Pond Boss Forums POND CONSTRUCTION Selecting a site new excavated pond questions

Hi everyone-
New to the forum, although I've been lurking for some time now. I need some advice and was hoping I could get some help here. This is my situation. We own some land in north central Indiana, and are trying to decide if we can put a pond on it (in it?) or not. The spot that we have available is relatively flat pasture, and because of setback restrictions, we have an area slightly more than 1 acre to work in. The footprint is rectangular, roughly 175'x 375', running lengthwise from west to east. The land slopes about 4' from the west side down to the east side.
I know that this will have to be an excavated pond.
I have had three excavators out to look at it, and so far, this is what has happened.
#1 dug three test pits, one at each end of the site, and one in the middle. At the east pit, we discovered topsoil to about three feet, then a vein of clay about two feet thick, and then a sandy, gravelly mix. We hit water in the clay, which filled up the hole to about 42" from the ground. He eventually dug this hole about 8-9 feet deep, but it began to cave in at the sides, and he stopped digging at that point. The reason it began to cave in was that under the clay, he hit sand. The center pit was essentially the same, but we had to dig deeper to hit water/ clay, because the ground has sloped up about one foot at this point, midpoint on the site, about 125' from the east pit. The west pit had to be dug even deeper, and we ended up discovering topsoil down about two feet, and then a sand/ gravel mix, all the way down to about six- seven feet.
This excavator originally suggested that we scrape spoil into a "dike" around the south, east, and north perimeters of the pond, to level the site with the higher western edge, and then excavate out the center. He was unable to determine if the water we struck was water table, or a spring. He was unhappy with the sandy/ gravelly mix we found under the clay in test pit #1, and doesn't seem too enthused about the possibility of a pond in this site.
The second excavator looked at #1's test pits, and said the water was "artesian" (a spring), because he believed that the water was higher than the lake (level) that is adjacent (appr 400 yards to the north) of our property. (Based on looking at a topo map) After digging a test pit of his own, on the west edge of the site, he changed his mind and said that he thought the water was, in fact, water table. Not too sure what to make of this guy...
The third excavator has looked at the site and existing test pits. His opinion is that the water in the pits is water table, and he believes that the correct way to do the project is similar to excavator #1, by making a dike around the perimeter to level the site, except that he believes that due to striking the water table, the pond will never fill up all the way, and I will have to drill a well to periodically top off the pond.

So there you are- three excavators, three different opinions.

I'm more confused now than when I started.

Some background info:
I have bought and read "Perfect pond- want one?".
I have used the county website to check what they claim is the watershed for the area. Our land is the "last stop" before all the water in this watershed runs off into the previously mentioned lake, and according to the county website, it's about 495 acres. The last two springs, which have admittedly been much wetter than normal, the east end of this pasture has been ankle- deep in running runoff, for a couple of weeks at at a time.
When we build our house, in two- three years, we plan to install an open loop geothermal system, and discharge into the pond.
So there are three sources of water- water table (if the water in the pits is, in fact, the water table and not a spring), or a spring. Heavy spring runoff. And eventual future geothermal discharge. (four, if you count normal seasonal rainfall)
What's stopping me are these questions.
If we have hit the water table, and it is (right now) 42" underground, won't any amount of water added to the pond just run right into the water table, and never raise the pond level? And if that's the case, do I have to dig down to the water table, and then excavate out the pond into the water table to it's actual desired depth?
Then, do I just have to have a pond with long, sloping (4/1 or 5/1) edges, down to the waterline? The reason that this is a concern is because of the shape of the site- rectangular- and we don't want to end up with a long, narrow canal- like pond. If the proposed "dikes" are built up four feet, to level the site, and then we have to dig down another four to six feet just to hit clay (and water)- that's eight feet+. At a 5/1 slope, the sides will taper for 40' before they hit the waterline. (Even a 4/1 slope will be 32' down to waterline.) Between both sides (north and south), eighty feet is used up, and the site is only 175' at the widest. That's going to make for a long, narrow, unnatural looking pond.

I known this has been a long post, and I appreciate anyone taking the time to read it, and to add whatever input you have. If I've made mistakes in my analysis of the site and situation, please let me know. I also don't know if I'm asking the right questions, either of the excavators, or here, so if you think there's anything that I'm not asking, please let me know. Thanks all-
Dave

Dave. WELCOME! First off not an expert, Im sure they will be along soon. My pond is similiar to yours as in that it is dug into the watertable. It will not hold water long term above the watertable depth. That being said it does always have some water in it even if it has not rained. We did have to make the sides steep because of limited space. My water table started at around 5-6 feet in nothing but sand, sand and more sand. Stay tuned for the people who really know what they are talking about. Paul

Dave:

Welcome from another Hoosier. I have a situation that is somewhat similar to yours. A dug pond, high water table, sandy soil, spoils from the pond go where?

With the high water table, are you planning on having a basement in the future house? If so, will the lowest point of the basement be above that water table in a wet spring? Could some the spoils be compacted in the future house area to raise it for a basement?

Yes, the pond level will fluctuate with the water table, but you can pump water into the pond to keep the level high as long as 1) you are pumping in quicker than it's going out
2) you aerate the well water by running "bouncing" it over something to allow dissolved gasses to outgass, and the water to get oxygenated.
3) you are willing to pay REMC,NIPSCO or AEP their going rate for electric. If you are thinking of pumping water into the pond, you are probably looking at a 1 hp/27 gpm pump running 2/3 of the month starting towards the end of June thru October. You could go with a bigger pump and run it for less time, which is what I'm debating now.

There are products that will slow down the seepage, but as long as you are in the water table, I doubt that you will completely seal the bottom unless you can get a couple of feet of clay compacted when the pond is dug.

The contractor should be able to figure where the mean pond level will be, and should plan a spillway for high water flows in the Spring without washing away your berm or levee on the low side of the pond. If we get a rain in Early Spring like we did in 2004, with that watershed you will have a tremendous amount of water running thru the pond.

If you are having second thoughts about the contractor at this early stage, keep looking.

Just curious on who you've had out (contractors). If you don't want to answer publicly, you can private message me.

My pond's water level is approximately 3' below grade. My bladder tanks for the well are in an old milk house that has it's floor roughly 5' below grade. I had water coming into the room where the bladder tanks are both last and this spring, but it's been dry for the past 2 months. When the well was drilled, the water level in the casing was 12' below grade. In early Spring, I can usually hit water at less than 3', and I will have water standing in the woods right next to the pond when it starts to thaw in the Spring anywhere from a couple inches deep to over 18" of water like this Spring.

Hello Indiana Dave and welcome. I'm not an expert either but my pond design is similar to yours, I also live in slightly North Central Indiana and I have the open loop geothermal system (great choice by the way). Nothing like a $250 electric bill in the dead of winter for a 5000 sq ft total electric house.

My test pits showed mostly clay but while excavating we started running into alot of loomey material. The operator suggested bagging the pond plan and making a park like setting in the middle of the clearing created after about 50 trees had been removed. I reminded him that was not the plan and to keep digging (not that I recommend this risky proceeding). I was going to have my pond one way or another. After digging deeper we transitioned back to clay again. To this day it holds water like a bathtub. I wish you well and hope it all works out for you. Major difference is that I didn't have the water table issue.

Welcome to the forum glad to have you.
I have seen ponds in the water table fill up and stay full but I have also seen it the other way, and I do not know how to tell the difference before the pond is finished.

Are the test holes still open and have they filled up or they at the same level as when they where dug. That will tell us something.

Please keep us posted. The more information we have the better decisions we can make.

Hi Otto

Glad to be here and getting the benefit of everyone's experience. To answer your question, the test holes are still there. They were first dug 3&1/2 weeks ago. As time has gone by, the water level in the holes has slowly been dropping. This is consistent with mostly dry weather we have been having. There is still water in the easternmost hole- it is the deepest hole, and dug at the lowest end of the site, so it stands to reason that if this is, in fact, the actual water table that we have hit, it would still have water. The other two holes are dry, but they are not as deep as #1, and they are further up the slope (to the west). I suspect that if we just dug them deeper, we would hit water. I was also thinking that if there was a way for the excavator to dig down to water in the second and third holes, and then to shoot a laser from one water level to the next, we could get a better idea if the water in each hole is at the same level, and if it is, that would probably mean that we have actually hit the water table in each hole, and we would know how far down it is. Can that be done, does that make sense, and is it something that we should do?

So if you don't know ahead of time whether or not a water table pond will fill or stay at the water table height, how do you plan for the finished pond? Do you have to make plans (configuration, expense, etc) for both contingencies, and see how it goes as you dig? (Plan for the worst, hope for the best?) What would you tell a potential customer about this situation?
Thanks again-
Dave

Dave
If the water is droping in the test holes, it will more than likely do that with the pond.

Check around the aera and see if there are any other ponds and how they hold water, that will give us more information.

We are working on a pond that has a water table that is about 7 feet below ground level and goes up and down with the seasons.

This pond will be dug about 1 foot above the water table.A liner will be installed and covered. There will be some valves installed to allow water to come in, if the water table raises, but will not let it drain.
Yes you can have a pond put it may take some planing and out of the box thinking.

Do not give up--look around and see what your neighbors have done.
keep us posted.

Otto

Thanks for the input. I thought that if we broke into the water table, the pond level would probably then fluctuate with it- thanks for confirming that. My neighbor immediately to the south has a small pond, don't know how old it is, and he said that he has been supplementing it with a well for several years, because of seasonal flucuation, but it is beginning to hold water better now. Maybe it is finally sealing itself (sediment?) and I may just have to go through the same process.
I'm going to use the county website to find other local ponds with the arial photo feature, and then I'm going to make the rounds, introduce myself, and see what others have done. I'll let you know as I get more info.
There's always a way to make something work- just depends on how much money and effort you have available to make it happen.

Dave

Good job