Environmental Engineering Reference
In-Depth Information
of contaminated soils and sludges in on-site land treatment units (LTUs).
Indigenous microorganisms were expected to break down the target con-
taminants to less harmful and less mobile constituents.
Two types of impacted soils exist at the site. The first is soil from a
holding cell that had been stabilized with rice hulls and fly ash (pH approx-
imately 10) as part of earlier emergency remedial activities. The second is
soil from a process area contaminated by spills, leaks, and open air drying
during wood treatment activities. The current evaluation was conducted
only on contaminated material from the process area. The process area soils
had unusually high concentrations of PAHs (13,000 mg/kg, average) and
PCP (1500 mg/kg, average). Even with the high contaminant levels, the soil
maintained microbiological activity.
7.3.2 Soil characterization
The metal and mineral content and physical characterization of the soil from
the POPILE site, El Dorado, AR, were determined prior to the initiation of
the first pilot study. A complete presentation of the soil characterization was
reported by Hansen et al. (1999). Pertinent portions are summarized in Table
7.7 to supply an overview of the study conditions.
The initial chemical characterization included total Kjeldahl nitrogen (as
well as nitrate, nitrite, and ammonia), total organic carbon, and total phos-
phate. Chemical and physical properties examined included pH, soil buffer
capacity, cation exchange capacity, and field moisture capacity (FMC).
The FMC, as defined by the U.S. Department of Agriculture Natural
Resources Conservation Service, is the moisture content of the soil expressed
as a percentage of the oven dry weight after the gravitational or free water
Table 7.7
Initial Characterization of the Original
POPILE Soil Used in the Pilot Studies
Test/Compound
POPILE Soil
Atterburg limits
Plastic limit: 17
Liquid limit: 23
Classification: clay/silt
Particle size distribution
Sand: 33%
Fines: 67%
Metals (mg/kg)
Iron-combined forms
10,500
Magnesium
3800
Barium
700
Zinc
30
Lead
10
Mercury
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