Considerations for Monitoring Permeable Ground-Water Treatment Walls

Abstract

Permeable ground-water treatment walls (PTWs) have been implemented as a means by which innovative ground-water treatment technologies can be applied in-situ. Though not widely addressed in the technical literature, the ground-water monitoring program for a PTW at a commercial site should consider several factors including: (1) design elements of the PTW; (2) the remediation process to be implemented through the PTW; (3) the distribution of contaminants in the affected aquifer; (4) ground-water sampling methods; and (5) regulatory issues. Also, the compliance monitoring well network within the PTW and sampling plan should be designed to assure that (1) design ground-water residence time goals within the PTW are achieved prior to sampling; (2) the uniformity of ground-water flow through the PTW is accounted for; and (3) ground-water samples are collected using techniques (e.g., micropurging) that reduce the potential for collecting nontreated ground water from down- or upgradient of the PTW. A case study illustrates the concepts used to develop a ground-water monitoring program for a PTW that was accepted by regulatory agencies for a commercial site.