Integrated Ocean Drilling Program Expedition 341S was an engineering expedition dedicated to two separate projects. One was the first deployment of the Simple Cabled Instrument for Measuring Parameters In Situ (SCIMPI) on the Cascadia margin. The second was replacement of the CORK in Hole 858G for formation pressure monitoring in the Middle Valley axial rift of the Juan de Fuca Ridge. Both installations were targeted to be incorporated into the NEPTUNE observatory network.

SCIMPI is a new observatory instrument designed to study dynamic processes in the subseabed based on a simple and low-cost approach. SCIMPI was successfully installed in Hole U1416A. The final tool string consisted of nine modules, with three of these including pressure sensors (modules 1, 5, and 9, at 8, 117, and 234 meters below seafloor, respectively). The second operation with SCIMPI was the deployment of a single module (with a seafloor connector and command module, dubbed SHRIMPI) in Hole U1416B.

The new CORK that was to be installed in Hole 858G was constructed with a simplified seal system designed to survive the overpressures and high temperatures at this location. The new CORK was not installed because the old CORK could not be removed from Hole 858G.