Clover, South Carolina
Clover, SC — 2017-Present
Chlorobenzene; as well as lower concentrations of several other VOC constituents in shallow soils and groundwater (0 to approximately 40 feet below ground surface).
To evaluate the potential for utilizing phytoremediation in highly contaminated areas and evaluate the remedial and hydraulic impact of the TreeWell system on chlorobenzene-impacted groundwater and soil.
The TreeMediation implementation consisted of 19 TreeWell units which were installed in 20 by 20 foot spacing at approximately 30 feet below ground surface. Subsurface conditions consisted of saprolite soil and weathered rock. One month after the February 2017 installation, alternations of willow and poplar trees were planted in each unit, excluding the four units located in the burn pit area, where both poplar and black locust trees were planted in each unit. Black locusts were planted as a contingency for the possibility of elevated salinity resulting from degradation of the chlorobenzene. A monitoring network consisting of shallow and deep (nested) piezometers, pressure transducers, conductivity sensors, weather stations, and camera tubes were installed to monitor the effectiveness of the TreeWell system to enhance biodegradation of the COC in shallow soils and groundwater and exert hydraulic influence on shallow groundwater.
Results to Date:
For the 2017-2021 growing seasons, tree growth and viability were observed to be “very good” for the entire TreeWell unit plantation. The tree health assessments do not show any significant indicators of plant stress. The height and canopy of most of the trees in the TreeWell units have continued to increase. Overall, the TreeWell units are performing as designed. Chemical data collected from groundwater monitoring wells and from piezometers located in TreeWell units show significant levels of VOCs, particularly chlorobenzene. Data from monitoring wells TW-24, TW-20 and TW-10 show relatively high (25,000 to 50,000 µg/L) concentrations of chlorobenzene. Nested piezometers in TreeWell units 13 and 14 are adjacent to these three monitoring wells and show chlorobenzene concentrations ranging from 230 to 3,200 µg/L suggesting movement of VOCs into TreeWell units with higher concentration typically in the upper water column.