vvEPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S7-80-181 Mar. 1981
Project Summary
Reconnaissance Study of
Leachate Quality from Raw
Mined Oil Shale—Laboratory
Columns
E. Bates, R. Wolf, and D. McWhorter
This report contains the results of a
laboratory-based reconnaissance
study of potential water quality prob-
lems associated with leachate from
surface storage of raw shale. Since
laboratory tests are not capable of
simulating field conditions, the results
of this study must be viewed only as a
general indicator of the water quality
that can be expected in leachatesfrom
raw shale. A major purpose of the
study was to investigate whether or
not more realistic and comprehensive
field tests are warranted.
Eight different materials were sub-
jected to leaching. Four of the mate-
rials were raw mined shales obtained
at different locations in the Colorado
oil shale region. The other four mate-
rials were samples of shales and soils
that had been exposed to natural
leaching processes. The four previ-
ously exposed materials provide a
background or baseline that assisted
in placing the results for the mined
shales in an appropriate perspective.
This Project Summary was devel-
oped by EPA's Industrial Environ-
mental Research Laboratory, Cincin-
nati, OH. to announce key findings of
the research project that is fully docu-
mented in a separate report of the
same title (see Project Report order-
ing information at back).
Introduction
In this study, leaching was conducted
by passing de-ionized water through1
columns of each material. All of the
materials described previously were
subjected to saturated leaching testing,
and most were also subjected to unsat-
urated leaching. Samples of the
effluents were collected and subjected
to chemical analyses, which were per-
formed at the analytical laboratory in
the Chemistry Department at Colorado
State University under the direction of
Dr. Rodney Skogerboe. The electrical
conductivity of the effluent from the
columns was measured at short time
intervals by means of a flow-through
probe and a data logger. Grain size
analyses were made for each material.
Samples for the experiments were ob-
tained through the cooperation of the
Rio Blanco Oil Shale Company, the
Colony Development Project, the U.S.
Bureau of Mines, Occidental Oil Shale
Corporation and Union Oil Company.
Funding for this study was provided
through EPA Grant No. R806278.
In one set of tests, the initial saturated
leaching was followed by a second sat-
urated leaching after a period of drain-
age and aeration. The tests on the soils
and previously exposed shales were
conducted to provide a basis for com-
parison of the results from the raw
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mined shales. The results indicate that
leachates from mined shales will
contain dissolved solids at levels sub-
stantially greater than the background
levels as indicated by the soils and pre-
viously exposed shales. This study
indicates that the trace elements Al, B,
F, Zn, Pb and possibly Mo occur in the
leachates from some of the mined
shales in quantities significantly greater
than in the leachates from the back-
ground materials. All other trace
elements considered in this study were
present in the effluents from the mined
shales in about the same concentration
as observed in the leachates from the
soils and previously exposed shales.
Description of Samples
Two samples of raw shale were ob-
tained from federal lease tract C-a with
the cooperation of Rio Blanco Oil Shale
Company. One of these is a sample of
mixed ore from the R-5 and Mahogany
zones and is designated C-a R-5/
Mahogany in the remainder of this
report. The second sample is the trim-
mings from the service shaft.
A sample of unretorted shalefrom the
Mahogany zone was obtained with the
cooperation of Colony Development
Operations from the mine on Parachute
Creek. This sample was extracted from a
stockpile of minus 1/2 inch material
that was mined approximately 6 years
ago. This sample is called Colony raw
shale through the report.
The fourth raw shale sample was ob-
tained from the U.S. Bureau of Mines
site in Horse Draw. This material is from
a drift at 4208 MSL elevation in the
saline zone and had been stockpiled
outside for approximately 6 weeks.
Soil samples were collected from two
locations. The sample designated
Colony soil was obtained in the vicinity
of the crusher and stockpile at the
Colony site on Parachute Creek and was
scraped directly from the surface. The
second sample was obtained from the
B-horizon exposed in a small cut in
Cottonwood Gulch on the C-b federal
lease tract. These samples are desig-
nated Colony soil and C-b soil, respec-
tively.
The other two materials tested are
designated Colony naturally leached
and Union naturally retorted. The first is
talus slope material collected near the
mine on Parachute Creek. This material
has been exposed to weathering and
leaching and is presumed to be in
approximate equilibrium with the sur-
face environment. The material desig-
nated as Union naturally retorted shale
is shale that has burned under natural
conditions and was obtained near the
portal of Union's mine on Parachute
Creek.
Results
A summary of the range of observe)
concentrations for all parameter:
measured is presented in Table 1. Tabli
2 compares the maximum concentra
tions of some of the more significan
trace elements in raw shale leachatei
with maximum concentrations frorr
naturally occurring materials. The con
centrations of Al, B, F, Mo, Pb, and Zr
were found to be significantly greater ir
the leachates from some of the mine(
shales than in the corresponding
samples from the previously exposec
materials. The levels of all other trace
elements produced by the mined shale:
were comparable to those observec
from the soils and previously exposec
shales. Elevated concentrations of Al, B
F, and Zn were measured in leachate:
from the USBM raw shale. The larges
values of Al concentrations were pro-
duced from the unsaturated leachinq
tests and the second cycle of saturatec
leaching. No consistent relation be
tween Al concentration and the volume
of effluent was found.
Fluorine concentrations in the
leachates from the mined shales were
generally greater than from the previ-
ously exposed materials. Concentra-
tions of F decreased rapidly with the f irsi
pore volume of effluent from the USBM
and C-a R-5/Mahogany mined shales
and then approximately stabilized. A
Table I. Summary of the Range of Observed Concentrations
Para-
meter Units
Al mg/1
As
B
Ba
Be
Ca
C1
CO,
Cr
Cu
EC pmhos/cm
F mg/1
Fe
HCO,
H9
K "
Li "
Mg
Mn
MO
Na
Ni
NO,
Fb
pH
Se mg/1
Si
Sn
SO.
TDS
Zn
USBM Raw
Shale
0.34-754
<0.005
024-43
0.061-017
<0025
36-750
<1 0-560
01-1.1
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Table 2. Comparison of Trace Element Concentrations from Raw Mined
Shales with Those from Soils and Previously Exposed Shales
Soils & Previously Exposed Drinking
Raw Mined Shales Shales Water Criteria
Ele-
ment
Al
As
B
Ba
Be
Cr
Cu
F
Fe
Hg
Li
Mn
Mo
Ni
Pb
Se
Si
Sn
Zn
Max. Cone.
Observed
mg/1
7.54
<0.005
43
0.48
<0.025
0.68
0.69
75
1.8
0.0035
3.1
3.2
5.18
0.60
1.9
<0.01
23.28
1.28
6.8
Max. Cone.
Test Yielding Observed
Max. Cone. mg/1
USBM, Unsaturated 0.37
<0.005
USBM, #2 Saturated 0.99
Colony Raw, #2 Sat. 0.50
<0.025
USBM, m Saturated 0.71
C-a R-5/Mahog., Unsat. 0.38
USBM, m Saturated 25
USBM, m Resaturated 0.52
USBM, #2 Saturated <0.0005
USBM, #2 Saturated 0.51
USBM, #2 Saturated 0.97
C-a R-5/Mahog., Unsat. 0.84
USBM, #2 Saturated 0.075
USBM, #/ Saturated 0.38
<0.01
C-a R-5/Mahog., Unsat. 20. 7
USBM, #2 Saturated 1.37
USBM, #1 Saturated 0.65
Test Yielding
Max. Cone.
Colony Soil
C-b Soil
Colony Nat.
Union Nat. Ret.
Colony Soil
C-b Soil
Colony Soil
Union Nat. Ret.
Colony Soil
Colony Soil
C-b Soil
Colony Soil
C-b Soil
Colony Soil
Colony Soil
0.05
....
1.0
0.05
1.0
1.8
0.30
0.002
0.05
0.05
0.0 /
5.0
similar leaching effect for the soils was
observed, but the concentration of F in
leachate from the other materials did
not decline significantly. After the con-
centration was approximately stable,
the range of F concentrations for the
mined shales was 1 -25 mg/l. Only the
USBM shale yielded F concentrations
consistently greater than 10 mg/l.
The concentration of Zn in the
effluent from the USBM shale was con-
sistently greater than for any of the
other materials tested. The other mined
shales yielded Zn concentrations com-
parable to those obtained in the back-
ground materials.
From comparisons of the maximum
observed concentrations of various
parameters with drinking water criteria,
it is concluded that even the worst
leachate from the columns do not
exceed 100 times drinking water stand-
ards for measured parameters. The
maximum concentrations of Cr, F, Fe,
Hg, Mn, N03, Pb, S4, TDS, and Zn were
found to exceed drinking water criteria,
however. After leaching, the minimum
concentrations generally fell well below
the standards with the exception of F.
Leaching of Common Species
The most convenient indicator of the
quantity of the common species Ca, Mg,
Na, Cl, HC03, SO* in the leachate is the
electrical conductivity (EC) of the solu-
tion. A measure of the leachability of
these species is the rate at which the EC
declines with the volume of throughput.
Figure 1 shows such a relationship for
the USBM raw shale. The two sets of
data in the upper block are those ob-
tained under saturated leaching condi-
tions; the black circles being the initial
run and the open circles being the
resaturated run.
Because the columns were quite
permeable and saturated from the top,
the residence time of the first few
hundred ml of water was much smaller
than the mean residence time. This
short residence time and probable chan-
neling of flow caused the dissolved
solids in the first sample to be less than
the maximun. In the preparation of
Figure 1 and similar graphs, only values
after the maximum were used. This
tends to laterally shift the straight line in
a rather arbitrary way, but has no affect
on the slope of the lines.
The rate of leaching of the common
species for the USBM raw shale is
practically the same in all three of the
experiments. After the initial saturated
leaching had been completed, the
column was allowed to drain and
become aerated for 108 days. Leaching
was initiated again and the data indi-
cated by the open circles were obtained.
The full report contains similar figures
for leaching characteristics of USBM
and Colony raw shales. Colony naturally
leached shale, and Union naturally
retorted shale under both saturated and
unsaturated conditions.
70.0
O
1
I"
a
I
Uj
0.1
After Aeration
slope = -0.977
r2 = 0.970
slope = 0.934
r2 = 0.889
I L
0.1
1.0
10.0
100.0
Pore Volumes
Figure 1. Leaching characteristics of USBM raw shale.
» U,S, aOVERNMBIT PRINTING OFFICE. 1981-757-OU/70Z3
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Recommendations
It is recommended that the chemical
constituents of the leachates generated
under field conditions be determined.
(Such a study is now being conducted by
Colorado State University under the
sponsorship of EPA and with the active
assistance of the Area Oil Shale Office
(USGS), Rio Blanco Oil Shale Company,
Cathedral Bluffs Oil Shale Company,
and DOE). The completed laboratory
study indicates that particular emphasis
should be placed upon the total dis-
solved solids and trace elements Al, B,
F, and Zn, although only B and F were
found at significantly elevated levels in
all of the mined shales tested. There
was some indication that Mo concentra-
tions in leachates from the C-a R-5/
Mahogany mined shale are significantly
above background values. It is recom-
mended that this element be given addi-
tional study. It is recommended that the
sulfur chemistry be given additional
attention. There is a need to determine
the levels of sulfur species other than
sulfate in the leachates.
E. Bates and R. Welfare with the Industrial Environmental Research Laboratory,
USEPA, Cincinnati, OH and D. McWhorter is with Colorado State University,
Fort Collins, CO.
E. Bates is the EPA Project Officer (see below/.
The complete report, entitled "Reconnaissance Study of Leachate Quality from
Ra w Mined Oil Shale—Laboratory Columns," (Order No. PB 81-129017; Cost:
$8.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
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