Re[2]: SEDIMENT AND REGS -Reply

[Craig D Brown <CBROWN@envc.sandia.gov>]

In response to the 15 mrem/yr cleanup limit, a few issues
have been brought up that could use clarification:

1.  Instrumentation detection limits:  In reality, the detection
limits of laboratory analytical techniques should be included
in this discussion.  If you are making cleanup decisions for
soils and structures based on field instrument detection you
aren't even close.  The 15 mrem/yr is based on an
environmental pathway analysis (e.g., the RESRAD family of
codes) using the results of soil samples, contamination
surveys, etc.  For example, the cleanup standard (using 15
mrem/yr) for Ra-226 in soil using a residential land-use
scenario could be as low (or lower) as 1 pCi/g, most likely
not detectable using normal field survey techniques.  Note
that this is 1/5 of the current DOE standard.

2.  It was brought up that a cost-benefit analysis regarding
the 15 mrem/yr cleanup standard would be nice to see.  I
would refer you to NUREG-1496, Volumes I and II.  Although
they don't go out to 1000 mrem/yr, they do cover the 0.03
-100 mrem/yr levels.  You generally find that, for this span,
the "knee" in the curve for highly contaminated cleanups
occurs at about 3 mrem/yr.  This is probably why the NRC
is proposing that 3 mrem/yr be the "ultimate" standard, with
ALARA studies performed between 3 and 15 mrem/yr (at
least in these documents published Aug. 1996).

3.  In comparing the 15 mrem/yr to operational 100 mrem/yr
limits you will find, at least in the DOE world, that DOE
Order 5400.5 (and the draft of 10 CFR 834) requires that
exposures exceeding 10 mrem/yr to offsite receptors be
reported to HQ.  How many DOE sites do you think would
like to make this report (and see it in the local newspaper). 
I may be wrong on this account, I have not dealt with an
extensive list of DOE sites.

4.  Comparing the "risk" numbers that EPA provides in the
draft of 40 CFR 196, and the technical basis documents, to
some of EPA's other "risk" numbers it can be seen that they
assign 3E-04 to 15 mrem/yr.  I'm not sure how they came
up with this number but all of the dose/risk numbers that I
have seen have been relatively inconsistent.  At least they
haven't gone with the 1E-06 value used in Subpart S.  Not
that I would call this a risk based approach, just throwing
out the documented data.

The above doesn't necessarily mean that I agree with the 15
mrem/yr cleanup standard, just that I have tried to make the
best of it and to study it.  I'd be happy if someone would just
provide the rules of the game (how else can you win).

Only the opinions of:

Craig D. Brown
cbrown@envc.sandia.gov