Pond Boss Forums POND CONSTRUCTION Soil questions New Dam is Seeping...Right?

Hello All,

I poured over this site prior to my project, but there is only so much you can learn before you just go ahead and do it. I took a week or so off work and rented a Deere 655c highlift and got started. We had originally, 15 years ago, had two smaller ponds that had dwindled to nothing as muskrats and cattle knocked down our dam that came with the property. This time around, I wanted to dig one large lake mainly for swimming in the summertime, as this is a weekend getaway for all of us.

In the heat of July, I dug a deep hole at the head of the spring where I installed a discharge pump with a float relay so that I could divert the 3,750 gallons an hour that enter the lake bed. This worked flawlessly and allowed me to come back in at rather temperate October for excavation. I dug the basic shape and did an 80% of the excavation myself, moving as much material out of the lake/pond area as possible. I later assessed that a dam would be too much to tackle with the vacation time I had left so I contacted a local contractor with experience. They finished out the dam and put a final grade on everything. We also had them put in an extensive concrete spillway with large rock laid down first. The thought was that the water would come in at the rate of 3,750 gallons per hour and would excite down the concrete spillway at the same rate. Granted there would be some evaporation, but not enough to make a drastic change in our flow.

After a solid two and half months of fill time, and several storms, the lake is still not overflowing and draining down the spill way. My concern is that the water is exciting beneath the concrete spillway, working its way under the initial lip, or sneaking underneath the key to the dam itself. The most frustrating thing about a project that I made so personally my own, is that I did not get to finish it myself, nor could I be there to oversee the final build.

If you watch my video and then take a look at the photos (sorry they are not the best), you can see that I have some seepage below the dam. The photos and video were taken well after a rain, and the moisture is not from precipitation. Will this “fix itself”? What can be done?

I essentially need a little info before I speak with my contractor. Can you guys arm me with info or theories as to what is going on here? My main concern is that wherever there is a leak, it will get worse over time and eventually break. As you know these projects take considerable time and money and since I paid someone a considerable amount to finish up the final and critical 20%, I want it done right.

Should I be concerned about this seepage?

Any thoughts or suggestions would be a huge help and be much appreciated as I have already exhausted all my friends endless ‘what ifs?’


Photos
http://danielheggarty.smugmug.com/

Bad video, but a video for reference
http://www.youtube.com/watch?v=EHSB3szuniA&list=HL1326488490&feature=mh_lolz

I am no expert by any means, but the seepage I see from the still pictures does not equate to 3750 gallons per hour. If there are not other leaks, there should be a net gain in the pond. Seepage at a rate lower than the fill rate really is no big deal IMHO, especially considering how much it would cost to fix.

Give your pond a little more time to fill and settle in. It took mine three months to fill all the way and that is with quite a bit of different rain and snow melt events. At one point we had >= 80GPM entering on only one of the 4 significant sources of water, but this event topped it off and then some.

My pond volume is 3.7M gallons with 16acres or so of area to draw from.

A few questions: Is the pond lever rising or staying the same?

What soil types do you have? It may not be all up to the dam on losing water, there may be other exits as well such as through a porous group of materials that leads off to "nowhere" (springs have to start someplace).

If the level is stuck at some point regardless of rain and inflow, it is likely you will need to seal the pond somehow, and at minimum find the leak and seal it.

I'll let the true experts chime in (I have only read the book, I didn't write it).

Same here, I didn't write it either.

Tell us more about how the pond was constructed, and the type of soil.

Was the dam built with a core trench that was tied into good soil?

Are there any springs in the bowl of the pond (below the water level)?

Was the pond lined with clay and compacted? If so, what was it compacted with, and how thick is the liner?

60 gpm is certainly going somewhere and I expect that the wet spots behind the dam tell the answer. It could be improperly cored or the dam poorly packed. How was it packed?

Hello All,

The pond/lake is located in southern Missouri in the iron belt. I am not familiar with all the types of soil, but from my limited knowledge it is high in red iron based clay and good for making projects such as this. While digging I put my good dam clay off in the field to be used in the dam's key, but as I ran out of vacation time and was not around to oversee the final steps of the build, I cannot comment on the depth or quality of the key or core trench. This is my biggest fear...

There are some slower springs seeping in from the bottom but I do not know the rate. While I was excavating, they were extremely slow.

To my knowledge, it was not lined, but simply shaped with dozer to create the final bowl shape.

Again, I was not there to see the construction of the final dam, and I presume that they simply packed the dam with equipment that they had, a track hoe and dozer. The final 20% of the project was completed in two days with just two pieces of equipment, track hoe and dozer. The spillway had large rock hammered into the earth with the track hoe while the concrete was sloped into location with the track hoe. There was no finishing crew with floats and trowels so there are gaps in the concrete work. I would have preferred a more finished surface...

At one point, after a big sleet/rain/snow, water had gotten over the top of the spillway, but just trickled into the unfinished concrete and "disappeared". Several weeks later, the water level had dropped a foot and has seemed to of stabilized. Well, stabilized with the seepage on the backside of the dam...

I want to contact my contractor to see if there is anything that can be done, but first with a better "forum education" of possibilities. I deferred to his local expertise in the area as I wanted the job done correctly and to last for at least 10 to 15 years. He is the pond guy in the area. Without knowing exactly how the dam was constructed, I presume that the key is faulty. If this the case, do I have any leverage here? Will it eventually fail? Will it eventually increase the amount of seepage leaving me with a slowly dwindling pond level?

Wife questions: Will it fix itself? How long should I cross my fingers?

Thoughts, ideas, speculations, rambles, all are welcome. What do you think?

Unfortunately, it won't fix itself.

The cracks in the concrete spillway:

When the water runs into the cracks, and disappears, it's probably carrying dirt with it, and creating voids under the concrete. I'll bet there isn't any reinforcing steel in that concrete, which would hold it all together. I'm afraid that the cracks will keep getting bigger and bigger, until a large rain event comes along and washes some of the concrete away, or collapses the spillway. All concrete cracks. Period. It's just a matter of how large the cracks get.

Are there any other ponds in the area that are constructed in a similar fashion from the same contractor? Can you talk with the owners to see how they are holding up? If he's been doing this for that length of time, there should be some around to look at....

At the very least, when I contact the contractor about your concerns, I'd see if his concerns mimic yours.

Typically a pond will take a few months to get the soil saturated in the pond basin. But, if after a few months, the water is still trickling out, then I'd start to worry. I'm a bit concerned now about the concrete spillway and the cracks with the water disappearing in the cracks.

Personally if I were you I would smash up the existing spillway into lumps, and then use those for a foundation of a new spillway using metal screen, rebar, and crack-resistant concrete. That would give you a chance to see what is going on underneath and do something about it before it becomes a problem.

My first thought is you have sprung a leak someplace. Perhaps that large rock smashed in there is the root cause as water could go around the perimeter where it contacts soil as the dam settles. I would definitely get the contractor out there for opinions. People who have typically been in business that long will want to rectify problems before losing future work.