Soil radon concentrations

Indexes Using Permeability and Soil Radon Concentrations... 

Birchard, G.F. and Libby, W.F., 1980. Soil radon concentration changes preceding and following four magnitude 4.2 - 4.7 earthquakes on the San Jacinto fault in Southern California. J. Geophys. Res., 85 3100-3106. 

In theory, the application of radon barriers should be adequate to avoid elevated radon levels in houses. In practice, however, a backup radon mitigation system has been found essential for maintaining indoor radon concentrations below 4 pCi/L in most homes studied. In the recent radon-resistant residential construction projects conducted by U.S. EPA and/or private builders, several of the homes designed to be radon resistant have contained radon concentrations above 4 pCi/L. In each of those houses, a backup system consisting of an active (fan-assisted), or passive (wind-and-stack-effect-assisted), SSD system was installed at the time of construction. When mechanical barriers failed to adequately control radon, the soil depressurization methods were made operational. 

In summary, it is worthwhile to continue the installation of a vapor barrier that serves as the added valid function of moisture barrier. More comprehensive installation measures and more expensive materials may be merited in areas where the radon source is strong because of either high radon concentrations or high soil gas how rates. 

In addition to the above measurements, indexes using soil concentrations in combination with permeability measurements have been suggested by some researchers.4142 As elaborated on later in this section, these methods have been successful in establishing relationships between some of the site measurements and indexes, and indoor radon concentrations for specific areas and regions. 

In buildings with indoor radon concentrations greater than 4pCi/L, the majority of the radon is produced in the soil and enters the building through foundation openings. The radon gas found in soils is... 

Several studies have been attempted to make simple correlations between radon or radium concentrations in the soil and indoor radon concentrations.4344 No significant correlations were made between these variables. 

The major drawback to using the Florida study to support the correlation between indoor and soil measurements was that the indoor measurements were obtained from 3-day closed-house charcoal measurements, and soil radon was obtained from 1-month alpha track measurements buried 1 ft beneath the soil surface. Comparisons of charcoal and alpha track data are generally not recommended since they are quite different measurement techniques, and represent radon levels over different time periods. However, the study was subjected to numerous quality control checks including deployment of alpha track detectors in 10% of the houses to obtain a check on indoor air measurements made by charcoal canisters. In spite of the measurement drawbacks, the study indicates that soil radon measurements taken alone are not a dependable predictor of potential indoor radon concentration. 

The major difference between these data and the Florida survey data in Table 31.3 is that this portion of the NEWHEP data was collected from newly constructed houses where passive radon-resistant construction features were being tested. There are no data on control houses in the same area that did not have those built-in features, making it difficult to compare soil radon measurements with indoor radon concentrations. It appears, however, that passive-only building techniques do not consistently result in indoor radon levels below 4 pCi/L. 

Radon dissolves into groundwater from rocks or soils. When the water is exposed to the atmosphere, some of the dissolved radon is released. As a rule of thumb, there is an increase of about 1 pCi/L in the air inside a house for every 10,000 pCi/L of radon in the household water.50 Higher radon levels have been observed in individual rooms when water is heated or agitated, such as during shower use.51 Builders should be aware that houses require groundwater as the house water supply could have a radon problem. The only way to be certain that the groundwater is not a potential radon source is to have the water from the well tested. Some states and private companies provide test kits for this purpose. It should also be noted that radon concentrations in water, like radon concentrations in the air, can vary significantly. 

It is clear that some proper planning in the design phase of new houses can lead to less likelihood of indoor radon problems and make provision for lower cost modifications later to mitigate against such problems. The experience in Sweden is that houses with low radon concentrations can be constructed on high risk soils by proper design and construction practices. 

Radon concentration in soil gas at depths well below the surface can be estimated from ... 

As noted in Table I, average surface radium concentrations appear to vary by about a factor of 20. This can also be seen from the distributions from the NARR data. Soil permeabilities, on the other hand, have much larger variations, and thus, in principle, may have a greater influence on the spatial variations in average indoor radon concentrations that have been observed. As with the case of surface radium concentrations, the spatial variability of air permeabilities of soils is an important element in developing a predictive capability. 

Age column is given in years, rock column is portion of rock used in a foundation, fireplace or wall in square feet, height of ceiling in ieet. Area is in square feet. Blanks in furnace column indicate no use of furnace, tightness A is average, T is tight, D is drafty, as stated by the homeowner, soil column shows soil from granite bedrock in a foundation, fireplace or wall. Water column is radon concentration in pCi/1. 

The same is true of the geographical distribution of the uranium concentration in glacial till, the most common soil type in Finland (Geological Survey of Finland, 1985). The sometimes very large effect of ground permeability is the main reason that the details of the radon concentration distribution differ from the distribution of other radiation parameters. 

Radon from the soil enters into buildings by convective flow of soil gas. Transport by diffusion is normally insignificant. In houses with very high radon concentration, diffusion need not be considered because it can only provide an insignificant fraction of the source strength. There are three conditions necessary for infiltration of soil gas containing radon into the building from the soil ... 

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