GROUND WATER IN SPEARFISH VALLEY
Prepared for:
U.S. Environmental Protection Agency
1860 Lincoln St.
Denver, Colo. 80295
and
City of Spearfish, S.D.
Prepared by:
Perry H. Rahn, Ph.D.
Cert. Prof. Geol. Scientist #3724
201 Franklin St.
Rapid City, SD 57701
and
. Arden D. Davis
S.D. School of Mines & Technology -•
Rapid City, SD 57701

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INTRODUCTION
There has been concern that septic tanks are polluting ground
water in the developing areas adjoining Spearfish, S. D. Of particular
interest is the possibility that septic tanks do not have a required
4 ft of unsaturated zone below the septic tank, as required by S. D.
law. The U. S. Environmental Protection Agency (EPA), the S. D.
Department of Environmental Protection, the Lawrence County Commissioners,
and officials from the cities of Spearfish and Belle Fourche have been
studying the problem.
On April 27, 1979, the U. S. EPA agreed to extend their study of
the ground-water conditions in Spearfish Valley, just north and west of
Spearfish. A contract was arranged for this study through the City of
Spearfish and Scott Engineering.
GEOLOGY
The area of interest for this study is the lowland north and west
of the City of Spearfish in Sections 28, 29, 32, 33, T. 7 N., R. 2 E.,
and Sections 4, 5 8, and 9, T. 6 N., R. 2E.
The geology of the area is shown in Figure 1. The area of shallow
water table is in the lowland, which consists of alluvium underlying
the flood plain (Qal) and, in some places, the young terrace deposits
(Qty). The alluvium typically consists of sandy gravel (Figure 2),
which grades into coarse boulder (alluvial fan) deposits at the mouth
of Higgins Gulch and other canyons to the south. The alluvium is about
10 to 30 ft thick.

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OBSERVATION WELLS
On April 18 and 19, 1979, ten observation wells (EPA-1 to EPA-10)
were drilled by Francis-Meador-Gellhaus, Incorporated (Figure 3). The
wells are located so as to optimize information concerning the water
table. All wells were logged and flushed to ensure hydraulic connection
with ground water. The location of the ten wells is shown in Figure 4.
Forty-three additional wells were also monitored for this study.
Some of these wells are unused water wells and some are observation wells
drilled by the City of Belle Fourche for earlier studies. Several of
these wells were always dry during this study and no information other
than their location (Figure 4) is noted.
Water levels in the 53 monitoring wells were measured approximately
every week during the period April 18 to July 14. A water level indicator
was used to measure the static level (Figure 5). Table 1 shows the raw
data. The depth to the water table was plotted as a function of time
(Figure 6). Graphs are not included for those wells which were nearly
always dry (e.g. EPA-1, 64, 81-84, etc.). For each well shown in Figure
6, the highest water-table position was determined.
WATER-TABLE CONDITIONS
Figure 7 shows a contour map of the seasonal high water table.
This map is based on data from 46 observation wells, springs, seeps, and
perennial streams, in conjunction with topographic maps and aerial photo-
graphs .
The water-table contours indicate that ground water in the alluvial
aquifer moves north-northeasterly from the Higgins Gulch area and thence

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northerly in Spearfish Valley.
Water coming down Higgins Gulch from the Black Hills disappears in
the SE 1/4 of SE 1/4 of Sec. 6. Down-valley, springs occur in Higgins
Gulch, in the SE 1/4 of SW 1/4 of Sec. 28. It is believed there is a
good exchange between surface water and ground water in alluvium through-
out the valley.
Figure 8 is an isopach map of the unsaturated zone. This map shows
that the water table is near the surface (less than 10 ft) in the lower
reaches of the flood plain near the Belle Fourche infiltration gallery,
but is generally more than 20 ft deep in the southwestern half of the
study area.
DISCUSSION
The direction of flow of ground water (Figure 7) in the surficial
alluvial aquifer indicates that contamination of the Belle Fourche gallery
could occur from sources in the Higgins Gulch area. It would appear,
however, that houses in this area (i.e. south of 1-90) are not in violation
of septic tank codes because the water table is over 15 ft deep. The water
table is quite shallow, however, in the Hope Weiss property and adjoining
areas near the Belle Fourche gallery (Figure 9).
Another source of contamination is at the mouth of Higgins Gulch
(Figure 10), in NE 1/4 of NE 1/4 of Section 7. At this point water flows
out of the Black Hills and sinks into coarse (alluvial fan) boulder gravel.
Manure from a barn and corral can be seen in the water where it sinks into
the alluvium.
It should be pointed out that in 1979 the spring and early summer
were unusually dry (Table 2). Therefore under normal conditions the

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seasonal high water table may be higher than the 1979 data indicate.
It is believed that under normal precipitation the water table may be
about 5 to 10 ft higher in the Higgins Gulch area than indicated in
Figure 7.

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Geologic map of the study area. The bedrock consists of the
Permian Minnekahta Limestone and older sedimentary rocks (P)
and the Triassic Spearfish Formation (TR) . The surficial
deposits consist of Quaternary alluvium (Qal), a young
Quaternary terrace deposit (Qty), and an old Quaternary
terrace deposit (Qto). Mapped by P. H. Rahn, July, 1979.

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Figure 2. Alluvium exposed in a road cut in a terrace deposit in
SE 1/4 of SE 1/4 of Section 5.

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Figure 3. Drilling observation well EPA-1.

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Figure 4. Map of Spearfish Valley showing location of observation wells.

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Figure 5- Measuring the static level in observation well EPA-5. The
2" PVC casing and the Soiltest water level indicator probe
can be seen.

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65
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Figure 7. Water-table contour map. Contour interval is 10 ft. All
***	Gr°UIld W3ter WOuld flow
DerDencJic.ular to che. contours.

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ZC«* iWc
		 		v
Figure 8. Isopach nap of the unsaturated zone. The contcur level 	
10 ft. Areas where the water table is less than 10 ft deep
are shown with diagonal shading.
is

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Figure 9. View of the Belle Fourche Infiltration gallery area, looking
southwest. Spearfish Creek is on the left. Hope Weiss
property adjoins the gallery area to the south. Crow Peak
is in the background.

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Figure 10. Contaminated water at mouth of Higgins Gulch. Manure lies
in the water at this point.

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Table 1. Data for monitoring wells.
WATER LEVELS - SPEAP.FI5K VALLEY PROJECT
Well Number
E?A-1
EPA-2
EPA-3
EPA-U
EPA-5
EPA -6
EPA-7
EPA-8
EPA-9
SPA-10
wee C. G.
Peters #1
Peters #2
Pascoe
Nicholes
1
2
6
7
8
5
1C
11
-£
c
D
13
1h
15
17
50
51
c-i
c-3
c-U
D-l
D-2
D-3
61
65
67
68
69
85
Ground
Slev.
3638.20
3703.01
366U.65
3612.39
3665.23
3706.lh
3U78?
3516
3U71
3U18.57
3622.79
3U32.10
3U33.20
3^31.62
3U29.27
3U26.77
3li23.U9
3U20.3U
3U15.66
3U07.13
3^05.95
3399.07
3U07.27
3UII1.27
3U33.10
3U32.36
3U36.51
31; ill. 53
3U32.27
3U31.ii9
3UU6.59
3Uiil.86
3I1L6.L5
3U60.55
3U66.37
3U67.65
3U86.11
3^69.5U
3163.75
3^53.35
3liU7.30
3560
jlev. - To:
of Casing
36L0.6?
3703.38
3668.10
3612.U7
3665.73
3707.17
3U781
3516
3U71
3U19.02
3623.U3
3U32.87
3U3U.12
31x32.52
3li.30.27
3U27.73
3U2U.55
3U21.25
3U16.U1
3ii.OS.l5
3ii06.85
3100.36
3UC8.69
3U15.37
3U33.50
3u33.19
3U36.91
3UU.53
3U33.35
3U32.51
3iiU6.59
3I1UI.86
3U51.83
3U67.32
31x69.50
3U68.75
3U88.30
3U69.5U
3U58.75
3U53.35
3U50.h6
3580
Ht. of
Casing
2.U9
.37
3.U5
.08
.50
1.03
0
0
0
.U5
Static Water Level
(ft below ground)
May 5, '79
.77
.92
.90
1.00
.96
1.06
.91
.75
1.02
.90
1.29
1.12
1.10
.uc
.83
0
0
1.08
1.02
0
0
5.38
6.77
3.13
1.10
2.19
0
0
0
2.66
0
Hi.95
20.U2
21.68

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WATER LEVELS - SPEAR?ISH VALLEY PROJECT
Static Water Level (ft below ground)
iVell Number
May 17-19, '79
June 1, '79
June 8, '79
June 15j
EPA-1
>21.81
dry
dry
dry
EPA-2
19.09
M
18.98
ti
SPA-3
21.25
n
21. 2U
21.38
EPA-U
13.17
13.17
13.05
13.27
EPA-5
20.51
18.62
18.77
18.92
EPA-6
16. UO
17.02
dry
16.99
EPA-7
16.83
13.65
13.19
13.00
EPA-8
2U.20
23.U5
23.35
2 3.U6
EPA-9
20.95
20.U6
20.77
20.77
EPA-10
7.97
6.11
6.03
6.15
Wee C. G.
13.15
13.62
13.U6
12.60
Peters #1
19.20

17.50
16.67
Peters #2
17.68
15.85
la.83
13.81
Pascoe
21.53
21.U5
21.25
21.U2
Nicholes
33.01
33.75
33.UU
33.67
1
10.5U

10.50
10. UU
2
12.62

12.U8
12.71
U
13.20

12.95
13.16
5
11.10

10.73
10.99
6
10.5U

10.27
10.52
7
10.09

9.75
10.05
8
8.80

8.36
8.78
9
6.23

5.90
6.27
10
1.58

1.61
2.21
11
6.02

5.87
6.12
3
6.67

6.69
6.75
C
11.53

11.75
11.39
D
16. UO

16.53
16.67
13
9.77

9.18
9.U5
lit
9.21

8.82
9.05
15
11.29

10.79
10.92
17
10. U6

>9.90
dry
50
9.9U

9.3U
9.61
51
10.25

9.73
10.00
C-l
10.90

10.31
10.71
C-3
5.31

3.81
U.19
C-U
10.18

9.16
9.U3
D-l
dry

6.56
6.73
D-2
1U.39

12.60
12.72
D-3
15.23

13.28
13.UO
61
1U.16

10.79
9.98
65
dry

6.98
7.13
67
13. UU

12.27
12.17
68
8.35

7.96
o.OO
69
7.U2

7.31
7.35
85
30.60

20.5U
27.10

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V/ATZR LEVELS - 3FEAR?ISH VALLEY PROJECT
Static Water Level (ft below ground)
tfell Number
June 22, '79
June 29, '79
July 5, '79
3PA-1
dry
dry
dry
ro*
•J* c
ii
tl
it
EPA-3
21.38
21.U0
21.38
epa-U
13.27
13.55
13.7U
epa-5
19.13
19.52
19.75
EPA-6
16.97
16.92
17.01
EPA-7
13.00
13. U6
13.U6
EPA-8
23.35
23.50
23.51
EPA-9
20.80
20.81;
20.80
SPA-10
6.03
6.06
6.lii
Wee C. G.
12. US
13.11
13.OU
Peters #1



Peters #2
12.75
12.81
12.U2
Pascoe
21.1*8
21.96
22.17
Nicholes



1
10.08
10.21
10.28
2
12.06
12.37
12.37
h
12.7h
12.90
12.93
5
IO.LiO
10.63
10.73
6
9.36
10.19
10.3U
7
9.2U
9.61
9.78
8
8.07
8.37
8.56
9
5.59
5.85
5.96
10
1.U3
1.71
1.86
11
5.73
5.58
5.98
3
6.61
6.65
6.77
C
11.77
11.91
11.96
D
16.U2
16.56
16.67
13
8.95
9.30
8.95
Ih
8.57
3.78
8.57
15
10.50
10.69
10.5u
17
dry
dry
>9.38
50
9.06
9.52
9.07
51
9.1*5
9.93
9.52
C-l
10.35
10.56
9.82
C-3
3.7U
U.21
3.22
C-h
9.00
9.17
8.33
D-l
6.56
6. Lit
6.50
D-2
12.22
12.86
12.58
D-3
12.SU
13.59
13.18
61
S.hh
1C.L1
10.21
65
7.10
dry
dry
67
11.9u
11.96
12.10
68
7.7 9
7.63
7.90
69
7.22
7.25
7.21
85
23.33
23.77
2U.U6
July 1U, '79
10. UO
9.12
3.73
10.31
dry
9.23
9.58
10.15
3.36
8.95
6.U8
12.60
12.09
7.92
7.32

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WATER LEVELS - SPEARFISH VALLEY PROJECT
Distance (below ground)	Elevation of
Well Number to Highest Water Level	Highest Water Level
EPA-1
> 21.81
<3616.39
SPA-2
18.98
3684.03
EPA-3
21.23
3643.42
EPA-4
13.Oli
3599.35
EPA-5
18.60
3646.63
EPA-6
16.33
3689.31
EPA-7
12.96
3465.04 ?
EPA-8
23.33
3492.67
EPA-9
20.44
3450.56
EPA-10
6.00
3412.57
Wee C. G.
12.44

Peters #1
16.55

Peters #2
12.35

Pascoe
21.24
3601.55
Nicholes
32.94

1
10.06
3122. 04
2
12.04
3421.16
4
12.72
31x18.90
5
10.38
31*15,19
6
9.84
3416.93
7
9.23
3414.26
8
8.04
3412.30
9
5.56
3410.10
10
l.Iil
3405.72
11
5.70
3400.25
3
6.59
3392.49
C
11.52
3395.75
D
16.39
3397.88
13
8.91
3424.19
14
8.54
3423.82
15
10.25
3426.66
17
> 9.38
<3432.15
50
9.03
3423.24
51
9.43
3422.06
C-l
9.72
3436.87
c-3
3.10
3438.76
C-4
8.25
3438.20
D-l
6.42
3454.13
D-2
12.17
3454.20
D-3
12.80
3454.85
61
9.42
3476.69
65
6.94
3462.60
67
11.92
3446.33
68
7.78
3445.57
69
7.19
34-:0.6l
85
20.2
3560

-------
1979
0.79
1.02
0.81
1.31
1.95
2.85 (swe.O'0
II.54
All data are Inches.
So dcvv1~ c>-£
>o
b )Ck
d r \ -er i~ ^ °-
.A o^efo.ae
1
O
3
u
c
6
n
Q
i pr^'/>- Q
^ OV\^vA' I ,1 sb
7""^ 10
"J	"Si
12
12
Ik
15
16
17
18
19
20
21
-?o
23
2k
25
25
27
2°
29
30
Total
V5"
June
Jif. y
r\ r\h
v' • L
0.0k
0
0
0
0
0
0
0
o
o
0.16
0
0
0
0
0
0
0
0.?k
Q
0.02
0.12
0
0.27
0.06
o.lk
0.71
0.05
0
0
0
0
0.03
0
0
0.02
0
0.23
0
0
a rvQ
•J • ^ - -
0
0
/>

0.70
0.72
0
0.72
0.13
0.19
0.09
0
0.22
0.05
o
0
0.03
0
0
0
0
A
J
0.0?
0
0
0
o
0
0
0
A
'.J
0.03
0.6k
0
A
0.26
c
^ po
V « ^ ,
O.C-k
C.06
0.10
0
T»
1
o.o:
0.'-5
0.67
0
0
0.02
- -
A?
o .
1.85
2.?1
2.°5
Table 2. Precipitation data. Supplied by Stuart Reed of Homestake
Sawmill and the U. S. Weather Bureau.

-------