Funnel‐and‐Gate Performance in a Moderately Heterogeneous Flow Domain

Abstract

AbstractThe funnel‐and‐gate ground water remediation technology (Starr and Cherry 1994) has received increased attention and application as an in situ alternative to the typical pump‐and‐treat system. Understanding the effects of heterogeneity on system performance can mean the difference between a successful remediation project and one that fails to meet its cleanup goals.In an attempt to characterize and quantify the effects of heterogeneity on funnel‐and‐gate system performance, a numerical modeling study of 15 simulated heterogeneous flow domains was conducted. Each realization was tested to determine if the predicted capture width met the capture width expected for a homogeneous flow domain with the same hulk properties. This study revealed that the capture width of the funnel‐and‐gate system varied significantly with the level of heterogeneity of the aquifer.Two possible remedies were investigated for bringing systems with less than acceptable capture widths to acceptable levels of performance. First, it was determined that enlarging the funnel and gate via a factor of safety applied to the design capture width could compensate for the capture width variation in the heterogeneous flow domains. In addition, it was shown that the use of a pumping well downstream of the funnel and gate could compensate for the effects of aquifer heterogeneity on the funnel‐and‐gate capture width. However, if a pumping well is placed downstream of the funnel and gate to control the hydraulic gradient through the gate, consideration should be given to the gate residence time in relation to the geochemistry of the contaminant removal or destruction process in the gate.