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Station Removal Procedure

Introduction:

Although PASSCAL station installations can vary according to the type of equipment being used, removal is relatively straightforward and similar between station designs and equipment. 

Station removal requires input from the landowner.  The landowner should be aware that a site is being removed, and they may have special requests, such as leaving behind some of the consumables, not filling-in the holes, etc.

Station removal has 3 main goals:
• To correctly stop data acquisition, and safely retrieve waveform data recorded by the station since the previous service;
• To remove all equipment without damage to the equipment, clearing dirt from the equipment, and pack them in their shipping containers;
• To clean the site, restore the original contours of the site, and any other special requests from the landowner (e.g., sow grass seed).

A simple station with easy vehicular access should take around 1 man-hour to remove.

Record-keeping of equipment and their condition as they are removed from the site is important.

The landowner may require posts and concrete pads to be removed.  A handy piece of equipment for this is the automotive hi-lift jack.  A 3-ton, 48” high model is inexpensive and easy to use.  Slings and/or a 3’ length of chain will also be required.

Worksheets

Sensor removal:

Removing the sensor from the vault requires considerable care.  If the sensor requires that the masses be locked before moving the sensor, do so!

  • With the Guralp CMG-3T, this is accomplished via an electrical command issued from the “Break-out Box” (BoB).  Press both Enable and Lock buttons on the BoB for at least 8 seconds until the red LED on the Bob starts to blink.  Wait until the blinking red LED is extinguished on the BoB and then check the mass positions which should now show large (> |7| volts) negative or positive voltages.   An external 12V power source may be required to perform the mass locking as the primary batteries may be too exhausted to complete this procedure.  Should this procedure be necessary, connect a fresh 12V battery to the BoB using a supplied ring/alligator clip to 10-socket connector cable, and repeat the mass-lock procedure.
  • With the Streckeisen STS-2 and Guralp CMG-3T ESP, use the appropriate screw- or allen-drivers to mechanically lock the mass’ before lifting the sensor from the vault.

If the sensor has been covered in dry sand, carefully remove the sand away from the top of the sensor. The cable should be removed and the cap immediately fitted to the connector.  Gently lift the sensor from the vault, screw the leveling feet into the body of the sensor, and place the sensor in it’s shipping container.  Pack the sensor cables and control box into the same container.  When transporting the container in a vehicle, ensure that the case travels upright, and is securely fastened as close to the mid-point of the vehicle’s wheelbase as possible.