ORLANDO, Fla. — A new engineering report says ongoing ground movement beneath the evacuated Rialto Apartments is most likely tied to deep-seated sinkhole conditions and extends across the entire building.
The 140-page structural and geotechnical investigation was prepared by Simpson Gumpertz & Heger for property owner Northland after more than 350 residents were forced to evacuate the Sand Lake Road complex in March.
Channel 9 first reported the evacuation in March after residents described loud popping sounds, cracking and doors that would not open.
Engineers point to sinkhole conditions
The new report says investigators found downward displacement across the entire building footprint, supported by under-slab voids, uneven slab elevations and satellite monitoring data.
Engineers said portions of the property have moved downward by about 2 inches on average since 2016, with greater movement near the most heavily damaged apartments.
The report says the movement has been occurring since at least April 2016 and remains ongoing.
Engineers concluded the most likely cause is soil moving into voids in underlying limestone, conditions commonly associated with karst or sinkhole activity.
The investigation found no evidence that plumbing, drainage, fire protection systems or other building utilities caused the ground movement.
Large void was only part of the problem
Channel 9 reported in April that engineers had found a roughly 15-foot-wide, 3-foot-deep void beneath two stacks of apartments.
The final report says that void caused some of the most severe damage, but investigators also found smaller voids throughout the building.
Engineers said damage was visible throughout the complex, although the most extensive damage remained concentrated around Units 145 and 147.
Emergency stabilization work was later completed beneath those units. Channel 9 reported in July that the property remained uninhabitable even after that work was finished.
Report finds structural damage
Engineers said the building currently meets two criteria under Florida law used to define structural damage involving excessive floor and foundation movement.
The report recommends filling voids beneath the entire building to restore support to the concrete slab.
But engineers cautioned that grouting alone would not stop the broader downward movement.
Additional stabilization could include more extensive grouting or deep foundation systems, but the report says the site presents a particular challenge because competent rock is more than 200 feet below ground.
Engineers said they will next determine whether a reliable long-term mitigation solution is feasible.
If one is possible, options for the most heavily damaged portion of the building could include localized repairs, lifting and releveling portions of the structure, or removing and reconstructing affected sections.
The Rialto has remained empty since the March evacuation.
Channel 9 has also reported on the financial impact on displaced tenants, including cash assistance offered by the property owner and a later agreement offering money in exchange for waiving certain legal claims.
County says no immediate life safety risk
Orange County’s Division of Building Safety said it received the final structural and geotechnical report Sept. 17.
In a statement, the county said the report outlines possible causes of the subsurface anomaly beneath the Rialto Apartments and potential options for long-term stabilization.
The county pointed to the report’s recommendation that engineers next determine whether mitigation measures are “reliably feasible.”
Because the building remains unoccupied, the county said there is no immediate risk to life safety.
Building Safety officials said they will continue periodically monitoring the property until the owner decides how to move forward and submits permit applications and supporting documents for review under the Florida Building Code.
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