Government sampling in Arapahoe County’s 111ALFP aquifer found manganese in all tested samples, with levels ranging from about 10 to 8100 micrograms per liter, and a median near 2870 micrograms per liter; none exceeded federal health-based thresholds.
What Changes for a Large Household, a Second Home, or Seasonal Property
Manganese concentration in groundwater itself does not vary by household size, but water usage patterns influence treatment demands. Larger households or properties with intermittent occupancy, such as second homes or seasonal residences, may require equipment that can handle fluctuating water volumes or longer idle periods without risking buildup or reduced effectiveness. Choosing a system that accommodates these variations helps maintain consistent manganese control at the tap.
How Public-System Records Differ from Private-Well Testing in What They Establish
The U.S. Geological Survey's data represent several wells sampled in the 111ALFP aquifer within Arapahoe County and provide insight into typical groundwater manganese levels across this area. These data do not reflect manganese levels in any specific well, including private household wells. To understand the manganese concentration in your own water supply, direct testing of your well or tap water is necessary. Public system results serve as an informative baseline rather than an individual water quality guarantee.
How Manganese Enters Groundwater or the Distribution System in This Region
Manganese naturally occurs in soils and rocks that make up the aquifer beneath Arapahoe County. Over time, groundwater flowing through these geological formations can dissolve manganese compounds. Seasonal changes, water table fluctuations, and redox conditions can affect manganese solubility and mobility, leading to detectable manganese in sampled wells throughout this aquifer system.
How the Treated Water Differs at the Tap Once the Documented Technology Is in Place
Water treatment equipment designed to address manganese, such as the Pentair Black Manganese Stains Filter, works by reducing manganese concentrations in supplied water to minimize potential staining on fixtures, improve water clarity, and mitigate taste effects that manganese may cause. The treated water presents these aesthetic and operational improvements, helping maintain plumbing and appliance performance while preserving the water's suitability for household uses.
How Many Samples and Wells Stand Behind the Figures, and What a Small Sample Means
This manganese dataset includes 183 results collected from three wells sampled over a 15-year span in Arapahoe County’s 111ALFP aquifer. While this provides a robust regional snapshot, it does not capture all local variations or temporal changes in manganese levels at any single point of use. Individual well conditions may differ due to depth, location, and other aquifer characteristics, so personal water testing remains essential for tailored treatment decisions.
These findings derive from U.S. Geological Survey groundwater monitoring specific to the 111ALFP aquifer in Arapahoe County, Colorado, accessible at waterdata.usgs.gov/monitoring-location/394333103525100/.
Where this information comes from
Source: USGS groundwater sampling. Sampled 2025-12-12. These figures describe groundwater sampled in this area. They are not a test of any individual private well - only a test of that well can establish its own water.
On record: U.S. Geological Survey sampling of Manganese in the 111ALFP aquifer (Arapahoe County): 183 results from 3 wells, median 2870.0 ug/L, range 9.66-8100.0 ug/L; none above any federal threshold
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