SAN DIEGO — The City Planning Department is proposing a major up-zoning for the uptown area.

The new plan would allow developers to build roughly 20,000 new units over the next three decades, potentially taking the populations of Hillcrest, Midtown, Mission Hills, City Heights and Bankers Hill from 51,000 to 113,000.

Residents are feeling whiplash from the major shift from slow growth to exponential development.

“Development of apartments in this neighborhood is on fire,” said Keith Lalimo, a resident from Hillcrest.

The plan would not guarantee development, but the up-zoning would simply untie the hands of developers to build dozens of 20-30-story skyscrapers in a place more accustomed to single-family residences with a few four and eight apartment buildings spread through the communities.

“The mayor and our city council that we voted for, and felt that they would represent us are not representing the homeowners and renters of this area,” said George Wedemeyer, a former Hillcrest town councilmember.

Local city activists say this proposal came out of the blue, only turning up in the news without residents knowing what was under discussion.

“Explain them to the public, not just put it in the newspaper,” Wedemayer said.

The mayor, city council and the planning department declined an interview, but instead released this statement:

“Hillcrest is a unique part of our City, and this plan has truly been a collaborative effort between community members, businesses and all those who care about the future of the area… We also want to ensure we give people who would like to live there the opportunity to do so and that small businesses have an environment in which they can thrive.”

Community members will have until Nov. 17 to lodge their concerns with the city before the city council takes up the issue.