vvEPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory >
Cincinnati OH 45268
Research and Development
EPA-600/D-84-143 Aug. 1984
ENVIRONMENTAL
RESEARCH BRIEF
Quality and Quantity of Leachate from Raw Mined Colorado Oil Shale
David B. McWhorter
Introduction
Commercial utilization of the vast energy resource repre-
sented by the oil shale deposits in Colorado, Wyoming, and
Utah is more nearly a reality now than ever before. Raw
mined shale piled on the ground surface constitutes a
relatively permeable mass of particles ranging in size from
silt and clay to boulders that readily accommodate
infiltration of incident precipitation. A portion of the waters
that infiltrate the piles is evaporated and a portion
percolates downward and eventually becomes seepage
from the pile.
Fragmentation of raw shale and placement in a different
hydrogeochemical environment creates the potential for
the release of undesirable chemicals into waters contacting
the materials. A previous laboratory study suggested that
the potential was sufficient to warrant a field data collection
program. A cooperative field study was initiated on April 1,
1980, under IEPA Cooperative Agreement CR8O7513. The
major objective of the research was to determine the
quantity and quality of leachate generated in storage piles
of raw mined oil shale by establishing subsurface collector
systems at various depths beneath the surface in order to
intercept percolate through the piles. A secondary objective
was to compare the data from the field with that generated
from laboratory columns to assist in the assessment of
leaching columns as a useful test of potential chemical
release.
The research was originally conceived as a cooperative
project among Colorado State University (CSU), U.S.
Environmental Protection Agency (EPA), the U.S. Geo-
logical Survey (USGS) Area Oil Shale Off ice (now the BLM
Oil Shale Project Office) and the Rio Blanco Oil Shale
Company. The first leachate collection systems were
installed on Federal lease tract C-a under that agreement
and the first leachate sample was collected in August 1980.
Subsequently, the scope of work was broadened to include
a similar installation on Federal lease tract C-b in coopera-
tion with the Cathedral Bluffs Shale Oil Company. The
leachate collection systems at C-b were constructed during
the fall, 1980. The results reported herein were obtained
during the 1981 -1983 study period.
Construction of Collection Systems
That seepage of percolate through the raw shale piles at C-a
and C-b lease tracts occurs at less than full saturation is
dictated by the fact that the rate of supply from precipitation
is intermittent and nominally less than the saturated
hydraulic conductivity of the materials. The pressure of the
percolating solution is less than atmospheric under such
circumstances. Even though methods: for measuring and
sampling seepage at negative gage pressures are available,
the decision was made to utilize an impervious surface
buried in the pile as a collection mechanism. The rationale
included the fact that the materials are quite coarse and,
therefore, little change in the flow pattern would be induced
by artifically creating a perched water table on the
impervious surface of the collector. !
Materials and Methods \
The collection system installed at C-a includes three
collectors buried beneath raw shale at depths of 5,10, and
15 feet beneath the surface of the shale. Each collector
consists of a 10 foot by 10 foot square (93,000 cm2) of.
impervious material, contoured so that the intercepted*
percolation is conducted to a drain pipe located near the
center of the collector (Figure 1). In construction of the
collectors, the first step was preparation of a sand bed upon
which a continuous sheet of polyethylene was placed. The
foundation, upon which the sand bed was prepared, is
natural ground that was graded to form small pads for the
collectors. A hole of appropriate size was cut in the
polyethylene through which the outer drain pipe can be
raised through the sheet from the bottom. The outer drain
pipe was 11/4-inch diameter PVC and served the dual
-------
Polyethylene
sheet •
Teflon
sheet
Inlet to
overflow
Perforations
Gravel filter
Teflon filter
Teflon funnel
Sand cushion
\'.v-v'v':' Concrete
PMC pipe
PVC pipe to overflow bottle
Teflon tube to sample bottle
Figure 1. Construction details of the buried collectors—C-a tract.
functions of conductor pipe for the inner drain tube and as a
drain pipe for any percolate that was collected on the
polyethylene sheet.
Inside the outer drain pipe, a teflon tubing was placed. The
inner drain tube was connected to a teflon funnel that
projected upward through the polyethylene sheet. Concrete
was placed around the PVC pipe and supported the teflon
funnel as shown in Figure 1. A teflon screen (filter) was
situated in the funnel. The next step was to place a thin
layer of gravel-size material over the top of the concrete and
funnel. The screen in the funnel prevents the gravel from
entering the teflon tubing.
The entire 10 foot by 10 foot area was covered with a teflon
sheet. It was not possible to obtain a single teflon sheet of
the size required, so it was necessary to overlap several
stripsthatwerecutapproximately 11 feet long. The width of
each strip was about 30 inches. The overlap was of a
shingle type so that leakage through the teflon was
minimized. Directly above the teflon filter, holes were
drilled through the teflon sheet so that percolate collected
on the teflon sheet would pass directly into the funnel and
then into the inner drain tube. As shown in Figure 1, a hole
wasformed in the concrete. The purpose of this hole was to
provide for flow of any percolate collected between the
teflon and polyethylene sheets to the outer drain pipe.
The function of each collector, constructed as described
above, is visualized as follows. Percolate through the
overlying raw shale will first encounter the teflon sheet.
Most of the intercepted percolate passes over the teflon
.sheet and into the funnel and inner drain tube. In the event
that a portion of the percolate makes its way through the
teflon via the overlapping joints or punctures, it is collected
ion the underlying polyethylene sheet and conducted to the
outer drain pipe. In this way, any percolate issuing from the
jnner tube will have contacted only teflon. The total
jpercolate from both the inner and outer drains is indicative
of the quantity of percolate intercepted.
The inner and outer drain tubes conduct the percolate by
gravity from the collectors to sample bottles located in a
small shelter at the toe of the shale pile. The teflon inner
lines are connected to teflon sample bottles as shown in
Figure 2. The sample bottles designated A, B, and C are 2
liter bottles with teflon connections. Figure 3 shows the
idetails of the connections to the bottles and of the teflon
block in which the resistance/temperature probe is fixed.
Note that the connections to each sample bottle are
[designed so that bottle A must fill before percolate is
transported to bottle B. Bottle B is the second bottle to fill
and so on. Percolate in excess of six liters is collected in the
large overflow bottle (D). Bottles D and E are both
polyethylene containers of approximately 40 liter capacity.
IThe collectors established at the C-b lease tract are a very
similar construction. At the C-b site efforts were made to
turn up the edges of the teflon and polyethylene sheets to
* form a somewhat deeper collector than those established at
| the C-a site. The purpose was to minimize any tendency for
iflow to be diverted around the collectors by the somewhat
greater piezometric head in the water directly above the
collector surface as compared to that exterior to the
-------
Polyethylene sheet overflow
collection line
Teflon collector
line
Resistance/temperature
Probes
Sample *«.
overflow bottle
Figure 2. Schematic of the collection bottle arrangement.
Teflon tee
Outflow to
next bottle,
Inflow from
lysimeter
EC probe
Inflow from
EC device
,tutflowto
Air
vent
Teflon block
Sample bottle
Figure 3. Details of the electrical conductivity.
collector but at the same elevation. The only other
significant difference is the depth of burial. At the C-b site,
the collectors are buried to depths of 10, 15, and 20 feet.
The corresponding depths at C-a are 5, 10, and 15 feet. At
the time of construction, the collectors were located on the
edge of existing shale storage piles. Subsequent growth of
the piles has made the collectors integral parts of piles and
no artificial boundary effects are present to our knowledge.
Placement of Raw Shale
The raw shale placed over the collectors at C-a was
extracted from the R-5 zone near the base of the first retort
(retort "zero"). The material mucked from blasts 1,2, and 3
on May 8,16, and 30 with roof elevations of 6106 feet (48
feet below top of R-5), 6121 feet (33 feet below top of R-5),
and 6141 feet (13 feet below top of R-5) was placed in three
piles on the surface from which;shale was taken for
placement in the period May 18-22. The material directly in
contact with the teflon sheets was hand placed to minimize
the probability of puncture. After this hand-placed layer
was completed, some 10-12 inches of material were
shoveled on to the collectors by hand. Subsequent lifts
were placed with a front-end loader. During this period,
alternate loads were taken from blast 1 and blast 2 piles so
that the bottom two-thirds of the shale over the collectors is
a mixture of muck from blasts 1 and 2. Approximately the
upper third of the shale over the collectors came from the
muck pile from blast 3 and was placed in the periods of June
9-11 and June 17-18.
The raw shale at C-b was placed on the collectors during the
period of December 8-10,1980. Material mucked from the
intermediate void level of the ventilation-escape shaft and
the service shaft was utilized. The material from the V-E
shaft came from an interval between elevations 5245 and
5265 feet. The extraction interval from the service shaft
was 5340-5360 feet. Both intervals are in the "B" Groove,
an interval of lean oil shale at the baste of the rich Mahogany
zone. The materials were placed on the collectors in the
same manner as utilized at C-a. It is estimated that the final
mixture of materials over the collectors is 40% from the V-E
shaft and 60% from the service shaft.
Data Collection and Analysis Procedures
Precipitation
Precipitation is measured at both field installations with
recording rain gages. The recording rain gage at C-a is
located approximately 150 feet north of the collectors at a
site where it is undisturbed by other operations at the site. A
recording gage is installed immediately adjacent to the 10-
foot collector at the C-b installation. Tract personnel collect
the charts, and service and maintainlthese gages. Copies of
the charts are sent to Colorado State University. Any
differences in precipitation as interpreted by tract and CSU
personnel are reconciled and a final record of cumulative
precipitation at both sites is prepared. No chemcial analysis
of incident precipitation has been -made. Insofar as the
chemistry of both the precipitation and shale are site-
specific, so also is the quality of the leachate.
Leachate Volume •
All leachate collected on the teflon or polyethylene sheets is
routed to collection vessels through drain lines as pre-
viously described. Generation of leachate is sporadic in
response to random precipitation and snow melt. No
attmept was made to measure instantaneous seepage
rates. Rather, a record of cumulative volume of leachate for
each collector is prepared. Members of the staffs at Rio
Blanco and Cathedral Bluffs monitor the volumes of
leachate in all of the collection vessels at the respective
sites. From time to time, CSU personnel are on site and
make the measurements, but usually the tract personnel
forward the volume measurements to CSU for tabulation.
Sampling for chemical analysis is focused on the teflon
bottles labeled A, B, and C (Figure 2). These bottles are
emptied and volumes recorded on a very frequent basis,
while the overflow bottles designated D and E are emptied
less frequently. Volumes are recorded only when the
-------
bottles are emptied. This procedure sometimes results in
abrupt increases in leachate volume that are related to the
vessels being emptied rather than to a flow event. Overall
correspondence between precipitation and leachate gen-
eration is not masked by this procedure; however, instan-
taneousf low rates calculated from the record of cumulative
leachate volume would be unreliable.
Sampling
Provision was made for a flow-through electrical conduc-
tivity probe and thermocouple to be located in the teflon
collection line, upstream of the collection bottles. For one
period during 1980, a data logger was used to record
electrical conductivity (EC) and temperature of the leachate
at the C-a facility. Unreliable operation of this equipment
forced abandonment of its use, however. Field temperature
and EC were measured at the time the bottles were
sampled for chemical analysis.
The staffs of Rio Blanco and Cathedral Bluffs monitored the
collectors and took the samples as they became available.
The samples were chilled and CSU personnel were notified.
CSU personnel traveled to the site and returned the
samples to the CSU laboratory where they were prepared
for analysis. In some instances, the samples were shipped
directly to CSU. Each sample was divided into 3 aliquots,
one of which remained as raw leachate, one of which was
filtered through a 0.45 micron filter, and one of which was
filtered and acidified with nitric acid. Normally these
procedures are accomplished in the field, but since the
samples often remained in the collection bottles in the field
for periods up to a few days before sampling occurred, little
would be gained by field preparation.
Laboratory Leaching Tests
An objective of this project was to assess laboratory
leaching tests relative to their utility as predictors of the
quality of waters in field-generated leachates. Samples of
the raw shales directly overlying the shallowest collectors
at both sites C-a and C-b were brought to the laboratory and
subjected to the ASTM extraction test entitled "Proposed
Methods for Leaching of Waste Materials." This ASTM test
"is intended to determine collectively the immediate
surface washing and the time-dependent diffusion-con-
trolled contributions to leaching from the waste." Only the
water shake extraction test was performed. A known dry
weight of raw shale (700 g in these tests) was placed,
together with 2800 cm3 of distilled water, in a vessel and
closed. The vessel was agitated by a modified paint-shaker
apparatusthat imparted both lateral and vertical reciprocat-
ing motion to the vessel. Agitation was continued for 48
hours, after which the solid-liquid mixture was allowed to
separate by gravity for about one hour. The solution was
decanted into a compressed nitrogen barrel filtering
apparatus and filtered through a 0.45-micron filter. The
filtered solution was preserved for chemical analysis.
Column leach tests had been performed previously on a few
raw shales. These same materials were subjected to the
test described above. The results of the water shake
extraction are compared with data from the column tests in
a subsequent section.
Chemical Analysis
A list of chemical parameters and the method used for their
determination is given in Table 1. As part of the quality
control program practiced in the laboratory, EPA samples
with known and variable concentrations were analyzed
with each group of samples. If results for the known
samples deviated more than 10 percent from the true value,
analyses were repeated until satisfactory agreement was
obtained. Samples were occasionally spiked with a known
and multiple standard additions were run to check complete-
ness and determine sample matrix effects. Standards are
run and instruments are recalibrated with a frequency
sufficient to detect and correct instrument drift and other
problems that sometimes arise.
Table 1. List of Parameters and Methods
Parameter
Method
pH
EC
ALK
HCO3
CO3
HSCO3
TDS
F
Cl
P04
N03
SO4
Zn
Fe
Co
Li
V
NH3
B
Cd
Be
Mg
P
Si
Mo
Mn
Ni
Na
Cu
Al
Ca ,
Ba
K
Cr
Sr
Pb
Ag
Tl
Se
As
Hg
Total N
Electrode
Wheatstone bridge
Titration
Calculation from ALK
Calculation from ALK
Calculation from ALK
At 180° gravimetric
Ion chromatography
Ion chromatography
Ion chromatography
Ion chromatography
Ion chromatography
Atomic adsorption
Atomic adsorption
Atomic adsorption
Atomic adsorption
Flameless atomic adsorption
Ion selective electrode
Inductively coupled plasma
Atomic adsorption
Inductively coupled plasma
Atomic adsorption
Inductively coupled plasma
Inductively coupled plasma
Inductively coupled plasma
Inductively coupled plasma
Atomic adsorption
Atomic adsorption
Atomic adsorption
Inductively coupled plasma
Atomic adsorption
Inductively coupled plasma
Inductively coupled plasma
Atomic adsorption
Inductively coupled plasma
Atomic adsorption
Atomic adsorption
Flameless atomic adsorption
AA (Hydridegeneration)
AA (Hydridegeneration)
Cole vapor cell
Kjehdahl
-------
Results
Precipitation and Leachate Volume
The volumes of precipitation and leachate generated at
both experimental sites were measured. Figure 4 shows
the cumulative volume of leachate measured during each
year from the collector buried at a depth of 20 feet on the
C-b lease tract. Also shown in Figure 4, for comparison, is
the cumulative precipitation measured at C-b. The monthly
plotting interval masks the fact that the collector system
responds to precipitation but with a lag of some 5-10 days.
A total of (3.15 cm of leachate was measured in 1981,
representing 20 percent of the precipitation measured over
the same time period. The C-b, 10-foot and C-b, 15-foot
collectors produced 4.36 cm (14 percent) and 6.39 cm (21
percent) of leachate, respectively. The total volume of
leachate collected over the study period at C-b ranged from
11.52 cm to 17.02cm, and represents 12% and 17% of the
total precipitation, respectively. Such volumes of percolate
are large in the perspective of anticipated natural recharge
rates for the area. The relatively large volumes are
attributed to the fact that the piles are very pervious and
bare of vegestation, both conditions which tend to minimize
runoff and evapotranspiration losses that operate on the
undisturbed ground.
The close agreement between measured volumes of
leachate from the 15-foot and 20-foot collectors on the C-b
tract suggest that the volumes measured in these two
collectors are the most reliable volume data collected in the
study. The cumulative leachate volume from the 5-foot
collector at a C-a is shown in Figure 5 along with the C-a
precipitation. Again, there is a correspondence between
the two curves, and the volume collected is 16 percent of
the precipitation total. Volumes of leachate from the 10-
foot and 15-foot collectors at C-a are 6.67 cm and 6.26 cm,
respectively. It is speculated that settlement subsequent to
construction caused the collectors at C-a to become tilted,
and hence, less effective. Even though similar settlement
may have occurred at C-b, the substantially higher rise of
the edges provided on the C-b collectors is thought to have
prevented settlement from reducing the effectiveness of
the collectors. With the exception of the 10-foot collectors
at C-a, all collectors have been effective in producing
samples for chemical analysis. Presumably, the ineffi-
ciency of the collectors affects only the volume and not the
quality of the leachate.
Electrical Conductivity and pH
Electrical conductivity (EC) and pH were measured in the
field at the time each sample was collected. Figure 6 shows
the EC and pH of leachate produced from the two reliable
collectors at C-a. The pH of leachate from the two collectors
ranges from 6.9 to 7.9. There is no apparent pattern or trend
in the pH data. The mean EC values are approximately
30,600/umhos/cm and 18,300 yumhos/cm for the 15-foot
and 5-foot collectors, respectively. Among the possible
explanations for the difference between the two mean
values is the possibility that the materials overlying the
collectors is not the same. Different residence times and
variations in the partial pressures of carbon dioxide and
oxygen with depth may also contribute. No trend toward
lower EC is discernible in these data and is not yet expected
in view of the relatively small quantities of throughput that
have occurred to date.
•9-
CJ
220
I
J5 10
1
O 0
17
of 6
5
OJ A
•S
**- O
o o
I2
I /
-------
N30
ra
-^20
i-
• 5 ft collector
° 15 ft collector
•5 ft collector
»15 ft collector
Oj 1981 1982 1983
Figure 6. Electrical conductivity and pH for C-a collectors.
• 10 ft collector
• 15 ft collector
o'°
5.
!<
tf
• 1111 • 111111.111111111111111111
•70 ft collector
0/5 ft collector
7S82
1983
Figure 7. Electrical conductivity and pH for C-b collectors.
section. The third contrast with the C-a data is that the EC of
leachate at C-b did not increase with depth. This observa-
tion casts doubt on different residence times as a viable
explanation of the observed differences in EC for the 5-foot
and 15-foot collectors at C-a. As was the case for C-a, the
data in Figure 7 do not exhibit a trend toward lower EC with
increasing time.
Quality of Leachate
Many of the samples collectedfrom bottles A, B, and C were
prepared for chemical analysis. Analyses of waters con-
tained in bottles B and C did not often differ significantly
from those of bottle A water. Presentation and discussion of
data from bottle A only is contained in this report. The
chemical analyses reported herein represent approximately
70 percent of the total number of such analyses performed
on leachate samples. The remaining analyses were from
bottles B and C and occasional duplicate runs.
The major ion chemistry of leachate from the C-a collectors
is presented in Tables 2 and 3. The waters are saline with
total dissolved solids concentrations ranging upwards of
70,000 mg/l. Dissolved constituents are dominated by
magnesium and sulfate. The concentration of calcium in
Jeachate from both collectors suggests that the calcium
concentration is controlled by the solubility of calcium
Sulfate. The magnesium concentration does not appear to
be solubility controlled.
Tables 4 and 5 contain data on the major ion composition of
ileachates collected at C-b. In contrast with C-a, the
concentration of dissolved solids in C-b leachate is much
•lower. Also, the composition of the C-b leachates is
dominated by sodium and sulfate rather than magnesium
and sulfate. As in the C-a leachates, it appears that the
icalcium concentration is controlled by the solubility of
calcium sulfate. A complete explanation for the marked
differences between the leachates at C-a and C-b remains
iunknown. However, it is known that the C-b shale came
from an interval of lean shale with a greater in-situ
ipermeability than at C-a. This lean shale is expected to be of
a different composition than the rich layer mined at C-a. The
larger permeability of the lean shale could also have
resulted in more effective pre-leaching by groundwater
prior to mining.
The concentration of nitrates in the leachate from both C-a
and C-b is greater than was anticipated. One obvious
source for nitrates is residual from the explosives used in
! mining the shale. If this is indeed the major source, it is
expected that a trend toward lower nitrate concentrations
should be observed as a result of washing the residual
explosive from the particle surfaces. Throughput volumes
to date are too small to expect observation of a decreasing
trend at this time.
Tables 6 and 7 present a summary of selected trace element
concentrations observed in the leachate from C-a. Similar
data for C-b are contained in Tables 8 and 9. Analyses for
several other trace elements were performed, but those
; shown in Tables 6 through 9 are most significant. Fluoride
! concentrations in leachate from the C-a collectors ranged
between 8.5 and 36.1 mg/l. Concentration of F observed in
', the C-a, 15-foot collector was significantly greater than in
the 5-foot collector leachate. Fluoride concentrations in C-b
leachate ranged from 4.2 to 10.5 mg/l and the data do not
i show any trend with depth of collector. The concentrations
i of fluoride observed in the field-generated leachates are
: similar to those measured in a previous column leaching
i study, although the raw shales in the columns were not
duplicates of those that overlay the collectors.
Concentrations of zinc and boron are similar in the C-a and
C-b leachates, but both are significantly less than the
'. maximum values observed for these elements in the
1 previous column leaching tests. Again, the difference
! results from differences in materials used in the two
' studies. Mo concentrations are generally similar at the two
, sites. The Mo data at C-b show a significant decreasing
| trend with time in 1981, but recovered in 1982. Concentra-
i tions of the other elements in these tables are similar for
; both sites arid with respect to depth. No reliable time trends
toward lower concentrations are discernible in the trace
' element data. Again, it is emphasized that only a small
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1
Table 2.
Date
4/03
5/07
7/15
8/11
9/14
10/09
11/19
Mean**
4/03
5/07
7/13
8/24
9/10
10/O5
11/19
Mean**
* Balance =
**Exclusive
Table 3.
Date
Major Ion Composition of C-a Leachate — 1981
Ca Mg Na K SO4
meq/l
22.0
35.9
37.3
23.9
30,9
31.9
29.9
31.6
29.5
28.2
25.6
32.4
26.5
26.5
28.9
28.0
86.4
401.3
415.3
368.8
293.6
340.5
396.4
369.3
327.3
600.3
662.0
695.7
703.5
713.0
749.2
637.3
16.3
43.3
40.7
40.2
30.4
32.3
42.2
38.2
42.4
56.6
51.3
55.2
53.1
53.5
58.7
54.7
C-a,
0.2
0.3
0.2
0.2
0.2
0.2
0.2
0.2
C-a,
0.3
0.3
0.2
0.2
0.3
0.2
O.2
0.2
Cl
HCO3
NO3
TDS
mg/l
Balance*
%
5 Foot Collector
98.3
568.0
416.4
445.6
310.2
335.2
487.2
427.1
2.1
4.9
4.5
5.4
3.0
3.5
6.2
4.6
3.2
6.6
6.0
5.7
6.3
6.5
6.6
6.3
10.4
34.2
33.3
27.1
25.8
24.0
27.2
28.6
8720
32960
32630
30950
24230
26850
32860
30080
+ 3.6
-12.1
+ 3.6
- 5.7
+ 1.5
+ 4.7
- 5.8
15 Foot Collector
486.4
768.7
624.6
764.1
770.4
680.8
822.4
738.5
8.5
11.3
9.3
10.6
8.4
11.6
10.6
10.3
2.6
3.7
6.6 ,
5.7
6.2
5.4
4.1
5.3
26.2
31.0
31.6
30.5
24.0
30.2
33.9
3O.2
26210
47040
49700
54820
5453O
54520
59477
53350
-13.4
- 8.6
+ 4.8
- 1.8
- 1.7
+ 4.3
- 2.0
(meq Cations - meq Anions)/Total meq
of sample on 4-3 • • '
Major Ion
Ca
Composition of C-a Leachate— 1 982,
Mg
Na
1983
K SO4
meq/l
Cl
HCO3
NO3
(
TDS
1 mg/l
Balance*
%
C-a, 5 Foot Collector
3/16/82
5/27
6/07
7/01
8/04
9/21
Mean**
6/21/83
3/16/82
4/12
5/17
6/02
7/01
8/04
9/21
Mean**
6/21/83
20.1
20.0
18.9
18.8
22.7
20.2
20.1
12.2
24.0
23.5
22.0
19.4
, 20.2
16.3
17.8
19.9.
12.2
196.3
360.1
339.9
373.7
397.4
341.6
362.5
253.5
665.4
786.8
812.8
733.3
765.4
1002
1128
871.4
•
22.1
37.8
26.3
21.4
32.4
34.7
30.5
24.1
61.3
53.7
57.0
55.2
57.4
70.0
64.8
59.7
52.9
0.3
0.2
0.2
0.3
0.2
0.2
0.2
0:1
C-a,
0.3
0.2
0.2
0.2 ,
0.2
0.4
0.4
0.3
0.1
25.0
482.5
383.1
414.3
424.7
453.9
431.7
311.9
2.1
5.3
5.1
5.9
5.0
3.9
5.0
4.6
4.6
6.1
3.2
5.4
5.6
5.5
5.2
4.O
11.6
22.6
22.1
22.6
17.3
21.4
21.2
16.3
17480
' 29810
29550
; 28900
26440
29520
: 28840
24500
- 5.4
-10.5
- 3.5
- 3.9
0.0
-10.0
- 7.0
1 5 Foot Collector
796.8
743.3
946.7
784.9
816.2
862.0
891.1
840.7
801.8
7.3
8.2
8.5
9.3
10.3
1O.9
8.9
9.4
8.6
3.8
4.5
4.9
6.2
6.7
7.8
9.5
6.6
5.1
27.2
32.1
37.6
36.6
39.0
33.9
35.3
35.8
25.3
57350
62190
6567O
64900
66570
71320
\ 71960
67100
'• 54200
- 5.3
+ 4.6
- 5.6
- 1.8
- 1.7
+ 8.7
+12.3
' -
* Balance -• (meq Cations - meq Anionsj/Total meq
**Exclusive of sample 3/16 -
-------
Table 4.
Dote
Major Ion Composition ofC-b Leachate—1981
Ca Mg Na K
meq/l
SO4!
Cl
HCO3
NOs
TDS
mg/l
Balance
4/08
4/21
5/12
6/19
7/23
8/21
9/10
10/09
11/23
Mean
4/08
5/12
6/19
7/08
8/21
9/10
10/09
11/23
Mean
C-b, 10 Foot Collector
12.2
17.8
18.1
26.8
30.4
22.5
24.5
31.4
18.5
22.5
17.5
19.0
21.7
26.0
26.5
27.0
24.4
21.0
22.9
12.8
10.9
14.2
15.2
18.6
19.7
21.2
23.2
24.9
17.9
12.8
16.2
18.7
20.1
22.4
23.8
25.2
28.0
20.9
48.3
42.1
45.2
45.7
45.7
46.5
45.7
44.4
45.2
45.4
49.2
46.5
48.7
47.4
48.3
47.8
45.2
47.4
47.6
0.2
0.2
0.2
0.1
0.1
0.2
0.2
0.1
0.2
0.2
69.2
65.6
63.5
65.8..
83.7
86.4
85.4
82.0
88.7
76.7
0.4
0.4
0.5
0.3
0.3
0.3
0.3
0.3
0.5
0.4
C-b, 15 Foot Collector
0.1
0
0.1
0.1
0.2
0.2
0.1
0.2
0.1
74.4
75.8
71.6
87.9
93.3.
94.5
80.8
89.8
83.5
0.4
0.4
0.4
0.3
0.3
0.3
0.5
0.5
0.3
C-b, 20 Foot Collector
3.3
2.9
2.6
2.9
3.0
3.0
3.1
3.2
2.5
2.9
3.4
2.7
2.8
2.5
2.7
3.1
3.3
2.4
2.9
4.9
3.5
3.9
2.2
1.8
1.6
1.3
1.3
2.2
2.5
2.6
2.8
1.9
1.7
1.4
1.1
0.9
2.0
1.8
5950
5140
5690
6120
6930
7120
7260
7230
6590
6450
6030
6200
6830
7260
7650
7740
7560
7120
7050
-1.8
- 0.2
+ 5.6
-11.0
+ 3.6
- 0.8
+ 1.2
+ 7.1
- 2.2
0.5
0.4
8.3
1.1
0.2
0.3
5.8
1.4
4/21
5/12
6/19
7/23
8/21
9/10
11/23
Mean
20.5
17.9
28.4
26.4
26.0
18.5
22.0
22.8
15.2
15.1
17.9
20.5
21.8
22.9
20.7
19.2
40.6
38.5
44.4
44.4
45.7
45.2
45.7
43.5
0.2
0.1
0.2
0.1
0.1
0.1
0.3
0.1
65.5
68.6
68.4
83.5
83.5
80.8
86.2
76.6
0.5
0.7
0.7
0.7
0.7
0.7
0.6
0.7
2.3
2.4
2.4
2.3
2.4
2.5
2.0
2.3
2.9
3.3
2.7
2.5
2.1
2.1
3.3
2.7
5580
5590
6360
6980
7160
7310
6580
6510
+ 2.8
- 1.8
+10.7
+ 1.6
+ 2.9
+ 0.6
- 1.5
volume of leachate has been collected relative to the pore
volume of the shale overlying each collector. In an attempt
to provide a more meaningful overview of the entire data set
on leachate quality, the data were searched for the
maximum value of each species. The results are shown in
Table 10. In preparation of this table, a few obvious outliers
were ignored. The maximum value of 113 mg/l for fluoride
may be an outlier, but this could not be determined with
confidence. Given the large number of measurements
made over the nearly three years of study, the probability
that the tabulated value of any particular species rs
exceeded a significant fraction of the time is considered to
be very small. Thus, Table 10 presents a reasonable worst-
case picture for the shales studied.
Laboratory Leaching Tests
The ASTM water shake extraction tests for the materials
overlying the collectors were performed and are compared
with field data in this section. Table 11 contains the
! chemical analysis for the filtrate from the water shake
extraction test.
; The large water-to-shale ratio and the vigorous agitation
used in the water shake tests makes it reasonable to expect
: that the dissolved solids concentration in the filtrate is
' indicative of the total soluble salt content of the shales. A
dry weight of 700 g of each shale was agitated in 2.8 liters
[ of distilled water. The concentrations of total dissolved
j solids given in Table 11 are readily converted tosoluble salt
; contents on a weight basis. The soluble salt content of the
! C-a raw shale is 9.7 g/kg and of the C-b shale is 2.8 g/kg.
The effect of water-to-shale ratio on this determination was
! investigated by repeating the test on the C-a shale, using
165 g of dry shale in 3.3 liters of water (i.e., a 20:1 ratio
; instead of a 4:1). The soluble salt content for this test was
13.5 g/kg, some 39 percent greater than determined with
the smaller water-to-shale ratio. Two other materials
; (USBM raw shale and TOSCO II retorted shale) were
similarly tested with similar results. The 20:1 water-to-
8
-------
Table S. Major Ion Composition of C-b Leachate—1982, 1983
Date
Ca
Mg
Na
K S04
meq/l
Cl
HC03
NOa
TDS
mg/l
Balance*
4/05/82
5/18
6/21
7/12
8/04
9/03
Mean
20.1
20.0
22.3
22.9
21.4
23.0
21.6
24.6
27.7
28.5
29.2
30.3
28.7
28.2
40.0
43.5
50.5
60.9
45.2
46.5
47.8
C-b, 10 Foot Collector
0.1
0.1
0.2
0.1
0.2
0.2
0.2
78.5
102.9
77.2
89.9
81.6
82.0
85.4
0.3
0.4
O.4
0.3
0.4
0.4
2.3
2.9
3.1
3.0
3.5
2.8
1.2
1.2
0.7
0.5
0.2
0.6
0.4
2.9
0.7
6080
7160
7200
7430
7300
7300
7080
+ 1.5
- 8.1
+ 11.0
+ 9.4
+ 6.2
+ 6.8
C-b, 15 Foot Collector
4/05
5/18
6/21
7/12
8/04
9/16
Mean
6/21/83
11.6
21.0
14.1
22.8
22.7
21.4
18.9
21.8
32.7
33.2
30.2
31.1
35.7
38.3
33.5
32.0
53.3
48.7
49.1
66.1
46.1
47.8
51.8
29.5
0.1
0.2
0.2
0.2
0.1
0.1
0.2
0.1
87.6
104.1
90.8
90.6
108.7
87.9
94.9
114.5
0.4
0.5
0.5
0.5
0.5
0.4
0.5
0.9
2.2
2.6
2.6
2.7
2.8
2.7
2.6
2.4
1.3
1.2
0.8
0.6
0.5
2.0
1.1
3.6
7180
7890
7670
7620
7640
7570
7600
6890
- 3.3
- 2.5
- 0.6
+12.0
- 3.6
+ 7.3
-18.6
C-b, 20 Foot Collector
4/05/82
5/27
6/21
7/12
8/04
9/16
Mean
6/21/83
20.1
18.5
22.9
23.5
23.9
20.6
21.6
25.2
22.9
17.3
24.6
25.3
28.8
19.3
23.0
31.0
35.2
37.4
56.1
48.7
46.5
47.0
45.1
48.9
0.1
0.1
0.2
0.2
0.1
0.1
0.1
0.2
77.4
82.0
84.1
86.8
79.5
71.8
80.3
104.5
0.4
0.6
0.5
0.5
0.7
0.4
0.5
0.5
2.0
2.2
2.1
2.3
2.4
2.1
2.2
2.1
1.1
2.7
0.2
1.7
1.4
4.3
1.9
1.0
' 5940
5900
6720
7060
6980
6240
6470
' 7910
i
- 1.6
- 8.8
+ 8.9
+ 3.4
+ 8.3
+ 5.2
- 1.3
* Balance = (meq Cation - meq Anions)/Total meg
shale ratio yielded soluble salt contents 38 and 29 percent
greater than did the 4:1 ratio for USBM raw shale and
TOSCO II retorted shale, respectively.
This study investigated the degree .to which the TDS
concentration in the shake test filtrate can be used to
predict the TDS concentration in field-generated leachate.
The simplest method for accomplishing this is the highly
questionable premise that the total weight of dissolved
solids is independent of the volume of water in which they
are dissolved. Data in the above paragraph and other
chemical principles suggest that this is a false premise.
Nevertheless, if such a calculation would provide even
roughly correct estimates of TDS, it would be useful. The
in-place dry bulk density of the shales overlying the
collectors is estimated at 1.4 g/cm3. The porosity is also
estimated to be 0.45. When the pores are saturated, the
corresponding water-to-shale ratio is 0.32. Thus, the TDS
concentration in the filtrate from the 4:1 water-to-shale
shake test ca n be converted to the corresponding val ue with
a 0.32:1 ratio by multiplying by 4/0.32= 12.5. Oathis basis.
the 2427 mg/l value for the C-a raw shale converts to"
30,200 mg/l. This is surprisingly close agreement with the
1981 field measured value of 30,080 mg/l at the 5-foot
depth (see Table 2). A similar calculation for the C-b raw
shale yields 8875 mg/l as comparedito an average of 6450
mg/l measured from the 10-foot collector in 1981. Again,
this is a reasonable agreement considering that the bulk
density and porosity of the raw shale piles in the field are
only estimated values.
The above indicated agreement between measured and
calculated values of TDS concentration is believed to be
largely fortuitous, however. The chemical composition of
the filtrate from the shake tests bears little resemblance to
that of the field-generated leachates as shown in Table 12.
The disparity in the compositions of the filtrates and the
field leachates is not surprising. The concentrations of one
or more of the constituents in the field leachate may be
solubility controlled. The much greater water-to-shale ratio
in the shake tests is expected to remove this constraint on
concentration. For example, the 3.5 percent Ca in C-a
-------
Tab/a 6.
Date
Selected Trace Elements in
F
Zn
C-a Leachatt
B
'.—1981
Si
Mo
Mg/.l
Mn
Ni
At
Sr
C-a, 5 Foot Collector
4/03
5/07
7/15
8/11
9/14
10/09
11/19
8.5
12.5
11.9
..
9.0
9.2
11.3
0.218
0.401
0.270
0.154
0.202
0.176
0.203
0.216
0.445
0.510
0.480
0.550
0.520
0.472
4.6
2.9
3.3
3.1
4.4
4.2
3.6
<0.05
! <0.05
<0.05
; <0.05
<0.05
<0.05
0.22
0.439
3.060
2.500
2.070
2.300
1.950
0.710
0.18
0.67
0.61
0.29
0.31
0.25
0.23
1.1
0.7
<0.02
0.1
<0.02
<0.02
0.31
4.2
7.9
7.3
6.5
5.0
5.2
6.8
C-a, 1 5 Foot Collector
4/03
5/07
7/13
8/24
9/10
10/05
11/19
Table 7.
Date
17.8
22.0
20.2
..
..
19.0
23.0
0.118
0.175
0.281
0.183
0.201
0.186
0.129
Selected Trace Elements in
F
Zn
0.377
0.480
0.500
0.380
0.480
0.510
0.495
2.3
2.2
2.8
1.1
1.9
2.9
2.8
i <0.05 .
• <0.05
<0.05
[ <0.05
; <0.05
1 <0.05
0.21
0.793
2.230
2.500
2.000
1.970
2.200
1.000
0.29
0.51
0.63
0.26
0.28
0.18
0.10
0.7
0.6
<0.02
<0.02
<0.02
<0.02
0.10
6.8
10.9
10.2
8.5
8.0
6.6
7.8
C-a Leachate— 1982 \
B
Si
i Mo
Mg/l
Mn
Ni
Al
Sr
C-a, 5 Foot Collector
3/16
6/07
7/01
8/3O
9/21
14.2
16.7
19.4
20.3
36.1
0.012
0.182
0.158
0.113
0.211
0.071
0.658
0.719
..
-
2.4
6.4
5.7
5.1
2.6
<0.05
' 1.12
' 1.11
! 0.38
<0.03
0.016
1.83
1.29
0.14
0.37
0.017
0.66
0.63
0.20
0.20
<0.02
4.15
5.28
<0.50
<0.50
2.0
7.8
8.3
7.7
6.8
C-a, 1 5 Foot Collector
3/16
4/12
6/02
7/01
7/19
8/04
9/21
30.4
24.3
22.4
32.6
28.6
30.0
42.2
O.111
0.128
0.188
0.243
0.255
0.393
0.311
0.296
0.430
1.54
1.28
1.05
1.39
-
7.0
6.0
13.2
<0.5
<0.5
5.8
1.3
<0.05
<0.05
0.61
0.66
0.36
, , 0.50
<0.03
1.01
0.05
2.34
1.84
1.46
2.21
0.37
0.13
0.05
1.12
1.08
0.66
0.20
0.75
1.72
<0.02
4.37
1.68
1.26
1.70
<0.5
9.7
2.9
8.3
9.3
15.4
13.4
11.0
leachste represents 31.6 meq/l which is approximately the
saturated value for a calcium sulfate solution. The much
greater 23.2 percent Ca in the shaker filtrate represents
only 17.5 meq/l, well below the concentration for a
saturated calcium sulfate solution. Apparently, the con-
centration of calcium in the field leachate is limited by the
solubility of calcium sulfate, but is not so limited in the
shake test.
Similar considerations are expected to apply for the trace
elements. Table 13 compares the concentrations of selected
trace species in the shaker filtrate with field values. The
shake values have been multiplied by 12.5 to convert them
to.approximately the water-to-shale ratio believed to
represent field conditions. Again, there is little or no
quantitative correspondence between the measured and
calculated concentrations.
Conclusions
The results of the investigation of the quantity and quality of
leachate from raw shale piles .warrant the following
conclusions. It is emphasized that the results and con-
clusions reported herein are specific to the shales studied.
10
-------
1
Table 8. Selected Trace Elements in C-b Leachate—1981
Date
Zn
Si Mo
Mg/l
Mn
Ni
Al
4/08
4/21
5/12
6/19
8/21
9/10
10/09
11/23
8.7
6.9
6.4
6.4
1O.5
10.4
6.1
6.6
0.052
0.155
0.455
0.154
0.173
0.188
0.194
0.127
0.626
0.494
0.269
0.394
0.650
0.650
0.690
0.478
C-b, 10 Foot Collector
4.9
4.2
3.2
4.5
5.9
5.7
5.9
3.7
C-b, 15 Foot Collector
4/08
5/12
6/19
7/08
8/21
9/10
10/09
11/23
9.6
6.5
6.9
10.5
10.3
10.2
6.4
6.4
0.189
0.155
0.306
0.239
0.28O
0.319
0.373
0.172
0.456
0.299
0.486
0.550
0.580
0.600
0.590
0.479
4.0
3.0
4.8
4.6
4.8
5.1
5.0
3.6
6.9
3.4
3.3
1.8
1.0
0.6
0.7
1.9
C-b. 20 Foot Collector
Sr
11.3
6.9
5.2
2.5
1.6
1.2
0.49
2.21
0.140
0.117
0.100
0.150
0.200
O.180
0.150
0.081
0.33
0.23
O.31
0.31
0.13
0.14
O.JO
0.071
2.5
1.6
2.8
2.5
<0.02
-------
Table 9. Selected Trace Elements in C-b Leachate—1982
Date F Zn B Si
Mo
Mn
M
Al
Mg/l
7. No trends toward improvement in quality with time
were observed. The volumes of leachate generated in
the study period are small relative to the pore volume
of the shales overlying the collectors. Improvement in
quality is not likely until the volume of leachate
exceeds at least 0.5 pore volumes.
The author may be contacted at the Department of
Agricultural and Chemical Engineering, Colorado State
University, Fort Collins, CO 80523.
Sr
C-b, 10 Foot Collector
4/05
6/21
7/06
7/12
8/04
9/08
4.23
5.55
5.80
5.81
4.72
6.88
0.021
<0.001
0.004
0.296
0.041
0.003
0.370
0.94
0.64
0.89
0.99
--
6.7
11.4
7.0
7.6
9.2
3.9
-------
1
Table 10.
Species
HCO3
COa
TDS
F
Cl
P04
NO3
SO4
Zn
Fe
Co
Li
NH3
B
Cd
Be
Mg
P
Si-
Mo
Mn
Ni
Na
Cu
Al
Ca
Ba
K
Cr
Sr
Pb
Ag
Tl
Se
As
Hg
Maximum Observed Concentrations
Concentration
mg/l
579
5.68
72660
113
366
0.28
2564
45900
0.597
2.02
1.17
0.339
2.55
1.97
0.168
0.3OO
12830
7.0
13.2
1.5
2.34
1.12
2030
0.073
5.28
505
0.822
16.4
O.290
15.4
1.036
0.012
0.007
0.013
O.OO7
O.003
Location
C-a, 15 Ft
C-a, 15 Ft
C-a. 15 Ft
C-a, 15 Ft
C-a. 15 Ft
C-b. 20 Ft
C-a, 15 Ft
C-a, 15 Ft
C-a, 15 Ft
C-a, 15 Ft
C-a, 15 Ft
C-b. 10 Ft
C-a, 5 Ft
C-b. 15 Ft
C-a. 15ft
C-b, 10 Ft
C-a, 15 Ft
C-a, 15 Ft
C-a. 15 Ft
C-b, 10 Ft
C-a, 15 Ft
C-a, 15 Ft
C-a, 15 Ft
C-b, 10 Ft
C-a, 5 Ft
C-a, 15 Ft
C-b. 10 Ft
C-a, 15 Ft
C-a. 15 Ft
C-a, 15 Ft
C-a, 15 Ft
C-a, 15 Ft
C-a, 15 Ft
C-a, 15 Ft
C-b, 2O Ft
C-b. 20 Ft
Date
9/21/82
7/19/82
8/16/82
7/26/82
7/01/82
2/25/82
7/26/82
5/10/82
8/16/82
8/1 1/82
8/23/82
7/26/82
8/30/82
7/26/82
7/26/82
7/O6/82
9/06/82
8/04/82
6/02/82
7/O6/82
6/02/82
6/02/82
8/02/82
7/06/82
7/01/82
3/22/82
9/23/82
7/19/82
6/02/82
7/19/82
8/1 1/82
3/17/82
4/12/82
7/01/82
8/04/82
2/25/82
Table 1 1. Chemical Analysis of Water Shake Extraction Test
Parameter
pH
EC
ALK
HzCOa
HCO3
CO3
TDS
F
Cl
P04
NOa
SO4
Zn
Fe
Co
Li
V
NHS
B
Cd
Be
Mg
P
Si
Mo
Mn
Ni
Na
Cu
Al
Ca
Ba
K
Cr
Sr
Pb
An
Ag
Tl
Se
As
Hg
Total N
fimhos/cm
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
-.-. ju / 1
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
C-a*
Raw
8,22
2500
124.4
2.OO
149.6
1.06
2427\
1.52
84:5
0.8
112]
1480
0.015
0.011
-------
Tabla 12.
Comparison of Composition of Shake Test Filtrates
with 1981 Field Leachates
Constituent
Percent of Total Milliequivalents
C-a Raw Shale C-b Raw Shale
Shake Field Shake Field
Ca
Mff
Na
K
SO*
HCO*
Cl
/VO3
23.2
18.9
6.8
0.2
41.0
3.3
3.2
2.4
3.5
40.8
4.2
~0
47.2
0.4
0.4
3.2
13.1
16.4
17.4
1.9
34.4
12.1
0.4
1.0
13.3
10.6
26.9
0.1
45.5
1.7
0.2
1.5
Table 13. Trace Element Concentrations in Shake Filtrate
Compared with 1981 Field Leachate Values
Concentration, mg/l
C-a C-b
Element Shake* Field Shake* Field
F
Zn
B
Si
Mo
Mn
Ni
Al
Sr
19.0
0.188
2.075
37.5
3.75
0.662
O.088
2.5
63.8
10.4
0.232
0.456
3.7
<0.05
2.290
0.363
<0.3
6.1
29.9
0.100
1.50
23.8
7.2
0.13
0.08
2.9
23.8
7.8
0.187
0.531
4.8
3.9
0.14
O.20
<1.3
9.0
'The shake values have been multiplied by 12.5 to convert them to
approximately the water-to-shale ratio believed to represent field
conditions.
14
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