Sonoma County grape growers aiming to convert forested hillsides with neat rows of vineyards will have to prove their projects won't damage local waterways under draft regulations released Thursday.
The new rules, proposed by Sonoma County Agricultural Commissioner Tony Linegar, would prohibit tree removal on the steepest of slopes, keep vineyards 50 to 100 feet away from unstable hillsides, and require three years of follow-up to ensure the regulations are effective.
"The ultimate goal of these standards is to protect water quality," Linegar said.
The new restrictions would fundamentally alter the way the wine industry farms on hillsides, increase the costs of vineyard development and hurt small farmers the hardest, said Nick Frey, president of the Sonoma County Winegrape Commission.
"We run the risk that we're essentially going to price a lot of small guys out of the market," said Frey. Forty percent of Sonoma County's nearly 60,000 acres of grapes are grown in vineyards of 20 acres or less, he said.
The proposals reflect a growing unease over vineyard projects that encroach on undeveloped hillsides as growers seek to capitalize on Sonoma County's reputation as a world-class grape growing region. Over the past several decades most of the easily developed agricultural land suitable for grapes has been converted to vineyards.
Hillside vineyard planting has been halted since January when the Sonoma County Board of Supervisors issued a four-month moratorium to allow time to craft new rules.
County officials were concerned that several pending vineyard projects would require removing large numbers of trees, something existing regulations do not restrict.
Two Annapolis-area proposals call for the conversion of more than 1,900 acres of forest into land for wine grapes. Those two projects — the 146-acre Artesa Vineyard proposal and the 1,769-acre Preservation Ranch project — would be subject to the updated regulations, Linegar said.
The county allows the development of hillside vineyards on slopes up to 50 percent under an erosion control ordinance passed in 2000. But the ordinance, known as Vineyard Erosion and Sediment Control Ordinance, or VESCO, contains no restrictions specific to tree removal, something Linegar has called an "oversight."
Tree roots help with slope stability, and tree canopies help slow surface runoff, he said. Under current rules, a vineyard or orchard project is "Level 2" if the slopes involved are over 15 percent grade for normal soils or 10 percent for highly erodible soils.
A project will be subject to the new regulation if it is Level 2 and calls for removing more than half an acre of trees. Under the new rules, when soils are unstable, or are "cohesionless," tree removal will not be allowed on grades above 40 percent. For those between 25 and 40 percent, a "slope stability analysis" will have to be performed by a licensed geologist to ensure it is safe to remove trees.
It should be "common sense" that people shouldn't be removing trees from steep unstable slopes, Linegar said. "We want to prohibit removing trees from active landslides," he said.
In addition, vineyards will need to be set back 50 feet below a grade of 50 percent or more and 100 feet above such a grade.
Hilltop vineyards also will face additional scrutiny. On flat hilltops with unstable soil, the vineyard project will face the same scrutiny as Level 2 projects.