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Prairie Meadows Soil Samples. For Allender Butzke Engineers, Inc. By Scott Schlorholtz, MARL at ISU. Samples Received. Sample 1 (rec’d 8/04/2005) – from a problem area of the race track Sample 2 (rec’d 8/08/2005) – from a problem area of the race track
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Prairie Meadows Soil Samples For Allender Butzke Engineers, Inc. By Scott Schlorholtz, MARL at ISU
Samples Received • Sample 1 (rec’d 8/04/2005) – from a problem area of the race track • Sample 2 (rec’d 8/08/2005) – from a problem area of the race track • Uncontaminated (rec’d 8/08/2005) – from a “good” area of the race track
Tasks • Ascertain why the problem area of the race track had a different color than the uncontaminated area of the track • Evaluate if there are any significant differences between the problem area and the uncontaminated area
Work plan • Evaluate bulk and clay mineralogy via X-ray diffraction (XRD) • Evaluate bulk chemistry via X-ray fluorescence (XRF) • Evaluate morphology by microscopy • Conduct sieving or size separation tests to investigate the physical properties of the soil samples
Summary • The particle size analysis experiments indicated that sample 1 had less sand than the uncontaminated sample; and hence, sample 1 contained a larger fraction of silt and clay. • Bulk sieving (#8 mesh sieve) indicated the presence of a significant amount of agglomerates in samples 1 and 2.
Summary • X-ray diffraction indicated that the minerals present in the bulk samples were similar. It was noted that the clay fraction of sample 1 contained significant amounts of calcite and feldspar. These minerals were not present in the clay fraction of the uncontaminated sample. Sodium montmorillonite was not explicitly identified in the clay fraction of any of the samples; however, the identification process was complicated by the fact that the major clay mineral in the samples appeared to be a calcium montmorillonite.
Summary • Bulk chemical analysis via XRF indicated that the chemical composition of the uncontaminated sample and sample 1 were very similar. Only calcium, aluminum and iron appeared to vary significantly. The trace elements present in the two samples were also very similar.
Summary • The morphology of the uncontaminated sample was significantly different than samples 1 and 2. The uncontaminated sample was primarily composed of individual particles exhibiting little or no agglomeration. Samples 1 and 2 were composed of agglomerations of particles. Simple washing broke down the agglomerations in sample 1.
Summary • Microscopy indicated that the agglomerates were composed of individual particles held together by an interstitial material. • The interstitial material was very finely divided. It had a chemical composition that was similar to the bulk soil with evidence of discrete calcium-bearing particles.
Conclusions • Most of the agglomerations in samples 1 and 2 were composed of individual particles that were weakly (no cementation was evident) held together by an interstitial material. There was considerable evidence that the agglomerations also covered the clay nodules in the samples (i.e., dark cores of particles covered by white surface material). This suggests an influx of a “sticky” material into the uncontaminated soil.
Conclusions • The bulk mineralogy and bulk chemistry of both the uncontaminated soil and sample 1 were consistent with those commonly observed for soils (only inorganic constituents were measured). No extraneous elements (at major, minor or trace levels) were identified which would have suggested that the soil was contaminated by a potentially hazardous waste material.
Conclusions • The information gathered by this study was consistent with the intrusion of drilling mud into the uncontaminated soil. Since the uncontaminated soil is placed directly on a compacted base of limestone (both coarse and fines) the drilling mud probably picked up some fines while it was traveling through the compacted base. This would explain the presence of calcite in the clay mineral fraction of sample 1.
Comments • An alternative explanation of the presence of calcite in sample 1 would be that during prior removal of the soil, some of the base material was scraped up with the soil. This explanation is weak because it fails to explain the physical agglomerations that were noted. In addition, then one would have expected to see some coarse calcite fragments in samples 1 and 2. These particles were not observed.
