1. Highgate Springs area: Rio Tinto Canadian Exploration (1972)(described in Dorsey and Vanacek, 1983) and Dorsey and Vanacek (1983)
   

2. Milton and Colchester area: McKeown (1951), Vanacek and Dorsey (1983); Whitten (1988a and 1988b); Vermont Geological Survey/Vermont Dept. of Health (2000); Kim and Thompson (2002).
   

3. Middlebury area: Middlebury College Environmental Studies 360 Class (Ryan et al., 2002).
   

Because of the numerous studies that show elevated radioactivity or radionuclide levels in the Clarendon Springs Formation in the northern half of Vermont, it is the judgement of the Vermont Geological Survey that the entire Clarendon Springs Formation statewide be included in this category.

Vt nure preferred anomalies.shp: Three of the preferred uranium anomalies from the NURE airborne surveys have been checked on the ground and found to have elevated radioactivity and radionuclide levels. The two preferred anomalies in Milton and Colchester were confirmed by the ground-based work of Vanacek and Dorsey (1983); Vermont Dept. of Health (Whitten, 1988a, 1988b); Vermont Geological Survey/ Vermont Dept. of Health (2000); and Kim and Thompson (2002). The preferred anomaly in the Monkton and Starksboro area was confirmed via ground-based work of Corr (2002), in a Middlebury College Senior Thesis in the Geology Department.


Category 2v2.* files This coverage represents as described on the Compilation and Assessment of Radioactivity Data in Vermont map legend "Category 2- elevated radioactivity indirectly measured in these areas via airborne or stream sediment surveys". These areas were delineated via airborne gamma ray spectrometer surveys and analysis of radioactive elements such as Uranium or Thorium in stream sediments. The geochemical measurement of U and Th in stream sediments is considered an indirect method because stream sediments are mobile and have likely been transported some distance from their source. This coverage was assembled from the parts of a number of other coverages which are:

Vt nure preferred anomalies.* files All preferred NURE airborne uranium anomalies that were not checked on the ground are part of this coverage.

Vt nure secondary anomalies.* files All secondary NURE airborne uranium anomalies that were not checked on the ground are part of this coverage.

Vt nure stream.* files All Uranium or Thorium/Uranium anomalies found in stream sediments in Vermont by the National Uranium Resource Evaluation (NURE) (Koller, 1979a and 1979b) are part of this coverage.

700+cps.shp, 500-700cps.shp These data layers were derived from U.S. Geological Survey Aeroradioactivity Map (Popenoe, 1964). The layers were merged into a single coverage. The 500-700 counts/second and 700+ counts/second layers were chosen from the Popenoe (1964) map because: 1) Popenoe (1964) considered 500-700 counts/second and 700+ counts/second intervals to represent medium high and high levels of radioactivity, respectively, in the text of his map; 2) Polygons in the 500-700 counts/second and 700+ counts/second range overlap with a number of polygons from the NURE airborne uranium surveys and stream sediment surveys; 3) Peter Thompson, who formerly worked for a uranium exploration company as a Geologist agreed that 500 counts/second and above was considered high (Thompson, pers. Comm., 2002).

The coverages Vt nure preferred anomalies.shp, Vt nure secondary anomalies.shp, Vt nure stream.shp, and 700+cps.shp, 500-700cps.shp were merged together to make the Category 2 layer for this map.

No Data.* files This data layer represents the area of Vermont not covered by any known airborne or ground-based radioactivity surveys. The only data available for this area is the public water supply well locations (Pwsgwonly.* files).

Category 3v2.* files This coverage represents as described on the Compilation and Assessment of Radioactivity Data in Vermont map legend "Category 3- elevated radioactivity not measured in these areas other than public water supply wells with elevated gross alpha and some uranium occurrences (includes unsurveyed areas between flight lines) ". This category encompasses all areas not included in category 1, Category 2, and No Data layers.

Geodetic Information NAD 83 Vermont Stateplane coordinates (Zone 5526) in meters

References:
Corr, B., 2002, Source Identification of the Starksboro Radionuclide Anomaly: A Field, Geochemical, and Petrographic Study of Elevated Radon Levels, Middlebury College Senior Thesis, 50 p.

Doll, C., 1961, Centennial Geologic Map of Vermont, Vermont Geological Survey, scale- 1:250,000.

Dorsey, R.J. and Vanacek, D.M., 1983, Geologic and Radiometric Survey of the Clarendon Springs and Highgate Formations at the O=Brien Farm: Highgate Springs, Vermont, Vermont Geological Survey Open File Report 1983-1.

Kim J. and Thompson, P., 2002, Bedrock and Radionuclide Mapping in the Colchester Quadrangle, Vermont, Geological Society of America Abstracts with Programs, v. 34, #1, p. 17.

Koller, G.R., 1979a, Albany 1 degree X 2 degree NTMS area Connecticut, Massachusetts, New Hampshire, Hew York, and Vermont, Data Report, National Uranium Resource Evaluation, Hydrogeochemical and Stream Sediment Reconaissance, Savannah River Laboratory, Aiken, South Carolina, 59 p..

Koller, G.R., 1979b, Glens Falls 1 degree X 2 degree NTMS area Connecticut, Massachusetts, New Hampshire, Hew York, and Vermont, Data Report, National Uranium Resource Evaluation, Hydrogeochemical and Stream Sediment Reconaissance, Savannah River Laboratory, Aiken, South Carolina, 53 p..

McHone, J.G. and Wagener, H.D., 1980, Uranium Resource Evaluation, Glens Falls Quadrangle New York, Vermont, and New Hampshire: U.S. Dept. of Energy, Grand Junction, Colorado, 40 p..

McKeown, F.A., 1951, Reconnaissance of Radioactive Rocks of Vermont, New Hampshire, Connecticut, Rhode Island, and Southeastern New York: U.S. Geological Survey Report TEI-67 for U.S.A.E.C., Oak Ride, TN, 48 p..

Mineral Resource Data System for Vermont (MRDS), U.S. Geological Survey digital database.

Field, M.T. and Truesdell, D.B., 1980, Uranium Resource Evaluation, Albany Quadrangle Massachusetts, New York, Connecticut, Vermont, and New Hampshire: U.S. Dept. of Energy, Grand Junction, Colorado, 57 p..

Parker, R., Whitten, E., and Selleck, 1988, Geologic controls on the distribution of Uranium and associated Radon in the Clarendon Springs Dolomite (Upper Cambrian-Lower Ordovician), Milton, Vermont: Green Mountain Geologist, v. 14, #4, p. 7.

Popenoe, P., 1964, Aeroradioactivity of parts of east-central New York and west-Central New England, U.S. Geological Survey Geophysical Investigations Map GP-358, scale- 1:250,000.

Ryan, P., Trombulak, S., Aldrich, L., Ausprey, I., Brower, B., Calvi, B., Groff, S., Hicks, C., Johnston, K., McBride, M., Perlow, L., Yazwinski, M., 2002, A Survey of Groundwater Composition in Northern Addison County, Vermont: Geologic Sources of Contamination, Environmental Science Practicum research report: Environmental Studies Program, Middlebury College, Middlebury, Vermont.

Texas Instruments, 1976, Airborne Geophysical Survey of a Portion of New England, U.S. Energy Research and Development Administration Open File Report GJO-1666-1, 73 p.

Vanacek, D.M. and Dorsey, R.J, 1983, Geologic and Radiometric Survey of the Sweeney Farm: Milton, Vermont, Vermont Geological Survey Open File Report 1983-2.

Vermont Geological Survey, 2000, Memo to the Vermont Dept. of Health regarding "Colchester/Milton Radionuclides", 6 p., 2 figures.

Whitten, E., 1988a, Paleoenvironmental interpretation and history of Uranium enrichment and resultant Radon gas genesis of the Clarendon Springs Dolomite, Milton, Vermont, Green Mountain Geologist, v. 15, #1, p. 11-12.

Whitten, E., 1988b, The Geology, Radioactivity, and Uranium Mineralization of the Clarendon Springs Dolostone, Milton, Vermont, Senior Thesis in the Environmental Studies Department, University of Vermont, 95 p..

These coverages were digitized from original 1:250,000 scale maps and data and, therefore, use at this scale is recommended. Accuracy may diminish when enlarged beyond this scale.

The only way to determine with certainty if groundwater from a particular well has elevated radionuclide levels is to have the water tested by a certified lab. The Vermont Department of Health recommends that all private well owners test their wells for naturally-occurring alpha radiation every 5 years. This map should not be used as a replacement for detailed, site-specific studies by competent technical personnel.

This map (and the other eight maps in this series) displays geological and geophysical data compiled from surveys conducted at various times over several decades. The information used in preparing the map(s) represents the best data possessed by the Vermont Agency of Natural Resources at the time of production. The data is subject to revision at any time and the map user should contact the Vermont Agency of Natural Resources to determine whether there have been any changes in the data on which the map was based.

Although every effort has been made to faithfully portray the information from the surveys, the Agency of Natural Resources cannot vouch for the accuracy of the data on which the map(s) was based. No warranty as to the accuracy or the usefulness of the data on the map(s) is expressed or implied.


*GIS Data available from Vermont Geological Survey, 103 South Main Street, Waterbury, Vermont 05671, 802/241-3608, marjorie.gale@state.vt.us