Tier 2 Notice
On Sept. 25, 2025, UC Davis sent a Tier 2 Notice to Davis campus students, faculty and staff with information about recent test results and California’s new drinking water standards for hexavalent chromium. While campus water remains safe to use, state regulations require us to share this notice for transparency.
California recently set the nation’s first drinking water standard for hexavalent chromium (chromium-6). Two UC Davis wells, which provide a small portion (6%) of Davis campus water, tested slightly above this new limit.
In compliance with the standard, we shared with the Davis campus community a Tier 2 Notice about recent water quality testing. This type of notice is required whenever test results exceed a state standard but the situation does not pose an immediate health risk.
You can continue to use campus water for drinking, cooking, and all other uses. This FAQ answers common questions about the new standard, what the results mean, and how UC Davis is addressing the issue with a long-term solution.
- Is it safe to drink tap water?
Yes. You can continue to use UC Davis tap water for drinking, cooking, research, and all other needs—there is no need to use an alternative supply. The quality of our water has not changed; what has changed are California’s regulations, which were updated to provide the nation’s strongest drinking water protection.
- What is chromium?
- Chromium is an odorless, colorless, naturally occurring metallic element found in soils throughout California and many other parts of the world. The two primary forms of chromium are trivalent chromium (chromium-3) and hexavalent chromium (chromium-6). Trivalent chromium is nontoxic and is an essential nutrient for humans and animals. Hexavalent chromium can form naturally in groundwater under certain conditions. Exposure to it over a period of many years has been linked to potential health concerns.
- How is hexavalent chromium regulated in drinking water?
Drinking water is regulated through safety limits called Maximum Contaminant Levels (MCLs) — these set the highest amount of a substance allowed in public drinking water systems.
- - The U.S. Environmental Protection Agency (EPA) sets a federal MCL of 100 parts per billion (ppb) for total chromium, which includes both trivalent chromium (chromium-3) and hexavalent chromium (chromium-6).
- - California has a more protective limit of 50 ppb for total chromium.
- - In 2024, California adopted a separate MCL of 10 ppb specifically for hexavalent chromium (chromium-6) — making it the only state in the nation with a drinking water standard focused just on hexavalent chromium.
- Does UC Davis water have hexavalent chromium?
Yes, in small amounts. UC Davis has multiple water sources. The primary source for UC Davis water is the Woodland-Davis Clean Water Agency, which supplies nearly two-thirds of campus water. This supply is in compliance with all state and federal drinking water standards.
The remaining water comes from five groundwater wells. Three of the wells are in compliance with all state and federal drinking water standards. Two have average hexavalent chromium at levels slightly above the state threshold, but otherwise meet all state and federal drinking water standards. Together these two wells only contribute about 6% of the total campus water supply. The presence of hexavalent chromium in these two wells is due to natural processes, not any current or former industrial activities.
These two wells are primarily used for fire protection and as back-up sources during times of peak demand. The university has decreased use of these two wells, though it continues to keep them operable in case of an emergency or periods of peak demand. As explained in more detail below, these two wells will be decommissioned in 2028.
- How much hexavalent chromium is in UC Davis water?
The hexavalent chromium levels in each of our water sources can fluctuate over time but averages remain consistent year-over-year. The two Davis campus wells that do not meet the new standard have average levels of 11 and 12 parts per billion (ppb). The majority of Davis campus drinking water supply comes from the Woodland-Davis Clean Water Agency — hexavalent chromium levels in the treated surface water are most recently 0.21 ppb. The weighted average of hexavalent chromium across all campus water sources is 1.8 ppb — well below the new state limit.
Hexavalent Chromium Levels (parts per billion, ppb)
Sample Date Domestic Well 2
Domestic Well 4A
Domestic Well 5
Domestic Well 6A[1]
Domestic Well 7A[1]
Treated Surface Water from WDCWA[2]
11/19/2024 ND (<0.10)
4.8
4.9
7.5
9.5
-
2/19/2025 ND (<0.050)
4.7
2.5
3.4
11*
-
5/27/2025 ND (<0.050)
2.6
4.6
19*
14*
-
8/26/2025 ND (<0.050)
3.3
3.1
18*
9.8
-
8/14/2025 -
-
-
-
-
0.21
Annual Average at
Each SourceND
3.9
3.8
12*
11*
0.21
Percent of Annual Water Supply 4%
10%
15%
3%
3%
64%
Weighted Annual
Average Concentration
for Water System1.8%
ND: Not detected
[1] All results above the 10 ppb limit for hexavalent chromium are marked with an asterisk (*).
[2] Sampling of the Woodland-Davis Clean Water Agency (WDCWA) supply is not required quarterly due to consistently low concentrations reported.
[3] The sum of all sources does not equal 100% due to a rounding error.- What is the university doing to address this?
UC Davis has been planning for these heightened safety requirements and is taking proactive steps.
To address the new hexavalent chromium standard:
- - UC Davis is investing $37.8 million to build a new surface water treatment plant, after which the university will be able to retire the two affected wells. The university anticipates that the new plant will be operational by Summer 2028, in accordance with the phased timeline established in the new regulation.
- - UC Davis has already significantly reduced use of these two wells for the Davis campus potable water supply.
The university remains committed to providing a safe water supply for the campus community, and to meeting all state and federal health standards.
- If no action by individuals is needed, why do we have to send a notice out?
- State regulations require water systems to notify users of results that exceed the drinking water standards, even if — as in our case — the water supply remains usable and there is no need for users to turn to an alternative supply. The university complies with all state and federal drinking water standards.
- Why are the results being shared now?
UC Davis details all water quality test results each year in our Annual Water Quality Report. The results of hexavalent chromium groundwater well tests in 2024 were published in the most recent report. The university received the latest quarterly test results on September 10, 2025.
Because the average of the last four quarterly test results at two campus wells was slightly above California’s new hexavalent chromium standard, state regulations require that UC Davis send a Tier 2 Notice within 30 days of the most recent test. Tier 2 Notices are shared when results exceed a standard but do not pose an immediate health risk. Had there been an urgent health risk, the campus community would have been notified immediately.
- Who receives potable water from the UC Davis water system?
- The UC Davis water system provides potable water to the Davis campus, including buildings and facilities on the core, south, and west areas of campus. Some locations, such as Cuarto Student Housing, Graduate Student Housing at 8th and Wake, and other buildings within the City of Davis, receive water from the City of Davis system. This notice applies only to the Davis campus and does not pertain to UC Davis Health in Sacramento or other university facilities outside of Davis.
- Who can I contact with questions about water quality?
- For more information about the UC Davis water supply, contact UC Davis Facilities Management at fmcommunications@ucdavis.edu or (530) 752-1655. For more information about California water standards and hexavalent chromium, please refer to the California Water Boards fact sheet.