The Two Twelve Medical Center in Chaska is only 18 months old, but it's already expanding.

Last week, the Chaska City Council gave the go-ahead for a proposed three-story addition next to the center, which is on a 16-acre site near the intersection of Highways 212 and 41.

The current four-story building, owned and operated by Ridgeview Medical Center, provides emergency and urgent care services and houses about 20 other medical clinics. It has about 177,000 square feet of space.

The new building would provide about 64,000 square feet of additional space.

Two Twelve opened on Feb. 1, 2011, and Ridgeview officials said they have received increased interest from other clinics that want to expand or relocate there.

A Ridgeview spokeswoman declined to identify the likely new tenants or the project's cost because they have not been finalized.

The company hopes to break ground on the expansion this fall.