Piezometer Installation for Safety Evaluation of General Edgar Jadwin Dam

Opportunity

Located in Honesdale, PA, the General Edgar Jadwin Dam is a 108-foot high, earth core dam that impounds water only under flood conditions. The U.S. Army Corps of Engineers (USACE) wanted to investigate the dam’s core out of concern that part of its construction could affect the dam’s integrity during a flood.

Challenge

Montrose team members were contacted by the USACE to perform the geotechnical investigation and install piezometers throughout the core of the dam and at its base. The use of drilling fluids in the dam’s compacted core would have to be minimized, and some of the piezometers would need to be drilled at an angle off of the dam’s side. Additionally, the Montrose team would have to carry out the drilling at the top of the dam during harsh winter conditions.

Solution

Montrose experts used sonic drilling methods to conduct the geotechnical investigation and obtain continuous cores throughout the dam. The use of sonic drilling also helped the team minimize the introduction of fluids under pressure into the subsurface. While drilling fluids were necessary to cool the drill bit and minimize the friction in the compacted core, the team established numeric controls to limit the amount of fluid used. The angle of the boring was measured prior to installing each of the 18 piezometers through the core of the dam and throughout its base. After eight weeks, the project was complete and the core of the dam was found to be more compact than originally believed, meaning the structure was safer than anticipated. The USACE was impressed with the quality of the investigation’s final report, as well as the Montrose team’s perseverance under challenging site conditions.