Ensemble Investments LLC of Phoenix is proposing a 308-unit apartment tower with a half-acre public plaza on a blighted property on Delaware River piers that was the site of a deadly nightclub collapse in 2000.

Under the plan being presented to Philadelphia community groups ahead of its formal application for zoning approvals, the Pier 34/35 South apartment building would rise 22 stories, Mark Sanderson, a principal with Digsau, the project's architect, said in an email this week.

The site plan places the tower on the partially submerged Pier 34 at 735 S. Christopher Columbus Blvd. near Fitzwater Street, just south of the Residences at Dockside condominium building. It would have about 100 parking spaces in a garage behind the building, the minimum allowed under the area's zoning, though more spots could be set aside for residents at a public lot across the street, Sanderson said.

The adjacent Pier 35, now completely underwater during high tides, would be restored and landscaped into a public space inspired by Spruce Harbor Park, a summertime attraction with hammocks and food stalls farther up the waterfront at Penn's Landing, he said. It also would have a 5,000-square-foot retail structure at its base, facing South Columbus Boulevard.

Under its current design, the tower would stand 244 feet, the maximum permitted on the central Philadelphia's waterfront for projects making the most of available "bonuses" that let developers add height in exchange for including features seen as benefiting the larger community, he said. The project will get most of the way to that height through bonuses offered for public space, bike paths and retail.

Ensemble acquired the two-pier parcel in 2007, seven years after three women died at the site when a nightclub then on the property collapsed into the river.

The company is also developer of the Courtyard by Marriott hotel in the South Philadelphia Navy Yard.