����������������������

�������������������������������

������������������������������������������������

���������������������������������������������������

�����������������������������������

������������������������������������������

���������������������������������������������������������������������������������������������
Cover photo descriptions:

1. (upper left) View from the left bank of the Yuba River at Daguerre Point Dam, looking across from Daguerre Point Dam. M.P. Hunerlach, 2001.

2. (center) View from Daguerre Point looking upstream at the Yuba River flood plain filled with hydraulic mining debris prior to dredging. USGS Archive Photo, G.K. 

Gilbert, 1906.

3. (lower right) View from the left bank abutment of the Daguerre Point Dam looking upstream at large piles of coarse dredge tailings and eroding training walls. 

M.P. Hunerlach, August 2001.

4. (upper right) Piston activated sand pump dumping sample of sand and gravel into stainless steel troughduring churn drilling. M. P. Hunerlach, 2001.
Geochemistry of Mercury and other Trace 

Elements in Fluvial Tailings Upstream of 

Daguerre Point Dam, Yuba River, California, 

August 2001

By Michael P. Hunerlach, Charles N. Alpers, Mark Marvin-DiPasquale, 

Howard E. Taylor, and John F. De Wild

In cooperation with the Bureau of Reclamation and the California Department of Fish and Game 

Scientific Investigations Report 2004-5165

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2004

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

World Wide Web: http://www.usgs.gov/

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Hunerlach, M.P., Alpers, C.N., Marvin-DiPasquale, M., Taylor, H.E., and De Wild, J.F., 2004, Geochemistry of mercury 

and other trace elements in fluvial tailings upstream of Daguerre Point Dam, Yuba River, California, August 2001: U.S. 

Geological Survey Scientific Investigations Report 2004-5165, 66 p.
iii

Contents

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

Introduction ................................................................................................ 2

Daguerre Point Dam and the Yuba Goldfields ................................................... 2

Fish Habitat and Environmental Concerns ...................................................... 5

Purpose and Scope ................................................................................. 6

Acknowledgments ................................................................................. 6

Hydrogeological Setting and Mining History ......................................................... 6

Geology of Gravel Deposits ........................................................................ 6

Mining Effects in the Lower Yuba River ......................................................... 7

Overview of Mercury Use in Historical Mining ................................................ 7

Dredging ............................................................................................. 8

Study Design and Methods .............................................................................. 10

Drilling Methods .................................................................................... 10

Hydrologic Conditions during Study ............................................................ 11

Diversion of Browns Valley Irrigation Ditch ................................................ 11

Discharge and Water Quality ............................................................... 12

Collecting and Processing Samples ............................................................ 12

Laboratory Methods .............................................................................. 14

Particle-Size Distribution ..................................................................... 14

Heavy Mineral Concentration and Grain-Size Separation .............................. 14

Analysis of Mercury and Methylmercury ................................................ 14

Analysis of Trace Elements and Major Elements .......................................... 14

Mercury Methylation and Demethylation Potentials .................................... 14

Quality Assurance and Quality Control ......................................................... 15

Particle-Size Distribution ..................................................................... 15

Mercury, Methylmercury, and Trace Elements .......................................... 15

Results ...................................................................................................... 17

Particle-Size Distribution ........................................................................... 17

Residual Sandy Fraction Plus Gravel ...................................................... 17

Sandy Fraction ................................................................................. 17

Silty Fraction ................................................................................. 17

Clay-Silt Fraction .............................................................................. 17

Synthesis and Spatial Distribution ......................................................... 19

Mercury Geochemistry ........................................................................... 21

Trace Elements .................................................................................... 26

Heavy Mineral Concentrates ..................................................................... 27

Gold Tenor and Speciation .................................................................. 27

Mercury Speciation ........................................................................... 30

Other Heavy Minerals ........................................................................ 35

Mercury Methylation and Demethylation Potentials .......................................... 35

Discussion ................................................................................................ 40

Relation of Sediment Characteristics to Mining History ....................................... 40
iv

Loss of Mercury during Drilling .................................................................. 41

Environmental Factors Influencing Mercury Methylation and Demethylation ............ 41

Implications for Downstream Mercury Transport ............................................. 42

Implications for Geomorphology and Hydrogeology .......................................... 42

Summary ................................................................................................... 43

References Cited .......................................................................................... 44

Appendixes ................................................................................................ 47

Appendix A. Description of Drill Sites, Daguerre Point Dam, California ..................... 48

Appendix B. Particle-Size Distribution of Sediments, Daguerre Point Dam, California ... 49

Appendix C. Particle-Size Distribution and Microscopic Observations of Heavy 

Minerals, Daguerre Point Dam, California ............................................. 54

Appendix D. Quality Assurance and Quality Control Data for USGS Laboratories, 

Daguerre Point Dam, California ......................................................... 56

Appendix E. Plate 1. Map of Bedrock Elevation Contours, Daguerre Point Dam, 

California .................................................................................... 64

Glossary of Placer Terms ................................................................................. 66

Figures

Figure 1. Map showing location of study area, Daguerre Point Dam, California ............ 3

Figure 2. Aerial photograph showing Yuba Goldfields and location of training walls, 

Daguerre Point Dam, California ......................................................... 4

Figure 3. Map with contours representing elevation of top of bedrock, Daguerre Point 

Dam, California ........................................................................... 5

Figure 4. Map showing chronology of dredging upstream of Daguerre Point Dam, 

California .................................................................................... 8

Figure 5. Map showing distribution of residual hydraulic mine tailings upstream of 

Daguerre Point Dam, California ......................................................... 9

Figure 6. Aerial photograph showing locations of drilling upstream of Daguerre Point 

Dam, California ........................................................................... 10

Figure 7. Photo of churn drill at site DPD-2, Daguerre Point Dam, California .................. 11

Figure 8. Flow-sheet showing drilling and processing of sample flow-stream ............... 13

Figure 9. Bar chart diagram showing particle-size distribution of residual sandy fraction 

plus gravel at each drill hole, Daguerre Point Dam, California ..................... 18

Figure 10. Ternary diagram showing particle-size classes of sandy fraction, silty fraction, 

and clay-silt fraction, Daguerre Point Dam, California .............................. 20

Figure 11. Graph showing summary of particle-size distributions, Daguerre Point Dam, 

California .................................................................................... 22

Figure 12. Graph showing down-hole concentration of total mercury in different sediment 

fractions, Daguerre Point Dam, California ............................................. 23

Figure 13. Graph showing boxplots of total mercury concentration in different sediment 

fractions, Daguerre Point Dam, California ............................................. 24

Figure 14. Graph showing relation of methylmercury and total mercury in the clay-silt 

fraction (centrifuge tube solids), Daguerre Point Dam, California .................. 28

Figure 15A. Graphs showing the relation of gold and mercury in the clay-silt fraction, 

Daguerre Point Dam, California ......................................................... 29

First time use of glossary terms are in italics and linked to the glossary.
v

Tables

Table 1. Description of drill sites upstream of Daguerre Point Dam, California ............ 11

Table 2. Particle-size distribution and depth profiles of the residual sandy fraction plus 

gravel, Daguerre Point Dam, California ................................................ 19

Table 3. Particle-size distribution and depth profiles of the sandy fraction, Daguerre 

Point Dam, California ..................................................................... 19

Table 4. Particle-size distribution and depth profiles of the silty fraction, Daguerre Point 

Dam, California ........................................................................... 21

Table 5. Particle-size distribution and depth profiles of the clay-silt fraction, Daguerre 

Point Dam, California ..................................................................... 21

Table 6. Total mercury and methylmercury concentrations in the sandy fraction, 

Daguerre Point Dam, California ......................................................... 25

Table 7. Mercury concentrations in the silty and clay-silt fractions from sample 

processing streams, Daguerre Point Dam, California ................................. 26

Table 8. Mercury and methylmercury concentrations in the clay-silt fraction after 

centrifuge separation, Daguerre Point Dam, California .............................. 27

Table 9. Total mercury concentration (ng/g dry weight) for sieved fine particle sizes, 

Daguerre Point Dam, California ......................................................... 28

Table 10A. Concentration of selected elements in sediment screened to less than 0.060 

millimeter, Daguerre Point Dam, California ............................................. 31

Table 10B. Trace-element concentrations in fine-grained Daguerre Point sediment and 

sediment quality criteria (ecological toxicity), Daguerre Point Dam, California ... 35

Table 11. Potential rates of mercury methylation and methylmercury degradation, 

Daguerre Point Dam, California ......................................................... 38

Table 12. Concentrations of acid volatile sulfur and total reduced sulfur in selected 

samples, Daguerre Point Dam, California ............................................. 39

Table A1. Drill hole lithology, Daguerre Point Dam, California .................................... 48

Table A2. Physical description of sediments used to determine mercury methylation and 

demethylation potentials, Daguerre Point Dam, California ........................... 48

Figure 15B. Graph showing the relation of gold and mercury in the clay-silt fraction for each 

drill hole, Daguerre Point Dam, California ............................................. 30

Figure 16. Scanning electron micrograph of broken gold-amalgam fragment from a gold 

grain, Daguerre Point Dam, California ................................................... 36

Figure 18. Scanning electron micrograph of elemental mercury in clay-silt fraction from 25 

to 30 feet in drill hole DPD-2, Daguerre Point Dam, California ........................ 37

Figure 17. High-magnification scanning electron micrograph of gold-amalgam particle 

showing pitted surface, Daguerre Point Dam, California .............................. 37

Figure 19. Graph showing geometric mean of gold tenor and heavy mineral concentrates, 

Daguerre Point Dam, California ......................................................... 38

Figure 20. Graph showing relation between rates of mercury methylation potential and 

mercury demethylation potential, Daguerre Point Dam, California .................. 39

Figure 21. Graph showing ratio of mercury methylation potential (MP) to mercury 

demethylation potential (DP) as function of sediment pH, Daguerre Point Dam, 

California .................................................................................... 40

Figure 22. Graph showing carbon-14 end-product ratio (CO2/C) from mercury demethylation 

experiments as a function of sediment pH, Daguerre Point Dam, California ...... 41
vi

Table B1. Particle-size distribution of the sandy fraction plus gravel for sizes ranging from 

75 millimeters to 0.075 millimeter, Daguerre Point Dam, California .................. 49

Table B2. Particle-size distribution of the sandy fraction from 4 millimeters to 0.00025 

millimeter, Daguerre Point Dam, California ............................................. 50

Table B3. Particle-size distribution of the silty fraction from 2 millimeters to 0.00025 

millimeter, Daguerre Point Dam, California ............................................. 51

Table B4. Particle-size distribution of the clay-silt fraction from 2 millimeters to 0.00025 

millimeter, Daguerre Point Dam, California ............................................. 52

Table B5. Silty fraction suspended-sediment concentrations, Daguerre Point Dam, 

California .................................................................................... 53

Table C1. Particle-size distribution and gold tenor of heavy mineral concentrates, 

Daguerre Point Dam, California ......................................................... 54

Table C2. Microscopic observations of heavy mineral concentrates, Daguerre Point Dam, 

California .................................................................................... 55

Table D1. Chemistry of Yuba River water used during drilling near Daguerre Point Dam, 

California, August 24, 2001 ............................................................... 56

Table D3. Mercury concentrations in standard reference water samples, blanks, and 

spikes, Daguerre Point Dam, California ................................................ 56

Table D2. Mercury concentrations of blanks taken during drilling, August 28, 2001, 

Daguerre Point Dam, California ......................................................... 56

Table D4. Results for trace and major elements in standard reference material, Daguerre 

Point Dam, California ..................................................................... 57

Table D5. Digestion blanks for trace elements and major elements, Daguerre Point Dam, 

California .................................................................................... 59

Table D6. Spike recoveries for trace elements, Daguerre Point Dam, California ............ 60

Table D7. Comparison of replicate analyses of trace and major elements in digested 

sediments, Daguerre Point Dam, California ............................................. 61

Table D8. Replicate analyses of total mercury and methylmercury by the U.S. Geological 

Survey Wisconsin District Mercury Laboratory, Daguerre Point Dam, 

California .................................................................................... 63

Conversion Factors, Spatial Datums, Acronyms and 

Abbreviations, and Chemical Elements

Multiply By To obtain

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

foot (ft) 0.3048 meter (m)

gallon (gal) 3.785 liter (L)

pound (lb) 0.4536 kilogram (kg)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F = (1.8 × °C) + 32

Spatial Datums

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD) – a geodetic datum derived from a general adjustment of the first-order level nets of 

the United States and Canada, formerly called Sea Level Datum of 1929. Horizontal coordinate 

information is referenced to the North American Datum of 1983 (NAD83) unless otherwise noted.
vii

Acronyms, Abbreviations, and Chemical Elements

Acronyms

AVS acid volatile sulfur

CVAFS cold vapor atomic-fluorescence spectrometry

CVO Cascades Volcanic Observatory

DOC dissolved organic carbon

DP demethylation potential

DPD (Used with site numbers) Daguerre Point Dam 

EDX energy dispersive X-ray

GC gas chromatography

IAEA International Atomic Energy Agency

ICP–AES inductively coupled plasma–Atomic Emission Spectrometry 

ICP–MS inductively coupled plasma–Mass Spectrometry

LOI loss on ignition

MDL method detection limit

MP methylation potential

PEC probable effects concentration

QA-QC quality assurance–quality control

RPD relative percent difference

rpm revolutions per minute 

SEM scanning electron microscope

SRM standard reference material

SRWS standard reference water sample

TEC threshold effects concentrations

TRS total reduced sulfur

USGS U.S. Geological Survey

WDML Wisconsin District Mercury Laboratory

Abbreviations

cm centimeter

cm3 cubic centimeter

g gram

kg kilogram

kg/yd3 kilogram per cubic yard

L liter

μCi/100 μL microcurie per 100 microliters

μg microgram

μg/g microgram per gram (part per million)

μm micrometer

μS/cm microsiemens per centimeter 

mCi/mg millicurie per milligram

mg milligram

mg/kg milligram per kilogram (part per million)

mg/L milligram per liter

mg/yd3 milligram per cubic yard 

mL milliliter

mm millimeter

mV millivolt

nCi/100 μL nanocurie per 100 microliters 

ng nanogram

ng/g nanogram per gram (part per billion) 

ng/g/d nanogram per gram (of dry sediment) per day; also ng/g dry sed/d

ng/L nanogram per liter

nmol/g dry sed nanomole per gram dry sediment

s second
viii

~ approximately

> greater than

< less than

Chemical Elements

Al aluminum

As arsenic

B boron

Ba barium

Be beryllium

Bi bismuth

B boron

Ca calcium

Cd cadmium

Ce cerium

Cl chloride

Co cobalt 

Cr chromium

Cs cesium

Cu copper

Dy dysprosium

Er erbium 

Eu europium 

Fe iron

Gd gadolinium

Hg mercury

Ho holmium 

K potassium

Lu lutetium 

Mg magnesium

Mn manganese 

N2 nitrogen gas

Na sodium

Nd neodymium

Ni nickel

O2 oxygen gas

Pb lead

Pr praseodymium

Rb rubidium

S sulfur

Sb antimony

Se selenium

Si silicon

Tb terbium 

Tl thallium

Tm thulium 

U uranium

V vanadium

Y yttrium

Yb ytterbium 

Zn zinc

Chemical Compounds and Isotopes

14C radio-labeled carbon

14CH3

HgCl methylmercury chloride with radio-labeled carbon

CH3

203Hg+ methylmercury ion with radio-labeled mercury

CH4 methane

14CH4 methane with radio-labeled carbon 

CH2Cl2 methylene chloride

14C-MeHg methylmercury with radio-labeled carbon

14CO2 carbon dioxide with radio-labeled carbon

CuSO4 copper sulfate

HCl hydrochloric acid

HF hydrofluoric acid

Hg0 elemental mercury

Hg2+ mercuric ion

Hg(II) divalent mercury

203Hg(II) radio-labeled divalent mercury

HgT total mercury

HNO3 nitric acid

KBr potassium bromide

MeHg methylmercury (monomethylmercury)

NaBEt4 sodium tetraethyl borate
Geochemistry of Mercury and other Trace Elements in 

Fluvial Tailings Upstream of Daguerre Point Dam, Yuba 

River, California, August 2001

By Michael P. Hunerlach, Charles N. Alpers, Mark Marvin-DiPasquale, Howard E. Taylor, and

John F. De Wild

Abstract

This study was designed to characterize the particle-size 

distribution and the concentrations of total mercury (HgT), 

methylmercury (MeHg), and other constituents in sediments 

trapped behind Daguerre Point Dam, a 28-foot-high structure 

on the lower Yuba River in California. The results of the study 

will assist other agencies in evaluating potential environmental impacts from mobilization of sediments if Daguerre Point 

Dam is modified or removed to improve the passage of anadromous fish. Methylmercury is of particular concern owing to 

its toxicity and propensity to bioaccumulate. A limited amount 

of recent work on hydraulic and dredge tailings in other 

watersheds has indicated that mercury and MeHg concentrations may be elevated in the fine-grained fractions of placer 

mining debris, particularly clay and silt. Mercury associated 

with tailings from placer gold mines is a source of continued 

contamination in Sierra Nevada watersheds and downstream 

water bodies, including the Sacramento–San Joaquin Delta 

and the San Francisco Bay of northern California.

Churn drilling was used to recover sediments and heavy 

minerals at 5-foot intervals from six locations upstream of 

Daguerre Point Dam. Maximum depth of penetration ranged 

from 17.5 to 35 feet below land surface, resulting in 31 discreet drilled intervals. Drilling in permeable, unconsolidated 

sediments below the streambed of the Yuba River released a 

significant volume of water along with the sediment, which 

complicated the sampling and characterization effort. Overflow of a silty fraction sampled at the drill site contained 

suspended sediment consisting predominantly of silt and 

clay, with HgT concentration ranging from 33 to 1,100 ng/g 

(nanogram per gram) dry weight. A sandy fraction, collected 

after sieving sediment through a 2-millimeter vibratory screen, 

contained from 14 to 82 percent sand and 1 to 29 percent silt 

plus clay, and had HgT concentrations ranging from 6.8 to 81 

ng/g dry weight. A clay-silt fraction, sampled from material 

remaining in suspension after the sandy fraction settled for 15-

20 minutes, contained mercury concentrations from 23 to 370 

ng/g dry weight. Concentrations of MeHg were less than the 

detection limit (<0.001 ng/g dry weight) in 30 of 31 samples 

of the sandy fraction. In the suspended clay-silt fraction, 

MeHg was detected in 16 of 31 samples, in which it ranged in 

concentration from 0.04 (estimated) to 0.61 ng/g wet weight.

Potential rates of mercury methylation and demethylation were evaluated in seven samples using radiotracer 

methods. Mercury methylation (MeHg production) potentials 

were generally low, ranging from less than 0.15 to about 1.6 

ng/g/d (nanogram per gram of dry sediment per day). Mercury 

demethylation (MeHg degradation) potentials were moderately 

high, ranging from 1.0 to 2.2 ng/g/d. The ratio of methylation potential (MP) to demethylation potential (DP) ranged 

from less than 0.14 to about 1.4 (median = 0.24, mean = 0.44, 

number of samples = 7), suggesting that the potential for 

net production of MeHg in deep sediments is generally low. 

The MeHg production rates and MP/DP ratios were higher 

in the shallower interval in two of the three holes where two 

depth intervals were assessed, whereas the MeHg concentrations were higher in the shallower interval for all three holes. 

A similar spatial distribution was found for concentrations 

of solid-phase sulfide (measured as total reduced sulfur and 

likely representing iron-sulfide and iron-disulfide compounds), 

which were much higher in shallower samples (about 700 to 

about 2,100 nanomoles per gram, dry sediment) than in deeper 

samples (32 to 55 nanomoles per gram, dry sediment) in these 

three holes. If reduced sulfur compounds are oxidized to 

sulfate as a consequence of sediment disturbance, the activity of sulfate-reducing bacteria might be stimulated, causing a short-term increase in methylation of inorganic Hg(II) 

(divalent mercury). The extent of increased Hg(II)-methylation 

would depend on the reactivity of the inorganic Hg(II) fraction 

associated with these sediments, which is currently unknown.

The relation between HgT concentration and particle 

size was evaluated quantitatively using a suite of 15 samples, 

which were separated into 6 size fractions using screens with 

the following sieve sizes: 2,000, 500, 297, 149, 60, and 30 

μm (micrometer). A trend toward higher concentrations of 

mercury in samples having finer particles was observed. This 

trend is consistent with data obtained for other bulk samples 

(sandy, silty, and clay-silt fractions), which indicate higher 

concentrations of mercury associated with larger proportions 

of clay-size material (less than 4 μm). 
2 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California

Heavy-mineral concentrates were prepared to evaluate gold concentrations and to make direct observations of 

elemental mercury and gold-mercury amalgam. Elemental 

mercury (Hg0) was observed coating gold and gold-amalgam

grains and was isolated with the aid of a stereo microscope. 

Using a scanning electron microscope, Hg0 and mercury-rich 

gold amalgam were observed on the surfaces of individual 

gold grains. Spherules of liquid Hg0 up to 6 μm in diameter 

were observed in association with platy, aluminosilicate minerals and iron oxides. 

In addition to mercury, concentrations of several other 

trace elements in the fine-grained sediment trapped behind 

Daguerre Point Dam are of potential environmental concern. 

Median concentration values of arsenic, chromium, copper, 

and nickel from 19 sediment samples (screened to less than 

0.060 millimeter) were higher than consensus threshold effects 

levels for ecological toxicity, and maximum concentrations of 

lead, mercury, and zinc were also above the threshold effects 

levels.

Introduction

Improved passage of anadromous fish is a significant 

issue for resource agencies throughout the Pacific Northwest, 

including northern California. A proposed fish-passageimprovement project in the lower Yuba River is located at 

Daguerre Point Dam (fig. 1), in the center of the Yuba Goldfields. The proposed fish-passage-improvement alternatives 

include dam removal or modification, which would likely 

release sediments trapped behind Daguerre Point Dam to 

downstream environments. The Yuba Goldfields area has been 

affected by several generations of mining of alluvial gold and 

gravel deposits by various methods, dating back to the California Gold Rush of 1849. Mercury is known to be a contaminant in gold-mining wastes because of its use in amalgamation. This study addresses concerns about mercury and other 

constituents in potentially released sediments trapped behind 

Daguerre Point Dam.

Daguerre Point Dam and the Yuba Goldfields 

Daguerre Point Dam is a 28-foot-high structure located 

about ten miles east of Marysville, California, in the Yuba 

Goldfields (fig. 1). The dam sits on a bedrock bench in the 

piedmont plain of the ancestral Yuba River. A cut 600 feet 

wide and 25 feet deep was dug in the bedrock bench for 

the footing of the dam, which was completed in 1910. The 

Yuba Goldfields (fig. 2) consist of more than 8,000 acres of 

dredged landscape and represent one of the largest tracts of 

mining debris in northern California. Sediment stored behind 

Daguerre Point Dam is a mixture of material from a variety of 

sources, reflecting several periods of historical mining in the 

Yuba River watershed. In addition, some sediments unaffected 

by mining may exist very near Daguerre Point Dam.

Prior to hydraulic mining and dredging, the Yuba River 

traversed the northern Sierra Nevada and discharged into the 

Sacramento Valley (fig. 1), depositing vast quantities of goldbearing gravels in a large alluvial plain. Gold dredging began 

in California in March 1898 (Aubrey, 1910), with the working 

of auriferous, alluvial deposits at the mouths of the Feather, 

Yuba, and American Rivers. One of the largest alluvial concentrations of gold in California is within the Yuba Goldfields, 

where over 5 million ounces of gold have been produced from 

more than 1 billion cubic yards of material. Parts of the Yuba 

Goldfields were mined multiple times by evolving dredging 

methods. Each new period of dredging dug deeper and recovered smaller gold particles as technology improved. Today, 

the only recent gold-dredging operation in the conterminous 

United States is in areas of previously mined gravels in the 

Yuba Goldfields, including tailings from hydraulic gold mines 

that were discharged to the Yuba River prior to construction 

of Englebright Dam (fig. 1) in 1940 and unworked gold-bearing gravel at and near the contact with metamorphic bedrock, 

reaching depths of nearly 140 feet below the water surface.

The Daguerre Point Dam was built in the early 1900s to 

retain mining debris from hydraulic mines in the upper Yuba 

River watershed. This was one of the early attempts to retain 

the large quantities of hydraulic mining debris that was being 

transported down the Yuba River channel. Prior to dam construction, the river carried most of the hydraulic mining debris

in the watershed to the edge of the Central Valley, where the 

lower gradients caused the debris to be deposited, filling and 

choking the river channel. 

The first attempt to constrain tailings and debris in the 

lower Yuba River was made using a structure known as Barrier Number 1, located about 1 mile downstream of the Parks 

Bar Bridge and 4.5 miles upstream of Daguerre Point (fig. 1). 

Barrier Number 1, constructed in 1905, was 14 feet high and 

constrained 1,690,000 cubic yards of gravel that were transported in the river channel during the winter and spring of 

1906 (Gilbert, 1917). Of this total, 920,000 cubic yards were 

constrained upstream of the barrier during the January 1906 

flood alone. However, Barrier Number 1 failed the following 

year, in March 1907. Many acres of farmlands were repeatedly destroyed by flooding and silting in the Yuba River, Bear 

River, and American River watersheds, and properties in the 

cities of Marysville and Sacramento were threatened frequently by the rise of river beds. 

After Daguerre Point Dam was completed in 1910, it 

rapidly filled to capacity with sediment and debris that moved 

downstream during flooding in 1911. The level of the streambed 

at Daguerre Point Dam was established in 1911. The present-day alluvial sediments in the Yuba River are comprised 

predominantly of mining debris that contains mercury from 
Figure 1. Map showing location of study area, Daguerre Point Dam, California.

Introduction 3

������� ��������

�������

�������

���������� Yuba City

���������������

������������

�����������

���

����

�����������

�

�

���������

��������

���������

���������

�����������������

�����������

�����������

���������������

�������������

����

����

��������

���������

����������

� �������

� ������������

����������������������������������������������������������������������������������

��������������������������������������������������

��

��

��

�����

�����

������

������

�������

��������

����������

���������

����

�����

� ���� �

�������������

���������

������������

���������

����������

�������

�������

�������

����������

�����

�����

�����������

��������������� � � � � � �

�

� �

�

�

�

�����������

���������������
Figure 2. Aerial photograph showing Yuba Goldfields and location of training walls, Daguerre Point Dam, California.

4 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California

���������������

���������������

��

�������� ������� �������� �������

�������

�������

�������

�����������

� ������

� �����������

������������������������

�����������������������������������������

����������������������������������������������������������

����������������������

������������������������������������������������������������������������������������������������

����������������������� ��

the processing of gold-bearing gravels both in hydraulic mines 

and early dredging operations (Alpers and Hunerlach, 2000). 

The Daguerre Point Dam was constructed in a cut above 

and to the north of the original Yuba River channel. The bedrock under Daguerre Point Dam is a portion of the Daguerre 

Point Terrace, a feature that facilitated the construction of a 

low dam at a relatively low cost. The current position of the 

Yuba River behind the Daguerre Point Dam is north of its premining channel (fig. 3) and above its prior streambed elevation. Flood water was directed to and over the dam by large 

walls constructed of tailings stacked by specially constructed 

dredges. These constraining walls are known locally as training walls and currently hold the Yuba River in its position 

upstream of the dam (fig. 2). The training walls, which were 

constructed using dredge tailings, force the Yuba River to flow 

as far north as possible, allowing deeper gravels in the southern part of the Yuba Goldfields to be mined more economically and with less environmental impact than if the river’s 

original course had been maintained. Downstream of Daguerre 

Point Dam, the Yuba River has abandoned the training walls 

and resumed a meandering course through the fluvial tailings. 

Down cutting of the streambed below the dam has exposed the 

bedrock of Daguerre Point.
Figure 3. Map with contours representing elevation of top of bedrock, Daguerre Point Dam, California.

Introduction 5

�����

�����

�����

�����

�����

�����

��

��

���

���

��

��

��

���

��

��

��

���

���

��

���

��

��

���

��

��

���

���

���

���

����

���

���

���

���

���

��

��

��

��

���

��

�������� �������� ��������

������

�������

������

���������

���������

���������

�����������

� ��� ������

� ��� �����������

����

�����������

������������������������

��������

�������������������������

�������������������������

��������������������������������������

�������������������������������������������

������������������� ������������������������������������������������

�����������������������������������������

�����

�����������������������������������������������������

������������������������������������������������

�������������

��

���

������������������������������������������������������������������������������������������������

�������������������������

������������������������

��

Fish Habitat and Environmental Concerns

A reconnaissance study in the northwestern Sierra 

Nevada (Slotton and others, 1997) indicated that mercury 

bioaccumulation in fish and biota is widespread and correlates in general with areas of historical gold mining. Alpers 

and Hunerlach (2000) combined the data from Slotton and 

others (1997) with historical mining records to demonstrate an 

overall correlation between mercury bioaccumulation and the 

intensity of hydraulic mining in the watersheds of the western slope of the northern Sierra Nevada. Mercury associated 

with tailings from placer gold mines is a source of continued 

contamination in Sierra Nevada watersheds and downstream 

water bodies, including the Sacramento–San Joaquin Delta 

and the San Francisco Bay of northern California (fig. 1). The 

Yuba River is one of the most intensely mined areas and also 

has some of the highest levels of mercury bioaccumulation. 

May and others (2000) documented significant bioaccumulation of MeHg in fish in Lake Englebright, located on the Yuba 

River several miles upstream of Daguerre Point Dam, and in 

four other reservoirs as well as several stream sites affected by 

hydraulic mining in the Yuba River and Bear River watersheds. 
6 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California

There are several species of anadromous fish, including 

steelhead trout and four distinct runs of Chinook salmon, for 

which available habitat in California has been greatly reduced 

by dams on rivers. There is considerable interest among 

federal and state agencies in restoring anadromous fish habitat 

and improving passage and survival of these fish in areas such 

as the lower Yuba River.

Fish ladders presently provide some passage of anadromous fish at Daguerre Point Dam; however, improved passage is needed (California Department of Water Resources, 

2003). Of the six types of anadromous fish that are known 

to migrate into the Yuba River, four (white sturgeon, green 

sturgeon, striped bass, and American shad) are blocked by 

Daguerre Point Dam, and two (fall-run Chinook salmon, and 

steelhead trout) are hindered by inadequate fish ladders at the 

dam. Proposed modifications to Daguerre Point Dam intended 

to improve fish passage might result in release of sediments 

stored behind the dam to downstream environments. Increased 

sedimentation in downstream water bodies, including the 

Sacramento–San Joaquin Delta and the San Francisco Bay, 

could cause physical degradation of fish habitat by siltation, 

or chemical degradation by release of contaminants such as 

mercury (or methylmercury) or other trace metals that are 

presently stored in sediments behind Daguerre Point Dam. 

Purpose and Scope

Removal or modification of the Daguerre Point Dam is 

being evaluated by various stakeholder agencies as a way to 

improve the ability of anadromous fish to access about 12 

miles of the Yuba River below Englebright Dam (fig. 1). The 

purpose of this report is to provide data and information about 

the sediment trapped behind Daguerre Point Dam, specifically 

(1) the association of particle-size distribution and mercury 

and methylmercury concentration, and (2) the potential for 

mercury methylation and demethylation. Of particular concern 

to stakeholders is the distribution of silt- and clay-sized 

particles, which, if released to downstream environments, 

could cause degradation of fish habitat. This report presents 

the first characterization of mercury concentrations in 

sediments trapped behind Daguerre Point Dam, an area that 

has been affected by multiple periods of gold mining and 

associated mercury use.

Acknowledgments

The authors thank the numerous individuals at the U.S. 

Geological Survey (USGS) and other agencies who made this 

report possible. Personnel who assisted with field work for 

this study include Connie Clapton (California State University 

Sacramento Foundation) and Karl Davidek (USGS). USGS volunteer Michael J. Hunerlach and student intern Nick Kanowski 

helped with field logistics. Assistance by USGS personnel in 

the laboratory was provided by Ronald Antweiler, Dale Peart, 

Terry Plowman, and David Roth in Boulder, Colorado; by Mark 

Olson and Shane Olund in Middleton, Wisconsin; by Jennifer 

Agee and Le Kieu in Menlo Park, California; and by Daniel 

Gooding in Vancouver, Washington. Individuals from Cal 

Sierra Development Incorporated who facilitated understanding of the stratigraphy during drilling include Ben Coleman 

and Tony Massey, and especially Alberto Ramirez, who shared 

his vast knowledge of placer geology and mining history. 

Walter Cotter of the Browns Valley Irrigation District assisted 

in gaining access to the sampling sites. Ted Frink of the California Department of Water Resources and Paul Wisheropp 

of Entrix, Inc. participated in useful discussions regarding the 

hydrogeology of the lower Yuba River. John Nelson of the 

California Department of Fish and Game assisted with securing funding for this study in cooperation with the U.S. Bureau 

of Reclamation.

Hydrogeological Setting and Mining 

History

Geology of Gravel Deposits

The extensive gravel deposit in the Yuba Goldfields is 

located within Yuba County, north-central California, in the 

topographic transition zone between the western foothills of 

the Sierra Nevada and the eastern margin of the Great Valley 

(fig. 1). The Yuba Goldfields is one of three large floodplains 

that drain the principal gold-mining region of the northern 

Sierra Nevada in California; the others are the goldfields of 

the Feather River and the American River. Gravels in the Yuba 

Goldfields were deposited over the past 50 million years, 

beginning with the Eocene erosion of the Sierra Nevada; the 

gravels filled a large alluvial channel where the Yuba River 

currently emerges from the foothills. The ancestral Yuba 

River incised a deep channel into the metavolcanic bedrock

in the reach between Parks Bar and Daguerre Point. About 

three miles upstream of Daguerre Point, the paleo-channel

bifurcates and the bedrock gradient increases to the southwest 

around Daguerre Point (fig. 3). Daguerre Point is a metavolcanic greenstone barrier that formed the right bank of the deep 

channel where the ancestral Yuba River emptied onto a vast 

alluvial plain. About 0.7 miles south of Daguerre Point, the 

river channel begins to widen and the gravel deposit is more 

than 2 miles wide. The deposit rests on terraces that were 

uplifted and eroded at different times. The lowest bedrock of 

the channel reaches a depth of 100 feet below sea level southeast and south of Daguerre Point. The ancestral Yuba River 

followed the deep channel around Daguerre Point. The present 

Yuba River flows north of and parallel to the ancestral, deep 

channel, west to the confluence of the Feather River (fig. 1). 

Typically, the surface of the exposed gravel bars and the bed 

of the Yuba River upstream of Daguerre Point Dam are well 

armored with coarse gravel to a depth of several feet.

Gold particles were released during periods of erosion 

from rich, gold-bearing quartz veins in the upper Yuba River 
Hydrogeological Setting and Mining History 7

watershed of the Sierra Nevada. Numerous gold-bearing quartz 

veins and veinlets of Middle Jurassic age exist in greenschist 

metamorphic grade host rocks in the Sierra Nevada. Abundant 

fine-grained gold particles were deposited in the flood-plain

gravels of the modern Yuba River during several phases of 

glacial erosion in the Pleistocene. Quaternary gravels overlie 

older, Tertiary-aged volcanic rocks, post-volcanic gravels, 

and coarse gold-bearing gravels from the Tertiary Yuba River 

(Lindgren, 1911). Deltaic siltstones and sandstones of the 

Eocene Ione Formation overlie marine conglomerates of 

the Late Cretaceous Chico Formation, which form the basal 

contact with the Mesozoic metavolcanic greenstone bedrock. 

Rounded and subangular-to-subrounded clasts of coarse 

granite, rhyolite, and metavolcanic rocks dominate the lithology of the Quarternary gravels in a matrix of sand and silt. 

Thin horizons of sand, sandy silt, and silty clay formed lenses 

of variable thickness that extend throughout the deposit as a 

result of ancient flooding and natural levee breaching by the 

Yuba River as it meandered across a vast alluvial plain.

Mining Effects in the Lower Yuba River

Rich, shallow deposits of gold-bearing gravel near Parks 

Bar, about seven miles upstream of the present Daguerre Point 

Dam, were first worked around 1850. Soon after these shallow 

deposits were exhausted by river mining, miners exploited 

Quaternary terrace deposits at an elevation higher than that 

of the present river, which led miners to older, Tertiary-age 

deposits of the ancestral Yuba River. Around 1852, hydraulic mining of the Tertiary-age gravel deposits began farther 

upstream and continued for more than 32 years (Alpers and 

Hunerlach, 2000). Hydraulic mining moved nearly 500 million cubic yards of sand, gravel, and silt in the Yuba River 

system to the edge of the Central Valley, where much of it was 

deposited, filling and choking the Yuba River channel. Similar 

activity in other Sierra Nevada watersheds displaced approximately 1 billion additional cubic yards; the Yuba River was the 

site of more hydraulic mining debris than any other watershed 

in California (Lindgren, 1911; Gilbert, 1917). 

The gold-rich placer deposits of the present Yuba River 

are mostly confined to the river banks, bars, benches, and 

flood plains. Small-scale placer mining in nearby streams and 

the active channel of the Yuba River ceased because the channel was buried by the large influx of hydraulic mining debris. 

Hydraulic mining occurred locally at Sicard Flat and Smartville (fig. 1), but was eventually terminated along with other 

hydraulic mining in the Sierra Nevada by the Sawyer Decision of 1884. Debris from hydraulic mining continued to be 

transported into the Yuba River, reaching a thickness of more 

than 80 feet within the Yuba Goldfields. The slurry of debris

washed onto the Yuba River flood plain contained as much as 

57 percent silt and sand (Gilbert, 1917) along with a high proportion of black sand and fine-grained gold, floured mercury, 

and amalgam. In an attempt to prevent flooding, Barrier Number 1 was constructed about 4.5 miles upstream of Daguerre 

Point in 1905 (Mining and Scientific Press, 1905). Prior to the 

completion of Daguerre Point Dam, Barrier Number 1 failed 

in March 1907, causing a large volume of debris to be transported by the Yuba River past the Daguerre Point location. 

Overview of Mercury Use in Historical Mining

Liquid mercury (quicksilver) was used extensively from 

the 1850s through the mid-1900s for gold recovery in the 

Sierra Nevada. Mercury was first used during initial mining of 

placer gold deposits in riverbeds in the 1850s and its use was 

especially prevalent in hydraulic mining operations. Prior to 

the Sawyer Decision of 1884, hydraulic mining was largely 

unregulated. The Caminetti Act of 1893 allowed hydraulic 

mining to continue in the Sierra Nevada under the oversight of 

the California Debris Commission, and the activity continued 

until the 1930s (Yeend, 1974; Hagwood, 1981). More than 8 

million pounds of mercury were lost to the environment during 

historical gold mining in the Sierra Nevada (Hunerlach and 

others, 1999; Alpers and Hunerlach, 2000; Churchill, 2000). 

Many of the historical mine sites remain as significant sources 

of mercury contamination as well as eroding sediment. 

Mercury from the upstream mine sites has been partially 

transformed to MeHg and is currently bioaccumulating in 

fish in foothill reservoirs, including Englebright Lake on the 

Yuba River (May and others, 2000). For example, fourteen 

samples of smallmouth bass from Englebright Lake, ranging 

in total length from 285 to 358 mm, had HgT concentrations 

in skinless fillets of axial muscle tissue ranging from 0.53 to 

0.96 parts per million (wet basis) (May and others, 2000). 

The data on mercury in fish tissue has led to fish consumption advisories for reservoirs and selected stream reaches in 

the Yuba River and Bear River watersheds, east and southeast, 

respectively, of the Daguerre Point Dam (Klasing and Brodberg, 2003).

Beginning in 1898, mercury also was used to recover 

gold collected using dredges. Up to 3,000 pounds of mercury 

was used per dredge per week (Janin, 1918). Mercury losses 

from riffles in gold-recovery sluices onboard the dredges in the 

Yuba Goldfields were from 2 to 5 percent per season, compared with the range of 10 to 30 percent per season for hydraulic mining (Alpers and Hunerlach, 2000; Churchill, 2000). 

 However, gold dredges commonly recovered more 

mercury than they lost because of their efficient recovery of 

heavy sand- and silt-sized particles and the fact that much of 

the material being dredged was either hydraulic tailings or 

previously dredged ground. Historical records from the Yuba 

Consolidated Goldfield indicate that dredging near Daguerre 

Point Dam took place on a nearly continuous basis from 1904 

through 1968. Compilation of annual data for dredged areas 

indicates that dredging can be divided into three main periods: 

1904-15, 1916-34, and 1942-68 (fig. 4). The mining company records indicate that extensive areas were re-dredged and 

that this was done primarily as technology improved allowing 

deeper digging. The area of the present Yuba River channel
�����

�����

�����

�����

�����

�����

���������� ���������� ����������

���������

���������

���������

����������������

���

� ����� ����������

� ��� ����������

�����������

���������������������

���������������������

���������������������

�����

������������������������������������������������

����������������������������������������������������������

�����������������������������������������������������������������������������������������������������������������

����������������������������������������������������������������������������������������������������������������

Figure 4. Map showing chronology of dredging upstream of Daguerre Point Dam, California.

8 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California

upstream of Daguerre Point Dam was dredged primarily during 1916-34. The area north and west of this dredged area was 

apparently not dredged and most likely represents residual 

hydraulic mine tailings and (or) a mixture of hydraulic mine 

tailings and early dredged tailings (fig. 5). 

Recovery of gold and gold-mercury amalgam was 

further enhanced starting around 1918 by installing jigs on 

the dredges. Early testing of heavy mineral concentrates from 

dredging showed a gain of 10 pounds of mercury for every 

100 tons of black sand processed, corresponding to a mercury 

concentration of about 50 parts per million. Mercury use in the 

Yuba Goldfields stopped in 1990 (Alberto Ramirez, Mining 

Engineer, Cal Sierra Development Incorporated, oral commun., 2002); today, mercury is recovered as a by-product of 

gold and sand recovery.

Dredging

The bucket-line dredge was invented and first used in 

California around 1898, 14 years after the cessation of major 

hydraulic mining in the Sierra Nevada. In August 1904, mining operations began on the Yuba River near Hammonton (fig. 

1) using the Yuba No. 1 and No. 2 bucket-line dredges; these 

were the first of their type to be able to dig 60 feet below the 

water line (Aubrey, 1910). Gold dredging was the first attempt 

to recover both the gold lost during hydraulic mining and the 

very fine gold distributed naturally in the gravel deposits of the 

Yuba River flood plain.

The gold dredge dug a deep trench across the alluvial

plain using a series of buckets on a seamless conveyor. Within 

this trench, the dredge floated in a large pool and dumped 
�����

�����

�����

�����

�����

�����

���������� ���������� ����������

���������

���������

���������

����������������

���

� ����� ����������

� ��� ����������

�����������

���������������������

���������������������������������������������������������������

����������������������������

���������������������

���������������������

�����

������������������������������������������������

����������������������������������������������������������

�����������������������������������������������������������������������������������������������������������������

����������������������������������������������������������������������������������������������������������������

Figure 5. Map showing distribution of residual hydraulic mine tailings upstream of Daguerre Point Dam, California.

Hydrogeological Setting and Mining History 9

the processed gravel behind it as it progressed across the 

landscape. The gold-bearing gravel was separated inside 

the dredge into coarse and fine fractions. The fine fraction, 

consisting of sand, silt, and clay, was discharged into the pool 

and the coarser material was discharged to the rear and to the 

sides of the dredge. As a result, two distinct types of deposits 

accumulated in the pool inside the trench. A mixture of clay, 

silt, and sand, typically tens of feet thick, accumulated at the 

bottom of the pool, whereas gravel was stacked in piles up to 

43 feet above the surface of the pool. The volume of gravel 

was not reduced by removing the clay and sand that previously 

occupied the interstices between the pebbles and coarse gravel. 

The total volume of the post-dredging deposits is greater than 

that of the undredged gravel and debris as a result of disruption and sorting of the material.

Since 1904, dredging has been the principal form of 

mining in the Yuba Goldfields. Dredging re-worked most 

of the hydraulic tailings that were deposited on top of the 

younger gold-bearing river gravels (Aubrey, 1910). By 1910, 

there were as many as 15 dredges operating near Hammonton 

(fig. 1). As dredging technology evolved and the top gravels were exploited, dredges were rebuilt to allow digging 

to greater depths below the water surface. Digging depths 

typically ranged from 60 to 80 feet below the water surface 

through 1939 and from 100 to 125 feet from 1939 to 2003. In 

1959, four dredges mined more than 16 million cubic yards 

of gravel. Between 1898 and 2003, more than 1 billion (109) 

cubic yards of gold-bearing gravel were dredged in the Yuba 

Goldfields. In August 2001, only the Yuba No. 21 dredge was 

operating; operations on Yuba No. 21 have been halted since 

January 29, 2003 because of the sinking of this dredge.

At present (2004), no gold-mining dredges are operating in the Yuba Goldfields. Today, the extensive residual piles 

of coarse gravel are an important source of aggregate and 

sand. Water flowing through the gravels creates large tracts 

of wetland ponds throughout the mined landscape. In 1910, 
Figure 6. Aerial photograph showing locations of drilling upstream of Daguerre Point Dam, California.

10 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California

� ����������

����������

�����

�

�����������������������������������������������������������

�����������

���������

���������

���������������

���������� ���������� ����������

���������

���������

������������������������������

����������������������������������

�����

����

�����

�����

����

�����

�����

�����

�����

���������������

�����������������

������������������������������������������������������������������������������������������������

�������������������������

fine-grained silt and sand were channeled to a “settling basin” 

about 2 miles south of Daguerre Point that was more than 

1,200 acres. Because of the increased value of sand in recent 

years, miners have inverted the discharge of processed material from the dredge, sending the coarse gravels to the bottom 

of the pond while saving sand and fine-grained sediment for 

further processing.

Study Design and Methods

Drilling Methods

During August 2001, the USGS drilled a series of six 

holes (fig. 6) behind the Daguerre Point Dam, in the bed of 

the Yuba River. Site descriptions and locations are given in 

table 1. Based upon the lithology of the sediments behind 

the Daguerre Point Dam and evaluation of historical mining 

records, a churn drill (fig. 7) was selected for drilling and collecting composite samples. Churn drilling is used in deep or 

wet ground where sampling by pits, trenches, or other drills is 

not feasible and where quantitative recovery of heavy minerals is required. The churn drill uses a heavy steel casing with 

a drive shoe at the bottom, a chisel-shaped bit, and a sand 

pump for removing the sample from the hole. The sand pump 

is a vacuum pump made of a hollow steel cylinder, 8 feet long 

and 4 inches in diameter, equipped with a valve and a piston (or 

sucker rod) that travels the whole length of the cylinder. The piston goes to the bottom of the pump when lowered; when drawn 

up rapidly, it produces a vacuum, which draws in sand, silty 

water, gravel, and small cobbles. This method is very efficient 

for sampling alluvial material in which heavy minerals such as 
Figure 7. Photo of churn drill at site DPD-2, Daguerre Point Dam, 

California.

USGS station number Drill hole Depth

(ft)

Drilling 

start date Site descriptions Latitude (north)

Longitude 

(west)

391231121263201 DPD-1 0–17.5 8/14/2001 The sample location is at the far SW end of a gravel bar 

on the right bank side of the Yuba River about 200 ft 

upstream of Daguerre Point Dam.

39°12′34′′ 121°26′36′′

391241121262401 DPD-2 0–35 8/15/2001 The sample location is at the far NE end of a gravel bar 

on the right bank side of the Yuba River about 400 ft 

upstream of Daguerre Point Dam.

39°12′41′′ 121°26′24′′

391302121252101 DPD-3 0–20 8/20/2001 The sample location is at the far NE end of a gravel bar 

on the right bank side of the Yuba River about 1.2 mi 

upstream of Daguerre Point Dam.

39°13′02′′ 121°25′21′′

391256121254801 DPD-4 0–30 8/21/2001 The sample location is near the SW end of a gravel bar 

on the right bank side of the Yuba River about 0.8 mi 

upstream of Daguerre Point Dam.

39°12′56′′ 121°25′48′′

391231121263201 DPD-5 0–20 8/24/2001 The sample location is near the SE end of a gravel bar 

on the left bank side of the Yuba River about 200 ft 

upstream of Daguerre Point Dam.

39°12′31′′ 121°26′34′′

391236121262701 DPD-6 0–30 8/27/2001 The sample location is near the SE end of a gravel bar 

on the left bank side of the Yuba River about 600 ft 

upstream of Daguerre Point Dam.

39°12′36′′ 121°26′27′′

Table 1. Description of drill sites upstream of Daguerre Point Dam, California.

[USGS, U.S. Geological Survey. ft, foot; mi, mile. DPD, Daguerre Point Dam]

Study Design and Methods 11

gold and gold-amalgam may be widely dispersed in unconsolidated sediments (Wells, 1973). 

Drilling with the churn drill was accomplished by driving 

a 6-inch diameter steel casing to the desired depth interval and 

extracting the contents by means of the piston-plunger, which 

sucks up the contents of the discrete interval. If necessary, 

the material at the bottom of the hole was “churned” (broken 

up using the chisel-shaped bit) for several minutes to break 

up resistant rocks or hardpan clay layers. If necessary during 

churning, a hose was used to pump Yuba River water into the 

hole. It is estimated that 1 to 10 gallons of Yuba River water 

was introduced during the drilling of each 5-foot interval. 

Water quality in the Yuba River during drilling is discussed in 

a later section of the report. Sediment lithology was recorded 

for each 5-foot interval (table A1).

Hydrologic Conditions during Study

Diversion of Browns Valley Irrigation Ditch

The intake to the Browns Valley irrigation ditch (fig. 6) 

diverts water for agricultural use about 1.3 miles upstream of 

Daguerre Point Dam. Flow is diverted from the main Yuba 

River through a 40-foot-wide diversion channel. It was necessary to cross this channel to drill-holes DPD-3 and DPD-4. 

To maintain an uninterrupted flow of 200 ft3/s (cubic foot per 

second), three 48-inch-diameter culverts were installed in the 

bed of the Browns Valley irrigation ditch and the mouth of the 

diversion was narrowed. A temporary gravel bridge was constructed over the corrugated steel culverts while the minimum 

flow required by the irrigation district was allowed to pass 
12 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California

through. This bridge allowed access to a 1-mile-long meander island in the river bed, located between 0.8 and 1.5 miles 

upstream of Daguerre Point Dam, while drill-holes DPD-3 and 

DPD-4 were drilled and sampled. Upon completion of drilling, 

the culverts were removed, the mouth of the diversion ditch 

was widened to its original configuration, and the diversion 

channel walls were stabilized with locally available gravels. 

Discharge and Water Quality

The flow rate of the Yuba River changes with the seasons 

in response to the Mediterranean climate of northern California and to minimum flow requirements mandated for fish habitat (California State Water Resources Control Board, 2003). 

Discharge in the Yuba River and major tributaries is managed 

for the purposes of flood control, electric power generation, 

irrigation, and aquatic habitat. During drilling in August 2001, 

the Yuba River above Daguerre Point Dam had a moderate 

flow rate with an average discharge of 1,607 ft3/s. 

Because some Yuba River water was pumped into each 

open hole during drilling, a water-quality sample was collected 

to determine whether significant concentrations of mercury or 

methylmercury were added to the downhole sediments. A grab 

sample for water quality was collected from the main channel of the Yuba River between drill-hole numbers DPD-6 and 

DPD-2 (fig. 6). Analytical results for the water-quality sample 

are given in table D1.

Collecting and Processing Samples

A flow chart describing the sample collection and processing procedures is shown in figure 8. Sediment samples 

from the six drill holes were composited in 5-foot intervals, 

with minor exceptions described below. Samples of sediment 

and produced water from the churn drill were transferred into 

an acid-rinsed, stainless steel trough and then allowed to flow 

into an acid-rinsed, 5-gallon plastic bucket. For most intervals, 

three to four 5-gallon buckets were partially filled with sediment for each 5-foot interval, for a total retained volume of 12 

to 15 gallons. A volume of 10 to 65 gallons of water containing fine sediment was discarded (silty fraction; yellow areas in 

figure 8). The silty fraction was sampled by collecting 1 L per 

5-gallon bucket of discharged drill water; the 1-L subsamples 

were composited in a 20-L teflon-lined, stainless-steel churn, 

from which 1-L subsamples were drawn for analysis of HgT

concentration and particle-size distribution. For selected intervals at this stage, a 0.5-L subsample of the retained material 

was taken for analysis of mercury methylation and demethylation potential and related ancillary parameters.

The retained sediment for each 5-foot interval was 

transferred to an acid rinsed, stainless-steel, 76-cm-diameter 

vibratory screen (manufactured by SWECO) with openings of 

2 mm. For each interval, fine-grained sediments were separated from the greater-than 2-mm sediments with recirculated 

process water. Unscreened sediment was continuously washed 

on top of the vibratory screen until no fine material was seen 

on the gravel. The gravel fraction that did not pass through the 

screen was set aside in clean, plastic, 5-gallon buckets. The 

sandy fraction that passed through the 2-mm screen (sand, silt, 

and clay) was homogenized in an acid-rinsed, plastic tub. 

After stirring it in the plastic tub to a slurry-like consistency using acid-rinsed plastic spoons, the sandy fraction 

was subsampled for HgT, particle-size distribution, and trace

metals in a 1-L, acid-rinsed plastic bottle that was subsequently chilled on wet ice. An additional 1-L subsample of the 

sandy fraction was taken for archive purposes and frozen on 

dry ice. Samples for analysis of HgT and MeHg in the sandy 

fraction were collected in acid-rinsed 60-mL Teflon vials 

and frozen immediately on dry ice. After the sandy fraction 

was allowed to settle for 15–20 minutes, a sample of the very 

fine-grained suspended sediment, the clay-silt fraction, was 

collected in an acid-rinsed, 30-mL Teflon centrifuge tube and 

frozen immediately on dry ice for HgT and MeHg analyses. 

A composite sample of the clay-silt fraction was collected for 

analysis of particle-size distribution and HgT in a 1-L, plastic 

bottle, which was chilled. After subsampling was complete, all 

buckets and subsamples were weighed and the excess volume 

of the clay-silt fraction was discarded by decanting. 

The residual sandy fraction that remained after decanting 

was recombined with the gravel fraction (more than 2 mm) 

and sent to Cal Sierra Development Incorporated for standard 

sieve analysis of particle-size distribution of particles at least 

0.075 mm. The heavy mineral fraction was separated from the 

sample using a conventional screen with openings less than 2 

mm, then concentrated using a gravity shaker table. The concentrated heavy-mineral fraction was air-dried and weighed. 

For each interval, visible gold and gold-amalgam grains were 

separated from the heavy metal fraction by panning and were 

hand picked with the aid of a microscope. 

Heavy-mineral concentrates and gold analysis were 

processed and calculated by Cal Sierra Development Incorporated. The heavy-mineral concentrates were dried and sieved 

by USGS personnel using the following screen sizes: 1 mm, 

0.5 mm, 0.25 mm, and 0.063 mm. Individual grains of gold 

and gold-amalgam were hand selected using a stereo binocular microscope and subsequently mounted for examination 

using the USGS scanning electron microscope (SEM) and 

energy dispersive X-ray (EDX) analyzer in Menlo Park, Calif. 

Relatively large visible grains of gold were observed during 

drilling in holes DPD-1 and DPD-5, which correlates with 

the higher gold tenor and visual gold particles observed in 

concentrates from these locations. 

The residual sandy fraction from 15 intervals in holes 

DPD-4, -5, and -6 was sieved for additional analysis of HgT

as a function of grain size. These samples were separated 

by sieving into six size-bins (also referred to as particle-size 

subclasses) using screens with the following sieve sizes: 

2,000, 500, 297, 149, 60, and 30 μm (micrometer). Material 

from 500 to 2,000 μm (2 mm) is referred to as coarse sand; 

material between 297 and 500 μm is considered to be medium 

sand; 149 to 297 μm is fine sand; and 60 to 149 μm is very 
Figure 8. Flow-sheet showing drilling and processing of sample flow-stream.

Study Design and Methods 13

������

�����

�����������

���������������������

������������������

��������������

�������

���������

����������������

����������������

��������������

�����

��������

�����������������

�������������

������������������ ����������

�����

������

�����������������������������

��������

����������

��������

���

�������

������

��������� ��������

���

���������������

���������������

������

����������� ���������

���������

���������

���������

��������������������

����������������������

�����������������

����������������������������������

�����������������

����������������

������������������

������������������������

��������������������

�����������������������

�����������������������

�������������

��������������

��������������

������������������

��������������������

����������������������

�������

�����������

������

�������

������

�������

���

����������

���������������������

���������������

����������������

�������������

������������������
14 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California

fine sand. The material between 30 and 60 μm is referred to as 

coarse silt, and the material passing through the 30 μm-screen 

consists of medium and fine silt with clay.

Laboratory Methods

Particle-Size Distribution

The residual sandy fraction plus gravel was analyzed by 

Cal Sierra Development Incorporated. Particle size was evaluated for a suite of 31 samples representing individual drilled 

intervals. The samples were separated into 10 size fractions 

using screens with the following sieve sizes: 75, 50, 25, 4.75, 

2.36, 1.18, 0.60, 0.30, 0.15 and 0.075 mm (table B1). 

Particle-size distributions in the sandy, silty, and clay-silt 

fractions were determined by the USGS Cascades Volcanic Observatory (CVO) sediment laboratory in Vancouver, 

Washington. Conventional sieving was used to determine the 

size distribution of coarse material from 2 to 0.063 mm. The 

particle-size distribution of material smaller than 0.063 mm 

was determined using a SediGraph 5100 particle-size analyzer. 

The particle-size distributions determined by the SediGraph 

for these subsamples are described as 14 size fractions ranging 

from 0.063 mm to 0.00025 mm (equal to 0.25 μm). The results 

of sieving and using the Sedigraph were combined to make a 

single distribution of particle sizes for each subsampled fraction (tables B2, B3, and B4).

Heavy Mineral Concentration and Grain-Size 

Separation

Cal Sierra Development Incorporated used a gravity 

shaker-table to separate heavy mineral concentrates from the 

bulk-sediment samples. Individual gold and gold-amalgam

grains were counted and a gold tenor was calculated based on 

the initial volume of the sample. Concentrates of the heavy 

minerals were returned to the USGS for further analysis. 

The heavy mineral concentrates were air-dried, weighed, and 

sieved using the following screen sizes: 1 mm, 0.5 mm, 0.25 

mm, and 0.063 mm. Particle-size separates were weighed and 

compared to original weights to determine a percentage distribution (table C1). Individual grains of gold and gold-amalgam

were hand-selected using a stereo binocular microscope and 

subsequently were mounted for examination by SEM and 

EDX. Mineral grains were identified by morphology, and their 

overall abundance was visually estimated (table C2).

Analysis of Mercury and Methylmercury

Analysis of HgT in the silty fraction, the clay-silt fraction, 

and the six sieved, fine particle-size bins was by the USGS 

National Research Program laboratory in Boulder, Colorado, 

using cold-vapor atomic fluorescence spectroscopy (CVAFS) 

without amalgamation. Complete digestion of sediment 

samples was done in a microwave oven using HCl-HNO3-HF 

in Teflon containers. Approximately 100 mg of dry material 

was used for each digestion. Additional details regarding the 

analytical method and related quality-assurance procedures are 

described by Alpers and others (2000). 

Analysis of HgT and MeHg in the sandy fraction and the 

clay-silt fraction (centrifuge tubes) was done at the USGS 

Wisconsin District Mercury Laboratory (WDML) in Middleton, Wisconsin, using CVAFS methods with double amalgamation. Methylmercury was isolated using ethylation-extraction methods described by Olson and DeWild (1999) and by 

DeWild and others (2002). 

Prior to analysis, sediments were digested using HCl and 

HNO3 at room temperature in Teflon containers. For MeHg 

analysis, solids (0.5 to 1.0 g) were placed into a centrifuge 

tube. Potassium bromide (KBr), copper sulfate (CuSO4), 

and methylene chloride (CH2Cl2) were sequentially added. 

The mixture was allowed to react for an hour and then was 

shaken for an hour to ensure complete extraction of the MeHg. 

Following shaking, the samples were centrifuged to break 

any emulsion that had formed. An aliquot of the CH2Cl2 was 

cleanly transferred to a vial containing reagent water. These 

vials were placed in a heating block until all CH2Cl2 evaporated and the MeHg was back-extracted into the reagent water. 

The pH of the extractant was adjusted to 4.9 (to maximize 

ethylation potential) using acetate buffer. The extractant then 

was ethylated using sodium tetraethyl borate (NaBEt4) and 

allowed to react for 15 minutes. After reaction with NaBEt4, 

the extractant was purged with nitrogen gas (N2) for 20 minutes and the ethylated Hg species were collected on a sample 

trap containing Carbotrap. These ethylated Hg species were 

desorbed thermally from the sample trap, separated using a 

gas chromatographic (GC) column, reduced using a pyrolytic 

column, and detected using a cold vapor atomic fluorescence 

spectrometry (CVAFS) detector. 

Analysis of Trace Elements and Major Elements

Analysis of trace elements and major elements in sediment samples was done by the USGS research laboratory in 

Boulder, Colorado, using inductively coupled plasma (ICP) 

methods. Samples were digested with strong acids in Teflon 

containers in a similar manner to the HgT analyses. Trace

elements other than mercury were analyzed by ICP-Mass 

Spectrometry (ICP-MS); major elements (Ca, Mg, Na, K, Si, 

Fe, and Mn) were analyzed by ICP-Atomic Emission Spectroscopy (ICP-AES). Additional details regarding analytical 

procedures are described by Alpers and others (2000) and 

Taylor (2001).

Mercury Methylation and Demethylation 

Potentials

Mercury methylation and demethylation rate potentials 

were analyzed for seven samples collected from drill-holes 

DPD-1, -3, -5 and -6. Two depth intervals (shallow and deep) 

were sampled from three of the four drill holes; only a deep 

interval was sampled from hole DPD-6. Sediment from each 
Study Design and Methods 15

analyzed section was transferred to a acid-cleaned, plastic 

5-gallon bucket. A screen with 2-mm openings was used to 

collect a subsample, which was transferred to an acid-cleaned, 

glass mason jar; the jar was filled completely with sediment to 

minimize atmospheric oxygen. Upon collection, samples were 

stored temporarily on wet ice until refrigerated (5 °C). Storage 

time was 3–16 days before subsampling at the USGS laboratory in Menlo Park, California. Physical descriptions of each 

sediment sample along with the collection date, location, and 

estimated in-place sediment temperature at the time of collection were tabulated (table A2).

All subsample processing for microbial assays and ancillary sediment characterization was done in a glove bag flushed 

with nitrogen gas (N2) to maintain anaerobic conditions. 

Sediment from each subsampled interval was transferred to a 

clean zip-lock bag and manually homogenized. Subsamples 

for each process or analyte were taken from the homogenized 

sample using acid-cleaned, stainless-steel tools. The sediment 

was weighed (± 0.1 g precision) and placed into the appropriate containers.

Standard radiotracers were used to measure potential 

rates of both MeHg production (Hg(II) methylation) and 

MeHg degradation (demethylation) (Marvin-DiPasquale and 

others, 2003). An amendment containing 1.5 μCi/100 μL of 

radio-labeled divalent mercury (203Hg(II)), with a half-life 

of 46.5 days, was used per 3.0-g sediment sample for the 

MeHg-production rate assay. The 203Hg(II) specific activity 

of the injection solution was 1.15 mCi/mg, which resulted in 

a total Hg(II) amendment of 436 ng/g wet sediment. Mercury 

demethylation rates were determined by amending separate 

subsamples with MeHg tagged with radio-labeled carbon 

(

14C-MeHg or 14CH3

HgCl) at a concentration of 9.4 nCi/100 

μL, resulting in total MeHg additions (as Hg) of 10.5 ng/g 

wet sediment. Sample sets for each interval tested for both 

microbial Hg(II)-methylation (MeHg production) and demethylation (MeHg degradation) assays consisted of duplicate, live 

(incubated) samples and one control sample killed by flash 

freezing at the beginning of the experiment (time zero). Both 

MeHg production and degradation sample sets were incubated 

simultaneously for 4 hours at 19 °C. It is assumed that both 

Hg-transformation processes are first-order for the purposes 

of calculating potential rates (Marvin-DiPasquale and others, 

2003). Potential rates are subsequently calculated as the product of the radiotracer-derived rate constant and the final concentration of radiotracer amendment in the whole sediment, 

and are thus independent of the amount of original Hg(II) or 

MeHg that might have been present in each sample.

Each of the seven sediment depth intervals was subsampled for several ancillary chemical parameters, including, pH, 

oxidation-reduction (redox) potential, loss-on-ignition, acid 

volatile sulfide, and total reduced sulfur. The pH and oxidation-reduction (redox) potential were determined by inserting an electrode directly into sediment. Organic content was 

measured by weight loss on ignition (American Public Health 

Association, 1981). Two forms of sulfur—acid volatile sulfur 

and total reduced sulfur—were determined using methods 

described by Ulrich and others (1997). Organic content and 

both forms of solid-phase sulfur were measured in duplicate 

samples from each sediment depth interval. 

Dissolved organic carbon (DOC) concentrations were 

assessed by adding deionized water (Milli-Q, 10 mL) to the 

sediment (10 g) to obtain enough pore water for analysis. The 

exact weight of the sediment and the water added per tube was 

recorded, and subsequent pore-water analyte concentrations 

were calculated taking this pore-water dilution into account. 

Samples were shaken until they became a homogenous slurry, 

which was then centrifuged (3,000 rpm for 15 minutes) in 45-

cm3 polystyrene, screw-cap tubes. The resulting supernatant 

was filtered (0.45-μm nylon syringe, in-line filter) inside an 

O2-free glove bag. The DOC samples were frozen until analysis, which was done using high-temperature oxidation with 

infrared detection (Qian and Mopper, 1996).

Quality Assurance and Quality Control

Particle-Size Distribution

The SediGraph 5100 Particle Size Analyzer determines particle size by the highly accurate and reproducible 

X-ray sedimentation method which measures the gravityinduced settling rates of different size particles in a liquid 

having known properties. The SediGraph instrument at 

CVO is calibrated daily using garnet reference material and 

analysis conditions recommended by the manufacturer. Each 

sample processed through the SediGraph system was analyzed in duplicate. Comparison of the two analyses should 

indicate agreement within 10 percent for each size class. If 

this criterion was not met, then the system was checked for 

malfunctions and the sample was re-analyzed a third time. 

If the disagreement persisted, the sample was removed and 

the equipment was thoroughly cleaned and inspected, and a 

calibration check was done before further analysis. All final 

results satisfied the quality-assurance criterion.

Mercury, Methylmercury, and Trace Elements 

The reliability of field and laboratory methods used for 

characterization of mercury, methylmercury, and trace element concentrations in this study was assessed by analyzing 

blank, spiked, and replicate samples collected or prepared 

during environmental sampling. In addition, standard reference materials (SRM) were analyzed routinely with each batch 

of environmental samples at each laboratory. Detailed results 

are provided for replicates, blanks, spikes, and SRMs for the 

USGS laboratories in Boulder, Colorado, and Middleton, Wisconsin (tables D2-8). In general, the blanks and spike recoveries for HgT

, MeHg, and trace elements were within acceptable 

ranges for these analytes. Also, analyses of SRMs for HgT, 

MeHg, and trace elements were within acceptable ranges at 

both USGS laboratories. 

The sample of Yuba River water collected during drilling 

of hole DPD-5 had very low concentrations of HgT in both 
16 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California

filtered and unfiltered splits; concentrations of HgT were less 

than 1.2 ng/L (table D1). Concentrations of MeHg in the Yuba 

River water were below the method detection limit (<0.04 

ng/L) in both filtered and unfiltered splits. This indicates that 

the injection of water during drilling likely had a negligible 

chemical effect on concentrations of HgT and MeHg in the 

sediment samples that were recovered. 

Possible contamination of environmental samples at all 

steps in the procedures, including collection and processing 

through laboratory analysis, was evaluated by analyzing field 

blanks consisting of deonized (Milli-Q) water. After cleaning 

the sampling equipment in the field, deionized water was put 

in contact with the sampling and sample-processing equipment 

and then poured into sample bottles and preserved in a manner 

identical to that for the environmental samples. Four unfiltered 

equipment blanks and one filtered process blank were taken 

after the drilling of hole DPD-6 (table D2). In general, the 

field blank mercury concentrations were less than 2.5 ng/L, 

indicating no significant mercury contamination.

 Total mercury concentration in laboratory blanks analyzed by the USGS laboratory in Boulder, Colorado, ranged 

from 0.2 to 1.2 ng/L (table D3). A spike experiment consisting of an addition of 5 ng/L to a laboratory blank gave a HgT

concentration of 5.14 ng/L, a recovery of 103 percent, which 

is well within the acceptable range. 

Three different standard reference water samples (SRWS) 

for HgT were analyzed by the Boulder, Colorado laboratory, as 

summarized in table D3. Based on a total of 25 to 32 observations of each SRWS, the analyzed concentrations were consistently within the standard deviation of most probable values. 

The standard reference material Buffalo River Sediment 2704 

(National Institute of Standards and Technology) was digested 

six times (table D4). Averaged results for all trace elements of 

primary interest (As, Cd, Cr, Cu, Ni, Pb, Sb, and Zn) agreed 

with concentrations certified within the published standard 

deviations. Digestion blanks for trace elements and major elements (table D5) generally contained an insignificant amount 

of trace elements of primary interest, with minor exceptions. 

Three separate spike recovery experiments for selected elements (As, Ca, Cd, Cu, Fe, Mg, Pb, and Zn) were consistently 

in the acceptable range of 92 to 112 percent (table D6).

The standard reference material for MeHg used by the 

USGS laboratory in Middleton, Wisconsin, was IAEA-405, 

a polluted marine sediment provided by the International 

Atomic Energy Agency. The certified concentration of MeHg 

in IAEA-405 is 5.49 ng/g (dry weight), with a 95 percent 

confidence interval from 4.96 to 6.02 ng/g. The certified value 

was determined using a distillation procedure that has been 

shown to form significant amounts of artifact MeHg when 

the MeHg fraction is less than 1 percent of the inorganic pool 

(Hintelmann and others, 1997; Hintelmann, 1999), which is 

true for IAEA-405. Using the same extraction method for 

MeHg determination that was used in this study, multiple 

analyses (19) by the USGS Wisconsin laboratory resulted in a 

76 percent recovery of the SRM literature value. Because the 

certified value may be biased high and multiple analyses from 

the USGS laboratory produced a consistently lower value, the 

accepted range of recovery for this standard has been established at 55 to 95 percent. During the analysis of MeHg in 

samples for the present study, four analyses of IAEA-405 gave 

concentrations of 4.21, 4.50, 4.85, and 5.20 ng/g (dry weight), 

which correspond to recoveries ranging from 76.7 to 94.7 percent, within the accepted range of recovery for the laboratory.

Two types of replicate sediment subsamples were 

analyzed: (1) replicate subsamples digested separately (field 

replicates) and (2) replicate subsamples from a single digestion (laboratory replicates). Varied results of analyses of field 

replicates indicate sample inhomogeneity or inconsistent 

sampling technique, whereas the comparison of laboratory 

replicates indicates variability in analytical results. A measure 

of variability between replicate samples is the Relative Percent 

Difference (RPD), defined as the absolute value of the quotient 

of the difference between two values and their average: 

RPD = |(r1-r2)/[(r1+r2)/2]|,

where r1 and r2 are the replicate analyses. Acceptability of 

values of RPD depends on several factors, including proximity 

to the method detection limit (MDL) and natural heterogeneity factors. For most constituents in concentrations well above 

the MDL, RPD values less than 15–25 percent are expected, 

whereas larger RPD values are expected for concentrations 

near the MDL. Field replicates of unprocessed samples may 

have larger RPD values than laboratory replicates of processed 

(filtered or digested) samples because of a greater degree of 

inhomogeneity in unprocessed samples.

Results for three pairs of field replicate samples analyzed 

for trace and major elements by the USGS research laboratory 

in Boulder, Colorado, are compared (table D7). Values of RPD 

for the principal trace elements of interest (As, Cd, Cr, Cu, Ni, 

Pb, Sb, and Zn) were consistently less than 11 percent for at 

least two of the three replicate pairs. 

Results of replicate subsamples analyzed by the USGS 

Wisconsin District Laboratory are compared (table D8). Values 

of RPD for four laboratory replicates of HgT in the clay-silt 

fraction range from 1.7 percent to 38.1 percent, with a geometric mean of 8.4 percent; RPD values for four laboratory 

replicates of HgT in the sandy fraction range from 1.1 percent 

to about 30 percent, with a geometric mean of 4.5 percent. Two 

field replicate samples of the clay-silt fraction and one field 

replicate of the sandy fraction were collected. Values of RPD 

for HgT in the field replicates of the clay-silt fraction range 

from 1.3 to 5.9 percent; the RPD value for the sandy fraction is 

43.6 percent, indicating a high degree of inhomogeneity. Such 
Results 17

inhomogeneity of mercury distribution in coarser material is 

an expected manifestation of the “nugget effect,” because of 

the nonuniform distribution of gold-mercury amalgam grains 

and mercury-stained gold grains. At least one analysis of each 

of the sediment samples chosen for replicate analysis of MeHg 

was below the MDL, so it was not possible to calculate RPD 

values. A high degree of variability is typical for constituents 

near the MDL.

Results

Particle-Size Distribution

Several sediment fractions from each drilled interval were 

analyzed for particle-size distribution. Detailed particle-size 

analysis of the following sediment fractions was done: (1) 

residual sandy fraction plus gravel, (2) sandy fraction, (3) silty 

fraction, and (4) clay-silt fraction.

Residual Sandy Fraction Plus Gravel

The particle-size distributions of the residual sandy fraction plus gravel from the 31 drilled intervals varied moderately 

between drill-hole locations (fig. 9). The most abundant size 

classes were sand (defined in table 2 as 0.075 to 4.75 mm) 

and gravel (>4.75 mm), as summarized in table 2. Gravel 

concentration varied from 2 to 85 weight percent and generally decreased with depth in all drill holes except for DPD-2, 

where gravel concentration increased with depth to about 

25 feet, followed by a sharp decrease at 35 feet. There was a 

moderate increase of gravel from 15 to 30 feet in hole DPD-6. 

The increase in the 5- to 10-foot and 15- to 20-foot intervals 

in hole DPD-5 was probably due to fragments of weathered 

bedrock that were broken during drilling. Sand concentration 

varied from 14 to 82 weight percent and generally increased 

with depth in holes DPD-1, -2, -3, and -4. Sand decreased with 

depth in drill-hole DPD-6. Drill-hole DPD-5 had two distinct 

sand lenses between 0 and 10 feet and 10 and 20 feet. Silt and 

clay (<0.075 mm) concentrations varied from 1 to 29 weight 

percent and generally increased with depth in holes DPD-1, 

-3, and -4 and generally decreased with depth in hole DPD-6. 

In hole DPD-5, the silt and clay correlate with the sand lenses. 

Hole DPD-2 showed a decrease in silt and clay proportions 

down to 25 feet and an increase in the 25- to 35-foot interval.

Sandy Fraction

The sandy fraction (consisting of a slurry of sand, silt, 

and clay) was homogenized in a plastic tub after being sieved 

through the 2-mm vibratory screen. Sand was the most dominant size class in this fraction, as shown in table 3 and figure 

10. The concentration of sand (defined as 0.063 to 2 mm) in 

this fraction ranged from about 65 to 98 percent, concentration 

of silt (0.004 to 0.063 mm) ranged from about 2 to 32 percent, 

and the concentration of clay (<0.004 mm) ranged from about 

0.1 to 3.4 percent. 

Silty Fraction

The silty fraction (material in suspension in the slurry collected as overflow from the collection buckets and composited 

in a churn at the drill site, fig. 8) consisted mostly of silt and 

clay with minor amounts of fine sand (table 4, fig. 10). Particlesize distributions ranged from about 0.2 to 11 percent sand, 7 to 

61 percent silt, and 35 to 91 percent clay. 

To quantify losses of sediment (and mercury) from the 

suspended silty overflow fraction, a set of 22 samples were 

analyzed for total sediment concentration and 16 selected 

sample intervals were analyzed for distribution of particle 

sizes 2 mm through 0.00025 mm. The 16 selected samples 

ranged from about 20 to 73 percent silt and from about 27 to 

80 percent clay. Total suspended sediment concentrations in 

the silty fraction samples ranged from about 2,400 mg/L to 

254,000 mg/L (table B5).

Clay-Silt Fraction

The clay-silt fraction consisted of silt- and clay-sized 

particles that passed through the 2-mm vibratory screen separation and remained in suspension after settling for 15 to 20 

minutes (fig. 8). There was a high concentration of clay-sized 

particles relative to silt in this fraction (table 5). The silt (0.004 

to 0.063 mm) concentration in this fraction ranged from about 

9 to 70 percent. Clay (<0.004 mm) concentration in this fraction ranged from about 26 to 91 percent. Sand (>0.063 mm) in 

this fraction constituted less than 1 percent except in the 25- to 

30-foot depth intervals in drill-holes DPD-2 and 6, which had 

about 29 and 18 percent sand, respectively, and in the 30- to 

35-foot interval of DPD-2, which had 5 percent. Higher concentrations of silt and clay in some intervals are probably due 

to the breaking up of large masses of clay during separation 

with the vibratory screen. 
Figure 9. Bar chart diagram showing particle-size distribution of residual sandy fraction plus gravel at each drill hole, Daguerre Point 

Dam, California.

mm, millimeter.

18 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California

�����������������������������������

�����������������������

�������������������������

�������������������������������

�����

�����

����

���

�����

�����

�����

�����

����

� �� �� �� �� ��� � �� �� �� �� ���

�����

�����

����

���

�������������� ��������������

�������

�����

����

���

�����

�����

�����

�����

����

���

��������������

����������������

�����

�����

�����

�����

�������

�������

����

���

����������������

���������������� ����������������

���������������� ����������������

�����������
Drill hole/Depth

(ft) Silt and clay Sand Gravel

Size (mm) < 0.075 0.075 – 4.75 > 4.75

Weight percent

DPD–1

0–5 4 49 47

5–10 9 44 47

10–15 13 46 41

15–17.5 29 68 2

DPD–2

0–5 8 48 44

5–10 3 51 46

10–13.5 3 53 45

13.5–15 2 49 49

15–20 1 58 41

20–25 1 34 65

25–30 8 69 23

30–35 19 81 0

DPD–3

0–5 2 41 57

5–10 3 44 53

10–15 2 48 49

15–20 4 82 14

DPD–4

0–10 4 43 53

10–15 2 44 54

15–20 4 55 41

20–25 1 14 85

25–30 9 66 25

DPD–5

0–5 6 56 38

5–10 5 43 52

10–15 12 54 34

15–20 1 33 66

DPD–6

0–5 11 42 47

5–10 3 49 48

10–15 3 51 45

15–20 3 43 54

20–25 3 38 58

25–30 1 26 73

Table 2. Particle-size distribution and depth profiles of 

the residual sandy fraction plus gravel, Daguerre Point Dam, 

California.

[DPD, Daguerre Point Dam. ft, foot; mm, millimeter. >, greater than; <, less 

than] Drill hole/Depth

(ft) Clay Silt Sand

Size (mm) <0.004 0.004 – 0.063 0.063 – 2

Weight percent

DPD–1

0–5 0 14 86

5–10 0 18 82

10–15 1 27 72

15–17.5 4 32 64

DPD–2

0–5 0 8 92

5–10 0 6 94

10–13.5 0 4 96

13.5–15 0 5 95

15–20 0 3 97

25–30 0 6 94

30–35 1 26 73

DPD–3

0–5 0 4 96

5–10 0 6 94

10–15 0 7 93

15–20 .2 8.5 91.3

DPD–4

0–10 0 3 97

10–15 0 2 98

15–20 0 4 96

20–25 0 4 96

25–30 0 8 92

DPD–5

0–5 0 6 94

5–10 0 6 94

10–15 0 8 92

15–20 0 5 95

DPD–6

0–5 0 9 91

5–10 0 6 94

10–15 0 3 97

15–20 0 8 92

20–25 0 11 89

25–30 1 13 86

Table 3. Particle-size distribution and depth profiles of the 

sandy fraction, Daguerre Point Dam, California.

[DPD, Daguerre Point Dam. ft, foot; mm, millimeter. <, less than]

Results 19

Synthesis and Spatial Distribution

Some of the sandiest sediments were found in the deepest 

sections of the drill holes (table 2). Sand exceeded 80 percent 

in the deepest intervals of DPD-2 and DPD-3 and almost 70 

percent in the deepest intervals of DPD-1 and DPD-4. A total 

silt and clay content of about 19 percent was measured in the 

lowest interval of sediment from DPD-2. The high sand and 

silt value for the lowest depth interval of hole DPD-2 may 

actually be due to sediment stratification from previous dredging operations. The highest silt and clay content, 29 percent, 

was measured in the deepest interval of hole DPD-1 (15- to 

17.5-foot depth) and is probably due to decomposed bedrock. 

This site was located closest to the Daguerre Point Dam. 

Overall ranges in particle-size distribution for the residual 

sandy fraction plus gravel and the sandy, silty, and clay-silt 

fractions from 0.00025 to 50.8 mm are compared on a semilog plot (fig. 11). There is a clear separation in the size distributions between the two coarse fractions (residual sandy fraction 
���� � �� �� �� �� �� �� �� �� �� ���

����

�

��

��

��

��

��

��

��

��

��

���

����

�

��

��

��

��

��

��

��

��

��

���

��������������

������������������

��������������

�������������������

�������������������

�������������������

��������������������������������������

��������������������������������������

�����������

Figure 10. Ternary diagram showing particle-size classes of sandy fraction, silty fraction, and clay-silt fraction, 

Daguerre Point Dam, California.

20 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California
Drill hole/Depth

(ft) Clay Silt Sand

Size (mm) <0.004 0.004 – 0.063 >0.063

Weight percent

DPD-2

0–5 56 44 0

5–10 57 43 0

15–20 64 35 1

20–25 58 40 2

25–30 35 60 5

30–35 40 59 1

DPD-3

15–20 91 7 2

DPD-4

10–15 52 44 4

15–20 46 48 6

DPD-5

0–5 90 10 0

5–10 74 25 1

10–15 41 57 2

15–20 76 22 2

DPD-6

0–5 41 58 1

5–10 76 18 6

10–15 74 22 4

15–20 71 28 1

20–25 51 47 2

25–30 61 28 11

Table 4. Particle-size distribution and depth profiles of the silty 

fraction, Daguerre Point Dam, California.

[DPD, Daguerre Point Dam. ft, foot; mm, millimeter. >, greater than; <, less 

than]

Drill hole/Depth

(ft) Clay Silt Sand

Size (mm) <0.004 0.004 – 0.063 >0.063

Weight percent

DPD-2

20–25 90 9 1

25–30 26 45 29

30–35 58 37 5

DPD-3

0–5 91 9 0

5–10 78 22 0

10–15 74 26 0

15–20 28 70 1

DPD-4

10–15 76 24 0

15–20 74 26 0

20–25 74 26 0

25–30 71 29 0

DPD-5

0–5 49 51 0

5–10 80 20 0

10–15 72 28 0

15–20 61 39 0

DPD-6

0–5 39 61 0

5–10 52 48 0

10–15 65 35 0

15–20 50 49 1

20–25 49 51 0

25–30 39 43 18

Table 5. Particle-size distribution and depth profiles of the claysilt fraction, Daguerre Point Dam, California.

[DPD, Daguerre Point Dam. ft, foot; mm, millimeter. >, greater than; <, less 

than]

Results 21

plus gravel and sandy fraction) and the two fine fractions (silty 

and clay-silt fractions), which represent the suspended material 

at two places in the sample-processing stream (fig. 8). The 

residual sandy fraction plus gravel (brown in fig. 11) shows 

the widest range of distributions. The sandy fraction (green in 

figure 11) fits mostly within the range of distributions of the 

residual sandy fraction plus gravel. The clay-silt fraction (blue 

in figure 11) contains some particles of fine and very fine sand 

that did not settle during the 15 to 20 minute period. The silty 

fraction (yellow in figure 11) contains the highest proportion 

of clay-sized particles and fits well within the range of distributions of the clay-silt fraction, which also includes a high 

proportion of suspended clay-sized particles.

Mercury Geochemistry

There is a high degree of spatial variability in mercury concentrations for each of the different particle-size fractions. Total 

mercury concentrations generally increase with depth in holes 

DPD-2, -3, and -6 in all particle-size fractions; the variations 

with depth are less systematic in the other three holes (fig. 12). 

Total mercury concentrations generally increase as sediment 

decreases in grain-size (fig. 13). Mercury concentrations in the 

sandy fraction are consistently lower than the concentrations in 

the other, finer-grained fractions by a factor of between about 

3 and 30 (fig. 12). Total mercury concentrations in the sandy 

fraction ranged from 6.8 ng/g to 80.7 ng/g dry weight (table 

6). Total mercury concentrations in the silty fraction ranged 

from 33 to 1,100 ng/g (table 7). Total mercury concentrations 
Figure 11. Graph showing summary of particle-size distributions, Daguerre Point Dam, California.

22 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California

�

��

��

��

��

���

����������������

������������������

������������������

��������������

��������������

�����������������

�������������

���� ���� ������ �������� ����

������ ����� ���� ��� � �� ��� �������

�

����

������������

in the clay-silt fraction ranged from 23 to 370 ng/g (table 

7). Concentrations of HgT in the centrifuge tube solids (wet 

weight) ranged from 0.3 to about 320 ng/g (table 8). (Note 

that centrifuge solids are reported only on a wet weight basis 

because limited material precluded accurate determination of 

water content.)

Fifteen subsamples of the sandy fraction were separated 

by sieving into six sediment bins (particle-size subclasses) 

to evaluate the effect of particle size on HgT concentration. 

Median values for mercury concentration increased sharply 

as the size decreased (table 9). The median values in the sand 

subclasses ranged from 1.9 ng/g in coarse sand (dry weight 

for all values), to 4.4 ng/g in medium sand, to 8.6 and 7.5 ng/g 

in fine and very fine sand, respectively. In sharp contrast, the 

median value for coarse silt was 21.6 ng/g, and for the finest 

size subclass (less than 30 μm [0.030 mm], containing medium 

silt, fine silt, and clay), the median concentration was 43.3 ng/g. 

As indicated in figures 12 and 13 and in tables 6-8, the HgT

concentration in the sandy fraction is consistently lower than 

that in the silty and clay-silt fractions from the same depth 

interval. If it is assumed that separation into various size fractions did not change the fundamental chemical properties of 

the sediment with regard to the concentration of mercury, it 

can be inferred that the fine silt (~0.004 to ~0.015 mm) and 

clay (less than about 0.004 mm) size fractions must contain, 

on the average, higher mercury concentrations than the two 

finest subclasses represented in table 9. Physical separation of 

the fine silt and clay particle size classes followed by mercury 

analysis would be the preferred manner to test this assertion; 

ultra-clean methods for doing such separations are currently 

being researched by the USGS.

Methylmercury (MeHg) concentrations were determined 

in two fractions: the sandy fraction and the clay-silt fraction 

solids isolated by centrifugation (fig. 8). In the sandy fraction, 

concentrations of MeHg were less than the MDL of 0.001 ng/g 

in all but one of 31 sampled intervals; the 0- to 5-foot interval 

of hole DPD-5 had a MeHg concentration of 0.083 ng/g (table 

6). MeHg concentrations were above the MDL in about half of 

clay-silt fraction solids; where detected, the concentration of 

MeHg ranged from 0.04 (estimated) to 0.61 ng/g, wet weight 
�����

�����

�

��

���

�����

������

�

��

���

�����

������

�

��

���

�����

������

��� ���� ����� �������

��� ���� ����� �����

��� ���� ����� �����

�����

��� ���� ������� ������� ����� ����� ����� �����

�����

���� ����� ����� ����� �����

�����

����������������������������

���������������������������

������������������������������

���������������������������

�������������������������������

�����

��� ���� ����� ����� ����� �����

�����������

������������������������������������

Figure 12. Graph showing down-hole concentration of total mercury in different sediment fractions, Daguerre Point Dam, 

California.

Results 23
�

��

���

�����

������

����������������

���������������

���������������

��������������

������������������

����������������

����

����

����

����

�������

���������������

��������������

������������������������������������������������

�����������

�����������������

���������������

���������������

���������������

���������������

������

Figure 13. Graph showing boxplots of total mercury concentration in different sediment fractions, Daguerre Point 

Dam, California.

24 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California

(table 8). Detection limits were higher for the clay-silt fraction 

solids because the samples collected in 30-mL TeflonTM centrifuge tubes were small, and less solid material was available 

for digestion. Seven of the 16 sample intervals with detectable 

MeHg had MeHg concentrations greater than 0.1 ng/g; these 

intervals were from five separate drill holes: DPD-1, -2, -3, -4, 

and -5. Drill-hole DPD-3 was the only hole in which MeHg 

was detected in samples from all depth intervals. A large 

degree of heterogeneity with regard to MeHg concentrations 

was observed in the study area.

The relation between concentrations of MeHg and HgT in 

the silt-clay fraction solids was plotted to identify drilled intervals having relatively high concentrations of MeHg (fig. 14). 

In figure 14, the diagonal lines represent constant values of 

the ratio of MeHg to HgT. Samples for which MeHg concentrations were below detection are plotted at half of the MDL 

for MeHg with an error bar representing the possible range of 

MeHg concentrations from zero to the MDL (zero values do 

not exist on logarithmic axes). The maximum possible values 

of MeHg/HgT for these samples can be seen in figure 14. Four 
Drill hole/Depth

(ft) Date Time

Methylmercury Total mercury

Concentration

(ng/g wet)

Detection limit

(ng/g wet)

Concentration

(ng/g wet)

Concentration

(ng/g dry)

DPD–1

0–5 8/14/01 1100 LTD 0.001 26.7 32.9

5–10 8/14/01 1800 LTD .001 9.2 11.4

10–15 8/14/01 1430 LTD .001 14.5 17.5

15–17.5 8/14/01 1500 LTD .001 7.3 10.9

DPD–2

0–5 8/15/01 1200 LTD 0.001 8.3 10.1

5–10 8/15/01 1400 LTD .001 11.5 14.1

10–13.5 8/15/01 1600 LTD .001 13.2 16.5

13.5–15 8/15/01 1030 LTD .001 8.8 10.8

15–20 8/16/01 1200 LTD .001 18.2 20.6

20–25 8/16/01 1330 LTD .001 16.9 20.3

25–30 8/16/01 1500 LTD .001 34.4 44.9

30–35 8/16/01 1700 LTD .001 60.5 80.7

DPD–3

0–5 8/20/01 1030 LTD 0.001 7.5 9.2

5–10 8/20/01 1100 LTD .001 19.3 24.3

10–15 8/20/01 1330 LTD .001 26.6 34.4

15–20 8/20/01 1500 LTD .001 33.8 43.0

DPD–4

0–10 8/21/01 1300 LTD 0.001 9.9 11.9

10–15 8/21/01 1530 LTD .001 19.9 24.4

15–20 8/22/01 0900 LTD .001 16.5 21.3

20–25 8/22/01 1100 LTD .001 6.1 7.5

25–30 8/22/01 1230 LTD .001 14.2 17.5

DPD–5

0–5 8/24/01 1030 0.083 0.001 22.9 28.5

5–10 8/24/01 1130 LTD .001 19.8 23.8

10–15 8/24/01 1430 LTD .001 10.1 12.3

15–20 8/24/01 1530 LTD .001 9.4 12.0

DPD–6

0–5 8/27/01 1530 LTD 0.001 5.5 6.8

5–10 8/28/01 0930 LTD .001 8.1 9.9

10–15 8/28/01 1130 LTD .001 8.6 10.8

15–20 8/28/01 1330 LTD .001 9.3 11.6

20–25 8/28/01 1430 LTD .001 17.3 21.8

25–30 8/28/01 1530 LTD .001 57.2 70.1

Table 6. Total mercury and methylmercury concentrations in the sandy fraction, Daguerre Point Dam, California.

[DPD, Daguerre Point Dam; ft, foot; ng/g wet, nanogram per gram wet weight; ng/g dry, nanogram per gram dry weight; LTD, less than detection limit]

Results 25

of the samples that have the highest concentrations of MeHg 

(from holes DPD-1, -2, -4, and -5) also have the highest values 

of MeHg/HgT, in the range of 0.2 to 0.5 percent. Another interval from hole DPD-4, which has relatively low concentrations 

of MeHg and HgT, has a value of MeHg/HgT of about 0.2. All 

other intervals for which MeHg was detected have values of 

MeHg/HgT between 0.01 and 0.1 percent. 

The relation between HgT concentration (in clay-silt 

fraction solids from centrifugation) and gold concentration 

(in heavy mineral concentrates) is shown in figure 15A. The 

highest gold tenor values, greater than 100 mg/yd3, were seen 

in three intervals from hole DPD-1; these intervals had low 

concentrations of mercury also (about 18 to 33 ng/g, wet 

weight; also see table 8). Six intervals had gold tenor values 

between 50 and 100 mg/yd3; three of these samples were from 

hole DPD-5, the others were from DPD-2 and 4 (table C1). 

Mercury concentrations in these six intervals ranged from 

33 to 207 ng/g (wet weight) (table 8). Gold tenor in other 
Drill hole/

Depth

(ft)

Date Time Silty fraction

(ng/g dry)

Clay-silt fraction

(ng/g dry)

DPD–2

0–5 8/15/01 1200 56 —

5–10 8/15/01 1400 190 —

10–13.5 8/15/01 1600 — —

13.5–15 8/16/01 1030 — —

15–20 8/16/01 1200 260 —

20–25 8/16/01 1330 280 310

25–30 8/16/01 1500 1,100 210

30–35 8/16/01 1700 500 320

DPD–3

0–5 8/20/01 1030 — 170

5–10 8/20/01 1100 — 170

10–15 8/20/01 1330 — 370

15–20 8/20/01 1500 190 200

DPD–4

0–10 8/21/01 1300 — —

10–15 8/21/01 1530 230 310

15–20 8/22/01 0900 220 250

20–25 8/22/01 1100 — 150

25–30 8/22/01 1230 — 98

DPD–5

0–5 8/24/01 1030 190 160

5–10 8/24/01 1130 300 350

10–15 8/24/01 1430 230 180

15–20 8/24/01 1530 85 61

DPD–6

0–5 8/27/01 1530 33 23

5–10 8/28/01 0930 80 77

10–15 8/28/01 1130 230 260

15–20 8/28/01 1330 330 240

20–25 8/28/01 1430 310 310

25–30 8/28/01 1530 280 240

Table 7. Mercury concentrations in the silty and clay-silt 

fractions from sample processing streams, Daguerre Point Dam, 

California.

[Samples analyzed by the U.S. Geological Survey laboratory in Boulder, Colo. 

DPD, Daguerre Point Dam. ft, foot; ng/g wet, nanogram per gram wet weight; 

ng/g dry, nanogram per gram dry weight; —, no data]

26 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California

intervals ranged from trace amounts (estimated at 1 mg/yd3) 

to about 170 mg/yd3 (table C1); these intervals had the full 

range of mercury values (0.3 to 315 ng/g, wet weight) (table 

8). Geometric means of gold tenor and mercury concentration 

were computed for each drill hole and are plotted in figure 

15B along with standard deviations. This plot indicates that 

hole DPD-1 is distinct from the other five holes in terms of 

both gold and mercury content, and hole DPD-5 is somewhat 

elevated in gold tenor relative to the drill-holes DPD-2, -3, -4, 

and -6.

Trace Elements

Concentrations of trace elements and major elements 

were determined for material screened to less than 0.060 mm 

in 19 drilled intervals from holes DPD-1, -4, -5, and -6 (table 

10A). Samples from 2 of the 19 intervals were analyzed in 

duplicate. In addition to mercury, some trace elements that 

may harm the environment if fish passage is improved are 

arsenic, antimony, cadmium, chromium, copper, lead, nickel, 

and zinc. Minimum, median, and maximum values for the 

19 intervals for the trace elements of potential environmental 

concern are shown in table 10B, together with sediment-quality criteria. The sediment-quality criteria are Threshold Effects 

Concentrations (TEC) and Probable Effects Concentrations 

(PEC) that were compiled by MacDonald and others (2000) 

based on values with regard to limits for ecological toxicity 

accepted by various agencies and researchers. 

Four of the trace elements from the 19 intervals analyzed 

have median concentrations that exceed the TEC values of 

MacDonald and others (2000): arsenic, chromium, copper, 

and nickel (table 10B). For three of these metals (Cr, Cu, and 

Ni), all 19 concentrations measured in this study exceeded the 

TEC value limit. In addition, the maximum concentrations of 

lead, mercury, and zinc were above the TEC values. Median 

concentrations exceeded the PEC value for only chromium 

and nickel.

It is possible that the arsenic, chromium, copper, and 

nickel in the Daguerre Point sediments exist in forms that are 

less bioavailable than those in the other areas on which the 

TEC and PEC values are based. Site-specific toxicity testing is 

required to determine if these trace elements pose a significant 

risk to aquatic life.

Analyses of gold concentrations from the sieved fraction, 

less than 0.060 mm, ranged from less than detection (<0.005 

mg/kg [or μg/g]) to a maximum value of 0.017 mg/kg (table 

10A). In comparison, the gold tenor values from the heavy 

mineral concentrates ranged from trace (~1 mg/yd3) to 170 

mg/yd3 (table C1). These data can be compared by converting the geochemical data to a volumetric basis using a density 

of 1,500 kg/yd3. The converted range of measured values is 

<8 mg/yd3 to 26 mg/yd3. These values are within the overall 

range of the gold tenor values derived from the heavy-mineral 

concentrates, but are generally lower. Apparently, some of 

the gold, especially in intervals with higher tenor, exists as 

material coarser than 0.060 mm, likely in sand-sized particles. 

Another important factor in interpreting gold concentrations 

is the nugget effect. The analyses in table 10A are based on 

very small samples (about 100 mg), whereas the heavy-mineral concentrates (table C1) are based on much larger samples 

(several kg). Therefore, the gold tenor results from the heavymineral concentrates are considered to be more representative 

of actual in-place gold concentrations. 
Drill hole/Depth

(ft)

Centrifuge 

tube No. Date Time

Methylmercury Total mercury

Concentration

(ng/g wet)

Detection limit

(ng/g)

Concentration

(ng/g wet)

DPD–1

0–5 EXT013 8/14/01 1100 0.182 0.02 70.6

5–10 EXT058 8/14/01 1200 LTD .01 33.3

10–15 EXT024 8/14/01 1430 LTD .06 21.3

15–17.5 EXT075 8/14/01 1500 LTD .05 17.9

DPD–2

0–5 EXT080 8/15/01 1200 LTD 0.02 33.4

5–10 EXT077 8/15/01 1400 LTD .02 88.1

10–13.5 EXT057 8/15/01 1600 0.230 .02 86.4

13.5–15 EXT020 8/16/01 1030 .137 .03 n/a

15–20 EXT066 8/16/01 1200 LTD .02 114

20–25 EXT055 8/16/01 1330 LTD .009 69.7

25–30 EXT054 8/16/01 1500 LTD .006 247 1

25–30 EXT074 8/16/01 1500 LTD .07 244

30–35 EXT069 8/16/01 1700 .04E .04 315

DPD–3

0–5 EXT011 8/20/01 1030 0.261 0.01 0.3

5–10 EXT022 8/20/01 1100 .063 .009 88.0

10–15 EXT010 8/20/01 1330 .049 .01 295

15–20 EXT018 8/20/01 1500 .072 .07 136

DPD–4

0–10 EXT029 8/21/01 1300 LTD 0.009 83.6

10–15 EXT039 8/21/01 1530 0.611 .07 143

15–20 EXT030 8/22/01 0900 .107 .02 173

20–25 EXT065 8/22/01 1100 .04E .14 19.5

25–30 EXT079 8/22/01 1230 .056 .010 114

DPD–5

0–5 EXT049 8/24/01 1030 0.318 0.02 138

5–10 EXT042 8/24/01 1130 .056 .01 207

10–15 EXT061 8/24/01 1430 LTD .14 158

15–20 EXT072 8/24/01 1530 LTD .09 50.2

DPD–6

0–5 EXT062 8/27/01 1530 LTD 0.12 28.3

5–10 EXT032 8/28/01 0930 LTD .14 58.4

10–15 EXT014 8/28/01 1130 0.081 .08 173

15–20 EXT028 8/28/01 1330 LTD .13 205

20–25 EXT046 8/28/01 1430 .069 .04 198

25–30 EXT012 8/28/01 1530 LTD .06 204 1

25–30 EXT019 8/28/01 1530 LTD .07 196

Blank2 EXT052 8/28/01 1630 LTD n/a n/a 1

Field replicate.

2

Field blank.

Table 8. Mercury and methylmercury concentrations in the clay-silt fraction after centrifuge separation, Daguerre Point Dam, 

California.

[DPD, Daguerre Point Dam; No., number; LTD, less than detection; E, estimated; ft, foot; ng/g wet, nanogram per gram wet weight; n/a, not applicable]

Results 27

Heavy Mineral Concentrates

Gold Tenor and Speciation

The highest tenor of gold concentration found was 170 

mg/yd3 in drill-hole DPD-1 near the bedrock contact (table 

C1). Drill-hole DPD-5 had relatively high gold concentrations 

in all three tested intervals. Drill-hole DPD-2 had moderate 

gold concentrations at certain intervals. Drill-holes DPD-3, 

-4 and -6 had the lowest gold concentrations, except for the 

15- to 20-foot interval of DPD-4. Visible grains of gold (sandsized) were observed in drill cuttings during drilling of holes 

DPD-1 and -5.
Drill hole/Depth

(ft)

Medium and fine 

silt, with clay Coarse silt Very fine sand Fine sand Medium sand Coarse sand

Size (mm) <0.030 0.030 – 0.060 0.060 – 0.149 0.149 – 0.297 0.297 – 0.500 >0.500

Concentrations of mercury (ng/g)

DPD–4

0–10 57.4 17.5 5.3 3.0 2.0 0.9

10–15 63.1 25.1 18.7 8.6 6.0 1.0

15–20 182 24.1 19.5 13.7 8.0 4.8

20–25 9.5 2.2 2.3 9.8 6.9 22.5

25–30 43.3 4.6 7.3 24.9 24.0 38.9

DPD–5

0–5 74.0 24.8 16.4 6.8 4.3 2.3

5–10 130 25.3 232 9.1 4.4 2.9

10–15 109 46.5 12.8 7.3 3.3 2.0

15–20 27.1 7.7 3.5 3.6 3.5 2.9

DPD–6

0–5 9.9 2.3 0.2 0.4 2.2 1.3

5–10 24.1 21.6 5.8 2.0 1.8 .5

10–15 24.1 21.6 5.8 2.0 1.8 .5

15–20 26.9 15.0 24.2 11.9 27.3 .5

20–25 24.4 50.4 17.9 10.1 10.3 .5

25–30 80.3 55.1 7.5 34.7 7.1 1.9

Minimum 9.5 2.2 0.2 0.4 1.8 0.5

Median 43.3 21.6 7.5 8.6 4.4 1.9

Maximum 182 55.1 232 34.7 27.3 38.9

Table 9. Total mercury concentration (ng/g dry weight) for sieved fine particle sizes, Daguerre Point Dam, California.

[ft, foot; mm, millimeter; ng/g, nanogram per gram; >, greater than; <, less than; DPD, Daguerre Point Dam]

�������������������������������������������������

��������������������������������������������������

�� ��� �����

�����

����

���

���

����

�����

�����

�����

�����

�����

�����

�����

������������

���������������

�������������

�������� ����

Figure 14. Graph showing relation of methylmercury and total mercury in the clay-silt fraction (centrifuge tube solids), Daguerre Point 

Dam, California.

MeHg, methylmercury; HgT , total mercury; %, percent.

28 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California
�����������������������������������������

���������������������������������������������

�

�

��

���

���

���

���

��� ���

��������

���������������

�������������

���������

������������

������������

����������

����������

����������

����������

����������

����� ����� ����� ����� ����� �����

������������

����������

�����������

Figure 15A. Graphs showing the relation of gold and mercury in the clay-silt fraction, Daguerre Point Dam, 

California.

Results 29
�����������������������������������������������

� �� ��� ��� ��� ��� ���

���������������������������������������������

���

�

��

���

���

���

������

������

������

������

�����

�����

�����������

���������������������������������������

�����������������������������������������

����������������������������������������

Figure 15B. Graph showing the relation of gold and mercury in the clay-silt fraction for each drill hole, Daguerre Point Dam, California.

30 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California

Gold grains were generally well rounded (fig. 16) and 

range in size from 0.25 mm to almost 2 mm. Although 

elemental mercury was not observed with the naked eye on 

individual gold-grains, evidence of mercury was found with 

the aid of a binocular microscope and was confirmed with 

SEM observations, described in the next section. 

Mercury Speciation

An SEM with EDX analyzer was used to observe individual microscopic gold grains, which showed evidence of 

mercury amalgamation. These gold grains had a pitted surface 

texture with shrinkage cracks (fig. 17) that yielded moderate 

to strong mercury spectra. The shrinkage cracks may indicate 

a surface amalgam layer from which some mercury has been 

lost. A grain of gold amalgam from the 0- to 5-foot interval of 

hole DPD-1 showed 10- to 30-μm stacked platelets of coarsegrained amalgam. Gold amalgam is very soft and brittle and 

readily breaks away from parts of gold grains that do not 

contain mercury (fig. 16). 
Drill hole/Depth

(ft)

Al

Aluminum

As

Arsenic

Au

Gold

B

Boron 

Ba

Barium

Be

Beryllium

Bi

Bismuth

Wt% μg/g μg/g μg/g μg/g μg/g μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

DPD-1

0–5 4.3 0.2 6.5 0.5 0.006 0.002 46 7 278 13 0.65 0.04 0.21 0.06

5–10 3.9 .3 7.2 .7 .006 .005 78 10 385 32 .82 .04 .12 .03

10–15 8.5 .1 8.0 .3 .008 .003 207 12 507 2 1.1 .1 .43 .08

15–17.5 9.0 .3 8.8 .5 .006 .000 75 9 441 18 1.2 .0 .14 .02

DPD-4

0–10 3.9 0.2 11 1 0.006 0.003 99 0 441 24 0.81 0.15 <0.04 0.02

10–15 5.1 .1 32 2 .008 .004 128 1 591 0 1.0 .1 <.04 .03

15–20 5.6 .2 20 1 .012 .002 96 3 755 5 1.0 .1 <.04 .01

20–25 3.8 .2 10 1 .005 .000 157 5 330 17 .74 .06 .11 .01

25–30 5.9 .0 14 0 .008 .003 83 13 442 1 .97 .10 .06 .07

DPD-5

0–5 7.2 0.1 22 0 0.009 0.007 126 6 904 0 1.5 0.1 0.26 0.06

5–10 5.6 .1 22 0 .017 .003 167 2 488 9 1.1 .0 <.04 .07

10–15 5.5 .1 23 0 <.007 .001 129 5 486 2 1.1 .1 .19 .01

15–20 3.6 .2 11 0 .007 .004 49 4 269 3 .90 .07 .23 .12

DPD-6

0–5 3.3 0.1 4.7 0.4 <0.005 0.001 73 7 260 9 0.71 0.09 0.06 0.02

5–10 3.6 .1 7.4 .1 <.005 .001 82 1 377 1 .76 .06 .11 .04

10–15 6.7 .2 17 0 .007 .002 77 7 477 9 1.2 .0 .29 .02

15–20 7.1 .2 11 0 <.005 .002 103 1 413 18 1.0 .0 1.1 .1

20–25 8.0 .1 14 0 .006 .002 43 2 600 17 1.1 .1 .20 .01

25–30 6.4 .2 20 1 .009 .003 134 14 414 19 1.6 .1 .26 .05

Minimum 3.3 4.7 <0.005 43 260 0.65 <0.04

Median 5.6 11 .006 96 441 1.02 .14

Maximum 9.0 32 .017 207 904 1.6 1.1

Table 10A. Concentration of selected elements in sediment screened to less than 0.060 millimeter, Daguerre Point Dam, California.

[ft, foot; Wt%, weight percent; Avg, average; SD, standard deviation; DPD, Daguerre Point Dam. μg/g, microgram per gram; <, less than]

Drill hole/Depth

(ft)

Ca

Calcium

Cd

Cadmium

Ce

Cerium

Co

Cobalt

Cr

Chromium

Cs

Cesium

Cu

Copper

Wt% μg/g μg/g μg/g μg/g μg/g μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

DPD-1

0–5 1.6 0.1 0.20 0.01 16 0 16 1 88 3 0.54 0.11 42 2

5–10 .89 .05 .19 .02 14 1 19 1 131 7 .71 .07 42 2

10–15 1.9 .0 .22 .03 32 0 30 1 161 6 2.7 .1 52 1

15–17.5 1.5 .1 .25 .01 28 1 24 1 155 7 1.4 .1 61 2

DPD-4

0–10 1.7 0.0 0.14 0.03 17 1 26 1 159 2 1.0 0.1 63 3

10–15 1.8 .1 .28 .10 19 1 38 1 195 2 1.5 .3 98 4

15–20 1.7 .1 .31 .01 16 1 31 0 172 1 1.2 .1 103 2

20–25 2.5 .1 .21 .03 8.2 .0 34 1 167 0 .5 .0 97 4

25–30 1.7 .1 .23 .05 19 0 47 2 136 5 1.2 .1 115 2

DPD-5

0–5 3.5 0.0 0.48 0.05 37 1 43 1 244 2 1.7 0.1 94 3

5–10 1.9 .1 .40 .06 21 1 33 1 190 8 1.0 .0 106 3

10–15 1.8 .0 .29 .05 19 0 27 1 189 7 1.5 .1 75 2

15–20 .95 .02 .24 .03 9.5 0.0 35 1 155 5 1.0 .1 54 1

DPD-6

0–5 1.2 0.0 0.19 0.02 13 1 16 0 90 4 2.2 0.0 43 2

5–10 1.3 .0 .16 .03 14 1 15 0 117 1 .55 .06 40 1

10–15 1.8 .0 .40 .02 15 0 37 0 188 6 2.4 .1 108 2

15–20 1.8 .1 .30 .04 14 0 36 2 146 2 1.5 .0 104 2

20–25 2.1 .0 .31 .02 16 0 30 1 143 6 1.4 .1 85 4

25–30 .80 .03 .55 .02 7.7 .4 48 0 147 3 1.0 .1 127 3

Minimum 0.80 0.14 7.7 15 88 0.5 40

Median 1.7 .25 16 31 155 1.2 85

Maximum 3.5 .55 37 48 244 2.7 127

Results 31
Table 10A. Concentration of selected elements in sediment screened to less than 0.060 millimeter, Daguerre Point Dam, California.—

Continued

[ft, foot; Wt%, weight percent; Avg, average; SD, standard deviation; DPD, Daguerre Point Dam. μg/g, microgram per gram; <, less than]

Drill hole/Depth

(ft)

Dy

Dysprosium

Er

Erbium

Eu

Europium

Fe

Iron

Ga

Gallium

Gd

Gadolinium

Ho

Holmium

μg/g μg/g μg/g Wt% μg/g μg/g μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

DPD-1

0–5 1.3 0.1 0.72 0.03 0.34 0.01 3.8 0.1 10 0 1.3 0.1 0.26 0.00

5–10 1.3 .0 .79 .03 .37 .02 4.6 .2 13 1 1.4 .1 .27 .02

10–15 3.5 .0 1.9 .0 1.0 .0 5.7 .1 17 0 3.6 .0 .66 .01

15–17.5 3.1 .2 1.6 .0 .89 .00 6.1 .1 18 0 3.2 .1 .58 .01

DPD-4

0–10 1.3 0.0 0.77 0.03 0.38 0.04 4.9 0.1 12 1 1.3 0.0 0.22 0.01

10–15 1.5 .1 .85 .06 .42 .04 7.7 .0 15 0 1.5 .0 .30 .01

15–20 1.5 .1 .90 .00 .45 .02 7.1 .2 16 0 1.6 .0 .32 .00

20–25 1.2 .1 .72 .05 .31 .01 6.7 .3 12 0 1.1 .1 .25 .01

25–30 1.6 .1 .93 .03 .48 .03 7.5 .7 16 0 1.6 .0 .31 .00

DPD-5

0–5 2.4 0.0 1.31 0.04 0.72 0.03 9.6 0.0 20 1 2.5 0.1 0.46 0.02

5–10 1.6 .0 .93 .03 .53 .02 6.8 .3 16 0 1.8 .0 .33 .01

10–15 1.5 .1 .80 .05 .41 .01 6.7 .4 16 0 1.5 .1 .28 .01

15–20 .85 .02 .52 .01 .26 .01 5.6 .2 13 0 .87 .06 .17 .01

DPD-6

0–5 .88 .02 .49 .02 .23 .01 4.6 .1 11 0 .80 .03 .17 .01

5–10 .93 .04 .51 .01 .25 .01 4.8 .1 11 0 .85 .05 .18 .01

10–15 1.6 .1 .91 .02 .38 .03 7.7 .2 17 1 1.5 .1 .28 .01

15–20 1.3 .1 .71 .01 .38 .01 7.1 .3 16 1 1.3 .1 .26 .01

20–25 2.2 .0 1.3 .0 .59 .02 6.9 .1 17 0 2.2 .1 .43 .00

25–30 .91 .06 .51 .03 .24 .01 7.7 .2 20 1 .90 .05 .18 .01

Minimum 0.85 0.49 0.23 3.8 10 0.80 0.17

Median 1.5 .80 .38 6.7 16 1.5 .28

Maximum 3.5 1.9 1.0 9.6 20 3.6 .66

Drill hole/Depth

(ft)

K

Potassium 

La

Lanthanum

Li

Lithium

Lu

Lutetium

Mg

Magnesium

Mn

Manganese

Mo

Molybdenum

Wt% μg/g μg/g μg/g Wt% μg/g μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

DPD-1

0–5 0.59 0.03 7.3 0.1 5.7 0.4 0.11 0.01 0.56 0.02 711 30 4.4 0.7

5–10 .77 .02 5.9 .5 7.8 .8 .11 .01 .39 .02 750 37 2.9 .5

10–15 .79 .01 14 0 13 0 .28 .01 .65 .01 1,260 19 3.8 .4

15–17.5 .79 .03 12 1 18 0 .25 .01 .91 .01 740 34 1.5 .9

DPD-4

0–10 0.74 0.05 7.1 0.5 8.6 0.3 0.098 0.007 0.97 0.01 1,050 29 13 0

10–15 .78 .02 7.9 .5 14 1 .12 .00 1.6 .0 960 25 51 2

15–20 .81 .02 6.4 .0 16 1 .14 .00 1.5 .0 972 46 9.9 .5

20–25 .56 .03 2.9 .1 9.7 .5 .09 .01 .93 .05 1,720 28 33 2

25–30 .95 .02 7.0 .2 16 0 .13 .01 1.6 .1 2,340 188 10 0

DPD-5

0–5 1.3 0.0 15 0 11 1 0.18 0.01 1.5 0.0 1,980 21 14 0

5–10 .90 .03 8.7 .2 15 1 .14 .00 1.5 .1 1,750 101 9.1 .5

10–15 1.0 .0 8.0 .1 12 0 .124 .010 1.1 .1 1,230 63 91 3

15–20 .62 .01 3.7 .1 8.7 .5 .068 .006 .44 0.01 1,590 18 39 0

DPD-6

0–5 0.60 0.02 4.7 0.1 4.0 0.3 0.073 0.00 0.62 0.01 759 22 5.5 0.9

5–10 .64 .01 5.3 .2 4.7 .2 .076 .004 .70 .00 743 29 4.6 .5

10–15 .96 .04 6.2 .3 17 0 .13 .01 1.4 .0 1,480 43 26 0

15–20 .88 .02 5.8 .2 16 0 .11 .00 1.4 .1 1,440 79 5.1 .6

20–25 .83 .02 7.7 .2 19 1 .18 .01 1.0 .0 1,280 17 7.7 .3

25–30 .96 .02 2.8 .1 24 1 .080 .001 .76 .00 2,200 31 2.2 .2

Minimum 0.56 2.8 4.0 0.068 0.39 711 1.5

Median .79 7.0 13 .12 1.0 1,260 9.1

Maximum 1.3 15 24 .28 1.6 2,340 91 

32 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California
Table 10A. Concentration of selected elements in sediment screened to less than 0.060 millimeter, Daguerre Point Dam, California.—

Continued

[ft, foot; Wt%, weight percent; Avg, average; SD, standard deviation; DPD, Daguerre Point Dam. μg/g, microgram per gram; <, less than]

Drill hole/Depth

(ft)

Na

Sodium

Nd

Neodymium

Ni

Nickel

P

Phosphorous 

Pb

Lead

Pr

Praseodymium

Rb

Rubidium

Wt% μg/g μg/g μg/g μg/g μg/g μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

DPD-1

0–5 1.1 0.0 7.0 0.3 42 2 540 13 6.1 0.4 1.8 0.0 17 1

5–10 .98 .05 6.8 .6 48 3 451 37 8.2 .6 1.6 .0 23 2

10–15 1.1 .0 17 0 73 2 377 10 11 0 4.1 .0 24 1

15–17.5 .91 .03 15 1 88 1 407 5 11 0 3.7 .2 24 1

DPD-4

0–10 0.97 0.01 7.3 0.0 75 1 699 9 9.3 0.7 1.8 0.1 16 1

10–15 1.1 .0 8.0 .1 121 0 1,010 16 17 1 2.1 .0 23 1

15–20 1.1 .1 7.5 .0 100 1 732 52 20 1 1.8 .0 23 1

20–25 1.5 .1 4.3 .0 103 5 659 6 8.7 .6 1.0 .1 7.0 .3

25–30 .99 .01 8.3 .1 100 3 635 33 13 0 2.0 .1 24 1

DPD-5

0–5 1.6 0.0 14 0 94 3 1,230 51 20 0 3.5 0.0 35 1

5–10 1.2 .1 9.0 .0 112 3 787 21 16 1 2.3 .1 22 1

10–15 1.2 .0 7.9 .2 86 3 765 45 41 0 2.0 .1 28 1

15–20 .89 .03 4.3 .1 90 2 376 20 105 0 1.0 .0 12 0

DPD-6

0–5 1.2 0.1 4.3 0.1 36 1 1,190 14 6.4 0.2 1.1 0.1 13 1

5–10 1.0 .0 5.0 .2 47 1 634 16 7.8 .1 1.3 .1 16 1

10–15 1.2 .0 6.9 .3 107 3 859 19 163 1 1.6 .0 29 0

15–20 1.3 .0 6.4 .3 96 3 726 8 15 1 1.6 .1 23 1

20–25 1.0 .1 8.9 .2 87 4 765 27 23 1 2.2 .1 17 0

25–30 .56 .03 3.7 .2 147 5 797 46 25 1 .88 .05 13 1

Minimum 0.56 3.7 36 377 6.1 0.88 7.0

Median 1.1 7.3 90 726 15 1.8 23

Maximum 1.6 17 147 1,230 163 4.1 35

Drill hole/Depth

(ft)

Re

Rhenium

S

Sulfur 

Sb

Antimony

Sc

Scandium

Se

Selenium

Sm

Samarium

Sr

Strontium

μg/g Wt% μg/g μg/g μg/g μg/g μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

DPD-1

0–5 <0.003 0.001 0.03 0.01 0.85 0.15 7.3 0.7 <0.8 1.3 1.5 0.1 160 8

5–10 <.003 .000 .04 .00 .83 .06 6.9 .8 <.8 .1 1.6 .2 126 9

10–15 <.003 .001 .04 .01 .92 .03 16 1 .8 .6 3.8 .1 191 6

15–17.5 <.003 .001 .02 .01 .85 .06 17 0 <.8 .2 3.3 .0 147 6

DPD-4

0–10 <0.004 0.002 0.30 0.01 1.1 0.2 8.1 0.9 <0.9 0.5 1.5 0.1 246 3

10–15 <.004 .006 1.2 .0 2.7 .4 12 1 1.4 .4 1.7 .1 206 2

15–20 .004 .002 .37 .02 1.8 .1 16 0 <.9 1.3 1.7 .1 196 14

20–25 .003 .001 .18 .00 .88 .00 15 1 1.6 .2 1.1 .1 168 8

25–30 <.004 .002 .17 .00 1.1 .1 14 1 <.9 .5 1.8 .0 158 3

DPD-5

0–5 0.003 0.003 0.06 0.01 1.6 0.1 14 1 <1 0 2.8 0.1 301 2

5–10 <.004 .003 .04 .01 1.3 .2 14 1 <.9 .3 1.8 .0 203 14

10–15 .003 .002 .05 .01 5.1 .1 10 1 <1 0 1.7 .0 212 7

15–20 <.003 .000 <.02 .01 16 0 6.2 .4 <.8 .4 .97 .03 127 5

DPD-6

0–5 <0.003 0.001 0.02 0.01 0.65 0.03 5.6 0.5 0.9 0.6 0.86 0.10 183 8

5–10 <.003 .001 .06 .00 .72 .03 6.5 .9 <.8 .1 1.0 .0 181 6

10–15 <.003 .001 .05 .01 19 0 11 1 <.8 .2 1.6 .0 189 2

15–20 <.003 .001 .02 .02 1.3 .1 11 1 <.8 .7 1.4 .1 190 4

20–25 .004 .001 .10 .00 3.8 .0 14 1 <.8 .8 2.2 .0 202 8

25–30 <.003 .001 .03 .00 1.7 .0 12 0 <.8 .2 .93 .00 90 4

Minimum <0.003 <0.02 0.65 5.6 <0.8 0.93 90

Median <.003 .05 1.3 12 <.8 1.6 189

Maximum .004 1.2 19 17 1.6 3.8 301

Results 33
Table 10A. Concentration of selected elements in sediment screened to less than 0.060 millimeter, Daguerre Point Dam, California.—

Continued

[ft, foot; Wt%, weight percent; Avg, average; SD, standard deviation; DPD, Daguerre Point Dam. μg/g, microgram per gram; <, less than]

Drill hole/Depth

(ft)

Tb

Terbium

Te

Tellurium

Th

Thorium

Ti

Titanium

Tl

Thallium

Tm

Thulium

U

Uranium

μg/g μg/g μg/g Wt% μg/g μg/g μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

DPD-1

0–5 0.21 0.01 <0.07 0.03 2.5 0.0 0.31 0.01 0.05 0.02 0.11 0.01 1.0 0.0

5–10 .22 .01 <.07 .04 2.5 .1 .60 .02 .18 .09 .12 .01 1.6 .1

10–15 .56 .01 <.07 .04 5.6 .1 .76 .02 .19 .05 .28 .00 1.9 .1

15–17.5 .48 .01 .09 .03 6.4 .2 .65 .01 .19 .01 .26 .02 1.9 .1

DPD-4

0–10 0.20 0.00 0.09 0.08 2.0 0.0 0.31 0.01 0.26 0.06 0.087 0.003 1.2 0.1

10–15 .24 .02 .07 .04 2.8 .1 .44 .02 .19 .03 .13 .01 1.9 .1

15–20 .26 .01 .10 .03 2.5 .1 .55 .02 .21 .03 .13 .01 1.6 .1

20–25 .18 .00 .10 .03 .9 .0 .41 .02 .13 .02 .11 .00 .94 .06

25–30 .26 .00 <.05 .02 2.6 .1 .46 .02 .19 .01 .13 .01 1.3 .1

DPD-5

0–5 0.36 0.00 <0.09 0.02 4.4 0.1 0.88 0.02 0.46 0.06 0.19 0.01 2.2 0.1

5–10 .27 .00 .13 .04 3.0 .1 .54 .03 .30 .05 .13 .00 1.8 .0

10–15 .23 .02 .17 .11 3.1 .1 .56 .03 .24 .11 .126 .012 1.8 .0

15–20 .15 .01 .11 .00 1.5 .0 .57 .02 .12 .02 .071 .003 1.3 .0

DPD-6

0–5 0.14 0.01 0.09 0.03 1.6 0.1 0.37 0.01 0.14 0.01 0.078 0.005 1.2 0.0

5–10 .15 .01 <.07 .03 1.8 .0 .40 .01 .16 .06 .075 .004 .99 .03

10–15 .23 .01 .10 .07 2.7 .1 .54 .01 .20 .02 .12 .01 1.6 .1

15–20 .22 .00 <.07 .02 2.5 .1 .54 .02 .18 .03 .11 .01 1.4 .1

20–25 .34 .00 .10 .03 3.3 .0 .55 .03 .17 .04 .18 .01 1.6 .1

25–30 .14 .01 .27 .04 2.3 .1 .55 .01 .23 .09 .075 .002 2.0 .1

Minimum 0.14 <0.05 0.9 0.31 0.05 0.071 0.94

Median .23 .09 2.5 .54 .19 .12 1.6

Maximum .56 .27 6.4 .88 .46 .28 2.2

Drill hole/Depth

(ft)

V

Vanadium

W

Tungsten

Y

Yttrium

Yb

Ytterbium

Zn

Zinc

Zr

Zirconium Mass

Digested

(g) μg/g μg/g μg/g μg/g μg/g μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

DPD-1

0–5 135 6 0.48 0.03 6.4 0.3 0.68 0.06 62 3 43 3 0.101

5–10 175 10 .83 .04 6.2 .4 .73 .06 64 3 60 2 .102

10–15 217 5 1.3 .0 16 0 1.8 .1 92 3 77 2 .101

15–17.5 218 8 1.1 .1 14 0 1.7 .0 94 5 75 3 .100

DPD-4

0–10 136 8 0.66 0.01 5.8 0.5 0.65 0.05 81 4 43 2 0.106

10–15 221 4 1.1 .0 7.1 .3 .88 .02 138 14 50 1 .106

15–20 257 1 1.1 .0 7.0 .0 .85 .05 114 5 53 0 .102

20–25 200 10 .61 .03 6.0 .2 .65 .04 90 1 252 97 .100

25–30 221 1 .91 .02 7.3 .0 .86 .02 115 13 47 0 .101

DPD-5

0–5 333 9 1.3 0.0 12 0 1.3 0.1 163 7 77 1 0.133

5–10 225 7 1.2 .0 7.9 .2 .90 .01 109 9 54 1 .108

10–15 231 10 1.1 .0 7.0 .2 .76 .02 111 2 58 2 .132

15–20 195 6 .82 .03 4.0 .1 .46 .01 82 1 54 2 .101

DPD-6

0–5 149 6 0.44 0.01 4.9 0.2 0.44 0.02 61 2 36 1 0.103

5–10 168 3 .48 .02 4.9 .3 .49 .02 66 1 40 2 .101

10–15 229 6 1.0 .1 7.2 .2 .85 .00 132 3 60 1 .105

15–20 222 8 .85 .00 6.3 .1 .71 .03 118 3 53 1 .103

20–25 207 8 .92 .02 10 0 1.2 .0 109 3 59 2 .101

25–30 219 7 1.4 .1 3.8 .1 .47 .00 144 3 69 2 .101

Minimum 136 0.44 3.8 0.44 61 36 0.100

Median 218 .92 7.0 .76 109 54 .102

Maximum 333 1.4 16 1.8 163 252 .133

34 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California
Metals Concentrations (mg/kg) Consensusbased TEC1

Consensusbased PEC Minimum Median Maximum 1

Arsenic 4.7 11 32 9.79 33

Antimony .65 1.3 19 NG NG

Cadmium .14 .25 .55 .99 4.98

Chromium 88 155 244 43.4 111

Copper 40 85 127 31.6 149

Lead 6.1 15 163 35.8 128

Mercury .018 .13 .32 .18 1.06

Nickel 36 90 147 22.7 48.6

Zinc 61 109 163 121 459

1

Values from MacDonald and others (2000). 

Table 10B. Trace-element concentrations in fine-grained 

Daguerre Point sediment and sediment quality criteria (ecological 

toxicity), Daguerre Point Dam, California.

[Mercury concentrations based on analysis of clay-silt fraction separated by centrifugation (table 8). Other metal concentrations based on analysis of material 

screened to less than 0.060 mm (table 10A). Bold values exceed TEC concentrations; TEC, threshold effects concentration. PEC, probable effects concentration; NG, not given; mg/kg, milligram per kilogram (parts per million)]

Results 35

Elemental mercury spherules from 4 to 6 μm in diameter 

were observed on a grain of gold amalgam from the 30- to 

35-foot interval of drill-hole DPD-2 (fig. 18). These mercury 

spherules are associated with platy aluminosilicate minerals 

and iron oxides less than 0.4 μm in diameter. In addition, a 

gold-amalgam grain with mercury was observed in a sample 

from the 25- to 30-foot interval of drill-hole DPD-2. 

Other Heavy Minerals

 Quantities of heavy minerals in concentrates prepared 

from drilled sediment intervals upstream of Daguerre Point 

Dam vary with the type of mining. Higher concentrations of 

heavy minerals tend to be associated with undredged hydraulic 

tailings, whereas lesser amounts are associated with undisturbed, pre-mining gravels (fig. 19). Individual euhedral to 

subhedral grains of pyrite, magnetite, spessartine garnet, 

chromite, ilmenite, zircon, and sphene were observed in the 

heavy-mineral concentrates (table C2).

Magnetite, chromite, and ilmenite were the most common 

minerals in the mineral concentrates. The highest concentration 

of pyrite grains was found in the 0- to 5-foot interval of hole 

DPD-1. Pyrite concentrations were also relatively high in the 

20- to 25-foot interval of DPD-2 and the 5- to 10-foot interval of 

DPD-3. Concentrations of pyrite grains tended to increase as 

the grain-size decreased in the heavy-mineral fraction, which 

may be a consequence of breakage during churn drilling. Finegrained pyrite (<1 mm) with coarsely crystalline textures may 

represent detrital sulfides from gold-quartz lode mines nearby 

in Browns Valley that were active before 1942 and were transported via Dry Creek, just upstream of DPD-3 (figs. 1 and 3). 

Zircon grains were less abundant than other heavy minerals

and were randomly distributed throughout the particle sizes. 

Garnets were found in the 0.500- to 1-mm size fractions of 

most intervals; the proportions of garnet were highest in the 

deeper sections of holes DPD-1, DPD-2, and DPD-3 (table 

C2).

Mercury Methylation and Demethylation 

Potentials 

In other studies, it has been shown that surface sediments 

typically have a much higher potential for MeHg production than deeper sediments (Marvin-DePasquale and others, 2003). The amount of radiotracer 203Hg(II) converted to 

CH3

203Hg+ (MeHg with radiotracer Hg) ranged from <0.03 to 

0.31 percent per day for deep core samples from DPD, which 

corresponds to Hg-methylation potential rates of less than 

about 0.15 to 1.57 ng/g dry sed/d (table 11). This range is at 

the low end of Hg-methylation rates. This trend reflects the 

general decrease in overall microbial activity with sediment 

depth, as organic matter needed to drive heterotrophic microbial metabolism decreases with depth. In addition, the activity 

of sulfate-reducing bacteria is limited at greater depths where 

pore-water sulfate tends to be depleted (Marvin-DiPasquale 

and Capone, 1998). Because this bacterial group is primarily 

responsible for Hg-methylation (Compeau and Bartha, 1985; 

Gilmour and others, 1992), we can expect Hg-methylation to 

decrease with increasing depth. Such depth profiles have been 

observed in other systems and in shallower sediment profiles 

(Marvin-DiPasquale and others, 2003). For two holes (DPD-1 

and DPD-3) of the three from which samples were taken at 

two depths, the upper layer sample had the higher 203Hg(II)-

methylation rate. The opposite trend occurred at hole DPD-5, 

which likely represents original Yuba River bed sediment, 

below the zone impacted by hydraulic mining debris. 

The amount of 14CH3HgCl that degraded to 14CO2 + 14CH4

(combined) in the deeper sediments ranged from 6.5 to 17.7 

percent per day, which corresponds to 1.0 to 2.2 ng/g dry 

sed/d (table 11). In general, the overall decrease in microbial 

activity likely is due to labile organic matter decreasing with 

depth and likely accounts for this vertical trend. However, 

unlike the situation for Hg-methylation, which is promoted 

primarily by sulfate-reducing bacteria, a wider variety of heterotrophic bacterial groups can carry out MeHg degradation; 

aerobes, denitrifiers, sulfate reducers, and methanogens have 

been implicated in this process (Oremland and others, 1991; 

Marvin-DiPasquale and Oremland, 1998). Similar to the trend 

for Hg-methylation, the upper portions of drill-holes DPD-1 

and DPD-3 had higher MeHg-degradation rates than the lower 

portion, and the reverse vertical trend was observed for drillhole DPD-5. In fact, the deeper zone of DPD-5 exhibited the 
����������������������

������������

Figure 16. Scanning electron micrograph of broken gold-amalgam fragment from a gold grain, Daguerre Point 

Dam, California.

36 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California

highest MeHg degradation rate in the entire sample set (N = 

7). These results suggest that this deeper layer of original 

bed sediment had generally higher microbial activity than the 

overlying sediment, composed largely of hydraulic mining

debris. The sediment layers with the greatest microbial activity 

gave rise to both increased levels of MeHg and higher levels of 

14C-MeHg degradation. Further, there was a generally positive 

relation, albeit statistically insignificant (P = 0.12), between 

203Hg(II)-methylation and 14C-MeHg demethylation potentials 

(fig. 20).

Characterization of ancillary environmental variables 

revealed that samples from the upper intervals of core holes 

DPD-1, -3, and -5 generally had higher levels of solid-phase 

reduced sulfur than samples from the deeper intervals (table 

12); the sulfur as acid volatile sulfide (AVS) ranged from 11 

to 854 nmol/g dry sediment, and total reduced sulfur (TRS) 

ranged from 32 to 2,060 nmol/g dry sediment. Conversely, 

loss on ignition (LOI), a proxy for organic matter, ranged from 

0.35 to 1.14 percent by weight and was higher in the deeper 

intervals for all of these profiles. In contrast, the trend in pore 

water DOC (8 to 63 mg/L) was not consistent with the trend in 

LOI. Sediment percent dry weight ranged from 68 to 87 percent, sediment pH ranged from 6.8 to 7.8, and sediment redox 

ranged from –409 mV to +477 mV. That the highest redox 

values were for the deeper samples from holes DPD-3 and -6 

(table 12) was unexpected. The deeper sediments were buried 

many years ago (as discussed in a later section of the report), 

and the upper part of the core from DPD-3 was –379 mV. While 

oxygenated ground-water inflow can not be excluded as an 

explanation (inflow of Yuba River water through porous gravel), 

it is also possible that the high redox values reflect oxidation of 

these sediments during the sample collection and processing. 

If the latter is true, then the MeHg production and degradation 

potential assays also could have been similarly affected. 

No significant relations were found between MeHg 

production or degradation potential and any of the above-mentioned environmental variables. However, the ratio of Hg(II)-

methylation potential to MeHg degradation (or demethylation) 
Figure 17. High-magnification scanning electron micrograph of gold-amalgam particle showing pitted surface, 

Daguerre Point Dam, California.

Figure 18. Scanning electron micrograph of elemental mercury in clay-silt fraction from 25 to 30 feet in drill hole DPD-2, 

Daguerre Point Dam, California.

Results 37

����������

��������

potential (MP/DP, table 11) is highest for the two samples 

with highest sediment pH; the data were fit with non-linear, 

second-order polynomial function (fig. 21). Furthermore, using 

a multiple linear regression, we found that 96 percent of the 

variability in the 203Hg-methylation rates could be explained 

by three variables (pH, Eh, and DOC) with the following equation:

203Hg-methylation = 1.30[pH] – 1.12 × 10-3[Eh

]

– 1.98 × 10-2[DOC] – 8.45,

for R2 = 0.96 and P < 0.01, where R is the regression correlation coefficient and P is the probability value.
��

���

�����

�����

�����

�����

�����

�����

����������������������������������������������������

���������������������������������������������

��

��

��

���

���

���

���

�

� �� �� �� �� ���

������������������

������������������

�������

��������

Figure 19. Graph showing geometric mean of gold tenor and heavy mineral concentrates, Daguerre Point Dam, California.

Drill hole/

Depth

(ft)

203Hg(II)-

methylation

(%/day)1

203Hg(II)-

methylation

(ng/g dry sed/d)2

14C-MeHg 

degradation

(%/day)3

14C-MeHg

degradation

(ng/g dry sed/d)4

MP/DP pH 14CO2 /

14C-total5

DPD-1

0–5 0.08 (0.03) 0.42 (0.15) 12.6 (0.1) 1.5 (0.0) 0.28 6.8 0.91

10–15 <.03 <.15 6.5 (0.7) 1.0 (0.1) <.15 6.8 1.00

DPD-3

3–5 0.31 (0.19) 1.57 (0.94) 9.9 (3.3) 1.1 (0.4) 1.37 7.8 0.50

15–20 <.03 <.15 8.1 (0.1) 1.0 (0.1) <.15 7.2 .90

DPD-5

3–5 0.05 0.27 9.0 (2.2) 1.1 (0.1) 0.24 7.4 0.56

15–20 .29 (0.01) 1.55 (0.03) 17.7 (0.6) 2.2 (0.3) .72 7.5 .25

DPD-6

25–30 <0.03 <0.15 8.2 (2.1) 1.1 (0.3) <0.14 7.0 0.80

Median 0.05 0.27 9.0 1.1 0.24 7.2 0.8

Mean n/a n/a n/a n/a 0.44 n/a n/a

1 Percentage of radiolabeled 203Hg(II) recovered as 203Hg-methylmercury after 4-hour incubation, expressed on a per day basis.

2 Hg-methylation potential normalized to sediment dry weight and calculated based on an amendment of 436 nanogram 203Hg(II) per gram weight sediment.

3 Percentage of radiolabeled 14CH3

HgCl recovered as 14CO2 plus 14CH4 after 4-hour incubation, expressed on a per day basis.

4 MeHg-degradation potential normalized to sediment dry weight and calculated based on an amendment of 10.5 nanogram 14CH3

HgCl(as Hg) per gram wet 

sediment.

5 14CO2 /14C-total; this ratio gives some indication of whether the MeHg degradation pathway was largely oxidative (resulting in 14CO2

) or reductive (resulting 

in 14CH4).

Table 11. Potential rates of mercury methylation and methylmercury degradation, Daguerre Point Dam, California.

[Standard deviations from the mean are given in parentheses when there are two replacates. CH3

203Hg+

, methylmercury ion with radio-labeled mercury. 203Hg(II), 

radio-laveled divalent mercury; 14C-MeHg, methylmercury with radio-labeled carbon; 14CH3HgCl, carbon-14 labeled methylmercury choloride; MP/DP, Hgmethylation/MeHg-degradation ratio, based on potential rate data; 14CO2

, carbon dioxide with radio-labeled carbom; 14CH4, methane with radio-labeled carbon; 14C-Total, the sum of 14CO2

 + 14CH4. %/day, percent per day; DPD, Daguerre Point Dam. ft, foot; ng/g dry sed/d, nanogram per gram dry sediment per day; <, 

less than; n/a, not applicable]

38 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California
��������������������

��

���������

���

���

���

���

���

���

�� ��� ��� ��� ���

���������������������������������������������

���������������������������������������������

���������������������������������������������������������������������������������������������

Figure 20. Graph showing relation between rates of mercury methylation potential and mercury 

demethylation potential, Daguerre Point Dam, California.

Table 12. Concentrations of acid volatile sulfur and total reduced sulfur in selected samples, Daguerre Point Dam, California.

[Acid volatile sulfur (AVS) assay = FeS; total reduced-sulfur (TRS) assay = FeS and FeS2; TRS-AVS = FeS2. DOC, dissolved organic carbon; DPD, Daguerre 

Point Dam. ft, foot; nmol/g dry sed, nanomole per gram dry sediment; mV, millivolt; mg/L, milligram per liter]

Drill hole/

Depth

(ft)

Sediment Pore water 

DOC 

(mg/L)2

Acid volatile sulfur 

(nmol/g dry sed)

Total reduced sulfur 

(nmol/g dry sed)

Percentage 

weight loss on 

ignition

pH

(standard units)

Redox Eh

(mV)1

Percentage 

dry weight

DPD–1

0–5 854 2,056 0.40 6.8 -335 84 10

10–15 19 34 1.14 6.8 -290 68 39

DPD–3

3–5 766 1,193 0.25 7.8 -379 87 27

15–20 19 32 .60 7.2 477 83 12

DPD–5

3–5 183 698 0.35 7.4 -409 81 63

15–20 16 55 .53 7.5 -379 80 8

DPD–6

25–30 11 649 0.72 7.0 249 77 11 1 Eh

 = Em + Er, where Em = the measured value (in mV) taken with the platinum electrode and Er is the temperature-dependent correction for a standard hydrogen reference electrode (+207 to +211 mV).

2 Sediment was first diluted with Milli-Q water to obtain enough sample for dissolved organic carbon analysis.

Results 39
������������

�������������������

� ����������

�

���

���

���

���

���

���

���

���

��� ��� ��� ��� ��� ��� ���

��

�����

Figure 21. Graph showing ratio of mercury methylation potential (MP) to mercury demethylation potential 

(DP) as function of sediment pH, Daguerre Point Dam, California.

40 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California

Discussion

Relation of Sediment Characteristics to Mining 

History 

On the basis of results of this study and historical 

accounts, we hypothesize that the highest concentrations of 

mercury in sediments within the Yuba Goldfields are associated with undredged hydraulic mining tailings and the earliest 

dredged sediments. The dredging history of the area upstream 

of Daguerre Point Dam (fig. 4) is well documented. Field 

observations indicate that the area immediately north and 

west of the area dredged during 1916–34 consists primarily 

of remobilized hydraulic mine tailings (fig. 5). Because of the 

action of the Yuba River and the proximity to dredge tailings, 

it is likely that some of the sediment in this area consists of a 

mixture of hydraulic tailings and dredge tailings. Drill-holes 

DPD-5 and DPD-6 intersected sediments interpreted to consist 

of a mixture of hydraulic tailings and dredge tailings from 

the period 1916–68. The lowest concentration of mercury 

was found in drill-hole DPD-1, located in an area containing 

gravel relatively undisturbed by mining, according to analyses of mercury, gold, and heavy mineral concentrates (figs. 

15 and 19). We suggest that the relatively low concentration 

of mercury (10.9 to 32.9 ng/g dry weight) in sediments from 

hole DPD-1 was transported to this location as bed load during flood events. Similarly, elevated gold values in the upper 

5-foot intervals of DPD-2 and -5 (fig. 15A) may be because 

of flood gold deposition. Generally, moderate concentrations 

of mercury (7.50 to 80.7 ng/g dry weight) in sediments from 

holes DPD-2, -3, and -4 were consistent with that in dredged 

and re-dredged sediments. Exceptions were the two deepest 

intervals of hole DPD-2, which may have higher mercury concentrations as a result of mixing with hydraulic mine tailings. 

The distribution of mercury corresponds well with that of 

gold and gold-mercury amalgam grains. The highest mercury 

concentration observed in this study was 1,100 ng/g, in the 

silty fraction of the 25- to 30-foot interval of hole DPD-2 

(table 7); this anomalously high concentration was probably 

caused by a particle of amalgam, thus producing a nugget 

effect. This high concentration correlates with observations of 

abundant amalgam and traces of mercury in the heavy-mineral 

concentrate from the same interval (table C2).

There is a positive correlation between HgT concentration 

and the abundance of fine particles. In general, the finer the 

average particle size, the higher the concentration of HgT, indicating that most mercury is associated with the finer particlesize fractions of the sediments. This relation is demonstrated 

by the consistently lower concentrations of HgT in the sandy 

fraction compared with the finer grained silty and clay-silt 

fractions (figs. 12 and 13), and by the consistent increase in 

median mercury concentrations of sieved sediment fractions 

with decreasing grain size in the sand and silt size subclasses 

(table 9). Similarly, a positive relation between higher mercury 

concentration and finer particle size in dredge tailings and 

hydraulic mine tailings has been documented previously for 

sediment fractions <2 mm and <0.063 mm in the Clear Creek 
���������������������

��

���������

�

���

���

���

���

���

���

��� ��� ��� ��� ��� ��� ���

��

���������������������

Figure 22. Graph showing carbon-14 end-product ratio (CO2/C) 

from mercury demethylation experiments as a function of sediment pH, Daguerre Point Dam, California.

Discussion 41

drainage basin in Shasta County in northern California (Ashley and others, 2002).

The relation between the gold tenor in each drill hole 

and the mass of heavy mineral concentrates (fig. 19) helps 

to distinguish hydraulic mine tailings from dredge tailings. 

Hydraulic mine tailings contain a significantly higher proportion of heavy minerals (table C2), which are partially removed 

during dredging, thus decreasing the amount in dredge tailings. 

Upstream of Daguerre Point Dam, dredge tailings are distinguished by many discordant lenses of fine-grained sediment 

because of the different settling velocities of particles in old 

dredge ponds and infilling with coarser sediment from past 

dredging and flooding.

Loss of Mercury during Drilling

Drilling in permeable sediments below the elevation of 

the Yuba River produced a significant volume of water along 

with sediment, which complicated the sampling and characterization effort. Overflow generated from each drill hole 

contained suspended sediment consisting predominantly of 

silt and clay (silty fraction, figs. 8, 10, and 11). Because the 

highest concentrations of mercury observed in this study are 

in the relatively fine-grained fractions, it is clear that some 

mercury was lost. To calculate the in-place concentration of 

mercury in sediments prior to drilling, it is necessary to combine mercury concentration data for the various size fractions 

produced from the process stream (fig. 8). The total amount of 

mercury in the sediment deposit behind Daguerre Point Dam 

remains uncertain because we do not know quantitatively the 

proportion of fine material lost from every drilled interval in 

the overflow streams (silty fraction and clay-silt fraction). The 

volumes and (or) masses of material recovered and discarded 

were determined for each drilled interval. For the selected 

intervals for which the concentration of suspended sediment 

was determined in the waste streams, a mass balance approach 

can be used to estimate the relative proportions of fine and 

coarse sediment in the in-place deposit. Mass balance calculations were not completed as part of this report, but could be 

done with existing data (tables 3-9, tables B1-B5).

Environmental Factors Influencing Mercury 

Methylation and Demethylation

Although only seven samples were used to calculate the 

potential rates of mercury methylation and demethylation 

(table 11) in this study, it was encouraging to find that a combination of factors controlling the availability of Hg(II) to sulfate-reducing bacteria could be used to explain essentially all 

of the variability in the Hg-methylation potential rate measurement. No comparable combination of environmental factors 

adequately explained the variability in 14C-MeHg-degradation 

(mercury demethylation). However, there was a decrease in 

the 14CO2/(14CO2 + 14CH4) end-product ratio (simplified as the 

ratio CO2/C) with increasing pH (fig. 22). It has been reported 

that this ratio increases with increasing sulfate concentration 

(and presumably increasing rates of microbial sulfate reduction) in Florida Everglades sediments (Marvin-DiPasquale and 

others, 2000). Methylmercury degradation can proceed by a 

number of pathways, including reductive mer detoxification 

(Robinson and Tuovinen, 1984) and oxidative demethylation 

(Oremland and others, 1991, 1995). In the former process, 

MeHg degrades to CH4 as a detoxification response by bacteria 

to high levels of MeHg. In the case of oxidative demethylation, 

CO2 alone or CO2 plus CH4 are the primary end-products, and 

it has been hypothesized that the outcome depends on whether 

the dominant bacterial groups responsible for the degradation 

are sulfate reducers or methanogens, respectively (MarvinDiPasquale and others, 2000). Thus, the shift to lower values of CO2

/C in the end-product of MeHg degradation with 

increasing pH may imply differences in the primary microbial 

communities in different pH environments at different depths.

The correspondence of elevated concentrations of 

reduced sulfur (AVS and TRS) with Hg-methylation potential 

in the shallow samples from holes DPD-1 and -3 may have 

been at least partially affected by the process of sampling. As 

the reduced sulfur-rich cores were being taken, some oxygenated, overlying water likely entered the coring hole and 

was mixed with the deep sediment substrate. The sediment 

was then homogenized in a bucket in the open atmosphere, 

which likely reoxidized some reduced sulfur to sulfate. Prior 

to drilling, the in-place sulfate concentrations may have been 

very low, or fully depleted, below the top few feet of the sediment profile. Thus, the sampling process may have stimulated 

sulfate-reducing bacteria, previously limited by low sulfate 

concentrations. Theoretically, this could have initiated a pulse 
Implications for Downstream Mercury Transport

Because elemental mercury has a strong propensity to 

flour, agitating and disturbing contaminated sediments cause 

it to break down into continuously smaller particles. The grain 

size of elemental mercury observed in this study was 6 μm 

and less (fig. 18). Larger particles of mercury are commonly 

observed in close proximity to hydraulic mines (Hunerlach and 

others, 1999), and the grain size is reduced during fluvial transport downstream. If sediments from Daguerre Point Dam were 

released downstream, further breakdown of elemental mercury 

particles would lead to increased surface area, which could lead 

to a higher degree of reactivity and potential for oxidation and 

methylation. 

Concentrations of MeHg in the sediments behind Daguerre 

Point Dam are relatively low; therefore, MeHg alone probably 

would not be a significant risk if the sediments were released in 

conjunction with a fish passage improvement project. However, 

inorganic mercury associated with these sediments, especially 

the finer grained fractions, could transform to MeHg after it 

is released. The relatively high levels of reduced-S buried in 

these sediments could stimulate Hg methylation should the 

environment of these currently buried sediments be changed 

from reducing to oxidizing. The extent of increased Hg(II)-

methylation would depend on the reactivity of the inorganic 

Hg(II) fraction associated with these sediments, which is currently unknown. It is also unknown how long this stimulation 

would last; it likely depends on the extent of reoxidation of 

reduced-S pools, the amount and depth of sediment removed, 

the characteristics of downstream depositional areas, the 

amount of microbially available Hg(II), and the final disposition of the dredged material. 

Implications for Geomorphology and 

Hydrogeology

Data from historical exploration drill holes to the east 

and southeast of Daguerre Point, made available to the USGS 

by Cal Sierra Development Incorporated, made it possible to 

construct bedrock elevation contours (fig. 3, plate 1). Drillhole depth and bedrock elevation data were interpreted by 

the USGS and plotted to create a contour map showing the 

elevation of the top of bedrock. The resulting map was then 

compared with a 1941 bedrock contour map from the Yuba 

Consolidated Goldfield records and a historical map (Weatherbe, 1907) of the Yuba River channel near Daguerre Point. 

Both maps confirm a bifurcation of the deeper and older channel of the Yuba River Channel upstream of the Daguerre Point 

Dam and a pre-dam flow path to the south south-west around 

the outcrop of Daguerre Point (fig. 3, plate 1).

Bedrock elevation at Daguerre Point Dam is about 30 

feet above the lowest elevation of deposited hydraulic mine 

tailings, indicating that the gravel bed of the Yuba River 

was lower before being inundated with debris. An estimated 

300,000,000 cubic yards of hydraulic mining debris was 

deposited in the bed of the Yuba River, which varied from 12 

to 30 feet in depth (Weatherbe, 1907). Historical cross-sectional data generated in the 1940s by the Yuba Consolidated 

Goldfield show that tailings from hydraulic mine debris ranged 

in thickness from 16 to 82 feet, almost 50 feet greater than 

previously reported (Gilbert, 1917). Free elemental mercury 

(that has not been fully absorbed into gold grains found within 

tailings) may be available for dispersion through abrasion 

when disturbed.

The range in elevation from the crest of Daguerre Point 

Dam to the lowest bedrock south of the dam varies from 200 

to 225 feet (plate 1). If Daguerre Point Dam is removed to 

improve fish passage, the Yuba River could attempt to reestablish its original channel course to the south of Daguerre 

Point, eroding hydraulic mine debris and dredge tailings. The 

northern abutment of Daguerre Dam is anchored in an excavated portion of an older natural levee along the right bank of 

the Yuba River. Prior to construction of Daguerre Point Dam, 

the older channel turned south and flowed around the more 

resistant topographic high point of Daguerre Point. During 

flood stage in 1997, the Yuba River flowed both over and 

around Daguerre Point Dam and through the Yuba Goldfields 

following the older channel. About one mile south of Daguerre 

Point, the ancestral Yuba River flowed southwest to west, 

through a deep narrow gorge (plate 1, fig. 3). Reconstruction 

of the contour lines for the bedrock surface using the historical 

drill-hole data, together with results of this study, shows a geologically controlled bend to the southwest that has apparently 

contributed to the deep incision of the older channel during its 

early history. 

Downstream of Daguerre Point Dam, coarse gravels and 

cobbles are found within the training walls, and in buried 

lenses upstream of the dam and throughout the dredged 

portion of the goldfields. The coarse, unconsolidated gravel 

deposits typically have a high hydraulic conductivity, which 

allows rapid seepage of ground water. Ground-water seepage through the training walls may affect flow in the main 

channel of the Yuba River. One possibility is that subsurface 

flow occurs along the bedrock-gravel contact and (or) through 

coarse gravel lenses in a deeper channel (the former river 

channel) to the south of the present channel. The flow in the 

deeper channel re-enters the main channel of the lower Yuba 

River approximately 1 to 1.5 miles downstream of Daguerre 

Point Dam.

42 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California

of Hg-methylation activity and an increase in MeHg concentration. Although this is speculative (higher Hg-methylation 

potentials were also seen at the deeper depth for drill-hole 

DPD-5), the discussion is relevant to the situation that might 

occur should the sediments be dredged, excavated, or eroded 

as part of a fish passage improvement project. 
Comparing drill-hole data from this USGS report with 

historical drill-hole data and bedrock contour maps indicates a wide range of distribution in the types of previously 

mined sediments stored upstream of the Daguerre Point Dam. 

Hydraulic mine tailings contain the highest concentration of 

mercury and gold-amalgam and, therefore, should be of greatest concern for downstream transport. Fine-grained lenses of 

hydraulic mine sediments buried by dredge tailings may be 

remobilized if the relatively coarse-grained dredge tailings are 

eroded due to river degradation in response to dam removal

We observed subsurface flows through the previously 

mined, coarse-grained dredge tailings (such as training walls 

and other cobble-rich berms) upstream of the Daguerre Point 

Dam. In response to topographic gradients, subsurface flows 

increase toward the deeper bedrock depression of the ancestral Yuba River channel and toward lower-elevation wetlands 

ponds throughout the Yuba Goldfields. The topographic gradient in the bedrock elevation surface to the south indicates that 

the Yuba River near and upstream of Daguerre Point Dam may 

be a losing stream. A recent water-balance analysis (ENTRIX, 

2003) concluded that some loss of flow may occur from the 

Yuba River channel between Englebright Dam and Marysville, but total flow from the river channel could not be fully 

addressed with available data. The ENTRIX (2003) analysis 

also concluded that additional flow enters the Yuba River 

(either as ungaged surface flow or ground-water flow), resulting in higher flows at Marysville than water balance calculations indicated.

Our recent observations indicate that a substantial portion 

of the fine-grained material has been eroded from the base of 

the training walls used to stabilize the Yuba River channel; 

the fine-grained material has been deposited in isolated ponds 

within the dredged rows of tailings. Removal of Daguerre 

Point Dam may allow velocities to increase and cause the 

Yuba River to scour and migrate back to its original channel in 

the south by undercutting both the training walls and rows of 

dredge tailings. If a new flow path is established, large quantities of debris and tailings would be available for the Yuba 

River to transport downstream, which could either enhance 

or degrade fish habitat, depending on the fish species and the 

sediment transport characteristics.

It is interesting to note that, from October 1905 to October 1906, the total detrital load (mostly hydraulic tailings) of 

the Yuba River near the Daguerre Point Dam location was 

calculated to be 7,200,000 cubic yards and consisted of 31 

percent silt, 26 percent sand, and 43 percent gravel (Gilbert, 

1917). The average grain-size distribution from the six USGS 

drill holes (residual sandy fraction plus gravel, table 2) is 6 

percent silt and clay, 49 percent sand, and 45 percent gravel. 

The decrease in silt and increase in sand may be attributed to 

concentration of fines caused by dredging, to stratification of 

sand-silt lenses in settling ponds, and, to a lesser extent, to 

the loss of fine material (silty and clay-silt fractions) during 

drilling. 

Particle-size distribution varies greatly and depends on 

the type of mining and the amount of reworking of hydraulic 

debris and earlier dredge tailings. About 55 percent of the 

sediment stored behind Daguerre Point Dam is sand-size and 

smaller. Because the stratigraphy and particle-size distribution 

is highly variable, there may be a larger proportion of silt and 

clay in sediments throughout the Yuba Goldfields. In general, 

these finer particle sizes contain more mercury and are widely 

distributed in the fluvial tailings upstream of Daguerre Point 

Dam. 

Summary

The Daguerre Point Dam was built in the early 1900s 

to retain mining debris from the hydraulic placer-gold mines 

in the upper Yuba River watershed. The current position of 

the Yuba River behind the Daguerre Point Dam is north of its 

original pre-mining channel and above its prior stream bed 

elevation. At present, the lower Yuba River below Daguerre 

Point Dam has abandoned the training walls constructed in 

the early 1900s and has assumed a meandering course through 

the fluvial tailings. Hydraulic mine tailings from the upper 

Yuba River watershed and local sources, as well as previously 

unmined gravels upstream of the Daguerre Point Dam, were 

dredged almost continually between 1904 and 1968; some 

areas were dredged multiple times to progressively increasing depth. Mercury and gold-amalgam lost from previous 

hydraulic mining operations have been recovered since 1904 

by dredging, which has been the principal method of mining 

in the Yuba Goldfields. More than 1 billion cubic yards of 

gold-bearing gravel have been dredged in the Yuba Goldfields. 

Dredging was active until 2003, when this activity stopped 

because of a sunken dredge.

Drill-hole data from this study compared with historical 

drill-hole data and bedrock elevation contour maps indicate 

a wide range of distribution in the types of previously mined 

sediments stored behind Daguerre Point Dam. About 55 percent of sediment presently stored upstream of Daguerre Point 

Dam is sand size or smaller. The highest concentrations of 

mercury are associated with the finer particle sizes, especially 

in the residual (undredged) hydraulic mine tailings. These tailings are thickest closest to the dam and attenuate with depth 

upstream from USGS drill-hole DPD-2 to DPD-3. 

Typically, the surface of the exposed gravel bars and the 

bed of the Yuba River upstream of Daguerre Point Dam are 

well armored with coarse gravel to a depth of several feet. 

Hydraulic mine tailings stored upstream of the dam can be 

transported during flood stage. Although most of the fine particles pass over the dam, some consisting of the heaviest minerals, including gold and gold-mercury amalgam, can become 

trapped in the interstices of the gravel. The remnant portions 

of the training walls upstream of the dam contain some of the 

earliest dredged material and continue to supply fine-grained 

sediment to the river bed as they erode. 

Concentrations of mercury and several other trace elements in the fine-grained sediment trapped behind Daguerre 

Summary 43
Point Dam are of potential environmental concern. Median 

concentration values of arsenic, chromium, copper, and nickel 

in clay-silt separates (less than 0.060 millimeter) were higher 

than consensus threshold effects levels for ecological toxicity; 

maximum concentrations of lead, mercury, and zinc were also 

above the threshold effects levels. Total mercury concentrations were 3 to 30 times higher in fine-grained fraction than in 

the sandy fraction. Although concentrations of methylmercury 

are relatively low in sediments trapped behind Daguerre Point 

Dam, there is a potential for converting a significant portion 

of inorganic mercury to methylmercury if these sediments are 

released to the lower Yuba River below Daguerre Point as a 

consequence of fish passage improvement projects. Oxidation 

of reduced sulfur in the sediments would produce aqueous sulfate; given the right environmental conditions, the additional 

sulfate could stimulate sulfate-reducing bacteria, which are 

thought to be the principal microbes that methylate mercury. 

Additional testing is needed to make more quantitative predictions of the consequences of sediment remobilization in this 

system. 

References Cited

Alpers, C.N., and Hunerlach, M.P., 2000, Mercury contamination from historic gold mining in California: U.S. Geological Survey Fact Sheet 061-00, 6 p., also available at 

http://ca.water.usgs.gov/mercury/fs06100.html.

Alpers, C.N., Taylor, H.E., and Domagalski, J.L. eds., 2000, 

Metals transport in the Sacramento River, California, 

1996–97. Volume 1. Methods and Data: U.S. Geological 

Survey Water-Resources Investigations Report 99-4286, 

429 p., also available at http://water.usgs.gov/pubs/wri/

wrir_994286/.

American Public Health Association, 1981, Section 209G: 

Volatile and fixed matter in nonfilterable residue and in 

solid and semisolid samples, in Franson, M.A.H., ed., Standard Methods form the Examination of Water and Wastewater (15th ed): Washington, D.C., American Water Works.

Ashley, R.P., Rytuba, J.J., Rogers, Ronald, Kotlyar, B.B., 

and Lawler, David, 2002, Preliminary report on mercury 

geochemistry of placer gold dredge tailings, sediments, 

bedrock, and waters in the Clear Creek Restoration Area, 

Shasta County, California. U.S. Geological Survey OpenFile Report 02-401, 47 p.

Aubrey, L.E., 1910, Gold dredging in California: California 

State Mining Bureau, Bulletin 57, 312 p.

Bureau of Land Management, 2001, Land status map of the 

Yuba Goldfields: Bureau of Land Management, Folsom 

Field Office, 63 Natoma Street, Folsom, Calif.

California Department of Water Resources, 2003, Daguerre 

Point Dam – Yuba River, in Fish passage improvement: An 

element of CALFED’s Ecosystem Restoration Program: 

Bulletin 250-2002, Public Review Draft, v. 2, p. 4-15 to 4-

16, also available at http://www.isi.water.ca.gov/fish/ChapterFront/Front%20Matter.pdf.

California State Water Resources Control Board, 2003, Order 

vacating Water Right Decision 1644 and adopting revised 

Water Right Decision 1644 following consideration of additional evidence specified by Yuba County Superior Court, 

Order WR 2003-0016, 57 p., also available at http://www.

waterrights.ca.gov/hearings/WaterRightOrders/WRO2003-

16.pdf.

Churchill, R.K., 2000, Contributions of mercury to California’s environment from mercury and gold mining activities: 

Insights from the historical record, in Extended abstracts for 

the U.S. EPA sponsored meeting, Assessing and managing mercury from historic and current mining activities, 

November 28-30, 2000, San Francisco, Calif. p. 33-36 and 

S35-S48.

Compeau, G.C., and Bartha, R., 1985, Sulfate-reducing bacteria: Principal methylators of mercury in anoxic estuarine 

sediment: Applied and Environmental Microbiology, v. 50, 

no. 2, p. 498-502.

De Wild, J.F., Olson, M.L., and Olund, S.D., 2002, Determination of methyl mercury by aqueous phase ethylation, followed by gas chromatographic separation with cold vapor 

atomic fluorescence detection: U.S. Geological Survey 

Open-File Report 01-455, 14 p., also available at http://

wi.water.usgs.gov/pubs/ofr-01-445/ofr-01-445.pdf. 

ENTRIX, 2003, Daguerre Point Dam Fish Passage Improvement Project, 2002 Water Resources Studies, prepared for 

California Department of Water Resources and U.S. Army 

Corps of Engineers, Stakeholder Review Draft, June 2003, 

47 p.

Farrar, J.W. 1998, Results of the U.S. Geological Survey’s 

analytical evaluation program for standard reference water 

samples: T-153 (trace constituents), M-146 (major constituents), N-57 (nutrient constituents), N-58 (nutrient 

constituents), P-30 (low ionic strength constituents), GWT-3 

(ground -water major constituents), and Hg-26 (mercury) 

distributed in April 1998: U.S. Geological Survey Open-File 

Report 98-391, 160 p. 

Gilbert, G.K., 1917, Hydraulic-mining debris in the Sierra 

Nevada: U.S. Geological Survey Professional Paper 105, 

154 p.

Gilmour, C.C., Henry, E.A., and Mitchell, R., 1992, Sulfate 

stimulation of mercury methylation in freshwater sediments: 

Environmental Science and Technology, v. 26, p. 2281-

2287.

44 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California
Hagwood, J.J., 1981, The California Debris Commission: 

A history of the hydraulic mining industry in the western 

Sierra Nevada of California, and of the government agency 

charged with its regulation: Prepared for the U.S. Army 

Corps of Engineers, Sacramento, Calif., 102 p. 

Hintelmann, H., 1999, Comparison of different extraction 

techniques used for methylmercury analysis with respect 

to accidental formation of methylmercury during sample 

preparation: Chemosphere, v. 39, p. 1093-1105.

Hintelmann, H., Falter, R., Ilgen, G., and Evans, R.D., 1997, 

Determination of artifactual formation of monomethylmercury in environmental samples using stable Hg2+ isotopes 

with ICP-MS detection-calculation of contents applying 

species specific isotope addition: Fresenius’ Journal of Analytic Chemistry, v. 358, p. 363-370.

Hunerlach, M.P., Rytuba, J.J., and Alpers, C.N., 1999, Mercury contamination from hydraulic placer-gold mining in 

the Dutch Flat mining district, California, in Morganwalp, 

D.W., and Buxton, H.T., eds., U.S. Geological Survey Toxic 

Substances Hydrology Program – Proceedings of the Technical Meeting, Charleston, South Carolina, March 8-12, 

1999: U.S. Geological Survey Water-Resources Investigations Report 99-4018B, v. 2, p. 179-190. 

Janin, Charles, 1918, Gold dredging in the United States: U. S. 

Bureau of Mines Bulletin 36, 120 p.

Klasing, Susan, and Brodberg, Robert, 2003, Evaluation of 

potential health effects of eating fish from selected water 

bodies in the northern Sierra Nevada foothills (Nevada, 

Placer, and Yuba Counties): Guidelines for sport fish 

consumption: California Environmental Protection Agency, 

Office of Environmental Health Hazard Assessment, 48 p., 

also available at http://www.oehha.ca.gov/fish/pdf/SierraLakesAdvisoryfinal.pdf.

Lindgren, W., 1911, The Tertiary gravels of the Sierra Nevada 

of California: U.S. Geological Survey Professional Paper 

73, 226 p.

MacDonald, D.D., Ingersoll, C.G., and Berger, T.A. 2000, 

Development and evaluation of consensus-based sediment 

quality guidelines for freshwater ecosystems: Archives of 

Environmental Contamination and Toxicology, v. 39, p. 

20-31.

Marvin-DiPasquale, M., Agee, J., Bouse, R., and Jaffe, B., 

2003, Microbial cycling of mercury in contaminated pelagic 

and wetland sediments of San Pablo Bay, California: Environmental Geology, v. 43, no. 3, p. 260-267.

Marvin-DiPasquale, M., Agee, J., McGowan, C., Oremland, 

R.S., Thomas, M., Krabbenhoft, D., and Gilmour, C., 2000, 

Methylmercury degradation pathways: A comparison 

among three mercury-impacted ecosystems: Environmental 

Science and Technology, v. 34, no. 23, p. 4908-4916.

Marvin-DiPasquale, M.C., and Capone, D.G., 1998, Benthic 

sulfate reduction along the Chesapeake Bay central channel. I. Spatial trends and controls: Marine Ecology Progress 

Series, v. 168, p. 213-228.

Marvin-DiPasquale, M.C., and Oremland, R.S., 1998, Bacterial methylmercury degradation in Florida Everglades peat 

sediment: Environmental Science and Technology, v. 32, no. 

17, p. 2556-2563.

May, J.T., Hothem, R.L., Alpers, C.N., and Law, M.A., 2000, 

Mercury bioaccumulation in fish in a region affected by 

historic gold mining: The South Yuba River, Deer Creek, 

and Bear River Watersheds, California, 1999: U.S. Geological Survey Open File Report 00-367, 30 p., also available 

at http://ca.water.usgs.gov/archive/reports/ofr00367/index.

html.

Mining and Scientific Press, 1905, Control of hydraulic 

mining debris in California by the Federal Government, 

September 2, 1905, p. 152-155 

Olson, M.L., and De Wild, J.F., 1999, Low-level collection 

techniques and species-specific analytical methods for 

mercury in water, sediment, and biota, in Morganwalp, 

D.W., and Buxton, H.T., eds., U.S. Geological Survey Toxic 

Substances Hydrology Program—Proceedings of the Technical Meeting, Charleston, South Carolina, March 8-12, 

1999: U.S. Geological Survey Water-Resources Investigations Report 99-4018B, v. 2, 11 p., also available at http://

wi.water.usgs.gov/pubs/WRIR-99-4018-B/.

Oremland, R.S., Culbertson, C.W., and Winfrey, M.R., 1991, 

Methylmercury decomposition in sediments and bacterial 

cultures: Involvement of methanogens and sulfate reducers in oxidative demethylation: Applied and Environmental 

Microbiology, v. 57, no. 1, p. 130-137.

Oremland, R.S., Miller, L.G., Dowdle, P., Connell, T., and 

Barkey, T., 1995, Methylmercury oxidative degradation 

potentials in contaminated and pristine sediments of the 

Carson River, Nevada: Applied and Environmental Microbiology, v. 61, p. 2745-2753.

Peart, D.B., Antweiler, R.C., Taylor, H.E., Roth, D.A., and 

Brinton, T.I., 1998, Re-evaluation and extension of the 

scope of elements in US Geological Survey Standard Reference Water Samples: Analyst, v. 123, p. 455-476.

Qian, J., and Mopper, K., 1996, Automated high-performance, 

high-temperature combustion total organic carbon analyzer: 

Analytical Chemistry, v. 68, no. 18, p. 3090-3097.

Robinson, J.B., and Tuovinen, O.H., 1984, Mechanisms of 

microbial resistance and detoxification of mercury and 

organomercury compounds: Physiological, biochemical, 

and genetic analyses: Microbiology Reviews, v. 48, no. 2, p. 

95-124.

References Cited 45
Slotton, D. G., Ayers, S.M., Reuter, J.E., and Goldman, C.R., 

1997, Gold mining impacts on food chain mercury in northwestern Sierra Nevada streams (1997 revision), Appendix 

B in Larry Walker Associates, Sacramento River watershed 

mercury control planning project-report for the Sacramento 

Regional County Sanitation District: Sacramento, Calif., 

Larry Walker Associates, 74 p.

Taylor, H.E., 2001, Inductively coupled plasma-mass spectromity: Practices and techniques: Academic Press, San Diego, 

Calif., 294 p.

Ulrich, G.A., Krumholz, L.R., and Suflita, J.M., 1997, A rapid 

and simple method for estimating sulfate reduction activity 

and quantifying inorganic sulfides: Applied and Environmental Microbiology, v. 63, no. 4, p. 1627-1630.

Weatherbe, D’Arcy, 1907, Dredging for gold in California: 

Mining and Scientific Press, 217 p.

Wells, John, 1973, Placer examination—Principles and practice: Bureau of Land Management Technical Bulletin 4, 209 

p.

Yeend, W.E., 1974, Gold-bearing gravel of the ancestral Yuba 

River, Sierra Nevada, California: U.S. Geological Survey 

Professional Paper 772, 44 p.

46 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California
Appendixes

Appendixes 47
Table A1. Drill hole lithology, Daguerre Point Dam, California.

[ft, foot; DPD, Daguerre Point Dam]

Drill hole/Depth

(ft) Date Time Lithology

DPD-1

0–5 8/14/01 1200 sandy gravel with light brown, quartz-rich silt

5–10 8/14/01 1200 sandy gravel with medium brown, quartz-rich silt

10–15 8/14/01 1200 dark brown silty clay with some gravel and increasing black sands; VG observed in fines

15–17.5 8/14/01 1500 reddish brown silty clay and angular greenstone rock, bedrock

DPD-2

0–5 8/15/01 1200 very coarse sand-rich gravel with cobbles

5–10 8/15/01 1400 up to 50 per cent quartz-rich sandy gravel with light brown silty clay

10–13.5 8/15/01 1600 greenstone boulder 

13.5–15 8/16/01 1030 quartz-rich sand with abundant pebbles

15–20 8/16/01 1200 large cobbles with sub-rounded sand and pebbles; some angular fractured gravel

20–25 8/16/01 1330 80 per cent fine-grained silty sand and increasing silt with depth

25–30 8/16/01 1500 silty sand with some gravel and increase in reddish clay 

30–35 8/16/01 1700 quartz-rich sand

DPD-3

0–5 8/20/01 1030 large cobble and gravel with quartz-rich sand

5–10 8/20/01 1100 gravel and quartz-rich sand; some sandy silt

10–15 8/20/01 1330 gravel and sand with reddish brown silty clay

15–20 8/20/01 1500 70-80 per cent sandy silt with some gravel

DPD-4

0–10 8/21/01 1300 compacted quartz-rich sandy gravel with large greenstone fragments

10–15 8/21/01 1530 quartz-rich sandy gravel with iron-stained pebbles; wood at 14.5 feet

15–20 8/22/01 900 20 per cent quartz sand and reddish brown to light brown silt

20–25 8/22/01 1100 sand-rich gravel with 20 per cent sandy silt

25–30 8/22/01 1230 dark reddish brown silty clay with large pebbles; “hardpack” at 28 feet; increase in greenish sand

DPD-5

0–5 8/24/01 1030 gravelly sand

5–10 8/24/01 1130 40 per cent quartz-rich pebbly sand with light brown silty clay

10–15 8/24/01 1430 increasing sand with medium brown silty clay

15–20 8/24/01 1530 quartz-rich sandy silt with increasing greenstone fragments; broke cable at 20 feet

DPD-6

0–5 8/27/01 1530 quartz-rich pebbly sand; light brown silty clay

5–10 8/28/01 930 reddish brown silty clay with quartz pebbles and sand 

10–15 8/28/01 1130 20 per cent quartz pebbles; sand, and reddish brown silty clay

15–20 8/28/01 1330 quartz pebbles, sand, and reddish brown silty clay

20–25 8/28/01 1430 25 per cent sand with pebbles and cobbles; reddish brown silty clay with greenstone rocks

25–30 8/28/01 1530 pebbly sand, increasing dark brown silty clay

Table A2. Physical description of sediments used to determine mercury methylation and demethylation potentials, Daguerre Point 

Dam, California.

[ft, foot; °C, degrees Celsius; DPD, Daguerre Point Dam]

Site

Depth

interval

(ft)

Collection 

date

Subsampling 

date Sample description

Sediment

temperature

(°C)

Incubation

temperature

(°C)

DPD-1 0-5 8/14/01 8/30/01 About a 50–60 percent sandy silt with a gray/white color 18 19

DPD-1 10-15 8/14/01 8/30/01 A silty clay with a high percentage of decomposed greenstone; sample was a reddish brown color and represents 

the gravel/bedrock interface.

18 19

DPD-3 3-5 8/20/01 8/30/01 60-70 percent quartz-rich sandy silt with a gray/white color; 

some pea-gravel and small cobbles.

18 19

DPD-3 15-20 8/20/01 8/30/01 70-80 percent sandy silts with a dark reddish brown color. 18 19

DPD-5 3-5 8/24/01 8/30/01 Pebbly sand with light brown silts and clays of which about 

40 percent is a quartz-rich sand.

20 19

DPD-5 15-20 8/24/01 8/30/01 Sandy silt with small pebbles and a high percentage of 

greenstone; at about 17.5 ft, large angular boulders of 

greenstone were encountered (probably bedrock of the 

Daguerre Point outcrop near the drill hole).

20 19

DPD-6 25-30 8/27/01 8/30/01 Pebbly sand with reddish brown silty clays and lots of 

broken greenstone rock.

unknown 19

Appendix A. Description of Drill Sites, Daguerre Point Dam, California

48 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California
Table B1. Particle-size distribution of the sandy fraction plus gravel for sizes ranging from 75 millimeters to 0.075 millimeter, Daguerre 

Point Dam, California.

[DPD, Daguerre Point Dam; ft, foot; mm, millimeter; g, gram; —, no data]

Drill-hole/Depth

(ft) Percentage of particles passing through sieve Sample 

mass

(g)

Screen 

opening size

(mm)

75 50 25 4.75 2.36 1.18 0.60 0.30 0.15 0.075

DPD-1

0–5 — — 95.4 53.1 40.4 31.5 24.5 17.5 9.3 3.8 2,330.9

5–10 — — 78.1 53.4 45.7 40.3 34.3 25.2 17.1 9.3 1,329.5

10–15 — 72.0 67.9 58.8 56.7 54.2 49.9 43.4 34.2 12.9 2,253.6

15–17.5 — — — 97.5 96.8 90.2 82.7 68.9 58.9 29.2 808.2

DPD-2

0–5 — 96.8 89.2 55.9 45.0 37.3 29.3 20.1 13.1 7.5 963.8

5–10 — 97.2 87.1 53.9 37.6 25.2 14.2 6.7 4.1 2.5 1,443.2

10–13.5 94.6 92.8 80.9 55.3 44.2 35.1 21.6 8.3 4.4 2.6 1,535.7

13.5–15 96.7 92.7 90.6 50.3 39 30.7 18.4 6.4 3.2 1.7 1,917.4

15–20 — 99.2 93.1 59.2 43 28.7 14.8 6.2 2.9 1.5 1,476.8

20–25 — 98.0 81.4 35.1 23.5 14.2 7.1 3.6 2.1 1.2 1,448.8

25–30 99.7 99.1 86.8 77.0 71.8 65.3 54.4 37.4 18.3 7.9 1,047.6

30–35 — — — — 99.9 99.6 97.9 82.5 45.9 18.7 573.1

DPD-3

0–5 97.8 90.9 80.8 42.9 30.3 20.5 10.8 5.3 3.0 1.5 1,294.1

5–10 98.0 94.6 84.2 46.8 36.4 27.5 15.3 7.6 4.5 2.5 1,849.8

10–15 97.1 89.6 71.0 50.1 47.5 44.7 36.2 14.6 6.2 2.5 1,761.2

15–20 99.6 97.5 92.7 85.4 81.7 75.8 61.9 22.9 7.8 3.5 1,488.9

DPD-4

0–10 — 93.4 81.5 45.1 33.8 25.9 17.2 9.9 6.2 3.5 2,319.5

10–15 — 99.0 88.1 45.7 36.6 32.3 25.1 8.8 4.1 2.1 2,107.9

15–20 — 95.0 94.0 58.6 50.0 45.9 39 16.2 8.5 3.7 2,028.9

20–25 — 98.1 95.1 15.1 6.6 4.0 3.2 2.5 1.7 1.0 2,527.9

25–30 — 98.9 97.7 75.1 65.9 55.1 45.3 30.6 17.9 8.8 2,571.2

DPD-5

0–5 — — 98.96 61.53 43.49 33.13 25.21 16.56 10.51 5.94 1,516.5

5–10 — 99.26 95.5 47.92 36.49 29.82 23.55 15.02 9.26 5.28 1,058.7

10–15 — — 86.49 65.76 55.99 49.03 40.53 27.16 18.52 11.81 1,192.5

15–20 — — — 34.01 8.83 1.57 1.29 1.03 .78 .59 282.8

DPD-6

0–5 — 99.55 98.19 52.52 39.55 32.05 26.74 21.05 16.07 10.63 1,942.4

5–10 — 15.84 89.6 51.97 39.37 30.22 22.2 13.39 7.04 2.65 1,490.7

10–15 — 99.6 94.55 54.49 46.48 38.49 27.08 12.85 6.53 3.05 2,037.4

15–20 — 99.09 85.92 46.16 36.94 28.67 19.24 9.52 5.32 2.67 1,718.3

20–25 — — 88.06 41.81 30.59 24.22 17.98 11.57 7.13 3.45 2,363.1

25–30 — 95.71 76.88 27.07 20.98 15.42 8.51 3.06 1.45 .79 1,826.0

Appendix B. Particle-Size Distribution of Sediments, Daguerre Point Dam, California

Appendixes 49
Table B2. Particle-size distribution of the sandy fraction from 4 millimeters to 0.00025 millimeter, Daguerre Point Dam, California.

[DPD, Daguerre Point Dam; ft, foot; mm, millimeter]

Drill-hole/ 

Depth

(ft) 

Percentage of particles passing through sieve and sedigraph

Screen

opening size 

(mm)

Sieve Sedigraph

4 2 1 0.5 0.25 0.125 0.063 0.045 0.032 0.024 0.016 0.012 0.008 0.006 0.004 0.003 0.002 0.001 0.0005 0.00025

DPD-1

0–5 100 99.8 82.0 63.6 44.9 27.4 13.9 1.5 1.0 0.7 0.5 0.4 0.3 0.2 0.2 0.1 0.1 0.0 0.0 0.0

5–10 100 99.9 85.3 65.6 44.3 30.2 18.6 2.6 1.9 1.5 1.1 .9 .6 .5 .5 .4 .3 .2 .1 .0

10–15 100 99.9 87.1 72.4 57.9 45.0 28.1 5.9 3.9 2.8 1.9 1.6 1.3 1.1 1.0 .9 .8 .6 .5 .3

15–17.5 100 99.9 96.8 89.8 77.9 59.7 35.5 10.6 8.6 7.3 5.9 5.3 4.5 3.9 3.4 3.1 2.6 1.9 1.4 1.1

DPD-2

0–5 100 99.8 81.7 57.2 32.6 18.0 8.0 0.5 0.4 0.3 0.2 0.2 0.1 0.1 0.1 0.0 0.0 0.0 0.0 0.0

5–10 100 99.8 70.6 37.0 16.9 10.4 6.3 .3 0.3 .2 .2 .1 .1 .1 .1 .0 .0 .0 .0 .0

10–13.5 100 99.9 82.5 44.8 16.0 7.6 4.0 .1 0.1 .1 .1 .1 .0 .0 .0 .0 .0 .0 .0 .0

13.5–15 100 99.6 80.5 41.1 13.3 7.4 4.8 .2 0.2 .2 .1 .1 .1 .1 .1 .0 .0 .0 .0 .0

15–20 100 99.4 68.8 29.4 9.1 4.1 2.6 .1 0.1 .1 .0 .0 .0 .0 .0 .0 .0 .0 .0 .0

25–30 100 99.9 91.0 77.0 50.3 20.0 5.8 .3 0.2 .2 .1 .1 .1 .1 .1 .1 .0 .0 .0 .0

30–35 100 100.0 99.6 96.8 78.6 49.8 26.7 6.1 4.5 3.5 2.6 2.2 1.6 1.4 1.1 .9 .7 .4 .2 .2

DPD-3

0–5 100 99.4 70.4 36.1 18.2 10.0 4.4 0.2 0.1 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

5–10 100 99.8 75.3 35.9 17.1 10.3 5.7 .3 0.2 .2 .1 .1 .1 .1 .1 .0 .0 .0 .0 .0

10–15 100 99.9 90.1 61.3 23.0 13.3 7.3 .5 0.4 .3 .2 .2 .2 .1 .1 .1 .1 .1 .0 .0

15–20 100 100.0 94.3 76.6 31.7 14.9 8.7 .7 0.6 .5 .4 .4 .3 .2 .2 .1 .1 .1 .0 .0

DPD-4

0–10 100 99.7 78.0 40.9 16.9 8.3 3.3 0.1 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

10–15 100 99.9 86.9 58.4 13.6 5.9 2.4 .1 0.0 .0 .0 .0 .0 .0 .0 .0 .0 .0 .0 .0

15–20 100 100.0 93.2 75.7 29.7 13.1 4.2 .1 0.1 .1 .1 .0 .0 .0 .0 .0 .0 .0 .0 .0

20–25 100 99.7 62.5 36.4 18.8 8.9 4.1 .1 0.1 .1 .1 .1 .0 .0 .0 .0 .0 .0 .0 .0

25–30 100 99.8 82.4 59.3 33.0 16.6 8.4 .6 0.4 .3 .3 .2 .2 .2 .1 .1 .1 .0 .0 .0

DPD-5

0–5 100 99.9 76.9 49.3 24.0 11.4 5.9 0.3 0.2 0.2 0.1 0.1 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0

5–10 100 99.9 80.9 52.9 23.6 11.2 6.2 .3 0.3 .2 .2 .2 .1 .1 .1 .1 .0 .0 .0 .0

10–15 100 99.9 86.4 59.7 28.3 16.1 8.4 .6 0.4 .3 .2 .2 .1 .1 .1 .1 .0 .0 .0 .0

15–20 100 99.8 94.6 78.7 48.7 24.5 4.7 .2 0.1 .1 .1 .0 .0 .0 .0 .0 .0 .0 .0 .0

DPD-6

0–5 100 99.6 79.5 56.8 34.7 19.3 8.9 0.6 0.4 0.3 0.2 0.1 0.1 0.1 0.1 0.1 0.0 0.0 0.0 0.0

5–10 100 99.7 82.1 58.7 34.4 17.5 6.2 .3 0.2 .1 .1 .1 .0 .0 .0 .0 .0 .0 .0 .0

10–15 100 99.7 78.5 45.8 14.6 5.7 2.7 .1 0.0 .0 .0 .0 .0 .0 .0 .0 .0 .0 .0 .0

15–20 100 100.0 79.2 50.8 25.2 14.9 7.8 .5 0.4 .3 .2 .2 .2 .1 .1 .1 .1 .0 .0 .0

20–25 100 99.9 80.7 57.9 36.4 22.3 10.8 1.0 0.8 .6 .5 .5 .4 .3 .3 .2 .2 .1 .1 .1

25–30 100 99.9 75.1 37.9 18.9 15.3 13.6 1.8 1.7 1.6 1.5 1.3 1.1 1.0 .8 .7 .6 .4 .3 .2

50 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California
Table B3. Particle-size distribution of the silty fraction from 2 millimeters to 0.00025 millimeter, Daguerre Point Dam, California.

[Initial sample from suspended-sediment overflow (SSO). DPD, Daguerre Point Dam; ft, foot; mm, millimeter]

Drill hole/

Depth

(ft)

Percentage of particles passing through sieve and sedigraph

Screen

opening size

(mm)

Sieve Sedigraph

2 1 0.5 0.25 0.125 0.063 0.045 0.032 0.024 0.016 0.012 0.008 0.007 0.004 0.003 0.002 0.001 0.0005 0.00025

DPD-2

0–5 100 100 100 100 100 100 100 98 97 94 89 79 70 56 47 35 21 12 6

5–10 100 100 100 100 100 100 100 99 98 93 88 79 70 57 47 36 21 11 5

15–20 100 100 100 100 100 99 99 98 97 94 90 83 75 64 56 45 32 22 12

20–25 100 100 100 100 100 98 95 94 92 86 81 73 66 58 52 45 33 23 13

25–30 100 100 100 100 99 95 94 92 87 76 66 52 44 35 29 24 17 12 8

30–35 100 100 100 100 100 98 98 98 96 88 78 62 52 39 33 26 18 13 9

DPD-3

15–20 100 100 100 100 100 98 99 99 98 98 98 96 94 91 88 85 80 77 75

DPD-4

10–15 100 100 100 100 99 96 95 91 88 84 77 69 62 52 44 38 26 18 13

15–20 100 100 100 100 99 94 91 87 82 74 70 60 54 46 42 36 28 19 11

DPD-5

0–5 100 100 100 100 100 100 99 99 98 98 98 96 94 91 88 85 80 77 75

5–10 100 100 100 100 100 99 100 100 100 100 99 94 87 74 64 51 33 21 9

10–15 100 100 100 100 100 98 98 97 93 85 77 65 55 41 32 23 13 9 3

15–20 100 100 100 100 100 98 100 100 100 99 99 94 88 76 66 53 33 17 2

DPD-6

0–5 100 100 100 100 100 99 98 97 93 85 77 65 55 41 32 23 13 9 3

5–10 100 100 100 99 97 94 100 100 100 99 99 94 88 76 66 53 33 17 2

10–15 100 100 100 100 99 96 100 100 100 99 98 93 85 74 65 53 36 24 12

15–20 100 100 100 100 100 99 100 100 99 96 93 88 82 71 62 50 34 21 12

20–25 100 100 100 100 100 98 98 96 94 89 82 71 63 51 44 36 25 18 12

25–30 100 100 100 99 94 89 100 99 98 95 91 83 74 61 52 41 25 15 7

Appendixes 51
Table B4. Particle-size distribution of the clay-silt fraction from 2 millimeters to 0.00025 millimeter, Daguerre Point Dam, California.

[Initial 2-millimeter separation from SWECO stainless steel vibratory separator. DPD, Daguerre Point Dam; ft, foot; mm, millimeter]

Drill hole/

Depth

(ft)

Percentage of particles passing through sieve and sedigraph

Screen

opening size

(mm)

Sieve Sedigraph

2 1 0.5 0.25 0.125 0.063 0.045 0.032 0.024 0.016 0.012 0.008 0.006 0.004 0.003 0.002 0.001 0.0005 0.00025

DPD-2

20–25 100 100 100 100 100 100 100 100 99 99 98 96 93 90 84 75 54 36 20

25–30 100 100 99 96 84 71 70 67 63 54 47 38 32 26 22 17 12 9 6

30–35 100 100 100 100 99 95 95 93 88 79 73 66 62 58 56 54 51 49 47

DPD-3

0–5 100 100 100 100 100 100 99 99 98 98 98 96 94 91 88 85 80 77 75

5–10 100 100 100 100 100 100 100 100 100 99 99 97 90 78 67 53 34 20 9

10–15 100 100 100 100 100 100 100 100 100 100 99 94 87 74 64 51 33 21 9

15–20 100 100 100 100 100 99 98 93 86 75 64 51 41 28 23 16 8 3 0

DPD-4

10–15 100 100 100 100 100 100 100 100 100 99 99 94 88 76 66 53 33 17 2

15–20 100 100 100 100 100 100 100 100 100 99 98 93 85 74 65 53 36 24 12

20–25 100 100 100 100 100 100 100 100 99 98 98 94 87 74 64 50 35 23 13

25–30 100 100 100 100 100 100 100 100 99 96 93 88 82 71 62 50 34 21 12

DPD-5

0–5 100 100 100 100 100 100 100 99 99 97 91 75 63 49 40 30 20 12 6

5–10 100 100 100 100 100 100 100 100 100 99 99 95 90 80 72 59 41 25 13

10–15 100 100 100 100 100 100 99 100 99 99 96 91 84 72 64 52 35 21 11

15–20 100 100 100 100 100 100 100 100 99 94 88 78 71 61 56 49 41 34 26

DPD-6

0–5 100 100 100 100 100 100 98 97 93 83 74 61 51 39 32 23 13 7 4

5–10 100 100 100 100 100 100 100 99 97 92 87 74 65 52 43 33 20 12 6

10–15 100 100 100 100 100 100 100 99 98 95 91 84 76 65 56 45 31 20 13

15–20 100 100 100 100 100 100 100 99 96 90 83 71 62 50 43 34 24 16 10

20–25 100 100 100 100 100 99 99 97 95 88 81 69 60 49 42 33 24 17 11

25–30 100 100 99 95 89 82 82 80 77 71 65 56 48 39 34 27 20 14 9

52 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California
Table B5. Silty fraction suspended-sediment concentrations, 

Daguerre Point Dam, California.

[ft, foot; mg/L, milligram per liter; DPD, Daguerre Point Dam]

Drill hole/Depth

(ft)

Sediment concentration

(mg/L)

DPD-2

20–25 2,400

25–30 116,000

30–35 79,500

DPD-3

0–5 2,400

5–10 5,000

10–15 12,400

15–20 147,600

DPD-4

0–10 6,100

10–15 7,200

15– 20 6,100

20–25 7,100

25–30 19,300

DPD-5

0–5 10,800

5–10 10,400

10–15 18,600

15–20 40,000

DPD-6

0–5 30,400

5–10 9,400

10–15 13,800

15–20 33,400

20–25 100,500

25–30 254,400

Appendixes 53
Drill Hole/

Depth

(ft)

Total 

weight

(g)

Particle sizes (mm) Number of 

gold grains 

observed

Estimated gold 

weight

(mg)

Gold grade/

tenor

(mg/yd3)

1 to 2

(percent)

0.5 to 1.0

(percent)

0.25 to 0.50

(percent)

0.063 to 0.25

(percent)

< 0.063

(percent)

DPD-1

0–5 6.7 0.0 0.0 10.0 85.0 5.0 1 Trace 11

5–10 11.2 .0 .0 7.0 91.0 2.0 23 2.1 120

10–15 31.7 .0 2.0 4.0 90.0 4.0 115 4.4 170

15–17.5 11.3 .0 .0 1.0 94.0 5.0 17 1.9 160

DPD-2

0–5 15.5 0.0 2.0 15.0 81.0 2.0 17 1.1 76

5–10 46.8 .2 1.0 35.0 63.0 1.0 7 .1 2

10–13.5 28.3 .0 1.0 29.0 69.0 1.0 10 1 40

13.5–15 38.2 .3 1.0 22.0 76.0 1.0 12 1 16

15–20 64.6 .0 1.0 22.0 76.0 1.0 25 3.2 75

20–25 50.1 .0 1.0 24.0 74.0 1.0 19 1.8 45

25–30 666.9 .0 .0 25.0 74.0 1.0 43 1.9 19

30–35 81.5 .0 .0 3.0 95.0 2.0 1 .3 7

DPD-3

0–5 17 1.0 1.0 33.0 64.0 1.0 8 0.2 11

5–10 61.1 1.0 2.0 34.0 62.0 1.0 16 2.1 44

10–15 129.4 .0 .0 7.0 91.0 2.0 15 1.4 31

15–20 367.3 .0 .0 52.0 47.0 1.0 15 .8 9

DPD-4

0–10 42.5 0.0 1.0 33.0 65.0 1.0 8 0.5 16

10–15 44.3 .0 1.0 21.0 77.0 1.0 15 1 20

15–20 28 .0 2.0 2.0 95.0 1.0 25 2.3 90

20–25 4 .0 .0 3.0 94.0 3.0 6 .1 3

25–30 109.9 1.0 1.0 33.0 64.0 1.0 6 Trace 11

DPD-5

0–5 17.6 0.0 0.6 12.5 82.4 1.1 15 0.8 80

5–10 61.4 .2 .5 14.5 81.3 2.0 23 1.1 60

10–15 25.2 .4 .4 4.8 90.9 2.8 14 1 72

15–20 0 0 0 0 0 0 0 0 0

DPD-6

0–5 27.1 0.0 0.7 5.2 91.5 1.5 6 0.2 14

5–10 23.5 .0 .4 3.8 94.9 .9 4 Trace 11

10–15 69.2 .0 .3 36.3 62.3 .4 3 Trace 11

15–20 52.1 .0 .2 52.4 45.9 .4 5 .2 4

20–25 18.7 .0 .5 17.1 80.7 .5 3 .1 6

25–30 16.8 .0 .6 44.0 55.4 .6 6 Trace 11

1

 Assigned a value of 1.

Table C1. Particle-size distribution and gold tenor of heavy mineral concentrates, Daguerre Point Dam, California.

[DPD, Daguerre Point Dam. ft, foot; g, gram; mm, millimeter; mg, milligram; mg/yd3, milligram per cubic yard. <, less than]

Appendix C. Particle-Size Distribution and Microscopic Observations of Heavy Minerals, Daguerre 

Point Dam, California

54 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California
Drill Hole/

Depth

(ft)

Number of 

gold grains 

observed

Estimated 

gold weight

(mg)

Gold Mercury Amalgam 

(gold-mercury) Pyrite Magnetite Garnets (0.5-1 mm) Chromite

Other 

(ilmenite, 

zircon, 

sphene)

DPD-1

0–5 1 Trace F — x xxx x x x x

5–10 23 2.1 F-UF — — x x x x x

10–15 115 4.4 1-C, F-UF — — x xx x x xx

15–17.5 17 1.9 F-UF — — x x xx x xxx

DPD-2

0–5 17 1.1 VF — — x x x x x

5–10 7 .1 VF — — x xx x x x

10–13.5 10 1 F-VF — — xx x x x x

13.5–15 12 1 F-UF — — xx xx x x x

15–20 25 3.2 C-UF — x xxx xx x x x

20–25 19 1.8 F-UF — — x xx xx xx x

25–30 43 1.9 F-UF x xxx x xxx x xxx x

30–35 1 .3 C — x xx xx — xx —

DPD-3

0–5 8 0.2 F-VF — — xx x xx x x

5–10 16 2.1 F-VF — x xx xx xxx xx x

10–15 15 1.4 C-VF — x x xxx — xxx x

15–20 15 .8 F-VF — xx x xxx x xxx xx

DPD-4

0–10 8 0.5 F-VF — — xxx xx xx x x

10–15 15 1 F-VF — — xx xx x x x

15–20 25 2.3 F-VF — — x x — x x

20–25 6 .1 VF — — xxx x — x x

25–30 6 Trace VF — — x xxx x xxx x

DPD-5

0–5 15 0.8 F-UF — — xx x x x x

5–10 23 1.1 F-VF — — x xx x x x

10–15 14 1 F-VF — — x x x x xxx

15–20 0 0

DPD-6

0–5 6 0.2 VF — — x x — x x

5–10 4 Trace VF — — x x — x x

10–15 3 Trace UF — — x xx x x x

15–20 5 .2 UF — — x xx — x x

20–25 3 .1 F-UF — — xx x x x x

25–30 6 Trace VF — — xx x — x x

Table C2. Microscopic observations of heavy mineral concentrates, Daguerre Point Dam, California.

[DPD, Daguerre Point Dam. Observations: X, trace; XX, abundant; XXX, very abundant; C, coarse; F, fine; VF, very fine; UF, ultra fine. mg, milligram, mm, 

millimeter; —, not observed]

Appendixes 55
Field measurements

Site Time pH

Specific

conductance

(μS/cm)

Dissolved 

oxygen

(mg/L)

Temperature

(°C)

Yuba River at Daguerre Point Dam 15:00 6.7 72 11.2 18

Laboratory measurements

Site Time Replicate

Total mercury, 

filtered

(ng/L)

CO

SD

(ng/L)

Total mercury, 

unfiltered

(ng/L)

CO

SD

(ng/L)

Methylmercury, 

filtered

(ng/L)

WI

Methylmercury, 

unfiltered

(ng/L)

WI

Yuba River at Daguerre Point Dam 15:00 1 of 2 0.5 0.1 1.0 0.2 <0.04 <0.04

Yuba River at Daguerre Point Dam 15:00 2 of 2 .7 .1 1.1 .1 n.d. n.d.

Method detection limit .4 .4 .04 .04

Table D1. Chemistry of Yuba River water used during drilling near Daguerre Point Dam, California, August 24, 2001.

[Laboratory location: CO, Colorado; WI, Wisconsin. μS/cm, microSiemens per centimeter; mg/L, milligram per liter; °C, degrees Celsius; SD, standard deviation of triplicate analyses; ng/L, nanogram per liter; n.d., not determined; <, less than]

Table D2. Mercury concentrations of blanks taken during drilling, August 28, 2001, Daguerre Point 

Dam, California.

[Analyses done at U.S. Geological Survey laboratory in Boulder, Colorado. SD, standard deviation of triplicate analyses; 

SWECO, manufacturer of vibratory separator; ng/L, nanogram per liter; <, less than; —, not applicable]

Time

Total mercury

unfiltered

(ng/L)

SD

(ng/L)

Total mercury, 

filtered

(ng/L)

SD

(mg/L)

Equipment blank–stainless steel trough 16:00 2.3 0.1 — —

Equipment blank–5-gallon plastic bucket 16:02 <.4 .2 — —

Equipment blank–25-gallon plastic tub 16:04 .4 .3 — —

Equipment blank–SWECO vibratory screen 16:06 2.1 .1 — —

Process blank 16:08 — — 1.3 .0

Table D3. Mercury concentrations in standard reference water samples, blanks, and spikes, Daguerre Point Dam, California.

[Analyzed at U.S. Geological Survey research laboratory in Boulder, Colorado. SD, standard deviation; ng/L, nanogram per liter; na, not available]

Number 

of

observations

Analyzed Most probable value

Reference or comment Total

mercury

(ng/L)

SD

(ng/L)

Total

mercury

(ng/L)

SD

(ng/L)

Standard reference water sample

Hg-7 25 237 23 240 na Peart and others (1998)

Hg-15 32 388 20 390 na Peart and others (1998)

Hg-26 29 698 27 700 90 Farrar (1998)

Laboratory blanks

1.2 0.2

.7 .1

.6 .1

.2 .1

Spike

5-ng/L spike of laboratory blank 5.14 recovery = 103 percent

Appendix D. Quality Assurance and Quality Control Data for USGS Laboratories, Daguerre Point 

Dam, California

56 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California
Table D4. Results for trace and major elements in standard reference material, Daguerre Point Dam, California.

[Avg, average of three replicate analyses; SD, standard deviation; Wt%, weight percent; μg/g, microgram per gram; na, not applicable]

Field ID

Al

Aluminum

Wt%

As

Arsenic

μg/g

Au

Gold

μg/g

B

Boron

μg/g

Ba

Barium

μg/g

Be

Beryllium

μg/g

Bi

Bismuth

μg/g

Ca

Calcium

Wt%

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

Buffalo River Sediment 2704 5.6 0.1 24 0 0.019 0.002 128 1 304 3 2.0 0.1 0.65 0.04 1.6 0.1

Buffalo River Sediment 2704 4.7 .2 22 1 .012 .003 233 10 353 1 1.6 .1 .64 .05 2.0 .0

Buffalo River Sediment 2704 5.3 .2 23 1 .012 .000 215 6 363 2 1.9 .1 .67 .03 1.9 .1

Buffalo River Sediment 2704 3.5 .1 21 1 .015 .005 183 10 313 6 2.0 .1 .78 .02 1.7 .1

Buffalo River Sediment 2704 3.1 .1 22 0 .011 .002 135 15 224 10 1.7 .1 .58 .01 2.3 .0

Buffalo River Sediment 2704 5.3 .2 21 0 .011 .000 212 5 387 12 1.7 .0 .62 .02 2.4 .1

Average 4.6 1.0 22 1.2 .013 .0 184 44 324 58 1.8 .2 .66 .07 2.0 .3

Buffalo River Sediment 

(Bold numbers, certified) 6.11 .16 23.4 .8 na na na na 414 12 na na na na 2.60 .03

Field ID

Cd

Cadmium

μg/g

Ce

Cerium

μg/g

Co

Cobalt

μg/g

Cr

Chromium

μg/g

Cs

Cesium

μg/g

Cu

Copper

μg/g

Dy

Dysprosium

μg/g

Er

Erbium

μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

Buffalo River Sediment 2704 3.9 0.1 43 1 15 0 139 3 5.9 0.1 105 1 2.0 0.1 1.1 0.0

Buffalo River Sediment 2704 3.7 .1 25 1 14 1 132 1 4.7 .0 101 1 2.8 .0 1.5 .0

Buffalo River Sediment 2704 3.6 .0 38 0 14 0 133 2 4.3 .0 100 3 2.5 .1 1.3 .0

Buffalo River Sediment 2704 3.5 .0 18 0 13 0 126 5 4.1 .1 98 3 2.1 .1 1.2 .0

Buffalo River Sediment 2704 3.5 .2 27 1 13 1 129 7 2.9 .0 102 0 3.0 .1 1.7 .1

Buffalo River Sediment 2704 3.4 .0 37 0 13 0 121 2 3.3 .0 99 1 2.6 .0 1.4 .0

Average 3.6 .2 31 10 14 1 130 6 4.2 1.1 101 3 2.5 .4 1.4 .2

Buffalo River Sediment 

(Bold numbers, certified)

3.45 .22 72 na 14.0 .6 135 5 6 na 99 5 6 na na na

Field ID

Eu

Europium

μg/g

Fe

Iron

Wt%

Ga

Gallium

μg/g

Gd

Gadolinium

μg/g

Ho

Holmium

μg/g

K

Potassium

Wt%

La

Lanthanum

μg/g

Li

Lithium

μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

Buffalo River Sediment 2704 0.52 0.03 4.3 0.3 15 0 2.0 0.2 0.39 0.01 2.0 0.1 14 0 46 1

Buffalo River Sediment 2704 .74 .02 3.9 .2 14 1 3.1 .2 .54 .01 2.0 .0 14 0 41 2

Buffalo River Sediment 2704 .70 .03 4.1 .0 14 0 2.7 .1 .46 .00 2.0 .1 16 0 42 0

Buffalo River Sediment 2704 .55 .03 3.9 .2 13 0 2.3 .0 .40 .01 1.8 .1 9.0 .2 41 0

Buffalo River Sediment 2704 .73 .00 4.1 .2 13 0 2.9 .0 .60 .03 1.2 .1 11 0 39 1

Buffalo River Sediment 2704 .77 .02 4.2 .1 13 0 2.8 .0 .53 .01 1.9 .0 16 0 36 1

Average .67 .11 4.1 .2 14 1 2.6 .4 .49 .08 1.8 .3 13 3 41 3

Buffalo River Sediment 

(Bold numbers, certified)

1.3 na 4.11 0.10 15 na na na na na 2.00 .04 29 na 47.5 4.1

Field ID

Lu

Lutetium

μg/g

Mg

Magnesium

Wt%

Mn

Manganese

μg/g

Mo

Molybdenum

μg/g

Na

Sodium

Wt%

Nd

Neodymium

μg/g

Ni

Nickel

μg/g

P

Phosphorous

μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

Buffalo River Sediment 2704 0.17 0.00 0.91 0.02 597 36 4.6 0.6 0.52 0.04 12 0 59 1 1,050 34

Buffalo River Sediment 2704 .24 .02 .51 .00 530 31 3.9 .3 .46 .04 16 1 45 3 969 59

Buffalo River Sediment 2704 .21 .01 .62 .01 562 6 4.0 .3 .41 .00 16 0 44 1 1,030 8

Buffalo River Sediment 2704 .19 .00 .16 .01 521 22 3.9 .6 .45 .02 11 0 43 1 964 30

Buffalo River Sediment 2704 .26 .00 .49 .02 550 29 3.9 .6 .55 .02 14 1 42 0 1,050 12

Buffalo River Sediment 2704 .21 .00 1.1 .0 560 11 4.0 .0 .47 .00 18 0 41 1 1,010 9

Average .21 .03 .62 .32 553 27 4.1 .3 .48 .05 15 3 46 7 1,012 38

Buffalo River Sediment 

(Bold numbers, certified)

.6 na 1.20 .02 555 19 na na .547 .014 na na 44.1 3.0 998 28

Appendixes 57
Field ID

U

Uranium

μg/g

V

Vanadium

μg/g

W

Tungsten

μg/g

Y

Yttrium

μg/g

Yb

Ytterbium

μg/g

Zn

Zinc

μg/g

Zr

Zirconium

μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

Buffalo River Sediment 2704 3.1 0.0 103 2 1.7 0.1 9.8 0.2 1.1 0.0 457 9 163 2

Buffalo River Sediment 2704 3.0 .0 96 5 1.5 .0 12 1 1.5 .1 438 6 138 8

Buffalo River Sediment 2704 3.0 .1 97 2 2.5 .0 11 0 1.3 .1 438 12 132 3

Buffalo River Sediment 2704 2.9 .1 91 2 1.5 .1 10 0 1.2 .0 432 14 153 4

Buffalo River Sediment 2704 2.8 .1 91 4 1.6 .1 15 0 1.8 .1 415 8 824 279

Buffalo River Sediment 2704 2.7 .1 90 4 1.4 .1 10 0 1.4 .0 424 3 531 217

Average 2.9 .2 95 5 1.7 .4 11 2 1.4 .3 434 14 323 290

Buffalo River Sediment 

(Bold numbers, certified)

3.13 .13 95 4 na na na na 2.8 na 438 12 300 na

Field ID

Pb

Lead

μg/g

Pr

Praseodymium

μg/g

Rb

Rubidium

μg/g

Re

Rhenium

μg/g

S

Sulfur

Wt%

Sb

Antimony

μg/g

Sc

Scandium

μg/g

Se

Selenium

μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

Buffalo River Sediment 2704 161 4 3.4 0.1 104 0 0.003 0.001 0.47 0.00 4.2 0.1 6.6 1.1 1.3 0.1

Buffalo River Sediment 2704 178 1 4.1 .0 61 3 <.003 .001 .45 .01 4.1 .2 7.2 .1 1.1 .1

Buffalo River Sediment 2704 167 0 4.3 .0 79 1 .003 .000 .48 .01 3.7 .0 6.9 .6 1.4 .6

Buffalo River Sediment 2704 150 4 2.8 .0 49 2 .004 .001 .43 .00 3.8 .1 4.9 .1 .8 .6

Buffalo River Sediment 2704 147 8 3.4 .1 8.6 .7 .003 .002 .46 .00 3.6 .1 8 0 1.4 .0

Buffalo River Sediment 2704 141 0 4.5 .0 60 0 .002 .002 .45 .02 3.7 .0 11 0 1.8 .1

Average 157 14 3.7 .7 60 32 .002 .002 .46 .02 3.9 .2 7.4 2.0 1.3 .3

Buffalo River Sediment 

(Bold numbers, certified)

161 17 na na 100 na na na .397 .004 3.79 .15 12 na 1.12 .05

Field ID

Sm

Samarium

μg/g

Sr

Strontium

μg/g

Tb

Terbium

μg/g

Te

Tellurium

μg/g

Th

Thorium

μg/g

Ti

Titanium

Wt%

Tl

Thalium

μg/g

Tm

Thulium

μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

Buffalo River Sediment 2704 2.5 0.0 121 2 0.34 0.01 0.14 0.02 6.5 0.1 0.46 0.00 0.88 0.07 0.17 0.00

Buffalo River Sediment 2704 3.5 .2 103 5 .47 .02 .21 .02 7.1 .3 .42 .02 .89 .02 .24 .01

Buffalo River Sediment 2704 3.3 .1 112 3 .42 .01 .18 .01 7.1 .1 .43 .00 .86 .03 .20 .01

Buffalo River Sediment 2704 2.6 .1 106 4 .36 .01 .13 .01 4.6 .0 .42 .02 .81 .00 .18 .00

Buffalo River Sediment 2704 3.2 .0 90 1 .50 .00 .14 .01 4.7 .3 .43 .00 .79 .06 .26 .00

Buffalo River Sediment 2704 3.7 .0 130 1 .45 .02 .18 .05 4.9 .1 .38 .01 .77 .12 .20 .00

Average 3.1 .5 111 14 .42 .06 .16 .03 5.8 1.2 .42 .03 .83 .05 .21 .03

Buffalo River Sediment 

(Bold numbers, certified)

6.7 na 130 na na na na na 9.2 na .457 .018 1.06 .07 na na

Table D4. Results for trace and major elements in standard reference material, Daguerre Point Dam, California.—Continued

[Avg, average of three replicate analyses; SD, standard deviation; Wt%, weight percent; μg/g, microgram per gram; na, not applicable]

58 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California
Table D5. Digestion blanks for trace elements and major elements, Daguerre Point Dam, California.

[Avg, average of three replicate analyses; SD, standard deviation; μg/L, microgram per liter; mg/L, milligram per liter; <, less than]

Field ID

Al

Aluminum

μg/L

As

Arsenic

μg/L

Au

Gold

μg/L

B

Boron

μg/L

Ba

Barium

μg/L

Be

Beryllium

μg/L

Bi

Bismuth

μg/L

Ca

Calcium

mg/L

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

Digestion Blank 12 1 <0.1 0.1 <0.004 0.002 <6 4 0.1 0.0 0.04 0.04 0.10 0.03 0.02 0.02 

Digestion Blank 13 2 <.1 .1 <.004 .002 <6 0 .1 .0 <.03 .03 .07 .03 <.02 .01 

Digestion Blank <8 19 .1 .0 <.004 .005 6 3 .3 .5 <.03 .03 .29 .20 .03 .03 

Digestion Blank <8 3 <.1 .1 <.004 .001 6 6 <.1 .1 <.03 .01 <.02 .002 <.02 .02 

Digestion Blank 311 12 <.1 .1 <.004 .001 <6 5 2.2 .0 <.03 .02 <.02 .005 .06 .03 

Field ID

Cd

Cadmium

μg/L

Ce

Cerium

μg/L

Co

Cobalt

μg/L

Cr

Chromium

μg/L

Cs

Cesium

μg/L

Cu

Copper

μg/L

Dy

Dysprosium

μg/L

Er

Erbium

μg/L

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

Digestion Blank <0.02 0.03 0.033 0.002 <0.02 0.02 <2 1 0.14 0.03 0.36 0.29 <0.004 0.002 <0.008 0.004

Digestion Blank <.02 .01 .029 .001 <.02 .01 <2 2 .12 .04 .16 .07 <.004 .003 <.008 .002

Digestion Blank .14 .10 .012 .002 .03 .01 <2 1 .10 .15 1.8 2.1 <.004 .006 <.008 .004

Digestion Blank .04 .02 .021 .002 <.02 .006 <2 2 <.04 .05 .21 .15 <.004 .004 <.008 .003

Digestion Blank .03 .01 .20 .01 <.02 .009 <2 2 .19 .00 .09 .05 .009 .003 <.008 .001

Field ID

Eu

Europium

μg/L

Fe

Iron

μg/L

Ga

Gallium

μg/L

Gd

Gadolinium

μg/L

Ho

Holmium

μg/L

K

Potassium

mg/L

La

Lanthanum

μg/L

Li

Lithium

μg/L

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

Digestion Blank <0.004 0.003 22 39 <0.01 0.00 <0.005 0.002 <0.002 0.001 <0.04 0.01 0.010 0.002 <0.1 0.1

Digestion Blank <.004 .001 <20 8 <.01 .01 <.005 .006 <.002 .000 <.04 .02 .014 .001 <.1 .2

Digestion Blank <.004 .001 <20 7 <.01 .00 <.005 .009 <.002 .001 .18 .10 .008 .002 .2 .3

Digestion Blank <.004 .000 <20 13 <.01 .003 <.005 .002 <.002 .001 <.04 .02 .008 .001 <.1 .08

Digestion Blank <.004 .002 37 5 <.01 .006 .009 .002 <.002 .001 <.04 .02 .069 .003 <.1 .09

Field ID

Lu

Lutetium

μg/L

Mg

Magnesium

mg/L

Mn

Manganese

μg/L

Mo

Molybdenum

μg/L

Na

Sodium

mg/L

Nd

Neodymium

μg/L

Ni

Nickel

μg/L

P

Phosphorous

μg/L

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

Digestion Blank <0.002 0.000 <0.005 0.002 0.2 0.2 <0.5 1.0 <0.1 0.1 0.01 0.01 0.85 0.09 <20 10 

Digestion Blank <.002 .000 <.005 .000 <.2 .0 <.5 .6 <.1 .0 <.01 .01 .85 .07 <20 8 

Digestion Blank <.002 .001 .014 .015 .3 .5 <.5 .5 .1 .2 <.01 .00 2.3 1.3 29 12 

Digestion Blank <.002 .001 <.005 .000 <.2 .1 <.5 .5 <.1 .0 <.01 .01 1.7 .2 21 14 

Digestion Blank <.002 .000 .032 .010 .7 .3 <.5 .1 <.1 .1 .07 .02 .32 .05 <20 8 

Field ID

Pb

Lead

μg/L

Pr

Praseodymium

μg/L

Rb

Rubidium

μg/L

Re

Rhenium

μg/L

S

Sulfur

mg/L

Sb

Antimony

μg/L

Sc

Scandium

μg/L

Se

Selenium

μg/L

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

Digestion Blank 0.25 0.20 0.005 0.001 <0.03 0.02 <0.003 0.001 <0.2 0.1 <0.04 0.01 <1.0 0.1 <0.8 0.7

Digestion Blank .20 .05 .003 .001 <.03 .01 <.003 .002 <.2 .1 <.04 .06 <1.0 .8 <.8 .2

Digestion Blank 1.1 .9 <.002 .001 .31 .39 <.003 .001 <.2 .2 .25 .11 <1.0 .4 <.8 .4

Digestion Blank .13 .02 <.002 .001 <.03 .01 <.003 .001 <.2 .1 <.04 .04 <1.0 .4 <.8 .4

Digestion Blank .09 .02 .018 .001 .29 .03 <.003 .001 <.2 .1 <.04 .02 <1.0 .2 <.8 .5

Appendixes 59
Field ID

U

Uranium

μg/L

V

Vanadium

μg/L

W

Tungsten

μg/L

Y

Yttrium

μg/L

Yb

Ytterbium

μg/L

Zn

Zinc

μg/L

Zr

Zirconium

μg/L

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

Digestion Blank 0.006 0.010 <0.3 0.1 0.02 0.02 0.014 0.003 <0.004 0.002 <0.9 0.3 0.07 0.02

Digestion Blank .005 .001 <.3 .4 <.02 .01 .009 .004 <.004 .003 <.9 .4 <.05 .01

Digestion Blank .005 .001 .3 .2 <.02 .02 .007 .008 <.004 .004 13 14 .06 .02

Digestion Blank .005 .004 <.3 .1 <.02 .01 .006 .003 <.004 .003 2.1 1.0 .09 .08

Digestion Blank .005 .002 <.3 .2 <.02 .01 .024 .004 <.004 .002 1.2 .0 .17 .08

Field ID

Sm

Samarium

μg/L

Sr

Strontium

μg/L

Tb

Terbium

μg/L

Te

Tellurium

μg/L

Th

Thorium

μg/L

Ti

Titanium

μg/L

Tl

Thalium

μg/L

Tm

Thulium

μg/L

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

Digestion Blank <0.01 0.01 <0.2 0.2 <0.001 0.000 <0.06 0.04 0.004 0.004 <4 6 <0.04 0.07 <0.002 0.001

Digestion Blank <.01 .00 <.2 .0 <.001 .001 <.06 .01 .003 0.002 <4 3 <.04 .02 <.002 .001

Digestion Blank <.01 .01 .2 .3 <.001 .001 <.06 .05 .005 0.005 <4 3 <.04 .00 <.002 .001

Digestion Blank <.01 .01 <.2 .0 <.001 .001 <.06 .03 .003 0.002 <4 3 <.04 .06 <.002 .001

Digestion Blank .01 .01 1.2 .4 .003 .000 <.06 .02 .024 0.005 <4 3 <.04 .04 <.002 .000

Table D5. Digestion blanks for trace elements and major elements, Daguerre Point Dam, California.—Continued

[Avg, average of three replicate analyses; SD, standard deviation; μg/L, microgram per liter; mg/L, milligram per liter; <, less than]

Table D6. Spike recoveries for trace elements, Daguerre Point Dam, California.

Date

As

Arsenic

Ca

Calcium

Cd

Cadmium

Cu

Copper

Fe

Iron

Mg

Magnesium

Pb

Lead

Zn

Zinc

Percentage recovery

11/7/2003 112 105 100 102 102 101 99 104

11/21/2003 99 102 104 102 106 101 107 101

12/16/2003 109 102 107 106 102 92 106 110

60 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California
Table D7. Comparison of replicate analyses of trace and major elements in digested sediments, Daguerre Point Dam, California.

[Avg, average of three replicate analyses; Wt%, weight percent; SD, standard deviation; μg/L, microgram per liter; ft, foot; dup., duplicate; <, less than; RPD, 

relative percent difference; na, not applicable]

Drill hole Depth

(ft)

Al

Aluminum

Wt%

As

Arsenic

μg/g

Au

Gold

μg/g

B

Boron

μg/g

Ba

Barium

μg/g

Be

Beryllium

μg/g

Bi

Bismuth

μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

DPD-4 10-15 5.1 0.1 32 2 0.008 0.004 128 1 591 0 1.01 0.13 <0.04 0.03

DPD-4, dup. 10-15 6.6 .2 32 1 .011 .003 146 20 673 6 1.12 .14 <.05 .06

DPD-4 15-20 5.6 .2 20 1 .012 .002 96 3 755 5 1.02 .05 <.04 .01

DPD-4, dup. 15-20 5.0 .2 19 1 .008 .001 116 1 689 4 1.03 .03 <.04 .09

DPD-5 5-10 5.6 .1 22 0 .017 .003 167 2 488 9 1.07 .04 <.04 .07

DPD-5, dup. 5-10 5.4 .2 23 0 .012 .003 134 1 451 3 1.1 .1 <.04 .05

RPD RPD RPD RPD RPD RPD RPD

DPD-4 10-15 27.1 0.2 35.2 13.0 13.0 10.8 20.9

DPD-4 15-20 10.2 7.4 39.3 18.1 9.2 1.0 1.2

DPD-5 5-10 4.3 4.9 38.1 22.0 7.9 6.2 .0

Drill hole

Ca

Calcium

Wt%

Cd

Cadmium

μg/g

Ce

Cerium

μg/g

Co

Cobalt

μg/g

Cr

Chromium

μg/g

Cs

Cesium

μg/g

Cu

Copper

μg/g

Dy

Dysprosium

μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

DPD-4 1.76 0.07 0.28 0.10 19 1 38 1 195 2 1.5 0.3 98 4 1.5 0.1

DPD-4, dup. 3.27 .03 .31 .05 25 0 37 1 148 1 1.5 .1 95 3 2.6 .0

DPD-4 1.69 .06 .31 .01 16 1 31 0 172 1 1.2 .1 103 2 1.5 .1

DPD-4, dup. 1.48 .03 .17 .08 13 0 31 1 154 1 1.0 .1 98 3 1.4 .0

DPD-5 1.90 .09 .40 .06 21 1 33 1 190 8 1.0 .0 106 3 1.6 .0

DPD-5, dup. 1.57 .04 .43 .05 18 0 34 1 186 7 1.3 .1 111 2 1.3 .1

RPD RPD RPD RPD RPD RPD RPD RPD

DPD-4 59.9 9.3 28.5 1.8 27.8 0.6 2.4 55.6

DPD-4 13.3 57.9 20.8 1.0 10.9 17.4 4.4 4.7

DPD-5 19.0 7.0 13.5 1.7 2.0 27.5 4.2 20.4

Drill hole

Er

Erbium

μg/g

Eu

Europium

μg/g

Fe

Iron

Wt%

Ga

Gallium

μg/g

Gd

Gadolinium

μg/g

Ho

Holmium

μg/g

K

Potassium

Wt%

La

Lanthanum

μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

DPD-4 0.85 0.06 0.42 0.04 7.7 0.0 15 0 1.5 0.0 0.30 0.01 0.78 0.02 7.9 0.5

DPD-4, dup. 1.45 .05 .75 .02 6.9 .1 14 0 2.5 .0 0.51 .00 0.83 .03 11.8 .0

DPD-4 .90 .00 .45 .02 7.1 .2 16 0 1.6 .0 0.32 .00 0.81 .02 6.4 .0

DPD-4, dup. .80 .04 .42 .03 5.9 .1 15 0 1.3 .0 0.27 .01 0.80 .03 5.1 .2

DPD-5 .93 .03 .53 .02 6.8 .3 16 0 1.8 .0 0.33 .01 0.90 .03 8.7 .2

DPD-5, dup. .74 .02 .40 .06 7.2 .2 17 0 1.3 .1 0.27 .01 0.92 .03 7.1 .0

RPD RPD RPD RPD RPD RPD RPD RPD

DPD-4 52.0 57.2 11.2 1.8 51.3 52.9 5.8 39.8

DPD-4 11.3 8.4 18.2 9.7 16.9 18.9 1.5 21.8

DPD-5 22.8 27.7 5.2 3.9 31.1 19.6 2.0 20.4

Drill hole

Li

Lithium

μg/g

Lu

Lutetium

μg/g

Mg

Magnesium

Wt%

Mn

Manganese

μg/g

Mo

Molybdenum

μg/L

Na

Sodium

Wt%

Nd

Neodymium

μg/g

Ni

Nickel

μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

DPD-4 14 1 0.12 0.00 1.6 0.0 960 25 51 2 1.09 0.00 8.0 0.1 121 0

DPD-4, dup. 17 1 .22 .00 1.7 .0 976 121 57 7 1.51 .03 12.3 .1 120 4

DPD-4 16 1 .14 .00 1.5 .0 972 46 9.9 .5 1.14 .06 7.5 .0 100 1

DPD-4, dup. 15 1 .12 .00 1.2 .0 931 28 9.6 .8 1.03 .05 6.5 .0 98 2

DPD-5 15 1 .14 .00 1.5 .1 1,750 101 9.1 .5 1.17 .07 9.0 .0 112 3

DPD-5, dup. 17 0 .11 .00 1.5 .0 1,780 17 8.8 .1 1.14 .04 7.3 .0 112 3

RPD RPD RPD RPD RPD RPD RPD RPD

DPD-4 16.2 60.5 8.5 1.7 9.5 32.4 41.7 1.1

DPD-4 9.1 13.2 21.5 4.4 3.6 10.4 14.9 1.4

DPD-5 13.5 22.4 1.5 1.7 3.4 2.8 20.8 .2

Appendixes 61
Drill hole

P

Phosphorus

μg/g

Pb

Lead

μg/g

Pr

Praseodymium

μg/g

Rb

Rubidium

μg/g

Re

Rhenium

μg/g

S

Sulfur

Wt%

Sb

Antimony

μg/g

Sc

Scandium

μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

DPD-4 1,010 16 17 1 2.1 0.0 23 1 <0.004 0.006 1.16 0.01 2.7 0.4 12 1

DPD-4, dup. 866 28 17 0 3.2 .1 30 1 <.004 .002 .31 .02 3.0 .4 6 0

DPD-4 732 52 20 1 1.8 .0 23 1 .004 .002 .37 .02 1.8 .1 16 0

DPD-4, dup. 644 16 20 1 1.5 .1 18 1 <.004 .002 .37 .01 1.9 .2 12 0

DPD-5 787 21 16 1 2.3 .1 22 1 <.004 .003 .04 .01 1.3 .2 14 1

DPD-5, dup. 832 19 17 1 1.9 .1 23 0 <.004 .002 .04 .01 1.4 .2 13 0

RPD RPD RPD RPD RPD RPD RPD RPD

DPD-4 15.4 0.2 41.5 27.2 na 115.0 10.2 70.1

DPD-4 12.9 2.7 17.0 21.4 na .1 5.0 30.0

DPD-5 5.5 5.2 18.7 5.8 na 12.9 7.2 11.3

Table D7. Comparison of replicate analyses of trace and major elements in digested sediments, Daguerre Point Dam, California.—

Continued

[Avg, average of three replicate analyses; Wt%, weight percent; SD, standard deviation; μg/L, microgram per liter; ft, foot; dup., duplicate; <, less than; RPD, 

relative percent difference; na, not applicable]

Drill hole

Se

Selenium

μg/g

Sm

Samarium

μg/g

Sr

Strontium

μg/g

Tb

Terbium

μg/g

Te

Tellurium

μg/g

Th

Thorium

μg/g

Ti

Titanium

Wt%

Tl

Thallium

μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

DPD-4 1.4 0.4 1.7 0.1 206 2 0.24 0.02 0.07 0.04 2.8 0.1 0.44 0.02 0.19 0.03

DPD-4, dup. 1.8 .8 2.8 .0 205 5 .44 .00 .07 .02 4.1 .1 .30 .00 .35 .00

DPD-4 <.9 1.3 1.7 .1 196 14 .26 .01 .10 .03 2.5 .1 .55 .02 .21 .03

DPD-4, dup. <.9 .7 1.5 .0 171 2 .23 .01 .12 .07 2.2 .1 .50 .01 .19 .00

DPD-5 <.9 .3 1.8 .0 203 14 .27 .00 .13 .04 3.0 .1 .54 .03 .30 .05

DPD-5, dup. 1.0 .1 1.5 .1 196 7 .21 .00 .11 .02 2.4 .1 .53 .01 .24 .04

RPD RPD RPD RPD RPD RPD RPD RPD

DPD-4 25.8 49.4 0.1 57.7 1.5 38.7 37.9 60.2

DPD-4 na 6.7 13.5 13.9 14.7 12.4 9.6 10.4

DPD-5 na 18.8 3.6 22.6 16.0 22.5 1.4 22.4

Drill hole

Tm

Thulium

μg/g

U

Uranium

μg/g

V

Vanadium

μg/g

W

Tungsten

μg/g

Y

Yttrium

μg/g

Yb

Ytterbium

μg/g

Zn

Zinc

μg/g

Zr

Zirconium

μg/g

Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD Avg SD

DPD-4 0.13 0.01 1.9 0.1 221 4 1.1 0.0 7.1 0.3 0.88 0.02 138 14 50 1

DPD-4, dup. .22 .01 1.9 .0 223 4 1.1 .0 13.0 .1 1.45 .05 135 5 50 2

DPD-4 .13 .01 1.6 .1 257 1 1.1 .0 7.0 .0 .85 .05 114 5 53 0

DPD-4, dup. .11 .00 1.6 .1 241 7 .98 .03 6.5 .2 .83 .01 113 10 48 2

DPD-5 .13 .00 1.8 .0 225 7 1.2 .0 7.9 .2 .90 .01 109 9 54 1

DPD-5, dup. .104 .006 1.7 .1 225 5 1.2 .0 6.3 .2 .74 .03 132 17 54 1

RPD RPD RPD RPD RPD RPD RPD RPD

DPD-4 49.8 1.1 0.7 0.1 59.0 49.3 2.0 0.2

DPD-4 15.8 1.2 6.3 8.6 7.3 1.7 1.3 9.6

DPD-5 25.1 3.6 .3 1.7 22.8 19.7 19.3 .5

62 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California
Table D8. Replicate analyses of total mercury and methylmercury by the U.S. Geological Survey Wisconsin District Mercury 

Laboratory, Daguerre Point Dam, California.

[All replicates are laboratory replicates unless otherwise noted. DPD, Daguerre Point Dam; RPD, relative percent difference; r1, replicate 1; r2, replicate 2; r3, 

replicate 3; E, estimated value. ft, foot; ng/g, nanogram per gram; <less than; —, no data]

Drill hole Depth

(ft)

Replicates Laboratory replicates Field replicates

Methylmercury, wet Total mercury, wet Total mercury Total mercury

r1

 (ng/g)

r2

 (ng/g)

r3

 (ng/g)

r1

 (ng/g)

r2

 (ng/g)

r3

 (ng/g)

RPD

(r1, r2)

(percent)

RPD

(r1, r3)

(percent)

RPD

(r2, r3)

(percent)

Clay-silt fraction (Centrifuge tubes)

DPD-1 5-10 <0.012 0.165 <0.01 33.3 22.7 — 38.1 — —

DPD-1 15-17.5 <.05 <.05 — 17.9 24.0 — 29.4 — —

DPD-2 25-30 <.006 <.007 <.07 247 240 1244 2.6 1.3 1.4

DPD-6 25-30 <.06 <.08 .05E 204 208 1196 1.7 4.1 5.9

Drill hole Depth

(ft)

Replicates Laboratory replicates

Total mercury

Field replicates

Methylmercury, dry Total mercury, dry Total mercury

r1

(ng/g)

r2

(ng/g)

r3

(ng/g)

r1

(ng/g)

r2

(ng/g)

r3

(ng/g)

RPD

(r1, r2)

(percent)

RPD

(r1, r2)

(percent)

Sandy fraction

DPD-2 0-5 <0.001 <0.001 <0.001 10.1 11.0 — 8.3 —

43.6

—

—

—

DPD-2 15-20 <.001 <.001 — 13.2 120.6 — —

DPD-2 20-25 <.001 <.001 — 20.3 15.0 — 30.4

DPD-4 15-20 <.001 <.001 <.001 21.3 21.6 — 1.5

DPD-5 15-20 <.001 <.001 — 12.1 11.9 — 1.1

1

 Field replicate

Appendixes 63
�����

�����

�����

�����

�����

�����

������� ������� ������� 

������

������

������

��������������������������

Appendix E. Plate 1. Map of Bedrock Elevation Contours, Daguerre Point Dam, California.
������� ������� �������

� ����� ����������

�������������������������������������������

������������������������������������������������

������������������������������������������

���������������������������������������������������������������������������������

���������������������������������������������������

�������������������������������������������

�����������

�������������������������������������������������������������������������

������������������������������

����

���

���

���

���

�������������

��

��

��

��

���

���

���

���

�����

������������������������
Glossary of Placer Terms

(adapted from Wells, 1973)

Alluvial. Deposited by a stream.

Alluvial Gold. Gold found in association with water-worn 

material.

Amalgam. An alloy of mercury with gold or another metal. 

In the case of placer gold, a gold amalgam will contain nearly 

equal proportions of gold and mercury. Mercury placed in the 

riffles of a sluice box forms a gold amalgam as a result of its 

chemical affinity for gold.

Auriferous. Containing gold.

Bedrock. The solid rock underlying auriferous gravel, sand, 

clay, and other sediments, and upon which the alluvial gold 

rests. Bedrock may be composed of igneous, metamorphic, or 

sedimentary rock.

Black Sand. Heavy grains of various minerals which have a 

dark color and usually accompany gold in alluvial deposits. 

The heavy minerals may consist mostly of magnetite, ilmenite, 

and hematite associated with other minerals such as garnet, 

rutile, zircon, chromite, amphiboles, and pyroxenes. In Western gold placers, the black sand content is commonly between 

5 and 20 pounds per cubic yard of gravel.

Bucket-Line Dredge. A dredge in which the material excavated is lifted by an circular chain of buckets. The type of 

bucket-line dredge generally employed in placer mining is 

a self-contained digging, washing, and disposal unit, operating in a pond and capable of digging more than 100 feet 

below water. The dredge backfills its working pit (pond) as it 

advances.

Channel. A stream-eroded depression in the bedrock, ordinarily filled with gravel. See – Tertiary Channel.

Churn Drill. A portable drilling machine arranged to successively raise and drop a heavy string of tools suspended from 

a drill line. By means of successive blows, the formation is 

chopped up and the hole deepened.

Color. A particle of metallic gold found in the pan or on a 

gravity-concentrator table after a sample has been washed.

Debris. The tailings from hydraulic mines.

Flood Gold. Fine-size gold flakes carried or redistributed by 

flood waters and deposited on gravel bars as the flood waters 

recede. Flood gold sometimes forms superficial concentrations 

near the upstream end of accretion bars.

Floodplain. That portion of a river valley adjacent to the river 

channel which is built of sediments during the present regimen 

of the stream and which is covered with water when the river 

overflows its banks at flood stages.

Floured Mercury (Quicksilver). The finely granulated 

condition of quicksilver, produced by its agitation during the 

amalgamation process. A thin film of oxide coating on small 

globules of quicksilver prevents them from reuniting once they 

are separated.

Fluvial. Of, or pertaining to rivers; produced by river action, 

as a fluvial plain.

Heavy Minerals. The accessory detrital minerals of high specific gravity. The black sand concentrate commonly referred to 

in the mining of placer deposits would more properly be called 

a “heavy-mineral” concentrate.

Hydraulic Mining. A method of mining in which a bank of 

gold-bearing earth or gravel is washed away by a powerful jet 

of water and carried into sluices where the gold is separated 

from the earth or gravel by its specific gravity.

Jig. A machine in which heavy minerals are separated from 

sand on a screen in water by imparting a reciprocating motion 

to the screen or by water pulsing through the screen. Where 

the heavy mineral is larger than the screen openings, a concentrate bed will form on top of the screen. Where the heavy mineral particles are smaller than the screen openings, a fine-size 

concentrate will fall through and be collected in a trap beneath 

the screen.

Nugget effect. Anomalously high precious metal assays 

resulting from the analysis of samples that may not adequately 

represent the composition of bulk material tested due to nonuniform distribution of nuggets in the material sampled.

Placer. A place where gold is obtained by washing; an alluvial 

or glacial deposit, as of sand or gravel, containing particles of 

gold or other valuable minerals.

Placer mining. The form of mining in which the surficial 

detritus is washed for gold or other valuable minerals. When 

water under pressure is employed to break down the gravel, 

the term Hydraulic Mining is generally employed.

Quicksilver. Elemental mercury, a liquid at room temperature.

River Mining. The mining of part or all of a river bed after 

by-passing the stream by means of flumes or tunnels or by use 

of wing dams to divert the river from the working area.

Riffle. A groove in the bottom of an inclined trough or sluice, 

for arresting gold contained in sands or gravels. 

Tailings. The washed material which issues from the end of a 

sluice or other recovery device in a placer mining operation. 

The tailings from hydraulic mines are generally referred to as 

debris in legislative documents.

Tenor. The percentage or average content of an ore. As 

commonly used, it is synonymous with an approximate or a 

general value rather than a precisely known value.

Tertiary Channel. Ancient gravel deposits, often auriferous, 

composed of stream alluvium of Tertiary age. Tertiary gravel 

deposits are abundant in the Sierra Nevada gold belt of California; many have been covered by extensive volcanic eruptions and subsequently elevated by mountain uplifts. They are 

now found as deeply-buried channels, high above the present 

stream beds.

Trace. A very small quantity of gold, usually a speck too 

small to weigh.

66 Geochemistry of Mercury and other Trace Elements in Fluvial Tailings, Daguerre Point Dam, California
Hunerlach and others—Geochemistry of Mercury and Trace Elements in Fluvial Tailings, Daguerre Point Dam, California—Scientific Investigations Report 2004-5165

Printed on recycled paper