Drilling the Holes

Boreholes at Lajitas were drilled with available waterwell equipment.
Access to the sites was one of the principle restrictions that had to be considered (the other was radio telemetry line-of-sight). A two man contract crew accomplished drilling all the required holes within a week without problems except for a number of rock damaged tires.

Locations and access had been scouted during a prior trip. The drilling crew completed about two holes holes per day.

Distant shot of drilling operation.

Preparing to drill

While, air drilling in limestone can be a dusty operation, it causes far less impact on the surrounding countryside than a more conventional vault excavation. The holes were drilled oversized such that there would be sufficient clearage to cement the casing from the surface down.

Once the hole is drilled and before the casing is set, several feet of a cement grout is poured into the bottom of the hole. This will form the 'floor' of the borehole vault.

Lowering the casing into the hole.

The casing is then carefully lowered into this slurry, plumbed, and then left while the slurry sets (usually overnight).

Plumbing the casing

Waiting for the 'floor' to harden

On the next day, the cemeting is completed by pouring a slurry around the outside of the casing until the entire length is cemented. The top of the casing is capped to seal out rain water and rocks from interested children.

Completed borehole-vault ready for installation
This particular borehole-vault was 40 feet deep (the others are all 20 feet). It was done as a test and demonstration to explore borehole-vault installations in deeper holes. Installing the seismometer in this hole was no more difficult than the shallower holes.

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