GINOWAN, Okinawa — Soil at an Aug. 13 Marine Corps helicopter crash site will be surveyed Tuesday at Okinawa International University.
The survey, to be conducted by the Marines, city of Ginowan and Okinawa Prefecture, is to check for possible contamination of the area by a low-level radioactive isotope used in the CH-53D Sea Stallion helicopter, prefectural officials said. The isotope is used in a rotor safety device and ice detector, Marine officials said; U.S. Embassy officials stated that any possible radiation exposure would pose no risk to humans.
The Sea Stallion crashed after losing control of the tail rotor, according to U.S. investigators’ preliminary findings. It clipped the university administration building before hitting the ground and bursting into flames.
The three crewmen were rescued and treated at the U.S. Naval Hospital on Camp Lester. No civilians were injured. School was out for summer recess.
“Our residents are concerned about possible contamination of their community by toxic materials,” said Tadanobu Higa, director of Okinawa’s Military Affairs Office. “After the crash they saw Marines in protective gear recover wrecked equipment and monitor the air with a Geiger counter.
“It is important to erase any anxiety that our residents hold,” he said. “It is the intention of all concerned organizations, including the military, that maximum efforts are made to remove any fear that residents have concerning the environment. Anything that is left unknown just makes the residents suspicious and uneasy.”
If the area is deemed safe after Tuesday’s survey, soil and underground water from the site will be sampled and tested at a later date, Higa said.
According to a U.S. Embassy news release, a radiation detector was used by safety and rescue personnel to find and account for equipment in the wreckage.
The rotor safety device, called an In-Flight Blade Inspection System, used a low-level radioactive isotope, strontium-90.
The device includes six separate casings containing strontium-90, according to the Embassy.
“Five of the six cases were recovered from the crash site,” the press release stated. “Evidence strongly indicates one was vaporized in the burnt and melted wreckage and is no longer identifiable.”
The amount of radioactive material believed consumed in the fire poses no risk to humans, the Embassy stated. “The amount equates to an exposure much less than a normal chest x-ray.”
According to a Marine Corps response to a Stripes query, the sensor used by rescue crews at the scene of the wreckage was an Eberline model E-140N count meter, which locates flight safety devices in aircraft wreckage.
“These safety devices contain very small quantities of low-level radioactive material,” said 2nd Lt. Antony Andrious. “In order to conduct a thorough investigation, all parts of the aircraft must be recovered. The detector is used when locating flight safety devices becomes difficult.”
Andrious said the In-flight Blade Inspection System is attached to the helicopter rotor blades to alert the pilot to any cracks or weaknesses in the blades.
He said any soil removed from the wreckage site was “being examined by aircraft accident investigators for pieces of the aircraft, not for soil contamination.”
“Once the evaluation is complete, Nansei Environmental Laboratory will test the soil,” he said.
“If found contaminated, the soil will be treated or disposed of following Japanese environmental laws. The soil is being stored in approved hazardous-material containers. “
The embassy announced that the Marine Corps, in coordination with a Japanese company, will conduct an environmental impact study of the site.
