NOTRA was contracted by GAS s.r.l. of Italy to develop an underwater UXO mapping system that could be used to survey a 100 meter wide corridor across a 40 kilometer length of a former Russian military test range in the Caspian Sea.  Building upon the experience gained developing the "NOTRA Super Coil" (a flex loop two meter EM-61 coil with enhanced detection depth), Notra recommended a 7m wide transmitter loop with 6 receiver coils powered by a Geonics EM-61 HP system.

Specifically, NOTRA was responsible for:

• Theoretical Design of a transmitter/receiver array that could detect large UXO to a depth of 3 meters below the seabed;
• Dry ground testing and verification of the theoretical system;
• Design and implementation of the transmitter/receiver system into a robust survey platform.  The system was designed for round the clock data collection for a period of up to two months at water depths of up to 9 meters and speeds of up to 3 knots;
• Field testing and modifications to the array and electronics in Lake Ontario and the Ottawa River prior to deployment;
• Integration of the geophysical system with a 34 meter vessel in Kazakhstan.  This included the integration of gyro, DGPS, Depth meter and depth sensor instrumentation to the geophysical data collection program;
• Development of HSE documentation and Data Quality Control and Assurance protocols.

In October and November 2008, the system (referred to as the Caspian Monster or Mega Coil) successfully completed over 1,500 line kilometers of surveying with a sample swath width of 7 meters.  The platform and electronics were sufficiently robust to endure continuous data collection throughout that time with only 4 reported down time hours for minor maintenance, despite dozens of encounters with subsurface obstructions such as fishing nets.  The system was robust enough to be able to continue data collection even when entangled in the fishing nets.

This same system has since been used for a 28 Ha surface survey in Alberta, Canada, and can quickly be configured to have a swath width ranging from 4 meters to 12 meters.

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