The U.S. Geological Survey collected groundwater samples from Benton County’s aquifer 111ALVM, including results from three separate wells between 2011 and 2017. These samples showed iron was detected at concentrations ranging from 13.2 to 146.0 micrograms per liter (µg/L), with a median value of 25.7 µg/L. One sample was below the reporting limit. All wells sampled were between 18 and 80 feet deep. Importantly, none of these measurements exceeded any federal health-based standards for iron, indicating no regulatory violation in this area-wide sampling.
If your well taps water from depths similar to sampled wells
When your household water source is from a well within the depth range of 18 to 80 feet, the iron concentration in your water may be similar to these reported values, although only direct water testing can confirm your specific situation. Iron bacteria thrive where iron and organic material co-occur in groundwater, causing slime deposits and staining. The depth of your well influences both iron presence and bacterial activity because microbial conditions and iron availability can vary significantly with depth.
If you notice slime buildup or staining but are unsure of its cause
Iron bacteria differ from other common water issues like iron oxidation or manganese deposits by producing a slimy biofilm that clogs pipes and fixtures. The presence of iron in the aquifer as shown by USGS sampling explains part of the environment that supports iron bacteria, but staining or deposits without slime may indicate oxidized iron rather than active bacterial growth. Confirming the problem requires professional water analysis focused on bacterial presence.
If you want to understand where the iron in your area’s groundwater originates
In Benton County’s aquifer 111ALVM, naturally occurring iron dissolves from minerals in soil and rock as groundwater flows through them. This iron can become available to iron bacteria, which consume it while producing iron-rich slime films. Unlike contamination from human sources, this is a natural geologic process consistent over time and location in the aquifer.
If you compare your own water results to federal guidelines
Federal standards do not set maximum allowable levels specifically for iron bacteria, but iron concentration is a useful proxy for assessing the potential for bacterial growth. The USGS data show iron levels well below any health-based limits, meaning the presence of measured iron alone does not indicate a safety issue. Instead, high iron concentrations may affect water taste, color, and cause staining, which are managed differently than health risks.
If you want to interpret median and range values as a homeowner
The median iron value of 25.7 µg/L in area samples means half the measured concentrations were below this level and half above, giving a sense of typical iron presence in Benton County’s aquifer. The range from 13.2 to 146.0 µg/L represents variability over multiple wells and sampling events, reflecting changes in local geology and conditions. As a homeowner, your individual well’s iron might be near the median or closer to either end of this range, but only your water test determines this.
What you should not conclude: Area sampling shows regional iron levels but does not establish the quality or safety status of your specific well water. Detection of iron in the aquifer is normal and does not in itself prove iron bacteria contamination or a health risk. Testing your own water is essential to determine if iron bacteria treatment is needed in your home.
For residential water supplies showing iron bacteria presence, the Fleck Iron Bacteria & Slime Filter ships ready to configure and can effectively reduce iron bacteria and slime buildup, improving water clarity and protecting plumbing and appliances. This system is designed for households experiencing iron bacteria-related issues and offers a documented solution tailored to common problems linked to iron in groundwater such as that found in Benton County.
Where this information comes from
Source: USGS groundwater sampling. Sampled 2017-09-25. 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 Iron in the 111ALVM aquifer (Benton County): 4 results from 3 wells, median 25.7 ug/L, range 13.2-146.0 ug/L; none above any federal threshold