Division of Air Quality Monitoring and Quality Assurance

Laurel Air Quality Monitoring Site

Monitoring Siting Criteria for the Laurel Air Quality Monitoring Site

Introduction

The Code of Federal Regulation Title 40 Part 58 covers Ambient Air Quality Surveillance. Appendix E to Part 58—Probe and Monitoring Path Siting Criteria for Ambient Air Quality Monitoring contains specific location criteria applicable to State and Local air Monitoring Stations (SLAMS) ambient air quality monitoring probes and inlets. These siting criteria are necessary to ensure the uniform collection of compatible and comparable air quality data. The probe siting criteria discussed in Appendix E must be followed to the greatest extent possible, although there may be situations where some deviation from the siting criteria may be necessary. Specific siting criteria that are phrased with a "must" are defined as requirements and exceptions must be approved through the waiver provisions. However, siting criteria that are phrased with a “should” are defined as goals to meet for consistency but are not requirements.

The Laurel site, located at the corner of Laurel Street and East Tudor Road in Anchorage, is a particulate matter (PM) monitoring site. Monitoring objectives for Laurel are gathering data on highest concentrations of PM₁₀ pollutants expected in an area and impact of significant sources (i.e., road dust). The site consists of one continuous PM₁₀ Met One Beta Attenuation Monitor (BAM). Laurel is a Special Purpose Monitoring (SPM) site.

Placement and Spacing

The table below has siting criteria as outlined in 40 CFR 58, Appendix E. The criteria were reduced to show only relevant criteria for the site.

Particulate Matter (PM2.5 & PM10)

Applicable Section	Siting Criteria	Observed
Horizontal and Vertical Placement	2-15 meters above ground level for neighborhood or larger spatial scale, 2-7 meters for microscale spatial scale sites and middle spatial scale PM10-2.5 sites. 1 meter vertically or horizontally away from any supporting structure, walls, etc., and away from dusty or dirty areas. If located near the side of a building or wall, then locate on the windward side relative to the prevailing wind direction during the season of highest concentration potential.	Criteria Met. 6.4 meters.
Spacing from Minor Sources	For neighborhood or larger spatial scales avoid placing the monitor near local, minor sources. The source plume should not be allowed to inappropriately impact the air quality data collected at a site. Particulate matter sites should not be located in an unpaved area unless there is vegetative ground cover year-round.	Criteria Met. Maximum impact site, winter graveled streets.
Spacing from Obstructions (a)	To avoid scavenging, the inlet must have unrestricted airflow and be located away from obstacles. The separation distance must be at least twice the height that the obstacle protrudes above the probe inlet.	Criteria Met.
Spacing from Obstructions (b)	The inlet must have unrestricted airflow in an arc of at least 180 degrees. This arc must include the predominant wind direction for the season of greatest pollutant concentration potential. For particle sampling, a minimum of 2 meters of separation from walls, parapets, and structures is required for rooftop site placement.	Criteria Met.
Spacing from Trees (a)	To reduce possible interference the inlet must be at least 10 meters or further from the drip line of trees.	Criteria Met.
Spacing from Trees (b)	No trees should be between source and probe inlet for microscale sites.	Criteria Met.
Spacing from Roadways	Spacing from roadways is dependent on the spatial scale and average daily traffic count. See 40 CFR 58 Appendix E Section 6.3(b) and Figure E-1 for specific requirements.	Criteria Met. 11 meters to Tudor Road.