When a leading Western Pennsylvania          D’Appolonia obtained 37 DC resistivity
development and construction firm spe-       profiles at the project site using a multi-
cializing in institutional and educational   electrode measurement system manu-
facilities and the oldest and most re-       factured by Iris Instruments of Orleans,
spected developer and manager of stu-        France. The readings were made using
dent housing in the country joined           a pole-dipole configuration with up to
forces to develop, finance, and con-         24 electrodes separated by a distance of
struct new student housing on the cam-       either 15 or 30 feet. The total length of
pus of Clarion University, they did not      geophysical survey was nearly 16,000
expect that their construction activities    feet. The data were processed as three-
would be impacted by the presence of         d i me n s io n al b lo c ks u s in g t h e
                                                                   RES3DINV soft-

                                                                 The geophysical
                                                                 survey proved to be
                                                                 extremely effective
                                                                                           Opening to abandoned mine at Clarion, PA.
                                                                 for targeting borings
                                                                 in locations where        The overall result of the program was
                                                                 mine workings pos-        that the geophysical exploration pro-
                                                                 sibly were present.       gram was able to rule out the presence
                                                                 Even more signifi-        of mine workings across most of the
                                                                 cantly, the geo-          site, thus minimizing the need for sub-
                                                                 physical exploration      surface drilling. The construction of the
                                                                 program indicated         student housing facilities was com-
                                                                 clearly the areas         pleted on the originally projected
                                                                 where mining voids        schedule, and the combination of geo-
                                                                 were not present.         physical exploration and targeted sub-
                                                                                           surface drilling reduced what could
                                                                 The portion of the        have been excessive costs to accom-
                                                                 site where mine           plish characterization of the site.
Field setup of resistivity equipment.
abandoned mine workings. Construc-           wo r k i n gs  we r e
tion had already commenced when              known to exist was
backhoe excavations revealed previ-          well defined, and
ously unknown mine workings at a             the mine layout plan
depth ranging from 20 to 50 feet in the      suggested that the
5-foot-thick Lower Clarion Coal seam.        mine shafts spread
                                             out laterally from
The problem facing the developer was         the known site en-
that construction had already started,       try, but did not
the extent of the mine workings was          penetrate deeply
unknown, and the site was quite large,       into the hill where
covering more than 65 acres. If a con-       construction was
ventional program of subsurface drill-       planned. In areas
ing to map the mine voids had been           away from the area
undertaken, construction would not           that was known to
have been able to proceed on schedule,       be mined, geophysi-
and the extensive subsurface investiga-      cal anomalies were
tion would have been very costly.            encountered that
D’Appolonia and the site exploration         borings were subse-
contractor worked together to develop a      quently able to con-
program of geophysical exploration           firm were not re-
combined with borehole drilling to           lated to the aban-      Results of 3-D analysis depicting the resistivity at the level of the
identify the extent of the abandoned         doned mine work-        flooded mine workings in the lower Clarion Coal.
mine workings.                               ings.

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