City works to try to prevent repeat of sewage spills

The flock took off in all directions, which caused the lines to swing. The swinging lines hit each other three times, which caused the circuit breaker to turn off and try to re-engage — three times. Both the circuit breaker and backup generators operate on a 10-second timer, Swensen said they later discovered.

“After the third time, the computer was so confused, it just quit,” he said.

That interruption in systems power resulted in the sewage release.

Less than a month later, some routine maintenance was scheduled at the same treatment plant.

Sensors in a wet well needed to be recalibrated. A company, Jacobs, was hired to do the work. Jacobs staff called the control room to turn off the sensors while the maintenance was completed, but somehow the sensors were not taken offline, Swensen said.

The sensors began reading that water was coming into the well and started pumping water out, even though the levels were actually decreasing. This continued until the well ran dry and introduced air into the system. Swensen said this caused the system to stop, and before they could manually repair the system, untreated water was released.

Changes made

City staff and Jacobs, the subcontractor with CH2M, are taking this opportunity to re-evaluate their process and make any necessary infrastructure improvements.

For example, staff reset the generator timer to restart after five seconds to offset with the circuit breaker timers to avoid any future timing issues. Any work on the wet well and pumps by contractors from Jacobs will be supervised by a staff operator to ensure water levels remain sufficient. Communication and notification procedures will also be updated.

To prevent a future bird incident, Swensen said, operators are talking with Clark Public Utilities to put spacers between the power lines so if they move, they move together, thus preventing any power surges.

The city is also in the process of designing an independent emergency pumping system that would ensure that wastewater goes through the treatment process regardless of the primary pumping system’s status.

Staff is also working toward a $12.5 million project to modernize the system control and data acquisition system, as well as a $10 million electrical system overhaul.

Some city councilors want to see more done.

“The one thing I didn’t hear is what the city is going to do better,” said Councilor Alishia Topper. “It took us more than four days to inform residents in the community about the occurrence.”

Topper also asked for staff to consider how much it would cost to completely overhaul the wastewater treatment plant and ensure it’s in working order.

“I know those price tags can be big … but I still would be interested in seeing those numbers,” she said.

Councilor Bart Hansen asked that the city evaluate all of its facilities to see what backups exist and take a more holistic approach.

“Whether it be birds, whether it be cars, tornadoes, hurricane winds, snow, whatever you might like it to be, the idea that you completely rely on someone else to control your destiny is a little bit difficult,” Hansen said. “You’ve got to have an adequate backup in order to address those issues.”