Table 8. Geophysical testing of DCR-treated RMA Basin F soil sample no.
24216.
Optimum
Unconfined
Hydraulic
Maximum
moisture
compressive
density
content
strength
(permeability)
(Mg/m3)
Sample
(%)
(MPa)
(cm/s)
Raw material
(soil-amended sludge)
N.A.
N.A.
Very low
N.A.
Soil-amended sludge
1.6 107
plus 27.4% DCR reagents
1.65
14.3
1.31
Analyses completed by Southern California Soil & Testing and WallaceKuhl & Associates.
N.A. = Not analyzed.
Geophysical properties testing
uted to simple dilution with the CaO reagent. In
While the heterogeneous raw untreated start-
other cases, however, microencapsulation and/
ing material was a dry and friable soil/silt mix-
or macroencapsulation also played a role in re-
ture with a very low unconfined compressive
ducing pesticide leachability.
strength (UCS), the DCR-treated product exhib-
DCR is different from cement- or pozzolan-
ited a very impressive UCS of 1.31 MPa (Table 8).
based approaches in that it does not rely solely on
A maximum density of 1.65 Mg m3 was obtained
formation of a monolithic structure of hydrated
at 14.3% moisture content, and the permeability
silicates and carbonates to incorporate and/or
(hydraulic conductivity) was very low at 1.6E-7
macroencapsulate the hazardous constituents. The
cm s1 and in the range of that required for clay
DCR process first traps the mobile organic con-
cap materials. Once compacted into a hydro-
stituents into nonmobile, hydrophobic, pulver-
phobized soil body (as in an onsite Class I land-
ized solids literally at a submicron level (microen-
fill) additional isolation of the contaminates
capsulation). Then, as with other cement- or
would be derived from a combination of micro-
pozzolan-based approaches, it is possible to take
and macroencapsulation. Because of the low per-
advantage of macroencapsulation in large, com-
meabilities and hydrophobic, water-repelling na-
pact soil bodies when appropriate. These hydro-
ture of the compacted material, water could not
phobic compacted soil bodies are surrounded by
easily penetrate the soil body, and with in situ
a self-healing CaCO3 crust that increases in thick-
ness and stability with time. Unfortunately, the
permanence and water-repellency of the material
accelerated nature of this treatability work (to
would improve with time.
date) has not allowed time to achieve any benefit
of additional microencapsulation due to this
gradual carbonation process. Such in situ carbon-
CONCLUSIONS
ation might serve to improve TCLP results as
well as reduce permeability and leachability in a
Based on the results observed to date and pre-
groundwater environment.
sented in this report, it is clear that the DCR pro-
These studies demonstrate the value of addi-
cess can be used to treat the Basin F waste soil
tional work to optimize the DCR mix design. Such
nonthermally to produce a dry, homogeneous,
optimization would include determinations of: 1)
soil-like material with desirable physical proper-
the lime-milk concentrations to optimize the re-
ties that on compaction can achieve the following
lease of ammonia to the emissions control sys-
treatment goals: reduction of all leachable volatiles
tem; 2) the amount of benign oil to adequately
to nondetectable levels, confinement of all metals
suppress odor, improve permeability, and aid in
to below RCRA TCLP levels, and a decrease in
solubilization/transfer of the pesticides onto the
pesticide leachability to levels approaching RCRA
CaO during the pre-DCR mixing phase; 3) the
standards. For example, endrin TCLP concentra-
degree of hydrophobicity necessary for this par-
tion was reduced from 74 g/L to 2028 g/L
ticular waste; and 4) the amount of reagent neces-
(regulatory limit = 20 g/L). In several cases, re-
sary to provide homogeneity and complete vola-
ductions in pesticide leachability could be attrib-
tile removal.
15
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