PIERCE
LAND
CLEARING
A pond that drops all summer is not always leaking. Here is how to tell the three causes apart from the bank in a week, which one bentonite fixes, which one needs a dozer, and what each repair costs at our published rates.
Set a five gallon bucket of water on the bank next to the pond and mark both levels. A Texas pond loses a quarter inch a day or so to evaporation in July and August, and the bucket loses the same. If after a week the pond has dropped an inch or more further than the bucket, water is leaving through the ground or the dam, and that is a repair. Seepage through the basin is fixed by sealing, most often with sodium bentonite worked into the floor and banks, and on a half acre that starts around one truckload of clay plus machine time. A leak through or under the dam is a dirt job: the dam is opened, a compacted clay core is built into it, and it is closed again. A pond that was dug too shallow in porous ground usually needs both, which is why the Lockhart pond we rebuilt in September went deeper, steeper and sealed in the same four days.
Most calls we get about a pond that will not hold water start with the wrong diagnosis. The owner has decided it is the soil, or a neighbor has told them it is the dam, and neither has measured anything. The fixes cost very different money, so the week you spend with a bucket is the cheapest part of the whole project. This page walks through the test, the three causes, and what we do about each.
Fill a bucket with pond water and set it on the bank, level, where it gets the same sun and wind as the pond. Drive a stake at the water line of the pond and mark the level, and mark the level in the bucket. Leave both for seven days with no rain. Then read them.
The bucket can only lose water to evaporation. The pond loses water to evaporation plus whatever is leaving through the ground and the dam. So the difference between the two drops is your leak, measured in inches per week. In a Central Texas summer the bucket will drop about an inch and a half to two inches over the week. If the pond dropped two inches, you do not have a leak, you have August. If it dropped four or five, you have a leak worth fixing. If it dropped a foot, the pond has a hole in it somewhere and the next job is finding where.
Do the test in dry weather. A rain in the middle of the week ruins the reading, because the pond catches runoff and the bucket does not. And do it in summer if you can, because that is when the losses are largest and easiest to read.
A pond in this part of Texas gives up somewhere around five feet of water a year to the sky, most of it between May and September. A shallow pond feels it worst. Six feet of water at center in June can be three feet by September with nothing wrong at all, because the same inches come off a shallow pond as a deep one and the shallow pond has fewer to spare. Wind across open water adds to it. A pond with no trees on the south side in a bare pasture loses more than one with some shelter.
The fix for evaporation is depth, not sealing. Ten feet at center gives the pond cool water under the warm layer and enough volume that a dry summer takes the level down instead of taking the pond. Our published pond price list is built on six feet of depth, and when we walk a site with an owner who has lost a shallow pond to summer, the conversation is almost always about going to eight or ten.
This is the one bentonite fixes. Water moves down through the floor and out through the banks because the soil has more sand, silt or gravel in it than clay, and the pore space between the grains lets water through. It is the common failure on the sandy ground across Bastrop, Caldwell, Lee and Fayette counties, on the gravel benches along the rivers, and on any Hill Country limestone site where the basin was cut into fractured rock.
The signs are steady loss with no wet spot anywhere, a pond that fills with a big rain and is down again within weeks, and the same rate of loss whether the pond is full or half full. A seeping pond does not usually show you where the water goes. It just goes.
The repair is to seal the soil. On a drained pond that means spreading sodium bentonite across the floor and banks at a rate matched to the soil, tilling or blading it into the top four to eight inches, and compacting it. The clay swells when it wets and closes the pore space. How much you need, and what it costs with our trucks and machines, is worked through on the bentonite sealing page, which has a calculator. If the pond is also too shallow, sealing it as it sits is money spent on a pond that will still lose most of its water to August, and the honest answer is a rebuild that goes deeper and seals in the same job.
A dam leaks in three ways. Water moves through the fill because the dam was built by pushing loose dirt up in one lift instead of compacting it in layers. Water moves under the dam because no core trench was cut into solid ground before the fill went on, so it travels along the old topsoil line. Or water moves along the outside of a pipe, a drain or an overflow that was set through the dam without a proper collar, and slowly cuts a channel around it.
The signs are a wet spot or a soft place on the downstream face or at the toe of the dam that stays wet in dry weather, cattails or willow growing in a line below the dam, a small flow you can see in the creek below it after weeks without rain, or a whirlpool near the pipe when the pond is full. A dam leak often gets faster with time as the channel opens up, which is why it should not wait.
The repair is dirt work, not clay. The dam is cut open along the leak, a trench is cut down into solid ground, and a core of good clay is placed in compacted lifts before the dam is rebuilt over it. A pipe leak means pulling the pipe and resetting it with anti seep collars. We do this work with the same dozer and excavator that build a new pond, and it is quoted after a site walk because no two dam leaks are the same size.
| What you see | Most likely cause | The fix |
|---|---|---|
| Pond and bucket drop about the same, level falls all summer, refills with rain | Evaporation on a shallow pond | Deepen the pond, no sealing needed |
| Pond drops well past the bucket, no wet spot anywhere, loses water at the same rate full or half full | Seepage through the basin | Bentonite seal, or rebuild and seal if it is also shallow |
| Wet spot or green line below the dam in dry weather, flow in the creek below, level drops fast when full then slows | Leak through or under the dam | Open the dam, cut a core trench, rebuild with a compacted clay core |
| Whirlpool or bubbling near the overflow pipe, wet channel along the pipe outlet | Piping along the pipe | Pull and reset the pipe with anti seep collars |
| Pond built by a previous owner or contractor, never held water from day one | Usually shallow and unsealed on porous ground, sometimes a dam with no core | Rebuild: deeper, steeper banks, sealed, dam rebuilt if needed |
The last row is the one we see most. A pond that has never held water was almost always dug fast in the wrong soil with no attention to the dam, and the owner has been told it will “seal itself over time.” It will not. The Lockhart rebuild is what that job looks like when it is done right.
Every number below comes from rates we publish on this site, not from a national average.
Sealing. Sodium bentonite comes to the site by the truckload, 21 tons a load, and a job takes whole loads. A half acre pond on sandy silt at the supplier’s rates needs about 24 tons, which means two loads, and a quarter acre on the same ground fits in one. The clay is spread with a skid steer and worked in and compacted with a dozer, and the dozer starts at $3,000 a day plus transport. The day count depends on the pond and is set on the site walk. The calculator gives you loads and a starting number for your pond.
Dam repair. Quoted after a site walk. It is dozer and excavator time at our published day rates, and how many days depends on the length of the dam and whether a pipe has to come out. We will tell you which on the walk.
Rebuild. A pond that needs to go deeper and be sealed is priced like a new pond of the finished size, with the old basin stripped first. Lockhart, a half acre rebuilt to ten feet with a bentonite seal, ran $20,000 to $22,000 over four days. Paige, a half acre taken two feet deeper where the cut reached clay, ran $9,000 to $10,000 over three days with no bentonite at all. Rosanky, a mud hole rebuilt as an acre and a half 15 feet deep on a site that actually catches the creek, ran $50,000 to $55,000 over thirteen days. Our price list starts a new half acre at $19,200 for six feet of depth.
Roughly a quarter inch a day in July and August to evaporation, more on a windy open site. Over a month that is six to eight inches with nothing wrong. A pond losing that much a week has a leak.
Sometimes a little, as silt settles into the floor, but a pond that is losing water fast through sandy or gravelly ground will not fix itself. If it did not hold water the first year it will not hold it the fifth.
Bentonite can be sprinkled onto the surface of a full pond and some of it settles into the leak, but it is the least reliable method and uses the most clay. We seal drained ponds, where the clay can be worked into the soil and compacted. Most owners let the pond go down over a dry stretch or pump it before we arrive.
For a large ranch pond a liner is expensive, easy to puncture with cattle and equipment, and hard to repair. Bentonite becomes part of the soil and can be added to later, and it is what we use.
That usually points at the dam or the top of the banks rather than the floor. When the water is high enough to reach a weak spot in the dam or a porous layer near the top of the bank it leaks, and when it drops below that layer the loss slows. The bucket test at two different levels will show it.
No. We do not dredge a pond with water in it. Once a pond is drained we clean out silt, deepen it and reshape it with a dozer and excavator, which is the rehab work described on its own page.
Send the pond size, how much it drops in a week and a photo of the dam, and you get back which problem you have and a starting number for the fix.