APPENDIX C BOREHOLE GEOPHYSICAL SURVEYS BY GEOVISION, … Report-Appendix C.pdf · rock, (I): D 420...

51-1-10079-028

APPENDIX C

BOREHOLE GEOPHYSICAL SURVEYS

BY GEOVISION, INC.

51-1-10079-028 AC/wp/ADY 51-1-10079-028 C-i

APPENDIX C


BY GEOVISION, INC.

TABLE OF CONTENTS

Page

C.1. GENERAL .......................................................................................................................C-1

C.2. ACOUSTIC TELEVIEWER SURVEY ..........................................................................C-1

C.3. NATURAL GAMMA RAY LOGGING .........................................................................C-1

C.4. INDUCTION LOGGING ................................................................................................C-2

FIGURES

Televiewer and Natural Gamma Ray Surveys by GeoVision (63 pages)

51-1-10079-028 AC/wp/ADY 51-1-10079-028 C-1

APPENDIX C


BY GEOVISION, INC.

C.1. GENERAL

GEOVision of Corona, California performed acoustic televiewer and natural gamma logging in boring B-12. Their report is attached to this appendix. Borehole televiewer surveys are down hole logging techniques that provide an image of the borehole surface. Geologic features such as sedimentary bedding and fractures commonly can be imaged in borehole televiewer surveys. These images include the boring depth, inclination and size. With this information the orientation can be calculated. Bedding and discontinuity attitudes obtained from the borehole televiewer surveys are also included on the B-12 boring log in Appendix B.

Previously, GEOVision performed acoustic and televiewer logging of boreholes B-1 and B-7 (August 15, 2012) and induction and natural gamma logging in borings B-1, B-3, and B-4 through B-11, optical and acoustic televiewer logging in boring B-10, and acoustic televiewer logging in boring B-11 (December 19, 2012).

C.2. ACOUSTIC TELEVIEWER SURVEY

The GEOVision borehole televiewer survey was performed using a RG Borehole Televiewer, or equivalent. The borehole acoustic televiewer utilizes acoustic waves to image the internal surface of the borehole. Because it is acoustic, and not optical, it does not require clear water to operate. The resulting images can be laid out vertically almost like a physical core. The instrument has a built-in fluxgate magnetometer to maintain orientation accuracy throughout the

be mapped, but oriented in space to provide an orientation angle relative to north, and a dip angle at a measured depth. This analysis is done after the data collection using specialized software tools. The acoustic televiewer requires a stable, fluid filled, uncased borehole between 67 and 150 mm diameter.

C.3. NATURAL GAMMA RAY LOGGING

GEOVision performed natural gamma ray logging for boring B-12. Natural gamma ray logging is a method of measuring naturally occurring gamma radiation to characterize the rock in a borehole. Natural gamma radiation in rock typically increases with increasing clay content;

51-1-10079-028 AC/wp/ADY 51-1-10079-028 C-2

therefore, it can be used to identify lithology and stratigraphy in boreholes or wells. In particular, shale usually emits more gamma rays than other sedimentary rocks, such as sandstone, because radioactive potassium is a common component in their clay content. This difference in radioactivity allows the gamma tool to distinguish between shale and non-shale rock types. The gamma ray log, like other types of well logging, is done by lowering an instrument down the hole and recording gamma radiation variation with depth. The resultant logging allows for the selection of contacts between geologic units. Because gamma radiation can penetrate steel, plastic and fluids, the logging can be done in cased holes, and uncased holes with or without drilling fluid.

C.4. INDUCTION LOGGING

GEOVision performed induction logging in boring B-12. Induction logging is a method of well logging measures electrical conductivity. Most rock materials are essentially insulators, while their enclosed fluids are conductors. The results can be used to characterize rock porosity and permeability.

C.5. REFFERENCES

ASTM International (ASTM), 2006, Annual Book of Standards-Construction, v. 4.08, soil and rock, (I): D 420 D 5611: West Conshohocken, Pa

Ulusay, Resat and Hudson, J. A., eds., 2007, The complete ISRM suggested methods for rock characterization, testing and monitoring: 1974-2006: Ankara, Commission on Testing Methods, International Society of Rock Mechanics, 628 p.

Shannon & Wilson, Inc., 2012a, Final Geotechnical Report, White Point Landslide: Report prepared by Shannon & Wilson, Inc., Glendale, Calif., W. O. E1907483, for City of Los Angeles Geotechnical Engineering Group, Los Angeles, Calif., August, 467 p.

Shannon & Wilson, Inc., 2012b, Final Addendum Geotechnical Report No. 1, White Point Landslide: Report prepared by Shannon & Wilson, Inc., Glendale, Calif., W. O. E1907483, for City of Los Angeles Geotechnical Engineering Group, Los Angeles, Calif., August, 500 p.

WHITE POINT LANDSLIDE

BORING B-12

TELEVIEWER AND NATURAL GAMMA SURVEYS

April 19, 2013 Report 13120-01 rev 0

GEOVision Report 13120-01 White Point Boring B-12 Surveys rev 0 April 19, 2013 Page 1 of 63

WHITE POINT LANDSLIDE

BORING B-12

TELEVIEWER AND NATURAL GAMMA SURVEYS

Prepared for

Shannon & Wilson, Inc. 664 West Broadway

Glendale, California 91204 (818) 543-4560

Prepared by

GEOVision Geophysical Services 1124 Olympic Drive

Corona, California 92881 (951) 549-1234 Project 13120

April 19, 2013 Report 13120-01 rev 0


TABLE OF CONTENTS

TABLE OF CONTENTS ............................................................................................................................... 3

TABLE OF FIGURES ................................................................................................................................... 4

TABLE OF TABLES..................................................................................................................................... 4

TABLE OF APPENDICIES........................................................................................................................... 4

INTRODUCTION........................................................................................................................................... 5

SCOPE OF WORK ....................................................................................................................................... 5

INSTRUMENTATION ................................................................................................................................... 6

ACOUSTIC TELEVIEWER INSTRUMENTATION ...................................................................................................... 6

INDUCTION / NATURAL GAMMA INSTRUMENTATION ............................................................................................ 8

MEASUREMENT PROCEDURES ............................................................................................................. 10

ACOUSTIC TELEVIEWER MEASUREMENT PROCEDURES ................................................................................... 10

INDUCTION / NATURAL GAMMA MEASUREMENT PROCEDURES.......................................................................... 10

DATA ANALYSIS....................................................................................................................................... 12

ACOUSTIC TELEVIEWER ANALYSIS.................................................................................................................. 12

INDUCTION / NATURAL GAMMA ANALYSIS........................................................................................................ 13

RESULTS ................................................................................................................................................... 13

ACOUSTIC TELEVIEWER RESULTS .................................................................................................................. 13

INDUCTION / NATURAL GAMMA RESULTS......................................................................................................... 13

SUMMARY.................................................................................................................................................. 14

DISCUSSION OF TELEVIEWER RESULTS .......................................................................................................... 14

DISCUSSION OF INDUCTION / NATURAL GAMMA RESULTS ................................................................................ 14

QUALITY ASSURANCE .................................................................................................................................... 15

TELEVIEWER DATA RELIABILITY...................................................................................................................... 15


Table of Figures Figure 1: Concept illustration of televiewer probe......................................................................................17

Figure 2. Boring B-12, Acoustic Deviation Projection................................................................................21

Figure 3. Boring B-12, Induction and natural gamma logs ........................................................................22

Table of Tables Table 1. Boring locations and logging dates..............................................................................................16

Table 2. Logging dates and depth ranges .................................................................................................16

Table 3. Televiewer Deviation Data Summary ..........................................................................................16

Table 4. Boring B-12, Acoustic Structure depth, dip azimuth, dip and description....................................18

TABLE OF APPENDICIES

APPENDIX A PROCESSED TELEVIEWER LOGS WITH FRACTURE AND

BEDDING DEPTHS, DIPS, AND DIP AZIMUTHS

APPENDIX B ACOUSTIC TELEVIEWER BASED CALIPER LOGS

APPENDIX C INDUCTION AND NATURAL GAMMA LOGS


INTRODUCTION

Acoustic televiewer images, induction data and natural gamma data were collected in one

uncased rock boring at the White Point Landslide in San Pedro, California. Data acquisition was

performed on April 12, 2013 by Victor Gonzalez of GEOVision. Analysis and report

preparation was performed by Victor Gonzalez and Emily Feldman and reviewed by Robert

Steller of GEOVision. The work was performed under subcontract with Shannon & Wilson,

Inc., with Steven Diem serving as the point of contact for Shannon & Wilson.

This report describes the field measurements, data analysis, and results of this work.

SCOPE OF WORK

This report presents the results of induction, natural gamma and acoustic televiewer logs

collected in one uncased nominal 3.86 inch diameter boring, as detailed in Table 1. The purpose

of these studies was to supplement open fracture location information obtained during Shannon

& Wilsons rock coring program and to acquire fracture and bedding depths, azimuths and dips

as an aid in locating potential landslide failure planes.


INSTRUMENTATION

Acoustic Televiewer Instrumentation

Acoustic televiewer data were collected using a Robertson high resolution acoustic televiewer

probe (HiRAT), controlled by Robertsons HiRAT program, version 11. The total length of the

probe as used in this survey is 5.2 feet, with the sensor head located 0.5 feet above the bottom

end of the probe, as illustrated in Figure 1. The probe receives control signals from, and sends

data to, instrumentation on the surface via a 4-conductor armored cable. The cable is wound

onto the drum of a winch and is used to support the probe. Cable travel is measured to provide

probe depth data, using a sheave of known circumference fitted with a digital rotary encoder.

The probe and depth data are transmitted by USB link from the Micrologger unit to a laptop

computer where it is displayed and stored on hard disk. The probe is centered in the boring by

two sets of flat spring centralizers.

In this application, this probe is useful in the following studies:

Measurement of boring inclination and deviation from vertical

Determination of need to correct soil and geophysical log depths to true vertical depths

Acoustic imaging of the boring wall to identify fractures, dikes, and weathered zones,

and determine dip and azimuth of these features

This system produces images of the boring wall based upon the amplitude and travel time of an

ultrasonic beam reflected from the formation wall. The ultrasonic energy is generated by a

piezoelectric transducer at a frequency of 1.4 MHz. A periodic acoustic energy wave is emitted

by the transducer and travels through the acoustic head and boring fluid until it reaches the

interface between the boring fluid and the boring wall. Here a portion of the energy is reflected

back to the transducer, the remainder continuing on into the formation. By careful time

sequencing, the piezoelectric transducer acts as both the transmitter of the ultrasonic pulse and

receiver of the reflected wave. The travel time of the energy wave is the period between

transmission of the source energy pulse and the return of the reflected wave measured at the

point of maximum wave amplitude. The magnitude of the wave energy is measured in dB, a

unit-less ratio of the detected echo wave amplitude divided by the amplitude of the transmitted


wave. The strength of the reflected signal depends primarily upon the impedance contrast of the

boring fluid and the boring wall formation. In these rock borings, the contrast between the water

filling the boring and the rock formation generally provides high contrast. The changes in

reflectance between rock types provide imaging of healed fractures in the parent rock.

The acoustic wave propagates along the axis of the probe and then is reflected perpendicular to

this axis by a reflector that focuses the beam to a 0.1-inch diameter spot about 2 inches from the

central axis of the probe. This reflector is mounted on the shaft of a stepper motor enabling the

position of the measurement to be rotated through 360 . Sampling rates of 90, 180 and 360

measured points per revolution are available. During these surveys, data were collected at 360

samples per revolution, providing an equivalent horizontal pixel size of approximately 0.052

inches on the boring wall. It should be noted that during logging the probe is moving vertically

in the boring, so that the measured points describe a very fine pitch spiral.

The probe contains a fluxgate magnetometer to monitor magnetic north, and all raw televiewer

data is referenced to magnetic north. The processed data is referenced to true north, using a

declination of 12.5 degrees east for this site and dates, obtained from the NOAA declination web

site (http://www.ngdc.noaa.gov/geomag-web/#declination). Also, a three axis accelerometer is

enclosed in the probe, and boring deviation data is recorded during the logging runs, to permit

correction of structure dip angle from apparent dip, (referenced to boring axis), to true dip

(referenced to a vertical axis) in non-vertical borings. The probe is centered in the boring by two

sets of flat spring centralizers.

The data are presented on a computer screen for operator review during the logging run, and

stored on hard disk for later processing.


Induction / Natural Gamma Instrumentation

Formation conductivity and natural gamma data were collected using a DUIN model dual

induction probe, manufactured by Robertson Geologging, Ltd. The probe is 7.5 feet long, and

1.5 inches in diameter.

This probe is useful in the following studies:

Bed boundary identification

Strata correlation between borings

Strata geometry and type (shale indication)

The probe receives control signals from, and sends the digitized measurement values to, a

Robertson Micrologger II on the surface via an armored 4 conductor cable. The cable is wound

onto the drum of a winch and is used to support the probe. Cable travel is measured to provide

probe depth data, using a sheave of known circumference fitted with a digital rotary encoder.

The probe and depth data are transmitted by USB link from the Micrologger unit to a laptop

computer where it is displayed and stored on hard disk.

An Electro-Magnetic (EM) induction probe consists of transmitter and receiver coils. An

alternating current is applied to the transmitter coil, causing the coil to radiate a primary EM

field. This primary EM field generates eddy currents in subsurface materials, which give rise to a

secondary EM field. The secondary EM field is measured as an alternating current in the receiver

coils, which is proportional to formation conductivity. The probe coil spacing is optimized to

achieve high vertical resolution, minimal borehole influence and large radius of investigation.

The Robertson focused dual induction probe has effective coil spacings of 1.6 and 2.6 feet,

operates at a frequency of 39 kHz, has 1 millisiemens/meter resolution, and operates over a 5 to

3000 millisiemens/meter conductivity range.

Natural gamma measurements rely upon small quantities of radioactive material contained in soil

and rocks to emit gamma radiation as they decay. Trace amounts of uranium and thorium are

present in a few minerals, where potassium-bearing minerals such as feldspar, mica and clays


will include traces of a radioactive isotope of potassium. These emit gamma radiation as they

decay with an extremely long half-life. This radiation is detected by scintillation - the production

of a tiny flash of light when gamma rays strike a crystal of sodium iodide. The light is converted

into an electrical pulse by a photomultiplier tube. Pulses above a threshold value of 60 KeV are

counted by the probe's microprocessor. The measurement is useful because the radioactive

elements are concentrated in certain soil and rock types e.g. clay or shale, and depleted in others

e.g. sandstone or coal.


MEASUREMENT PROCEDURES

Acoustic Televiewer Measurement Procedures

Boring B-12 was logged with the acoustic televiewer below water level. In accordance with the

manufacturers recommended procedures, the probe was inspected and tested prior to entering

the boring. The probe was then positioned with the collar of the probe positioned at grade, and

the electronic depth counter was set to 4.72 feet, corresponding to the offset between collar and

imaging unit. The probe was lowered to the bottom of the boring, where data acquisition was

started on the laptop computer. The rotational scan resolution was set to 360 samples per

revolution, giving a horizontal pixel size of 0.035 inches. The probe was then raised at a

nominal rate of 3 feet per minute to static water level with an acquisition rate of 250

samples/foot, giving an equivalent vertical pixel size of 0.004 feet (approximately 0.05 inches).

This file was then closed and reviewed on the computer screen. Upon completion of the

measurements, the probe zero depth indication at grade was verified prior to removal from the

boring.

Induction / Natural Gamma Measurement Procedures

Boring B-12 was logged with the DUIN probe, which is not sensitive to the presence of water or

non-conductive casing. The probe was positioned with the top of the probe at ground surface,

and the electronic depth counter was set to the specified length of the probe. The probe was

lowered to the bottom of the boring where data acquisition was begun, and the probe was

returned to the surface at 10 feet/sec, collecting data continuously at 0.05-foot spacing, as

summarized in Table 2. Measurements followed ASTM D6726-01 (Re-approved 2007)

Conducting Borehole Geophysical Logging Electromagnetic Induction. This probe was not

calibrated in the field, as it is used to provide qualitative measurements, not quantitative values,

and is used only to assist in picking transitions between stratigraphic units, as described in

ASTM D5753-05 (Reapproved 2010), Planning and Conducting Borehole Geophysical

Logging. A functional test was performed prior to the logging run by placing a coil with an


effective conductivity value over the probe, and recording the resultant output of the system at

each conductivity value.

Natural gamma was not calibrated in the field, as it is a qualitative measurement, not a

quantitative value, and is used only to assist in picking transitions between stratigraphic units, as

described in ASTM D6274-10, Conducting Borehole Geophysical Logging Gamma.

Upon completion of the measurements, the probe zero depth indication at the depth reference

point was verified prior to removal from the boring.


DATA ANALYSIS

Acoustic Televiewer Analysis

The acoustic televiewer data were processed using Robertsons RGLDIP software, version 6.2.

Sinusoidal projections of fractures in the boring walls were interactively picked on the un-

wrapped televiewer image, and are presented on the logs as blue sinusoids superimposed over

the televiewer image. Bedding features, where identifiable, were picked on the same images,

and are presented on the logs as green sinusoids. The sinusoidal projections were processed

using the standard boring gauge of 3.86 inches to calculate apparent dip angle. True dip was

calculated, correcting for the plunge of the borings using the recorded data from the

accelerometers located in the probes, and presented in arrow format, with true dip indicated by

the arrow position across the plot. Azimuth of dip (not strike), is indicated by the direction of

the arrow tail, with true north being up. These values are presented with the comments to the

right of the arrow plots, as dip azimuth followed by dip angle.

The televiewer images were also processed to create a simulated core image of the borings. It

must be noted that the simulated core image represents a core that would have the full 3.86 inch

diameter of the boring, not the diameter of any cores removed during drilling, so that direct

comparison between the two is not possible. Also, the unwrapped image is viewed from the

perspective of an observer in the center of the boring looking outward. The simulated core

image is viewed form the outside of the boring looking inward, so there is a reversal of the

position of east and west relative to north between the two images.

The acoustic televiewer data were also processed to extract the deviation data and produce an

ASCII file and plots of boring deviation, as well as a 4-arm caliper log, derived from the acoustic

travel time data.


Induction / Natural Gamma Analysis

No analysis is required with the induction and natural gamma data; however depths to

identifiable boring features were compared to verify compatible depth readings on all logs.

Using WellCAD software version 4.3, these data were converted to LAS and PDF formats for

transmittal to the client.

RESULTS

Acoustic Televiewer Results

Acoustic televiewer images and dip data are presented in Appendix A. Acoustic Televiewer

based caliper logs are presented in Appendix B. Both are provided in PDF format as well.

Fracture and bedding depth, dip and azimuth of dip data are provided on the multi-page log

sheets in Appendix A, in Table 4 and in Microsoft Excel® format for input into stereonet analysis

programs.

Acoustic boring deviation data for B-12 are presented graphically in Figure 2, and summarized

in Table 3. Deviation data plots in Acrobat format and deviation data at 1.0-foot stations are

presented in ASCII format.

Induction / Natural Gamma Results

Induction data are presented in a combined log plot with natural gamma data as a single page log

in Figure 2. The multi-page, 1in:10ft scale, log is presented in Appendix C and on the disk (CD-

R) that accompanies this report.


SUMMARY

Discussion of Televiewer Results

Boring B-12 was drilled in soft fractured rock with a rotary mud diamond core bit, and produced

good televiewer images. The upper portion of the boring is intensely fractured. Many hairline

and healed fractures are present. The use of the acoustic televiewer data for the location of open

fractures is recommended, as the travel time function of the acoustic televiewer clearly

delineates areas where there is material absent from the boring wall. This is visible on the

acoustic televiewer derived caliper plots contained in Appendix B.

The boring exhibits a deviation of 0.8 degrees, deviating a horizontal distance of 1.75 feet over

the 129.5 foot depth boring, as summarized in Table 3. This corresponds to a maximum depth

error of 0.01 percent, which does not warrant adjustment of depth values on the logs.

Discussion of Induction / Natural Gamma Results

Conductivity and natural gamma profiles suggest interbedding of varying materials, and

correspond with changes in the televiewer logs.


Quality Assurance

These televiewer measurements were performed using industry-standard or better methods for

both measurements and analyses. All work was performed under GEOVision quality assurance

procedures, which include:

Use of NIST-traceable calibrations, where applicable, for field and laboratory

instrumentation;

Use of standard field data logs;

Use of independent verification of orientation and plunge by comparison of measured values

to as built information and reference structures, such as casing shoe or water surface, when

available.

Televiewer Data Reliability

Depth indications are very reliable with estimated precision of +/- 0.2 feet. Estimated precision

of dip and azimuth of dip is +/- 5 degrees. Standardized field procedures and quality assurance

checks add to the reliability of these data.


BORING DATES COORDINATES (1) ELEVATION (1)

DESIGNATION LOGGED NORTHING EASTING (FEET, MSL)

B-12 4/12/2013 (1) Coordinates provided by Shannon & Wilson

Table 1. Boring locations and logging dates

BORING TOOL AND RUN NUMBER

DEPTH RANGE (FEET)

OPEN HOLE (FEET)

DEPTH TO BOTTOM

OF CASING (FEET)

SAMPLE INTERVAL

(FEET)

DATE LOGGED

B-12 INDUCTION/GAMMA 01 129.8 2.5 130 3 0.05 4/12/2013B-12 ACOUSTIC TELEVIEWER 01 1.9 129.5 130 3 0.004 4/12/2013

- PROBE DID NOT TOUCH BOTTOM OF BORING

Table 2. Logging dates and depth ranges

BORING MEAN DEVIATION

AND AZIMUTH (DEGREES TN)

SURVEY DEPTH (FEET)

VERTICAL DEPTH (FEET)

DEPTH ERROR (FEET)

HORIZONTALOFFSET (FEET)

B-12 0.8 N178.9 129.46 129.44 0.02 1.75

Table 3. Televiewer Deviation Data Summary


Figure 1: Concept illustration of televiewer probe


Table 4. Boring B-12, Acoustic Structure depth, dip azimuth, dip and description

Depth Dip Structure

(feet) azimuth Dip

description

11.1 N335 37 Primary-structure Planar Bedding



19.2 N043 73 Fracture Planar Hairline-fracture


































Depth Dip Structure

(feet) azimuth Dip

description

















80.9 N094 1 Fracture Planar Open-fracture
























Depth Dip Structure

(feet) azimuth Dip

description

































Figure 2. Boring B-12, Acoustic Deviation Projection


Figure 3. Boring B-12, Induction and natural gamma logs


APPENDIX A

PROCESSED TELEVIEWER LOGS WITH FRACTURE AND BEDDING DEPTHS, DIPS, AND DIP AZIMUTHS


White Point Landslide Boring B-12 Acoustic Televiewer Features rev 1 Sheet 1 of 18


APPENDIX B

ACOUSTIC TELEVIEWER BASED CALIPER LOGS


White Point Landslide Boring B-12 Acoustic Televiewer Derived Caliper rev 1 Sheet 1 of 18


APPENDIX C

INDUCTION AND NATURAL GAMMA LOGS


Depth

Feet

1in:10ft

Natural Gamma

B-12

0 200CPS

Conductivity (short-spacing)

0 400mS/m

Conductivity (long-spacing)

0 400mS/m

0

10

20

30

40

50

60

70


Depth

Feet

1in:10ft

Natural Gamma

B-12

0 200CPS

Conductivity (short-spacing)

0 400mS/m

Conductivity (long-spacing)

0 400mS/m

80

90

100

110

120


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