Expansion plans for a nearly century old rock quarry on Stony Point Road west of Cotati earned unanimous approval Tuesday from the Sonoma County Board of Supervisors.

The quarry, owned by rock and soil supplier Soiland Co. Inc., earned a 20-year use permit that allows the 73-acre operation to expand by 14 acres and dig down an additional 40 feet, to 80 feet above sea level.

Annual mining levels could rise from a current upper limit of about 397,000 tons, based on a rolling five-year average, to a fixed limit of 480,000 tons.

The go-ahead came over the opposition of some neighbors concerned about noise from blasting and rock crushing at the site.

"If you stand at my parents' home, it's so loud. We can't even use our backyard sometimes," said Kim Martens, whose parents Maria and Jack Martens live on West Sierra Avenue, across from the quarry.

A county environmental study showed noise levels do not rise to prohibited levels and found no other significant impacts to neighbors or natural resources.

Neighbors were also worried about the affect on their groundwater, saying their wells have dried up because of the quarry.

Mike Morrison, a planning consultant for the project, said no evidence existed to support most of those claims.

"The quarry has been a good neighbor over the years and will continue to be a good neighbor," Morrison said.

Going into the hearing, county planning commissioners recommended a list of 65 operating conditions, including measures to further limit noise and other environmental impacts.

Supervisors added two conditions, ordering the quarry to work on giving neighbors more specific times for its weekday blasting activity and relocating a crushing operation to the bottom of the rock pit to limit noise.

Including the import of other materials, total annual sales from the site will be limited to 600,000 tons. The current level is about 380,000 tons.

A quarry has existed on the site for more than 90 years. Developer Marv Soiland held an interest in it starting in 1973 and through his company has been an exclusive owner along with his children Mark and Marlene Soiland for the last two decades.

You can reach Staff Writer Brett Wilkison at 521-5295 or brett.wilkison@pressdemocrat.com.