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Water Resources Series No. 67
EFFECTS OF SURFACE MINING UPON SHALLOW AQUIFERS IN THE EASTERN POWDER RIVER BAS IN, WYOMING
Richard W. Davis Paul A. Rechard May 1977
Water Resources Research Institute University of Wyoming Laramie, Wyoming
This report is a completion report to the U.S. Forest Service SEAM program as a result of work under Cooperative Agreement No. 16-574-CA. ABSTRACT OF WATER RESOURCES SERIES NO. 67
This is a report summarizing WRRI ground water research activities at the Belle Ayr Mine during FY 1976-77. The year's activities focused upon aquifer recharge, hydrology of the alluvial valley floor along
Caballo Creek, and reclaimed spoil hydrogeology. Recharge to
Wasatch formation overburden aquifers amounts to less than one percent of the area's precipitation. Direct recharge to coal underlying the Wasatch formation is too small to measure. Significant recharge to or discharge from the coal occurs where alluvium and coal are in direct contact. Recharge probably also occurs via scoria units.
Underflow through the Caballo Creek alluvium is less than 0.4 acre feet per month. This is because the alluvial sands are so fine and silty that transmissivities are very low.
Permeability of reclaimed spoil, determined by slug tests, is less than 100 gallons per day per foot. Quality of ground water in the spoil ranged from a total dissolved solids content of 1170 mg/l to 2490 mg/l in
October 1976. TABLE OF CONTENTS
Page
INTRODUCTION ...... 1
HYDROGEOLOGY OF BELLE AYR MINE AREA. . 5
Methodology ...... • 5
Well Construction •. 5
Aquifer Tests. . 8
Water Sampling 9
Interpretation. . . . 14
Aquifer Parameters . . . 14
Recharge . . • • . . . 15
Caballo Creek Alluvium Underflow . . . 25
IMPACTS AND CONCLUSIONS ...... • • • • 2 7
HYDROGEOLOGY OF SPOIL REPLACEMENT AT BELLE AYR MINE. • • • 2 9
RECO"MMENDATIONS FOR FUTURE WORK. . • 35
REFERENCES 36
APPENDIX A ALLUVIAL WELL LOGS . . . 37
APPENDIX B STATIC WATER LEVELS IN UNINSTRUMENTED WELLS. . 41
APPENDIX C STATIC WATER LEVELS IN INSTRUMENTED WELLS. . . . . 43
ii LIST OF TABLES
TABLE Page
I MONITOR WELL INVENTORY FOR AMAX'S BELLE AYR MINE. 6
II SUMMARY OF 1976 AQUIFER SLUG TEST DATA FOR WELLS .. 10
III SUMMARY OF AQUIFER PUMP TEST DATA FROM 1974-75 TESTS. . 11
IV 1976 FIELD DATA ON AQUIFER SAMPLING ACTIVITIES. . . . 12
V RESULTS OF LABORATORY ANALYSES OF GROUND WATER SAMPLES. 13
VI CHANGES IN GROUND WATER STORAGE IN CABALLO CREEK ALLUVIUM . 19
VII COMPLETION SUMMARY FOR WELLS DRILLED IN RECLAIMED SPOIL 30
VIII SUMMARY OF AQUIFER TEST DATA FOR RECLAIMED SPOIL WELLS. . . 32
IX FIELD DATA ON SPOIL WATER SAMPLING ACTIVITIES . 33
X RESULTS OF LABORATORY ANALYSES OF WATER SAMPLES FROM
RECLAIMED SPOIL ... 33
XI WATER LEVELS IN' RECLAIMED SPOIL 34
XII STATIC WATER LEVELS IN UNINSTRUMENTED WELLS 42
iii LIST OF FIGURES
Figure Page
1. Location Map--Drainage Basin of Caballo Creek and Location
of AMAX Belle Ayr Mine . 2
2. WRRI Instrumentation 3
3. Alluvial Cross Section along Caballo Creek near Belle Ayr Mine 16
4. Average Alluvial Well Water Levels ...... 17 5. Geologic Cross Section along T-7 Road Showing Static Water
Levels in the Various Hydrologic Units 20
6. Potentiometric Surf ace in the Coal ...... 22 7. Water Levels in BAS-13, -14, and -15 Wells . . . 23 8. Water Levels in Instrumented Wells WRRI-7, 481, and N-1 44
9. Water Levels in Instrumented Wells N-11, N-13, and WRRI-5 45
10. Water Levels in Instrumented Wells WRRI-8, WRRI-9, and WRRI-12 46
11. Water Levels in Instrumented Wells N-3, N-5, and N-6 . . . . 47
iv INTRODUCTION
This is a progress report on activities and results obtained from a continuing monitoring and study program evaluating the effects of surf ace mining upon shallow aquifers in the AMAX Belle Ayr mine area of the Eastern Powder River Basin. It primarily discusses events during
1976. The work has been funded by the United States Forest Service and the University of Wyoming under SEAM Coop Agreement 16-574-CA and by
AMAX Coal Company. Because of the availability of data from previous work by Wyoming Water Resources Research Institute (WR.RI) at AMAX's
Belle Ayr Mine (Figures 1 and 2), the mine and the region around it have been the focus of work to date.
Although it is intended for this study to continue throughout the period of strip mining at Belle Ayr Mine, the research is funded on a year~to-year basis. The original long-term objectives were to:
1. Determine regional impacts of dewatering and destruction of the coal aquifer and overburden at the Belle Ayr Mine.
2. Postulate the feasibility of recharging the ground water system through diversion of surf ace flows into abandoned mine sites.
Because of the short-term nature of the funding available for research, specific objectives are set for each year's work. Objectives funded by SEAM for the period covered by this report were to:
1. Determine the amount of recharge being received by the shallow aquifers from (a) infiltrated precipitation within the Caballo Creek Basin and (b) vertical leakage from deeper aquifers.
2. Begin accumulating data on the hydrologic characteristics of reclaimed,· strip mined material provided reclamation progressed to the point where it was feasible.
1 DRAINAGE BASIN OF CABALLO CREEK AND LOCATION OF AMAX BELLE AYR MINE
GILLETTE
Oroinoge Area = 212 Sq. Ml.
N
0 5 E3 E3 E3 SCALE - MILE 1
Figure 1 2 Figure 2
INSET ][
BAS-180
R.71W. R.70W. -~~~~--"T~-;l.~~_...--,~~
I .4BN. r.4BN.~~~~-+~~~-~~~~~~~-~--1f-\~~~-F::..+-=~;-=~4.--t-~.-~~C'::"'~~~-r--'-::-tlt I T.47 N. ------'------Railroad
_ - - Rood ~AS·/7£
'I I \ ,___..,_,,,,,,-· ~A§_·ll'O ',,esAS-178 · sls-=-rtc ' \.,,__ s-2"\'\ " : I .· ,' LBAS-llH ~/./ WRR~ ~fAS-ll'A
1, I ...... ,
EXPLANATION N WATER RESOURCES RESEARCH INSTITUTE • Weather Station Stale of Wyomin9 O Pump Discharge - Totoliz 1ng Permit Boundary No. 214 C AMAX COAL _9~0MP~_fj't A Streomf!ow Gaging Stations - i'lecorder REVIS!ONS OAT[ 8't t:. Strromflow Go91ng Stot1on - Periodic Obser•Otion 6-~ 1 tm BELLE AYR MINE • Air Quality Station e Instrumented Water Wells i • NPDES Monitoring and Samp1tn9 Station • Unonstrumented Water Wells WRRI INSTRUMENTATION Aquatic Biota Monitoring Sites 0 3000 0 CAMPBELL COUNTY, WYOMING Bacteriological Sampling Sites H i===t I 0 SCALE• FEET T 47, 48 N., R 70, 71 W, 6th PM
1----1~-& DRAWN BY 3. Determine the present chemical quality of water from the various aquifers and the probable effects upon that quality of changes in ground water regime caused by mining reclamation.
A fourth objective was originally proposed to SEAM for FY 1976.
However, sufficient funds were not available for SEAM to finance the research. That objective was:
To determine the hydrologic characteristics of the alluvium in Caballo Creek valley and its hydrologic relationships to aquifers in older geologic units and to Caballo Creek surf ace runoff.
AMAX Coal Company indicated an interest in funding this latter study for one year and accomplishments of that research are included here.
4 HYDROGEOLOGY OF BELLE AYR MINE AREA
Methodology
Well Construction
Methods of drilling and completing wells used in the continuing monitoring and study program have been changing and evolving rather continuously since the program began. The basis for changes in methods has been prior experience. Much of the data presented in earlier reports were from open, uncased exploration holes. Water levels were necessarily some indefinable average of hydraulic heads in the various aquifers weighted in some proportion by transmissivity values.
Shortly after WRRI began studying the area for AMAX in 1973, certain of these original wells were cased. These are the "N" series wells listed in Table I. The locations and construction details of all wells used are listed in Table I. Note that no packers were used around the well casings so that water levels in the "N" well are probably still a composite of those in all units penetrated. Water from aquifers above the perforated zones is able to move down the outside of the casings to enter the perforations.
During 1974 the "WRRI" series wells were drilled. Those wells which were perforated in unconfined aquifers were usually completed similar to the "N" series wells. In artesian aquifers, however, construction of piezometers was attempted. A 9~" hole was drilled to the top of the aquifer, neat cement was poured in the hole, and 6-inch ID PVC casing was set in the cement. A bit was then run through the casing to drill out the cement plug ("packer" in Table I), the hole was drilled to total
5 TABLE I
MONITOR WELL INVENTORY FOR AMAX'S BELLE AYR MINE
Elevation Cement Location u M.P. l Total Casing Packer Perfer. Well W.z:o. Coord. Ground I-<:s Ht. M.P.l Depth Depth Depth Interval Casing 0 No. Ft. No. Ft. E. Sec. T(N) R(W) (ft) t/l (ft) Location (ft) (ft) (ft) (ft,de2th) Formation Desc. Notes Drilled 481 1252205 447588 27 48 71 4573.8 s Rag Base 160 100 l 100-160 Coal 6" PVC Abd.-6/76 2-73 N-1 1253465 444850 27 48 71 4574.8 s 1.8 Hsg Base 190 130 1 130-190 Coal 4" PVC 2-73 N-3 1245905 443180 3 47 71 4531. 0 s llO 50 1 50-110 Coal 4" PVC 2-73 N-3A 1245900 443130 3 47 71 4531 llO 50 Coal 4" PVC 4-75 N-5A 1252330 442750 28 48 71 4503.l Tc 1. 7 Hsg Base 125 125 1 40-125 W2 & Coal 4" PVC 4-28-75 N-5B 1252350 442750 28 48 71 4500.7 Tc Csg Top 135 135 40-135 W & Coal 4" PVC 4-28-75 N-6 1247953 4414~5 33 48 71 4512.l s Hsg Base 140 75 75-140 Coal 2-73 N-11 1256457 4382 7 28 48 71 4571.5 s 2.2 Hsg Base 207 207 140-200 2-73 N-13 1251950 435850 29 48 71 4539.0 s 190 190 80-170 Coal 3-73 N-13A 1249764 448475 29 48 71 4539 190 80 80-170 Coal PVC 7-27-74 WRRI-2 1249764 448425 35 48 71 4480 T 36 30 30- 36 Coal PVC 4-28-74 'lo.'RRI-3 1254409 445905 27 48 72 4620 T 206 166 166 166-206 Coal 4" PVC 3-15-74 WRRI-5 1248504 445350 34 48 71 4518.0 T Hsg Base 135 70 70 70-135 Coal 4" PVC 3-15-74 7-24-74 WRRI-5A 1248504 445350 34 48 71 4520 T Csg Top 135 70 1 70-135 ~l 4" PVC WRRI-7 1252920 443500 27 48 71 4542.5 Tc 1.2 Hsg Base 329 317 235 257-317 4" & 6" 3-15-74 PVC WRRI-·7A 1252920 443500 27 48 71 4541.5 Tc 1.9 Csg Top 329 317 235 257-317 FU 4" & 6" 4-27-74 PVC WRRI-7B 1252910 443543 27 48 71 4541.1 Tc 0.4 Csg Top 329 3i7 235 257-317 FU 4" & 6" Lost Circ. 4-28-74 PVC 240' WRRI-8 1250440 441870 33 48 71 4474.4 Tc 3.2 Hsg Base 20 20 Qal4 4" PVC 7-22-74 WRRI-9 1250330 452650 35 48 71 4446.1 Tc 2.3 Hsg Base 20 20 Qal 4" PVC 7-22-74 WRRI-10 1248350 429360 31 48 71 4510.6 Tc Hsg Base 281 188 188 188-281 Coal 6" PVC 10-25-74 WRRI-lOA 1248360 429410 31 48 71 4410. 2 Tc 1.3 Csg Top 215 268 200 200-268 Coal PVC 10-26-74 WRRI-11 1248420 429410 31 48 71 4512.1 Tc Hsg Base 194 194 90-194 w 4" PVC 10-27-74 1Heasuring point 2Wasatch formation 3Fort Union formation elastics '+caballo Creek alluvium Sc;- Geophysical Logs S• Sample Logs
Elevation Sources Are: Leveling Surveys (S), Topographic Maps (T), and Combinations of the Two (Tc) TABLE I (Cont.)
Elevation Cement w Location !J M.P,l Total Casing Packer Perfer. $.; Well Wyo. Coord. Ground ;:) Ht. M.P.l Depth Depth Depth Interval Casing 0 No. Ft. No. Ft. E. Sec. T(N) R(W) (ft) C/l (ft) Location (ft~ ~f;J {ft~ ~ft 1 deEth~ Formation Desc. Notes Drilled WRRI-12 1248320 429360 31 48 71 4510.8 Tc 2.4 Hsg Base 20 Qal Premine Well - 1 - BAS-13A 1254310 441350 28 48 71 4562.4 Tc 1.2 C::sg Top 170 170 0-5 150-170 w 2" PVC 9-75 BAS-13B 1254300 441350 28 48 71 4562.1 Tc 1. 7 Csg Top 260 260 170 180-260 Coal 2" PVC 9-75 BAS-13C 1254290 441350 28 48 71 4561. 0 Tc 1.4 Csg Top 300 300 270 280-300 FU 2" PVC 9-75 BAS-14A 1251980 441950 28 48 71 4515.7 Tc 1.4 Csg Top 72 72 0-5 62-72 w 2" PVC 9-75 BAS-14B 1252010 441930 28 48 71 4515.7 Tc 0.8 Csg Top 175 175 85 155-175 Coal 2" PVC 9-75 BAS-14C 1252000 441950 28 48 71 4515.0 Tc 1. 5 Csg Top 220 220 190 200-220 FU 2" PVC 9-75 BAS-15A 1250510 441860 33 48 71 4471. l Tc 1.2 Csg Top 40 40 Surf. 20-40 w 2" PVC 9-75 BAS-15B 1250530 4418~0 33 48 71 4470.9 Tc 1.2 Csg Top 100 100 70 80-100 Coal 2" PVC 9-75 BAS-15C 1250490 441860 33 48 71 4471.4 Tc 0.9 Csg Top 160 160 130 140-160 FU 2" PVC 9-75 BAS-16 1254567 449841 26 48 71 4605 T Grd Lev 204 None Coal None Dry, Abd. 12-75 BAS-17A 1250040 452520 35 48 71 4451.0 T 0.9 Csg Top 20 20 17-23 Qal 2" PVC 1-76 BAS-17B 1250800 452730 35 48 71 4446.3 Tc 0.8 Csg Top 20 20 17-23 Qal 2" PVC 1-76 BAS-17C 1250790 452350 35 48 71 4440.0 Tc 1.9' Csg Top 14 14 ll-14 Qal l~" Stl For pumping 1-76 BAS-17D 1250845 452180 35 48 71 4440.7 Tc 1.0 Csg Top 14 14 ll-14 Qal 2" PVC 1-76 BAS-17E 1251460 452520 35 48 71 4447.5 Tc 1.0 Csg Top 20 20 17-20 Qal 2" PVC 1-76 BAS-17F 1252443 452358 26 48 71 4463.0 Tc 0.8 Csg Top 18 18 15-18 Coal 2" PVC 1-76 BAS-17G 1253071 452440 26 48 71 4444.5 Tc Swl 1-20- - Scoria None Open pit 1-76 76 BAS-17H 1250340 452980 35 48 71 4442.7 Tc 1.4 Csg Top 20 zo 17-20 Qal 2" PVC 1-76 BAS-18A 1250472 441810 33 48 71 4471.1 T 1.1 Csg Top 14 14 11-14 Qal 2" PVC 1-76 BAS-18B 1250720 441820 33 48 71 4480.3 Tc 1.4 Csg Top 18 18 15-18 w 2" PVC 1-76 BAS-18C 1250760 441960 33 48 71 4475.3 Tc 1.4 Csg Top 19 19 15-18 w ? 2" PVC 1-76 BAS-180 1251030 441810 33 48 71 4479.l Tc 1.6 Csg Top 20 20 17-20 Qal 2" PVC 1-76 BAS-18E 1250500 441840 33 48 71 4471.5 Tc 0.4 Csg Top 12 12 9-12 Qal l~" Stl For pumping 1-76 BAS-l9A 1248350 429390 31 48 71 4510. 3 Tc LS Csg Top 17 17 14-17 Qal 2" PVC 1-76 BAS-19B 1248630 429460 31 48 71 4510.0 Tc 0.6 Csg Top 17 17 14--17 Qal 2" PVC 1-76 BAS-19C 1248620 429520 31 48 71 4509.1 Tc 1.1 Csg Top 18 18 15-18 Qal 2" PVC 1-76 BAS-190 1248610 429620 31 48 71 4510 T 1.3 Csg Top 19 19 16-19 Qal 2" PVC 1-76 BAS-19E 1248970 429440 31 48 71 4520.1 Tc 1.6 Csg Top 30 30 27-30 Qal 2" PVC 1-76 Belle Ayr 1246850 441968 33 48 71 4545 T 1.3 Csg Top 280 218 120 168-218 Coal 5" PVC 9-75 5 Belle Ayr 1249990 440900 33 48 71 4545 T Csg Top 160 138 88 88-138 Coal 5" PVC 9-75 6 Belle Ayr 1249500 4344~0 5 47 71 4510 T 0.8 Csg Top 100 100 40 40-100 Coal 5" PVC 9-75 7
1 Measuring point depth, and 4" PVC casing was set inside the 6 11 casing. In some cases
the packer seems to have been damaged by vibrations during the second
stage of drilling so that the cement seal was damaged.
During the past year a third group of wells, labeled "BAS" in
Table I, were drilled. These wells, if not drilled in alluvium, were
completed with a gravel pack opposite the casing perforations. Where
the well was perforated in a confined aquifer the gravel was topped with
a cement plug around the outside of the casing just above the aquifer
of interest. Wells completed in this manner have been reliable piezometers
in all cases.
Wells drilled in Caballo Creek alluvium were constructed with a
saw-slotted two inch PVC casing. Wells which were constructed as potential
pumping wells were completed with a three foot screened, brass drive point.
Drive points were used because previous experience in other projects
indicated that fine silts and sands would quickly fill pumped wells with
slots larger than 0.01 inch. All well locations are indicated on Figure 2.
Aguif er Tests
It was originally planned to conduct two types of tests on the wells.
Those completed in Wasatch, coal and elastic Fort Union strata were to be
pumped with jet pumps and the specific capacities used to estimate
aquifer parameters. Well yields were so low, however, that minimum
practical pumping rates could not be sustained.
Alluvial sediments were to be pumped using a centrifugal pump. Again, well yields were too low to sustain minimum obtainable pumping rates.
As a result of these difficulties, "slug" tests were used to determine
transmissivities and storage coefficients. A slug test consists of
8 suddenly injecting or removing a known volume of water from a well and measuring the rate of recovery. In wells drilled with water or air, as most of the BAS series wells were, experience has shown the trans missivities so determined to be quite reliable in low yield aquifers
(T < 1000 gpd/ft). Storage coefficient values are believed to be much less reliable. Results of the tests are shown in Table II. Data from
Davis (1975) are shown in Table III for comparison.
Water Sampling
During the month of October, efforts were made to sample additional wells not previously sampled. Before sampling, each well was jetted with air at least once to remove contaminants. The amount of water produced prior to sampling is given in Table IV. All the samples were
"thiefed," that is, a steel container was lowered into the well and allowed to fill. Certain field tests were run on the samples so obtained.
Field data on the samples are given in Table IV. Laboratory analyses have been done on bottled, unacidized samples from some wells by the
Wyoming State Agricultural Laboratory in Laramie. Results of the analyses, run subsequent to the defined completion date of this study (September
30, 1976) are shown in Table V.
9 TABLE II
SUMMARY OF 1976 AQUIFER SLUG TEST DATA FOR WELLS Values of "aquifer thickness" for slug tests are the same as length of saturated and perforated casing interval, not necessarily the same as the lithologic aquifer thickness
Aguif er Parameters Test Date Aquif. Well of Geo!. Trans. Thick. Perm Storage 2 No. Test fm. (g2d/ft2 {ft) {g2d/ft 2 Coe ff Comments
BAS-3 10-27-76 Spoil 65 8 8 -0.04 Poor data BAS-4A 10-27-76 Spoil 132 3 44 - .0004 BAS-13A 10-6-76 Wasatch 93 20 4.7 -0.20 BAS-13B Coal >1000 >13 < 3 min 10-6-76 80 5 Recovery complete BAS-13C 10-6-76 F. U. 1 100 20 5.0 -4xl0- ...... BAS-14A 10-6-76 Wasatch 82 10 8.2 .. 0.04_5 Poor data 0 BAS-14B 10-6-76 Coal 4.5 20 0.2 .. 4xl0 BAS-14C 10-6-76 F. U. 20 No recovery after 15 min 4 BAS-ISA 10-6-76 V. F. 2& 1200 20 60 -4x10- Wasatch BAS-lSB 10-6-76 Coal 5.3 20 0.3 -4x10-l BAS-15C 10-6-76 F. u. 20 No recovery after 5 min BAS-17B 10-27-76 V. F. 120 6 20. -10-1 BAS-17E 10-27-76 V. F. 56 3 17 -0.0004 >128 BAS-17F 10-27-76 Coal >256 2 1 Recovery complete 2 min BAS-18C 12-9-76 v. F. 93 2 46 -10- -10-4 BAS-19D 12-9-76 v. F. 105 3 35 4 BAS-19E 12-9-76 v. F. 15 3 5 -10-
1Fort Union 2 Caballo Creek alluvium TABLE III
SUMMARY OF AQUIFER PUMP TEST DATA FROM 1974-75 TESTS
Length Final Aguifer Parameters Test Date Observ. of Prod. Draw- Spec. Aquif. Perm Well of Type Well Test Rate down Cap. Geol. 1 Trans. Thick. (gpd/ Storage No. Test . Test No. ~Min.2 ~s2m2 {ft2 {s2m/ftl fm. ~SEd/ft2 ~ft2 ft22 Coe ff Comments N-3A 6- 5-74 Pump N-3 30 1.0 12 0.08 Coal 1353 62 22 0.01 Pumped well dry
N-5A 5- 5-74 Pump N-5B 1020 19.4 2.() 9.7 Coal 6175 100 62 0.0018 No packer in either well N-13A 7-27-74 Pump N-13 660 6.05 8.1 0.75 Wasatch 3495 54 65 0.0054 No packer in either well
WRRI-7A 5- 4-74 Pump WRRI-7B 1440 17.6 6.3 2.3 F.U. 1528 60 25 0.0022 Shale packer w/o cement
WRRI-lOA 11-21-75 1Pump VRRI-10 585 6.8 0.53 12.8 Coal 3542 90 39 0.0038 No packer in obs. well
1 F.U. • Fort Union formation elastics
Note: Results are from "successful" tests only. Other tests were attempted but due to extremely low transmissivities, the tests could not be completed. TABLE IV
1976 FIELD DATA ON AQUIFER SAMPLING ACTIVITIES
Well Site Analysis
Wyo. Ag. Vol. Alkalinity Lab. of Water Elect. (ppm) Date Sample Pumped Cond. Temp. Well Comments No. Sampled No. (g?l.) Aquifer pH (µmhos) (oC) Total co 3
BAS-13A 10-6-76 4.56 Wasatch 9.8 1550 8 0 223 BAS-13B 10-6-76 1.44 Coal 8.9 750 8 0 428 I-' BAS-13C 10-6-76 1.23 F. U. 8.5 1000 8 0 548 N BAS-14A 10-6-76 7-1212 3.46 Wasatch 8.0 2000 9 0 428 BAS-14B 10-6-76 4-1214 3.58 Coal 7.7 2500 10 0 462 BAS-14C 10-6-76 7-1213 1.36 F. U. 8.0 950 .lQ 0 308 BAS-15A 10-6-76 5 Wasatch 7.6 5150 9 0 428 BAS-15B 10-6-76 12 Coal 7.5 1300 8 0 548 BAS-15C 10-6-76 8 F. U. 8.0 1100 8 0 462 BAS-17B 10-27-76 7-1473 0 V. F. 7.7 2800 10 Very strong odor nitrates BAS-17E 10-27-76 7-1474 0 V. F. 7.4 2100 9 Very strong odor nitrates BAS-17F 10-27-76 7-1475 0 ·Coal 7.5 9 Very strong odor nitrates BAS-18C 12-9-76 0 V. F. 8.1 1850 9 BAS-19D 12-9-76 0 V. F. 8.0 3000 7 BAS-19E 12-9-76 0 V. F. 7.7 4800 8 Very strong odor nitrates TABLE V
RESULTS OF LABORATORY ANALYSES OF GROUND WATER SAMPLES
1976 Total Chemical Analyses (mg/l) Diss. Elect. Well Date Analysis Solids Cond. No. Sampled No. Ca Mg Na K B Fe co HC0 Cl N0 (mg/l) pH (µmhos) 3 3 504 3
BAS-14A 10-6-76 7-1212 230 95 240 12 0.04 0.9 o.o 500 110 900 1.1 1970 7.4 2310
~ BAS-14B 10-6-76 7-1214 270 93 300 12 0.02 0.8 o.o 570 78 1100 0.2 2330 7.4 26.'..0 w BAS-14C 10-6-76 7-1213 47 11 180 9.3 0.01 1.4 0.0 360 13 240 o.o 708 8.0 1030
BAS-17B 10-27-76 7-1473 190 110 360 23 4.9 1.3 o.o 490 20 1300 0.4 2400 7.3 2790
BAS-17E 10-27-76 7-1474 360 120 180 30 5.8 1.1 0.0 400 10 1500 0.0 2560 7.6 2660
BAS-17F 10-27-76 7-1475 11- 45 11- 25 3.3 0.2 0.0 140 6.3 530 0.1 980 6.9 1230 Interpretation
Aquifer Parameters
The well systems constructed during the past year at sites BAS-13,
-14, and -15 (Figure 2) were designed and located to provide information on aquifer recharge and on interactions between the various aquifers.
All of these wells and a number of the new alluvial wells were tested by the "slug test" technique. Results are shown in Table II. 2 Wasatch permeability values average about 6.5 gpd/ft • Alluvial permeabilities average about 25 gpd/ft 2 . Data from Davis (1975, Table II) for the coal show an average permeability of about 43 gpd/ft 2 • Tests of coal strata in BAS-13B, -liB, and -15B_ '~~uggest an average permeability much 2 less than 43 gpd/ft . The data from the 1975 report are possibly too high because of poor well completions. Leakage from overlying aquifers, especially in the observation well, would cause erroneously small draw- downs which would be interpreted as high transmissivity (T) values.
In order to determine which of the two sets of data -was correct, a
simple test was devised using observed drawdowns around the present mine
pit. Two wells, 481 and N-1, were reportedly destroyed when the pit
highwall was about 500 feet distant. Declines in water level from Spring
1973 to time of destruction were used to calculate values of T, assuming
the pit was simulating an infinite line sink with constant head and no
aquifer recharge. The T values would be total values for the Wasatch
overburden plus coal. The calculations gave an approximate T value of
43 gpd/ft at well 481 and of 33 gpd/ft at well N-1. If the coal is
assumed to be contributing nearly all of the dewatering effects, perme 2 abilities of 0.7 and 0.5 gpd/ft respectively are obtained for the coal.
14 The values are far closer to the slug test values in Table II than pump
test values in Table III.
Test data from wells at several mines in the Gillette area also sug
gest that the slug test data are more reasonable. For these reasons, the
slug test values (Table II) of T are used in the rest of this report
although it is recognized that usually pump test data are preferable.
Recharge
When computing precipitation recharge to the ground water, it is
helpful to consider three areas at Belle Ayr Mine. Each is underlain at
or near the surface by a different lithology. The first of these areas
is the Caballo Creek valley. Figure 3 shows cross sections of the valley
at study locations. Changes in ground water storage are indicated by variations in water levels in the BAS-17, -18, and -19 series wells.
Figure 4 shows the average monthly water levels in Caballo Creek alluvium
at BAS-17 (below the mine), BAS-18 (at T-7 road above the mine), and
BAS-19 (Dunlap Lake). Water levels in alluvial wells below the mine rose
in February and March, 1976, stayed high until the months of July and
August, then began to decline. By September or October, nearly all water levels had receded to the levels of the previous winter. The
inception of high water levels coincided with the first snow melt and
Spring runoff along Caballo Creek. Above the mine, water levels remained relatively constant until August or September when they fell sharply.
The variations in water levels were used to estimate changes in ground water storage components from month to month. Changes for each area near the alluvial wells were calculated by averaging water level changes within each of the alluvial well batteries (excluding BAS-17F). Changes
15 I I/ .I I N-61 I ._____ ...... ______.:;-115
...,,'Yn= CA8ALLO CK ti ~ f --- WRRI ·-12 0c n ~ ,~ : - BAS /9A z ,....~ r BAS 198 )> g ~ 1--- -0 17A r !. ..., ~ I r ,., I l> ..,,~ r "l'Tl t"i A-123 ~ >- I :. ·~,., 1-1 t.i • -i i\i. ,i ' 8-165 I ~ CfiBALLO CK -.J CD I~ \ B.t.S ITC I'll BAS 170 r :::0 I ~ 0 0 )> A A A :E A (JI (JI -~Y'v 0 (JI 0 UI i:;) o_ 0 o_ ~ )> ELEVATION t-i z CD ~ rn 0 < 0 0 0 )> i1 CABALLO CK I'll 0 ---BAS 17£ :J O ::or °' ~.,, c f11 r 3: ~ z,,, c I :t' c ~ ::t I l z -i "< !? I BAS /BA f11 .,. -< - ~' 0. z :» RAILROAD !.t er rn' \ -< :.: l> I BAS 188 -< :u () --- 8-215 ~:. 1.. 0 ::v \ -~ r- ,~ -t .,, :I:?' ~cog z !'Tl CJ) JI I BAS 180 I er.,. '
J F M A M J J A S 0 N D +2.0 eo.o~ ~ -2.J
en-... +2.0 ..J E w ,._=> w"O>o -1
+2.0
-2.0
Figure 4: Average Alluvial Well Water Levels.
17 2 in ground water storage above the mine (alluvial area = 0.84 mi ) and 2 below the mine (alluvial area = 0.48 mi ) were then calculated (Table
VI). A specific yield of 6% was used to estimate the amount of recharge represented by the water level variations. The specific yield used is a rather arbitrary assumption and subject to change after further work.
The changes calculated in Table VI are negligible in comparison to other hydrologic budget components.
The second area of recharge by precipitation is on unaltered Wasatch lithologies outside the Caballo Creek valley. As in the 1975 report, the method described in Ferris, et al. (1962, p. 131) assuming a "line sink" and steady recharge was used. Water levels in BAS-13A and -14A were analyzed. The position of the line sink used and the general hydrogeologic picture are shown in Figure 5. The ground water divide was placed 5500 feet north of the line sink. Using a value of 345 gpd/ft for T, a recharge rate of 0.05 inches per year was obtained. If the data from the 1975 report (p. 25) are corrected for T values, a recharge of 0.14 inches per year is obtained. This latter figure is very close to another value, 0.16 inches per year, given in the 1975 report (p. 22). For this report, a working value of 0.15 inches of precipitation per year is assumed to be reaching the overburden aquifers. This equals 8.0 acre feet of water per square mile per year. Again, recharge of the Wasatch aquifers by pre cipitation does not appear significant in comparison to other components of the area's hydrologic budget. This conclusion tends to be supported by Winograd (1974) and Mann (1976).
The third type of area in which direct recharge by precipitation occurs is underlain by scoria. The existing well system, until very recently, was not designed to evaluate this source. During Fall 1976
18 TABLE VI
CHANGES IN GROUND WATER STORAGE IN CABALLO CREEK ALLUVIUM
Changes are in acre feet within Belle Ayr Mine Boundary with precipitation equivalents in inches shown in parenthesis.
Data are for the calendar year of 1976
Month Above Below Mine Mine
February -0.02 (-0.90) +0.05 (+1.25)
March +0.02 (+0.90) +0.02 (+0.50)
April +0.01 (+0.45) 0.00 (0.00)
May -0.01 (+0.45) 0.00 (0.00)
June 0.00 (0.00) 0.00 (0.00)
July }-0.03 }(-1.34) }-0.05 }(-1.25) August
September -0.02 (-0.90) -0.04 (-1. 00)
October +0.04 (+l. 79) 0.00 (0.00)
November -0.01 (-0.45) -0.01 (-0.25)
19 ...... ~ ·~ Cl) Note: Perforated intervals in wells ~ Cb I at BAS-13, -14, and -15 are ~ ':""·~ (j ~ indicated by dashed vertical () lines. 0....., (§ ""' ...., ...... ~ ~ c:: ...... HORIZONTAL SCALE I ...... I ~ I ·~ "" 0 500 1000 feet I ~ :; CJ) 2 IJJ OVERBURDEN (SHALE, SILTSTONE, 8 SANDSTONE) > 4500 0 a:> N ct 0 t- IJJ IJJ .a. I I I ----- ~ • I 4400 I I ------z I I I I WYO OAK I Q I COAL I I- I I I I i I ~ I IJJ I I I I ..J I I IJJ .L I ' 4300 ..L 28* I * I FORT UNION FORMATION CLASTIC SEDIMENTS ..&.' Figure 5: Geologic cross section along T-7 Road showing static water levels (swl) in the various hydrologic units. AMAX Coal Company drilled two wells in the scoria. These, combined with well BAS17F may yield data during 1977 which would provide insight into this problem. The general experience of WRRI hydrologists in the Powder River Basin has led to the conclusion that scoria outcrops are probably the single most important zones of aquifer recharge. Maps of unconfined water tables normally show ground water levels to be high in such areas, indicating recharge. Fortunately, few of the scoria outcrops are dis turbed by mining. However, if reclaimed spoil is interposed between scoria and coal, the hydrologic characteristics of the spoil become critical to determination of the regional effects of mining upon ground water systems. As explained in the METHODOLOGY section, improvements have occurred in well construction since the 1975 report. The new wells have yielded data which forced a reevaluation of earlier conclusions. This has been especially true of water levels in the coal. Figure 6 shows the latest evaluation of potentiometric levels in the coal using data from wells believed to be reliable piezometers. Recharge to the coal at Belle Ayr Mine is not directly due to pre cipitation. As shown on Figure 7, there is a marked head difference between coal and overburden water levels with the coal having the lower head. Data from BAS13C, -14C, and -15C show the Fort Union potentio metric heads are yet lower than those in the coal. This is opposite to the conclusion reached in the 1975 report. The coals and deeper Fort Union sediments are generally being recharged by water moving downward from overlying aquifers. The high vertical head differences and the very low rate of infiltration to overlying Wasatch formation overburden 21 Figure 6 R.71 W. R.70W. I N ______IL------N ...... ------jio."i ~.,,£ I I I ..,/U-"A I~0 -· ," ...... EXPLANATION N WATER RESOURCES RESEARCH INSTITUTE e WHtlltr StOliOll ...... ,..... 0 PUt11p Ditcllortt - Totolizinq ~llAX COAL .. C.9MM!(Y ...... ,lle.Z14C A StrtOtllf!ow Got111t Station• - ~•coreltf ll. Strf'-'lo•· Gttillt Station - Periodic Obsenatinn BELLE AYR MINE • Ntr ...., Stet• • Instn1111ented Water Well• 1 POTENTIOMETRIC SURFACE • .,., ---int .... S.••nt 9fati9tl • u""""-tnttd Woter w.1i. IN COAL 0 sooo .... ,_...... 0 A4'fftle llot• MoRiterilll Silet H t==t I CAMF-£!ELL COu1~':'Y, WYOMING a ...... ,...... SCALE' FEET T 47, 48 N, R 10, 71 'II , 6tll P l'I. ~ LllllJrlC...... ~ ...... ,. 4485 I 31:\ X------>f-.----:11----->f.--.v, . ------er-~\!""-----~ o----·- l4A ~ 4475- 4465 15A .,,...@___ ~------~ ..,., ------~ -· ~ - . e--- z ,_ 4455 o~ l-- - ()c= _J E 4445 w ...... 0 ..J (]l wt:: 41.1·60 > r.: w c: o------..-. _J CJl 4440 15C ,~--+-----~----+ ------>~- --r. 4450 x- .... ------+------·. __}(_ +------,....x~-··· 13C,.....,,...... ,,...... 0------~ ' 4440 \_...-o---°, '-, 14C ...... 0 4430L .... ,~- I I I I I I I I I I I I I I 0 N D J F M t-\ M J J A s 0 N 19"{5 1976 MONTH OF YE/\11 Figure 7: Water Levels in BAS-13, -14, and -15 Wells. 23 indicate that vertical recharge to the coal must be nearly negligible in most areas. FigureS' 5 and 6 indicate that Caballo Creek alluvium receives most of the water from Wasatch aquifers beneath the bordering highlands along the stream valley. Since the aquitards between coal and alluvium are either thin or absent from the T-7 road eastward, signifi cant exchange of water between alluvium and coal probably does occur. Along T-7 road the exchange results in recharge to the coal. Analysis of hydraulic gradients and T values show that in the reach between the pit and T-7 road about 0.14 gallons per day are leaked from alluvium to coal per foot of valley length. It should be emphasized that this value is for the T-7 road area only. Upstream, because the aquitards are assumed to thicken westward, recharge should be less. Down stream in the vicinity of the BAS-17 series wells, discharge from the coal into the alluvium may be occurring. Figure 6 shows a "valley" in the potentiometric heads in the coal trending northwest-southeast north of Caballo Creek. This particular trend in ground water data has been noted by Don Tait, hydrogeologist for Atlantic Richfield Company (personal communication), at A.R.Co. 's Black Thunder Mine about 25 miles south of Belle Ayr Mine. It is a common fracture trend in the northern great plains area. Slug test values of T (Table II) in the coal show an increase as the axis of the "valley" is approached. It is hypothesized that the "valley" is due to an in crease in transmissivities along a northwestward trending fracture zone. Water in the zone is draining southeastward toward Caballo Creek. The drainage is presently intercepted by Belle Ayr Mine. Because of the high T values, the drainage creates a lower potentiometric head than in the alluvium of Caballo Creek at T-7 road and induces recharge from 24 Caballo Creek. The amount of recharge is, as before, very minor when compared to other components of the total hydrologic budget. The coal is probably also recharged along the coal/scoria interface. However, there are no site specific data at Belle Ayr Mine with which to support this hypothesis. The conclusion is based upon work by WRRI personnel at other mines in the area. Caballo Creek Alluvium Underflow Figure 3 shows alluvial cross sections across Caballo Creek. These cross sections, combined with data on alluvial transmissivities in Table II and hydraulic gradients from Table VII in Appendix B were used to estimate the volume of water moving down-valley through the alluvium. Data from January 20, 1976 were selected for analysis in order to avoid the com plications caused by stream/aquifer interactions during and shortly after periods of stream flow. Underflow values were 0.24 acre-feet/month (ac ft/mo) at Dunlap Lake, 0.07 ac-ft/mo at T-7 road, and 0.37 ac-ft/mo below the mine at the sediment pond. There is a loss of water in both stream and underflow between Dunlap Lake and T-7 road. Either evapotranspiration or recharge to the coal must be the recipient of this water. Values of underflow calculated here should be treated as minimum values. Although none of the wells used in determining underflow pene trated highly permeable layers, there is a possibility that such aquifers exist. AMAX personnel have reported that when drilling in the vicinity of well WRRI-10 during 1974, a test hole had to be abandoned because of excessive water production from the base of the alluvium. It is quite possible that the thalweg of the original Caballo Creek channel cut in 25 bedrock contains highly permeable gravels of very limited lateral extent. Until the existence of such gravels and their extent can be confirmed, however, there is no way to evaluate their hydrologic function. 26 IMPACTS AND CONCLUSIONS Observed drawdowns of water levels around the operating pit have been very restricted both in area and amount to this time. Only three wells, WRRI-7, N-1, and 481 (Figure 8) have shown dewatering effects to this time. There appear to be no measurable dewatering effects at distances in excess of one fourth mile from the pit. As noted earlier, the pit is probably located in a northwestward trending zone of high transmissivity. Unless the pit should encroach upon a zone of highly permeable scoria, it is unlikely that it will ever produce more water than it does now. Changes in water level should also be greatest along the fracture zone. Water level declines measured to date are probably as large as are likely to be measured. Recharge to the coal aquifers due to leakage from overburden Wasatch aquifers is insignificant. Recharge or discharge to the coal aquifers through alluvial deposits where Caballo Creek approaches and crosses the outcrop are probably a significant proportion of the total water exchange. It is hypothesized that nearly all of the remaining water exchange takes place along the coal/scoria interface. The most important properties of alluvium and scoria with respect to recharge of the coal are probably their capacity to accept large amounts of precipitation, transfer it quickly beyond the reach of evapotranspiration, and provide a reservoir for slowly transferring the water to the coal throughout the drier parts of the year. Calculated underflow through the Caballo Creek alluvium is insig nificant compared to stream flow in Caballo Creek. Underflow varied from 0.07 acre-feet/month at T-7 road to a maximum of 0.37 ac-ft/mo 27 below the mine. The underflow measured below the mine is probably a combination of seepage from the mine's settling ponds and recharge from scoria beds bordering the valley at that point. Hydraulic gradients are from the scoria north of the alluvium (BAS-17F) toward the creek. It is doubtful if the mining operations have had much effect upon the amount of water leaving the site as alluvial underflow. Water levels in the alluvium are essentially the same as those in the ponds along Caballo Creek east of the pit. Until alluvial water levels drop below the channel bottom, evaporation from the ponds will be the main discharge variable. Underflow changes will not be significant. 28 HYDROGEOLOGY OF SPOIL REPLACEMENT AT BELLE AYR MINE During 1976, for the first time, sufficient reclaimed overburden or "spoil" became available in which to construct a set of monitor wells. Locations and construction details of these wells are given in Table I. The wells were designed and located to accomplish three objectives: 1. Measure the interaction between the channel of Caballo Creek being reconstructed in the spoil and the spoil aquifers. 2. Determine vertical chemical and hydraulic gradients in the spoil. 3. Determine the aquifer parameters of various horizons in the spoil. In particular a pump test with multiple observation wells was planned in the basal spoil strata. Drilling and casing wells in reclaimed spoil has proven very difficult because of the unconsolidated, heterogeneous nature of the materials penetrated. A well tends to cave rapidly each time the bit is withdrawn to run casing or add drill stem. Air or plain water are not sufficient as drilling fluids in most cases. Water, thickened with additives to prevent caving and loss of drilling fluid, must normally be used. Problems were also encountered due to consolidation and shifting of the spoil material. Wells were constructed immediately after completion of topsoiling and grading the spoil. In at least two of the wells listed in Table VII, BAS-3, and -4A, the casing is believed to have collapsed. In the future the spoil will be given at least 90 days to consolidate before wells are constructed in it. 29 TABLE VII COMPLETION SUMMARY FOR WELLS DRILLED IN RECLAIMED SPOIL Ground Depths ..-I QJ QJ ~ Location Elev. () Casing (ft) > () Casing State 1-1 m m Well W~o. Coo rd. T R (ft ::i Ht. Packer Perf. 1-1 p., Drill Diam. Type Permit Date t!> Geoll No. Ft. North Ft. East Sec (N) (W) abv.msl) ~ (ft.) Total Casing Base Intvl. Fm. Bit (in.) Casing No. Drilled BAS-1 1,250,637 447,007 34 48 71 4482.8 s 2.6 54 54 34 34-54 x Spoil 2 PVC 8-14-76 BAS-2 1,250,363 446,719 34 48 71 4546.3 s LS 106 106 86-106 x Spoil 2 PVC 8-15-76 BAS-3 1,250,354 446, 733 34 48 71 4546.4 s 2.3 133 133 103 113-133 x Spoil 4 PVC 8-15-76 BAS-4A 1,250,304 446,767 34 48 71 4546.7 s 2.4 132 132 102 112-132 x Spoil 2 PVC 8-16-76 BAS-4B 1,250,304 446, 775 34 48 71 4546.1 s 2.5 150 150 119 129-149 x Spoil 2 PVC & F. U. 2 PVC 8-17-76 w 0 F. U. = Fort Union elastics below the Wyodak Coal The bottom of the spoil was encountered at 132 feet depth in BAS-4B. This was the first well in ithis location and drilling was continued to 149 feet total depth in order to verify the contact. All but three feet of the perforated interval in this well is open to Fort Union sediments below the coal mine. Some initial sampling and testing have been completed in 1976. The aquifer tests consisted of slug tests conducted in two of the wells. Results are shown in Table VITI. Well.BAS-3 is the only well completed to date with casing large enough to admit a submergible pump. However, a pump could not be placed below water level and it seems likely that the casing may have collapsed as suggested above. Permeabilities in the two wells appear to be about the same as in undisturbed coal of over burden. As water levels rise higher in the spoil wells, additional testing is planned. Field and laboratory water sample data are given in Tables IX and X. Total dissolved mineral content of the water is not greatly different from water in undisturbed coal or overburden. Additional sampling and more extensive laboratory analyses are planned during 1977. Water quality will be monitored on a bimonthly basis in either BAS-3 or -4A. Water level monitoring on a monthly basis was begun in December 1976. Water level data collected to this time are listed in Table XI. The only serious anomaly encountered to this time is the large difference in water levels in BAS-4A and -4B. These wells are very close to each other. Well 4B is completed in the basal 3 feet of the spoil and in the underlying Fort Union. Well 4A is completed in the basal 20 feet of spoil. The large head difference does not seem logical and will be investigated further during early 1977. 31 TABLE VIII SUMMARY OF AQUIFER TEST DATA FOR RECLAIMED SPOIL WELLS Aguif er Parameters Test Date Aquif. Well of Type Geol. Trans. Thick. Perm Storage 2 No. Test Test fm. (gpd/ft) (ft) (gpd/ft Coef f Comments BAS-3 10-27-76 slug Spoil 65 8 8 -0.04 Poor Data BAS-4V 10-27-76 slug Spoil 132 3 44 -0.0004 TABLE IX FIELD DATA ON SPOIL WATER SAMPLING ACTIVITIES Vol. Well Site Analysis Lab. of Water Method Elect. Alkalinity Well Date Sample Pumped of Cond. Temp. (ppm) No. Sampled No. (gal.) Aquifer Collection pH (µmhos) (°C ) co Total Connnents 3 BAS-3 10-6-76 7-1215 0 Spoil 8.5 2100 6 0 514 10-27-76 7-1471 0 Spoil 8.6 2500 6 BAS-4B 10-27-76 7-1472 0 Spoil 8.3 1700 8 VJ VJ TABLE X RESULTS OF LABORATORY ANALYSES OF WATER SAMPLES FROM RECLAIMED SPOIL Total Diss. Elect. Analysis No. Chemical Analyses (mg/l) Well Date Lab. Solids Cond. Fe HC0 Cl N0 (mg/l) pH (~mhos) No. Sampled Name Number Ca Mg Na K B co3 3 so4 3 BAS-3 10-6-76 WAL 7-1215 200 89 240 13 0.10 0.9 o.o 630 8.5 730 3.1 1740 7 .4 . 2160 BAS-3 10-27-76 WAL 7-1471 280 120 290 18 1.1 0.9 o.o 550 11 1400 7.9 2490 7.3 2740 BAS-4B 10-27-76 WAL 7-1472 96 37 280 12 0.60 0.7 0.0 860 23 260 0.2 1170 7.3 1730 TABLE XI WATER LEVELS IN RECLAIMED SPOIL Water Levels (ft) Well SeEt· 92 1976 Oct. 27 z 1976 Dec. 15 2 1976 No. Depth Elev. Depth Elev. Depth Elev. BAS-1 Dry <4429 Dry <4429 Dry <4429 BAS-2 106. 7 4441.1. 107 .1 4440.7 BAS-3 125.1 4423.6 123.5 4425.2 123.4 4425.3 BAS-4A 129.1 4420.0 125.1 4424.0 127.6 4421.5 BAS-4B 105. 3 4443.3 86.1 4462.5 85.9 4462.7 34 RECOMMENDATIONS FOR FUTURE WORK 1. Continue to monitor the alluvial well systems (BAS-17, -18, and -19) on a monthly basis. These wells promise to provide considerable in sight into the processes occurring beneath alluvial valley floors. 2. Complete the program of slug testing the alluvial wells. In addition, another attempt should be made to obtain a valid pump test from the wells equipped with well points. Such a test is the only way to obtain a better estimate of specific yield which is needed to obtain a better estimate of ground water storage changes. 3. Attempt to determine whether or not a highly permeable gravel layer of limited lateral extent and heretofore not penetrated follows the axis of Caballo Creek Valley. A combination of geophysical explo ration followed by drilling of wells is the recommended mode of study. 4. Continue to monitor water levels in the BAS-13, -14, and -15 series wells on a monthly basis. 5. Examine quarterly conditions in the mine along the east highwall as it approaches the scoria beds. 6. If sufficient funds should become available for a testing and drilling program, additional research on scoria hydrology and its role as a recharge site should be done. The region south of Caballo Creek would be the best site as mining is not scheduled to begin there for some years, and it is unlikely that pit dewatering has seriously altered conditions there. The program is likely to be somewhat expensive as scoria is a very difficult medium in which to drill and case wells. 35 REFERENCES Davis, Richard W., 1975. Results of a Hydrological Investigation of AMAX's Belle Ayr Mine and Vicinity near Gillette, Wyoming. Wyoming Water Resources Research Institute, Water Resources Series No. 57. Ferris, J. G., et al., 1962. Theory of Aquifer Tests. U.S. Geo logical Survey, Water-Supply Paper 1536-E. Mann, John F., Jr., 1976. Wastewaters in the Vadose Zone of Arid Regions: Hydrologic Interactions. Ground Water, vol. 14, no. 6, pp. 367-373. Winograd, I. J., 1974. Radioactive Waste Storage in the Arid Zone. Trans., Am. Geophys. Union, vol. 55, no. 10, pp. 884-894. 36 APPENDIX A ALLUVIAL WELL LOGS 37 Well Logs for BAS-17 This series of wells was drilled in January 1976 to investigate hydrological conditions in the alluvium below Belle Ayr Mine. BAS 17A BAS 17B 0 - 17 Sandy clay 0 - 10 Clay 17 - 20 Gravel, sand, clay 10 - 18 Sandy clay 17 Hit water 18 - 20 Sandy clay Total Depth 20 Water BAS 17C BAS 17D 0 - 14 Sandy clay 0 - 14 Sand, gravel, clay 14 Hit bedrock Bed Rock 14 feet Water Water Total Depth 14 Total Depth 14 BAS 17E BAS 17F 0 - 12 Sandy clay 0 - 12 Sand gravel clay 12 - 18 Sand and gr av el 12 Hit coal 18 - 20 Gravel sand 18 Water Water BAS 17G BAS 17H Scoria Pit 0 - 17 Sandy clay 17 - 20 Gravel sand 20 Foot Total Depth Water 38 Well Logs for BAS-18 This series of wells was drilled in January 1976 to investigate hydro geological conditions in the alluvium immediately above Belle Ayr Mine. BAS 18A BAS 18B 0 - 7 Sand 0 - 5 Sand clay 7 - 14 Coarse sand 5 - 13 Clay 14 Bed rock water 13 - 18 Shale BAS 18C BAS 18D Total depth 18.5 0 - 17 Gravel clay sand 1 - 3 Top soil 17 - 20 Fine blue sand 3 - 5 Gravel Water at 14.2 feet 5 - 9 Sandy clay 9 Water 14 Bedrock? BAS 18E 0 - 7 Sand 7 - 12 Coarse sand 12 Bed rock water? 39 Well Logs for BAS-19 This series of wells was drilled in January 1976 to investigate hydro geological conditions in the alluvium near the western margin of the Belle Ayr Mine at Dunlap Lake. BAS 19A BAS 19B 0 - 17 Sand 0 - 17 Sand 17 Bed rock BAS 19C BAS 19D 0 - 18 Sand 0 - 19 Sand 18 Bed rock 19 Bed rock BAS 19E 0 - 13 Clay 13 - 30 Sand 30 Bed rock Total Depth 20 ft 40 APPENDIX B STATIC WATER LEVELS IN UNINSTRUMENTED WELLS 41 Table XII STATIC WATER LEVELS IN UNINSTRUMENTED WELLS 0 '°,... ..;r u \D I ,.... ,.... '°,.... ,.._N '° ,.... ,.... ,.... ,... \D ,... ,.... ,... \0 I '°,...,.._I I "'I '° '° '° \D ,.... '° '° '° \D M "'I I I ,... I,.._ '°,...,... '° I I I ,...,...'° ,.... co 10 0 '°I I I I 0 I I I I NO '°... ~ N MN N ~~ M ... N NO\ ·-I ... Well I °'I N ..;r"' °' - N I I I I I I I I I I I ,...,....I I I 0-· ..!. ..!. ... N M M-:t \D ...... -· \D °'~ ...... No. '* "'"' '° '° -~ WRRI-2 18 WRRI-3 109.6 WRRI-8 8.36 8.12 10.80 12.l 12.02 WRRI-7 116.0 WRRI-9 9.31 9.25 9.60 9.03 11.1 11.5 11.55 WRRI-10 30.1 25.10 24.10 24.25 24.40 34.8 24.6 WRRI-lOA 31. 75 31.6 31.95 32.10 32.30 32.88 33.2 WRRI-11 6.8 3.80 3.95 4.00 4.95 4.8 WRRI-12 10.28 10.38 10.35 11.82 BAS-lJA 80.8 80 77.5 80.80 81.90 82.30 83.25 82.85 BAS-13B 113.5 112. J 114.1 112.50 113.90 118.35 115. 75 115.2~ BAS-13C 112.3 110.8 110.9 118.10 114.80 119. 75 114:78 113. 75 BAS-14A 37.1 36.2 36.08 36.15 36.30 36.45 36.59 36.5 BAS-14B 60.3 59.3 60.21 67.95 67.50 67.75 68.40 67.9 .i;:.. 74.05 75.67 81.60 80.55 80.01 86.20 85.0 1:-.,) BAS-14C 74 BAS-15A 12.9 9.03 9.4 10.67 8.40 8.70 8.95 10.00 9.9 9.7 BAS-15B 19.1 16.34 13.J 13.25 13.15 14.15 14.60 14.85 14. 7 14.7 BAS-15C 22.5 21.66 20.1, 18.17 17.60 17.80 17.80 17.70 18.9 18.7 BAS-16 ~ Dry Hole-~ Not Cased BAS-l7A 15. 71 14.90 15 14.60 14.40 14.80 14.45 15.4 15.81 15.7 BAS-l 7B 11.L.8 10 .... 9.40 9.05 9.45 9.30 11.0 11.5 11.4 BAS-17C 5. 16 3 2.00 3.95 2.90 3.00 3.29 3.4 BAS-170 4.69 3.4 3.80 4.9 2.45 2.70 4.67 4.6 BAS-l 7E 11.% lU. l !U.UU 'J. /U 9.65 9.20 10.~ 11. Zl 11.4 BAS-17F 15. ·;3 16 15.7 15.60 15.75 15.95 16.5 16.12 16.2 BAS-17G 0.0 BAS-17H 9.41 8. '• 8.1 8.0 8.40 7.85 10.6 11.42 11.6 BAS-18A 8.25 7.73 7.9 8.21 7.65 7.90 7.35 9.00 9.1 8.9 BAS-188 17.39 18 17.17 16.95 17.00 17.15 17.20 18.75 17.g BAS-18C 13.79 12.8 12.88 12.70 7.00 13.15 12.85 13. 75 13.5 BAS-180 15 .117 15.5 15.17 15.10 15.20 15.05 15.70 15.83 15.85 BAS-18E 7.68 9.0 5.67 7.25 8.00 8.35 9.20 12.1 8.6 BAS-19A 8.65 9.·1 8.5 8.40 8.70 8.75 I 10.40 10.25 10.0 BAS-198 7 • .56 10 7.4 7.50 7.80 7.85 9.15 9.2 9.1 BAS-l9C 8.18 8.5 7.7 7.70 8.15 8.15 9.45 9.2 9.1 BAS-190 9.20 9_.; 8.9 8.70 9.15 9.10 10.30 10.l 10.0 BAS-19E 19.09 18.5 18.5 18.50 18.55 18.50 19.40 19.8 19.8 Belle Ayr 5 76.55 76.3 76.40 77.30 77.20 77.43 78.1 Belle Ayr 6 Belle Ayr 7 16.00 115.10 APPENDIX C STATIC WATER LEVELS IN INSTRUMENTED WELLS 43 STATIC WATER LEVELS AT BELLE AYR MINE WRRI 7 + 481 a a a x N 1 C) a C) a a lf) l..f) tj' -cl' a C) C) C) a a ~ CJ::J tj" tj" tj' 'Cf' a a a a . C) C) co co tj' tj' .+:"' ~ 'Cf'.--,. .+:"' _J _j en (..)) ~ oL: >C: C:> COa ocn cr:tj" 'd'CC tj' 'd' 1--d' -d-1- lJ.._ l.J.... a C) _p O_J ~ -~ (f)(\J ~lj) "'d" 'd' tj'~ ..:f' Mtt M'PI\ JL sr NV Dt: l"'B ,... JU P1IC nt: nt: l"'B ~ JU !'IC Ot: Dt: fB P'1" JU P\C n 74 75 76 Figure 8: Water levels in instrumented wells WRRI-7, 481, and N-1. The abrupt change in water level in well N-1 occurred in June 1974 when a recorder was installed. It is probably poor data and is treated as spurious in making calculations for this report. STATIC WATER LEVELS AT BELLE AYR MINE N 11 + N 13 a a C) x WRRI 5 a a - 0 0.J (\J U) U) ~ tj' a C) C). C). C) C) a C) ~ ~ C) C) C). C). C) 0 +:-- a:) a:J V1 tj' tj' ~ ~--... _J _J en CJ) ~ a::L >~ ~> CDc::) om CI: a 0 _p O_J ~ -~ ~ ~()) -d' tj' -d' -ti' ,.)\ I"« ~ JL s,- NV DC P"B 'N' JU !'IC Qt: Ot: P"B ,,,,. .JU l'IC ac: Dt: l'B ,,,,. .JU f'C 7.:J 74 75 76 Figure 9: Water levels in instrumented wells N-11, N-13, and WRRI-5. STATIC WATER LEVELS AT BELLE AYR MINE WRRI 8 + WRRI 9 C) C) x WRRI12 C)- C) a C)' a a a C) a 74 75 76 Figure 10: Water levels in instrumented wells WRRI-8, WRRI-9, and WRRI-12. STATIC WATER LEVELS AT BELLE AYR MINE N 3 + N 5 0 a C). C). 0 a r- r- 'd" tj" "Ct' C) a C) a . Lf) 1.1') co c:.o tj" tj" "Ct' 'Cf" 0 C) 0 . 0 . a a co co .+:"-- tj' tj' ...... ~ "Ct'_... _J _J en en ~ aL >C:: C::> CQ.n LJ')a::l ccm mo: tj' ~ .,_-cl' ~I- LL LL 0 C) _p O_J •:s::: ~ UJU) ~(J) tj' tj' ~ "Ct'~ ~ f"fll JL 9" NV OC rre ~ JU ~ oc DC rra f'rP JU Pc. oc DC l"'B l"lr JU PC 7, 14 7S 76 Figure 11: Water levels in instrumented wells N-3, N-5, and N-6.