Century of deterioration
The first to get fixed is Lockington Dam in southern Shelby County, where work started last fall on the concrete conduit showing the most wear and tear.
While the dams are largely earthen, each have concrete openings that allow the river to flow through. The conduits allow only the amount of water the downstream river channel can handle to prevent flooding, according to MCD.
The flood control district protects roughly 1 million people and more than 47,000 properties in Butler, Hamilton, Miami, Montgomery and Warren counties.
Lockington Dam and the others were last patched in the 1970s with sprayed concrete.
During recent work on Lockington, engineers found freeze and thaw cycles have not only forced patched portions from the main wall, but damage from temperature swings is found deep into the original concrete where water has penetrated.
“Not only is the shotcrete falling off and deteriorating, but the walls behind the shotcrete continue to deteriorate,” Rinehart said. “So now we’re addressing all of the deterioration over the past hundred years.”
The original concrete was poured in sections about five feet high and 30 feet wide, leaving small voids between the massive blocks.
“We see the most extensive deterioration around these construction joints,” Rinehart said.
Sunesis Construction Co., based in West Chester, has replaced 15 vertical feet of deteriorating concrete with new on the upstream right spillway wall at Lockington Dam.
The first $2.5 million phase of work on the dam also includes a new drainage system to keep water from collecting along the back of the wall.
“We’re not only fixing the problem we’re enhancing something, so the problem hopefully 100 years from now isn’t the same,” Rinehart said.
As many as two more projects will be required on Lockington, the system’s northern-most dam, according to MCD.
Trial and error
Current work on the Lockington Dam will help the flood control district predict the extent of the damage to the system’s other dams and how to fix them, said Don O’Connor, MCD’s chief of construction and planning.
A big challenge was getting workers in the right position to perform the hydrodemolition, O’Connor said.
The contractor first considered installing platforms into the wall, but determined that was not feasible. They put a lift into the water, but that didn’t work when water rose a foot above normal. They considered working from barges and tried a crane, O’Connor said.
After trial and error, the contractor settled on using lift trucks with articulated arms that could reach to the work surface while parked behind the wall.
“This method they found has really allowed them to be work faster and be much more efficient,” O’Connor said.
Work at Lockington Dam also revealed that concrete sections normally in shade had deeper deterioration — up to two feet at points — while sections typically facing the sun had less damage, O’Connor said.
“That’s going to help us estimate the removal amounts on the other dams and be more accurate on upcoming projects,” he said.
MCD hasn’t determined which dam will be tackled next. It did receive an $850,000 FEMA grant to help pay for the structural analyses for the Englewood, Germantown and Taylorsville dams — a process that could take two years, according to MCD.
Built to protect
MCD was formed after the Great Flood of 1913 caused widespread destruction — and 360 deaths.
Up to 20 feet of water covered parts of downtown Dayton. Towns up and down the Great Miami River were flooded as well: Piqua, Troy, Tipp City, West Carrollton, Miamisburg, Franklin, Middletown and Hamilton. As many as 65,000 people were displaced and property damage totaled more than $100 million.
A community effort after the flood led to the formation of the MCD in 1915. The engineer Arthur Morgan designed the system built between 1918 and 1922 that included the five dry dams and 43 miles of levees and channel improvements.
More than 2,000 workers built the dams and levees simultaneously. Costing then $30 million, it was the largest public works project in the world at the time. An additional 12 miles of levee were built later.
Rinehart said the price tag on the new rehabilitation could run between $30 million and $40 million.
“We don’t have good, hard numbers, but it’s safe to assume it’s going to be several tens of millions (of dollars),” he said.
Assessment may rise
While the assessment for property owners hasn’t gone up since 2013, that might change in 2023.
Owners of properties in Butler, Hamilton, Miami, Montgomery and Warren counties that flooded in 1913 pay two annual Miami Conservancy assessments. One is for maintenance of the dams, levees and related flood protection features. The second, the Dam Safety Initiative, is for capital improvements to the five dams and the fund that will cover the repair work in coming years.
An individual assessment is based primarily on the 1913 flood depth at a property and its current tax value. Properties that receive a higher level of protection generally have a higher assessment.
The flood control assessments from property owners, cities and counties in the 1913 flood area account for about $6.54 million of MCD’s 2020 revenue. The five counties that receive flood protection, along with communities in Clark, Greene, Preble and Shelby counties, also pay into an aquifer preservation fund projected to raise a little more than $904,000 to meet MCD’s 2020 budget of nearly $10.3, according to MCD.
The Dam Safety Initiative was approved in 1998 to collect a little more than $26.6 million and assessments began in 1999. The Conservancy Court, a body of nine Common Pleas Court judges from the counties that governs the board and approves financing, granted an extension through 2022 to collect an additional $3.9 million, but that’s when the authority ends.
Rinehart said MCD will likely ask the Conservancy Court in early- to mid-2020 to retire the existing Dam Safety Initiative and start a new authority beginning in 2023 with an adjusted assessment — one likely higher.
“A new assessment to allow us to collect sufficient funds to pay for all these projects,” he said.
Routine maintenance and large repairs can’t be deferred indefinitely, O’Connor said.
“We know the materials that are used to build our public infrastructure don’t last forever,” he said. “It’s important not to wait too long. The longer you wait, the more expensive it gets, and the higher the chance of failures happening.”