The U.S. Environmental Protection Agency proposed approval of Arizona’s State Implementation Plan (SIP) on Jan. 15, 2014. Maricopa County is closer than ever to meeting the federal government’s air quality standards for course dust particles, known as PM-10 (particulate matter 10 microns in diameter or less).
The EPA will begin a 30-day comment period in a few weeks, after it has officially posted the proposal to the Federal Register.
The SIP, technically referred to as the 2012 Five Percent Plan for the Maricopa County Nonattainment Area, aims to reduce the inventory of PM-10 in Maricopa County by 5 percent per year, until the attainment year of 2012. The plan, which included more than 50 dust control measures, such as forecasting for high dust generation days, sharing best management practices across key industries, paving dirt roads, restricting wood burning and managing off-road vehicle use, led to a greater than 16 percent reduction in course dust particles (10,000 tons of PM-10) in Maricopa County since the end of 2007.
The DEQ uses 19 monitoring sites throughout Maricopa County, also referred to as Area A, to measure the concentration of PM-10 in the air. When the monitors register a concentration higher than allowable federal standards, the county receives an exceedance. Vital to the success of Arizona’s SIP was convincing the EPA to exclude exceedances on those days when a natural event occurred, such as a dust storm like a haboob or a wildfire, when dust control mitigation efforts are ineffective.
In 2004, the Arizona DEQ began flagging these exceptional events. After reviewing 133 days when air quality standards were exceeded, the EPA agreed to reclassify 131 of them as exceptional events and excluded them from Arizona’s attainment record. This is the first time the EPA has approved this type of exception under its new Exceptional Event policy.
In addition to health-related problems that accompany days when the PM-10 standards are exceeded, Arizona risked losing federal transportation funding if it did not develop and implement a plan to significantly improve air quality in Maricopa County. Pinal County has recently started working on a similar plan to address air quality issues there.
The efforts of all the state lawmakers were lauded by Speaker of the House Andy Tobin for their role in developing the plan, especially former Representative Amanda Reeve, who served as Chair of the Environment Committee.