EM61-MK2A Surveys

The EM61-MK2A is a time domain metal detector which can locate ferrous and non-ferrous metals with high precision and in high resolution. The EM61 operates by inducing eddy electric currents in metals, which as a result produce secondary magnetic fields. The EM61 then measures strength and decay of the secondary magnetic fields, confirming the presence of metal(s).

The EM61 comes equipped with an Archer handhold computer. The Archer computer allows for visual interpretation and review of the data while in the field, quick data collection, and removable flash memory for extended survey time. The EM61 also comes equipped with a GPS for easy surveying of the collected data.

The EM61 is effective in locating the position and approximate dimensions of:

  • Underground storage tanks
  • Buried drums
  • Utilities
  • Infrastructure
  • Construction and industrial waste
  • Buried metallic waste
  • Unexploded ordinance

Pre-construction Magnetic Anomaly Investigation Project

In March 2015, Subtronic was contracted to identify any potential metal scrap and reinforced concrete in the subsurface in anticipation of new construction at a site. The site was covered in dirt and gravel, with no outward signs of metal or utilities. Over the course of three days, the site was surveyed using GPR, the EM61, and scanned for utilities. The EM61 was able to easily identify anomalous magnetic zones, and a site map was created for our client.

DEHEP xylene METAL DETECTIONdwg_recover-24x36


Buried UST Investigation Project

In December 2013, Subtronic performed a geophysical survey at a local industrial facility in search of underground storage tanks (USTs). Using a grid setup, ~65,000 ft² (1.5 acres) were able to be scanned with the EM61 in a day. The EM61 detected small anomalous areas (less than 3 ft²) relating to buried utilities and reinforced concrete slabs. Using the EM-61, Subtronic was able to determine that there were no buried USTs on site.

pleasanton EM-61 web image


The + marks indicate the GPS position of the EM61 during data collection. The shaded contour map peaks and nulls represent magnetic anomalies. The southeastern side of the site was not collected because a temporary fence blocked off the area.

Magnetic Anomaly Excavation Project

In July 2015, Subtronic was contracted to locate any magnetic anomalies at a local industrial facility before they they were going to excavate a large area. Using the EM61, Subtronic was able to quickly perform magnetic surveys over a large area, accurately locating any magnetic anomalies as you can see below.

EM 61 plot witH contours-24x36a