Frequently asked questions: City of San Angelo distribution system contamination



1. Did the contamination come from the City’s water plant?


No. Through coordination between the City of San Angelo and the Texas Commission on Environmental Quality (TCEQ), it was determined that chemical contaminants entered into the city’s distribution system only in the northeastern area of the city (PaulAnn) and not from the city’s water plant.


2. How could chemical contaminants have entered the City’s distribution system?


The City is still investigating the cause of the contamination.


3. Are there any treatment technologies that could have been used at the City’s water plant to prevent this contamination?


Based on laboratory analysis and investigation, the City believes the contamination area is limited to the PaulAnn area in the northwest part of the city, which is several miles from the City water treatment plant at Lone Wolf reservoir. The water was contaminated after the water had left the treatment plant.


4. Why did the City issue a do-not-use order instead of the more common boil water notice?


At the time of issuance of the do-not-use order, the City and TCEQ suspected that the contamination involved some form of volatile organic compounds, which evaporate from water rapidly, typically creating a strong odor. However, neither the City nor TCEQ had certified laboratory results identifying exactly what the contaminants were. To protect public health and safety, the City agreed that the most protective approach at that time was to impose a do-not-use order until more investigation had been conducted.


5. Once the City knew what the contaminants were, why wasn’t the do-not-use order changed to a boil water order?


The major contaminants were identified as benzene, acetone and naphthalene, which are all volatile organic compounds. The act of boiling water would likely result in significant release of the contaminants from the water into the household. These chemicals can pose health hazards from ingestion (drinking, swallowing or consuming) or inhalation (breathing into your lungs).


6. Why did the City only release the higher-pressure plane area first?


The City verified that the higher-pressure plane was physically separated from the lower pressure plane prior to the contamination event, which ensured that any contamination in the lower-pressure plane could not physically move into the higher-pressure plane.


7. Why has the City only released portions of the distribution system in phases?


The City and TCEQ have been coordinating to evaluate the City’s water distribution system to determine areas of the lower pressure plane not at risk from the contaminants. As these areas are identified, they are being released to less restrictive measures.


8. Why isn’t the City using filter media approved by EPA to reduce organics in the water to stop using chloramine?


The processes used at the City’s water plant do include filter media approved by the EPA. While there are technologies that can reduce organics, such as granular activated carbon (GAC), the use of GAC on its own will not allow for changing the City’s disinfection approach from the use of chloramines. The treatment approach used at the City’s water plant is an EPA-approved and condition-appropriate approach to produce safe drinking water.


9. Could the chemical contamination be a terrorist or other malicious attack?

A malicious attack is an unlikely scenario based on the contaminants identified and the localized area impacted (PaulAnn area). The ultimate source of the contamination is still being investigated by the City and TCEQ at this time and further information will be provided when available.


10. When will the rest of the City’s distribution be released for normal use?


The City and TCEQ are continuing to coordinate on distribution system sampling as well as implementation of the City’s comprehensive flushing plan for the PaulAnn area. Following coordinated agreement between the City and TCEQ in the late evening of Feb. 10, City staff began to implement the flushing plan around 11 p.m. At this time, we are also awaiting TCEQ’s sampling laboratory results. Until those results have been received, the current do-not-drink order for the white area and the current do-not-use order for the red area must continue to be maintained. As soon as the next round of laboratory results come in for the TCEQ, the City and TCEQ will coordinate on potentially converting the white do-not-drink area to normal water use, though the current do-not-use order in the red area is anticipated to remain in effect until flushing and post-flushing sampling has been completed. As of the evening of Feb. 11, the City has received all laboratory results for field testing in the white area and all results met every state and federal regulated limit for drinking water; unfortunately, TCEQ’s lack of receipt of its test results of samples taken to confirm the City’s passing test results will further delay release of any of the restrictions in place at this time.


11. When did the City first learn about the contamination?


The City was contacted by a City resident in the PaulAnn area on Friday, Feb. 5, 2021 about an odor complaint. City staff visited the resident’s house on Friday and verified (along with the resident) that there were no further odors from the resident’s water. The City did not receive further complaints on Saturday. Three complaints came in from that area on Sunday. The number of complaints rapidly increased Monday morning in the PaulAnn area of the City’s distribution system. At that time, the City notified TCEQ and began field testing in the area to try to identify the potential area of contamination to support physically isolating the contaminated area from the rest of the City’s distribution system.


1. What should people do to clean dishes or other items that may or may not have been exposed to any of the contaminants?


Dishes should be cleaned using normal household detergents.


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