Economics of Ground Freezing for Management of
Uncontrolled Hazardous Waste Sites
Thayer School of Engineering, Hanover, HH
Prepared for
Municipal Environmental Research Lab.
Cincinnati, OH
Get 84
FB85-121I27
^
it
ii
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EPA-600/D-84-270
October 1984
THE ECONOMICS OP GROUND FREEZING FOR
MANAGEMENT OF UNCONTROLLED HAZARDOUS WASTE SITES
by
John M. Sullivan, Jr.
Daniel R. Lynch
Dartmouth College
Hanover, Hew Hampshire 03755
Iskandar K. Iskandar
U.S. Army Cold Regions Research and Engineering Laboratory
Hanover, New Hampshire 03755
Project Officer
Janet M. Houthoofd
Solid and Hazardous Waste Research Dlvisior.
Municipal Environmental Research Laboratory
Cincinnati, Oil 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION' AGENCY
CINCINNATI., OHIO 452S8
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TECHNICAL REPORT DATA
fPttau trcdlnstntfliont l
conditions. The system is limited to temporary r.rcntment due to maintenance expenses.
Ground freezing has the added features of low noise and minimal environmental
disturbance.
17.
KEY WORDD AND DCCUMENY ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
C. COSATI Iicld/Croup
IB. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
E?A Form 2210-1 (R««. 4-77) PREVIOUS EDITION » OBSOLETE
19. SECURITY CLASS ir/i'J
UNCLASSIFIED
NO. of PAGE;
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ID. StCUHi-r CLASS /r/i»i pectl
•JNCLASSIFIFl)
27. PRICI
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The economics of Ground Freezing for Management
of Uncontrolled Hazardous rfaste Sites
John A. Sullivan, Jr.
Daniel R. Lynch, Ph.D.
Thayer School of Engineering
Dartmouth College
Hanover| Aev Hampshire
Istcandar tC. Iskandar, Ph.D.
U.S. Army Cold Regions Research and engineering Laboratory (CRR£
Hanover, New Hampshire
ABSTRACT
Ground freezing for hazardous waste containment is an
alternative to the traditional and expensive slurry wall or
grout curtain barrier technologies. The parameters
quantified in this analysis of it include thermal
properties, refrigeration line spacing, equipment
mobilization and freezing time constraints.
The economics of tne process is discussed based en the
Poetsch method for ground freezing. Vertical drill holes
with concentric refrigeration lines are spaced along the
desired iraezinu .Unei. A header or manifold system provides
coolant to an interior pipe, with the return line being the
outer casing. A self-contained refrigeration system pumps
coolant around the freezing loop. Temperature-measuring
instrumentation is appropriately placed to monitor the
progress of the freeze front.
Soil parzimeters significantly affect the cost analysis.
Fine-grained soils with high moisture retention can double
the overall barrier expense compared to coarse-grained soils
-------
with low moisture characteristics. The data needed to
calculate the required thermal parameters for technical and
economic assessment of ground freezing are routinely
obtained during the geotechnical and hydrologic site
examination. Consequently, there are no additional site
examination costs for the ground freezing treatment.
High-moisture-retention soils require long
refrigeration times due to their latent heat capacity. They
require closer refrigeration line spacing and higher
refrigeration power than low moisture soils for the same
tine period constraint. Plotting costs for equipment
rental, drill expanses, fuel costs and tine as a function of
refrigeration line spacing produces an overall expense
estimate that can bo used to ccsparc ground freezing witli
other barrier construction technologies. Preliminary
results showed ground freezing to be an economically
competitive alternative to slurry wall and grout curtain
construction for a wide range of thermal conditions. The
system is limited to temporary treatment due to maintenance
expenses. Ground freezing has the added features of low
noise and minimal environmental disturbance.
-------
111
Acknowledgments and Disclaimer
This work was supported by the U.S. Environmental Protection
Agency (EPA), Disposal Branch, Solid and Hazardous Waste
Division, and the U.S. Army Cold Regions Research and
Engineering Laboratory (CRR£L), Hanover, M.H., under
Interagency Agreement Od 930130-01-0. A portion of the work
was conducted at the Thayer School of Engineering at
Dart-mouth College in Hanover. The authors acknowledge the
assistance of Janet Houthoofd, project offic er, £PA.
Citation of brand nasses dees not constitute an endorsement
by either EPA or CRREL. The information contained in this
publication represent.*! the authors* opinions and not those
of £PA or CRREL.
-------
1v
List of Tables
fable I: Jnit Costa for Ground Freezing Equipment and Supplies
Table II: Syabol Definitions and Units
Table III: Slurry Wall and Frozen Ground Construction Estimates
Table IV: Thermal Parameter Effects on Cost and Tims Performance
-------
List of Figures
Figure 1: Soil Freezing Methods - a) brine, b) LS2
Figure 2: Thermal Conductivity as a Function of itoisture Content
for a Fine-Grained Satur-ated Soil (Lunardini, 1981)
figure 3: Economic Overview for EPA Test Case (1000 x 40 x 3 feet)
Figure U: Hypothetical Train Car Toxic Spill - Plan View
Figure 5: economic Overview for Train Car Spill Example
Figure 6: economic Overview for Coarse-Grained, High Moisture Soils
Figure 7: economic Overview for Coarse-Grained, Low Moisture Soils
Figure 8: Economic Overview for Fine-Grained, High Moisture Soils
Figure 9: economic Overview for Fine-G.-a.tned, Low Moisture Soils
Figure 10: Cost and Drill Spacing as a Function of Time
-------
ISTROOUCTIOa
Artificial ground freezing is not a new tecnnology.
There exists a 100-year tradition of shaft sinking in which
ground freezing has been used. The increasing application
of ground freezing for civil engineering projects in recent
years is mainly due to the following advantages:
1) In principle, ground freezing can be used in all
types of soils.
2) Ground freezing is a very flexible construction
method which can meet many boundary conditions and
requirements.
3) Very little or no environmental concern is associated
with the method when dealing with soils for civil
engineering purposes.
During ground freezing tho temperature of the soil
water is lowered below the freezing point, the freezing
temperature of soil solutions is not 32°F (0°C) as for pure
water, since dissolved ions in the soil lower the freezing
point. However, empirical relations exist that quantify the
0_K
freezing point of soils. It might be argued that the
freezing point of hazardous waste is much lower than that of
soil systeos. While this is a valid point, artificial
freezing is don? in the soil surrounding the hazardous waste
and not in the waste itself. Therefore, uncontaminated soil
data are usable. When the soil temperature is lowered to
the freezing point important changes begin to" occur in soil
properties. The strength, of the soil is substantially
-------
increased and the soil permeability decreases. The
potential use of ground freezing in hazardous waste remedial
action is based on these two important points. The increase
in soil strength upon freezing means that a frozen zone of
soil can be formed around or underneath a hazardous waste
site or between the site and an uncontaminated environment
without adding concrete, slurry walls, steel sheet pile
walls, or grout for injection. Also, the frozen zone of
soil becomes practically impermeable.
The first use of artificial freezing was in 1362 in
Swansea, Wales. The purpose was to support a mine shaft
project, which was used for mine production, material and
personnel access, ventilation, and emergency escape exits.
In 1o83 Pootsch patented a method of ground freezing with
cooling pipoa fcmiori, with some modification, is still in
use. In this method vertical dr
-------
An open loop system which uses an expendable coolant
such as liquid nitrogen (LM2) has the advantage over brine
freezing in that it achieves a much lower temperature
(-321°f or -196°C) in a very short time. Therefore, LS2 is
useful in emergency cases where time is limited. Also, the
fast freezing- of contaminated soil by LN2 will result in
immobilization of chemicals, as the soil water (with
contaminants) will freeze in situ. Brine freezing, on the
other hand, has the advantage of freezing the soil walls in
a more regular shape. Temperature measuring instrumentation
is appropriately placed for monitoring the progress of the
freeze front. Figure 1 shows a schematic representation of
the two freezing methods.
Q
According to Braun and Hash the use of ground freezing
in the raining industry has advantages over conventional
me'croos (dewatering, grouting, slurry walls, caissons):
1) It does not require extensive geological data.
2)" It serves several temporary functions, such as
support of an excavation, groundwater control and
structural underpinning.
3) It is adaptable to practically any size, shape or
depth.
4) Excavation can be kept unobstructed as no bracing or
sheathing is usually required.
5) It does not disturb the groundwater quantity or
quality
-------
EXPAHSlOn VALVE
BR1HE
pump
COmPRESSOR
SSB&rt niTf^JwSSSa
•jW7J>l^C|il •«••>?•'•*••«•«>*
££8§? D UI Li g«S?S9a^
-***-*" v«v.«^f«;a
iy^di^l^o
-------
6) It is environmentally acceptable, as no chemicals
will be added, and there is less disturbance to the
site.
Through 1973, more than 200 deep mine shafts had been driven
q
by artificial soil freezing.7
In addition to its use in the mining industry, ground
i •
freezing has been used for construction of open excavations
and deep unsupported construction trenches. For example, it
was used during the construction of subways in Moscow, and
in Zurich. ' About 70 inclined tunnels and over 30
excavations were made by soil freezing. The use of ground
freezing in the Moscow project saved 700 tons of metals and
500 cubic meters of timber, and the project was completed 11
to 12 tnonths early. ' This project was circular, with a
40-o diameter and 20-n average depth. The frozen wall
thickness was 5.6m. •
In North America, artificial freezing has been used
G
since 1833. In 1959 it was necessary to enlarge a twin
railroad tunnel in Montreal. Construction problems arose
because of the presence of a plastic layer of -clay in the
soil and because the tunnel was located under the city and
ran beneath service pipelines and two large buildings.
Artificial soil freezing was successfully utilized in this
project.12
In 1964 liquid nitrogen (LN2> wns used for artificial
soil freezing in Argenteuil, France. In this project a
collector sewage pipe housed in a tunnel broke. The sewage
flooded the tunnel and seaped to a nearby stream. The
-------
influx was stopped by circulating LH2 tnrougn 25 freezing
probes. Later a concrete wall was constructed between the
polluted area and the fresh water stream. ^
The economics of ground freezing as a means of
hazardous waste containment is discussed below. These cost
analyses are based on existing construction practices and
proven freezing technologies. The data needed to calculate
thermal parameters required for technical and economic
assessments of ground freezing are routinely obtained during
the geotechnical and hydrologic site examinations. This
site-specific information is required to evaluate the
1U
technical feasibility of tho containment alternatives. The
thermal data are obtained primarily from soil texture,
moisture content and temperature 2S3Si:rssGnt3. The specific
heat of soils depends primarily on the water content since
the volumetric heat-capacity ratio for water to most dry
soils is about 5. The thermal conductivity of
coarse-grained soils is significantly larger than that of
fine-grained soils. Both saturated soil types exhibit a
decrease in thermal conductivity with increasing water
content. Moisture content measurements determine the
latent-heat energy requirements and establish whether or not
the soil is saturated. A saturated soil system is desirable
for an impermeable frozen barrier, and is assumed throughout
this analysis. Lunr*dini 3 provides extensive data relating
these site examination measurements to soil thermal
properties. As an example, figure 2 displays thermal
-------
FINE-GRAINED SATURATED SOILS
2.5
2_
o
£ 1.5
o
CJ
0
UNFROZEN SOIL
\
FROZEN SOIL
II I IT I II
20
MOISTURE CONTENT (I DRY UEIGHT)
i
50
-------
8
conductivity as a function of moisture content for a
fine-grained saturated soil.
ECCiJOrtIC COHSIOERATIOSS
There are no additional site exaaination costs for the
ground freezing treatment, as opposed to alternate
containoent modes. Therefore, the economics of the
3ita-3pQOific investigation (i.e. geotechnical, hydrologic
and lab filter-cake permeability testing) are unchanged from
the EPA estimate of $20,000 - $80,000.14
Tabl6 I lists unit costs for mast of the equipment
required for ground freezing. Equipment aobilization
involves transport of the boring rig. refrijArat-.ion units,
piping and site-clearing equipment. Th« sit* preparation
requirements for ground freezing are relatively low. The
barrier must be saturated with water if the soil Moisture
content is inadequate. Land clearing is necessary for
equipment access along the freezing route. £xcavation and
heavy duty land clearing are not usually required for ground
freezing. Capital costs include drilling and pipe system
expenses. The drill-hole steel casings are not recovered at
the completion of the project. However, the header system
and interior cooling lines can be rented en a monthly basis.
Energy requirements involve rental of the refrigeration
units, electrical consumption and expendable coolants if
used.
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Table I: Unit Costa for Ground Freezing
Equipment and Supplies.
steel casing
6 in. ID steal casing
Drive shoe
5) Slack steel pip*18
2 in. dia.**
3 in. dia.
6) Self-contained refrigeration units
7 ton refrigeration
110 ton refrigeration
7) Liquid H^9
8) Electricity
0.7 A*
1.5 A ,
3,000 r
Month -
rental costs
par L.F. of
pipe
100 L.F.
2450/A
1100/A-
0.31 /IT
1 2 3
1.40 0.85 0.
,.60 0.90 0.
2.50 1.00 0.
9/L.F.
12/L.F.
15/L.F.
75/wll
0.22/L.F./M
C.36/L.F./M
150/day
2000/week
1.23/100 ft3
0.10 per kwh
65
70
75
• All prices include parts, labor, operating and profit for
subcontractor unless otherwise noted.
»» 2 in. pipe ($5.20/L.F.) - Rent at 2 yr. writeoff - 0.22/L.F./M
3 in. pipe ($8.6G/L.F.) - Rent at 2 yr. writeoff = 0.36/L.F./M
A s c>cre, ¥ s square yard, L.F. = lineal foot, *. - month
-------
10
The time constraint for the frozen wall plays a primary
role in the cost estimate. Mechanical refrigeration units
rated at 5-110 tons of refrigeration are readily
available. These units provide the manifold system with
reusable coolant at -4°r (-20°C) when operated within their
appropriate capacity range. Expendable LM2 is available in
large quantities when the demand for a rapid freezing front
is required. For this system, the expanded N- gas is vented
directly to the atmosphere. The refrigeration units are
replaced with LM_ tanks and control valves that regulate the
LN_ flow based on the vent temperature.
20
Sanger and Sayles provide a scund methodology for
thermal computations of frozen ground. Their energy
requirements and freezing time estimates are somewhat aore
conservative than those predicted by finite element
simulations and actual field measurements. ' However,
for this preliminary economic analysis their predictions are
appropriate. Sanger and Sayles predict the expenditure of
energy based on reasonable assumptions about the heat
transfer process in the soil. The energy per unit length,
Q, time, t, and power per unit length, P, required to freeze
a cylinder of radius R is a function of the soil thermal
properties, thermal conductivity, k, thermal capacity, c,
latent heat of fusion, L, and the temperature difference
20
between the coolant and soil.
Ignoring second-order effects they derived the energy
estimate to be
-------
11
whare the first term in brackets accounts for the energy
*
required to reduce the unfrozen soil temperature from T_
down to freezing. The second term of £q. (1) is the energy
associated with the trar^formation from unfrozen soil to
frozen soil at the freezing temperature, i.e. the latent
heat of fusion, L. The last term describes the energy used
in reducing the frozen soil temperature from freezing to the
refrigeration temperature. The time required to freeze the
column to a radius R is
R2U
and the power requirement is
2irk T
.
tn(R/r0)
where the symbol definitions and units are as given in Table
II. The total power requirement is larger than that
expressed in Eq. (3) due to inefficiencies in the
refrigeration system. A 15 percent thermal loss along the
header system is assumed. The refrigeration system is
conservatively rated at 0.21 ton of refrigeration per
horsepower. *" The energy required for brine purap« and
-------
12
Table II: Symbol Definitions and Units.
a A factor which when multiplied by R defines the
radius of temperature influence on the freeze pipe.
Dimensionless - usually 3 < ar < 5.
j, c~ Volumetric specific heat capacity for frozen
and unfrozen soils, respectively. Btu/ft^/°F (cal/cnrV°C)
J, kg Theraal conductivity for frozen and
unfrozen soils, respectively. Btu/hr/ft/°F (cal/s/ca/°C)
Latent heat of fusion. Btu/ft3 (cal/ca3)
Latent heat effects plus heac requirements of unfrozen
soil.20
1'r-1)
>£ — ' c T
22
P . Power per unit length of pipe. Btu/hr/ft (cal/s/ca)
0 Freezing energy per unit length of pipe. Btu/ft (cal/on)
R Radius of frozen soil column, ft (cm)
r Radius of freeze pip*?, ft (cm)
T2 Absolute value of (unaffected soil temperature - freeze
temperature) °F (°C)
T Absolute value of (pipe temperature - freeze
te-nperature) . °F (°C)
t Time to freeze soil to a radius of R. s (s)
-------
13
cooling fans is estimated at 20 percent of the refrigeration
load.
The economics for ground freezing and slurry wall
construction are based on a 3-foot wall thickness. Once the
soil columns merge according to Eq. (2) Sanger and Sayles
approximate the frozen soil thickness at 0.79 times the soil
column diameter. If this wall thickness is less than 3
feet, the wall increases in thickness as a planar front
according to separate aquations in [20]. This design
thickness is a limitation of the slurry wall excavation
equipment and not a result of structural support or
permeability requirements; nevertheless, we have used it for
the frozen wall to establish a baseline comparison.
Examining Eqs. (1) and (2) one notes that the energy
and tine requirements are proportional to the square of th«.
radius of each cylinder. Initially, one might expect an
economic advantage for a thin-wall construction via multiple
cylinders of small radius. However, the final cost analysis
shows intermediate-radius cylinders as the mo si- economical
due to the reduced number of drill holes reqjir?d. In
addition to the economic gains, a thicker well has greater
seepage resistance, although this is uno.uantifled in t^is
analysis.
Once the frozen wall is formed, a reduced refrigeration
load maintains the wall while the contained hazardous waste
is being treated or removed for proper disposal. The
maintenance economics are conservative ^s they are baaed on
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14
a wall that continues to increase in thickness. The
maintenance power requirement is half that of £q. (3) for
soil columns having diameters (1/.79) times the design
thickness. (The factor 1/2 enters because each soil column
has merged with adjacent frozen columns.) This power
I
requirement coupled with equipment rentals and manpower
comprise the maintenance expense of the wall. A substantial
amount of time exists after the refrigeration unit is
removed due to the latent heat stored in the frozen wall.
If the wall facial area is large compared to the thickness a
one-dimensional melt analysis is applicable. Carslaw and
23
Jaeger J provide an analytic solution for .a simplified
one-dimensional melt problem. The region x > 0 is initially
solid at the melting temperature. The wall face at x s 0 is
raised to a constant temperature above the melting
temperature. The position of the frozen'/unfrozen plane is
given by
X « 2\(t k^)1* (4)
where the numeric constant, X , is a function of trie thermal
soil properties. For the frozen wall situation melting
occurs on both sides. Rearranging Eq. (U) the time required
to melt the wall (i.e. X = 1.5 feet) is
X2
4x*(k2/cJ
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15
It should be noted that the specific heat capacity of the
frozen wall increases the actual wall energy storage.
However, this additional energy storage was not included in
the melting analysis.
iXAMPLc CASES
Case (1):
Tho hypothetical situation is a 10-acre hazardous waste
site located 150 miles from the drilling and refrigeration
contractors. The EPA Handbook for Remedial Action at Xaste
Disposal Sites recommends a slurry wall 1000 ft long and 3
it wide to be placed down to the bedrock on the up-gradient
side of the site. The depth to the bedrock averages ^0
feet. Table III summarizes £?A slurry wall estimates and
our artificial ground freezing estimates for saturated
coarse quartz sand initially at U5°F (7.2°C). Figure 3
plots the cost as a function of freezing rod spacing. It
can be seen from Table III that artificial ground freezing
is an acceptable solution, provided the containment time
requirement is short (less than 135 days). Thereafter, the
daily maintenance costs make the ground freezing alternative
unattractive. Examining fig. 3 one can see that as the
drill spacing becomes tighter, the fuel costs, equipment
rentals and time for wall completion are reduced. These
results agree with Eqs. (1) and (2). A tight drill spacing
yields small frozen soil column radii. This reduces the
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16
Table III: Slurry Wall and Frozen Ground
Construe tier; Estimates.
Activity Unit Costs
A. SLURRY WALL14
Testing - geotechnical, hydrologic
and lab filter cake permeability N.A.
Equipment Mobilization - hydraulic
backhoe, bulldozer, slurry mixer, etc. N.A.
Total Costs
$20,000 - $80,000
$20,000 - $80,000
Slurry trsnching, excavation, mixing -
and backfilling $45-$70/TT $200,000 - $310,000
Maintenance
Overall
Average
M.A. $240,000 - $470,000
$355,000
3. ARTIFICIAL GnCunD rnEc^IwG
Testing - geotechnical, hydrologi.2
and lab filter cake permeability
Equipment Mobilization, clear,
4 inch drill casing
Rent - refrigeration, 4 in. header
2 in. pipes, manpower
Energy consumption
Maintenance
Extra melt time due to latent heat
M.A
$21.4/5f2
$6.9^
$5.7/Y2
W.SV^/d
$20,000 - $80,000
$95,000
$30,500
$25,500
ay $1400/day
25 days
(numeric constant in Eq. (4) s .1614)
Overall
Average
•Maintenance * $171,000-$231,000
'Maintenance * $200,000
* See Table I for unit costs, ir is square yards for depth x linear
dimension. A 3-foot wall thickness is assumed in all calculations.
" Figure 3 at 13 day freeze time with 214 drill holes.
-------
FROZEN WALL 1000 X 3 X 40 FT
500 _
400 J
SOLID
OVERALL COST
DRILL EXPENSE
FUEL COSTS
EQUIPMENT REiv4TAL
DAYS
g 300
200 J
too J
0
i ' '
2
130D
t.20
10
Y
S
6
8
DRILL SPACING (FT)
-------
18
overall energy requirement and permits use of less expensive
refrigeration equipment. The drawback of the close drill
spacing is the expense associated with the drilling
operation. The lineal footage of piping, a drive shoe for
each well drilled, and the labor charge per vertical foot
drilled overwhelm all other economic parameters.
Case (2):
Consider the situation where a derailed chemical car
disperses a toxic substance over an area adjoining s
railroad track, fig 4. Surrounding towns impose a time
constraint on the chemical and transportation companies for
containment of the waste. A preliminary week is requir'td to
define the hazardous spill and obtain general site test
results. Initial drill samples estimate the barrier depth
at 15 feet. Assuming the pollutant diffuses horizontally
one foot per day the frozen wall is planned at a radius of
130 fe.et. This information is used to generate the economic
overview presented in figure 5. The optimum cost design
call;, for a 3.8-foot drill spacing with a 12-day freezing
time. If there is insufficient tiae remaining to freeze the
soil before the tirae constraint is reached the drill spacing
is reduced, with an associated increase in overall costs.
The thermal properties us«d in bonh of the above
examples are those determined by O'Neill for saturated
quartz sand. The following cases show the economic and time
dependence as a function of thermal parameters based on the
-------
CONNECTICUT RIUER
FREEZE RING
PLACEMENT
130 FT"
RADIUS
1111 i 11.
00 FT
200 FT
UlTERSTflTE 4, ROUTE 5
-------
TRAIN SPILL 130 FT
250
200 J
SOLID
8 150
o
a 100
- OVERALL COST
« DRILL EXPENSE
- FUEL
« EQUIPMENT RENTAL
» DAYS
50-
0
I i j r , i T
2345
0
-------
21
train spill example geometry. Using data from Lunardini '
for saturated soils the full range of soil texture and
moisture content effects is examined. Table IV summarizes
the optimum dosign configuration for the various soils, and
figures 6-9 show the econoaio overview of each soil system.
The results show that increasing the soil moisture content
increases the time required to establish a frozen wall. For
these high-moisture soils, mechanical refrigeration would
need a tight drill spacing to satisfy the same time
constroint in the train oar spill case. However, an
expendablo LH2 system with a 2.5-ft drill spacing
establishes an iaparacabla birrier within eight days of
pumping. This compares to a 22-day refrigeration time for a
mechanics! systes undar the saso conditions of saturated
fine-grained soil with a 405 moisture content, fig 8. The
LN2 frozen uall assumed a -75°? (-60°C) vent temperature for
the freezing pipes. The economics of expendable coolants
are variable and generally hard to quantify. Veranneman and
Rebhan approximate Lt<2 consuaption at 800 kg of LH2 per a^
of frozen soil. Stoss and ValK ^ approximate the LM./brine
expense ratio at 2 for large freezing projects (>700ar) with
maintenance periods exceeding 30 days. Consequently, once
the Lf»2 system establishes the barrier, a mechanical
refrigeration unit maintains the system (luring the waste
treatment process.
-------
Table IV: Thereal Parameter Effects on Cost and Tleut
Performances for Saturated Soils
Saturated
Soil
Texture
Coarse
Grain
Fine
Gvaln
O'tletl!"
Thermal
Vopertlss
ki
C3l
crns^C*
.00653
.00972
.00264
.00472
.009
-
Cl C2
cal
Cm3°C
.44
.44
.47
.46
.398
.71
.54
.72
.56
.589
L
cal
cP"
40
15
40
15
23.5
tfolstura
Content
S of Dry
. Kaight
40
10
40
10
.
Cost lisa
$/yard2 of ^
Perlesster ""*
%
64 15
46 10
82 22
56 14
-
Figure
6
7
8
9
3,5
Cost estimate based on a wall 816 ft. round, TiS ft. deep.
For comparfson: Slurry wall21* $75/y2 of wall
-------
COARSE-GRAIfCD, HIGH OTSTOE SYSTEM
250 _
200-1
SOLID
« OVERALL COST
» DRILL EXPENSE
» FUEL COSTS
DAYS
§ 150
o
CJ
100 J
50
0
I ' I
2 3
r.30 D
A
Y
S
L20
5
nr j r T
7 8
0
DRILL SPACING (FT)
-------
COARSE-GRAIiCa LOU WISTUHE SYSTEH
250 _
200
SOLID
OVERALL COST
DRILL EXPENSE
FUEL COSTS
sa
DAYS
8 150
o
CJ
0
DRILL SPACINS (FTJ
-------
FINE-GRAINED, HIGH HOISTURE SYSTEM
250 _
200 J
§ 150
o
iou j:
50 -I
0
SOLID
OVERALL COST
DRILL EXPENSE
FUEL COSTS
1 I ' I
2 3
i ' \.
4 5
130 D
A
Y
S
120
110
Ut
DRILL SPACING' (FT)
-------
250 _
200 J
\
SOLID
UN msnx SYSTEH
- OVERALL COST
« DRILL EXPENSE
» FUEL COSTS
DAYS
§ 150
o
§
100
50 J
0
D
A
120
1.10
0
4
5
6
7
8
ro
o>
-------
An alternate economic overview is presented in figure
10 in which we introduce • constraint on the raaxiaua
allowable freozing time. The minimum coat for a given
gooaetry and thermal conditions is plotted as a function of
aaxiaun allowable freezing tiaaj t is the optimal (least
cost) freezing time froa the unconstrained figure 5. If the
time constraint is greater than t then the optimua spacing
is selected. For tiae constraints less than t the cost
rises following the curves as in fig. 5. Figure 10 was
constructed using the train spill data.
CONCLUSIONS
Ground freezing as a moans of hazardous nasto
containment can be a cost effective operation for a large
rango of thermal conditions. Soil parameters were shown to
significantly affect the cost analysis. Fine-grained soils
with high moisture retention can double the overall barrier
expense .compared to that of coarse-grained soils with low
moisture characteristics. However, irragardldss of the
thermal conditions presented herein, tne drilling operation
was the primary cost factor whenever a time constraint less
than or equal to the optimum spacing was imposed, the
economic advantage of ground freezing over alternate barrier
technologies is limited to temporary treatment sites due to
the thermal maintenance expense.
-------
X15FT
o
120 J
100 J
S 80J
60
40 J
t I T
0
SPACINQ
•HININUH COST
\
\
T-rT-rr-j-
_5 D
R
I
« t
A
C
-.2 I
N
•I I T » I IT
\ 20 25
\
-------
REFERENCES
1. Isfcondar, I.K., "Impact of Froozing on the Level of
Contaminants in Uncontrolled Hozardous Haste Sites -
Phase I", £PA prcliaijnary report, unpublished, 1984. -
2. douyoucor, G.J. and M.M. rtoCcol, "Tha Freezing Point
Xethod 09 a New Moans of Measuring the Concentration
of the Soil Solution Oiroctly in tho Soil", Michigan
Agricultural Experiment Station Technical Bulletin
92*, 44 pp., ',915.
3, Bouyoucos, G.J. end M.rt. .teCool, "Further Studies on
the Freezing Point Lowering of Soiis", Michigan
Agricultural tsporias.vt station Technical Bulletin
#31, .51 pp.,' 1916.
4. Souyoucos, G.J. and M.M. ttcCocl, "The Correct
Esplanatior for .the Heaving of Soils, Plants and
Pavosents", Journal of tho Aaorican Society of
Asronoay, 20:480-491., 1928.
5. Pago, F.rf. and I.K. Iskondar, "Ceocheaistry of Subssa
Poraefrost at Prudhoa 3ay, AlasUa0, CRREL. SR 73-14,
U.S. Army Cold Regions Research and Engineofing
LawCrstcry, Hanover-, nu., *97S.
6. ASHRAE Handbooks, 1^981 Fundanantalg Handboolc ch 1.
and 1892 Applications Handbook ch 54, Pub. Aaarican
Society of Heating, Refrigeration and
Air-Conditioning Engineers, Inc.
7. Iskandar, I.K., unpublished soil freeza data, CRHiL,
1984.
3. Braun, 3. and W.R. Hash, "Ground
Applications in Underground Mining Construction",
Proceedings, Third International Symposium on Ground
Freezing, J.S. Aray Colti Region," ?.c3earch. and
Engineering Laboratory, rianover, NH., 1982.
. .9. - -Sadovsky, A. and fa. A. Doraian, "Artificial /reezing
and Cooling of Soils at t.^.c Construction",
Proceedings, Second International Symposium on Ground
Freezing, Norway., 1980.
10. Doraan, Xa. A, "Artificial Freezing of Soil in Subway
Construction", In Russian. Isd-vo. Transport, USSR.,
1971
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