Holding back contaminated water
This bulkhead inside the Argo mine in Idaho Springs was one of the first Central City/Clear Creek Superfund projects. It stops water contaminated with heavy metals from spilling out of the mine. Instead, the water is piped to a water filtration plant to be filtered before being released into Clear Creek.
GILPIN AND CLEAR CREEK COUNTIES - The Colorado Department of Public Health and Environment (CDPHE) and Environmental Protection Agency (EPA) held a fourth meeting on October 3, 2024, on the status of cleaning up the Central City-Clear Creek Superfund site, at the Gilpin County Courthouse in Central City.
CDPHE Communication Specialist Branden Ingersoll acted as the moderator for the meeting, which included representatives and presentations from both CDPHE and the EPA. The agencies are still evaluating the data from testing mining waste piles in 2022 and 2023, and they continue to work though technical issues before finalizing their Feasibility Study and proposed plan. The CDPHE project lead for this phase, Kyle Sandor, continued to express optimism that remediation projects on residential properties would start in the summer of 2025.
Ingersoll spoke about how the superfund site was established and the different methods that can be used to remediate a mining waste pile. There was an extended question and answer session after Ingersoll’s presentation.
The first designated superfund site was the Love Canal in Niagara Falls, New York, after the discovery in the late 1970s that 22,000 tons of hazardous waste had seeped into basements and backyards causing birth defects and cancer.
The massive cleanup and investment required for the project led to the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), which was signed into law in December of 1980. CERCLA provided federal funding to clean up toxic sites, which subsequently became known as Superfund sites.
In 1983, the EPA recognized that the drainage of contaminated water from five mining tunnels (Argo, Big Five, National, Gregory Incline, Quartz Hill) flowing into Clear Creek posed a risk to the environment and human health, so the entire Clear Creek drainage was designated as a superfund site that year. The Argo mine also had part of a mine tailing waste pile actually in Clear Creek.
The Gold King mine spill in 2015 exemplifies the dangers of mine tunnel discharge. About three million gallons of contaminated water was released into the Animas River in Silverton, turning the river yellow, killing fish, and endangering drinking water for Durango.
Early remediation efforts here focused on stopping the discharge of contaminated water from the tunnels, building water filtration plants, and excavating the Argo mill tailings in Clear Creek. The water filtration plant on North Clear Creek below Black Hawk handles tunnel discharge that gets piped to North Clear Creek. Ingersoll finished his presentation by providing a review of the different remediation methods that are used to clean up contaminated sites. Any or all of these methods can be used for remediating a mining waste pile on residential property, depending on the engineering interventions required.
The first method is called Capping. The area above the Triangle Lot in Central City is an example of capping. This is the process of covering contaminated material with a variety of materials in order to prevent the contaminants from being spread into the environment via rainwater, snowmelt, or other forms of transport. Caps can include concrete, clay, asphalt, and vegetation.
Excavation is the physical removal of contaminated materials and relocating them to another site, called a repository. Excavation is required when there are significantly elevated contaminant concentrations and immediate action is needed. Clean material is then brought in and replaces the contaminated material that has been removed.
Repositories are places that are purchased for the sole purpose of storing contaminated material. The Church Placer Repository is centrally located in Gilpin County north of Idaho Springs. Contaminated material is placed in trenches or cells which are designed to prevent leakage or dispersal and are then capped and revegetated.
The third method that Ingersoll described is call In-Situ Treatment, which is an in-place treatment. This method involves the addition of amendments to the soil, like limestone, to neutralize soil acidity and promote vegetative growth that limits contact with mine waste. The In-Situ method is used when excavation near a building could risk undermining its foundation.
Sandor reiterated that CDPHE was working to get real estate experts to attend future meetings to answer questions about buying and selling properties which have been designated for cleanup.
A recording of the meeting, including the PowerPoint slides, can be found at the CDPHE website (cdphe.colorado.gov/hm/central-city-clear-creek). It is the October 3, 2024 meeting recording under Presentations.
For more information about the Central City-Clear Creek Superfund OU5 project, contact Branden Ingersoll (720-810-7912 or Branden.Ingersoll@state.co.us), or Valerie Doornbos (720-786-7292 or Doornbos.Valerie@epa.gov). Gilpin County Public Health Director Alisa Witt (303-582-5803 or awitt@gilpincounty.org) can also answer questions about lead and heavy metal contamination.
