Pond Boss Forums POND CONSTRUCTION Building a dam Basic theory question

I am summing the courage to crawl onto my D6 and make a mess of the valley that my house overlooks. The urge to construct a pond to enjoy with my kids is drowning out the static of the "non-believers."

My site will dam a natural drainage, which will have gravel content for several feet I am sure. I have done a lot of research on this site to date and the best I can get out of anyone is: It might work. The NRCS guys wanted me to use another location, but that's really not the point. I tried to politely explain that I already had stock water (7 small ponds existing), but they didn't really want to talk about it. This site drains 160 acres, and the local ASCS guy said it way too big for him to design the dam. I had a guy shoot the site, and we figured with a 20 ft embankment, it would be around 7 acres of surface water. I decided I would just core the dam, build it 2:1 slope on both sides, make it twelve feet wide at the top, and put in a pipe and a spillway. I will size the spillway by adding 15 feet to one-half of the total acres drained, or 95 feet. Well, I am rambling so I will quit.

My basic theory question is this: If I core trench the dam, do I still have to remove all the gravely soil from the basin? I get conflicting answers to this question. Some references say that as long as the dam is a water-proof barrier, then it will backup standing water on pourous material. Other references say that I need a good clay lining over the entire pond basin area. This will make a big difference in the amount of time spent on the dozer, and I need to know before I start.

Thanks for the great site.

Troy

I would answer you question with one phrase, "Better safe than sorry." You can still loose a lot of water by seepage on the pond bottom regardless of how well built the dam is. Additionally in my opinion forgo the pipe and use an obove ground natural overflow. Pipes just beg to leak even with the right precautions.

Just my two cents. I don't build ponds but I have three going on five. I have lots of clay in my soil and still have more seepage than I would like on two of them.

Thanks for the reply Cecil.

By above ground overflow, do you mean just use the "emergency spillway" for all the drainage needs. Do you know anything about putting in a pipe for winter livestock water? Or is this also a leaky-dam waiting to happen. I do have cattle and presently have to chop ice in the deep of winter, but I could spend the money on a freeze-proof waterer and eliminate the extra pipe from the lake project.

Troy

Yes, that is what I have on one of my ponds for overflow, but I route the water into a pipe above ground on top of the dam. That is, the emergency overflow starts out as a stone lined trench on top of the dam and is funnelled into a pipe opening (still on top but covered) and drops out of the end of the pipe into a ditch. The pipe keeps the outflow from cutting into the dam at the end. You may need more than one for the size of you pond. I just don't have faith in pipes that go through dams regardless of what you do to stop waterflow from following the pipe.

As far as a water supply for cattle I have no esperience there. But I have seen something on it on the Internet somewhere regarding the construction of ponds. I would do an extensive search under "pond construction." I may have seen something from the Department of Agriculture.

Thanks for the reply again Cecil,

How does one determine the depth of his core? Is this a guessing game? I mean, if you just dig down to "good material" could there still be gravel under you that you can't see?

Thanks

Troy

The USDA has an excellent technical reference booklet called Ponds-Planning, Design, and Construction has plenty of formulas for calculating everything for pond construction.
Robert B

Troy:

First, I want to disqualify myself from being an expert. I am still in the very early learning stages and seek guidance here regularly.

While I certainly don't have the answers, I did wonder about a few things in your post.

Without knowing your average local precip amounts, I would be concerned about how well a 7 acre pond will handle 160 acres of drainage. The basic equation makes me think you may need to build your dam and overflow to handle a high volume.

I also wondered about the 2:1 slop on both sides of the dam. That seems pretty darn steep to my uneducated self. My dam was 4:1 (as in 4 feet of horizontal slope for each 1 foot of height) on both sides. Don't quote me, but I seem to recall that like NRCS recommends at least 3:1 on the downhill side. With potentially a lot of drainage and overflow & potentially not the greatest material ("gravel content"), I'd error on the side of safety and consider a less steep dam.

From what I've gathered perusing expert advice on these forums, I would think the safest strategy would be to get the entire area you wish to hold water down to non-porous material. The dam being downhill may not prevent water from leaching out sideways or something.

I hesitate to mention, but in reading the first paragraph of your post I noticed "house", "pond", "kids", and "drowning" in that order. I can't swim worth a hoot and I remember reading where someone stated that 12' as the maximum depth the average person can dive unassisted to help rescue someone. I don't know if that is accurate and it may or may not be something to consider.

Finally, enjoy that pond whenever you get it built. I had a valley that begged to be a pond for about 14 years. It finaly is. :-)

Jeff

Rangersedge,

Thanks for the input. I think your fear of the water, or fear of being underneath it, has let you read hidden messages into my opening paragraph. LOL

I really hope that it holds water long enough to be a good place to swim. If it makes you feel better I hold an advanced lifesaving card and was a lifeguard in my younger days. Man was that a long time ago.

I agree with you on the slope calculations, and I meant to type that I was going to make it 3:1 on both sides, not 2:1.

I think the 160 acres of drainage will be of concern. I may have to overbuild the dam and allow for the lake to flucuate in level quite a bit. A sort of a watershed project I guess.

I am really wanting to try this project, but am still hesitant. I think its the reality of maybe doing all the work and not having a pond that holds water. With just one machine it will be quite a project to remove all of the gravely material out of the basin. Do I also need to remove all the timber? Most of this area is clear and planted to fescue, but some is in woods.

Troy

Robert,

Thanks, I will see if I can find a copy of that book.

Troy

Troy The depth of the core trench is based on the soil layers in the pond,water table, and clay content in soil below trench. Test holes dug and perked will give you an estimate on how deep you can go also dozer time. Dig your test holes 3 foot deeper than you plan to go on a 1 acre pond 8 test holes and soil samples will give you a fair picture of what the pond will yeild in depth and work time.
Good luck

Good question I run into that situation up here quite often. We do not have limestone but sedimentry blue stone it depends on how the vain of the rock is running and how much there is in the shallows we leave it alone. In deeper parts of the pond it is a call that depends on water feed and springs when we dig the deep holes in the pond are dug first and then we will let them sit and see how much water loss we get due to rock formations if it is alot will cap with a 2 foot bed of clay and moveto another spot and try for better results.
It is hard for me to explain on this board unless my feet are planted on the soil you are moving and the surronding terrain. I have dug ponds with rock bottoms and they do just fine with their existing water supply,and others have a hard time maintaining constant water level.
I would say 70% of the ponds we build are on the side of a mountain and it takes alot of thought and planning . My dozer man is amazing he shares the same vision of the finished pond that I do 90% of the time, the other 10% is begging him to get a little deeper.
When building a pond with rock bottom the key factor is water supply year round and if your soil can retain the water

Good luck

William ,Thankyou look at the situation this way cut a hole in and see what happens. If your satisfied with the water retention then continue on you have your own dozer. Another way get a hoe for the week and carve out several deep holes and build your pond around them,after the holes are in you can control any water that comes in by inter-connecting them and send out the out flow.
Then you can take your time with the dozer and carve it the way you want and at the same time you will not be pushing mud. Just a note start with your first hole nearthe outflow or spillway and work back. Remember no soup bowls!

Good Luck
Scott

Be careful of trying to mend a core trench into rock the water might follow out same principal of applying weep collars to a outflow pipe

Sealing levee/core trench to bedrock. When dealing with a rock-bottom pond what is the best or most practical way to seal the soil to the rock? Especially when dealing with a levee pond? (I used decent clay soil where the levee meets the bedrock but I am still concerned that if I do not have water loss there now that eventually I will.) I cannot pack clay on top of the bedrock anywhere but the levee as it is too shallow of water for my likings already. Thoughts? (Sooner or later my pond will be expanding and I'll have to create a new levee and go through the process again)

This is a tough situation. Forget pouring concrete it does not bond and expand at the same rate as stone .In a couple of cases we made a sediment pool and dumped 80%clay material cleaned of rock and dug down. We then mixed the sediment pit wiyh a 4"pump and then pumped over the rock formation in layers.This process took over a week to seal up rock in stages. The slurry was like a milk shake and done in four layers,then capped off with 2 foot of soil. Maybe this is helpfull or gives you an idea.
Scott

Hey William... haven't seen such a trenching beast around here for rock. If I find someone with one the costs might be prohibitive? I'll ask around.
Thanks.

What kind of bedrock is under your pond site? Have you looked into the possability that someone would want to dig some of it for you?

Troy, here's some advice. Yes, you should be able to build your own pond. Do more homework. Get and study the handbook referred in earlier posts. It's excellent.
Coring the dam is a must. How deep? Soils tell you. Core as deep as you need to, to build a solid foundation on which to build your dam. Look at Mike Otto's story in Nov/Dec issue of Pond Boss. It's focus is core trenching. I have seen core trenches as deep as 20 feet, as shallow as 2.
The core trench also acts as an underground barrier against leakage. Water seeks the path of least resistance, and if your core trench is the lowest point, vertically, of your lake site, it will be an effective barrier against leakage, even if soils upstream are questionable. Water goes downhill.
Regarding bedrock problems..rock trenchers are great, but quite expensive. I have also worked on sites where pros dynamite bedrock to go deep enough to build the appropriate dam. Again, costly.

Thanks Bob,

I am getting a better attitude about it the more I learn. I know as bull-headed as my wife says that I am, I will pursue this to the end once started; that may cost me. I ordered a book off the pond boss website last year, and I will get the book mentioned earlier. I will take a lot of digital pictures of my progress and share the experience good or bad.

One thing that I am still puzzled on though. After I remove the top soil, how do I determine how far to push the soil beyond the core? If I end up removing enough soil while I am pushing up the dam, does this mean I've already done the "core-trench"?

Thanks

Troy

Bob,

Can I order a year of back issues for 03?

I see on the website that only 93-96 are available.

Thanks Troy

Troy if you need someone to host your pics just let me know...I'm currently in the design process of a website and am planning to host many sites and many pictures. Best of luck.

Chris