A PRELIMINARY ASSESSMENT OF
MERCURY POLLUTION IN NAVAJO RESERVOIR
COLORADO - NEW MEXICO
Prepared by
Environmental Protection Agency
Office of Enforcement
Division of Field Investigations - Denver Center
Denver, Colorado
June, 1971
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TABLE OF CONTENTS
CHAPTER I.
CHAPTER
CHAPTER III.
CHAPTER IV.
CHAPTER V.
INTRODUCTION
SUMMARY AND CONCLUSIONS
DESCRIPTION OF AREA.
SUMMARY OF MERCURY POLLUTION DATA
A. MERCURY CONCENTRATIONS IN FISH
B. MERCURY CONCENTRATIONS IN WATER
C. MERCURY CONCENTRATIONS.IN SEDIMENTS
POTENTIAL SOURCES OF MERCURY
A. NATURAL SOURCES
Erosion
Mineral Deposits
Mineral Springs
B. MAN-MADE SOURCES
Municipal and Industrial Sources
Mining Activity
Pesticides
Four Corners Power Plant
REFERENCES
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CHAPTER I. INTRODUCTION
Widespread concern following the closing in 1970 of Lake St. Clair betwi n
Michigan and Canada to all fishing, as the result of mercury pollution, gexi-
eratecI a wave of mercury surveys all across the Nation. Samples of fish tak
from Navajo Reservoir by the New Mexico Department of Health and Social Sei’i-
ices contained mercury concentrations anly slightly below the Federal Food and
Drug Administration’s guideline of 0.5 parts per million of mercury s.s the
upper limit for fish consumed by humans. No known industrial sources of oer
cury were located in the watershed. Waterquality samples taken at various
locations in the vicinity of Navajo Reservoir showed only negligible levels of
mercury present. The source of the mercury contamination thus remained a mys-
tery.
On January 19, 1971, the New Mexico Department of Health and Social Serv-
ices notified the Region VI office of the Environmental Protection Agency (EPA)
in Dallas, Texas, that they planned to conduct an investigation of the San Juan
River Basin above Navajo Reservoir in an attempt to locate the sources of mer-
cury contamination. Technical assistarkcE from EPA was requested in view of the
interstate nature of the problem and the location of much of the basin in Colo-
rado.
On February 23, 1971, the Director of the Region VI Enforcement Section,
EPA, requested the assistance of the Division of Field Investigations - Denver
Center - in complying with the New Mexico request since Colorado is not in
Region VI. With the concurrence of the Region VIII Water Quality Office, EPA,
in Denver, areview of available data and information was initiated preparatory
to an evaluation of the need and scope of field investigations in cooperation
with the New Mexico study. This review disclosed that later sampling by the
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Colorado Department of Health included many fish containing mercury at le eLs
greater than the FDA standard.
This report summarizes present information on mercury contamination i i
the Navajo Reservoir area. Potential atural and man-made sources of murcury
in the upper San Juan River Basin and adjacent areas are defined and evaluated.
Present information is inadequate to define the actual cause of the met-
cury contamination and field investigations of potential sources are needed
to provide information from which pollution abatement measures can be developed.
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CHAPTER II. SUMMARY AND CONCLUSIONS
I. Levels of mercury contamination exceeding the allowable maximum limit
of 0.5 parts per million established by the Food and Drug Administra-
tion have been found in fish taken from Navajo Reservoir, on the San
Juan River in northern New Mexico and southern Colorado. The elevatcd
mercury concentrations are indicative of a health hazard which sh iild
be abated.
2. Available water quality data indicate only negligible levels of mercury
are present in streams feeding Navajo Reservoir.
3. There are no known significant man-made sources of mercury in the drain-
age area of Navajo Reservoir. The population is sparse, with Pagcsa
Springs, Colorado (population 1,500) the only sizable community in the
watershed. There are no known active or abandoned draining mines in
the watershed. No known industrial sources are present in the watershed.
About 75,000 acres of irrigated farmland are located upstream from the
reservoir. Production.of small graincrops is minimal, indicating the
probability that only minor usage is made of mercurial fungicides.
4. Potential natural sources of mercury include erosion of low-level mercury
bearing rock formations, mineral springs and mineral deposits. It is
estimated that the average annual discharge of 8.4 million tons of sedi-
ment to Navajo Reservoir may contain 1.3 tons of mercury eroded from
rock formations (primarily shales and volcanic rocks) in the upstream
areas Mineral springs in the Pagosa’ Springs area are believed to
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contribute very small amounts of mercury. Sediments in the area of the
springs, however, may contain sufficient mercury to cause a local ccn-
tamination problem. There are no known mercury-bearing mineral. depo its
in the watershed although such deposits exist in nearby drainage areas.
5. The Four Corners Power Plant near Farmington, New Mexico, is belie’ ed
to emit substantial quantities of mercury to the atmosphere in stack
gases derived from burning of mercury-bearing coal. It is theoretical-
iy possible for mercury from this source to be precipitated out over the
Navajo Lake watershed. Present information is inadequate to assess the
potential magnitude of such contamination.
6. Available information would indicate that the mercury contamination in
Navajo Lake is low level and the sources are diffuse. Location and
quantification of mercury sources will thus be difficult.
7. Quantification of stack emissions of mercury from the Four Corners Power
Plant and evaluation of meteorological conditions with a view toward de-
fining the potential transport of mercury to the Navajo Lake drainage
• area is needed.
8. Mercury from natural sources is probably transported by sediments. If
mercury from the Four Corners Power Plant is reaching the watershed, it
is also probably transported on fly ash particles which would appear in
the sediments. A survey of the mercury content of sediments at key lo-
cation in the watershed is needed. Sample locations should include
Vallecito Reservoir on the Los Pinos River, the Pagosa Springs area, and
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both the Los Pinos and San Juan arms of Navajo Reservoir.
9. Additional fish samples should be obtained fromNavajo Reservoir and
other locations in the watershed to evaluate the areal extent of con-
tamination of aquatic life and to. verify that a definite health hazard
exists.
10. Navajo Reservoir is primarily located in New Mexico but extends upstream
into Colorado. Much of the drainage area is located in Colorado. If
the source of mercury contamination is located in Colorado, an inter-
state pollution problem exists. If the Four Corners Powe - Plant is the’
source of mercury, both an interstate air pollution problem and an inter-
state water pollution problem exist. The mercury contamination poses ‘a
health hazard to citizens of both Colorado and New Mexico.
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CHAPTER III. DESCRIPTION OF AREA
Navajo Reservoir is located on the San Juan River near the New Mexico-
Colorado boundary, 40 miles east of Farmington, New Mexico (see Figure Ill-i).
The reservoir, with a storage capacity of 1.7 million acre-feet, is part of
theColorado River Storage Project operated by the Bureau of Reclamation.
With a maximum surface area of more than 15,000 acres, the reservoir extends
35 miles up the San Juan River and 13 miles up the Los Pinos (Pine)River.
Maximum depth at Navajo Dam is 388.feet. A major portion of the reservoir
is located in New Mexico.
.A drainage area of 3230 square miles, located primarily in Colorado,
feeds the reservoir. In addition to the San Juan River, the Los Pinds and
Piedra Rivers flow directly into the reservoir.
The San Juan River and its tributaries head high in the San Juan Moun-
tains which form the watershed boundary on the north and east. The San Juan
River flows southwestward to Navajo Dam and then continues westward past
Farmington, New Mexico, to the Four Corners and Lake Powell on the Colorado
River. Elevations range from 6,000 feet at the reservoir water surface to
more than 13,000 feet in the San Juan Mountains.
Annual precipitation ranges from less than 15 inches at the reservoir to
more than 50 inches in the high mountain areas. Most of the watershed’s animal
runoff of about one million acre-feet originates in the Colorado mountains.
Runoff is seasonal, with most of the volume produced by spring snow melts.
Low streamfiow conditions occur in the fall.
Easily eroded shale formations are exposed in the high plateau ccimtry of
the lower watershed. Thunderstorms during the summer produce isolated cases of
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FIGURE Ill-i. Location Nap
BLA JOING
H
E
r c ’. T-•
A N J U
A
N
/
\. b
R
•F4Ev COMB
M
K I
C AlL Er
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heavy surface runoff from these formations which contribute to •the heavy sedi-
merit, load carried by the San Juan River.
The watershed is sparsely populated with a total population of about
20,000. Pagosa Springs (population 1,500) is the only sizable community in
the basin.
The Bureau of Reclamation’s Pine River project supplies irrigation water
from Vallecito Reservoir on the Los Pinos River to about 50,000 acres of
farmland along the lower Los Pinos and San Juan Rivers immediately above
Navajo Reservoir. An additional 25,000 acres of irrigated farmland are
scattered about other portions of the watershed.
Recreational use of the reservoir, including fishing, boatin rnd swim-
ming, is significant. Navajo Lake State Park is located near Navajo Darn.
Four Corners Power Plant, a major coal—fired electric generating plant,
is located about 50 miles, west-southwest of ‘the reservoir at an elevation of
about 5,000 feet. Air pollution from the power plant is of such magnitude
that it is visible ‘at times in the watershed area.
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CHAPTER IV. SUMMARY OF MERCURY POLLUTION DATA
Only a limited amount of data is available to evaluate the extent of
mercury pollution in Navajo Reservoir and surrounding areas. A1.l of the
data have been collected within the pa t year. A few fish san ples taken ii’
September, 1970, showed significant mercury concentrations, and were the Eir .t
indication that a mercury problem existed. Several sets of water quality
samples were subsequently taken from Navajo Reservdir and from strear s. tn-
butary to Navajo Reservoir. No source of mercury was identified by these
samp1 s No sediment sample data have been reviewed.
A. MERCURY CONCENTRATIONS IN FISH
In the late summer, 1970, the New Mexico State Department of Health and
Social Services collected fish samples from Navajo Reservoir and the nearby
Animas River. Analysis of these samples by the Food and Drug Administration
revealed mercury concentrations ranging from 0.09 to 0.40 ppm. All of the
samples exhibiting the higher levels catne.frorn Navajo Reservoir. The Navajo
Reservoir data collected by New Mexico are shown in Table IV-l.
Table IV-l. Mercury Concentrations
in Fish Samples Collected by New Mexico
Type of Fish Sample Description Mercury Concentration (ppm )
Catfish and Trout (8 cat. & 1 trout) 0.34
Bluegills 0.40
Carp (1 - 8 lb. fish) 0.38
Bluegills (S fish - 5.4 oz. avg.) 0.37
Salmon (2 fish - 1.5 lb. ea.) 0.09
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Catfish and trout samples from the Animas River in New Mexico averaged
0.13 ppm mercury. Six trout samples from various streams in Colorado, also
analyzed by FDA, contained mercury concentrations ranging from a trace, to
0.07 ppm. All of these samples were ‘taken below areas of known mining ac-
tivity where some mercury is known to be present in mineral deposits. The
‘mercury levels present in the Navajo Reservoir fish samples were thus several
times higher than the levels observed in fish from streams which probably re-
,ceive ome mercury contamination.
Following ‘the report of apparent fish contamination, as revealed by the
New Mexico sampling, the Colorado Department of Health collected water and
fish samples from Navajo Reservoir and tributary streams. .T ie water data
were not available to DFI-DC, but it is’ reported that mercury was not de-
tected in the water samples. However, the fish samples had many values ex-
ceeding 0.5 ppm, with one chub reported. at 8.9 ppm. The fish data for the
samples collected and analyzed by the Colorado Department of Health are shown
in Table IV-2.
The Food and Drug Administration has established a guideline of 0.5 ppm
• as the maximum allowable mercury concentration in fish transported in inter-
state commerce for human consumption. A number of water bodies across the
country have been closed to commercial and/or sport fishing because of mercury
levels in fish which exceed this guideline. The observed mercury levels in
many of the Navalo Reservoir fish exceed the FDA guideline. The mercury con-
tamination present is a health hazard which should be abated. The public
• should be warned of the danger involved in eating fish from Navajo Reservoir.
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Table IV-2. Mercury Concentrations in
Fish Samples Collected by Colorado Department of Health
‘ pecies Length (in.) Weight (lb-oz) Hg (ppm )
Oct 29,1970
Brown Trout 20 3 - 0 0.90
Rainbow Trout 13 0 - 10 0.34
Rainbow Trout 13 0 - 14½ 0.27
Catfish 10½ 0 - 6 0.38
Catfish 18 2 - 1 0.55
Catfish 19½ 2 - 12 0.44
Catfish 21 4 - 2 0.37
Catfish 22 4 - 6 0.50
Chub 11½ 0 - 6 0.36
Chub 12 0 -11 0.78
Chub 14 0 - 12½ 8.90
Chub 14 0 - 15 1.30
Chub 14½ .0 - 15½ 1.40
Chub 15 I - 1 1.20
Carp 16½ 2 - 0 0.37.
Carp 15 2 - 4 0.98
Carp 16½ 2 - 9 0.34
Sucker 16 7 - 12 0.36
Sucker 18 2 - 0 0.46
Sucker .17 . 2 - 3 0.24
Sucker 21 3 - 5 0.46
Nov 23,1970
Chub 14½ 0 - 15 1.10
Chub 14½ 0 - 13 0.90
Chub 11½ 0 - 7 1.12
Chub 13 0 - Ii 1.54
Rainbow Trout 15 1 - 2 0.16
Rainbow Trout 13½ 0 - 13 0.10
Rainbow Trout 14½ . 0 - 14 0.39
Rainbow Trout 12 0 - 8 0.14
Rainbow Trout 13½ 0 - 11 0.23
Sucker 18½ 2 - 3 0.08
Sucker 19 2 - 1 0.07
Bullhead 9 0 - 6 1.01
Bullhead 9½ . 0 - 5½ 0.56
Catfish 12½ 0 - 10 0.35
Carp 17 2 - 1 0.30
Brown Trout 16½ 1 - 4 0 34
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Additional fish samples should be obtained from Navajo Reservoir to
better define the extent of contamination present. Samples from other parts
of the San Juan River drainage area, such as Vallecito Reservoir, should be
collected to check for possible mercury contamit ation in additional areas
and to attempt to isolate possible mercury sources.
B. MERCURY CONCENTRATIONS IN WATER
On October 12, 1970, the U. 6. Geological Survey collected water samples
from five Colorado locations in the drainage area of Navajo Reservoir as part
of a nationwide reconnaissance survey of the occurrence of selected minor
elements in surface waters. (10) Samples were taken from Vallecito Creek
near Bayfield, Navajo River near Edith, San Juan River near Carracas, Piedra
River near Arbdles and Los Pinos River at La Boca. , Total mercury concentra-
tions in all of these samples were reported as less than the analytical detec-
tion limits of 0.5 migrogram per liter.
Water samples were collected from the San Juan River at the inlet to
Navajo Reservoir, from’the Navajo River at its confluence with the Piedra
River and from the Piedra River near Arboles, by the Colorado State Depart-
ment of Health, on November 2, 1970. ‘Analysis of the samples by USGS indi-
cated the same low mercury concentrations as found in the October survey.
Both surveys were conducted during the fall low-flow season. Sediment
concentrations in the streams would be at a minimum. If the mercury is being
transported by sediments as expected, the above surveys would not detect such
mercury. The surveys did indicate that no significant quantities of mercury
were being transported in solution.
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C. MERCURY CONCENTRATIONS IN SEDIMENTS
As discussed in the following chapter, a potential means of transport
of mercury in the watershed is by attachment to sediments. Sediments re-
leased by erosion are also a potential source of mercury. Mercury-bearing
sediments on the bottoms of streams and reservoirs can form a reservoir where-
by mercury is recycled into the biomass, through uptake by bottom-feeding
aquatic organisms. - . .
No sediment data from the Navajo Lake area have been reported. Sedi-
ment samples from’various points in Navajo Lake and tributary areas are
needed to attempt to isolate mercury sources.
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CHAPTER V. POTENTIAL SOURCES OF MERCURY
Within the drainage area of Navajo Reservoir there are few industrial
activities. Population density is also light. There are thus few potential
man-made sources of mercury. However, air pollution from the Four Corners
Power Plant near Farmington, New Mexico, passes over the watershed a signi-
ficant amount of the time and is a potential source of mercury contamination.
Geological conditions within the watershed are indicative of a potential
minor contribution of mercury from natural sources. Erosion of rock forma-
tions containing low levels of mercury and the mineral springs discharge at
Pagosa Springs are possible sources.
In general, the mercury contamination appears to be derived from diffuse
sources rather than any significant point source. If the Four Corners Power
Plant is a significant point source, the mercury is entering the watershed as
diffUse contamination through dispersion of fallout over large areas. Identi-
fication and quantification of specific sources would thus be difficult in
the field.
A. NATURAL SOURCES 0
Erosion
• Natural erosion and weathering processes release sediments and dissolved
solids from rock and sediment formations to the ‘aquatic environment. Where
these sediments are derived from mercury-bearing rocks, the sediments cud
transporting water would be expected to contain some mercury. Although mer-
cury l.2vels in most natural formations are very low, the large volume of Ledi-
*
ment produced in a watershed each year can contribute a. significant amount of
me :cury.
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Within the drainage area of Navajo Reservoir, a total of 15 sedimentary
and three igneous formations with significant areal extent have been identi-
fied.
Geological formations and their main lithologic composition are listed
in Table V-i for Colorado areas and Table V-2 for New Mexico areas.
These formations can be divided into four groups by predominant composi-
tion as follows:
1. •Crystalline - extrusive and intrusive igneous, and metamorphic
• (gneiss and schist)
2. Unconsolidated Sediments gravel & sand; interglacial deposits,
I
landslides and mudf lows
3. Shales
4. Sandstones
Crystalline Rocks -- these are represented by schist, gneiss, granite,
and basalt. All of these rocks are found in the high mountain rim formed by
the Continental Divide and the San Juan Mountains which border the east and
north portion of the basin in the State of Colorado. Because of the high
altitude, these rocks are located in areas of high precipitation (50-60 inches
per year) which contribute much of the watershed’s surface runoff.
Analysis for mercury content of a large number of rock samples from rock
formations of the type found in the San Juan Basin has been performed by the
U. S. Geological Survey (USGS). For igneous rocks, the mercury content av-
eraged 100 parts per billion (ppb).
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Table V-i
San Juan River Drainage Basin
Stratigraphic Column’
Colorado (Lithology)
Sandstone & shales
Sandstone shales w.
Volcanic Tuff.
Sandstone & shales w.
Volcanic Tuff.
Klmv Sandy shales
K Sandstone & shales
‘Kmc Sandy shales
Dakota sandstone
Morrison Formation
Jurasico (yen thin)
Perrnian and Pennsylvanian
undivided
Cuttler & Rico Formation
und ivided
Qls
Qpd
Qf
Thb -
Tw
Ta
Kmp
Gravel & inter-glacial
deposit
Gravel
Sands tones
(
(
(
(
(
(
(
(
(
(
(
C
(
C
C
(
C
C
(
(
(
Land slides & mud flows
Post-Durango deposits
Florida Gravel
Blanco Basin Formation
(thin)
Wasatch Formation
Animas Formation
McDermott Formation
Lewis shale & Mesaverde
Grp. undivided
Cretaceous undivided
Mancos shale
Unconsoli -
dated
Sed iments
Shale s
Sandstones
( Kd
(
C Jtn
(
( Jo
C
( Cpm
C
( Ccr
Sands tone
Sands tone
Sands tone
Ls. sandstone, shale
Sands tone
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Table V-I (continued)
San Juan River Drainage Basin
Stratigraphic Column
Colorado
Potosi Volcanic Series
Intrusives
Pre-Cambrian - Schists
and Gneiss
Pre-Cambrian granite
Crys talline
Rocks
(
(
(
(
(
(
(
(
C
Tpv
Tc a
.Tei
Pes
Peg
( Lithology )
Extrus ive
Intrus ive
Metamorphic
Intrusive
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Table V-2
Sari Juan River Drainage Basin
Stratigraphic Column
New Mexico (Lithology )
( •Tsi San Jose’ Formation Sandstone, shales
(
( Tka Animas Formation Sandstone, shales.
Shales ( Volcanic Tuff,
C
( KI Lewis Shale Sandy shales
C
( Kmv Mesaverde Group Sandy shales
Hard Rocks ( Tki Intrusive Rock of Intrusive
various ages
Shale ( TKOa Ojo Alamo Sandstone Shales, sandstone
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Unconsolidated Sediments -- These formations primarily include land-
sJ.ides and mud’f lows at the foot of the steep face of the San Juan Moun-
tains. Most of these are composed of debris from volcanic and metamorphic
rocks at an altitude of 9,000 feet, where annual precipitation ranges be-
tween 25 and 40 inches, or gravel and sand interglacial deposits, chiefly in
theLos Pinos River Valley, at an altitude of 7,000 feet where precipitation
averages 15 to 20 inches annually.
On the basis of the possible source material (igneous rocks with a high
mercury content) and analysis ofsoils in unmineralized areas, it is estimated
that unconsolidated sediments contain 50 ppb of mercury.
Shales -- Shale formations are largely interbedded with sandstones,
sandy shale and volcanic tuff. Shale outcrops occur in two-thirds of the
lower portion of the basin, at altitudes ranging from 6,000 to 8,000 feet, where
precipitation varies from 10 inches in the lower part of the valley to 30
inches in the higher outcrops.
The average mercury content of various shale formations as determined
by the USGS ranged from 60 to 280 ppb. (2) A mercury content of 190 ppb was
selected as a representative average for the shales present in the basin..
Sandstones - - Included. in this group are some Pennsylvanian-Permian line-
stones and shales. These formations outcrop between the igneous rocks and
shales in the north central part of the basin, at altitudes around 9,000 feEt
• where precipitation ranges from 20 inches to 30 inches.
An average of mercury contents of Jurasic, Triassic and Upper Paleozoic
geolc.gic formations as determined by the USGS was selected as a repre ent tive
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-7.
mercury content for this group. The average selected was the same as for
shal2, 190 ppb.
‘ Sd ’diment’ Yields No information is available on the unit sediment con—
tribution of each type of formation. The total sediment contribution of the
drainage area is known. It is also known that the more erosion resistant forma-
tions are located in areas of high precipitation and the easily eroded materials
are located in low rainfall areas. It was assumed that these factors would
tend to produce a somewhat uniform average sediment yield from all areas of
the drainage area. Sediment yields from each of the four groups were estim-
ated on the basis of relative proportion of drainage area. Errors in estim-
ating the source of sediments would produce small errors in the total estimated
mercury contribution, since the mercury content of rocks in this area varies
over a small range as discussed above.
Average annual sediment and dissolved solids loads carried by the San Juan
River near Blanco, New Mexico, about 15 miles downstream from Navajo Dam have
been estimated by the USGS for the 1914-57 period. (3) ‘ This record pr cedes
the closure of Navajo Dam. The drainage area of 3230 square miles at Navajo
Dam is about 91% of the drainage area at the Blanco gaging station. There is
little tributary inflow between Navajo Dam and Blanco. A major portion of the
sediment load formerly passing Blanco is thus probably trapped in Navajo Reser--
voir. Based on the relative proportions of the Navajo Dam and Blanco gage drain-
age areas, it is estimated that the average annual sediment and dissolved solids
loads • ontributed to’ Navajo Reservoir total 8.5 and 0.17 million tons peer jear,
respectively.
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The estimated outcrop area of each of the four types of formations was
obtained from geological maps. These areas and relative fractions of. the
drainage area are shown in Table V-3. The total sediment load for the drain-
aga area is distributed to formation types on the basis of area size, in Table V-3.
Mercury Loads - - Total mercury loads were computed for each formation type by
multiplying the sediment load by the average mercury content of the parent rock.
These mercury loads are shown’ in Table V-3. It is estimated that the average
annual contribution of mercury to Navajo Reservoir from sediment erosion is
about 1.3 tons per year.
It is probable that most of the mercury is attached to the sediments and
transported in streams in the sediment load. A minor amount [ nay be in solution.
If it is assumed that the amount of mercury in solution is proportional to the
ratio’of dissolved solids to sediments, about two percent or 50 pounds,of mer-
cury would be carried by the annual runoff of one’ million acre-feet. This
level of contamination would not be measurable. A breakdown of mercury loads
by dissolved and sediment fractions is shown in Table V-3.
Mineral Deposits
Mercury’ is present in a number of types of mineral deposits including im-
portant metal ores. Drainage from such deposits may contain significant mercury
loads.
A review of literature on mineral deposits in Colorado and New Mexico was
made to determine if any known mercury-bearing minerals are located in the drain-
age area of Navajo Reservoir. No record of such deposits in this area was found
although minor mercury deposits exist in nearby areas.
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Rock Type
TABLE V-3. Sediment and Mercury Loads
Outcrop
Area
Percent of
Drainage
Sediment
Contribution
Mercury
Content
Mercury Load
.(T/yr.)
(Sq. Mi..)
Area
•
(ppm)
Dissolved
Sediments
Total
Igneous
661
20.4
1.75
0.10
.003
0.172
.0.175
Unconsolidated
359
11.1
.95
0.05
.001
0.047
0.048
Sediments
Shales
1902
58.8
5.06
0.19
0.019
0.942
0.961
Sandstones
271
8.3
.
0.71
0.19
0.003
0.132
0.135
Total
3230
98.6
8.47
--
0.026
1.293
1.319
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In the LaPlata district, located in the headwatérsof the LàPlata River
in the San Juan Mountains west of the study area, the following mercury min-
erals have been found: hypogene cinnabar contemporaneous with native gold;
Coloradoite, a widespread mercury telluride; and native mercury derived from
the breakdown of Coloradoite. Cinnabar was also found in a mine about 10 miles
north of Durango in the Animas River drainage. Mercury concentrations above
background levels are present in mine, drainage from the Red Mountain Tunnel
north of Silverton, indicating the probable presence of mercury in mineral de-
posits in the Animas River headwaters.
A possible commercial grade deposit of cinnabar has been located in the
Gunnison River drainage near the Continental Divide north of the study area.
A portion of the Rio Grande River drainage intervenes between this deposit and
the study area.
The lack of any known mercury deposits or mining activity in the study
area would suggest that the possibility of any significant mercury contribu-
tion from mineral sources is remote.
Mineral prings
A number of mineral springs with a total flow of about two cubic feet
per second are located at Pagosa Springs in the headwaters of the San Juan
River. Mercury concentrations slightly above background levels have been found
in similar springs located in volcanic areas. Due to the low mercury levels and
small flows, it is doubtful that these springs could be a significant source of
mercury
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Sediment deposits in the vicinity of mineral springs have been found
to contain elevated concentrations of mercury in some cases. If such sedi-
ments .are present at Pagosa Springs, a localized mercury problem affecting
aquatic life in the area might exist. It is doubtful that such sedin’.ents
could, contribute a significant mercury load to downstream areas.
B • MAN -MADE SOURCES
Municipal and Industrial Sources
The drainage area of Navajo Reservoir is sparsely populated. Pagosa
Springs, with a population of about 1,500, is the only sizable community in
the basin. Due to the small population, it is doubtful if the use of mer-
curic compounds for domestic purposes is a significant mercury source.
There are no known industrial sources of mercury in the area. As dis-
cussed below, the Four Corners Power Plant, located outside the drainage area,
may be an industrial source of mercury contamination in the watershed.
Mining Activity
As discussed above, mercury is sometimes found in combination with other
mineral deposits such as gold ores. The presence of active of abandoned mines
would thus be indicative of potential mercury sources. There are no known
• . . . (4) . • • .
significant mineral finds. Mining activity is thus ruled Out as a me
cury source.
Pesticides
The use of fungicides containing mercuric compounds for treatment. of grain
seeds before planting has resulted in high levels of mercury in seed-eating birds
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in several grain farming areas of the Great Plains. Such treated seed was
fed to ahog whose mercury-tainted flesh resulted in several deaths in a
family in Alamagordo, New Mexico. The extent to which mercuric fungicides
can be transported into the aquatic environment isnotwell defined. Extens-
ive use of such fungicides would pose an external source Of mercury introduced
into a watershed which would. warrant investigation.
About 75,000 acres of irrigated farmland are located upstream of Navajo
Reservoir. About two-thirds of this acreage is located in the Bureau of Rec-
lamation t s Pine River project on the lower Los Pinos and San Juan Rivers im-
mediately above the reservoir. Return flows from this area could transport
mercury-bearing sediments from farmland directly into the reservoir.
Improved pasture, alfalfa, wheat, oats and barley are the main crops
grown in the Pine, River project. Contact with local agricultural experts pro-
duced the information that small grain production has declined in the area in
recent years. The amount of treated seed presently used was not known but
probably is minimal.
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13
Four Corners Power Plant
Mercury is found in low concentrations in coal. The burning of coal in
fossil-fueled electric generating plants releases mercury to the atmosphere
which can be carried for long distances before returning to earth. Due to its
large size, the Four Corners Power Plant west of Farmington, New Mexico, is a
potential source of significant mercury contamination of the Navajo Reservoir
watershed.
De cription of Plant -- The Four Corners Power Plant is a major fossil-
fueled electric generating plant located 15 miles west of Farmington and about
50 miles west-southwest of Navajo Reservoir. The plant has five units with a
total generating capacity of about 2,085 megawatts. The first two units,
with a total generating capacity of 350 megawatts, were placed in operation
in 1963. Unit 3, with a 225-megawatt capacity, was completed in 1964. These
three units are served by two 250-foot stacks.
Units 4 and:5 are identical, with a755 megawatt generating capacity each,
and are served by indIvidual 300—foot stacks. Unit 4 was completed in July 1969
and Unit 5 has recently been placed in operation.
The plant burns low grade, high-ash coal from a mining area located a few
miles east of the plant. The high ash content has caused a major problem with
fly ash removal from stack gases. Mechanical dust collectors installed on the
first three units proved to be much less efficient in fly ash removal than de-
signed, achieving about 78 percent removal efficiency. The estimated stack
emissions from the three units total 270 tons per day of fly ash. (5)
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14
Electrostatic precipitators have been installed on units 4 and 5, with
design ash removal efficiency of 97 percent. Such precipitators are also
planned for the initial three units. If the precipitators on the new units
are operating as designed, placing these two units in operation increased fly
ash emissions to about 350 tons per day. (5) There is reason to believe that
the precipitators are operating below design efficiency.
Bottom ash and collected fly ash from units 1, 2 and 3 are sluiced to a
large settling pond. The decant from the pond is discharged to the San Juan
River via Chaco Wash. Ash from units 4 and 5 is returned to the coal mining
area.
Cooling water is recycled to Morgan Lake, a large cooling pond. Makeup
water is obtained from the San Juan River. Boiler blowdown is discharged to
the San Juan River.
Air Pollution -- Air pollution, primarily the result of the large fly ash
emissions, has caused much controversy in New Mexico and Colorado. Plans for
other large power plants in the Four Corners area have added fuel to the con-
troversy. As a result, a number of studies of air pollution from the Four
Corners Power Plant have been undertaken. Unfortunately, with exception of a
theoretical study reportedly conducted by a Dr. Ryder of NASA in Albuquerque,
all of these studies dealt with emissions of particulates and oxides of suIfur.
The results of Dr. Hyder’s study were not obtained for review, but reportedly
show that the Four Corners Power Plant poses a theoretical source of mercury
pollution in the Navajo Reservoir area.
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15.
The State of New Mexico and several conservation groups have recently
filed Suit in Albuquerque, to force the plant to meet pollution standards.
A July. 8 article in the Denver Post , reporting on the suit, cites .a merc’iry
emission of 6000 pounds per year from the Four Corners plant. stacks.
The various air pollution studies do provide an indication of the long
distances that fly ash from the plant can be transported in the atmosphere.
A theoretical study prepared by the Public Health Service, Department of
Health, Education, and Welfare in January 1970, concluded that the plume
from the plant might produce a direct effect on visibility in the vicinity
of Los Alamos, New Mexico, located 130 miles southeast, a total of five to
l0 days per. year. (5) Los Alamos is further away from the plant than the
farthest boundaries of the Navajo Lake drainage area and is not in the direc.
Lion of the prevailing winds.
Due to a number of complicated factors, it is not possible to estimate
the percentage of time that the plant plhrne. would be over the drainage area.
Examination of wind data indicates that the plume frequently travels toward
the watershed, however.
A definite pattern of surface wind speedand direction changes exists
in the vicinity of the plant, as shown by wind data obtained at Farmington.
As shown by the wind rose in Figure V-i, surface winds are primarily westerly
(blowing from west to east) or east-northeasterly. The westerly winds occur
during the warm afternoon and evening periods. Late at night and early in
the morning, cold air drainage from the San Juan Mountains produces the down-
S
slope easterly winds. The surface wind pattern would indicate that winds
blow in the direction of Navajo Lake more than 10 percent of the time.
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Af\JNUAL SURF/\CE WIND ROSE
F/ RM I NGTON
1953 — February
N E VV i 4 E>( I C 0
1 58
1-3 4-1213-24__>24
—I
MILES PER HOUR
o 1 2 3 45
________
PER CENT
tvia r C h
“V
N
S.
Figure V-i
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16
Since the plume is released at a height of about 300 feet above the
ground surface and warm-air buoyancy elevates the plume considerably higher,
wind patterns aloft are of more significance in determining the direction of
plume travel. No wind data for upper air layers are available at Farrningtcn
However, in their analysis of plume movement, the Public Health Service
utilized wind data for about 300 meters above the ground surface at Albuquer-
que, New Mexico, as representative of upper air movement at Four Corners. (5)
Examination of the wind rose for (ipper air layers at Albuquerque, shOwn in
Figure V-2, indicates that winds are from the sojthwest quadrant almost 50
percent of the time. It is probable that the plume frequently penetrates
the cool surface drainage wind layer present in-the morning and is carried
easterly by winds aloft. The plume thus may frequently be carried eastward
during the entire day. It would appear that the plume moves in the general
direction of the Navajo Reservoir drainage area from 10 to 50 percent of the
time.
Mercuri Content of Coal -- A substantial amount of research has been done on
the composition of coal and coal ash. Unfortunately, this research did not
evaluate mercury content with the exception of two recent efforts. One study
reported by the University of Miami evaluated the mercury content of coal
from 36 American sources including one Colorado source and three other west-
ern sources. (8) Mercury content ranged from 90 to 33,000 ppb and averaged
3,300 ppb. The Colorado sample, from Pitkin County, contained 220 ppb of
mercury. -
A June 1971 study of the mercury content of 17 samples of coal from
sources utilized by power plants in Colorado and the Four Coniers Power Plant
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1; f t,
r.- J( )! i:.1)( J
4 1 —
300 1Ve ors Above Ground
% t.
vi..
Jo nuory,
July and
1962, !S63
(3E;9 days,’- .’
738 soundings)
E
(300 meters
r’ h ‘
I LI
o4 1EC
>18
rur; ) = iIiiiI11
knots
Figure V-2
0 2 4 6 8 10 12
N
S
Apri l 3
per COIn
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1.7
was conducted by the Colorado State Department of Health. (7) Mercury con-
tent ranged from none to 80 ppb. These mercury levels are very low compaL’ed
to th results reported by the Miami study. The Colorado study also repr rt
no mercury present in two samples of fired ash.
Stack Emissions of Mercury -- Two factors are of importance in det.erminin
the amount of mercury which is emitted in stack gases from the Four Corners
Plant, the mercury content àf the coal burned and the removal which might be
effected by air pollution controls. Due to the high temperatures present in
the combustion chambers and stacks of the power plant, it would seem likely
that the mercury would leave the stack in vapor form and little or no removal
along with the fly ash retained by dust collectors would be achieved. Thus,
100 percent emission of mercury from the coal could be assumed.
Based on their mercury content value of 70 ppb and a coal consumption
of 9.1 million tons per year with all five units in operation, the Colorado
study reported a mercury emission from Four Corners Power Plant of 1280 pounds
per year. (7) The validity of this value has not been tested. The low mer-
cury content found by Colorado in comparison with the Miami study would indi-
cate the possibility of a much higher total emission. A mercury content of
220 ppb comparable to the Pitkin County, Colorado, sample would yield an
annual mercury emission of about 4,000 pounds. A mercury content of 1.0 ppm,
more in line with the national average and values reported in other countries,
would yield a stack emission of 9.1 tons per year or 18,200 pounds.
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18
Mercury Transport to Navajo Lake - - Little is known of how mercury i .’
transported in a stack plume once outside the hot stack. It could move as
a vapo, , as particles of condensed mercury or attached to fly ash paiticles,
The state of mercury in the plume would greatly affect the amount whi’.± could
precipitate out in the Navajo Lake watershed.
The rate at which particulate matter settles out of the plume is deper-
ent upon atmospheric conditions. Under constant conditions, the coarser par-
ticles would settle out first with finer particles transported longer distances.
If mercury attaches to fly ash particles with the same selectivity as to sedi-
ments in water, a major portion ofthe mercury would be carried by the finer
particles.. The potential for long-distance transport of mercury may exist.
It is significant tc note that Navajo Reservoir occupies the center of
.a semicircular ernbayment in the Continental Divide. As a result, particu-
lates carried by west winds which stagnate against the Divide would ultimately
be deposited in the reservoir. The topographic conditions are ideal to cause
Navajo Reservoir to serve as a trap for much of the mercury emitted by the
Four Corners Plant.
Air masses moving eastward from the vicinity of the Four Corners Power
Plant would be forced upward by the orographic effects of the San Juan Noun-
tains. Cooling of the air mass would result, triggering precipitation in
manj cases. Such precipitation could remove particulate matter from the air
by rain out and as nuclei for raindrops. Condensed mercury vapor could also
- form raindrop nuclei. Significant amounts of mercury might be deposited in
the higher elevations of the study area in this manner. Due to its small size,
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19
fly ash precipitated in this area could be carried long distances as suspended
solids in surface runoff. If attached to fly ash particles, the mercury
could thus be carried downstream to such locations as Vallecito Reservoir
and Navajo Reservoir.
From the data available, it would be pure speculation to attempt to make
an accurate estimate of the amount of mercury transported from Four Corners
to the Navajo Reservoir drainage area. It would appear reasonable, however,
that as much as one-third of the 4L:otal stack emissions might be transported
• to the vicinity of Navajo Reservoir. • If the total emissions are as high as
nine tons per year and half of the amount transported to the area is precipi-
tated on the watershed, the Four Corners plant would •be contributing 1.5 tons
of mercury per year, an amount about the same as natural sources. Neasure-
ments of stack emissions and a detailed meteorological study are needed to
evaluate this possibility.
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REFERENCES
1. U. S. Geological Survey, U. S. Department of the Interior, “Mercury in
the Environment”, USGS Professional Paper 713, Tables 2, 3 and 5.
2. U. S. Geological Survey, U. S. Department of the Interior, “Mercury in
the Environment”, USGS Professional Paper 713, Table 18.
3. U. S. Geological Survey, U. S. Department of the Interior, “Water Re-
sources of the Upper Colorado River Basin -- Technical Report”, Geo-
logical Survey Professional Paper 441, Washington, D. C 0 , 1965.
4. Eckel, Edwin B., “Minerals of Colorado - A 100-Year Record”, Geological
Survey Bulletin 1114, Washington, D. C., 1961.
5. Diyision of Control Agency Development, Bureau of Abatement and Control,
Consumer Protection and Environmental Health Service, Public Health
Service, U. S. Department of Health, Education, and Welfare, “Estimates
of Air Pollution Concentrations from Four Corners Power Plant, New
Mexico”, January, 1970.
6. Colorado Liaison Office, Bureau of Mines, .U. S. Department of the In-
terior, “Energy Development in the Four Corners Area - Air Pollution
Considerations”, Denver, Colorado, June 1971.
7. Sorrels, Donald, Chief, Technical Services, Air Pollution Control Divi-
sion, Colorado Department of Health, “Report on Mercury in Coals Used
in the State of Colorado”, Denver, Colorado, June 9, 1971.
8. Friedman, Irving, and Norman Peterson, “Fossil Fuels as a Source of Mer-
cury Pollution”, Science , Vol. 172, June 4, 1971.
9. Food and Drug Administration, Public Health Service, Department of Health,
Education, and Welfare, letter transmittal of results obtained for fish
samples (at selected sampling stations in the States of Colorado, New
Mexico, and Utah) analyzed for mercury, Denver, Colorado, October 1970.
10. U. S. Geological Survey, U. S. Department of the Interior, “Reconnaissance
of Selected Minor Elements in Surface Waters of the United States,
October 1970”, Geological Survey Circular 643, prepared in cooperation
with U. S. Bureau of Sport Fisheries and Wildlife, Washington, D.C., 1971.
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