Engineers believe they have found a solution to keep the federal government from labeling vast new stretches of Highland as being at high risk for flooding.
The idea is fairly simple — create a larger opening for water to flow underneath the CSX railroad tracks at Poplar Street. But while the idea is straightforward, it’s implementation may prove a little more complex.
The Federal Emergency Management Agency is currently in the drafting stage for its Map Modernization Program as it relates to Highland. FEMA periodically updates its flood maps to take into account new developments, changes in topography, etc., and how those changes may alter what areas would be considered to be at a greater risk for flooding.
Preliminary map updates for Highland show the Special Flood Hazard Area as potentially being tripled since the maps were last updated in 1986.
If that were to happen, the end result of the program could have a terrible impact on the community, city leaders said. Property owners finding their land and buildings in the new floodplain would be required to purchase flood insurance at increased rates. Also, new structures built within the area would be subject to new building standards that would add large costs to and could discourage future development.
In January, the city commissioned Oates Associates Inc., a Collinsville engineering firm, to take a look at FEMA’s calculations and see if they could come up with ideas to mitigate increase to the potential increase to the Special Flood Hazard Area in the city.
David Oates and Steve Keil from Oates Associates recently presented findings to city leaders.
Oates said that the firm noticed a specific change in the flood plain when they were looking at the maps. The Lindenthal Creek and Laurel Branch flood areas had vastly increased, especially north of the CSXT train crossing on Poplar Street and U.S. Highway 40. He said that this was because of a culvert under the railroad.
While looking at the culvert, the engineers saw the original 100-year-old had been modified to be smaller, almost cutting the volume of water in half that can pass through its opening. This caused the flood plain above the culvert to be raised by up to six or seven feet above the 1986 flood line, affecting 52 more properties and 124 additional acres. But the area downstream from the culvert is depicted to be two to three feet lower.
“If the water backs up behind the culvert, it has nowhere to go,” Oates said.
It has not been specified when this change was made to the culvert, but Oates said he suspects it was done sometime after the release of the 1986 flood maps.
Oates suggested a couple options to fix the issue at the culvert.
The most expensive route would be completely replacing the culvert with two 12-by-10-foot culverts. This would cost the city about $1 million, just for construction. The other option would be to insert six, 48-inch pipes above the existing culvert. The second course would cost about $500,000.
Oates said that completing either of these projects should allow enough water to pass through the culvert to restore the city’s flood plain to the 1986 lines.
There is one hitch in both plans, however. During construction, the city would have to ensure rail traffic could continue to flow. The cost to keep the trains running is unknown. There is also no plan yet on how to do so. It would have to be coordinated with the railroad and other government entities.
The the city has another problem — time.
“We’re dealing with two of the slowest bureaucracies in the country,” said Oates, referring to FEMA and the Federal Railroad Administration.
It is estimated that the flood maps will be finalized late in 2018, according to Oates.
City Manager Mark Latham said it is imperative that the city fixes that problem before that time. If it does not, it will be harder to fix the maps once they are finalized.
Latham said the next step is securing an agreement between Highland and the railroad, which will allow the city to sit down with the railroad’s engineers to review the study’s findings and options. After plans are made, Latham said that they must be approved by both the council and the railroad. Then the actual time to finish the construction and coordinate with FEMA must be factored in.
“The time could run out,” Latham said.
But Latham said that if there is a chance the city might be able to remedy this issue, they must try.
“I mean, it’s possible,” Latham said. “We are still hopeful.”
Public Meeting on Flood Plan
The city will hold a public meeting will at City Hall, 1115 Broadway, from 4:305:30 p.m. on Wednesday, Aug. 9 to discuss the findings of a study presented by Oates Associates Inc. in regards to the Federal Emergency Management Agency’s Map Modernization Program.