Evaluation of Collection‐Well Parameters for DNAPL

Abstract

Results from a field program to collect data for the evaluation of alternative collection‐well design parameters for the hydraulic containment and removal of dense non‐aqueous‐phase liquids (DNAPL) and aqueous‐phase liquids (APL) are described. The Cooper‐Jacob method is utilized to estimate the aquifer transmissivity and storage coefficient. Estimates of hydraulic conductivity and permeability from drawdown data for DNAPL and APL are derived to indicate how the relationships from fluids principles may be successfully employed for the design of recovery systems. The diameter of the pumping‐well casing or borehole is shown to not influence the long‐term volume of DNAPL that can be pumped. Large‐diameter wells are found to take longer to equilibrate and allow intermittent but high‐volume pumping for short durations. With small‐diameter wells, a larger drawdown is obtained for the same pumping rate, and this collects more APL; but the small‐diameter well creates a larger gradient and thus more incentive to move the DNAPL for recovery.