Pond Boss Forums POND CONSTRUCTION Building a dam Dam with two pipe spillways

Not sure this is the right place for this, but here goes.

I bought my place two years ago. It has a 1.7 acre spring-fed pond with a steady flow through. When I bought it, it has a stand-pipe overflow drain and an old culvert spillway that had broken and was deteriorated. The springs flow so much that water constantly comes out of the stand-pipe and also ran in the culvert. The water had begun to run around the end of the culvert and cause the dam to erode.

So the first thing I did was hire a local contrator to repair the dam. This was before I subscribed to Pond Boss and before I had found this forum, so I just did what he told me. What he recommended and installed was a second PVC spillway that pulled water off the surface of the pond and dumped it in the creek behind the dam.

Here is a picture.



The two arrows point to the stand-pipe and the new PVC pipe.

Here is another picture showing the intake. (and the homemade trash guard).



Both pipes flow constantly. The PVC pipe fills up a 5 gallon bucket in 1-2 seconds and the flow from the stand-pipe is similiar.

After I subscribed to Pond Boss and found this forum I became more edumacated and in additon to all the other challenges my pond presents, I now see its not a good idea to draw water off the top. See my posts atfor my other issues:
http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Number=103339#Post103339

So my questions are:

1. Is this a big enough issue to go to the trouble and expense of fixing?

2. If yes, then what would you prose?

3. Since both pipes handle normal water flow, do I still need an emergency spillway?

Thanks.

I wouldn't worry about it. Many here don't have bottom fed spillways, it may be better in some cases but it is not absolutely necessary in order to have a good fishing hole.

I would say an emergency spillway is always a good idea. Here in Bryan, we got 18 inches of rain in 12 hours about 3 years ago. Granted that is extremely rare, but if you get hit with the residual from a hurricane just right, you will wish you had. Spending a few hundred to a thousand on a dozer to make the spillway is money well spent in my opinion. Even if it costs more, you will be able to sleep when it is storming outside at night.

Sorry I just read the entire post, yes you need an emergency spillway.

Yes, you should always have an emergency spillway, but I would need to know how much watershed you have and some other information. You are welcome to contact me at mikeotto@ottosdirtservice.com or call the office between 8 and noon at 1.800.882.3478 and let Sheri set up a phone appt. with me.
Otto

I did a phone consult with Otto in December. He was very friendly and informative. I would highly recommend giving him a call.

I also have an overflow pipe. Can't remember if it is an 18 or 20 inch pipe. When we get a hard, quick rain...like tornado weather, it is almost like Niagra Falls back there. Does anyone have 'pictures' of the best way to set up the outflow side of the pipe to make sure you do not have washing problems, or problems with debris hanging up on it.
From the edge of the pipe to the 'drop off' is about five or six feet, slightly sloped. But then it drops straight down about five or six feet. I have been thinking about using some treated landscape timbers...slightly v'ed out from the pipe opening, then concrete the open area and round up the sides. But then what do I do about the big drop off? I found out Thursday night, that much water can move a 40-50 lb rock quite easily! The drop off part is on my neighbor's pasture land. I don't think he would mind (I'd make sure) something reasonable but wouldn't want to step on his goodwill!

pond girl:

Here is how my second pond's drain pipe outlet is setup. There is a bowl which holds water when the drain is running. This way the energy of the falling water is partially expended when it hits the water in the bowl. You can see the bowl is lined with rock big enough to reamin in place with water flowing.

This particular output is an 8" pipe with rocks about the size of a football. Since the pond filled in February, it has been successfully resisting any erosion or movement that has incuded a full 8" of water entering the pipe.

For a much larger pipe, like yours, larger rocks (MUCH larger, as you have noticed), a concrete basin, or very well anchored timbers would be needed to resist the flow of the water. But I think having a water basin to discharge into would also be useful in your situation, regardless of what you line or form it with.

The nrcs in our area generally just makes sure that the pipe extends out from the toe of the dam about 8 to 10 ft enough so that the outflow want cut into the dam. My 30 inch pipe has cut a huge hole but this happened the first time it had a full discharge. Once the hole is cut it generally stays full of water and no longer cuts any further because the out flow simply hits a pool of water when it discharges. Then it flows out of the pool and down the natural stream that existed prior to the pond.

What I did here on my place was water 5 cement bags and let them harden up and then set them where my 18" pipe dumps the water. It has been very effective at dissipating the energy for the last 3 months or so. Only time will tell how it will work long term, but worst case scenario, I am out $15. If you are concerned about the water moving the concrete bags, stick pieces of rebar in the sides as you place them and then water them in place to make them set.

I had someone else mention using the concrete while still in the bags. I'm sure some kind of 'rod' would be required to hold against the pressure of the water. Would you put anything under the bags of concrete? Small gravel, some kind of liner?
I like the idea of having the 'bowl' but I'm afraid there just isn't enough room. If it would stop raining I would get a picture for you.
Another idea: would it be simpler/safer to go to the rice well company and get a 5 or 6 foot length of pipe to fit over the mouth of the existing pipe and extend past the drop off point?

Home Depot sells Rebar in 1 ft lengths or you can save $4 and buy a 10ft piece and cut it yourself. Make a "pad" of the concrete bags side by side, front to back, etc. Just keep it one layer deep. When you put down the first bag, stick the piece of rebar into the side about six inches where you will have adjoining bags. When you put the next bags on, you will need to slide the bags onto the rebar as you set them like a shish-kabob. If you do it in place like this, just try to put some water on the bags before the first rain to get it to start setting. If it rains real hard and the paper washes off to fast, it doesn't look nearly as nice. As long as you keep the bags relatively tight together, you shouldn't need to worry about them getting washed out underneath. If 80lb bags of concrete are too heavy, you can get 40lb bags for about 50 cents less, but you will end up spending twice as much because they are much smaller.

You could install a siphon without cutting into the dam. It would only have to be buried just below the surface.