SARDINE CANYON — Cache Valley is, in essence, connected to the rest of the world by a single strand. And even the tiniest hint that the strand may become frayed or torn or broken makes local business and government types extremely nervous.

"It is our lifeline," said Cache Chamber President Bobbie Coray.

The strand is the stretch of U.S. 89 that chugs upward from I-15's Brigham City exit, meanders through Sardine Canyon and drops into Cache Valley. It is the only major access — and by far the fastest — from Cache Valley to Salt Lake City International Airport. Local government leaders continually have to reassure the valley's collection of high-technology and manufacturing businesses that the corridor will remain unencumbered.

"We have companies who threaten us, 'If you slow this road down in any way, shape or form, we're leaving,' " said Cache County planner Mark Teuscher.

It's probably no surprise, then, that a proposed development in Sardine Canyon has made Cache Valley types awfully jittery. A developer is proposing to build up to 350 homes just north of the hamlet of Mantua, and its residents would commute to parts north and south via the all-important Sardine Canyon road — a possible increase of 3,500 car trips per day.

"We had not thought about private development in the canyon," Coray said. "We thought it was all national forest. We could essentially get landlocked."

It's not so much the increase in traffic that's the problem — it's where it's coming from. An increase in cars from Logan or Brigham City is OK, up to a point, but travelers who start in the middle necessarily slow down the folks who are already zipping along at 60 miles an hour.

The property isn't even within Cache County borders — it's in Box Elder County, and will likely be annexed into Brigham City — so, legally, there isn't a single thing Cache County can do to influence the process.

As you might imagine, Brigham City officials are bemused and perhaps a bit impatient with all the fuss from their northern neighbors.

"I think they need to understand and deal with the fact that there will be development along that corridor," said Brigham City planner Paul Larsen.

The developers could minimize the traffic's impact by adding acceleration and deceleration lanes or even building an interchange, and they may well have to do that. That stretch of U.S. 89 is a limited-access state road, so the Utah Department of Transportation has to approve any access changes to it.

"They (Cache County leaders) have some legitimate concerns," said UDOT Region 1 engineer Rex Harris. "There are things that can be done. It could actually turn out to be a very expensive proposition for the developers. But we have to balance it — obviously there are personal property rights involved, too."

At bottom, Teuscher said, "all we're asking for is (for Brigham City) to recognize that we use that road, too. We want to work with them — we don't want to prevent them from development. But all we can do is ask them nicely."