A demonstration of a Phytoremediation Groundwater Treatment system was conducted at the Carswell Naval Air Station (NAS) Golf Club in Fort Worth, Texas to investigate the ability of purposely planted eastern cottonwood trees, Populus deltoides, to help remediate shallow TCE-contaminated groundwater in a subhumid climate. Specifically, the study was undertaken to determine the potential for a planted system to hydraulically control the migration of contaminated groundwater, as well as biologically enhance the subsurface environment to optimize in-situ reductive dechlorination of chlorinated ethenes present (trichloroethene and cis-1,2-dichloroethene) in the shallow aquifer system beneath a portion of the golf course. Populus deltoides, like other phreatophytes, have long been recognized as having the ability to tap into the saturated zone to extract water for metabolic processes. Based upon this characteristic the species was considered well suited for applications where shallow aquifers are contaminated with biodegradable organic contaminants. A planted system of cottonwood trees is believed to effectuate two processes that aid and accelerate contaminant attenuation. First, transpiration of groundwater through the trees is believed to be able to modify and hopefully control the hydraulic groundwater gradient. This can minimize the rate and magnitude of migrating contaminants downgradient of the tree plantation. Secondly, the establishment of the root biomass, or rhizosphere, promotes microbial activity and may enhance biodegradative processes in the subsurface.