EAST BRANCH DAM INVESTIGATION

Johnsonburg, Pennsylvania

ACT was contracted to performed investigative diamond drilling and borehole testing in the rock foundation at the USACE East Branch Dam. A total of 19 holes were cored using a HQ-3 wireline core barrel, to depths of 320 feet. The holes varied in inclination from vertical to as much as 40° from vertical. The investigative work was performed to assist in mapping the bedrock surface elevation and to provide details on the permeability of the foundation.

We worked alongside the overburden drilling contractor at the site, and supplied and installed the pvc overburden casing through which our exploratory holes were drilled. Installation of the overburden casing required multiple stage backfilling in order to grout and seal the annular space surrounding the casing. The multiple stage process ensured that the earthen embankment materials were not subjected to unnecessary head pressures and prevented grout losses during installation.

Water pressure testing water performed in stages within the exploratory holes using real-time monitoring to assess the permeability of the rock. In addition to the water testing, boreholes were also tested using a bentonite slurry. Borehole imaging was performed to provide images of fractures, joints, bedding planes, and voids within the rock foundation.

Client: US Army Corps of Engineers, Pittsburgh District

Owner: US Army Corps of Engineers, Pittsburgh District