AUBURN, N.H. (AP) – Interstate 93 first opened in 1963, triggering a massive wave of residential growth as southern New Hampshire fell within easy reach of Boston.

Now, plans call for widening the clogged and sometimes dangerous interstate from Massachusetts to Manchester, restoring, at least for a while, an easy commute. That comes as good news to many workers in towns like Salem and Windham.

But it may not be such good news for smaller towns where the interstate expansion is expected to foster greater residential growth.

A state Department of Transportation study estimates the expansion will add about 35,000 people to the region and eat up 15,000 acres or more to build new homes – over and above growth already expected to take place. The affected towns include some that are a fair distance from the Massachusetts line.

As the flow of cars shoots up a wider interstate, Auburn – just east of Manchester, and about 18 miles from Massachusetts – would be at the end of a northbound fountain of traffic.

Its classic New England town hall, a converted church dating back to 1836, overlooks Lake Massabesic. With fewer than 5,000 residents and roughly 7,300 acres of developable land remaining, it is poised to attract new residents looking for rural charm and a better value on homes than they can get near Boston.

Yet the town’s master plan, updated in 2002, doesn’t mention the potential for growth that a wider interstate could trigger. Growth estimates in the plan are based on the patterns of the previous 10 years.

Some worry that towns like Auburn lack the planning and zoning tools to control or direct a surge in growth. The result could be overcrowded roads and schools and the loss of valuable natural resources.

“If we wait until the project is under way or complete, the forces of change will be so great that efforts to manage them will be overwhelmed and doomed to failure,” wrote J. Mark Lennon of the Josiah Bartlett Center for Public Policy.

Developers have little doubt there will be a flurry of growth.

“It’s a gold mine,” said Richard Eaton, a developer who lives and works in Auburn. He and other developers expect Massachusetts residents to account for much of the demand.

“They can get so much more home for the money here,” said Steve Febonio of Maverick Development. He estimates that buyers from Massachusetts account for about a third of the homes he has built in Auburn.

“We’ve got a lot of people who want that rural setting,” Febonio said.

Towns south of Auburn – including Derry, Londonderry, Salem and Windham – are intimately familiar with the growing pains from a major highway project. Londonderry, for example, more than doubled in population between 1960 and 1970.

But towns immediately adjacent to the interstate are running out of developable land and all have extensive experience in controlling and directing growth.

Londonderry’s growth management ordinance has been invoked to limit housing permits issued in each of the last two years and has been invoked four times previously.

In contrast, Auburn has never had to refuse a building permit because it exceeded the total allowable under its growth ordinance. (It has restricted the number of permits any one developer could get in a single year).

The state Department of Transportation has allocated $3.5 million to help 26 towns plan for potential growth due to the interstate expansion. But the department is still evaluating what services to offer and is still gathering comment. That means money won’t be available to towns until just before the groundbreaking, which is expected in about a year.

Some say that is too little, too late, and too few communities will get help.

Bill Cass, the I-93 project manager, disagrees, though he acknowledges that “the timing is tough.” He said key approvals and financing only recently fell into place.

Regional planning commissions already are working to help towns prepare.

The concerns go beyond housing developments and the loss of open space. Some fear growth will change the nature of their communities.

Auburn Selectman Harland Eaton, Richard’s uncle, already sees big changes in his town.

Unlike towns to the south, over half of Auburn’s residents were born in New Hampshire. Only 11 percent commute to work out of state compared with 51 percent in Salem. Eaton, who grew up here, remembers when everyone knew his neighbors.

But when he watched people waiting in line to vote last year, he remembers being struck by the fact they weren’t talking.

“They don’t know each other. They don’t do the small talk. They’re too busy in their lives,” he said.

Nancy Girard, a lawyer with the Conservation Law Foundation, said that’s one of the overlooked consequences of residential sprawl and rising home prices.

“They’re willing to add to their commute to have the American Dream,” she said, but the time new arrivals spend commuting takes away from time they could spend developing relationships with neighbors.

“That has a way of affecting the social capital of the community,” she said.