Carlyss, LA — 2015-Present
Benzene, chlorobenzene, toluene, diphenyl ether, and phenol; and lower concentrations of several other VOC constituents in shallow soils and groundwater (0 to approximately 30 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 VOCs in the groundwater.
The TreeMediation implementation consisted of 90 TreeWell units among three different locations in Carlyss, Louisiana. TreeWell units were installed in 20 by 20 foot spacing at 25 feet below ground surface. In December, 2015, a set of hackberry, Russian olive, live oak, and black locust trees were planted in each of the 18 TreeWell units during Phase I in the first Carlyss location. One set of units was filled with engineered soil, a second set filled was with a mixture of soil and ZVI, and a third set was filled with a mixture of soil, ZVI, and Daramend. Phase II began in June, 2017, when Black locust and willow trees were planted in 18 additional TreeWell units which were installed with the same parameters in a second Carlyss location. Finally, in December, 2019, Phase III of the project commenced as 51 additional straw TreeWell units were installed in the third Carlyss location, with 35 willow and 25 black locust trees were planted in March, 2020. A monitoring network consisting of piezometers 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 2016-2019 growing seasons, tree growth and viability were observed to be “very good” for the entire TreeWell study. The vertical profile of groundwater VOC concentrations within the TreeWell units show that VOCs are attenuating within all the TreeWell units. Units with ZVI or ZVI and Daramend in the backfill exhibit more attenuation than units with only loam soil in the backfill.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. The backfill media is reducing VOC concentrations as designed and to date, there are no obvious signs of VOC phytotoxicity. Additionally, the straw wells are functioning as designed to transmit target groundwater into the TreeWell units.