PRSN Puerto Rico

In June 2019 we worked with the Puerto Rico Seismic Array (PRSN) team to install 10 sites on Puerto Rico, Culebra and St Croix (US Virgin Islands). This work was coordinated through KBRwyle and USGS Albuquerque Seismic Laboratory, with equipment furnished by IRIS/NSF.

Most of the cased boreholes installed at PRSN were part of a program to upgrade existing vault style sensor emplacements, which are vulnerable to flooding. Many sites were damaged after Hurricane Maria came through the island the previous year.

The gen 1 "RED" drill from the ATA project was outfitted with suspension, wheels, hitch and 4 trailer jacks, enabling the rig to be towed on local roads. With the addition of a portable 375 cfm compressor, we were able to use the cased percussion borehole system developed for ATA.

After rig is towed into place, jacks are deployed and wheels removed. Drill mast is raised and adjusted to plumb, and drilling commences. Rig remains connected to towing vehicle for additional stability. Using this approach, no additional anchoring of rig is necessary.

Hammer drilling at a site co-located with a PBO DDBM station. Most of the geology consisted of medium to hard sandstone. Auger drilling would have required a large rig with plenty of torque and downpressure. However, using the percussion hammer enabled us to use a lightweight rig, as all of the "hard work" is done by the hammer and not by the rig.

After completion of cased borehole, a sealing plug is inserted into the bottom of the casing, and grout is pumped through a checkvalve in the plug and into the annulus between casing and rock. Grout pump is pictured on left.