Document ID: EPA-R08-OW-2007-0153-0048
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2008-10-27T04:00Z

Appendix A: FINDINGS OF FACT

ASSINIBOINE AND SIOUX TRIBES OF THE FORT PECK RESERVATION 

Decision Document for UIC Program Approval under Section 1425 of the
SDWA

RE:	Factual information on the potential for direct effects from
existing and future Class II underground injection activities of
nonmembers within the exterior boundaries of the Fort Peck Reservation
on the health, welfare, political integrity, and economic security of
the Assiniboine and Sioux Tribes that are serious and substantial.

	This document is organized to present information relating to nonmember
Class II underground injection activities within the exterior boundaries
of the Fort Peck Indian Reservation and the potential effects of these
activities, if unregulated or improperly managed, on underground sources
of drinking water (USDW) used by the Fort Peck Tribes (Tribes) or their
members.  The information summarized below first demonstrates the manner
in which the underground injection control program protects USDWs from
contaminants associated with Class II underground injection activities
and thus generally protects human health and welfare and economic and
political interests.  The document then describes the Fort Peck
Reservation, including the various USDWs located on the Reservation, the
Tribes’ uses of those USDWs, and the Class II underground injection
activities occurring on the Reservation.  Finally, the document provides
a specific and relevant example of actual impacts on the Tribes’ use
of these USDWs from nonmember oil production activities.  These facts
support EPA’s finding that there are USDWs afforded protection under
the Safe Drinking Water Act (SDWA) within the Reservation used by the
Tribes or their members (and thus that the Tribes or their members could
be exposed to contaminants present in, or introduced into, those USDWs),
and that nonmember  underground injection activities have the potential
to directly affect the Tribes’ health and welfare and political and
economic interests in a way that is serious and substantial.

The discussion below is organized under the following four headings:

A.	The role of the underground injection control program in protecting
human health and welfare, and political and economic interests.

B.	The potential surface and ground water quality impacts related to
Class II underground injection activities.

C.	The relationship of nonmember Class II underground injection
activities on the Fort Peck Reservation to the Tribes’ use of
underground and surface sources of drinking water.

D.	A specific and relevant example of actual impacts on Tribal use of
underground sources of drinking water from nonmember oil production
activities on the Fort Peck Reservation.

	A.	The Role of the Underground Injection Control Program in Protecting
Human Health and Welfare, and Political and Economic Interests

	The federal underground injection control (UIC) program was established
by Congress under the SDWA, 42 U.S.C. Section 300f, et seq.   In the
SDWA, Congress directed the Environmental Protection Agency (EPA) to
promulgate regulations with minimum requirements for preventing
underground injection that could endanger present and potential future
drinking water sources.  (See 42 U.S.C. Sections 300h (b)(1) and
(d)(2).)  The minimum requirements that EPA promulgated are in 40 CFR
Parts 124 and 144 - 48.

	In keeping with the Congressional intent to prevent endangerment both
to current and potential future underground sources of drinking water,
EPA defined the term “underground sources of drinking water” or
“USDWs” to mean an aquifer or its portion:

(a)	(1) Which supplies any public water system; or

(2) Which contains a sufficient quantity of ground water to supply a
public water system; and 

(i) currently supplies drinking water for human consumption; or

(ii) contains fewer than 10,000 milligrams per liter (mg/l) total
dissolved solids (TDS); and

(b)	Which is not an exempted aquifer.  [40 CFR Section 144.3]

	Congress defined the term “endangerment” in the following way:

Underground injection endangers drinking water sources if such injection
may result in the presence in underground water which supplies or can
reasonably be expected to supply any public water system of any
contaminant, and if the presence of such contaminant may result in such
system’s not complying with any national primary drinking water
regulation or may otherwise adversely affect the health of persons.  [42
U.S.C. Section 300h (d)(2)]

	To prevent endangerment, EPA’s regulations state that any injection
activity that may allow the movement of fluid containing any contaminant
into USDWs is prohibited, if the presence of that contaminant may cause
a violation of the primary drinking water regulations under 40 CFR Part
141, or other health based standards, or may adversely affect the health
of persons.  (See 40 CFR Sections 144.12(a) and 144.82(a).)

	The protection of all underground sources of drinking water via proper
regulation of underground injection activities helps ensure that human
health will be protected from disease and exposure to toxic materials
through various uses (e.g., consumption) of drinking water.  This
protection is basic to the health, welfare, political integrity, and
economic security of communities potentially affected by underground
injection activities.

									

	B.	The Potential Surface and Ground Water Quality Impacts Related to
Class II Underground Injection Activities

	Class II underground injection well fluids pose a potential for
contamination because of the constituents typically found in these
fluids.  Specifically, these fluids are generated from oil and
gas-related activities.  Generally, these fluids or “brines” contain
very high levels of total dissolved solids (TDS), typically between
5,000 to 100,000+ mg/l.  In addition to common constituents such as
chloride, these fluids have been found to contain petroleum
hydrocarbons, radium and other radioactive materials, additives such as
corrosion inhibitors (GAO, 1989), as well as other contaminants
including arsenic, benzene, polycyclic aromatic hydrocarbons (PAH)
(Remediation Technologies, Inc., 1991), cadmium, and lead (EPA, 1987).

	  EPA has found that contamination of USDWs can occur from unregulated
or improperly managed Class II underground injection activity. 
Specifically, the potential for contamination of USDWs can occur through
a variety of “pathways of contamination,” or pathways in which
injected fluids can enter USDWs, having escaped the well or zone into
which the fluids are injected.  These pathways are:

1.	migration of fluids through a leak in the casing of an injection well
and directly into a USDW;

		2.	vertical migration of fluids through improperly abandoned and
improperly completed wells in the vicinity of injection well operations;

3.	direct injection of fluids into or above a USDW;

4.	upward migration of fluids through the annulus which is the space
located between the injection well’s casing and the well bore.  This
can occur if there is sufficient injection pressure to push such fluid
into an overlying USDW;

5.	migration of fluids from an injection zone through the confining
strata over or underlying a USDW.  This can occur if there is sufficient
injection pressure to push fluid through a stratum which is either
fractured or permeable and into the adjacent USDW; and

6.	lateral migration of fluids from within an injection zone into a
portion of that stratum considered to be a USDW.  In this scenario,
there may be no

impermeable layer or other barrier to prevent migration of such fluids
(EPA, 1980).

	The federal UIC program has established minimum requirements to ensure
that Class II underground injection activities will not contaminate
USDWs.  There are two major technical requirements designed to protect
USDWs:  (1) injection wells must have mechanical integrity to ensure
that leaks do not result in significant movement of fluids into a USDW
(pathways one and four); and (2) an area of review is conducted for
newly drilled and converted injection wells to ensure that existing,
improperly completed, and abandoned wells within that area of review
(i.e., area of endangering influence) do not provide avenues for
vertical migration into USDWs (pathway two) (Osborne, 1991).  The UIC
program has also established requirements to control a number of
operating conditions, including injection pressure and volume, where
necessary to prevent contamination from pathways five and six.

	Figure 1 illustrates contamination pathways one and four through
failure of a well’s mechanical integrity.  A well does not have
mechanical integrity if:  (1) there are significant leaks in the well
tubing, casing, and packer; or (2) there is significant fluid movement
into a USDW adjacent to the well casing.  The absence of leaks in the
tubing, casing, and packer can be determined by pressure testing the
casing/tubing annulus of a conventional injection well while the well is
shut-in (see Figure 2).  Figure 3 is an illustration of the potential
problems associated with improperly plugged wells within the radius of
endangering influence of the injection well.  This radius is defined as
the point where the injection pressure gradient intersects the base of
the lowermost USDW.  The injection pressure gradient represents the
level to which fluids would rise in a hypothetical well at a given
location.  Therefore, determination of this pressure gradient is
important in determining whether any improperly plugged wells could
facilitate movement of contaminated fluid up into an overlying USDW.  In
cases where the calculated radius of endangering influence exceeds the
minimum quarter-mile area of review (see Figure 3), this radius becomes
the area of review within which all wells penetrating the confining zone
must be identified (Osborne, 1991).

 	In addition to potential impacts to USDWs, these migratory pathways
can allow for the contamination of surface water either: (1) through
upward migration (via the injection or other well) of injected fluid to
the surface which discharges into a water body; or (2) where
contaminated USDWs are hydrogeologically connected with surface water. 
Surface water  contamination can impair water quality and associated
designated uses, creating potential impacts to the health, welfare,
political integrity, and economic security of affected tribal or other
communities (see Appendix B: “Decision Document: Assiniboine and Sioux
Tribes of the Fort Peck Indian Reservation, Application for Treatment as
a State Under Section 303 of the Clean Water Act,” 1996, for a more
detailed discussion of the Fort Peck Tribes’ uses of Reservation
surface waters and the potential impacts on the Tribes and their members
of surface water contamination).

	Once present in USDWs through one or more of the pathways of
contamination noted above, the chemical constituents of these injected
fluids can have impacts on human health and  welfare, political
integrity, and economic security that are both serious and substantial. 
Health-related impacts can occur from domestic uses of this water
involving consumption, skin contact, and inhalation.  Health effects in
persons consuming water exceeding drinking water standards for Class II
injected fluid-related contaminants include:  cancer (from exposure to
benzene, arsenic, radium, and PAH), neurological and developments
effects (from exposure to lead and arsenic), and damage to specific
organs such as the kidney (from exposure to cadmium).  Health effects
from skin contact (e.g., via bathing and washing) and inhalation (e.g.,
via showering and cooking) at levels above concentrations equivalent to
drinking water standards include cancer (from exposure to benzene and
PAHs) (see e.g., EPA’s Integrated Risk Information System website at  
  HYPERLINK "http://www.epa.gov/iris"  http://www.epa.gov/iris  for a
summary of the health effects data, guidance for dermal risk assessment,
and methods for inhalation dosimetry) (EPA, 1987, 1991, 1992, 1994,
2000, and 2001).

	Serious and substantial impacts to human health and welfare, political
integrity, and economic security can also occur in a number of ways when
USDWs and associated water wells are contaminated with Class II injected
fluids.  Specifically: 1) treatment of contaminated well water and
ground water clean up; 2) development of alternative drinking water
sources (e.g., drilling of new wells); 3) inaccessibility of USDWs to
industry (e.g., for manufacturing processes), agriculture (e.g., for
irrigation), and ranching (e.g., for livestock watering); 4) inability
of  communities to retain and/or attract jobs and tourism; 5) lost wages
and jobs; 6) increased medical costs; and 7) costs associated with
hauling water, purchasing bottled water, and installing and maintaining
home water treatment systems (EPA, 2003).

	Finally, serious and substantial impacts to human health and welfare,
political integrity, and economic security can occur when USDWs or
surface water interconnected to USDWs used by tribal members or other
local communities for ceremonial or cultural purposes become
contaminated.  For example, the Fort Peck Tribes frequently use surface
water in their traditional ceremonies for consumption, immersion as part
of baptism, preparation of traditional foods, and associated
recreational activities (Sonosky, Chambers, Sachse, Endreson, & Perry,
2003).

	Therefore Class II underground injection activities, if left
unregulated or improperly managed, generally have the potential to
contaminate surface as well as underground sources of drinking water,
thereby potentially having an effect on the health, welfare, economic,
and political interests of tribes, their members and nonmembers alike
that are serious and substantial.

	C.	The Relationship of Nonmember Class II Underground Injection
Activities on the Fort Peck Reservation to the Tribes’ Use of
Underground and Surface Sources of Drinking Water

	The Fort Peck Indian Reservation (the Reservation) is located in
northeastern Montana’s glaciated plains and is bound by the Missouri
River on the south, the Milk River and Porcupine Creek to the west, Big
Muddy Creek on the east, and on the north by 48 degrees 38 minutes north
latitude.  (See Figure 4).  The Reservation’s population consists of
about 52% Tribal members and 48% nonmembers.  Agriculture is the primary
economic activity for both sectors of the population.  The Reservation
is composed of 45% trust and allotted land and 55% fee land.  The
majority of fee lands are owned by nonmembers (Moon, 1996).  The
attached color map (see Figure 5) shows that Tribal member and nonmember
land ownership is interspersed throughout the Reservation (Fort Peck
Tribes and Thamke, 2000).  Class II underground injection activity
occurs in various oil fields across the Reservation and has been
conducted primarily by nonmembers. 

	The EPA has regulated Class II injection wells located within the
external boundaries of the Reservation since June 25, 1984 (see 49 Fed.
Reg. 20138), consistent with the definition of “Indian lands,”
which, in 40 CFR Section 144.3, EPA defines as Indian country as defined
at 18 U.S.C. Section 1151.  There are currently 23 Class II injection
wells operating within the external boundaries of the Reservation. 
Figure 5 shows the locations of these injection wells and other
injection wells that have been operational in the past.  This map also
shows that these wells are located throughout the Reservation.  Most of
the active wells are located on nonmember-owned fee land (personal
communication with Debi Madison, Fort Peck Tribes, August 24, 2000). 
These wells are completed into, in increasing depth, the Judith River,
Dakota, Nisku, and Firemoon Formations, all of which are overlain by the
Bearpaw Shale Formation.  This impermeable shale layer underlies the
shallow ground water aquifers used by Tribal members and nonmembers for
domestic uses (see below), and is depicted in a cross-sectional view in
Figure 6.

	Ground water is the primary source of water supply, and is also the
primary source of drinking water across the Reservation.  Aquifers used
by Tribal members and nonmembers for various domestic purposes (e.g.,
drinking, livestock, and irrigation) are (in increasing depth): the
Quaternary deposits (alluvial and glacial deposits), Flaxville
Formation, Fort Union Formation, and a combination of the Fox Hills
Sandstone and the lower part of the Hell Creek Formation (Thamke, 1991).
 Generally, these formations underlie both Tribal trust and nonmember
owned fee lands throughout the Reservation (Fort Peck Tribes and Thamke,
2000).  The green and yellow shaded areas in Figure 5 cover much of the
Reservation and represent where all of these formations are exposed
directly at/near the surface (note: the glacial deposits are not shown).
 All formations are generally interconnected across the Reservation and
typically occur within 1000 feet of the surface.  Precipitation (rain
and snow) provides recharge to these formations, either where these
formations are exposed at/near the surface, or via overlying formations.
 Ground water flow for the nonbedrock formations (Quaternary deposits,
Flaxville, and Fort Union) is primarily towards, and intermixes with,
various surface water drainages (or “watersheds”) that generally run
north to south across the Reservation (Montana Bureau of Mines and
Geology, 1987).  As noted above, these formations are underlain by the
relatively impermeable Bearpaw Shale as depicted in Figure 6.  

	In 1991, the United States Geological Survey (USGS) inventoried a
number of water supply wells throughout the Reservation.  The results
showed:  (1) 78 domestic (e.g., drinking water) wells, of which 35
tapped alluvial or glacial aquifers, 14 tapped the Flaxville, 14 tapped
the Fort Union, and 15 tapped the Fox Hills/Hell Creek; (2) 17 wells
primarily used for livestock, of which six tapped the alluvial or
glacial aquifers, one tapped the Flaxville, two tapped the Fort Union,
and eight tapped the Fox Hills/Hell Creek; (3) three wells primarily
used for irrigation, of which one tapped the Flaxville and two tapped
the Fox Hills/Hell Creek; and (4) one commercial well, which tapped the
Fox Hills/Hell Creek (Thamke, 1991).  Some of these water supply wells
have been and continue to be used by Tribal members across the
Reservation (personal communication with Debi Madison, Fort Peck Tribes,
October 31, 2003).

	The alluvial aquifers generally follow along the major stream valleys
and are used for most ground water withdrawals (Thamke, 1991).  Alluvial
wells range from 15 to 50 feet in depth (Craigg and Thamke, 1995). 
Glacial aquifers are present in most of the Reservation, but water
yields differ greatly with location (Thamke, 1991).  Wells completed in
glacial deposits generally range from 70 to 120 feet in depth (Craigg
and Thamke, 1995).  The Flaxville aquifer is present in the northern and
central parts of the Reservation, and the Fort Union aquifer is present
in the north-central and eastern parts.  The Fox Hills-lower Hell Creek
aquifer is present in all areas of the Reservation, except the extreme
south-central and western parts, and is the second most common source of
ground water withdrawals.  Chemical analyses of water samples from
selected wells (four alluvial wells, two glacial wells, two Flaxville
wells, two Fort Union wells, and two Fox Hills-lower Hell Creek wells)
throughout the Reservation were performed by the Montana USGS in 1989. 
The analytical results indicated ambient TDS concentrations from 221 to
2,280 mg/l (Thamke, 1991) for these formations.  Ground water with TDS
concentrations up to 2,000 mg/l is readily consumed without treatment. 
Therefore, much of the ground water found in these shallow aquifers
across the Reservation is of drinkable quality, and all ground water
with TDS concentrations less than 10,000 mg/l are protected as USDWs
under the SDWA’s UIC regulations. 

	The above discussion and associated figures demonstrate that land
ownership on the Fort Peck Indian Reservation is very significantly
“checkerboarded,” and that underlying ground water aquifers used for
various domestic purposes (e.g., consumption) are generally
interconnected across the Reservation and within local watersheds where
intermixing with surface water occurs. Consequently, any current or
future ground water contamination resulting from unregulated or
improperly managed Class II underground injection activities conducted
by nonmembers can migrate into USDWs or interconnected surface waters
used by Tribal members, thereby directly impacting their health,
welfare, political integrity, and economic security in a way that is
serious and substantial.  

	The discussion that follows illustrates the potential for such impacts
by demonstrating how an improperly managed oil production well actually
impacted USDWs used by Tribal members.  While production wells are not
regulated by the UIC program, this discussion demonstrates that these
impacts did occur via the fourth established pathway of contamination
noted in Section B above and thus reflect potential impacts of
UIC-regulated activities.

	D.	A Specific and Relevant Example of Actual Impacts on Tribal Use of
Underground Sources of Drinking Water from Nonmember Oil Production
Activities on the Fort Peck Reservation

	Oil production activity by nonmembers has occurred, and continues to
occur, across the Reservation.  This includes the East Poplar Oil Field,
located in the southeastern part of the Reservation within the Poplar
River drainage.  This Oil Field is approximately ten miles
upstream/gradient from the town of Poplar.  (See Figure 4).  Poplar is
located at the mouth of the drainage and has Tribal member and nonmember
residents.  The Oil Field is located on lands with checkerboarded
ownership:  17% are Tribal trust lands, 35% are alloted lands held in
trust for individual Tribal members, and 48% are fee title lands
(personal communication with Debi Madison, Fort Peck Tribes, November
25, 1996).  The majority of fee lands are owned by nonmembers.  This Oil
Field has produced oil since the early 1950s.  Brine from the East
Poplar Oil Field is produced primarily from the Charles Formation of the
Madison Group, beginning at 5,300 feet below the land surface, and
ranges in TDS concentration from 16,000 to 201,000 mg/l (Levings, 1984).
 

	The presence of brine-related contamination in the Quaternary alluvium
along the Poplar River was first noted in the late 1970s, when
landowners reported increased salinity in their domestic well waters
(Thamke and Craigg, 1997).  Since then various field studies have been
conducted to determine the occurrence, extent, and movement of any
ground water contamination.  The contamination of the Quaternary aquifer
system (i.e., alluvium and glacial deposits) was formally documented in
a study published in 1984 through a USGS Reconnaissance Evaluation
(Levings, 1984).  This aquifer system is the sole developed drinking
water source for local (Tribal member and nonmember) residents (Thamke
and Craigg, 1997).    

	This report, along with subsequent USGS reports issued through 2003,
found that brine from oil production-related activities is the source of
shallow, Quaternary aquifer contamination as well as contamination of
surface water (i.e., the Poplar River) interconnected to this ground
water.  In one of these subsequent reports, the USGS identified at least
32 different wells completed into the Quaternary aquifers located within
the East Poplar Oil Field.  These included water wells that served the
domestic needs of local residents as well as livestock (Thamke, Craigg,
and Mendes, 1996).  Some of these domestic water wells were owned by
Tribal members ((Nathan Wiser, EPA Region 8, May 1, 2001).  

	The USGS’s most recent (December 2003) report provides additional
information on domestic water wells that were contaminated by oil
production-related activities, including the M-31 well, an Indian-owned
domestic water well that has been abandoned.  The earliest sampling data
(1985) from this well showed a TDS concentration of 2,930 mg/l.  A
series of additional samples was then taken from this well over the next
15 years that indicated considerable contamination.  The latest
available sampling data (2000) shows a TDS concentration of 60,800 mg/l.
 By this time, the water collected from the M-31 had become similar in
quality to the brine produced from the East Poplar Oil Field (Thamke and
Midtlyng, 2003).  

	The EPA has subsequently conducted its own sampling, including samples
from various domestic water wells in this same area.  Among its results,
EPA’s sampling of the M-31 abandoned Tribal water well showed benzene
concentrations between 58 - 78 micrograms per liter.  EPA’s
health-based drinking water standard for benzene is 5 micrograms per
liter.  Benzene is a volatile organic compound known to cause cancer in
humans (Mears, Risner, and Janik, 1999).

	Concluding that this contamination may present an imminent and
substantial endangerment to human health, and based on its review of
published USGS reports and results of its own field investigations, EPA
has issued a series of emergency orders against various companies that
had conducted oil production-related activities in this Oil Field.  EPA
has sought, among other things, to identify the possible source(s) of
contamination by obtaining records of company oil production activities
including exploration, production and injection wells, surface
facilities (e.g., tanks and pipelines), and geologic and hydrologic
field data related to such activities (Mears, Risner, Janik, 1999).  

	Upon review of these records, EPA confirmed an earlier USGS report of
an active source of ground water contamination contributing to the same
plume impacting the M-31 Tribal well noted above.  Specifically, EPA
concluded that an abandoned oil production well completed into the
Charles Formation, the Mesa Biere #1-22, had been improperly plugged. 
As a result, brine from this pressurized formation was flowing up the
well bore and into the overlying Quarternary aquifers.  EPA subsequently
ordered the current well owner to stop this well from leaking, which
appears to have been achieved by the re-drilling and plugging of this
well.  Additionally, EPA has determined that the historical use of
unlined surface pits was also a contributing source of contamination. 
As a result of the contamination documented within this Oil Field,
EPA’s enforcement actions required approximately 20 Tribal and
non-Tribal member households be provided bottled water for drinking and
other domestic purposes (Nathan Wiser, EPA Region 8, February 3, 2003).

	This example of documented ground water contamination demonstrates the
importance of properly managing brine under pressurized conditions
common to the operation of wells associated with oil production-related
activities on the Fort Peck Indian Reservation, including both
production and injection wells.  The improper plugging of the Mesa Biere
#1-22 production well created a pathway for brine to migrate from a
highly saline production formation into overlying USDWs used by local
residents, including Tribal members.  As noted in Section B above, this
pathway of contamination can also occur from unregulated or improperly
managed Class II underground injection activities, thereby directly
affecting the health, welfare, political integrity, and economic
security of the Fort Peck Tribes and all persons living on the Fort Peck
Indian Reservation in a way that is serious and substantial.

REFERENCES

Craigg, S.D., and Thamke, J.N., 1995, The effects of oil-field brines on
aquifers - Brine Disposal in the East Poplar Oil Field, Fort Peck Indian
Reservation, northeastern Montana, in Carter, L.M.H., ed., Energy and
the Environment - Application of geosciences to decision-making; Program
and Short Papers; Tenth V.E. McKelvey Forum on Mineral and Energy
Resources, 1995:  U.S. Geological Survey Circular 1108, p. 95-98.

Environmental Protection Agency, 1980, Underground Injection Control
Regulations:  Statement of Basis and Purpose, Washington, DC.

Environmental Protection Agency, National Primary Drinking Water
Regulations; Benzene (1987); Final Rule (52 FR 25690), Cadmium (1991);
Final Rule (56 FR 3526), Lead (1991); Final Rule (56 FR 26460), PAH
(1992); Final Rule (57 FR 31776), Radium (200); Final Rule (65 FR
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& Drinking Water, Washington DC.

Environmental Protection Agency, 1987, Report to Congress:  Management
of Wastes from the Exploration, Development, and Production of Crude
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Emergency Response, Washington DC.

Environmental Protection Agency, 1994, Methods for Derivation of
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Environmental Protection Agency, 2001, Draft:  Risk Assessment Guidance
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Environmental Protection Agency, 2003, Final Draft:  Ground Water Report
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GAO/RCED-89-97

House of Representatives Report No. 93-1185, 93rd Congress, 2nd Session
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Levings, G.W., 1984, Reconnaissance evaluation of contamination in the
alluvial aquifer in the East Poplar Oil Field, Roosevelt County,
Montana:  U.S. Geological Survey Water-Resources Investigations Report
84-4174.

Madison, D.D., Fort Peck Tribes, Personal Communications on November
25th, 1996, November 24th, 2000, and October 31st, 2003.

Mears, C.E., Risner, M.T., and Janik, D.J., 1999, Environmental
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SDWA-8-99-68.

Montana Bureau of Mines and Geology, 1987, Report MBMG-178:  Groundwater
Resources of the Fort Peck Indian Reservation, Emphasis on Aquifers of
the Preglacial Missouri River Valley.

Moon, D.L., 1996, Appendix of EPA Region 8’s Decision Document: 
Approval of Fort Peck Tribes Application for Program Approval Under
Section 303(c) of the Clean Water Act.

Osborne, P.S., 1991, Program Overview, Underground Injection Control,
EPA Region 8, 2nd Ed. 

Remediation Technologies, Inc., 1991, On-site Remediation of Oily
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Petroleum Environmental Research Forum c/o Conoco, Inc. Ponca City, OK.

Sonosky, Chambers, Sachse, Endreson, & Perry, LLP, 2003, Letter to Fort
Peck Chairman Arlyn Headdress Regarding Tribes’ Underground Injection
Control Primacy Application, p. 4.

Thamke, J.N., 1991, Reconnaissance of Ground-Water Resources of the Fort
Peck Indian Reservation:  U.S. Geological Survey Water Resources
Investigation Report 91-4032. 

Thamke, J.N., and Craigg, S.D., 1997, Saline-water Contamination in
Quaternary Deposits and the Poplar River, East Poplar Oil Field,
Northwestern Montana: U.S. Geological Survey Water Resources
Investigations Report 97-4000.

Thamke, J.N., Craigg, S.D., and Mendes, T.M., 1996, Hydrologic Data for
the East Poplar Oil Field, Fort Peck Indian Reservation, NE Montana: 
U.S. Geological Survey Open-File Report.

Thamke, J.N., Midtlyng, K.S., 2003, Ground-water Quality for Two Areas
in the Fort Peck Indian Reservation, NE Montana, 1993-2000: USGS
Water-Resources Investigations Report 03-4214.

Wiser, N. M., 2001, EPA Region 8, Fact Sheet on East Poplar Oil Field
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