Good morning, everyone. I'm in the process of planning out an approximate 1/2 acre bass pond for my 5 acre property.
The general layout pictured is my rough idea. It will be fed by a dry creek bed that will run 300' or so along a swale on the edge of my property, catching rain water from my garage and house(bottom of picture). The overflow will likely be at the back of the pond and run over to a ravine inside the woodline that goes down to the river. I'm pretty sure that we get enough rain and runoff to fill the pond and keep it well full, as well as a high water table(I think), but am not opposed to digging a well to keep it fed.
The plan is to have it about 10-15' off the tree line along the west, possibly drop a decent sized tree in the middle for habitat, and end up with a depth in the middle of about 10-12'. I'm in NE Ohio and we have a ton of clay in our soil. Was thinking the clay layer, 12-36" can be dug up and then used to line the bottom of the pond once it's dug to depth.
My brother suggested having his buddy come out with a small excavator and dig a test hole, about 10' across and 5' deep, just to see how it holds water. Lol
Any input or suggestions would be appreciated. Thanks.
You can either have a sealed pond or a water table pond.
Normally a sealed pond is filled with surface water that is collected to the pond location. OTOH, if your pond still has a connection to the water table, then that is always going to be the equilibrium water level in your pond.
Your test hole idea is a "must have" requirement before planning your pond construction project. However, you need some modifications.
My property has about two feet of good topsoil, then the subsoil starts grading into more clay-rich material. Down about six feet, I usually strike a layer of sand. It might be two inches thick, it might be two feet thick. Either way, groundwater immediately starts filling my hole as soon as the sand layer is cut with the bucket. I can then dig several more feet into a pure clay layer.
Overnight, the excavator trench will always "hold water" due to the clay bottom. However, the water level is usually just a few inches above the layer of sand. That would then indicate exactly where the water level would be in my pond if I made a water table pond in that location. Six feet below the natural ground elevation is usually an ugly pond. However, if you had very thick sand layers, and no clay, then that would be the only type of pond you could build (without a pond liner).
However, if you have clay available at your pond location, then a correctly constructed pond with compacted clay lifts can seal off all of the sand layers that are connected to the groundwater.
I would just use the excavator to dig some simple bucket-width trenches. With no loose material in the hole, take samples from the bucket and keep a log of the material at 6" intervals. You can tell topsoil from sand layers. For the stuff in between, try to make a small snowball out of moist material. If you can do that, mark that layer as clay bearing. If you can then roll the snowball into a snake in your palms, mark that layer as clay. If you can feel sand grains in your palms, mark it as sandy clay.
Also note any other personal observations, including color. You don't have to be a perfect geologist, you just need to be consistent in your descriptions. Your subsoils may be uniform throughout your pond basin area. However, they may be highly variable.
I would take as many samples around your pond basin as time permits. However, if you don't have any rocks or hardpan, then you can excavate a trench down to max. equipment depth pretty quickly. Can you leave one trench open overnight? (No people, cattle, dogs, etc. able to fall in!) The overnight water level will give you a decent estimate of your water elevation for a water table pond. (Unless your water table is highly variable over the course of a year. In that case, it is only giving you a "snapshot".)
Several other issues:
1.) I don't see a topographic map. If you are actually building a dam in a dry creek bed, then you will probably get TOO MUCH WATER. That sounds like a strange problem. However, a 4" rain can turn a dry creek bed into a raging flow that is going to try to do everything in its power to rip out your dam.
2.) Excavating a 1/2-acre pond is going to give you a lot of material (spoils) to dispose of on your farm. Do a rough calculation of your pond volume, and then add 20-25% more because spoils always get bigger (fluff).
Good luck on your new pond project! I hope the info above gives you some additional thoughts while you are putting your eyeballs on the project.
Thanks for all the information. I'll definitely chew on all of this as I plan things out...
I plan to have an expert come and assess my plans before I do anything, obviously, but I'd like to have my ducks in a row.
The topography of my property is mostly flat on the front half. A very slight grade down towards where the pond will be... The pond area drawn on this picture has about 30" of fall from west to east on the map. The idea it to have kind of a hybrid of excavated/embankment dam on the east side, utilizing the material dug up for the pond itself.
We've only got about 4-6" of topsoil here, if that... it totally sucks for gardening and whatnot but I'm hoping it's a silver "lining" for the pond. Lol
Deepest holes I've ever dug were 3' or so for post holes and it's pretty much nothing but clay after about that 4-6" mark.
A little ways, about 100' or so, past the north end of my pond layout, the yard starts to grade down towards the river, a drop of about 30' in elevation over 300', give or take. After some recent research, I've found that our water table is estimated to be at about 30' depth or so in this area. Good information if I ever have to dig a well to feed the pond, but just from hearsay, ponds in this area don't need much help staying full. *shrugs*
As I said, I won't do anything until I talk to someone locally with experience, but I will start mapping everything out and dig a test hole or two.
The dam and the area around the pond basin will be all clay after the pond is constructed. You need to get good topsoil over all of that and seed it ASAP after finishing the pond to prevent erosion from carrying your clay back into the deep spots of your pond.
