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County: split groundwater sampling at Bonko View Lake landfill shows PFBA below health value but vinyl chloride above intervention limits in one well
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Summary
Sherburne County reported split groundwater sampling at Vanko 1 (Bonko View Lake landfill): PFBA was detected in all wells but below Minnesota Department of Health health‑based values; vinyl chloride results in one well have been above intervention limits since about 2008; 1,4‑dioxane has appeared intermittently since 2021. Staff said split samples were comparable to landfill samples and monitoring will continue through the post‑closure period.
County staff provided an update on split groundwater sampling at Vanko 1 (the Bonko View Lake landfill) during the April 21 meeting, reporting routine monitoring results and additional PFAS testing.
The presenter identified in the record as June (county sampling presenter) said the county split‑sampled monitoring wells last fall and added PFAS analysis to the usual tests for dissolved metals, volatile organic compounds and inorganics. June said perfluorobutanoic acid (PFBA) showed up in all wells but the measured concentrations were below the Minnesota Department of Health’s health‑based value for that compound. She said split sample results were "pretty comparable" to the landfill operator’s results and that there were no major outliers in the event.
June described site‑specific trends: "Vinyl chloride has been showing up in that well since about 2008, and then all those results have been above the intervention level," and she said 1,4‑dioxane began appearing in results around 2021 and has occurred intermittently since. She explained monitoring uses a GUISDAP spatio‑temporal analysis tool to smooth between sampling events and help identify trends.
Staff said they will continue the post‑closure monitoring schedule (spring and fall sampling), will continue residential groundwater sampling in the area, and will notify residents with letters that include results and explanatory information. The county is coordinating with the landfill operator and the Minnesota Pollution Control Agency on post‑closure oversight and license extensions.
Board members asked clarifying questions about well depths, stratigraphy and notification; staff confirmed residents receive letters and that staff had not yet received responses from residents. No immediate remedial action was announced; monitoring and coordination will continue through the landfill’s post‑closure period.
Sources: county presentation and staff comments at the April 21, 2026 Sherburne County Board meeting.
