Mesa County, Colorado: drinking water report. Mesa County on Colorado's Western Slope has about 155,000 residents, with Grand Junction as the county seat.
Mesa County on Colorado's Western Slope has about 155,000 residents, with Grand Junction as the county seat. Water comes from the Colorado River and local reservoirs, managed by Ute Water Conservancy District and the City of Grand Junction. The county sits in a former uranium mining and milling region, and the Colorado River at Grand Junction carries dissolved salts and naturally occurring minerals from across its upper basin.
Uranium mill tailings from the Cold War era were piled along the Colorado River in Grand Junction for decades before a massive DOE cleanup moved over 4.3 million tons of material to a disposal cell in the 1990s. According to DOE's 2024 long-term surveillance report, residual contamination in groundwater near the former mill sites includes uranium, vanadium, and selenium at concentrations above background levels.
The Colorado River at Grand Junction is naturally high in TDS – averaging 500 mg/L – from dissolution of the Mancos Shale and other geological formations in the upper basin. A 2024 USGS study found selenium at 4 ppb in the river at Grand Junction – below the MCL of 50 ppb but part of the river's natural mineral load.
Mesa County's Colorado River supply carries the mineral signature of the upper basin, and the uranium milling legacy adds a contamination dimension that other Western Slope communities do not face. Treatment plants manage these inputs, but the source water starts with a higher mineral baseline.
Check your water for current data. For the high-TDS water typical of the Western Slope and any residual uranium-related concerns, reverse osmosis provides effective household treatment. Our water filter guide covers systems suited to Colorado River basin water. Pull your detailed report for trends, and visit our Colorado page for statewide context.