sr 77/oracle road multimodal corridor profile study final report - Pima ...

vehicle miles traveled (VMT). On April 25 2000, EPA approved Arizona’s request to reclassify
the Tucson region as in compliance with the national standard for CO pollution. To ensure that
future violations of the CO standard do not occur, the Pima Association of Governments
developed and submitted to EPA a Limited Maintenance Plan (LMP). EPA approved the LMP,
effective July 10, 2000. The Tucson CO maintenance area incorporates the Tucson metropolitan
region as far north as the Pima County line, and includes the SR 77 Corridor within Pima
County.
One of the requirements of the LMP is that PAG use microscale air quality monitoring of the top
three highest volume intersections and the top three highest congested intersections in the PAG
region. The intersection of Ina Road and Oracle Road, which is the highest volume intersection
along SR 77, was ranked #2 in the PAG region by volume in 1999. The microscale model
resulted in an eight-hour CO average concentration of 5.4 ppm. The intersection was modeled
again in 2001, resulting in an eight-hour CO average of 5.8 ppm. These results are well below
the NAAQS for CO of 9 ppm for an eight-hour average. The role of PDEQ in the LMP is to
monitor air quality in the region and announce when CO levels exceed 85 percent of the eighthour
standard.
4.10.2 Ozone
Ground-level ozone concentrations have remained relatively steady, according to PDEQ, with
2001 summertime measurements approaching but not exceeding the NAAQS. When two or
more of the monitoring sites exceed 0.0084 ppm for the one-hour average, the American Lung
Association issues an ozone advisory to the public. There were no advisories issued in 2001.
(The year 2001 is the most recent year for which annual air quality data have been summarized.)
4.10.3 Particulate Matter
PM 10 refers to particulate matter with an aerodynamic diameter of 10 microns or less, while
PM 2.5 refers to particulate matter with an aerodynamic diameter of 2.5 microns or less. In 1999,
Pima County violated the PM 10 Standard set by the EPA. After this violation, which included
four exceedences of the NAAQS, PDEQ provided technical documentation that showed the
exceedences to be the result of natural events. A Natural Events Action Plan (NEAP) was
submitted to ADEQ and EPA in June 2001. The NEAP boundary incorporates eastern Pima
County, and contains the SR 77 Corridor within Pima County. The plan allows Pima County to
remain in attainment for PM 10 , following the Best Available Control Measures outlined in the
NEAP in an effort to protect public health and welfare on days with high ambient levels of PM 10 .
The highest reading in 2001 was 149 ug/m 3 , which was recorded at the monitoring site located at
2498 North Geronimo Avenue (within the SR 77 Corridor).
PM 2.5 has been linked to health problems including respiratory and heart conditions, and can also
contribute to poor visibility and urban haze. There have been no exceedences of that NAAQS
for PM 2.5 .
4.10.4 Nitrogen Dioxide and Sulfur Dioxide
The portion of the corridor within Pima County is in attainment for both nitrogen dioxide (NO 2 )
and sulfur dioxide (SO 2 ). NO 2 averages about 34 percent of the standard and SO 2 averages
SR 77/Oracle Road Multimodal Corridor Profile Study May 2007
Final Report Page 4-15