#70 Sand 500ml Soltro!

Phase Content Profile after 82 Minutes

100

80

60

Elevation in cm

40

20

0.1 0 or 0.2 03 04 0.5
Phase Content

Figure 31. Phase content profile of 500ml Soltrol spill in #70 sand. A back front has started
to develop.

#70 Sand 500mI Soltrol
Phase Content Profile after 17 Hours
120

100

80

60

Elevation in cm

40

20

0 — +
-0.1 oO 0.1 0.2 0.3 0.4 0.5
Phase Content

Figure 32. Phase content profile of 500m! Soltrol in #70 sand. A gradual decrease in phase
content behind the front can be observed.

52


compartments filled with water, respectively. The seventh and eighth columns give the water
content, as calculated from Equation (31), with the initial count rate through the empty box. The
last two columns (9 and 10) give the water content as calculated following Equation (42). The
average and the standard deviation were calculated for the seven measurements. The average
was compared with the theoretical water content and a theoretical error was calculated. The
suite of calculations was performed for both Cesium and Americium.

116


SECTION 4
MATERIALS AND METHODS

This section describes the sands and the NAPL that were used in the experiments. This
discussion is followed by a detailed description of the apparatus and techniques used to perform
the column and tank experiments.

4.1. SAND CHARACTERIZATION

Various sands, identified by characteristic mesh sizes from #8 to #125 ,have been used
in experiments conducted at the University of Colorado. In this study, #70 sand and #125 sand
have been selected as test media for vadose zone experiments. Both sands have been
characterized based on their grain size distribution and on their lithology (Held, 1993).

The grain size distribution was obtained with two different methods:

- Standard Method for Sieve Analysis of Fine and Coarse Aggregates (ASTM C 136). Test
samples are split representatively, dried at 110°C, weighed and dry sieved in a
mechanical sieve shaker for 5 minutes. The analysis was conducted in the porous media
laboratory of the Civil, Environmental, and Architectural Engineering Department.

- Settling Tube Analysis as employed in the sedimentology laboratory at INSTAAR, Boulder,
Colorado. The procedure is automated, and data acquisition is handled by computer
software from CIMAX Inc., Breckenridge, Colorado.

A microscopic investigation was performed and the results were compared visually to standard
charts (Powers, 1953). The characterization for both sands is compiled in Table 1.

Figure 5 and Figure 6 give the grain size distribution for #70 and #125 sand, respectively.
The filled squares show the grain size fraction as determined with the dry sieving method; the
empty squares give the grain size fraction measured with the settling tube. It can be seen from
the graphs that both sands are well sorted and fairly uniform.

18


Elevation
om

69
68
67
66
65
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
4g
48
47
46
45
44
43
42
4
40
39
38
37

Time
min

251
252
252
253
254
254
255
255
256
257
257
258
258
259
260
260
261
261
262
263
263
264
265
265
266
266
267
268
268
269
269
270
271
271
272
273
273
274
274
275
276
276
277
277
278
279
279
280
280
281

Soltrol
Content

0.268172
0.269798
0.264001
0.247496
0.247172
0.249213
0.227322
0.201217
0.207671
0.209191
0.199154
0.191679
0.190148
0.166872
0.136943
0.101618
0.04978
0.018463
0.005528
0.003289
0.007262
-0.00237
0.001498
0.001117
-0.00372
-0.00225
+0.00205
0.00104
0.005
0.00714
0.00117
0.00524
0.002832
0.002303
0.001559
-0.007
0.004645
-0.00011
0.00577
0.001388
0.003264
0.001559
0.002086
-0.00667
~0.00111
-0.00169
0.000234
0.003263
0.003813
0.008445,

147


Elevation Time Soltrol Time Soltrol

cm min Content min Content
120.00 263.00 0.12 410.00 0.13
119.00 263.00 0.10 411.00 0.12
118.00 264.00 0.10 411.00 0.13
112.00 268.00 0.12 415.00 0.14
111.00 268.00 0.13 415.00 0.13
110.00 269.00 0.13 416.00 0.13
109.00 269.00 0.13 417.00 0.15
108.00 270.00 0.13 417.00 0.13
107.00 271.00 0.14 418.00 0.14
106.00 271.00 0.14 419.00 0.15
105.00 272.00 0.11 419.00 0.15
104.00 272.00 0.12 420.00 0.15
103.00 273.00 0.14 420.00 0.14
102.00 274.00 0.14 421.00 0.14
101.00 274.00 0.14 422.00 0.16
100.00 275.00 0.11 422.00 0.12
99 00 276.00 0.12 423.00 0.14
98.00 276.00 0.13 424.00 0.14
97.00 277.00 0.11 424.00 0.13
96.00 277.00 0.16 425.00 0.16
95.00 278.00 0.14 426.00 0.16
94.00 279.00 0.12 426.00 0.12
93.00 279.00 0.11 427.00 0.12
92.00 280.00 0.12 427.00 0.13
91.00 280.00 0.14 428.00 0.12
90.00 281.00 0.14 429.00 0.13
89.00 282.00 0.11 429.00 0.14
88.00 282.00 0.13 430.00 0.13
87.00 283.00 0.12 431.00 0.12
86.00 283.00 0.13 431.00 0.15
85.00 284.00 0.14 432.00 0.15
84.00 285.00 0.14 433.00 0.14
83.00 285.00 0.10 433.00 0.12
82.00 286.00 0.12 434.00 0.13
81.00 286.00 0.10 435.00 0.12
80.00 287.00 0.11 435.00 0.12
79.00 288.00 0.12 436.00 0.12
78.00 288.00 0.12 436.00 0.13
77.00 289.00 0.15, 437.00 0.14
76.00 290.00 0.14 438.00 0.14
75.00 290.00 0.14 438.00 0.15
74.00 291.00 0.11 439.00 0.14
73.00 291.00 0.12 440.00 0.12
72.00 292.00 0.15 440.00 0.16
71.00 293.00 0.12 441.00 013
70.00 293.00 0.14 442.00 0.12
69.00 294.00 0.14 442.00 0.16
68.00 294.00 0.13 443.00 0.14
67.00 295.00 0.14 444.00 0.14
66.00 296.00 0.14 444.00 0.14
65.00 296.00 0.14 445.00 0.15,
64.00 297.00 0.14 445.00 0.14
63.00 297.00 0.12 446.00 0.16
62.00 298.00 0.12 447.00 0.16
61.00 299.00 0.14 447.00 0.15
60.00 299.00 0.15 448.00 0.16
59.00 300.00 0.15 449.00 0.16
58.00 300.00 0.15 449.00 0.15

142


EPA/600/R-94/197
November 1994

AN EXPERIMENTAL EVALUATION OF TWO SHARP FRONT
MODELS FOR VADOSE ZONE NON-AQUEOUS PHASE
LIQUID TRANSPORT

by

Tissa Illangasekare, Dobroslav Znidaréié, Gabriele Walser
Department of Civil, Environmental and Architectural Engineering
University of Colorado
Boulder, Colorado 80309

and

James Weaver
Robert S. Kerr Environmental Research Laboratory
United States Environmental Protection Agency
Ada, Oklahoma 74820

CR-816807

Project Officer

James Weaver
Processes and Systems Research Division
Robert S. Kerr Environmental Research Laboratory
Ada, Oklahoma 74820

U.S. Environmental Protection Agency
Region 5, Library (PL-12J)

77 West Jackson Boulevard, 12th Floor
Chicago, IL 60604-3590

ROBERT S. KERR ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
ADA, OKLAHOMA 74820

& Printed on Recycled Paper


1 nuation i San

The lumped attenuation coefficient of sand depends on the bulk density which is related
to porosity. The attenuation coefficient for one sand grain is a constant, but the void space
between the grains differs depending on the packing of the sand. Thus, the lumped attenuation
coefficient of the sandy material changes. It is not possible to measure the attenuation coefficient
of one sand grain or to pack the sand in a way that no void spaces exist. However, by measuring
the lumped attenuation coefficients for a known bulk density, a relation between attenuation
coefficient and bulk density can be found; and the attenuation coefficient for sand independent
of bulk density can be calculated. The following steps were taken to determine the relationship
between bulk density and attenuation coefficient for sand. The sand was first weighed and
loosely filled into the plexiglass compartment box. The volume of the sand was determined using
measurements of the compartment size. From the sample weight and volume, the bulk density
was determined. From the known mineral density, the porosity was calculated. Then the
attenuation coefficient was determined with the gamma system. The procedure was repeated
with different degrees of sand compaction, obtained by shaking the container a few times. The
attenuation coefficient was determined for four values of bulk density. For graphing the results,
it was assumed that for zero bulk density the attenuation coefficient is zero, since the absorbance
of air is negligible (Figure 83). Using the four measured points and the point in the origin for a
linear regression, the following relationships between bulk density, p,, and lumped attenuation
coefficient, U, were found:

U = 0.236 cm’g'cm" p, for Americium, with a standard error of the coefficient =
0.0015,
U = 0.063 cm*g'cm" p, for Cesium, with a standard error of the coefficient = 0.0006.

The lumped attenuation coefficients for sand without void spaces with a mineral density of 2.65
are then:

U = 0.625 cm" for Americium,
U = 0.167 cm" for Cesium.
1.3.1 Phi Phase System:

The multi-chambered plexiglass box was used to produce two-phase and three-phase
mixtures of known phase content. Filling three compartments of the box with sand and one
compartment with fluid gives a theoretical volumetric phase content of 33%; filling two
compartments with fluid gives a volumetric phase content of 67% (Tables 10 through 12).

Every experiment included four different measurements: one measurement through the
empty box (/,), one through the box when three compartments are filled with sand (gy), and two
measurements with three compartments filled with sand and one or two compartments filled with
water (/, Water and /, Water, respectively). The volumetric phase content of the liquid phase was
calculated in three ways: first, the volumetric phase content was calculated with the incident
radiation through the dry sand (Equation (30)); second, with the incident radiation through the
empty box (Equation (31)). Equation (29) assumes that the bulk density of the sand is constant

112


# 70 Sand 750ml Spill
Water and Soltrol Phase Content

120

100

80) Water [Front Soltrol Backfront

60

o| =

Elevation in cm

i

Soltrol Front

20

0.1 0 O41 0.2 0.3 0.4 0.5
Phase Content

Figure 45. Water and Soltrol content profiles for 750ml spill in #70 sand. Gamma scans
were taken 189 minutes after spill was started. A constant rainfall rate of
9.5cm/hour was applied 86 minutes after the spill was started.

One experiment was conducted to observe possible mobilization of the NAPL (Figure 35).
One day after a 750 ml Soltro! spill in the #125 sand, a constant rainfall rate of 9.5 cm/hour was
applied to the column. The column was at residual Soltrol saturation when the rainfall was
started, except at the lower end of the column where a capillary fringe zone had built up. A two-
hour rainfall did not change the amount of Soltrol in the upper part of the column; the only
observed effect was that the water pushed the Soltrol out of the capillary fringe zone.

5.4 SPILL EXPERIMENTS IN THE TWO-DIMENSIONAL TANK

Tank experiments were conducted to observe two-dimensional behavior of NAPL spills
in the vadose zone. These experiments were designed to be comparable to the column
experiments. A 30 cm wide spill zone was created in a 120 cm wide tank that was packed with
#70 sand. The volume of Soltrol applied to the tank resulted in a ponding depth of Soltrol above
the sand of 9.5 cm, which corresponds to the 9.5 cm ponding depth for a 500 ml spill in the
column. In Figure 47 the front movements of two tank experiments and one column experiment
are compared. The front position for the tank experiment was taken as the front elevation directly
below the center of the spill. The Soltrol plume had a U-shape, thus the front at the edges of the
fluid body lagged behind the front at the center of the body; but by no more than 2 cm.

61


Elevation
cm

Elevation
om

118

Time
min

Time
min

222
222
223
223
224
225
225
226
226
227
228
228
229
229
230
231
231
232
232
233
234
234
235
235
236
237
237
238
238

Soltrol
Content

Soltrol
Content

0.139204
0.133433
0.120415
0.139868
0.154603
0.159364
0.157828
0.166068
0.163941
0.168992
0.172905
0.164331
0.166436
0.160692

0.16764
0.164345
0.165241
0.178225,
0.187165
0.190479
0.200235,
0.203275

0.19896
0.200759
0.203814
0.214399
0.219305
0.234544
0.242499

Time
min

68
68
69
69
70
71

Time
min

1338
1338
1339
1340
1340
1341
1344
1342
1343
1343
1344
1344
1345
1346
1346
1347
1347
1348
1349
1349,
1350
1350
1351
1352
1352
1353
1353
1354
1355

145

Soltrol
Content

0.004448
0.004911
-0.00001
-0.0039
0.00382
0.001178

Water
Content

0.144979
0.153465
0.103516
0.128181
0.164198
0.162028
0.150073
0.218776
0.192452
0.130889
0.152698
0.115811
0.1441
0.134828
0.019168
-0.03607
0.024211
0.01175
0.02476
~0.027
0.03894
0.036962
0.03289
0.00399

0.021249

Time
min

116
V7
118
118
119
119
120
121
121
122
123
123
124
124
125
126
126
127
127
128
129
129
130
130
131
132

Soltrol
Content

0.091675,
0.081596
0.091364
0.088822
0.084104
0.094409
0.113314
0.092202
0.101028

0.12352
0.113991
0.125324
0.115629
0.105687
0.143456
0.148412
0.116055
0.124304
0.126784
0.132102
0.141992
0.115677
0.136252
0.125966
0.134604

0.13885,

0.12746
0.145441
0.122564

Soltrol
Content

0.000901
0.004064
0.011956
0.00114

0.005882
-0.0058
-0.00698
~0.00041
-0.00096
0.000967
0.00416
0.001721
0.00465
0.005246
0.005169
-0.00216
0.001984
0.00212
~0.00054
-0.00131
0.00525
-0.00353,
0.000072
-0.00176
0.000754
0.006763


No. 125 Sand 1000mI Soltrol
Front Position after 190 Minutes

100 Wl _Experimental Dato
a — = _— Three Parameter Sharp Front Model
got Sa, Kinematic Mode!

70
60
50
40
30r
20F
10

Elevation (cm)

-0.1

Figure 56. Phase content profile comparison between model and experimental results.

72


P, = Pry - Py (4)

nw

The magnitude of the pressure difference depends on the radius of curvature and the surface
tension at the fluid-fluid interface. In a porous medium, the pore geometry and the fluid saturation
determine the radius of the interface and thus the capillary pressure. Low values of the capillary
pressure are associated with large pores, and on the contrary high values of capillary pressure
are associated with small pores.

3.1.5 Capillary P Saturation Relationshi

To obtain the relationship between saturation and capillary pressure, various test
procedures have been developed by petroleum engineers and soil scientists. In general, the
sample is de-saturated by increasing the capillary pressure in known increments. The sample
is allowed to reach equilibrium after each pressure change. Measured values of the change in
saturation and pressure are used to determine the so-called "capillary pressure-saturation curve."
It is also common to plot the capillary pressure as a function of the volumetric water content, the
curve is then referred to as "water retention curve" or "water characteristic curve." Example
results are presented in Section 6. The measured capillary pressure curves depend on the pore
geometry, the fluid-fluid interactions and the wettability. Thus the curve incorporates the
underlying multiphase interactions in a form that is used in modeling.

The capillary pressure versus saturation relationship can be defined either when the
sample is drained from full wetting-fluid saturated conditions or when the wetting phase is allowed
to enter the sample and displace the nonwetting fluid. Usually these curves are measured on a
drainage cycle. A minimum capillary pressure is required before the sample starts de-saturating
from initially saturated conditions. At this point the non-wetting fluid, such as air, can enter the
porous sample. This minimum pressure is called the “air-entry pressure," or if the non-wetting
phase is not air, "threshold pressure." Experimental results show that the wetting fluid remains
in the sample at high capillary pressures. The limiting value of saturation when capillary pressure
increases no longer cause a release of the wetting fluid is commonly called the “residual
saturation."

3.1.6 Permeability and Relative Permeability
Permeability is a function of the porous medium only, whereas hydraulic conductivity

depends both on fluid and porous medium properties. The relationship between the hydraulic
conductivity and the soil permeability and fluid properties is given by:

Kk - Keg (5)
yb

where K is the hydraulic conductivity, k is called the intrinsic permeability and is presumed to be
a property of the media, p is the fluid density, g is the acceleration due to gravity, and p is the

8


here show only data collected with Americium. The Cesium results confirmed the Americium
results in most cases qualitatively, in some cases exactly. In cases where both scans presented
quantitatively good results, the calculation for the spills was performed as for a two-phase system.
The incident radiation was taken through the dry sand, and water and oil phases were calculated

separately.

121


TIME ELEVATION PONDING BACK

DEPTH FRONT

MINUTES cM cM cM
100 85

120 83 106
150 80.5

180 78

210 77

250 74.5

381 69.5

1020 59

1320 55.5

SPILL M #70 SAND 1000 ML SOLTROL SPILL
RAIN 500MU/HR AFTER 167 MINUTES

TIME ELEVATION PONDING BACK FRONT WATER DEPTH
MINUTES cM cM cM CM
oO 120 19

1 113

2 Ww

3 108.5

4 107 13.2

5 105.5 12.5

6 104 12.1

7 103 11.7

8 101.5 11.2

9 100.5 10.8

10 99 10.4

W 98 10

12 97 9.6

13 96 9.4

14 95 8.9

15 94 8.6

16 93 8.2

17 92 8

18 91.3 75

19 90.5 7.3
20 89.7 7
22 88.3 65
24 86.5 5.8
26 85 5.3
28 84 45
30 83.2 4

32 81 3.5

34 80 2.9
36 78.2 25
38 7 2
40 75.7 1.5
44 73.7 0.6
47 719 0
50 70.8 119
53 69 114
57 67.3
60 66
65 64 108
70 62
75 60 99
80 58 87

127


Elevation
om

83
82
81
80
79
78

Elevation
om

120
119
118
117
116
115
114
113
112
Wt
110
109
108
107

Time
min

1249
1249
1250
1250
1251
1252
1252
1253
1253
1254
1255
1255
1256
1256
1257
1258
1258
1259
1259
1260
1261
1261
1262
1263
1263
1264
1264
1265
1266
1266
1267
1267
1268
1269
1269
1270
1270
1271
1272
1272

Time
min

1417
1418
1418
1419
1419
1420
1421
1421
1422
1422
1423
1424
1424
1425
1430

Water
Content

0.077735
0.094697
0.049286

0.01101
0.023659
0.066486
0.046878
0.023156
0.060458

0.03812
0.050764
0.036535,
0.013385
0.039373
0.068717
0.039945
0.047844

0.00843
0.053083
0.048417
0.033969
0.100541
0.047587
0.089722
0.112153
0.082801
0.050501
0.049626
0.184415
0.066327
0.131352
0.096103
0.074364
0.046109
0.006254
0.091823
0.018015,
0.005031
0.095541
0.043731

Water
Content

0.368587
0.259888
0.213705,
0.255747
0.235806
0.216977
0.307343
0.226397
0.265674
0.257841
0.259977

0.26701
0.288946
0.254451
0.242645

Soltrol
Content

0.14502
0.136693
0.150148
0.166063
0.172334
0.152912
0.156467
0.170615
0.155228
0.180875
0.189875
0.202349
0.208023
0.177336
0.163614
0.180036
0.164875
0.171898
0.151373
0.137047
0.100832

0.01536
0.004238
0.002282

-0.00846

0.00298
0.004803
0.010695,

-0.03786
0.001468.
0.019
0.012
0.003419
0.008607
0.016362
0.01634
-0.00119
0.002088
~0.02121
0.008592

Soltrot
Content

-0.01598
0.038901
0.035303
0.016989
0.035807
0.055252
0.019061
0.053054
0.043824

0.0488
0.046029
0.04799
0.047493

0.062805
0.072009

182

Time
min

1388
1389
1390
1390
1391
1391
1392
1393
1393
1394
1394
1395
1396
1396
1397
1397
1398
1399
1399
1400
1400
1401
1402
1402
1403
1403
1404
1405
1405
1406
1406
1407
1408
1408
1409
1409
1410
1411
1411
1412

Time
min

1518
1519
1519
1520
1521
1521
1522
1522
1523
1524
1524
1525
1525
1526
1531

Water
Content

0.363334
0.255176
0.288842
0.324796
0.323171
0.292324
0.318004
0.347007
0.255328
0.390817

0.28437
0.404945,
0.362385
0.397175,
0.392436
0.313786
0.269912
0.257062
0.291328
0.138643,
0.208714
0.107473
0.023096
0.114893
0.051437
0.084547
0.069573

0.01695
0.144497
0.052768
0.115168
0.050554
0.067412

0.04026
0.021432
0.049697
0.002754
0.070656
0.006093
0.053601

Water
Content

0.151874
0.144045
0.099395
0.078074
0.150682
0.155736
0.145331,
0.157919
0.186251
0.156269
0.154379
0.129385
0.163284
0.242275
0.116878

Soltrol
Content

0.098357
0.127433
0.123204
0.113955
0.115085
0.128546
0.113833
0.108627
0.155616
0.124135
0.155787
0.113331
0.137089
0.127407
0.121525
0.158915
0.191577

0.20697
0.206691
0.269448

0.22217

0.19062

0.13632
0.035009
0.036119
0.012322
0.001111
0.020761

0.0207
0.004799

0.01379
0.013187
0.010181
0.010171

0.00837

-0.00584
0.007612

-0.00834
0.006813
0.000927

Soltrol
Content

0.011343
0.034503
0.034845
0.05089
0.026869
0.030551
0.050912
0.042162
0.032063
0.050653
0.057661
0.066557
0.058252
0.038
0.09421


Elevation
cm

35
34
33

Elevation
cm

120
119
118
117
116
115,
114
13
112
qd
110
109
108
107
106
105
104
103
102
101

Time
min

Time
min

120
120
121
121
122
122
123
123
124
124
125
125
126
126
127
127
128
128
129
130

Soltrol
Content

Soltrol
Content

0.109185
0.13508
0.139412
0.1388
0.146128
0.145665
0.155995
0.162719
0.155592
0.154525,
0.161459
0.172154
0.16468
0.174349
0.176445
0.181949
0.192551
0.184965,
0.196635
0.195548

Time
min

53
54
55
55
56
56
57
57

58

59
60
60
61
61

Elevation
cm

119
117
115
113
111
109
107
105
103
101
99
97
95
93
91
89
87
85
83
81

171

Soltrol
Content

0.001381
0.00537
0.000853
0.004277
-0.00352
0.00212
0.00478
0.00112
0.00186
0.00537

-0.0107
0.00997
0.00901
0.00769
0.00838
0.00655

Time
min

174
175
175
176
176
477
177
178
179
179
180
180
181
181
182
182
183
184
184
185

Time
min

93
94
94
95
95
96
96
97
97
98
98
99
99
100
100
101
101
102
102
103
104
104
105
105
106
106
107
107
108
108
109
109
110
110
WW

Water
Content

0.022596
0.049853
0.034437
0.01122
0.027283
0.033178
0.02291
0.014256
0.03526
0.004643,
-0.01465
0.023935
0.03122
0.03694
0.085124
0.039559
0.057081
0.102681
0.069012
0.035836

Soltro!
Content

0.333674
0.332245
0.329068
0.330891
0.33203
0.328328
0.330552
0.327372
0.325339
0.313994
0.288732
0.175899
0.05306,
0.001652
-0,00243
0.00584
-0.00685
-0.00594
0.001275
0.003101
0.003255
0.000215.
-0.0005
0.001131
0.00045
0.002684
0.009521
0.003812
0.00385
0.002506
0.001023
0.00113
0.004774
0.0014
0.002491

Soltro!
Content

0.132895
0.129024
0.147994
0.156578

0.16413
0.164993
0.192861
0.185089
0.183976
0.203913
0.221793

0.21545
0.229573
0.235493
0.231261
0.280542
0.243386
0.239705
0.238562
0.267795


Table 4 KOPT parameter values for the #125 and #70 sands

KOPT parameter values for the #125 and #70 sands

Parameter #125 sand #70 sand
Saturated Hydraulic | 8.5 m/d 15 m/d
Conducti 5

Brooks and Corey 4 | 2.88 2.44
Porosity, 7 0.41 0.41
Residual Water 0.22 0.30
Saturation

Water Saturation 0.22 0.30

Air entry head, h,. 0.4280 m 0.2683 m
Oil viscosity, y, 3.78 cp 3.78 cp
Oil density, p, 0.85 g/cm? 0.85 g/cm®
Residual oil 0.05 0.05
saturation

Water surface 65 dyne/cem 65 dyne/cm
tension

Oil surface tension 24 dyne/cm 24 dyne/cm
Initial Ponding

depth, H,

1000 mi spill 0.1890 m 0.1890 m
750 ml spill 0.1420 m 0.1420 m
500 ml spill 0.0947 m 0.0947 m
Radius 0.025 m 0.025 m

The observed and calculated front position, back front position and ponding depths are
graphed in Figure 51 along with the model results. Both models matched the experimental data
reasonably well. !n the each of the models, the NAPL is assumed to be instantaneously applied
to the sand surface. In actuality, some small time was required for the ponding depth to reach
its full extent as the NAPL was poured into the column. The capillary suction head for the front
and the back-front were adjusted in the three-parameter model until the model fit the data. The
fitted model then predicted the ponding time accurately. The KOPT model over-predicted the
ponding time; however, it predicted the front accurately without the need to fit any parameters
beyond considering the effect of variation in hydraulic conductivity. Three profiles were created
with each model and compared with the profiles obtained from the gamma scans (Figure 51
through Figure 53).

67


level, as well as the flow rate of the liquid, could be adjusted with regulating valves. The column
was filled until the fluid reached a level of about 10 cm above the sand.

SATURATING THE COLUMN WITH THE LIQUID PHASE

090505556
POSS SOOSOS

ES

2221
9OSS555508
OOOSOHOHOS

Vacuum Pump

Figure 10. Saturating the sand filled column with wetting fluid.

The vacuum pump was disconnected and the fluid reservoir connected to the bottom of
the column was lowered to create the desired level of suction. The column was allowed to drain
for a minimum of 2 days. Residual saturation throughout the column was achieved by water
draining through the porous plate. A suction head of 3 m of water was applied to the porous
stone. The porous stone prevented air from channeling through the plate. As long as air was
prevented from being pulled out of the sand, the full suction was applied to the water phase; and
the sand was brought to residual saturation over the whole length of the column without the
creation of a capillary fringe zone. The top of the column was covered with plastic wrapping, to
avoid drying the top of the sand. The porous stone was removed from the bottom of the column
after having obtained the uniformly residual saturated column. Air could now escape freely
through the bottom of the column. Thus, the initial water saturation in the soil column was similar
to the initial condition assumed in the computer models.

Gamma scans were taken after each of the above steps to obtain attenuation coefficients
and the saturation distribution down the column. Gamma absorption was measured down the

25


The bulk density of the solid phase and the volumetric saturation of one liquid phase can be
calculated simultaneously.

Porosity and bulk density are interrelated in the following way:

n = 1-8 (44)

Ps
where 9, is the bulk density and p, is the density of the solid grain (for sand p, = 2.65 g/cm’).

1.2 CONFIGURATION OF THE GAMMA SYSTEM

The physical setup of the gamma system is described in the following chapter.

1.2.1 Radiation Source

Various gamma emitting sources have been used by other investigators. Garder and
Calissendort (1967) found the isotopes Cesium 137 (Cs) and Americium 241 (Am) to be most
convenient and useful for laboratory work in soil physics. Cesium 137 has a half-life of 30 years
and an energy peak at 0.662 MeV and Americium 241 has a half-life of 458 years and a lower
energy peak at 0.060 MeV. The half-lives are sufficiently long so that decay corrections are not
required for laboratory measurements. The experimental setup described in this report contains
a Cesium source with 50 mCi strength and an Americium source with a strength of 200 mCi.
Using two different sources of gamma radiation gives the advantage of being able to solve for two
unknowns, i.e. bulk density and’saturation of a single fluid or for known bulk density saturation
of two fluids, simultaneously. The two sources can be used by alternating the exposure from
each source or arranging the sources in a collinear fashion. Collinear measurements have the
advantage of saving time.

The sources are enclosed in a shielded lead housing (Figure 73). The two sources with
the housing are mounted diametrically in a rotating inner cylinder mounted on a bearing. A
second fixed lead cylinder encloses the inner cylinder. The outer cylinder has a 0.5 cm diameter
collimation hole aligned with the detector. The inner cylinder with the radiation sources can be
rotated in such a way that one of the sources is in front of the collimation hole. In this position,
the second source gets located diametrically opposite to the first. During a measurement, the
stronger Cesium source is rotated to the back, while the Americium source is in front. In this
configuration, the radiation from both sources is detected simultaneously by the detector. All the
tests which are reported here were conducted using this source configuration which produces two
energy peaks in the spectrum. The distance between source collimation hole of the source and
the detector is 34 cm.

96


14

12

»— Experiment 1
10 fF oo Experiment 2
| o—o Experiment 3

Hydraulic Conductivity (m/d)

20 30 40 50 60 70 80
Distance from Bottom of Column (cm)

Figure 15 Variation in #125 sand hydraulic conductivity along the length of the
chromatography columns.

Table 2. Hydraulic conductivity for #125 sand

if — rae |
Hydraulic Conductivity
Experiment Average K, (m/d)

Long Column 1 7.70
Long Column 2 6.09
Long Column 3

32


Elevation Time Soltrol Time Soltrol Time Soltrot

om min Content min Content min Content
61.00 238.00 0.24 292.00 0.24 345.00 0.25
60.00 239.00 0.24 292.00 0.24 346.00 0.24
59.00 239.00 0.24 293.00 0.24 346.00 0.25
58.00 240.00 0.24 293.00 0.23 347.00 0.24
57.00 240.00 0.24 294.00 0.24 347.00 0.23
56.00 241.00 0.24 294.00 0.23 348.00 0.23
55.00 242.00 0.24 295.00 0.24 349.00 0.23
54.00 242.00 0.24 296.00 0.24 349.00 0.23
53.00 243.00 0.23 296.00 0.23 350.00 0.27
52.00 243.00 0.22 297.00 0.22 350.00 0.24
51.00 244.00 0.21 297.00 0.22 351.00 0.22
50.00 244.00 0.21 298.00 0.22 351.00 0.22
49.00 245.00 0.21 298.00 0.22 352.00 0.22
48.00 245.00 0.20 299.00 0.21 352.00 0.23
47.00 246.00 0.20 299.00 0.21 353.00 0.21
46.00 246.00 0.18 300.00 0.21 353.00 0.23
45.00 247.00 0.16 300.00 0.21 354.00 0.21
44.00 247.00 0.10 301.00 0.20 354.00 0.22
43.00 248.00 0.02 301.00 0.20 355.00 0.22
42.00 248.00 0.02 302.00 0.19 355.00 0.21
41.00 249.00 0.03 302.00 0.19 356.00 0.22
40.00 249.00 303.00 0.17 356.00 0.19
39.00 250.00 304.00 0.15 357.00 0.18
38.00 251.00 304.00 0.13 358.00 0.18
37.00 251.00 305.00 0.10 358.00 0.417
36.00 252.00 305.00 0.05 359.00 0.18
35.00 252.00 306.00 0.01 359.00 0.18
34.00 253.00 306.00 0.01 360.00 0.17
33.00 253.00 307.00 -0.02 360.00 0.15
32.00 254.00 307.00 -0.03 361.00 0.12
31.00 254,00 308.00 0.03 361.00 0.11
30.00 255.00 308.00 0.03 362.00 0.08
29.00 255.00 309.00 -0.03 362.00 0.04
28.00 256.00 309.00 -0.03 363.00 0.01
27.00 256.00 310.00 0.03 363.00 0.01
26.00 257.00 310.00 -0.03 364.00 -0.02
25.00 258.00 311.00 -0.02 364.00 0.02

157


# 70 Sand 750ml Spill

Water and Soltrol Phase Content

120

100

1

80

\

6° Soltrol Front

Elevation in cm

40

\

20 Water Content

0.1 O 0.1 0.2 0.3 0.4 0.5
Phase Content

Figure 40. Water and oil content for 750ml Soltrol spill in #70 sand. Soltrol front seems to
displace the residual water.

5.3 RAINFALL EXPERIMENTS IN THE LONG COLUMN

To observer and record the behavior of the spilled fluid during a rainfall event, simulations
were conducted where water was applied at the soil surface after the Soltrol spill. A number of
rainfall experiments were conducted where water and oil fronts were observed visually. The
phase content profiles were recorded with the gamma system. A comparison between front
movement of a 500 ml spill in #125 sand with and without simulated rainfall is shown in Figure 42.
In one experiment a rainfall of 500 ml/hour (9.5 cm/hour) was started 45 minutes after the spill
occurred. The water pushed the oil front downward compared to the front without rain.

The water for the rainfall simulation was dyed dark green with food coloring. This made
it possible to observe the water front moving downward. However, in the sand that was reddened
from residual Soltrol, the water front was hard to observe; and in some cases a water front could
not be observed visually. In these cases, the water front position was determined from the
gamma data. Such was the case for the spill shown in Figure 42. From the gamma scan, it was
found that the water front was nearly at the same location as the Soltrol front (Figure 34). The
water front caught up with the Soltrol front soon after the rain had started; then both fronts moved
together. Figure 43 and Figure 44 show two spills conducted in the #70 sand: the first with 1000
mi Soltrol, the second with 750 ml Soltrol. In both cases, the rainfall was started more than 1
hour after the spill occurred. For both experiments, the water front could be observed. The water
front moved with almost constant speed, as seen from the elevation versus distance curve being
close to a straight line. This behavior was a result of the constant water flux applied to the

57


Elevation Time Soltrol Time Soltrol Time Water Soltrol

cm min Content min Content min Content Content
62.00 35.00 0.00 77.00 0.00 151.00 0.25 0.11
61.00 36.00 0,00 78.00 0.00 152.00 0.23 0.12
60.00 37.00 0.00 78.00 0.01 152.00 0.23 O11
59.00 37.00 0.00 79.00 0.00 153.00 0.22 0.13
58.00 38.00 0.00 80.00 0.00 153.00 0.25 O11
57.00 80.00 0.00 154.00 0.24 0.12
56.00 81.00 0.00 155.00 0.25 O11
55.00 82.00 0.00 155.00 0.21 0.13
54.00 82.00 0.00 156.00 0.19 0.14
53.00 83.00 0.00 156.00 0.20 0.14
52.00 83.00 0.00 157.00 0.22 0.13,
51.00 84.00 -0.01 158.00 0.18 0.14
50.00 85.00 0.00 158.00 0.20 0.14
49.00 85.00 0.00 159.00 0.28 0.12
48.00 86.00 0.00 159.00 0.23 0.13
47.00 86.00 0.00 160.00 0.26 0.12
46.00 87.00 0.00 161.00 0.21 0.14
45.00 88.00 0.00 161.00 0.30 0.12
44.00 88.00 0.00 162.00 0.27 0.13
43.00 89.00 0.00 163.00 0.23 0.14
42.00 90.00 0.00 163.00 0.21 0.16
41.00 90.00 0.00 164.00 0.27 0.14
40.00 91.00 0.01 164.00 0.27 0.14
39.00 91.00 0.01 165.00 0.18 0.17
38.00 92.00 0.00 166.00 0.22 0.16
37.00 93.00 0.00 166.00 0.41 0.20
36.00 93.00 0.00 167.00 0.18 0.18
35.00 94.00 0.00 167.00 0.19 0.19
34.00 94.00 0.00 168.00 0.12
33.00 95.00 0.00 169.00 0.19
32.00 96.00 0.00 169.00 0.03
31.00 96.00 0.00 170.00 0.13
30.00 97.00 0.01 170.00 0.05
29.00 98.00 0.00 171.00 0.06
28.00 98.00 -0.01 172.00 0.09
27.00 99.00 0.00 172.00 0.04
26.00 99.00 0.00 173.00 0.07
25.00 100.00 0.00 173.00 0.06
24.00 101.00 0.00 174.00 0.06
23.00 101.00 0.00 175.00 0.07
22.00 102.00 0.00 175.00 0.08
21.00 102.00 0.00 176.00 0.03
20.00 103.00 0.00 177.00 0.12
19.00 104.00 0.01 177.00 0.08
18.00 104.00 0.00 178.00 O14
17.00 105.00 0.00 178.00 0.08
16.00 105.00 0.00 179.00 0.08
15.00 106.00 0.00 180.00 0.04
14.00 107.00 0.00 180.00 0.05
13.00 107.00 0.00 181.00 0.05
12.00 108.00 0.00 181.00 0.06
11.00 109.00 0.00 182.00 0.05
10.00 109.00 0.00 183.00 0.05
9.00 110.00 0.00 183.00 0.04
8.00 110.00 0.00 184.00 0.04

144


The phase content calculations were performed as follows. The equations defining the
attenuation coefficients and illustrating their usage in the measurement of phase contents are
given in Appendix 1. The variables and parameters used in the calculation are also defined in
Appendix 1. In all three scans, that were described earlier, the gamma radiation /, was
measured first through the empty column. These readings were used as a standard for correcting
the count rate for detector sensitivity changes in subsequent measurements.

The first scan produced values of the initial radiation, /,, through the dry sand. From the
second scan, the lumped attenuation coefficient for the liquid phase was calculated. Scanning
the empty column first, then the portion of the column filled with the liquid phase, allowed the
calculation of the lumped attenuation coefficient (the attenuation coefficient density). The
radiation measured through the fully saturated sand /, was corrected using /, from the first and
the second measurement. The phase content could then be calculated using the corrected |, /,
and the lumped attenuation coefficient.

After draining the column, the radiation through the partly saturated sand was measured.
The phase content was calculated as above, with the attenuation coefficient calculated from the
second scan.

In the spill experiments, a known volume of Soltrol was applied to the top of the column
and allowed to infiltrate through the sand. The Soltrol was dyed with Automate Red, allowing
visual observation of the front movement. At the same time, the gamma system was used to
obtain phase content profiles along the length of the column. The scan through the residually
saturated column was used to determine the initial count rate, |. The soil column was also
scanned while the Soltrol was still ponded on top of the sand; the attenuation coefficient for
Soltrol was calculated from this measurement. Soltrol content profiles during the spill were thus
computed.

In the rainfall experiments, the rainmaker was placed on top of the column. Water was
dyed green with food coloring so the water front could be observed. The food coloring did not
change the viscosity or surface tension of the water (Szlag and Illangasekare, 1992).

The porosity of the sand pack must be known to calculate saturations from the volumetric
phase contents that are determined with the gamma system. When calculating the error in the
saturations, the error in the porosity has to be accounted for. Three techniques were used to
calculate the porosity of the sand:

1. Gravimetric Procedure: The weight of the sand used to fill the column and the volume of the
sample can be used directly to calculate the bulk density and porosity. The disadvantage of this
approach is that mass of the sand cannot be determined exactly, because of spill losses during
the filling of the column. Also, the use of total weight and volume gives only an average porosity
for the whole sample. Assuming that not more than 400 g of sand are lost and the error in
measuring the height of the sand is at most 1 cm, the maximum relative error in determining the
average porosity for the whole column is +3%.

28


#70 Sand 750ml Soltrol Spill
Rain 500mI/hr after 86 minutes

120
100
80
60
40

Elevation in cm

20

0 50 100 150 200 250 300 350
Time in minutes

[=~ Front —* Ponding —*— Rain

Figure 44. 750ml Soltrol spill on #70 sand with rainfall application starting after 86 minutes.
The rainfall rate was held constant at 9.5 cm/hour.

Figure 45 and Figure 46 show profiles obtained with the gamma system. A profile taken
189 minutes after the spill started and 103 minutes after the rainfall started can be seen in
Figure 45. The gamma scan confirmed that the water and the Soltrol back fronts are in the
same location. This is a clear indicator that the water was pushing the Soltrol downward in a fully
saturated NAPL "bank". Behind the Soltrol back front, the water and oil saturations added up
to one. However, limitations of measurement accuracy of the gamma system prevented the
measurement of small entrapped air saturations. It is important to note that the water did not
seem to mobilize any of the entrapped Soltrol. Even at the top of the column where the most
water had passed by, the Soltrol content is still 0.1. However, the Soltro! slug displaced some
of the residual water, which was assumed to be irreducible in both models evaluated in this study.

No water front could be observed visually in the 500 mi spill in the #125 sand. However,
the gamma scan in Figure 46 shows that a water front existed; but it was so close to the Soltrol
front that it cannot be recognized visually. The Soltro! bank was very small, due to the small spill
volume.

60


Elevation Time Water Soltrot Time Water Soltrol

cm min Content Content min Content Content
98 1430 0.29057 0.050668 1531 0.176401 0.061053
97 1431 0.287298 0.046145, 1532 0.170125 0.059504
96 1431 0.26068 0.051689 1533 0.165808 0.049301
95 1432 0.283807 0.04307 1533 0.162368 0.049015
94 1433 0.276167 0.045633 1534 0.242623 0.035419
93 1433 0.309292 0.044902 1534 0.211326 0.052446
92 1434 0.227712 0.089483 1535 0.161224 0.080127
91 1434 0.370408, 0.045192 1536 0.246984 0.07114
90 1435 0.299906 0.067954 1536 0.21238 0.075006
89 1436 0.231711 0.076214 1537 0.15908. 0.073262
88 1436 0.315814 0.030642 1537 0.217598 0.040701
87 1437 0.194199 0.080837 1538 0.160322 0.067983
86 1437 0.325086 0.037184 1539 0.264746 0.041053
85 1438 0.288764 0.064254 1539 0.183187 0.080305
84 1439 0.36143 0.042797 1540 0.262525 0.048805,
83 1439 0.341279 0.048673 1540 0.238141 0.046352
82 1440 0.282841 0.066755 1541 0.177443 0.075968
81 1440 0.283161 0.069261 1542 0.161341 0.078385
80 1441 0.279097 0.065775 1542 0.230765 0.050933
79 1442 0.304016 0.05405 1543 0.205736 0.06407
78 1442 0.211042 0.092654 1543 0.120027 0.093676
7 1443 0.259886 0.082576 1544 0.183639 0.069701
76 1443 0.245979 0.080958 1545 0.2145 0.065893
75 1444 0.268496 0.077729 1545 0.256107 0.039977
74 1445 0.317788 0.068233 1546 0.208945 0.070336
73 1445 0.329733 0.069375, 1546 0.250291 0.075802
72 1446 0.353927 0.075663 1547 0.297049 0.057576
71 1446 0.24364 0.118347 1548 0.270093 0.070153
70 1447 0.309804 0.091961 1548 0.23152 0.079991
69 1448 0.310654 0.0865 1549 0.193834 0.078305
68 1448 0.346445 0.072318 1549 0.178007 0.086096
67 1449 0.35818 0.075738 1550 0.218807 0.070771
66 1449 0.292448 0.109846 1551 0.139574 0.093953
65 1450, 0.294617 0.132708 1551 0.255396 0.049995
64 1451 0.317714 0.123567 1552 0.243774 0.064055
63 1451 0.31714 0.134098 1552 0.159496 0.093016
62 1452 0.321702 0.116491 1553 0.21075 0.083457
61 1452 0.314409 0.12493 1554 0.257605 0.084269
60 1453 0.338841 0.124129 1554 0.313137 0.098916
59 1454 0.316347 0.132426 1555 0.281543 0.142427
58 1454 0.367118 0.120528 1555 0.31886 0.142484
57 1455 0.326676 0.127204 1556 0.2477 0.181318
56 1455 0.335393 0.128116 1557 0.267296 0.149283
55 1456 0.23145 0.150114 1557 0.30417 0.127259
54 1457 0.275174 0.124975 1558 0.282376 0.130498
53 1457 0.308645 0.062583 1558 0.228082 0.141792
52 1458 0.231476 0.032215 1559 0.200328 0.144014
51 1458 0.277801 -0.00762 1560 0.232239 0.113402
50 1459 0.306735 0.01604 1560 0.176993 0.107952
49 1460 0.240395 -0.00836 1561 0.168685 0.048875,
48 1460 0.247856 -0.01789 1561 0.164603 0.00131
47 1461 0.201419 0.004632 1562 0.150843 -0.00789
46 1461 0.294729 -0.02922 1563 0.200403 -0.02396
45 1462 0.272732 ~0.02382 1563 0.123615 -0.00157
44 1463 0.209996 0.0031 1564 0.159382 -0.00887

183


1.2.2 Solid Scintillation Counting System

Radiation is detected using a thallium activated sodium iodide crystal and a photomultiplier
tube. As the ionizing radiation interacts with the fluor crystal, a portion of its energy is transferred
to the fluor molecules causing excitation of the orbital electrons. Electrons returning to their
original energy level emit the absorbed energy as electromagnetic radiation in the visible or near
ultraviolet region. The photomultiplier is employed in close proximity to the fluor crystal to convert
the photons to photoelectrons which are greatly amplified by secondary electron emission through
nine series of dynodes to a sizable electrical pulse. The detector used with this system is a 2
inch diameter and 2 inch thick Nal(Tl) scintillation photomultiplier tube (ORTEC 905-3). All other
components of the counting system were manufactured by ORTEC, Oak Ridge, Tennessee. A
preamplifier is used to shape the detector signal and to make the signal to cable noise ratio as
high as possible. A second amplifier (ORTEC 575A) gives extra amplification and minimizes
pulse overlap by shortening the time of duration of each amplifier pulse by clipping the pulse. The
electronic system has a specific deadtime after every radiation pulse detected, in which no further
impulses can be measured. The total deadtime during a measurement depends on the number
of registered pulses and is shown by the software in percent. Positive pulse shaping was
selected. This indicates the presence of only positive portions of the pulse.

A multi-channel analyzer (ORTEC 918A ADCAM) is used to select pulses of the desired
energy. Pulses are counted using a timer-counter unit. EG&G Ortec ADCAM software is used
to analyze the signals and present the results on a PC. A well regulated and highly stable
voltage is required for the operation of the photomultiplier tube. The model used with this system
is ORTEC 556.

A schematic diagram showing the different components of the gamma system is given in
Figure 73.

97


Spill J

#70 Sand 500 mi Soltrol Spill

Elevation
com

120.00
118.00
116.00
114.00
112.00
110.00
108.00
106.00
104.00
102.00
100.00
98.00
96.00
94.00
92.00
90.00
88.00
86.00
84.00
82.00
80.00
78.00
76.00
74.00
72.00
70.00
68.00
66.00
64.00
62.00

Elevation
om

120.00
118.00
116.00
114.00
112.00
110.00
108.00
106.00
104.00
102.00
100.00
98.00
96.00
94.00
92.00
90.00
88.00
86.00
84.00
82.00

Time
min

3.00
3.00
4.00
4.00
5.00
6.00
6.00
7.00
7.00
8.00
8.00
9.00
9.00
10.00
11.00
11.00
12.00
12.00
13.00
13.00
14.00

Time
min

52.00
52.00
53.00
53.00
54.00
54.00
55.00
56.00
56.00
57.00
57.00
58.00
58.00
59.00
59.00
60.00
61.00
61.00
62.00
62.00

Porosity: 0.47

Soltrol
Content

0.32
0.31
0.32
0.31
0.17
0.02
0.00
0.01
0.01
0.01
0.01
0.01
0.00
0.01

Soltrol
Content

0.25
0.23
0.23
0.25
0.29
0.30
0.30
0.31
0.30
0.30
0.31
0.30
0.29
0.25
0.05
0.00
0.01
0.00
0.00
0.00

Bulk Density grav.: 1.40g cm®

Temperature Soltrol; 22°C

Time
min

16.00
16.00
17.00
17.00
18.00
18.00
19.00
19.00
20.00
21.00
21.00
22.00
22.00
23.00
23.00
24.00
25.00
25.00
26.00
26.00
27.00
27.00
28.00
29.00
29.00
30.00

Time
min

74.00
74.00
75.00
76.00
76.00
77.00
77.00
78.00
78.00
79.00
79.00
80.00
81.00
81.00
82.00
82.00
83.00
83.00
84.00
84.00

160

Soltrol
Content

0.30
0.31
0.31
0.32
0.30
0.31
0.31
0.31
0.30
0.27
0.02
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.01
0.00
0.01

Soltrol
Content

0.21
0.18
0.18
0.19
0.22
0.26
0.27
0.28
0.30
0.31
0.31
0.30
0.28
0.28
0.27
0.26
0.07
0.01
0.00
0.00

Time
min

32.00
33.00
33.00
34.00
34.00
35.00
35.00
36.00
37.00
37.00
38.00
38.00
39.00
39.00
40.00
40.00
41.00
42.00
42.00
43.00
43.00
44.00
44.00
45.00
46.00
46.00
47.00
47.00
48.00
48.00

Time
min

99.00
100.00
100.00
101.00
101.00
102.00
103.00
103.00
104.00
104.00
105.00
105.00
106.00
106.00
107.00
108.00
108.00
109.00
109.00
110.00

Soltrol
Content

0.31
0.31
0.31
0.31
0.31
0.30
0.30
0.31
0.30
0.31
0.31
0.30
0.23
0.01

Soltrol
Content

0.14
0.17
0.14
0.16
0.18
0.22
0.24
0.24
0.26
0.27
0.30
0.31
0.29
0.28
0.28
0.28
0.29
0.27
0.06
0.00


Table 12. Volumetric content of water and organic phase in sand-water-organic mixture

Three compartments filled with sand, one filled with Soltrol
and one with water.

Am Cs water content oil content
Fay /Mwa+1so Vay Hwa+1so With lary With lary

37639 4359 105418 71739 0.349 0.280

38261 3917 105630 71722 0.333 0.307

37240 4282 106489 71927 0.361 0.277

37752 4303 105915 70418 0.388 0.270

37914 4260 105602 70463 0.379 0.276

36665 3970 105874 70816 0.369 0.285
37579 4179 105821 72186 0.338

average 0.360 0.284

std 0.019 0.011

std % 5.366 3.982

theoretical phase content 0.333 0.333

theoretical error -7.892 14.910

Denominator k = 0.046

The volumetric content of water and organic phase were determined simultaneously. The
first two columns give the count rate for Americium through the dry sand and through the sand-
water-oil mixture, respectively. The third and forth columns give the count rates for Cesium. The
fifth and sixth columns give the volumetric phase content for water and oil, calculated with
Equations (37) and (38), respectively. The average and the standard deviation of seven
measurements were calculated and compared to the theoretical phase content. It can be seen
that calculations of two phases simultaneously may lead to error up to 15%.

1.4 ANALYSIS OF TEST RESULTS

The results showed that a number of rules have to be followed in order to obtain accurate
results with the gamma system. It has been shown that random decay of the radioactive source
leads to a randomness in the count rate. The standard deviation of the count rate is equal to the
square root of the count rate. Thus, the count rate has to be sufficiently large to avoid a large
percentage error. The count rate can be increased by increasing source strength or by increasing
counting time. Increase in the source strength may lead to detector fatigue and should be
avoided. The counting time can be increased only if the variable to be measured within the
sample does not change rapidly and long measurement times are acceptable. A compromise
between source strength and measurement time has to be found. In this research,
measurements in spill and rainfall experiments needed to be conducted in short time intervals.
A measurement time of 20 seconds was chosen for all of the spill experiments. The absorption
of the column was small; thus, without using any absorbers, the observed dead time was above
the threshold which was found to lead to detector fatigue (10% dead time). An aluminum (1.5

119


Figure 19.

Figure 20.

E 06
S
iat
A 04
— P,(S) Proc. 1
0.2 ---- P,(S) Proc 2

0 0.05 = 0.1 0.15
Time (d)

0.2

Comparison of front positions as simulated using KOPT in #125 sand for the
capillary pressure curve parameters determined by approaches 1 and 2.

1
0.8
E 06
Ss
ist
A 04
— P,(S) Proc 1
0.2 ---- P.(S) Proc 2

0 0.05 0.1 0.15
Time (d)

0.2

Comparison of front positions as simulated using KOPT in #70 sand for the
capillary pressure curve parameters determined by approaches 1 and 2.

38


= Measured Front Position

100 — KOPT Front Position
° Measured Ponding Depth
80 + — - KOPT Ponding Depth

Elevation in Centimeters
a (o>)
oO oO

ine)
oO
T

°
p=

500 1000 1500 2000
Time in Minutes

oO

Figure 65 Adjusted KOPT simulation of the 500 ml spill in the #70 sand

80


SECTION 1
INTRODUCTION

There are approximately 180,000 confirmed releases of petroleum products and other
chemicals from underground storage tanks. The magnitude of this problem has led to the
creation of a number of regulatory programs at both the state and federal level. Managers of
these programs are required to make decisions concerning underground storage tank sites, but
must do so with limited resources. These managers recognize that in making technically
defensible decisions, models play a role in some circumstances. An example is the siting of
storage tank facilities. In some states, monitoring frequency must be based on the estimated
arrival time of a leaked petroleum hydrocarbon at the water table. Arrival time estimates can best
be made from flow model results.

Leaking underground storage tanks and accidental spills result in contaminant releases
in the unsaturated zone. The organic liquid then travels downward until it reaches the water
table. Typically, organic and other chemical wastes are only marginally soluble in water, and
therefore persist as a separate liquid phase for some distance and time from the initial spill
location. The separate phase material may exist either as continuous bulk phase or as
discontinuous pockets of "residual" material. Although direct human exposure to non-aqueous
phase liquid (NAPL) is generally minimal, the persistence of the NAPL hinders cleanup efforts and
provides a long-term source of contamination into the ground water through leaching of more
soluble components. The presence of NAPLs has been identified by the United States
Environmental Protection Agency (1992) as a major problem at superfund sites and a major
reason for the failure of pump and treat remediation schemes to meet their cleanup goals in a
reasonable amount of time.

Transport and entrapment behavior of NAPLs in soils depends on the distribution and
interaction of three fluid phases, namely water, NAPL and air. The effective control of
groundwater contamination requires assessment and remediation of these multiple fluid phases
occurring in soils. Guiding any assessment and remediation efforts are field data and models for
the interpretation of that data. Unfortunately, neither are widely available for separate phase
contaminants. Several models have been reported in literature, for example those of Faust
(1985), Baehr and Corapcioglu (1984), Abriola and Pinder (1985), Osborne and Sykes (1986),
Kuppusamy et al. (1987), Kaluarachchi and Parker (1989), Faust et al. (1989) and Kueper and
Frind (1991). These models are based on concepts currently used to describe petroleum
reservoir behavior (e.g. Muskat et al., 1937; Peaceman, 1977) despite the different goals and
needs for modeling near-surface, localized contaminant movement. Despite a number of
simplifying assumptions, these models remain complex; and have proven useful in situations
where extensive site and contamination characterization have been justified.

Complex models, such as those listed above, however, may not always be the most
desirable tool for a given field problem. Accurate simulations using such models may require
large computing resources, and there may be a significant investment in training users to set up
the model, run it properly and interpret the output. A large amount of field data and transport
parameter values are required to run such a model. In addition to the parameters for aqueous
phase solute transport (such as hydraulic conductivity, dispersivity, sorption parameters),


ABSTRACT

Recent research efforts on the transport of immiscible organic wastes in subsurface
systems have focused on the development of numerical models of various levels of sophistication.
However, in real field applications, the site characterization data needed to obtain the model
parameters are either difficult to obtain or are not easily available. As an alternative, a number
of simple sharp front models which require relatively less data have been developed. Less
rigorous data requirements and simplicity of use allows these types of models to be used as
screening tools in risk assessment and remediation design. Laboratory experiments have been
conducted to test two such models developed by the authors. Fundamental transport parameters
for the media were determined using a flow-pump system. One-dimensional spill simulations of
a non-aqueous phase liquid were conducted in vertical soil columns. Ponding depth and front
location were tracked visually. A dual-source gamma system was tested and then used to obtain
saturation profiles of the water and oil phases. The profiles indicate the existence of a sharp front
at the leading edge of the infiltrating oil phase. At the trailing end of the infiltrating oil, a gradual
decline in saturation was observed. One of the models, which is similar in concept to the Green-
Ampt type infiltration models, assumes sharp leading and trailing fronts. It deviates from the
experimental results for long modeling times. The second model based on kinematic wave
formulation and the method of characteristics approximates the gradual decline in saturation
behind the front and simulates the spill behavior well. Based on these experimental evaluations,
the suitability and limitations of these simple models are determined. Simulated rainfall
experiments have been conducted to observe extent of mobilization of the organic phase through
water application. Water pushes the organic phase as a slug in front of the water phase (piston
displacement). However, the water mobilizes nearly none of the organic phase below a phase
content of 0.1. Two-dimensional experiments were conducted in a tank to test the applicability
of the one-dimensional models to a two-dimensional situation. The saturation profiles were again
determined using the dual-gamma system. The vertical movement of the organic phase in the
tank experiments differed little from the movement in the column experiments, indicating the
applicability of one-dimensional models to the vertical infiltration of immiscible fluids in the
unsaturated zone of a homogeneous soil.

This report was submitted in fulfillment of CR-816807 by the University of Colorado at
Boulder under the partial sponsorship of the U.S. Environmental Protection Agency. This report
covers a period from July 1990 to August 1992 and work was completed as of August 1992.


Elevation Time Soltrol Time Soltrol

cm min Content min Content
57.00 301.00 0.14 450.00 0.14
56.00 302.00 0.15 451.00 0.14
55.00 302.00 0.16 451.00 0.17
54.00 303.00 0.14 452.00 0.14
53.00 303.00 0.13 453,00 0.15,
52.00 304.00 0.13 453.00 0.16
51.00 305.00 0.15 454.00 0.16
50.00 305.00 0.15 454.00 0.15,
49.00 306.00 0.15 455.00 0.15,
48.00 307.00 0.15 456.00 0.13,
47.00 307.00 0.13 456.00 0.14
46.00 308.00 0.16 457.00 0.14
45.00 308.00 0.14 458.00 0.14
44.00 309.00 0.15 458.00 0.15
43.00 310.00 0.14 459.00 0.13
42.00 310.00 0.13 460.00 0.13
41.00 311.00 0.14 460.00 0.14
40.00 311.00 0.13 461.00 0.13
39.00 312.00 0.14 462.00 0.17
38.00 313.00 0.13 462.00 0.16
37.00 313.00 0.17 463.00 0.16
36.00 314.00 0.13 463.00 0.15
35.00 314.00 0.13 464.00 0.14
34.00 315.00 0.15 465.00 0.13
33.00 316.00 0.14 465.00 0.14
32.00 316.00 0.20 466.00 0.16
31.00 317.00 0.18 467.00 0.16
30.00 317.00 0.20 467.00 0.17
29.00 318.00 0.20 468.00 0.19
28.00 319.00 0.22 469.00 0.22
27.00 319.00 0.19 469.00 0.20
26.00 320.00 0.21 470.00 0.22
25.00 321.00 0.20 471.00 0.20
24.00 321.00 0.19 471.00 0.19
23.00 322.00 0.20 472.00 0.16
22.00 322.00 0.17 472.00 0.16
21.00 323.00 0.18 473.00 0.16
20.00 324.00 0.16 474.00 0.15
19.00 324.00 0.16 474.00 0.13
18.00 325.00 0.14 475.00 0.13,
17.00 325.00 0.13 476.00 0.11
16.00 326.00 0.13 476.00 0.13
15.00 327.00 0.10 477.00 0.13,
14.00 327.00 0.12 478.00 0.12
13.00 328.00 0.10 478.00 0.11
12.00 328.00 0.09 479.00 0.12
11.00 329.00 0.09 479.00 0.13
10.00 330.00 0.08 480.00 0.13
9.00 330.00 0.09 481.00 0.13
8.00 331.00 0.08 481.00 0.10

143


5.1.3 Estimation of Brooks-Corey Parameters

The large amount of data obtained with the flow pump was reduced to van Genuchten
model parameters. Since KOPT is designed to use Brooks and Corey model parameters, two
approaches were used to estimate equivalent Brooks and Corey model parameters from the given
van Genuchten model parameters. In the first approach, a water/air curve was generated using

van Genuchten's model. The nonlinear fitting program RETC (van Genuchten et al., 1991) was
then used to determine Brooks and Corey parameters for this "data" set.

The approximate conversion equations between Brooks and Corey model parameters and
van Genuchten parameters developed by Lenhard et al. (1989) were used in the second
approach. The Lenhard et al. (1989) equations are

1

m 1
a= —Z 1-05" (25)
Tom | )
(es) :
ae) 26
hay = SBM — em ee)
a
where:
m-1-4 (27)
n

(where n is a parameter of the van Genuchten model) and S, is defined by Lenhard et al.'s (1989)
empirical relation

S, = 0.72 - 0.35 exp (-n‘) (28)

The values of the van Genuchten parameters from the flow pump data were converted to
equivalent Brooks and Corey model parameters using this set of equations. Plotted model curves
for both approaches are shown in Figure 17.

35


Elevation Time Soltrol Time Soltrot Time Soltrol

cm min Content min Content min Content
120.00 78.00 0.27 106.00 0.26 154.00 0.20
119.00 78.00 0.28 107.00 0.26 154.00 0.20
118.00 79.00 0.27 107.00 0.26 155.00 0.21
117.00 79.00 0.27 108.00 0.26 155.00 0.22
116.00 80.00 0.27 108.00 0.26 156.00 0.23
115.00 80.00 0.27 109.00 0.26 156.00 0.24
114.00 81.00 0.26 109.00 0.31 157.00 0.25
113.00 82.00 0.26 110.00 0.31 157.00 0.24
112.00 82.00 0.26 110.00 0.31 158.00 0.25
111.00 83.00 0.26 111.00 0.31 158.00 0.25
110.00 83.00 0.26 111.00 0.31 159.00 0.24
109.00 84.00 0.26 112.00 0.31 159.00 0.25
108.00 84.00 0.26 112.00 0.31 160.00 0.25
107.00 85.00 0.25 113.00 0.31 160.00 0.26
106.00 85.00 0.26 113.00 0.30 161.00 0.27
105.00 86.00 0.26 114.00 0.31 161.00 0.28
104.00 86.00 0.26 115.00 0.31 162.00 0.28
103.00 87.00 0.26 115.00 0.31 163.00 0.28
102.00 87.00 0.26 116.00 0.31 163.00 0.28
101.00 88.00 0.26 116.00 0.31 164.00 0.29
100.00 88.00 0.26 117.00 0.30 164.00 0.29
99.00 89.00 0.26 117.00 0.31 165.00 0.29
98.00 89.00 0.29 118.00 0.31 165.00 0.29
97.00 90.00 0.31 118.00 0.30 166.00 0.30
96.00 91.00 0.30 119.00 0.31 166.00 0.30
95.00 91.00 0.30 119.00 0.30 167.00 0.30
94.00 92.00 0.31 120.00 0.31 167.00 0.30
93.00 92.00 0.30 420.00 0.30 168.00 0.31
92.00 93.00 0.30 121.00 0.30 168.00 0.31
91.00 93.00 0.31 121.00 0.31 169.00 0.30
90.00 94.00 0.31 122.00 0.30 169.00 0.31
89.00 94.00 0.31 122.00 0.31 170.00 0.30
88.00 95.00 0.31 123.00 0.30 170.00 0.30
87.00 95.00 0.30 124.00 0.31 171.00 0.31
86.00 96.00 0.31 124.00 0.31 172.00 0.30
85.00 96.00 0.32 125.00 0.31 172.00 0.31
84.00 97.00 0.30 125.00 0.31 173.00 0.30
83.00 97.00 0.31 126.00 0.30 173.00 0.31
82.00 98.00 0.31 126.00 0.31 174.00 0.31
81.00 98.00 0.30 127.00 0.31 174.00 0.31
80.00 99.00 0.31 127.00 0.31 175.00 0.30
79.00 100.00 0.30 128.00 0.31 175.00 0.31
78.00 100.00 0.31 128.00 0.30 176.00 0.30
77.00 101.00 0.31 129.00 0.30 176.00 0.31
76.00 101.00 0.31 129.00 0.30 177.00 0.31
75.00 102.00 0.31 130.00 0.31 177.00 0.30
74.00 102.00 0.30 130.00 0.31 178.00 0.30
73.00 103.00 0.31 131 00 0.30 178.00 0.25
72.00 103 00 0.25 131.00 0.30 179.00 0.25
71.00 104.00 0.25, 132.00 0.30 179.00 0.26
70.00 104 00 0.21 133.00 030 180.00 0.25
69.00 133.00 0.30 181.00. 0.25
68.00 134.00 0.30 181.00 0.26
67.00 134.00 0.30 182.00 0.25
66.00 135.00 0.30 182.00 0.25
65.00 135 00 0.30 183.00 0.25
6400 136.00 0.30 183.00 0.25
63.00 136.00 0.24 184.00 0.27

154


5.5 TESTING OF THE COMPUTER MODELS

Two computer models were used to simulate the NAPL spills in the column. The Three
Parameter Sharp Front Model and the Kinematic Oily Pollutant Transport (KOPT) Model were
compared and tested using the data from Soltrol spill experiment conducted in the long column.

The KOPT model was run with independently measured parameters for the #125 sand.
The following input parameters were used: for Soltrol, a residual oil saturation of 0.05; for the
sample, a porosity of 0.4 and a residual water saturation of 0.22. The complete set of parameters
for the KOPT model is listed in Table 4. The three-parameter model was run with the same
parameters; however, the capillary suction at the front and at the back-front are parameters
which have to be fitted when running the model. The suction parameters cannot be estimated
from independent experiments. The first spill with 500 ml Soltrol in #125 sand was used to
calibrate the three-parameter model. The following values were found to give a good fit between
model and experimental results: a front suction head of 0.3 cm and a back front suction head
of 21 cm. For both models, the initial ponding depth was calculated by dividing the volume of
NAPL spilled by the cross-sectional area of the column. The initial ponding depths were 18.9
cm, 14.2 cm and 9.45 cm for the 1000 ml, 750 ml, and 500 ml spills, respectively.

66


#125 Sand 750ml Soltrol Spill

120
100
80
Front

60

40

Elevation in cm

204 Ponding

0 100 200 300 400 500 600
Time in minutes

TM Experimental Data —— Kinematic Model

Figure 59. Front movement of 750ml spill in #125 sand, comparison between KOPT and
experimental results.

By adjusting the parameters used in KOPT, the model may be forced to match the
experimental results. The selection of the parameter values is not entirely arbitrary as each
model parameter has a unique effect on the front position. For example, increasing the hydraulic
conductivity generally increases the depth of the front as the liquid at all saturations tends to
move faster. Increasing the air entry head, h,,, increases the front depth during infiltration, as
there is a greater contribution of capillary suction with increasing h,,. Of course, if the front
position is increased during infiltration, it will also be deeper during redistribution. The front speed
during redistribution, however, is unaffected by changing h,, as h,, is not used in the kinematic
wave solution for redistribution (Equation (15)) . Decreasing the Brooks and Corey A causes the
curvature of the front-time plot to increase, because lower ) values are associated with wider
pore size distributions. In materials with wide pore size distributions, the effective conductivity
K,,(S,) drops off rapidly with decreasing saturation, here illustrated for the water phase by the
Brooks and Corey (1964) relationship

S, -£.]
1-S,, (29)

Kew (Sw) Ky

—-

e=3+

ein

Since e€ is proportional to a constant plus 1/A, as 4 decreases, ¢ increases. So for materials with
wide pore size distributions (low A), the effective conductivity to water decreases rapidly with

75


United States Office of Research and EPA/600/R-94/197
Environmental Protection Development November 1994
Agency Washington DC 20460

SEPA An Experimental
Evaluation of Two
Sharp Front Models for
Vadose Zone Non-Aqueous
Phase Liquid Transport

»> D>


1.3.1 Modifications of the Gamma System

Proper alignment of source and detector is an important prerequisite for good performance
of the gamma system. In order to align the detector, elongated, oval-shaped slits were drilled into
the bottom plate of the detector, thus allowing the detector to be moved in three directions to
obtain the desired alignment. The detector can then be bolted down to the platform in the
optimum position. By moving the detector in increments, the position was determined where the
detector would read the maximum count rate. The detector was fastened down when proper
alignment was indicated through the highest observed count rate. To maintain proper alignment
of the signal, the source also needs to be secured to the platform. The gamma source is in
danger of being moved slightly whenever the platform moves up or down. The gamma source
was bolted tightly to the platform to prevent any movements during vertical motion of the source
platform.

It is assumed that by securely fastening the source and detector to their platforms, the
alignment will not change. However, the platforms on which the detector and the source are
mounted move in relation to each other when moved up or down; thus the alignment between
source and detector changes depending on the elevation at which the measurement is taken.
However, initial calibration allows for correction of the count rate for the misalignment, assuming
that the alignment is always the same for each vertical position.

Electronic shift in the detector moves the Americium and Cesium peak from their
theoretical position on an energy scale. The software used (EG&G) integrates only over a set
range of energy. If the peak shifts (partly) out of this region, the integration procedure does not
capture the whole peak. There is also a limit to the width of the integration region. To eliminate
this problem, a new integration scheme was developed (Campbell, 1992) to allow a wider region
for the integration. This method tries to avoid problems with a shifting peak. However, most of
the measurements for this research were conducted before the new software was finished. The
calibration described in this report pertains to the original EG&G software. A comparison between
the two integration schemes was performed; and no difference was found between them.

1.3.2 Determination of Warm-Up Time

It has to be assumed that the measurements with the gamma system are not accurate
unless the detector is at steady state, which requires some warm-up time. Thus, the warm-up
time for the gamma system was established, by using the following test. The system was
completely shut off overnight, and a measurement was started right after the unit was turned on.
The measured radiation intensity of Americium through a standard absorber changed for the first
20 minutes and stayed constant from then on (Figure 76a). The measured intensity of Cesium
was constant from the start of the measurement (Figure 76b). It can be concluded that for this
configuration of the gamma system, the warm-up time is 20 minutes until the readings for
Americium stay constant.

101


Tank A

#70 Sand 9.5cm Soltrol Ponding Depth

Temperature Soltrol: 23°C.

Elevation
cm

120
119
118
W17
116
115
114
113
112
qn
110
109
108
107
106
105
104
96
95
94
93
92
91
90
89
88
87

Time
min

Soltrol
Content

0.335185
0.350383
0.360118
0.362661
0.353848
0.337875
0.350075,
0.355796
0.3607
0.34467
0.343592
0.391261
0.414393
0.396858
0.363273
0.361114
0.35
0.160614
0.054263
0.005208
0.00838
+0.01059
0.02013
-0.01364
0.01121
0.00222
0.00455,
0.01385
0.00707
-0.0037
-0.00541
-0.00375
-0.00421
0.010074
0.002807
0.00158
-0.00719
0.00608
-0.00353
0.01113
-0.00297
0.00657
-0.00169
~0.00305
-0.00298
-0.00133
~0.00412
-0.00685,
~0.00655,
~0.00707
0.00104
-0.00964
0.00713
0.0041
0.001775

105
106
106

175

Soltrot
Content

0.145101
0.151197
0.166528
0.185728,
0.18599
0.175085
0.174667
0.174366
0.178328
0.15549
0.138024
0.159517
0.187042
0.193214
0.179339
0.206203
0.23
0.262985
0.268566
0.271967
0.26277
0.25282
0.234971
0.236328
0.256615
0.270824
0.27964
0.267809
0.231042
0.128614
0.038376
0.002689
0.003575
0.009323
0.005136
0.000364
-0.0067
-0.0042
-0.00139
-0.00624
-0.00523
-0.00188
0.00382
-0.00403
-0.00349
0.00271
-0.00635
-0.00866
-0.00529
-0.00372
-0.00819
-0.00707
~0.00134
0.0104
~0.00277

Time
min

121
122
122
123
124
124
125
126
126
127
127
132
133
134
134
135
135
136
137
137
138
139
139
140
140
141
142
142
143

144
145,
145,
146
147
147
148
149
149
150
151
151
152
152
153
154
154
155
156

Soltrol
Content

0.14083
0.144964
0.140674

0.14324
0.133752
0.113024
0.118653
0.141232
0.156462
0.142047
0.147203

0.20316
0.217242
0.219895
0.227894
0.229355,
0.215374
0.207881
0.203004
0.215822
0.233348
0.245742

0.24828
0.240389
0.242788
0.247158
0.243009
0.247298

0.26311
0.251949
0.240123
0.231562
0.251949
0.124374
0.027653

~0.00241
0.001611
0.000841
-0.00308
0.000781
-0.00364
-0.0016
0.000125
-0.0047
0.0019
-0.00593
-0.00099
0.00863
0.00435


SPILL P_ #125 SAND 750 ML SOLTROL SPILL
RAIN 500 ML/HR AFTER 22 HOURS

TIME

MINUTES

CONAN YNDA0

300

SPILL D #125 SAND 1000 ML SOLTROL SPILL

TIME

MINUTES

Zooahso

13
16

ELEVATION PONDING

cM

120
116.5
114
113
112.3
111.5
110.8
110
109
108.2
108
106
104.7
103.5
102
101
99

96

94
91.5
89.5
88

86
83.5
82

80

79
775
75
73.5
72

70

67

56

53

46

DISTANCE
cM

120
117
114.5
113
1
109.5
108
106
104

DEPTH
cM

PONDING

DEPTH
cM
19

17.5

124

BACK
FRONT
CM


Spill D Bulk Density grav.: 1.67g cm?

#125 Sand 1000 mi Soltrol Spill Porosity: 0.37
Elevation Soltrol Soltrol
cm Content Content
after after
6 hours 27 hours
114.14 0.082366 0.091152
111.6 0.142187 0.064798
109.06 0.091357 0.069389
106.52 0.109112 0.064
103.98 0.142605 0.075153
101.44 0.109846 0.092247
98.9 0.160281 0.076759
96.36 0.143359 0.051913
93.82 0.186652 0.099619
91.28 0.161901 0.108893
88.74 0.197024 0.107505
86.2 0.169978 0.089045
83.66 0.239673 0.097301
81.12 0.222566 0.092384
78.58 0.231926 0.10736
76.04 0.274829 0.139032
73.5 0.304318 0.142354
70.96 0.317352 0.123591
68.42 0.273139 0.134211
65.88 0.266491 0.121273
63.34 0.291925 0.109406
60.8 0.281703 0.101675
58.26 0.343395, 0.16055
56.72 0.292227 0.10303
53.18 0.28433 0.114969
50.64 0.26855 0.146399
48.1 0.31173 0.151808
45.56 0.274124 0.176784
43.02 0.280544 0.138455
40.48 0.268412 0.178901
37.94 0.255917 0.181523
35.4 0.23372 0.250728
32.86 0.16046 0.22861
30.32 0.079091 0.25895
27.78 0.00193 0.270626
25.24 0.04131 0.268964
22.7 0.02677 0.29604
20.16 0.000306 0.38219
17.62 0.005551 0.39054
15.08 0.01449 0.316351
12.54 0.03344 0.286392

152


rd

DE:

~~)

RS OLS

FOREWORD

EPA is charged by Congress to protect the Nation's land, air and water systems. Under
a mandate of national environmental laws focused on air and water quality, solid waste
management and the control of toxic substances, pesticides, noise and radiation, the Agency
strives to formulate and implement actions which lead to a compatible balance between human
activities and the ability of natural systems to support and nurture life.

The Robert S. Kerr Environmental Research Laboratory is the Agency's center of expertise
for investigation of the soil and subsurface environment. Personnel at the Laboratory are
responsible for management of research programs to: (a) determine the fate, transport and
transformation rates of pollutants in the soil, the unsaturated and the saturated zones of the
subsurface environment; (b) define the processes to be used in characterizing the soil and
subsurface environments as a receptor of pollutants; (c) develop techniques for predicting the
effect of pollutants on ground water, soil, and indigenous organisms; and (d) define and
demonstrate the applicability of using natural processes, indigenous to the soil and subsurface
environment, for the protection of this resource.

Light nonaqueous phase liquids (LNAPLs) are one of the most common, yet complex,
subsurface contaminants. Although the LNAPL itself remains distinct from the subsurface water,
chemical constituents of the LNAPL can cause serious ground water contamination. Because
of the number of parameters which determine the flow and transport of LNAPL contaminants,
models are needed to assess the impacts of this kind of contaminant. Models are derived from
a certain conceptualization of the flow and from theoretical principles. Before model results can
be accepted, there needs to be testing of the models with experimental data. This report
describes a set of experiments that were designed to test two models for LNAPL flow in the
vadose zone, and the comparison of the models against the data. As a result of the study, there
is a clearer understanding of the abilities and limitations of these models.

C Lev Lita &/ [laf
Clinton W. Hall, Director

Robert S. Kerr Environmental
Research Laboratory


Elevation
om

120

106

Time
min

1614
1615
1615
1616
1616
1617
1618
1618
1619
1619
1620
1621
1621
1622
1627
1627
1628
1628
1629
1630
1630
1631
1631
1632
1633
1633
1634
1634
1635
1636
1636
1637
1637
1638
1639
1639

1640
1641
1642
1642
1643
1643
1644
1645
1645
1646
1646
1647
1648
1648
1649
1649
1650
1651
1651
1652
1652

Water
Content

0.099299
0.083579
0.072562
0.059697
0.051822
0.093766
0.091534
0.110886
0.143819
0.123151
0.165009
0.129995
0.135897,
0.149208
0.091378
0.144688
0.175418
0.181729
0.127456
0.16576
0.158323
0.151458
0.231703
0.198277
0.20321
0.187102
0.152129
0.156417
0.197846
0.210148
0.178734
0.113472
0.184015,
0.137339
0.189683
0.185799
0.146014
0.201541
0.138815
0.18777
0.122137
0.172322
0.195035,
0.160347
0.154111
0.197118
0.148312
0.164346
0.179721
0.162082
0.137765
0.175702
0.102128
0.234009
0.190371
0.255789
0.228852
0.282847

Soltrol
Content

0.02202
0.048354
0.042834
0.041956
0.056324
0.055203
0.053666
0.040651
0.034404
0.053359
0.041218
0.051944
0.057053
0.057743
0.089324
0.058669
0.045101
0.037301
0.061107
0.046309
0.060312
0.076068
0.063182
0.063709
0.047485,
0.037537
0.060156
0.068696
0.058619
0.060002

0.06356
0.085417

0.0562
0.081122
0.060616
0.061229
0.073604

0.05847
0.075818
0.073524
0.104369
0.096589

0.07849
0.091739
0.091089
0.060282
0.086098
0.070255
0.069543
0.066642
0.082798
0.072233
0.106718
0.106609

0.149036
0.140009
0.153947
0.138625

184


Countrate after Start-Up (Am)
350

345

Countrate |
(Thousands)
o
a
S$

wo
yo
o a

w
a

aw
So

°
o

20 30 40 50 60
Time in Minutes

Figure 76. Delay in reading of constant count rate after start-up (Am).

102


TWO BOTTOM PARTS OF SAMPLE CELL

wat

O-RING 2-153

273,

Gh ee

Figure 8. Aluminum fitting for bottom part of sample cell. Sizes are given in inches.

The top aluminum fitting of the sample cell was used to create controlled rainfall. A small
cell was built that consisted of a 4 cm tall piece of the same kind of plexiglass tube that was used
for the column. A bottom plate was glued to this plexiglass tube. Five holes were drilled in the
bottom plate, and hypodermic needles were inserted into the holes. These needles served as
rainfall ports. The rainfall cell was closed at the top with the top aluminum fitting, and filled with
water supplied through the valves. Since the cell was closed on all sides, except for the small
needle openings, water pressure built up inside the cell. The water pressure regulated the
amount of water flowing through the needles and thus the simulated rainfall rate. The water
pressure itself was regulated by the height of a supply reservoir placed above the cell. By fixing
the elevation of the reservoir, a controlled rainfall rate was established. A calibration was
performed before every experiment, during which the amount of water leaving the cell per unit
time was measured for each elevation of the supply reservoir above the cell.

23


5.6 THE THEORETICAL RELATIONSHIP BETWEEN THE MODELS

The relationship between the three-parameter model and KOPT is discussed below. The
basic conceptual framework for both models is essentially the same. A pulse of NAPL is applied
at the surface of a homogeneous porous media, containing a uniform water saturation. The pulse
begins and ends abruptly. Both models assume that the leading edge, or front, of the NAPL is
sharp. As demonstrated by Smith (1983) and Charbeneau (1984), that all other things being
equal, the sharp front models track the location of the true front.

10 ]
8
°
oO 6
2
Zo
a 4
2
0

0 02 04 06 08 1
So

Figure 66. Schematic representation of the slope of the effective conductivity function.

Intuitively, one expects to treat the leading edge as a front. The nature of the function
defining the wave speed is what determines if there is to be a discontinuity (sharp front) at the
leading edge of the incoming liquid (Weaver, 1991). Figure 66 shows a monotonically increasing
OK,,/dS, function as would result from use of the Burdine (1953) and Brooks and Corey (1964)
relative permeability model. When the NAPL release begins, the transition along the boundary
is from some low saturation, S,, to some high saturation, S,,. Because the characteristic speeds
are determined by the dK,/0S, and that function is monotonically increasing, the characteristic
speeds increase from S, to S,. The result is that the characteristics associated with the high
saturation, S,, move faster than those associated with the low saturation, S,. These (and other
characteristics between S, and S,) must cross at some point in the domain (Figure 67, point A).
Beyond that point, the classical method of characteristics solution doesnot hold, as it predicts the
non-physical situation where multiple saturations are associated with points in the solution
domain. For such situations, the solution is supplanted with the generalized solutions or jump
conditions. When the boundary transition is abrupt, however, there is immediate generation of
a front (Figure 68). Thus, based on the abrupt release scenario used for the two models, the

82


#70 Sand 750mI Soltrol Spill

120
100

80 Front

60

Elevation in em

40

20 Ponding

0 100 200 300 400 500 600
Time in minutes

TM Experimental Data —— Kinematic Model

Figure 61. Front movement for 750ml spill in #70 sand, comparison between KOPT and
experimental results.

The forced match of KOPT to each of the experiments in the #70 sand will be considered
in turn. Generally, KOPT lags the experimental data for most of the duration of the 1000 ml spill
and the curvature of the plot is too low. Thus the hydraulic conductivity and 1 were targeted for
change. It turned out that in order to match the data, the entry head also had to be increased.
Figure 63 shows the revised simulation of the experiment. |Table 6 shows the adjusted
parameter values for each of the experiments.

77


measured parameter data. There appears to be a tendency in KOPT to under predict the
infiltration rates. Quantitative agreement of KOPT simulations with the experimental results
depends on the accuracy of the input parameters. KOPT allows the reduction of the NAPL
saturations behind the NAPL front during redistribution. The resulting saturation profiles, however,
are highly idealized in comparison to the measured profiles. In summary, prediction of NAPL
infiltration and redistribution by the three-parameter model is limited by the need to fit the model
to transient flow experimental data, which is not likely to be available for field problems. KOPT
predictions are generally limited by the ability to measure the input parameters, primarily the
hydraulic conductivity. Although the observed displacement of the residual water violated the
assumptions of the models, at least in these cases, the models were still able to fit the
experimental results reasonably well.

The following recommendations are derived from this work:

1. The University of Colorado, three-parameter model should be revised to include the effects
of reduced NAPL saturation behind the wetting front. Kinematic or other appropriate theories
should be used to accomplish this revision. The ability to predict flow experiment behavior with
fitted parameter sets from previous experiments should then be reevaluated.

2. The assumptions in the RSKERL KOPT Green-Ampt infiltration model should be reevaluated,
based on the apparent inability of KOPT to accurately predict the ponding time of the
experiments. This work should focus on the assumptions underlying kinematic models in general
and could be accomplished using kinematic models for water flow in the unsaturated zone. The
use of kinematic models for water, rather than for NAPL, permits the use of relative permeability
expressions (for water) that are more well-established than those for the NAPL; thus one source
of uncertainty would be eliminated. .

3. Simple models such as these should be included in screening methodologies for subsurface
NAPL flow. The simple models are of sufficient accuracy to be acceptable for screening
calculations. The primary factor which will limit accuracy of model predictions is the ability to
determine the model parameter values. This statement is true for both simple and complex
models. The complexity of the model used for a particular analysis should be appropriate for the
availability of data, the level of detail of the analysis, and the ability to test model predictions.

4. Further experimental work should be performed on the effects of rainfalls on displacement of
NAPLs in the unsaturated zone. The experiments presented in this report suggest that rainfalls
can cause NAPL banks to form. This behavior was predicted by a model developed by Weaver
(1991), but was not used in this work because it requires restrictive assumptions concerning the
boundary and initial conditions. Some of the qualitative behavior predicted by the model,
however, appears to be consistent with the experimental results.


#70 Sand

Visually Observed Front Movement

120

100 + Front Elevation

500ml Soltrol Spill

80

60

Elevation in cm

40

Ponding

1000m
Ss
p007mE
0

50 100 150 200 250 300 350
Time in minutes

Figure 27. Front elevation versus time for three spills, 500ml, 750m! and 1000m! Soltrol on
#70 sand.

47


Spill N

#70 Sand 750 ml Soltro! Spill
Rain 500m\/hour after 86 minutes.

Elevation
cm

115
114
113
112
1
110
109
108
107
106
105
104
103
102
101
100
99
98
97
96
95
94
93
92
ot

Porosity: 0.48

Water
Content

0.0021
0.021777
0.024549

0.0135
0.009536

0.01279

0.0234
0.00719
-0.02569
0.00513
-0.01745
0.03513
0.01843
-0.01576
-0.00637

-0.0066
0.014298
-0.00681
-0.00504
0.045165
0.024269
0.063355.
0.034546
0.039022
0.034515,
0.070401
0.048104
0.041587
0.056925,
0.076364
0.063285
0.038303
0.077923
0.059252

0.06711
0.086986,
0.087412
0.087937
0.095409
0.012663
0.062379
0.045206
0.047899

0.05624
0.041488
0.045979
0.036653,
0.073485,
0.042619
0.027008
0.045546

Bulk Density grav.: 1.39g cm*

Temperature Soltrol: 21°C
Temperature Water: 24°C

Residual water content: 0.06.

Soltrol
Content

0.436065
0.413878
0.399624
0.417071
0.400511
0.407971
0.417602
0.409034
0.410186
0.404954
0.406887
0.410969
0.406296
0.405126
0.400578
0.398688
0.385375
0.390456
0.384054
0.291223
0.185312
0.081416
0.041725
0.015172
0.007598
0.00017
0.008655
0.007629
0.003662
-0.00215
0.00202
0.007975
0.00362
0.003331
0.013714
0.015609
0.008011
0.012111
0.00328
0.017714
0.00524
0.00276
0.003382
0.00632
0.003214
0.0012
0.006206
0.01006
0.000257
0.010582
0.003159

164

Time
min

32
32
33
33
34
35
35
36
36
37
37
38
38
39
39

Water
Content

0.020082
0.005478
0.01243
0.00579
0.004664
0.0171
0.01399
0.0336
0.05216
0.0156
0.013324
0.01365
0.007238
0.00883
0.017353
0.01226
-0.02152
-0.03101
~0.01643
-0.00428
0.002645
-0.01593
-0.00675
0.0173
-0.0305
0.008034
0.03066
-0.0298
-0.01833
0.01634
0.006168
0.01412
~0.00205
0.01823
0.042915
-0.02025,
0.025825,
0.045757
0.029589
-0.00193
-0.01929
-0.01017
-0.00161
0.067099
0.062777
0.060637,
0.064453
0.055944
0.076373
0.056413.
0.068445,
0.041902
0.049095

Soltrol
Content

0.415094
0.419199
0.41538
0.413683
0.401148
0.413873
0.404229
0.411386
0.417362
0.409714
0.39179
0.408329
0.393551
0.399143
0.392564
0.409243
0.402164
0.412982
0.414145
0.405086
0.397021
0.403012
0.403795
0.408682
0.410149
0.394425,
0.416712
0.413679
0.409451
0.409847
0.396108
0.40303
0.39128
0.395289
0.382415
0.405123
0.383095
0.372582
0.380606
0.388573
0.378288
0.362655,
0.291322
0.115503
0.022412
0.00191
0.00182
0.00412
-0.00702
0.000667
0.00859
0.002838
0.000235


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and Radiation Techniques in Soil Physics and Irrigation Studies - International Atomic Energy
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Green, W.H., and G.A. Ampt, 1911. “Studies on Soil Physics," Journal of Agricultural Science,
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Held, R.J., 1993. "Investigation of Fingering of Dense Non-Aqueous Phase Liquids in Saturated
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Honarpour, M.C., L. Koederitz, and A.H. Harvey, 1986. “Relative Permeability of Petroleum
Reservoirs," CRC Press Inc., Boca Raton, Florida.

\llangasekare, T.H., P. Brody, and D.D. Reible, 1987a. “A Model for Two-Dimensional Transport
of Concentrated Organics in Saturated and Unsaturated Soils," Proceedings of Seventh Annual
American Geophysical Union Hydrology Days, Fort Collins, Colorado.

Illangasekare, T.H., P. Brody, and D.D. Reible, 1987b. "A Model for Two-Dimensional Transport
of Concentrated Organic Waste in the Unsaturated Zone," Proceedings of International
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Netherlands.

Illangasekare, T.H., and D.D. Reible, 1987a. "A Simple Model for Transport of Free-Phase
Organics in Unsaturated Zones of Aquifers," Proceedings NWWA Conference on Solving
Groundwater Problems with Models, Denver, Colorado.

llangasekare, T.H., and D.D. Reible, 1987b. "A Study of Transport and Entrapment of
Concentrated Organics in the Unsaturated Zone," Proceedings of International Conference on
New Frontiers for Hazardous Waste Management, Pittsburgh, Pennsylvania.

Kaluarachchi, J.J., and J.C. Parker, 1989. “An Efficient Finite Element Method for Modeling
Multiphase Flow," Water Resources Research, Vol. 25, No. 1, pp 43-54.

Kueper, B.H., and E.O. Frind, 1991. “Two-Phase Flow in Heterogeneous Porous Media; 1. Model
Development," Water Resources Research, Vol. 27, No. 6, pp 1049-1057.

Kuppusamy, J.J., J. Sheng, J.C. Parker, and R.J. Lenhard, 1987. "Finite Element Analysis of
Multiphase Immiscible Flow Through Soils,"\Water Resources Research, Vol. 23, No. 4, pp 625-
632.

Lenhard, R.J., J.C Parker, and S. Mishra, 1989. "On the correspondence between Brooks-
Corey and van Genuchten models,” Journal of Irrigation and Drainage Engineering, Vol. 15, No.
4, pp 744-751.

89


Tank B

#70 Sand 9.5cm Soltrol Ponding Depth
Rain 12000mVh after 22 hours

Rain end after 24 hours

Residual water content assumed constant at 0.06.

Elevation
cm

Time
min

Water
Content

0.06239
0.064171
0.018889
0.081584
0.091061
0.123558
0.116566
0.088546
0.138062
0.105408

0.11099
0.101597
0.147845
0.157013
0.061979
0.060853
0.051959
0.049788
0.023055
0.070986
0.080244
0.059032
0.034132
0.079058
0.030363
0.000945
0.058244
0.055242
0.069321
0.053829
0.045889
0.114024

Soltrol
Content

0.380415,
0.369694
0.373156
0.34694
0.34845
0.336452
0.339065
0.360088
0.342297
0.338063
0.337725
0.349861
0.334453,
0.332685
0.022284
0.00721
0.01241
0.0154
-0.0047
0.01429
0.0125
-0.00628
0.018775
-0.00586
0.001083
-0.00147
0.01405
~0.00764
-0.00861
-0.00675
-0.00604
-0.03315,

178

Water
Content

0.051818
0.016052
0.052969
0.049894
0.01144
0.046766
0.090354
0.104996
0.002361
0.112462
0.135694
0.087892
0.111108
0.117092
0.122808
0.088845,
0.05419
0.111406
0.074253
0.040554
0.075849
0.107507
0.103747
0.00511
0.046281
-0.0013
0.10958
0.084242
0.079702
0.011301
0.096011
0.056034
0.091905
~0.02254
0.01057
0.020959
0.022164
0.055111
-0.01289
0.055679
0.039006
0.07637
0.092931
0.070676
0.11497
0.015448
0.075492
0.061327
0.074612
0.040309
0.16001
0.123636

Soltrot
Content

0.177212
0.219551
0.173085
0.167317
0.196705
0.194484
0.191042
0.201764
0.261831
0.241555
0.256734
0.29352
0.314377
0.3297
0.279154
0.279213
0.284217
0.255271
0.24899
0.231928
0.174763
0.077763
0.017674
0.018305
0.00719
0.004376
-0.04072
0.01592
0.01304
0.016097
0.01511
0.01411
-0.03
0.011075
0.007369
0.0025
-0.00589
~0.01909
0.009454
-0.01407
0.000006
-0.01091
-0.01888
-0.01785
-0.03699
0.00046
-0.02616
0.01598
0.01992
-0.00888
0.0462
0.02491


Elevation Time Soltrol Time Soltrol

cm min Content min Content
34.00 1059.00 0.00
32.00 1060.00 0.00

163


No.125 Sand 500ml! Soltrol
Front Position after 48 Minutes
100
80)
€
& 60)
8
3 40
wu
= Fikse'Parameter Sharp Front Model
— —- Kinematic Model
20)
° ri
-0.1 0.0 1 0.2 0.3 0.4 0.5
Phase Content
Figure 51. Phase content profile comparison between models and gamma scan. Soltrol is

still ponding at the surface.

No.125 Sand 500m! Soltrol
104 Minutes

100,

80

60)

40)

Elevation (cm)

20)

-0.1 0.0 0.1 0.2 0.3 0.4 0.5
Phase Content

Figure 52. Phase content profile comparison between models and gamma scan.

68


2. Use of a single spectrum of the gamma system: From the first measurement through the
empty column and the dry sand, a lumped attenuation coefficient for the sand can be calculated.
Knowing the attenuation coefficient, the bulk density can be calculated. Problems with this
approach are that the path length through the column cannot be determined very exactly (81 +1
mm), which decreases the accuracy of the lumped attenuation coefficient. The lumped
attenuation coefficient has a relative error of 1%. The mass attenuation coefficient as calculated
in the error propagation calculations has a relative error of +3%. Thus the total error in
determining the porosity is 4%. An advantage of this approach is that the bulk density can be
calculated at any desired location along the column.

3. Use of two spectra of the gamma system: The Americium and Cesium spectra can be used
to calculate bulk density and phase content simultaneously. However, the summation of the
random errors of both spectra leads to high errors in the porosity measurements. The error in
the calculation of porosity is about +7%.

\f experimental conditions allow for it, the bulk density should be determined gravimetrically
and with a single spectrum measurement. Only if a measurement through dry sand is not
possible, the two spectrum measurement to determine bulk density should be used.

4.5 TWO-DIMENSIONAL TANK EXPERIMENTS

Spill experiments were conducted in a two-dimensional vertical tank (180 x 120 cm x
5 cm) to investigate the two-dimensional movement of a NAPL in the unsaturated zone. The tank
walls were made of glass-lined plexiglass walls. The glass lining protected the plexiglass walls
from aggressive chemicals, while the 1.9 cm thick plexiglass provided the necessary wall strength
to support the soil sample.

The tank was packed with sand using the following procedure. Approximately 5 cm thick
layers of sand were placed in the tank through a funnel attached to a long tube. Every layer was
then mixed by pulling a long rod through the soil before the next layer of sand was poured in.
A nearly homogeneous packing was thus achieved. Two valves at the bottom of the steel end
walls of the tank permitted saturating the sand with water from the bottom to minimize the
entrapment of air. Unlike the one-dimensional column, the tank could not be completely air-
evacuated. The water was drained from the bottom of the tank to create the unsaturated zone.
The bottom of the tank had been filled with a layer of coarse gravel to prevent the valves from
getting plugged with fines during desaturation. A capillary fringe formed at the bottom of the
tank, because there was no provision for desaturation of the sand through a porous plate. All
experiments were stopped when the spill front reached a point 15 cm above the saturated zone.
Up to this depth, the assumption of uniform residual saturation held true for the experiments.

The spill experiments in the tank were conducted in a manner similar to the column
experiments. The Soltrol was applied in a 30 cm wide slug, with a maximum ponding depth
corresponding to the ponding depth in the column. PVC pipes with an outside diameter equal
to the tank width were used to retain the infiltrating Soltrol within the source region. These
barriers penetrated about 5 cm into the sand (Figure 14).

29


Elevation Time Water Soltro! Time Water Soltrol

cm min Content Content min Content Content
119 257 0.236304 0.060133 286 0.290339 0.052462
117 258 0.239956 0.077781 286 0.244356 0.066779
115 259 0.216507 0.081337 287 0.255862 0.069245
113 259 0.213728 0.087926 287 0.217388 0.088693
114 260 0.234525 0.087599 288 0.194816 0.091504
109 260 0.203073 0.097679 289 0.247605 0.085901
107 261 0.249328 0.087763 289 0.262235, 0.077606
105 261 0.236474 0.086281 290 0.253059 0.082573
103 262 0.202755, 0.108536 290 0.268187 0.080298
101 262 0.202582 0.117352 291 0.244845 0.098575
99 263 0.221312 0.115818 291 0.253744 0.102754
97 263 0.234767 0.117641 292 0.282258 0.103684
95 264 0.251781 0.123358 292 0.293098 0.104344
93 265 0.219186 0.140182 293 0.278322 0.125301
1 265 0.306258 0.119054 294 0.293429 0.129956
89 266 0.293141 0.128174 294 0.330107 0.118657
87 266 0.29926 0.141492 295 0.313999 0.129884
85 267 0.279315 0.145057 295 0.283878 0.148978
83 267 0.262188 0.15557 296 0.315134 0.143008
81 268 0.299975 0.153649 296 0.270039 0.164807
79 268 0.293739 0.161926 297 0.318291 0.149236
77 269 0.312737 0.162069 297 0.333206 0.136037
75 269 0.267543, 0.171436 298 0.282293 0.159372
73 270 0.255471 0.180474 298 0.293712 0.158408
71 271 0.268374 0.179908 299 0.241943 0.185006
69 271 0.233942 0.196161 300 0.225005, 0.196234
67 272 0.256176 0.188821 300 0.295491 0.168389
65 272 0.250755, 0.192989 301 0.279028 0.173439
63 273 0.219511 0.210159 301 0.301968 0.170135
61 273 0.26 0.197421 302 0.242073 0.193253
59 274 0.23021 0.209667 302 0.246361 0.191141
57 274 0.256778 0.20123 303 0.249593 0.193854
55 275 0.21519 0.221577 303 0.242212 0.195181
53 275 0.263777 0.202243 304 0.208726 0.209672
51 276 0.190807 0.24485 304 0.245528 0.201359
49 277 0.160426 0.272479 305 0.265931 0.197708
47 277 0.109634 0.326434 306 0.301205 0.188368
45 278 0.075805 0.369031 306 0.255559 0.210886
43 278 0.11384 0.364382 307 0.253478 0.203375,
4 279 0.069354 0.378734 307 0.264056 0.206668
39 279 0.096327 0.370862 308 0.232859 0.218233
37 280 0.057551 0.390308 308 0.236952 0.23008
35 280 0.100549 0.371543

174


b) Sand #70 and water (Figure 22).

As for the previous experiment, the same scanning time of 20 seconds was used. Two
scans were repeated at every location. After 2 scans, the gamma system moved 1.25 cm
vertically down to the next scanning location.

The porosity of the sand as determined gravimetrically was 0.48. The average porosity
calculated from the Americium scan was 0.55. The residual saturation was found to be
approximately 0.25, measured with Americium. The height of the capillary fringe was 0.2 m. The
gamma data agree well with the Brooks and Corey suction-saturation curves derived from the flow
pump data using approaches 1 and 2.

#70 Sand

Water-Air Capillary Pressure Curve

1.60
1.40
1.20
1.00

-».
0.80 a.
0.60
0.20 .
0.00 Sa
0.20

0.00 0.20 0.40 0.60 0.80 1.00 1.20
SATURATION

SUCTION HEAD (m)

TM Gamma System (Am) —+~ Model Parameter (1) —*- Model Parameter (2)

Figure 22. Suction-saturation profile for #70 sand and water-air.

41


Attenuation Coefficient of Water
Am

1
0.9
08
307
E06
805
5
Bos
3
B03
2
0.2
0.4
0

0 2 4 6 8 10 12
Sample Thickness in cm

Figure 79. Attenuation coefficient of water (Am).

Attenuation Coefficient of Water

Cs
2.5
2
<
s
Eis
8
2
&
24
:
8
<
0.5
0
0 2 4 6 8 10 12

Sample Thickness in cm

Figure 80. Attenuation coefficient of water (Cs).

110


TEST WITH #125 SAND

1.
Ez 1.0)
5 Gamma System
:
§
So Flow Cell

oo +

0.0 02 04 06. 08 10 12
‘SATURATION

Figure 26. Comparison of suction-saturation profile as measured with Americium gamma
scan and with flow pump.

5.2 SPILL EXPERIMENTS IN THE LONG COLUMN

After residual water saturation was established, Soltrol spills were performed in the long
column. A slug of Soltro! was applied to the top of the column. The movement of the Soltrol was
observed visually, and the front location and ponding depth were recorded. Simultaneously,
gamma scans were performed to determine the phase content of Soltrol along the length of the
column. Comparisons of the visually observed front location with the gamma data showed that
the visually observed front coincided with the front detected by the gamma system.

Six different spill experiments were performed with spill volumes of 500 ml, 750 ml and
1000 mI Soltrol, respectively, on columns packed with #70 and #125 sand. The visually observed
front elevations are shown in Figure 27 and Figure 28 for sand #70 and sand #125, respectively.
The top of the sample was assumed to be at 120 cm for all experiments.

46


TANK B

#70 SAND - SOLTROL PONDING DEPTH 9.5 CM

RAIN 12000 ML/H AFTER 22 HOURS.

RAIN END AFTER 24 HOURS

RESIDUAL WATER CONTENT ASSUMED CONSTANT AT 0.06.

TIME
MINUTES

wo
SHLCMVOMERWKY+0

30
40
50

130
180
300
420
1200
1342
1414
1450
1556
2700

ELEVATION
cM

120
113
114
109.5

107

PONDING DEPTH

131

cM

9.5
5.8

2.8
25
1.9
1.2
0.7


c) Sand #125 and Soltrol (Figure 23).

The scanning time for this experiment was 20 seconds at every point. Two scans were
repeated at every location. After 2 scans, the gamma system moved 1.25 cm vertically down to
the next scanning location.

The porosity of the sand as determined gravimetrically was 0.37. The average porosity
calculated from the Americium spectrum was 0.41. The residual saturation was found to be
approximately zero, the height of the capillary fringe was 0.2 m. The gamma data agree well with
the Brooks and Corey suction-saturation curves derived from the flow pump data using
approaches 1 and 2.

#125 Sand

Soltrol—Air Capillary Pressure Curve

1.40

1.20

0.60

0.40
0.20

SUCTION HEAD (m)

0.00

0.20
0.00 0.20 0.40 0.60 0.80 1.00 1.20

‘SATURATION

TM Gamma System (Am) —+- Model Parameter (1) —* Model Parameter (2)

Figure 23. Suction-saturation profile for #125 sand and Soltrol-air.

42


No.125 Sand 1000mI Soltrol
Front Position after 100 Minutes
100
i)
!
80 '
€
2 60
©
= 40 !
Fs
rs ee I
20; = Experimenta! Dato
— — - Three Porometer Shorp Front Model
Kinematic Model
0
-0.1 0.0 01 0.2 0.3 0.4 0.5
Phase Content

Figure 55. Phase content profile comparison between model and experimental results.

The influence of hydraulic conductivity on the KOPT model results was investigated.
Previous uncertainty analysis with KOPT (Weaver et al., 1992) has demonstrated that the
hydraulic conductivity is a dominant parameter of the model. In Figure 58, data from two 1000
ml spills in the #125 sand have been compared to the KOPT model predictions for three hydraulic
conductivities (the average K, of 8.50 m/d and also +/- one standard deviation 5.79 m/d and 11.21
m/d). The conductivities were selected to represent the average hydraulic conductivity from the
experimental determination, and the average plus and minus one standard deviation. It can be
seen that both experiments fall within the predicted boundaries for one standard deviation of the
hydraulic conductivity, and that accurate determination of hydraulic conductivity plays an important
role in determining how closely the model can match the experimental results. As expected,
the location of the front is highly dependent on the saturated hydraulic conductivity.

Comparisons of data from all the #70 sand experiments with the KOPT model are shown
in Figure 59 through Figure 62. The hydraulic conductivity for the #70 sand was not measured
as it was for the #125 sand. The hydraulic conductivity used in KOPT was selected,so as to
match the 1000 ml experimental result at approximately 250 minutes. This value was then used
to simulate the 500 mi and 750 ml releases. In each case, KOPT over predicted the time of
ponding. KOPT also somewhat under predicted the front speed during infiltration. These two
features of the simulations suggest that the chosen hydraulic conductivity is too low for the 750
and 1000 ml experiments, as the long ponding time indicates a relatively low flux
in the sand.

71


Table 6 Adjusted KOPT parameter values for the #70 sand

Adjusted KOPT parameter values for the #70 sand

Parameter 1000 mi spill 750 mi spill

Saturated Hydraulic | 20 m/d 18 mid 10 m/d
Conductivity, K,

Brooks and Corey A | 0.25 0.25 0.4
Porosity, n 0.41 0.41 0.41
Residual Water 0.30 0.30 0.30
Saturation

Water Saturation 0.30 0.30 0.30

Air entry head, h,, 0.4000 m 0.4000 m 0.2683 m
Oil viscosity, p, 3.78 cp 3.78 cp 3.78 cp

Oil density, p, 0.85 g/cm*® 0.85 g/cm® 0.85 g/cm*®
Residual oil 0.05 0.05 0.05
saturation

Water surface 65 dyne/cm 65 dyne/cm 65 dyne/cm
tension

Oil surface tension 24 dyne/cm 24 dyne/cm 24 dyne/cm
Ponding depth, H, 0.1890 m 0.1420 m 0.0947 m
Radius 0.025 m 0.025 m 0.025 m

After obtaining a reasonable fit to the 1000 ml spill experiment, the same parameter set
was used for the 750 ml spill. This approach was suggested by the similar match to the data that
was found for the original parameter set (Figure 61 and Figure 62). Only a small reduction in
hydraulic conductivity was necessary to force the model to fit the experimental results (Figure 64).
It appears that both experiments are reasonably well fit by one parameter set and that the
variation is similar to that due to the variation in hydraulic conductivity (Figure 58). For the 500
ml experiment, however, the original simulation had KOPT leading the data rather than following
it, as it did for the 750 ml and 1000 ml experiments. Thus the hydraulic conductivity must be
lowered in the 500 ml spill. As for the other fitted simulations, the Brooks and Corey 4 had to
be decreased to fit the data. Figure 65 shows the revised simulation of the 500 ml spill
experiment.

81


Water/Air (1)
Water/Air (2)
Scaled Oil/Air (1)
Scaled Oil/Air (2)

Capillary Head (m H,0)

Vy v0,

ee

Dhan 7 DOAAAAAAAADA AAA ATID
MPADAABAAAAAABDAAAADARA DOO,

02 0.4 06 08 1
Saturation

Figure 18. Water/air and scaled oil/air pressure curves for #125 sand using Brooks and
Corey parameters.

Table 3 shows a comparison of the parameters obtained by each approach. With the first
approach (nonlinear fitting with RETC), a range of values was obtained during the fitting; and the
95% confidence limits are shown in parenthesis for each parameter in the table. For each fitting,
the residual water saturation was held to the value originally determined from the measured data.

36


APPENDIX 2 EXPERIMENTAL FRONT MOVEMENT DATA

SPILL H #125 SAND 500 ML SOLTROL SPILL
VISUALLY OBSERVED FRONT MOVEMENT

TIME ELEVATION
MINUTES. cM
0) 120
1 116
2 115
3 113
4 112
5 m1
6 110
8 109
10 108
12 106
14 105
16 104
18 103
a 101
24 100
27 99
31 97
35 95
38 94
40 93
43 92
44 91.5
AT ot
50 90
55 88
60 87
65 86
70 85
80 84
90 82
100 81
110 80
120 79
135 7
150 75
220 68
240 64
270 62
300 60
335 57
900 21

PONDING BACK
DEPTH FRONT
cM cM
9.5
7
75
6
5
4
3
2
1
oO

118.5
118
117.5
Vi7
414
WW
110
108
106
103
101
100
98

97

122


1.3.5 Detector Sensitivity

Detector sensitivity is defined as the amplification factor of an incoming signal (one
detected gamma ray) to the output signal sent to the computer. Change in sensitivity means that
the same amount of detected gamma rays does not necessarily yield the same output voltage.
Observed count rates thus may change even if there is no change in actual count rate. The
detector sensitivity depends on the temperature of the detector crystal, which in turn depends on
room temperature and detector history (i.e. previous radiation on the detector, total run time of
the detector) which cannot necessarily be quantified. It is therefore assumed that the detector
adds another random element to the fluctuations in the count rate measurements. Count rates
through a number of absorbers were measured on different days in order to evaluate fluctuations
of the intensity measurements due to the source plus the detector variations. All measurements
were conducted with the same standard absorber. Measurements through the absorber were
taken on randomly selected days and times to find the maximum variability in the count rate. The
standard deviation for these measurements was about one order of magnitude larger than the
square root of the count rate (Tables 8a and 8b). If the whole measurement can be conducted
within a short time period, problems due to changing detector sensitivity are minimized. Longer
measurements would be influenced by changing detector sensitivity. For long measurements,
the count rate through a standard absorber has to be taken before and after the measurement,
and any changes have to be accounted for in the calculation of the absorbance. For short
measurements where the incident radiation cannot be measured before the measurement (e.g.,
the column through which the incident radiation is measured, is already filled with sand and
water), the incident radiation through a standard absorber is measured before every sample
exposure. By knowing the change in count rates through the standard absorber, the incident
count rate can be corrected.

Table 8a. Count statistics for Americium

Absorber Am Am Average Std. Dev. Square root
wee ® IL cays day 2 day 3
2.5cm|} 646849 627394 636045 636763 7959 798
5.0. cm 399178 393543 395933 396218 2309 629
[75cm 245226 242473 245629 244443 1402 494
10.0 cm 150340 148680 149441 149487 678 387
12.5 cm 90161 81765 79555 83827 4569 290

106


Table 10. Volumetric water content in sand-water mixture
Three compartments filled with sand, one or two filled with water

Am

U(water) = 0.197655 calc. with ly | calc. with f, | calc. with
Equation
37(42)

ae r 1h wa |wa [wa |wa fwa [wa

sand | comp. | comp. contt | cont2 | contt | cont2 | contt | cont2

q) (9)
696423
697342
700459
697945
699347
698219
698018

avg 0.333 | 0.665] 0.289] 0.620] 0.161] 0.493
std 0.011 | 0.012] 0.009 | 0.008} 0.080} 0.226
| Theoret. Water Content | 0.333 | 0.667 | 0.333 | 0.667 | 0.333} 0.667

Theoret. Error% | -0.04| 0.278] 13.31 | 6.955] 51.73| 26.1
——————————
Cs

U(water) = 0.08065

lay 4 ry h wa
water water cont

99474 197228 | 0.323 | 0.641
95478 | 81080] 65925] 199638} 0.266 | 0.603 | 0.089] 0.425
101295] 82495| 66073 | 202258 | 0.334} 0.695 | 0.082] 0.443
98706 199303 | 0.312
99865, 200227 | 0.335
98483 198368 | 0.332

0.690
0.606
0.653

0.317 | 0.648
0.024 | 0.036

avg
std

theoret. wa cont

theoret. error

The test box was used to determine the volumetric water content in a defined sand-water
mixture. The first four columns give the measured count rates through the box for three
compartments filled with sand, three compartments filled with sand plus one compartment filled
with water, three compartments filled with sand plus two compartments filled with water, and
through the empty box, respectively. The fifth and sixth columns give the water content as
calculated from Equation (30) with the initial count rate through the dry sand for one and two

115


cm thickness) absorber was placed in front of the source to decrease the radiation.

Detector sensitivity was defined as the amplification factor of an incoming signal (one
detected gamma ray) to the output signal sent to the computer. The detector sensitivity was
shown to have a large influence on the measurements. Temperature changes the amplification
gain of the photo multipliers inside the detector (Cathey, 1958). A constant temperature is
necessary to achieve good measurements. However, the detector temperature depends not only
on the environment temperature, but also on the time the detector has already been subjected
to radiation and possibly even the amount of radiation.

As has been shown during the calibration experiments, the detector sensitivity did not
change within "short" time periods; thus all measurements performed later were conducted within
the same day, if possible. Every experimental measurement was preceded by a measurement
through a standard absorber (which could be an aluminum block or the top part of the empty
column). The count rate was then corrected according to the change in the count rate through
the standard. A 5% change in the count rate through the standard meant that the count rate in
the experiment was accordingly adjusted with a 5% increase (or decrease). Also, no
measurements were performed earlier than one hour after the equipment had been turned on to
insure maximum detector stability.

It was also seen that the attenuation coefficient is dependent on radiation strength. In the
physical sense, the attenuation coefficient depends only on the material and the wave length, not
on the radiation strength. The observed dependence on radiation strength results from the
changing detector sensitivity. Radiation strength as seen by the detector depends not only on
the actual strength of the source, but on the absorbance of absorbers, sample and sample holder.
It is important to note that absorbance might also depend on the location of the sample between
source and detector. A consistent source-sample-detector configuration was maintained during
all experiments. Ideally the attenuation coefficients are measured in the same setting as the
actual experiments are performed. This was done for all the column and tank experiments to
insure the greatest accuracy for the measurements.

In general the results obtained from measurements with the Cesium source are not as
reliable as results measured with Americium. The high energy radiation emitted by the Cesium
source is subject to very small absorption. Thus, the change between incident radiation (dry
sand) and sample radiation (saturated sand) is very little. Hence a change in count rate due to
changing detector sensitivity may have a large effect. Ideally, the Cesium source would be
replaced with another radioactive source emitting a lower energy gamma radiation. However
sources with a lower energy and a long half-life are not generally used in industry or research and
are extremely expensive. Most gamma systems are therefore equipped with an Americium and
a Cesium source. A lower accuracy for the Cesium measurements has to be accepted. It was
thus decided for the spill experiments to calculate the bulk density gravimetrically and use the
Americium counts for calculations of phase content for single-phase systems. Cesium counts
were only used for measurements involving two-phase systems (spill experiments with rainfall).
Spill experiments in immobile, residually water saturated columns can be treated as single-phase
experiments, if the residual saturated column is measured and this measurement is used as the
incident radiation, which is assumed to be constant. In all experiments the results were
calculated with Americium and Cesium; however, when not stated otherwise the results presented

120


Spill P Bulk Density grav.: 1.58g cm?

#125 Sand 750 mi Soltrol Spill Porosity: 0.40
Rain 500mi/hour after 22 hours. Temperature Soltrol: 22°C
Rain stopped after 24 hours. Temperature Water: 15°C
Residual water content assumed constant at 0.06.
Elevation Time Soltrot Time Soltrol Time Soltrol
cm min Content min Content min Content
118 4 0.321395 35 0.325105 a4 0.304382
117 5 0.329321 36 0.323595, 85 0.313989
116 5 0.309421 37 0.309167 86 0.307862
115 6 0.31455 37 0.312641 86 0.296759
114 7 0.305153 38 0.308274 87 0.286766
113 7 0.298672 38 0.300319 87 0.28335,
112 8 0.297413 39 0.30346 88 0.28884
11 8 0.303576 40 0.3073 89 0.301457
110 9 0.277599 40 0.30692 89 0.300374
109 10 0.198615 a 0.302484 90 0.306737
108 10 0.102212 a 0.311327 90 0.305699
107 "1 0.029248 42 0.306257 91 0.309914
106 12 0.002517 43 0.298406 92 0.300653
105 12 -0.00058 43 0.308721 92 0.308305
104 13 -0.00266 44 0.308584 93 0.305177
103 13 -0.00066 45 0.304366 93 0.296264
102 14 0.002342 45 0.303474 94 0.307834
101 15 0.004893 46 0.310281 95 0.307007
100 15 -0.00208 46 0.310277 95 0.308135
99 16 0.003454 47 0.310326 96 0.308367
98 16 0.003402 48 0.317247 96 0.312844
97 17 -0.00502 48 0.303642 97 0.305466
96 18 -0.00888 49 0.302242 98 0.301831
95 18 -0.00261 49 0.298496 98 0.304773
94 19 0.00512 50 0.302162 99 0.308075
93 19 0.001176 51 0.310644 99 0.307153
92 20 0.001017 51 0.29687 100 0.302338
ot 2 -0.00238 52 0.301701 101 0.307091
90 21 -0.00052 52 0.286235, 101 0.312527
89 22 0.004406 53 0.213451 102 0.310579
88 23 0.00081 54 0.082764 102 0.298235
87 23 0.000389 54 0.027531 103 0.308088
86 24 -0.00086 55 0.002169 104 0.305079
85 24 -0.00259 55 -0.00638 104 0.299197
84 25 0.002906 56 0.002443 105 0.308752
83 26 0.001231 57 -0.01 105 0.288178
82 26 -0.0014 57 0.007103 106 0.29696
81 27 -0.0059 58 -0.00598 107 0.293014
80 27 0.004867 58 0.007562 107 0.292916
79 59 -0.00414 108 0.277381
78 60 -0.00579 108 0.256315
77 60 0.002348 109 0.247997
76 61 -0.00665 110 0.233654
75 62 0.008068 110 0.183608
74 62 0.00143 re 0.097119
73 63 0.001818 111 0.04173
72 63 -0.00379 112 0.012097
71 64 -0.00845 113 -0.00341
70 65 0.002241 113 0.000023
69 65 -0.00058 114 0.003362
68 66 0.000091 115 0.004117
67 66 0.001278 115 0.00383
66 67 -0.90144 116 0.00905


Elevation Time Water Soltrol Time Water Soltrol

cm min Content Content min Content Content
118 1370 0.189657 0.074102 1421 0.212848 0.059755
W17 1370 0.146245, 0.082651 1421 0.123033 0.092178
116 1371 0.134889 0.087135, 1422 0.133262 0.081021
115 1372 0.16821 0.0727 1423 0.115881 0.090367
114 1372 0.116747, 0.097788 1423 0.154487 0.084018
113 1373 0.197937 0.084007 1424 0.146357 0.096124
112 1373 0.199128 0.09246 1424 0.193332 0.095055
111 1374 0.155115 0.116601 1425 0.12922 0.121463
110 1375 0.220114 0.099398 1426 0.218619 0.093449
109 1375 0.205702 0.096529 1426 0.228079 0.091134
108 1376 0.233603 0.084963 1427 0.230086 0.090058
107 1376 0.17787 0.110805, 1427 0.136259 0.122137
106 1377 0.215108 0.101051 1428 0.194052 0.10054
105 1378 0.183121 0.10746 1429 0.196762 0.103846
104 1378 0.164539, 0.113864 1429 0.203374 0.100511
103 1379 0.164385, 0.118774 1430 0.220207 0.093676
102 1379 0.17439 0.112528 1430 0.170265, 0.111053
101 1380 0.198703, 0.101959 1431 0.19997 0.10651
100 1381 0.196052 0.102152 1432 0.198103 0.109272
99 1381 0.159228 0.120629 1432 0.206597 0.104014
98 1382 0.186667 0.117361 1433 0.22515 0.096471
97 1382 0.157373 0.125338 1433 0.193686 0.109942
96 1383 0.169935, 0.121097 1434 0.223513 0.096971
95 1384 0.192451 0.117019 1435 0.225039 0.103036
94 1384 0.251293 0.098934 1435 0.172337 0.124004
93 1385 0.146025, 0.130904 1436 0.232413 0.098981
92 1385 0.207926 0.115224 1436 0.173501 0.121781
91 1386 0.237593 0.104099 1437 0.216766 0.10973
90 1387 0.144546 0.142185 1438 0.161671 0.131259
89 1387 0.187412 0.121261 1438 0.181872 0.123189
88 1388 0.157863 0.136476 1439 0.112287 0.151414
87 1388 0.204124 0.117088. 1439 0.169721 0.129767
86 1389 0.201097 0.121375 1440 0.236576 0.109869
85 1390 0.138762 0.141005, 1441 0.241702 0.110118
84 1390 0.190477 0.122302 1441 0.232258 0.115202
83 1391 0.110413 0.14457 1442 0.18195 0.133562
82 1391 0.089402 0.157571 1442 0.227379 0.121473
81 1392 0.075945 0.161106 1443 0.179764 0.138468
80 1393 0.053337 0.174399 1444 0.258818 0.115333
79 1393 0.078503 0.165744 1444 0.234533 0.120144
78 1394 0.04114 0.166164 1445 0.24548 0.12846
7 1394 -0.0061 0.174165. 1445, 0.314115 0.101009
76 1395, 0.010551 0.167865 1446 0.32578 0.104585
75 1396 -0.01496 0.175652 1447 0.266255 0 12523
74 1396 0.038017 0.1689 1447 0.307685 0.113659
73 1397 0.01927 0.170207 1448 0.271483 0.123688
72 1397 0.080263 0.149756 1448 0.219466 0.137853
71 1398 -0.02305, 0.179057 1449 0.269451 0.124603
70 1399 0.083366 0.158691 1450 0.258704 0.132316
69 1399 0.016731 0.179565 1450 0.230429 0.137672
68 1400 -0.01165 0.181961 1451 0.215273 0.146575
67 1401 0.01997 0.160554 1451 0.181957 0.162188
66 1401 0.055544 0.152028 1452 0.263721 0.135284
65 1402 0.008081 0.159582 1453 0.16172 0.167395
64 1402 0.068431 0.134269 1453 0.186802 0.155454
63 1403 0.059402 0.131527 1454 0.177893 0.15598
62 1404 0.000244 0.133785, 1454 0.219496 0.132148
61 1404 0.021465 0.131075 1455 0.159442 0.160555
60 1405 0.023348 0.135525 1456 0.139538 0.170692

148


DISCLAIMER

The information in this document has been funded in part by the United States
Environmental Protection Agency under CR-816807 to the University of Colorado at Boulder. The
authors also acknowledge funding from the EPA Great Plains-Rocky Mountains Hazardous
Substance Research Center and equipment support from the National Science Foundation. It
has been subjected to the Agency's peer and administrative review, and it has been approved
for publication as an EPA document. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.

All research projects funded by the U.S. Environmental Protection Agency that make
conclusions or recommendations based on environmentally related measurements are required
to participate in the Agency Quality Assurance Program. This project was conducted under an
approved Quality Assurance Project Plan and the procedures therein specified were used.
Information on the plan and documentation of the quality assurance activities are available from
the Principal Investigator.


Elevation
cm

120.00
119.00
118.00
117.00
116.00
115.00
114.00
113 00
112.00
111.00
110.00
109.00
108.00
107.00
106.00
105.00
104.00
103.00
102.00
101.00
100.00
99.00
98.00
97.00
96.00
95.00
94.00
93.00
92.00
91.00
90.00
89.00
88.00
87.00
86.00
85.00
84.00
83.00
82.00
81.00

Time
min

899.00
899.00
900.00
900.00
901.00
902.00
902.00
903.00
903.00
904.00
904.00
905.00
905.00
906.00
906.00
907.00
907.00
908.00
909.00
909.00
910.00
910.00
911.00
911.00
912.00
912.00
913.00
913.00
914.00
914.00
915.00
915.00
916.00
917.00
917.00
918.00
918.00
919.00
919.00
920.00
920.00
921.00
921.00
922.00
922.00
923.00
924.00
924.00
925.00
925.00
926.00
926.00
927.00
927.00
928.00
928.00
929.00
929.00
930.00

Soltrol
Content

0.05
0.05
0.05
0.04
0.04
0.05
0.05
0.06
0.05
0.06
0.06
0.06
0.06
0.06
0.07
0.07
0.07
0.08
0.07
0.08
0.08
0.07
0.06
0.07
0.07
0.06
0.06
0.06
0.07
0.08
0.07
0.08
0.07
0.08
0.08
0.08
0.07
0.08
0.09
0.09
0.09
0.08
0.08
0.08
0.08
0.08
0.09
0.09
0.09
0.09
0.09
0.10
0.11
0.11
0.12
0.12
0.11
0.12
0.12

138


Traversing Gantry System
Motion translator motor
Rigid coupling
Tt
Q N
q
Thempson S
shaft —> S
q
q
H S
32 toot B
flume y
Ball _,4
di th screwy
S Soil
8 N
5 a
R Gamma . na =
Q sources a detector
Aluminum H
Plattorm \
/ Ball bushing
Hcotimation
Ny Port
§ H |<—_Thompson
q shaft
q
N q
q . S
S S
Horizontal N S
« motor _ SI i 2 y "
ear
Thompson shatt
head/rack oa a + +  anipiliow block

Figure 74. Computer automated traversing gantry system (after Armbruster, 1990).

99


#125 SAND SOOML SOLTROL SPILL

Change in Front Movement with Rainfall
120

100

— 80 no Rainfall
£
§ 60 A
2 Start Rainfall
3 after 45 Minutes
& 40

20

0)

0 50 100 150 200 250 300 ©8350

Time in Minutes

Figure 42. Comparison between rainfall application and no rain for 500ml Soltrol spill in
#125 sand.

#70 Sand 1000mlI Soltrol Spill
Rain 500ml/hr after 167 Minutes

z
3S

Elevation in cm

pr oaoaan
sés8 S68

ae

50 100 150 200 250 300 350

Time in Minutes
RAIN: SOOmI/pr

[ —TM SPILL FRONT —+~ PONDING = WATER FRONT

°

Figure 43. 1000m! Soltrol spill on #70 sand with rainfall application starting after 169 minutes.
The rainfall rate was held constant at 9.5cm/hour.

59


The suction-saturation relationship measurements in #70 and #125 sand for water and
Soltrol were conducted with a large number of measurement points. This was expected to
increase the accuracy of the suction-saturation curve. The suction-saturation curve for #125 sand
and water was measured with the largest number of observations: 9 measurements over 20
seconds every 1.25 cm along the column length of 140 cm. This resulted in over 1000
measurements per column scan. One column scan took approximately 10 hours. Part of the
reason for taking so long was the slow processing of data by computer integration at every scan
point. The slow XT computer was subsequently replaced by a faster AT (286 PC) machine. The
number of measurements per step was also reduced from nine to two for the next measurements.
The suction-saturation curve for nine measurements per step produced results which are in good
agreement with the flow pump measurements (Figure 26) and the curves parameterized from flow
pump data.

45


Elevation Time Water Soltrol Time Water Soltrol

cm min Content Content min Content Content
109 1 -0.00605 0.228421 146 0.206981 0.090989
108 91 0.011992 0.218539 147 0.171666 0.109689
107 92 0.02121 0.232044 147 0.201489 0.097334
106 92 -0.03051 0.237543 148 0.15615 0.121053
105 93 -0.00343 0.220387 148 0.189729 0.116199
104 93 -0.00778 0.227932 149 0.160903 0.130014
103 94 ~0.02422 0.245168 149 0.189334 0.130138
102 94 0.01186 0.257878 150 0.195649 0.142742
101 95 -0.03223 0.275399 150 0.177031 0.154491
100 95 0.002654 0.271863 151 0.237925 0.138043
99 96 0.018802 0.259855 151 0.221911 0.153349
98 96 -0.0087 0.270393 152 0.185897 0.172979
97 97 0.0132 0.292161 152 0.205324 0.169737
96 97 0.006032 0.300987 153 0.192156 0.186786
95 98 0.011961 0.296928 153 0.214664 0.171516
94 98 -0.0207 0.299525" 154 0.148386 0.197688
93 99 -0.02953 0.30899 154 0.189197, 0.18497
92 99 0.003333 0.298718 155 0.165128 0.202099
ot 100 0.015468 0.298666 155 0.189162 0.193066
90 100 -0.02006 0.308923 156 0.173717 0.202995,
89 101 0.04854 0.313236 156 0.172978 0.202177
88 104 -0.00489 0.302811 157 0.183894 0.19959
87 102 0.022442 0.299859 157 0.166785, 0.208403
86 102 0.01772 0.327471 158 0.174723 0.207461
85 103 0.005251 0.330999 158 0.162955, 0.202781
84 103 -0.03341 0.363687 159 0.170111 0.210764
83 104 -0.01059 0.359557 159 0.161521 0.210105
82 104 0.02473 0.373286 160 0.177936 0.207978
81 105 -0.01093 0.377271 160 0.144711 0.226641
80 105 0.023235, 0.374419 161 0.151869 0.225546
79 106 0.021165 0.373624 161 0.203353 0.201965
78 106 0.006692 0.387854 162 0.176867 0.213113
77 107 0.00614 0.390446 162 0.195188 0.200659
76 107 0.023209 0.371627 163 0.154749 0.21482
75 108 0.01695 0.372594 163 0.135938 0.228269
74 108 0.023749 0.35892 164 0.165928 0.218631
73 109 0.380152 164 0.142003 0.228474
72 109 0.363572 165 0.15949 0.225929
71 110 0.372731 165 0.139761 0.22603
70 110 0.368509 166 0.169607 0.219998
69 qt 0.383671 166 0.167785 0.219563
68 Wi 0.371026 167 0.162655, 0.22039
67 112 0.003839 0.360974 167 0.159116 0.218361
66 12 0.01382 0.37202 168 0.158203 0.219687
65 113 0.0109 0.367767 168 0.166471 0.216898
64 113 0.01944 0.372904 169 0.158695 0.212992
63 114 0.01347 0.363123 169 0.167614 0.217657
62 114 -0.0028 0.36403 170 0.152086 0.221567
61 15 0.360622 170 0.185208 0.211461
60 115 0.360684 171 0.176736 0.212884
59 116 0.355766 171 0.162644 0.217736
58 Ni7 0.002361 0.323213 172 0.156262 0.225235
57 N17 0.029263 0.205877 172 0.140765 0.230212
56 118 0.072158 0.068899 173 0.17926 0.219342
55 118 0.100058 0.013461 173 0.158846 0.229055
54 119 0.079208 0.017385, 174 0.170585 0.225101
53 119 0.118315. 0.004975 174 0.16892 0.227589
52 120 0.072457 0.018005, 175 0.184322 0.222699
51 120 0.079455 0.013836 175 0.160628 0.236005

166


In = Inp@ ~OwUaw + Po Uuadx (35)

e ~OwUew + 9QUcdx (36)

Io = | cD

Equations (35) and (36) are solved simultaneously to yield volumetric phase content for
water and oil:

I, I
Upain-&2 - Uggin 42

6, = Io |, (37)
” (Yow Uso - Usw Uco)x
Unwin 22. ~ Ugyin 22
own), awn (38)
8 =

(Yew Ugo - Usw Yeo) x

In the above equations, /, is the count rate through the dry sand. /, can be expressed with the
count rate through the empty box, using Equation (30):

Ib = Le Usajox (39)

The lumped calibration constant U cannot be used when the bulk density of a sample is
determined with the gamma system. Equation (34) can then be rewritten as:

ly = lap @ (Has Pa * SW Uaw)x (40)

Ion (es Pa t+ Oy Uy) x (41)

These are two equations for Americium and Cesium with two unknowns, the bulk density and
volumetric water content. It can be seen that the bulk density can only be calculated for

94


Table 1. Characterization of #70 and #125 sands

#70 Sand #125 Sand
a) Grain size
average particle size, d., 0.185mm 0.103mm
(from dry sieving)
uniformity coefficient, deo/d,o 1.86 1.45
b) Grain form very angular to sub-angular to
sub-angular, rounded,
spherical to sub- spherical
prismoidal
c) Sorting very well to well very well sorted
sorted
d) Maturity immature mature
e) Modal components
Lithoclasts 1% -
Quartz, clear 55% 95%
Quartz, milky 25% -
Feldspar 8% 3%
Muscovite 5% -
Biotite 5% 1%
Accessories: Zircon,
Hematite, Rutile, Garnet about 1% about 1%
f) Porosity for medium
compaction 0.45 0.39

19


Residual Oil Saturation

Depth

Residual Liquid Saturation
Water Saturation

Figure 4.

Assumed saturation profile for the Three-Parameter Sharp Front Model.

28, og a - Moy = 16
at 1 3g C8) az H 0 (16)

where 6 is the volumetric content of organic phase [*], K(8) is the permeability as a function of
phase content [L’), y, is the pressure head [L], z is the depth of infiltration [L].

It can be seen that the total head gradient during infiltration is constant, both under

constant ponding and falling head conditions. The gradient can be determined from the head
at two points, i.e. the head at the ground surface and the head at the front (Figure 1). The head
gradient is:

oe. Linz) -
oe 7 zlttz) - MODI (17)

15


3

lead container Suppl
Cesium source
Colomation Port
Soil
LY Base & = lampiit Lo] Set P
-- SS) ---- ~~ — MT. in. UU,
My PreAme Anal. c
I
Nal Crystal | i
Photo Multiplier Tube Vert. Horiz.
Americium source Motor Motor
Rotating interior
cylinder ——_—I
A
| Source Opto.
Elec.
Motor Relay

Figure 73. Schematic of computer controlled traversing gantry and gamma data
acquisition system (after Armbruster, 1990).

1.2.3 Traversing Mechanism

The principle of the gamma attenuation necessitates, external to the soil sample, a
radioactive source on one side of the test sample and a scintillation detector on the other side.
The setup for these measurements consists of fixed and moving frames (Figure 74). The sample
is attached to the fixed frame. The detector and source assembly are placed on the platforms
of a moving frame. Horizontal and vertical movements are motor driven and can be controlled
through software specifically designed for this purpose. The software automatically shuts off the
motors while the measurement is taken, so there is no electronic interference between the
detector and the motors.

1.2.4 Test Box

Following Bazaraa and Morel-Seytoux (1979), a multi-chambered plexiglass box was
constructed for the testing of the Gamma system (Figure 75). The effective path length traversed
by the gamma radiation may be precisely controlled by sequentially filling compartments with the
material being tested. The path length was measured with mechanical tools to an accuracy of
1mm. An aluminum plate (10 mm) was used as a standard absorber.

98


Elevation
cm

62.00
61.00
60.00
59.00
58.00
57.00
56.00
55.00
54.00
53.00
52.00
51.00
50.00
49.00
48.00
47.00
46.00
45.00
44.00
43.00
42.00
41.00
40.00
39.00
38.00
37.00
36.00
35.00
34.00
33.00

Time
min

Soltrol
Content

Time
min

137.00
137.00
143.00
144.00
144.00
145.00
145.00
146.00
146.00
147.00
147.00
148.00
148.00
149.00
149.00
150.00
151.00
151.00

155

Soltrot
Content

0.22
0.18
0.10
0.03
-0.01
-0.02
~0.02
-0.02
0.02
0.01
-0.02
-0.01
0.01
0.02
0.01
0.02
0.02
-0.02

Time
min

184.00
185.00
185.00
186.00
186.00
187.00
187.00
188.00
188.00
189.00
190.00
190.00
191.00
191.00
192.00
192.00
193.00
193.00
194.00
194.00
195.00
195.00
196.00
197.00
197.00
198.00
198.00
199.00
199.00
200.00

Soltrol
Content

0.25
0.24
0.24
0.25
0.23
0.23
0.22
0.21
0.19
0.15



Elevation
cm

120.00
119.00
118.00
117.00
116.00
115.00
114.00
113.00
112.00
111.00
110.00
109.00
108.00
107.00
106.00
105.00
104.00
103.00
102.00
101.00
100.00
99.00
98.00
97.00
96.00
95.00
94.00
93.00
92.00
91.00
90.00
89.00
88.00
87.00
86.00
85.00
84.00
83.00
82.00
81.00
80.00
79.00
78.00
77.00
76.00
75.00
74.00
73.00
72.00
71.00
70.00
69.00
68.00
67.00
66.00
65.00
64.00
63.00
62.00

Time
min

367.00
368.00
369.00
369.00
370.00
370.00
371.00
371.00
372.00
372.00
373.00
373.00
374.00
374.00
375.00
376.00
376.00
377.00
377.00
378.00
378.00
379.00
379.00
380.00
380.00
381.00
381.00
382.00
382.00
383.00
384.00
384.00
385.00
385.00
386.00
386.00
387.00
387.00
388.00
388.00
389.00
389.00
390.00
390.00
391.00
391.00
392.00
393.00
393.00
394.00
394.00
395.00
395.00
396.00
396.00
397.00
397.00
398.00
398.00

Soltrol
Content

0.09
0.09
0.09
0.10
0.12
0.13
0.14
0.15,
0.15,
0.15
0.15
0.14
0.15
0.13
0.13
0.13
0.13
0.13
0.12
0.13
0.13
0.13
0.14
0.13
0.13
0.13
0.13
0.13
0.13
0.14
0.13
0.13
0.13
0.13
0.14
0.16
0.16
0.16
0.16
0.15
0.15
0.15
0.14
0.16
0.15
0.17
0.17
0.16
0.18
0.19
0.21
0.22
0.22
0.23
0.23
0.23
0.24
0.24
0.24

158


Elevation Time Soltrot Time Soltrot Time Soltrol

com min Content min Content min Content
58.00 146.00 0.00 175.00 0.00 203.00 0.00
56.00 146.00 0.00 175.00 0.00 204.00 0.00
54.00 147.00 0.01 176.00 0.01 204.00 0.00
52.00 147.00 0.00 176.00 0.01 205.00 0.00
50.00 148.00 0.01 177.00 0.01 205.00 0.00
48.00 148.00 0.01 177.00 0.00 206.00 0.00
46.00 149.00 0.00 178.00 -0.01 206.00 0.00
44.00 149.00 0.01 179.00 -0.01 207.00 0.01
42.00 150.00 0.00 179.00 0.01 208.00 0.01
40.00 151.00 0.00 180.00 0.00 208.00 0.00
38.00 151.00 0.00 180.00 -0.01 209.00 0.01
36.00 152.00 0.01
Elevation Time Soltrol Time Soltrol
cm min Content min Content
120.00 215.00 0.13 1035.00 0.09
118.00 215.00 0.11 1036.00 0.07
116.00 216.00 0.12 1036.00 0.07
114.00 217.00 0.14 1037.00 0.08
112.00 217.00 0.16 1038.00 0.10
110.00 218.00 0.18 1038.00 0.12
108.00 218.00 0.17 1039.00 0.11
106.00 219.00 0.18 1039.00 0.12
104.00 219.00 0.17 1040.00 O11
102.00 220.00 0.18 1040.00 0.11
100.00 220.00 0.21 1041.00 0.13
98.00 221.00 0.23 1041.00 0.14
96.00 222.00 0.24 1042.00 0.14
94.00 222.00 0.25 1043.00 0.15
92.00 223,00 0.25 1043.00 0.15
90.00 223.00 0.28 1044.00 0.16
88.00 224.00 0.28 1044.00 0.19
86.00 224.00 0.27 1045.00 0.19
84.00 225.00 0.27 1045.00 0.19
82.00 225.00 0.27 1046.00 0.19
80.00 226.00 0.27 1046.00 0.22
78.00 227.00 0.10 1047.00 0.21
76.00 227.00 0.01 1048.00 0.24
74.00 228.00 0.01 1048.00 0.22
72.00 228.00 0.00 1049.00 0.23
70.00 229.00 0.01 1049.00 0.24
68.00 229.00 0.00 1050.00 0.22
66.00 230.00 0.00 1050.00 0.22
64.00 231.00 0.00 1051.00 0.22
62.00 231.00 0.00 1051.00 0.18
60.00 232.00 -0.01 1052.00 0.06
58.00 232.00 0.00 1053.00 0.01
56.00 233.00 0.00 1053.00 0.00
54.00 233.00 0.00 1054.00 0.00
52.00 234.00 -0.01 1054.00 0.00
50.00 235.00 0.01 1055.00 0.00
48.00 235.00 0.01 1055.00 0.01
46.00 236.00 -0.01 1056.00 0.00
44.00 236.00 -0.01 1057.00 0.00
42.00 237.00 0.00 1057.00 0.01
40.00 237.00 0.01 1058.00 0.00
38.00 1058.00 0.00
36.00 1059.00 0.00

162


SECOND SCANNING

Figure 12. Setup for second scan through fully saturated sand. Water is ponding on top
of sand.

THIRD SCANNING

Figure 13. Setup for third measurement through partially saturated sand.

27


Elevation
cm

Time
min

207
208
208
209
209
210
210
aii
ait
212
212
213
213
214
214
215
215
216
216
217
217
218
219
219
220
220
221
221
222
222
223
223
224
224
225
225
226
226
227
227
228
228
229
229
230
230
231
231
232
232
233
233
234
234
235,
235
236
236
237

Water
Content

0.192774
0.195179
0.159506
0.176238

0.18202
0.181726
0.175744

0.15007
0.154756
0.165962
0.147759
0.180137
0.153657
0.190578
0.161468

0.16807
0.159354
0.219149
0.178564
0.166979
0.205682
0.168699
0.186284
0.143084
0.130015.
0.153211

0.12715
0.120798
0.137465
0.163926
0.151861
0.180475,
0.157808
0.144398
0.153256
0.156112

0.17701

0.20781
0.168711
0.166432
0.146123
0.181502

0.13288
0.215018
0.183802
0.168196
0.180275,
0.188921
0.182757
0.197966
0.163351
0.179693
0.165376
0.193399
0.134813,
0.127916
0.161476
0.189092
0.173606

Soltrot
Content

0.12986
0.137563
0.150583

0.13632
0.140489
0.143658
0.145356
0.152555,
0.156087
0.149461

0.15195
0.148418
0.152612

0.14649
0.155877
0.160164
0.163551
0.158842

0.18348
0.187385,
0.182357

0.18734
0.175737
0.190746
0.200492
0.188861
0.192942
0.197469
0.193048
0.186154
0.188678
0.185053

0.19453
0.198124
0.196483
0.197965
0.192433
0.191214
0.200335,

0.20097
0.214465,
0.199311
0.219292
0.193142
0.211836
0.213815,
0.210876

0.20561
0.206011
0.202048
0.216811
0.207118
0.207331

0.20517
0.228695,
0.231759
0.215973

0.20322
0.210795,

168


geometrical configuration of the system stays exactly the same between different measurements.

Table 9. Lumped attenuation coefficient of water

Cs

standard deviation U(water) ‘standard deviation
of the regression of the regression

0.194 0.077 3.080¢e-04
0.191 0.074 4.140e-04
0.195 0.071 3.900e-03
0.198 0.081 3.000e-04

total standard deviation: total standard deviation:
0.0024 0.0034

The lumped attenuation coefficient was determined four times. The results and the
standard deviation for each determination are listed. An overall standard deviation of the four
experiments was calculated. The graphs below (Figure 79) show the data for one determination
of the lumped attenuation coefficient for Americium and Cesium.

1.3.7 of Apparent At fion Coefficient on B h

Attenuation coefficients are material constants, which do not change. It was observed,
however, that the measured or apparent, attenuation coefficients seemed to change for different
measurements. This does not mean that the attenuation coefficient actually changes, but the
poor measurement techniques lead to apparent changes. Variable detector sensitivity, poor
collimation and poor spectral windowing can cause a change in apparent attenuation coefficients.
Thus further experiments were conducted to investigate the stability of the measured attenuation
coefficients.

A test was conducted to determine whether the apparent attenuation coefficient of water
is dependent on the radiation strength. The radiation strength was changed by placing different
absorbers in front of the radiation source. For Cesium, it was found that the attenuation
coefficient was too low for either very high or very low incident radiation. For a small band of
incident radiation, the attenuation coefficient was almost constant (Figure 79). However, the
attenuation coefficient seems to decrease slightly when the incident radiation increases. For
Americium, the attenuation coefficient is a function of the incident radiation (Figure 80). The
attenuation coefficient was graphed versus the 30 second count rate. The dependence of the
attenuation coefficient on count rate shows that the attenuation coefficients are not constant. The
count rate is a measure of radiation strength. The radiation strength is a function of the radiation
source, the shielding of the source, the attenuation of the sample container and the distance
between source and sample, and sample and detector. It is important to note that the source-
sample-detector geometry and the material and geometry of the sample container may influence
the attenuation coefficients.

108


SPILL #70 SAND 750 ML SOLTROL SPILL
RAIN 500 ML/HR AFTER 86 MINUTES.

TIME ELEVATION PONDING WATER FRONT
MINUTES cM cM cM
0 120 14.2

1 113

2 12

3 110.5 10.6

4 109 10.2

5 108 9.8

6 106.5 9.2

7 105.5 8.4

8 104.5 8.1

9 103.5 7.6

10 102.3 7.2

WW 101.1 6.8

12 100.1 6.4

13 99.2 6

14 98.5 5.7

15 97.5 5.4

16 96.8 51

17 96 48

18 95.2 44

19 94.3 44
20 93.5 37
22 91.8 3.3

24 90.4 27

26 88.9 2.2

28 87.3 1.5

30 85.9 1

32 84.5 0

34 83.7

36 83

40 81.4

45 79.8

50 77.9

55 761
60 74.5
65 73
70 714
75 70.4
80 69
86 67.3
90 66.5
96 65.2

100 64.1

105 63.2 110
115 61.3 95
120 60.1 90
125 58.3 86
130 58 85
135 56.8 83
140 54.6 81
145 52.8 73
150 50.2 69
155 47.4 65
160 45.3 61
165 43 59
170 40.6 56

129


Spill M

#70 Sand 1000 ml Soltrol Spill
Rain 500m\/hour after 197 minutes.

Elevation
cm

120

Time
min

Soltrol
Content

0.38078
0.375924

0.37668
0.378568
0.375065

0.37321
0.371031
0.373713
0.365993
0.368771
0.366413,
0.372206
0.371737
0.363836
0.368107,
0.375115
0.371829
0.360849
0.370519

0.36304

0.36725
0.362401
0.359936
0.331833
0.247436
0.145503,
0.064516

0.02844

Bulk Density grav.: 1.549 cm*

Porosity: 0.42

Temperature Soltrol: 21°C

Temperature : 24°C

Residual water content: 0.09.

Time
min

Soltrol
Content

0.382045
0.378838
0.380073
0.376006
0.376569
0.37063
0.368886
0.373408
0.368896
0.369257
0.365636
0.369567
0.368245
0.368642
0.370051
0.374197
0.369012
0.368216
0.369471
0.361226
0.366363
0.364112
0.367113
0.364345
0.370771
0.360914
0.359397
0.369124
0.360417
0.362968
0.362053
0.354929
0.368426
0.361734
0.368548
0.359956
0.36311
0.363388
0.363703
0.364781
0.357003
0.363778
0.36157
0.358426
0.350583
0.347682
0.316525
0.180121
0.081155
0.014973
-0.00157
0.000109
-0.00339

Time
min

Soltrol
Content

0.172758
0.218248
0.236879
0.238478
0.246606
0.245382
0.263249
0.272684
0.269281
0.266618
0.277642
0.275143,
0.279838
0.280328
0.284853
0.28706
0.298654
0.305934
0.317301
0.328764
0.328229
0.333405
0.338522
0.347776
0.347226
0.34394
0.340401
0.349505
0.346429
0.34239
0.339208
0.346113.
0.347363
0.34175
0.339961
0.345558
0.346061
0.339826
0.339924
0.337306
0.344133,
0.347123
0.338315.
0.335977
0.335429
0.334882
0.337923
0.340998
0.33737
0.337792
0.332524
0.3364
0.338311


Integration of the Soltrol phase content for the 500 ml spill, #125 sand experiment shown
in Figure 33 gives values close to the total spill volume of 500 ml. The profile taken at 357 min.
gives a total Soltrol volume of 482 ml, 470 ml at 406 min., and 346 ml at 930 min. After 930 min.,
part of the Soltrol volume has already drained out of the columns. This integration shows that
the gamma systems accounted for approximately the correct total volume of the spill.

Integration of the Soltrol phase content profiles in Figure 34, at 263 minutes and 410
minutes, gives total Soltrol volumes of 812 and 811 ml, respectively. The profiles were taken
after the rainfall began at 45 minutes. The volume estimates were much higher than the actual
spill volume of 500 ml. The reason for the large error is that both gamma spectra had to be used
for the calculation of two unknown phase contents: water and Soltrol. This approach led to a
larger error in the absolute values of phase content, as explained in Appendix 1. In the profiles
after 263 min. and 410 min., the calculated water volume was negative, and the Soltrol content
was too high. Thus the profiles give qualitative information about the shape of the Soltro! and
water fronts, but do not give quantitative values for the phase contents. The phase content data
for all profiles are given in Appendix 3.

51


Table 7. Random variation comparison

fn Gs

2.5m 420746 215399
422512 213736

| 422794 215162 |f Average 422212 | Average 215693

421951 218724 if Standard Dev. 726|Std. Dev. 1551

422748 215636 |} Square root 650 | Square root 464
421769 214287
422962 216905
5.0 cm 253828 176889
253825 174382

253610 175343 |] average 253945 | average 175679

253592 175540 |] std 284] std 885,

254257 174949 |] square root 504 | square root 419
254178 175677
254328 176973
7.5m 153991 142146
152582 141825

153482 141351 |] average 153264 | average 142260

153650 140603 |} std 484) std 1139

153393 144475
153129 142727
152618

‘square root 391 | square root 377

10.0 cm 93437 116292
94467 115674
93861 114680 }f average 93862 | average 115584
93774 116150 }] std 382| std 692
93286 ‘square root 340
I 94001
94206
12.5cm 57010
57826
57807 95165 jf average 57414 | average 93801
57471 94940 |] std 363] std 1031
57082 93348 lf square root 240] square root 306
56956 92001

The count rate was measured through the standard absorber for five different times for
both Americium (Am) and Cesium (Cs). For every length of time, seven measurements were
done. The measurements are averaged and the standard deviation was calculated. The
standard deviation was in the same order of magnitude as the square root of the average.

105


No.125 Sand 500m! Soltrol
Front Position after 303 Minutes
100
80)
E a [on
2 60) 1
©
& !
3 i
& woe
Ww
20 = 2 BEER ey rn
—— Kinematic Model "P
0!
~01 0.0 01 0.2 0.3 0.4 0.5
Phase Content

Figure 53. Phase content profiles comparison between models and experimental results.

Neither of the models represented the true shape of the profile exactly. Both models
assume a sharp front at the leading edge of the NAPL. The experimental results, however,
showed some degree of smearing of the front. The experimental data deviated from a sharp
front mainly after the amount of moving Soltrol became very small. Thus the sharp front models
tracked the experimental data with fair accuracy. Since the speed of the sharp front matches
the speed of the spreading front (Equation (10)), the exact shape of the front is unimportant in
determining its speed. This fact explains the ability of the sharp front models to match the
experimental data to the degree that they do. The trailing edge (back front) exhibited a gradual
decrease in phase content; it does not resemble the sharp front assumed by the three-parameter
model nor the kinematic wave solution of KOPT exactly. The maximum phase content behind
the front decreases as the Soltrol moves downward. The KOPT model allows reduction of the
maximum NAPL phase content, while the three-parameter model assumes that the phase content
behind the front is always at full saturation. Since the three-parameter model has been fitted to
this data set, the front is tracked accurately despite the assumed NAPL saturation behind the
front.

69


4.2 CHARACTERIZATION OF THE TEST FLUID

A lighter-than-water liquid, Soltrol 220, was used as the test fluid in all the experiments.
Soltrol 220 is an isoparaffinic solvent, manufactured by Phillips Petroleum Company. It is a
colorless liquid mixture of C13 to C17 hydrocarbons, with a boiling point between 232°C and
288°C (Material Safety by Phillips Petroleum Data Sheet). Its solubility in water is negligible,
which makes it ideal for experiments as a NAPL. The second reason to choose Soltrol for lab
experiments is its low toxicity. Soltrol has a low vapor pressure of 0.004 psi, and its vapor is
heavier than air. The specific gravity is 0.809 at 15°C. At 23°C, the density is 0.789 g cm*,
kinematic viscosity as 6.12 centistokes, surface tension with water 42 dynes cm", surface tension
with air 27 dynes cm’' (Szlag and Illangasekare, 1992).

The gamma attenuation coefficient of Soltrol is very similar to that of water. Following
the work of Lenhard and Parker (1987), 1-iodoheptane was mixed with Soltrol to increase the
attenuation coefficient of Soltrol. A volume ratio of 1 to 9 of iodoheptane to Soltrol was used.
The chemical formula of iodoheptane is CH,(CH,),I. Adding iodoheptane changes the kinematic
viscosity of Soltrol to 4.8 centistokes at 23°C. The viscosities of Soltrol and the Soltrol-
iodoheptane mixture are temperature dependent (Figure 7). The viscosity of the Soltrol (90%)
and iodoheptane (10%) mixture was also determined by measurement at the US EPA Kerr
Laboratory in Ada, Oklahoma. The procedure followed was ASTM D445, which used Cannon-
Fenske viscometers suspended in a constant temperature water bath. At 25°C, the viscosity of
the mixture was 3.78 cp and the density 0.85 g cm®. At Kerr Laboratory, the Soltrol surface
tension was measured and found to be 24 dynes cm’.

Automate Red Dye (Morton International) was used to color the Soltrol. This water
insoluble dye is soluble in petroleum products and insoluble in water. Very small amounts suffice
to give the Soltrol a bright red color, but the dye does not change any of the physical properties
affecting the flow of Soltrol. (Szlag and Illangasekare, 1992)

4.3. SAMPLE CELL AND COLUMN

Two columns were used in the experiments. The first was a small cell with a height of
4cm. It was used for parameter determination experiments. The spill simulations were done
in a 180 cm column. The columns consisted of a clear plexiglass tube with an inside diameter
of 8.2 cm. Aluminum end covers were constructed to fit the top and bottom of the plexiglass
tubes of both the cell and the column. The top and bottom fittings were designed to make an
airtight seal to allow for evacuation of the fluids (air or water) from the sample. Valves were
provided in both end fittings for the entry and exit of air and water. The bottom fitting contained
a removable high-air-entry-value porous plate, through which the sample could be de-saturated.

O-rings were used to create an airtight seal around the plexiglass tube. The top fitting
contained a porous metal plate which allowed for uniform air entry at the top of the soil surface
(Figure 7). Two valves were connected to the porous metal plate. The bottom fitting consisted
of two parts (Figure 8). The lower part held a porous ceramic plate, that was connected to the
two valves. The porous ceramic plate had to fit tightly inside the aluminum end cover to prevent

21


air phase flow is included in the model. The back front, in that case, connects two continuous
waves which are also a part of the boundary transition from high to low saturation. Even though
they can be valid components of a method of characteristics solution, sharp back fronts are not
likely to persist because of strong smoothing by gravity and capillary gradient forces.

87


multiphase transport parameters are needed (interphase partition coefficients, capillary pressures
and relative permeabilities) for each different zone or material present in the field. The latter
properties are not well understood and are difficult to obtain for field problems. Site data is
usually incomplete because of monetary, safety and regulatory limitations. Historical records of
pollutant releases are normally nonexistent, although such knowledge should be precisely defined
in a model. Sampling limitations often result in situations where the spatial distribution and the
total mass of contaminants cannot be defined. These limitations may require many
approximations when running a model.

"Sharp front" models, which are computationally efficient and simple to apply, may prove
useful for certain applications. Although they contain a number of simplifying assumptions, such
models are based on qualitative understanding of the physical behavior of NAPLs in soils. A
model (the Three Parameter Sharp Front Model) has been developed based on laboratory
experiments of transport and entrapment behavior of organics in the saturated and unsaturated
zone (Illangasekare et al., 1987a, 1987b; Illangasekare and Reible, 1987a, 1987b; Reible and
Illangasekare, 1989). This model assumes sharp fronts at the advancing and drainage fronts of
the NAPL and utilizes three parameters which characterize the soil and the fluid. These
parameters consist of a capillary drive term at each front and the effective conductivity of the
NAPL. From a parallel development, similar models were developed from kinematic wave theory.
These are the Kinematic Oily Pollutant Transport (KOPT) (Weaver et al. 1994a) and Kinematic
Rainfall and Oily Pollutant Transport (KROPT) Models (Charbeneau et al. 1989). Both of these
implementations were for one-dimensional downward transport in uniform soils. KROPT includes
the effect of individual rainfall events on the NAPL. Here the kinematic wave theory predicts the
displacement of the NAPL into "NAPL banks," which move ahead of infiltrating water (Charbeneau
et al., 1989). The intensity of rainfall, soil properties and/or NAPL properties may cause the
kinematic theory not to apply to some or part of the simulation. Currently, improved dynamic
approximations are being developed at RSKERL (Weaver, 1989, 1991). These have been shown
to be general models which include the kinematic model as a special case (Weaver, 1991).
Theoretical results so far suggest that there are two flow regimes for the dynamic model. One
is characterized by incomplete displacement of the NAPL into a NAPL bank and the other by
complete by-passing of the NAPL by the water phase (Weaver, 1991).

Although NAPL flow through the vadose zone is significant for certain problems, as
discussed in the introduction, interactions with the water table and dissolution of chemical
constituents of the NAPL are an obvious problem. For NAPLs lighter than water, KOPT has
been linked with an approximate model for oil lens development at the water table, dissolution
of the chemical contaminant of interest, and subsequent transport to a receptor well (Weaver et
al., 1994b). Thus the simple models have applicability to the vadose zone itself and as a means
of approximating contaminant loadings to lenses at the water table and ground water
contamination.


No. 125 Sand 1000mI Soltrol
Front Movement

Elevation (cm)

0 40 80 120 160 200 240 280 320 360 400
Time (min)

Figure 54. Front movement for 1000m! spill, comparison between model and experimental
results.

Both models were tested on a spill of 1000 ml Soltrol (Figure 54). The same capillary
suction head at front and back front were used as determined in the calibration for the 500 mI
spill, since the suction heads are supposed to be material constants (fluid and soil). The KOPT
model again approximates the front very closely; however, the three-parameter model deviates
considerably from the experimental results. Use of the earlier calibrated suction heads did not
yield an accurate prediction of the spill behavior with a different spill volume. This is a serious
shortcoming of the three-parameter model. The profile comparisons (Figure 55 through
Figure 57) show that the actual front is behind the three-parameter model front. This effect is due
primarily to the assumption of full saturation behind the front, as evident in Figure 56, where the
three-parameter model front is well ahead of the experimental data.

70


#70 Sand 500ml Soltrol Spill

Elevation in cm

0 200 400 600 800 1000 1200 1400
Time in minutes

TM Experimental Data —— Kinematic Model

Figure 60. Front movement for 500m! spill in #70 sand, comparison between KOPT and
experimental results.

decreasing saturation, S,. This phenomena results in front vs. time plots where the front speed
decreases sharply with time and has a large curvature. Table 5 summarizes parameter
adjustments that were used to fit the experimental data for the #70 sand.

Table 5 Summary of KOPT Model Parameter Adjustments

Parameter Adjustments

Parameter Direction Effect

Saturated Conductivity increase Increase depth of front at all
times

Air entry head, h,, increase Increase depth of front especially
during infiltration

Brooks and Corey 2 decrease Increase curvature of the front-
time plot

76



Figure 26.
Figure 27.
Figure 28.
Figure 29.
Figure 30.
Figure 31.
Figure 32.

Figure 33.
Figure 34.

Figure 35.
Figure 36.
Figure 37.
Figure 38.
Figure 39.
Figure 40.
Figure 41.
Figure 42.
Figure 43.
Figure 44.

Figure 45.

Figure 46.

Figure 47.
Figure 48.

Figure 49.
Figure 50.

Figure 51.

Comparison of suction-saturation profile as measured with Americium

gamma scan and with flow pump. ......... 0.0.0 c eee eee eee eee eee 46
Front elevation versus time for three spills, 500ml, 750ml and 1000mi
Soltrol on #70 sand. ©... 2... eee ete 48

Front elevation versus time for three spills, 500ml, 750ml and 1000mI
Soltrol in #125 sand. ......
Comparison between two identical experiments with 1000m! Soltrol in

#125 sand. 2. ee tent ee 50
Phase content profile of 500ml Soltrol in #70 sand. Soltrol is still ponding

on top of Sand. 2.1... teens 50
Phase content profile of 500m! Soltrol spill in #70 sand. A back front has.
started to develop. 2.0... eee nee 52
Phase content profile of 500m! Soltrol in #70 sand. A gradual decrease

in phase content behind the front can be observed. ..............-.-- 52
Set of phase content profiles for 500ml Soltrol spill in #125 sand......... 53

Set of phase content profiles for 500ml Soltrol spill in #125 sand. Rain
started 45 minutes after spill. ...............
Set of phase content profiles for 750ml Soltro! spill in #125 sand. Rain

started 20 hours after spill... 0... eee 54
Set of phase content profiles for 1000ml Soltrol spill in #125 sand........ 54
Set of phase content profiles for 500m! Soltrol spill in #70 sand. ........ 55
Set of phase content profiles for 750ml Soltrol spill in #70 sand. ........ 55
Set of phase content profiles for 1000ml Soltrol in #70 sand. ........... 56
Water and oil content for 750ml Soltrol spill in #70 sand. Soltrol front

seems to displace the residual water. ........ 0.0.00. cee ee ee eee ee 57
Front elevation versus time for 500m! Soltrol spill in #125 sand, included

are gamma scanning time and location. .......... 00-05: e cece eeeee 58
Comparison between rainfall application and no rain for 500ml Soltrol

spill in #125 sand. 2.0... eee eee 59
1000m! Soltrol spill on #70 sand with rainfall application starting after

169 minutes. The rainfall rate was held constant at 9.5cm/hour..........- 59
750ml Soltrol spill on #70 sand with rainfall application starting after 86

minutes. The rainfall rate was held constant at 9.5 cm/hour. ........... 60

Water and Soltrol content profiles for 750m! spill in #70 sand. Gamma

scans were taken 189 minutes after spill was started. A constant rainfall

rate of 9.5cm/hour was applied 86 minutes after the spill was started. .... 61
Water and Soltrol phase content for a 500ml soltrol spill in #125 sand.

Gamma scans were taken 168 minutes after spill was started. A

constant rainfall rate of 9.5cm/hour was applied 45 minutes after the spill

was started. 2.0... ttt ee eee 62
Comparison in front movement between tank and column experiment. .... 63
Set of phase content profiles for 9.5cm Soltrol spill in # 70 sand in the
tank, 2. eee eee ee 64
Soltrol spill front movement in tank with rainfall application. ...........- 64
Set of phase content profiles for 9.5cm Soltrol spill in #70 sand in the
tank with rainfall, 2.0... ke ee eee eee 65
Phase content profile comparison between models and gamma scan.
Soltrol is still ponding at the surface... . 2.6.0... cee eee eee 68

viii


Test for Hysteresis (Am)

N N a
°o a co)

Count Rate
(Thousands)
a

Pe rn tn

o

°
a

So
3S

10 20 30 40 50 60 70 80
Time in minutes

°

Figure 77. Test for hysteresis (Am).

Test for Hysteresis (Cs)

45
Pers. = = -", ee pea il

Count Rate
(Thousands)
rs
&

25

20
oO 10 20 30 40 50 60 70 80

Time in minutes

Figure 78. Test for hysteresis (Cs).

104


#125 SAND 1000ML SOLTROL

Comparison between KOPT and Experiment

1208

100

80

60
Ks = 5.79 m/d

40

ELEVATION IN cm

20

0 50 100 150 200 250 300 350 400 450 500
TIME IN minutes

TM Experiment H © Experiment 2 |

Figure 58. Front movement comparison between experiment and KOPT for different
hydraulic conductivities.

#70 Sand 1000mI Soltrol ‘Spill

120

100

80

60

40

Elevation in em

20

Ponding

0 50 100 150 200 250 300 350 400
Time in minutes

= Experimental Data —— Kinematic Model ‘|

Figure 62. Front movement for 1000m! spill in #70 sand, comparison between KOPT and
experimental results.

74


Elevation
cm

68
67
66
65
64
63
62

Elevation
om

120
419
118
117
116
115
114
113.
112
qa
110
109
108
107
106
98
97
96
95
94
93
92
91

89
88
87
86
85
84

Time
min

204
204
205
205
206
207
207
208
208
209
210
210
rani
ran]
212
213
213
214
214
215
216
216
217
217
218

Time
min

1226
1227
1228
1228
1229
1229
1230
1231
1231
1232
1232
1233
1234
1234
1239
1240
1240
1241
1241
1242
1243
1243
1244
1244
1245
1246
1246
1247
1247
1248

Water
Content

0.049027
0.032258
0.093953
0.057846
0.00731
0.094133
0.012585
0.091366
0.067975
0.147115
0.096795
0.014242
0.104995
0.037091
0.136409
0.039244

0.05097
0.037171
0.078995
0.098603
0.003281
0.118572
0.057905
0.029507
0.077562

Water
Content

0.02332
0.03017
-0.00779
-0.03034
0.002413
0.00825
0.026991
0.015507
0.047997
0.055527
0.055224
0.062351
-0.0088
0.047135
0.050996
0.031119
0.021728
0.020452
0.052854
0.041061
0.025922
0.113544
0.100192
0.032008
0.025945
0.049708
0.00416
0.0781
0.090382
0.077282

Soltrol
Content

-0.01757
-0.00482
0.02826
0.01206
0.005621
-0.02187,
0.00917
0.01119
0.00716
-0.01454
-0.01076
0.0193
-0.01306
0.010273
0.0228
0.013291
0.015203
0.016244
-0.00499
0.01629
0.007773
0.03376
0.01273
-0.00866
~0.01226

Soltrol
Content

0.037382
0.055837
0.058641
0.060362
0.057691
0.068463
0.062563
0.061348
0.056271
0.055438
0.060521

0.06196
0.095897
0.083827
0.105359
0.105919
0.096087
0.098398
0.080594
0.083615,
0.109952
0.092294
0.122851
0.144407
0.121785
0.104739
0.133281
0.117669
0.136476
0.148831

181

Time
mn

254
255
256
256
257
257
258
259
259
260
260
261
262
262
263
264

265
265
266
267
267
268
268
269

Time
min

1366
1367
1367
1368
1369
1369
1370
1370
1371
1372
1372
1373
1373
1374
1379
1379
1380
1381
1381
1382
1382
1383
1384
1384
1385
1385,
1386
1387
1387
1388

Water
Content

0.048683
0.079431
0.041314
0.020381
0.03174
0.030242
0.021972
0.072438
0.125094
0.094205
0.161875
0.062796
0.042648
0.060832
0.113
0.027359
0.119477
0.109016
0.058646
0.040834
0.04937
0.075749
0.06724
0.00797
0.086693.

Water
Content

0.348018
0.313075,

0.28648

0.24598
0.292191
0.334267
0.337171
0.305849
0.307626
0.319626
0.322862
0.328212
0.339784
0.342437
0.274335
0.342551
0.344141
0.356734
0.358073
0.325879
0.303862

0.30723

0.44837
0.395905
0.360926
0.391729
0.289643
0.345085
0.339724
0.415638

Soltro}
Content

0.01602
0.02347
0.01196
0.001515
-0.00727
-0.00505
0.005342
0.01227
-0.01389
0.003436
-0.02097
0.0004
0.013224
0.005819
-0.0149
0.013644
0.01712
~0.00718
-0.0032
0.002267
-0.0059
0.01939
-0.01961
0.016575
-0.00961

Soltrol
Content

0.001628
0.036929
0.03427
0.043673
0.033524
0.020225
0.02745,
0.040872
0.048635
0.044778
0.04098
0.040562
0.046287
0.057573
0.099505
0.053176
0.0574
0.047866
0.044207
0.065058
0.070697
0.083691
0.042531
0.059132
0.066131
0.051406
0.092478
0.080709
0.095237
0.07362


Top View

ke Pie Pit Pit Pid >|
25cm 25cm 25cm 25cm 25cm

7.
Side View

i
1o)
‘9
iss)

Yv

Figure 75. Multichambered plexiglass box for testing the gamma system

1.3 TESTING PROCEDURES FOR THE GAMMA SYSTEM

Since the gamma system was the primary instrument used in the collection of phase
content data during spill experiments, it was tested extensively. The following chapter describes

the testing of the gamma system.

100


Su 3

Depth

Time
Figure 70.

Abrupt boundary transition from high to low saturation, which generates a
continuous wave.

85


Elevation
cm

Elevation
cm

119
117
115
113
qu
109
107
105
103

Time
min

161
161
162
162
163
163
164
165
165

Time
min

201
202
202
203
204
204
205
205
206
206
207
207
208
208
209
210
210
2i1
ai
212
212
213
213
214
214
215
216
216
217
217
218
218
219
219
220
221
221
222
222
223
223
224

Soltrol
Content

0.151574
0.047519
0.010692
0.000492
0.00059
0.00182
0.0014
-0.00166
-0.00365

Water
Content

0.239309
0.257014

0.25558
0.261764
0.238647
0.271055
0.257131
0.225081
0.247826
0.260028
0.195924
0.177262
0.183549
0.091556
0.075163

0.05993
0.050638.
0.047858
0.056674
0.035375
0.048282
0.078261
0.075063
0.050809
0.038783
0.028314
0.091452
0.042391
0.050134
0.069004
0.081507
0.045036
0.033726
0.048818
0.045707
0.034196
0.068016

0.10154
0.108332
0.059817
0.103307
0.071794

Elevation
com

Soltrol
Content

0.072972
0.086041
0.088396
0.097207
0.111259
0.105498

0.11721
0.128984
0.129007
0.134835
0.173374
0.192864
0.205545,
0.258207
0.276195
0.256753
0.272592
0.255742

0.23904
0.241361
0.241561
0.252176
0.249853
0.262873
0.262018
0.277179
0.255687,
0.277617
0.279428
0.275723
0.274692

0.30608
0.309254
0.320688.
0.343354
0.344799
0.343669
0.341012
0.346361
0.349368

0.34935
0.349391

173

Time
min

Time
min

230
230
231
231
232
232
233
233
234
235
235
236
236
237
237
238
238
239
239

241
241
242
242
243
243
244
244
245
245
246
247
247
248
248
249
249
250
250
251
252
252
253

Water
Content

Water
Content

0.264158
0.213852
0.242138
0.231937
0.205524
0.216627
0.247397
0.225929
0.244003
0.270293
0.244638
0.202503
0.259148
0.248581
0.238882
0.261449
0.302674

0.26048
0.286256
0.251627
0.250592
0.263255.

0.23406
0.232628
0.171168

0.13149
0.077367
0.111522

0.07708
0.071849
0.091689
0.038945
0.044974
0.035743
0.069342
0.072242

0.07532
0.065596
0.103279
0.050104
0.055066
0.045147
0.059356

Soltrol
Content

Soltrol
Content

0.069247
0.090368
0.088358
0.097169
0.108806
0.112457
0.096923
0.107072
0.112685
0.111939
0.125769
0.155727
0.142019
0.154967
0.163657
0.163081
0.158145
0.170112
0.166893
0.186039
0.189527
0.185158
0.208158
0.216524
0.264934
0.318537
0.366255
0.358893
0.370646
0.359889
0.338395,
0.337643
0.324756
0.322487
0.318906
0.325357
0.337503
0.355909
0.332727
0.360161
0.361036
0.359836
0.350412


Elevation
cm

Elevation
cm

120
119
118
117
116
115
114
113
112
it
110
109
108
107
106
105
104

96

95

94

93

92

a1

89

85
84
83
81
79

76
75

Time
min

54
55
55
56
57
57
58
59
59
60

61
62
62
63

Time
min

171
171
72
173
173
174
174
175
176
176
W77
178
178
179
179
180
185
186
186
187
187

189
189
190
191
191
192
192
193
194
194
195
196

197
197

199

Soltrot
Content

-0.00237
0.000953
0.00139
0.001473
0.001255
-0.00158
~0.00245
~0.00245
0.010421
0.002574
0.000394
0.001256
0.00041
0.001243
0.004851
0.001872

Soltrot
Content

0.113639
0.119516
0.122855
0.133055
0.13609
0.123831
0.124824
0.126251
0.125343.
0.111306
0.091076
0.107388
0.127332
0.133719
0.125217
0.131232
0.171888
0.177524
0.185131
0.191158
0.188585,
0.176972
0.171484
0.173469
0.19082
0.212616
0.225083
0.218606
0.215071
0.223459
0.22426
0.226133
0.227559
0.24931
0.266689
0.256118
0.2405
0.230234
0.209973

Time
min

107
108
108
109
110
110
wt
141
112
13
113
114
115,
115
116
117

176

Soltrot
Content

-0.00117
-0.00123
0.00372
0.00035
0.003253
0.00086
0.001656
0.003835
0.007418
0.005267
-0.00438
0.003093
-0.00178
0.00127
0.003285.
0.002311

Time
min

Soltro}
Content


No. 125 Sand 500ml Soltrol

HWY)

Elevation (cm)
2 @
gS

~
S

= peu coc go> <M Ow wY k ©
ow 2 2 8 F > ee 8 as
3 93 2 33 3 33 3 3 33
BOF F FS F F F F 5 5 5S 5
i?)
0.35

Phase Content

Set of phase content profiles for 500m! Soltrol spill in #125 sand.

Figure 33.
No. 125 Sand 500m! Soltrol
Rain 500mI/hr after 45 Minutes
120)
100}
€ 8 By =
Ss a 3
3 3
8 6 5 5
8
3
iw 40
~
20 3.
5
OF se 05 >
Woter Phase Content
Figure 34. Set of phase content profiles for 500ml Soltrol spill in #125 sand. Rain started

45 minutes after spill.

53


gave slightly different results (Figure 29). This was not surprising as differences between
nominally identical experiments were expected. Two possible explanations for the results are that
there were differences in the packing of the columns, which led to variations in hydraulic
conductivity; and that there were variations in the water saturation between the two experiments.
However, the differences between the repeated experiments were small. Comparing two spills
in #125 sand with 500 ml Soltrol shows that both fronts move almost simultaneously, until rainfall
commenced in one of the experiments (Figure 42).

The gamma scans show the shape of the oil content profiles along the column. Three
example profiles are shown here, while the complete set of profiles is shown later. The data are
given in Appendix 3 in tabular form. Figure 30 shows an infiltration profile in #70 sand, while
there was still ponding at the soil surface. Figure 31 and Figure 32 show the profile after
redistribution of the Soltrol has begun. The times given in the figures are the exact times after
the beginning of the spill at which the front was measured. The porosity of the #70 sand in this
spill was 0.47; the residual water content approximately 0.1.

Figure 33 through Figure 39 show all of the Soltrol phase content profiles measured with
the gamma system for infiltration of 1000 ml, 750 ml , 500 ml in the #70 and #125 sands. The
earlier of the profiles show that the sample reached full saturation behind the front. However,
after longer times, the saturation behind the front decreased until the Soltrol was near residual
saturation throughout the column.

49


P= pgd (9)

where 9 is the liquid density, g is the acceleration due to gravity, and d is the depth of ponding.
The ponding depth helps drive liquid into the unsaturated zone. The capillary pressure gradient
at the soil surface has a number of important influences on unsaturated zone flow. During
infiltration, one influence of the capillary pressure gradient is to provide an additional driving force,
which is commonly called capillary suction. The magnitude of this force depends on the soil
properties and the antecedent liquid content. For infiltration, the combined effects of gravity, the
imposed pressure gradient, and the capillary pressure gradient must be included in a model in
order to properly compute the mass of liquid drawn into the profile (Weaver and Charbeneau,
1992),

3.2.2 _Kinemai I Model

In the Kinematic Oily Pollutant Transport (KOPT) Model, the kinematic and dynamic
behavior is approximated in two parts: one for infiltration and one for redistribution (Weaver et al.,
1994a). For infiltration, a version of the Green-Ampt (1911) model is used, which includes the
effects of gravity, ponding at the surface, and capillary suction on the infiltrating liquid. This
model accounts for the capillary suction of the media but does not include the effect of the
capillary pressure gradient on the shape of the front. Thus the model assumes a sharp front at
the leading edge of the infiltrating liquid. Behind the sharp front, a constant NAPL saturation is
assumed to exist. Charbeneau (1984) presented a theoretical discussion which demonstrated
that since sharp front models derive from mass conservation, the mean displacement of the true
front matches that of the sharp front. Figure 1 shows the relationship which is maintained
between the true and sharp fronts. The speed of the sharp front is given by:

Wz, b-G (10)

at n(S, - $)

where z, is the position of the front, q, is the NAPL flux ahead of the front, q, is the NAPL flux
behind the front, S, is the NAPL saturation ahead of the front, and S, is the NAPL saturation
behind the front. S, and q, are zero when the NAPL invades a pristine medium as they represent
the antecedent conditions. The flux, q,, is given by the Green-Ampt model

Marg
Mes 2+ [Rho - wy, (11)
2

‘m

% = Kn Zz
f

where K, is the saturated conductivity to NAPL, K,, is the maximum conductivity to NAPL during
infiltration, H, is the NAPL ponding depth at the surface, w is the NAPL head, the subscripts on

11


a) Water-air capillary pressure curve in sand #125 (Figure 21)

The scanning time for this experiment was 20 seconds at every point. Nine scans were
repeated at every location. After nine scans, the gamma system moved 1.25 cm vertically down
to the next scanning location.

The porosity of the sand as determined gravimetrically was 0.41. The average porosity
calculated from the Americium scan was 0.39. The residual saturation was found to be
approximately 0.2; the height of the capillary fringe was 0.5 m. The gamma data agree well with
the Brooks and Corey suction-saturation curves derived from the flow pump data with approaches
1 and 2.

#125 Sand

Water—Air Capillary Pressure Curve

SUCTION HEAD (m)

-0.50
0.00 0.20 0.40 0.60 0.80 1.00 1.20

‘SATURATION

—— Gamma System (Am) —+~ Model Parameter (1) —*— Model Parameter (2)

Figure 21. Suction-saturation profile for #125 sand and water-air.

40


The following steps were taken to calculate the saturation from the gamma count rate.
The count rates were corrected for detector sensitivity by using measurements taken through a
standard absorber. The count rate through the empty column was used as the standard count
tate. However, this correction was usually very small compared to the random variation in the
measurement. Measuring |, along the length of the column would allow the use of one |, for
every point in the column. Even though all attempts were made to pack the column
homogeneously, some small scale variations of porosity along the column are possible. The
changes in |, over the length of the column due to the small variations of porosity were smaller
than the random error in the measurement of |,. Thus, |, was averaged over the whole column.
The same was true for the porosity. The saturation was then computed from the phase content
by using the porosity averaged from the gamma system measurements.

The suction-saturation curve for both sands with water that were measured with the
gamma system have similar entry pressure and residual saturation as do the curves that were
created from flow pump experiments. The suction-saturation curves for Soltrol showed a lower
capillary fringe than for water due to the lower interfacial tension. The measurements with
Americium show a large random variation, but the averaged values have a good accuracy. It was
found that the attenuation coefficient is different for the #70 sand than for the #125 sand. The
#70 sand was sieved from crushed sandstone, whereas the #125 came from naturally deposited
material. The different composition of the two sands was responsible for the different attenuation
coefficients.

The porosity as determined with the gamma system was generally higher than the porosity
found gravimetrically. A possible explanation is an error in path length. A higher value of porosity
(about 5%) was measured when the path length through the column was 3 mm shorter than that
which was assumed for the calibration. If the gamma system does not shoot through the center
of the column (along a diameter), but was off-centered by a maximum of 1.10 cm, the path length
may change up to 3 mm (Figure 25).

re 4.10¢
I= 3.95¢1
x . 1061

333

Figure 25. Schematic of the scanning path through the sample column. If the gamma
detector moves 1.10 cm sideways from the center (x=1.1 cm), the actual path
length measured is 3 mm less than assumed (2I=7.9 cm, while 2r=8.2 cm).

44


No. 125 Sand 1000mI Soltrol
Front Position after 250 Minutes
100;r
90h La] s Experimental Data
1 == = Thee Ferameter Shorp Front Model
80
-— 70OFr t
£ I
& 60F |
S 50} boo
3 40F
4 30F \
20+ . a ;
10r i
0 f f | fl j
-0.1 0.0 0.1 0.2 0.3 0.4 0.5
Phase Content

Figure 57. Phase content profile comparison between model and experimental results.

73


Elevation
cm

36.00
35.00
34.00

Time Soltrol Time
min Content min
198.00

195.00

196.00

Soltrol
Content

0.00

0.01
0.00

135

Time
min

273.00
273.00

Soltrol
Content

0.00
0.00


TIME ELEVATION PONDING BACK FRONT WATER DEPTH

MINUTES. cM CM cM CM
90 55

100 52 81

110 49

125 45

145 cal

167 36 120
169 35.5 100
194 32 80.5
220 28 75
230 120 66
240 26 54.5,
255 24 49.5
265 22 43
275 17 38.5
285 13 34
295 9 26
308 3

128


SECTION 3
THEORETICAL BACKGROUND

The purpose of this section is to summarize some of the important principles and define
the parameters that control the flow of immiscible fluids in porous media. The application of these
to the infiltration and redistribution of liquids in the vadose zone is described. The basis of the
KOPT and Three Parameter Sharp Front Model are then described.

3.1. FLOW OF IMMISCIBLE FLUIDS THROUGH POROUS MEDIA

3.1.1. Porous Media

In the most general sense, a porous medium is a solid body containing voids or pores.
Bear (1972) describes it as a volume occupied by a multi-phase matter in which at least one
phase is solid and at least one is non-solid. This definition includes solid material and gases or
liquids which occupy the void space. The solid phase is called the solid matrix. The space within
the porous medium domain that is not part of the solid matrix is referred to as pore space.

Pores in a porous medium may be either interconnected or isolated. The interconnected
pore space is termed effective pore space. A fluid can only flow if at least part of the pore space
is interconnected. Most natural porous materials have a random void structure. Pore size, shape
and interconnectedness characterize the void space on the microscopic or pore scale.
Macroscopically, effective porosity, n, is defined as the volume fraction of the medium that
consists of interconnected pores which may conduct fluid.

3.1.2 's Law

Darcy's law provides a relationship between the specific discharge and the hydraulic
gradient. Mathematically, Darcy's law may be expressed by the equation

q = -KVh (1)

where q is the Darcy velocity or specific discharge, K the coefficient of proportionality or hydraulic
conductivity and h is the hydraulic head. The Darcy velocity is a macroscopic flux defined over
a representative element or bulk area. This area is taken to be normal to the direction in which
the gradient of h is measured. Hydraulic conductivity for a fully saturated medium depends on
fluid density and viscosity, as well as the size and distribution of the pores.

Darcy's equation can also be applied when the medium is partially saturated. In this case,
the pressure difference will be determined by capillary forces in addition to gravitational forces.
The conductivity of the medium for either phase depends on fluid phase content of the medium.


TIME

MINUTES.

175
180
185,

190
195
200
205
210
215
220
225
230
235
240
245

TANK A

ELEVATION PONDING
DEPTH

cM cM

#70 SAND - SOLTROL PONDING DEPTH 9.5 CM

TANK EXPERIMENT

VISUALLY OBSERVED FRONT MOVEMENT

TIME
MINUTES.

ELEVATION

cM

120

110.7
109.8
107

105.5
104

103.5
102.5
101.5
100.3

98.5

130


#125 Sand

Visually Observed Front Movement

120

100 Front Elevation
5 80 500mi Soltrol Spill
£
5 60
2 40

20 a

Ponding
0 = eer
te} 50 100 150 200 250 300 350

Time in minutes

Figure 28. Front elevation versus time for three spills, 500ml, 750ml and 1000m! Soltro! in
#125 sand.

As the Soltrol infiltrated downward, the rate of propagation of the front declined. It can be
seen that the larger spill volumes of fluid penetrated faster into the sand due to the additional
driving force from the greater ponding depths.

By comparing the profiles for #70 sand and #125 sand, it can be seen that in the
beginning of the spills, the oil penetrated faster into the #70 sand than into #125 sand and
ponding ended much faster for the coarser sand. This behavior was expected as the #70 sand
has a higher hydraulic conductivity than the #125 sand (15 m/d vs. 8.5 m/d). However, the speed
of movement decreased faster for #70 sand, and the oil movement in later stages of
redistribution was slower than for #125 sand. The reason for this was the larger average pore
size and porosity of the #70 sand. The larger the porosity, the faster was the decrease in the
amount of free flowing liquid phase; and with a smaller amount of oil available for flow, the flow
slowed down. It seems that the Soltrol movement depended mainly on the amount of Soltrol
pushing behind the front. A highly oil saturated zone behind the front pushed the front faster than
a lesser saturated zone. Since #70 sand has a larger porosity than #125 sand, the saturation
dropped faster below full saturation. At that point in time the front slowed down markedly. Thus
the front in the #70 sand slowed down faster than in #125 sand. This was specifically marked
for the 500 ml Soltro! spill, where the front was slower in #70 sand soon after ponding ends.

The first experiment with 1000 ml Soltrol in #125 sand, was repeated twice. The
experiments were named H and D and are so named in the Appendices. These experiments

48


CONTENTS

DISCLAIMER .. 2... 6. tenet ett ii
FOREWORD ..... 0.0... cc ete ete e eet ee iii
ABSTRACT 2.0... ee ee ee ee eee iv
FIGURES ©2001 teen eee nee vii
TABLES «20. nn ene e nent eens x
1. INTRODUCTION .. 2.0.0... 6c ec eet ene ene 1
1.1 OBJECTIVES 3
2. CONCLUSIONS AND RECOMMENDATIONS ............ 02.000 e eee ee eens 4
3. THEORETICAL BACKGROUND ....... 0.6... cece ccc cee eee 6
3.1. FLOW OF IMMISCIBLE FLUIDS THROUGH POROUS MEDIA . 6
3.1.1 Porous Media ............ 00-00. eee ee eee eee we. 6
3.1.2 Darcy's Law 2.0... 2 ee cee eee 6
3.1.3 Fluid Saturation .... 0.2... ee ee eee 7
3.1.4 Capillary Pressure 7
3.1.5 Capillary Pressure-Saturation Relationship a. 8
3.1.6 Permeability and Relative Permeability ..................... 8
3.1.7 Governing Equations of Multiphase Flow in Porous Media ....... 9
3.2 SHARP FRONT MODELS .............. 00-020 cece eee ... 10
3.2.1 Infiltration and Redistribution s+. 10
3.2.2 Kinematic Oily Pollutant Transport (KOPT) Model ............. 11
3.2.3. Three-Parameter Sharp Front Model...................00-- 14
3.2.4 Comparison of the Models ......... 0.0.0.0 c ee eee eee eee 17
4. MATERIALS AND METHODS ........... 0.0.0. 18
4.1. SAND CHARACTERIZATION ................-00005 18
4.2 CHARACTERIZATION OF THE TEST FLUID ........... oe. 21
4.3. SAMPLE CELL AND COLUMN ...............-...2.00005 oe. 21
4.4 EXPERIMENTAL PROCEDURES FOR COLUMN EXPERIMENTS . wee. 24
4.5 TWO-DIMENSIONAL TANK EXPERIMENTS ................-2--0-- 29

5. RESULTS AND DISCUSSION ........... 0000s cece eects

5.1. DETERMINATION OF MODEL INPUT PARAMETERS ....
5.1.1 Hydraulic Conductivity ..............-...00.
5.1.2 | Suction-Saturation Measurements in the Small Cell
5.1.3 Estimation of Brooks-Corey Parameters 35
5.1.4 Comparison Between Suction-Saturation Curve Estimated from



Elevation Time Water Soltrol Time Water Soltrol

cm min Content Content min Content Content
50 121 0.060267 0.021747 176 0.156299 0.240446
49 121 0.075933 0.020877 177 0.162142 0.248383
48 122 0.085141 0.0052 177 0.099237 0.283836
47 122 0.05814 0.005564 178 0.109774 0.286074
46 123 0.061648 0.00492 178 0.089905, 0.317966
45 123 0.063874 0.00139 179 0.00825 0.376745
44 124 0.08412 0.0066 179 0.028591 0.374102
43 124 0.042494 0.006602 180 -0.00782 0.391797
42 125 0.068497 0.00218 180 0.011563 0.386313
a 125 0.066523 0.001345 184 0.01597 0.408361
40 126 0.072138 0.003327 181 0.01514 0.388966
39 126 0.098947 -0.00193. 182 0.01935, 0.401654
38 127 0.071426 0.003283 182 0.004017 0.398619
37 127 0.070858 0.006232 183 0.01617 0.402514
36 128 0.077555 0.002881 183 0.02289 0.401456
35 128 0.08199 0.00324 184 0.023933 0.377691
34 129 0.089298 0.002095 184 0.015658 0.385259
33 129 0.061944 0.014541 185 0.04831 0.368877
32 130 0.096124 0.004179 185 0.069403 0.366537
31 130 0.108651 0.00072 186 0.033693 0.376103
30 131 0.089279 0.007056 186 0.066177 0.366537
29 131 0.087401 0.007195 187 0.042906 0.374579
28 132 0.09958. 0.006608 187 0.071789 0.361509
27 133 0.115403 0.006201 188 0.024662 0.369361
26 133 0.102845 0.009456 188 0.117155 0.224971
25 134 0.094817 0.004839 189 0.092692 0.114325
24 134 0.094007 0.00393 189 0.05557 0.044422
23 135 0.09646 0.00755. 190 0.072773 0.0089
22 135 0.093639 0.01065 190 0.053973 0.005443
a 136 0.050796 0.003306 191 0.068047 0.000132
20 136 0.06146 0.00309 191 0.046103 0.002342
19 137 0.055359 0.00484 192 0.06032 0.00442
18 137 0.067513 0.00699 192 0.058187 -0.0009
7 138 0.059252 0.00413 193 0.029373 0.007116
16 138 0.056705 0.001 193 0.057959 -0.00279
15 139 0.033281 0.008964 194 0.038233 0.007165
Elevation Time Water Soltrol
cm min Content Content
115 198 0.158447 0.041455
114 199 0.088609 0.172532
113 199 0.169189 0.111806
12 200 0.208869 0.084312
114 200 0.208635 0.087846
110 201 0.180898 0.094052
109 201 0.184568 0.085904
108 202 0.188848 0.084934
107 202 0.157865 0.097205
106 203 0.172016 0.093064
105 203 0.147474 0.10888
104 204 0.141321 0.106529
103 204 0.189481 0.092579
102 205 0.171868. 0.105292
101 205 0.15171 0.121853
100 206 0.192056 0.112672
99 206 0.193703 0.119625
98 207 0.177577 0.124196

167


Elevation
com

120.00
119.00
118.00
117.00
116.00
115.00
114.00
113.00
112.00
111.00
110.00
109.00
108.00
107.00
106.00
105.00
104.00
103.00
102.00
101.00
100.00
99.00
98.00
97.00
96.00
95.00
94.00
93.00
92.00
91.00
90.00
89.00
88.00
87.00
86.00
85.00
84.00
83.00
82.00
81.00
80.00
79.00
78.00
77.00
76.00
75.00
74.00
73.00
72.00
71.00
70.00
69.00
68.00
67.00
66.00
65.00
64.00
63.00
62.00

Time
min

207.00
208.00
208.00
209.00
209.00
210.00
210.00
211,00
211.00
212.00
212.00
213.00
213.00
214.00
214.00
215.00
216.00
216.00
217.00
217.00
218.00
218.00
219.00
219.00
220.00
220.00
221.00
221.00
222.00
222.00
223.00
224.00
224.00
225.00
225.00
226.00
226.00
227.00
227.00
228.00
228.00
229.00
229.00
230.00
230.00
231.00
231.00
232.00
233.00
233.00
234,00
234.00
235.00
235.00
236.00
236.00
237.00
237.00
238.00

Soltrol
Content

0.13
0.12
0.13
0.15
O15,
0.17
0.18
0.18
0.17
0.18
0.17
0.17
0.18
0.17
0.17
0.18
017
0.17
O17
0.18
0.18
0.19
0.18
0.19
0.19
0.19
0.20
0.20
0.21
0.21
0.21
0.21
0.22
0.22
0.23
0.24
0.25
0.25
0.26
0.27
0.26
0.25
0.26
0.25
0.25
0.26
0.25
0.25
0.25
0.25
0.25
0.26
0.26
0.25
0.25
0.25
0.25
0.25
0.24

Time
min

261.00
261.00
262.00
262.00
263.00
263.00
264.00
264.00
265.00
265.00
266.00
266.00
267.00
267.00
268.00
268.00
269.00
270.00
270.00
271.00
271.00
272.00
272.00
273.00
273.00
274.00
274.00
275.00
275.00
276.00
276.00
277.00
278.00
278.00
279.00
279.00
280.00
280.00
281.00
281.00
282.00
282.00
283.00
283.00
284.00
284.00
285.00
285.00
286.00
287.00
287.00
288.00
288.00
289.00
289.00
290.00
290.00
291.00
291.00

156

Soltrol
Content

0.10
0.10
0.10
0.11
0.12
0.14
0.15
0.16
0.16
0.16
0.14
0.15,
0.15
0.15
0.15,
0.15
0.15,
0.14
O15,
0.15,
0.15,
0.16
0.16
0.16
0.15
0.16
0.16
0.16
0.16
0.17
0.16
0.17
0.17
0.17
0.17
0.18
0.18
0.19
0.19
0.21
0.22
0.22
0.24
0.24
0.25
0.25
0.26
0.26
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.24
0.24

Time
min

314.00
315.00
315.00
316.00
316.00
317.00
317.00
318.00
318.00
319.00
319.00
320.00
320.00
321.00
321.00
322.00
323.00
323.00
324.00
324.00
325.00
325.00
326.00
326.00
327.00
327.00
328.00
328.00
329.00
329.00
330.00
331.00
331.00
332.00
332.00
333.00
333.00
334.00
334.00
335.00
335.00
336.00
336.00
337.00
337.00
338.00
338.00
339.00
340.00
340.00
341.00
341.00
342.00
342.00
343.00
343.00
344.00
344.00
345.00

Soltrol
Content

0.10
0.10
0.10
0.14
0.12
0.14
0.15
0.16
0.16
0.16
0.15
0.14
0.13
0.14
0.13
0.14
0.14
0.13
0.13
0.13
0.14
0.14
0.14
0.14
0.14
0.14
0.14
0.14
0.14
0.14
0.14
0.15
0.15
0.14
0.17
0.15
0.16
0.16
0.17
0.17
0.17
0.19
0.18
0.20
0.23
0.22
0.20
0.22
0.23
025
0.25
0.25
0.25
0.25
0.26
0.25
0.26
0.26
0.26


No. 70 Sand 9.5cm Soltrol
Rain 22cm/hr after 22 Hours for 2 Hours

€
2
<
2
°
8
&
Pr =

2 SP NR yp yey wD

~ 2 © NG 8 GB B

3 3 > > 5 3 =

2 32 3 3 2 8 8 8 8

5 2 2 ©¢ @ e@ ge

5 5 § § § § §

ao 6 &@ @&

com = Sottrot

Phase Content Water

Figure 50. Set of phase content profiles for 9.5cm Soltrol spill in #70 sand in the tank with
rainfall.

65


Grain size distribution
#70 sand

grain size fraction [%]

Sar 04 1
grain size [mm]
Figure 5. Grain size distribution for #70 sand. Measured with dry sieving method (filled
squares) and settling tube method (empty squares).
Grain size distribution
#125 sand
SJ
s
g
g
G
<
s
oO
Bor 0.1 1 10
grain size [mm]
Figure 6. Grain size distribution for #125 sand. Measured with dry sieving method (filled

squares) and settling tube method (empty squares).

20


The rainfall started 22 hours after the spill. At 23 hours the water front caught up with the Soltro!
front, and pushed the Soltro! front downward. At 24 hours the water front passed the Soltrol front
and started exiting the tank, while the Soltrol front was still above the bottom of the tank. The
rainfall was stopped when the water reached the bottom of the tank. After the rainfall was
stopped, the Soltrol front resumed it's pre-rainfall migration rate. The same can be observed from
the phase content profiles (Figure 50).

#70 Sand Soltrol Spill
Starting with Ponding Depth 9.5cm

120

110
Soltrol Front

2 eo S
$6 8

2nd a Gperivet

N
fo)

Elevation in cm

1st Tank Experiment

60 7
50 Colurnn Experiment
40

ie) 100 200 300 ¢00 500 600 700 800 S00 1000
Time in Minutes

Figure 47. Comparison in front movement between tank and column experiment.

63


Elevation
cm

61.00
60.00
59.00
58.00
57.00
56.00
55.00
54.00
53.00
52.00
51.00
50.00
49.00
48.00
47.00
46.00
45.00
44.00
43.00
42.00
41.00
40.00
39.00
38.00
37.00
36.00
35.00

Time
min

931.00
931.00
932.00
932.00
933.00
933.00
934.00
934.00
935.00
935.00
936.00
936.00
937.00
937.00
938.00
939.00
939.00
940.00
940.00
941.00
941.00
942.00
942.00
943.00
943,00
944.00
944.00

Soltrol
Content

0.11
0.10
0.14
0.12
0.11
0.08
0.07
0.06
0.05,
0.05
0.06
0.07
0.07
0.08
0.08
0.09
0.09
0.06
0.04
0.05
0.05
0.07
O11
O11
0.09
0.06
0.03

139


No. 70 Sand 1000mI Soitrol
Rain 500mI/hr after 169 minutes

120
vl
= 80
&
& 60
°
8
A
im 40F =
~“ a = =
3 8 & @ ¢ S FB Yes
aps 3 3 F ~ So 2 8 8
5 5 3 3 3 3 3 2
Sr rr
oO
. Soltrol <- 04 ->
Woter Phase Content

Figure 39. Set of phase content profiles for 1000mlI Soltrol in #70 sand.

In general the gamma profiles taken during the spill show a sharp front at the leading edge
of the Soltrol slug and a diffusive back front during the redistribution phase of the spill. During
infiltration, the sand reached a maximum Soltrol saturation behind the front. When redistribution
began, the maximum saturation Soltrol behind the front decreased. All of the simulations
presented below were based on the assumption that the phase content of the residual water was
constant and did not change during the spill. However, some experiments where Soltrol and water
saturations were both determined indicate that Soltro! displaced some of the residual water
(Figure 40). Actually, in well sorted sand like the ones that were used in these experiments,
irreducible saturation is much lower (~5%) than the residual saturation we obtained (Personal
communication, A.T. Corey, 1993). Release of water may also be due to the fact that the
interfacial tension between Soltrol and water is about half of the surface tension of water.

The profiles were not taken at one point in time, because it takes about 40 minutes to
complete the measurements from top of the column to the bottom. Figure 41 shows the front
movement of a spill and the location of the gamma scan. The diagonal lines signify the
downward moving gamma system. The time it takes to scan one profile is the horizontal distance
between the beginning and the end of one diagonal scan line. It can be seen that the front
moved before the complete profile was scanned. Hence, the same liquid mass might be
measured twice leading to overestimation of the Soltrol volume.

56


(equation (10)).

Figure 3 shows a schematic of depth modeled by KOPT as a function of saturation.
During infiltration the NAPL is assumed to fill a fixed portion of the pore space from the release
point to the sharp front. During redistribution the NAPL saturation varies with depth as
determined by the continuous wave of Figure 2. The sharp front remains at the leading edge of
the NAPL body, but the NAPL saturations behind the front can be reduced.

AB Continuous Wave

WR

Depth

Time

Figure 2. Base characteristic plane for the KOPT model showing the sharp front and
continuous wave which comprise the solution.

13


Simulated rainfall was applied across the total length of the tank from a 5 cm diameter
PVC pipe with 86, 1 mm holes. The rainfall rate was regulated by controlling the number of
holes through which water was allowed to flow. The rainfall rate was calibrated before every
experiment. Green food coloring was applied to the rainwater to observe the water front in the
soil. The observed outline of the fluid front was traced manually on the tank wall and later

transferred to paper.

Figure 14. Schematic of a spill in the tank.

30


Elevation
cm

Time
min

1493
1493
1494
1494
1495
1496
1496
1497
1497
1498
1499
1499
1500
1500
1501
1502
1502
1503
1503
1504
1505
1505
1506
1506
1507
1508
1508
1509
1509
1510
1511
1511
1512
1512
1513
1514
1514
1515
1515
1516
1517
1517
1518
1518
1519
1520
1520
1521
1521
1522
1523
1523
1524
1524
1525
1526
1526
1527
1527

Water
Content

0.115838,
0.065231
0.162207
0.120098
0.115342
0.094805
0.121346
0.09438
0.138762
0.186386
0.126535
0.190156
0.183173
0.151218
0.175737
0.168375,
0.133456
0.129029
0.197049
0.197929
0.217584
0.13869
0.259071
0.171773
0.272299
0.222305
0.229145
0.220628
0.190466
0.277376
0.272957
0.263115
0.256208
0.259806
0.270841
0.266627
0.280435
0.249207
0.220444
0.208149
0.250906
0.148623,
0.174418
0.163573
0.173
0.139739
0.182027
0.165833
0.171598
0.160237
0.166245,
0.169404
0.232623
0 254598
0.138983
0.14647
0.159429
0.158867
0.154249

Soltrol
Content

0.100936
0.119766
0.083157
0.104282
0.117123
0.125817
0.118018
0.124045
0.110468
0.097228
0.116942
0.093685
0.099742
0.115075
0.110644
0.114088
0.122018
0.122154
0.102719
0.106968
0.106734
0.132964
0.096413.
0.128152
0.102031
0.116873
0.118235
0.128201
0.139519
0.114196
0.121322
0.126254
0.127574
0.120467
0.120139
0.127637
0.122583
0.135872
0.144672
0.144098
0 117634
0.151004
0.138138
0.141622
0.138408
0.155967
0.144798
0.152995
0.155905
0.159549

0.17084
0.168451
0.153225
0.140716
0.177721
0.169235

0.16835
0.156214
0.153087

150


#125 Sand 1000mI Soltrol

Visually Observed Front Movement
120

100
Front Movement
80
60

40

Elevation in cm

20

’onding
fxp. 5D

ie)
ie) 50 100 150 200 250 300 350 400 450
Time in minutes

Figure 29. Comparison between two identical experiments with 1000mI Soltrol in #125
sand.

#70 Sand 500m! Soltrol
Phase Content Profile after 21 Minutes
120

100

80

60

Elevation in cm

40

20

-0.1 0 0.1 0.2 0.3 0.4 0.5
Phase Content

Figure 30. Phase content profile of 500ml Soltrol in #70 sand. Soltrol is still ponding on top
of sand.

50


Equations (16) and (17) :

dz, Z+H+h,
®t = K,~-7 7" (18)

where ©, is the volume fraction of organic phase behind front [*], K,, is the effective organic
phase conductivity behind front [L/T], h, is the effective capillary suction at sharp front [L], H_ is
the ponding depth [L], and z, is the depth of infiltration [L]

Equation (18) is solved for three parts of the NAPL release. The first part is infiltration
under constant ponding conditions, the second is infiltration under falling head conditions, and the
third is redistribution after all of the NAPL has entered the medium and a drainage front is starting
to develop. Since it is assumed that the zone between the two fronts is always at full saturation,
the permeability is constant during each of these processes.

First, the equation is solved for constant head ponding of the infiltrating fluid. The ponded
depth is designated by H. The differential equation can be solved with the initial conditions of z,
= 0 for t = 0 to give:

8 z,+ H+ hy
= —"fz,-(H es 19)
t K,(7 (H+ h,) In( H+h, ] (19)

Secondly, equation ((18)) is solved for the period when the ponded depth is declining.
During the falling head period, no material is added; thus the depth of the ponding organic phase
at any time can be given by a simple mass balance:

Hy = %2+H (20)
where H, = cumulative amount of liquid added [L]. Including this mass balance into the

differential front movement equation and integrating from z, = z,, at t = t, results in the following
equation:

8 z+ Mb
= t + >——[z, - - H,|In(———
t ht ey? 2 - Mp (aH!
(21)
hy, + Hy
where = 2
Me 1-6

16


Elevation
cm

61.00
60.00
59.00
58.00
57.00
56.00
55.00
54.00
53.00
52.00
51.00
50.00
49.00
48.00
47.00
46.00
45.00
44.00
43.00
42.00
41.00
40.00
39.00
38.00
37.00
36.00
35.00

Time
min

307.00
308.00
308.00
309.00
310.00
310.00
311.00
311.00
312.00
312.00
313.00
313.00
314.00
314.00
315.00
315.00
316.00
317.00
317.00
318.00
318.00
319.00
319.00
320.00
320.00
321.00
321.00

Soltrol
Content

0.01
0.00
0.01
001
0.01
-0.01
0.00
-0.01
-0.01
0.00
0.00
0.00
-0.01
0.01
-0.01
0.00
0.00
0.00
0.01

Time
min

358.00
359.00
359.00
360.00
360.00
361.00
361.00
362.00
363.00
363.00
364.00
364.00
365.00
365.00
366.00
366.00
367.00
367.00
368.00
368.00
369.00
370.00
370.00
371.00
371.00
372.00
372.00

137

Soltrol
Content

0.04
0.02
0.03
0.02
0.01
0.00
0.01
0.00
0.00
0.00
0.00
0.00
0.01
0.00

Time
min

406.00
407.00
408.00
408.00
409.00
409.00
410.00
410.00
411.00
411.00
412.00
412.00
413.00
413.00
414.00
415.00
415.00
416.00
416.00
417.00
417.00
418.00
418.00
419.00
419.00
420.00
421.00

Soltrol
Content

0.09
0.07
0.06
0.04
0.03
0.01
0.01
0.01
0.00
0.00
0.00
0.01
0.00
-0.01
0.00
0.00
0.00
0.00
-0.01
-0.01
-0.01
-0.01
0.00
0.00
0.01
0.01
-0.01


sharp front is expected for the leading edge of the infiltrating liquid.

Depth

Oo

Front

Time
Figure 67. | Continuous boundary transition from low to high saturation.
S Su
g
[om
o
a
Front
Time
Figure 68.

Abrupt boundary transition from low to high saturation which is immediately
resolved into a discontinuity.

83


Elevation
cm

Elevation
em

115
114
113
112
111
110

Time
min

Time
min
88
88

89
89

90

Water
Content

Water
Content

0.022644
0.055459
0.06938
0.078093
0.041314
0.02089

Soltrol
Content

Soltrot
Content

0.156551
0.182696
0.162365
0.167817
0.193194
0.207253

165

Time
min

Time
min

143
144
144
145,
145
146

Water
Content

0.064315
0.027563
0.095963
0.05727
0.084154
0.085811
0.090741
0.077892
0.071837
0.083629
0.116087
0.073912
0.099507
0.075754
0.075725
0.06341
0.068737
0.064166
0.078085.
0.050592
0.061946
0.048876
0.071824
0.057461
0.09276
0.084912
0.072391
0.053982
0.071546
0.066908
0.06512
0.085681
0.101994
0.045738
0.130186
0.094898
0.09689
0.101672
0.069094
0.048835
0.0494
0.061252
0.040356
0.032076
0.052453
0.064478
0.041998
0.056759

Water
Content

0.072491
0.107793
0.180822
0.213918
0.217118
0.190631

Soltrol
Content

-0.00019
0.008226
-0.00927
0.006669
0.0025
0.00216
0.000776
0.010098
0.012652
0.012699
0.0019
0.013418
0.006069
0.014068
0.011621
0.003127
0.000941
-0.00178
-0.00678
0.004157
~0.00149
0.008604
-0.00188
0.008032
-0.00013
0.00101
0.003344
0.006252
0.008956
0.008329
0.018392
0.006983
0.00194
0.015103
0.00171
0.008647
0.008789
-0.00088
0.004156
0.011686
0.005208
-0.00338
0.003319
0.003279
-0.00062
-0.00571
0.002677
-0.00037

Soltrol
Content

0.149466
0.174561
0.105462
0.090573
0.095836
0.100615.


Table 3. Equivalent Brooks and Corey parameters.

Equivalent Brooks and Corey Parameters

Approach 1 Approach 2
(nonlinear fitting with (Lenhard et al. (1989)
RETC) Conversion Equations)

#125 Sand
h.. (cm) 42.8 (42.19,43.29) 56.6
Xu 2.88 (2.70,3.06) 3.76
Swe 0.22 0.22
#70 Sand
h,. (em) 26.83 (26.39,27.25)
a 2.44 (2.29,2.59)
S, 0.30

wr

Although the air entry heads, h,,, were consistently higher for approach 2, the scaled oil/air
curves remained relatively close. Since KOPT is relatively insensitive to the capillary pressure
curve parameters, at least during infiltration (Weaver et al., 1992), the model results were not
greatly affected by these values. Figure 19 illustrates the effect of variation in the capillary
pressure curve parameters used in KOPT for simulating the 1000 ml Soltro! spill in the #125 sand.
The higher entry head had the effect of causing the front to be displaced downward. The result
was due primarily to the increase in capillary suction during ponded infiltration. The effect of the
procedure for determining the Brooks and Corey parameters was also examined for #70 sand
(Figure 20) and found to be similar to that for the #125 sand.

37


Elevation in Centimeters

DD
oO

w
So

ho
Oo

= Measured Front Position
— KOPT Front Position

° Measured Ponding Depth
--- KOPT Ponding Depth

ie

0 100 200 300 400 500 600

Time in Minutes

Figure 63 Adjusted KOPT simulation of the 1000 ml spill in the #70 sand

78


Elevation
cm

Time
min

237
238
238
239
239
240
240
241
241
242
242
243
243
244
244
245
245
246
246
247
247
248
248
249

Water
Content

0.160175
0.157986

0.17089
0.153454

0.15006
0.173378

0.17079
0.165479
0.189581
0.183579
0.196487
0.227302

0.18677
0.177735
0.206018
0.183987
0.166645
0.135436
0.125499
0.147409
0.144637
0.147388
0.121985
0.126341

Soltrol
Content

0.214959
0.219362
0.210099

0.22209
0.217396
0.213209

0.22051
0.216855
0.208458
0.211463
0.209028
0.193052
0.212231
0.207444
0.198866

0.20882
0.214743
0.229005
0.230917
0.215785,
0.209865,
0.214136
0.217448
0.221398

169


No. 70 Sand 500mI Soltro!

if}

a
S 60
©
&
= 40
a
wo xX w -$ofob.g-
ay ~ © StISESESt ats tyyr
3 >
5 2 3 3 3f343°3°3 3823
505065 SF § § SF F
ol a
O.3-

Phase Content

Figure 37. Set of phase content profiles for 500mi Soltrol spill in #70 sand.

No. 70 Sand 750ml Soltrol
Rain 500mI/hr after 86 Minutes

120,
100

80)

uw 681

60.

Elevation (cm)

40)

uw GZZ

uid 7 |
Ul 9g

20}

i?)
m sotto: (- 0.5 —>
Woter Phase Content

Figure 38. Set of phase content profiles for 750ml Soltrol spill in #70 sand.

55


120

« Measured Front Position
100 — KOPT Front Position

© Measured Ponding Depth
— - KOPT Ponding Depth

foe)
oO
r

Elevation in Centimeters
aS oOo
Oo la}

0 100 200 300 400 500 600
Time in Minutes

Figure 64 Adjusted KOPT simulation of the 750 ml spill in the #70 sand

79


Figure 83.

Figure 84.

Attenuation Coefficient of Sand
Am

slope = 0.236 cm*2 / g

Absorbance div. sample thickness

0 #025 05 O75 1 125 15 175 2
Bulk Density in g/cm*3

Attenuation coefficient versus bulk density for #125 sand (Am).

Attenuation Coefficient of Sand
Cs

0.15

0.14 lope = 0.063 cm*2 / g

0.05

Absorbance div. sample thickness

0 #025 05 O75 1 125 15 175 2
Bulk Density in g/em*3

Attenuation coefficient versus bulk density for sand #125 (Cs).

114


Table 11a. Volumetric content of organic phase in sand
Three compartments filled with sand, one or two filled with Soltrol

Am calc with lay calc with ly
Iayy 4, Soltrot 1, Soltrol ly So conti Socont2 |Soconti | So cont2
(1) (2) (3) (4) (5) (6) @” (8)

42372 6968 1125 711148 0.328 0.660 0.333, 0.665,
41197 7424 1631 714854 0.312 0.588 0.323 0.599
41608 7251 1401 715648 0.318 0.617 0.327 0.626
41250 6618 980 718232 0.333 0.681 0.344 0.692
41417 7286 1789 717223 0.316 0.572 0.327 0.582
41493 7206 1454 717690 0.319 0.610 0.329 0.620
40796 7281 1840 718012 0.314 0.564 0.327 0.577
avg 0.320 0.613. 0.330 0.623
std 0.007 0.041 0.007 0.039
theoretical water cont 0.333 0.667 0.333 0.667

theoretical error % 4.015 8.047 0.983 6.531

Cs cale with lay calc with /,
egy J, Soltrol J, Soltrol Io So contt So cont2 So contt So cont2
(1) (2) (3) (4) (5) (6) @ (8)

110399 89681 77091 244441 0.439 0.758 0.330 0.649
110187 91878 75849 247998 0.384 0.789 0.309 0.714
111275 91009 75121 252515 0.425 0.830 0.367 0.773
109966 90099 74006 246966 0.421 0.836 0.342 0.757
- 108925 91661 74816 248440 0.364 0.793 0.318 0.747
109528 89834 76908 248353 0.419 0.747 0.360 0.688
109500 90577 75271 242186 0.401 0.792 0.289 0.680
avg 0.407 0.792 0.331 0.715
std 0.024 0.031 0.026 0.042
theoretical water content 0.333 0.667 0.333 0.667
theoretical error % 22.218 718.814 0.765 -7.322

The test box was used to determine the volumetric Soltrol content in a defined sand-Soltrol
mixture. The first four columns give the measured count rates through the box for three
compartments filled with sand, three compartments filled with sand plus one compartment filled
with Soltrol, three compartments filled with sand plus two compartments filled with Soltrol and
through the empty box respectively. The fifth and sixth columns give the Soltrol content as
calculated from Equation (30), with the initial count rate through the dry sand for one and two
compartments filled with Soltrol, respectively. The seventh and eighth give the Soltrol content,
as calculated from Equation (31), with the initial count rate through the empty box. The average
and the standard deviation were calculated for the seven measurements. The average was
compared to the theoretical Soltrol content, and a theoretical error was calculated. The suite of
calculations was performed for both Cesium and Americium.

117


TOP PORTION OF SAMPLE CELL

CLEARANCE 18-24
POROUS STONE:
ORDG 2153

3500:
ar Tif] eye
Wl 3250 . mi} #838
Wt J ni} —t fT
Wa yor scr sss 7 it a
i i " no 8
ul i " WI
tt q it tl
ia fy th

5.258

6000.

Figure 9. Aluminum fitting for top part of sample cell. Sizes are given in inches.

4.4 EXPERIMENTAL PROCEDURES FOR COLUMN EXPERIMENTS

In all experiments, it was necessary to pack the test cell or column as uniformly as
possible with sand (Armbruster, 1990). To achieve a homogeneous filling, a long tube of smaller
diameter was placed inside the long column, and the sand was poured into the inner tube. The
sand was allowed to fall through eight holes in the tube (four sets each located approximately 30
cm and 60 cm above the column end) into the larger column. By slowly lifting the tube while the
sand filled the column, the formation of sand layers was avoided. Pouring of the sand was
stopped when the top of the sand was about 20 cm below the top of the column. The supply
container holding the sand was weighed before and after filling the column to determine the
amount of sand used in the packing. The volume of the sand pack was calculated from the
height of the sample and was used with the known weight to estimate the porosity.

Next, the sand was completely saturated with the wetting phase (water or Soltrol,
depending on the particular experiment). A vacuum was applied at the top of the column, or
sample cell, to remove all air from the sand. After the air had been removed, the liquid was
allowed to enter through the bottom of the column (Figure 10). The wetting phase was first pulled
through the porous plate to ensure complete saturation of the plate. After the porous plate had
been saturated, the saturation process was continued through the side port above the porous
plate to permit a faster flow rate. This procedure ensured minimum air entrapment. The vacuum

24


Elevation
cm

Elevation
com

118
117
116
115,
14
113
112
41
110
109
108
107
106
105

Time
min

1405
1406
1407
1407
1408
1408
1409
1410
1410
1411
1444
1412
1413
1413
1414
1414
1415
1416
1416
1417

Time
min

1484
1485
1485
1486
1486
1487
1488
1488
1489
1490
1490
1491
1491
1492

Water
Content

0.0006
-0.04689
0.02447
-0.00473
0.010884
0.084457
-0.00687
0.04028
0.006018
0.013007
0.019332
0.033616
0.0191
0.023031
0.00636
~0.0008
~0.02643
0.033023
0.006973
0.004372

Water
Content

0.061236
0.044601
0.006856
0.032048

0.08351
0.081976
0.090117

0.08964
0.090645
0.124996
0.161922
0.103073
0.105764
0.119324

Soltrol
Content

0.148847

0.16538
0.148865,
0.161537
0.167168
0.167571
0.208782
0.215462
0.199385
0.183799
0.168031
0.157454

0.17212
0.149938
0.161386
0.159746,
0.172443
0.150608.
0.165142
0.172147

Soltrol
Content

0.08141
0.080946
0.093891
0.092214
0.079274
0.090446
0.100017
0.107004
0.110578
0.102127
0.089849
0.102376
0.106999
0.100525

149

Time
min

1456
1457
1457
1458
1459
1459
1460
1460
1461
1462
1462
1463
1463
1464
1465
1465
1466
1466
1467
1468
1468
1469
1469
1470
1471
1471
1472
1472
1473
1474
1474
1475
1475
1476
1477
1477
1478
1478
1479
1480

Water
Content

0.122175
0.14633
0.205754
0.205078
0.159125,
0.187102
0.162255,
0.147996
0.136272
0.068797
0.022058
0.01704
0.04864
0.05013
0.0463
0.009199
0.0198
0.002291
0.03322
-0.01984
0.03142
-0.0283
0.029261
-0.00162
-0.02767
0.10046
-0.06853
0.10423
~0.08295
-0.08867,
0.0519
-0.05169
-0.09289
-0.03094
-0.09616
0.11323
0.07694
-0.0668
-0.11033
0.11824

Soltrol
Content

0.179691
0.172853
0.151969
0.157801
0.170924
0.169052
0.185849
0.193578
0.204128
0.219681
0.225937
0.231223
0.222632
0.208662
0.195959
0.174433
0.174243
0.169585,
0.17926
0.180829
0.194223
0.18433
0.158068
0.165354
0.172547
0.210637
0.217613
0.226376
0.206278
0.217552
0.210588
0.205241
0.193792
0.176691
0.206175
0.2206
0.225417
0.223501
0.235993
0.229901


Elevation
cm

100
99
98
97

Time
min

130
131
131
132
132
133
133
134
134
135
135

136
137
137
138
138
139
139
140
140
141
142
142
143
143
144
144
145
145
146
146
147
147
148
148
149
149
150
150
151
151
152
152
153
153
154
155
155
156
156
157
157
158
158
159
159
160
160

Soltrol
Content

0.201461
0.202318
0.203005
0.218628

0.22772
0.226875,
0.229624
0.241596
0.248672
0.245526
0.252386
0.272771
0.301661
0.280627
0.264297
0.262558
0.277086
0.276444
0.267789
0.275319
0.282532
0.296788
0.315689
0.305748
0.307222
0.313109
0.320344

0.31875
0.325898
0.338214
0.329491
0.337143
0.338994
0.343167
0.350017
0.346027
0.344354
0.346087
0.336756
0.338081
0.344609
0.334673
0.335217
0.338111
0.339635
0.332614
0.334614
0.339048
0.336308
0.333189
0.339338
0.335224
0.340667

0.34266
0.341741
0.336567
0.327185
0.305856
0.273611

Elevation

om

172

Time
min

185
186
186
187
187
188
188
189
190
190
191
191
192
192

193
194
194
195
196
196
197
197

Water
Content

0.068783
0.055828

0.04292
0.069708
0.060701
0.069072
0.102566
0.073502

0.07688
0.083597
0.026087
0.059297
0.082529
0.044919
0.092513
0.109599
0.104569
0.063194
0.076791
0.091378
0.046074
0.062484
0.099056

Soltrol
Content

0.271208
0.270481
0.278495
0.274293

0.28319
0.286798
0.282693
0.315018
0.310709
0.330754

0.35338
0.344513
0.337559
0.357007
0.337607

0.33774
0.349641
0.362871
0.352688
0.349946
0.363852
0.327034
0.061648


NOoOBRWON +

8a
8b

tla
11b

TABLES

r Page

Characterization of #70 and #125 sands
Hydraulic conductivity for #125 sand ..
Brooks and Corey parameters ................
KOPT parameter values for the #125 and #70 sands .
Summary of KOPT model parameter adjustments .. .
Adjusted KOPT model parameters for the #70 sand . .
Random variation comparison...............
Count statistics for Americium .
Count statistics for Cesium .. .
Attenuation coefficient of water
Volumetric water content in sand-water mixture ............. 0.000000 eee
Volumetric content of organic phase in sand ............... 0000020 e eee
Volumetric content of the organic phase calculated with Equation (42) ........ 118
Volumetric content of water and organic phase in sand-water-organic mixture ... 119



APPENDIX 3 EXPERIMENTAL PHASE CONTENT PROFILES

Spill H Bulk Density grav.: 1.53g cm*
#125 Sand 500 mi Soltrol Spill Porosity: 0.42
Temperature Soltrol: 23°C
Gamma Scan Data Residual Water Content: 0.06
Elevation Time Soltrol Time Soltrol Time Soltrol
om min Content min Content min Content
120.00 3.00 0.32 9.00 0.32
119.00 4.00 0.31 9.00 0.32 21.00 0.34
118.00 4.00 0.31 10.00 0.32
117.00 5.00 0.30 10.00 0.30 21.00 0.33
116.00 5.00 0.29 11.00 0.29
115.00 6.00 0.31 11.00 0.31 22.00 0.33
114.00 6.00 0.30 12.00 0.30
113.00 7.00 0.30 13,00 0.31 22.00 0.33
112.00 8.00 0.29 13.00 0.29
111.00 14.00 0.31 23.00 0.34
110.00 14.00 0.30
109.00 15.00 0.29 23.00 0.32
108.00 15.00 0.30
107.00 16.00 0.28 24.00 0.33
106.00 16.00 0.22
105.00 17.00 0.09 24.00 0.28
104.00 17.00 0.01
103.00 18.00 -0.01 25.00 0.26
102.00 18,00 -0.01
101.00 19.00 -0.01 26.00 0.13
100.00
99.00 26.00 0.00
98.00
97.00 27.00 0.00
96.00
95.00 27.00 -0.01
94.00
93.00 28.00 0.01
92.00
91.00 28.00 0.00
120.00 34.00 0.29 58.00 0.22 86.00 0.17
119.00 34.00 0.29 58.00 0.24 86.00 0.18
118.00 35.00 0.28 59.00 0.25 87.00 0.19
117.00 35.00 0.28 59.00 0.25 87.00 0.19
116.00 36.00 0.27 60.00 0.25 88.00 0.19
115.00 37.00 0.28 60.00 0.26 88.00 0.20
114.00 37.00 028 - 61.00 0.26 89.00 0.21
113.00 38.00 0.28 62.00 0.27 89.00 0.22
112.00 38.00 0.27 62.00 0.27 90.00 0.22
111.00 39.00 0.28 63.00 0.28 90.00 0.24
110.00 39.00 0.28 63.00 0.27 91.00 0.25
109.00 40.00 0.27 64.00 0.27 91.00 0.25
108.00 40.00 0.27 64.00 0.27 92.00 0.26
107.00 41.00 0.28 65.00 0.27 92.00 0.26
106.00 41.00 0.27 65.00 0.27 93.00 0.27
105.00 42.00 0.28 66.00 0.27 93.00 0.27
104.00 42.00 0.27 66.00 0.27 94.00 0.26
103.00 43.00 0.28 67.00 0.28 95.00 0.27
102.00 43.00 0.28 67.00 0.28 95.00 0.28

132


Spill O

#125 Sand 500 ml Soltrol Spill

Rain 500mV/hour after 45 minutes. Temperature Soltrol: 22°C
Gamma Scan Data Temperature Water: 25°C
Residual water content assumed constant at 0.06.

Elevation Time Soltrol Time Soltrol Time Water Soltrol
cm min Content min Content min Content Content
120.00 0.00 0.32 42.00 0.26 116.00 0.27 0.08
119.00 1.00 0.33 43.00 0.28 117.00 0.31 0.07
118.00 1.00 0.28 43.00 0.25 117.00 0.13 0.08
112.00 5.00 0.33 47.00 0.34 121.00 0.34 O11
111.00 5.00 0.30 47.00 0.32 121.00 0.26 0.10
110.00 6.00 0.30 48.00 0.31 122.00 0.23 O11
109.00 7.00 0.21 49.00 0.30 123.00 0.24 0.10
108.00 7.00 0.11 49.00 0.31 123.00 0.22 O14
107.00 8.00 0.03 50.00 0.31 124.00 0.29 0.08
106.00 8.00 0.00 50.00 0.31 124.00 0.16 0.13
105.00 9.00 0.01 51.00 0.30 125.00 0.29 0.09
104.00 10.00 0.00 52.00 0.30 126.00 0.24 0.10
103.00 10.00 0.01 52.00 0.29 126.00 0.25 0.10
102.00 11.00 0.00 53.00 0.30 127.00 0.21 0.11
101.00 12,00 0.00 53.00 0.30 127.00 0.23 0.11
100.00 12.00 0.00 54.00 0.29 128.00 0.25 0.09
99.00 13.00 0.00 55.00 0.29 129.00 0.29 0.08
98.00 13.00 0.00 55.00 0.29 129.00 0.23 0.09
97.00 14.00 0.00 56.00 0.29 130.00 0.31 0.07
96.00 15.00 0.01 56.00 0.29 130.00 0.13 0.13
95.00 15.00 0.00 57.00 0.29 131.00 0.26 0.09
94.00 16.00 0.00 58.00 0.28 132.00 0.32 0.06
93.00 16.00 0.00 58.00 0.28 132.00 0.32 0.06
92.00 17.00 0.00 59.00 029 133.00 0.28 0.07
91.00 18.00 0.00 60.00 0.28 133.00 0.23 0.09
90.00 18.00 0.00 60.00 0.29 134.00 0.24 0.09
89.00 19.00 0.00 61.00 0.29 135.00 0.30 0.06
88.00 19.00 0.00 61.00 0.29 135.00 0.24 0.09
87.00 20.00 0.00 62.00 0.29 136.00 0.33 0.06
86.00 21.00 0.00 63.00 0.28 136.00 0.23 0.10
85.00 21.00 0.01 63.00 0.28 137.00 0.30 0.08
84.00 22.00 0.00 64.00 0.20 138.00 0.25 0.09
83.00 22.00 0.00 64.00 0.09 138.00 0.31 0.07
82.00 23.00 0.00 65.00 0.02 139.00 0.34 0.06
81.00 24.00 0.01 66.00 0.00 140.00 0.28 0.08
80.00 24.00 0.01 66.00 0.00 140.00 0.24 0.09
79.00 25.00 0.00 67.00 0.00 141.00 0.27 0.08
78.00 26.00 0.01 67.00 0.01 141.00 030 0.09
77.00 26.00 0.01 68.00 0.01 142.00 0.27 0.09
76.00 27.00 0.00 69.00 0.01 143.00 0.27 0.09
75.00 27.00 0.00 69.00 0.00 143.00 0.27 0.09
74.00 28.00 0.00 70.00 0.00 144.00 0.27 0.09
73.00 29.00 0.00 70.00 0.00 144.00 0.23 O11
72.00 29.00 0.00 71.00 -0.01 145.00 021 O11
71,00 30.00 0.00 72.00 0.00 146.00 0.29 0.08
70.00 30.00 0.00 72.00 0.00 146.00 0.34 0.07
69.00 31.00 000 73.00 0.00 147.00 0.26 0.10
68.00 32.00 0.00 74.00 0.00 147.00 0.25 0.10
67.00 32.00 0.00 74.00 0.00 148.00 0.21 0.13
66.00 33.00 0.00 75.00 0.00 149.00 0.21 0.12
65.00 33.00 0.00 75.00 0.00 149.00 020 0.13
64.00 34.00 0.00 76.00 0.00 150.00 0.23 0.12
63.00 35.00 0.00 77.00 0.00 150.00 0.27 0.11

140


Elevation Time Soltrol Time Water Soltrol

cm min Content min Content Content
89 239 0.260508 1355, 0.05216 0.15331
88 240 0.269769 1356 0.011215 0.130933
87 240 0.274374 1356 0.040745 0.118616
86 241 0.294818 1357 0.041364 0.120189
85 242 0.30007 1358 0.066012 0.115927
84 242 0.305125, 1358 0.04305 0.156652
83 243 0.294226 1359 0.01823 0.153011
82 243 0.291864 1359 0.018016 0.145269
81 244 0.283499 1360 0.05205, 0.170474
80 245 0.288854 1361 -0.00805 0.157846
79 245 0.274299 1361 0.0184 0.16242
78 246 0.279486 1362 0.013879 0.148417
77 246 0.279621 1363 0.074105, 0.13355
76 247 0.270216 1363 -0.02664 0.175079
75 248 0.287927 1364 0.005915, 0.16989
74 248 0.277774 1364 0.013661 0.17147
73 249 0.282282 1365, 0.006543 0.177525
72 249 0.270404 1366 0.02705 0.193801
71 250 0.260624 1366 0.01723 0.181935,
70 251 0.272595 1367, 0.007295 0.179006

146


5.1.4  C ‘ison Betwee! fion-' ration Cul im: from Flow-P: nd
Gamma Measurements

The water/air and Soltrol/air suction-saturation curves were determined with the gamma
system for the #125 and #70 sands. The column was first filled with sand, then completely
saturated with the wetting fluid (water or Soltrol), and allowed to drain under gravity. The
drainage water reservoir was held near the bottom of the column. The coordinate origin for the
graphs was set at the elevation of the reservoir where the liquid phase pressure was atmospheric.
All graphs of the suction-saturation curves show a fully saturated zone of sand at negative
elevations, i.e. below the water (Soltrol) level, and a fully saturated capillary fringe above the
water (Soltrol) level. Water (or Soltrol) at the top of the column is at residual saturation. The
gamma data were compared with the suction saturation curves derived from the Brooks and
Corey parameters, which in turn are obtained, as described before, by converting the van
Genuchten parameters from the flow pump data with two different approaches. The gamma
saturation was calculated from the phase content with the porosity calculated from the gamma
scans. This resulted in full saturation values close to 1, and was thus found acceptable.

39


Figure 52.
Figure 53.

Figure 54.
Figure 55.
Figure 56.
Figure 57.
Figure 58.
Figure 59.
Figure 60.
Figure 61.
Figure 62.

Figure 63.
Figure 64.
Figure 65.
Figure 66.

Figure 67.
Figure 68.

Figure 69.
Figure 70.

Figure 71.

Figure 72.
Figure 73.

Figure 74.
Figure 75.
Figure 76.
Figure 77.
Figure 78.
Figure 79.
Figure 80.
Figure 81.
Figure 82.
Figure 83.
Figure 84.

Phase content profile comparison between models and gamma scan. .... 68
Phase content profiles comparison between models and experimental

results. 0 ee tees 69
Front movement for 1000mI spill, comparison between model and

experimental results. 2.6.2... eee 70
Phase content profile comparison between model and experimental

results. 2. eee 71
Phase content profile comparison between model and experimental

results. 2... ee ee eee 72
Phase content profile comparison between model and experimental

results. 26 eee ete eens 73
Front movement comparison between experiment and KOPT for

different hydraulic conductivities. 2.0.0.6... . cece eee ee ee eee 74
Front movement of 750m! spill in #125 sand, comparison between

KOPT and experimental results... 2... 2.00 ee ee 75
Front movement for 500m! spill in #70 sand, comparison between KOPT

and experimental results. ... 2... 2.0 eee 76
Front movement for 750ml spill in #70 sand, comparison between KOPT

and experimental results. 6.0.0... ee eee 77
Front movement for 1000mI spill in #70 sand, comparison between

KOPT and experimental results. .... 0.0.6... e eee 74
Adjusted KOPT simulation of the 1000 ml spill in the #70 sand ......... 78
Adjusted KOPT simulation of the 750 mi spill in the #70 sand .......... 79
Adjusted KOPT simulation of the 500 ml spill in the #70 sand .......... 80
Schematic representation of the slope of the effective conductivity

fUNctiON. ©... 6. tte eee 82
Continuous boundary transition from low to high saturation. ............ 83
Abrupt boundary transition from low to high saturation which is

immediately resolved into a discontinuity. .............--...00.00085 83
Continuous boundary transition from high to low saturation. ............ 84
Abrupt boundary transition from high to low saturation, which generates

a continuous wave. . see 85
Schematic representation of the effect of the relative permeability

derivative on the leading and trailing edges of the NAPL body. ......... 86
Radiation source housing (after Armbruster, 1990). .................. 95
Schematic of computer controlled traversing gantry and gamma data

acquisition system (after Armbruster, 1990). ................0..000. 98
Computer automated traversing gantry system (after Armbruster, 1990). .. 99
Multichambered plexiglass box for testing the gamma system ......... 100
Delay in reading of constant count rate after start-up (Am). ........... 102

Test for hysteresis (Am). .............00.
Test for hysteresis (Cs)... 0.0... ccc cece eee eee

Attenuation coefficient of water (AM). . 1.20... eee eee 110
Attenuation coefficient of water (Cs)

Attenuation coefficient of Soltrol and iodoheptane mixture (Am). ........ 111
Attenuation coefficient of Soltrol and iodoheptane mixture (Cs). ........ 111

Attenuation coefficient versus bulk density for #125 sand (Am).
Attenuation coefficient versus bulk density for sand #125 (Cs)..........

ix


Averaging the 17 individual measured conductivities gives a value of 8.50 m/d with a standard
deviation of 2.71 m/d. The values were averaged to give a single measured K, value for use in
KOPT. The standard deviation was used to show the variability associated with packing the
sand in simulations presented later in this report (Figure 58).

For the #70 sand, long column experiments were not performed to determine the hydraulic
conductivity. In this case, however, the hydraulic conductivity was adjusted until data from the
1000 ml spill was matched by the KOPT model. This value of 15.0 m/d was then used without
further manipulation in the simulations of the 500 ml and 750 ml spills.

5.1.2 uction- ration Measurements in the Small Cell

Steady state suction-saturation profiles for #125 sand for water were measured in the
small cell. These measurements had the purpose of verifying the suction saturation profiles
obtained with the flow pump. Suction was applied to the cell via the porous bottom plate. A
water reservoir in direct connection with the sample through the porous plate was lowered in
steps below the sample to achieve a number of defined suction heads. After gradual lowering
of the water reservoir, one had two wait until the extra water was drained from the sample. The
duration of this waiting period depended on the suction change and the starting saturation, but
is usually the order of hours or days. Thus, a measurement of a large number of points was not
feasible. Saturation was measured with the gamma system, using only the Americium source.
The porosity was determined gravimetrically. The capillary suction head versus saturation for two
experiments are graphed in Figure 16. Only a few points were obtained; however, it can be seen
that the points can be connected to form the typical suction-saturation curve, but as can be
expected these measurements are less precise than the flow pump data. !n addition to the larger
number of data points, the flow pump gives the suction-saturation relationship much quicker than
the gamma system with the small cell.

33


and included in the lumped attenuation coefficient. These calculations can be done for Cesium
and Americium separately. However, since the bulk density of sand for this experiment was not
previously determined, only an average value for the attenuation coefficient of the sand could be
used. The third method of calculation used the Americium and Cesium counts simultaneously
to calculate the phase content independent of the bulk density (Equation (42)).

Calculations with the incident radiation measured through sand produced the best results.
It is important to note that measurements with Americium seem more reliable than measurements
with Cesium. The attenuation of Cesium is very weak; the results from the Cesium spectrum are
therefore more susceptible to small fluctuations. This can also be seen in the results where
Cesium and Americium counts were used simultaneously for the calculations because the
calculated phase contents are not as close to the theoretical values as those results calculated
only from the Americium source. The calculations with the incident radiation through the empty
box showed the largest deviation from the true value.

It seems ideal to measure the incident radiation through the dry sand and rely on the
calculation of the phase content with the Americium data. However, this assumes bulk density
is constant. Changes in bulk density when saturating the sand will cause some error. If large
changes in bulk density occur, calculations of the phase content have to be done with Americium
and Cesium spectra simultaneously. Then bulk density and phase content can be calculated
independently of each other. No error from a change in bulk density will then affect the
calculations, however, a larger error resulting from the Cesium spectrum has to be considered.

Three-phase mixtures do not allow for the measurement of the bulk density. The bulk
density should be determined gravimetrically before the system is saturated. It has to be
assumed that the bulk density does not change after saturation. A better assumption is that the
bulk density does not change when an organic phase is introduced after the sand has already
been saturated with water. In three-phase systems, the bulk density should be determined when
the matrix is fully saturated.

113


y refer to points behind (1) and ahead of the front (2), and z, is the front position. The integral
in Equation (11) is evaluated using a procedure developed by Neuman (1976), so that all
parameters of the model are based upon the fundamental measured porous media properties.
K,, is generally taken as one-half the maximum effective conductivity to the NAPL based on field
observation of water infiltration (Bouwer, 1966).

During redistribution, no more liquid is drawn into the profile. The imposed pressure can
obviously be dropped from a model. The gradient of the capillary pressure is also dropped as
it does not affect the mean displacement speed of the front. The sharp front approximation is
retained in KOPT, but now flow is driven only by gravity. Thus the redistribution model is a
kinematic model. The multiphase Darcy's Law, which is used in the previous jump equation 11,
becomes

% = K,(S,,8,) (12)

where the subscripts "o" and "w" refer to NAPL and water respectively, and a fixed amount of
water in the pore space is assumed. In three phase systems, as evident in equation (12), the
effective conductivity to the NAPL phase depends, at least, on the water saturation. Neglecting
hysteresis, the phase conservation equation (7) for the NAPL can be simplified and expanded to

9S, , 1 OK 0S,

—~—2—2 = 9 13)
ot n oS, oz (19)
Application of the method of characteristics gives
DS, : aS, az aS, - 0 (14)
Dt ot dt oz
along characteristics defined by
az _ 1 OK, (15)

dt on aS,

The KOPT model equations (11 and (15)) are all in the form of ordinary differential equations,
which are solved relatively easily by a Runge-Kutta technique (Weaver and Charbeneau, 1992).
Figure 2 shows a schematic representation of KOPT model results. In the figure the NAPL
application begins at time "A" and ends at time "B."._ The results show a sharp front at the
leading edge of the infiltrating NAPL and a continuous wave after infiltration ends. The process
which follows after the infiltration ends is known as redistribution. During redistribution, the
continuous wave is defined by characteristic lines which each represent a constant value of NAPL
saturation. The continuous wave defines the distribution of the NAPL during redistribution, as
well as determining the rate of advance of the various NAPL saturations. In this figure, a
constant infiltration rate is used so that, initially, the sharp front moves at a constant rate. Once
the characteristics intersect the front, its speed slows since the saturation at the front decreases

12


3.1.3 Fluid Saturation

The simultaneous flow of one or more immiscible liquids and a gas, e.g. air, is often
described as unsaturated or partially saturated flow. Under unsaturated conditions the void space
of a porous material may be partially filled with one or more of the liquids with gas filling the
temaining pore space. The amount of the void space which is occupied by each fluid affects the
flow through the porous medium.

The saturation at a point or reference volume, with respect to a particular fluid, is defined
as the fraction of the void volume occupied by that particular fluid. Thus for water the saturation,
S,, is defined as

volume of water in the medium (2)
total volume of voids in the medium

Ww

The saturations of all the fluids occupying the void space must sum to 1.

Fluid phase content can also be expressed as volume fraction of the total volume of a
porous medium in which it is contained. The latter is called the "volumetric water content" or
“phase content," and in most literature is designated by 8. The relationship between the fluid
saturation, S,, and volumetric content, @,, of fluid f is expressed as:

®, = Sn (3)

where n is the effective porosity.

Press

Two fluids are mutually immiscible because the net attractive force between their
molecules differs. For example, the net attractive force between molecules of a gas is generally
lower than that between molecules of a liquid. Likewise the net attractive force between
molecules of a nonpolar liquid is lower that that between molecules of a polar liquid, like water.
Along the interface between the fluids, the differing forces of molecular attraction lead to an
interfacial tension which causes the fluids to remain distinct, i.e., to be immiscible. When the
fluids are in contact with a solid surface, similar interfacial forces exist between the solid and the
fluids. Generally one fluid is more strongly attracted to the solid surface than the other. This fluid
is called the wetting fluid and the other fluid is called the nonwetting fluid. The nature of the
interaction (i.e., which fluid is wetting) depends on the fluid properties and the nature of the
surface.

In a porous medium when two immiscible fluids are in contact, a discontinuity in pressure
exists across the interface that separates them. The difference in pressure is called the capillary
pressure, P,, and is defined as the pressure difference between the nonwetting, P,,,,, and wetting
fluids, P,,:


Flow-Pump Data and Gamma Measurements
5.2. SPILL EXPERIMENTS IN THE LONG COLUMN .......
5.3 RAINFALL EXPERIMENTS IN THE LONG COLUMN

5.4 SPILL EXPERIMENTS IN THE TWO-DIMENSIONAL TANK ...........- 61
5.5 TESTING OF THE COMPUTER MODELS ................ 002s eee? 66
5.6 THE THEORETICAL RELATIONSHIP BETWEEN THE MODELS ........ 82
REFERENCES .... 2.2... tenet ee 88
APPENDIX 1. DESCRIPTION AND TESTING OF THE DUAL-GAMMA SYSTEM ...... 92

1.1. THEORY OF THE DUAL-GAMMA SYSTEM .............0 0000 e eee

1.2 CONFIGURATION OF THE GAMMA SYSTEM ........
1.2.1 Radiation Source ...............-. 0 eee
1.2.2 Solid Scintillation Counting System . .
1.2.3 Traversing Mechanism .........
1.2.4 Test Box 2.0... 66. eee eee

1.3 TESTING PROCEDURES FOR THE GAMMA SYSTEM ..
1.3.1 Modifications of the Gamma System ..........
1.3.2 Determination of Warm-Up Time .............
1.3.3 Overloading of the Detector ................
1.3.4 Random Variation ............. 0. eee eee eee
1.3.5 Detector Sensitivity ........... 00.00. e eee
1.3.6 Determination of the Attenuation Coefficients .................
1.3.7 Dependence of Apparent Attenuation Coefficient on Beam

Strength 0.0... eet nes 108

1.3.8 Attenuation Coefficient of Test Fluid (Soltrol) ..............-.-. 109

1.3.9 Attenuation Coefficient of Sand ......... 02.0.0. eee eee eee 112

1.3.10 Phase Saturation of Multi-Phase Systems -. 112

1.4 ANALYSIS OF TEST RESULTS ............ 00. cece eee 119
APPENDIX 2. EXPERIMENTAL FRONT MOVEMENT DATA ..........--.-+--0+5 122
APPENDIX 3. EXPERIMENTAL PHASE CONTENT PROFILES ...........---.-5- 132

vi


TIME DISTANCE PONDING BACK

DEPTH FRONT

MINUTES cM cM cM

21 101
27 98 12
31 97
36 95
a 93.5
46 91.5
51 89.5 9
56 87.5
61 86.5
71 83
81 80 6
ot 775
101 75
113 72 4
123 69
131 67
141 64 2
151 62
161 59 oO
171 56 417
176 55 110
181 54 107
191 52 106
203 50 105
ait 49 104
221 475 101.5
236 46 97
248 44 91
261 42.5
271 4 89
301 38 86
331 34 81
361 a 74
406 29.5 72

SPILL! #125 SAND 1000 ML SOLTROL
MANUALLY OBSERVED FRONT MOVEMENT

TIME ELEVATION PONDING
DEPTH

MINUTES cM cM

0 120 19

1 115.5,

2 112.5

3 Wt

4 110

5 109 15

6 108 14.5

7 107 14

8 106.5 13.8

9 106 13.6

10 105 13.3

12 103 12.7

15 101 12.3

17 100 12

20 98.5 11.6

125


1.3.3 Overloading of the Detector

The objective of this test was to determine whether exposure of the detector to the un-
attenuated radiation will overload the detector. Reginato (1974) reported that the detector shows
a hysteresis after being exposed to an overload of radiation, i.e. the detector stays saturated (up
to about 30 minutes) even after the radiation beam is taken away from the detector. This would
mean that after any prior exposure of the detector to the un-attenuated source, the detector may
not measure accurately. This problem was investigated with the following procedure (similar to
the one reported by Reginato, 1974). The detector was first exposed to the un-attenuated source
for 5 minutes. Afterwards, the gamma intensity through a standard absorber was measured for
80 minutes. A constant intensity was found which did not decrease over time (Figure 77). It can
be assumed that the radiation source in our experiment is weak enough so it does not cause any
long lasting, over-saturation of the detector, even if there is no absorber between source and
detector.

A second test was conducted to determine whether overloading of the detector led to
fatigue in the detector during the measurement. High radiation causes fatigue in the detector
which leads to unstable readings of the count rate. A high count rate per second (high dead time)
has to be avoided. Repeated measurements were conducted through different absorbers over
a 3-hour period. For an absorber which had little absorption (a thin aluminum sheet), the count
rate for repeated 30 second counts varied widely over the 3-hour test period. The count rate
through a highly absorbing aluminum block, however, stayed fairly constant. It was shown that
for dead times below 10%, detector fatigue does not cause large variations in the Americium
count rate. No such clear limit could be found for the Cesium count rate. It is possible that due
to the higher energy of the Cesium radiation, there is always some degree of detector fatigue.

1.3.4 Random Variation

Fluctuations in the intensity of the gamma radiation are due to the random nature of the
radioactive process. Repeated measurements give the statistical standard deviation of the
process if the measurements are done right after each other, and it is assumed that the detector
sensitivity does not change over a short period of time (Stillwater and Klute, 1988). Repeated
measurements were conducted through different absorber thicknesses. For each absorber the
measurement was repeated seven times. These seven measurements were averaged and the
standard deviation calculated. As expected, the number of counts was found to decrease with
increasing thickness of the absorber. The standard deviation of the measurements for the
Americium source is roughly in the same order of magnitude as the square root of the number
of counts (Table 7). For any natural process which follows a Poisson distribution, the standard
deviation is the square root of the count number. Radioactive decay follows this distribution. By
confirming this result with our measurements, it could be concluded that for measurements
repeated in a short time period, only radioactive decay produces the random variability in the
Americium count rate; and no other random factors influence the measurement. The Cesium
count rate has a higher variability as explained above with detector fatigue due to the high energy
gamma radiation.

103


’ #125 Sand 500m! Soltrol Spill
Water and Soltrol Phase Content

120

100

80

607 Water Fr

Elevation in cm

40

20

Soltrol Front

~0.1 0 on 0.2 03 0.4 0.5
Phase Content

Figure 46. Water and Soltrol phase content for a 500ml soltrol spill in #125 sand. Gamma
scans were taken 168 minutes after spill was started. A constant rainfall rate
of 9.5cm/hour was applied 45 minutes after the spill was started.

It can be seen that there was no significant difference between the column and tank
experiments. The difference between the two tank experiments seems larger than the difference
between tank and column experiment. It can be concluded that the column experiments are a
valid approximation of contaminant movement through the
vadose zone in coarse homogeneous systems. The observed outline of the spill front in the tank
also confirmed the validity of the one-dimensional assumption. The width of the spill area was
30 cm; maximum width of the plume was 40 cm. Thus, lateral spreading due to capillary forces
on both sides was only 5 cm. The lateral spreading relative to the total width will be small for
spills over a large area.

The gamma profiles for the tank experiment are shown in Figure 48. The profiles were
taken along the vertical center line of the spill. The profiles exhibit a leading-edge sharp front and
a slow decrease in phase content behind the front. No data could be collected at the elevation
of 100 cm because a steel bar from the tank frame impaired the measurement. These profiles
show the same characteristics as the profiles measured in the column. _

A rainfall experiment was conducted in the tank with rainfall occurring over the whole
length of the tank, not only in the spill zone. This completely prevented further lateral expansion
of the Soltrol body. On the contrary, a narrowing of the downward moving body was observed.
This was possibly due to the fact that a high rainfall rate of 21 cm hour’ was used. The visually
tracked front movement is shown in Figure 49. This intense rainfall sped up the front movement.

62


Thirdly, the differential equation is solved for the redistribution period after ponding has
ended. For redistribution, the head gradient is redefined as the head gradient between the
infiltrating front and the drainage front:

ah _ hte) - hleq) (22)
az 2, - 2y

where z, = elevation of the drainage front [L]. A mass balance can be written as:

My = (2; - 2g) + 8,24 (23)

where 9, = residual organic phase content [*]. Integrating from z, = Z,. at t = t, gives:

(8, - 89) (Ay - hg) Zz, + He
I
0, In ( Zn * Hy ]

8
t= b+ Gla 22 -
(24)

~ Hy + (8, - 89) (A; - Ag)
6,

where H, =

Equations (19), (21), and (24) in combination define the three-parameter model. The effective
conductivity, K,,, and the capillary drive heads at the two fronts define the three model
parameters.

3.2.4 Comparison Model:

In form, the infiltration portion of the KOPT model is identical to the Three-Parameter
Sharp Front model. However, in their basic formulation, the models differ in two ways. First a
constant water saturation above residual is allowed in KOPT, but in the three parameter sharp
front model the water saturation is at residual. The reason for this assumption in KOPT is that
the effects of any recharge water flowing past trapped NAPL phases should be incorporated in
field scale simulations. It is recognized that the effects of injection of a NAPL may be to displace
water from the pore space (Weaver, 1991). Second, the parameters for KOPT are all determined
from the basic multiphase flow parameters such as hydraulic conductivity, fluid densities and
viscosities, and parameters of the capillary pressure curve. In the three parameter sharp front
model, lumped parameters that are determined by experiment are used for the effective NAPL
conductivity behind the front, K,,, the head at the front h(z,), and the head at the back front, h(z,).

During redistribution, KOPT uses a diffuse drainage wave for the saturation distribution,
so that the assumed distribution shows a smooth variation with depth. The three parameter
sharp front model uses a sharp front for redistribution as indicated in Figure 4. Thus the NAPL
distribution during redistribution appears like a slug. The relationship between the assumptions
for redistribution is discussed further in Section 6.

17


Elevation
cm

120.00
119.00
118.00
117.00
116.00
115.00
114.00
113.00
112.00
111.00
110.00
109.00
108.00
107.00
106.00
105.00
104.00
103.00
102.00
101.00
100.00
99.00
98.00
97.00
96.00
95.00
94.00
93.00
92.00
91.00
90.00
89.00
88.00
87.00
86.00
85.00
84.00
83.00
82.00
81.00
80.00
79.00
78.00
77.00
76.00
75.00
74.00
73.00
72.00
71.00
70.00
69.00
68.00
67.00
66.00
65.00
64.00
63.00
62.00

Time
min

276.00
276.00
277.00
277.00
278.00
278.00
279.00
280.00
280.00
281.00
281.00
282.00
282.00
283.00
283.00
284.00
284.00
285.00
285.00
286.00
286.00
287.00
288.00
288.00
289.00
289.00
290.00
290,00
291.00
291.00
292.00
292.00
293.00
293.00
294.00
294.00
295.00
296.00
296.00
297.00
297.00
298.00
298.00
299.00
299.00
300.00
300.00
301.00
301.00
302.00
303.00
303.00
304.00
304.00
305.00
305.00
306.00
306.00
307.00

Soltrol
Content

0.11
0.11
0.11
0.10
0.10
0.12
0.11
0.13
0.12
0.14
0.14
0.13
0.15
0.14
O15,
0.15
0.15
0.16
0.17
0.17
0.19
0.20
0.21
0.23
0.23
0.23
0.22
0.22
0.21
0.22
0.21
0.21
0.21
0.20
0.20
0.19
0.20
0.20
0.20
0.20
0.19
0.18
0.17
0.16
0.16
0.15
0.15
0.15
0.14
0.14
0.12
0.13
0.11
0.09
0.06
0.04
0.03
0.03
0.03

Time
min

327.00
327.00
328.00
328.00
329.00
329.00
330.00
330.00
331.00
331.00
332.00
333.00
333.00
334.00
334.00
335.00
335.00
336.00
336.00
337.00
337.00
338.00
338.00
339.00
339.00
340.00
341.00
341.00
342.00
342.00
343.00
343.00
344.00
344.00
345.00
345.00
346.00
346.00
347.00
347.00
348.00
349.00
349.00
350.00
350.00
351.00
351.00
352.00
352.00
353.00
353.00
354.00
354.00
355.00
356.00
356.00
357.00
357.00
358.00

136

Soltrol
Content

0.09
0.10
0.11
0.10
0.10
0.11
0.11
0.12
0.11
0.13
0.13
0.12
0.13
0.13
0.14
0.14
0.14
0.15
0.15
0.16
0.17
0.17
0.18
0.19
0.20
0.20
0.19
0.20
0.20
0.21
0.20
0.21
0.20
0.20
0.20
0.19
0.19
0.19
0.19
0.20
0.19
0.18
0.18
0.17
0.16
0.15
0.15
0.15
0.15
0.15
0.14
0.16
0.16
0.15
0.14
0.13
0.09
0.07
0.06

Time
min

375.00
375.00
376.00
377.00
377.00
378.00
378.00
379.00
379.00
380.00
380.00
381.00
381.00
382.00
382.00
383.00
384.00
384.00
385.00
385.00
386.00
386.00
387.00
387.00
388.00
388.00
389.00
389.00
390 00
390.00
391.00
392.00
392.00
393.00
393.00
394.00
394.00
395.00
395.00
396.00
396.00
397.00
397 00
398.00
398.00
399.00
400.00
400.00
401.00
401.00
402.00
402.00
403.00
403.00
404.00
404.00
405.00
405.00
406.00

Soltrol
Content

0.08
0.10
0.10
0.09
0.09
0.10
0.10
0.11
0.10
0.11
0.11
O11
0.12
0.12
0.12
0.13,
0.13
0.13
0.13
0.13
0.14
0.14
0.15
0.17
0.17
0.17
0.17
0.18
0.19
0.19
0.19
0.19
0.19
0.19
0.19
0.18
0.18
0.18
0.18
0.19
0.18
0.17
0.17

0.15,
0.15
0.15
0.15,
0.15
0.15,
0.15
0.15
0.16
0.16
0.16
0.16
0.15
0.14
0.12


1.1 OBJECTIVES

The primary intent of this study was to generate accurate data sets that describe the flow
of a NAPL in the vadose zone. These data can be used to obtain an understanding of the
transport behavior of NAPLs in the vadose zone and to test simulation models.

The specific objectives of this research were:

1) To develop laboratory techniques and instrumentation necessary for the estimation
of soil and fluid parameters critical to porous media flow.

2) To perform parameter estimation for selected sands and fluids.

3) To develop experimental techniques to simulate spills in unsaturated media with
given boundary conditions.

4) To perform spill simulations in one- and two-dimensional systems and generate a
data base on the vertical infiltration of NAPLs in the vadose zone.

5) To test two simple computer models (the Three Parameter Sharp Front Model and

KOPT) against the experimental results.

The objectives were realized through the following steps: A flow pump system was used
to obtain accurate values for the capillary suction-saturation relationship and hydraulic
conductivity. A dual-gamma attenuation system was calibrated for correct phase content
measurements in multiphase systems during spill experiments. The conductivity of a fine sand
(#125) and a coarse sand (#70) to water and a lighter than water organic test fluid, Soltrol, were
determined using a flow pump. The flow pump system and the gamma system were used
independently to obtain the capillary pressure versus saturation relationships for the two sands.
A column setup was developed to conduct spill experiments in homogeneously packed sand that
was residually saturated with water. Spill experiments with Soltrol were conducted in the column
and a two-dimensional tank. Saturation was measured continuously during the spills using the
gamma system. Computer simulations with the CU-Three Parameter Sharp Front model and the
KOPT model were conducted. The experimental results were used to evaluate the two models.


Elevation Time Soltrol Time Soltrol Time Soltrol

cm min Content min Content min Content
95.00 127.00 0.26 163.00 0.25 241.00 0.24
94.00 128.00 0.25 164.00 0.24 241.00 0.23
93.00 128.00 0.24 164.00 0.24 242.00 0.22
92.00 129.00 0.23 165.00 0.23 242.00 0.22
91.00 129.00 0.24 165.00 0.24 243.00 0.23
90.00 130.00 0.22 166.00 0.22 243.00 0,22
89.00 131.00 0.22 166.00 0.23 244.00 0.22
88.00 131.00 0.20 167.00 0.22 245.00 0.21
87.00 132.00 0.20 167.00 0.21 245.00 0.22
86.00 132.00 0.20 168.00 0.20 246.00 0.21
85.00 133.00 0.18 169.00 0.19 246.00 0.20
84.00 133.00 0.17 169.00 0.19 247.00 0.20
83.00 134.00 0.14 170.00 0.19 247.00 0.20
82.00 134.00 0.11 170.00 0.19 248,00 0.20
81.00 135.00 0.06 171.00 0.19 248.00 0.20
80.00 135.00 0.03 171.00 0.15 249.00 0.19
79.00 136.00 0.01 172.00 0.12 249.00 0.18
78.00 136.00 0.01 172.00 0.08 250.00 0.17
77.00 137.00 0.01 173.00 0.04 250.00 0.16
76.00 138.00 0.01 173.00 0.03 251.00 0.15
75.00 138.00 0.01 174.00 0.02 251.00 0.15
74.00 139.00 0.01 174.00 0.02 252.00 0.14
73.00 139.00 0.01 175.00 0.02 253.00 0.11
72.00 140.00 0.00 175.00 0.02 253.00 0.10
71.00 140.00 0.00 176.00 0.01 254.00 0.08
70.00 141.00 0.01 177.00 254.00 0.06
69.00 141.00 0.02 177.00 255.00 0.05
68.00 142.00 0.01 178.00 255.00 0.04
67.00 142.00 0.01 178.00 256.00 0.03
66.00 143.00 0.01 179.00 256.00 0.02
65.00 143.00 0.01 179.00 257.00 0.02
64.00 180.00 257.00 0.01
63.00 180.00 258.00 0.01
62.00 181.00 258.00 0.01
61.00 181.00 259.00 0.01
60.00 182.00 260.00 0.00
5900 182.00 260.00 0.00
58.00 183.00 261.00 0.01
57.00 184.00 261.00 0.00
56.00 184.00 262.00 0.00
55.00 185.00 262.00 0.00
54.00 185.00 263.00 0.00
53.00 186.00 263.00 -0.01
52.00 186.00 264.00 0.00
51.00 187.00 264.00 0.00
50.00 187.00 265.00 0.00
49.00 188.00 265.00 0.01
48 00 188.00 266 00 -0.01
47.00 189.00 267.00 0.00
46.00 189.00 267.00 0.00
45.00 190.00 268.00 0.00
44.00 191.00 268.00 0.00
43.00 191.00 269.00 -0.01
42.00 192.00 269.00 -0.01
4100 192.00 270.00 -0.01
40.00 193.00 270.00 0.01
39.00 193.00 271.00 0.00
38.00 194.00 271.00 0.00
37.00 194.00 272.00 0.00

134


Elevation
cm

74
73
72
71
70
69

199
200
201
201
202
202

Soltrot
Content

0.108384
0.02375
0.004511
0.001703
0.003089
0.00327

177


NAPL Viscosity
Soltrol 220

|

‘Soltrol 220 + 140doheptane (9.1)

Kinematic Viscosity cS

0 a y
15 20 25 30 35 40 45 50
Temperature C

Figure 7. Kinematic viscosity of Soltrol, Soltrol + iodoheptane and water versus
temperature. (Szlag and Illangasekare, 1992)

air from leaking around it. An o-ring alone did not completely seal the system, so epoxy was
used to glue the porous plate in place. The second part of the bottom connection was the fitting
around the sample tube that closed off the bottom of the tube with a flexible mesh to prevent the
sand from leaving the column when the porous plate was removed. The flexible mesh provided
for full contact between the sand and the porous plate. An additional valve was placed in the
side of the bottom fitting to allow for drainage or imbibition of water into the sample without flow
through the porous plate. Permitting part of the flow to bypass the porous plate avoided two
problems. First, a low flow rate, due to the low hydraulic conductivity of the plate, was avoided.
Second, the ceramic porous plate had very fine pores, and fine particles suspended in the water
were found to clog the pores. For these reasons, it was advantageous to drain only the
minimum amount of water through the porous plate.

22


Elevation
om

61.00
60.00
59.00
58.00
57.00
56.00
55.00
54.00
53.00
52.00
51.00
50.00
49.00
48.00
47.00
46.00
45.00
44.00
43.00
42.00
41.00
40.00
39.00
38.00
37.00
36.00
35.00
34.00
33.00
32.00
31.00
30.00
29.00
28.00
27.00
26.00
25.00

Time
min

399.00
399.00
400.00
401.00
401.00
402.00
402.00
403.00
403.00
404.00
404.00
405.00
405.00
406.00
406.00
407.00
407.00
408.00
409.00
409.00
410.00
410.00
411.00
411.00
412.00
412.00
413.00
413.00
414.00
414.00
415.00
415.00
416.00
416.00
417.00
418.00
418.00

Sottrol
Content

0.24
0.23
0.23
0.23
0.22
0.23
0.22
0.23
0.23
0.24
0.23
0.23
0.24
0.23
0.23
0.24
0.23
0.23
0.24
0.22
0.23
0.23
0.20
0.20
0.18
0.18
0.19
0.18
0.18
0.17
0.17
0.18
0.17
0.15
0.13
0.12
0.10

159


Elevation Time Water Soltrot Time Water Soltrol

cm min Content Content min Content Content
120 71 0.06304 0.103591 121 0.020878 0.082231
119 71 0.00051 0.159539 122 0.008307 0.128111
118 72 0.04831 0.113125, 123 0.04982 0.125537
V7 72 0.063109 0.105738 123 0.033241 0.096678
116 73 0.020461 0.140301 124 0.016525 0.103042
115 74 0.05107 0.136033 124 0.060802 0.102015
114 74 0.007961 0.16343 125 0.049795 0.119406
113 75 0.056531 0.149604 126 0.072495. 0.105232
112 75 0.068307 0.149985 126 0.014301 0.136346
WwW 76 0.043392 0.16961 127 0.079443 0.122078
110 77 0.021388 0.184017 127 0.09504 0.115977
109 77 0.070542 0.17769 128 0.077831 0.132534
108 78 0.124284 0.186548 129 0.089806 0.134665
107 78 0.098089 0.23377 129 0.025054 0.182857
106 83 0.034825 0.293614 134 0.081933 0.250379
98 84 0.103537 0.251334 135 0.074515 0.222408
97 84 0.040309 0.278249 135 0.065986 0.231579
96 85 0.073002 0.245978 136 0.034469 0.238025
95 86 0.127658 0.224697 136 0.029531 0.237577
94 86 0.194962 0.206828 137 0.092313 0.213862
93 87 0.102187 0.241174 138 0.02471 0.25015
92 87 0.126211 0.248295 138 0.116506 0.228601
a1 88 0.147292 0.260559 139 0.173677 0.240552
90 89 0.117993 0.276845 139 0.139867 0.250609
89 89 0.091245 0.250434 140 0.070315 0.264513
88 90 0.035697 0.241383 141 0.136546 0.215304
87 90 0.07336 0.156725, 141 0.080838 0.245786
86 ot 0.046362 0.070324 142 0.058556 0.257572
85 92 0.049721 0.017088 142 0.14331 0.233878
84 92 0.050697 -0.00288 143 0.120687 0.234752
83 93 0.066847 0.01217 144 0.043572 0.227313
82 93 0.047436 0.01241 144 0.048251 0.113123
81 94 0.04072 0.01165, 145 0.004174 0.036761
80 95 0.076525 -0,02626 145, 0.056081 0.01368
79 95 0.072024 -0.01669 146 0.003983 0.002256
78 96 0.083231 -0.0301 147 0.070559 0.02605
77 96 0.115089 0.04043, 147 0.010544 0.001978
76 97 0.119113 1.04369 148 ~0.04346 0.014748
75 98 0.084432 02904 148 0.085139 -0.02502
74 98 0.054914 1.00424 149 0.020909 0.005849
73 99 0.101987 01557 150 0.095654 -0.01682
72 99 0.078151 ~0.00455 150 0.049965, 0.005506
71 100 0.080859 -0.01488 151 0.052975 0.002653
70 101 0.077882 0.01273 152 0.044588 ~0.00571
69 101 0.011603 0.00028 152 0.150569 0.04915.
68 102 0.047944 ~0.00919 153 0.044848 -0.00488
67 102 0.03383 0.002316 153 -0.019 0.007031
66 103 0.018084 0.00288 154 0.063714

65 104 0.041562 -0.00488 155 0.04021

64 104 0.072307 -0.02005, 155 0.051499

63 105 0.027178 0.000315. 156 0.149511

62 105 0.119163 0.02432 156 0.003151

61 106 0.096294 0.0154 157 0.092654

60 107 0.081111 -0.00431 158 0.065792

59 107 0.11991 0.01067 158 0.073981

58 108 0.116474 -0.00949 159 0.153732

57 109 0.046988 0.007862 159 0.039614

179


Stillwater, R., and A. Klute, 1988. “Improved Methodology for a Collinear Dual-Energy Gamma
Radiation System," Water Resources Research, Vol. 24, No. 8, pp 1411-1422.

Szlag, D.C., and T.H. Illangasekare, 1992. "Experimental Investigation in Modeling of Immiscible
Liquid Entrapment n Porous Media," Proceedings of Conference on Hazardous Waste Research.

United States Environmental Protection Agency, 1992. "Evaluation of Ground-Water Extraction
Remedies: Phase II," Summary Report, USEPA, Office of Emergency and Remedial Response,
Vol. 1, Washington, D.C. PB92-963346.

Weaver, J.W., 1989. "Multiphase Flow Modeling by the Method of Characteristic Approximations,"
EPA/EPRI Environmental Research Conference, Groundwater Quality and Waste Disposal,
Washington, D.C.

Weaver, J.W., 1991. “Approximate Multiphase Flow Modeling by Characteristic Methods," US
Environmental Protection Agency, EPA/600/2-91/015.

Weaver, J.W., R.J. Charbeneau, and B.K. Lien, 1994a, "A Screening Model for Nonaqueous
Phase Liquid Transport in the Vadose Zone Using Green-Ampt and Kinematic Wave Theory’,
Water Resources Research, 30(1), 93-105.

Weaver, J.W., B.K. Lien, R.J. Charbeneau, J. Tauxe, J. Provost, 1994b. "The Hydrocarbon Spill
Screening Model (HSSM) Users Guide", US Environmental Protection Agency,
EPA/600/R-94/039a.

van Genuchten, M.T., 1980. "A Close-for Equation for Predicting the Hydraulic Conductivity of
Unsaturated Soils," Soil Science Society of America Journal, Vol. 44, pp 892-898.

91


Elevation
com

101.00
100.00
99.00
98.00
97.00
96.00
95.00
94.00
93.00
92.00
91.00
90.00
89.00
88.00
87.00
86.00
85.00
84.00
83.00
82.00
81.00
80.00
79.00
78.00
77.00
76.00
75.00
74.00
73.00
72.00
71.00
70.00

120.00
119.00
118.00
117.00
116.00
115.00
114.00
113.00
112.00
111.00
110.00
109.00
108.00
107.00
106.00
105.00
104.00
103.00
102.00
101.00
100.00

99.00

98.00

97.00

96.00

Time
min

44.00
44.00
45.00
46.00
46.00
47.00
47.00
48.00
48.00
49.00
49.00
50.00
50.00
51.00
51.00
52.00
53.00
53.00
54.00
54.00

114.00
115.00
115.00
116.00
116.00
117.00
117.00
118.00
118.00
119.00
119.00
120.00
120.00
121.00
122.00
122.00
123.00
123.00
124.00
124.00
125.00
125.00
126.00
126.00
127.00

Soltrol
Content

0.27
0.28
0.28
0.28
0.28
0.27
0.26
0.22
0.15
0.07
0.02
0.00
0.01
0.00
0.01
0.00
0.00
0.00
0.00
0.00

0.16
0.16
0.17
0.16
0.16
0.18
0.18
0.19
0.19
0.21
0.22
0.23
0.24
0.24
0.25
0.26
0.26
0.27
0.28
0.27
0.28
0.28
0.28
0.28
0.28

Time
min

68.00
68.00
69.00
69.00
70.00
71,00
71.00
72.00
72.00
73.00
73.00
74.00
74.00
75.00
75.00
76.00
76.00
77.00
78.00
78.00
79.00
79.00
80.00
80.00
81.00
81.00
82.00

150.00
150.00
151.00
151.00
152.00
153.00
153.00
154.00
154.00
155.00
155.00
156.00
156.00
157.00
157.00
158.00
158.00
159.00
159.00
160.00
161.00
161.00
162.00
162.00
163.00

133

Soltrol
Content

0.27
0.28
0.28
0.27
0.28
0.27
0.26
0.24
0.23
0.22
0.21
0.19
0.15
0.08
0.04
0.02
0.00
0.00
0.00
0.00
0.01
0.00
0.00
0.00
0.01
0.01
0.01

0.13
0.14
0.15,
0.14
0.14
0.16
0.16
0.16
0.16
0.18
0.19
0.19
0.20
0.21
0.22
0.23
0.23
0.25
0.26
0.27
0.28
0.28
0.28
0.28
0.27

Time
min

96.00

96.00

97.00

97.00

98.00

98.00

99.00

99.00
100.00
100.00
101.00
101.00
102.00
103.00
103.00
104.00
104.00
105.00
105.00
106.00
106.00
107.00
107.00
108.00
108.00
109.00
110.00
110.00
111.00
111.00
112.00
112.00

228.00
228.00
229.00
229.00
230.00
230.00
231.00
231.00
232.00
232.00
233.00
233.00
234.00
234.00
235.00
235.00
236.00
237.00
237.00
238.00
238.00
239.00
239.00
240.00
240.00

Soltrol
Content

0.27
0.28
0.27
0.27
0.28
0.27
0.25
0.24
0.23
0.23
0.22
0.21
0.21
0.19
0.17
0.14
0.10
0.06
0.03
0.01
0.00
0.00
0.00
0.00
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01

0.11
0.12
0.13
0.12
0.12
0.13
0.13
0.14
0.13
0.15,
0.15,
0.15
0.16
0.17
0.16
0.17
0.18
0.19
0.20
0.21
0.23
0.24
0.25
0.26
0.25


When the boundary transition is reversed (from S,, to S,), the characteristics do not cross
and a fan-shaped wave is created. This situation occurs at the end of the NAPL release and is
illustrated in Figure 69 and Figure 70. In Figure 69 the boundary transition from S,, to S, is
gradual, resulting in a continuous wave which originates from a zone along the surface. When
the boundary transition is abrupt (Figure 70), the wave is said to be a centered simple wave. It
is remarkable that in this case, discontinuous boundary data do not generate a discontinuity in
the solution. In general the occurrence of a discontinuity in the solution depends both on the
boundary data and the wave speed, which in this case is determined by the dK,/oS, function.

transition
Sy k¢—> S.

Depth

Time

Figure 69. Continuous boundary transition from high to low saturation.

The KOPT model is based on this assumed scenario: an abrupt jump up in saturation
followed by an abrupt jump down in saturation. The model results are seen to be a composite
of the discontinuity of Figure 68 and the continuous wave of Figure 70. When profiles are
constructed from the solution, they have low saturations near the surface since their
characteristics move slowly. High saturations are found deeper in the profile as their
characteristics move relatively fast. The profiles end at the sharp front which can be viewed as
enforcing a mass balance condition.

If the profiles are perturbed, the sharp front tends to persist; because on the front, high
saturations move faster than low saturations (Figure 71). The speed difference assures that the
characteristics do not separate and spread the front. The neglected capillary pressure gradient
term is balanced by the tendency of the front to persist. On the trailing edge, the saturations tend
to separate because of the same speed difference. Thus the gravity term tends to create sharp
fronts on the leading edge of the infiltrating liquid and also contributes to spreading of the wave
on the trailing edge.

84


SECTION 2
CONCLUSIONS AND RECOMMENDATIONS

The objective of this project was to generate data for testing unsaturated zone NAPL flow
models. Procedures were developed for measuring transient NAPL and water flow in the
unsaturated zone using dual gamma attenuation. Methods were also developed for measuring
necessary model parameters using the flow pump. The gamma attenuation system provides a
convenient way for the non-destructive measurement of fluid phase contents in laboratory soil
columns and two-dimensional soil tanks. Phase content of one- and two-phase systems can be
measured during the experiment. However, great care has to be taken to obtain accurate
measurements when using the gamma system. The suction-saturation curves measured with the
gamma system agreed well with those measured with the flow pump setup. Hydraulic
conductivity was measured with the flow pump setup.

A number of spill experiments were conducted in a one-dimensional column and in a two-
dimensional tank. The sand was packed dry, completely saturated with water and then drained
to residual saturation. Then a measured volume of NAPL was applied at the surface. These spill
experiments conducted on residually water saturated soils showed that the Soltrol front moves,
in some cases, quickly during infiltration, when there is Soltrol ponded at the soil surface. Once
the ponding ends the rate of movement of the front decreases rapidly. The leading edge of the
LNAPL body remained largely sharp, while the trailing edge became diffuse. Although the water
content in the columns was reduced to residual before beginning the experiment, the Soltrol
mobilized some of the residually entrapped water. Release of water was not unexpected because
the Soltrol/water interfacial tension is less than half of the surface tension of water.

The simulated rainfall experiments demonstrated that incoming water has the ability to
displace mobile NAPL into a bank moving ahead of the water front. Once the NAPL saturation
in the bank is reduced below the maximum, the water bypasses the NAPL front. The simulated
rainfalls, however, did not completely remove the NAPL, demonstrating that some NAPL remained
trapped in the unsaturated zone even under the action of infiltrating rainwater. Infiltration of the
NAPL, on the other hand, sometimes caused displacement of the residual pore water.

Simulations of the transient column experiments were performed using the three-
parameter model of the University of Colorado and the KOPT model of RSKERL. These models,
although apparently based on diverse assumptions, are related by the fact that they are both
generalized method of characteristics solutions for a pulse release of NAPL at the ground surface.
With appropriate choices of parameter values, both models can be made to reproduce the
observed NAPL front position as a function of time. The three-parameter model requires a fitting
procedure for determination of its input parameters, so that accurate application of the model to
situations with no measured front locations is difficult. This model assumes that the NAPL
saturation behind the front remains fixed during redistribution. This assumption caused the model
to over predict the front position when parameters were used from the previous experiment to
simulate a subsequent experiment. To apply this model without field calibration, it i necessary
to develop methods to estimate the model parameters directly from the soil-water-NAPL
characteristics. KOPT was seen to match the qualitative behavior of the NAPL front by using

4


Lenhard, R.J. and J.C. Parker, 1987. “Measurement and Prediction of Saturation and Pressure
Relationships in Three-Phase Porous Media Systems," J. Contam. Hydr., Vol. 1, pp 407-424.

McMaster, W.H., N. Kerr Del Grande, J.H. Mallet, J.H. Hubbell, 1969. “Compilation of X-ray cross
sections," Section Il, Lawrence Radiation Laboratory, University of California, Livermore.

Manna, M., 1991, Suction-Saturation Measurements in Soils Using the Flow Pump Technique,
Masters Thesis, University of Colorado, Boulder, Colorado.

Mualem, Y., 1976, "A New Model for Predicting the Hydraulic Conductivity of Unsaturated Porous
Media", Water Resources Research, Vol. 12, pp 513-522.

Muskat, M., R.D. Wykoff, H.G. Botset, and M.W. Meres, 1937. "Flow of Gas-Liquid Mixtures
Through Sands," Transactions, American Institute of Mining, Metallurgical and Petroleum
Engineers, Vol. 123, pp 69-96.

Neuman, S. P., Wetting front pressure head in the infiltration model of Green and Ampt, Water
Resources Research, 12, 564-566, 1976.

Nofziger, D.L., and D. Swartzendruber, 1974. "Material Content of Binary Physical Mixtures as
Measured with a Dual Energy Beam of X-Rays," J. Appl.Physics, Vol. 45, pp 5443-5449.

Oak, M.J., and R. Ehrlich, 1985. A New X-Ray Absorption Method for Measurement of Three-
Phase Relative Permeability," SPE 14420, Presented at the 60th Annual Conference of the
Society of Petroleum Engineers, Las Vegas.

Osborne, M., and J. Sykes, 1986, "Numerical Modeling of Immiscible Organic Transport at the
Hyde Park Landfill," Water Resources Research, Vol. 22, No. 1, pp 25-33.

Peaceman, D., 1977. “Fundamentals of Numerical Reservoir Simulation," Development in Petro.
Science 6, Elsevier Publishing Co., pg 167.

Powers, M.C., 1953. "A New Roundness Scale for Sedimentary Particles," Journal of
Sedimentary Petrology, Vol. 23, No. 2, pp 117-119.

Reginato, R.J., 1974. “Count Rate Instabilities in Gamma Ray Transmission Equipment," Soil Sci.
Amer., Vol 38, pp 156-157.

Reible, D.D., and T.H. Illangasekare, 1989. “Subsurface Processes of Non-Aqueous Phase
Contaminants," Reviewed Book Chapter in Intermedia Pollutant Transport Modeling and Field
Measurement, Editors D. Owen and I. Keplan, Plenum Press.

Reible, D.D., T.H. Illangasekare, D.V. Doshi, and M.E. Malhiet, 1990. “Infiltration of Immiscible
Contaminants in the Unsaturated Zone," Ground Water, Vol. 28, No. 5, pp 685-692.

Smith, R.E., 1983, "Approximate Soil Water Movement by Kinematic Characteristics", Soil Science
Society of America Journal, Vol. 47, pp 3-8.

90


Elevation
cm

120

Time
min

109
110
110
111
112
112
113
113
114
115
115
116
116

172
173
174
174
175,
175
176
177
177
178
178
179
180
180
185
186
186
187
187
188
189
189
190
190
191
192
192
193
193
194
195
195,
196
196
197
198
198
199
199
200
201
201
202
202
203

Water
Content

0.049074
0.043412
0.153542
0.150973
0.046848
0.126721
0.063305
0.058329
0.034526
0.023134
0.042207
~0.04709
0.01048

0.001371
0.039336
0.014275
0.031769
0.004804
0.056856
0.023833
0.004239
0.044059
0.091984
0.061844
0.040491
0.03982
0.073496
0.018644
0.10056
0.076629
0.120584
0.00514
0.098119
0.055873
0.115753
0.108956
0.042962
0.098682
0.004156
0.0851
0.100481
0.113349
0.10784
0.188303
0.078859
0.035891
0.068935
0.062215
0.053684
0.050216
0.059099
0.048239
0.086785
0.04755
0.109883
0.105132
0.040983
0.010541

Soltrol
Content

0.003027
0.008223
0.02176
-0.01907
0.00691
0.01329
0.00172
0.01178
~0.00333
0.00822
0.01424
0.027945
0.025293

0.072323
0.099751
0.091799
0.081291
0.097076
0.088281
0.115389
0.131317
0.121062
0.101434
0.116314
0.130626
0.140506
0.140322
0.226593
0.187849
0.198936
0.177334
0.218495
0.189425
0.218545
0.216521
0.248787
0.278782
0.227986
0.257825
0.23175,
0.236072
0.240667
0.2487
0.206529
0.244043
0.235064
0.198469
0.093804
0.011078
-0.00489
-0.0205
0.01192
-0.01809
0.001841
0.01592
~0.0243
~0.00327
0.007763

180

Time
min

160
161
161
162
162
163
164
164
165
165
166
167
167

223
224
224
225
226
226
227
227
228
229
229
230
230
231
236
236
237
238
238
239
239
240
241
244
242
242
243
244

245
245
246
247
247
248
248
249
250
250
251
251
252

253
254

Water
Content

0.091239
0.095945,
0.067757
0.099333
0.102863
0.056211
0.085473
0.066734
0.01412
0.137599

0.01705
0.060079
0.091521

0.050346
0.051439
0.003084
0.038798
-0.00306
0.058709
0.019412
0.063083
0.035113
0.055456
0.0528
0.035441
0.056993
0.04433
0.054956
0.043834
-0.0308
0.151635
0.033177
0.091142
0.041862
0.102707
0.182012
0.139889
0.119859
0.041539
0.089311
0.083117
0.064025,
0.106715
0.042896
0.071397
0.031108
0.02831
0.131387
0.038204
0.053143
0.137887
0.135458
0.07991
0.024185
0.108426
0.013208
0.114873,
0.01383

Soltrol
Content

0.00682
-0.00277
-0.00582
-0.00669
0.01192
0.004683
-0.00934
-0.00508
0.009975
-0.03535
0.004333
0.01286
-0.01684

0.046257
0.080425
0.084552
0.068961
0.095195
0.079487
0.105965,
0.086636
0.107674
0.104245
0.108858
0.123088
0.119735,
0.140363,
0.188828
0.17887
0.20167
0.139383
0.180793
0.173322
0.205556
0.202114
0.211981
0.218448
0.206367
0.230724
0.218558
0.223075,
0.251456
0.248232
0.262097
0.235311
0.249845
0.253589
0.202461
0.19935,
0.110735
0.01626
0.03503
0.01364
0.000966
-0.00986
0.012928
-0.03171
0.013029


combinations of one solid phase and one liquid phase. With two liquid phases, three unknowns
in only two equations would be present. Solving the two equations simultaneously yields
solutions analogous to Equations (37) and (38).

i) i)
In -€2 - In 42
a 2 ee (42)
” (Ucwtas - Uawbes)X
i) i)
Usyin 42 - Uyyin 22
° - cw |, ‘AW I (43)
es

(YewHas - Uawbes)*

TT

El lear ing Plate. | 2
* ze
1; _|&
as | a | aa
| ]

i

7

9.00

Figure 72. Radiation source housing (after Armbruster, 1990).

95


Elevation
cm

Time
min

1653
1654
1654
1655
1655
1656
1657
1657
1658
1658
1659
1660

Water
Content

0.203331
0.266334
0.223111
0.148463
0.169797
0.122262
0.025402
0.092049
0.055426
0.158824
0.086434
0.102159

Soltrol
Content

0.15988

0.13949
0.144302
0.160737
0.148268
0.149697
0.131732
0.038992
0.016816

0.02134
0.000933
0.003652

185 wv-s. Government PRINTING OFFICE: 1994 - 650-006/00216


Attenuation Coefficient of Soltrol
Am

slope: 0.632 1/cm

Absorbance In(lo/I)
-

1 T T T T r T T ,

2 3 4 5 6 7 8 9 10
Sample Thickness in cm

Figure 81. Attenuation coefficient of Soltrol and iodoheptane mixture (Am).

Attenuation Coefficient of Soltrol
Cs

°
N

S
o

S
uv

slope: 0.056 1/cm

o 9
ag

°
re

Absorbance In(lo/I)

2 3 4 5 6 7 8 9 10 W
Sample Thickness in cm

Figure 82. Attenuation coefficient of Soltrol and iodoheptane mixture (Cs).

11



#125 SAND 500ml SOLTROL 10/15/91

\ VAs Al LTV EV 1
ao Ne a \E VT V ET

60 LH
rt |
in|

100

30

=
*

|

[| ee
| —+

50 +

oo VV Ty
10 \ fe

ELEVATION IN cm

[Pe PONONG

0
0 50 100 150 200 250 300 350 400 450
TIME IN MINUTES

— SCANS. PRFORMED

Figure 41. Front elevation versus time for 500ml Soltrol spill in #125 sand, included are
gamma scanning time and location.

surface, which led to a constant water flux in the sand, and the observed movement of the water
front. Even when the water enters the region where there was still large amounts of the slower
moving Soltrol, the water phase did not slow down.

The graphs (Figure 43 and Figure 44) show a distinct bend in the Soltrol front where the
water front began to push the Soltrol slug down. Later, however, the water front caught up with
the Soltrol front. The point in time when the water front caught the Soltrol was determined by the
amount of rainfall and the time when the rainfall started. The water front passed the Soltrol front
when the phase content in the Soltro! slug decreased below the maximum saturation. The
reduction in Soltrol content was attributable to the residual Soltrol content and the finite volume
of the spill; as the front got deeper, more of the spilled volume of the Soltrol was trapped at the
residual saturation. Eventually the phase content behind the front decreased because of
continuity. This behavior can be best seen on the phase content profiles (Figure 38 and
Figure 39).

58


No. 70 Sand 9 Scm Soltrol Ponding Depth

' ra “4

@

Elevotion (cm)
2

40} w z 3
6 & & 8
3 3
20} 3 3 3 3
o
<- 03 ->

Phase Content

Figure 48. Set of phase content profiles for 9.5cm Soltrol spill in # 70 sand in the tank.

#70 Sand Soltrol Spill
Starting with Ponding Depth 9.5cm

Soltrol Front

Rain Stort
at 1340 Minutes

Elevation in cm

80
Rain End
70 | at 1455 Minutes
60 ra
50
40
ie) 500 1000 1500 2000 2500 3000

Time in Minutes

Figure 49. Soltrol spill front movement in tank with rainfall application.

64


dynamic viscosity.

The concept of relative permeability was first postulated by Muskat et al. (1937). Their
work consisted of extending Darcy's law to two-phase systems. The term relative permeability
is used to describe the effect of the degree of saturation on the hydraulic conductivity of a
particular phase. It is also defined as the ratio of the permeability of a fluid at a specific
saturation to the permeability under completely saturated conditions. Relative permeabilities, for
wetting, k,,, and non-wetting phases, k,,,, are given by:

Ky Kaw (6)

The sum of the relative permeabilities for all phases is always less than one, because of
interference between phases sharing the same flow channels. This interference is directly related
to the wettability characteristics of the soil grains and the fluids (Honarpour et al., 1986).

3.1.7 i tions in Porous

The sharp front models presented below are based on a simplified version of the mass
conservation law for multiphase flow system. (See, for example, Abriola and Pinder, 1985).
Assuming that the porosity and density of each fluid are constants, and that the flow is one
dimensional gives a phase conservation equation for fluid f

not + 8%
ot oz

= 0 (7)

where q, is the darcy flux of fluid f. In equation (7), effects of dissolution, volatilization and
partitioning of the NAPL are ignored. Such phenomena can be incorporated into a simplified
model by assuming that they do not alter the fluid properties of the NAPL and that the NAPL is
not completely lost by these processes (Weaver et al., 1994a).

The flux, q,, in equation (7) is given by a modified form of Darcy's law ((1)) that includes
multiphase phenomena; that is, it includes the capillary pressure and relative permeability:

kk, oP,
= - (:)
iad [0 oz ®)

where k, is the relative permeability of the matrix to fluid f, P, is pressure in phase f and z has
been taken as positive downward. The capillary pressure is included implicitly in equation (8)
as each fluid pressure P, is related to the other fluid pressures through capillary pressure
relationships (equation (4)).


Spill |

#125 Sand 1000 mi Soltrol Spill

Elevation
com

120.00
119.00
118.00
117.00
116.00
115.00
114.00
113.00
112.00
111.00
110.00
109.00
108.00
107.00
106.00
105.00
104.00
103.00
102.00
101.00
100.00
99.00
98.00
97.00
96.00
95.00
94.00
93.00
92.00
91.00
90.00
89.00
88.00
87.00
86.00
85.00
84.00
83.00
82.00
81.00
80.00
79.00
78.00
77.00
76.00
75.00

Time
min

15.00
16.00
16.00
17.00
17.00
18.00
18.00
19.00
19.00
20.00
20.00
21.00
22.00
22.00
23.00
23.00
24.00
24.00
25.00
25.00
26.00
26.00
27.00
27.00
28.00
28.00
29.00
29.00
30.00
31.00
31.00

Soltrol
Content

0.32
0.32
0.32
0.32
0.31
0.32
0.31
0.32
0.27
0.26
0.26
0.26
0.26
0.26
0.26
0.26
0.26
0.26
0.26
0.26
0.26
0.26
0.25
0.18
0.07
0.01
0.01
0.02
0.01
-0.01
0.02

Bulk Density grav.: 1.58g cm*

Porosity: 0.40

Temperature Soltrol: 25°C
Residual Water Content: 0.08.

Time
min

32.00
33.00
33.00
34.00
34.00
35.00
36.00
36.00
37.00
37.00
38.00
38.00
39.00
39.00
40.00
40.00
41.00
41.00
42.00
42,00
43.00
43.00
45.00
45.00
46.00
46.00
47.00
47.00
48.00
48.00
49.00
49.00
50.00
50.00
51.00

153

Soltrol
Content

0.26
0.27
0.32
0.32
0.31

0.32
0.31

0.31

0.31

0.31

0.31
0.32
0.31
0.31
0.31
0.31
0.32
0.32
0.31
0.31
0.31
0.31
0.31
0.31
0.31
0.31
0.31
0.31
0.31
0.31
0.29
0.25
0.13
0.05
0.01

Time
min

52.00
53.00
53.00
54.00
54.00
55.00
55.00
56.00
57.00
57.00
58.00
58.00
59.00
59.00
60.00
60.00
61.00
61.00
62.00
62.00
63.00
63.00
64.00
64.00
65.00
66.00
66.00
67.00
67.00
68.00
68.00
69.00
69.00
70.00
70.00
71.00
71.00
72.00
72.00
73.00
73.00
74.00
75.00
75.00
76.00
76.00

Soltrol
Content

0.32
0.31
0.32
0.31
0.31
0.32
0.32
0.31
0.31
0.31
0.31
0.31
0.31
O31
0.31
0.30
0.31
0.31
0.30
0.30
0.30
0.30
0.30
0.31
0.30
0.31
0.30
0.30
0.30
0.30
0.30
0.30
0.31
0.31
0.30
0.30
0.28
0.26
0.26
0.25
0.24
0.17
0.07
0.00
0.01
0.01


APPENDIX 1 DESCRIPTION AND TESTING OF THE
DUAL-GAMMA SYSTEM

An automated gamma system was used for measurement of saturation and bulk density.
Theory, configuration and testing of the gamma system are described in this appendix.

1.1 THEORY OF THE DUAL-GAMMA SYSTEM

Use of gamma spectroscopy for the measurement of bulk densities and fluid saturation
of porous media is based on the exponential law for monoenergetic gamma radiation. This is a
modified form of Lambert's law for light transmission through an absorbing medium. In gamma
spectroscopy, the rate of energy transmission is described in terms of counts or counts per unit
of elapsed time. A count refers to a recorded gamma emission. If the detected count rate can
be compared with and without absorbing material present, it can be seen that the count rate is
lower with absorbing material present. If the effective absorption rate of the material is known,
then it is possible to predict the mass (or volume) of the material.

If , represents the initial energy intensity emitted from a gamma source and entering an
absorbing material, then the energy, /, emerging from the opposite side is given by:

I= Lever (30)

where pJ is the mass attenuation coefficient of the material, p is the material density and x is the
path length through the material traversed by the gamma energy. The emerging intensity / may
be given in terms of either a count rate or as a total number of counts. For our application, / is
equal to the total number of counts recorded within a specified energy range or “region of
interest."

Essential to the application of gamma theory is the knowledge of the energy absorbing
characteristics of the materials present. Attenuation rates of gamma radiation differ widely
between air, different fluids and soils. It is important to note that for our application the
attenuation of gamma radiation by air is assumed to be negligible. This can be justified by noting
that the attenuation coefficient of air is of the same order of magnitude as the attenuation
coefficient for water (McMaster et al., 1969). However, air density is about three orders of
magnitude smaller than the density of water; and thus, attenuation by air is about three orders
of magnitude smaller than attenuation by water.

The mass attenuation coefficient, 1, of a material describes the rate of gamma energy
absorption. Units of measurement of the mass attenuation coefficient are in cm’/g. This
coefficient differs not only between materials but also for different energy levels of sources of
gamma radiation (i.e. Americium and Cesium sources used in our dual-gamma system). Mass
attenuation coefficients can be determined using Equation (30) and solving for py. The procedure
which will be used to determine the attenuation coefficient will be described later.

92


c | § Infiltration
rot 8 Profile
fo) 5 |
a ro
a
xa
i
| = Redistribution
Profile
L _
0

Liquid Saturation

Figure 3 Schematic of a KOPT depth vs. saturation profile

3.2.3 _Three-Parameter Sharp Front Model

The Three-Parameter Sharp Front Model is a lumped parameter model which adopts the
Green-Ampt (Green and Ampt, 1911) formulation used in infiltration processes of water in
unsaturated soils. The model assumes a piston front of the chemical completely displacing the
air in the available pore space. The available pore space is the total pore space minus the pore
space used by residual water, which is assumed to be immobile. The model also assumes a
sharp drainage front during redistribution. Thus, the medium is completely saturated between the
two fronts and at residual oil and water saturation behind the drainage front (Figure 4).

This idea is put into a mathematical form by combining Darcy's Law with the continuity
equation (Illangasekare and Reible, 1987a; Reible et al., 1990):

14


d) Sand #70 and Soltrol (Figure 24)

The scanning time for this experiment was 20 seconds at every point. Two scans were

repeated at every location. After 2 scans, the gamma system moved 1.25 cm vertically down to
the next scanning location.

The porosity of the sand as determined gravimetrically was 0.49. The average porosity
calculated from the Americium spectrum was 0.52. The residual saturation was found to be
approximately 0.2; the height of the capillary fringe was 0.1 m. The gamma data show the same

entry pressure as the Brooks and Corey suction-saturation curves derived from the flow pump
data with approaches 1 and 2.

#70 Sand

Soltrol—-Air Capillary Pressure Curve

SUCTION HEAD (m)

“0.00 0.20 0.40 0.60 0.80 1.00 1.20
SATURATION

TM Gamma System (Am) —+~ Model Parameter (1) —*- Model Parameter (2)

Figure 24. Suction-saturation profile for #70 sand and Soltrol-air.

43


REFERENCES

Abriola, L.M., and G.F. Pinder, 1985. "A Multiphase Approach to the Modeling of Porous Media
Contamination by Organic Compounds, 1. Equation Development," Water Resources Research,
Vol. 21, No. 1, pp 11-18.

Armbruster, E.J., 1990. "Study of Transport and Distribution of Lighter than Water Organic
Contaminants in Groundwater," Masters Thesis, University of Colorado, Boulder, Colorado.

Baehr, A., and M.Y. Corapcioglu, 1984. “A Predictive Model for Pollution from Gasoline in Soils
and Groundwater," Petroleum Hydrocarbons and Organic Chemicals in Ground Water, National
Water Well Association, Washington, Ohio. No. 225, American Chemical Society.

Bazaraa, A.S., and H.J. Morel-Seytoux, 1979. “Users Manual for a Gamma Attenuation System
for the Determination of Water Content in Soils," Report HYDROWAR Program, Eng. Res. Cent.,
Colorado State Univ., Fort Collins, Colorado.

Bear, J., 1972. “Dynamics of Fluids in Porous Media," Dover Publications Inc., New York, New
York.

Bouwer, H., 1966. "Rapid field measurements of air entry value and hydraulic conductivity of soil
as significant parameter in flow system analysis", Water Resources Research, 2, 729-738.

Brooks, R.H., and A.T. Corey, 1966. “Hydraulic Properties of Porous Media," Hydrology Papers,
No. 3, Colorado State University, Fort Collins, Colorado.

Burdine, N.T., 1953. “Relative Permeability Calculations from Pore-Size Distribution Data," Petr.
Trans., Am. Inst. Mining Metal. Eng., Vol. 198, pp 71-77.

Campbell, J., 1992. "Nonaqueous Phase Liquid (NAPL) Flow Through Heterogeneous Porous
Media: Experimental Study and Conceptual Model Development," Masters Thesis, University of
Colorado at Boulder.

Charbeneau, R.J., 1984, "Kinematic models for soil moisture and solute transport," Water
Resources Research, Vol. 29, pp 699-706.

Charbeneau, R.J., J.W. Weaver, and V.J. Smith, 1989. “Kinematic Modeling of Multiphase
Transport in the Vadose Zone," EPA /600/2-89/035.

Cathey, L., 1958. "Fatigue in Photomultipliers, "RE Transactions on Nuclear Science, Vol. NS-5,
pp 109-114.

Faust, C.R., 1985. "Transport of Immiscible Fluids within and below the Unsaturated Zone: A
Numerical Model," Water Resources Research, Vol. 21, No. 4, pp 587-596.

88


length of the column at 1.0 cm intervals. In the first Gamma scan, taken before the introduction
of water, the attenuation was measured along the 20 cm long empty portion of the column, as
well as the sand-packed portion (Figure 11). In the second scan, taken after saturating the
column, the attenuation was measured through the part of the empty column, the liquid filled
portion, and the saturated sand pack (Figure 12). In the third scan, taken after draining the
column, the attenuation was measured through the empty column, and the partly saturated sand
(Figure 13).

FIRST SCANNING

ef
eae | | ea sen

$00b66000000000060600
$98$60608065566000000!

a

Figure 11. Setup for first scan through dry sand.


Elevation
om

80.00
78.00
76.00
74.00
72.00
70.00
68.00
66.00
64.00
62.00
60.00
58.00
56.00
54.00
52.00
50.00
48.00
46.00
44.00
42.00
40.00
38.00
36.00
34.00

Elevation
cm

120.00
118.00
116.00
114.00
112.00
110.00
108.00
106.00
104.00
102.00
100.00
98.00
96.00
94.00
92.00
90.00
88.00
86.00
84.00
82.00
80.00
78.00
76.00
74.00
72.00
70.00
68.00
66.00
64.00
62.00
60.00

Time
min

63.00
63.00
64.00
65.00
65.00
66.00
66.00
67.00
67.00
68.00
69.00
69.00
70.00
70.00

Time
min

128.00
129.00
129.00
130.00
130.00
131.00
132.00
132.00
133.00
133.00
134.00
134.00
135.00
135.00
136.00
137.00
137.00
138.00
138.00
139.00
139.00
140.00
140.00
141.00
142.00
142.00
143.00
143.00
144.00
144.00
145.00

Soltrol
Content

0.01
0.00
0.00
0.00
0.00
0.01
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.01

Soltrol
Content

0.17
0.14
0.13
0.15
0.17
0.22
0.21
0.22
0.23
0.25
0.28
0.28
0.28
0.28
0.27
0.28
0.29
0.29
0.23
0.03
0.01
0.01
0.00
0.00
0.00
0.01
0.00
0.00
0.00
0.01
0.00

Time
min

85.00
86.00
86.00
87.00
87.00
88.00
88.00
89.00
90.00
90.00
91.00
91.00
92.00
92.00
93.00
94.00
94.00
95.00
95.00

Time
min

157.00
158.00
158.00
159.00
159.00
160.00
161.00
161.00
162.00
162.00
163.00
163.00
164.00
164.00
165.00
166.00
166.00
167.00
167.00
168.00
168.00
169.00
169.00
170.00
171,00
171.00
172.00
172.00
173.00
173.00
174.00

161

Soltrol
Content

0.01
0.00
0.00
0.00
0.00
0.01
0.01
0.01
0.00
0.00
0.01
0.00
0.00
0.00
0.00
0.00
0.00
-0.01
0.01

Soltrol
Content

0.15,
0.12
0.13
0.15
0.17
0.20
0.19
0.20
0.19
0.22
0.28
0.27
0.26
0.26
0.27
0.28
0.29
0.28
0.28
0.17
0.02
0.01
0.00
0.01
0.00
0.01
0.00
0.01
0.01
0,00
0,00

Time
min

110.00
111.00
411.00
112.00
113.00
113.00
114.00
114.00
115.00
115.00
116.00
117.00
117.00
118.00
118.00
119.00
119.00
120.00
121.00
121.00
122.00
122.00
123.00
123.00

Time
min

186.00
186.00
187.00
187.00
188.00
189.00
189.00
190.00
190.00
191.00
191.00
192.00
192.00
193.00
194.00
194.00
195.00
195.00
196.00
196.00
197.00
197.00
198.00
199.00
199.00
200.00
200.00
201.00
201.00
202.00
203.00

Soltrol
Content

0.00
0.00

0.00
0.00
0.01
0.00
0.00
0.00
0.00
0.00
0.00
0.01
0.01
0.00
0.01
0.01
0.00

Soltrol
Content

0.15
0.13
0.12
0.13
0.14
0.18
0.19
0.19
0.19
0.19
0.22
0.25
0.25
0.25
0.26
0.27
0.29
0.29
0.27
0.27
0.24
0.05
0.01
0.01
0.00
0.01
0.00
0.00
0.00
0.00
0.01


TIME ELEVATION PONDING

DEPTH
MINUTES cM CM
24 96 11
28 94 10.2
34 91 9.4
4 88 8.4
45 86 8
50 84 7.4
55 82.5 6.8
60 81 6.2
65 79 5.7
70 775 51
80 74 44
90 71 3.2
100 68 23
110 65 1.4
120 61.5 0.6
125 60.5 oO
127 59
143 56
150 54
165 52
180 49
300 34

SPILL J #70 SAND 500 ML SOLTROL SPILL
VISUALLY OBSERVED FRONT MOVEMENT

TIME ELEVATION PONDING BACK
DEPTH FRONT

MINUTES. cM CM cM

O 120 9.5

1 115.5 75

2 114 7

3 113 6.8

4 112 6.3

5 11 6

6 110 5.6

7 109 5.3

8 108 5.2

10 107 45

12 105.5 5

14 104 3.5

16 103 3

18 102 2.6

20 101 2.2

22 100 2

24 99 1.5

27 98 14

30 96.5 0.6

35 94.5 oO

40 93.5 119

45 92.5 17

50 92 116

60 90 114

72 88 114

80 87

90 86 108

126


3.2 SHARP FRONT MODELS

In this section, the principles of infiltration are presented along with a discussion of the two
computer models: the Kinematic Oily Pollutant Transport Model the Three-Phase Sharp Front
Model.

3.2.1 __ Infiltration and Redistribution

Infiltration and redistribution of liquids in the unsaturated zone are driven by gravity and
pressure gradients. The pressure gradient may be divided into component of applied pressure,
such as that due to the weight of the liquid, and a component due to the capillary pressure in the
soil or porous medium. The contribution to flow in the unsaturated zone of each of these driving
forces is described below. Gravity acts throughout infiltration and redistribution and must always
be included in the model. The magnitude of the gravity contribution is, at most, equal to the
magnitude of the effective conductivity of the medium. Pressures may be imposed on the system
during infiltration. For example, ponding of liquid at the surface provides a positive pressure, P,
equal to

Saturation

Zi

Depth, z

Figure 1. Schematic representation of the relationship between sharp fronts and true
spreading fronts.

10


No. 125 Sand 750ml! Soltrol
Rain 500mI/hr after 20 hours

120
sof

paddos uoy

2
i]

Elevation (cm)
a
5

4r-> ow SPR ov
3 fF = 7s Bo
3 3 3, 3 7 “Sk .
207 > a 3 a o z 2
a F z
a 3
A 1
03>
. Soltrol Phase Content

Water

Figure 35. Set of phase content profiles for 750ml Soltrol spill in #125 sand. Rain started
20 hours after spill.

No. 125 Sand 1000mI Soltro!

120
od |
€ 80
2
.
& 60 a
8 3
40) °
= _ > N

8 8 # 6 alole 6 r%
20 3 ° PON

2 2 3 3 3 323 3 3

55 5 22 5 5 2a.
0)

0.30

Phase Content

Figure 36. Set of phase content profiles for 1000m! Soltrol spill in #125 sand.

54


SPILL O #125 SAND 500 ML SOLTROL SPILL
RAIN S500ML/HR AFTER 45 MINUTES

TIME ELEVATION PONDING DEPTH

MINUTES cM cM
oO 120 9.5
2 115 7
3 114 6.8
4 112.5 6.2
5 114.3 5.8
6 110.5 5.5
7 110 5.3
8 109.4 49
9 108.7 46
10 108 45
13 106.3 3.9
15 105 3.5

20 102 25

27 99 1.3

30 98 1

35 95.5 0.2

36 95 o

40 94.3

45 93.5

50 92.5

53 90.7

55 89.5

58 88

60 87

65 84.5

70 82

80 775

85 75

90 72.5

95 69.5

100 67

105 65

110 63

115 60

120 57.5

125 56

132 52

135 50

140 47

145 43

150 4

155 39

160 35

165 32

170 29

123


Table 8b. Count statistics for Cesium

Absorber Cs Cs Cs Average Square Root

Thickness
NM and} day 1 day 2 day 3

222672 232268 221602 225514
194077 195370 188036 192494
155698 162304 157686 158563
129029 133198 128501 130243
107162 108229 106172 107188

The count rate through different absorber for 60 seconds repeated on 3 different days for
Americium and Cesium. The count rates are averaged over the 3 days and the standard
deviation was calculated. The standard deviation was about one order of magnitude larger than
the square root of the average.

1.3.6 Determination of the Attenuation Coefficients

The lumped attenuation coefficients, U, for different materials were determined using the
following procedure. First the total counts, /,, were recorded through the empty multi-chambered
plexiglass box (Figure 75). Attenuation due to the box is thus included in the initial count. The
five compartments of the box were then sequentially filled with the test material (sand, water or
oil). The effective path length through the material traversed by the gamma radiation can thus
be precisely determined by adding the widths of the compartments filled with the test material.
From Equation (30) it can be seen that plotting the natural logarithm of the ratio (/,/) against path
length results in a straight line. A linear regression is performed, and the resulting slope of the
line is equal to the lumped attenuation coefficient of the test material. Potential error due to the
random nature of gamma emission was reduced by averaging seven separate scans at each of
five measured path lengths.

The measurement of the attenuation coefficient for water was repeated four times. The
lumped attenuation coefficients, the standard deviation of the regression, and the standard
deviation between the four measurements are given in Table 9. The mean value of U for water
was 0.195 cm" for Americium and 0.076 cm" for Cesium. The total standard deviation of U for
four measurements was 0.0024 cm‘ for Americium and 0.0034 cm" for Cesium. The graphed
results of one lumped attenuation coefficient determination can be seen in Figure 79.

As also can be seen in Table 9, the standard deviation for a single determination of the
U for water (from each seven measurements for five different path lengths) is smaller than the
standard deviation between the four measurements conducted on different days. Changing
detector sensitivity as described above might cause the larger variability between separate
measurements. Also, changes in detector-sample-source configuration may lead to different
results of the measurement. The distance of the sample to the source influences the absorption,
even if the distance between source and detector is constant. It is therefore important that the

107


Improvements in collimation and spectral windowing were completed after these
experiments. Source and detector were realigned and the integration software was rewritten to
improve spectral windowing. However, the effects of these improvements on the stability of the
attenuation constants was not tested. It is still good policy to assume changes in apparent
attenuation coefficients may occur. If the system allows for it, the measurement of the attenuation
coefficient should be conducted in the same sample container as the actual saturation
measurements, thus the same apparent attenuation coefficient would be used throughout all
measurements. This procedure was followed in all experiments.

1.3.8 Attenuation Coefficient of Test Fluid (Sottrol)

The attenuation coefficient of Soltrol was found to be close to the attenuation coefficient
of water (Oak and Ehrlich, 1985). A different attenuation coefficient between the two fluids (water
and oil) is required to determine the saturation of two fluids in a three-phase system (sand, water
and oil). Therefore, Soltrol was mixed with iodoheptane, where the latter has a larger attenuation
(Oak and Ehrlich, 1985) coefficient and is easily soluble in Soltrol. Following the work of Lenhard
and Parker (1987), a ratio of 1:9 by volume of 1-iodoheptane to the mineral oi! Soltrol 220 was
used. The lumped attenuation coefficient for the doped Soltrol was found to be 0.632 cm" for
Americium and 0.056 cm" for Cesium (Figure 81). The standard deviation of the regression was
0.00698 cm" for Americium and 0.000691 cm’ for Cesium.

109


Number
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.

Figure 9.

Figure 10.
Figure 11.
Figure 12.

Figure 13.
Figure 14.
Figure 15.

Figure 16.
Figure 17.

Figure 18.

Figure 19.

Figure 20.

Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.

FIGURES

Page
Schematic representation of the relationship between sharp fronts and
true spreading fronts... 6.0... tenes 10
Base characteristic plane for the KOPT model showing the sharp front
and continuous wave which comprise the solution. .................. 13

Schematic of a KOPT depth vs. saturation profile ............... 14
Assumed saturation profile for the Three-Parameter Sharp Front Model.... 15
Grain size distribution for #70 sand. Measured with dry sieving method

(filled squares) and settling tube method (empty squares). ............. 20
Grain size distribution for #125 sand. Measured with dry sieving method

(filled squares) and settling tube method (empty squares). ............. 20
Kinematic viscosity of Soltrol, Soltrol + iodoheptane and water versus
temperature. (Szlag and Illangasekare,1992)..................0000. 22
Aluminum fitting for bottom part of sample cell. Sizes are given in

INCHES. 6... cee eee eee 23
Aluminum fitting for top part of sample cell. Sizes are given in inches. ... . 24
Saturating the sand filled column with wetting fluid... 2... ........02.4 25
Setup for first scan through dry sand. ................. 0000000 eeue 26
Setup for second scan through fully saturated sand. Water is ponding

on top of sand. ..... 6... cette eee 27
Setup for third measurement through partially saturated sand. .......... 27
Schematic of a spill in the tank. ... 2.0.0.0... 0c eee ee eee 30
Variation in #125 sand hydraulic conductivity along the length of the
chromatography columns. .......... 0.00000 e cee cee eee eee eee 32
Suction-saturation curve measured in the small cell. ................. 34
Suction-saturation curve for #125 sand. Comparison between flow

pump and gamma system data for small cell. .................0.00. 34
Water/air and scaled oil/air pressure curves for #125 sand using Brooks

and Corey parameters. ..... 00... ccc eee eens 36

Comparison of front positions as simulated using KOPT in #125 sand for
the capillary pressure curve parameters determined by approaches 1

Comparison of front positions as simulated using KOPT in #70 sand for
the capillary pressure curve parameters determined by approaches 1

ANd 2. ee ett eee teens 38
Suction-saturation profile for #125 sand and water-air................. 40
Suction-saturation profile for #70 sand and water-air.................. 41
Suction-saturation profile for #125 sand and Soltrol-air. . 42
Suction-saturation profile for #70 sand and Soltrol-air, 43
Schematic of the scanning path through the sample column. If the

gamma detector moves 1.10 cm sideways from the center (x=1.1 cm),

the actual path length measured is 3 mm less than assumed (2I=7.9 cm,

while 2r=8.2 cm). eee e eee eee 44


AKo 1 8Sq

Saturation

Depth

Figure 71. Schematic representation of the effect of the relative permeability
derivative on the leading and trailing edges of the NAPL body.

In the three parameter model, a sharp front is assumed on the trailing edge of the liquid
NAPL. There are at least two reasons for the occurrence of such a front. First, if the derivative
of the relative permeability is not monotonically increasing as assumed in KOPT, then the
boundary transition from high to low saturation can generate a sharp front. All that is required
is that dk,,/0S, is not a monotonically increasing function. Models devefoped by Mualem (1976)
and Stone (1970) have non-monotonically increasing 9k,,/0S, functions. If the relative
permeabilities are well described by these functions, then back fronts would be expected. The
second reason for the existence of a back front is resistance due to air phase flow. Weaver
(1991) shows that a back front is needed in method of characteristics models when unidirectional

86


SECTION 5
RESULTS AND DISCUSSION

The experimental results and the model evaluation are presented and discussed in this
section. Hydraulic conductivity and the capillary suction-saturation relationship for #70 and #125
sand for water and Soltrol were measured. These parameters were needed as input to the
computer models. The model results were compared with the experimental results.

5.1. DETERMINATION OF MODEL INPUT PARAMETERS

Hydraulic conductivity is the single most sensitive input parameter for the KOPT and
Three-Parameter-Sharp-Front models. The KOPT model also uses Brooks and Corey parameters
for the capillary pressure versus saturation curve as input values in order to calculate permeability
as a function of saturation. The Three-Parameter-Sharp-Front model assumes full saturation
behind the front, thus capillary pressure versus saturation and permeability versus saturation are
not used. Experiments with the flow pump, a small column at RSKERL, and the gamma system
were used to obtain accurate values for hydraulic conductivity and capillary pressure versus
saturation curves.

5.1.1 Hydraulic Conductivity

The value of the hydraulic conductivity used in the KOPT model simulations for the #125
sand was determined as follows. A meter long, 5.0 cm diameter, chromatography column was
fitted with sampling ports spaced at 10 cm intervals along the length of the column. The sand
was allowed to fall through a tube, which was gradually raised as the column was filled. Carbon
dioxide was passed through the column to displace air before saturating the column with water.
De-aired ground water was then used to saturate the column. Any entrapped carbon dioxide
dissolved rapidly in the water, thus the column became fully saturated.

Manometers attached to the ports allowed measurement of the head drop along the length
of the column. Steady state was established in the column and measurements were made after
approximately 2 hours of flow. The variation of hydraulic conductivity along the column was
determined by this procedure. Figure 15 illustrates variation of hydraulic conductivity along the
length of the column. The average hydraulic conductivities from three experiments are shown
in Table 2.

31


Elevation Time Water Soltrol

cm min Content Content
45 1528 0.101796 0.174772
44 1529 0.124403 0.166265,
43 1529 0.1583 0.151789
42 1530 0.155863 0.160407
Al 1530 0.117311 0.174846
40 1531 0.129716 0.16813
39 1532 0.090141 0.192192
38 1532 0.150839 0.169155
37 1533 0.118676 0.170757
36 1533 0.07105 0.176235
35 1534 0.114519 0.160796
34 1535 0.052259 0.187935
33 1535 0.121778 0.17587
32 1536 0.00313 0.222959
31 1536 0.052774 0.205294
30 1537 0.04636 0.252437
29 1538 -0.0588 0.266917
28 1538 0.04835, 0.253028
27 1539 -0.08856 0.234422
26 1539 -0.02005, 0.205467
25 1540 0.04287 0.209988
24 1541 0.06391 0.228482
23 1541 0.14335 0.268172
22 1542 0.1131 0.257297
21 1543 -0.10331 0.248302
20 1543 0.11041 0.23797

151


Table 11b. Volumetric content of the organic phase calculated with Equation (42)

Calculated with /-values from Table 5a.

average

standard deviation

theoretical volume content

theoretical error %

118


In multi-phase systems, the attenuation due to each phase must be incorporated into
Equation (30). For the case of sand and water, this equation takes the form,

I = Ip@ (Pets + Bw Pw%w) (31)

where the subscripts s and w stand for sand and water, respectively. The initial count rate /, is
defined as the count rate through the empty container, before it is filled with sand and water.
Thus redefining the initial count rate eliminates the need to consider the absorption by the
material of the column, or any container which is used to hold the sample. For further
simplification, the new initial count rate, /,, can be taken through dry sand. That is, attenuation
due to the soil is implicit in /,; and any further attenuation is only due to the presence of water.
This leads back to Equation (30).

As the pores of the soil are partially saturated with water, the true path length through the
water, x, cannot be measured. Only the path length through the total sample, x, is known. The
following relation between x, and x is assumed to hold true:

Xy = Sx (32)
where n is the porosity of the sample and S the water saturation.

A lumped calibration constant (Nofziger and Swartzendruber, 1974), U, can be defined for
each material present and for each gamma energy:

Uny = BawPo Ujg = HaoPo (33)
Ucw = BewPw Uso = BooPo
where A and C stand for Americium and Cesium sources, respectively.
Rewriting Equation (31):
l= Ip @ Ws * NSU y)x (34)

The lumped attenuation coefficient U, for the sand is always measured through porous sand, the
porosity is therefore implicit in U, and does not need to be considered in the path length in the
formulation given in Equation (34). When volumetric phase content 6 needs to be introduced the
relation 6 = nS is used.

Saturation of two fluids can be determined with a dual gamma system by writing Equation
(34) for each gamma source:

93


SUCTION SATURATION RELATION
#125 SAND AND WATER

3.0
-
SAMPLE 1
€E +
uD SAMPLE 2
& 2.07
a +
g
g
y
z
&
5 :
3 1.0 . +
a =
3 2
:
0.0 smal
0.0 0.2 0.4 0.6 0.8 1.0

SATURATION

Figure 16. Suction-saturation curve measured in the small cell.

TEST WITH #125 SAND

£ rol bl Gamma System
2 /
8 "
a
rad
@
os Flow Cell
fom
o
Oo

bay 02 on 06 2

Saturation
Figure 17. Suction-saturation curve for #125 sand. Comparison between flow pump and
gamma system data for small cell.

34