325 Matheson Blvd. E.DEMONSTRATION OBJECTIVES:
Ontario L4Z 1X8
tel (905)-629-8959 / fax (905)-629-7379
to EM techniques - their strengths and limitations
- An opportunity to see
and utilize some of the equipment
- Review of selected case histories
to discuss potential applications and experiences
Geonics EM31 terrain conductivity meter
EM31 is an excellent tool for defining spatial variations in soil conductivity
which can infer changes in soil type or thickness, fill versus natural soils,
areas of inorganic soil contamination and distribution of buried metallic objects.
Although used successfully on occasion to map organic contamination, it is unlikely
that this tool would provide direct detection of organic contamination but may
possibly yield preferential flow paths or other geologic indicators.
system operates at a fixed frequency of 9.8 KHz whereby the transmitting coil
emits a non-focused electromagnetic oscillation (primary field) and the receiving
coil measures changes in amplitude of secondary magnetic fields induced to flow
in conductive media (soils or metallic targets). The recorded values are directly
proportional to the bulk electrical properties within the exploration limits of
the system (typically 5 to 6 metres) and are referred to as 'apparent conductivity'
in units of mS/m.
- This system also measures the ratio of the secondary
magnetic field to the primary field and this ratio produces an indication of ferrous
metallic targets which are referred to 'in-phase' readings recorded in ppt deviation
from the expected norm of zero.
- Individual data points are typically acquired
over a regular grid pattern with detailed coverage requiring readings at 1-metre
intervals over survey lines spaced 2 metres apart. Lower densities of spatial
coverage will result in lower resolution data and possible un-mapped targets.
Spatial coverage in arduous terrain can be obtained by positioning the EM31 by
GPS and processing the data by random gridding algorithms.
- Acquired data
are digitally captured by the data logger then subsequently dumped for processing.
Processing activities including data sorting, editing for redundancy and QC\QA
readings, gridding and contouring. Case history contour maps of brine plume mapping,
buried object (UST) detection and utility mapping will be discussed.
can be difficult to interpret EM31 data acquired in close proximity to existing
metallic targets (i.e. vehicles, fences, buildings, underground utilities, etc.)
since the highly electrically conductive nature of these targets can tend to mask
other features which can be adjacent, yet hidden below the ground.
RD400 Pipe and Cable Locator
- Definition of the routing of pipes
and cables can assist hazardous waste site investigations by identifying potential
contaminant pathways and areas where caution must be exercised during sampling
- The system essentially operates by inducing an AC electromagnetic
signal to flow from the transmitter along a target conductor and completing the
circuit by encouraging the signal to return to a ground stake. The inferred routing
of the target conductor is determined by mapping the amplitude (minimum or maximum)
of the induced secondary magnetic field emanating from the energized conductor.
- This system consists of a separate transmitter and receiver. The receiver
can operate at 4 user-defined frequencies (65 KHz, 33 KHz, and 8 KHz and ambient
60 Hz) and the frequency selection is dependent on the size and depth of the target
conductor and the cultural clutter (i.e. number of nearby metallic utilities)
present in the subject area.
- The system operates by three different modes:
direct connection whereby the transmitter is coupled directly to the target line;
induction mode whereby current is induced on the target line by the use of a ring
clamp, or; ambient mode whereby only the receiver is used to map naturally occurring
current flowing on underground conductors. Each method has benefits and limitations
depending on site conditions but the most reliable information is obtained by
using the direct connection method. Each of the three methods will be demonstrated.
- Caution must be exercised in heavily urbanized areas since the transmitted
signal can 'jump' to adjacent metallic utilities and the operator can easily be
fooled into mis-locating the target line. However, in the hands of an experienced
operator who is careful and diligent, the routing of individual utilities in highly
congested areas can be mapped and recorded.
- The spatial data are typically
captured by post-surveying of the recorded paint marks by total station or GPS
methods. These spatial data are then produced as map products.
For more technical information, please contact Geonics Limited at 905-670-9580
Radiodetection Canada Limited at 905-660-9995
is a private, Canadian-owned company providing subsurface mapping services to
companies from Mississauga to Hong Kong since 1988. We offer unparalleled experience
in the application of subsurface mapping techniques to assist with geotechnical,
engineering, and environmental projects. With registered Professional Geoscientists
on staff, our technicians are extensively trained and certified.
the high-resolution engineering and environmental contract geophysical consulting
firm multiVIEW Geoservices Inc, the multiVIEW group of companies were consolidated
under the banner of multiVIEW Locates Inc. in 2003. With the goal of providing
the most thorough and accurate locate of any underground utility network, multiVIEW
provides a variety of subsurface mapping services to engineers, architects, contractors,
utilities, excavators, landowners and property managers.
The Utility Division
provides longer-term contract utility locating services specifically for utility
companies. For example, since 2001 multiVIEW has been contracted by Toronto Hydro
where we have delivered a monthly performance rating of virtually 100%, with not
one single incident of damage to underground Toronto Hydro plant due to locator
With professional staff committed to the utility protection industry,
we understand that our work extends to the safety and well-being of the general
public. multiVIEW will perpetuate this commitment through continuous investments
in technology, focusing on our most valuable resource - our staff, and maintaining
unparalleled customer service. multiVIEW is presently a member in good standing
with the National Utility Locating Contractors Association, the Electrical Distributors
Association, the Ontario Regional Common Ground Alliance, the Toronto Construction
Association and the Building Owners and Managers Association. We are proud to
be the contractor of choice for all our customers.