Water supplied to homes in Bismarck, Burleigh County, originates from surface water sources managed by the City of Bismarck's public system. This system serves over 72,000 residents through more than 21,000 connections. Federal monitoring under EPA's Unregulated Contaminant Monitoring Rule (UCMR3) collected data on chromium-6 (hexavalent chromium, Cr(VI)) during 2013 to 2015, providing a documented baseline of chromium-6 occurrence in the source water before household taps.
Why California Set a 10 µg/L Limit for Chromium-6 and Its Meaning Beyond the State
California established a maximum contaminant level (MCL) of 10 micrograms per liter (µg/L), or parts per billion, specifically for chromium-6 based on statewide health risk assessments. This regulatory action is unique to California and does not apply federally or in North Dakota. EPA has not set a federal MCL for chromium-6; instead, it maintains a total chromium MCL of 100 µg/L, which aggregates all oxidation states. Bismarck's water system results showed chromium-6 detections well below California's threshold, with the highest recorded concentration at 0.7 µg/L. These findings indicate chromium-6 is present but at levels substantially lower than California's guideline and far below total chromium limits. Therefore, California's limit offers perspective but does not directly define the safety or compliance status of Burleigh County water.
Geogenic Hexavalent Chromium in Arid and Alkaline Aquifers Versus Industrial Sources
Chromium-6 can appear in water through natural geological processes or industrial activities such as plating and manufacturing. In arid or alkaline aquifers, hexavalent chromium typically leaches naturally from certain rock formations, a process termed geogenic origin. The City of Bismarck's surface water supply may reflect contributions from such natural sources rather than industrial contamination, as it has no EPA health-based violations related to chromium-6 on record. Understanding whether chromium-6 arises from natural or industrial origins can influence treatment choices and monitoring strategies.
How Seasonal or Multi-Year Variation Shows in the Record
The UCMR3 data for chromium-6 in Bismarck's system covers monitoring over several months from May 2013 to February 2014. During this time, chromium-6 was detected consistently in all eight samples, with a median concentration of 0.6 µg/L and a maximum of 0.7 µg/L. These levels show limited seasonal variation in the data collected but do not represent continuous monitoring or detailed temporal fluctuations. Long-term or more frequent testing would be necessary to detect potential changes over multiple years or seasons.
The Household or Facility Symptoms That Do and Do Not Point to This Problem
Chromium-6 itself is a microscopic dissolved chemical and does not cause immediate taste, odor, color, or staining changes in water. Homeowners experiencing symptoms such as discoloration, corrosion, or metallic taste should consider other causes because chromium-6 presence at measured levels typically does not produce sensory effects. Detecting chromium-6 relies on laboratory analysis rather than household observation. Hence, visible or organoleptic signs generally do not indicate chromium-6 issues specifically.
Which Fixtures, Appliances, or Processes Are Affected First and Why
Appliances and plumbing fixtures that use or heat water, such as water heaters, dishwashers, or ice makers, may expose occupants to chromium-6 dissolved in water. However, chromium-6 does not precipitate to cause scale or deposits in plumbing like some minerals do. The primary concerns involve ingestion or prolonged exposure rather than immediate appliance damage. Understanding the flow rate and daily household water demand can help evaluate whether filtration technologies are sufficient to handle chromium-6 concentrations typically detected in Bismarck.
What a Certified Laboratory Test for This Constituent Reports and How to Read It
A certified laboratory report for chromium-6 in water provides concentration in micrograms per liter (µg/L or ppb). Laboratories use specialized analytical methods sensitive enough to detect levels at or below 0.03 µg/L, which is the reporting threshold used by EPA during UCMR3. It is essential to note that a detection above this threshold is not a violation, hazard, or safety failure—only a measurement. Testing your home water specifically determines your actual chromium-6 level, which may differ from public system averages and requires interpretation against available guidelines or personal risk tolerances.
Choosing a management approach for chromium-6 involves balancing technical options with household needs. Technologies like the Autotrol Chromium-6 Filter ship ready to configure and can provide targeted chromium(VI) reduction to align with monitoring data and household water use. This equipment exemplifies modern ion exchange technology designed specifically for hexavalent chromium challenges.
In summary, Burleigh County’s public water system shows chromium-6 present at low microgram per liter levels without health-based violations. Understanding local data, natural sources, detection methods, and affected household points informs a prudent path toward water treatment decisions. The Autotrol Chromium-6 Filter offers one documented technical method to address chromium(VI) concerns as part of that path.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2014-02-11. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for City of Bismarck (ND0800080), ND: 16 results across 2 listed contaminants, 16 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L