U.S. Geological Survey

Radon Potential of the Upper Midwest

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TABLE 1. RADON INDEX MATRIX

		POINT VALUE
FACTOR	1	2	3
INDOOR RADON (average)	< 2 pCi/L	2 - 4 pCi/L	> 4 pCi/L
AERIAL RADIOACTIVITY	< 1.5 ppm eU	1.5 - 2.5 ppm	> 2.5 ppm
GEOLOGY	negative	variable	positive
SOIL PERMEABILITY	low	moderate	high
ARCHITECTURE TYPE	mostly slab	mixed	mostly basement

SCORING:

		probable screening
Rn potential category	point range	indoor Rn average
LOW	3-8 points	< 2 pCi/L
MODERATE	9-11 points	2 - 4 pCi/L
HIGH	12-17 points	> 4 pCi/L

TABLE 2. CONFIDENCE INDEX MATRIX

		POINT VALUE
FACTOR	1	2	3
INDOOR RADON DATA	Sparse/no data	fair coverage/quality	good coverage/quality
AERIAL RADIOACTIVITY	questionable/no data	glacial cover	no glacial cover
GEOLOGIC DATA	questionable	variable	proven geol. model
SOIL PERMEABILITY	questionable/no data	variable	reliable, abundant

SCORING:

LOW CONFIDENCE	4 - 6 points
MODERATE CONFIDENCE	7 - 9 points
HIGH CONFIDENCE	10 - 12 points

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13 October 1995