[Federal Register Volume 59, Number 196 (Wednesday, October 12, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-25204]


[[Page Unknown]]

[Federal Register: October 12, 1994]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[WA5-1-5539a, WA27-1-6612a; FRL-5078-9]

 

Approval and Promulgation of Implementation Plans: Washington

AGENCY: Environmental Protection Agency.

ACTION: Direct final rule.

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SUMMARY: Environmental Protection Agency (EPA) conditionally approves a 
revision to the State implementation plan (SIP) submitted by the State 
of Washington for the purpose of bringing about the attainment of the 
National ambient air quality standards (NAAQS) for particulate matter 
with an aerodynamic diameter less than or equal to a nominal 10 
micrometers (PM-10). The implementation plan was submitted by the State 
to satisfy certain Federal requirements for an approvable moderate 
nonattainment area PM-10 SIP for Tacoma, Washington.
DATES: This final rule will be effective on December 12, 1994 unless 
adverse or critical comments are received by November 14, 1994. If the 
effective date is delayed, timely notice will be published in the 
Federal Register.

ADDRESSES: Written comments should be addressed to: Montel Livingston, 
SIP Manager, Environmental Protection Agency, Air and Radiation Branch 
(AT-082), 1200 Sixth Avenue, Seattle, Washington 98101.
    Documents which are incorporated by reference are available for 
public inspection at the Air and Radiation Docket and Information 
Center, Environmental Protection Agency, 401 M Street, SW., Washington, 
DC 20460. Copies of material submitted to EPA may be examined during 
normal business hours at the following locations: EPA, Region 10, Air & 
Radiation Branch, 1200 Sixth Avenue (AT-082), Seattle, Washington 
98101, and the State of Washington Department of Ecology, 4450 Third 
Avenue SE., Lacey, Washington 98504.

FOR FURTHER INFORMATION CONTACT: Claire Hong, Air and Radiation Branch 
(AT-082), Environmental Protection Agency, 1200 Sixth Avenue, Seattle, 
Washington 98101, (206) 553-1813.

SUPPLEMENTARY INFORMATION:

I. Background

    The Tacoma, Washington, area was designated nonattainment for PM-10 
and classified as moderate under sections 107(d)(4)(B) and 188(a) of 
the Clean Air Act (CAA), upon enactment of the Clean Air Act Amendments 
(CAAA) of 1990.1 See 56 FR 56694 (November 6, 1991) (official 
designation codified at 40 CFR 81.348). The air quality planning 
requirements for moderate PM-10 nonattainment areas are set out in 
subparts 1 and 4 of part D, title I of the Act.2 EPA has issued a 
``General Preamble'' describing EPA's preliminary views on how EPA 
intends to review SIPs and SIP revisions submitted under Title I of the 
Act, including those State submittals containing moderate PM-10 
nonattainment area SIP requirements (see generally 57 FR 13498 (April 
16, 1992) and 57 FR 18070 (April 28, 1992)). Because EPA is describing 
its interpretations here only in broad terms, the reader should refer 
to the General Preamble for a more detailed discussion of the 
interpretations of title I advanced in this notice and the supporting 
rationale. In this rulemaking action on the State of Washington's 
moderate PM-10 SIP for the Tacoma nonattainment area (referred to as 
Tacoma or the Tacoma Tideflats), EPA is applying its interpretations 
taking into consideration the specific factual issues presented. 
Additional information supporting EPA's action on this particular area 
is available for inspection at the address indicated above. Those 
States containing initial moderate PM-10 nonattainment areas (those 
areas designated nonattainment under CAA section 107(d)(4)(B)) were 
required to submit, among other things, the following provisions by 
November 15, 1991:

    \1\ The 1990 Amendments to the Clean Air Act made significant 
changes to the Act. See Pub. L. No. 101-549, 104 Stat. 2399. 
References herein are to the Clean Air Act, as amended (``the 
Act''). The Clean Air Act is codified, as amended, in the U.S. Code 
at 42 U.S.C. 7401, et seq.
    \2\ Subpart 1 contains provisions applicable to nonattainment 
areas generally and subpart 4 contains provisions specifically 
applicable to PM-10 nonattainment areas. At times, subpart 1 and 
subpart 4 overlap or conflict. EPA has attempted to clarify the 
relationship among these provisions in the ``General Preamble'' and, 
as appropriate, in today's notice and supporting information.
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    1. Provisions to ensure that reasonably available control measures 
(RACM) (including such reductions in emissions from existing sources in 
the area as may be obtained through the adoption, at a minimum, of 
reasonably available control technology (RACT)) shall be implemented no 
later than December 10, 1993;
    2. Either a demonstration (including air quality modeling) that the 
plan will provide for attainment as expeditiously as practicable but no 
later than December 31, 1994, or a demonstration that attainment by 
that date is impracticable;
    3. Quantitative milestones which are to be achieved every three 
years and which demonstrate reasonable further progress (RFP) toward 
attainment by December 31, 1994; and
    4. Provisions to ensure that the control requirements applicable to 
major stationary sources of PM-10 also apply to major stationary 
sources of PM-10 precursors except where the Administrator determines 
that such sources do not contribute significantly to PM-10 levels which 
exceed the NAAQS in the area (see sections 172(c), 188, and 189 of the 
Act).
    Additional provisions are due at a later date. States with initial 
moderate PM-10 nonattainment areas were required to submit a permit 
program for the construction and operation of new and modified major 
stationary sources of PM-10 by June 30, 1992 (see CAA section 189(a)). 
The Washington State Department of Ecology (WDOE) submitted the new 
source review requirements for this area on October 22, 1993. EPA will 
address that submittal in a separate Federal Register document.
    Such States also were required to submit contingency measures by 
November 15, 1993, which become effective without further action by the 
State or EPA, upon a determination by EPA that the area has failed to 
achieve RFP or to attain the PM-10 NAAQS by the applicable statutory 
deadline (see CAA section 172(c)(9) and 57 FR 13510-13512 and 13543-
13544). EPA addresses the contingency measures the State has submitted 
for Tacoma in part II.8 of the discussion below.

II. This Action

    Section 110(k) of the Act sets out provisions governing EPA's 
review of SIP submittals (see 57 FR 13565-13566). Section 110(k)(4) of 
the Act authorizes EPA to approve a plan revision based on a commitment 
by the State to adopt specific enforceable measures by a date certain, 
but not later than one year after the date of approval of the plan 
revision. EPA would then assess the approvability of the submittal 
after the State fulfilled its commitment. However, if the State fails 
to comply with its commitment, section 110(k)(4) provides that a 
conditional approval shall be treated as a disapproval. If the 
conditional approval is converted to a disapproval, the sanctions clock 
under section 179 of the Act and the Federal implementation plan clock 
under section 110(c)(1) of the Act will begin.
    In this action, EPA is granting conditional approval of the plan 
revisions submitted to EPA for Tacoma, Washington, on November 15, 1991 
and June 30, 1994 (hereafter generally referred to as a single 
submittal), except for the following elements of the SIP which are 
described below or in the Technical Support Document associated with 
this rulemaking. EPA is approving these following elements without 
conditions: exclusion from precursor controls, the monitoring network, 
the procedures for consultation and public notification, the provisions 
for revising the plan and the adequacy of funding and authority.
    EPA conditionally approves the submittal because it does not fully 
meet certain applicable requirements of the CAA for moderate PM-10 
nonattainment areas. The submittal does not meet the requirements to 
provide for the implementation of RACM (including RACT), to demonstrate 
timely attainment of the PM-10 NAAQS (or demonstrate that timely 
attainment is not practicable), and to provide for quantitative 
milestones and reasonable further progress. See CAA sections 172(c)(1), 
189(a)(1)(C), 189(a)(1)(B) and 189(c). Some of the control measures 
relied on to satisfy these requirements have not been made enforceable 
emission limitations. CAA sections 110(a)(2)(A) and 172(c)(6). However, 
the State has submitted a commitment to adopt specific enforceable 
measures on or before January 1, 1995, and to address the applicable 
requirements of the Act. In its June 30, 1994 SIP revision, the State 
committed to submitting federally enforceable emission limits to EPA by 
January 1, 1995 for the following major stationary sources identified 
in the SIP: Buffelen Woodworking, Continental Grain, Continental Lime, 
Domtar Gypsum, Puget Sound Plywood, USG Interiors, US Oil and Refining, 
Woodworth, Kaiser Aluminum and Chemical Corporation and Simpson Tacoma 
Kraft Company.
    The submittal is substantive and contains some specific enforceable 
control measures. Accordingly, EPA is conditionally approving the 
submittal, as authorized under section 110(k)(4) of the CAA. EPA also 
approves, without conditions, the separable exclusion from precursor 
controls as described in part II.5 below, the monitoring network, the 
procedures for consultation and public notification, the provisions for 
revising the plan and the adequacy of funding and authority.

Analysis of State Submission

1. Procedural Background

    The Act requires States to observe certain procedural requirements 
in developing implementation plans and plan revisions for submission to 
EPA. Section 110(a)(2) of the Act provides that each implementation 
plan submitted by a State must be adopted after reasonable notice and 
public hearing.3 Section 110(l) of the Act similarly provides that 
each revision to an implementation plan submitted by a State under the 
Act must be adopted by such State after reasonable notice and public 
hearing.
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    \3\Also section 172(c)(7) of the Act requires that plan 
provisions for nonattainment areas meet the applicable provisions of 
section 110(a)(2).
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    The EPA also must determine whether a submittal is complete and 
therefore warrants further EPA review and action (see CAA section 
110(k)(1) and 57 FR 13565). EPA's completeness criteria for SIP 
submittals are set out at 40 CFR part 51, appendix V. EPA attempts to 
make completeness determinations within 60 days of receiving a 
submission. However, a submittal is deemed complete by operation of law 
if a completeness determination is not made by EPA six months after 
receipt of the submission.
    The State of Washington Department of Ecology conducted a public 
hearing to receive public comment on the State implementation plan 
revision for PM-10 in Tacoma on November 7, 1991. WDOE adopted the 
implementation plan for the area on November 15, 1991, and submitted it 
to EPA the same day. In 1994, the plan was revised to amend its request 
for conditional approval. WDOE conducted a public hearing to obtain 
public input on this revision on February 17, 1994. The letter revising 
the request for conditional approval was submitted to EPA on June 30, 
1994. The November 15, 1991 and June 30, 1994 SIP submittals were 
reviewed by EPA to determine completeness in accordance with the 
completeness criteria set out at 40 CFR part 51, appendix V. Letters 
dated May 12, 1992 and August 1, 1994, were forwarded to the WDOE 
indicating the completeness of the submittals and the next steps to be 
taken in the review process.

2. PM-10 Emissions Inventory

    Section 172(c)(3) of the Act requires that nonattainment plan 
provisions include a comprehensive, accurate and current inventory of 
actual emissions from all sources of relevant pollutants in the 
nonattainment area. The emissions inventory should also include a 
comprehensive, accurate and current inventory of allowable emissions in 
the area. See, e.g., CAA section 110(a)(2)(K). Because the submission 
of such inventories are necessary to an area's attainment demonstration 
(or demonstration that the area cannot practicably attain), the 
emissions inventories must be received with the attainment/
nonattainment demonstration submission (see 57 FR 13539).
    WDOE submitted an emissions inventory of estimated actual emissions 
for the base year of 1987 and the attainment year of 1994. The 24-hour 
emission inventory identified three major source categories 
contributing to particulate matter in the Tacoma Tideflats. These are, 
in descending order of greatest contribution, industrial stack 
emissions (66 percent); vehicle resuspended road dust (18 percent); and 
industrial fugitive emissions (13 percent). Other contributing sources 
were area sources, such as residential wood combustion and motor 
vehicle exhaust. The emission inventory is dominated by one point 
source, the Simpson Tacoma Kraft Company (Simpson), a paper pulp 
producer, which accounts for 45 percent of the emission inventory.
    For sources within the nonattainment area, the emissions inventory 
provides a comprehensive list of particulate sources and utilizes 
appropriate factor and estimations that were available at the time the 
SIP revision was prepared. However, the emission inventory may 
underestimate the impact of PM-10 sources outside of the nonattainment 
area. Possibly due to where the nonattainment area boundaries were 
drawn, there may be a significant source of PM-10 outside of the 
nonattainment area. As is discussed in the Technical Support Document 
(TSD), substantial evidence indicates that imported residential wood 
combustion accounts for a large portion of the PM-10 in the Tacoma 
Tideflats. For further information, the reader is referred to the TSD 
accompanying this action, which is available at the EPA address 
indicated above.
    The emissions inventory estimating actual emissions along with 
additional available information provides a sufficient basis for 
determining the technical adequacy of the attainment demonstration for 
this area consistent with the requirements of section 172(c)(3) of the 
Clean Air Act.4 An additional attainment year emission inventory 
issue, relating to the attainment demonstration, and other 
requirements, is the use of actual instead of allowable emission 
estimates for projecting attainment. This issue will be discussed in 
more detail under the demonstration section of this document. Again, 
the reader is referred to the TSD corresponding with this action for 
further information.
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    \4\The EPA issued guidance on PM-10 emissions inventories prior 
to the enactment of the Clean Air Act Amendments in the form of the 
1987 PM-10 SIP Development Guideline. The guidance provided in this 
document appears to be consistent with the Act. See CAA section 193.
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3. RACM (Including RACT)

    As noted, the initial moderate PM-10 nonattainment areas must 
submit provisions to ensure that RACM (including RACT) are implemented 
no later than December 10, 1993 (see CAA sections 172(c)(1) and 
189(a)(1)(C)). The General Preamble contains a detailed discussion of 
EPA's interpretation of the RACM (including RACT) requirement (see 57 
FR 13539-13545 and 13560-13561).
    In broad terms, the State should identify available control 
measures evaluating them for their reasonableness in light of the 
feasibility of the controls and the attainment needs of the area. A 
State may reject available control measures if the measures are 
technologically infeasible or the cost of the control is unreasonable. 
In addition, RACM, does not require controls on emissions from sources 
that are insignificant (i.e. de minimis) and RACM does not require the 
implementation of all available control measures where an area 
demonstrates timely attainment of the NAAQS and the implementation of 
additional controls would not expedite attainment. 57 FR 13540-13544.
    Washington's control strategy for the Tacoma area provides for 
attainment of the 24-hour standard based on control of industrial 
emissions, fugitive industrial emissions including resuspended road 
dust, and residential wood combustion. However, as indicated below, 
some of the control measures are deficient because they are not 
reflected in enforceable emission limitations. See CAA sections 
110(a)(2)(A) & 172(c)(6). The State has committed to address this 
deficiency and, based on section 110(k)(4) of the CAA, EPA is 
conditionally approving the submittal relative to the RACM (Including 
RACT) requirement. The available control measures to be implemented in 
Tacoma include the following:
a. Industrial Controls
    The largest single reduction in the projected emission inventory 
results from the control of industrial stack emissions. As stated 
earlier, Simpson accounts for 45 percent of the emission inventory. In 
1991, Simpson replaced the #2,3,4,5 hogged fuel boilers and #1 oil 
boiler at the mill with a new hogged fuel boiler. Emissions from the 
new boiler represent a 984 kg/day reduction in emissions, almost half 
of Simpson's previous emissions, or roughly 19 percent of the total 
baseline emissions inventory.
    In addition, changes in industrial processes resulted in decreased 
emissions; for example, U.S. Oil and Refining and Simpson changed fuel 
sources to burn natural gas. The SIP assumes that emissions from mobile 
sources will grow modestly from 1987 to 1994. Even including these 
growth projections, the overall reduction in industrial PM-10 stack 
emissions due to implementation of controls for all sources combined is 
projected to be 17 percent of the base year's inventory. However, these 
industrial changes and controls have not been expressed as enforceable 
emission limitations. As discussed earlier, WDOE has committed to 
submit enforceable emissions limits on the industrial sources by 
January 1, 1995.
b. Industrial Fugitive and Resuspended Road Dust
    The Tacoma emission inventory identified industrial fugitive 
emissions and resuspended road dust as significant contributors of 
particulate matter to the airshed. The Puget Sound Air Pollution 
Control Agency (PSAPCA) is a local air pollution control agency that 
has jurisdiction over four counties in Washington State; PSAPCA's 
jurisdiction includes the Tacoma Tideflats. PSAPCA's fugitive dust 
regulation (Regulation I, section 9.15) was designed to reduce fugitive 
dust from commercial and industrial activities and also to reduce dust 
emissions from paved and unpaved roads and parking lots.
    PSAPCA requires ``Best Available Control Technology (BACT)'' under 
section 9.15 for all fugitive emissions from all incinerators, boilers, 
manufacturing equipment and air pollution control equipment. The Tacoma 
attainment plan lists and documents emission reductions from several 
major facilities that were required to pave roads or add PM-10 controls 
as the result of PSAPCA's application of section 9.15. Puget Sound 
Plywood, Lone Star, Woodworth and Buffelen were required to either pave 
roads or modify production processes to comply with section 9.15. The 
SIP estimates that the application of section 9.15 would result in a 
reduction of 73 kg/day of fugitive emissions from industrial sources. 
After accounting for an increase of 39 kg/day due to industrial growth, 
the net total reduction from the base year to the attainment year of 
fugitive emissions is 34 kg/day. EPA accepts the emission reductions 
claimed from this control measure as reasonable. Since it is generally 
impractical to source test fugitive emission sources, a SIP must rely 
on calculated emission estimates, and control efficiency estimates, to 
arrive at emission reduction estimates.
    Control of resuspended road dust is a significant component of 
section 9.15. PSAPCA applies the same section 9.15 BACT provisions to 
dust emissions from both private and public paved and unpaved roads. In 
addition, all private roadways adjoining paved public roads and all 
commercial properties with access points abutting paved public roads in 
the Tacoma nonattainment area are required to implement BACT to 
stabilize vehicular entrances and exits. The control measure also 
appropriately prioritized preventing material deposition on roadways 
over mitigating measures after deposition. Looking specifically at the 
control of resuspended road dust, the plan uses an overall emission 
reduction credit of 37 percent from resuspended road dust. EPA accepts 
this estimate as reasonable.
c. Residential Wood Combustion
    As previously noted, there is a substantial body of evidence 
indicating that imported residential wood combustion is a large source 
of Tacoma's PM-10. All three receptor models concluded that woodsmoke 
was one of the main sources of particulate matter in the Tacoma 
Tideflats area. The most recent receptor modeling study suggested that 
residential wood combustion was an unexpectedly strong source of PM-10. 
This is also supported by the Saturation Study conducted by EPA. 
Additional discussion of the impact of imported residential wood 
combustion can be found in the TSD associated with this action. Because 
of the likely impact of imported residential wood combustion on 
Tacoma's airshed, the available control measures adopted for 
residential wood combustion are discussed here.
    PSAPCA initiated a voluntary woodsmoke curtailment program 
throughout its four county jurisdictional area, including Tacoma, in 
the winter of 1987-88. The program changed to mandatory curtailment 
beginning with the 1988-89 heating season, pursuant to WAC 173-433 and 
the PSAPCA Regulation I, Article 13. The curtailment program is a two 
stage plan. At Stage I, which is imposed when ambient PM-10 levels 
reach 75 g/m3, the use of uncertified stoves and 
fireplaces are banned. At Stage II, imposed when PM-10 levels reach 105 
g/m3, all woodheating (fireplaces, certified and 
uncertified woodstoves) is prohibited. The program exempts homes with 
no other source of heat. WDOE and PSAPCA regulations contain additional 
controls, including the prohibition of all fuels except dry, seasoned 
wood in woodheating devices. Plume opacity for woodheating devices is 
limited to 20 percent, with brief exceedances allowed for fire starting 
and stoking. PSAPCA serves as the primary enforcement agency for the 
curtailment and opacity portions of the control program. Both WDOE and 
PSAPCA administer public education programs targeted at residential 
wood burning. Throughout the State, WDOE also enforces a ban on the 
sale of uncertified woodstoves.
    The strength and depth of the legislated woodsmoke program, and the 
size and historical effectiveness of the agencies involved, 
demonstrates to EPA's satisfaction that the Tacoma area is achieving a 
sufficient compliance rate to justify the 70 percent emission reduction 
credit taken for these measures. A more detailed analysis of the 
Washington woodsmoke curtailment plan is contained in the TSD. Since 
PSAPCA administers the woodsmoke curtailment program throughout its 
four-county jurisdictional area and the program affects sources both 
within the nonattainment area and in adjoining areas, the 70 percent 
emission reduction credit is applicable to both residential wood 
combustion generated in the nonattainment area and imported residential 
wood combustion.
    As indicated, where sources of PM-10 contribute insignificantly to 
the PM-10 problem in the area, EPA's policy is that RACM does not 
require the implementation of potentially available control measures. 
57 FR 13540. Further, EPA has indicated that for some sources in areas 
which demonstrate timely attainment, RACM does not require the 
implementation of otherwise available control measures that are not 
``reasonably'' available because their implementation would not 
expedite attainment (see 57 FR 13543). In the Tacoma situation, EPA 
believes the significant sources, as well as several less significant 
sources, of PM-10 in the area have been reasonably controlled. Thus, 
EPA believes that RACM does not require the implementation of 
potentially available control measures or technology for other de 
minimis sources of PM-10 in the area. Further, EPA believes 
implementation of such additional controls in this area would not 
expedite attainment.
    A more detailed discussion of the individual source contributions, 
their associated control measures and an explanation as to why certain 
available control measures were not implemented, can be found in the 
TSD. EPA has reviewed the State's explanation and associated 
documentation and concludes that it adequately justifies the control 
measures to be implemented. However, as addressed in more detail in 
part II.4 below, not all of the emission reductions necessary to ensure 
expeditious attainment of the PM-10 NAAQS are embodied in enforceable 
emission limitations. Thus, EPA is conditionally approving the control 
measures submitted for Tacoma, based upon a commitment by the State 
that it will submit to EPA by January 1, 1995, legally enforceable 
emission limits for the significant stack sources in Tacoma. See CAA 
section 110(k)(4). This conditional approval is discussed further in 
the section below.

4. Demonstration

    As noted, the initial moderate PM-10 nonattainment areas must 
submit a demonstration (including air quality modeling) showing that 
the plan will provide for attainment as expeditiously as practicable 
but no later than December 31, 1994 (see section 189(a)(1)(B) of the 
Act). The General Preamble sets out EPA's guidance on the use of 
modeling for moderate area attainment demonstrations (57 FR 13539). 
Alternatively, if the State does not submit a demonstration of 
attainment, the State must show that attainment by December 31, 1994, 
is impracticable (CAA section 189(a)(1)(B)(ii)).
    Several studies have been conducted to determine sources of 
particulate matter in the Tacoma nonattainment area. WDOE and PSAPCA 
employed pollutant dispersion models in the Tacoma nonattainment area 
using both guideline and non-guideline models. Neither RAM (guideline) 
nor WYNDvalley (non-guideline) yielded results that were well 
correlated to measured values. It is difficult to determine precisely 
why dispersion modeling failed to yield acceptable values in the Tacoma 
Tideflats when similar approaches have proven successful elsewhere, but 
the TSD raises possible explanations, including where the boundaries of 
the nonattainment were drawn and how the background PM-10 concentration 
was established. The reader is referred to the ``Description of Air 
Quality Modeling'' section of the TSD associated with this action for 
further information.
    In addition to dispersion modeling, three receptor modeling studies 
were conducted in the Tacoma Tideflats to try to determine source 
contribution of PM-10. Separate from these receptor modeling studies, a 
saturation study was conducted to determine the site of maximum impact 
in the Tacoma nonattainment area. Unfortunately, no single study 
conclusively apportions the amount of PM-10 attributable to different 
sources. As is discussed in the TSD, EPA has reservations about each of 
these studies because of study design flaws, errors in conducting the 
study, or changing composition of particulate matter in the airshed. 
See the ``Attainment Demonstration'' section of the TSD for a longer 
discussion of the individual studies.
    Faced with several studies, none of which were definitive, the WDOE 
attempted to address several diverse scenarios to demonstrate 
attainment and maintenance of the PM-10 NAAQS in the area. The SIP 
contains three demonstrations of attainment and maintenance all using 
rollback, a modified attainment demonstration that EPA may accept on a 
case-by-case basis. The first demonstration presented in the SIP is 
based on receptor modeling and proportional rollback; the second used a 
dispersion modeling study and proportional rollback; and the last was 
based on straight rollback. Tacoma's SIP meets the criteria for using 
rollback as outlined in EPA guidance (Attachment 5 of''PM-10 Moderate 
Area SIP Guidance: Final Staff Work Product,'' April 2, 1990). EPA's 
primary concern about the demonstrations in the SIP is that they 
underestimate the amount of PM-10 from residential wood combustion 
coming into the nonattainment area from surrounding areas.
    As discussed in the TSD, EPA believes that when looking at the 
receptor modeling and saturation studies as a whole, there is a 
substantial body of evidence indicating that residential wood 
combustion was and is a major source of PM-10 in the airshed. As 
discussed in the TSD, this residential wood combustion is probably 
being imported into the nonattainment area, and a conservative lower 
bound estimate is that 35-45 percent of the PM-10 in the Tacoma 
Tideflats on the design day is attributable to residential wood 
combustion. A more detailed discussion of this point can be found in 
the ``Attainment Demonstration'' of the TSD.
    EPA notes that there has been uncertainty over source contribution 
in the Tacoma nonattainment area despite numerous efforts by PSAPCA, 
WDOE, EPA and other entities to characterize the airshed. In reviewing 
the SIP, EPA has considered all relevant studies referenced in the SIP 
as well as additional information, such as the saturation study. Based 
on these studies, EPA finds that imported residential wood combustion 
is a much larger source of PM-10 than currently accounted for in the 
SIP.
    To evaluate the impact of imported residential wood combustion into 
the nonattainment area, the TSD associated with the rulemaking contains 
a rollback analysis that incorporates a relatively conservative 
estimate of the residential wood combustion being imported into the 
nonattainment area. As noted earlier, Tacoma's SIP meets the criteria 
for using rollback. In the ``Attainment Demonstration'' discussion of 
the TSD, EPA sets out a rollback scenario that incorporates the 
estimate that 35-45 percent of the PM-10 in the Tacoma Tideflats on the 
design day is attributable to residential wood combustion. A mandatory 
residential woodsmoke curtailment program is being imposed over a four-
county area that includes the Tacoma Tideflats and surrounding 
contiguous areas. As discussed earlier in section II.3 of this 
document, PSAPCA's mandatory woodstove curtailment program warrants a 
70 percent control measure credit. After applying control measure 
credit for the mandatory woodstove curtailment program, the rollback 
scenario presented in the TSD demonstrates; to EPA's satisfaction, that 
the PM-10 NAAQS will be attained by 1994.
    Assurance of attainment and maintenance rests with the SIP's 
control measures. The SIP contains a broad array of control measures 
aimed at both industrial and residential sources. Based on the emission 
inventory and related information about the estimated contribution from 
residential wood combustion, these control measures, when they are made 
fully enforceable (see below), will be sufficient to ensure attainment 
and maintenance.
    It should be noted that a major problem with the attainment 
demonstration is the attainment year emission inventory used for point 
(stack) sources. The inventory was based on actual emission estimates. 
EPA's Guideline on Air Quality Models (Revised, July 1986) generally 
requires use of allowable emissions in inventories for the purposes of 
modeling attainment of the NAAQS (see also CAA sections 110(a)(2)(A), 
110(a)(2)(K) and 172(c)(6) of the Act). The requirement takes into 
consideration possible increases from existing sources allowed by their 
permits, registrations, or other regulatory mechanisms and ensures that 
the control measures relied on in the SIP are based on enforceable 
emission limitations. WDOE and PSAPCA, based on comments from EPA, were 
not able to demonstrate that all point source emissions in the 
nonattainment area would be unable to increase significantly above 
actual levels. Consequently, there is no objective assurance, or 
legally enforceable mechanism in place, to restrict a point source from 
emitting above the estimated actual rate, should the source have the 
physical capacity. Therefore, to ensure that the NAAQS will be 
protected in the Tacoma nonattainment area, the currently allowable 
emission limits must be reduced.
    Despite the fact that Tacoma has been monitoring daily at the site 
determined to be the site of maximum impact and has not had an 
exceedance of the NAAQS at any monitor in four years, there are no 
legal limits in place to prevent future increases from a few industrial 
facilities that could consequently threaten attainment of the NAAQS. On 
June 30, 1994, WDOE submitted a request for conditional approval of the 
Tacoma nonattainment plan based on a commitment to reconcile the 
actual/allowable emission limitation issue and thereby establish an 
enforceable attainment demonstration. WDOE's commitment includes a 
schedule to issue regulatory orders to appropriate point sources within 
the nonattainment area that will restrict emissions (i.e. establish 
allowable emission limitations) at or below the ``actual'' emission 
estimates used in the attainment demonstration. EPA conditionally 
approves the attainment demonstration for Tacoma on the basis of this 
commitment. See CAA section 110(k)(4). The revisions to the emission 
limitations for the affected sources will make enforceable the actual 
emission limitations already being achieved and implemented in the 
area.
    Like the attainment demonstration, Tacoma's SIP contained three 
maintenance demonstrations. The first demonstration is based on 
receptor modeling and proportional rollback; the second used a 
dispersion modeling study and proportional rollback; and the last was 
based on straight rollback; however, the last demonstration failed to 
show maintenance through 1997. EPA believes that the failure of the 
third demonstration to show maintenance through 1997 is due to the 
SIP's low estimate of imported residential woodsmoke.
    In the ``Evaluation of Attainment Demonstration'' section of the 
accompanying TSD, EPA considered additional information and analyses in 
assessing the maintenance demonstration, including using rollback that 
differs from the SIP in its estimate of the amount of residential wood 
combustion affecting the airshed. EPA believes that after evaluating 
all of the studies of the Tacoma Tideflats, there is sufficient 
evidence to support an interpretation that imported residential wood 
combustion is a much stronger source of PM-10 than currently accounted 
for in the SIP. Similar to the demonstration of attainment presented in 
the ``Attainment Demonstration'' of the TSD, EPA believes a greater 
background value that accounts for a large importation of residential 
woodsmoke should be employed in the maintenance demonstration. Using 
the emission inventory, growth factors, and point source emission 
levels presented in the SIP, considering additional information about 
the contribution of residential wood combustion and employing the same 
background value as was used in the attainment demonstration discussed 
in the TSD, the rollback analysis demonstrates maintenance through 
1997, and would therefore satisfy the initial quantitative milestones 
due for this area, as discussed in part II.6 below. However, as with 
the attainment demonstration, some of the control measures relied on to 
demonstrate continued maintenance of the PM-10 NAAQS in the SIP are 
deficient because they are not reflected in enforceable emission 
limitations. See CAA sections 110(a)(2)(A) & 172(c)(6). The State has 
committed to address this deficiency and, based on section 110(k)(4) of 
the CAA, EPA is conditionally approving the submittal relative to the 
quantitative milestone and reasonable further progress requirements 
discussed below.
    The accompanying TSD discusses the dispersion, receptor and 
saturation studies conducted in the Tacoma Tideflats, estimates the 
amount of PM-10 attributable to residential wood combustion, and 
presents a rollback demonstration for attainment and maintenance that 
incorporates the estimate that 35-45 percent of the PM-10 in the Tacoma 
Tideflats on the design day is attributable to residential wood 
combustion. The reader is referred to the TSD associated with this 
document for a more detailed discussion of any of these points.

5. PM-10 Precursors

    The control requirements which are applicable to major stationary 
sources of PM-10, also apply to major stationary sources of PM-10 
precursors unless EPA determines such sources do not contribute 
significantly to PM-10 levels in excess of the NAAQS in that area (see 
section 189(e) of the Act). The General Preamble contains guidance 
addressing how EPA intends to implement section 189(e) of the Act (see 
57 FR 13539-13540 and 13541-13542).
    The three receptor modeling studies conducted in the Tacoma 
Tideflats show that sulfates and nitrates are not a significant portion 
of the Tacoma PM-10 in the airshed. The three studies are discussed in 
the TSD. The two receptor modeling studies conducted during the 1980s 
show that nitrates accounted for less than 4 percent of the total PM-10 
sampled mass, while sulfates contributed even less measuring less than 
2.5 percent.
    The third receptor modeling study, the Evaluation of the 
Atmospheric Deposition of Toxic Contaminants to Puget Sound study was 
conducted in the Tacoma Tideflats during 1989 and 1990. The Atmospheric 
Deposition Study collected fine particulate ( 2.5 
m) and coarse particulate ( 50 m). Most of 
the precursor particles would be occurring in the fine particle range. 
The analysis of the fine particles showed that SO4 was 9.3 percent 
of the total mass of fine particles, while NO3 accounted for 
approximately 5 percent of total mass of fine particles. As discussed 
in the ``Evaluation of Attainment Demonstration'' in the accompanying 
TSD, the Atmospheric Deposition Study was conducted during a period 
when the airshed was considerably cleaner than the design year. 
Moreover, control measures were in place during the Atmospheric 
Deposition Study's sampling period; five of the sampling days occurred 
during a ban on the use of uncertified woodstoves. Therefore, the 
results of this study are likely to show less PM-10 due to woodsmoke 
than probably occurred during the design year. Correspondingly, the 
study's assessment of the amount of SO4 and NO3 found in the 
airshed is likely to be greater on a percentage basis than would have 
been the case during the design year.
    Due to the relatively small amount of sulfates and nitrates in the 
airshed, EPA has determined that it is unlikely that precursors do not 
contribute significantly to PM-10 levels which exceed the NAAQS in 
Tacoma. In addition to these receptor analyses, a review of the 
emissions inventory for this area did not reveal any major stationary 
sources of PM-10 precursors. The effect of this finding is to exclude 
major stationary sources of PM-10 precursors from PM-10 nonattainment 
area control requirements.
    While EPA is making a general finding about the contribution of PM-
10 precursors for Tacoma, the determination is based on the current 
character of the area including the existing mix of sources in the 
area. It is possible, therefore, that future growth could change the 
significance of precursors in the area. The EPA intends to issue future 
guidance addressing such potential changes in the significance of 
precursor emissions in an area.

6. Quantitative Milestones and Reasonable Further Progress (RFP)

    The PM-10 nonattainment area plan revisions demonstrating 
attainment must contain quantitative milestones which are to be 
achieved every three (3) years until the area is redesignated 
attainment and which demonstrate RFP, as defined in section 171(1), 
toward attainment by December 31, 1994 (see section 189(c) of the Act). 
Reasonable further progress is defined in CAA section 171(1) as such 
annual incremental reductions in emissions of the relevant air 
pollutant as are required by Part D or may reasonably be required by 
the Administrator for the purpose of ensuring attainment of the 
applicable NAAQS by the applicable date.
    While section 189(c) plainly provides that quantitative milestones 
are to be achieved until an area is redesignated attainment, it is 
silent in indicating the starting point for counting the first 3-year 
period or how many milestones must be initially addressed. In the 
General Preamble, EPA addressed the statutory gap in the starting point 
for counting the 3-year milestones, indicating that it would begin from 
the due date for the applicable implementation plan revision containing 
the control measures for the area (i.e., November 15, 1991 for initial 
moderate PM-10 nonattainment areas). See 57 FR 13539. As to the number 
of milestones, EPA believes that at least two milestones must be 
initially addressed. Thus, submittals to address the SIP revisions due 
on November 15, 1991 for the initial moderate PM-10 nonattainment areas 
must demonstrate timely attainment of the PM-10 NAAQS, the second 
milestone should, at a minimum, provide for continued maintenance of 
the standards.5
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    \5\ Section 189(c) provides that quantitative milestones are to 
be achieved ``until the area is redesignated attainment.'' However, 
this endpoint for quantitative milestones is speculative because 
redesignation of an area as attainment is contingent upon several 
factors and future events.
    EPA believes it is unreasonable to require planning for each 
nonattainment area to cover quantitative milestones years into the 
future because of the possibility that such time may elapse before 
an area is in fact redesignated attainment. On the other hand, EPA 
believes it is reasonable for States initially to submit a 
sufficient number of milestones to ensure that there is continuing 
air quality protection beyond the attainment deadline. Addressing 
two milestones will ensure that the State continues to maintain the 
NAAQS beyond the attainment date for at least some period during 
which an area could be redesignated attainment. However, in all 
instances, additional milestones must be addressed if an area is not 
redesignated attainment within the time period covered by the 
initial milestones.
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    In implementing RFP for this initial moderate area, EPA has 
reviewed the attainment demonstration and control strategy for the area 
to assess whether the initial milestones have been satisfied and to 
determine whether annual incremental reductions, different from those 
provided in the SIP, should be required in order to ensure attainment 
of the PM-10 NAAQS by December 31, 1994 (see CAA section 171(1)). As 
indicated, the State of Washington's PM-10 SIP for Tacoma demonstrates 
attainment in 1994 and maintenance through 1997, and therefore would 
satisfy RFP and initial quantitative milestones (see 57 FR 13539) if 
all of the control measures relied upon were reflected in enforceable 
emission limitations. However, as discussed previously, WDOE and PSAPCA 
based attainment and maintenance demonstrations on actual emission 
estimates instead of the required allowable rates. The State has 
committed to adopt the necessary enforceable allowable emission limits 
by January 1, 1995. Accordingly, as with other requirements discussed 
elsewhere in this document, EPA is conditionally approving the 
submittal relative to the RFP and initial milestone requirements. CAA 
section 110(k)(4).

7. Enforceability Issues

    All measures and other elements in the SIP must be enforceable by 
WDOE and EPA (see CAA sections 172(c)(6), 110(a)(2)(A) and 57 FR 
13556). EPA criteria addressing the enforceability of SIP's and SIP 
revisions were stated in a September 23, 1987, memorandum (with 
attachments) from J. Craig Potter, Assistant Administrator for Air and 
Radiation, et al. (see 57 FR 13541). Nonattainment area plan provisions 
must also contain a program that provides for enforcement of the 
control measures and other elements in the SIP (see CAA section 
110(a)(2)(C)).
    WDOE's control measures and regulations for control of Particulate 
Matter, which are contained in the SIP, are addressed above under the 
section headed ``RACM (including RACT).'' These control measures apply 
to the types of activities identified in that discussion including, for 
example, fugitive emissions from point sources; vehicle resuspended 
road dust; and residential wood combustion. The SIP provides that the 
affected activities will be controlled throughout the entire 
nonattainment area.
    The TSD contains further information on enforceability requirements 
including enforceable emission limitations; a description of the rules 
contained in the SIP and the source types subject to them; test methods 
and compliance schedules; malfunction provisions; excess emission 
provisions; correctly cited references of incorporated methods/rules; 
and reporting and recordkeeping requirements.
    Both WDOE and PSAPCA have responsibilities in the implementation 
and enforcement of control measures in the Tacoma nonattainment area. 
PSAPCA retains authority over all area sources and all but the two 
stationary sources in Tacoma that are regulated by the Department of 
Ecology. PSAPCA has many compliance inspectors and, as discussed 
further in the TSD, EPA considers PSAPCA's staffing level adequate to 
ensure that the Tacoma attainment plan is fully implemented. As a 
necessary adjunct of its enforcement program, PSAPCA also has broad 
powers to adopt rules and regulations, issue orders, assess penalties, 
require access to records and information, and receive and disburse 
funds. The Washington State Department of Ecology has adequate 
authority to implement and enforce the plan in the event PSAPCA fails 
to make a good faith effort to implement and/or enforce the 
regulations.
    The two point sources in the Tacoma nonattainment area not under 
PSAPCA's jurisdiction are the Simpson Tacoma Kraft Company and Kaiser 
Aluminum and Chemical Corporation. These sources are regulated by the 
Washington State Department of Ecology. The Washington State Department 
of Ecology's legal authorities, personnel and funding sources are 
discussed in the accompanying TSD. EPA finds these authorities and 
funding mechanisms adequate to ensure that the State will be able to 
enforce the control measures in the Tacoma nonattainment area.
    Controls on area sources, such as the residential wood combustion 
program and the fugitive dust control program are also enforceable. 
Discussion and justification of EPA's reasoning can be found in the 
control measure section of this document and the TSD.
    However, as discussed elsewhere in this document, the use of actual 
emission estimates rather than the significantly higher emission limits 
allowed in the current WDOE or PSAPCA regulations is unacceptable. 
WDOE, PSAPCA, and EPA could only enforce the allowable emissions that 
are currently contained in the WDOE or PSAPCA regulations. There are no 
mechanisms for any of the regulatory agencies to enforce the emission 
estimates used in the attainment and maintenance demonstration because 
they are well below the legal limits allowed in the WDOE or PSAPCA 
regulations.
    A discussion regarding the use of actual instead of allowable 
emissions contained in the demonstration portion of this document 
provides background for the enforceability decision. The Region is 
granting a conditional approval of the Tacoma attainment plan based on 
the commitment contained in the June 30, 1994, submittal which will 
make the emissions from point sources enforceable at or below the 
levels used to demonstrate attainment and maintenance. EPA will need 
additional technical documentation from WDOE if the emission levels in 
the regulatory orders are greater than those used in the attainment and 
three year maintenance demonstrations. Additionally, WDOE would need to 
provide cogent attainment and maintenance demonstrations in order for 
the SIP to be fully approved.

8. Contingency Measures

    As provided in section 172(c)(9) of the Act, all moderate 
nonattainment area SIP's that demonstrate attainment must include 
contingency measures (see generally 57 FR 13510-13512 & 13543-13544). 
These measures must be submitted by November 15, 1993, for the initial 
moderate nonattainment areas. Contingency measures should consist of 
other available measures that are not part of the area's core control 
strategy. These measures must take effect without further action by the 
State or EPA, upon a determination by EPA that the area has failed to 
make RFP or attain the PM-10 NAAQS by the applicable statutory 
deadline.
    Assessing the adequacy of Tacoma's contingency measures is tied to 
the attainment demonstration because Tacoma has submitted industrial 
emissions controls in excess of those needed to demonstrate timely 
attainment of the PM-10 NAAQS as a contingency measure. As discussed 
above, Simpson's boiler replacement alone represents a 984 kg/day 
reduction in emissions, almost half of Simpson's previous emissions, or 
roughly 19 percent of the total baseline emissions inventory. Based on 
the rollback discussion provided in the accompanying TSD, the Tacoma 
SIP contains emissions limits and contingency measures that provide for 
reductions greater than the 25 percent contingency measure emissions 
reduction value suggested in the General Preamble (57 FR 13543-13544). 
Further discussion can be found in the ``Contingency Measure'' section 
of the accompanying TSD.
    The contingency measures submitted as part of the Tacoma SIP ranged 
from a commitment to implement mobile source controls to crediting the 
emission limitations already existing in the SIP that would be in 
excess of those needed to address the RACM (including RACT) 
requirement. The two mobile source contingency measures in the 1991 SIP 
were directed at reducing emissions from diesel vehicles: (1) the 
establishment of an inspection and maintenance (I/M) program, and (2) 
the reduction in sulfur content of on-highway diesel fuel. In 1993, 
Washington State expanded its I/M program to include the Tacoma area, 
and the desulfurization program was implemented nationally.
    Only the measures that are being implemented prior to a 
determination that the area has failed to timely attain or achieve RFP, 
that would be in excess of those necessary to provide for timely 
attainment of the PM-10 NAAQS and that, therefore, go beyond RACM 
(including RACT) can be relied on as contingency measures. The measures 
will provide for continued emissions reduction progress beyond the core 
control strategy. Further, because the State would implement these 
precautionary measures prior to a determination that the area has 
failed to timely attain the NAAQS or achieve RFP, these measures 
essentially provide advance contingency benefit and satisfy the 
requirement that they ``take effect . . . without further action by the 
State, or the Administrator.'' EPA believes it would be unreasonable to 
penalize or otherwise discourage the State from taking the arguably 
more precautionary air quality management step of accelerating the 
implementation of these contingency measures.
    However, it cannot be determined whether these measures are in 
excess of those necessary to provide for expeditious attainment and 
necessary to address RACM (including RACT) until the State addresses 
the deficiencies associated with its core control strategy. As 
indicated elsewhere, the State has committed to convert measures 
necessary to address RACM (including RACT) to enforceable emission 
limitations. Until this commitment is fulfilled, EPA cannot conclude 
that the contingency measures go beyond the core control strategy.
    Therefore, EPA is conditionally approving these contingency 
measures. Due to the submission of emission reductions that are 
purportedly in excess of those necessary to demonstrate timely 
attainment and necessary to satisfy RACM as a contingency measure, 
final approval or disapproval of these contingency measures must be 
determined when WDOE submits the regulatory orders establishing 
enforceable emission limits for the stationary sources in the Tacoma 
Tideflats.

III. Implications of This Action

    EPA conditionally approves the plan revisions submitted to EPA for 
the Tacoma, Washington, nonattainment area on November 15, 1991, and 
June 30, 1994, except for the following elements which EPA approves in 
full. EPA also approves, without conditions, the separable exclusion 
from precursor controls as described in part II.5 above, the monitoring 
network, the procedures for consultation and public notification, the 
provisions for revising the plan and the adequacy of funding and 
authority. EPA will assess the final approvability of the submittals 
EPA is conditionally approving after the State fulfills its commitment 
to submit enforceable emission limitations by January 1, 1995. If the 
State fails to comply with its commitment, the conditional approval 
will become a disapproval.

IV. Administrative Review

    This action has been classified as a Table 2 action by the Regional 
Administrator under the procedures published in the Federal Register on 
January 19, 1989 (54 FR 2214-2224), as revised by an October 4, 1993, 
memorandum from Michael H. Shapiro, Acting Assistant Administrator for 
Air and Radiation. OMB has exempted this regulatory action from 
Executive Order 12866 review.
    Under section 307(b)(1) of the Clean Air Act, petitions for 
judicial review of this action must be filed in the United States Court 
of Appeals for the appropriate circuit by December 12, 1994. Filing a 
petition for reconsideration by the Administrator of this final rule 
does not affect the finality of this rule for the purposes of judicial 
review nor does it extend the time within which a petition for judicial 
review may be filed and shall not postpone the effectiveness of such 
rule or action. This action may not be challenged later in proceedings 
to enforce its requirements. (see CAA section 307(b)(2), 42 U.S.C. 
7607(b)(2)).
    The EPA is publishing this action without prior proposal because 
the Agency views this as a noncontroversial amendment and anticipates 
no adverse comments. This action will be effective on December 12, 1994 
unless adverse comments are received by November 14, 1994. If the EPA 
receives adverse comments, the direct final rule will be withdrawn and 
all public comments received will be addressed in a subsequent final 
rule based on the proposed rule (please see the proposed rule 
published, simultaneously, in the proposal section of this Federal 
Register).
    Under the Regulatory Flexibility Act, 5 U.S.C. 600 et seq., EPA 
must prepare a regulatory flexibility analysis assessing the impact of 
any proposed or final rule on small entities. 5 U.S.C 603 and 604. 
Alternatively, EPA may certify that the rule will not have a 
significant economic impact on a substantial number of small entities. 
Small entities include small businesses, small not-for-profit 
enterprises, and government entities with jurisdiction over populations 
of less than 50,000.
    Conditional approvals of SIP submittals under section 110 and 
subchapter I, part D of the CAA do not create any new requirements, but 
simply approve requirements that the State is already imposing. 
Therefore, because the Federal SIP-approval does not impose any new 
requirements, EPA certifies that it does not have a significant impact 
on small entities affected. Moreover, due to the nature of the Federal-
State relationship under the CAA, preparation of a regulatory 
flexibility analysis would constitute Federal inquiry into the economic 
reasonableness of State action. The CAA forbids EPA to base its actions 
concerning SIPs on such grounds. Union Electric Co. v. U.S. E.P.A. , 
427 U.S. 246, 256-66 (S.Ct. 1976); 42 U.S.C. 7410(a)(2).
    If the conditional approval is converted to a disapproval under 
section 110(k), based on the State's failure to meet the commitment, it 
will not affect any existing State requirements applicable to small 
entities. Federal disapproval of the State submittal does not affect 
its State-enforceability. Moreover, EPA's disapproval of the submittal 
does not impose a new Federal requirement. Therefore, EPA certifies 
that this disapproval action does not have a significant impact on a 
substantial number of small entities because it does not remove 
existing State requirements nor does it substitute a new Federal 
requirement.
    Nothing in this action should be construed as permitting or 
allowing or establishing a precedent for any future request for 
revision to any State implementation plan. Each request for revision to 
the State implementation plan shall be considered separately in light 
of specific technical, economic and environmental factors and in 
relation to relevant statutory and regulatory requirements.

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental relations, Particulate matter, Reporting 
and recordkeeping requirements.

    Note: Incorporation by reference of the Implementation Plan for 
the State of Washington was approved by the Director of the Office 
of Federal Register on July 1, 1982.

    Dated: September 20, 1994.
Gerald A. Emison,
Acting Regional Administrator.

    Part 52, chapter I, title 40 of the Code of Federal Regulations is 
amended as follows:

PART 52--[AMENDED]

    1. The authority citation for part 52 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

Subpart WW--Washington

    2. Section 52.2470 is amended by adding paragraph (c)(48) to read 
as follows:


Sec. 52.2470  Identification of plan.

* * * * *
    (c) * * *
    (48) On November 15, 1991, the Director of WDOE submitted to EPA a 
PM-10 nonattainment area SIP revision for the purpose of bringing about 
attainment of the National ambient air quality standards (NAAQS) for 
particulate matter with an aerodynamic diameter less than or equal to a 
nominal 10 micrometers (PM-10). The implementation plan was submitted 
by the State to satisfy certain Federal Clean Air Act requirements for 
an approvable moderate nonattainment area PM-10 SIP for Tacoma, 
Washington.
    (i) Incorporation by reference.
    (A) Letters dated November 13, 1991 and June 30, 1994 from WDOE to 
EPA submitting revisions to the State of Washington SIP.
    (B) State Implementation Plan for Particulate Matter in the Tacoma 
Tideflats, Pierce County, including appendices A-F, dated November 
1991, and adopted November 14, 1991.
[FR Doc. 94-25204 Filed 10-11-94; 8:45 am]
BILLING CODE 6560-50-F