Friday
April 6, 1990
Part VII
Environmental
Protection Agency
Hazardous and Solid Waste; Conditional
Variance to Department of Energy Waste
Isolation Pilot Plant; Notice of Proposed
Decision
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Federal Register / Vol. 55. No. 67 / Friday, April 6. 1990 / Notices
ENVIRONMENTAL PROTECTION
AGENCY •
[FRL-3753-3]
Notice Proposing To Grant a
Conditional Variance to the
Department of Energy Waste Isolation
Pilot Plant (WIPP) From Land Disposal
Restrictions
AGENCY: Environmental Protection
Agency.
ACTION: Notice of proposed decision.
SUMMARY: The Environmental Protection
Agency (EPA) is today proposing to
grant a conditional no-migration
variance to the U.S. Department of
Energy (DOE). This variance would
allow DOE to place hazardous waste
subject to the land disposal restrictions
of the Resource Conservation and
Recovery Act (RCRA) in DOE's Waste
Isolation Pilot Plant (WIPP) near
Carlsbad, NM, for the limited purposes
of testing and experimentation. DOE
submitted a petition to EPA under 40
CFR 268.6 requesting a no-migration
variance from the RCRA land disposal
treatment standards on the grounds that
treatment was unnecessary to protect
human health and the environment
because there would be no migration of
hazardous constituents from the
disposal unit. After a review of DOE's
petition and supporting information,
EPA has tentatively concluded that DOE
has demonstrated, to a reasonable
degree of certainty, that hazardous
constituents will not migrate out of the
WIPP disposal unit during the testing
period proposed by DOE.
DATES: Comments on this proposed
decision should be submitted on or
before June 5,1990.
EPA notes that it is providing the
• public a 60-day comment period on this
proposed decision, which is longer than
it generally provides for site-specific
actions. For example, the Agency allows
30 days for comments on proposed no-
migration variance decisions for
underground injection wells, and 45
days for comments on RCRA permits.
The Agency has provided extended time
for comment on today's proposal
because of the scope of the record, and
because it is the Agency's first proposed
decision on a variance request under 40
CFR 268.6. EPA, however, considers the
extended comment period sufficient,
and does not intend to grant any further
extensions to the period.
Comments on today's proposal should
be addressed to the docket clerk at the
following address: U.S. Environmental
Protection Agency, RCRA Docket (OS-
305), 401M Street, SW., Washington, DC
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20460. One original and'two copies
should be sent and identified by
regulatory docket reference number F-
90-NMWP-FFFFF. The docket is open
from 9 a.m. to 4 p.m., Monday through
Friday, excluding Federal holidays.
Docket materials may be reviewed by
appointment by calling (202) 475-9327.
Copies of docket materials may be made
at no cost, with a maximum of 100 pages
of material from any one regulatory
docket. Additional copies are $0.15 per
page.
A copy of the record supporting this
proposal is also available to the public
in Albuquerque, New Mexico, at the
National Atomic Museum Library,
Building 20358, Wyoming Boulevard,
Kirkland Air Force Base, from 9 a.m. to 5
p.m., Monday through Friday; and in
Carlsbad, New Mexico, at the WIPP
Office and Information Center, 101W.
Greene Street, from 7:30 a.m. to 4:30 p.m.
Public hearings on this proposed
decision have been scheduled for May
22,1990, in Carlsbad, New Mexico, at
the Park Inn International, 3706 National
Parks Highway, beginning at 9:00 a.m.,
and for May 23 to 26,1990, in
Albuquerque, New Mexico, at the
Albuquerque Convention Center, 401
Second St. NW. The hearing on May 23
in Albuquerque will begin at 1:00 p.m.;
the hearing on subsequent days will
begin at 9 a.m. Persons interested in
testifying at either hearing should
telephone 1-800-955-9477 to register.
Requests to testify must be received by
May 11,1990.
FOR FURTHER INFORMATION CONTACT:
General questions about the regulatory
requirements under RCRA should be
directed to the RCRA/Superfund
Hotline, Office of Solid Waste (05-305),
U.S. Environmental Protection Agency,
Washington, DC 20460, 800-424-9346
(toll free) or 202-382-3000 (local).
Specific questions about the issues
discussed in this notice should be
directed to Matthew Hale, Office of
Solid Waste (OS-341), U.S.
Environmental Protection Agency, 401 M
Street, SW., Washington, DC 20460, at
202-382-4746.
SUPPLEMENTARY INFORMATION:
I. Background
A. RCRA Land Disposal Restrictions:
No-Migration Variances
The Hazardous and Solid Waste
Amendments (HSWA) of 1984, which
amend the Resource Conservation and
Recovery Act (RCRA), imposed
substantial new requirements on the
land disposal of hazardous waste. In
particular, the amendments prohibit the
continued land disposal of hazardous
wastes, unless the wastes meet the
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treatment standards specified by EPA.
"Land'disposal" is defined to include
placement "in a landfill, surface : •
impoundment, waste,pile, injection-well,
land treatment facility, salt dome
formation, salt bed formation, or
underground mine or cave" (RCRA
section 3004(k)).
The statute requires EPA to establish
treatment standards for wastes subject
to the land disposal restrictions; these
standards define when a hazardous
waste may be land disposed. In its
implementing regulations, EPA has
established these standards based on
the best demonstrated available
technology (BOAT). The HSWA
amendments also lay out specific dates
by which the land disposal restrictions
become effective, beginning with
November 8,1986, for solvents and
dioxins. By May 8,1990, restrictions will
be in effect for all wastes that were
listed or identified as hazardous before
November 8,1984, although EPA may
extend the land disposal prohibition
dates for up to two years if it finds a
lack of national treatment capacity. EPA
may also grant a 1-year case-by-case
capacity extension, which can be
extended once, in certain circumstances.
Once the land disposal prohibition date
for a specific waste has passed, that
waste cannot be placed in a land
disposal unit, unless it has been treated
to meet or otherwise meets BDAT
standards, or "unless the Administrator
determines that the prohibition * * * is
not required in order to protect human
health and the environment for as long
as the waste remains hazardous * * *
(RCRA sections 3004 (d)(l), (e)(l), and
(g)(5).) This determination must be
based on a demonstration by the facility
owner/operator "that there will be no
migration of hazardous constituents
from the disposal unit or injection zone
for as long as the wastes remain
hazardous." (RCRA sections 3004 (d)(l),
(e)(l), and (g)(5J.) A determination under
this authority is referred to as a "no-
migration" variance; a request from a
facility owner/opera tor for such a
variance .is called a "no-migration"
variance petition.
The Agency first promulgated no-
migration standards under 40 CFR 268.6
on November 7,1986. These regulations,
which apply to land disposal units other
than underground injection wells, codify
the statutory standard for no-migration
variances, specify information to be
included in variance petitions, and
establish procedures for the granting or
denying of a variance (November 7,
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13069
1986, 51 FR 40572).1 EPA amended the
regulations on August 17,1988 (53 FR
31138), to add further procedural
requirements and standards. EPA is now
developing additional no-migration
standards, including a generic definition
of "no-migration," for land disposal
units other than underground injection
wells. The Agency expects to propose
these standards in the near future. In
conjunction with this proposal, EPA has
also developed draft no-migration
variance petition guidance, a copy of
which is available hi the docket for this
rulemaking.
The current standards and procedures
for no-migration variances (for units
other than injection wells) are laid out hi
40 CFR 268.6. Under this section,
persons seeking a no-migration variance
must submit a petition to the EPA
Administrator "demonstrating, to a
reasonable degree of certainty, that
there will be no migration of hazardous
constituents from the disposal unit or
injection zone for as long as the wastes
remain hazardous." Petitions must
identify the waste and the specific unit
that is the subject of the petition;
provide waste analysis; characterize the
unit, including background conditions;
provide monitoring to confirm that no
migration has occurred after the
disposal has begun; and demonstrate
compliance with other federal, state,
and local laws.
Under 40 CFR 268.6, the Administrator
must publish a tentative decision to
grant or deny a no-migration variance
for public comment in the Federal
Register. EPA is required to publish final
decisions in the Federal Register, after
considering and responding to public
comments. Variances may be valid for
up to 10 years, but for no longer than the
term of the facility permit. (Variances,
however, may be reissued after their
term has expired.) If petitions are
•granted, facility owners/operators must
report changes in operating conditions
from those described in the petition and
notify EPA if hazardous constituents are
detected migrating from the unit. If
migration is detected, further disposal of
wastes subject to the petition is
suspended.
To date, EPA has received 24 no-
migration variance petitions submitted
in accordance with 40 CFR 268.6.
Today's notice, which addresses
disposal of mixed radioactive and
hazardous waste in a mined salt bed, is
the Agency's first proposed decision on
any of these petitions. The other
1 On July 26,1988, the Agency also promulgated
standards under 40 CFR 148 for no-migration
variances for underground injection wells (53 FR
28122).
petitions submitted under § 268.6
primarily address land treatment
operations. They are purrently under
Agency review. In addition, EPA has
received approximately 65 no-migration
petitions under 40 CFR part 148 for
underground injection wells. Of these
petitions, one has been granted final
approval, several have been granted
preliminary approval, and certain others
have been withdrawn.
B. Regulatory Status of Mixed Wastes
The hazardous wastes that are subject
to today's notice are "mixed wastes."
Mixed wastes are defined as a mixture
of hazardous wastes regulated under
Subtitle C of RCRA and radioactive
wastes regulated under the Atomic
Energy Act (AEA). Because section 1004
of RCRA excludes "source," "special
nuclear," or "byproduct material," as
defined by the Atomic Energy Act from
the definition of RCRA "solid waste,"
there has been some confusion in the
past as to the scope of EPA's authority
over mixed wastes under RCRA. EPA
clarified this question in a Federal
Register notice on July 3,1986. EPA's
clarification stated that the Section 1004
exclusion applies only to the radioactive
portion of mixed waste, not to the
hazardous constituents. Therefore, a
mixture of "source," "special nuclear,"
or "byproduct materials," and a RCRA
hazardous waste must be managed as a
hazardous waste, subject to the
requirements of RCRA subtitle C (that
is, RCRA standards for management of
hazardous waste). EPA's oversight
under RCRA, however, extends only to
the hazardous components of the mixed
waste, not to the radionuclides
themselves; the radionuclides (and any
risks they may pose) are instead *' '
addressed under the AEA. DOE
subsequently confirmed and clarified
this interpretation in an interpretive
rule, published in the Federal Register
on May 1,1987.
EPA's July 3,1986 interpretation went
into effect immediately in states not
authorized to administer the RCRA
hazardous waste program—that is, in
the ten states and territories where EPA
directly regulates hazardous wastes
under federal RCRA regulations. At the
same time, the July 3,1986 notice
informed authorized states that they are
required to apply for and receive
authorization from EPA to regulate
mixed waste under RCRA. Until an
authorized state has received mixed
waste authorization, mixed waste is not
considered to be hazardous under
federal RCRA regulations in that state.
To date, fourteen states or territories
have obtained authority to regulate
mixed waste under the state RCRA
hazardous waste program, bringing the
total tfo twenty-four states and
territories where mixed wastes are
subject to'the RCRA hazardous waste
requirements.
Mixed wastes, like other hazardous
wastes, are subject to the land disposal
restrictions. Treatment standards for
mixed wastes containing solvents and
dioxins—which are generally based on
levels achieved through incineration—
went into effect on November 8,1986,
and November 8,1988. Disposal
prohibitions for mixed wastes
containing "California list" wastes went
into effect on July 8,1987. The remaining
mixed wastes (for example, mixed
wastes exhibiting a toxicity
characteristic) are included hi the "third
thirds" category; the effective date of
the land disposal restrictions for wastes
in this category is May 8,1990. In a
recent proposal, however, EPA proposed
a two-year national capacity variance
for mixed wastes falling into the third
thirds (54 FR 48492, November 22,1989).
If this variance is retained in the final
regulation, the effective date of land
disposal restrictions for these wastes
would be extended until May 8,1992.
It should be noted that the facility
addressed in today's proposal is located
in New Mexico, a state that has not yet
been authorized for mixed waste. EPA
recently proposed to grant the state
mixed waste authorization (55 FR 10076,
March 19,1990), and expects a final
decision on this question in the near
future. Until the state has been
authorized for mixed waste, however,
mixed waste is not a RCRA hazardous
waste in the State of New Mexico and
the Federal land disposal restrictions do
not apply to it.
C, WIPP Project
1. Introduction
In March 1989, the Department of
Energy (DOE) submitted a no-migration
variance petition for its Waste Isolation
Pilot Plant (WIPP), a program to dispose
of mixed transuranic (TRU) radioactive
and hazardous waste in a mined salt
bed near Carlsbad, New Mexico. DOE
has designed the WIPP as a permanent
repository for TRU wastes that are
generated and stored at ten DOE sites
around the country.2 These wastes,
2 The DOE facilities that would send wastes to
the WIPP are Idaho National Engineering
Laboratory, Idaho Falls, Idaho; Rocky Flats Plant,
Golden, Colorado; Los Alamos National Laboratory,
Los Alamos, New Mexico; Argonne National
Laboratory, Argonne, Illinois; Savannah River Plant,
Aiken, South Carolina; Oak Ridge National
Laboratory, Oak Ridge, Tennessee; Hanford
Reservation, Richland, Washington; Mound Plant,
Continued
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Federal Register / Vol. 55, No. 67 / Friday. April 6, 1990 / Notices
which result from the production of
nuclear weapons, consist of a variety of
materials, including tools, equipment,
protective clothing, and other material,
contaminated during the production and
reprocessing of plutonium; contaminated
organic and inorganic sludges;
contaminated process and laboratory
wastes; and contaminated items from
decontamination and decommissioning
activities at DOE installations.
Wastes emplaced in the WIPP will be
limited to transuranic (TRU) wastes, a
specific category of radioactive wastes.
TRU wastes are defined as wastes
contaminated with alpha-emitting
radionuclides with atomic numbers
greater than 92 (.that is, heavier than
uranium) in concentrations of greater
than 100 nanocuries per gram of waste.
In addition, TRU wastes by definition
have half-lives of greater than 20 years,
although the actual half-lives of
radionuclides in waste to be placed in
the WIPP are often hundreds or
thousands of years. Two types of TRU
wastes are targeted for the WIPP: (1)
Contact-handled (CH) wastes, which
have a measured radiation dose rate at
the container surface of 200 millirems
per hour and can be safely handled
without special equipment when
drummed; and (2) remote-handled (RH)
wastes, which have a measured
radiation dose rate at the container
surface of above 200 millirems per hour
and must be heavily shielded with lead
for safe handling. The upper limit for
radiation dose rate of RH wastes to be
placed in the WIPP is 1,000 rems per
hour. The great majority (97%) of the
wastes that will be shipped to the WIPP
will be contact-handled. TRU wastes are
distinguished from high-level
radioactive waste, such as used reactor
fuel, and low-level radioactive waste.
Other treatment and disposal strategies
' are being developed for high-level and
low-level wastes.
A significant portion of the waste
destined for the WIPP (up to 60%,
according to current DOE estimates) is
contaminated with RCRA hazardous
waste, making this waste a "mixed
waste" potentially subject to RCRA
jurisdiction, although the concentration
of hazardous constituents in these
wastes is generally very low. The
hazardous wastes in question are
primarily solvents and EP toxic metals,
especially lead. Of these wastes, the
solvents are currently subject to
treatment standards under the land
disposal restrictions, and the EP toxic
metals will be subject by May 1990 (or
May 1992 at the latest). DOE intends, at
this time, to dispose of these wastes in
the WIPP without treating them in
conformance with BDAT standards.3 As
a result, DOE has applied for a no-
migration variance for the mixed wastes
to be emplaced in the WIPP.
2. History of the WIPP Project
The effort to locate a permanent
disposal site for TRU waste began over
30 years ago, when the National
Academy of Sciences recommended that
radioactive waste be permanently
disposed of in salt beds. After a decade
of experimentation, and the rejection of
one site for technical reasons, the
Atomic Energy Commission, the Oak
Ridge National Laboratory (ORNL), and
the U.S. Geological Survey (USGS)
began a formal selection process for a
site hi 1973. A set of selection criteria
addressing factors such as stratigraphy,
hydrogeology, seismicity, population
density, and land ownership, were
defined, and the USGS reviewed most of
the larger rock-salt deposits in the
United States against these criteria. On
the basis of this review, USGS selected
eastern New Mexico as the area best
satisfying the site-selection criteria.
After further review against detailed,
site-specific criteria (e.g., minimum
distances were set from the Capitan reef
aquifer, existing boreholes, and
dissolution fronts), the WIPP site was
chosen in 1975.
The WIPP project was authorized by
Congress in the Department of Energy
National Security and Military
Applications of Nuclear Energy
Authorization Act of 1980. DOE began
construction of the repository in the
early 1980s. Construction of the surface
buildings, the underground experimental
rooms, and the first underground
disposal rooms is noyv essentially
complete.
3. Description of WIPP
The WIPP repository is an
underground mine, located
approximately 2,150 feet below the
surface in the Salado Formation—a
2,000-foot-thick salt bed that extends
laterally for approximately 36,000
square miles. The land in the area of the
WIPP is owned by the Federal
government and administered by the
Bureau of Land Management. The four-
mile by four-mile plot of land overlying
the repository has been temporarily
withdrawn from public use by the
Miamisburg. Ohio: Lawrence Livermore National
Laboratory. Livermore, California; and Nevada Test
Site. Mercury, Nevada.
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3 Since the no-migration petition was first
submitted, DOE has formed an Engineering
Alternatives Task Force that, among other things,
will consider treatment alternatives for TRU wastes
before they are disposed of at the WIPP.
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Department of Interior; it is now under
the con'tr&l of DOE. The repository is
designed'to hold TRU wastes that are
currently stored at-the ten DOE .-'•.'
generating facilities, as well as new .
TRU wastes that will be generated over
the next 25 years. If the WIPP site is
eventually determined to be a
permanent repository, the underground
waste disposal area of the WIPP will
cover 100 acres, with a total design
capacity of 6.45 million cubic feet (or
approximately 850,000 barrels of waste).
To date, 15 acres of underground
disposal rooms have been mined.
Although DOE has conducted
extensive studies of the WIPP site and
the repository's performance,
uncertainties remain. For example,
concerns have been raised ever the
possibility that gas generated
underground at the WIPP will, ove: the
long term, build up to unacceptable
pressures, leading to possible releases
from the repository. To address this and
other questions, DOE plans to conduct
testing over a 5-year period. This period
will involve in-situ tests with actual
TRU wastes underground, as well as
other investigations. Under DOE's
current plans, the in-situ tests would
initially involve wastes amounting to
approximately 0.5% of the total
repository capacity. From these tests,
DOE expects to demonstrate compliance
with EPA's standards for disposal of
radioactive materials (40 CFR part 191
subpart B) and long-term no-migration of
RCRA hazardous constituents, as well
as to identify any engineering
modifications that may be necessary to
meet these standards.
DOE is also considering the need for
an "operations demonstration" during
the 5-year test period. The purpose of i
this demonstration, which might involve
up to an additional 3 to 8% of the total
WIPP capacity, would be to show DOE's
operational readiness to ship waste to
the WIPP and to place it underground.
If DOE is unable to meet EPA
hazardous and radioactive waste
disposal standards at the conclusion of
the test period, it has committed to
remove all wastes from the WIPP.
If the WIPP proves acceptable as a
permanent repository, DOE will then
begin full-scale disposal of waste at the
site. Drums, metal boxes, and canisters
of waste will be shipped to the WIPP
from the generating sites and placed in
the underground rooms. Under current
plans, the wastes will be backfilled with
crushed salt and the rooms sealed. After
an operating period of approximately 25
years, DOE plans to seal the shafts of
the mine with cement and clay plugs
and compacted salt, and decommission
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13071
the facility. After decommissioning, the
salt of the Salado Formation will creep
inward on the waste and is expected to
encapsulate the waste within 60 to 200
years.
Access to the WIPP site will be
restricted during operations and
decommissioning, and possibly for
longer periods. The Department of
Interior temporarily withdrew the lands
on the WIPP site from public use in 1983,
allowing DOE to begin construction of
the facility. Before DOE can place waste
at the site, however, either Congress or
the Department of Interior must take
new land withdrawal action. In
addition, DOE and the State of New
Mexico have'agreed to prohibit in
perpetuity all subsurface mining,
drilling, and resource exploration
unrelated to the WIPP project at the
WIPP site. The Federal government has
acquired, or is in the process of
acquiring, the entire surface and
subsurface estate at the WIPP site,
including leasehold interests in
subsurface resources. Finally, to prevent
drilling in the vicinity of the repository
in the distant future, DOE intends to
place permanent warning markers at the
site.
D. Regulatory Status of the WIPP
The WIPP is located in the State of
New Mexico, which is expected to
receive authorization for mixed waste in
the near future. (See 55 FR 10076, March
19,1990.) Once mixed waste becomes
subject to the RCRA hazardous waste
regulations in New Mexico, the WIPP
will be eligible for RCRA interim status.
Facilities "in existence" (which includes
those under construction] at the time a
waste is identified as hazardous may
obtain interim status by submitting a
Part A permit application to EPA or the
appropriate state. If DOE submits the
approriate application to New Mexico
and secures interim status, it will be
legally authorized to receive mixed
waste—subject, of course, to the land
disposal restrictions. The WIPP must
also comply with interim status
standards, codified at 40 CFR part 265,
and obtain a RCRA permit under 40 CFR
parts 264 and 270.
The interim status requirements of
part 265 establish general facility
standards. For example, the WIPP will
be required under these standards to
have a waste analysis plan for its mixed
waste, a contingency plan describing
procedures that DOE will take hi the
case of an emergency, and a closure
plan describing how the facility will be
closed. At the same time, DOE will be
required to submit a RCRA Part B permit
application to the State of New Mexico
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no later than six months after a request
by the state.
The RCRA permit for the WIPP, which
would be issued by New Mexico, would
establish detailed operating, closure,
and post-closure conditions for the
facility in accordance with 40 CFR
subpart X. (As a geological repository,
the WIPP is regulated under the RCRA
category of subpart X "miscellaneous
units.") The permit's scope would
potentially extend to all facility
activities related to mixed waste. In this
respect, the permit is significantly
broader than the no-migration variance,
which addresses the specific issue of
whether hazardous constituents will
migrate from the WIPP disposal unit. At
the same time, the permit provides an
opportunity to ensure that DOE manages
the facility in a way that ensures that
migration will not occur.
As discussed earlier, EPA's authority
under RCRA over waste destined for the
WIPP extends only to mixed hazardous
and radioactive waste, and it is further
limited to the hazardous components of
the mixed waste. The potential release
of radioactive material from the WIPP is
addressed under the Atomic Energy Act
(AEA). EPA has promulgated standards
under the AEA limiting releases
associated with the disposal of
radioactive wastes. These standards,
which are codified at 40 CFR part 191,
consist of two parts: Subpart A dealing
with releases during the operational
phase of a permanent disposal facility,
and subpart B, dealing with long-term
releases after decommissoning. Under
an agreement with the State of New
Mexico, DOE will comply with the
Subpart A standards, beginning with the
initial receipt of waste at the WIPP,
before the facility has been designated
as a permanent repository. The Subpart
B standards have been remanded to
EPA by the U.S. Court of Appeals for the
First Circuit, and therefore are not in
effect at this tune. DOE, however, has
agreed with the State of New Mexico to
demonstrate compliance with the
remanded standards before a final
decision is made to dispose of waste
permanently in the repository. This
decision will be made on the basis of
data gathered during the test phase at
the WIPP.
Finally, EPA emphasizes that today's
proposal addresses only the specific
question of whether hazardous
constituents will or will not migrate
from the WIPP for the purposes of the
RCRA no-migration variance. Issues
raised by the transportation of waste to
the WIPP site, or by the handling and
possible treatment of waste before it
F4701.FMT...[16,30]...7-08-88
reaches the WIPP, are beyond'the scope
of this itotice.
II. Summary of DOE Petition
DOE initially submitted its no-
migration petition for the WIPP in early
March 1989, with two addendums
submitted on October 1,1989, and
January 22,1990. For the convenience of
commenters, DOE has consolidated the
various parts of the petition and
reprinted them as a single document,
dated March 1990. This consolidated
document has been placed in the public
docket for today's proposal as DOE's
complete no-migration variance petition.
This petition, which consists of six
volumes, provides the information
required by 40 CFR 268.6, including
facility description, site
characterization, waste
characterization, description of
anticipated repository performance,
modeling of potential environmental
releases, air monitoring plan, seal
designs, demonstration of compliance
with other federal, state, and local
requirements, and other items. EPA has
carefully reviewed this document and
concluded that, together with other
materials submitted by DOE in support
of the petition, it constitutes a complete
submission, providing sufficient
information for EPA to propose a
tentative decision oji the variance
request. 'I
Beyond the petition itself, several
documents have been critical to EPA's
review and its proposed decision. Two
documents, in particular, are important
adjuncts to DOE's petition: DOE's "Draft
Final Plan for the Waste Isolation Pilot
Plant Test Phase: Performance
Assessment" (December 1989, DOE/
WIPP 89-011) and its "Draft Waste
Retrieval Plan" (January 1990, DOE/
WIPP 89-022). The first document
provides important details on DOE's
planned activities during the test phase;
the second describes the procedures by
which DOE will retrieve waste from the
repository if it cannot demonstrate the
long-term acceptability of the facility.
DOE's test plans and the retrievability
of any waste placed in the WIPP are
central considerations in the approach
EPA is proposing today.
In addition, EPA has paid particular
attention to DOE's Draft and Final
Supplemental Environmental Impact
Statements (April 1989 and January
1990, DOE/EIS-0026-FS), which discuss
in detail many aspects of facility
performance; the Design Validation
Report (October 1986, DOE/WIPP 86-
010), which discusses the validation of
the design for underground openings;
and DOE's draft "Final Safety Analysis
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Report" (June 1989. WIM>2-3). Also
particularly-important has been DOE's
"Safety Analysis Report for the
TRUPACT-II Shipping Package" (June ,
27,1989), which provides information on
waste compatibility, gas release, and
other questions developed by DOE to
support the Nuclear Regulatory
Commission's approval of waste
shipment. Beyond these sources, DOE
provided EPA with several hundred
additional reports, studies, and other
documents, as background support to
the no-migration petition.
These, and all other documents
considered by EPA in reaching its
proposed decision, have been included
in the public docket for this rulemaking.
The docket also contains a complete list
of items considered.
III. Summary of Proposed Decision
EPA is proposing today to grant a
"conditional" no-migration variance to
the DOE for the WIPP. This variance
would allow DOE to place mixed waste
subject to the RCRA land disposal
restrictions in the WIPP for testing and
experimentation to determine whether
the site is appropriate for the long-term
disposal of mixed waste. The proposed
variance would be restricted to mixed
wastes emplaced in the WIPP repository
for the purpose of testing and
experimentation designed to show the
long-term acceptability of the WIPP
(that is, its confonnance with standards
for permanent disposal of radioactive
and hazardous wastes). DOE would not
be allowed to conduct an "operations
demonstration," involving the placement
of waste underground for the purposes
of demonstrating that the facility is
operationally ready to receive waste.
Furthermore, DOE would not be allowed
to begin the permanent disposal of
waste subject to RCRA land disposal
' prohibitions at the site under today's
proposal. Finally, DOE would be
re.quired to remove all wastes subject to
the variance from the repository if it
could not demonstrate no migration of
hazardous wastes over the long term. (It
should be noted that DOE has
committed to conducting such a removal
in its no-migration variance petition, as
well as in a consent agreement with the
State of New Mexico.)
In support of today's proposal, EPA
has tentatively determined that there is
a reasonable degree of certainty that
hazardous constituents will not migrate
from the WIPP disposal unit during the
test period. In making this tentative
determination, EPA has considered all
possible routes of release, but has
focused in particular on the release of
volatile constituents in the course of
testing and the potential for these
S-041999 0145(09)(05-APR-90-14:18:43)
constituents to migrafe out of the WIPP
unit through the ventilation shaft.
Because of the nature of the tests that
will be conducted, and their relatively
short duration, EPA believes that
release of hazardous constituents from
the unit through brine, salt, or other
geologic media is implausible during the
test phase.
The retrievability of waste placed in
the WIPP during the test phase is central
to the conditional variance EPA is
proposing today; therefore, EPA also
reviewed both the technical feasibility
of retrieval and the practicability of
DOE's retrieval plan. EPA has
tentatively concluded that retrieval of
wastes from the WIPP can be
accomplished safely, and that DOE's
commitment to retrieval, if it proves
necessary, is satisfactory. Finally, EPA
has considered the general design,
construction and mine maintenance
program at the WIPP, and has concluded
that the mine is well-designed and will
remain stable (with proper
maintenance) during^the test period and
well beyond.
Although today's proposed variance is
specifically based on a finding of no
migration of hazardous constituents
from the unit during the test phase, EPA
has thoroughly reviewed available
information on the expected long-term
performance of the WIPP repository.
Given the geologic stability of the area;
the depth, thickness, and the very low
permeability of the salt formation in
which the repository has been mined;
and the properties of rock salt as an
encapsulating medium, EPA believes
that the WIPP is a promising site for a
permanent mixed-waste repository.
Nevertheless, a number of uncertainties
related to the long-term performance of
the WIPP remain—for example, the
extent and effects of gas generation, the
effect of brine inflow into the repository,
and the influence of a "disturbed rock
zone" around the mined repository. DOE
will be investigating these uncertainties
in the test phase at the WIPP, and it will
review whether technical modifications
to the repository design or the waste are
necessary to ensure compliance with the
regulatory standards.
Before DOE can permanently dispose
of untreated mixed wastes in the WIPP,
it must demonstrate no migration over
the long term—that is, it must
successfully address current
uncertainties about long-term WIPP
performance. Information gathered by
DOE during the test phase will be
central to such a demonstration. Any
EPA decision to grant (or deny) a
variance for permanent disposal will be
made with full opportunity for public
F4701.FMT...(l6,30]...7-08-88
comment, as prescribed in 40 CFR
268.6(gl;
The specific conditions of today's
proposed variance for the test phase-are
listed in Section V of this notice. The .
basis for EPA's tentative decision and
the major issues addressed in the course
of EPA's review are discussed in the
following section. EPA has also
developed a background document,
which discusses in more detail the
geology of the site, repository
performance, waste characterization,
and air monitoring. This document is
available in the public docket for this
proposed action.
IV. Discussion of Issues and Basis of
Proposed Finding
A. Definition of No Migration for as
Long as the Waste Remains Hazardous
Section 268.6(a) of 40 CFR states that
petitioners for a no-migration variance
must demonstrate, to a reasonable
degree of certainty, that hazardous
constituents will not migrate from the
disposal unit or injection zone for as
long as the waste remains hazardous.
EPA proposes to interpret this standard
to mean that hazardous constituents
cannot migrate from the unit at
hazardous levels. In other words, to
show "no migration," the petitioner must
demonstrate that constituents released
from the unit do not exceed health-
based standards at the point where they
exit from the unit.
EPA adopted this interpretation of "no
migration" in its final standards for
underground injection wells under 40
CFR part 148 (53 FR 28122, July 26,1988),
and it is taking the same approach in its
review of other no-migration petitions
submitted under section 268.6. EPA
believes that this interpretation of the
no-migration standard is a permissible
reading of the statute, because the
logical focus of the statutory language is
whether what escapes from the unit is
hazardous. The ultimate judgment
required by the statute is whether the
prohibition on land disposal "is required
in order to protect human health and the
environment," a determination that will
depend on the concentration levels of
constituents. Similarly, in making this
determination, the Agency must take the
toxicity of waste constituents into
account, which necessarily involves
consideration of the concentration of the
constituents.
The legislative history of the statute
likewise indicates that the no-migration
demonstration should focus on whether
what migrates is hazardous. The Senate
Report states that "the Administrator is
required to find that the nature of the
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13073
facility and the waste will assure that
migration of the waste will not occur
while the was'tes still retain their
hazardous characteristics in such a way
that would present any threat to human
health and the environment." S. Rep. No.
284, 98th Cong., 1st Sess., 15. Waste
constituents migrating from a unit at
allowable risk to human health and the
environment satisfy this standard, as
negligible harm to human health and the
environment would result.
The statute refers to migration of
"hazardous constituents" without
defining the term. In other EPA
regulations, the term "hazardous
constituents" normally has regulatory
consequence only if the concentrations
of hazardous constituents are significant
enough to pose a risk above allowable
levels. (See 52 FR 32453, August 27,1987,
which describes the Agency's use of the
term in the listing, delisting, closure, and
groundwater protection standard
regulations.] It is a reasonable
construction of the statute that Congress
intended the same approach here. It is
possible that Congress was equating
wastes and hazardous constituents, so
that when Congress stated that there
shall be "no migration of hazardous
constituents * * * for as long as the
wastes remain hazardous," it was
referring to waste constituents whose
migration is prohibited for as long as
they remain hazardous, i.e., are at
hazardous levels. The passage from the
Senate Report cited above appears to
support this reading, since its uses the
terms "waste" and "constituent"
interchangeably.
EPA acknowledges that the statute
could also be interpreted as requiring
that a single molecule of any hazardous
constituent (i.e., substances listed in
Apendix VIII of 40 CFR part 261] may
not migrate for as long as the waste in
-the unit remains hazardous. EPA
believes that this is not a.preferred
reading of the statute, given that the
health and environmental concerns
focus on whether hazardous levels of
constituents leave the unit, and not
whether hazardous levels remain in the
unjt. The alternative reading is not
compelled by the statutory language nor
the legislative history, and is not
necessary to protect human health and
the environment. A zero molecule
standard would be impossible to meet,
both because it is impossible to monitor
or realistically model the fate of
individual molecules (or atoms) of waste
constituents and because certain waste
constituents are substances that persist
indefinitely. Congress simply would
have forbidden all land disposal of
untreated hazardous waste if this were
S-041999 0146(09)(05-APR-90-14:18:46)
its intent. Congress, however, expected
that some individual land disposal units
might be able to satisfy the standard. S.
Rep. No. 284 at 14; H. Rep. No. 198, 98th
Cong., 1st Sess. at 34; S. 9153. In
addition, even under this latter reading,
nonhazardous levels of constituents
would be allowed to migrate once
wastes in the unit were no longer
hazardous. Thus, EPA believes the
appropriate focus is on whether
constituents ever migrate at hazardous
levels. The Natural Resources Defense
Council has challenged this Agency
construction of RCRA in the context of
EPA's regulations for underground
injection at 40 CFR part 148. NRDC v.
EPA No. 88-1657 (B.C. Cir.). The court
decision is pending.
In establishing hazardous levels of
hazardous constituents—that is, the
levels of a compound that would fail the
no-migration standard—EPA proposes
to rely on peer-reviewed health and
environmental effects data, where
available. These data are based for the
most part on the drinking water
Maximum Contaminant Levels (MCLs),
surface water quality criteria (Ambient
Water Quality Criteria, 45 FR 79318,
November 18,1980; 49 FR 5831, February
15,1984; 50 FR 30784, July 29,1985),
verified Reference Doses (RiDs) for
systemic toxicants developed by the
Agency's Risk Assessment Forum
(Verified Reference Doses of USEPA,
ECAO-CIN-475, January 1986), and
Risk-Specific Doses (RSDs) for
carcinogens developed by the Agency's
Carcinogen Assessment Group. EPA
typically combines these dose levels
with standard exposure numbers for
each medium (e.g., groundwater and air)
to obtain allowable health and
environmental exposure levels. The
standard exposure numbers assume
direct human exposure at the point of
compliance or, to be specific, the unit
boundary. This is consistent with the
approach EPA promulgated in the 40
CFR part 148 regulations for no-
migration petitions for underground
injection wells.
Finally, the statute requires the
petitioner to demonstrate no-migration
for "as long as the waste remains
hazardous." Typically, EPA would judge
this demonstration on the basis of an
understanding of the waste
transformation process and of the long-
term performance of the disposal site, in
combination with predictive modeling.
In many cases, hazardous wastes can be
expected to .degrade' over time, limiting
the scope oFpredictive modeling
required. For example, in the case of
land treatment facilities—which are
specifically designed to degrade organic
F4701.FMT...[16,30]...7-08-88
wastes through microbial action—
degradation of hazardous constituents
might take place over a 90-day time
period. In other cases, degradation.will
take significantly longer. In the context
of underground injections, EPA provides
that, if petitioners can demonstrate no-
migration over a 10,000-year period, they
will have met the statutory standards
(40 CFR 148.20). Petitioners may also
demonstrate that their wastes would be
nonhazardous or otherwise immobilized
on the basis of a showing of chemical
transformation or fate. (Id.)
In the case of the WIPP, heavy metals
such as lead will not degrade, and
therefore will remain hazardous
virtually indefinitely—certainly far
beyond the predictive capabilities of
any models. For this reason, EPA
believes that its final determination
concerning the WIPP's conformance
with the no-migration standard over the
long term must rest on the Agency's
professional judgment regarding the
containment properties of the Salado
formation within the vicinity of the
WIPP, and on any transformation or
immobilization of wastes within the
unit. The Agency's views on the long-
term acceptability of the WIPP are
discussed in Section IV.F of this notice.
At the same time, predictive modeling
can act as a check and provide insight
into the long-term performance of the
site. In its no-migration petition, DOE
has modeled possible waste migration
out of the WIPP through brine flow
along the sealed shafts over a 10,000-
year period. Under this model,
hazardous constituents would not come
anywhere near the upper edge of the
Salado formation within the modeling
period. (DOE's modeling exercise is
discussed in more detail in section IV.F
of this notice.) Because of the
uncertainties of long-term modeling,
EPA believes that, for the purposes of
determining compliance with RCRA no-
migration standards, it is not
particularly useful to extend this model
beyond 10,000 years into the future.
While modeling over longer periods had
certain uses—for example, in comparing
the performance of different
repositories—EPA questions whether
models have the precision to be used in
making a meaningful prediction of
whether a specific unit will or will not
meet no-migration standards after many
thousands or millions of years. The
Agency, however, does believe that
modeling over a 10,000-year period
provides a useful tool in assessing the
long-term stability of the repository and
the potential for migration of hazardous
constituents. In summary, the Agency is
not proposing a specific limit on the time
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Federal Register / Vol. 55, No. 67 / Friday, April 6, 1990 / Notices
over which no-migration must be
demonstrated. Instead, it believes that
the final determination should be based
primarily on a knowledge of the geologic
conditions at the site, supported by
modeling.
B. Unit Definition
The definition of the disposal unit's
boundary is critical to any decision on a
no-migration variance. The boundary of
the unit will define the point of
compliance; that is, the point at which
potential migration would be measured.
If waste constituents migrated beyond
this point at hazardous levels, a
variance could not.be granted, while
movement of wastes within the unit
boundary would be acceptable. In the
case of the WIPP, the question of the
unit boundary is of particular
importance, because there is limited
regulatory precedent for defining the
boundary of geologic repositories, and
because of the general absence of clear
engineered barriers designed to contain
the waste.
Under current regulations, a
"hazardous waste management unit" is
defined as a "contiguous area of land on
or in which hazardous waste is placed,
or the largest area in which there is
significant likelihood of mixing
hazardous waste constituents in the
same area" (40 CFR 260.10). This
definition on its face allows
considerable flexibility when it is
applied to underground repositories.
Clearly, the salt bed formation in the
vicinity of the repository represents a
contiguous "area" of land in which the
waste is placed. The regulatory
definition does not preclude the
inclusion of at least a portion of the
surrounding formation in the "disposal
unit." It provides little guidance,
however, on where the exact points of
compliance should be drawn.
EPA has discussed the issue of unit
definition in a draft guidance on no-
migration petition variances for land
disposal units other than underground
injection wells. In this guidance, EPA
explained that, for units with engineered
barriers, the unit boundary should be
considered the outermost extent of the
engineered barrier. Thus, for a landfill,
the outer boundary of the unit would be
the outside of the berms and engineered
liners (either clay or synthetic). In the
case of units without such barriers,
other rules would have to apply. For
example, the boundary of an unlined
land treatment unit would be set at the
base of the maximum treatment zone
(which cannot exceed a depth of 5 feet
from the soil surface). In this case, EPA
has recognized that the purpose of a
land treatment unit is to allow some
S-041999 0147(09)(05-APR-90-14:18:49)
movement of a waste down into the soil,
as it is being treated, absorbed, or
transformed. However, if constituents
move out of the treatment zone at
hazardous levels, migration from the
unit has occurred. In its draft guidance,
EPA also recognizes that .defining the
unit boundary of a geological repository
raises special issues. Although the
guidance does not discuss the specific
issues raised by these units, it states
that their boundaries should be defined
on a site-specific basis.
One final precedent should be
mentioned. RCRA 3004 (d), (e), and (g)
require that a no-migration variance be
' based on no migration of hazardous
constituents from the disposal unit or
the injection zone. EPA discussed the
meaning of the term "injection zone" in
its recent regulations establishing
standards for no-migration variances for
underground injection wells. In the
preamble to those regulations, EPA
explained that an injection zone is
defined in 40 CFR 146.3 as "a geologic
formation, group of formations, or part
of a formation receiving fluids through a
well." The Agency went on to clarify
that the injection zone inpludes
confining material as well as the more
permeable material into which the
waste is injected (53 FR 28122, July 26,
1988). EPA emphasizes that, for the
purposes of RCRA compliance, it
considers the WIPP to be a
miscellaneous land disposal unit rather
than an injection well. Therefore, the
relevant standard for the WIPP is the
"unit boundary," rather than the
"injection zone." The underground-
injection rule, nevertheless, does define
the concept of no-migration in the
context of somewhat similar
underground disposal and, thus, has
some relevance to the WIPP.
The boundaries of the WIPP must be
defined in light of these general
precedents, as well as the specific
circumstances of the facility. As
described earlier, the WIPP is an
underground geologic repository mined
within a relatively homogeneous salt
bed. After waste has been placed in the
WIPP and the shafts have been sealed,
the salt bed will creep and encapsulate
the waste. If the WIPP works as
intended, the encapsulating salt will act
as a barrier and prevent the migration of
the waste out of the immediate vicinity
of the mined area. Clearly, migration of
hazardous constituents at hazardous
levels from out of the sealed repository
into unconfined aquifers lying above or
below the salt bed would constitute
migration from the unit; similarly,
movement of constituents at such levels
via air to the surface atmosphere during
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the operations of the facility would alsp^
constitute migration.4 Beyond these
general limits, however, there is. no
immediately obvious point where the
boundaries of the underground
repository must be drawn. In today's
notice, the Agency discusses
alternatives for defining the WIPP
boundary and proposes an approach
that, it believes, fully protects human
health and the environment, meets the
statutory and regulatory standards, and
accurately reflects the particular
situation of an underground salt-bed
repository.
To begin with, the immediate
underground disposal area and the
shafts of the WIPP are clearly within the
disposal unit. The shafts, however, are a
hypothetical route of migration out of
the salt bed as a result of brine flow.
The Agency proposes that the point of
compliance, for the purpose of assessing
migration out of the unit by way of the
shafts, be defined as the point where the
Salado formation (i.e., the salt bed)
meets the overlying Rustler formation.
This is the point at which migrating
constituents could be expected to
escape from the long-term engineered
barrier designed to contain the waste—
that is, the compacted salt shaft seal
ending at the top of the Salado
formation—and potentially move into an
overlying aquifer. Although the
possibility of human or significant
environmental exposure is virtually
nonexistent at this point, EPA belives
that compliance with the no-migration
standard should nevertheless be
measured there. The appropriate
standard is whether hazardous
constituents have migrated from the unit
at hazardous levels, not whether
exposure is likely or whether the
concentration of hazardous constituents
will be signficantly reduced in the
course of migration outside the unit
boundary.
The point of compliance for the WIPP
is more difficult to define if hazardous
constituents move through the salt bed
itself, rather than along sealed shafts.
Theoretically, hazardous constituents
may migrate laterally or horizontally in
the salt bed—for example, along
4 The Agency believes that it must consider the
air exposure pathway in assessing the no-migration
standard. The statute does not limit the
environmental pathways to be considered in making
the no-migration demonstration. Moreover, given
the policy goal of the land disposal prohibition
provisions to end land disposal of wastes that have
not been treated to satisfy the section 3004(m)
standards, except for wastes disposed of in units
that meet the rigorous no-migration standard, it is
not appropriate to ignore a major environmental
pathway in assessing whether the no-migration
standard is met.
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13075
fractures or'anhydrite marker beds. The
Agency believes1 that, considering the
purpose and design of the WIPP, a
certain amount of movement within the
confining salt bed should be considered
movement within the unit. The
underground repository has been
designed so that the salt bed will creep,
encapsulate the waste, and contain it. If
the WIPP works as planned, there will
be limited movement of contaminants
into the salt bed, but the constituents
will be effectively blocked from
potential routes of release. In this
respect, movement within the salt bed is
analogous to movement within the
treatment zone of a land treatment
facility, the engineered clay liner of a
landfill or surface impoundment, or the
confinement material of an injection
zone. EPA therefore proposes that the
disposal unit include at least part of the
surrounding Salado formation, bounded
on top by the Rustler formation and
underneath by the Castile formation.
The Salado formation, it should be
noted, extends horizontally for
approximately 36,000 square miles.
While EPA believes, for the reasons
stated above, that some movement from
the original repository through this bed
should not constitute "migration from
the unit," it also believes that unlimited
lateral movement would be inconsistent
with the overall integrity of the disposal
practice. The Salado formation
surrounding the WIPP (unlike an
underground injection zone) is very low
in permeability and is intended to
encapsulate and confine the waste. If
the waste disposed of at the WIPP
moved laterally for significant distances
into the encapsulating formation, the
repository clearly would not be
operating as intended, and the integrity
of the disposal practice would be called
into question. It would be hard in this
case to argue that migration was not
occurring.
Extensive lateral migration might also
be problematic because there are a
number of potential routes of waste
migration in the Salado formation
outside of the immediate vicinity of the
WIPP. These include numerous
boreholes and mines, both old and
currently operating, and localized areas
of salt dissolution. If wastes moving
laterally from the WIPP reached these
possible routes of migration, hazardous
constituents could conceivably be
released to overlying aquifers. To
address this concern, EPA believes that
it is appropriate and necessary to set
lateral boundaries on the movement of
waste within the Salado formation,
beyond which "migration" from the unit
would be considered to occur.
S-041999 0148(09)(05-APR-90-14:18:52)
After reviewing the specifics of the
WIPP site; the Agency has tentatively
concluded that the 4-mile by 4-mile
WIPP land withdrawal area represents
the most appropriate lateral boundary of
the disposal unit. This area is clearly
defined, relatively limited in size
(compared to the Salado formation), and
coincident with the land under DOE
control. The Agency has carefully
reviewed the geology of this specific
area, and has tentatively concluded that
no realistic routes of migration lie within
it—other than the hypothetical route of
escape up the shaft seals. Defining the
unit boundary at the edge of the WIPP
site, therefore, would effectively isolate
the wastes from possible routes of
migration beyond the immediate limits
of the WIPP site and confine it to an
area whose geology EPA has examined
in detail. At the same time, this
boundary will allow some relatively
limited movement of hazardous
constituents through the encapsulating
salt, which as discussed above is
consistent with the design of the WIPP.
In addition, as discussed below, the
possibility of human intrusion resulting
from future drilling operations would be
minimized because of federal control of
the land area and mineral rights in
perpetuity, as well as other institutional
controls that will be required at the site.
EPA believes that this approach is not
only consistent with current practice,
but also reflects Congressional intent. '
The legislative history of the 1984
amendments states that "hi determining
appropriate confinement from which
migration should not be allowed to
occur the terms disposal unit or
injection zone should be construed * * *
in terms of overall integrity of the
disposal practice, keeping in mind, in
particular the potential for
contamination of groundwater or
surface water resources" (S. Rep. No.
284 98th Cong., 1st Sess. at 15). If
hazardous constituents disposed of at
the WIPP remain within the Salado
formation and within the WIPP land
withdrawal area, the overall integrity of
the disposal practice will clearly be
intact, and any potential for
contamination of groundwater, surface
water, or other resources will be
eliminated.
Another option considered by EPA
was to define the unit boundary as the
walls of the salt mine, or alternatively
as the furthest extent of the disturbed
rock zone surrounding the excavated
area. (The rock surrounding the open
repository has been found to fracture as
a result of salt creep. The disturbed rock
zone is believed to extend one to five
meters beyond the mine walls.) The
F4701.FMT...[16,30]...7-08-88
Agency has-rejected.this approach'in ._
today's proposal because defining the
unit boundary at this-point would run -, •
contrary to the intended performance of
the WIPP. The WIPP is designed to
confine wastes within the salt bed, not
to prevent any movement of constituents
into the surrounding salt formation as
the formation encroaches on the waste
and encapsulates it. For example, it is
possible that waste would migrate
limited distances laterally along
horizontal marker beds within the
Salado formation. Yet this migration, as
long as it remained within the
immediate vicinity of the original
repository, would in no way threaten the
"overall integrity of the disposal
practice." Drawing the unit boundary
right at the repository walls or at the
furthest extent of the disturbed rock
zone therefore would be inappropriately
limiting, and would not accurately
reflect the intended performance of the
WIPP. For these reasons, EPA has not
proposed the mine walls or the
disturbed rock zone as the WIPP unit
boundary. (It should be noted that the
proposed unit boundary at the WIPP is
based on site- and unit-specific
considerations, which may not apply to
other types of units.)
The preceding discussion focuses on
• long-term migration of hazardous
constituents, once the repository has
been sealed. It is also possible that
hazardous constituents'will migrate
from the unit via air during the operation
of the WIPP. It is clearly a permissible, if
not mandated, construction of the RCRA
no-migration provisions to consider an
air pathway as part of the no-migration
demonstration. The statute requires the
demonstration of encompass ."no
migration of hazardous constituents for
as long as the waste remains
hazardous," and consequently includes
all potential migration pathways. In
addition, there is no logical reason to
ignore the air migration pathway in
assessing no-migration petitions. For
this reason, EPA is proposing to
consider migration via air at the WIPP.
Air migration at the WIPP would be a
potential concern during both testing
and oeprations at the facility. During
these activities, bins and drums
underground will be vented to prevent
buildup of gas pressure within the
containers. To ensure mine safety, the
repository will be ventilated, with
exhaust air flowing up an air shaft and
out into the general atmosphere. This
shaft, therefore, represents a possible
route of escape for hazardous
constituents from the disposal unit.
The Agency proposes that the point of
compliance for the air route during
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operations be,defined as the point
where vented repository air exits from
the exhaust shaft and enters into the
general atmosphere. During its
operational period, the WIPP is in effect
an enclosed or "covered" unit, with a
single point of air release. Once
hazardous constituents have exited from
the point of release and entered the
general atmosphere, EPA believes that
migration from the enclosed unit has
occurred. Up until that point, however,
air emissions are contained within the
repository, and should not be considered
to have migrated from the unit. This
proposed approach is consistent with
the approach EPA is considering for
covered surface impoundments or waste
piles. In its draft guidance for no-
migration petitions, EPA has defined
"the outer limit of any engineered
barrier over the unit (roof, dome, etc.)"
as the air point of compliance for
covered units. For the WIPP, the outer
limit of the engineered barrier over the
unit is the point of release from the
shaft. (In the case of the WIPP, the
question of where in the air exhaust
migration is measured is in fact moot.
Because the shaft is nothing more than a
vent, concentrations of hazardous
constituents will be the same at all
points in the shaft. Therefore, for all
practical purposes, the unit boundary for
air releases could be defined as
anywhere in the shaft.)
In summary, the Agency is proposing
the following points of compliance for
determining no migration from the
WIPP:
1. For upward movement out of the
repository (e.g., along shaft seals): The
point of contact between the Salado and
the Rustler formation.
2. For downward movement: The
point of contact between the Salado and
the Castile formation.
3. For lateral movement: The
boundary of the 4 X 4 mile WIPP land
withdrawal area within the Salado
formation.
4. For air migration: The point where
the air exhaust shaft releases to the
ambient environment.
The Agency solicits comments on
these proposed points of compliance as
well as on other alternatives.
C. Conditional Variance
As described earlier, DOE intends to
begin WIPP operations with a 5-year
test program. The purpose of this
program is to demonstrate the long-term
acceptability of the WIPP and to show
compliance with EPA's disposal
standards for TRU wastes. Although
substantial information on the long-term
performance of the WIPP has been
gained over the last fifteen years,
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important issues remain, particularly in
relation to gas generation. DOE plans to
investigate these and other issues during
the test period. The results of this
investigation may confirm the
acceptability of the WIPP as currently
planned, or may identify necessary
engineering or other modification to the
waste or the facility. It is also possible
that, at the conclusion of the test period,
the WIPP will fail to meet AEA or RCRA
standards for permanent disposal. In
this case, DOE will be required, and has
committed, to remove the waste from
the underground repository and seek
another disposal strategy.
The no-migration variance EPA is
proposing today would allow DOE to
place waste in the WIPP for the purpose
of conducting tests or experiments to
demonstrate the long-term acceptability
of the facility. The variance would be
granted on the condition that DOE
remove waste placed underground for
testing if its performance assessment
fails to show that the WIPP meets the
no-migration standard;over the long
term. Testing and experimentation
would include the bin and alcove tests
outlined in DOE's draft test plan for the
WIPP, but would not include the
"operations demonstration." This
demonstration is aimed at showing the
readiness of the WIPP to receive waste,
but not to show its long-term
acceptability. The variance would have
to be modified, or a revised variance
issued, before untreated mixed waste
subject to the RCRA land disposal
procedures could be placed in the WIPP
for purposes other than testing or
experimentation. Modification or
reissuance of the variance, in this case,
would take place according to the full
variance approval procedures of 40 CFR
268.6(g). For example, the operations
demonstration would riot be allowed
under the variance proposed today
without public notice in the Federal
Register, opportunity for public
comment, and EPA approval.
EPA believes that a conditional
variance, limited to testing and
experimentation, is appropriate for the
WIPP because the Agency has
tentatively concluded that migration will
not occur during the test phase. In
addition, WIPP shows promise as a
permanent disposal site. Because of the
possible consequences of gas generation
as well as other uncertainties, however,
DOE cannot at this time demonstrate
no-migration of hazardous constituents
over the long term. The conditional
variance proposed today would provide
DOE with the opportunity to conduct
this in-situ testing on gas generation
with actual mixed waste, while ensuring
that no migration occurs during the test
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period itself, and that wastes will be .
removed from the WIPP if the " ,
demonstration ultimately cannot be . -, •
made.
EPA notes that the concept of a
conditional no-migration variance for
the WIPP is consistent with the
approach it intends to propose in other
cases as well. For example, EPA is now
considering "conditional" no-migration
variances for a number of land
treatment demonstrations involving
petroleum refinery wastes. The purpose
of these demonstrations is to provide
data necessary to show no-migration
during full commercial operation, as
well as to allow EPA or an authorized
state to collect data to set specific
permit conditions. Under a "conditional"
variance, a demonstration could
proceed, as long as the facility operator
could show that no migration would
occur during the demonstration, and that
the long-term demonstration for a
permanent disposal had a reasonable
chance of succeeding. If the
demonstration succeeded, permanent
disposal could then begin. If it failed, the
operator would be required to remove
the waste placed during the
demonstration and dispose of it
according to RCRA Subtitle C
requirements. Similarly, EPA is also
reviewing a no-migration variance
petition for the temporary storage of
untreated hazardous waste in a pile
before incineration. In this case, the
facility owner would be required to
demonstrate that no migration would
occur during the storage period; the
owner would also be required to remove
the pile completely at the end of the
storage period. EPA believes that the
approach it is proposing today for the
WIPP is similar to the approach it is
considering for land treatment
demonstrations and temporary storage
in waste piles. Today's proposal would
allow placement of untreated hazardous
waste in the WIPP for the limited
purpose of testing, as long as migration
did not occur during the test period, and
the waste would be removed if long-
term no-migration could not be
demonstrated. See also 51 FR 40605
(November 7,1986), where the Agency
indicated that a potential no-migration
situation would be one involving storage
in a land disposal unit where wastes
would be removed at the end of the
storage period.
Section V of this notice describes in
detail the specific conditions of the
proposed variance. The key condition is
the restriction of the variance to the
placement of wastes in the WIPP for
purposes of testing and experimentation.
This condition would allow DOE to
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13077
conduct the testing outlined in its
petition and other sources—specifically,
the bin and alcove-scale tests described
in DOE's "Draft Final Plan for the Waste
Isolation Pilot Plant Test Phase:
Performance Assessment" (December
1989, DOE/WIPP 89-011). (EPA
recognizes that DOE's test plan is
currently in draft form, and that a final
version is not expected until May 1990.
If the activities described in the final
document differ substantially from those
in the draft, EPA will provide the public
with an opportunity to comment on how
the changes might affect the proposed
variance.)
As an alternative to the approach
proposed today, EPA considered the
possibility of setting'a specific limit on
the amount of waste that might be
placed in the WIPP. The Agency,
however, has tentatively rejected this
approach. It is difficult at this time to
estimate exactly how much waste may
have to be placed in the WIPP to satisfy
testing needs. DOE currently estimates
that the initial phases of the test period
will require waste amounting to 0.5% of
the total capacity of the WIPP, but the
actual amount finally needed is likely to
depend on the results of early tests, as
well as the extent to which it is
necessary for DOE to explore different
engineering modifications. EPA thus
believes that any specific quantity limit
would be difficult to justify, and might
artificially constrain legitimate and
necessary testing. The Agency solicits
comments on the appropriateness of its
proposed approach and on the
advisability of a volume limit on the
waste that may be placed in the WIPP
under the variance. It also solicits
comments on the specific limit that
might be imposed, as well as the
justification for setting such a limit.
EPA also considered, but is not
proposing, a time limit on the
conditional variance, other than the
regulatory limit of ten years, which
applies to any no-migration variance (40
CFR 268.6(h)). DOE's current plans, as
outlined in the December 1989 draft
Final Plan for the Waste Isolation Pilot
Plant Test Phase (DOE/WIPP 89-011),
call for the development of a "final EPA
compliance report" four years after first
placement of waste in the WIPP, and a
final "disposal phase decision" after five
years. One option, therefore, would be
for EPA to limit any conditional
variance to five years. EPA, however,
has tentatively rejected this approach
because it believes that, like limits on
volume of waste placed, specific time
limits could artificially constrain
legitimate testing. Instead, EPA believes
that restricting placement to wastes
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used in testing and experimentation will
sufficiently-limit activities under the
conditional exemption.
EPA also notes that today's variance
applies only to the activities and
conditions described in DOE's no-
migration variance petition and in the
supporting material provided by DOE.
These were the activities and conditions
that EPA reviewed in proposing to grant
the variance, and therefore they define
the limits and scope of that variance.
This requirement is enforced through 40
CFR 268.6(e), which requires that facility
owners/operators subject to a variance
report to EPA "any changes in
conditions at the unit and/or the
environment that significantly depart
from the conditions described in the
variance and affect the potential for
migration of hazardous constituents
from the unit * * *" If a significant
change from the petition is planned—for
example, a significant change in testing
plans or the addition of a test—the
owner/operator must notify EPA 30
days in advance, and the change cannot
take place without Agency approval.
Where the change affects the basis of
the no-migration finding, it could not
occur before EPA modified the variance
through the variance issuance
procedures of 40 CFR 268.6. In the case
of unplanned changes (e.g., significant
new information related to repository
performance is discovered), EPA must
be notified within 10 days of learning of
the unplanned change. If the information
warrants such a step, EPA may require
that the variance be modified, or it may
revoke the variance.
D. Retrievability
As a condition of granting the no-
migration petition during the test phase,
the Agency is proposing to require that
DOE remove all TRU waste subject to
this variance from the underground
repository if the no-migration
demonstration cannot be made for
permanent disposal. EPA believes that
DOE has reasonably demonstrated that
the waste can be retrieved by: (1)
Successfully performing mock retrieval
demonstrations, (2) providing technical
information to show that waste can be
removed from the underground
repository, (3) demonstrating mine
stability during the test phase, and (4)
storing the waste in retrievable
containers. DOE has committed to
removing the waste, if it cannot
demonstrate compliance with the no-
migration standards for permanent
disposal or the disposal standards of 40
CFR 191 for radioactive waste.
DOE's commitment to retrieve test-
phase waste has been clearly delineated
in several documents, including the
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"Working-Agreement for Consultation.
and Cooperation" with the State of New
Mexico (Article IV).5 This document
establishes, under Public Law 96-164,
eight milestones that must be met before
the retrievability decision can be made.
Key milestones outlined in that
agreement include development of a
waste retrieval plan and conduct of
mock retrieval demonstrations of CH
and RH TRU waste. Successful mock
retrieval demonstrations have been
conducted at the site, and no unsafe
conditions occurred during the
demonstrations. These demonstrations
have been described in two DOE
documents, "Report of the Remote-
Handled Transuranic Waste Mock
Retrieval Demonstration" (May 1987)
and "Final Report for the Contact-
Handled Transuranic Waste Mock
Retrieval Demonstration" (January
1988), which have been included in the
docket for this proposed decision. DOE
has also developed a draft retrieval
plan; under the retrieval plan, an
additional alcove retrieval simulation
will be conducted. The final waste
retrieval plan is expected to be
published in April 1990. If there are
significant changes in the final plan
affecting the no-migration decision, EPA
will reopen the comment period to allow
comment on those changes.
The stability of rooms during the test
period has at times been raised as an
issue. The repository rooms have
experienced a creep closure rate, at
least initially, that is three times what
was originally predicted. (The closure
rate has been measured at a few inches
per year, although the rate depends
somewhat on room size.) As a result,
early room closure and fracturing of
walls or ceilings have been a concern.
DOE will address this concern in the
alcove test rooms by reducing their size
(and thus increasing stability), rock
bolting the backs (roofs), and
constructing standoff walls in those
alcoves to be backfilled with salt.
(Standoff walls are walls placed
between the drums and the repository
walls to ensure that room closure does
not impinge.on the backfilled drums.)
The bin-scale test rooms will be rock
bolted to insure stability, and will not be
sealed. The Agency has reviewed the
design of the test rooms, including the
use of rock bolts, and believes that the
rooms will be stable during and after the
test phase. The petition also indicates
5 In addition. DOE has committed to removing
test-phase waste in the Final Supplemental
Environmental Impact Statement for WIPP (Volume
1, page 2-15) and in its no-migration variance
petition.
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that during the test phase all waste will
be placed in the repository in a readily
retrievable manner, i.e., all wastes will
be in retrievable containers, and wastes
will not be backfilled (except in the case
of two alcoves, where "standoff" walls
will be used). After reviewing the
material DOE provided with its petition,
EPA has tentatively concluded that the
measures to be taken will allow for the
safe removal of the waste within the
time-frame required for the test phase.
Since room stability and waste
containment are critical to the assurance
of waste retrieval at the end of the test
phase, EPA is proposing to require that
all waste emplaced in the repository
during that period be placed in a
readily-retrievable manner. By "readily-
retrievable," EPA means adoption of the
specific measures identified in DOE's
petition to maintain room stability (i.e.,
room size, rock bolting, and standoff
walls) and the use of easily-retrieved
waste containers (boxes, bins, drums).
Significant changes to these conditions
would require a modification to the
variance.
The draft retrieval plan identifies
several options for alternative storage of
the TRU waste if it is retrieved. While a
specific storage and disposal alternative
or site was not selected, the Agency
believes that DOE has made a
satisfactory commitment to remove the
waste, if considered necessary. To
ensure that any mixed waste removed
from the repository is handled
appropriately, EPA has included as a
condition the requirement that removed
waste be managed in accordance with
RCRA subtitle C requirements.
E. Post-Closure Controls
Although today's proposed variance
for the WIPP is based on a finding of no-
.migration during the test period, EPA
has extensively reviewed a significant
body of information related to the long-
term performance of the WIPP. In this
review, EPA has focused on the
"undisturbed" performance of the
repository. In other words, the Agency
has not specifically reviewed or
assessed possible releases from the
WIPP that might occur if the facility
were disturbed as a result of human
intrusion—for example, in the course of
oil and gas exploration at some point in
the future. EPA believes that, in the
context of RCRA no-migration variance
decisions, the question of human
intrusion, either during operations or
after closure, is best addressed through
a consideration of the likelihood of
intrusion, and the imposition of controls
to make such intrusions unlikely events.
EPA emphasizes that this approach to
human intrusion is consistent with its
general approach under RCRA, both in
permitting and variances. Under RCRA,
EPA typically relies on institutional
controls (both active and passive)
imposed through general regulatory
standards and site-specific conditions
(e.g., in RCRA permits) to ensure that
access to a hazardous waste disposal
site is appropriately restricted. EPA
believes that any permanent no-
migration variance for the WIPP will
have to impose long-term passive
institutional controls, such as land
withdrawal, records, and markers—to
ensure that the likelihood of human
intrusion is appropriately reduced, even
after active control of the facility has
ceased and any permits at the site may
have terminated.
The specific conditions that EPA
might impose in a no-migration variance
for the WIPP to reduce the possibility of
human intrusion in the future would be
addressed in the context of any decision
that EPA might make on a variance for
permanent disposal. Thus, for today's
proposal, which applies solely to the test
period, the issue of human intrusion in
the distant future is not relevant.
Nevertheless, EPA notes that DOE has
taken, or has committed to taking,
several important steps to reduce the
possibility of human intrusion after
closure of the facility. The most
important of these steps, which would
likely be conditions for a no-migration
variance for permanent disposal, are
described below.
First, DOE states that the site will
remain under federal jurisdiction in
perpetuity, and therefore it or successor
agencies will be in a position to restrict
access. Furethermore, in August 1987,
DOE and the State of New Mexico
agreed to prohibit in perpetuity all
subsurface mining, drilling, or resource
exploration on the WIPP site unrelated
to the WIPP project. Finally, the Federal
government owns the entire surface and
subsurface estate at the WIPP site, with
the exception of a single potash
leasehold interest; DOE states it is now
negotiating with the owner of that
leasehold interest. DOE also states that,
at WIPP closure, it will notify all state
and county planning, deed and record
offices, oil and gas commissions, and
other agencies, to prevent access by
unknowing parties. It will also place
permanent warning markers at the site,
as required by 40 CFR part 191
standards.
These specific controls, and perhaps
others, would constitute assurances
against human intrusion for the variance
for permanent disposal. But in one area
EPA believes a specific condition may
be appropriate for today's proposed
variance. As mentioned above, DOE is
now attempting to secure a potash '
leasehold interest at the site; it has
indicated that it will resolve this issue,.,
by mid-May 1990. EPA, however, is
concerned about the possibility that this
interest might not be secured before
mixed waste is placed in the WIPP.
Therefore, it is proposing to require, as a
condition of a variance for the test
phase, that DOE must certify to EPA
that it has secured control of the entire
surface and subsurface estate at the
WIPP (including the potash leasehold),
before waste is placed in the WIPP. At
the same time, EPA notes that the
current land withdrawal at the WIPP
site prohibits mining, and any future
land withdrawal is likely to include a
similar prohibition. Therefore, EPA
solicits comment on the appropriateness
and the need for this proposed
condition.
F. Site Geology and Hydrology
40 CFR 268.6(a) requires that a
petitioner seeking a no-migration
variance provide a comprehensive
characterization of the disposal unit site.
For a facility such as the WIPP, this
characterization must address the
regional and site-specific geologic and
hydrologic characteristics in the vicinity
at the site. This section of the preamble
describes the general site geology and
hydrology of the WIPP.
EPA believes that DOE has provided
sufficient information to demonstrate
that hazardous constituents will not
migrate from the unit by any geologic
pathway during the WIPP test period.
(For a discussion of this issue, see
sections IV.J and IV.K of this notice.)
Furthermore, the general area of the site
has been shown to be geologically
stable, and the confining unit (that is,
the Salado Formation) appears to be a
good medium for disposal, given its
thickness, general homogeneity, and low
permeability. In addition, the relative
remoteness of the site and the limited
ground water in the area, while not
relevant to a no-migration finding under
RCRA, were an important consideration
in site selection. While several
uncertainties remain concerning the
long-term performance of the repository,
the Agency believes that the site will
not present a problem during the test
phase. These uncertainties are being
investigated by DOE as part of the test
program. Data from this assessment will
be essential in any EPA finding of no-
migration with respect to the permanent
disposal of waste at the WIPP.
1. Site Overview
The WIPP site is located in
southeastern New Mexico, in the Pecos
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13079
Valley section of the southern Great
Plains physiographic province, a broad
highlands that slopes gently eastward
from the Basin and Range physiographic
province. The site is located in the
northern section of the Delaware Basin,
which is a portion of the larger Permian
Basin of the Texas/New Mexico area.
The Delaware Basin is a broad, oval
north-south trending trough, in which
there are over 6,100 meters of structural
relief on top of the Precambrian
basement. The basin rocks show little
deformation, and have undergone only
minor tectonic activity since the end of
Permian time, approximately 225 million
years ago. In ascending order, the
Permian units at the site are the
Delaware Mountain Group of the
Guadalupian Series (Brushy Canyon,
Cherry Canyon, and Bell Canyon
Formations), followed by the Ochoan
Group (the Castile, Salado, and Rustler
Formations, and the Dewey Lake Red
Beds). Above these formations is the
Triassic Dockum Group (undivided),
followed by Quaternary deposits of the
Pleistocene Epoch (Gatuna Formation
and Mescalero Caliche). The rocks
described above represent
approximately 4,000 meters of the
stratigraphic column at the site. The
repository is located in the Salado
Formation, approximately 655 meters (or
2,150 feet) below the surface.
2. Castile Formation Hydrogeology
The Castile Formation is the rock
formation directly underlying the
Salado. At the WIPP site it is
approximately 400 meters thick and is a
major halite-bearing unit. The halites,
which are of varying purity and
thickness, are separated by three
relatively thick anhydrite and carbonate
beds. Significant volumes of fluid are
.usually not encountered in the
formation. However, reservoirs of
pressurized gas and brine have been
found in the Castile.
Borehole ERDA-6, drilled in 1975,
encountered a reservoir of pressurized
brine in the Castile Formation, about 8
kilometers from the current WIPP site.
More recently, Borehole WIPP-12,
located about 1.5 kilometers from the
site center, encountered another brine
reservoir in the Castile. Data from
recent geophysical studies have led
DOE to assume that the WIPP-12
reservoir may extend underneath a
portion of the waste emplacement s
section of the repository. However, the
brines are 250 meters or more
stratigraphically below the repository
horizon, and there appears to be no
natural mechanism that would cause the
movement of these brines to the
repository. Uranium disequilibrium
studies performed on the brine in both
the ERDA-6 and the WIPP-12 reservoirs
indicate that the fluids are between
360,000 and 800,000 years old; there is
also no evidence to show contributions
from present precipitation. Furthermore,
the brines are saturated with respect to
halite, so there is no mechanism for
halite dissolution from the fluids.
Consequently, after reviewing the data,
the Agency has concluded that these
brine reservoirs do not present a threat
to the integrity of the repository under
undisturbed conditions. (DOE is
assessing the possible effects of a
borehole penetrating through the
repository and into an underlying
Castile brine pocket, leading to the
upward flow of brine into the repository.
The issue of possible human intrusion is
discussed in section IV.E of this notice.)
3. Rustler Formation Hydrogeology
The Rustler Formation is the rock unit
that overlies the Salado Formation. It is
composed of five members, in ascending
order: The unnamed member at the
Rustler/Salado contact, the Culebra
Dolomite, the Tamarisk Member, the
Magenta Dolomite, and the Forty-Niner
Member. Two of the members will be
discussed in this notice, because one is
in contact with the proposed unit
boundary of the disposal unit (unnamed
member), and the other member
overlying it is the most significant
water-bearing stratum (Culebra
Dolomite).
The unnamed lower member of the
Rustler Formation is a layered sequence
of siltstone, gypsum/anhydrite, and
halite. Near the WIPP site the average
thickness of this member is
approximately 35 meters. It contains a
siltstone water-producing portion, which
may be hydraulically continuous with
the upper Salado residuum and any
dissolution member of the upper Salado.
However, since the Rustler-Salado
contact contains water that is saturated
with respect to halite, it is not capable
of dissolving pure halite.
The member directly above the
unnamed lower member is the Culebra
Dolomite. If migration from the
repository were to occur, this formation
is considered the most important
potential pathway for release to the
environment. The Culebra is a finely
crystalline, locally argillaceous and
arenaceous, vuggy dolomite, with an
average thickness at the site of
approximately 10 meters. As a result of
fracturing, Culebra transmissivities
(which are very low) have been found to
range over six orders of magnitude near
the WIPP site.
Approximately 60 wells have been
completed in the Culebra since WIPP
studies began; water-level
measurements have been taken for most
of these wells over the life of the prdje.c.t. •
In these measurements, a good
correlation was found to exist between
water-level measurements from well to
well at the site. However, limited
quantities of the water in the formation
drained into the shafts of the facility
with the drilling of the construction and
salt handling shaft. This, coupled with
wide variations in fluid density within
the formation and very low hydraulic
gradients, have made flow directions
difficult to define, particularly in the
southern area of the site. The freshwater
head contours at wells in the area
indicate a southwestern flow direction
across Nash Draw, a southern flow
direction across the WIPP site, and an
area of apparent western flow south of
the site (apparent because of low
hydraulic gradients). In this instance, it
is noteworthy to remember that the
Culebra Formation is approximately 400
meters above the respository level,
meaning that, under undisturbed
conditions, the potential for hydrologic
interference by the Culebra into the
Salado or the possibility of the Culebra
being a sink for contaminants from the
respository is very low.
As mentioned above, the
geochemistry of the Culebra formation
waters is highly variable. The total
dissolved solids (TDS) concentration of
the Culebra in the area of the WIPP
varies from 10,000 to greater than
200,000 mg/L. These values render the
waters of the Culebra at the site
considerably saline and not a source of
drinking water. It has been noted that
the variability of the salinity of the
Culebra waters is such that modern flow
directions within the Culebra do not
appear consistent with modern salinity
distribution. This provides evidence that
there is no modern contribution of
recharge water into the Culebra at the
WIPP site. Evidence suggests that the
Culebra has been hydrologically
isolated for several thousand years.
The Agency believes that the DOE has
adequately described the general
hydrologic and geologic conditions for
the Rustler Formation for the purposes
of this petition, hi addition, during the
performance assessment, DOE will
continue to measure the hydrologic
responses of the Rustler with respect to
flow direction. This assessment should
serve to confirm and refine the current
understanding of the uppermost water-
bearing stratum in the area.6
6 It should be reiterated that these studies, while
pertinent to an understanding of hydrology in the
Continued
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4. Salado Formation Hydrogeology
Because the repository has been
constructed in the'Salado Formation, the
Salado is the formation of the most
interest at the WIPP site. It is located
between the Castile and Rustler
Formations. The Salado is informally
divided into three members: An
unnamed upper member, the McNutt
potash zone (the informal regional name
for the unnamed middle member], and
an unnamed lower member. The
rationale for this division is the type and
composition of laterally-consistent beds
of halite, polyhalite, and anhydrite, with
varying amounts of other potassium-
bearing minerals. The beds of anhydrite
and polyhalite alternate with the thicker
beds of halite within the Salado. Indeed,
approximately 85 to 90 percent of the
Salado is pure halite. The composition
of the Salado and the Castile
Formations are similar, but the lateral
extent of the two formations differ.
Unlike the Castile, the Salado is not
confined to the Delaware Basin, but
extends well beyond the Capitan Reef
complex onto the Northwestern Shelf
and Central Basin Complex.
The porosity of the Salado is
extremely low. While the near-field
permeability (immediately surrounding
the mined repository) is estimated to
range from 1 x 10 E-14 to 2.5 x 10 E-ll
m2 (0.01 to 25 microdarcies, where one
darcy « 10 E-4 m2), with an average of
approximately 0.3 microdarcy, the far-
field permeability has been measured at
approximately 10 E-20 m2 (one
nanodarcy). The Salado Formation was
initially thought to contain only very
small amounts of water (brine). This
liquid was postulated to be held only
.within the small pockets of the salt
crystals themselves (intragranular).
Later research, however, showed that
the brine was also situated in the
interstices of the individual crystals
(intergranular), or it saturated very thin
and discontinuous pockets and layers of
clay.
This is the fluid that has been seen at
the WIPP in the form of brine seeps.
These studies showed that the brine
content of the Salado may be
approximately 2 percent by volume. The
question of brine inflow and formation
permeability is discussed in more detail
in the next section.
arcs, arc nol directly relevant to the Agency's
decision on a no-migration variance, even for
permanent disposal. If contaminants pass beyond
the Salado at greater than health-based levels,
migration has occurred regardless of the fate of the
contaminants in the Rustler formation.
5. Geologic Stability
The geologic stability of the WIPP site
is a key element in any no-migration
finding for long-term disposal at the
repository. In the course of its review of
.DOE's petition, EPA addressed a
number of questions related to site
stability, the most important of which
are brine inflow into the facility,
potential for dissolution of the Salado
Formation, seismicity, and the
occurrence of maker beds in the Salado
Formation. These questions are
discussed below.
a. Brine inflow. There are two main
potential sources for brine infiltration
into the repository: Leakage from the
Rustler formation above the WIPP and
brine inflow from the Salado Formation
into the WIPP.
While there has been some leakage
from the Rustler Formation down each
of the four WIPP shafts into the
repository, the leakage rate does not
exceed 0.06 liters per second, even when
the shaft is unlined and no effort is
made to correct the situation. This is not
considered a problem with respect to
the overall integrity of the Salado, but
did lead to inflow of water into the
facility. As a result, the WIPP shafts
have been concrete-lined and grouted
through the Rustler Formation,
successfully eliminating the inflow into
the shafts. This will be adequate (with
proper maintenance) to control leakage
from the Rustler over the operating life
of the facility, at which time the shaft
seals will be constructed. Therefore, the
shafts do not contribute fluid to the
repository, and thus do not threaten the
unit through dissolution or provide a
driving force for the transport of
hazardous constituents from the
underground.
Underground experience with the
WIPP has also allowed more
information to be gathered on the
occurrence and movement of brine
within the Salado. The movement of
brine in the area immediately
surrounding the repository (the
disturbed rock zone) has consisted of
small, low flow "weeps" that commonly
develop on the walls and ceiling of an
excavation shortly after the mining of an
area. It has been observed that the
weeps generally occur at random
intervals along planes of heterogeneity
within the repository, which means
along clay and anhydrite seams found
within the Salado. Only rarely does the
inflow from a particular weep exceed
the evaporation rate of the mine
ventilation. In this case, the small
amounts of brine will accumulate on the
salt surface (usually at a rate of a few
tenths of a milliliter per day) until the
flow from the weep diminishes, which
usually occurs within" a few months. Th'e
current view, -accepted by EPA, is that... .
brine movement into the repository is
from the disturbed rock zone, and may
be the result of stress-driven flow, with
little or no contribution of flow from the
far-field (which is the area beyond the
zone affected by the underground
workings). The fluid inflow question is
an important one because brine is a key
factor in gas generation, which is
partially caused by the corrosion of the
waste containers. Gas generation may
affect the amount of time required for
creep closure of the facility, and, if gas
pressure is sufficient, it could also
fracture surrounding walls or seals. Gas
may also generate enough pressure to
drive liquid out of the repository. (The
question of gas generation is discussed
later in this section.)
Because of these uncertainties, DOE
has developed several conceptual
models to predict brine movement
within the Salado Formation. One model
is based on far-field Darcy flow. It
assumes that the Salado is hydraulically
saturated in the far-field, that fluid flow
is the controlling or limiting factor in the
long term, and that fluid flow can be
modeled effectively through the Darcy
equation. (Darcy flow means that fluid
flow is directly proportional to the
pressure gradient, even when these
gradients are very low.) The other
concept for modeling the Salado
assumes that Darcy permeability is
valid only in those regions that have
been significantly distrubed. In this
approach, the far-field Salado
permeability would be essentially zero
under any pressure gradient, and brine
would flow into or out of the WIPP
(along with any hazardous constituents)
only in response to the formation of a
disturbed rock zone in which
deformation of the halite produced
interconnected porosity. A third model,
which falls between these two
approaches, assumes that there is some
interconnected porosity within the
Salado even under undisturbed
conditions, and that fluid flow would
take place in the near field in the
absence of mechanical disturbance, but
there would be no far-field fluid flow
due to the absence of sufficient
gradients.
Currently it is not certain that the
different models of fluid flow within the
Salado have significantly different
impacts to the long-term behavior of the
repository. In general, interpretations
assuming Darcy flow in the far-field are
conservative in that they do not result in
a zero far-field flow rate and do not
indicate maximum amounts of brine
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13081
inflow. Based on the models, however,
DOE estimates that the-brine inflow
might total'40.6 m3 in 200 years, the
estimated date by which the repository
will be closed. This is a relatively small
volume of liquid, representing 1.2
percent of the initial room volume. DOE
believes that this amount of brine would
be absorbed by salt backfill that will be'
placed around the waste.
To verify these results, DOE has
scheduled Salado Formation fluid flow
behavior studies for the test period at
the WIPP; during these studies, DOE will
validate the models against in-situ data,
and will evaluate the fluid flow
characteristics of the Salado in the
shafts and in the salt surrounding the
disposal rooms'.
During the test phase, DOE will also
refine the current understanding of the
hydraulic characteristics of the Salado
Formation, including: (1) The state of the
hydraulic saturation in the far-field; (2)
the driving forces for fluid flow; and (3)
the relevant flow paths. As a result of
these studies, DOE will obtain a better
understanding of the long-term rates of
brine inflow, and the long-term fate of
wastes placed in the repository.
b. Seismicity. The WIPP site is located
hi an area of low seismic risk. The
possibility is extremely low that faulting
at the site is of a magnitued that could
significantly affect site integrity.
Geophysical investigations performed at
the site show that no major faults occur
in the area, and that those minor faults
that are present do not appear
physically to displace repository-horizon
strata. The Agency agrees with the
conclusion presented by the petitioner
that regional tectonic activity is not an
issue in terms of maintaining repository
integrity.
c. Dissolution features. Because halite
of the Salado formation is soluble in
waters that are undersaturated with
. respect to the minerals in halite,
removal of salt surrounding the
repository by dissolution could affect
repository performance and provide a
route of migration out of the facility. In
reviewing the potential for dissolution at
the WIPP, EPA considered: [1) The
influence of a dissolution front at nearby
Nash Draw; (2) the possibility of shallow
dissolution at the WIPP; (3) the
likelihood of climatic changes affecting
the hydrologic system, including the
dissolution rate; and (4) the effect of
deep-seated dissolution on repository
performance and the origin of "breccia
pipes" found near WIPP.
The nearest major geomorphic feature
to the WIPP is Nash Draw, which is
approximately eight kilometers
northwest of the site. Nash Draw is an
undrained physiographic depression
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which probably developed as a result of
differential dissolution of the anhydrite,
gypsum, and halite beds of the Rustler
and Upper Salado Formations. It is
believed that dissolution on top of the
massive Salado Formation produced a
uniform lowering of the land surface
within Nash Draw, while surficial
features were produced and modified by
dissolution of the Rustler Formation.
The dissolution process also produced
individual sink holes within Nash Draw,
which vary in size from a few tens of
meters to approximately two kilometers
across. There are also very small
sinkholes elsewhere in the area.
The shallow dissolution features in
the WIPP area where formed during
wetter climatic periods, primarily during
the formation of the Pleistocene Gatuna
Formation. Even during the period of
greatest dissolution, only units within
approximately 75 meters of the surface
were affected. Shallow dissolution can
only become a major process in the
Salado, which is over 250 meters from
the ground surface, if large quantities of
halite-unsaturated water gain access to
the Rustler Formation. Several factors
will inhibit this process. The geologic
units above the Salado are confining
layers with transmissivities so low as to
prevent recharge of surface water. Since
the Rustler/Salado contact contains
water that is staturated with respect to
halite, it is not capable of dissolving
additional halite. Lastly, the head-
gradient from the Rustler/Salado
contact is upward through the Rustler,
which means that if water did exist and
flow through this area, it would flow
away from the Salado.
Significant increases in precipitation
in the area of the WIPP could in theory
increase the likelihood of surface
dissolution. Data, however, indicate that
the Quaternary climate of the past
500,000 years has for the most part
remained semi-arid, with limited periods
of increased precipitation. For example,
the Mescalero Caliche, a type of
formation characteristics of warm, semi-
arid climates, has remained intact since
its formation approximately 500,000
years ago; its continued presence is
evidence that the climate has been
relatively dry since its formation. As
part of the performance assessment,
DOE is studying further the possible
effects of significant climatic changes on
the WIPP.
Another type of dissolution feature
found in the region is breccia pipes, or
dome-like features of fractured rock.
Four of these domal features occur in
the immediate vicinity of the WIPP area.
Two of these have been drilled and
tested. These features appear to be the
result of localized, deep-seated
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dissolution wherein a void is created
and overlying material collapses into the
void, hirthe Delaware Basin, these,
breccia pipes form where soluble units
overlie the Capitan Reef aquifer system.
The pipes are formed by dissolution of
the rock and the subsequent collapse of
overlying beds, followed by differential
solution of upper units, producing
subsidence of ground around the
collapsed pipe and creating a brecciated
"domal" structure. There are two
proposed scenarios for collapse:
formation of a cavern inside the Capitan
and dissolution and collapse of
overlying units, or influx of water to the
Salado from an outside source through
fractures, resulting in Salado dissolution
and collapse. EPA agrees with DOE in
its conclusion that formation of these
features will not affect the WIPP site
because the Capitan Formation,
necessary as a fluid source for
dissolution, does not underlie the WIPP
site.
d. Occurrence and significance of
marker beds. The occurrence of 46
correctable marker beds throughout the
Salado indicates that the formation
exhibits lateral continuity. Geologic
mapping within the repository and
shafts further supports this contention.
The WIPP repository is bounded by
two markers beds (MB), an upper MB
138 and an underlying MB 139. Marker
Bed 139 is located approximately 1.5
meters below the floor of the repository,
and is composed by anhydrite,
polyhalite, and halite. It varies in
thickness from 0.3 to 1.3 meters, with an
average thickness of 0.8 meter. The bed
is fractured in the area below the
repository as a result of the excavation
of the repository. This marker bed is a
potential contaminant migration
pathway if fluids/gases were to exist in
sufficient quantities to allow a driving
force. DOE will review the possible role
of Marker Bed 139 during the test phase,
and will evaluate the need for specific
approaches designed to control
migration through the bed, including
grouting and excavation of the fractured
portions.
Marker Bed 138 lies approximately 9
to 10 meters above the repository and is
composed of microcrystalline, partly
laminated anhydrite that contains
scattered halite growths. This bed is
typically 0.25 meters thick, and has a
very thin clay seam at the base.
Detailed assessment of marker beds
surrounding the repository is important
because these beds may act as parting
surfaces during repository closure and
may also serve as fluid migration
pathways. DOE is conducting a number
of studies to provide a full
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understanding of the significance of
these marker beds with respect to
repository performance. The role of
these beds and Iww the performance
assessment will address outstanding
issues such as fluid migration pathways
are discussed later in this notice.
e. Ground-water modeling. In its no-
migration variance petition, DOE
provided the results of ground-water
modeling that address the possible
migration of hazardous constituents in
the Salado Formation. The modeled
pathway was one in which wastes
moved downward from the waste
storage panels, through the underlying
salt, and into Marker Bed 139. Waste
then moved laterally through this bed to
the vertical shafts and upward through
the seals and salt backfill within the
shaft. DOE modeled this scenario using
the SWIFT ffi code, a widely accepted
code used to assess contaminant
transport underground, and made very
conservative assumptions—for example,
one-dimensional flow, constant
concentration source of 100 percent
solubility, high longitudinal
dispersivities, and no retardation or
attenuation of wastes.
Results of the SWIFT m modeling
indicate that the maximum distance
from the source of a 10 ppt (part per
trillion) concentration level is 350 meters
after 10,000 years, assuming a
dispersivity value of 10. This is
significant, because the 10 ppt "front"
would not have reached the sealed
shafts by 10,000 years, and would still
be over 400 meters from the top of the
Salado Formation. Even with an
unrealistic dispersivity value of 100, and
10 ppt contaminant front would still be
240 meters from the top of the Salado.
These results indicate that if the
enhanced permeability of the marker
bed is limited to the area around the
• disturbed rock zone, and the
permeabilities of the constructed seals
are low, contaminants will not migrate
vertically up the shaft beyond the unit
boundary under the modeled scenario
and within the period of the model. If
significant fracturing of rock were to
occur or the seals were to fail, however,
more extensive migration might occur.
Although DOE considers these
conditions unlikely, it will evaluate them
during the test phase.
G. Repository Performance
1. Construction and Maintenance of the
Repository
The WIPP repository was excavated
according to accepted industry
techniques, and has been under Mine
Safety and Health Administration
(MSHA) oversight and inspection since
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1987. The basic mine design is "room
and pillar," in which large rooms are
excavated from the salt bed and the
structural support is provided by the
intact pillars of salt that remain. The
width of the pillars is determined by the
structural properties of the in-situ
material. During and after construction,
some fracturing of the repository walls
has been observed. As a result, rock
bolts have been used extensively
throughout the underground openings.
These bolts retard fracturing and are
used in areas of the mine that will
remain open for extended periods of
time, such as the waste unloading areas
and the main access drifts. Roofs of
many high traffic areas are pattern
bolted for extra safety. Both resin and
mechanical bolts are used in most areas.
The bolts are tested to meet MSHA
standards by MSHA-qualified
personnel.
The room and pillar type of
excavation is used in various mining
activities, such as anthracite and potash
mining. In fact, much structural
information for the WIPP repository was
derived from the potash industry
experience from mining the Salado
Formation. As a result, the Agency is
satisfied with the procedures used by
DOE with respect to the basic
construction of the WIPP underground.
The Agency believes that DOE has
demonstrated, with reasonable
certainty, the stability of the WIPP
repository during the period of the
proposed variance.
2. Closure Mechanisms
One of the most attractive
characteristics of bedded salt is its
plasticity, which enables it over time to
flow or "creep," a process that enables
fractures in the salt to heal at feasible
repository depths. The National
Academy of Sciences' original
recommendation of salt as a repository
medium was based in part on the
assumption that the salt would creep to
closure and that the salt pillars (or the
room and pillar concept) would provide
sufficient support to prevent premature
collapse and failure of the repository.
There are four major elements of the
closure mechanism for the WIPP
underground: (1) Brine inflow (discussed
earlier); (2) rate of closure of the
repository; (3) the disturbed rock zone
and Marker Bed 139; and (4) gas
generation (which is discussed in the
next section).
The observed closure behavior of the
openings at the facility is more rapid
and more complex than originally
anticipated. The total macroscopic wall-
to-wall and ceiling-to-floor closure to
date have proved, at least initially, to be
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approximately three times the predicted
value. Under the most favorable
conditions, the more "rapid closure
would result-in time estimates of 60 to.. •
200 years for closure to a near final
state, depending on the initial waste and'
backfill density, brine influx rate, gas
generation rate, and creep closure rate.
One of the tasks of the performance
assessment is to ascertain in more detail
the specific mechanisms and timing of
repository closure.
EPA believes that the creep closure
process will be a step-functioned
phenomena, in which slabs of halite, or
variable size, will break along fractures
and fall into the remaining open space
of the mine, or will be involved in floor
heave. These fractures will occur mainly
along pre-existing microfractures,
incipient joints, and bedding planes,
following the excavation of underground
openings at the WIPP facility. These are
the fractures that make up the disturbed
rock zone, which is a zone of rock in
which mechanical properties have
changed in response to the excavation.
The term "near-field" describes the rock
within the disturbed rock zone, and "far-
field" describes the rock outside the
zone. The disturbed rock zone extends
approximately 1 to 5 meters from the
excavation.
Underground observations of the
disturbed rock zone indicate that
coherent creep of the Salado Formation
outside of the disturbed rock zone is the
dominant structural process involved in
the closure of the repository. The
disturbed rock zone, however, may
serve as a sink for some or all of the
brine that seeps into the rooms and
shafts. It may also enlarge the effective
room dimensions by moving the area at
or near atmospheric pressure to its outer
limits. This would increase the time
required for complete closure of the
repository openings, allowing the
potential for increased brine
accumulation. It as also been suggested
that, if the fractures in the disturbed
rock zone or Marker Bed 139 in
particular do not heal, they might serve
as a route for migration for hazardous
waste or radionuclides. A major portion
of the test phase will be devoted to
exploring the extent and behavior of the
disturbed rock zone.
3. Gas Generation in Waste Disposal
Rooms
Microbial and radiolytic
decomposition of the waste and
corrosion of containers will generate a
large quantity of gas. This may result in
the pressurization of the waste disposal
rooms, particularly if the rate of gas
production exceeds the rate at which
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13083
gas could be consumed in chemical
reactions or be diffused into the host
rock. This pressurization could become
a driving force for the migration of
radionuclides and/or hazardous
constituents. If gas pressure exceeds
lithostatic pressure, it may result in
near-field fracturing of the Salado
Formation, impede the structural closing
of the repository, or result in gases or
brines escaping around the shaft and
panel seals. (Seal design will be
discussed hi section IV.H.) While this is
a question that DOE is addressing as
part of the performance assessment, it
will not be a concern during the test
phase.
From the viewpoint of long-term
performance of the WIPP, the
fundamental questions are whether
brine inflow will be sufficient to
saturate backfill, waste, and the
disturbed rock zone, either before or
after compaction of the repository to the
final mechanical state, and whether the
far-field permeability will be sufficient
to dissipate brine and/or gas pressures
at or near the final repository state at
some fluid pressure below lithostatic
pressure.
The impacts of potential gas
generation cannot be fully assessed at
this time. The most important factor
with regard to impacts at the site is the
rate at which gases will be produced. To
some extent, gases may be absorbed
into the Salado Formation. The results
of experiments performed during the test
phase will help quantify the rate of gas
generation within the repository, and
will determine if any additional
engineering modifications or safeguards
are needed to meet the long-term
performance goals.
4. Evaluation of Engineered Alternatives
The potential for releases as a result
of the interactions among wastes, brine,
and gas at the WIPP has led DOE to
consider whether some type of waste
treatment process or some other system
modification may be required. Several
engineered components might be added
to the system to mitigate the effects of
gas generation, wastes might be treated
before placement to reduce the amount
of gas generated, or other measures
taken. DOE formed a task force to
review and evaluate the technical
effectiveness of waste, backfill, and
facility design modifications in
mitigating problems associated with gas
generation. Engineered alternatives that
might provide improved performance
will be included in the WIPP
experimental programs.
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H. Seal Design
The WIPP repository is connected to
the ground surface by four mine shafts
ranging in diameter from 3.7 meters to
6.1 meters. These shafts are used to
remove excavated salt, provide fresh air
intake, provide for exhaust air outflow,
and handle waste, personnel and
construction equipment. At site closure,
these shafts must be filled and plugged
to prevent the escape of hazardous
constituents. In addition, each panel and
drift of the repository itself must
eventually be sealed to prevent
migration of wastes to the shaft seals
and minimize release in the event of a
penetration. Since DOE will not be
installing permanent seals during the
test phase, the variance proposed today
does not require an approved final
design. However, for the Agency to be
assured that an implementable design
will be available at the end of the test
phase, it has required DOE to provide in
its petition a reference design and a plan
for development of a detailed design.
The primary function of the seal
system is to limit the release of
hazardous constituents (and
radionuclides} through the shafts and
past the unit boundary. For the purpose
of the no-migration petition, hazardous
constituents must not escape from the
seal system in excess of health-based
levels, and the seals must be capable of
limiting the inflow of ground water from
overlying water-bearing zones.
Furthermore, the seals must function
effectively for as long as the waste
remains hazardous.
In its petition, DOE has developed a
two-phase reference seal design. The
first phase provides a "short-term"
barrier to fluid flow and is designed to
function for at least 100 years. The
purpose of this "short-term" barrier is to
provide containment until the long-term
barrier of compressed salt consolidates.
The second phase provides the long-
term barrier to fluid flow and is
expected to become effective at
approximately the 100-year time frame.
DOE has chosen salt as the principal
long-term barrier to fluid flow from the
repository. Salt has been selected
because: (1) It is compatible with the
surrounding host rock, providing long-
term mechanical and chemical stability
unmatched by any other material
considered; (2) it is emplacable with
conventional techniques; and (3)
emplaced crushed salt is expected to
reconsolidate as a result of creep
closure of the mine and shaft openings,
resulting in a fluid conductivity
approaching that of the host rock salt.
Laboratory testing and numerical
modeling have demonstrated the
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feasibility of rock salt as the long-term
seal; however, complete consolidation of
the salt columns within the shafts and'
mine drifts- is expected to take up to 100 •
years. Therefore, DOE has proposed a
short-term seal system to provide waste •
containment during the period of salt
seal consolidation.
The materials chosen for the short-
term seals must satisfy the following
criteria: (1) They must provide an
effective fluid barrier; (2) they must be
emplacable in the mine environment; (3)
they must provide mechanical and
chemical stability for at least 100 years;
and (4) they must be compatible with
and capable of containing the hazardous
waste constituents found in the TRU
wastes. (Although the Senate legislative
history indicates that the no-migration
applicant must "sustain the burden of
meeting this standard without the use of
artificial barriers such as liners" (S. Rep.
No. 284 at 15), EPA does not read this
language as precluding assessment of
artificial barriers for temporary
containment. The concern expressed in
the legislative history is that artificial
barriers do not provide indefinite
containment. Since the artificial seals at
the WEPP would only provide a barrier
to migration during the temporary period
(i.e., 100 years) between closure and
consolidation of the permanent salt seal,
the concern expressed in the legislative
history does not appear to be
presented.)
DOE's ongoing seal development
program has evaluated a number of seal
materials for use in short-term seals,
including clays, grouts, concretes, and
asphalt. After substantial investigation,
including laboratory and small-scale
field testing, literature review, and
modeling, DOE has proposed a.
multicomponent reference or conceptual
design for the short-term seals. The
reference seal materials chosen were
concrete and sodium bentonite (a type
of clay). They are expected to satisfy the
above criteria, although their
effectiveness will be the subject of
further study during the test phase.
Within the repository shafts there will
be three major seal subsystems—the
water-bearing zone seal system, the
upper shaft -seal system, and the lower
shaft seal system. The water-bearing
zone and upper shaft seal systems are
located in the Rustler Formation, while
the lower shaft seal system is in the
Salado Formation. The water-bearir"
zone seal system is composed of a 4-
meter-thick compacted sodium bentonite
seal sandwiched between massive IO-
meter-thick concrete bulkheads. The
upper shaft seal system is composed of
three 4-meter-thick sodium bentonite
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Federal Register / Vol. 55, No. 67 / Friday, April 6. 1990 / Notices
seals, each sandwiched between
massive concrete bulkheads 10 meters
in thickness. The redundant nature of
the approximately 60-meter-long shaft
system in the Salado Formation can be
expected to assure that water-bearing
zones are isolated from the shafts.
The lower shaft seal system, which
will be in the Salado formation, is
expected to function for the long term.
This seal system will be composed
primarily of compacted crushed salt,
ultimately returning the shaft area to a
state of permeability to fluids
comparable to that of intact host rock
salt. The expected height of the final
column of reconsolidated salt in each of
the four shafts is approximately 200
meters.
A short-term seal will be installed at
the top of the Salado formation, above
the compacted crushed salt column. The
seal will be composed, from top to
bottom, of (1) a 10-meter-thick concrete
bulkhead, (2) a 4-meter-thick compacted
sodium bentonite seal, (3) a 5-meter-
thick preconsolidated crushed salt core,
(4) a 4-meter-thick compacted sodium
bentonite seal, and (5) a 10-meter-thick
concrete bulkhead. This upper
component will provide redundant
protection of the preconsolidated salt
from infiltration by water from strata
above the Salado formation. The
concrete used in this seal, and all other
seals within the Salado formation, will
be salt saturated to increase
compatibility with the host rock. At the
bottom of each shaft another short-term
seal similar to the one emplaced at the
top of the Salado formation will provide
a base for the shaft's preconsolidated
salt seal, and will limit the movement of
fluids between the salt column and the
repository itself. A redundant seal
similar to the two mentioned above is
also proposed to be located within the
Salado formation just below the Vaca
' Triste marker bed, which is a halitic
siltstone approximately 240 meters
above the repository horizon.
DOE also intends to place a series of
horizontal seals within the drifts and
panels of the repository itself, and along
the four long North-South access drifts
leading to the panels. The purpose of
these seals is to provide an interval
within each panel that has a
permeability to fluids comparable to the
permeability of undisturbed host rock
salt. These seals will be composed of a
preconsolidated salt core (either tamped
salt or salt block) with 10-meter
concrete bulkheads at each end.
Considerable overexcavation is
anticipated within the drift and panel
seal areas just prior to placement of the
seals to reduce the disturbed rock zone
S-04I999 0157(09)(05-APR-90-14:19:18)
and remove areas of Marker Bed 139,
which might permit migration of the
waste constituents. Swelling clays are
not now included in the panel and drift
seal design.7
In its petition, DOE provided a
reference design for this seal system. A
significant portion of test phase
activities is devoted to seal system
development based on the reference
design. To characterize seal system
behavior and performance more fully,
DOE is conducting an in-situ and
laboratory testing, analysis, and design
program. The primary activities or
issues addressed by the program are:
1. Geochemical stability. Additional
laboratory work is necessary to confirm
that short-term components will perform
adequately throughout their design life.
During the test phase, DOE will evaluate
the potential for chemical degradation
for the seal materials as a result of
interaction with the hazardous waste
(and other waste) to be disposed of in
the repository.
2. Crushed salt consolidation. The
effect of consolidation on crushed salt
properties requires verification with
further laboratory tests, including an
expansion of the testing program to
include brine-saturated crushed salt.
Consolidation rates of crushed salt
under deviatoric loading will be
determined. Measurements will then be
made on samples saturated with brine
to determine how fluid-filled pores
inhibit compaction. The extent to which
reconsolidation is accelerated by
moisture will be measured in tests on
samples containing controlled quantities
of added brine. The relationship
between reconsolidation, density, and
permeability will also be determined.
3. Cementitious materials
development. DOE will also investigate
anhydrite bonding concrete, principally
to support the development of material
to seal Marker Bed 139 as well as
anhydrite markerbeds of less
importance. Testing of previously-
developed concretes will continue.
4. Crushed-salt consolidation
modeling. DOE will update the
numerical crushed salt consolidation
model to include the latest data from
laboratory tests. Calculations will be
made of crushed salt consolidation in
proposed seal excavation shapes to
guide the choice of seal shapes for rapid
consolidation to high density and low
permeability.
5. Seal system design integration. An ^
architectural/engineering contractor will
prepare a design for the WIPP sealing
system after evaluating the results of the
testing and model development .
activities. The design will provide the •
basis for preparing a WIPP construction
design.
6. Small- and large-scale seal tests.
DOE'has placed a number of vertical
and horizontal bore holes in the
experimental area of the repository.
Various candidate seal materials have
been placed in these boreholes to
provide in-situ data on their efficacy. To
more fully simulate the effects of the
disturbed rock zone and to test
emplacement techniques, DOE will
emplace large-scale seals during the test
phase. These seals will simulate typical
panel seals, and will be composed of
crushed salt or salt blocks and
concrete.8
The Agency believes that DOE's seals
development program, as outlined in the
no-migration variance, is appropriate.
The reference materials currently
selected exhibit key properties of
mechanical and chemical stability,
emplaceability, and hydraulic
impermeability. The overall seal design
is redundant and calls for seals in
critical portions of the repository and
shafts. The test phase will address
outstanding data needs, verify existing
data, and develop new models, as well
as improve models developed
previously. Information developed
during the test phase will be used to
develop a preliminary seal design
suitable for a construction design.
The Agency solicits comments on
DOE's current reference design as well
as DOE's program for developing a
preliminary seal design during the test
phase.
/. Waste Characterization
1. Waste Sources and Types
The TRU wastes intended for
emplacement in the WIPP are generated
at the ten DOE facilities involved in
production operations and research and
development activities related to
national defense. Many of the processes
conducted at the DOE generating
facilities are typical manufacturing
operations—machining, degreasing,
foundry operations, assembly,
laboratory operations, etc.; the major
difference is the use of radioactive
7 In addition to isolating each panel from the rest
of the repository, the panel seals will also function
as a barrier for backfilled salt placed in each panel.
The backfilled salt and other absorbent or getter
material will aid in the encapsulation of the waste
material, absorb brine infiltrating individual rooms,
and reduce the time necessary for final closure.
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8 DOE is also continuing to participate in
international salt seal development programs.
Advanced programs with salt, bentonite, and
concrete are being conducted concurrent to the DOE
program in Sweden, Canada, Germany, and the
Netherlands.
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materials to produce defense-related
materials. The wastes that are generated
from these processes include: (1)
Laboratory hardware such as glassware,
ring stands, piping, and other metal
structures, (2) cellulosic materials such
as towels, tissues, and wiping cloths, (3)
protective gloves and clothing; (4)
inorganic process sludges, many of
which are stabilized, (5) various plastic,
rubbers, and resins, (6) stabilized
organic wastes, and (7) worn out or
contaminated equipment and tools. The
specific DOE facilities that generate
these wastes are:
Rocky Flats Plant, Golden, CO
Idaho National Engineering Laboratory,
Idaho Falls, ID
Los Alamos National Laboratory, Los
Alamos, NM
Argonne National Laboratory-East, Argonne,
IL
Savannah River Plant, Aiken, SC
Oak Ridge National Laboratory, Oak Ridge,
TN
Hanford Reservation, Richland, WA
Mound Plant, Miamisburg, OH
TABLE 1—VOLUMES OF WASTE BY WASTE TYPE
Lawrence Livermore National Laboratory,
Livermore, CA
Nevada-Test Site, Mercury, NV
While' the wastes originate from
numerous sources within each facility,
they have been categorized, into four
general waste types based upon their
physical form and primary chemical
content (i.e., organic or inorganic). These
types, an example of each, and the
approximate volumes of waste they
represent, are depicted in Table 1.
Waste type
Solidified aqueous or homogeneous inorganic solids
(Waste Type 1).
Solid inorganics (Wast Type II)
Solid organics (Waste Type III)
Solidified organics (Waste Type IV)
Total
Examples
Wastewater Treatment Sludges; Cemented inorganic process solids; Solidified aqueous
wastes.
Graphite waste; Metal waste — tools, equipment; Glass waste; Pyrochemical salt waste
Combustible waste — paper rags soft plastics, cloth coveralls; Filter wastes* Leaded rubber
Exchange resins.
Solidified lab waste; Solidified solvents
Volumes
(ft3)1
800,000
850 000
1 750 000
100,000
3,500,000
•The volumes reflect previously generated wastes plus the expected volumes that will be generated during the operating life of the WIPP facility.
As can be seen.the largest percentage
(approximately 75%) of waste is solid
organic- and inorganic-types wastes—
paper, protective clothing, tools,
equipment, etc.—while solidified
organics (the waste that is expected to
contain the highest amount of toxicants)
will comprise a relatively small
percentage of waste (approximately 3
percent).
All wastes to be sent to the WIPP
must comply with the Waste
Acceptance Criteria (WAG) established
by the DOE WIPP Project Office. (These
criteria are normally referred to as the
WIPP-WAG.) These criteria specify
requirements regarding the physical,
chemical, and radiological
. characteristics of the wastes, as well as
package labeling requirements. For
example, the WIPP-WAG prohibits
wastes containing free liquids except in
residual amounts.9 Therefore, wastes
8 One of the concerns expressed by EPA over the
long-term fate of the wastes is the potential for
liquids contained in the wastes to be released due
to increased pressure after the closure of the
repository and, thus, creating the potential for
movement of hazardous constituents. As a result of
this concern, DOE provided information which
indicates that the potential for liquids to be released
from the solidified inorganic process sludges (Waste
Type I) during the closure period is minimal. Similar
assurance needs to be provided for the solidified
organic sludges and the wastes that are stabilized
by the addition of absorbent. Since the repository
will remain open during the testing period, the
potentials for liquid release is not a concern during
the testing period. However, additional data will be
necessary before the Agency can reach a decision
on the operational and post-operational periods.
S-041999 0158(09)(05-APR-90-14:19:22)
destined for emplacement at the WIPP
must be in a solid or solidified form.
Similarly, corrosive materials and
nonradioactive pyrophorics are also
prohibited by the WIPP-WAC.
Therefore, all corrosive materials must
be neutralized or processed to render
them noncorrosive, and all nonnuclide
. pyrophorics must be stabilized or
processed to render them nonhazardous.
The WIPP-WAC also place limits on the
radionuclide levels allowed in
individual waste packages. Compliance
with the WAG is verified by a
combination of process controls: visual
inspection during waste packaging, real-
time radiography, nondestructive
radiological assay, and waste sampling.
DOE requires that each waste generator
or storage site certify that all wastes
meet the WIPP-WAC requirements prior
to being sent to the WIPP.
2. Waste Characterization Data
DOE's characterization of the RCRA
hazardous constituents in the TRU
wastes to be emplaced at the WIPP
facility is primarily based upon best
engineering judgment, considering the
processes from which the wastestreams
originate, the materials used in each
process, and the technologies used in
treating the wastes. In compiling these
data, DOE grouped wastes together into
Content Codes which comprise wastes
of similar types (e.g., combustibles,
metals, etc.). Each Content Code
indicates where the waste is stored or
generated and consists of one or more
Item Description Codes (IDCs). These
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IDCs are site-assigned codes for wastes;
they represent more detailed waste
descriptions than are contained in the
Content Codes. For example, Content
Code RF116 represents combustible
wastes currently being generated at
Rocky Flats. This Content Code is
composed of IDC 831 (dry
combustibles), IDC 832 (wet
combustibles), and IDC 833 (plastics).
(The Content Code 116 wastes
previously generated at Rocky Flats and
currently stored at the Idaho National
Engineering Laboratory are designated
as ID 116.)
In support of its petition, DOE
provided information on each of 138
Content Codes. For the various codes,
the information was provided in two
parts. The first part contains a
description of the waste in the Content
Code and its corresponding IDCs. This
description includes flow diagrams and
narrative descriptions of the processes
which generate the waste, as well as
identification of the RCRA hazardous
constituents that are used in the process
and estimated concentrations for each
of the hazardous constituents expected
in the waste.
In using process knowledge to
establish the identity and concentration
of RCRA hazardous constituents in
particular wastestreams, DOE assumed
that, if a constituent was used in a
process contributing to a wastestream,
then the constituent would be present in
the treated waste. DOE notes that this is
a conservative approach since many of
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Federal Register / Vol. 55, No. 67 / Friday, April 6. 1990 / Notices
the identified constituents (i.e., the
solvents) are very volatile and are likely
not to be present in the wastestreams, or
are present at very low levels.
The second part of the Content-Code-
specific information references
available analytical data; these data,
DOE argues, support its conclusions on
waste composition based upon process
knowledge. These data include results
from total volatile organic analysis, total
metals analysis, Toxicity Characteristic
Leaching Procedure (TCLP) tests for
organics and metals, Extraction
Procedure (EP) tests for metals, and
headspace gas analysis for organics.
Except in a few cases, all the analytical
results represent wastes that were
generated at the Rocky Flats Plant, the
Idaho National Engineering Laboratory,
or the Los Alamos National Laboratory.
Total volatile analysis data were
reported for 15 samples. Thirteen of the
samples represented Waste Type I and
two represented Waste Type IV. Total
metals analysis data were reported for
six samples. These samples represented
Waste Type I and were also tested for
the RCRA hazardous waste
characteristics of ignitability,
corrosivity, and reactivity.
TCLP results were reported for ten
samples, all representing Waste Type I.
Nine of the samples were analyzed for
organics and metals while one was
analyzed for organics only. EP toxicity
test results were reported for fifteen
samples. All these samples represented
Waste Type I.
Two sets of gas headspace analysis
results were provided. In the first set,
results were reported for 22 samples.
Ten samples represented Waste Type I;
five samples represented Waste Type II;
three samples represented Waste Type
HI; and four samples represented Waste
Type IV. In the second set, headspace
analysis results were reported for 209
samples.10 Thirty-two samples
represented Waste Type I; 78 samples
represented Waste Type II; 77 samples
represented Waste Type III; and 23
samples represented Waste Type IV. In
both sets of headspace data, the
samples were analyzed for numerous
gases, including nine organics.
It should be noted that one of the
goals of DOE's waste characterization
program is to ensure that the wastes
used in the experimental or test phase
are representative of all of the wastes
that will be placed in the WIPP facility
during its operational period. DOE
believes that wastes from Rocky Flats
(newly generated) and the Idaho
National Engineering Laboratory (stored
and newly generated) will be
representative of wastes from the other
10 Forty-one gas headspace samples were also
analyzed for wastes generated at the Los Alamos
National Laboratory. These analyses indicate that
no RCRA VOCs were detected in the headspace.
facilities because Rocky Flats .will )
generate 46% of the newly generated
waste" over the next 26 years and JNEL
contains"62% of the stored waste that
will be shipped to the WIPP facility,'
much of which was generated at Rocky
Flats. DOE further notes that Rocky
Flats produces wastes described by
most of the Content Codes.
3. Summary of Waste Characterization
Data
The RCRA hazardous constituents in
the wastes destined for the WIPP are
certain toxic metals and both
halogenated and nonhalogenated
solvents. Based upon the process
information and analytical data, DOE
compiled a table (Table 2-1 of the
Waste Analysis Plan) which identifies
the RCRA hazardous constituents and
estimated concentrations expected to be
present in each Content Code. The
maximum estimated concentrations of
the predominant hazardous constituents
are presented in Table 2.
The toxic metals cadmium, chromium,
lead, mercury, selenium, and silver are
predominantly present in discarded
tools and equipment, solidified inorganic
sludges, and cemented laboratory
liquids. Lead is the most prevalent EP
metal and is present mostly in lead-lined
gloves, aprons, and gloveboxes; lead
bricks; and piping.
TABLE 2—MAXIMUM ESTIMATED CONCENTRATION VALUES
Hazardous Constituent '
Acotono ........ •
Butanol
Mothylene chloride. ...... »- •
Tetrachloroethylene « *
1,1,1-Ttrichloroethane •
Trichtoroethytene •
Loud ..«.....»...«...»..».»
Morcury ....»».....««.....«»
Selenium
Sjivor
'The following chemicals in this table are defined in the hazardous waste regulations solt
methanol, and (4) xylene. The other chemicals identified in the table are defined as toxic in the n
Key.T3»<1 ppm;T2=Fewppm;T=<0.1%;T=<1%; M=1-10%; D=>10%.
Waste Type I
T
T
T
T
T
T
T
T
T
T
T
T
T
T2
T2
jly for their ignit
azardous waste r<
Waste Type II
T
T
T
T
T2
T
D
T1
T2
T2
ability characteris
jgulations.
Waste Type III
T
T2
T
T2
T
T
T
T
T
D
T
D
T
Waste Type
D
T
M
T
D
M
M
M
T
T3
T
tics: (1) Acetone, (2) butanol,
IV
(3)
The primary halogenated organic
compounds identified as being present
in the wastes are tetrachloroethylene,
trichloroethylene, methylene chloride,
1,1,1-trichloroethane, carbon
tetrachloride, and l,l,2-trichloro-l,2,2-
trifluoroethane. These constituents are
regulated as hazardous under RCRA due
to their toxicity. The compounds are
commonly used as degreasing solvents
to clean metal surfaces and to solubilize
other compounds. As indicated in table
2, DOE estimates that halogenated
organics are not present in any of the
Type I, II, or III wastestreams at greater
than 1%.
The primary nonhalogenated organic
compounds identified as being present
in the wastes are xylene, acetone,
methanol, and butanol. These
constituents are regulated as hazardous
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13087
under RCRA due, to their ignitability
only. Like the halogenated compounds,
these compounds are used as degreasers
and solubilizers. As indicated in Table
2, DOE estimates that these constituents
also are not present in any of the Type I,
II, or HI wastestream at greater than 1%.
4. DOE's Analysis of Waste
Compatibility
DOE used the compositional data
described above to perform analyses to
demonstrate the compatibility of the
various wastes to be emplaced in the
WIPP. DOE first identified potential
incompatibilities; it then analyzed the
potential incompatibilities to determine
whether or not they would actually
occur. In performing these analyses,
DOE considered wastes to be
incompatible if the potential existed for
any of the folowing reactions: Corrosion,
explosion, heat generation, gas
generation (flammable gases), pressure
build-up (nonflammable gases), and
toxic by-product generation.
To identify incompatibilities, DOE
listed the materials and chemicals (with
their estimated concentrations)
contained in each Content Code
according to 41 reaction groups (e.g.,
metals and compounds, caustics, etc.).
That is, for each Content Code, all
pertinent reaction groups were
identified. DOE then identified all of the
reaction group combinations that could
occur within the same Content Code and
between different Content Codes
(assuming that wastes with different
Content Codes are mixed).
DOE performed compatibility
analyses for Rocky Flats wastes (both
within each Content Code and across
Content Codes) and for wastes across
all sites. In analyzing compatibilities
within each Rocky Flats Content Code,
19 potential incompatibilities were
identified. DOE evaluated each of the 19
cases and concluded that the required
processing (prior to placing the waste
into the containers) would eliminate the
potential incompatibility.
DOE's analysis of potential
incompatibilities across Rocky Flats
Content Codes were designed to
simulate a scenario in which individual
waste containers within TRUPACT-II
containers were breached and the
contents mixed. DOE identified six
potential reactions due to
incompatibilities. DOE discussed each
of the potential incompabilities and
concluded that, based upon a more
detailed analysis of the identity and
concentration of constituents within the
reaction groups, the reactions would not
occur.
In its analysis of compatibility of
wastes across all sites, DOE considered
S-041999 OI60(09X05-APR-90-14:19:27)
reaction of wastes with brine as well as
with wastes from other Content Codes.
DOE identified 59 potential
incompatibilities. After further
evaluation, however, DOE concluded
that the wastes would not result hi a
reaction.
5. Agency Analysis of Data
In comparing the process descriptions
with DOE's judgments as to the
identification of RCRA hazardous
constituents in the wastes, the Agency
believes that DOE's estimates to be
reasonable in most instances. The
Agency agrees with DOE's assertion
that assuming all hazardous constituents
associated with a process to be present
in the resultant wastestreams provides
for a conservative approach. Further, the
process descriptions suggest that the
hazardous solvent constituents are not
expected to be present in the wastes in
high concentrations,11 except for Waste
Type IV—Solidified Organics. (The
Agency notes that Waste Type IV will
account for only 3 percent of the wastes
that are to be emplaced in the WIPP
facility.) With respect to those wastes
that contain toxic heavy metals, while
these wastes may contain significant
concentrations of certain metals (e.g.,
lead), the Agency believes that the
potential for these constituents to leach
from the waste (and escape into the
environment) is minimal, considering the
form of the waste.
While this information is an important
basis for the Agency's conclusions, it
should be noted that in certain instances
DOE's judgments were not always
correct. In particular, in a number of
cases, DOE predicted that hazardous
constituents would not be present in
certain wastes; however, the analytical
results for these wastes indicated that
hazardous constituents were present,
albeit in low concentrations. Therefore,
the engineering judgments must be
viewed in concert with other
information (i.e., analytical data).
With respect to the analytical results,
the Agency is concerned with the
quality of DOE's analytical data. For
most of the data, DOE has been able to
provide little or no information as to
sampling plans and sample handling
procedures. Thus, the Agency is unable
to evaluate the extent to which the
11 While the data indicate that Waste Types I, II,
and HI may contain up to 1% of certain volatile
organics. the Agency would expect that most of the
wastes that contained these constituents (not every
Content Code contained each of the hazardous
constituents identified in Table 2) would contain
them at much lower levels based on waste type, the
volatility of these solvents, and the manner in which
these wastes are generated. This point is to some
extent confirmed by the analytical data.
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samples are-representative of the
wastes, although the Agency recognizes "
that analytical data was provided for all
the various wastes generated at Rocky
Flats and the Idaho National
Engineering Laboratory. In addition,
much of the data contain no indication
as to whether appropriate quality
assurance/quality control measures
were employed. As a result of these
shortcomings, the Agency believes that
additional analytical data will be
required before the Agency can consider
DOE's petition for the operational and
post-operational period. Nevertheless,
the Agency believes that sufficient
information was provided for DOE to
proceed with testing during the five-year
test phase. In particular, as is described
later in today's notice, the
concentrations at the unit boundaries
(using DOE's waste characterization
estimates) are expected to be well
below health-based levels. Therefore,
even if the characterization data
underestimate the hazardous constituent
concentrations by an order of
magnitude, the boundary concentrations
would still be expected to be below
hazardous levels. In addition, during the
test phase, the monitoring described in
Section IV.K of today's notice will
confirm that no migration of hazardous
constituents occurs during this period.
Should problems develop, the wastes
will be retrievable.
The Agency has also evaluated DOE's
analysis of waste compatibility. The
Agency agrees with DOE that no
incompatible reactions should occur as
a result of possible waste mixing. The
Agency reached this determination for
Rocky Flats wastes (both within each
Content Code and across Content
Codes) and for waste across all DOE
generator sites.
Finally, it should be noted that for
DOE to demonstrate no migration for the
operational and post-operational
periods, it will be necessary for it to
extrapolate information gained during
the test phase to behavior of the wastes
during the later phases. Thus, the
Agency is proposing to require that DOE
provide to the Agency the results of
detailed waste characterization and
analyses performed on the waste to be
emplaced in the WIPP during the test
phase (see Section V of today's notice);
in addition, as already indicated, the
Agency believes that during the test
phase additional waste characterization
data will need to be developed for those
wastes to be emplaced during the
operational phase. While DOE believes
that the wastes to be used in the test
phase (from Rocky Flats and Idaho
National Engineering Laboratory, as
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-^^^—^^^——^^^^•^^^•^^•••^^^^^^^^•••^^••••^^^^•••^^^^^^^^•^•^^M^MI^Mi^^^Bi^^^^^^*
described in section IV.I.3, above) are
representative of the wastes to. be
emplaced in the WIPP, the Agency
recognizes that variations in the
composition of wastes from different
facilities—even though the processes
are similar—are not uncommon. The
Agency therefore believes that
additional waste analysis will be
necessary to demonstrate more clearly
that the wastes from Rocky Flats and
Idaho National Engineering Laboratory
that are to be emplaced in the WIPP
during the test phase are, in fact,
representative of all of the wastes
scheduled for emplacement in the WIPP
facility.
J. No-Migration Demonstration
During the test phase, DOE intends to
conduct two types of in-situ tests
involving mixed wastes: bin-scale and
alcove tests. In the bin-scale
experiments, waste will be placed in
specially designed bins with various
combinations of brine, backfill, and gas
getter materials. In the alcove tests,
drummed wastes will be placed in
sealed alcoves. (These tests are
described in more detail in section IV.L
of this notice.) The Agency assessed the
possible levels of hazardous volatile
organic constituents at the unit
boundary during these experiments for
the organic solvents most commonly
present in TRU mixed wastes. The
proposed unit boundary for the air
pathway is the point where the air
exhaust shaft releases to the ambient
environment at the WIPP. As discussed
in section IV.K, air is the only plausible
pathway during the test phase for
migration from the land disposal unit.
In the bin-scale experiments,
headspace gases will be vented into the
bin discharge system whenever the bins
become pressurized through a pressure
relief valve installed on each bin. The
gases will then be passed on to the
exhaust shaft. Since the purpose of the
experiments is to gather data on the gas
generation potential for the various
types of wastes intended for disposal at
the WIPP, the rate of gas generation can
only be estimated from data gathered in
previous laboratory studies. In its
review of the gas generation data, the
Agency concluded that the possibility
that health-based levels might be
exceeded in the exhaust shaft could not
be eliminated. Therefore, the DOE has
provided for the inclusion of a carbon
canister in the bin gas discharge system
to remove any volatile organic
constituents released from the bins.
Given the uncertainty inherent in
conducting the experiments, the Agency
agrees that such a control device is
appropriate. (Although this part of the
no-migration demonstration depends on
the integrity of artificial containment
mechanisms, EPA does not believe the
use of air control devices for a
temporary period (i.e., the operational
period) precludes an approval of the no-
migration petition. As noted earlier in
the discussion of the temporary seals,
EPA does not read the legislative history
(S. Rep No. 284 at 15) as precluding EPA
from considering the integrity of
artificial barriers during a limited
period.)
To be assured that there is no
migration above health-based levels, the
Agency is proposing to require the
carbon adsorption control device to be
installed in the bin discharge system of
each room be designed to achieve a
control efficiency of at least 95
percent.12 The Agency believes a 95
percent control efficiency is readily
achievable by carbon adsorption
systems (see 52 FR 3748, February 5,
1987). In addition, the Agency is
proposing to require that certain records
be maintained in the facility operating
record to ensure that the above
requirement is met and that the spent
carbon (which will contain the
hazardous constituents) will not be
improperly regenerated or disposed. In
particular, the following records would
have to be kept in the facility operating
record: (1) The date and time when the
carbon in the control device is replaced
with fresh carbon and when samples are
collected for monitoring carbon
breakthrough, along with records of the
monitoring results; (2) engineering
design analyses used to size the control
device and to determine the frequency
of carbon replacement; and (3) a signed
certification that all carbon removed
from the control device is regenerated or
reactivated by a process that minimizes
the release of organics to the
atmosphere by means of a condenser,
thermal vapor incinerator, catalytic
incinerator, or similar emission control
system; is incinerated in a device that
meets the performance standards of 40
CFR part 264, subpart O; or is disposed
i^ouifipiiciiiue wmi reuerai ana state
regulations.
The Agency used for its assessment
the concentrations of volatile organic
compounds measured in the headspace •.
of 209 drums'and standard waste boxes. -.
sampled at random from waste form
categories generated at the Rocky Flats
Plant and stored at Idaho National
Engineering Laboratory. The waste form
categories .when sampled were expected
to comply with the requirements of the
WIPP-WAC, although upon subsequent
visual examination and radionuclide
reassay DOE found only 179 of the
original 209 to be WAG certifiable (after
modifying the initial WAG assessment
to allow a free liquid residual of up to 1
percent by volume). The Agency views
the analytical results from these
headspace samples as being semi-
quantitative, for the reasons previously
described in section IV.I of this notice.
The results of the Agency's
assessment are shown in Table 3 below
along with levels of regulatory concerns.
The Agency conservatively assumed
that both rooms reserved for the bin-
scale experiments are filled to capacity.
The capacity of each room is 120 bins;
therefore, the total number of bins is
240. The Agency then assumed an
average gas generation rate of 5 moles
per drum per year, a figure the DOE
characterizes as representing the upper
bound of the range of credible gas
generation rates (Test Plan: WIPP Bin-
Scale CH TRU Waste Tests, January
1990; SAND89-0462). Each bin can hold
the equivalent of 6 drum volumes of
waste. Therefore, DOE's upper bound
gas generation rate is equivalent to a
total gas generation rate from all 240
experimental bins of 0.5 cubic meters
per day.13 The DOE has specified the
general ventilation rate through the
repository as 425,000 cubic feet per
minute which is equivalent to 17,000,000
cubic meters per day. This entire volume
of air is exhausted at the exhaust shaft
and is available to mix with any gases
released from the bin discharge system.
The resulting dilution factor at the
exhaust shaft if 34,000,000. The dilution
factor is applied to the average
headspace concentrations, together with
the control device efficiency, to
calculate the concentration of
constituents in the exhaust shaft.
12 While DOE has submitted a preliminary design
of the carbon adsorption control device, the Agency
has not been able to determine with the information
provided what control efficiency the device will
achieve. Therefore. EPA is proposing to require that
the carbon adsorption control device be designed to
achieve at least a level of 95 percent efficiency.
13 The Agency notes that even if the gas
generation rate is higher (e.g., 25 moles per drum per
year), the concentrations at the unit boundary
would still be below health-based levels, given the
requirement for a carbon adsorption system with a
95 percent control efficiency.
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TABLE 3—TEST PHASE COMPLIANCE POINT CONCENTRATIONS IN AIR
Constituents
Carbon tetrachloride ;
Methvlene chloride.
Trichloroethylene . .
1,1 1-Trichloroethane
1,1,2-Trichloro-1,2,2-trifluouroethane
Average
headspacd
concentrations
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the underground repository, make the
possibility of fire or explosion extremely
unlikely. The Agency notes that, while
DOE is planning to monitor the
repository for explosive or flammable
gases, monitoring is limited to three
fixed locations within the repository.
The Agency, therefore, is soliciting
comment on whether routine monitoring
should be conducted with portable
explosimeters to detect any localized
buildup of methane, hydrogen, or other
flammable gases underground.
In accordance with the requirements
of 40 CFR 268.6(c), the petition includes
an air monitoring plan which describes
DOE's plan to monitor for the presence
of organic solvent vapors and other
volatile organic compounds at the unit
boundary during the test phase. The
monitoring plan involves localized
monitoring of gases released during the
course of experimental activities with
TRU mixed wastes, confirmatory
monitoring at the underground
repository exhaust shaft, and
background monitoring at the main air
intake shaft. The Agency is proposing to
require that DOE implement the air
monitoring plan submitted with the
petition, subject to the clarifications and
modifications discussed below.
The Agency is proposing to require
that the monitoring in the exhaust shaft
begin 30 days prior to the emplacement
of any experimental wastes
underground. Monitoring of the bin-
scale experiment rooms under today's
proposal would have to commence prior
to emplacement of any bins containing
TRU wastes in the rooms. Monitoring of
the alcoves would have to commence
prior to the initiation of experiments in
the alcoves, after the alcoves are sealed
and prior to any purging of the alcove
atmosphere. The Agency does not
believe that monitoring of the alcoves
should be required to begin with
'emplacement of the first drum of waste.
The DOE has demonstrated that
migration above health-based levels will
not occur if as many as 85,000 waste
drums are emplaced in the repository
prior to sealing the rooms. By
comparison, only 3,850 drums of
experimental waste are to be emplaced
in the alcoves. Given the small number
of drums and given that monitoring will
be conducted in the exhaust shaft during
the emplacement of waste drums in the
alcoves, the Agency has concluded that
monitoring of the alcoves may begin
when the alcove experiments are
initiated.
1. Location and Frequency
The monitoring plan provides for air
monitoring at the following underground
locations: (1) The gas discharge system
for each of two rooms containing the
experimental bins; (2) the ventilation air
intake and outlet passageways serving
the two rooms containing the bins; (3)
the atmospheres within the five alcoves
containing wastes; (4) the exhaust shaft;
and (5) the main air intake shaft. (See
the Background Document for a diagram
that indicates the specific monitoring
points.) Flow rates will be monitored at
the downstream end of the gas
discharge system for the bins and at the
exhaust shaft. The Agency is also
proposing to require that the leakage
rate of the sealed alcoves be measured
by means of the injection of tracer gases
into the atmosphere within each alcove
and monitoring of the tracer gas levels.
The Agency believes this is necessary to
ensure the validity of the data collected
from the alcoves. As provided for in the
monitoring plan, air concentrations in
the exhaust shaft will be calculated from
the analytical results from the bin and
alcove samples and the measured air
flow and alcove leakage rates. ,
Monitoring of the exhaust shaft and the
mam ah- intake shaft will provide
additional measurements for
comparison with the calculated
concentrations.
To obtain representative samples,
DOE will collect integrated 24-hour
samples at all locations with the
exception of the alcoves, where the gas
composition is expected to remain
relatively stable over time. Grab
samples are judged to be sufficient for
monitoring the alcoves.
Initially, samples will be collected
daily at all locations except for the
exhaust shaft and the main air intake
shaft. After 30 days of daily sampling at
a monitoring location, the frequency of
sampling at that location may be
reduced from daily to weekly if the
monitoring results are relatively
constant over time, as indicated by a
relative standard deviation (RSD) of not
more than 25 percent over the last 30-
day period for any targeted constituent.
DOE requested in its petition that the
monitoring frequency be allowed to be
reduced further, from weekly to
monthly, if after 12 weeks the RSD of
any targeted constituent was not more
than 25 percent. The Agency is
concerned that monitoring on a monthly
schedule may not adequately detect or
characterize changes in air releases that
may occur with the inclusion of new
waste forms in experimental bins and
alcoves as the testing program
progresses. Therefore, the Agency is
proposing that, at a minimum, samples
be collected weekly. The Agency is also
proposing that the exhaust shaft and air
intake locations be monitored weekly
for the same reasons. However; the
Agency is soliciting comment on
whether 1o allow a further reduction in
monitoring'frequency. In addressing'•this
point, commenters should specify a
sampling frequency and the rationale for
selecting a particular frequency.
EPA believes, however, that in no
event should the monitoring frequency
for the bin discharge system be reduced
to less than 20 percent of the minimum
time required for the consumption of the
total working capacity of the carbon
adsorption system. The Agency believes
this requirement is necessary to ensure
that, should the total working capacity
of the carbon bed be exceeded
prematurely and breakthrough occur,
the event will be detected in sufficient
time to take corrective action and
replace the carbon charge.
In the event that weekly monitoring
results exhibit increased variability, the
Agency believes that daily sampling
should be reinstituted. Therefore, the
Agency is proposing to require that daily
sampling be resumed if the calculated
RSD for the preceding 4-week period at
a monitoring location exceeds 75
percent for any targeted constituent.
Daily sampling would have to continue
until such time as the criteria for a
reduction in frequency to weekly
sampling are met again.
2. Hazardous Constituents
Air monitoring will be conducted for
the organic solvents most commonly
present in the wastes destined for the
WIPP facility. The constituents
specifically targeted for routine
quantitation in the monitoring plan are
carbon tetrachloride, methylene
chloride, trichloroethylene, 1,1,1-
trichloroethane, and 1,1,2-trichloro-
1,2,2,-trifluoroethane. In addition to
these five compounds, the presence of
other volatile organics will be
investigated and evaluated for possible
inclusion in the monitoring program.
Specifically, the Agency is proposing to
require that any volatile organic
compound be targeted for routine
quantitation if the average estimated
concentration at the point of sampling is
1 ppm or .more during any 4-month
period and the compound is detected in
at least 10 percent of the samples
collected from the gas discharge system
from either room containing bins or 50
percent of the samples collected from
any alcove. The Agency believes that
identification and semiquantitative
analysis of other compounds is
reasonable and necessary as a
precautionary requirement, given the
limited waste sampling and analysis
data available at DOE's waste-
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13091
generating sites and the limitations on
those data., ' .
To carry ont this requirement most
effectively, EPA is proposing to require
that DOE implement standard operating
procedures that will provide positive
identification of the following
compounds: Perchloroethylene;
chloroform; bromoform; dichloroethane;
dichloroethylene; toluene; and
chlorobenzene. These hazardous
constituents have been identified by
DOE as being present in TRU mixed
wastes at low concentrations and can
be determined quantitatively with the
TO-14 method. Therefore, the Agency
believes these constituents are good
candidates for inclusion in the
monitoring program as targeted
constituents if detected in significant
amounts.15
As a criterion for inclusion of a
constituent as one targeted for routine
quantisation, the Agency is proposing to
allow a higher frequency of detection for
the alcoves than for the bins because
once an alcove is filled with
experimental wastes and sealed and the
experiment begins, the composition of
the alcove gases is expected to change
only slowly. In contrast, because each
bin represents a separate experiment, a
highly heterogeneous and time-varying
composition of gases is expected in the
bin discharge system.
Although the Agency believes that
monitoring for the five target
constituents listed above in conjuction
with specific criteria for inclusion of
additional constituents is sufficient, the
Agency is soliciting comment on
whether other constituents should be
targeted for routine quantitation.
3. Sampling and Analysis
The monitoring plan provides for
sampling and analysis to be performed
using EPA Compendium Method TO-14.
• The Agency believes the method is well
suited for routine monitoring of the more
toxic and most prevalent organic
solvents found in TRU mixed wastes.
The method is capable of detecting the
hazardous constituents targeted for
quantitation with a sensitivity below 1
part per billion. Samples will be
collected in pressurized six liter
SUMMAR passivated stainless steel
canisters. Sample storage stability has
been demonstrated for a variety of
volatile organic compounds with this
type of container. Individual canisters
15 The Agency notes that most other volatile
organic constituents found in TRU mixed wastes are
listed as hazardous in 40 CFR part 261 because of
their exhibiting the characteristic of ignitability
rather than their being toxic. Such constituents are
generally only hazardous when present at high
concentrations.
are required to be certified clean and
free of leaks prior to each usage. The
method requires that all samplers,
including pumps and -valves, also be
certified to ensure cleanliness and
reliable sample recovery.
Samples will be analyzed by high-
resolution gas chromatography, followed
by full scanning mass spectrometry
(GC/MS/SCAN) to provide the
capability to identify a wide variety of
volatile organic compounds. Cryogenic
focusing can be used to concentrate
samples as needed to meet analytical
detection limits. The GC/MS analytical
system is required to be certified clean
with humidified zero air prior to sample
analysis. Consistent with "Test Methods
for Evaluating Solid Waste, Physical/
Chemical Methods" Method 8240 "Gas
Chromatography/Mass Spectrometry for
Volatile Organics" (EPA Publication
SW-846, Third Edition), the Agency is
proposing to require that an average
response factor for each target analyte,
as determined by a five-point instrument
calibration, be used for quantitation.
(Target analytes are the five
constituents initially targeted plus any
other constituents subsequently targeted
for routine quantitation based on the
criteria described previously.) In
addition, the initial calibration and any
subsequent recalibrations would be
required to satisfy the criterion that any
single response factor differ by no more
than 25 percent from the average of the
five. However, if it can be demonstrated
that the instrument response is
nonlinear, the initial calibration and any
subsequent recalibrations would have to
satisfy the criterion that any single
response factor differ by no more than
25 percent from the expected value
derived from regression analysis. For
the purpose of investigating the
presence of other volatile organic
compounds, EPA proposes that a
forward search of the National Bureau
of Standards library of mass spectra be
performed on each sample analyzed.
4. Quality Assurance and Quality
Control
The Agency is proposing to require
that standard operating procedures be
adopted to ensure the validity of the
monitoring data. These would cover a
range of activities, including sampling
and analysis certification procedures,
instrument calibration checks, duplicate
sampling, audit cylinder sampling,
technical systems audits, and data
quality audits.
All flow measurement instrumentation
used in the calculation of exhaust shaft
concentrations would have to be
calibrated in accordance with EPA
Reference Method 2 "Determination of
Stack Velocity and Volumetric -Flow
Rate (Type S Pitot Tube)," Method 2A
"Direct Measurements of-Gas Volume
Through Pipes and Small Ducts" (40 CFR
part 60 appendix A), or an equivalent
method approved by EPA. EPA is also
proposing to require that the
calibrations be performed quarterly due
to the possible effect of salt aerosols in
the repository enivironment on flow
measurement instrumentation.
To ensure sample integrity, Method
TO-14 requires that all sample canisters
be cleaned, pressure tested, and
certified with humidified zero air
initially and following each sampling
event prior to reuse. Method TO-14 also
requires that all samplers (which
includes pumps, valves, and peripheral
equipment used for sampling) be
removed from service for routine
maintenance and be leak tested and
certified with humidified zero air and
humidified gas calibration standards.
The monitoring plan submitted by DOE
indicates that all samplers will be
certified on a quarterly schedule.
Method TO-14 requires that GC/MS
tuning be performed daily with 4-
bromofluorobenzene to verify proper
analytical system functioning, that
instrument calibration be checked daily
with a one point midrange humidified
calibration gas standard for each
targeted analyte, and that the GC/MS
analytical system be certified clean with
humidified zero air daily prior to sample
analysis. Consistent with SW-846
Method 8240, the Agency is proposing to
require that the instrument be
recalibrated by a full five point
calibration if the response factor from
the calibration check differs by greater
than 25 percent of the average or
expected response factor. All gas
calibration standards must be traceable
to a National Bureau of Standards
standard reference material or an EPA-
approved certified reference material.
To ensure that constituents are
capable of being detected with the
necessary degree of sensitivity, the
Agency is proposing to require that the
method limit of quantitation be
established for each target analyte prior
to the initiation of the monitoring
program and that it be reevaluated
annually thereafter in accordance with
the specifications in "Report on
Minimum Criteria to Assure Data
Quality" (EPA/530-SW-90-021,
December 12,1989). The Agency is
further proposing to require that the
method limit of quantitation be
determined separately for the bin,
alcove, and exhaust shaft monitoring
locations due to the possible occurrence
of differential matrix effects associated
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Federal Register / Vol. 55, No. 67 / Friday, April 6. 1990 / Notices
with the presence of salt aerosols in the
repository environment.
In addition to the implementation of
canister and sampler certification and
analytical calibration procedures,
routine quality control procedures must
be implemented to evaluate data
accuracy, precision, and completeness.
In order to evaluate the accuracy of the
monitoring data, the Agency is
proposing to require that recovery
samples be collected from audit
cylinders and analyzed at a frequency of
10 percent at each monitoring location.
In order to evaluate the precision of the
monitoring data, the Agency is also
proposing to require that duplicate
samples be collected and analyzed at a
frequency of 10 percent at each
monitoring location, including the
exhaust shaft. In addition, the Agency is
proposing to require that data
completeness be evaluated by data
validation audits at a frequency of not
less than 5 percent. The Agency believes
that data validation is an essential part
of the monitoring program and that the
proposed audit frequency represents an
adequate but not burdensome level of
quality control. To ensure that any
sampling and analysis problems which
may occur are detected and corrected,
accuracy, precision, and completeness
would have to be tracked and evaluated
after every 10 quality control analyses.
DOE's monitoring plan indicates that
a systems audit will be conducted at the
start of the monitoring program. The
Agency is proposing to require that
systems audits be performed not only
prior to the initiation of the monitoring
program but also semi-annually
thereafter to be consistent with good
operating practice. In addition,
corrective action must be taken
whenever a condition or practice is
found which is outside system
specifications or standard operating
procedures, or which could reasonably
be expected to compromise the ability of
the monitoring program to meet
established quality assurance objectives
for data acceptability.
The Agency is also proposing to
establish specific quality assurance
objectives for data acceptability for the
WIPP air monitoring program consistent
with method capability and good
operating practice. DOE has raised
concerns regarding the establishment of
specific quality assurance objectives
due to the presence of salt aerosols in
the underground repository
environment. EPA believes that regular
maintenance of sampling equipment will
adequately address sampling and
analysis difficulties imposed by the
repository environment. The Agency
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believes the following quality assurance
objectives are .achievable: plus or minus
10 percent for relative accuracy as
indicated by the relative difference
between the measured concentration
recovered from a sampler and the
known concentration of the targeted
analyte in the audit gas cylinder; 15
percent for precision as indicated by the
relative difference between field
duplicate samples; 90 percent for data
completeness as adjusted statistically to
account for the results of data validation
audits; and 0.5 part per billion by
volume for method limit of quantitation
or one fifth of any established health-
based level for a targeted constituent,
whichever is greater. The Agency is
therefore proposing to require these as
quality assurance objectives for data
acceptability and to require that
corrective action be taken whenever
these objectives are not being met.16
5. Reporting
If during the course of the monitoring
program migration above health-based
levels of any hazardous constituent is
detected, DOE is required under 40 CFR
268.6[f)(2) to notify the Administrator in
writing within 10 days. To determine
whether migration has occurred (i.e.,
any of the targeted constituents exceed
health-based levels at the unit
boundary), the Agency is proposing that
concentrations be averaged over an
annual time period. This is consistent
with the approach the Agency is taking
in providing guidance to other parties
submitting no-migration petitions to the
Agency. The Agency believes that
concentrations should be averaged over
an annual time period because the
health-based levels are derived by
assuming chronic or lifetime exposures.
The Agency is further proposing that the
incremental contribution from the land
disposal unit, over and above measured
background levels at the site, be used in
making the determination. The Agency
does not believe that background levels
should be a reason for the Agency to
18 DOE has recently submitted data from an
experimental study designed to address the
question of what quality assurance objectives can
be achieved in the underground repository
environment (see Research Triangle Institute,
Analysis of Very Volatile Organic Compounds in
Canisters from the Waste Isolation Pilot Plant,
March 20,1990). Because the experimental data
were submitted very recently, the Agency has not
had the time to evaluate it. However, EPA will
evaluate these data in comparison to the proposed
quality assurance objectives in today's notice. The
Agency solicits public comment on DOE's
experimental study results, and on what specific
quality assurance objectives EPA should require
DOE to meet.
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deny or revoke the variance -proposed iti
today:s notice.17
In order that-the Agency be notified at
the earliest possible time of any- •.
likelihood that migration is occurring,
the Agency is proposing to require that
DOE notify the Administrator in writing
within 10 days if during any three-month
period the average concentration of any
hazardous constituent measured or
calculated in the exhaust shaft over and
above background levels exceeds a
health-based level established by the
Agency. In addition, the Agency is
proposing to require the submittal of
annual data summaries and summaries
of data accuracy, precision, and
completeness at each monitoring
location, together with calculated
concentrations at the exhaust shaft and
documentation of the actual method
limit of detection achieved for each
targeted analyte. These data would have
to be submitted to the Chief, Technical
Assessment Branch, Characterization
and Assessment Division, Office of
Solid Waste, U.S. Environmental
Protection Agency. In addition,
documentation on all aspects of quality
assurance and quality control as
described in "Report on Minimum
Criteria to Assure Data Quality" (EPA/
530-SW-90-021, December 12,1989)
must be maintained in the WIPP facility
operating record and be available for
inspection by the Agency.
L. Performance Assessment
A primary objective of the test phase
is to demonstrate compliance with the
applicable standards that would govern
long-term disposal of TRU wastes in the
WIPP. These standards will include 40
CFR part 191 for disposal of the
radioactive wastes and 40 CFR 268.6 to
demonstrate no migration of the
chemical hazardous constituents of the
TRU mixed waste. The process through
which DOE will investigate compliance
with these standards is called
performance assessment. This will
consist of an analysis of all aspects of
repository performance under all
conditions of interest as well as
experiments to collect data and verify
models used in the analyses. The
analytical and experimental processes
will be coordinated to arrive at
predictions of repository performance.
During the test phase, DOE has an
extensive and varied series of
experiments planned. For example, the
test plan contains 66 different categories
of supporting activities for the
17 As described previously, DOE plans to perform
monitoring of background levels in the main air
intake shaft.
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13093
performance assessment, of which 30
involve in-situ experiments of different
types. These experiments will include
measurements'to better define the
characteristics of the surrounding
geology, as well as studies of the
performance of each component of the
repository system (e.g., seals, backfill,
etc.). Most of these activities involve
experiments that do not use radioactive
wastes.
One of the major areas of uncertainty
to be addressed during the test phase,
however, is the amount of gas that may
be generated from the waste proposed
for disposal at the WIPP. Gas will
primarily be generated by corrosion of
the waste containers, microbial
decomposition of the waste and
radiolysis of the waste. Gas generation
is important because the amount of gas
generated could affect the way in which
the repository reconsolidates over time,
and the amount of brine that may flow
into the repository. Too much gas
generation could even lead to extra
fracturing in the surrounding geologic
media and could create pathways for
waste migration.
DOE plans to conduct several types of
gas-generation experiments in the
underground repository. One series of
tests would use instrumented metal bins
containing specially-prepared
transuranic wastes and various
combinations of backfill, brine, and gas
getter materials. These bin-scale
experiments are to be conducted in
three phases. Phase I will involve
approximately 48 waste-filled bins of
different waste compositions and
backfills. Phase 2 will incorporate
another 68 bins with more moisture
conditions, gas-getter materials and
supercompacted high-organic and low-
organic wastes. The details of Phase 3 of
the bin-scale tests will be defined later.
DOE, however, anticipates that these
•tests will be based on new
developments, the results of Phases 1
and 2, and future data needs.
In addition to underground bin-scale
tests, the DOE test plan proposes
underground alcove tests with TRU
wastes. A test alcove is a room mined in
the salt with one blind end and one open
end sealed with a leak-tight closure
plug. Each of the six planned alcoves is
approximately 100 feet long, 25 feet
wide, and 13 feet high. A total of 3,850
drums of TRU wastes will be emplaced
in five of the six alcoves; one alcove will
be left empty to provide gas reference
baseline data. These tests will continue
until the data acquired are sufficient to
provide confidence in the reliability of
the information being obtained.
DOE will also study modifications to
the backfill material, repository design,
and the wastes that may reduce the gas
generation problem. Types of
modifications to be considered will
include waste compaction, waste
processing (e.g., incineration or
immobilization), modifying the storage
room or panel configuration, and other
changes in the WIPP design, such as
modified seals. DOE has established an
Engineered Alternatives Task Force to
evaluate such potential modifications.
Whenever feasible, modifications that
appear beneficial will be'included in the
test program so that their effects on gas
generation and repository performance
can be measured. (Some of these
modifications will not have a direct
bearing on gas generation, but will
affect other aspects of repository
performance, such as brine inflow, that
may affect potential releases of waste
from the respository).
At the end of the test phase, DOE
expects to be in a position to predict the
amounts of gas generated by different
combinations of waste forms, container
materials, and repository design steps
such as gas getters, backfill
modifications, etc. The effects of gas
generation on long-term repository
performance will then be predicted by
analytical models, with validation of
certain aspects of these models by in-
situ testing. The net result of all of these
activities will be recommendations
about the appropriate waste forms and
repository design to use for the WIPP, or
even whether the WIPP is appropriate to
use for permanent disposal of
transuranic wastes. These
recommendations will be based in part
upon comparisons with the various EPA
standards for radioactive and hazardous
wastes.
The Agency believes that gas
generation and its effects are significant
questions that need to be better
understood before a decision can be
made as to the use of WIPP as a
permanent repository. The Agency
believes that DOE has laid out a
reasonable approach for defining the
amount of gas that should be generated
by different combinations of waste and
engineering controls. Perhaps the most
difficult part of the problem is predicting
the effects of different levels of gas
generation on long-term repository
performance. In its comments on DOE's
test plan, the Agency has requested that
DOE publish, as soon as possible, a
summary of its models, describing the
effects of gas generation, and more
information about its plans to validate
these models. DOE has agreed to
develop a summary of the current status
of its performance assessment,
scheduled for June 1990.
In addition, DOE plans to develop
annual "consequence analysis reports"
throughout the test program to document
the project's progress, and it has agreed
to give periodic briefings on the project
to EPA, the National Academy of
Sciences WIPP Panel, the State of New
Mexico, and the Environmental
Evaluation Group (EEG) (an
organization established by act of
Congress to provide an independent
technical evaluation of the WIPP). To
ensure that EPA is adequately informed
of the progress of the test phase, EPA is
proposing to require that DOE provide
annual reports describing tests
conducted to date (including results),
modifications to the test plan, and a
summary of DOE's understanding of the
repository performance.
V. Conditions of Proposed Variance
AS a condition of granting this
proposed variance from the land
disposal restriction requirements, EPA is
proposing that the following conditions
be met fay DOE:
(1) No wastes subject to this variance
may be placed in the WIPP repository
for purposes other than testing or
experimentation to determine the long-
term viability of the WIPP. In
accordance with 40 CFR 268.6(e), EPA
must be notified before DOE conducts
any testing or experimentation not
within the scope of the "Draft Final Plan
For the Waste Isolation Pilot Plant Test
Phase: Performance Assessment"
(December 1989, DOE WIPP 89-011).
Placement of waste for the primary
purpose of conducting an operations
demonstration is prohibited under this
variance.
(2) All wastes placed in the WIPP
under this variance must be removed if
DOE's Performance Assessment cannot
demonstrate compliance with the
standards of 40 CFR 268.6 with respect
to permanent disposal of mixed waste in
the repository. Hazardous wastes
removed from the WIPP must be
handled in accordance with RCRA
subtitle C requirements. (A condition of
40 CFR 268.6(a)(5) is in compliance with
other applicable Federal, State and local
laws. Therefore, removal will also be
required-under this variance if DOE
cannot comply with 40 CFR part 191
standards for the disposal of radioactive
materials.)
(3) All wastes placed in the WIPP
under this variance must be placed in a
readily retrievable manner, as described
in section IV.D of this notice.
(4) DOE must provide to the EPA
Office of Solid Waste annual written
reports on the status of DOE's
performance assessment during the test
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phase. These reports must include: a
description of the tests'to date and their
results, modifications to the test plan, a
summary of DOE's current
understanding of the repository's
performance, and an annual summary of
air monitoring data required in item 6
below.
(5) DOE must install and operate a
carbon adsorption control device
designed to achieve a control efficiency
of 95 percent in the discharge system of
the bin experiment rooms. DOE must
monitor the control device outlet
airstream in accordance with the
monitoring plan described in section
IV.K of today.'s.notice, and it must
maintain design and operating records
as described in section IV.J.
(6) DOE must implement the air
monitoring plan described in section
IV.K.
(7) Before placing waste in the
repository, DOE must certify to EPA that
it has secured control of the entire
surface and subsurface estate at the
WIPP site.
(8) DOE must provide to EPA the
results of detailed waste
characterization and analyses
performed on the waste to be emplaced
in the WIPP during the test phase.
Beyond these specific conditions, the
wastes placed by DOE in the WIPP and
DOE's activities under this variance
must be consistent with those described
in the petition. Under § 268.6(e), DOE
must notify EPA of "any changes in
conditions at the unit and/or
environment that significantly depart
from the conditions described in the
variance and affect the potential for
migration of hazardous constituents
from the unit* * *." If the change is
planned, EPA must be notified in writing
30 days in advance of the change; if it is
unplanned, EPA must be notified with in
ten days".
Under" §"268.6(f),4f DOE determines
that there has been migration of
hazardous constituents from the
repository in violation of part 268, it
must suspend receipt of restricted
wastes at the unit and notify EPA within
ten days of the determination. Within 60
days, EPA is required to determine
whether DOE can continue to receive
prohibited waste in the unit and
whether the variance should be revoked.
Finally, under § 268.6(h), the term of
today's proposed variance would run for
ten years from the date of approval.
Dated: April 2,1990.
Don R. Clay,
Assistant Administrator for Solid Waste and
Emergency Response,
[FR Doc. 90-8092 Filed 4-5-90; 8:45 am]
BILLING CODE 6560-50-M
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