This article is a quick update as promised in the last Article about the Dam, where I said,
“There is still a very real “Non-Zero” chance that this LLO Project during March and April 2025 ends in catastrophic failure of Lake Petit Dam (and literally bankrupts and destroys the community of Big Canoe, GA).
A quick recap on what the LLO is, and why work is being done.
The Lower Level Outlet (LLO) is an 800+ foot long 36″ diameter pipe that runs through the bottom of Lake Petit Dam. It’s entrance is almost 1/2 way between the Dam, and Eagle Island, about 100 feet under water. The exit is down beside the Ballfield (that concrete structure down in the drainage ditch). The pipe is buried very deep, well below the ballfield road level on lower side of the Dam.
The purpose of the LLO is to act as a LEGALLY REQUIRED emergency drain for the lake. It is LEGALLY REQUIRED to be operated once per year, but in the 53 year life of Lake Petit Dam it never has been. FOBC reporting forced GA Safe Dams to finally mandate a compliance test 2 years ago, but the test failed as the old, rusty parts of the opening mechanism failed. As part of that test a Giant Plug was placed into the Pipe. They crawled it all the 800+ feet through the bottom of the Dam, and placed it at the entrance of the pipe… all the way at the bottom of the lake.
There is a hinged “Gate” at the bottom of the Lake that opens and shuts the entrance to the LLO Pipe. The work they are doing now requires them to totally remove that Gate (Update: Getting conflicting info on whether the Gate will actually be removed and replaced, or simply opened with newly installed stem guide mechanisms), leaving the LLO Pipe wide open (except for that Giant Plug wedged inside the LLO Pipe). The LLO Pipe that the Plug is tightly expanded into the concrete pipe. I am told that it is a fine line of getting the proper seal, vs fracturing the concrete.
Correction: In the original it was stated, “Concrete gets weaker and more brittle with age.” In a wet environment such as the inside of the Dam, this is incorrect. Thank you to an astute reader for catching the error, and educating me on certain properties of concrete in moist environments.
Risk Point #1: The moment they take off (or Open) that Gate, the Plug will experience the full force and pressure of Lake Petit Dam will for the 1st time. It is going to have to sustain it’s position throughout a lengthy replacement the process that will involve disturbance and vibration at the pipe entrance as a new gate mechanism is installed. If it holds, then great. If it fails, then the full pressure of Lake Petit bursts through that pipe and continues to flow for over a week at the highest pressure and volume imaginable through 53 year old, settled pipe joints… until either the dam collapses via internal hemorraghing, or the lake simply drains down to empty. It is NOT a Zero Chance scenario that the plug doesn’t hold. I am sincerely praying for the safety of any divers doing this work, because if the plug gives way… those men die, and get sucked into the pipe. Period. Sorry for the corrections… but getting information from the POA involves a process of Confidential Sources and Design Reviews. Doing the best we can given the intentional nontransparency of the Board/Management.
Let us assume the Plug holds and the Gate replacement is successful. In this event they test the movement of the gate under no load, meaning they move it open and shut while the plug is still in place. It’s a rather simple procedure. Shouldn’t be any problem… yet.
Risk Point #2: GA Safe Dams is then requiring they test the Gate under real conditions. As soon as the Gate is installed and proven to work, the Gate will be shut, and the Plug will be removed. Then the Opening and Shutting of the Gate will be repeated under real world conditions. They will open the gate with the full force of the lake water pressure flow engaged. High Pressure water will flow through the 53 year old LLO Concrete Pipe. The Pipe has settled over the years, and the Joints are not as aligned as when brand new. If the force and weight of water running through the pipes dislodges or shifts a portion of piping, you could experience internal hemorraghing inside the Dam, which could lead to a full collapse.
OR… it could just hold, but the damage to the pipes be so apparently bad, that we go back to the drawing board, which honestly only has one solution… drain the lake, dig up the core of the Dam, and replace the LLO Pipe with a new LLO Pipe. Hint: $$$$$$$
But if the non-Zero chance Scenario of either #1 or #2 occurs… then it is an even bigger $$$$$$$$$$. The Dam fails rapidly, and all downstream lake dams collapse. The water infrastructure system for the community (and eastern Pickens County) gets destroyed. Sewer Systems gone. Possible loss of life… definite loss of structures, bridges (Main Entrance Road/Covered Bridge & Cove Road are gone). Property values gone. Lawsuits flying.
Which is why the documentation website, LakePetitDam.com was created… to document 50+ years of illegal negligence in the event it is needed for litigation.
But it is just a non-zero chance. The most common wording of a question I get (and I do get them frequently) is.. what do you think? A 10% chance of failure? I think so, but I won’t play guessing games on what a narrower range of odds that something bad, or good, happens.
I will say that one thing that really, REALLY bothers me… is that they still won’t release the Camera Inspections of the inside of the LLO Pipe (not even to GA Safe Dams). I was told by an insider that saw them that there was settling, and leakage in the joints. I talked to an industry professional that does this sort of work, and has decades of experience, and he stated that if true this would be disturbing, and that it was subsequently very disturbing that those camera records wouldn’t be available, and that due to the LLO Pipes NEVER having been tested under operational load – these camera reports would be of high significance. But we have professional engineers recommending this… so you just have a hard time believing this isn’t safe. Right? Except I was initially told by a source years ago that it had been conveyed that this approach did indeed have risk associated.
Anyway, whatever happens will happen, and we should know soon one way or the other…. BUT, I do believe that the POA needs to publicly give a heads up for the periods of time that the LLO Gate will be removed, and then as the Gate is actually tested in real world conditions, as those will be the high risk periods of time. Let’s just say that I won’t be doing walking laps at the ballfield during either of those times.
IF there is not a collapse / disaster scenario, then perhaps we can breath a sigh of relief, and start focusing on raising money we don’t have for the Spillway Project.
Peace,
– david / publisher / property owner
Focus on Big Canoe, GA
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