Modeled Top of the Older Bedrock Geomodel Unit (pmtop_f)
The pmtop_f grid represents the modeled elevation of the top of the Older Bedrock geomodel unit 
at a 500 foot resolution. It is one grid of a geomodel that consists of eleven grids and a spatial 
extent polygon shapefile.  As part of a U.S. Geological Survey Groundwater Resources Program 
study, a three-dimensional …