The existing pond was small, but seemed nice for watering livestock.

Michael Gray is an outstanding builder of ponds and earthmover near Nashville, Tennessee. A few years ago, he was called in by a local landowner who wanted to renovate and enlarge an old farm pond.

Michael and his dad met up with a recently retired Lt. Colonel in the Army who was ready to retire and move to the farm. Upon retirement, she wanted to be able to see a beautiful pond and go fishing every day.

The pond was about a quarter acre in size and seemed to hold water fairly well…which is always a good sign for guys who build ponds. They have an innate fear of leaky ponds, especially ones where they and their equipment are involved.

The problem all around Nashville is rocks. They have plenty of rocks around and under the soils there.

We decided to excavate a new core trench to build a bigger dam.

During their meeting, Michael and his dad noticed a number of things. The pond was quite old and likely had siltation. They also noticed heavy erosion due to cattle tromping around the pond edge for many years. The dam seemed well built, especially since the pond seemed to holding water quite well. Slopes were still pretty good along the dam and the spillway was more than adequate. It showed minimal erosion.

They met several times, discussed several options and then came up with a plan.

They decided to raise the dam, which meant the pond would grow as large as two acres, a substantial size increase. They also decided to check the core of the existing dam, especially since new dirt and water would mean added weight to the smaller, existing structure. Plus, with a new core, the pond would be less likely to leak with the added head pressure from water.

Alas, as we excavated, we did find several places where water was obviously seeping through the dam.

The time arrived to go to work on the project. They drained the pond to a workable level and began removing topsoil from the pond area. As work progressed, Michael thought it was time to have a look at the inside of this dam. He started digging into the embankment hoping to find a nice core and all the good things a pond should offer, along with great fishing. But, what he found was a mixture of topsoil, gravel, clay, and mud. He had to break the news to the Lt. Colonel that the dam would need a new core, or maybe its first core.

Even today, after quite a few years in business, Michael doesn’t like to be the bearer of this type of news. But, because an earthmover never knows what he’ll find until he digs deeper into a project, he has to be ready to adjust. He made the call, discussed what needed to be done, and moved forward with construction of a new core.

The new core trench is shaping up.

As he dug the new core, removing all the poor material and breaking out a few layers of rock, he could see where the pond had been leaking over its life. From its seemingly steady water level, he didn’t expect this pond leaked. Not only was there slimy pond mud in and through the sand and gravel that was on top of the rock, it had also oozed in-between the rocks. He finally reached a good, solid rock foundation. Feeling good about the core trench, he cleaned it up, and got rid of all the loose material lying on top of the rock. Then he and his crew started backfilling the core with good, compactable clay excavated nearby.


A new problem cropped up. We found a rock outcropping in a side of the new part of the dam.

As they moved forward, raising and widening the dam up out of the ground and reshaping the inside of the pond, a new problem reared its ugly head. Seemingly out of nowhere, they started hitting all kinds of rock on one side. At first, Michael thought this might be good rock that would make an excellent fish structure, but this didn’t turn out to be the case. As more rock was uncovered, it revealed roots going into the rocks, caked topsoil, and all sorts of junky soils.


Rock was removed and the spot sealed with clay.

Once again, he had to make the call to the Lt. Colonel and explain what was going on. He explained what was found and talked about what was going on. A core trench in most cases will seal the pond. But in some locations, such as this one, the type of rock they were dealing with is a real problem. It’s a karst form of limestone, commonly found in areas of Tennessee, which weathers and erodes underground. The rock has all kinds of crooks, curves, and holes that want to take water away and leave a dry hole in its wake. He explained they would have to cut the rock out and reseal the side to prevent it from leaking. He originally thought they would have to buy rock for the spillway, but were able to scratch off that expense because they had truckloads of rock coming out of the pond that could be used for riprap. They reached an agreement on the rock problem and moved on.

Pond finished and ready for water.

After the rock was removed, they moved forward sealing this portion of the pond. They spread thin layers of clay in six-inch lifts and compacted it to get the proper seal. Once the area was sealed, they continued to build the dam in similar lifts with compaction. After the dam reached the desired height, they installed pipes for the principal spillway. Then an auxiliary spillway was cut for times when pipes couldn’t handle heavy rain events. When all the construction was complete, they spread topsoil around the pond area above the water line and added the walking trail the Lt. Colonel requested. As soon as it fills with water, she will have a beautiful pond and will be able to fish every single day, just as she dreamed.

By Bob Lusk with Michael Gray