Quarterly Journal of Engineering Geology, 29, $39-$57. 0481-2085/96 $07.00 © 1996 The Geological Society The Geology and Hydrogeology of the Sellafield Area Groundwater chemistry in the Sellafield area: a preliminary interpretation

Hydrochemical investigations form an important part of the Nirex Site Characterization Programme at Sellafield. They support the development of a conceptual hydrogeological model of the area as it is now, are the main basis for reconstructing the palaeohydrogeological evolution of the area over the recent geological past (which will assist predictions of future evolution) and allow characterization f the baseline hydrochemical conditions in the potential repository rock volume. The deep hydrochemistry of the area of interest is dominated by its location on the margin of the East Irish Sea Basin. To the west of the potential repository zone, the influence of basinal brines has been a feature of the deep sedimentary ocks and the Borrowdale Volcanic Group (BVG) basement for a considerable period of geological time. Th