Final Remedial Action Completion Report for the ... - Rvaap.org

Remedial Action Completion Report
June 2008
3.5.3 Field Quality Control Sampling Procedures
Remediation of Soils and Dry Sediments at RVAAP 08-11 (LLs 1-4)
Page 3-14
At a minimum, field QC sampling procedures included the collection of duplicate samples at a
frequency of one per 10 samples collected or as otherwise specified by the field screen method
vendor.
3.5.4 Summary of Field Screen Results
On-site field screening was performed for metals, PCBs, and the explosives TNT and RDX prior
to collecting the multi-increment samples for off-site confirmatory analysis. In general, the
results of the field screen analyses for metals and explosives worked well to guide confirmatory
multi-increment sampling to produce results below cleanup goals with the exception of three
multi-increment confirmatory sample locations (LL2ss-049-cs, LL3ss-072-cs and LL4ss-108-cs)
for metals and one confirmatory sample location (LL1ss-038-cs) for TNT. The field screen
results using the Ensys ® PCB Soil Test System were not as favorable as for the metals and
explosives and tended to provide continuous suspect positive results.
3.5.4.1 PCB Field Screening
Field determinations of PCBs in soil samples were initially performed through implementation of
colorimetric analyses using the PCB Ensys ® Soil Test System. This is a pass/fail test and the
determination of PCBs concentration in the sample was determined by reading with a
spectrophotometer. The color of the sample was compared to the reference standard provided
with the field kit.
As mentioned previously, the field screen results for the PCB Ensys ® Soil Test System
continuously provided suspect positive results for PCBs. In order to provide an adequate
comparison of the PCB field screen test kits to actual concentrations in the soils, Shaw submitted
a pre-confirmation sample for laboratory analysis. The PCB field screen result indicated a
concentration in the soil that was above the applicable cleanup goal; whereas, the laboratory
result confirmed that the result was actually well below the cleanup goal, thus reducing the
confidence level the PCB test kits were providing.
As a second alternative for evaluating PCBs in soil, Shaw utilized an on-site gas chromatograph
(GC) with an electron capture detector (ECD). The ECD is an ultra sensitive GC that will only
sense those substances that it is electron capturing, and is especially sensitive to halogens that
contain chlorine elements such as PCBs. Through use of the GC-ECD, field screen results
produced valid representation of PCB concentrations with a success rate of greater than 93%.
Only one confirmatory sample (LL1ss-029-cs) of the 15 submitted for laboratory analysis for
PCBs reported an exceedance of the cleanup goal.
3.5.4.2 TNT and RDX Field Screening
Field determinations of TNT and RDX in soil samples were performed through implementation
of colorimetric analyses using the TNT or RDX Ensys ® Soil Test System. As with the PCB kits
this is a pass/fail test. This test system provides the materials in pre-measured and pre-packaged
form eliminating labor intensive procedures of reagent preparation. The working range of the
field test for TNT and RDX is 2 to 40 mg/kg. This range is several orders of magnitude below
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