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High Reservoir Rupture Update

Lewiston, Idaho – Since the High Reservoir rupture occurred on January 18, 2023, the City of Lewiston has cooperated with its insurance company in the investigation to identify the cause of the rupture. To date, the investigation is still ongoing.

The Mayor and City staff are dedicated to finding a resolution to this situation. Nearly two months have passed since the event, and the City wanted to provide an update on what has been discovered through the investigation thus far.

At approximately 3:41 am on January 18, 2023, City water staff received a phone call from the Lewiston Police Department Dispatch Center. The caller described large amounts of water running across 16th Avenue in the proximity of the High Reservoir. The first water employee to respond was at the scene by approximately 3:45 am. The initial thought was that there could be a break in the transmission main that feeds the reservoir, as it is a large diameter pipe and there was a lot of water seen coming from the site.

Additional staff began arriving on the scene between 3:55 am and 4:10 am. Staff immediately began attempting to locate the source of the water. Hindering their efforts was the total darkness and thick fog that blanketed the valley that morning. It was clear that the water was coming from the area of the High Reservoir, but it wasn’t clear whether it was coming from a transmission line or the reservoir itself. At this time, staff had not received any alarms, alerts, or error messages from the Supervisory Control and Data Acquisition (SCADA) system used to monitor and operate the water system.

Using flashlights, staff observed water overflowing from the top of the reservoir and spilling over the side. As they observed this, they began hearing loud noises coming from the reservoir and moved away as they were concerned for their safety. City water staff moved immediately to a safer location, still trying to better understand what was happening. At this moment, the northwest corner of the reservoir collapsed and a large wall of water was released. Staff immediately moved farther back as it was not clear how much of the reservoir wall would collapse.

Once staff cleared the area of immediate danger, they logged into the SCADA system.  SCADA still indicated that the system was operating normally. Based on this abnormality, water staff contacted the contracted SCADA programmer to try and troubleshoot the situation.

At this time, staff began to focus on notifying emergency services and determining the impacts of the water that was released from the reservoir. The water manager immediately initiated Incident Command System (ICS) protocols and established the ICS command post at the nearby police training facility.

What is known at this time is that the High Reservoir was filling beyond its capacity on the morning of January 18, 2023. There is no indication that any control system alarms or notifications were communicated to the water staff as the reservoir continued to overflow with water. Even after the rupture, the monitoring system showed that everything at the reservoir was operating normally.

A review of the most recent inspection reports does not indicate any known structural deficiencies at the High Reservoir. In 2017, treated water was found in a neighboring property to the east of the reservoir. Through inspections, a crack within the reservoir lining was discovered, as well as a broken sideboard that appeared to be leaking into the neighboring property. The crack in the concrete and the broken sideboard was repaired in the same year. Since those repairs, no other treated water has been reported outside of the reservoir until the January 18, 2023 event.

Any person who experienced property damage from the High Reservoir rupture can contact the City’s Risk Manager for more information at 208-746-3671, ext. 6213.