DA Smith (formerly Agapito Associates, Inc. Field Services) drilled at Dominion Energy's Roanoke Rapids concrete buttress dam in 2007, 2009, and again in 2014-15 as part of an ongoing investigation of the dam’s structural stability. Tasks included core drill, in situ stress measurements using the United States Bureau of Mines (USBM) Borehole Deformation Gage (BDG) method, borehole imaging, core logging, permeability testing, and geotechnical instrument installation.
In 2007, DA Smith completed the following:
Two of the drill sites were on the emergency overflow section of the dam that is less than 6 feet wide. The drill rig was disassembled down to five parts at the toe of the dam, and then lifted to the crest of the dam with a high-reach crane and reassembled. A work deck was built on-site to provide a safe work location on the narrow crest.
Core was structurally logged, depth marked, striped, photographed, and boxed. A high-resolution borehole image was made of each borehole. Holes were grouted with cementitious grout.
Vibrating wire piezometers and proving rings were installed with lightning protection and connected to a data logger system. Signal cables were run through conduit. A summary report of all field activities, stress determinations, core logs, borehole images, and instrumentation installation details was generated.
In 2009, the following tasks were completed:
In 2014-15, DA Smith completed core drilling and 74 USBM BDG overcoring runs in seven vertical holes up to 62 feet deep to measure in situ stress. Measurements were conducted according to specifications prepared by HDR Engineering, Inc. of the Carolinas, and were ultimately used for thermomechanical modeling of the dam.