On March 19, 2015, the Sacramento Metro Air Quality Management District (SMAQMD) proposed to revise its California Environmental Quality Act (CEQA) thresholds of significance for fine and coarse particulate matter (i.e. PM2.5 and PM10). The proposed CEQA threshold revisions would align with existing SMAQMD new source review (NSR) thresholds and reduce deterioration of ambient air quality and significant environmental impacts.

CEQA Guidelines allow lead agencies to adopt "thresholds of significance" to assist in determining whether a project may have a significant effect on the environment. When environmental impacts are below thresholds of significance, and therefore "less-than-significant," then the Initial Study Checklist would become a Negative Declaration or Mitigated Negative Declaration. CEQA Guidelines requires an Environmental Impact Report (EIR) when environmental impacts exceed established thresholds of significance. SMAQMD adopted the current CEQA thresholds in 2002 and is now in the process of reviewing the thresholds of significance for NO2, SO2, CO, PM10, and PM2.5. As previously stated, SMAQMD is proposing to revise only the PM2.5 and PM10 thresholds at this time. The current SMAQMD particulate matter CEQA thresholds, which are based on the California Ambient Air Quality Standard, are summarized in Table 1.

Table 1. Current SMAQMD Particulate Matter CEQA Thresholds
PollutantProject LevelCumulative
PM2.512 µg/m3 (Annual)None
PM1050 µg/m3 (24-hour)2.5 µg/m3 (24-hour)
20 µg/m3 (Annual)1.0 µg/m3 (Annual)

The proposed particulate matter thresholds will differ depending on whether a project has applied Best Available Control Technology (BACT) or best management practices. For projects that have not, the proposed particulate matter threshold is zero. For projects that have applied BACT or best management practices, the proposed significance thresholds are presented in Table 2. These thresholds have been developed based on the SMAQMD BACT and emission offsets thresholds for particulate matter as defined in SMAQMD Rule 202. Consistent with federal and state emission reduction strategies, thirteen other California air districts have also implemented this approach to significance thresholds.

Table 2. Proposed SMAQMD Particulate Matter CEQA Thresholds

The public comment period on the proposed revisions ends on May 27, 2015. A public hearing will be held to discuss adoption of the proposed particulate matter CEQA thresholds of significance on May 28, 2015. More information can be found here.