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The City of Mount Vernon will need to allocate about $150,000 over the next three years if it intends to move forward on resolving erosion issues at the riverfront.
Estimates and details of possible solutions to the rapid soil loss came during a special meeting held last week.
In less than five years, 384 tons of sediment have washed away from the 616-foot stretch of riverbank.
Last year, the city obtained a Land and River Enhancement grant to fund a feasibility study on ways to fix the problem.
Engineers held an initial meeting in February to discuss preliminary findings. At the latest meeting, they presented their final results, and three possible solutions with cost estimates for each.
The plan with which the city intends to move forward will cost approximately $340,000. The design, known as Longitudinal Peaked Stone Toe Protection, would place riprap along the existing streambank to stabilize the toe of slope. Riprap is a layer of well-graded rocks used to protect against erosion.
Currently, the erosion is occurring because high velocity river water is washing out portions of the bank, causing clumps of dirt to slump into the water below. This design would redirect those erosive waters away from the bank. Certain native grasses and low-lying shrubs would also be planted to clump loose soil and stabilize the area.
Concrete and steel sheet retaining wall designs were also discussed at the meeting, but with estimated costs ranging from $3.1 to $3.3 million, both alternatives proved too costly and unrealistic for the city.
The engineers said the cheaper LSTP plan could last a lifetime if it is properly installed and maintained.
The LSTP design was the most economical option, but Mount Vernon will still need to come up with money to build it.
Mount Vernon can apply for a $100,000 LARE grant every January. This would cover the next stage of the process – engineering and survey study costs. The city can then re-apply for another grant in January 2019 to cove part of stage three: construction costs.
Even with this aid, Mount Vernon would still be responsible for paying about $140,000 for the project. The engineers said the city would need to budget and fundraise the rest if they want to move forward.
Mayor Bill Curtis said he plans to discuss the project and potential fundraising efforts with Mount Vernon Barge, Mount Vernon Fleeting Service and other river-based companies. The barge company also said the city can use its crane and barges during construction.
The next steps and timeline
In their final meeting, the engineers laid out a timeline for the city.
Jeff Boeckler, a resource consultant with North Water, will begin the preliminary permitting process this month, but soon, the city will need to take over this aspect as well.
Luckily, the project is devoid of obstacles like wetlands and endangered species, so Boeckler said the permitting process should be relatively easy.
To help avoid delays, Boeckler suggested that the city submit its engineering plans and permitting paperwork at the same time as the LARE grant application in January.
If all goes well, construction could be complete by late 2019.
Boeckler classified the riverfront erosion as severe, but noted that the situation will not worsen significantly in the next two to three years.
Currently, about half a foot of sediment from this location washes into the Ohio River each year. The rate of erosion could increase during heavy storms and rainy seasons when sediment is heavier.
Mount Vernon City Council unanimously approved to move forward with the LSTP design at its April 13 meeting.
Curtis said he did not plan to set aside money in Mount Vernon’s budget next year for the project, since the next LARE grant will cover all of the engineering costs.
With other large, costly projects on the horizon, Curtis said the city needs to prioritize what to tackle first.
“We know that the erosion is an issue, but we also know it isn’t immediately a major issue,” he said. “This is a big sum of money, and it isn’t the only thing on our to-do list.”