Controversy in the historically quiet Angwin community is threatening to hijack the county political process.

Opponents of Pacific Union College's plan to develop some of its Angwin land are trying to use the Napa County General Plan process to undermine the college's plans. They warn that St. Helena and surrounding areas should brace themselves for a significant increase in traffic if the project is successful.

But county planners say the project's impacts won't be clear until its details are finalized and a detailed Environmental Impact Report is prepared.

During a presentation last week of the county General Plan, Angwin's Pat Griffith said PUC's plan for several hundred homes and a new village square would result in a sharp increase in traffic, and require PG&E to install new buried cables.

"Both of these issues are going to directly affect St. Helena," Griffith said.

The issue of whether to adjust Angwin's urban bubble is intertwined with PUC's plans to build an environmentally friendly "eco-village" in conjunction with Seattle-based developer Triad Communities.

Napa County Planning Director Hillary Gitelman said it's difficult to quantify the proposal's impact on traffic and utilities without a project-specific EIR. The draft General Plan's EIR takes a more general approach, making conservative estimates of how growth allowed by the plan would affect traffic.

The draft General Plan's EIR notes that increased development in Angwin would increase traffic on Deer Park Road, Howell Mountain Road and Silverado Trail. At peak hours, northbound Deer Park Road between Silverado Trail and Sanitarium Road could even reach the stop-and-go conditions of "Level of Service F," defined as traffic volume exceeding the road's capacity.

Several county roads are already at Level of Service F, most notably sections of Highway 29 between Yountville and St. Helena.

But a project-specific EIR will be necessary to estimate how much traffic will be a direct result of Angwin's development, Gitelman said. That more focused EIR will calculate the eco-village's impact not just on Deer Park, Howell Mountain and the Trail, but on local Angwin roads.

"We haven't gotten down to that level of detail," Gitelman said. "If PUC comes forward and files an application with the county, we'll have to do that detailed analysis."

The draft General Plan includes three possible maps: one would leave the urban bubble untouched, another would prevent the proposed "Farm" neighborhood included in PUC's previous plans, and the third would allow the project to proceed as originally conceived. The second two maps would require a countywide Measure J vote.

In front of the county planning commission, PUC public relations consultant Peter Bartelme told the commission the college "does not accept any revisions in the boundary of the urban bubble."

"Altering the bubble diminishes the value of the land and is therefore inconsistent with the stated policy of the draft General Plan to support Pacific Union College," he said. "Our private property is a valuable asset, whether it is developed or not."