A Land Use Tool for AERMOD Urban/Rural Classification John Glass South Carolina – BAQ

EPA 40 CFR Part 51, Appendix W Rural-Urban Classification Section 7.2.3: c. Land Use Procedure: (1) Classify the land use within the total area, Ao, circumscribed by a 3km radius circle about the source using the meteorological land use typing scheme proposed by Auer 73; (2) if land use types I1, I2, C1, R2, and R3 account for 50 percent or more of Ao, use urban dispersion coefficients; otherwise, use appropriate rural dispersion coefficients. d. Population Density Procedure: (1) Compute the average population density, p per square kilometer with Ao as defined above; (2) If p is greater than 750 people/km2, use urban dispersion coefficients; otherwise use appropriate rural dispersion coefficients. e. Of the two methods, the land use procedure is considered more definitive. Basis for urban/rural determination

SC-BAQ before 2008 AQ modeling guidelines (2001): ”With few exceptions, all of SC is considered to be rural. Typically, the areas in the large metropolitan areas of the state (Greenville/Spartanburg, Columbia, and Charleston) will meet one of the … definitions of urban.” ►Limited population-based checking by SC-BAQ for facilities claiming “Urban” near metro “cores”

SC-BAQ starting in 2008 Objective “Urban-Rural” Tool Based on preferred LAND USE method Uses GIS/ArcView “Bridge” from Auer’s scheme to NLCD 2001

Auer vs. NLCD 2001 Auer – “Urban” NLCD 2001 <5 % 0-20 % 24 20-50 % Type Use Vegetation Pervious No. I1 Heavy Industrial <5 % 0-20 % Dvlpd, hi intensity 24 I2 Light Industrial 20-50 % Dvlpd, med intensity 23 C1 Comm. <15 % 50-80 % Dvlpd, low intensity 22 R2 Compact Residential <30 % R3 <35 % Use only NLCD classes 23 & 24 for “Urban.” Roughly equate %pervious to %vegegation.

User’s Basic Steps 1. Open “Land Use” tool in ArcView 2. Enter Lat/Lon of facility 3. Create buffer (circle) at r=3 km 4. Activate % land use algorithm 5. Sum % for NLCD categories 23 & 24 (≥50%=URBAN, <50%=RURAL)

Example: Downtown Columbia Constructed with the ArcGIS model builder using the buffer tool and spatial analysis tool.

Results - % Land Use Algorithm 50% "Urban" Results export to Access database

Compare 2 downtown locn’s Before 2008 2008+ North (yellow) Urban? Rural (46%) South (black) Urban (50%) Locations are ~half mile apart. B4 land-use tool, SC-BAQ likely would’ve accepted urban AERMOD run for both locations (limited checking, and near “core” of Columbia) . Now, land-use tool suggests northern locn is “rural.”

John Glass, 803-898-4074, glassjp@dhec.sc.gov COMMENTS ?? QUESTIONS ?? John Glass, 803-898-4074, glassjp@dhec.sc.gov