I need the help of the F.F. brain trust!

[wheelinguy]

We have been trying to get our pond up and working properly for a couple of years now, poorly constructed by the original excavator.  We discovered a seep last year and thought we had it fixed.  I have a friend with a mini excavator (JD 50), he helps me out with things like this and I loan him my tractor and dump trailer, seems like a good swap to me.  Anyway the pond is leaking again, I don't want to dig it up again and I'm looking for some ideas.   I was thinking about digging out a spot below the headwall and standing a culvert upright at the same height as the drain pipe.  My thought is that the pressure will equalize between the pond and the culvert and the leak will stop.  I know there are holes in my theory, how do you seal the culvert so the water doesn't just go around it, won't the pressure in the pond be greater than the pressure in the culvert.  Throw me some ideas, you guys always seem to have some good ones. 

[yukon cornelius]

several years ago we had a leaking pond and someone recommended bentonite. its a powder clay they use to seal around well casing. we got out in a little boat just out from the shore and dumped it around. sealed it fast! never had another problem.

[yukon cornelius]

one other thing I forgot to add. is that on a pipe through a dam they always use a flat plate on the pipe to stop the leaking around it

[beenthere]

So wheelinguy, what did you do to plug/fix the leak this last time?

[moosehunter]

When you run a pipe through your pond dyke (wall) you need to have a collar on the pipe somewhere in the wall. I cut two pieces of scrap osb about 30 " square and put a hole in the middle that the pipe could slide through. Separate the two boards buy 4 inches or so and fill with concrete.

[scsmith42]

Usually putting Bentonite at the source of the leak will do the trick.  It has something like a 9:1 expansion rate.  Basically it is a high expanding clay.

[dgdrls]

whats the source material the pond is built with?
where is it leaking?  through the base material or is there built up material ?

Is the leak transporting material?   

In theory the leak would stop if it doesn't get around the culvert.
You could also upset the leak by digging  into it and the head pressure will fail the remaining material
and the pond could drain :(,

give us some more details.

best DGDrls

[wheelinguy]

I have contacted some sources about Bentonite clay, it has an 18:1 expansion rate.  The leak is somewhere in the headwall.  Originally we drained the pond until the leak stopped, at that point there had already been a small failure s it was easy to trace where the weak spot was.  We dug down and found clusters of small boulders that created the leak.  We excavated more material, which is mostly clay mixed with stone, carefully sorted through it and discarded any rocks or other debris.  The excavator put down thin layers and compacted them with his bucket and repeatedly driving over the layers until they were well compacted.  The pond does not and never has leaked around the drain thankfully.  It is hard to pinpoint where the leak is this time.  The leak last time was at about 4 feet down the headwall, this time the water a couple of feet higher than that before it starts to leak. but the water doesn't show up in the stream bed until an elevation that would be consistent with the bottom of the pond, so I believe it is leaking either into the headwall and trickling down through it to the bottom or its a pressure thing where we get enough water in the pond that it can overcome something and leak out the bottom. 

[Raider Bill]

do you have a liner in it?

[giant splinter]

do you have a liner in it?

The liner question is important and a few more details of the construction of your pond would help in nailing down the causes and helping with any conclusions and recommendations. Is the culvert you mention an overflow or a drain located near the base of the headwall?.
A few photographs of the earthen fill showing the hight of the head wall as well as the length, width and cross sectional profile including the culvert pipe and how you sealed the pipe off.
Any ideas of the volumetric content of the pond, if its large and deep (acre/feet) if its relatively small just a rough guess is good enough. The location of and estimated depth of water at the deepest point where supported by fill.

[reride82]

The bentonite solution could work, the problem with this instance is that it'll expand before it gets where it is needed. But I also know of an older solution where old timers would fence the pond off for pigs, and turn a few pigs loose for a while around the pond. When they wallow in the mud and muddy the water, the muddied water via the fine soil suspended in the water will slowly fill the void that is allowing the pond to leak. This is usually only used on a slow leak. By headwall, I assume this is an earthen dam pond. During construction, was there a good connection made between the dam and the existing soil? I.E., was the topsoil and any weak soil removed before dam construction began? Otherwise, this creates a seam for water travel.

Levi

[SPIKER]

will need some photos but sounds like there needs to be some sort of pressure leak that as level builds up the water slowly is pushed thru the dam area.   That or it is leaking down and thru a crack along the bedrock then coming up and out into the creek running away from the pond.   Is it loss of water height visible over days or weeks or??   How big of a pond is it smaller throw a stone across or fire up a speed boat to get to the other side type thing.?   what is downstream is the failure of the dam capable of causing damage to others property downstream ?    Issues that dictate how fast you fix vs must fix vs ah let it leak till it self corrects.
m

[John Mc]

...By headwall, I assume this is an earthen dam pond. During construction, was there a good connection made between the dam and the existing soil? I.E., was the topsoil and any weak soil removed before dam construction began? Otherwise, this creates a seam for water travel.

Yeah, you definitely need to clear away the base of the dam area, down to something that will seal well, before building up the dam.  Even better: after clearing away the weak soil, dig a sort of "keyway" along what is going to be the base of the dam. What fills this keyway, and makes up the bulk of your dam should be clay.

[landscraper]

Sealing a pipe through a dam is a theoretical exercise.  Anti-seep collars are all fine and well until you go to compact around them, and around the haunches of the pipe.  Easier said than done, and you usually end up with a pocket of unconsolidated soils in the critical phreatic zone of the dam.  Best ones I've ever been able to accomplish were formed collars of concrete, left open to cure, and then the shrink crack was grouted with non-shrink grout or such.  Then jumping jack the backfill carefully. 

Otherwise, read up on graded filter diaphragms as a way of controlling seepage through dams.  A little harder to implement, but more effective in the long run - or so they say today. 

[wheelinguy]

I'll try to answer all the questions that I can.  Yes I mean earthen dam when I say headwall. No there is no liner in the pond, the material here is all blue/grey, clay dig a hole and put water in it you either wait for it to evaporate or get it out some other way.  The pond is approx. 50' wide by 100' long, the dam stretches the 100' length, at its deepest it is 15-16'.  The topsoil, stumps etc were all pulled off and set to the side, but that is one of my biggest fears is that there was not a solid connection made at the base! My intent with the culvert was not to breach the dam but to "catch the leak at its lowest point in the stream bed and then stand the pipe vertically to attempt to stop the leak, think atmospheric pressure or an old water level.  My thought was that if the top of the culvert was at the same height as the top of the drain that it would potentially stop the leak, of course that does not take into account the pressure of the water.   We found someone locally who carries bentonite clay so we are going to attempt that first as it would be the fastest right now.  Oddly we found it at a plumbing supply house? 

[giant splinter]

The details and dimensions shed some better light on the project at hand, also the fact that your biggest fear was the connection made at the base may not be solid. I think your concern about the "solid connection at the base" is valid by all accounts.
A 15-16' column of water behind an uncertified fill, built without a keyway and built without a preliminary soils investigation or geotechnical supervision including density testing and a compaction report may be somewhat less than what is required for projects of this type. The bentonite solution might be a reasonable fix in this case if it permeates the soils and sets up in the critical areas.
The other alternatives are far more expensive and anything short of an engineered, impermeable stabilization fill might not help fix the situation.
I suggest talking to a local geotechnical engineering firm or an engineering geologist to get the best ideas on how to stabilize your project.

[beenthere]

Best bet would be to get the original excavator/dam builder back to do the job right. Or get your money back for having someone do it wrong.

[Sixacresand]

I designed earthen dams for sediment ponds in a previous life.  The most dam failures occurred using horizontal pipes at the bottom of the dam with tall risers.  Several things could happen:  water pressure in deep water would break seals or crush pipe, especially metal pipes that evenually rust out.  The soil around the horizontal pipe and anti seep collars would not be compacted sufficently, causing water to channel through the dam. Heavy equiment traveling over buried pipe during dam constuction can bend metal pipe connections causing them to leak.  The best senarios IMO are PVC siphon systems or angeled culverts  buried shallow in the dam with a short verticle riser.  As for the original post, Bentonite is good fix.

[wheelinguy]

Thanks to everyone for the suggestions, the Bentonite will be here on Wednesday and I'll let you know how it works out!