Chromium-6 Information

Is My Water Safe to Drink?

Yes. Your tap water remains safe to drink, cook with, and use for daily household needs. Myoma Dunes Mutual Water Company (MDMWC) has issued this notice because a new, more stringent state drinking water standard for chromium-6 has gone into effect — not because there has been any sudden change in your water quality. Chromium-6 occurs naturally in groundwater throughout the Coachella Valley, including in the wells that supply MDMWC's customers.

What Is Chromium-6?

Chromium is a naturally occurring metallic element found in rocks, soil, and groundwater throughout California, including the Coachella Valley. It exists in two primary forms in the environment:

• Trivalent chromium (chromium-3)An essential nutrient found in many foods and widely recognized as safe.
• Hexavalent chromium (chromium-6)A form that can occur naturally as chromium-3 weathers and oxidizes in rock and sediment, and which has been linked to potential health concerns with long-term exposure.

In the Coachella Valley, chromium-6 forms naturally as groundwater moves through local sediments and rock formations containing chromium. It is not the result of any industrial spill, leak, or contamination event in MDMWC's system.

The State's Drinking Water Standard

California is the only state in the nation with a drinking water standard specific to chromium-6. The state's Maximum Contaminant Level (MCL) for chromium-6 is 10 parts per billion (ppb). For comparison, the federal standard — used in every other state — regulates total chromium (chromium-3 and chromium-6 combined) at 100 ppb, ten times less strict than California's chromium-6-specific standard.

A brief regulatory history:

• 2014California adopted its first chromium-6 MCL of 10 ppb.
• 2017A court invalidated that MCL, finding the state's economic feasibility analysis insufficient.
• 2024After completing a new economic analysis, the state re-adopted the 10 ppb MCL, effective October 1, 2024.

This means the underlying water quality in the Coachella Valley has not changed — what has changed is the strength of the regulation applied to it.

What Is MDMWC Doing About It?

MDMWC is committed to meeting the state's chromium-6 regulation while keeping the cost of compliance as low as possible for our customers. Achieving compliance takes time and may involve one or more of the following approaches:

• Continued monitoringOf all active wells in accordance with state requirements.
• Evaluating treatment technologiesCapable of reducing chromium-6 to below the MCL.
• Blending water from multiple sourcesTo bring the running annual average into compliance.
• Taking a source offline and/or developing new wellsWhere feasible.
• Pilot studies for multiple treatment methods are underway.

As required by state regulation, MDMWC will continue to issue public notices as required until our system's chromium-6 levels consistently meet the 10 ppb standard. This webpage will be updated as new information becomes available.

Will This Affect My Water Bill?

MDMWC is evaluating the most cost-effective path to compliance and will keep customers informed before proposing any rate changes tied to chromium-6 compliance.

MDMWC's Monitoring Results

MDMWC routinely tests its wells and distribution system for chromium-6 in accordance with state monitoring requirements. Detailed results are published in our Annual Water Quality Report.

Quarterly Notices

Download all quarterly notices (combined PDF) →