A rezoning that would allow the number apartments on an East Riverside site to triple got the thumbs-up from the Austin City Council Thursday.

Flats on Burton, owner 1900 Burton Drive, can redevelop the apartments on the five-acre site under vertical mixed-use zoning, which allows up to 385 multifamily units and 9,000 square feet of office and retail space. Valued by the county at valued at $12.3 million, the site is currently home to the 134-unit, 1970s-era Easton Hills apartments.

The increased density allowance that comes with the zoning exchange requires that at least 10 percent of the new rental units, or about 38, be designated as affordable housing for households earning under 80 percent of the region’s median family income. The developer can also pay a fee in lieu of providing on-site affordable housing.

Flats on Burton has not made available specifics of the development, including planned building heights or whether units will be rental or for sale. Any affordable units for sale would be required to remain affordable for 99 years after the first sale; rental units would need to remain affordable for 40 years.

The city requires that the developer comply with tenant notification and relocation assistance provisions outlined in its land development code.