Technology Status Report: In Situ Flushing - CLU-IN

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In Situ Flushing Project Summaries GWRTAC Case Study Database the first, waterflooding step, 144,000 gallons (28 PV) of water was cycled between the delivery and recovery drain lines (dual drains) to displace all mobile free-phase oil, and allow subsequent soil flushing performance determination where only residual oil remained. The second soil flushing step consisted of delivery of 30,000 gallons of flushing solution into the test cell. The flushing solution was a mixture of alkaline agents, polymer, and surfactants determined from laboratory test studies; the information below summarizes the composition of the various solutions. Initially as part of the soil flushing step, 10,000 gallons (2 PV) of Polystep A-7R was used to produce reusable wood-preserving oil, followed by 10,000 gallons (2 PV) of Makon-10R to achieve lower cleanup levels. After the first 20,000 gallons of flushing solution delivery, 10,000 gallons (2 PV) of water was delivered to continue fluid movement while waiting for the arrival of additional flushing solution. Then, 10,000 additional gallons (2 PV) of Makon-10R was delivered to the cell to complete the soil flushing step. Lastly, in a reconditioning step, the cell was flooded with 150,000 gallons (30 PV) of water to displace mobilized oil and soil-washing solution remaining in the aquifer. (Mann, 1993). The flushing solutions used were the Makon-10R System and the Polystep A-7R System (Mann, 1993). The Makon-10R System was comprised of alkaline agents Na2CO3 (0.825% by wt) and NaHCO3 (0.65% by wt), polymer Xanthan Gum Biopolymer (1,050 mg/L), and surfactant Makon-10R(a) (1.4% by wt). The Polystep A-7R System was comprised of alkaline agents Na2CO3 (0.1% by wt) and NaHCO3 (0.72% by wt), polymer Xanthan Gum Biopolymer (1,050 mg/L), and surfactant Polystep A-7R(b) (1% by wt). (a) Ethoxylated nonylphenol (b) Sodium dodecyl benzene sulfonate A total of 1,900 gallons of PAH-contaminated oil was removed from the test cell. On average, primary oil recovery reduced oil concentration from 93,000 to 15,500 mg/Kg and in situ soil flushing further reduced oil to a final concentration of 5,100 mg/Kg, a 94% overall reduction. More agressive techniques or in situ bioremediation were recommended to further reduce contaminant concentration. Flushing solution additives were 61 to 99% recovered. In addition, the removal of oil increased the soil bulk permeability form 15 to 30 Darcy. (Mann, 1993). "The primary result of the small-scale field demonstration was a decision to proceed to a largescale effort. The large-scale pilot was performed in an area in which waterflood oil recovery had been applied in 1988. Sheet-pile walls were driven to isolate a test cell with the dimension of 130 by 130 feet. Chemical solutions were delivered to a central 120-foot delivery drainline. Fluids were produced from two 120-foot recovery drainlines spaced 60 feet from and parallel to the delivery drainline. During the 235-day pilot test, approximately 7,400 pounds of polymer, 39,700 pounds of surfactant, and 81,900 pounds of alkaline agents were delivered to the subsurface. Through the delivery of chemicals and subsequent flushing of mobilized oil and residual chemicals, an equivalent of approximately 23,600 gallons of oil were produced. The corresponding reduction in soil contaminant concentrations was from an initial concentration of approximately 25,000 mg oil/kg soil to a final concentration of 4,000 mg oil/kg dry soil. Final concentrations ranged from 290 Ground-Water Remediation Technologies Analysis Center Operated by Concurrent Technologies Corporation Appendix - Page 56 of 164 Copyright GWRTAC 1998 Revision 1 Tuesday, November 17, 1998
In Situ Flushing Project Summaries GWRTAC Case Study Database to 11,000 mg oil/kg dry soil, reflecting the impact of preferred flow paths within the contaminated interval (Pitts, et al., 1993). While large amounts of mass were removed from the site, it was also recognized that the remaining subsurface alluvial contamination, together with the contamination in the underlying bedrock, would act as a long-term source of groundwater contamination. Groundwater approaching equilibrium with this remaining contamination would contain dissolved PAH at concentrations near the concentrations present under the initial conditions. Thus, it was recognized that implementation of in situ soil flushing would likely not eliminate or reduce the need for continuation of current groundwater containment practices in place at the site. During the in situ soil flushing process, fluids were generated that were characterized by stable oil/water emulsions, high contaminant concentrations, high organic content, elevated pH, high alkalinity, and high salinity. These characteristics made the fluids very difficult to treat. The need for an effective and efficient process for treatment of the fluids is evident through consideration of the volume of fluids that would be generated in full-scale application of the soil flushing method (100 acres). Based on extrapolation of the 1989 in situ soil flushing pilot test, approximately 275 million gallons of fluid with these characteristics would be produced in a full-scale application. Considering effluent recycling and chemical reuse, fluid discharge, and residuals management, no complete process was identified for the treatment of fluids produced during in situ soil flushing (Sale and Piontek, 1992). Full-scale applications of the chemically enhanced recovery technique would require an extensive piping network and large amounts of fluids and chemicals. Based on extrapolation from the 1989 pilot test, full-scale in situ soil flushing would require more than 125 million gallons of soil flushing solution containing more than I million pounds of polymer, nearly 10 million pounds of surfactant, and approximately 16 million pounds of alkaline agents. Based on the limited risk reduction achieved, unresolved technical issues, and implementation costs on the order of $500,000 per acre, this technology is no longer being considered at the site (CH2M HILL, 1993)." Report(s)/Publication(s) (Additional Information Sources): CH2M HILL. 1990. "Union Pacific Railroad Laramie Tie Plant In Situ Treatment Process Development Program: Milestone IV Report." CH2M HILL. 1993. "UPRR Laramie Tie Plant Site Draft Corrective Measures Study Report." Submitted to U.S. Environmental Protection Agency, Region VIII, Denver, Colorado. Mann et al., 1993: Innovative Site Remediation Technology Soil Washing/Soil Flushing, Vol. 3 of 8, WASTECH, William C. Anderson, P.E., DEE, Ed., American Academy of Environmental Engineers, 1993 Piontek, K.R., and Simpkin, T.J. 1994. "Practicability of In Situ Bioremediation at a Wood- Preserving Site." In Bioremediation of Chlorinated and Polycyclic Aromatic Hydrocarbon Compounds, R.E. Hinchee, A. Leeson, L. Semprini, and S.K. Ong, Eds., Lewis Publishers, pp. 117- 128. Pitts, M.J., Wyatt, K., Sale, T.C., and Piontek, K.R. 1993. "Utilization of Chemical-Enhanced Oil Recovery Technology to Remove Hazardous Oily Waste from Alluvium," SPE/DOE paper no. Ground-Water Remediation Technologies Analysis Center Operated by Concurrent Technologies Corporation Appendix - Page 57 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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