A coding error in Pflugerville Surface Water Treatment Plant's regulations system was responsible for the city's Dec. 24 water treatment issue, according to Darren Strozewski of DCS Engineering, an engineering consultant firm based in Travis County. The programming error occurred during a 2.5 hour time frame on Dec. 24, potentially affected 80,000 gallons of water, or 2% of the city's daily water usage, according to a Jan. 13 city news release.

“This was not a recurrence that I wanted to happen," Strozewski said before council at its Jan. 14 meeting.

The Texas Commission on Environmental Quality issued a Tier 2 violation to the city of Pflugerville Jan. 10 for its programming error—specifically, that Train No. 2 in the city's water treatment plant incorrectly identified had passed a membrane integrity test. The Tier 2 violation, Strozewski said, does not suggest that the city's water supply has been compromised, adding it is safe for residents to consume.

The plant's automated system regularly performs a direct membrane integrity tests once a week. For TCEQ's direct membrane integrity tests, water supply passes the exam if it is less than .33 pounds per square inch per minute, or PSI.

Train No. 2 had a registered amount of 0.35 PSI/minute, but the city's software system—owned by SUEZ Water Technologies—incorrectly reported the test had passed and returned the train to water production. The city has since been manually testing each of the treatment plant's membrane integrity exams to ensure that the error is not repeated, City Manager Sereniah Breland said. In addition, SUEZ has already worked with DCS Engineering to update the coding formula in the city's current water plant software.


Breland said the city has performed membrane repairs on Trains No. 1, 2 and 4; replaced the city's river pumps, with three now online and a fourth purchased; submitted to TCEQ a contact time study to ensure that the treatment plant's water is effectively administering chlorine to kill viruses; have relocated its Manville Water Company distribution line; and went out for quotes on standard operating procedures.

Moving forward, Council Member Doug Weiss requested Breland present quarterly public updates on the city's asset management processes, including tracking equipment, program implementation and the equipment's life cycle and durability.