Because of the unexpected bounty of this year’s harvest, many grapes were left on the vines in Napa Valley. This included both the usual second crop that’s generally not used in a good year, but also many prime-quality grapes: Many wineries that had contracted for the fruit had processed all they could use.

Noticing the unusually large surplus hanging in the fields, Oscar Renteria, a vintner, grower owner of Renteria Vineyard Management had an idea: Let his employees use his equipment to pick the grapes and turn them into bulk wine for sale.

He took the idea to John Wilkinson, managing partner of Bin to Bottle custom winery and a small grower.

Wilkinson thought it was a great idea and offered to also share the results with his staff if they wanted to make the wine. Thinking of issues like liability and the chance that the market might weaken, Wilkinson suggested that Renteria pay the workers and deduct that cost along with his winemaking costs from the revenue when the wine was sold.

After the bulk wine is sold — usually in the spring — they’ll split it, 80 percent to the vineyard workers and 20 percent to the winery employees, based on the usual split Bin to Bottle uses to make bulk wine on speculation. Both agreed.

Renteria employs about 90 people full time, and about 350 total during busy season, but this work was done by foremen, managers and supervisors. He paid them to pick the grapes and also had to rent nine forklifts in addition to the ones he owns. It turned out to be a significant haul. Renteria said, “This year, the second crop was good, too.”

Renteria farms 1,500 acres, 52 acres owned by his family, and a number of his customers also agreed to donate the surplus grapes. The project gleaned the grapes from Rombauer, Frank Family, Bosche, Juliana, Gomez and Beller vineyards.

Wilkinson reported getting 36 tons altogether, which included cabernet sauvignon, merlot, cabernet franc, zinfandel, all from top vineyards. Wilkinson says this kind of bulk wine never sells for less than $20 per gallon, and generally goes for more. That should return $55,000 to $75,000 after expenses once the bulk wine is sold.

Renteria estimates that 12,000 to 13,000 acres of Napa County vineyards had surplus crop, typically one-tenth ton per acre. “That’s 1,000 tons,” he said.

It turned out that the supervisors and foremen of the vineyard company hadn’t picked in a long time, and they became competitive — and a bit tired, Renteria said, adding that they also weren’t as fast as the guys who pick full-time and average $17 to $18 per hour.According to Wilinson, the process had another benefit: The supervisors got a better understanding of the economics of winemaking and realized that the wineries don’t just make a big profit off their work.

The five winemakers at Bin to Bottle made the wine. “The staff at Bin to Bottle loved this idea,” said Wilkinson. “They took the wine from start to finish, allowing them complete control over the wine; normally, they have to task directions from the winemakers of their client companies.”

They also became competitive, trying to outdo their peers, he said.

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Toshi Wakayama, one of Bin to Bottle’s winemakers, said, “This gives us a chance to show what we can do.” His colleague, winemaker Franc Dusak added, “It’s a nice way to incentivize us to make good wine. We are the consultants in this project.”

In addition to this profit sharing, Renteria and Wilkinson offer many other benefits to their workers, including food during harvest — Renteria said he spent $16,000 on burritos this year.

Wilkinson likes to surprise workers with treats. Once, he unexpectedly chartered a bus to take them to a ball game. He’s also arranged parties and feasts with no warning.

The workers are considering producing their own label, which could become a powerful brand, especially at valley events. Otherwise, Wilkinson said he expects to sell the bulk wine including for his company’s clients’ 65 brands.

“This type of profit sharing is very valuable to the workers,” said Renteria.

Wilkinson added, “This is a also powerful incentive to stay with Bin to Bottle. It’s expensive to train people and have them leave.”