Geogenic Hexavalent Chromium in Arid, Alkaline Aquifers Versus Industrial Plating Sources
A common misinterpretation is assuming all chromium-6 in water arises from industrial pollution. In El Paso County, data from the Security Water System (serving 20,000 residents via 7,519 connections) shows chromium-6 present in surface water sources typical of many arid, alkaline aquifers. This contrasts with chromium-6 from industrial plating, which tends to come from localized contamination rather than broad regional geochemistry.
The EPA's Unregulated Contaminant Monitoring Rule (UCMR3) sampling from 2013 to 2015 detected chromium-6 in every tested sample for this system, with levels ranging from 0.03 to 0.89 micrograms per liter (µg/L, or parts per billion). These values reflect background regional conditions, not an industrial release.
Trivalent Versus Hexavalent Chromium: Why Total Chromium Results Cannot Answer the Question
Laboratory results often report total chromium, the sum of chromium-3 (trivalent) and chromium-6 (hexavalent) forms, but this measurement alone doesn't reveal the amount of chromium-6 specifically. For El Paso County, total chromium results from the public system ranged up to 0.9 µg/L, comparable in scale to chromium-6 levels.
Chromium-3 generally poses less concern in water treatment contexts due to lower mobility and toxicity. Therefore, knowing total chromium does not clarify the chromium-6 concentration relevant to health and aesthetic considerations. Specific testing for chromium-6 is necessary to understand the relevant portion in household water.
Why California Set Its Own 10 µg/L Limit and What That History Means for a Reader Elsewhere
California has developed a public health goal for chromium-6 in drinking water of 10 micrograms per liter. This guideline is not a federal standard but reflects state-level risk assessments and precautionary policy. The highest chromium-6 concentration recorded for Security Water System is well below this benchmark, supporting system compliance with federal health-based regulations, which currently do not include a maximum contaminant level for chromium-6 specifically.
This context helps households in El Paso County understand that the federal data imply no health-based violation exists in their public water source even though chromium-6 is present.
What Changes for a Large Household, a Second Home, or a Seasonal Property
Household size, home occupancy patterns, and property usage can influence water quality experience despite identical source water. Larger families or homes with higher water demand may see more prominent effects from dissolved solids or mineral concentrations, including any chromium species.
Seasonal properties or second homes may have water sitting in pipes longer between uses, possibly affecting chromium speciation or baseline concentration at the tap. Understanding these differences can guide when and how to test individual household water versus relying solely on regional system data.
A Worked Example: Reading the Record's Median and Range as a Homeowner Would
The Security Water System results include 44 chromium-6 measurements, all above the detection level of 0.03 µg/L. The median chromium-6 concentration was 0.485 µg/L, with a highest recorded value of 0.89 µg/L. These figures mean that, for half the samples, chromium-6 was below about 0.5 µg/L and never above one microgram per liter.
As a homeowner assessing concerns from these numbers, it is clear the water routinely contains chromium-6 at low levels far beneath California's precautionary 10 µg/L and the total chromium federal limit of 100 µg/L. Still, individual household testing is necessary for precise water quality decisions.
How Public-System Records Differ from Private-Well Testing in What They Establish
The EPA data represent broad public system monitoring, describing water quality as it leaves a utility's treatment and distribution facilities. This record does not reflect specific conditions at individual taps or private wells, where plumbing materials, well depth, and local geology influence water chemistry.
Private well owners in El Paso County should obtain testing that directly measures chromium-6 at their point of use. Public system monitoring is valuable for general understanding but cannot substitute for personalized results when making household water treatment choices.
To address chromium-6 concerns, WaterSoftenerPlus offers the Fleck Chromium-6 Filter, a system designed to be shipped ready to configure for effective chromium(VI) treatment tailored to residential needs.
In conclusion, the 2013-2015 EPA UCMR3 monitoring data for Security Water System show chromium-6 presence as a regional feature in El Paso County's surface water supply with no health-based violations reported. For accurate individual household assessment, direct chromium-6 testing remains essential. For further details, refer to the EPA's online public water system records.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2014-10-27. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for Security WSD (CO0121775), CO: 88 results across 2 listed contaminants, 80 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L