"bobad" has a good comment" Sandy topsoil takes longer to soak, as it will wick the water farther from the pond."
Mike Otto (expert pond builder) says "...but it can take a long time for the ground to saturate when filling for the first time."
Both are very good points. Depending on how well the pond basin is constructed and how well it is compacted it could take a long time for the soils to become saturated with water. Worst case, they may never become fully saturated or the water in certain areas may find a pathway through the pond basin - thus forming a leak that could increase or decrease over time. Generally, tighter denser soils will require less time for saturation compared to more loosly compacted "lighter" soils that take longer periods to become water logged. There are numerous variables here with regards to pond seepage or leakage. As always it all depends.
Pond leakage and or seepage is all about density of the soil, degree or amount of clay and compaction. A soils person once told me all ponds with basins built of soil will leak; it just depends on the degree of leakage. Just one small area of an entire pond basin where soils are more loose or loosly compacted can result in an area where water seepage beyond the pond basin can occur. Obviously the larger the seepage area the more the leakage.
Causes and life histories of leaks are varied. Some leaks can get worse and some leaks can become reduced over time. It all depends.
Obviously the more marginal ones soils for building a properly sealed pond the greater the chance of leaks and then the more the contractor has to, or should take more provisions during construction in marginal or less than ideal soils.
As an example of excellent soils for building ponds, I my area our soils typically have a high quality yellow or even blue clay in the deeper ground strata. These blue clays when properly compacted create a very water tight pond basin. These ponds have almost no measureable or noticable water loss due to soil absorption when the pond is first filled by pumping it full. These new freshly compacted and unfilled basins are often composed of a layer of dark blue-gray, shiny, slick appearing almost rock hard clay. It is diffciult to pound stakes in these well compacted clay pond basins. These compacted clays form a basin that is for all practical purposes impervious to seepage. Water will wick up the bank from the water level, but seepage through the well compacted core trench is essentially none or at most minimal. The exceptions almost always occcr where areas were not well compacted and or contained small pockets of loose grainy soils.
Poor compaction can be due to using improper equipment and or getting in a hurry and trying to compact too thick of layers of soil. Adequate pressure of equipment from compacting soil will only be effective to a certain depth. As the depth or layer of soil increases the effectiveness of compaction pressure applied to the surface becomes reduced with increasing depth. That is why it is best to usually compact layers of soil that are only around 6"-8" thick so the entire layer gets adequately compacted. A greater thickness of soil layers usually results in poor compaction between the two layers. The best compaction tool for soil is a sheepsfoot roller that has many large round prongs of "teeth" like projections. These tools are designed for compacting soil. These "teeth" serve to knit the soil layers together which minimizes water seepage between layers. Water always seeks the path of least resistance which often occurs between two layers or "sheets" of improperly compacted soil.
IMO when you create a pond by just essentially creating a dam from an excavated basin you can expect that there will be at least some areas where the soil in the basin will be loose enough to allow water seepage to excape from the basin. Believing otherwise would be very optimistic.
Many ponds are build utilizing a dam and watershed to help keep the pond full of water. If a pond regularly receives watershed runoff or stream inputs, the affects of pond seepage or leakage is minimized.
For reference, many of the well built, well sealed excavated ponds in my area of Ohio have essentially no or little watershed area and with approximately 34" of rainfall per year the ponds rarely loose more than 12"-18" of water during the summer. Over winter and spring the ponds are usually back to briming full or overflowing via the overflow pipe. The state health department of Ohio now recommends that if the pond is built for DOMESTIC water use, the pond should have no watershed in order to reduce the amount of chemical runoff from the area surrounding the pond.
Ideally when a pond is built, (remember you dig holes and you build ponds), one should create a clay liner or core trench (at least 12 inches thick) throughout the entire basin to optiminally seal the entire basin not just build a dam. The best (and most expensive) pond builders in my area use clay liners (core trenches) 8ft-10 ft thick for excavated ponds. Their ponds very seldom leak. Very often in pond building, you get what you pay for. However, just because you pay a lot of money to have a pond built does not guarantee the pond will be built properly. As always one should get several opinions and estimates and CHECK references when having a pond built. Do your homework it could pay very big dividens and reduce headaches in the long term.
Bottom line, IMO and experience, finding a leak is often more difficult and time consuming that fixing the leak once you know where it is. Also I highly recommend that all those thinking of building a pond or those with pond seepage problems that they purchase the pond building book titled - "Perfect Pond... Want One" by Bob Lusk. See this website for how to order the very educational and informative book. Money very well spent in my opinion.
Last edited by Bill Cody; 03/12/08 08:23 PM.
