One year after a fluoridation pump malfunctioned and flooded the pipes in some Sandy homes with tainted water, a new report released Thursday outlined the problems that led to the incident and provided recommendations to ensure it wouldn’t happen again.

The 181-page investigative review, mandated by the Utah Division of Drinking Water and the Salt Lake County Health Department, provides an hour-by-hour and day-by-day account of the causes of the over-fluoridation and the responses by city officials from Feb. 4, 2019, the day before fluoride entered the water system, to Feb. 19.

The report also makes several recommendations on how the city could improve its emergency response processes — including around public notification and communication with residents, several of whom expressed frustration in the wake of the incident that they hadn’t been notified of the problems sooner.

Tom Ward, Sandy Public Utilities director, said in a news release accompanying the report that it provided the city with “valuable insight into the causes of the fluoride overfeed event and identifies improvements. Sandy City is systematically implementing these recommendations and will continue to work diligently with county and state regulators to ensure Sandy drinking water is safe,” he added, noting that the city has implemented 30 of the 35 recommendations and is working on the rest.

Ward was placed on paid administrative leave last February as investigators looked into the over-fluoridation incident. Sandy Mayor Kurt Bradburn reappointed him last summer, after a separate report concluded the city should have warned affected households sooner but deemed its operational response was “generally within normal industry standards.”

While experts say fluoride is beneficial in small doses, unsafe levels can cause a number of health issues.

Residents in the affected Sandy area reported gastrointestinal problems and stomach cramping and pains after drinking the water and expressed concerns about the short- and long-term effects of that exposure for themselves, family members and pets. They also worried about the impacts on their homes, where acid from the fluoride had corroded some pipes.

Hansen, Allen & Luce, the outside firm that compiled the report released Thursday, identified two main causes of the fluoride event: that the dosing pump at the city’s Paradise Valley Well was in a manual setting during a computer hardware upgrade at the well and that a faulty safety flow switch that falsely indicated a setting that would prevent the fluoride pump from running.

When a communication alarm at the well house was cleared, it also cleared the flow switch alarm and the fluoride pump began running.

Officials had originally concluded that the pump had malfunctioned because of a power outage.

The outside review notes that the city took a number of “positive actions,” including beginning a prompt investigation as soon as complaints about water quality began filtering in. Afterward, officials conducted water samples, flushed the distribution system and performed door-to-door notifications.

But the city’s efforts suffered from a “lack of documentation,” which “caused problems for each agency involved” in the response. Water system operators, for example, did not document the houses that had received the first public notification on Feb. 7, which may have led to confusion, the report states.

City officials also made several missteps in sampling — at first gathering too few in the early stages of the event and then taking too many in the midst of a “Do Not Drink Order." The Division of Drinking Water and Salt Lake County now believe that decision “may have taken away from the quality of the samples,” the report states, noting that a more strategic sampling plan would have saved time and been more effective.

Finally, the report points to several errors in communication to residents. Sandy officials had removed required items from a public notification; had not delivered information provided in emails or text messages to all of the necessary parties in a timely manner, which created confusion; and did not proactively use social media and news media to inform the affected residents.

“Building public trust cannot wait until a negative event occurs,” the report states. “The public should regularly hear of the positive things drinking water professionals are doing every day to supply clean water and protect public health.”

The report released last summer also concluded that backing up notifications with a widespread media announcement would have been the most effective way to ensure residents were not drinking contaminated water and could have dispelled concerns about a lack of transparency. Such a response, however, appeared to have been stymied by concern it would trigger panic.