RE: EPA/NRC MEMORANDUM OF UNDERSTANDING

["Richard Orthen" <rorthen@EARTHSCIENCES.NET>]

Doug,



The Table 1 consultation triggers were developed using EPA's CERCLA risk

assessment framework, i.e., either (1) ARAR's, (2) Hazard Index = 1.0, or

(3) 0.0001 excess cancer risk.  For example, the radium-226/thorium-232 5

pCi/g triggers are UMTRCA soil standards, while the total uranium trigger

(mg/kg) is based on a hazard index (HI) of 1.0 using EPA's soil screening

calculator.  For most of the remaining Table 1 nuclides, the soil

concentrations (pCi/g) are assigned at the 0.0001 excess cancer risk level

using the EPA Preliminary Remediation Goals (PRG's) calculator, adjusted for

the PRG nominal risk level of 0.000001.



The exposure scenarios were parameterized using default "reasonable maximum"

values found in EPA OSWER documents like "Soil Screening Guidance for

Radionuclides" and "Supplemental Guidance for Developing Soil Screening

Levels for Superfund Sites."



It is important to note that the triggers do NOT account for migration into

groundwater or, obviously, more restrictive state regulations regarding

groundwater quality.



Hope this helps.



Rick Orthen

Sr. Project Manager

Earth Sciences Consultants, Inc.

Export, PA



-----Original Message-----

From:	owner-radsafe@list.vanderbilt.edu

[mailto:owner-radsafe@list.vanderbilt.edu] On Behalf Of Doug Schult

Sent:	Friday, June 13, 2003 10:24 AM

To:	radsafe@list.vanderbilt.edu

Subject:	EPA/NRC MEMORANDUM OF UNDERSTANDING



In the EPA/NRC Memorandum Of Understanding on the D&D of radiologically

contaminated sites, reference is made to Table 1. Table 1 lists

radionuclides specific activity concentrations for two different

exposure senarios(Residential and Industrial/Commercial). Does anyone

know what the activity concentrations in Table 1 are based on and how

they were calculated.



Thanks for your help.



Doug

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