City plans to temporarily suspend construction of Miami’s ‘deepest’ underground parking lot

MIAMI –Miami building officials have decided to suspend construction of the city’s “deepest” underground parking lot to conduct a comprehensive engineering assessment after a series of groundwater violations and complaints from affected Brickell residents.

An aerial view of the evacuation site on Tuesday showed water pooling in another 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 and Economic Resources said Tuesday that water “will continue to flow to the site” until they fix “what’s called the tremie seal.” “. They said it was an operational issue rather than an environmental violation.

City building officials said Friday’s breach should be capped tomorrow and when it does, they will issue a stop work order on this project and bring in three engineers to assess the impact, the if applicable, of the project on the surrounding properties.

A d

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

Related story: Construction next to a Brickell condo poses safety concerns

Mandy Karnauskas lives in Brickell Townhouse, next to the Una Residences under construction. She said the second upwelling at Una happened a day after her management company emailed them saying their structural engineer claimed their property was suffering the effects of the first breach in the construction site in October.

A d

The management company claimed that the project was causing soil erosion, which led to the displacement of brick pavers from their tiki hut area.

“We see the ground moving, part of our property sinking and our little tiki picnic huts starting to crumble,” Karnauskas said.

Ant Yapi Civic Construction, the general contractor for Una Residences, said “our team is addressing these leaks as they occur, and there is no evidence of impact to surrounding properties. “.

Related story: Will Miami’s Deepest Underground Garage Cause Biscayne Bay Trouble?

“I think it’s a really good idea to pause and check things out,” said Shimon Wdowinski of Florida International University’s Environmental Institute.

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 “take care of the ground under the buildings” to “assess the property of the soil at the site or next to the site to see if there have been any changes in the soil.”

A d

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

As for the seismic test engineer, Wdowinski said that person would collect data on “ground motion, elastic ground motion, to see how much movement of the neighborhood of the building” can occur to “assess whether there is a problem that can cause damage to buildings.

Of his focus, Wdowinski said what he would be looking for in these engineering reports would be data on any possible potential damage due to ground movement and “if there is any damage to buildings due to this nearby construction. “.

Excavation is underway at 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 underground basement “that will become Miami’s deepest and most expensive underground garage.”

A d

According to ConstructionDive.com, the project managers used a “deep soil mixing construction process to create a watertight tub-like structure that protects the building’s concrete floor above the tub from groundwater and forms the garage base”.

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 southern Florida, our team experienced a series of minor leaks during the excavation process… The source of these leaks is groundwater, which does not interact with Biscayne Bay nor the drinking water that comes from of the Biscayne aquifer.

“Our team is addressing these leaks as they occur, and there is no evidence of impact to surrounding properties. Because the water table extends across South Florida, Water intrusion of this nature is common during the early stages of high-rise developments in the area. We anticipate that additional leaks may occur as construction progresses.”

A d

In a letter to some area residents obtained by Local 10 News on Tuesday, the DERM director said, “The ground we live on in Miami-Dade County is very porous and contains groundwater. Therefore, when excavating in Miami-Dade County, it is common to encounter ground water as you dig into the ground. He said contractors will typically try to mitigate the amount of groundwater they encounter by “sealing or sealing the ground…before they begin excavation.”

The contractors, he wrote, will also use a dewatering technique that involves pumping out any infiltrating water “to help keep the area dry while they do their work,” which includes the when they form and pour the concrete.

“Unfortunately, in this specific case, it appears that the soil sealing works during the excavation did not work properly and that there was groundwater that seeped into the evacuation area. “, wrote the director of the DERM.

A d

According to city building records on Monday, inspectors noted that as water continued to enter the site, a retention pond was created with fill soil to limit flooding.

Project issues in shallow groundwater

Following the initial breach in October, Ant Yapi of Civic Construction said, “Flooding has occurred at the UNA Residences construction site due to groundwater intrusion.”

Rachel Silverstein of Miami Waterkeeper said, “It’s very difficult to do underground construction 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 building underground parking here in Miami can be very complicated.

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

A d

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

The groundwater breach in October occurred on an evening when Local 10 News meteorologist Julie Durda said South Florida suffered “coastal saltwater flooding”, and Local 10 meteorologist News Jordan Patrick explained that the full moon helped create the King Tides phase that we expect until Thursday.

“We live in an environment with very shallow groundwater,” Wdowinski said. “That’s why most houses don’t have a basement here. I think it’s a design issue, does it justify having deep parking in a situation where we have such a shallow water table? »

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

A d

“There are just more challenges here in Miami with porous limestone, aquifers and bodies of water,” Russell said, adding that as long as it is deemed “safe,” the city will continue to allow this type. of projects.

Indeed, Russell said, “in the Florida building code, that’s acceptable,” adding, “my job here is to make sure they meet permit requirements from an environmental perspective.”

Closer scrutiny in an era of post-Surfside building collapse

Some residents of neighboring buildings in Brickell have expressed concern about another incident like the collapse of the Surfside condo.

Related story: Brickell residents fear the worst after parking lot floods at luxury condo site

In 2020, Wdowinski published the results of his groundbreaking research. By analyzing space radar data, the CRF researcher “identified the 12-story Champlain Towers South condominium as the only location on the east side of the barrier island where land subsidence was detected from 1993 to 1999.”

A d

Wdowinksi added that “land subsidence by itself would probably not cause a building to collapse.” the structural integrity of buildings and projects along our coastline.

“What happened at Surfside, the tragic collapse there, put everyone on alert and rightly so because we don’t see situations like that, it was scary,” Wdowinski said. “Several years before the collapse there was this construction of a new property south of the Champlain South towers, so maybe that analogy puts people on their toes and it’s good that people are aware of the situation and let the engineers do their job, to make sure we don’t have a similar situation again.

Wdowinski added that another lesson learned from Surfside is monitoring buildings after they’re built.

A d

“I think that if we learn something from the Tours Champlain Sud, it’s that it’s not enough to check when they make these buildings, but also afterwards, things can cascade afterwards, so we have to continue to monitor these buildings. buildings, especially when it gets old.

Copyright 2021 by WPLG Local10.com – All rights reserved.

Bonny J. Streater