The latest standoff between so-called "alt-right" protesters and their antifascist adversaries on Oct. 8 was a sleepy affair, attended by less than 150 people.

But cops are racking up overtime hours policing these fringe protesters.

The Portland Police Bureau spent $1.9 million on overtime policing protests between July 2016 and June 2017. That breaks down to about 31,300 hours of personnel time—the equivalent of a 15-year career.

And that doesn't include any of the material costs associated with protests that can include food and water for officers and pepper spray, rubber bullets and other material resources used to control crowds.

Assistant Chief Chris Davis says overtime pay accounts for most of the costs associated with protests for the bureau.

"We have to try to find out as much as we can to find out what the [protesters'] plan is and try to assess the risks," Davis says. "That's at least as much art as it is science."

It is an expensive art. Here are the most costly protests in recent months.

Portland Police Overtime Costs for Patrolling Protests This Spring and Summer

(Joe Riedl)
(Joe Riedl)

April 29

A "patriot rally" along Southeast 82nd Avenue following a canceled community parade

Overtime cost: $28,480

(Christine Dong)
(Christine Dong)

May 1

Organized labor May Day marches

Overtime cost: $175,180

(William Gagan)
(William Gagan)

June 4

An alt-right "free speech" rally in the wake of a double slaying on a MAX train

Overtime cost: $84,673

(Daniel Stindt)
(Daniel Stindt)

Aug. 6

A "Patriot Prayer" rally at Tom McCall Waterfront Park that turned into a brawl

Overtime cost: $22,120

Total Portland police overtime for protests in fiscal year 2017: $1.9 million

Correction: Due to an editor's error, this story originally stated that Aug. 6 event took place near the Waterfront Blues Festival. That was a June 30 Patriot Prayer rally.