based on the EPA's determination that the SJV cannot practicably attain
the standard by the applicable attainment date of December 31, 2021.
    Under section 188(c)(2) of the Act, the attainment date for a
Serious area ``shall be as expeditiously as practicable but no later
than the end of the tenth calendar year beginning after the area's
designation as nonattainment . . .'' The EPA designated the SJV as
nonattainment for the 2012 PM2.5 NAAQS effective April 15,
2015.\248\ Therefore, upon final reclassification of

the SJV as a Serious nonattainment area, the latest permissible
attainment date under section 188(c)(2) of the Act, for purposes of the
2012 PM2.5 NAAQS in this area, will be December 31, 2025.
---------------------------------------------------------------------------

    \248\ 80 FR 2206.
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    Under section 188(e) of the Act, a state may apply to the EPA for a
single extension of the Serious area attainment date of up to five
additional years, which the EPA may grant if the state satisfies
certain statutory conditions. Before the EPA may extend the attainment
date for a Serious area under section 188(e), the state must: (1) Apply
for an extension of the attainment date beyond the statutory attainment
date; (2) demonstrate that attainment by the statutory attainment date
is impracticable; (3) demonstrate that it has complied with all
requirements and commitments pertaining to the area in the
implementation plan; (4) demonstrate to the satisfaction of the
Administrator that the plan for the area includes the most stringent
measures that are included in the implementation plan of any state or
are achieved in practice in any state, and can feasibly be implemented
in the area; and (5) submit a demonstration of attainment by the most
expeditious alternative date practicable.\249\
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    \249\ For a discussion of the EPA's interpretation of the
requirements of section 188(e), see General Preamble Addendum,
42002; 65 FR 19964 (April 13, 2000) (proposed action on
PM10 Plan for Maricopa County, Arizona); 67 FR 48718
(July 25, 2002) (final action on PM10 Plan for Maricopa
County, Arizona); and Vigil v. EPA, 366 F.3d 1025, amended at 381
F.3d 826 (9th Cir. 2004) (remanding EPA action on PM10
Plan for Maricopa County, Arizona but generally upholding the EPA's
interpretation of CAA section 188(e)).
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B. Clean Air Act Requirements for Serious Area Plans

    Upon reclassification as a Serious nonattainment area for the 2012
PM2.5 NAAQS, California will be required to submit
additional SIP revisions to satisfy the statutory requirements that
apply to Serious PM2.5 nonattainment areas, including the
requirements of subpart 4 of part D, title I of the Act.
    The Serious area SIP elements that California will be required to
submit are as follows:
    1. Provisions to assure that BACM,\250\ including BACT for
stationary sources, for the control of direct PM2.5 and
PM2.5 precursors shall be implemented no later than four
years after the area is reclassified (CAA section 189(b)(1)(B));
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    \250\ The EPA defines BACM as, among other things, the maximum
degree of emission reduction achievable for a source or source
category, which is determined on a case-by-case basis considering
energy, environmental, and economic impacts. (General Preamble
Addendum, 42010 and 42014). BACM must be implemented for all
categories of sources in a Serious PM2.5 nonattainment
area unless the State adequately demonstrates that a particular
source category does not contribute significantly to nonattainment
of the PM2.5 standard. (Id. at 42011, 42012).
---------------------------------------------------------------------------

    2. a demonstration (including air quality modeling) that the plan
provides for attainment as expeditiously as practicable but not later
than December 31, 2025, or where the state is seeking an extension of
the attainment date under section 188(e), a demonstration that
attainment by December 31, 2025, is impracticable and that the plan
provides for attainment by the most expeditious alternative date
practicable and not later than December 31, 2030 (CAA sections
189(b)(1)(A), 188(c)(2), and 188(e));
    3. plan provisions that require RFP (CAA section 172(c)(2));
    4. quantitative milestones that are to be achieved every three
years until the area is redesignated to attainment and that demonstrate
RFP toward attainment by the applicable date (CAA section 189(c));
    5. provisions to assure that control requirements applicable to
major stationary sources of PM2.5 also apply to major
stationary sources of PM2.5 precursors, except where the
state demonstrates to the EPA's satisfaction that such sources do not
contribute significantly to PM2.5 levels that exceed the
standard in the area (CAA section 189(e));
    6. a comprehensive, accurate, current inventory of actual emissions
from all sources of PM2.5 and PM2.5 precursors in
the area (CAA section 172(c)(3));
    7. contingency measures to be implemented if the area fails to meet
RFP (including quantitative milestones and related reports) or to
attain by the applicable attainment date (CAA section 172(c)(9)); and
    8. a revision to the NNSR program to lower the applicable ``major
stationary source'' \251\ thresholds from 100 tpy to 70 tpy (CAA
section 189(b)(3)) and to satisfy the subpart 4 control requirements
for major stationary sources of PM2.5 precursors (CAA
section 189(e)).
---------------------------------------------------------------------------

    \251\ For any Serious area, the terms ``major source'' and
``major stationary source'' include any stationary source that emits
or has the potential to emit at least 70 tpy of PM10 (CAA
sections 189(b)(3)).
---------------------------------------------------------------------------

    As discussed in section IV.E of this proposed rule, California
submitted NNSR SIP revisions for the SJV to address the subpart 4 NNSR
requirements for Serious PM2.5 nonattainment areas on
November 20, 2019. The EPA is evaluating this SIP submission and will
act on it in a separate rulemaking.
    Finally, reclassification of the SJV as Serious nonattainment for
the 2012 annual PM2.5 NAAQS would lower the de minimis
threshold under the CAA's general conformity requirements (40 CFR part
93, subpart B) from 100 tpy to 70 tpy for PM2.5 and
PM2.5 precursors.\252\ In this case, however,
reclassification would have no impact on the applicable general
conformity de minimis thresholds, because the SJV is already subject to
the 70 tpy de minimis threshold for PM2.5 and all
PM2.5 precursors as a result of the EPA's previous actions
reclassifying the area as Serious nonattainment for the 1997 annual and
24-hour PM2.5 NAAQS and the 2006 24-hour PM2.5
NAAQS.\253\
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    \252\ 40 CFR 93.153(b), 81 FR 58010, 58126.
    \253\ 80 FR 18528 and 81 FR 1514, respectively.
---------------------------------------------------------------------------

C. Statutory Deadline for Submission of Serious Area Plan

    When the EPA reclassifies a nonattainment area to a higher
classification, the CAA sets the parameters for establishing deadlines
for attainment plan SIP submissions for that higher classification. The
State has already made submissions intended to address the Serious area
attainment plan requirements for the 2012 PM2.5 NAAQS for
the SJV, yet the EPA reclassification rulemaking must still establish
the submission deadlines, as discussed in the following paragraphs.
Among other things, such deadlines make clear the time frame for any
future SIP submission should the State find the need to withdraw any
particular element of the Serious area plan requirements (i.e., without
the submittal of a replacement element meeting the completeness
criteria).
    For an area reclassified as a Serious nonattainment area before the
applicable attainment date under CAA section 188(b)(1), section
189(b)(2) requires the state to submit the required BACM provisions
``no later than 18 months after reclassification of the area as a
Serious Area'' and to submit the required attainment demonstration ``no
later than 4 years after reclassification of the area to Serious.''
Section 189(b)(2) establishes outer bounds on the SIP submission
deadlines as necessary or appropriate to assure consistency among the
required submissions and to implement the statutory requirements.
    The Act provides the state with up to 18 months after final
reclassification of an area to Serious to submit the required BACM
provisions. Because an up-to-date emissions inventory serves as the
foundation for a state's BACM/BACT determination, the PM2.5
SIP Requirements Rule requires the state to submit the emissions
inventory required under CAA section 172(c)(3) within 18

months after the effective date of final reclassification.\254\
Similarly, because an effective evaluation of BACM/BACT measures
requires evaluation of the precursor pollutants that must be controlled
to provide for expeditious attainment in the area, if the state chooses
to submit an optional precursor insignificance demonstration to support
a determination to exclude a PM2.5 precursor from the
required control measure evaluations for the area, the EPA requires
that the state submit any such demonstration by this same date. An 18-
month time frame for submission of these plan elements is consistent
with both the time frame for submission of BACM/BACT provisions under
CAA section 189(b)(2) and the time frame for submission of subpart 1
plan elements under section 172(b) of the Act.\255\
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    \254\ 81 FR 58010, 58077.
    \255\ Section 172(b) requires the EPA to establish, concurrent
with nonattainment area designations, a schedule extending no later
than three years from the date of the nonattainment designation for
states to submit plans or plan revisions meeting the applicable
requirements of sections 110(a)(2) and 172(c) of the CAA.
---------------------------------------------------------------------------

    The PM2.5 SIP Requirements Rule also establishes a
specific deadline for submission of the attainment demonstration and
attainment-related plan elements following discretionary
reclassification, which is the earlier of four years from the date of
reclassification, or the end of the eighth calendar year after
designation.\256\ In this case, the earlier of these two dates will be
the end of the eighth calendar year after designation--i.e., December
31, 2023. The attainment-related plan elements required within the same
timeframe as the attainment demonstration are as follows: (1) The RFP
demonstration required under section 172(c)(2); (2) the quantitative
milestones required under section 189(c); (3) any additional control
measures necessary to meet the requirements of section 172(c)(6); and
(4) the contingency measures required under section 172(c)(9). Although
section 189(b)(2) generally provides for up to four years after a
discretionary reclassification for the state to submit the required
attainment demonstration, given the timing of this reclassification
action less than two years before the Moderate area attainment date, it
is appropriate in this case for the EPA to establish an earlier SIP
submission deadline to assure timely implementation of the statutory
requirements.
---------------------------------------------------------------------------

    \256\ 81 FR 58010, 58077.
---------------------------------------------------------------------------

    Finally, the PM2.5 SIP Requirements Rule establishes a
regulatory requirement that the state submit revised NNSR program
requirements no later than 18 months after final reclassification.\257\
The Act does not specify a deadline for the state's submission of SIP
revisions to meet NNSR program requirements to lower the ``major
stationary source'' threshold from 100 tpy to 70 tpy (CAA section
189(b)(3)) and to address the control requirements for major stationary
sources of PM2.5 precursors (CAA section 189(e)) \258\
following reclassification of a Moderate PM2.5 nonattainment
area as Serious nonattainment under subpart 4. Pursuant to the EPA's
gap-filling authority in CAA section 301(a) and to effectuate the
statutory control requirements in section 189 of the Act, the
PM2.5 SIP Requirements Rule requires the state to submit
these NNSR SIP revisions, as well as any necessary analysis of and
additional control requirements for major stationary sources of
PM2.5 precursors, no later than 18 months after the
effective date of final reclassification of the SJV as Serious
nonattainment for the 2012 PM2.5 standard. This due date
will ensure that necessary control requirements for major sources are
established in advance of the required attainment demonstration. An 18-
month timeframe for submission of the NNSR SIP revisions also aligns
with the statutory deadline for submission of BACM and BACT provisions
and the broader analysis of PM2.5 precursors for potential
controls on existing sources in the area.
---------------------------------------------------------------------------

    \257\ Id. at 58078.
    \258\ Section 189(e) requires that the control requirements
applicable to major stationary sources of PM2.5 also
apply to major stationary sources of PM2.5 precursors,
except where the state demonstrates to the EPA's satisfaction that
such sources do not contribute significantly to PM2.5
levels that exceed the standard in the area.
---------------------------------------------------------------------------

    Accordingly, if we finalize our proposal to reclassify the SJV as a
Serious nonattainment area for the 2012 PM2.5 NAAQS,
California would be required to submit the emissions inventory required
under CAA section 172(c)(3), the BACM/BACT provisions required under
CAA section 189(b)(1)(B), and any NNSR SIP revisions required to
satisfy the requirements of CAA sections 189(b)(3) and 189(e) for the
2012 PM2.5 NAAQS no later than 18 months after the effective
date of a final reclassification action. Additionally, California would
be required to submit the Serious area attainment demonstration and all
attainment-related plan elements no later than the end of the eighth
calendar year after designation--i.e., by December 31, 2023.
    We note that the 2018 PM2.5 Plan submitted on May 10,
2019, includes a Serious area plan containing an attainment
demonstration, emissions inventory, attainment-related plan elements,
and BACM/BACT provisions. Also, the State submitted a SIP revision for
the Serious area NNSR requirements on November 20, 2019. The EPA
intends to evaluate and act on the Serious area plan and NNSR SIP
submissions for the 2012 PM2.5 NAAQS in the SJV through
separate rulemakings, as appropriate.

VI. Reclassification of Areas of Indian Country

    Eight Indian tribes are located within the boundaries of the SJV
nonattainment area for the 2012 PM2.5 NAAQS. These tribes
include Big Sandy Rancheria of Western Mono Indians of California, Cold
Springs Rancheria of Mono Indians of California, Northfork Rancheria of
Mono Indians of California, Picayune Rancheria of Chukchansi Indians of
California, Santa Rosa Indian Community of the Santa Rosa Rancheria,
California, Table Mountain Rancheria, Tejon Indian Tribe, and Tule
River Indian Tribe of the Tule River Reservation, California.
    We have considered the relevance of our proposal to reclassify the
SJV as Serious nonattainment for the 2012 PM2.5 standard for
each tribe located therein. We believe that the same facts and
circumstances that support the proposal for the non-Indian country
lands also support the proposal for reservation areas of Indian country
\259\ and any other areas of Indian country where the EPA or a tribe
has demonstrated that the tribe has jurisdiction located within the SJV
nonattainment area. The EPA is therefore proposing to exercise our
authority under CAA section 188(b)(1) to reclassify areas of Indian
country geographically located in the SJV nonattainment area. Section
188(b)(1) broadly authorizes the EPA to reclassify a nonattainment
area--including any Indian country located within such an area--that
the EPA determines cannot practicably attain the relevant standard by
the applicable attainment date.
---------------------------------------------------------------------------

    \259\ ``Indian country'' as defined at 18 U.S.C. 1151 refers to
the following: ``(a) all land within the limits of any Indian
reservation under the jurisdiction of the United States Government,
notwithstanding the issuance of any patent, and including rights-of-
way running through the reservation, (b) all dependent Indian
communities within the borders of the United States whether within
the original or subsequently acquired territory thereof, and whether
within or without the limits of a state, and (c) all Indian
allotments, the Indian titles to which have not been extinguished,
including rights-of-way running through the same.''

---------------------------------------------------------------------------

    Directly-emitted PM2.5 and its precursor pollutants
(i.e., NOX, SO2, VOC, and ammonia) are emitted
throughout a nonattainment area and can be transported throughout that
nonattainment area. Therefore, boundaries for nonattainment areas are
drawn to encompass both areas with direct sources of the pollutant
problem as well as nearby areas in the same airshed. Initial
classifications apply to the entire nonattainment area, i.e., they
exactly match the nonattainment area boundaries. The EPA believes this
approach best ensures public health protection from the adverse effects
of PM2.5 pollution. Therefore, it is generally
counterproductive from an air quality and planning perspective to have
a disparate classification for a land area located within the
boundaries of a nonattainment area, such as the reservation areas of
Indian country contained within the SJV PM2.5 nonattainment
area. Violations of the 2012 PM2.5 standard, which are
measured and modeled throughout the nonattainment area, as well as
shared meteorological conditions, would dictate the same conclusion.
Furthermore, emission increases in portions of a PM2.5
nonattainment area that are left classified as Moderate could
counteract the effects of efforts to attain the standard within the
overall area because less stringent requirements would apply in those
Moderate portions relative to those that would apply in the portions of
the area reclassified to Serious.
    Uniformity of classification throughout a nonattainment area is
thus a guiding principle and premise when an area is being
reclassified. In this particular case, we are proposing to determine,
based on the State's demonstration and current ambient air quality
trends, that the entire SJV nonattainment area, including all
reservations areas of Indian country and any other area located within
the SJV where a tribe has jurisdiction, cannot practicably attain the
2012 PM2.5 standard by the applicable Moderate area
attainment date of December 31, 2021.
    In light of the considerations outlined above that support
retention of a uniformly-classified PM2.5 nonattainment
area, and our proposal to find that it is impracticable for the area to
attain by the applicable attainment date, we propose to reclassify the
entire SJV nonattainment area, including reservation areas of Indian
country and any other area of Indian country located within it where
the EPA or a tribe has demonstrated that the tribe has jurisdiction, as
Serious nonattainment for the 2012 PM2.5 standard.
    Generally, the effect of reclassification is to lower the
applicable ``major source'' threshold for purposes of the NNSR program
and the Title V operating permit program from 100 tpy to 70 tpy,\260\
thus subjecting additional new or modified stationary sources to these
requirements. Reclassification also lowers the de minimis threshold
under the CAA's general conformity requirements from 100 tpy to 70
tpy.\261\ In this case, however, reclassification would not change the
``major source'' thresholds because, as a result of the EPA's January
2016 reclassification of the SJV as a Serious nonattainment area for
the 2006 PM2.5 NAAQS, the area is already subject to the 70
tpy major source threshold for Serious PM2.5 nonattainment
areas in CAA section 189(b)(3).\262\ Likewise, reclassification would
have no impact on the applicable general conformity de minimis
thresholds, because the SJV is already subject to the 70 tpy de minimis
threshold for PM2.5 and all PM2.5 precursors as a
result of the EPA's previous reclassification of the area as Serious
for the 2006 PM2.5 NAAQS.\263\
---------------------------------------------------------------------------

    \260\ CAA sections 189(b)(3) and 501(2)(B).
    \261\ 40 CFR part 93, subpart B.
    \262\ 81 FR 2993.
    \263\ Id. and 40 CFR 93.153(b).
---------------------------------------------------------------------------

    The EPA has contacted tribal officials to invite government-to-
government consultation on this rulemaking effort.\264\ The EPA
specifically solicits additional comment on this proposed rule from
tribal officials. We note that although eligible tribes may seek EPA
approval of relevant tribal programs under the CAA, none of the
affected tribes will be required to submit an implementation plan as a
result of this reclassification.
---------------------------------------------------------------------------

    \264\ We sent letters dated March 3, 2021, to tribal officials
offering government-to-government consultation. See also a summary
of the EPA's outreach to tribes in the San Joaquin Valley;
memorandum dated August 3, 2021, from Rory Mays, Air Planning
Office, Air and Radiation Division, EPA Region IX, to Docket No.
EPA-R09-OAR-2021-0543. We did not receive any request for
consultation.
---------------------------------------------------------------------------

VII. Review of Contingency Measure Element for the 2006
PM2.5 NAAQS

A. Requirements for Contingency Measures

    With one exception, the SIP requirements for contingency measures
that apply to areas classified as Serious for the 2006 PM2.5
NAAQS are the same as those described in section IV.H.1 of this
document for areas that are classified as Moderate for the 2012
PM2.5 NAAQS and cannot practicably attain the NAAQS by the
statutory attainment date, and thus, are not repeated here. However, in
addition to the contingency measures requirements that apply to
Moderate areas with adequate impracticability demonstrations, states
with areas classified as Serious must identify and adopt contingency
measures to address the potential for the area to fail to attain the
NAAQS by the applicable attainment date.

B. Summary of State's Contingency Measure Element for 2006 PM2.5 NAAQS

    The EPA deferred action on the contingency measure element of the
2018 PM2.5 Plan for the 2006 PM2.5 NAAQS when we
took final action on the other elements in the 2018 PM2.5
Plan for that NAAQS.\265\ In this section of this document, we are
proposing action on the contingency measure element of the 2018
PM2.5 Plan for the 2006 PM2.5 NAAQS.
---------------------------------------------------------------------------

    \265\ 85 FR 44192, at 44193 (July 22, 2020).
---------------------------------------------------------------------------

    The 2018 PM2.5 Plan addresses the contingency measure
requirement for the 2006 24-hour PM2.5 NAAQS by reference to
the contingency measure portion of a December 2018 SIP submission that
involved enhanced enforcement of CARB regulations in the SJV, a
commitment to amend the District's residential wood burning rule (i.e.,
District Rule 4901) to include contingent provisions, and updated
emissions estimates for the year following the attainment year for use
in evaluating whether the emissions reductions from the contingency
measures are sufficient.\266\ Recently, CARB withdrew the enhanced
enforcement portion of the December 2018 SIP submission as it pertained
to the 2006 PM2.5 NAAQS in the SJV.\267\
---------------------------------------------------------------------------

    \266\ 2018 PM2.5 Plan, App. H (revised February 11,
2020), H-24 to H-26.
    \267\ Letter dated March 19, 2021, from Richard W. Corey,
Executive Officer, CARB, to Deborah Jordan, Acting Regional
Administrator, EPA Region IX, with enclosures.
---------------------------------------------------------------------------

    Accordingly, we have evaluated the relevant portions of the 2018
PM2.5 Plan and District Rule 4901 (specifically, section
5.7.3 of Rule 4901) for compliance with the applicable requirements for
Serious areas for the 2006 PM2.5 NAAQS.
    With respect to the District contingency measure, the 2018
PM2.5 Plan calls for the District to amend District Rule
4901 to include a requirement in the rule with a trigger that that
would be activated should the EPA issue a final rulemaking that the SJV
failed to meet a regulatory requirement necessitating

implementation of a contingency measure. In response to the commitment
made in the 2018 PM2.5 Plan, in June 2019, the District
adopted amendments to Rule 4901 including a contingency measure (in
section 5.7.3 of the amended rule), and CARB submitted the amended rule
to the EPA for approval as an attachment to a letter dated July 19,
2019.\268\ The EPA has taken final action to approve amended Rule 4901,
but in that approval, we noted that we were not evaluating the
contingency measure in section 5.7.3 of revised Rule 4901 for
compliance with all requirements of the CAA and the EPA's implementing
regulations that apply to such measures.\269\ Rather, we approved the
measure into the SIP because it strengthened the rule by providing a
possibility of additional curtailment days, and thus potentially
additional emissions reductions. We indicated that we would evaluate
whether this provision, in conjunction with other submitted provisions,
meets the statutory and regulatory requirements for contingency
measures in future actions. In this proposal, we are now evaluating
District Rule 4901, specifically, section 5.7.3, for compliance with
the requirements for contingency measures for purposes of the 2006
PM2.5 NAAQS.
---------------------------------------------------------------------------

    \268\ Letter dated July 19, 2019, from Richard W. Corey,
Executive Officer, CARB, to Mike Stoker, Regional Administrator, EPA
Region IX.
    \269\ 85 FR 44206 (July 22, 2020) (final approval of District
Rule 4901); 85 FR 1131, 1132-33 (January 9, 2020) (proposed approval
of District Rule 4901).
---------------------------------------------------------------------------

    District Rule 4901 is designed to limit emissions generated by the
use of wood burning fireplaces, wood burning heaters, and outdoor wood
burning devices. The rule establishes requirements for the sale/
transfer, operation, and installation of wood burning devices and for
advertising the sale of seasoned wood consistent with a moisture
content limit within the SJV.
    The rule includes a two-tiered, episodic wood burning curtailment
requirement that applies during four winter months, November through
February. During a level one episodic wood burning curtailment, section
5.7.1 prohibits any person from operating a wood burning fireplace or
unregistered wood burning heater but permits the use of a properly
operated wood burning heater that meets certification requirements and
has a current registration with the District. Sections 5.9 through 5.11
impose specific registration requirements on any person operating a
wood burning fireplace or wood burning heater and section 5.12 imposes
specific certification requirements on wood burning heater
professionals. During a level two episodic wood burning curtailment,
operation of any wood burning device is prohibited by section 5.7.2.
    Prior to the 2019-2020 wood burning season, the District imposed a
level one curtailment when the PM2.5 concentration was
forecasted to be between 20-65 [micro]g/m\3\ and imposed a level two
curtailment when the PM2.5 concentration was forecasted to
be above 65 [micro]g/m\3\ or the PM10 concentration was
forecasted to be above 135 [micro]g/m\3\. In 2019, the District adopted
revisions to Rule 4901 to lower the wood burning curtailment thresholds
in the ``hot spot'' counties of Madera, Fresno, and Kern. The District
lowered the level one PM2.5 threshold for these three
counties from 20 [micro]g/m\3\ to 12 [micro]g/m\3\, and the level two
PM2.5 threshold from 65 [micro]g/m\3\ to 35 [micro]g/m\3\.
The District did not modify the curtailment thresholds for other
counties in the SJV, and those levels remained at 20 [micro]g/m\3\ for
level one and 65 [micro]g/m\3\ for level two.
    The District's 2019 revision to Rule 4901 also included the
addition of a contingency measure in section 5.7.3 of the rule,
requiring that 60 days following the effective date of an EPA final
rulemaking that the SJV has failed to attain the 1997, 2006, or 2012
PM2.5 NAAQS by the applicable attainment date, the
PM2.5 curtailment levels for any county that has failed to
attain the applicable standard will be lowered to the curtailment
levels in place for hot spot counties. The District estimates that the
potential emissions reduction in direct PM2.5 would be in
the range of 0.014 tpd (if the contingency is triggered in Kings County
but not the other non-hot-spot counties) to 0.387 tpd (if the
contingency is triggered in all five of the non-hot-spot counties), but
there would be no emissions reduction if, at the time of the
determination of failure to attain the 2006 PM2.5 NAAQS by
the attainment date, violations of the 2006 PM2.5 NAAQS were
only observed at monitors in the hot-spot counties.\270\ Corresponding
potential emissions reduction in NOX would be in the range
of 0.002 tpd to 0.060 tpd, respectively, but as noted in the preceding
paragraphs there may be no emissions reduction if the violations are
monitored in the hot-spot counties only.\271\
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    \270\ See Table B-13 in Appendix B from the District's Final
Staff Report (June 20, 2019) for revisions to Rule 4901.
    \271\ NOX emissions reductions from the contingency
measure are based on the District's estimates for direct
PM2.5 emissions using the ratio of direct
PM2.5 to NOX in Table 1 of the District's
Final Staff Report (June 20, 2019) for revisions to Rule 4901.
---------------------------------------------------------------------------

    The 2018 PM2.5 Plan also provides estimates of regional
emissions in the year following the attainment year with which to
evaluate the sufficiency of the emissions reductions from the
contingency measure (i.e., section 5.7.3 of Rule 4901). For the 2006
PM2.5 NAAQS, the attainment year is 2024 and the year after
the attainment year is therefore 2025.\272\ Based on Table H-5 in the
2018 PM2.5 Plan, the annual average emission reductions from
2024 to 2025 due to baseline measures and CARB and the District's
aggregate tonnage commitment are estimated to be 0 tpd direct
PM2.5 and 5.2 tpd NOX. For comparison purposes,
one year's worth of RFP (based on emissions estimates in the 2018
PM2.5 Plan) is approximately 0.6 tpd direct PM2.5
and 18.4 tpd NOX.\273\
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    \272\ 85 FR 44192, 44192.
    \273\ One year's worth of RFP is based on the difference between
the emissions estimates for 2013 and 2024 in Table H-6 of Appendix
H, divided by 11 (i.e., the number of years from 2013 to 2024).
---------------------------------------------------------------------------

C. EPA Evaluation and Proposed Action

    For the 2006 PM2.5 NAAQS, we have similarly evaluated
the contingency measure demonstration in the 2018 PM2.5 Plan
and associated contingency provision of the 2019 amendment to Rule
4901. Specifically, we have evaluated the contingency provision in
District Rule 4901 (i.e., section 5.7.3 of the rule) against the
requirements of CAA section 172(c)(9) and 40 CFR 51.1014 for both
attainment and RFP contingency measures, the latter of which also
includes submittal of quantitation milestone reports and compliance
with quantitative milestones.
    As noted in our summary of the State's submission, the contingency
provision in District Rule 4901 is structured to provide for
implementation if the area fails to attain the 2006 PM2.5
NAAQS, not before, and is therefore consistent with CAA section
172(c)(9). However, as structured by the District, the contingency
provision of Rule 4901 (i.e., section 5.7.3) would provide for
emissions reductions only in Kings, Merced, San Joaquin, Stanislaus,
and/or Tulare counties, not the ``hot spot'' counties of Fresno, Kern,
and Madera, and only if a violating monitoring site (i.e., a site where
the collected data represent a violation of the NAAQS) is located in
said county. In other words, if the EPA's determination of failure to
attain the NAAQS by the applicable attainment date indicates violations
at monitoring location sites in Fresno and Kern (``hot spot'' counties)
and Tulare (non-hot-spot county) counties, the contingency

provision would provide for emissions reductions by lowering the wood
burning curtailment thresholds in only Tulare County. The ``hot spot''
counties are already subject to the lower wood burning curtailment
thresholds in the rule and thus would not be affected by the finding of
failure to attain determination and the other non-``hot spot'' counties
(i.e., other than Tulare County in this example) would not be subject
to the lower wood burning curtailment thresholds.
    In accordance with 40 CFR 51.1014, the contingency provision in
District Rule 4901 identifies a specific triggering mechanism. In this
case, the triggering mechanism in the rule is the EPA's final
determination that the SJV has failed to attain the 2006
PM2.5 NAAQS by the applicable attainment date.\274\ The rule
also specifies a timeframe within which its requirements become
effective after a failure-to-attain determination (i.e., on and after
60 days from the effective date of the EPA's final determination), and
would take effect with minimal further action by the state or the EPA.
However, the contingency provision in District Rule 4901 does not
address the potential for State failures to meet a quantitative
milestone, submit a quantitative milestone report, or failure to meet
an RFP requirement.\275\
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    \274\ Section 5.7.3 of Rule 4901 states that ``the District
shall notify the public of an Episodic Curtailment for the
PM2.5 curtailment levels described in Sections <IP_ADDRESS>
and <IP_ADDRESS> for any county that has failed to attain the applicable
standard.'' (emphasis added) We interpret this to mean that the
District would apply the more stringent curtailment provisions for
any county identified in the EPA's final rule making the
determination that the San Joaquin Valley failed to attain the
applicable PM2.5 NAAQS.
    \275\ We note that section 5.7.3 of District Rule 4901 applies
the lower thresholds ``on and after sixty days following the
effective date of EPA final rulemaking,'' which is appropriate as a
contingency measure trigger for a failure to attain by the
applicable attainment date given that the EPA conducts rulemaking to
make such determinations. However, for the three other contingency
triggers, i.e., State failures to meet a quantitative milestone,
submit a quantitative milestone report, or failure to meet an RFP
requirement, the EPA may not conduct rulemaking but instead make the
determinations through correspondence directly to the state. Thus,
we recommend that section 5.7.3 of District Rule 4901 be amended to
refer to ``EPA final determinations'' rather than to ``EPA final
rulemaking'' when the rule is amended to include the additional
contingency measure triggers.
---------------------------------------------------------------------------

    In addition, the contingency measure provision of Rule 4901 is not
structured to achieve any additional emissions reductions if the EPA
finds that the monitoring locations in the ``hot spot'' counties (i.e.,
Fresno, Kern, or Madera Counties) are the only ones in the SJV that are
violating the 2006 PM2.5 NAAQS as of the attainment date. To
qualify as a contingency measure, a measure must be structured to
achieve emissions reductions, if triggered, and the contingency
provision of District Rule 4901 provides for such reductions only under
certain circumstances and should be revised to provide for additional
emissions reductions in the SJV (if triggered) regardless of which
monitoring site(s) is determined to be violating the 2006
PM2.5 NAAQS as of the attainment date.\276\
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    \276\ The EPA believes that the most straightforward remedy
under these circumstances would be for the District to amend section
5.7.3 of Rule 4901 to extend the lower wood burning curtailment
thresholds region-wide if the EPA determines that the area has
failed to attain the 2006 PM2.5 NAAQS by the applicable
attainment date.
---------------------------------------------------------------------------

    Next, we considered the adequacy of the section 5.7.3 of District
Rule 4901 from the standpoint of the magnitude of emissions reductions
the measures would provide (if triggered). Neither the CAA nor the
EPA's implementing regulations for the PM2.5 NAAQS establish
a specific amount of emissions reductions that implementation of
contingency measures must achieve, but we generally expect that
contingency measures should provide for emissions reductions
approximately equivalent to one year's worth of RFP, which amounts to
reductions of approximately 0.6 tpd of direct PM2.5 and 18.4
tpd of NOX for the 2006 PM2.5 NAAQS in the
SJV.\277\ As noted in our summary of the State's submission, the
emissions reductions from the contingency provisions in District Rule
4901 would amount to approximately 0.00 tpd to 0.387 tpd of direct
PM2.5, which equates to approximately 0% to 67% of one
year's worth of RFP for direct PM2.5. With respect to
NOX emissions reductions, the contingency provisions in
District Rule 4901 would amount to approximately 0.00 tpd to 0.06 tpd,
which equates to approximately 0% to 0.3% of one year's worth of RFP
for NOX.
---------------------------------------------------------------------------

    \277\ The calculation of one year's worth of RFP is based on
dividing the values in column E of table H-6 of Appendix H (updated
February 11, 2020) of the 2018 PM2.5 Plan by 11, i.e.,
the number of years between 2013 and 2024. As part of the EPA's
final approval of the State's attainment plan for the 2006
PM2.5 NAAQS, we concluded that ammonia, SOX,
and VOC emissions do not contribute significantly to ambient
PM2.5 levels that exceed the 2006 PM2.5 NAAQS
in the San Joaquin Valley. 85 FR 17382, at 17390-17396 (March 27,
2020) (proposed rule); finalized at 85 FR 44192 (July 22, 2020).
---------------------------------------------------------------------------

    The State's contingency measure element in the 2018
PM2.5 Plan provides the larger SIP planning context in which
to judge the adequacy of the amount of emission reductions resulting
from the contingency measure by calculating the surplus emissions
reductions estimated to be achieved in the year after the attainment
year. More specifically, the 2018 PM2.5 Plan identifies
additional NOX reductions in the year following the
attainment year of 2024. For the SJV, the estimates of additional
reductions in the post-attainment year (2025) are 0 tpd direct
PM2.5 and 5.2 tpd NOX.\278\ Generally, we will
consider such surplus emissions reductions in evaluating the
sufficiency of the emissions reductions from contingency measures
identified by the state, however, in this case, because the identified
contingency measure may result in no emissions reductions, the larger
planning context is not relevant to our review of the sufficiency of
the contingency measure.
---------------------------------------------------------------------------

    \278\ These estimates are based on the annual average emission
reductions from 2024 to 2025 due to baseline measures and CARB and
the District's aggregate tonnage commitment in Table H-5 of Appendix
H (updated February 11, 2020) of the 2018 PM2.5 Plan. We
also note that Table H-13 of Appendix H indicates that the year-
over-year reductions for purposes of the 2006 PM2.5 NAAQS
is 0.1 tpd direct PM2.5 and 4.2 tpd NOX.
However, the estimates in Table H-13 reflect emissions changes
associated only with mobile sources whereas the appropriate
comparison includes the entire emissions inventory.
---------------------------------------------------------------------------

    For these reasons, we propose to disapprove the contingency measure
element of the 2018 PM2.5 Plan under CAA section 179(c)(9)
and 40 CFR 51.1014 with respect to the State's Serious area attainment
plan for the 2006 PM2.5 NAAQS in the SJV. While the
contingency measure provision of the 2019 amendment to Rule 4901 has an
adequate triggering mechanism for failure to attain, we propose to
disapprove it because it may result in no emissions reductions if the
area fails to attain the NAAQS by the applicable attainment date.
Furthermore, as the contingency measure element and the contingency
provision of Rule 4901 lack any to-be-triggered measure for failure to
meet a quantitative milestone, submit a quantitative milestone report,
or failure to meet an RFP requirement, we propose that the submission
is also inadequate for RFP contingency measures.
    Lastly, if the EPA finalizes the proposed disapproval of the
contingency measure element for the 2006 PM2.5 NAAQS, the
area would be eligible for a protective finding under the
transportation conformity rule because the 2018 PM2.5 Plan
reflects adopted control measures and contains enforceable commitments
that fully satisfy the emissions reductions requirements for RFP and
attainment for the 2006 PM2.5 NAAQS.\279\
---------------------------------------------------------------------------

    \279\ 40 CFR 93.120(a)(3).

---------------------------------------------------------------------------

VIII. Summary of Proposed Actions and Request for Public Comment

    Under CAA section 110(k)(3), the EPA is proposing to approve the
following elements of the 2016 PM2.5 Plan and 2018
PM2.5 Plan submitted by California to address the CAA's
Moderate area planning requirements for the 2012 PM2.5 NAAQS
in the SJV nonattainment area:

    1. The 2013 base year emissions inventories in the 2016
PM2.5 Plan, as revised in the 2018 PM2.5 Plan,
as meeting the requirements of CAA section 172(c)(3) and 40 CFR
51.1008(a);
    2. The reasonably available control measures/reasonably
available control technology demonstration in the 2016
PM2.5 Plan, as supplemented in the 2018 PM2.5
Plan, as meeting the requirements of CAA sections 172(c)(1) and
189(a)(1)(C);
    3. The demonstration in the 2016 PM2.5 Plan that
attainment by the Moderate area attainment date of December 31,
2021, is impracticable as meeting the requirements of CAA section
189(a)(1)(B)(ii) and 40 CFR 51.1011(a);
    4. The reasonable further progress demonstration in the 2016
PM2.5 Plan, as revised in 2018 PM2.5 Plan, as
meeting the requirements of CAA section 172(c)(2) and 40 CFR
51.1012(a);
    5. The quantitative milestones in the 2016 PM2.5
Plan, as revised in the 2018 PM2.5 Plan and the Valley
State SIP Strategy, as meeting the requirements of CAA section
189(c) and 40 CFR 51.1013(a)(1); and
    6. The motor vehicle emissions budgets for 2022 in the 2018
PM2.5 Plan as shown in Table 6 of this proposed rule
because they are derived from an approvable RFP demonstration and
meet the requirements of CAA section 176(c) and 40 CFR part 93,
subpart A. With respect to the budgets, we are proposing to limit
the duration of the approval of the budgets to last only until the
effective date of the EPA's adequacy finding for any subsequently
submitted budgets. We are proposing to do so at CARB's request and
in light of the benefits of using EMFAC2017-derived budgets prior to
our taking final action on the future SIP revision that includes the
updated budgets.

    Pursuant to CAA section 110(k)(3), the EPA proposes to disapprove
the contingency measure element of the 2016 PM2.5 Plan for
the 2012 PM2.5 NAAQS, as revised in the 2018
PM2.5 Plan and supplemented by section 5.7.3 of District
Rule 4901, and the contingency measure element of the 2018
PM2.5 Plan for the 2006 PM2.5 NAAQS, as
supplemented by section 5.7.3 of District Rule 4901, because, among
other reasons, the elements include no specific measures to be
undertaken if the state fails to submit a quantitative milestone report
for the area, or if the area fails to meet RFP or a quantitative
milestone. In addition, with respect to the contingency measure element
in the 2018 PM2.5 Plan for the 2006 PM2.5 NAAQS
(as supplemented by section 5.7.3 of District Rule 4901), the element
includes a specific measure that may not result in any emissions
reductions following a failure to attain the 2006 PM2.5
NAAQS by the applicable attainment date under certain circumstances.
    If we finalize the disapproval of the contingency measure elements
as proposed, the offset sanction in CAA section 179(b)(2) would apply
in the SJV 18 months after the effective date of a final disapproval,
and the highway funding sanctions in CAA section 179(b)(1) would apply
in the area six months after the offset sanction is imposed.\280\
Neither sanction will be imposed under the CAA if the State submits and
we approve, prior to the implementation of the sanctions, a SIP
revision that corrects the deficiencies that we identify in our final
action. The EPA intends to work with CARB and the SJVUAPCD to correct
the deficiencies in a timely manner.
---------------------------------------------------------------------------

    \280\ 40 CFR 52.31.
---------------------------------------------------------------------------

    In addition to the sanctions, CAA section 110(c)(1) provides that
the EPA must promulgate a federal implementation plan (FIP) addressing
any disapproved elements of the plan two years after the effective date
of disapproval unless the State submits, and the EPA approves, the
required SIP submittal. As a result of the EPA's December 6, 2018
determination that California had failed to submit the required
contingency measures for the 2006 PM2.5 NAAQS and the 2012
PM2.5 NAAQS, among other required SIP submissions for the
SJV,\281\ the EPA is already subject to a statutory deadline to
promulgate a FIP for this purpose no later than two years after the
effective date of that determination.\282\
---------------------------------------------------------------------------

    \281\ 83 FR 62720.
    \282\ Id.
---------------------------------------------------------------------------

    Also, because we previously approved the Serious area plan RFP and
attainment demonstrations and the motor vehicle emissions budgets for
the 2006 PM2.5 NAAQS,\283\ and because in this proposed rule
we are proposing to approve the Moderate area plan RACM, additional
reasonable measures, and RFP demonstrations, and motor vehicle emission
budgets for the 2012 PM2.5 NAAQS, we are proposing to issue
a protective finding under 40 CFR 93.120(a)(3) to the disapproval of
the contingency measures elements. Without a protective finding, the
final disapprovals would result in a conformity freeze, under which
only projects in the first four years of the most recent conforming
Regional Transportation Plan (RTP) and Transportation Improvement
Programs (TIP) can proceed. Generally, during a freeze, no new RTPs,
TIPs, or RTP/TIP amendments can be found to conform until another
control strategy implementation plan revision fulfilling the same CAA
requirements is submitted, the EPA finds its motor vehicle emissions
budget(s) adequate pursuant to Sec.  93.118 or approves the submission,
and conformity to the implementation plan revision is determined.\284\
Under a protective finding, the final disapproval of the contingency
measures elements would not result in a transportation conformity
freeze in the SJV PM2.5 nonattainment area and the MPOs may
continue to make transportation conformity determinations.
---------------------------------------------------------------------------

    \283\ 85 FR 44192.
    \284\ 40 CFR 93.120(a)(2).
---------------------------------------------------------------------------

    Finally, pursuant to CAA section 188(b)(1), the EPA is proposing to
reclassify the SJV PM2.5 nonattainment area, including
reservation areas of Indian country and any other area where the EPA or
a tribe has demonstrated that a tribe has jurisdiction within the SJV,
as Serious nonattainment for the 2012 PM2.5 standard based
on the agency's determination that the SJV cannot practicably attain
the standard by the Moderate area attainment date of December 31, 2021.
Upon final reclassification as a Serious area, California will be
required to submit, within 18 months after the effective date of the
reclassification, an emissions inventory, provisions to assure that
BACM shall be implemented no later than four years after the date of
reclassification, and any NNSR SIP revisions required to satisfy the
requirements of CAA sections 189(b)(3) and 189(e). California will also
be required to submit, by December 31, 2023, a Serious area plan that
satisfies the requirements of part D of title I of the Act. This plan
must include a demonstration that the SJV will attain the 2012
PM2.5 standard as expeditiously as practicable but no later
than December 31, 2025, or by the most expeditious alternative date
practicable and no later than December 31, 2030, in accordance with the
requirements of CAA sections 189(b) and 188(e).
    We note that the 2018 PM2.5 Plan, submitted concurrently
with the 2016 PM2.5 Plan on May 10, 2019, includes a Serious
area attainment demonstration, emissions inventory, attainment-related
plan elements, and BACM/BACT provisions. The State also submitted a SIP
submission for the Serious area NNSR requirements on November 20,

2019. The EPA intends to evaluate and act on the Serious area plan and
NNSR SIP submissions for the 2012 PM2.5 NAAQS in the SJV
through separate rulemakings, as appropriate.\285\
---------------------------------------------------------------------------

    \285\ We are establishing deadlines for submittal of SIP
revisions that have already been submitted to timely address any
elements that may be withdrawn in the future.
---------------------------------------------------------------------------

    In addition, because the EPA is proposing to similarly reclassify
reservation areas of Indian country and any other area of Indian
country where the EPA or a tribe has demonstrated that the tribe has
jurisdiction within the SJV PM2.5 nonattainment area as
Serious nonattainment for the 2012 PM2.5 standard,
consistent with our proposed reclassification of the surrounding non-
Indian country lands, the EPA has invited consultation with interested
tribes concerning this issue. Although eligible tribes may seek the
EPA's approval of relevant tribal programs under the CAA, none of the
affected tribes will be required to submit an implementation plan as a
result of this reclassification.
    We will accept comments from the public on these proposals for the
next 30 days. The deadline and instructions for submission of comments
are provided in the DATES and ADDRESSES sections at the beginning of
this proposed rule.

IX. Statutory and Executive Order Reviews

    Additional information about these statutes and Executive Orders
can be found at http://www.epa.gov/lawsregulations/laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review, and Executive
Order 13563: Improving Regulation and Regulatory Review

    The proposed actions are not a significant regulatory action and
were therefore not submitted to the Office of Management and Budget
(OMB) for review.

B. Paperwork Reduction Act (PRA)

    The proposed actions do not impose an information collection burden
under the PRA because they do not contain any information collection
activities.

C. Regulatory Flexibility Act (RFA)

    I certify that the proposed actions will not have a significant
economic impact on a substantial number of small entities under the
RFA. The proposed actions will not impose any requirements on small
entities. This proposed rule would approve or disapprove State plans as
meeting federal requirements and would not impose additional
requirements beyond those imposed by State law. Additionally, the
proposed rule would reclassify the SJV nonattainment area as Serious
nonattainment for the 2012 PM2.5 NAAQS and would not itself
regulate small entities.

D. Unfunded Mandates Reform Act (UMRA)

    The proposed actions do not contain an unfunded mandate of $100
million or more as described in UMRA, and does not significantly or
uniquely affect small governments. This proposed rule would approve or
disapprove State plans as meeting federal requirements and would not
impose additional requirements beyond those imposed by State law.
Additionally, the proposed rule would reclassify the SJV nonattainment
area as Serious nonattainment for the 2012 PM2.5 NAAQS and
would not itself impose any federal intergovernmental mandate. The
proposed actions would not require any tribe to submit implementation
plans.

E. Executive Order 13132: Federalism

    The proposed actions do not have federalism implications. They will
not have substantial direct effects on the states, on the relationship
between the national government and the states, or on the distribution
of power and responsibilities among the various levels of government.

F. Executive Order 13175: Coordination With Indian Tribal Governments

    Executive Order 13175, entitled ``Consultation and Coordination
with Indian Tribal Governments'' (65 FR 67249, November 9, 2000),
requires the EPA to develop an accountable process to ensure
``meaningful and timely input by tribal officials in the development of
regulatory policies that have tribal implications.'' ``Policies that
have Tribal implications'' is defined in the Executive Order to include
regulations that have ``substantial direct effects on one or more
Indian tribes, on the relationship between the Federal government and
the Indian tribes, or on the distribution of power and responsibilities
between the Federal government and Indian Tribes.''
    Eight Indian tribes are located within the boundaries of the SJV
nonattainment area for the 2012 PM2.5 NAAQS: The Big Sandy
Rancheria of Western Mono Indians of California, the Cold Springs
Rancheria of Mono Indians of California, the Northfork Rancheria of
Mono Indians of California, the Picayune Rancheria of Chukchansi
Indians of California, the Santa Rosa Indian Community of the Santa
Rosa Rancheria, California, the Table Mountain Rancheria, the Tejon
Indian Tribe, and the Tule River Indian Tribe of the Tule River
Reservation, California.
    The EPA's proposed actions on the SIP elements submitted by
California to address the Moderate area requirements for the 2012
PM2.5 NAAQS and the contingency measure requirement for the
2006 PM2.5 NAAQS would not have tribal implications because
the SIP is not approved to apply on any Indian reservation land or in
any other area where the EPA or an Indian tribe has demonstrated that a
tribe has jurisdiction. In those areas of Indian country, the proposed
actions on the SIP submittals do not have tribal implications and will
not impose substantial direct costs on tribal governments or preempt
tribal law as specified by Executive Order 13175.
    The EPA has concluded that the proposed reclassification might have
tribal implications for the purposes of Executive Order 13175, but
would not impose substantial direct costs upon the tribes, nor would it
preempt tribal law. The proposed reclassification from Moderate to
Serious for a PM2.5 NAAQS would typically affect the EPA's
implementation of the new source review program because of the lower
``major source'' threshold triggered by reclassification (70 tons per
year for direct PM2.5 and precursors to PM2.5).
However, because the SJV nonattainment area is already classified as
Serious for the 1997 and 2006 PM2.5 NAAQS, the lower
thresholds already apply within the nonattainment area, and the
proposed reclassification from Moderate to Serious for the 2012
PM2.5 NAAQS would have no additional effect. The same is
true for any tribal projects that require federal permits, approvals,
or funding. Such projects are subject to the requirements of the EPA's
general conformity rule, and federal permits, approvals, or funding for
the projects would typically become more difficult to obtain because of
the lower de minimis thresholds triggered by reclassification but, in
this case, the lower de minimis thresholds already apply within the
SJV.
    Given the potential implications, the EPA contacted tribal
officials during the process of developing this proposed rule to
provide an opportunity to have meaningful and timely input into its
development. On March 3, 2021, we sent letters to leaders of the eight
tribes with areas of Indian country in the SJV nonattainment area
inviting government-to-government consultation on the rulemaking
effort. We requested that the tribal leaders, or their

designated consultation representatives, notify us of their interest in
government-to-government consultation by April 5, 2021. We intend to
continue communicating with all eight tribes located within the
boundaries of the SJV nonattainment area for the 2012 PM2.5
NAAQS as we move forward in developing a final rule. The EPA
specifically solicits additional comment on this proposed rule from
tribal officials.

G. Executive Order 13045: Protection of Children From Environmental
Health Risks and Safety Risks

    The EPA interprets Executive Order 13045 as applying only to those
regulatory actions that concern environmental health or safety risks
that the EPA has reason to believe may disproportionately affect
children, per the definition of ``covered regulatory action'' in
section 2-202 of the Executive Order. The proposed rule is not subject
to Executive Order 13045 because it would approve or disapprove a State
plan implementing a federal standard, and reclassify the SJV
nonattainment area as Serious nonattainment for the 2012
PM2.5 NAAQS, triggering Serious area planning requirements
under the CAA. This proposed action does not establish an environmental
standard intended to mitigate health or safety risks.

H. Executive Order 13211: Actions That Significantly Affect Energy
Supply, Distribution, or Use

    This proposed rule is not subject to Executive Order 13211, because
it is not a significant regulatory action under Executive Order 12866.

I. National Technology Transfer and Advancement Act

    This rulemaking does not involve technical standards.

J. Executive Order 12898: Federal Actions To Address Environmental
Justice in Minority Populations and Low-Income Population

    The EPA has determined that the proposed actions will not have
potential disproportionately high and adverse human health or
environmental effects on minority or low-income populations because
they do not affect the level of protection provided to human health or
the environment. The proposed actions would only approve or disapprove
State plans implementing a federal standard, and reclassify the SJV
nonattainment area as Serious nonattainment for the 2012
PM2.5 NAAQS, triggering additional Serious area planning
requirements under the CAA.

List of Subjects

40 CFR Part 52

    Environmental protection, Air pollution control, Ammonia,
Incorporation by reference, Intergovernmental relations, Nitrogen
dioxide, Particulate matter, Reporting and recordkeeping requirements,
Sulfur dioxide, Volatile organic compounds.

40 CFR Part 81

    Environmental protection, Air pollution control, Particulate
matter.

    Authority: 42 U.S.C. 7401 et seq.

    Dated: August 25, 2021.
Elizabeth Adams,
Acting Regional Administrator, Region IX.
[FR Doc. 2021-18764 Filed 8-31-21; 8:45 am]
BILLING CODE 6560-50-P


[Federal Register: August 11, 2006 (Volume 71, Number 155)]
[Notices]
[Page 46215]
[DOCID:fr11au06-53]

=======================================================================
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DEPARTMENT OF ENERGY

Federal Energy Regulatory Commission

[Docket No. RP03-36-018]

Dauphin Island Gathering Partners; Notice of Negotiated Rate

August 7, 2006.
    Take notice that on July 10, 2006, Dauphin Island Gathering
Partners (Dauphin Island) tendered for filing as part of its FERC Gas
Tariff, First Revised Volume No. 1, the following tariff sheets, with
an effective date of August 9, 2006.

Twenty-Sixth Revised Sheet No. 9
Twenty-First Revised Sheet No. 10
Eighth Revised Sheet No. 359

    Any person desiring to intervene or to protest this filing must
file in accordance with Rules 211 and 214 of the Commission's Rules of
Practice and Procedure (18 CFR 385.211 and 385.214). Protests will be
considered by the Commission in determining the appropriate action to
be taken, but will not serve to make protestants parties to the
proceeding. Any person wishing to become a party must file a notice of
intervention or motion to intervene, as appropriate. Such notices,
motions, or protests must be filed in accordance with the provisions of
section 154.210 of the Commission's regulations (18 CFR 154.210).
Anyone filing an intervention or protest must serve a copy of that
document on the Applicant. Anyone filing an intervention or protest on
or before the intervention or protest date need not serve motions to
intervene or protests on persons other than the Applicant.
    The Commission encourages electronic submission of protests and
interventions in lieu of paper using the ``eFiling'' link at http://www.ferc.gov.
 Persons unable to file electronically should submit an

original and 14 copies of the protest or intervention to the Federal
Energy Regulatory Commission, 888 First Street, NE., Washington, DC
20426.
    This filing is accessible online at http://www.ferc.gov, using the

``eLibrary'' link and is available for review in the Commission's
Public Reference Room in Washington, DC. There is an ``eSubscription''
link on the Web site that enables subscribers to receive e-mail
notification when a document is added to a subscribed docket(s). For
assistance with any FERC Online service, please e-mail
<EMAIL_ADDRESS>or call<PHONE_NUMBER> (toll free). For

TTY, call<PHONE_NUMBER>.

Magalie R. Salas,
Secretary.
[FR Doc. E6-13146 Filed 8-10-06; 8:45 am]

BILLING CODE 6717-01-P


Drinking Water Criteria Document for Cyanogen Chloride and Metabolites EPA/ OW/ OST/ HECD Final draft A 1 APPENDIX A. BENCHMARK DOSE MODELING RESULTS A. Introduction Benchmark dose ( BMD) modeling was performed to identify potential critical effect levels as alternatives to the study NOAEL/ LOAELs for derivation of the HAs for cyanide, and by extension, cyanogen chloride. BMD modeling was not conducted for thiocyanate, because thiocyanate was not chosen as the surrogate for calculation of effect levels for cyanogen chloride.

Results of the BMD modeling are described below and summarized in Table A 1.

B. Methods Benchmark Dose The cyanide data sets considered for dose response modeling were all continuous endpoints. The modeling was conducted according to draft EPA guidelines ( U. S. EPA, 2000e)

using Benchmark Dose Software ( BMDS version 1.3.1), available from the U. S. EPA ( U. S. EPA,

2001b). The methods and models applied to the continuous endpoints are presented here.

The continuous endpoints of interest with respect to cyanide toxicity were quantitatively summarized by group means and measures of variability ( standard errors or standard deviations). Drinking Water Criteria Document for Cyanogen Chloride and Metabolites EPA/ OW/ OST/ HECD Final draft A 2 The BMDS software provides three models ( the Hill, power, and polynomial models) for modeling of continuous data. Linear fits to the data were incorporated into the analysis by allowing the power and polynomial models to simplify to linear equations as dictated by the data.

The mathematical models fit to the data are defined here. In all cases, µ ( d) indicates the mean of the response variable following exposure to " dose" d.

The polynomial model is defined as:

µ ( d) =   0 +   1 d + ... +   n dn where the degree of the polynomial, n, was set less than or equal to the number of dose groups in the experiment being analyzed. Note that U. S. EPA ( 2000e) recommends the use of the most parsimonious model that provides an adequate fit to the data. It may appear that the use of a polynomial model with degree possibly as great as the number of dose groups would not yield the most parsimonious model. However, allowing the model to have that degree is not the same as forcing the model to have that degree; in the model fitting, if fewer parameters ( e. g., a lower degree polynomial) is adequate and consistent with the data, then the fitting will reflect that fact and a more parsimonious model will be the result. For these analyses, the values of the   parameters allowed to be estimated were constrained to be either all nonnegative or all nonpositive ( as dictated by the data set being modeled, i. e., nonnegative if the mean response Drinking Water Criteria Document for Cyanogen Chloride and Metabolites EPA/ OW/ OST/ HECD Final draft A 3 increased with increasing dose or nonpositive if the mean response decreased with increasing dose).

The power model is represented by the equation:

µ ( d) =   +  d  where the parameter   is restricted to be nonnegative. [ The linear model is obtained when   is fixed at a value of 1. The linear model was not separately fit to the data; if the result of fitting the power model does not result in the linear form,   = 1, then the linear model does not fit as well as the more general power model, by definition.]

The Hill model is given by the following equation:

µ ( d) =   + ( vdn) / ( dn + kn))

where the parameters n and k are restricted to be positive ( in fact, n > 1).

In the case of continuous endpoints, one must assume something about the distribution of individual observations around the dose specific mean values defined by the above models. The assumptions imposed by BMDS were used in this analysis: individual observations were assumed to vary normally around the means with variances given by the following equation: Drinking Water Criteria Document for Cyanogen Chloride and Metabolites EPA/ OW/ OST/ HECD Final draft A 4   i 2 =  2

[ µ ( d i)]   where both  2 and   were parameters estimated by the model.

Given those assumptions about variation around the means, maximum likelihood methods were applied to estimate all of the parameters, where the log likelihood to be maximized is ( except for an additive constant) given by L =   [( N i/ 2)

ln(   i 2) + ( N i  1) s i 2/ 2  i 2 + N i{ m i  µ ( d i)} 2/ 2  i 2]

where N i is the number of individuals in group i exposed to dose d i, and m i and s i are the observed mean and standard deviation for that group. The summation runs over i from 1 to k ( the number of dose groups).

Goodness of Fit Analyses For these continuous models, goodness of fit was determined based on a likelihood ratio statistic. In particular, the maximized log likelihood associated with the fitted model was compared to the log likelihood maximized with each dose group considered to have a mean and variance completely independent of the means and variances of the other dose groups ( model A2 Drinking Water Criteria Document for Cyanogen Chloride and Metabolites 11 If and when BMDS suggested that a homogeneous variance model was appropriate, the log likelihood of the fitted model was compared to the likelihood maximized assuming independent means but a single, constant variance for all dose groups ( the fitted model also assumed that to be the case in such cases). This was also model A2.

EPA/ OW/ OST/ HECD Final draft A 5 in BMDS output). 1 It is always the case that the latter log likelihood will be at least as great as the model associated log likelihood, but if the model does a " reasonable" job of fitting the data,

the difference between the two log likelihoods will not be too great. A formal statistical test reflecting this idea uses the fact that twice the difference in the log likelihoods is distributed as a chi square random variable. The degrees of freedom associated with that chi squared test statistic are equal to the difference between the number of parameters fit by the model ( including the parameters  2 and   defining how variances change as a function of mean response level) and twice the number of dose groups ( which is equal to the number of parameters estimated by the " model" assuming independence of dose group means and variances). Parameters hitting boundary values were not included for determining degrees of freedom.

Acceptable fit was defined as a goodness of fit p value greater than or equal to 0.1, or a perfect fit when there were no degrees of freedom for a statistical test of fit. Choice of 0.1 is consistent with current U. S. EPA guidance for BMD modeling ( U. S. EPA, 2000e). If a model was judged to provide a reasonable BMDL estimate, but the p value criterion of 0.1 was not met,

the rationale for waiving the p value criterion is provided in the discussion of the results.

Goodness of fit statistics are not designed to compare different models, particularly if the different models have different numbers of parameters. Within a family of models, adding Drinking Water Criteria Document for Cyanogen Chloride and Metabolites EPA/ OW/ OST/ HECD Final draft A 6 parameters generally improves the fit. BMDS reports the Akaike Information Criterion ( AIC) to aid in comparing the fit of different models. The AIC is defined as   2L+ 2p, where L is the loglikelihood at the maximum likelihood estimates for the parameters, and p is the number of model parameters estimated ( ignoring parameters assuming values at the boundaries of their allowable ranges). When comparing the fit of two or more models to a single data set, the model with the lesser AIC was considered to provide a superior fit.

Definition of the BMR and Corresponding BMD and BMDL For the continuous models, BMDs were implicitly defined as follows:

  µ ( BMD)  µ ( 0)   =    1 where   1 is the model estimated standard deviation in the control group. In other words, the BMR was defined as a change in mean corresponding to some multiplicative factor of the control group standard deviation.

The value of   used in this analysis was 1.0. This value was chosen based on EPA draft guidelines for BMD analyses ( U. S. EPA, 2000e), in the absence of a clear biological rationale for selecting an alternative response level. It is roughly consistent with ( though slightly more conservative than) a choice of 1.1, which according to Crump ( 1995) corresponds to an additional Drinking Water Criteria Document for Cyanogen Chloride and Metabolites EPA/ OW/ OST/ HECD Final draft A 7 risk of 10% when the background response rate was assumed to be 1%, with normal variation around the mean ( and constant standard deviation).

Choice of BMDL The following guidance was followed with regard to the choice of the BMDL to use as a point of departure for calculation of a health advisory. This guidance is consistent with recommendations in U. S. EPA ( 2000e). For each endpoint, the following procedure is recommended:

1. Models with an unacceptable fit are excluded.

2. If the BMDL values for the remaining models for a given endpoint are within a factor of 3,

no model dependence is assumed, and the models are considered indistinguishable in the context of the precision of the methods. The models are then ranked according to the AIC, and the model with the lowest AIC is chosen as the basis for the BMDL.

3. If the BMDL values are not within a factor of 3, some model dependence is assumed, and the lowest BMDL is selected as a reasonable conservative estimate, unless it is an outlier compared to the results from all of the other models. Note that when outliers are Drinking Water Criteria Document for Cyanogen Chloride and Metabolites EPA/ OW/ OST/ HECD Final draft A 8 removed, the remaining BMDLs may then be within a factor of 3, and so the criteria given in item 2. would be applied.

4. The BMDL values from all modeled endpoints are compared, along with any NOAELs or LOAELs from data sets that were not amenable to modeling, and the lowest NOAEL or BMDL is chosen.

C. Modeling Results Short term Studies Several of the short term studies on cyanide toxicity summarized in Table VIII 2 could not be modeled. The human studies typically reported a single dose level, no control group, and often small sample sizes, and so could not be modeled. LD 50 and mortality studies were not modeled, because they did not evaluate sensitive endpoints. The drinking water and feed studies of Palmer and Olson ( 1979) were not modeled, because no measure of variability was reported for the continuous endpoints evaluated.

The only short term study that could be modeled was the study of Kreutler et al. ( 1977),

in which rats were exposed to cyanide in the diet, and thyroid effects were evaluated. In this study, there were only two dose groups, so only a linear model could be fit to the endpoints from Drinking Water Criteria Document for Cyanogen Chloride and Metabolites 2These values doses differ from those shown in the BMDS output by a factor of 87/ 40, because of a correction to the dose conversions made after the BMD modeling. Since dose enters the modeling in a linear form, such posthoc corrections can be done.

EPA/ OW/ OST/ HECD Final draft A 9 that study. The BMDS output for the thyroid weight endpoint suggested that a model with constant variance ( as opposed to a model with dose group specific variances depending on the group means) would be the preferred approach. When such a model was fit to the data, the goodness of fit was satisfactory ( p = 0.34) and the BMD and BMDL estimates were 17.4 and 14.6 mg CN/ kg day, respectively2. For the endpoint of increased plasma TSH, the variances did not appear to be constant; the linear model with group dependent variances fit the data as well as possible ( i. e., the fit was as good as the model maximizing the likelihood, model A2 in BMDS parlance). The BMD and BMDL for plasma TSH were 2.6 and 2.1 mg CN/ kg day, respectively.

Because the slope of the dose response for this endpoint was much greater than that for thyroid weight, lower values were calculated for the BMD and BMDL. Plasma TSH was the more sensitive of the two endpoints modeled. Although the BMDL calculated for plasma TSH was one of the lower BMDLs calculated for cyanide, confidence in this value is limited, based on the absence of information on the shape of the dose response curve, and due to the significant degree of extrapolation below the single data point of 87 mg CN/ kg day. Drinking Water Criteria Document for Cyanogen Chloride and Metabolites EPA/ OW/ OST/ HECD Final draft A 10 Longer term Studies As for the short term studies, several of the longer term studies for cyanide ( summarized in Table VIII 2) did not report data in a form that could be modeled. Data from the study by Kamalu ( 1993) were not modeled due to concerns about the relevance of the results in dogs ( see Chapter V), and because no incidence data were reported for the observed histopathology. The results of Jackson ( 1988) were not modeled because the quantitative results were not reliable.

The data were reported only as the average across males and females, but the number of males/ females per group varied, and the endpoints of interest ( T3, T4, fighting, victimization)

have different baselines for males and females. Howard and Hanzal ( 1955) did not report any adverse effects, and so that study could not be modeled.

One of the longer term studies ( Philbrick et al., 1979) tested only a single positive dose,

although the study included two parallel experiments. In one experiment ( designated here as the (+) control experiment), the rats received a normal diet, while in the second experiment ( the ()

control experiment), the rats received a diet deficient in methionine, iodine, and vitamin B 12.

Linear models were fit to the data for both thyroid weight and thyroxine ( T4) secretion for each of these experiments. In all four cases, BMDS suggested that a constant variance model was the preferred option. In all four cases, the fits of the constant variance, linear model was satisfactory ( p values all greater than 0.14). Consistent with the larger response noted at the single dose tested, the BMDs and BMDLs calculated for the data sets for the animals given deficient diet Drinking Water Criteria Document for Cyanogen Chloride and Metabolites 3These values doses differ from those shown in the BMDS output by a factor of 44/ 30, because of a correction to the dose conversions made after the BMD modeling.

EPA/ OW/ OST/ HECD Final draft A 11 were smaller than the corresponding values for the animals given the normal diet; within a given diet, similar values were calculated for BMDLs for both endpoints. For the animals given the normal diet, the BMDL was 19 mg/ kg day, for both the thyroid weight and T4 secretion endpoints. For the animals given the deficient diet, the BMDL for T4 secretion was 12 mg/

kgday slightly lower than the BMDL of 13 mg/ kg day for thyroid weight. 3 Thus, the BMDL for this study was 19 mg CN/ kg day in rats fed a normal diet and 12 in rats fed a deficient diet, both based on decreased T4 secretion. Interestingly, these values are comparable to the BMDL for increased thyroid weight in Kreutler et al. ( 1977), even though Philbrick et al. ( 1979) was an 11.5 month study, while exposure was for 2 weeks in Kreutler et al. ( 1977). This supports the conclusion in Chapter VIII that this endpoint does not progress with increasing exposure duration, although again the conclusion is limited due to the use of only one dose level in both studies. In addition, as noted in Chapter V, the observed thyroid effects may be adaptive, rather than adverse. Philbrick et al. ( 1979) also reported histopathological evidence of neurological effects, but this endpoint could not be modeled, because no quantitative results were reported.

In a developmental toxicity study, Tewe and Maner ( 1981) exposed rats to two dose levels of cyanide in the diet throughout mating, gestation, and lactation; decreased daily body weight gain was observed in the weanlings and this endpoint was modeled. Even though no control group was included ( the low exposure group did have some CN exposure), a linear model Drinking Water Criteria Document for Cyanogen Chloride and Metabolites 4These values doses differ from those shown in the BMDS output by a factor of 34.3/ 32.8, because of a correction to the dose conversions made after the BMD modeling.

EPA/ OW/ OST/ HECD Final draft A 12 could be fit to the data and BMDs could be estimated based on imputed ( model predicted)

background means and standard deviations. There was no indication that the variance depended on dose group ( through group mean weight gains), so a constant variance model was fit to the data. The fit was perfect, and the BMD and BMDL estimates were 23 and 15 mg CN/ kg day,

respectively. 4 The NTP ( 1993) study included several endpoints potentially related to cyanide exposure.

For the female rats and mice, the only endpoint of interest was relative liver weight. The doseresponse for that endpoint was non monotonic for both species. For both species, BMDS suggested that the preferred approach would be to treat the variances as if they were constant.

For female rats, despite the non monotonicity, the polynomial model fit with borderline adequacy ( p = 0.09), whereas the tests of fit for the power and Hill models suggested a poorer fit ( p values of 0.05 and 0.02, respectively), but that is an artifact of the fact that the latter two models have more parameters ( as also reflected in the greater AICs for the latter two models). The fit of the data was good in the region of the BMDL, and fit to the control standard deviation was good. In addition, visual fit to the control and lower doses was generally reasonable, except for the outlier datapoint ( second lowest dose). In any case, with BMD estimates very similar across models, the polynomial model would be the model of choice ( with the smallest AIC), so the BMD and BMDL selected as the best estimates for increased relative liver weight in female mice endpoint are 11 Drinking Water Criteria Document for Cyanogen Chloride and Metabolites 5 Although, it should be noted that the BMDS output has an error somewhere because the likelihood reported for model A1 is different for the polynomial run and the power model run. Model A1 does not depend on the model, and so should be the same for both runs. In any case, the fit is unacceptably poor for either model.

EPA/ OW/ OST/ HECD Final draft A 13 and 8.7 mg CN/ kg day, respectively. However, confidence in the BMDL is limited because a clear increase was seen only at the high dose.

For relative liver weight in female mice, the non monotonicities in the data were such that the polynomial and power models defaulted to linearity, and still could not achieve an adequate fit ( p values of 0.008 and 0.005, respectively5). Even for the Hill model, which accommodates more " downward" curvature than do the power or polynomial models, the fit was poor ( p = 0.02).

Although the Hill model might otherwise be the preferred model for this data set, it might be best not to use BMD or BMDL estimates from any model for relative liver weight changes in female mice. The steep slope of the Hill model in the low dose region also resulted in a very low BMDL that does not appear to be otherwise consistent with the data for this endpoint. In addition, the flat slope of the dose response curve at all cyanide doses suggests that the control relative liver weight may have been abnormally low, leading to a low BMDL.

Both male rats and male mice in the NTP ( 1993) study exhibited responses related to reproductive toxicity. For these endpoints, however, the study authors only reported the results in the control group and at the top three dose levels. All significant endpoints were modeled. In rats, the endpoints modeled were left epididymis weight, left cauda epididymis weight, left testis weight, spermatid head ( per testis), spermatid count, and percent motility. With the exception of Drinking Water Criteria Document for Cyanogen Chloride and Metabolites EPA/ OW/ OST/ HECD Final draft A 14 the motility endpoint, BMDS suggested that constant variance models were preferred, and these models are therefore the basis of the BMD estimates for the other male rat endpoints in the NTP ( 1993) study.

For left epididymis weight, all of the models fit adequately ( p values all greater than or equal to 0.22). The polynomial and power models defaulted to the same linear model, while the Hill model captured more of the curvature, resulting in a BMD estimate that was a little more than 3 times smaller than that for the linear model ( 2.7 as opposed to 8.2). Moreover, the BMDL estimate from the Hill model ( 0.79) was about 7 times less than the BMDL from the linear model.

Therefore, according to the draft EPA guidelines ( U. S. EPA, 2000e), the results from the Hill model would be the preferred ones to use.

For left cauda epididymis weight, the polynomial and power models defaulted to the same linear model. The Hill model captured more of the curvature and fit the data better, based on the AIC values. The BMD for the Hill model was 1.5 ( compared to 8.4 for the linear model) but,

unfortunately the Hill model failed to estimate a BMDL. It is difficult to recommend use of the BMD or BMDL from the linear model, given that the Hill model did describe the data better and provided a BMD estimate less than the BMDL estimate from the linear model. Therefore, no BMDL was identified for this endpoint. Drinking Water Criteria Document for Cyanogen Chloride and Metabolites EPA/ OW/ OST/ HECD Final draft A 15 For left testis weight, the polynomial and power models defaulted to the same linear model. The Hill model did capture more of the curvature and resulting curve passed through all of the observed means, but the additional parameters necessary to do so result in an AIC that is greater than the AIC for the linear model. The BMD for the linear model was 7.0 ( compared to 5.0 for the Hill model) and the BMDL for the linear model was 4.9. The linear model estimates ( shown in Table A 1 as polynomial/ power model) are the preferred values for this data set, since the BMDLs are within a factor of three and the AIC is smaller for the linear model.

For spermatid heads per testis, the polynomial and power models defaulted to the same linear model. The Hill model captured more of the curvature in the data but, like the previous two data sets, the improvement was not enough to offset the need to estimate an additional parameter ( i. e., the AIC for the Hill model was larger than that for the linear model). However,

given that the BMDL estimates differ by more than a factor of three and both models fit adequately ( p values all greater than or equal to 0.58) the model with the smaller BMDL would be the recommended one. The Hill model is therefore preferred for this data set and it yields a BMD estimate of 8.3 with a lower bound of 1.3.

Very similar results were observed for spermatid count as for spermatid heads per testis.

In this case also, the Hill model is preferred over the linear model resulting from fitting either the power or polynomial models ( the former has a BMDL more than three times smaller than the Drinking Water Criteria Document for Cyanogen Chloride and Metabolites EPA/ OW/ OST/ HECD Final draft A 16 latter), and it gives the same BMD and BMDL estimates as for spermatid heads per testis ( 8.3 and 1.3, respectively).

For the sperm motility endpoint, the polynomial and power models both defaulted to linearity, but they did not converge to the same result. The linear model to which the power model defaulted fit the data slightly better than did the polynomial model ( which did not default to a linear model), based on the maximized log likelihood and the AIC, but neither fit describes the data well at all. The non monotonicities in the data make it difficult to fit these monotonic models and, in addition, the variances are not well represented by the models ( also due to the fact that the models impose monotonicity in variance but such monotonicity is absent in the data). On the other hand, the Hill model gives only a slightly better maximized likelihood, but the added number of parameters in that model make the AIC larger than that for the linear models and the fit to the data is still poor. No BMD results should be used for the motility endpoint.

For male mice in the NTP ( 1993) study, the endpoints in which effects were seen were the male reproductive endpoints of decreased left epididymis weight and decreased left cauda epididymis weight; both endpoints were modeled. In the case of epididymis weight, the polynomial and the power models both defaulted to a linear model, but because of some bug in BMDS, not to the same linear model. The linear model parameter estimates for the power model yielded a slightly better ( larger) log likelihood and therefore a slightly lower AIC. Either of these linear models is better than the Hill model ( which has a larger AIC because of the extra Drinking Water Criteria Document for Cyanogen Chloride and Metabolites EPA/ OW/ OST/ HECD Final draft A 17 parameters needed to be estimated). Hence the power ( linear) model is the preferred model for this endpoint; it estimates a BMD of 25, with a lower bound of 18.

For left cauda epididymis weight, BMDS had several problems. As in the previous case,

the polynomial and power models defaulted to linear models but not the same linear models. The fit for the power model was slightly better, on the basis of the AICs, even though the chi squared goodness of fit p values could not be estimated because the model designated as A3 in BMDS ( to which the fitted model is normally compared) yielded a log likelihood that was so much worse than all the other models that it was obviously in error. This error was also indicated by the fact that the likelihood for that model was different for each of the three model runs, even though it should be the same no matter which model is fit. The fit of the Hill model was so bad ( corresponding observed and predicted means not even close to one another) that it was considered a failed run. Nevertheless, the fit of the polynomial linear model was visually satisfactory ( similar to the fit of the linear model fit to the left epididymis weight data set above)

and close enough to the power linear model in terms of log likelihood that the BMD and BMDL from the polynomial model output ( 20 and 12, respectively) can be considered adequate for an initial analysis.

Overall, results of the BMD modeling for the NTP ( 1993) study supported the conclusion from comparison of NOAELs/ LOAELs that the rats were more sensitive than mice to the male reproductive effects of cyanide. Similarly, the BMD modeling data also found that male Drinking Water Criteria Document for Cyanogen Chloride and Metabolites EPA/ OW/ OST/ HECD Final draft A 18 reproductive endpoints tended to be more sensitive than increased liver weight in female rats or mice. Overall, the most sensitive endpoint in this study was decreased left epididymis weight in male rats, with a BMDL of 0.79 mg/ kg day. This BMDL is supported by a BMD of 1.5 mg/

kgday for the Hill model for decreased left cauda epididymis weight ( for which BMDS could not estimate a BMDL), and by BMDLs of 1.3 mg/ kg day for decreased spermatid heads/ testis and decreased spermatid count. Only preliminary results could be obtained for BMD modeling of the mouse data in the NTP ( 1993) study, but the lowest BMDL of 12 mg/ kg day ( for decreased left caudal epididymis weight) is higher than the rat BMDL in the study. Drinking Water Criteria Document for Cyanogen Chloride and Metabolites EPA/ OW/ OST/ HECD Final draft A 19 Table A 1 Benchmark Dose Modeling Results for Cyanide Study Endpoint Model AIC G o F pvalue BMDa BMDL Kreutler et al., 1977 Thyroid Weight Linear 192.844b .34c 17.4 14.6 Plasma TSH Linear 309.486 1.0d 2.6 2.1 Philbrick et al., 1979; (+) control Thyroid Weight Linear 24.838b .14c 38 19 Thyroxine Secretion Linear  23.120b .14c 37 19 Philbrick et al., 1979; () control Thyroid Weight Linear 15.674b 1.0d 21 13 Thyroxine Secretion Linear  23.120b .14c 19 12 Tewe and Maner, 1981 Daily BW Gain Linear  24.266b 1.0d 23 15 NTP, 1993; female rats Relative Liver Weight Polynomial 133.910b .09c 11 8.7 Power 135.881 .05 12 8.6 Hill 137.881 .02 12 Failed NTP, 1993; female mice Relative Liver Weight Polynomial 188.390b .008b 14 11 Power 188.390b .005b 14 11 Hill 186.149 .02b 0.64 0.18 NTP, 1993; male rats Left Epididymis Weight Polynomial  274.730b .22b 8.2 5.6 Power  274.730b .22b 8.2 5.6 Hill  273.765b .69c 2.7 0.79 Left Cauda Epididymis Weight Polynomial  312.753b .08b 8.4 5.6 Power  312.753b .08b 8.4 5.6 Hill  314.828 .35b 1.5 Failed Drinking Water Criteria Document for Cyanogen Chloride and Metabolites Study Endpoint Model AIC G o F pvalue BMDa BMDL EPA/ OW/ OST/ HECD Final draft A 20 Left Testis Weight Polynomial  171.981b .81b 7.0 4.9 Power  171.981b .81b 7.0 4.9 Hill  168.410 .43c 5.0 1.8 Spermatid Heads per Testis Polynomial 98.363b .70b 11 6.9 Power 98.363b .70b 11 6.9 Hill 99.962b .58b 8.3 1.3 Spermatid Count Polynomial 227.040b .70b 11 6.9 Power 227.040b .70b 11 6.9 Hill 228.642 .58b 8.3 1.3 Motility Polynomial 147.508 .001b 19 8.5 Power 144.243b .002b 15 6.7 Hill 147.583 .007c Failed Failed NTP, 1993; male mice Left Epididymis Weight Polynomial  378.489 .12c 22 Failed Power  378.910b .14c 25 18 Hill  374.586 .12c 21 Failed Left Cauda Epididymis Weight Polynomial  409.479 Failed 20 12 Power  409.568a Failed 20 Failed Hill Failed aBMD and BMDL are based on benchmark response of 1SD. Results are presented in units of mg/ kg day. BMD and BMDL estimates in bold type are the estimates judged to be the best estimates to use for the quantitative dose response assessment for each chemical. For some data sets, none are bolded because of poor model fits or inability of BMDS to obtain BMDL estimates. " Failed" indicates that BMDS was unable to produce the estimate or the information required to be able to present a value.

bCorrected from erroneous BMDS output. Errors were identified in the degrees of freedom ( DF) provided in the output for the fitted model in several cases. For these cases, the AIC was calculated independently using the log likelihoods provided in the output and the correct number of DF. Similarly, the goodness of fit pvalues were corrected by calculating manually the chi square p value using the appropriate number of DF.

cBased on a comparison of the fitted model to the model maximizing the likelihood ( i. e. model with independent means and variances for each dose group, model A2 from BMDS). Drinking Water Criteria Document for Cyanogen Chloride and Metabolites Study Endpoint Model AIC G o F pvalue BMDa BMDL EPA/ OW/ OST/ HECD Final draft A 21 dA fit that maximizes the likelihood ( i. e., gives a likelihood as great as that for model A2) is assigned a pvalue of 1.0, even if there were no degrees of freedom for a formal statistical test.