Conceptual Site Model - Argonne National Laboratory

WVDP Phase 1 CSAP(northern portion) likely are affected. Because Cs-137 is predominant, this area of contaminationis known as “the cesium prong” (DOE 2009 Table 2-17, DOE 2010 Section 3.11.5).As originally deposited, surface soil activity concentrations should have decreased towards thenorth, away from WMA 1. However, the surface features of many areas within the WVDPpremises have been reworked significantly since the release; as a result, the current spatial anddepth distribution of soil contamination may be significantly different than the original footprint.In addition, the surface soil contamination likely has been naturally spread by erosion and runoffinto surface drainage features; this phenomenon may have enlarged the area impacted bydeposition, although detailed data regarding this effect are not available. (DOE 2010 Section3.11.5)Finally, other releases from the Process Building stack may have produced minor impacts. Theseother releases include the 1968 failure of a dissolver off-gas system filter, resulting in 0.28 Ci ofparticulate activity, and the 1968 failure of a vessel off-gas system filter, resulting in the March1968 releases to exceed the monthly allowance by 15 percent. (DOE 2010 Section 3.11.5)I.4.2Other Known and Suspected ReleasesThere are no known or suspected releases that originated within WMA 10.I.5 Existing DataExisting data sets for this area include:• In 1982, static direct exposure readings were collected across the WVDP premises(WVNSCO 1982). Most of WMA 10 was covered by these measurements on a 10-mgrid. Figure I.10 shows these results color-coded by the exposure readings encountered,with the data overlain on a 1977 aerial photograph. These data show very distinct spatialtrends associated with gross activity, ranging from near background or at backgroundconditions at the southern end of WMA 10 to significantly elevated activity levels in thenortheastern corner adjacent to the Process Building. These patterns may have beenassociated with patterns in surface soil contamination, or may have been associated withRev. 1 I-5