Pond Boss Forums POND CONSTRUCTION Soil questions Springs? Asset or Liability

I am still cleaning out some of the topsoil from valleys and etc. in my lake (more info. under Building a Dam). I have topsoil about six feet deep in many spots... Which leads me to a dilemna...

In cleaning some topsoil out of a ditch, I noticed water coming out. Overnight, it filled up some and I'm thinking it is a spring (there are a lot of springs in the area).

I am enthused about the potential upside of having springs, but I am concerned about the possibility of having a large siphon (spring) near the bottom of my lake.

I could probably fill the area back in with clay and pack it. It would have about 25' of water above it so lots of pressure. Should I fill the area with Clay and forget the topsoil or dig out the rest of the topsoil and not worry about the spring becoming a siphon?

Thanks!

Any geologists or engineers on board?

Rangersedge,
I'm no geologist or engineer & I don't play one on the internet. I was waiting to see if someone with experience would respond. But I do have an opinion.
If it were mine I would have to remove the topsoil. I would have to know what I was dealing with. The topsoil, unless it is clay shouldn't be able to contain the spring if it is very strong therefore the soil around the spring should be saturated. If not it must be a small spring at the point of entering the topsoil which will hopefully be easy to seal and I would rather not have a layer of topsoil between the spring & my clay liner.
Just my opinion ...
Ric

i have to agree with ric s. it sounds a lot like my experience. had a spring in what was to be the 26 foot or so deep end. it was putting out lots of water in middle of summer (is the spring producing in the heat of summer?) i initially was concerned like you were, and had the dozer guys pack 2 feet of clay over the spring. overnight it had pushed through it...they wound up building a small levy about 3 feet high to contain the water so that they could work in a dry area. when they filled in the dam, the spring was about to start pouring over the temporary mini levy! so, if your water source is running water in middle of the heat of summer, and you pack it and it busts through, my own experience is..it will add to your pond and not back flow somewhere. the water level within a year was 23 feet. no major leaking problems. i could also drive around in the boat and actually feel the area that was cooler around the spring "central" compared to the rest of the pond. good luck. hope this helps. mark

Thanks for the input.

Even though no water was on top, when I ran over the topsoil in the area with the tractor and dirt scoop, they tried to take the short cut to China. That is why I started with the trackhoe.

I will dig out a bunch more of the topsoil and either take my chances with it holding water or try to pack it with clay.

I have lots of clay in the general area so it would be easy to pack if it won't fill up over the spring level. Therefore, that isn't really a concern. My main concern is that it would become a relatively slow & constant leak when the lake gets near full.

I'm somewhat inclined to dig out the topsoil and take my chances. What are the upsides and downsides to springs?

Thanks!

I cleaned out a very small pond with a backhoe and hit a seep spring. It seemed like a good idea at the time (springtime). However, rain can get scarce in North Central Texas and now it is a liability.I used a hose to put some water into the pond. It went down a lot quicker than usual. I aasume it is seeping backwards.

Dave: That is my fear. Mark is fortunate to have such a strong spring. I wouldn't worry if mine flowed that well, but mine is more of a seep from a wide area. Ric's point about clay serving as a much better barrier than good topsoil is spot on. I guess the logical thing to do is dig the topsoil out more and see what it looks like then... I have plenty of clay to pack back into it if necessary. Thanks! Jeff

rangersedge, i am not sure...i initially thought your spring was at the deepest spot...which at 25 feet would be a lot of pressure. or is it seeping out at the level of near full stage (less pressure?) also, is it in a flat area, or is it on the edge of a hill? if it is not in the deepest part, i would think you could give it a shot and see what happens. if the water drops down below it, then cover it up later with clay/bentonite or whatever. i was really lucky to have a strong spring...there are 2 other small springs around the property that are dry during summer...if i had built the dam past those, probably would have the dilemma you are facing...tough decision...i'd say totally depends on where in the depth your spring is located and flat/or hillside. mark

Mark: There are a lot of small springs on the property. The ones which I uncovered will have about 25 feet of water over them... Well... Make that between 22 and 25 feet of water. They are in a valley between the island and the north bank. The water is currently about 8 feet in deepest part and this portion would be under about 6 feet of water if not for some dirt blocking water from getting to the area where I dug out the topsoil. Jeff

Rangersedge,
Is it possible that the "spring" is actually comming from the captured water on the other side of the dirt barrier through a fisser or possibly a tree root?
Ric

Ric: That is possible, but I don't think that is the case in this instance. The water is coming from the side nearest the north side of the island. I now have water coming into where I've been digging from the same side many places down that valley with some of those places being above current water level. Jeff

rangersedge, can you recall if the springs were running in the heat of the summer? if not, then i think i would do my best to pound them over with clay.

As best I can remember, the ground around that area was very "mushy", but not really wet.

Unfortunately, today was the first time that I read this thread but its a good topic so I'll try to answer. Hydrogeologists rarely if ever use the term "spring". Instead we think about aquifers, which can be loosely classified as water table, confined or "perched". The concepts are really simple but of course there is quite a bit of jargon.

Oversimplifying there are basically two things that will determine whether the "spring" will add or subtract water. The first is the vertical and lateral extent of the permeable material (aquifer). If it is an isolated sand lens that is surrounded by clay, there is little potential for water to move in or out of your pond. If it is a thick aquifer that has a regional extent there may be great potential for water flow. Think of this as the diameter of a pipe. The larger the pipe, the more flow. You would need to install borings, test pits or look at water well records to evaluate the capability of the aquifer (transmissivity).

The second major factor is the hydraulic head or gradient. Confined aquifers generally have a hydraulic head that is elevationally higher than the top of the aquifer. This is due to pressure from overlying sediments, or because the aquifer is hydraulically connected to upland areas that have higher water levels. Groundwater moves from areas of high head to low head (downgradient). Note that downgradient can be up! If you cut through the confining layer water flows out because of the higher head, which is sometimes called "artesian" or a "spring". If you were to put a drive point or well in the permeable material that is creating the spring, the water level would eventually stabilize in the well and you could measure it. If the stabilized water level in the well is lower than your expected pond level (it sounds like it would be), then there would be the potential for the pond to leak. The rate of the leak is determined by the size of the hole (diameter of the spring), the difference between the pond level and the hydraulic head of the aquifer (gradient) and the transmissivity of the aquifer. The higher head of the filled pond forces water out through the spring and into the aquifer.

If the water level is near the expected pond level, it would fill your pond, and if enough water was available, it could keep the pond full all year with relatively cool water (groundwater temp is equal to your area's mean annual temperature). Also realize that the water is coming from somewhere and it is possible that wetlands or ponds upgradient from you could go dry when the "plug" is pulled. When the pond level is equal to the head of the aquifer you have reached equilibrium and there is no flow in or out. Of course natural systems never attain equilibrium because of rainfall, evaporation, leaking confining layers, etc., so there is always a small potential in one direction.

From the above discussion, my guess is that you hit an isolated seam, or an aquifer without much head above your 25-foot depth. Adding 25-feet of water will put some stress on the system. The safe thing to do would be to patch it. Sorry about the long post, hope that helped.

Steve, thanks for the info....very informative and interesting. your expertise will prove to be very valuable to people on this site, including myself; appreciate ya. mark

Thanks for the additional responses. It is now muddy / slick enough that I can't do much more to it and the potential "spring" areas are now under several feet of water. I am planning on draining as much as possible (down to the ten foot level probably) from the pond next spring or early summer to do some additional work on the lake. I can look at digging the topsoil out more and packing clay at that time or possibly might be able to determine that it isn't leaking. Frankly, at this point, I'm hoping for the latter. I don't know how long the soil will take to dry out enough to do much after being underwater for a few months.

Well done, Steve!

Steve,.....that was a work of art!