Using waterproofed linings is another method of reducing excessive seepage in ponds with coarse-grained and fine-grained soils. Polyethylene, vinyl, butyl-rubber membranes, and asphalt-sealed fabric liners are gaining wide acceptance as linings for ponds because they virtually eliminate seepage if properly installed.

Thin films of these materials are structurally weak, but if not broken or punctured, they are almost completely watertight. Black polyethylene films are less expensive and have better aging properties than vinyl. Vinyl, on the other hand, is more resistant to impact damage and is readily seamed and patched with a solvent cement. Polyethylene can be joined or patched with a special cement.

All plastic membranes need to have a cover of earth or earth and gravel not less than 6 inches thick to protect against punctures. Butyl-rubber membranes need not be covered except in areas traveled by livestock. In these areas, use a minimum of 9 inches on all types of flexible membranes. Make the bottom 3 inches of cover no coarser than silty sand.

Clear the pond area of all undesired vegetation; fill all holes and remove roots, sharp stones, or other objects that might puncture the film. If the material is stony or of very coarse texture, cover it with a cushion layer of fine-textured material before placing the lining.

Some plants may penetrate the vinyl and polyethylene films. If nutgrass, johnsongrass, quackgrass, and other plants with high potential for liner penetration are present, sterilizing the subgrade is desirable, especially the side slopes. Several good chemical sterilizers are available commercially. Sterilization is not required for covered butyl-rubber linings 20 to 30 mils thick.

Lay the linings in sections or strips, allowing a 6-inch overlap for seaming. Make the vinyl and butyl-rubber linings smooth but slack. Polyethylene should have up to 10 percent slack. Be extremely careful to avoid punctures. Anchor the top of the lining by burying it in a trench dug completely around the pond at or above the normal water level. Make the anchor trench 8 to 10 inches deep and about 12 inches wide.

Previous Page - Chemical Additives