Re-examination of aquitard intergrity using new methods

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Contamination of aquifers is an increasing problem globally and in many regions. The degree and timing of the contamination is governed by the characteristics of the aquitard (low permeability layer) that overlies the aquifer. Aquitard integrity refers to the capability of the aquitard to protect the underlying aquitard from contamination. This research has two goals: the first is to develop a new method for determining aquitard integrity by acquiring information from a single drill hole at each study location, and the second is to apply this method in an investigation of two important clayey aquitards: one located in southwestern Ontario and the other in Winnipeg. The new method involves a combination of four activities: rotosonic drilling, installation of a new type of monitoring device in the rotosonic holes, squeezing of porewater from the rotosonic cores, and the use of x-radiography of cores. Much information can be obtained from the same hole because of recent advances in drilling / coring technology and advances in multilevel monitoring technology. The three main data types are detailed hydraulic head profiles, environmental isotopes (i.e. tritium, 18O, 2H, carbon-14) and X-radiography of aquitard cores. X-radiography is a technique that has existed for many decades but it has been little used in studies of aquitard integrity and I believe it will add much value. Other more conventional data will also be obtained from the holes, however the major new insights and overall value concerning aquitard integrity are expected to come from the above- mentioned combination. Rotosonic drilling provides large-diameter core at reasonable cost in essentially all types of nonindurated deposits and the core holes are easily used for installation of multilevel monitoring systems for head profiles. Also, the cores provide water by squeezing for isotope and other analyses.