Technology Status Report: In Situ Flushing - CLU-IN

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In Situ Flushing Project Summaries GWRTAC Case Study Database GWRTAC ID: FLSH0022 Project Name: Hill Air Force Base, UT (Test 1, OU 1 - Cosolvent Solubilizatio City: Layton State/Province: UT Primary GWRTAC Personal Communication Source (Name/Organization): Project Summary: Jon Ginn U.S. Air Force Report(s)/Publication(s) (GWRTAC Source): Ground-Water Remediation Technologies Analysis Center (GWRTAC), 1996: Surfactants/Cosolvents, Technology Evaluation Report TE-96-02, Dr. Chad T. Jafvert, Purdue University, for GWRTAC, Pittsburgh, PA, December 1996, available at www.gwrtac.org Rice University, 1997: Technology Practices Manual for Surfactants and Cosolvents, Rice University, 6100 Main Street, Houston, TX 77005-1892, February 1997 Sillan, R.K., M.D. Annable, and P.C.S. Rao, Editors, 1997: Executive Summary, "In-Situ Cosolvent Flushing for Enhanced Solubilization of a Complex NAPL: Comprehensive Field-Scale Evaluation", Draft Final Report, CRADA CR-821990, May 1997. U.S. Environmental Protection Agency (EPA), April 1995: Status Report: Cosolvents, EPA 542-K- 94-006, U.S. EPA OSWER (5102W), TIO, Washington, DC, available at www.gwrtac.org The following was excerpted from Ground-Water Remediation Technologies Analysis Center (GWRTAC), 1996: Surfactants/Cosolvents, Technology Evaluation Report TE-96-02, Dr. Chad T. Jafvert, Purdue University, for GWRTAC, Pittsburgh, PA, December 1996, available at www.gwrtac.org, U.S. Environmental Protection Agency (EPA), April 1995: Status Report: Cosolvents, EPA 542-K-94-006, U.S. EPA OSWER (5102W), TIO, Washington, DC, available at www.gwrtac.org, Rice University, 1997: Technology Practices Manual for Surfactants and Cosolvents, Rice University, 6100 Main Street, Houston, TX 77005-1892, February 1997, and Sillan, R.K., M.D. Annable, and P.C.S. Rao, Editors, 1997: Executive Summary, "In-Situ Cosolvent Flushing for Enhanced Solubilization of a Complex NAPL: Comprehensive Field-Scale Evaluation", Draft Final Report, CRADA CR-821990, May 1997: Hill AFB Operational Unit 1 (OU1) consists of two fire training areas, two chemical disposal pits, and two landfills. The primary contaminant is LNAPL (light lubricating oils, jet fuel). At OU1, the design of each test is process dependent, however, each test cell (of nine test constructed test cells) that will undergo some type of flushing is basically the same. Each cell is constructed of sheet piling driven into a clay layer approximately 30 feet below the surface, each occupying a rectangular surface area of 3 m x 5 m. The sheet piling has inter-locking grout-sealed joints to hydraulically isolate the cell from its surroundings. This type of containment is sometimes referred to as a Waterloo Barrier system. The poorly sorted sand and gravel aquifer is approximately 15 to 20 ft below the surface to the clay aquitard. Four injection and three extraction wells are located on the opposite 3 m sides of each cell. Well screens are variable from the clay layer to above the Ground-Water Remediation Technologies Analysis Center Operated by Concurrent Technologies Corporation Appendix - Page 48 of 164 Copyright GWRTAC 1998 Revision 1 Tuesday, November 17, 1998
In Situ Flushing Project Summaries GWRTAC Case Study Database water table. In the interior are 12 evenly spaced sampling wells, each with nested ports at 5 vertical depths. The hydraulic conductivity of the saturated potion of the upper sand and gravel unit at OU1 is 10-1 to 10-2 cm/sec based on aquifer test data, and 10-2 to 10-5 cm/sec based on slug test data. The saturated zone pore volume (PV) within each cell is variable from 1,000 to 2,500 gallons per cell. For all of the flushing experiments (those with surfactants, cosolvents, and cyclodexdrin), the flushing rate will be approximately one pore volume per day. Prior to and after treatment of each cell, a partitioning tracer test has or will be performed. The mix of tracers will be designed according to the expected volume of NAPL within the cell before and after treatment. Among the tracers, hexanol and dimethylpentanol may be included. For Test 1, at OU1, a mixture of 70% ethanol, 12% n-pentanol, and 28% water was used as flushing solution. This was the first test performed at Hill AFB and was a comprehensive, fieldscale evaluation of in-situ cosolvent flushing for enhanced remediation of NAPL-contaminated aquifers. The experiment was conducted in a hydraulically-isolated test cell (about 4.3 m x 3.5 m or 14.1 x 11.5 feet) constructed in a surficial sand-gravel-cobble aquifer, underlain by a deep clay confining unit. This surficial aquifer was contaminated with a multi-component NAPL as a result of jet fuel and chlorinated solvents disposal during the 50’s and 60’s. Prior to all testing, the water table in the cell was raised to 5 meters (16.4 feet) below ground surface to saturate the NAPL smear zone, necessary due to a water table decline from drought conditions in the few years prior to the test. At the test site, the LNAPL mixture occurred as a coating on particles and as globules in pore spaces in the groundwater and above it in the vadose zone. Analysis of soil cores taken from the test cell prior to cosolvent flushing indicated the following: (1) the NAPL was located in a 1.5 meter (4.9 feet) smear zone immediately above the clay confining unit; (2) the largest amounts of NAPL were near the water-table position prior to test cell installation (5.8 m (19.0 feet) below the ground surface (bgs)); and (3) NAPL penetrated about 0.5 m (1.6 feet) into the confining unit via sand stringers near the aquifer-aquitard interface. Soil core analysis was also used to estimate NAPL saturation within the test of 1.6 to 3.8%. A series of non-reactive and reactive tracer tests were conducted to characterize hydrodynamic properties and NAPL distribution. A non-reactive tracer test was first conducted (using bromide and a mixture of methyl alcohols) to characterize the hydrodynamic characteristics of the saturated zone within the test cell; these data were used to guide the design of other tests in the cell. Results from this test showed a highly variable flow velocity distribution within the test cell. The first field test of inter-well partitioning tracers (IWPT) was conducted as an alternative to the traditional intrusive techniques (i.e. soil coring) to quantify both the residual NAPL volume and distribution within the test cell. Data from the IWPT test estimated an average NAPL saturation of 4.6 to 5.4% (approximately 250 L or 66 gallons). The IWPT test data indicated that the NAPL saturation was highly variable within the test cell and increased with depth and from the eastern end (EW-1 side) to the western end (EW-3 side) of the cell. The in-situ cosolvent flushing technique provides accelerated site clean up due to enhanced solubilization or mobilization of NAPL, and enhanced desorption of sorbed contaminants. The fieldscale cosolvent flushing test consisted of pumping about 40,000 L (10,568 gallons) (approx. nine pore volumes) of a ternary cosolvent mixture (70% ethanol, 12% n-pentanol, and 18% water) through the test cell over a period of 10 days, followed by flushing with water for another 20 days. Behavior of the cosolvents and solubilized NAPL constituents during the cosolvent and subsequent water flood was monitored with aqueous samples from three extraction wells and 60 multi-level sampling points (12 nested wells at 5 depths). Extraction well fluids with alcohol concentrations Ground-Water Remediation Technologies Analysis Center Operated by Concurrent Technologies Corporation Appendix - Page 49 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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