radon accumulation on carbon absorbtion units

[Joseph_Guido@radian.com (Joseph Guido)]

     We are proposing to install a carbon filter array for the treatment of 
     VOC contaminated groundwater.  This same water has a radon 
     concentration of 1500 pCi/L.  Initial dose estimates put the exposure 
     rate at 1ft from each of 6 vessels is 2.5 mR/hr.  (this is based on a 
     flow rate of 600 gpm and 100% collection efficiency).
     
     My questions are:
     
     1) Does anyone know a more reasonable estimate for the collection 
     efficiency of radon on carbon beds or appropriate referance?
     
     2) If my dose calculations are in fact accurate, would I be subject to 
     part 20 requirements - i.e. posting, monitoring, training?
     
     3) What offsite dose guidelines are applicable?  
     
     
     ......
     
     Joe Guido
     Health Physicist
     Radian International
     joseph_guido@radian.com