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. This test is used on geomembranes that are in direct contact with the supporting sub-grade or a GCL. Procedures for this method are specified in ASTM standard D7002.
The bare liner test is to detect electrical current flowing through a hole in the geomembrane liner using a small amount of water that is temporarily placed in contact with the liner using a squeegee.
One output of an LLSI power supply is connected to earth ground or the GCL and the second output is connected to the scanning sensor through an LLSI electronic leak detection unit. When the water in the leak contacts earth ground or the GCL, a circuit is established and the electrical current will increase. The LLSI electronic leak detector unit converts the increase in the current to an audible tone indicating the presence of leak.
The Spark Test
The Spark Test is covered under ASTM D7240 – Electrical Leak Location Using Geomembranes with an Insulating Layer in Intimate Contact with a Conductive Layer via Electrical Capacitance Technique.
To leak test geomembranes for damage using this method, the conductive layer is charged using a contact pad. A conductive wand or brass brush is guided over the top of the liner. When an electrical connection is made between the wand and the conductive bottom layer, a visible spark is observed and an audible alarm is sounded identifying the hole in the liner. The method is best when there are multiple penetrations through the liner that could cause grounding using other leak location methods.