DEPARTMENT OF CONSERVATION1
Michael F. Byrne, Director
PB95-191276
EPA No. 530-R-95-013b
Application of; Geophysics
to
Acid Mine Drainage Investigations
Report Prepared
for
Western Governor's Association
USEPA Grant No. X-820497-01-0
by
Kit Custis
California Department of Conservation
Office of Mine Reclamation
801 K Street, MS 09-06
Sacramento, California
95814-3529
September 1994
Pete Wilson, Governor
State of California
Douglas P,. Wheeler, Secretar
Resources Agency
U.S. Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Bou!ev^J 12th Floor
Chicago, IL 60604-359
rtocyctod/Racyclabto
Printed on paper that contains
at toast 50% recycled few
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Table of Contents
Volume II
Page
EXECUTIVE SUMMARY v.
I; INTRODUCTION
PURPOSE AND SCOPE 1.
ACKNOWLEDGEMENTS 1.
II. SITE INVESTIGATIONS
SPENCEVILLE MINE
MINE SITE HISTORY, GEOLOGY AND HYDROLOGY 5.
GEOPHYSICAL SURVEYS
£>.C. Resistivity Surveys 8.
Electromagnetics Surveys 9.
Self Potential Surveys 11.
CONCLUSIONS 13.
RECOMMENDATIONS 13.
SPENCEVILLE MINE REFERENCES • 14.
LEVIATHAN MINE
MINE SITE HISTORY, GEOLOGY AND HYDROLOGY 37.
GEOPHYSICAL SURVEYS
General Discussion 38.
Electromagnetics Surveys • 39.
Self Potential Surveys 40.
Magnetometer Surveys 41.
CONCLUSIONS 43.
RECOMMENDATIONS 43.
LEVIATHAN MINE REFERENCES 44.
IRON MOUNTAIN MINE
MINE SITE HISTORY, GEOLOGY AND HYDROLOGY 61.
GEOPHYSICAL SURVEYS
General Discussion 63.
Electromagnetics Surveys 63.
Self Potential Survey 64.
Magnetometer Survey 65.
CONCLUSIONS 65.
RECOMMENDATIONS 66.
IRON MOUNTAIN MINE REFERENCES 66.
WALKER MINE
MINE SITE HISTORY, GEOLOGY AND HYDROLOGY 79.
GEOPHYSICAL SURVEYS
General Discussion 81.
D.C. Resistivity Surveys . .. 81.
Electromagnetics Surveys 82.
Magnetometer Surveys 83.
CONCLUSIONS . 84.
RECOMMENDATIONS , 84.
WALKER MINE REFERENCES 85.
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List of Figures
Volume n
•Page
1. General location map of mine sites investigated 3.
2. Location map of Spenceville mine 17.
3. Topographic and hydrologic map of Spenceville mine 18.
4. Regional geologic map of Spenceville mine 19.
5. Geologic cross section of Spenceville mine pit 20.
6. Spenceville mine geophysical survey grid and topography 21.
7. SpenceVille D.C. resistivity VES1 data and equivalence profiles 22.
8. Spenceville D.C. resistivity VES2 data and equivalence profiles 23.
9. Spenceville D.C. resistivity VES3 data and equivalence profiles 24.
10. Spenceville D.C. resistivity pseudo-conductivity profile 25.
11. Spenceville EM31 horizontal dipole contour map 26.
12. Spenceville EM31 vertical dipole contour map 27.
13. Spenceville EM31 vertical dipole decibel contour map 28.
14. Spenceville EM34-3 10m horizontal dipole contour map 29.
15. Spenceville EM34-3 10m vertical dipole contour map 30.
16. Spenceville EM34-3 20m horizontal dipole contour map 31.
17. Spenceville EM34-3 20m vertical dipole contour map 32.
18. Spenceville EM34-3 40m horizontal dipole contour map 33.
19. Spenceville EM34-3 40m vertical dipole contour map 34.
20. Spenceville self potential contour map 35.
21. Spenceville self potential, EM31-VD, total dissolved solids
and pH profiles along Little Dry Creek 36.
22. Location map of Leviathan mine 45.
23. Leviathan mine topographic and geophysical survey line map 46.
24. Leviathan mine regional hydrologic map 47.
25. Leviathan mine schematic map of ponds and piping 48.
26. Leviathan mine Line 1 EM data and geoelectric cross section 49.
27. Leviathan mine Line 2 EM data and geoelectric cross section 50.
28. Leviathan mine Line 3 EM data and geoelectric cross section 51.
29. Leviathan mine Line 4 EM data and geoelectric cross section , 52.
30. Leviathan mine Line 5 EM data and geoelectric cross section 53.
ii.
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List of Figures
Volume II
Page
31. Leviathan mine Line 6 EM data and geoelectric cross section 54.
32. Leviathan mine Line 7 EM data and geoelectric cross section 55.
33. Leviathan mine Line 1 SP and magnetometer profiles 56.
34. Leviathan mine Line 2 SP and magnetometer profiles 57.
35. Leviathan mine Line 3 SP and magnetometer profiles 58.
36. Leviathan mine Line 4 SP and magnetometer profiles 59.
37. Leviathan mine Line 5,6 and 7 magnetometer profiles 60.
38. Iron Mountain mine location and regional hydrology map 69.
39. Iron Mountain mine Old/No. 8 mine geophysical survey Ike map 70.
40. Iron Mountain mine Old/No. 8 mine EM31 horizontal dipole contour map 71.
41. Iron Mountain mine Old/No. 8 mine EM31 vertical dipole contour map . 72.
42. Iron Mountain mine Old/No. 8 mine EM34-3 10m horizontal dipole contour map 73.
43. Iron Mountain mine Old/No. 8 mine EM34-3 20m horizontal dipole contour map 74.
44. Iron Mountain mine Old/No. 8 mine EM34-3 40m horizontal dipole contour map 75.
45. Iron Mountain mine Old/No. 8 mine self potential contour map 76.
46. Iron Mountain mine Old/No. 8 mine magnetometer contour map 77.
47. Iron Mountain mine Old/No. 8 mine Line 4 EM, magnetometer and SP profiles 78.
48. Walker mine location map 87.
49. Walker mine topographic and geophysical survey line map 88.
50. Walker mine D.C. resistivity VES1 data and geoelectric section 89.
51. Walker mine D.C. resistivity VES2 data and geoelectric section 90.
52. Walker mine D.C. resistivity VES3 data and geoelectric section 91.
53. Walker mine D.C. resistivity VES4 data and geoelectric section 92.
54. Walker mine Line 1 EM data and geoelectric cross section 93.
55. Walker mine Line 2 EM data and geoelectric cross section 94.
56. Walker mine Line 3 EM data and geoelectric cross section 95.
57. Walker mine Line 4 EM data and geoelectric cross section 96.
58. Walker mine Line 5 EM data and geoelectric cross section 97.
59. Walker mine Line 1 and 2 magnetometer profiles 98.
60. Walker mine Line 3 and 4 magnetometer profiles > 99.
61. Walker mine Line 5 magnetometer profile 100.
111.
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EXECUTIVE SUMMARY
Four mine sites were targeted to evaluate the application of geophysics to acid mine drainage
(AMD). Where possible, sites with existing water quality monitoring data were selected to
facilitate verification of geophysical results. Geophysical survey techniques were reasonably
successful in identifying high conductivity anomalies thought to be directly correlated with acidic
ground water. The results of the field investigations are summarized as follows:
Electromagnetic (EM) surface methods were successful in detecting and mapping acidic
ground water in mine waste piles.
D.C. resistivity methods were successful in developing vertical profiles of acidic mine
waste material that correlated well with electromagnetic survey data.
Self potential surface surveys were successful in detecting acidic ground water flow from
mine waste ponds.
Magnetometer surveys were successful as quality control for distinguishing between an
increase in subsurface conductivity due to buried man-made iron or steel objects, and
higher conductance from acidic ground water or high conductance soils, rock or mine
waste.
Conventional surface geophysical methods can be used to detect, map and monitor acidic
ground water emanating from mine workings, mine waste piles and storage ponds.
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I. INTRODUCTION
PURPOSE AND SCOPE
Geophysical field investigations were undertaken to evaluate the utility of surface geophysical
techniques in detecting and monitoring ground-water pollution from mine waste in the western
United States. Staff of the Department of Conservation, the California Regional Water Quality
Control Boards, the California Water Resources Control Board, and the U.S. Geological Survey
were consulted regarding mines as good candidates for geophysical investigations of AMD.
Spenceville copper mine, Leviathan sulfur mine, Iron Mountain copper mine, and Walker copper
mine were selected (Figure 1), and field investigations were undertaken using conventional D.C.
resistivity, electromagnetic, self potential and magnetic methods. It was found that the source
and extent of AMD can be identified, known ground-water flow paths correlate well with
geophysical anomalies, subsurface layering of mine waste piles can be mapped with some surface
geophysical methods, and leakage from waste impoundments is detectable by some surface
geophysical methods. The following sections present the results of the four geophysical
investigations, by individual mine site.
ACKNOWLEDGEMENTS
This report was prepared under a grant from the U.S. Environmental Protection Agency through
the Western Governors' Association (Grant X-820497-01-0). The project was administered by
Mr. Stephen Hoffman of the Office of Solid Waste and Emergency Response, U.S.
Environmental Protection Agency. The project was conducted under the guidance of Messrs.
James Pompy and Dennis O*Bryant of the Office of Mine Reclamation (DOC-OMR) of the
California Department of Conservation. Technical review and assistance was provide by Messrs.
Michael Hunerlach, Charles Alpers, and F. Peter Haeni of the U.S. Geological Survey, and Mr.
Roger Chapman of the California Department of Mines and Geology (retired). Field assistance
was provided by Ms. Catherine Gaggini and Mr. Steve Newton-Reed of the DOC-OMR, and
Messrs. Michael Hunerlach, Scott Haralin and William Hardy of the U.S. Geological Survey,
Sacramento Office. Special thanks go to Mr. William Croyle of the Central Valley Regional
Water Quality Control Board, Ms. Catherine Schoen of the Tahoe Regional Water Quality
Control Board, Mr. Rick Sugarek of Region IX USEPA, and Mr. Steve Muir of WZI
Corporation for their assistance, without which this project would not have been possible.
1.
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N
Figure 1. General location map of mine sites investigated.
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* ' II. SITE INVESTIGATIONS
SPENCEVILLE MINE
MINE SITE HISTORY, GEOLOGY AND HYDROLOGY
Spenceville copper mine is adjacent to the historic town of Spenceville in the southwestern corner
of Nevada County, California (Figure 2). The now-abandoned site is primarily in Section 26,
T.15 R, R. 6 E., Mount Diablo Baseline, approximately 3,000 feet (914 meters, m) east of the
boundary between Nevada and Yuba counties. The disturbed area encompasses approximately
10 acres (2.5 hectares) bounded on the east and south by Little Dry Creek and Dry Creek,
respectively (Figure 3).
The Spenceville copper mine site was discovered in 1862 when a well dug at Purtzman's Ranch
intersected a copper deposit (Gudde, 1975). Spenceville mine became largest copper producer in
Nevada County and one of the longest operating copper mines in the state (Aubury, 1908). By
1908, one million pounds of copper had been produced. The mine yielded one million dollars in
copper and iron pyrite (Bradley, 1930). Although small, Spenceville mine has some historic
significance. It was the first in California whose pyrite was used for the manufacture of sulfuric
acid. The mine was also among the first to introduce and successfully operate using the copper
cementation process (Aubury, 1908). In the copper cementation process, the copper ore is heap
roasted and then leached. A copper cement precipitates as the leachate is then run over scrap
iron.
The San Francisco Copper Company worked the underground Spenceville copper mine for 13
years, beginning in 1875, using the cementation process to extract copper from approximately
150,000 tons (136,000 metric tons) of ore that had an average grade of 5% copper. In 1882 the
mine workings collapsed and mining was continued in an open pit. In 1887 the price of copper
fell and mining ceased. In 1890, the Imperial Paint and Copper Company began milling the
hematite waste rock, created by the heap roasting, for red paint pigment and continued leaching
the waste pile to extract copper. In 1897, the Spence Mineral Company dewatered the open pit
and began mining pyrite which was shipped to the San Francisco Bay area to make sulfuric acid
using a new process. Workings of the underground mine are reported to extend to a depth of
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150 feet (46 m), while the open pit was a maximum of 75 fee"t (23 m) deep. The last production
at the mine was between 1916 and 1918 when water was pumped from the open pit onto the
waste piles, to precipitate copper cement.
Spenceville mine is within the Foothill Copper Belt which runs along the western foothills of the
Sierra Nevada (Heyl, 1948). This copper belt extends from the foothills east of Fresno,
California to just north of Oroville, California. Spenceville mine is in the northern portion of the
belt in a formation called the Smartville Complex (Beard and Day, 1987, Xenophontos, 1984).
The Smartville Complex is a Jurassic rifted arc sequence of older submarine volcanic rocks and
sheet dikes and younger plutonic rocks. The unit was deformed and accreted to the North
American continent during the Late Jurassic Nevadan orogeny. The youngest intrusive rocks in
the complex are diorite to granodiorite plutons that may be related to the Sierra Nevada
batholith.
The bedrock units exposed in the vicinity of the mine site include undivided volcanic and
metavolcanic rocks with subsidiary autobreccia of upper Jurassic age and the diorite and
granodiorite Pilot Peak Pluton, as shown in Figure 4 (S.S. Papadopulos and Associates, 1988).
Overlying the bedrock are two sedimentary deposits: an older, Eocene age terrace deposit
composed of well-indurated, iron-oxide-cemented, cobble conglomerate and a sandstone; and a
I
younger, Quaternary age, poorly cemented, stream gravel and cobble conglomerate crops out east
of Little Dry Creek.
The older, iron-oxide-cemented terrace deposit is exposed in the upper walls of the open pit and
along the western bank of Little Dry Creek. This unit consists of a lower, dark-reddish-brown,
subangular-to-rounded, well-sorted, cobble conglomerate and an upper, reddish-brown pebbly
sandstone. The unit was deposited on an eroded bedrock surface that has a relief of 1 to 7 feet
(0.3 m to 2 m). A thickness of as much as 8 feet (2.4 m) is observed in outcrops and 25 feet (7.6
m) in drill holes (S.S. Papadopulos and Associates, 1988).
Geologic structures in the vicinity of the mine site include the northwest trending Spenceville
fault zone (Jennings, 1992) approximately 3 miles (5 km) west of the mine site. This fault zone
consists of a series of short, branching, dip-slip faults that form a zone approximately 0.5 to 4
miles (0.8 to 6.5 km) wide. Aligned with the fault zone are several linear valleys. ,The valley
closest to the mine is along the upper reach of Little Dry Creek (Page and others, 1984).
6.
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S.S. Papadopulos and Associates (1988) evaluated the importance of fractures on the movement
of ground water in the mine site area as part of a hydrogeologic assessment report (HAR) for
the mine. They noted that Page and others (1984) reported for the foothills surrounding the
mine site that fractures within the upper 200 feet (60 m) supply most of the ground water to
domestic wells. S.S. Papadopulos and Associates (1988) evaluated the nature of the fracture
systems at the mine site using nearby outcrops of bedrock and core samples taken during drilling
of five monitoring wells at the mine site. They found that the bedrock fractures are generally
randomly oriented due to overprinting during the intrusion of the Pilot Peak Pluton. In their
evaluation of the bedrock hydraulic conductivity, using slug tests, S.S. Papadopulos and
Associates found that it was anisotropic, with horizontal values averaging 0.11 ft/day (4 x 10*
cm/sec) and vertical values averaging 0.0071 ft/day (2.5 x 10"* cm/sec).
In the central portion of the Spenceville copper mine is a flooded open pit. The pool's surface
area is approximately one-half acre (0.2 hectares) and maximum depth approximately 60 feet (18
m). Surrounding the pit on the west and north are piles of waste rock and roasted ore waste that
were deposited on the side of a hill. Little Dry Creek flows south and is approximately 80 feet
(24 m) southeast of the open pit. It joins Dry Creek approximately 400 feet (122 m) south of the
mine pit. Little Dry Creek flows in a 2-to-4-feet- (0.6 m-to-1.2 m-) deep channel cut into the
iron-oxide cemented terrace deposit. Little Dry Creek now flows all year due to an agreement
between the California Department of Fish and Game and a local irrigation district.
Approximately 0.5 ftVsec (14 liters/sec) flow is supplied to the upper reach of the creek between
April 15 and October 15 (S.S. Papadopulos and Associates, 1988). Dry Creek is a perennial
stream that discharges into Bear River approximately 6 miles (9.7 km) south of the mine.
Estimates of the 100-year peak discharge for Little Dry Creek and Dry Creek are 4,300 ftVsec
and 14,300 ftVsec (121 mVsec and 405 mVsec), respectively (S.S. Papadopulos and Associates,
1988).
The Eocene age, iron-oxide cemented terrace deposit has an important role in the hydrology of
the mine site. The water level in the open pit is generally higher than in Little Dry Creek. Pit
water discharges as ground water into Little Dry Creek primarily through the terrace deposit
along fractures, along partings in the cementation, and at the contact with the underlying bedrock
(Figure 5). The hydraulic gradient between the pit water and Little Dry Creek is approximately
0.02. Numerous seeps along the west bank of Little Dry Creek are marked by deposits of
aluminum and iron hydroxides. The pit water and runoff from the mine waste piles also
7.
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discharge into Little Dry Creek during some winter storms. "The discharge of the mine water has
clearly affected the portion of Little Dry Creek adjacent to the mine and causes periodic
pollution to Dry Creek when major storm events create large surges of AMD runoff.
The open pit contains approximately 6 million gallons (23 million liters) of acidic water (pH =
2.5). This water has a high concentration of sulfate (1,300 to 14,000 milligrams/liter [mg/L]) and
iron (120-4,500 mg/L), and concentrations of copper (30 to 230 mg/L) and zinc (20 to 220 mg/L)
that are near to slightly above the soluble threshold limit concentration (STLC) (S.S.
Papadopulos and Associates, 1988). The specific conductance of the pit water ranges from 1,150
to 11,000 micrbSiemens/cm (/aS/cm). Little Dry Creek has a specific conductance of
approximately 130 /xS/cm upstream of the mine to 160 /xS/cm downstream.
GEOPHYSICAL SURVEYS
D.C. Resistivity Surveys
Geophysical studies were undertaken at Spenceville mine to evaluate the extent of ground-water
pollution surrounding the open pit and to evaluate whether an anomaly from the AMD ground-
water flow through the terrace deposit could be detected. These geophysical studies included
three D.C. resistivity soundings (VES) and one profile, using the Wenner array. Data were
collected in the area between the open pit and Little Dry Creek as shown in Figure 6. Resistivity
was measured with a Geohm 3 portable resistivity meter. The results of the VES surveys were
interpreted as four-layer models and are shown in Figures 7 through 10. An upper more resistive
zone (resistivity ranging from approximately 55 to 417 ohm-m [=2 to 18 mS/m conductivity])
approximately 2 to 5 feet (0.6 m to 1.5 m) thick is interpreted as unsaturated sandy surface soils.
A higher moisture content or higher clay content results in slightly lower resistivity at the surface.
A middle 2.5-to-8-foot- (0.8-to-2.4-m-) thick zone of lower resistivity rock (resistivity ranging
from approximately 9 to 30 ohm-m [=110 to 33 mS/m conductivity]) is interpreted to be the
fractured, iron-oxide terrace deposit through which AMD is flowing. Below this conductive zone
is higher resistivity rock (resistivity ranging from approximately 275 to 500 ohm-meters [2 to 4
mS/m conductivity]), which is the volcanic bedrock. While the thickness and conductance of the
terrace deposit vary, the longitudinal conductance (h/p) is more consistent, ranging from 53 to 96
mS/m. Figures 7 through 9 are plots of the best-fit section thicknesses and resistivities, and the
8.
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maximum and minimum thickness equivalent resistivity sections for VES1, VES2 and VES3 which
are all possible interpretations of the data. Equivalent sections are generated by varying the
thickness and resistivity such that the fit error does not exceed 6 percent above the best-fit error
(Interpex, 1988).
The resistivity profile was run for approximately 280 feet (85 m) subparallel to Little Dry Creek.
Figure 10 is a contoured pseudo-cross section showing conductivity in mmhos/m (= mS/m).
Areas of shallow high conductivity were found in the northeast (stations 0- to 20-feet [0- to 6-m])
and in the southwest (stations 260- to 280-feet [79- to 85-m]). A deeper zone of high
conductivity that does not reach the surface was found centered around the 140-foot (43-m)
station. The shallower zones are likely highly conductive due to high salt concentrations and high
moisture content in the near surface soils. The deeper anomaly may represent either a zone of
high sulfide mineralization, i.e. pyrite, or more likely a greater percentage of AMD in the terrace
deposit due to increased fracturing or reduced cementation.
Electromagnetic Surveys
Electromagnetic (EM) ground conductivity meter surveys were conducted across the flat area
around the open pit using the Geonics EM31 and EM34-3 instruments in horizontal and vertical
dipole modes with 3.7,10, 20, and 40 meter (12, 33, 66 and 131 ft) intercoil spacings. Prior to
conducting the EM surveys, an approximately 30-foot- (9-m-) square grid was established,
measured with a tape and marked with lath and surveyor's paint (Figure 6). Northing and easting
coordinate values shown on the figures are approximate footages derived from surveys conducted
for the HAR (S.S. Papadopulos and Associates, 1988).
Most of the EM survey area is flat except for the open pit vertical wall and the waste rock slopes
along the western edge of the study area. There are also scattered areas of metal debris, fencing
and dense vegetation that restricted access. To minimize the effect of topography, EM data were
collected parallel to slopes and at least one intercoil spacing distance away from the pit. Areas
of metal and dense vegetation were avoided. EM ground, conductivity contours along the western
edge of the study area likely show some impact from the waste rock slopes. EM contours
adjacent to the open pit may be influenced by the high specific conductance of the AMD pit
water but the trend of increasing ground conductivity toward the pit is clearly established at
•
distances greater than the EM intercoil spacing. This suggests a minimal impact from the vertical
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pit wall-on the EM readings.
The depth of instrument response for the Geonics EM31 and EM34-3 instruments differs
depending upon which dipole mode is used. Response depth for the horizontal dipole is
approximately 0.75 times the intercoil spacing and for the vertical dipole approximately 1.5 times
the intercoil spacing (McNeill, 1980 and 1990). Thus for the EM31 horizontal dipole with an
intercoil spacing of 3.7 meters (12 ft), the response depth is 9 feet (2.8 m), and 18 feet (5.6 m)
for the vertical dipole mode. Figure 13 is a modification of the EM31 vertical dipole data using
the normalization procedure suggested by Greenhouse and Slaine (1986). The values of
conductivity are expressed in decibels (dB) based on an arbitrary background value. A value of
0 dB is equal to background, whereas a value of 6 dB is approximately 2 times background.
Greenhouse and Slaine (1986) suggest ±4 or more dB from background is needed to be exceed
the level of natural noise. The advantage of normalizing the data to background is that
important patterns may become more obvious and comparisons can be made over time when the
value of background may change due to climatic changes, such as variation in soil moisture
content
Figures 11 and 12 show contours of ground conductivity measured with the EM31, horizontal and
vertical dipoles, respectively. The results of the EM31 show a halo of high conductivity at the
southern end of the open pit. In Figure 12, two lobes of high conductivity extend south and
southeast from the pit toward Little Dry Creek. Both lobes reach Little Dry Creek in areas
where AMD seepage along fractures is observed. Since the maximum response depth of the
EM31 is approximately 18 feet (5.6 m), these contours probably reflect the extent that AMD-
polluted ground water has penetrated the iron-oxide cemented terrace deposit.
Figures 14 and 15 show the contours of conductivity obtained with the EM34-3 at an intercoil
spacing of 10 meters with horizontal and vertical dipole response depths of 25 feet (7.5 m) and
50 feet (15 m), respectively. The 10-meter horizontal dipole contours show a high conductivity
halo approximately the same size as the EM31 produced halo. The high conductivity lobe
extending south is less pronounced, but may still reach the creek. The lobe extending southeast
from the pit is slightly broader than that found with the EM31. The 10-meter vertical dipole
contours show a broader halo with higher ground conductivity.
> _ >
•
Figures 16 and 17 show contours of the conductivity from the 20-meter intercoil spacing with
10.
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horizontal and vertical dipole response depths of 50 feet (15m) and 98 feet (30 m), respectively.
These data suggest the high conductivity halo is much narrower than at shallower depths. The
20-meter horizontal dipole shows an anomalous, northeast trending, elliptical area of high
conductivity centered approximately 100 feet (30 m) south of the pit, suggesting an area of
increased mineralization or flooded underground workings. An historic photo taken of the
dewatered open pit at the time of the Imperial Paint Company operations (=»1890s) shows an adit
extending southward from about half-way down the southeasternmost wall of the pit (photo from
DOC files). On the 20-meter vertical dipole contour map, the high conductivity lobe from the
south end of the pit has narrowed and shifted to the east of the area of the 20-meter horizontal
dipole anomaly.
Figures 18 and 19 show the contours of the conductivity from the 40-meter intercoil spacing with
horizontal and vertical dipole response depths of 89 feet (30 m) and 196 feet (60 m), respectively.
These contours show that the high conductivity halo has all but disappeared, suggesting reduced
penetration of AMD into the bedrock below a depth of 100 feel (30 m). The 40-meter
horizontal dipole contours show a negative anomaly centered approximately 40 feet (12 m) south
of the pit This negative anomaly corresponds with a 20-meter horizontal dipole anomaly and
may be an indication of metal buried in the underground workings. The negative anomaly is not
found with the 40-meter vertical dipole.
Self Potential Surveys
A self potential (SP) survey was conducted at the mine site in the area south of the open pit to
evaluate whether the ground-water seepage from the pit into Little Dry Creek could be detected.
The SP survey was conducted on the same 30-foot grid used for the EM surveys using porcelain
pot electrodes filled with a copper sulfate solution, a 1,500-foot (460-m) reel of insulated wire,
and a high impedance digital voltmeter. Figure 20 shows the contours of the SP survey data with
a large negative voltage anomaly at the southeastern comer of the pit. This is the area of most
of the seepage into Little Dry Creek. There is also a weaker negative lobe extending southward
from the southern pit wall, aligning with the high conductivity lobe seen in the EM31 vertical
dipole contours (Figure 13).
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In addition to collecting EM and SP data on the 30-foot grid, a 300-foot- (91-m-) long linear
survey with a 5-foot (1.5-m) spacing was run along the western bank of Little Dry Creek (Figure
6). This survey was done to determine if the SP and EM31 vertical dipole responses could be
correlated with the quality of the water at the edge of the creek. Total dissolved solids and pH
were tested along the water's edge with a special effort to collect seepage before dilution. The
fixed self-potential electrode was placed on a barely-submerged muddy bench at the southeastern
comer of the open pit.
The pH was measured with a temperature compensating Oakton WD-00605-55 portable
microprocessor pH/mV meter with an accuracy of ±0.01 pH units. The meter was calibrated in
the field using 4.01 pH and 7.01 pH standard solutions. Total dissolved solids were measured
with a Cole-Palmer DiST ATC dissolved solid tester, models 1491-60 (10 to 1,990 ppm [parts per
million]) and 1491-61 (100-10,000 ppm), which are temperature compensating and have an
accuracy of ±2% full scale. Total dissolved solid meters were calibrated using 300 ppm (447.1
/unhos) and 3,000 ppm (3,920 /xmhos) conductivity standard solutions.
Figure 21 shows plots of the self potential, EM31 vertical dipole, total dissolved solids, and pH
measurements taken along the 300-foot (91-m) traverse on the west bank of Little Dry Creek.
The 0-foot station is at the southwestern, downstream end. The area of greatest seepage is
clearly shown between the 190-foot and 260-foot (58-m to 79-m) stations by the increase in total
dissolved solids and decrease in pH. Negative SP readings correlate well with the water quality
data, showing a relative low of approximately 30 mV near the 210-foot (64-m) station. The
EM31 vertical dipole data show a much broader increase in conductivity near the center of the
survey line. The highest EM conductivity values are slightly downstream of the greatest visible
seepage, near the 170-foot (52-m) station. This EM anomaly corresponds to the area where the
EM31 high conductivity lobe reaches Little Dry Creek (Figures 12 and 13).
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CONCLUSIONS
Conclusions that can be reached from the resistivity, EM and SP geophysical surveys conducted
at Spenceville mine are:
D.C. resistivity soundings were able to identity the higher conductivity and thickness of
the terrace deposits. The value of resistivity'measured with D.C. resistivity is similar to
that measured with the EM31.
Electromagnetic ground conductivity meters EM31 and EM34-3 were able to identify a
high conductivity halo around the open pit, and several narrow high conductivity lobes
extending south and southeast from the southern portion of the open pit. These high
conductivity zones may represent penetration of AMD ground water into the terrace
deposits and fractured bedrock or may be zones of high sulfide mineralization. The EM
data suggest a decrease in the extent of the halo with depth.
The 20-meter and 40-meter horizontal dipole measurements suggest that there are either
flooded underground workings centered 40 to 100 feet (12 to 30 m) south of the
southeastern comer of the pit, or a zone of high sulfide mineralization.
A low-voltage, self potential anomaly correlates well with the area of known AMD
seepage from the open pit into Little Dry Creek, and with the shallow high conductivity
lobe extending southward as seen in the EM31 vertical dipole and EM34-3 10-meter data.
There is good correlation between the water quality data taken along the west bank of
Little Dry Creek (pH and total dissolved solids) and self potential data. Correlation
between water quality and the EM31 vertical dipole is less definitive.
RECOMMENDATIONS
A clean-up and reclamation plan for Spenceville mine is being developed. This plan will likely
require the filling of the open pit and periodic treatment of the AMD ground water to raise the
pH and reduce soluble metals. The rise in pH may cause the specific conductance of the ground
water to be lowered. Following treatment of the pit water, a reduction in specific conductance
should be reflected in subsequent conductivity measurements taken by the EM31 and EM34-3
instruments. Since the source of the AMD, primarily pyrite, cannot be fully removed, it is likely
that the pH will decrease over time and the specific conductance increase. Periodic treatment
may be necessary. The following recommendations are made regarding additional geophysical
surveys:
13.
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o kin order to assess the effectiveness of the ground-water treatment, a baseline EM survey
should be conducted across the flat eastern portion of the mine site including the filled
pit area.
o Periodic EM surveys should be conducted and compared to the baseline survey. Water
quality data, specifically pH, sulfate, and specific conductance, taken from monitoring
wells should be evaluated to determine whether there is a correlation with EM
conductivity measurements.
o Effectiveness of the ground-water treatment program might be measured in part by the
reduction in the size of the high conductivity halo surrounding the filled pit.
SPENCEVILLE MINE REFERENCES
Aubury, L.E., 1908, The Copper Resources of California, Bulletin No. SO: California State
Mining Bureau, p. 191-195.
Beard, J.S., and Day, H.W., 1987, The Smartville Intrusive Complex, Sierra Nevada, California:
The Core of a Rifted Volcanic Arc, Geological Society of America Bulletin, v. 99, p. 779-
791.
Bradley, W.W., 1930, Report XXVI of the State Mineralogist, State of California: Division of
Mines, p. 95-96.
Greenhouse, J.P., and Slaine, D.D., 1986, Geophysical Modelling and Mapping of Contaminated
Groundwater Around Three Waste Disposal Sites in Ontario: Canadian Geotechnical
Journal, v. 23, no. 3, p. 372-384.
Gudde, E.G., 1975, California Gold Camps: University of California Press, Berkeley, California,
p. 95.
Heyl, G.R., 1948, Foothill Copper-Zinc Belt of the Sierra Nevada, California, in O.P. Jenkin,
compiler, Copper in California, Bulletin 144: California Division of Mines, p. 11-29.
Interpex, Inc., 1988, RESDC™-08, D.C. Resistivity Interpretation Software, Users Manual, Golden,
Colorado.
Jennings, C.W., 1992, Preliminary Fault Activity Map of California, DMG Open-File Report 92-
03: California Division of Mines and Geology.
McNeill, J.D., 1980, Electromagnetic Terrain Conductivity Measurements at Low Induction
Numbers, Technical Note TN-6: Geonics Limited, Mississauga, Ontario, Canada, 15 p.
McNeill, J.D., 1990, Use of Electromagnetic Methods for Groundwater Studies, in S.H. Ward,
editor, Geotechnical and Environmental Geophysics, Investigations in Geophysics No. 5,
Volume I, Review and Tutorial: Society of Exploration Geophysicists, Tulsa, Oklahoma,
p. 191-218.
14.
-------
Page, R.W., Antilla, P.W., Johnson, K.C., and Pierce, MJ., 1984, Ground-Water Conditions and
Well Yields in Fractured Rocks, Southwestern Nevada County, California: U.S.
Geological Survey Water Resource Investigations Report 83-4262, 38 p.
S.S. Papadopulos & Associates, 1988, Spenceville Copper Mine, Spenceville Wildlife
Management and Recreation Area, Nevada County, California, Hydrologic Assessment
Report, 2 Volumes, prepared for California Department of Fish and Game, Rancho
Cordova, California, April 7,1988.
Xenophontos, C. 1984, Geology, Petrology and Geochemistry of Part of the Smartville Complex,
Northern Sierra Nevada Foothills, California: PhD. Dissertation, University of California,
Davis, 446 p.
15.
-------
I2t°22'30"
R.TE.
I2I°22'30'
Area covered by
map above
39*00'
Figure 2. Location map of Spenceville mine (from S.S. Papadopulos and Associates, 1988).
17.
-------
R6E.
SPENCEVILLE
MINE
EXP.I.ANAT
O N
-•soo—
Figures.
18.
Probable location of main shaft
Approximate location of mine tailings
Standing .water (reservoir, stock pond, etc.)
Dry, abandoned well
Perennial Stream
Intermittent Stream
Topographic contour. Interval is IOO feet
*
Topographic and hydrologic map of Spenceville mine (from S.S. Papadopulos and
Associates, 1988).
-------
PILOT PEAK
PLUTON
EXPUANATION
TERTIARY TO QUATERNARY
PILOT PEAK PLUTON
Undifferenfiafad diorile, granodiorife.
and quartz diorlle
UPPER JURASSIC IGNEOUS ROCKS
Suva
Slvu
Ssdu
Smarf villa Upper Volcanic Unit
Smart villa Lower Volcanic Unit
Smarlville Sheeted Dike Unit
Lithologic boundary
Anticline
Dike, showing Grientafibn
Inferred fault
39°OS'
Map •ImpllNad from X»nophonto», 1984
MILE
Figure 4. Regional geologic map of Spenceville mine (from S.S. Papadopulos and
Associates, 1988).
-------
NW
SE
Polcnllomclrlc
Sur fac• —
Pit
Br
Tailings
RoadFill
--Tie.
Little Dry
Creek
*niiti\niiiiiMiTrn*.
X
.
HI
Br
Tts -
Ttc -
Br -
mine tailing
terrace gravels and cobbles, Quaternary age
weathered sandstone, Eocene age •
iron oxide cemented terrace deposit, Eocene age
bedrock, undivided volcahics and metavolcanics, Jurassic age
Qti
Figure 5. Geologic cross section through Spenceville mine pit and Little Dry Creek (from
S.S. Papadopulos and Associates, 1988).
-------
SPENCEVILLE.
4400 4450 4500 4550 4600 4650 4700 4750 4800 4850
5725
5675
5625
5575 -
5525 -
5475 -.
5425 *
• '. /.• •/ .1 > -
•••• • •-- ••:./',W/;:':6At.
*a& S.-'//.JA^-*f/ /^
! i!.f. 'J/'X<* »/ fff'/^/7 •
....-•&--. •*"••>,.' • v.> eey.-' ^y
% ' ' ,» --- ^ •}*/•• •/" •*
> ^ ^ •" '• ;5r ^ ^ x.. .''/•./ CC-
^.^-v ..y-oa.,^/. 0/>
L 1_ 7:t-*'H_^4: I
- 5725
- 5675
- 5625
^ 5575
- 5475
- 5425
5375 -
5325 -
- 5375
i
i—i
I
- 5325
- 5225
- 5175
5125
5075
4400 4450 4500 4550 4600 4650 4700 4750 4800 4S50
EASTING
Figure 6. Spenceville mine geophysical survey grid and topography. Grid coordinates are in
feet, local datum. Dots are geophysical data points. Topographic contour interval
5025
-------
1000
o.
100 —
10
SPENCEVILLE VES1
WENNER ARRAY
1 1—I—1—I I I I
10
A-SPACING
-------
1000
?
,0,
10
SPENCEVILLE VES2
WENNER ARRAY
I I I I I I 11
10
100
£
ui
o
10
.
4 —
8 —
12 —
16 —
1 1 1 1 I 1
SSOnflMIl "*|*M
111 I
1 j
14—
76ohm-m I
, !
|
Mohm-m
ill i i i i i i i i
MINIMUM
i
BEST ;
454ohm- i i 1
1
, , | , ....ill
—
100
RESISTIVITY (ohm-m)
1000
Figure 8. Spenceville mine D.C. resistivity VES2 data and interpretation with equivalence
profiles. VES location shown on Figure 6.
23.
-------
1000
100 —
f£
01
10
,, I
SPENCEVILLE VES3
WENNER ARRAY
O
10
A-SPACING (feel)
100
4 —
8 —
12 —
16
417ohnvm
9ohnvm
SOOohnHn
_MM)MUML._
i I
BEST I
—,
!
__ =
MAXIMUM
I ' I
10 100
RESISTIVITY (ohm-m) .
1000
Figure 9.
24.
Spenceville mine D.C. resistivity VES3 data and interpretation with equivalence
profiles. VES location shown on Figure 6.
-------
0
SPENCEVILLE PSUEDO-CONDUCTIVITY, PROFILE
CONDUCTIVITY INTERVAL
2 nil I
20 40 60
100
120 140 160
DISTANCE (feet)
180 200 220 240 260 280
Figure 10. Spenceville mine D.C. resistivity psuedo-conductivity profile. Depth is apparent
based on a-spacing geometry. Location of profile shown on Figure 6.
-------
4400 44B0 4500 4550 4600 4650 4700 4750 4800 4850
5725 -
5675 -
5625 -
5575 -
5525 -
5475 -
5425 -
5375 -
5325 -
5275 -
5225 -
5175 -
5125
5075
5025
COMXCTIVITY INTERVAL
2 mil I ImhosXm
- 5725
- 5675
- 5625
- 5575
- 5525
- 5475
- 5425
- 5375
- 5325
- 5275
- 5225
- 5175
- 5125
- 5075
4400 4450 4500 4550 4600 4650 4700 4750 4800 4850
5025
Figure 11.
26.
Spenceville mine EM31 horizontal dipole contour map. Grid coordinates in feet.
Dots are geophysical data points.
-------
4400 4450 4500 4550 4600 4650 4700 4750 4800 4850
5725 -
- 5725
- 5675
- 5625
CONTOUR INTERVAL
2 mil I lSl«m«n«/m
5175 -
5125
5075
c 5075
5025
4400 4450 4500 .4550 4600 4650 4700 4750 4800 4850
502E
Figure 12. Spenceville mine EM31 vertical dipole contour map. Grid coordinates in feet.
Dots are geophysical data points.
27.
-------
4400 4450 4500 4550 4600 4650 4700 4750 4800 4850
5725 -
5675 -
5625 -
5575 -
5525 -
5475 -
5425 -
5375 -
5325 -
5275 -
5175 -
5125
5075
CONTOUR INTERVAL
2 0«c Iblee ( dB)
- 5725
- 5675
- 5625
- 5575
- 5525
- 5475
- 5425
- 5375
- 5325
5275
5225- // Vfc/V/^5^\\ W///r^ / / / 6225
- 5175
- 5125
^ 5075
5025
4400 4450 4500 4550 4600 4650 4700 4750 4800 4850
Figure 13. Spenceville mine EM31 vertical dipole decible contour map. Grid coordinates in
feet. Dots are geophysical data points.
28.
5025
-------
4400 4450 4500 4550 4600 4650 4700 4750 4800 4850
5725 -
5675 -
5625 -
CONTOUR INTERVAL
2 mil I iS temens/m
5125
5075
- 5725
- 5675
- 5625
- 5575
- 5525
- 5475
- 5425
- 5375
-i 5325
- 5275
- 5225
- 5175
5125
- 5075
5025
5025
4400 4450 4500 4550 4600 4650 4700 4750 4800 4850
Figure 14. Spenceville mine EM34-3 10-meter horizontal dipole contour map. Grid
coordinates in feet. Dots are geophysical data points. 29.
-------
4400 4450 4500 4550 4600 4650 4700 4750 4800 4850
5725 -
5675 -
5625 -
5575 -
5525 -
5475 -
5425 -
5375 -
5325 -
5275 -
5225 -
5175 -
5125
5075
5025
CONXCTIVITY INTERVAL
2 mil I tmho*/m
- 5725
- 5675
- 5625
- 5575
- 5475
- 5425
- 5375
- 5325
- 5275
- 5225
- 5175
- 5125
- 5075
4400 4450 4500 4550 4600 4650 4700 ' 4750 4800 4850
5025
Figure 15. Spencevilie mine EM34-3 10-meter vertical dipole contour map. Grid coordinates
in feet. Dots are geophysical data points.
30.
-------
4400 4450 4500 4550 4600 4650 4700 4750 4800 4850
5725 -
i i i i i i
CONTOUR INTERVAL
4 mil I lSl»m*ns/m
I I I I I I I I I ' I I I I I I
5125
5075 -
- 5725
- 5675
- 5625
- 5575
- 5525
- 5475
- 5425
- 5375
- 5325
- 5275
- 5225
- 5175
- 5125
5075
5025
4400 4450 4500 4550 4600 4650 4700 4750 4800 4850
5025
Figure 16. Spenceville mine EM34-3 20-meter horizontal dipole contour map. Grid
coordinates in feet. Dots are geophysical data points.
31.
-------
4400 4450 4500 4550 4600 4650 4700 4750 4800 4850
5725 -
5675 -
.5625 -
5575 -
5525 -
5475 -
5425 -
5375 -
5325 -
5275 -
5225 -
5175 -
5125 -
5075 -
5025
I I I I I I T I I I I I I I I I I I .
CONTOUR INTERVAL
4 mil I lSl«m»n«/m
- 5725
- 5675
- 5625
- 5575
r 5525
- 5475
- 5425
- 5375
- 5325
- 5275
- 5225
- 5175
- 5125
- 5075
J 1 1 1 5025
4400 4450 4500 4550 4600 4650 4700 4750 4800 4850
Figure 17. Spenceville mine EM34-3 20-meter vertical dipole contour map. Grid coordinates
in feet. Dots are geophysical data points.
32.
-------
4400 4450 4500 4550 4600 4650 4700 4750 4800 4850
5725
5675
i i i i i i i i i i
CONTOUR INTERVAL
2 mil I. IS I e me n s /m
- 5725
- 5675
- 5625
- 5575
- 5475
- 5425
O
i—i
I
5125 -
5075 -
- 5375
- 5325
- 5275
- 5225
- 5175
5125
5075
5825
5025
4400 4450 4500 '4550 4600 4650 4700 4750 4800 4850
Figure 18. Spenceville mine EM34-3 40-meter horizontal dipole contour map. Grid
coordinates in feet. Dots are geophysical data points. 33
-------
4400 4450 4500 4550 4600 4650 4700 4750 4800 4850
5725
5675
5625
5575 -
5525 -
5475 -
5425 -
5375 -
5325 -
5275 -
5225 -
5175 -
5125 -?
5075 -
5025
i i i
I I I I I I I I T I
CONTOUR INTERVAL
2 mil I iSlemensXm
I I L_U \ 1
- 5725
- 5675
- 5625
- 5575
- 5525
- 5475
- 5425
- 5375
- 5325
- 5275
- 5225
- 5175
- 5125
- 5075
5025
4400 4450 4500 4550. 4600 4650 4700 4750 4800 4850
Figure 19. Spenceville mine EM34-3 40-meter vertical dipole contour map. Grid coordinates
in feet. Dots are geophysical data points.
34,
-------
4400 4450 4500 4550 4600 4650 4700 4750 4800 4850
5725
5675
5625 -
- 5725
- 5675
- 5625
CONTOUR INTERVAL
5 mil I Ivol ts
4400 4450 4500 4550 4600 4650 4700 4750 4800 4850
Figure 20. Spenceville mine self potential contour map. Grid coordinates in feet. Dots are
geophysical, data points.
35.
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120-1
96-
9ELF-POTENTIM.
I I I I I I I I
eo tea
' DICTANOE
I i i i i I i i i i I i i i i I
toe 160 aoo 260
DISTANCE SM-NE
-------
LEVIATHAN MINE
MINE SITE HISTORY, GEOLOGY AND HYDROLOGY
Leviathan sulfur mine is an abandoned open pit mine near Monitor Pass approximately 2.5 miles
(4 km) north of Highway 89 and 8 miles (13 km) east of the town of Markleeville in Alpine
County, California (Figure 22). The mine site covers approximately 245 acres (100 hectares) of
disturbed lands in Sections 15 and 22, T.10N., R.21E., Mount Diablo Baseline. The area
investigated for this report is in the southern portion of the mine site near the open pit mine.
Geophysical surveys were conducted on the roads and slopes adjacent to three of four lined acid
mine drainage (AMD) evaporation ponds constructed on a waste dump that fills the Leviathan
Creek drainage (Figure 23).
Leviathan mine was first operated in 1863 to produce copper sulfate for processing silver ore at
the Comstock mines of Virginia City, Nevada (Taxer and other, 1991; and Graves, 1992). A
1,000-foot-long (300-m) adit was approximately 200 feet (60 m) below a second upper adit.
Mining ceased in 1872 due to depletion of copper sulfate. The underground mine reopened in
the 1930s to produce sulfur. In 1951 the Anaconda Copper Company purchased the mine and
began extracting sulfur from an open pit, to be used in processing copper ore at their Yerington
Nevada facility. The mine closed in 1962 due to high costs of the remote operation and a
reduced need for sulfur.
The initial open pit mining operation removed 200 feet (60 m) of overburden from the sulfur ore
body and deposited it in a dump on the north side of the pit. As the pit depth increased, waste
material was placed into the Leviathan Creek drainage to the south. Geotechnical boring in 1983
showed the depth of waste material in Leviathan Creek drainage to be a maximum of 130 feet
(40 m) with a maximum of 46 feet (14 m) in the area of the geophysical surveys for this study
(Brown and Caldwell, 1983). The open pit eventually reached a depth of 350 feet (106 m) and
consumed all of the older underground workings except for the No. 5 adit near the entrance of
the open pit. By 1982, Leviathan Creek had cut through the waste pile. Surface erosion and
creek underflow had created significant sedimentation and AMD inflows to Leviathan Creek,
Byrant Creek and the Carson River. The regional drainage pattern is shown on Figure 24.
37.
-------
In 198?"Leviathan mine remediation began, including channelizing Leviathan Creek through and
beneath the waste pile, regrading and contouring of the open pit and waste pile, placing •gravel
subdrains in the open pit and in the waste pile to collect ground water and water from seeps and
springs, constructing four AMD evaporation ponds totaling 11.4 acres (4.6 hectares), and placing
piping to direct AMD ground water from the open pit and No. 5 adit into and through the
system of ponds. Figure 25 is a schematic plan of the ponds, piping and subsurface drains in the
area of the geophysical surveys.
The sulfur ore body of Leviathan mine was an elliptical lense of elemental sulfur that had a
maximum thickness of 90 feet (27 m) and a length of at least 2,400 feet (730 m). Heavy metals
associated with the sulfur, which are now found in the AMD, include arsenic, copper and nickel.
Bedrock beneath the Leviathan Creek waste pile consists of Tertiary age andesitic breccias and
tuffs (Herbst and Sciacca, 1982; and Graves, 1992). Waste material beneath the evaporation
ponds is silty sand with numerous visible small pieces of elemental sulfur.
Major water pollution problems from the mine were first noted in 1952, when a fish kill
associated with the reopening of the old mine shafts occurred along Byrant Creek and the Carson
River. A second fish kill occurred in 19S9 along 10 miles (16 km) of the Carson River below the
confluence with Bryant Creek. The remediation measures undertaken in the early 1980s have
reduced the effects of AMD pollution. Water quality parameters monitored at the mine site
include pH, total dissolved solids, sulfate, aluminum, arsenic, iron, and nickel. The level of total
dissolved solids on lower Leviathan Creek averages 1300 mg/L, sulfate 600 mg/L, aluminum 15
mg/L, arsenic 034 mg/L, iron 122 mg/L, nickel 0.74 mg/L, and a pH 4.9. A pH of 25 was
measured in the evaporation ponds during the geophysical survey for this project
GEOPHYSICAL SURVEYS
General Discussion
Geophysical surveys were undertaken in the area of evaporation ponds nos. 1, 3 and 4 to evaluate
the application of electromagnetic (EM) ground conductivity meters (Geonics EM31 and EM34-
3) and self potential (SP) at detecting subsurface flow of AMD ground water. The surveys were
also made to evaluate whether EM methods can be used to model the layering and water quality
38.
-------
of the waste fill. EM and SP surveys were conducted along the roadways and slopes adjacent to
the evaporation ponds as shown in Figure 23. A sample spacing of 30 feet (9 m) was established
using a tape, and marked with lath and surveyor's paint. The SP survey points were the same as
the EM points on all lines except line 1, which was extended to the east to parallel line 3 on the
south side of pond no. 3.
A magnetometer survey was also run along the lines to determine whether the high level of noise
found in portions of the EM data was due to buried ferrous metal. Magnetometer stations at 10-
foot (3-m) intervals were paced off between the 30-foot-spaced EM stations.
Electromagnetic Surveys
Seven electromagnetic ground conductivity meter surveys were completed along the roadways and
benches in the slopes adjacent to ponds nos. 1,3 and 4. They were conducted with the Geonics
EM31 and EM34-3 instruments using vertical and horizontal dipole modes at 3.7, 10, 20, and 40
meter (12, 33,66, and 131 ft) intercoil spacings. Figures 26 through Figure 32 show the
measured ground conductivity and geoelectric cross sections interpreted from the data using
Interpex EM34PLUS software (Interpex, 1989).
EM data were erratic suggesting either a high degree of heterogeneity in the waste material,
varied moisture content from buried springs, varied ground water quality, or a combination of the
three. To minimize the impact of topography, surveys were run along the center of roadways and
berms. If there was sufficient area, preliminary testing was done at differing distances from the
change in slope to find the most stable distance.
The modeling results of the EM surveys are that the waste pile has a thin surface layer of very
high conductivity material with values from 150 to 800 mmhos/m. This high conductivity may
reflect weathering of the sulfur, which produces a low pH and high sulfate content each of which
causes a significant increase in conductivity. An interesting feature is the rise in EM31
conductivity along line 2 at the contact with the recently constructed levee around pond no. 3
(Figure 27).
39.
-------
Below the very high conductivity surface layer is a high conductivity layer typically 15 to 50 feet
thick (4.5 to 15 m) with a conductivity that ranges from 40 to 180 mmho/m. This layer is
interpreted to be the waste material. Some of the variation in the conductivity may be due to
variations in moisture content or quality of the ground water. The level of ground water in the
waste pile is unknown. However, site maps show historic seeps, springs and subdrain placement.
A large seep is visible at the toe of the slope between ponds nos. 3 and 4. It is interesting to
note that on line 1 the conductivity values of the horizontal dipole begin to rise near the visible
seep while the vertical dipole values do not (Figure 26).
The lowermost EM model layer is interpreted to be the underlying volcanic breccia and
tuffaceous bedrock. The modeled conductivity of the bedrock varies from 10 to 85 mmhos/m.
These values are similar to those found by Graves (1992), who conducted a series of EM34
surveys in the open pit, in the area to the east of ponds, and along the southern edge of pond no.
2. Apparent conductivity values of 50 to 60 mmhos/m were observed by Graves (1992) in areas
underlain by volcanic bedrock probably similar to bedrock beneath the evaporation pond area.
The depth of the geoelectric contact between the waste material and the bedrock appears to be
greater than might be expected from analyzing old borehole data of the waste pile thickness and
present ground elevation (Brown and Caldwell, 1983). This difference may be caused by
weathering and saturation by AMD of the upper bedrock surface, or errors in the model
interpretation caused by the heterogeneity of the waste material.
Self Potential Surveys
Self potential surveys were conducted along EM survey lines 1, 2, 3 and 4. Survey line 1 was
extended 420 feet (128 m) to the east to provide data for a comparison with line 3. The survey
was conducted using porcelain electrodes filled with copper sulfate solution, a 1,500-foot (460-m)
reel of wire and a high-impedance voltmeter. The fixed reference electrode was placed in the
AMD water at the west end of pond no. 3. Periodic SP readings were taken at the reference
electrode to allow for drift correction. Results of the SP surveys indicate that the method can be
used to locate areas of ground-water seepage, subsurface drains and possibly pipelines.
The SP survey along line 1 shows an erratic but steadily decreasing voltage from the 100-foot
station (30-m) to a large negative anomaly at the 600-foot station (183-m) (Figure 33). This
40.
-------
initial erratic negative SP voltage corresponds with a seepage drain shown east of pond no. 4
(Figures 23 and 25). The large negative SP anomaly corresponds with several buried springs and
a seepage drain. The EM data for line 1 do not show a strong response to this area of seepage
(Figure 26). It should be noted that the negative low is up the road and upslope from an
observable area of seepage in the slope between pond nos. 3 and 4.
The SP survey along line 2 revealed an area of nearly flat SP voltages for the first 330 feet (100
m) (Figure 34). SP voltage was erratic on the remainder of the line. A large positive anomaly of
approximately 18 millivolts (mV) was observed across the last two stations and corresponds to a
positive anomaly observed at the beginning of SP line 3 (Figure 35). The cause of this anomaly
is unknown but apparently corresponds with the edge of the levee constructed around pond no. 3.
A negative anomaly at the 120-foot station (37-m) of line 3 corresponds to a monitoring well and
buried 12-inch (30-cm) PVC overflow pipe from pond no. 3 (Figure 25). A large positive
anomaly is at the 240-foot (73-m) station and a small negative anomaly at the 300-foot (91-m)
station. The cause of the positive anomaly is unknown, but the small negative anomaly is located
to the 12-inch PVC pipe connecting ponds nos. 2 and 3. Also the schematic drawing (Figure 25)
shows a 12-inch PVC seepage drain running parallel to the east and south levees of pond no. 3.
The SP survey data from line 4 were somewhat erratic with SP voltage varying from 3 to 9 mVs
but the overall variation is much less than observed in other lines. The positive anomaly at the
75-foot (23-m) station is likely due to a buried stormwater drain pipe that crosses the survey line
(Figure 25). The erratic nature of SP line 4 data may reflect the buried gravel seepage drain that
apparently runs parallel to the survey line.
Magnetometer Surveys
To evaluate whether the erratic EM data were due to buried ferrous metal objects,
magnetometer surveys were run along all seven of the EM survey lines. Magnetometer stations
were spaced at 10-foot (3 m) intervals. Total magnetic field surveys were conducted using a
Geometries G-856 instrument with a single proton precession sensor. At least 2 measurements
were taken at each station. Data were recorded when readings were within one tenth gamma.
Times of readings were recorded. Measurements at the first station of each line were taken at
the beginning and end of each survey to correct for drift.
41.
-------
Results of the magnetometer surveys are shown in Figures 33 through 37. Station data are
plotted along with a running five point average curve that smooths erratic reading and provides a
better plot of trends in the data.
Figure 33 shows the survey line 1 data to be erratic for the first 200 feet (61 m). This area lies
above a seepage drain (Figure 25), corresponds to erratic SP data (Figure 33) and to slightly
erratic EM data (Figure 26). The cause of the magnetic anomaly may be metal buried in or near
the drain gravel or the pipe. The magnetic readings also become somewhat erratic at the east
end of line 1. This is in the area of the pipeline between ponds nos. 2 and 3 (Figure 25) and
* _ ^^^
corresponds with an EM31 anomaly found in line 3 (Figure 28). This magnetic low may be due
to metal buried in thrust/anchor blocks at pipe joints or metal seepage collars placed along the
pipe.
Line 2 shows a steady fall in magnetometer values near the 270-foot (82-m) station (Figure 34).
This low is between two peaks in the EM31 and 10-m vertical dipole data (Figure 27), and is
near the point when the SP data becomes erratic.
Magnetometer readings of line 3 show a broad magnetic low, centered around the 240-foot (73-
m) station (Figure 35). This low corresponds with a peak in SP voltage and is approximately 70
feet (21 m) offset from a peak in the EM data (Figure 28).
Magnetometer readings of line 4 are relatively flat except for those near the 200-foot (61-m)
station (Figure 36). This area is above a large reinforced concrete pipe that runs drainage of
Leviathan Creek beneath the waste pile (Figure 25). The anomaly may be the steel
reinforcement in the pipe. Similar responses were seen in magnetometer line 5 (Figure 37). The
EM data also show a strong negative anomaly at the end of lines 4 and 5 (Figures 29 and 30).
Lines 6 and 7 shows strong magnetic responses to the presence of the concrete reinforced
Leviathan Creek drainage structure (Figure 37).
42.
-------
CONCtUSIONS
Conclusions that can be reached from the EM, SP and magnetometer surveys at Leviathan mine
are:
o Electromagnetic ground conductivity meters can be used to evaluate layering and AMD
ground-water flow in mine waste piles. Heterogeneities of the waste pile due to mixing of
materials, variation in water quality, and topographic relief introduce some error in the
model interpretation of layering and conductivity.
o Self potential surveys can be used to locate subsurface drains, pipes and ground-water
flows. The SP response over seeps generally gives a negative anomaly.
o Where magnetometer data were erratic, EM data were also erratic. However, the reverse
was not always true. Wider EM intercoil spacing data correlated better with broad
magnetic anomalies, suggesting a deep source for the high conductivity.
o The magnetometer generally responded with positive and negative anomalies over buried
pipes and drains and steel-reinforced open channels. There is some correlation between
EM anomalies and the magnetometer anomalies, particularly for lines 4, 5, 6 and 7.
o Magnetometer surveys should be done in conjunction with EM conductivity surveys over
waste piles or where buried structures are present, to help determine if anomalies are due
to ferrous metal objects.
RECOMMENDATIONS
Remediation measures for Leviathan mine continue. Efforts are being made to reduce the
underflow of water from Leviathan Creek that seeps through, the waste pile and generates AMD.
In addition, study of the surface and ground-water hydrology continues, in order to better
manage the water balance of the ponds. The following recommendations are made for possible
additional geophysical studies:
o Consideration should be given to conducting seismic refraction surveys in the Leviathan
Creek drainage above the channelization structures to determine the depth of alluvial fill.
material. These studies would aid in the design of any cutoff walls or grout curtains
placed to reduce underflow.
o If the depth and contour of the waste pile-bedrock contact are of interest, e.g. in selecting
locations for ground-water monitoring or extraction wells, then seismic refraction surveys
should be conducted along the roadways.
43.
-------
Additional SP surveys conducted along a grid could be undertaken to help delineate areas
of ground-water seepage. Those areas identified by large negative SP anomalies would
be potential ground-water extraction locations.
Repeat EM surveys could monitor remediation measures to reduce underflow.
LEVIATHAN MINE REFERENCES
Brown and Caldwell Consulting Engineers, 1983, Leviathan Mine Pollution Abatement Project-
Design Report and Draft Environmental Impact Report, prepared for Regional Water
Quality Control Board, Lahontan Region, South Lake Tahoe, California, 189 p.
Graves, K.L., 1992, Terrain Conductivity Mapping of the Leviathan Sulfur Mine for the Location
of Acid Mine Drainage, Master's Thesis, California State University, Sacramento, 52 p.
Herbst, CM., and Sciacca, J.E., 1982, Geology of the Leviathan Sulfur Mine and Vicinity,
California: State Water Resources Control Board, Division of Technical Services,
Sacramento, California.
Interpex Limited, 1989, EMK-M1"*, EM Interpretation Software, Golden, Colorado.
Taxer, EJ., Churchill, JJ., and Gill, R.S., 1991, A History of the Leviathan Mine Pollution
Abatement Program, Alpine County, California, prepared for the California Regional
Water Quality Control Board, Lahontan Region, South Lake Tahoe, California, 18 p.
44.
-------
.
South K
Lake Tahoe*.X
f PEAK
\
LEVIATHAN
ALPINE co
LEVIATHAN/
MINE
Figure 22. Location map of Leviathan mine.
45.
-------
P Spring
4-27 Depth (feet) of Waste
Rock based on
Preradin Exploration
Figure 23. Leviathan mine topography and geophysical survey line locations map (after
Brown and Caldwell, 1983)
46.
-------
NEVADA
DOUGLAS CO.
Figure 24. .Leviathan mine regional hydrology map (after Graves, 1992).
47.
-------
*.
GO
IOWIK
UVIAIIIAH
CIIA4NU -
O Hinholcs
A Monitoring Uellt
O Pond Over MUM St'
O Stum Utltr Drop Inltts
IMCI SI*J
IRIBUT/Wt CIIAHNfl I
18" PVC
Figure 25. Leviathan mine schematic map of ponds and piping, no scale (after Brown and
Caldwell, 1983).
-------
VO
^300-350 mmhos/rn
a
o
1751
200+
m 25
i
SCALE
0 25
m
3.7 m
10 m
20 m
40 m
3.7 m
10 m
20 m
40 m
SCALE - 1: 1200
Figure 26. Leviathan mine Line 1 EM data and geoelectric. cross section.
for: CA DOC
U.S. Geological survey
tati Set: LVEN.I
Date: NOV 93
Line: Li
EPA AMD & GEOPHYSICS
LEVIATHAN MINE
ALPINE COUNTY. CALIF.
Azimuth: N10H
-------
Ui
o
100+
SCALE
m 25 o 25 m
1 ' ' SCALE - 1: 1200
Figure 27. Leviathan mine Line 2 EM data and geoelectric cross section.
150+
175+
tn '
2004
a
o
3.7 ffl
10 m
20 m
40 m
3.7 m
10 m
20 m
40 m
for: CA DOC
U.S. Geological Survey
Data Mt: LVEM.2
cm • nw
Date: NOV 93
Line: Lg
EPA AMD fi GEOPHYSICS
LEVIATHAN MINE
ALPINE COUNTY. CALIF.
Azimuth: N20H
-------
2001
1504
175*
m 25
SCALE
o
3.7 ffl
10 m
20 m
40 m
3.7 m
10 in
20 m
40 m
25 m
SCALE - 1: 1000
Figure 28. Leviathan mine Line 3 EM data and geoelectric cross section.
for: CA DOC
U.S. Geological Survey
Dit« Set: IVtHLi
Oatt: MOV 93
Line: L3
EEA AMD 6 SEQEHYSltS
LEVIATHAN MINE
ALPINE COUNTY. CALIF.
Azimuth: N10W-N55H
-------
Lft
m 20
SCALE
o
BO*
20 m
- 1: 480
Figure 29. Leviathan mine Line 4 EM data and geoelectric CTOSS section.
3.7 m
10 m
20 m
40 m
3.7 m
10 m
20 m
40 m
0
for: CA DOC
to U.S. ecological Survey
D*tl Sit: LVENL4
tvlMMl: mi 1 DIM
Date: MOV 93
Line: U
\ — EPA AMD S GEOPHYSICS
LEVIATHAN MINE
ALPINE COUNTY. CALIF.
Azimuth: N3BE
-------
3.7 m
10 m
20 m
40 m
3.7 m
10 m
20 m
40 m
OJ
Figure 30.
m 25
SCALE
0
25
i
m
: SCALE - 1: 750
Leviathan mine Line 5 EM data and geoelectnc cross section.
for: CA DOC
U.S. Geological Survey
Mtl Sit: LVEMLS
*: nai c «u
Date: NOV 93
Line: L5
EPA AMD 6 6EOPHYS1C5
LEVIATHAN MINE
ALPINE COUNTY. CALIF.
Azimuth: N38E
-------
150
3.7 m
10 m
20 m
40 m
3.7 m
10 m
20 m
40 m
m 25
QUHL.C
0
mine
Line 6 EM
data
25
I
and geoelectric
m
SCALE -
1: 750
cross section.
for:
>r U.S
teti Sit:
MlMM: M
CA DOC
. Geological Survey
lVCMLt
1
-------
a
o
a
o
3.7 m
10 m
20 m
40 m
3.7 m
10 m
20 m
40 m
I/I
m 50
Figure 32.
SCALE
50
I
m
• SCALE - 1: 1200
Leviathan mine Line 7 EM data and geoelectric cross section.
for: CA DOC
tr U.S. Geologic*! Survey
Dili Sit: LVEM.7H
*: mi c OM
Date: NOV 93
Line: L7
EEA AMD S GEOPHYSlCT
LEVIATHAN MINE
ALPINE COUNTY. CALIF.
Azimuth: EM-N45M
-------
in
52000 -i
CO
51
o
51600-
51200-
50800•
LEVIATHAN MINE
MAGNETOMETER LINE 1
CORRECTED DATA
B-PT AVERAGE
0
200
-rrr-r
400
600
800
i i i I i
1000
1200
0-1
LEVIATHAN MINE SP LINE 1
-15 —i i l l I I i I I 1
I I IIIIIIII.
400 600
Die tone© (fee
1200
Figure 33. Leviathan mine Line 1 SP and magnetometer profiles.
-------
51800-i
CO
51600 -
o
51400 -
LEVIATHAN MINE
MAGNETOMETER LINE 2
CORRECTED DATA
5-PT AVERAGE
51200-
0
« I '
100
i i i
200
300
I I I I I I I I I
400
i I i i i i i i i i
500
600
LEVIATHAN MINE SP LINE 2
Figure 34.
200 300 -400
Die ton ce ( fee t)
Leviathan mine Line 2 SP and magnetometer profiles.
600
-------
-------
52000 -i
CO
51500-
CD
51000 -
50500•
LEVIATHAN MINE .
MAGNETOMETER LINE 4
CORRECTED DATA
5-PT AVERAGE
0
I I I I I I I I I | I I I I I I I I I | I I I I I I I I I | I
50 100 150
200
250
300
O
>
OL
CO
-2-3
-4-
-6-
-8-
LEVIATHAN MINE SP LINE 4
-10
0
i i i I i i i i i i i i i | i i i i i i i i i | i M M .
50 100 150 200
Dls Lonco ( fee t)
Figure 36. Leviathan mine Une 4 SP and magnetometer profiles.
250
300
-------
ON
O
51500-1
51000-
LEVIATHAN MINE
MAGNETOMETER LINE 7
• • • • CORRECTED DATA
5-PT AVERAGE
50500 | I | I I I I I I I | I I I
0 100
500
600
52000-q
51000-1
O 50000-E
49000-
LEVIATHAN MINE
MAGNETOMETER LINE 6
CORRECTED DATA
6-PT AVERAGE
0
I I I I I I I I I | I I I I I I
100
I f I I I I I I I I I | ' ' I I I I I I I | I
200 300 400
500
600
52000-
50000-
LEVIATHAN MINE
MAGNETOMETER LINE 5
CORRECTED DATA
B-PT AVERAGE
0
I I I I I i I I I I I | I I I I i I I I i | I r
50 100 150 200
Die tance ( fee t)
Figure 37. Leviathan mine One 5,6 and 7 magnetometer profiles.
300
-------
IRON MOUNTAIN MINE
MINE SITE HISTORY, GEOLOGY AND HYDROLOGY
Iron Mountain mine is 9 miles (14.5 km) northwest of Redding, Shasta County, California
(Figure 38). The mine site covers an area of approximately 4,000 acres (1,600 hectares) in the
steep foothills of the southern Klamath Mountains. The mine is in Sections 2 and 3, T.32N.,
R.6W., and Sections 34 and 35, T33N., R.6W., Mount Diablo Baseline. Iron Mountain is
drained by two creeks: Slickrock Creek on the west and Boulder Creek on the east. The creeks
are tributaries to Spring Creek which today drains into Keswick Reservoir, a water supply
reservoir on the Sacramento River.
Iron Mountain mine is the southwesternmost mine of the West Shasta Mining District, a 9-mile-
(14.5-km-) long, 1-mile- (1.6-km-) wide, N.25°E. trending zone of sulfide mineralization (Kinkel
and Albers, 1951; and Kinkel and others, 1956). The West Shasta Mining District produced
silver, gold, copper, zinc and pyrite. Iron Mountain mine is in an Early Devonian sequence of
volcanic and sedimentary rocks. The disseminated and massive sulfide ore deposits mined at Iron
Mountain are enclosed by the Balaklala rhyolite, a 3,500-foot- (1,000-m-) thick unit of soda-rich
rhyolitic flow and pyroclastic rocks. The main ore minerals are chalcopyrite (CuFeSz), sphalerite
(ZnS) and pyrite (FeS). Iron Mountain mine derives its name from the gossan cap on the sulfide
mineralization. The gossan cap was formed by oxidation of the sulfides and leaching of the sulfur
and most metals leaving behind a hydrated iron oxide skeleton. Iron Mountain mine comprises
four major and a number of smaller underground workings, an open pit, a sidehill quarry and
numerous tailing dumps and waste piles.
Iron Mountain mine was discovered in 1865 and claimed as a potential source of iron ore. In
1879, silver and gold were discovered in the gossan and mined until 1894. In 1895, copper
sulfides were discovered beneath the gossan in the area now called the Old mine. From 1896 to
1907, the Old mine was worked underground producing at least 1.6 million tons (1.45 metric
tons) of copper ore at an average grade of 7 percent. Silver and gold were also extracted. In
1907 a disseminated chalcopyrite ore body, was discovered beneath the Old mine and worked
underground. This mine, the No. 8 mine, produced approximately 820,000 tons (744,000 metric
tons) of copper ore. From 1929 to 1942 the gossan in the vicinity of the Brick Flat Pit, near the
61.
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crest of Iron Mountain, was again mined for silver and gold. This sidehill mine was known as the
Quarry. Miffe'wdste and overburden materials were cast over the slope into the Slickrock Creek
drainage. Waste rock blocked Slickrock Creek and caused noticeable increases in sedimentation
downstream. In 1933, flood water breached a waste rock dam on Slickrock Creek. From 1955 to
1962, Brick Flat Pit was an open pit massive pyrite mine. The waste rock and overburden were
cast into the Slickrock Creek drainage. In 1955, a massive landslide in the waste pile deposited
60 to 80 feet (18 m to 24 m) of debris on top of the Old mine and No. 8 mine portals and moved
the drainage course of Slickrock Creek 40 feet (12 m) to the west. In 1956, all underground
mining at Iron Mountain ceased and in 1963 all mining ended (CH2M Hill, 1993; Kinkel and
others, 1956; and Kinkel and Albers, 1951).
Iron Mountain mine has released AMD into the Sacramento River watershed for more than 50
years (CH2M Hill, 1993). AMD is generated when precipitation infiltrates the massive sulfide
deposits of the mountain and exits from the old underground workings. Some AMD is also
released when surface waters flow through the waste rock that fills the Slickrock Creek drainage.
Iron Mountain has among the most acidic mine waste streams in the world. The mines on Iron
Mountain discharge an average of more than one ton of toxic metals into the Sacramento River
drainage every day. The mine is the single largest point discharge of toxic metal into one of
California's largest water systems. Toxic metal discharge from Iron Mountain has created major
problems in the Sacramento River ecosystem, affecting a $30 million-a-year commercial fishing
industry and directly threatening the winter-run chinook salmon, a species listed as threatened
under the Endangered Species Act
The area selected for geophysical investigation is in the western portion of the mine site at the
toe of a large waste pile that fills the Slickrock Creek drainage and covers the portals of Old
mine and No. 8 mine (Figures 38 and 39). The study area is square with sides of approximately
300 feet (91 m) (Figure 39). The surface rises approximately 50 feet (15 m) from south to north.
A large south draining wash occupies the eastern portion of the study area, creating undulating
topography. There are several springs in the study area that contribute an estimated one-third of
the volume of all of the AMD point discharges at Iron Mountain (CH2M Hill, 1993). The
source of the seepage is thought to be the underground workings of either Old mine or No. 8
mine or both, hence the name Old/No.8 seep. Most of the discharge in the study area comes
from one spring which has been captured and directed into a stainless steel flume. Monitoring of
62.
-------
the Old/No.8 seep has been sporadic but historic data indicate that flow rates range from IS to
•
230 gallons per minute (gpm) (1 to 14 liters/sec [1/s]) with an average of 60 gpm (3.8 1/s). Water
quality measurements taken since 1983 show concentrations of copper from the spring average
133 mg/L and reach 250 mg/1. Zinc averages 55 mg/L with a high of 140 mg/L, cadmium
averages 0.49 mg/L with a high of 1.17 mg/L, sulfate averages 7,000 mg/L, total dissolved solids
average 11,150 mg/L and pH values average 2.58 with a low of 1.15 (CH2M Hill, 1993).
Subsequent to these geophysical investigations, an extraction well was installed west of an open
vertical shaft above the Old/No. 8 mine. Observations in the shaft at the time of the survey
indicated that the ground-water level was approximately 75 feet (23 m) below the surface in the
northern portion of the study area. Pumping of this well has dried up the springs in the study
area.
GEOPHYSICAL SURVEYS
General Discussion
Geophysical surveys were undertaken in an area surrounding the Old/No.8 seep in order to
determine whether surface geophysical methods could identify the source of the AMD springs.
Three geophysical methods were used, electromagnetic (EM) ground conductivity using the
Geonics EM31 and EM34-3, self potential (SP), and magnetometer. Surveys were run along five
linear traverses approximately parallel to the slope of the waste pile as shown in Figure 39.
Sampling stations were established every 30 feet (9 m) for the EM34-3 and SP, using a tape, and
marked with lath and surveyor's paint. Magnetometer and EM31 spacings were taken at 5-foot
(1.5-m) spacings established by pacing between marked 30-foot stations.
Electromagnetic Surveys
Electromagnetic ground conductivity surveys were conducted along five linear traverses using the
Geonics EM31 and EM34-2 instruments. EM31 readings were taken in the horizontal and
vertical dipole modes at an intercoil spacing of 3.7 meters (12 ft). EM34-3 measurements were
taken in the horizontal dipole mode only at 10, 20, and 40 meter (33, 66, and 131 ft) intercoil
spacings. EM34-3 readings were taken in the horizontal dipole mode only because irregularities
63.
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of the waste rock pile made it difficult to tune the instrument.
*'
Contours of the EM survey data are shown on Figures 40 through 44. EM31 horizontal and
vertical contours show high-conductivity shallow ground surrounds two springs, the largest spring
and a much smaller one located approximately 130 feet (40 m) to the east (Figures 40 and 41).
The conductivity contours appear to coalesce downslope toward Slickrock Creek. This may be
due to a merging of infiltrating AMD surface water or a flattening of the topographic rise that
separates the two springs. The EM34-3 10-meter data indicate a much larger area of high
conductivity surrounds the largest spring (Figure 42). With an increase in the intercoil spacing,
*
the EM data show .that the center of the high conductivity anomaly shifted to the east and, at an
intercoil spacing of 40 meters, is approximately midway between the springs. Because of the 50
feet (15 m) of topographic relief across the study area, some reduction in the extent of the EM
anomalies has probably occurred. The probable increase in distance between the surface and the
AMD ground water upslope from the springs should reduce the apparent ground conductivity
Self Potential Survey
A self potential (SP) survey was conducted using the same 30-foot sampling stations as the
EM34-3 surveys. The purpose of the survey was to evaluate whether SP measurements could
identify the source of the largest spring. The SP survey was conducted using porcelain pot
electrodes filled with a copper sulfate solution, a 1,500-foot (460-m) reel of wire, and a high
impedance digital voltmeter. The fixed reference electrode was placed several hundred feet to
the west of the survey grid. Figure 45 shows the contours of the SP survey data. The contours
show a large negative SP anomaly at the 90-foot (27-m) station of line 4. This anomaly is
approximately 90 feet (27 m) north-northeast of the largest spring and approximately 40 feet (12
m) south of a collapsed vertical shaft above the Old/No. 8 mine.
The results of the SP survey indicate that the source of the ground water supplying the largest
spring is probably an adit that connects with the vertical shaft visible at the surface. Subsequent
to this survey, an extraction well was constructed approximately 40 feet (12 m) west of the
vertical shaft in an attempt to capture the source of the seepage. Pumping of this well at a rate
of 230 gpm (14.5 1/s) effectively stopped the surface seepage.
64.
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Magnetometer Survey
>
A magnetometer survey was conducted over the EM and SP survey lines to evaluate whether
buried ferrous metal objects caused the high conductivity readings. The total magnetic field
survey was conducted using a Geometries G-856 instrument with a single proton precession
sensor. At least two measurements were made and the times recorded at each station. When
repeat measurements were within 0.1 gamma, the value was recorded. The first station of line 1
was read before and after surveying each line to allow for correction of diurnal drift. Figure 46 is
a contour map of the corrected magnetometer data. The figure clearly shows four magnetic
anomalies along line 4. The three western anomalies are associated with debris surrounding the
abandoned shaft. Their narrow width suggests a near surface metal source. The source of the
eastern anomaly is unknown because the area is within the large wash and covered with large
waste pile debris.
As a comparison, EM, SP and magnetometer data collected along line 4 were plotted in profile
(Figure 47). These plots show that the EM31 horizontal dipole responded to the sources of the
magnetic anomalies. The EM34-3 10-meter horizontal dipole may have sensed the magnetic
objects on the western end, but the other intercoil spacings do not appear to be affected. The
low point of the SP anomaly occurs between two magnetic anomalies, suggesting that buried
metal may influence the strength or be the cause of the SP anomaly. However, the success of the
extraction well at stopping the seepage is evidence that the SP anomaly is caused by ground-water
flow.
CONCLUSIONS
Conclusions that can be reached from the electromagnetic ground conductivity, self potential and
magnetometer surveys conducted at the Old/No.8 seep at Iron Mountain are:
o EM surveys identified zones of high conductivity, unsaturated zone material surrounding
two observed AMD springs originating in a waste rock pile. The centers of high
conductivity shifted from the springs to a point midway between them as the EM intercoil
spacing increased.
65.
-------
o Self potential survey data show a low negative voltage anomaly upslope from the largest
AMD spring and downslope from an abandoned mine shaft. Subsequent construction
and'ptrtlping of an extraction well in the vicinity of the SP anomaly stopped the springs,
suggesting that the SP anomaly was caused by ground-water flow.
o Magnetometer data indicate four buried ferrous metal objects. Three are associated with
the abandoned mine workings. Some response to the metal objects was seen in the EM31
and EM34-3 10 meter measurements. Deeper EM measurements show no response.
o Topographic relief may have reduced the extent of the EM anomalies upslope of the
springs. This may also explain the differences between the centers of the EM anomalies
and the SP anomaly.
RECOMMENDATIONS
Remediation of the Old/No.8 seep was begun several months after this study was completed.
Today there are no surface springs, and pumped ground water is drained directly into the
stainless steel flume. Follow-up geophysical surveys would be of interest in evaluating whether
the anomalies observed are altered by the change in ground-water flow caused by the extraction
well. The following are recommendations regarding additional geophysical surveys at the
Old/No.8 seep area:
o Additional EM31 and EM34-3 surveys could be undertaken to evaluate whether there is a
change in the anomaly pattern, in particular, whether the center of the anomaly will
continue to shift with depth.
o A repeat SP survey should be conducted to evaluate whether the low negative voltage
anomaly was due to ground-water flow or buried metal objects. This survey would be of
particular importance because it may show the increase in conductance of the ground
water does not rule out the use of SP surveys to track ground-water movement.
IRON MOUNTAIN MINE REFERENCES
CH2M Hill, 1993, Public Comment Remedial Investigation and Feasibility Study, Old/No.8 Mine
Seep, Iron Mountain Mine, Redding, California, prepared for U.S. Environmental
Protection Agency, Region DC, EPA Contract No. 68-W9-0031, EPA Work Assignment
No. 31-01-9N17, CH2M Hill Project No. RDD69017.TS.02.
Kinkel, Jr., A.R., and Albers, J.P., 1951, Geology of Massive Sulfide Deposits at Iron Mountain,
Shasta County, California: Division of Mines Special Report 14,19 p.
66.
-------
Kinkel, Jr., A.R., Hall, W.E., and Albers, J.P., 1956, Geology and Base-Metal Deposits of West
Shasta Copper-Zinc District, Shasta County, California: U.S. Geological Survey
Professional Paper 285, 156 p.
67.
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BRICK FLAT
PIT
IRON
MOUNTAIN
OLD/NO.8
MINE SEEP
SHASTA'LAKE
HORNET PORTAL
RICHMOND
PORTAL
LAWSON PORTAL
MINNESOTA FLATS
SPRING CREEK
RESERVOIR
WHISKEYTOWN
LAKE
KESWICK
RESERVOIR
Figure 38. Iron Mountain mine location and regional hydrology map (from CH2M Hill,
1993).
69.
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LAQ
EXTRACTION
WELL
2 large rocks
& small pine
150 FEET
Figure 39. Iron Mountain mine Old/No.8 mine geophysical survey line map. (Map by M.
Huneriach, 9/6/93)
70.
-------
20 40 60 80 100 120 140 160 180 200 220 ' 240 260 280 300
300
I I I I I I I I I I I
CONTOUR INTERVAL
4 mil I lSl«m»i»«/m
EXTRACTION
WELL
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300
Figure 40. Iron Mountain mine Old/No.8 mine EM31 horizontal dipole contour map. Grid
coordinates in feet.
71.
-------
0 20 40 60 90 100 120 140 160 180 200 220 240 260 280 300
300
I I I I I I I I
CONTOUR INTERVAL
4 mil I lSl«iMn*Xm
EXTRACTION
WELL _.
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300
Figure 41.
72.
Iron Mountain mine Old/No.8 mine EM31 vertical dipole contour map. Grid
coordinates in feet.
-------
0 20 40 60 80 100 120 1-40 160 180 200 220 240 260 280 300
300
- 280
CONTOUR INTERVAL -J
2 mU I
20 40 60 80 100 120 140 160 180 200 220 240 260 280 300
Figure 42. Iron Mountain mine Old/No.8 mine EM34-3 10-meter horizontal dipole contour
map. Grid coordinates in feet. •
73.
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0
20 40 60 80 100 120 140 160 180 200 220 240 260 290 300
CONTOUR INTERVAL
1 mil I lSl«rr»it«Xm -
20 40 60 80 100 120 1-40 160 180 200 220 240 260 280 300
Figure 43.
74.
Iron Mountain mine Old/No.8 mine EM34-3 20-meter horizontal dipole contour
map. Grid coordinates in feet.
-------
20 40 60 80 100 120 140 160 180 200 220 240 260 280 300
300
CONTOUR INTERVAL
1 mil I lS\«m*n«Xm
EXTRACTION
WELL
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300
Figure 44. Iron Mountain mine Old/No.8 mine EM34-3 40-meter horizontal dipole contour
map. Grid coordinates in feet.
75.
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300
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300
300
CONTOUR INTERVAL
mil I Ivol t«
20 40 60 80 100 120 140 160 180 200 220 240 260 280 300
0
Figure 45.
76.
Iron Mountain mine Old/No.8 mine self potential contour map. Grid coordinates
in feet.
-------
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300
OUR INTERVAL ...••'
50 gemmae .• • *
_ • * -^
i i -I i i i i i I i i
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300
Figure 46. Iron Mountain mine Old/No.8 mine magnetometer contour map. Grid
coordinates in feet.
77.
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IRON MOUNTAIN
OLD 4 No. 8 MINE
SELF-POTENTIAL LINE A
100 168
STATION (f««t)
-Be
r-0
—60
200
—100
250
60
IRON MOUNTAIN
OLD fc N». 8 MINE
MAONETOCTER. LINE 4
100 160
STATION (f««t)
53000
»-H
> 6-
U
IRON MOUNTAIN
OLD t ND. 8 MINE
EM-31 t Ett-31. LINE 4
- 10m K)
-20m HD
40m K)
3.7m K)
100
200
-5
-6
250
STATION (f««t)
Figure 47. Iron Mountain mine Old/No.8 mine Line 4 EM, magnetometer and SP profiles.
78.
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WALKER MINE
MINE SITE HISTORY, GEOLOGY AND HYDROLOGY
Walker copper mine is approximately 15 miles (24 km) east of Quincy, Plumas County, California
(Figure 48). The mine site is divided into two areas of disturbance: the portal and the tailings
disposal site. The portal area is on private lands within Section 12, T.24N., R.11E., Mount
Diablo Baseline (MDB). The tailings disposal site is approximately 1 mile (1.6 km) to the west
and downstream of the portal, at the confluence of Dolly and Little Grizzly creeks. The tailing
area is primarily in Sections 7 and 18, T.24N., R.12E., MDB. The mine site and tailings areas
are 5,700 feet to 6,200 feet above mean sea level.
The Walker copper mine is in the southern end of the Plumas Copper Belt, an 18-mile- (29-km-)
long, roughly N.20W.-trending zone of copper and iron sulfide mineralization. The Plumas
Copper Belt is one of California's most significant copper mineralized zones that is wholly or
closely associated with granitic intrusions (Smith, 1970). Walker mine produced copper and
minor quantities of gold and silver from about 1920 to 1943 (Dames and Moore, 1991). During
the years 1922 to 1930, the mine produced more than 80 million pounds (36 million kg) of
copper. Chalcopyrite (CuFeSj) was the principle ore but chalcocite (CujS) and tetrahedrite
(Cu10(Fe,Zn)2Sb4S13) were also mined. The mine extends approximately 3,000 feet (914 m) into
the mountain and then follows the main vein that trends N.20W.-N.33W. and dips 32°-70°NE. for
±7,000 feet (2,100 m). Along this main vein five different ore bodies were mined, the south,
central, north, 712 and Piute. Bedrock in the mine consists of a fine-grained, black, andalusite-
garnet schist and cordierite hornfels, and an intrusive quartz diorite (Smith, 1970). Granitic
bedrock is exposed at the edges of the tailings pile and is presumed to be continous beneath the
waste pile.
The ore was milled at a site approximately 1 mile (1.6 km) south of the mine and approximately
0.75 miles (1.2 km) east of the tailings pile. The tailings were piped as a slurry to a meadow at
the confluence of Dolly and Little Grizzly creeks. A small dam was constructed on Dolly Creek
and a levee was built along Little Grizzly Creek to impound the tailings (Figure 49). Water
evaporated from the tailing slurry and left a barren, fine-grained, well-graded, silty sand to clayey
silt that covers approximately 100 acres (40 hectares). The tailings pile is gently sloping,
79.
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unvegetated and capped with a white to light brown, silty sand vulnerable to winds. Dust clouds
*
from the tailings are commonly blown to the tops of the mountains to the east.
Dolly Creek flows through the northern portion of the mine tailings, cutting a ravine
approximately 20 feet (6 m) deep. Surface flows of Little Grizzly Creek are diverted against the
base of a mountain by a 30- to 50-foot- (9- to 15-m-) high tailings levee at the angle of repose.
The'creek is west of its thahveg shown on historic maps. Surface flows for the 100-year rainfall
event are estimated to have a peak flow of 3,900 ftVsec (110 mVsec) for Little Grizzly Creek and
920 ftVsec (26 mVsec) for Dolly Creek (Dames and Moore, 1991).
Walker mine and tailings pile have a history of pollution, AMD and heavy metal contamination.
In 1958, the Central Valley Regional Water Quality Control Board (CVRWQCB) adopted waste
discharge requirements for the tailings pile (CVRWQCB Resolution No. 58-81). The Board's
orders were revised in 1986 (CVRWQCB WDR Order No. 86-073) and established water quality
criteria for upstream and downstream monitoring stations on Dolly and Little Grizzly creeks.
Shallow surface samples of the tailings had pH values ranging from 4.6 to 7.2, and electrical
conductance ranging from 100 to 510 mmho/cm (Dames and Moore, 1991). Subsurface samples
taken during construction of seven monitoring wells and in seven additional exploration
boreholes found soil pH values ranging from 3.8 to 7.8. Static-acid-generation-potential tests
found that more than 50 percent of the tailing samples from the boreholes had a neutralization-
potential/acid-generation-potential (NP/AGP) ratio, indicating a marginal to likely potential for
generating acid (WESTEQ 1993). Total heavy metal concentrations hi the tailings range from 26
to 2,700 mg/kg for copper, 25 to 200 mg/kg for zinc, 3.1 to 140 rag/kg sulfate, and 8,000 to 52,000
mg/kg for iron (WESTEQ 1993). Changes in surface water quality as measured in samples along
Dolly Creek upstream and downstream of the tailings pile indicate an increase in electrical
conductance as great as 100 ftmho/cm, an increase as much as 0.75 mg/L for copper, and an
increase as much as 0.04 mg/L for zinc. On Little Grizzly Creek, increases in electrical
conductance were as high as 155 jamho/cm; copper 0.03 mg/L; and zinc 0.05 mg/L (WESTEQ
1993).
The ground water in the tailings pile as tested hi seven monitoring wells has an electrical
conductance ranging from 95 to 542 jtmhos/cm, total dissolved solids from 82 to 360 mg/L, no
detectable dissolved copper (<0.05 mg/L), no detectable dissolved zinc (<0.05 mg/L), sulfate
80.
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from no detectable (<0.5mg/L) to 240 mg/L, dissolved iron from no detectable (<0.05 mg/L) to
51 mg/L, and dissolved arsenic from no detectable (<0.01 mg/L)'to 0.007 mg/L (William Croyle,
CVRWQCB, personal communication, 1994).
GEOPHYSICAL SURVEYS
General Discussion
Geophysical surveys were undertaken at the Walker mine tailings pile to evaluate whether a
change in ground conductivity could be mapped in the subsurface and whether surface geophysics
could be used to establish the buried thalweg of Little Grizzly Creek. CVRWQCB staff are
interested in finding the low point in the ground-water flow beneath the tailing pile.
To accomplish these goals, five survey lines were established as shown in Figure 49. Four lines
trend roughly northeast-southwest, perpendicular to Little Grizzly Creek, and one tine trends
northwest-southeast perpendicular to Dolly Creek. EM31 and EM34-3 surveys in both horizontal
and vertical dipole modes with intercoil spacings of 3.7,10,20 and 40 meters (12,33, 66 and 131
ft) were conducted along each tine. Four D.C. resistivity Wenner array soundings (VES) were
conducted on the tines perpendicular to Little Grizzly Creek. As a follow-up, magnetometer
surveys were run on all five tines to locate possible buried ferrous metal objects. EM stations
were spaced at 50-foot (15-m) intervals and magnetometer stations at 10-foot (3-m) intervals.
EM stations were surveyed with a hip chain and marked with wooden lath. Magnetometer
stations were paced-off between lath stakes. VES stations were placed near the presumed
thalweg of the buried Little Grizzly Creek channel.
D.C. Resistivity Surveys
Four D.C. resistivity Wenner array soundings (VES) were conducted at selected locations on
tines 1, 2, 3 and 4 as shown on Figure 49. Resistivity measurements were made using the Geohm
3 portable resistivity meter. The results of the VES surveys were interpreted as two, three and
four layer models and are shown in Figures 50 through 53. Two of the soundings (WKVES1 and
WKVES3) did not penetrate to the granitic basement but the other two clearly reached the
81.
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resistive bedrock.
'*
In general, the VES surveys indicate an approximately l-to-10-foot- (0.3-to-3-m-) thick resistive
layer at the surface (1,220 to 4,140 ohm-m; 0.2 to 0.8 mS/m conductivity). This layer is
interpreted to be the upper dry vadose zone, the thickness being controlled by the depth to
ground water and the amount of capillary rise. The conductivity increases with depth. A two
layer zone of relatively high conductivity (2 to 20 mS/m; 48 to 430 ohm-m resistivity) with a total
thickness ranging from 27 to 40 feet (8 to 12 m) overlies' a high resistivity granitic basement. The
high conductivity zone overlying the bedrock is interpreted to be within the saturated and
capillary zones of the tailings. Conductivity values for the saturated zone were modeled to range
from 8 to 11 mS/m (126 to 90 ohm-m). The gradual increase in conductivity with depth suggests
a reduction in the quality of ground water and may reflect a decrease in pH and an increase in
total dissolved solids.
Electromagnetic Surveys
Electromagnetic ground conductivity surveys were conducted along each of five survey lines using
the Geonics EM31 and EM34-3 in both horizontal and vertical dipole modes with intercoil
spacings of 3.7,10,20 and 40 meters (12,33,66 and 131 ft). Data stations were placed at 50-foot
(15-m) increments. EM survey data were interpreted to create geoelectrical sections using
EMTX-34I'LUS software (Interpex, 1993). Figures 54 through 58 are plots of the horizontal and
vertical dipole data and the interpreted geoelectric section for each line. Several of the lines
encountered sharp negative anomalies that are interpreted to be buried ferrous metal objects,
such as pipes or rail lines.
The geoelectric sections of the tailings material based on EM surveys are similar to the D.C.
resistivity soundings. EM data are interpreted as 3 layer models. An uppermost lower-
conductivity zone that generally varies in thickness from 8 to 16 feet (2.5 to 5 m), underlain by a
15-to-25-foot- (4.5-to-7.5-m-) thick more-conductive zone. The lowermost layer at a depth of 36
to 40 feet (11 to 12 m) is interpreted to be low conductivity granitic bedrock.
EM line 3 (Figure 56) found a low point in the basement at near the 180-meter (600-foot) station
which is interpreted to be near the buried thalweg of Little Grizzly Creek. For other EM
82.
-------
sections, the location of the thalweg is less definitive but was placed where the bedrock begins to
•
rise. The p\ot of the buried thalweg based on EM surveys is shown in Figure 49. Also plotted
on the figure is a thalweg interpreted from the topography of an old, small scale (4 inches = 1
mile) geologic map (Ewing, 1927). The location of the thalweg based on EM surveys is roughly
parallel to that of the old topography except in the northwesternmost area along Dolly Creek.
At this location the old topography shows an earlier impoundment and tailings pond.
The geoelectric data of line 5 is less accurate than data of the other lines due to an increase in
the level of noise apparently caused by buried metal objects indicated by the magnetometer
^
surveys discussed below.
Magnetometer Surveys
To evaluate whether the sharp departures in the EM data and other high conductivity readings
are caused by buried ferrous metal objects, magnetometer surveys were undertaken along each of
the five lines. Total field surveys were done with the Geometries G-856 instrument with a single
proton precession sensor. At least two measurements were made at each station and the times
recorded. When repeat measurements were within one tenth gamma, the value was recorded.
The first station was read before and after surveying each line to allow for correction of diurnal
drift. Figures 59, 60 and 61 are plots of the magnetometer data. The data have been smoothed
using a 5-point weighted running average.
The results of the magnetometer surveys indicate that there may be numerous buried objects
along line 1 that cause variation or noise in the readings. The sharp departures seen in the EM
survey are not predominent in the magnetometer survey, suggesting the objects are deeply buried
or not predominantly ferrous metal. Line 2 is fairly flat and indicates little buried ferrous metal.
Line 3 is likewise fiat except for near station 825-feet (250-m). Line 4 is slightly noisy suggesting
some buried metal objects. Line 5 has the greatest magnetic anomaly of all lines. The narrow
anomaly is near the 650-foot (200-m) suggests a large ferrous metal object buried near the
surface. This is near the present channel of Dolly Creek. A large buried metal object would
account for the erratic nature of the EM data near this point.
83.
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CONCLUSIONS
Conclusions that can be reached from the D.C. resistivity, EM and magnetometer geophysical
surveys conducted at the Walker mine tailings area are:
o D.C resistivity VESs identified an uppermost low-conductivity zone that probably
represents a dry vadose zone; a middle higher conductivity zone, representing saturated
and near saturated tailings with water quality that decreases with depth; and a very high
resistivity granitic basement
o Geoelectric sections interpreted from EM data were similar to those interpreted from
D.C resistivity VESs data.
o EM ground conductivity meter surveys using the Geonics EM34-3 were able to identify
the contact between the tailings and the underlying granitic bedrock. The probable
buried thalweg of Little Grizzly Creek is mapped and is in general agreement with an old
topographic map.
o Magnetometer surveys indicate buried ferrous metal objects are numerous along lines 1
and 4. A large object is apparently buried near the surface where line 5 crosses Dolly
Creek. The other two magnetometer surveys, lines 2 and 3, revealed few metal objects.
RECOMMENDATIONS
A reclamation plan is being developed for revegetating the Walker mine tailings to reduce
sediment and metal load to Little Grizzly Creek, and to stop dust storms. The following
recommendations are made regarding additional geophysical surveys at Walker mine tailings pile:
^
o If further definition of the thalweg of Little Grizzly Creek is needed, additional EM
surveys should be made along lines perpendicular to the flow, between existing lines.
o EM borehole surveys (Geonics EM39) should be run in each of the PVC-cased
monitoring wells to determine hi detail the nature of the vertical conductivity variations
and confirm the increase hi conductivity with depth.
o Correlation between the monitoring well water quality data (pH, electrical conductance,
sulfates, total dissolved solids, etc.) and the surface and borehole EM readings should be
established. This information should be used to determine the level of pollution needed
to cause a recognizable surface anomaly.
84.
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Consideration should be given to conducting a more densely gridded EM survey to
identify "hot spots" of acid production or heavy metal concentration. Correlation between
water quality data and EM readings, along with forward modeling, can establish what
level of pollution might be recognizable by such surveys. Pollution levels should be at
least 4 dB above background values (- 1.5 times background).
Magnetometer surveys should be run with the EM surveys to identify buried ferrous metal
objects. Consideration should be given to conducting a vertical gradient magnetometer
survey to allow for contouring of the data collected at different times and to reduce the
errors introduced by correcting for diurnal drift.
WALKER MINE REFERENCES
Dames and Moore, 1991, Final Report, Walker Mine Tailings Rehabilitation Study, Plumas
National Forest, for U.S. Forest Service, Job No. 03619-019-044: Dames and Moore,
Sacramento, California, 26 p.
Ewing, S.C., 1927, Geology and Ore-Deposits of the Mt. Ingalls District, Plumas County,
California, M.S. Thesis Stanford University, Palo Alto, California, 176 p.
Interpex Limited, 1989, EMR-^11"*, EM Interpretation Software, Golden, Colorado.
Smith, A.R., 1970, Trace Elements in the Plumas Copper Belt, Plumas County, California,
Special Report 103: California Division of Mines and Geology, Sacramento, California,
26 p.
WESTEC, Inc., 1993, Monitoring Well As-Built and Waste Characterization Program for the
Walker Mine Tailings, WESTEC Project No. 27502, Report No. 732, prepared for U.S.
Forest Service, Quincy, California, 15 p.
85.
-------
MT. INGALLS
LOOKOUT, 0
o fj\ WALKER MINE
Figure 48. Walker mine location map.
87.
-------
104 ,
-«-
W-1 ,
BOREHOLE LOCATION
WELL LOCATION
p- "" s 500'
THALWEG FROM 1927 MAP
THALWEG FROM EM SURVEYS
Figure 49. Walker mine topographic and geophysical survey line map (after WESTEC, 1993).
88.
-------
1000 —
w
Ul
IT
100 —
WALKER VES1
WENNER ARRAY
FIT ERROR-SJ*
10 100
A-SPAdNG (feet)
I I F 1 IT -
1000
11)1
1—i—i i, t i i.
1830 ON
4 —
8 —
12 —
16 —
239ohnvm
20
MAXIMUM t
—i 1—i—i—i i i i | 1 1—i—i—r i i i
100 1000 10000
RESISTIVITY (ohm-m)
Figure 50. Walker mine D.C. resistivity VESl data and interpretation with equivalence
profiles. VES location shown on Figure 49. Of>
oy.
-------
100000
10000 —
(0
8
eg
1000 —
100
J 1—I I I I 111 I I I I I I 11
WALKER VES2
WENNER ARRAY
I I I 11 III 1—I—I I I I
FIT ERROR.30%
10
A-SPACING (feet)
r] 1—i—r i i 11
100 1000
120 —
160
' ' '
i » mil i
434ohiiHn
L
95 oonwn
7360 ohm-m
BEST
MAXIMUM
10
100 1000
RESISTIVITY (ohm-m)
10000
Figure 51.
90.
Walker mine D.C. resistivity VES2 data and interpretation with equivalence
profiles. VES location shown on Figure 49.
-------
10000
J 100° —
CO
55
til
UJ
I
100 —
10
-J ' I I I I I _l_
WALKER VES3
WENNER ARRAY
. FIT ERROR • MM
~l 1 1 'I III
10
A-SPACING )teet)
1 1 1 I I. I 1
100
4—1
8 —
12 —
16 —
20
J 1 I I I fill 1 1 i i i i nl i "i ,
OOoftm-fn
10
2963ehnHn
BEST
MWOMUM,
100 1000
RESISTIVITY (ohnwn)
i i i i 11
10000
Figure 52.
Walker mine D.C. resistivity VES3 data and interpretation with equivalence
profiles. VES location shown on Figure 49.
91.
-------
10000
E
j 1000.
o.' ..
in
w
in
te.
\u
1
100 —
10
WALKER VES4
WENNER ARRAY
FIT ERROR'S*
I I I I I I 11
1 I I I I r
10
A-SPAC1NG
100
1000
i i i 11 ml
mil
28 ohi MI
10 —
1300 OMiwn
MMMUM
20 —
117«hm4n
BEST
IMXMUM
M.OOOoh(TMn
30
10
100 1000 . 10000
RESISTIVITY (ohm-m)
100000
Figure 53. Walker mine D.C. resistivity VES4 data and interpretation with equivalence
profiles. VES location shown on Figure 49.
92.
-------
ODDDDDiDDaan
12-22 mmhoMn
I—I—I—I—I—h^H—I—I
1004
200+
300+
400+
500+
m 100
SCALE
o
100 m
SCALE - 1: 3750
600+
a
o
3.7 m
10 m
20 m
40 m
3.7 m
10 m
20 m
40 m
Figure 54. Walker mine Line 1 EM data and geoelectric cross section.
for: CA DOC
U.S. Geological Survey
Dltl Sit: MCEM.1
tatt: II MOV 03
Line:
hHA AMU GEOPHYSICS
HALKER MINE
PLUMAS COUNTY, CALIFORNIA
Azimuth: N40E
-------
HI 50
SCALE
o
50
i
m
300+
a
o
a
o
SCALE • 1: 1900
Figure 55. Walker mine Line 2 EM data and geoelectric cross section.
for: CA DOC
U.S. Geological survey
toll Sit: WIEM.2
Oitt: IS NOV ft}
Line:
3.7 m
10 m
20 m
40 m
3.7 m
40 m
20 m
40 m
BbUHHYb'IUb1
WALKER MINE
PLUHAS COUNTY. CALIFORNIA
Azimuth: H40E
-------
12.5
•s 10-
200+
250*
m so
SCALE
o
50
i
m
SCALE - 1: 1700
Figure 56. Walker mine Line 3 EM data and geoelectric cross section.
for: CA DOC
12.5
Ho -g
^7.5
300+
D
0
4
3.7 n
10 n
20 n
40 n
o
c.
to
t-«
CO
a
a
o
U.S. Geological Survey
Ditl lit: WEN.3B
Dttr II NOV 93
Line: 3
AMU
3.7 m
10 m
20 m
40 m
WALKER MINE
PLUHAS COUNTY. CALIFORNIA
Azimuth: N50E
-------
3504
3004
m 50
SCALE
o
so m
j
SCALE - 1: 2000
Figure 57. Walker mine Line 4 EM data and geoelectric cross section.
for: CA DOC
tr U.S. Geological Survey
3504
Mil Stt: MCEML4
Oltt: IS NOV 93
Line: 3
a
o
•f
X
3.7 n
10 n
20 n
40 n
3.7 n
10 n
20 n
40 n
WALKER MINE
PLUHAS COUNTY. CALIFORNIA
Azimuth: N20E
-------
m 100
SCALE
0
100 m
Figure 58. Walker mine Line 5 EM data and geoelectric cross section.
a
o
3.7 m
10 m
20 fli
40 m
3.7 m
10 m
20 m
40 m
: 2B57
for: CA DOC
tr U.S. Ceolpgical Survey
filU Stt: MCEMLB
WM-* «••••*
Ottt: 11 NDV 83
Line: 5
1 F-PA AMU Li'tUMHYS I L'S
HALKER
PLUMAS COUNTY.
Azimuth:
MINE
CALIFORNIA
N50M
-------
53000q
52S00 -
o
g
o
O
52000 -r
51500T
51000
WALKER MINE
MAGNETOMETER LINE 2
CORRECTED DATA
5-PT AVERAGE
200
300 400 500 600
Dts tonce ( fee O
700
52400-1
V)
o
e
o
O
52200 -
52000 -
51800
WALKER MINE
MAGNETOMETER LINE 1
CORRECTED DATA
5-PT AVERAGE
1000
Dts tonce ( fee I)
1250
1500
Figure 59. Walker mine Line 1 and 2 magnetometer profiles.
-------
52200-]
52000-
E
o
O
51800-
51600
0
WALKER MIKE
MAGNETOMETER LINE 4
CORRECTED DATA
5-PT AVERAGE
' ' 'l00' ' '200' ' '300' ' 400' ' 500' ' '600' 700 800 900 1000 1100
Die tonce ( feet)
53000-i
CD
o
e
o
O
52500-
52000-
51500-
0
CORRECTED DATA
B-PT AVERAGE .
100
" I '
200
WALKER MINE
MAGNETOMETER LINE 3
300 400 500 600
Die tonce ( feet)
700
i I
800
900
Figure 60. Walker mine Line 3 and 4 magnetometer profiles.
-------
o
S
3
8
LO
60
souuuu
100.
U.S. Environmental Protection Agen
,
Jackson Boulevard 12th F
Chicago, IL 60604-3590
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