RAFAEL CAMILO GUTIÉRREZ, Ph.D.ENGINEERING · CONSTRUCTION

Opening case · Evidence and decisions

1321 Flatbush Avenue

On November 11, 2026, a three-story mixed-use building in Brooklyn collapsed into a neighboring excavation. Eight people died. What can the available evidence establish, and what must a project manager verify before work proceeds?

Case snapshot · November 13, 2026 · Cause under investigation

Watch the footage

Observe the sequence and direction of visible movement. The footage shows a fatal event and its immediate aftermath. The timeline below provides a text alternative.

Read the site from above

Elevated photograph of the Flatbush excavation and adjacent buildings
NBC photo gallery ↗
Pause and discuss · What can we identify?

Locate the excavation, debris and adjoining walls. Mark features obscured by the viewing angle. Request survey and inspection records for the conditions below grade.

What happened

  1. Before the collapse. Demolition and construction activity had taken place next door. Excavation was underway at 2625 Bedford Avenue at the time of the collapse. ABC News
  2. November 11, around 4:01 p.m. NYC received the emergency call. The building fell into the adjoining excavation and the side of another building was damaged. NYC Mayor’s Office · CBS New York
  3. Overnight into November 12. Emergency crews used drones and other tools during the search. Rescue operations concluded Thursday. Aerial views help orient the reader to the debris and neighboring properties. CBS New York · ABC News

What the evidence establishes

The collapse reached the excavation next door. The investigation is examining the building and adjacent construction.

What still needs verification

The initiating failure, the exact sequence below grade, and the contribution of excavation or other conditions remained open. Compare the foundation geometry, approved and actual work sequences, support installation records, and movement data before drawing conclusions.

Investigation status · Associated Press, November 13 ↗

How could the load path change?

Use each hypothesis to decide which evidence to request. The initiating failure was still under investigation as of November 13.

Foundation support

If excavation removes support within the footing’s influence zone, settlement or rotation can follow. Compare surveyed footing elevations, excavation limits and the installed underpinning sequence.

Lateral restraint and construction sequence

Each cut changes the height of retained soil and the support condition. Compare the approved stages with daily logs and inspection records. Check when each brace or tieback began carrying load.

Water, movement and prior conditions

Review groundwater observations, dewatering logs, crack surveys, movement readings and timestamps. Correlate changes with activities before assigning a mechanism.

Test two excavation stages

Compare the 10 ft baseline with your proposed cut. This classroom model assumes dry, level, cohesionless backfill, Kₐ = ⅓ and γ = 120 pcf. Select a uniform surcharge to see its contribution. These inputs describe a hypothetical section.

TopBase
Blue: soil pressure. Gold: added uniform surcharge pressure. Diagram scale stays fixed as you change the inputs.

Show the calculation

Soil: ½KₐγH². Surcharge: KₐqH. Divide the sum by 1,000 to convert lb per ft of wall to kip per ft. Real braced excavations require a project-specific design pressure envelope, including evaluation of groundwater, construction loads and support stiffness.

Decide whether to release the next cut

Simulation · separate from the actual Flatbush investigation

The approved sequence holds excavation at 10 ft until the first support level is installed and inspected. The crew wants to cut to 15 ft. Monitoring is within limits, but that support inspection has no sign-off.

Select your action and the record you need.

Discussion comments · Connect the model to the case
  • Which measurements would distinguish settlement of a footing from movement of the retaining system?
  • Which records would show whether a support was in place before the next cut?
  • Under the same assumptions, compare 10 ft and 15 ft. Explain why the soil contribution increases faster than the surcharge contribution.

Make the call as Project Manager

Classroom scenario. During excavation beside an occupied building, the survey team flags movement above the project’s stop-work threshold. What do you do first?

Before authorizing the next stage, check that the temporary support design and sequencing are approved, inspection hold points are signed off, and monitoring has defined thresholds and response ownership. Compare the local requirements for protecting adjoining properties and monitoring during excavation. NYC DOB · Lot-line construction and monitoring ↗

Write a short technical case brief

In 100–150 words, document two confirmed facts, one open technical question, the record that could answer it, and one PM action before the next excavation stage. Cite at least one source.

0 words

From the case to the game

Follow the loads through each construction stage

Excavation support can limit soil movement, underpinning can transfer an adjacent foundation’s load to a suitable bearing level, and bracing can restrain lateral movement. Their role depends on the stage, the design and how the work is verified in the field.

In FieldLab, you’ll practice that same reasoning by placing shores on two levels, tracing reactions to the base, changing wall brace geometry and checking when a crew may proceed. Your job is to explain what carries the load at each stage and what evidence justifies the next decision.

After your last mission, register your class attendance on the results screen.