(NVR) - Opus One winery convinced county Planning Commissioners on Wednesday that its success warrants doubling wine production and making other changes, despite some public concerns about cumulative impacts.

“I think it is a well-designed change for this winery that is minimally impactful,” Commissioner Michael Basayne said before the commission granted unanimous approval.

Wine legends Robert Mondavi and Baron Philippe de Rothschild founded Opus One in 1979. Located in Oakville in the heart of Napa Valley, the winery makes only one wine.

The building itself opened in 1991 and is one of the more striking sights along Highway 29. Green lawns slant upward to meet the walls of the front building, which seems to be rising out of the earth with some of the landscape still clinging to it.

Opus One is permitted to produce up to 110,000 gallons of wine annually. Despite the limit, it produced 170,590 gallons in 2012 and 116,580 gallons in 2015. It wants to change its permit so it can produce up to 250,000 gallons annually, a county report said.

The winery also asked to expand its 80,000-square-foot winery by 51,906 square feet for a fermentation tank room, barrel preparation area, storage, conference rooms, offices and other uses. New structures would be built to the rear of the winery.

Basayne said the appearance of Opus One is iconic. He noted the architectural firm that designed it also designed San Francisco’s Transamerica pyramid.

“It’s very obvious the changes proposed will not be visible from the passersby on Highway 29,” Basayne said.

Opus One CEO David Pearson said the expansion is designed by Scott Johnson, who designed the original winery.