confined) water pressure (or groundwater head) in the
limestone aquifer (aquifer 2) with respect to the reference scenario reaches
maximum values of up to 3 to 9 m in the Maurits area (see Fig. 46). In the Emma
concession, the maximum groundwater pressure increase is calculated to be 1 m.

Fig. 46:

Increase of groundwater head in second aquifer - average case scenario

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- results worst case scenario
In the worst case scenario a rise of the mine water up to 110 mNAP in the Wurm
valley is assumed. In this modelling scenario, a fixed groundwater head of
110 mNAP is applied to the upper layer of the Carboniferous (layer 20) in the
Wurm valley. The area with the fixed head is shown in Fig. A3.1 (Appendix 3).
As a result of the fixed head at 110 mNAP and the high conductivity of the
mined areas in this scenario the head of 110 mNAP reaches into the Emma
concession (Fig. A3.2, Appendix 3). In the Maurits concession, the calculated
mine water heads lie between 25 mNAP and 50 mNAP.
The rise of the mine water results in an increase of the groundwater level in the
upper aquifer. The largest effect is visible in the eastern mine concessions (Julia,
Hendrik, Laura, Domaniale, and Neu Prick). In these regions, an increase
between 0,5 and 3,0 m of the groundwater table is calculated in respect to the
reference scenario (Fig. A3.3). In the Maurits concession, increases of 0,25 to
0,5 m are calculated.
The calculated rise of the (confined) water pressure (or groundwater head) in the
limestone aquifer (aquifer 2) with respect to the reference scenario reaches
maximum values up to 9 m in the Maurits area (Fig. A3.4, Appendix 3). In the
Emma concession, the maximum groundwater pressure increase is calculated to
2,2 m.
- results best case scenario
For the best case scenario the natural inflow of groundwater to the Carboniferous
as a result of groundwater recharge is simulated. The amount of inflow is defined
as the amount of natural recharge coming from the infiltration area in Germany,
which has a surface area of 14 km2. For this area, the specific recharge is
5,3 m3/min.

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The calculated pressures in the Carboniferous are lower than the pressures
calculated in the worst case scenario for the Emma and the other southeastern
concessions. In most of the southeastern concessions, pressures are calculated to
be between 50 and 75 mNAP (Fig. A3.5, Appendix 3). In the Maurits area,
pressures lie between 25 and 50 mNAP.
For the first aquifer the calculated rise related to the reference scenario is smaller
than in the worst case scenario especially in the eastern concessions but quite
comparable to the average case scenario. Overall, the maximum effect is a head
increase of about 0,5 m (Fig. A3.6, Appendix 3).
The head calculated in the limestone aquifer (aquifer 2, Fig. A3.7, Appendix 3)
shows large differences, between 5 and 9 m in the valley of the river Maas,
which is similar to the results in the worst case scenario. In the eastern
concessions Emma and Oranje Nassau I, III, IV, the calculated rise of the
groundwater head is less than 1 m.

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7

Assessment of the impact potential

7.1

Introduction

page 77

The estimation of areas that might be affected by the impacts of rising mine
water provides the basis for the further risk analysis. Based on model
calculations, two areas of influence are defined for
- wetting and for
- changes in groundwater quality.
The areas of influence are calculated in the steady-state model, in this case, the
final situation, in which mine water will not rise any further.

7.2

Potential Impact Areas

7.2.1 Wetting
The areas of influence are based on calculations performed with IBRAHYM. The
calculations showed that rising mine water in parts of the research area will cause
increases in hydraulic head in layers in the overburden. This is in agreement with
measurements carried out with the mine water monitoring network.
The increase of the head in the Carboniferous, which is completely saturated
(flooded), has resulted in a decrease in infiltration from the overburden over the
last few decades. This has caused an increase in the head in the overlying layers,
which is also seen in the measurements obtained by the mine water monitoring
network. The increase in head subsequently influences the head in the more
shallow layers, but due to the presence of semi-permeable layers (aquitards,
layers with a low hydraulic conductivity) the increase is small.

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In large parts of the research area the groundwater table is found at a larger depth
(more than 3,5 m below the surface level). The calculated increase of the
groundwater level (aquifer 1) in the average scenario lies between 0,25 and
0,5 m, mainly in the Maurits concession and partly in the Julia concession. In
areas with a higher groundwater table, generally observed in the “beekdalen”
(valleys), a smaller increase of the groundwater level is calculated, with increases
up to 0,1 m.
The depth of the groundwater table is approximated at 3,5 m below the surface
level because it is assumed that an (limited) increase in heads in layers with
deeper groundwater level will not lead to possible damage to agriculture, nature,
infrastructure or structures with basements.
The largest calculated increase in the phreatic groundwater level of 0,5 m occurs
in the Maurits and Julia concessions in areas where the groundwater table lies
well below 3,5 m below the surface. This increase will therefore not lead to water
nuisance.
Calculations with the IBRAHYM model show that in the most likely case (the
average case) wetting can occur in the Geleenbeek Valley near Geleen and
Schinnen, and locally near the river Maas. In the worst case scenario, wetting
could occur in other Valleys, like the Rode Beek and Anselderbeek.

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Fig. 47:

Potential impact areas “wetting”

page 79

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page 80

7.2.2 Groundwater quality
The potential areas of influence for a change in groundwater quality are also
calculated with IBRAHYM. Potential impact areas are defined as areas where a
significant upward mine water flux is expected from the Carboniferous to the
overburden. The upward flux is caused in the final situation of the head of the
mine water is higher than the water levels in the shallow aquifers. This is
observed mainly in the Emma concession. In other regions, the situation is the
other way around: the groundwater level in the overlying groundwater reservoirs
is higher than the piezometric heads in the Carboniferous, which results in a
downward flux. The profiles below show in which areas an upward or downward
flux is expected, based on model calculations.
Based on the calculation with the groundwater model IBRAHYM and the
differences in geohydrological conditions of the subsoil, two main potential
impact areas are defined for the average case scenario (yellow area in Fig. 48;
see Fig. 49 and Fig. 50):
- potential impact area I:
The upward flux of mine water is calculated in an area southwest of the
Heerlerheide fault. Groundwater from the limestone aquifer (the Maastricht
formation) in this area is being extracted by industry and the drinking water
company WML. This area can be divided into an area south of the Benzenrade
fault (area Ia) and an area between the Benzenrade fault and the Heerlerheide
fault (area Ib).
- potential impact area II:
Here the upward flux of mine water is calculated in an area north of Heerlerheide
fault.

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Fig. 48:

Potential impact areas for change of groundwater quality

page 81

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Fig. 49:

Potential impact area near profile 1 (shown schematically)

Fig. 50:

Potential impact area near profile 2 (shown schematically)

page 82

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page 83

Furthermore a potential impact area III (blue area in Fig. 48) is calculated
considering the worst case scenario. As discussed in chap. 6.4 this is a highly
unlikely scenario, but out of a scientific point of view it cannot be excluded
totally.

7.3

Potential impacts on groundwater quality

7.3.1 Approach
The volume of mine water that flows from the Carboniferous into the overlying
aquifers in the potential impact areas, how long this process takes, and what
changes in groundwater quality this causes is mainly dependent on the
geohydrological characteristics/properties of the subsurface.
As indicated, mostly the top 20 m of the Carboniferous formation was not mined,
and can be considered as an important aquitard providing resistance to upward
flow. This is not the case everywhere, however. In some regions the 20 m zone is
not intact because of upward drillings, mine shafts, local mine workings, or
naturally occurring zones with a higher hydraulic conductivity (“hydraulic
windows“; Fig. 41). These hydraulic connections form so-called “threats” that
cause the rise of deep groundwater levels and the subsequent impact of that rise
on the quality of shallow groundwater levels (Fig. 51).
In the modelling process the effect of hydraulic windows on groundwater flow
was researched by introducing these windows into the model and applying a low
hydraulic conductivity. The hydraulic resistance of the layers overlying the
Carboniferous was also taken into account. The individual drillings and shafts
were not included in the model, mainly because these local connections also have
a very local effect on the groundwater level.

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Fig. 51:

page 84

Bow-Tie-Analysis - Threats triggering quality change and wetting

The extent to which groundwater quality, within the potentially affected areas,
can be influenced by rising mine water is dependent not just on the
characteristics of the subsurface but also on geochemical processes. Based on the
model calculations with IBRAHYM, streamlines were determined and the
changes in the chemical composition of mine water and in travel times were
calculated.
To determine the potential risks of mine water rising towards the groundwater
reservoirs in the overburden, the following analyses were performed:
- First the problem is analysed; possible effects on groundwater quality were
identified. Based on the model schematisation the flow paths and travel time
of mine water were determined.
- Then, the water balance of the groundwater model was analysed. Based on the
fluxes as calculated by the groundwater model, the ratio between mine water
and groundwater was calculated for the groundwater layers.
- The third step was to calculate the ratio of mine water and groundwater using
the 3D transport model MT3DMS.

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- The fourth step was to perform a hydrogeochemical simulation of mine water
flowing upwards with the PHREEQC programme.
- The final step was to calculate the chloride concentration using the 3D
transport model MT3DMS.

7.3.2 Analysis of possible effects on groundwater quality
In the potential impact area I, mine water flows from the top layer in the
Carboniferous aquifer, through the Vaals/Aachen sandy formation into the
limestone aquifer, where groundwater extractions are situated (Fig. 52). Tab. 5
shows the characteristics of these layers.

Fig. 52:

Mine-/Groundwater flow paths in potential impact area I

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Tab. 5:

page 86

Characteristics flow path Carboniferous-Aachen/Vaals- Maastricht/Gulpen

Formation

Characterisation

Maastricht/Gulpen

limestone

Vaals

fine to very fine
sands, loamy to
clayey

Aachen

Carboniferous

Activities

Hydraulic
characteristics

Groundwater
extraction wells

kh = 5 - 10 m/day
in upper part till
0,01 m/day
for deeper
limestone layers

Thickness at
potential impact
areas

Ia ca. 20 - 60 m
Ib ca. 30 - 40 m

Kv = 0,001 m/day
none
Porosity = 0,3
(assumed)

alternation of fine
sand layers with
layers consisting of
black/grey clay

none

Carboniferous

Former mining
activities

Ia 50 - 60 m
Ib 30 - 40 m

Kv=0,001 m/day
Porosity = 0,3
(assumed)

Ia < 10 m
Ib 0 m

due to mining
activities a high
transmissivity is
assumed

To calculate the expected travel time for mine water between the top of the
Carboniferous layer to the bottom of the Maastricht/Gulpen layer, the head
difference between these two layers is read out of the model results. The worstand average case model have been used.
In Tab. 6 an overview is given of the calculated head difference between the
Carboniferous and Maastricht/Gulpen, for both scenarios. The difference is
presented for the two potential impact areas.
The travel distance (distance between top Carboniferous and bottom
Maastricht/Gulpen), is extracted from the groundwater model for the two
locations.

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Tab. 6:
Head difference between top Carboniferous and bottom Maastricht
(limestone aquifer)

Potential impact area

Calculated head difference
between
Carboniferous and Maastricht (limestone aquifer)
average case

worst case

[m]

[m]

Ia

3

14

Ib

5

25

Now, using the hydraulic characteristics from Tab. 6 the travel times are
calculated. The result is shown in Tab. 7.
Tab. 7:

Calculated travel times

Calculated travel times
Potential impact area
average case

worst case

[a]

[a]

Ia

1.750

370

Ib

1.050

200

Tab. 7 gives a first indication of the possible risk in the two defined areas. In
areas Ia and Ib there is a risk of mixing of mine water and groundwater. First
(indicative) calculations indicate that the highest risk is in the centre of Emma
concession.
In these calculations it is assumed that there are no hydraulic windows and that
the hydraulic conductivity of the unmined layer between the Carboniferous and
the Aachen and Vaals formations is still present.

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In the next paragraph a water balance analysis is described to determine the scale
of mixing (i.e. what amount of mine water will mix with fresh groundwater) near
hydraulic windows.

7.3.3 Water balance analysis of effect on groundwater quality
In the previous chapters the upward flowing of mine water has been described.
Using the water balance tool from the groundwater model the relative amount of
mine water that reaches the Maastricht/Gulpen layer can be determined. In every
layer mixing takes place with regional fresh groundwater. This process is shown
schematically in Fig. 53.

Fig. 53:

Schematic presentation mixing of mine water with groundwater

The water balance for both the worst case model and the average case model has
been analysed. This is done for the two different areas. For each of these areas
the vertical flux and the horizontal flux is extracted from the worst case
groundwater model as well as from the average case groundwater model. To
determine the maximum fraction mine water entering the aquifer the following
basics have been used:

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- the concentration mine water in the top of the Carbon layer is set to 100 %;
- the concentration mine water in the layers above is initially set to 0 %;
- thus the natural groundwater has a mine water concentration of 0 %;
- mixing takes place in the complete water balance area;
- in the layer in which the wells are located, all water flowing towards the well
is natural groundwater not influenced by mine water except for the vertical
flux, which comes from the layers underneath;
- the presented result is based on steady-state situation, and is therefore the
result of indefinite mixing;
- no processes such as retardation due to adsorption or dispersion are taken into
account.
In this way the maximum fraction mine water in the aquifer is estimated. Since
no geochemical processes are taken into account this is to be considered as a
worst-case from the geochemical point of view. Tab. 8 shows the results of the
water balance analysis.
From the water balance analysis it follows that the highest risk is at potential
impact area Ib. In this area the groundwater model calculates the largest vertical
flux.
Tab. 8:

Summary of results

maximum fraction mine water in wellfield
Well location
average case

worst case

[%]

[%]

Potential impact area Ia

0,1

1,1

Potential impact area Ib

0,5

24,8

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7.3.4 Transport model analysis of effect on groundwater quality
Since estimating the fraction of mine water to enter the wells in the defined
potential impact areas based on the water balance method can easily overestimate
this fraction, additional calculation have been made with a transport model.
Based on the groundwater model such as described in chap. 6 this 3D transport
model is created. The transport model is based on the IBRAHYM groundwater
model. The transport model can be used to calculate concentrations based on the
calculated groundwater head and -fluxes. With these calculations processes such
as dispersion can be taken into account.
In the transport model, in the Carboniferous layers a “mine water concentration”
of 100 % is assigned to the complete Carboniferous layer.
Using the transport model the distribution of mine water and chloride can be
calculated for a selected time period. In this case, a time period of 100 years is
set. Fig. 54 shows the result for mine water.
Worst case model (14) - percentage mine water at well locations
10

9

8

percentage [%]

7

6
area 1a
5
area 1b
4

3

2

1

0
0

10

20

30

40

50

60

70

years from now

Fig. 54:

Percentage mine water at wellfields in area Ia and Ib

80

90

100

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In area Ia there is no significant influence of mine water calculated in wellfields
in this area. The maximum concentration of mine water is calculated in area Ib,
north of Benzenrade fault and south of the Heerlerheide fault after 100 years:
approximately 2,5 % of mine water is calculated in the aquifer.
This result corresponds with the result of the water balance analysis: area Ib it is
most likely that a fraction of mine water eventually enters the aquifer. The
calculated fraction is approximately 2,5 %. This is much lower than the fraction
that has been calculated with the water balance analysis (25 %). The difference is
most likely due to the worst case approximation that has been used in the water
balance calculation.
Based on the water balance and transport calculations three scenarios are defined
for hydrogeochemical simulations with the PHREEQC programme (Tab. 9). The
potential fraction mine water is based on the high end expectations, in order not
to underestimate possible impacts of mine water on shallow groundwater wells.
Tab. 9:

Mixing scenarios abstraction wells

Scenario

fraction
mine water

dilution
factor

Remarks

1

1,0 %

0,01

maximum expected contribution of mine water to extracted water at
area Ia
- worst case area la,

2

2,5 %

0,025

3

25 %

0,25

- maximum expected contribution of mine water to extracted water,
area lb
worst case, area Ib (based on water balance calculations)

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7.3.5 Hydrogeochemical simulations
The chemical composition of mine water is quite different from the groundwater
in the aquifers of areas Ia and Ib. Along the flow path between the coal seams of
the Emma concession and groundwater wells at areas Ia and Ib water quality will
change due to different hydrogeochemical processes. Estimation of the potential
impact of mine water on the quality of abstracted groundwater at potential impact
areas Ia and Ib is divided in 5 steps, following the source-path-threatened-object
method:
- Define mine water quality (source)
- Estimate groundwater quality change top Carboniferous (path)
- Estimate groundwater quality change in Aachen/Vaals formation (path)
- Estimate groundwater quality change in Maastricht formation (path)
- Estimate groundwater quality change in future abstraction wells (threatened
object)
Groundwater travel time between coal seams and abstraction wells is calculated
with MODFLOW. Mixing fractions between mine water and groundwater are
quantified with MODFLOW. The PHREEQC programme (www.usgs.gov) is
used to quantify the expected change in water quality due to hydrogeochemical
processes along a flow path (1D-model).
- Mine water quality
Water quality in mines is influenced by pyrite-oxidation, since mine water was
abstracted and the mines were vented. This will result in mine water with high
sulphate content and a low pH (acidic). The mine water is therefore probably
enriched with trace metals. Chloride content of mine water is influenced both by
deep thermal water and water from the above lying layers and is in the range of

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150 - 1.400 mg/l for areas Ia and Ib. Mine water composition is generated with
PHREEQC. The following assumptions are made (see Tab. 10):
- Groundwater composition of the sample “Emma 54” (zone III), documented in
KIMPE (1963) is used as characteristic composition for groundwater in the
vicinity of coal seams;
- Oxygen is added to oxidise pyrite, simulating conditions in vented mines;
- Equilibrium with pyrite and goethite is assumed.
Pyrite oxidation causes high sulphate concentrations and acid conditions. Fe2+
(iron) will increase due to dissolution of pyrite, but when no more pyrite is
available, it will oxidise to Fe3+ and precipitate as goethite. Chloride
concentration is not influenced by pyrite oxidation.
Tab. 10:

Generated quality mine water
Mine water
Sample Emma 54
(from KIMPE, 1963)
in vicinity of coal seam
in contact with oxygen
(measured)
(calculated)

Parameter

pH

[-]

8,5

1,85

Ca

[mg/l]

14

14

Mg

[mg/l]

5

5

K

[mg/l]

16

16

Na

[mg/l]

1.204

1.205

Cl

[mg/l]

1.359

1.359

Fe

2+

[mg/l]

0

0

Fe

3+

[mg/l]

0

2

SO4

[mg/l]

5

1.925

HCO3

[mg/l]

949

949

EC-measured

[µS/cm]

4.770

EC-calculated

[µS/cm]

4.948

10.389

[%]

-0,49

-0,38

Ionic balance error

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Trace elements such as Cd, Zn, Ni, Sn, Cu, Cr, Co and As may be present in
mine water, due to impurities of pyrite. Under acid conditions (pH < 4 to 5),
heavy metals are very mobile. Arsenic is also mobile at higher pH-levels.
Water samples have been taken in the vicinity of mine waste rock tip
(“mijnsteen”), showing these trace elements (WITTEVEEN+BOS, 2011; Tab. 11).
Tab. 11: Water samples of the Emma Mine waste rock tip (water samples from 2006,
WITTEVEEN+BOS, 2011)
Parameter

Value

pH

[-]

4,58

EC

[µS/cm]

920

Arsenic (As)

[µg/l]

5,28

Cadmium (Cd)

[µg/l]

2,43

Chrome (Cr)

[µg/l]

0,51

Nickel (Ni)

[µg/l]

45,1

Zinc (Zn)

[µg/l]

105

- Groundwater quality change Top Carboniferous
Water quality is influenced by the mineral composition of the rocks and the
water-rock interaction. Minerals that can be found in mine waste rock are clayminerals, quartz, siderite, pyrite, halite, ankerite/Fe-dolomite, calcite, rutile,
dickite, feldspar and chlorite (WITTEVEEN+BOS, 2011).
The most important minerals to be considered are sources of iron and carbonate
minerals, which define the buffer capacity, such as pyrite, siderite, calcite and
dolomite.
At top of the Carboniferous, in many places there is a clay layer, known as the
Baggert (VAN ROOIJEN ADVIEZEN, 1998). This layer is represented by clay-

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minerals illite and chlorite. Calcite and dolomite are not abundant in this clay
layer. In the PHREEQC calculations, it is assumed that these minerals are not
present in this clay layer, to avoid overestimating of the buffer capacity of this
layer.
Calculating the effect of buffering with PHREEQC, it assumed that equilibrium
is reached between water and rock (no kinetics are taken into account because of
the very slow transport of groundwater, less than 1 m/a). Gypsum, gibbsite and
goethite are allowed to precipitate if oversaturated.
Through buffering, pH will change form acid to (nearly) neutral (6,78) conditions
(Tab. 12). Since no calcite and dolomite buffering is assumed, calcium
concentration is not changed when mine water comes in contact with the clay
layer. Chloride concentration is not changed (significantly), because it doesn’t
react with the minerals taken into account. Sulphate decreases, due to
precipitation of pyrite. Aluminium concentration increases, due to weathering of
clay minerals, but precipitates to gibbsite at neutral pH levels.
Tab. 12:

Expected water quality at top Carboniferous
Parameter

Mine water
at coal seams
in contact with oxygen

Mine water
arriving at
top Carboniferous

pH

[-]

1,85

6,78

Ca

[mg/l]

14

14

Mg

[mg/l]

5

789

K

[mg/l]

16

0

Na

[mg/l]

1.205

1.213

Cl

[mg/l]

1.359

1.368

Fe

(2+)

[mg/l]

0

1

Fe

(3+)

[mg/l]

2

0

SO4

[mg/l]

1.925

1.289

HCO3

[mg/l]

949

4.041

Al

[mg/l]

0

0,0007

EC-calculated

[µS/cm]

10.389

8.995

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- Groundwater quality change Aachen/Vaals formation
Passing through the Aachen (if present) and the Vaals formations, mixing will
occur between water flowing upwards from the Carboniferous formation and
water currently present is the Aachen/Vaals formation. Furthermore, interaction
between rock and water will take place.
- Mixing waters
Groundwater quality at the top of the Carboniferous at areas I and II (Emma
concession) before mine water rising can be described as a CaHCO3-type (type I)
or a NaHCO3-type (Type II), based on KIMPE (1963), as described in ROSNER
(2011). NaHCO3-type occurs where Vaals sands are present with a significant
thickness, resembling ion exchange related to glauconite sands. CaHCO3-type
occurs at the top of the Carboniferous layer for situations where the Maastricht
limestone aquifer is more directly in contact with the top of the Carboniferous
(impact area II, not to be considered here, due to absence of groundwater
extractions in this area).
These water types are characterised by a high HCO3-content (400 - 650 mg/l) and
a high Ca or Na content. Chloride is low (< 20 mg/l), SO4 is low (< 20 mg/l) and
pH ranges from 7,8 - 8,7. Only a limited number of ions were analysed in KIMPE
(1963).
These water types developed as a result of groundwater flow from
Maastricht/Vaals layers downwards, towards the Carboniferous layer, driven by
the abstraction of mine water. The water quality at the top of the Carboniferous is
not influenced by mining activities in a situation before mine water rise occurs.
The PHREEQC programme is used to calculate the mixed water concentration
between Vaals water and Carboniferous water (Tab. 13). Vaals water is

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represented by the “Emma 68” sample documented in KIMPE (1963).
Oversaturated minerals are allowed to precipitate in this calculation.
Tab. 13:

Calculated mixed water Carboniferous-Vaals

Parameter

Mine water
arriving at
top Carboniferous

Vaals water
Sample Emma 68
(from Kimpe, 1963)
(measured)

Mixed Mine water
top Carboniferous Vaals water

pH

[-]

6,78

8,7

6,9

Ca

[mg/l]

14

2

3

Mg

[mg/l]

789

0

395

K

[mg/l]

0

4

2

Na

[mg/l]

1.213

267

745

Cl

[mg/l]

1.368

18

699

Fe

(2+)

[mg/l]

1

0

0

Fe

(3+)

[mg/l]

0

0

0

SO4

[mg/l]

1.289

19

659

HCO3

[mg/l]

4.041

653

2.349

Al

[mg/l]

0,0007

0

0,0004

EC measured

[µS/cm]

EC-calculated

[µS/cm]

924
8.995

1.078

5.022

More or less conservative mixing occurs mixing both waters.
- Minerals in Aachen/Vaals
The Vaals formation consists mainly of fine sands with glauconite and clay
layers (“leem”). Glauconite is a secondary mineral, deposited in shallow water of
marine origin.
2+

3+

3+

The general formula of glauconite is (K,Na)(Mg,Fe ,Fe )(Fe ,Al)(Si,Al) O (OH) . The
4

10

2

stoichiometry of glauconite is different across the world. Glauconite is associated
with organic

matter and calcite. It will degrade to clay minerals

(montmorillonite). In the Vaals formation the most reactive components are
probably calcite, dolomite, pyrite, montmorillonite, illite and organic matter.

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It is assumed that an equilibrium is reached between water and minerals (no
kinetics are taken into account due to the very slow transport of groundwater,
1 m/a or less). Degradation of organic matter is irreversible.
Sulphate concentration is decreased, due to changed redox conditions (Tab. 14).
Potassium (K) concentration is increased, due to weathering of K-feldspar.
Calculated pH is increased from 6,90 to 7,55.
Tab. 14:

Expected water quality top Vaals

Parameter

Mixed Water
Mine water
Carboniferous /
Vaals-water

Mine water
arriving at the top of
Vaals formation

pH

[-]

6,9

7,55

Ca

[mg/l]

3

25

Mg

[mg/l]

395

11

K

[mg/l]

2

56

Na

[mg/l]

745

750

Cl

[mg/l]

699

703

Fe

(2+)

[mg/l]

0

0

Fe

(3+)

[mg/l]

0

0

SO4

[mg/l]

659

161

HCO3

[mg/l]

2.349

573

Al

[mg/l]

0,0004

0,0032

EC-calculated

[µS/cm]

5.022

3.767

- Groundwater quality change Maastricht
Groundwater from the top of the Vaals formation enters the Maastricht limestone
formation. The limestone formation consists of 50 to 95 % CaCO3. Equilibrium
with calcite is assumed (no kinetics). Calcite is more abundant than in the
Aachen/Vaals formation. Water quality does not change significantly, because
within the Vaals formation, the groundwater quality was already assumed to be
in equilibrium with calcite (Tab. 15).

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Tab. 15:

page 99

Expected water quality Maastricht/Vaals

Parameter

Mine water
at the top of
Vaals formation

Mine water
at
Maastricht formation

pH

[-]

7,55

7,55

Ca

[mg/l]

25

25

Mg

[mg/l]

11

11

K

[mg/l]

56

57

Na

[mg/l]

750

751

Cl

[mg/l]

703

704

Fe

(2+)

[mg/l]

0

0

Fe

(3+)

[mg/l]

0

0

SO4

[mg/l]

161

172

HCO3

[mg/l]

573

574

Al

[mg/l]

0,0032

0,0032

EC-calculated

[µS/cm]

3.767

3.780

- Expected water quality area Ia and Ib
To identify the current groundwater quality of the Maastricht formation at areas
Ia and Ib, measurements at the Craubeek wellfield are used. Water quality data
for this Craubeek wellfields is available since 1970 for individual wells (WML,
1970 - 2014, only samples with an absolute ionic balance error < 10 %, n=200;
Tab. 16). Chloride concentrations vary between 17 and 35 mg/l. Sulphate
concentrations vary between 43 and 95 mg/l. Maximum nitrate concentration is
15,8 mg/l. Based on the average water quality, a characteristic water quality for
the area I is calculated (Tab. 17). Iron is set to 0, because in most cases iron
concentrations are (near) zero, if nitrate is present. Furthermore, the HCO3
concentration is recalculated to minimise the ionic balance error.

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Tab. 16:

page 100

Measured water quality abstraction Wells Craubeek

Parameter

Minimum

Maximum

Average water quality

pH

[-]

7

7,6

7,2

Ca

[mg/l]

122

170

141

Mg

[mg/l]

2,7

14,1

8,9

K

[mg/l]

1

6

2

Na

[mg/l]

3

7,6

5,7

Cl

[mg/l]

17

35,5

23,9

[mg/l]

0

15

0,4

NO3

[mg/l]

0,5

15,8

5,1

SO4

[mg/l]

43

95

67,5

HCO3

[mg/l]

320

370

344,8

EC-calculated

[µS/cm]

485

805

651

Fe

(2+)

Tab. 17:

Characteristic shallow groundwater quality

Parameter

Average
measured
water quality
area Ia and Ib

Assumed
characteristic
water quality
area Ia and Ib

pH

[-]

7,2

7,2

Ca

[mg/l]

141

141

Mg

[mg/l]

8,9

8,9

K

[mg/l]

2

2

Na

[mg/l]

5,7

5,7

Cl

[mg/l]

23,9

23,9

[mg/l]

0

0 (set to 0)

NO3

[mg/l]

5,1

5,1

SO4

[mg/l]

67,5

67,5

HCO3

[mg/l]

344,8

384,3 (recalculated)

EC-calculated

[µS/cm]

651

EC-calculated

[µS/cm]

740

[%]

0,0

Fe

(2+)

Ionic balance error

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- Mixing of water at the abstraction wells
Groundwater, originated at the coal seams flows upwards and reaches the
abstraction wells after a period of more than 50 years. Mixing of water types in
the formations traversed occurs. Based upon the MODFLOW mixingcalculations the effects of scenarios are calculated: expected “average” case, and
worst case, both for areas Ia and Ib. The scenarios are given in Tab. 9. Results of
these scenarios are given in Tab. 18; in red concentrations exceeding the
maximum measured values for a period without mine water influence are
indicated.
For scenario 1 (area 1a), expected chloride concentration is slightly above the
measured maximum value, but below the “drinkwater norm” (150 mg/l). For the
scenarios 2 chloride concentration is higher, but below 100 mg/l.
For the “worst case north of the Benzenrade fault” (area Ib, scenario 3), chloride
concentration is 365 mg/l. Compared to the other scenarios chloride
concentrations are high, due to a higher assumed upward flux in this worst case
scenario. Chloride is an inert element and does not react with rocks, but is only
influenced by mixing with other waters. The calculated concentrations are
directly linked to the assumed chloride concentration in mine water (1.359 mg/l).
Sodium (Na) is expected to increase, but is expected to stay below 100 mg/l.
Sulphate concentration is expected to increase slightly, but will stay below the
“drinkwater norm” (150 mg/l), for scenario 1 and 2. In the worst case scenario
north of the Benzenrade fault (scenario 3) the concentration of sodium, sulphate
and carbonates are above the maximum measured values.

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Tab. 18:

page 102

Results scenarios water quality change at wells Craubeek

Parameter

Craubeek
water quality

Mine water
in
Maastricht
formation

Mixing
scenario 1

Mixing
scenario 2

Mixing
scenario 3

Measured
maximum
value 19702014,

area 1a
(average
case)

area 1a
(worst case)

area Ib
(worst case)

ionic balance
error <10 %

area 1b
(average
case)
pH

[-]

7,2

7,6

7,2

7,3

7,5

7,6

Ca

[mg/l]

141,1

24,6

138,8

135,3

82,9

170,0

Mg

[mg/l]

8,9

11,0

8,9

9,0

9,9

14,1

K

[mg/l]

2,0

56,5

3,1

4,7

29,4

6,0

Na

[mg/l]

5,7

751,1

20,7

43,1

379,5

7,6

Cl

[mg/l]

23,9

704,2

37,6

58,0

365,2

35,5

Fe

[mg/l]

0,0

0,0

0,0

0,0

0,0

15,0

NO3

[mg/l]

5,1

0,0

2,7

0,0

0,0

15,8

SO4

[mg/l]

67,5

171,8

79,5

93,3

130,7

95,0

HCO3

[mg/l]

384,3 *)

574,2

388,2

394,0

480,0

370,0

*) recalculated, already above maximum value
in red colour: concentrations exceeding the maximum measured values

- Heavy metals
Mobility of most heavy metals depends on pH (amongst others). A large change
in pH is not to be expected, pH will stay in the range 7,0 to 7,5, so mobility of
metals is limited. Besides low mobility, dilution plays an important role in the
expected concentration in the abstracted wells; the expected fraction for mine
water relative to “shallow groundwater” is 0,01 to 0,025. It is not to be expected
that measurable concentrations of trace elements from mine water will be
detected in the abstracted water.

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The expected development of the groundwater quality along a flow path from the
coal seams to the shallow groundwater at the wellfields is summarised in Fig. 55
for some critical parameters. Mine water pH is below 2 and rises fast along the
flow path to a value between 7 and 8. Chloride and sulphate concentration both
decrease along the flow path from values between 1.250 and 2.000 mg/l towards
values below 100 mg/l at the shallow wellfields in the chalk aquifer.

Fig. 55:
Development groundwater quality between coal seams and wellfield,
scenario 1

Fig. 56 shows the expected development of groundwater quality for scenario 2.
The calculated values at the wellfields are higher than for scenario 1, but are still
below 100 mg/l for chloride and sulphate. The expected groundwater quality at
the wellfields for scenario 3 are higher than for scenarios 1 and 2 (Fig. 57). A
chloride concentration of 365 mg/l is calculated, and for sulphate the expected
concentration at the wellfields is 131 mg/l. Based on the 1D PHREEQC
calculations, chloride is identified to be the largest threat for the groundwater
quality in the Maastricht aquifer.

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Fig. 56:
Development groundwater quality between coal seams and wellfield,
scenario 2

Fig. 57:
Development groundwater quality between coal seams and wellfield,
scenario 3

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7.3.6 Three dimensional chloride transport simulation
Since a possible increase of chloride concentration at areas Ia and Ib is identified
as the largest threat to water quality, additional 3D transport calculations are
made for chloride, to get a better insight into this possible threat. Distribution of
the chloride concentrations at the Carboniferous formation is assigned based on
the evaluations of ROSNER (2011; see Fig. 18). Chloride concentration in the
Aachen/Vaals and the Gulpen/Maastricht formations is set to 50 mg/l. Dispersion
is included in the model.
Fig. 58 shows the result for the chloride concentration at the well locations
during the calculated period (100 years). From Fig. 58 it follows that only for
groundwater extraction north of Benzenrade fault (area Ib) an increase in the
chloride concentration is calculated, starting after 30 years and increasing to
1 mg/l, relative to the starting concentration in this well. In the other wells no
significant increase of chloride is calculated.
Worst case model (14) - chloride concentrations at well locations
(initial concentration is set at 50 mg/l)
52,0

Concentration [mg/l]

51,5

51,0

area 1b

50,5

area 1a

50,0

49,5

49,0
0

10

20

30

40

50

60

years from now

Fig. 58:

Calculated chloride concentrations in area Ia and Ib

70

80

90

100

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8

Discussion

8.1

Verification

page 106

As shown in Fig. 29, only a few deep observation wells are available in the area
of the mining concessions. Therefore it is not possible to calibrate the
groundwater model in the same way normal groundwater modelling studies are
calibrated. Instead of calibrating, the measurements are compared with the
calculated heads of the different scenarios. In the following figures, the
calculated heads are shown in the graphs of measured groundwater heads. In
these graphs the relevant groundwater extractions are also displayed.
In Fig. 59, Fig. 60 and Fig. 61, the measured heads for wells B60C0860,
B60C0839 and B52B0837 are shown. Furthermore, the calculated heads for the
Maastricht formation are displayed. For B60C0860 the calculated heads from the
different scenarios do not differ much. Filter 3, which is situated in the
Maastricht formation, shows a rise in the groundwater level. At the end of the
available data the head reaches a height of 42,2 mNAP. In all three wells, the
measured heads have not reached the calculated head yet.
The increase in head in the Maastricht formation that has already occurred can
not only be caused by rising mine water. In the deep aquifers in southern
Limburg, there is a known long-term fluctuation in heads caused by precipitation
and evaporation, that is also observed in deeper layers. In these deeper layers the
fluctuation is attenuated and temporally shifted relative to the shallower aquifers.
Additionally, the groundwater extraction by DSM in Geleen was reduced
between 1996 and 2006. The increase in head was therefore larger in that period
than before and after that period. Between 2006 and 2014 a gradual increase in
heads is observed from 35 mNAP to 41mNAP, which is assumed to be largely
caused by rising mine water.

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Fig. 59:

Measured and calculated heads B60C0860

Fig. 60:

Measured and calculated heads B60C0839

page 107

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Fig. 61:

page 108

Measured and calculated heads B62B0837

In the case of the wells -860 and -839, the calculated head lies beneath the
phreatic groundwater table. In the end situation, there will still be infiltration in
these areas. The head of the Maastricht formation in well -837 has already
reached the phreatic groundwater table. The calculated head lies above the
phreatic head and the head in the Maastricht formation. It must be considered that
the observations in piezometer -837 are strongly influenced by changes in
groundwater extraction discharges. In the area around piezometer -837 the
drinking water company of Limburg (WML) has ended several groundwater
extractions (pumping stations Rivieren and Barrier) and increased the capacity of
others (pumping station Craubeek).
In Fig. 62, the heads for observation well -838 are shown. Both the phreatic head
and the head of the Maastricht formation lie above the calculated heads.

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Fig. 62:

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Measured and calculated heads B62B0838

Fig. 63 shows the rise of the mine water and the measured groundwater levels in
the chalk aquifer. The groundwater level in the basement at the beginning of the
measurements in 1980 was at least 200 m lower than the groundwater level in the
overburden. Nevertheless the rising mine water level constantly reduces the
leakage rate from the overburden to the basement. Therefore the speed of the
water rise in the monitoring wells -860 and -839, the two far most wells in the
northwest, is decreasing.

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Fig. 63:

8.2

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Rising mine water and groundwater heads in the chalk aquifer

Plausibility of the parameters and assumptions made

The most important parameters and assumptions made in this modelling study
are the following:
- the stage of the river Wurm (eastern model boundary);
- the hydraulic conductivity in the Carboniferous;
- upward flux from the Carboniferous into the overburden;
- boundary conditions at the river Maas (western model boundary).
In the following paragraphs, these issues are being discussed.

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8.2.1 The conductivity of the Carboniferous
- Unmined Carboniferous
Different literature shows different values for the hydraulic conductivity of the
unmined Carboniferous. In the groundwater model IwanH, which has been
developed especially for South Limburg, the Carboniferous has been given a
conductivity of 1∙10-3 m/d. Values given in literature indicate a conductivity
between 10-8 and 10-10 m/d. To calculate a worst case scenario, the value of
1∙10 3 m/d is applied to the unmined Carboniferous.
- Mined Carboniferous
There is very little data on the hydraulic conductivity of the mined Carboniferous
formation, but based on literature and the pumping tests that were carried out for
the mine water project in Heerlen, it is assumed that the conductivity is relatively
high. In the model the calculations were carried out with a conductivity of
250 m/d. Sensitivity analysis demonstrated that the hydraulic conductivity of the
mined Carboniferous is not a major influencing factor on the heads in the
Carboniferous. Lowering the hydraulic conductivity from 250 to 50 m/d results
in an increase of the head near the Wurm of around 5 m. It can be concluded that
the model results are not sensitive to changes in the hydraulic conductivity of the
Carboniferous formation.
- Hydraulic windows
As explained before, in the upper 20 m of the Carboniferous, areas with a large
inflow of groundwater from the overburden have been added to the model. These
inflows are most likely caused by sandy deposits of the Carboniferous. Because
of the sandy properties, these hydraulic windows have been given a conductivity
of 5 m/d. Sensitivity analysis showed that the calculated heads in the

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Carboniferous and overlying aquifers are relatively insensitive to changes in the
hydraulic conductivity of the hydraulic windows. However, the hydraulic
conductivity does affect the travel times of mine water to overlying layers. The
travel times are significantly shorter in regions where hydraulic windows are
found.

8.2.2 Boundary conditions at the river Maas
It is known that there is no connection between the Maurits concession and the
Belgian mines on the other side of the river Maas. It is presumed that this barrier
is only a few hundred metres wide. This barrier has been translated into the
model by adding a horizontal flow barrier on the river Maas in the layers of the
Carboniferous. In all the other model layers, the head at the river Maas can
fluctuate freely. This leads to an upward flow from the Carboniferous into the
overburden. As a result of this upward flow, heads in the overlying aquifers rise,
especially in the chalk aquifer.
- Applicability of model results.
Sensitivity analysis performed with the model shows that the results are
relatively insensitive to changes in the boundary conditions at the Maas river.

8.2.3 Model structure
In 2009, TNO delivered a geological model of South Limburg called REGIS-II
v2.1. This model contains information about the different geological formations,
its thickness and presence. REGIS-II v2.1 contains the formations from the
youngest Holocene deposits through the Aachen formation. Any deeper

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formations are not included in REGIS-II v2.1. Based on this model, the
groundwater model IBRAHYM has been built.
- Comparing REGIS-II v2.1 and REGIS-II v2.2
Currently TNO is working on an update of REGIS-II, named REGIS-II v.2.2. In
this version, recent data from mapping projects will be taken into account when
working out the updated geological model. For this project, the available data for
South Limburg have been provided. The used groundwater model is based on
REGIS-II v2.1, and is not yet updated with the newest data. To oversee the
consequences of a new geological model and its impact on the modelling results,
the different layers of REGIS-II v2.1 and REGIS-II v2.2 have been compared by
TNO in the framework of the study in hand. The comparison and its conclusions
are displayed in WITTEVEEN+BOS, 2015).
The comparison shows that there are relevant differences between the two
REGIS models. This is partially due to the reinterpretation of data from drillings,
even though the relevance of this information is limited for the regional
groundwater model. The province of Limburg and the water boards are updating
and calibrating the IBRAHYM model.

8.2.4 Accuracy
In 2015 Deltares updated and recalibrated the groundwater model IBRAHYM. It
must be underlined, that IBRAHYM is a large, regional groundwater model and
is not meant to predict groundwater heads at a small scale. Because of the
complex geohydrological system in South Limburg and the steep gradients in the
groundwater, deviations will occur. In the report by Deltares these deviations are
mentioned. 60 % of the deviations lie between -4,0 and -1,5 m. This means, that

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in many cases the calculated heads are too low. This should be taken into account
by interpreting the modelling results.
In this report the effects of density-flow of groundwater are not taken into
account. Saline mine water is (slightly) heavier than fresh water, and this will
have an (minor) impact on groundwater heads.

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9

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Bow-Tie-Analysis

A general overview about the systematic of the Bow-Tie-Analysis is given in
chap. 2.3.4. With the results of the investigations in hand two Top Events have
been identified regarding the Hazard “rising mine water”:
- change quality of deep groundwater (WG 5.2.4; Fig. 48)
- wetting of stream valleys (WG 5.2.5; Fig. 47)
The single Bow-Ties for these top events are given in Appendix 4 and
Appendix 5. In the following the relevant factors of the Bow-Tie are discussed.
In the Bow-Tie systematics approach a distinction is made between prevention
control measures and recovery control measures. “Prevention control measures”
are measures implemented to reduce the probability of occurrence of the socalled “Threats”. “Recovery control measures” are measures that are
implemented when the top event (e.g. changing quality of deep groundwater)
occurs, and that are designed to reduce the “Consequences” of such an
occurrence or mitigate them altogether.

9.1

Top Event: Change quality of deep groundwater (WG 5.2.4)

9.1.1 Threats, Consequences
As a result of rising mine water, especially in the Emma concession, water will
flow upwards through layers with a higher conductivity, through hydraulic
windows and through badly sealed boreholes and mine shafts. As a result,
extracted water by the drinking water company or industry can be influenced.

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9.1.2 Prevention Controls
- Pumping of mine water
In practice, the threats can only be mitigated by preventing a further rise of mine
water by starting to pump out mine water again. This is a measure that could
introduce significant consequences. The pros and cons of restarting the pumping
of mine water are discussed in the final integrated risk analysis of this project.
- Locations and discharge of groundwater extraction wells
For new groundwater extractions it is recommended to research the presence of
hydraulic windows, and the location and discharge of the proposed wells and let
the well configuration be determined by these results.
- Research
The presumed effects of rising mine water are partly based on the modelling
performed with the groundwater model IBRAHYM. This model was calibrated
using data on groundwater levels, in which no relationship was presumed with
rising mine water. It is recommended to recalibrate the model, taking into
account the effect of rising mine water. Also, we recommend to install
piezometers that are screened in the Carboniferous formation. This data will be
valuable input for the future recalibration of the model. Recalculating the effects
of rising mine water with the recalibrated model and with the new monitoring
data is highly recommended.

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9.1.3 Recovery Controls
If groundwater quality is influenced by rising mine water which in turn
influences the quality of water extracted by industry or drinking water production
companies, then the following recovery control measures can be implemented:
- Monitoring of groundwater quality
- Reducing, stopping or moving groundwater extraction wells
- Regional development planning
In the “Provinciaal Omgevingsplan Limburg”, the province Limburg formulates
policy with respect to groundwater extraction and protection, among other
methods through the designation of environmental protection zones around wells,
or creating drilling free zones. It is recommended to determine whether
additional policies should be added with respect to rising mine water.
- Gebiedsdossiers
As a result of the Water Framework Directive and the Groundwater Directive
governments in the EU (or in this case the provincial municipality) are required
to protect/guarantee the (chemical) quality of groundwater. They are required to
implement the necessary measures to prevent or mitigate the introduction of
pollutants to groundwater. In that context, the province Limburg drafted
gebiedsdossiers for every drinking water and industrial groundwater extraction
for human consumption. In these gebiedsdossiers the current situation (the goal,
discharge and the depth of the extraction, current water quality and identifiable
trends), possible future threats, and measures to mitigate the contamination of
groundwater, are described. In these gebiedsdossiers the rise of mine water has
not been identified as a possible threat. It is recommended to update the
gebiedsdossiers with this extra risk and make agreements on monitoring and
potential measures.

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9.2

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Top Event: wetting of stream valleys (WG 5.2.5)

9.2.1 Threats, Consequences
It cannot be entirely ruled out that locally, in the valleys, the phreatic
groundwater levels will rise. Though the calculated increases are relatively small,
in regions where the groundwater table lies close to the surface, there may be an
increase in water nuisance from high groundwater levels, especially in buildings
with unsealed cellars.

9.2.2 Prevention Controls
In order to prevent damage to structures, there are numerous measures that can be
implemented such as drainage, pumps, etc. This research does not answer the
question which measure should be implemented in which situation. These are
highly dependent on local variables, such as the location, characteristics of the
subsurface, water management, type of structure etc. These require custom
solutions for each individual situation, should groundwater levels rise as a result
of rising mine water.

9.2.3 Recovery and Escalation Controls
- The knowledge about rising mine water and potential impact areas should be
made available for the municipalities, province, and Water Board;
- If wetting occurs or is predicted, the local situation with regard to
geohydrology should be checked and the relationship between mine water rise
- increase of groundwater - and damage should be investigated;

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- When an increase of water nuisance occurs, immediate measures could be
taken, like drainage, pumps, sealing cellars etc. As stated in chap. 9.2.2. these
measures highly depend on local variables, and require custom solutions for
each situation.

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10

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Monitoring

In this report, possible effects of the mine water rise have been investigated.
Mine water rise can lead to an upward flow of mine water into overlying
aquifers. Most of all this is the matter in the Emma concession and partially in
the Oranje Nassau and Hendrik concessions. One of the consequences can be that
the composition of extracted water by industries and the drinking water company
is affected negatively.
The investigation is based on an analysis of the water system. Hypotheses
resulting from this analysis are verified with the groundwater model IBRAHYM.
In groundwater model studies model results are usually calibrated and verified
using measured groundwater heads and water balances. This is done by
recalculating an event or period that occurred at an earlier date. In the case of the
rising mine water, verification is barely possible. The mine water level is only
measured in five shafts (shaft I Wilhelmina, shaft II Oranje Nassau I, shaft II
Julia, and Beerenbosch II and Willem II shafts (Domaniale)) meaning only in the
eastern mine area. There are no data available, neither for the western part
(concessions Emma and Maurits) nor for the Belgian concessions.
Measurements have been carried out on only a few locations in the overlying
formations: namely, in the four groundwater monitoring wells of the
“Mijnwatermeetnet” and in the area of the groundwater extractions from WML
in the Voerendalerveld. Measuring the groundwater head in the Carboniferous is
crucial for the following reasons:
- These measurements give insight into the actual situation and the groundwater
heads in the future.

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- Such a system can obtain information about the structure of the underground
and parameters in area where this information is currently missing, for
example about the conductivity of the hydraulic windows. Based on this
information, the groundwater model can evolve from the ”conceptual model”
to become a predicting model.
- Collecting data about the groundwater quality and the development of the
quality is important. Especially in areas where the drinking water supplies
might be affected in the future, like Voerendalerveld, but also around
industrial groundwater extractions where groundwater is extracted for the
production of food. With respect to these extractions measurements can form
the basis for an early warning system.
- Delivering accurate information as a basis for other effects like induced
seismicity and land movements.
We advise to construct 5 new deep observation wells, all with a filter in the
Carboniferous and the above lying aquifers. The locations and motivations for
the single wells are presented in Tab. 19. Additionally an observation well near
het Loon in Heerlen is advised. This well could provide more information about
the measured decline in groundwater head in this area.
North of the Heelerheide fault zone in impact area II it is also likely to expect
mine water will intrude in the overlying formations. In this area there are no
(deeper) groundwater extractions present, so there is no actual threat. However,
since we do not have any information about the mine water level and
groundwater levels in this area, it is adviced to construct an observation well.

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Tab. 19:

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Monitoring - proposed observation wells

Concession

Description

Purpose

Maurits/
Emma

I.
next to well
B60C0860

-

II.
Eastern
boundary
Maurits
concession
III.
next to well
B60C0839

-

-

Monitoring joint effect of rising mine water in Dutch and Belgian
concessions
Delivering information about boundary conditions at the Belgian border
Delivering information about the gradient steep between Emma and
Maurits and alongside about the east-west flow of mine water in the
Carboniferous
Makes it possible to correlate measured heads in the mine water wells
with the since 1980 measured water levels
Delivering information about the presence and workings of hydraulic
windows
Delivering data to verify model assumptions and improve the prediction
of effects
Measuring the development of the groundwater quality
Alarming by possible threats for the groundwater quality near the
groundwater extraction in Schinnen (early warning system)

Emma

IV. Southeastern
part
Voerendalerveld
(near well
B62B0838)

-

Monitoring rising heads in the Carboniferous and overlying formations
Detailed information about the top of the Carboniferous
Measuring the development of the groundwater quality
Alarming by possible threats for the groundwater quality near the
drinking water extractions (early warning system)

Emma

V.
near well
B62B0837

-

Monitoring rising heads in the Carboniferous and overlying formations
Measuring the development of the groundwater quality
Alarming by possible threats for the groundwater quality near the
groundwater extraction Hoensbroek (early warning system)

Oranje
Nassau

VI

-

Monitoring heads in the Chalk formation
Confirmation of indications for a huge decline of the head, probably due
to loss of groundwater from the Chalk into the Carboniferous.

-

Monitoring rising heads in the Carboniferous and overlying formations
Measuring the development of the groundwater quality

‘t Loon Heerlen
Oranje
Nassau

VII
North of
Heerlerheidefault

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Summary and conclusions

11.1 Groundwater quality
Hydraulic contact between Carboniferous (containing mine water) and
overburden layers can result in the exfiltration of mine water towards these
covering layers. Subsequently, water from this covering layer can flow towards
nearby shallow aquifers. Hydrogeochemical reactions can occur along flow
paths.
The location of these hydraulic contacts in mining areas is important; both in the
current situation and in the future, under rising mine water conditions. To
identify these contacts and their impact, several soil survey maps have been
studied, such as maps with the top level of the Carboniferous, thickness and
characteristics of covering layers, contact with shallow aquifers nearby, and
characteristics of these shallow aquifers (permeability etc.). Furthermore,
information is collected about the situation during mining activities. Were there
specific circumstances during mining, which affected this hydraulic contact?
Subsequently, the effect of mine water rise on the occurrence of these contacts is
calculated.
The composition of mine water is very different, compared with groundwater in
shallow aquifers nearby. Mine water can have a high salt content and can contain
heavy metals or additives used in the mining industry. Mine water can be very
acidic and deoxidised. If mine water is mixed with water from shallow aquifers,
several hydrochemical reactions will take place. These reactions may cause the
dissolution and precipitation of minerals, which in turn, influences groundwater
quality. Contamination by arsenic is a particular risk.

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The chemical composition of mine water is quite different from the groundwater
in the aquifers. Along the flow path between the coal seams and groundwater
water quality will change due to different hydrogeochemical processes. To
determine the potential risks of rising mine water towards the groundwater
aquifers the following analyses were performed:
- First the problem was analysed; possible effects on groundwater quality were
identified. Based on the model schematisation the flow path and travel time of
mine water was determined.
- Then, the water balance of the groundwater model was analysed. Based on the
fluxes as calculated by the groundwater model the ratio between mine water
and “clean” water was calculated for the groundwater layers.
- The third step was to calculate the ratio of mine water and “clean” water,
using the 3D transport model MT3DMS.
- The fourth step was to perform a hydrogeochemical simulation of mine water
flowing upwards with the PHREEQC programme.
- The final step was to calculate the chloride concentration using the 3D
transport model MT3DMS.
Based on the groundwater calculations, sulphate and chloride were identified to
be the largest threat for the groundwater quality in the impact areas. Here an
increase in the chloride and sulphate concentration was calculated, starting 30
years after the rise of mine water had ended, and gradually increasing during the
next 70 to 100 years near “hydraulic windows”. Where the top of the
Carboniferous has not been excavated, travel times are much longer.

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In the most likely case, the concentrations of chloride can increase to a level of
700 mg/l at the Top Vaals/Bottom Maastricht. The concentrations of sulphate can
increase to a maximum level of approximately 150 mg/l.
However, due to mixing it has to be expected that further upward flow and
mixing with “chalk” water will decrease the concentration of sulphate and
chloride. In the report the consequences of a gradual increase of chloride and
sulphate concentrations for present groundwater extractions are investigated. The
calculations show that, due to mixing, the concentrations of chloride and sulphate
will not exceed 1 mg/l in impact area Ib. In area 1a there is no increase of
chloride calculated. So, for groundwater extractions the consequences seem to be
very limited.
The mobility of most heavy metals depends on pH value (amongst others). A
large change in the pH value is not to be expected: it will stay in the range 7 to
7,5, so the mobility of metals is limited. Besides low mobility, dilution plays an
important role in the expected concentration in the Maastricht aquifer and
extraction wells; it is not to be expected that measurable concentrations of trace
elements from mine water will be detected in the abstracted water.
North of the Heelerheide fault zone in impact area II, it is also likely to expect
mine water will intrude in the overlying formations. In this area there are no
(deeper) groundwater extractions at present, so there is no actual threat. Also in
this area a further decrease of the concentrations will take place, due to mixing
with shallow groundwater.
It is not expected that the quality of shallow groundwater will be influenced due
to rising mine water.

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11.2 Wetting
Due to mine water rise, groundwater levels nearby mined areas can also rise.
Change in shallow groundwater can lead to wetting.
A groundwater model is used to estimate the effect of mine water rise on phreatic
groundwater levels. Assumptions have been made about the amount of water
exfiltrating from the Carboniferous towards the shallow aquifers. These
assumptions were made upon measurements of mine water level over the past
decades, since the mine water pumps stopped. The IwanH-groundwater model
was used to calculate the effects. First of all the current situation has been
calculated (average situation) and evaluated (depth of groundwater level relative
current surface level was calculated). Subsequently, the estimated effect of rise of
groundwater levels, due to mine water rise was evaluated.
Due to the rise of mine water, shallow groundwater level will also rise in part of
the investigation area. Since groundwater levels are relatively deep in the major
part of the study area, the calculated rise will not lead to damage in that area.
Calculations with the IBRAHYM model show that in the most likely case (the
average case) wetting can occur in the Geleenbeek Valley near Geleen and
Schinnen, and locally near the river Maas. The rise of shallow groundwater levels
will be relatively low: a maximum of 0,1 to 0,25 m is calculated. In general it is
not to be expected that this will lead to severe damage to housing, nature or
agriculture.

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11.3 Bow-Tie-Analysis and monitoring
For mitigating or preventing the effects of mine water rise on groundwater
quality, the following recommendations are made:
- An important threat is the presence of hydraulic windows, i.e. zones with
higher permeability between the Carboniferous and the overlying aquifers.
Some of these hydraulic windows are identified in the report, but it cannot be
excluded that more windows are present. It is advised to do geohydrological
research when new groundwater extractions are being planned or the
extraction of groundwater will increase.
- The authorities are advised to conduct a policy for the protection of
groundwater extractions, which is an obligation of the Water Frame Work
Directive and the Groundwater Directive, in “het Provinciaal Omgevingsplan
Limburg” and the “gebiedsdossiers”.
- The Province of Limburg and the Water Board are advised to take into
account the effects of rising mine water, when recalculating the protection
zones of drinking water extractions
For the handling of potential water nuisance the following recommendations are
made:
- The knowledge about rising mine water and potential impact areas should be
made available for the municipalities, province and Water Board.
- If wetting occurs or is predicted, the local situation with regard to
geohydrology should be checked and the relation between mine water rise increase of groundwater - damage should be investigated.

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- Potential impact areas need to be considered by the planners of building
projects, especially in areas where local water nuisance already occurs.
- Proposal for monitoring.
Since there is no information on the groundwater level in the Carboniferous in
the major part of our study area, it is advised to install seven deep monitoring
wells. The required data will help to improve the model and the predictions of
mine water and groundwater rise.

Deventer, 31. August 2016/02. December 2016

Dipl.-Geol. Nancy Sevriens-Visser

Drs. Arie Biesheuvel

ir. Jaap H. Spaans

Aachen, 31. August 2016/02. December 2016

Dr. Michael Denneborg

Aachen, 31. August 2016/02. December 2016

Dr.-Ing. Michael Heitfeld

Dr. Peter Rosner

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Steinkohlenbergwerken im rechtsrheinischen Ruhrkohlenbezirk zur

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WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

page 130

Untertageverbringung von Abfall- und Reststoffen.- Unveröffentlichtes
Gutachten im Auftrag des Landesamtes für Wasser und Abfall NRW.
KIMPE, W.F.M. (1963): Geochemie des eaux dans le houiller du Limbourg (PaysBas).- Verhandelingen van het Koninklijk Nederlands Mijnbouwkundig
Genootschap, Vol. 21, Teil 2, S. 25-46, 16 Abb..
KLEIN, J. - DELTARES (2015): Grondwaterkwaliteitsdata tbv steenkoolwinning
Limburg.
MENKOVIC, A. EN VERNES, R. - TNO - AFDELING GEO-MODELLERING (2015):
Antwoord op de vragen uit de memo van W+B met de verschilkaarten tussen
de REGIS-II v2.1 en REGIS-II v2.2 modellen.
PAAS, N. (1997): Untersuchungen zur Ermittlung der geochemischen Barriere

von Gesteinen aus dem Umfeld untertägiger Versatzräume im
Steinkohlengebirge des Ruhrkarbons. DMT-Berichte aus Forschung und
Entwicklung, Heft 54. Bochum.
PATIJN, R. J. H. (1961): Overzichtskaart Carboon-oppervlak Limburgs
Mijngebied.
PROVINCIE LIMBURG (2015): Geodataportaal, shapefiles retrieved from:
http://portal.prvlimburg.nl/geo_dataportaal/viewer.do
ROSNER, P. (2011): Der Grubenwasseranstieg im Aachener und Südlimburger
Steinkohlenrevier

-

Eine

hydrogeologisch-bergbauliche

Analyse

der

Wirkungszusammenhänge.- Diss. RWTH Aachen, 194 S., 67 Abb., 7 Tab.,
4 Anh., 7 Anl.; Aachen.
SHGM

-

STUDIEGROEP

MIJNSLUITINGEN“ (1975):

„HYDROGEOLOGISCHE

GEVOLGEN

VAN

DE

Het stijgende mijnwater in de gesloten Zuid-

Limburgse mijnen.- 31 p., 5 Tab., 6 maps; Maastricht.
TÖNIS, R. EN MENKOVIC, A. - TNO (2015): Analysis of Top Carboniferous map
of South-Limburg, Ministerie van EZ

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page 131

TNO (2015): Database Dinoloket, groundwater levels and underground data
retrieved from www.dinoloket.nl (30.03.2015).
TNO (2015): Database REGIS-II v2.1 and REGIS-II v2.2.
VAN ROOIJEN ADVIEZEN, STAATSTOEZICHT OP DE MIJNEN & PROVINCIE
LIMBURG (1998): Het mijnwater - stand van zaken voorjaar 1998.- Rapport
Provincie Limburg, 23 S., 7 Abb., 4 Bijlagen; Maastricht.
VAN ROOIJEN ADVIEZEN (2011): Syllabus voor de cursus Geologie van Limburg,
N.V. Waterleiding Maatschappij Limburg
VAN ROOIJEN ADVIEZEN (2015): Waterstanden Tongeren Sands (memo, Na-

ijlende effecten steeenkolenwinning Zuid-Limburg)
WALLBRAUN

A.

(1992):

Einfluß

der

Schollenrandstörungen

in

der

Niederrheinische Bucht auf den Grundwasserabfluß.- Dissertation RWTH
Aachen.
WEDEWARDT, M. (1995): Hydrochemie und Genese der Tiefenwässer im RuhrRevier.- DMT-Berichte aus Forschung und Entwicklung, H. 39, 250 S.,
60 Abb., 10 Tab., 2 Anl.; Bochum.
WITTEVEEN+BOS

(2010):

Schematisatie

ondiepe

ondergrond,

Provincie

Limburg, Mt932-1/mome/067, concept 01 8 maart 2010.
WITTEVEEN+BOS (2011): Literatuuronderzoek naar de verspreiding van

verontreiniging uit mijnsteen naar het grond- en oppervlaktewater in
Parkstad Limburg, MT1010-1/mome/011 definitief 17 oktober 2011.
WITTEVEEN+BOS (2012): Gebiedsdossier winning Craubeek, Provincie Limburg,
Mt900-14/mome/169, definitief 13 februari 2012.
WITTEVEEN+BOS

(2012):

Gebiedsdossier

winning

Schinveld,

Provincie

Limburg, Mt900-14/mome/165, defintief 10 januari 2012.
WITTEVEEN+BOS (2015): Notitie, Vergelijking Regis 2.1 en 2.2, 2 juni 2015

Appendix 1

Na-ijlende gevolgen steenkolenwinning
Zuid-Limburg
Final report
on the results of the working groups
5.2.4 - groundwater quality
5.2.5 - groundwater quantity
Diepteligging van het Carboon oppervlak in het model Na-ijl effecten
Mijnbouw Zuid-Limburg by VAN ROOIJEN ADVIEZEN, 2015

by
Projectgroup
"Na-ijlende gevolgen van de steenkolenwinning in ZuidLimburg"
(projectgroup GS-ZL)

on behalf of
Ministerie van Economische Zaken - The Netherlands

Aachen (D), Deventer (NL), 31. August 2016

Na-ijlende gevolgen steenkolenwinning Zuid-Limburg
WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

Appendix 1

Diepteligging van het Carboon oppervlak in het model
Na-ijlende gevolgen van de steenkoolwinning in Zuid-Limburg

Als basis van het model voor het project worden de meest recente resultaten van
het TNO project REGIS gebruikt. In REGIS zit echter niet de diepteligging van
het Carboon oppervlak (TC). Aanvankelijk werd door TNO een aanvullende
kaart geleverd voor dit niveau. Deze computerkaart werd onafhankelijk van de
REGIS resultaten geconstrueerd en bleek dermate zware problemen te bevatten
dat omgezien werd naar een alternatief. Na uitvoerig en tijdrovend overleg tussen
de modelbouwers van het project en TNO werd besloten dat de REGIS gegevens
van TNO worden gebruikt voor de TC in het gebied zuidwestelijk van de
Heerlerheide Breuk en dat uit het reeds bestaande Ibrahym model de TC ten
noordoosten van deze breuk wordt gebruikt.
Bij het bestuderen van de diepteligging van de basis Laag 19 van het Ibrahym
model (die moet overeenkomen met de Top Carboon) bleken hierin echter zeer
grote verschillen te zitten met de toch erg goed gedocumenteerde kaart TC van
Patijn uit 1961. Ten noordoosten van de Feldbiss toont Ibrahym duidelijk
geringere TC diepten terwijl ten zuidwesten van deze breuk de TC Ibrahym juist
aanmerkelijk dieper ligt dan op de kaart Patijn. Afgezien van het daardoor sterk
verminderde effect op de verschillen langs de Feldbiss en de mogelijke gevolgen
daarvan voor watertransport over de breuk heen, zullen hierdoor ongetwijfeld
problemen ontstaan met de dikteverdeling van de verschillende deklagen van het
Carboon, zeker daar waar het Carboon omhoog komt tot niet ver onder maaiveld,
zoals in het zuidoosten van het modelgebied. Daar ligt bijvoorbeeld, bij boring
62 E-341 (schacht Nulland) TC op +117 m NAP. Op het Carboon ligt ca 15
meter fijn, slibhoudend zand van de Formatie van Tongeren (Laagpakket van
Klimmen) en daarop een sterk kleiig, ca 15 meter dik
pakket met
bruinkoolinschakelingen (Laagpakket van Goudsberg), onder een pleistocene
bedekking met Maasgrind en löss van ca 10 meter dik. Als nu, volgens Ibrahym,
de TC iets onder +70 m moet liggen, dan moet daar ook een veel dikker Tertiair
pakket worden geïnterpreteerd, met bovenin waarschijnlijk een deel van de
watervoerende laag van de Formatie van Breda. Ook elders leidt dit tot
afwijkingen van de werkelijke opbouw boven het Carboon, waardoor naar alle
waarschijnlijkheid de resultaten van het modelonderzoek kunnen worden
beïnvloed.

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Appendix 1

Hieronder enkele resultaten van de vergelijking van TC Ibrahym en de kaart
Patijn.

Tussen 1ste NO Hoofdbreuk en Feldbiss
In het noordwesten ligt TC Ibrahym (meer dan) 200 meter te hoog. Zie boringen
24 en 25 (resp. 69 en XLV op kaart Patijn). De fout neemt af naar het zuidoosten.
Bij boringen 108 en 219 (XLII en 86) is dit nog een verschil van ca 100 meter.
Ter hoogte van Tevenerheide ca 80 meter en bij boring 27 (82) bij
Abdissenbosch ligt TC Ibrahym nog 50 meter hoger dan in de boring gevonden
en op kaart Patijn aangegeven. Verder naar het zuidoosten neemt het verschil af
maar gaan de Ibrahym lijnen dwars door de daar goed gedocumenteerde TC
topografie van Patijn, waardoor verschillen weer (zeer plaatselijk) oplopen tot 50
of 60 meter. Bij de Julia ligt TC Ibrahym weer plaatselijk rond 75 meter hoger
dan TC Patijn, terwijl daar toch grote zekerheid te vinden is door boringen en
schachten Julia (b.v. boring 100 Patijn). Dan verzint Ibrahym rond 700 meter ZO
van de schachten Julia ineens een sprong in TC van meer dan 100 meter. Het is
niet duidelijk waarop dit is gebaseerd. Daardoor komt verder naar het zuidoosten
de TC Ibrahym juist beduidend dieper dan bij Patijn en lopen de lijnen ook vaak
haaks op elkaar.

Tussen Feldbiss en Heerlerheide Breuk
In het noordwesten, bij Wintraak, legt Ibrahym de TC duidelijk te diep.
Verschillen met Patijn tot 50 meter zijn de norm. Vergelijk boringen 60C-294
(64 bij Patijn) en 60D-4 (84 Patijn). Ibrahym TC ligt resp. 50 en 55 meter te diep.
Interessant is dan wel de Duitse hoek bij Hillensberg, waar Ibrahym de grens
volgt met een sprong omhoog. Hierdoor komen de verschillen met Patijn daar
bijna te vervallen, maar de dieptelijnen van Ibrahym kruisen die van Patijn
veelal. Dan verder naar het zuidoosten, het gebied Douvergenhout, Oirsbeek en
Amstenrade. TC Ibrahym weer aantoonbaar te diep. Verschil met Patijn weer
rond 50 meter. Vergelijk boringen 60D-39, 40, 42, 65, 67, 68, 164 en 169 (resp.
LI, 66, XL, 49, 65, XIX, IX en XXI bij Patijn). Een grillige wirwar van
dieptelijnen TC van Ibrahym volgt in het gebied Treebeek – Brunssum, met TC
Ibrahym vaak 50 - 70 meter dieper dan de in boringen en schachten aangetoonde
werkelijkheid. Het is volslagen duister waarop de kennelijk computergestuurde
Ibrahym lijnen zijn gebaseerd. Ook verder naar het zuidoosten, waar het Carboon
oppervlak omhoog komt tot boven NAP, ligt TC Ibrahym tot wel 80 meter dieper
dan bij Patijn, zoals bij coördinaat 197.000 - 322.500 in Heerlen (-70 en +10 m)

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Appendix 1

en bij 199.350 – 322.700 in Schaesberg (-40 en +40m). En dit verschil blijft
onverdroten doorlopen verder zuidoostelijk. Zo ligt TC Ibrahym bij de schachten
SM Wilhelmina nog steeds 50 meter dieper dan bij Patijn (+10 i.p.v. +60m) en
60 meter dieper bij Neu Prick (+80 i.p.v. +140m. Opvallend is ook dat TC
Ibrahym de lijnen soms ongestoord door goed gedocumenteerde breukjes aan
Top Carboon laat lopen.

Klimmen, 28 juli 2015

P. van Rooijen.

Appendix 2

Na-ijlende gevolgen steenkolenwinning
Zuid-Limburg
Final report
on the results of the working groups
5.2.4 - groundwater quality
5.2.5 - groundwater quantity
Comments on REGIS-II v2.1 and REGIS-II v2.2
by VAN ROOIJEN ADVIEZEN, 2015

by
Projectgroup
"Na-ijlende gevolgen van de steenkolenwinning in ZuidLimburg"
(projectgroup GS-ZL)

on behalf of
Ministerie van Economische Zaken - The Netherlands

Aachen (D), Deventer (NL), 31. August 2016

Na-ijlende gevolgen steenkolenwinning Zuid-Limburg
WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

Appendix 2

Bevindingen bij de geologische aandachtspunten,
Model na-ijl effecten Mijnbouw Zuid-Limburg

Bij de opbouw van een grondwater stromingsmodel voor het inschatten van de
na-ijlende effecten van de Zuid-Limburgse steenkoolwinning werd door de
modelbouwers een aantal onduidelijkheden gevonden in de aangeleverde
basiskaarten. Deze werden als aandachtspunten geregistreerd en door Van
Rooijen Adviezen nader bekeken en geëvalueerd.
Als basis voor het model wordt ten noordoosten van de Heerlerheide Breuk de
kaart Ibrahym genomen voor de Top Carboon en voor het gebied ten zuidwesten
van deze breuk vormt een TNO kaart de basis voor Top Carboon. Voor de
deklagen van het Carboon wordt REGIS als uitgangspunt genomen. Bij de
aandachtspunten gaat het met name om grotere dikteverschillen tussen eerder
door TNO gemaakte kaarten (REGIS 2.1.) en de meest recente constructie
(REGIS 2.2.).
In het algemeen moet worden opgemerkt dat het qua hydrologie weinig zal
uitmaken of een sedimentinterval tot de Formatie van Maastricht of tot de
Formatie van Houthem wordt gerekend. Het gaat wat doorlatendheid betreft
immers slechts om de bovenste zone van het gehele chalk pakket. Aan alles wat
zich van de chalk op grotere diepte bevindt onder het chalk oppervlak moet een
(zeer) geringe doorlatendheid worden toegeschreven. Bij dikteverschillen kan het
van belang zijn om welk laagpakket het binnen een formatie gaat. Lokaal kan
bijvoorbeeld de bovenste zone van de Formatie van Tongeren, het vaak zeer
kleiig ontwikkelde laagpakket van Goudsberg, dermate afsluitend zijn dat zich
daaronder in het zandige laagpakket van Klimmen een eigen grondwaterstand
vormt die sterk afwijkt van de freatische waterstand maar ook van de waterstand
in het Carboon (b.v. in gebied Heerlen-Kerkrade).

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Appendix 2

Punt 1
Hier ligt een aantal diepe waterputten van DSM. Het gaat hier vooral om dikten
Tongeren (de Goudsberg laag) en Maastricht. Het laagpakket van Goudsberg is
hier waarschijnlijk slechts ca 5 meter dik. Verwarrend is de afhankelijkheid van
oude lithologische beschrijvingen van de boringen. Het pakket kleiig zand en
zandige klei wordt per boring anders beschreven zodat men er alle kanten mee op
kan, en ook is gegaan kennelijk. Het is een combinatie van diverse lagen van de
Formatie van Rupel en de F. van Tongeren. Ook in de oorspronkelijke REGIS
kartering leidde dit eerst tot enorme verschillen in dikte Goudsberg. Lijkt dus van
weinig belang, mits de gemodelleerde doorlatendheden geen grote verschillen
laten zien. Maastricht is hier dikker dan in de omgeving; Houthem juist dunner.
Gaat hier dus (grotendeels?) om stratigrafische toewijzing van de chalk (zie
boven). Het totale pakket chalk is hier waarschijnlijk rond 110 meter dik,
waarvan ca 40 m Houthem. Waarom hier dan relatief dunne Houthem laag is
gegeven in REGIS 2.2. is onduidelijk, maar hydrologisch dus minder van belang.
Punt 2
Hier ligt boring 60D-655 met een pakket Maastricht en Vaals samen van 100
meter. Kimpe (1961) verdeelt dit onder in ruim 35 m Maastricht en 65 m Vaals.

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Appendix 2

TNO ziet hierin 80 m Maastricht en 20 m Vaals omdat de beschrijving veel
“mergel” vermeldt. Maar deze is vanaf 37 m onder de top Maastricht al kleiig en
vermengd met glauconiet zand, zodat de interpretatie van Kimpe verantwoord is.
Harde banken komen ook in Vaals voor. REGIS 2.1. geeft Maastricht een dikte
van 80 m en 2.2. insgelijks. Maar in beide gevallen is de dikte duidelijk groter
dan in de omgeving. Bij Vaals laat REGIS juist het omgekeerde zien, met voor
het gebied anomaal geringe dikten. Duidelijk is dat zowel 2.1. als 2.2.
onverantwoord zijn hier en een revisie nodig is overeenkomstig de interpretatie
uit 1961.
Punt 3
Dit punt ligt ca 150 meter ZW van de diepboring 60D-1039 uit 1993. Hier is
Goudsberg 7½ m dik en Maastricht ruim 30 m. Wezenlijke verschillen lijken hier
niet te bestaan tussen REGIS 2.1. en 2.2. Hooguit een miniem verschil in dikte
Tongeren zand 1, maar dit is niet te baseren op de lithologie van boring 1039 en
dus slechts een onbetekenende computer interpretatie. De aanleiding tot het
geïnterpreteerde verschil van meer dan 10 meter in kaart verschil Tongeren is
onduidelijk, niet te baseren op de lithologische beschrijving van boring 1039 en
dus van geen belang.
Punt 4
Hier is naar mijn weten geen boring. Als er ook geen seismiek over dit punt loopt
is deze situatie heel vreemd. Terwijl ca 1250 m zuidelijk van dit punt nog 80 m
Maastricht en geen Houthem aanwezig is zou hier, tegen de Geleen Breuk, juist
geen Maastricht meer zijn en wel ca 50 m Houthem. Lijkt geen kwestie van
stratigrafische indeling. Van groter hydrologisch belang is dat NW van dit punt 4
bij de Maas geen Houthem meer zou zijn, maar ook geen Maastricht. In ’t geheel
geen chalk dus meer (REGIS 2.2.)!?? Is er in aangrenzend België soms een
boring? Vraag voor TNO.
Punt 5
Maastricht of Houthem. De situatie is hier inderdaad vreemd. Er liggen drie oude
diepboringen in deze tektonische schol op een lijn NW-ZO. Dicht bij de Maas,
60C-25, heeft ca 80 m kalksteen van -320 tot -397. 2250 meter verder ZO ligt
60C-83 met 150 m kalksteen van -179 tot -329 m en nog 1900 m verder ZO ligt
boring 60C-162 met ca 55 m kalksteen van ca -210 tot -265 m NAP. Al is de
lithologische beschrijving vaak vaag, ook het verloop van de ondiepe
bruinkoolhoudende laag Ville wijst op een gelijkmatige daling van de lagen naar
het NW. De conclusie lijkt hier voor de hand te liggen dat bij punt 5, dat min of
meer overeenkomt met boring 60C-83, een oude topografische bult zit in het

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Appendix 2

erosievlak top chalk. Voorheen werd de chalk hier voor het overgrote deel
toegeschreven aan het Paleoceen, Houthem dus. Maar TNO ziet dit nu kennelijk
als Maastricht. De veranderde toewijzing maakt hier het verschil. Hydrologisch
van weinig of geen belang dus (vergelijk REGIS profiel Li-8-zuid).
Punt 6
Moet op dezelfde schol liggen als punten 4 en 5. Hier geen boring bekend. Lijkt
dus geheel een computer interpretatie. Ca 2500 m ZO ligt nog boring 60C-323 in
deze schol, met chalk van -220 tot -300 m. Toegewezen aan Maastricht eerder.
Nu hier 60-70 m Maastricht en 10-20 m Houthem. Kan dus nog goed zijn. Maar
de computer geeft in 2.1. en 2.2. een verschillend diepteverloop tussen boringen
60C-323 en 162 (zie punt 5), waardoor hier verschil ontstaat. Van weinig belang.
Aanhouden 2.2. oké.
Punt 7
Dikte Maastricht hier in REGIS 2.1. zeer plaatselijk ca 30 m geringer dan in
omgeving. In 2.2. is deze anomalie verdwenen. Bij Vaals zijn deze verschillen
juist omgekeerd. Ter plaatse van punt 7 ligt boring 60D-443 met 60 m Maastricht
en ruim 55 m Vaals. Dat komt redelijk overeen met 2.2., zodat 2.1. als foutief
moet worden gezien. Aanhouden 2.2. dus oké.
Punt 8
In 2.2. is hier Vaals bijna 30 m dunner, maar Maastricht juist meer dan 20 m
dikker dan in 2.1. Het dichtst in de nabijheid ligt boring 417, ca 500 m NW van
punt 8, met kalksteen van -35 tot -105 m en daaronder bijna 60 m Vaals tot aan
het Carboon oppervlak (ca -165 m). De dikte Maastricht in 2.1. is duidelijk te
gering en in 2.2. iets aan de dikke kant. Versie 2.2. is voor Maastricht dus iets
beter. Voor Vaals is versie 2.1. duidelijk beter (dikte bijna 60 m) dan 2.2. (ruim
30 m). Dit is te verklaren door de afwezigheid van Vaals ca 1200 m naar het
ONO (boring 418), waar het kalksteen pakket direct op het Carboon ligt. De
computer heeft zich daardoor mogelijk teveel laten beïnvloeden.
Punt 9
Vergelijkbaar met punt 7, alhoewel aan de andere (ZW) kant van de Benzenrade
Breuk. Maastricht in 2.1. meer dan 100 m dik. In 2.2. ruim 70 m. Vaals is in 2.1.
minder dan 10 m en in 2.2. tussen 40 en 50 m dik. Dichtbij ligt boring 60D-650
met ca 55 m Maastricht en ruim 60 m Vaals. Een nog wat dikker Vaals en minder
dik Maastricht zou hier beter zijn, maar 2.1. was abnormaal afwijkend. Ook hier
aanhouden 2.2. dus beter.

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Appendix 2

Punt 10
Ingeknepen tussen Benzenrade Breuk en Revieren Breuk maakt de computer hier
vreemde bokkensprongen die niet kunnen worden onderbouwd met
boorgegevens. Bij Kasteel Revieren is het pakket Maastricht + Vaals tezamen
rond 150 m dik, misschien iets meer. Hiervan zal Maastricht 70 à 75 m dik zijn.
REGIS 2.1. maakt dit zeker 10 m dikker maar 2.2. is met een dikte van 30-40 m
duidelijk anomaal, en het verschil dus ook. Voor Vaals hanteert 2.1. een dikte
van 70 à 80 m (?), maar 2.2. meer dan 100 m, met een navenant verschil van
meer dan 20 meter. Hier is REGIS 2.1. duidelijk te verkiezen boven 2.2. en dit
punt tussen de breuken behoeft aanpassing.
Punt 11
Het probleem is hier het verloop van de Kunrade Breuk. De computer weet hier
geen weg mee. Mede op grond van een aantal nieuwe boringen werd door Van
Rooijen al een herinterpretatie gemaakt van het verloop van deze breuk, waarbij
de bochtige aansluiting van voorheen onderscheiden breukdelen bij punt 11 niet
nodig is en in plaats daarvan een “en echelon” verloop van de breukdelen
ongeveer parallel aan elkaar werd voorgesteld. De WZW-ONO verbinding net
door de kerk van Klimmen komt dan te vervallen en in plaats daarvan lopen de
laaggrenzen in zuidoostelijke richting relatief sterk omhoog tussen de
breukdelen. Eerder werd dit met TNO besproken bij de REGIS kartering. Bij
punt 11 is basis Tongeren aannemelijk bij ca +90 m, basis Maastricht bij +10 à
+20 m. Aken is (waarschijnlijk) afwezig. Top Carboon (basis Vaals) is moeilijk
vast te stellen. Patijn geeft hier, bij gebrek aan gegevens, geen duidelijkheid en
de Kunrade Breuk lijkt in ’t geheel geen effect op Top Carboon te hebben in de
kaart uit 1961. Aannemelijk is dat het Carboon oppervlak ook sterk omhoog
loopt naar het ZO tussen de breukdelen hier en dat bij punt 11 een Top Carboon
verwacht kan worden van rond -70 m of hoger. De dikte van Vaals komt in dat
geval in de orde van 80 meter en Maastricht zou 70 à 80 m dik zijn. Maar veel is
hier nog speculatief zonder aanvullend onderzoek.
Punt 12
Het gaat hier, bij Hoeve Lindelauf te Voerendaal, weer om de verschillen in
dikten Vaals en Maastricht tussen REGIS 2.1. en 2.2. Niet ver af ligt boring
62B391, maar deze is summier en onduidelijk beschreven. Omdat het effect van
de Kunrade Breuk ook hier onduidelijk is blijft de geologische situatie nogal
speculatief. De waarschijnlijke dikten zijn voor zowel Maastricht als Vaals
tussen 55 en 60 meter. De interpretatie REGIS 2.1. moet dan ook worden
verworpen en 2.2. kan worden aangehouden.

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Appendix 2

Punt 13
Een verschil in dikte Maastricht van 20-30 m langs de grens met Duitsland.
REGIS 2.2. laat hier Maastricht verdwijnen. Maar er is zeker nog (veel)
kalksteen en ook verder zuidelijk, zeker op de grotere hoogten. Dat wordt dan
Gulpen genoemd, maar het onderscheid is moeilijk. Hier net in de faciësovergang
van Gulpen in het zuidwesten naar Vaals verder noordoostelijk, waardoor
dikteverhoudingen gecompliceerd worden. De Maastricht dikte van 40-50 m ZO
van punt 13 (2.1.) is niet te onderbouwen en dat geldt dus ook voor het verschil
in dikte. Beter om hier het totale kalksteen pakket te modelleren voor
hydrologisch onderzoek.
Punt 14
Dikten Vaals 80-90 m in 2.1. en 50-60 m in 2.2. Dikten Aken hier 0 m (2.1.) en
rond 30 m (2.2.). Kennelijk is het onderste deel van het hier ruim 80 m dikke
pakket zand met kalksteeninschakelingen nu door TNO aan Aken toegewezen
i.p.v. aan Vaals. Kimpe (1961) beschouwt het pakket van de
kalksteeninschakeling en het onderliggende groene, glauconiethoudende zand als
Vaals (boring 504, Geulle, ca 500 m NNW van punt 14) en er is weinig reden om
daarvan af te wijken. De herziening van REGIS 2.2. is dus discutabel, maar mag
voor het hydrologisch model geen verschil maken.
Punt 15
Bij Spaubeek. Ca 400 meter NNO van boring 60C-373. De Benzenrade Breuk
ligt op de kaart Kimpe (1961) bijna 300 m ten noordoosten van dit punt en ook
aan maaiveld zal de breuk waarschijnlijk nog NO van dit punt liggen i.p.v.
zuidwestelijk daarvan zoals in REGIS aangegeven. Hoe dan ook lijkt deze breuk
hier weinig of geen effect meer te hebben. Het probleem ligt hier blijkbaar in de
dikte Vaals. In REGIS 2.1. is deze 10 à 20 m, in 2.2. net boven 40 m. Maar bij
gebrek aan boorgegevens lijkt een dikte van 30 m of iets meer hier en verder
noordwestelijk een redelijke aanname. Het verschil bij punt 15, dat
waarschijnlijk ook ZW van de breuk ligt, lijkt dus niet relevant. Wel zijn er
aanwijzingen dat de zone waarin de kalksteen direct op Carboon ligt, rond 2½
km ZO van punt 15, (aanmerkelijk) groter is dan in de kaart dikte Vaals 2.2. is
aangegeven. De zone strekt zich mogelijk uit van boring 418 via boring 390 (?)
tot bij de boring 60C-839, die destijds juist werd gemaakt i.v.m. de mogelijkheid
van het omhoog komen van mijnwater naar het dekterrein, maar rond 10 meter
boven het Carboonoppervlak moest worden gestopt.

Na-ijlende gevolgen steenkolenwinning Zuid-Limburg
WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

Appendix 2

Punt 16
Vaals is hier kennelijk in 2.2. tussen 10 en 20 meter dikker dan in 2.1. Maar
Aken komt hier niet voor en bij Maastricht is geen verschil tussen 2.1. en 2.2.
Basis chalk hier rond -75 m (klopt in 2.2. en 2.1.). Dikte Vaals in 2.2. ca 60 m, in
2.1. rond 47 m. Basis Vaals ca -137 m in kaart Top Carboon TNO. Klopt dus
aardig met 2.2. Waarschijnlijk eerdere Top Carboon kaart afwijkend. REGIS 2.2.
dus aanhouden.
Punt 17
Het gaat hier kennelijk om de dikte Vaals. Omdat de Top Carboon hier onzeker
is valt, met een basis kalksteen van rond +60 m, slechts een globale uitspraak te
doen over de dikte van Vaals. Bij een aangenomen basis Vaals van -50 m zou dat
110 m moeten zijn. Dat komt beter overeen met REGIS 2.2., maar groot is het
verschil met 2.1. niet.
Punt 18
Geen Maastricht en wel of geen Vaals. Daar draait het hier om. Punt 18 ligt 500
m ZZW van boring 62B-351, waar geen Maastricht werd gevonden maar wel een
dunne laag Vaals (ca 7 meter). Maar ca 1250 m NNO van punt 18 en ruim 750 m
NNO van boring 351 liggen de boringen ’t Loon, met iets meer dan 20 meter
Maastricht en geen Vaals. Nog eens 650 m verder NNO ligt boring 279, met
meer dan 20 m (mogelijk rond 27 m ?) Maastricht en daar is een Vaals dikte van
rond 15 m aannemelijk. Ook de boring HLN2, op het ABP terrein Heerlen, heeft
15 m Maastricht terwijl in REGIS 2.2. nog 0-10 m dikte wordt gegeven.
Kennelijk is de boring bij Hoeve Terworm wel meegenomen in REGIS 2.2. maar
de boringen ’t Loon en HLN2 niet. Dit behoeft aanpassing. Ook de opwaartse
boring (820) vanuit het mijngebouw, 350 m WNW van boringen ’t Loon, geeft
overigens wel 20 m Maastricht maar geen Vaals. Bij de voormalige
Vroedvrouwenschool (Park Imstenrade) ligt boring 439 waar het Carboon direct
wordt overdekt door Tongeren. Hier zit dus een gat in Vaals, maar 2.2. geeft hier
nog 10-20 m van deze formatie.
Punt 19
Dikten Vaals ruim 70 m (2.1.) en 40-50 m (2.2.). Dikten Aken 0-10 m (2.1.) en
bijna 20 m (2.2.). Het probleem hier bij Vliek, Ulestraten, tussen de Geulle Breuk
en het verlengde van de Schin op Geul Breuk, lijkt te liggen in de snelle omslag
van het dikteverschil in Aken tussen REGIS 2.1. en 2.2. Maar in deze schol nam
de dikte Aken in 2.1. van ZO naar NW af tot 0 m bij de A2 en neemt die in deze
richting juist toe in 2.2. Vandaar dat het verschil bij punt 19 snel oploopt. Net als

Na-ijlende gevolgen steenkolenwinning Zuid-Limburg
WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

Appendix 2

bij punt 14 gaat de diktetoename hier van ZO naar NW gepaard met de
dikteafname van Vaals in de nieuwe TNO interpretatie. Ook hier mag dit
hydrologisch van weinig of geen belang zijn.
Punt 20
Een geïsoleerd voorkomen van Aken in dikte boven 50 meter. Ten westen,
noordwesten en dichtbij ten zuiden zijn dikten van net boven 30 m aanwezig.
Ten noordoosten ligt een systeem van breuken. Weinig houvast hier. Maar ca
200 m ZZO van punt 20 ligt boring 62B-492, met Vaals tot rond 77 m diepte (=
ca +65m). Daaronder ligt een pakket grijze zandige klei en kleiig zand tot 142 m
diepte (= 0 m NAP) dat als Aken kan worden genomen o.a. op grond van
paleontologisch onderzoek. Dikte zou dan inderdaad 65 m bedragen. Het
probleem is echter dat de Top Carboon in deze boorbeschrijving niet is
aangegeven en het overigens wat speculatieve Carboon oppervlak in de kaart
Patijn rond +25 m zou moeten liggen. Daarmee zou de Aken dikte worden
gereduceerd tot rond 40 m en de beschrijving van dit traject in de boring kunnen
slaan op de verweerde Carboonlaag i.p.v. op Aken. De sterk afwijkende dikte in
REGIS 2.2. zou daarmee deels komen te vervallen, maar onzekerheid blijft.
Punt 21
Het zal hier gaan om de Formatie van Maastricht. Maar ook aan de toewijzing
aan Maastricht versus Houthem. In dit gebied komt ca 20 à 30 meter kalksteen
voor die door Kimpe (1961) grotendeels wordt geïnterpreteerd als Maastricht.
Ook TNO zag hierin vooral Maastricht (profiel Li-8-zuid). Ten westen van de
nabijgelegen NNW-ZZO lopende “aftakking” van de Heerlerheide Breuk
interpreteerde TNO de kalksteen echter ineens als Houthem, terwijl het
dikteverloop van het kalksteenpakket en het toch redelijk consistente verloop in
diepteligging van het pakket hier geen aanleiding voor lijken te geven. Nieuwere
boringen zijn hier niet bekend. Ter plaatse van punt 21 is er dan ook geen
aanwijzing voor het “hoog” in Bottom Houthem (en ook niet in Bottom
Tongeren!) en de wulpse kronkelingen in de dieptelijnen van Bottom Houthem.
Ook is er geen grond voor het gat in Maastricht ca 1500 meter ZZO van punt 21
(hier precies boring 60D-68!) waar Houthem juist 20-30 m dik zou zijn volgens
REGIS 2.2. De diktetoewijzingen maken de zaak in dit gebied zo gecompliceerd,
terwijl het kalksteenpakket eigenlijk juist redelijk gelijkmatig naar het
noordwesten in diepte toeneemt. Voor model van belang dus slechts Bottom
Maastricht en Bottom Tongeren.

Na-ijlende gevolgen steenkolenwinning Zuid-Limburg
WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

Appendix 2

Conclusie
Concluderend kan worden opgemerkt dat REGIS 2.2. een aantal verbeteringen
bevat t.o.v. 2.1. Maar op een aantal plaatsen is ook revisie van 2.2. noodzakelijk.
De verschillen mogen dan soms voor hydrologisch onderzoek van minder belang
zijn, maar hebben stratigrafisch en structureel wel degelijk betekenis.
Aanvullende opmerkingen
Naast de boven besproken aandachtspunten kunnen de volgende opmerkingen
worden gemaakt:
Rond coörd. 192.500-328.000 valt, net ten zuiden van de Heerlerheide Breuk, de
anomaal grote dikte van Maastricht op in REGIS 2.2. en in 2.1. Geen verschil
van betekenis dus tussen de beide versies, maar deze dikteanomalie is discutabel
en waarschijnlijk ontleend aan de boorinformatie van boring 60D-287. De
boorbeschrijving geeft “mergel” aan van 92-195 m diepte. Maar mergel werd in
deze oude steenkoolboringen als beschrijving vaak gebruikt voor wat verhard
kleiig zand. Beter verantwoord lijkt het dan ook om hierin Kimpe (1961) te
volgen en Maastricht te interpreteren van 92-173 meter diepte.
Rond coörd. 183.500-332.000 is Maastricht anomaal dun in zowel 2.1. als 2.2.
Ruim 500 m naar het NNW ligt boring 60C-190, ook nog in de zone met geringe
Maastricht dikte. Van de ca 80 m beschreven kalksteen werd door Kimpe slechts
de onderste 30 meter als Maastricht onderscheiden. Het pakket daarboven werd
gezien als Houthem. Maar Kimpe laat de dikte Maastricht (geleidelijk)
teruglopen tot 0 meter verder noordwestelijk bij de Maas, en toenemen ten koste
van Houthem naar het zuidoosten, in tegenstelling tot de REGIS interpretatie,
waardoor deze anomalie van Maastricht dikte ontstaat. En waar de dikte
Maastricht gering is laat REGIS (2.1. en 2.2.) de dikte Houthem anomaal groot
zijn. Het gaat hier dus weer om een discutabele stratigrafische toewijzing van het
kalksteenpakket en voor het model zou dit van minder belang hoeven te zijn,
zoals ook bij andere aandachtspunten al is opgemerkt.
Bij coörd. 187.300-332.700 ligt een dikteanomalie voor Tongeren. Maar ook ligt
hier boring 60C-206, met minimaal een Tongeren dikte van -293 tot -378 m,
alhoewel Kimpe hier een dikte van meer dan 200 m aangeeft. Maar de Tongeren
dikte is 800 m ten noorden van boring 206 zeker niet minder. Hier ligt boring
165, met minimaal Tongeren van -320 tot -420 m (Kimpe: 245 m dik) maar daar
geeft REGIS 2.2. een dikte van 60 m aan. Kortom, deze anomalie is volledig
ongefundeerd en de stratigrafie is hier nog verre van duidelijk.

Na-ijlende gevolgen steenkolenwinning Zuid-Limburg
WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

Appendix 2

De breuken zijn op de verschillende kaarten nog niet gelijk aangegeven. In
REGIS 2.2. kaarten Bottom Vaals en Maastricht wordt in dieptelijnen een
breukje gesuggereerd dat van rond coörd. 187.500-322.500 naar het NNW loopt
en daar aansluit op de ingetekende breuk. Dit is de interpretatie die door Van
Rooijen destijds tijdens het REGIS onderzoek aan TNO werd voorgelegd op
grond van een kartering in dit gebied van Top Kalksteen. De breuk moet dan wel
ook in de 2.2. kaarten worden ingetekend i.p.v. het oude breukverloop en
eveneens op kaarten van de andere niveaus moeten worden aangepast. In de
nieuwste kaart Bottom Tongeren is deze aanpassing overigens al duidelijk
verwerkt.
Bij aandachtspunt 11 is de discussie over het verloop van de Kunrade Breuk al
aan de orde geweest. De onnodige, bochtige breukverbinding door de kerk van
Klimmen is op de meeste aangeleverde kaarten nog te zien, maar op de nieuwste
kaart Bottom Tongeren 2.2. correct verlaten. Verdere aandacht hiervoor is nog
nodig.
Rond de Julia worden kronkelingen in de kaart Bottom Tongeren getoond die
wel erg afwijken van de hier goed gefundeerde kaart Patijn (1961). Ook grote
verschillen hier met de meest recente TNO kaart Top Carboon, terwijl Tongeren
hier toch direct op Carboon ligt.
Bij coörd. 194.300-322.450 valt de Top Carboon (laatste kaart TNO) net ten
noordoosten van de Benzenrade Breuk weg tot -100 m. Hier ligt boring Hoeve
Terworm, met Top Carboon op -16 m. Deze boring is kennelijk nog niet
meegenomen in kaart TC maar wel in de REGIS kaart Bottom Tongeren. Ook ca
2250 m NO van deze locatie zit tegen de Heerlerheide Breuk een onverantwoord
gat in de TC kaart met een diepte van rond -100 m.

Klimmen, 15 augustus 2015.
Drs. P. van Rooijen.

Appendix 3

Na-ijlende gevolgen steenkolenwinning
Zuid-Limburg
Final report
on the results of the working groups
5.2.4 - groundwater quality
5.2.5 - groundwater quantity
Modell scenarios - calculated heads for worst case
and best case scenarios

by
Projectgroup
"Na-ijlende gevolgen van de steenkolenwinning in ZuidLimburg"
(projectgroup GS-ZL)

on behalf of
Ministerie van Economische Zaken - The Netherlands

Aachen (D), Deventer (NL), 31. August 2016
(Rev. a: 02. December 2016)

Na-ijlende gevolgen steenkolenwinning Zuid-Limburg
WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

Appendix 3

Appendix 3: Model scenarios - calculated heads for worst case and
best case scenarios

Fig. A3.1:

The Wurm valley with the fixed head zone for the worst case secenario

Na-ijlende gevolgen steenkolenwinning Zuid-Limburg
WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

Fig. A3.2:

Appendix 3

Calculated groundwater head in the Carboniferous – worst case scenario

Na-ijlende gevolgen steenkolenwinning Zuid-Limburg
WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

Fig. A3.3:

Difference in phreatic groundwater head - worst case scenario

Appendix 3

Na-ijlende gevolgen steenkolenwinning Zuid-Limburg
WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

Fig. A3.4:

Increase water pressure second aquifer - worst case scenario

Appendix 3

Na-ijlende gevolgen steenkolenwinning Zuid-Limburg
WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

Fig. A3.5:

Mine water pressure in the Carboniferous - best case scenario

Appendix 3

Na-ijlende gevolgen steenkolenwinning Zuid-Limburg
WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

Fig. A3.6:

Difference in phreatic groundwater table - best case scenario

Appendix 3

Na-ijlende gevolgen steenkolenwinning Zuid-Limburg
WG 5.2.4 - groundwater quality and WG 5.2.5 - groundwater quantity Final report

Fig. A3.7:

Appendix 3

Increase of groundwater head in the second aquifer - best case scenario

Appendix 4

Na-ijlende gevolgen steenkolenwinning
Zuid-Limburg
Final report
on the results of the working groups
5.2.4 - groundwater quality
5.2.5 - groundwater quantity
Bow-Tie-diagram change groundwater quality

by
Projectgroup
"Na-ijlende gevolgen van de steenkolenwinning in ZuidLimburg"
(projectgroup GS-ZL)

on behalf of
Ministerie van Economische Zaken - The Netherlands

Aachen (D), Deventer (NL), 31. August 2016
(Rev. a: 02. December 2016)

5.2.4 Groundwater quality
Threats

Upwards flow
hydraulic windows

Upwards flow
drillings and shafts

Prevention Controls

Regulation of
groundwater
extraction in
potential impact
area Ia/b

Regulation of
groundwater
extraction in
potential impact
area Ia/b

Change
configuration
wells in potential
impact area Ia /b

Research hydr .
connections in
the potential
impact areas

Monitoring
groundwater level

Monitoring
groundwater level

Hazard/Top Event

Monitoring
mine water
level

Monitoring
mine water
level

Monitoring
groundwater
quality

Monitoring
groundwater
quality

HAZARD
Rising mine water

Recovery Controls

Detailed
monitoring ground
water potential
impact areas

Development
Change wells in Reduce extraction Replace extraction
early warning
potential impact in potential impact in potential impact
system (water
area I a /b
area I a /b
area I a/b
motion)

Detailed
monitoring ground
water potential
impact areas

Development
Change wells in Reduce extraction
early warning
potential impact in potential impact
system (water
area I a/b
area I a/b
motion)

Regulation of
groundwater
extraction in
potential impact
area Ia/b

Monitoring
groundwater level

Monitoring
mine water
level

Monitoring
groundwater
quality

Replace extraction
in potential impact
area I a/b

Consequences

Extracted water
(drinking water ) quality
influenced

Extracted water
(industrial food
production ) quality
influenced

TOP EVENT
Changing quality of deep
groundwater

Regional
development
planning area in
potential impact
areas I/II

Upwards flow
unknown hydraulic
windows

Escalation Controls

Awareness-raising

Future applicability of
groundwater for
human use influenced

Communication

Social unrest

App. 4

Appendix 5

Na-ijlende gevolgen steenkolenwinning
Zuid-Limburg
Final report
on the results of the working groups
5.2.4 - groundwater quality
5.2.5 - groundwater quantity
Bow-Tie-diagram wetting

by
Projectgroup
"Na-ijlende gevolgen van de steenkolenwinning in ZuidLimburg"
(projectgroup GS-ZL)

on behalf of
Ministerie van Economische Zaken - The Netherlands

Aachen (D), Deventer (NL), 31. August 2016
(Rev. a: 02. December 2016)

5.2.5 Groundwater quantity
Threats

Prevention Controls

Hazard/Top Event

Recovery Controls

Escalation
Controls

Consequences

Immediate
measures
(drainage)

Wet cellars

HAZARD
Rising mine water

Upwards flow from
deeper aquifer

Develop early
warning system

Restrictions
catchment area

Monitoring
groundwater
level

Monitoring
mine water
level

Detailed
monitoring groundwater potential
impact areas

Construction
guidelines

Awareness-raising

Communication

TOP EVENT
Upwards flow drillings
and shafts

Upwards flow unknown
hydraulic windows

Monitoring
groundwater
level

Develop early
warning system

Develop early
warning system

Geoh . research

Monitoring
groundwater
level

Monitoring
mine water
level

Wetting stream
valleys

Social unrest

Monitoring
mine water
level

App. 5

200000

5

210000

220000

Legend
!

!

!

340000

190000

340000

180000

National border
Project area

Mining concessions South Limburg

Mining concessions Belgium and Germany
Tectonic fault top surface
Potential impact areas

Changing quality of deep groundwater
average case scenario
worst case scenario

330000

average case scenario
worst case scenario

b

legend

a

mining concessions, tectonic faults

Rev.

02.12.2016
09.08.2016

Description

Date

320000

320000

base map: TOP25raster, sheets 68D Sittard, 68G Brunssum, 69B Maastricht, 69E Heerlen
© Het Kadaster, Apeldoorn

Ministerie van Economische Zaken

"Na-ijlende gevolgen steenkolenwinning Zuid-Limburg"

Projectgroup GS-ZL

Jean-Bremen-Straße 1-3, D-52080 Aachen Tel.: +49 241/70516-0 Fax: +49 241/70516-20

Naming: Na-ijlende gevolgen steenkolenwinning Zuid-Limburg,
WG 5.2.4/5.2.5 - groundwater quality / quantity - final report

Drawing No.: 107-17-001b
Edited:

Name: P. Rosner
Date: 31.08.2016

180000

190000

200000

210000

Drawn:

Name: M. Paffen
Date: 31.08.2016

Reviewed:

Name: M. Heitfeld
Date: 31.08.2016

Scale
1:125.000
Plan 1

220000

310000

Potential impact areas, overview
310000

Y:\GIS\1_Uebersichtsprojekte\Niederlande\_Anlagen\5_2_4_Ground_water\plan_01_overview_v2_Rev_a.mxd

330000

Wetting stream valleys