Since the 1970s, Ashland Inc. has owned and operated a repackaging and distribution facility for petroleum and industrial chemicals. Soil and groundwater at the site were impacted with petroleum hydrocarbons and chlorinated solvents at levels exceeding Wisconsin’s soil and groundwater standards. While there was never a major spill, small quantities of petroleum product and solvents had been inadvertently released over time. Under the Resource Conservation and Recovery Act (RCRA), Ashland was required to remediate. The initial Corrective Measures Study (CMS) recommended a $1.5 million “dig-and-haul” approach. Ashland contacted TRC for assistance, and together, the team pursued a groundbreaking alternative.
TRC revised the CMS to handle the soil and groundwater problems in-situ through phytoremediation and natural attenuation. The plan met the Wisconsin Department of Natural Resources’ (WDNR) standards, and the Agency granted approval for the first project of this kind in Wisconsin. TRC worked with Ecolotree to install 500 hybrid poplar trees. TRC also engineered lowflow aeration and drip irrigation systems and used a mixture of soil amendments to provide the trees with optimal growing conditions. Since the WDNR had not previously permitted full-scale phytoremediation at a RCRA site, this project came under particular regulatory scrutiny.
By working closely with the WDNR throughout the project, Ashland and TRC were able to implement a cost-effective, innovative corrective action plan that cost 30-60 percent less than the original proposed method. The trees are taking up contaminated shallow groundwater, and the rate of biodegradation of VOCs in the groundwater has accelerated in the area downgradient from the trees. For Ashland, phytoremediation was not only a viable option for cleaning up heavily contaminated soil and groundwater, but also a remedy that caused minimal disturbance to neighbors and transformed an industrial eyesore into a greenspace along a river.