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SR 510 Yelm Loop Phase 2 Improvement Project: Supplemental Environmental Assessment and Online Public Meeting – Air quality and water resources

Air quality

The Build Alternative would have no significant adverse effects associated with air quality. The Yelm area of Thurston County complies with standards for CO, HC, NOx, O3, PM2.5 and PM10; no analysis is required for these pollutants.

The primary air quality pollutants in the study area are Mobile Source Air Toxics (MSATs). Because the estimated vehicle miles traveled (VMT) represent only a small increase over the No Build Alternative, it is expected there would be no appreciable difference in overall MSAT emissions. 

The Build Alternative is also expected to help reduce greenhouse gas emissions by reducing stop-and-go traffic, creating more consistent speeds, improving traffic flow, and providing for enhanced bicycle and pedestrian connectivity. Potential temporary localized air quality impacts could be experienced related to dust and construction emissions.

For more information

To read more about the study approach, existing conditions, and effects on air quality, please see Section 3.3 Air Quality (PDF 218KB).

Water resources

Construction of the Build Alternative could have a temporary effect on surface and groundwater resources. Once constructed, there would be an increase in runoff from the addition of paved surfaces. Runoff from new pavement would be infiltrated or similarly managed for quantity control. There would be no encroachment into the floodplain areas near Yelm Creek. Increased stormwater treatment of runoff, where currently there is none, would provide some benefit to nearby surface water bodies and groundwater resources in the Build Alternative corridor.

A Temporary Erosion and Sediment Control (TESC) Plan and a Spill Prevention, Control, and Countermeasures (SPCC) Plan would be implemented and BMPs would be used to protect surface water and groundwater resources.

For more information

To read more about the study approach, existing conditions, and effects on water resources, please see Section 3.5 Water Resources (PDF 1.3MB)​.