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Detroit releases report on suspected cause of mysterious 'ground shift'

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City of Detroit
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An aerial view of the ground shift, and the scrapyard experts believe caused it.

What caused a southwest Detroit roadway to heave and crack last fall? A new city report says it’s found the most likely answer.

The “ground shift” near Fort and Dearborn streets on Sept. 11 shook the surrounding area, caused the roadway to buckle, and forced the demolition of a building. Now, an engineering firm’s report commissioned by the city says the most likely culprit was a nearby scrapyard.

The report from Somat Engineering says metallic scrap heaps at Fort Iron and Metal were simply so heavy that they caused “soil failure” in the underlying clay soils.

"The weight of the stockpiled mill scale material exceeded the shear strength capacity of the underlying clay soils," the report found.

Other factors "may have contributed to the incident and/or to the timing of the incident, but the primary cause of the soil failure was the load imposed by the mill scale stockpile.”

Investigators ruled out several competing scenarios, including a gas main explosion or water main break. They originally suspected that saturated ground caused by heavy rainfall also played a role, but the report found that likely had “no significant effect.”

City officials noted that the scrapyard was operating legally at the time the ground gave way, but the incident — and others nearby — were causing them to review the city's rules.

In a statement regarding the report, the Southwest Detroit Community Benefits Coalition said the fact that storage piles are regulated by height, rather than weight, is something that “needs to be addressed.”

The group said it’s concerned more extreme and wet weather due to climate change heightens the need for more stringent regulations. "This incident, and now two dock collapses [on the Detroit River] were all caused by piles that were too heavy—and due to unregulated and unmonitored conditions.”

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