Hydraulic characterization and design of a full-scale biocurtain

This paper describes the design and hydraulic characterization of a cost-effective biocurtain that is currently being used to remove carbon tetrachloride from an aquifer in Schoolcraft, Michigan, Novel aspects of the design are the use of closely spaced wells to recirculate solutes through a biocurtain, well screens spanning the vertical extent of contamination, and a semipassive mode of operation, with only six hours of low-level pumping per meek. This design was developed by coupling now and transport simulations with a cost optimization algorithm, based on initial hydraulic conductivity data and system design constraints from a previous pilot-scale experiment adjacent to the current site. The hydraulic conductivity of the site was characterized using permeameter analysis on more than 200 samples from continuous well cores that were collected during well installation. The subset of available conductivity data was used to predict tracer transport through the biocurtain during system operation. Observed tracer concentration arrival histol ies during initial system operation confirmed model predictions. Modeling also established that closely spaced wells operated for brief periods each week could effectively deliver the agents needed for remediation across the biocurtain, This was confirmed during long-term operation of the system, which has resulted in highly efficient contamination degradation. The delivery well design methodology is expected to be broadly applicable at other sites where flow can be recirculated between a series of delivery wells.