Pond Boss Forums POND CONSTRUCTION Building a dam Help with levee ISSUES please.

New here. I'll do my best to describe my situation.

I have a 7 acre, spring-fed pond in North Mississippi that I've had for about 5 yrs. The levee atop the culvert is approximately 15 ft wide. The culvert is covered by approx 2 ft of clay, etc. I've just discovered a few issues that concern me:
1) Constant battle w/beavers. Trapped beavers a few years ago - but they're back.
I have built a "cage" around culvert to minimize their damage and frequently have to clean it out. Recently, with beavers help, water has risen almost to level of top of culvert. I cleaned it out this weekend and noticed a few other issues. 2) High-water level has allowed water to get behind culvert, eroding some of the adjacent dirt on one side of the culvert (maybe 4 ft horizontally).
3) Being spring-fed, the "drain-out" side displaces a high volume of water - which has eroded the ground below. The "fall" is about 15 to 20 ft. straight down. I've recenty learned that this dam blew out about 6 years ago - and was rebuilt. When they rebuilt dam, there was no riprap, etc. positioned on "drainout" side - which obviously has contributed to the erosion.

Also an emergency spillway, which has eroded to the point of probably being useless.
Oh yeah, also have cattle using levee as pathway.

All the makings of a disaster, eh?

Here's my question: How much time do I have? (I'm diligently keeping water at lowest level). Anything that I can do? Can this be repaired? I don't have $$ to start from scratch.

Thanks for any advise or insight.

KFish

Welcome to PB. Can you post pictures? Do you have a leak at this time ? There are some very good pond builders here but they need to see what you are describing.

"High-water level has allowed water to get behind culvert, eroding some of the adjacent dirt on one side of the culvert (maybe 4 ft horizontally)." - Can you fill this by hand and compact the clay ?

Thx. Great site!
Don't think it's leaking all the way thru yet - as I poked around and could feel solid ground about 4 ft back. Gap is about 25% of circumference of 24" culvert. Are you suggesting I dig down from top of levee and re-pack?

KFish

No - just add clay and pack to fill the hole and seed. Pictures would sure make giving suggestions easier.

Hey Larry,

Listen to these guys, they know what they are talking about. You will get great advise from the folks on this site.

Billy

Your question about how long you have is kinda tough to answer. Maybe only one dang good rain.

If dirt has eroded from the SIDE of the culvert, then I would think there MUST be flow. Either it would be coming from inside a rusted culvert pipe or it's running alongside the pipe. Either way it could get real bad real fast.

The high water has contributed to the erosion on side of culvert. (Culvert is black 24" corrigated PVC.) This "gap" doesn't appear to go all the way thru yet. Hopefully, by cleaning out the debris from culvert, water level has dropped (probably 1.5 ft) and relieved pressure on culvert, and bought me some add'l time.
In response to previous post re: re-packing clay, seems like it would be easier to dig "down" from top (about 24" to culvert) and fill vs. try to pack from side.
Meanwhile, still have spillout side to contend with...
All insight and advice appreciated.

KFish

I beleive Theo is one who suggested putting old chainlink fencing on the dam to discourage animal burrowing.

Mod's Note: I didn't think this up, but I have mentioned it. About half the time, I wish I'd done it.

I've never had to do this but think it would make sense to mix in a bunch of bentonite when trying to repack.

You may want to consider constructing a concrete apron at the entrance to the culvert. Perhaps you could fill the void with concrete or a concrete slurry at the same time.

Digging from the top would remove any existing vegetation.

You dont mention what the spring flow rate is but you might consider adding another smaller overflow pipe just to deal with the spring flow. You could run the exit side down to the lower level to a convienint place to protect it from erosion. This would eliminate the constant erosion from the 15-20' fall of water from the 24" culvert.

I have been thinking about this for the last few days since I have basically the same situation and Kfish and I are neighbors. What about attaching more of the corrugated pipe of the same diameter with an elbow to extend the outflow down the levee to the base of the levee. The erosion is from the back splash as the water leaves the pipe and if the outflow of water is moved off of the levee, shouldn't this take care of the erosion problem? Of course, you would still need some riprap rock or concrete to keep from having a new erosion problem at the base of the levee.

Also, couldn't you do the same thing on the lake side of the levee to move the intake out into the lake and sink the intake end of the pipe in deep water? This would also serve the additional purpose of pulling the less fertile and lower oxygenated water as opposed to the good surface water. You would have to install a vent in the top of the pipe to keep it from turning into a siphon. I would assume the the beavers would not dive into 10 or so foot deep water to try to stop the flow.

Does any of this make sense?

Billy - Thought of same thing re: outflow pipe extension. Is there an easy way to attach to existing pipe? Perhaps a coupler sleeve?

KFish

Don't know how easy if might be, but I know that when the black corrugated pipe is used for sewer lines and stuff like that, they have to have some sort of coupling to attach the pipe together. Hopefully, someone here on the Pond Boss site has some experience with this.

If by "corrugated PVC pipe" you are referring to ABS plastic pipe they come in two types. One has couplings the other has bell ends and fit into each other. As for the erosion at the outlet the NRCS in my area recommends you extend the outlet 8 ft minimum from the base of the dam. If your out flow is anything like mine don't waist money on riprap it will just get blown down stream. The outlet will cut a hole but it fills with water and becomes a micro pond and erosion will stop once it cuts the pond it needs at max outflow. The intake side may be getting cut from the water rushing in the pipe from all directions when the water level gets above it. Generally you should pour a small concrete pad around the intake side to prevent this. I have also seen pipes bent up at 90 deg from water pressure and debris when the intake is not ancored some how. Good luck

I like a precut exit "pond" with a rip rap liner. When filled with draining water, the pool takes up most of the energy from the water running out of the pipe. The rip rap keeps the hole from getting any bigger.

Theo that looks great and I agree in most cases your method is a good one. I believe in cases like mine it would be a waist of money and effort.

What about the idea of sinking the intake extension out in the lake in deeper water as an alternative to installing a siphon device or changing the spillway design? Seems to me that it operate the same way that a siphon design works without the siphon function. Does that make any sense? Also should take care of the problem with beavers clogging up the intake opening.

Nonsense, RT. You'd just need slightly larger rip rap.

Say, the size of a Volkswagon.

I just want some of that water!

Bill this is a great idea. My contractor suggested the same method to me to prevent debri from cloging the intake. I did not listen to him and ended up building a trash rack instead.

All great ideas and much appreciated!
However, I'm having trouble visualizing the intake pipe extension. Are you saying to add more culvert pipe (lakeside) and angle it down to depths?
Seems like I've seen ideas similar to this as a beaver deterrent, using a smaller, say 6 or 8 inch pvc (perforated?) pipe extended out into lake which would run thru culvert, thereby eliminating the annoying sound that attracts the beav. Same principle?

Thanks again.
KFish

Yes exactly

I would add more culvert pipe angled down rather than smaller PVC so that the same volume of water could pass thru the spillway. I would use solid walled culvert down to the depth desired, then perforated pipe on the end to allow for the deep water to flow thru instead of surface or shallow water. Did what I say make sense?

Yes very much so.