The fire began shortly after 3 p.m., said Acting Battalion Chief Angel Bobo of the Richmond Fire Department, the lead agency.
The ridge, which is traversed by hiking trails and power lines, extends south of the hill known as Nicholl Knob and is part of the East Bay Regional Park District's Miller-Knox Regional Shoreline park.
Bobo said the fire was reported at 3:02 p.m. and that Richmond firefighters arrived five minutes later.
Fire agencies were juggling resources Sunday between the Richmond fire and a simultaneous fire in Franklin Canyon. No one was reported injured and no structures had been affected late Sunday in the Richmond fire.
The fire was on the east side of the ridge along Canal Boulevard and uphill from a wastewater treatment plant.
The fire was under control at 5:40 p.m., Bobo said. A park district helicopter made several water drops over the rough terrain of the fire area, and trucks from the state Office of Emergency Services ferried water to the top of the ridge.
Crews remained posted on and around the smoldering ridge Sunday evening. The fire is under investigation.
A wind-fanned Saturday afternoon grass and brush fire that climbed a ridge and threatened homes on the other side was sparked by a lawnmower, Rodeo-Hercules Fire Chief Gary Boyles said.
"A homeowner was attempting to clear vegetation around his home with a John Deere riding lawnmower when he hit a rock," Boyles said. "That did it."
The fire began shortly before 4 p.m. off Malachite Court in an area of some of the city's largest and most expensive homes. Houses on Malachite have sold for $1.3 million and $1.25 million within the last year, real estate records show.
The homeowner ran to get a water hose but by the time he got it extended, the fire was climbing over the ridge and downhill on the other side toward Finch Court and Falcon Way, Boyles said.
Residents on Finch Court and on Falcon Way praised firefighters for the speed and the intensity of their response.
At least two helicopters dumped water on the blaze, which covered about 10 to 15 acres by the time firefighter controlled it about two hours later. By then, it had come to within 10 feet of some back-yard fences, Boyles said.
About 20 to 25 houses were threatened, Boyles said. No one was injured and no houses were damaged.
"It came to about 100 feet from me," said one Falcon Way resident, Kurt Warr, who stood at his back-yard fence with his hose at the ready. "I saw it coming over the ridge. I was pretty worried."
So were Finch Court residents Rupinder Kaler and Bassey Effiong.
"My family evacuated," Kaler said. Neighbors knocked on doors and many residents took their families and moved their cars from the area, a family member of Kaler's said.
