Ore Knob Mine Tailings Pile C Watershed Restoration Plan by fdh56iuoui

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									        Ore Knob Mine Tailings Pile –
         Watershed Restoration Plan




                         Prepared by:


           Robert C. Borden and Mehnroosh Behrooz

Department of Civil, Construction and Environmental Engineering
                North Carolina State University
                       Campus Box 7908
                      Raleigh, NC 27606




                      January 1, 2009
                                 ACKNOWLEDGEMENTS

We gratefully acknowledge the financial and technical support provided by the U. S. Environmental
Protection Agency and the North Carolina Division of Water Quality 319 Program. Special thanks also to
Mr. Russell Reeves for providing access to his property for this research.




                                                  i
                                               TABLE OF CONTENTS
LIST OF TABLES.............................................................................................................................iii

LIST OF FIGURES ...........................................................................................................................iii

1.0                  SCOPE OF THIS PLAN............................................................................................1
2.0                  SOURCE IDENTIFICATION...................................................................................1
2.1                  Geology, Site History, and Physical Characteristics .................................................1
2.2                  Chemistry of Acid Mine Drainage.............................................................................1
2.3                  History of Site Restoration Activities ........................................................................2
2.4                  Site Hydrology ..........................................................................................................3
2.5                  Pollutant Budgets .......................................................................................................6
2.6                  Summary ....................................................................................................................8
3.0                  MANAGEMENT APPROACHES............................................................................10
3.1                  AMD Treatment Technologies ..................................................................................10
3.1.1                Dry Cap Installation and Surface Water Diversion ...................................................10
3.1.2                Wet Cap Installation ..................................................................................................11
3.1.3                Passive Neutralization Technologies ........................................................................11
3.1.4                Active Neutralization Technologies .........................................................................12
3.1.5                Aerobic Ponds and Wetlands .....................................................................................12
3.1.6                Anaerobic Bioreactors ...............................................................................................13
3.2                  Potential Treatment Alternatives ...............................................................................13
3.2.1                Active Treatment Only ..............................................................................................14
3.2.2                Surface Water Diversion, Dry Cap Installation and Passive Neutralization .............14
3.2.3                Wet Cap Installation and Passive Neutralization.......................................................15
3.3                  Management Alternatives Summary..........................................................................16
4.0                  REQUIRED POLLUTANT LOAD REDUCTIONS ................................................16
5.0                  TECHNICAL AND FINANCIAL SUPPORT REQUIRED.....................................16
6.0                  PUBLIC EDUCATION .............................................................................................17
7.0                  SCHEDULE AND MILESTONES ...........................................................................17
8.0                  PERFORMANCE CRITERIA ..................................................................................18
9.0                  MONITORING PROGRAM .....................................................................................19
9.1                  Baseline Monitoring Program....................................................................................19
9.2                  Treatment System Monitoring Program ....................................................................19
9.3                  Analytical Methods....................................................................................................20
9.4                  Qualitative Monitoring Program................................................................................20
10.0                 REFERENCES ..........................................................................................................20




                                                                     ii
                                          LIST OF TABLES
Table 2.1    Characteristics of watersheds contributing flow to the tailings pile ........................6
Table 2.2    Average parameter values in surface water monitoring stations within
             the Peak Creek watershed. .....................................................................................8
Table 2.3    Average dissolved pollutant budget for Ore Knob Branch watershed. .................9




                                         LIST OF FIGURES
Figure 2.1   Topographic map of Ore Knob Branch watershed
             (From Laurel Springs NC Quadrangle, 1984) .........................................................4
Figure 2.2   Aerial photograph of tailings pile showing watershed boundary and location
             where four primary tributaries enter tailings pile (A, B, C and D). .......................5
Figure 2.3   Surface water monitoring locations directly adjoining the tailings pile
             and within the Peak Creek watershed. .....................................................................7




                                                         iii
                     Ore Knob Mine Watershed Restoration Plan
1.0    SCOPE OF THIS PLAN

This plan has been developed as the first step in restoration of Ore Knob Branch and Peak Creek
in the New River watershed of North Carolina. Both streams are included in the North Carolina
303(d) list and are impaired due to release of acid mine drainage and acidic, metal rich sediments
from a former copper/zinc mine on Ore Knob Branch. The impaired waters of Ore Knob Branch
then discharge into Peak Creek which eventually flows into the South Fork of the New River.

2.0    SOURCE IDENTIFICATION

Ore Knob Branch (0.9 mi.) and Peak Creek (2.9 mi.) within the New River Basin are listed as
303(d) impaired waters (Category 5) due to discharge of acid mine drainage with high iron,
copper and zinc and low pH from a former copper/zinc mine and tailings pile located near Ore
Knob. Ore Knob Branch and Peak Creek (below the mine) regularly receive a poor
bioclassification.

2.1    Geology, Site History, and Physical Characteristics

Ore Knob, near Jefferson, North Carolina, is the location of a massive fissure-type sulfide
deposit. The steeply dipping vein varies from 8 to 18 ft thick and extends over 4000 feet long
along the contact between the Carolina gneiss and the adjoining muscovite – biotite schist.
Pyrrhotite, pyrite, chalcopyrite, quartz, biotite and amphiboles are the principal minerals in the
vein (Kinkel 1967; Rankin and Stuckey 1943). The bedrock underlying the tailings
impoundment is the Carolina gneiss which consists of highly metamorphosed alternating
muscovite schist and quartz-biotite granitic gneisses.

The Ore Knob deposit was discovered before the Civil War. Between 1871 and 1883, it was
worked intensively, yielding twenty-five million lbs of copper ore from 11 openings and one
main shaft. Further mining activity was limited until the mine was reopened in the late 1950s.
From 1957 to 1962, Appalachian Sulphides, Inc. operated a mine and processing facility at the
site. The extracted ore was ground in a processing facility located in the Little Peak Creek
watershed. Copper, gold, and silver were extracted using a froth flotation and cyanide leaching
process. Most waste tailings were pumped to a large tailings impoundment located on Ore Knob
Branch. However, a portion of the tailings were dumped in a small hollow adjacent to the
processing facility. Acid mine drainage from the processing area and associated waste piles has
impaired water quality in Little Peak Creek. However, water quality conditions in the Little
Peak Creek are outside the scope of this plan.

2.2    Chemistry of Acid Mine Drainage

Waste rock and mill tailings produced from mining operations often contain an abundance of
sulfide minerals including pyrite (FeS2), pyrrhotite (FexSx), chalcocite (Cu2S), chalcopyrite
(CuFeS2), galena (PbS), millerite (NiS), and sphalerite (ZnS). These wastes are often deposited
in impoundments or piles. Exposure of sulfide minerals in the piles to atmospheric oxygen (O2),

                                                 1
and rain percolation through the tailings ultimately leads to the oxidation of the tailings and
formation of acid mine drainage (AMD). AMD is low-pH water that typically contains high
concentrations of SO4, ferrous iron (Fe+2), ferric iron (Fe+3), and other metals. A variety of other
metals may also be present in the tailings and can be mobilized as a result of sulfide oxidation or
due to the low pH of the AMD. Within the tailings pile, the pH may be near neutral. However,
if AMD containing dissolved Fe+2 discharges to the surface and reacts with oxygen, a solid ferric
hydroxide precipitate is produced and free protons (H+) are released according to the reaction.

                          Fe2+ + ¼ O2 + 2½ H2O → Fe(OH)3 (solid) + 2 H+

Primary factors controlling the amount and strength of AMD are the relative amounts of sulfide
minerals, water and oxygen. For sulfides to oxidize, both oxygen and water must be present.
Water serves not only as a reactant, but also as a reaction medium and a product-transport
solvent. The rate of sulfide oxidation is controlled by the availability of sulphides within the
waste rock particles and the availability of oxygen at the mineral grain surfaces. Gaseous oxygen
can be transported deep into the pile interior by thermal or wind-induced convective transport
and molecular diffusion. Within highly stratified or less permeable piles, diffusive transport may
dominate and oxygen transport will be controlled by the moisture-dependent bulk diffusion rates.
As the diffusion rate of oxygen in water is four orders of magnitude less than in air, the rate of
oxygen diffusion will vary throughout the pile depending on the local water content. In water
saturated piles, oxygen transport is minimal resulting in little AMD production. In unsaturated
piles, there is a complex relationship between particle size and oxidation rate. Fine-grained
materials are oxidized more rapidly in the presence of oxygen (Janzen et al. 2000). However,
fine grained layers can also act as moisture-retention barriers to oxygen diffusion, whereas
coarser layers can be dryer and can allow rapid oxygen penetration.

2.3       History of Site Restoration Activities

In the early 1990’s, the State of North Carolina completed a variety of different restoration
activities at the site with the objective of restoring the water quality in Ore Knob Branch and
Peak Creek. These restoration activities were conducted under a grant from the U.S.
Environmental Protection Agency pursuant to Section 319 of the Clean Water Act (Ore Knob
Reclamation Project, Section 319 Grant Program, NC Division of Water Quality). Restoration
activities conducted under this program included the following:

      •   Installation of anoxic limestone drains (ALDs) to treat flow from the mine adits before it
          enters the large tailings pile. The ALDs were effective in increasing the pH of these
          seeps to around 5 or better. However, water released from the ALDs flows back into the
          tailings impoundment where it is re-contaminated. As such, the ALDs did not
          significantly improve water in the downstream surface water.
      •   Construction of an artificial wetland at the head of the tailings impound as a retention
          area for precipitation of oxidized metals. This area was also seeded with wetland species.
      •   The tailings impoundment was reshaped to a safer slope and revegetated to reduce
          erosion. However, the revegetation was not successful deep gullies formed in the
          embankment face.


                                                   2
      •   The tailings surface was revegetated through addition of dry municipal sludge and lime
          as soil conditioners to decrease the acidity of the tailings material and provide nutrients
          that would support vegetation. These efforts were initially successful in establishing a
          vegetative cover. However, the grass died off after a few years and most of the tailing
          surface is devoid of vegetation.
      •   The water level of the pond below the tailings impoundment was lowered to minimize
          acidic seeps from the face of the dam as groundwater from the upper pond flowed
          through the tailings area. Wetland species seed was sown in the area below the tailings
          impoundment and around the pond.

Overall, these efforts did not substantially improve water quality conditions in Ore Knob Branch
or Peak Creek. A 1996 Memo from the NC Division of Environmental Management, Biological
Assessment Group concluded “efforts and money expended to lessen impact from the abandoned
Ore Knob copper mine have produced no demonstrable improvement in water quality of nearby
Peak Creek and Little Peak Creek. Drainage from the mine continues to eliminate most of the
stream fauna in three miles of Peak Creek and two miles of Little Peak Creek” (Lenat, 1996). In
2005, Ore Knob Branch (0.9 mi.) and Peak Creek (2.9 mi.) within the New River Basin were
classified as ‘Not Supporting’ due to discharge of acid mine drainage with high iron, copper and
zinc and low pH from a former copper/zinc mine located near Ore Knob (NCDENR 2005).

In 2003, the US Army Corps of Engineers (USACE) completed an initial planning study to
develop alternatives for restoration of the Ore Knob area under Section 206 of the Water
Resources Development Act of 1996 (PL 104-3031) (USACE 2003). The purpose of this project
was to restore the aquatic ecosystem of those reaches of stream that are impacted by acid mine
drainage (AMD) from the Ore Knob mine. Major recommendations of this study included (1)
re-grading and revegetation of the tailings impoundment; (2) construction of an open limestone
channel and aerobic wetlands upgradient of the tailings impoundment; (3) stabilization of the
embankment face by brush-layering followed by revegetation, and (4) reconstruction of an
existing drainage pipe to reduce contact between water and the tailings. Funding to complete
this work was to be provided jointly by the federal government through the USACE and the
North Carolina Clean Water Management Trust Funds. Unfortunately, the federal government
has not been able to provide their portion of the funding and the planned work has not yet been
completed.

2.4       Site Hydrology

A topographic map of the Ore Knob Branch watershed is shown in Figure 2.1. At the point
where Ore Knob Branch joins Peak Creek, the watershed drainage area is 0.5 square miles. The
mine shaft, multiple mine adits and the former tailings impoundment are all located in the upper
end of the watershed.




                                                    3
Figure 2.1    Topographic map of Ore Knob Branch watershed
              (From Laurel Springs NC Quadrangle, 1984)

The tailings pile covers approximately 22 acres with a maximum tailings depth of approximately
70 ft at the center of the embankment face. Available information suggests that the
impoundment was constructed by first installing a small dam across Ore Knob Branch at the
approximate location of the existing embankment face. A drop-inlet and 24-inch reinforced
concrete pipe (RCP) were installed to provide drainage. Over time, the embankment forming the
dam was progressively raised to provide additional storage for the accumulated tailings. The
                                              4
drop-inlet is located about 1,600 feet from the face of the tailings. However, the outlet of the
pipe is currently covered by tailings, probably as a result of slope failure on the tailings
embankment face. The surface elevation near the embankment face is approximately 20 ft
higher than near the drop-inlet causing water to pool in this area, forming a small wetland.

Figure 2.2 shows an aerial photograph of the tailings pile and watershed that contributes flow to
the pile. Most of the watershed is wooded. However, a portion of the watershed was logged in
the late 1990s. There are four small tributaries that enter the tailings pile at locations A, B, C and
D. During storm events, surface runoff collects in shallow pools near locations A, B, C and D.
The water level in these pools varies in response to seasonal trends in precipitation.




Figure 2.2     Aerial photograph of tailings pile showing watershed boundary and location
               where four primary tributaries enter tailings pile (A, B, C and D).

                                                  5
The estimated location of the 24 inch concrete drainage pipe that passes through the tailings pile
is also shown in Figure 2.2. In 2007, the water level in the pool at location A was high and the
drainage pipe inlet was submerged. However, the water level gradually declined over 2008 due
to an extended drought and the drainage pipe intake was exposed. During low water periods, a
small amount of flow can be seen entering the drainage pipe. However, the downstream end of
the pipe is not visible and there is no obvious discharge point. It is not clear whether the pipe has
collapsed or the downstream end of the pipe is buried.

Essentially all runoff from tributaries B, C, D, and the tailings pile surface infiltrates into the
tailings pile and eventually discharges as a series of springs or seeps on the downstream
embankment face. Much of the inflow from tributary A is also believed to infiltrate into the
tailings pile. However, a portion of the flow may be carried into the pile by the drainage pipe.
How far the water is carried into the pile before it is released from the pipe into the tailings pile
is unknown.

Estimated average annual flows for each of the tributaries and undifferentiated portions of the
watershed are shown in Table 2.1. These estimates were developed assuming the average
discharge per acre of this watershed is 28.3 inches per year. The average discharge of the South
Fork of the New River near Jefferson, NC (USGS 03161000) from 1925 and 2007 was 427 cubic
feet per second (cfs) or 28.3 inches per year. The actual discharge associated with the tailings
pile surface may be somewhat higher than the estimated value because: (1) evapotranspiration
will be limited by the absence of vegetation; and (2) the high infiltration capacity of the tailings.
Additional information on the tailings pile hydrology, groundwater flow and infiltration
characteristics are presented in Borden and Behrooz (2008).

Table 2.1      Characteristics of watersheds contributing flow to the tailings pile
                Subarea                      Area          Average Discharge
                                             Acres        cubic feet      gallons
                                                           per year     per minute
                Tailings Pile Surface          22         2,260,000          32
                Tributary A                    73         7,499,000         107
                Tributary B                    25         2,568,000          37
                Tributary C                    20         2,054,000          29
                Tributary D                     8          822,100           12
                Undifferentiated Areas         11         1,130,000          16
                Total                         159        16,334,000         232


2.5    Pollutant Budgets

Borden and Behrooz (2008) present the results of a multi-year monitoring study to identify the
major sources of pollution in the Ore Knob Branch watershed. Major results from this work are
presented here. Sampling stations monitored by Borden and Behrooz (2008) are shown in Figure
2.3.



                                                  6
Figure 2.3     Surface water monitoring locations directly adjoining the tailings pile and within
               the Peak Creek watershed.

Average values for each of the monitored surface water parameters are presented in Table 2.2.
Table 2.2 also includes 15A NCAC 2B standards for freshwater aquatic life for comparison. pH
was well below the surface water quality standard of 6 in all sampling stations within the Ore
Knob Branch watershed. The only station that met the pH standard was SW-8 which is a
background station not impacted by the mine. Dissolved iron, sulfate and hot acidity
concentrations discharging from the tailings pile (SW-4 and SW-5) are much higher than water
entering the pile, indicating most acidity is produced within the pile. Dissolved iron and sulfate
levels in SW-1 are significantly higher than in SW-3 indicating the upstream mine and adits do
contribute substantial amounts of AMD.

Surface water discharging from the tailings pile (SW-4 and SW-5) contains extremely high
concentrations of Fe, SO4 and acidity. As this water migrates down stream along Ore Knob
Branch to SW-7, the pH decreases to 3.1, presumably due to oxidation of Fe+2 to Fe(OH)3 and
H+. At the point where Ore Knob Branch discharges into Peak Creek (SW-7), the stream still
carries 285 mg/L acidity. Average Cu concentrations entering the tailings pile from the upstream
watershed were very high (1-2 orders of magnitude above standard). Cu concentrations
discharging from the tailings pile were somewhat lower, but still over 40 times the surface water
standard. There was only a small decline in Cu during transport downstream through Ore Knob
Branch, indicating little Cu attenuation other than dilution. Cu concentrations in Peak Creek just
prior to discharge to the New River were near the analytical detection limit (0.05 mg/L) obtained
in this project. Zn concentrations entering the pile were high and increased due to AMD
production within the pile.


                                                7
Table 2.2         Average parameter values in surface water monitoring stations within the Peak
                  Creek watershed.
                                NC
                            Freshwater
                             Standard     SW-1        SW-3        SW-4         SW-5       SW-7        SW-8        SW-9
      Redox Pot. (mV)            -            535         490          510         605        593         430         411
      Field pH                  6-9          4.04        3.78         3.82        3.18       3.09        7.30        5.63
      Temp. (oC)                 -              16          16           16         17          18          16         16
      DO (mg/L)                 5.0            3.6         3.1          1.1       10.6         7.4         6.8         5.2
      Lab. pH                    -           3.74        3.30         3.93        3.65       3.82        6.93        5.65
      Acidity (mg/L)             -            170         105        1996          928        285           24           9
      Alkalinity (mg/L)          -               2           0            0          0           0          15           2
      Diss. Fe (mg/L)           1.0            62          12       1330           408          65           0           2
      Diss. Mn (mg/L)            -               1           0            8          4           2           0           0
      Diss. Al (mg/L)            -           0.96        2.07       41.29         9.80       5.19        0.12        0.22
      Diss. Ca (mg/L)            -             43           34         233         160          64           4           6
      Diss. K (mg/L)             -              10           8           29         17           9           2           2
      Diss. Mg (mg/L)            -               6           1           55         26           9           1           2
      Diss. Na (mg/L)            -               4           2            5          4           3           3           2
      Diss. Cu (mg/L)          0.007         0.54        0.29         0.37        0.28       0.21        0.05        0.05
      Diss. Zn (mg/L)          0.050         0.66        0.22        3.43         1.37       0.57        0.09        0.09
      Diss. Cl (mg/L)           230      <2.5        <2.5        <2.5         <2.5       <2.5        <3.5        <3.5
      Diss. Si (mg/L)            -              12          10           13         15          11           5           5
      Diss. Br (mg/L)            -       <2.5        <2.5        <2.5         <2.5       <2.5        <2.5        <2.5
      Diss. NO2 (mg/L)           -       <2.5        <2.5        <2.5         <2.5       <2.5        <2.5        <2.5
      Diss. NO3 (mg/L)           -       <2.5        <2.5        <2.5         <2.5       <2.5        <2.5        <2.5
      Diss. PO4 (mg/L)           -       <2.5        <2.5        <2.5         <2.5       <2.5        <2.5        <2.5
      Diss. SO4 (mg/L)           -            275         141       3674         1547         619          15          27
      Tot. S (mg/L)              -              91          60       1141          475        187            1           8



2.6      Summary

The primary pollutant sources within the Ore Knob Branch watershed are believed to be: (a)
erosion of the tailings pile embankment face; (b) adits that release AMD from the former
underground mine upstream of the tailings impoundment; and (c) AMD generated within the
tailings pile.

Under current conditions, there is no water induced erosion from the tailing pile surface, since
there is minimal surface water discharge from the tailings pile surface. There is a potential for
current erosion of the embankment face and there is visible evidence of large gullies forming in
the past. However, a hardpan has developed on much of the embankment face and appears to
reduce surface erosion. Given the high uncertainty in the current erodibility of the embankment
soils, accurate estimates of pollutant loss associated with soil erosion from the embankment face
cannot be developed.

Table 2.3 shows a dissolved pollutant budget for the tailings pile and Ore Knob Branch that was
developed based on measured concentrations in two influent tributaries (SW-1 and SW-3), Ore
Knob Branch immediately downstream from the tailings pile (SW-5) and at the downstream end
of Ore Knob Branch (SW-7), just upstream of where it joins Peak Creek. Annual flow rates
were estimated from the long-term average flow rates of the South Fork of the New River near
                                                         8
Jefferson, NC and the watershed drainage area (see Table 2.1). Pollutant concentrations in SW-3
were assumed to be representative of areas not directly impacted by the mine (tributaries B, C, D
and the undifferentiated areas). SW-5 was assumed to be representative of the total load
discharging from the tailings pile.

Table 2.3        Average dissolved pollutant budget for Ore Knob Branch watershed.

Units                    Units   Acidity    Fe           SO4       Mn      Al       Cu       Zn
         Ave. Conc.      mg/L        170        62          275     1.17    0.96     0.54     0.66
SW-1
         Load            Kg/yr    36,117    13,059       58,260      248      203     115      141
         Ave. Conc.      mg/L        105        12          141     0.20    2.07     0.29     0.22
SW-3
         Load            Kg/yr    19,535     2,252       26,305       37      385      54       41
Total In Load            Kg/yr    55,652    15,311       84,565      285      588     169      182

            Ave. Conc.   mg/L        928       408          1547    3.87    9.80     0.28      1.37
SW-5
            Load         Kg/yr   428,802   188,616       714,913   1,787   4,529     129       635

            Ave. Conc.   mg/L        285        65           619    1.70    5.19     0.21      0.57
SW-7
            Load         Kg/yr   265,320    60,758       576,436   1,584   4,828     196       532

The pollutant budget presented in Table 2.3 shows that the large majority of the acidity, Fe, SO4,
Mn, Al and Zn originates within the tailings pile. Fe+2 and associated acidity are produced in the
unsaturated zone near the tailings pile surface where atmospheric oxygen diffuses into the pile
and reacts with sulfide minerals and water. The Fe+2 is then transported to the water table with
infiltrating rain water and eventually transported out of the tailings pile where it reacts with
oxygen, forming Fe(OH)3 and H+. The estimated Cu load discharging from the pile is somewhat
lower than entering the pile, indicating the pile might remove some Cu. However, Cu
concentrations in the pile discharge are still 40 times surface water standards.

Most pollutants appeared to be transported conservatively through Ore Knob Branch with
essentially no removal. For example, the ratios of total pollutant load discharging from Ore
Knob branch at SW-7 divided by the load entering from the tailings pile at SW-5 were between
81% and 107% for SO4, Mn, Al, and Zn. Some Fe and acidity appear to be removed,
presumably due to sedimentation of ferrihydrite within the riparian zone. A Student’s T test
analysis (1-tail, paired) indicates the total load released from SW-5 was significantly greater than
from SW-7 for Fe (α = 0.01) and acidity (α =0.05). It is not known whether this material is
permanently removed from the stream, or may be resuspended during high flow events. The
total load of Cu discharging from Ore Knob Branch was estimated to be 151% of the Cu entering
from the tailings pile. However, the Cu loads from SW-5 and SW-7 were not statistically
different (α =0.14).




                                                     9
3.0     MANAGEMENT APPROACHES

The loading analysis presented in Table 2.3 indicates that the largest source of SO4, Fe+2 and
acidity to the Ore Knob Branch is oxidation of iron rich tailings immediately below the tailings
pile surface. Some particulate material will also be generated through erosion of the
embankment face. However, the relative importance of erosion is unknown given the hardpan
that has developed on much of the embankment face. High concentrations of dissolved copper
(Cu) and zinc (Zn) are released from both the upstream watershed and the tailings pile. Cu and
Zn are toxic to aquatic life and are transported downstream through Ore Knob Branch with little
attenuation. Restoration of aquatic life to Ore Knob Branch will require control of both: (a)
acidity released from the Ore Knob tailings pile; and (b) Cu and Zn released from the upstream
watershed and tailings pile.


3.1     AMD Treatment Technologies

There are a variety of different technologies available to manage and/or treat AMD including use
of dry and wet covers to reduce AMD production, passive and active neutralization systems, and
bioreactors. Short descriptions of potential technologies are presented below along with a brief
discussion of their potential application to Ore Knob.

3.1.1   Dry Cap Installation and Surface Water Diversion

AMD production from the tailings pile could be significantly reduced by constructing a dry cap
over the tailings pile surface combined with diversion of surface water away from the tailings
pile.

A variety of low permeability caps have been used to limit infiltration and oxygen transport into
tailings piles including clay, synthetics and combinations of these materials. The design,
construction and costs for these caps are similar to those used for sanitary landfills (URS
Corporation 2003, PIRAMID 2003). The caps are typically composed of multiple layers
including: (a) a low permeability layer on top of the waste material; (b) a drainage layer placed
on top of the low-permeability layer to promote lateral drainage and reduce infiltration; (c) two
feet of fill to protect the cap; and (d) topsoil and a vegetative cover to control erosion. The low
permeability layer may be composed of a geomembrane, compacted clay layer, or geosynthetic
clay liner. Construction costs for this type of cap typically vary from $100,000 to $500,000 per
acre. Hauser et al. (1999) report an average construction cost of for $446,000 per acre for eight
US Air Force landfills varying in size from 7 to 30 acres.

Diversion of surface water and ground water would also be required to prevent discharge of
concentrated AMD from the pile. Surface and ground water diversion will be somewhat
complicated since the tailings pile is located at the bottom of a 159 acre natural valley. Any rain
falling in the valley, not removed by evapotranspiration, naturally flows through the tailings pile.

Surface and ground water could be prevented from entering the tailings pile by constructing
either: (a) diversion channels in native material around both sides of the tailings pile; or (b) a

                                                  10
network of channels over the surface of the tailings pile. In either case, the channels would need
to have a high flow capacity to transport water during large storm events. Construction of the
channels in native material would be complicated by the presence of shallow bedrock at many
locations. Any channels constructed on the tailings pile surface would need to be lined with non-
erodible material to protect the underlying cap.

3.1.2   Wet Cap Installation

Release of Fe+2 and acidity to Ore Knob Branch could also be reduced by limiting the transport
of oxygen into the tailings pile by inundating or covering waste material with water. The water
cover reduces AMD production by limiting the availability of oxygen since oxygen diffusion
through water is approximately 10,000 times lower than through air (MEND 1996, PIRAMID
2003). Wet covers are commonly used at active mines where sulfide rich tailings are placed
behind an earthen dam and the water level is maintained several feet above the tailings surface.
At sites with favorable topographic conditions, wet covers can be very cost effective. An
important advantage of the wet cap approach at Ore Knob is that it would eliminate the need for
a system of channels to divert surface water. However, the wet cover would not eliminate any
acid already produced in the tailings. Inundating the tailings could result in a temporary increase
in AMD release from acid previously produced within the tailing pile (Feasby et al 1999). Two
general approaches could be used to generate a wet cover at Ore Knob
   A. The existing tailings pile could be modified to retain water by regrading the tailings
      surface, construction of small earthen embankment near the crest of the existing
      embankment, construction of a spillway to safely transport water down the embankment;
      and installation of a low permeability bentonite cutoff wall.
   B. Construction of a new earthen dam a short distance downstream from the current
      embankment face. The existing tailings pile surface would also need to be regraded to a
      uniform elevation to reduce the height of the new dam.

Alternative A could potentially be significantly less expensive than alternative B. However,
significant site investigation would be required to determine if alternative A is technically
feasible.

3.1.3   Passive Neutralization Technologies

There are several passive neutralization approaches that could potentially be used to treatment of
AMD released from the mine and tailings pile including anoxic limestone drains (ALDs), open
limestone channels, and successive alkalinity producing systems (SAPS) (PIRAMID 2003). All
of these approaches increase alkalinity and pH by bringing the AMD in contact with high-
calcium limestone. Under aerobic conditions, Fe and Al will coat the limestone surface,
reducing reactivity and potentially leading to plugging (URS Corporation 2003). However if the
AMD is anaerobic, Fe fouling is significantly reduce. In ALDs, the AMD is treated before it is
exposed to oxygen, reducing plugging. Successive alkalinity producing systems (SAPS) have a
layer of compost or other biodegradable organic material overlying a layer of limestone. The
organic layer is designed to remove dissolved oxygen and reduce Fe+3 to Fe+2, reducing the
potential for armoring of the limestone. Following treatment in ALDs or SAPS, the neutralized

                                                11
AMD must be oxygenated in an aerobic pond or wetland to covert Fe+2 to Fe(OH)3. The
Fe(OH)3 is then removed by settling.

ALDs and SAPS can be effective for treating acidic, Fe rich water. However, some plugging
with Al and other metals does occur, which must be removed by periodic flushing or system
reconstruction. Additional compost must be periodically added to SAPS to maintain anaerobic
conditions. For both systems, there is an upper-limit to the amount of alkalinity that can be
added in a single unit. Consequently, treatment of concentrated AMD may require several sets
of SAPS and settling ponds in series. In both ALDs and SAPS, relatively long contact times
between the AMD and limestone are required for alkalinity generation. As a result, these
systems can be very large and require significant land area for construction.

Passive neutralization systems are often less effective in removing Cu, Mn, and Zn. Some Cu
and Zn can be removed through precipitation as carbonate minerals or co-precipitation with
ferrihydrite. However, removal efficiencies are variable (URS Corporation 2003, PIRAMID
2003). At Ore Knob, the ALDs previously installed to treat AMD discharging from the mine
adits appear to be reasonably effective at removing Fe and acidity. The total amount of Fe+2 and
associated acidity entering the pile from upstream is relatively low, indicating acidity is being
neutralized and ferric iron precipitated in the upstream wetland. However, Cu and Zn
concentrations entering the tailings pile from upstream are high, indicating Cu and Zn removal in
the ALDs is low.

3.1.4   Active Neutralization Technologies

At many sites, there is not sufficient space to install passive treatment systems and active
treatment systems are employed. These systems typically consist of: (a) chemical storage bin or
tank; (b) chemical feed system, (c) aeration device; and (d) settling pond. Common chemicals
used for acid neutralization include pebble quick lime (CaO), hydrated lime (Ca(OH)2), caustic
soda (NaOH), ammonia, and soda ash (NaHCO3). Unit costs for the quick lime and hydrated
lime are lower than for other chemicals. However, costs for handling and mixing lime are
somewhat higher. Typically, the chemical (base) is added to provide sufficient alkalinity
followed by aeration to convert Fe+2 to Fe(OH)3. The Fe(OH)3 is then removed in a settling
basin. Facilities are provided to allow periodic removal of the accumulated Fe(OH)3 sludge with
off-site disposal. At Ore Knob, the sludge could contain elevated levels of Cu and Zn, increasing
disposal costs.

3.1.5   Aerobic Ponds and Wetlands

Aerobic ponds and wetlands are used to oxygenate water from neutralization systems and
provide sufficient contact time for precipitation and settling of Fe(OH)3. Ponds typically require
less area and are designed to allow periodic removal of accumulated sludge. Wetlands are
similar, but typically larger and are filled with several feet of soil, gravel, and/or rocks so that
water flows over the substrate surface. Some heavy metal removal will occur through co-
precipitation with Fe(OH)3. Heavy metals can also be removed in wetlands through sorption to
plant material and precipitation as sulfides in the organic rich sediments. However, the extent of
metals removal appears to be highly variable. Generally, aerobic wetlands are only effective

                                                 12
when used as a final polishing step for treatment of AMD with relatively low levels of pollutants
(PIRAMID 2003).

3.1.6   Anaerobic Bioreactors

One of the most effective methods for removing Cu and Zn is through addition of H2S to
produce metal sulfide precipitates (URS Corporation 2003). The aqueous solubility of Cu2S and
ZnS are very low, so high removal efficiencies are possible. H2S is typically produced
biologically by contacting the SO4 rich AMD with biodegradable organic carbon. The
biodegradable organic carbon can be added in a passive system containing compost or an active
system receiving a liquid substrate (e.g. molasses, alcohols, etc.) (MEND 1996). Under
anaerobic conditions, certain sulfate reducing bacteria (SRB) will convert SO4 present in the
AMD to H2S, causing Cu and Zn to precipitate.

First-generation passive bioreactors typically used composted cow manure or mushroom
compost (Filipek et al. 1992; Schafer and Filipek 1995). More recent bioreactors use a
combination of limestone, sawdust and alfalfa hay in place of manure because this combination
(1) provides alkalinity; (2) provides significantly greater permeability; and, (3) appears to be a
better energy source for the bacterial community. Cow manure is typically added only in small
quantities as an inoculum to supply an initial source of active SRBs. In theory, these systems
could operate unattended. However in practice, all systems tested to date have required
significant maintenance after 3 or 4 years due to operational problems including depletion of
biodegradable material, short-circuiting due to compaction of the substrate and clogging,
increasing acid and metal loads, and desaturation of the system (URS Corporation 2003). In
summary, these ‘passive’ systems often require significant maintenance.

Soluble substrate bioreactors have been recently been developed to overcome some of the
common operating problems with solid substrate bioreactors (URS Corporation 2003). In
soluble substrate systems, a high energy substrate such as methanol, ethanol, or ethylene glycol
is added at a controlled rate based on the required level of sulfate reduction. Sodium hydroxide
may also be added to neutralize pH and provide optimum conditions for sulfate reduction. The
sulfate reducers are supported on a non-reactive matrix (typically large cobbles) with a very high
permeability, reducing the potential for short-circuiting due to clogging of the matrix. Soluble
substrate systems will require on-going operation and maintenance. However, they have the
potential for improved long-term performance.


3.2     Potential Treatment Alternatives

Water quality problems at Ore Knob are severe and cannot be cost-effectively solved using any
one treatment technology. In this section, several alternatives are proposed that could potentially
be used to restore water quality in Ore Knob Branch. These alternatives typically consist of
several technologies used together.




                                                13
3.2.1   Active Treatment Only

One potential approach for treating AMD at Ore Knob would be to make minimal modifications
to the tailings pile and focus on treatment of AMD released from the tailings pile. For the
purposes of this analysis, the system was designed for an average flowrate of 230 gallons per
minute (gpm) and peak flow of 460 gpm. Average influent concentrations were assumed to be
equal to the average concentrations at SW-5 measured by Borden and Behrooz (2008).
Preliminary sizing and cost information were generated using the computer program AMDTreat
4.1c (US OSM 2008). Default values for treatment unit design parameters and unit costs were
used in all cases. Funds for land purchase are not included in the cost estimate.

In theory, a passive system consisting of several SAPS and settling ponds in series could be used
to treat AMD released from the tailings pile. However, this system would require at least 30
acres of land for construction. Sufficient land is not available downstream of the tailings pond to
construct this large system.

Sufficient land is available for construction of an active neutralization system. This system
would consist of a storage silo and feed system for mixing approximately 1 ton per day of pebble
quick lime, followed by a settling pond to aerate the water and settle Fe(OH)3. An access road
and associated infrastructure would be provided for monthly delivery of 30 tons of pebble quick
lime and annual removal of 8,000 cubic yards of sludge from the settling pond. Total
construction cost is estimated to be approximately $200,000 with operation and maintenance
(O&M) costs of approximately $150,000 per year. Major reconstruction of the system would
likely be required once every 10 – 20 years. O&M costs would continue indefinitely under this
alternative. Active treatment would be effective in dramatically reducing the Fe, Al and acidity
load to Ore Knob Branch. Some removal of Mn, Cu and Zn would probably also occur.
However, pilot tests would be required to accurately estimate the extent of Mn, Cu and Zn
removal.

3.2.2   Surface Water Diversion, Dry Cap Installation and Passive Neutralization

AMD release to Ore Knob Branch could be controlled using a combination of surface water
diversion, dry cap installation and passive neutralization. The passive neutralization system
would be installed down stream from the tailings pile. For the purposes of this analysis, the
passive system was designed assuming: (a) an average flowrate of 230 gallons per minute (gpm);
(b) peak flow of 460 gpm; (c) the pollutant load from the upstream watershed (SW-1) is
unchanged; and (d) the pollutant load released from the tailings pile is reduced by 90%. Funds
for land purchase are not included in the cost estimate.

The proposed system would consist of: (a) regrading of the tailings pile surface; (b) construction
of a 22 acre multi-layer cap over the tailings pile ($450,000 per acre); (c) construction of a
network of lined channels to collect surface water and safely transport it over the tailings pile
surface; (d) construction of a series of SAPS and settling ponds downstream of the tailings pile
(10 acres total). Estimated costs for construction of this alternative are summarized below.



                                                14
        Regrading and surface water diversion                    1,000,000
        Cap construction                                         9,900,000
        SAPS and settling ponds                                  1,500,000
        TOTAL                                                   12,400,000

O&M costs are expected to be on the order of $150,000 per year for maintenance of the
diversion channels, impermeable cap, compost addition to the SAPS, sludge disposal, monitoring
and general maintenance. In addition, major reconstruction would likely be required once every
10 – 20 years.

This alternative would be effective in dramatically reducing the Fe, Al and acidity load to Ore
Knob Branch. Some removal of Mn, Cu and Zn would probably also occur. However, pilot
tests would be required to accurately estimate the extent of Mn, Cu and Zn removal.

3.2.3   Wet Cap Installation and Passive Neutralization

AMD release to Ore Knob Branch could be controlled by constructing an earthen dam a short
distance downstream from the embankment face to flood the tailings pile. The tailings pile
would be regraded to a roughly uniform elevation to reduce the required height of the dam. A 20
acre aerobic wetland would then be constructed on top of the tailings pile to treat AMD entering
from the upstream watershed. The proposed wetland would be four times larger than required
based on treatment of the influent AMD. However, constructing a wetland over the entire
tailings pile would prevent reoxidation of the underlying tailings, provide wildlife habitat, and
may enhance Cu and Zn removal. A 0.2 acre SAPS pond and 0.1 acre settling pond would be
constructed downstream of the new earthen dam to treat the small amount of seepage through the
dam and the underlying bedrock. For the purposes of this analysis, the SAPS and pond were
designed for an average flowrate of 12 gallons per minute (gpm) with an influent concentration
equivalent to SW-3. Funds for land purchase are not included in this estimate.

Estimated costs for construction of this alternative are summarized below.
       Construct new earthen dam (200,000 yd3 x $25/yd3)          5,500,000
       Spillway (lump sum)                                          500,000
                                                 3         3
       Regrading existing tailings (150,000 yd * $10/yd )         1,500,000
       Aerobic wetland construction (20 acres)                   1,100,000
       SAPS and settling pond                                        50,000
       TOTAL                                                      8,650,000

O&M costs are expected to be on the order of $25,000 per year for maintenance of the SAPS,
settling ponds, earthen dam. In addition, major reconstruction of the SAPS and settling pond
would likely be required once every 10 – 20 years.

This alternative would be effective in dramatically reducing the Fe, Al and acidity load to Ore
Knob Branch. Significant removal of Mn, Cu and Zn is also expected to occur in the oversized
aerobic wetland. However, field monitoring would be required to accurately estimate the extent
of Mn, Cu and Zn removal. If excessive concentrations of heavy metals continue to be


                                                15
discharged to Ore Knob Branch, an aerobic bioreactor could be constructed to provide additional
treatment.

3.3    Management Alternatives Summary

Discharge of iron and acidity to Ore Knob Branch could be dramatically reduced with an active
treatment system consisting of lime addition, addition and settling. This system could be built at
a reasonable cost within the limited land area available. However, costs for chemical addition,
sludge disposal and general maintenance would be high, and would continue indefinitely.

AMD release from the tailings pile could be controlled using either dry or wet capping
approaches. However, capital cost for these measures are expected to be very high. An
alternative approach would be form a wet cap by constructing a small earthen dam on top of the
existing tailings pile and installing a bentonite slurry wall within the pile. This approach could
potentially be significantly less expensive than the dry and wet cap alternatives evaluated.
However, a more detailed geotechnical evaluation is required to determine if this approach is
technically feasible.


4.0    REQUIRED POLLUTANT LOAD REDUCTIONS

Table 2.2 shows average pollutant concentrations entering (SW-5) and discharging (SW-7) from
Ore Knob Branch. Dissolved iron, copper and zinc would have to be reduced by over 99%, 98%
and 95%, respectively, to meet water quality standards. There are no currently available
technologies that can provide these high removal efficiencies. Consequently, a treatment train
approach will be required.

Those technologies that provide the highest pollutant removal at the lowest cost should be
implemented first. Field monitoring can then be conducted to determine what additional
restoration measures will be required.


5.0    TECHNICAL AND FINANCIAL SUPPORT REQUIRED

Monitoring results obtained in this project have provided a good database to define the extent of
water quality problems at Ore Knob and identify general remedial alternatives. A detailed
feasibility study should now be conducted to identify potential remedial alternatives and develop
accurate estimates of capital and long-term O&M costs for each alternative. Once this study is
complete, financial support requirements can be determined.

Funds for this project will be requested from the NC Clean Water Management Trust Fund, NC
DENR Section 319, the NC Environmental Defense, the USACE Section 206 program, and US
EPA.




                                                16
6.0    PUBLIC EDUCATION

A public education and outreach program should be developed as part of any Watershed
Restoration activities. This program should include information on current water quality
conditions in Ore Knob Branch, Peak Creek and potential impacts to the New River.
Information should also be provided to nearby property owners on potential impacts to private
wells and measures they can take to reduce exposure. Any outreach program should be
coordinated with NC Environmental Defense, the New River Community Partners, and the
National Committee for the New River to enlist local citizens in various aspects of the project.


7.0    SCHEDULE AND MILESTONES

Two primary alternatives have been identified for restoration of Ore Knob Branch: (a) active
chemical treatment of the tailings pile discharge; and (b) capping the tailings pile and passive
treatment of residual AMD. Active treatment has a much lower initial cost, but high O&M costs
that continue indefinitely.

The next step in restoring Ore Knob Branch is to prepare a detailed feasibility study of potential
restoration alternatives. This study should consider both short-term capital costs and long-term
O&M costs, along with potential funding sources. Once this study is complete, a detailed
schedule and milestones can be developed. Preliminary milestones for active and passive
treatment over the next thirty years are outlined below.

Active Treatment Schedule and Milestones
       Year 1        Complete feasibility study and detailed design.
       Year 2       Construct treatment system and begin operation. Beneficial impacts of
                     treatment should be immediately apparent.
       Year 2 – 12 Monthly chemical addition, annual sludge removal, routine maintenance
                     and monitoring.
       Year 5        Based on results from first 4 years of operation, determine if additional
                     treatment measures are required to meet water quality standards.
       Year 12      Major system reconstruction and maintenance.
       Year 13 – 22 Monthly chemical addition, annual sludge removal, routine maintenance
                    and monitoring.
       Year 22       Major system reconstruction and maintenance.
       Year 23 – 30 Monthly chemical addition, annual sludge removal, routine maintenance
                    and monitoring.

Passive Treatment Schedule and Milestones
       Year 1        Complete feasibility study and detailed design.
       Year 2        Regrade tailings pile, construct wet or dry cap.
       Year 3        Construct passive treatment system. Beneficial impacts of treatment
                     should be immediately apparent.
       Year 3 – 13 Routine monitoring and maintenance. Annual sludge removal.


                                                17
       Year 7       Based on results from first 4 years of operation, determine if additional
                    treatment measures are required to meet water quality standards.
       Year 13      Major system reconstruction and maintenance.
       Year 14 – 23 Routine monitoring and maintenance. Annual sludge removal.
       Year 23      Major system reconstruction and maintenance.
       Year 24 – 30 Routine monitoring and maintenance. Annual sludge removal.


8.0    PERFORMANCE CRITERIA

The waters of the Ore Knob Branch and Peak Creek are designated as Class B waters for primary
recreation and also as Trout Waters. Below is a summary of the water quality standards per 15A
NCAC 2B .0219 for various pollutants encountered in the AMD. The objective of any
watershed restoration program should be to reduce pollutant loadings to a level that Ore Knob
Branch and Peak Creek consistently meet these standards.

                                  Parameter Concentration (mg/L)
                                     pH      6.0 – 9.0 standard units
                                     SO4               N/A
                                      Al               N/A
                                     Cu               0.007
                                      Fe                1.0
                                     Mn                N/A
                                     Zn               0.050
                                    DOa                 6.0
                                           a
                                  Turbidity             10
                              a
                                  Trout Waters Standards

In addition to traditional chemical standards, DENR-DWQ classifies each stream in the state
based on its’ ability to support appropriate aquatic life. This classification is based on an
examination of the number of taxa present in stream samples (EPT S) and the North Carolina
Biotic Index (NCBI or BI) which summarizes the pollution tolerance data of all taxa present.
Ore Knob Branch and Peak Creek has been classified as ‘Poor’ (DENR 2004) based on the
macroinvertebrates present. The watershed restoration program should be to improve conditions
to ‘Good’ or at least ‘Good-Fair’.

The ultimate goal of this project is restoration of appropriate aquatic life to Ore Knob Branch and
Peak Creek. The monitoring program described in Section 9.0 is intended to document the
chemical parameters that lead to the poor classification. Biotic monitoring should also be
conducted to document progress towards returning aquatic macroinvertebrates and fish to Ore
Knob Branch and Peak Creek. Once all elements of the Watershed Restoration Plan are
implemented, we anticipate there will be substantial improvement in the water quality of Ore
Knob Branch and Peak Creek. This is expected to include a large reduction in dissolved sulfate,
iron, aluminum, copper and zinc and increase in pH in the stream. These changes in chemical
parameters are expected to be accompanied by a measurable improvement in EPT taxa richness
and abundance. If recovery is slower than expected based on measured reductions in pollutant

                                                    18
loading from the mine area and/or restoration of appropriate stream biota, additional stream
restoration activities may be considered using active restoration technologies.


9.0    MONITORING PROGRAM

9.1    Baseline Monitoring Program

The baseline monitoring program will start prior to the implementation of restoration measures
and with continue throughout the life of the project. This database will enable us to identify
variability in the sampled parameters according to the hydrologic changes of the area. Wet and
dry conditions will be characterized during the entire project.

Monitoring sites are shown in Map 2.3. Below is a description of each site:

SW-1      Ponded surface water / wetland at upstream end of tailings impoundment. This
          location is representative of upstream water released from the watershed and adits
          before it enters the tailings pile.
SW-3      Ponded water on surface of tailings pile. This water is not believed to be impacted by
          the mine adits but has been in contact with tailings.
SW-4      Seep on embankment face. This location is representative of concentrated acid seeps
          discharging from the tailings pile.
SW-5      Stream downstream of entire tailing pile including water that may have passed through
          the drainage pipe in the tailings pile. Samples from this location represent the total
          pollutant load discharging from the pile to Ore Knob Branch
SW-7      Ore Knob Branch about 500 ft upstream of where it joins Peak Creek. This location is
          selected to represent water quality in Ore Knob Branch after there has been sufficient
          time for AMD discharged from the tailings pile to oxidize, releasing H+.
SW-8      Peak Creek about 400 ft upstream of where it joins Ore Knob Branch. This location is
          selected to be representative of background water quality in this area.
SW-9      Peak Creek about 600 ft upstream of where it joins New River. This location is
          selected to be representative of the total pollutant load carried by Peak Creek and
          Little Peak Creek prior to discharge to the New River.

At each of these sites a sample is to be collected quarterly for analysis of pH, acidity, sulfates,
aluminum, copper, iron, manganese and zinc. EPT S and NCBI of macroinvertebrates will also
be measured SW-7, SW-8 and SW-9.

9.2    Treatment System Monitoring Program

At a minimum, passive technologies will be monitored quarterly for the same parameters as the
surface water. Additional monitoring parameters may also be included, depending on the
treatment technology selected.




                                                 19
9.3    Analytical Methods

Samples will be analyzed following standard EPA procedures (EPA, 2002) as indicated below:

                           Parameter            EPA Standard Method Number

                  Acidity (as CaCO3, mg/L)                   305.1
                  Aluminum (Total, mg/L)                     202.1
                  Copper (Total, mg/L)                       220.1
                  Iron (Total, mg/L)                         236.1
                  Lead (Total, mg/L)                         239.1
                  Manganese (Total, mg/L)                    243.1
                  Oxygen (Dissolved, mg/L)                   360.1
                  Sulfate (as SO4 , mg/L)                    375.1
                  Turbidity (NTU)                            180.1

9.4    Qualitative Monitoring Program

If a passive treatment system is implemented, the dry cap, diversion channels, and/or earthen
dam should be visually inspected annually throughout the life of the project to ensure the system
is operating as expected. Once every ten years, a professional engineer should inspect the site
and provide recommendations on maintenance or reconstruction required.


10.0   REFERENCES

Borden, R.C. and M. Behrooz, 2008. Ore Knob Mine Tailings Pile – Hydrologic and
Geochemical Characterization, Report submitted to NC Dept. Environment and Natural
Resources, 319 Program, Raleigh, NC.
Feasby, D.G., G.A. Tremblay and C.J. Weatherell, 1999. A Decade of Technology Improvement
to the Challenge of Acid Drainage – A Canadian Perspective. MEND Secretariate, CANMET,
Natural Resources Canada.
Filipek, L.H., J. Gusek, and T.R. Wildeman, 1992, Wetland Design for Hazardous Waste/
Mining Operations. Presented at Mining, Exploration and the Environment '92, SME. Bellevue,
WA.
Filipek, L.H., 1995, Factors to Consider in Designing Passive Treatment of Mine Drainage.
Presented at Northwest Mining Association 101st Annual Convention. Spokane, WA.
Hauser, V.L., D.M. Gimon, D.E. Hadden, B.L. Weand, 1999. Survey of Air Force Landfills,
their Characteristics and Remediation Strategies, Prepared for the Air Force Center for
Environmental Excellence, Brooks AFB, TX.
Janzen, M.P., R.V. Nicholson, J.M. Scharer, 2000. Pyrrhotite reaction kinetics: reaction rates for
oxidation by oxygen, ferric iron, and for nonoxidative dissolution. Geochim. Cosmochim. Acta
64, 1511–1522.

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Kinkel, A.R., Jr., 1967. The Ore Knob Copper Deposit North Carolina, and Other Massive
Sulfide Deposits of the Appalachians, Geological Survey Professional Paper 558, Washington,
DC.
Lenat, D. 1996. Memorandum to Ken Eagleson, Subject: Biomonitoring of Peak Creek near Ore
Knob Mine, Ashe County, April 1996.
Mine Environment Neutral Drainage (MEND) Program, 1996. Review of Passive Systems for
Treatment of Acid Mine Drainage – Phase II, Ontario, Canada.
North Carolina Department of Environment and Natural Resources (NCDENR). Division of
Water Quality (DWQ), 2005. New River Basinwide Water Quality Plan, Raleigh, NC.
PIRAMID Consortium, 2003. Engineering Guidelines for the Passive Remediation of Acidic
and/or Metalliferous Mine Drainage and Similar Wastewaters.
Rankin, H.S., and J.L. Stuckey, 1943. Copper Deposits of Western North Carolina, Tennessee
Valley Authority and NC Div. Mineral Resources.
URS Corporation, 2003. Passive and Semi-Active Treatment of Acid Rock Drainage from Metal
Mines – State of the Practice, Prepared for U.S. Army Corps of Engineers.
US Army Corps of Engineers (USACE), Huntington District and NCDENR DWQ. March 2003.
Ore Knob Aquatic Restoration Project: Draft Detailed Project Report and Environmental
Assessment. Huntington, VA.
US Office of Surface Mining, Pennsylvania Department of Environmental Protection, West
Virginia Department of Environmental Protection, 2008. AMDTreat, Version 4.1c
(http://amd.osmre.gov/default.htm).




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