This file is a digital polygon representation of the areal extent of abandoned underground coal mines and surface mines in the Boulder-Weld coal field, Denver Basin, Colorado. This file was created as part of the Front Range Infrastructure Resources Project (FRIRP) of the USGS, and provides information pertaining to energy resource issues within the Colorado Front Range urban corridor in and near the Denver metro area. These data contributed to the publication titled as follows: Maps 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: U.S. Geological Survey Geologic Investigations Map I-2735, 1:48000-scale.
In 1996, the U.S. Geological Survey (USGS) initiated a Front Range Infrastructure Resources Project (FRIRP) to provide relevant information to the public, land-use planners, and decision-makers regarding the location and characteristics of water, mineral, and energy resources along the Front Range corridor in Colorado. Energy resource issues within the FRIRP project area include the impacts of historic coal mining, particularly in regard to the potential for subsidence over abandoned mines in recently developed areas or in areas currently being evaluated as residential, commercial, and (or) industrial building sites. In order to address this issue, the USGS and the Colorado Geological Survey (CGS) jointly undertook the development of digital data (coverages) based on previously published maps showing the location and distribution of abandoned underground coal mines in the Boulder-Weld coal field north and northwest of Denver, Colorado. Mining in the coal field began in the early 1860s and continued into the 1970s with the last mine closing in 1979 because of fire. Although much of the surface expression of mine development has been removed or masked by increasing urban and residential development, subsurface features of underground mining, such as shafts and open mine rooms, are still present. Because of this, there continues to be a potential for subsidence in abandoned mine areas. Such areas may require special considerations with regard to development and surface subsidence potential. It should be noted, however, that these data do not in any way provide the information necessary for a complete and accurate estimation of the subsidence potential in any specific area of the coal field. For this reason, users requiring more detailed information regarding subsidence potential should consult with the Colorado Geological Survey, 1313 Sherman Street, Room 715, Denver, Colo., 80203; 303-866-2611; <URL:http://geosurvey.state.co.us>.
The digital coverage of the extent of abandoned underground coal mines is based on a previously published map compiled by the consulting firm of Amuedo and Ivey for the Colorado Geological Survey in the early 1970s (see Myers and others, 1975). The primary intent of the coverage is to show the extent of the abandoned mine workings within the Boulder-Weld coal field.
publication date
These data are considered more accurate at scales of 1:48,000 or smaller. It should be noted that these data do not in any way provide the information necessary for a complete and accurate estimation of the subsidence potential in any specific area of the coal field. For this reason, users requiring more detailed information regarding subsidence potential should consult with the Colorado Geological Survey, 1313 Sherman Street, Room 715, Denver, Colo., 80203; 303-866-2611; <http://geosurvey.state.co.us>.
U.S. Geological Survey, Box 25046, MS 939, Denver Federal Center
Mine extent polygons were compared visually with background Tiff images of mine extent derived from photographic reproduction of mine information as depicted in Myers an others (1975).
ArcInfo software is used to create and maintain topological relationships between features. Polygonal features begin and end at the same point, contain no overshoots or undershoots, and contain a single label.
Dataset complete as representation of undermined areas based on Myers and others (1975), with some modifications to mine extent based on more recent unpublished data of the Colorado Geological Survey.
map showing mined areas of the Boulder-Weld coal field, Colorado
The following discussion addresses some of the processes and caveats to the development of the mine extent map, as reported in Myers and other, 1975. 1. The original mine maps from which the mined extent is determined may have been poorly surveyed and could contain inherent inaccuracies. Post-1920s mine maps tend to be better than earlier maps, which are often only sketches. 2. Maps for many of the smaller or older mines were not available, and these mines may not be represented on the map. 3. Areas where coal has been removed by "poaching" are not shown on the maps. In some cases, coal has been poached as much as 200 ft beyond mapped mine boundaries. 4. Available mine maps may not show the maximum extent of mining in all cases. For this reason, it is estimated that the actual mine limits are within 500 ft of where they are plotted on the maps in at least 90% of the cases. In most cases, this digital coverage of mine extent closely adheres to the interpretations of Myers and others (1975), and for this reason, this coverage is subject to the same caveats listed above. However, modifications to the original data, based on more recent unpublished studies by the Colorado Geological Survey, were made where needed. These modifications typically resulted in the exclusion of some areas previously reported as undermined, and the inclusion of additional areas that were determined to be undermined in more recent unpublished studies conducted by the CGS, and in published studies of Lowrie (1966) and Colton and Lowrie (1973).
The digital polygon data representing undermined areas were compiled from analog data plotted on a 1:24,000-scale composite base map (clear film) representing all or parts of nine USGS 7.5' topographic quadrangles within the coal field boundary. To facilitate the scanning and digitization procedures required to create the coverage, photographic reproductions were made on scale-stable mylar for each 7.5' quadrangle area within the coal field area rather than creating a single photographic reproduction of the entire composite map. Each 7.5' segment was then electronically scanned, and converted to a Tagged Image File Format (TIFF) image that could be imported into Environmental Systems Research Institute (ESRI) ArcInfo software for coverage development. The mine extent polygon coverage was developed from the on-screen digitization of mine boundaries as delineated in the 7.5' quadrangle TIFF images. In some cases mine extent polygons as represented by Myers and others (1975) were modified based on more recent unpublished data of the Colorado Geological Survey.
The dataset contains attributes associated with Arc/Info coverage datasets. No additional attributes are available.
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Box 25286 Denver Federal Center
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Mined areas geographic features for the Colorado Front Range
ArcIMS Image Map Service
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U.S. Geological Survey, Box 25046, MS 939, Denver Federal Center
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