The pond dam has been 95%finished since May 2021 and holds water very well. The soil used in the dam is all clay and rocks that were dug out. In September we had the first heavier rain since completion and part of the top of dam had dropped a few inches. Recently we had heavy rain and the same thing, but this time it dropped almost a foot. We have not had water this high yet and no known leaks. The pictures show it better. Could it be that the clay has gaps and is settling or is it seepage? Water is about 8 inches from the drainage pipe.
I'm guessing that the dam wasn't compacted in 6"-8" lifts with a sheepsfoot roller? When you say "The soil used in the dam is all clay and rocks that were dug out." does that mean that the rocks that were dug out of the pond were put in the dam along with the soil?
If so, I'd recommend draining the pond, removing all the riprap from the back side of the dam, removing the dam, cutting in a core trench and properly constructing the dam (including properly compacting the dam) without the rocks in the soil.
Better to bite the bullet and do it now vs. having the dam wash out on you further down the road when you have fish in it.
I know that's not what you wanted to hear, but if the dam was not properly compacted when it was built there is no way to "fix" it that I know of.
Sam, I'm no expert, but my ears perked up when you said the dam was all clay & rocks. Rocks cause obvious problems, but too much clay can create issues just as too little clay. You want a mix of other soils with the clay, otherwise the dam will tend to crack as it goes through a wet/dry cycle.
Of course, you might have just meant you had adequate clay for the job, in which case this is not a concern. Keep an eye on things, my neighborhood lake washed out ten years ago and caused a lot of problems due to an improperly constructed dam!
I'm no dam expert (pun intended) but if the water is on the left side of the dam, and that 'movement' is on the right side, or far side from the water, then it would seem to me the load of the water has pushed almost all the way through the dam itself which would be a bad scenario.
In the best case, that 'movement' would be from maybe not sloping the downstream side of the dam gradually enough.
Again, I'm no expert on this stuff.
Excerpt from Robert Crais' "The Monkey's Raincoat:" "She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."
If it looks like the face of that slope has moved, then you have slumping.
If it doesn't look like any movement, then probably just a void that was poorly compacted when they were building up the back of the dam..
Originally Posted by esshup
I'm guessing that the dam wasn't compacted in 6"-8" lifts with a sheepsfoot roller? .
Agree with these two - looks like poor compaction. Find out from the contractor what they did. Fill and compact those ruts and the area around them. Call Mike Otto and send him pics and get advice. firstname.lastname@example.org - Contact Mike Otto (Texas 940-736-5333) and Michael Gray (your area email@example.com (615) 308-5752).
Mike Otto will have way more expertise in this area then I do but Ive moved a good bit of dirt for a living for 30 yrs, in your case the back side of the dam was not compacted adequately, it is settling and sliding all at the same time, all may not be lost but reality is it probably wont stop any time soon so filling the top is just a temporary fix till it settles, slides more. the front of the dam may well be compacted enough to hold water just fine but inevitably the back side of the dam usually gets the least attention. as long as the dam is not leaking I would redo the back of the dam, key in the base and track it in a dozer width or two all the way to the top and then fill your top in properly.
All the really good ideas I've ever had came to me while I was milking a cow.
Upon further inspection there is no movement at the bottom of the dam but it seems this are wasnt sloped as well as the rest of dam. I also do suspect it wasnt compacted as well on this end too as during construction this side was steeper and had issues with compacting. Now there is more soil but wasnt compacted well. Once this snow melts well lower the water several feet and redo this section. I added a few pictures for better angles if anyone sees anything else.
This is the third pic from the second set of pictures:
That photo looks like a collapse into a void space.
I also agree with RAH, about the view looking a little more worrisome! Assuming your core trench was constructed about the mid-line of the dam, then it looks like part of your collapse feature includes a section of the core trench!
I am not a dam construction expert, but your situation is starting to look like a recipe for disaster.
Have the contractor who built your pond out there right away and see if he'll resolve this issue. You're one big rain away from serious issues, likely collapse. Call Michael Gray and get him out there for another opinion how to fix it.
I see two big issues.
1) Shifting soils suggest poor construction. 2) Not enough freeboard for storage of big water inflow.
Don't wait, get on it now.
Teach a man to grow fish... He can teach to catch fish...