The Environmental Protection Agency proposed on Oct. 19 to approve Pinal County, Arizona’s construction-site dust rules into the state’s federally enforceable air plan. The rules already apply locally. Pinal County’s air district adopted them Jan. 25, 2023, and Arizona sent them to EPA that February. Comments on the Federal Register proposal close Nov. 18.
The rules cover the West Pinal County PM10 nonattainment area, about 1,325 square miles between Phoenix and Tucson that takes in all or part of Apache Junction, Casa Grande, Coolidge, Eloy, Florence, Queen Creek and Maricopa. EPA bumped the area from Moderate to Serious nonattainment in June 2020 after it missed its 2018 attainment date.
What the Pinal County dust permit requires
Article 3 of the county code is the construction piece. Any dust-generating operation that disturbs 0.10 acre (4,356 square feet) or more needs a dust permit, and the application has to include a dust control plan covering measures before, during and after the work. Permitted sites must hold dust to 20% opacity on the property and keep visible emissions from crossing the property line. Post a sign telling the public how to file a dust complaint on projects of 5 acres or more. Complete district dust control training once every three years. Put up no-trespassing signs when activity stops for 30 days or longer. On a high dust risk forecast day, either keep meeting the standards or stop dust-generating work and stabilize disturbed areas for the day.
The paperwork is daily. Permitted sites keep self-inspection records for each day of dust work, covering crusted or damp soil, trackout and cleanup, water used for dust control and suppressant applications. Records stay for two years, or five at a facility with a Title V operating permit. Smaller sites skip the signs and training but still have to meet the same opacity and stabilization standards and keep records of what they applied and when.
The package also drops an old high-wind exemption, section 4-3-190. EPA says the county moved those conditions into other parts of Article 3 rather than deleting them.
Why federal enforceability matters for contractors
Once rules are in an approved state implementation plan, they’re enforceable by EPA and through citizen suits under the Clean Air Act, not only by the county. A contractor’s dust log becomes evidence in more than one forum.
The lag cuts both ways. In a companion proposal on the area’s attainment plan, EPA said preliminary monitoring data suggest the control strategy may not have cut emissions as much as modeled, and it acknowledged that its own delays in adding the submitted rules to the plan have delayed their federal enforceability and possibly the rate of compliance. That proposal would set an attainment date of Dec. 31, 2026.
Construction’s share of the PM10 problem
Construction isn’t the main source here. The 2017 inventory puts it at 2.7% of annual PM10, behind unpaved private roads at 31.5%, agricultural roads at 24.7% and public unpaved roads at 16.2%. But construction sites are the easiest sources to see and the easiest to inspect, and Pinal’s growth corridor keeps adding them.
EPA has been working through a backlog of state program actions this month, from Colorado’s Class VI permits to the WOTUS rewrite. For site contractors in Casa Grande or Queen Creek, this one changes less on day one than it does on the day someone files a complaint.