Preliminary Report on Mercury

Geochemistry of Placer Gold Dredge

Tailings, Sediments, Bedrock, and

Waters in the Clear Creek Restoration

Area, Shasta County, California

By Roger P. Ashley,1 James J. Rytuba,1 Ronald Rogers,2

Boris B. Kotlyar,1 and David Lawler3

Open-File Report 02–401

2002

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey

editorial standards or with the North American Stratigraphic Code. Any use of trade, firm, or

product names is for descriptive purposes only and does not imply endorsement by the U.S.

Government.

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

1

 U.S. Geological Survey, Menlo Park, California.

2

 U.S. Bureau of Land Management, Redding, California.

3

 U.S. Bureau of Land Management, Sacramento, California.
ii

TABLE OF CONTENTS

Abstract............................................................................................................................... 1

Introduction ........................................................................................................................ 1

Mining History ................................................................................................................... 2

Geology .............................................................................................................................. 3

Sample Sites ....................................................................................................................... 4

Field Sampling Methods..................................................................................................... 5

Dry sediments and tailings ........................................................................................... 5

Wet sediments and tailings............................................................................................ 6

Waters ........................................................................................................................... 6

Analytical Methods ............................................................................................................ 7

Sediments and rocks ..................................................................................................... 7

Waters ........................................................................................................................... 8

Results For Dry Sediments and Tailings ............................................................................ 8

Results For Wet Sediments and Tailings ............................................................................ 9

Effect of Sample Treatment on Analytical Results, and Implications .............................. 10

Results For Waters ............................................................................................................ 11

Conclusions ...................................................................................................................... 13

References ........................................................................................................................ 14
iii

TABLES

1–Locations and descriptions of sample sites in and near the Clear Creek Restoration

Project area

2–Comparison of preparation and analytical procedures used for solid samples by ALS

Chemex and Frontier Geosciences laboratories

3–Mercury and methylmercury concentrations in dredge tailings and sediment samples

4–Concentrations of major and minor elements in dredge tailings and sediment samples,

determined by ICP-MS and ICP-AES

5–Field parameters for water sample sites and concentrations of major anions, mercury,

and methylmercury in waters

6–Concentrations of major and minor cations in waters, determined by ICP-MS and ICPAES

ILLUSTRATIONS

1–Locations of samples in the Clear Creek study area

2–South Pond, on the flood plain of Clear Creek, showing clouds of fine sediment from

local tailings used to fill the pond

3–East Pond, a marshy pond occupying an abandoned channel (meander scar) on the

flood plain of Clear Creek

4–Pond 3, a shallow pond occupying a meander scar on the flood plain of Clear Creek

5–Dragline dredge stacker tailings, Spring Creek

6–Dredge sluice tailings (sand, silt, and clay), overlain by stacker tailings (pebbles and

cobbles), exposed in wall of Schmidt Pit, Shooting Gallery area. Bulk mercury concentrations in the various tailings layers are shown

7–Red Pond, an abandoned dredge pond fed by high-chloride springs

8–Conglomerate of the Tehama Formation, exposed in prospect tunnels beneath the

Nomlaki Tuff, at Red Pond

9–Mercury concentrations in bedrock, unmined conglomerate, dredge stacker tailings,

and dredge sluice tailings, as a function of grain size

10–Mercury concentrations in sediments from ponds, hydraulic mine drainage tunnel,

and Clear Creek

11–Methylmercury concentrations in sediments from ponds, hydraulic mine drainage

tunnel, and Clear Creek

12–Comparison of total mercury concentrations in sediments and tailings determined by

two different methods (ALS Chemex method and Frontier Geosciences method)
iv

13–Mercury concentrations in waters, showing amounts of dissolved and suspended

mercury

14–Methylmercury versus total mercury concentrations in waters

15–Sulfate versus total mercury concentrations in waters

16–Iron versus total mercury concentrations in waters

17–Chloride versus total mercury concentrations in waters

18–Chloride versus lithium and boron concentrations in waters
1

Abstract

Clear Creek, one of the major tributaries of the upper Sacramento River, drains the

eastern Trinity Mountains. Alluvial plain and terrace gravels of lower Clear Creek, at the

northwest edge of the Sacramento Valley, contain placer gold that has been mined since

the Gold Rush by various methods including dredging. In addition, from the 1950s to the

1980s aggregate-mining operations removed gravel from the lower Clear Creek flood

plain.

Since Clear Creek is an important stream for salmon production, a habitat restoration

program is underway to repair damage from mining and improve conditions for

spawning. This program includes using dredge tailings to fill in gravel pits in the flood

plain, raising the concern that mercury lost to these tailings in the gold recovery process

may be released and become available to biota. The purposes of our study are to

determine concentrations and speciation of mercury in sediments, tailings, and water in

the lower Clear Creek area, and to determine its mobility.

Mercury concentrations in bedrock and unmined gravels both within and above the mined

area are low, and are taken to represent background concentrations. Bulk mercury values

in flood-plain sediments and dry tailings are elevated to several times these background

concentrations. Mercury in sediments and tailings is associated with fine size fractions.

Although methylmercury levels are generally low in sediments, shallow ponds in the

flood plain may have above-normal methylation potential.

Stream waters in the area show low mercury and methylmercury levels. Ponds with

elevated methylmercury in sediments have more methylmercury in their waters as well.

One seep in the area is highly saline, and enriched in mercury, lithium, and boron, similar

to connate waters that are expelled along thrust faults to the south on the west side of the

Sacramento Valley. This occurrence suggests that mercury in waters may at least in part

be from sources other than placer mining.

Introduction

The Klamath Mountains of northern California and southwestern Oregon have produced

significant amounts of gold, both from placer and lode deposits. The most important

placer deposits occur along the major rivers, including Clear Creek and the Trinity,

Klamath, and Smith Rivers, and their tributaries (Clark, 1970). The placers of lower

Clear Creek, which are the subject of this report, have been mined intermittently by

various methods since the 1850s (Clark, 1970; Averill, 1933), with the result that all the

alluvial gravel forming the flood plain of Clear Creek and most of the gravel capping

adjacent terraces has been disturbed. In addition, in recent decades gravel has been

removed from the lower Clear Creek alluvial system for aggregate.
2

Through most of the placer mining period, mercury was used for recovery of gold by

amalgamation, resulting in contamination of the sediment that was processed. Elevated

levels of mercury have been recognized as a water quality problem throughout the

Sacramento River basin (Domagalski, 1998; Domagalski and others, 2000). Sources of

this mercury include mercury mines in the Coast Ranges and mercury losses from gold

mining operations, both placer and lode, in the Klamath Mountains and Sierra Nevada.

Habitat restoration for migratory salmon has been underway in the lower Clear Creek

basin since 1998. Mercury contents of the sediments impounded behind Saeltzer Dam,

in the upper part of the lower Clear Creek basin, were examined as part of a floodway

rehabilitation project involving removal of the dam (Yahnke, 2001). Sediments that

have been exposed to mercury have been used for flood plain restoration, and may be

used in the future. The purpose of this study is to determine how much mercury has

been added to the sediments, how it is distributed within them, how it may be released,

and whether unusual amounts of methylmercury are associated with sediments under

any conditions. In addition we have looked at mercury and methylmercury

concentrations in springs, ponds, and Clear Creek itself within and above the restoration

area, to determine whether significant amounts of mercury are being leached from

sediments into waters, and whether there are conditions permitting high rates of

methylation. A study of mercury levels in biota is being carried out concurrently to

determine whether amounts of methylmercury greater than background levels are

entering the food chain in the area.

Mining History

Following the initial discovery of gold in gravels of the Trinity River in 1848, placer

deposits were the main source of gold in the region until the 1880s (Clark, 1970). Gold

was discovered in Clear Creek in 1849. Several mining camps were established in the

lower Clear Creek drainage basin, including Whiskeytown, Horsetown, Shasta, and Igo.

For the first few years, crude methods were used to mine the gravels in the active channel

and adjacent flood plain; mercury was not available for gold recovery.

In the mid-1850s hydraulic mining was developed. In this mining method, hydraulic

monitors were used to excavate off-stream gravels, especially in paleochannels or on

benches. Extensive systems of sluices charged with mercury were used to recover the

gold. Hydraulic mining of the terrace deposits in the lower Clear Creek area likely took

place mainly before 1884, at which time most hydraulic mining in tributaries of the

Sacramento and San Joaquin Rivers was shut down by judicial decree (Sawyer Decision).

From the 1880s until World War I, lode and placer mines produced roughly equal

amounts of gold in the Klamath Mountains. Gold production declined in the 1920s, but

revived in the 1930s as many dredges were put in operation, returning placer deposits to

prominence. The placer deposits of lower Clear Creek supported numerous dredging
3

operations (Averill, 1933). Large areas in the lower Clear Creek valley and some

tributary drainages were dredged during this period, using both drag-line and bucket-line

dredges. Most mining operations were forced to close in 1942 in response to War

Production Board Order L-208, and few were able to reopen after World War II.

Bedrock in the area hosts some narrow and shallow gold-quartz veins that yielded small

but rich pockets. The most productive of these was the Yankee John mine, located about

3 km north of the center of the study area. The French Gulch district, the largest lode

gold district in the Klamath Mountains, lies in the Clear Creek drainage basin north of

Whiskeytown, above the main placer-mining areas.

Aggregate mining began in the lower Clear Creek basin in the 1950s. Gravel has been

obtained both from in-stream and off-stream pits. Mining in-stream and in the adjacent

flood plain ceased in the 1980s, but off-stream mining continues.

Geology

The Klamath Mountains in northern California consist of a series of northwest- to northtrending terranes, or belts of deformed and metamorphosed sedimentary and volcanic

rocks ranging in age from Ordovician to Jurassic (Irwin, 1972, 1981). These belts

represent a stack of east-dipping thrust plates; from east to west the belts comprise

progressively younger rocks. The thrust-fault zones that bound the plates contain

ultramafic bodies that are mostly serpentinized. Numerous granitic plutons ranging in

age from Devonian through Cretaceous intrude the terranes. Groups of plutons of similar

age form belts that parallel the trends of their host rocks (Irwin, 1985).

The Clear Creek drainage basin lies entirely within the Eastern Klamath Terrane, the

easternmost and oldest of the belts recognized in the Klamath Mountains. The upper part

of the basin, in the French Gulch area and northward, is dominated by slates of the

Bragdon Formation of Mississippian age. The lower part of the basin is underlain by

metavolcanic rocks of Devonian or older age, including the Copley Greenstone and the

Balaklala Rhyolite, and granitic rocks including the Mule Mountain stock of Devonian

age, and the Shasta Bally batholith of Early Cretaceous age (Strand, 1962; Albers, 1964;

Kinkel, Hall, and Albers, 1956; Fraticelli and others, 1987).

The oldest rocks in the Great Valley province are nearly unmetamorphosed Late Jurassic

and Cretaceous marine sedimentary rocks of the Great Valley sequence, which crops out

along the west side of the Sacramento Valley. Lithologies include mudstone, graywacke,

conglomerate, and shale. There are small exposure areas of both Lower and Upper

Cretaceous on the north side of Clear Creek (Strand, 1962).

Formations of Tertiary and Quaternary age occupy most of the area of the Great Valley

province, including lower Clear Creek. Tertiary rocks in the lower Clear Creek area are
4

included in the Tehama Formation of Pliocene age (Helley and Harwood, 1986). It

consists of sandstone and siltstone with lenses of conglomerate derived from the Coast

Ranges and Klamath Mountains to the west and north. The Tehama grades eastward into

the Tuscan Formation, which consists of volcanic and volcaniclastic rocks erupted and

transported from volcanic vents in the Cascades volcanic province to the east.

The Nomlaki Tuff Member of the Tehama Formation is locally exposed in the bluffs and

gulches incised into the terrace on the north side of Clear Creek. Some of the best

exposures are in drainage cuts and tunnels related to hydraulic mining. The Nomlaki is a

dacitic ash-flow tuff, water-reworked in some areas (Helley and Harwood, 1986). In the

vicinity of lower Clear Creek it is typically a white or pale gray massive, non-welded

pumice lapilli tuff. Its stratigraphic position is at or near the base of the Tehama

Formation, and it has been dated at 3.4 Ma (Evernden and others, 1964).

The Tehama Formation is overlain unconformably by the Red Bluff Formation of

Quaternary age, which forms a thin veneer of red, weathered gravels. Helley and

Harwood (1986) interpret the Red Bluff as a sedimentary cover on a widespread

pediment surface that formed in the Sacramento Valley between 450 Ka and about 1.08

Ma. It occupies the broad flat divide between lower Clear Creek and Dry Creek to the

south, and scattered patches remain on the north side of Clear Creek. It probably covered

the terrace on the north side of Clear Creek that was extensively mined by hydraulic

methods.

The flood plain of Clear Creek, including low terraces adjacent to the active stream

channel, is underlain by alluvium of Holocene age. The bulk of this material is probably

gravel and sand. As a result of restricted sediment supply in the current hydrologic

regime, at many places the stream has eroded down to a hard-pan clay layer.

Sample Sites

Samples were collected to characterize mercury species and associated elements in gold

placer tailings, bedrock, sediments, and stream and pond waters in and adjacent to the

Clear Creek restoration area. Samples were collected from August 27 to 29, 2001, during

late summer base stream-flow conditions. During the time of sampling, the weather was

stable and no precipitation occurred. Field sites are shown on Figure 1 and listed and

described in Table 1 along with all samples collected at each site. The geographic

coordinates in Table 1 were obtained in the field using a hand-held Global Positioning

System (GPS) unit.

Field samples are clustered in four parts of the area (Figure 1 and Table 1). The eastern

group of samples (21CC1,2,3,4,5,6,7) includes sediments and waters from three ponds in

the floodplain. South Pond (Figure 2), the largest of the three, was an aggregate pit. The

other two, designated East Pond (Figure 3) and Pond 3 (Figure 4), probably represent
5

remnants of abandoned channels. South Pond and Pond 3 were filled in summer 2001 as

part of the restoration program.

The next group of samples to the west (21CC8,9,10,11) include hydraulic mine tailings,

water and tailings from a hydraulic mine drainage tunnel, and the Nomlaki tuff, which

forms the substrate beneath the gravels that were mined by hydraulic methods. In

addition, sediments and water from Clear Creek were sampled; this site is immediately

above the restoration project area, but still within the reach that was mined.

The cluster of samples toward the west end of the area (21CC12,13,14,15,16) comprises

mainly tailings. One site yielded gravel from drag-line dredge stacker piles along Spring

Creek, an intermittent tributary of Clear Creek (Figure 5). The second site yielded gravel

from probable bucket-line dredge stacker piles on a low Clear Creek terrace. The third

site is a backhoe trench dug in probable bucket-line dredge tailings on the same low

terrace, both coarse stacker tailings and fine sluice tailings, at the site of a former rifle

range known as the “Shooting Gallery” (Figure 6). Also in the Spring Creek drainage is

an impoundment remaining from dredging known as “Red Pond” (Figure 7), which

catches water from saline springs. Adjacent to Red Pond are exposures of Tehama

Formation gravels beneath the Nomlaki Tuff that contain prospect and short drift mine

tunnels (Figure 8). We sampled Red Pond water and sediment, and unmined gravel from

a drift tunnel.

The westernmost samples (21CC18,19) are located at the U.S. Geological Survey stream

gauging station known as the “Igo Gauge.” This site provided water and sediment

upstream from the mined area.

Field Sampling Methods

Dry sediments and tailings

We separated material coarser than 2 mm (the lower size limit for gravel in the standard

Wentworth size classification scheme) from material finer than 2 mm (the upper size limit

for sand in the Wentworth scheme), using a steel wire-mesh screen. We did not attempt

to separate any finer fractions in the field, because dry sieving done by hand is ineffective

in removing fines from coarser particles. Also we did not homogenize and split bulk

material to provide all subsamples; we screened approximately 5 kg of material dug from

a shallow hole or cut from trench walls at each site. Separate grab samples dug from the

same holes or cuts supplied material for the bulk subsamples.

All dry tailings subsamples were placed in pre-cleaned and certified borosilicate glass

jars with TeflonTM seals (I-CHEMTM Series 300). The maximum amount of material

retained for any subsample was generally 1-2 kg.
6

Wet sediments and tailings

Wet sediments and tailings were wet-sieved in the field using stainless steel sieves and 1-

2 liters of ambient water. The sieves used are dedicated to handling of materials expected

to have low levels of mercury and other metals; however, we have not run blanks to

determine whether these sieves contribute significant amounts of metals to samples.

Although several size fractions were obtained at some sites, those analyzed and reported

here are >2 mm, <2 mm, <63 μm, and unsieved bulk.

Certified TeflonTM-sealed I-CHEMTM glass jars (the same as for dry sediments) were used

for subsamples analyzed for metals. Polycarbonate jars (100 ml capacity) were used for

mercury subsamples. These were frozen with dry ice immediately after collection

(freezing time approximately 20-30 minutes), and kept frozen until analysis.

Waters

Spring and stream waters were grab samples collected in 1-liter HDPE bottles; all

subsamples for analysis of metals and anions were removed from the same 1-liter bottle.

Water sampling protocols used here, including bottle preparation and sample

preservation, generally follow those of Water Resources Division of the U.S. Geological

Survey for trace metals (Horowitz and others, 1994). Field filtrations were generally done

with disposable 25 mm-diameter sterile cellulose acetate filters (0.45 μm openings) and

disposable syringes.

For metals determinations, both filtered and unfiltered subsamples were preserved with

Ultrex-grade HNO3

, acidified to pH<2, and stored in HDPE (high-density polyethylene)

bottles pre-rinsed with similar trace-metals grade acid. Subsamples for anion

determinations were filtered, stored in HDPE bottles, and chilled to <4°C until analysis.

Subsamples for alkalinity determinations were treated similarly but were not filtered.

Sampling for mercury analysis followed ultra-clean sampling and handling protocols

(Bloom, 1995, Gill and Fitzgerald, 1987) during the collection of field samples and

analysis to avoid introduction of mercury. Subsamples for mercury analysis were

separate grab samples collected in 1-liter borosilicate bottles (I-CHEMTM Series 300,

spot-checked for mercury levels by Frontier Geosciences) with excluding TeflonTM caps

(to eliminate head space), and kept chilled to <4°C until analysis.

During every sampling event, a field blank was collected by processing de-ionized water

and collecting the same subsamples (except for alkalinity) by the same procedures as

used for the field samples.
7

Water parameters including pH, conductivity, and temperature were measured in the field

with a battery-powered pH meter (Orion Model 290, with low-maintenance sealed gel

triode electrode) and a specific conductivity meter (Orion Model 120). The pH triode,

which has automatic temperature compensation, was also used for temperature

measurements. Dissolved oxygen concentrations were determined with a CHEMets

colorimetric field test kit (CHEMetrics, Inc.).

Laboratory blanks and acid blanks were processed periodically to determine whether our

equipment, containers, reagents, and procedures introduced significant contamination.

Analytical Methods

Sediments and rocks

Multi-element analyses for all dry sediments and rocks were performed in the

laboratories of ALS Chemex. Bulk samples were ground in a zirconia ring mill and

subjected to a near-total four-acid digestion. Major elements were determined by

inductively coupled plasma-atomic absorption spectroscopy (ICP-AES). Minor elements

other than mercury were determined by inductively coupled plasma–mass spectrometry

(ICP–MS). Mercury was determined by cold vapor atomic absorption spectroscopy

(CVAAS) following methods similar to those described by Crock (1996) and O’Leary

and others (1996).

Mercury and methylmercury analyses for all wet sediments were carried out at Frontier

Geosciences. Some dry sediments analyzed by Chemex were also analyzed by Frontier.

For total mercury, the sediment was leached with cold aqua regia, followed by stannous

chloride (SnCl2

) reduction, two-stage gold amalgamation, and cold vapor atomic

fluorescence spectroscopy (CVAFS) detection. Methylmercury was obtained by acid

bromide/methyl chloride extraction followed by aqueous phase ethylation, isothermal gas

chromatographic (GC) separation, and CVAFS detection (Horvat, Bloom, and Liang,

1993). Results were reported on both a wet- and dry-weight basis.

Chemex and Frontier sample preparation steps are shown for comparison in Table 2.

Chemex preparation utilizes a relatively large split, which is pulverized. The Chemex 4-

acid digestion dissolves all but a few resistant minerals such as zircon. It is important to

note that our samples were treated as rocks rather than soils, except that crushing was not

needed, so no sieving was performed in the laboratory; bulk sample including clasts as

large as 1-2 cm diameter was processed. Frontier’s preparation avoids handling and uses

a strong leach (aqua regia), which removes elemental mercury, adsorbed mercury,

mercury in amalgams, and combined mercury including mercury sulfide, but does not

affect silicate minerals. Material coarser than sand size, however, is not included in

Frontier’s leach.
8

Waters

Alkalinity as CaCO3

 was determined in the laboratory by titration with H2SO4 using

Gran’s technique (Orion Research, Inc., 1978), within 2-4 days after sample collection.

Sulfate, chloride, nitrate, and fluoride concentrations were determined by ion

chromatography (Fishman and Pyen, 1979).

Cations were analyzed by inductively coupled plasma–atomic emission spectrometry

(ICP–AES) and inductively coupled plasma–mass spectrometry (ICP–MS). Ion

chromatography and alkalinity analyses were performed by U.S.G.S. laboratories under

the direction of Paul Lamothe. The ICP-AES analyses were determined by U.S.G.S.

laboratories under the direction of Paul Briggs. Duplicate water samples, blank samples,

and U.S.G.S. Water Resource Division standard reference waters were analyzed with the

data set.

At Frontier Geosciences samples were handled in a Class-100 clean air station monitored

routinely for low levels of total gaseous mercury. An ultra-clean mercury trace metal

protocol was followed, including the use of rigorously cleaned and tested TeflonTM

equipment and sample bottles and pre-screened and purified reagents. Laboratory

atmosphere and water supply are also routinely monitored for low levels of mercury.

Primary standards used in the laboratory were NIST-certified or traceable to NISTcertified materials. Monomethylmercury (MMHg) standards were made from pure

powder and calibrated against NBS-3133, and cross verified by daily analysis of Certified

Reference Material DORM-2 (National Research Council of Canada Institute for

National Measurement Standards, 1999). EPA Method 1631 was used. Total mercury

was determined by bromine monochloride (BrCl) oxidation followed by SnCl2

 reduction,

two-stage gold amalgamation, and detection by cold vapor atomic fluorescence

spectroscopy (CVAFS) (Bloom, Crecelius, and Fitzgerald, 1988). Methylmercury was

liberated from water using an all-TeflonTM distillation system. Distilled samples were

analyzed using aqueous phase ethylation with purging onto Carbotrap, isothermal gas

chromatographic (GC) separation, and CVAFS detection (Bloom, 1989). To address

accuracy and precision, quality assurance measures were employed with the following

minimum frequency: laboratory duplicates, one per ten samples; method blanks, three per

analytical batch; filtration blanks, one per ten samples; and spike recovery or standard

reference material, one per ten samples.

Results For Dry Sediments and Tailings

Figure 9 shows results for dry tailings, sediments, and bedrock samples; analytical data

are shown in Tables 3 and 4. The bedrock category consists of pebble composites for

metamorphic rocks and plutonic rocks (6-10 pebbles each) and Nomlaki Tuff from an

exposure in a hydraulic mine drainage cut. The pebbles came from the gravel being used

at the time of sampling to fill South Pond, which was from the flood plain in the vicinity
9

of that pond. Metamorphic rock types dominate the Clear Creek sediments. Granitic

rock clasts are common but subordinate to metamorphic types. These materials all show

relatively low mercury values (10-30 ng/g). All subsamples of unmined gravel from the

Tehama Formation (>2 mm, <2 mm, and bulk) did not have detectable levels of mercury,

at a 10 ng/g threshold. These limited data suggest that background mercury values in the

area are relatively low, and a background range of <10-30 ng/g is assumed here for

comparison purposes.

The remaining categories in Figure 9 represent results for dredge stacker tailings in the

Spring Creek area, tailings at the Shooting Gallery, and hydraulic tailings at the hydraulic

mine drainage cut. The Clear Creek gravel reported here is from a gravel bar adjacent to

the active channel. At all sites where bulk material was analyzed, it is enriched in

mercury relative to probable background values, but values for the >2 mm fraction are

lower than the bulk values. In several cases the <2 mm fraction is higher than the bulk

value, as expected from the relatively lower values for the >2 mm fractions, but the two

Spring Creek sites show lower values for the <2 mm fraction than for bulk material.

Either sampling or analytical error or both may account for this apparently anomalous

relationship between values for bulk versus coarse and fine fractions.

Figure 6 shows in more detail the relationship between mercury concentrations and grain

size. The photo shows part of the wall of the backhoe trench sampled at the Shooting

Gallery site. Here the coarse tailings at the top of the section are very poorly sorted, and

mercury is clearly enriched in the <2 mm fraction, which includes sand, silt, and clay

(values for the fractions from this layer are those shown in Figure 9). The layer below

contains the finest material in the section (silt-clay), which shows the highest mercury

value (160 ng/g), whereas sand interbedded with and underlying the silt-clay shows an

intermediate value of 90 ng/g. Bulk values for the >2 mm portion of the coarse upper

layer approach background (40 ng/g).

Various criteria have been proposed for evaluating mercury levels in bulk sediments (U.S.

Environmental Protection Agency, 1997). The lowest of these is the U.S. EPA Threshold

Effects Level (TEL), at 130 ng/g. This is a proposed lower limit for effects on biota,

above which there is potential for observable effects such as bioaccumulation and

biomagnification. Only the fine sediment fractions at the Shooting Gallery site exceed

this level.

Methylmercury values for dry tailings and sediments are all very low, ranging from

<0.015 ng/g to 0.387 ng/g, indicating that no extraordinary conditions favorable for

methylation of mercury occur in these materials in the area.

Results For Wet Sediments and Tailings

Figure 10 shows results for wet sediments and tailings. Mercury values for bulk material

from the South Pond exceed any bulk values obtained for dry tailings. This material was
10

local tailings being used at the time of sampling to fill the South Pond. Bulk sediments

from the other two ponds, which were still undisturbed at the time of sampling, are

slightly elevated but close to background levels. Sediment from the mouth of the

hydraulic mine drainage tunnel, which probably represents hydraulic tailings, is also

clearly enriched in mercury. Bulk sediment from the active channel of Clear Creek west

of the restoration project area showed a mercury concentration similar to those in South

Pond and the hydraulic drainage tunnel, whereas mercury in Clear Creek sediment at the

Igo Gauge is at background levels.

At all sites where silt-clay size material (<63 μm) was separated and analyzed, it shows

substantially higher mercury concentrations than bulk material, regardless of the bulk

mercury concentration. Mud from Red Pond, which is similarly fine-grained, has a

mercury level similar to fine-grained material at other sites. Bulk mercury values are

generally below the EPA TEL of 130 ng/g, whereas fine fractions all exceed it.

Figure 11 shows results of methylmercury analyses for the same sites and subsamples as

shown in Figure 10. Methylmercury generally shows the same tendency to be enriched

in the fine fraction relative to bulk material. With the exception of Red Pond,

methylmercury generally accounts for about one percent of total mercury present, which

indicates normal rates of conversion of mercury to methylmercury. Conditions in Red

Pond, however, apparently strongly favor methylation processes.

We have not attempted to evaluate atmospheric deposition of mercury, which could add

to total mercury in sediments and tailings in the area (Fitzgerald and others, 1998).

Notable increases in mercury concentrations in soils and sediments from atmospheric

deposition, however, are likely to be restricted to within a few centimeters of the surface

(see, e.g., Rood and others, 1995). Also we have not yet attempted to evaluate mercury

vapor emission and redeposition, which could reduce or redistribute mercury. The

observation that finer grain-size materials generally show the highest mercury

concentrations, which is anticipated based on the gold recovery processes used, suggests

that gold mining is the main source of mercury in the area.

Effect of Sample Treatment on Analytical Results, and Implications

About 60 percent of the sediment and tailings samples, both wet and dry, were analyzed

by both Chemex and Frontier laboratories using different methods of preparation and

analysis (see section on analytical methods for sediments and rocks, and Table 2).

Results are compared in Figure 12. Identical results fall on the 1:1 line in the figure. The

lines on either side of the 1:1 line show a two-standard deviation analytical error

envelope. The analytical error is not rigorously determined from replicate analysis, but

rather is estimated from laboratory experience. The comparison plot demonstrates that

samples with low mercury concentrations (less than 30 ng/g) show similar results by both
11

methods. At higher mercury concentrations, samples whose median grain size is sand

size or smaller also yield similar results by both methods. Results that fall outside the

envelope, considered likely to be significantly different, are all for samples with large

median grain size, and in all cases the Frontier analyses show the higher mercury values.

Because the Frontier analysis method does not include material from the silicate clasts,

which are likely low in mercury, this indicates that much of the mercury present is

associated with sand or smaller grain sizes and localized in aqua regia-leachable mineral

grains or coatings on silicate grains. The mercury in leachable grains and coatings is also

incorporated in the Chemex analyses, but the pulverization and digestion includes lowmercury material from clasts. Although mercury losses from the Chemex drying step

cannot be ruled out, the similarity between Chemex and Frontier results for other

samples, especially those having relatively high mercury concentrations and relatively

small grain size, suggest that such losses are not significant.

Results For Waters

Figure 13 shows results for waters, which were sampled at the same sites as wet

sediments (Figures 10 and 11; data in Tables 5 and 6). The stacked bars show the total

mercury concentrations, as well as proportions of dissolved versus suspended mercury.

“Dissolved” mercury is here operationally defined as the concentration of mercury

measured in an aliquot passing a 0.45 μm filter. The filtration was done in the laboratory

under ultra-clean mercury-free conditions (see section on analytical methods for waters).

Except for water impounded at the outlet of the hydraulic mine drainage tunnel, total

mercury values are generally low, and similar to many values for waters obtained

elsewhere in the Sacramento River Basin (Domagalski, 1998; Domagalski and others,

2000a,b). In all cases the majority of the mercury present (about 60-90 percent) is

associated with suspended particles, which is also typical of waters elsewhere in the

Sacramento River basin. Proposed aquatic life criteria for total mercury in water span a

wide range. As is the case with the criterion for sediment, this is the level above which

there is evidence of potential for observable effects in biota, not necessarily including

bioaccumulation and biomagnification. The lowest proposed criterion for chronic effects

in fresh-water aquatic life (12 ng/L total recoverable mercury) is shown on Figure 13 for

reference. It was first recommended by EPA in 1986, and is the level recommended by

BLM’s National Applied Resource Sciences Center (Barkow, 1999). In April 1999 EPA

issued a guideline of 770 ng/L (dissolved mercury) for chronic effects in fresh-water

aquatic life. The 50 ng/L level shown on Figure 13 is the California Water Quality

Standard. This number, proposed in 1997, refers to total recoverable mercury and is a

human health standard. Only the drainage tunnel sample exceeds the 12 ng/L level, but

low values are generally anticipated during the low-flow late-summer conditions under

which we obtained the samples.
12

With the exception of the Igo Gauge site, where mercury is low in all media, total

mercury values in waters show no obvious correlation with mercury levels in bulk or fine

sediments at the same sites.

Figure 14 shows amounts of methylmercury versus total mercury for unfiltered waters.

Lines of equal proportions of methylmercury are shown for reference (note that the scales

for both axes and the intervals between the percentage lines are logarithmic).

Methylmercury values for most of the stream and pond waters fall within the range seen

elsewhere in the Sacramento River Basin (Domagalski, 1998, 2000b). In these waters

between 1 and 10 percent of total mercury is methylmercury, which is within the range of

values commonly seen in relatively uncontaminated surface waters with normal

methylation potential (see e.g., Kelly and others, 1995). Proportions of methylmercury

are high in Red Pond and Pond 3, producing absolute values higher than those reported

by Domagalski (1998, 2000b). At the time of sampling these ponds were shallow, warm,

and contained decaying organic matter. The high proportion of methylmercury in Pond 3

is particularly significant, as it shows that conditions in shallow ponds on the flood plain

may favor methylation of mercury. Further work is needed to explain the extraordinarily

low methylmercury level seen in water in the hydraulic drainage tunnel.

Sulfate values are in the normal range seen in West Coast rivers (Hem and others, 1990);

however, values in East Pond and the hydraulic drainage tunnel are comparable to the

highest values seen in river waters (Figure 15). Prospect tunnels in the gravels of the

Tehama Formation exposed above Red Pond in the Spring Creek valley contain finegrained pyrite that is now being oxidized, because the tunnels provide drainage and have

thus lowered the water table. At the time of sampling, a small area of pyrite-bearing

conglomerate was also exposed at the north edge of the Clear Creek flood plain near

Pond 3. This exposure was too small to determine its relations to other units, but it

probably represents Tehama Formation material covered by thin Recent alluvium. These

exposures suggest that the Tehama Formation contains pyrite-bearing reduced zones.

Where exposed to oxidation, these zones could be sources of sulfate in waters.

Figure 15 shows that in the Clear Creek area sample suite, waters with relatively high

sulfate concentrations also have relatively high total mercury values. Methylmercury,

however, shows no consistent relationship to sulfate, because methylmercury levels in

Red Pond and Pond 3 are relatively high, whereas the methylmercury level in the

hydraulic drainage tunnel water is relatively low (Figure 14).

Iron concentrations vary greatly in the waters sampled (Figure 16), but are high only in

the Red Pond, as anticipated from the observation that iron oxyhydroxide precipitates on

the bottom and on pond vegetation during the summer months (Figure 7). The high iron

in Red Pond can be explained in light of other chemical characteristics, as discussed

below. Pond 3 showed surprisingly high iron, although no iron mineral precipitates were

observed. The source of iron in Pond 3 is not obvious, but oxidizing sulfides in nearby

bedrock are a possible source for iron, as well as sulfate. Note that data for filtered
13

samples are used in Figure 16, because we do not have unfiltered iron data for all

samples. In all cases where we have iron analyses for both unfiltered and filtered

subsamples, the unfiltered values are several times the filtered values. This indicates that

the majority of iron in the waters is present in suspension, probably as iron oxyhydroxide

particles or coatings on other particles, a condition that is commonly seen in natural

waters.

Chloride concentrations (Figure 17) in pond and stream waters, which fall between about

1.5 and 5 ppm, are in the normal range for surface waters near the Pacific Ocean (Hem

and others, 1990). The higher concentrations in East Pond and Pond 3 (about 10-15 ppm)

are within the range seen, but since both are shallow small-volume ponds, the values

more likely reflect effects of evapoconcentration.

Red Pond has an extremely high chloride concentration (13,000 mg/L), approaching that

of seawater (approximately 30,000 mg/L). High-chloride waters that represent connate

fluids from the Great Valley sequence at depth appear in springs to the south along the

west side of the Sacramento Valley, and contribute to fluids in The Geysers geothermal

field (Donnelly-Nolan and others, 1993) and to ore-forming fluids and groundwaters at

the McLaughlin gold deposit (Rytuba and others, 1993). A contribution from such highsalinity fluid probably also accounts for the elevated chloride concentration in the

hydraulic mine drainage tunnel. Although such fluids may be enriched in mercury, total

mercury does not correlate with chloride at these two sites.

High boron and lithium values are distinguishing geochemical features of the Great

Valley connate fluids. As Figure 18 shows, high concentrations of these elements

accompany the chloride in the Red Pond water, and confirm that connate water is a major

component in the seeps that feed Red Pond. The intermediate boron and lithium values

seen in the hydraulic drainage tunnel water, in approximately the same ratio to Red Pond

water as chloride, confirm that it contains a small contribution of connate water. The

contributions of connate waters at these sites suggests that waters of deep-seated origin

may contribute mercury to the surface environment in the Clear Creek area, and that gold

mining may not be the only source of mercury.

Conclusions

The following preliminary conclusions are drawn from the results of mercury

determinations reported here.

1) Background mercury values are low, as determined from bedrock, clasts in gravels,

and unmined auriferous gravels.

2) Bulk mercury values in sediments and tailings are elevated to as much as several times

background concentrations.
14

3) Mercury and methylmercury in sediments and tailings are associated with fine grainsize fractions.

4) Mercury and methylmercury values are relatively low in Clear Creek stream waters

and ponds on the Clear Creek flood plain.

5. High-salinity connate waters enter the surface environment in the area through springs

and seeps. Some mercury in waters in the area may be from this source.

These conclusions are considered preliminary, primarily because the number of sample

sites is relatively small, and the data for waters are derived from only one sampling event.

Thus for solids, spatial variations cannot be evaluated and the full range of mercury

values cannot be determined. For waters, which vary both spatially and temporally, a

single sampling event is not enough for reliable characterization.

Characterization of mercury concentrations and speciation in inorganic media of the

Clear Creek system will continue in 2002 and 2003, in coordination with studies of

mercury in biota. Detailed studies of mercury mobility are underway, focussed on finegrained size fractions, and colloids that may be released from sediments and tailings.

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TABLE 1. Locations and descriptions of sample sites in and near the Clear Creek Restoration Project area

Field

no.

Map

no.

Latitude Longitude SEDIMENT SAMPLES WATER SAMPLES Description

Bulk

sediment

Sediment

>2mm

Sediment

<2mm

Sediment

<63um

Unfiltered

unacidified

Filtered

unacidified

Filtered

acidified

Unfiltered

acidified

Alkalinity Total

carbon

21CC01 1 40° 29.911' 122° 24.942' 21CC01WAS 21CC01WBS

F

21CC01W 21CC01WA 21CC01WB 21CC01Wd 21CC01WT

C

South Pond, north side,

clear

21CC02 2 40° 30.259' 122° 24.419' 21CC02WBS 21CC02WAS

F

21CC02W 21CC02WA 21CC02WB 21CC02Wd 21CC02WT

C

East Pond

21CC03 3 40° 29.871' 122° 24.925' 21CC03SA

21CC03WSAB

21CC03WSF

B

21CC03W 21CC03WA 21CC03WB 21CC03WC 21CC03Wd 21CC03TC South Pond, south side,

turbid

21CC04 4 40° 29.886' 122° 24.997' 21CC04SA Fill material, west side of

South Pond

21CC05 5 40° 29.886' 122° 24.997' 21CC05S Composite of metamorpicrock pebbles from fill, west

side of South Pond

21CC06 6 40° 29.886' 122° 24.997' 21CC06S Composite of igneous-rock

pebbles from fill, west side

of South Pond

21CC07 7 40° 30.026' 122° 24.926' 21CC07S

21CC07ASB

21CC07B 21CC07W 21CC07A 21CC07Wb 21CC07Wc 21CC07d Pond 3

21CC08 8 40° 29.795' 122° 27.476' 21CC08SC 21CC08SF1

21CC08SF2

Coarse tailings (pebbles,

cobbles) at drainage cut

21CC09 9 40° 29.795' 122° 27.476' 21CC09S Nomlaki Tuff at drainage

cut

21CC10 10 40° 29.700' 122° 27.300' 21CC10SB1

21CC10SB2

21CC10A 21CC10c 21CC10b 21CC10d Water ponded on tailings

at outlet of drainage tunnel

21CC11 11 40° 29.719' 122° 27.393' 21CC11SB1

21CC11SB2

21CC11SC 21CC11SF 21CC11SVF 21CC11W 21CC11A 21CC11b 21CC11d Bed of Clear Creek and

gravel bar upstream from

(west of) project area

21CC12 12 40° 30.038' 122° 29.257' 21CC12B 21CC12W 21CC12A 21CC12B

1,2

21CC12d Red Pond

21CC13 13 40° 30.076' 122° 29.236' 21CC13B 21CC13SC 21CC13SF1

21CC13SF2

Drift-mine tunnel in gravels

beneath Nomlaki Tuff,

near Red Pond

21CC13 13 40° 30.076' 122° 29.236' 21CC13ST Nomlakai Tuff at drift-mine

tunnel, near Red Pond

21CC14 14 40° 29.911' 122° 29.169' 21CC14SB 21CC14SC 21CC14SF1

21CC14SF2

Dredge stacker tailings,

Spring Creek

21CC15 15 40° 29.734' 122° 29.150' 21CC15CL1

21CC15CL2

Sluice tailings (clay-silt)

exposed in backhoe

trench, Shooting Gallery

21CC15 15 40° 29.734' 122° 29.150' 21CC15SC1

21CC15SC2

Sluice tailings (coarse

sand) exposed in backhoe

trench, Shooting Gallery

21CC15 15 40° 29.734' 122° 29.150' 21CC15SF1

21CC15SF2

Sluice tailings (fine sand)

exposed in backhoe

trench, Shooting Gallery

21CC16 16 40° 29.734' 122° 29.150' 21CC16B

21CC16SB

21CC16SC 21CC16SF Stacker tailings (cobbles,

pebbles, sand) in backhoe

trench, Shooting Gallery

21CC17 17 40° 29.753' 122° 29.150' 21CC17SB 21CC17SC 21CC17SF1

21CC17SF2

Dredge stacker tailings,

Spring Creek

21CC18 18 40° 30.862' 122° 31.487' 21CC18SB1

21CC18SB2

21CC18W 21CC18WA 21CC18WB

1, 2

21CC18WC

1, 2

21CC18wd Bed of Clear Creek at

USGS Gauging Station

21CC19 19 40° 30.862' 122° 31.487' 21CC19SB1

21CC19SB2

Beach sand at USGS

Gauging Station, Clear

Creek

Color code:

Red: analyzed by Frontier Geosciences, Inc.

Green: analyzed by ALS Chemex, Inc.

Black: analyzed by U.S. Geological Survey, Mineral Resource Surveys, Denver
Table 2. Comparison of preparation and analytical procedures used for solid

samples by ALS Chemex and Frontier Geosciences laboratories

ALS Chemex Frontier Geosciences

Step (in sequence)

(1) Dry 60°C —

(2) Remove split 250 g 0.5g

(3) Pulverize To >85% <75μ —

(4) Digest/leach HF-HNO3-HClO4-HCl Aqua regia (HCl-HNO3)

(5) Analysis* CVAA CVAFS

*Mercury detection method only. The same chemical procedure for

extraction of mercury from solid samples is used by both laboratories.
Table 3. Mercury and methylmercury concentrations in dredge tailings and sediment 

samples

Field site Map Subsample Sample Total Hg, ppb Total Hg, ppb Methyl Hg, ppb

no. number material Chemex Frontier Frontier

21CC01 1 21CC01WAS Bulk 134 0.588

21CC01WBSF <63μm 295 1.18

21CC02 2 21CC02WBS Bulk 24.9 0.639

21CC02WASF <63μm 190 2.07

21CC03 3 21CC03SA Bulk 90

21CC03WSAB Bulk 109 0.225

21CC03WSFB <63μm 269 1.02

21CC04 4 21CC04SA Bulk 30

21CC05 5 21CC05S Bedrock 30

21CC06 6 21CC06S Bedrock <10

21CC07 7 21CC07S Bulk 30

21CC07ASB Bulk 22.9 0.574

21CC07B <63μm 275 3.00

21CC08 8 21CC08SC >2mm 20

21CC08SF1,2 <2mm 30 60.1 0.387

21CC09 9 21CC09S Bedrock <10

21CC10 10 21CC10SB1,2 Bulk 70 114 0.299

21CC11 11 21CC11SB1,2 Bulk 40 118 0.699

21CC11SC >2mm 30

21CC11SF <2mm 60

21CC11SVF <63μm 204 0.775

21CC12 12 21CC12B Bulk 160 31.1

21CC13 13 21CC13B Bulk <10

21CC13SC >2mm <10

21CC13SF1,2 <2mm <10 2.89 <0.015

21CC13ST Bedrock <10

21CC14 14 21CC14SB Bulk 50

21CC14SC >2mm 30

21CC14SF1,2 <2mm 40 51.0 0.064

21CC15 15 21CC15CL1,2 Bulk 160 134 0.046

21CC15SC1,2 Bulk 90 99.5 <0.015

21CC15SF1,2 Bulk 90 104 <0.015

21CC16 16 21CC16B Bulk 70

21CC16SB Bulk 202 0.026

21CC16SC >2mm 40

21CC16SF <2mm 140

21CC17 17 21CC17SB Bulk 60

21CC17SC >2mm 20

21CC17SF1,2 <2mm 40 29.7 0.101

21CC18 18 21CC18SB1,2 Bulk 20 22.5 0.188

21CC19 19 21CC19SB1,2 Bulk 20 13.1 0.020
Table 4. Concentrations of major and minor elements in dredge tailings and sediment samples, determined by ICP-MS 

and ICP-AES

Field site Map no. Subsample no. Sample mtl Ag Al As Ba Be Bi Ca Cd Ce Co Cr

Units— ppm % ppm ppm ppm ppm % ppm ppm ppm ppm

21CC03 3 21CC03SA Bulk 0.82 5.57 9 485.5 0.8 0.07 1.55 0.18 26.6 9.4 123

21CC04 4 21CC04SA Bulk 0.6 5.57 8.8 460.5 0.6 0.07 1.7 0.16 24.5 9 105

21CC05 5 21CC05S Bedrock 0.46 3.17 6.2 542.7 0.55 0.05 0.17 0.08 15.1 2.6 112

21CC06 6 21CC06S Bedrock 0.4 6.52 1 650.1 0.9 0.05 0.72 <0.02 16.95 2.2 57

21CC07 7 21CC07S Bulk 0.3 5.42 4.4 407 0.65 0.05 1.35 0.12 14.75 6.4 126

21CC08 8 21CC08SC >2mm 0.28 5.27 4 471.5 0.75 0.07 1.35 0.1 13.85 5.6 133

21CC08SF1 <2mm 0.24 5.59 3.2 479 0.75 0.1 1.2 0.14 17.6 6 156

21CC09 9 21CC09S Bedrock 0.3 7.3 1.6 867.2 1.35 0.05 1.3 0.12 26.8 4 51

21CC10 10 21CC10SB1 Bulk 0.22 6.29 7.4 444 0.85 0.06 2 0.12 16.65 12.3 168

21CC11 11 21CC11SB1 Bulk 0.22 5.86 7.8 406 0.7 0.07 2.5 0.22 17.4 7.7 160

21CC11SC >2mm 0.24 5.83 7.6 403.5 0.55 0.07 2.9 0.18 11.75 10.5 162

21CC11SF <2mm 0.22 5.57 9.8 459.5 0.75 0.1 1.65 0.14 31.4 5.1 163

21CC13 13 21CC13B Bulk 0.2 6.62 6.6 210 0.4 0.22 1.45 0.04 8.5 11.1 171

21CC13SC >2mm 0.2 6.99 6.2 174 0.55 0.16 1.65 0.1 8.2 14.1 165

21CC13SF1 <2mm 0.2 6.42 7.8 541.1 0.75 0.22 1.85 0.14 13.55 15.8 202

21CC13ST Bedrock 0.3 6.71 2.4 777.2 1.5 0.32 1.05 0.18 29.8 2.7 59

21CC14 14 21CC14SB Bulk 0.22 5.29 5.4 544.3 0.75 0.09 1.5 0.16 18.8 9.5 143

21CC14SC >2mm 0.26 5.1 5.6 560.3 0.8 0.15 1.45 0.14 18.4 9.1 146

21CC14SF1 <2mm 0.22 6.22 7 425 0.75 0.14 1.5 0.14 22.2 13.8 237

21CC15 15 21CC15CL1 Bulk 0.26 7.34 7.2 412 0.85 0.14 1.45 0.08 25 11.5 109

21CC15SC1 Bulk 0.5 5.3 5.2 413.5 0.7 0.07 1.25 0.06 23 6.5 146

21CC15SF1 Bulk 0.44 6.03 5.2 441.5 0.65 0.07 1.3 0.06 28.3 9.6 162

21CC16 16 21CC16B Bulk 0.3 5.88 5.8 411 0.7 0.09 1.4 0.08 23.3 10.8 114

21CC16SC >2mm 0.36 5.9 4.4 327.5 0.55 0.08 1.6 0.08 18.35 9.8 131

21CC16SF <2mm 0.32 6.78 6.6 427.5 0.8 0.12 1.35 0.12 25 13.3 177

21CC17 17 21CC17SB Bulk 0.26 6 4.4 299 0.65 0.1 2.7 0.1 12.05 11.5 156

21CC17SC >2mm 0.28 5.91 4.8 338.5 0.7 0.09 2.1 0.1 13.15 9.6 133

21CC17SF1 <2mm 0.28 6.47 7.4 385.5 0.75 0.13 1.6 0.14 16.2 14.3 143

21CC18 18 21CC18SB1 Bulk 0.24 6.13 4.2 344 0.85 0.07 2.3 0.14 170.5 7.9 179

21CC19 19 21CC19SB1 Bulk 0.26 6.08 1.6 631.1 0.95 0.07 1.6 0.1 19.55 8.6 152

Table 4–1
Table 4. Concentrations of major and minor elements in dredge tailings and sediment samples, determined by ICP-MS 

and ICP-AES

Field site Map no. Subsample no. Sample mtl

Units—

21CC03 3 21CC03SA Bulk

21CC04 4 21CC04SA Bulk

21CC05 5 21CC05S Bedrock

21CC06 6 21CC06S Bedrock

21CC07 7 21CC07S Bulk

21CC08 8 21CC08SC >2mm

21CC08SF1 <2mm

21CC09 9 21CC09S Bedrock

21CC10 10 21CC10SB1 Bulk

21CC11 11 21CC11SB1 Bulk

21CC11SC >2mm

21CC11SF <2mm

21CC13 13 21CC13B Bulk

21CC13SC >2mm

21CC13SF1 <2mm

21CC13ST Bedrock

21CC14 14 21CC14SB Bulk

21CC14SC >2mm

21CC14SF1 <2mm

21CC15 15 21CC15CL1 Bulk

21CC15SC1 Bulk

21CC15SF1 Bulk

21CC16 16 21CC16B Bulk

21CC16SC >2mm

21CC16SF <2mm

21CC17 17 21CC17SB Bulk

21CC17SC >2mm

21CC17SF1 <2mm

21CC18 18 21CC18SB1 Bulk

21CC19 19 21CC19SB1 Bulk

Cs Cu Fe Ga Ge Hf In K La Li Mg

ppm ppm % ppm ppm ppm ppm % ppm ppm %

1.25 29.8 2.77 12.15 0.25 0.8 0.04 0.87 13.5 20 0.93

0.9 35.6 3.11 11.45 0.25 0.8 0.035 0.81 12.5 17.2 1.15

0.9 19.2 1.68 7 0.1 0.9 0.02 0.68 8.5 19.6 0.53

0.7 8.8 0.88 17.85 0.15 0.6 0.005 3.71 8 9.8 0.79

0.85 23 2.09 10.5 0.2 0.6 0.03 0.82 8 12.8 0.65

0.8 22.2 2.43 10.4 0.15 0.8 0.03 0.74 8 14 0.94

1.05 22.8 1.91 10.95 0.15 0.5 0.02 1.02 9.5 14.2 0.64

3.5 13.6 1.49 15.05 0.2 3.6 0.025 1.76 13.5 23.8 0.3

1.45 34 3.67 12.85 0.2 1 0.035 0.96 8.5 31 1.15

0.8 30.6 3.13 12.4 0.2 0.8 0.04 0.75 9 15.2 1.13

0.75 31.2 3.69 12.95 0.25 0.9 0.045 0.64 6.5 15.8 1.47

0.9 30.4 2.1 10.5 0.2 0.5 0.03 1 16.5 13.2 0.66

0.85 85 3.13 12.4 0.15 0.5 0.065 0.68 4 38.2 1.97

0.8 110.5 3.71 12.55 0.15 0.5 0.065 0.56 4 41.4 2.48

1.15 143.1 2.98 11.75 0.15 0.5 0.06 0.73 7 45.4 1.66

4 50.2 2.65 14.1 0.15 3.6 0.025 1.97 14 22.4 0.3

1.3 42.8 3.5 12.75 0.25 1.2 0.045 0.71 13 24.2 1.32

1.25 50 3.41 12.15 0.2 1.2 0.05 0.65 11.5 24.2 1.28

1.2 61.6 4.21 14.4 0.25 1.1 0.065 0.69 12.5 32.2 1.62

1.65 57.8 3.54 16.35 0.2 1.4 0.07 0.73 11 51.8 1.16

1.05 27.2 2.43 10.2 0.2 0.8 0.035 0.83 11.5 25.2 0.73

1.05 28.2 2.4 10.65 0.2 0.9 0.04 1.04 13 23.2 0.61

1.15 39.2 3.22 13.45 0.3 1.2 0.04 0.71 11.5 35.4 1.11

0.85 30.4 3.59 11.35 0.25 1 0.04 0.63 9.5 28 1.46

1.4 46.2 3.21 13.9 0.25 1.1 0.045 0.86 11.5 41.6 1.02

0.9 44 4.2 13.75 0.2 0.9 0.05 0.56 6.5 33.8 1.52

0.85 37.6 3.59 12.6 0.25 0.9 0.06 0.55 7 28.4 1.45

1.45 57 4 14.75 0.25 1.1 0.06 0.74 8.5 60.8 1.45

0.65 25.2 2.82 14.45 0.35 0.7 0.045 0.79 67 12.2 0.97

1.7 17 2.08 14.5 0.15 0.4 0.025 1.2 11 23.2 0.89

Table 4–2
Table 4. Concentrations of major and minor elements in dredge tailings and sediment samples, determined by ICP-MS 

and ICP-AES

Field site Map no. Subsample no. Sample mtl

Units—

21CC03 3 21CC03SA Bulk

21CC04 4 21CC04SA Bulk

21CC05 5 21CC05S Bedrock

21CC06 6 21CC06S Bedrock

21CC07 7 21CC07S Bulk

21CC08 8 21CC08SC >2mm

21CC08SF1 <2mm

21CC09 9 21CC09S Bedrock

21CC10 10 21CC10SB1 Bulk

21CC11 11 21CC11SB1 Bulk

21CC11SC >2mm

21CC11SF <2mm

21CC13 13 21CC13B Bulk

21CC13SC >2mm

21CC13SF1 <2mm

21CC13ST Bedrock

21CC14 14 21CC14SB Bulk

21CC14SC >2mm

21CC14SF1 <2mm

21CC15 15 21CC15CL1 Bulk

21CC15SC1 Bulk

21CC15SF1 Bulk

21CC16 16 21CC16B Bulk

21CC16SC >2mm

21CC16SF <2mm

21CC17 17 21CC17SB Bulk

21CC17SC >2mm

21CC17SF1 <2mm

21CC18 18 21CC18SB1 Bulk

21CC19 19 21CC19SB1 Bulk

Mn Mo Na Nb Ni P Pb Rb Re S Sb

ppm ppm % ppm ppm ppm ppm ppm ppm % ppm

345 1.7 1.5 3.1 24.8 230 7 25.2 <0.002 <0.01 0.75

395 0.95 1.59 2.3 20.6 230 5.5 17.3 <0.002 <0.01 0.75

100 2.1 1.04 2.4 19.6 400 4.5 23.2 <0.002 0.03 0.65

115 1 1.86 2.3 2.6 110 6.5 65.1 <0.002 <0.01 0.1

240 1.9 1.77 1.9 18.6 170 4.5 18.2 <0.002 0.01 0.5

285 0.85 1.7 2.4 20 280 5 20.2 <0.002 0.01 0.5

255 2.2 1.64 2.2 16 180 6 25.8 <0.002 <0.01 0.4

330 2 2.51 6.2 5.6 80 12.5 46.8 <0.002 <0.01 0.8

505 1.8 1.57 2.9 39 250 5.5 23.3 <0.002 0.02 0.65

415 1.2 1.5 2.2 22.6 200 5 16.6 <0.002 0.01 0.7

505 0.95 1.52 2.2 33.4 240 4.5 14.1 <0.002 0.01 0.6

245 3.5 1.82 1.5 15.8 180 6.5 22.3 <0.002 <0.01 0.6

400 2.85 1.61 1.8 27.2 10 31.5 10.3 0.002 0.37 1.65

465 2.5 1.53 1.5 35 30 9.5 8.8 0.002 0.49 0.55

360 2.2 1.56 1.9 27.8 40 22.5 14.5 0.002 0.96 1

325 2.6 2.32 6 7.8 50 16 57.1 <0.002 0.01 0.9

385 2.05 0.93 3.2 33 200 8 24.2 <0.002 <0.01 0.65

340 2.05 0.8 3.1 34.4 170 8 23.8 <0.002 <0.01 0.75

550 1.3 1.23 2.9 36.2 190 12.5 16.2 <0.002 0.01 0.65

410 1.4 1.77 4.9 32.4 130 7 20.4 <0.002 <0.01 0.65

265 2.45 1.37 2.2 18.4 140 5 22.1 <0.002 <0.01 0.45

370 1.25 1.59 2.6 17.2 100 6.5 23.7 <0.002 <0.01 0.45

435 2.05 1.65 3.4 30.6 230 5.5 21.2 <0.002 <0.01 0.6

480 2.05 1.67 2.6 28.6 220 4 16.7 <0.002 <0.01 0.55

550 1.45 1.71 3.4 28 140 6.5 22.4 <0.002 <0.01 0.6

495 1 1.32 2.2 35 210 6.5 11.4 <0.002 0.01 0.6

465 0.9 1.59 2.7 28.2 280 5 13.5 <0.002 0.01 0.65

470 1.45 1.73 3.1 47.6 260 11 18.9 <0.002 0.01 0.7

430 2.95 2.55 2.4 18.6 220 6 14.9 <0.002 0.02 0.4

325 1.05 2 3.2 22 160 9 35.6 <0.002 <0.01 0.4

Table 4–3
Table 4. Concentrations of major and minor elements in dredge tailings and sediment samples, determined by ICP-MS 

and ICP-AES

Field site Map no. Subsample no. Sample mtl

Units—

21CC03 3 21CC03SA Bulk

21CC04 4 21CC04SA Bulk

21CC05 5 21CC05S Bedrock

21CC06 6 21CC06S Bedrock

21CC07 7 21CC07S Bulk

21CC08 8 21CC08SC >2mm

21CC08SF1 <2mm

21CC09 9 21CC09S Bedrock

21CC10 10 21CC10SB1 Bulk

21CC11 11 21CC11SB1 Bulk

21CC11SC >2mm

21CC11SF <2mm

21CC13 13 21CC13B Bulk

21CC13SC >2mm

21CC13SF1 <2mm

21CC13ST Bedrock

21CC14 14 21CC14SB Bulk

21CC14SC >2mm

21CC14SF1 <2mm

21CC15 15 21CC15CL1 Bulk

21CC15SC1 Bulk

21CC15SF1 Bulk

21CC16 16 21CC16B Bulk

21CC16SC >2mm

21CC16SF <2mm

21CC17 17 21CC17SB Bulk

21CC17SC >2mm

21CC17SF1 <2mm

21CC18 18 21CC18SB1 Bulk

21CC19 19 21CC19SB1 Bulk

Se Sn Sr Ta Te Th Ti Tl U V W

ppm ppm ppm ppm ppm ppm % ppm ppm ppm ppm

<1 0.6 153.5 0.35 0.05 3.8 0.2 0.18 0.9 113 1.1

<1 0.4 144.5 0.2 0.05 2.6 0.21 0.16 0.7 122 1

<1 0.2 29 0.2 0.05 2 0.11 0.16 1.2 81 0.4

<1 1 243 0.2 0.05 2.4 0.08 0.3 0.5 17 2.7

<1 0.8 163 0.2 <0.05 2.2 0.15 0.12 0.6 74 0.7

<1 0.4 130 0.2 0.05 2.4 0.17 0.14 0.9 104 0.6

<1 0.4 211 0.2 0.05 2.8 0.14 0.14 0.7 66 0.6

<1 0.8 208 0.6 <0.05 8 0.2 0.36 2.8 40 1.5

<1 0.4 209 0.25 0.1 3 0.24 0.18 0.8 141 1.7

<1 0.4 128 0.2 0.1 2.4 0.2 0.14 0.7 138 0.6

<1 0.6 140 0.2 0.05 2 0.22 0.12 0.7 150 0.7

<1 0.2 235 0.15 0.2 3.2 0.13 0.18 0.6 77 0.5

<1 0.6 155.5 0.15 0.45 0.8 0.21 0.08 0.4 159 4.4

<1 0.6 160 0.15 0.4 0.8 0.21 0.08 0.4 161 4.3

<1 0.6 280 0.15 0.45 1 0.19 0.1 0.5 149 4.8

<1 0.8 174.5 0.6 <0.05 9 0.16 0.48 3.5 35 2.5

<1 0.6 75.6 0.25 0.05 3.2 0.23 0.18 1.2 160 0.8

<1 0.6 73 0.25 0.05 3.4 0.22 0.18 1.2 166 0.9

<1 0.8 109.5 0.3 0.15 2.6 0.27 0.16 1 159 1.3

<1 0.8 139 0.45 0.1 3.8 0.39 0.18 1.4 145 1.9

<1 0.6 136 0.2 0.05 2.6 0.16 0.14 0.8 107 0.7

<1 0.4 151 0.2 0.05 3 0.21 0.14 0.8 98 0.8

<1 0.6 130.5 0.3 0.1 3.2 0.24 0.16 1.1 126 0.9

<1 0.4 79.7 0.2 0.05 2.4 0.25 0.12 0.9 146 0.9

<1 0.6 148.5 0.3 0.1 3.2 0.27 0.18 1.1 125 1.3

<1 0.4 106.5 0.2 0.1 1.8 0.24 0.1 0.7 161 0.8

<1 0.6 112.5 0.2 0.05 2 0.23 0.1 0.7 153 1.1

<1 0.6 129.5 0.25 0.15 2.4 0.28 0.14 1 148 1.1

<1 1.6 207 0.25 0.05 8.6 0.19 0.1 1.2 93 0.9

<1 0.6 288 0.3 <0.05 4 0.19 0.24 0.8 60 0.7

Table 4–4
Table 4. Concentrations of major and minor elements in dredge tailings and sediment samples, determined by ICP-MS 

and ICP-AES

Field site Map no. Subsample no. Sample mtl

Units—

21CC03 3 21CC03SA Bulk

21CC04 4 21CC04SA Bulk

21CC05 5 21CC05S Bedrock

21CC06 6 21CC06S Bedrock

21CC07 7 21CC07S Bulk

21CC08 8 21CC08SC >2mm

21CC08SF1 <2mm

21CC09 9 21CC09S Bedrock

21CC10 10 21CC10SB1 Bulk

21CC11 11 21CC11SB1 Bulk

21CC11SC >2mm

21CC11SF <2mm

21CC13 13 21CC13B Bulk

21CC13SC >2mm

21CC13SF1 <2mm

21CC13ST Bedrock

21CC14 14 21CC14SB Bulk

21CC14SC >2mm

21CC14SF1 <2mm

21CC15 15 21CC15CL1 Bulk

21CC15SC1 Bulk

21CC15SF1 Bulk

21CC16 16 21CC16B Bulk

21CC16SC >2mm

21CC16SF <2mm

21CC17 17 21CC17SB Bulk

21CC17SC >2mm

21CC17SF1 <2mm

21CC18 18 21CC18SB1 Bulk

21CC19 19 21CC19SB1 Bulk

Y Zn Zr

ppm ppm ppm

8.7 58 26.5

7.6 58 23.5

6.3 42 34

5.5 12 11.5

8.1 38 16

7.8 44 26

5.3 40 15

8.4 44 126

8.1 64 30.5

7.4 56 25

9.3 58 29

5.4 42 15.5

6.4 50 15.5

7.9 60 14.5

9 62 14.5

8.5 64 148.5

10.6 62 44

9.2 64 47

12.4 70 36.5

10.8 66 47

6.4 42 27.5

7 40 29.5

10 54 39.5

9.5 56 30.5

9.3 56 36.5

9.1 62 29

9.2 52 31.5

11.6 70 35

13.1 52 15.5

5.5 48 8.5

Table 4–5
Table 5. Field parameters for water sample sites and concentrations of major anions, mercury, and methylmercury in 

waters

Field site Date pH Temperature Conductivity Alkalinity Total Hg Total Hg Methyl Hg Methyl Hg

Units— pH units °C μS ppm, as CaCO3 ng/L ng/L ng/L ng/L

Subsample— (in situ) (in situ) (in situ) Unfiltered Unfiltered Filtered Unfiltered Filtered

21CC1 8/27/01 8.18 35.3 129.4 64 2.95 0.85 0.087 0.033

21CC2 8/27/01 6.93 31.9 206 73 7.79 0.92 0.454 0.107

21CC3 8/28/01 6.62 24.0 145.5 67 3.54 0.81 0.235 0.039

21CC7 8/28/01 6.65 23.8 220 83 9.98 3.96 4.730 2.280

21CC10 8/28/01 6.92 20.3 1320 97 50.7 2.94 0.061 0.042

21CC11 8/28/01 7.27 21.2 104.3 39 3.75 0.69 0.037 0.038

21CC12 8/29/01 5.57 24.7 36300 * 10.4 2.97 6.72 0.902

21CC18 8/29/01 7.33 18.3 69.2 40 1.55 0.55 0.027 0.018

*Not determined; pH of subsample measured in laboratory was 4.17

Table 5–1
Table 5. Field parameters for water sample sites and concentrations of major anions, mercury, and methylmercury in 

waters

Field site

Units—

Subsample—

21CC1

21CC2

21CC3

21CC7

21CC10

21CC11

21CC12

21CC18

*Not determined; pH of subsample measured in laboratory was 4.17

Chloride (Cl) Fluoride (F) Sulfate (SO4) Nitrate (NO3)

ppm ppm ppm ppm

Filtered Filtered Filtered Filtered

1.7 0.09 1.8 <0.08

13 1.1 13 <0.08

5.1 0.2 <1.6 <0.08

8.8 0.2 3.5 <0.08

260 0.7 24 0.9

4.3 0.1 1.9 <0.08

13000 <0.08 2.8 <0.08

5.1 0.2 <1.6 <0.08

Table 5–2
Table 6. Concentrations of major and minor cations in waters, determined by ICP-MS and ICP-AES

CATION CONCENTRATIONS IN FILTERED WATERS

Field site Subsample no. Ag Al As B Ba Be Bi Ca Cd Ce Co Cr Cs

Units— μg/L μg/L μg/L μg/L μg/L μg/L μg/L mg/L μg/L μg/L μg/L μg/L μg/L

Method— ICP-MS ICP-MS ICP-MS ICP-AESICP-AES ICP-MS ICP-MS ICP-AES ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS

21CC1 21CC1WB <3 7.98 2 8 9.6 <0.05 0.03 11 <0.02 0.01 0.11 <1 < 0.01

21CC2 21CC2WB <3 1.44 2 13 22 <0.05 0.02 21 <0.02 < 0.01 0.05 <1 < 0.01

21CC3 21CC3WB <3 1.9 2 7.9 26 <0.05 0.01 12 <0.02 < 0.01 0.12 <1 < 0.01

21CC7 21CC7B <3 5.48 11.9 18 34 <0.05 0.01 19 <0.02 0.14 0.7 <1 < 0.01

21CC10 21CC10B <3 1.32 3 86 220 <0.05 0.01 110 <0.02 < 0.01 0.09 <1 < 0.01

21CC11 21CC11B <3 1.83 <1 10 8.4 <0.05 0.006 6.4 <0.02 < 0.01 <0.02 <1 < 0.01

21CC12 21CC12B1 <3 25.4 24.6 2600 2500 <0.05 0.18 2600 0.05 1.98 11.6 <1 0.28

21CC12 21CC12B2 <3 24.5 26.5 2600 2500 <0.05 0.07 3000 0.04 1.87 11.3 <1 0.26

21CC18 21CC18WB1 <3 1.89 <1 35 8.6 <0.05 < 0.005 7.4 <0.02 < 0.01 0.02 <1 < 0.01

21CC18 21CC18WB2 <3 2.38 <1 20 7.4 <0.05 < 0.005 6 <0.02 < 0.01 0.02 <1 < 0.01

CATION CONCENTRATIONS IN UNFILTERED WATERS

Field site Subsample no. Ag Al As B Ba Be Bi Ca Cd Ce Co Cr Cs

Units— μg/L μg/L μg/L μg/L μg/L μg/L μg/L mg/L μg/L μg/L μg/L μg/L μg/L

Method— ICP-MS ICP-MS ICP-MS ICP-AESICP-AES ICP-MS ICP-MS ICP-AES ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS

21CC3 21CC3WC <3 252 3.5 11 31 <0.05 < 0.005 12 <0.02 0.46 0.37 <1 0.02

21CC7 21CC7C <3 30.5 13 22 36 <0.05 < 0.005 20 <0.02 0.23 0.76 <1 < 0.01

21CC10 21CC10C <3 3.7 3 85 210 <0.05 < 0.005 100 <0.02 < 0.01 0.1 <1 < 0.01

21CC11 21CC11C <3 6.74 <1 10 8.1 <0.05 < 0.005 5.9 <0.02 0.01 0.02 <1 < 0.01

21CC18 21CC18WC1 <3 5.91 <1 11 6.9 <0.05 < 0.005 5.2 <0.02 < 0.01 0.03 <1 < 0.01

21CC18 21CC18WC2 <3 6.66 <1 11 6.9 <0.05 < 0.005 5.2 <0.02 0.01 0.03 <1 < 0.01

Table 6–1
Table 6. Concentrations of major and minor cations in waters, determined by ICP-MS and ICP-AES

CATION CONCENTRATIONS IN FILTERED WATERS

Field site Subsample no. Cu Dy Er Eu Fe Fe Ga Gd Ge Ho K La Li

Units— μg/L μg/L μg/L μg/L mg/L μg/L μg/L μg/L μg/L μg/L mg/L μg/L μg/L

Method— ICP-MS ICP-MS ICP-MS ICP-MS ICP-AES ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-AES ICP-MS ICP-MS

21CC1 21CC1WB <0.5 < 0.005 < 0.005 < 0.005 0.21 208 < 0.02 < 0.005 < 0.02 < 0.005 0.35 0.01 0.5

21CC2 21CC2WB 0.52 < 0.005 < 0.005 < 0.005 0.048 <50 < 0.02 < 0.005 < 0.02 < 0.005 0.74 < 0.01 0.5

21CC3 21CC3WB <0.5 < 0.005 < 0.005 < 0.005 0.58 616 < 0.02 < 0.005 < 0.02 < 0.005 0.4 < 0.01 0.7

21CC7 21CC7B 0.5 0.02 0.02 0.01 1 1040 < 0.02 0.03 < 0.02 0.006 1.1 0.06 1

21CC10 21CC10B <0.5 < 0.005 < 0.005 0.02 <0.02 <50 < 0.02 < 0.005 < 0.02 < 0.005 2 0.01 22.1

21CC11 21CC11B 0.88 < 0.005 < 0.005 < 0.005 <0.02 <50 < 0.02 < 0.005 < 0.02 < 0.005 0.38 < 0.01 2

21CC12 21CC12B1 17.5 0.16 0.13 0.31 5.9 4830 0.2 0.26 < 0.02 0.04 27 2.24 1750

21CC12 21CC12B2 17 0.2 0.11 0.29 5.4 4820 0.2 0.25 < 0.02 0.04 29 2.12 1720

21CC18 21CC18WB1 0.64 < 0.005 < 0.005 < 0.005 <0.02 <50 < 0.02 < 0.005 < 0.02 < 0.005 0.7 < 0.01 1.9

21CC18 21CC18WB2 0.62 < 0.005 < 0.005 < 0.005 <0.02 <50 < 0.02 < 0.005 < 0.02 < 0.005 0.51 < 0.01 1.8

CATION CONCENTRATIONS IN UNFILTERED WATERS

Field site Subsample no. Cu Dy Er Eu Fe Fe Ga Gd Ge Ho K La Li

Units— μg/L μg/L μg/L μg/L mg/L μg/L μg/L μg/L μg/L μg/L mg/L μg/L μg/L

Method— ICP-MS ICP-MS ICP-MS ICP-MS ICP-AES ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-AES ICP-MS ICP-MS

21CC3 21CC3WC 1.1 0.066 0.04 0.02 3.1 3850 0.09 0.076 < 0.02 0.02 0.53 0.23 1.8

21CC7 21CC7C 0.8 0.04 0.03 0.02 1.7 1900 < 0.02 0.04 < 0.02 0.009 1.2 0.09 1.9

21CC10 21CC10C <0.5 < 0.005 < 0.005 0.02 <0.02 <50 < 0.02 0.005 < 0.02 < 0.005 2 0.02 24.6

21CC11 21CC11C 0.65 < 0.005 < 0.005 < 0.005 0.035 <50 < 0.02 < 0.005 < 0.02 < 0.005 0.42 < 0.01 2.7

21CC18 21CC18WC1 0.58 < 0.005 < 0.005 < 0.005 0.035 <50 < 0.02 < 0.005 < 0.02 < 0.005 0.4 < 0.01 2.2

21CC18 21CC18WC2 0.6 < 0.005 < 0.005 < 0.005 0.035 <50 < 0.02 < 0.005 < 0.02 < 0.005 0.39 < 0.01 2

Table 6–2
Table 6. Concentrations of major and minor cations in waters, determined by ICP-MS and ICP-AES

CATION CONCENTRATIONS IN FILTERED WATERS

Field site Subsample no. Lu Mg Mn Mo Na Nb Nd Ni P Pb Pr Rb Sb

Units— μg/L mg/L μg/L μg/L mg/L μg/L μg/L μg/L mg/L μg/L μg/L μg/L μg/L

Method— ICP-MS ICP-AES ICP-MS ICP-MS ICP-AES ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS

21CC1 21CC1WB < 0.1 5.6 9.6 0.2 7 0.03 < 0.01 0.5 < 0.01 <0.05 < 0.01 0.73 <0.1

21CC2 21CC2WB < 0.1 5.4 3.5 0.72 13 0.02 < 0.01 0.6 < 0.01 <0.05 < 0.01 0.3 0.2

21CC3 21CC3WB < 0.1 6 225 < 0.2 7.1 0.02 < 0.01 0.4 < 0.01 <0.05 < 0.01 0.61 <0.1

21CC7 21CC7B < 0.1 6.1 619 0.63 8.9 0.02 0.09 1.6 0.03 0.06 0.02 1 <0.1

21CC10 21CC10B < 0.1 3.6 3.1 0.56 120 0.02 0.02 2.2 0.1 <0.05 < 0.01 1.24 <0.1

21CC11 21CC11B < 0.1 5.8 2.5 < 0.2 3.4 < 0.02 < 0.01 1.1 < 0.01 <0.05 < 0.01 0.31 <0.1

21CC12 21CC12B1 < 0.1 40 6140 1.62 5500 0.06 0.84 61.7 < 0.01 0.75 0.19 41.9 0.3

21CC12 21CC12B2 < 0.1 35 6130 1.66 5600 0.1 0.77 57.4 < 0.01 0.72 0.2 42 0.26

21CC18 21CC18WB1 < 0.1 6.2 5.3 < 0.2 6.4 < 0.02 < 0.01 1.8 < 0.01 <0.05 < 0.01 0.31 <0.1

21CC18 21CC18WB2 < 0.1 6.1 5 < 0.2 3.8 < 0.02 < 0.01 1.8 < 0.01 <0.05 < 0.01 0.31 <0.1

CATION CONCENTRATIONS IN UNFILTERED WATERS

Field site Subsample no. Lu Mg Mn Mo Na Nb Nd Ni P Pb Pr Rb Sb

Units— μg/L mg/L μg/L μg/L mg/L μg/L μg/L μg/L mg/L μg/L μg/L μg/L μg/L

Method— ICP-MS ICP-AES ICP-MS ICP-MS ICP-AES ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS

21CC3 21CC3WC < 0.1 6 291 < 0.2 7.2 < 0.02 0.31 0.8 0.04 0.2 0.07 0.92 <0.1

21CC7 21CC7C < 0.1 6.3 699 0.54 9.4 < 0.02 0.12 1.7 0.05 0.09 0.03 0.99 <0.1

21CC10 21CC10C < 0.1 3.5 3.7 0.53 110 < 0.02 0.02 2.2 0.1 <0.05 < 0.01 1.28 <0.1

21CC11 21CC11C < 0.1 5.3 4.5 < 0.2 3.3 < 0.02 < 0.01 1.2 < 0.01 <0.05 < 0.01 0.33 <0.1

21CC18 21CC18WC1 < 0.1 6.2 7.1 < 0.2 2.4 < 0.02 0.01 1.8 < 0.01 <0.05 < 0.01 0.32 <0.1

21CC18 21CC18WC2 < 0.1 6.1 7.3 < 0.2 2.3 < 0.02 0.01 1.9 < 0.01 <0.05 < 0.01 0.31 <0.1

Table 6–3
Table 6. Concentrations of major and minor cations in waters, determined by ICP-MS and ICP-AES

CATION CONCENTRATIONS IN FILTERED WATERS

Field site Subsample no. Sc Se Si Sm SO4 Sr Ta Tb Th Ti Tl Tm U

Units— μg/L μg/L mg/L μg/L mg/L μg/L μg/L μg/L μg/L μg/L μg/L μg/L μg/L

Method— ICP-MS ICP-MS ICP-AES ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS

21CC1 21CC1WB 0.6 < 1 4 < 0.01 < 2 102 < 0.02 < 0.005 0.01 < 0.1 0.08 < 0.005 0.03

21CC2 21CC2WB 1.1 < 1 5.7 < 0.01 11 196 < 0.02 < 0.005 0.01 0.2 <0.05 < 0.005 0.008

21CC3 21CC3WB 1 < 1 5.5 < 0.01 < 2 111 < 0.02 < 0.005 0.01 < 0.1 <0.05 < 0.005 0.005

21CC7 21CC7B 1.6 < 1 8.8 0.02 < 2 213 < 0.02 0.005 0.02 0.4 <0.05 < 0.005 0.02

21CC10 21CC10B 6.9 2.1 37 < 0.01 16 1780 < 0.02 < 0.005 0.008 0.4 <0.05 < 0.005 0.28

21CC11 21CC11B 0.9 < 1 6.1 < 0.01 < 2 35.7 < 0.02 < 0.005 < 0.005 < 0.1 <0.05 < 0.005 0.03

21CC12 21CC12B1 17.7 < 1 11 0.14 5 66800 < 0.02 0.04 0.03 7 <0.05 0.02 0.01

21CC12 21CC12B2 9.6 < 1 10 0.16 4 67400 < 0.02 0.03 0.03 5.8 <0.05 0.02 0.007

21CC18 21CC18WB1 1.7 < 1 6.1 < 0.01 < 2 27.2 < 0.02 < 0.005 < 0.005 0.5 <0.05 < 0.005 0.03

21CC18 21CC18WB2 1.4 < 1 6 < 0.01 < 2 25.3 < 0.02 < 0.005 < 0.005 0.4 <0.05 < 0.005 0.03

CATION CONCENTRATIONS IN UNFILTERED WATERS

Field site Subsample no. Sc Se Si Sm SO4 Sr Ta Tb Th Ti Tl Tm U

Units— μg/L μg/L mg/L μg/L mg/L μg/L μg/L μg/L μg/L μg/L μg/L μg/L μg/L

Method— ICP-MS ICP-MS ICP-AES ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS

21CC3 21CC3WC 1.5 < 1 5.8 0.06 < 2 118 < 0.02 0.01 0.04 14.3 <0.05 0.005 0.02

21CC7 21CC7C 2.2 < 1 9 0.04 2 226 < 0.02 0.006 0.02 1.9 <0.05 < 0.005 0.02

21CC10 21CC10C 8.8 1.9 36 < 0.01 19 1830 < 0.02 < 0.005 0.006 0.7 <0.05 < 0.005 0.29

21CC11 21CC11C 1.2 < 1 5.7 < 0.01 < 2 36.9 < 0.02 < 0.005 < 0.005 0.3 <0.05 < 0.005 0.03

21CC18 21CC18WC1 1.2 < 1 6 < 0.01 < 2 25 < 0.02 < 0.005 < 0.005 0.2 <0.05 < 0.005 0.03

21CC18 21CC18WC2 1.2 < 1 5.9 < 0.01 < 2 25.2 < 0.02 < 0.005 < 0.005 0.3 <0.05 < 0.005 0.03

Table 6–4
Table 6. Concentrations of major and minor cations in waters, determined by ICP-MS and ICP-AES

CATION CONCENTRATIONS IN FILTERED WATERS

Field site Subsample no. V W Y Yb Zn Zr

Units— μg/L μg/L μg/L μg/L μg/L μg/L

Method— ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS

21CC1 21CC1WB 0.9 < 0.02 0.01 < 0.005 7.2 < 0.05

21CC2 21CC2WB 0.4 < 0.02 < 0.01 < 0.005 24.8 < 0.05

21CC3 21CC3WB 0.2 < 0.02 < 0.01 < 0.005 2 < 0.05

21CC7 21CC7B 1.3 < 0.02 0.2 0.02 3.8 < 0.05

21CC10 21CC10B 2.3 < 0.02 0.09 0.005 5.6 < 0.05

21CC11 21CC11B 0.5 < 0.02 0.01 < 0.005 1 < 0.05

21CC12 21CC12B1 <0.1 < 0.02 2.83 0.13 9 < 0.05

21CC12 21CC12B2 <0.1 < 0.02 2.76 0.13 7.5 < 0.05

21CC18 21CC18WB1 0.2 < 0.02 0.01 < 0.005 2 < 0.05

21CC18 21CC18WB2 0.4 < 0.02 0.01 < 0.005 1 < 0.05

CATION CONCENTRATIONS IN UNFILTERED WATERS

Field site Subsample no. V W Y Yb Zn Zr

Units— μg/L μg/L μg/L μg/L μg/L μg/L

Method— ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS

21CC3 21CC3WC 1 < 0.02 0.32 0.03 10.4 < 0.05

21CC7 21CC7C 1.9 < 0.02 0.28 0.02 17.1 < 0.05

21CC10 21CC10C 2.6 < 0.02 0.09 < 0.005 23 < 0.05

21CC11 21CC11C 0.5 < 0.02 0.02 < 0.005 3 < 0.05

21CC18 21CC18WC1 0.4 < 0.02 0.02 < 0.005 0.7 < 0.05

21CC18 21CC18WC2 0.4 < 0.02 0.03 < 0.005 2.5 < 0.05

Table 6–5
Figures 1-8 are provided as separate Adobe Acrobat .pdf files. Clicking on a figure

number will activate a link to that figure.

Figure 1–Locations of samples in the Clear Creek study area

Figure 2–South Pond, on the flood plain of Clear Creek, showing clouds of fine sediment

from local tailings used to fill the pond

Figure 3–East Pond, a marshy pond occupying an abandoned channel (meander scar) on

the flood plain of Clear Creek

Figure 4–Pond 3, a shallow pond occupying a meander scar on the flood plain of Clear

Creek

Figure 5–Dragline dredge stacker tailings, Spring Creek

Figure 6–Dredge sluice tailings (sand, silt, and clay), overlain by stacker tailings (pebbles

and cobbles), exposed in wall of Schmidt Pit, Shooting Gallery area. Bulk

mercury concentrations in the various tailings layers are shown

Figure 7–Red Pond, an abandoned dredge pond fed by high-chloride springs

Figure 8–Conglomerate of the Tehama Formation, exposed in prospect tunnels beneath

the Nomlaki Tuff, at Red Pond
0

5 0

100

150

200

250

Bedrock

Sample site

Hg in ppb

< 2 mm

> 2 mm 

 Bulk sed

 Bedrock 

Unmined

gravels

below tuff

Tunnel site

Clear Creek

gravel bar

West of

project

Tailings

Drainage

cut in tuff

Tailings

Lower Spring

Creek

Tailings

Shooting

Gallery

Tailings

Upper Spring

Creek

Metamorphic (peb

ble composite)

Tuff (outcrop)

Figure 9. Distribution of mercury in bedrock, unmined conglomerate, and dredge stacker

tailings and dredge sluice tailings as a function of grain size. Igneous (peb

<10 ng/g

ble composite)