multiView Locates Inc.

325 Matheson Blvd. E.
Mississauga, Ontario L4Z 1X8
toll-free 1-(800)-363-3116
tel (905)-629-8959 / fax (905)-629-7379
Email: info@multiview.ca

• Introduction to EM techniques - their strengths and limitations
• An opportunity to see and utilize some of the equipment
• Review of selected case histories
• Opportunity to discuss potential applications and experiences
  

GEOPHYSICAL EQUIPMENT

Geonics EM31 terrain conductivity meter

• The 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.
• This 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.
• It 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.

Radiodetection 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 work.
• 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
  or Radiodetection Canada Limited at 905-660-9995
  
  

multiVIEW 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.

Born from 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 error.

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.