Tucson Water FAQ's on Water Quality

[Updated 10/13/2018]

In response to the 9/30/2018 Arizona Daily Star article on Tucson’s water quality, you may have questions on Perfluorinated Compounds (PFC’s), the Tucson Airport Remediation Project / Advanced Oxidation Project (TARP / AOP), or other concerns. The Fact Sheet below was prepared to address some of the misleading information in the article. In addition, Tucson Water has received a number of specific questions from our customers, social media discussions, our Mayor and Council, and the press. Answers to those FAQ’s are provided below and this list will be updated frequently. Please reach out if you have any additional questions for us!

Click here for a Fact Sheet about PFC's issued in response to the 9.30.18 Arizona Daily Star Article. pdf


Posted 10/13/2018

Q. Tucson Water’s Fact Sheet of October 1 states that the water delivered from TARP is not contaminated, but the City is suing PFC manufacturers claiming that our groundwater is contaminated. Those two positions appear to contradict each other, can that be explained?

A. PFC’s have been detected in wells located in the northwest part of the community, wells that serve the non-potable reclaimed water system, wells down-gradient from Davis Monthan Air Force Base, and from wells within the TARP facility. We have deployed a range of strategies to ensure that this water is not delivered to customers. These strategies range from turning wells off to developing blending and treatment options. The water we are delivering to customers is indeed safe as we are not delivering (nor have we delivered) water that exceeds even 50% of the non-regulatory health advisory for PFC’s. And, we have instituted an Interim TARP Operating Plan to further reduce PFC’s in the water.


Q. The science is not settled on PFC’s.

A. We have tracked the science over many years, participate in active research on PFC treatment, and make conservative decisions to protect public health. Any water we deliver that contains measurable PFC’s is below 50% of the health advisory and our internal operating target is less than 18 ppt.


Q. How is this fair to south side residents? Are they now receiving water containing PFC’s in the same area that they historically received water with harmful concentrations of TCE in the past?

A. The water being delivered from TARP is safe and is not delivered to residents of Tucson’s South Side. The South Side has received its drinking water from other sources since 1984 and currently this water is sourced from Avra Valley and the Santa Cruz Well Field, where Colorado River water is recharged and recovered. The water delivered to South Side residents has no measurable PFC’s.


Posted 10/5/2018

Q. People are confused and uncertain what to think about the safety of PFC’s in drinking water because of the different agency opinions and reports. [Question for Director Thomure] Would you drink it and would you give it to your children? Do you or did you ever in the TARP delivery area?

A. I (Tucson Water Director Tim Thomure) drink this water every day at work, and I have worked downtown for most of my career in Tucson. The Tucson Water Headquarters and City Hall are both located right in the heart of the TARP / AOP delivery zone. Our Plant 1 site is located at the very start of the TARP / AOP delivery zone and I drink the water there as well. The first house that my wife and I lived in together was located within the TARP / AOP delivery zone, and our kids were in grade school during those years and they drank the water. Our beloved cat, Ricky, also drank the water and lived to be 21 years old. We now live in another part of Tucson, and our young cat, Jack, drinks Tucson Water every day.

Q. There are widely different opinions on what is an appropriate level of PFAS (e.g. PFC’s) to be in drinking water, and many states have widely different standards and guidelines. Given that, what makes you think that the water served to the TARP customers until recently with up to 30 ppt PFAS was safe to drink? Why do you trust the EPA advisory level compared to the other recommendations and state standards of lower levels?

A. The US EPA is the regulatory agency that oversees the Safe Drinking Water Act and is the recognized authority for the water industry. The process and methods that US EPA uses to develop their water quality standards are robust, consistent, and well understood. Often, the first step before a regulatory standard is set by US EPA is for them to issue a Health Advisory. Health Advisories are non-regulatory and provide conservative guidance to protect public health. Finally, they are based on peer-reviewed scientific data.


Q. What was false about the Star headline Sunday (9.30.18)?

A. Tucson Water did not serve water “by mistake.” The water that was served was not “contaminated.” So, no part of the headline was correct. The water served was below 50% of the non-regulatory health advisory. The headline was misleading and harmful to Tucsonans.


Q. Why do you think the Star’s usage of the word contamination was inaccurate in Sunday’s story?

A. All water contains various compounds, including many natural and sometimes man-made compounds. Contaminated water contains compounds above health-based regulatory limits or health advisories. This does not and did not.


Q. Do you know yet when you’ll be releasing to us and the public the results of your latest sampling in the TARP delivery area?

A. The latest sampling results are expected to be received from the laboratory on or about October 9. Preliminary data indicates that the internal operational target of 18 ppt will be met in the delivery zone, but that is not confirmed until we receive the data from all sample points.


Q. I spoke to another TARP delivery area resident, [name redacted], and he told me that 3 or 4 weeks ago, he began to notice a bad sometimes nasty metallic taste in his water. He said it was sometime in mid-September but he wasn’t sure if it was before or after Sept. 17 when you temporarily shut the TARP plant down. Do you know if such a taste is a symptom of PFAS in the water?

A. We have not seen any information that there would be a metallic taste to water containing PFC’s, especially at concentrations below 50% of the Health Advisory. 


Q. What is the basis for your Fact Sheet, that peoples’ water is safe to drink?

A. The water delivered from the TARP / AOP facility is tested regularly for all drinking water standards. It is also tested for the compounds that are being removed through treatment (TCE and 1,4 Dioxane) and through blending (PFC’s). Water delivered from TARP / AOP is in compliance with regulatory standards and non-regulatory Health Advisories. Specifically for PFC’s, EPA’s 2016 Health Advisory of 70 ppt is a conservative guideline that we adhere to throughout the system.


Q. What about the Agency for Toxic Substances Disease Registry (ATSDR) study from 2018? Is that report’s recommendations preferable to EPA’s advisory from a public health standpoint?

A. We have reviewed the ATSDR study and are have considered the recommendations from that study to develop our internal operational target of 18 ppt. We do not conclude from that study that water containing PFC’s above 18 ppt is dangerous to public health. Our research on this matter shows that ATSDR made it clear that its recommendations are not intended to be cleanup or health effects standards. To use them as such is a misuse of that report. We are tracking this issue closely and rely heavily on US EPA for our guidance. In the interim, we have set our internal operational target to be extremely conservative.

Posted 10/4/2018

Q. What water was being served, from what facility, and how long was this water served?

A. Water has been served from the TARP / AOP facility for many years, and it has been safe throughout that time. Tucson Water uses multiple sample points to insure that the water delivered from TARP / AOP meets the required limits for TCE and 1,4 Dioxane; and we also have sampled for PFC’s at these various sample points. There is no regulatory limit for PFC’s, although USEPA has issued a conservative Health Advisory of 70 parts per trillion (ppt). PFC’s measured from TARP / AOP have been approximately 30 ppt (less than 50% of the Health Advisory) and Tucson Water recently modified operations of TARP/ AOP to further reduce the concentrations of PFCs

Q. The article talks about a “mistake” from Tucson Water. What was that mistake and did it affect my water quality?

A. Tucson Water uses hundreds of sample locations to monitor water across our system, including several at or near the TARP / AOP facility. Our review of PFC data at TARP / AOP indicated that one sample point was providing water quality results that did not match other points, even though they should have been consistent. We researched the issue and found that one sample point was installed incorrectly in 2000 and was sampling water from the wrong pipeline. This was indeed a mistake. However, the mis-located sample point does not mean that water was served that violated standards or exceeded the Health Advisory, as verified by the other sample points. Public health was protected due to our use of multiple sources of data.

Q. If the water from TARP / AOP was already safe, why did Tucson Water recently shut-down three wells in the TARP / AOP area?

A. All wells at TARP / AOP have varying concentrations of contaminants including TCE, 1,4 Dioxane, and PFC’s. Water from these nine wells is pumped, mixed, and brought to the TARP / AOP facility for treatment – none of it is delivered to any customer prior to blending and treatment. For TCE and 1,4 Dioxane, the TARP / AOP facility is effective at removing these compounds to well below any applicable standards. The TARP / AOP facility was not designed to remove PFCs; therefore, the PFC concentrations are managed by blending and might also be incidentally reduced by carbon that is used as part of the overall treatment process. Tucson Water shut-down the three wells recently to reduce the amount of PFC's entering the TARP / AOP facility so that blending can further reduce the concentrations of PFC's exiting TARP. Prior to the wells being shut-down, the PFC's exiting TARP were approximately 30 ppt, which is less than 50% of the Health Advisory. With those three wells out of service, PFC concentrations are expected to be below 18 ppt or less, which will be verified by ongoing monitoring.

Q. How is Tucson Water managing PFC’s in other parts of the system?

A. PFC’s (also known as PFAS) were detected when Tucson Water began to voluntarily test for these non-regulatory compounds in our various water supplies. Tucson Water has the following operating protocols for PFC's:

  • Production wells that directly enter the system that have measured PFC's above 70 ppt are offline and disconnected from the system (5). One additional well that meets this criteria, Y-004A, is available only as a back-up supply during a Fire Flow event in the northwest part of our system, where it would be heavily diluted to below 70 ppt.

  • Production wells that directly enter the system that have measured PFC's between 18 and 70 ppt are offline and physically locked out, but could be activated in an emergency (2).

  • Production wells that directly enter the system that have measured PFC's below 18 ppt are offline, but could be run remotely by the system operator if needed, with notification to the Director (3).

  • Wells that feed the TARP / AOP facility do not serve customers directly and are operated under an overall strategy designed to insure that the water delivered from the TARP / AOP facility is well below 70 ppt, with a voluntary operational target of 18 ppt or less.