During a May 2011 golf-tournament in Ponte Vedra, Florida, the Florida Department of Transportation (FDOT), with assistance from the United States Department of Energy (DOE) Radiological Assistance Program (RAP), performed a radiation survey of the surrounding area using a truck-mounted portable scanner. DOT and DOE reported an instance of elevated gamma radiation from along Solana Road.
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Calculated dose rates from DOT and DOE measurements were found to be as high as 1.21 millirem per hour (mrem/hr). This roughly correlates to an annual exposure of 7.623 millirem per year (mrem/yr). The Florida Department of Health (DOH) responded and collected samples of soil for analysis by gamma spectroscopy. Samples collected by DOH showed thorium232 at 80 picocuries per gram (pCi/g) and radium226 at 47 pCi/g. Based on the levels of contamination found, DOH requested EPA assistance to further characterize the nature and scope of the contamination.
Prior to development into a beachside resort and golfing community, the city of Ponte Vedra was known as “Mineral City”. The National Lead Company operated a sand mine along 17 miles of oceanfront, removing the small percentages of heavy metal-bearing minerals in the sands. Minerals such as rutile and illmenite were recovered for their titanium content, which was needed during World War I for steel production. The operation was started in 1914 and continued into the 1920s when the mine was closed due to a depressed demand for steel after the war. One of the ancillary minerals in the sand is monazite. Although monazite is a naturally-occurring radioactive material (NORM), it is believed that concentrating monazite during the mineral separation process may have produced tailings piles. While actual production records are not available, it is believed that this technologically-enhanced naturally-occurring radioactive material (TENORM) could have later been used as fill or simply knocked down and spread out once the mine closed and the property was developed.
In order to investigate the possibility that tailings were used over large areas of Ponte Vedra Beach, EPA and DOH initiated a neighborhood-wide assessment in November of 2011. ERRB requested assistance from the Radiological Emergency Response Team (RERT). RERT and the Superfund Technical Assistance and Response Team (START) performed a survey of over 600 acres of residential properties surrounding 7 Solana Road using a van-mounted scanner Mobile Radiation Directional Scanning System (MRDSS) that is able to determine radiation levels at a distance. Prior to surveying, RERT determined the average background concentration in the area, which was confirmed to be 6 µrem/hr, or about 38 mrem/year. The MRDSS travelled the public thoroughfares and compared the readings to background levels. The site-specific threshold for determining whether further characterization was warranted on a property agreed to by EPA and DOH was 100 mrem/yr over the background level, which equates to 138 mrem/year.
Once characterization for a given property was complete, the property was assigned to one of three tiers based on the exposure dose rate of the occupants.
• Tier 1 – If the derived dose rate is less than 100 mrem/yr above background, no further investigation will be conducted under this program.
• Tier 2 - If the derived dose rate is below 500 mrem/yr above background but exceeds 100 mrem/yr above background, further action may be warranted on a case-by-case basis.
• Tier 3 - If the derived dose rate exceeds 500 mrem/yr above background prioritization for further action should be given.
Only the properties surrounding 7 Solana Road exhibited gamma radiation levels above the threshold of 138 mrem/yr. RERT and START collected dose rate data from points on the 7 Solana Road property as well as along the roadway and public sidewalks down Solana Road and Rutile Drive. Although exposure values with hand-held instruments taken from the roadway did not indicate any areas with exposure values over the site-specific threshold of 138 mrem/year, the more sensitive instrumentation on the van-mounted scanner indicated several areas which possibly exceeded this threshold located at some distance off the roadway coinciding with 13 properties near 7 Solana Road. Additional assessment is recommended for these other properties.
Only one property, 7 Solana Road, is currently assigned to Tier 3. The 4 properties immediately adjacent to and across the street from 7 Solana Road should be considered as Tier 2 properties. Nine additional properties surrounding 7 Solana Road may also be included in Tier 2, but additional investigation is necessary to fully define them. All other properties surveyed as part of the RSE are considered to be in Tier 1 and will not be investigated further unless new information is presented.
During the November 2011 investigation, RERT collected samples of the soil on 7 Solana Road and submitted it to the National Air and Radiation Environmental Laboratory (NAREL) for spectrographic analysis. NAREL confirmed the presence of both thorium and uranium decay-chain daughter products. After review of the data by EPA toxicologists, it was determined that radium226 and radium228 were the two leading risk radionuclides on the property. Spectrographic analysis showed the average activity of radium226 in the top 10 inches of soil was 281 pCi/g and fell to 85.3 pCi/g at approximately 30 inches below the surface. Radium 228 activity ranged from 643 pCi/g to 112 pCi/g within the same depth range.
Based on the presence of elevated gamma radiation emanating from radium-bearing soils identified during the removal site investigation and a review conducted by EPA's Technical Services Section, the EPA Region 4 conducted a removal action at 7 Solana Road. Further assessment activities on neighboring properties are being conducted by the FLDOH.