Pond Boss Forums POND CONSTRUCTION Building a dam Can I just use a culvert in my dam as my spillway?

I am about to start construction on a new pond that will be about six acres. I am wondering if there is a reason why I can't just put a culvert in my dam as my spillway.

Thanks,
Pat

As in through the dam or on top of as in an emergency spillway?

If through it depends on what kind of pipe you mean by "culvert." Also you will need at least one collar to prevent water from following the pipe through and creating a washout.

As in through the dam as the main spillway. I have about 70 acres of watershed and what I was thinking of doing was putting in one 36" culvert as my main spillway and then another 18" slightly higher just in case.

Not sure the 18" will do much if the main pipe is 3'. Need an emergency spillway if the 3' pipe cannot handle the flow.

Thanks for the response.

I will have an emergency spillway, but what I was wondering is if it is alright to just use a culvert instead of building a stand pipe and all of that.

Pat, Cecil & RAH gave you excellent advise - make sure you have a collar AND an emergency spillway. Failure of either one case cause you to loose your dam...

If you are talking about a metal culvert, they typically rust out in about 20 years.

Go to the local NRCS office and see if they can help you properly size the pipe(s). It will all depend on amount of watershed, rainfall, etc., etc.

You really only want to do this once. If you plan on too small of a culvert, then the whole dam could be washed out. If that happens, you'll be looking at spending just as much $$ or more as you did doing it wrong the first time.

Thanks I will contact NRCS, but I am pretty confident with the pipe size, because the dam is going to be my current driveway and I have had a 36" culvert in it since I built the driveway eight years ago and it has never been any where near 1/3 full. All I am doing is raising the culvert in order to make my pond.

I was really thinking about the plastic culvert that is smooth on the inside. What would be best?

I think that double wall correcgated plastic with smooth interior is still recommended. The key is to size it to the watershed, have sufficient freeboard on your dam, and have a good emergency spillway that you will hopefully never need. Another factor is the differenctial height of the inlet and outlet on the pipe. Once the pipe is running full, greater drop means more flow.

Thanks for the help guys.

I am sure there are more questions to come.

I wouldn't use a metal culvert pipe they tend to expand and contract more in the heat because they are metal which inturn will end up causing water to leak around the metal and through the damn and eventually wash out. Plus eventually they will rust out

Thanks. I will be using plastic.
By the way I contacted the NRCS, which I had never even heard of before, and they are going to meet me Wednesday morning.

Thanks for all of the help guys.

They are part of USDA, and it's your tax dollars at work. Might as well get some use out of them as long as you are paying for them!

I agree 100% and I need all of the help I can get.

If you are installing just a horizontal culvert, rather than a standpipe, do you still need a collar?
The contractor who rebuilt my pond last year filled the old metal culvert with concrete and installed a 30" horizontal PVC pipe at water level. He didn't install a collar. 99% of the time it is above water level.

Anti-seep colars are typically used on horizontal pipes but their use is somewhat controversial. Some say use two, and some say don't use any. I have one pond with one and one without. Neither leaks, but they were packed well and I have good clay.

NRCS sized the culvert (galvanized steel rather than plastic - not sure why, that's what the contractor recommended) at 18" for my watershed. I wish I'd have went with 24. We've had 2 '100 year' rain events since the pond was build (how can you have 2 100 year rain events in the space of 5 years? Wouldn't that indicate they're named wrong?) and both times the water was over the top of the culvert and created a siphon that sucked out a LOT of dirt and riprap from around the mouth of the culvert. I REALLY didn't like that.

I have an emergency spillway but I believe it's a bit too high for my taste. It's on my list of to-do's to drop it down 6" or so.

I didn't have time to plan the pond I had built in the spring of 2012. I was presented with two days free use of a big trackhoe, a big dozer, a big road roller, and more -- all with very experienced operators. I was given about 12 hours notice that they would build a pond for me while they were waiting for permits and vehicles to move their heavy equipment off my land, where they were upgrading a powerline right-of-way. Did I say that they did this for FREE?

Consequently, I didn't have a standpipe available -- not even culverts. They did a great job, and pulled out of my yard a day and a half later. It rained hard. My new pond nearly filled up. The 25-foot wide by 150-foot long dam varied by less than about an inch from one end to the other.

I ordered 20-ton of 6-8 rip-rap for the emergency overflow. I bought a 100 foot roll of 10-inch corrugated drain pipe.

I cut the corrugated pipe into three 33-foot long pieces. I used my backhoe to dig a 3-foot deep by 4-foot wide trench across one end of the dam. I put the three pieces of corrugated pipe in the trench and backfilled it, while compacting it by driving over it each time I added about 3-4 inches of dirt.

I dug a similar trench at the other end of the dam, but it was about 2-1/2-foot deep by 4-foot wide. The bottom of this trench was approximately level with the top of the three pieces of pipe. I lined the bottom and sides of this trench with landscaping cloth and rip-rap. Each front-end-loader load of rip-rap continued to compact the first trench as I drove over it.

I've never had any seepage around the three pipes that are the primary drain. The emergency rip-rap overflow has had water go through it one time, and that was just recently. We got about 4-inches of rain in about an hour. The pond suddenly rose by about 18 inches.

I still want to put in a drain that pulls from the bottom, and that allows me to completely drain the pond.

Until then, I do wish that I would have put in the double wall corrugated/smooth pipe. I find that the corrugations catch sticks, which then catch everything else, effectively shutting that pipe until I can run something through it to break the dam. It only happens once or twice a year -- but that is still way too often for me.

Good luck with your new pond.

Ken

I would always rather have the culvert take all the water. Emergency spillways can get washed out easier. Your tube can never be too big.

If the rain event is too big and your culvert does not draw it down fast enough then the water will go over the dam which could easily wash a hole in the dam.

I had one that did not have a collar installed and seemed to be packed well and started leaking around the sides within a year. I had him take it out and fill. My .62 acre pond only has a stone lined emergency spill way now, however, I don't rely on watershed water and in fact had a berm put around the pond to keep it out. I can run a well to any of the ponds on the property so have no lack of water issues.

Also due to my trout pond overflow to this pond where well water comes in 24/7 7 months of the year water is constantly flowing out of the emergency spill way but no erosion problems or other problems. I will say it does funnel into a concrete opening that has a sewer pipe mount into it to drop water into the highway ditch.

Personally I think the wise thing to do is to have both a pipe with collar(s) and an emergency spillway. Better safe than sorry.

I did not mean to suggest omitting an emergency spillway, just that a big pipe is good in addition to the spillway.

My shortest outlet tube is 40' long which may help prevent leaks.

Sorry my bad.