Impeller logging and open borehole dilution testing have been used in boreholes across the aquifer under pumped and ambient flow conditions.   These datasets have been interpreted to produce vertical permeability, and in some cases hydraulic head profiles; permeability profiles showed good correlation with those of packer tests . New approaches for the analysis of, and treatment of errors in, borehole dilution and impeller logging data will be presented at the meeting.

The data suggests that high water inflow just below the borehole casing is very common in the confined part of the aquifer and may indicate a laterally continuous, permeable layer probably related to periglacial weathering..  Permeable zones also occur at greater depths across the Chalk aquifer, but these are much better developed in the unconfined aquifer owing to larger flow rates. These data will be incorporated into the ground water flow model of the region, leading to a refinements in the particle tracking analysis used to define well-head protection zones, and predict the behaviour of saline incursion in the aquifer.