Pond Boss Forums INTRO Questions & Observations Need Advice on Soil Probes & Sampling

I have tried for over two years to get my local NRCS guys to came out and take soil samples for our potential pond locations. I don't think "in a few months" is ever going to happen!

I always dig a few test pits on the farm every time I am doing some work with a rental backhoe or mini-excavator. I have a decent idea of my soil profiles around the farm.

However, the soils at my best pond locations are generally loamy sands that have an increase in clay content with depth. However, this soil WILL NOT hold water. Fortunately, I have a good layer of blue clay at depth in many locations for potential ponds.

To create my excavated ponds, I am going to have to create clay blankets in lifts for the sides of the ponds. I suspect this will be much easier to do when I have blue clay from depths of about 8' to 14'. I can excavate to the pond design depth without punching through my bottom seal, yet still have enough clay to seal the sides.

While planning this work, I realized it would be very helpful to have extremely accurate soil samples so I can pick my best sites and NOT excavate a 1-acre hole that I cannot seal.

My latest idea is to hire a nearby firm with a geoprobe unit and take lots of samples while I am still in the planning stages. (This method essentially vibrates a hollow rod into the ground. You then pull out the soil sample in a clear lexan sleeve for examination.) This testing will be a little pricey, but I think it will be worth the investment.

Does anybody have any recommendations on how to optimize my soil sampling? (As regards the procedures, sampling grid, etc.)

Did anyone encounter difficulties with this method?

Does anyone have any alternative suggestions?

Thanks,
FishinRod

Does the soil profile vary that much across your place? I ask because I have 4 ponds on my place in central Indiana and ran into the same general soil structure on all 4. For me, the biggest challenge was random sand veins located pretty deep running through my clay. They got interrupted by the dam core on the first 3 ponds (4th pond is still down 30" from full pool and has not gone through a Summer yet). No idea how much the soil cores might cost, but do you think your soil structure varies that much over relatively short distances? Sorry that I can't really help with your current plan on taking cores, but I wish you good luck!

RAH, thanks for the input.

Yes, my soil profile and lateral heterogeneity appear to be highly variable, based upon my sparse sampling.

I have hit some sand veins that were 2' thick. I have also failed to reach good clay in some of my holes. (However, I could only get down about 8.5' with the mini-excavator.)

There are "wet spots" in our prairie grass areas that have sedges and willow trees growing amongst the grasses. I am pretty sure those areas have a solid clay layer below the permeable soils. I have hit solid wet clay in all of the test pits in those areas.

However, running a dozer and excavator combo on wet clay at the bottom of the hole is going to add a significant amount of time/money to the pond excavation.

I am hoping to have some basal clay in the drier areas, but that might be the reason they are drier!

I am pretty sure my project will be like your first three ponds - I am going to have to seal off some sand veins. I am just trying to make sure I have the materials at the excavation site to accomplish that goal!



P.S. How far apart are your three ponds? I think you watched the excavation in a few of yours. How much variability did you observe in the "bowl" of your ponds before the dirt guys started re-distributing the material?

I built the second 2 ponds myself and watched the first 2 being built. All had similar soil profiles. Blue clay about 10 feet deep but with some sand veins running horizontally like old creek beds. My furthest ponds are about 1/3 of a mile apart with other 2 about equally spaced in between.

You said the dam cores cut off the sand veins that were running downslope.

Did you have to seal the "sides" of your ponds, or was the dip of the soil beds steep enough that the dam core trenches cut off the water flow that was moving through the sand veins? (Such that water could not move laterally from your ponds and then down slope past the outside corners of the core trenches?)

P.S. Were the sand veins in the soil horizons above the blue clay later, or actually running through the clay layer?

The sand ran through a red clay layer over the top of the grey clay. In one pond an entire sand lens (1/4" thick) separated the two clay layers in addition to having some sand veins. The core trench was deeper than the sand veins and lens so it cut off the exit routes. The sand veins were functioning like field tiles before the core trenches blocked them off. There were also some sand "pits" filled with water that acted like quick sand, so that was a bit scary. I actually got the dozer stuck in one quick-sand pit halfway down the slope on the non-dam side of my 3rd pond and had to dig out on the slope below to release the water so I could get past it with the dozer heading down hill (fortunately that pond had a bottom drain). On my second pond, the contractor hit a sand vein which spouted water like a fire hydrant and added 3' of water to the bottom of the pond in about an hour (0.9 acre pond). That pond did not get any deeper. On the upper ends of the ponds, the sand veins act as springs. Fortunately, the water coming in seems to always be high enough that my first 3 ponds stay pretty full, even in a drought. Its too early to say how things will work out on the 4th pond.

RAH - Thanks for all of that additional information!

It is amazing how similar our soil profiles are considering the distance between our properties.

Our sand veins also act as springs. However, our surrounding topography is pretty flat. The potentiometric surface of the spring water is just barely above the sand veins.

I would have to dig my ponds 18' deep to have a 12' max. depth below the springs that are 6' below the current ground level.

Our creek has gone up almost a foot in the last two months, with essentially zero rain in the watershed. When the trees and tallgrass prairie go dormant, the cessation of transpiration greatly increase the net flows of the springs to the creek! It kind of freaked me out the first few dry falls.

I too fret over my ponds and potential leaks. I wish you good luck and hope my 4th pond seals too. Next year I only have wetland projects planned.

I suspect you are going to have a lot of fun on your wetlands projects!

I hope you are creating new wetlands. I believe modifying existing wetlands still falls under some strict regulatory requirements. (Even if you are improving them!)

Thanks for the help, and good luck on Pond #4.

Yes - adding new wetlands. Our best wetlands so far were built on former farmland by the Indiana DOT to mitigate wetlands that they removed due to road projects. Instead of accepting compensation, we asked them to build an adjacent "upland" wetland and prairie, The whole area turned out great.