By Eric Curl
Nov. 30, 2022 – Bad soil struck again.
Essentially, that’s the finding of the engineering firm investigating the collapse of a section of Hutchinson Island’s riverwalk in June.
An excavation of the riverwalk’s failed bulkhead revealed that voids developed behind the sea wall over time, due in large part to Hutchinson’s “notoriously poor soil conditions”, according to an email John Giordano, with Thomas and Hutton, sent to the county’s engineering department in late October. While prefacing the correspondence by stating it may be “impossible to pinpoint the exact conditions or series of events that lead to the failure of the bulkhead”, Giordano went on to say that the earthquake that day may have moved material into the voids, inducing a domino effect of soils moving toward the wall and creating an imbalanced load on the wall and supporting anchors.
The increased loading led to the failure of the support anchors, compounding the problems by allowing the wall to move out and create additional room for further soil movement, Giordano said.
Chatham County is now taking steps to repair and rebuild the collapsed riverwalk. On Oct. 21, the county commission approved a $493,500 engineering services contract with Thomas and Hutton to design the rebuild of the sea wall. The increase followed an emergency $100,000 engineering contract and an almost $3 million emergency repair contract with TIC to stabilize the wall after the bulkhead’s failure. A construction contract, and it’s price tag, will go before the commission for consideration after the design is completed.
Hutchinson has experienced previous failures along a different section of the riverwalk. In 2000, a 30-foot portion collapsed about three weeks before the opening of the newly constructed convention center. About five months later, a 10-year-old boy suffered some minor scrapes and bruises after a five-foot section of the riverwalk collapsed and he fell into a waist-high hole.
Bad soil was also blamed for those past collapses.
Thomas and Hutton could not say whether any of the other sections of the Hutchinson riverwalk could fail for the same reason.
“Bulkheads are retaining wall systems and consist of many components which require ongoing maintenance and inspection and since T&H is not involved in any of these activities, we have no way of telling this,” Giordano wrote in an emailed response to inquiries from Savannah Agenda.
To prevent the damaged portion of the riverwalk from collapsing again, the engineering firm reviewed new soil borings and evaluated surrounding conditions before selecting a design for the repairs, Giordano said.
“The current design for the repair includes deep foundations which are driven into the marl soil layer (our area’s version of bedrock)” Giordano said. “These piles will support not only the bulkhead, but also the deadman tie-back system, the pavers, stairs, landscaping and utilities.”
However, Giordano said, the repaired system will also require ongoing maintenance and inspection to ensure it continues to function as designed.
Hutchinson’s riverwalk isn’t the only riverwalk in Savannah getting some costly improvements. The city is getting ready to fund almost $2.6 million in additional improvements to the pedestrian walkway across the Savannah River along the east end of the Eastern Wharf development.
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