The owners of Southridge Mall will ask the Des Moines City Council for changes to the development plan for the shopping center to allow the construction of a 52-unit, four-story senior living apartment building. Norm Forget, property manager at Southridge, said the project could lead to additional development at the sprawling mall property. In recent years the owner, the Macerich Co., has spent about $15 million on improvements and Des Moines Area Community College has spent another $15 million for its Southridge campus. Forget has courted a variety of the projects and is hoping to renovate interior portions of the shopping center. The council will consider the change during its meeting on Monday.