The developer chosen to oversee the creation of a new megaproject on the abandoned 400-acre Army ammunition site in Arden Hills is seeking to make it far more urban than the city has planned.

Minneapolis-based development firm Alatus LLC envisions 250 fewer single-family homes than are called for in the city's master plan — and as many as 795 more apartments and condos.

"You realize you've bypassed Minneapolis and St. Paul at this point for overall density," Mayor David Grant told senior members of the development team on Monday night.

Alatus chief Bob Lux responded that the quest is for vitality. "A place where the streets aren't empty, but have people on them," he added. "I know there are challenges with density; but there are also benefits."

During the first informal workshop between the two sides last week, it emerged that Alatus wants to build multifamily structures as tall as 12 stories — an idea that drew pained reactions from some council members.

"If I buy a million dollar house on the hill," said Council Member Brenda Holden, "I end up looking at skyscrapers. They want to see green."

"We're not downtown," said Council Member Fran Holmes, adding that she worries about the site coping with traffic from that many people.

The other partner in the project, Ramsey County, which bought the land, long has warned that greater density would be needed and even desirable, both to allow the developer to make money and to create enough activity on the site to justify mass-transit investments.

Ramsey County Commissioner Rafael Ortega last winter predicted that "the tiebreaker will be to put this before the development community, at which point both of us — city and county — will face the reality of what's doable."

Planners hope that the new A Line transitway, offering frequent, light rail-like bus service, can be extended north past Roseville's Rosedale Center into Arden Hills. The odds for that improve when the number of potential riders grows.

Monday night's session led to a consensus that council members should go on a tour to see what the proposed building products look like close up. .

"We could talk density for hours," the mayor said at one point. "We will need to come back to this probably more than once."

Alatus argued that the high density represents just a sliver of the totality of Arden Hills. "We need some volume," Lux said, "to make this work."

City staffers said they expect to have informal work sessions on Sept. 19, Oct. 3 and Oct. 17 to nail down a compromise and move toward the formal approvals needed.