Pond Boss Forums POND CONSTRUCTION Selecting a site Pond on top of limestone rock

Hello, my name is Nathan Stone from Sumner County, in Middle Tennessee. I have a small farm which I grew up on, which currently has a small stock pond, but has another, better (larger) pond site, where I'm preparing to build another dam, creating a pond on the order of 1-1/2 acres. The pond that exists currently was probably built back in the 30's. It held water consistently until the late eighties when we had an extended period of drought and the pond dried up as far as I know for the first time ever. When it dried the clay liner cracked and the pond didn't hold afterwards. I built a home on the property a few years ago and when the excavators were here I had them take their track loader and work the bottom of the old pond and raise the dam and earthen spillway 2 ft. After that it would fill and then slowly seep down to a level about 8 ft below the dam. Over time the pond began to drain more rapidly after filling and I noticed that a small cavern had opened on one side of the pond basin back up toward the head end of the pond, allowing water to drain into it. I can see the limestone bedrock down in the hole under about 4-5 ft of soil. I have a D5 dozer and I plan to strip the banks of vegetation (10-12" sycamores, this cavern developed at the base of one of the large trees), cut 2-3 ft of clay off the banks, fill this hole with large rock rubble, then concrete, then at least 2 ft of clay (maybe some bentonite over the cavern)and compact back in the 2-3 ft of clay I stripped from the banks of the basin. The other pond site is above this one and has a similar cavern I'll have to deal with. On the second, new site, I plan to strip all of the existing trees and top dirt and work the clay underneath, to try to expose any areas of weakness and deal with them as they appear. There are a lot of sinks and underground stream passages on the farm. Both of my pond sites are below the elevation of all of the sinks I know of, but I do have these small passages to deal with. I believe this geology is known as 'karst' formation and I know it is not recommended to build ponds on it. I'm a mechanical engineer/farmboy who has an independent streak and a dozer and I intend to try to pull it off, I feel like it's doable with the proper attention to detail. I'm looking for advice from anyone who has dealt with this type of geology to find out what has been tried and what did/didn't work. Any advice is much appreciated.

Hey Tn Hillbilly,

How do you know you don't have another Mammoth Caves under you? Big Bucks!

What can I say. I'm a capitalist!

TN Hillbilly,

I'm not familiar with your type of geology, but agree with Robinson that straight clay would give you a much better chance at success than including ruble, rock, and concrete first. Good clay solves just about any pond problems we have, but haven't encountered one like yours. You have a real challenge ahead. I wish you success.

Thanks for all the replies. I know it will be quite a chore to make this come out the right way.

Robinson, Pressure grouting sounds like a great idea. Certainly the grout would be able to find it's way into all the cracks and crevices. I'll have to get some folks out here to take a look and see what that might cost. My biggest problem would be getting the grout to the pond. When I mentioned using rubble and concrete I was thinking that it would provide support for the clay liner above. I'm afraid if I pack clay into the hole without something to support it that water will eventually find it's way through and set up a slow trickle into the hole, gradually eroding a larger passage through the liner.

Cecil, If you'll volunteer to crawl down the hole to do a little spelunking to check it out, I'll split any future profits with you! But just in case the commercial cave business doesn't pan out, I have a bucket of grout I need you to carry in with you.

Meadowlark, Thanks for the well wishes, for sure this hole will be covered deep with Sumner County's finest.