Installation of the Groundwater Monitoring System to Borehole DH-2

Wakahama, Hiroshi*; Nakata, Mitsuhiko*; Hiroki, Minenari*; Futakuchi, Katsuhito*; Okada, Akio*

This report describes the results of installation of the long-term groundwater monitoring system into borehole DH-2 as a part of the Regional Hydrogeological Study and Mizunami Underground Research Laboratory Project. DH-2 was driglled with 100mm diameter through Toki-granite to the depth of 501meter below the ground level, in which 5inch-steel-casing pipe was inserted to the depth of 171m. The monitoring system was composed of concentrically arranged seven open PVC(polyvinyl chloride)-stand-pipes("Piezo-pipes"), housed within outer 4inch PVC-casings, followed by 3inch PVC-casings, packers and several stainless steel units. In the system, seven monitoring zones were isolated by expandable rubber type packers inflating with water. From the view point of quality assessment, leak-off tests were conducted for all of 7 packers before the shipment and the installation at the site. In terms of individual casing joints, air-tight inspections were carried out ...