With plenty of potential suspects to consider (harbor deepening, surrounding construction), the cause of Hutchinson Island’s riverwalk collapse in June came down to a familiar foe - with some assistance from an uninvited guest. That is the conclusion of the engineering firm Chatham County hired to design the repairs. Meanwhile, there is apparently nothing technically wrong with the riverwalk along the east end of the Eastern Wharf on the other side of the Savannah River. Still, the city is planning to invest an additional $2.6 million towards reconstructing a portion of it. Both projects are the latest in a series of costly fixes applied to the waterfront walkways over the years. Read all about them in this week’s edition of Savannah Agenda Property Matters.
Stay engaged Savannah, Eric Curl
The city is preparing to fund almost $2.6 million in improvements to a closed section of the Savannah Riverwalk east of downtown in order for luxury housing construction along the mixed-use Eastern Wharf development to proceed.
The proposed project consists of adding support to the eastern end of the public riverwalk’s anchoring system after it was discovered that anchor tiebacks installed in 2010 extend onto the private development, according to city spokesperson Keturah Greene-Luckett. The additional work is needed to prevent the anchors from being severed by foundation construction at Eastern Wharf, and thus destabilize the riverwalk, Greene-Luckett said. The issue was discovered in 2017 and plans for the improvements were previously submitted in 2019, but the city did not have funding for the work at the time, she said.
The closed section of the riverwalk runs along a northeastern portion of Eastern Wharf that is being developed for housing by Patrick Malloy Communities. The Upper East River community will feature homes ranging from the “$600,000s to the $4 millions”, according to the website. The developer did not respond when Savannah Agenda reached out via email and phone for this article.
Collins Engineering was hired to design the improvements, while Parker Marine Contracting is the project’s general contractor, according to the latest building permit application submitted for the project in October. The developer of Eastern Wharf is constructing the repairs and will be reimbursed by the city, Greene-Luckett said.
A costly history
The latest plan is not the first time the riverwalk fronting the Eastern Wharf development has needed costly improvements since it was constructed in the late 2000s. In 2008, the city spent about $1.2 million in additional contract work, bringing the total to about $10 million, to stabilize the bulkhead after the seawall was dislodged by the removal of some unexpected wood pilings.
Less than two years later, another $3.8 million in repairs and improvements were needed after structural problems were discovered along a 448-foot section of the 2,000-foot structure. Those costs were picked up by the insurer of the project’s design and engineering firm, Thomas and Hutton, in exchange for the city and its contractor, TIC, agreeing to not seek any claims as a result of the work suspension and repairs. This was when the tiebacks the city is now planning on replacing were installed.
The city and the city’s third-party consultant reviewed the plans at the time and agreed on the repairs, according to John Giordano, with Thomas and Hutton. There were no failures of the existing tiebacks designed by Thomas and Hutton that were installed in 2010, Giordano said.
The city agrees that Thomas and Hutton is not liable for the additional improvements now being planned. Since the 2010 repairs were completed, the property ownership has changed hands and the development plan has changed, and the city has decided to construct a system that further removes the risk of damaging the anchor tiebacks, Greene-Luckett said.
Across the river
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 Thomas and Hutton’s John Giordano 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.