We are providing site investigation and remediation services to an industrial client on a site located on the coast of South Carolina, which is a source of groundwater contamination for 1,4-dioxane and other volatile organic compounds (VOCs). The site included a 10,000 square foot warehouse and a pack parts cleaning facility. The pack parts cleaning operation was discontinued in 1991, and the buildings were subsequently demolished, leaving only the concrete pad. In 2007, the industrial client installed a phytoremediation system at the site to accelerate the attenuation of the lingering, low levels of site-specific compounds in shallow groundwater. In January 2011, the South Carolina Department of Health and Environmental Control (SCDHEC) requested that the client develop phytoremediation effectiveness standards and determine whether additional corrective actions were necessary for the site. The objective of the presentation is to highlight our site investigations, remediation efforts, and innovative remediation technologies, including phytoremediation of 1,4-dioxane and the possible use of TreeWell® systems.
In 2011, we were asked by our industrial client to evaluate the phytoremediation site and to develop effectiveness standards and identify additional corrective actions. In addition, we prepared a feasibility study (FS) in 2015, which included potential remedial options. The existing phytoremediation trees were taking up VOCs from the shallow (surficial) aquifer, but the tree roots were not impacting VOCs that were located in the bottom portion of the surficial aquifer. In addition, VOC concentrations were not diminishing in the groundwater indicating there was still a source onsite. SCDHEC responded in 2017 and requested additional lower aquifer and offsite investigations before they would approve the FS. The FS recommended removing the remaining building foundations, excavating impacted vadose zone soils under the foundation, bringing in clean fill soil, and expanding/ enhancing the phytoremediation trees.
In 2020, we completed a soil removal action that uncovered the former sump and possible source area. The contaminated soil above the water tables was removed and replaced with clean fill material. Natural attenuation processes are being further examined through university studies including the isolation of 1,4-dioxane degrading bacteria from the site aquifer samples. In addition, installation of an expanded phytoremediation system (including the potential use of TreeWell® systems developed by Dr. Edward Gatliff of Applied Natural Sciences, Inc. and planting an additional mix of trees) will occur in the next several years.