Analyzing a Large PFAS Dataset at a Complex Plating Company Site in New Hampshire

The New Hampshire Plating Company (NHPC) superfund site (the Site) sits on 13 acres in Merrimack, NH. Operations at the facility from 1962 to 1985 discharged an estimated at 35,000 to 60,000 gallons of wastewater per day into unlined waste lagoons. Contaminants of concern (COCs) identified at the Site include PFAS, chlorinated solvents, metals, cyanide, and 1,4-dioxane. Following extensive remedial activities starting in 1987 and years of monitoring, a supplemental remedial investigation in 2015 discovered a variety of per- and polyfluorinated alkyl substances (PFAS). PFAS are hypothesized to have been used as wetting agents and fume suppressants (WA/FS), as was common practice in the electroplating industry back to the 1950’s. 

In 2022, GZA completed 2 rounds of sampling from a total of 74 wells located on and around the Site. Groundwater samples were analyzed for 70 PFAS, resulting in a large and complex dataset. In total, 36 unique PFAS were detected from 9 different groups, with at least one PFAS present in samples from each of the 74 wells. A variety of data visualization and statistical analysis tools were employed to analyze the data. Pinwheel graphs and PFAS-specific form of bar chart were used to visualize patterns. Statistical tools, including correlation analysis, and principal component analysis, were used to look for potential groups within the data. Taken together, these reveal the complex nature of PFAS distribution in the area and the potential for multiple sources of PFAS.