Using Fiber Optics and Vibrating Wire Piezometers to Characterize an Aquifer During Ground and Aquifer Freezing

Sarah Lupton Hydrogeologist Newmont Mining Corporation Leeville Location

Carlin Trend Leeville >100 Mil Ounces

2 Leeville Plan of Operations and Shaft Location

3 Geologic and Hydrogeologic Setting

Geology/Hydrogeology • Vinini formation (Upper Plate) Comprised mainly of chert, siltstone rock Highly Fractured • Carbonates (Lower Plate) – Host rock to the Carlin Trend Type ore – Actively dewatered • Roberts Mountain Thrust Fault (RMTF) – Thrust fault zone is the contact between the upper Vinini formation and the lower carbonate rocks – Defines the bottom of the UP aquifer – Acts as a hydraulic barrier

4 Opportunity

5 HGT-1 Boring Location

6000’ Elevation Top of UP Aquifer 5600’ Elevation 50’ HGT-1 Upper Plate (Vinini)

Roberts Mountain Trust

Fault: Top of Shaft #3 Ventilation UP/Bottom of LP 4175’ Elevation Dewatered Lower Lower Plate (Carbonates) Plate

Bottom of HGT-0001 Top of LP Aquifer @ ~4050’ Elevation Fiber Optic Overview

Pulse laser down optical wire and the back scatter is measured

Spectrum of backscattered light is a function of temperature and measured by a distributed temperature sensing (DTS) machine 7 HGT-1 Installation

8 Fiber Optic Installation

9 VWP Installation

10 VWP and Fiber Optic Installation

11 Cable Organization

12 HGT-1 As-Built

Piezometer Design and Construction:

• Over drilled original geotechnical boring to 1,950’.

• Removed 5.5 inch casing & perforated 8.625 inch casing

• Used 2.375 inch fiberglass pipe as structural installation rod, because of it’s heat conductance properties.

• Installed seven VWP’s, one fiber optic, and two heating elements on the fiberglass pipe.

• Grouted VWP’s and fiber optics in place through 2 inch tremie.

13 VWP Data

14 Fiber Optic Data

15 Fiber Optic Data

Temperature vs. Depth in HGT‐00001, 12/12/12

Temperature (C )

16.5 17 17.5 18 18.5 19 19.5 20 20.5 21 900

925

950

975 (ft.)

1000 Surface

1025 Ground

1050 Below

1075 Distance

1100

1125

1150 16 Fiber Optic Data

17 Implied Thermal Conductivity

18 Implied Thermal Conductivity

19 Future Work

• Further analysis of temperature and pressure data • Monitor of induced aquifer temperature gradient propagation from ground freezing • Heat pulse and dotted line pulse cable heating system • Potential for an additional boring instrumented with a fiber optic and VWP at a greater distance from shaft

20 Acknowledgements

Chris Cottingham Newmont Mining Corporation

Matt Vitale Meridian Geoscienc, LLC

Frank Selker SelkerMetrics, LLC

John Selker SelkerMetrics, LLC

Julie Huff SelkerMetrics, LLC