Lesson 7: Deep Burials

What is Considered a Deep Burial

A deep burial is when the subjects is buried deeper than can be reached with a probe strike. Subjects at these depths become much more difficult to successfully rescue, and their survivability becomes less than 20%.

Challenges in Searching for Deep Burials

All stages of an avalanche search become significantly more challenging in the case of a deep burial.

  • Transceiver Search Phase: Flux lines bending towards the poles of the antenna may result in a large area on the surface where there is little change in distance on the read-out.
  • Pinpointing: The subject will be too deep to be located with a probe.
  • Excavation and Triage: Prolonged and difficult excavation efforts will take much more time than the transceiver and probe portions, and must factor into the searcher’s mental map and triage decision making.

Recognizing Deep Burials

Searchers must recognize a deep burial situation in order to successfully apply strategies to overcome it. A deep burial is likely a relatively large distance minimum and a wide area of similar distance indication results from bracketing in a fine search. Many searchers in exercises doubt the large distance reading when they cannot get any closer, and may waste time continuing their fine search; however, the distance reading at close range is fairly reliable and accurate.

As soon as deep burial are suspected, rescuers must take quick actions to maximize the potential for successful recoveries. These actions include:

  • Immediately starting excavation efforts while applying deep-burial transceiver search techniques.
  • Making prompt triage decisions in order to optimize survival chances for subjects who have not yet been found.

Burial Deeper than Probe Length

Pinpointing with a probe is not possible if the minimum read-out is greater than the available probe length. In this case, once the suspected burial location has been obtained, shovelers will need to move two meters upslope and clear away enough snow until a probe strike can be obtained. Once the probe strike has been obtained, shovelers can reposition downhill from the probe and begin shovelling

Search Techniques

The recommended search technique for deep burials depends on the type of transceiver being used. Digital transceivers without analog mode should use the diamond method, whereas digital transceivers with analog mode should use the fine search in a circle method.

Digital Transceivers – Diamond Method.

  1. Identify that it is a deep burial (>probe length).
  2. Send shovelers half a burial depth downslope from the approximate centre of the burial and have them begin shovelling.
  3. Use a strict bracketing method and mark the points where the distance readings begin to rise rapidly. These will be the corners to form a diamond.
  4. Mark the centre of the diamond by crossing lines between the diamond’s corners and probe striking the centre as far as the probe will go. This point will be approximately above the buried transceiver perpendicular to the snow slope.
  5. Reposition the shovelers 2m above the centre point and have them shovel a corridor until the corridor floor is within probe striking distance.
  6. Fine search and probe at the floor of the corridor while the shovelers reposition downhill and begin shovelling.

Digital Transceivers with Analog Mode – Fine Search in a Circle Method.

  1. Identify that it is a deep burial (>probe length).
  2. Send shovelers half a burial depth downslope from the approximate centre of the burial and have them begin shovelling.
  3. Turn the transceiver to analog mode (mode 3 in Barryvox transceivers) and hold it vertically.
  4. Use a strict bracketing method to find the location of the first spike.
  5. Move away from this marked point, still holding the antenna vertically until the volume of the transceiver signal fades. Continue half this distance farther away from the spike.
  6. From this point, make a circle around the first point until another signal is received, and perform another fine search. Use an object to mark this second point.
  7. Holding the transceiver horizontally, search on the line directly between the two points to determine the lowest reading. This will be directly above the buried subject. If no second spike was detected along the circle, then the first spike was the burial location. Probe strike the burial location to almost the full depth of the probe.
  8. Reposition the shovelers 2m above the centre point and have them shovel a corridor until the corridor floor is within probe striking distance.
  9. Fine search and probe at the floor of the corridor while the shovelers reposition downhill and begin shovelling.