The planned vineyard project would remove about 14,000 carbon-sequestering trees. Walt Ranch planned in return to preserve 248 acres of woodlands. But the courts thought some of this land might already be undevelopable.

Applicant Hall Brambletree Associates in May presented to the county a revised proposal it said provides “overwhelming mitigation.”

A conservation easement would preserve up to 124 acres of Walt Ranch woodlands that otherwise could be developed. The land is not restricted because of steep slopes or watersheds, proponents said.

Hall Brambletree would also plant 16,790 oaks. It would monitor the trees and replant if necessary so at least 80% survive after five years.

“Hall also wishes to disincentive the relentless opposition that has resulted in years of delay,” Mike Reynolds of Hall Brambletree wrote to the county.

To do this, Hall Brambletree is willing to plant yet another 16,790 oaks for a total of 33,580— but only if no one challenges the county approval.

Planning, Building and Environmental Services Director David Morrison issued a tentative approval that is to become final on Oct. 1. His decision can be appealed to the county Board of Supervisors. The issue could also potentially return to the courts.

The Center for Biological Diversity has been among the project opponents. Senior Attorney Aruna Prabhala on Wednesday said the group is still reviewing the new greenhouse gas mitigation proposal.

“We are very interested to see what the project proponent has proposed to address one of the most significant impacts of the development,” she said.

Christina Benz of the Napa Sierra Club referred to a video featuring Napa Students for Climate Action that says one old oak sequesters more carbon dioxide than 5,500 oaks planted over eight years.

"It will take a very long time to make up the damage done by this vineyard conversion," Benz said.

Walt Ranch is 2,300 acres located in the mountains between the city of Napa and Lake Berryessa, near the rural community of Circle Oaks. The project involves planting 209 acres of vineyards. A total of 316 acres would be disturbed when roads and other components are included.

The Napa County Board of Supervisors approved the project in 2016. Challenging the decision in Napa County Superior Court were the Center for Biological Diversity, the Living Rivers Council, the Sierra Club, the Circle Oaks County Water District, and the Circle Oaks Homes Association.

Napa County Superior Court in 2018 found in favor of Napa County on an array of issues brought up by opponents. But the 1st District Court of Appeal in 2019 ruled that the greenhouse gas issue must be revisited.

Vineyard development in the mountains away from the Napa Valley floor has become controversial in general. Some say the county should do more to protect trees and water quality. Others say the county already has strict environmental laws in place.

Walt Ranch is perhaps the highest profile case of vineyard development in the mountains. Craig and Kathryn Hall of HALL Wines in St. Helena have pursued the project for close to 15 years. Opponents in packed meetings have held signs saying "No to soil erosion" and "Halt Walt."

Reynolds wrote to the county that the latest greenhouse gas mitigation proposal actually covers a bigger, now-discarded version of the project that would have cut down twice as many trees.

Also, 97% of Walt Ranch burned in the 2017 and 2020 fires. Most of the sequestered carbon that would be released by clearing trees is already in the atmosphere, he wrote.

These factors would justify revising downward the estimate of project greenhouse gas emissions. But Hall Brambletree won't pursue this option. Doing so would expose the new calculations to further scrutiny and legal review, he wrote.

“In addition, the fires have scarred the landscape and we welcome the opportunity to use the Walt Ranch (greenhouse gas) mitigation as an opportunity to help repair it,” Reynolds wrote.

Whether Hall Brambletree has arrived at a solution to the greenhouse gas issue that will diffuse the controversies and allow the vineyards to be planted remains to be seen.