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BlcPHERSON ON RAINFALL STATISTICS. 421 (Paper No. 4115.) " Bristol Waterworks : Rainfall-Statistics and Notes on Wet and Dry Cycles." By JOIIN AMBROSE MCPHERSON, M. Inst. C.E.

In 1999, Argonne National Laboratory-East (ANL-E) designed and installed a series of engineered plantings consisting of a vegetative cover system and approximately 800 hybrid poplars and willows rooting at various predetermined depths. The plants were installed using various methods including Applied Natural Science's TreeWell ® system. The goal of the installation was to protect downgradient surface and groundwater by hydraulic control of the contaminated plume. This goal was to be accomplished by intercepting the contaminated groundwater with the tree roots, removing moisture from the upgradient soil area, reducing water infiltration, preventing soil erosion, degrading and/or transpiring the residual VOCs, and removing tritium from the subsoil and groundwater.The U.S. EPA Superfund Innovative Technology Evaluation Program (SITE) and ANL-E evaluated the demonstration. The effectiveness of the various plantings was monitored directly through groundwater measurements and samples, and indirectly via soil moisture probes, plant tissue analysis, microbial studies, geochemical analysis, and sap flow monitoring. A weather station with data logging equipment was installed. ANL-E modeled the predicted effect of the plants on the groundwater using MODFLOW. The demonstration has lasted three growing seasons and continues. This paper presents the results of the sampling, monitoring, and modeling efforts to date. The project was not only successful in reducing the groundwater contaminant flow and the contaminants at the source; it also provides insight into the techniques that are useful for measuring and predicting the effectiveness of future similar projects.