The kale is out of the bag.

The Giants are moving their home and visiting bullpens to center and right-center field and shortening the dimension of the field slightly, although probably not as much as hitters might like, The Chronicle has learned.

Folks attending a Topgolf event at Oracle Park this week witnessed the long-awaited construction project to remove part of the bleachers to make way for the bullpens, which were on the field for the ballpark’s first 20 seasons and a safety hazard for players.

Workers have ripped out rows of benches on either side of the kale garden beyond the center-field fence and put up construction fencing.

According to a person who has seen the designs, the bullpens largely will be side by side beyond the fence.

The long 8-foot wall that runs from the angle in left-center to the farthest point of Triples Alley, 421 feet from home plate, will be moved up about 4 to 6 feet and lowered a foot to accommodate the new bullpens, making it a bit easier to hit the ball out.

A triangle in Triples Alley will remain but will be a bit shorter than 421 feet from the plate because of the way the new fence is angled. The yellow line painted on the brick Willie Mays Wall, which separates homers from balls in play, will be moved slightly toward right field.

Other dimensions are not changing.

The new bullpens are part of a larger project that will add a terrace beyond center field where fans can congregate. The Giants are ripping out about 400 seats.

They already have told season-ticket holders the bullpens will be moved off the field. The club plans to send them final renderings when they are complete.

The changes conform to what Giants President and CEO Larry Baer told The Chronicle in a Giants Splash podcast in September.

“I don’t think the view is going to be, ‘Bring in the fences to make it a hitter-friendly ballpark’ and do anything in the extreme,” Baer said on the podcast. “There would be, as a result of some of the work that we do, some changes in the dimensions as well.”

Asked if Triples Alley would disappear, he suggested it would not, calling it “a signature of the ballpark. I don’t think there’s any desire in our four walls to get rid of it. Whatever 421 (feet) become, if it changes, I think the major thrust of the ballpark will not change in that respect.”

So, Oracle will remain a pitchers’ park.

The Giants were one of three big-league parks that still had the bullpens on the field. The others are Oakland and Tampa Bay. But the foul territory at the Coliseum is so expansive, fielders chasing foul balls rarely reach those mounds.

Moving the bullpens in San Francisco was not a simple task given the park’s relatively small, 13-acre footprint.

Players have tripped over the mounds at Oracle chasing foul balls, not only causing them to fall down and miss the balls, but also leading to injuries.

The issue came to a head when Giants left fielder Mac Williamson tripped on the mound and crashed head-first into the wall aside the Giants bullpen in April 2018, causing a concussion that destroyed his season.

Topgolf attendees who saw the work probably noticed the kale garden was still there, with construction occurring around it.

Good news for health-conscious fans: The kale garden will stay.

Henry Schulman is a San Francisco Chronicle staff writer. Email: hschulman@sfchronicle.com Twitter: @hankschulman