EPA--908/4-77 -002
SUB IRRIGATED ALLUVIAL VALLEY FLOORS
A Reconnaissance of Their Properties and Occurrence
on ~oal Resource Lands in the Interior Western United States
DRAFT
U.S. Environmental Protection Agency
Region VIII, Office of Energy Activities
1860 Lincoln Street
Denver, Colorado 80295
March 1977

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EPA-908/4-77-002
SUB IRRIGATED ALLUVIAL VALLEY FLOORS
A Reconnaissance of Their Properties and Occurrence
on Coal Resource Lands in the Interior Western United States
DRAFT
U.S. Environmental Protection Agency
Region VIII, Office of Energy Activities
1860 Lincoln Street
Denver, Colorado 80295
March 1977

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SUBIRRIGATED ALLUVIAL VALLEY FLOORS
- A Racotwiiasanca of Their Properties and Occurre
Coal Resource Lands is The Interior Western
March 1977
tatea*
John E. Hard
Chief, Research & Applic
Den B. Kimball
Environmental Protection TSffiiologlst
Shirley 7, Lindsay
Terrestrial Biologist
Jack Schmidt, Larry Erlckson
Consulting Geologists
U. S. Environmental Protection Agency, Region VIII
Denver, Colorado
Introduction
Concern for Alluvial Valley Floors
and the Impacts of Surface Coal Mining
Concern has been expressed regarding the long-term impacts of surface coal mining
on lands in the veetern United States currently or potentially useful for agriculture.
Part of this concern bears on disruption of these lands used by wildlife. In particu-
lar, there are questions regarding the potential Impact of coal extraction in certain
lowland areas of the seal-arid West where shallow ground vatar and/or soil moisture
is adequate to support growth of gresses and forbs through the dry months. These
land Atui| located along drainage channels end referred to recently as "alluvial
valley floors" (National Academy of Sciences, 1974), are most important in seml-arld
and arid climates because water is "stored" In the alluvium, enabling vegetation to
continue growth during the months of low rainfall. Apparently, soil moisture, and
psrhaps some near-surface ground water, sublrrlgates the vegetation.
The character of the vegetation Is a function of both depth to water table
(depth to saturated zone) and quality of the soil moisture and ground water. The
depth to water table, as well as seaaonal variations in this parameter, may be criti-
cal in determining the composition of the vegetation. Tot example, if the saturated
zone la sufficiently near the ground surfece to permit capillary migration of ground
w,t*r to the surface, subsequent evaporation may cause accumulation of salts. Under
such conditions, the vegetetlon may be comprised principally of salt-tolerant species,
such as alkali sacaton (Sporobolus alroldes). Similarly, the configuration and
moisture retention characteristics of the capillary and remaining unsaturated zone
¦•y b* tha most critical elements of the ground water system thet supports vegeta-
tive cowsunitias in the lowland areas. However, no one has yet reported on the
essential functions critical to sustained growth of vegetation In these areas.
Alluvial valley floors are used for gracing and for production of hay. Both
domesticatsd and wild animals are attracted by the more vigorous vegetative growth
end the presence of surface weter In these lowland areas. The alluvial valley floor
areas Include the principal surface water accumulation points, as well as points of
ground water recharge and discharge.
The composition of vegetetlon In sublrrlgatad alluvial valley floors is import-
snt since some grass and legume species are more desirable as hay. Some vegetative
* This article is based on a draft report balng developed by the authors. However,
no official eupport or endorsement by the Environmental Protection Agency or any
other agency of the federal government Is Intended or should be Inferred.

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species develop root systems that extend perhaps ten meters deep to obtain
sufficient water, but many grass species favored for hay are more shallow rooted
(i.e., on the order of two meters in depth). Examples of these grasses include such
native species as Canada wildrye (Elymus canadensis), little bluestern (Andropogon
acoparlym), and blue grama (Bou'reloua gracilis). The relatlvelysMllow, fibrous
nature of root systems characteristic of these grasses is docu^Rv by Heath et al.
(1973) and Weaver (1968). The deeper-rooted species inclu^Jk	woody plants
which serve a useful role in supporting game anlaa^^^KUWB^BOv^^and forage for
domesticated animals such as cattle or sheep. Uat^flfc^faBvu£iup.ive growth of an
alluvial valley Includes native greases. At times vwUwpl valley floor may in-
clude alfalfa; however, alfalfa is generally considAsS^ Te a deep-rooted phreato-
phyte and may also be grown outside an alluvial vallef^ The alluvial valley can be
Important for agriculture in that it not only provides forage during the growing
season, but also can provide sufficient vegetative growth for forage to be cut and
stored for winter use. It is often possible to obtain three cuttings of hay in sub-
irrigated alluvial valley floors.
The agricultural and wildlife uses of lands in the interior western United
States* have been prominent since they provide the principal source of income.
Though oil end gas production and now coal mining have provided some development and
economic support to the region, they are activities which remove a non-renewable re-
source and which might be considered temporary compared to farming, ranching, fish-
ing, hunting and enjoyment of scenery. It is important to insure that the agricul-
tural and recreational economy is as strong, if not stronger, after mining as it was
prior to mining. Thus, if the alluvial valley floor is critical to the success of
a ranch or to the maintenance of local wildlife populations, these vital functions
must be protected - at least until such time aa it is demonstrated that the alluvial
valley floor's usefulness may be efficiently and economically replaced by an alter-
native source of domestic fodder and/or wildlife habitat.
Surface mining of coal has the potential, in the western United States, to
teaiporarily, and even permanently, change the ground water flow system. If the mine
involves disturbances of saturated strata or aquifers, It is likely that while
mining, the local water table(s) will drop somewhat and ground water flow will be
intercepted by, or will be directed toward the mine pit. But this Is a temporary
situation, since in most cases the water table will be reestablished after mining is
completed and the mine pits are backfilled and graded. However, if the mining dis-
turbs confining streta that serve to isolate aquifers** which have significantly
different potentlooMtric heada, such as that which appears to occur in the Sarpy
Creek watershed in southeastern Montana, there may be a significant change in the
depth to water efter mining and reclamation.
Changes in the water table will also affect the postmining use of sublrrigeted
alluvial valley floors. If changes In the depth to the water table are more than
a few meters, it appears reasonable to expect some effects on vegetation In lowland
areas. Phreatophytes (alfalfa, for example) are especially sensitive to changes in
the depth to available water. Grasses with fibrous root systems are not able to
penetrate deeply into the substrate. Such vegetation may be adversely affected if
the post-oiniag water table is deeper or if the post-mining moisture holding capa-
city of the growth medium is significantly reduced. Effects on vegetation could
involve a shift toward deeper-rooted and more drought-resistant vegetation, or a
shift to shallow-rooted vegetation (the latter If the depth to water Is decreased).
Thus strata functioning as relatively Impermeable lower boundaries for water tables
in the alluvial valley floors might have to be recreeted after mining to prevent
undeeirable lowering of the weter table.
* The term "interior western United States" is loosely used to include North Dakota,
South Dakota, Montana, Wyoming, Colorado, Utah, Mew Mexico, and Arizona.
** Aquifer: relatively permeable rock containing and conducting sufficient ground
water to yield significant quantities of water to wells and springs.

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Extensive mining of an alluvial valley floor, even when followed by reclamation,
has the potential to produce Impacts on uses of that water, both at the nine site
and wherever the affected water flows. Overburden material (or spoil) returned to
the mined area is in many cans more susceptible to oxidation and leaching of the
elements than was the undisturbed overburden. Salts concentrations often Increase
after mining and are noteworthy since high salt concentrationssoil solution
impede the uptake of water by plant roots. High aodlumcoagnwatSns (relative to
calcium and magnesium) can also detrimentally affec^^feoflkdtflbcwre and conse-
quent uptake of water sad oxygen by plants.	\
Table I contains repreeentatlve results of groAA^t«^quality measurements
collected by the Montana Bureau of Mines and Geology^nrom two surface coal mining
areas in southeastern Montana. Examination of this limited amount of water quality
data first suggests that concentrations are highly variable and conclusions csnnot
be drawn. However, the analyses of ground waters near Decker, Montana, do suggest
that spoiled overburden contains water with higher concentrations of most elements
than water obtained from undisturbed overburden and coal (the strong exception is
the carbonate ion). Spoils waters at the Decker mine are higher in specific con-
ductance than waters collected from the shallow alluvium, undisturbed overburden,
and coal. The Increase Is due, principally, to calcium, sodium, blcarbonats, and
sulfate concentrations. However, indicative of data variability is the fact that
the second-highest specific conductance at Decker mine was found in a ssmple col-
lected from undisturbed overburden, and that concentration is higher than one of the
spoil water samples collected at the seme mine.
Water quality data from ground water samples collected near Colstrip, Montana,
show trends similar to thoae collected near Decker (Table I). Spoils water is some-
what higher in specific conductance than waters from undisturbed overburden and coal.
The Ions contributing chiefly to this lncreaae are calcium, magnesium, bicarbonate,
and sulfata. Although sodium content was higher in Decker spoils water, it is lower
in Colstrip soils water than In undisturbed overburden and coal. On the other hand,
magnesium levels are higher In Colstrip spoils water, but about the sane In spoils
and undisturbed overburden at Decker.
It should be noted that the data In Table I are from samples which do not neces-
•""¦7 represent e long term, "before and after mining" analysis (i.e., no samples
were collected In the same area before and after mining a particular location.)
Thus comparison of the quality of water in undisturbed overburden and spoils does
not necessarily Indicate expected water quality following complete "reclamation".
t w* do conclude that spoiled overburden contains ground water of poorer
quality than in nearby undisturbed overburden end water-bearing coal seams, and thus
that nevly spoiled overburden has the potential, at leeat in selected clrcumstsnces,
to produce ground water of relatively poorer quality. Whether deterioration in
water quality will significantly affect overlying vegetation Is not known. However,
Initial stands of vegetation on regraded lands at the Decker mine appear to be
healthy one and two years following seeding. In the case of coal mining near Decker,
Montana*, it has been projected that spoils water will have dissolved solids content
ranging from 4,000 to 7,000 ag/1, principally sodium and sulfate, (USDI and State of
Montana, 1976). It la also concluded that in spite of these high levels of dis-
solved solids in ground water, the cumulative impacts of the Decker operations ad-
jacent to the Tongue River Reservoir on reservoir water quality, and thus on water
uses, will be insignificant and difficult to detect.
il
Rahn (1976) has statistically analysed tventy-elght ground and surface water
samples collected from eight mines** in northeaatern Wyoming and aouthaaatern
* Current mining at the Decker and Rosebud mines at Colstrip does not involve direct
disturbance of sublrrlgated alluvial valley floors.
**Wyodak Mine, Big Horn Mine, Decker Mine, Rosebud Mine (Colstrip), Big Sky Mine,
Hidden Water Mine (abandoned), Antelope Mine, and Bell Ayr Mine. Appendix 1 pro-
vides a more complete llatlng of surface coal mines examined for alluvial valley
floors in this report.

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IHulC 1
SELECTED WATER QUALITY ANALYSES OF
GROUND WATER NEAR DECKER AND COLSTRIP MONTANA
Alluvium1
Alluvium1
Overburden
(undisturbed)'
Coal1
Spoils water]
Spoils water1
Alluvium?
Alluvium?
Overburden
(undisturbed)?
Overburden
(undisturbed)?
Coal-Rosebud?
Coal-McKay?
Spoils water?
Spoils water?
Spoils water?
Spoils water?
Specific Conductance
Mmhos/cm Ca
Mg
Concentrations 1n milligrams per liter (ppm]
Na K HC03 C03 SO4 S10?
I - Dissolved
CI F
N0a
Fe
pH(
920
85
57
36
8
420
0
176
21
7
1.0
1.3
0.00
7.6
2620
86
185
350
12
626
0
1152
27
11
0.3
0.3
0.01
7.9
5060
31
13
1355
9
1996
19
1320
8.6
16
0.4
32.0
0.2
8.4
1660
6
0.4
450
4
1139
23
8
9.0
16
2.6
0.0
0.9
8.5
4390
67
66
995
16
1546
0
1248
13
30
0.6
1.0
6.5
7.2
7281
202
63
1640
16
882
0
3464
20
21
0.3
2.0
0.23
6.8
4240
402
924
500
8
334
0
5390
15
33
0.2
32.0
0.07
8.2
2470
234
184
143
8
576
0
1110
25
13
0.2
1.2
0.1
7.5
483
46
34
6
2
234
0
58
11
7
0.1
15
0.2
7.9
3140
20
8
745
4
258
0
140Q
6
13
0.5
0.2
0.08
8.2
2490
141
288
93
6
923
0
919
12
7
0.0
1.1
0.01
7.6
2540
217
199
160
8
594
0
1140
21
117
0.2
1.0
0.1
7.5
4860
481
748
23
11
697
0
3640
17
3.2
0.2
0.3
0.3
7.3
2990
333
317
58
12
629
0
1670
21
14
0.1
4.4
0.15
6.9
2300
208
238
34
6
618
0
1060
18
7
0.0
1.5
0.18
7.6
2920
317
269
60
9
724
0
1440
17
9.2
0.1
1.3
3.0
7.7
Note: These data were not collected from identical locations before and after mining and thus do not provide
a comparison between disturbed and undisturbed spoils other than 1n a general sense.
1)	Van Voast, W.A. and R.B. Hedges. 1975. Hydrogeologlc aspects of existing and proposed strip
coal mines near Decker, southeastern Montana. Montana Bureau of Mines and Geology, Bulletin 97.
2)	Van Voast, W.A. and R.B. Hedges. 1975. Hydrogeologlc conditions and projections related to
mining near Colstrlp, southeastern Montana. Montana Bureau of Mines and Geology.
Preliminary Paper subject to revision.

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Montana and concluded Chat:
"Water in spoils was found to b« significantly more highly alnea^lzed
natural ground water In tarns of total dissolved solids, carf6ntiagn«8ium,
and sulfate. Spoils water exceeds the recomaended d^^Jk^aMex%lmlts in
these and other ions (manganese and cadmium),	3^data^Cl tiLt the water
could be used for long-term irrigation.11	% WwjL
These higher concentrations will probably decreastime as material is
leached, and chemical forms change, but the rate of decrease is uncertain. McWhorter
et al. (1977) have estimated, for northwestern Colorado, that if 20 cm of water in-
filtrates into the spoils annually it would take 680 years to reduce conductivities
by 95 percent if weathering la not considered, and longer if weathering 1b consi-
dered.
Mining of an area upstream or "upgradlent"* of an alluvial valley floor also
affects the water resource and the character of the drainage system in terms of flow,
carrying capacity of the channel, and channel stability (or resistance to erosion).
Specific impacts are dependent upon the local and regional hydrology. Surface mining
in, as well as outside, an alluvial valley floor can, for example, Involve the diver-
slon of streams. Often such diversions hove been done without adequate regard for
the slope of the channel (I.e., stream gradient). Though diversions could be gen-
erally considered as lengthening stream channels (since streams are being diverted
away from their channels) and, therefore, as reductions in stream gradients, past
diversions include the straightening of meandering streams such as the Belle Fourche
River (Wyoming) resulting in a steeper gradient and diversions causing both lower and
steeper gradients of streams such as Little Youngs Creek (Wyoming). If the gradient
is significantly steepened, erosive capabilities of the drainage system are increased
in the area of steepening. Concurrently, Increased sedimentation will probably occur
, * Po«t-mining grade of the stream is equally critical. Significant
P lng o portions of a disturbed stream channel will result in progressive up-
stream channel and bank erosion end downstream deposition until, at some future
time, equilibrium is again reached. Channel depths and widths will change as a re-
sult of the dlsturbsnce of equilibrium.
Surface mining of shallow coals in the western United States is now occurring
in areas which have been identified aa alluvial valley floors, in this report, and
includ* th* Ball« Ayr, Eagle Butte, Cordero, Wyodak, PSO #1,
and Big Horn mines in Wyoming (see Appendix 1 for locations). Mining at these sites
has not been reported as adversely affecting alluvial valley floors other than where
alluvial valley floors ere actually removed during mining or where spoil is placed
°n the surface of the valley floor. Nor have premising Investigations of hydrology,
vegetation, or operational hydrollc monitoring been comprehensively analysed to pre-
dict the presence or absence of longer-term impacts of mining on these alluvial
valley floors.
There is no strong evidence of chronic water pollution caused by the current
coal mining operations in the interior western United States. There is limited
!	quality degradation in some streams such as Little Youngs
Creek in northern Wyoming (due to intrusion of spoiled overburden into the alluvial
T	2° Water quality data collected along Little Young* Creek are presented
in Table 2. Samples collected la 1976 Indicate a significant increase in total sul-
fates and dissolved solids serosa the disturbed area. The data also show a seasonal
Increase in total dissolved solids unrelated to the mine (upstream).
Maasurementa of impacts on water by surface mining in the western Dnited States
are limited. One must utilise sophisticated water sampling and analysis devices
suited to allow sampling during infrequent runoff events, from remote locations, and
* "Upgradient" and "downgradient" refer to locations higher or lower along the
potentiometric surfece of the water table relative to the point of reference.

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wtoLL -
RECONNAISSANCE WATER QUALITY INFORMATION COLLECTED ALONG LITTLE YOUNGS CREEK
AND YOUNGS CREEK, NORTHERN WYOMING VICINITY OF NEW SURFACE COAL MIKE
WATER QUALITY DETERMINATIONS
Location
Date
Conductivity
mhos/cm
Total
Dissolved
Solids (mg/1)
Total
Suspended
Solids (mg/1)
Sodium
(¦g/D
Calcium
(mg/1)
Sulfate
<"*»/!)
Cadmium
Chromium
(ug/1)
Copper1
(ub/1)
Lead1
Mercury
(ug/1)
Nickel
("9/)
Zinc1
(ug/J
1.	Little Youngs Creek May 76 527
at Montana-Wyoming Jul 76 788
State Line. R39E, Nov 76 1010
T 10S, NW, NE 22.
Upstream of mine
operation.
2.	Little Youngs Creek May 76 526
R84W.T58N, NE 22. Jul 76 981
Immediately upstream
of overburden
storage and haul
road area.
3.	Little Youngs Creek May 76 541
East Side of County Jul 76 977
Road. R84W.T58N, W, Nov 76 1500
SW. NW 23. Down-
stream of mine
operation.
4.	Youngs Creek at May 76 996
Sheridan - Decker Jul	76	1298
Road, State Highway Nov	76	1790
338. R83W, T58N, SW.
NW 30.
5. Discharge Pond
at Mine Site - no
discharge at time.
R84W, T58N, NW,
NE 22.
Nov 76 1500
308
502
690
316
652
328
662
1010
670
952
1400
1020
114
69
38
190
96
754
168
53
114
11
46
36
14
20
30
14
37
14
37
145
40
60
95
140
53
70
37
52
72
53
70
40
74
62
47
40
110
80
238
120
170
200
180
450
260
380
738
425
<5
10
25
5
30
25
<10
20
40
5
50
<0.2
0.2
<0.2
40 20
5 <10
60 <0.2
5 <0.2
10 <10
<£>
%
25 20	<0.2
5 <<10	<0.2
0.2
:25
25
<25
45
15
20
<25 60
25 20
30
100
<25
20
5
1) Concentrations are total (Dissolved + Suspended). Others, unless noted, are dissolved.

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from ground water aquifer*. Nonetheless, such monitoring la required. Only with the
reaulta of measurements at existing mines can projections be made for future mines.
Considering then the probable importance of subirrigated alluvial valley floora,
and the potential for disrupting the hydrologic and biologic functiona thereof, it
was considered appropriate to evaluate the amount of land that would be clasaified
as subirrigated alluvial valley floora. This paper reporta efforts directed at the
identification of alluvial valley floora as those areaa are defined in nropoaed
national legialaeioa. Appendix 2 provides quotations from leglalat^00oposala and
Committee Conference Reporta that have addressed mining in allm^aWTal!^ floora.
Theae proposals may be summarized as indicating that an ¦IMMvVT %oor is:
*	V	IP
-	A geologic unit comprlaed of several parta: an ^ktAraAuK^pmed to
abandoned or burled) atraam channel (perennial, wlmnt, or ephemeral),
a flood plain, and aa adjacent low terrace, inclu^jf Slluvium with suffi-
cient soil depth and suitable texture to support perennial grasses suit-
able for grazing or other agricultural use, and with aufficlant channel
stability to allow agricultural use;
-	A hydrologic unit in which the natural surface water and ground water la
adequate to support agricultural activities auch aa hay production, by
virtue of aufflclent moisture held available to enable continued growth
of suitable vegetation during the dryer summer and fall months;
-	A topographically-defined area in which the floor plain and adjacent low
terraces may be Irrigated by simple spreading of ephemeral waters and/or
by simple diversion of natural flow*, and
-	An area of land uaed for farming.
This report Includes both a recotmalasanca identification of subirrigated allu-
vial valley floors, through analysis of surface features, and a preliminary analyais
of hypothetical subsurface condltlona that appear representative of ectual condi-
tions. It waa not possible to Investigate the actual usee or productivity of those
areas mapped aa alluvial valley floora. In the context of proposed leglalation, it
la therefore Inappropriate to directly tranafer the areaa of alluvial valley floora
presented herein to an impact on surface-mineable coal since the proposed legisla-
tion appliaa to fermed areaa (and to water quantity and quality) and "farmed areas"
are not identified. It Is similarly Inappropriate to conclude that this study has
adequately documented the hydrologic and biological systema that exist In alluvial
valley floors. We have, however, attempted to provide an analyais of specific im-
pacts on the hydrologic system that may reault from surface methods of mining shal-
low coala. This study draws upon research performed by others to initiate an
analysis of whether those functions of alluvial valley floors deemed critical in the
study can be reestablished during mining and reclamation.
Reaaarch to Date
The concept of alluvial valley floora utilized recently is new to those not
directly aaaociated with western agriculture. Little reaeerch has been initiated on
the geohydrologie and biologic inter-relationships within alluvial valley floora or '
on land uaa actlvltiea conducted therein. This section discusses pertinent investi-
gation reported to date.
* We aasme that the practice of epreadlng flood watera lneludea simple furrows and
temporary atraam diversions, but excludes extenalve grading of land and/or construc-
tion of canala. These latter efforta may be uaed to convey water from streams and
impoundment! to high terraces covered with thin alluvium and colluvlum and lying
outside the subirrigated alluvial valleys.

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The United States Geological Survey of the U. S. Department of the Interior
conducted a field reconnaissance mapping of alluvial valley floors In the three-
county portion of the Powder River Basin of southeastern Montana In 1975 (Malde and
Boyles, 1976). In that study alluvial valley floors were defined as those low ter-
race and flood plain areas of drainages whose vegetation, in terms of species and
cover, reflected the near surface availability of water. Terraces generally not
higher than 1.5 meters above the channel floor of small streams andnotdllgher than
2.5 meters above the channel floor of principal screams were incUid*"Imthe alluvial
valley floor description. Areas obtaining all or the vast	wlker for
vegetation from ditch Irrigation were not knowingly inoMwTj	^
Malde and Boyles had no direct ground water data ju^nmri^jlheir criteria and
had to depend on knowledge of geologic and biologic phencnfbP The areas mapped as
alluvial valley floors supported vegetation systems dominated by grasses and often
mixed with silver sagebrush (Artemisia cm) along small streams and in the upper
reaches of large streams. Greasewood (Sarcobatus) and big sagebrush (Artemisia tri-
dentata) were absent or rare in the alluvial valley floors mapped by Malde and
Boyles. Greasewood and big sagebrush were usually considered Indicators of deeper
ground water and thus to be located outside the alluvial valley floor.
Malde and Boyles found that: (1) larger alluvial valley floors were found along
the larger streams of the study area; (2) alluvial valley floor width generally In-
creases In the downstream direction; (3) alluvial valley floors are generally con-
tinuous upstream from the mainstem of major rivers to the point where vegetative
and terrace characteristics are lost; and (4) comparing the areas mapped with coal
resource data, less than three percent of the area of strlppable coal in the south-
eastern Montana study area is overlain by alluvial valley floors. Thus the size of
alluvial valley floors was found, In practice, to be a direct function of annual
flows, but to be a relatively small area of the entire coal region in southeastern
Montana. We have visited the area between Blrney Day School and Decker, Montana,
mapped by Malde and Boyles and, based on our agreement with their mapping boundaries,
concur with their findings, though the vegetation and topographic criteria may not
be completely applicable for ell climates and physiographic provinces in other areas
of Montana and the interior western United States.
Malde and Boyles1 work is reconnaissance to the extent that no direct measure-
ment of ground water levels, soil moisture, species composition, productivity, or
land use was made. However, It is one of two published mappings of alluvial valley
floors and provides a good estimate of the nature and extent of such areas in the
Powder River Basin of the Northern Great Plains. In the recent past, their efforts
have been further confirmed by detailed field mepping of alluvial deposits by the
U. S. Geological Survey (Malde, personal communication, 1976).
A similar field reconnaissance study and mapping was recently conducted by the
Water Quality Bureau, Montana Department of Health and Environmental Sciences in
Dawson, Richland, and Garfield Counties In the Wllliston Basin of northeastern Mon-
tana (Schmidt, 1977). This area, underlain by strlppable lignite deposits, has a
different physiography, climate, and land use pattern than the area studied by Malde
and Boyles. Notable differences include the presence of glacial till and glacial
landforms, the occurrence of many saline soils, the existence of larger deposits of
gravel which outcrop in valley areas, and recent changes in land use for wheat and
hay production. The major difference was the inclusion of somewhat higher terraces
In the definition of alluvial valley floors since field surveys gave evidence of
8ubirrlgation at higher elevations above the stream channel than were found by Malde
and Boyles. Schmidt found significant concentrations of silver sagebrush outside
the alluvial valley floor areas. These differences illustrate the regional diversity
of alluvial valley floors due to climate, hydrology, and physiography and demonstrate
the need for field assessments of alluvial valley floors If one is to be certain of
their nature and of their role in local land use patterns.
More specifically, Schmidt found vegetative evidence of shallow ground water on
terraces 2,5 meters above the stream channel along small streams and on three-meter

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high terreces adjacent Co larger streams In the northeastern Montana study area.
Along the Yellowstone and Missouri Rivers, somewhat higher terraces exhibit sublrrl-
gated vegetative characteristics. Such characteristics are exhibited on nearly all
small tributary streams In regions of wheat farming, producing a network of small
alluvial valley floors In the headwaters. It appears then that sublrrlgatlon of
desirable agricultural forage may occur In a slightly larger area In northeastern
Montena than in the area of southeastern Montana studied by Malde ani^pyles.
Alluvial valley floors in the northeastern Montana study MuXgre^hown by
Schmidt to exhibit the following additional characterlstlc^MnMLwPfco^ose in
southeastern Montana: (1) a substantial percentage of^m^EmnfSuukin meat grow-
ing areas are in marsh areas which presently receive e^En^ntoflTveter flow from
nearby fields; (2) a substantial percentage of valley fSomwKlt slight to severe
salinity problems; and (3) larger portions of valley floofcmire covered, as well as
underlain, by thicker, poorly sorted alluvial valley gravels. This last factor can
preclude production of sufficient grass for hay production and wildlife usage if the
gravel deposit outcrops so as to limit the near-surface water retention capacity and
provide poor plant growth medium characteristics. However, the gravels may remain
highly productive aquifers and can be Important aa areas of recharge to downstream
alluvial valley floors.
In northeastern Montana, Schmidt found that wheat farmers viewed the drainage
areas, including alluvial valley floors, as obstacles to development. This appears
to be true also In North Dakota. Over the past ten years the amount of land utilized
for wheat has- grown while hayed lands have decreased (in northeastern Montana). How-
ever, ranchers in Dawson County, Montana, interviewed by Schmidt indicated that the
amount of land used for hay production will probably increase in response to higher
hay prices and recent lower wheat prices. Thus the amount of alluvial valley floor
land used for hay production may also Increase in the near future. These types of
changes show that assessments of land use in an area must be conducted over several
years and supplemented by interviews with farmers and ranchers if the agricultural
role of the valleys is to be determined. In any one year, an alluvial valley floor
may be used only for unimproved rangeland, wildlife habitat and water drainage. Of
course, regardless of land use, the physical or natural characteristics of subirrl-
gated alluvial valley floors probebly remain.
Methods Used to Identify Alluvial Valley Floors
This reconnaissance review of alluvial valley floors in existing and proposed
surface coal mine areas in the interior weatern United Statea was performed utiliz-
ing aerial Imagery, reconnaissance field work of other agencies, and limited field
investigations by the authors. Data from a wide variety of sources were used to
develop the concluelons and hypotheses that follow.
A tabulation of the locations (I.e., township, range, and section) of lease
tracts for existing and proposed surface coal mines in the interior western United
States was provided by the TJ. S. Bureau of Mines, Intannountain Field Operations
Center, Denver, Colorado. Since a field review of the ninety-two Identified mine
sites was not possible due to time and budgetary constraints, color and color In-
frared aerial Imagery were obtained for the majority of mine sites. U. S. Geolo-
gical Survey topographic maps, generally at a scale of 1:24,000, were also obtained
when available. The eerial Imagery facilitated the assessment of reletive heights
of stream terraces, widths of lowland areas, and vigor and general types of vegeta-
tion. The topographic maps served es bese maps and permitted more accurate identi-
fication of elevetions and location of land unit boundarlee.
It ahould be noted that the mine sites considered in this analysis of alluvial
valley floors Include only those sites scheduled to be in production in the next

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few years*. The site location information contains only general descriptions of the
leasehold areaa to the nearest full section and Includes areas that do not contain
strippable (i.e., surface mineable) coal. Alluvial valley floor determinations In
this report therefore relate specifically to the description for each mine site as
listed in Appendix 1. As a result, identified alluvial valley floors may encompass
areas other than those underlain by strippable coal. This situation j^ulted from a
lack of detailed Information with respect to the locations of strl^^o^^ coal within
the proposed mining areas.
The classification of lowland areaa within the leq^^AJl	alluvial
valley floors was based principally on the following crT
(1)	underlain by alluvial deposits, where known;
(2)	on floodplalns and low terraces assumed to be the surface features of
alluvial deposits;
(3)	In areas exhibiting vigorous vegetative growth in comparison to adjacent
areas and thus where sublrrlgatlon is likely; and
(4)	where valley width is greater than fifteen meters.
Lowland drainage areas, floodplaln and low terrace, were assumed to have rela-
tively thick (on the order of a few meters) alluvial deposits. The higher lnter-
stream areas and minor alluvial washes are assumed to have thin ^veneers of alluvium
rather than the thicker deposits of water-borne silt and sand materials which are
more suitable for growth of forage. Or, they may be sufficiently high and above the
water table such that sublrrlgatlon does not occur during the dryer months. As noted
In the Introductory section, in order to support vegetation typical of an alluvial
valley floor, the character of this alluvial material must be such that sufficient
water is retained for continued plant growth during the dry sumner and fall months.
Thus areas with a thin veneer of colluvium overlying unweathered strata and gravel-
filled areas do not generally qualify as alluvial valley floors since too little soil
Is present. Also, thick, fine-grained silts or clays (such as lacustrine or playa
deposits) may be too impermeable to hold sufficient watar for sublrrlgatlon of the
alluvial valley floor vegetation complex.
Lowland areas more than 1.5 meters (on minor atresias) and more than 2.5 metera
(on principal streams) In elevation above the water level In the channel, or above
the intermittent or ephemeral channel bottom, were generally considered to be out of
the alluvial valley floor If Infrared aerial photography did not show vigorous vege-
tative growth during times of lower rainfall and relative to surrounding areas. Simi-
larly , narrow streams incised more than 1.5 meters were generally assumed to indicate
a water table too deep to sustain agricultural crops. However, It should be noted
that crops grown in some situations could be sublrrlgated by a ground water system
far outside the channel and low terraces of the valley floors. In these instances,
the water table may be maintained by bedrock aquifers which recharge the colluvium.
While this study did not Identify any such cases of significance, the potential for
such situations remains.
The minimum fifteen-meter width for an alluvial valley floor designation repre-
sents what is perhaps a lower limit of practical "farmablllty" and geologic stabili-
ty. In fact, the fifteen-meter width represents a practicable limit to Identifica-
tion of elevations and boundaries on both topographic maps and aerial photographs.
It is recognized that, particularly in the Northern Great Plains, some narrower val-
ley floors are stable, sublrrlgated, and farmed. However, it wes assumed for this
analysis that these narrower valleys are not essential to agricultural operatlona.
It is likely that the narrower drainages located upstream of the alluvial valley
floors serve as wildlife habitats to sum degree. Further, the water supplies for
* An original listing of coal mine sites was developed in 1975 as representing
western mines to be in production In 1979. That list was corrected by removing
eome sites that were scheduled to be underground operations and by adding a few
existing mines. However, production estimates were not updated.

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alluvial valley floors are, most 1Italy, accumulated In and paaa through chase
narrower valleys. Thus their disturbance may be as Important as the disturbance of
the actual alluvial valley floor. But those upstream areas were not napped here.
Schmidt (1977) did map Che upstream wildlife areas In the areas of northeastern Mon-
tana he Investigated.
Aerial Imagery was utilised to aaeees the relative vigor of v^Rtal^n in low-
land areaa. Relative vigor was ahown in color Infrared aerial ^UMweraLacted
during the drier months since tha more vigorously growing ve^fca®e^| empfciaalsed
at this time. Whan this sign (of growth) la noted, the ^¦«L5tSwjkr is also
identifying araaa where shallow ground water is likely t!EUB^y£le or soil
moisture is maintained at a level high enough to sustain ck^Astatlon. There is
no equally direct indication of tha quality of ground waten^iough large differences
in the quality of ground water would be reflected by the composition of vegetation.
It was not possible to aaaaaa tha spaclea included in the vegetation of sub-
irrigated lowland araaa uaing aerial luagery. Therefore, the methodology incor-
porated the uae of available ground level photographa and other site-specific infor-
mation gathered by lnveatigators at a number of mine sites*. Therefore the vegeta-
tive data preaented are neither detailed nor complete since field surveys ware not
performed.
Alluvial valley floor dealgnatlons ware verified where hay cropping In tha val-
ley floor waa observed in the eerial imagery. However, occasional dlfficultiea were
encountered in identifying alluvial valley floors. Storage reservoirs located in
the alluvial valley floors may reatrlct the extent of downstream flooding and
usually lncreaae the subirrlgated area by ralalng the local water table In the
vicinity of tha Impoundment• Such uncertainties in mapping, and others that exist
where irrigated landa border the alluvial valley, were not completely reaolved during
the inveatigatlon. However, the effects of these impedimenta to accurate mapping
were conaldered trivial for the sites evaluated.
The methods used here to Identify alluvial valley floors are therefore largely
empirical. A definition of a complex interrelationship of geologic, hydrologlc,
biologic, and topographic conditions that have surface, subsurface, time-related and
uaa-ralaead components was attaapted. Since this was done without benefit of ade-
quate field data, it is llkaly that the definition will improve as field data are
compiled.
It Is concluded that alluvial vallay floors can be mapped in the manner used
here with reaeonable certainty. Geological, ground water, and vegetative studies
would surely refine this analysis, but such inveatigationa would require additional
time and field efforts. The reconnalaaance methodology utilised for thia report may
remain a suitable technique for initially identifying alluvial valley floors. Fur-
ther calibration with ground truth and aubaurfaca data to confirm its accuracy would
be dealrable. But it la believed that the procedures used adequately identify the
alluvial valley floor araea that are subirrlgated. What Is not Identified is the
hydrologlc system that aupports tha subirrigation.
* Mines for which ground-truth data were available In aone form and which had been
viaited include Black Mesa, Kayanta, Craig, Edna, Energy (1, 2 & 3), Seneca, Colo-
wyo, Absaloka, Big Sky, Circle Wast, Rosebud (MI), Decker, Savage, Spring Creek,
Youngs Creek, Navajo, San Juan, Star Laka, Baulah, Center, Falkirk, Gaacoyne, Glen-
harold, Husky, Indian Read, Velva, Alton, Eagle Butte, Belle Ayr, Big Horn, Black
Thunder, Coal Creak, Cordero, Dave Johnston, East Gillette, Jacobs Ranch, Jim Brld-
ger, Laka SaSmet, Madlelae Bow, North Rawhide, PSO #1, Roaebud CUT), Semlnoe, Soran-
ion, Welch, Whitney, and Wyodak (See Appendix 1 for locations).

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Results of Assessment of Alluvial Valley Floors
Land Surface of Alluvial Valley Floors
Eighty-seven of ninety-two existing or proposed surface coal mine sites were
studied. The nine sites are located in an eight-state area (Washington, Arizona,
New Mexico, Colorado, Utah, Wyoming, Montana and North Dakota). All stajfff except
Washington are loosely grouped tinder the tern "interior western Unite^pta^p".
Using the methodology discussed in the previous section,
vial valley floors were denoted on topographic naps or, lf^i
available, on aerial photographs. These then provided the^k
measurements. Due to space constraints in preparing this reg
topographic maps nor the aerial photographs have been reprodu
able for reference at selected locations*.
Table 3 provides the results of the planimeter analysis. The total leased area
studied consisted of 369,836 hectares**. Within this area, 11,002 hectares of allu-
vial valley floors were Identified. This amounts to 2.97 percent of the coal mine
lease areas described in Appendix 1. Malde and Boyles (1976) determined that just
under three percent of the strlppable coal reserves of the three-county portion of
the Powder River Basin they studied were overlain by alluvial valley floors.
Of the total of eighty-seven mine sites, fifty-nine (6BZ) contained areas iden-
tified as alluvial valley floors. The two mines on Black Mesa, Arizona, were com-
bined and both contained alluvial valley floors. Twelve mine sites of seventeen
analyzed in Colorado contained alluvial valley floors. Nine mine sites of the seven-
teen analyzed in Montana contained areas mapped as alluvial valley floors. Of the
seven mine sites studied in New Mexico, only one contained an area designated as
alluvial valley floor. Of the eleven mine sites investigated in North Dakota, all
but one appeared to involve some part of alluvial valley floors. Neither of the
Utah sites involved alluvial valley floors, while in Wyoming twenty-five of the
thirty-one mine sites reviewed showed portions of areas designated as alluvial val-
ley floors. The single site In Washington Included an alluvial valley floor.
The largest single alluvial valley floor identified was a 1,046 hectare lowland
area within the Glenharold Mine "leasehold" (Mine Number 47 or ND-5). However, the
area so identified consisted almost entirely of a segment of the alluvial valley
flobr of the Missouri River. Without the Missouri River alluvial valley floor area,
about ten hectares of alluvial valley floors would be involved in the leasehold. It
is probable that the coal now mined at the Glenharold Mine does not continue under
the Missouri River. This mine site is an example of one where a large area of allu-
vial valley floor within the leasehold Is not indicative of an equally large impact
on the amount of strlppable coal.
A similar example is at the Craig Mine (Mine Number 5 or C-4), in northwestern
Colorado. The coal in this area of the Tampa River alluvial valley floor is reported
to be too deep for surface mining (Rural Elsctrlflcatlon Administration, 1974). The
alluvial valley floor Identified for the Navajo Mine (Mine Number 36 or NM-2) is in
the San Juan River Valley, north of the northern-most limit of mining to date. The
alluvial valley area identified for the Indian Head Mine (Mine Number 49 or ND-7)
* Maps are on file in one copy at the Environmental Protection Agency, Office of
Energy Activities, 1860 Lincoln St., Denver, CO. Aerial photography is similarly
available. Single copies of the aerial photographs have been sent to the appro-
priate states.
** 1 hectare ¦ ,00386 square miles, or 2.4704 acres.
is <31 allu-
58 were not
~lanimeter
kelther the
'here, but are avail-

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TABLE 3
AREAS OF LAND IDENTIFIED
AS ALLUVIAL VALLEY FLOORS AT EXISTING &
WESTERN COAL MINE SITES4
Mine Reference
Number
Mine Name
Total area within
legal boundaries shown
1n Appendix 1
(m1z) (Hectares)
Area Identified
as Alluvial Valley
Floor ("AVF")
(m1z) (hectares)
1.
A-l
Black Mesa
55.10
14,271
0.40
104

A-2 •
Kayenta


2.
C-l
Black Diamond Strip
1.03
267
...d

3.
C-2
Canadian Strip
0.91
236
0.03
8
4.
C-3
Corley Strip (S&A)
10.37
2,686


5.
C-4
Craig (Yampa)
48.23
12,492
1.36
352
6.
C-5
Denton Strip
2.07
536


7.
C-6
Edna Strip
15.30
3,963
0.66
171
8.
C-7
Energy Strip 1,2,3
50.08
12,971
2.93
759
9.
C-8
Crizzly Creek Strip
2.99
774
0.87
225
10.
C-9
Jewel Strip
1.01
262


11.
C-10
Marr Strip #1
3.85
997
0.16
41
12.
C-ll
Nucla Strip
1.97
510


13.
C-l 2
Seneca Strip #2





(Includes Seneca #1)
16.53
4,281
0.25
65


Seneca #2W
8.73
2,261
.08
21


Seneca #2Y
2.35
609
.03
8
14.
C-l 3
Williams Fork Strip
5.34
1,383
1.22
316
15.
C-l 4
Moon Lake
29.21
7,565
1.75
453
16.
C-l 5
Colowyo
16.98
4,398
0.36
93
17.
M-lc
Absaloka I
(2.99)
(744)


18.
M-2
Absaloka II
40.21
10,414
1.40
363
19.
M-3
Absaloka III



(Includes Absaloka I)
24.06
6,232
1.40
363
20.
M-4
B1g Sky
8.04
2,082


21.
M-5
Circle West
77.25
20,008
2.50
648
22.
M-6
Coal Creek
0.92
238


23.
M-7
Rosebud (Colstrip)
56.22
14,561
1.20
311
24.
M-8
Decker East
5.96
1,544
0.28
72
25.
M-9
Decker North Included
1n Decker #1
(West)—

26.
M-10
Decker #1 (West)
5.97
1,546
0.12
31
27.
M-n
PM Strip
1.07
277


a - Analysis performed In Sept. 76; Photography obtained 1n 1973-76.
b - A ¦ Arizona, C ¦ Colorado, M » Montana
c - Mine #17 1s not added 1n Individually since Mine #19 Includes the same area,
d - Dashes Indicate no alluvial valley floor within tract.

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TABLE 3 (Cont'd)
Mine Number8 Mine Name Total Area...	"AVF" Area...
				(ml2)	(hectares) f mlz) (hectares)
29.	M-12 East Sarpy Creek 20.71 5,364	0.09 23
30.	M-13 Savaqe 5.00 1 ,295	— —
31.	M-14 Spring Creek 10.99 2 ,846	0.24 62
32.	M-17 Square Deal	4.19	1 ,085 —		
33.	M-l5	Storm King	1.07	277
34.	M-16 Younos Creek 9.01 2 ,334	0.02 5
35.	NM-1	McKlnley	24.41	6 ,322
36.	NM-2 Navajo 88.48 22,916	2.08 539
37.	NM-3	San Juan	12.65	3,276
38.	NM-4 Star Lake 45.42 11,764	(0) (0)
—In need of thorough field Investigation to
determine role of AVF 1n Southwest (See text)
39.
NM-5
Sundance
1.02
264
—
...
40.
NM-6
West York Canyon Strip
17.51
4,535
—
...
42.
NM-8
EPNG
10.22
2,647
—
...
43.
ND-1
Beulah North & South
13.92
3,605
0.05
13
44.
ND-2
Center
5.82
1 ,507
0.21
54
45.
ND-3
Falkirk (Underwood)
60.89
15,770
1.41
365
46.
ND-4
Gascoyne
7.98
2,067
0.45
117
47.
ND-5
Glenharold
21.43
5,550
4.04
1,046
48.
ND-6
Husky Strip
2.93
759
—

49.
ND-7
Indian Mead
8.17
2,116
0.16
41
50.
ND-8
Larson (Noonan)
10.04
2,600
0.25
65
51.
ND-9
Nelson
0.99
256
0.28
72
53.
ND-11
Sprecker
1.00
259
0.07
18
54.
ND-12
Velva
5.98
1 ,549
0.07
18
55.
U-l
Alton
64.89
16,807
...

56.
U-2
Energy Strip
4.20
1 ,088


61.
WA-2
Central 1a
0.95
246
0,37
96
62.
WY-1
Eagle Butte(Belle Ayr
North)7.64
1 ,979
0.11
28
63.
WY-2
Belle Ayr (South)
11.28
2,922
1.16
300
64.
WY-3
B1g Horn
6.95
1,800
0.94
243
65.
WY-4
Black Butte
35.38
9,163
0.02
5
66.
WY-5
Black Thunder
12.99
3,364
0.06
16
67.
WY-6
Buckskin
2.07
536
0.05
13
68.
WY-7
Caballo
15.24
3,947
0.67
174
70.
WY-9
Cordero
11.96
3,098
0.33
85
71.
WY-10
Dave Johnston
37.61
9,741
1.45
376
72.
WY-11
East Antelope
1.00
259

...
73.
WY-12
East Gillette
11.63
3,012
2.61
676
74.
WY-13
Elko
0.97
251
...
...
a - NH » New Mexico, ND - North Dakota, U ¦ Utah, WA ¦ Washington, WY ¦ Wyoming

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TABLE 3 (Cont'd)
Mine Number Mine Name
Total
(ml2)
Area...
"AVF"
Area...
(hectares)
(ml2)
(hectar
17.79
4,608
...

10.21
2,644
0.28
72
1.15
298
...

41.28
10,692
0.05
13
37.63
9,746
0.58
150
27.74
7,185
0.22
57
1.98
513
0.10
26
22.95
5,944
2.49
645
1.01
262
0.06
16
21.36
5,532
0.34
88
14.89
3,856
0.11
28
17.95
4,649
0.11
28
19.37
5,017
0.12
31
24.60
6,371
...

38.53
9,979
...
• ••
8.78
2,274
0.89
230
3.05
790
0.89
230
3.29
852
1.22
316
8.04
2,082
0.83
215
75.
WY-14
FMC
76.
WY-15
Jacobs Ranch
77.
WY-16
Grass Creek
78.
WY-17
J1m Brldger
80.
WY-18
Lake De Smet
81.
WY-19
Medicine Bow
82.
WY-20
Muddy Creek
83.
WY-21
North Rawhide
84.
WY-22
P.S.n.fl
85.
WY-23
Rlmrock
86.
WY-24
Rochelle
87.
WY-25
Rosebud
88.
WY-26
Semlnoe #1
89.
WY-27
Semlnoe #2
90.
WY-28
Sorenson & Elkol
93.
WY-29
Twin Creek
94.
WY-30
Welch
95.
WY-31
Whitney
96.
WY-32
Wyodak
1427.94
36S3TJF
JOB" TT',002

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la likewise locatoH north of the cool presnntly surf.ice minenhle nnd within a
drainage chnnnel not Uktllv to be mined. The Wfllch Mlno (Vine Number 94 or WY-30)
is not located In the Torip,ue River alluvial valley floor, but the description of the
lease area Includes 8.89 (hectares of alluvial valley floor.
On the other hand, the Wyodak Mine (Mine Kumber 96 or W7-32KllKur^itly lo-
cated entj-iuly witiiin the' alluvial valley floor of Donkey Cre^^ nhlMhi Asy Mine
(Mine Number 95 or WY-31) is proposed to be located partiallJ^^efiLMJ^alflw-ial val-
ley floor (37% of lease tract Is an alluvial valley	Mine
(Mine Number 63 or WT-2) is operating in an alluvial valll^®fl|jm^The Big Horn
Mine (Mine Number 64 or WY-3) has involved the alluvial valaRoor of a stream
tributary to the Tongue River and lies adjacent to the alluwSl valley floor of the
Tongue River. As we shall explain in the next section, more area than that sug-
gested by Table 3 may be affected by avoidance of alluvial valley floors during min-
ing in cases where the mines are adjacent to an otherwise impact the hydrology of
subirrigated alluvial valley floors.
Since valley areas examined at mine sites located in more arid climates did not
show equal evidence of year-around sublrrigation (equal to that shown in the semi-
arid areas of the Northern Great Plains), only a few alluvial valley floors were
Identified for New Mexico, Arizona, Utah, and southwestern Wyoming. This reconnais-
sance investigation did not find the vegetation of most drainages in New Mexico,
Arizona, Utah, cr southwestern Wvrnnin* to show vigorous growth during the dry months.
However, It may be that the spring and winter precipitation in these lowlands is
sufficient for enough forage to be produced at those tlaies to make a significant
positive impact on grazing. The lowland areas in the arid climates nay be important
by virtue of their providing some degree of protection from wind. These attributes
of alluvial valley floors do not appear to be addressed in the legislative proposals
and were not measured during the assessment described herein. A detailed field
study of the role of lowland drainage areas in agriculture and of the critical geo-
hydrologic factors supporting that role is especially needed in the New Mexico, Ari-
zona, and southwestern Wyoming coal regions.
It is noted again that the percent "imposition", or surface conflict between
alluvial valley floors and the surface of coal mine tracts cannot be translated
directly to coal production "losses", since loss is determined by the technology
available to mine the particular coal under site-specific geologic and hydrologic
circumstances. The data in Table 3 could be directly translated into an effect on
shallow coal only if, for simplicity, it were assumed that (1) all alluvial valley
floors on mine leaseholds overlie shallow coal; (2) no coal underlying an alluvial
valley floor can be mined; (3) the coal were evenly distributed over the tract such
that the percentage of coal affected was the same as the percentage of land in the
alluvial valley floor, and (4) mining of coal adjacent to the alluvial valley floor
was compatible with protection of the valley's hydrologic system. (The second
assumption would be based on a further assumption that the subirrigated alluvial
valley floors could not be reclaimed.) Under these assumptions the percentage of
cor1 remo**"'' wor-future production on the leasehold would be 2.97 percent.
However, that translation may be misleading because additional coal might be affected
because of its relationship with the subirrigated alluvial valley floor; or less
coal might be affected if the valley floor could be reclaimed. The following section
attempts to project impacts of a ban on the mining of alluvial valley floors on the
shallow coal resource. This will be done by analyses of a few hypothetical, yet
reasonable, geologic-hydrologic situations. A more comprehensive analysis would re-
quire the evaluation of site-specific circumstances and field measurements to deter-
mine what mining technologies might be utilized and how the mining operation might
be developed to protect the Integrity of the alluvial valley floor.
Tha point remains though, that the percentages that may be calculated to show
areas of land overlying surface mineable coal based on the data in Table 3 do not
represent the amount of coal that will be affected If reclamation after mining these
and adjacent lands cannot reestablish the critical hydrologic balance that supports
the alluvial valley floor.

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Hypothetical Coal Mining Situations In Alluvial Valley Floors
In order to better describe the amount of strlppable coal affected by restric-
tions on mining of alluvial valley floors, this section Investigates s^^cted hypo-
thetical mining situations in alluvial valley floors. The situatia^B^fcamined in
which maintenance of pit wall stability adjacent to alluvial	may re-
quire setting aside additional amounts of coal. Also examiy^aflR^Kat^is In
which hydrologic complexity appears to preclude success	affected
alluvial valley floors. It must be remembered that the mSJIitKrjWollow are
baaed not on exhaustive field investigations, but rather	to generalize
surface and subsurface conditions according to principles^Jl^rology and geology.
While there is confidence that situations such as these exilt, field Investigations
may show them to be rare, oversimplified, or even too complex. But whatever the con-
ditions are, they cannot be ignored or their analysis postponed since judgements as
to their compatibility with surface mining of coal must be made now.
We have assumed for purposes of calculations that an "average" alluvial valley
floor is 200 meters wide and, as noted above, that any coal under the floors must be
left undisturbed. In certain cases, coal may be removed up to the border of the
alluvial valley floor. Such cases might exist if the coal were relatively thin
(three to six maters for western coal), covered by thin yet sufficient overburden to
pexnit regradlng to a similar elevation and topography, and in relatively simple hy-
drologic situations such as a thick alluvial aquifer that can be reestablished through
selective placement of spoiled overburden. In other cases, pit wall stability or
perhaps maintenance of a stream may require leaving a coal barTler outside the allu-
vial valley floor, thereby increasing the amount of "lost" coal. We have assumed
the pit wall stability situation to be one where pit wall stability requires main-
tenance of a 45° slope (1:1) on the active highwall such that 60 meters of the coal
seam extending away from each side of the alluvial valley could not be mined. The
60-meter value is obtained by assuming that the mine pit will be 60 meters deep and
that a 1:1 highwall slope will be maintained. Since the coal lies along the base of
the right triangle (45°) created by the 1:1 slope, at least 60 meters of the coal
seam would be left in place. This increases "lost" coal from the 200-meter width
lying directly under the alluvial valley floor to 320 meters, or a 60 percent in-
crease in the amount of coal that would not be mined in this situation. Based then
on the three percent value calculated in the initial analysis of alluvial valley
floors overlying coal lands (Table 3), this "pit wall stability" situation would
increase the amount of coal "lost" or "withdrawn" to about five percent.
Additional coal may also be lost if the coal in an alluvial valley floor is
covered by relatively thin overburden, since this coal may offset the higher extrac-
tion costs of coal lying outside the alluvial valley floor and covered by thicker
overburden. That is, the coal overlain by thin overburden in the alluvial valley Is
relatively cheap to mine and can be used to balance the higher expense of extracting
coal lying under thick overburden in the highlands. If this overburden factor enters
Into consideration when marketing coal from a leasehold and the "pit wall stability"
situation is also encountered, the amount of coal "lost" could double to about ten
percent. Note again, that these calculations are hypothetical. Actual field situa-
tions would have to be studied before firm estimates of the amount of coal lost could
be made.
In other extreme cases, mining in the entire drainage area could be prohibited
unless it were deemed possible to maintain and reestablish critical geohydrologic
characteristics such as effective aquldudes* and water quality. Such would be the
case if reclamation could not reestablish the essential functlona of an alluvial val-
ley floor supportsd by a perched water table (thus lowering the water table), or if
* Aquldudes: Relatively inpermeable rock capable of absorbing water slowly, but
functions as an upper or lower boundary to an aquifer. Does not transmit ground
water rapidly enough to supply a well or spring.

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mining caused the plant growth medium to change significantly in permeability and
chemistry, thus affect In?, plant productivity, ground cover density, or npecinn com-
position. Of course, If the impact of mining were one of deterioration of wiiter qua-
lity to the point of adversely Affecting water use, no coal nearns that nreimdrolo-
gically upgradient of alluvial valley floors, or which are related to th^^fcirri-
gated system could be mined without reducing the productivity and uyk^TtheVlluvial
~alley floor to a degree proportional with the watershed area af^cnj||^^A wmld be
inappropriate to mine such areas until pollution control tec^u^E^tSuwKllable,
regardless of other potentials for successful grading, reve|EadMij^H»Eal sub-
irrigation of the mined area. Finally, If a number of lndivlwS^ttn&al valley
floors occurred on one mine tract, it is likely that avoldancraM ffiese areas would
result in Isolated, small blocks of coal that might be unecononnal to mine. In
these examples, the entire leasehold could be determined uneconomical to mine.
A better estimate of the impacts of mining alluvial valley floors might be
made by examining a number of f situations that appear characteristic of the western
United States coal regions. Emphasis in the examination is on the geologic and hy-
dro logic situation existing in, and in the immediate vicinity of, the subirrigated
alluvial valley floor.
Figure 1 portrays the hydrologic cycle in a simplified form. It depicts how
water may become available to vegetation as precipitation, as overland flow in the
unsaturated and the canlllxrv zones, in the saturated zor.e beneath the water table,
or as locally "perched" water.
Figure 2 shows the concept of multi-aquifer systems where waterbearing strata
are separated by confining beds or aquicludes containing semi-permeable strata. The
aquifers may have completely independent flow systems providing significantly differ-
ent piezometrlc surfaces (i.e., height to which water will rise in a well) and flow
directions. Aquicludes permit minor amounts of water to pass. The permeability of
aquifers may involve connected pore space formed during deposition and/or secondary
permeability (i.e., fracture permeability) formed after deposition. The shallow
coals of the interior western United States gain most of their permeability, and
therefore their role as part of the shallow aquifer system, from fracturing. Blast-
lag of overburden and coal during mining may Increase the permeability both of
aquifers and aquicludes. This artificial fracturing is important when aquicludes
lvediately beneath the coal separate aquifers with significantly different water
preaeuree or piezometrlc heads, or strata containing water of differing quality.
It appears likely that in many cases sublrrlgatlon in an alluvial valley floor
occurs through a single, shallow, unconfined aquifer. This single aquifer includes
stresm alluvium comprised of gravels, sands, silts, and thin clays. In the coal re-
gions of the western United States, this shallow aquifer nay also Include a coal seam
and associated sandy strata. The first case, shown in Figure 2, depicts a situation
where ground water is discharged to a stream (i.e., a gaining or effluent stream).
Figure 3 illustrates a case of recharge where the stream recharges a ground water
aquifer (1.3., a losing or Influent stream) and hence provides shallow waters for the
alluvial valley floors.
Figures 4, 5, and 6 illustrate three simplified geohydrologic situations that
could exist in alluvial valley floors. Using these hypothetical situations, we have
attempted to assess the impact of mining and reclamation on the hydrologic system
and, based upon this analysis, tried to ascertain whether elning would be compatible
vlth the objective of mining only where reestabllshment of vegetetlve productivity
and speclee composition wee assured. Figure 4 represents a situation with a single
coal seam which serves as the bottom portion of a shallow aquifer system. The aqui-
fer Includes sandstone, siltstone, gravel, and alluvium. The aquifer is unconfined
and la assumed to discharge some water to the stream through the alluvium. Reclama-
tion of this area after surface mining of the coal at a mine of typical size (less
than 1,000 hectares) should result in the water table returning to pre-mlnlng levels.
. However, If multiple minl.ig operations cause the entire coal-sandstone aquifer to be
: disturbed throughout the regional watershed so as to drastically change the perinea-

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precipitation
transpiration
•voporotion
•41
me#®
•ofuratod
xont
ground *ot«r flow
•oil
sfrtam
channol
Figure I
Simple Precipitation-Runoff-Infiltration Cycle.
Unconfined Ground Water Aquifer.
(Semi-confining strata create "perched" water table conditions)

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Figure 2 Simple Two. Aquifer Ground Water System
Showing Subirrigated Alluvial Valley Floor.
(Ground wafer discharges to stream alluvium and gravel.
Water in lower aquifer well rises above that of upper,
unconfined aquifer)

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Figure 3 Effluent (Losing) Stream Recharges Ground
Water Aquifer Comprised Of Sandstone
And Coal. (*qal* denotes alluvium)

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siltstont
alluvial vollty floor
sandstone
shol^
Figure 4 Single Sandstone, Siltstone And Coal Aquifer
Intercepted By Stream Alluvium (qal) And
Gravel And Providing Subirrigation To Alluvial
Valley Floor.

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bltstce
gravel.
—~aI -~-7 J.	Jm.^-

jillsione
sandstone
Figure 5 Multiple Sandstone, Siltstone And Coal Aquifers
With Differing Directions Of Flow And Ground
Water Pressures. {Upper aquifer supports alluvial (qal) aquifer
and the alluvial valley floor)

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silt stone
grove'
sandstone
siltstone
Figure 6 "Perched" Alluvial Aquifer With Alluvium (qal) And
Gravel Supplied By Upstream Runoff And Seeps
Issuing From Upper Coal And Siltstone Aquifer.

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bllity of recharge and discharge areaa, Che post-mining water table might change sig-
nificantly. This potential for cumulative impacts from more than one mine necessi-
tates the initial qualification on size of 1,000 hectares.
If appropriate water quality is maintained after reclamation, the valley area
shown in Figure 4 would appear reclalmable at least with regard to rees|^lishment
of the ground water system in terms of flow, depth to water, quantit^oT^Low, and
quality. Deposition of spoils by draglines and return of the postftoAbjg ^^ography
to an average elevation about the same as before mining shoul^Besifl^m an wquifer
transmlssivity* and a depth of water about equal to that	Of re-
maining concern would be the reestabllshment of the capiljEron^H^punf the field
capacity*** of the rock/soil in the root zone. These do a^kdb^k^&ve been re-
established in some mined areas outside alluvial valley floomJmere adequate soil
has been redistributed on the regraded areas.
Figure 5 portrays a multiple "coal aquifer" system which is also considered to
be possible in certain areas of the Interior West's coal regions. The figure shows
again a gaining stream where the unconflned upper coal-sandstone aquifer supplies
water to the alluvial valley floor. The lower coal aquifer is confined by the shale
which permits only minor leakage of water. The direction of leakage depends upon
the relative pressures in the two coal-sandstone aquifers. Similar to the case
shown in Figure 4, mining and reclamation of only the upper coal seam (as shown in
Figure 5) sight result in little disturbance to the alluvial aquifer system provid-
ing the regional hydrologlc system and water quality were maintained. However, min-
ing the lower coal seam (as shown in Figure 5) could result in a combination of aqui-
fer water pressures which could be either lower or higher than that existing prior
to mining. If the elevation of the water table were changed significantly, vegeta-
tion formerly dependent on the upper aquifer water for growth could be "waterlogged"
or "waterstarved", depending on whether water pressure in the underlying aquifer
were either significantly higher or lower than that of the upper aquifer. The dis-
charge to the alluvium from the bedrock aquifer is typical of the area near Gillette,
Wyoming (USGS, 1974).
Figure 6 presents a case where the alluvial aquifer subirrigatlng the alluvial
valley floor is separated from regional sandstone-coal aquifers by the clayey shale
stratum. Mining of these areas would result in disruption of the natural semi-con-
fining layer of clayey shale. If this layer were not restored, it is conceivable
that the alluvial aquifer would lose or gain water from the backfilled area of the
mlned-out coal leading to a change In the elevation of the water table. Again,
whether a loss or gain occurs depends on the potentlometrlc level of the water into
underlying strata.
Figure 7 depicts in more detail an alluvial aquifer containing lenses of rela-
tively impermeable strata which create "perched" water tables which support grasses
and other vegetation suitable as forage. Mining of coal beneath such an aquifer
would most likely break these lenses and, in the situation portrayed, permit the
perched water table to drop. It would be necessary to deposit spoiled overburden in
a selective manner and to reform compact lenses in order to attempt reestablishment
of tha critical functions of the alluvial valley floor in this situation, It is the
opinion of some experts consulted during this analysis that recreation of the rela-
tively impermeable strata would be impossible. Studies by Rahn (1976) indicate that
the truck/scraper-dumped spoils at the Big Horn Mine have a laboratory coefficient of
permeability of 0.16 meters/day (4gpd/ft ). This Is essentially equal to that of
tha undisturbed sandstone overburden measured nearby. Since this Is at the high end
* Transmlssivity: The rate at which water in an aquifer is transmitted through the
saturated thickness of an aquifer with a unit width and a unit hydraulic gradient.
** Capillary zone: The zone in which water migrates upward a characteristic dlatance
from the water table or saturated zone, where the distance Is dictated by the struc-
ture of the pore spaces and chemistry of the fluid and the solid.
*** yield capacity: The amount of water held in the soil after the gravitational
water has drained away.

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-Alluvial Volley Floor	
alluvium
water table
perched on
clay lenses
BttV.v-.v.i
-,.. - ,-i .£=> >*
•oil
siltslone

•'•	' i
... v -.-iSffsSi' ¦;' p; coo i-?*;- *•- •.
' •;-v-.r'v;.vvr>.w. ;
Figure 7 Detailed Section Across Alluvial Valley Floor
And Alluvial Aquifer Showing Locally Perched
Water Tables.

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of permeabilities expected of poor aquifers or aquicludes (which may have permeabi-
lities of 1.0 to 0.01 gpd/ft or 0.04 to 0.0004 meters/day), it is suggested that
more compaction than that performed at Zip, I'orn is necessary to achieve lower per-
meabilities. thin compaction over and above that performed at the Big Horn Mine
appears necessary to recreate zones of "perched" water.
The water supply to the alluvial valley floor (as shown in Figure 7) couli also
be the alluvial aquifer (I.e., underflow) and this would require that the UjWf
recharge located upstream would have to be protected. This locally comsl^^ slma-
tlon could also exist In any of the situations shown in previous f^ur9L~^^
Of the three hydrologlc situations shown In Figures 4, 5de-
tailed perched system of Figure 7, the multiple aquifer system %wku|ingure 5
appears the most difficult to reestablish. The situation shown	6 Is also
difficult to reestablish. Both cases require the recreation of tSi effective semi-
confining layer, a reclamation practice not yet attempted on such a scale. The
perched aquifer system of Figure 7 could be difficult to reestablish for the same
reason. The single unconflned aquifer system shown in Figure 4 appears to have the
highest probability for reestablishment.
Based upon many assumptions which are given below, we suggest that In the situa-
tion shown in Figure 4 no coal would be removed from production because the cri-
tical features of the hyirologic system could be reestablished. The situation shown
in Figure 5' would necessitate leaving the second, deeper coal seam in place if pres-
sures of ground water were sufficiently out of balance and the combined post-mining
pressure (or water table elevation) was deemed to adversely affect the sublrrigation
system. The situation portrayed in Figure 6 would require leaving the clayey shale
in the vicinity of the alluvial valley floor in place and thus would require leaving
sufficient coal under the shale to maintain the confining bed. The upper coal would
be mineable. In the case of the alluvial valley floor in Figure 7, we suggest that
the hydrologlc system could be reestablished and that all the coal shown could be
extracted If very selective placement and additional compaction of spoil in a manner
not now used in western surface mining were required.
In order to judge the probability for successful reclamation of these hypothe-
tical alluvial valley floors and reestablishment of their essential functions, we
have made the following assumptions:
1.	The post-mining topography and elevation would be very similar
to that existing prior to mining such that the approximate distance
from the ground surface to the water table was retained;
2.	The post-mining stream gradient (and flow) achieved the same quasi-
stable equilibrium state existing prior to mining in terms of erosion
and sedimentation;
3.	A suitable plant growth medium was reestablished after mining;
4.	Vegetative productivity and species composition were reestablished
after mining;
5.	The areas of ground water recharge were not modified;
6.	Water quality was maintained; and
7.	It would not be economically feasible to reestablish aquicludes over
large areas. j
The first two assumptions would not be correct in Instances where the overburden
thldaiess is thin relative to coal thickness. In such cases, post-mining topo-
graphy would be lowered by many meters. Those situations have not been examined on
a mlne-by-mine basis but must instead be examined on a regional basis that encom-
passes entire bsslna.

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Hot specifically addressed in detail as yet are disturbances to areas of ground
water recharge for alluvial valley floors. Obviously, water providing subirrigation
must be introduced into the alluvial and bedrock aquifers at some location. Little
surface recharge to most alluvial aquifers takes place in the immediate alluvial val-
ley floor area of any one mine. Therefore, one may envision that the aquifers shown
In the preceding cross sections are connected to areas into which sufficient preci-
pitation infiltrates to replenish the ground water. And the areas shown in thA
Figures are connected to surface watersheds which collect water during pe^^ramf
high flow that can be spread over the alluvial valley floors. If thesatui^jtjea^
areas of recharge are disturbed, the water supply in the alluvial	Ar
be significantly affected.
Nor has the topography of the alluvial valley floor been acHSft^liddreased.
Surface water flow may be sufficient to supply valley floor vegeOHPon. In all
cases shown in the preceding figures, it will be necessary to recreate a low flood
plain and a stable drainage system after mining. The flood plain may be necessary
for periodic flooding and simple spreading of flood waters to restore soil moisture.
The stable drainage system is necessary to control erosion and sedimentation. Sta-
bility was the aspect of alluvial valley floors of greatest concern to members of
the "Study Committee on the Potential for Rehabilitating Lands Surface Mined for
Coal in the Western United States" (National Academy of Sciences, 1974, p. 45). Had-
ley and King (1977) are developing a paper which identifies the problem of recreat-
ing a quasi-equilibrium* in stream channels once the longitudinal profile is dis-
turbed during surface mining.
The most complete published data describing an alluvial valley floor situation
Imown to the authors is that of Van Voast and Hedges (1975). Though Van Voast and
Hedges' objective did not include an assessment of agriculturally-important subirri-
gated areas, the hydrologic cross sections developed and analyses performed by them
are pertinent to this analysis of alluvial valley floors. Figure 8 is a topographic
map showing the alluvial valley floor identified by this reconnaissance study along
the East Fork of Armells Creek and the locations of three cross sections developed
by Van Voast and Hedges. The cross sections are reproduced, in generalized form,
in Figure 9. Cross sections B-B' and C-C' intersect the alluvial valley floor of
the East Fork of Armells Creek.
The East Fork of Armells Creek is described by Van Voast and Hedges as inter-
mittent in the area west of Colstrlp, Montana, and perennial downstream of the town.
Inmediately vest of the north-south road the East ?ork is somewhat Incised, and the
sublrrlgated alluvial valley floor is relatively narrow. During two field inspec-
tions conducted In 1976, no hay cropping was observed in the area shown.
Two surface-mineable coal seams exist in the Colstrlp area, an upper Rosebud
seam and a lower McKay seam, separated by "lnterburden" ranging in thickness from
one to twenty meters. Van Voast and Hedges describe the lnterburden as including
local aquifers of sandstone and clayey silt. Water has been obtained from aquifers
below the McKay seam for use at Colstrlp. Water levels in the alluvium and McKay
coal seam near the East Fork of Armells Creek are estimated by Van Voast and Hedges
to fluctuate about one meter between the spring and early summer recharge periods,
aad the fall.
Van Voast and Hedges have concluded that the water in the coal-seam aquifers is
at least partially confined and that the alluvium along the East Fork of Armells
Creek receives discharge from these aquifers. This water then flows downstream in
the alluvial aquifer. However, in cross section A-A' (Figure 9), the Rosebud Coal
Is reported to be recharged by the alluvium. This cross section is located west of
* The state of balance or grade in a stream cross section whereby conditions of
approximate equilibirium tend to be established in a reach of the stream as soon as
a more or less smooth longitudinal profile has been established, even though down-
cutting may continue (American Geological Institute, 1972).

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1 Figure 8 Topographic Map Showing Alluvial Valley Floor And
*	1	Hydroiogic-Geologic Profiles Across East Fork Armells
Creek Near Colstrip, Southeastern Montana.
(Pr-.t ('.•*	*>t

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Eart^fork	
Armells Creek
•• ° °c °°° <¦ a °0°
o n n	O o O n	. a
SAND
ROSEBUD COAG& ifej ^
wHroi^eaasEi!TT-Sf-'j M Kic/'/T
Figure 9 Three Hydrologic - Geologic Profiles Across East
Fork Armells Creek And Location Of Alluvial
Valley Floor.
(Profile data from VanVoosf and Hedges, 1975. Locations of
profiles shown on Figure 8) *t •• $"•«

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Olluviol volley floor
ROSEBUD
East Fork
Armells Creek
SILT
CLAY
Figure 9 Three Hydrologic - Geologic Profiles Across East
Fork Armells Creek And Location Of Alluvial
Valley Floor.
(Profile data from VonVoast and Hedges, 1975. Locations of
profiles shown on Figure 8) mi to scale

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alluvial valley floor
East Fork
Armells Creek
~^.T—_
CLAY
Figure 9 Three Hydrologic - Geologic Profiles Across East
Fork Armells Creek And Location Of Alluvial
Valley Floor.
(Profile data from VanVoast and Hedges, 1975. Locations of
profiles shown on Figure 8) mi n scale

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the mapped alluvial vallejy floor. In cross section B-B1, the gravels are recharged
by discharges from the underlying McKay coal, Indirectly by discharges from the
Rosebud coal, and by surface flow along the channel. Farther downstream and out of
the surface-mineable coallarea (cross section C-C'), the creek receives discharge
from Che gravels and adjafcenc consolidated materials. Thus the stream alluvium loses
water in the upstream reaches and gains water from the bedrock materials through most
of the all-* ial vai.ay floor areas. The clay layers shown in cross sections B-B' and
C-C' have not been thoroughly described but appear to have potential to hold soma
water in the overlying silt so as to be available for suhirrigation.
Mining of the coal seams shown outside the alluvial valley floor in Figure 9
will interrupt the flow of water from the coal seam aquifers to the alluvium during
mining. Intercepted water of acceptable quality could be discharged back into the
streaa (downstream) during mining. Assuming that spoiled overburden removed outside
the alluvial valley floor is placed by draglines and/or scrapers (without additional
compaction) to approximate the pre-mining configuration of the surface and that water
quality is maintained, we concur with Van Voast's and Hedges' preliminary findings
hydrologic system could be reestablished along the margins of the East Fork
of Armells Creek. However, the geologic system in the creek itself should probably
not be disturbed since the ^establishment of the semi-confining clay layers would
be more difficult. Final opinions in this matter would be dependent on more detailed
field Investigations.
Alluvial valley floors overlying a confined coal aquifer appear to create a most
difficult situation to mine and reclaim if it is necessary to recreate the confinlna
bed or aquiclude. Thus these situations pose problems for the extraction of under-
lying and nearby shallow coals. Substantial lowering of the land surface (elevation)
as would occur when mining thick coals under thin overburden could also create situa-
tions (shallow water tables and steep surface channels) creating Impediments to the
reeatablishment of subirrlgated alluvial valley floors. The greater the area of
alluvial valley floors on a leasehold, the greater the likelihood that it will not
be possible to mine shallow coal by surface methods without adverse impacts on the
alluvial valley floors.
While It Is obviously necessary to assess the impacts of alluvial valley floor
designations on the coal reserves in a site-specific manner, it is suggested that
the average amount of coal affected would be about ten percent on a lease tract con-
taining coal under an alluvial valley floor. This ten percent was developed earlier
In this section by assuming the need to maintain highwall stability along the allu-
vial valley floor and the concurrent loss (for economic reasons) of coal under thick
overburden. Further refinement of this estimate necessitates additional geohydro-
logic and specific mining plan information. Such refinement, presently necessary on
a site-specific basis, could decrease or increase this estimate. Obviously there
can be situations in which little coal could be mined in a single leaseable coal unit
slnca water quality deterioration will be assured. It is believed that at least a
few places exist where essential functions of subirrlgated alluvial valley floors
can recreated flft«r mining. A subsequent section of this report suggests lnfor-
mstiua requirements necessary to males pra-mining evaluations of such Impacts

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Illustrations of Alluvial Valley Floors
Photographs are provided on the following pages to assist the reader in
Identifying alluvial valley floor areas. The photographs are representative of allu-
vial valley floors in Montana, Wyoming, and Colorado. Plates 1 and 2 were taken in
spring and fail of 1976 along the East Fork of Arraells Creek. Plate 1 jftfmev to-
ward the southwest "cross the East Fork near County Highway 315. ThAcMinne^b.s
marked by the bushes In the center background of the photographw^£^Vro?«RroSfl Is
covered principally with grasses and big sage. The alluvia^%|^m ruhnkrea Is
about 200 meters wide at this point and Is napped as includi*'IrlrwXi^area within
the lower terrace which Is barely visible In the center of ti^LA^^aph (see arrow).
Plata 2 was taken about five kilometers west of Colstrlp from north side of the
East Fork valley. The stream channel area Is barely visible where subirrlgated brush
shows In the left center of the photograph (see arrow). A short distance upstream
of this point the alluvial valley floor ends. The stream channel is deeply incised
at this location, and the valley floor Is a narrow flood plain not more than 100
maters wide. The upland valley is bordered by clinker outcrops associated with the
Rosebud coal seam.
Plate 3 Is a view of the Yellowstone River near Fallon, Montana. Drainages of
this magnitude are characterized by wide flood plains, and the alluvial valley floor
may extend up into the higher terraces. Though not examined in the field, it is
likely that the lower terrace in the distant center of the photograph (see arrow) is
an alluvial valley floor. The boundary of the alluvial valley floor along the near
side of the valley appears to coincide with the dirt road in the foreground.
Plate 4 shows the Tongue River in the vicinity of Birney Day School, Montana.
The arrows show the general extent of the alluvial valley floor. Here the alluvial
valley floor is relatively broad and appears to be within the flood prone area
(areas which have a one In 100 chance on the average of being inundated during any
year). The foreground in Plate 4 is near the coal outcrop and, at this point, the
surface mineable coal does not underlie the Tongue River (Halde and Boyles, 1976).
In the vicinity of the area shown in Plates 5 and 6, the coal does extend under
the alluvial valley floor of the Tongue River. This area is upstream of that shown
In Plate 4. Plate 5 Is a view of the Tongue River looking souch-southwest. The
southern edge of the alluvial valley floor borders the low hills to the south (see
arrow). Plate 5 shows this broad, irrigated field in November 1976. Plate 6 was
taken earlier in May 1976, looking southwest of the upstream portion of the Tongue
River and shows the western boundaries of the alluvial valley floor (see arrow).
The northern Halt of the alluvial valley floor la evident along the dirt road in
tha foreground of Plate 6 (see arrow). This alluvial valley floor is cropped for
bay and has a ditch irrigation system.
Plate 7 shows the Tongue River near Decker, Montana. The Tongue River Reservoir
la visible on the left side of the photograph, while the channel of Spring Creek Is
located at the foot of the low hill extending into the flat area on the right. The
loading alius of the Decker Mine are along the horizon and right of center. The low-
land area here produces hay, and the vegetation shows healthy growth during the drier
months. Prior to establishment of the reservoir, it is possible the subirrlgated
area was somewhat smaller. The principal alluvial valley floor in the area remains
the relatively narrow valley of Spring Creek (see arrow). The remaining flat area
requires additional investigation before It could be judged an alluvial valley floor.
%
Plates 8 and 9 are photographs taken In the fall of 1976 along the Spring Creek
drainage basin, about eight kilometers west of the Tongue River. Plate 8 Is a view
of a wet area along the South Fork of Spring Creek where ground water appears to be
discharged. No area of alluvial valley floor has been Identified between this area
and Cha lower portion of Spring Creek shown in Plate 7. This wet area occurs along
about 200 meters of the stream channel. Plate 9 shows a small ephemeral tributary
to the South Fork of Spring Creek. This is not mapped as an alluvial valley floor
because of its narrowness, but denser vegetation shows evidence of some water

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retention and protection In the smell, entrenched drainage.
Plate 10 shows a small ephemeral drainage channel lying between Deer and Coal
Creeks, northeast of Decker, Montana, and east of the Decker West mine. The rocky
material surrounding the flume Is principally of clinker (I.e., baked sha^ and fused
coal ash), the principal surficial material at this location. The	rela-
tively vigorous vegetative growth during the drier months and is d^Xtielkas an
alluvial valley floor up to the terrace partially visible betsrf%t^^^Rup^>f
people (see arrow). Plate 11 Is taken nearby at Deer Cre^J^^UrgQkMKbutary of
the Tongue River, which also contains an alluvial valley^oJEMiJfcorlhern limit of
which la indicated by the arrow. The vegetation of this a^jttpWncipally graasee
and is heavily used by stock.
Plate 12 is a view of Little Youngs Creek., a tributary to the Tongue River in
Wyoming near the Wyoming-Montana border. Here overburden stripping and storage has
begun to encroach on the alluvial valley floor (see Table 2), The alluvial valley
floor is about 100 meters wide in this area.
Plate 13 shows the Tongue River near Kleenburn, Wyoming, north of Sheridan.
The terrace levels are evident along the distant side of the river. Coal and clinker
outcrops rim the valley. The alluvial valley floor Is fairly broad at this location
(aee arrowa).
Plates 14, 15, and 16 provide views of some of the tributary streams in north-
western Wyoming. Plate 14 shows Little Rawhide Creek, a tributary to the Little
Powder River north of Gillette, Wyoming. This area is within the alluvial valley
floor which is approximately 50 meters wide at the location shown. The minor ter-
races in the alluvial valley floor area (aee arrow) are included.
I	Plate 15 shows Caballo Creek, a tributary to the Belle Fourche River in north-
! eastern Wyoming, an upetream view toward the northeast. The alluvial valley floor
is approximately 200 meters wide along the original (natural) channel. The width
varies with the entrance of tributaries. The water impoundment* is a result of the
mining operation. Strippable coel extends under this valley. A number of terraces
are evident in the background (see arrows) and delineate the alluvial valley floor.
!	Plate 16 was taken In the Little Thunder Basin area at the gauging station
' installed on Little Thunder Creek. This Intermittent channel has not been mapped as
! sn alluvial valley floor though certainly the Impounded run-off water (perched on
silt end/or bedrock) is of velue to stock and wildlife.
Plates 17 and 18 were taken in northwestern Colorado. Plate 17 shows a reach
of the Tampa River Sixteen Kilometers west of Craig, Colorado, where the alluvial
valley floor is quite broad. The nearest coal mining activity is presently six kilo-
meters east. While this particular area has not been thoroughly investigated, the
alluvial valley appears to extend to the low bluffs in the middle of the photograph
(see arrows). Plate 18 Is a view along Fish Creek located southwest of Steamboat
Springs, Colorado, where spoiled overburden has been placed In the drainage channel.
The alluvial valley floor at this point was 150 meters wide. The original stream
channel has been filled and the man-eude channel along the left of the photograph
was in the process of being moved farther to the right at the tine of the photograph.
A railroad embankment rims the right side of the alluvial valley floor (see arrow).
* Impoundments created by post-mining grading may be beneficial if the Impoundment,
and the impounded water are safe and suitable for their Intended use. Unfortunately,
the incorrect assumption is often made that all impoundments are good for the semi-
arid West. High evaporetlon rates which concentrate salts in the impoundments and
leaching of spoils will cause some Impounded water to be unfit for continual use.
Impoundments constructed upgradlent of spoils and intercepting ground water have a
much greater likelihood of containing water suitable for agricultural and wildlife
uses than do surface water Impoundments and other impoundments intercepting water
' that has passed through spoils.

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Plate 1 - East Fork of Armells Creek, Near Colstrip, [bwANA

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Plate 2 - East Fork of Armells Creek, West of Colstrip, Montana

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•*••••;. .
¦ - i'-.-j fe« i .v. S3
I '"V. '¦¦ *





. T-^ ...
V : ,•:¦¦¦;•.>• 7-
Plate 3 - Yellowstone River in Vicinity of Fallon, Montana

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Plate 4 - Tongue River at Birney Day School, Montana

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Plate 5 - Tongue River near Confluence with Four Mile Creek

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Plate 6 - Tongue River near confluence with Four Nile Creek

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Plate 7 - Confluence of Tongue River and Spring Creek

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Plate 8 - South Fork of Spring Creek

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t
t:
i
r

Plate 9 - Tributary to Spring Creek

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-¦¦y-. ->«t. r_; ¦ <•• '-V/V *'-•*
ecr-^crr.* >•. <>?iL >• •" /.- f.
8«SSl~r'2i2riBv £ <*'.--.. ?v:"
• <% |
^ '.iV i
,>¦15^
r iW*r* ..-

^ i y .-«*5>jr;

1
&
I
i
h
&


Plate .10 - Minor Triblttary to Tongue River

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Plate .11 -
Deer Creek east of Decker, Montana

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mymm
Plate 32 - Little Youngs Creek north of Acme, Wyoming

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Plate 13 - Tongue River near Aoc, Wyoming

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Plate 14 - Little Raw Hidh Creek north of Gillette, »Jyoming

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Plate 15 - Caballo Creek south of Gillette, Wyoming

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§
h
%
*
i
t

(
9.
Plate 15 - Little Thunder Creek east of Reno Junction, Wyoming

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Plate 17 - Ya/ta River west of Craig, Colorado

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Plate 18
-Fish Creek south of Hilner, Colorado

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Suggested Information Requirements for Applications to Mine Alluvial Valley Floorn
This reconnaissance report was Initiated to provide a basis for subsequent
evaluations of the coal! reservps affected by provisions for the protection of allu-
vial valley floors in proposed surface mining control and reclamation legislation.
In the process of collecting information, it has been necessary to evaluate the
potential impact of surface, mining on alluvial valley floors. Aa the available in-
formation was compared with the known characteristics or results of surface coal
mining and reclamation, information needs were identified. While It appears possible
to reclaim certain hypothetical alluvial valley floor systems, natural anaterns have
enormous variability. In order to provide a data base from which ^tflfcredictlons
aa to the success of reclamation can be made, there are lnformal^^freq&rements for
the planning and pre-planning stages of a coal mine. I^:l^%aJRoafiln& which in-
clude alluvial valley floors, these information requlr^A^LteUK&si^. This
section contains, as Table 4, a proposed list of requir^sl^^WElrcrmation and
for projections of future effects to be Included In minAJ^nFTnvolving alluvial
~alley floors.
It appears possible to develop judgements as to the appropriateness of mining
alluvial valley floors fTom the information submitted in response to these require-
ments (Table 4) and expansions thereof baaed upon experiences in other areas. Any
approvals granted to mine alluvial valley floors based upon satisfactory responses
to these requirements would be further conditioned upon (1) long-term hydrologic and
biologic monitoring, and (2) posting of sufficient bond to correct adverse situations
auch aa prolonged deterioration of water quality. Since many of the more complex
ground and surface water situations would necessitate reclamation procedures that
have not been thoroughly tested, It would appear reasonable to require operators and
users of coal to bear the responsibility for pre-mlning Investigations, much of the
post-mining monitoring required to warn of problema, to document success, and to
correct failures.
Table 4 lists much of the information required for any mining plan with or with-
out an alluvial valley floor. Under Chapter 30, Code of Federal Regulations, Sub-
part 211.10, there are numerous information requirements for mining plans. States,
In varying degrees, have requirements for specific information In mining plans.
Table 4 does contain requirements that are more specific than some of those In
effect, especially In terms of Indicating the detail and accuracy of the information
supplied. Emphasis In Table 4 Is on the definition of the hydiologic system, bio-
logic Interactions, the geology of the system in terms of the role of strata in
other surface and subsurface systems (such as in supporting vegetation and transmitt-
ing water), in demonstrating that reclamation will reestablish critical elements of
the natural system, and that continued use of surface and subsurface resources will
be possible. It would be inappropriate to place the burden of proof on the regula-
tory agency. Therefore, the applicant must demonstrate (to the agency's satisfac-
tion) that reclamation of alluvial valley floors will be successful. It is possible
that with experience, the Information requirements and the necessity for proof will
decrease. Table 4 la not a list of all possible requirements, but is an attempt to
obt	i.u*uxmacion to provide understanding of the critical functions of an
alluvial valley floor. It may Be argued that Table 4 outlines a research project
since the requirements proposed therein can be debated according to one's Interests,
and that, as experience is gained, certain Information requirements will be of
little use in evaluating alluvial valley floors. However, until such a priority
list can be established on the basis of field investigations, Table 4 represents an
appropriate summary of requirements.
Prior to an applicant's submission of the information represented by the outline
of Table 4, it la necessary for land and resource planning entities to identify allu-
vial valley floors using (at least) reconnaissance methods. The land planning pro-
cess should also identify the land and reaource values of the areas. Applicants
for mining plan approvals! can better develop the information In Table 4 needed to
evaluate the plans after the role of the alluvial valley floor in the regional/state
land and resource management system is defined. It seems appropriate for planning

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entities to concurrently determine the role and lon^-terra value at alluvial valley
floors. Only in thia manner could the Impact of mining be completely evaluated.
ral Regula-
TABLE 4
PROPOSED REQUIREMENTS TOR INFORMATION FOR COAL MINING
PLANS INVOLVING ALLUVIAL VALLEY FLOORS (SURFACE OPERATIONS)
I. Geologic Information
IA. Regional Geologic Map of acale 1:250,000 showing formation
location of type sections and sources of information,
25 kilometers of mine tract having ephemeral and
80 kilometers of perennial streams (vhere the strl
"area of operations" as defined in 30 CFR 211.2,
tlons).
3. Regional structure Map of acale of 1:250,000 showing^ major fracture and fault
systems in area covered by Regional Geologic Map (IA.), vlth measured atti-
tudes (dip and strike) of major formations and the major geologic struc-
tures (may be included on Regional Geologic Map).
IC.	Area of Operations Geologic, Topographic, and Structure Map of scale
1:24,000 (contour interval where required 3.3 meters or less) showing all
strata of contrasting lithologies, attitudes, fracture patterns and faults
located within the area of operations and/or with reference to type sec-
tions located outside the area. Map to be prepared from base data having
a horizontal accuracy of + 5 meters when denoting significant changes in
bedrock lithology or structure.
ID.	Affected Area Geologic and Structure Cross Sections of scale (vertical and
horizontal 1:24,000 for affected area and 1:4800 for the area of opera-
tions showing all strata of contrasting lithologies and their attitude
when such strata are located between the surface and within 70 meters be-
low the deepest coal seaa to be mined by surface methods or to a depth of
200 meters of the premlning ground surface (within the area of operations)
whichever most adequately represents the affected hydrologic system. Show
locations of all points of detailed measurements. Locate cross sections
on appropriate Geologic Maps. Provide et least two cross sections, one
perpendicular to the general strike of strata within the affected area,
one parallel to the strike, and any other cross sections deemed necessary
to show departures from these sections (departures in terms of structure
and lithology) where the departures affect the hydrology, overburden toxi-
city, or mining procedures. (Note: "Affected Area" defined in 30 CFR
211.2).
IE.	Detailed Llthologlc Logs of Cored Drill Holes located on transects across
the sublrrigated alluvial valley floor area(a) where such areas are lo-
cated within the area of operations. Logs to show changes in lithology
from the premining ground surface to a depth which includes 70 meters of
the strata lying beneath the deepest coal seam proposed to be extracted.
Cbithology based upon visual observations and any appropriate geophysical
logs.) Provide at a acale of 1:200 in the vertical. These core holes
will transect the alluvial valley floors and any related deposits as
designated by the regulatory authority in sufficient number to provide
the location to stratlgraphie (llthologlc) markers across the entire cross
section (IF.) to within 2 meters and to show changes in strata that may
affect the hydrology, overburden toxicity or mining procedures. (See
also "Detailed Cross Sections of Alluvial Valley Floor Areas" (IF.) and
requirements for hydrology data (III)).
17. Detailed Cross Sections of Alluvial Valley Floor areas based upon the
"Detailed Llthologlc Logs of Cored Drill Holes" which show significant
changes in subsurface lithology under the areas designated by the regula-
tory authority as alluvial valley floor areas (includes hydrologically-
1) "Regulatory Authority" refers to the public body with responsibility to review
and approve mining plans for surface coal mines.

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related alluvial deposits). The Cross Sections will generally be
developed at two locations (longitudinally) along each alluvial val-
ley floor area crossing the area of operations unless a lack of homo-
geniety requires the preparation of additional detailed cross sections
along the longitudinal profile. All cross sections will be prepared
at a vertical scale of 1:400 and at a converted horizontal scale and
will show alluvial materials, lenses, weathered zones, and major frac-
ture systems, in addition to the lithologic changes. An accuracy of + 2
meters In the vertical data will be demonstrated by the ap^^cant by use
of statistical tests of field data.
Detailed Chemical and Physical Information characte^cA^ajm overburden
material scheduled to be disturbed in the ai^^RbJHkeBns^ This Infor-
mation will be prepared and related to Cro^^a^BnXjkJ&prea for the
affected area (ID.) and those prepared for	^alley floor areas
(IF.). Samp lea will be collected and an a 1 y z	r e sent all strata of
thickness exceeding 1 meter that are shown toWe of significantly differ-
ent chemical (or physical character 50Z in quantitative analyses) unless
directed by the regulatory authority to provide other information.
Parameter
Procedure
pH (determination on
paste)
Conductivity mmhos/cm
of saturation extract
Saturation percentage
Calcium - Report on meq/L
of the extract.
Magnesium - Report in meq/L.
Sodium - Report in meq/L.
SAR (Sodium Absorption Ratio)
calcium, magnesium and sodium
from the above procedures 4,
5 and 6.
Boron - Hot water extract
reported as ppm.
Particle size distribution
(mechanical analysis). Re-
port the percent of vfs (140-
270) sieve size separately.
U.S.D.A. Handbook 60 "Diagnosis and
Improvement of Saline and Alkali Soils"
Page 102.
U.S.D.A. Handbook 60, Pages 88 and
89.
U.S.D.A. Handbook 60, Page 84, Method
2 and 3a.
Preparation of extract U.S.D.A. Hand-
book 60, Page 84, Method 2 and 3a.
By atomic absorption spectrophoto-
metry (see Perkln-Elmer Analytical
Methods).
Some as for Calcium.
Same as for Calcium.
U.S.D.A. Handbook 60, Page 26, Calcu-
lation preferable.
N«+ ~ \j(CA** + Mg~)/2 - SAR
OR
by nomogram procedure (20b), Page 102
and 103, U.S.D.A. Handbook 60.
U.S.D.A. Handbook 60, Page 142,
Method 73b.
A.S.A. Agronomy Monograph No. 9,
Method 43-5, Pages 562-566. If EC is
4 or more mmhos/cm include field tex-
ture determination.
Cadmium (ppm)
DTPA extractable. Soil Science Soc.
of Aasrlca Proceedings, Vol. 35.
No. 4, 1971, P 6C0-602.

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Copper (ppm)
Lead (ppm)
Iron (pom)
Manganese (ppm)
Zinc (ppm)
Nickel (ppm)
Mercury (total ppb)
Selenium (ppm)
Molybdenum (ppm)
Boron (ppm)
Nitrate (NOJ)
Amonlum (NH^)
DTPA extractable. Soil Science Soc.
of America Proceedings, Vol. 35, No. 4,
1971, P 600-602.
DTPA - same as copper.
DTPA - 0.1N Ammonium nitrate or 0.1N
Ammonium acetate or 0.005N nitric acid.
Ref: Diagnostic criteria for planta
and soils by Chapman.
Scvnce Soc.
0^35, No. 4,
DTPA extractable. gfcol
of America Pr«0|Rdl
1971, P
Same as
Polarographic waves. ASA Agronomy
Monograph No. 9, Pages 885-887, Method
56-6 or describe procedure.
Acid soluble soil Hg by cold vapor
ualng varlan techtron. AA6 and varian
Hg Kit. Ref: W.R. Hatch and W.L. Ott,
Analytical Chemistry, Vol. 40, No. 14,
December, 1968.
Analysis for the sum of selenate,
selenlte, and water soluble organic Se.
Ref: ASA Agronomy Monograph No. 9,
Page 1122, Method 80-3.2.
Acid Ammonium oxalate method 74-2,
P 1054-1057. ASA Agronomy Monograph
No. 9.
Same as in Soil Survey A-8.
Sane as In Retopsoiled layer B-l.
Same as in Retopsoiled layer B-l.
Type and percentage of clay. Physical and chemical properties as
they may affect texture or chemistry of overburden, stability of
material and hydrology of overburden.
Physical data reported are to Include:
1.	Bulk density of undisturbed overburden.
2.	"Bulk density" of sample approximating physical state after mining
("post mining state"). See also Section VI.
3.	Particle size distribution of "post mining state" of overburden
materials. See also Section VI.
4.	Particle size distribution of overburden samples crushed to state
which approximates maximum exposure (to leaching of elements) of
mineralogical forms.
i
For the area of operations, such data will be collected on a maximum spacing
of one hole per 16 hectares. Within the alluvial valley floor area and

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within nny area of overburden which may he deposited In the alluvial
valley floor area the maximum spacing should be reduced to one core hole per
10 hectares unless the results of analysis from the 16-hectare spneing
demonstrate, to the satisfaction of the regulatory authority, that no addi-
tional variations tn chemical or physical properties of overburden materials
would be found using a denser core hole network in the alluvial valley floor.
Soils Information
IIA.	Area of Operations Soils Hap by soil series and phases scaleLnlKDOO clear-
ly showing all soil mapping unit boundaries to a horizontal ^Ecunfccy of
+ 10 meters. Areas of highly contrasting soils that^»M^^(iMhr™pr lar-
ger in size and areas of low contrasting soils	lar-
ger in size are to be delineated. The nap will Mi a des-
cription of each soil series, any soil associatio(^,\e«i50j(kmplexes, and
each mapping unit, the latter described in terms oVMP^dominant slope and
range, typical parent material, typical depths and Yange thereof, kinds of
soils and the percent of each kind of soil in mapping unit and the degree
of consistency of the soli association over the area of operations. Show
locations of samples. Describe erodability of soils and soil associations
in their undisturbed and disturbed states as observed and/or calculated.
Erodability must Include that of the disturbed state.
IIB.	Detailed Soils For Alluvial Valley Floor Area, scale 1:400, clearly show-
ing all soil mapping unit boundaries to a horizontal accuracy of + 2 meters
with areas of minor or Included highly contrasting soils that are 0.5
hectares or larger In size and areas of low contrasting soils that are 1
hectare or larger in size delineated. A description in detail similar to
that required for the "Area of Operations Soils Map (IIA.)" will accompany
this more detailed map(s). (The Alluvial Valley Floor Areas will be desig-
nated by the regulatory authority.)
IIC.	Chemical and Physical Information Describing Soil Profiles in Area of
Operations Present in tabular and narrated forms based upon analysis of
soil profiles to a depth of 2.0 meters in the area of operations and to a
depth of 4.0 meters within areas of alluvial valley floors, or to Indi-
cated bedrock if this occurs at shallower depths. Samples are to be col-
lected at a minimum of two locations for each soil phase. Underlying soft,
loamy, flilty, or sandy strata are to be sampled to a depth of 30 cm below
the weathered soli material. After the profile has been exposed and des-
cribed, collect representative (.and continuous) four-liter samples from
each specific genetic horizon (top to bottom horizon) except the surface
15 cm. The surface layer Is to be sampled from 0 to 15 cm. Genetic hori-
zons of less than 8 cm in thickness need not be sampled. Genetic horizons
or layers greater than 60 cm shall be divided into equal parts so that no
sample (of four liters) represents a soli layer of greater than 60 cm.
Each sample will be analyzed as follows - unless the regulatory authority
determines, based upon preliminary data, that the number of samples ana-
lyzed can be reduced:
Parameter
pH (determination on
paste)
Conductivity - mmhos/cm
of saturation extract.
Procedure
U.S.D.A. Handbook 60 "Diagnosis and
Improvement of Saline and Alkali
Soils", Page 102.
D.S.D.A. Handbook 60, Pages 88 and 89.
Saturation percentage
U.S.D.A. Handbook 60, Page 84, Method
2 and 3a.

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Parameter
Procedure
Calcium - Report on meq/L
of the extract.
Magnesium - Report in meq/L.
Sodium - Report la meq/L.
SAR (Sodium Adsorption
Ratio) calcium, magne-
sium end- sodium from the
above procedures 4, 5, and 6
Boron - Eot water extract
reported as ppa.
Particle size distribution
(mechanical analysis) Report
the percent of vfs (140-
270) sieve size separately.
Trace mineral analysis as
directed by the regulatory
authority.
Clay content.
Change in physical character-
istics as a result of removal
and redeposltion.
IID.	Continuous Soil Temperature Data recorded in lowland and highland areas and
on differing aspects of slopes representative of the area of operations.
These data should be collected for at least one year to show seasonal
changes. Temperatures are to be regularly collected.
IIE.	Calculations of Soil Loss of soils within the area of operations in their
observed state and in various states of diaturbance expected during min-
ing operations. The "constants" assumed for each soil association will be
stated and the sources of information will be shown.
IIZ. Hrdrolonic Information
IIIA. Regional Hydrologlc Map of scale 1:250,000 showing all surface drainage
channels, major points of water diversions, zones of recharge to the
ground water systems and significant areas of ground water discharge
within the surface drainage watersheds covering the geographical area
within 80 km of the area proposed for operations. Overlay with, or pre-
pare separately, contour maps of ground water table of piezometric sur-
faces of water in each significant aquifer to be disturbed by mining
using contour Intervals of no more than IS o and shoving all data points.
IIXB. Detailed Hydrologlc Map of the Area of Operations, scale 1:24,000, in-
cluding the ground water basin(s) that supply ground water to the area
of operations (Including any alluvial valley floor area). Show all
stream channels, recharge ar.d discharge areas, all outcrops and sub-
crops of shallow aquifers in a form compatible with the "Area of
Preparation of extract U.S.D.A. Hand-
book 60, Page 84, Method 2 and 3a. By
atomic absorption spectrophotometry
(see Perkln-Elmer Analytical Methods).
Same as for Calcium.
Same as for Calcium.
U.S.D.A. H.
Calculate
Na + V (Ca*\	2 *- SAR
by nomogram procedure (20 b), Pages
102 and 103, U.S.D.A. Handbook 60.
U.S.D.A. Handbook 60, Page 142, Method
73b.
A.S.A. Agronomy Monograph No. 9,
Method 43-5, Page 562-566. If EC is
4 or more mmhos/cm include field
texture determination.

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Operations Ce<^lop,tc and Structure Map" (IC.). Provide a bnse and contour
map of water C.iblen or plezometrli: r;ur£.ir.rn of w.iccr In e;\ch MlRnlftc.int
aquifer to be'iIHturbcd hv mining (InclurttnR ,iny .nqulfer lying lf>*q than
70 m below tlid deepest conL scam to be mined) find the highest undisturbed
aquifer in the area of operations; perched water table conditions where
observed, will, be indicated. Contour intervals will not exceed 2 m ex-
cept in special Instances of steep ground water gradients, and should be
presented with an accuracy of 15 percent. Flow lines shall be in indi-
cated. (Preparation of this nap will require the drilling of observa-
tion wells, or piezometer nests cased to ensure reception of—water from
be
should
n".)
sallow aqui-
d 1W at least
area of opera-
permeability ,
only one aquifer during testing and sampling. Ceologic
obtained when the wells are drilled: see "Geologictflipi
IIIC.	Detailed Information describing the characteri^fifeeWt
fern shall be obtained from aquifer pumpinSp^*-^' -L-t—
two separate locations in each aquifer locaBdWttViiH tl
tions. Data submitted will include field me^BuBq^enks of
transmissivity and the storage coefficients, ^^ore samples will be used
to obtain laboratory estimates of pre- and post-mining permeabilities.
Construction details of all wells used in preparing the information will
be supplied. Pumping tests conducted in the areas designated by the re-
gulatory authority as alluvial valley floor areas shall be designed to
identify leakage between alluvial aquifers and deeper aquifers to be dis-
turbed by mining (as well as leakage between multiple aquifers that may
be disturbed). Locations of recharge to any alluvial valley floors will
be identified and their role in the recharge cycle will be identified.
All information will be reviewed and approved (as to its accuracy and
interpretation) by a second independent and qualified party.
IIID.	Water Quality Analyses of ground water samples collected (at least tvice
and not closer together in time than four months), from all wells used in
preparing the "Detailed Hydrologic Map of the Area of Operations" shall be
submitted. Timing of sample collection will, at a minimum, coincide with
seasonal highs and lows in water table or piezometric surfaces. Samples
shall represent as closely as possible aquifer water and shall not be con-
taminated by the well casing, cement, or drilling fluids. Analyses may be
reduced if sufficient information is submitted to the regulatory authority
to permit affirmation of consistency of water quality. Water Quality
Analyses will Include:
Parameter
Procedure
pH
specific conductance
(mmho/cm at 25 C)
Field meter
Vheatstone bridge
turbidity (Jackson units)
total alkalinity as CaCO
Ong/1)
total acidity (mg/1)
oil and grease (mg/1)
Turbidimeter
Titration; electrometric; manual or
automated method—methyl orange
Electrometric end point or
phenolphthaleln end point
Liquid-Liquid extraction with
trichlorotrlfluoroethane
carbonate (mg/1)(meq/1)
bicarbonate (mg/l)meq/l)
Titration, electrometric; manual or
automated method—-methyl orange
Titration; electromatic; manual or
automated method—methyl orange

-------
Parameter
Procedure
chloride (mg/1)(ineq/1)
sulfate (mg/1)(meq/1)
calciwa (mg/1) (meq/1)
magnesium (mg/1)(meq/1)
aodiun (mg/1) (meq/1)
potassium (mg/1) (meq/1)
fluoride (mg/1)(meq/1)
nitrate plus nitrate as N
(total)
orthophosphate aa P (total)
aluminum (Al) (Mg/1)
cadmium (Cd)
chromium (Cr)
coppar (Cu)
iron (Fa)
laad (Pb)
manganese (Mn)
selenium (Se)
vanadium (V)
zinc (Zn)
Sodium Adsorption Ratio
»rlll be calculated
baorption
i colofliBQCrlc | fXdBMI
Silver nitrate; mercuric nitrate;
automated colorimetric-ferricyanide.
Gravimetric; turbidimetric; auto-
mated colorimetric-barium chloranilate
EDTA titration;
Atomic absorptl
Flame
Atomic alio'
photoaetr'
Distillation—SPADNS
Automated (cadmium reduction); auto-
mated (hydrazine reduction)
Direct single reagent; automated
single reagent or stannous chloride.
Atomic absorption
Atomic absorption
Atomic absorption
Atonic absorption
Atomic absorption
Atomic absorption
Atomic absorption
Atomic absorption
Atomic absorption
Atomic absorption
Variations in water quality analyses collected on one day at the two
locations in an aquifer greater than 25 percent will require that addi-
tional samples be collected and analyzed and, possibly that additional
drill holes be Installed and sampled to provide adequate information to
explain the variations.
HIE. An Inventory of all Existing Wells and Springs within 8 km of the area
of operations shall be prepared In tabular form and locations shown on a
map with a scale of 1:24,000. The following Information shall be in-
cluded: location, indicated condition of well (casing, completion,
observed situations that could explain unusual data), surface owner,
water ase, land surface elevation, well depth, aquifer(s), depth to
static water level, method of water production, water level during
pumping, discharge and any existing water quality data (and source of
water quality data).

-------
ITIF. Surface Drainage Hydrology Information shall be submitted In tabular,
graphic and narrative formats providing flow data (duration, low flow,
flood frequency analyse*) for USfiS stations located nearest the proposed
nine, enctwncen of recurrence floods (up to a minimum of 100-year recur-
rence intervals) for flow in each stream physically disturbed by mining
and for streams presently receiving discharge from the disturbed areas,
identification of all surface water diversions and impoundments for a
distance of 35 km downstream of the area of operations, and providing
longitudinal profiles of all streams to be physically reconstructed after
mining (or significantly disturbed so as to change the gradi^t at a
scale of 1:4300 with no vertical exaggeration. In streamf"®? in tribu-
taries to alluvial valley floors, the sediment load^rthltfl b^determined
and the stability of the channels shall be evalMflBkd^VCMin^k roughness
factors and channel durability shall be ded|^Bm
-------
associations or| communities baaed upon two or more dominant species
accompanied by narrative describing species, succesaional stage, capabi-
lities of land,[growth rates or productivity, and current uses of vege-
tation (used for grazing, wildlife, crops).
tVB. Vegetation Inventory map of Areas Designated as Alluvial Valley Floors,
<
-------
reclamation, or until equilibrium conditions are approached - based upon
experience, and laboratory simulations of post-mining (and reclamation)
conditions.
VIC. Post-reclamation Topographic Map of Area Operations showing all drainage
courses, scale 1:4800, and showing expected changes as a result of materi-
al compaction.
VXD. Post-reclamation longitudinal profiles along all reconstructed drainage
channels, including the stream upstream and downstream; scale 1:400 for
profiles of disturbed streams, scale 1:4800 for entire length of stream
affected by disturbance (for a distance of not leas than 5 km
and downstream of area of operations or to headwaters, whichewr^fS t«
lesser upstream distance) with latitudinal cross sections#4^elpea»teuMr
to the drainage channel) for all reconstructed alluvM^wflpy	^
100 a intervals and for all major tributaries thereto^
form, methods of creating channel stability, expected lUM>mffc«.ns for
floods with recurrence intervals up to 100 years, methMj^channel
armor (e.g., clay, gravel) and post-mining sources of channel armor.
VIE. Illustrated narrative of post-mining subsurface hydrologic system ex-
pected in areas designated as alluvial valley floor areas. Show all re-
created aquifers, expected locations of piezometric surfaces of confined
aquifers, and water levels expected over local layers of less permeable
strata (perched water tables) If any. Describe fluctuation in water
table and recreation of subirrigation conditions. Provide comparisons
between pre-mining and projected post-mining vegetative systems with
estimates of levels of production of forage, ground cover density,
species composition, and description of expected root systems in terms of
depth and structure. Wherever possible utilize quantitative flow and che-
mical quality simulation models to project post-mining situation.
VIF. Estimation of Ground Water Recharge and Discharge Characteristics after
mining in relation to areas designated as alluvial valley floor areas
within and downstream of the area of operations. Identification of
difficulties of reestablishing pre-mining ground water system (flow,
quality, and depth to water). Identification of effects of coal mining
in areas adjacent to the proposed area of operations.
VIG. Plans for post-mining monitoring of hydrologic and biologic systems of
alluvial valley floors.
-------
Summary and CorelusIons
Reconnaissance mapping of subirrigated alluvial valley floors was conducted to
determine how much land minht be involved if SDecial leqislatlon evolved to protect
areas of agricultural importance, and, indirectly, how much coal miqht be affected
if mining of alluvial valley floors was determined to be environmentally unacceptable.
This reconnaissance effort defines the limits of subirrigated alluvial valley floors
adequately enough to serve as a basis for making first estimates of surface mineable
coal that may be affected if the alluvial valley floors cannot be mined, A recon-
naissance study does not provide sufficient Information to estimate how much of the
coal that lies outside the alluvial valley floor might be affected. That^^lysls
appears possible only with additional experience 1n mines located a^atf] options.
Including those outside alluvial valley floors, or with ilrtillajryi^niiTflltij wifnrim
tlon that accurately describes the alluvial valley floor MjWfcKghi. aft* wial Re-
source, and the effect of the reclamation procedures propo»^j9S»sl2hfc!ys1s does
confirm the suggestions of others that about three percent ok «ms»rlppable coal
resources of the western United States underlies subirr1gate%H nivial valley floors.
The impact of alluvial valley floor protection requirements on the amount of surface
mineable coal available may be expected to be about 1096 if reclamation 1s not possi-
ble. In the judgement of the authors, only where there 1s a considerable density of
alluvial valley floors is it likely that mining plans cannot be developed to exclude
mining of such areas. It is likely that the critical functions of some alluvial val-
ley floors can be reestablished except where complex surface and ground water systems
are present and when shallow ground water quality is severely degraded as 1t passes
through spoils.
This reconnaissance Identification of the topographic (with some regard for geo-
morphology) and vegetative characteristics of alluvial valley floors within lands
leased for coal extraction by surface methods provides a basis for estimating that
three percent of the leaseholds 1n the interior western United States are overlain
by alluvial valley floors. These alluvial valley floor designations encompass a
land unit with a geohydrologic and biologic interrelationship that may be critical
to the viability of an agricultural economy. However, the economic importance of
the alluvial valley floor has not been assessed.
Alluvial valley floors are quite common in the Montana, Wyoming, and Colorado
areas of coal development, but are less conmon 1n the coal regions of North Dakota,
southwestern Wyoming, Utah, New Mexico, and Arizona, "Less common" refers to the
size and amount of land identified as alluvial valley floors. For example, the mines
examined 1n Arizona included areas of alluvial valley floors, but the area Involved
was less than 0.5 percent of the land area examined. Identification of these allu-
vial valley floors was accomplished through the use of aerial imagery, topographic
maps, previous studies, and knowledge gained from past site visits.
Though 1t has been found to be a unique circumstance when any existing western
coal mine 1s located entirely within an alluvial valley floor, alluvial valley floors
may be supported by a coal seam aquifer system* that extends out from the alluvial
valley. Therefore, the effects of mining an area of recharge may extend to an allu-
vial valley floor. In this case, the amount of coal affected could easily be raised
1f reclamation were not possible (e.g., if shallow ground water quality were de-
graded so as to Interfere with use 1n the alluvial valley). In alluvial valley
floors containing relatively thick coals overlain by thin overburden as well as in
areas where alluvial aquifers are in a sense "perched" over the aquifer surface mine-
able coal, all coal may have to be withheld at least untn the details of the natu-
ral system and the proposed mining plan provide the necessary assurance that areas
may be reclaimed, at least to pre-mining productivity (and land uses).
* A moderately fractured coal seam which, often in combination with sandy strata,
transmits sufficient water to be classified as an aquifer.
-------
It is possible that in alluvial valley floor may be restored if the plant-
supportinq functions are principally dependent on the homnoeneous physical water-
holdinq characteristics of the plant qrowth medium and where there is no hydroloqic
complexity. In this casei restoration of the plant qrowth medium appears feasible.*
In some cases, alluvial ground v/aters may be "perched", and reclamation will require
recreation of differing zones of permeabilities and complex aquifer systems.
It ma., be that some Standard mining methods such as selective placement and com-
paction of overburden can approximately recreate strata with low permeabilities 1n
reclaimed areas. Rahn (1976) has suggested (but not demonstrated) this with Infor-
mation gathered in Montana and Wyoming. It may be possible to utilize clinker to
recreate permeability 1f spoils are otherwise impermeable, the other hand, the
importance of the capillary and unsaturated zone in sustaining vegetation on alluvial
valley floors is not known. Until this role is defined and until 1t is^Wfrmined
whether the plant growth medium can be reestablished in a manner wUclffconmnues to
support the grasses at a level equal to or better than that e*|p^lS\p
-------
adversely affect the waters of an alluvial valley floor. At this stage in our
understanding of the hydrologlc impacts of mining shallow coals 1n the West, there
Is dependence upon site-specific investigations, such as those at the Decker, 8elle
Ayr, Big Horn, Wyodak, Gascoyne, and Rosebud (MT) mines. It 1s hoped that some Im-
proved assessment of regional Impacts on water quality as a result of Increased coal
mining will be developed 1n the near future.
In addition, much uncertainty remains regarding the role of the alluvial valley
floor 1n the regional economic system. As yet, no land use and productivity analyses
have adequately evaluated the alluvial valley floor's contribution to the agricultural
and recreational economic sectors.
Since this analysis of sublrrlgated alluvial valley floors was prec1n£M^ by
proposed legislation, 1t 1s appropriate to use the findings of th1s_regfcnW|Tss»ce
investigation to evaluate technical aspects of the proposed lecds<||0fcl^(rak¦plaids,
Including alluvial valley floors, should be mined unless propj^mwcfytwe
essential functions can be restored. Such planning would be ^cmuSuVsl^he
applicant's demonstration that the procedures proposed will adAmt^j^restore, or
Improve upon, those characteristics of the natural system that WFrently dictate
existing environmental equ1lbr1um.
Information In this paper suggests that selected areas of sublrrlgated alluvial
valley floors could be mined and tne long-term agricultural productivity reestab-
lished in time. Thus, Instead of sddresslng only a ban on mining in alluvial val-
ley floors, this paper also reports on an alternative procedure - that of requiring
an applicant to submit a detailed environmental analysis, the content of which 1s
proposed. The detailed environmental analysis would involve extensive requirements
for both baseline Information and demonstration that proposed reclamation techniques
are Hkely to be successful. There must be sufficient data to permit regulatory
agencies to make the judgement that the essential functions of the alluvial valley
floor will be successfully restored and/or protected. The reclamation methods pro-
posed must have been demonstrated under similar circumstances. Though a ban would
directly Involve only three percent of the strlppable coal reserves, It would pro-
bably make uneconomic the mining of an additional amount of coal due to the need to
leave coal 1n place for pit wall stability and due to the difficulty 1n creating
logical mining units.
Alluvial valley floors which have sufficient sub1rr1gat1on to support agricul-
tural use (harvesting of hay, for example) are, conceptually, Important to the eco-
nomy of the western United States. They must be protected. In view of the uncer-
tainties caused by the few mining plans submitted to mine alluvial valley floors, it
may be appropriate to temporarily defer surface mining of coal 1n sublrrlgated allu-
vial valley floors until a well-defined and comprehensive research program has pro-
vided additional Information concerning the effects of mining under complex hydrolo-
glc conditions.
Acknowledgements
The authors are Indebted to Dr. Harold E. Malde and Mr. Richard Keefer (USGS)
who kindly made available the results of their field work and also Mr. Richard Hadley
who made available his expertise In the area of hydrology and eroslonal stability of
stream channels.
The efforts of an advisory group set up to assist with and review the findings
are also appreciated. This group consisted of, 1n addition to Mr. Malde and Mr. Kee-
fer, J. Herrmann (EPA), J. Mayberry (USGS), J. Ferry (EPA), R. Holmes (EPA), E. Ar-
thur (EPA), and A. Lees (FEA).
I
There are, of course1, differences of opinion between the authors and the advisory
group, and the opinions offered 1n this report are those of the authors, and thus do
not necessarily reflect the positions of members of the advisory group.
-------
All aerial fmaqery was collected under the direction of the Remote Sensing Opera-
tions Branch, Rpmote Srnsinq Division, Environmental r'onltorinq and Support Labora-
tory of the II. S. Environmental Protection Aqency. Most Interpretations of the
aerial Imaqery were performed by the Reirote Sensing Laboratory of Lockheed Electro-
nics Company, Inc., under EPA contract #68-03-2153. The financial and technical sup-
port thus provided by the Office of Research and Development of the U. S. Environ-
mental Protection Agency 1s gratefully acknowledged.
References Cited
American Geologic Institute, 1972. Glossary of Geology. AGI, Washington, D.C..
G. R. McAfee, Jr. and C. L. Wolf (editors).
Hadley, R. F. and N. J. King, 1977. Alluvial Valley Floors and Surface
the Western United States. Report 1n draft for review. U.	«
the Interior, Geological Survey, Denver, Colorado.	*
Heath, M. E., D. S. Metcalfe, and R. F. Barnes, 1973. Forages
Press, Ames. 755 pp.
Malde, H. E. and J. M. Boyles, 1976. Maps of alluvial valley floors and strfppable
coal 1n forty-two 7h-m1nute quadrangles, Big Horn, Rosebud, and Powder River
Counties, southeast Montana: USGS Open File Report 76-162.
McWhorter, D. 8., J. W. Rowe, M. W. Van Hew, R. L. Chandler, R. K. Skogerboe,
D. K. Sunada, G. V. Skogerboe, 1977. Surface and subsurface water quality
hydrology 1n surface mined watersheds. U. S. EPA, Industrial Environmental
Research Laboratory, Cincinnati.
National Academy of Sciences, 1974. Rehabilitation potential of Western Coal
Lands — A report to the Energy Policy Project of the Ford Foundation.
Balllnger Publishing Company, Cambridge, Massachusetts. 198 pp.
Rahn, P.H., 1976. Potential of Coal Strip Mine Spoils as Aquifers 1n the Powder
River Basin: Project Completion Report. Old West Regional Commission.
Rural Electrification Administration, 1974. Final Environmental Impact Statement.
Schmidt, J., 1977. Alluvial Valley Floors 1n East-central Montana and Their
Relation to Strippable Coal Reserves; Reconnaissance Report. U.S. Environ-
mental Protection Agency, Region VIII, In cooperation with State of Montana.
United States Department of Interior and State of Montana, Department of State
Lands, 1976. Oraft Environmental Impact Statement, Proposed Plan of Mining
and Reclamation — East Decker and North Extension Mines. Decker Coal Com-
pany, B1g Horn County, Montana.
U. S. Geological Survey, 1974. Shallow Ground Water 1n Selected ^reas 1n the Fort
Union Coal Region. By the Ground Water Subgroup of Water Work Group,
Northern Great Plains Resources Program. USGS Open File Report 74-48.
Van Voast, W.A., and R. B. Hedges, 1975. Hydrogeologlc Aspects of Existing and
Proposed Strip Coal Mines near Decker, southeastern Montana. Montana
Bureau of Mines and Geology, Bulletin 97.
Van Voast, W. A., and R. B. Hedges, 1975. Hydrogeologlc Conditions and Projec-
tions Related to Mining Near Colstrip, southeastern Montana. Montana
Bureau of Mines and Geology, Billings, Montana.
Weaver, J. E., 1968. Prairie Plants and Their Environment. U. of Nebraska
Press, Lincoln. 276 pp.
-------
Mine	Operator
A-l	Black Mesa	Peabody Coal
A-2	Kayenta	Peabody Coal
C-1	Black Diamond Strip	Canon Coal Corp.
C-2	Canadian Strip	R. Flesch & Son, Inc.
C-3	Corley Strip (S&A)	Cwon Coal Co.
C-4	Craig	Utah International
C-5 Denton Strip	Mllner Coal Co.
C-6 Edna Strip	Pittsburgh & Midway
C-7	Energy Strip #1	Energy Fuels Corp.
Energy Strip 12
Energy Strip #3
C-8	Grizzly Creek Strip	Sunflower Energy
C-9	Jewel Strip	Horner Coal Co.
C-10	Marr Strip #1	Kerr Coal Co.
C-ll	Nucla Strip	Peabody Coal Co.
C-12	Seneca Strip #2	Peabody Coal Co.
C-13	Williams fork Strip	Empire Energy Corp.
C-14 		Moon Lake Electric
C-15	Colowyo	W.R. Grace
M-l	Absaloka (Sarpy Creek)	Westmoreland Resources
M-2	Absaloka II	Westmoreland Resources
Appendix 1
State (& County)
Legal Description
Arizona
Arizona
Colorado
Colorado
C olorado
(Navajo)
(Navajo)
(Fremont)
(Jackson)
(Fremont)
Colorado (Moffat)
Colorado (Routt)
Colorado (Routt)
Colorado (Routt)
Colorado (Jackson)
Colorado (Las Animas)
Colorado (Jackson)
Colorado (Montrose)
Colorado (Routt)
Colorado (Moffat)
Colorado
Colorado
Montana (Big Horn)
Montana (Big Horn)
T34-36N, R13-16W
T34-36N, R13-16W
T20S, R70W, 24
T8N, R78W.2
T20S, R69W, 6,7,18,19,30,31
720S, R70VI, 1,12,13,24
T6N, R90W, 29-32
T5N, R90W, 5-8, 17, 18
T6N, R91W, 11-16,21,23-29,33-36
T5N, R91W, 1-5, 9-11
T6N, R86W, 20-21
T4N, R85W, 7,18,19
T5N, R85W, 19,30,31
T4N, R86W, 12-14,19,23-25
T5N, R86W, 25,36
T4N, R86W, 7,8,9,17,18,19,30
T4N, R87W, 11-14,23-25
T5N, R85W, 6,7,18,19,30,31
T5N, R86W, 1,2,3,10-15,18-21,24,25
27-34
T5N, R87W, 23-26,35,36
T6N, R86W, 34-36
T7N, R80W, 32,39
T6N, R80W, 4
T30S, R65W, 31
T9N, R78W, 25,2
T8N, R78W.2,
T47N, R16W,
T5N, R87W, 1-
T6N, R87W, 2,!
T5N, R91W, 6
T6N, R91W, 29-3'
T4N, R89W
T3N, R93W, 2-4,8^
T4N, R93W, 27,28,'
TIN, R37E, 23,25,J
T2N, R36E, 1-4,8-14,23-26
TIN, R36E, 1-4,8-14,23-26
TIN, R37E, 4-9,17-21,28-33
,24-27,34-36
-------
Hine	Operator
M-3	Absaloka III	I stmoreland Resources
M-4	Big Sky	P iabody Coal Co.
M-5	Circle West	Birllngton Northern
M-6	Coal Creek	J.H. Schoonover
M-7	Rosebud	Western Energy Co.
M-8	Decker East	Decker Coal Co.
M-9	Decker North	Decker Coal Co.
M-10 Decker II (West)	Decker Coal Co.
M-ll	PM Strip	PM Coal Co.
M-12	East Sarpy Creek	AMAX Coal Corp.
M-13	Savage	Knife River Coal Co.
M-14	Spring Creek	Pacific Power & Light
M-15	Storm King	Divide Coal Mining Co.
M-16	Youngs Creek	Shell Oil
NM-1	McKlnley	Pittsburgh & Midway
State (& County)
Legal Description
Montana (B1g Horn)
Montana (Rosebud)
Montana (McCone)
Montana (Musselshell)
Montana (B1g Horn)
Montana
Montana
Montana (Big Horn)
Montana (Musselshell)
Montana (Big Horn)
Montana (Richland)
Montana (Big Horn)
Montana (Musselshell)
Montana (Big Horn)
New Mexico (McKinley)
T1S, R37E, 1,2
T1S, R38E. 2-5,8-10
TIN, R38E, 17-21 ,25,29-32
TIN, R37E, 1-3,10-15,22-27,34-3u
TIN, R41E, 13-15,21-23,26,27
T21N, R45E, 19,26-35
T20N, R45E, 2-8,10-13,17,18
T20N, R44E
T20N, R46E
T8N, R25E, 16
T2N, R38E, 12,13,23-25
TIN, R39E, 1-5
T2N, R39E, 19,28,36
TIN, R40E, 1-6,8-16
T2N, R41E, 13-15,22-35
TIN, R42E, 7,17,18
T2N, R42E, 18-20,28-30,32
T9S, R41E, 7,8,18
T9S, R40E, 12-14
T9S, R40E, 3,4,9,10
T8S, R40E, 33,34
T9S, R40E, 9,10,15-17,21,22
T6N, R26E, 23
T2N, R37E, 1,2,11 ,12,23-27,35,36
TIN, R37E, 1,12
TIN, R38E, 5-7,8,17
T2N, R38E, 5-8
T20N, R57E, 22
T8S, R39E, 1
T8S, R40E, 3
T6N, R26E.23
T9S, R38E, 14-
T8S, R38E
T8S, R37E
T16N, R21N
TUN, R20W, 31-34,36
T16N, R20W, 2,4-8,jM0R7ft-18,
21 ,22,26-28,31
26-28

-------
Mine
NM-2 Navajo
Operator
Utah International
NM-3 San Juan
NM-4 Star Lake
Western Coal Co.
Peabody Coal Co.
NM-5 Sundance	Amcoal, Inc.
NM-6 West York Canyon Strip Kaiser Steel
NM-7
NM-8
Gamerco
ND-1 Beulah South (and
North)
ND-2 Center
Carbon Coal Co.
Hesa Resource C0.EPN6
Knife River Coal
Baukol-Noonan
NO-3 Falkirk
North American Coal
ND-4 Gascoyne
NO-5 Glenharold
Knife River Coal Co.
Consolidation Coal Co.
State (& County)
New Mexico (San Juan)
New Mexico (San Juan)
New Mexico (McKlnley)
New Mexico (McKlnley)
New Mexico (Colfax)
New Mexico (McKlnley)
New Mexico (San Juan)
North Dakota (Mercer)
(Oliver)
North Dakota (Oliver)
North Dakota (McClean
(Washburn
North Dakota (Bowman)
North Dakota (Oliver)
Legal Description
T29N, R15W, 8-10,15-17,20-22,28-32
T28N, R15W, 7-9,16-21,28-32
T28N, R16W, 25,34-36
T27N, R15W, 31
T26N, R15W, 6,7,18,19
727N, R16W, 1-3,10-12,14,15,22-27
34-36
T26N, R16W, 1-3,9-16,22-27,33-36
T25N, R16W, 1-5,8-17,20-24
T30N, R15W, 2-4,9,10,15,16,21,22
27,28,33,34,20
T20N, R7W, 3,9-16,22-27,36
T20N, R6W, 16-22,26-36
T19N, R6W, 1-5,9-12
T19N, R7W, 6,7
T19N, R7W, 1
T14N, R17W, 9
T30N, R19E, 2-4,9-11
T31N, R9E, 20-22,27-29,32-35
T16N, R9W, 33
T15N, R19W, 2-4,10-16,21,22
T23N, R14W, 27-33
T24N, R15W, 24-26
T143N, R87W, 6,7,8,18
T143N, R88w, 1,2,11-14
T144N, R87W, 8,9,16,17
T142N, R84W, 23-25,35,36
T142N, R83W, 21,30
T141N, R84W,
T146N,	R82W
T146N,	R83W,
T146N,	R81W,
T145N,	R82W,
T145N,	R83W,
T145N,	R81W,
T131N,	R99W,
7144N,	R84W, 3-5,8-
23
T143N,	R84W, 5,6
pt 21
,23-26,35-36
,30,31
.#
,18-20
-------
Mine
ND-6 Husky Strip
ND-7 Indian Head
Operator
Husky Industries
North American Coal
ND-8	Larson (Noonan)
ND-9	Nelson
ND-10	Smlth-Ulman
ND-11	Sprecher
ND-12	Velva
U-1	Alton
Baukol-Noonan
GEO Resources
NL Industries
Sprecher Coal Co.
Consolidations Coal Co.
Utah International
and Nevada Electric
U-2	Emergy Strip
U-3	Mill Draw
U-4
U-5
WA-1	Carbon River
WA-2	Centralla
WY-1	Eagle Butte
WY-2	Belle Ayr
WY-3	Big Horn
WY-4	Black Butte
Consolidation Coal Co.
Energy Plus, Inc.
Peabody Coal Co.
Resources Company
Donald Hume
Washington Irrigation
and Development
AMAX Coal Corp.
AMAX.
Big Horn Coal Co.
Black Butte Coal Co.
WY-5 Black Thunder	ARCO
WY-6 Buckskin
Shell Oil
State (ft County)	Legal Description
North Dakota (Stark)
North Dakota (Mercer)
North Dakota (Burke)
North Dakota (Williams)
North Dakota (Adams)
North Dakota (Grant)
North Dakota (Ward)
Utah
Utah (Emery)
Utah (Uintah)
Utah
Utah
Washington
Washington (Lewis)
Wyoming (Campbell)
Wyoming (Campbell)
Wyoming
Wyoming (Sweetwater)
Wyoming (Campbell)
Wyoming (Campbell)
T139N, R95W, 7,8,17
T143N, R87W, 6,7
T144N, R88W, 19,28-33
T143N, R88W, 6
T144N. R89W, 24-26,36
T143N, R89W, 1
T162N, R94W, 3-5,8-11,14-16
T154N, R100W, 17
T129N, R94W, 5-8
T129N, R95W.1
T134N, R90W, 29
T152N, R81W, 28,34-36
T151N, R81W, 1,2
T40S, R5W, 4,5,7-9.17,19.29,13,
14 23-27 34
T39S, R6W, 11-14,23-27,34,35
T40S, R6W, 3-5,8-10
T39S, R5W, 6,7,17-20,29-33
T39S, R4W, 23-27,32-35
T40S, R4W, 2-9,18,19
T22S, R6E, 22,27,28,33,34
T3S, R22E, 8
T15N, R1W, 28
T51N,
T47N,
T48N, R71
T57N, R841
T19N, R1001
R72W, 16,21-23,26-28,34,35
R71W, 3-j
32-35
1-23,27
7,9-11,14-16
8,29,31,32
T18N, R101W,1
T42N, R70W,
T43N, R70W, 1
T52N, R72W, 32'
T51N, R72W, 5
,27-29,33-35
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Mine
WY-7 Caballo
WY-8 Coal Creek
WY-9 Cordero
WY-10 Dave Johnston
Operator
rater 011
Peabody Coal Co.
Jjnoco
Pacific Power & Light
WY-11	East Antelope
WY-T2	East Gillette
MY-13	Elkol
WY-14	FHC
Best Coal Co.
Kerr-McGee
Kemmerer Coal Co.
FMC
WY-15 Jacobs Ranch
WY-16 Grass Creek
WY-17 Jim Brldger
Kerr-McGee
Northwestern Resources
Bridger Coal Co.
WY-18 Lake OeSmet
WY-19 Medicine Bow
Texaco
Arch Minerals
WY-20 Muddy Creed
WY-21 North Rawhide
Crater Oil Co.
WY-22 P.S.0.#1
WY-23 Rimrock
Public Service Co. of
Oklahoma
Energy Development
State (& County)
Wyom1ng{Campbell
Wyoming
Wyoming (Campbell)
Wyoming (Converse)
Wyoming
Wyoming (Campbell)
Wyoming
Wyoming (Lincoln)
Wyoming (Campbell)
Wyoming (Hot Springs)
Wyoming (Sweetwater)
Wyoming
Wyoming (Carbon)
Wyoming (Fremont)
Wyoming (Campbell)
Wyoming (Sheridan)
Wyomi ng
Legal Description
T48N, R70W, 7,18,19
T48N, R71W, 11-16,21-24,26-28
T43N, R70W, 3,4
T46N, R71W, 2,3,
T47N, R71W, 13-15,22-24,26,27,34,35
T35N, R74W, 18,19
T36N, R74W, 2,6,7,10,11
T35N, R75W, 1-3,10-13,16,24,36
T36N, R75W, 1-3,10-12,14-16,21,22
27,28,33-36
7A1N R71U I1!
T50n! R71W» 5,6,8,9,20-22,27-29,
33,34
T21N, R116W, 20
T20N, R117W, 11-14,22-24,26,27,28,34
T20N, R116W, 17-20,30
T19N, R117W, 4,10
T43N, R69W, 6,7
T43N, R70W, 1-3,10-15
T46N, R99W, 26
T21N, R100W, 7,16-22,26-29,33-36
T20N, R100W, 2-5,8-15,22-27,35
T21N, R101W, 2,3,10-14
752N, R82W
T23N, R83W, 5-9,17-20,29,31-34
T24N, RB4W, 25
T24N, R84W, 28-33
T23N, R84W, 1,11-14,25,35
T6N, R1E, 17,20
T52N, R72W, 31,33
T51N, R72W, 3-6,9-15,31,1
T50N, R71W, 7,18,19,30
T50N, R72W, 1,12,13,24
T58N, R84W, 22
722N, R82W, 2-10,14,15,18,2
26,28,30,32,34
723N, R82W, 32
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Mine
WY-24	Rochelle
WY-25	Rosebud
WY-26	Semlnoe #1
WY-27	Semlnoe #2
WY-28	Sorenson & Elkol
WY-29	Twin Creek
WY-30	Welch
WY-32	Wyodak
Operator
Rochelle Coal Co.
Rosebud Coal Co.
Arch Minerals
Arch Minerals
Kemnerer Coal Co.
Rocky Mountain Energy
Welch Coal Co.
Wyodak Resources
State (& County)
Legal Description
Wyoming	T41N, R70W, 1-5,8-12,17
T41N, R69W, 6,7,18
T42N, R69W, 31
Wyoming (Carbon)	T22N, R81W, 2,3,10,11
T23N, R80W, 21,28,29,31,32
T23N, R81W, 16,20,21,27,28,33-36
Wyoming (Carbon)	T22N, R83W, 1-18,21-24
T22N R84W 2 12
Wyoming (Carbon)	T22N, R81W, 4,7-9,16,17
T23N, R81W, 7,8,18,22,26,32
T23N, R82W, 12,13
T22N, R82W, 1,12
Wyoming (Lincoln)	T21N, R116W, 4-7,17-21,28-33
T21N, R117W, 24-26
T20N, R1170, 1-4,9-11,14-16,21,22
T22N, R116W, 16,17,20-22,27-29,32,33
Wyoming (Lincoln)	T21N, R116W, 5-9,15-18
Wyoming	T57N, R83W, 6
T57N, R84W, 1
T58N, R83W, 31
Wyoming	T50N, R71W, 9,10,15,21 ,22,27,28,33
T50N, R72W, 3


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Appendix 2
"ALLUVIAL VALLEY FLOOR"
Legislative Directions and Interpretations
Definition of Alluvial Valley Floor Consistent with HR 9725:
"'alluvial valley floors' means the unconsolidated
deposits holding streams where water availability i
for sublrrigatlon or flood Irrigation agricultural
Source - 701(27) HR 25(94th)
FURTHER DESCRIPTION
"Alluvial valley floors refers to those unconsolidated deposits formed by streams
(Including their meanders) where the ground water level 1s so near the surface that
1t directly supports extensive vegetation or where flood stream flows can be diverted
for flood Irrigation."
Source - p. 65, Conference Report HR 9725 (95th).
"...alluvial valley floors are the upper, near-horizontal surface of the unconsoli-
dated stream-laid deposits which border perennial, Intermittent, or ephemeral
streams. The alluvium that makes up the stream-laid deposits 1s composed of clay,
silt, sand, gravel, or similar detrital material that has been, or is being, trans-
ported and deposited by streams. Alluvial valleys within this definition are tra-
versed by perennial or Intermittent streams or by ephemeral stream channels: are
irrigated in most years by diversion of natural flow or ephemeral flood flow on the
modern flood plain and adjacent low terraces, or by sublrrigatlon of the flood plain
by underflow: and are used for the production of hay and other crops that are an In-
tegral part of an agricultural operation."
Source - ibid.
"Excluded...are the colluvlal and other superficial deposits that normally occur
along the valley margins, are higher than the modern flood plain and low terraces,
are not Irrigated by diversion of natural flow or by ephemeral flood flow, and are
not sublrrlgated by underflow."
Source - Ibid.
"Alluvial valley floors do not Include upland areas which are generally overlain bv
a thin veneer of colluvial deposits composed chiefly of debris from sheet erosion,
deposits by unconcentrated runoff or slope wash, together with talus, other mass
movement accumulation and wind blown deposits."
Source - p. 83, Conference Report HR 25(94th)
"...alluvial valley floors must be (an) integral part of a drainage network that tra-
verses the area...These are part of a through flowinq stream (hydrologlc) system and
are not small areas of Isolated Internal drainage."
Source - p. 65, Conference Report HR 9725(95th)
152! characteristics of alluvial valley floors which are essential for agricultural
5 delude: (1) sufficient runoff to allow for flood water irrigation each year;
(2} development of flood plain and low terraces where water can be spread easily
without significant mechanical alteration of the surface; and (3) shallow ground
water where sublrrigatlon 1s used and (which) therefore regulres a minimum of valley
floor dissection so that ground water 1s not drained."
Source - pp. 82-83, Conference Report HR 25(94th)
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"The essential hydrologic functions (to be preserved) are the inherent properties of
alluvial valley floors controlling the availability of water under a wide range of
natural conditions. Such properties include for Instance: interaction between ground
and surface water; varying degrees of permeability throughout the deposit; infiltra-
tion rates; flow direction and gradients; capability of accumulating, holding and re-
leasing water through drought and seasonal cycles; stability with respect to storm
and flood runoff conditions J and maintaining quality of vater available to the agri-
cultural uses."
Source - p. 83, Ibid.
"The areas Involved are those limited sites where natural
atrippable coal and where sufficient water is available t
diversion from screams."
Source - ibid.
the alluvial valley floor provision was directed to such lands in arid and semi-arid
coal mining areas where they (the lands) form the backbone of the agricultural and
ranching operation which, in turn, form the basis of the existing regional economic
system and where the agricultural and ranching operations could not survive without
hay production from the alluvial valley floors. (Derived from p. 64, Conference Re-
port HR 9725)
It was recognized that tmdar site-specific circumstances, it ia possible to mine on
alluvial valley floors and still be able to assure the maintenance of hydrologic
functions of the area (p. 64, ibid and a lesser degree in p. 83, Conference Report
HR 25)
APPLICATION 0? ALLUVIAL VALLEY FLOOR PROVISION
tinder proposed subsection 510(b)(5), the Ace Is Interpreted to prohibit mining
in alluvial valley floors if:
510(b)(5)(A) such interrupts, discontinues, or prevents farming on those
alluvial valley floors. Excluded are undeveloped range lands
which are not significant to farming on alluvial valley floors
and lands the regulatory authority finds that even if farming
is prevented, they are of such small acreage so as to have
negligible Impact on the farm's production; or
510(b)(5)(B) would adversely affect the quantity or quality of water
(surface and underground) that supplies the alluvial valley floor.
There is also a "grandfather clause" 510(b)(5) for commercially producing
operations permitted by a State to operate in an alluvial floor or adjacent to an
alluvial valley floor which follows after 510(b)(5)(B), and reads:
"Proviaed, that this paragraph (5) shall not affect those surface coal
mining operations which in the year preceding the enactment of this
Act 0L1 produced coal in commercial quantities, and (2) were located
within or adjacent to alluvial valley floors or had obtained specific
permit approval by the State regulatory authority to conduct surface
coal mining operations within said alluvial valley floors".
In applying the proposed language of the Bill, we assume the word "Impact" is
used in the context of a harmful impact on the farm's production but it 1s not sped"
fied what a negligible Impact means and thus the discretionary powers of the regu-
latory authority may be unduly strained without more definitive criteria.
"Undeveloped range land" is somewhat ambiguous, but in the context of alluvial
valley floors, we assume that undeveloped range lands are those lands within
alluvial valley floors used randomly by grazing anicals and which are not cropped
for hay or otherwise harvested in a mechanical manner. This wording Is in need of
more clarity.
:urd^bove
b and
sublr:
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Provision (B) is assumed to be directed en protect the quantity and quality of
water In those alluvial talley floors with farming activities so that there will be
no adverse reduction of Agricultural production. We assume that "production" refers
principally to grass, griin, alfalfa, or hay as used for fodder. No criteria are
gives to assist with application of the work "adverse".
In a procedural sense, we sre not clear as to how the provision will apply If
a surface owner of an alluvial valley floor does not choose to reestablish an agri-
cultural activity on that land after mining; that Is, whether mining would
mltted.
CURRENT REGULATIONS - ALLUVIAL VALLEY FLOORS
Under Title 30 Code of Federal Regulations Part 211.40(a)
operator oust utilize the best practicable commercially svallal
minimize, control, or prevent disturbances of the hydrologlc re^,	,
"(tv) Protecting the quality, quantity and flow Including the depth of both
upstream and downstream surface and ground water resources of those valley
floors which provide water sources that support slgnlficsnt vegetation or
supply significant quantities of water for other purposes, by such measures
as, but not limited to, relocating and maintaining the gradient of streams,
avoiding mining, Installing, reestsbllshlng, or replacing aquifers and
aqulcludes, and replacing soil..." (30 CFR 211.40(a) (7) (iv).
Definitions:
Valley floors - "channelwaye, flood plains*, and adjacent low terraces of
atresias that ars flooded during periods of high flow and that are under-
lain hy unconsolidated stream-laid deposits. Excluded are higher ter-
races and slopes underlain by colluvial and other surflcial deposits
normally occurring along valley margins." (211.2(qq))
Significant vegetation - "farm crops, including grasses and forbes, that
are integral parts of agricultural or ranching operations and the natural
vegetation of forests or meadows with significant recreational, watershed,
agricultural, or wildlife habitat value." (211.2(11))
Note similarities between these existing regulations and language In Conference
Reports accompanying RR 9725 and HR 25.
RECENT USAGES OP ALLUVIAL VALLEY FLOOR PROVISION
As of February, 1977, two bills are before the 95th Congress that address sur-
face mining control and reclamation. HR 2, before the House Is similar to proposala
made In 1976. That bill says:
"No permit, revision, or renewal application shall be approved unless
the application demonstrates...that...(5) the proposed surface coal
mining operations, if located west of the one hundredth meridian west
longitude, would -
(A1 not Interrupt, discontinue, or prevent farming on alluvial
valley floors that are irrigated or naturally snbirrlgated, but,
excluding undeveloped range lands which are not significant to
•Flood plain refers to relatively smooth land adjacent to a channel constructed by
the present flow In its existing rsglmen and covered by water when the water over-
flows its banks. It Is built of alluvium carriad by the water during floods and
deposited in the sluggish watar beyond the Influence of the current. (Modified
from American Geological Institute, 1972, p. 267.) Flood plain size increases
with a decrease in the prtobabla frequency of a flood. The flood plain used to
define sn slluvial valley' floor in the context of this effort has generally coin-
cided with the annual flood plain which exceeds bank-full stage about every tvo
years.
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faming on said alluvial valley floors «nd chose lands chat Che
regulatory authority finds that If tha farming Chat will be In-
terrupted, discontinued, or prevented Is of such small acreage
as to be of negligible Impact on the fans'a agricultural produc-
tion, or
(B) not adversely affect the quantity or quality of water in sur-
face or underground water systems that supply these valley floors
In of subsection (B)(5)." (|510(b)(5), HR 2)
Tha Senate version, S7, under consideration says:
"No permit, revision, or renewal application shall be approved unless
application affirmatively demonstrates...that...(5) the proposed sur-
face coal mining operation, if located weBt of the one hundredth meri-
dian west longitude, would not have a substantial adverse effect on
alluvial valley floors underlain by unconsolidated stream laid deposits
where farming can be practiced in the form of irrigated, flood irrigated,
or naturally sublrrlgated hay meadows or other crop lands (excluding un-
developed range lands), where such valley floors are significant to the
practice of farming or				- --	- - -
or ranching operations
ly feasible."
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO. 2.
EPA 908/4-77-002
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
SUBIRRIGATED ALLUVIAL VALLEY FLOORS: A RECONNAISSANCE
OF THEIR PROPERTIES AND OCCURRENCE ON COAL RESOURCE
LANDS IN THE INTERIOR WESTERN UNITED STATES.
5.	REPORT DATE
March. 1977
6.	PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
John E. Hardaway, Dan B. Kimball, Shirley F..Lindsay
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection-Agency
Office of Energy Activities
1860 Lincoln Street
Denver, CO 80295
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Draft report
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
EPA has no plans at present to revise or republish this as a final report. (3/80)
16. ABSTRACT -
This draft report discusses the possible impacts which surface coal mining
might have upon certain lowland areas in the semi-arid West where shallow ground
water and/or soil moisture presently supports the growth of grasses and forbs
through the dry summer months. These lowland areas, located along drainaqe
channels and referred to recently as "alluvial valley floors" (National Academy
of Sciences, 1974), are most important in semi-arid and arid climates because
water is stored in the alluvium, enabling vegetation to continue growth during
montns of low rainfall. Alluvial valley floors are used for grazing and pro-
duction of hay, and include points of surface water accumulation and ground water
recharge and discharge. Surface mining of coal has the potential, in the western
United States, to temporarily, and even permanently, chanqe the ground water
flow system. Reconnaissance mapping of subirrigated alluvial floors was conducted
to determine how much land might be involved if special legislation evolved to
protect areas of agricultural importance,' and indirectly, how much coal might
be affected if mining of alluvial valley floors was determined to be environmen-
tally unacceptable.
'7. KEY WORDS AND DOCUMENT ANALYSIS
1. DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Coal mining Site surveys
Surface mining Arid land
Environmental impacts Semi arid land
Ground water
Water table
Grazing land
Surface water
Alluvial valley floors
Subirrigation
Western United States

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