There are a number of circumstances that are unique to the Antelope and Coachella valleys which make it difficult to develop a local control strategy that satisfies CAA requirements. For example, with little in the way of local emissions, and with the significant growth projected for both desert areas it is difficult to satisfy the reasonable further progress requirements of the CAA. There is strong evidence that pollutant transport from the South Coast Air Basin to the Antelope and Coachella valleys is the primary cause of the ozone nonattainment status of both areas. As a result, the District believes that aggressive control of the South Coast Air Basin emissions is an effective strategy to substantially improve air quality in the Antelope and Coachella valleys. Each of these issues is addressed in further detail below.

Regulatory Requirements

State Implementation Plan requirements under Title I of the CAA depend on the severity of the nonattainment problem. For the Antelope Valley and the Coachella Valley, the CAA requirements for moderate through severe areas must be addressed. Thus, the areas are subject to the reasonable further progress requirements of the CAA, as discussed in Chapter 6 for the South Coast Air Basin; these requirements are intended to ensure that each ozone nonattainment area provide for sufficient VOC emission reductions to attain the ozone national ambient air quality standard. These requirements are more difficult to meet for areas with low existing emissions and significant population growth, since the VOC reductions are relative to the 1990 emissions and activity levels. For example, the CAA requires three percent VOC emission reductions beginning in 1997. If an area experiences population growth such that VOC emissions increase by 15 percent over 1990 levels, then the area must develop regulations that achieve VOC reductions of at least 18 percent (i.e., the 3 percent rate-of-progress requirement plus the 15 percent increase from population growth). The expected population growth for the Antelope and Coachella valleys is significant; thus the rate-of-progress requirements of the CAA cannot be met for either area unless further local controls are implemented.

The CAA also requires that "severe-17" ozone nonattainment areas, such as the Antelope and Coachella valleys, demonstrate attainment of the federal ozone air quality standard by November 15, 2007 using a U.S. EPA-recommended photochemical grid model and EPA-approved modeling techniques. The South Coast Air Basin modeling domain, as shown in Figure 8-1, was expanded to include the Antelope Valley and Coachella Valley so that this CAA requirement could be addressed. It is clear from available data that federal ozone standard exceedances in the Antelope and Coachella valleys largely result from pollutant transport from the upwind South Coast Air Basin. Photochemical grid modeling for the 1994 AQMP, using the U.S. EPA-approved Urban Airshed Model, shows that attainment of the ozone standard is possible with the proposed control strategy described in the 1994 AQMP for the South Coast Air Basin, and control of locally generated emissions via state and federal regulations. This Plan carries forward the 1994 AQMP control approach for the Antelope and Coachella valleys.

Population Growth

Both the Antelope Valley and the Coachella Valley are rapidly growing areas, as shown in Table 8-1. By 2020, the population in the Antelope Valley is expected to nearly triple from 1990 levels and the Coachella Valley population is projected to more than double. It is clearly more challenging to meet the rate-of-progress requirements of the CAA in such rapidly growing areas.

TABLE 8-1

Historical Population and Population Forecasts

        Area              1980          1990        2000        2010        2020     

South Coast Air        ~10,500,000   13,022,000  14,798,000  16,653,000  18,926,000  
Basin                                                                                

Antelope Valley          101,000      235,000                                        
                                                   375,000     532,000     706,000   

Coachella Valley         139,000      267,000                                        
                                                   319,000     389,000     475,000   

Air quality modeling is an integral part of the planning process to achieve clean air. The CAA requires that ozone nonattainment areas designated as serious and above be required to use a photochemical grid model to demonstrate attainment. The photochemical grid model (or air quality simulation model) recommended by the U.S. EPA for ozone analyses is the Urban Airshed Model with the Carbon Bond Mechanism IV chemistry (UAM). UAM is an urban-scale, three-dimensional, grid-type, numerical simulation model. It is designed for computing ozone concentrations under short-term, episodic conditions lasting one to three days. UAM is also the recommended model for ozone analysis by the ARB.

It is desirable to perform ozone air quality analyses using several different meteorological episodes. Chapter 5 describes the meteorological episodes used to project future air quality. Performance evaluations of the four meteorological episodes are discussed in Technical Report V-B of the 1994 AQMP.

Future-year air quality projections in the Antelope and Coachella valleys are presented in detail in Appendix V; the results are summarized in Figure 8-8 for the Antelope Valley and Figure 8-9 for the Coachella Valley. The peak predicted ozone concentrations are shown for the baseline and controlled 2007 simulations for each of the four meteorological episodes modeled. "Baseline" assumes no further control beyond existing rules and regulations and "Control" assumes implementation of the proposed control strategy described in Chapters 4 and 7. As illustrated, the federal ozone standard, shown by a solid horizontal line at 12 pphm in the figures, will be exceeded in one of the four episodes in the Antelope Valley and in two of the four episodes in the Coachella Valley if the AQMP control is not implemented. However, with the implementation of the control strategy, the federal one-hour ozone air quality standard is attained for all four episodes in both the Antelope and Coachella valleys.

The reasonable further progress requirements in the CAA are intended to ensure that each ozone nonattainment area provide for sufficient precursor emission reductions to attain the ozone National Ambient Air Quality Standard. More specifically, Section 182(c)(2) requires that each serious and above ozone nonattainment area achieve actual VOC emission reductions of at least three percent per year averaged over each consecutive 3-year period beginning six years after enactment of the Act until the area's attainment date (i.e., November 15, 2007 for the Antelope and Coachella valleys). This is called the "post-1996 rate-of-progress" requirement of the CAA.

Introduction

The Coachella Valley is currently designated nonattainment for PM10. Unlike the Basin, where PM10 exceedances are due primarily to PM10 precursor pollutants, the Coachella Valley's elevated PM10 levels are strongly tied to local fugitive dust problems. Accordingly, instead of relying on District rulemaking to achieve attainment, previous planning documents have proposed local control to meet the area's air quality objectives. This approach allows local Coachella Valley governments, industry, and citizens to take an active part in improving the Valley's air quality. As a result of this approach, various local dust control programs and two District "backstop" rules have been developed. These programs have resulted in significant improvements in the Valley's air quality.

Background

Under the 1990 federal Clean Air Act (CAA), the Coachella Valley was originally designated as a "moderate" PM10 nonattainment area. In response to CAA requirements for "moderate" areas, the District developed the "State Implementation Plan for PM10 in the Coachella Valley" (90-CVSIP) which was adopted by the Governing Board in November 1990. The 90-CVSIP proposed implementation of reasonably available control measures (RACM) for fugitive dust sources no later than December 10, 1993. Modeling contained in the 90-CVSIP demonstrated attainment of the national ambient air quality standards (NAAQS) for PM10 would occur by December 31, 1995, one year after the statutory limit for moderate nonattainment areas.

The CAA specifies that any area which cannot attain the standards by December 1994 would subsequently be reclassified as a "serious" nonattainment area. In January 1993, the U.S. EPA completed its initial redesignation process, and included the Coachella Valley among five nationwide areas redesignated as "serious," effective February 8, 1993. The CAA further specifies that a SIP revision is due within 18 months of the redesignation date (i.e., August 8, 1994) and that a demonstration of attainment must be submitted within four years of the redesignation date (i.e., February 8, 1997). Among other requirements, the "serious" area SIP must ensure the implementation of "best available control measures" (BACM). The District prepared and later adopted the 1994 Coachella Valley PM10 SIP revision (94-CVSIP) in July of 1994.

1997 PM10 Maintenance Plan

Under the CAA, an area can be redesignated as attainment if, among other requirements, the U.S. EPA determines that the NAAQS have been attained. Section 175A of the CAA states that any district that submits a request under Section 107(d) for redesignation of a nonattainment area to attainment must submit a revision of the applicable SIP that demonstrates attainment for at least 10 years after the redesignation. U.S. EPA guidance states that a determination of compliance with the NAAQS must be based on three complete, consecutive calendar years of quality-assured air quality monitoring data. Air quality is monitored at two locations in the Coachella Valley and results indicate that there were no PM10 exceedances in 1993 or 1994. In 1995, the 24-hour standard was exceeded once and this led to an exceedance of the annual average standard. This exceedance occurred on a day where the maximum hourly wind gusts exceeded 50 mph for each hour of the day.

The U.S. EPA has recently developed a natural events policy that permits, under certain circumstances, the exclusion of air quality data attributable to uncontrollable natural events (e.g., volcanic activity, wildland fires, and high wind events). With the exclusion of air quality data from the one 24-hour exceedance in 1995, the Coachella Valley has experienced three consecutive years without an exceedance of the PM10 standards and, consequently, would be eligible for redesignation to attainment. Based on the supporting meteorological data regarding the one high wind event in 1995, the District is preparing a maintenance plan for the Coachella Valley. In accordance with U.S. EPA guidance, the major elements of the plan are as follows:

• a demonstration of attainment with the PM10 standards based on the three most recent years of ambient data;
• a maintenance plan, including contingency measures, to ensure continued attainment for the next ten years; and
• a Natural Events Action Plan pursuant to the Natural Events Policy.

The Coachella Valley Maintenance plan will be prepared as a separate document. It will be released for public review and submitted to the U.S. EPA in lieu of the attainment demonstration prior to February 8, 1997.

The Antelope Valley and the Coachella Valley are designated as "severe-17" ozone nonattainment areas and as such must demonstrate reasonable further progress and attainment according to federal Clean Air Act requirements. The District's proposed control strategy includes two components: a strategy for the South Coast Air Basin as described in Chapter 4 and control of locally generated emissions in the Antelope Valley and Coachella Valley via regulations at the state and federal level. Photochemical grid modeling, using a U.S. EPA-approved model and methodologies, demonstrates that the federal one-hour ozone standard will be met by November 15, 2007 for the Coachella Valley as required by the CAA. However, the federal ozone air quality standard will be met in the Antelope Valley by 2010. For PM10, the Antelope Valley is an unclassified area with no current planning requirements; for the Coachella Valley, a PM10 maintenance plan will be submitted with a request to U.S. EPA for redesignation to attainment status.