1. Map showing the extent of mining, locations of mine shafts, adits, air shafts, and bedrock faults, and thickness of overburden above abandoned coal mines in the Boulder-Weld Coal Field, Boulder, Weld, and Adams counties, Colorado Author/Creator: Geological Survey (U.S.) Publication/Creation: [Reston, Va.?] : The Survey, 2001 Resource Type: Map Edition: Version 1.0. Access & Availability: Loading