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The Irish Midlands have a unique landscape resulting from the retreat of the last ice age and subsequent post glacial deposition, forming extensive areas of raised peat bog. These natural resources have been used extensively for the supply of energy from domestic peat cutting to the generation of electricity on a large scale. In order to manage these vast areas there is a need for an accurate method to assess the remaining reserves and to aid future production planning. To achieve this a LIDAR survey was carried out to provide elevation data over the entire infrastructure, and accurate peat thickness data is required for approximately 35,000Ha of production bog. GPR was used to provide this thickness information and the accuracy of the data was confirmed by peat probing. The survey showed three distinct GPR signatures associated with the presence of the three main sub-peat soils, namely gravels, plastic clays and shell marls, as well as from internal peat layers. This paper describes the work carried out at Blackwater Bog, an area of 1,890Ha of raised bog east of the River Shannon in County Offaly and presents examples of the different GPR responses.

This paper presents the results of field geophysical testing and laboratory testing of peat from Carn Park and Roosky raised bogs in the Irish Midlands. The motivation for the work was highlight the importance of these areas and to begin to attempt to understand the reasons for the failure of the bogs despite them having surface slopes of some 1°. It was found that the peat is typical of that of Irish raised bogs being up to 8 m thick towards the "high" dome of the bogs. The peat is characterised by low density, high water content, high organic content, low undrained shear strength and high compressibility. The peat is also relatively permeable at in situ stress. Geophysical ERT and GPR data shows a clear thinning of the peat in the area of the failures corresponding to a reduction in volume from dewatering by edge drains / peat harvesting. This finding is supported by detailed water content measurements. It was also shown that the peat base topography is relatively flat and indicates that the observed surface movement has come from within the peat rather than from the material below the peat. Potential causes of the failures include conventional slope instability, the effect of seepage forces or the release of built up gas in the peat mass.Further measurements are required in order to study these in more detail.

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