Reference quads for emergency response reconnaissance developed for use by the US Environmental Protection Agency. Grid cells are based on densification of the USGS Quarterquad (1:12,000 scale or 12K) grids for the continental United States, Alaska, Hawaii and Puerto Rico and are roughly equivalent to 1:6000 scale (6K) quadrangles approximately 2 miles long on each side. Note: This file is a regional subset that has been extracted from a national file 6K quad file. Each regional extract includes a 20 mile buffer of tiles around each EPA Region. To access the national layer (size is greater than 80MB), go to https://edg.epa.gov/data/Public/data/OSWER/6kquads_epa.zip.