THE DIRT: 30-year Water Quality Trends show improvements are being made
Water quality data was collected throughout the Bunker Hill Superfund Site before remediation work began, giving a reference point to compare data as work is completed. The United States Geological Survey (USGS) recently studied data going back 30 years to determine if water quality has improved after decades of remedial work.
Data from 1990 to 2018 indicate there is a dramatic downward trend in dissolved zinc concentration and loads throughout the South Fork Coeur d’Alene (SFCDA) River and Main Coeur d’Alene (CDA) River to the Spokane River. The total lead concentrations and loads also decreased at Pinehurst and Spokane River locations, but at Harrison, data indicates there may be a slight increase. Overall, total lead concentrations and loads have decreased 25-75% over this period except for loads at Harrison.
The USGS observed a sharp decrease in dissolved zinc concentrations and loads during the first part of the 30-year trend but that decrease flattened out over time. Similarly, total lead initially trended downward at most of the locations sampled with the exception of Harrison where an increase was observed from 1999-2009 and a flat trend in more recent years.
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