Saying south county traffic troubles are a regional concern, American Canyon leaders want the extension of a key north-south route to be paid for by a future countywide transportation sales tax increase.

The $57 million extension of Newell Road to South Kelly Road, which would include a $20 million interchange, would be a frontage road along Highway 29, according to the plan discussed by the American Canyon City Council Thursday.

“In all probability there will be a (transportation sales tax),” said Mayor Leon Garcia, who also chairs the Napa County Transportation and Planning Agency. Measure H, a countywide transportation sales tax on the ballot in June of 2006, failed to pass.

Garcia said a group that includes Supervisor Bill Dodd is having “very preliminary” discussions on the formulation of a new countywide transportation sales tax measure in 2008. Dodd on Friday called the discussions “way, way preliminary.”

The mayor spoke as the American Canyon City Council discussed the possible formation of a 17-member group headed by City Councilwoman Cindy Coffey to educate the public on the need to direct the sales tax revenues to build the Newell Road extension.

City Councilmen Don Callison and Ed West, who said they want to ease tensions between the city and Napa County, questioned the need for such a committee, saying the city needs instead to work with the other jurisdictions.

This will make the city look like “cowboys,” West said.

“I just don’t see how this committee is going to lead us to the dance,” said West, who plans to discuss the matter with Dodd.

City Manager Rich Ramirez said Friday that the City Council will discuss the scope of work for the committee on Tuesday.

In addition to building Newell Road, the city still plans to widen Highway 29 from four to six lanes, a project estimated at $67 million, and to extend Devlin Road on the west side of Highway 29 to the north.

The Devlin Road connection would require the construction of a bridge over Fagan Creek, Ramirez said. The bridge — and who will pay for it — is part of ongoing discussions between the city and county officials as they hammer out an agreement on where the city’s future northern boundaries will be, he said Friday.

Transportation mitigation fees charged to new developments will pay for widening Highway 29, according to Omni Means, the city’s traffic consultant.

Under the best scenario, the extension of Newell Road would not be complete until four or five years after the passage of a transportation sales tax, Ramirez said.

Any widening of Highway 29 from four to six lanes would not take place for 15 years, he said. As of Friday, the city has about $20,000 in transportation mitigation fees available for the project, Ramirez said.

The city, which now charges transportation-related fees of $3,954 for every new home, could increase the transportation mitigation fee to $4,331 early next year, Ramirez said.

Omni Means President H. Ross Ainsworth estimates traffic on Highway 29 will increase by 67 percent over the next 30 years. Up to 70 percent of the trips will be regional traffic, he said. An estimated 55,000 cars travel through town daily, according to Napa County Transportation and Planning Agency.

The agency, which studies traffic and transportation issues in Napa County, has led a series of community workshops since early fall to evaluate Napa County’s transportation needs for the next 30 years. The first  public meeting was in September in American Canyon.

So far, NCTPA’s board has not had formal discussions on a new sales tax, stressed Jim Leddy, NCTPA’s executive director. Other groups in the community have had discussions for the past 18 months, he said.

On Thursday, Michele Castagnola, the longtime American Canyon Planning Commission chairwoman, said her daily commute to Napa takes 55 minutes one way.

“We need to do something.”