Well Water in Broomfield, Colorado

Broomfield County · Population ~74,000 · Aquifer: Municipal surface water; Denver Basin bedrock + alluvial wells on the fringe

Hardness: Hard (characteristic of Denver Basin groundwater)

Broomfield's Municipal Water Is Surface Water

Broomfield's supply comes from two inputs: treated water purchased from Denver Water, and raw water delivered via the federal Colorado–Big Thompson (C-BT) Project and the Windy Gap Project, which the city treats at its own conventional Water Treatment Facility. Future storage will come from the Chimney Hollow Reservoir Project. The city also runs a non-potable reclaimed-water system for irrigating parks. No authoritative published municipal-versus-well percentage exists for Broomfield; as a dense Denver-metro suburb it is overwhelmingly municipal, with wells a rural-fringe phenomenon.

Where the Wells Are, and What They Draw From

Broomfield sits on the northwestern edge of the Denver Basin, where the basin thins toward the foothills (Precambrian granite bounds the basin just to the west). Wells in and around Broomfield draw from a dual groundwater system documented by the USGS: shallow alluvial aquifers along the creeks that enter the basin here (Boulder Creek, Big Dry Creek, Saint Vrain, Coal Creek), and the Denver Basin bedrock aquifer system — the stacked Dawson, Denver, Arapahoe, and Laramie–Fox Hills sandstones. Bedrock wells can run deep, hundreds to around 2,000 feet. Toward the foothills, wells increasingly hit shallow alluvium and fractured edge bedrock rather than the thick basin-center sandstones.

Well-Water Quality Concerns

The authoritative basin-wide study (USGS SIR 2014-5051, sampling 2003–05) found that radon exceeded the lower proposed EPA drinking-water standard in more than 90 percent of Denver Basin bedrock samples — the Front Range granitic sediments are the natural source. Total dissolved solids, sulfate, iron, and manganese exceeded benchmarks in roughly 10–20 percent of bedrock samples. Arsenic, nitrate, and selenium exceeded standards in 1 percent or fewer of bedrock samples, but were highest in the shallow water-table (alluvial) wells, where TDS and sulfate exceeded benchmarks in half or more of samples and pesticides and VOCs were frequently detected (though below drinking-water standards).

For Broomfield County specifically, a USGS model estimates roughly a 4 percent probability of a well exceeding the 10 µg/L arsenic limit. We found no documented PFAS exceedance in Broomfield-area private wells or in the municipal supply — the only documented local PFAS activity is wastewater monitoring, which is not a drinking-water finding.

Denver Basin Depletion

Broomfield lies within the Denver Basin footprint, where the USGS has documented significant long-term water-level decline in the bedrock aquifers, treated as a finite, slow-to-recharge resource. USGS Professional Paper 1257 reported more than 500 feet of decline in local areas, and other USGS work found declines on the order of 10–40 feet per year in parts of the heavily pumped Arapahoe aquifer. The largest documented declines are further south in Douglas and El Paso counties; for Broomfield's rural wells, the practical implication is that deeper bedrock wells can face falling yields and rising mineralization over time.

What Broomfield Residents Should Know

If you're on municipal water (most residents): your water is treated surface water meeting all standards; review the city's annual Drinking Water & Health report for current detections.

If you're on a private well (the rural fringe): test for radon (very common in the bedrock here), arsenic, TDS, sulfate, iron, manganese, bacteria, and nitrate. See our testing guide and radon page.