Some 2.2 million water customers in the U.S. city of Houston were under a boil water notice for two days last week following a power outage that dropped pressure at its East Water Purification Plant.
The Texas Commission on Environmental Quality (TCEQ) required the boil water notice for the nation’s fourth-largest city out of an abundance of caution related to the pressure loss. However, several city officials noted in local media interviews that they did not think the risk warranted the notice due to the minimal amount of time the pressure loss occurred.
“We believe the water is safe but, based on regulatory requirements when pressure drops below 20 PSI, we are obligated to issue a boil water notice,” stated a Tweet from Houston Mayor Sylvester Turner’s office on November 28. “The city is submitting its plan to TCEQ for approval tonight.”
Turner noted in a press conference that he was aware of how issuing the notice would affect schools, businesses, and scheduled surgeries, and wanted to be absolutely certain it was necessary.
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Of 21 city-wide water system sensors, 14 sensors recorded a water pressure drop for less than two minutes and two more showed low pressure for less than 30 minutes, local officials explained. Five of the 21 sensors never fell below 20 PSI.
The water pressure dropped below the commission’s required minimum of 20 PSI on the morning of November 27. The amount of time the pressure drop occurs is not a factor under the commission’s guidelines. The drop increased the potential for contaminants to be introduced, as well as the risk of backflow, officials warned.
As Houston tried to get the boil water order rescinded, not one of its 29 laboratory samples showed any water contamination, officials said.
The power outage occurred due to a failed transformer and failed backup transformer. Despite a 20-year, $56-million contract for heavy-duty diesel generators at its three water purification plants, Houston officials said they were unable to connect to them due to the failure of the two city-owned transformers that malfunctioned. They could not connect to any power source.
“Even had the backup generators been on, we would have had the same problem,” said Houston Public Works Director Carol Haddock at a press conference.
The East Water Purification Plant was built in 1954 and the city has spent tens of millions of dollars in upgrades in recent years.
Many local residents were critical of how the boil water notice rolled out. Initially, it was communicated through an evening media advisory and a post on Twitter. However, many residents said they did not learn of the notice until the following morning, when news outlets announced that local schools would be closed. The notice occurred later in the day, well after the recorded pressure drop, but communications had been delayed as local officials pursued discussions with the TCEQ about the legal requirements around the boil water notice.
Next, Mayor Turner said he asked the head of the city’s homeland security department to alert residents of a city-wide boil water notice via text message; however, the process took longer than he had expected.
Before returning to normal use, Houston Water customers needed to first flush their home water systems by running faucets on cold for at least one minute.