City plans to temporarily pause construction of Miami’s ‘deepest’ underground parking garage

MIAMI – Miami building officials decided to pause construction of the city’s “deepest” subterranean parking garage to conduct a holistic engineering evaluation after a series of groundwater breaches and complaints from concerned Brickell residents.

On Tuesday, an aerial view over the evacuation site showed the pooling of water in a different section of the cavernous pit where water bubbled to the surface on Friday in a second breach.

A spokesperson for Miami-Dade County’s Department of Regulatory & Economic Resources said Tuesday that the water “will keep coming into the site” until they fix “what’s known as the tremie seal.” They said that is an operational issue rather than an environmental violation.

City building officials said Friday’s breach is expected to be capped tomorrow and when it is, they will issue a stop-work order on this project and bring in three engineers to evaluate what impact, if any, the project is having on surrounding properties.

This will include a geotechnical engineer, a structural engineer, and a seismic testing engineer. Miami Commissioner Ken Russell said this was being done as a precautionary measure and that the building department will cover the engineering costs as all three engineers will report their findings to the city.

Related story: Construction next door to a Brickell condo causes safety problems

Mandy Karnauskas lives in Brickell Townhouse, next to the Una Residences under construction. She said the second upwelling of water at Una happened one day after her management company sent them an e-mail saying that their structural engineer claimed their property is experiencing impacts from the construction site’s first breach in October.

The management company claimed the project is causing soil erosion, which has caused the brick pavers in their tiki hut area to shift.

“We see the ground actually moving, a piece of our property is sinking, and our little tiki picnic huts are starting to keel over,” Karnauskas said.

Ant Yapi Civic Construction, the general contractor for Una Residences, has stated that “our team is remediating these leaks as they happen, and there is no evidence of impacts on surrounding properties.”

Related story: Will Miami’s deepest underground garage cause problems for Biscayne Bay?

“I think it is a very good idea to pause and check the situation,” said Shimon Wdowinski, of Florida International University’s Institute of Environment.

Wdowinski is an expert in land subsidence, sea-level rise, sinkhole activities, wetland hydrology, earthquakes, and other natural hazards. He said the geotechnical engineer will “deal with the earth underneath the buildings” to “evaluate the property of the soil at the building site or next to the building site to see if there were any changes to the soil.”

Wdowinski said the role of a structural engineer would be to evaluate if there is “any damage to the buildings” with an analysis that would consist of “looking if the columns or the walls or any new cracks formed in the building, to see if there were any changes to the building itself.”

As for the seismic testing engineer, Wdowinski said that person would collect data about “the movement of the ground, the elastic movement of the ground, to see how much movement of the vicinity of the building” may be happening to “evaluate if there is a problem that may cause damage to the buildings.”

From his subject matter lens, Wdowinski said what he would be looking for in those engineering reports would be data about any possible, potential damage due to the movement of soil and “if there are any damage to the buildings due to this construction nearby.”

The excavation is happening on the site for a proposed new “ultra-luxury” condo tower. On its website, developer OKO Group claims the waterfront site at 175 SE 25th Rd. will feature a 47-story luxury residential tower, Una Residences, with units starting at $2 million. It will also include a three-level subterranean basement “which will become Miami’s deepest, most expensive underground garage.”

According to ConstructionDive.com, project leads were using a “deep-soil-mixing construction process to create a waterproof bathtub-like structure that protects the building’s concrete mat above the tub from groundwater and forms the base of the garage.”

The general contractor’s statement, which was sent on behalf of William J Real of Civic Construction Company, Inc. reads in part, “As is the case with any high-rise development in South Florida, our team has experienced a series of minor leaks during the excavation process ... The source of these leaks is the water table, which does not interact with Biscayne Bay or the drinking water that comes from the Biscayne Aquifer.

“Our team is remediating these leaks as they happen, and there is no evidence of impacts on surrounding properties. Because the water table spans across South Florida, water intrusion of this nature is common during the early stages of high-rise developments in the region. We anticipate that additional leaks may take place as construction moves forward.”

In a letter to some nearby residents obtained by Local 10 News on Tuesday, DERM’s director said that “the ground we live on in Miami-Dade County is very porous and it contains groundwater. Therefore, when excavating in Miami-Dade County, it is common to encounter the groundwater table as you excavate down into the ground.” He said contractors will commonly try to mitigate against the amount of groundwater they encounter by “sealing or grouting the ground … before they start the excavation.”

Contractors, he wrote, will also use a dewatering technique that involves pumping out any water that does seep in “to help keep the area dry while they conduct their work” which includes when they form and pour concrete.

“Unfortunately, in this specific case, it appears that the work to seal the ground at the excavation has not worked adequately and they have had groundwater seeping into the evacuation area,” the DERM director wrote.

According to city building records, on Monday inspectors noted that with water continuing to enter the site, a holding pond was made with backfill soil to limit flooding.

Challenges of the project in the shallow water table

Following the initial breach in October, Ant Yapi, of Civic Construction, said, “flooding took place on the UNA Residences construction site due to intrusion from the water table.”

Rachel Silverstein, of Miami Waterkeeper, said, “It is very difficult to do construction underground in South Florida because we have very porous limestone rock beneath us. We also happen to have a shallow water table. You only have dry rock for a short time before you hit the water, so it can be very complicated to construct underground parking here in Miami.”

This is one of the reasons she said you don’t see basement construction in South Florida homes like in other parts of the country.

The Una Residences underground garage may consider itself the deepest, but building subterranean garages is not uncommon for Miami, said Miami Commission Ken Russell, who pointed to the recently completed underground garage at Brickell City Center.

The groundwater breach in October happened on an evening when Local 10 News Meteorologist Julie Durda said South Florida experienced “seawater coastal flooding,” and Local 10 News Meteorologist Jordan Patrick explained the full moon helped to create the King Tides phase we expect through Thursday.

“We live in an environment with very shallow groundwater,” Wdowinski said. “That is why most houses don’t have basements here. I think it is a question of design, does it justify to have a deep parking garage in a situation where we have such a shallow groundwater level?”

Wdowinski said that question is better answered by the project’s architects and the engineers who approved it. Russell said it’s a standard engineering process.

“It just has more challenges here in Miami with porous limestone and aquifers and bodies of water,” Russell said, adding that as long it has been deemed “safe” the city will continue to permit these types of projects.

That is because, Russell said, “in the Florida building code this is acceptable,” adding, “my job here is making sure they are meeting requirements of permits from an environmental perspective.”

Extra scrutiny in a post-Surfside building collapse era

Some residents in nearby Brickell buildings said they are concerned about another incident like the Surfside condo collapse.

Related story: Brickell residents fear the worst after flooding of parking garage at luxury condo site

In 2020, Wdowinski published the findings of his groundbreaking research. Analyzing space-based radar data, the FIU researcher “identified the 12-story Champlain Towers South condominium as the one place on the east side of the barrier island where land subsidence was detected from 1993 to 1999.”

Wdowinksi added that “land subsidence in and of itself likely would not cause a building’s collapse.”He said in a post-Surfside era, it is understandable that there would be extra scrutiny from nearby residents and city building officials related to soil foundation and the structural integrity of buildings and projects along our coastline.

“What happened in Surfside, the tragic collapse there, put everybody on alert and justifiably because we don’t see situations like that, it was scary,” Wdowinski said. “Several years before the collapse there was this building of a new property south of the Champlain Towers South, so maybe this analogy is putting people on alert and it is good that people be on top of the situation and let the engineers do their work, to make sure we are not going to have a similar situation again.”

Wdowinski added that another lesson learned from Surfside is monitoring buildings after they are constructed.

“I think that if we learn something from the Champlain Towers South, it is that it is not enough to check it when they do these buildings, but also afterward, things can cascade afterward, so we need to continue monitoring these buildings, especially when it ages.”