Vice Mayor Richard Fimbres asked Tim Thomure, Tucson Water Director questions about the water supply. What follows is the responses Vice Mayor Fimbres received from Thomure.
Is the water is safe to bathe with, cook with and to drink. Yes, the water is safe for all uses. It was also safe during the time period discussed in the article (prior to 8/23). The Perfluorinated Compounds that were detected at that time were below 50% of the current Health Advisory. The actions we took to modify operations when we restarted the plant on 9/17 were designed to reduce the PFC concentrations even further, even though they were already below 50% of the Health Advisory.
Questions have been asked about the water being served from the mistaken sampling point and how long was this water served? Water has been served from the TARP facility for many years, and it has been safe throughout that time. The mis-located sample point does not mean that water was served that violated standards or exceeded the Health Advisory. Tucson Water uses multiple sample points to insure that the water delivered from TARP meets the required limits for TCE and 1,4 Dioxane; and we also have sampled for PFCs at these various sample points. The mis-located sample point was indicating the absence of PFCs, but other sample points indicated they were present at 30 parts per trillion (ppt) or less. The current HA is 70 ppt. Tucson Water modified operations of TARP to further reduce the concentrations of PFCs, even though they were already below 50% of the current Health Advisory.
Questions have also been asked about the mistaken sample point and the detection of PFAS in the water and whether any contaminated water was mistakenly served? The water being delivered from TARP was below 50% of the Health Advisory for PFCs. The mis-located sample point does not mean that water was served that violated standards or exceeded the Health Advisory, as verified by other sample points.
Questions were asked about the three wells in the TARP area that were shut down and how and when the PFAs were detected? All wells at TARP have varying concentrations of contaminants including TCE, 1,4 Dioxane, and PFCs. 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 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.
PFCs (also known as PFAS) were detected when Tucson Water began to voluntarily test for these non-regulatory compounds in our various water supplies. As has been documented previously, Tucson Water has the following operating protocols for PFCS's:
•Wells that directly enter the system that were above 70 ppt are shut-down and disconnected
•Wells that directly enter the system that were between 18 and 70 ppt are locked out, but could be used in an emergency water supply need (e.g. a major outage in part of the system)
•Wells that directly enter the system that have detectable PFCs that are below 18 ppt are normally turned off, but can be used to meet peak demand, if needed
•Wells that feed the TARP 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.