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VEGETATrvE REMEDIA-nON PxocEss OFFExs AnvANTAcEs ovEP,TFAnrnONA, PuMr-ANo-TRzAr TF-cHNoLoc Es matter In a humid climate, trees are provided with more than enough I water and nutrients in the surface few feet of soil not only to survive, but to thrive Plants will naturally conserve their resources and will typically expend only the energy necessary to maintain reasonable viability At this site,this translates into rooting activity being contained in the surface few feet of soil where soil physical conditions are favorable and water and nutrients are adequate for reasonable growth Thus, planting a tree and wanting for it possibly to develop rooting activity to the aquifer 16 feet below the surface was not an acceptable alternative 111EEMFDIA110N VERSUS PUMP-AND-TREAT Experience is demonstrating that standard pump-and-creat technology is often falling short as a remedial option Even where viable, pump-and- treat technology maybe cost-prohibitive Water in an aquifer preferentially follows the path of least resistance If some or all of a contaminant occurs in a section of the aquifer where water is more tightly held (especially in capillary pores), this water will nor become a significant part of the Properly designed, Pumping stream This problem undoubtedly demonstrates one of the Tree-Mediation primary fallacies of using standard pump-and-treat systems to address the influences the root cleanup of contaminated zones of an aquifer system to develop to TreeMediation is a localized and steady process that is even capable the aquifer, drawing of extracting capillary water Properly designed, TreeMediarion influences coater and the root system to develop to the aquifer,drawing water and contaminants contamznanta up up through soil pores Many contaminants will then be absorbed into the through soil pores. plant or affected by the microbial populations associated with the rhizosphere--the biologically active zone surrounding the root system This process removes contaminants from the groundwater or limits contaminant migration to the groundwater Pump-and-Treat CapabLUtles of Phreatophytes It has long been recognized that phreatophytic crops and trees are effective at rooting very deeply—to 100 feet and more In fact, phreato- phytes have been studied as a nuisance in the semiarid to and regions of the western United States where water is scarce These plants are known to affect water availability by significantly lowering groundwater levels Diurnal fluctuations of wells were reported in the 1940s and attributed to a grove of nearby cottonwood trees (USDA, 1955) Aquifer levels at other locations were reported to have dropped 5 feet during the growing season due to water consumption by phreatophytes It has been reported that a single willow tree "uses and loses over 5,000 gallons of water in one summer day"(Miami Conservancy District, 1991) This seemingly phenom- enal figure is comparable to what 0 6 acres of the phreatophyte alfalfa can transpire in one day (Schwab et al , 1957) and is plausible when the leaf surface area of a fairly large willow tree is considered At a site in southwestern Ohio, cottonwood trees demonstrated considerable pumping capacity, even in a relatively humid environment A fairly ideal situation was available where two 40-f6ot-tall cottonwood RF-mED ATioN/Summmx 1994 345