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Public Notice

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Computer software error causes surface water treatment violation

The Public Notice is going out to Pflugerville homeowners the week of January 21. Please allow a few days for you to receive your paper copy. The Public Notice is sent to Southwest Utilities dba Windermere Utility Company and Manville Water Supply Corporation customers to meet TCEQ’s public notification requirements. 

What Happened

The City of Pflugerville received a Notice of Violation from the Texas Commission on Environmental Quality (TCEQ) on January 10, 2020 as the result of a computer software programming error at the Surface Water Treatment Plant. During a routine Membrane Integrity Test (MIT) on December 24 at the City of Pflugerville Surface Water Treatment Plant, the alert notification software incorrectly indicated that a filtration membrane’s integrity was within state and federal levels and “passed” the automated test.

While reviewing the MIT reports approximately 5 hours later, a City water operator discovered the computer programming error and the affected membrane was immediately shut down, assessed and manually re-tested. The manual re-test confirmed the membrane was operating within state and federal regulations. However, as a result of the computer error, for a period of approximately 2.5 hours, the filtration membrane had a decay rate of .35 pounds per square inch (PSI) per minute which exceeds the state and federal guideline of .33 PSI per minute or less. A decay rate is one of several tests run to measure membrane effectiveness. The amount of water potentially impacted represents less than 2% of the City’s daily gallon water usage, or approximately 80,000 gallons out of six million produced that day.  

While the treatment violation doesn’t mean cryptosporidium is present, decay rates and turbidity levels are indicators of the filtration necessary to remove cryptosporidium if it were.

The City sent water to a third party lab for cyptosporidium testing and it came back on January 21 with a report of none detected.

Media release;: Software error causes surface water treatment violation


December 25, 2019: The error was discovered at 12:45 a.m. for a test run at 6:55 p.m. on December 24, 2019.
December 27, 2019: TCEQ was notified when TCEQ offices reopened after the holiday.
January 6: City representatives met with TCEQ to discuss incident and public notification
January 7: Manville and Windermere Utility notified.
January 9: TCEQ approved the City's public notice letter. 
January 10: City received the official notice of violation (NOV)
January 13: The Public Notice was sent to the printer for printing and mailing, posted on the City website and social media channels, and media outlets were notified to help communicate the message to our customers. The letter is anticipated to mail from the post office on January 21 and be in resident mailboxes by January 25. 
January 14: There was an item on the public City Council worksession agenda at 5 p.m. to discuss the recent TCEQ Public Notice and violation. View the presentation online.
January 21: The City sent water to a third party lab for cyptosporidium testing and it came back on January 21 with a report of none detected.

Water Reports

Improvements at the Surface Water Treatment Plant

We have made several improvements at the plant including:
1.      Membrane repairs on trains 1, 2 and 4  
2.      New airline installed
3.      Turbidity meter moved
4.      River pump replaced, permeate pump replaced and a blower replaced.
5.      Software reprogrammed

1.      Membrane repairs with additional training of operators to conduct in-house membrane repair
2.      Valve replacement
We are committed to improving the infrastructure in our water system and specifically at our surface water treatment plant. 

Frequently Asked Questions


Is my water safe to drink?

City of Pflugerville water meets or exceeds state and federal drinking water standards. 

Does this apply to Manville and Southwest Water customers?

Yes. Because the City is wholesale water provider to the Southwest Utilities dba Windermere Utility Company PWS ID TX2270161 and Manville Water Supply Corporation PWS ID TX2270033, the public notice is being provided on behalf of these systems to their customers to meet TCEQ’s public notification requirements.

What is a membrane integrity test (MIT)?

The MIT is one of several indicators to determine membrane filtration effectiveness at the Surface Water Treatment Plant. A weekly MIT is routinely conducted on each plant membrane. There were no issues indicated in other treatment protocols or tests during the time of the computer software error. Immediately following this incident, the turbidity level, which is measure of the clarity of the water and a secondary measure of the membrane effectiveness, was compliant with TCEQ, state and federal requirements.  

What water tests does the City conduct regularly?

Every day, the City conducts numerous ongoing tests to water during the treatment and distribution process. For example, turbidity, one of several indicators of the water’s clarity, is checked every 5 minutes, or 288 times per day per membrane. A MIT is conducted weekly on each of the City’s five water filtration membranes. In addition, the City monitors chlorine residuals continuously across the distribution system.  City reports are provided above.

Was the computer error fixed?

Yes. The outsourced programming team at Suez Water Technologies, who is responsible for computer software programming, has identified the source of the error and made corrections.

City staff immediately implemented the requirement that the water treatment operators will confirm manually that MIT testing functions meet TCEQ standards regardless of what the computer programming displays. The City’s top priority is health and safety of its citizens.

The City now automatically keeps filtration membranes offline until a MIT data audit is complete and any discrepancies, if found, are resolved. Fortunately, the prompt data check conducted by the City water operator helped to prevent the error on December 24 from going undetected.  

Who was notified about this issue?

The City wishes to be transparent with our community. The City is mailing a public notice to all utility customers including City of Pflugerville, Manville Water Supply Corporation and Southwest Water Company as required by TCEQ. In addition, the City notified the Pflugerville Pflag, Community Impact Newspaper and the Patch to help communicate the information to help ensure as many citizens receive the notice as quickly as possible. The City posted this information on the website on January 13 and linked to it from the website homepage prominently to provide a resource for residents. The City posted on the City Facebook page and Twitter to notify residents of the Public Notice. For additional information, please call City Communications at 512-990-6115.

What is cryptosporidium?

Cryptosporidium is a parasite that occurs in natural waterway and can cause symptoms including diarrhea, cramps, and headaches. Inadequately treated water may contain disease-causing organisms.  These organisms include bacteria, viruses, and parasites that can cause symptoms such as nausea, cramps, diarrhea, and associated headaches. Please contact your medical provider for additional information.

Is cryptosporidium in city water?

The treatment violation does not mean cryptosporidium is present. The violation relates to a failed Membrane Integrity Test (MIT) which is one of several indicators of the effectiveness of filtration provided by the membranes for cryptosporidium if it were to ever be present in the water supply.  

The State of Texas requires that all occurrences of cryptosporidiosis be reported by medical staff to the county health department. In 2019, Travis County had 52 reports of cryptosporidiosis and two (2) of those came from medical offices located in Pflugerville. If any resident is concerned about their health, they are encouraged to contact their medical provider.

Lab test: The City sent water to a third party lab for cryptosporidium testing and it came back on January 21 with a report of none detected.

What Happened back in November?

In November 2019, the City several Tier 2 and a Tier 3 violations from TCEQ related processes in the water plant including programming, monitoring and reporting. There were issues with plant membranes, zebra mussels and reporting functions. The water plant treatment reports could not confirm that the City properly filtered for cryptosporidium.

While we have the same violation from the TCEQ, a failure to filter for cryptosporidium, the failure to quit producing after the negative test is the failure. In a list of formulates and upgrades, this one was missed. The City relies on vendors and experts to create formulas as we don't have full-time SCADA programmers on staff. 

Information on the November 2019 incident

For additional information, please call City Communications at 512-990-6115.