What are preferred options for an overflow for a small pond? Approx 50' diameter, maybe 6' deep. It was built on a slope years ago so there is a dam on the lower side with a steel culvert at the bottom of the dam that was blocked off unless the pond needed to be drained for some reason. The customer wants me to replace it with something more modern, presumably with some sort of stand pipe so excess water doesn't spill over the dam.
you can make a siphon and install it with the pond full if you like.
Vertical stand pipe using either SDR-35 or SCH40 PVC, sized accordingly to acreage that drains into it, not necessarily pond size. 4" minimum diameter if its in open country, 6-8" minimum if its likely to get debris, could take even large if it has a lot of water flowing through it. You'll need to drain the pond partially to install it, we do quite a few of these on old ponds that are leaking. If doing it with the pond full, pump or siphon the pond down about 3-4' (you can get by with less, but your over flow ends up real close to the bank. Start out as far as you can without letting water get in to your excavation, trench straight down 3-4' then carry a 1/4" per foot grade on your trench all the way through the dam. If you want to drain the pond completely just trench through the dam, same height and location as the original pipe. Along with a vertical stand pipe every pond should also have an earthen emergency overflow (flat broad based ditch, seeded down in KY31 Fescue or the like). Grade of emergency overflow should be 8-12" above water level on a small pond. Below are some pics are of a pond with an old metal overflow that was leaking that we replaced. Dug through old pipe, poured concrete plug and filled old stand pipe: New vertical stand pipe installed: Anti-siphon collars:
Another small pond we recently redid, trenched through the dam, drained, and dredge all the muck, reshaped dam and new 8" stand pipe. This one is closer to the bank than I like, but customer wanted to be able to reach it with a rake to remove debris. Earthen emergency overflow is flat area directly on the right side of dam. Wish I had some closer pics but this is it:
I'll second the sizing the pipe on the drainage area and not the pond size. Either way, there should be an emergency spill way at least 1' lower than the breast height of the pond/dam to prevent a catastrophic failure incase the pipe cant handle the flow.
The 20’ wide grassed spillway always seems superfluous until hurricane season comes.
Thanks for all the input. The customer ordered a gasketed concrete elbow and pipe. 10" I think. I'll find out for sure when things dry out enough for me to go back and do the work.
Snap some pics of that 10" concrete elbow. Interesting.
So it turns out the customer ended up making his own stand pipe base with a 10" gasketed PVC elbow cast in concrete and a 4" drain. Here it is upside down: Ready to install
We'll see how long it takes the pond to fill
Not being nit-picky but the 10" and 4" pipe is backwards. Bells go uphill on gravity drainage pipe, storm and sanitary. Reason being with the bells laid downhill the lip can catch debris and clog overtime.
Yeah I would have put the bells uphill also but that's the way he wanted to do it. He's done all the project design so I'm just the machine operator on this job
Be sure and tell him he's wrong after you get paid.
Haha good idea. I really don't think it'll be a problem, otherwise I would have said something.
Hopefully yall put some anti-seep collars around those pipes? Two pipes close together like that look like a good spot for leakage in the future. Otherwise, looks like it should work fine. Interesting idea on the concrete cast elbow, never seen it done like that before.
Nope, just filled around them with liquefied clay.
Yeah I do like the pre-cast 90. Might just have to use that idea in the future on temp sediment ponds.
Forgot to post earlier - 5 days
Just curious, did you mean anti-seep in your post up above with the pictures where it says anti-siphon? What did you make the collars out of?
Yes I mistyped, meant anti-seep collars. We make them out of 1/2" PVC board, comes in 4x8 sheets from Lowes. It's not cheap but you can get several out of a sheet. For pipes 8-12" we make them 2'x2', cut the hole to fit as tight as possible around the pipe, then seal with silicone. Adjust size accordingly for larger or smaller pipes.
I dug a pair of small ponds in the last few weeks. The area has several springs so the topsoil was so wet I could hardly do anything before stripping it off. Underneath was rocky with ledge in some places. The holes started filling up as I dug them. First job for my "new" dozer. The hump in the middle is ledge. This is the upper pond. Lower pond has ledge too.
The upper pond has a 10" overflow (similar to the previously mentioned ponds) that directly feeds the lower pond. I kept the water in the upper pond as long as possible to make digging the lower pond easier. Then I dug through the upper dam to install the pipe for the overflow. Was quite a gush for a few minutes. Lining the upper pond with clay: This clay is beautiful! No rocks at all, really amazing that it comes out of the ground like this.
In order to save some money, we decided to use 10" SDR only for the first 20 feet through the dam and then switch to black culvert for the remainder of the distance to the lower pond. The SDR is obviously loose in the bell of the culvert so it took a little head scratching to get them to work together. One gasket from the culvert and one from the SDR did the trick. It seated together quite snugly so I'm sure it will be as good a seal as regular culvert connections. I also packed around the joint with clay. Check out my twin boom excavator Added a drain to the side of the culvert to catch ground water and send it to the lower pond.
Checking the dam elevations: Stand pipe installed: The elbow cost almost $500...
I guess I forgot to take a picture- the lower pond has a stone retaining wall that the overflow with go over like a waterfall. The top stone is visible in this picture: Just waiting to fill now.
Very tidy, nice work. Also nice looking country!
Nice work! Well done. A side note on connecting dissimilar pipe material - if in doubt pour a concrete collar around the connection. See those details on commercial plans all the time.
We (the customer and I) thought about that, but since it won't be under any pressure, and any leaks will be caught by the French drain, we figured it's no big deal if it leaks a little. I was quite surprised at how tightly they fit. I couldn't pull them apart by hand after assembly. I will definitely use the concrete method for anything more critical.
It took almost 4 months for the drought to end and the ponds to fill. Upper pond: Lower pond:
Turned out nice! Really like the overflow.
Does anyone use Hydraulic mud/cement /plug/stop around the joints, or is that just not the right stuff? We used that in the past when fitting 4" drain pipes to a concrete catch basin.
I did some of that last year at a high school near by.
Nice work Materthegreater
FWIW we use bag concrete or mortar mix for storm structures and hydraulic for sanitary sewer.
That's how we do it too.
Looks a lot better with water in it