Golf course irrigation ponds are one of the first items that are installed when a golf course is constructed (see Figures 1 and 2). The grass for each hole requires the irrigation pond to be constructed and be leak free before grass sod can be laid. It is important that these ponds do not leak because the beauty of the course relies heavily on water and this water comes from these irrigation ponds. The ponds are not overly large and are single lined with a 60-milthick Woven Coated Polyethylene Geomembrane. The perimeter of the ponds are decorative and therefore when full will look like natural ponds with a rock and concrete border around the perimeter of the pond. Inside the ponds the geomembrane is covered with approximately 1.5 feet (0.5m) of sand along the floor and up the side slopes (see Figure 2). The sand maybe reinforced with geocells as shown in Figure 2This sand connects with the concrete perimeter of the pond and therefore little, if any, of the geomembrane is exposed.

For electrical leak location surveys, and especially for single lined sites, it is important that around the perimeter of any cell that is tested the geomembrane be exposed. This is needed to create electrical isolation and that any current in the cell stays in the cell and does not leak out around the perimeter instead of only through actual holes in the geomembrane. However, this does not mean leaks cannot be found when there is little or no electrical isolation. Many times, leaks will be found in the center of the cell away from the perimeter where sensitivity is not as good. For these two irrigation ponds, leaks were found near the edge where there was not isolation and sensitivity/accuracy should be the lowest (see Figures 3 and 4). One would expect only a large leak to be detectable, if any, near the edge but in this case small holes were detected closer than 20 feet (6 m) away from the edge. For example, Figure 3 shows a hole in Pond #1 at an extrusion weld. Figure 4 shows a puncture in the geomembrane in Pond #2.

It is always better to have electrical isolation around the perimeter of your pond or site when performing an electrical leak location survey. This does not mean that a leak location survey is not a viable option for leaks if this isolation is not present. Leaks can and are routinely detected without this isolation and not just larger holes or damage. With the correct setup and detail taken when collecting the data even small damage can be found near the edge. These defects are easiest to be seen when the data is obtained with close attention being paid to every measurement individually.