Dive Brief:

• Work has restarted at Miami-based developer OKO Group's Una Residences, a 47-story, 135-unit residential tower in the Brickell section of Miami, after it stopped in November. Upon orders from city building officials, construction was paused last month due to groundwater breaches and complaints from nearby residents, according to local Miami television station WPLG. 
• After conducting a review of the site, the Miami Building Department and a team of three independent engineers "concluded that the water intrusion that took place earlier this year has caused no impacts on surrounding structures and that construction of Una can now continue," the project's contractor, William J. Real, founder and CEO of Civic Construction Co., said in prepared remarks for Construction Dive.
• The building, which the developer says will have the largest subterranean garage in Miami, is located just feet away from the Biscayne Bay waterfront. Residents at the neighboring Brickell Townhouses expressed concern to WPLG about construction causing soil erosion, cracks in concrete and the ground moving.

Dive Insight:

Miami-based developer OKO Group has ambitious plans for the 236-car, 100,000-square-foot parking garage at Una Residences, which is buried three stories below ground and is designed to serve as a watertight foundation for the structure. 

The construction team is using advanced technology, design and engineering to build the garage. The project, which began earlier this year, required workers to drill 800 holes 50 feet deep into the ground and fill them with concrete and water. The interlocking pillars created a cement block that is hollowed out to build the garage, according to OKO Group.

In an email to Construction Dive, Quentin Suckling, a structural engineer with Australia-based Sheer Force Engineering, said basement construction is one of the higher-risk elements in the building industry because there are more unknowns.

"When constructing a deep basement adjacent to an existing building with shallow foundations, some movement of the existing building may be inevitable, especially if the neighboring building is sufficiently close to the proposed new basement," Suckling said.

If things go wrong, it can lead to significant structural damage to neighboring buildings. If the basement is not sufficiently watertight, that can also lead to issues.

"If not rectified, excessive leaking can have adverse effects on neighboring buildings as this can lead to a drawdown of the water table and subsidence of neighboring foundations," Suckling said.

Construction close to a shoreline can also open up a host of problems if not done right because it can be lower than the water table and sit within a saltwater environment, he said.

"If the basement is not adequately detailed to protect the main structural elements from the corrosive effects of the saltwater environment, degradation of the basement walls may occur," Suckling said. "This can lead to premature failure of the wall which can have serious impacts on close neighboring buildings."

In its statement to Construction Dive, Real said the company "will continue to work with the city of Miami and its team of independent consultants to ensure construction progresses safely." 

Surfside concerns linger

The Champlain Towers South condominium collapse in Surfside, Florida, which killed 98 people on June 24, has led to increased scrutiny on how construction work affects nearby properties, according to Jonathan Kurry, a Miami-based partner at global law firm Reed Smith.

"I think there is certainly much much more focus on things that could cause damage [next door], especially in light of Surfside," he told Construction Dive.

At Surfside, a class-action complaint updated on Nov. 10 alleges that the towers were "badly damaged and destabilized" because of excavation and construction at the neighboring 18-story Eighty Seven Park condominium, according to court documents.

The suit, filed in Miami-Dade Circuit Court on behalf of the collapse's victims and their families, alleges that 8701 Collins Development ignored warnings about vibrations and other issues from residents of Champlain Towers South. 

Law firm Greenberg Traurig, attorneys for Eighty Seven Park developer Terra Group, responded to Construction Dive with a background fact sheet claiming that the construction team at Eighty Seven Park did not cause any structural damage to CTS and that neither "their work or equipment was capable of damaging the reinforced concrete that failed."