t '

science fora changing world

RESULTS FROM GEOTHERMAL LOGGING, AIR AND CORE-WATER CHEMISTRY 

SAMPLING, AIR-INJECTION TESTING, AND TRACER TESTING IN THE NORTHERN 

GHOST DANCE FAULT, YUCCA MOUNTAIN, NEVADA, NOVEMBER 1996 TO 

AUGUST 1998

Water-Resources Investigations Report 99-4210

U.S. Department of the Interior 

U.S. Geological Survey

Prepared in cooperation with the 

NEVADA OPERATIONS OFFICE 

U.S. DEPARTMENT OF ENERGY 

Interagency Agreement DE-AI08-97NV12033
Results from Geothermal Logging, Air and 

Core-Water Chemistry Sampling, Air-Injection 

Testing, and Tracer Testing in the Northern Ghost 

Dance Fault, Yucca Mountain, Nevada, 

November 1996 to August 1998

By Gary D. LeCain, Lawrence O. Anna, and Michael F. Fahy

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 99-4210

Prepared in cooperation with the 

NEVADA OPERATIONS OFFICE 

U.S. DEPARTMENT OF ENERGY 

Interagency Agreement DE-AI08-97NV12033

Denver, Colorado 

2000
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Charles G. Groat, Director

Trade names: SEAMIST, FRACMAN, CLUSTRAN

The use of firm, trade, and brand names in this report is for identification purposes only and does 

not constitute endorsement by the U.S. Geological Survey.

For additional information write to:

Chief, Earth Science Investigations Program

Yucca Mountain Project Branch

U.S. Geological Survey

Box 25046, Mail Stop 421

Denver Federal Center

Denver, CO 80225-0046

Copies of this report can be purchased 

from:

U.S. Geological Survey 

Information Services 

Box 25286 

Federal Center 

Denver, CO 80225
CONTENTS

Abstract.................................................................................................................................................................................. 1

Introduction............................................................................................_^ 2

Northern Ghost Dance Fault Alcove and Borehole Construction ......................................................................................... 5

Geology of the Northern Ghost Dance Fault Alcove............................................................................................................. 6

Test and Analysis Methods.................................................................................................................................................... 7

Geothermal Logging in Borehole NAD-GTB#la........................................................................................................ 7

Pneumatic Pressure Monitoring in Borehole NAD-GTB#la...................................................................................... 7

Chemical Sampling in Borehole NAD-GTB#la......................................................................................................... 7

Chemical Sampling in the Northern Drill Room Boreholes........................................................................................ 8

Single-Hole Air-Injection Testing and Analysis in Borehole NAD-GTB#la............................................................. 8

Cross-Hole Air-Injection Testing and Analysis in the Northern Drill Room Boreholes............................................. 10

Test Methods...................................................................................................................................................... 10

Analysis Using Type Curves.............................................................................................................................. 11

Numerical Analysis Using AIR3D.................................................................................................................... 13

Discrete-Feature Analysis Using FRACMAN................................................................................................... 13

Cross-Hole Tracer Testing and Analysis in the Northern Drill Room Boreholes....................................................... 14

TestMemods........................................................^ 14

Analysis Using Type Curves.............................................................................................................................. 15

Discrete-Feature Analysis Using MAFIC ......................................................................................................... 16

Test Results............................................................................................................................................................................ 17

Results from Geothermal Logging in Borehole NAD-GTB#la.................................................................................. 17

Results from Pneumatic Pressure Monitoring in Borehole NAD-GTB#la................................................................. 18

Results from Chemical Sampling in Borehole NAD-GTB#la.................................................................................... 18

Results from Chemical Sampling in the Northern Drill Room Boreholes.................................................................. 22

Results from Single-Hole Air-Injection Testing in Borehole NAD-GTB#la.............................................................. 23

Results from Cross-Hole Air-Injection Testing in the Northern Drill Room Boreholes............................................. 24

Analysis Using Type Curves.............................................................................................................................. 24

Numerical Analysis Using AIR3D.................................................................................................................... 26

Discrete-Feature Analysis Using FRACMAN................................................................................................... 29

Results from Cross-Hole Tracer Testing in the Northern Drill Room Boreholes........................................................ 34

Analysis Using Type Curves.............................................................................................................................. 34

Discrete-Feature Analysis Using MAFIC ......................................................................................................... 34

Summary.................................................................................................................................................................^ 43

References Cited......................................................................................................._^ 46

FIGURES

1-2. Maps showing:

1. Location of the Nevada Test Site and the Exploratory Studies Facility at Yucca Mountain..................................... 3

2. Location of the Ghost Dance Fault, Northern Ghost Dance Fault Alcove and potential repository at

Yucca Mountain........................................................................................................................................................ 4

3-6. Schematic diagrams showing the:

3. Northern Ghost Dance Fault Alcove and test boreholes................................................................................... 5

4. Borehole liner, access ports, and support equipment........................................................................................ 8

5. Single-hole air-injection testing system............................................................................................................ 9

6. Cross-hole air-injection testing system............................................................................................................. 11

7. Temperature plot showing the geothermal logs from borehole NAD-GTB#la........................................................ 17

8. Schematic diagram showing borehole NAD-GTB#la intersection with the Ghost Dance Fault and the

locations of the downhole-monitor intervals............................................................................................................. 18

CONTENTS III
9-17. Graphs showing:

9. Barometric pressure and the pressure responses in the isolated intervals in borehole NAD-GTB#la............. 19

10. Pressure response times distance with time divided by distance squared measured in the footwall

during cross-hole air-injection test 22 and the type curve for spherical flow ................................................... 25

11. Pressure response times distance with time divided by distance squared measured in the fault zone

during cross-hole air-injection test 16 and the type curve for radial flow......................................................... 25

12. pressure responses times distance with time divided by distance squared measured in the

hanging wall during cross-hole air-injection test 19 and the type curve for spherical flow.............................. 26

13. pressure with time measured during air-injection test 16 monitor intervals 6, 15, and 16 located at 

4.4, 4.5, and 4.1 meters from the injection interval and the numerical model predicted pressure 

response at a distance of 4.5 meters from the injection interval....................................................................... 30

14. Pressure changes measured during cross-hole air-injection test 25 and the pressure changes

simulated by the discrete-feature model........................................................................................................... 32

15. Pressure changes measured during cross-hole air-injection test 36 and the pressure changes

simulated by the discrete-feature model........................................................................................................... 33

16. Pressure changes measured during cross-hole air-injection test 32 and the pressure changes

simulated by the discrete-feature model........................................................................................................... 33

17. Sulfur hexafluoride tracer arrival plot during tracer test 10 and type curve match........................................... 36

18. Stereonet plot showing a lower hemisphere plot of transport-porosity values and the three-dimensional

orientation, by bearing and plunge, of the associated tracer tests............................................................................. 37

19-22. Graphs showing:

19. Longitudinal-dispersivity values and test scale for tracer tests performed at or near Yucca Mountain............ 38

20. Tracer-arrival plot for tracer test 17 SF6 and tracer-arrival plot predicted by the discrete-feature model........ 39

21. Tracer-arrival plot for tracer test 21 SF6 and tracer-arrival plot predicted by the discrete-feature model........ 40

22. Tracer-arrival plot for tracer test 15 SF6 and tracer-arrival plot predicted by the discrete-feature model........ 41

23. Diagram showing particle paths predicted by the discrete-feature model for two particles..................................... 42

TABLES

1. Locations, elevations, inclinations, bearings, and depths of the Exploratory Studies Facility

Northern Drill Room Major Faults Boreholes #1, #2 and #3.................................................................................. 6

2. Results of the chemical analysis of the gas-phase samples from borehole NAD-GTB#la.................................... 20

3. Results of the tritium analysis of core-water samples from borehole NAD-GTB#la............................................ 21

4. Results of the chemical analysis of gas-phase samples from borehole NDR-MF#1.............................................. 22

5. Results of the chemical analysis of gas-phase samples from borehole NDR-MF#2.............................................. 23

6. Results of the University of Miami tritium analysis of core-water samples from borehole NDR-MF#1............... 23

7. Permeability values from air-injection testing in borehole NAD-GTB#la............................................................. 24

8. Permeability and porosity values from cross-hole air-injection testing using borehole NDR-MF#2 for

injection and borehole NDR-MF#1 for monitoring................................................................................................ 27

9. Permeability and porosity values from cross-hole air-injection testing using borehole NDR-MF#3 for

injection and borehole NDR-MF#1 for monitoring................................................................................................ 27

10. Permeability and porosity values from cross-hole air-injection testing using borehole NDR-MF#3 for

injection and borehole NDR-MF#2 for monitoring................................................................................................ 28

11. Permeability and porosity values from cross-hole air-injection testing using borehole NDR-MF#1 for

injection and borehole NDR-MF#3 for monitoring................................................................................................ 28

12. Permeability and porosity values from cross-hole air-injection testing using borehole NDR-MF#1 for

injection and borehole NDR-MF#2 for monitoring................................................................................................ 28

13. Statistical summary of permeability values from the type-curve analytical solutions of cross-hole

air-injection testing of the northern Ghost Dance Fault.......................................................................................... 29

14. Statistical summary of porosity values from the type-curve analytical solutions of cross-hole air-injection

testing of the northern Ghost Dance Fault.............................................................................................................. 29

15. Input parameters of the six fracture sets used to produce the FRACMAN discrete-features model...................... 31

16. Input parameters of the three additional fracture sets used in the fault zone to produce the

FRACMAN discrete-features model....................................................................................................................... 31

IV CONTENTS
17. Transmissivity distributions and equivalent permeability values for the discrete-feature model........................... 32

18. Results of tracer-test analysis by type curves......................................................................................................... 35

19. Statistical summary of the northern Ghost Dance Fault transport-porosity and longitudinal-dispersivity

values by geologic structure.................................................................................................................................... 36

CONVERSION FACTORS, ABBREVIATIONS, AND VERTICAL DATUM

Multiply By To obtain

centimeter (cm)

cubic meter (m3)

cubic meter per second (m3/s)

kilogram per cubic meter (kg/m3)

kilogram per cubic meter per second (kg/m3/s)

kilometer (km)

kilopascal (kPa)

liter (L)

meter (m)

square meter (m2)

square meter per second (m2/s)

meter per second (m/s)

micrometer (|Llm)

millimeter (mm)

Pascal (Pa)

Pascal second (PaXs)

standard liter per minute (sLpm)*

0.394

35.341

15,852.0

0.062

3.72

0.6214

0.145

0.264

2.281

10.765

645.9

196.850

3.94 x 10'7

0.0394

1.45x104

10.0

0.2642

inch

cubic foot

gallon per minute

pound per cubic foot

pound per cubic foot per minute

mile

pound-force per square inch

gallon

foot

square foot

square foot per minute

foot per minute

inch

inch

pound-force per square inch

poise

gallons per minute

In this report, the term standard means a measurement taken at a temperature of 0 degree Celsius and atmospheric pressure of 

101.3kilopascals.

TU is tritium unit and corresponds to one 3H atom per 10 18 atoms of hydrogen.

Temperature in degree Celsius (°C) can be converted to degree Fahrenheit (°F) as follows: 

°F=1.8(°C) + 32

The permeability equations use kelvin. To convert kelvin (K) to degrees Fahrenheit (°F) use the following formula: 

°F = 9/5(K)-459.67

Sea level: In this report "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929) a geodetic datum 

derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level 

Datum of 1929.

CONTENTS
ADDITIONAL ABBREVIATIONS

DLS detailed line survey

DOE Department of Energy

DTN data tracking number

ESF Exploratory Studies Facility

GDF Ghost Dance Fault

GTB geothermal borehole

MF major fault

NAD northern access drift

NDR northern drill room

NGDFA Northern Ghost Dance Fault Alcove

PDB Pee Dee Belemnite Formation of North Carolina

pmc percent modern carbon

ppm parts per million

TU tritium units

Tptpmn Tertiary Paintbrush Topopah Spring crystal-poor middle nonlithophysal

USGS U.S. Geological Survey

YMP Yucca Mountain Project

VI CONTENTS
Results from Geothermal Logging, Air and CoreWater Chemistry Sampling, Air-Injection Testing, 

and Tracer Testing in the Northern Ghost Dance 

Fault, Yucca Mountain, Nevada, November 1996 to 

August 1998

By Gary D. LeCain, Lawrence O. Anna, and Michael F. Fahy

Abstract

Geothermal logging, air and core-water 

chemistry sampling, air-injection testing, and 

tracer testing were done in the northern Ghost 

Dance Fault at Yucca Mountain, Nevada, from 

November 1996 to August 1998. The study was 

done by the U.S. Geological Survey, in cooperation with the U.S. Department of Energy. The 

fault-testing drill room and test boreholes were 

located in the crystal-poor, middle nonlithophysal 

zone of the Topopah Spring Tuff, a tuff deposit of 

Miocene age. The drill room is located off the 

Yucca Mountain underground Exploratory 

Studies Facility at about 230 meters below ground 

surface. Borehole geothermal logging identified a 

temperature decrease of 0.1 degree Celsius near 

the Ghost Dance Fault. The temperature decrease 

could indicate movement of cooler air or water, 

or both, down the fault, or it may be due to 

drilling-induced evaporative or adiabatic cooling. 

In-situ pneumatic pressure monitoring indicated 

that barometric pressure changes were transmitted 

from the ground surface to depth through the 

Ghost Dance Fault. Values of carbon dioxide 

and delta carbon-13 from gas samples indicated 

that air from the underground drill room had 

penetrated the tuff, supporting the concept of a 

well-developed fracture system. Unconnected 

carbon-14-age estimates from gas samples ranged 

from 2,400 to 4,500 years. Tritium levels in borehole core water indicated that the fault may have 

been a conduit for the transport of water from the 

ground surface to depth during the last 100 years. 

Cross-borehole air-injection testing identified three zones that had different permeability 

and porosity values. The three zones corresponded to the structural units: footwall, fault 

zone, and hanging wall. The fault zone is a highpermeability zone associated with the main trace 

of the Ghost Dance Fault. Type-curve analysis 

indicated that the arithmetic mean of permeability 

values and of porosity values from the three struc1 O

tural units are: footwall 8.7 x 10 meter squared, 

and 0.04; fault zone 18.1 x 10" 12 meter squared, 

and 0.13; hanging wall 5.0 x 10" 12 meter squared, 

and 0.04. The three individual zones were homogeneous and isotropic. Numerical analysis using 

the U.S. Geological Survey AIR3D computer 

code indicated that the permeability and porosity

1 O

values were: footwall 10.0 x 10 meter squared, 

and 0.07; fault zone 20.0 x 10" 12 meter squared, 

and 0.20; hanging wall 5.0 x 10" 12 meter squared, 

and 0.05. Analysis using a discrete-featurenetwork model successfully matched the pressure 

responses from the tests in the footwall and in the 

hanging wall but not in the fault zone. The 

discrete-feature-network model replicated the 

fracture networks and permeability in the footwall 

and hanging wall, but the fault zone was too 

broken to be analyzed using a discrete-feature 

model. Results from the discrete-feature model

Abstract
indicated that it may be possible to increase the 

scale of the discrete-feature simulations to predict 

pressure responses at larger dimensions for areas 

that have fracture networks similar to the fracture 

networks in the footwall and hanging wall of the 

Ghost Dance Fault.

Cross-hole convergent-tracer tests had 

advective traveltimes that ranged from 0.011 to 

1.110 days. Longitudinal-dispersivity values 

ranged from 0.06 to 2.63 meters. Tracer tests done 

in the footwall of the Ghost Dance Fault had 

transport-porosity values that ranged from 0.003 

to 0.032 and had an average of 0.013. Tracer tests 

done in the fault zone had transport-porosity 

values that ranged from 0.004 to 0.034 and had an 

average of 0.014. Tracer tests done in the hanging 

wall had transport-porosity values that ranged 

from 0.001 to 0.070 and had an average of 0.013. 

The wide range in transport-porosity values may 

indicate that the test scale was smaller than the 

representative elementary volume. The tracer tests 

did not identify any directional control; slow and 

fast tracer-transport pathways occur in the same 

direction and plunge. Particle tracking using the 

discrete-feature model identified flow paths that 

were as much as six times longer than the linear 

distance. The long flow paths are a partial explanation of the large transport-porosity values. 

Results from the discrete-feature model indicated 

that it may be possible to increase the scale of the 

discrete-feature simulations to predict traveltimes 

at larger dimensions for areas that have fracture 

networks similar to the footwall and hanging wall 

of the Ghost Dance Fault.

INTRODUCTION

The Yucca Mountain Project (YMP) is a scientific study by the U.S. Department of Energy (DOE) to 

evaluate the potential for geologic disposal of highlevel radioactive waste in an unsaturated-zone desert 

environment. The potential repository site at Yucca 

Mountain is located approximately 130 kilometers 

(km) northwest of Las Vegas, Nevada, near the DOE 

Nevada Test Site (fig. 1). The U.S. Geological Survey

(USGS) has been conducting geologic and hydrologic 

studies of the potential repository site for the DOE. 

These studies are to quantify the geologic and hydrologic characteristics of Yucca Mountain and to 

conceptualize and model gas and liquid flow at the 

potential repository site.

Geothermal logging, air and core-water chemistry sampling, air-injection testing, and tracer testing 

were done at Yucca Mountain in the northern Ghost 

Dance Fault (GDF). The GDF was accessed through 

the Northern Ghost Dance Fault Alcove (NGDFA) that 

was constructed off the Yucca Mountain underground 

Exploratory Studies Facility (ESF). The goals of the 

fault testing were to quantify the permeability values, 

porosity values, tracer-transport characteristics (transport porosity and longitudinal dispersivity), and fluid 

ages of water in the GDF and the volcanic rocks (tuff) 

of the footwall and the hanging wall. The permeability, porosity, and tracer-transport characteristics of 

these tuffs control the movement of fluids in Yucca 

Mountain. Study of these parameters provides a 

conceptual understanding of local fluid flow in the 

unsaturated zone at Yucca Mountain. Quantified 

values of these parameters can be used in numerical 

modeling of the unsaturated zone to estimate fluid flux 

and transport through the mountain. Potential fluid 

movement in Yucca Mountain includes the transmission of water from the surface to the potential repository horizon, and below the horizon, and the 

transmission of gases from the potential repository 

horizon to the ground surface. Knowledge of the 

spatial and directional variability of the permeability 

and tracer-transport characteristics of the GDF is 

needed to formulate conceptual models and is needed 

as input to flow and transport models that attempt to 

represent the flow system at Yucca Mountain. This 

report presents the results from geothermal logging, 

gas and core-water chemistry sampling, air-injection 

testing, and tracer testing done in the NGDFA from 

November 1996 through August 1998. The location of 

the NGDFA and its relation to the potential repository 

are shown in figure 2.

Data presented in this report are classified as 

quality assured and non-quality assured. The qualityassured designation indicates that the data were 

collected following a YMP-approved quality-assurance program. The non-quality assured designation 

does not reflect on the accuracy or validity of the data 

but does indicate that the data may not have been

Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
36°45' -

Nevada 

Test Site 

Boundary

Amargosa Valley 

(Lathrop Wells)

116°20'

Base from U.S. Geological Survey 

1:250,000, Death Valley, California: 

Nevada, 1970

10 KILOMETERS

10 MILES

Figure 1. Location of the Nevada Test Site and the Exploratory Studies Facility at Yucca Mountain.

INTRODUCTION
Drill Hole Wash Fault

Exploratory Studies Facility 

Bow Ridge Fault

Northern Ghost Dance 

Fault Alcove

Potential repository

Solitario Canyon Fault

1 KILOMETER

J_________

1 MILE

Figure 2. Location of the Ghost Dance Fault, Northern Ghost Dance Fault Alcove, and potential repository at 

Yucca Mountain.

Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
collected under a YMP-approved quality-assurance 

program. As a part of the YMP quality-assurance 

program the data presented in this report are identified 

by data tracking numbers (DTN). A summary of the 

data, the DTNs, and the data quality-assurance status 

are included at the end of this report. All data 

presented in this report, with the exception of the 

tritium data, are classified as quality assured.

NORTHERN GHOST DANCE FAULT 

ALCOVE AND BOREHOLE 

CONSTRUCTION

The NGDFA was constructed in the YMP ESF 

during the second half of 1996 and the first half of 

1997. The NGDFA consists of two sections the 

northern GDF Access Drift (NAD), which provided

access to the northern GDF Drill Room (NDR), which 

in turn provided a drilling and test room where test 

boreholes could be drilled into the fault (fig. 3). The 

NAD is located 3,737 m into the ESF (measured from 

the north entrance) and is about 230 m below the 

ground surface. The NAD and the NDR were excavated using a continuous miner. The NAD was initially 

constructed at a heading of due east (fig. 3) to a depth 

of 105 m (measured from the ESF centerline). From 

the face of the NAD, borehole NAD-GTB#la was 

drilled horizontally, at a heading of due east, to a 

depth of 60 m and penetrated the GDF at a depth of 

about 49 m. A downhole video log was run on 

November 1, 1996, and a geothermal log on 

November 7, 1996. After the geothermal logging was 

completed, excavation of the NAD continued to a 

depth of 134.4 m, eliminating the upper 29.4 m of 

borehole NAD-GTB#la. Geothermal logging,

V)

LLJ

Q

i

cc 

o

Q. 

X

LU

GHOST DANCE FAULT ZONE

HANGING WALL

BOREHOLE NDRMF #1

BOREHOLE 

NDRMF #3

BOREHOLE NDRMF #2

NORTHERN GHOST DANCE 

FAULT ACCESS DRIFT

FOOTWALL EAST

NORTHERN GHOST DANCE FAULT 

DRILL ROOM

BOREHOLE 

NDRMF #3

BOREHOLE 

NDRMF #2

BOREHOLE 

NDRMF #1

FRONT VIEW

OVERHEAD VIEW

Figure 3. Northern Ghost Dance Fault Alcove and test boreholes.

NOT TO SCALE

NORTHERN GHOST DANCE FAULT ALCOVE AND BOREHOLE CONSTRUCTION 5
hydrochemistry sampling, and air-injection testing 

were done in the remaining section of the borehole. 

After the testing was completed, construction of the 

NAD continued to a depth of 174 m. The NAD intersected the GDF at a depth of 152.1 to 152.7 m.

Following construction of the NAD and the 

NDR (May 1997), three horizontal boreholes were 

drilled from the NDR into the GDF. The boreholes 

were parallel and in a triangular configuration (fig. 3). 

The boreholes were dry-drilled and cored. A tracer gas 

of 1.0 part per million (ppm) sulfur hexafluoride (SF$) 

was added to the drilling air. The borehole diameter 

was 10 cm and the core diameter was 6.2 cm. The 

locations, elevations, inclinations, bearings, and 

depths of the three Major Faults (MF) boreholes are 

listed in table 1.

Boreholes MF#1 and MF#2 were drilled in May 

and June 1997. Borehole MF#3 was drilled in October 

1997. Following the completion of each borehole, 

downhole video and caliper logs were run.

Table 1 . Locations, elevations, inclinations, bearings, and 

depths of the Exploratory Studies Facility Northern Drill 

Room Major Faults Boreholes #1, #2, and #3

Borehole

MF#1

MF#2

MF#3

Elevation 

(meters)

1,072.0

1,072.0

1,075.3

Inclination

+00°39'58"

+00°27'44"

+01°42'07"

Bearing

N271°14' 08"

N270°49'41"

N271°29'02"

Depth 

(meters)

30.5

30.6

34.4

GEOLOGY OF THE NORTHERN GHOST 

DANCE FAULT ALCOVE

The NGDFA and the MF boreholes are located 

in the crystal-poor, middle nonlithophysal zone, 

Topopah Spring Tuff (Tptpmn) of Miocene age. Borehole NAD-GTB#la was drilled from the hanging 

wall of the GDF through the fault and into the footwall. The initial geologic interpretations of the fault 

and the broken zone (interval of intense fracturing) 

were based on video and caliper logs from borehole 

NAD-GTB#la (DTN: LARO831422AQ97.001). The 

video logs identified the fault location at about 154 m 

from the ESF and identified a 12-m-wide broken zone. 

The 12-m-wide broken zone extended from 143 to 

155 m, was variably brecciated, and consisted of fractured rock that had matrix- and clast-supported breccia 

zones. Following NAD excavation through the fault, 

geologic mapping identified the GDF as being located

between stations 152.1 and 152.7 m on the right wall 

at spring line. The exposed brecciated zone is a 0.6- to 

1-m-thick, matrix-supported, uncemented fault breccia 

that is derived from the wall rock. The footwall is 

intensely fractured from 152.7 m to 153.7 m and is 

slightly fractured from 153.7 m to 157.7 m. The 

hanging wall is moderately to intensely fractured from 

142.1 m to the fault at 152.1 m. Distinct planes along 

the hanging wall and the footwall were not evident, 

and no slickensides were visible. The GDF is a normal 

fault with a strike/dip of 180/80 on the footwall and 

175/82 on the hanging wall. The fault offset is approximately 3 m. The fault breccia is 60 percent matrix that 

consists primarily of clay- to sand-size particles and 

40 percent rotated clasts that are angular to subangular 

and are as much as 20 cm in size. Average clast size is 

about 5 cm, and clasts are derived from the wall rock. 

No secondary calcite or silica/opal was visible in the 

breccia or surrounding rock (G.L.W. Eatman and 

others, Bureau of Reclamation, written commun., 

1997, p. 168).

The three boreholes (MF#1, MF#2, and MF#3) 

intersected the GDF at depths of 13.6, 13.9, and 

12.7 m, respectively. Downhole video and caliper logs 

identified an intensely fractured zone that extended 

from the main trace of the GDF about 1 m into the 

footwall and 3 m into the hanging wall. The intensely 

fractured zone is herein referred to as the "fault zone." 

Drilling logs (DTN:LARO831422AQ97.002) describe 

the footwall core samples as an ash-flow tuff that is 

densely welded, devitrified, and pale red; has minor 

pumice that is light gray to pale red; and that contains 

rare felsic and mafic lithic fragments that are 10 by 

20 millimeters (mm) thick. The hanging wall is 

described as an ash-flow tuff that is grayish-orange 

pink; has 5 percent or less pumice that is very light 

gray, moderately flattened, and generally 10 mm or 

less in size; and has rare lithic fragments that are pale 

red to very light gray, angular to rounded, and are 2 to 

5 mm in diameter. The footwall had a crushed appearance and tight anastomosing fractures of short length. 

The rock in the hanging wall is intact; pumice and 

lithic fragments are clearly visible. The fractures in the 

hanging wall are long and have various orientations. 

Many of the fractures in the hanging wall have 

measurable apertures (G.L.W. Eatman and others, 

Bureau of Reclamation, written commun., 1997).

Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
TEST AND ANALYSIS METHODS

Field testing of the GDF was done from 

November 1996 to August 1998. The testing included: 

(1) video, caliper, and geothermal logging, (2) pneumatic monitoring, (3) gas and water chemistry 

sampling, (4) single and cross-hole air-injection 

testing, and (5) cross-hole tracer testing. The gas and 

water samples were analyzed for CO2, 613C, 14C, and 

3H. Air-injection and tracer-test analysis included 

analytical and numerical methods.

Geothermal Logging in 

Borehole NAD-GTB#1a

Geothermal logging was done in borehole 

NAD-GTB#la on November 7, 1996, and on 

December 3, 1996. The first geothermal log 

(November 7) was done when the borehole collar was 

located at 105 m from the ESF centerline and the borehole depth was 60 m. The second geothermal log was 

obtained on December 3 after the NAD had been 

extended to 134.4 m and the upper 29.4 m of the borehole had been excavated. The downhole-temperature 

logging tool consisted of a thermistor that had a very 

low thermal mass and was attached to a thin (approximately 100 urn) copper foil. The sensor was pressed 

against the borehole wall by a steel bowspring. The 

temperature resolution is approximately one millionth 

of a degree Celsius, and the temperature stabilization 

time is 1 second (John Sass, U.S. Geological Survey, 

oral commun., 1997). The first phase of logging was to 

insert the temperature logging tool to the bottom of the 

borehole and allow the tool to equilibrate for 5 to 10 

minutes. Following equilibration, the temperature 

logging tool was withdrawn from the borehole and a 

continuous temperature profile was obtained. To limit 

heating caused by friction between the sensor and the 

borehole wall, the withdrawal speed was limited to 

1 m per 3 minutes. This slow withdrawal limited the 

friction heating to 0.01 °C or less.

Pneumatic Pressure Monitoring in 

Borehole NAD-GTB#1a

In-situ pneumatic pressures were monitored in 

borehole NAD-GTB#la from December 19,1996, to 

January 10, 1997. The downhole pneumatic pressures

were monitored using a 30-m-long borehole liner and 

an uphole pressure transducer. The borehole liner is a 

flexible tube, 0.1 m in diameter, that is inverted into 

the borehole using internal pressure. The borehole 

liner contains 10 access ports that are connected to the 

uphole borehole collar by small-diameter nylon tubes. 

A schematic of the liner, access ports, and tubes is 

shown in figure 4. Once installed into the borehole, 

the internal pressure of the liner is maintained at 3.4 to 

6.9 kPa. The internal pressure forces the liner against 

the borehole wall, isolating the borehole and creating 

monitor intervals of about 0.25 m in length that are 

separated from each other by from 1.5 to 3.0 m. Each 

isolated downhole-monitor interval contains an access 

port that was connected to a nylon tube that extended 

from the access port up the boreholes to the NDR. The 

nylon-access-port tubes were then connected to a solenoid valve and pressure transducer, and the pneumatic 

pressures in the isolated downhole-monitor intervals 

were recorded by a data logger.

Chemical Sampling in 

Borehole NAD-GTB#1a

Gas-phase chemistry samples were collected in 

borehole NAD-GTB#la from December 4, 1996, to 

January 14, 1997, using the borehole liner (fig. 4). To 

obtain gas samples, the nylon-access-port tubes were 

connected to peristaltic pumps, and gas samples were 

pumped from the isolated downhole-monitor intervals. 

Gas samples for carbon-14 analysis were collected in 

molecular sieves. Gas samples for delta carbon-13 

analysis were collected in mylar balloons. Before the 

gas sampling, the monitor intervals were pumped to 

evacuate any atmospheric and drilling-injected air. 

Carbon dioxide (CO2) and SF6 (used as a drilling-air 

tracer) were monitored using a gas chromatograph 

throughout the pumping period to assess the removal 

of the atmospheric and drilling-injected air and to 

determine when the gas sample represented that of 

rock gas. Stable CO2 concentrations at levels substantially higher than atmospheric air (350 ppm) or alcove 

air (450 ppm) indicated that the gas being pumped 

from the borehole was rock gas. Low SF6 concentrations (on the order of 0.01 ppm) also indicated that the 

drilling air had been successfully removed from the 

isolated downhole-monitor intervals. Water samples 

for tritium analysis were obtained from core from the 

borehole by using a vacuum distillation system. Most

TEST AND ANALYSIS METHODS
NYLON TUBES

BOREHOLE

CRANK

CANISTER

Figure 4. Borehole liner, access ports, and support equipment.

of the tritium analyses were done by the USGS in 

Denver, Colorado, and a few samples were sent to the 

University of Miami, Florida. The USGS used a liquid 

scintillation counter. The University of Miami used 

enriched samples and a gas-proportional counter; 

therefore, the Miami results had smaller standard deviations.

Chemical Sampling in the Northern Drill 

Room Boreholes

Gas-phase chemistry samples were collected in 

boreholes MF#1 and MF#2 from August 4 to August 

20, 1998, using the borehole liner (fig. 4). The gas 

sampling and analysis were identical to those done in 

borehole NAD-GTB#la. Water samples for tritium 

analysis were obtained from core from borehole MF#1 

and analyzed at the University of Miami.

Single-Hole Air-Injection Testing and 

Analysis in Borehole NAD-GTB#1a

Single-hole air-injection testing was done in 

borehole NAD-GTB#la from January 15 to February 

23, 1997. A schematic of a single-hole air-injection 

testing system is shown in figure 5. The field equipment consisted of the downhole-packer system, the 

air-injection system, and the data-acquisition system. 

Test intervals were selected from a review of the 

borehole video logs. Following the selection of a test 

interval, two pneumatic packers were inserted into 

the borehole and straddled the selected test interval. 

The packers then were inflated, using compressed 

air, isolating the test interval. After the packers were 

inflated and the pressure in the test interval had 

stabilized, compressed air was injected into the 

isolated test interval through a nylon tube that 

connected the test interval to an uphole air compressor. 

Sulfur hexafluoride was added to the injection air as a 

tracer (10.0 ppm), and the air-injection rate was 

controlled and monitored by mass-flow controllers. 

The absolute pressure and temperature in the test 

interval were monitored by a pressure transducer and a 

thermistor mounted between the downhole packers. 

All data were recorded on a data logger. The pressure 

responses measured in the test intervals usually 

showed an initial pressure increase followed by a 

period of decreasing pressure. The period of 

decreasing pressure was due to water redistribution 

(LeCain, 1998). Air injection was continued until the 

test-interval pressure neared steady state approximately 10 minutes. Twelve of the 13 test intervals had 

lengths of 1 m; one test interval had a length of 12 m.

Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
NORTHERN GHOST DANCE 

FAULT ACCESS DRIFT

FRACTURE 

AIR FLOW

FRACTURES

NOT TO SCALE

Figure 5. Single-hole air-injection testing system.

Initial permeability values were calculated for 

each test using a modified version of the Hvorslev 

(1951, p. 31, case 8) steady-state solution. The solution is for elliptical flow when the length of the injection interval is substantially greater than the radius of 

the injection interval. The analysis was developed to 

evaluate flow in an equivalent porous medium (gravel 

and alluvium). Application of the method to fractured 

tuff assumes that the fracture-flow system is sufficiently connected and extensive so that the fractured 

tuff could be treated as an equivalent porous medium. 

The full derivation of equation 1 is presented in 

LeCain (1997, p. 6 and 7).

PSC Qs

k =

In \-?-

L (PSS2 -P20 ) Ts

(1)

Q.sc

- standard pressure, in pascals;

= flow rate at standard conditions, in cubic

meters per second;

\JL = dynamic viscosity, in pascal seconds; 

L = injection-interval length, in meters; 

rw = borehole radius, in meters; 

T = injection air temperature, in kelvin; 

Pss = pressure at steady state, in pascals; 

PQ = pressure at time zero, in pascals; and 

Tsc = temperature at standard conditions, in

kelvin.

To evaluate turbulence, multiple tests at variable 

flow rates were done on each test interval. Air-injection rates ranged from 10 to 800 standard liters per 

minute (sLpm). A more detailed examination of turbulence in air-injection testing in fractured rock is available in LeCain (1998). Ramey (1982) developed the 

generalized equation,

where 

k = permeability, in meters squared; where

Hw = BQ + CQ' (2)

TEST AND ANALYSIS METHODS
Hw = drawdown, in meters;

B = formation-loss term, in seconds per meter

squared;

Q - flow rate, in cubic meters; 

C = well-loss term, units dependent on exponent

n; and 

n = exponent less than 2.

The first term on the right of equation 2 represents laminar flow conditions where Darcy's law is 

valid. The second term represents non-Darcian flow 

due to turbulence in the borehole or in the fractures. 

The drawdown during Darcian (laminar) flow can be 

represented by the first term only. During non-Darcian 

flow, the second term needs to be included. Air-injection testing in fractured rock generally involves a 

combination of laminar and turbulent fracture flow.

Equation 2 was modified for air-injection testing 

by substitution of (Pss2- P#2) for drawdown, and both 

sides of the equation were divided by the flow rate 

(Qsc) to yield equation 3,

Q, sc

(3)

where

Pss = steady-state pressure squared, in pascals 

squared; and

^

PQ = pressure squared at time zero, in pascals

squared.

Assuming that n = 2.0, equation 3 indicates that 

an arithmetic plot of the steady-state (Pss2- P02)/QSC 

values, from multiple flow-rate tests, on the y-axis and 

the Qsc values on the x-axis gives a y-intercept equal 

to B when Qsc is zero. As Q approaches zero, Darcy's 

law is valid; that is, there are no turbulent or inertial 

effects. Equations 1 and 3 can then be combined in 

equation 4 to provide a laminar-flow air-injection 

permeability value that is based on the zero-flow 

intercept B.

, _

M- (4)

Non-Darcian flow was identified as a decrease 

in the calculated permeability values with increasing 

flow rates. A check was done by preparing arithmetic

and log-log plots that had the air-injection pressure 

squared differences (Ps 2 - P02) on the y-axis and the 

flow rate (Q) on the x-axis. Darcian (laminar) flow 

(Hw = BQ) was indicated by a linear arithmetic plot 

and a log-log plot with a slope of one. A nonlinear 

arithmetic plot and a log-log plot that had a slope 

greater than one indicated non-Darcian flow. A slope 

of zero would indicate laminar flow, and a positive 

slope would indicate turbulence. The plot was extrapolated to the y intercept, and the intercept was used in 

equation 4 to calculate the fractured-rock permeability 

values presented in this report.

Cross-Hole Air-Injection Testing and 

Analysis in the Northern Drill Room 

Boreholes

Test Methods

Cross-hole air-injection tests were done 

between the three NDR boreholes in three phases from 

August 1997 to June 1998. Cross-hole testing 

consisted of injecting air into an isolated interval of 

a borehole (injection borehole) and monitoring the 

pressure response in isolated monitor intervals in other 

boreholes (monitor boreholes). The first phase of 

testing was done following the construction of boreholes MF#1 and MF#2; the testing consisted of 

11 tests using borehole MF#1 as the monitor borehole 

and borehole MF#2 as the injection borehole. 

Following the construction of borehole MF#3, the 

second phase of testing was done; testing consisted of 

13 tests using boreholes MF#1 and MF#2 as monitor 

boreholes and borehole MF#3 as the injection borehole. The third phase of testing consisted of 13 tests 

using boreholes MF#2 and MF#3 as monitor boreholes and borehole MF#1 as the injection borehole. 

The injection borehole was instrumented with the 

same dual-packer gas-injection system used in the 

single-hole air-injection testing. The monitor boreholes were each fitted with 10 packers that separated 

each monitor borehole into 10 pressure-monitor intervals. A schematic of the NDR cross-hole air-injection 

testing system is shown in figure 6. The packer lengths 

for the monitor boreholes ranged from 1.0 to 8.0 m, 

and the monitor-interval lengths ranged from 0.6 to 

4.0 m. Each packer was connected to an uphole 

packer-inflation panel by a 0.5-mm high-pressurenylon inflation tube. The packer-inflation panel was

10 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
BOREHOLE

,NDRMF#3

INJECTION OR PUMPED INTERVAL

PACKERS

NOT TO SCALE

Figure 6. Cross-hole air-injection testing system.

used to inflate the packers and to monitor the 

individual packer-inflation pressures. Each monitor 

interval was connected to an uphole pressure-transducer panel by a 1.0-mm nylon tube. Each monitorinterval tube had a dedicated pressure transducer that 

measured the absolute pressure in the monitor intervals. In addition, the tubes could be disconnected from 

the pressure transducers and used for gas sampling or 

tracer-gas injection. The air-injection rate for the

cross-hole testing was 500 sLpm and was monitored 

and controlled by mass-flow controllers. Air was 

injected until the pressure in the injection interval and 

in the monitor intervals neared steady state, about 3 

hours.

Analysis Using Type Curves

Type-curve analysis included an initial examination of the shape and the steady-state values of the

TEST AND ANALYSIS METHODS 11
pressure responses in the injection and the monitor 

intervals. The pressure responses were examined to 

identify any patterns that would indicate any effects of 

direction or location on the permeability and porosity 

of the fractured tuff. The initial examination included 

composite log-log plots that were normalized by plotting the monitor-interval pressure squared differences 

times the radial flow distance on the y-axis and time 

divided by the radial flow distance squared on the 

x-axis. If the medium is homogeneous and isotropic, 

the normalized data plots will form a single curve. 

Following the initial examination, type-curve 

matching was used to analyze the pressure responses 

of the monitor intervals. The analysis of tests done in 

the hanging wall and the footwall assumed a spherical 

flow geometry and used the complementary error 

function to estimate permeability and porosity values. 

The analysis was developed to evaluate flow in an 

equivalent porous medium; therefore, application of 

the method to fractured tuff assumes that the fractureflow system is sufficiently connected and extensive so 

that Jthe fractured tuff could be treated as an equivalent 

porous medium. The full solution is presented in 

LeCain (1995, p. 12). The analysis assumed that the 

injection and the monitor intervals could be represented as points in a large homogeneous and isotropic 

system. The solution defines the change in dimensionless pressure as,

(5)

nkrP? Tsc

(9)

where

erfc = complementary error function; 

PD = dimensionless pressure; 

P= pressure, in pascals; 

PI= initial pressure, in pascals; 

rD= dimensionless radius; 

rw = well radius, in meters; 

r= radius, in meters; 

tD = dimensionless time; 

k= permeability, in square meters; 

t = time, in seconds;

(|) = porosity, in cubic meters per cubic meter; 

ji= gas dynamic viscosity, in pascal seconds; 

c= average gas compressibility, in pascal . 

qD = dimensionless flow; 

Psc= pressure at standard conditions, in pascals; 

Z= gas constant (assumed to be 1.0), dimensionless;

T= temperature, in kelvin; 

qsc= gas flow at standard conditions, in cubic

meters per second; and 

Tsc= temperature at standard conditions, in

kelvin.

A log-log plot of the pressure-squared differences on the y-axis and time on the x-axis (t = 0 at 

start of the injection test) was overlaid on the type 

curve defined by equation 5 and a match point was 

selected. By using the match point variables, the 

permeability value is

where k = (10)

2 2 

(P ~P\f ) and porosity is calculated by

(7)

ktc

D

D

(11)

* -~

kt

_ 2

Analysis of the tests done in the fault zone 

assumed a radial flow geometry and used a modified 

(8) version of the Theis (1935) exponential integral function to estimate the permeability and porosity values.

12 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
The solution defines the change, in dimensionless 

pressure (Earlougher, 1977, p. 192) as

where

Ei= exponential integral function.

The parameters used in equation 12 are identical to 

those defined for equation 5 except for,

* Tsc

(13)

where 

h = length of the injection interval, in meters.

A log-log plot of the pressure squared differences on the y-axis and time on the x-axis (t = 0 at 

start of the injection test) was overlain on the type 

curve and a match point was selected. By using the 

match point variables, the permeability value is

k =

AP2 /i

(14)

Porosity is calculated by using the same equation that 

was used in the spherical flow solution, equation 11.

Numerical Analysis Using AIR3D

Following the type-curve analysis, a numerical 

model of the northern GDF flow system was developed using the USGS finite-difference model AIR3D 

(Joss and Baehr, 1995). Computer code AIR3D adapts 

the ground-water flow simulator MODFLOW 

(McDonald and Harbaugh, 1988) for use with threedimensional air flow in unsaturated flow systems. A 

finite-difference numerical model of the footwall, fault 

zone, and hanging wall was developed. The numerical 

model was based on the geological interpretations of 

the NAD and the NDR (G.L.W. Eatman and others, 

Bureau of Reclamation, written commun., 1997); the 

borehole video logs; and personal inspection of the 

NAD footwall, fault zone, and hanging wall. The

model used an equivalent continuum approach that 

had a grid of 40 layers, 25 columns, and 25 rows. The 

model layers had a constant 2-m dimension, whereas 

the column and row dimensions ranged from 0.1 m at 

the center of the grid to as much as 10 m at the boundaries. The dimensions were selected to ensure 

boundary effects would not affect the simulation 

results. The model assumed a heterogeneous flow 

system that had three homogeneous-isotropic zones. 

The three zones corresponded to the footwall, fault 

zone, and hanging wall. The model was scaled, and the 

grid nodes were identified that matched the air-injection and monitor intervals in order to replicate the 

three-dimensional cross-hole air-injection field testing. 

The model was run using air-injection grid nodes and 

mass-flow rates that replicated selected field tests. At 

the completion of the model run, plots of the grid-node 

pressure responses, which represented monitor intervals, were visually compared to the field-test pressure 

responses. By using these comparisons, the simulated 

permeability and porosity values were adjusted, and 

the model was rerun. The rerun pressure responses 

again were compared to the field pressure responses. 

This iterative process was repeated using different 

permeability and porosity values, different air-injection grid nodes, and different monitor-interval grid 

nodes until a satisfactory match between the simulated 

pressure responses and the field pressure responses 

were obtained.

Discrete-Feature Analysis Using FRACMAN

Following the analytical and the numerical 

analysis, a discrete-feature network (DFN) model was 

developed using the computer code FRACMAN 

(Dershowitz and others, 1994). The objective of the 

DFN modeling was to develop a fracture-flow model 

that represents the GDF fracture system more accurately than the equivalent porous-medium models. 

A better understanding of the fracture-flow process 

may be valuable for predicting flow and transport at 

other locations and at different scales. The DFN 

analysis used the forward modeling approach of 

FRACMAN to develop a three-dimensional DFN 

model. The geometry and spatial distributions for the 

fracture systems in the model were based on the 

detailed line survey (DLS) fracture data from the NAD 

and NDR. The DLS fracture mapping mapped only 

fractures with trace lengths greater than 30 cm (DTN:

TEST AND ANALYSIS METHODS 13
LARO970808314224.014). Fracture lengths ranged 

from 30 cm to 22 m.

The DLS fracture data were analyzed using 

CLUSTRAN fracture-analysis software and visual 

inspections of equal-area Schmidt plots. Fracturedistribution types and fracture amounts were defined 

for orientation, size, intensity, and dispersion. Fracture 

intensity was based on the scale-independent ratio of 

fracture area to rock volume. The fractures were classified into fracture sets based on their dip and strike. 

The fracture-set lengths were analyzed to determine a 

mean, standard deviation, and distribution type. The 

fracture data were used to estimate an effective fracture radius (or size) from the trace length distribution 

using the FRACMAN-FRACSYS module.

Fracture size is related to fracture area per rock 

volume and is a direct input parameter into the threedimensional DFN model. The FRACSYS algorithm 

allows an initial estimate of the fracture size distribution and simulates a length distribution. The initial 

estimate was changed by optimization algorithms until 

the simulated length distribution matched the mapped 

length distribution from the DLS. The optimized estimate then was used as the fracture size distribution for 

the DFN model. This process was used to analyze each 

fracture subunit of the network. The process eliminates censoring and truncation bias. To minimize fracture-orientation bias, more than one orientation of 

tunnel segments was used; the orientations were 

normalized to the number of fractures and included 

into one orientation distribution pool. Mapped fault 

data were included exactly as mapped in the NAD and 

NDR. Physical features, such as boreholes and 

tunnels, were replicated to the scale and location of the 

measured field boundaries.

The DFN model was calibrated by the generation of 10 DFN simulated fracture systems based on 

the CLUSTRAN fracture data base. The fracture characteristics of the 10 simulated fracture systems then 

were compared to the DLS field data. When the simulated DLS number of fractures per meter was within 

one standard deviation of the field DLS, the fracture 

component of the DFN model was considered calibrated. Following the model calibration, transmissivity 

values for fractures were assigned to the fracture 

systems. The DFN transmissivity values were based 

on the results of the single-hole and the cross-hole airinjection testing. The single-hole and cross-hole tests 

from the field used pneumatic conditions; however, the

FRACMAN modeling code simulated hydraulic 

conditions. As a result, pneumatic parameters of pressure and flow rates were converted to hydraulic parameters in the DFN model. The DFN model then 

simulated the cross-hole air-injection field tests. The 

simulated pressure responses then were compared to 

the field-measured pressure responses. This iterative 

process was repeated until the model results matched 

the field results, indicating that the geometric, 

hydraulic, and spatial properties were acceptable. 

Three cross-hole air-injection tests were simulated 

tests 25, 32, and 36. The injection intervals of the three 

tests were located in borehole MF#1. The injection 

interval for test 25 was in the hanging wall, the injection interval for test 32 was in the fault zone, and the 

injection interval for test 36 was in the footwall. The 

monitor intervals were in boreholes MF#2 and MF#3 

and were located throughout the footwall, the fault 

zone, and the hanging wall.

Cross-Hole Tracer Testing and Analysis in 

the Northern Drill Room Boreholes

Test Methods

Cross-hole convergent-tracer tests were done 

between intervals that had cross-hole pneumatic 

connections. Convergent-tracer testing used the same 

equipment as the cross-hole air-injection testing 

(fig. 6) except that the air compressor was replaced 

with a vacuum pump. The interval isolated by the 

dual-packer assembly was pumped at about 30 sLpm, 

creating a pneumatic gradient toward the pumped 

interval. When the flow system reached steady state, a 

slug of SF6 (0.3 to 0.6 L of 10-percent SF6) and a slug 

of helium (He) (0.3 to 0.6 L of 10-percent He) were 

released in monitor intervals in a different borehole. 

The tracers flowed along the pneumatic gradient to the 

pumped interval where the tracer concentrations were 

measured using a gas chromatograph for the SF6 and a 

mass spectrometer for the He. The pumping rate was 

controlled by mass-flow controllers; the pneumatic 

gradient was monitored by pressure transducers. 

Tracer-release concentrations were selected so that the 

peak concentration at the pumped interval approached 

35 ppm. Because the zone of decreased pressure 

around the pumped interval was small, limited by the 

pumping rate, the linear distances between the tracer 

release interval and the pumped interval were gener14 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
ally limited to less than 7 m. Twenty-one cross-hole 

tracer tests were done in three phases from November 

1997 to June 1998. The three phases of convergenttracer testing followed the three phases of the crosshole air-injection testing. Tests 1 through 8 used borehole MF#2 as the pumped borehole, and isolated intervals in borehole MF#1 were used for tracer release. 

During tests 1 through 8, the He and the SF6 tracers 

were released simultaneously in the same isolated 

interval in borehole MF#1. During tests 9 through 16, 

borehole MF#3 was the pumped borehole; the He 

tracer was released in isolated intervals in borehole 

MF#2, and the SF6 tracer was released in isolated 

intervals in borehole MF#1. During tests 17 through 

21, borehole MF#1 was the pumped borehole; the He 

tracer was released in isolated intervals in 

borehole MF#3, and the SF6 tracer was released in 

isolated intervals in borehole MF#2.

Analysis Using Type Curves

The cross-hole tracer tests were analyzed using 

type curves (Moench, 1995). The method assumes that 

the fracture system can be treated as an equivalent 

porous medium and is based on mass conservation and 

Pick's law. Solute transport is described by the advection-dispersion equation. The details of this derivation 

are beyond the scope of this report but are given in 

Bear (1979, starting on p. 239). The solution was used 

with air and gas tracers and assumes that gas compression effects are minimal; this is a reasonable assumption because the tracer-test pressure gradients were 

less than 15.0 kPa (16.7 percent of atmosphere). The 

dual-porosity radial-flow analytical solution (Moench, 

1995, p. 1824) was used to solve the porous-medium, 

advection-dispersion equation:

1

r

where

r= 

DL=

C=

R =

t=

\rDL ^-)-v ^- = R -=r \ L drj dr dt

radial distance, in meters;

longitudinal pneumatic dispersion, in

square meters per second;

tracer concentration, in kilograms per cubic

meter;

velocity, in meters per second;

tracer retardation, dimensionless; and

time, in seconds.

Type curves were generated for a range of Peclet 

numbers using the analytical solution for radiallyconvergent flow for a single-porosity system. The 

single-porosity type curves are log-log plots of dimensionless concentration (Cj) as a function of dimensionless time (tj) where:

(r -rw )

M

(16)

and

(17)

where

h = length of tracer release interval, in meters;

§T = transport porosity, in cubic meters per 

cubic meter;

rw = well radius, in meters;

M= mass of released tracer, in kilograms;

ta = advective travel time, in seconds.

The tracer test data were plotted as log-log plots 

of normalized concentration as a function of time:

c-c

r '-'max

(18)

where

Cfr= background tracer concentration, in kilograms per cubic meter;

Cmax = maximum pumped tracer concentration, in 

kilograms per cubic meter.

The rising portion of the data curves were 

matched to the type curves. Matching only the rising 

portion of the curves ignored the diffusion process 

because it was assumed that the effect of diffusion is 

minimal on the rising limb of the breakthrough curve. 

The normalized tracer curves and curve matching 

provided estimates of the advective traveltime (time to 

the center of mass) and the Peclet numbers.

TEST AND ANALYSIS METHODS 15
The Peclet number is defined as equation in one dimension as described by Bear (1972, 

p. 617) and presented in equation 21.

r 

a

(19)

where

a = longitudinal dispersivity, in meters.

The transport porosity was determined by

[71

(20)

where

q= gas pump rate, in cubic meter per second.

A limitation of the type-curve analysis was that 

the solution assumed an idealized radial-flow geometry while the field-flow geometry was a combination 

of spherical and leaky radial flow. To compensate for 

the nonideal flow geometry, the analysis assumed 

that the tracer release interval component (h) of 

equation 20 was a constant 8.0-m "effective length." 

The "effective length" was based on an estimated 

8.0-m maximum zone of influence (measurable pressure drawdown) extending out from the pumped 

interval during tracer testing. Use of an "effective 

length" provided some compensation for the greater 

advective traveltimes caused by the nonradial flow 

components. The calculated transport porosity (sometimes called effective porosity) is a composite of the 

physical factors that influence the movement of the 

tracer from the release point to the pumped interval. 

These parameters include, but are not limited to, the 

fracture-flow path length, the number of fractures, the 

fracture-aperture distribution, the rugosity of the 

fracture walls, the tortuosity of the flow path, matrix 

interaction, and sorption. No attempts were made to 

estimate the diffusion coefficients because of the difficulty of defining an equivalent radius in a fractureflow system that is nonuniform.

Discrete-Feature Analysis Using MAFIC

The MAFIC code (Miller and others, 1994), in 

combination with the DFN model developed in 

FRACMAN, was used to analyze the gas-tracer-transport tests. The MAFIC code uses the solute-transport

(21)

where

V= Darcian velocity, in meters per second; 

dL = longitudinal dispersivity, in meters; 

D = coefficient of molecular diffusion, in square

meters per second; 

x= length, in meters; 

c = the solute concentration, in kilograms per

cubic meter; 

t = time, in seconds; 

Qs= external source, in seconds ; 

Cs = concentration of tracer at external source, in 

kilograms per cubic meter.

The solute transport was simulated using a 

particle-tracking method. The method represents the 

concentration of solutes in the solvent using a finite 

number of discrete particles of equal mass. Each 

particle represents a fraction of the total solute. Initial 

conditions imply that all particles are initially located 

in the fractures. At each time step, particles are moved 

according to a deterministic advective component and 

a stochastic dispersive component. Particles were 

introduced at a source (tracer-release interval) in the 

first 200 seconds of the simulation and were removed 

at a specified sink (pumped interval). Average concentrations and total particle mass were calculated at the 

end of each time step. The advective component was 

proportional and parallel to the velocity vector at the 

current particle location. The dispersive component 

was proportional to the square root of the advective 

component (Miller and others, 1994). Mass transfer 

between the matrix and fractures was ignored.

The DFN model simulation that best matched 

the cross-hole air-injection tests 25, 32, and 36 was 

used to model the tracer-transport field tests. Three 

tracer field tests were modeled: tracer-test number 17, 

where the pumped interval was in the hanging wall; 

tracer-test number 21, where the pumped interval was 

in the footwall; and tracer-test number 15, where the 

pumped interval was in the fault zone. For all tests, the 

sink (pumped intervals) was in borehole MF#3, and 

the source (tracer release intervals) was in MF#1 and 

MF#2.

16 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
TEST RESULTS

Caliper and video logging was successful in 

borehole NAD-GTB#la and in boreholes NDR-MF#1, 

2 and 3. The caliper and video logs were used to identify geologic features and to locate test intervals. 

Geothermal logging, pneumatic monitoring, gas and 

water chemistry sampling, and single-hole air-injection testing were successfully done in borehole NAD 

GTB#la. Gas and water chemistry sampling, single 

and crosshole air-injection testing, and cross-hole gastracer testing were successfully done in the NDR boreholes.

Results from Geothermal Logging in 

Borehole NAD-GTB#1a

The geothermal logs from November 7 and 

December 3, 1996, from borehole NAD-GTB#la 

(DTN: GS970383122410.005) are shown in figure 7. 

Both logs showed near-surface temperature gradients 

that indicated ventilation effects to depths of 3 to 5 m. 

The geothermal log from November 7, 1996, 

completed when the NAD face was at 105 m from the 

ESF centerline, identified a 0.1 °C temperature 

decrease throughout the 38- to 50-m long, 12-m-wide 

broken zone (143 to 155 m from the ESF centerline)

that had been identified in the video log. The temperature decrease could indicate movement of cool air, or 

water, or both, down the 12-m-wide broken zone. The 

barometric pressure was rising on November 6 and 7, 

1996, and supports the concept of cool, shallow air 

moving down the 12-m-wide broken zone. The 

geothermal log from December 3, 1996, completed 

when the NAD face was at 134.4 m from the ESF 

centerline, did not show the previously recorded 

temperature drop in the 12-m broken zone but identified a 0.05°C temperature increase at or near 

the main trace of the fault (49 m in the borehole and 

154 m from the ESF centerline). The barometric pressure was decreasing on December 2 and 3, 1996, 

which supports the concept of deep, warm air moving 

up the main trace of the GDF. The stabilization of the 

temperature in the 12-m-wide broken zone between 

November and December indicated that the November 

temperature drop may have been due to drillinginduced evaporative cooling or gas-expansion 

adiabatic cooling. Other temperature fluctuations may 

be due to drilling effects or, possibly, due to the variable borehole diameter. A more thorough understanding of the effect of barometric pressure on the 

temperature in the GDF and the 12-m-wide broken 

zone require geothermal logging during a range of 

barometric pressure fluctuations.

COJD

CO

LU 

U

CO 

LU 

LLJ 

CC 

O 

LLJ 

Q

22.3

22.2

22.1

22

III 21.9 

CC

cr 21.8

LLJ 

Q.

^. 

LLJ 

h- 21.7 -

21.6

November?, 1996 

Decembers, 1996

10 20 30

DEPTH, IN METERS

40 50 60

Figure 7. Temperature plot showing the geothermal logs from borehole NAD-GTB#1a.

TEST RESULTS 17
Results from Pneumatic Pressure 

Monitoring in Borehole NAD-GTB#1a

A schematic diagram of borehole NADGTB#la and the locations of the isolated downholemonitor intervals used for pneumatic monitoring are 

shown in figure 8. The liner was installed to maximize 

the number of monitor intervals that intersected the 

12-m-wide broken zone (143 to 155 m measured from 

the ESF centerline) that had been identified in the 

borehole video log. The barometric pressure and the 

downhole-monitor interval pressures for December 26 

to 31,1996 (DTN: GS970283122410.003), are shown 

in figure 9. The downhole-monitor interval pressures 

identified limited barometric pressure attenuation and 

small time lags. Comparison of the downhole-monitor 

intervals pressure fluctuations (0.56 to 0.83 kPa) to the 

barometric-pressure fluctuation (1.07 kPa) indicated 

that the permeability of the rock is relatively high. 

Monitor intervals 2, 3, and 7 had the smallest attenuations. Monitor intervals 4, 6, 8, and 9 had the largest 

attenuations, and monitor intervals 1,5, and 10 had 

intermediate attenuations. Pressure monitoring 

showed no correlation between the amount of pressure 

attenuation and the distance from the NAD and no 

correlation between pressure attenuation and the 

distance from the main trace of the GDF. The amount 

of attenuation shows no pattern and may be random. 

The randomness may be due to the small size of the 

downhole-monitor intervals (borehole-surface-contact 

area of approximately 0.07 m2). The small monitor

interval area may result in the downhole-monitor intervals contacting the borehole at locations that do not 

have fractures and, therefore, are not well connected to 

the fracture system. A poor connection to the fracture 

system may explain why monitor interval 1, which 

was closest to the NAD, had a larger attenuation than 

monitor intervals 2 and 3, which are at greater 

distances from the NAD and would be expected to 

have larger pressure attenuations. Monitor interval 10 

was the farthest from the NAD and, therefore, would 

be expected to have the largest attenuation of the NAD 

barometric-pressure change. The intermediate attenuation measured in monitor interval 10 may indicate that 

the barometric pressure changes were transmitted 

from the ground surface through the GDF to depth. 

The larger attenuation measured in monitor interval 9, 

which also was close to the main trace of the fault, 

may be due to the small monitor interval area and to a 

poor connection to the fracture system. The noise 

recorded in monitor interval 5 was probably due to a 

faulty solenoid valve.

Results from Chemical Sampling in 

Borehole NAD-GTB#1a

The results of the chemical analysis of the gasphase samples from borehole NAD-GTB#la are 

presented in table 2. (DTN: GS970283122410.002) 

During the drilling of borehole NAD-GTB#la, an 

error in the operation of the SF6 tracer-gas-injection

Hanging Wall 

Mair

135 140 145 150

i i i

1 2 34 ;. 5 6 7 89

i 1

 '

Footwall 

race

155 160 ie

r i i i

10

A A A

(11.1) (13.1) (14.4) 

EXPLANATION

.\ :; -; Matrix-supported breccia <v\\\ Core-water tritium concentration, in tritium units (TU)

Clast-supported breccia 2 Location of monitor interval

Relatively less fractured rock

Figure 8. Schematic diagram showing borehole NAD-GTB#1a intersection with the Ghost Dance Fault and the 

locations of the downhole-monitor intervals.

18 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
Barometer 

Interval 1 

Interval 2 

Interval 3 

Interval 4 

Interval 5

 Interval 6

 Interval 7

 Interval 8

 Interval 9

 Interval 10

Noon Noon Noon

12/25/96 12/27/96 12/29/96

Figure 9. Barometric pressure and the pressure responses in the isolated intervals in 

borehole NAD-GTB#1 a.

system occurred. On November 1, 1996, at the drilling 

depth of 160.5 to 161.5 m, the valve on the SF6 tracergas cylinder was opened, and about 800 liters (L) of 

10-percent SF6 was pumped into the borehole. The 

presampling pumping period was extended in an 

attempt to remove the excess SF6. Final SF6 concentrations in 7 of the 10 monitor intervals were less than 

0.01 ppm (table 2), indicating that the presample 

pumping removed most of the drilling air. The higher 

SF6 concentrations in monitor intervals 6, 9, and 10 

(0.058, 0.815, and 0.030 ppm) may be associated with 

the large pneumatic attenuations measured in monitor 

intervals 6, and 9. The elevated SF6 values may be due 

to restricted presampling pumping rates due to poor

connections to the fracture system and low tuff matrix 

permeability, or may be due to sorption of SF6 by the 

tuff matrix or fault breccia. Monitor interval 10 had a 

residual SF6 concentration of 0.030, but unlike 

monitor intervals 6 and 9, monitor interval 10 had an 

intermediate pressure attenuation and does not fit the 

model. Although monitor interval 9 had the largest

1 ^

SF6 concentration, it also had the lightest 8 C ratio 

(-16.18) and the oldest 14C age (4,500 years) (table 2). 

The carbon values indicated that the presampling 

pumping had removed most of the drilling air from 

monitor interval 9.

Gas-phase CO2 concentrations ranged from 660 

to 1,175 ppm (table 2). The CO2 values increased with

TEST RESULTS 19
Table 2. Results of the chemical analysis of the gas-phase samples from borehole NAD-GTB#1a

[ppm, parts per million; PDB, Pee Dee Belemnite; %c, parts per thousand; pmc, percent modern carbon; %, percent]

Monitor 

interval

1

2

3

4

5

6

7

8

9

10

Depth 

(meters)

139.1

142.2

143.7

145.2

146.8

148.3

149.8

151.3

152.9

155.9

SF6 

(ppm)

0.001

0.000

0.000

0.001

0.004

0.058

0.000

0.008

0.815

0.030

CO2 

(ppm)

713.0

660.0

711.0

925.0

996.0

976.0

1,075.0

1,079.0

1,175.0

1,067.0

813C 

(%*) 

(standard is 

PDB)

-14.18

-14.11

-14.17

-15.10

-15.46

-15.39

-15.58

-14.81

-16.18

-15.89

14C 

(pmc)

69

75

72

64

67

68

71

61

58

66

14Cage 

(years)

3,100

2,400

2,700

3,700

3,300

3,200

2,800

4,100

4,500

3,400

14C age

+(%)

1.0

1.2

1.8

0.8

1.0

1.4

1.3

0.8

1.0

0.7

distance from the NAD (r = 0.89). The correlation 

indicated that NAD air had moved a minimum of 

13.9 m into the tuff. Monitor intervals 1, 2, and 3 had 

the lowest CO2 concentrations and slightly heavier 

513C ratios, indicating the highest component of NAD 

gas. Both the low CO2 and the slightly heavier 513C 

ratios are probably due to the close location of monitor 

intervals 1, 2, and 3 to the NAD and to the subsequent 

mixing of the rock gas with NAD air. As discussed in 

the pneumatic monitoring section, monitor intervals 2 

and 3 had minimal pressure attenuation, supporting 

the concept of a well-developed fracture connection to 

the NAD. Gas-phase 513C values decreased with 

distance from the NAD (r = 0.84), again indicating 

that air from the NAD has penetrated the tuff.

Uncorrected 14C-age estimates from gas 

samples ranged from 2,400 to 4,500 years (table 2). 

Monitor intervals 2, 3, and 7, which had the minimum 

pressure attenuations, had 14C-age estimates of 2,400, 

2,800, and 2,900 years, respectively. Monitor intervals 

1,5, and 10, which had intermediate pressure attenuations, had 14C-age estimates of 3,000, 3,300, and 

3,400 years, respectively. Monitor intervals 4, 6,8, and 

9, which had the maximum pressure attenuations, 

had 14C-age estimates of 3,700, 3,200, 4,000, and 

4,500 years, respectively. The 14C-age estimates of the 

monitor intervals are directly correlated to the amount 

of pressure attenuation measured during pneumatic 

monitoring (r = 0.75, ranked 1 to 10 with 1 the 

smallest pressure attenuation). The age/attenuation

correlation indicated that air from the NAD had penetrated the tuff through the fracture system.

The results of the tritium analysis of water 

distilled from core samples from borehole 

NAD-GTB#la (DTN: GS970283122410.002, and 

DTN: GS990183122410.001) are listed in table 3. The 

table 3 tritium analysis results are classified nonquality assured. Eight samples at six depths had 

tritium levels that were significant at two standard 

deviations. The eight samples each has a 95.4-percent 

probability of being greater than zero and, therefore, 

positive for tritium. Assuming that the tritium levels 

are not due to contamination, the presence of measurable tritium indicates that water has been transported 

from the ground surface to the depth of the NGDFA 

during about the last 100 years (8 half-lives).

There are few reliable estimates of the natural 

tritium levels in the atmosphere before the 1952 

advent of atmospheric thermonuclear testing greatly 

increased the tritium background levels. Best estimates of tritium levels in pre-1952 precipitation vary 

with location and season but are in the range of 4 to 

25 tritium units (TU) (Fritz and Fontes, 1980, p. 22). 

By using a conservative assumption that pre-1952 

precipitation at Yucca Mountain had a tritium content 

of 25 TU, and by using a tritium half-life of 

12.3 years, the 1997 tritium content of core water from 

borehole NAD-GTB#la that was derived from 1952 

precipitation would be 2.0 TU. Therefore, some 

component of the water in core-water samples, which

20 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
Table 3. Results of the tritium analysis of core-water samples from borehole NAD-GTB#1a 

(These data are classified as non-quality assured)

Distance from 

exploratory studies 

facility centerline 

(meters)

135.3 1

142.1

142.41

143.1 1

143.5

144.5

144.9 1

145.4

146.2

147.5 1

148.3

148.9

148.92

149.9

150.4

151.1

151.7

152.0

152.0

154.4

154.9

155.0

155.0

155.2

155.22

156.41

Tritium units 

(TU)

1.4

-2.5

1.2

1.2

5.2

-1.4

0.8

0.3

-0.2

0.3

1.1

11.1

8.6

0.6

5.4

6.3

4.3

6.3

2.4

9.2

5.1

7.3

2.2

12.2

14.4

0.8

Standard deviation

0.4

2.9

0.4

0.4

3.0

2.9

0.7

3.0

4.4

0.4

3.0

4.1

4.1

3.0

3.0

4.0

4.0

4.1

4.1

4.1

4.0

4.0

4.0

4.2

4.2

0.5

Tritium units 

minus two 

standard 

deviations

0.6

0

0.4

0.4

0

0

0

0

0

0

0

2.9

0.4

0

0

0

0

0

0

1.0

0

0

0

3.8

6.0

0

Analysis by the University of Miami, Miami, Florida. 

2Replicate sample.

had tritium levels greater than 2.0 TU, had some 

contact with the atmosphere in the last 45 years (post1952 atmospheric thermonuclear testing). Three corewater samples at two depths had tritium values greater 

than 2.0 TU at two standard deviations (table 3). These 

tritium values indicated that water had traveled from 

the land surface to the depth of the borehole in the last 

45 years. The proximity of the elevated tritium 

samples to the main trace of the GDF and to the 

12-m-wide broken zone (fig. 8) indicated that the fault 

is a conduit for the transport of water from the land 

surface through the nonwelded tuff of the Paintbrush 

Group and down to the Tptpmn. A less conservative 

approach assumes that the pre-1952 precipitation at

Yucca Mountain had a tritium content of 4 TU. By 

using a pre-1952 tritium level of 4 TU, the 1997 

tritium content of core water from borehole 

NAD-GTB#la that was derived from 1952 precipitation would be 0.32 TU. This less conservative 

approach indicated that the eight core-water samples 

that were positive for tritium at two standard deviations (table 3) have a component of post-1952 water. 

However, interpretation of tritium levels as low as 0.4 

to 1.0 TU requires consideration of the possibility that 

the samples were contaminated during drilling, core 

logging, or packaging and shipping. As tritium levels 

decrease and significance is assigned, the effect of 

even short periods of atmospheric exposure and small

TEST RESULTS 21
amounts of contamination becomes larger. The actual 

tritium levels from pre-1952 precipitation at Yucca 

Mountain probably are between 4 and 25 TU and vary 

with the seasons. In summary, the core-water tritium 

data from borehole NAD-GTB#la indicated that the 

fault is a conduit for the rapid transport (less than 

100 years) of water from the land surface to the 

Tptpmn.

Results from Chemical Sampling in the 

Northern Drill Room Boreholes

The results of the chemical analysis of the gasphase samples from borehole MF#1 are listed in 

table 4. Gas-phase CC>2 concentrations in borehole 

NAD-MF#1 (DTN: GS981283122410.006) ranged 

from 741 to 913 ppm. Gas-phase 513C values ranged 

from -14.79 to -13.81 per mil. Gas-phase 14C ages 

ranged from 2,500 to 3,600 years. There was no correlation between the parameters and depth. The monitor 

interval centered at 12.5 m was in the foot wall, and the 

monitor intervals centered at 18.6, 21.6, and 24.7 m 

were in the hanging wall. The monitor interval 

centered at 15.5 m was located in the fault zone. The 

data indicate that the gas samples are a mixture of 

NGDFA air and rock gas. The monitor interval 

centered at 15.5 m had the lowest CO2, largest 513C, 

and youngest 14C age, all indicating that the gas 

sample from the fault zone had the greatest mixing 

with NGDFA air. The mixing was probably due to 

(1) the high permeability of the fault zone, as identified in the air-injection testing; (2) the NAD penetration of the fault, providing a short flow path; and (3) 

the 17 months that elapsed between the NAD penetration of the fault in March 1997 and gas sampling in 

August 1998.

The results of the chemical analysis of the gasphase samples from borehole NDR-MF#2 are listed in 

table 5. Gas-phase CO2 concentrations in borehole 

NDR-MF#2 (DTN: GS981283122410.006) ranged 

from 711 to 896 ppm. Gas-phase 513C values ranged 

from -15.04 to -13.45 per mil. Gas-phase 14C ages 

ranged from 2,600 to 3,500 years. There is no correlation between the parameters and depth. The monitor 

interval centered at 12.2 m was in the footwall, and the 

monitor intervals centered at 18.3, 21.3, and 24.4 m 

were in the hanging wall. The monitor interval 

centered at 15.2 m was in the fault zone. The data indicated that the gas samples are a mixture of NGDFA air 

and rock gas. The monitor interval centered at 15.2 m 

had the lowest CO2, second largest 513C, and largest 

percent modern carbon, all indicating that the gas 

sample from the fault zone had the greatest mixing 

with NGDFA air. The mixing was probably due to 

(1) the high permeability of the fault zone, as identified in the air-injection testing; (2) the NAD penetration of the fault, providing a short flow path; and (3) 

the 17 months that elapsed between NAD penetration 

of the fault in March 1997 and gas sampling in August 

1998.

The results of the tritium analysis done by the 

University of Miami of core-water samples from 

borehole NDR-MF#1 (DTN: GS990183122410.004) 

are listed in table 6. The table 6 tritium analysis results 

are classified as non-quality assured. The monitor 

interval centered at 13.8 m was in the footwall, and the 

monitor interval centered at 15.2 m was in the fault 

zone. Both samples had tritium levels that were signifTable 4. Results of the chemical analysis of gas-phase samples from borehole NDR-MF#1

[ppm, parts per million; PDB, PeeDee Belemnite; %c, parts per thousand; pmc, percent modern carbon; 

%, percent]

Depth 

(meters)

12.5

15.5

18.6

21.6

24.7

C02

(ppm)

870

741

884

913

743

513C

(%o)

(standard 

is PDB)

-14.3

-13.8

-14.6

-14.8

-14.4

14C 

(pmc)

72

74

71

65

71

14C age 

(years)

2,700

2,500

2,800

3,600

2,800

14C age

±(%)

1.3

2.5

2.1

1.4

2.0

22 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
Table 5. Results of the chemical analysis of gas-phase samples from borehole NDR-MF#2

[ppm, parts per million; PDB, Pee Dee Belemnite; %o, parts per thousand; pmc, percent modern carbon; 

%, percent]

Depth 

(meters)

12.2

15.2

18.3

21.3

24.4

C02 

(ppm)

736

711

111

836

896

513C

(%c)

(standard 

is PDB)

-13.4

-13.5

-14.1

-15.0

-15.0

14C 

(pmc)

73

73

65

73

66

14Cage 

(years)

2,600

2,600

3,600

2,600

3,400

14Cage

±(%)

0.8

1.6

1.4

1.9

0.7

icant at two standard deviations and have 95.4 percent 

probabilities of being greater than zero and positive 

for tritium. Assuming that the tritium levels are not 

due to contamination, the presence of measurable 

tritium indicates that water has been transported from 

the ground surface to the borehole in about the last 

100 years (8 half-lives). Using the conservative 

assumption that pre-1952 precipitation at Yucca 

Mountain had a tritium content of 25 TU, the data do 

not indicate post-1952 water. Using a pre-1952 tritium 

level of 4 TU, the data indicated that both borehole 

NDR-MF#1 core-water samples have a component of 

post-1952 water. In summary, the core-water sample 

tritium values from borehole MF#1 indicated that the 

fault is a conduit for the rapid transport (< 100 years) 

of water from the land surface through the nonwelded 

tuff of the Paintbrush Group and down to the Tptpmn.

Results from Single-Hole Air-Injection 

Testing in Borehole NAD-GTB#1a

The permeability values from single-hole airinjection testing in borehole NAD-GTB#la (DTN:

Table 6. Results of the University of Miami tritium analysis 

of core-water samples from borehole NDR-MF#1 (These 

data are classified as non-quality assured)

Depth 

(meters)

13.8 

15.2

Tritium 

units 

(TU)

1.6

2.2

Standard 

deviation

0.5 

0.6

Tritium units 

minus two 

standard 

deviations

0.6 

1.0

GS970383122410.004) are presented in table 7. Airinjection testing identified three zones that had 

different permeability values. The three zones correspond to the structural units: footwall, hanging wall, 

and a high-permeability fault zone similar to that identified in the NDR boreholes. The fault zone in GTB#la 

is a subsection of the 12-m-wide broken zone. The 

fault zone extends from 15.0 to 18.4 m and is 

composed of a brecciated zone associated with the 

main trace of the fault and the adjacent, intensely fractured hanging wall. Permeability values from the 

hanging wall ranged from 0.1 to 2.5 x 10" 12 m2 and

had an arithmetic mean of 1.1 x 10" 12 m2 and a

1 ^y *7 geometric mean of 0.5 x 10 m . The fault zone

permeability values ranged from 8.5 to 11.1 x 10" 12 m2 

and had arithmetic and geometric means of 10.0 x 

10" 12 m2. The permeability values of the footwall 

ranged from 0.2 to, 2.1 x 10" 12 m2 and had an arith-

-\r\ r\

metic mean of 1.0 x 10 m and a geometric mean of 

0.7 x 10" 12 m2. The permeability value of the 12-mlong test interval that straddled the hanging wall, fault

1O O _ _ _ zone, and footwall was 5.7 x 10 m . The mean 

permeability values of the Tptpmn from the surfacebased air-injection testing ranged from 0.37 to 2.7 x 

10" 12 m2 (LeCain, 1997, p. 23). Comparison of the 

permeability values from borehole NAD-GTB#la to 

the surface-based values indicated that the permeability values for the hanging wall and the footwall are 

in the surface-based range, but the fault-zone permeability values are several factors larger. The most 

probable explanation for the increased permeability in 

the fault zone is increased fracturing associated with 

the GDF.

TEST RESULTS 23
Table 7. Permeability values from air-injection 

testing in borehole NAD-GTB#1a (These tests were 

done when the northern access drift face was 

located at 134.4 meters from the ESF)

-12 [Permeability values are 10 meter squared]

Depth 

(meters)

1.9-2.9

2.8-3.8

6.5-7.5

8.3-9.3

13.2-14.2

15.0-16.0

15.8-16.8

17.4-18.4

18.7-19.7

19.6-20.6

21.1-22.1

22.3-23.2

8.7-20.7

Structural unit

Hanging wall

Hanging wall

Hanging wall

Hanging wall

Hanging wall

Hanging wall 

(fault zone)

Hanging wall 

(fault zone)

Brecciated zone

(fault zone)

Footwall

Footwall

Footwall

Footwall

Hanging wallBrecciated

zone-Footwall

Permeability 

values

0.1

0.6

0.1

2.5

2.3

11.1

8.5

10.5

2.1

1.3

0.5

0.2

5.7

Results from Cross-Hole Air-Injection 

Testing in the Northern Drill Room 

Boreholes

Analysis Using Type Curves

The initial examination of the pressure 

responses in the monitor intervals identified three 

zones that had different pressure responses. These 

three zones correspond to the structural units: footwall, fault zone, and hanging wall. The normalized 

pressure responses and theoretical type curves for 

monitor intervals located in the footwall, fault zone, 

and hanging wall are shown in figures 10, 11, and 12, 

respectively. In a homogeneous and isotropic medium, 

the normalized pressure plots would form a single 

curve. In a heterogeneous medium, the pressure data 

from monitor intervals in highly permeable zones will 

have an early t/r2 response and the less permeable 

zones will have a delayed \Jr~ response. Directional 

effects would be identified as pressure variability 

increasing in the direction of lower permeability. 

Although the curves in figures 10, 11, and 12 are not

perfectly matched, they are very similar, and with a 

few exceptions the pressure responses are within a 

factor of two; the pressure variability may indicate that 

the test scale was smaller than the representative 

elementary volume. The normalized pressure 

responses indicated no correlation between pressure 

response and direction. The identification of three 

zones with different pneumatic characteristics, and the 

absence of directional effects, indicated that the 

northern GDF test area was heterogeneous with three 

zones of different permeability and that the three 

zones were isotropic.

Following the initial examinations, the pressure 

responses of the monitor intervals were analyzed using 

spherical- and radial-flow type curves. The analysis 

assumed that the matrix was water filled; this is 

reasonable because no delayed storage components 

were identified in the pressure responses. Tests done in 

the footwall and hanging wall best matched the spherical-flow model. Tests done in the fault zone best 

matched a radial-flow model; the data also indicated 

some leakage. The radial-flow model best matched the 

fault zone because the higher permeability fault zone 

was bounded by the lower permeability footwall and 

hanging wall, which restricted the gas flow to a leakyradial-flow geometry. The permeability and porosity 

values from the type-curve analysis are presented in 

tables 8 through 12. Statistical summaries of the 

permeability and porosity values by structural unit are 

presented in tables 13 and 14. The pressure responses 

and locations of the monitor intervals for the individual cross-hole air-injection tests are available in the 

YMP data packages DTN: GS980183122410.001 and 

GS981183122410.005.

Statistical summaries of the permeability and 

porosity values from the type-curve analytical solutions of cross-hole air-injection testing are listed in 

tables 13 and 14. The arithmetic mean permeability 

and porosity values of the three structural units are: 

footwall 8.7 x 10 ~ 12 m2, and 0.04; fault zone 18.1 x

,-12 10' 12 mz, and 0.13; hanging wall 5.0 x 10' 1Z mz, and 

0.04. The type-curve analysis indicated that the 

permeability and porosity values of the three individual structural units were independent of direction. 

The analysis identified boundary effects when the 

monitor interval and the air-injection interval were 

located in different structural units, and when a 

monitor interval was located immediately adjacent to 

an adjoining structural unit. The type-curve analysis 

identified a heterogeneous flow system that had three

24 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
CO 

DC 

LJJ

LJJ

2

CO 

LJJ

1 hQ 

HI 

DC

o

CO 

CO

o

CO

g 

5

1,000

100

10 Interval #7 - Interval #17

A Interval #8 - Interval #18

X Interval #9 » Interval #19

)K Inerval # 10 Type Curve

+ Interval #16

Q ] ______I I I I I I I I I______I I I I I I I I I______I I I I I I I I I______| | | I I I I I I I I I I I I I I

'0.01 0.1 1 10 100 1,000 

SECONDS PER METER SQUARED

Figure 10. Pressure response times distance, with time, divided by distance squared 

measured in the footwall during cross-hole air-injection test 22, and the type curve for 

spherical flow.

CODC LU

in

2

CO111 2

IQ 

111 

DC 

<

O 

CO

CO

O 

CO

g 

5

1,000 F

100 -

Interval # 6 

Interval # 15 

Interval # 16 

Type Curve

0.01

0.01 10 100

SECONDS PER METER SQUARED

1,000

Figure 11. Pressure response times distance, with time, divided by distance squared 

measured in the fault zone during cross-hole air-injection test 16, and the type curve for 

radial flow.

TEST RESULTS 25
1,000 CO 

GC 

LJJ

LJJ

CO 100 

LJJ

Q 

LJJ 

GC 

<

o

CO 

CO

O 

CO

g 

^

10

0.1

X X

 Interval # 1

 Interval # 2

A Interval # 3

x Interval # 4

 Interval #11

I I I I I I I

0.01

+ Interval #12

. Interval #13

Interval #14

 Type Curve

i i 11111

0.1 1 10 100

SECONDS PER METER SQUARED

1,000

Figure 12. Pressure response times distance, with time, divided by distance squared 

measured in the hanging wall during cross-hole air-injection test 19, and the type curve for 

spherical flow.

different homogeneous isotropic structural units 

corresponding to the footwall, fault zone, and hanging 

wall. Comparison of the NDR cross-hole permeability 

values to the single-hole permeability values from 

borehole NAD-GTB#la indicates reasonable agreement between the arithmetic means for the fault zone 

(values within a factor of 2) but differences 

approaching a factor of 5 in the hanging wall and 

almost an order of magnitude in the footwall. The 

permeability differences may be real or they may be a 

scale effect due to the smaller test scale of the singlehole GTB#la testing. Overall, the NGDFA cross-hole 

permeability values for the Tptpmn are larger than the 

range of the surface-based permeability values for the 

Tptpmn (0.37 to 2.7 x lO'^m2) (LeCain, 1997, p. 23). 

The increased permeability is probably due to 

increased fracturing associated with the GDF. 

Although the monitor interval pressure responses did 

not indicate a dual-porosity system, and the analysis 

assumed that the matrix was water filled, the porosity 

values were greater than expected and indicate a 

porosity component in addition to the fracture 

porosity. Fracture porosity generally ranges from 10~2 

to 10'5 (Freeze and Cherry, 1979, p. 408). Visual 

examinations in the NAD indicated that the fault-zone 

fracture porosity may be larger than 10"2 . Possible 

explanations of the additional porosity include airfilled lithophysal cavities and/or air-filled matrix pores 

in direct contact with the fractures.

Numerical Analysis Using AIR3D

By using geologic information from the DLS, 

geologic mapping, visual inspection of the NAD 

and NDR, and borehole video logs, a numerical model 

of the northern GDF flow system was developed 

using the USGS finite-difference model AIR3D (Joss 

and Baehr, 1995). The numerical model grid was 

40 layers, 25 columns, and 25 rows. The model layer 

thickness was a constant 2 m, while the column and 

row widths ranged from 0.1 m, at the central nodes, up 

to 10.0 m at the outer boundaries. The X, Y, Z scale of 

the model was 76.1 by 76.1 by 80.0 m, respectively. 

The lower boundary was no flow (representing the 

water table) and the other five boundaries were 

constant head. To minimize boundary effects, the 

model scale was large compared to the field-testing 

scale. The footwall was assigned layers 1 through 20, 

the fault zone layers 21 and 22, and the hanging wall 

layers 23 through 40. The relative locations of the 

model air-injection and monitor intervals were 

selected to match the field tests. The initial model run 

used the arithmetic-mean permeability and porosity 

values from the type-curve analysis for the footwall, 

fault zone, and hanging wall. Pressure responses from 

the numerical model were visually compared to the 

pressure responses from field testing. By using these 

comparisons, the permeability and porosity values of 

the model were adjusted and the model was rerun; the 

model pressure responses again were compared to the

26 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
Table 8. Permeability and porosity values from cross-hole air-injection testing using borehole NDR-MF#2 for injection and 

borehole NDR-MF#1 for monitoring

[Permeability values are 10~12 meter squared; porosity is in parentheses; --, no data; FZ, fault zone; PFZ, partial fault zone, defined as a monitor interval 

located in the fault zone and footwall]

Test . t'njeC,t;°"

number lnt*rva' d(fh 

(meters)

1 25.9-30.6

2 25.9-28.9

3 22.8-25.9

4 21.3-24.3

5 19.2-22.2

6 15.2-18.3

7 11.6-14.6

8 8.8-11.9

9 5.2-8.2

10 3.7-6.7

11 1.5-4.5

Injection 

interval 

structural unit _

Hanging wall

Hanging wall

Hanging wall

Hanging wall

Hanging wall

Fault zone

Partial fault zone

Footwall

Footwall

Footwall

Footwall

Permeability and porosity values from monitor intervals 

located in borehole NDR-MF#1

Hanging Wall

1

5.1 

(.03)

5.4 

(-03)

3.8 

(.01)

2.0 

(.01)

1.4 

(.01)

-

-

-

--

-

-

2

5.9

(.07)

7.0 

(.05)

3.7 

(.01)

1.5 

(.01)

0.8 

(.01)

~

-

-

-

-

-

3

6.3 

(-06)

6.5 

(.05)

3.3 

(.02)

1.3 

(.01)

0.7 

(.02)

-

-

--

-

-

-

4 5

_

: ::

4.7 

(.06) -

1.2 

(.06) -

0.7 1.3 

(-04) (.07)

0.9 0.7

(.03) (.02)

13.2

(.14)

__

..

..

._

~

-

FZ

6

_

_

_

9.2

(.15)

5.1

(.05)

9.3

(.05)

14.4

(.06)

10.5

(.04)

-

PFZ

7

_

_

~

18.1

(.17)

9.4

(.11)

9.4

(-06)

1.1

(.02)

6.7

(.03)

-

Footwall

8

_

_

_

_

::

-

17.2

(.18)

12.0

(.04)

6.2

(-05)

5.4

(.04)

9.8

(.05)

9

_

_

--

-

-

10.7

(.03)

5.1

(.05)

4.3

(.05)

6.2

(-03)

10

_

_

_

-

--

-

10.8

(.02)

6.4

(.05)

5.5

(.06)

8.9

(.05)

Table 9. Permeability and porosity values from cross-hole air-injection testing using borehole NDR-MF#3 for injection and 

borehole NDR-MF#1 for monitoring

[Permeability values are 10~12 meter squared; porosity is in parentheses; --, no data; FZ, fault zone; PFZ, partial fault zone, defined as a monitor interval 

located in the fault zone and footwall]

Test 

number

12

16

17

19

21

22

23

Injection 

interval depth 

(meters)

26.4-34.3

12.3-17.3

3.5-8.5

24.5-26.5

18.5-20.5

8.7-10.7

3.2-5.2

Injection 

interval 

structural unit

Hanging wall

Fault zone

Footwall

Hanging wall

Hanging wall

Footwall

Footwall

Permeability and porosity values from monitor intervals 

located in borehole NDR-MF#1

Hanging Wall

1

6.2

(.04)

-

-

5.7

(.03)

5.4

(-02)

-

-

2 3

8.0 5.4

(.06) (.04)

-

-

6.1 3.6

(.03) (.03)

6.0 3.8

(.03) (.02)

~

-

4

8.0

(.06

25.3

(.30)

-

5.7

(.06)

-

-

-

-

5

~

~

15.3

(.15)

-

12.4

(-02)

3.5

(.08)

-

-

FZ

6

-

-

7.0

(.05)

13.2

(.05)

-

-

21.9

(.40)

9.3

(-05)

13.4

(.04

PFZ

7

-

--

13.2

(.16)

9.3

(.03)

--

-

--

-

10.1

(-07)

10.8

(-03)

8

-

-

22.2

(.22)

9.9

(.04)

--

-

--

-

15.9

(.12)

10.8

(.03)

Footwall

9

-

~

19.7

(.16)

7.0

(.03)

--

-

--

--

11.8

(.07)

4.4

(.01)

10

-

-

--

__

8.1

(.03)

--

-

--

-

13.6

(.05)

5.2

(.01)

TEST RESULTS 27
Table 10. Permeability and porosity values from cross-hole air-injection testing using borehole NDR-MF#3 for injection and 

borehole NDR-MF#2 for monitoring

[Permeability values are 10" 12 meter squared; porosity is in parentheses; , no data; FZ, fault zone; PFZ, partial fault zone, defined as a monitor interval 

located in the fault zone and footwall]

Test 

number

12

16

17

19

21

22

23

Injection 

interval depth 

(meters)

26.4-34.3

12.3-17.3

3.5-8.5

24.5-26.5

18.5-20.5

8.7-10.7

3.2-5.2

Injection 

interval 

structural unit .

Hanging wall

Fault zone

Footwall

Hanging wall

Hanging wall

Footwall

Footwall

Permeability and porosity values from monitor intervals 

located in borehole NDR-MF#2

Hanging Wall

11

7.5 

(.06)

-

--

-

8.0 

(.09)

8.0 

(.04)

-

--

--

12 13

5.3 4.9 

(.06) (.03)

..

5.9 2.7 

(.09) (.02)

6.0 4.2 

(.05) (.04)

..

-

14

12.8 

(.07

20.0

(.23)

--

7.4 

(.05)

--

-

--

15

10.4

(.09)

--

13.2 

(.05)

3.3 

(.03)

12.7

(.10)

--

FZ

16

_

6.6

(.05)

12.0

(.04)

~

20.0

(.22)

8.4

(.02)

13.3

(.04)

PFZ

17

_

11.5

(.05)

5.4

(.01)

 

_

5.2

(.02)

8.2

(.02)

18

~~

13.3

(.06)

5.5

(.02)

_

6.3

(.02)

7.9

(.03)

Footwall

19

~~

~

-

5.3

(.02)

6.9

(.02)

7.7

(.03)

20

~~

-

--

--

-

_

_

-

34.1

(.10)

Table 11. Permeability and porosity values from cross-hole air-injection testing using borehole NDR-MF#1 for injection and 

borehole NDR-MF#3 for monitoring

[Permeability values are 10" 12 meter squared; porosity is in parentheses; --, no data; FZ, fault zone; PFZ, partial fault zone, defined as a monitor interval 

located in the fault zone and footwall]

Test 

number

25

Injection 

interval depth 

(meters)

25.8-27.8

Injection 

interval 

structural unit .

Hanging wall

Permeability and porosity values from monitor intervals 

bore located in borehole NDR-MF#3

Hanging Wall

1 2

5.1 4.0

3

4.9

(.02) (.03) (.04)

32

36

13.3-15.3

5.5-7.5

Fault zone

Footwall

..

..

..

-

--

-

4

3.1

(.02)

31.4

(.10)

-

5

8.8

(-07)

12.2

(.14)

~

FZ

6

-

~

26.1

(.07)

15.5

(.05)

PFZ

7

~

-

27.3

(.07)

16.2

(.20)

8

~

~

9.0

(.06)

9.9

(.05)

Footwall

9

-

-

15.3

(.07)

10.0

(.06)

10

-

"

~

--

~

--

Table 12. Permeability and porosity values from cross-hole air-injection testing using borehole NDR-MF#1 for injection and 

borehole NDR-MF#2 for monitoring

[Permeability values are 10 meter squared; porosity is in parentheses; --, no data; FZ, fault zone; PFZ, partial fault zone, defined as a monitor interval 

located in the fault zone and footwall]

Test 

number

25

32

36

Injection 

interval depth 

(meters)

25.8-27.8

13.3-15.3

5.5-7.5

Injection 

interval 

structural unit .

Hanging wall

Fault zone

Footwall

Permeability and porosity values from monitor intervals 

located in borehole NDR-MF#2

Hanging Wall

11

5.8

(.04)

~

-

12 13

4.0 2.2

(.04) (.01)

..

__

-

14

6.1

(.03)

20.8

(.19)

-

15

17.2

(.10)

37.9

(.27)

23.6

(-16)

FZ

16

~

-

27.3

(.08)

11.7

(.06)

PFZ

17

~

~

11.5

(.06)

9.6

(.04)

18

~

~

15.7

(.06)

8.8

(.04)

Footwall

19

~

--

16.5

(-06)

9.3

(-04)

20

--

--

-

--

28 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
Table 13. Statistical summary of permeability values from 

the type-curve analytical solutions of cross-hole air-injection 

testing of the northern Ghost Dance Fault

-12 [Permeability values are 10 meter squared]

Structural 

unit

Hanging wall 

Fault zone 

Footwall

Permeability 

values 

arithmetic 

mean

5.0 

18.1 

8.7

Permeability 

values 

range

0.7-12.8 

7.0-37.9 

1.1-34.1

Permeability 

values 

geometric 

mean

4.1 

14.6 

7.8

pressure responses from the field. This iterative 

process was repeated until a qualitative best match 

between the pressure responses from the model and 

the pressure responses from the field testing was 

obtained. The pressure responses from three monitor 

intervals of field test 16 and the AIR3D numerical 

model predicted pressure response are presented in 

figure 13. The three monitor intervals were located in 

the fault zone at distances of 4.4, 4.5 and 4.1 meters 

from the air-injection interval. The numerical model 

predicted pressure response is for a linear distance of 

4.5 m. The numerical model used a fault-zone permeability value of 20 x 10" 12 m2 and porosity value of 

0.20, which were ultimately selected as the values 

providing the qualitative best match.

The AIR3D numerical model permeability and 

porosity values that best matched the observed field199 test pressure responses are: footwall 10.0 x 10 m , 

and 0.07; fault zone 20.0 x 10" 12 m2, and 0.20; 

hanging wall 5.0 x IO' 12 m2, and 0.05. These values 

are very similar to the type-curve values and indicate 

close agreement between the two methods; however, 

there are additional considerations. The pressure 

responses from the numerical model replicated the 

field data from the fault zone more accurately than the 

data from the footwall and the hanging wall. The 

early-time field data (< 100 seconds) from the footwall 

are a closer match when the model-footwall permeability and porosity values are 5.0 x IO" 12 m2 and 0.05. 

The same is true for the hanging wall where permeability and porosity values of 3.0 x 10" 12 m2, and 0.03 

provide a better fit to the early-time field data. 

However, the late-time field data (>100 seconds) indicated a higher permeability and porosity; therefore, 

the best-match permeability and porosity values are a 

compromise to best fit both the early- and late-time 

data. An alternative model would use the lower permeability values for the hanging wall and the footwall

and would assume a constant-head boundary, such as a 

large fracture, to account for the late-time rapid stabilization of the pressure responses. Because the field 

work (geologic mapping, fracture mapping, borehole 

logging, and air-injection testing) does not indicate 

any physical feature that could act as a constant-head 

boundary, a compromise needs to be made; therefore, 

the best-match permeability and porosity values are a 

reasonable match to the field data. Other possible 

interpretations include a high-permeability connection 

of the fracture system to the NDR and the NDR is the 

constant head boundary or possibly the footwall and 

hanging wall would be better represented using a dualporosity model. As already noted, the pressure 

responses did not indicate a dual-porosity system (no 

delayed storage); however, the large porosity values 

indicate that the assumption of a water-saturated 

matrix may be questionable.

Discrete-Feature Analysis Using FRACMAN

The CLUSTRAN analysis identified six statistically significant fracture groups in the NGDFA. The 

strike and dip of the fracture planes in degrees are: 

059/88,075/84,125/84, and 332/63; minor subsets are 

at 192/87 and 199/63. The fractures are moderately to 

steeply inclined, trend in a northerly and in a northwesterly direction, and have nonuniform spacing. 

There was no apparent correlation between length and 

orientation, even though fractures that parallel the 

NGDFA had a greater probability of having long 

lengths. The analysis indicated that the fracture 

lengths follow log-normal, power law, and exponential 

distributions. The six fracture sets, and their statistical 

parameters were used as input to the FRACSYS algorithm of the FRACMAN code to generate a statistical 

fracture system that represented the NGDFA. Ten 

stochastic DFN realizations were generated, and the 

fracture characteristics of the simulated fracture 

systems then were compared to the DLS field data 

from the NGDFA. When the stochastically generated

Table 14. Statistical summary of porosity values from the 

type-curve analytical solutions of cross-hole air-injection 

testing of the northern Ghost Dance Fault

,3 /rv,3 [m /m , cubic meter per cubic meter]

Structural 

unit

Hanging wall 

Fault zone 

Footwall

Arithmetic 

mean 

(m3/m3)

0.04 

0.13 

0.04

Arithmetic 

range 

(m3/m3)

0.01-0.09 

0.05-0.27 

0.01-0.12

Geometric 

mean 

(m3/m3)

0.03 

0.10 

0.03

TEST RESULTS 29
100

0)

o

C/3

g 

5

LLJ 

DC 

D 

C/3 

C/3 

LJJ 

DC 

0.

§

LJJ 

Q

r 0.1

0.01

Interval 16

Interval 6

10 100

TIME, IN MINUTES

1,000 10,000

Figure 13. Pressure, with time, measured during air-injection test 16 for monitor intervals 6,15, and 16 

located at 4.4, 4.5, and 4.1 meters from the injection interval, and the numerical model predicted pressure response at a distance of 4.5 meters from the injection interval.

DFN fracture data were within one standard deviation 

of the DLS field data, the DFN model was calibrated. 

The input parameters for the six fracture sets used to 

generate the DFN model are listed in table 15. An 

additional three fracture sets that were applied to the 

intensely fractured 4-meter-wide fault zone are listed 

in table 16. The additional three fracture sets are based 

on a visual inspection of the fault zone and were 

included to compensate for the high density of fractures with trace lengths less than 0.3 m that were not 

included in the DLS.

Following the development of the fracture 

system, transmissivity values were assigned to the 

fractures. The initial transmissivity values were 

derived from the permeability values from the typecurve analysis of the cross-hole air-injection tests. The 

transmissivity distributions and the equivalent permeability values for the FRACMAN-DFN model footwall, fault zone, and hanging wall that best matched 

the cross-hole pneumatic field-testing data are listed in

table 17. The transmissivity values are based on an 

interval length of 2 m.

The permeability values from the DFN model 

are larger but generally in close agreement with the 

permeability values from the type curve and the 

AIR3D analysis. The steady-state pressure responses 

from cross-hole air-injection test 25 and the simulated 

steady-state pressure responses from the DFN model 

are presented in figure 14. The injection interval for 

test 25 and monitor intervals 1, 2, 3, 4, 5, 11, 12, 13, 

and 14 were located in the hanging wall of the GDF. 

Monitor intervals 6,1, 15, and 16 were located in the 

fault zone and monitor intervals 8, 9, 10, 17, 18, 19, 

and 20 were located in the footwall. The simulated 

pressure responses from the DFN model were similar 

to the field-testing pressure responses and indicated 

that the DFN model had replicated the fracture 

network and fracture permeability of the hanging wall. 

The steady-state pressure responses from the crossso Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
Table 15. Input parameters of the six fracture sets used to produce the FRACMAN discrete-features model 

[--, not applicable; k, permeability; SD, standard deviation; m2/m3 , square meter per cubic meter]

Fracture 

set

1

2

3

4

5

6

Table 16.

Model 

type

Baecher

Baecher

Baecher

Baecher

Baecher

Baecher

Strike/dip 

(degrees)

059/88

075/84

125/84

332/63

192/87

199/63

Orientation

Pole 

orientation 

trend/plunge 

(degrees)

329/02

345/06

035/06

242/27

099/03

109/27

Distribution 

type

Fisher

Fisher

Fisher

Fisher

Fisher

Fisher

Input parameters of the three additional fracture sets used in

_.. . Equivalent Dispersion ^ ..

(M radms

w (meters)

50

35

25

25

36 0.277

20

the fault zone to produce the

Distribution 

type

Truncated

log-normal

Truncated

log-normal

Truncated

log-normal

Truncated

log-normal

Truncated

power law

Truncated

exponential

Size

Mean / SD 

(meters)

0.614/0.27

0.62/1.8

0.97/2.06

0.56/0.8

2.5

0.54

FRACMAN discrete-features m

[--, not applicable; k, permeability; SD, standard deviation; m2/m3 , square meter per cubic meter]

TEST RESULS

w

Fracture 

set

1

2

3

Model 

type

War zone 

War zone

War zone

Strike/dip 

(degrees)

035/90 

000/90

315/90

Orientation

Pole 

orientation 

trend/plunge 

(degrees)

125/00 

090/00

045/00

Distribution 

type

Fisher 

Fisher

Fisher

_. . Equivalent Dispersion ^ .. 

flrt radius 

w (meters)

50 

50

50

Distribution 

type

Truncated 

log-normal

Truncated 

log-normal

Truncated 

log-normal

Size

Mean / SD 

(meters)

0.5/1.0 

0.5/1.0

0.5/1.0
Table 17. Transmissivity distributions and equivalent permeability values for the discrete-feature model

[m2/s, meter squared per second]

Structural 

unit

Footwall 

Fault zone 

Hanging wall

Distribution 

type

Log-normal 

Log-normal 

Log-normal

Transmissivity mean 

(m2/s)

9.06X10-04 

9.06x1 0'04 

2.3 1x1 0'04

Transmissivity 

standard deviation 

(m2/s)

2.30X10-04 

2.30X10'04 

8.30XKT04

Permeability 

mean 

(m2)

45.3x10-12 

45.3X10'12 

11.6X10'12

hole air-injection test 36, and the DFN model-simulated steady-state pressure responses are presented in 

figure 15. The injection interval for test 36 was located 

in the footwall of the GDF. The monitor intervals were 

the same as in test 25. The simulated pressure 

responses were similar to the field pressure responses 

and indicated that the DFN model had replicated the 

fracture network and the fracture permeability of the 

footwall. The steady-state pressure responses from the 

cross-hole air-injection test 32 and the DFN modelsimulated steady-state pressure responses are 

presented in figure 16. The injection interval for test 

32 was in the fault zone. The monitor intervals were 

the same as in tests 25 and 36. The simulated pressure

responses from the DFN model were generally higher 

than the field pressure responses by a factor of 3. To 

correct this discrepancy, the fracture intensity and 

transmissivity values for theJDFN fault zone were 

increased as much as an order of magnitude. However, 

the changes did not have a substantial effect on the 

simulated pressure responses. A dual-porosity model 

was run to determine if matrix porosity, associated 

with the breccia located in the fault zone, had any 

effect on the simulated pressure responses; the simulated pressure responses decreased slightly but did not 

change substantially. Only matrix porosity values of 

50 percent decreased the DFN model-simulated pressure responses to field-test values. Although core

1.00

CO

Q. 

O

111 0.50

DC

Z>

CO

CO

LU

DC

Q.

LU 

Q

0.25

0.00

I I I I I I I I I I I T

 A Field Test 25

-- -- Simulation 2

i i i i i i I I I I

o 1 56 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

MONITOR INTERVAL

Figure 14. Pressure changes measured during cross-hole air-injection test 25 and the pressure 

changes simulated by the discrete-feature model.

32 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
0.5

< 0.4

O 

CO

CL 

O

d 0.3

LLJ

DC

Z>

CO n? CO °'2

LU

DC

Q_

LU 0.1 

Q

1 I I I I I I I I I I I I I I I I I I I

 Field 

 .. «... simulated

i i i i i J__L

0 1 2 3 4 56 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

MONITOR INTERVAL

Figure 15. Pressure changes measured during cross-hole air-injection test 36 and the pressure 

changes simulated by the discrete-feature model.

CO

0.5

0.4

o

CO

£

O

^ 0.3

LU 

DC

z>

CO 02 CO °^ 

LU 

DC 

CL

LU 0.1 

Q

I I I I I I I I 1 I I I I I I 1 I T

 Field Test 32 

f -- --, ....... simulated ~ "

9 '

I I I I I I I I

0 1 2 3 4 56 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

MONITOR INTERVAL

Figure 16. Pressure changes measured during cross-hole air-injection test 32 and the pressure 

changes simulated by the discrete-feature model.

TEST RESULTS 33
analysis from borehole MF#3 indicated rubble zones 

and dense fracturing in the fault zone, a 50-percent airfilled porosity was considered too large to be realistic.

The DFN model indicated that cross-hole airinjection tests done in the GDF hanging wall and footwall can be simulated accurately using the DLS fracture-mapping data; and, because the model is based on 

real fracture data, the DFN will produce a more realistic fracture-flow model. The DFN model of the fault 

zone was not as successful because the intense fracturing of the fault zone was not adequately represented 

in the DLS fracture data. The DLS fracture mapping 

was limited to fractures with trace lengths greater than 

0.3 m; most of the fractures in the fault zone, although 

numerous, had trace lengths less than 0.3 m and were 

not mapped nor were they adequately represented by 

the three additional fracture sets. The AIR3D numerical modeling indicated that, due to the high fracture 

density, the fracture zone is probably better simulated 

as an equivalent porous medium. Because the DFN 

provides a model of the footwall and hanging wall that 

is closer to reality, it may be possible to increase the 

scale of the DFN simulations to predict pressure 

responses at larger dimensions for areas that have fracture systems similar to the GDF hanging wall and 

footwall.

Results from Cross-Hole Tracer Testing in 

the Northern Drill Room Boreholes

Analysis Using Type Curves

The cross-hole tracer tests were analyzed using 

type curves (Moench, 1995). The results of the tracertest type-curve analysis are listed in table 18. Several 

tracer tests were unsuccessful because of equipment 

failure or other unforeseen problems. A plot of a 

typical tracer test and type-curve match is presented in 

figure 17. Peclet numbers ranged from 3 to 22 except 

for a single test that resulted in two Peclet numbers of 

80 (table 18). Advective traveltimes ranged from 0.011 

to 1.110 days. Transport-porosity values ranged from 

0.001 to 0.070. Longitudinal-dispersivity values 

ranged from 0.06 m to 2.63 m. Tracer tests 1 through 8 

generally had similar tracer arrival plots for He and 

SF6 . The similar plots indicated that the small He 

molecule did not diffuse more readily into the small 

matrix pores and that the larger SF6 molecule was not 

adsorbed onto tuff materials as it has been shown to do

(Rattray and others, 1995); or, the effects are small and 

of the same order of magnitude.

A statistical summary of the northern GDF 

transport-porosity and longitudinal-dispersivity values 

by geologic structure are listed in table 19. Tracer tests 

done in the footwall of the GDF had transport-porosity 

values that ranged from 0.003 to 0.032 with an average 

value of 0.013. Tracer tests done in the fault zone had 

transport-porosity values that ranged from 0.004 to 

0.034 with an average value of 0.014. Tracer tests 

done in the hanging wall had transport-porosity values 

that ranged from 0.001 to 0.070 with an average value 

of 0.013. Tracer tests done in the footwall of the GDF 

had longitudinal-dispersivity values that ranged from 

0.42 to 1.54 m with an average of 1.03 m. Tests done 

in the fault zone had longitudinal-dispersivity values 

that ranged from 0.37 to 1.38 m with an average of 

0.62 m. Tests done in the hanging wall had longitudinal-dispersivity values that ranged from 0.06 to 

2.63 m with an average of 0.76 m.

The wide range of transport-porosity and longitudinal-dispersivity values may indicate that the test 

scale was smaller than the representative elementary 

volume. Figure 18 is a lower hemisphere plot showing 

the direction and plunge of the tracer tests and the 

calculated transport-porosity values. The plot does not 

indicate any directional control; slow and fast tracer 

transport pathways occur in the same direction and 

plunge. The tracer data and locations of the pumped 

and tracer release intervals for the individual crosshole tracer tests are available in the YMP data packages DTN: GS980283122410.003 and 

GS981183122410.005.

A plot of the longitudinal-dispersivity values 

with test scale for several NTS fractured-rock tracer 

test programs, including the NGDFA tracer testing, is 

shown in figure 19. The plot indicated that the longitudinal-dispersivity values increase with test scale. The 

data for the Amargosa Tracer site are from Gelhar and 

others (1992) and the C-wells data are from Fahy 

(1997).

Discrete-Feature Analysis Using MAFIC

The MAFIC computer code (Miller and others, 

1994) was used to simulate tracer flow in the DFN 

model developed using FRACMAN. The MAFIC 

code uses a three-dimensional network of triangular 

finite elements for either a single- or a dual-porosity 

mode. The MAFIC code simulates solute transport

34 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
Table 18. Results of tracer-test analysis by type curves

[He, helium; SF6, sulfur hexafluoride; -, no data; m3/m3 , cubic meter per cubic meter]

Test number 

and tracer

IHe

1SF6

2He

2SF6

3He

3SF6

4He

4SF6

5He

5SF6

6He

6SF6

7He

7SF6

8He

8SF6

9He

9SF6

lOHe

10SF6

HHe

11SF6

12He

12SF6

13He

13SF6

14He

14SF6

15He

15SF6

16He

16SF6

17He

17SF6

17SF6

14He

14SF6

15He

15SF6

16He

16SF6

17He

17SF6

17SF6

Structural 

unit

Footwall

Footwall

Fault zone

Fault zone

Hanging wall

Hanging wall

Hanging wall

Hanging wall

Hanging wall

Hanging wall

Hanging wall

Hanging wall

Footwall

Footwall

Footwall

Footwall

Hanging wall

Hanging wall

Hanging wall

Hanging wall

Hanging wall

Hanging wall

Hanging wall

Hanging wall

Footwall

Footwall

Footwall

Footwall

Fault zone

Fault zone

Fault zone

Fault zone

Hanging wall

Hanging wall

Hanging wall

Hanging wall

Hanging wall

Fault zone

Fault zone

Fault zone

Fault zone

Hanging wall

Hanging wall

Hanging wall

Linear 

distance 

(meters)

4.81

4.81

4.78

4.78

4.78

4.78

5.48

5.48

6.02

6.02

5.29

5.29

4.61

4.61

4.57

4.57

6.37

6.30

4.97

6.04

7.90

8.78

5.06

4.32

4.23

4.65

6.60

6.52

4.88

4.13

6.89

5.39

7.03

5.38

5.38

6.53

8.75

4.30

5.19

5.02

5.25

4.21

5.04

5.04

Advective 

traveltime 

(days)

0.212

0.235

0.153

0.130

0.032

0.032

0.366

--

0.162

0.129

0.600

0.575

0.028

0.028

0.218

--

0.580

0.570

0.077

0.083

1.110

0.334

0.137

0.208

0.251

0.066

~

--

0.453

0.142

0.433

--

0.195

0.100

0.159

0.219

--

0.050

--

0.092

--

0.172

0.060

0.011

Peclet 

number

8

6

11

8

80

80

12

--

9

9

11

5

3

3

3

--

9

-

6

22

3

22

5

11

3

11

--

--

11

11

5

--

8

5

11

6

--

8

--

9

--

5

5

22

Longitudinal 

dispersivity 

(meters)

0.60

0.80

0.43

0.60

0.06

0.06

0.46

-

0.67

0.67

0.48

1.06

1.54

1.54

0.91

--

0.71

--

0.83

0.27

2.63

0.40

1.01

0.39

1.41

0.42

-

--

0.44

0.37

1.38

--

0.88

1.08

0.49

1.09

--

0.54

-

0.56

--

0.84

1.01

0.23

Transport 

porosity 

(m3/m3)

0.019

0.032

0.014

0.012

0.002

0.002

0.018

~

0.005

0.004

0.030

0.029

0.003

0.003

0.023

--

0.018

0.018

0.005

0.003

0.015

0.003

0.070

0.017

0.003

0.005

--

--

0.034

0.018

0.011

--

0.004

0.005

0.008

0.006

--

0.004

--

0.006

--

0.019

0.004

0.001

TEST RESULTS 35
111 

O

o

O

HI 0.1

Q 

HI 

N

DC 

O

0.0

TYPE CURVE

01 0.1

TIME SINCE INJECTION, IN DAYS

Figure 17. Sulfur hexafluoride tracer arrival plot during tracer test 10 and type curve match.

using an advective particle-tracking approach. Solute 

dispersion was simulated stochastically using orthogonal, normally distributed, longitudinal and transverse 

dispersion vectors. Because of the small scale (<10 m) 

and the short transport times (<200 minutes) diffusion 

was assumed to be negligible. The DFN-MAFIC 

model was set up to model the SF6 convergent-tracer 

tests 15, 17, and 21. The simulations used the same

pumping rates used in the field testing, about 5.0 x 

10-04 m3/s a flm(i viscosity of 1.8 x 

10'5 Pa x s. The MAFIC code limits the number of

tracer particles to less than 1,000; therefore, the 

number of tracer particles ranged from 927 to 995. 

The simulations used a longitudinal-dispersivity value 

of 1.0 m, derived from the type-curve analysis, and 

assumed that the transverse dispersivity was 10 

percent of the longitudinal value (0.1 m).

A normalized simulated-tracer-arrival curve and 

the normalized field data from tracer test 17 are 

presented in figure 20. Background SF6 concentrations 

during tracer tests 15,17, and 21 were low, generally 

less than 0.1 ppm with a maximum of less than

Table 19. Statistical summary of the northern Ghost Dance Fault transport-porosity and 

longitudinal-dispersivity values by geologic structure

[m /m3, cubic per cubic meter; arithmetic mean in parentheses]

Geologic structure

Footwall 

Fault zone 

Hanging wall

Transport-porosity range 

(m3/m3)

0.003-0.032 

(0.013)

0.004-0.034 

(0.014)

0.001-0.070 

(0.013)

Longitudinal-dispersivity range 

(meters)

0.42-1.54 

(1.03)

0.37-1.38 

(0.62)

0.06 - 2.63 

(0.76)

36 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
0.018

WEST - EAST

0.014

0.002

SOUTH

Figure 18. Stereonet plot showing a lower hemisphere plot of transport-porosity values and the threedimensional orientation, by bearing and plunge, of the associated tracer tests.

1.0 ppm, and therefore were not compensated for in 

the analysis. During tracer test 17, the SFg tracerrelease interval and the pumped interval were located 

in the hanging wall. The peak arrival time was 

200 minutes. The early-time simulated values were a 

close match to the field data except for the simulated 

values near 60 to 80 minutes. The spikes in the simulated curve may be because of the limited number of 

tracer particles or because there was not a sufficient 

number of time steps to smooth the curve. Generally, 

the simulated tracer arrival was a close match to the 

field data; therefore, the DFN model had replicated the 

fracture flow and transport in the GDF hanging wall.

A normalized simulated-tracer-arrival curve and 

the normalized field data from tracer test 21 are

presented in figure 21. During tracer test 21, the SF6 

tracer-release interval and the pumped interval were 

located in the footwall. The simulated peak-arrival 

time was 55 minutes. The peak arrival time during the 

field test was 95 minutes. The shapes of the two curves 

are similar, including curve spreading and tailing; first 

and last arrival times also are similar. The spikes in the 

simulated curve may be because of the limited number 

of tracer particles or because the number of time steps 

was insufficient to smooth the curve. The 40-minute 

difference between peak arrival times may indicate 

that the simulated fractures have better connections 

from source (tracer release interval) to sink (pumped 

interval) than the true fracture network. Although the 

peak-arrival times are different, the DFN model

TEST RESULTS 37
100

CO

cr

UJ

10

CO

cr

UJ

o_

CO 

Q

Q

b 0.1 

O

0.01

.*» 

 Northern Ghost Dance Fault Alcove

 C Wells

o Amargosa Tracer Site

i i i______i___, I,,

10 100

TEST SCALE, IN METERS

1,000

Figure 19. Longitudinal-dispersivity values and test scale for tracer tests performed at or near Yucca Mountain.

provides a more realistic numerical understanding of 

fracture flow and transport in the footwall than the 

equivalent continuum approach.

The traveltimes measured during the fault-zone 

tracer testing did not indicate that the transport 

porosity of the fault zone was higher than the footwall 

nor the hanging wall, despite the increased fracturing 

in the fault zone. A normalized simulated-tracerarrival curve and the normalized field data from test 15 

are presented in figure 22. During tracer test 15, the 

SF6 tracer-release interval and the pumped interval 

were located in the fault zone. The simulated tracer 

test was not a close match to the field data. The peakarrival time for the simulated test was 50 minutes. The 

peak-arrival time of test 15 was 190 minutes. A dualporosity model was run to determine if an increase in 

the total porosity would produce a peak-arrival time 

that was more consistent with the field data. Simulated 

tracer-arrival times that approached the field-arrival 

times were accomplished only when matrix porosities 

were increased to 50 percent. Although core analysis 

from borehole MF#3 indicated rubble zones and dense 

fracturing in the fault zone, a 50-percent air-filled 

porosity was considered too large to be realistic.

Representative fracture geometry is difficult to extract 

from these broken zones and the fault-zone intense 

fracturing was not captured in the DLS. As was 

concluded from the cross-hole air-injection testing 

analysis, the DFN model did not adequately represent 

the fault-zone fracture system.

The flow paths of two particles during the DFN 

simulation of tracer test 17 are presented in figure 23. 

A particle tracker was used to visualize the flow path 

from the source (tracer-release interval) to the sink 

(pumped interval). The tracking indicated that the 

particles followed a tortuous and indirect route. The 

flow paths indicated that the travel distances of the 

tracked particles were up to six times longer than the 

linear distance. The long, tortuous flow paths are a 

partial explanation for the high transport-porosity 

values (up to 0.070) compared to the true fracture 

porosity that usually ranges between 10"2 to 10"5 

(Freeze and Cherry, 1979, p. 408). The variability in 

the length of the flow paths also indicated that a 

drawn-out arrival-time tail may not necessarily be a 

result of matrix diffusion but could be a result of a 

complex, variable, nonlinear tracer-transport route.

38 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
100

0.01

100 1,000 10,000

TIME, IN MINUTES

Figure 20. Tracer-arrival plot for tracer test 17 SF6 and tracer-arrival plot predicted by the discretefeature model.

The DFN model indicated that tracer tests done 

in the GDF hanging wall and footwall can be accurately simulated using data from DLS fracture 

mapping; and, because the DFN model is based on 

real fracture data, the DFN approach results in a more 

realistic transport model. The DFN model of the GDF 

fault zone was not as successful because the intense 

fracturing was not adequately represented by the DLS 

fracture data and therefore was not adequately represented in the model. The DLS fracture mapping was 

limited to fractures with trace lengths greater than 

0.3 m; most of the fractures in the fault zone, although 

numerous, had trace lengths less than 0.3 m. The DFN

modeling indicated that, due to the high fracture 

density, the fracture zone is probably better modeled 

as an equivalent porous medium. Because the DFN 

model is based on real fracture data, it provides a more 

accurate model of the footwall and hanging wall fracture-flow system, as opposed to the equivalent porousmedium approach. Because the DFN model provides a 

model that is closer to reality, it may be possible to 

increase the scale of the DFN simulations to predict 

transport at larger dimensions for areas that have fracture systems similar to the fracture systems of the 

GDF footwall and hanging wall.

TEST RESULTS 39
100 i 

QC

LU 

O

o 

o

£ 0.1 h

QCHQ 

LU 

N

CC

O

0.01

 Field

- Simulated

10 100

TIME, IN MINUTES

1,000 10,000

Figure 21. Tracer-arrival plot for tracer test 21 SF6 and tracer-arrival plot predicted by 

the discrete-feature model.

40 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
100

CE ILLI 

O

O 

O

CE

LU 0.1

CE IQ 

LLJ 

N

CE 

O

0.01

10 100 1,000

TIME, IN MINUTES

Field 

 Simulated

10.000

Figure 22. Tracer-arrival plot for tracer test 15 SF6 and tracer-arrival plot predicted by the 

discrete-feature model.

TEST RESULTS 41
-2

Figure 23. Diagram showing particle paths predicted by the discrete-feature model for two particles.

42 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
SUMMARY

Geothermal logging, air and core-water chemistry sampling, air-injection testing, and tracer testing 

were done in the northern Ghost Dance Fault (GDF) at 

Yucca Mountain, Nevada. The goals of the fault 

testing were to quantify the permeability values, 

porosity values, tracer-transport characteristics (transport porosity, longitudinal dispersivity), and fluid ages 

of the GDF and the volcanic rocks (tuff) of the footwall and hanging wall. The GDF testing was part of 

the Yucca Mountain Project (YMP) scientific study 

done by the U.S. Geological Survey in cooperation 

with the Department of Energy (DOE) to evaluate the 

potential for geologic disposal of high-level radioactive waste in an unsaturated-zone desert environment.

The Northern Ghost Dance Fault Alcove 

(NGDFA) consists of two sections the Northern 

Ghost Dance Fault Access Drift (NAD) and the 

Northern Ghost Dance Fault Drill Room (NDR). The 

NAD is located 3,737 m into the Exploratory Studies 

Facility (ESF) (measured from the ESF north 

entrance) and is about 230 m below the land surface. 

The NAD was constructed at a heading of due east and 

was initially constructed to a depth of 105 m 

(measured from the ESF centerline). From the face of 

the NAD, borehole NAD-GTB#la was drilled horizontally, at a heading of due east to a depth of 60 m. 

Borehole NAD-GTB#la penetrated the GDF at a 

depth of approximately 49 m. A downhole video log 

was run on November 1, 1996, and a geothermal log 

was run on November 7, 1996. After the geothermal 

logging was completed, excavation of the NAD was 

continued to a depth of 134.4 m, eliminating the upper 

29.4 m of borehole NAD-GTB#la. Following the 

construction, geothermal logging, air-injection testing, 

and chemistry sampling were done in the remaining 

section of borehole NAD-GTB#la. After the testing 

was completed, construction of the NAD continued to 

a depth of 174 m. The NAD intersected the main trace 

of the GDF at 152 m. Following completion of the 

NAD, the NDR was excavated at a heading of due 

north to a depth of 24 m. Following construction of the 

NDR, three test boreholes were drilled from the NDR 

into the GDF. The boreholes had western headings, 

were near horizontal, were parallel, were 30.5, 30.6, 

and 34.4 m in depth, and were oriented in a triangular 

configuration with 4.2-m sides.

The NGDFA and the boreholes are in the 

crystal-poor, middle nonlithophysal zone of the

Topopah Spring Tuff (Tptpmn). Borehole 

NAD-GTB#la was drilled from the hanging wall of 

the GDF, through the fault and into the footwall. The 

initial geologic interpretations of the fault and the 

broken zone (zone of intense fracturing) were based 

on the video log from borehole NAD-GTB#la. The 

video log identified a 12-m-wide broken zone that was 

variably brecciated, and consisted of fractured rock 

that had matrix- and clast-supported breccia zones. 

Excavation through the GDF revealed no distinct 

planes along the hanging wall and footwall and no 

slickensides. The GDF is a normal fault with a 

strike/dip of 180/80 on the footwall and 175/82 on 

the hanging wall. The fault offset is approximately 

3 meters. No secondary calcite or silica/opal was 

visible in the breccia or surrounding rock. Downhole 

video and caliper logs done in boreholes MF#1, 

MF32, and MF#3 identified an intensely fractured 

zone that extended from the main trace of the GDF 

about 1 m into the footwall and 3 m into the hanging 

wall. The intensely fractured zone is herein referred to 

as the "fault zone."

The geothermal log from borehole 

NAD-GTB#la indicated penetration of the NGDFA 

ventilation to depths of 3 to 5 m and a 0.1 °C temperature decrease throughout the 12-m-wide broken zone. 

The temperature decrease could indicate movement of 

cool air or water, or both, down the 12-m-wide broken 

zone. A geothermal log done at a later date did not 

record the previously measured temperature drop 

across the 12-m-wide broken zone but identified a 

0.05°C temperature increase at or near the main trace 

of the GDF. The temperature increase may indicate 

deep, warm air moving up the main trace of GDF. The 

stabilization of the temperature of the 12-m-wide 

broken zone may indicate that the earlier measured 

temperature drop may have been due to drillinginduced evaporative cooling or gas-expansion adiabatic cooling. Other temperature fluctuations may be 

due to drilling effects or possibly due to the variable 

borehole diameter. A more thorough understanding of 

the effect of barometric pressure on the temperature in 

the fault and 12-m-wide broken zone requires that 

geothermal logs be done during a range of barometric 

pressure fluctuations.

In-situ pneumatic pressures monitored in 

borehole NAD-GTB#la indicated limited barometric 

attenuation and small time lags. Comparison of the 

downhole-monitor interval pressure fluctuations 

(0.56 to 0.83 kPa) to the barometric-pressure fluctuaSUMMARY 43
tion (1.07 kPa) indicated that the permeability of the 

rock is high. Pressure monitoring showed no correlation between the amount of pressure attenuation and 

the distance from the NAD and no correlation between 

pressure attenuation and the distance from the main 

trace of the GDF. The amount of attenuation shows no 

pattern and may be random. The intermediate attenuation measured in monitor port 10, located farthest from 

the NAD, may indicate that the barometric pressure 

changes were transmitted from the land surface to 

depth through the GDF.

Gas-phase chemistry samples were collected in 

borehole NAD-GTB#la. The gas-phase CO2 concentrations ranged from 660 to 1,175 ppm. The CO2 

values increased and the 813C values decreased with 

increasing distance from the NAD (r = 0.89, and r = 

0.84). The CO2 and 813C values indicated that air from 

the NAD has penetrated the tuff, supporting the 

concept of a well-developed fracture connection to the 

NAD. Uncorrected 14C-age estimates from gassamples ranged from 2,400 to 4,500 years. The 14Cages from the monitor intervals are directly correlated 

(r = 0.75) to the degree of pressure attenuation that 

was measured during pneumatic monitoring. The 

age/attenuation correlation indicated that air from the 

NAD had penetrated the tuff through the fracture 

system. Tritium analysis (classified as non-quality 

assured) on core water identified eight samples at six 

depths that had tritium levels significant at two standard deviations. Three of the samples, at two depths, 

indicated that water had traveled from the land surface 

to depth during the last 45 years. The proximity of the 

elevated tritium values to the main trace of the GDF 

indicated that the fault is a conduit for the transport of 

water from the land surface through the nonwelded 

tuff of the Paintbrush Group and down to the Tptpmn.

Gas-phase chemistry samples were collected in 

boreholes MF#1 and MF#2. The gas-phase CO2 

concentrations ranged from 711 to 913 ppm. Gasphase 813C values ranged from -15.04 to -13.45. Gasphase 14C ages ranged from 2,500 to 3,600 years. 

There was no correlation between the parameters and 

depth. The data indicated that the gas samples were a 

mixture of NGDFA air and rock gas. A gas-sample 

from a monitor interval in the fault zone had the lowest 

CO2, largest 813C, and youngest 14C age, all indicating 

mixing with the NGDFA air. The mixing is probably 

due to (1) the high permeability of the fault zone, as 

identified in the air-injection testing; (2) the NAD 

penetration of the GDF, providing a short flow path;

and (3) the 17 months that elapsed between the NAD 

fault penetration in March 1997 and the gas sampling 

in August 1998. Tritium analysis (classified as nonquality assured) of core water from the two samples 

from borehole MF#1 had tritium levels significant at 

two standard deviations. The NDR borehole tritium 

data indicated that the fault is a conduit for the rapid 

transport (< 100 years) of water from the land surface 

through the nonwelded tuff of the Paintbrush Group 

and down to the Tptpmn, assuming that the tritium 

levels are not due to contamination.

Single-hole air-injection testing was done in 

borehole NAD-GTB#la. The permeability values of 

the hanging wall ranged from 0.1 to 2.5 x 10' 12 m2 

with an arithmetic mean of 1.1 x 10" 12 m2 and a 

geometric mean of 0.5 x 10" 12 m2. In the fault zone, a 

zone of increased permeability associated with the 

GDF, permeability values ranged from 8.5 to 11.1 x 

10"12 m2 and had arithmetic and geometric means of 

10.0 x 10" 12 m2. The permeability values of the footwall ranged from 0.2 to 2.1 x 10" 12 m2 with an arithmetic mean of 1.0 x 10" 12 m2 and a geometric mean of 

0.7 x 10" 12 m2. Comparison of the permeability values 

from borehole NAD-GTB#la to the Tptpmn permeability values from the surface-based testing program 

(0.37 to 2.7 x 10" 12 m2) indicated that the permeability 

values for the hanging wall and the footwall are in the 

same range as the surface-based values, while the 

fault-zone permeability values are several factors 

larger. The higher permeability values of the faultzone may be due to increased fracturing associated 

with the GDF.

Cross-hole air-injection tests were done 

between the three boreholes drilled from the NDR. 

Analysis of the pressure responses in the monitor 

intervals identified three zones where the monitor 

intervals had different pressure responses. These three 

zones corresponded to the structural units: footwall, 

fault zone, and hanging wall; the fault zone corresponds to the intensely fractured zone that extended 

from the main trace of the GDF 1 m into the footwall 

and 3 m into the hanging wall. Pressure responses did 

not change with direction. The type-curve analysis 

indicated a heterogeneous flow system that had three 

different homogeneous isotropic structural units corresponding to the footwall, fault zone, and hanging wall. 

The arithmetic mean permeability and porosity values 

of the three structural units are: footwall 8.7 x 10" 12 

m2, and 0.04; fault zone 18.1 x 10' 12 m2, and 0.13; 

hanging wall 5.0 x 10" 12 m2, and 0.04. Comparison of

44 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
the cross-hole permeability values from the NDR to 

the single-hole permeability values from borehole 

NAD-GTB#la indicated close agreement between the 

arithmetic means for the fault zone (values within a 

factor of 2) but differences approaching a factor of 5 in 

the hanging wall and almost an order of magnitude in 

the footwall. The permeability differences may be real 

or they may be a scale effect due to the smaller test 

scale of the single-hole GTB#la testing. The crosshole permeability values from the NDR are larger than 

the permeability values from the surface-based testing 

of the Tptpmn. The increased permeability is probably 

due to increased fracturing associated with the GDF.

A numerical model of the northern GDF flow 

system was developed using the USGS finite-difference model AIR3D. The model incorporated the 

geologic information from the detailed line survey 

(DLS), geologic mapping, visual inspection of the 

NAD and NDR, and borehole video logs. Pressure 

responses from the numerical model were visually 

compared to the pressure responses from the field 

tests. By using these comparisons, the model permeability and porosity values were adjusted, the model 

was rerun, and the simulated pressure responses again 

compared to the pressure responses from the field 

tests. The numerical model estimates of the permeability and porosity values were: footwall 

10.0 x 10'11 m2, and 0.07; fault zone 20.0 x 10' 12 m2, 

and 0.20; hanging wall 5.0 x 10' 12 m2, and 0.05. These 

values are very similar to the analytical type-curve 

values and indicate agreement between the two 

methods.

Following the type-curve and the AIR3D 

numerical analysis, a discrete-feature network (DFN) 

model of the NGDFA was developed using the 

computer code FRACMAN. The DFN analysis used 

the forward modeling approach of FRACMAN to 

develop a three-dimensional DFN model. The 

approach derived the geometry and spatial distributions of the fracture system used in the model from the 

DLS and the fracture data from the NAD and NDR. 

Following the development of the fracture system, 

transmissivity values were assigned to the fractures. 

The initial transmissivity values were derived from the 

permeability values from the type-curve and AIR3D 

analysis of the cross-hole air-injection tests. The transmissivity values were adjusted and the model was 

rerun until the simulated pressure responses from the 

DFN model were similar to the pressure responses 

from the cross-hole air-injection field tests. The simulated pressure responses from the DFN model were a 

close match with the field-test pressure responses from 

the hanging wall and footwall but not a close match 

with the field-test pressure responses from the fault 

zone. The pressure responses in the fault zone from the 

DFN model were generally higher than the pressure 

responses in the fault zone from the field tests; this 

may be because the high fracture density of the fault 

zone is better simulated as an equivalent porous 

medium.

Cross-hole convergent-tracer tests were done 

between intervals that had cross-hole pneumatic 

connections. The cross-hole tracer tests were analyzed 

using type curves. The initial type-curve analysis 

ignored the diffusion process because diffusion was 

assumed to be minimal on the rising limb of the breakthrough curve. Peclet numbers ranged between 3 and 

22 with a single test resulting in two Peclet numbers of 

80. Advective traveltime ranged from 0.011 to 1.110 

days. Transport-porosity values ranged from 0.001 to 

0.070. Longitudinal-dispersivity values ranged from 

0.06 to 2.63 m. Testing indicated no preferential He 

diffusion nor SF6 absorption. Tracer tests done in the 

footwall of the GDF had transport-porosity values that 

ranged from 0.003 to 0.032 with an average of 0.013. 

Tracer tests done in the fault zone had transportporosity values that ranged from 0.004 to 0.034 with 

an average of 0.014. Tracer tests done in the hanging 

wall had transport-porosity values that ranged from 

0.001 to 0.070 with an average of 0.013. The large 

range in transport-porosity values may indicate that 

the test scale was smaller than the representative 

elementary volume. The tracer tests did not indicate 

any directional control; slow and fast tracer transport 

pathways occur in the same direction and plunge.

The MAFIC computer code, combined with the 

DFN model, was used to simulate the cross-hole tracer 

tests. Because of the small test scale (<10 m) and short 

transport times (<200 minutes) diffusion was assumed 

to be negligible. As expected, the simulated tracerarrival plots were close matches with the tracer arrival 

plots from the field tests done in the hanging wall and 

the footwall but not in the fault zone. As identified in 

the DFN cross-hole air-injection model, the intense 

fracturing in the fault zone is not adequately represented by the DFN model. Particle tracking using the 

MAFIC code identified flow paths that were as much 

as six times longer than the linear distance. The long, 

tortuous flow paths are a partial explanation for the 

high transport-porosity values (up to 0.070) compared

SUMMARY 45
to the true fracture porosity that usually ranges 

between 10"5 and 10"2. The variability in the length of 

the flow paths also indicated that a drawn-out arrivaltime tail may not be a result of matrix diffusion but 

could be the result of a complex, variable, nonlinear 

tracer-transport route.

Although some limitations were identified in 

dealing with intensely fractured zones, the DFN model 

indicated that pressure tests and tracer tests done in the 

hanging wall and footwall of the GDF can be accurately simulated using data from fracture mapping. By 

using the DFN model, it may be possible to increase 

the scale of the simulations to determine traveltimes at 

larger dimensions for areas that have similar fracture 

networks as the fracture networks of the hanging wall 

and footwall of the GDF.

REFERENCES CITED

Bear, Jacob, 1972, Dynamics of fluids in porous media: 

New York, American Elsevier Publishing Co., 764 p. 

NNA. 19911127.0046

Bear, Jacob, 1979, Hydraulics of groundwater: New York, 

McGraw-Hill, 569 p. 

NNA. 19890906.0184

Dershowitz, W., Lee, G., Geier, J., Hitchcock, S., and La 

Pointe, PR., 1994, FRACMAN version 2.5 Interactive discrete feature data analysis, geometric modeling 

and exploration simulation: Redmond, Wash., Golder 

Associates, Inc. User Documentation, 171 p. 

MOL. 19970310.0091

Earlougher, R.C., 1977, Advances in well test analysis: 

Society of Petroleum Engineers Monograph Series, 

Millet the Printer Inc., Dallas, Texas, 264 p. 

NNA. 19900104.0471

Fahy, M.F., 1997, Dual-porosity analysis of conservative 

tracer testing in saturated volcanic rocks at Yucca 

Mountain in Nye County, Nevada: International 

Journal of Rock Mechanics and Mining Science, 

v. 34, no. 3-4, paper no. 074, 5 p. 

MOL. 19980211.0272

Freeze, R.A., and Cherry, J.A., 1979, Groundwater: 

Prentice-Hall Inc., Englewood Cliffs, N.J., 604 p. 

TIC#3476

Fritz, P., and Fontes, J. Ch., 1980, Handbook of environmental isotope chemistry: Amsterdam, Elsevier 

Scientific Publishing Co., 545 p. 

TIC#243187

Gelhar, L.W., Welty, Claire, and Rehfeldt, K.R., 1992, A 

critical review of data on field-scale dispersion in aquifers: Water Resources Research, v. 28, no. 7, p. 1955-

1974.

MOL. 19980514.0053

Hvorslev, M.J., 1951, Time lag and soil permeability in 

ground-water observations: Vicksburg, Miss., U.S. 

Army Corps of Engineers, Waterways Experiment 

Station, Bulletin 36, 50 p. 

TIC#238956

Joss, C.J., and Baehr, A.L., 1995, Documentation of

AIR3D, an adaptation of the ground-water-flow code 

MODFLOW to simulate three-dimensional air flow in 

the unsaturated zone: U.S.Geological Survey OpenFile Report 94-533, 154 p. 

MOL. 19990706.0174

LeCain, G.D.,1995, Pneumatic testing in 45-degree-inclined 

boreholes in ash-flow tuff near Superior, Arizona: 

U.S. Geological Survey Water-Resources Investigations Report 95-4073, 27 p. 

MOL. 19960715.0083

LeCain, G.D., 1997, Air-injection testing in vertical boreholes in welded and nonwelded tuff, Yucca Mountain, 

Nevada: U.S. Geological Survey Water-Resources 

Investigations Report 96-4262, 33 p. 

MOL. 19980310.0148

LeCain, G.D., 1998, Results from air-injection and tracer 

testing in the upper Tiva Canyon, Bow Ridge Fault, 

and upper Paintbrush contact alcoves of the exploratory studies facility, August 1994 through July 1996, 

Yucca Mountain, Nevada: U.S. Geological Survey 

Water-Resources Investigations Report 98-4058,28 p. 

MOL. 19980625.0344

McDonald, M.G., and Harbaugh, A.L., 1988, A modular 

three-dimensional finite-difference ground-water flow 

model: U.S. Geological Survey Techniques of WaterResources Investigations, book 6, chap. Al, 586 p. 

NNA. 19870729.0113

Miller, I. Lee, G., Dershowitz, W, and Sharp, G., 1994, 

Matrix/fracture interaction code (MAFIC) with solute 

transport: Redmond, Wash., Golder Associates, Inc., 

User Documentation version 81.4, 58 p. 

MOL.19961122.0411

Moench, A.F., 1995, Convergent radial dispersion in a 

double-porosity aquifer with fracture skin Analytical solution and application for a field experiment in 

fractured chalk: Water Resources Research, v. 31, 

no. 8, p. 1823-1835. 

TIC#233132

Ramey, H.J., 1982, Well-loss function and the skin effect 

A review: Geologic Society of America, Special Paper 

189, p. 265-271. 

TIC#245159

46 Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air-Injection Testing, and Tracer Testing in the 

Northern Ghost Dance Fault, Yucca Mountain, Nevada, November 1996 to August 1998
Rattray, G.W., Striegl, R.G., and Yang, I.C., 1995, Adsorption of sulfur hexafluoride onto crushed tuffs from the 

Yucca Mountain Area, Nye County, Nevada: U.S. 

Geological Survey Water-Resources Investigations 

Report 95-4057, 29 p. 

MOL. 19970331.0042

Theis, C.V., 1935, The relation between the lowering of the 

piezometric surface and the rate and duration of 

discharge of a well using ground-water storage: American Geophysical Union Transcript no. 16, p. 519-524. 

NNA. 19870729.0100

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

Data description

Borehole video and caliper logs GTB#la

Borehole video and caliper logs MF#1, 2, and 3

BOR Detailed Line Survey of the NAD and NDR

Geothermal logs GTB#la

Pneumatic monitoring GTB#la

Gas-phase chemistry GTB#la

Gas-phase chemistry MF#1

Gas-phase chemistry MF#2

Tritium data GTB#la (USGS)

do

Tritium data MF#1 (U of Miami)

GTB#la, single-hole air-k

2-D air-injection tests

3-D air-injection tests

2-D tracer tests

3-D tracer tests

Data tracking number

LARO831422AQ97.001

LARO83 1422AQ97.002

GS9708083 14224.014

GS970383 12241 0.005

GS970283 12241 0.003

GS970283122410.002Q

GS98 1283 12241 0.006

GS98 1283 12241 0.006

GS970283 122410.002

GS990183122410.001

GS990183122410.004

GS970383 122410.004

GS980183122410.001

GS981 183122410.005

GS980283 12241 0.003

GS981 183122410.005

QA 

status

Q

Q

Q

Q

Q

Q

Q

Q

J non-Q

'non-Q

'non-Q

Q

Q

Q

Q

Q

Computer software identification numbers

1. AIR3D, U.S.Geological Survey documented computer code: ESP 22.01

2. CLUSTRAN, Bureau of Reclamation documented computer code: ESP 5.21

3. FRACMAN, Colder and Associates documented computer code: ESP 14.01 

'non-Q, non-quality-assured data.

REFERENCES CITED 47

 & U.S. GOVERNMENT PRINTING OFFICE: 2000 573-082 / 47016 Region No. 8