[Federal Register Volume 82, Number 137 (Wednesday, July 19, 2017)]
[Notices]
[Pages 33106-33122]
[FR Doc No: 2017-15182]

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ENVIRONMENTAL PROTECTION AGENCY

[EPA-HQ-OAR-2014-0609; FRL-9965-08-OAR]

Criteria for the Certification and Recertification of the Waste
Isolation Pilot Plant's Compliance With the Disposal Regulations;
Recertification Decision

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice; recertification decision.

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SUMMARY: With this notice, the Environmental Protection Agency (EPA or
the Agency) recertifies that the U.S. Department of Energy's (DOE)
Waste Isolation Pilot Plant (WIPP) continues to comply with the
``Environmental Standards for the Management and Disposal of Spent
Nuclear Fuel, High-Level and Transuranic (TRU) Radioactive Waste.''
    This action represents the Agency's third periodic evaluation of
the WIPP's continued compliance with the disposal regulations and WIPP
Compliance Criteria. The WIPP Compliance Criteria implement and
interpret the disposal regulations specifically for the WIPP. As
directed by Congress in the WIPP Land Withdrawal Act (WIPP LWA), this
``recertification'' process is required every five years following the
WIPP's initial receipt of TRU waste on March 26, 1999 (e.g., March
2004, March 2009), until the end of the decommissioning phase. For each
recertification--including the one being announced with this action--
the DOE must submit documentation of the site's continuing compliance
with the disposal regulations to the EPA for review.
    This recertification decision is based on a thorough review of
information submitted by the DOE, independent technical analyses, and
public comments. The Agency has determined that the DOE continues to
meet all applicable requirements of the WIPP Compliance Criteria, and
with this action, recertifies the WIPP facility. This recertification
decision does not otherwise amend or affect the EPA's radioactive waste
disposal regulations or the WIPP Compliance Criteria. In addition,
recertification is not subject to rulemaking or judicial review, nor is
it linked to the resumption of disposal activities at the WIPP
facility. The EPA has also identified areas in which the DOE's
technical analyses and justifications could be improved for the next
recertification application.

FOR FURTHER INFORMATION CONTACT: Ray Lee, Radiation Protection
Division, Mail Code 6608T, U.S. Environmental Protection Agency, 1200
Pennsylvania Avenue Washington, DC 20460; telephone number: (202) 343-
9463; fax number:<PHONE_NUMBER>; email address<EMAIL_ADDRESS>
Copies of the Compliance Application Review Documents (CARDs)
supporting this action and all other recertification-related
documentation can be found in the Agency's electronic docket found at
www.regulations.gov (Docket ID No. EPA-HQ-OAR-2014-0609).

SUPPLEMENTARY INFORMATION:

Table of Contents

I. General Information
II. What is the WIPP?
    A. Background
    B. Impacts of the February 2014 Incidents on the Repository
III. Compliance Certification History
    A. 1998 Certification Decision
    B. 2006 Recertification Decision
    C. 2010 Recertification Decision
IV. With which regulations must the WIPP comply?
    A. Compliance with Radioactive Waste Disposal Regulations & the
WIPP Compliance Criteria
    B. Compliance with Other Environmental Laws and Regulations
V. Continuing Compliance with the WIPP Compliance Criteria
    A. Annual Change Reports
    B. Monitoring the Conditions of Compliance
    1. Panel Closure Rulemaking
    2. Quality Assurance
    3. Waste Characterization
    4. Passive Institutional Controls
    C. Inspections
V. What is the EPA's 2017 Recertification Decision?
    A. Performance Assessment and the EPA's Standards
    B. Summary of the EPA's Review
    C. What information did the Agency examine to make the final
decision?
    D. Content of the Compliance Recertification Application
(Sec. Sec.  194.14 and 194.15)
    1. Changes to the Disposal System Identified by the DOE
    a. Update to the Drilling Rate and Borehole Plugging Patterns
    b. Replacement of Option D Panel Closure System With Run-of-Mine
Salt Panel Closure Design
    c. Modeling of Open Areas in the Repository
    d. The DOE's Revised Estimate of the Probability of Encountering
Pressurized Brine
    e. Revised Corrosion Rate of Steel
    f. Revised Effective Shear Strength of the WIPP Waste
    g. Revised Repository Water Balance
    h. Variable Brine Volume
    i. Revised Colloid Parameters
    j. New Actinide Solubility Code (EQ3/6)
    2. Other Key Issues Identified by the EPA During Review
    a. Actinide Solubilities
    b. Solubility Uncertainty Distribution
    c. Plutonium Oxidation States
    E. Performance Assessment: Modeling and Containment Requirements
(Sec. Sec.  194.14, 194.15, 194.23, 194.31 through 194.34)
    1. Overview
    2. Sensitivity Studies
    a. The SEN1 Study
    b. The SEN2 Study
    c. The SEN3 Study
    d. The SEN4 Study
    i. Overview
    ii. Cumulative Effects of the Changes Evaluated by Release
Pathway
    aa. Direct Brine Releases
    bb. Spallings Releases
    cc. Cuttings and Cavings Releases
    dd. Releases From the Culebra
    ee. Insights from the SEN4 Study
    3. How the Four Sensitivity Studies Affect the WIPP Compliance
    F. Additional Requirements
    1. Waste Characterization (Waste Inventory (Sec.  194.24)
    2. Peer Review (Sec.  194.27)
    G. Individual and Groundwater Protection Requirements
(Sec. Sec.  194.51 Through 194.55)
VII. How has the public been involved in the EPA's WIPP
Recertification activities?
    A. Public Information
    B. Stakeholder Meetings
    C. Public Comments on Recertification
VIII. Where can I get more information about the EPA's WIPP-related
activities?
    A. Supporting Documents for Recertification
    B. The WIPP Web site & WIPP-NEWS Email Listserv
    C. Dockets
IX. What is the EPA's role in future WIPP activities?

Abbreviations

CARD Compliance Application Review Document
CFR Code of Federal Regulations
DOE U.S. Department of Energy
EPA U.S. Environmental Protection Agency
FR Federal Register
NMED New Mexico Environment Department
OAR Office of Air and Radiation
Pa Pascal
PBRINE Parameter: Probability Distribution of Encountering Brine
RCRA Resource Conservation and Recovery Act
SEN Sensitivity Study
TRU Transuranic
TSD Technical Support Document
WIPP Waste Isolation Pilot Plant
WIPP LWA WIPP Land Withdrawal Act

I. General Information

A. How can I get copies of this document and other related information?

    1. Docket. The EPA has established a docket for this action under
Docket ID No. EPA-HQ-OAR-2014-0609. Publicly available docket materials
are available either electronically at http://www.regulations.gov or in
hard copy at the Air and Radiation Docket in the EPA

Docket Center, (EPA/DC) EPA West, Room B102, 1301 Constitution Ave.
NW., Washington, DC. The EPA Docket Center Public Reading Room is open
from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal
holidays. The telephone number for the Public Reading Room is (202)
566-1744, and the telephone number for the Air and Radiation Docket is
(202) 566-1742. As provided in the EPA's regulations at 40 CFR part 2,
and in accordance with normal EPA docket procedures, if copies of any
docket materials are requested, a reasonable fee may be charged for
photocopying.
    2. Electronic Access. You may access this Federal Register document
electronically through the U.S. Government Publishing Office Web site
at https://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR.

II. What is the WIPP?

A. Background

    The Waste Isolation Pilot Plant (WIPP) is a disposal system for
defense-related transuranic (TRU) radioactive waste. The WIPP Land
Withdrawal Act (WIPP LWA) of 1992 defines TRU waste as materials
containing alpha-emitting radioisotopes, with half-lives greater than
twenty years, in concentrations greater than 100 nanocuries per gram
(nCi/g), except for (A) high-level radioactive waste; (B) waste that
the Secretary has determined, with the concurrence of the
Administrator, does not need the degree of isolation required by the
disposal regulations; or (C) waste that the Nuclear Regulatory
Commission has approved for disposal on a case-by-case basis in
accordance with part 61 of title 10, Code of Federal Regulations (CFR).
Developed by the U.S. Department of Energy (DOE), the WIPP is located
near Carlsbad in southeastern New Mexico. At the WIPP, the DOE disposes
of radioactive waste 655 meters (2,150 feet) underground in an ancient
salt layer which will eventually creep and encapsulate the waste. The
WIPP has a total capacity to dispose of 6.2 million cubic feet of
waste.
    Congress initially authorized the development and construction of
the WIPP in 1980 ``for the express purpose of providing a research and
development facility to demonstrate the safe disposal of radioactive
wastes resulting from the defense activities and programs of the United
States.'' \1\ To further facilitate the development and operation of
the WIPP, Congress passed the WIPP LWA in 1992 and amended it in 1996.
The WIPP LWA only allows TRU radioactive waste generated by defense
activities associated with nuclear weapons to be emplaced in the WIPP
and explicitly prohibits high-level waste or spent nuclear fuel from
being disposed of at the WIPP.
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    \1\ Department of Energy National Security and Military
Applications of Nuclear Energy Authorization Act of 1980, Pub. L.
96-164, section 213.
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    Most TRU waste proposed for disposal at the WIPP consists of items
that have become contaminated as a result of activities associated with
the production of nuclear weapons or with the clean-up of weapons
production facilities, e.g., rags, equipment, tools, protective gear
and organic or inorganic sludges. Some TRU waste contains hazardous
chemicals used during weapons production, research and development and
cleaning/maintenance/deactivation activities. Some of the waste
proposed for disposal at the WIPP is known as legacy waste and has been
stored for decades at various federal facilities across the United
States, including major generator sites such as the Idaho National
Laboratory, Los Alamos National Laboratory and Oak Ridge National
Laboratory, and smaller generators such as Argonne National Laboratory
and Lawrence Livermore National Laboratory. These facilities continue
to generate small quantities of TRU waste. All TRU waste which the DOE
plans to ship to the WIPP is subjected to the EPA's WIPP waste
characterization requirements at 40 CFR 194.24.
    The WIPP LWA provides the EPA the authority to oversee and regulate
the WIPP. The WIPP LWA requires the EPA to conduct three main tasks, to
be completed sequentially, to reach an initial compliance certification
decision. First, the WIPP LWA requires the EPA to finalize general
regulations for the disposal of highly-radioactive waste.\2\ The EPA
published these disposal regulations, located at subparts B and C of 40
CFR part 191, in the Federal Register in 1985 and 1993.\3\
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    \2\ WIPP LWA, section 8(b).
    \3\ 50 FR 38066-38089 (September 19, 1985) and 58 FR 66398-66416
(December 20, 1993).
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    Second, the WIPP LWA requires the EPA to develop criteria, via
rulemaking, to interpret and implement the general radioactive waste
disposal regulations specifically as they apply to the WIPP. In 1996,
the Agency issued the WIPP Compliance Criteria (40 CFR part 194).\4\
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    \4\ 61 FR 5224-5245 (February 9, 1996).
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    Third, the WIPP LWA requires the EPA to review the information
submitted by the DOE every five years to demonstrate continued
compliance with the disposal regulations and determine whether or not
the WIPP continues to be in compliance.\5\ The Agency issued the
initial certification decision on May 18, 1998 (63 FR 27354-27406).
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    \5\ WIPP LWA, section 8(d).
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B. Impacts of February 2014 Incidents on the Repository

    Since the EPA's initial certification, operation of the WIPP
proceeded without substantial interruption until 2014. However, two
events took place at the WIPP in February 2014 that led the DOE to
suspend emplacement of additional waste in the facility for nearly
three years. On February 5, a salt haul truck caught fire. Workers were
evacuated, and the underground portion of the WIPP was shut down. On
February 14, a second event occurred when a continuous air monitor
alarmed during the night shift, signaling a detection of radiation. The
continuous air monitor was measuring exhaust from waste panel 7, where
waste emplacement had recently begun. Radiological contamination of the
underground caused an indefinite suspension of waste handling
activities.
    After implementing numerous corrective actions, the DOE resumed
limited waste emplacement on January 4, 2017, and also resumed limited
shipments from waste generator sites. Resumption of waste emplacement
at the WIPP is unrelated to the EPA's recertification decision, which
is primarily concerned with compliance with the EPA's long-term
disposal requirements. However, the DOE has acknowledged that recovery
from the radiological release will result in design changes to the
repository, which will need to be considered from that longer-term
perspective. These changes include installation of a new ventilation
shaft and modification of the waste panel layout to accommodate the
premature closure of planned waste emplacement capacity in panel 9. The
DOE is still reviewing options and has not provided any specific plans
to the EPA. The EPA will review these changes as more information
becomes available and they are incorporated into future recertification
applications. The EPA recognizes that the current recertification
decision is based on a repository design that is likely to change, but
the current application contains the information necessary to reach a
decision without knowing the details of the future changes. It is not
unprecedented for the EPA to conduct a recertification review with the
knowledge that the DOE will submit a request to change an aspect of the
disposal system design.

    The EPA expects that any issues associated with repository design
changes will be appropriately addressed in responding to change
requests from the DOE and in subsequent recertification applications.
However, because these design changes are likely to be substantial, the
EPA believes it is necessary for the DOE to ensure that future
compliance recertification applications are as robust and technically
defensible as possible. To that end, the EPA discusses in Section VI.D
specific aspects of future compliance recertification applications that
the Agency believes would benefit from independent technical review, or
otherwise from thorough consideration of more recent scientific
information and understanding of chemical processes anticipated to take
place within the repository. The EPA strongly believes that
incorporating such reviews and information into future applications
will increase public confidence in the DOE's compliance demonstrations
and facilitate the Agency's review.

III. Compliance Certification History

A. 1998 Certification Decision

    The WIPP LWA, as amended, required the EPA to evaluate whether the
WIPP complied with the EPA's standards for the disposal of radioactive
waste. On May 18, 1998 (63 FR 27354-27406), the EPA determined that the
WIPP met the standards for radioactive waste disposal. This decision
allowed the DOE to begin placing radioactive waste in the WIPP,
provided that all other applicable health and safety standards, and
other legal requirements, were met. The WIPP received the first
shipment of TRU waste on March 26, 1999. The complete record and basis
for the EPA's 1998 certification decision can be found in Air Docket A-
93-02.
    Although the EPA determined that the DOE met all of the applicable
requirements of the WIPP Compliance Criteria in the original
certification decision, the EPA also found that it was necessary for
the DOE to take additional steps to ensure that the measures actually
implemented at the WIPP (and thus the circumstances expected to exist
there) were consistent with the DOE's compliance certification
application and with the basis for the EPA's compliance certification.
As a result, the EPA included four explicit conditions in the WIPP
certification of compliance (see 40 CFR part 194, Appendix A; WIPP
Recertification Background Document in Docket No. EPA-HQ-OAR-2014-
0609). These conditions are discussed in Section V.C of this document.

B. 2006 Recertification Decision

    The first recertification process, which occurred in 2004-2006,
included an EPA review of all changes made at the WIPP facility since
the original 1998 certification decision. The Agency received the DOE's
first compliance recertification application on March 26, 2004. The EPA
issued the completeness determination \6\ for the 2004 Compliance
Recertification Application by letter to the DOE on September 29, 2005
(see 70 FR 61107-61111, October 20, 2005). On March 29, 2006, the EPA
officially recertified the WIPP facility for the first time (71 FR
18010-18021, April 10, 2006).
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    \6\ A ``completeness determination'' is an administrative step
by the Agency to notify the DOE and the public that the Agency has
enough information to conduct a final technical review of the DOE's
application. It does not reflect any conclusion regarding the WIPP's
continued compliance with the radioactive waste disposal regulations
at 40 CFR part 191 and the compliance criteria at 40 CFR part 194.
The completeness determination represents the start of the six-month
period specified in the WIPP LWA for issuance of the recertification
decision.
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C. 2010 Recertification Decision

    Following receipt of the DOE's second compliance recertification
application on March 24, 2009, the EPA requested additional information
from the DOE and the DOE responded with the requested supplemental
information. All pertinent 2009 Compliance Recertification Application
correspondence was placed in the docket (Docket ID No. OAR-2009-0330 on
www.regulations.gov) and linked to on the WIPP Web site (https://www.epa.gov/radiation/certification-and-recertification-wipp#tab2). On
June 29, 2010, the EPA sent a letter to the DOE announcing that the
DOE's recertification application was complete (75 FR 41421-41424, July
16, 2010). The EPA's second recertification of the WIPP compliance was
published on November 18, 2010 (75 FR 70584).

IV. With which regulations must the WIPP comply?

A. Compliance With Radioactive Waste Disposal Regulations & the WIPP
Compliance Criteria

    The WIPP must comply with the EPA's radioactive waste disposal
regulations, located at subparts B and C of 40 CFR part 191. These
regulations limit the amount of radioactive material which may escape
from a disposal facility, and protect individuals and ground water
resources from dangerous levels of radioactive contamination. In
addition, the compliance recertification application and other
information submitted by the DOE must meet the requirements of the WIPP
Compliance Criteria at 40 CFR part 194. The WIPP Compliance Criteria
implement and interpret the general disposal regulations specifically
for the WIPP, and clarify the basis on which the EPA makes the
certification decision.

B. Compliance With Other Environmental Laws and Regulations

    In addition to the EPA's radioactive waste disposal regulations,
the WIPP must also comply with a number of other federal laws and
regulations pertaining to public health and safety or the environment,
including, for example, the Solid Waste Disposal Act (also known as the
Resource Conservation and Recovery Act (RCRA)) (42 U.S.C. 6901 et seq.)
and the EPA's environmental standards for the management and storage of
radioactive waste (subpart A of 40 CFR part 191). Various regulatory
agencies are responsible for overseeing the enforcement of these
federal laws and regulations. For example, enforcement of some parts of
the hazardous waste management regulations has been delegated to the
State of New Mexico. The State is authorized by the EPA to carry out
the State's RCRA programs in lieu of the equivalent federal programs,
and New Mexico's Environment Department (NMED) reviews the DOE's permit
applications for treatment, storage, and disposal facilities for
hazardous waste, under Subtitle C of RCRA. NMED's RCRA authority, such
as issuing a hazardous waste operating permit for the WIPP, is not
affected by the EPA's recertification decision. The DOE is responsible
for biennially reporting to the EPA and the State of New Mexico on the
WIPP's compliance with all applicable federal laws pertaining to public
health and safety (WIPP LWA Sec.  9).\7\ This action does not address
the WIPP's compliance with environmental or public health and safety
laws and regulations other than the EPA's radioactive waste disposal
regulations (40 CFR part 191) and the WIPP Compliance Criteria (40 CFR
part 194).
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    \7\ Compliance with these laws and regulations is addressed in
the site's Biennial Environmental Compliance Report (BECR).
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V. Continuing Compliance With the WIPP Compliance Criteria

    The EPA monitors and ensures continuing compliance with the EPA
regulations through a variety of activities, including the following:
review and evaluation of the DOE's annual change reports, monitoring of

the conditions of compliance, addressing planned change requests,
inspections of the WIPP site and inspections of waste characterization
operations. Because of the 2014 incident, the EPA also reviewed health
and monitoring data to ensure the radiological releases remained below
the limits of subpart A of 40 CFR part 191 and the Clean Air Act
National Emissions Standards for Hazardous Air Pollutants at 40 CFR
part 61, subpart H.
    The DOE must timely report any planned or unplanned changes in
activities or conditions pertaining to the disposal system that differ
significantly from the most recent compliance application and, at least
annually, report any other changes in disposal system conditions or
activities (40 CFR 194.4(b)(3), (4)). The Department must also report
any releases of radioactive material from the disposal system (40 CFR
194.4(b)(3)(iii)). In addition, the EPA may request additional
information from the DOE at any time (Sec.  194.4(b)(2)). These
requirements assist the EPA with monitoring the performance of the
disposal system and evaluating whether the certification should be
modified, suspended or revoked.

A. Annual Change Reports

    In addition to reporting significant changes to the WIPP disposal
system, the DOE is required to report at least annually other changes
to the conditions or activities concerning the WIPP disposal system (40
CFR 194.4(b)(4)). The DOE submitted the first annual change report in
November 1998.
    The DOE's annual change reports reflect the progress of quality
assurance and waste characterization inspections, minor changes to the
DOE documents, information on monitoring activities and any additional
EPA approvals for changes in activities. All correspondence and
approvals regarding the annual change reports can be found in hard copy
in the Air Docket A-98-49, Categories II-B2 and II-B3.

B. Monitoring the Conditions of Compliance

    1. Panel Closure Rulemaking. Waste panel closure systems are
required by the State of New Mexico during the WIPP's operational
phase. Since they are a feature of the disposal system design, the EPA
requires panel closures to be included in the long-term modeling of the
repository. The panel closures impact long-term disposal system
performance because they can impede brine and gas flow between waste
panels. As originally promulgated, the WIPP Certification Condition 1
required the DOE to implement the Option D panel closure system at the
WIPP, using Salado mass concrete.\8\ By final action published October
8, 2014, the EPA modified Condition 1 to remove the specific reference
to Option D and generally require that the DOE close filled waste
panels as specifically approved by the EPA (40 CFR part 194, Appendix
A, as amended; 79 FR 60750-60756). With the same action, the EPA
approved a design which primarily consists of 100 feet of run-of-mine
salt. The DOE submitted a performance assessment \9\ to support its
request to change the panel closure system design. The DOE asserted
that the performance assessment demonstrated that a panel closure
design using run-of-mine salt would be compliant with the EPA's
disposal regulations (40 CFR part 191). The modification to the WIPP
Certification Condition 1 also removed the requirement for the Agency
to make future panel closure design changes by formal rulemaking.
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    \8\ ``Salado'' mass concrete refers to concrete made using
Salado brines instead of fresh water.
    \9\ Performance assessment is an important tool used in various
contexts or evaluations relating to the WIPP and such assessments
are mentioned in different circumstances throughout this notice,
especially in Section VI.E. In general, performance assessment
means: ``an analysis that: (1) Identifies the processes and events
that might affect the disposal system; (2) examines the effects of
those processes and events on the performance of the disposal
system; and (3) estimates the cumulative release of radionuclides,
considering the associated uncertainties, caused by all significant
processes and events'' (40 CFR 191.12). Performance assessment, for
example, is required to show compliance with containment
requirements (40 CFR 191.13).
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    2. Quality Assurance. Certification Condition 2 requires each TRU
generator site to establish and execute a quality assurance program for
waste characterization activities. Section 194.22 establishes quality
assurance requirements for the WIPP. The DOE must adhere to a quality
assurance program that implements the requirements of ASME NQA-1-1989
edition, ASME NQA-2a-1990 addenda, part 2.7, to ASME NQA-2-1989
edition, and ASME NQA-3-1989 edition (excluding Section 2.1 (b) and
(c), and Section 17.1).The EPA determined that the 2014 Compliance
Recertification Application provides adequate information to verify the
establishment and implementation of each of the applicable elements of
the ASME NQA-1-1989.The EPA has also verified the continued proper
implementation of the Nuclear Quality Assurance Program through
periodic audits conducted in accordance with Sec.  194.22(e).
    The EPA's determination of compliance with 40 CFR 194.22 can be
found in Table 1 of the 2014 Compliance Recertification Application
CARD 22. Between March 2008 and April 2012, the EPA conducted several
quality assurance audits and found the site-specific quality assurance
programs to be adequate. The EPA conducted quality assurance audits at
several waste generator sites and entities supporting the WIPP
Performance Assessment activities at Los Alamos and Sandia
Laboratories. The EPA also audited the quality assurance program of the
Carlsbad Field Office.
    3. Waste Characterization. Certification Condition 3 requires TRU
waste generator sites to have waste characterization systems approved
by the EPA. The Agency has conducted numerous audits and inspections at
waste generator sites in order to implement Condition 3 and the
relevant provisions of 40 CFR part 194, including Sec.  194.8. The EPA
inspected site-specific TRU waste characterization programs implemented
to (a) characterize physical and radiological components in individual
waste containers and (b) demonstrate compliance with the WIPP waste
disposal requirements at 40 CFR 194.24.
    To support the 2014 Compliance Recertification Application, the DOE
reported the EPA's waste characterization inspections and approvals
between January 2007 and December 2012 (see Table 1 in CARD 8). The EPA
evaluated previously approved site-specific waste characterization
program for continued compliance in accordance with 40 CFR 194.24, as
well as changes to the systems of controls approved as part of the
baseline (initial) approvals, and concluded them to be technically
adequate. The TRU waste sites approved by the EPA to ship contact-
handled TRU waste to the WIPP facility in accordance with the
requirements of Sec.  194.8 since the 2009 Compliance Recertification
Application are as follows: Advanced Mixed Waste Treatment Project,
Hanford's Richland Laboratory, Idaho National Laboratory, Los Alamos
National Laboratory, Oak Ridge National Laboratory and Savannah River
Site. Since the 2009 Compliance Recertification Application, the TRU
waste sites approved by the EPA to ship remote-handled TRU waste to the
WIPP facility in accordance with the requirements of Sec.  194.8 are
Argonne National Laboratory, Bettis Atomic Power Laboratory, General
Electric Vallecitos Nuclear Center, Idaho National Laboratory, Oak
Ridge National Laboratory and Savannah River Site. Since the 2009
Compliance

Recertification Application, no waste characterization occurred at
Bettis Atomic Power Laboratory, General Electric Vallecitos Nuclear
Center, Hanford's Richland Laboratory and Oak Ridge National
Laboratory.
    During the period covered by the 2014 Compliance Recertification
Application, all site-specific waste characterization systems of
controls at active TRU waste generator sites had necessary baseline
approvals. Over the years, when warranted, the EPA approved
modification to waste characterization program components. Notices
announcing the EPA inspections or audits are routinely published in the
Federal Register and also announced on the Agency's WIPP Web site
(https://www.epa.gov/radiation/epas-role-waste-isolation-pilot-plant-wipp) and WIPP-NEWS email listserv.\10\
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    \10\ For more information on the WIPP-NEWS email listserv, see
Section VIII.B below.
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    Records of the EPA's quality assurance correspondences and waste
characterization approvals can be found in Air Docket A-98-49,
Categories II-A1 and II-A4, respectively, as well as online in Docket
ID No. EPA-HQ-OAR-2001-0012 on www.regulations.gov.
    4. Passive Institutional Controls. Certification Condition 4
requires the DOE to submit a schedule and plan for implementing passive
institutional controls, including markers and other measures indicating
the presence of the repository. The standards under the WIPP
Certification Condition 4 do not require the submission of any reports
until the final compliance recertification application prior to closure
of the WIPP. The EPA has not received any submissions from the DOE
during the period addressed by the 2014 Compliance Recertification
Application and has not taken any actions relating to Condition 4. The
EPA anticipates that it will evaluate the DOE's compliance with
Condition 4 of the certification when the DOE submits a revised
schedule and additional documentation regarding the implementation of
passive institutional controls. Once received, the information will be
placed in the EPA's public dockets, and the Agency will evaluate the
adequacy of the documentation. After receiving Condition 4 submissions
from the DOE, and during the operational period when waste is being
emplaced in the WIPP (and before the site has been sealed and
decommissioned), the EPA will verify that specific actions identified
by the DOE in the compliance certification application, and
supplementary information (and in any additional documentation
submitted in accordance with Condition 4) are being taken to test and
implement passive institutional controls.

C. Inspections

    The WIPP Compliance Criteria provide the EPA the authority to
conduct inspections of activities at the WIPP and at off-site
facilities which provide information relevant to compliance
applications (40 CFR 194.21). The Agency has conducted periodic
inspections to verify the adequacy of information relevant to
certification applications. The EPA has conducted annual inspections at
the WIPP site to review and ensure that the monitoring program meets
the requirements of Sec.  194.42. The EPA has also inspected the
emplacement and tracking of waste in the repository. The Agency's
inspection reports can be found in Air Docket A-98-49, Categories II-A1
and II-A4, as well as online at www.regulations.gov, Docket ID No. EPA-
HQ-OAR-2001-0012.

VI. What is the EPA's 2017 Recertification Decision?

    The EPA determines, in accordance with WIPP LWA Sec.  8(f)(2), that
the WIPP facility is in compliance with the final disposal regulations,
subparts B and C of 40 CFR part 191. Compliance recertification ensures
that accurate and up-to-date information is considered in the
determination that WIPP remains in compliance with these radioactive
waste disposal regulations. The EPA makes this recertification and
determination of continued compliance following the ``Criteria for the
Certification and Recertification of the WIPP's Compliance with the 40
CFR part 191 Disposal Regulations'' (WIPP Compliance Criteria, 40 CFR
part 194), including the WIPP certification conditions (40 CFR part
194, Appendix A).

A. Performance Assessment and the EPA's Standards

    The disposal regulations at 40 CFR part 191 include requirements
for containment of radionuclides. The containment requirements at 40
CFR 191.13 specify that releases of radionuclides to the accessible
environment \11\ must be unlikely to exceed specific limits for 10,000
years after disposal. The DOE assesses the likelihood that the WIPP
will meet these release limits through a process known as performance
assessment.
---------------------------------------------------------------------------

    \11\ The accessible environment is defined in 40 CFR 191.12 as
(1) The atmosphere: (2) land surfaces; (3) surface waters; (4)
oceans; and (5) all of the lithosphere that is beyond the controlled
area.
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    The disposal regulations provide that there must be a reasonable
expectation that cumulative releases of radionuclides from the WIPP and
into the environment over 10,000 years will not exceed specified
quantities of these radionuclides (40 CFR 191.13 and Appendix A). A
reasonable expectation standard is used because of the long time period
involved and the nature of the events and processes at radioactive
waste disposal facilities leads to uncertainties about future
performance. The DOE's probabilistic performance assessments assess the
likelihood of environmental radionuclide release so that future
uncertainties are accounted for in the calculations through the use of
alternative scenarios and variations in values of uncertain parameters
via probability distributions.
    The containment requirements in 40 CFR 191.13 are expressed in
terms of ``normalized releases.'' At the WIPP, the specific release
limits are based on the estimated amount of waste in the repository at
the time of closure, and the projected releases are ``normalized''
against these limits (Sec.  194.31). Normalized releases are expressed
as ``EPA units''. The EPA units are calculated by dividing all the
combined projected releases by the total combined radioactivity of all
the waste in the repository.
    The DOE must demonstrate, in each 5-year compliance recertification
application, that the total average of combined releases are below two
compliance criteria at a higher probability of occurrence and a lower
probability of occurrence. These compliance points are as follows:
    1. For a probability of 0.1 (a 1 in 10 chance) in 10,000 years,
releases to the accessible environment will not exceed 1 EPA unit, and
    2. For a probability of 0.001 (a 1 in 1,000 chance) in 10,000
years, releases to the accessible environment will not exceed 10 EPA
units.
    DOE evaluates four release mechanisms in the WIPP performance
assessment modeling:
    Cuttings and cavings. This consists of material that gets brought
to the surface when a borehole intersects waste in a WIPP waste panel.
The cuttings are the material intersected by the borehole itself and
the cavings material is waste that fails around the borehole, collapses
into it and is brought to the surface.
    Spallings. This is solid material that fails and gets brought to
the surface under high pressure conditions in the

repository. This only occurs when the pressure is above 8 megapascal
\12\ (MPa).
---------------------------------------------------------------------------

    \12\ ``Pascal'' is a unit of pressure, defined as 1 kg/m-sec\2\.
---------------------------------------------------------------------------

    Direct Brine Releases. This is a release of dissolved actinides in
brine when there is sufficient brine and high pressure in the
repository (i.e., above 8 MPa) and brine saturations are above residual
saturation (i.e., brine is not ``trapped'' between pore spaces) as a
borehole intersects a waste panel. The contaminated fluid is brought to
the surface over a period of hours to days.
    Releases to the Culebra. This occurs when contaminated brine from
repository is introduced via a borehole to the Culebra Dolomite and
then moves to the edge of the accessible environment (i.e., the
boundary established by the WIPP LWA).
    The DOE estimates the potential releases from these release
mechanisms, i.e., the cumulative releases, for comparison with the
specified limits provided in 40 CFR part 191, Appendix A. The DOE is to
provide in the application overall mean calculated releases and the
upper 95th confidence limit of that mean.

B. Summary of the EPA's Review

    After reviewing the DOE's documentation and additional studies that
the DOE conducted at EPA's request, the aspects of the performance
assessment of most interest to EPA are those that affect the direct
brine release mechanism, by which actinides \13\ dissolved in brine are
transported to the surface during a drilling intrusion. Direct brine
release is the overall dominant release mechanism at the low
probability compliance point, and is influenced primarily by the
availability of liquid (i.e., brine) in the repository, the
availability of radionuclides to dissolve in that liquid (i.e.,
inventory and solubility) and the pressure in the repository (providing
a motivating force for dissolved radionuclides to move out of the
repository).
---------------------------------------------------------------------------

    \13\ Actinide means any of the series of fifteen metallic
elements from actinium (atomic number 89) to lawrencium (atomic
number 103) in the periodic table. They are all radioactive, the
heavier members being extremely unstable and not of natural
occurrence.
---------------------------------------------------------------------------

    The key issues involving these aspects of the repository are: (1)
The actinide solubility, which is addressed through changes to the
geochemical database, colloid contribution updates and the
determination of the actinide solubility uncertainty; (2) the
probability of hitting a brine pocket under the repository; (3) the
steel corrosion rate and steel's interactions with hydrogen sulfide and
magnesium oxide (affecting the gas pressure); and (4) the overall
modeling of direct brine releases that involve the interactions of
items 1-3 plus the conditions of the repository (e.g., panel and drift
permeability and porosity) that can influence the pressure
characteristics of the waste areas. These issues are discussed in more
detail in Section VI.D, along with other issues that are noteworthy but
have more limited impact on performance assessment results.
    The following information describes the EPA's compliance evaluation
related to the disposal regulations and Compliance Criteria.

C. What information did the Agency use to make the decision?

    In general, compliance applications must include information
relevant to demonstrating compliance with each of the individual
sections of 40 CFR part 194 to determine if the WIPP will comply with
the Agency's radioactive waste disposal regulations at 40 CFR part 191,
subparts B and C. The EPA begins the compliance recertification
evaluation once the EPA receives a complete compliance recertification
application (40 CFR 194.11).
    To make this decision, the EPA evaluated basic information about
the WIPP site and disposal system design, as well as information which
addressed the various compliance criteria. As required by 40 CFR
194.15(a), the DOE's 2014 Compliance Recertification Application
updated the previous submission in 2009.
    On March 26, 2014, the DOE submitted the compliance recertification
application. The EPA began to identify areas of the application where
additional information was needed. On October 10, 2014, the EPA gave
public notice of the compliance recertification application and opened
the official public comment period (79 FR 61268). On January 13, 2017,
the EPA sent a letter to the DOE stating that the DOE's recertification
application was complete. On March 10, 2017, the EPA issued a Federal
Register notice announcing the completeness determination and stating
that the public comment period would close one month later, on April
10, 2017 (82 FR 13282). The compliance recertification application
completeness-related correspondence can be found in Docket ID No. EPA-
HQ-OAR-2014-0609 on www.regulations.gov.
    The EPA relied on materials prepared by the Agency or submitted by
the DOE in response to the EPA requests. For example, the EPA requested
that the DOE conduct specific, additional modeling calculations for the
performance assessment, known as sensitivity studies. The purpose of
these studies was to evaluate the impact on performance assessment
results of changing specific parameter values. The studies aided the
EPA in determining how significant the differences in some parameter
values were to a demonstration of compliance. The four sensitivity
studies and the EPA's evaluation of them are discussed in more detail
in Section VI.E.
    To determine whether the WIPP facility continues to be in
compliance with the final disposal regulations, the EPA engaged in a
technical review of the compliance recertification application against
the WIPP Compliance Criteria. The Agency focused the review on areas of
change identified by the DOE since the 2010 recertification decision.
    The Agency produced many documents during the technical review and
evaluation of the compliance recertification application. The EPA's
Compliance Application Review Documents (CARDs) correspond in number to
the sections of 40 CFR part 194 to which the documents primarily
relate. Each CARD enumerates all changes made by the DOE relating to a
particular section of the rule or certification criterion, and
describes the EPA's process and conclusions. The EPA also prepared
technical support documents (TSDs) to address specific topics in
greater detail. Both the CARDs and the TSDs for this recertification
decision can be found in Docket ID No. EPA-HQ-OAR-2014-0609 on
www.regulations.gov. Together, the CARDs and TSDs thoroughly document
the EPA's review of the DOE's compliance recertification application
and the technical rationale for the Agency's decisions.
    In summary, the EPA's recertification decision is based on the
entire record available to the Agency, which is located in the public
docket dedicated to this recertification (Docket ID No. EPA-HQ-OAR-
2014-0609 on www.regulations.gov). The record consists of the 2014
Compliance Recertification Application, supplementary information
submitted by the DOE in response to the EPA requests for additional
information, technical reports generated by the EPA, the EPA audit and
inspection reports, and comments submitted on the DOE's application and
the EPA's completeness review during the public comment period. All
pertinent 2014 Compliance Recertification Application correspondence
was placed in the docket and linked to via the EPA's WIPP Web site
(https://www.epa.gov/

radiation/certification-and-recertification-wipp).

D. Content of the Compliance Recertification Application (Sec. Sec.
194.14 and 194.15)

    The DOE's WIPP compliance applications must include, at a minimum,
basic information about the WIPP site and disposal system design,
including information about the following topics: the geology,
hydrology, hydrogeology and geochemistry of the WIPP disposal system
and the WIPP vicinity; the WIPP materials of construction; standards
applied to design and construction; background radiation in air, soil
and water; and past and current climatological and meteorological
conditions (40 CFR 194.14). Section 194.15 states that the DOE's
recertification applications shall update this information to provide
sufficient information for the EPA to determine whether or not the WIPP
facility continues to be in compliance with the disposal regulations.
    1. Changes to the Disposal System Identified by the DOE. In Section
15 of the 2014 Compliance Recertification Application, the DOE
identified changes to the disposal system between the 2009 Compliance
Recertification Application and 2014 Compliance Recertification
Application and changes to technical information relevant to Sec. Sec.
194.14 and 194.15. Noteworthy changes identified by the DOE in the 2014
Compliance Recertification Application include the following: an update
to the parameters defining drilling rate and plugging pattern,
revisions to the calculations of the probability of encountering a
pressurized brine reservoir, replacing the Option D panel closure
design with run-of-mine salt, modeling open areas in the repository,
revision of the steel corrosion rate, revision of the effective shear
strength of waste, revisions of the repository water balance including
variable brine volumes for radionuclides to dissolve and revisions of
the colloid parameters.
    Before determining that the compliance recertification application
was complete, the EPA raised numerous technical questions with the DOE,
as described below. For each topic, a brief summary is provided of how
the DOE addressed the issue in the 2014 application, followed by the
EPA's perspective on the change, including any follow-up analyses
requested. The DOE also updated the waste inventory. This topic is
discussed in Section VI.F.1.
    Since the initial Compliance Certification performance assessment,
the DOE's calculated releases in performance assessments have increased
with every performance assessment until the 2014 Compliance
Recertification Application performance assessment. The changes the DOE
made to the performance assessment in the current application reduce
the calculated releases. For example, the calculated release of
radionuclides at the low probability compliance point (a likelihood of
less than a one in 1,000 chance), was assessed by the DOE in the 2009
Compliance Recertification Application as 0.72 EPA Units, but in the
2014 Compliance Recertification Application, the similar calculated
release initially was assessed as 0.261 EPA Units.
    Changes that reduce the calculated releases involve the shear
strength of the waste, revised steel corrosion rate, incorporating
water balance as part of the chemical model implementation as it
relates to steel corrosion and interactions with the magnesium oxide
engineered barrier, correcting errors associated with brine volume mass
balance and calculation of actinide solubility and the change to how
the DOE calculates the probability of hitting a brine pocket under the
repository. In general, the result of the DOE's methodology changes is
to reduce calculated releases by about a factor of two between the 2009
and 2014 Compliance Recertification Applications at both the 0.1 and
0.001 probability compliance points.
    The EPA has identified issues with some of these changes, but even
with changes the EPA asked the DOE to investigate, projected releases
stay well under the numerical release limits. For example, at the 0.001
probability compliance point where the EPA normalized release limit is
10 EPA units, the changes the EPA requested resulted in increased
releases from 0.261 EPA units in the DOE's 2014 performance assessment
to 0.299 EPA units in sensitivity study SEN3 and 0.541 EPA units in
sensitivity study SEN4. The sensitivity studies are discussed in depth
in Section VI.E.
    a. Update to the Drilling Rate and Borehole Plugging Patterns. As
with previous recertification applications, the DOE updated the
Delaware basin drilling rates based on the methodology previously
approved. For the 2014 Compliance Recertification Application, the
drilling rate increased to 0.00673 boreholes per km\2\ per year
(equivalent to 67.3 boreholes/km\2\ over the 10,000-year regulatory
period) compared to that used in the 2009 performance assessment
baseline calculation, which was .00598 boreholes per km\2\ per year (or
59.8 boreholes/km\2\ over 10,000 years). The Agency accepted the DOE's
drilling rate increase.
    The DOE also updated information on the type of plugs installed in
exploratory, disposal and resource extraction boreholes. There are
three types of borehole plugs used in the Delaware basin. There are
boreholes that are continuously plugged through the entire salt
section, and the DOE reports a slight increase in the use of this
design. There are boreholes plugged with a two-plug configuration (at
the Salado/Rustler and the Bell Canyon/Castile Formation interfaces).
This two-plug design also slightly increased from that used in the 2009
application. There is also a three-plug configuration (i.e., borehole
plugs at the Rustler/Salado, Salado/Castile and Castile/Bell Canyon
interfaces); the DOE reports a slight decrease in this configuration.
The Agency accepted the DOE's update to the change in the plugging
patterns.
    b. Replacement of Option D Panel Closure System with the Run-of-
Mine Salt Panel Closure Design. Part of the design for the WIPP
includes the use of a closure system to separate the waste rooms in a
panel from active areas in the mine, which can affect long-term brine
and gas flows within the repository. As part of the design, the panel
closure system that is installed needs to be represented in the
modeling of long-term performance.
    On September 28, 2011, the DOE provided a change request to the EPA
(Docket EPA-HQ-OAR-2013-0684) to modify the panel closure system design
specified in Appendix A of 40 CFR part 194 from that of a concrete
monolith plug, noted as Option D, to a 100-foot long barrier consisting
of run-of-mine salt (EPA 2013; 2014). The panel closure system
performance assessment release calculations were well within the
numerical limits established in 40 CFR 191.13. The EPA approved the
DOE's use of the proposed run-of-mine salt closure design (79 FR 60750,
Oct. 8, 2014) (Docket EPA-HQ-OAR-2013-0684-0004 on
www.regulations.gov).
    The DOE incorporated the run-of-mine salt design for panel closures
into the 2014 Compliance Recertification Application. To evaluate this
change, the Agency reviewed a broad set of information related to the
evolution of salt repository properties, including run-of-mine salt and
adjacent disturbed rock zone in the WIPP repository setting (Salt
Characteristics TSD \14\). From this

review, the Agency's interpretation of the data is that healing of the
run-of-mine salt in the panel closures, the surrounding disturbed rock
zone and open areas should occur within about the first 200 years of
post-closure instead of the relatively asymptotic closure for the 200-
10,000 years used by the DOE. The DOE's use of the longer period of
time assumes permeability and porosity for the salt will be low within
200 years, but not at the very low end state properties of intact
halite.
---------------------------------------------------------------------------

    \14\ ``Technical Support Document for Section 194.23: Technical
Review of Salt Aggregate, Disturbed Rock Zone, and Open Drift
Healing Characteristics'' in Docket ID No. EPA-HQ-OAR-2014-0609.
---------------------------------------------------------------------------

    To identify the potential effect of the difference in the
repository properties between what the EPA has identified may be
applicable and what the DOE modeled, the Agency requested that the DOE
analyze the repository performance using parameter values for the run-
of-mine salt panel closure system and adjacent disturbed rock zone that
simulate complete healing. The DOE did this in the sensitivity study
SEN3 discussed in Section VI.E. The calculated releases increased for
direct brine releases and spallings releases in SEN3, but overall
releases remained well within the numerical limits of 40 CFR 191.13 and
the EPA concludes that there is a reasonable expectation that the
repository remains in compliance with the numerical limits at 40 CFR
191.13, and 40 CFR part 191, Appendix A.
    If the DOE determines, in light of the announced decision to
abandon the area previously designated for panel 9, that worker safety
considerations preclude installing panel closures in affected areas of
the repository, the DOE's treatment of panel closures in performance
assessment may be more appropriately addressed in the context of
modeling open areas representative of no panel closures. The Agency
will review future panel closure modeling in the context of future
facility design changes.
    c. Modeling of Open Areas in the Repository. In the 2014 Compliance
Recertification Application, the DOE increased the modeled volume of
the open rooms and drifts by approximately forty percent to accommodate
future planned experiments. These new areas are located north of the
waste area drifts and are to be separated from the waste area by two
sets of run-of-mine salt panel closures. For the 2014 Compliance
Recertification Application performance assessment, the DOE modeled
these areas as open for the entire 10,000-year regulatory period even
though it is expected that the creep closure process will close the
open areas within a few hundred years (Overview TSD \15\). The Agency
evaluated the impact of the DOE's assumption to model these areas as
open (relatively large porosity and high permeability) by requesting
the DOE perform sensitivity study SEN2, where the non-waste rooms and
open drifts are assumed to have creep closed during the entire 10,000-
year regulatory period.
---------------------------------------------------------------------------

    \15\ ``Overview of Changes Between PABC-2009 and CRA-2014 WIPP
Performance Assessments'' in Docket ID No. EPA-HQ-OAR-2014-0609.
---------------------------------------------------------------------------

    The results from the SEN2 studies indicate modeling creep closure
and healing of the operations and experimental areas (i.e., non-waste
areas) of the repository was shown to have little effect on the
prediction of total releases from the repository although, relative to
the 2014 Compliance Recertification Application performance assessment,
a slight increase in spallings releases does occur if these areas are
assumed to creep closed. This is a result of higher pressures occurring
in panels. See Section VI.E for discussion of the SEN2 study.
    If, in the future, there are repository design changes that result
in more non-waste drifts mined or left open in the facility, the issue
of open areas will need to be re-evaluated in the context of those
design changes, as releases could be expected to increase in that
circumstance. The DOE's plan to abandon panel 9 would leave large areas
of open space in the repository in the panel 9 drifts and possibly no
panel closures for multiple panels. Performance assessment modeling
should address these expected future repository conditions. The EPA
believes that an independent technical review of issues related to salt
behavior and modeling of open areas would be of benefit to the DOE as
it further develops its plans.
    d. The DOE's Revised Estimate of the Probability of Encountering
Pressurized Brine. Highly pressurized zones of brine (i.e., pressurized
brine reservoirs) occur in the Castile Formation below the Salado
Formation, which is the formation that hosts the WIPP. If a future
driller encounters a Castile pressurized brine reservoir and brine
enters the waste panels, it can dissolve radionuclides that then could
be transported up a borehole to the surface. In the modeling of the
repository, the probability of a future borehole intersecting a waste
panel and a Castile brine reservoir below the repository is denoted by
the parameter name PBRINE. Because the probability of hitting a brine
pocket is uncertain, it is represented by a probability distribution,
and the actual value of the PBRINE parameter for an individual model
run is sampled from the PBRINE probability distribution.
    In the 2014 Compliance Recertification Application, the DOE changed
the basis it used to develop the probability distribution for parameter
PBRINE. The DOE's revision to the estimated probability of a future
driller encountering pressurized brine relies heavily on voluntarily
reported drilling logs \16\ combined with an updated probability
distribution. The DOE eliminated from consideration site-specific data
collected through geophysical detection methods, which had previously
been incorporated into the PBRINE parameter.
---------------------------------------------------------------------------

    \16\ Kirchner, T., T. Zeitler, and R. Kirkes. 2012. Evaluating
the Data in Order to Derive a Value for GLOBAL:PBRINE. Memorandum to
Sean Dunagan dated December 11, 2012. ERMS 558724. Carlsbad, NM:
Sandia National Laboratories.; EPA Completeness Comment 1-23-6;
Docket EPA-HQ-OAR-2014-0609-0004.
---------------------------------------------------------------------------

    The EPA has several concerns regarding the DOE's update to the
PBRINE parameter,\17\ including the DOE's elimination of the site
geophysical data leading to estimates of the potential for brine
encounters based only on the voluntary data reported by the driller,
and that more recent site data supports the potential for more brine
under the repository than the DOE or the EPA had previously considered.
For a more in-depth discussion of these issues, see the PBRINE TSD.\18\
The EPA's concerns were significant enough that the EPA developed a
modified methodology for determining the probability distribution for
parameter PBRINE in the WIPP performance assessment calculations.
---------------------------------------------------------------------------

    \17\ See Completeness Question 1-23-6, Probability of
Encountering a Castile Brine Pocket and subsequent clarifying
questions, as well as the PBRINE TSD, for more detail in Docket ID
No. EPA-HQ-OAR-2014-0609.
    \18\ ``Probability of Encountering Castile Brine Beneath the
WIPP Waste Panels Using the TDEM Block Method.''
---------------------------------------------------------------------------

    The Agency's revision to the PBRINE parameter was incorporated into
Sensitivity Study SEN4. The study results indicate the modified PBRINE
probability distribution contributed to an increase in estimated direct
brine releases and increased the total releases at the 0.001 low
probability compliance point to roughly double those in the 2014
Compliance Recertification Application performance assessment.\19\
Because the Agency is unable to accept the DOE approach used to define
the PBRINE parameter, the EPA views the updated probability
distribution used in

the SEN4 study as the baseline for PBRINE in future performance
assessments. The EPA will evaluate alternative approaches proposed by
the DOE. See Section VI.E for more discussion of the SEN4 study.
---------------------------------------------------------------------------

    \19\ DOE 2014 Appendix PA, Sections PA-9.3 and PA-9.5 Kirchner
2013 and the EPA, 2017 Technical Support Document.
---------------------------------------------------------------------------

    e. Revised Corrosion Rate of Steel. The WIPP corrosion rate model
includes anoxic corrosion (i.e., corrosion in the absence of oxygen) of
iron in the waste containers. This corrosion is caused by hydrogen
sulfide gas produced from the microbial degradation of cellulosic,
plastics and rubber materials from the contaminated rubber gloves and
KimwipesTM included in the waste.
    The EPA reviewed the 2014 Compliance Recertification Application
model and had concerns with the way the model addressed expected
repository carbon dioxide concentrations in the experimental derivation
of corrosion rates. The EPA also found that the model did not
incorporate hydrogen sulfide induced steel passivation,\20\ which could
result in an overestimation of corrosion in the longer-term. Once steel
is passivated, hydrogen sulfide consumption will decrease significantly
as corrosion will be limited by the ability for the gas to diffuse
through the iron sulfide coating the outer surface of the container.
---------------------------------------------------------------------------

    \20\ Passivation refers to the creation of an outer coating
layer on the steel canisters due to the interaction of iron and
sulfide.
---------------------------------------------------------------------------

    In addition, other components of this model, which the DOE
considered to be minor, may have more impact. Calculations of the
potential lead inventories at the WIPP only include current waste
containers without accounting for the maximum potential of future
containers.
    To address the EPA's concerns about corrosion, part of the DOE's
SEN4 sensitivity study involved turning off the hydrogen sulfide
corrosion parameter to simulate steel passivation. These changes
resulted in a slight increase in gas pressures as well as a decrease in
the saturation of the waste area because both hydrogen gas and water
were eliminated from the end products. Results from this study
indicated that projected releases would remain within the limits of 40
CFR 191.13. Therefore, the EPA accepts the corrosion approach
incorporated in the 2014 Compliance Recertification Application. See
Section VI.E for more discussion of the SEN4 study.
    To ensure that future performance assessments adequately address
the mechanisms that affect gas generation in the repository, it would
be appropriate for the DOE to update the corrosion model to better
address steel passivation and account for radiolysis and address lead
corrosion to be consistent with the expected inventory of the
repository.
    f. Revised Effective Shear Strength of the WIPP Waste. The
parameter TAUFAIL represents waste shear strength and is used in
calculating potential releases of waste materials from the WIPP
repository when a drilling operator drills a borehole through the
waste. The drilling mud will apply a hydrodynamic shear stress to the
punctured waste and cause it to erode and be transported up the
borehole to the surface. The sheared waste transmitted to the surface
is called ``cavings''. A higher shear strength means the material is
less likely to break into pieces and be transported up a borehole. The
parameter TAUFAIL has an uncertain value which is sampled from a range
of experimental values for individual model runs. In the 2014
Compliance Recertification Application, the DOE updated the mean and
lower bound for the TAUFAIL parameter value distribution based on a
suite of laboratory flume tests specifically designed to represent the
range of values for the WIPP waste.
    In the 2009 Compliance Recertification Application the lower bound
value was 0.05 Pa, while for the 2014 Compliance Recertification
Application the lower bound of the distribution was increased to 2.22
Pa (the mean value from the laboratory flume tests). The upper bound of
the distribution, 77 Pa, remained the same. The EPA believes the DOE's
overall approach of using experimental data to revise the TAUFAIL
parameter is reasonable; however, the EPA had concerns with the DOE's
lower ``bounding'' range value derived from the experiments. The Agency
was concerned that three of the five low shear-strength tests had
highly scattered results. The DOE attributed the scatter to pre-test
sample damage and/or a high degree of variability in sample
preparation, rather than testing an equivalent suite of samples. As a
result, the mean of the low shear strength test results may not be
truly representative of low shear strength samples.
    In the SEN4 study, the EPA requested the DOE include the lowest
shear-strength flume test results (1.6 Pa) as the bounding value,
rather than the average (2.22 Pa). The SEN4 results indicate modifying
the lower range to include the lowest value as the bounding value
insignificantly impacted releases. This is due to the fact that the
change from 2.22 Pa to 1.6 Pa (i.e., from the mean of experimental
values to the lowest experimental value) is much less than would be the
change from the 0.05 Pa used in previous performance assessments to
either the 1.6 Pa or the 2.22 Pa values. Based on these results, the
EPA accepts the DOE's range of values used in the 2014 Compliance
Recertification Application, though for future performance assessments
the EPA believes it is more appropriate for the DOE to use the lower-
bound result instead of the mean. See Section VI.E for more discussion
of the SEN4 study. See also the TAUFAIL TSD.\21\
---------------------------------------------------------------------------

    \21\ ``Technical Support Document for Section 194.23: EPA Review
of Proposed Modification to the Waste Shear Strength Parameter
TAUFAIL'' in Docket ID No. EPA-HQ-OAR-2014-0609.
---------------------------------------------------------------------------

    g. Revised Repository Water Balance. Repository water balance is
the culmination of multiple chemical reactions that produce or consume
water and affect actinide concentrations in the brine. These reactions
include microbial degradation of the cellulosic, plastic and rubber
materials, the anoxic corrosion of iron in the steel waste canisters,
and reactions of the magnesium oxide (MgO) used to control carbon
dioxide (CO2) buildup in the repository. Magnesium oxide, in
particular, reacts with brine and results in hydromagnesite
(Mg5(CO3)4(OH)24H2
O), which consumes water in the process.
    Previous compliance recertification applications only included
anoxic corrosion in water balance calculations. The 2014 Compliance
Recertification Application includes an assessment of the microbial
degradation of the cellulosic, plastic and rubber material, the anoxic
corrosion of iron in the steel waste canisters and reactions of the
engineered barrier. The DOE did not change the rates for microbial
cellulosic, plastic and rubber material degradation and water
production from the 2009 Compliance Recertification Application. As
discussed previously, the DOE revised steel corrosion rates. The DOE
developed magnesium reaction rates for the compliance recertification
application based on previous studies (Chemistry TSD \22\).
---------------------------------------------------------------------------

    \22\ ``Technical Support Document for Section 194.24: Evaluation
of the Compliance Recertification Actinide Source Term, Gas
Generation, Backfill Efficacy, Water Balance and Culebra Dolomite
Distribution Coefficient Values'' in Docket ID No. EPA-HQ-OAR-2014-
0609.
---------------------------------------------------------------------------

    Although changes to each of these parameters is minor, the
reactions will have a cumulative effect. Based on previous exchanges
with the DOE (see comment 2-C-5 in Docket ID No. EPA-HQ-OAR-2014-0609)
as well as the SEN4 sensitivity study, the water balance updates do not
appear to significantly affect the WIPP performance. However, the EPA

recommends that the DOE re-evaluate the water balance issue for future
performance assessments to address questions associated with
interactions involving magnesium oxide (e.g., hydration rates in the
water balance calculations), and as previously discussed in Section
VI.D.1.e, the associated steel corrosion model and passivation
processes.
    h. Variable Brine Volume. Brine volume plays an important role in
calculating actinide and organic ligand concentrations. In previous
performance assessments, the DOE calculated concentrations of these
species using the minimum brine volume needed for a direct brine
release, regardless of how much brine is projected to be released. This
failed to account for dilution and thus resulted in an overestimation
of organic ligand concentrations as well as actinide releases. To
correct for this in the 2014 Compliance Recertification Application,
the DOE adjusted actinide and organic ligand concentration calculations
to incorporate multiple brine volumes. The DOE continues to calculate
actinides and organic ligand concentrations at the minimum brine volume
required for a release. However, the DOE now also calculates
concentrations by dissolving these species at volumes 2, 3, 4 and 5
times the minimum volume to simulate larger volume releases. Thus,
concentrations at 5 times the volume will be lower than those
calculated at the minimum volume because more brine will be present to
dilute these aqueous species. The EPA finds that this approach
realistically addresses the issue of variable brine volumes involved in
a direct brine release and accepts this model for the compliance
recertification application.
    i. Revised Colloid Parameters. Colloids are particles larger than
molecules that can be suspended in the WIPP brine. Because colloids
migrate more rapidly through the subsurface than actinides dissolved in
solution, colloids are an important contribution to actinide mobility
during a direct brine release. Intrinsic colloids are actinide
macromolecules that eventually increase in size. Microorganisms are
considered large colloids capable of mobilizing actinides because of
actinide sorption to their charged cell walls or because of actinide
bio-uptake.
    In the original Compliance Certification Application, the colloid
parameters were based on experimentally derived values examining
actinide macromolecules or actinides sorbed onto biomass (e.g.,
Completeness Comment 3-C-9 in EPA-HQ-OAR-2014-0609-0010). Since then,
the DOE has performed multiple new investigations to update the
intrinsic and microbial colloid parameters. These investigations
prompted the DOE to reduce the contribution of colloids in the 2014
performance assessment.
    Because of issues with experimental data used to develop the 2014
colloid contributions to actinide solubility, the 2014 performance
assessment calculations using those experimental results may
underestimate colloidal concentrations, and therefore, actinide
solubility. However, the EPA finds that the use of an updated
uncertainty distribution for actinide solubility in the SEN4
sensitivity study provides adequate information to determine that an
increase in colloid concentrations would not cause releases to exceed
the disposal standards. The EPA recommends that additional review of
the experimental results would benefit the DOE's treatment of colloid
formation mechanisms in future performance assessments. The EPA's
review of this topic is provided in the Chemistry TSD. See Section VI.E
of this document for discussion of the SEN4 study.
    j. New Actinide Solubility Code (EQ3/6). Prior to the 2014
Compliance Recertification Application, the DOE used the Fracture
Matrix Transport (FMT) geochemical modeling code for actinide
solubility calculations. The DOE has since moved actinide solubility
calculations to the EQ3/6 code using the database DATA0.FM1, which
contains the values needed to calculate chemical speciation of the
ions, actinides and minerals present in the WIPP. The move to EQ3/6 is
logical as the program is widespread and has been used in other the DOE
projects. EQ3/6 can provide more robust calculations than FMT,
particularly in dynamic reaction-path calculations. The EPA accepts the
move to the EQ3/6 code. For additional discussion on this topic see the
EQ3/6 TSD.\23\
---------------------------------------------------------------------------

    \23\ ``EQ3/6 Computer Code Evaluation'' in Docket ID No. EPA-HQ-
OAR-2014-0609.
---------------------------------------------------------------------------

    2. Other Key Issues Identified by the EPA During Review. The EPA
identified three key topics where the Agency believes new information
can be incorporated into future compliance recertification
applications. These topics relate to the chemical conditions within the
repository and are of fundamental importance in determining the
potential for releases of radionuclides from the disposal system. These
topics are discussed in more detail in the Chemistry TSD.
    a. Chemical Database. Actinide solubility, or the ability for
actinide solids to dissolve in brine, is important in calculating
releases. In performance assessment calculations, these radionuclides
include americium, curium, neptunium, plutonium, thorium, and uranium.
Americium(III) solubility is used to predict plutonium(III) and
curium(III) concentrations while thorium(IV) is used to predict
plutonium(IV), neptunium(IV) and uranium(IV).
    The EPA's review identified that the DOE's update of the chemical
assumptions used in the actinide solubility database (DATA0.FM1) did
not reflect all data available prior to the DOE's data cut-off date of
December 31, 2012.The EPA raised several issues (in Docket ID No. EPA-
HQ-OAR-2014-0609-0010) about americium and thorium solubility and
speciation and in response, the DOE modified the database to produce
DATA0.FM2. However, the EPA identified flaws in the modified database
that need to be corrected before it can be considered to be of
sufficient quality for use in recertification. The EPA concluded that,
even with identified data gaps, the original DATA0.FM1 database was of
higher quality and provided sufficient information to support a
determination of continued compliance. The DOE's updates of the
chemical database for future performance assessments should more
comprehensively incorporate recent data.
    b. Revised Radionuclide Uncertainty Distribution. The DOE also
examined the uncertainty distribution used to model the +III and +IV
actinide concentrations in the performance assessment by comparing
modeled solubility calculations to experimental data from multiple
reports and peer-reviewed studies. These studies include solubility
measurements from americium, thorium and their analogues using a
specific set of criteria (Chemistry TSD; 2014 Compliance
Recertification Application, Appendix SOTERM-2014 Section 5.1.3).
During the performance assessment solubility calculations, this
uncertainty distribution is sampled and used in calculating dissolved
actinides in a release.
    After reviewing the actinide solubility uncertainty distribution
for the 2014 Compliance Recertification Application, the EPA identified
relevant studies that were not considered in developing this
distribution, as well as identifying studies that should have been
excluded from consideration, based on the DOE's evaluation criteria.
Using relevant studies would result in a revised actinide solubility
uncertainty distribution with overall higher +III

actinide solubility. The DOE included a revised solubility uncertainty
distribution based on the EPA's input in the sensitivity study SEN4.
The higher actinide solubility used in the SEN4 study contributed to
higher releases compared to the 2014 performance assessment, although
releases in the SEN4 study still remain below the regulatory limits.
See Section VI.E for more discussion of the SEN4 study.
    The EPA recommends that updating the actinide solubility
uncertainty distribution should be part of the update to the
geochemical database. This would include incorporating new solubility
data for thorium and americium under the WIPP repository conditions,
and re-evaluating how studies are included in or excluded from the
DOE's analyses.
    c. Plutonium Oxidation State. Oxidation states refer to an actinide
ion's charge. Actinides with a higher charge likely exist in
environments with greater oxygen content while actinides with lower
charges likely exist where there is less oxygen. Although plutonium has
multiple oxidation states including +VI, +V, +IV, and +III, the WIPP
model assumes plutonium oxidation state is dominated by the +III or +IV
charge in the aqueous phase due to the rapid removal of oxygen in the
repository. Identifying the dominant oxidation state is particularly
important as plutonium(III) is much more soluble than plutonium(IV). To
address this uncertainty, the plutonium oxidation state model does not
calculate oxidation state but instead considers plutonium(III) in 50%
of the realizations and plutonium(IV) in the other 50%. Since the 2009
Compliance Recertification Application, experiments have verified that
the iron metal corrosion of the WIPP waste containers largely mediate
the conditions conducive to plutonium(IV) and plutonium(III) oxidation
states. While experiments have confirmed the WIPP conditions post-
closure, the debate has shifted towards whether plutonium(IV) or
plutonium(III) is dominant in the WIPP conditions, or whether they will
be present in equal proportions. More recent experimental information
leads the EPA to believe that, under the WIPP conditions, aqueous
plutonium(III) will be the dominant state of plutonium and will exist
in equilibrium with the different solid plutonium phases present. In
addition, organic ligands, iron and microbial processes will also
increase the likelihood that plutonium(III) will dominate in solutions.
    While the sensitivity studies did not directly test the presumption
that +III and +IV species would be equally present, the SEN4 study
indirectly examined this proposition by including a modified solubility
uncertainty distribution that was more heavily weighted toward higher
+III solubility (see Section VI.E.2.d). Both the compliance
recertification application and the SEN4 study indicate plutonium
release levels will be below the compliance points. Combined with the
related analysis of the actinide solubility uncertainty distributions,
the Agency can accept the DOE's assumption that the plutonium(III) and
plutonium(IV) oxidation states will each occur 50% of the time in
performance assessment calculations for the current recertification.
However, because of the available data that the EPA has identified
supporting the presence of plutonium(III) over plutonium(IV), the EPA
believes this issue is of sufficient significance to benefit from
independent technical review of the available data and the assumption
that both plutonium oxidation states will occur equally under the WIPP
conditions. The EPA's review of the plutonium oxidation state issue is
addressed more thoroughly in the Chemistry TSD.

E. Performance Assessment: Modeling and Containment Requirements
(Sec. Sec.  194.14, 194.15, 194.23, 194.31 through 194.34)

    1. Overview. Section VI.A provided a basic description of the
requirements in 40 CFR 191.13 and the performance assessment process
required to show compliance with those standards. This section provides
additional information on performance assessment and how it is
evaluated by the EPA in the compliance recertification application. As
described earlier, the DOE must use the performance assessment to
demonstrate compliance with the containment requirements in 40 CFR
191.13. The containment requirements are expressed in terms of
``normalized releases.'' The DOE assembles the results of the
performance assessment into complementary cumulative distribution
functions, which indicate the probability of exceeding various levels
of normalized releases (Sec.  194.34).
    For both of the DOE's 2004 and 2009 Compliance Recertification
Applications, the EPA requested that the DOE modify those respective
performance assessments to (1) address completeness and technical
issues raised during the EPA review process and with these
modifications, and (2) assure the disposal regulations were met.
    These additional sets of calculations have been termed by the DOE
to be performance assessment ``baseline calculations'' and the EPA has
considered these calculations as updated ``baselines'' for each
respective compliance recertification application. The EPA then used
these baseline calculations for the comparison performance assessment
in each of the DOE's subsequent five-year compliance recertification
applications.
    In this recertification review process, the Agency proceeded
differently than in the past. During the completeness review, the EPA
identified issues with parameters or approaches used by the DOE in the
calculations. These have been discussed in Section VI.D. The Agency
requested that the DOE conduct additional calculations so the EPA could
better understand how alternative parameter values would affect
repository performance. These calculations, or sensitivity studies as
they have been referred to, are summarized below and are the subject of
a TSD.\24\ With the completion of these sensitivity studies, the Agency
has decided not to request another set of performance assessment
baseline calculations as was done for previous recertifications. The
Agency believes that the sensitivity studies, coupled with the DOE's
documentation, provide a reasonable expectation that the WIPP complies
with the radioactive waste disposal regulations at 40 CFR part 191 and
the compliance criteria at 40 CFR part 194. Further, with the February
2014 incidents and the DOE's resulting need to change the facility
design,\25\ the Agency felt it was not necessary or appropriate at this
time to conduct additional calculations using a facility design that
will be changed in the near future.
---------------------------------------------------------------------------

    \24\ ``Review of EPA Sensitivity Studies of the DOE CRA-2014
WIPP Compliance Recertification Performance Assessment'' in Docket
ID No. EPA-HQ-OAR-2014-0609.
    \25\ The DOE has stated that it intends to abandon plans to use
the area previously designated as waste panel 9 for waste
emplacement because of worker safety issues (``Installation of
Ventilation Barriers and Prohibiting Personnel Access to Equivalent
Panel 9 Areas,'' Letter from Todd Shrader, DOE, to Alan Perrin, EPA
dated April 18, 2017, Docket ID No. EPA-HQ-OAR-2014-0609). The DOE
also plans to develop a new ventilation shaft to increase airflow in
the mine, which is limited after the February 2014 incidents.
---------------------------------------------------------------------------

    The Agency requested that the DOE conduct four sensitivity studies
(labeled as SEN1, SEN2, SEN3 and SEN4) to address technical concerns
raised during the EPA's 2014 Compliance Recertification Application
review. The EPA has compared these sensitivity results to the DOE's
2014 performance assessment calculations. The purpose of these
sensitivity studies is to provide an understanding of how repository

compliance would be affected when modifying specific inputs in the 2014
performance assessment calculations. A brief explanation of those
selected parameters is provided below.
    The ability of salt openings and aggregates to quickly compress,
consolidate and ``heal'' within a few hundred years, mostly due to the
creep-closure process, is one of the unique properties of bedded salt
geologic units that make them potentially suitable to use as nuclear
waste repositories. The DOE's 2014 performance assessment parameter
values assigned to the non-waste rooms, the panel closure system and
the adjacent disturbed rock zone did not reflect the creep-closure and
rapid healing of these areas that the EPA expects to occur. That is,
the DOE did not use permeability, porosity, residual gas and brine
saturations and capillary pressures reflective of in-situ (i.e.,
undisturbed) conditions.
    Three of the EPA requested sensitivity studies, SEN1, SEN2 and
SEN3, focused on modifying parameters to test how assuming complete
creep-closure and healing of these areas would impact long-term
performance through modifying values related to the permeability,
porosity and two-phase flow parameter values for the run-of-mine salt
panel closure system, the disturbed rock zone and non-waste areas for
the 10,000-year modeled period. The fourth sensitivity study, SEN4,
investigated the cumulative effects and impact on repository
performance by making changes to five important parameter values as
well as using an updated numerical code.
    As with the 2014 performance assessment, all of the sensitivity
studies had three replicate calculation sets and included the same
future scenarios. The four scenarios are briefly described below:
    (1) The undisturbed scenario--where the repository is not impacted
by human activities,
    (2) The E1 Scenario--where one or more boreholes penetrate a
Castile brine reservoir and also intersect a repository waste panel,
    (3) The E2 Scenario--where one or more boreholes intersect a
repository waste panel but not a brine reservoir, and
    (4) The E1/E2 Scenario--where there are multiple penetrations of
waste panels by boreholes of either the E1 or E2 type, at many possible
combinations of intrusion times and locations for either E1 or E2
drilling type of event.
2. Sensitivity Studies
    a. The SEN1 Study. The intention of the SEN1 study was to determine
the impact on repository performance by modeling the stepped (i.e.,
gradual) reduction in porosity, permeability, residual gas and brine
saturation, and capillary pressures that reflect creep-closure and
healing of the open rooms and disturbed rock zone during the first 200
years after repository closure. The DOE was then to model these areas,
from 200 years to 10,000 years, as fully healed.
    This study had to be terminated because the numerical flow code
used in these calculations produced non-physical and unrealistic
results when these parameters were modified in time-intervals to
reflect healing. The Agency accepted termination of this study, in
part, because modeling changes in these values for the first 200 years,
a relatively short time compared to the 10,000-year regulatory time
period, would not be as important to long-term repository performance.
The Agency considered that the SEN2 and SEN3 studies described below
adequately addressed the issues targeted by the SEN1 study because the
latter two studies both modeled the open and disturbed areas as fully
healed for the entire 10,000-year regulatory time period, essentially
bounding the conditions specified for the SEN1 study.
    b. The SEN2 Study. This study tested the impacts on repository
performance by modeling the non-waste areas and open drifts as
completely creep-closed during the entire 10,000-year regulatory
period. In this study, parameter values for all the non-waste areas
(i.e., the operations and experimental room open drifts) and adjacent
disturbed rock zones were modified. The permeability and porosity were
reduced to that of intact halite. The residual brine and gas
saturations were also increased to better reflect healed conditions and
capillary pressures (the pressure needed for fluid to flow between
pores) were increased.
    Compared to the 2014 Compliance Recertification Application
performance assessment, the SEN2 study waste room pressures generally
increased and brine saturations decreased. The most affected primary
release mechanism saw an increase in solid waste moving up a borehole
(spallings) because this release mechanism increases when waste panel
pressure increase. All other release mechanisms remained essentially
unchanged from the 2014 performance assessment calculations. Total
spallings releases remained small compared with cuttings, cavings and
direct brine releases. Spallings releases therefore did not materially
contribute to total repository releases in either SEN2 or the 2014
Compliance Recertification Application.
    c. The SEN3 Study. For the SEN3 study, the DOE assumed that the
panel closure system, the adjacent disturbed rock zone and the non-
waste areas and open drifts are healed for the 10,000-year regulatory
period. The DOE reduced porosity and permeability in the repository,
increasing initial residual brine and gas saturations, and invoking
two-phase flow parameters for intact halite. Using these modifications
effectively isolated the individual waste panels and the non-waste
areas from one another for the entire modeled period due to limited
brine and gas flows between areas of the repository.
    The modifications made in the SEN3 study caused increases in waste-
panel pressures and decreases in waste panel saturations. The dominant
releases were from spallings, which are only dependent on a waste panel
pressure high enough to force solids to the surface, and direct brine
releases, which are dependent on having sufficient brine in the waste
panels coupled with high enough pressure to force brine to the surface.
The release mechanism that increased the most was for spallings, and
the increase was seen at both the low and high probability compliance
points. The impact on direct brine release was primarily at low
probabilities because this release depends on both high waste panel
pressure and high saturation conditions, the combination of which were
less likely to occur in this study.
    Factoring in all combined releases, the total mean and low-
probability (0.001 probability) releases increased by approximately 15%
from the initial 2014 Compliance Recertification Application results,
although the upper bound of the 95% confidence interval was essentially
the same as in the 2014 Compliance Recertification Application (0.384
EPA Units in the 2014 Compliance Recertification Application and 0.387
EPA Units in SEN3). Total releases did not exceed the EPA's WIPP
release limits.
    The parameter values used in the SEN3 study created a ``tight''
repository (panel closure system, disturbed rock zone and non-waste
rooms) in which brine and gas flow is limited. The study results
indicate that such conditions may produce calculated releases higher
than the more open and brine- and gas-conducive set of conditions
presented by the DOE in the 2014 Compliance Recertification
Application.
d. The SEN4 Study
    i. Overview. The fourth sensitivity study was intended to
understand the cumulative effects on repository performance by making
changes to

several parameters that the Agency questioned in the completeness
review. This study also incorporated a DOE-corrected version of the
DRSPALL code, which calculates waste that is released up a borehole to
the surface. This study does not address all of the EPA's completeness
questions, but provides significant insights as to the degree in which
some parameter values of interest to the EPA impact releases. Note, the
parameter changes in SEN2 and SEN3 representing creep closure were not
made in the SEN4 study, so the results reflect the 2014 Compliance
Recertification Application creep closure assumptions. The
modifications requested for this study are provided below:
     Use the EPA's updated distribution for the probability of
intersecting a waste panel and a Castile brine reservoir, denoted as
the PBRINE parameter and discussed in Section VI.D.1.d previously.
     Use the revised data set for the plutonium oxidation state
uncertainty distribution discussed in Section VI.D.2.c.
     Modify the lower limit for the parameter that predicts
waste strength, denoted as the parameter TAUFAIL discussed in Section
VI.D.1.f.
     Use the updated version of the computer code DRSPALL that
models waste carried up a borehole. After the 2014 performance
assessment calculations had been completed and submitted to the EPA,
the DOE discovered an error in the computer code, DRSPALL. The DOE
corrected this error and reported it to the EPA. For the SEN4 study,
the EPA requested that the DOE use the corrected version.
     Eliminate the hydrogen sulfide reaction with iron as
discussion in Section VI.D.1.e.
     Use the correct modeled length for north panel closure.
The WIPP repository design includes two sets of panel closures emplaced
at the north end of the repository. For the 2014 performance assessment
calculations, the DOE modeled the ``effective'' length of only one
panel closure rather than two. The EPA requested that the DOE increase
the effective length of the modeled north waste panel to be consistent
with the facility design.
    ii. Cumulative effects of the changes evaluated by release pathway.
    aa. Direct Brine Releases. Direct brine releases are a function of
actinide solubility, repository pressure and brine saturation. Of these
changes, the most significant are the revised solubility uncertainty
distributions that increase the concentration of the more soluble
plutonium(III) in repository brine, the increased likelihood of a
higher probability of hitting a brine pocket and the iron sulfidation
reaction stoichiometric coefficient changes. The combined effects of
these changes increased direct brine calculated releases and total mean
low probability (0.001) repository releases to about twice those of the
2014 Compliance Recertification Application performance assessment
(0.541 EPA Units for SEN4 versus 0.261 EPA Units for 2014 performance
assessment).
    bb. Spallings Releases. Spallings releases are affected in SEN4 by
a combination of corrections using the updated version of the DRSPALL
code as well as increases in repository pressure. Repository pressure
was generally increased in SEN4 as a result of the updated distribution
of the PBRINE parameter, the increased length of the northernmost panel
closure and the updated iron sulfidation reaction stoichiometric
coefficients. The combined effect of these changes was to increase
spallings releases by about half an order of magnitude. However,
spallings releases remained low compared to direct brine releases and
the effect of this increase in spallings on total mean releases was
minimal.
    cc. Cuttings and Cavings Releases. Cavings releases were affected
by the Agency's requested reduction of the lower bound of the
distribution for the TAUFAIL parameter. The small reduction in the
lower bound did not have a meaningful effect on total mean releases.
    dd. Releases from the Culebra. Releases from lateral flow through
the Culebra Dolomite are a function of actinide solubility, repository
pressure, and brine saturation. These are affected by the revised
solubility uncertainty distributions, the increased likelihood of
sampling higher values for the PBRINE parameter, the increased length
of the northernmost panel closure and removal of the iron sulfidation
reactions. The combined effect of these changes on Culebra releases was
too small to have a meaningful effect on total mean repository
releases.
    ee. Insights from the SEN4 Study. In the SEN4 study, the most
significant effects on repository performance were an increase in
direct brine releases and, by extension, an increase in total low
probability repository releases. The Agency concludes that these
increases were primarily the result of updating the solubility
uncertainty distributions, updating the distribution of PBRINE and
incorporating hydrogen sulfide steel passivation. The remaining
changes, updating the TAUFAIL lower bound, using the corrections in the
code DRSPALL and correcting the panel closure length, provided
important updates and corrections to the performance calculation but
had only a negligible effect on total mean releases. As in the previous
sensitivity studies, the total mean releases, the upper 95% confidence
limit on those means and all individual vectors in the three replicates
remained below regulatory limits in SEN4.
    3. How the Four Sensitivity Studies Affect the WIPP's Compliance.
The results indicate that modifications to the selected parameters
reported in these evaluations increased calculated releases. However,
the total mean releases, the upper 95% confidence limit on those means,
and all individual vectors in the three replicates remained below the
EPA's WIPP release limits.
    These sensitivity studies were intended to address a subset of the
EPA technical issues. These studies do not address all the technical
issues identified in the EPA's 2014 Compliance Recertification
Application review. The major issues identified in the EPA's review
primarily influence the direct brine releases and how the performance
assessment addresses those releases. The EPA recommends that,
especially with respect to calculating direct brine releases, the DOE
re-evaluate the implementation of features, events and processes, along
with model assumptions, to ensure their appropriate integration in the
2019 Compliance Recertification Application. The EPA has identified two
areas in particular (modeling of open areas and plutonium oxidation
states) that the Agency believes would greatly benefit from independent
technical review for consideration in the DOE's 2019 Compliance
Recertification Application.

F. Additional Requirements

    This section summarizes the EPA's review as it relates to specific
sections of the WIPP Compliance Criteria in 40 CFR part 194 that do not
directly involve performance assessment.
    Information on continuing compliance activities related to waste
characterization (40 CFR 194.8 and 194.24), inspections (Sec.  194.21)
and quality assurance (Sec.  194.22) may be found in Section V of this
document.
    The DOE did not conduct any activities during the period covered by
the 2014 Compliance Recertification Application related to future state
assumptions (Sec.  194.25), expert judgment (Sec.  194.26) or assurance
requirements (Sec.  194.41-46). See the corresponding CARDs for more
discussion. Information on passive institutional controls, which is an
element of the assurance

requirements, may also be found in Section V.B.4.
    1. Waste Characterization (Waste Inventory) (Sec.  194.24). Section
194.24 generally requires the DOE to identify, quantify and track the
important chemical, radiological and physical components of the waste
destined for disposal at the WIPP. The DOE collects data from generator
sites and compiles the waste inventory on an annual basis. The DOE's
2012 Annual Transuranic Waste Inventory Report (ATWIR 2012), which was
used for the 2014 Compliance Recertification Application, reflects the
disposal intentions of the waste generator sites as of December 31,
2010. The DOE classified the wastes as emplaced, stored or projected
(to-be-generated). The DOE used data from the WIPP database to identify
the characteristics of the waste that has been emplaced at the WIPP.
The projected wastes were categorized similarly to existing waste
(e.g., heterogeneous debris, filter material, soil).
    The EPA reviewed the compliance recertification application and
supplemental information to determine whether these documents provided
a sufficiently complete estimate and description of the chemical,
radiological and physical composition of the emplaced, stored and
projected wastes proposed for disposal in the WIPP. The Agency also
reviewed the DOE's description of the approximate quantities of waste
components (for both existing and projected wastes). The EPA found that
the radionuclides, cellulosic, plastic and rubber materials, organic
ligands, oxyanions and cements in the waste are being appropriately
tracked and characterized. In the 2014 Compliance Recertification
Application, there is an update on the inventory of curium and
neptunium, which remain in concentrations well below their solubility
limits even after accounting for decay. The EPA accepts this updated
inventory, which is relatively similar to the one used in the 2009
Compliance Recertification Application. See the Baseline Inventory TSD
\26\ for more information.
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    \26\ ``Technical Support Document for Section 194.24: Review of
the Baseline Inventory Used in the Compliance Recertification
Application (CRA-2014)'' in Docket ID No. EPA-HQ-OAR-2014-0609.
---------------------------------------------------------------------------

    2. Peer Review (Sec.  194.27). Section 194.27 of the WIPP
Compliance Criteria requires the DOE to conduct peer review
evaluations, when warranted, of conceptual models, waste
characterization analyses, and a comparative study of engineered
barriers. The required peer reviews must be performed in accordance
with the Nuclear Regulatory Commission's NUREG-1297, ``Peer Review for
High-Level Nuclear Waste Repositories,'' which establishes guidelines
for the conduct of a peer review exercise. The DOE has conducted one
peer review since the 2009 Compliance Recertification Application to
establish radiological properties for two waste streams, titled the
``Savannah River Site Historical Radiochemistry Data Peer Review,''
demonstrating its compliance with the requirements of Sec.  194.27.
    Based on a review and evaluation of the 2014 Compliance
Recertification Application and supplemental information provided by
the DOE (Docket ID No. EPA-HQ-OAR-2014-0609-0330), the EPA determines
that the DOE continues to comply with the requirements of 40 CFR
194.27.

G. Individual and Groundwater Protection Requirements (Sec. Sec.
194.51 Through 194.55)

    Sections 194.51 through 194.55 of the WIPP Compliance Criteria
implement the individual protection requirements of 40 CFR 191.15 and
the groundwater protection requirements of subpart C of 40 CFR part
191. Assessment of the likelihood that the WIPP will meet the
individual dose limits and radionuclide concentration limits for ground
water is conducted through a process known as compliance assessment.
Compliance assessment uses methods similar to those of performance
assessment (for the containment requirements in 40 CFR 191.13 and
Appendix A) but is required to address only undisturbed performance of
the disposal system. That is, compliance assessment does not include
human intrusion scenarios (i.e., drilling or mining for resources).
Compliance assessment can be considered a ``subset'' of performance
assessment, since it considers only natural (undisturbed) conditions
and past or near-future human activities (such as existing boreholes),
but does not include the long-term future human activities that are
addressed in the performance assessment.
    In the 2014 Compliance Recertification Application, the DOE re-
evaluated each of the individual and groundwater requirements. The DOE
updated the data for ground water quantity determination to define an
underground source of drinking water for purposes of calculating
groundwater concentrations and doses. In the 2014 Compliance
Recertification Application, the DOE used 2011 (U.S. Bureau of Census
2013) census data to update the number of persons per household.\27\
The DOE continued to use the 2009 compliance recertification
application data for the average household water consumption values.
The water consumption data show that the average per capita consumption
is 273 gallons per day.\28\ The DOE concludes that the sub-criterion of
5 gallons per minute rate of production from a well continues to
accurately define an underground source of drinking water \29\ and any
change in this sub-criterion is not warranted as a result of applying
more current water-consumption data to the calculation.
---------------------------------------------------------------------------

    \27\ 2014 Compliance Recertification Application Appendix IGP-
2014, Table IGP-3
    \28\ 2014 Compliance Recertification Application Appendix IGP-
2014, Table IGP-3
    \29\ 2014 Compliance Recertification Application Appendix IGP-
2014, Section IGP-3.1.1)
---------------------------------------------------------------------------

    The updates made by the DOE in the 2014 Compliance Recertification
Application did not significantly impact the conclusions regarding the
groundwater standard in the Compliance Certification Application. The
DOE did not change the criteria for making underground source of
drinking water determinations, and for the 2014 Compliance
Recertification Application evaluation, the maximum potential dose
remains below the Compliance Certification Application value calculated
and continued compliance with the individual protection standard is
maintained. The DOE states that the conservative bounding analysis used
for the 1998 certification decision compliance assessment is still
applicable for 2014 Compliance Recertification Application.\30\
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    \30\ 2014 Compliance Recertification Application Appendix IGP-
2014, Section IGP-4.0
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    The EPA finds the DOE in continued compliance with 40 CFR 194.51-
194.55 requirements.

VII. How has the public been involved in the EPA's WIPP recertification
activities?

A. Public Information

    The EPA interacts with the public through various means. The EPA's
main mechanism for distributing information is the EPA Web site and
email messages via the WIPP-NEWS listserv. The EPA will also
occasionally have meetings, in person or via teleconferences or
webinars.
    Throughout the recertification process, the Agency posted pertinent
new information and updates on the EPA WIPP Web site (https://www.epa.gov/radiation/epas-role-waste-isolation-pilot-plant-wipp). All
pertinent recertification documents

(including the DOE-submitted recertification materials, correspondence,
Federal Register notices, outreach materials, hearing transcripts as
well as TSDs) are available for review or download (in Adobe PDF
format) via the electronic docket dedicated to the 2014-2017
recertification process (http://www.regulations.gov, Docket ID No. EPA-
HQ-OAR-2014-0609).
    Since October 2014, the EPA has sent out numerous announcements
regarding the recertification schedule and availability of any WIPP-
related documents on the EPA WIPP Web site and the dockets, as well as
details for the Agency's June 2015 stakeholder meetings in New Mexico
and January 2017 stakeholder webinar (via Adobe Connect).

B. Stakeholder Meetings

    As discussed in the WIPP LWA, the recertification process is not a
rulemaking and public hearings are not required. However, the EPA held
a series of stakeholder meetings in June 2015 (Carlsbad and
Albuquerque, NM) as well as a stakeholder webinar in January 2017 (via
Adobe Connect software, with public hosting locations in Carlsbad and
Albuquerque, NM) to provide information and updates about the
recertification process. In an effort to make these meetings as
informative as possible to all attending parties, the EPA listened to
stakeholder input and concerns and tailored the meetings around the
public as much as possible. The first meeting was held on June 16,
2015, in Carlsbad, New Mexico and consisted of one three-hour afternoon
session. The second public meeting was held on June 17, 2015, in
Albuquerque, New Mexico, with afternoon and evening sessions.
    The main purpose of these meetings was to discuss the EPA's
recertification process and timeline, as well as the DOE's application
and important changes at the WIPP since the last recertification in
2010. The meetings featured brief presentations on the aforementioned
topics, as well as a facilitated discussion. In response to stakeholder
suggestions, the DOE staff members were also on hand to provide
information and answer any stakeholder questions. Staff from the New
Mexico Environment Department (NMED) were present as observers. Public
participants were encouraged to provide comments to the EPA for
consideration during review of the DOE's 2014 Compliance
Recertification Application.
    The EPA also held a stakeholder webinar using the Adobe Connect
software on January 12, 2017. The Agency hosted the webinar from
Washington, DC, with physical hosting locations set up in both Carlsbad
and Albuquerque, NM, to accommodate members of the public as well as
the DOE and NMED staff. The main purpose of this webinar was to inform
the public of the current recertification schedule and provide updated
technical information related to stakeholder questions and comments
received at the June 2015 meetings.
    All of the issues raised at these meetings have been addressed by
the EPA in Section VII.C of this document or in the CARDs under the
relevant section and are available in the public docket
(www.regulations.gov, Docket ID No. EPA-HQ-OAR-2014-0609).

C. Public Comments on Recertification

    The EPA posted the recertification application on the Web site
immediately following receipt. The EPA formally announced receipt of
the recertification application in the Federal Register on October 10,
2014. The notice also officially opened the public comment period on
the recertification application.
    For recertification, the EPA sought public comments and input
related to changes in the DOE's application that may have a potential
impact on the WIPP's ability to remain in compliance with the EPA's
disposal regulations.
    The comment period for the recertification application closed on
April 10, 2017, approximately two years and six months after it
initially opened. This closing date was 30 days after the EPA's
announcement in the Federal Register that the recertification
application was complete.
    The EPA received 17 sets of written public comments during the
public comment period. The EPA considered significant comments from the
written submissions and the stakeholder meetings in the evaluation of
continuing compliance. The EPA addresses these comments in CARDs that
are relevant to each topic. In addition, a listing of all comments
received and responses to each is included in Appendix 15-C of CARD 15.
Two specific comments are addressed here.
    Comment: One comment addressed shipment of waste from Argonne
National Lab. Citing the EPA's inspection reports, the commenter stated
that he believed that the DOE had shipped and emplaced at the WIPP
waste from the Lab that contained spent nuclear fuel and high level
waste. He correctly stated that the WIPP LWA bans the transport to and
disposal at the WIPP of high level radioactive waste and spent nuclear
fuel. He wanted to know (a) how the EPA failed to uncover that the
Argonne Lab was to ship spent nuclear fuel to the WIPP and approved
this disposal, (b) how the EPA assures that this waste will not be sent
to the WIPP, (c) how much of this waste has been sent to the WIPP, and
the identity of all waste of these types, (d) what authority allowed
the shipment and disposal of these prohibited wastes, and (e) how the
EPA did not bar the DOE's shipment and disposal of these wastes.
    In a related comment, on February 3, 2017, the DOE, responded to
this commenter and stated that the Argonne Lab waste is derived from
atomic energy defense activities and did not contain any spent nuclear
fuel (see EPA-HQ-OAR-2014-0609-0042). The DOE acknowledged that the
WIPP LWA prohibits the disposal at WIPP of spent nuclear fuel and also
acknowledged that some of the waste from the Argonne Lab was debris
from specimens taken from fuel pins that were originally irradiated in
commercial nuclear reactors. However, the DOE commented that the
statutory definition of spent nuclear fuel does not speak directly to
the issue of whether debris from specimens of commercial fuel rods is
spent nuclear fuel. The DOE explained that, here, the debris--although
including material that originated from fuel pins that had been
irradiated in nuclear reactors--resulted from research and development
activities at Argonne. The DOE stated that to try to segregate debris
originating from irradiated fuel pins from other waste would be
technically infeasible and cost prohibitive and would increase worker
exposure. The DOE asserted that resolution of whether the material
should be considered spent nuclear fuel was within its discretion and
that it was its longstanding practice to classify such debris as waste
and not spent nuclear fuel. In response to the DOE's February 3, 2017
comment, the original commenter resubmitted his original comment.
    EPA Response: Under the WIPP LWA, the focus of the EPA's present
recertification determination is whether the WIPP continues to comply
with the final disposal regulations. Although--as the commenter notes
and the DOE acknowledges--the WIPP LWA bans disposal at the WIPP of
spent nuclear fuel, the disposal regulations, themselves, currently do
not expressly address disposal of spent nuclear fuel. The WIPP LWA
incorporates the definition of spent nuclear fuel found in the Nuclear
Waste Policy Act of 1982: ``fuel that has been withdrawn from a nuclear
reactor following irradiation, the constituent elements of which have
not been separated by reprocessing.'' 42 U.S.C. 10101(23) (as
incorporated by

WIPP LWA Sec. 2(15)). There seems to be no dispute that waste from the
Argonne Lab includes some quantity of material that is not presently in
the intact physical form of fuel withdrawn from a reactor following
irradiation,\31\ but is fragments of or particulates from fuel pins
withdrawn from a reactor following irradiation. The DOE states that the
fragments or particulates resulted from research and development
activities on test specimens from fuel pins withdrawn from a reactor
following irradiation and claims that treatment of such material as
other than spent nuclear fuel is consistent with the intent of the WIPP
LWA. The DOE also asserts that attempting to segregate the fuel pin
fragments and particulates from other debris shipped to the WIPP is
infeasible and cost prohibitive and would increase worker exposure.
---------------------------------------------------------------------------

    \31\ There also seems to be no doubt that, as to the material in
question, the ``constituent elements'' have not been ``separated by
reprocessing.''
---------------------------------------------------------------------------

    Reasonable contentions may be made that fragments and particulates
resulting from research and development activities on specimens from
fuel withdrawn from a nuclear reactor following irradiation (``pieces
of pieces'' of fuel pins) do not meet the statutory definition of spent
nuclear fuel. The practical considerations of feasibility, cost, and
worker safety associated with attempting to segregate such particulates
from other waste shipped to the WIPP bear consideration. It is not
essential, however, to the EPA's present recertification decision to
attempt to definitively resolve this issue, because the current
disposal regulations do not expressly address disposal of spent nuclear
fuel.
    On an on-going basis, aside from the periodic recertification of
the WIPP, the EPA communicates with the DOE concerning the
characterization of WIPP waste. The DOE provides the EPA with
documentation relating to WIPP waste streams, including but not limited
to, waste from the Argonne National Laboratory, and including
documentation for both contact handled and remote handled TRU waste
streams. The relevant information is confirmed by analyzing individual
waste containers using the EPA approved processes, procedures and
equipment. These steps allow the DOE to demonstrate that waste
containers for WIPP disposal meet the EPA's WIPP waste limits for
physical and radiological contents of the waste. So, concerning the
waste shipped from Argonne National Laboratory, the EPA evaluated the
waste characteristic information prepared for remote handled waste. The
DOE provided historical information to document that waste generated
from laboratory experiments at Argonne was defense related, and through
radiological assay concluded that the waste in question met the
definition of TRU waste and was appropriate for disposal at the WIPP.
Following this determination, Argonne provided this waste for
characterization. Radiological and physical characterization confirmed
that the TRU waste in question (a) is remote handled waste; (b)
exhibits the characteristics of debris waste; and (c) meets the
regulatory limits of the EPA's WIPP waste acceptance requirements at 40
CFR 194.24.
    The EPA thoroughly inspects and approves the waste characterization
processes in place at all waste characterization sites including
Argonne National Laboratory. As part of the waste characterization
inspections and approvals, the EPA is responsible for evaluating the
adequacy of characterization methods used to identify and measure
radiological and physical contents of the TRU waste that affect the
long term containment and isolation of waste at the WIPP and for
ensuring that the WIPP-bound waste meets the disposal requirements
under 40 CFR 194.24.
    Comment: Another commenter disagreed with the DOE's proposed
revision of the PBRINE parameter. The commenter noted that the DOE's
2014 approach resulted in a lower probability of intersecting a brine
pocket than was used in the original certification and previous
recertifications, and finds this to be ``invalid.'' The commenter
recommends using a fixed value of 60% probability, based on historical
well testing and geophysical data. The commenter also disputes a number
of the DOE's underlying assumptions for revising the approach,
including the DOE's view of the geophysical data as unreliable and what
the commenter sees as the DOE's misinterpretation of more recent
drilling data.
    EPA Response: The EPA agrees with the commenter that the DOE's
revised approach raises concerns. In particular, the EPA does not agree
with the DOE's conclusions regarding the geophysical data. However,
after reviewing the data again, the EPA disagrees with the commenter
that a fixed probability of 60% is necessary. The EPA notes that 60%
was the high end of the probability distribution used in performance
assessments prior to 2014, with a mean probability of 30.5%, as
recognized by the commenter. The updated approach developed by the EPA
uses the geophysical data, but also incorporates newer drilling
information into the probability distribution. The EPA believes this
approach is sound and is acceptable for use in future performance
assessments. The EPA will evaluate future proposals by the DOE to
update the method for determining PBRINE. The EPA's review is discussed
further in Section VI.D.1.d of this document and in the PBRINE TSD.

VIII. Where can I get more information about the EPA's WIPP-related
activities?

A. Supporting Documents for Recertification

    The CARDs discuss DOE's compliance with each of the individual
requirements of the WIPP Compliance Criteria. The CARDs also list the
EPA TSDs and any other references used by the EPA in rendering the
decision on compliance. All TSDs and references are available in the
Agency's dockets, via www.regulations.gov (Docket ID No. EPA-HQ-OAR-
2014-0609), with the exception of generally available references and
those documents already maintained by the DOE or its contractors in
locations accessible to the public. For more detailed information on
the technical issues considered in the EPA's recertification decision,
see the TSDs.

B. The WIPP Web site & WIPP-NEWS Email Listserv

    For more general information and updates on the EPA's WIPP
activities, please visit the WIPP internet homepage at <https://www.epa.gov/radiation/epas-role-waste-isolation-pilot-plant-wipp>. All
pertinent recertification-related documents (including the DOE-
submitted recertification materials, letters, Federal Register notices,
outreach materials, etc.) are available for review or download in Adobe
PDF format. The Agency's WIPP-NEWS email listserv, which automatically
sends messages to subscribers with up-to-date WIPP announcements and
information, is also available online. Any individuals wishing to
subscribe to the listserv can join by visiting <https://lists.epa.gov/read/all_forums/subscribe?name=wipp-news> and providing all requested
information to register.

C. Dockets

    In accordance with 40 CFR 194.67, the EPA maintains public dockets
via www.regulations.gov (Docket ID No. EPA-HQ-OAR-2014-0609) that
contain all the information used to support the Agency's decision on
recertification. The Agency maintains the formal hard

copy/paper docket in Washington, DC, as well as informational dockets
in three locations in the State of New Mexico (Carlsbad, Albuquerque,
and Santa Fe). The docket consists of all relevant, significant
information received to date from outside parties and all significant
information considered by the EPA in reaching a recertification
decision regarding whether the WIPP facility continues to comply with
the disposal regulations.

IX. What is the EPA's role in future WIPP activities?

    The EPA's regulatory role at the WIPP does not end with this
recertification decision. The Agency's future WIPP activities include
additional recertifications every five years (the next being scheduled
to be submitted by the DOE in March 2019), review of the DOE reports on
conditions and activities at the WIPP, assessment of waste
characterization and quality assurance programs at waste generator
sites, announced and unannounced inspections of the WIPP and other
facilities and, if necessary, modification, revocation or suspension of
the certification.
    As a result of the February 2014 incidents at the WIPP, the DOE
will be making changes to the repository design. The DOE has indicated
that it no longer plans to use panel 9 for waste operations due to the
worker safety hazards in that location, so an alternative panel will be
needed. This decision may also have implications for panel closures in
the panels accessed through the panel 9 drifts (i.e., panels 3-6). In
addition, the DOE is planning a new ventilation shaft that will allow
for increased airflow through the underground operations area. The EPA
will be keeping abreast of the DOE's requested changes and will make
that information available as it is received.
    As described in Section VI of this notice, the EPA's review of the
2014 Compliance Recertification Application identified where the DOE's
technical basis for the modeling has limitations with assumptions used
or with the basis for some parameter values. The EPA concerns with
these limitations were generally addressed by the results of the SEN
studies. While this approach of using a series of sensitivity studies
to examine identified limitations was sufficient in the context of this
compliance recertification application, it was to some extent driven by
the known upcoming physical changes in the repository. The EPA would
prefer to be able to evaluate a complete revised performance assessment
in future compliance recertification application reviews. The EPA
recommends that the performance assessment technical basis be evaluated
for improvement in these areas: (1) Calculations of actinide
solubility, (2) modeling the chemical conditions in the repository, and
(3) modeling direct brine releases.
    Although not required by the Administrative Procedure Act (APA),
the WIPP LWA or the WIPP Compliance Criteria, the EPA intends to
continue docketing all inspection or audit reports and annual reports
and other significant documents on conditions and activities at the
WIPP, as well as formal communications between the two agencies.
    The EPA plans to conduct future recertification processes using an
administrative process generally similar to that described in today's
action.

    Dated: July 10, 2017.
Sarah Dunham,
Acting Assistant Administrator, Office of Air and Radiation.
[FR Doc. 2017-15182 Filed 7-18-17; 8:45 am]
BILLING CODE 6560-50-P