Pond Boss Forums POND CONSTRUCTION Soil questions Test hole?

I have a water well no more than 200 ft. from the proposed pond site. The soil sample report the water well company gave me said I have yellow clay from 2-17 feet gray shale after that. All the neighbors have about the same soil sample with their water wells.

Three ponds close to the area that all hold water one is no more than 200 yards away.

Should I dig a test hole at the spot I want to put a pond?

The more you know, the better decisions you make. I would dig test holes at pond site. Well logs are really helpful, but I have seen dirt change within feet, especially in low spots where ponds are built. It will cost a few dollars to dig test holes with a backhoe, but it will be well worth it to know where your soils are, and how you can use them to build the pond.

Thanks for the reply Mr. Lusk. I will do it.

By the way thanks for the forum & magazine, They're wonderful sources of information.

Glad to do it. Pretty fun stuff...and this forum has some amazing people with fabulous knowledge. Every time I come here, the learning curve is steep.

As always Bob gives great advice. Your profile doesn't list your location but if you are in a glacial terrain like Michigan, it is not unusual to have 20-feet of clay and move 50-feet in any direction and have 20-feet of sand & gravel. If you knew that the clay was a part of a former lake bed sediment, you could have a little more confidence of it being laterally extensive.

Stream channels that once drained an area can end up being buried creating sand and gravel seams. They can meander all over the place, become braided channels and reform back to a single channel. Just imagine any little creek that you've seen. It doen't take a very thick seam to cause a significant pond leak when leakage occurs nonstop 24/7. Test pits are a great idea.

I'd make a few trenches (not just holes) perpendicular to the long axis of your pond. You may not see the actual sand layer but if you get seepage into the pit, you'll know its there. Leave the trenches open for a little while so that you can look for seepage.

I dug the test holes. Soil in all test holes was suitable for a pond with no need to bring in any from outside sources. The problem I ran into was the ground water. We had close to 67 inches of rain last year and 6 inches already this year. The holes were dug about 12-14ft deep and about 7-8ft the ground water was coming into the hole. The contractor said he was able to do the pond now, but he would wait until August or September to be safe, if he were me. He said it would take him longer at this point than if he waited till the ground water lowered. I decided to wait until late summer. This information the contractor gave me sounds about right. What do you think?

Well, I would be a little concerned. You indicated that groundwater seepage occurred into the excavation at 7-8 feet below ground level. How high did it rise? If it rises to near surface you may be able to have a groundwater fed pond.

Keep in mind that the seepage came in via permeable conduits (probably sand seams), which will also allow seepage to occur in the opposite direction. If you are in a high water table condition right now as the contractor indicated, the water table will be lower during dry months. How much lower is the question. If your pond is hydraulically connected to the regional water table, it will always try to equilibrate to that level, so there is potential that it could drain down to that 7-foot level if the water table falls that low (or lower).

You may need to seal this seepage layer to prevent leakage. It depends on the extent of the permeable seepage layer and whether it is hydraulically connected to a larger groundwater reservoir that could accept your pond's volume. Remember that an increase in head (water level) will drive water in the other direction (out).

The proximity of other ponds is a promising sign. I would be more concerned if you are elevationally above them, especially if that 7-foot seepage layer is coincident with the water level of the neighbor's ponds. How were those ponds constructed and what are the water levels in those ponds compared to your property? It would have been nice to pump the water out of the test pit for a while to see if it was a "limitless" or "limited" supply. That would have given you some idea of the reverse seepage potential.

The test holes were dug Friday, and by Sunday the levels were about the same depth. They did not rise to ground level. They may have been at 6 1/2 ft. below ground level. Some of the other ponds are higher and some lower. 3 out of 5 ponds in our area ( all within 600 yards ) were constructed by this contractor. The other ponds have never gone dry, as the owners have told me, all are about the same depths (10-15 ft). Our property is about about half way down in a small valley (elv. 576ft). We are on farm land that has been used that way for at least 50 years. The fields around us drain toward a man made bar ditch, from there the water goes to ponds down the way. There was top soil about 3ft down, top soil/clay mix 2-6ft, Yellow clay from there.

It sounds like you have thin pressured sand seams within the clay. They are fairly common in clay soils in Michigan. During the summer time you can drill a hole and have no water down to 20-feet. During the spring or fall a hole at the same location may have a water level that is actually above ground level. Unfortunately I'm usually dealing with contamination and this process will smear contaminants across the entire range of fluctuation increasing cleanup costs.

The quantity of water is generally small and there is usually little or no connection between sand seams. The water is considered "perched" and not in connection with the regional water table. You can get a better look at this when you excavate. The amount of sand present can be quite small.

Based on the scenario you describe with the neighbor's ponds and an experienced contractor it sounds like there is a high probability of success. He would have quite a mess in that clay if he started the project before things dried up. If leakage occurs, you'll know the most likely depth/location. Now that's a lot of speculation on my part!

Good Luck with your pond project. Please keep us updated on how things work out.

Grandview, Texas, is in the blackland prairie of Texas. On top sits clay type topsoils, rich and fertile. Those topsoils extend from a few inches to several feet. Most of the time, blackland prairie land sits atop heavy clay based subsoils. Water tends to percolate slowly, then run laterally into watershed creeks. It's not unusual for water to slowly percolate from above, and collect in test holes, especially when we have consistent wet weather as Grandview has.
The main reason your contractor wants to wait is to be most efficient doing what he does. Moving wet dirt is more expensive than moving moist dirt.
As expansive as the blackland prairie is, it's not as likely to see sand or gravel seams, except where prairie meets direct drainage into a creek or stream. The water you have is not actually ground water, rising with an aquifer. It's moving from the top down, slowly.
Blackland absorbs water like a sponge, then slowly releases moisture. Remember how that dirt cracks when dry?
Study what Steve has written. He knows much more than I do. At the same time, learn more about your subsoils. That's where you decision comes from, while working with a competent contractor. It makes sense to get your local soil survey from the NRCS, study it, and then make a decision with your earthmover.

Thank you both for the information, I will go to the NRCS and get as much information from them as a can. They have not been that helpful in the past. The soil in the summer can get cracks as much as 3 inches across, But when wet sticks to you like glue. This is just a blessing, I need to get all the information I can before I get started. This forum and the books are going to help. I can wait to have something my family and I can enjoy, rather than despise. I will let you know what happens along the way.