Private Well Water Testing in Colorado
County-by-county USGS area-risk estimates for private wells across Colorado — arsenic exceedance probability and private-well population — plus how to test your own well at a Colorado-certified laboratory.
Colorado private-well risk summary
Counties covered
63
Colorado counties with modeled risk data.
People on private wells
area estimate339,643
estimated across covered Colorado counties.
Average arsenic risk
area estimate6%
average modeled chance a well exceeds 10 µg/L arsenic across covered counties.
Colorado counties
- El Paso County3% arsenic exceedance (area estimate)32,962 people on private wells
- Jefferson County3% arsenic exceedance (area estimate)28,312 people on private wells
- Douglas County3% arsenic exceedance (area estimate)19,266 people on private wells
- Weld County7% arsenic exceedance (area estimate)18,704 people on private wells
- La Plata County3% arsenic exceedance (area estimate)18,299 people on private wells
- Adams County6% arsenic exceedance (area estimate)15,227 people on private wells
- Elbert County4% arsenic exceedance (area estimate)15,059 people on private wells
- Boulder County3% arsenic exceedance (area estimate)13,847 people on private wells
- Park County3% arsenic exceedance (area estimate)10,706 people on private wells
- Arapahoe County5% arsenic exceedance (area estimate)10,652 people on private wells
- Larimer County4% arsenic exceedance (area estimate)10,030 people on private wells
- Garfield County4% arsenic exceedance (area estimate)9,532 people on private wells
- Logan County6% arsenic exceedance (area estimate)8,900 people on private wells
- Teller County4% arsenic exceedance (area estimate)8,773 people on private wells
- Pueblo County3% arsenic exceedance (area estimate)7,271 people on private wells
- Fremont County6% arsenic exceedance (area estimate)6,002 people on private wells
- Chaffee County7% arsenic exceedance (area estimate)5,963 people on private wells
- Grand County3% arsenic exceedance (area estimate)5,365 people on private wells
- Alamosa County60% arsenic exceedance (area estimate)5,276 people on private wells
- Rio Grande County24% arsenic exceedance (area estimate)4,956 people on private wells
- Morgan County6% arsenic exceedance (area estimate)4,951 people on private wells
- Clear Creek County2% arsenic exceedance (area estimate)4,584 people on private wells
- Eagle County3% arsenic exceedance (area estimate)4,330 people on private wells
- Pitkin County3% arsenic exceedance (area estimate)4,186 people on private wells
- Gunnison County4% arsenic exceedance (area estimate)4,100 people on private wells
- Routt County3% arsenic exceedance (area estimate)4,085 people on private wells
- Gilpin County2% arsenic exceedance (area estimate)3,653 people on private wells
- Conejos County23% arsenic exceedance (area estimate)3,415 people on private wells
- Yuma County5% arsenic exceedance (area estimate)3,350 people on private wells
- Kit Carson County5% arsenic exceedance (area estimate)3,202 people on private wells
- Archuleta County3% arsenic exceedance (area estimate)3,129 people on private wells
- Summit County2% arsenic exceedance (area estimate)2,909 people on private wells
- Custer County4% arsenic exceedance (area estimate)2,608 people on private wells
- Saguache County19% arsenic exceedance (area estimate)2,483 people on private wells
- Washington County5% arsenic exceedance (area estimate)2,387 people on private wells
- Mesa County5% arsenic exceedance (area estimate)2,316 people on private wells
- Moffat County5% arsenic exceedance (area estimate)2,201 people on private wells
- Las Animas County3% arsenic exceedance (area estimate)2,194 people on private wells
- Bent County4% arsenic exceedance (area estimate)2,143 people on private wells
- Denver County5% arsenic exceedance (area estimate)2,064 people on private wells
- Montrose County6% arsenic exceedance (area estimate)1,992 people on private wells
- Lake County3% arsenic exceedance (area estimate)1,778 people on private wells
- Lincoln County3% arsenic exceedance (area estimate)1,575 people on private wells
- Montezuma County4% arsenic exceedance (area estimate)1,423 people on private wells
- Baca County5% arsenic exceedance (area estimate)1,352 people on private wells
- Huerfano County2% arsenic exceedance (area estimate)1,212 people on private wells
- Costilla County17% arsenic exceedance (area estimate)1,155 people on private wells
- San Miguel County3% arsenic exceedance (area estimate)1,152 people on private wells
- Phillips County5% arsenic exceedance (area estimate)1,070 people on private wells
- Otero County4% arsenic exceedance (area estimate)1,005 people on private wells
- Rio Blanco County6% arsenic exceedance (area estimate)1,001 people on private wells
- Ouray County4% arsenic exceedance (area estimate)758 people on private wells
- Delta County5% arsenic exceedance (area estimate)622 people on private wells
- Cheyenne County4% arsenic exceedance (area estimate)534 people on private wells
- Prowers County4% arsenic exceedance (area estimate)534 people on private wells
- Sedgwick County6% arsenic exceedance (area estimate)527 people on private wells
- Crowley County3% arsenic exceedance (area estimate)524 people on private wells
- Jackson County3% arsenic exceedance (area estimate)463 people on private wells
- Dolores County3% arsenic exceedance (area estimate)442 people on private wells
- Kiowa County4% arsenic exceedance (area estimate)410 people on private wells
- Mineral County3% arsenic exceedance (area estimate)285 people on private wells
- Hinsdale County3% arsenic exceedance (area estimate)232 people on private wells
- Broomfield County4% arsenic exceedance (area estimate)205 people on private wells
Find a Colorado-certified testing lab
Get your well tested at a Colorado-certified laboratory. We list certification programs by state.
These figures are USGS area estimates: statistical groundwater models describing how likely elevated contaminant levels are across a county. They are not designed to predict the concentration in any single well. Only testing your own well reveals its water quality.
By TapWaterData Editorial
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