Onondaga Creek Contaminant Investigations

August 9, 2017

Chazen developed a conceptual model describing saline mudboils active along Onondaga Creek in the Tully Valley. Chazen’s contaminant investigation identified source and plume migration mechanisms and included mitigation recommendations.

Chazen’s hydrogeologists reviewed the specific mechanisms associated with the unique geologic conditions in Tully Valley. Historic halite solution mining caused structural geologic damage including sinkhole development, collapsed rock over solution cavities, general land subsidence, and hillside fissures. Former overland flow and shallow groundwater appear to continue migrating into formerly-isolated deep rock salt formations, stimulating ongoing brine generation long after formal halite mining operations have ceased. Aquifer pressures move brine upward toward mudboils, springs, and saline wetlands.

Some remedial work has been completed by the property owner, including grouting of former brine mining boreholes and surfacewater diversion from sinkholes. Chazen developed a suite of additional remedial options for consideration, concentrating on methods to limit freshwater entry into the former solution mining chambers, and opportunities to grout primary plume pathways to the Tully Valley mudboils and related discharge points.

Chazen used existing published reports and site inspections. Other Chazen remedial groundwater investigations also included installation of monitoring wells, and soil and groundwater sampling, all following professional investigation protocols and work plan and reporting requirements under brownfield, inactive hazardous waste, or spill program guidance.