Improvements appear to be in the future to make Gahanna's city-owned Creekside parking garage floor flood-worthy.
Mayor Laurie Jadwin said the city learned that when the garage was constructed nearly 15 years ago, a required permit for flood-plain use wasn't obtained. Improvements are now needed to comply with applicable regulations, she said.
Planning and construction began on the Creekside development over 15 years ago, including the parking garage.
Originally approved by City Council in 2004, the construction process lasted from May 2005 through the grand opening in May 2008.
Because the development was constructed in a flood plain, the use permit was required, Jadwin said.
"It doesn't appear the garage flooring was built to meet flood requirements," she said. "There is no current damage to the garage, and Creekside residences and businesses are safe and secure."
Nonetheless, Jadwin said, parts of the garage could be susceptible to damage if Big Walnut Creek were to reach flood stage.
"While the parking garage eventually will need to be repaired, it will remain open for the foreseeable future," she said.
Carrin Wester, city communications manager, said the Federal Emergency Management Agency requested a flood-proof certificate before Jadwin took office.
In her first week as mayor, Jadwin said, she learned a search by the city staff hadn't found the permit.
She said a plan immediately was developed, including expanding the search and identifying contingency steps in the event it couldn't be located.
The search went on for nearly two months and involved gathering and searching records and reaching out to companies, contractors and individuals who previously had worked on the project.
"During this time, our team proactively planned for the possibility that we would be unable to locate the permit and began a search for an engineering firm that had the expertise to survey the garage and develop a plan to issue a new permit," Jadwin said.
When the permit couldn't be found, Gahanna City Council on April 6 approved a surveying and engineering contract with DLZ Corp. of Columbus for $177,337.50.
On Aug. 28, after months of monitoring and surveying, the city received a draft report of more than 100 pages.
Timothy Hampshire, DLZ engineer, provided key findings of the report to council during a Sept. 8 committee meeting.
Hampshire said his firm looked at whether "no-rise" and "flood-proofing" certificates could be issued for the structure.
A no-rise certificate states a structure didn't cause any detrimental changes in flood-plain elevations. A flood-proofing certificate states a structure's interior would remain reasonably dry in a flood, for insurance purposes.
"When we began looking at the flood-proofing certificate, we needed to look at the impact of a high-water event, basically a 100-year event in Big Walnut Creek and its impact on the underground portions of the structure," Hampshire said. "The 100-year event is the bar that FEMA has set with regards to flood-proofing insurance requirements."
He said findings show the garage's large walls would be structurally adequate during a high-water event.
Hampshire said a bigger issue is the garage's concrete floor being a thin, lightly re-enforced slab on a gravel bed.
Hampshire said a high-water ground event could create enough water pressure to lift the floor slab. Water then could enter the garage, either from under the slab or where the slab meets the concrete walls.
He said unlike the floor, some other maintenance issues could be addressed quickly and inexpensively.
"I think consideration needs to be given to remediating that floor slab and possibly putting in a structural floor slab in order to accommodate the hydrostatic water pressures, just like the walls appear to have been designed for," Hampshire said.
Jadwin said the city must resolve the issue as soon as possible.
Hampshire said a no-rise certificate could be issued for the garage, but a flood-proofing certificate currently could not.
"Although this construction issue pre-dates my administration, we nonetheless are responsible for resolving this problem now," Jadwin said. "We know this news comes at a difficult financial time for the city, as we are in a global economic downturn as a result of the COVID-19 pandemic."
She said the city is identifying feasible remediation options and the project's financial effects.