Dam Projects A-R

In 2019, DA Smith (formerly Agapito Associates, Inc. Field Services) cored six horizontal holes up to 40 feet deep into the right abutment of the Boundary Dam as part of a major rock slope stabilization project undertaken by the dam owner, Seattle City Light.  Drilling was conducted while suspended from ropes below the dam’s Level 6 bridge deck located approximately 110 ft above the Pend Oreille River.  DA Smith partnered with Apex Rock Fall Mitigation, LLC, a subsidiary of Drill Tech Drilling & Shoring, Inc., who provided technical rock face climbing support, who provided technical rock face climbing support.  

Holes were cored HQ3 and reamed to a final 5.5-inch diameter to accommodate grouted anchors.  DA Smith assisted with video inspection of the boreholes for characterizing rock mass structure.  DA Smith also tested the rock mass permeability through the anchor zones using an inflatable packer and specially fabricated, suspended low pressure-low flow hydro tester. 

In 2009, DA Smith (formerly Agapito Associates, Inc.) completed drilling and overcore stress measurements under contract to HDR at the Duke Energy (Duke) Keowee Dam Spillway located at the Oconee Nuclear Station near Seneca, South Carolina. The purpose of the program was to drill observation core holes and measure stress in the concrete ogee of the Gates 1 and 4 spillway bays. Tasks included: 

• Six NX wireline (NXWL) observation and concrete sampling core holes were drilled: two angle core holes into the west end wall from a work deck in the Gate 1 spillway bay; two angle core holes drilled into the east end wall from a work deck in the Gate 4 spillway bay; and two vertical NXWL core holes, one through each of the abutments adjacent to spillway bays 1 and 4
• Core was structurally logged, photographed, boxed, and stored
• In situ stress measurements were conducted at 5-foot intervals down vertical holes drilled from the spillway bars in Gates 1 and 4
• Video logging was completed in boreholes using an OBI-40 optical televiewer; collected a 360° borehole wall image, borehole dip, tool azimuth, and tool internal temperature.  The OBI-40 image azimuth may be influenced by the steel in the gates
• Hole were abandoned with tremie-placed cementitious grout 

DA Smith drilled at Dominion Energy's Roanoke Rapids concrete buttress dam in 2007, 2009, 2014, and 2020 as part of an ongoing investigation of the dam’s structural stability. Tasks include core drilling, 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 2020, DA Smith drilled three vertical exploration core holes on the South Non-overflow Section of the dam to measure in situ horizontal stresses in the core of the dam and foundation bedrock.  The 2020 holes twinned similar holes drilled by DA Smith in 2014.  A total of 51 USBM BDG overcore stress measurements were completed, providing comparative data with stress measurements taken in 2014.  Optical and acoustic televiewer logs were produced for each borehole.  Fracture tables with stereo net diagrams were generated from discontinuities digitally mapped in the borehole walls.  Holes were completed with DGSI (Slope Indicator) 2 ¾-inch-diameter quick connect inclinometer casing.  Ultimately, campaign results were documented in a comprehensive technical report.

2007-2015

In 2007, DA Smith (formerly as Agapito Associates, Inc. Field Services) completed the following:

• Drilled two 6-inch-diameter core holes vertically through the dam and into the foundation. 
• Drilled four HQ3 core holes through the dam for observation and instrumentation. 
• Completed two stress determination holes using the USBM BDG overcore method. A total of 18 stress measurements were made at depths ranging from 6.5 to 63.5 feet deep. 
• Installed vibrating wire piezometers, lightning-protected proving rings, and dataloggers. 
• Performed high-resolution borehole imaging of all holes. 
• Core drilled through the emergency spillway from the narrow crest of the dam. 

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:

• Installed two inclinometer casings in HQ core holes drilled through the dam and 50 feet into bedrock.
• Installed three Geokon® Soft Inclusion Stress Cells (SISCs) in Block 26 of the emergency spillway.
• Video surveyed holes using a WC1750 Slimline Dual View Camera.
• Conducted permeability testing of the foundation bedrock.
• Complete unconfined compressive strength (UCS) tests on selected samples of concrete and bedrock.
• Prepared a final report. 

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. 

In 2004, DA Smith (formerly Agapito Associates, Inc. Field Services) completed drilling, instrumentation, and overcore in situ stress measurements for Acres International at the Robert Mosses Niagara Dam, operated by the New York Power Authority.  The program was designed to determine the current stress condition in specific areas of the dam and foundation bedrock. The project comprised seven vertical holes drilled from galleries inside the dam and two angled holes drilled on the downstream face of the dam, allowing a total of 17 stress measurements in concrete and three measurements in bedrock. 

Drilling was completed using DA Smith's compact CP-65 air-powered core drill. Strict environmental controls required recirculation and controlled disposal of drill water and cuttings. Special security clearance was required. The program was completed without incident, yielding reliable stress measurement data for engineering analysis.