API PUBL 7105 : 1997

1.2 OBJECTIVE AND SCOPE

The objective of the work described in this report was to prepare a brief technical analysis of the radium concentration limit of 30 pCi/g in pipe scale and sludge left near the surface of remediated oil field sites and returned to unrestricted public access. Analysis of this limit was based on modelling of the potential transfer of radioactivity through environmental pathways and of potential exposures to people using the remediated oil field site. Estimated exposures and doses were compared to regulatory limits and guidelines. This document may also serve as the basis for discussion on limits with state regulators, for example concerning part N of the draft recommendations from the Conference of Radiation Control Program Directors (CRCPD).

The scope of work included an assessment of potential dose and indoor radon concentration from radioactivity in pipe scale and sludge to users of remediated pits, rank battery sites, and land firms. The assessment considered existing sites and future sites that have been and will be remediated under the criterion that all material containing Ra-226 at concentrations greater than 30 pCi/g will be disposed by alternate means. Therefore, potential doses from NORM containing Ra-226 concentrations in excess of 30 pCi/g were beyond the scope of this report. In this assessment, an estimated distribution of radium concentration in waste (based on Otto's data 1989), ranging from 30 pCi/g down to natural background levels, was included as an integral component of the pathways and exposure models. This fundamental difference in waste characterization sets this assessment apart from all previous work. The probabilistic method used for calculating the potential doses and indoor radon concentrations are consistent with the new policy announced by EPA's Science Policy Council in February 1997 which recommends application of these methods.