Technology Status Report: In Situ Flushing - CLU-IN

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In Situ Flushing Project Summaries GWRTAC Case Study Database the water table at a depth of approximately 7 to 10 feet below ground surface. The LNAPL is composed of Varsolâ which was used as the facility dry cleaning solvent and was stored in underground storage tanks until the 1970s. PCE replaced Varsolâ as the dry cleaning solvent at that time because of the fire hazard represented by Varsolâ. Phase 2 of the DNAPL investigation combined laboratory and modeling studies to design a partitioning interwell tracer test (PITT) for measuring the volume and relative distribution of DNAPL at the site. Laboratory studies were conducted using DNAPL and sediments collected from the site, and resulted in the selection of a suite of tracers suitable for a PITT under the site specific conditions at Site 88. Then, using information gained during the Phase 1 field investigation, a geosystem model of the site was constructed for preliminary PITT-design simulations using UTCHEM, a three-dimensional fluid flow simulator for multiphase and multi-component chemical composition simulations. UTCHEM is an EPA-approved simulator developed by the University of Texas at Austin. The objective of the UTCHEM simulations was to determine the preliminary design flow rates and test duration of the PITT. The PITT design consists of nine wells in a 3X3X3 line-drive wellfield configuration, with three injector wells and six extractor wells; the three injectors are configured as a central line wells in the nine-well array. For tracer injection and extraction, the wells are screened from approximately 16 to 20 feet below ground surface and terminate in the clay aquitard. The area formed by the PITT wells is 20 feet wide by 30 feet long, with a resulting interwell distance of 15 feet between any given injector and extractor. The size of the PITT wellfield was economically constrained by the time required for tracers to travel the interwell distance between injectors and extractors through the low permeability shallow aquifer which is composed of fine to very-fine sand (Kavg @ 0.3 ft/day or 10-4 cm/sec). Design modeling suggested that the PITT would require approximately 35 to 50 days to be completed in the DNAPLcontaminated aquifer at Site 88. Since Building 25 is still fully operational as the Base dry cleaning facility, the PITT wells were installed outdoors on the north side of the building to minimize logistical conflicts with the dry cleaning operations during the PITT and subsequent SEAR. Phase 3 of the DNAPL source-zone investigation included field implementation of the PITT as well as several additional field activities required prior to the PITT. First, free-phase DNAPL recovery was undertaken by means of a water flood to minimize the amount of free-phase DNAPL in the test zone. Secondly, a conservative interwell tracer test (CITT) was conducted to evaluate the preliminary PITT design (i.e. flow rates, test duration) as determined by the Phase 2 design modeling. A CITT provides empirical evidence of the degree of aquifer heterogeneity present in the test zone, thus allowing PITT design revisions to be made before starting the PITT, and thereby ensuring the success of the PITT. Bromide was used as a conservative tracer for the CITT, and tracer breakthrough was measured at the six extractor wells to determine the actual tracer residence time in the interwell swept pore volume between a given pair of injection and extraction wells. The results of the CITT showed that only minor changes were needed in the injection and extraction design flow rates for the final design of PITT. The PITT began on May 13, continued for 40 days, and was terminated on June 22, 1998. PITT data analysis revealed that 87 gallons of DNAPL is present in the 4,800gallon swept pore volume of the test zone. DNAPL saturations in the test zone are highest in the area adjacent to the north wall of the building, at approximately 4%, and decrease in a northerly direction away from the building to about 0.4% saturation at a distance of approximately 20 feet north of Building 25. The PITT provides baseline data on DNAPL conditions in the test zone prior to the SEAR. The SEAR demonstration with surfactant recycling will be conducted in early 1999. The SEAR will be Ground-Water Remediation Technologies Analysis Center Operated by Concurrent Technologies Corporation Appendix - Page 80 of 164 Copyright GWRTAC 1998 Revision 1 Tuesday, November 17, 1998
In Situ Flushing Project Summaries GWRTAC Case Study Database immediately followed by a second PITT to measure the volume of DNAPL remaining in the test zone. PITT 1 and PITT 2 will be compared to evaluate the effectiveness (i.e. performance assessment) of the surfactant flood to remove DNAPL from the test zone at Site 88. The DNAPL source-zone investigation at Camp Lejeune was co-funded by Navy ESTCP and Navy LANTDIV, and was conducted in a teaming arrangement between DE&S and Baker Environmental (the LANTDIV CLEAN program contractor at Camp Lejeune). The above funding and teaming arrangement remains in place for the SEAR and PITT 2. Report(s)/Publication(s) (Additional Information Sources): None Ground-Water Remediation Technologies Analysis Center Operated by Concurrent Technologies Corporation Appendix - Page 81 of 164 Copyright GWRTAC 1998 Revision 1 Tuesday, November 17, 1998
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Technology Status Report Technology
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ABSTRACT This technology status rep
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LIST OF TABLES Table Title Page 1 I
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1.0 INTRODUCTION / PURPOSE OF STATU
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a laboratory-scale project. As illu
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3.1 Flushing Solutions 3.0 ANALYSIS
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(approximately eight) full-scale pr
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Table 1. In Situ Flushing - Summary
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Table 3 In Situ Flushing - Geology
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Table 4 In Situ Flushing - Recovere
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Full-Scale/Commercial 26% Figure 2.
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Site Remediation 25% Figure 4. In S
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NAPL Removal 34% Figure 6. In Situ
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Figure 8. In Situ Flushing - Distri
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Number of Projects 35 30 25 20 15 1
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Number of Case Studies 45 40 35 30
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25 ft and 50 ft and 10 ft and 100 f
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Unconfined Aquifer 65% Figure 16. I
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In Situ Flushing Project Summaries
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Technology Status Report: In Situ Flushing - CLU-IN

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