I-CORP’s staff have been performing liner integrity and leak location surveys since 1987. They have been performing plastic pipe, geomembrane, and seam failure analyses since 1981, and have been performing liner CQA since 1982. Consequently I-CORP has developed the most appropriate, cost-effective, integrated suite of mobile technologies for locating leaks and flaws in lining systems in the industry worldwide, suitable for both CQA and problem resolution applications. These technologies are:
1. Various versions of the original patented electrical method, which can be performed at a rate of about 9000 m 2 (90,000 ft 2) per day:
- The water lance method, which directs a positively charged stream of water on to the surface of the exposed geomembrane. When the water contacts the negatively charged subgrade through a hole in the liner, current flows and is recorded. Holes about 0.5 mm diameter can be pinpointed. Thus, there is no need to fill a pond to do a survey.
- Wading in liquid with a handheld probe to measure the iso-potential contours in the liquid while a constant potential gradient is applied between the liquid above the geomembrane and the leaked liquid, or subgrade, below the geomembrane. Again, 0.5 mm holes can be pinpointed. A soil cover on the liner, covered by liquid, is not a problem Wading in liquid with a handheld probe to measure the iso-potential contours in the liquid while a constant potential gradient is applied between the liquid above the geomembrane and the leaked liquid, or subgrade, below the geomembrane. Again, 0.5 mm holes can be pinpointed. A soil cover on the liner, covered by liquid, is not a problem –
- When the water is too deep for wading, a remote probe can be dragged from one side of the pond to the other, thereby reproducing the wading survey. Leak size and location sensitivities are a function of the presence, depth, topography, and chemistry of any soil/sludge cover.
- When there is sand, drainage stone, or solid waste, above the liner two copper/copper sulfate standard half cells are used to measure the potential gradient (or resistance) contours on top of the cover layer at orthogonal grid nodes. In this case a constant commutated current (5 to 100 mA) is imposed across the geomembrane. The commutation helps I-CORP INTERNATIONAL Inc. distinguish between changes due to leaks and local variations in cover layer lectrical conductivity. Sensitivity is a function of cover layer thickness, conductivity (and variability), and liner features (trenches, toe of slope, riser pipes) but 1 mm holes under about 750 mm of sand are detectable to within a few centimeters. A combination of features may reduce location sensitivity to between 500 mm and 1 m.
2. A novel infrared spectrometry technology used to locate leaks in both geomembrane and compacted clay caps. This method requires no surface preparation (no elec-trically insulting trench around the periphery, or no placement of an electrode under the cap) – it simply measures methane distribution (to 0.1 ppm) above the cap. Holes are located to within about 600 mm. Depending on topography we can survey 100 ha (250 acres) or more per day. This method can be adjusted for other gasses depending on waste composition and gasses emitted. And there are ways to extend this methodology (and speed) to bottom liners. This service is only available from I-CORP.
3. Revolutionary infrared thermography (IRT) on exposed geomembrane seams (particularly suited to potentially troublesome tie-in seams) will NONDESTRUCTIVELY continuously evaluate seam bond strength (no more destructive sample holes, destructive testing, nor extrusion seams around destructive sample patches). IRT will identify leaks, partially penetrating channels, internal voids, and internal foreign matter (sand, bentonite) that, while not leaking at the time of testing could potentially develop into leaks during service. A hard copy videotape record of every millimeter of seam can be provided in the report. No other technology generates a continuous hard copy of test data. This technology will also eventually preclude the need to perform air channel, vacuum box, air lance, and maybe even spark testing. Seams can be interrogated at speeds of 5 to10 km/hr. This new technology is again only available from I-CORP.
4. A special protocol, first performed by I-CORP at the end of 1997, for the location of leaks in GCL liners. Requires no sophisticate electrical or infrared equipment. It simply requires specific capabilities of an underdrain pumping system, therefore may not be applicable to all GCL liners. Leak locations throughout the liner are visually observed all at the some time – a very graphic demonstration of the existence of leaks.
This integrated suite of technologies is a unique resource from which can be selected individual or combinations of methods to rapidly and economically perform almost any type of liner integrity or leak location survey. And when the leak has been found, should it be necessary, I-CORP has the materials science/failure analysis expertise to assess the cause of the leak and to help assign responsibility for its occurrence.
In addition we can point you in the direction of the better providers of any of the increasing number of in-situ systems that continuously monitor for leakage and, to various degrees, locate leaks when they occur. Some of these systems are even designed to degrade so they become ineffective when it is very expensive to repair a known leak! Now, if only we could develop a practical method of remotely repairing a leak under 30 m of waste. We’re working on it. We will be honored to work with you on well-planned CQA projects or at a moment’s notice to resolve an urgent problem – Anywhere – Worldwide. Contact I-CORP first, or when you have run out of options.
