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