Navy expands PFAS well testing near MCAS Yuma as questions remain about groundwater contamination

Private-well owners in parts of the Yuma area may qualify for free testing. The Navy plans to revisit wells sampled in 2023 while expanding its search for potentially affected drinking water.

By Dan Bustard | Yuma Informed

The Navy is expanding its search for PFAS chemicals in private drinking-water wells near Marine Corps Air Station Yuma, returning to properties tested three years ago and asking more homeowners for permission to sample their water.

The reason is what investigators have already found beneath the air station. Certain PFAS chemicals have been detected in groundwater at concentrations exceeding the military's interim action levels for private drinking water.

What remains unclear is whether those chemicals have reached additional private wells beyond the installation.

That distinction matters. Finding PFAS in groundwater at MCAS Yuma does not automatically mean the water coming from a nearby homeowner's tap is contaminated. The expanded testing is intended to help answer that question.

The Navy and Marine Corps have published a sampling map, program information and results from earlier testing.

Is your well in the testing area?

The expanded sampling area covers portions of the Yuma community surrounding the air station.

In an October 5 report, KAWC described the area as stretching from La Mesa Linda southwest toward Padre Ranchitos and east of Avenue 3E.

Those landmarks offer a general idea of where testing is taking place, but they are not enough to determine whether a particular property qualifies.

The Navy's official program page includes a map identified as Figure 2 showing the areas where the military is seeking permission to sample private drinking-water wells.

Residents who rely on private wells within those boundaries are encouraged to contact the program.

Homeowners served by the City of Yuma's Main Street or Aqua Viva water treatment facilities do not need to participate in this private-well sampling program, according to the Navy.

For residents who are unsure whether their property qualifies, the program provides two ways to ask:

• Phone: 800-374-7843
• Email: MCASYumaPFAS@aecom.com

The Navy originally advertised sampling appointments from September 30 through October 7, 2026, between 8 a.m. and 6 p.m., with additional times available upon request.

Those advertised dates have passed. As of October 8, the official program page had not established a new cutoff date. Residents interested in testing should contact the program to find out whether appointments are still being scheduled.

General questions can also be directed to MCASYuma_Media@usmc.mil.

Why the Navy is expanding its search

PFAS are a group of manufactured chemicals used in numerous industrial and consumer products. Some resist breaking down in the environment, which is one reason contamination can remain a concern long after the original use has stopped.

At military installations, one familiar source is firefighting foam.

The Naval Facilities Engineering Systems Command, commonly called NAVFAC, identifies the historical use of firefighting foam during training, testing, firefighting and emergency response as the most common activity that could have released PFAS at MCAS Yuma.

Private-well sampling began in May 2023, initially concentrating on an area approximately one mile downgradient from a known release area. In ordinary terms, that means investigators focused on wells in the direction groundwater was believed to be moving away from the release.

The military now considers a larger testing area necessary because of groundwater findings at the installation.

The Navy also wants to resample wells tested in 2023, citing improvements in laboratory testing methods.

Better testing methods can provide a more complete picture of what is present in the water. They do not, by themselves, establish that contamination has increased since the earlier samples were collected.

What the first five wells revealed

The Navy has published results for five private drinking-water wells sampled during the 2023 investigation.

The findings offer some reassurance for those particular wells, although they leave the larger question unresolved.

Of the five wells:

• One had no PFAS detections.
• Four had PFAS detections below the military's current interim action levels.
• None had PFAS concentrations at or above those action levels.

The Navy does not identify individual properties in its published results table.

There is also an important distinction between finding a chemical and finding it at a concentration that triggers government action.

Four wells had detectable PFAS. That does not mean they exceeded the military's thresholds for providing a response.

The results cannot tell residents what may be present in wells that were never sampled.

As of October 8, the Navy's public program page contained no results from the expanded 2026 private-well sampling effort.

What counts as too much PFAS?

This is where the numbers can become confusing.

The military uses interim action levels for responding to PFAS in private drinking-water wells. The Environmental Protection Agency has separate drinking-water standards for public water systems.

Those numbers are not the same.

According to the Navy's September 2026 fact sheet, the Department of War's interim action levels for private wells are:

ChemicalMilitary private-well action levelEPA public-water standard

PFOA

12 ppt

4 ppt

PFOS

12 ppt

4 ppt

PFNA

30 ppt

10 ppt

PFHxS

30 ppt

10 ppt

GenX (HFPO-DA)

30 ppt

10 ppt

Hazard index for specified PFAS mixtures

3

1

Ppt means parts per trillion. The hazard index is a separate calculation used to evaluate certain chemical mixtures, not a concentration measured in ppt.

The mixture calculation applies when at least two of four chemicals are present: PFHxS, PFNA, HFPO-DA and PFBS.

The figures illustrate why a resident might see a detectable amount of PFAS, or even a concentration above an EPA public-water standard, without reaching the military's interim threshold for action at a private well.

The two sets of standards serve different regulatory purposes and should not be treated as interchangeable.

NAVFAC says the military will review and update its policy if applicable EPA requirements change.

What happens if a well exceeds the military's limits?

The Navy and Marine Corps say they will respond when testing finds PFAS at or above the applicable military interim action levels.

Depending on the circumstances, longer-term options could include connecting a property to a public water supply or installing a drinking-water treatment system.

The military also has a bottled-water provision.

According to NAVFAC, when PFOA or PFOS concentrations, individually or combined, exceed 70 parts per trillion, bottled water can be provided for drinking and cooking while a longer-term solution is arranged.

That 70-ppt figure is a separate threshold for the bottled-water response. It should not be confused with the lower interim action levels used to determine when other action may be necessary.

Under the federal cleanup process, final remedies are intended to address drinking-water wells to EPA public-water standards or background levels.

For homeowners, the immediate question is simpler: What is in their water, and what happens if testing finds a problem?

When will homeowners receive results?

The Navy says preliminary laboratory results should be available approximately 30 days after samples are collected.

Those results must then undergo an independent third-party quality review.

Validated results are expected to reach property owners and tenants approximately three months after sampling.

That means residents should not expect a final answer immediately after providing a water sample.

The program's published schedule also means results from different properties may become available at different times, depending on when their samples were collected.

What about PFAS and biosolids in Yuma?

PFAS has already become part of a broader environmental discussion in Yuma, including questions surrounding biosolids and agricultural operations.

Yuma Informed has separately examined those issues in its reporting on PFAS and AgTech biosolids.

But the investigations should not be combined without evidence connecting them.

The MCAS Yuma records reviewed for this report do not establish a connection between PFAS associated with the air station and AgTech biosolids.

The Navy's investigation concerns groundwater findings at MCAS Yuma and private drinking-water wells in the surrounding study areas.

Both subjects deserve scrutiny. They are not automatically the same contamination problem simply because PFAS is involved.

For now, the clearest picture comes from the limited sampling already completed: five private wells tested in 2023, four with detectable PFAS, and none above the military's current interim action levels.

The expanded testing should provide more information about surrounding wells.

Until those results are available, residents with private drinking-water wells in the mapped area have a practical option: check whether their property qualifies and request sampling directly from the Navy's program.

Official information: MCAS Yuma PFAS Private Drinking-Water Well Sampling Program