Geomembrane leak location surveys of surface impoundments and tanks can be conducted with water covering the geomembrane. Surveys are conducted using a probe while wading or standing on the side slopes, or using a sensor that is towed across the impoundment. Procedures for this method are specified in ASTM standard D7007.
Shallow Water Surveys
For the wading survey mode the survey personnel wade in the water and systematically scan the submerged liner to locate any leaks. For this method, a water depth of between six and 30 inches (150 and 750 mm) is required. Temporary survey lanes are established across the bottom and are scanned with overlapping coverage. The liner field seams that can be located are double-checked. When detected, leaks are located to within one inch (25 mm) or less and immediately marked. The side slopes can be surveyed with deeper water using a long probe that is systematically scanned along the side slopes.
Deep Water Surveys
If the water in the geomembrane lined pond, impoundment, or tank is too deep or the water in the pond is unsuitable for personnel to wade, then the towed probe survey mode is used. While standing on the top of the side slopes, survey personnel systematically pull the probe back and forth across the bottom of the pond along temporary survey lines. When detected, the distances to the leaks are immediately marked on the liner of the closer side slope.
Geoelectric leak location survey of the soil-covered geomembrane is a very cost-effective method for finding leaks.
BARE LINER SURVEYS
To avoid the logistics of flooding the geomembrane with water, the exposed geomembrane can be tested for leaks using a water puddle test.