I have an established pond that has been around for more than 15 years. The dam is a straight 90 degree drop down to the water and over the last 2 years larger chunks of dirt/clay have fallen causing the reducing the buffer of dirt/clay I have for my dam. If this continue in certain areas the dam will be completely be gone. My dam is pretty lengthy (maybe 75 yards). On top my dam I have grass established but it is not holding the dirt/clay from falling. Although there is a 90 degree drop to the water the water follows roughly a 3/1 drop.

Now to my question. I believe my best course of action is to bring in some stone to line to dam, but I'd like to get your take on which stone is the best to use and also which ones to avoid. I have heard that certain limestones become very mossy which is something I would like to avoid. Thoughts?

I know in this case pictures would help so I'll work on trying get those.

It sounds like in your case the shape of the stone will be pretty important so it doesn't roll off. Rip-rap and larger chunks of it with smaller stones and gravel between should do the job. Our local suppliers have dolomite, which is a form of limestone that is non-porous. It does not get mossy.

Best to use what's available nearby. Size should be softball to volleyball size as riprap. If you have a choice, granite is good. Limestone is good, too. It won't grow much algae on it, but acts to buffer the water if needed.

How about posting a picture of the inside face of the dam with an object in there for a size perspective?

MB, depending on your situation, that mossiness might be a good thing. Shelter for YOY, and good surface for periphyton growth.

Hope you have a nearby quarry for large rock.

Trucking is expensive.

Thank you for all the feedback so far. It is greatly appreciated. As requested, here are some pictures to help give you some perspective.

[img]https://photos.google.com/photo/AF1QipNQ-v6ogBqKT6HmGjVYqAQg5DBb-1x7UeOcD7r1[/img]
[img]https://photos.google.com/photo/AF1QipOmku_WBPVCTKSnb8ggC9jj9Jnm3Y_SxMD5zgqu[/img]
[img]https://photos.google.com/photo/AF1QipOdxZx5c8iSAJ5dPWDRuBlblkw5iArQ2OQDvIZa[/img]

I do have a quarry that is just a few miles away and a couple others that are within 30 miles, so I'm hoping they can help me out. Before contacting them I want to absorb all of your opinions and lessons learned. I look forward to the additional feedback.

Get this error. Pictures do not display.

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Here's another attempt to share the pictures.

[img:left]https://goo.gl/photos/RdfEsVd5KRDPtQTY9[/img]
[img:left]https://goo.gl/photos/wBGbpvRdyp7jUtP59[/img]
[img:left]https://goo.gl/photos/NzAQYuEMZjz1vucf9[/img]
[img:left]https://goo.gl/photos/7NU5RKSfa6fK9Lrd6[/img]
[img:left]https://goo.gl/photos/mg4bSMNA4XPAd4jr6[/img]

Do you have room to pull the slope of the dam back to a 1:3 slope and use the dirt to raise the dam? This could be done with a compact excavator.

Ditto that. I had to do some similar work to my dam so I set up with my backhoe as close to the edge as I could get and then reached out to about 2 ft deep water and pulled in from there, gently increasing the slope to about 1:4. Then I backed up a bit and rolled the top edge of the dam. A rolled edge does not allow the water to speed up too much as it drains. Fast water means fast erosion.

After I was done, I turned around and used the loader bucket to back drag and pack the new work from the water's edge over the top of the dam.

Wish I could take credit for thinking of this solution, but a contractor suggested it when a "pond builder" left me with a steep drop off at the dam and too little free-board. It still amazes me that folks that make a living, in part building ponds, have not understood some basic principles of pond building. I recently had a contractor respectfully suggest that using a sheep's-foot on the dam was unnecessary and compacting with the dozer was satisfactory. I will say that he said he would do what I wanted and I know he will. I also think he is a good operator and is willing to learn. We are getting swamped with rain on this pond project, and I hope we get a dry spell. Got another inch in the last couple hours.

Rah, my guy I used bought himself a Cat 953LPG (Low Ground Pressure). He seriously thought it meant that it provided "low ground pressure" for more compaction. I thought he might quit on me when I said it meant a wider track is used for even less compaction and a lower PSI....He was stubborn and maybe not the brightest crayon, but he did as I asked, and hopefully learned along the way.