We use a Geonics EM61 Mark II, which is a powerful time domain metal detector that is able to detect both ferrous and non-ferrous metal using a single transmitter coil and two receiver coil. It generates a magnetic field from the transmitter inducing eddy currents in nearby metal objects. The Geonics EM-61 Mark II detects a single 200-litre (55 gal) drum at a depth of over 3 meters (10 feet) beneath the instrument, yet is relatively insensitive to nearby cultural interference, such as fences, buildings and power lines. Response is a single, sharply defined peak, greatly facilitating quick & accurate location of the target. Depth of the target can usually be estimated from the width of the response.