Re: 2X Background Reference

[c0etxlim@mrd42.mrd.usace.army.mil (Luke I. McCormick)]

    I have seen references to 2X background used for screening purposes,
    but would suggest that not be used as a clean-up criteria.  Background
    (that sea of deadly radiation we live in) becomes a very flighty
    term when you begin to deal with clean-up limits at a site.  e.g.
    are you referring to annual background EDE to the most exposed individual?
    or background soil concentrations for a specific radionuclide? 
    Please remember that EDE from background is a dynamic figure. 
    Sunspots, barometric pressure and rainfall will effect this value.
    Soil concentration background for a particular radionuclide is
    much easier to measure but still requires a measure of care when
    explaining this to regulators and the public.  e.g. at one of our sites
    radium-226 concentration in the "clean" soils was measured at a 
    number of sites and the 'average' (mean) background was determined.
    the ROD for the site selected 5 pCi/gm Ra-226 over background as the
    cleanup goal.  unfortunately, the fill soil for reconstruction
    was required to be 'background'.  Since, for an average of samples,
    1/2 will be below the mean and 1/2 will be above the mean,  the fill
    requirement to be at 'background' (defined as the mean background)
    eliminated half of the soils in the area. Since fill could not be
    obtained that would reliably be 'background', we were literally in a hole.

    To remedy the situation
    soils were trucked from the other end of the state (which happened
    to have a lower natural concentration) for use as fill. (At a nice fee)  

    Lesson learned. Specify background, in particular, soils with 
    concentrations below the upper 95.5% confidence limit (2*sigma)
    will be considered at background. 

    I am trying to work up some guidance for background determination on
    Corps sites.  If anyone has some good stuff I would appreciate it.
    I have the EPA 's "Guidance for Data Usability in Risk Assessment", 
    but am not thrilled with their background determination.
 
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 
>   Does anyone know the document(s) that references 2x background as a
>   possible guidance value for site cleanup?
> 
>   Meg MacLeod
>   meg_macleod@abbsmtp.abb.com
>