Although BHF Environmental Ltd offers a full range of geophysical services our primary function is to undertake electrical leak location surveys (ELLS) to locate perforating damage to geomembranes. Perforating damage can be located in plastic liners used in the construction of the following:
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Landfill Cells
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Leachate lagoons
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Ponds
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Reservoirs
Established in 1994, BHF Environmental Ltd is one of the very few companies worldwide having extensive experience of both mobile or walk-over electrical leak location surveys and built-in monitoring systems. Most companies offering these services specialise in one or other system. To date BHF have completed over 400 surveys in 15 countries with over 5 000 000 sq. metres of liner surveyed or monitored. Permanent monitoring systems are installed at one hundred and fifteen sites in the UK, Belgium, Croatia, S. Korea, Poland, Mauritius the Czech and Slovak Republics and in Hungary.
Leaks are detected and located by mapping the electric potential across the tested area. If the plastic geomembrane is not perforated, the voltage generated across the geomembrane produces a very low current flow and a relatively uniform voltage distribution. If there is perforating damage to the plastic liner, electric current flows between the inner and outer power electrodes through the puncture in the otherwise insulating membrane. This causes a localised anomaly in the distribution of electric potential. The electrical leak location survey (ELLS) can be applied in two ways:
The often-termed “Mobile” leak location test system performed with a fully portable set of equipment.
The “Permanent” leak location test system with at least some components permanently installed on site (usually electrodes and connecting cables installed under the geomembrane).
Other Geophysical Services Available
By using a variety of geoelectrical methods, magnetometry, thermometry and gravimetry BHF environmental offers cooperation in solving problems within the following fields:
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Environmental geology and engineering (site investigation for new landfills, electrical leak detection tests, geological survey and monitoring of old landfills, detection and delineation of contaminant plumes,...)
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Engineering geology (site and ground investigation for all types of structures, location of old mines and cavities, detection and definition of bedrock, detection of heterogenities/faults in soil and rock formations, survey of landslide areas,...)
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Hydrogeology (location of water well, geotermal springs, definition of water protection zones, definition of groundwater flow direction, location of leaks from reservoirs, inspection of dikes,...)
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Corrosion survey
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Location of old ammunition
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Archaeological survey (location of shallow buried objects in the ground or in structures such as walls, pavements, cellar floors,...)
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Mineral prospecting
BHF Environmental Ltd offers a range of services to the geophysical, geotechnical and environmental fields. The company has mostly specialised in applied geoelectrics. Along with the standard geophysical/geoelectrical methods the company also offers electrical leak detection surveys. To detect and locate leaks in plastic membranes, the company uses the GECO system. This application of geoelectrics is widely used as an effective tool in the process of Construction Quality Assurance in many countries, mostly for landfill liners.
With our GECO system the locating of any perforating damage to the geomembrane is rapid, accurate and cost effective. The system utilises the insulating properties of geomembranes. An electric current is applied across the protective layer placed over the membrane. Subsequently, the electric potential is mapped over the inspected area. Anomalies in electric field indicate the geomembrane damage.
This application of geoelectrics is widely used as an effective tool to check the integrity of plastic geomembranes and has been accepted as a standard method in the process of Construction Quality Assurance of landfill liners in many countries.
BHF environmental have personnel with extensive experience in this type of survey. The company has successfully completed more than 300 leak location surveys worldwide having received commissions from landfill owners, earthworks contractors, consultants and liner installers.
THE GECO SYSTEM
Electrical Leak Location Surveys
Mobile or ‘Walk-over‘ Survey
This version of the system is carried out by a field crew using a fully portable set of equipment. At landfills, this version is used after completion of emplacement of the protective liner covering, prior to the tipping of waste. As the major cause of liner damage results from the use of heavy plant in the construction process, the walkover survey is considered to be sufficient in many cases.
Modified techniques are also available for exposed geomembranes forming containment ponds, reservoirs or leachate lagoons.
Long Term Monitoring ("Permanent System")
The walkover survey can only detect the perforating damage prior to the tipping of waste. However, this may not be sufficient to ensure the long term integrity of the geomembrane. Especially at the early stages of landfilling the tipping of waste can adversely affect geomembrane integrity. Also, some hidden defects (e.g. on extrusion welds) can pass all tests and fail at a later date. The permanently installed system will detect this damage at the stage when the geomembrane is perforated.
The system consists of an array of sensing electrodes placed under the membrane and connected via cables to a monitoring terminal located at the perimeter of the survey area. Several modifications of a data acquisition system are available (manual, semi-automatic, fully automatic).
