Mine Mapping and Surveying - Coal Waste Impoundments: Risks, Responses, and Alternatives - page 67

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. The 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 coordinate transformation that is based upon the
alignment of surface features.
Surface horizontal and vertical controls 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 North 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 the 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 useful
for 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,