THE DIRT: The Central Treatment Plant’s upgrades are making an impact!

There are many clean-up actions and remedies currently taking place in the Bunker Hill Superfund Site that are intended to improve the water quality of the South Fork of the Coeur d’Alene River. These remedies often take time before their effectiveness is quantified and determined. Recent studies have shown that some of these remedies are making great improvements.

The Central Treatment Plant (CTP) that is located near the Central Impoundment Area (CIA) in Kellogg was upgraded and completed in 2021 to treat groundwater and mine water waste. The CTP upgrades were necessary to treat and meet current, more stringent discharge requirements. The design included a groundwater collection system that consists of a soil bentonite cutoff wall between the CIA and Interstate 90 that blocks contaminated groundwater flow to the river. The contaminated groundwater is pumped back to the CTP where it is treated and discharged back into the SFCDA following current water quality standards. The CTP was also designed to treat Acid Mine Drainage, which is acidic and laden with metals, that continually flows out of the Bunker Hill Mine.

The United States Geological Survey (USGS) did a seepage study to help understand the impacts of the upgrades at the CTP to surface water. They utilized data collected in 2017 which was before the upgrades were made. They sampled again in 2022 to look at differences after completing the remediation. A seepage study measures the amount of water at two points and subtracts the upstream from the downstream to get the specific portion coming into or out of the river. They must also factor in inputs and outputs, like tributaries coming in or anything exiting out.