Pond Boss Forums POND CONSTRUCTION Soil questions Watershed or Groundwater Pond?

Hello everyone! I’ve been learning so much from the forum over the past year, and messaging some of you, I really appreciate all the guidance thus far! Time for my first post:
Myself and 3 others purchased property in central Michigan (LP) that has an existing 1.3 acre cleared area, basically a basin that had sand removed by previous owners down to an average depth of 4 ft. (Red outline in attached image). There are a few pockets in the basin that are 1-3 ft deep that remain full of water throughout the summer. In the picture these are bigger because it was more in the wet fall/winter. We are hoping to be able to create a 1.0 acre pond in the blue outlined area. And use some of the spoils to fill in the green area up to grade to make more high and dry area near the pond. Every one of my neighbors within a mile or two has a pond. I know there is clay underneath the sand, but I’m not sure at what depth the clay starts yet. The local well data says sand for 10-15 ft, then solid clay for another 80 ft. I’ve been trying to convince the other property owners that we need to rent a mini ex or similar and get some samples taken. I tried getting a deep sample hole with a backhoe, we got down about 4 ft from grade and water started seeping in pretty quickly so we stopped.
I’ve read a few books and searched the forum, but could I please get some help answering a few of the following questions I haven’t found answers to yet?
1. It’s a relatively low, flat area for hundreds of acres around us. It’s very wet in the spring to the point where the 4ft basin is full and the surrounding grade has some sitting water puddles. How do I know if I should line the dug pong with clay like a watershed pond and try to hold onto that early season water and summer rain, or leave it as sand and let the ground water seep in and have a ground water pond? I do still need to talk to NRCS office to determine how big if any the watershed is around the site.
2. Currently we are on the waiting list for someone with a dragline to dredge the pond basin to 14 ft depth next summer (water depth, not 14’ below grade). However, he says if he hits hard clay at any point before full depth he has to stop. As mentioned, I’m trying to get down to the clay beforehand with sampling to see if it’s something he can dig though before he gets here with his equipment.
If we sample the soil and find the dragline will not be suitable, is it possible for us to dig a few deep holes and pump the water out consistently enough that we would be able to hire a dozer operator to dig the pond? Or would we never get it pumped dry enough for a tracked vehicle to be down in every area of the pond bottom? I don’t really understand yet what happens to a wet area once you start digging down. If anything higher than the deepest point will dry out, or if water will continue to seep in everywhere and stay muddy.
3. Let's say the dragline guy starts but can't get past heavy clay at 10 ft depth, is finishing the pond to full depth with an excavator or dozer going to be any more daunting now that the pond is a lot deeper, versus if we chose to forgo the dragline and go right to pumping the small amount of water we currently have and using an excavator and/or dozer right from the start? (Aside from having to pump more water out).
Thank you to everyone I have already bugged with my questions. I’ve loved doing all the research and seeing what everyone else is doing with their ponds!

-Travis

Welcome to the forum. Talk to the NRCS first. That will help determine what route you take. With enough watershed you can have a lined pond to hold the water.

A groundwater pond will be harder to manage. I am in my 3rd year of a drought here, and my pond has been between 6' and 8' low (vertical measurement) for 3 1/2 years now.

#1. Talk to NRCS

#2 Even with pumping you most likely will NOT be able to use a dozer down in the bottom. You could use an excavator to dig it out, swing 180°, put it in an off road dump truck or have a dozer push it out of the way. Even with the dragline (which is the slowest way to move dirt), digging in water doesn't allow you to see what you are doing. You better have a boat on site, with a sonar unit to check depth if you are digging in water.

#3 You will have to run the numbers dollar wise to see if running a dragline is cheaper than running an excavator. NOT a mini excavator, a real one that has a 24' reach or so with a 36" wide bucket.

I'm in the process now of trying to figure out a way to put out a fire. I can't go into too many specific details, but I was contacted to design a 20 acre pond. The property owner decided not to hire us to supervise the project, just do the design/drawing and answer a few questions. After roughly 6 acres were dug, he asked if I could come over and check the pond depth. (the contractor is digging in water - he elected NOT to pump the water out and keep it pumped out as he dug.) The ground is not sand or clay, but peat. The contractor is using a long stick excavator.

The deepest part I found was 5' but the majority of it is roughly 3' deep (checked with sonar). Even though he was digging to the required 18'-20' depth, my opinion is that as he was pulling the bucket up from the bottom, the material was washing out of the bucket and getting distributed back all over the pond.

I was able to contact Mike Otto and told him about the situation. I gave the property owner Mikes contact information and he is supposed to be talking to him yesterday or today. I'd love to get Mike up here and have him put boots on the ground on-site. Time will tell.

Another project that is in the works is a 6.5 acre pond. That dirt contractor told the property owner that if he hit water he would dig a french drain all around the pond site, and make it 10' deeper than the pond max depth. He'd then use solid pipes for risers and connect up dewatering pumps to the french drain and suck water out of the ground to keep the pond site dry. That pond will be 20' deep so he'd go down 30' to install the french drains. That dewatering alone would cost about 25%-33% of the total pond budget. He dug a pond not too far from there that was 5 acres and he had ten 6" pumps running to dewater the area while the pond was constructed.

The test holes showed 6'-8' of loamy dirt with solid blue clay beneath that. He dug test holes down 20 feet. IIRC the excavator he used for the test holes was an 80,000# unit with a 28' or 30' dig depth.

Scott, digging a hole without de watering sounds like a losing effort to me.

If it were me, and it’s not, I would start over and dig the hole upstream (uphill) or depending on terrain, downhill. Then pump from that pond into the new one. Use the spoils to fill the old hole.

Travis, that is going to be a VERY challenging environment to build a pond. I have a similar situation on our farm, but at a much smaller scale - so it is more manageable.

A 15' thick layer of unconsolidated (loose) sand is going to be tough. As the dragline or excavator removes sand below the water level, adjacent sand will just flow into the newly created low spot. You may have seen sand pit operations in your area that have created a deep pond. Usually they use a dredge to pump out wet sand and water. Only after they have sold thousands of tons of sand does a pond with significant depth get created.

I believe you should try again to get samples with the backhoe or mini-excavator. You did not need to quit digging when you hit water last time. Keep excavating in the same slot trench next time. If the sand is mixed with some clay material it may stay in place and you can dig down to the max depth of your equipment and see if you encounter the underlying clay layer. If the sand is flowing, then you will not be able to dig down to maximum depth. The sides of your slot trench will start collapsing and your hole will get wider. Try several spots on your property. If the sand layer has a variable thickness, or has some areas with significant clay mixed in (to make it stable), then you may be able to construct a pond in that area. (If the clay layer is 15' deep everywhere, then you are beyond the maximum depth of a typical backhoe or mini-excavator. If that is the case, you will need to pay a contractor with a larger excavator to dig your sample sites.)

If your sand layer will flow when wet, then the only feasible way to create a "sealed type" of pond is to drain your working area and work with dry sand. The method would be to create the deepest sump possible and pump out water to a distant location so that it did not just return to your pond by re-entering the sand layer. (If your have a 15' thick sand layer, it might not even be possible for you to pump your pond area dry.) After you get the water level down to the clay layer, you can pull clay up with an excavator and start lining and compacting the sides of your pond with clay to eventually seal the sand layer. If you can create a sealed pond to the depth you desire, you will then have to have a means of keeping if full of water. On your flat ground, I don't believe the watershed will direct enough water into your pond. However, you would still have an excellent groundwater supply of water in the areas outside of your "sealed" pond. You could use your little areas that are 3' deep and pump water into your pond. That is not much cost since you are barely "lifting" the water and not pumping it very far. However, you must determine if that is legal in Michigan. I believe that type of operation is legal in some states and illegal in other states.

Sorry for the bad news, I think it is going to be difficult and/or very expensive for you to build the pond you are describing, IF I am understanding the ground conditions correctly. (Hopefully I am wrong.)

However, the good news is that your neighbors do have ponds. Obviously there is some viable way to build ponds in the area. Have you struck up a friendship with any of the neighbors yet? Asking them how they constructed their ponds, or asking them to show you their pond site might be a huge benefit.

Perhaps they are on lower ground and they only had a foot thickness of the sand layer. In that case, they just needed to dig their pond in the clay and the groundwater in the sand layer keeps their pond mostly full. Perhaps their sand layer is absent, and they just excavated into the clay and created a surface run-off (watershed) pond. You should be able to determine if they have that type of pond from the satellite images. The pond should be in a topographic depression and have a more or less straight dam on the low side.

Keep gathering more info and posting on Pond Boss. We will try to help you as much as possible. (I am a geologist, not a pond building expert. So the more accurate information you can give me about the ground materials, the more accurate estimates I can give you about how they will react to your construction operations. However, remote information given over the internet is never as valuable as the advice given by a good pond-builder that is on location. The hard part is determining if you have a "good" pond builder!)

Good luck on your future pond! I hope you can manage to pull off some favorable outcome.

Thank you everyone for all the information! I know I've still got a long road ahead, but getting these questions answered makes me feel much better.

I did talk to my closest neighbor, his pond is 3-4 acres and is 550 yards west of our proposed site. He said his pond was built by selling the sand (as FishinRod mentioned above). He's had more sand removed every few years. I haven't asked him yet if he found clay at some point. But he doesn't seem to be super into the pond as far as being concerned with the details.

I should add that we had soil borings done near our pond. Closest one was about 25 yards north of the proposed pond edge. The soil borings were part of an environmental study we had to have done when purchasing the property. Our property has an old township dump on it (also no soil can be removed from the property, i.e. sand). I asked the environmental consultant what type of soil was in the sample near the pond area. They said there was "a silty type of clay" about 10 ft down. These borings were done at the grade, not in the basin, which would put the clay in the basin only about 5-6 ft below the current sand level in the basin (I'm hoping).

I left a voicemail with the local NRCS office today regarding watershed information. Hoping we can get a mini ex to dig some samples yet before winter. This last spring/early summer (which was a dry one) it was June before we were be able to get any type of equipment out into the pond area due to it staying wet.

I attached a couple pics just for the heck of it. The October picture (taken standing on North side of pond) from last weekend is current state of basin. Only two 1-2' deep water pockets are present, one right up front and one way in the back. The March picture (taken from West side of pond) shows how much water it has in the spring. The island that was left is about where the pile of sand is we have since created shown in October pic.

I'll post an update when I hear back from NRCS. Thanks!

Other than the dragline guy, have you contacted any other local pond digging companies? They would have local knowledge. I talked to a number of companies in the southern LP, and all were using long-reach, 60' excavators. PM if you would like some info.

Yes, I did get a quote from one other pond building company that uses the traditional excavator. I'll shoot you a PM too. Thanks.

Do you have some place on the property to place a big spoils pile of sand?

The long-reach excavators can't move as much material per dollar spent, but they sure do have some flexibility in creating some depth in awkward places.

I haven't done the spoils math yet because we haven't decided on a final size of the pond yet (depending on final cost, right now looking at 1.0-1.5 acres). But I do know we have about 1/2 acre of land that wraps around a side of the pond that needs to be raised up about 6 feet, and another 1/2 acre of land around another part of the pond that needs to be raised up about 3 feet.

This area of our property is real wet in the spring, so we're trying to make a high and dry spot for each of us to put up a mini cabin. And directly behind these spots we have about a 2 acre clearing that we'd love to add more dirt to as well. I know the closer to the pond the better, so that would be a last resort.

I wish we could sell our sand, but due to the old township dump on our property, the entire parcel (160 acres) is currently considered "contaminated", so no dirt is allowed be taken off the property.

re: adding dirt. If you want stuff to grow on it. use a bulldozer, scrape off the top 2'-3' of soil (before you hit the sand) stockpile it, spread out the pond dirt, put the topsoil back on top. That's the only way you will be able to grow on it.

I agree with esshup on the good dirt. If you collect any good topsoil on your property while using heavy equipment, try to keep it separate from your sand spoils as much as you reasonably can.

It is way easier to make attractive surroundings with good dirt that you only have to move 50 yards, compared to trucking in topsoil.


P.S. Have you taken any good water samples from your pond and submitted them to a lab to check the levels of the known contaminants on the property? I would hate to see you spend a lot of money on a pond project, only to find out that your pond water cannot support fish, or that you cannot eat any of the fish you catch.

Further, if the pond property is "contaminated" to some government standard, but not so contaminated that it would affect recreational usage, then I would warn that piling up sand MIGHT facilitate the release of essentially immobile contaminants into your pond water or new hunting cabin yard.

Contaminants in ground water can become static and stay in place near the site of the original pollution source. Especially if there is very little gradient for movement or subsurface flow of the ground water. However, if you excavate water-laden sand that is polluted and place it in spoils piles above grade, then the sand will be subject to flushing by each subsequent rain event. Over time, you may wash all of the contaminants out of the piled sand and mobilize them into your pond water. (Depending on the type of contaminant and some other variables.)