OKTIBBEHA COUNTY – Supervisors are considering three options to either rehabilitate or decommission the dam at Oktibbeha County Lake that are estimated to cost between $5.4 million and $11.2 million.
WSP USA Environmental and Infrastructure, the engineering firm overseeing the project, will finalize design drawings and cost estimates for each of the three options before supervisors cast their votes.
District 3 Supervisor and Board President Marvell Howard said the goal is to have a draft plan ready by winter of this year once the preferred alternative is determined.
“In December, they will come back with some drawings so that we can decide on which option we want to go with,” he told The Dispatch after the meeting. “Once we decide and the board votes, then it will be presented to (the Mississippi Soil and Water Conservation Commission).”
Of the three proposed plans, the most costly, at $11.2 million, is rehabilitating the lake with a high-hazard dam, said Scott Taylor, an engineer with WSP and project manager for the lake. Rebuilding it with a significant-hazard dam is the cheapest option, at $5.4 million.
Decommissioning the lake would cost $8.1 million.
The county, working with the National Resources Conservation Service and the Mississippi Soil and Water Conservation Commission, applied for an NRCS Watershed Rehabilitation Program grant in February 2022, which will largely cover costs for the project.
The grant provides full funding for improvements made for flood prevention, while improvements that are primarily recreational only receive 50% funding. Taylor said flood prevention is the primary purpose for each of the three plans, but if NRCS chooses to categorize it differently, the funding structure could change.
“Right now, all of our analysis was for flood reduction,” Taylor said. “NRCS may say … ‘You’re only getting minimal flood reduction, it’s a recreation dam. Recategorize it as recreation, and we’ll still pay for part of it, but not to the level of that flood reduction point.’”
The county will be responsible for covering costs related to real property rights. Once the project is finished the county will also have to cover all operations and maintenance costs, currently projected to be about $5,000 annually.
The lake was built in 1965 primarily for recreation, but in 2020, the county essentially drained it after officials reported the dam was in imminent danger of breaching. Mississippi Engineering Group estimated work to repair the levee and upgrade the spillways to standards would cost between $15 million and $17 million.
High-hazard vs. significant hazard
A “high hazard” designation applies to dams where failure could result in loss of life or serious damage to buildings, public utilities or major transportation routes. Taylor said high hazard dams must hold 41 inches of rain without flowing over the top. The dam currently doesn’t meet that standard, so the $11.2 million rehabilitation plan includes raising its height by two feet.
“It’s two feet low,” he said. “We said if we’re going to do an option, let’s leave the water what it (was). We started at that same elevation of the old riser and went up, but we didn’t have enough elevation to hold the whole (probable maximum precipitation) before it overtopped the dam.”
The study indicated raising the dam wouldn’t impact nearby homes, but it would require rebuilding the road and spillway, adding to the total cost. Installing a new principal spillway riser, replacing a reinforced concrete box culvert and rebuilding the roadway are major expenses in the high hazard plan.
The “significant hazard” classification means dam failure wouldn’t cause loss of life, Taylor said, but it may pose a threat to main roads and servicing public utilities. He said this plan wouldn’t require raising the dam’s elevation, but four homes within the flood zone would need to either be elevated or purchased by the county for removal.
“Everybody within the flood inundation area, we have to do something with their house because you can’t have a house that may get inundated during a breach,” Taylor said.
The significant hazard rehabilitation would also include installing a new spillway riser and removing/replacing nine box culverts.
Decommissioning still on the table
Decommissioning the lake and dam is still an option, but it’s not as simple or inexpensive as it may seem, Taylor said.
“Decommissioning means we remove the unsafe situation as it is,” he said. “We don’t do anything with the houses downstream. We take this dam away. Some say, ‘Well, why don’t we just cut a hole in it and call it a day?’ Well, there’s cars driving over it every day, school buses driving over it every day, and we have to do something with … all the dirt that you dig up from that.”
If supervisors go with decommissioning the lake, the main embankment will be removed down to the original ground elevation. It would involve removing about 180 cubic yards of reinforced concrete and more than 200,000 cubic yards of dirt.
Then the road running over the dam would need to be constructed and the former stream channel in the reservoir area would need to be restored. The dam’s principal spillway inlet structure and conduit would be removed.
That plan is still eligible to be covered by the NRCS grant.
Public reaction
Reactions from both the public and the supervisors at Monday’s meetings ranged from hopeful optimism about rehabilitating the lake to concerns about whether it’s worth restoring.
Daniel Gadke, a resident of Bulldog Cove, said it would be a mistake not to rehabilitate the lake.
“If we decommission the lake … what we’re all doing is, we’re agreeing forever to never problem solve how to make that lake a part of this growth and how to make the lake a part of the county and the economy and the future of Starkville,” Gadke said.
George Sills said the lake will continue to be a problem for the county if it isn’t decommissioned.
“The challenge of that lake is you’re never going to have the recreation that everybody thinks it’s going to be,” he said. “I see it as a money pit. Eventually it’s going to have to be rehabilitated again.”
District 4 Supervisor Pattie Little said she would like to see the lake rehabilitated.
“A lot of people live out there and have a vested interest,” she told The Dispatch after the meeting. “They build their houses out there. They live out there. It’s been there for 60-plus years. My personal feeling is if we can get it classified for (flood prevention) and get the money there, we’re ready to go.”
District 3 Supervisor and Board President Marvell Howard, who lives near the lake, shared the same sentiment. He’s not sure why anyone would be against rehabilitating the lake if the federal government is footing the bill, he said.
“The board has been extremely supportive of trying to get this issue taken care of, but myself personally, I’ve had my shoulder against this boulder for over eight years,” he said. “… It’s a head scratcher for me that you’ve got people that’s fighting not to get federal dollars to take care of this project.”
In the meantime, design drawings and costs for each option will be finalized for supervisors to evaluate before making a final decision. Once a preferred alternative is decided, WSP will prepare a draft plan including a watershed plan and an environmental assessment to present to NRCS. After approval and funding are secured, the plan can be implemented.
McRae is a general assignment and education reporter for The Dispatch.
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