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View Full Version : Leaking Pond, PLEASE HELP!


SummersOff
05-22-2008, 10:47 AM
Well I have been delaying posting this for a while, but I need some serious help. Almost three years ago my wife and I had a pond dug, my best guess is it is around a quarter to a third of an acre. It has a field tile that brings in water. When we get a good rain the tile runs massive amounts of water into the pond and unless it is extremely dry we always have at least a little bit of water running into the pond. The pond has been so full that it goes over the overflow twice once last spring and once this spring. But within a few weeks it looses around 70% of the water, which is a ton of shoreline that becomes exposed. When they dug the pond they "key locked" it, this meant they dug down around the inside of the pond and mixed the soil. The builder told me that it would take around two years to "seal" itself off because the soil is a bit less than desirable but insured us that it would be fine after a few years. I looked into bringing in clay, or a liner or even "key locking around the outside of the pond, all of which are expensive. I have no outside leak from the dam or anything like that. I have thought about bringing in some clay and trying to spread and tamper it down myself, but am afraid to put in all the money and effort if it doesn't work. The builder came out a month ago and said he would bring out a pump that we could run out of our well for a few months to try and keep the pond full and "seal" the top part of the pond off, I'm a bit skeptical (plus he hasn't contacted me yet). Also it seems as if the pond always goes down to close to the same level. Thank you for reading this really long post and any suggestions would be much appreciate it.

Fishman
05-22-2008, 09:47 PM
I'de probably go the route of using the builder.

Bentonite clay might work, but sounds like you might be putting a bandaide on a bullet wound.

Bob4246
05-22-2008, 10:28 PM
I work for a Geotechnical Engineering firm, and we deal with this problem fairly often. You may have a sand and gravel deposit somewhere within the sidewall or bottom of the pond excavation. The water leaches out through the sand and gravel. During wet weather, the pond fills. During dry periods, the water drains out to the lowest part of the deposit of sand and gravel. If the sand deposit is in the sidewall, that would explain the pond always leaking to the same elevation.

Typically, this is addressed during construction by "undercutting" or overexcavating the sand and gravel (usually 2 feet) and replacing it with compacted clay. Sometimes topsoil is used to backfill the undercut, depending on availability of material.

When the builder indicated the pond would "seal" itself in a year or two, I believe he assumed silt would accumulate on the bottom to seal the sand. Unfortunately, this does not always happen. If your pond is filled by "clear" water runoff, it will contain very little silt. And the silt that does accumulate on the pond BOTTOM won't necessarily seal something halfway up the sidewall of the embankment.

Next time the pond is at it's drained level, walk the banks just above the waterline and look at the exposed soil. Is there sand and gravel present? You might even see some water leaking back into the pond just above the waterline. If you determine the leak is in an isolated area, you might be able to fix it yourself with bentonite. If it is a large area, you may need the help of an excavator...

Sorry for the long winded post. Feel free to PM me with any questions.

SummersOff
05-23-2008, 11:00 AM
Bob thanks for all the info. Check your PM's. Keep the advice coming guys.

PondFin@ic
05-23-2008, 12:10 PM
I agree with Bob. When I dug my pond there was a vein of sandy gravel mixed with a little clay and water was trickling into the core trench 2/3 of the way to the bottom. We dug in, removing the sand about 3' deep in addition to the 3-4' wide core trench and packed it with clay using the excavator bucket. My pond relies on surface drainage alone and has nearly the minimum amount of watershed recommended. It dropped 2 1/2' in the drought last summer, the lowest ever. That was acceptable because 1/4" per day loss to evaporation is normal.

The tile you described sounds like you probably have too much water coming in. A lot of water flowing through will make it difficult to control weeds with chemicals.

Could you describe you overflow structure a bit more? Is it a pipe, earthen, standpipe or siphon?

SummersOff
05-23-2008, 01:31 PM
Pond Fin,

Thanks for the input as well. I plan to walk the shoreline again and see what I can see this weekend.

The water coming into my pond is one of those black drainage pipes that has been piped over from near the front of my property from an old field tile. It only bring in large amounts of water when we get heavy rains. I will agree with you one the weeds though. I have lots of them right now, but haven't done anything about them because of the low water situation I am more concerned with the lack of water and don't feel like putting any money in chemicals or grass carp if it isn't going to hold water.

Thanks again for the post and keep them coming.

PondFin@ic
05-23-2008, 03:48 PM
This may help as well http://govdocs.aquake.org/cgi/reprint/2003/616/6160060.pdf

ESS-13 may deserve some research too. It's been around for at least 20 years but you don't hear about it much. I believe there are some new formulations available for easier application than what was stated in the above document.

SummersOff
05-23-2008, 05:31 PM
thanks again Pondfin. I looked up some things on the ESS 13 and talked to one of the sales people. It is a relly neat product and they were very helpful. They suggested that for my situation I try and drain a few more inches of water off the pond and then rent a jump jack to try and better compact the soil. They said that might be enough to make a signifcant difference and then if I see a more consistant slow seapage their product might be of use. At least that sounds like a cheap place to start, but I am still open to suggestions.