Federal Register: RULES Air quality implementation plans; approval and promulgation; various States; air quality planning purposes; designation of areas: [40 CFR Parts 52 and 81]

ENVIRONMENTAL PROTECTION AGENCY

Environmental Protection Agency

CFR Citation: 40 CFR Parts 52 and 81

EPA ID: [EPA-R09-OAR-2006-0041; FRL-8045-1]

NOTICE: RULES

ACTION: Air quality implementation plans; approval and promulgation; various States; air quality planning purposes; designation of areas:

DOCUMENT ACTION: Direct final rule.

SUBJECT CATEGORY: Approval and Promulgation of Implementation Plans; Designation of Areas for Air Quality Planning Purposes; State of Arizona; Particulate Matter of 10 Microns or Less; Finding of Attainment for Yuma Nonattainment Area; Determination Regarding Applicability of Certain Clean Air Act Requirements

DATES: This rule is effective on May 15, 2006, without further notice, unless EPA receives adverse comments by April 13, 2006. If adverse comment is received, EPA will publish a timely withdrawal of the direct final rule in the Federal Register informing the public that the rule will not take effect.

DOCUMENT SUMMARY: EPA is taking direct final action under the Clean Air Act to determine that the Yuma nonattainment area in Arizona has attained the National Ambient Air Quality Standards (NAAQS) for particulate matter with an aerodynamic diameter less than or equal to a nominal 10 micrometers (PM10). This determination is based upon monitored air quality data for the PM10 NAAQS during the years 19982000. EPA also finds that the Yuma area is currently in attainment of the PM10 NAAQS, and based on this finding, EPA is determining that certain Clean Air Act requirements are not applicable for so long as the Yuma area continues to attain the PM10 NAAQS.

SUMMARY: Arizona,

SUPPLEMENTAL INFORMATION

Throughout this document, wherever ``we,'' ``us,'' or ``our'' are used, we mean the Environmental Protection Agency (EPA).
Table of Contents
I. Background
A. What National Ambient Air Quality Standards (NAAQS) Are Considered in Today's Finding?
B. What Is the Designation and Classification of This
PM10 Nonattainment Area?
C. How Do We Make Attainment Determinations?
II. What Is the Basis for EPA's Determination That the Yuma Nonattainment Area Has Attained the PM10 NAAQS?
III. What Are the Applicable Planning Requirements for the Yuma Nonattainment Area As a Result of EPA's Attainment Determination? IV. EPA's Final Action
V. Statutory and Executive Order Reviews
I. Background
A. What National Ambient Air Quality Standards (NAAQS) Are Considered in Today's Finding?

Particulate matter with an aerodynamic diameter of less than or equal to 10 micrometers (PM10) is the subject of this action. The NAAQS are limits for certain ambient air pollutants set by EPA to protect public health and welfare. PM10 is among the ambient air
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pollutants for which EPA has established a healthbased standard.

PM10 causes adverse health effects by penetrating deep into the lungs, aggravating the cardiopulmonary system. Children, the elderly, and people with asthma and heart conditions are the most vulnerable.

On July 1, 1987 (52 FR 24634), EPA revised the NAAQS for particulate matter with an indicator that includes only those particles with an aerodynamic diameter less than or equal to a nominal 10 micrometers. See 40 CFR 50.6. The 24hour primary PM10 standard is 150 micrograms per cubic meter [mu]g/m\3\ with no more than one expected exceedance per year. The annual primary PM10 standard is 50 [mu]g/m\3\ as an annual arithmetic mean. The secondary PM10 standards, promulgated to protect against adverse welfare effects, are identical to the primary standards.
B. What Is the Designation and Classification of This PM10 Nonattainment Area?

Upon enactment of the 1990 Clean Air Act Amendments (CAA or ``Act''), PM10 areas meeting the requirements of either (i) or (ii) of section 107(d)(4)(B) of the Act were designated nonattainment for PM10 by operation of law and classified ``moderate.'' These areas included all former Group I PM10 planning areas identified in 52 FR 29383 (August 7, 1987) and further clarified in 55 FR 45799 (October 31, 1990), and any other areas violating the NAAQS for PM10 prior to January 1, 1989 (many of these areas were identified by footnote 4 in the October 31, 1990 Federal Register document). A Federal Register notice announcing the areas designated nonattainment for PM10 upon enactment of the 1990 Act Amendments, known as ``initial'' PM10 nonattainment areas, was published on March 15, 1991 (56 FR 11101). A subsequent Federal Register document correcting some of these areas was published on August 8, 1991 (56 FR 37654). These nonattainment designations and moderate area classifications were codified in 40 CFR part 81 in a Federal Register document published on November 6, 1991 (56 FR 56694). All other areas in the nation not designated nonattainment at enactment were designated unclassifiable (see section 107(d)(4)(B)(iii) of the Act).

The Yuma planning area was listed by EPA as a Group I area (see 52 FR 29383, August 7, 1987) and was designated nonattainment for PM10 by operation of law and classified ``moderate.'' In accordance with section 189(a)(2) of the CAA, Arizona was to submit a state implementation plan (SIP) by November 15, 1991 demonstrating attainment of the PM10 standards by December 31, 1994 for the Yuma area.\1\
\1\ Arizona submitted a moderate area plan for the Yuma area on November 14, 1991; EPA found this plan to be incomplete on May 14, 1992. Arizona submitted a revised plan for Yuma on July 12, 1994. EPA found the revised plan to be complete but has not taken action on it.

C. How Do We Make Attainment Determinations?

Pursuant to sections 179(c)(1) and 188(b)(2) of the Act, we have the responsibility of determining within six months of the applicable attainment date whether, based on air quality data, PM10 nonattainment areas attained the NAAQS by that date. The ``applicable attainment date'' is December 31, 1994 for areas, such as Yuma, that were designated as ``moderate'' nonattainment for PM10 by operation of law under the 1990 Amended Act. Determinations under section 179(c)(1) of the Act are to be based upon an area's ``air quality as of the attainment date.'' Section 188(b)(2) is consistent with this requirement.

Generally, we will determine whether an area's air quality meets the PM10 NAAQS for purposes of section 179(c)(1) and 188(b)(2) based upon data gathered at established state and local air monitoring stations (SLAMS) and national air monitoring stations (NAMS) in the nonattainment area and entered into the EPA's Air Quality System (AQS) database. Data entered into the AQS has been determined to meet federal monitoring requirements (see 40 CFR 50.6; 40 CFR part 50, appendix J; 40 CFR part 53; 40 CFR part 58, appendices A and B) and may be used to determine the attainment status of areas. We will also consider air quality data from other air monitoring stations in the nonattainment area provided that the stations meet the federal monitoring requirements for SLAMS. All data are reviewed to determine the area's air quality status in accordance with our guidance at 40 CFR part 50, Appendix K.

Attainment of the annual PM10 standard is achieved when the annual arithmetic mean PM10 concentration over a three year period is equal to or less than 50 [mu]g/m\3\. Attainment of the 24hour standard is determined by calculating the expected number of days in a year with PM10 concentrations greater than 150 [mu]g/m\3\. The 24hour standard is attained when the expected number of days per year with levels above 150 [mu]g/m\3\ (averaged over a threeyear period) is less than or equal to one. Three consecutive years of air quality data are necessary to show attainment of the 24 hour and annual standards for PM10. See 40 CFR part 50 and appendix K. A complete year of air quality data, as referred to in 40 CFR part 50 Appendix K, includes all 4 calendar quarters with each quarter containing data from at least 75 percent of the scheduled sampling days.\2\
\2\ However, as explained in more detail in the following section of this notice, EPA guidelines allow for data substitution only under circumstances where data capture is at least 50 percent but less than 75 percent.
II. What Is the Basis for EPA's Determination That the Yuma Nonattainment Area Has Attained the PM10 NAAQS?

The Yuma PM10 nonattainment area is located in the lower Colorado River Valley in the southwestern portion of Yuma County. The PM10 nonattainment area consists of 456 square miles, which is roughly eight percent of the land area of Yuma County (5,500 square miles). Yuma County is located in the southwestern portion of Arizona that borders California and Mexico. The cities of Yuma and Somerton are the largest population centers in the Yuma PM10 nonattainment area. The city of Yuma, the county seat, is located below the convergence of the Gila and Colorado Rivers on the far western side of the PM10 nonattainment area. The city of Somerton is located in the southwestern portion of the PM10 nonattainment area. Agriculture is the primary industry in Yuma County. The Arizona Department of Economic Security predicts that Yuma County's population is expected to increase by 37.5 percent from 138,025 in 2000 to 189,783 in 2015.\3\ Approximately onehalf of the county's year round population resides in the city of Yuma. During the winter, Yuma County's population increases significantly due to seasonal residents. \3\ Arizona Department of Economic Security, 2006.

The Yuma PM10 nonattainment area has one SLAMS monitor operated by the Arizona Department of Environmental Quality (ADEQ). This monitor was located at the Yuma County Juvenile Center in the city of Yuma from 1988 until the second quarter of 2002, after which time it was relocated to the nearby Yuma County Courthouse, which is also located in the city of Yuma. ADEQ measures ambient (24houraverage) PM10 concentrations in Yuma at a frequency of once every six days.

Table 1 summarizes the PM10 data collected in Yuma from 19922005 and reported by ADEQ to the AQS database. Table 1 also indicates which years had
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four complete quarters of data (including any allowable data substitution \4\), making the data from that year eligible for use in determining whether the area has attained the PM10 NAAQS, if that year is followed by two consecutive years also with four complete quarters of data. As shown in Table 1, no exceedances of the 24hour PM10 NAAQS of 150 [mu]g/m\3\ were measured in Yuma during the 19921994 period and the annualaverage PM10
concentrations measured during that period were well below the corresponding standard of 50 Fg/m\3\. However, even with allowable data substitution, the data capture for Yuma was not sufficient for the 19921994 period to allow us to make a finding of attainment for the applicable attainment date of December 31, 1994.
\4\ The regulatory requirement for data capture in 40 CFR part 50, Appendix K, is 75 percent on a quarterly basis. According to the ``Guideline on Exceptions to Data Requirements for Determining Attainment of Particulate Matter Standards'' (see EPA document 450/ 487005, April 1987), when data capture is at least 50 percent but less than 75 percent, data may be substituted for the missing data. Per the abovereferenced guideline, monitoring data from the same quarter in any one of the years used to determine attainment may be substituted for missing PM10 data. The maximum
PM10 value that was observed in that quarter over the last three years is substituted for missing scheduled sampling days. Table 1.Summary of 24 Hour and Annual PM10 Concentrations ([mu]g/m\3\) for Yuma, 19922005 \1\ Year
1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Highest 24houraverage.............................. 62 65 66 75 103 108 112 100 132 \2\ 125 127 114 86 150 Annual average....................................... 29.0 33.9 37.3 41.5 52.1 42.4 39.7 36.7 \3\ 41.2 51.8 38.1 45.0 30.8 54.3 Four complete quarters?.............................. Yes Yes No Yes Yes No Yes Yes Yes No Yes Yes Yes \4\ NA \1\ The data summary in Table 1 includes substituted data and was analyzed according to the ``Guideline on Exceptions to Data Requirements for Determining Attainment of Particulate Matter Standards.'' See footnote 4. The fourth quarter in 1994, the second quarter in 1997, and the first and fourth quarters in 2001 were not eligible for data substitution. The incomplete data from these quarters was included in the calculation of the annual average for each of these years.
\2\ The highest measured 24houraverage concentration in 2001 was 150 [mu]g/m\3\, which is equal to the 24hour PM10 NAAQS, but which is not considered an ``exceedance.'' Under EPA regulations, an exceedance of the 24houraverage standard represents concentrations of 155 [mu]g/m\3\ or greater. See 40 CFR 50, appendix K.
\3\ Data substitution results in a conservative estimate of the annual average. See footnote 4. For example, the annual average for 2000 of 54.3 [mu]g/ m\3\ would be reduced to 42.3 [mu]g/m\3\ if data substition was not used. The method of data substitution was used to calculate annual averages for 19931997, 20002002, and 2004.
\4\ We have received AQS data from ADEQ through September 30, 2005. States are required to report data to AQS on a rolling basis and have until 90 days from the end of a given quarter to submit qualityassured monitoring data into AQS. See 40 CFR 58.28.

FOR FURTHER INFORMATION CONTACT Rebecca Rosen, EPA Region IX, (415) 9474152, rosen.rebecca@epa.gov.