OK – I’m having a sentimental moment about all this….
The Gun Lake Dam has been intertwined with my life for more than 20 years. I’ve seen amazing amounts of water pour over it as it maintains our lake level; and I’ve seen it either dribble water, or dry up completely. My grandkids like to take paddleboat or kayak rides down to see the dam and hear its not-quite-thunderous roar, complete with giggles and shrieks of “Don’t go over the waterfall, Grandma!!!” as if we’d paddled to the very edge of Niagara…
Of course, if we had gone over the edge, we’d just have clunked down on the other side. The water level was usually 8″ deep or so. Unlike some of the scary dams in Grand Rapids that readily drown people; ours was never much of a threat. Maybe a skinned knee?
There’s been some speculation (but how could we ever prove/disprove it?) that the fairly-strong earthquake 3 weeks prior to the late-May “Dam Emergency”, somehow caused some liquefaction under the dam. I find that believable, considering that the whole south end of the lake is basically a swamp. Water, that ever-pervasive eroder, started trickling UNDER the dam (that reaches maybe 6′ down), until it finally opened a hole?? And by May 27th, that hole was downright massive – EEEKS! (See my post titled “Saving The Lake”)
Anyway – the quick repairs saved the lake and the downstream farmers’ crops. The several-hundred-tons of rocks are holding the dam in place nicely, and are even kind of pretty to look at. I’ve seen a few fish swim upstream (and this will be a feature we’ll be encouraged to include when the new dam is constructed). But the dam-saving rocks are large, meaning that underneath the dam, it’s rather porous? So now, with a lower lake level, we have this: We might have more water passing under the dam, than going over it?
The green oblong is an area that didn’t get many upstream rocks (keep in mind that when the repair was done, it was after 10 PM, dark, and the water was extremely muddy with all the activity); the pink area is a series of “boils” (upwelling water) where the ground appears to have sunken; and the gold is an area of upwelling where the ground has not sunken.
This other section in the middle (gold) is where the original BIG boil first appeared; thanks to the filter fabric and rocks, it’s now down to a mere trickle compared to its scary-big self last May. There is also a “perched” (eroded) area on the NW end of the dam where it’s running between the concrete and the adjacent seawall – I’m assuming that the 1″ gap opened as the dam shifted during repairs? At any rate – Russ Yarger and Brian Cenci (Barry Co. Dam Inspector) are aware of these problems. The filter fabric should stop any huge erosion…..
I originally made it sound like maybe the repairs had been so fabulous, so indestructible, that the little dam could stay with us for many more years? I mean, the dam and I have history – we’re almost the same age. But now I realize the little dam is old and tired and leaky. (Fortunately, I’m not quite there yet….LOL!) It’s time to let a new one take its place.