Pond Boss Forums POND CONSTRUCTION Building a dam when does seepage become a problem!

OK,
I have talked before, about a month ago about my lake not filling up in the two years that I have built it.
Here is the senario........
First, Like I said before, the lake is 30 feet deep at full pool and 9 acres in size. Right now, the lake is about 4 acres and 20 feet deep. About 20 yards from the back of the dam in the creek channel, there is running water at a rate of about 18 GPM.
Now, Could some of this be from a spring or a spring head?
If it IS all from the pond, is this amount to be expected being the lake has this size?
There reall is no wet places behind the dam to speak of. I have two toe drians about 1/3 the way up the dam, and they have a constat drip, not much at all really coming out, this to me is to be expected from these toe drains.
But my only questions is about the water I see in the creek channel.

Here are a few questions I have related to this. First is the amount of flow in a stream bed SOLEY dependent in the water shed behind it? I mean after I put up my dam, All thats left behind the dam is 20 to 30 acres of water shed. Could a possible spring head be produced in this situation?

I am trying to make sure that what I am seeing is not a spring head, or even a comination of a little seepage and a spring head.

Big pond,
Does the water level of the lake drop noticeably?
If not heres a wag; you might have plugged a spring with your dam and now the spring is surfacing downstream.

Well not really I can't say it drops NEAR as fast as other on here who claim they have leaks and seepage problems....
I mean YES mine is DOWN, but so are a BUNCH of other ponds in North Georgia as well.

Your running water in the creek channel is most likely from your lake. A 4 acre lake would drop approximately 1/4" per day at that gpm. You can contact me directly at 940.665.2258 (phone answered by secretary 8 to 12 mon thru fri) or email me at mikeotto@ntin.net.

was this pond built on a year round or seasonal creek? was there water in the pond while you were digging it? after the dam was built, was there any flow below dam in creek, or did it appear after yer pond began filling? the timing of the flow relative to when you built pond would tell you a lot. sounds like my issue before renovation where the "weight" of the pond water (hydraulic pressure) was pushing flow (seepage) beneath dam, and the seep was daylighting some distance below the dam coming up in my creekbed like a spring. i had to drain and seal the bottom of my pond.

the amount of the leak is only indirectly related to the size of the lake. it is more directly related to the size of the "hole" it's leaking through. if its weeping through soil, its related to the hydraulic conductivity of the soil, in my case it was bedrock fractures....a fairly direct and large pathway for the water to travel through.

i didnt have any wet spots on my dam either, all the leakage was flowing below the dam (in the bedrock fractures) until the pressure equalized enough for it to escape in the creekbed some disance away from the toe of the dam.

it doesnt sound good to me that yer toe drains constantly drip. sounds like there could be some dam construction issues?? although i have no experience with this.

my couple of cents.

This was a GOOD response!
Yes, when the core was dug, We were lifting out large bolders out. All along the creek bank you can see bolders here and there before we started the dam. I would guess that I might have the same kind of leak that you have. Mine is as you say the dam is dry, but the old creek bed has flowing water.
Yes this creek pretty much ran all year long.

I can dare say for certain that I had rocks in the area of where my dam was built. Like I said before the contrator pull out a few big ones when he was cutting the core. I geuss the question is what do I do now?

if it was a year round creek, this likely indicates your water table was (is) at the same depth as pond bottom, which if not sealed properly could reverse flow and allow seepage out the lower sides or bottom of dam even if cored.....the problem COULD BE your pond basin particularly at the deepest levels.

in general, my sense is you have an issue that needs corrected on the lake side of the dam, the fix of which could be attempted in varying degrees of difficulty and cost.

since you have otto's ear, go ahead and call him, discuss the problem. i'm sure he can speak to potential solutions better than I. let us know what he advises, we can all learn from this.

WOW!!!!
Another good POST!!!
So let me get an understanding here, Sense I have a creek that flows year round it is possible that the water table was at the level as the creek, now that I have put up this dam I have raised the dam to where the water table has found a new way to leak out down stream!!!!

WOW!! Is this what you tring to say?

I can tell you for SURE that we spent good effort on the core trench, It is in deed 20 feet or better in most spots.
But "dave in el dorado ca" mentioned about the creek channel now that intresting. We did not do ANYTHING about the creek channel at the bottom of the lake we just left it like it was....
I guess I could dig this out quit a bit and re pack it with Clay...

sounds like you did your homework on the dam construction, but even if cored to 20 feet, and you have transmissive geology (material that lets water easily pass through it) below the core, you could get enough hydraulic pressure to drive seepage beneath the core and eventually out and up the other side into creekbed. in this case, the trick is to seal at a minimum the deepest parts of pond (probably the creek bed path) subject to the greatest hydraulic pressure once the pond has water in it.

in my case i concentrated compacted clay only in the deepest areas (and the old creek channel in the deep end), plus i couldnt afford to truck in sufficient clay for the entire pond basin. my "upstream" portion of the pond is still basically bedrock and probably seeps some, but it is much shallower (less hydraulic pressure), and likely only seeps into "downstream" deeper portions of pond as most of my losses this year were from evaporation.

let us know what otto says, and good luck big pond.

I think you might have HIT the nail on the head!! I think your RIGHT!!!
Now the only thing is to convince my self to loose 2,000.00 worth of fish and 2 years worth of growth!!!

big pond, i saw yer post over on questions and observations..sounds like you made a final decsion......my advice is to wait until you talk to otto or others in your area, do as much research as possible before you do anything. there are other alternatives to digging that might work.

the best thing to do if possible is have a knowledgeable pond consultant inspect your situation, examine the dam, creek, review any pictures taken during construction.....you might end up diggin, but there might be other approaches....again good luck....leaky ponds bite.

Well, I have not made a total descion just quite yet. I was wondering if it is just possible to fix this thing from the back of the dam?

I need to find a TOP NOTCH proffesinal to come look at this situation and tell me what I need to do. But I don't know any one Mike Otto's Caliber over here inn Georgia...

Anther thing, the rate at which the pond is dropping is about an inch every two weeks. Don't know if this could be the "seepage" or evaporation. Mind you this reading came from a week ago and NOt this summer.

Seeping 2" a month is nothing to complain about. If you want a true measure of seepage vs evap. then put a chicken feed pan on the dam to serve as an evaporation pool, put a small fence around it to keep varmints out and compare the change in it's level to the change in the pond. Obviously you have a larger leak once the pond exceeds a particular elevation, otherwise your pond would be filling. I agree with otto that 18gpm should cause a loss of about .25"/day on a 4 acre area. If you are dropping only 1"/2 wks, your daily loss is on the order of .07"/day, so if all of the info you gave is accurate, all of the flow below the dam is not coming from the pond. I would suspect you have a leak in the side of the basin somewhere. Just my $.02

I am going to do this exprimet that YOU described...I am also going to keep a closer tab on thi lake level, to make sure on the amount of level drop. But I think I am close when I say 1" every two weeks though...

Contact your loacl NRCS office and find out what the evaporation rate is. The rate is variable and depends on the Temperature and humidity but can be 2" per month.