Publication Laka-library:
OPERA. Geological and geohydrological characterization of the Boom clay and its overburden

AuthorTNO, GJ.Vis, JM.Verweij
DateFebruary 2014

From the publication:

Geological and geohydrological characterization of the Boom Clay and its overburden

This desk-study presents the geological and geohydrological characteristics of a clay layer in the Dutch subsurface (Boom Clay, officially Rupel Clay Member). New depth and thickness maps show that the Rupel Clay Member is present in nearly the whole Dutch subsurface, up to a depth of ~1500 m. The thickness varies around a mean of 65 m. In the proposed disposal concept for OPERA, the repository depth is 500 meter with a clay thickness of 100 meter. Therefore for this study, a clay layer deeper than 400 m and thicker than 100 m has been selected. In the Netherlands three locations have been identified: Roer Valley Graben (Noord Brabant), Zuiderzee Low (Gelderland) and North Netherlands (Friesland). The Rupel Clay Member is not a homogeneous clay; both vertical and lateral grain-size trends are present. The calculated permeability of the clay is lowest in the north of the Netherlands and higher and more variable in the south and southeast and it generally decreases with increasing depth. The Roer Valley Graben is the only focus area where fresh groundwater flow extends to a depth of more than 400 m and may reach the Rupel Clay Member. Faults are known to cut through the clay layer, but are still poorly understood in the focus areas. A series of knowledge gaps has been identified, such as the mismatch of lithostratigraphic nomenclature between the Netherlands and neighbouring countries, measured geo(hydro)logical properties of the Rupel Clay Member and deposits above and below it in the focus areas, fault locations and properties, and groundwater flow measurements in the clay.

Deze bureaustudie presenteert de geologische en geohydrologische eigenschappen van een kleilaag in de Nederlandse ondergrond (Boomse Klei, officieel Rupel Klei Laagpakket). Nieuwe diepte- en diktekaarten laten zien dat het Rupel Klei Laagpakket in vrijwel de hele Nederlandse ondergrond aanwezig is tot een diepte