Time Domain Electromagnetics



TDEM

In the period of 1943 to 1945 over 40,000 acres of Parker Ranch land near the town of Waimea (Kamuela) on the Big Island of Hawaii was transformed almost overnight from serene pasture into a US Marine Corps training facility known as Camp Tarawa. Originally constructed by the Marine survivors of the Battle of Tarawa in the Gilbert Islands this new camp quickly soared in population to over 25,000 troops.  Before the war in the Pacific was over more than 50,000 soldiers had trained at the facility.  This must all have come as quite a shock to the people in sleepy little Waimea, who at the time only consisted of about 400 permanent residents... mostly all Parker Ranch employees.  Waimea, with its cool and moderate climate, was perfect at the time for those Marines suffering the effects of tropical diseases such as malaria. 

Two primary groups of Marines trained at Camp Tarawa.  The first to arrive, the 2nd Marine Division, were resident from December 1943 until the spring of 1944.  These soldiers went on to fight in the battles of Saipan, Tinian and Okinawa.  The second group, the 5th Marine Division, came in the fall of 1944 and trained until late December, 1944. When they left, it was to fight the horrific Battle of Iwo Jima. One of the local “puu”, or small cinder cone, was a perfect training site for what they would later face at Mount Suribachi on the southern tip of Iwo.

All this military activity took a toll on the land however, and over the years many unexploded remnants of the training have been found, in several instances with fatal outcomes.  Now the US government has funded a project to survey and locate unexploded ordinance on another 14,000 acres of this training area.  Follow-up projects are planned to remove items found and fully clear the area.

What you see above is a Bell Model 206L helicopter on the ramp of Waimea-Kohala Airport just outside of Waimea.  Workers are installing a Time Domain Electromagnetic (TDEM) induction system that will be used to detect metal objects or unexploded ordinance that may still be in the ground at the old training site.  Other applications for TDEM technology include identifying aquifers or detecting the presence of water or salt water intrusions in groundwater investigations, mapping aggregate deposits for quarry operators, mapping leachate in environmental investigations, or permafrost or other geologic features in geotechnical engineering.

The primary contractor for the government on this project is CH2M-Hill, with support from Battelle, and Pacific Helicopter Tours.  The survey and identification portion of the project is expected to take about two months. 

This work also goes straight to the heart of a key Hawaiian value, namely the concept of Malama 'Aina - Care for the Land.