United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
EPA/600/R-99/095a
September 1999
An In Situ Permeable
Reactive Barrier for the
Treatment of Hexavalent
Chromium and
Trichloroethylene in
Ground Water:
Volume 1
Design and Installation
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EPA/600/R-99/095a
September 1999
An In Situ Permeable Reactive Barrier for
the Treatment of Hexavalent Chromium and
Trichloroethylene in Ground Water:
Volume 1
Design and Installation
David W. Blowes1
Robert W. Gillham1
Carol J. Ptacek1
Robert W. Puls2
Timothy A. Bennett1
Stephanie F. O'Hannesin1
Christine J. Hanton-Fong1
Jeffrey G. Bain1
department of Earth Sciences
University of Waterloo
Waterloo, Ontario, Canada
2 Subsurface Protection and Remediation Division
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Ada, OK 74820
Cooperative Agreement No. CR-823017
Project Officer
Robert W. Puls
Subsurface Protection and Remediation Division
National Risk Management Research Laboratory
Ada, OK 74820
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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Notice
The U.S. Environmental Protection Agency through its Office of Research and
Development partially funded and collaborated in the research described here under
Cooperative Agreement No. CR 823017 to the University of Waterloo. It has been
subjected to the Agency's peer and administrative review and has been approved for
publication as an EPA document. Mention of trade names or commercial products
does not constitute endorsement or recommendation for use.
All research projects making conclusions or recommendations based on envi-
ronmentally related measurements and funded by the Environmental Protection
Agency are required to participate in the Agency Quality Assurance Program. This
project was conducted under an approved Quality Assurance Project Plan. The
procedures specified in this plan were used without exception. Information on the
plan and documentation of the quality assurance acitivities and results are available
from the Principal Investigator.
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Foreword
The U.S. Environmental Protection Agency is charged by Congress with protect-
ing the Nation's land, air, and water resources. Under a mandate of national
environmental laws, the Agency strives to formulate and implement actions leading
to a compatible balance between human activities and the ability of natural systems
to support and nurture life. To meet these mandates, EPA's research program is
providing data and technical support for solving environmental problems today and
building a science knowledge base necessary to manage our ecological resources
wisely, understand how pollutants affect our health, and prevent or reduce environ-
mental risks in the future.
The National Risk Management Research Laboratory (NRMRL) is the Agency's
center for investigation of technological and management approaches for reducing
risks from threats to human health and the environment. The focus of the
Laboratory's research program is on methods for the prevention and control of
pollution to air, land, water, and subsurface resources; protection of water quality in
public water systems; remediation of contaminated sites and ground water; and
prevention and control of indoor air pollution. The goal of this research effort is to
catalyze development and implementation of innovative, cost-effective environmen-
tal technologies; develop scientific and engineering information needed by EPA to
support regulatory and policy decisions; and provide technical support and informa-
tion transfer to ensure effective implementation of environmental regulations and
strategies.
Environmental scientists are generally familiar with the concept of barriers for
restricting the movement of contaminant plumes in ground water. Such barriers are
typically constructed of highly impermeable emplacements of materials such as
grouts, slurries, or sheet pilings to form a subsurface "wall." The goal of such
installations is to eliminate the possibility that a contaminant plume can move toward
and endanger sensitive receptors such as drinking water wells or discharge into
surface waters. Permeable reactive barrier walls reverse this concept of subsurface
barriers. Rather than serving to constrain plume migration, permeable reactive
barriers (PRB's) are designed as preferential conduits for the contaminated ground-
water flow. A permeable reactive subsurface barrier is an emplacement of reactive
materials where a contaminant plume must move through it as it flows, typically
under natural gradient, and treated water exits on the other side. The purpose of this
document is to provide detailed design, installation and performance monitoring data
on a full-scale PRB application which successfully remediated a mixed waste
(chromate and chlorinated organic compounds) ground-water plume. It was also the
first full-scale installation of this technology to use a trencher to install a continuous
reactive wall to intercept a contaminant plume. The information will be of use to
stakeholders such as implementors, state and federal regulators, Native American
tribes, consultants, contractors, and all other interested parties. There currently is no
other site which has used this innovative technology and reported on its performance
to the extent detailed in this report. It is hoped that this will prove to be a very
valuable technical resource for all parties with interest in the implementation of this
innovative, passive, remedial technology.
Clinton W. Hall, Director
Subsurface Protection and Remediation Division
National Risk Management Research Laboratory
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Abstract
A 46 m long, 7.3 m deep, and 0.6 m wide permeable subsurface reactive wall
was installed at the U.S. Coast Guard (USCG) Support Center, near Elizabeth City,
North Carolina, in June 1996. The reactive wall was designed to remediate hexavalent
chromium [Cr(VI)] contaminated ground water at the site, in addition to treating
portions of a larger overlapping trichloroethylene (TCE) ground-water plume which
has not yet been fully characterized. The wall was installed in approximately 6 hours
using a continuous trenching technique, which simultaneously removed aquifer
sediments and installed the porous reactive medium. The reactive medium was
composed entirely of granular iron, with an average grain size (d50) of 0.4 mm. The
reactive medium was selected from various mixtures on the basis of reaction rates
with Cr(VI), TCE and degradation products, hydraulic conductivity, porosity, and
cost.
The continuous wall configuration was chosen over a Funnel-and-Gate configu-
ration, based on three-dimensional computer simulations of ground-water flow and
contaminant transport, and cost. The simulations indicated that both configurations
could be designed to achieve the same capture areas and residence times with the
same volume of reactive material. However, initial cost comparisons suggested that
a reactive wall would have a lower material and installation cost than a Funnel-and-
Gate. Forthis site, the installation and material cost was approximately $7550 U.S./
linear meter for a 46 m long, 7.3 m deep and 0.6 m wide continuous reactive wall. The
minimum required width of the granular iron wall was determined from simulations of
TCE decay within the barrier, rather than Cr(VI) reduction because Cr(VI) reaction
rates are significantly faster. Simulations of contaminant transport within the granu-
lar iron wall indicate that 10,000 ug/L TCE, 900 ug/L cis-dichloroethylene (cDCE) and
101 ug/L vinyl chloride (VC) are reduced to less than maximum contaminant level
(MCL) values of 5, 70, and 2 ug/L respectively, within 0.3 m of travel through the wall
under the maximum flow velocities expected at the site.
The total project cost, including site assessment, reactive barrier design,
installation, soil treatment and follow-up, was approximately $985,000 U.S. The U.S.
Coast Guard anticipates that using this reactive barrier will result in a saving of $4
million U.S. in operation and maintenance costs over a 20 year period, compared to
a pump-and-treat system.
IV
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Table of Contents
Abstract iv
Table of Contents v
List of Tables vii
List of Figures viii
List of Appendices x
Introduction 1
Background 2
Site History 2
Geologic Setting 2
Conceptual Model of Plume Development 3
Remediation Strategy 3
Design Methodology 5
Introduction 5
Materials 5
Ground Water 5
Zero Valent Iron 5
Aquifer Materials 5
Methodology 5
Laboratory Batch Tests 5
Laboratory Column Tests 6
Analytical Procedures 6
Organic Anlysis 6
Inorganic Analysis 7
Geochemical Modeling 7
Flow and Reactive-Transport Modeling 7
Model Description 7
Model Limits and Grid 8
Hydraulic Parameters 8
Boundary Conditions 8
Reactive Barrier Configurations 8
Reactive-Transport Parameters 9
Results and Discussion 10
Column and Batch Tests 10
Batch Results 10
Organic 10
Inorganic 10
Geochemical Modeling-Inorganic Data 10
Column Results 11
Organic 11
High Flow Velocity Tests 12
Low Flow Velocity Tests 12
Inorganic Results 13
Chromium 13
Cations and Anions 13
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Eh, pH and Alkalinity 13
Geochemical Modeling 13
Determination of Reaction Parameters: Cr(VI) 15
Determination of Reaction Parameters: Halogenated Hydrocarbons 15
Reactive Barrier Designs 16
Final Selection of a Reactive Barrier 17
Final Reactive Barrier Design 17
Barrier Installation 18
Configuration 18
Site Preparation 18
Installation 18
Post-Installation Work 18
Barrier Costs and Performance 19
Conclusions 20
References 21
VI
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List of Tables
Table 1. Horizontal Hydraulic Gradients and Water Levels Observed in Monitoring Wells
Screened Between 3 and 4.5 m Below Ground Surface 26
Table 2. First-order Rate Constants forthe Dehalogenation of TCE, DCE Isomers,
and VC (after Johnson etal., 1996) 26
Table 3. Reactive Mixtures Used in Batch Experiments 26
Table4. Reactive Mixtures Used in Column Experiments 26
Tables. Column Flow Velocities and Hydraulic Properties of Reactive Mixtures
Used (afterO'Hannesin etal., 1995) 27
Table6. Method Detection Limits (MDL) 28
Table 7. Changes in TCE Concentration in Batch Experiments Over Time, for Reaction
and Control Vials. Three Reaction Vials and One Control Vial Were Sampled
at Each Time. Only TCE Was Analyzed 29
Table 8. Summary of Cr Removal in Batch Tests 30
Table 9. Inorganic Concentrations of All Columns for Both Influent and Effluent
Samples at Steady State Conditions 30
Table 10. First Detection of Cr at the 2.5 cm Sample Port in Each Column.
Predicted Breakthrough Volumes Calculated from These Data Are Shown 31
Table 11. First Order Rate Constants in Various Reactive Iron Mixtures (Rate Constants
Not Normalized to Surface Area) 31
Table 12. Hydraulic Properties and First-order Rate Constants for Peerless and
Master Builders Granular Iron 31
Table 13. Hydraulic Conductivity Values Used in Ground-water Flow Simulations
to Compare Relative Capture Areas and Residence Times of Two Barrier Designs 32
Table 14. Capture Areas for the Funnel-and-Gate Under Varying Aquifer Hydraulic
Conductivity Conditions 32
Table 15. Capture Areas for the Continuous Wall Configuration Under Varying Aquifer
Hydraulic Conductivity Conditions 32
Table 16. Ground-water Velocities and Residence Times within the Reactive Material
Zones of the Funnel-and-Gate and the Continuous Wall 33
Table 17. Hydraulic Parameters (Source of Values Indicated in Brackets) Used in
Ground-water Flow Modeling to Determine Minimum Barrier Dimensions 33
Table 18. Reactive-transport Parameters, Source Concentrations, and Minimum
Distance within Reactive Barrier before Contaminant Falls Below MCL 33
Table 19. Barrier Installation Project Costs in U.S.$ (Jim Vardy, Pers. Comm.) 34
VII
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List of Figures
Figure 1. Location map showing U.S. Coast Guard Support Center,
Elizabeth City, North Carolina 36
Figure 2. Plan view map showing total Cr concentrations (mg/L), and inferred
0.05 and 1 mg/L contours 36
Figure 3. Plan view map showing approximate locations of temporary wells,
cone penetrometer tests, river sampling, and deep wells (afterParsons
Engineering Science, 1994) 37
Figure 4. (a) Cross-section B-B', and (b) cross-section A-A' indicating total chromium
concentrations (mg/L), and inferred 0.05 mg/L and 1.00 mg/L contours
in June 1994 37
Figure 5. Cr concentration profiles (mg/L) at multilevel samplers in the approximate
locations of piezometer bundles ML11, ML21, and ML31, upgradient of
proposed Reactive Barrier (April 1996) 38
Figure 6. Plan view map showing TCE concentrations (ug/L), and inferred 5 and
100 ug/L contours 38
Figure 7. (a) Cross-section B-B', and (b) cross-section A-A' indicating TCE
concentrations (ug/L), and inferred 5 ug/L and 100 ug/L contours in June 1994 39
Figure 8. TCE concentration profiles (mg/L) at multilevel samplers in the approximate
locations of piezometer bundles ML11, ML21, and ML31, upgradient of
proposed Reactive Barrier (April 1996) 39
Figure 9. Cross-sections extrapolated from borehole log data 40
Figure 10. Geologic cross-section A-A' extrapolated from cone penetrometer test data 40
Figure 11. Geologic cross-section B-B' extrapolated from cone penetrometer test data 41
Figure 12. Water levels in wells screened 3 to 4.5 m below ground surface (ft.a.s.l.) 41
Figure 13. Conceptual model diagram 42
Figure 14. (a) Reductive p-elimination, and (b) hydrogenolysis reaction steps in
degradation of TCE (afterArnold and Roberts, 1997) 43
Figure 15. Schematic of the apparatus used in the column experiments 44
Figure 16. Model domain dimensions, with Funnel-and-Gate barrier shown
(all dimensions in m) 45
Figure 17. Model boundary conditions, with Funnel-and-Gate barriershown 45
Figure 18. (A) Funnel-and-Gate, and (B) permeable wall configurations used in
flow simulations [all dimensions in meters] 46
Figure 19. TCE concentration versus time in each of the four batch test mixtures 47
Figure 20. Batch test inorganic geochemistry for all mixtures, versus time 48
Figure 21. Cr(VI) concentration vs. time in each of the four batch test mixtures 49
Figure 22. Mineral saturation indices for batch tests, calculated with MINTEQA2 50
Figure 23. TCE concentration versus distance along all six columns at the
first flow velocity (FV1), approximately 61 cm/day (2 ft/day) 51
VIM
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Figure 24. TCM concentration versus distance along all six columns at the
first flow velocity (FV1), approximately 61 cm/day (2 ft/day) 51
Figure 25. cDCE concentration versus distance along all six columns at the
first flow velocity (FV1), approximately 61 cm/day (2 ft/day) 52
Figure 26. VC concentration versus distance along all six columns at the
first flow velocity (FV1), approximately 61 cm/day (2 ft/day) 52
Figure 27. TCE concentration versus distance along three columns at the
second flow velocity (FV2), approximately 30 cm/day (1 ft/day) 53
Figure 28. TCM concentration versus distance along three columns at the
second flow velocity (FV2), approximately 30 cm/day (1 ft/day) 53
Figure 29. cDCE concentration versus distance along three columns at the
second flow velocity (FV2), approximately 30 cm/day (1 ft/day) 54
Figure 30. VC concentration versus distance along three columns at the
second flow velocity (FV2), approximately 30 cm/day (1 ft/day) 54
Figure 31. Inorganic results for column 50MBSSAQat FV1 55
Figure 32. Inorganic results for column 50MBSS at FV1 56
Figure 33. Inorganic results for column 100MB at FV1 and FV2 57
Figure 34. Inorganic results for column lOOPLat FV1 and FV2 58
Figure 35. Inorganic results for column 50PLSSAQ at FV1 and FV2 59
Figure 36. Inorganic results for column 48PL/52AQ at FV1 60
Figure 37. Cr detection at the 2.5 cm sample port 61
Figure 38. Mineral saturation indices for column 50MBSSAQ at FV1 62
Figure 39. Mineral saturation indices for column 50MBSS at FV1 63
Figure 40. Mineral saturation indices for column 100MB at FV1 and FV2 64
Figure 41. Mineral saturation indices for column lOOPLat FV1 and FV2 65
Figure 42. Mineral saturation indices for column 50PLSSAQ at FV1 and FV2 66
Figure 43. Mineral saturation indices for column 48PL/52AQ at 78.4 PV and FV1 67
Figure 44. Experimental and calculated TCE concentration profiles in column 68
Figure 45. Experimental and calculated cDCE concentration profiles in column 68
Figure 46. Experimental and calculated VC concentration profiles in column 69
Figure 47. (A) Ground-water flow divergence in vicinity of a Funnel-and-Gate, and
(B) Capture area 70
Figure 48. Vertical ground-water flow divergence around a Funnel-and-Gate 71
Figure 49. Horizontal ground-water flow divergence around a Funnel-and-Gate 71
Figure 50. Ground-water flow divergence around a continuous wall 72
Figure 51. Predicted TCE, cDCE, and VC concentration profiles through the iron-filings wall 72
Figure 52. (a) Plan view, and (b) cross-sectional view of reactive barrier 73
Figure 53. Picture showing storage of granular iron at the site 74
Figure 54. Picture showing erosion control measures during installation 74
Figure 55. Picture showing trenching machine 75
Figure 56. Picture showing excavated aquifer sediments forming a soil slurry 75
Figure 57. Picture showing collapse of concrete 76
IX
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List of Appendices
Appendix A: Grain size distribution curves 79
Appendix B: Elemental and TCLP analyses 80
Appendix C: Bromide tracer test data (lab columns) 82
Appendix D: Batch test inorganic data 84
Appendix E: Batch test mineral saturation indices 85
Appendix F: Reactive column organic data 86
AppendixG: Reactive column inorganicdata 103
AppendixH: Reactive column mineral saturation indices 107
Appendix I: Analytical laboratory procedures 111
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Introduction
Ground water at the U.S. Coast Guard Support Center, Elizabeth City, NC (Figure 1), contains hexavalent chromium
[Cr(VI)] and trichloroethylene (TCE) derived from historical electroplating and degreasing operations. Site investigations
conducted since 1991 have shown maximum ground-water concentrations of greater than 10 mg/L Grand 19,000 ug/L
TCE; (Puls et al., 1994; Parsons Engineering Science, 1993, 1995, 1997). These concentrations exceed the maximum
contaminant level (MCL) values of 0.05 mg/L for Cr and 5 ug/L for TCE. The Cr and TCE ground-water plumes overlap,
and discharge to the Pasquotank River which borders the northern extent of the USCG Support Center.
The traditional method to remediate contaminated ground water is often a variant of a pump-and-treat system. These
systems pump both contaminated and uncontaminated ground water to an above-ground treatment facility where large
volumes of ground water are treated and discharged. Ground-water contaminant concentrations can be reduced to less
than MCL values with this method, but experience has shown that contaminant source zones can persist for very long
time periods due to mass transfer limitations (Mackay and Cherry, 1989). Inherent in the pump-and-treat method are
several disadvantages such as: long treatment times, large volumes of ground water to treat and discharge, operation
and maintenance costs, and loss of land-use. The limitations and disadvantages of the pump-and-treat method have
prompted questions regarding remediation goals, and alternative remediation methods (Mackay et al., 1993).
One alternative remediation technique that avoids the limitations of pump-and-treat is the use of passive in situ reactive
barriers (McMurty and Elton, 1985; Gillham and Burris, 1992; Gillham and O'Hannesin, 1992; Blowes and Ptacek, 1992).
In situ reactive barriers are composed of a permeable reactive material that passively removes contaminants from
flowing ground water. These barriers are installed in the subsurface, allowing continued use of the land. The barriers do
not require on-going maintenance or energy input, and above ground treatment and disposal of ground water is not
required. Blowes et al. (1995) describe a variety of contaminants which can be treated using subsurface permeable
reactive walls. In order to successfully remediate a plume, the reactive wall must be large enough that the entire ground-
water plume passes through it. An alternative reactive barrier design is the Funnel-and-Gate (Starr and Cherry, 1994).
The Funnel-and-Gate barrier utilizes cutoff walls to focus or funnel ground-water flow through a smaller in situ reactive
material zone.
A passive in situ barrier, composed of granular iron, was proposed as an innovative ground-water remediation
technology to treat both dissolved Cr(VI) and TCE in ground water at the USCG Support Center. Previous laboratory and
field studies indicated that reactive mixtures composed of granular iron can successfully remediate ground water
contaminated with Cr(VI) (Blowes and Ptacek, 1992; Puls et al., 1995; Blowes et al., 1997) and TCE (O'Hannesin and
Gillham, 1992; O'Hannesin, 1993; Gillham and O'Hannesin, 1994; Focht et al., 1996). Patents held by the University of
Waterloo coverthe removal of dissolved metals from ground waterthrough the in situ precipitation of harmless, insoluble
reduced metal phases in a permeable reactive mixture placed in the path of the contaminated ground water (U.S. Patents
5,362,394 and 5,514,279). A patent held by the University of Waterloo covers the in situ removal of dissolved
halogenated organic contaminants from water using zero valent iron installed in the pathway of the contaminated ground
water (U.S. Patent 5,266,213).
Laboratory batch and column tests were conducted using materials from the USCG Elizabeth City site to determine the
granular iron mixture which would be the best suited for simultaneously treating Cr(VI) and TCE contaminated ground
water. The reaction rates, hydraulic properties and cost of these mixtures were included in the selection criteria.
Peerless™ granular iron was selected for the reactive barrier.
Three-dimensional ground-water flow simulations were conducted to assess the relative efficiency of a Funnel-and-Gate
versus a continuous wall (Bennett, 1997). Simulations of contaminant transport through the reactive barrier under the
maximum flow conditions expected at the USCG site were conducted to determine the minimum barrier thickness
required to remediate contaminant concentrations, similar to those observed at the site, to less than MCL values.
The site preparation, trenching installation, follow-up soil treatment, and overall project costs, using the selected reactive
material and barrier configuration are described.
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Background
Site History
The U.S. Coast Guard Support Center, Elizabeth City, NC, has been the focus of numerous studies since the discovery
of a leak of acidic chromium solution beneath a former electroplating shop in 1988. The plating shop was in operation for
30 years, priorto its closure in 1984. Sediments beneath the plating shopfloorwere found to contain upto 14,500 mg/kg
Cr. The contaminated sediments were removed at that time. A subsequent site investigation indicated that a plume of
ground water containing Cr(VI) in excess of the MCL value extended from the electroplating shop, in Hangar 79, toward
the Pasquotank River (Figure 2) (Parsons Engineering Science, 1993,1994,1995). Sampling results from a monitoring
network of more than 40 wells indicated that the Cr(VI) plume was approximately 35 meters wide, and extended
65 meters from the hangarto the river. A series of water samples was taken from cone penetrometertest(CPT) locations
(Figure 3). The CPT ground-water samples indicate that the core of the Cr plume exists between approximately 4.5 -
6.1 m below ground surface. The bottom fringe of the plume, defined by the MCL value of 0.05 mg/L, extends to a depth
of approximately 7 m, as the plume nears the Pasquotank River (Figure 4). Multilevel sampling wells installed in the
vicinity of the proposed reactive barrier similarly indicated that the Cr(VI) plume predominates between depths of 4.5 and
6.5 m (Figure 5). Very low Cr(VI) concentrations were detected in two deep wells, MW21 and MW22, screened between
12 mand 15 m below ground surface. The maximum observed Cr(VI) concentration exceeds 10 mg/L(Puls etal., 1994).
In 1991, TCE was detected in ground-water samples collected during the Cr(VI) delineation program. The source of the
TCE is speculated to be an existing sewer manhole located adjacent to the electroplating shop (Parsons Engineering
Science, 1993). The TCE may be associated with the historical plating operations in Hangar 79, as TCE is commonly
used to degrease parts prior to chrome plating (Greenwood, 1971; Dennis and Such, 1972). The extent of the TCE in the
ground water has not been completely delineated to the west, south, and east of the apparent source area (Parsons
Engineering Science, 1993). The TCE plume overlaps the Cr(VI) plume, and is larger in lateral extent (Figure 6). Ground-
water samples taken during cone penetrometer testing indicate that a TCE plume exists between 4.5 and greater than
7.6 m below ground surface. The plume also extends to the west, where higher concentrations, and concentrations
greater than MCL exist at 9.1 m depth (Figure 7). Multilevel sampling wells installed in the vicinity of the proposed
reactive barrier similarly indicate that the TCE is heterogeneously distributed with depth (Figure 8). The full vertical extent
of the TCE has yet to be determined, but TCE concentrations of up to 580 ug/L have been observed in wells at 12 m
depth below ground surface (Parsons Engineering Science, 1993).
TCE concentrations that exceed MCL were detected in temporary wells installed near the riverbank (T1, T2, T3, T4, T5,
T6), with the highest concentrations of 2,400 ug/L observed in T1. TCE concentrations which exceed the MCL and
approach 8 ug/L were also observed in river water samples (R2, R11, R12, R21, R22) indicating that the TCE plume
impacts the river. The highest TCE concentration reported in sampling events since 1991 was 19,200 ug/L.
Geologic Setting
The contaminated surficial aquifer at the USCG site consists of Atlantic coastal plain sediments. Borehole log data
(Parsons Engineering Science, 1993) (Figure 9) indicate that the surficial aquifer is complex and heterogeneous,
composed of varying amounts of fine sands and silty clays. In general, the upper 2 m of the aquifer are sandy silty clays
which pinch out toward the north, toward the Pasquotank River, where fill sands have been added. Fine sands, with
varying amounts of silt and clay, and silty clay lenses form the lower portion of the shallow aquifer. Cone penetrometer
tests also indicate that the surficial aquifer is very heterogeneous with fine sands interfingered with silty clay lenses. The
thickness of these lenses varies from 0.3 m to more than 3 m (Figures 10 and 11). The aquifer is underlain at
approximately 18 meters depth by dense clay of the Yorktown Confining Unit.
Water level measurements indicate that the ground-water flows northwards toward the Pasquotank River (Figure 11). In
five monitoring events over a three year period, the general ground-water flow field downgradient of the plating shop
varied in direction from approximately N30° Wto N10° E (Figure 12). Water levels measured in the monitoring wells
fluctuate between approximately 1.5 and 2.1 m below ground surface. The calculated average horizontal hydraulic
gradient varies between 0.0011 and 0.0033 (Table 1).
Slug tests were conducted on monitoring wells with 1.5 m long, 2.05 cm diameter screened intervals between 3 m and
6 m below ground surface. Hydraulic conductivity values calculated from these tests vary from 0.1 m/day to 4.8 m/day
(Parsons Engineering Science, 1993).
A multiple borehole tracer test in wells screened between 3.9 to 5.9 m depth below ground surface was conducted by
Puls et al. (1995). Ground-water velocities of 0.13 m/day and 0.18 m/day were measured in this test. Assuming an
average gradient of 0.0023 and a porosity of 0.38, these velocities correspond to an average hydraulic conductivity of
approximately 26 m/day.
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Conceptual Model of Plume Development
The chromium plume exists in the ground water as a result of leakage from a chromic acid tank located in an old plating
shop in Hangar 79. The dissolved Cr(VI) water moves with the ground water. The general ground-water flow direction
varies between N30°Wand N1CTE, and the aqueous chromium plume extends northward toward the Pasquotank River.
The chromium plume is predominantly located in the silty-clayey fine sand unit, which underlies the surficial clay,
because hydraulic conductivities and thus ground-water velocities are the highest within this sandy unit (Figure 13a).
TCE exists in the ground water as a result of the release of pure-phase TCE into the subsurface. TCE is a dense
nonaqueous phase liquid (DNAPL) that is relatively immiscible with water, and has a relatively low solubility of
1 ,100 mg/L (Pankow and Cherry, 1996). Once released into the subsurface, pure-phase TCE migrates downward as a
result of its higher density than water. TCE will pond and spread laterally on lenses where small-scale variations in entry
pressure exist, due to differences in grain size or clay content. The sensitivity of TCE migration to fine scale structure of
sands has been previously documented (Poulsen and Kueper, 1992; Pankow and Cherry, 1996). Ponded TCE zones
can form multiple sources, and can be extremely difficult to delineate due to the random migration pathways which result
from its density and immiscibility.
Aqueous TCE plumes which extend from residual source zones will flow with the ground water. Dissolved TCE
concentrations within these plumes can be orders of magnitude greater than the MCL value of 5 ug/L. The larger lateral
extent of the TCE plume probably arises from the spreading and ponding of TCE, or possibly from multiple release
locations. The presence of TCE at depths of greater than 12 m most likely results from the downward migration of pure-
phase TCE due to its higher density (Figure 13b).
Remediation Strategy
Hexavalent chromium [Cr(VI)] is the oxidized valence state of chromium, and is a strong oxidant. The reduction of Cr(VI)
to the less soluble and therefore less mobile Cr(lll) valence state by a variety of reductants is thermodynamically
favorable and kinetically rapid (Schroeder and Lee, 1975; Hem, 1977; Earyand Rai, 1988; Palmer and Wittbrodt, 1991;
Palmer and Puls, 1 994; Wittbrodt and Palmer, 1 997). Reductants that are commonly found in soils include ferrous iron-
bearing minerals and organic matter. Laboratory experiments indicate that the reduction of Cr(VI) by aqueous ferrous
iron and ferrous salts under acidic conditions can be very rapid, reaching equilibrium within a matter of minutes (Eary and
Rai, 1988; Buerge and Hug, 1997). However, the reduction of Cr(VI) by ferrous iron bearing minerals involves the
dissolution of ferrous iron and can be significantly slower, taking tens of minutes to tens of hours depending on the pH
and the ferrous mineral (Earyand Rai, 1989; Earyand Rai, 1991). Blowesand Ptacek (1992) suggested that iron bearing
solids such as elemental iron (Fe°) and pyrite could be used in a porous subsurface reactive wall to reduce and remove
Cr(VI) from ground water under intermediate pH conditions. Their laboratory experiments indicated that the rate of Cr(VI)
removal by fine grained iron is greater than that for coarse grained iron and pyrite. Cr(VI) concentrations decreased from
25 mg/L to less than 0.05 mg/L within a matter of hours with high purity granular iron (0.5 - 1 mm diameter), as opposed
to tens of hours for iron chips or pyrite. Their results suggested that the reaction was surface area and pH dependent. A
similar surface area and pH dependence was found by Gould (1982), who determined a rate expression for the reduction
of Cr(VI) by Fe°:
d A (1)
where A is the surface area of zero-valent iron (cm2/L), and the rate constant k has a value of 5.45 x 1Q-5 L cnr2 min-1.
The reduction of Cr(VI) by Fe° produces ferric iron [Fe(lll)] and Cr(lll) and (eqn. 2). Chromium may be removed through
the precipitation or co-precipitation of mixed Fe(lll)-Cr(lll) hydroxide solid solution (eqn. 3; Earyand Rai, 1988; Puls etal.;
1994; Powell etal., 1995; Blowes etal., 1997) or mixed Fe(lll)-Cr(lll) (oxy)hydroxide solid (eqn. 4; Schwertmann, 1989):
Cre+ + Feo ^ Crs+ + Fes+ (2)
(1-x)Fe3+ +xCr3++ 3H2O <^» (CrxFe1_x)(OH)3(s) + 3H+ (3)
(1-x)Fe3+ +xCr3++ 2H2O ^ Fe1 xCrxOOH(s) + 3H+ (4)
Goethite (FeOOH) and Cr(lll) substituted goethite containing up to 27 mass % Cr(OH)3 have been identified as the
principal precipitates in this reaction (Blowes etal., 1997; Pratt etal., 1997). The substitution and incorporation of Cr(lll)
into ferric oxyhydroxides is similar to the findings of Eary and Rai (1988) who report a 3:1 stoichiometry for Fe/Cr in a
mixed hydroxide precipitate. These hydroxides have a minimum solubility between pH 7 and 10 (Rai etal, 1987; Sass
and Rai, 1987). In this pH range, Cr(lll) concentrations in equilibrium with Cr(lll) and mixed Cr(lll)-Fe(lll) hydroxides are
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less than the MCL. Thus, the reduction of Cr(VI) by zero-valent iron provides a method of treating Cr(VI) contaminated
ground water.
Elemental iron has also been found to promote the relatively rapid degradation of a wide range of halogenated aliphatics,
including TCE, dichloroethylene (DCE) and vinyl chloride (VC;) (Gillham and O'Hannesin, 1992; Gillham et al., 1993).
One proposed reaction scheme (Figure 14) suggests that the degradation of TCE by Fe° to non-toxic hydrocarbons
occurs via concurrent reductive p-elimination and hydrogenolysis reactions (Roberts et al., 1996; Arnold and Roberts,
1997). The reductive p-elimination pathway involves the breakdown ofTCEtochloroacetylene and acetylene intermedi-
ates. The alternative reductive-dechlorination pathway involves the breakdown of TCE to DCE isomers and VC
intermediates. The cis-dichloroethylene (cDCE) and VC intermediates are also of concern as they are carcinogenic and
have low MCL values of 70 and 2 ug/L, respectively. However, laboratory experiments indicate that cDCE and VC
account for less than 10% of the TCE breakdown products (Orth and Gillham, 1996), and that these chlorinated products
are themselves reductively-dechlorinated in the presence of Fe°. Laboratory experiments have indicated that the ultimate
end-products of both reaction pathways are ethene and ethane, with lesser amounts of other C1 to C4 hydrocarbons
(Sivavecand Horney, 1995; Orth and Gillham, 1996).
Batch experiments indicate that the TCE, cDCE and VC degradation reactions are pseudo first-order and dependent on
the surface area of iron (Gillham and O'Hannesin, 1994). The first-order rate constant appears to decrease with
decreasing degree of chlorination, and each subsequent dechlorination from TCE to cDCE to VC occurs more slowly. A
similar surface area and rate dependence was observed in the sequential dehalogenation of chlorinated methanes by
Fe° (Matheson and Tratnyek, 1994). Johnson et al. (1996) describe a pseudo first-order kinetic model for the
dehalogenation of various hydrocarbons by Fe°:
—^- = ksaaspm[P] (5)
where ksa is the specific reaction rate constant (L Ir1 rrr2), as is the surface area of Fe° (m2 g~1), and pm is the mass
concentration of Fe°(g L~1 of solution). The first-order rate constants forthe dehalogenation of TCE, DCE isomers and VC
by elemental iron, calculated from various batch and column experiments (Johnson et al., 1996), are given in Table 2.
These rates are significantly greater than those reported forthe abiotic hydrolysis of TCE under normal environmental
conditions, where half-lives are on the order of years (Vogel etal., 1987). The use of Fe°in subsurface reactive iron walls
has also been previously shown to successfully degrade a variety of halogenated organics in ground water (O'Hannesin
and Gillham, 1992; Focht etal., 1996).
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Design Methodology
Introduction
A series of batch tests were conducted in the laboratory to assess the potential effectiveness of various commercial iron
materials in simultaneous removal of both Cr(VI) and TCE from Elizabeth City site water. After identifying suitable iron
sources, column tests were undertaken to determine if the organic compounds would degrade under flowing conditions
through the various reactive materials. Parameters obtained from the column experiments would ultimately assist in the
design of a field treatment system.
Materials
Ground Water
Ground water for the batch and column experiments was collected from monitoring well MW34 at the USCG Support
Center. The site water was initially analyzed to determine the concentrations of TCE and Cr(VI) [750 ug/L and 8 mg/L,
respectively]. For the batch and column tests, TCE and Cr(VI) concentrations were increased to approximately
2,000 ug/L TCE and 10 mg/L Cr(VI).
Zero Valent Iron
Three different sources of commercially available iron were tested: Ada (batch test only), Master Builders™ (MB) of
Cleveland, Ohio, and Peerless™ (PL) Metals and Abrasives of Detroit, Michigan. The grain size of the iron ranged from
0.25 to 1.0 mm for both MB and PL. Ada iron was composed of 0.5 mm shavings of various lengths. The specific surface
area measurements were 1.1 and 0.81 m2/g for MB and PL, respectively, determined by the BET method (Brunauer et
al., 1938). Particle density measurements were 6.97 and 6.98 g/cm3forMB and PL, respectively, as determined with an
air compression pycnometer (Beckman model 930). Surface area and particle density measurements were not
performed for Ada iron due to the large particle size.
Aquifer Materials
Depending on the construction method used (i.e., the width of the excavation) it is often more cost effective to mix sand
with the granular iron. Natural sand from the site (AQ) and high purity silica sand (SS) were considered as potential
bulking agents. Elizabeth City aquifer material was selected to evaluate the potential benefit and complications
associated with using the native aquifer material in the reactive mixture. At the University of Waterloo, the materials were
dried and screened through a 2 mm sieve. The washed silica sand that was used ranged between 0.15 to 0.5 mm in
diameter. Grain size distribution curves are shown in Appendix A. Hydraulic conductivity measurements were performed
on all column mixtures. The column mixtures and hydraulic conductivities are described in the Methodology section of
this report. Elemental analysis and toxicity characteristic leaching procedures (TCLP) were conducted on both MB and
PL iron sources (Appendix B).
Methodology
Laboratory Batch Tests
Four batch tests were conducted using the three different sources of commercially available iron; Ada, MB, PL and a
combination of Elizabeth City aquifer material (AQ) and MB iron.
Each laboratory batch treatability test consisted of 60 samples prepared in 60 mL glass vials. Two types of samples were
prepared: blank vials, which contained only spiked site water, and reactive vials containing 6 g of an iron source, 6 g of
silica sand (SS) or aquifer material (AQ) along with the spiked site water (Table 3). The mass of iron to volume of solution
ratio in the reactive vials was 1 g: 9.4 mL.
For each treatability test, the site water was gravity fed into a 4 L glass bottle with a spigot at the bottom, and was stirred
on a magnetic stirrer for 30 minutes. The vials were filled by gravity flow, leaving no headspace, then sealed immediately
with aluminum crimp caps with Teflon®-lined septa. The test vials were filled in sequence of one blank and three reactive
vials. Sample bottles with no iron or sand were also filled at the beginning, middle and end of the pouring process, to
determine initial values of TCE, Cr(VI), redox potential (Eh) and pH. The test vials were then placed on a rotating disc
(three complete revolutions per minute), allowing for complete mixing without agitation.
At predetermined time intervals (sampling more frequent at early times), the vials were removed from the rotating disc
and samples were extracted for TCE analysis, Eh and pH measurements. Filtered samples (0.2 urn) were collected for
alkalinity and inorganic constituent analyses, including Cr(VI). Four vials were sacrificed for each sampling time: one
blank and triplicate reactive vials, allowing a maximum of fifteen sampling times. All tests were conducted at room
temperature (= 25 ° C).
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Laboratory Column Tests
Six column tests were conducted to determine the degradability of TCE, cDCE and VC and the removal of Cr(VI) under
flowing conditions, using mixtures containing a combination of Elizabeth City aquifer material (AQ), silica sand (SS), MB
iron and PL iron. The column mixtures used are listed in Table 4, and the hydraulic characteristics of these columns are
described in Table 5.
The columns were constructed of Plexiglas™ with a length of 50 cm (1.64 ft) and an internal diameter of 3.8 cm (1.5 in).
Sampling ports were positioned along the length of each column at distances of 2.5, 5,10,15, 20, 30 and 40 cm (1, 2,
4, 6, 8,12 and 16 in) from the inlet end (Figure 15). The columns also allowed for collection of samples from the influent
and effluent solutions. Each sampling port consisted of a nylon Swagelok® fitting (0.16 cm) tapped into the side of the
column, with a syringe needle (16G) secured by the fitting. Glass wool was placed in the needle to prevent the entry of
solid material. The needles were positioned such that the water samples were obtained along the central axis of the
column. Each sampling port was fitted with a Luer-Lok™ fitting, such that a glass sampling syringe could be attached to
the port to collect a sample. When not in operation the ports were sealed by Luer-Lok™ plugs.
Each column was carefully packed insuring that the mixture was homogeneously distributed. For columns containing the
50% iron and sand mixtures, aliquots of the sand-iron mixtures were packed in lifts, taking care to avoid layering by
roughening the surface of the preceding layer before adding the next layer. All measurements were determined
gravimetrically and are shown in Table 5. Porosity values ranged from 0.29 to 0.45. Pore volume measurements were
determined experimentally by weight and ranged from 166 to 254 mL. Iron mass to volume ratios and surface area to
volume ratios are shown in Table 5. The columns were initially flushed with carbon dioxide to avoid air entrapment during
wetting. Several pore volumes of distilled water were flushed through each column before the site waterwas introduced.
All column experiments were conducted at room temperature.
An Ismatec™ IPN pump was used to feed the solution from a collapsible Teflon® bag to the bottom influent end of the
column. The pump tubing was Viton®; all other tubing was Teflon® (0.33 cm I.D. x 1.52 cm O.D.). The columns were
sampled periodically overtime until steady-state organic concentration profiles were achieved. After removing stagnant
water from a sampling needle, 2.0 or 1.5 mL samples were collected from the sampling ports. Samples for organic
analyses were collected from each port.
The first set of column tests was started on March 31, 1995, with a flow velocity range of 0.43 to 0.79 m/day (1.4 to
2.6 ft/day = FV1) (Table 5). The second set of tests, which extended the period of operation of only three of the columns,
was conducted with a lower flow velocity of approximately 0.30 m/day (1 ft/day = FV2). Testing at FV2 was started on
May 26,1995. The lower velocity corresponds to the natural ground-water velocity at the site. The higher velocity is about
ten times greater, corresponding to the velocity expected in a funnel and gate configuration.
In the first set of tests (0.43 to 0.79 m/day), the five columns were sampled more than ten times for inorganic parameters.
Detailed sampling was conducted of the effluent and all column sample ports for Eh, pH, alkalinity, Cr and other ions.
Samples were collected in glass syringes to prevent oxidation during collection. A minimum of 8 mL was needed for
analysis. Eh and pH measurements were made in sealed containers. Filtered (0.2 urn) samples were analyzed for major
ions and trace metals at the University of Waterloo. A detailed column profile was obtained three times during the
experiment for each column and the effluent was sampled more often. Additional Cr(VI) profiles were obtained at five
different intervals to monitor Cr(VI) movement through the column.
At the lower flow velocity (FV2), sampling was conducted at least 7 times for Cr(VI) concentration. This included two
detailed sampling sessions of the column effluent and column ports as described above. Due to the reduced flow rate
and the large volume of sample required for analysis, only half of the column ports were sampled at a given sampling
session.
Analytical Procedures
Organic Analysis
All organic samples collected from the batch and column experiments were analyzed at the University of Waterloo.
Samples were analyzed within two days of collection. The analyses were performed on two types of gas chromato-
graphs. The less volatile halogenated organics such as TCE were extracted from the aqueous phase using pentane with
an internal standard of 1, 2-dibromoethane, at a water to pentane ratio of 2.0 to 2.0 mL (Henderson et al., 1976). The
samples were placed on a rotary shaker for 10 minutes to allow equilibration between the water and pentane phases.
Using a Hewlett Packard 7673 autosampler, a 1.0 uL aliquot of pentane with an internal standard was automatically
injected directly onto a Hewlett Packard series II gas chromatograph. The chromatograph was equipped with a 63Ni
electron capture detector (ECD) and DB-624 Megabore capillary column (30 m x 0.538 mm ID, film thickness 3 urn). The
gas chromatograph had an initial temperature of 50°C, with a temperature time program of 15°C/min reaching a final
temperature of 150°C. The detector temperature was 300°C. The carrier gas was helium and makeup gas was 5%
methane and 95% argon, with a flow rate of 30 mL/min.
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For the more volatile compounds, such as cDCE, tDCE and VC, a headspace was created in the samples with a ratio of
0.5 ml headspace to 1.5 ml aqueous sample. The samples were placed on a rotary shaker for 15 minutes to allow
equilibration between the water phase and gas phase. For analysis, a 50 uL gas sample was injected onto Photovac™,
Model 10S50 and/or Model 10S70, gas chromatograph equipped with a photoionization detector (PID). The Model
10S50 chromatograph was fitted with a TFE packed column with 5% SE-30 on Chromosorb G, AW-DMCS (100/120
mesh), with oven temperature of 30°C and carrier gas of ultra-zero with a flow rate of 10 mL/min. The model 10S70 was
fitted with a capillary column CP Sil5, with an isothermal oven temperature of 30°C and a flow rate of 3 mL/min.
Method detection limits (MDL) were determined for each compound as the minimum concentration of a substance that
can be identified, measured and reported with 99% confidence that the analyte concentration is greater than zero. The
MDLs were determined from analysis of samples from a solution matrix containing the analytes of interest. Detection
limits for all compounds studied, as given in Table 6, were determining using the EPA procedure for Method Detection
Limits (USEPA, 1982).
Standards for TCE and PCEwere run at the beginning of each day and an additional set of standards was run later in the
day or dispersed throughout the analysis run. Each sample and standard were spiked with an internal 1,2-dibromoethane
sample to ensure complete capture by the detector. Calibration curves were run with seven different standards plus a
blank. Similar to the VC and DCE analyses, the average of the relative percent differences was calculated to a cutoff limit
of 10%. The highest TCE standard run via this pentane extraction method was 2,500 u,g/L. The MDL for TCE and PCE
was 1 ug/L.
Standards for VC and DCE analysis were run twice per day. Approximately 30 samples were run during the day using a
gas chromatograph equipped with a photoionization detector (PID). Linear calibration curves were comprised of eight
different standards plus a blank. The relative percent difference for each standard was determined and if the average of
all the relative differences exceeded 10% then the analyses were repeated. The highest VC and c-DCE standards run via
headspace analysis were 700 u,g/L and 1,000 u,g/L respectively. The MDL for VC and DCE was 1 u,g/L.
Inorganic Analysis
Redox potential (Eh) was determined using a combination Ag/AgCI reference electrode with a platinum button (Orion
9678 BN). The electrode was standardized with ZoBell and Light solutions (Zobell, 1946; Light, 1972; Nordstrom, 1977).
Millivolt readings were converted to Eh using the electrode reading and the standard potential of Ag/AgCI electrode
(SHE) at a given temperature. The pH measurements were made using a combination of pH/reference electrode (Orion
Models 9172BN and 915600), standardized with the pH buffer 7 and 10 (NIST standard).
Cation analysis forCr(VI) was determined using a diphenylcarbazide colorimetric technique (Standard Methods, 1992,
3500-CrD). Other cation analyses, including Al, B, Ca, Cd, Cr(total), Fe, K, Mg, Mn, Na, Ni, Si, Sr, Zn and a suite of other
cations, were determined using an inductively coupled plasma Atomic Emission Spectrometer (ICP-AES) instrument
(Thermo Jarrell Ash Iris Plasma Spectrometer). The samples were acidified to a pH of 2 with nitric acid and stored at 4°C
until analyzed. These samples were analyzed at the Water Quality Laboratory (WQL) at the University of Waterloo.
Appendix I describes the analytical procedures used for cation analysis.
Anions including Br, Cl and SO4 were analyzed using a Dionex System 2000 Ion Chromatograph (1C) or a Waters 1C with
conductivity detectors. Appendix I describes the analytical procedures used for anion analysis. Alkalinity was measured
on filtered subsamples at the time of sample collection using a Hach® Digital Titrator, standardized H2SO4titrant and
bromocresol green-methyl red indicator. Because of the low sample volumes available for analysis, the detection limit for
alkalinity measurements varied from 2 mg/L CaCO3 for the batch experiments to between 5 and 8 mg/L CaCO3 for the
column experiments. Detection limits for the inorganic parameters are included in Table 6. The method detection limit for
Cr(VI) measured in the lab is between 0.2 and 0.4 mg/L. The MDL for total Cr concentrations on the ICP is 0.02 mg/L.
Due to the limited volume of sample available, duplicate measurements of alkalinity could not be conducted.
Geochemical Modeling
The geochemical speciation/mass transfer computer code MINTEQA2 (Allison et al., 1990) was used to aid in the
interpretation of inorganic aqueous geochemical data. The thermodynamic database of MINTEQA2 was adjusted to be
consistent with that of WATEQ4F (Ball and Nordstrom, 1991).
Flow and Reactive-Transport Modeling
Model Description
FRAC3D, a three-dimensional finite element computer model designed to simulate saturated-unsaturated ground-water
flow and chain-decay solute transport in porous or discretely-fractured porous formations (Therrien and Sudicky, 1996),
was used. FRAC3D has been verified and validated against analytical solutions. This model has been used previously
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fora number of Funnel-and-Gate ™ remediation scenario simulations (Shikaze and Austrins, 1995; Shikaze etal., 1995).
FRAC3D was chosen to model the Elizabeth City USCG site because of its versatility and applicability to chain-decay
solute transport (Bennett, 1997).
Model Limits and Grid
For the ground-water flow simulations, the model domain was 26mx18mx18m (Figure 16). The grid spacing was
varied from 0.15 m to 1.5 m, with the finer spacing located near the vertices of the reactive barrier.
For the reactive transport simulations, the model domain was 30 mx18 mx18 m. The grid spacing was varied between
0.03 m and 1.5 m, with the finer grid spacing within the vicinity of the reactive barrier. The finer grid spacing within the
vicinity of the reactive barrier was chosen to satisfy the grid Peclet number criteria and minimize numerical dispersion.
Hydraulic Parameters
The entire domain was assigned a uniform hydraulic conductivity, which only approximates the heterogeneous nature of
the aquifer. For the flow simulations, the hydraulic conductivity was varied between 0.1 and 26 m/day. These values
correspond to the lowest and highest hydraulic conductivity values calculated from slug and tracer tests at the site. A
uniform hydraulic conductivity was assigned to the domain to facilitate comparison of the hydraulic characteristics of the
different reactive barrier designs. This range in hydraulic conductivities was chosen to bracket the anticipated range in
calculated ground-water velocities within, and capture areas of, the reactive barriers. A simulation was also conducted
with an assigned hydraulic conductivity of 46.4 m/day. This corresponds to the average calculated hydraulic conductivity
for the reactive mixtures.
For the reactive transport simulations, the domain was assigned a hydraulic conductivity of 17 m/day. This value was
chosen as a realistic estimate of the maximum anticipated hydraulic conductivity. Using the maximum anticipated
hydraulic conductivity value will yield a conservative estimate of ground-water velocities and required residence times
within the reactive barrier.
Boundary Conditions
The boundary conditions are shown in Figure 17. The top, bottom, east and west boundaries were assigned as no-flow
boundaries (Type 2), and the north and south boundaries (Type 1) were assigned constant head values of 18 m and
18.0594 m, respectively. The west no-flow boundary is far enough from the reactive barrier, justifying the no-flow
assumption. The bottom no-flow boundary represents the Yorktown confining unit, which is a low hydraulic conductivity
confining clay layer. The east boundary represents a symmetry boundary, which runs through the center of the reactive
barrier. This configuration results in a uniform flow field from south to north, with a constant horizontal hydraulic gradient
of 0.0033. This hydraulic gradient corresponds to the maximum observed hydraulic gradient.
Reactive Barrier Configurations
For the ground-water flow simulations, two pilot-scale barriers composed of equal volumes of reactive material were
modeled (Figure 18). These two reactive barrier designs, a Funnel-and-Gate and a continuous wall, differ only in how
they are configured to intercept ground-water flow. The Funnel-and-Gate has a gate zone that contains the reactive
material, and relies on impermeable funnels to direct ground-water flow through this gate. The continuous permeable
wall is composed entirely of reactive material and does not rely on funnels to direct ground-water flow.
The funnels of the simulated Funnel-and-Gate were 6.06 m long, and 9.1 m deep. The simulated gate zone was 3.6 m
long, 2 m wide and 9.1 mdeep. For efficiency, the funnels were oriented perpendicularto the ground-water flow direction
(Starr and Cherry, 1994). The gate zone consists of three zones: an upgradient pea gravel zone; a central granular iron
zone; and a downgradient pea gravel zone. The 0.45 m wide pea gravel zones promote an even ground-water velocity
distribution and minimize any heterogeneities in ground-water flow through the 1.1 m wide granular iron treatment zone.
The total volume of granular iron within this simulated barrier was 35 m3.
The continuous wall configuration simulated was composed entirely of granular iron. It is 10 m long, 7.6 m deep, and
0.5 m wide. The total volume of granular iron in this simulated barrier was also 35 m3. For the reactive-transport
simulations, a 36 m by 7.6 m by 0.45 m continuous reactive wall was modeled.
Within the model domain, the reactive barrier was located with the center of its long axis coinciding with the east
symmetry/no-flow boundary. The barriers are "hanging" in these simulations, in that they do not intercept an underlying
low permeability unit. In this configuration, flow underneath the barriers is possible.
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Reactive-Transport Parameters
The goal of the reactive transport simulations was to determine the minimum thickness of a granular iron wall necessary
to degrade selected TCE, cDCE and VC concentrations to less than MCL values. Given the sparse TCE characterization
at the site, no attempt was made to accurately portray the TCE source zone. Two simulations were conducted in which
the anticipated and maximum observed TCE, cDCE, and VC concentrations were assigned to a source zone upgradient
of the wall. The source zone was a 12 m by 5 m plane of nodes located at the southern upgradient boundary of the
domain.
Longitudinal and transverse dispersivities were assigned values of 1.5 cm in the model, based on laboratory column
experiments. A bromide tracer solution was introduced into 50 cm long laboratory columns containing different granular
iron reactive mixtures. Longitudinal dispersivities between 0.6 and 1.7 cm were calculated by fitting the effluent
concentration vs. time data (Appendix C) to the one-dimensional advection-dispersion equation using CXTFIT (Toride et
al., 1995). Although it is generally accepted that laboratory scale dispersivity measurements do not accurately reflect
field scale problems, the longitudinal dispersivity value obtained from the 50 cm laboratory granular iron column may
reasonably represent the field dispersivity within a 45 to 60 cm granular iron wall. Previous studies have indicated that
laboratory values of transverse dispersivity are usually 0.05 to 0.2 times the longitudinal dispersivity (Freeze and Cherry,
1979; Klotz et al., 1980). Thus, assigning equivalent longitudinal and transverse dispersivity values may provide an
inaccurate representation of transverse spreading at the fringes of the simulated plume. However, the small value of
transverse dispersivity used is not expected to significantly influence declining TCE, cDCE and VC concentrations along
the centerline of the plume within the granular iron wall, or significantly bias the estimate of the minimum required
thickness of the iron wall.
TCE, cDCE and VC diffusion coefficients at 20°C were assigned values of 10.1 x 1Q-6 cm2/s, 11.4 x 1Q-6 cm2/s, and 13.3 x
10~6 cm2/s, respectively. These values were calculated using a semiempirical correlation equation developed for dilute
organic solutes in water (Wilke and Chang, 1955). The tortuosity was assigned a value of 0.8 for both aquifer and
granular iron media. Tortuosity values between 0.7 and 0.85 are typical for sands.
The distribution coefficient, Kd, was assigned a value of zero. This ignores the partitioning or adsorption of the organic
contaminants onto the granular iron or aquifer material within the wall, and results in no retardation of contaminant
transport. This assumption will yield conservative estimates of the minimum wall thickness in order to provide the
required ground-water residence time within the wall.
The reduction-precipitation reaction of Cr(VI) was not modeled because previous lab experiments indicated it to be the
most rapidly reduced contaminant in the granular iron. First-order reaction rates and molar transfer coefficients for the
reductive-dechlorination of TCE, cDCE and VC were incorporated into the reactive-transport model. The reactive
transport simulation was run for 100 days. This simulation time allows more than 10 pore volumes (PV) to pass through
the barrier and establish steady-state conditions.
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Results and Discussion
Column and Batch Tests
Batch Results
Organic
The results of the batch tests are plotted as a concentration ofTCE in |jg/L versus time in hours (Figure 19). The reactive
vial concentration values are averaged triplicate values. The concentration of TCE in blanks for all four experiments
shows minor fluctuations, but was relatively constant over time. The percent standard deviation for the reaction vial TCE
values are generally less than 5% (Table 7).
The reactive vials containing Ada iron and silica sand (AdaSS) showed a gradual decline in TCE concentration from an
initial concentration of 2,000 ug/L over the 313 hr duration of the test (Table 7, Figure 19). The reactive vials containing
the PLSS iron showed a more rapid decline in TCE concentration, with a concentration of 17 ug/L being reached by the
192 hr sampling. The most rapid loss of TCE was obtained using Master Builders™ (MB) iron. MBAQ and MDSS gave
similar results, with losses of about 95% of the initial TCE during the first 50 hours. The degradation rate for MBAQ
appeared to be slightly greater than MBSS.
Inorganic
Trends in the dissolved aqueous geochemistry measured during the batch experiments are plotted in Figure 20 and are
described in detail in Appendix D. Although the method detection limit for Cr(VI) in the laboratory is fairly high, the
similarity of total Cr and Cr(VI) concentrations in the spiked ground water suggest that Cr in this water is dominantly in
the Cr(VI) valence for the duration of the experiments. Early time removal of Cr(VI) from the spiked ground water solution
is shown in Figure 21. The reaction was rapid for all four batch tests, with complete removal within the first 70 minutes
(TableS). Cr remained below detectable levels (< 0.02 mg/LCr(VI)) during the remainder of all experiments (200 hours).
PLSS showed the fastest reaction (non-detect (nd) at 23 minutes), followed by MBSS (nd at 35 min) and Ada iron
(AdaSS) (nd at 70 min). Similar declines in Cr(VI) concentration were observed when natural Elizabeth City aquifer
material (MBAQ) was substituted for silica sand in the reactive mixture.
In all four batch tests, the pH increased from an initial value of 5.9 to between pH 7 and 8 (Figure 20; Appendix D) within
5 hours. The final pH was lowest for the AdaSS mixture (pH 7.04). The Eh dropped by at least 500 mV during the
experiments and by as much as 1,000 mV for the experiments using MBSS and PLSS. Iron corrosion and the reduction
of Cr(VI) by Fe° (eqn. 6, 7) are probably responsible for the observed pH-increase and Eh-decrease in the batch flasks.
2Fe° + O2 + 2H2O <^» 2Fe2+ + 4OH~ (6)
8H+ + CrO42- + Fe° <^» Fe3+ + Cr3+ + 4H2O (7)
Over the first 3-6 hours, the alkalinity increased rapidly from an initial value of 30 mg/L CaCO3, to near 150 mg/L CaCO3.
The alkalinity then decreased slowly until the end of the experiment.
Dominant ions in the batch water include Ca, Cl, Cr, Fe, Mg, Na, Si and SO4 (Appendix D). Analytical charge balance
errors of < 5% were regularly achieved. These species are at concentrations > 1 mg/L at some time during the
experiment. Most other dissolved species are present at concentrations < 1 mg/L during the experiment. Dissolved Fe
concentrations increased rapidly from < 0.05 mg/L (input) to maximum values between 1 and 64 mg/L within 5 hours, and
generally decreased slowly afterwards. The highest Fe concentrations were measured in the PLSS and the lowest in the
MBAQ mixture; the MBSS and AdaSS mixtures had mid-range values.
Dissolved Ca, Mn and Na concentrations increase slightly (~10%) from the input water composition during the batch
experiments. Dissolved Si concentrations decrease by ~70% from the input water composition of ~6 mg/L. Trends for
SO4 concentrations are not evident.
Geochemical Modeling - Inorganic Data
MINTEQA2 was used to calculate the state of saturation of the water with respect to a variety of minerals versus time and
batch composition. The results for ferrihydrite [Fe(OH)3], goethite, amorphous [Cr(OH)3], crystalline [Cr(OH) calcite
[CaCO3], dolomite [CaMg(CO3)2], siderite [FeCO3], aragonite [CaCO3], amakinite [Fe(OH)2], rhodochrosite [MnCO3],
quartz and amorphous silica are plotted in Figure 22 and are listed in Appendix E. As each batch reacts, similar trends
in the state of saturation of the water are observed.
Chemical analyses indicate that the Cr in the input water occurs almost entirely as Cr(VI). High pH and Eh conditions
preclude reduction to Cr(lll) in the absence of a reductant. MINTEQA2 calculations indicate that the batch input water is
undersaturated with respectto Cr(lll) bearing solids. This water would only approach saturation with respectto crystalline
and amorphous Cr(OH)3if the Cr(lll) concentration approached 50% of the total Cr concentration.
10
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With the exception of the AdaSS mixture, total Cr concentrations generally reach the detection limit within approximately
0.5 hours (Appendix D). After the detection limit for Crwas reached, Cr was assumed to be 50% of the MDL (i.e., Cr =
0.01 mg/L), with speciation based on the Eh. Using these assumptions, the calculated SI values for Cr(OH)3 after 0.5
hours indicate moderate supersaturation with respect to Cr(OH)3.
Between 0 and 0.5 hours, dissolved Crwas speciated with MINTEQA2 based on the measured Eh. During this period the
water in each batch experiment is supersaturated (SI ~ 2 to 3) with respect to Cr(OH)3 (a) and near equilibrium (-0.75 <
SI < 1.0) with respect to Cr(OH)3 (c) (Figure 22). Because of kinetic limitations, however, it is unlikely that amorphous or
crystalline Cr(OH)3 are precipitating and limiting the concentration of dissolved Cr in the short time of the experiments. It
is more likely that the Cr(lll) is incorporated into a mixed Fe(lll)-Cr(lll) oxyhydroxide precipitate, similarto those observed
in previous studies (Eary and Rai, 1988; Schwertmann, 1989; Powell et al., 1995; Blowes et al., 1997; and Pratt et al.,
1997). Although an analysis of solids from the batch flasks was not conducted, the reacted water is supersaturated with
respect to goethite.
The reduction of Cr(VI) to Cr(lll) is accompanied by the release of dissolved iron, as Fe°is oxidized to Fe3+ (eqn. 2). The
Fe3+ released during the Cr removal reaction may then be reduced to Fe2+ by the oxidation of Fe°,
2Fe3+ + Fe° -» 3Fe2+ (8)
Between 0 and ~0.5 hours, while Cr concentrations are measurable, Fe was not detected. The calculated saturation of
the water with respect to ferrihydrite, goethite and other Fe-bearing minerals during this time is based on the assumption
that the total Fe concentration is 10% of the MDL (i.e., Fe = 0.01 mg/L). Under this assumption, the water is near
equilibrium with respect to ferrihydrite (Appendix E). If a solid solution such as (CrxFe1 x)(OH)3 controls Cr(lll)
concentrations during this period, it is probable that this phase also controls Fe(lll) concentrations.
After ~0.5 hours, Fe concentrations rise sharply (Appendix D). Based on the measured Eh, this iron is dominantly in the
ferrous state. Because Fe(lll) concentrations are small and not quantified, predictions about the solubility control for
Fe(lll) cannot be verified without mineralogical study. As each batch ages (>0.5 hr), the water gradually becomes less
undersaturated with respect to amakinite.
Water in each of the batches is initially undersaturated with respect to calcite, dolomite and siderite (Figure 22). As the
pH and alkalinity increase during the batch experiments, the water gradually approaches equilibrium with respect to the
carbonate minerals calcite, aragonite and siderite. In particular, the water attains and exceeds saturation with respect to
siderite, generally within one hour of the start of the experiments. Dissolved Fe(ll) concentrations decrease gradually
after 3 hours in all but the AdaSS batch mixture. This decrease in Fe concentration possibly results from the precipitation
of siderite. Within 24 hours, equilibrium was also attained (SI = -0.20 to + 0.30) with respect to calcite, dolomite and
rhodochrosite in the MBAQ batch.
In each of the batch experiments, the water is near equilibrium (SI = -0.02 to 0.35) with respect to quartz (SiO2), and is
undersaturated with respect to amorphous silica at all times (SI = -0.5 to -1.0). Noted decreases in dissolved Si
concentrations may be attributed to the precipitation of amorphous silica or coprecipitation of silica with ferrihydrite or
goethite. The accumulation of SiO2 in iron oxyhydroxide coatings (goethite) surrounding zero valent iron grains has been
noted previously by Blowes et al. (1997). Noted increases in the concentrations of dissolved Ca and Mn may be
attributable to ion exchange or the gradual dissolution of trace amounts of minerals in the batch mixtures.
Column Results
Based on the results from the batch tests, the column tests focused on Master Builders™ and Peerless™ iron, with silica
sand and Elizabeth City aquifer as the mixing materials.
The site water was siphoned from 4 L amber bottles used for shipping into a collapsible 22 L Telfon® bag. As noted in
Appendix F by reservoir number (RN), all the site water could not be held in the collapsible bag and thus the reservoir had
to be filled five times over the course of the tests. Reservoirs a-c were used in the first set of tests (high flow velocity,
FV1) and reservoirs c-e in the second set (low velocity, FV2).
The main organic compounds detected in the site ground water were TCE, cDCE, trichloromethane (TCM; chloroform)
and VC, with concentrations of about 750, 50, 20, and 40 ug/L, respectively. Trace levels of tetrachloroethylene (PCE)
and trans-1,2-dichloroethylene (tDCE) were detected (2 ug/L each). The initial Cr(VI) concentration was 8 mg/L. In
increase both the initial TCE and Cr(VI) concentrations to approximately 1,600 ug/L and 10 mg/L, respectively, in order
to have an adequate amount of time to accurately determine declines in concentrations, the initial TCE and Cr(VI)
concentrations were increased to approximately 1,600 u,g/L and 10 mg/L, respectively.
Organic
Concentration profiles were measured along the columns at intervals of approximately 5-7 pore volumes. The results are
listed in Appendix F. The results, obtained when steady state conditions were reached, are plotted as concentration
11
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(|jg/L) versus distance (cm) along the column. In these columns, the profiles of most interest are the steady-state
concentration profiles, reached when the rate at which the contaminants were degrading was equal to the rate at which
they were entering the column. If the reaction is indeed first-order, then at steady-state, an exponential decline in
concentration along the column would be expected.
High Flow Velocity Tests
Steady-state concentration profiles for the six column tests are shown in Figures 23-26. At a flow velocity of
approximately 0.61 m/day (2 ft/day, FV1) a total of 40 to 50 pore volumes of spiked water had passed through the column
at the time the profiles shown in Figures 23-27 were determined. In this case, one pore volume corresponds to a
residence time ranging from 15-28 hours, depending upon the porosity of the particular packing material (Table 5). At
steady-state, initial concentrations of 1,600, 23, 50 and 40 ug/L were measured for TCE, TCM, cDCE and VC,
respectively.
Figure 23 shows a rapid decline in TCE concentration from an initial value of 1,600 ug/L to non-detectable values
between the 15 cm and 30 cm sampling ports for all six columns. As shown in Figure 24, from an initial concentration of
23 ug/L for TCM, a rapid decline in TCM concentration was observed with non-detectable concentrations occurring from
0.15 and 0.20 m (0.5 and 0.66 ft) along the column for all six columns.
The cDCE concentration increased from 50 ug/L to peak concentrations ranging from 65 to 94 ug/L at the 10 cm (0.33 ft)
distance for the 100PL, 50PLSSAQ and 48PL/52AQ columns, while the remaining columns peaked at concentrations of
approximately 180 ug/L (Figure 25). The cDCE concentration increased due to the dechlorination of TCE. The cDCE
concentration then gradually declined to effluent values of 120 and 70 ug/L for 50MBSS and 50MBSSAQ and < 8.4 ug/L
for all the other columns.
The VC concentration in the site water was about 40 ug/L, with the exception of the water used in the 48PL/52AQ
column. The 48PL/52AQ column test was conducted later, with an initial concentration of 12 ug/L VC. The VC
concentration declined steadily in four of the six columns (Figure 26). However, with both the 50MBSS and 50MBSSAQ
columns, fluctuations in VC concentrations were observed with effluent concentrations of approximately 20 ug/L
(Figure 26). These VC concentration fluctuations were attributed to the dechlorination of TCE and cDCE.
Though present at trace levels in the source water, PCE was only detected up to 0.05 m (0.16 ft) distance into the
columns. PCE concentrations were non-detectable for the remainder of the profiles for all columns (Appendix F). The
tDCE concentrations in the columns fluctuated due to the dechlorination of TCE, and due to the presence of trace levels
of tDCE in the source water. However, the highest tDCE concentration observed during the tests was 5.7 ug/L, and non-
detectable concentrations were observed beyond 0.2 m distance in all of the columns (Appendix F). Though the
compounds of greatest interest were TCE and the less chlorinated ethenes, analyses for TCM were performed since it
was detected in the water obtained from the site. Though TCM degraded rapidly, a portion of the initial TCM would
appear as dichloromethene (DCM). Previous experience indicated that DCM would not degrade in the presence of iron;
however, at the low initial TCM concentrations, any DCM that formed would be below the MCL for DCM. DCM analyses
were not performed.
Low Flow Velocity Tests
Steady-state concentration profiles of organic concentrations for the three column tests conducted at the low flow
velocity are shown in Figures 27-30. At a flow velocity of approximately 0.3 m/day (1 ft/day, FV2) another 35 to 75 pore
volumes of site water passed through the columns, giving cumulative pore volumes ranging from 85 to 125. At this flow
velocity, one pore volume corresponds to a residence time ranging from 34 -50 hours (Table 5). At steady-state, initial
concentrations of 1,400, 23, 75 and 12 ug/L were measured for TCE, TCM, cDCE and VC, respectively.
Because slower treatment of cDCE and VC was observed for both the 50MBSS and 50MBSSAQ columns at the high
flow velocity, these two mixtures were not tested at the second slower flow velocity. In addition, further testing of the
48PL/52AQ column at the lower velocity was not conducted because the hydraulic properties could potentially be
problematic.
For the three columns (100MB, 100PL and 50PLSSAQ), TCE and TCM showed a steady decline in concentration
(degradation) along the column length, with non-detectable concentrations measured between 0.2 and 0.30 m distance,
along the columns, as shown in Figures 27 and 28.
The rate of cDCE removal (Figure 29) was slower due to its appearance as an intermediate product of the dechlorination
of TCE. Thus the initial cDCE concentration of about 75 ug/L increased to peak concentrations ranging from 80 to
150 ug/L, at distances ranging from 0.1 - 0.17 m (0.33 - 0.55 ft) along the column. However, once the concentration
peaked, a steady decline in concentration was observed, with all three columns having non-detectable concentrations at
the 0.4 and 0.5 m (1.31 and 1.64 ft) distances along the column.
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The VC concentration declines steadily for all three columns, with minor fluctuations in concentrations (Figure 30). With
initial concentrations ranging from 8-11 ug/L, non-detectable concentrations were observed at the effluent end (0.5 m)
of the column.
Trace amounts of PCE and tDCE were present in the influent solution, however, declines in concentrations were
observed, with non-detectable concentrations beyond a distance of 0.1 m for all three columns (Appendix F).
Inorganic Results
Chromium
Figures 31 to 36 summarize the detailed sampling results for dissolved Cr(VI) for all six columns, including both flow
velocities. The first (high flow velocity) is indicated by FV1 in the figure caption, while the second (lower flow velocity) was
indicated by FV2. Refer to Table 5 for the calculated flow velocities in each column. Table 9 summarizes the results of
the inorganic analyses of samples from the influent and steady-state effluent for all six columns. Detailed column
chemistry is listed in Appendix G.
At FV1 (~61 cm/day), complete removal of Cr was observed within the first 2.5 cm of each column for more than 40 pore
volumes (Figure 31 - 36). Dissolved Cr concentrations dropped from maximum values of 11 mg/L input to non-detectable
levels (< 0.02 mg/L) before the 2.5 cm sample port during the first stage of the experiment, along the length of each
column. The 48PL/52AQ column was operated for 78 pore volumes at FV1. After 78 PV, measurable Cr was observed
only at the 2.5 cm port (Figures 36, 37).
After running all of the columns at FV1, three of the columns (100MB, lOOPLand 50PLSSAQ) were operated at a lower
flow velocity of 0.3 m/day (1 ft/day = FV2). All columns exhibited similar Cr properties at all of the times, regardless of the
solid reactive mixture. The column experiments were terminated after the treatment of 85-125 pore volumes. Final
cumulative pore volumes for these columns are 98, 115 and 135, respectively. Cr was not detected in the effluent at
termination of the experiments, although some Cr was detected at the 2.5 cm port as early as 69 pore volumes (100MB,
Figure 37) and as late as 101 pore volumes (50PLSSAQ, Figure 37). The appearance of Cr at the 2.5 cm port, and a total
column length of 50 cm, suggests that Cr(VI) could be effectively removed by any of the reactive mixtures in the columns
for 1380 - 2020 pore volumes (Table 10). This prediction is preliminary because many factors such as flow rate and input
Cr concentration may affect the actual breakthrough of Cr(VI) at the effluent end of the column.
Cations and Anions
Table 9 summarizes the inorganic analyses of samples from the influent and steady-state effluent for all six columns.
Appendix G includes all inorganic analytical data, including profile data.
There is little change in the Na, Fe, K, Cl and SO4 concentrations with passage of the waterth rough the column materials
(Appendix G and Table 9). The concentrations of Ca, Mg, Mn, and dissolved Si (as [H4SiOJ) decrease along the length
of the columns. In contrast, the concentrations of Ca, Mg and Mn in the batch experiments increased over the duration
of the experiments.
The Ca concentration decreases by ~ 8-12 mg/L, in all columns except 50MBSSAQ. Mg concentrations decrease
significantly (> 25%) in all but the 50MBSS column. Mn concentrations decrease from ~ 0.9 mg/L to < 0.2 mg/L within a
short travel distance in all columns. Dissolved H4SiO4 concentrations decrease sharply from ~31 mg/L to < 2 mg/L within
a short distance in the columns. These results suggest the removal of these dissolved cations through ion exchange or
mineral precipitation may be occurring.
Eh, pH and Alkalinity
In all cases, the pH rose from about pH 6.5 to pH 9 within the first 0.1 m of each column (Figures 31-36, Appendix G).
The pH values then remained constant throughout the length of the column. In all of the columns, the Eh values declined
from influent values of 300-400 mV(SHE),to nearO mV values within the first 0.1 m of the column (Figures 31-36). Pore
water alkalinity was maintained near 50 mg/L CaCO3 with slightly higher values observed near the influent end of the
column (Figure 31-36). All columns exhibited similar pH, Eh and alkalinity properties at all sampling times, regardless of
solid reactive mixture.
Geochemical Modeling
MINTEQA2 was used to calculate the saturation indices of a variety of minerals (ferrihydrite, goethite, amorphous
[Cr(OH)3], crystalline [Cr(OH)3], calcite, dolomite, siderite, amakinite, rhodochrosite, quartz, amorphous silica and
mackinawite [FeS]), along each of the columns (Figures 38-43, Appendix H). For comparison, the SI values calculated
at several pore volumes are plotted together on each figure. The figures show the results for measurements collected at
both the fast (FV1, low pore volume measurements) and slow velocities (FV2, high pore volume measurements).
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MINTEQA2 calculations suggest that the source water is generally close to equilibrium or undersaturated with respect to
amorphous Cr(OH)3, and undersaturated with respect to crystalline Cr(OH)3. High pH and Eh conditions limit Cr(lll)
concentrations in the source input water to low levels, as confirmed by the similarity of total Cr and Cr(VI) values
(Appendix D).
Trends in the SI values of crystalline and amorphous Cr(OH)3 are similar for each column composition and at all pore
volumes. However, because Cr concentrations generally are depleted to approximately analytical detection limits
beyond the first sampling port, SI values for Cr(OH)3 beyond the first port are overestimated. In a few cases, however,
significant measurable Cr concentrations (>1 mg/L) were detected at the 2.5 cm port (Appendix G). These include the
100MB column at 79 and 98 PV (at FV2), the 100PL column at 100.5 and 114.7 PV (FV2), the 50PLSSAQ column at
135.3 PV (FV2) and the 48PL/52AQ column at 78.4 PV (FV1). Calculated SI values for amorphous Cr(OH)3 range from
3.2 to 3.9, and for crystalline Cr(OH)3 range from 0.6 to 1.4.
As with the batch test results, it is not likely that a pure Cr(OH)3 phase would precipitate within the short duration of the
experiments. It is more probable that the Cr is removed by co-precipitation within a mixed Fe(lll)-Cr(lll) hydroxide solid
solution or mixed Fe(lll)-Cr(lll) (oxy)hydroxide solid, as has been observed previously (Eary and Rai, 1988; Schwertmann,
1989; Powell et al., 1995; Blowes et al., 1997; Pratt et al., 1997). The water samples that contain measurable
concentrations of dissolved iron are supersaturated with respect to goethite.
Goethite precipitation may passivate the iron filing surfaces over longer periods of treatment. At FV2 (31 cm/day) and a
maximum observed iron concentration of ~18 mg/L, the precipitation of goethite (molar volume 20.8 ml/mol) results in a
10% decrease in porosity over the length of the column in about 82 years.
The dissolved Fe concentration is below the analytical detection limit in the input water. Occasionally, higher dissolved
Fe concentrations (> 1 mg/L) are detected at the first (2.5 cm) and second (5 cm) sampling ports (Appendix G). This Fe
probably results from corrosion of the iron filings by oxygen and by water, and during the reduction of Cr(VI) to Cr(lll)
(eqn. 6, 7). Dissolved Fe concentrations are otherwise at analytical detection limits in all columns at all times. MINTEQA2
calculations indicate that at the 2.5 cm and 5 cm locations, Fe(ll) is the dominant dissolved Fe species. As in the case
for Cr, MINTEQA2 saturation index calculations for iron minerals are considered reasonable only at locations where
measurable iron concentrations were detected (0-5 cm). At these locations, the water is supersaturated with respect to
goethite (SI ~ 6), is near equilibrium with respect to ferrihydrite (SI ~ -0.5 to +1); and is undersaturated (SI ~ -2.5 to -4)
with respect to amakinite (Appendix H, Figures 38-43).
In parts of the column where the Fe concentrations are below the detection limit, the water along each of the columns
would be supersaturated with respect to goethite and would be near equilibrium with respect to ferrihydrite if an Fe
concentration of 0.01 mg/L (10% MDL) was assumed to be present. With the same assumption, the water would be
slightly undersaturated with respect to amakinite.
The input water for the columns is undersaturated with respect to calcite, aragonite, dolomite and siderite. Within each
column, the pH increases significantly downgradient from the source, and the alkalinity decreases slightly. The water
approaches equilibrium with respect to calcite and aragonite and becomes supersaturated with respect to dolomite
between the first and third sampling ports (10 cm). Precipitation of aragonite or calcite is consistent with the decrease in
alkalinity and dissolved Ca concentrations observed along the length of columns 50MBSS, 100MB, 100PL and
48PL/52AQ. Although the water is also slightly supersaturated with respect to calcite and dolomite in the 50MBSSAQ
column, dissolved Ca concentrations along the length of these columns remain relatively unchanged. The Ca
concentration decreases by approximately 12 mg/L. Assuming that this decrease is due to calcite precipitation (calcite
molar volume 35 ml/mol), a 10% decrease in the porosity of the first 10 cm of a column would occur in about 16 years
at the slower velocity (31 cm/d) or in about 9 years at the higher velocity (53 cm/d). These calculations suggest that
calcite or other carbonate mineral precipitation could adversely affect the permeability or reactivity of the granular iron
over longer treatment periods.
Because the behavior of Fe is linked to the geochemical reactions that remove the dissolved Cr, the trends for siderite
are unlike those of calcite and dolomite (Ca and Mg are not involved in the Cr removal reactions). In locations where Fe
concentrations are measurable, generally within the first 5 cm of the column (Figures 38-43), the water approaches
equilibrium with respect to siderite. The precipitation of siderite in this location may limit Fe mobility in the columns.
Beyond the first sampling port, calculations of pore-water saturation with respect to siderite assume Fe(ll) concentrations
that are 10% of the analytical detection limit (i.e., Fe=0.01 mg/L).
The water also approaches and attains equilibrium with respect to magnesite. The observed decrease in Mg
concentrations may be due to the precipitation of a magnesium carbonate or hydroxycarbonate.
The water is undersaturated, but approaches equilibrium with respect to rhodochrosite in each of the columns. In each
of the columns, equilibrium is reached at the first port of the columns at the slower flow velocity. At the higher flow
velocity, equilibrium is attained further along the column, suggesting the precipitation may be rate dependent. It is
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possible that precipitation of rhodochrosite or a less crystalline precusor limits dissolved Mn concentrations. The
observed sharp decrease in Mn concentrations at the first port is consistent with this conclusion.
The input waters are slightly supersaturated (SI = 0.58) with respect to quartz and are undersaturated with respect to
amorphous SiO2 (SI = -0.4). With the decreasing H4SiO4 concentrations along the length of each column, the water
becomes more undersaturated with respect to amorphous SiO2 (SI = -1 to -2). In the downgradient direction, the H4SiO4
concentration decreases sharply by the first or second sampling port. Kinetic limitations prevent the direct precipitation
of quartz. It is likely, therefore, that H4SiO4 concentrations decrease as a result of the coprecipitation of amorphous silica
with Cr and Fe bearing solids. The accumulation of SiO2 within iron oxyhydroxide coatings (goethite) surrounding zero
valent iron grains has been noted previously by Blowes et al. (1997). Palmer (1999) confirmed the presence of silica-
containing goethite and/or amakinite on the surface of iron filings collected from the downgradient side of the Elizabeth
City full-scale barrier. Although a discrete solid silica phase is not expected to form and thereby affect the reactivity of the
iron filings, the association of Si with mixed Fe(lll)-Cr(lll) hydroxide solid solution (eqn. 3) or mixed Fe(lll)-Cr(lll)
(oxy)hydroxide solid indicates that Si may contribute to the passivation of the granular iron surfaces over longer
treatment times.
Determination of Reaction Parameters: Cr(VI)
Data from the column tests were used as a basis for the selection of reactive materials for the reactive barrier. Chromium
concentrations decrease from approximately 1 0 mg/L to less than 0.05 mg/L (MCL) at the first sampling port (2.5 cm) for
69 to 101 PV, depending on the column reactive mixture (Table 10, Figure 37). At later times, Cr(VI) concentrations at
this port were above MCL. These results suggest that the reaction with Cr(VI) is very rapid and that the Cr front is
migrating slowly through some of the columns, possibly as a result of changing reactivity of the Fe° surface due to
precipitation. Cr(VI) concentrations in the column effluent are predicted to exceed the MCL value of 0.05 mg/L Cr after
1 ,400 to 2,000 pore volumes (Table 1 0). At an estimated flow velocity of 1 0 cm/day at the Elizabeth City site, this would
correspond to chromium breakthrough in a 0.5 m granular iron barrier within 19 to 28 years.
Determination of Reaction Parameters: Halogenated Hydrocarbons
Reaction rates for the reductive-dechlorination of TCE, cDCE and VC with various reactive mixtures were calculated
from column experiment data (O'Hannesin et al., 1995). The reaction rates were calculated to determine the relative
reactivity of different zero-valent iron mixtures, as well as for use in conjunction with reactive-transport modeling.
Concentration profiles along the column were obtained after 40-50 pore volumes had flowed through the column. Rate
constants for the reductive-dechlorination of the chlorinated organics were obtained by fitting a consecutive first-order
decay model, adapted from Hill (1977), to these profiles. The model assumes that of all the reaction products from TCE
degradation, x% of the TCE decays to cDCE, with the other (1-x) % of the TCE degrading to alternative breakdown
products such as chloroacetylene. Similarly, only y% of the cDCE decays to VC, with the remaining (1-y) % of the cDCE
degrading to alternative breakdown products such as acetylene. The first order rate expressions for the decay of TCE,
cDCE and VC are shown in eqn. 9 through 11.
(9)
(10)
(11)
where k1t k2, k3 represent first-order rate constants (d~1), and x, y represent mole transfer coefficients (mole %). The
molar transfer coefficients represent the mole percentage of the parent compound that degrades to a daughter product.
This model describes the first-order reductive-dechlorination of TCE, including the production or accumulation of cDCE
and VC breakdown products and their first-order decay.
Ground-water residence times within the column were calculated by dividing distances along the column by the ground-
water velocity. Rate constants and molar transfer coefficients were then calculated from non-linear least squares fit of
concentration versus residence time data to analytical solutions for eqn. 9 to 77 (eqn. 12, 13, 14 respectively):
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[TCE]f = [TCE]oe~k< (12)
FcDCEl =[cDCEl e~k* + —
L Jf L Jo k2-k,
d4)
-*,) (k3-k2)(k3-k,)
This model neglects the effects of dispersion and diffusion within the columns.
First-order rate constants and molar transfer coefficients for TCE, cDCE and VC are shown in Table 11. TCE
concentrations decrease more rapidly than the concentrations of cDCE and VC within the columns. Based on this
observation, the selection of the barrier width and reactive material will be based upon the reactivity of the reactive
mixtures toward cDCE and VC.
Comparison of the molar transfer coefficients of various reactive mixtures indicates that between 4 and 17% of the TCE
mass degrades to cDCE, and between 1 and 100% of the cDCE degrades to VC, with the remaining mass degrading to
other products. Previous laboratory experiments indicated that less than 10% of TCE degrades to chlorinated
degradation products (Gillham and O'Hannesin, 1994; Orth and Gillham, 1996). It should be noted that reaction rates
determined from the filtering procedures can be influenced significantly by one or two data points that fall off the trend.
The certainty in the calculated values therefore decreases with increasing scatter in the data. Normally this is the case
for compounds that degrade slowly or are present at low concentrations.
There appeared to be no substantial advantage in mixing sand with the iron materials, and there was the further concern
of segregation of the sand and iron during installation. Consequently, the sand-iron mixtures were eliminated as potential
candidates for the installation. The remaining two reactive materials, lOOPLand 100MB, were compared on the basis of
reaction rates, hydraulic properties (Table 12) and cost.
TCE, cDCE and VC steady-state concentration profiles with in the 100MB and 100PL columns after 40-50 pore volumes,
and calculated concentration profiles using least-squares fit parameters, are shown in Figures 44 through 46. The
surface area normalized reaction rates for TCE and cDCE were within 20% agreement for 1 0OPL and 1 00MB, while the
normalized rate for VC degradation was significantly greater for 100PL (Table 12). These normalized reaction rates are
similar to those reported by Johnson et al. (1996), shown previously in Table 2. The 100MB and 100PL columns also
have similar hydraulic conductivity and porosity values, which were the highest measured for all reactive materials.
These higher values may be advantageous in offsetting potential long-term precipitate formation, which may reduce the
hydraulic conductivity and porosity of the barrier. However, the cost of Peerless™ iron (~ $375 US/ton, 1995) was less
than that of Master Builders™ iron (~ $700 US/ton, 1995). Thus, 100 % Peerless™ iron (100PL) was chosen as the
reactive material, based on suitable reaction rates, desirable hydraulic properties and lower cost.
Reactive Barrier Designs
Five three-dimensional numerical flow simulations were performed to assess the relative efficiency of a Funnel-and-Gate
versus a continuous wall configuration (Bennett, 1997). In these simulations, the entire model domain was assigned a
uniform hydraulic conductivity (Table 13). A range in aquifer hydraulic conductivity values was simulated in order to
bracket the anticipated range of ground-water velocities, capture areas and residence times.
The capture area of a reactive barrier is the cross-sectional area of ground water intercepted by the reactive barrier
(Figure 47) and which flows through the reactive material. Capture areas were estimated from the ground-water flow
pathlines. These pathlines were traced from an upgradient grid of 0.3 m spacing. Pathlines that enter the "gate" zone of
a Funnel-and-Gate orthe continuous wall were considered to be within the capture area of that barrier. The capture area
results are presented as overall capture areas and as values relative to the total area of the front face of the Funnel-and-
Gate or continuous wall.
The simulated capture areas of the 15.8 m wide, 9.1 m deep, and 2 m thick Funnel-and-Gate barrier are shown in
Table 14. The impermeable funnels of a Funnel-and-Gate increase the capture area of the Gate (reactive material) zone.
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However, only a third to a half of the ground-water flow approaching the funnels is directed through the gate. A significant
volume of ground-water flows around and underneath the "hanging" Funnel-and-Gate, limiting the increase in capture
area (Figures 48, 49). The hydraulic conductivity of the aquifer also has an impact on the capture area of the Funnel-and-
Gate. The capture area of the barrier is larger when the hydraulic conductivity of the aquifer is less than that of the gate.
Based on the observed aquifer hydraulic conductivities, the capture area is expected to be between 67 and 85 m2 for the
Funnel-and-Gate configuration simulated.
The simulated capture areas of the 10.3 m wide, 7.6 m deep and 0.45 m thick continuous wall configuration are shown
in Table 15. Without funnels to intercept ground-water flow and increase the capture area of the reactive material, the
capture area of the wall is equal to or slightly larger than the face of the wall. The capture area of the wall increases by
only 14% when the hydraulic conductivity of the reactive material is two orders of magnitude greater than that of the
aquifer. Thus, there is only slight preferential ground-water flow through the barrier when the hydraulic conductivity of the
wall is much larger than the aquifer. Very little ground-water flow divergence is observed in the vicinity of the barrier
(Figure 50). The capture areas of a wall at the site are expected to be between 105% and 114%. This corresponds to a
capture area of 82 m2 to 89 m2 for the simulated pilot-scale configuration. These capture areas are very similar to those
obtained with the Funnel-and-Gate. If the hydraulic conductivity of the reactive media comprising the wall falls below that
of the aquifer, the capture area of the wall will be less than 100%, indicating that ground water will begin to preferentially
flow around it.
Residence times (Table 16) within the reactive material were calculated by averaging the component of the elemental
velocity vectors parallel to the shortest path through the barrier. This parameter indicates the minimum period of contact
between the contaminant and the reactive material. Similar residence times are calculated for the two barriers. The
residence time is expected to be between approximately 2 and 500 days, for the hydraulic conductivity range observed
within the aquifer. The similar residence times arise because both barriers have similar capture areas. The similar
capture areas indicate that the same volumes of ground water are flowing through both barriers, which have the same
volume of reactive material.
The funnels increase the capture area of the reactive material zone 2 to 2.6-fold. As a result, simulated ground water
velocities within the Funnel-and-Gate are approximately 2 to 2.6-fold greater than in the aquifer. The calculated ground
water velocities within the continuous wall are approximately equal to the velocities within the aquifer. These similar
velocities arise because there is only slight preferential ground water flow through the higher hydraulic conductivity
reactive material. The increased velocity within the reactive material, relative to the velocity in the aquifer, issimilartothe
increase in capture area of the reactive material zone. This similarity arises because the ground water velocity within the
reactive material is proportional to the volumetric ground water flux through it, and the flux is directly related to the
capture area of the reactive material zone.
These results indicate that for the Elizabeth City site, there are no hydraulic advantages of a Funnel-and-Gate over a
permeable wall in terms of both increased capture area and increased residence time. Both barrier designs can be
configured to achieve similar residence times and capture areas using the same volume of reactive material.
Final Selection of a Reactive Barrier
Final Reactive Barrier Design
The continuous wall was the reactive barrier design chosen for the site, based upon cost and flow modeling results. Flow
modeling indicated that, for the Elizabeth City site, there was no hydraulic advantage of a Funnel-and-Gate over a wall,
however initial cost estimates suggested that the wall configuration could be more cost-effective for this site.
Reactive transport simulations were conducted to determine whether a 36.4 m long x 7.6 m deep x 0.45 m thick
continuous wall composed entirely of granular iron (100PL) would provide a sufficient residence time to remediate TCE,
cDCE and VC concentrations similar to those at the site to less than MCL values, and under the maximum anticipated
flow conditions. Two simulations were conducted with different hydraulic parameters assigned to the granular iron which
comprise the barrier (Table 17).
The maximum anticipated flow conditions arise when the horizontal hydraulic gradient is 0.0033, and hydraulic
conductivity is 17 m/day. Under these flow conditions, the simulations indicate that 10,000 ug/L TCE, 900 ug/L cDCE,
and 101 ug/L VC will be reduced to MCL values within approximately 0.33 m of travel in the iron (Table 18).
VC requires the longest travel distance within the wall, or longest residence time, before it falls below its MCL value. This
is because VC has the lowest MCL value and is the last degradation product produced of the decay of TCE and cDCE.
A concentration profile through the center of the reactive wall is shown in Figure 51.
The final dimensions chosen for the reactive barrier were 46 mx7.3 mxO.6 m. The 46 m length and 7.3 m depth of the
barrier were felt to be sufficient to intercept the Cr(VI) plume, which is approximately 35 m wide and 6.5 m deep. A width
of 0.6 m was used to give a slight safety factor for residence time. A reactive medium composed entirely of Peerless™
granular iron was chosen for the barrier based on reactivity, hydraulic properties and cost.
17
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Barrier Installation
Configuration
The subsurface granular iron wall was oriented in an east-west direction, approximately perpendicular to the ground
water flow direction. It was installed on June 22,1996, beneath the parking lotdowngradientofthe electroplating shop in
Hangar 79. The granular iron was installed within a 0.6 m wide trench located between approximately 2 m and 7.3 m
depth (Figure 52). The top of the granular iron barrier was planned to coincide with the approximate depth of the water
table. The bottom of the barrier was the maximum depth of installation with the trenching machine employed.
Approximately 150 m3 of granular iron were required for the barrier. Using the laboratory measured bulk density of
2.72 g/cm3, this volume corresponded to approximately 450 tons of granular iron. Prior to installation, the granular iron
was shipped to the Elizabeth City site and stored beneath plastic sheets on the parking lot.
Site Preparation
An 80 m long and 1 m wide cut was made in the concrete parking lot to facilitate the trenching installation. Plastic sheets
with covered hay-bail berms were laid out on either side of the cut (Figure 53). The plastic sheets and berms were used
to prevent excavated soil from washing into the river. A high capacity pump and large tanker were also kept onsite in the
event that excavated materials exceeded the capacity of the bermed area.
A decontamination area was set up with plastic liners and hay-bails for the steam cleaning of all equipment. The parking
lot installation area was completely fenced off.
Installation
The installation was performed by Horizontal Technologies Inc. (HTI) using a continuous trenching machine. The
trenching machine (Figures 54, 55) used to install the subsurface barrier simultaneously removed aquifer material and
deposited the granular iron. Excavated aquifer material was brought to the surface by an excavating belt and then
conveyed to one side of the machine. A 0.6 m wide rectangular box, located behind the excavating belt, kept the trench
open while granular iron was poured in. A total of 280 tons of granular iron was placed into the trench. The mass of
granular iron used was significantly less than the 450 ton mass calculated using the laboratory bulk density for granular
iron. The lower mass of granular iron within the trench suggests that emplaced density may be less than the laboratory
density, and that the granular iron may not occupy the entire volume of the trench. The actual volume and shape
occupied by the granular iron is irregular, due to the compaction and slumping of aquifer material into the trench. Studies
using borehole radar, electromagnetics, and other geophysical techniques are planned to confirm the extent of the
granular iron zone.
The lower mass of granular iron within the wall is expected to have an impact on the surface area dependent reductive-
dechlorination rates. An emplaced granular iron density of 1.69 g/cm3, which is approximately 60% of the laboratory
measured bulk density, is calculated assuming that the granular iron fills the entire trench. At this density, the overall
surface-area dependent reaction rates may be as low as 60% of the laboratory measured values. Lower reaction rates
at this lower emplacement density, however, may be offset by an increase in porosity to as high as 0.62 and decrease
in ground water velocity within the granular iron. Alternatively, the granular iron thickness within the trench may be as low
as 37 cm at an emplaced density of 2.72 g/cm3. Under this extreme case, residence times would be only approximately
60% of the design value.
The aquifer material that was excavated by the trenching machine liquefied, forming a soil slurry on either side of the
trench (Figure 56). In addition, aquifer soils within the trench slumped in as the excavation proceeded. This simulta-
neously loaded and undermined the concrete pavement and led to the collapse of approximately 3 m of pavement on
either side of the trench (Figure 57).
Post-Installation Work
The concrete removed from the initial 80 m by 1 m trench cut was tested for VOCs and chromium. None was detected,
and this concrete was disposed of in the local landfill (Parsons Engineering Science, 1997). Excavated soils from the
trench were stockpiled on the site. Four samples and one duplicate were collected the day after installation and analyzed
for VOCs and Cr. Total Cr concentrations were found to be at background levels. However, TCE concentrations in the
soil exceeded MCL values, and therefore required additional management before disposal. The excavated soils were
taken to a Corrective Action Management Unit (CAMU). The CAMU consisted of a plastic liner surrounded by concrete
barriers. The soils were worked with earth moving equipment and then covered by plastic. Approximately one month
later, additional samples were taken and analyzed. TCE concentrations were found to be below the laboratory
quantitative limits. The USCG was then permitted to use the soil as a clean backfill at the Support Center. The trench was
backfilled with the natural excavated soils, followed by a coarse aggregate. This formed the subbase, which was
subsequently paved with asphalt.
18
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Barrier Costs and Performance
The total cost of the barrier installation, including the initial design work, soil treatment and follow-up work, was
approximately $985,000 U.S. (Table 19). The actual installation and granular iron costs are estimated to be approxi-
mately $350,000 U.S. This corresponds to an installation and materials cost of approximately $7550 U.S./linear meter for
the 5.3 m thick and 0.6 m wide continuous reactive wall.
An internal USCG report indicates that this reactive wall will lead to a cost savings of $4,000,000 U.S. over a 20 year
span compared to a traditional pump-and-treat system (USCG, Pers. Comm.). The report states that the installation
costs for the reactive barrier and a pump-and-treat system were comparable, however a cost savings results from the
lower monitoring and maintenance costs associated with the continuous reactive wall barrier. Annual costs are estimated
to be approximately $32,000 U.S. for the reactive wall compared to $200,000 U.S. for a comparable pump-and-treat
system. A similar cost analysis conducted by Manz and Quinn (1997) indicates that permeable treatment walls can result
in significant cost savings over a comparable ground-water extraction and treatment system. In their study of two sites,
they indicate that while capital costs vary, the annual estimated operation and maintenance costs for a treatment wall
were $20,000 and $27,120 U.S., as opposed to between $55,000 and $100,000 U.S. fora pump-and-treat system.
The long-term cost savings associated with a reactive barrier result from its lower operation and maintenance costs,
compared to a pump-and-treat system. However, the actual savings also depend on the initial capital costs for the barrier
installation and the estimated longevity of the reactive barrier. Previous studies with granular iron indicate that carbonate
and hydroxide minerals precipitate on the iron surfaces from anaerobic high alkalinity ground waters (Reardon, 1995;
Schuhmacher et al., 1997; Mackenzie et al., 1997). These precipitates can influence the long-term performance of the
barrier by potentially altering both the reactivity towards contaminants, and the hydraulic conductivity and porosity of the
barrier. Granular iron column experiments indicated minimal loss in reactivity toward Cr(VI) orTCE, even after more than
100 pore volumes passed through the columns (Blowes et al., 1992; O'Hannesin et al., 1995; Blowes et al., 1997;
Cippolone et al., 1997). Based on laboratory column data in this report, the extrapolated breakthrough of Cr(VI) is not
expected to occur for 19-28 years at ground water velocities of 10 cm/day. Other laboratory studies to assess the impact
of precipitate formation on ground water flow hydraulics within granular iron media indicated porosity losses that levelled
off at 5-15% (Mackenzie et al., 1997). These porosity losses were attributed mainly to H2 gas formation, and mineral
precipitation was suggested to have a more significant impact on porosity at later times. In future studies, cores will be
collected from the granular iron zone to assess the extent of precipitate formation.
19
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Conclusions
Ground-water flow simulations indicate that a Funnel-and-Gate and a continuous wall can be configured to achieve the
same capture area and residence time, with the same volume of reactive material. Therefore, there is no hydraulic
advantage in using a Funnel-and-Gate over a continuous wall. The choice of barrier design then depends on the logistics
and cost of the site-specific situation. For the Elizabeth City site, the wall configuration was selected.
The selection of the granular iron mixture that the reactive barrier would be composed of was based on reactivity,
hydraulic properties and cost. Fast reaction rates were desirable to minimize the amount of granular iron required and
high hydraulic conductivity and porosity are desirable to ensure that ground water preferentially flows through the barrier.
Of the reactive mixtures tested in laboratory batch and column experiments, the ones containing 100% granular iron had
the most rapid reaction rates for Cr(VI), TCE, cDCE and VC removal and the highest hydraulic conductivity and porosity
values. In the column tests, input concentrations of 11-12 mg/L Crwere depleted to < 0.02 mg/L over less than 10 cm
travel distance in the columns. Input TCE concentrations of 1,500-2,000 ug/L were reduced to non-detectable
concentrations (<1.7 ug/L) before reaching the half-way point (30 cm) in the columns. The PL and MB granular iron
materials tested had similar surface-area normalized reaction rates and hydraulic properties. A reactive material
composed entirely of Peerless™ brand granular iron was chosen forthe reactive barrier, with the final choice of granular
iron source based on reactivity, hydraulic properties and cost.
Contaminant reactive transport simulations indicate that 10,000 ug/L TCE, 900 ug/L cDCE, and 101 ug/L VC would be
reduced to less than MCL values in 0.33 m of travel within a reactive wall composed of this granular iron at a density of
2.72 g/cm3 and under the maximum anticipated ground-water velocity conditions. The final barrier width of 60 cm was
chosen to provide a safety factor for the treatment of TCE, cDCE, and VC contaminated ground water that is intercepted
by the barrier. The length and depth of the barrier were chosen to intercept the entire Cr(VI) plume.
The full-scale granular iron reactive wall was installed quickly and relatively inexpensively using a trenching technique,
although the maximum width and depth were dictated by the trenching machine configuration. The installation was
completed in 6 hours, with the only complication arising from the failure of the concrete pavement alongside the trench.
The speed and relatively low cost of the installation is attributed to the effectiveness of the trenching machine, which
simultaneously removed aquifer sediments and emplaced granular iron. The emplaced mass of the granular iron was
approximately 60% of that calculated, suggesting a lower emplacement density and smaller volume of granular iron
within the 60 cm trench. This lower iron density may result in slower reaction rates, due to decreased available mass and
surface area of granular iron. Alternatively, greater porosity in the wall may lower ground water velocities within the wall,
increasing the available reaction time. The extent or distribution of granular iron within the trench and the impact of the
lower mass of granular iron on reaction rates will be assessed in future studies.
20
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24
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Tables
25
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Table 1.
Horizontal Hydraulic Gradients and Water Levels Observed in Monitoring Wells Screened Between 3 and 4.5 m Below Ground
Surface
Water level
measurement date
October 1994
October 1993
March 1993
April 1992
September 1991
Range in observed water
levels (meters below top
of well casing)
1.57-2.06
1.61 -2.10
1.53-2.03
1.59-2.04
1.47-1.91
Range in observed water
levels (meters above sea
level)
0.18-0.25
0.15-0.21
0.23-0.37
0.18-0.31
0.31 -0.46
Approximate
horizontal hydraulic
gradient (m/m)
0.0029
0.0011
0.0033
0.0012
0.0025
Table 2.
First-order Rate Constants for the Dehalogenation of TCE, DCE Isomers, and VC (after Johnson etal., 1996)
Halocarbon
TCE
1,1 DCE
Trans 1,2-DCE
cis 1,2-DCE
VC
KsACLm^h'1)
(3.9 +
(6.4 +
3.6)xl(T4
5.5)xlO"5
(1.2 + 0.4)xl(r4
(4.1 +
(5+1
1.7)xlO"5
.5)xlO"5
Table 3.
Reactive MixturesUsed in Batch Experiments
Batch name
AdaSS
MBSS
PLSS
MBAQ
Iron
6 g Ada
6gMB
6gPL
6gMB
Silica Sand
6g
6g
6g
0
Aquifer Material
Og
Og
Og
6g
Table 4.
Reactive Mixtures Used in Column Experiments
Column
name
100PL
100MB
48PL/52AQ
50MBSSAQ
50PLSSAQ
50MBSS
Peerless
Iron
100%
48%
50%
Master Builders
Iron
100%
50%
50%
Silica Sand
25%
25%
50%
Elizabeth City Aquifer
Material
52%
25%
25%
26
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Table 5.
Column Flow Velocities and Hydraulic Properties of Reactive Mixtures Used (after O'Hannesin et ai, 1995)
Column Name
Mixture
Flow Velocity (FV)
(ft/day)
(cm/day)
Residence Time (hours)
Pore Volume (mL)
Porosity
Hydraulic Conductivity (cm/sec)
Bulk Density (g/cm3 )
Iron to Volume of Solution
Ratio (g:mL)
Surface Area to Volume of
Solution Ratio
(m2:mL)
50MBSS
50% MB Iron
50% Silica
FV1
1.8
55
21.6
233
0.41
6.7E-02
2.17
2.7: 1
2.97 : 1
50MBSSAQ
50% MB Iron
25% Silica
25%ECAQ
FV1
2.2
68
17.7
201
0.35
2.6E-02
2.33
3.3: 1
3.63 : 1
48PL/52AQ
48% PL Iron
52%ECAQ
FV1
2.3
71
17
189
0.33
8.9E-03
2.21
3.2: 1
2.59 : 1
50PLSSAQ
50% PL Iron
25% Silica
25%ECAQ
FV1
2.6
79
15.3
FV2
1.2
36
34
166
0.29
3.6E-02
2.20
3.78 : 1
3.06 : 1
100MB
100% MB Iron
FV1
1.4
43
27.7
FV2
0.8
24
0.8
254
0.45
8.6E-02
3.09
6.9: 1
7.6: 1
100PL
100% PL Iron
FV1
1.8
53
22.5
245
FV2
1.0
31
39
0.43
9.8E-02
2.72
6.4: 1
5.18: 1
FV1 = First flow velocity, Mar 31 - May 17, 1995
FV2 = Second flow velocity, May 26 - Aug 12, 1995
FV1* = First flow velocity, June 28 - Aug 12, 1995
-------
Table 6.
Method Detection Llimits (MDL)
Organic Compounds
Trichloroethene (TCE)
Chloroform (TCM)
Tetrachloroethene (PCE)
cis 1,2-Dichloroethene (cDCE)
trans 1,2-Dichloroethene (tDCE)
1,1-Dichloroethene (1,1-DCE)
Vinyl Chloride (VC)
Inorganic Compounds
Chromium VI [Cr(VI)]*
Chromium (total)
Iron (Fe)
Sodium (Na)
Magnesium (Mg)
Calcium (Ca)
Potassium (K)
Manganese (Mn)
Chloride (Cl)
Sulphate (SO4)
Alkalinity (as CaCO3)*
MDL (ug/L)
1.7
2.7
2.2
1.2
1.5
1.0
0.8
MDL (mg/L)
0.20-0.40
0.02
0.10
1.00
0.05
0.02
1.00
0.02
0.05
0.05
2-10
*MDL varied due to small sample volumes available for analysis
28
-------
Table 7. Changes in TCE Concentration in Batch Experiments Over Time, for Reaction and Control Vials. Three Reaction Vials and One
Control Vial Were Sampled at Each Time. Only TCE Was Analyzed
MBSS
Control
Time
(h)
0
0.20
0.50
0.77
1.0
1.5
3.0
6.0
10.8
24.1
48.0
120.9
192.8
313.4
TCE
fag/L)
1839
1970
1962
1900
1670
1786
1849
1798
1678
1670
1463
1652
1543
Reaction Vial
Average Standard % Standard
TCE Deviation Deviation
(fig/L) (ng/L)
1948 134 6.9
1489 16 1.1
1114 61 5.5
1113 40 3.6
954 23 2.5
845 18 2.1
705 23 3.3
597 22 3.6
474 20 4.3
268 13 4.8
96 2 1.8
24 2 7.2
9.1 1 14.9
2 0 0.0
AdaSS
Control
Time
(h)
0
0.25
0.50
0.75
1.0
1.5
3.0
5.7
10.8
23.9
120.9
192.3
313.3
TCE
fag/L)
1614
1658
1704
1812
1821
1786
1813
1665
1696
1519
1609
1467
Reaction Vial
Average Standard % Standard
TCE Deviation Deviation
(HK/L) (ng/L)
1800 83 4.6
1546 71 4.6
1565 17 1.1
1724 14 0.8
1744 22 1.2
1758 50 2.8
1775 20 1.1
1763 71 4.0
1646 37 2.2
1520 10 0.7
1307 91 7.0
655 43 6.6
45 43 95.4
PLSS
Control
Time
(h)
0
0.10
0.23
0.36
0.50
0.75
1.1
3.0
6.0
11.8
23.9
48.2
72.2
97.2
TCE
(HK/L)
1517
1505
1824
1812
1839.1
1726
1796
1740
1778
1575
1815
1678
1588
Reaction Vial
Average Standard % Standard
TCE Deviation Deviation
(ftg/L) (ftg/L)
1393 415 29.8
1588 29 1.8
1514 120 7.9
1393 239 17.2
1483 3 0.2
1415 35 2.4
1403 12 0.8
1213 18 1.5
1160 82 7.0
1040 33 3.2
782 18 2.4
528 8 1.4
298 19 6.4
131 15 11.1
MBAQ
Control
Time
(h)
0
0.10
0.27
0.42
0.58
0.75
1.0
3.0
6.0
11.5
24.0
48.0
96.2
167.9
TCE
(t*g/L)
1618
1602
1572
1635
1606
1589
1538
1648
1552
1573
1561
1624
1540
1417
Reaction Vial
Average Standard % Standard
TCE Deviation Deviation
(ftg/L) (ftg/L)
1561 114 7.3
1416 59 4.1
1250 35 2.8
1084 18 1.6
1003 21 2.1
913 16 1.8
879 40 4.5
636 8 1.2
482 34 7.0
299 17 5.6
149 13 8.9
48 7 14.4
11 2 16.9
3.2 1 40.6
29
-------
Table 8.
Summary of Cr Removal in Batch Tests
Batch ID
AdaSS
PLSS
MBSS
MBAQ
Cr(VI) Co (mg/L)
11.4
12.1
11.4
12.0
Time to Non-
detect (min)
70
23
35
43
Co = Initial Concentration
Table 9.
Inorganic Concentrations of All Columns for Both Influent and Effluent Samples at Steady-state Conditions
Cations
Chromium
Cr(total)
Iron
(Fe)
Sodium
(Na)
Magnesium
(Mg)
Calcium
(Ca)
Potassium
(K)
Manganese
(Mn)
Silica
(Si)
Anions
Chloride
(Cl)
Sulphate
(S04)
Alkalinity
(as HCO3)
FV
Influent
Cone.
50MBSS
50MBSSAQ
50PLSSAQ
48PL52AQ
100MB
100PL
mg/L
FV1
FV2
FV1
FV2
FV1
FV2
FV1
FV2
FV1
FV2
FV1
FV2
FV1
FV2
FV1
FV2
8.4
7.6
<0.1
<0.1
104
104
15
15
24
22
5.2
4.7
0.89
0.88
9.0
9.4
bd
NA
bd
NA
107
NA
15
NA
12
NA
4.4
NA
0.10
NA
0.51
NA
bd
NA
bd
NA
106
NA
12
NA
19
NA
4.4
NA
0.06
NA
0.57
NA
bd
bd
bd
bd
100
102
12.6
8.9
20
15
4.8
4.8
0.09
0.02
0.39
0.37
bd
NA
bd
NA
88
NA
0.8
NA
7.7
NA
4.1
NA
0.1
NA
0.7
NA
bd
bd
bd
bd
101
104
11
6.8
11
9
4.4
3.8
0.12
0.06
0.25
0.23
bd
bd
bd
bd
104
104
12
6.9
16
9.4
4.8
4.1
0.09
0.06
0.32
0.12
FV1
FV2
FV1
FV2
FV1
FV2
121
113
99
89
55
59
117
NA
95
NA
31
NA
123
NA
102
NA
57
NA
118
106
100
95
58
55
110
NA
81
NA
56
NA
119
118
97
92
39
33
116
110
99
90
52
31
30
-------
Table 10.
First Detection of Cr at the 2.5 cm Sample Port in Each Column. Predicted Breakthrough Volumes Calculated from these Data Are
Shown
Column
100MB
100PL
50PLSSAQ
48PL/52AQ
First detection ofCr at
2.5 cm port
(Pore Volumes)
69
82
101
78
Cr(VI)orCr(tot)
(mg/L)
0.53
0.09
0.11
3.77
Predicted Breakthrough at
Column Effluent
(Pore Volumes)
1380
1640
2020
1560
Table 11.
First Order Rate Constants in Various Reactive Iron Mixtures (Rate Constants Not Normalized to Surface Area)
REACTIVE MIXTURE
100% Master Builders
iron
50% Master Builders iron
50% Silica sand
50% Master Builders
25% Silica sand
25% Aquifer sed.
\QQ% Peerless iron
50% Peerless iron
25% Silica sand
25% Aquifer sed.
AVERAGE
TCE RATE
CONSTANT
1/D
(T1/2 HRS)
16.27
9.81
15.71
9.62
13.17
12.92
MOLAR
TRANSFER
COEFF.
(TCE^CDCE)
17%
8%
9%
7%
4%
9%
CDCE RATE
CONSTANT
[1/D]
(Tin HRS)
5.83
0.15
1.02
3.40
4.23
2.93
MOLAR
TRANSFER
COEFF. (CDCE
^•VC)
27%
100%
1%
100%
100%
VCRATE
CONSTANT
[1/D]
(Tin HRS)
6.31
1.27
1.08
10.61
10.99
6.06
Table 12. Hydraulic Properties and First-order Rate Constants for Peerless™ and Master Builders™ Granular Iron
Hydraulic Conductivity
Porosity
Surface Area
bulk density
TCE degradation rate, ki
cDCE degradation rate, k2
VC degradation rate, k3
TCE degradation rate, kiSA
cDCE degradation rate, k2
VC degradation rate, k3SA
UNITS
m/day
m2/g
g/cm3
d-1
d-1
d-1
L hr"1 m"2
L hr'1 in2
L hr'1 in2
100PL
84.7
0.43
0.81
2.72
9.62
3.40
10.61
7.82 xlO"5
2.76xlO'5
8.63X10'5
100MB
74.3
0.45
1.1
3.09
16.27
5.83
6.31
8.98 xlO"5
3.22xlO"5
3.48xlO'5
fc SA: Surface area normalized reaction rate constants
31
-------
Table 13. Hydraulic Conductivity Values Used in Ground-water Flow Simulations to Compare Relative Capture Areas and Residence Times
of Two Barrier Designs
SIMULATION
1
2
'l
j
4
5
VAQUIFER
cm/day
0.09
4.17
14.5
22.6
40.3
KAQUIFER
m/day
0.1
4.8
16.7
26.0
46.4
Pea gravel: porosity 0.35; hydraulic conductivity 864 m/day
Granular iron: porosity 0.38; hydraulic conductivity 46.4 m/day
Table 14.
Capture Areas for the Funnel-and-Gate Under Varying Aquifer Hydraulic Conductivity Conditions
Simulation
1
2
3
4
5
Kirnn
^-aquifer
464
10
3
2
1
Capture
Area
(m2)
85
83
79
70
67
Capture Area
(% of total
FUNNEL-AND-
GATE area)
59%
58%
55%
49%
47%
Area of Groundwater
directed to GATE (%
of FUNNEL area)
45%
44%
41%
35%
34%
Capture Area
(relative to
GATE area)
2.6 x
2.5 x
2.4 x
2.1 x
2.0 x
Total FUNNEL-AND-GATE™ area: 143 m2
Area of each (6.1 m wide by 9.1 m deep) FUNNEL: 55.2 m2
Area of (3.6m wide by 9.1 m deep by 2m thick) GATE: 32.76m2
Table 15.
Capture Areas for the Continuous Wall Configuration Under Varying Aquifer Hydraulic Conductivity Conditions
Simulation
1
2
3
4
5
-"-jmn
f^aauifer
464
10
3
2
1
Capture Area
(m2)
89
87
84
82
78
Capture Area (% of
total WALL area)
1 14%
111%
108%
105%
100%
Capture Area
(relative to WALL area)
1.1 x
1.1 x
1.1 x
1.1 x
1.0 x
Total area of (10.3 m wide by 7.6 m deep by 0.45 m thick) WALL: 78 m2
32
-------
Table 16.
Ground-water Velocities and Residence Times within the Reactive Material Zones of the Funnel-and-Gate and the continuous Wall
SIMULATION
1
2
3
4
5
Funnel-and-Gate™
Velocity
(m/day)
2.02 x 10~3
1.03 x 10"1
3.24 x 10"1
4.76 x 10"1
7.52 x 10"1
Velocity
relative to
aquifer
2.6
2.5
2.2
2.1
1.9
Residence
Time
(days)
525
10.29
3.27
2.23
1.41
Wall
Velocity
(m/day)
9.18 xlO"4
4.74 x 10"'
1.57 xlO"1
2.38 x 10"1
4.03 x 10"1
Velocity
relative to
aquifer
1.2
1.1
1.1
1.1
1.0
Residence
Time
(days)
495
9.59
2.90
1.91
1.13
Table 17. Hydraulic Parameters (Source of Values Indicated in Brackets) Used in Ground-water Flow Modelling to Determine Minimum
Barrier Dimensions
PARAMETER
Aquifer hydraulic conductivity
(Field estimates)
Aquifer porosity (Estimated)
Granular iron hydraulic
Conductivity (Lab estimates)
Granular iron porosity
(Lab estimates)
Horizontal hydraulic gradient
(Field estimates)
RANGE
OBSERVED
0.1 to 26 m/day
7.7 to 84.7 m/day
0.29 to 0.45
0.0011 to 0.0033
SIMULATION
1
17 m/day
0.38
43.0 m/day
0.40
0.0033
SIMULATION
2
17 m/day
0.38
84.7 m/day
0.43
0.0033
Table 18. Reactive-transport Parameters, Source Concentrations, and Minimum Distance Within Reactive Barrier Before Contaminant Falls
Below MCL
COMPOUND
TCE
cDCE
VC
MODEL PARAMETERS
Diffusion coefficient, D0 (cm2/s)
Rate Constant, k (day"1)
Transfer coefficient (%)
Source Concentration (ng/L)
10.1 x 10"6
9.62
7%
10,000
11.4 x 10"6
3.40
100%
900
13.3 x 10"6
10.61
N/A
101
MINIMUM DISTANCE WITHIN BARRIER
Simulation 1
Simulation 2
24 cm
23 cm
21 cm
20 cm
33 cm
32 cm
33
-------
Table 19. Barrier Installation Project Costs in U.S. Dollars (USCG, Pers. Comm.)
DESCRIPTION
COST
Preliminary work
Barrier Design
Barrier Construction
Post Installation work
Reports
Site Assessment
RFI Workplan
RFI Implementation
Model
Bench Test
Pilot Study
Design
Granular iron
Trenching Installation
Setup/cleanup
CAMU
RFI Report
CMS/Interim Report
Baseline Report
TOTAL
$60,000
$40,000
$ 50,000
$10,000
$25,000
$75,000
$35,000
$200,000
$150,000
$150,000
$40,000
$60,000
$50,000
$40,000
$985,000
34
-------
FIGURES
35
-------
Figure 1.
0 2 4
Approximate Scale (km)
Location map showing U.S. Coast Guard Support Center, Elizabeth City, North Carolina.
Pasquotank River
g MW39
MW38 <0-01
-------
E3T8
CPT27
1T1
B River sample
Q Temporary well
® Cone penetrometer
location
© Deep well (40-50 ft b.g.s.)
©
MW22
ill
MW21 A
©
. ,
N
4,°
Approx. Scale (ft)
HANGAR 79
j Plating
| Shop
Figure 3. Plan view map showing approximate locations of temporary wells, cone penetrometer tests, river sampling, and deep wells (after
Parsons Engineering Science, 1994).
(a) B
West
East
B'
5 .
10.
15.
20.
25.
30.
35.
BQL
K>l7'~, 1.00 —
0.05--.
0.011
7
1.26 •}
0.124 y
0 40
1 1
Approximate Scale (ft)
(b)
A
North
A'
CPT11 CPU 2
CPU 4 CPU 5 CPU 6
~"
OJS4
1.28 i — N
3.65 — V
0.815 „-•"
?''
1.22 °-^_
3.09
0.521
0.099 _ _
3.18
0.591
"^•0.05-
.--0.05 ---
0.795
1.97
0.0408
0.0923
--? ^
0.622 VK_
3.5~
b"b3~09"
0.0682
?-
.Q.QD4J I
"2^2 I
<0.'T3- ~ ^ I
0.269 ~ i
TOOT 1
O Groundwater flow direction
25
Approximate Scale (ft)
Figure 4. (a) Cross-section B-B', and (b) cross-section A-A' indicating total chromium concentrations (mg/L), and inferred 0.05 mg/L and 1 .00
mg/L contours in June 1994.
37
-------
ML11
0
<£ 2J
I 4
Q)
Q 6^
8
0
0
0
Figure 5. Cr concentration profiles (mg/L) at multilevel samplers in the approximate locations of piezometer bundles ML11, ML21, and ML31,
upgradient of proposed Reactive Barrier (April 1996).
\ \ ? ,
\ \ / i 175'0e'a MW35D
\ \ / i © u 0.0
\ \ / | MW33 ••
\ \ / i \\
\
00
O
z
Q
5
QQ
\
| MW20
\\
'v \
"Q\
\ \ \ MW27 /
\ \ © \ 13.0 / '62b"o
Q\ \ MW39 \ « /
wsa \ 440-° \ /
°'° \ \ Xx/ MW31 — "
* \ 5°°^ MW£ \
> SB '
fa MW16D
^T? 4300.0
\ CTi
© ._
MW/MW1J/ £
.•••
MW-13
TCE (jag/L)
June 1994
N
t
HANGAR 79
| Plating
| Shop I
0 10 20
meters
® Monitoring Well screened 10-15 ft b.g.s.
® Monitoring Well screened 15-20 ft b.g.s.
© Monitoring Well screened 20-25 ft b.g.s.
© Monitoring Well screened 40-50 ft b.g.s.
Not all wells are shown.
Figure 6.
Plan view map showing TCE concentrations (|ig/L), and inferred 5 and 100 |ig/L contours.
38
-------
(a) D West •« * East D
n CPT27 CPT22 CPT16 CPT30
_ 5 .
OJ
£ 1°-
3
T3 15
I! ™
O
Bi
£ 20.
o
£
£ 25.
O.
Q
•
35.
_?
f ? '*
r
BQL ^ ^. o
7.2
_?
~~x
100-s. N
V \
1500
« , —
?
-"""" ?
1 362 ?
1 4.91
115.9
o „ — — — — — ?
s* ' ~
-,. c _^' 0 40
,-— 5 1 1
. X Approximate Scale (ft)
BQL
(b) A -+ North A'
n CPT1 1 CPT1 2 CPT1 7 CPT1 3 CPT1 4 CPT1 5 CPT1 6
5 .
g
-------
q>
.Q
Q.
0)
Q
B1
Building 78
N
t
B1 ...
T
BUILDING 79
LITHOLOGY
Fine Sandy Silty Clay
Fine Sand
Silty Clayey Fine Sand
Figure 9. Cross-sections extrapolated from borehole log data.
A
North
CPT11
CPT12
CPT17
CPT13
CPT14
A1
CPT15 CPT16
Depth below groundsurface (ft)
oo oo isj isj — » — » en
en o en o en o
1 1 1 1 1 1 1 1
*•-
f
,
c\.
f
~~~j:^_
7
>
ayey fine sand
? - -
—
r
wmii
=
— -I
-
Clayey f
Fine Sand
^^^^
ne
ffi
wit
2
_
sand to Clay
---? '-*-.-.
i varying amo
1
£3
jnt
_J^>-Slltyline sand
-a-
s of silt and clay
O
7 X>~~"E
— -,
^2
ni
- O
±^
^—,
=
^
1
^
— '
i
Organic Matter
Fine Sand
Silty fine sand
Silty to clayey fine sand
Cemented sand to HardPan
Clayey fine sand
Sandy clay
Silty clay
Clay
0
25
Approximate Scale (ft)
!=!> Groundwater flow direction
Figure 10. Geologic cross-section A-A' extrapolated from cone penetrometer test data.
40
-------
u wesi •" •• tasi u
n CPT27 CPT22 CPT16 CPT30
5 _
Depth below groundsurface (ft
00 00 N> N> — » — »
en o en o en o
Clay
7 r-_-
r '— **•
—*
— i
— —
— *
•— j
^^*
^_
•
Fine Sand
Silty fine sand
Silty to clayey fi
Clayey fine san
Sandy clay
Silty clay
Clay
Cemented san
—
ZZ
1
ne
d
dt
'-, 7
--"^^ "~~"V
Clayey fine sand -•''
\ f
Fine Sand with varying amounts
of silt and clay
sand
0
.
. •
• .•
•
• .•
—
~^r
^•^
—
— ^
F^1^
r
0
7 -,-_-_-_-----------
40
1
Approximate Scale (ft)
o HardPan
zi
—
—
E
1
Figure 11. Geologic cross-section B-B' extrapolated from cone penetrometer test data.
September 1991
April 1992
Site map
October 1993
October 1994
Groundwater flow
direction
Extrapolated Water
level contour
' Water level contour
0 10 20
meters
Figure 12. Water levels in wells screened 3 to 4.5 m below ground surface (ft.a.s.l.).
41
-------
I 15.
o
D)
g 20.
_g
0)
.Q
25.
Q.
0)
30.
35.
Building
79
North
Pasquotank
River
25
i
Clayey fine sand to clay
| | Fine sand with varying amounts of silt and clay
<^ Groundwater flow direction
Approximate Scale (ft)
g
0)
0 .
5 .
10.
15.
D)
g 20.
o
25,
30,
35J
Building
79
I
» + North
Pasquotank
River v
Aqueous TCE plumes
25
•' •
U1
Clayey fine sand to clay
Fine sand with varying amounts of silt and clay
Approximate Scale (ft)
<^> Groundwater flow direction
Figure 13. Diagram of conceptual model Cr(VI) and TCE plume development.
42
-------
xc=c\
cr XH
TCE
(a)
4
Cl—C^C—H
Chloroacetylene
H—
Acetylene
Ethene
H\
H—C
(b)
H
C— H
Ethane
Figure 14. (a) Reductive p-elimination, and (b) hydrogenolysis reaction steps in degradation of TCE (after Arnold and Roberts, 1997).
43
-------
PLEXIGLASS
COLUMN
9-
EFFLUENT
SAMPLES
SAMPL1NG
h- PORTS
SOLUTION
RESERVOIR
INFLUENT
SAMPLING
PORT
TEFLON'
BAG
Q
PUMP
Figure 15. Schematic of the apparatus used in the column experiments.
44
-------
Sheet piling
NORTH
'$a Gravel
filings
dravel
Model domain bisects
the reactive barrier.
Y-axis parallels the
groundwater flow
direction.
Figure 16. Model domain dimensions, with Funnel-and-Gate barrier shown (all dimensions in m).
3D PERSPECTIVE VIEW
PLAN VIEW
No flow
Boundary
L,
Constant Head
h=0 = 18.0594m
Constant Head
h=60 = 18 m
Symmetry No flow
Boundary Boundary
qn = o qn = o
FRONT VIEW
No flow Boundary
No flow Boundary
Symmetry
Boundary
Figure 17. Model boundary conditions, with Funnel-and-Gate barrier shown.
45
-------
Impermeable Funnels
A
B
0.45
2 m thick Gate zone:
1.1 m thick iron-filings
zone, surrounded by two
0.45 m thick Pea gravel
zones.
Total Volume of iron-
filings: 35 m3
Total Volume of iron-
filings: 35 m3
Figure 18. (A) Funnel-and-Gate, and (B) permeable wall configurations used in flow simulations [all dimensions in meters].
46
-------
o>
LU
O
2500
2000
1500
1000 -
500 -
Input
0
••••v
0 50 100 150 200 250 300 350
2000
o>
0 50 100 150 200 250 300
Time (h)
-•- MBSS --v AdaSS -•- PLSS -O-- MBAQ
Figure 19. TCE concentration versus time in each of the four batch test mixtures.
350
47
-------
I
Q.
// ,,v-
__ __.. O
-v
10 15 20 25
10
15
20 25
o>
O
CO
80
60
40
20
0
0
10
15
20 25
10 15
l"\me (h)
20
25
20 25
MBSS -v- AdaSS -»-- PLSS
Figure 20. Batch test inorganic geochemistry for all mixtures, versus time.
MBAQ
48
-------
12
8 -
o>
E
_
O
4 -
0
0.0
0.5
1.0
Time (h)
1.5
2.0
MBSS •••V-- AdaSS
PLSS
MBAQ
Figure 21. Cr(VI) concentration vs. time in each of the four batch test mixtures.
49
-------
10 15 20 25
0 5 10 15 20 25
0 5 10 15 20 25
0 5 10 15 20 25
-•— MBSS -v- AdaSS —•— PLSS
Figure 22. Mineral saturation indices for batch tests, calculated with MINTEQA2.
MBAQ
50
-------
10
Trichloroethene (TCE)
FV = 61 cm/day 2 ft/day
20 30
Distance Along Column ( cm )
40
50
-B- 50MBSS —I— 50MBSSAQ -0- 50PLSSAQ -&- 100MB -X- 100PL -0- 48PL/52AQ
Figure 23. TCE concentration versus distance along all six columns at the first flow velocity (FV1), approximately 61 cm/day (2 ft/day).
25
20
Chloroform (TCM)
15
.o
"ro
o
O
10 -
5 -
FV = 61 cm/day (2 ft/day)
10
20 30
Distance Along Column ( cm )
40
50
- 50MBSS —I—50MBSSAQ -0-50PLSSAQ -A- 100MB -X- 100PL -0-48PL/52AQ
Figure 24. TCM concentration versus distance along all six columns at the first flow velocity (FV1), approximately 61 cm/day (2 ft/day).
51
-------
cis 1,2-Dichloroethene (cDCE)
250
FV = 61 cm/day 2 ft/day
10
20 30
Distance Along Column ( cm )
40
50
• 50MBSS
• 50MBSSAQ
• 50PLSSAQ
100MB-X-100PL
-48PL/52AQ
Figure 25. cDCE concentration versus distance along all six columns at the first flow velocity (FV1), approximately 61 cm/day (2 ft/day).
50
Vinyl Chloride (VC)
FV = 61 cm/day 2 ft/day
10
20 30
Distance Along Column ( cm )
40
50
-B- 50MBSS -I— 50MBSSAQ -0- 50PLSSAQ -&- 100MB -X- 100PL -0- 48PL/52AQ
Figure 26. VC concentration versus distance along all six columns at the first flow velocity (FV1), approximately 61 cm/day (2 ft/day).
52
-------
2000
Trichloroethene (TCE)
FV = 30.5 cm/day 1 ft/day
10
20 30
Distance Along Column ( cm )
40
50
Figure 27.
-B- 100MB —I— 100PL -0- 50PLSSAQ
TCE concentration versus distance along three columns at the second flow velocity (FV2), approximately 30 cm/day (1 ft/day).
Chloroform (TCM)
FV = 30.5 cm/day (1 ft/day)
10
20 30
Distance Along Column ( cm )
40
50
100MB
100PL
• 50PLSSAQ
Figure 28. TCM concentration versus distance along three columns at the second flow velocity (FV2), approximately 30 cm/day (1 ft/day).
53
-------
Cis 1,2-Dichloroethene(cDCE)
FV = 30.5 cm/day (1 ft/day)
10
20 30
Distance Along Column ( cm )
40
50
-B- 100MB —I— 100PL -0- 50PLSSAQ
Figure 29. cDCE concentration versus distance along three columns at the second flow velocity (FV2), approximately 30 cm/day (1 ft/day).
Vinyl Chloride (VC )
FV = 30.5 cm/day (1 ft/day)
0 10 20 30 40 50
Distance Along Column ( cm )
-B- 100MB —I— 100PL -0- 50PLSSAQ
Figure 30. VC concentration versus distance along three columns at the second flow velocity (FV2), approximately 30 cm/day (1 ft/day).
54
-------
50% MB Fe + 25% EC aquifer material + 25% sand
12
Q 4--
o -t-ae-
-B—B-
-B B-
150
10 20 30 40
-B
50
10 20 30 40
50
10 20 30 40
50
10 20 30 40
Distance (cm)
50
28 PV
48 PV
9PV
Figure 31. Inorganic results for column 50MBSSAQ at FV1.
55
-------
50% MB Fe + 50% sand
O 40
o 4
LU
-300 --
-600
150
El B El
10
10
10
20
20
20
-H-
30
30
30
-H-
40
40
40
10 20 30 40
Distance (cm)
28 PV
34 PV
54 PV
Figure 32. Inorganic results for column 50MBSS at FV1.
50
50
50
50
56
-------
O 4 --
X
CL
600
LU
100%MBFe
10
10
20
20
30
30
40
40
50
50
0 10 20 30 40
Distance (cm)
- FV1 24 PV -&- FV1 29 PV -©- FV2 47 PV
- FV2 79 PV -6- FV2 98 PV
50
Figure 33. Inorganic results for column 100MB at FV1 and FV2.
57
-------
600
LU
150
100% Peerless Fe
10
10
20
20
30
30
-B- FV1 26 PV -&- FV1 35 PV
-X-FV2 100 PV -0-FV2 115 PV
Figure 34. Inorganic results for column 100PL at FV1 and FV2.
40
40
10 20 30 40
Distance (cm)
50
50
50
- FV2 58 PV
58
-------
50% Peerless Fe + 25% EC aquifer material + 25% sand
600
LJJ
-300 - -
-600
150
a H
10
10
10
20
20
30
30
40
40
-Bl EB B
20 30 40 50
50
50
0 10 20 30 40
Distance (cm)
- FV1 30 PV -A- FV2 66 PV -O- FV1 5 PV
-FV2 117 PV -0-FV2 135 PV
50
Figure 35. Inorganic results for column 50PLSSAQ at FV1 and FV2.
59
-------
48% Peerless Fe + 52% EC aquifer material
12
X
CL
150
m D m
10
10
10
20
20
20
-H-
-H-
30 40
30 40
30
40
10 20 30 40
Distance (cm)
-B-55PV
Figure 36. Inorganic results for column 48PL/52AQ at FV1.
-ffi
50
50
50
50
60
-------
8
6 -
CD
E
O 4
i_
O
O
2 -
0
0
<^ 100MB
V 100PL
-•- 50PLSSAQ
-+-• 48PL/52AQ
*-r-
20
40
60 80
Pore Volumes
100 120 140
Figure 37. Cr detection at the 2.5 cm sample port.
61
-------
0 10 20 30 40 50
0 10 20 30 40 50
CO
0 10 20 30 40 50
CO
o
C/D
CD
-^
'i_
Q)
^
C/l
C/J
O
CO
I
g^
L_
O
c/i
10
Q)
-—
Q)
O
c/
-5
-10
0 10 20 30 40 50
Distance (cm)
-•— 8.6 PV •••v 27.7 PV
Figure 38. Mineral saturation indices for column 50MBSSAQ at FV1.
0 10 20 30 40 50
0 10 20 30 40 50
0 10 20 30 40 50
0 10 20 30 40 50
Distance (cm)
•— 48.1 PV
62
-------
I
Q.
10 20 30 40 50
Q)
10 20 30 40
Q)
0
-2
7'V.
Q)
CO
O
2
0
-2
-4
-6
-*-
-10
0 10 20 30 40 50
10 20 30 40
0 10 20 30 40
CD
O
O
C/D
4
2 -I
0
-2
0 10 20 30 40 50
Distance (cm)
-O- 27.9 PV •••V- 34.4 PV
Figure 39. Mineral saturation indices for column 50MBSS at FV1.
10 20 30 40
Distance (cm)
50
53.5 PV
63
-------
I
Q.
O
Q
0 10 20 30 40 50
0 10 20 30 40 50
0 10 20 30 40 50
Distance (cm)
-•— 24 PV • • -V • • 29.2 PV —•-
CO
O
tt)
0
-2
-4
-6
-8
-10
0
10 20 30 40
50
CD
-^
'i_
Q)
^
C/l
C/J
_
O
c/i
-—
Q)
O
c/
10 20 30 40
Distance (cm)
50
46.6 PV
79.2 PV
98 PV
Figure 40. Mineral saturation indices for column 100MB at FV1 and FV2.
64
-------
I
Q.
O
Q
C/D
CO
I
g^
i_
o
0 10 20 30 40 50
0 10 20 30 40 50
Distance (cm)
-•- 26 PV • • v • • 35 PV -•-
Q)
CO
O
10 20 30 40 50
CD
^
C/l
C/J
0 10 20 30 40 50
o
CO
__
o
c/i
0 10 20 30 40 50
Q)
Q)
o
O
C/D
10
5
0
-5
-10
\
V"
0 10 20 30 40 50
Distance (cm)
58 PV
100.5 PV-
114.7 PV
Figure 41. Mineral saturation indices for column 100PL at FV1 and FV2.
65
-------
0 10 20 30 40
Q)
-^
E
C3
O
Q
0 10 20 30 40 50
CO
CO
_
o
c/i
0 10 20 30 40 50
CD
Q)
10 20 30 40
Distance (cm)
•— 5.2 PV •••V-- 30.3 PV
50
Q)
CO
O
Q)
^
C/D
C/J
O
CO
__
o
c/i
Q)
Q)
O
O
C/D
6
3
0
-6
-9
.--V-
=*
0 10 20 30 40 50
0 10 20 30 40 50
0 10 20 30 40 50
10 20 30 40 50
Distance (cm)
66.2 PV -O-- 116.8 PV-
135.3PV
Figure 42. Mineral saturation indices for column 50PLSSAQ at FV1 and FV2.
66
-------
E -2t>
o -4
Q
H ~6
-8
-10
0
Q)
S 6
.
b 4
Q)
10
20
30
40
10 20 30 40
Distance (cm)
50
10 20 30 40
CO
O
tt)
£.
'
-2
-4
-6
•
•in .
• A A • ^ '
1 — • • ^ • 1
/"~
Q)
Q)
O
O
6
4
2
10
20
30
40
10 20 30 40
10 20 30 40
Distance (cm)
50
50
50
Figure 43. Mineral saturation indices for column 48PL/52AQ at 78.4 PV and FV1.
67
-------
O)
c
o
?
(0
•*-•
c
0)
o
c
o
o
10
20 30 40
Distance (cm)
50
60
100% Peerless
100% Master
Builders
100% Peerless
(calculated)
•100%
MasterBuilders
(calculated)
Figure 44. Experimental and calculated TCE concentration profiles in column.
200
0 10 20 30 40
Distance (cm)
50
60
n 100%
Peerless
• 100% Master
Builders
100%
Peerless
(calculated)
•100% Master
Builders
(calculated)
Figure 45. Experimental and calculated cDCE concentration profiles in column.
68
-------
100%
Peerless
100% Master
Builders
100%
Peerless
(calculated)
100% Master
Builders
(calculated)
0 10 20 30 40
Distance (cm)
50
60
Figure 46. Experimental and calculated VC concentration profiles in column.
69
-------
A
Groundwater
Flow Pathline
B
Groundwater flow is diverted both through and
around the Gate by the Impermeable Funnels.
Groundwater within the Capture Area flows
through the Gate zone.
Figure 47. (A) Groundwater flow divergence in vicinity of a Funnel-and-Gate, and (B) Capture area.
70
-------
Funnels
Figure 48. Vertical groundwater flow divergence around a Funnel-and-Gate.
FunneL Gate
Groundwater
Flow Pathlines
Figure 49. Horizontal groundwater flow divergence around a Funnel-and-Gate.
71
-------
FLOW DIRECTION
Groundwater
Flow Pathlines
Figure 50. Groundwater flow divergence around a continuous wall.
C
_g
'^—>
CD
^—>
c
CU
o
c
O
o
LU
O
Distance within iron-filings wall (cm)
1000
900
50
I
C
.0
'*—>
2
4—1
c
Q)
O
c
O
O
o
TD
c
CD
i_u
O
Q
O
Figure 51. Predicted TCE, cDCE, and VC concentration profiles through the iron-filings wall.
72
-------
(A)
A'-i
A—1
PLAN VIEW
HANGAR 79
squoranK mver
46 m
A
0.6 m
IRON FILINGS BARRIER
Length = 46 m
Width = 0.6 m
Depth = 2-7.3 m
GROUNDWATER
FLOW DIRECTION
Cr(VI) SOURCE ZONE
(B)
A
A1
7.
\
^fffffff^fffff^\ *—
te^^®^^^/ *-
3 m
5.
/ \
5 m
"^~~~~ Iron F
CR
0.2 m Asphalt pavement
0.6 m Coarse aggregate
0.6 - 1.2 m Excavated
natural soils
CROSS-SECTION A-A1
(Not-to-Scale)
0.6 m
Figure 52. (a) Plan view, and (b) cross-sectional view of reactive barrier.
73
-------
Figure 53. Peerless™ iron filings stored on site.
Figure 54. Plastic sheets laid down around trench for erosion control.
74
-------
Figure 55. Trenching machine used to install the 7.3 m deep, 0.6 m wide granular iron barrier.
Figure 56. Excavated aquifer sediments on either side of the trench.
75
-------
.'"•"- ->' - *,
•"*
-
''^ipAi **
Figure 57. Picture showing collapse of concrete pavement on either side of the trench.
76
-------
LIST OF APPENDICES
Appendix A: Grain size distribution curves
Appendix B: Elemental and TCLP analyses
Appendix C: Bromide tracer test data (lab columns)
Appendix D: Batch test inorganic data
Appendix E: Batch test mineral saturation indices
Appendix F: Reactive column organic data
Appendix G: Reactive column inorganic data
Appendix H: Reactive column mineral saturation indices
Appendix I: Analytical laboratory procedures
77
-------
This page intentionally left "BLANK."
78
-------
Appendix A: Grain size distribution curves
Grain Size Distribution Curves
Silica Sand (SS)
EC Aquifer (AQ)
MB Iron
PL Iron
Grain Diameter (mm)
79
-------
Appendix B: Elemental and TCLP analyses
Element
Al
B
Ba
Be
Cd
Ca
Cr
Co
Cu
Fe
Pb
Mg
Mn
V
Zn
Ni
P
Ag
Sr
Na
Mo
Ti
Zr
S
C
Si
Master (MB)
GX-27
wt%
0.0036
0.2910
0.0001
0.0001
0.0000
1.0043
0.1970
0.0058
0.2850
88.2000
0.0044
0.0030
0.5060
0.0159
0.0064
0.0577
0.0737
0.0004
0.0000
0.0000
0.0152
0.0149
0.0022
0.1400
2.4717
1.7400
Peerless (PL)
wt%
0.0019
0.1420
0.0002
<
<
<
0.1700
<
0.2500
82.7000
<
0.0013
0.5570
<
0.0073
0.0700
0.0750
<
<
<
0.0210
0.0156
<
0.1100
3.2440
2.3400
MDL
wt%
0.00050
0.00025
0.00005
0.00005
0.00010
0.00025
0.00010
0.00045
0.00010
0.00025
0.00100
0.00005
0.00005
0.00010
0.00005
0.00030
0.00160
0.00010
0.00005
0.01000
0.00020
0.00005
0.00010
0.01000
0.00100
0.01000
Total %
95.0384
89.7052
< = less than MDL
%Wt = ((mg/Kg)/1000000) *100
80
-------
Appendix B: Elemental and TCLP analyses
Toxicity Characteristic Leaching Procedure (TCLP)
Client ID MasterBuilder
***Volatiles*** (mg/L)
Benzene
Carbon Tetrachloride
Chlorobenzene
Chloroform
Methyl Ethyl Ketone
Tetrachloroethylene
Trichloroethylene
VinylChloride
1,2-Dichloroethane
1,1-Dichlorethylene
<0.05
<0.05
<0.05
<0.05
<0.10
<0.05
<0.05
<0.10
<0.05
<0.05
Peerless
<0.05
<0.05
<0.05
<0.05
<0.10
<0.05
<0.05
<0.10
<0.05
<0.05
Leach Blank
<0.05
<0.05
<0.05
<0.05
<0.10
<0.05
<0.05
<0.10
<0.05
<0.05
Leach Blank
Regulatory
0.05
1.0
100
6.0
200
0.7
0.5
0.2
0.5
0.7
***Semi-Volatiles*** (mg/L)
1 ,4-Dichlorobenzene
Hexachloroethane
Nitrobenzene
Hexachlorbutadiene
2,4,6-Trichlorophenol
2,4,5-Trichlorophenol
2,4-Dinitrotoluene
Hexachlorobenzene
Pentachlorophenol
Total Cresols
Pyridine
***Pesticides*** (mg/L)
Chlordane
Endrin
Heptachlor
Heptachlor Epoxide
Lindane
Methoxychlor
Toxaphene
***Metals***(mg/L)
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Selenium
Silver
Thallium
Zinc
<0.04
<0.04
<0.04
<0.04
<0.04
<0.08
<0.04
<0.04
<0.20
<0.12
<0.04
<0.01
<0.001
<0.0005
<0.0005
<0.005
<0.005
<0.025
<0.100
<0.200
1.07
<0.025
<0.025
<0.100
<0.025
<0.100
<0.0002
<0.040
<0.200
<0.025
<0.100
0.084
<0.04
<0.04
<0.04
<0.04
<0.04
<0.08
<0.04
<0.04
<0.20
<0.12
<0.04
<0.01
<0.001
O.0005
<0.0005
<0.005
<0.005
<0.025
<0.100
<0.200
0.431
<0.025
<0.025
<0.100
0.038
<0.100
<0.0002
<0.040
<0.200
<0.025
<0.100
0.153
<0.04
<0.04
<0.04
<0.04
<0.04
<0.08
<0.04
<0.04
<0.20
<0.12
<0.04
<0.01
<0.001
<0.0005
<0.0005
<0.005
<0.005
<0.025
<0.100
<0.200
0.281
<0.025
<0.025
<0.100
<0.025
<0.100
<0.0002
<0.040
<0.200
<0.025
NA
0.063
7.5
3.0
2.0
0.5
2.0
400
0.13
0.13
100
200
5.0
0.03
0.02
0.008
0.008
0.4
10.0
0.5
POL
0.10
0.20
0.20
0.025
0.025
0.10
0.025
0.10
0.0002
0.04
0.20
0.025
0.10
0.05
81
-------
Appendix C: Bromide tracer test data (lab columns)
TABLE H-1. Bromide concentrations (mg/L) during tracer tests.
COLUMN 101
COLUMN 102
COLUMN 110
| Date analyzed
S.N. 1234
10 0
20 0.38
30 0
40 1.28
44 12
46 25.9
48 41.6
50 56.6 L.F.(0.15)
55 75
60 85.7
66 88.1
68 110
70 83.8 98.2
73 104
75 89.3
76 104
77 104
80 98.2
90 98.2
93 107
97 112
98 111 LF.(0.12)
103 102
770 702 New Pump
120 99.5 New Pump
130 99.7 New Pump
140 93.7 New Pump
Date analyzed
S.N. 1234
10 0.4
20 0.48
30 0.35
40 0.58
45 8.63
50 30.2
53 46.3
55 57.2
57 63.5
60 75.4
64 H.F.(0.24) 75.4
68 L.F.(0.13) 75.5
69 80.6
70 78.4
72 82.2
75 94.7
78 82.4
79 106
80 110
82 91.8
85 91.9
90 99
100 98.8
110 103
115 91.1
120 110 97
130 96.8
139 100
140 119
150 101
160 102
(Date analyzed
S.N. 1 2 3
10 0.37
20 0.53
25 0.36
30 11.5 0.4
33 0.41
35 1.67
37 7.45
40 33.7
42 55.1
44 72.7
46 79.7
48 83.3
50 87.1
60 89.1
70 92.5
80 92.8
90 92
100 91.6
Column
101
102
110
Stock solution concentration |ig/L 104,100
Average flow rate mL/min 0.19
Composition 100% MB
(MB: Master Builders, PL: Peerless; AQ: Aquifer sediments)
104, 100
0.16
1 00% PL
93.8
0.17
52% PL/48% AQ
COMMENTS
S.N. indicates Sample Number (samples were taken every 30 minutes)
L.F. indicates Low Flow rate H.F. indicates High Flow rate
Column 101: Low flow in S.N. 98, Pump stops and is replaced, New pumping rate slightly lower
Column 102: No Flow in Samples 65, 66, 67
Date Analyzed: (1)10/26/95; (2)11/17/95; (3)12/8/95; (4)1/17/96
82
-------
Appendix C: Bromide tracer test data (lab columns)
Bromide tracer results Fmai Results(APni 1996)
COLUMN 101 Tracer Data
-1 0 _-mmm^^
0 8
o
O 06
0
0 4
0 2
0 A
0
«
/"*"'
J
/
/ ^ Measured
fr |
20 40 60
TIME (hrs)
COLUMN
100
on
o. 70
£.
"~" 60
0
O
o
0 20
10
n A
110 Tracer experiment data
* «> x
x^ <> — z — " — * —
f
/
f
j n
l| ^ Measured
/
^k A A4^
0 10 20 30 40 50
Time (hrs)
COLUMN 102 Tracer experiment
-ton ^
100 -
Q.
Q- 80
c
o
•^ en
"c
o 40 -
c
0
0 20-
n
,. ^^1
4
y
/
/
JL
4
£
K%
*
•
• M(
*
(TFIT
jasured
0 10 20 30 40 50 60
Time (hrs)
COLUMN MATERIAL
101 100% Master Builders (100 MB)
102 100% Peerless (100 PL)
110 48% Peerless/ (48 PL52AQ)
52% Aquifer material
Master Builders™ and Peerless™ are Iron
RESULTS
column
101
102
110
CASE1
V D
[cm/hr] [cm]
1.98 1.03
1.81 1.51
2.41 0.51
fixed R(R=1)
CASE 2
D R
[cm]
1.15 1.11
1.66 1.09
0.58 1.13
using lab velocity
Calculated (see (1) below)
porosity Pore vol.
[calc] [mL]
0.51 288
0.47 264
0.37 211
calc. from CXTFIT Velocity
Measured results
V
[cm/hr]
2.20
1.97
2.73
porosity Pore vol.
[lab] [mL]
0.45 254
0.43 245
0.33 189
from effluent flux
CASE 1: Finding unknowns (velocity, V, and dispersivity, D) assuming a known retardation of R=1.
CASE 2: Finding unknowns (dispersivity, D, and retardation, R) using lab. measured velocities
(1): Calculated porosity, and pore volume from CASE 1 velocity and lab. measured effluent flux.
83
-------
Concentrations in mg/L analysed at U.W. Water Quality Lab
Time (h) pH Eh (mV) CaCO3
Al
As Ba Ca Cd Co Cr Cr(VI) Cu Fe K Mg Mn Mo
Na
Ni
Pb
Si
Sr Zn
Cl SO4
00
Composition:
0
0
0.25
0.5
1.5
3
6
24.12
5.96
5.92
6.15
6.47
7.11
7.5
7.52
7.4
Composition:
0
0.25
0.5
0.75
1.5
5.72
23.85
5.96
5.99
6.09
6.12
6.33
6.71
7.04
Composition:
0
0.1
0.75
3
23.92
5.92
5.95
6.44
7.29
7.45
Composition:
0
0
0.1
0.1
0.27
0.42
0.75
3
6
24
24
6
6.03
6.14
6.14
6.26
6.3
6.46
6.83
7.48
7.87
7.87
MB+SS
368
551
459
188
34
-92
29
-378
Ada+SS
352
554
116
315
204
55
34
PL+SS
552
458
159
-266
-161
MB+AQ
611
630
563
563
608
418
184
62
23
-47
-47
23.7
43.4
51.7
92.6
138.4
140.5
137.8
100.2
51.8
36.0
47.0
53.1
80.0
125.2
134.3
39.1
42.4
94.7
155.5
117.4
45.9
25.0
49.7
49.7
62.3
67.0
79.2
123.8
124.5
121.3
121.3
0.12
0.03
0.16
0.16
0.15
0.19
0.18
0.08
0.14
0.13
0.12
0.14
0.17
0.14
0.21
0.12
0.12
0.14
0.07
0.15
0.11
0.06
0.13
0.11
0.09
0.05
0.06
0.17
0.09
0.13
0.11
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
<0.5
0.09
0.09
0.07
0.07
0.07
0.08
0.09
0.08
0.08
0.07
0.06
0.06
0.06
0.06
0.07
0.08
0.08
0.10
0.08
0.08
0.08
0.08
0.10
0.10
0.09
0.09
0.08
0.07
0.06
0.04
0.04
27.7
27.1
32.7
33.3
35.4
36.6
38.4
38.3
26.9
29.7
28.9
28.6
29.5
29.7
30.6
28.0
29.6
30.0
29.9
29.5
28.0
28.0
30.6
30.5
30.7
32.8
33.3
36.3
38.6
42.2
41.8
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
0.027
0.03
0.03
0.04
0.05
0.06
0.05
0.06
0.07
0.07
0.06
0.05
0.06
0.08
0.12
0.03
0.03
0.08
0.13
0.08
<0.1
<0 1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
11.69
11.45
2.81
0.02
0.01
0.01
0.00
0.01
11.45
7.47
3.37
0.71
0.02
0.00
0.00
11.99
4.92
0.02
0.00
0.00
11.79
11.82
7.17
7.11
3.88
0.46
0.02
0.00
0.00
0.00
0.008
11.6
11.4
2.6
0
0
0
0
0
11.3
7.2
3.3
0.6
0
0
0
12.1
4.9
0
0
0
11.6
11.7
7.4
7.2
3.9
0.4
0
0
0
0
0
0.00
0.01
0.01
0.01
0.01
0.01
0.02
0.02
0.00
0.00
0.02
0.01
0.01
0.00
0.01
0.02
0.02
0.01
0.00
0.00
0.01
0.02
0.02
0.02
0.01
0.01
0.00
0.01
0.01
0.01
0.00
<0.05
<0.05
<0.05
15.39
42.43
42.31
35.55
6.39
<0.05
<0.05
<0.05
0.09
15.52
42.70
42.14
<0.05
0.13
31.43
63.84
34.55
<0.05
<0.05
<0.05
<0.05
<0.05
0.05
6.90
20.98
16.20
1.21
1.20
<0.2
20.1
<0.2
<0.2
15.76
4.38
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
8.991
10.39
15.04
10.74
10.28
<10
11.92
11.56
11.96
12.5
12.97
17.6
17.3
18.0
17.9
18.3
18.4
18.4
17.6
17.3
18.2
17.9
17.6
18.3
17.9
18.5
18.0
18.5
18.7
18.7
18.3
17.3
17.4
16.7
16.7
16.5
17.0
16.9
17.7
17.7
18.4
18.2
0.94
0.91
1.17
1.71
2.51
2.98
2.88
2.01
0.92
1.04
1.11
1.21
1.76
2.33
2.76
0.96
1.22
2.39
3.67
3.66
0.96
0.96
1.05
1.03
1.20
1.48
2.02
2.98
2.88
1.59
1.58
0.01
0.00
0.01
<0.01
<0.01
<0.01
<0.01
0.00
0.01
0.02
0.01
0.04
0.05
0.16
0.24
<0.01
<0.01
<0.01
<0.01
<0.01
0.04
0.03
0.05
0.04
0.00
0.02
0.01
0.03
<0.01
0.02
0.05
96.3
94.4
98.8
97.6
99.5
100.4
100.5
97.6
93.9
98.2
96.9
95.6
98.4
97.0
101.1
101.6
104.2
106.9
107.4
106.3
101.1
101.1
100.7
103.7
105.9
112.3
112.6
112.5
113.7
115.0
114.4
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
0.03
0.13
0.25
0.34
0.66
1.27
0.56
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
0.01
<0.01
0.02
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
0.01
<0.01
0.05
<0.01
<0.01
0.02
<0.01
-0.03
0.00
0.00
0.02
0.06
<0.01
<0.01
<0.01
<0.01
<0.01
0.03
0.02
0.13
0.22
0.08
0.08
0.16
0.25
0.26
0.31
0.25
0.32
0.21
5.92
5.84
5.51
5.33
5.12
4.49
3.93
1.00
5.77
5.61
5.28
4.95
4.80
4.01
2.35
6.14
5.98
6.10
5.76
1.88
6.13
6.14
5.86
5.79
5.69
5.64
5.47
4.40
3.66
1.51
1.52
0.48
0.48
0.47
0.47
0.48
0.49
0.51
0.49
0.47
0.47
0.44
0.44
0.45
0.44
0.47
0.49
0.48
0.48
0.48
0.48
0.49
0.49
0.46
0.45
0.45
0.47
0.47
0.49
0.49
0.50
0.49
0.10
0.10
0.03
0.01
0.01
0.00
0.00
0.00
0.09
0.07
0.04
0.01
0.01
0.00
0.00
0.10
0.05
0.01
0.02
0.00
0.17
0.16
0.11
0.11
0.05
0.02
0.01
0.00
0.02
0.00
0.00
123
126
107
107
106
107
112
110
122
125
106
118
101
115
130
130
129
128
130
131
126
124
125
125
119
120
122
122
125
121
121
89.7
88.3
84
88.2
94.3
93.1
85.1 ^
91.5 -Q
(D
90.1 3
93.4 Q;
92.3 X"
89.4 _
87.6 Sr
84.4 —
99.9 X"
O
88.6 3"
96.5 r+
95.6 52
91.6 I-K
90.3 —
3
O
95.1 0)
97.5 3
97.5 o"
89.7 —
93.7 pj
91.2 I-K
90.1 ™
87.5
76.5
76.5
-------
Elizabeth City batch experiments
Saturation indices calculated by MINTEQA2
Based on UW Water Quality Lab data
Composition: MB+SS
Time (h) Ferrihydrite
Goethite Cr(OH)3 (a) Cr(OH)3 (c) Calcite Dolomite Siderite (d) Amakinite Aragonite Rhodochrosite Quartz SiO2
oo
en
0
0
0.25
0.5
1.5
3
6
24.1
Composition:
0
0.25
0.5
0.75
1.5
5.7
23.85
Composition:
0
0.1
0.75
3
23.9
Composition:
0
0
0.1
0.1
0.27
0.42
0.75
3
6
24
24
-0.844
0.087
0.960
0.794
0.477
-0.527
1.537
-8.610
Ada+SS
-1.110
0.153
-4.742
-0.279
0.660
-0.344
0.265
PL+SS
0.087
1.138
0.509
-4.154
-1.934
MB+AQ
0.164
0.191
0.289
0.289
0.395
1.049
0.35
-0.176
0.979
-0.197
-0.201
4.866
5.797
6.670
6.504
6.187
5.183
7.247
-2.899
4.600
5.863
0.968
5.431
6.370
5.366
5.975
5.797
6.848
6.219
1.556
3.776
5.874
5.901
5.999
5.999
6.105
6.759
6.06
5.534
6.689
5.513
5.509
-0.521
-0.867
2.397
0.566
0.920
0.816
-0.219
0.644
-0.521
2.608
2.398
1.760
0.417
-0.210
-0.444
-0.578
2.37
0.657
-0.006
0.535
-0.468
-0.428
2.783
2.78
2.03
1.789
0.525
-0.591
0.467
-0.135
0.979
-3.060
-3.407
-0.143
-1.973
-1.619
-1.724
-2.759
-1.896
-3.061
0.069
-0.142
-0.780
-2.122
-2.750
-2.984
-3.117
-0.169
-1.882
-2.545
-2.004
-3.007
-2.968
0.244
0.24
-0.509
-0.75
-2.015
-3.13
-2.073
-2.675
-1.561
-2.690
-2.479
-2.090
-1.526
-0.714
-0.307
-0.268
-0.459
-2.366
-2.453
-2.246
-2.169
-1.779
-1.225
-0.861
-2.511
-2.426
-1.608
-0.52
-0.52
-2.363
-2.597
-2.155
-2.157
-1.934
-1.837
-1.604
-1.018
-0.341
0.085
0.082
-5.280
-4.856
-4.143
-3.025
-1.417
-0.615
-0.558
-0.957
-4.626
-4.821
-4.404
-4.252
-3.468
-2.371
-1.644
-4.916
-4.759
-3.125
-0.946
-0.951
-4.637
-5.103
-4.276
-4.278
-3.84
-3.663
-3.205
-2.05
-0.723
0.108
0.099
-4.396
-6.263
-4.197
-0.106
1.099
1.479
1.421
-1.616
-4.048
-6.471
-3.932
-2.893
-0.298
0.677
1.015
-6.326
-3.687
0.167
1.308
1.283
-7.352
-7.975
-6.650
-6.650
-7.458
-3.593
-0.527
0.486
1.011
0.249
0.246
-8.384
-10.554
-8.332
-4.166
-2.480
-1.712
-1.745
-4.786
-8.377
-10.610
-8.087
-7.070
-4.435
-3.262
-2.622
-10.571
-7.937
-3.924
-2.143
-1.884
-11.587
-11.915
-10.778
-10.778
-11.564
-7.689
-4.532
-3.334
-2.160
-2.524
-2.844
-2.633
-2.245
-1.680
-0.868
-0.461
-0.422
-0.613
-2.520
-2.607
-2.401
-2.323
-1.933
-1.379
-1.015
-2.665
-2.580
-1.763
-0.674
-0.675
-2.517
-2.751
-2.310
-2.311
-2.089
-1.991
-1.758
-1.172
-0.495
-0.069
-0.073
-2.370
-2.170
-1.757
-1.053
-0.133
0.302
0.303
-0.021
-2.051
-2.122
-1.880
-1.763
-1.234
-0.581
-0.171
-2.191
-2.027
-0.944
0.268
0.289
-2.046
-2.271
-1.839
-1.847
-1.566
-1.409
-1.053
-0.358
0.239
0.306
0.304
0.379
0.374
0.347
0.333
0.316
0.260
0.199
-0.395
0.368
0.357
0.328
0.301
0.288
0.210
-0.021
0.396
0.383
0.391
0.367
-0.119
0.396
0.396
0.374
0.370
0.361
0.359
0.345
0.249
0.169
-0.214
-0.214
-0.603
-0.607
-0.634
-0.648
-0.665
-0.722
-0.782
-1.376
-0.614
-0.625
-0.653
-0.680
-0.693
-0.771
-1.002
-0.586
-0.598
-0.590
-0.614
-1.100
-0.586
-0.586
-0.607
-0.611
-0.620
-0.622
-0.636
-0.732
-0.812
-1.195
-1.195
^
^^J
^^J
(D
3
Q.
x"
m
• •
UJ
Q)
o"
3"
^D
CO
3
5"
(D
3
(0
Q)
C*
3
I-K
o'
3
5'
Q.
o'
(D
(0
These calculations assume that the t=0 Cr composition is dominantly Cr(VI) and that the Cr(lll)
concentration (0.01 mg/L) is one half the analytical detection limit.
Notes: (c) = crystalline (a) = amorphous (d) = disordered, or freshly precipitated
-------
Appendix F: Reactive column organic data
REACTIVE COLUMN
99
50MBSSAQ
Column Composition:
Pore Volume (PV):
Porosity:
Flow Velocity 1 (FV1):
Residence Time (FV1):
50 % Granular Iron - MasterBuilder
25 % Elizabeth City Aquifer Material
25 % Silica Sand
201 ml
0.35
2.2 ft/day (68 cm/day)
17.7hr
Distance Along Column (ft)
TCE
FV1
PCE
FV1
TCM
FV1
cDCE
FV1
PV
6.8
12.4
20.3
30.2
38.2
45.3
6.8
12.4
20.3
30.2
38.2
45.3
6.8
12.4
20.3
30.2
38.2
45.3
8.1
16.2
18.9
25.9
39.5
47.7
RN
a
a
b
b
b
c
a
a
b
b
b
c
a
a
b
b
b
c
a
b
b
b
c
c
0.00
Influent
1553
1464
1588
1795
1393
1580
1.6
1.8
2.4
2.3
2.8
1.7
25
21
22
26
18
18
61
58
69
55
50
70
0.08
0.16
0.33
0.50
Organic Concentration
888
992
1104
1160
1048
1090
0.9
nd
3.1
4.3
4.3
4.2
13
15
16
17
14
11
167
113
122
68
79
80
136
256
383
673
446
460
nd
nd
2.0
4.1
3.7
3.6
4.1
6.5
6.4
11
8.1
6.0
221
208
136
101
103
112
14
14
10
46
35
11
nd
nd
nd
2.8
2.9
1.7
0.2
0.4
2.4
4.2
2.9
2.6
204
198
222
155
145
137
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
0.4
nd
1.0
14
104
173
134
132
162
0.66
(Mfl/L)
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
83
99
155
112
189
1.00
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
8.2
64
103
124
1.31
nd
nd
nd
nd
nd
nd
0.3
8.6
nd
2.9
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
4.7
50
90
1.64
Effluent
nd
nd
nd
nd
nd
nd
2.2
2.4
3.0
4.4
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
41
70
nd = not detected
RN = reservoir number
86
-------
Appendix F: Reactive column organic data
REACTIVE COLUMN
99
50MBSSAQ
Column Composition:
Pore Volume (PV):
Porosity:
Flow Velocity 1 (FV1):
Residence Time (FV1):
50 % Granular Iron - MasterBuilder
25 % Elizabeth City Aquifer Material
25 % Silica Sand
201 ml
0.35
2.2 ft/day (68 cm/day)
17.7 hr
Distance Along Column (ft)
tDCE
FV1
VC
FV1
PH
FV1
Eh
FV1
PV
8.1
16.2
18.9
25.9
39.5
47.7
8.1
16.2
18.9
25.9
39.5
47.7
RN
a
b
b
b
c
c
a
b
b
b
c
c
0.00
Influent
1.2
2.1
1.9
nd
1.7
1.2
17
41
39
38
28
43
0.08
0.16
0.33
0.50
0.66
1.00
1.31
Organic Concentration ( ng/L)
0.2
1.8
1.5
nd
1.7
0.8
15
36
34
32
24
32
nd
1.1
0.9
nd
nd
nd
15
34
31
26
25
43
nd
nd
nd
nd
nd
nd
13
40
31
29
22
50
nd
nd
nd
nd
nd
nd
13
27
31
24
24
39
nd
nd
nd
nd
nd
nd
12
29
28
26
19
34
nd
nd
nd
nd
nd
nd
3.0
19
22
20
12
25
nd
nd
nd
nd
nd
nd
0.3
11
10
17
7.4
19
1.64
Effluent
nd
nd
nd
nd
nd
nd
nd
4.5
7.3
nd
9.2
16
pH Along Column
1.2
10.8
17.6
37.1
39.8
1.2
10.8
17.6
37.1
39.8
a
a
b
b
c
a
a
b
b
c
6.9
7.8
6.5
7.0
6.3
Redox Potential
386
350
369
275
354
8.0
8.6
7.4
8.9
7.2
Along
-47
-168
-144
218
-203
9.0
8.3
8.1
9.1
9.0
9.1
9.3
8.9
9.4
9.3
9.2
9.3
9.2
9.3
9.3
9.2
9.4
9.2
9.2
9.2
9.0
9.4
9.2
9.3
9.3
8.8
9.4
9.2
9.0
9.2
9.0
9.5
9.0
9.3
9.3
Column ( mV )
-139
-191
-16
317
-217
-157
-231
-132
-26
-256
-168
-218
-149
-44
-217
-205
-229
-126
-63
-140
-278
-260
-216
-67
-275
-269
-281
-150
61
-242
-38
274
-157
294
-42
nd = not detected
RN = reservoir number
87
-------
Appendix F: Reactive column organic data
REACTIVE COLUMN
100
50MBSS
PV
TCE
FV1
PCE
FV1
TCM
FV1
cDCE
FV1
4.2
10.7
18.3
26.4
33.9
42.9
4.2
10.7
18.3
26.4
33.9
42.9
4.2
10.7
18.3
26.4
33.9
42.9
7.2
12.8
19.4
27.5
38.4
RN
a
a
a
b
b
b
a
a
a
b
b
b
a
a
a
b
b
b
a
a
a
b
b
0.00
Influent
1584
1671
1538
1830
1621
1825
2.2
1.6
1.8
2.7
1.6
1.6
20
20
23
23
22
19
62
60
61
46
51
Column Composition:
Pore Volume (PV):
Porosity:
Flow Velocity I (FV1):
Residence Time (FV1):
Distance Along Column ( ft )
0.08
0.16
0.33
0.50
50 % Granular Iron - MasterBuilder
50 % Silica Sand
233 ml
0.41
1.8 ft/day (55 cm/day)
21.6hr
0.66
1.00
1.31
Organic Concentration ( ng/L)
835
899
1185
846
1246
1250
11.0
6.3
11.0
2.9
2.3
3.5
11
12
15
8.0
15
16
96
80
37
69
51
328
538
798
634
943
835
0.9
0.6
0.9
nd
1.0
1.5
8.0
11
13
6.0
8.5
7.8
209
108
154
96
95
13
85
172
197
260
204
nd
nd
0.3
nd
nd
nd
1.7
5.9
5.9
3.5
4.0
4.1
251
173
170
136
140
0.7
4.4
8.2
31
30
16
nd
nd
nd
nd
nd
nd
0.4
1.8
2.8
3.5
2.6
1.8
167
205
204
146
152
nd
1.0
nd
nd
2.3
nd
nd
nd
nd
nd
nd
nd
nd
0.5
1.2
1.8
nd
nd
134
163
187
156
152
35
14
18
15
13
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
8.2
119
204
127
183
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
69
168
98
132
1.64
Effluent
7.9
7.6
5.6
nd
1.9
nd
nd
0.4
nd
nd
nd
nd
0.4
nd
nd
nd
nd
nd
nd
12
137
62
122
nd = not detected
RN = reservoir number
88
-------
Appendix F: Reactive column organic data
REACTIVE COLUMN
100
50MBSS
tDCE
FV1
VC
FV1
PV
7.2
12.8
19.4
27.5
38.4
49.8
7.2
12.8
19.4
27.5
38.4
49.8
0.00
0.08
RN Influent
a
a
a
b
b
c
a
a
a
b
b
c
2.0
2.0
0.9
1.7
nd
1.3
32
37
15
37
40
35
1.0
1.1
1.1
1.5
nd
1.9
22
20
20
27
26
28
Column Composition:
Pore Volume (PV):
Porosity:
Flow Velocity I (FV1):
Residence Time (FV1):
Distance Along Column ( ft )
0.16
0.33
0.50
50 % Granular Iron - MasterBuilder
50 % Silica Sand
233 ml
0.41
1.8 ft/day (55 cm/day)
21.6hr
0.66
1.00
1.31
Organic Concentration ( ng/L)
1.0
1.0
0.9
1.4
nd
0.4
29
32
17
28
28
14
nd
0.4
0.4
0.7
nd
0.4
30
28
17
27
27
28
nd
nd
nd
0.2
nd
nd
25
29
19
31
28
29
nd
nd
nd
0.1
nd
nd
24
24
18
32
24
30
nd
nd
nd
nd
nd
nd
20
23
16
28
24
21
nd
nd
nd
nd
nd
nd
16
22
17
27
21
20
1.64
Effluent
nd
nd
nd
nd
nd
nd
12
26
16
20
21
20
pH Along Column
PH
FV1
Eh
FV1
5.1
13.8
21.8
29.8
44.0
5.1
13.8
21.8
29.8
44.0
a
a
a
b
b
a
a
a
b
b
6.5
6.6
7.3
6.5
7.0
Redox Potential
344
371
354
360
360
7.8
7.9
9.0
7.5
8.8
Along
-77
-120
9
31
159
8.4
8.7
9.2
7.8
9.1
Column ( mV )
-218
-121
65
-9
85
9.0
9.2
9.4
8.7
9.2
-204
-175
-187
-207
129
9.1
9.3
9.3
8.9
9.3
-221
-152
-265
-200
-7
9.0
9.3
9.4
9.0
9.2
-223
-206
-250
-239
-103
8.5
9.4
9.4
9.2
9.2
-197
-228
-201
-309
-201
8.6
9.4
9.4
9.2
9.2
-171
-310
-244
-279
-175
9.3
9.3
9.5
9.3
9.3
82
28
229
-181
156
nd = not detected
RN = reservoir number
89
-------
Appendix F: Reactive column organic data
REACTIVE COLUMN
101
100MB
TCE
FV1
FV2
PCE
FV1
FV2
nd =
RN =
PV
4.3
10.2
16.6
22.9
29.1
35.1
51.7
57.9
61.4
64.9
68.2
71.4
74.7
77.4
80.3
84.5
4.3
10.2
16.6
22.9
29.1
31.5
51.7
57.9
61.4
64.9
68.2
71.4
74.7
77.4
80.3
84.5
not detected
RN
a
a
a
b
b
b
c
d
d
d
d
d
d
e
e
e
a
a
a
b
b
b
c
d
d
d
d
d
d
e
e
e
0.00
Influent
1697
1634
1541
1691
1596
1825
1288
1462
1295
1214
1227
1069
861
1734
1436
1309
1.6
1.6
1.8
2.7
1.6
2.1
2.8
2.2
1.4
1.3
1.4
1.3
1.1
1.5
1.2
1.0
Column Composition: 100 % Granular Iron
Master Builders
Pore Volume (PV): 254 ml
Porosity: 0.45
Flow Velocity 1 (FV1): 1 .4 ft/day (43 cm/day)
Residence Time (FV1): 27.7 hr
Flow Velocity 2 (FV2): 0.8 ft/day (24 cm/day)
Residence Time (FV2): 50 hr
Distance Along Column (ft)
0.08
0.16
0.33
0.50
0.66
1.00
1.31
Organic Concentration ( ng/L)
1.2
177
378
649
602
857
713
848
386
975
1018
1016
791
1184
1203
1116
nd
0.4
0.7
nd
0.6
1.1
nd
0.7
nd
1.2
1.4
1.4
1.2
1.0
1.3
1.0
nd
2.6
48
6.8
16
78
95
212
265
465
691
746
674
890
1019
904
nd
2.0
1.5
11.5
7.7
1.0
nd
0.5
nd
nd
1.4
1.3
1.2
1.0
1.7
nd
nd
8.5
3.7
5.9
2.9
nd
1.4
nd
nd
nd
1.2
2.4
1.0
0.8
6.2
46
nd
2.4
1.9
5.3
0.4
nd
nd
nd
nd
nd
0.1
nd
0.5
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
1.64
Effluent
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
reservoir number
90
-------
Appendix F: Reactive column organic data
REACTIVE COLUMN
101
100MB
Column Composition:
Pore Volume (PV):
Porosity:
Flow Velocity 1 (FV1):
Residence Time (FV1):
Flow Velocity 2 (FV2):
Residence Time (FV2):
100 % Granular Iron
Master Builders
254 ml
0.45
1.4 ft/day (43 cm/day)
27.7 hr
0.8 ft/day (24 cm/day)
50 hr
Distance Along Column (ft)
TCM
FV1
FV2
cDCE
FV1
FV2
PV
4.3
10.2
16.6
22.9
29.1
35.1
51.7
57.9
61.4
64.9
68.2
71.4
74.7
77.4
80.4
84.5
7.1
12.1
17.4
23.7
32.4
39.0
53.7
55.1
58.8
62.3
65.7
69.0
72.0
75.7
78.7
RN
a
a
a
b
b
b
c
d
d
d
d
d
d
e
e
e
a
a
a
b
b
c
c
c
d
d
d
d
d
d
e
0.00
Influent
20
23
22
22
20
19
20
23
24
19
22
22
19
28
23
23
62
68
68
59
51
51
58
56
67
48
61
39
46
76
65
0.08
0.16
0.33
0.50
0.66
1.00
1.31
Organic Concentration ( |ig/L)
1.7
7.0
8.0
11.0
7.4
9.3
9.4
11
5.7
15
18
20
16
17
19
19
243
216
204
127
112
118
53
62
73
57
56
81
43
61
63
0.2
nd
0.8
1.9
1.9
3.3
3.3
4.6
4.4
6.4
9.2
11
12
6.9
12
12
209
242
256
156
228
182
130
118
118
145
129
47
56
74
59
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
1.0
1.3
1.8
2.8
nd
2.4
111
107
183
139
130
101
84
140
142
73
83
144
101
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
37
81
100
88
73
78
67
57
49
53
81
59
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
22
60
53
45
53
43
51
34
30
53
35
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
3
nd
3.5
5.8
7.8
6.4
5.1
5.6
7.4
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
1.64
Effluent
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
91
-------
Appendix F: Reactive column organic data
REACTIVE COLUMN
101
100MB
Column Composition:
Pore Volume (PV):
Porosity:
Flow Velocity 1 (FV1):
Residence Time (FV1):
Flow Velocity 2 (FV2):
Residence Time (FV2):
100 % Granular Iron
Master Builders
254 ml
0.45
1.4 ft/day (43 cm/day)
27.7 hr
0.8 ft/day (24 cm/day)
50 hr
Distance Along Column (ft)
tDCE
FV1
FV2
VC
FV1
FV2
PV
7.1
12.1
17.4
23.7
32.4
39.0
53.7
55.1
58.8
62.3
65.7
69.0
72.0
75.7
78.7
81.8
85.5
7.1
12.1
17.4
23.7
32.4
39.0
53.7
55.1
58.8
62.3
65.7
69.0
72.0
78.7
81.8
85.5
RN
a
a
a
b
b
c
c
c
d
d
d
d
d
d
e
e
e
a
a
a
b
b
c
c
c
d
d
d
d
d
e
e
e
0.00
Influent
2.0
2.0
1.1
1.9
nd
1.3
nd
0.6
1.4
0.8
1.4
3.9
2.8
1.8
5.7
1.0
1.3
34
37
15
38
40
38
17
15
33
28
26
10
6.9
12
9
11
0.08
0.16
0.33
0.50
0.66
1.00
1.31
Organic Concentration ( |ig/L)
nd
0.6
0.5
0.9
nd
0.6
nd
0.2
1.0
0.5
0.7
13.0
2.5
1.2
1.8
0.4
0.8
29
26
12
30
26
22
12
13
22
11
21
10
8.3
5.1
5.3
10
nd
nd
nd
nd
nd
nd
nd
nd
0.1
0.4
0.9
1.6
1.4
0.7
0.8
0.5
0.7
26
29
12
26
28
27
12
12
22
19
26
3.3
3.8
5.8
5.9
8.3
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
0.3
12
25
13
25
32
24
15
14
18
16
15
5.5
6.6
5.3
7.3
7.4
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
7.5
15
9.1
20
22
20
10
8.2
12
7.8
7.9
3.7
3.6
2.8
6.1
3.7
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
2.1
10
5.2
12
14
14
3.4
5.8
8.1
7.2
6.5
2.1
2.0
1.3
2.5
1.3
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
1.8
1.9
4.1
4.6
3.3
1.4
0.6
0.5
1.0
0.7
0.3
nd
0.1
0.1
0.1
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
0.2
0.7
0.9
0.7
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
1.64
Effluent
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
2.9
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
92
-------
Appendix F: Reactive column organic data
REACTIVE COLUMN
101
100MB
Column Composition:
Pore Volume (PV):
Porosity:
Flow Velocity 1 (FV1):
Residence Time (FV1):
Flow Velocity 2 (FV2):
Residence Time (FV2):
100 % Granular Iron
Master Builders
254 ml
0.45
1.4 ft/day (43 cm/day)
27.7 hr
0.8 ft/day (24 cm/day)
50 hr
Distance Along Column (ft)
PV
RN
0.00
Influent
0.08
0.16
0.33
0.50
0.66
1.00
1.31
Organic Concentration ( |ig/L)
1.64
Effluent
pH Along Column
pH
FV1
FV2
Eh
FV1
FV2
5.2
12.9
19.5
25.4
36.1
54.2
57.2
60.9
64.4
68.6
71.0
74.3
77.8
80.8
85.1
5.2
12.9
19.5
25.4
36.1
54.2
57.2
60.9
68.6
71.0
74.3
77.8
80.8
85.1
a
a
a
b
b
c
d
d
d
d
d
d
e
e
e
a
a
a
b
b
c
d
d
d
d
d
e
e
e
7.2
6.6
7.3
6.2
7.1
7.8
6.8
6.7
6.7
7.2
7.7
8.3
6.3
6.7
7.3
Redox Potential
351
386
332
336
366
278
315
309
286
284
272
291
289
245
8.7
9.0
9.0
8.0
9.0
9.3
9.1
8.8
8.2
9.2
9.3
9.4
7.8
8.1
8.9
Along
-213
-206
-159
-327
198
309
202
186
174
194
184
129
260
1
9.0
9.3
9.4
9.1
9.2
9.3
9.4
9.1
8.5
9.3
9.4
9.4
9.1
8.6
8.9
Column (
-289
-196
-268
-287
137
296
135
133
147
-97
164
-27
170
72
9.2
9.5
9.6
9.2
9.2
9.4
9.7
9.3
9.1
9.5
9.6
9.6
9.3
9.4
9.5
mV)
-256
-205
-329
-345
-168
-31
-7
-208
-137
-302
-195
-72
-100
-153
9.2
9.6
9.6
9.4
9.2
9.3
9.8
9.4
9.0
9.5
9.6
9.4
9.5
9.3
9.5
-297
-269
-437
-221
-347
-92
-14
-272
-174
-204
-108
-215
-145
-229
9.1
9.5
9.7
9.5
9.4
9.4
9.7
9.4
9.2
9.6
9.6
9.6
9.5
9.5
9.5
-274
-293
-380
-272
-265
-123
-129
-181
-257
-241
-145
-306
-232
-315
8.9
9.6
9.6
9.5
9.5
9.4
9.8
9.5
9.2
9.6
9.7
9.6
9.6
9.5
9.6
-222
-296
-432
-307
-349
-31
-37
-311
-347
-204
-282
-312
-199
-328
8.3
9.6
9.4
9.5
9.6
9.5
9.8
9.5
9.3
9.7
9.7
9.5
9.5
9.5
9.5
-197
-290
-447
-375
-254
-94
-107
-367
-290
-270
-196
-349
-209
-311
8.3
9.5
9.3
9.5
9.6
9.6
9.6
9.1
9.4
9.7
9.7
9.6
9.2
9.5
9.6
127
112
-443
-11
126
293
256
263
205
265
241
240
73
258
nd = not detected
RN = reservoir number
93
-------
Appendix F: Reactive column organic data
REACTIVE COLUMN
102
100PL
TCE
FV1
FV2
PCE
FV1
FV2
PV
4.0
10.3
16.9
24.5
32.6
41.0
65.2
72.2
77.8
81.9
85.8
91.2
95.2
98.7
102.
107.
4.0
10.3
16.9
24.5
32.6
41.0
65.2
72.2
77.8
81.9
85.8
91.2
95.2
98.7
102.
107.
0.00
Column Composition: 100 % Granular Iron
Peerless (-8 to 50 mesh)
Pore Volume (PV): 245 ml
Porosity: 0.43
Flow Velocity 1 (FV1): 1 .8 ft/day ( 53 cm/day )
Residence Time (FV1): 22.5 hr
Flow Velocity 2 (FV2): 1 .0 ft/day ( 31 cm/day )
Residence Time (FV2): 39 hr
Distance Along Column (ft)
0.08
RN Influent
a
a
a
b
b
b
c
d
d
d
d
d
d
e
5 e
1 e
a
a
a
b
b
b
c
d
d
d
d
d
d
e
5 e
1 e
1697
1750
1533
1830
1691
1825
1288
1462
1442
1214
1227
1069
815
1734
1436
1385
1.6
3.7
3.7
2.7
1.7
1.6
2.8
2.2
1.3
1.3
1.4
1.3
1.0
1.5
1.2
1.1
245
471
1159
1256
1263
1031
652
623
223
1010
1038
1035
639
837
1000
941
0.6
0.5
1.6
nd
1.2
1.0
nd
1.2
nd
2.6
6.7
1.9
1.0
1.1
1.4
1.0
0.16
0.33
0.50
0.66
1.00
1.31
Organic Concentration ( ng/L)
53
190
473
931
1020
897
894
861
971
1041
975
1016
821
1026
1002
1025
0.2
2.1
1.7
nd
1.0
0.8
nd
1.9
0.9
1.9
1.7
1.7
1.6
1.5
1.6
1.5
nd
24
15
123
153
306
303
287
270
559
745
718
730
836
739
781
nd
nd
0.3
nd
nd
nd
nd
1.2
nd
1.3
1.6
1.8
2.0
1.6
1.9
1.8
nd
15
5.1
13
5.3
7.9
18
6.7
6.6
9.2
22
56
76
97
95
147
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
12
3.5
4.4
1.0
0.8
2.4
2.2
nd
nd
1.1
0.7
1.2
1.2
1.7
2.4
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
1.64
Effluent
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd = not detected
RN = reservoir number
94
-------
Appendix F: Reactive column organic data
REACTIVE COLUMN
102
100PL
Column Composition:
Pore Volume (PV):
Porosity:
Flow Velocity 1 (FV1):
Residence Time (FV1):
Flow Velocity 2 (FV2):
Residence Time (FV2):
100 % Granular Iron
Peerless (-8 to 50 mesh)
245 ml
0.43
1 .8 ft/day ( 53 cm/day )
22.5 hr
1.0 ft/day (31 cm/day)
39 hr
Distance Along Column (ft)
TCM
FV1
FV2
cDCE
FV1
FV2
PV
4.0
10.3
16.9
24.5
32.6
41.0
65.2
72.2
77.8
81.9
85.8
91.2
95.2
98.7
102.5
107.1
7.1
12.2
17.9
25.7
36.6
47.9
67.5
69.1
73.3
79.0
82.8
88.3
92.3
96.5
100.3
104.2
RN
a
a
a
b
b
b
c
d
d
d
d
d
d
e
e
e
a
a
a
b
b
c
c
c
d
d
d
d
d
d
e
e
0.00
Influent
20
25
21
23
23
18
20
23
22
21
22
25
18
28
23
22
67
56
66
62
51
51
53
56
73
52
57
39
49
59
65
89
0.08
0.16
0.33
0.50
0.66
1.00
1.31
Organic Concentration ( |ig/L)
2.1
5.0
12
12
8.9
8.8
6.6
4.8
2.6
13
17
19
12
6.1
11
14
167
108
93
60
54
58
46
62
55
52
57
45
43
81
59
56
0.2
2.0
4.6
6.7
5.0
5.6
6.8
5.6
8.9
14
12
15
12
8.8
10
13
181
130
148
78
96
84
48
53
67
67
78
20
46
68
59
70
nd
0.3
0.7
2.0
1.2
2.2
2.7
2.5
2.3
3.5
6.1
6.0
6.5
5.6
4.9
5.7
94
108
136
98
107
94
59
78
84
109
93
51
53
97
71
100
nd
7.0
0.3
0.4
nd
nd
0.4
0.6
0.4
0.8
1.2
1.8
2.1
2.4
2.2
2.1
38
71
96
76
75
73
35
34
56
52
67
54
62
101
65
92
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
0.6
0.9
0.6
0.5
8.4
38
58
38
52
47
18
17
30
25
24
21
25
57
42
45
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
6.9
14
15
22
22
5.1
nd
5.3
7.6
0.9
2.7
3.6
8.7
5.4
5.5
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
3.8
8.7
12
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
1.64
Effluent
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
1.8
7.1
2.7
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
95
-------
Appendix F: Reactive column organic data
REACTIVE COLUMN
105
50PLSSAQ
Column Composition:
Pore Volume (PV):
Porosity:
Flow Velocity 1 (FV1):
Residence Time (FV1):
Flow Velocity 2 (FV2):
Residence Time (FV2):
50 % Granular Iron - Peerless
25 % Elizabeth City Aquifer Material
25 % Silica Sand
166 ml
0.29
2.6 ft/day (79 cm/day)
15.3hr
1.2 ft/day (36 cm/day)
34 hr
Distance Along Column (ft)
TCE
FV1
FV2
PCE
FV1
FV2
PV
3.5
9.5
21.9
33.8
42.0
51.4
76.0
84.3
89.6
94.4
99.4
104.3
109.5
113.8
119.0
124.5
3.5
9.5
21.9
33.8
42.0
51.4
RN
a
b
b
b
b
c
c
d
d
d
d
d
d
e
e
e
76.0 c
84.3 d
89.6 d
94.4 d
99.4 d
104.3 d
109.5 d
113.8 e
119.0 e
124.5 e
nd = not detected
RN = reservoir number
0.00
Influent
1553
1560
1724
1795
1524
1580
1288
1462
1246
1214
1227
1069
905
1734
1436
1282
1.6
4.2
6.4
4.5
6.7
2.1
2.8
2.2
1.3
1.3
1.4
1.3
1.2
1.5
2.0
2.3
0.08
0.16
0.33
0.50
0.66
1.00
1.31
Organic Concentration ( |ig/L)
1141
1205
1200
1216
1220
1123
838
1134
683
1242
1022
1056
912
1231
1177
1245
7.3
3.0
3.0
6.4
12
2.1
2.2
2.2
1.5
1.7
1.9
1.6
1.4
1.5
1.5
1.6
676
716
812
680
981
696
403
936
648
1020
916
1056
896
1112
1134
1144
1.2
nd
3.9
4.9
5.1
1.4
1.3
2.1
1.2
1.6
1.7
2.6
2.5
1.7
2.0
2.2
167
225
289
241
473
278
45
168
133
328
435
525
591
706
608
688
0.6
1.2
nd
nd
1.5
nd
nd
1.0
nd
1.1
1.1
1.3
1.4
nd
1.9
1.4
19
39
51
44
136
93
21
24
14
26
63
145
211
256
272
270
0.8
nd
nd
nd
0.8
nd
nd
nd
nd
nd
0.4
0.9
1.1
nd
nd
nd
5.4
12
12
13
14
22
nd
4.1
3.0
3.8
5.1
2.8
16
20
27
34
0.8
nd
nd
nd
0.8
nd
nd
nd
nd
nd
0.3
0.3
nd
nd
nd
nd
2.4
4.9
nd
nd
nd
nd
nd
1.6
nd
nd
1.2
0.9
nd
1.2
1.2
nd
1.6
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
9.2
7.9
nd
nd
nd
nd
nd
1.6
nd
nd
nd
nd
nd
1.2
1.5
nd
1.0
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
1.64
Effluent
4.3
7.1
nd
nd
nd
nd
nd
3.0
nd
nd
nd
nd
nd
2.8
nd
nd
19
21
14
11
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
96
-------
Appendix F: Reactive column organic data
REACTIVE COLUMN
105
50PLSSAQ
Column Composition:
Pore Volume (PV):
Porosity:
Flow Velocity 1 (FV1):
Residence Time (FV1):
Flow Velocity 2 (FV2):
Residence Time (FV2):
50 % Granular Iron - Peerless
25 % Elizabeth City Aquifer Material
25 % Silica Sand
166 ml
0.29
2.6 ft/day (79 cm/day)
15.3hr
1.2 ft/day (36 cm/day)
34 hr
Distance Along Column (ft)
TCM
FV1
FV2
cDCE
FV1
FV2
PV
3.5
9.5
21.9
33.8
42.0
51.4
76.0
84.3
89.6
94.4
99.4
104.3
109.5
113.8
119.0
124.5
4.6
16.3
20.2
28.5
43.6
54.4
78.3
80.1
85.7
90.8
95.5
100.8
105.7
110.9
116.0
120.7
RN
a
b
b
b
b
c
c
d
d
d
d
d
d
e
e
e
0.00
Influent
20
23
23
26
22
18
20
23
18
19
22
20
21
28
23
22
61
58
54
49
50
65
51
56
67
49
51
39
37
66
65
74
0.08
0.16
0.33
0.50
0.66
1.00
1.31
Organic Concentration ( |ig/L)
10
12
9.3
10
10
5.5
5.2
10
4.7
13
13
18
16
15
13
16
86
54
67
47
46
50
55
47
56
57
52
32
34
77
59
62
4.8
7.3
4.7
4.3
5.4
3.2
1.3
3.4
1.9
4.6
4.7
7.4
7.9
4.3
3.3
8.5
138
72
99
59
58
65
44
67
51
52
45
34
37
64
56
60
1.3
2.1
1.9
2.4
2.5
1.8
0.4
1.1
0.6
1.7
1.7
2.6
3.2
1.5
1.3
1.4
137
93
99
86
58
80
42
67
62
40
57
47
59
90
71
69
0.3
0.4
nd
0.8
0.6
0.9
nd
0.5
nd
0.8
0.7
1.3
1.7
1.2
0.8
0.7
110
94
81
51
54
60
47
51
46
31
57
51
71
88
50
83
nd
nd
nd
1.0
nd
nd
nd
nd
nd
nd
nd
nd
0.6
0.8
0.6
0.3
104
60
38
34
36
50
34
22
31
12
32
28
59
105
43
68
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
0.6
0.2
nd
39
29
30
22
17
22
4.3
0.6
9.2
6.1
6.7
6.7
14
27
21
20
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
16
16
17
19
8.3
9.3
nd
nd
nd
nd
nd
nd
nd
nd
3.5
nd
1.64
Effluent
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
6.1
8.7
18
4.6
3.7
8.4
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
97
-------
Appendix F: Reactive column organic data
REACTIVE COLUMN
105
50PLSSAQ
Column Composition:
Pore Volume (PV):
Porosity:
Flow Velocity 1 (FV1):
Residence Time (FV1):
Flow Velocity 2 (FV2):
Residence Time (FV2):
50 % Granular Iron - Peerless
25 % Elizabeth City Aquifer Material
25 % Silica Sand
166 ml
0.29
2.6 ft/day (79 cm/day)
15.3hr
1.2 ft/day (36 cm/day)
34 hr
Distance Along Column (ft)
tDCE
FV1
FV2
VC
FV1
FV2
PV
4.6
16.3
20.2
28.5
43.6
54.4
78.3
80.1
85.7
90.8
95.5
100.8
105.7
110.9
116.0
120.7
4.6
16.3
20.2
28.5
43.6
54.4
78.3
80.1
85.7
90.8
95.5
100.8
105.7
116.0
120.7
RN
0.00
Influent
1.1
2.1
1.7
nd
1.7
1.2
nd
0.6
1.3
0.8
1.4
1.3
1.7
0.9
5.7
1.2
16
41
39
36
27
43
17
15
33
28
26
10
6.6
12
8.1
0.08
0.16
0.33
0.50
0.66
1.00
1.31
Organic Concentration ( |ig/L)
1.1
1.2
1.3
nd
1.2
0.3
nd
0.1
1.3
1.0
1.3
2.0
1.7
1.9
3.5
0.7
19
27
28
24
20
25
16
14
22
19
26
7.5
4.7
6.9
7.3
1.0
1.0
1.3
nd
0.9
0.2
nd
nd
0.6
0.7
1.0
2.1
1.8
1.2
2.2
0.5
19
28
28
24
16
30
12
14
17
14
21
6.0
6.0
5.8
5.9
0.1
0.5
0.6
nd
nd
nd
nd
nd
nd
0.1
0.5
1.4
1.6
1.1
1.4
0.3
15
26
24
22
21
27
4.7
13
17
6.7
12
5.0
6.9
5.8
4.8
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
0.6
0.8
1.1
0.7
0.1
nd
14
21
18
17
12
23
9.1
8.9
13
6.0
17
2.4
4.9
4.2
3.8
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
0.2
nd
nd
0.3
nd
nd
12
15
8.3
13
12
15
5.4
3.7
8.4
0.9
10
1.3
3.9
2.4
4.5
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
7.7
12
10
6.6
5.8
8.6
2.2
1.5
4.1
2.4
3.5
0.1
1.9
2.4
2.6
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
5.4
7.5
6.8
6.7
3.2
4.6
nd
nd
nd
nd
0.2
nd
nd
0.5
0.2
1.64
Effluent
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
3.4
6.3
6.2
2.9
1.8
2.8
nd
nd
nd
nd
nd
nd
nd
nd
nd
98
-------
Appendix F: Reactive column organic data
REACTIVE COLUMN
105
50PLSSAQ
Column Composition:
Pore Volume (PV):
Porosity:
Flow Velocity 1 (FV1):
Residence Time (FV1):
Flow Velocity 2 (FV2):
Residence Time (FV2):
50 % Granular Iron - Peerless
25 % Elizabeth City Aquifer Material
25 % Silica Sand
166 ml
0.29
2.6 ft/day (79 cm/day)
15.3hr
1.2 ft/day (36 cm/day)
34 hr
Distance Along Column (ft)
PH
FV1
FV2
Eh
FV1
FV2
PV
RN
0.00
Influent
0.08
0.16
0.33
0.50
0.66
1.00
1.31
Organic Concentration ( |ig/L)
1.64
Effluent
pH Along Column
1.5
8.3
18.1
40.6
44.0
79.3
83.4
88.9
93.7
100.1
103.7
108.9
114.7
119.4
125.4
1.5
8.3
18.1
40.6
44.0
79.3
83.4
88.9
93.7
100.1
103.7
108.9
114.7
119.4
125.4
a
a
b
b
c
c
d
d
d
d
d
d
e
e
e
a
a
b
b
c
c
d
d
d
d
d
d
e
e
e
6.6
7.2
6.5
7.0
6.1
7.9
6.7
6.6
6.9
7.1
7.9
8.1
6.1
6.5
7.3
Redox Potential
386
340
312
275
345
257
334
266
317
293
329
281
233
293
257
8.2
9.0
6.8
9.3
7.2
9.1
9.0
8.0
8.2
9.0
9.2
9.2
7.8
7.3
8.4
Along
-264
-129
-191
19
-195
229
182
230
211
192
222
175
133
188
246
9.0
9.3
7.1
9.1
8.5
9.3
9.3
9.0
9.0
8.6
8.9
9.5
8.4
7.5
8.5
Column (
-102
-226
-247
51
129
239
171
227
79
191
207
147
35
253
259
9.1
9.3
7.3
9.1
9.3
9.2
9.7
9.2
8.9
9.6
9.6
9.4
9.2
9.0
9.3
mV)
-244
-224
-311
-116
-209
260
80
254
3
72
-152
-142
-186
-84
52
9.1
9.4
8.7
9.3
9.3
9.4
9.7
9.3
9.0
9.5
9.3
9.6
9.4
8.3
9.3
-281
-273
-349
-279
-192
-78
-44
-125
27
-187
-156
-265
-301
8
-290
9.1
9.4
8.8
9.1
9.1
9.2
9.6
9.1
8.2
9.4
9.6
9.5
9.4
9.3
9.2
-325
-265
-136
-204
-272
73
18
84
76
-117
-206
-224
-287
-158
-248
9.1
9.4
9.2
9.2
9.1
9.3
9.6
9.0
7.9
9.4
9.5
9.5
9.4
9.3
9.4
-271
-296
-143
-250
-275
-167
-84
-409
-8
250
-233
-225
-282
-247
-282
8.7
9.3
9.2
9.2
9.2
9.3
9.6
9.2
6.5
9.4
9.5
9.4
9.4
9.3
9.3
-295
-304
-218
-214
-232
-86
23
-362
-2
-212
-279
-202
-242
-346
-347
8.5
9.2
9.0
9.2
9.2
9.2
9.4
9.1
9.2
9.4
9.4
9.4
9.1
9.3
9.4
-59
188
-211
104
25
306
123
217
79
-83
256
245
156
77
138
nd = not detected
RN = reservoir number
99
-------
Appendix F: Reactive column organic data
REACTIVE COLUMN
110
48PL/52AQ
TCE
FV1
PCE
FV1
TCM
FV1
PV
3.2
9.2
18.8
28.7
33.0
36.7
46.7
58.0
3.2
9.2
18.8
28.7
33.0
36.7
46.7
58.0
3.2
9.2
18.8
28.7
33.0
36.7
46.7
58.0
RN
d
d
d
d
d
e
e
e
d
d
d
d
d
e
e
e
d
d
d
d
d
e
e
e
0.00
Influent
1219
1227
1166
916
538
1734
1436
1309
1.3
1.4
1.3
1.2
2.2
2.2
1.4
1.5
21
22
26
22
8.2
28
24
22
Column Composition: 48 % Granular Iron - Peerless
52 % Elizabeth City Aquifer Material
Pore Volume (PV): 189 ml
Porosity: 0.33
Flow Velocity I (FV1): 2.3 ft/day ( 71 cm/day )
Residence Time (FV1): 17 hr
Distance Along Column (ft)
0.08
0.16
0.33
0.50
0.66
1.00
1.31
Organic Concentration ( |ig/L)
803
864
1005
892
323
1231
1090
1105
0.4
0.8
1.1
1.1
nd
nd
1.0
nd
10
12
18
18
4.6
16
16
15
424
568
803
723
227
1039
848
955
nd
0.4
nd
nd
nd
nd
nd
nd
3.8
5.7
11
9.2
2.5
6.5
3.7
5.0
29
103
357
383
179
492
342
480
nd
nd
nd
nd
nd
nd
nd
nd
nd
2.3
5.2
4.8
2.0
3.2
1.0
0.6
nd
nd
50
82
25
32
13
33
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
2.4
2.1
1.0
0.8
0.4
0.2
nd
nd
2.1
5.3
3.5
3.7
1.1
1.5
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
0.9
nd
nd
0.4
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
1.64
Effluent
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd = not detected
RN = reservoir number
100
-------
Appendix F: Reactive column organic data
REACTIVE COLUMN
110
48PL/52AQ
Column Composition:
Pore Volume (PV):
Porosity:
Flow Velocity I (FV1):
Residence Time (FV1):
48 % Granular Iron - Peerless
52 % Elizabeth City Aquifer Material
189 ml
0.33
2.3 ft/day ( 71 cm/day )
17 hr
Distance Along Column (ft)
cDCE
FV1
tDCE
FV1
VC
FV1
PV
12.0
17.6
21.7
31.3
38.4
41.1
12.0
17.6
21.7
31.3
38.4
41.1
12.0
17.6
21.7
38.4
41.1
RN
d
d
d
d
e
e
d
d
d
d
e
e
d
d
d
e
e
0.00
Influent
41
41
37
36
57
65
3.9
1.8
1.6
nd
2.9
5.7
10.0
9.0
6.6
12.0
12.0
0.08
0.16
0.33
0.50
0.66
1.00
1.31
Organic Concentration ( |ig/L)
51
41
37
76
73
58
1.6
1.5
1.4
0.5
2.3
2.2
9.5
9.0
5.7
11.0
4.7
41
55
37
80
52
59
1.7
1.9
0.9
nd
1.4
2.9
8.0
6.4
4.8
6.8
5.3
26
65
34
77
94
65
0.8
1.3
0.6
nd
1.8
0.2
6.5
6.4
4.0
8.1
4.3
11
38
24
73
72
59
nd
0.1
nd
nd
1.1
1.2
4.8
8.4
3.9
5.9
3.7
0.2
23
21
64
51
32
nd
nd
nd
nd
0.7
nd
3.0
4.1
2.9
4.2
2.7
nd
2.3
3.5
13
11
6.6
nd
nd
nd
nd
nd
nd
0.7
1.5
1.3
1.9
1.0
nd
nd
nd
5.0
5.2
3.1
nd
nd
nd
nd
nd
nd
nd
0.2
0.2
1.3
0.5
1.64
Effluent
nd
nd
nd
6.5
3.9
2.1
nd
nd
nd
nd
nd
nd
nd
nd
0.1
1.2
0.4
nd = not detected
RN = reservoir number
101
-------
Appendix F: Reactive column organic data
REACTIVE COLUMN
110
48PL/52AQ
Column Composition:
Pore Volume (PV):
Porosity:
Flow Velocity I (FV1):
Residence Time (FV1):
48 % Granular Iron - Peerless
52 % Elizabeth City Aquifer Material
189 ml
0.33
2.3 ft/day ( 71 cm/day )
17 hr
Distance Along Column (ft)
PV
RN
0.00
Influent
0.08
0.16
0.33
0.50
0.66
1.00
1.31
Organic Concentration ( |ig/L)
1.64
Effluent
pH Along Column
pH
FV1
Eh
FV1
1.9
10.7
19.1
23.4
27.5
39.9
42.5
48.2
1.9
10.7
19.1
23.4
27.5
39.9
42.5
48.2
d
d
d
d
d
e
e
e
d
d
d
d
d
e
e
e
6.7
7.2
7.5
8.1
8.5
6.4
6.4
6.7
Redox Potential
344
298
264
256
298
322
294
313
8.4
9.1
9.1
9.1
9.2
7.2
7.3
7.9
Along
68
149
136
194
134
74
123
140
8.3
9.3
9.4
9.3
9.4
8.5
8.2
8.7
Column (
-15
93
121
175
51
150
115
103
7.8
9.2
9.5
9.4
9.4
9.1
9.0
9.0
mV)
-29
-115
74
155
-51
-295
-213
-132
7.2
9.0
9.4
9.3
9.6
9.1
9.1
8.9
22
-155
-49
86
-293
-404
-211
-176
7.2
9.0
9.1
9.2
9.2
9.1
9.1
9.0
192
-35
-205
-10
-139
-310
-361
-208
7.4
8.9
8.9
9.0
9.3
9.1
9.1
9.1
166
-159
-146
-24
-172
-455
-395
-170
7.2
9.0
8.0
9.1
9.3
9.1
9.1
9.0
127
-225
-153
-86
-219
-418
-399
-146
6.4
8.9
9.2
9.1
9.4
9.3
9.3
9.3
273
226
275
252
266
229
32
41
nd = not detected
RN = reservoir number
102
-------
Appendix G: Reactive column inorganic data
Elizabeth City reactive columns
Concentrations in mg/L, determined at UW Water Quality Lab
Distance along
column (cm)
50MBSSAQ at 8.6 PV
0
2.5
10
15
20
30
40
50MBSSAQat27.7PV
0
2.5
5
10
15
20
30
40
50
50MBSSAQat48.1 PV
0
2.5
5
10
15
20
30
50MBSS at 27.9 PV
0
2.5
5
10
15
20
30
40
50
50MBSS at 34.4 PV
0
2.5
5
10
15
20
30
40
50
50MBSS at 53.5 PV
0
2.5
5
10
15
20
30
40
50
PH
6.88
8.15
9.14
9.15
9.31
9.3
9.43
6.48
7.27
8.29
8.95
9.09
9.18
9.27
9.23
9.28
6.71
7.09
7.92
8.63
8.92
9.07
9.14
Eh (mV)
178
-10
-132
-145
-140
-169
-143
367
60
62
-14
-35
-8
-57
-94
-506
241
35
134
-39
-89
-76
-137
CO3
FV1 = 6i
29.4
17.4
32.7
38.1
27.0
36.9
26.3
24.3
49.6
33.3
45.7
44.9
42.5
29.5
34.7
26.0
38.9
42.7
50.0
39.5
40.9
49.0
44.4
SO,
3 cm/d
101.0
98.3
99.9
102.0
90.3
100.0
114.0
105.0
112.0
106.0
104.0
102.0
104.0
93.2
94.8
94.0
101.0
104.0
105.0
102.0
103.0
104.0
104.0
Al
<0.2
<0.2
<0.2
<0.2
<0.2
0.2
0.33
O.2
0.2
O.2
O.2
0.2
O.2
0.207
0.2
0.617
O.2
0.2
0.2
O.2
0.2
0.2
O.2
Ba
0.07
0.08
0.04
0.02
0.04
0.02
0.03
0.08
0.053
0.051
0.06
0.03
0.02
0.02
0.02
0.06
0.07
0.05
0.10
0.07
0.06
0.03
0.02
Ca
24
22.4
23.5
24.4
23.9
25.6
28.5
24
22.6
22.9
22.5
22.2
22.2
22.9
20.7
19.9
23.5
22.2
23.1
22.8
22.6
22.8
21.3
Cr
10.300
0.001
0.057
0.016
0.041
0.020
0.001
10.8
0.032
0.014
0.013
0.013
0.022
0.008
0.026
0.048
8.370
0.018
0.006
0.014
0.040
0.016
0.019
Fe
O.1
0.1
0.1
O.1
0.1
0.1
O.1
O.1
8.24
0.307
O.1
0.1
O.1
O.1
0.1
O.1
O.1
9.08
0.26
O.1
0.1
0.1
O.1
K
3.51
2.44
2.83
3.52
2.84
4.06
3.94
7.01
7
6.28
6.59
7.35
6.83
5.43
5.4
6.94
5.23
5.53
7.81
4.72
4.61
4.08
4.46
Mg
15.3
14.5
14.3
13.2
11
7.16
2.82
16.4
15.9
15.9
15.4
14.7
14.1
12.4
10.9
10
15
14.7
15
15
14.7
14.9
14.2
Mn
0.84
0.28
0.13
0.09
0.07
0.07
0.04
0.87
0.79
0.49
0.45
0.38
0.16
0.08
0.08
0.06
0.84
0.76
0.47
0.46
0.38
0.20
0.10
Na
96.8
94.2
95.4
101
94.6
96.7
98.9
105
104
103
119
104
103
101
99.7
97.9
103
102
97.6
102
103
103
103
Ni
O.1
0.1
0.1
O.1
0.1
0.1
O.1
O.1
0.1
O.1
O.1
0.1
O.1
O.1
0.1
O.1
O.1
0.1
0.1
O.1
0.1
0.1
O.1
Sr
0.47
0.43
0.44
0.45
0.43
0.31
0.18
0.43
0.40
0.40
0.40
0.39
0.40
0.41
0.41
0.39
0.41
0.38
0.40
0.39
0.40
0.40
0.42
H4SIO4
31.41
6.45
1.85
1.89
2.38
2.00
3.33
32.6
13.5
3.66
1.56
1.30
1.93
1.80
2.26
1.42
28.51
14.83
4.04
1.15
1.31
1.46
1.50
Zn
0.149
0.05
0.05
O.05
0.05
0.05
O.05
0.073
0.05
O.05
O.05
0.05
O.05
O.05
0.05
O.05
0.179
0.05
0.05
O.05
0.05
0.05
O.05
Cl
119
116
121
122
127
119
144
119
119
120
122
126
132
125
123
125
120
118
123
119
120
121
124
FV1 = 55 cm/d
6.38
6.9
7.19
8.31
8.59
8.92
9.12
9.12
9.39
7.32
7.41
8.33
8.88
8.93
8.94
9
9.24
9.33
6.5
7
7.3
8.46
8.82
8.95
9.06
9.18
9.17
307
56
54
196
324
91
149
321
330
451
113
431
237
90
-25
-105
-88
-77
297
107
23
283
2
-14
-88
-53
61
27.8
61.9
45.2
53.2
45.8
31.2
38.4
30.0
31.8
28.7
43.8
34.3
40.5
32.3
39.0
21.1
41.0
27.3
34.1
28.1
60.9
44.1
29.5
44.7
24.4
27.3
19.0
105
99
99
101
101
101
104
108
99
100
97
93
94
101
100
102
100
100
85
99
98
102
100
98
97
101
95
0.2
0.2
O.2
0.2
O.2
O.2
0.2
O.2
O.2
0.25
0.943
0.166
0.255
0.2
O.2
0.638
0.265
O.2
O.2
0.2
0.2
O.2
0.2
O.2
0
O.2
0.08
0.06
0.06
0.05
0.05
0.04
0.03
0.07
0.04
0.08
0.06
0.04
0.04
0.04
0.03
0.04
0.03
0.03
0.06
0.06
0.06
0.13
0.04
0.04
0.04
0.06
0.03
25
23.3
24
22.8
21.3
19.9
16.6
14.5
12.9
24.3
23
22.6
20.2
19.3
17
14.7
13.9
13.1
23.2
24.5
23.3
22.6
18.5
16.6
14.2
13
12.4
10.800
0.025
0.024
0.013
0.007
0.010
0.013
0.034
0.040
10.500
0.023
0.010
0.014
0.028
0.011
0.019
0.001
0.012
3.800
0.032
0.012
0.001
0.017
0.029
0.001
0.016
0.1
18.4
7.95
0.1
O.1
O.1
0.1
O.1
O.1
O.1
4.11
0.103
0.1
0.1
O.1
0.1
0.1
O.1
O.1
9.83
5.4
O.1
0.1
O.1
O.1
0.1
O.1
4.02
3
3.55
4.42
3.71
3.83
4.38
4.25
4.49
5.56
7.31
5.66
5.08
3.62
4.42
6.56
3.7
4.21
5.14
4.94
5.01
5.88
4.44
4.23
4.66
3.41
4.36
16
15.3
15.4
15
15.3
15.2
14.9
15
14.5
15.9
15.6
15.1
15.2
16.1
15.2
15.1
14.7
14.1
15.3
15.8
15.3
15.6
15.5
15.2
14.8
15
14.6
0.86
0.94
0.64
0.28
0.38
0.61
0.41
0.19
0.12
0.85
0.71
0.28
0.08
0.12
0.24
0.34
0.17
0.10
0.92
1.05
0.60
0.10
0.06
0.11
0.17
0.12
0.10
100
100
97.5
95.2
97.6
97.1
96.8
101
98.5
99
100
104
98.5
108
101
106
102
100
103
115
111
102
107
105
104
104
107
0.1
0.202
0.124
0.1
O.1
O.1
0.1
O.1
O.1
O.1
0.1
O.1
0.1
0.1
O.1
0.1
0.1
O.1
O.1
0.155
0.1
O.1
0.1
O.1
O.1
0.1
O.1
0.48
0.47
0.45
0.42
0.38
0.34
0.26
0.21
0.18
0.41
0.39
0.38
0.32
0.31
0.26
0.20
0.19
0.18
0.40
0.42
0.40
0.38
0.29
0.25
0.20
0.18
0.17
32.61
23.82
15.18
2.95
1.60
1.45
1.28
1.16
1.35
32.28
20.61
6.81
2.53
1.59
1.44
3.32
1.37
1.14
24.97
25.36
10.70
2.97
1.73
1.68
1.46
1.86
1.71
0.108
0.05
O.05
0.05
O.05
O.05
0.05
O.05
O.05
0.062
0.05
O.05
0.05
0.05
O.05
0.05
0.05
O.05
O.05
0.05
0.05
O.05
0.05
O.05
O.05
0.05
O.05
128
120
121
117
118
118
133
136
122
121
125
122
122
121
120
122
117
118
148
128
123
126
122
122
120
129
117
103
-------
Appendix G: Reactive column inorganic data
Distance along
column (cm)
100MB at 24 PV
0
2.5
10
15
20
30
40
50
100MB at 29.2 PV
0
2.5
5
10
15
20
30
40
50
100MB at 46.6 PV
0
2.5
2.5
10
15
20
30
40
100MB at 79.2 PV
0
2.5
10
20
50
100MB at 98 PV
0
2.5
5
10
20
30
50
100PLat26PV
0
5
10
15
20
30
40
50
100PLat35PV
0
10
15
20
30
40
50
PH
6.26
7.6
9.1
9.46
9.36
9.12
9.56
9.2
6.39
9.22
9.24
9.4
9.46
9.54
9.54
9.56
6.6
8.84
8.84
9.22
9.34
9.42
9.48
9.44
6.33
8.41
9.26
9.46
9.57
7.37
8.98
9.69
9.48
9.35
9.55
6.29
8.26
9.17
9.19
9.39
9.46
9.29
9.12
6.6
8.98
9.18
9.33
9.45
9.46
9.63
Eh (mV)
338
-86
-165
33
-145
-160
201
-24
561
-94
-139
-90
-45
-99
-149
-165
276
195
195
71
-29
-53
-67
-115
369
312
12
^19
-521
266
250
12
81
-171
318
317
57
-87
-165
-145
-194
-171
-42
561
-124
-170
-97
-107
-160
-63
Alkalinity
C03 SO,
FV1 = 43 cm/d
29.6 106
58.2 106
32.1 104
24.6 98
25.4 108
25.9 103
23.1 103
20.0 100
25.1 103
45.6 99
28.6 97
31.0 99
24.8 98
16.0 98
16.5 104
13.6 98
38.4 102
40.5 100
40.5 100
35.5 100
24.4 103
26.7 100
28.0 107
23.1 104
FV2 = 24 cm/d
32 98.1
77.0 93.8
47.0 91.4
39.5 94.2
16.3 98.1
35.4 95.5
26.7 85.7
31.1 85.2
12.7 90.0
23.1 89.6
19.5 91.6
FV1 = 53 cm/d
23.0 98
51.4 104
50.8 102
34.5 99
45.2 102
40.2 96
33.3 97
29.8 99
24.9 92
39.8 100
25.8 100
41.5 102
30.7 99
26.8 102
23.1 101
Al
O.2
0.209
O.2
O.2
0.26
0.238
O.2
0.2
0.32
0.707
0.2
0.2
O.2
0.2
0.2
O.2
0.2
0.2
0.369
0.662
0.2
O.2
O.2
0.2
O.2
0.20
0.20
O.20
0.20
0.20
O.20
O.20
0.20
O.20
O.20
0.20
O.20
O.2
0.2
0.2
O.2
0.2
0.2
O.2
0.2
0.2
0.219
O.2
0.2
O.2
O.2
0.2
Ba
0.08
0.07
0.03
0.02
0.03
0.03
0.02
0.03
0.08
0.18
0.04
0.02
0.03
0.02
0.02
0.02
0.03
0.08
0.06
0.13
0.02
0.02
0.02
0.02
0.02
0.07
0.14
0.01
0.01
0.02
0.07
0.04
0.03
O.20
O.20
0.20
0.03
0.08
0.05
0.04
0.04
0.03
0.04
0.05
0.06
0.08
0.03
0.03
0.03
0.04
0.04
0.05
Ca
24.7
24
13.2
11.2
10.2
9.31
<9
9.88
25.9
25.9
20.2
14.4
13
12.9
12.6
12.3
11.4
25.1
21.6
21.8
12.5
11.4
11.1
10.4
9.78
21.3
32.0
6.0
5.8
10.6
20.6
17.1
12.5
9.0
9.1
9.1
9.0
25.1
24.3
20
18
16.9
15.8
15.1
14.6
25
18.7
17.1
16.3
16
16.2
16.1
Cr(OH)2*
10.600
0.030
0.001
0.032
0.003
0.001
0.005
0.007
10.800
0.019
0.056
0.016
0.013
0.020
0.023
0.022
0.006
9.270
0.009
0.033
0.001
0.007
0.010
0.017
0.001
6.844
2.077
0.001
0.001
0.001
7.270
5.800
0.030
0.001
0.030
0.022
0.001
10.600
0.032
0.034
0.012
0.015
0.026
0.004
0.010
10.700
0.001
0.028
0.008
0.001
0.033
0.001
Fe
O.1
1.01
O.1
O.1
0.1
O.1
O.1
0.1
0.1
O.1
0.1
0.1
O.1
0.1
0.1
O.1
0.1
0.1
O.1
O.1
0.1
O.1
O.1
0.1
O.1
0.10
0.10
O.10
0.10
0.10
O.10
O.10
0.10
O.10
O.10
0.10
O.10
O.1
0.629
0.1
O.1
0.1
0.1
O.1
0.1
0.1
O.1
O.1
0.1
O.1
O.1
0.1
K
4.69
5.85
5.3
4.09
5.62
6.41
4.57
4.12
3.68
6.14
5.73
4.81
6.05
3.94
4.3
4.98
4.35
5.6
6.21
8.61
5.38
4.9
5.04
4.87
5.05
5.0
5.8
5.1
5.3
5.2
5.4
5.5
5.6
5.2
4.2
4.0
3.8
5.07
5.05
5.02
4.96
4.82
4.84
5.37
4.83
4.83
4.41
4.73
4.52
4.66
4.7
4.75
Mg
15.8
15.3
15
14.7
14.1
13
12
9.85
16
14.6
14.6
13.9
13.8
13.7
12.7
11.7
10.5
16.2
13.7
13.8
12.8
12.6
12.5
11.8
10.9
14.1
15.6
16.3
15.1
4.4
14.1
14.5
10.0
9.8
8.9
8.2
6.8
16.1
15.7
15.7
15.7
15.4
14.6
13.4
12.1
15.8
14.8
14.7
14.3
14.1
13.3
12
Mn
0.85
0.39
0.26
0.25
0.15
0.14
0.17
0.16
0.84
0.06
0.06
0.20
0.23
0.15
0.14
0.14
0.11
0.86
0.08
0.09
0.08
0.15
0.12
0.12
0.13
0.78
1.41
O.01
0.01
0.01
0.86
0.13
0.01
O.01
0.06
0.06
0.06
0.87
0.38
0.28
0.23
0.12
0.10
0.12
0.11
0.87
0.13
0.21
0.15
0.11
0.11
0.10
Na
101
97.5
97.9
101
98.1
97.6
102
103
99.9
94.7
97.2
98.3
97.2
101
101
101
101
108
102
107
103
101
103
102
99.6
110
111
108
107
105
99.3
102
102
100
106
105
104
102
101
99.8
102
100
99.8
101
100
99.3
101
102
101
104
105
104
Ni
O.1
0.101
O.1
O.1
0.1
O.1
O.1
0.1
0.1
O.1
0.1
0.1
O.1
0.1
0.1
O.1
0.1
0.1
O.1
O.1
0.1
O.1
O.1
0.1
O.1
0.20
0.20
O.20
0.20
0.20
O.20
O.20
0.20
O.20
O.20
0.20
O.20
O.1
0.1
0.1
O.1
0.1
0.1
O.1
0.1
0.1
O.1
O.1
0.1
O.1
O.1
0.1
Sr
0.46
0.44
0.19
0.14
0.13
0.10
0.11
0.13
0.44
0.37
0.26
0.16
0.14
0.13
0.12
0.12
0.11
0.44
0.37
0.36
0.17
0.15
0.14
0.13
0.12
0.388
0.602
0.060
0.062
0.143
0.38
0.30
0.23
0.11
0.12
0.12
0.12
0.47
0.44
0.33
0.29
0.26
0.25
0.23
0.23
0.43
0.28
0.25
0.23
0.23
0.24
0.24
H4Si04
32.54
9.30
1.10
0.73
0.84
0.65
0.75
0.65
32.52
9.41
1.28
0.70
0.70
0.93
0.67
0.95
0.39
32.32
15.82
17.20
0.98
0.78
0.53
0.92
0.87
30.7
30.4
1.4
1.1
1.4
31.4
28.6
15.4
3.1
0.4
0.8
0.8
32.63
5.69
1.21
1.01
0.90
1.56
0.71
0.81
32.92
1.24
1.01
1.23
1.01
0.85
1.00
Zn
0.113
0.05
O.05
O.05
0.05
O.05
O.05
0.05
0.092
O.05
0.05
0.05
O.05
0.05
0.05
O.05
0.05
0.097
O.05
O.05
0.05
O.05
O.05
0.05
O.05
0.010
0.010
0.010
0.010
0.010
0.138
0.088
0.017
0.049
0.137
0.081
0.013
0.121
0.05
0.05
O.05
0.05
0.05
O.05
0.05
0.086
O.05
O.05
0.05
O.05
O.05
0.05
Cl
125
129
125
122
132
123
120
118
123
121
117
119
122
123
126
124
121
119
119
116
121
116
127
123
115
115
111
115
115
116
113
113
120
113
118
110
123
122
118
122
110
114
111
124
121
121
124
124
124
123
104
-------
Appendix G: Reactive column inorganic data
Distance along Alkalinity
column (cm) pH Eh (mV) CO3 SO,
100PLat58PV
0 6.58
5 8.47
10 9.19
15 9.23
20 9.25
30 9.39
40 9.46
100PLat100.5PV
0 6.26
2.5 8.36
10 9.32
20 9.41
50 9.22
100PL at 114.7 PV
0 7.33
2.5 9.19
5
10 9.60
20 9.33
30 9.56
50 9.43
50PLSSAQ at 5.2 PV
0 6.84
2.5 8.68
5 9.04
10 9.2
15 9.26
20 9.22
30 9.15
40 9.31
50 9.16
50PLSSAQ at 30.3 PV
0 6.46
10 8.8
15 8.9
20 9.02
30 9.08
40 9.14
50 9.16
50PLSSAQ at 66.2 PV
0 6.58
2.5 8.18
5 8.94
10 9.06
15 8.95
20 8.96
30 9.08
40 9.22
50 9.17
50PLSSAQ at 116.8 PV
0 6.27
2.5 7.41
10 9.17
20 9.37
50 9.26
266
351
70
^9
-102
-133
-36
27.0
41.7
33.2
40.4
34.5
41.7
31.5
101
96
96
98
97
101
100
Al
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
Ba Ca Cr(OH)2*
0.08
0.04
0.02
0.02
0.03
0.03
0.03
24.5
22.9
16.3
14.8
14.6
13.9
13.2
10.500
0.023
0.001
0.001
0.001
0.022
0.029
Fe
0.1
O.1
O.1
0.1
O.1
O.1
0.1
K
5.13
5.8
5.24
5.17
4.4
4.75
4.11
Mg
15.7
14.5
14.3
14
13.8
13.2
12
Mn
0.86
0.16
0.05
0.07
0.08
0.10
0.08
Na
101
107
107
107
107
104
104
Ni
0.1
O.1
O.1
0.1
O.1
O.1
0.1
Sr
0.43
0.41
0.26
0.22
0.21
0.20
0.19
H4SiO4
32.47
8.82
1.99
1.36
1.29
1.24
1.24
Zn
0.133
O.05
O.05
0.05
O.05
O.05
0.05
Cl
118
116
115
116
119
119
122
FV2 = 31 cm/d
370
296
278
-512
156
319
260
248
21
86
99
34.5
58.6
47.0
36.6
12.3
35.9
35.2
24.2
23.1
16.0
18.6
99.6
95.1
92.4
95.9
109.0
93.9
87.3
84.6
90.9
89.6
88.9
O.20
0.20
0.20
O.20
0.20
0.20
O.20
O.20
0.20
O.20
0.20
0.20
0.08
0.10
0.03
0.02
0.03
0.07
0.04
O.20
0.20
O.20
0.02
0.03
22.9
27.4
9.1
6.5
14.1
22.7
18.8
6.6
11.5
9.7
9.5
9.4
7.255
1.203
0.001
0.001
0.004
7.790
6.190
0.136
0.001
0.021
0.001
0.001
O.10
0.10
0.10
O.10
0.10
0.10
O.10
O.10
0.10
O.10
0.10
0.10
6.0
5.1
5.5
5.0
4.4
4.1
4.3
2.1
4.8
4.3
4.5
4.1
14.9
14.9
15.8
15.1
6.0
14.9
15.0
5.7
9.2
7.4
7.4
6.9
0.84
1.05
0.01
O.01
0.01
0.89
0.09
0.01
0.01
0.02
0.02
0.06
113
107
111
109
107
107
105
54.4
106
105
104
104
O.20
0.20
0.20
O.20
0.20
0.20
O.20
O.20
0.20
O.20
0.20
0.20
0.401
0.494
0.141
0.085
0.227
0.40
0.31
0.11
0.18
0.13
0.13
0.14
31.8
21.6
7.5
1.2
1.4
32.5
29.6
11.4
8.3
2.9
2.1
0.4
0.010
0.010
0.010
0.010
0.010
0.279
0.081
0.189
0.016
0.022
0.034
0.083
117
113
109
114
115
117
113
109
118
107
110
FV1 = 79 cm/d
213
-88
-85
-135
-155
-11
-149
-104
36
355
-33
-44
-57
-124
-348
-68
259
109
133
-50
-38
-93
-105
-78
22
31.4
34.0
35.4
31.4
46.5
36.0
23.8
14.9
25.0
21.7
37.8
45.2
42.5
39.9
37.2
37.2
29.7
51.9
49.6
45.9
57.6
47.3
40.6
34.9
43.8
95
100
116
105
101
101
100
96
101
100
99
96
93
98
99
97
104
106
104
105
99
105
102
100
100
0.2
O.2
0.2
O.2
O.2
0.2
O.2
0.2
0.2
0.2
0.232
0.2
O.2
O.2
0.2
O.2
O.2
0.2
0.2
O.2
0.2
0.2
O.2
0.2
O.2
0.08
0.04
0.13
0.03
0.05
0.02
0.04
0.03
0.02
0.08
0.06
0.06
0.04
0.03
0.02
0.03
0.08
0.04
0.03
0.04
0.05
0.06
0.03
0.03
0.03
25.2
23.1
23.9
23.2
22.1
22.2
21.8
21.3
22.5
25.3
22.9
22.9
22.6
22.4
21.9
20.9
24.2
23
22.3
22.2
21.9
21.8
21.6
21.2
19.9
10.700
0.028
0.001
0.026
0.020
0.012
0.004
0.018
0.015
10.800
0.066
0.036
0.026
0.022
0.025
0.046
10.400
0.009
0.043
0.023
0.045
0.016
0.032
0.009
0.009
0.1
O.1
0.1
O.1
O.1
0.1
O.1
0.1
0.1
0.1
O.1
0.1
O.1
O.1
0.1
O.1
O.1
0.286
0.1
O.1
0.1
0.1
O.1
0.1
O.1
4.57
5.43
4.35
4.89
3.56
4.7
3.5
5.07
5.4
4.49
4.62
5.15
4.13
4.35
4.88
4.91
5.12
5.7
4.48
5.03
5.22
5.18
5.33
4.82
4.77
15.8
14.6
15.1
14.4
12.6
11.8
9.41
7.64
5.85
16.2
14.8
14.5
14.1
13.3
12.6
11.8
15.4
14.7
14.1
14
13.6
13.4
13.4
13
12.6
0.86
0.31
0.35
0.14
0.10
0.09
0.08
0.13
0.09
0.85
0.33
0.52
0.41
0.14
0.14
0.09
0.86
0.39
0.05
0.07
0.18
0.30
0.17
0.12
0.09
98.3
97.1
101
99.7
96.9
98
97.3
93.9
98.9
100
98.2
97.3
96.4
95.2
94.7
95.5
100
99.9
100
100
99.8
101
102
101
99.7
0.1
O.1
0.1
O.1
O.1
0.1
O.1
0.1
0.1
0.1
O.1
0.1
O.1
O.1
0.1
O.1
O.1
0.1
0.1
O.1
0.1
0.1
O.1
0.1
O.1
0.46
0.41
0.41
0.41
0.38
0.39
0.35
0.28
0.21
0.44
0.41
0.38
0.37
0.38
0.39
0.39
0.43
0.40
0.38
0.38
0.37
0.37
0.38
0.38
0.38
31.93
3.18
2.24
1.89
2.06
2.10
2.59
1.40
1.34
32.54
1.42
1.70
1.81
1.84
1.67
1.88
32.06
13.27
1.85
1.44
1.63
1.23
1.08
2.02
1.28
0.166
V
0.05
O.05
O.05
0.05
O.05
0.05
0.05
0.261
O.05
0.05
O.05
O.05
0.05
O.05
0.103
0.05
0.05
O.05
0.05
0.05
O.05
0.05
O.05
110
113
118
114
113
115
116
116
121
118
120
113
115
118
121
120
114
119
117
116
115
120
118
118
118
FV2 = 36 cm/d
364
99
197
^36
-121
26.3
58.6
50.7
44.8
41.9
99.0
95.6
92.3
82.5
87.7
O.20
0.20
O.20
0.20
0.20
0.08
0.12
0.03
0.03
0.03
22.1
23.8
16.6
14.5
14.9
7.128
0.001
0.001
0.001
0.001
0.01
0.62
0.01
0.01
0.01
5.4
5.6
5.2
5.4
6.2
14.6
15.5
17.5
18.1
11.1
0.82
2.93
O.01
0.03
0.01
108
105
106
105
105
O.02
0.02
O.02
0.02
0.02
0.383
0.428
0.319
0.280
0.302
30.6
25.7
1.8
1.7
1.7
0.010
0.010
0.010
0.010
0.010
117
114
115
114
111
105
-------
Appendix G: Reactive column inorganic data
Distance along
column (cm)
Alkalinity
pH Eh (mV) CO3
SO,
Al
Ba
Ca
Cr(OH)2*
Fe
K
Mg
Mn
Na
Ni
Sr
H4SiO4
Zn
Cl
50PLSSAQ at 135.3 PV
0
2.5
5
10
20
30
50
7.35
8.58
9.36
9.30
9.38
9.35
320
298
271
-286
178
321
34.4
45.0
30.0
39.8
32.8
26.5
86.3
90.3
92.3
99.6
96.7
94.8
<0.20
0.20
<0.20
<0.20
<0.20
<0.20
0.08
0.03
<0.20
0.04
0.04
0.04
0.03
22.8
20.5
8.54
16.8
15.4
15.5
14.6
7.810
1.610
0.001
0.001
0.001
0.023
0.001
<0.10
0.10
O.10
0.10
0.10
O.10
0.10
4.7
4.3
1.9
4.2
4.9
4.6
4.8
15.1
14.3
6.0
12.1
10.2
9.6
8.9
0.88
0.21
0.17
0.01
0.04
0.02
0.02
106
103
48.8
102
102
102
102
O.20
0.20
O.20
0.20
0.20
O.20
0.20
0.40
0.32
0.14
0.29
0.28
0.29
0.31
32.4
25.3
10.9
2.4
2.5
3.3
1.3
0.126
0.048
0.037
0.042
0.056
0.010
0.065
106
112
110
115
111
106
48PL/52AQ at 78.4 PV
0
2.5
5
10
15
20
30
40
50
7.34
8.69
8.7
9.08
9.42
9.36
9.63
9.81
9.87
315
298
256
258
16
207
-130
-38
271
FV1 = 71
31.3
30.5
31.6
39.8
25.4
41.9
37.5
25.2
33.8
cm/d
97.8
93.4
85.7
90.5
91.8
98.9
77.2
60.9
49.4
O.2
O.2
0.2
O.2
O.2
0.2
O.2
O.2
0.2
0.07
0.03
0.02
0.05
0.02
0.02
O.02
O.02
0.02
23.2
22.6
21.2
19.6
18.5
17.9
16.4
10.5
7.66
7.710
3.770
0.032
0.041
0.001
0.022
0.001
0.024
0.027
O.1
O.1
0.1
O.1
O.1
0.1
O.1
O.1
0.1
4.78
4.55
4.34
4.43
4.26
4.64
4.79
4.3
4.06
14.8
14.8
12.7
11.8
9.44
7.76
4.77
2.03
0.775
0.88
0.06
0.05
0.03
0.03
0.01
0.02
0.01
0.01
106
104
102
103
103
102
103
103
87.7
O.02
O.02
0.02
O.02
O.02
0.02
O.02
O.02
0.02
0.40
0.37
0.34
0.33
0.34
0.33
0.31
0.27
0.21
31.7
28.0
15.1
1.4
0.9
1.4
2.1
1.6
2.3
0.134
0.048
0.172
0.021
0.083
0.057
0.074
O.010
0.083
107
105
106
107
107
108
108
111
110
106
-------
Appendix H: Reactive column mineral saturation indices
Elizabeth City reactive columns
Saturation indices calculated by MINTEQA2
Based on UW Water Quality Lab data
Distance along
column (cm) Ferrihydrite Goethite Cr(OH)3 (a) Cr(OH)3 (c) Calcite Dolomite Siderite (d) Mackinawite Magnesite Rhodochro Aragonite Amakinite SI62 (a) pH Eh (mV)
50MBSSAQ at 8.6 PV
0
2.5
10
15
20
30
40
-1.317
-0.124
-0.161
-0.371
0.117
-0.397
0.757
FV1 = 68 cm/d
4.393
5.586
5.549
5.339
5.827
5.313
6.467
0.450
-0.099
1.893
1.335
1.744
1.431
-0.097
-2.089
-2.639
-0.646
-1.204
-0.795
-1.108
-2.637
-1.523
-0.516
0.663
0.750
0.725
0.878
0.863
-2.944
-0.923
1.412
1.534
1.414
1.505
1.024
-3.133
-1.491
-1.227
-1.169
-1.272
-1.124
-0.864
-50.583
-34.324
-26.399
-24.703
-26.792
-22.668
-26.902
-1.996 -1.204 -1.677 -6.516 -0.411
-0.982 -0.696 -0.670 -3.367 -1.108
0.175 -0.294 0.509 -2.299 -1.686
0.211 -0.433 0.595 -2.296 -1.687
0.115 -0.556 0.570 -2.054 -1.609
0.054 -0.517 0.723 -2.060 -1.686
-0.413 -0.834 0.709 -1.482 -1.493
6.88
8.15
9.14
9.15
9.31
9.30
9.43
178
-10
-132
-145
-140
-169
-143
50MBSSAQ at 27.7 PV
10
15
20
30
40
50
0.833
0.790
0.854
0.750
0.499
-9.057
6.543
6.500
6.564
6.460
6.209
-3.347
1.268
1.264
1.475
1.028
1.550
1.811
-1.272
-1.275
-1.065
-1.511
-0.990
-0.728
0.622
0.727
0.774
0.712
0.710
0.656
1.381
1.577
1.654
1.460
1.444
1.316
-1.703
-1.693
-2.314
-1.934
-1.386
-4.107
-41.534
-39.877
-44.964
-38.531
-32.613
0.713
-1.741
-1.845
-1.691
-1.727
-1.615
-1.838
8.95
9.09
9.18
9.27
9.23
9.28
-14
-35
-8
-57
-94
-506
50MBSSAQat48.1 PV
0
2.5
5
10
15
20
30
-0.765
-0.196
2.184
-0.117
-0.041
0.423
-0.295
4.945
5.514
7.894
5.594
5.669
6.133
5.415
0.314
1.066
0.873
1.287
1.745
1.338
1.412
-2.225
-1.474
-1.666
-1.253
-0.794
-1.202
-1.128
-1 .583
-1.195
-0.283
0.291
0.558
0.759
0.746
-3.065
-2.272
-0.456
0.700
1.229
1.635
1.618
-3.201
0.179
-0.733
-1.613
-1.273
-1.275
-1.140
-57.894
-29.674
-51.708
-35.106
-30.492
-33.683
-25.745
6.71
7.09
7.92
8.63
8.92
9.07
9.14
241
35
134
-39
-89
-76
-137
Notes: Calculations assume that the t=0 Cr composition is dominantly Cr(VI), and that the Cr(lll) concentration is
one half the analytical detection limit (0.01 mg/L)
(a) = amorphous
(c) = crystalline
(d)= disordered, or freshly precipitated
107
-------
Appendix H: Reactive column mineral saturation indices
Elizabeth City reactive columns
Saturation indices calculated by MINTEQA2
Based on UW Water Quality Lab data
Distance along
column (cm) Ferrihydrite Goethite Cr(OH)3 (a) Cr(OH)3 (c) Calcite Dolomite Siderite (d) Mackinawite Magnesite Rhodochro Aragonite Amakinite SI02 (a) pH Eh (mV)
50MBSS at 27.9 PV
0
2.5
5
10
15
20
30
40
50
-0.634
-0.114
0.370
1.398
1.104
1.002
0.914
0.914
0.755
FV1 = 55 cm/d
5.076
5.596
6.080
7.108
6.814
6.712
6.624
6.624
6.465
-0.007
1.076
1.246
1.255
0.996
1.156
1.263
0.853
-0.813
-2.546
-1.463
-1.293
-1.284
-1.544
-1.383
-1.276
-1.686
-3.353
-2.033
-1.210
-1 .034
0.120
0.290
0.392
0.565
0.403
0.584
-3.963
-2.305
-1.964
0.355
0.734
0.966
1.384
1.121
1.522
-3.689
0.438
0.244
-3.345
-6.474
-3.437
-4.857
-7.915
-8.803
-64.316
-30.776
-33.167
-66.376
-89.520
-57.258
-68.489
-95.041
-99.594
-2.504
-1.670
-1.504
-0.339
-0.129
0.245
0.144
0.364
-1.715
-0.852
-0.852
-0.227
0.022
0.293
0.210
-0.156
-0.289
-2.187 -7.547
-1.364 -3.239
-1.189 -3.010
-0.035 -5.540
0.135 -8.311
0.238 -4.744
0.410 -6.027
0.249 -8.979
0.429 -9.563
-0.395 6.38
-0.532 6.90
-0.727 7.19
-1.454 8.31
-1.721 8.59
-1.767 8.92
-1.848 9.12
-1.883 9.12
-1.890 9.39
307
56
54
196
324
91
149
321
330
50MBSS at 34.4 PV
0
2.5
5
10
15
20
30
40
50
1.049
1.749
2.158
1.020
0.997
0.769
-0.018
0.546
0.686
6.759
7.459
7.868
6.730
6.707
6.479
5.692
6.256
6.396
0.707
1.323
-1.312
1.288
1.588
1.181
1.416
-0.084
1.211
-1.833
-1.216
-3.852
-1.252
-0.951
-1.359
-1.124
-2.624
-1.328
-1 .090
-0.845
-0.050
0.478
0.401
0.438
0.164
0.613
0.486
-2.067
-1.562
0.022
1.133
1.023
1.127
0.639
1.553
1.306
-6.345
0.157
-6.851
-5.723
-3.429
-1.620
-1.431
-1.389
-1.817
-95.235
-43.329
-102.174
-79.383
-57.221
-39.794
-28.872
-33.581
-36.126
-1.551
-1.291
-0.502
0.080
0.048
0.115
-0.099
0.366
0.246
-0.778
-0.609
-0.330
-0.559
-0.404
-0.068
-0.003
-0.139
-0.395
-1.244
-0.999
-0.204
0.324
0.247
0.283
0.010
0.458
0.332
-0.400 7.32
-0.595 7.41
-1.085 8.33
-1.542 8.88
-1.740 8.93
-1.798 8.94
-1.431 9.00
-1.832 9.24
-1.951 9.33
451
113
431
237
90
-25
-105
-88
-77
50MBSS at 53.5 PV
0
2.5
5
10
15
20
30
40
50
-0.453
0.816
-0.018
1.128
0.863
0.835
0.341
0.759
0.887
5.257
6.526
5.692
6.838
6.573
6.545
6.051
6.469
6.597
0.121
1.257
0.998
-0.080
1.374
1.607
-0.077
0.919
1.334
-2.418
-1.283
-1.541
-2.619
-1.166
-0.933
-2.617
-1.621
-1.205
-1.850
-1.424
-0.812
0.176
0.253
0.493
0.266
0.368
0.191
-3.584
-2.741
-1.510
0.489
0.728
1.249
0.849
1.099
0.752
-3.487
-0.047
0.297
-5.496
-1.856
-1.705
-1.428
-1.823
-3.788
-63.999
-38.822
-29.982
-81.733
-42.554
-41.548
-31.818
-38.110
-55.504
-2.308
-1.891
-1.272
-0.261
-0.099
0.182
0.009
0.157
-0.013
-1.477
-1.016
-0.666
-0.634
-0.763
-0.385
-0.252
-0.351
-0.489
-2.004
-1.578
-0.966
0.022
0.098
0.339
0.111
0.214
0.036
6.50
7.00
7.30
8.46
8.82
8.95
9.06
9.18
9.17
297
107
23
283
2
-14
-88
-53
61
108
-------
Appendix H: Reactive column mineral saturation indices
Elizabeth City reactive columns
Saturation indices calculated by MINTEQA2
Based on UW Water Quality Lab data
Distance along
column (cm) Ferrihydrite Goethite Cr(OH)3 (a) Cr(OH)3 (c) Calcite Dolomite Siderite (d) Mackinawite Magnesite Rhodochro Aragonite Amakinite SI02 (a) pH Eh (mV)
100MB at 24 PV
0
2.5
10
15
20
30
40
50
100MB at 29.2 PV
0
2.5
10
15
20
30
40
50
100MB at 46.6 PV
0
2.5
2.5
10
15
20
30
40
100MB at 79.2 PV
0
2.5
10
20
50
100MB, 98 PV
0
2.5
10
20
30
50
-0.491
-1.725
-0.801
0.707
0.146
-0.634
0.636
0.838
0.504
0.454
-0.023
0.636
0.695
0.603
0.386
0.280
-0.512
1.034
1.034
0.859
0.772
0.712
0.667
0.538
0.078
1.135
0.829
0.689
-7.967
0.966
0.980
0.536
0.695
-0.235
0.644
5.220
3.985
4.909
6.417
5.856
5.076
6.346
6.548
6.214
6.164
5.687
6.346
6.405
6.314
6.096
5.990
5.198
6.744
6.744
6.570
6.482
6.422
6.377
6.248
5.788
6.845
6.539
6.399
-2.257
6.676
6.691
6.246
6.405
5.475
6.354
FV1 = 43 cm/d
-0.142
1.505
-0.078
1.624
0.607
-0.079
0.793
0.997
0.005
1.885
1.331
1.248
1.419
1.472
1.449
0.890
0.215
1.102
-0.074
0.218
0.989
1.134
1.345
-0.098
FV2 = 24 cm/d
-0.060
3.454
-0.085
-0.100
-0.111
0.728
3.907
-0.127
1.597
1.466
-2.806
-2.682
-1.035
-2.617
-0.915
-1.932
-2.618
-1.747
-1.543
-2.535
-0.654
-1 .209
-1.292
-1.121
-1.067
-1.091
-1.649
-2.324
-1.437
-2.613
-2.322
-1.551
-1.405
-1.194
-2.637
-2.600
0.915
-2.625
-2.639
-2.650
-1.810
1.367
-2.667
-0.942
-1 .074
-5.346
-2.132
-0.520
0.380
0.462
0.366
0.162
0.393
0.146
-2.050
0.798
0.482
0.584
0.526
0.379
0.382
0.283
-1.673
0.470
0.473
0.497
0.388
0.471
0.499
0.371
-2.082
0.509
0.329
0.381
0.406
-1.017
0.322
0.618
0.118
0.293
0.350
-4.160
-0.938
1.116
1.344
1.175
0.769
1.230
0.590
-4.013
1.759
1.249
1.497
1.382
1.062
1.042
0.831
-3.239
1.042
1.046
1.307
1.120
1.296
1.357
1.091
-4.046
1.004
1.396
1.485
0.734
-1.902
0.873
1.581
0.524
0.841
0.881
-3.810
-0.158
-1.214
-4.029
-1.287
-1.264
-7.239
-2.413
-6.975
-1.292
-1.241
-1.748
-2.699
-2.249
-1.591
-1.556
-3.335
-4.904
-4.905
-3.819
-2.624
-2.414
-2.336
-1.631
-3.874
-5.648
-2.800
-2.421
-3.615
-3.260
-6.379
-4.268
-5.197
-1.230
-9.280
-67.637
-18.113
-21.475
-54.533
-26.457
-22.297
-81.627
-42.720
-102.532
-32.535
-26.281
-34.942
-42.496
-35.125
-27.592
-25.469
-61.839
-72.418
-72.420
-57.604
-43.548
-40.792
-39.306
-31.588
-72.653
-85.706
-48.998
-41.899
1.502
-67.301
-82.565
-54.038
-62.202
-22.777
-99.621
-2.603
-0.993
0.162
0.308
0.234
0.033
0.263
-0.130
-2.537
0.387
0.194
0.339
0.281
0.109
0.086
-0.027
-2.539
-0.079
0.493
0.529
-0.246
-1.460
-0.024
0.389
-0.168
-0.026
-0.044
-1.814
-0.596
-0.014
0.015
-0.222
-0.305
-0.142
-0.263
-1.756
-0.586
-0.107
-0.007
-0.206
-0.277
-0.272
-0.399
-1.739
0.604
-1.352
-1.338
-1.394
-0.642
-0.366
-1.330
-0.717
-0.656
-0.625
-2.286
-0.674
0.225
0.307
0.212
0.008
0.239
-0.009
-2.205
0.644
0.327
0.430
0.372
0.225
0.227
0.129
-2.236
0.354
0.174
0.227
0.252
-1.173
0.168
0.463
-0.036
0.138
0.196
-7.816
-3.113
-2.333
-4.583
-1.989
-2.272
-7.638
-3.214
-7.850
-7.894
-3.901
-3.194
-3.859
-6.233
-7.554
-4.624
-5.439
-1.914
-9.628
-0.396
-0.941
-1.918
-2.155
-2.074
-2.149
-2.168
-2.159
-0.396
-1.868
-2.133
-2.161
-2.050
-2.212
-2.060
-2.451
-0.421
-0.436
-1.835
-1.989
-1.886
-0.412
-0.491
-1.590
-2.421
-2.092
-2.137
6.26
7.60
9.10
9.46
9.36
9.12
9.56
9.20
6.39
9.22
9.24
9.40
9.46
9.54
9.54
9.56
6.60
8.84
8.84
9.22
9.34
9.42
9.48
9.44
6.33
8.41
9.26
9.46
9.57
7.37
8.98
9.69
9.48
9.35
9.55
338
-86
-165
33
-145
-160
201
-24
561
-94
-139
-90
-45
-99
-149
-165
276
195
195
71
-29
-53
-67
-115
369
312
12
-49
-521
266
250
12
81
-171
318
109
-------
Appendix H: Reactive column mineral saturation indices
Elizabeth City reactive columns
Saturation indices calculated by MINTEQA2
Based on UW Water Quality Lab data
Distance along
column (cm) Ferrihydrite
50PLSSAQ at 5.2 PV
0 -0.842
2.5 -0.615
5 0.377
10 -0.286
15 -0.311
20 0.838
30 -0.363
40 0.558
50 0.889
50PLSSAQ at 30.3 PV
0 0.213
10 0.460
15 0.531
20 0.577
30 -0.208
40 -6.086
50 0.644
50PLSSAQ at 66.2 PV
0 -0.839
2.5 2.386
5 0.996
10 0.676
15 0.638
20 -0.033
30 0.080
40 0.623
50 0.878
50PLSSAQat116.8PV
0 -0.107
2.5 0.678
10 0.887
20 -6.943
50 0.209
50PLSSAQ, 135.3 PV
0 1 .044
2.5 1.106
10 0.775
20 -2.379
30 0.762
50 0.782
48PL/52AQ at 78.4 PV
0 1.037
2.5 1.080
5 1.078
10 0.935
15 0.734
20 0.775
30 0.473
40 0.439
50 0.390
Goethite
4.868
5.095
6.087
5.424
5.399
6.548
5.347
6.268
6.599
5.923
6.170
6.241
6.287
5.502
-0.374
6.354
4.872
8.096
6.706
6.386
6.348
5.677
5.790
6.333
6.588
5.603
6.388
6.598
-1.232
5.919
6.754
6.817
6.485
3.331
6.472
6.492
6.747
6.790
6.788
6.645
6.444
6.485
6.183
6.149
6.100
Cr(OH)3 (a) Cr(OH)3 (c) Calcite
FV1 = 79 cm/d
0.420
1.588
-0.077
1.551
1.433
1.218
0.765
1.389
1.317
0.079
1.964
1.704
1.557
1.479
2.756
1.800
0.197
1.079
1.777
1.503
1.795
1.340
1.647
1.093
1.095
FV2 = 36 cm/d
-0.129
-0.257
-0.081
-0.092
-0.085
0.720
3.348
-0.179
-0.051
1.487
-1.969
FV1 = 71 cm/d
0.716
3.720
1.650
1.754
-0.096
1.465
-0.119
1.455
-0.323
-2.119
-0.951
-2.616
-0.988
-1.106
-1.322
-1.774
-1.151
-1.222
-2.460
-0.576
-0.835
-0.982
-1.061
0.216
-0.739
-2.342
-1.460
-0.763
-1.037
-0.745
-1.199
-0.893
-1.447
-1.444
-2.668
-2.796
-2.620
-2.632
-2.625
-1.820
0.809
-2.719
-2.590
-1.053
-4.508
-1.824
1.180
-0.889
-0.785
-2.636
-1.075
-2.658
-1.085
-2.862
-1.511
0.283
0.614
0.684
0.875
0.744
0.514
0.427
0.559
-2.051
0.430
0.593
0.664
0.682
2.520
0.689
-1.816
-0.016
0.651
0.715
0.716
0.638
0.670
0.710
0.741
-2.216
-0.706
0.721
0.795
0.677
-1.002
0.263
0.657
0.755
0.677
0.545
-1.050
0.240
0.242
0.631
0.672
0.824
0.927
0.689
0.721
Dolomite
-2.927
0.665
1.330
1.462
1.811
1.515
0.964
0.709
0.833
-3.998
0.969
1.287
1.424
1.438
5.124
1.432
-3.532
0.071
1.405
1.532
1.526
1.365
1.435
1.509
1.586
-4.315
-1.301
1.768
1.994
1.530
-1.886
0.668
1.475
1.635
1.447
1.180
-1.999
0.594
0.560
1.343
1.354
1.591
1.625
0.972
0.758
Siderite (d)
-3.150
-1.438
-1.245
-1.452
-1.090
-2.435
-1.291
-1.706
-3.212
-3.933
-1.513
-1.386
-1.400
-1.191
-2.402
-1.502
-3.440
-0.611
-4.002
-1.472
-1.381
-1.215
-1.221
-1.515
-2.764
-3.943
-0.547
-5.697
-3.164
-1.190
-4.082
-6.012
-7.728
-1.025
-6.146
-8.604
-4.025
-6.436
-5.722
-6.602
-3.603
-6.477
-1.666
-3.881
-9.235
Mackinaw ite
-55.102
-28.593
-31 .962
-26.700
-24.308
-44.961
-24.075
-31.874
-51.499
-71.785
-37.336
-36.678
-35.956
-27.026
1.740
-35.705
-59.306
-50.500
-63.961
-37.327
-38.034
-30.294
-29.658
-34.833
-49.475
-71.403
-42.243
-76.537
1.387
-29.090
-75.392
-85.437
-90.157
-6.546
-75.998
-97.742
-74.463
-86.660
-80.315
-84.922
-51.466
-80.235
-31.547
-47.858
-96.377
Magnesite Rhodochro Aragonite Amakinite SI02 (a)
-1.991
-0.192
0.141
0.204
0.362
0.197
-0.125
-0.293
-0.300
-2.522
-0.035
0.121
0.186
0.183
2.030
0.169
-2.290
-0.487
0.179
0.243
0.237
0.153
0.191
0.225
0.271
-2.673
-1.169
0.473
0.625
0.279
-1.460
-0.169
0.243
0.306
0.196
0.060
-1.524
-0.220
-0.256
0.138
0.108
0.192
0.125
-0.292
-0.536
-1.203
-0.085
0.107
-0.263
-0.355
-0.433
-0.555
-0.374
-0.492
-1.739
0.014
0.276
0.199
-0.261
1.074
-0.441
-1.486
-0.174
-0.718
-0.551
-0.141
0.059
-0.175
-0.312
-0.422
-0.658
-0.249
-1.378
-0.774
-0.985
-1.161
-0.710
-0.808
-0.925
-1.007
-0.894
-1.268
-1.146
-1.252
-1.265
-1.666
0.128
0.460
0.530
0.721
0.589
0.360
0.273
0.404
-2.205
0.275
0.438
0.509
0.527
2.366
0.535
-1.971
-0.170
0.497
0.561
0.561
0.483
0.516
0.555
0.586
-2.370
-0.860
0.566
0.640
0.523
-1.158
0.108
0.503
0.600
0.522
0.391
-1.206
0.085
0.088
0.477
0.518
0.670
0.772
0.535
0.566
-6.602
-3.049
-2.468
-2.433
-2.175
-3.457
-2.220
-2.231
-4.153
-7.604
-3.038
-2.878
-2.728
-2.424
-4.516
-2.612
-7.889
-3.695
-6.928
-4.093
-2.238
-7.062
-7.852
-8.500
-2.034
-6.937
-9.341
-6.974
-7.988
-7.280
-7.838
-4.224
-7.402
-2.189
-3.983
-9.395
-0.405
-1 .426
-1.603
-1.696
-1.667
-1.653
-1.552
-1.843
-1.840
-0.396
-1.782
-1.711
-1.694
-1.693
-0.523
-1.693
-0.422
-0.499
-1.713
-1.769
-1.750
-0.399
-0.521
-1.618
-1.553
-1.483
-1.882
-0.408
-0.482
-0.750
-1.827
-2.037
-1.852
-1.736
-1.926
-1.785
PH
6.84
8.68
9.04
9.20
9.26
9.22
9.15
9.31
9.16
6.46
8.80
8.90
9.02
9.08
9.14
9.16
6.58
8.18
8.94
9.06
8.95
8.96
9.08
9.22
9.17
6.27
7.41
9.17
9.37
9.26
7.35
8.58
9.36
9.30
9.38
9.35
7.34
8.69
8.70
9.08
9.42
9.36
9.63
9.81
9.87
Eh (mV)
213
-88
-85
-135
-155
-11
-149
-104
36
355
-33
-44
-57
-124
-348
-68
259
109
133
-50
-38
-93
-105
-78
22
364
99
197
-436
-121
320
298
271
-286
178
321
315
298
256
258
16
207
-130
-38
271
110
-------
Appendix I: Analytical laboratory procedures
Cations
Ion analyses of the lab treatability samples were performed at the Water Quality Lab (WQL), University of Waterloo.
Analytical charge balance errors of < 5% were regularly achieved.
Cations were determined using an Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES) instrument
(Thermo Jarrell Ash IRIS Plasma Spectrometer). The instrument conditions were set according to the manufacturer's
instructions. Prepared mixed standards, with element concentrations of 10 mg/L, were run after every five to ten
samples. A commercial mixed standard was used to verify the prepared standards on a regular basis. Samples were run
in duplicate and were usually diluted due to the small sample volume available from the batch and column tests. Sample
analyses were repeated if the relative difference on the prepared standards exceeded 5%.
Anions
Anions including Br, Cl and SO4 were analyzed using a Dionex System 2000 Ion Chromatograph (1C) or a Waters 1C with
a conductivity detector. The Dionex 1C was capable of running 55 samples per day plus standards and the Waters 1C
could run 33 samples per day plus standards. Samples were run a minimum of two times and at different dilution ratios
to verify sample reproducibility and linearity of the calibration.
The 1C instrument was evaluated daily for calibration linearity. Three sets of standards were run at regular intervals:
1. A prepared mixed standard containing 2 mg/L Cl, 5 mg/L Br, 10 mg/L SO4, 5 mg/L NO3 and 10 mg/L PO4
2. an additional prepared mixed standard containing 0.4 mg/L Cl, 1 mg/L Br, 2 mg/L SO 1 mg/L NO and 2
mg/L P04
3. a commercial setpoint mixed standard at ion concentrations similar to standard #1
The two in-house standards were run after every eleven samples. The setpoint standard was run at least twice per day
as were blanks. Sample analyses were repeated if the relative difference on the setpoint standard exceeded 5%.
111
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