Pond Boss Forums POND CONSTRUCTION Soil questions cracks in the top of my dam

My newly built 2 acre lake dam has cracks in the surface. We have had 11 inches of rain including a 3 inch gully washer the other day. I walked the top of the dam about 3 days after the hard rain and I have long cracks about 6-8 inches deep on top running parallel the dam surface. It is soft to walk next to the cracks and will collapse in with your weight. These cracks are 30-60 ft long in places. Odviously it appears the rain is breaking the top layer down. I have 100 lbs of rye grass growing for about a month now. That probably has helped some. My freeboard is 20 ft wide and most of these cracks are kind of in the middle of it. Is this normall? Do I need to expect this for awhile on a new construction or do you think I have a major problem already beginning to develop?

Flame

Mine was the same the first year due to the clay drying and settling. Had the pond maker come out and he assured me that was normal for all the clay and dirt drying out, and now they are not visible any longer so I'm good with that. My guy has done hundreds in our area, and he wasn't concerned. See what the rest has to say.


Pat W

Without being there it's hard to say, but since that you've had that much rain the ground shouldn't be cracking because it's dry....

Clay shrinks when it dries out, swells when wet.

Ya might want to have the pond builder come back out for a look see.

With all the rain, could it be signs of a miniature "mudslide" that happened. Or possible of a bigger one to come?

I have the same problem, looks like a small mud slide took place and now have a 30' long fisher on the top and water side of the pond. The fisher was about 15" deep and 30' long. Contractor was not concerned and said we can add some soil to it when things dry up. That might not be for a couple of months.

Tgw1
Totally normal down here from what my builder says. When they dug mine the dirt was dampish and dried out it pulls apart. Not doing it any more. Pond is a year old now.


Pat W

TGW1, How old is your pond? Fortunantly my cracks are in the middle of a 20 ft wide freeboard. We just got another 1 and 1/2 inch rain and expect at least 1 inch more today and tomorrow. Pond is filling nicely with 5 ft at a pole in the deep end. TGW how large is your pond?

Hay there Flame, My pond is only a few months old and will be 3.5 acres of water at full stage with 15' as the deepest depths. Flame, where r u located in E Tex.

I am in Sabine County, right between Lake Sam Rayburn and Toledo Bend Resevoir only about 10 miles from the Louisiana border. Don't get much deeper East Texas than that.

I know the area. I used to hop back and forth fishing those two great lakes. you are right in the middle of some of the best fishing waters in the USA. Maybe some day all of us can fish each others ponds and learn from each other.

I now have over 7 foot water in my deepest part. Have had 19 inches of rain in 2 months. Got 8 inches in 48 hours!!! The cracks in the top of the dam have all but filled in. I guess it was just surface settling on the new pond. With that much rain I was pleasantly surprised that it did not get worse. It actually packed down and got better. Dodged a big one I think.

During the construction of our 3 acre pond (we built it ourselves with our own equipment) the NRCS guy said to put our best material in the center of the dam. So everything from the core trench below ground level and up through the middle of the dam was well mixed and compacted with the best clay we could find on the site. Anything that was gravely or had topsoil mixed in or was less desirable went on the back side as fill. It also was compacted but not near the effort was made on that dirt as what we did on the section in the very middle core of the dam.

What I am getting at (after thinking about this since you originally posted and I was very interested to see what answers you got and how it turned out) is that the entire dam may not have been of the same homogenous material or even of the same compaction level. If that happened to be the case, I can see where portions of the dam might settle differently than others. Particularly where you have had so much rain all at once where the settling might show up more compared to it doing so more slowly.

Just my thoughts on the subject. Not an expert so just guessing.

My dam started cracking the next year after I renovated in August and it filled by November. Never had a noticeable leak or anything. My dirt is almost all clay so I don't think I'd be too worried about it.

When they dig out moist clay to put in core it will dry out some what causing It to shrink (crack) plus a certain settling occurs. That's why the top middle section is higher than the ends , to account for settling. That way you end up with a level or slightly arched dam. That's how it was told to me when mine had a crack running parallel down the dam. Crack filled in with later rains


Pat

Snrub, I am betting you nailed down the cause of the cracks.....especially given the long, straight line nature of them where dissimilar materials and compactions would be.

My cracks occurred in very dry conditions causing me to think in my case it was clay drying out and shrinking. Down here on the coast we get 3-4" wide cracks in our yard during the dry season due to our gumbo soil shrinking. I'm sure everyone is right cause anything can do anything at any given time

Pat