Aerial Radiological Survey (FAQ)

What is the aerial radiological survey?

The survey is a project to use a helicopter to measure the existing radiation in the central Puget Sound area so we know what levels are already in our environment. This baseline information could be vital if there's ever a nuclear or radiation emergency; we could compare baseline levels to radiation levels after the event to see if they're increasing and if there's a health threat.

Why did you do the aerial radiological survey?

The survey was conducted to establish a baseline of current radiation levels in the largest population centers of the state of Washington – King and Pierce counties. In the event of a radiation emergency, this baseline (also known as normal radiation levels) will give us something to compare radioactive contamination too.

Did you do the aerial radiological survey because of Fukushima?

No. The planning of our aerial survey began well before the earthquake in Japan. We applied for a federal grant for this project in September 2009 and the grant was awarded to us in August 2010. The earthquake hit Japan in March 2011.

Who did the aerial radiological survey?

The state Department of Health contracted with the U.S. Department of Energy to do the aerial radiological survey. The contractor used a Bell 412 helicopter with special radiation detection and measuring gear attached to the fuselage.

Why use a helicopter for the aerial radiological survey?

Helicopters are capable of flying at low enough speeds and altitudes to measure certain radioactive materials reliably, consistently, and efficiently.

How much of King and Pierce Counties were surveyed?

The helicopter covered 345 square miles of King County from the eastern shore of Puget Sound to Redmond and SeaTac Airport to the intersection of I-5 and 104th. In Pierce County, 60 square miles were surveyed from Commencement Bay to South 56th Street and Union Avenue to South 1st Avenue.

How did you survey for radiation?

The helicopter flew a grid pattern over the survey area, using very sensitive radiation detection gear to measure levels of radiation. The helicopter flew close to the ground at relatively slow speeds to collect data. The information was then analyzed by special software programs.

How accurate are the survey results?

The aerial survey system has been used in many areas of the country and has a proven record of producing consistent, reliable, accurate results. The process includes quality control measures to assure the most accurate results and eliminate inconsistent or irregular readings. Pre-flight, in-flight, and post-flight calibration checks verified that everything was working properly.

Did you find unsafe radiation levels?

All radiation levels detected during the survey were well below levels of health concern. We expected to find very low levels of radiation at ground level, and the survey verified that. Most of the manmade sources were where we expected to find them at levels that pose no health risk.

There were some unexpected sources in locations we didn't expect to find manmade radiation activity, so we checked them out. All of them were from legal, legitimate, licensed sources and were below regulatory levels that pose no health risk.

What did you accomplish by doing the aerial radiological survey?

This project provided valuable information on normal levels of radiation in King and Pierce Counties. This information will be used as a baseline to compare if radiation levels change after a major disaster.

Are the aerial radiological survey results available to the public?

The summary report and the technical report are posted on our agency website.

Is there somebody I can talk to if I have questions?

If you have questions about the aerial radiological survey, call 360-236-3300 or e-mail (