Pueblo, Colorado — population about 113,000 — was built on steel. The Colorado Fuel and Iron (CF&I) mill operated from 1881 to 2000, making Pueblo the “Pittsburgh of the West.” The mill also left behind one of Colorado’s most significant industrial contamination sites.
CF&I Steel Mill: A Superfund Legacy
The former CF&I/Oregon Steel Works site spans hundreds of acres along the Arkansas River in southeast Pueblo. The contamination includes:
- Heavy metals — Decades of steel production deposited lead, arsenic, cadmium, chromium, and zinc in soils and slag piles across the property
- Petroleum products — Coke ovens and fuel storage areas contaminated soil and groundwater with petroleum hydrocarbons
- Slag piles — Massive deposits of steelmaking waste containing heavy metals. Some slag was also used as fill material in residential neighborhoods.
- Groundwater contamination — Industrial chemicals and metals have leached from the site into the shallow aquifer
The Colorado Department of Public Health and Environment (CDPHE) has overseen cleanup activities at the site for decades. Residential soil removal has occurred in some neighborhoods where slag fill was discovered, but groundwater remediation continues.
The site is currently being redeveloped. Parts of the former mill property are now the Steelworks Center of the West museum and commercial development. But contamination beneath the surface persists.
Arkansas River: Mining Contamination from Above
Pueblo’s drinking water comes from the Arkansas River via Pueblo Reservoir. The river originates near Leadville in the Rocky Mountains — one of the most intensely mined areas in Colorado’s history.
The upstream contamination legacy:
- Leadville Mining District — Over a century of gold, silver, lead, and zinc mining left behind mine waste, tailings, and acid mine drainage. The California Gulch Superfund Site in Leadville is one of the largest in Colorado.
- Heavy metals — Zinc, cadmium, lead, and manganese from upstream mining districts enter the Arkansas River through tributary streams and acid mine drainage
- Pueblo Reservoir — The reservoir provides some natural settling and dilution, but metals are still detectable in source water
- The Arkansas River is also Colorado’s most contested water — Multiple cities, agricultural districts, and interstate compacts compete for Arkansas River water, and flows are heavily managed
Pueblo’s water treatment plant, operated by the Pueblo Board of Water Works, uses conventional treatment to address the specific challenges of the Arkansas River source.
Colorado’s Water Scarcity
Water quantity is as significant a concern as water quality for Pueblo:
- Colorado River Compact obligations mean Colorado must allow water to flow to downstream states
- Climate change is reducing Colorado snowpack — the long-term source of Arkansas River water
- Growing Front Range cities (Colorado Springs, Denver metro) compete for limited water resources
- Pueblo Reservoir levels fluctuate with drought cycles, affecting both supply reliability and water quality (lower water levels can concentrate contaminants)
What the Data Shows
From Pueblo Board of Water Works’ most recent Consumer Confidence Report:
- All regulated contaminants within EPA limits
- Heavy metals from source water treated below MCLs in finished water
- Trihalomethanes and haloacetic acids within limits
- Lead at 90th percentile below action level
- No SDWA violations
What Pueblo Residents Should Do
- Near the former CF&I site — If you live in neighborhoods near the former steel mill, be aware of potential slag fill in residential soils. Contact CDPHE for information about your property.
- Private wells in southeast Pueblo — Groundwater contamination from the CF&I site may affect private wells. Test for heavy metals and petroleum compounds.
- Municipal water is treated — Pueblo’s treatment system handles the upstream mining-related metals effectively. Review the CCR annually.
- Lead in older homes — Pueblo has significant older housing stock. Test for lead if your home was built before 1986.
- Water conservation — In Colorado’s increasingly scarce water future, conservation isn’t optional. Every gallon saved extends Pueblo’s supply reliability.
Pueblo’s identity is shifting from steel town to something new. But the environmental legacy of its industrial past requires ongoing attention — both underground and in the river that feeds its water supply.
If you’re concerned about your water quality, a certified water treatment professional can test your water and recommend appropriate treatment solutions.