New Stanton, Pennsylvania

New Stanton, Pennsylvania

New Stanton, Pennsylvania

Site Location:
New Stanton, PA — 2014-Present

Contaminants:
Trichloroethene, as well as traces of other chlorinated VOCs.

Project Objective:
To reduce the potential for groundwater contaminants to migrate to surface water or off-site.

Implementation:
A pilot TreeMediation study was conducted in September 2014. Fifty-two TreeWell units were installed, and a mix of willow and hybrid poplar trees were planted to target migration pathways in shallow surface soils (up to 10 feet below ground surface) and shallow fractured shale bedrock (up to 30 feet below ground surface). Following the success of the pilot study, an additional 166 TreeWell units were installed in October 2016 in three plots downgradient from the pilot area. Sixty-two shallow units were installed approximately 17 feet below ground surface, and 112 units were installed, approximately 25 feet below ground surface. Due to increasingly wet conditions, deep holes in the north section were drilled to approximately 45 feet below ground surface. Alternations of willows, London planetrees, black locusts, hybrid poplars were planted in April 2017. Sixteen of the shallow units in the south section were allocated as modified TreeWell units, drilled to depths of 4.5-7 feet below ground surface, and planted with red twig dogwoods. Root camera tubes were installed in three of the units to monitor the root systems of each species of tree. Six piezometers and two nested piezometers were installed within individual TreeWell units to equip transducers, with the purpose of monitoring water levels.

Results to Date:
The growing seasons to date for the pilot study include 2014-2021, and the growing seasons for the three downgradient plots include 2017-2021. Tree growth and viability were observed to be “very good” for the entire TreeWell unit plantation. The tree health assessments do not show any indicators of plant stress. The height and canopy of most of the trees in the TreeWell units have continued to increase. Trees are displaying vigorous growth and, based on hydrogeologic monitoring data, are providing hydraulic capture. Preliminary hydrogeologic data suggest they are on track to perform as designed.