With the addition of the cities of Santa Rosa and Sonoma to the mix, the Sonoma Clean Power Authority has crossed a Rubicon of sorts.

It's still uncertain whether the authority board will accept the conditions the Santa Rosa City Council has attached to its membership vote. These include extra board seats for the city, additional protections for ratepayers and an easier way for the city to avoid financial penalties should it decide to pull out of the authority.

Nevertheless, if it does accept those conditions, the authority will move forward representing nearly 80 percent of all the ratepayers in the county. That's the kind of heft and credibility that it has needed as it enters negotiations to pick an operator for the system.

But while the effort moves forward on that front, there are some long-term issues that the cities and county have only begun to address. One concerns the local green-energy projects that advocates of Sonoma Clean Power hope will be created through reinvestment back into the community. But where are these projects going to be built?

Much attention has been give to a 20-megawatt, $100 million solar-panel system that is planned for 50 acres at the Charles M. Schulz-Sonoma County Airport. But at its peak, that would only provide enough power for about 10,000 homes in the county. Where would the other green energy projects be built?

A potential conflict is bubbling near Petaluma, where Sonoma County planners are considering zoning changes that, if approved, would open up thousands of acres of pasture to large-scale solar farms and other renewable-energy generating projects. In particular, the change would allow a proposed 23-acre solar installation on 130 acres of grazing land on the southeastern outskirts of Petaluma. Petaluma City Council members are clearly uneasy with the proposal.

During a discussion Monday night, the council voted to send the county a letter outlining its concerns, and asking that the county respect the tools that have long been used to prevent overdevelopment, including community separators, greenbelts and scenic gateways, into its communities.

Council members went so far as to refer to the zoning change as encouraging "sprawl."

"The cities each voted to contain themselves to not have urban sprawl," Councilwoman Teresa Barrett said. "Now you have the county putting sprawl in .<TH>.<TH>. and defeating the purpose of open space and urban growth boundaries."

This debate is not new. Many areas are facing similar clashes between the desire for renewable energy projects and the desire to preserve open space and agricultural lands.

The new zoning proposal is expected to go to the Board of Supervisors for a possible vote on Aug. 6. But before that vote occurs, the county would be wise to convene a broader discussion, with cities, about where it expects these kinds of zoning changes to occur.

Being in support of local clean energy projects and being in support of open space and ag preservation are not mutually exclusive ideas. But they do require an honest discussion about when and where those values conflict. The county can't afford to wait to decide this on a case-by-case basis.