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Building a Pond When Soil Conditions Are Less Than Perfect
Building a landscape pond is a great way to improve the value of your property. It's also fairly simple, although the work does involve a fair amount of manual labor. The good news is that whenever you are performing your own labor rather than hiring others to do it, the potential for saving money is substantial.
There are two primary methods for building a landscape pond: using a hard plastic liner shell or using a flexible liner. Flexible liners have advantages since they allow you to build a pond of whatever shape and size you want. In ideal circumstances, building a pond with a flexible liner is a matter of excavating a hole, cutting the flexible liner to size and installing it, then securing the edges with landscape stone and filling the pond with water. While the work can involve plenty of labor—digging, prying, cutting roots, and more—it is not very complicated and almost anyone can do it.
But the project becomes more complicated if your conditions are not ideal. When your building site has loose, sandy soil, for example, the walls of your pond won't hold their shape and may collapse people walk around the edges. The solution is to use concrete retaining wall blocks to shore up the sides of the excavation, before the flexible liner is installed.
Tools and Supplies You Will Need
- Garden hose
- Chalk or flour
- Shovel or spade
- Cement building blocks
- Retaining wall blocks
- Laser level
- Tape measure
- Hardware cloth (if needed)
- 25 feet of rope
- Pond liner
- Pond underlayment
- Natural stone
- River gravel or small smooth stone
Choosing a Flexible Liner
Building a pond is not an expensive project since most of the materials are relatively economical. But don't try to save money by buying a cheap liner, since this is the most important element. Flexible pond liners are generally made of one of two flexible materials: PVC or EPDM (ethylene propylene diene, a synthetic rubber). PVC liners are best suited for smaller ponds, while EPDM is a better choice for larger ponds. The liners are typically sold in sheets 12 x 15 feet or larger, which you will need to cut down to fit the shape and size of your pond. For very large ponds, it is possible to join two or more sheets together, using the same taping/patching materials used to repair a pond.
Better liners will use thicker EPDM rubber—a 45 mil product is recommended. PVC liners are typically thinner, but make sure to choose a product with a thickness of at least 30 ml.
- Check with your permitting and planning departments to see if building permits are required or if there are zoning restrictions. In some areas, protective fencing may be required around a yard with a pond.
- Before you begin digging, call your local utility locator service. This free service will help you avoid gas, electrical, water, and other vital services when you dig.
- Pick a dry time of year for this project, since excavation will be easiest in dry, loose soil. Work at times of the day when you have the most energy. Wear well-worn work clothes, as this is very dirty work and you may want to discard the clothes when finished.
- Allow plenty of time for the project. Depending on the size of the pond, it may well take you a month or more from the moment your shovel first contacts earth to the moment you turn on the hose to fill the pond
InstructionsContinue to 2 of 13 below.
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Lay Out the Pond Boundary
Start by outlining the pond site on the ground. The classic way to mark pond boundaries is with a garden hose, because it naturally forms wide, gradual curves. If you wish, you can now sprinkle flour or chalk around the hose to mark the edges of the pond.
It's a fairly common mistake to undersize a landscape pond. Most experts recommend that a healthy, balanced pond with plants and fish should be a minimum of 50 square feet (a surface area of 10 x 5 feet, or an 8-foot diameter, if the pond is circular. The depth of a standard landscape pond should be 18 to 24 inches, although depths up to 32 are possible with very large ponds.Continue to 3 of 13 below.
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Dig Out the Pond Border
Next, dig out the pond border. Make shovel-width cuts in the grass or dirt. For grass sod, it helps to use a spade which allows for narrower cuts. Slide the spade under the segmented turf to remove it. With the edges of the pond clearly marked, you can remove the hose.Continue to 4 of 13 below.
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Excavate the Center of Pond
After the pond perimeter is established, the long work of excavating the earth begins. First, remove all dirt within the border strip, but for moment, dig no deeper than the thickness of the border.
Next, excavate down to the lowest point in your pond, wherever that that might be located (normally it is near the center of the pond). This helps you establish a base-line for your pond's depth. No other part of the pond bottom should be excavated deeper than this point. From the center, you can now begin excavating out to the sides.Continue to 5 of 13 below.
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As your excavation moves downward and toward the sides of the pond, create flat-bottomed tiers, with each tier about 8 inches high. Concrete building blocks, with 8-inch sides, make perfect edges for these tiers.
The goal is for your pond to "step up" as it approaches the sides. A large pond with a 24-inch center depth can have as many as three tiers; smaller ponds may require just two. Keep the walls of the tiers relatively short, since this will simply the later step of adding rocks to the tiers. By keeping your levels short, you can span the vertical distance with one or two rocks.Continue to 6 of 13 below.
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Reinforce the Walls With Retaining Wall Blocks
As you approach the edges of the pond, reinforce then with retaining wall blocks laid over the top of the concrete building blocks. This is especially important where the building site has sandy, loose soil—these blocks help retain the pond's shape and height. Small retaining wall blocks give you better flexibility and are easier to work with.Continue to 7 of 13 below.
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Check for Level Frequently
A laser level is a highly valuable tool when building a pond. If you own a bubble level only, or no level at all, you should purchase a laser level, if only for this one project.
It's quite critical to check the tiers and edges of the pond frequently to make sure they remain level and that each tier is at the same height all around its edges. A pond that is slightly off level can't be filled to a uniform level.Continue to 8 of 13 below.
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Lay Hardware Cloth
If your yard has burrowing animals, such as groundhogs or moles, eventually they may find your pond and burrow upwards, piercing your expensive liner. To protect against this, purchase rolls of hardware cloth (1/4-inch grid) and lay it out all the way across the pond bottom. Then spread about at least 2 inches of dirt over the hardware cloth.Continue to 9 of 13 below.
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Measure and Cut the Liner
Pond liners are expensive, so it makes sense to wait until the excavation is complete to measure and buy a liner to fit the pond. The easiest way to do this is to use a rope to measure the pond in both directions. Begin by placing one end of the rope about 2 feet beyond the edge of the pond, then run the rope down into the pond, flush against the bottom of each tier, and up the other side of the pond, ending about 2 feet beyond the far edge. Use a tape measure to measure the rope to determine this dimension for the liner.
Take similar measurements for the perpendicular dimension of the pond, then measure the amount of rope required to span the pond. Unless your pond is irregularly shaped, these length and width measurements are all you need to buy a pond liner sufficient to cover your pond.Continue to 10 of 13 below.
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Install the Pond Underlayment
Before installing the liner, lay down an underlayment to cushion and protect the liner from roots, rocks, and other objects that may damage it. Specialty pond underlayment is available from landscape supply stores, or you can use pieces of old carpeting.Continue to 11 of 13 below.
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Install the Pond Liner
With a helper, lay the folded liner across the pond bottom. Then, unfold it so that it drapes over the sides of the pond. Be patient with this step as you slowly and painstakingly press the liner down onto the pond bottom, creating pleats. While the bottom may have just a few pleats, all of your sides will be pleated. These pleats will be hidden by the next step.
Trim down the edges of the liner so that no more than 1 to 2 feet of liner overhangs the side of the pond. Secure the edges of the pond liner with stones to hold it in place.Continue to 12 of 13 below.
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Add Rock to the Pond Walls
Cover side walls of the pond and each tier with natural stone. Start with large and medium-sized rocks, building up the sides until no pond liner is visible. After the walls are entirely covered, use small stones or smooth river pebbles to cover the bottom of the pond.Continue to 13 of 13 below.
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Fill the Pond With Water
Fill your pond with a garden hose. It will take several hours to fill the pond to its maximum level. If you are adding plants or fish, make sure to follow recommended practice for the types of fish and plants you are using. This can include allowing the water to stabilize for a period of time and/or adding chemicals or filtering equipment.