Frequently Asked Questions

In 2024, California tightened its standards on acceptable levels of chrome-6 (hexavalent chromium or chromium 6) in potable water to 10 parts per billion (ppb). 

Because Soquel Creek Water District exceeded the new MCL in three wells in the seascape area, we were required to send out the notice to all customers. The State of California is requiring municipalities, businesses, and schools to notify consumers about the updated standards and the agency's level of compliance with them. 

Chrome-6 (also called hexavalent chromium or chromium 6) is a form of the element chromium that occurs naturally in the environment. It is found in certain rocks and soils and can enter groundwater as these materials break down. 

Chromium is a naturally occurring metallic element found in rocks, soil, plants, volcanic dust, and even animals. In our area, chromium is present in the rocks and sediments of the Santa Cruz Mid-County Groundwater Basin, especially in the Aromas Red Sands aquifer. 

In our groundwater basin, rocks and sediments break down over time containing chromium-3, causing it to be naturally converted to chrome-6, which then seeps into groundwater supplies like ours. 

Chromium-3 (trivalent chromium) is a nutrient that the body needs in very small amounts to help with things like processing sugar and fat. Chrome-6 occurs naturally in the environment from the erosion of natural chromium deposits. It can also be produced by industrial processes. Together, Chromium 3 and Chrome-6 make up Total Chromium. 

The USEPA sets enforceable drinking water standards based on science to protect health. States must adopt these standards, but may also set stricter ones. 

Total chromium (which includes both chromium-3 and chrome-6):

• Federal standard for Total Chromium is 100 parts per billion (ppb).
• California standard for Total Chromium is 50 ppb

For Chromium 6

• There is no federal standard.
• California is the only place in the world that has a specific Chrome-6 standard of 10 ppb.

  
  

In 2014, the state set a chrome-6 MCL of 10 ppb, but it was invalidated in 2017 due to economic analysis issues. On April 17, 2024, California re-adopted a chrome-6 MCL of 10 ppb, effective October 1, 2024. Water systems have up to three years to comply. Details and documentation of the recent rulemaking process are on the State Water Board Hexavalent Chromium webpage. 

The District is still providing the same great, high-quality water we have been serving for over 60 years; the only thing changing is the State’s regulations. Most of the wells in our service area have levels below the new regulation. However, three wells have shown levels exceeding the new MCL.  

The District has been proactive in preparation for the new MCL. We are working with SWRCB to address the exceedance and comply with the MCL. We have completed the Environmental review and a pilot test using Reduction Coagulation Filtration (RCF) technology to remove chrome-6. Our compliance plan was approved by the State, and a design for a new treatment plant is currently underway to remove chrome-6 from the three affected wells.  

Yes. Tap water remains safe to drink, cook with, and use for all daily needs. Chrome-6 regulations address long-term exposure risks, not immediate health threats. The District continues to meet all other state and federal drinking water standards, which are among the strictest in the world. 

The average level in three of our wells is 3.2 parts per billion (ppb) and ranges from undectecable to 17 ppb. The new standard is 10 ppb.  

What is an MCL?
The Maximum Contaminant Level (MCL) is the maximum concentration of a chemical allowed in public drinking water systems. It is established by the U.S. Environmental Protection Agency (EPA) or the California State Water Resources Board (State Board).  

How much is a part per billion? 

A part per billion is equal to one drop in 660,000 gallons, the size of an Olympic-sized swimming pool

There is no immediate health threat, even in areas with levels of chrome-6 above 10 parts per billion. It is still safe to drink, cook with and use your tap water. The state regulates chrome-6 to reduce potential long-term risks. Some people who drink water containing chrome-6 above the maximum contaminant level (MCL) over many years may have an increased risk of cancer.  At an MCL of 10 ppb, the health risk from hexavalent chromium in drinking water is limited to a one-in-two-thousand chance of developing cancer during a lifetime (70 years) of exposure.*

California is the only state to regulate specifically chrome-6.

*State Water Board FAQ

Yes, it’s the same type of chemical—hexavalent chromium (chrome-6). However, the source and concentration are very different. In the Erin Brockovich case in Hinkley, California, chrome-6 came from industrial pollution—a power company discharged chemical waste directly into unlined ponds, contaminating groundwater.

The difference in levels of the chrome-6 is enormous.  The chrome-6 in Hinkley reaches levels of over 1,000 ppb.* The highest MCL we detected in our three wells that are over the 10 ppb is 17 ppb. 

*https://hinkleygroundwater.com/ has the Cleanup and Abatement Order No. R6V-2015-0068, issued by the Lahontan Regional Water Quality Control Board. That document includes hexavalent chromium concentrations as high as approximately 3,600 ppb in at least one monitoring well.