Figure 3. GSD falling within BU specification

ERDC TN-DOER-C13

July 2000

with the proposed BU. Depending upon the variability of the site, the GSD may be an average for

the whole site or a section or sections of the site under consideration. If the GSD is acceptable, it

should then be determined if the COC in the bulk material are at levels below all limiting

concentrations for the BU application. If all COC are at concentrations below the BU requirements

and the material GSD falls within the BU specifications for the entire site or portion under

consideration, no separation is needed and the material can be applied to the BU as is. This is

illustrated in Figure 3. The MRP evaluation in this case is simply to determine if the volumes

available on a one-time or recurring basis will meet the needs for the BU application under

consideration.

Figure 3. GSD falling within BU specification

If the bulk material does not meet requirements as is, the potential for separation to meet the

requirements must first be assessed in general terms. A number of factors should be considered:

preliminary targeted size or density cut, the technical difficulty of making the targeted separation,

potential for regulatory classification changes in concentrated residual materials. The simplest

separation from a technical perspective is a sand/silt separation. A silt/clay separation is technically

more difficult, but may be worth considering if removal of the clay would permit recovery and reuse

of the silt fraction as well. Acceptable COC levels in residual materials would be tied to any

threshold that may require an increased level of treatment or management compared to the

preseparation condition, e.g., the 50-ppm threshold for PCB triggering management under the Toxic