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4 Mine Mapping and Surveying A key element of assessment of the potential for breakthrough of coal slurry materials into underground mine workings is the accurate delineation of the extent of those workings with respect to the ground surface in the impoundment's basin area. This chapter deals with several aspects of that problem. The adequacy of existing mine maps and recommendations for the storage and preservation of maps make up the first part of the chapter. While mine maps provide information critical to the characterization of a site, there are significant limitations to some maps, particularly those for abandoned mines and mines operating before 1969. In addition, standard practice in mapping and surveying varies from site to site. When questions concerning the accuracy of maps remain, additional effort to locate underground workings is warranted. Chapter 5 reviews geophysical methods that can be applied to locate underground mines. SURFACE MAPS There are two primary sources of surface topographic mapping are the U.S. Geologic Survey's 7/-minute quadrangle maps and aerial topography. The U.S. Geological Survey's contour intervals vary according to the steepness of the terrain. A 40-foot contour interval is common for southern Appalachia. The generally accepted accuracy in surface elevation using these maps ranges from 20 to 40 feet. ~ contrast, mine maps are typically maintained to a tenth or hundredth of a foot. However, coa! companies commonly use aerial photography to determine topography for critical construction projects such as refuse impoundments, preparation plants, and mine portals. The contour intervals for aerial topographic measurements usually vary in sensitivity relative to the steepness of the local topography. It is common to have one or two foot contours for relatively flat terrain and as much as 5 to 10 foot in mountainous - 71
72 COAL WASTEIMPOUNDMENTS areas. Contours are generated from surveyed control points flagged at the time of the flight. Maps so determined also show man-made features such as roads, excavations, and buildings. Where closed-loop underground mine maps are available (see below), the accuracy in depicting the surface topography controls the accuracy by which the coal outcrop is located on a hillside. The committee recommends that adjacent to existing or proposed refuse impoundments, the coal outcrop locations) be determined using aerial topographic measure- ments. UNDERGROUND MINE MAPPING The use of inaccurate or incomplete mine surveys and maps may result in construction of an impoundment in an area not known to have been mined; if unknown mine workings are present, the impoundment could suffer unexpected structural failure (Franklin et al.', 1997~. In areas where impoundments are constructed near known or suspected underground mines, vertical and horizontal barrier distances between the mined area and the impoundment, as depicted on old maps or surveys, may not be accurate. Regulations' promulgated as a result of the Federal Coal Mine Health and Safety Act (30 C.F.R. § 75.1200-2 (b)), require closed-Ioop mine surveys. However, surveys for many older mines' were not closed. Furthermore, underground mine surveys may have been based on a foreman's notes or sketches that lack a reference point or a recognized coordinate system and therefore cannot be accurately located. These shortcomings are more common in small mines or room-and-pillar mines where a number of short panels were driven and extracted. Compounding the problem, some maps and records of older mines have been lost or destroyed. The condition and thickness of a barrier, whether composed of coal or other rock type, between an underground coal mine and a surface impoundment can be difficult to determine in the steep topography common in Appalachia. Yet, this information is needed to quantify the potential for breakthrough. The tools available to determine the extent of mining in an abandoned mine and the condition and thickness of the outcrop are not highly advanced. Although extensive drilling can be used; it may miss smaller mined or disturbed areas. In contrast to invasive drilling, geophysical techniques can obtain useful information without penetrating the Earth's surface. The objective of geophysical surveys is to constrain the physical characteristics of some three-dimensional volume of earth material, including the presence of voids. Although no geophysical technique
MINE MAPPING AND SUR KEYING 73 performs optimally under all geological and topographic conditions, multiple geophysical techniques may be necessary to reduce the probability for error to an acceptable level (see Chapter 5~. The primary use of underground mine maps is to determine accurately the dimensions of pillars and mine openings and to locate the mine with respect to the surface and any horizontally or vertically adjacent surface or other underground mines (Shackleford, 2001~. The following information relevant to site characterization is included on a typical underground mine map (30 C.F.R. §§ 75.1200, 1200-1~: · All pillared, worked out, and abandoned areas, pillar locations, sealed areas, future projections, adjacent mine workings within 1,000 feet, surface or auger mines, mined areas of the coalbed, and the extent of pooled water; Dates of mining, coal seam sections, and survey data and markers; Surface features (e.g., railroad tracks, public roads), coal outcrop, and 100-foot overburden contour-or other prescribed mining limit; Mineral lease boundaries, surface property or mine boundary lines, and identification of coal ownership. A coal section, which describes the mined thickness of the sequence of coal, rock, and partings, is listed on the mine map. Coal sections are typically recorded when a survey sped is set (see definition in glossary). The coal section permits calculation of mined coal tonnage, percentage of coal recovery, and percentage of reject (in-seam and out-of-seam rock). An example of a portion of a typical underground mine map is shown in Figure 4.1. Underground and surface mine maps are collected and stored both on the state level and by MSHA and OSM. Operators of underground mines are required to submit maps to MSHA at least annually for the approval of ventilation plans. These maps are maintained at the various MSHA district offices or archived at a central location until the mine closes. Following mine closure, a copy of the final map is forwarded to the OSM National Mine Map Repository in Pittsburgh, Pennsylvania (see below). Therefore, MSHA is a source of maps for active mines only. There is considerable activity at the state level concerning mine maps. For example, the Commonwealth of Virginia has embarked upon an ambitious program to accumulate mine maps and place them in a digital database (Sidebar 4.1~. Related activities underway in West Virginia and Kentucky are discussed in Sidebars 4.2 and 4.3. Comparison of the mapping
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MINE MAPPING AND SUR KEYING 75 SIDEBAR 4.1 Mine Maps and Storage, Commonwealth of Virginia Virginia's mine map repository is coordinated through the Virginia Department of Mines, Minerals, and Energy and relies upon the Division of Mineral Resources and the Division of Mined Land Reclamation. It contains 4,226 digitized and geo-referenced mine maps, representing 70 to 80 percent of the mined-out areas in the state. The remaining mines are not yet included because the maps lack sufficient information for accurate location, because mining occurred before Virginia required map records, or because Virginia has not yet acquired the maps from coal companies. The project began with 10,000 folded blueline mine maps and 30,000 microform or microfilm records. These maps ranged from the product of trained surveyors, referenced to state plane coordinates or local coordinates, to hand- drawn sketches lacking scale, a coordinate system, and reference points. Eliminating duplicates and earlier versions of the same mine was the department's initial task. Where possible, the Virginia Department of Mines, Minerals, and Energy locates mines using a global positioning system. In an effort to characterize errors in mine location, the department conducts random checks using the global positioning system and coal company survey records. The error for these maps is a function of the surveying accuracy, which in turn is related to the age of the mine. The closure error of mines using modem surveying techniques is 1:5,000 to 1:15,000. While older mines may not have been surveyed or if surveyed, a closed loop may not have been used to quantify error. Accuracy is predicated upon the methods used to locate the mine. The Virginia Department of Mines, Minerals, and Energy estimates the following degrees of accuracy: · +500 feet for features (stream, creek, road, etc.) that locate mines; · +80 feet for locations tied to U.S. Geological Survey topographic quad rangle sheets and +150 feet for those tied to geologic quadrangle sheets; · +10 feet for mines located by survey; and · +250 feet (at best) for abandoned mineland portal locations. In addition, a library was created to include digital U.S. Geological Survey 7/minute quadrangle maps, incorporating other data including gas wells, pipelines, and abandoned mine-lands projects. A set of quadrangle maps is available at nominal cost for all coal-producing counties in southwestern Virginia. A significant attribute of the Virginia program is that the digital data are accessible through industry-standard computer-aided design and geographic information systems programs. Once the mapping program is completed and all available mines have been entered in a geographic information systems database, the search for missing mines will continue with a comparison with the OSM database. SOURCE: 1. Duncan, Virginia Department of Mines, Minerals, and Energy (VDMME), personal communication 2001; and VDMME Division of Mineral Resources Maps and Publications (http://www.mme.state.va.us/DMR/DOCS/MapPub/map_pub.html).
76 COAL WASTEIMPOUNDMENTS SIDEBAR 4.2 Mine Maps and Storage, State of West Virginia West Virginia is in the process of creating a geographic information system inventory of coal resources that incorporates both geologic informa- tion and underground mine locations, at the standard 1:24,000 scale used for U.S. Geological Survey topographic and geologic quadrangle maps. Coal resource data include outcrop locations, structural contours of coal seams, total (coal plus partings) seam thickness, and percentage of in-seam partings. Stratigraphy and coal seam correlation are accomplished using core logs, geophysical (e-logs), measured coal outcrop sections, in-mine coal sections and bottom~f-seam elevations, coal bed discontinuities, and coal analyses (heating value per pound [Btu/lb)] and percentage of sulfur, and ash). The digital mine mapping system is in the initial stage of development. Mapping has been completed for Fayette County and the northern panhandle counties. The present focus of the project is the southern West Virginia coalfield, where the majority of current mining activity occurs. Underground, surface, and auger mines are being mapped. The West Virginia Geological and Economic Survey is concurrently mapping the location of impoundments that overlie old mine workings. Map records dating to the end of the 19th century are maintained on microfiche at two state agencies. Records for more than 100,000 mines are available for public inspection and copying. SOURCE: N. Fedorko, West Virginia Geological Survey, personal communi- cation, 2001. approaches in Virginia, West Virginia, and Kentucky indicates significant differences in scope of data collection, storage, and access. National Archive for Mine Maps OSM maintains a National Mine Map Repository in Pittsburgh, Pennsylvania (http://mmr.osmre.gov). Some maps in the repository were originally maintained in the U.S. Bureau of Mines files and were transferred to OSM. OSM accepts maps for inclusion in the repository from various sources, including the states, and makes the archived maps available upon request. OSM has no regulation requiring the submission of maps but does have informal arrangements with MSHA to provide copies of the final map for abandoned mines. In addition, some copies of mine maps are prepared to illustrate mine ventilation systems, and these maps may not contain all the mine map information required by 30 C.F.R. §§ 75.1200 and 75.1200-1. The repository may receive such copies in lieu of the final map. =
MINE MAPPING AND SUR VEGA 77 SIDEBAR 4.3 Mine Maps and Storage, Commonwealth of Kentucky Kentucky maintains paper copies of maps for approximately 150,000 mines at the Kentucky Department of Mines and Minerals. Mine locations and perimeters are recorded on U.S. Geological Survey topographic quadrangles. Hard copies of the mines maps are stored at the Department of Mines and Minerals and are available for public viewing. However, Kentucky coal companies do not contribute any mine maps to the OSM National Mine Map Repository (http://mmr.osmre.gov). Recently, Kentucky's auditor of public accounts recommended that the Department of Surface Mining, Reclamation, and Enforcement, the Division of Abandoned Mine Lands, and the Division of Mines and Minerals locate, scan, and digitize underground mine maps for Kentucky (Hatchett, 2001~. Distribution of mine location information is limited by the Department of Mines and Minerals. In accordance with state law, KRS 352.480, the mine license-holder (typically the operating company), mineral owner, mineral leaseholder, or mine operator must give written consent before a mine map can be copied. Adjacent or nearby property owners may secure a copy of mine maps by filing an affidavit alleging encroachment on property outside the ownership or leasehold. The maps are copied by a private firm and may take several days. The mine maps are not stored in digital format but are generally available for mines dating from 1948 to the present. SOURCE: Kentucky Mine Map Information Center (www.state.ky.us/agencies/ cppr/dmn/mmic.htrn). The collection of maps in the OSM repository is either voluntary from the states and other sources, or results from an informal arrangement with MSHA. As a result, OSM and state records differ in many instances. The committee concludes that the transfer of mine maps from MSHA to OSM should, be better coordinated. The committee recommends that MSHA work with OSM and state agencies to develop a coordinated and assertive approach to collecting and archiving mine maps. Records of the individual states should be compared with those of OSM to ensure that both have the identical mine map database. As mine maps from active operations are submitted to MSHA and state agencies, copies should be forwarded to OSM, so the archival data can be updated. MSHA, in coordination with OSM and the state agencies, should undertake a thorough and comprehensive effort to acquire maps of abandoned mines, concurrently with the updating of maps of active mines. This process should include canvassing mining communities, land- and mineral-holding companies, and former mine employees (engineers, geologists, landmen, surveyors, superintendents, and foremen), historical societies and courthouses to
78 COAL WASTEIMPOUNDMENTS acquire or copy mine maps from coal companies. The Federal Abandoned Mine Lands Fund could be a source of funding for this activity. Storage Risks Damage to archived mine maps can result from improper storage, natural aging of the materials used, water, fire, or other circumstances (Sidebar 4.4~. MSHA requires that underground mine maps be kept in an area on the surface to minimize the danger of loss by fire or other hazards (30 C.F.R. § 75.1200~. The committee concludes that electronic data storage can reduce the risk of permanent loss or damage of mine map data and improve the ability to maintain multiple backup files both on- and off-site. The committee recommends that upon receipt of a paper copy of a mine map, the state or federal agency should have it scanned into electronic data files. The original paper maps should be stored in fire- and flood-proof vaults, while electronic copies of mine maps should be stored on site with regular backup to an off-site facility. Mine Surveying Accurate mine maps will be critical to future site assessment for coal waste impoundments, as well as for other land-use decisions. An important component of an accurate map is the closure of the mine survey. Closure is a measure of the acceptable error within a closed-loop survey. Closure standards for surface surveys vary widely by state (Table 4.1) and type of real property (e.g., urban, suburban, or rural). MSHA regulations (30 C.F.R. § 75.1200-2) require operators of all underground mines to conduct a closed- loop survey, but do not specify the standard of closure and the distance between the last closed loop and the active face. The committee concludes that the establishment of uniform mine surveying and mapping standards is essential to ensure that underground coal mines are accurately located" with respect to other mines and surface structures, including refuse impoundments. Therefore, the committee recommends that MSHA set standards for minimum closure error for all underground closed-loop surveys and that a closed-loop survey be maintained within a standard distance (to be determined by MSHA). Mine elevations are also an important component of a mine survey. The mine elevations are posted on the map adjacent to each sped. The sped is the underground equivalent of an iron pin or steel rod that marks property comers
MINE MAPPING AND SUR KEYING 79 SIDEBAR 4.4 Kentucky Fire Destroys Mine Maps A fire on November 12, 1948, destroyed at least 30,000 mine maps at the Kentucky State Department of Mines and l\/linerals. This facility was housed in a University of Kentucky building, which also contained the Botany Department and the Kentucky Geological Survey. The Mines and Minerals Department lost, in addition to the maps, its reports, including safety records, inspection reports and recommendations. Many of these maps charted abandoned mines dating from 1884 to 1948. State geologic maps escaped the fire because they were kept at the home of the state geologist. The cost of damage was assessed at $200,000, but many of the lost records were irreplaceable. Mine maps are now stored at Kentucky's Mine Map Information Center. This center has operated the Mine Map Repository for the Kentucky Department of Dirges and I\ Morels for the past 28 years. The center currently houses 100,000 coal mine maps and 140,000 mine records. Although a few of the maps destroyed in the 1948 fire have been replaced, the majority of the maps in the repository date only from 1948. SOURCE: Courier-Journal (Louisville), 1948; Lexington Herald Leader, 1948. in a surface survey. The horizontal (x,y) location of each sped is referenced to the mine coordinate system. The z component is defined by the bottom- of-seam elevation, a critical component of mine surveying. Current surveying practice is to establish bottom-of-seam elevations by a level survey (30 C.F.R. § 75.1200-l~k)~. However, older mines sometimes used the top of the seam to refer to mine elevations. Hence, caution should be used in evaluating elevations on older maps. The primary use of elevation data is to track the flow path and potential total pressure Ready of water that may accumulate in the mine. The data can also be used for vertical location of the active mine in the framework of overlying and underlying seams, which may be actively mined or may contain abandoned mines, and for identification of undulations in the mine floor that frequently correlate with poor roof or floor conditions. The thickness of the outcrop barrier is critical to the evaluation of blow- out, blow-in, or breakthrough potential (see Chapters 3 and 6~. Because the last cut is typically left unbolted, the measurement must be made remotely from the protective cover of supported mine roof. Remote measurement can be routinely accomplished with laser or sonar equipment that indicates distance by the reflection of light and sound waves, respectively. The mine engineer or land surveyor should be responsible for the accuracy in documenting the extent of the final cut. Under no circumstances should the -
80 TABLE 4.1 Required State Surveying Closure Standards COAL WASTEIMP6UNDMEN~ State Mine Surveys Property Surveys AL IL IN KY None/federal MD OH ** 1 :5,000 PA TN None VA Same as rural WV 1 :10,000 for urban/commercial/high risk 1 :7,500 for suburban 1 :5,000 for rural ALTA* standards. None specified. 1:10,000 for urban/commercial/high risk 1 :5,000 for rural 1:15,000 for urban/commercial/high risk 1 :10,000 for suburban 1 :7,500 for rural 1 :5,000 for mountains and marshland 1 :5,000 for urban/commercial/high risk None specified. 1:10,000 for urban/commercial high risk 1 :7,500 for suburban 1 :5,000 for rural 1 :20,000 1 :1 0,000 None specified. * ALTA: American Land Title Association (1:15,000 urban, commercial/high risk; 1:10,000 suburban; 1:7,50~rural; 1:5,00~mountains and marshland) ** Data for Ohio: Mark Jones, Ohio State Board of Registration for Professional Engineers and Surveyors, personal communication, 2001. SOURCE: C. Gillian and M. Wooldndge, Alliance Consulting, personal communi- cation, 2001 mine foreman authorize the active section to be abandoned or pillars to be recovered until Me final depth of each heading has been recorded. The committee recommends that the mine foremen and surveyors be required to record the depth of the last cut taken to a level of accuracy to be determined by MSHA. It is imperative that any areas not completely surveyed be noted as such.
MINE MAPPING AND SUR KEYING 81 Coordinate Systems At least two and preferably three reference points are established on the surface, usually near the portal or shaft (30 C.F.R. § 75.1200-l~h)) before an underground mine is opened. These surface points are tied to a coordinate system (latitude and longitude, state plane, or local) (Sidebar 4.5), so as to enable mine workings to be accurately located in the framework of surrounding surface features. The surface points are a permanent reference that can be used if the portal or shaft location has become obscured by collapse or post-mining reclamation. Subsequent mine surveying and mapping is based upon a fixed point within the mine, a point-of-beginning, that is referenced to the surface points. The majority of active underground mines use the state plane coordinate system. The surface points are fixed surface monuments, tied to both the state plane system and at least one point referenced to latitude and longitude. Using state plane coordinates is advantageous because utilities (electric power lines, gas transmission lines), roads (federal, state, and county), and other planimetric features are typically referenced to the state plane system; and because U.S. Geological Survey topographic maps list both North American Datum 27 latitude and longitude and state plane coordinates, so mines can be located easily on commonly available maps. The committee concludes that the variety of mapping and coordinate systems in use at present increases the potential for misinterpretation or inaccuracy in underground mire locations. Therefore, the committee recommends that state plane coordinates or latitude and longitude and bottom-of-seam elevations as the map base reference. However, when using latitude and longitude, the mine operator should clearly designate whether the mapping is based upon North American Datum 27 or North American Datum 83. Elevations of seam bottom, used to establish the vertical position of the mine, must be referenced to mean sea level. Unfortunately, no uniform standard sets an appropriate coordinate system or the type and placement of surface reference points. The choice of a mine coordinate system can vary with the age of the mine, the operating company, the geographic location, or the mineral lessor. As expected, the largest variation in practice occurs in older mines (pre-1969) and small mines. Historically, local coordinate systems have been prevalent where a single entity owned the mineral rights to large, contiguous tracts. Where this practice continues, it is limited to specific properties controlled by mineral- holding companies. In these instances, a coordinate transformation between the local and state plane coordinates is given. Similarly, for small hilltop mines operating in remote areas, there was little economic justification for -
82 COAL WASTEIMPOUNDMENTS SIDEBAR 4.5 Coordinate Systems The most commonly used coordinate system today is latitude and longitude, which are defined by reference planes based on the Prime Meridian and the Equator (Snyder, 1987~. Latitude is measured in degrees north or south of the Equator, and longitude is measured in degrees east or west of the Prime Meridian. In the United States, the state plane system was developed to provide local reference systems that were tied to a national datum. This system divides the United States into more than 100 distinct grid zones and provides an easily used, flat grid that maintains a difference between geodetic and grid distance of 1:10,000 or better. The first state plane system was developed in the 1930s and was based on the North American Datum 1927 (NAD27) (in feet). This system has been largely superseded by the North American Datum 1983 (NAD83) (in meters), although maps in NAD27 coordinates are still in use. Mine surveyors can also use a local system based on an on-site monument. A grid is established based on direction and distance measured from the monument. These coordinate systems, because they do not take into account the curvature of the Earth, lose accuracy as the grid is extended away from the base station. In addition, these systems may be difficult to transform with other coordinate systems, especially if the on-site monument is displaced or unmarked. SOURCE: Dana, 1999. the time and expense associated with a closed-loop survey to tie the mine to a U.S. Geological Survey monument. Where large mineral-holding companies control mineral rights, considerable time and effort has often focused on establishing transfo~ma- tion equations between local and state plane coordinates. The equation involves a fixed rotation angle and lateral offset to convert from the local system to state plane coordinates. However, in some instances a single, unique coordinate transformation is not applicable to an entire property. Thus, conversion of a particular mine map from local to state plane coordinates, requires knowledge of the geographic limits of a particular coordinate transformation. The committee recommends that appropriate coordinate transformation equations be listed on the mine map. Where no coordinate transformation exists, extreme care must be used in referencing maps from abandoned mines into state plane coordinates or latitude and longitude. In these situations, the transformation may be based upon aligning creeks, roads, or other planimetric features to establish the mine location. However, the surveyor or engineer must recognize that the
MINE MAPPING AND SUR KEYING 83 location of these features may have been drawn freehand and not established by an accurate survey. The main objective of surveying is to depict accurately the underground mine workings; surface features are secondary. Furthermore, without survey stakes or monuments, the natural meandering of creeks over time and realignment of roads may invalidate a surface survey. Me committee concludes that surveys based on data not tied to stakes or monuments may not be accurate. The committee recommends that a qualifying statement accompany any crate transformation that is based upon the alignment of surface features. Surface hanzontal and vertical contraIs should be referenced to permanent survey monuments. The committee recommends that MSHA establish standards to improve and maintain the location of surface controls. Monuments should be referenced to state plane coordinates and at least one monument located in Norm American Datum 27 or 83, or latitude and longitude (Sidebar 4.5~. They should be anchored in rock and located so that they are not obliterated or obscured by reclamation and other activities associated with mine operation and closure. Monument locations should be established by closed-loop survey (with minimum closure errors consistent with underground surveying standards recommended above) from a fixed monument for which the accuracy of location is equal to that of a U.S. Geological Survey monument. The elevation of the surface monuments should be referenced to mean sea level and equal in accuracy to that of a U.S. Geological Survey monument. Identification of Geology and Coal Seams In some instances, companies require mine surveyors, foreman, and engineers to record geological observations or conditions in the mine floor or roof rock. However, this requirement is not universal. Roof falls, floor heave, and water or gas inflow are examples of where geologic information would commonly be noted on a mine map. As discussed in Chapters 3 and 6, the potential for subsidence is critical to quantifying the risk for slurry to enter the mine workings. Although geologic information is contained within He permit, site-specific data are important when mining adjacent to the outcrop. The committee concludes that the geologic information contained" within the mine permit documents and within company exploration and well records is usefulfor determining the presence and extent of potential ground weaknesses that could affect waste impoundments. Therefore, the committee recommends that MSHA work with the state regulatory agencies to determine which mine permit documents should be retained,
84 COAL WASTEIMPOUNDMENTS in what form, and for how long. Such information might include the presence of fractures, faults, joints, "hill-seams" (tension cracks), and water inflow from the roof or floor. The designation of a coal seam should be regarded as approximate, subject to verification based upon: seam elevation, seam thickness, and location of marker beds as obtained from core logs; elevations of seam bottom obtained Tom the mine map; or comparison with the elevations of overlying or underlying mines. Although several resources (e.g., Toothman, 1977; National Geologic Map Database's Geologic Names Lexicon at http://ngmdb.usgs.gov/Geolex/geolex_home.html) exist for designating a particular coal seam, the correct name is not always identified. For example, a coal seam may be referred to by several different names depending on geographic location, mine operator, absence of lateral geologic correlation, or economic value. This point is clearly illustrated by a few examples: In Pike County, Kentucky, the Pond Creek coal seam is also known as the Lower Elkhorn seam, which in West Virginia is synonymous with the No. 2 Gas seam. In Lynch, Kentucky, the geologic cross section shown on the U.S. Geological Survey 7/-minute geological quadrangle map describes the first three above-drainage seams as the Harlan, Kellioka, and Darby. However, on the same property they were referred to as the A, B. and C by one coal company and the 180, 240, and 260 by a second company. Upon crossing Black Mountain into Virginia, these seams are known as the Wilson, B (Marker), and Taggart. The committee concludes that coal seam names are potentially imprecise. Therefore, the committee recommends that coal seam names not be the sole basis for determining the vertical location of an abandoned mine. SUMMARY Accurate mine maps are critical to establishing the location of underground mine workings with respect to existing or proposed coal refuse impoundments. Mine maps are the primary means by which the thickness of the outcrop barrier (horizontal separation) or overburden thickness (vertical separation) are determined. The accuracy of mines operated since the 1970s, in which surveys were made with modern equipment and closed loops, are likely to be suitable for use in the design of an impoundment. Maps for older mines may or may not be suitable. Furthermore, unrecorded final cuts may compromise the accuracy. In such cases, additional investigation of the locations of abandoned mine workings in warranted. The next chapter describes geophysical methods for such investigations.
MINE MAPPING AND SUR VEY~G 85 In many instances, nonexistent, erroneous, or incomplete mine maps prevent knowing the extent, location, and depth of mined areas. Therefore, the committee recommends that MSHA work with OSM and state agencies to establish standards for mine surveying and mapping. These should include the following: . · Determining surface coal outcrop locations by aerial topo- graphic measurements, where adjacent to existing or proposed refuse impoundments, Implementing a coordinated and assertive approach to collecting and archiving mine maps, · Scanning paper copies of mine maps into electronic data files upon receipt, · Setting standards for minimum closure error for all underground closed-loop surveys and that a closed-loop survey be maintained within a standard distance (to be determined by MSHA), · Recording the depth of the last cut taken to a level of accuracy to be determined by MSHA, · Using state plane coordinates or latitude and longitude, and bottom-of-seam elevations as the map base reference, Listing of appropriate coordinate transformation equations on the mine map, Adding a qualifying statement to accompany any coordinate transformation that is based upon the alignment of surface features, Improving and maintaining the location of surface controls, Determining which mine permit documents should be retained, in what form, and for how long, · Avoiding the use of coal seam names as the sole basis for determining the vertical location of an abandoned mine. -
86 COAL WASTE IMPOUNDMENTS Mineral lease boundaries, surface property or mine boundary lines, and identification of coal ownership. A coal section, which describes the mined thickness of the sequence of coal, rock, and partings, is listed on the mine map. Coal sections are typically recorded when a survey sped is set (see definition in glossary; or Mining in Manitoba, 2001~. The coal section permits calculation of mined coal tonnage, percentage of coal recover, and percentage of reject (in-seam and out-of-seam rock). An example of a portion of a typical underground mine map is shown in Figure 4. ~ . Underground and surface mine maps are collected and stored both on the state level and by MSHA and OSM. Operators of underground mines are required to submit maps to MSHA at least annually for the approval of ventilation plans. These maps are maintained at the various MSHA district offices or archived at a central location until the mine closes. Following mine closure, a copy of the final map is forwarded to the OSM National Mine Map Repository in Pittsburgh, Pennsylvania (see below). Therefore, MSHA is a source of maps for active mines only. There is considerable activity at the state level concerning mine maps. For example, the Commonwealth of Virginia has embarked upon an ambitious program to accumulate mine maps and place them in a digital database (Sidebar 4.1~. Related activities underway in West Virginia and Kentucky are discussed in Sidebars 4.2 and 4.3. Comparison of the mapping approaches in Virginia, West Virginia, and Kentucky indicates significant differences in scope of data collection, storage, and access. National Archive for Mine Maps OSM maintains a National Mine Map Repository in Pittsburgh, Pennsylvania (http://mmr.osmre.gov). Some maps in the repository were originally maintained in the U.S. Bureau of Mines files and were transfe~ed to OSM. OSM accepts maps for inclusion in the repository from various sources, including the states, and makes the archived maps available upon request. OSM has no regulation requiring the submission Prepublication Version - Subject to Further Editorial Correction