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Title: Geologic, geochemical, microbiologic, and hydrologic characterization at the In Situ Redox Manipulation Test Site

Abstract

This report documents results from characterization activities at the In Situ Redox Manipulation (ISRM) Field Test Site which is located within the 100-HR-3 Operable Unit of the US Department of Energy`s (DOE`s) Hanford Site in Richland, Washington. Information obtained during hydrogeologic characterization of the site included sediment physical properties, geochemical properties, microbiologic population data, and aquifer hydraulic properties. The purpose of obtaining this information was to improve the conceptual understanding of the hydrogeology beneath the ISRM test site and provide detailed, site specific hydrogeologic parameter estimates. The resulting characterization data will be incorporated into a numerical model developed to simulate the physical and chemical processes associated with the field experiment and aid in experiment design and interpretation.

Authors:
; ;  [1]
  1. and others
Publication Date:
Research Org.:
Pacific Northwest Lab., Richland, WA (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
88835
Report Number(s):
PNL-10633
ON: DE95015839; TRN: 95:017888
DOE Contract Number:
AC06-76RL01830
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Jul 1995
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; HANFORD RESERVATION; SITE CHARACTERIZATION; AQUIFERS; HYDRAULIC CONDUCTIVITY; FIELD TESTS; HYDROLOGY; GEOLOGY; COMPILED DATA

Citation Formats

Vermeul, V.R., Teel, S.S., and Amonette, J.E. Geologic, geochemical, microbiologic, and hydrologic characterization at the In Situ Redox Manipulation Test Site. United States: N. p., 1995. Web. doi:10.2172/88835.
Vermeul, V.R., Teel, S.S., & Amonette, J.E. Geologic, geochemical, microbiologic, and hydrologic characterization at the In Situ Redox Manipulation Test Site. United States. doi:10.2172/88835.
Vermeul, V.R., Teel, S.S., and Amonette, J.E. Sat . "Geologic, geochemical, microbiologic, and hydrologic characterization at the In Situ Redox Manipulation Test Site". United States. doi:10.2172/88835. https://www.osti.gov/servlets/purl/88835.
@article{osti_88835,
title = {Geologic, geochemical, microbiologic, and hydrologic characterization at the In Situ Redox Manipulation Test Site},
author = {Vermeul, V.R. and Teel, S.S. and Amonette, J.E.},
abstractNote = {This report documents results from characterization activities at the In Situ Redox Manipulation (ISRM) Field Test Site which is located within the 100-HR-3 Operable Unit of the US Department of Energy`s (DOE`s) Hanford Site in Richland, Washington. Information obtained during hydrogeologic characterization of the site included sediment physical properties, geochemical properties, microbiologic population data, and aquifer hydraulic properties. The purpose of obtaining this information was to improve the conceptual understanding of the hydrogeology beneath the ISRM test site and provide detailed, site specific hydrogeologic parameter estimates. The resulting characterization data will be incorporated into a numerical model developed to simulate the physical and chemical processes associated with the field experiment and aid in experiment design and interpretation.},
doi = {10.2172/88835},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sat Jul 01 00:00:00 EDT 1995},
month = {Sat Jul 01 00:00:00 EDT 1995}
}

Technical Report:

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  • The In Situ Redox Manipulation (ISRM) experiment is being evaluated as a potential method to remove contaminants from groundwater adjacent to the Columbia River near the 100-D Area. The ISRM experiment involves using sodium dithionate (Na{sub 2}O{sub 6}S{sub 2}) to precipitate chromate from the groundwater. The treatment will likely create anoxic conditions in the groundwater down-gradient of the ISRM treatability test site; however, the spatial extent of this anoxic plume is not exactly known. Surveys were conducted in November 1997, following the peak spawning of fall chinook salmon. Aerial surveys documented 210 redds (spawning nests) near the downstream island inmore » locations consistent with previous surveys. Neither aerial nor underwater surveys documented fall chinook spawning in the vicinity of the ISRM treatability test site. Based on measurements of depth, velocity, and substrate, less than 1% of the study area contained suitable fall chinook salmon spawning habitat, indicating low potential for fall chinook salmon to spawn in the vicinity of the ISRM experiment.« less
  • The objective of the Tunnel Effluent Characterization Project at the Nevada Test Site was to characterize the tunnel effluents in terms of rate of discharge, pH, temperature, specific conductivity, turbidity, and aqueous chemistry. The parameters were monitored for one year to identify hazardous constituents within the effluent and to characterize temporal variations.
  • The purpose of this study was to quantify the influence of physical and/or geochemical heterogeneities in the Hanford 100D area In Situ Redox Manipulation (ISRM) barrier, which may be contributing to the discontinuous chromate breakthrough locations along the 65-well (2,300 ft long) barrier. Possible causes of chromate breakthrough that were investigated during this study include: (1) high hydraulic conductivity zones; (2) zones of low reducible iron; and (3) high hydraulic conductivity zones with low reducible iron. This laboratory-scale investigation utilized geochemical and physical characterization data collected on 0.5 to 1 foot intervals from four borehole locations. Results of this laboratorymore » study did not provide definitive support any of the proposed hypotheses for explaining chromate breakthrough at the Hanford 100-D Area ISRM barrier. While site characterization data indicate a significant degree of vertical variability in both physical and geochemical properties in the four boreholes investigated, lateral continuity of high conductivity/low reductive capacity zones was not observed. The one exception was at the water table, where low reductive capacity and high-K zones were observed in 3 of four boreholes. Laterally continuous high permeability zones that contain oxic sediment near the water table is the most likely explanation for high concentration chromium breakthrough responses observed at various locations along the barrier. A mechanism that could explain partial chromate breakthrough in the ISRM barrier is the relationship between the field reductive capacity and the rate of chromate oxidation. Subsurface zones with low reductive capacity still have sufficient ferrous iron mass to reduce considerable chromate, but the rate of chromate reduction slows by 1 to 2 orders of magnitude relative to sediments with moderate to high reductive capacity. The original barrier longevity estimate of 160 pore volumes for homogeneous reduced sediment, or approximately 20 years, (with 5 mg/L dissolved oxygen and 2 ppm chromate) is reduced to 85 pore volumes (10 years) when the wide spread 60 ppm nitrate plume is included in the calculation. However, this reduction in barrier lifetime is not as great for high permeability channels, as there is insufficient time to reduce nitrate (and consume ferrous iron). If the cause of laterally discontinuous breakthrough of chromate along the ISRM barrier is due to oxic transport of chromate near the water table, additional dithionite treatment in these zones will not be effective. Treatment near the water table with a technology that emplaces considerable reductive capacity is needed, such as injectable zero valent iron.« less
  • The purpose of this study was to quantify the influence of physical and/or geochemical heterogeneities in the Hanford 100D area In Situ Redox Manipulation (ISRM) barrier, which may be contributing to the discontinuous chromate breakthrough locations along the 65-well (2,300 ft long) barrier. Possible causes of chromate breakthrough that were investigated during this study include: i) high hydraulic conductivity zones; ii) zones of low reducible iron; and iii) high hydraulic conductivity zones with low reducible iron. This laboratory-scale investigation utilized geochemical and physical characterization data collected on 0.5 to 1 foot intervals from four borehole locations.Results of this laboratory studymore » did not provide definitive support any of the proposed hypotheses for explaining chromate breakthrough at the Hanford 100-D Area ISRM barrier. While site characterization data indicate a significant degree of vertical variability in both physical and geochemical properties in the four boreholes investigated, lateral continuity of high conductivity / low reductive capacity zones was not observed. The one exception was at the water table, where low reductive capacity and high-K zones were observed in 3 of four boreholes.Laterally continuous high permeability zones that contain oxic sediment near the water table is the most likely explanation for high concentration chromium breakthrough responses observed at various locations along the barrier. A mechanism that could explain partial chromate breakthrough in the ISRM barrier is the relationship between the field reductive capacity and the rate of chromate oxidation. Subsurface zones with low reductive capacity still have sufficient ferrous iron mass to reduce considerable chromate, but the rate of chromate reduction slows by 1 to 2 orders of magnitude relative to sediments with moderate to high reductive capacity.The original barrier longevity estimate of 160 pore volumes for homogeneous reduced sediment, or approximately 20 years, (with 5 mg/L dissolved oxygen and 2 ppm chromate) is reduced to 85 pore volumes (10 years) when the wide spread 60 ppm nitrate plume is included in the calculation. However, this reduction in barrier lifetime is not as great for high permeability channels, as there is insufficient time to reduce nitrate (and consume ferrous iron). If the cause of laterally discontinuous breakthrough of chromate along the ISRM barrier is due to oxic transport of chromate near the water table, additional dithionite treatment in these zones will not be effective. Treatment near the water table with a technology that emplaces considerable reductive capacity is needed, such as injectable zero valent iron.« less
  • A series of laboratory experiments and computer simulations was conducted to assess the extent of uranium remobilization that is likely to occur at the end of the life cycle of an in situ sediment reduction process. The process is being tested for subsurface remediation of chromate- and chlorinated solvent-contaminated sediments at the Hanford Site in southeastern Washington. Uranium species that occur naturally in the +6 valence state {approximately}(VI) at 10 ppb in groundwater at Hanford will accumulate as U(N) through the reduction and subsequent precipitation conditions of the permeable barrier created by in situ redox manipulation. The precipitated uranium willmore » W remobilized when the reductive capacity of the barrier is exhausted and the sediment is oxidized by the groundwater containing dissolved oxygen and other oxidants such as chromate. Although U(N) accumulates from years or decades of reduction/precipitation within the reduced zone, U(W) concentrations in solution are only somewhat elevated during aquifer oxidation because oxidation and dissolution reactions that release U(N) precipitate to solution are slow. The release rate of uranium into solution was found to be controlled mainly by the oxidation/dissolution rate of the U(IV) precipitate (half-life 200 hours) and partially by the fast oxidation of adsorbed Fe(II) (half- life 5 hours) and the slow oxidation of Fe(II)CO{sub 3} (half-life 120 hours) in the reduced sediment. Simulations of uranium transport that incorporated these and other reactions under site-relevant conditions indicated that 35 ppb U(VI) is the maximum concentration likely to result from mobilization of the precipitated U(IV) species. Experiments also indicated that increasing the contact time between the U(IV) precipitates and the reduced sediment, which is likely to occur in the field, results in a slower U(IV) oxidation rate, which, in turn, would lower the maximum concentration of mobilized U(W). A six-month-long column experiment confirmed that uranium accumulated in reduced sediment was released slowly into solution with U(W) concentrations at only slightly greater than influent U(W) concentrations. This experiment also demonstrated that dissolved chromate, another oxidant likely to be present in some field systems, did not increase the release rate of uranium into solution.« less