The sole graveyard tshift worker at a wastewater treatment plant in Gilbert could face domestic terrorism charges after police said he shuttered the facility overnight and endangered first responders.

Robert Olson, 43, was arrested after calling 911 shortly after midnight and then waiting two hours to surrender to a Gilbert police SWAT team. Olson’s actions didn’t put the public in danger but Gilbert police Sgt. Bill Balafas said first responders were at risk.

Olson was arrested on suspicion of criminal damage and disrupting a public facility. Federal charges could include suspicion of terrorism and terroristic threats.

Olson was armed with a handgun, which wastewater employees don’t normally carry, as he shut down numerous systems on the 50-acre site, Mesa utilities spokesman Ian Satter said.

“It was a shutdown of the entire system,” Satter said.

It ceased operations just after midnight. Automatic safety features prevented methane gas from reaching excessive levels and containment structures kept raw sewage on site, Satter said. Customers weren’t affected, he said.

Olson called 911 about 2:30 a.m., triggering Mesa and Gilbert SWAT to action. Olson surrendered two hours later and was booked into Maricopa County’s Fourth Avenue jail in Phoenix. Police would not discuss Olson’s motivations pending an ongoing investigation.

The plant resumed operations at 8 a.m. Additional employees were called in Friday to make repairs and they are still assessing what damage may have occurred, Satter said.

Olson had worked for Mesa for two years beginning in 2001, then was employed by Phoenix and Avondale. He returned in 2007 and passed FBI background checks both times. He is certified by the Arizona Department of Environmental Quality.

The plant, at 4400 S. Greenfield Road, is owned by Mesa, Gilbert and Queen Creek and treats water from all three communities. Mesa operates the plant, which can treat 16 million gallons a day but currently handles 9 million gallons. It opened in 2006 and has 16 employees. The treated water is used for crops and turf irrigation.

• Contact writer: (480) 898-6548 or ggroff@evtrib.com

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