RD&D-Programme 2004 - SKB

Table 1. Current status of site-specific key issues identified prior to the start of the site
investigation in Forsmark.
Key issue
The vertical extent and shape of the
tectonic lens.
Possible ore potential at depth.
Presence of gently-dipping fracture zones.
Possible occurrence of high rock stresses.
Status
Several boreholes have verified a depth in excess of 1,000 metres.
The presumed steep dip of the margins of the lens has been
verified for certain sections, for others investigations remain to
be done before the issue can be settled.
The issue has been studied particularly closely in conjunction with
the holes that have been drilled. No traces of mineralizations and/or
bedrock with ore potential have been detected within the lens. The
issue should therefore be able to be dismissed.
Highly conductive, gently-dipping fractures and fracture zones are
common down to a depth of about 200 metres. Only a few gentlydipping
fracture zones have been found at greater depth.
The measurements made so far have shown relatively high, but not
extreme, rock stresses. Additional measurements are planned in
order to obtain a better overall picture.
A4.2.2 Oskarshamn
The main argument for a site investigation in the Simpevarp area near Oskarshamn was the
combination of bedrock judged to be favourable and the advantages offered by Simpevarp for
industrial establishment in the form of available industrial land and infrastructure, proximity to
Clab and the Äspö HRL, and the planned co-siting of the encapsulation plant. The site investigation
started when the municipal council decided in March 2002 to allow SKB to initiate the
site investigation. The consultation process with the municipality and its working groups had
already started at that time and is well established today.
The investigations were focused on two subareas: The Simpevarp Peninsula with environs
and the Laxemar area west of there. These areas have different geological conditions, and the
investigations are based on somewhat different system solutions for a repository. A siting on
the Simpevarp Peninsula would mean that the surface facilities would also be located there.
A siting in the Laxemar area could entail either that certain above-ground facility parts are
located on Simpevarp (connected by tunnel to the repository) or that the entire facility is placed
in Laxemar.
Questions existed regarding the bedrock on the Simpevarp Peninsula due to a relatively high
frequency of fractures and thereby an uncertainty regarding the space available for a deep
repository. Given the advantages offered by the site in other respects, an investigation was
nevertheless judged to be warranted. The investigations on and around the peninsula started
immediately after the municipality’s decision, and the current situation can be summarized as
follows:
• A detailed geological survey has been performed.
• Three deep cored boreholes (1,000 metres) have been completed on the Simpevarp
Peninsula.
• The investigation area has been expanded to include Ävrö, Hålö and surrounding water
areas.
• A new cored borehole has been completed on Ävrö and an existing one has been made
available for measurements.
The results of the drilling on the Simpevarp Peninsula showed good mechanical and hydraulic
conditions to a great extent, despite a complex mix of different rock types. Based on these
results, it was decided to expand the area in the manner that has been done, since the Simpevarp
Peninsula itself is not considered to offer enough volume for a sufficiently flexible deep
repository solution.
388 RD&D-Programme 2004