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AUTHOR(S):
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R.A. McBride - rmcbride@lrs.uoguelph.ca
Department of Land Resource Science
University of Guelph
Guelph, ON, Canada
J.L. Ivey
Department of Land Resource Science
University of Guelph
Guelph, ON, Canada
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Installation of pipeline utilities (oil,
natural gas, water) in central Canada prior to the 1970’s often resulted in extensive
mixing of topsoil with subsoil materials within the easements due to largely
unregulated construction practices. The main objectives of this study were 1)
to develop a simple field protocol for the rapid delineation of the zone of
topsoil disturbance (or topsoil-subsoil mixing) around buried utilities on
agricultural land in southern Ontario, and 2) to characterize the zone of topsoil
disturbance in the vicinity of an existing pre-1970’s pipeline in terms of agronomically-important soil properties. The study was
carried out at six farm sites chosen along a pipeline easement (30+ years
old) in southern Ontario. Soil organic carbon content, CaCO3 content
and pH were found to be useful in delineating the zone of topsoil disturbance
around the buried utility. Standardized laboratory techniques for
determination of these three soil attributes were used to analyse
surface soil samples (Ap horizons) taken at 1.5 m
intervals along 45.7 m long transects oriented perpendicular to the easement.
In addition, rapid field tests for these same three variables were adopted/developed and tested, and two portable instruments
were evaluated for their usefulness for in situ soil property
measurements. In particular, a MinoltaTM
CR-310 Chroma Meter was successfully used to relate
moist soil colour to the organic carbon content of the surface soil. The
chromaticity coordinate a* (C.I.E. L*a*b* colour space notation) was shown to
provide good estimates of organic carbon content for soils of medium to fine
texture in this region of Ontario. The zone of topsoil disturbance was most
often characterized by an appreciable increase in %CaCO3
equivalent and pH, and a decrease in organic carbon content (dilution), over
the pipeline trench when compared to off-easement areas. The zone of topsoil
disturbance was usually a minimum of 15 m wide (i.e., the approximate width
of the original trench and workspace areas during construction), and
frequently much wider due most likely to wet soil conditions at the time of
construction, agricultural tillage translocation of topsoil over time, and
other factors. It is recommended that rapid on-site determinations of the
zone of topsoil disturbance should be based primarily on field estimates of
CaCO3 content (10% HCl) and organic
carbon content (a* chromaticity coordinate using a portable colorimeter).
Ref#: Abs-1-099
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