Nearly all of the rebar-and-concrete rods that will provide the foundation for the 283-space Depot Plaza underground garage and two apartment towers have been drilled.
The big hole behind Hotel Congress is taking shape as the Depot Plaza underground garage, and construction is expected to start by September on a six-story public housing tower atop the garage.
The $13.5 million, 283-space underground garage along Fifth and Toole avenues is the most substantial Rio Nuevo construction project so far, said Fran LaSala, assistant to the city manager.
Crews have drilled nearly all of the 114 caissons – rebar-and-concrete rods – into the ground for the foundation of the garage and two apartment towers. The support structure is up for about one-fourth of the upper parking deck to give the first inkling that the 242-by-246-foot space is not just an empty hole.
“Very soon you will see this rise from a hole to a tower,” LaSala said.
Depot Plaza includes the garage, a new 68-unit, Martin Luther King Jr. public housing tower for the low-income elderly and disabled; a proposed five-story private sector apartment tower, and the completed One North Fifth Apartments, which was renovated from the prior MLK Jr. public housing apartments.
For now, the action is in the 30-foot deep pit just east of the Ronstadt Transit Center.
Lloyd Construction crews have worked on four primary tasks since starting in late June:
• Digging the hole during July and August, where 4,590 truck loads removed 56,625 cubic yards of dirt and deposited it near Interstate 19 and Ajo Way.
• Removing the underground utility lines on that property.
• Shoring the walls.
• Drilling caissons into the ground.
Once the garage hole reached its depth in August, much of the work has entailed drilling 4- and 8-foot diameter holes in the ground every 27 feet to depths ranging from 52 to 69 feet. The first 87 caissons were installed from August to December and the final seven should be done by Thursday, said Doug Williams, Lloyd’s project superintendent.
This involves reinforced bars (rebar) encased in concrete that is poured from a hose suspended by the 180-foot tall crane that has become a downtown landmark since its arrival Dec. 29.
The Lloyd crew typically drills one hole while filling a second hole with concrete. Drilling and concrete pouring each take one day per caisson, Williams said.
As each 5 feet of the pit was dug, Lloyd Construction shored up the walls in the pit. This started with a 3- 1/2-inch layer of shotcrete – concrete that is shot out of a gun; then a layer of waterproofing; then a layer of reinforced steel; and a final 10 inches of shotcrete, said Jason Mejias, Lloyd’s on-site project manager.
Lloyd has about 35 employees on site for the caisson foundation work, but that will increase to 50 to 60 as the garage is built.
The first 70-foot section of upper deck framing was built in the past five weeks. Plywood lies on aluminum I-beams that rest on steel posts, Williams said.
Rebar will be installed on top of the plywood and, starting in June, 12 inches of concrete will get poured on the plywood-and-rebar base to create the vehicle surface.
Williams said the upper deck will be built in four sections.
The concrete ramp is already in place to link the upper and lower parking levels.
The street-level cap for the garage should be in place in September, at which time construction is set to start for the public housing structure at the west end of the garage. Tower construction should take about 12 months with tenants expected to be moved in by the start of 2011, said Ann Vargas, project supervisor in the city Community Services Department.
More than $15 million is in place for the $17 million MLK project, which is funded by a $9.8 million HOPE VI grant from the U.S. Housing and Urban Development Department, federal low-income housing tax credits, $750,000 each from federal and county HOME Investment Partnership funds, $2.2 million in city HOME Investment Partnership funds and $1.27 million in Pima County bonds, Vargas said.
The Downtown Tucson Development Co., headed by Scott Stiteler, intends to build a five-story, 60- to 80-unit private sector apartment tower at the east end of the garage.
Stiteler declined to say when he planned to start construction, but said he would discuss Depot Plaza when his development agreement for several downtown projects goes to the City Council by the end of May.
“That will include all the activities,” Stiteler said, referring to the Rialto Block, street-level businesses for One North Fifth, possible development for the Ronstadt Transit Center and other potential developments stretching from Sixth Street to Armory Park. “I don’t want to single out one (now) instead of the others.”
Construction crews dig holes and pour concrete last month for the Depot Plaza underground garage downtown. The bottom of the garage will be 30 feet underground.