Phytoremediation—The Natural Pump-and-Treat and Hydraulic Barrier System

Abstract

The use of “water-loving” trees as a supplemental remedy to conventional ground-water “pump-and-treat” systems was employed at a chemical manufacturing site in Texas. The approach entailed taking advantage of the extensive root systems of trees to extract contaminated ground water from the uppermost ground-water bearing zone located 30–35 ft below ground surface (bgs). Forty poplar and mulberry trees were planted along the southeastern property line of this site in order to control, stop, and/or retreat the contaminant plume from migrating off-site. This planting project, phytofence, is intended to complement and fortify the operation of an existing 10-well recovery system within that vicinity. The uptake of water by the mature trees in the future is expected to change the subsurface hydraulic gradient and create an adequate ground-water capture zone. In order to protect the underground utilities' piping networks from the tree roots near the ground surface, 10-in. HDPE casings that are 5 1/2 ft long were driven into the ground to surround each plant. This should also induce a deeper growth into the affected area.