Examining Minnesota’s historical radiation data

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Since the start of the nuclear age, the State of Minnesota has monitored radiation levels within its borders.  In recent decades, that responsibility has fallen to the Minnesota Department of Health (MDH), which conducts site-specific environmental testing to measure the presence of radiation in the state’s air and water.  

Since 2004, MDH has compiled its test results into annual environmental monitoring reports. The most recent report (for 2013) is currently available on the department web site. Public Record Media (PRM) has an archive of other radiation reports reaching back to 2004.

According to a reference on the MDH web site, Minnesota first began collecting radiation data in 1953.  Such data pre-dated the operation of the state’s nuclear plants, and was initially intended to gauge fallout from above-ground nuclear tests in the western United States.  

PRM’s 2011 request

PRM first sought information on the state’s radiation levels in 2011, after the release of a federal Nuclear Regulatory Commission (NRC) report that referenced a tritium leak at the Monticello nuclear facility in 2009.  Tritium is a radioactive form of hydrogen that can be formed during nuclear plant operation.  

PRM obtained MDH’s radiation monitoring reports for the period of the leak – including site-specific information relating to the Monticello nuclear facility. Those reports did not contain references to elevated tritium levels in nearby aquifers.

PRM subsequently requested all of MDH’s historical data relevant to above-ground atomic testing and nuclear facility operation. Such data pre-dates the publication of MDH’s environmental reports, and was sought to discover what long-term trends might exist in the state’s radiation levels.

Measurements in ground water

MDH measures ground water radiation at multiple sites throughout the state – including within municipalities like Alexandria, and at specific business locations such as the metro-area Crosstown Shopping Mall.

MDH’s Robert Smude is a supervisor in that agency’s Drinking Water Protection Unit, and he provided PRM with monitoring data for groundwater radiation levels that extended back to 1987.  The data comes from public well water samples, and is used to guage compliance with environmental standards established by the Safe Water Drinking Act.  

In correspondence with PRM, Mr. Smude indicated that Minnesota’s groundwater contains a certain amount of radiation from naturally-occuring uranium deposits found in the underlying soil.  Smude noted that MDH watched for traces of tritium in groundwater samples, as its presence would indicate man-made contamination, such as residue from past nuclear testing or other sources.  

Surface water monitoring

MDH also monitors radiation in surface water, air, and milk.  According to the most recent MDH monitoring report, surface water tests are conducted downstream from the state’s two nuclear plants (Monticello and Prairie Island), and are designed to indicate the presence of tritium and other radionuclides in those water supplies.

The pre-2004 surface water data held by MDH existed in a raw, digital form, with results reaching back to 1993. While compiling records for PRM’s data request, MDH staff searched for paper documents from earlier periods, but were ultimately unable to find such data.  In correspondence with PRM, MDH’s Lynn Belgea noted that the department was considering changing the way its web site referenced 1950s-era data, since all of its radiation data is on a 10-year retention schedule. According to Belgea, the fact that the department had the older monitoring data was due to an oversight in records disposal procedures.

Evaluating the data

After recieving MDH’s historical data, PRM shared the information with David Lochbaum, Director of the Nuclear Safety Project of the Union of Concerned Scientists.  Lochbaum reviewed the data set, and noted that it generally showed a positive trend over time. “By itself,” he noted, “the spreadsheet data is good news.  There’s ample margin between the highest measured tritium sample and the limit established to protect public health.”  

He further stated that “the majority of the high values come from sample points at or near the two operating nuclear power plants in the state.”  Even so, he noted that the highest tritium measurement (5830 picocuries per liter near Hastings) was “considerably below the EPA drinking water limit of 20,000 picocuries per limit.” He further observed that all of the other measurements in the data set were less than the tritium levels measured at Hastings.

MDH’s post-2004 environmental reports state that radiation levels in Minnesota fall within state and federal guidelines. This was the case even during the time frame when the Nuclear Regulatory Commission reported the tritium leak at the Monticello facility.

According to Lochbaum, trituim leaks elsewhere in the country have triggered an expanded radiation monitoring regime.  In particular, he noted that a large, 2005-era leak in Illinois led to additional site-based monitoring at nuclear plants across the country.  Such monitoring includes a reporting requirement, so that in the event that plant operators discover a tritium release, the release must be reported to state and federal authorities.  Lochbaum noted that the reporting threshold for tritium is low – even below the lowest value represented in the historical MDH data. 

Displaying the data

Due to the fact that MDH only held raw data for the pre-2004 period, PRM requested that the department compile the information within a spreadsheet format in order to display it in a readable fashion.  

PRM then reorganized the data, sorting it by location and date, and also condensed the field information for readability.  The re-formatted results are available on the PRM web site, and access to the original data is avaiable by request.