Local- and Repository-Scale Hydrodynamic Modeling for Geoscientific Characterization of a Candidate ILW/HLW Repository S
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/RFDODQG5HSRVLWRU\6FDOH+\GURG\QDPLF0RGHOLQJIRU*HRVFLHQWLILF&KDUDFWHUL]DWLRQRI D&DQGLGDWH,/:+/:5HSRVLWRU\6LWHLQ1RUWKHUQ6ZLW]HUODQG Ulrich Kuhlmann1, Paul Marschall2 1 TK Consult AG, CH-8050 Zürich, Switzerland 2 National Cooperative for the Disposal of Radioactive Waste, CH-5430 Wettingen, Switzerland 6,7('(6&5,37,21 Recent investigations within the scope of the Swiss program for disposal of high- and intermediate-level radioactive waste have concentrated on the Opalinus Clay located in the =UFKHU:HLQODQG of Northern Switzerland (Figure 1). The candidate host rock, a moderately over-consolidated claystone, is part of a thick sequence of Mesozoic and Tertiary sediments in the Molasse Basin with exceptional isolation properties resulting from its low hydraulic conductivity and homogeneity. The geoscientific information stems from a comprehensive site investigation program, including a 1000 m deep exploratory borehole at the village of Benken and a 3-D seismic survey of the surrounding area [1]. Hegau Bo
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Opalinus Clay investigation area in northeastern Switzerland
Location of profiles shown in next figure Exploratory borehole Benken
3D seismic survey area (Zürcher Weinland)
Border Switzerland – Germany
)LJXUH. Principal tectonic units of Northern Switzerland and adjacent areas. The Opalinus Clay investigation area lies in the tectonically stable Tabular Jura and is predominately covered by the sediments of the Molasse Basin. Also shown is the 3D seismic investigation area in the Zürcher Weinland and the location of the borehole at Benken.
1
Depth [m]
Hydraulic Head
LithoLog
Lithostratigraphy
Hydraulic Conductivity [m s -1]
[m asl] 404 m 500
10 -13
700
10 -11
10 -9
10 -7
Peat and Pleistocene lacustrine deposits 68.0
Till
Lower Freshwater Molasse
199.0
Bohnerz Formation (pisolitic iron ores)
Quaderkalk/ Massenkalk
M3
M3
Mittlere Malmmergel Wohlgeschichtete Kalke to Glaukonit-Sandmergel
M2
538.8 Murchisonae Beds
M4
M4
451.2 Anceps Oolite to Wedelsandstein Formation
M2 406
MD1
MD1
D2
D2
342
O4
O4 O5
Opalinus Clay
? O6
652.0 692.3
Jurensis Marls to Psiloceras Beds
O5 O6
O7 ?
L1
O7 L1
K1
Rhät to Gipskeuper
K1
465 K2
K2
?
811.4
Lettenkohle Trigonodus Dolomite
MK2 406 MK1
MK2
MK1
Hauptmuschelkalk Anhydrite Group (with rock salt)
975.6 983.3 1007.0
Wellengebirge Buntsandstein
B1
B1
Basement (crystalline rocks, older than 300 Ma) Altitude: 404.3 m asl
Long-term monitoring (status: March 2001)
? uncertain (see Nagra 2002a)
)LJXUH. Lithological sequence in the Benken borehole and the measured hydraulic heads and hydraulic conductivities The host rock formation is overlain and underlain by further thicknesses (100 to 150 m) of clay-rich sediments, also with good isolation properties. Above and below these clay-rich formations, the sequenc
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