Permeability Profiles in Granular Aquifers Using Flowmeters in Direct-Push Wells by Daniel Paradis 1,2 , Ren´ e Lefebvre 2 , Roger H. Morin 3 , and Erwan Gloaguen 2 Abstract Numerical hydrogeological models should ideally be based on the spatial distribution of hydraulic conductivity (K ), a property rarely defined on the basis of sufficient data due to the lack of efficient characterization methods. Electromagnetic borehole flowmeter measurements during pumping in uncased wells can effectively provide a continuous vertical distribution of K in consolidated rocks. However, relatively few studies have used the flowmeter in screened wells penetrating unconsolidated aquifers, and tests conducted in gravel-packed wells have shown that flowmeter data may yield misleading results. This paper describes the practical application of flowmeter profiles in direct-push wells to measure K and delineate hydrofacies in heterogeneous unconsolidated aquifers having low-to-moderate K (10 −6 to 10 −4 m/s). The effect of direct-push well installation on K measurements in unconsolidated deposits is first assessed based on the previous work indicating that such installations minimize disturbance to the aquifer fabric. The installation and development of long-screen wells are then used in a case study validating K profiles from flowmeter tests at high-resolution intervals (15 cm) with K profiles derived from multilevel slug tests between packers at identical intervals. For 119 intervals tested in five different wells, the difference in log K values obtained from the two methods is consistently below 10%. Finally, a graphical approach to the interpretation of flowmeter profiles is proposed to delineate intervals corresponding to distinct hydrofacies, thus providing a method whereby both the scale and magnitude of K contrasts in heterogeneous unconsolidated aquifers may be represented. Introduction It is generally recognized that the hydraulic conduc- tivity (K) heterogeneity of an aquifer controls ground- water flow and solute transport. Failure to adequately account for this heterogeneity is also known to be one of the main causes of remediation failures (de Marsily et al. 2005). In heterogeneous aquifers, the spatial dis- tribution of hydraulic properties may be complex and numerous direct and indirect estimates may be required to 1 Corresponding author: Natural Resources Canada, Geological Survey of Canada, Qu´ ebec, Canada; Daniel.Paradis@RNCan-NRCan. gc.ca 2 Institut National de la Recherche Scientifique, Centre Eau Terre Environnement, Qu´ ebec, Canada. 3 U.S. Geological Survey, Denver, CO, USA. Received March 2010, accepted August 2010. Journal compilation  2010 National Ground Water Association. No claim to original US government works. doi: 10.1111/j.1745-6584.2010.00761.x develop a realistic understanding of the hydrogeological system (Ouellon et al. 2008). Although the spatial defi- nition of aquifer heterogeneity has to rely in large part on the use of indirect data, often acquired from surface geophysical surveys (Rubin and Hubbard 2005), numer- ous direct measurements are also required to define the properties of individual lithologic units (hydrofacies) hav- ing a distinctive range of hydraulic conductivities (Frei et al. 2009). Therefore, a practical means of adequately quantifying the spatial distribution of hydraulic proper- ties under the constraints of a limited amount of time and resources is essential as part of a hydrologic characteriza- tion program aimed at identifying and defining aquifer K heterogeneity. Borehole flowmeter measurements obtained during pumping can efficiently determine the vertical distribu- tion of K in fractured rocks (Morin et al. 1988; Molz et al. 1989; Hess et al. 1992; Hanson and Nishikawa 1996; Paillet 1998; Crisman et al. 2001). However, previous 534 Vol. 49, No. 4–GROUND WATER–July-August 2011 (pages 534–547) NGWA.org