Principal Project Geoscientist
Weston Solutions, Inc.
Lisa Kammer has a B.S. in Geology from the University of Northern Colorado and a M.S. in Geology and Geophysics from Boston College. Her professional experience is serving a variety of clients largely in site investigations, characterization, and remediation, Superfund project management, RI/FS, long-term monitoring, and optimization of project and program management. Her focus areas are primarily on chlorinated solvents and emergent and recalcitrant compounds including 1,4DX and PFAS.
Re-Evaluation of Selected Remedy at a Superfund Site: A Success Story Complicated by Emerging Contaminants
Inaccessible 1,4-dioxane (1,4DX) in deep overburden and fractured bedrock at a Superfund site in southeastern New Hampshire continued to contaminate groundwater while the effectiveness of the implemented remedy (groundwater extraction and treatment) was diminished. Therefore, re-evaluation of the selected remedy was deemed necessary. To do this, additional data were collected over a multi-year period. The Amended Record of Decision (AROD) selected Monitored Natural Attenuation (MNA) of 1,4DX as the new remedy: a combination that had not previously been approved by the U.S. Environmental Protection Agency. The case for MNA, including a 10-year evaluation period, was made successfully by refinement of the Conceptual Site Model and development of additional lines of evidence. The prior remedy at this former waste bulking and recycling facility included a pump-and-treat system that employed conventional treatment processes for volatile organic compounds. In 2003, 1,4DX was discovered at the Site at concentrations in the hundreds of parts per billion. The treatment system was modified in 2005 to include High Pressure Oxidation (HiPOx) that successfully treated 1,4DX. A significant reduction in 1,4DX concentration was observed within the first 2 years. After 6 years of pump-and-treat with HiPOx, the system was deemed to be no longer operating in an efficient manner as influent concentrations often decreased below treatment standards, and the contaminant mass removal was small compared to the volume of water treated when considering the operation and maintenance costs. As such, additional site investigations were initiated utilizing an array of methods, including rebound studies, a microcosm study, transport modeling, trend analysis, back-diffusion modeling, design and implementation of treatability testing, and addressing remaining data gaps. Data gaps were primarily in the deep bedrock where downgradient sensitive receptors are located; therefore, a deep bedrock investigation was completed utilizing high-resolution characterization methodologies. Subsequent to the AROD, screening for per- and polyfluoroalkyl substances (PFAS) was conducted at the Site and their presence confirmed in both overburden and bedrock aquifers. Concentrations range in the low parts per trillion (ppt) to approximately 300 ppt. In general, PFAS are co-located with 1,4DX and other site contaminants. However, additional investigation of the protectiveness of the remedy is ongoing. Currently, NH has promulgated groundwater quality criteria for perfluorooctanesulfonic acid and perfluorooctanoic acid with proposed revisions to lower concentrations and criteria for additional PFAS compounds in progress. This presentation will detail the science behind MNA as an approved remedy for 1,4DX; offer lessons learned in dealing with 1,4DX and PFAS in the context of a site enmeshed in an established remedy; and how contingency remedies can be evaluated with an eye toward yet unknown remedial technologies.