EPA 40km Hexagons for Conterminous United States
This dataset of 40 square kilometer (sq. km) hexagons was created by the U.S. EPA's Environmental Monitoring and Assessment Program (EMAP) and is being released by the U.S. Geological Survey for public use. 
The 40 sq. km hexagons were derived from a grid consisting of a triangular array of points that cover the …