Comparison of Hydraulic Conductivity Determinations in Co-located Conventional and Direct-Push Monitoring Wells

Abstract : Determination of the hydraulic conductivity of a formation is needed for site assessment and remediation. This project examined whether direct-push (DP) monitoring wells can provide a measure of formation hydraulic conductivity similar to that provided by convention-ally installed hollow-stem auger (HSA) wells using single-well test methods (i.e., slug tests). Four test sites with co-located DP and HSA wells were used. Soil types at the test sites were primarily fine- to medium-sized sands. DP-well installation methods included both hydraulically driven cone penetrometer (CPT) wells and hammered wells. The CPT wells typically relied on formation collapse around the well screen to form the filter pack. The remaining DP wells were constructed with pre-pack filters. The DP wells ranged in diameter from 1/2 in. to 2 in., and the lengths and depths of the screens were matched as closely as possible to those of the HSA wells. Whenever possible, pneumatic slug tests were performed. Where the wells were screened across the water table, however, a packer was used in conjunction with the pneumatic test in the larger wells and a mandrel test method was used in the smaller wells.