Most garden ponds are created with flexible PVC plastic or rubber pond liners. Why? Because the liners are inexpensive and easy to install, and they provide unlimited creative opportunities in pond size and shape. Ponds with flexible liners are also easy to remove should your landscaping plans change in the future. Outlining the Shape

After clearing the site of of plantings and other obstructions, outline the shape on the ground. For irregularly shaped ponds, use a rope or garden hose to make the pond perimeter. For squares or rectangles, use batter boards, stakes, and string and employ the "3-4-5" triangulation method to make sure all corners meet at an exact 90-degree angle. For circular ponds, make a simple "compass" with a stake; sturdy rope; and a shapened stick or screwdriver. Scribe out the outline of the pond in the soil, and mark it with marking paint.

Calculating the Liner

To allow for pond depth, decide on the maximum depth of the pond, double it, and add this figure to the width and length of the rectangle. To allow for overlap, add an additional 24 inches to the width and length of the liner. This will provide 12 inches of overlap around the pond rim once the liner is installed.

Installing the Liner

1. Removing Sod. If you have located the pond in a lawn area, use a flat shovel to remove patches or strips of sod within the pond area, and about 6 to 12 inches beyond the perimeter.

2. Digging the Hole. Start by digging around the shelf perimeter to the depth of the shovel blade (9 to 12 inches); then remove all soil within the pond area, by layers, to the final depth. The sides should slope inward at about a 20-degree angle from the vertical. Slope the bottom of the excavaton about 1/2 to 1-inch per foot toward the center or toward one end; at the lowest point, dig a shallow (6 to 8 inch) sump hole to facilitate draining the pond.

3. Cutting Ledge for Edging Material. With a flat-blade shovel, cut a 12 to 15 inch-wide ledge around the pond rim to provide a flat, level surface on which to install the edging materials. Cut the ledge to a depth that will accommodate the combined thickness of the edging and any underlayment materials. The edging should extend at least, not under, one inch above the surrounding terrain to prevent runoff for entering the pond.

4. Checking Edges for Level. Once the pond is filled with water, the water level will quickly reveal any high or low spots around the pond rim. The easiest way to check the level of the pond is to place a 2x4 across the pond excavation, with each end resting on the the edging ledge. Place a levl on top of the board; then move the board to various points across the length and width while checking the level.

5. Preparing the Hole. Carefully inspect the excavation site for any sharp stones or projecting roots, and remove them. Place carpet padding or a 2 to 3 inch cushion of damp sand in the bottom of the excavation and on any shelves cut into the sides of the pond. Also pack damp sand into any voids in the sidewalls, such as where large rocks were removed. For an area that is very rocky or infested with roots lay down a fabric underlayment for additional protection.

6. Positioning the Liner. The best day to lay the liner is on a warm sunny day, this will help make the liner more flexible and easier to work with. Next, drape the liner loosely into the excavation, with an even overlap on all sides; then weight down the edges with a few smooth, flat stones or bricks. Once the liner is in place, start filling the pond with water.

7. Fitting the Liner. As the pond fills with water, adjust the liner to conform to the sides of the pond; smooth out as many creases and wrinkles as possible. As the pond fills, periodically ease off the stone weights to avoid overstreching the liner.

8. Trimming Excess Lining. Once the pond is full, trim off excess lining with a heavy pair of scissors or a utility knife. Leave enough liner around around the pond rim to extend underneath, and a few inches behind, the first course of edging stone. To keep the liner in place while adding edging, push 20d nails through the liner into the pond rim.

9. Adding Edging Material. If your using natural stones, make several trial arrangments until you find one that looks most natural. Large stones can be placed directly, but be careful because they might slip into the pond. If you use a mortar to set the stones allow it to cure, then scrub the edging with distlilled vinegar to neutralize the lime in the mortar. Drain the pond, rinse the liner, and refill the pond with fresh water.