18th September 2006

On 25th August David Hood met with Barry Ferguson of the Mourne Heritage Trust (MHT) to salvage 6 core boxes of G3 granite cores from the Silent Valley.

Background:
In the early 1960’s the Electricity Board of Northern Ireland undertook an investigation to determine if the area above and west of the Silent Valley could be used for as a pumped storage scheme to provide hydro-electric power. Twenty six boreholes were drilled into the granite bedrock ( 22 just to the east of Lough Shannagh, 1 near the mouth of Miner’s Hole River and the other 3 on the western side of the Silent Valley reservoir. The cores were stored in boxes (each with 4x3feet sections) and housed for many years in a green Nissen hut between the upper end of the Silent Valley reservoir and Ben Crom dam. The cores were logged in detail by Dr. Jack Preston and Diane Clegg in 1966 from QUB and reinterpreted by David Hood who included a detailed cross-section of the cores in his Ph.D. thesis (see Publications page). Sometime in the 1980’s the cores (and hut) were ‘discarded’ by the Water Service (Belfast Water Commissioners) and the cores dumped in an area east of the main workmen’s storage sheds in the Silent Valley.

These cores represented a very valuable source of geological information about the variation in granite type and composition with depth in the last Eastern Mourne Granite G3. Particularly Borehole 201 was a deep hole from the Miner’s Hole River and was cored to a depth of several hundred feet below datum.

David Hood spent several years trying to locate these cores after the hut and cores ‘disappeared’ from the Silent Valley. Eventually, he received information from the Water Service as to their whereabouts and arranged with the Mourne Heritage Trust to try to salvage some of the material.

The site was partially cleared of whin bushes by the MHT beforehand. The core and boxes were in a terrible state having been piled and dumped on top of each other and left to the elements for many years. The wood on the boxes was completely rotten and fell apart when it was moved. There were many lose cores lying around the site. However, after several hours work enough material was recovered to fill 6 new core boxes that were kindly manufactured by the MHT at the Silent Valley. Core was captured from a number of Boreholes and at various depths, although in many cases it was impossible to estimate the exact depths of cores. In some instances the borehole number and box number was legible inside the box lids but not the core depths. In a few instances core depths were seen on the cores and this helped tie down the approx depth of the core in the rest of that box. A range of different granite types were salvaged ranging from medium grained to very fine grained with both drusy (with some small crystals in vugs) to porphyritic varieties. Some material was captured from Borehole 201 in various parts of the hole, including the deepest part.

A number of photographs were taken on-site before, during and after the project. These are shown here .

It is hoped that some arrangement can be made between the Water Service and Mourne Heritage Trust to clean up, possibly slab and polish and put some of the cores on display in the Silent Valley. They represent an important part of the industrial and geological heritage of the Eastern Mourne granites and should be conserved.