Sacramento Metropolitan Air Quality Management District

The Sacramento Metropolitan Air Quality Management District covers Sacramento County. Its Guide to Air Quality Assessment in Sacramento County, first issued December 2009, is maintained chapter by chapter, and its thresholds live on a one-page SMAQMD Thresholds of Significance Table whose current revision is April 2020. The thresholds are adopted by Board resolution, so each block on the table carries its own adoption date.

Mass emission thresholds, all projects subject to CEQA

Pollutant	Construction	Operational
NOx	85 lb/day	65 lb/day
ROG (VOC)	None	65 lb/day
PM10	Zero, unless all feasible BACT and best management practices are applied, then 80 lb/day and 14.6 tons/yr	Same
PM2.5	Zero, unless all feasible BACT and best management practices are applied, then 82 lb/day and 15 tons/yr	Same

There is no mass threshold for SOx or CO. The criteria pollutant thresholds were adopted March 28, 2002 (Resolution AQMD2002018). The PM10 and PM2.5 mass thresholds replaced earlier concentration-based PM thresholds on May 28, 2015 (Resolution AQMD2015-022).

The PM rule is the distinctive feature. Any construction PM emission is significant unless the project commits to the district's Basic Construction Emission Control Practices, at which point the 80 and 82 lb/day values apply. Lead agencies attach the practices as conditions of approval or through the mitigation monitoring program.

Concentration thresholds, both phases

A project is significant if it causes an exceedance of a California ambient air quality standard or contributes substantially to one, where a substantial contribution is 5 percent or more of the standard. The table lists the standards it applies: CO 20 ppm for 1 hour and 9 ppm for 8 hours; NO2 0.18 ppm for 1 hour and 0.03 ppm annual; SO2 0.25 ppm for 1 hour and 0.04 ppm for 24 hours; lead 1.5 micrograms per cubic meter over 30 days; sulfates 25 micrograms per cubic meter over 24 hours; hydrogen sulfide 0.03 ppm for 1 hour; vinyl chloride 0.01 ppm for 24 hours; and the visibility standard. Revisions to the state standards become revisions to these thresholds automatically.

The basic construction practices

The district's Basic Construction Emission Control Practices sheet (revised July 2019) lists the dust practices that unlock the non-zero PM thresholds: water exposed surfaces twice daily; cover or keep two feet of freeboard on haul trucks, covered on freeways and major roads; wet power vacuum sweep visible trackout at least daily, no dry sweeping; limit unpaved road speeds to 15 mph; pave roads, driveways, sidewalks, and parking lots as soon as possible and lay building pads promptly after grading. The sheet adds exhaust practices: limit idling to five minutes with signage, carry current CARB off-road fleet compliance certificates, and maintain equipment to manufacturer specifications. Rule 403 makes dust control a legal requirement independent of CEQA.

Greenhouse gas thresholds, land development and construction

Phase	Threshold
Construction, all project types	1,100 metric tons CO2e per year
Operations	Consistency with the Climate Change Scoping Plan through best management practices, or equivalent on-site or off-site mitigation

Operational consistency is a two tier test, adopted April 23, 2020 (Resolution 2020-009):

• Tier 1, every project. BMP 1: designed and constructed without natural gas infrastructure. BMP 2: current CALGreen Tier 2, except every EV capable space is built EV ready.
• Tier 2, projects still above 1,100 metric tons per year after tier 1. BMP 3: residential projects cut vehicle miles traveled per resident 15 percent below the county average; office projects cut VMT per worker 15 percent; retail projects show no net increase in total VMT, consistent with SB 743. A project meeting the Office of Planning and Research's SB 743 de minimis criteria documents that instead.

Projects that skip tier 1 quantify the excess and provide equivalent mitigation. Projects that cannot meet tier 2 add further VMT measures. The district's operational screening table is calibrated to the 1,100 ton level. The GHG thresholds were first adopted October 23, 2014 (Resolution AQMD2014-028) and the land development threshold updated with the practices above in 2020.

Stationary sources and toxics

Impact	Threshold
Stationary source GHG, construction	1,100 metric tons CO2e per year
Stationary source GHG, operations	10,000 metric tons CO2e per year
Stationary source cancer risk	Incremental increase greater than 10 in a million at any off-site receptor
Stationary source hazard index	Greater than 1 at any off-site receptor

The toxics thresholds come from the district's AB 2588 program. The Board has not set a threshold for mobile or non-permitted sources of toxics, including construction diesel exhaust; Chapter 5 asks lead agencies to treat those case by case, considering equipment, duration, and distance to receptors.

Odor and CO

Odor is decided case by case under Appendix G and the district's Rule 402 nuisance prohibition, using the parameters in Chapter 7. Chapter 4 directs operational analyses through the district's operational screening table and to daily and annual quantification when a project exceeds it.

Where the thresholds are published

Sacramento Metropolitan Air Quality Management District, Guide to Air Quality Assessment in Sacramento County, December 2009 and chapter revisions: SMAQMD Thresholds of Significance Table, revised April 2020; Chapter 2 Environmental Review and Thresholds (April 2020); Chapter 4 Operational Air Quality Impacts; Chapter 5 Toxic Air Contaminants; Chapter 6 Greenhouse Gas Emissions (February 2021); Basic Construction Emission Control Practices (July 2019). Adopting resolutions: AQMD2002018, AQMD2014-028, AQMD2015-022, 2020-009.