Mapping Lost or Abandoned Pipes and Utilities at Two Former Refinery Sites in Michigan
K. Mwanda and W. Sauck
Dept. of Geosciences, Western
Michigan Univ.
The US EPA razed two former oil refinery sites in Michigan in the
late 1990s. They were antiquated and both had serious, long-term
spill and leakage problems. Removal of the surface equipment and
tanks did not address the entire problem, as considerable belowground
piping existed at both sites. Adequate remediation of the
subsurface contamination required knowledge of the locations of all
the buried utilities. Initial surveying was done at both the Carson
City and Kalamazoo sites using the magnetic
and electromagnetic
(EM) induction methods. Follow-up at specific locations was done
with GPR, electrical resistivity, spontaneous potential, and
induced
polarization
(IP).
Both sites showed numerous pipes of several types and of various
lengths. Use of both the magnetic
and EM methods allowed some
differentiation to be made between types of pipe, for example steel
pipe vs. reinforced concrete drainpipes. A number of buried, reinforced
foundations were also detected. At several locations, conductive
vadose-zone plumes appeared to emanate from the ends of the
abandoned pipelines. Considerable amounts of surficial steel fragments
resulting from the demolition process had to be cleared from
the sites prior to surveying. The
magnetic
response of most steel pipe
was dominated by permanent magnetization, in which each section
of pipe (between couplers) had a positive and a negative pole. A
number of pipes were verified by trenching; most were found less
than four feet below the surface, and their diameters ranged from 1
to 4 inches. GPR transects were limited to areas where background
conductivity was below 10 mS/m, as higher conductivity zones
caused severe ringing and radio signal attenuation. The maps of the
pipe locations were also very useful for guiding subsequent workwith
other electrical methods (directed toward stratigraphy and LNAPL
impacts) to areas clear of interfering, conductive pipe. At these sites
where as-built drawings of subsurface installations were non-existent,
high-resolution geophysics with at least two methods was very
successful in revealing the locations of all buried metallic structures.
AAPG Search and Discovery Article #90900©2001 AAPG Eastern Section Meeting, Kalamazoo, Michigan