Ellender Ferry, Louisiana

Ellender Ferry, Louisiana

Ellender Ferry, Louisiana

Site Location:
Ellender Ferry, LA — 2017-Present

Contaminants:
Benzene, chlorobenzene, toluene, diphenyl ether, and phenol; and lower concentrations of several other VOC constituents in shallow soils and groundwater.

Project Objective:
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.

Implementation:
The TreeMediation implementation consisted of 27 TreeWell at a site in Ellender Ferry, Louisiana. In October, 2017, 22 open-bottomed TreeWell units were installed 20 feet below ground surface, and 5 straw close-bottomed TreeWell units were installed 90 feet below ground surface. In September, 2018, black locust trees planted in the open-bottomed units (two trees were planted in several units), and cabbage palms planted in the straw units. 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 2018-2019 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.