GEOSTATISTICAL ANALYSIS OF THE BORDEN AQUIFER HYDRAULIC CONDUCTIVITY FIELD

A total of 11 vertical cores spaced 1 m apart along a single transect were extracted from the Borden aquifer at a location 60 m north-northe ast from the site studied by Sudicky previously. Examination of these cores shows the upper 1.5-2.0 m of the aquifer to be comprised of rela tively unstructured, fine to medium sands, underlain by a 0.1-0.8 m th ick peaty layer and a 0.1 m thick organic-rich horizon. Between depths of 3.05 and 6.10 m the aquifer is comprised of clean, horizontally be dded fine to medium sands similar to those examined by Sudicky previou sly. Statistical analysis of 642 subsamples of 5 cm length from this i nterval suggests that the permeability data may follow a log-normal di stribution, with a mean In-transformed permeability (m(2)) of -25.67 a nd a variance of 0.585. No consistent trend with depth was detected fo r ln-k, or for the mean and variance of ln-k on a core by core basis. Exponential, spherical, and Gaussian models all provided excellent fit s to the vertical experimental variogram calculated using the classica l estimator without the removal of outliers. These fits produced corre lation scales ranging from 0.16 to 0.23 m. Of the three theoretical mo dels, only the Gaussian model produced a reasonable fit to the horizon tal experimental variogram with a correlation scale of 4.8 m. A linear model was also found to fit the experimental variogram data well. In comparison with earlier results of Sudicky, and Woodbury and Sudicky, it can be concluded that similar deposits were examined in this study, particularly with respect to correlation structure. On the basis of s tatistical tests, however, it cannot be concluded that the mean and va riance of ln-k are stationary over the 60 m distance between the cores examined in this study and those of Sudicky. The results of this stud y indicate that the Borden hydraulic conductivity held is relatively u niform over the scale examined, but that it cannot be characterized by a single, spatially invariant statistical distribution.