This project will support the design, construction, and acquisition of borehole instrumentation that is an integral component of a hydrologic observatory network currently under construction on the eastern flank of the Juan de Fuca Ridge. As a key component of this engineering-based effort, the researchers will plan experiments to elucidate three-dimensional hydraulic properties and hydrogeologic processes in young oceanic crust. The project will lead to advances in observatory instrumentation (primarily CORKs) and special modifications and tools for servicing instrumented boreholes from ROV/HOV platforms. Such design efforts are required for the second phase of IODP Juan de Fuca rift flank drilling, following on the first phase completed on the JOIDES Resolution during Expedition 301 in mid-2004. Broader impacts of the proposed work include contributing to an understanding of seafloor hydrogeology, augmenting the scientific results from Expedition 301, contributing to the development of more robust observatory instrumentation, enchancing interdisciplinary collaborations among physical, chemical, and biological scientists, and training of students.