Chapter 4 Ore Knob

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4.1
CHAPTER 4
Ore KnOb Mine
Water Quality Issues & Restoration Efforts
Ore KnOb Mine
Mine HistOry
Ore Knob Mine is a former copper mine which was operated intensively from 1871 to 1883. Then limited
mining activities took place until 1957 when it was operated by Appalachian Sulphides Inc. For the next five to
six years, the mining company extracted the ore from 11 openings and one main shaft. Ore was then ground
in a processing facility in the Little Peak Creak drainage area. Using a froth flotation and cyanide leaching
process, Copper, gold and silver was extracted further.
The waste tailings from this process were mostly pumped into a large tailings impoundment located on Ore
Knob Branch. A smaller portion of the tailings were dumped in a small hollow adjacent to the processing
facility. The drainage from the processing facility and associated waste piles is an acidic toxic mix that has
contaminated the surface and ground water in the drainage area.
Figure 4-1: Photos taken oF the Waste/tailings Piles During a site Visit in December 2006 by DWQ. (toP
leFt: toP oF imPounDment Facing the settling PonD; toP right: looking north east across the imPounDment;
bottom: on imPounDment looking back across tailings Pile.)

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4.2
Figure 4-2: tailings imPounDment anD PonDs Features anD longituDinal ProFile (black & Veatch, 2008).
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E
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prof
ile
lin
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(
ins
et)
E
E
water controlstructure
pipe underneath tailings (inferred path)
Tailings Impoundment Features
and Longitudinal Profile
Ponds (water/swampy)
0 100 200 300 400
Feet
FIGURE 2-4
NAD 1983 State Plane North Carolina FIPS 3200 (feet)
o
PROJECTS\OreKnob\Report\MapDocs\Figure2-4_TailingsImpoundment_022308.mxd
February 23, 2008
Perennial Intermittent
Surface Water
culvertsettlingbasin dam concrete pipe inlet
collapsed pipe outflow
concretepipe inlet
spring
spring
seep
seep
seeps
settling basin
Tailings Impoundment
O r e K n o b B r a n c h
h e a d w at e r s
Contours (2-ft interval)
2 9 6 2
2 9 7 8
2 9 5 6
2 9 6 2
Ore KnobBranch
A'
A
2820
2840
2860
2880
2900
2920
2940
2960
2980
3000
3020
3040
3060
3080
0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100
Ground Distance (feet)
Elevation above MSL (feet)
~5x vertical exaggeration
settling basin dam settling
basin(dry)
starter
dam
upperdamface
current tailings impoundment surface
~76 ft ~30 ft southwestern corner of tailings (drainage from
the 19th century operations area)original topography(reconstructed basedon surrounding topography)
A
A'
~1,550 ft
Profile of the Tailings Impoundment
(current surface and reconstructed original topography)
North South
culvert
Ore Knob Branch
intermittent ponding
(approximate boundary)
tailings dam
collapsedpipe outflow
!
!
concretepipe inlet(projected)
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4.3
DescriptiOn Of cOntaMinateD area & iMpacts
The main area of the Ore Knob Mine that is impacting surface and ground water is the tailings pile which is a
little over 20 acres and holds most of the waste tailings from the mining operations. This is seen in Figure 4-2
as the area outlined in red. The tailings pile, estimated at 720,000 cubic yards, is held behind a 60 foot dam.
Behind the large dam is a settling basin held back by a smaller 20 foot dam. This smaller dam has a culvert
which drains directly to Ore Knob Branch.
Two small streams flow into the southern portion of the pile where it intermittently ponds (two blue lines at the
bottom left corner of Figure 4-2). A concrete pipe inlet drains the intermittent pond, bypassing majority of the
tailings pile and the larger dam, discharging into the settling basin. Two spring fed ponds, located on either
side of the northern portion of the pile, filter through the tailings and seeps through the larger dam where it
then collects in the settling basin.
The tailings piles as well as the mine shafts are causing acidic metal-laden runoff to contaminate surface and
groundwater on the site which then flows into Little Peak Creek, Ore Knob Branch and Peak Creek [AU#:
10-1-35-(2)b]. Multiple studies have been conducted since the early 1990’s to measure the impact on water
quality and the environment. These studies have detailed results within their respective study reports which
are discussed below.
restOratiOn activity HistOry (1990’s tO 2005)
Restoration efforts to the abandoned mine and its receiving streams began in the early 1990’s by the US Army
Corps of Engineers (USACE) and DWQ. Under Section 206 of the Water Resources Development Act of 1996
(PL 104-303), USACE published the Ore Knob Aquatic Restoration Project: Draft Detailed Project Report and
Environmental Assessment (March 2003). The goal of the project was defined “to return aquatic macrobiota
and fish to Peak Creek and Little Peak Creek.” Quantitatively, the project would restore up to 14.3 acres of
aquatic habitat (6.9 stream miles).
In order to meet the goals and objectives of the Ore Knob project, restoration of the former processing area
and reclamation of the tailings area, which include mine portals and shafts, would be necessary. This involves
three distinct treatments: (1) diversion of surface water runoff away from and around tailings; (2) isolation of
the tailings; and (3) passive treatment of acid discharge through the use of wetlands. Implementation of the
project was expected to restore 6.9 miles of aquatic habitat and 24 acres or more of terrestrial (wetland and
upland) habitat. Two million dollars was allocated for project study, design and construction, and operation
and maintenance costs. Even though, due to federal budget constraints, funding for the full Ore Knob Aquatic
Restoration Project was not provided, the 2003 document has been utilized in almost all Ore Knob restoration
projects since.
recent activity (2005 tO 2010)
319 Watershed Management Plan
In 2005, NCSU was awarded funding to develop a Watershed Management Plan for the Ore Knob Mine
area. This study included surface water monitoring for pH, DO, temperature, acidity and numerous metal
values. Averages for these values are summarized in Figure 4-4. These parameters were monitored at seven
locations within the area during the study. Locations of five of those monitoring stations are listed in Table 4-1
and shown in Figure 4-3.
table 4-1: monitoring locations For FiVe oF nine sites samPleD During 319 Project
statiON
#lOcatiON statiON
#lOcatiON statiON
#lOcatiON
1 Peak Creek 3 Discharge from tailings 5 Peak Creek just before
South Fork New River2Southern intermittent pond 4 Ore Knob Branch
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4.4
Results of the sampling indicated pH levels at all stations except one were significantly lower than the states
surface water quality standard of 6. The one station that was not below the standard was Site 1 which
is the only site upstream of the mines impacted area. Acidity levels were highest were the concrete pipe
discharges the tailings into the settling basin (Site 3). Copper was the only metal, sampled during this study,
that showed higher levels at Site 2 (located at the intermittent pond) than Site 3. Site 2 represents runoff from
the watershed area upstream (south) of the tailings pile as well as runoff that flows through the adits (a slightly
sloped passage into the mine) before it enters the intermittent pond at the south end of the tailings pile. Higher
copper levels at this site indicate signs of filtration of the metal as the water from the intermittent pond travels
through the tailings pile. All other metals shown in Figure 4-4 had a much higher value once discharged from
the tailings pile into the settling basin.
Site 4 (Figure 4-3), which is located on Ore Knob Branch just before its confluence with Peak Creek, results
showed that much of the contaminates were reaching Peak Creek. And Site 5, on Peak Creek just before its
confluence with the South Fork, results also showed evidence of the contaminates, but to a lesser degree.
The study concluded the primary sources of the contaminates/pollution were 1) erosion of the face of the larger
dam (north side of the dam), 2) adits that release acid mine discharge (AMD) from the former underground
mine that is upstream of the intermittent pond, and 3) AMD generated within the tailings pile. Due to the
contaminate levels found during this study and the degree of environmental and human health hazards, the
state coordinated with the EPA to have the mine designated as a Superfund site (Borden and Behrooz, 2009).
Figure 4-3: samPle locations For the 319 WatersheD restoration Plan Project FunDeD by the 319 grant*
Sou
t
h

F
o
r
k
P
e
a
k

C
r
e
e
k
Peak Cree
k
Li
t
t
l
e

P
e
a
k

C
r
e
e
k
Tailings
Pile
Ore

K
n
o
b

B
r
.
* Imagery by Google Earth
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4.5
Figure 4-4: aVerages For FiVe monitoring sites samPleD For the ore knob 319 Project
0
2
4
6
8
10
12
1 2 3 4 5
Alu
m
i
n
u
m

(
m
g
/
l
)
Stations
Aluminum (mg/l)
0
0.1
0.2
0.3
0.4
0.5
0.6
1 2 3 4 5
Co
p
p
e
r

(
m
g
/
l
)
Stations
Copper (mg/l)
NC Standard (0.007mg/l)
0
50
100
150
200
250
300
350
400
450
1 2 3 4 5
Ir
o
n

(
m
g
/
l
)
Stations
Iron (mg/l)
Evaluation Level (>1.0mg/l)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
1 2 3 4 5
Ma
n
g
a
n
e
s
e

(
m
g
/
l
)
Stations
Manganese (mg/l)
Evaluation Level (>0.2mg/l)
0
200
400
600
800
1000
1200
1400
1600
1800
1 2 3 4 5
Su
l
f
a
t
e

(
m
g
/
l
)
Stations
Sulfate (mg/l)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1 2 3 4 5
Zin
c

(
m
g
/
l
)
Stations
Zinc (mg/l)
NC Standard (0.05mg/l)
0
1
2
3
4
5
6
7
8
1 2 3 4 5
pH
Stations
Lab pH
NC Standard (6-9)
0
2
4
6
8
10
12
1 2 3 4 5
DO

(
m
g
/
l
)
Stations
DO (mg/l)
NC Standard ( 5mg/l)
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4.6
DWQ & Environmental Protection Agency Region 4 Activity
DWQ and EPA Region 4 conducted site visits in 2007 to check on the degradation status of the embankment
and tailings. During the February 2007 visit, the concrete pipe used to divert stream flow under the tailings
pile to the settling pond was blocked at both inlet and outlets causing the flow to filter through the tailings.
The 60 foot dam (Figure 4-5: top right) exhibited rills up to three feet deep along with numerous seeps. Storm
runoff and water seeping from the dam face would be collected in the settling pond before reaching Ore Knob
Branch; however, the settling pond had been completely filled with sediment which likely eroded from the face
of the dam. This surface and groundwater was monitored in 2007 and 2008 as part of a 319 grant project.
In April 2009, the site was proposed for the National Priority List which became official September 23, 2009.
Since that time, federal agencies developed a clean up effort based on past studies and stabilization efforts.
As of July 2010, actions have included:
£20,000 of 720,000 cubic yards of tailings and sediment excavated from the settling pond;
£Restored a freeboard in the settling pond so it now acts as a clarifier as water empties into Ore Knob
Branch;
£Completed the diversion channel designed to reroute 200 gallons per minute of surface water around the
tailings dam;
£Recycled soil and sediment excavated from the site to re-use throughout the rest of the site; and
£Completed a geotechnical stability analysis and a slope stability analysis for the tailings dam face.
In July of 2010, EPA Region 4 requested additional funding to complete the remaining restoration of the site.
This will cover the capping of the tailings impoundment and add vegetation throughout the site, excavate
tailings from Ore Knob Branch and excavate and stabilize the 1950’s mine and mill site. Federal sediment
and erosion controls will be put in place during the restoration efforts. However, federal measures are not as
preventive as state measures; therefore, elevated turbidity levels are expected to occur in Ore Knob Branch,
Peak Creek and possibly the South Fork until restoration is completed.
DWQ will continue to work with EPA as requested through the remainder of the project.
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4.7
Figure 4-5: Photos oF tailings Pile anD DoWnstream taken During a site Visit in july 2007 by DWQ. (toP
leFt: toP oF larger Dam Facing the settling basin; toP right: settling basin looking back toWarDs larger
Dam; bottom leFt: toP oF larger Dam looking back across tailings Pile; bottom right: ore knob branch
DoWnstream oF settling basin culVert.)

references
Black and Veatch. March 2008. Expanded Site Inspection Report Ore Knob Former Mine Site. CERCLIS ID:
NCN000409895. EPA Contract 68-W99-043, Work Assignment 700-SAEA-A4ND, Black and Veatch
Project 048700.08.83. Asheville, NC.
Borden, Robert C. and Behrooz, Mehnroosh. January 1, 2009. Ore Knob Mine Tailings Pile - Watershed
Restoration Plan. Department of Civil, Construction and Environmental Engineering. North Carolina
State University. NCDENR, 319 Program Funded. Raleigh, NC. (http://h2o.enr.state.nc.us/basin-
wide/319_Documents/documents/OreKnob_Watershed_Plan.pdf)
Note: URL addresses for hyperlinks found in this plan are listed in the Acronyms & Definitions Chapter.
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4.8