The fire, on the property of the Sky Tree Ranch horse-boarding and riding facility at 3295 Guerneville Road, burned 1,000 bales of hay weighing 65 tons inside the barn, a 50- by 60-foot aluminum structure enclosed on two sides.
The blaze was reported by neighbors at about 9:35 p.m. Monday and was contained in about 20 minutes, Lantz said.
Firefighters monitored the fire all day Tuesday and left the barn around 8:30 p.m., Lantz said. They let the hay burn out because there was no room on the property to spread it out, Lantz said.
Lantz estimated the value of the hay that burned at $8,500 to $9,000 and said the fire caused between $40,000 and $50,000 in damage to the structure. The aluminum barn, which was wired for lighting, melted and was destroyed in the blaze.
No people or animals were injured. The response included 22 firefighters and 10 pieces of equipment from Rincon Valley, Graton and Santa Rosa.
Firefighters kept the fire from spreading to another barn and a home on the property, Lantz said.