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f SEISMIC INVESTIGATION, GROUND WATER
SUPPLY DEVELOPMENT PROGRAM
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ABOUT 1.5 MILES NORTHEAST OF TRUCKEE, CALIFORNIA
FOR
TRUCKEE DONNER PUBLIC UTILITY DISTRICT,
r TRUCKEE, CALIFORNIA
COOKSLEY GEOPHYSICS, INC
CGI JOB NUMBER 01-012
August, 2002
22070 Palo Way, Suite 3
Palo Cedro, CA 96073
Phone: (630) 647-5615,Fax: (630)647-5964
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SEISMIC INVESTIGATION, GROUND WATER
SUPPLY DEVELOPMENT PROGRAM
ABOUT 1.5 MILES NORTHEAST OF TRUCKEE, CALIFORNIA
SUMMARY AND CONCLUSIONS
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In June, 2002, Cooksley Geophysics, Inc., Palo Cedro, California, conducted a seismic exploration
survey to obtain profiles depicting the subsurface geologic conditions. The project area is located
approximately 1.5 to 3 miles northeast of the town of Truckee, California. The survey was conducted
to determine the nature of the stratified clastic and volcanic units and the geologic structural features
that underlie the traverses. This information will be used by the client, Aqua Hydro Geologic
Consulting, Reno, Nevada, to plan and direct a ground water development program for the Truckee
Donner Public Utilities District.
Seismic traverse A, the northernmost of the two west-to-east lines, is 1.28 miles long, starts 500 feet
east of Highway 89, and extends eastward to approximately 200 feet west of I-80, Seismic traverse B
`3 is one mile in length, starting approximately 1,840 feet west of Highway 89 and ending 750 teet west
of I-80.
Shot holes for the explosives, used as the seismic sources, were generally drilled 20 meters(66 feet)
apart and to a depth of up to 20 feet. Sensor stations were thirty three(33)feet apart. A five-man
crew and a geophysicist were used in the data acquisition phase of this program. Data was acquired
using a 48-channel Bison 9048 seismic recording system and processed utilizing the SEISTRIX 3
software package.
The geologic setting in the vicinity of Truckee consists of older basement rocks(not exposed in the
(is project area)covered by younger volcanic flows and interbedded sediments derived from the erosion
fW of the volcanics. These younger lithologies(the Truckee (?)and Lousetown formations) are the
target formations for the groundwater surveys.
The Truckee Basin, as considered in this report, covers an area of approximately 120 square miles.
The basin is bound on the west by the crest of the Sierra Nevada, which also forms the divide
r> between the Great Basin (in which the Truckee Basin occurs)and the Pacific watershed. The
northern boundary is also the Great Basin divide, but in this location the divide no longer marks the
crest of the Sierras. To the southwest the basin follows the Truckee River upstream to where the
river flows out of Lake Tahoe. The southeast boundary is the drainage divide between a
southeasterly flowing watershed that drains directly into Lake Tahoe and the northerly flowing
watershed that drains into the Truckee Basin. The eastern boundary is marked by a north-trending
fault scarp that follows the trace of Martis Creek, then cross the Truckee River and continues further
north.
At the onset of uplift of the Sierra Nevada, sediments of the Truckee (?) Formation were poorly
consolidated and quite susceptible to deformation and slope failure. Through the early to middle
phases of Sierran uplift, the volcanic events which resulted in the deposition of the Lousetown
Formation occurred. In addition to being tilted and faulted, much of the volcanics in the Lousetown
was eroded off the crest of the Sierra, transported easterly, and was re-deposited in the vicinity of the
town of Truckee. This eroded material conceivably can be present within the upper sections of the
Lousetown and in the Quaternary glacial and fluvial deposits.
In the Truckee area, acceptable quantities of groundwater are found in sediments in both the Truckee
(?) and Lousetown formations. As mentioned in the preceding paragraph, both formations
experienced considerable deformation and erosion as a result of the Sierran uplift. This has rendered
the geologic setting as very complex. Although some wells have encountered groundwater, others
have not. A better understanding of the geology of the Truckee Basin will result in a more successful
search for groundwater resources.
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Seismic Investigation for TDPUD 1
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Cooksley Geophysics, Inc.
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TABLE OF CONTENTS
,..; SUMMARY AND CONCLUSIONS., . ....... .... ....... .... .. ......... ....... .... ...... .........
I ;
TABLEOF CONTENTS ............ ............ ............ ............ ......_.... ............ ............ ..........2
` INTRODUCTION ...... ............ ............ ............ ............ I........... ..........3
DATAACQUISITION ......... ............ ............ ............ ............ ............ ............ ..........
FieldOperations............ ............ ............ ............ ............ ............ ............ ..........3
iField Parameters........... ............ ....... .. . . . .. ............ ............ ............ ..........5
Importance of Source Point-Sensor Station Geometry-... ...... ..... ............ ..........
6
DATA PROCESSING ........... ............ ............ ............ ............ ....._..... ..........6
Basic Processing........... ............ ............ ............ ............ ............ ............ ......
6
Common Depth Point Stacking.. ............ ............ ............ ............ ............ ..........6
FKFiltering .... .... ............ ............ ............ ............ ............ ............ ..........
NMO Correction Used in Defining Velocity Units. ............ ............ ............ ..........6
GEOLOGICSETTING ............ ............ ............ ............ ............ ............ ............ ..........7
,., General ......... ............ ............ ............ ............ _.......... ............ .I........7
} Sequence of Rocks
Rhyolite and Andesite Tuffs....... ............ ............ ............ ............ .......... 7
7
Kate Peak Formation (?)............ ............ ............ ............ ............ ..........8
OldTruckee(?)Formation.... ............ ............ ............ ............ ............. ...... ...
er Sediments(Pos).. ............ ............ ............ ............ ............ ..........8
Lousetown Formation.... ............ . .. . . . ....8
. . . . .. ............ ..
Prosser Creek Alluvium Member of the Lousetown Formation..... ..........8
sAlluvial Deposits............ ........... ....... .... ............ .......... ..........9
INTERPRETATIONS ............ ............ ............ ............ ............ ............ ............ ........13
General ............ ............ ............ ............ ............ ............ ............ ........13
Line ............ ............ ............ ............ ............ ............ .._........ ...I.... 13
LineB ............ ............ ............ ............ ............ ............ ............ ........14
REFERENCES ... ........... ............ ............ ............ ............ ........
APPENDIX A Alder Drive Lithologic Log ............ ............ ............ ............ ............ ........ 16
APPENDIX B Photographs of Field Operations.. ............ ............ ............ ...... . ...... 18
ILLUSTRATIONS
iFIGURE 1 PROJECT SITE MAP........... ............ ............ ............ ............ ............ ......... 4
FIGURE 2 Interbedded Units of the Lousetown Formation ....... . ..... ............ ........1
FIGURE 3 Detail of Lousetown Formation.......... ............ ............ ............ ............ ........11
FIGURE 4 Alluvium and Prosser Creek Alluvium Member........... ............ 4........... ........12
SEISMIC SECTION Line A-INTERPRETED..... ............ ............ ............ ............ ........20
SEISMIC SECTION Line B-INTERPRETED..... ............ ............ ............ ............ ........21
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Seismic Investigation for TDPUD
Cooksley Geophysics, Inc.
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INTRODUCTION
From June 17 through June 28, 2002, Cooksley Geophysics, Inc., Palo Cedro, California, conducted
seismic exploration on two west-to-east trending lines located in an area about 1.5 to 3 miles
northeast of the town of Truckee, California. This work was executed at the request of Aqua Hydro
Geologic Consulting, Reno, Nevada, as part of a ground water supply development program for the
F Truckee-Donner Public Utilities District(TDPUD).
IJ
The purpose of this seismic exploration program was to obtain seismic profiles depicting the
subsurface geologic conditions beneath an area between Alder Hill to the west and Interstate
P Highway 80(1-80)to the east. In particular, the survey was directed to the observation of the
stratified clastic and volcanic units and the geologic structural features that underlie the traverses.
This information will be used by the client to plan and direct a well drilling program for the purpose of
developing ground water resources for the TDPUD.
Seismic traverse A, the northernmost of the two west-to-east lines, is 1.28 miles long, starts about
500 feet east of Highway 89, and extends eastward to about 200 feet west of 1-80. Traverse A is
#.: located approximately 2,000 feet south of the section line that separates sections 35 and 36, T18N,
s R16E, from sections 2 and 1, T17N, R16E. Seismic traverse B is one mile in length, starting about
1,840 feet west of Highway 89 and ending about 750 feet west of 1-80. Traverse B is about 750 feet
<.' north of the section line that separates sections 2 and 1 from sections 11 and 12, T17N, R16E. The
locations of the seismic lines are shown on the Project Site Map(Figure 1).
DATA ACQUISITION
i Field Operations
Seismic field data recording operations were conducted from June 17 through June 28, 2002. The
weather was generally warm and had no affect on field operations. The terrain is slightly hilly.
Approximately 2.3 miles of seismic data was acquired along the two seismic lines.
The shot hole drilling program started one week before the seismic recording phase. Shot holes for
the explosives were drilled 20 meters(66 feet)apart along the seismic lines. The sensor stations
were thirty three (33) feet apart, thus the explosives were normally placed two stations apart. The
exceptions were where the lines crossed Highway 89 and Prosser Dam Road. Shot holes were
placed at least two stations (66 feet)from the edge of the highways. The designed depth of the shot
holes was twenty(20)feet, but many of the holes were shallower due to rocky conditions. Several of
the holes were moved one station to encounter better drilling conditions or to avoid power lines and
z: buried utilities.
3
A five-man crew and a geophysicist were used in the data acquisition phase of this program. The
party chief/observer managed and supervised the crew, operated the seismograph, and transferred
the seismic data to 3.5-inch, 1. 4-megabyte disks. Four field assistants deployed seismic cables and
r sensors, prepared the recording site, and loaded and fired the seismic charges under the supervision
of a licensed blaster.
The data was acquired using a 48-channel Bison 9048 seismic recording system. Explosive charges
electrically detonated in shallow drill holes were the source of the seismic waves. The size of the
>: . charges varied from one-half pound to two pounds. The charges were detonated at depths ranging
from 3 feet to 20 feet.
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Seismic Investigation for TDPUD 3
Cooksley Geophysics, Inc.
Project Site Map
Figure 1
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Field Parameters
The following tabulates the field parameters used in recording the refraction data in this study:
# Channels recorded 48
Sensors per channel 1
? % Sensor frequency 10 Hz
Sensor spacing 33 ft
Spacing of Source Points (SP) 66 ft(average)
Common Mid-Point(CMP) coverage 12 fold
Recording sample rate 1.0 ms
Low cut filter 16 hz
(:I High cut fitter 200 hz
SP-sensor geometry(design) 792-33-0-33-792 (distance, in feet)for 33-ft.
sensor spacing
Importance of Source Point-Sensor Station Geometry
There is an inherent difficulty in obtaining near-surface data using the reflection seismic method. This
difficulty is made up of two basic problems. Both problems arise from the necessity of locating the
seismic source close to the sensors and using a sensor spacing which is closely spaced. The nearer
to the surface the reflections are, the closer the distance the source must be to the sensors and the
smaller the sensor spacing must be in order to record them.
A conservative assumption for recording reflection data entails a maximum angle of incidence (angle
of impingement of the ray path which represents the least time path of the reflected seismic wave)of
45 degrees. That portion of the wave front that exceeds this angle is assumed to experience too
much convolution, dispersion and phase shift to be reliable and useful in the CMP stacking process.
The equation relating the depth versus source point to sensor distance that yields less than 45
degrees is:
Z>
5.=
where Z is the depth to the reflector and x is the distance from the source point to the sensor
station.
The first of the two basic problems that must be confronted is to separate usable reflection data from
the large amplitude, lower frequency seismic waves[What is the source(s)of these waves?]which
are commonly propagating at lower velocity through the soil and weathered layers. This problem is
commonly solved by employing certain field and processing techniques that filter unwanted noise.
Such techniques discriminate noise from usable signal by filtering frequency and velocity of
propagation in the horizontal direction.
The second problem is knowing whether there is a stratified unit present in the near-surface formation
being investigated. Given the field parameters of this program, near-surface is considered as depths
of less than approximately 100 feet. If such a unit is absent, then no combination of closely spaced
source-sensor geometry will yield an event. In such a case, no assessment of data quality of the
near surface can be made.
Seismic Investigation for TDPUD 5
Cooksley Geophysics, Inc.
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DATA PROCESSING
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Basic Processing
The SEISTRIX 3 software package was used in processing the reflection data. Initial processing
consists of applying corrections to the data that allow for the source point-sensor geometry, and for
surface topography of the site. The first correction, termed normal moveout(NMO), is designed to
allow for the variation in the path length (and therefore travel time) between arrivals at sensors near
€ ' and distant from the source points. The second correction is termed the static correction, and allows
for elevation differences between the sensors and the elevation differences between the source
points. All sensor station data are referenced to a datum elevation, using a topographic map
obtained from the TDPUD and GPS data supplied by Aqua Hydro Geologic Consulting.
�1 Common Depth Point Stacking
In preparation for the stacking of twelve-fold coverage, each subsurface reflection point is defined
according to the geometry of the source point-sensor configuration. Then each trace from the
records that corresponds to energy reflected from a particular depth point is assigned to that depth
Po g g g process, all data traces in a trace gather are summed to
Y point' "trace other". burin the stacking
I. generate the resultant trace, which depicts the reflected waves at their respective stations on the
record sections. This stacking process has the effect of causing cancellation of signals that are not in
phase on all traces of the gather, and causes enhancement of those signals which are in phase.
Theoretically, this results in enhancement of the reflected energy and improvement of signal to noise
ratio(S/N).
i
` FK Filtering
FK filtering is the removal of energy from the seismic data by filtering the frequency (F)and the
spatial frequency(K, the number of cycles per unit of distance;the reciprocal of the wavelength). It is
normally employed to diminish the affect of that component of the noise, which horizontally traversed
the seismic line. FK filtering was employed over a narrow velocity range.
NMO Correction Used in Defining Velocity Units
Routine seismic data processing employs a velocity function that applies a time variant NMO
correction to the seismic recordings. This function accounts for the increase in average velocity with
depth, and thus the increase of velocity with time of recording. The average velocity at a given depth
and recording time is the weighted average of the various velocities of propagation the seismic wave
experiences while traversing down to, and returning from, that given depth. This velocity function
makes possible the display of the shallow, low velocity events along with the deeper, higher velocity
events.
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Seismic Investigation for TDPUD g
Cooksley Geophysics, Inc.
GEOLOGIC SETTING
General
The regional geologic setting consists of two main categories of rock units. The older category
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consists of metamorphic and igneous rocks of the Sierra batholith complex of Mesozoic age(about
65 to 225 million years before present(mybp)) (Bateman, 1961, and Birkeland, 1963). The younger
category consists of interbedded sedimentary and volcanic beds and lenses which unconformably
overlie the units of the older category. The younger rocks range in age from late Miocene to late
Pleistocene or perhaps Recent(15 to 0 mybp).
The area investigated occupies about two square miles situated between Alder Hill to the west and I-
80 to the east. The terrain is mildly hilly with glacial outwash exposed sporadically. The outwash
consists of sandy and clayey soil with some boulders, cobbles and gravel derived mainly from
volcanic rock units.
g ; For the purpose of finding and developing ground water, this investigation was directed entirely to the
younger category of rocks. Table 1 depicts the generalized stratigraphy of the rock units in the
younger category.
Younger Alluvium (Qal) Glacial, stream and slope wash deposits
Lousetown Formation QI Volcanic and sedimentary units
Pliocene sediments beds Ps Sand and gravel units
Older Pliocene sedimentary beds Interpreted from this seismic program ; sedimentary and
Pos volcaniclastic strata with local volcanic interbeds
Truckee Formation Tsv Sedimentary and volcanic(?) strata
f Kate Peak Formation Not mapped in this project area but are of volcanic origin
or Merten Formation
Older
Table 1 Generalized stratigraphic section of Late Miocene to Late Pleistocene units in the vicinity of
Truckee, California and adjacent areas of Western Nevada.
Sequence of Rocks (From older to younger)
Rhyolite and Andesite Tuffs
Birkeland (1963)cites Hudson (1951) in his description of the oldest of the younger sequence being
rhyolite and andesite tuffs exposed near Donner Pass (located 10 miles west of this study area).
These units are of Miocene (?) age. It is not known whether they underlie the subject area and, if
#, they do, how thick they might be.
Kate Peak Formation(?)
Andesite tuff breccia, flows and intrusive units are thought to be equivalent to the Kate Peak
Formation near Virginia City, Nevada and the Merten Formation on the west slope of the Sierra
Nevada. An age of Miocene and early Pliocene has been assigned by Gianeila (1936), Hudson
(1951)and Thompson(1956)to the Kate Peak. This unit has been mapped to within 0.5 mile west of
s seismic Line A and to within 2.5 miles west of Seismic Line B (Saucedo and Wagner, 1992). Its
thickness is not known and its ground water potential within the study area is not known.
Seismic Investigation for TDPUD 7
Cooksiey Geophysics, Inc.
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Truckee(7)Formation(Tsv)
Fluvial and lacustrine deposits are composed mainly of andesite-derived sand with some ash beds
and gravel, and are believed to overlie the Kate Peak Formation. This unit is similar in lithology and
position to what has been called the Truckee Formation (Thompson, 1956)and is equivalent in age
and lithology to the Coal Valley Formation (Bonham and Papke, 1969). An age of middle Pliocene is
given this unit. This unit is not exposed near Truckee or at the study site, but it is exposed
yi approximately eight miles northeast of Truckee. The thickness is not known.
a. Because of the sand and gravel beds within this unit, it should be regarded as potentially containing
ground water. One item of caution is that little is known of the lithology and thickness of this unit near
t ` the west side of the Truckee basin. The only sub-surface geologic information available prior to this
survey is from deep water wells and test borings within the basin. The seismic sections indicate
stratified units to depths in excess of 2500 feet. A major portion of this deep section is believed to be
i' the Truckee(?) Formation. Easterly dips of 10 to 16 degrees are exposed along Hwy 89 north of
Lake Tahoe and east of Truckee in the Truckee River canyon (Birkeland, 1963).
f
Older Sediments(Pos)
Horizontally bedded, older sediments (Pos) rest unconformably on the Truckee(?) Formation and
have been removed to a large extent by erosion. These beds, where present, appear to be erosional
remnants, commonly filling apparent drainages that have been eroded into the Truckee (?)
Formation.
y-, Lousetown Formation(Qt)
f
a Birkeland (1963)correlates basalt and a latite flow with the Lousetown Formation which is exposed in
the Virginia and Carson Ranges of western Nevada (Thayer, 1937; Thompson, 1956). The
correlation is based on:
1.) Similarity of rock types at the subject site and the volcanic flow units of the Lousetown Formation
exposed in the Carson and Virginia ranges in Nevada;
2.) The flows can be projected easterly across the Truckee Canyon to the Lousetown flows in the
Carson Range; and
3.) The flows occupy the same stratigraphic position as the Lousetown Formation in the Carson and
Virginia ranges. Potassium-argon ages ranging from 1.2 to 2.3 mybp have been determined
(Birkeland, 1963). This equates with early Pliocene to mid-Pleistocene. One source of potential
s% aquifers is lava-dammed deposits of gravel and sediments deposited in erosional depressions
during the Pleistocene.
In addition to the lava flows, the Lousetown contains layers of fluvial-and lacustrine material eroded
from older formations. These layers consist of sand-, pebble-and cobble-sized ciasts, principally
derived from volcanics, and interbeds of clay and silt(see Figures 2 and 3).
Prosser Creek Alluvium Member of the Lousetown Formation(Qai)
The Prosser Creek alluvium member, an upper unit of the Lousetown Formation, is shown by
Birkeland (1963, p. 1459) as occurring throughout a significant portion of the Truckee Basin. This
unit overlies the Truckee(?) Formation. This part lacustrine, part fluvial deposit is of middle
Pleistocene age. The unit is at least 120 feet thick east of Truckee and is overlain by undifferentiated
glacial outwash deposits and alluvium (Birkeland, 1963). On the profiles, the Prosser Creek alluvium
member is grouped as alluvium (Qal), and statigraphicly occurs in the lower portion of the Qal unit
(see Figure 4).
Seismic Investigation for TDPUD 8
Cooksley Geophysics, Inc.
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§ Alluvial Deposits(0-a g
Aa the middle Pleistocene, several episodes of glaciation have _ved detritus from the kn
p elevations of the Sierra Nevada to the Truckee basin. Throughout time sedimentation took place
in riversand streamsw in lakes, Asaresult, mew.*are composed m varying AA&s
Q @ both volcanic rock and the older igneous and metamorphic units @the Ae mn» = «
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Seismic Investigation for mmD 9
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Figure 2. Interbedded sedimentary units in the Lousetown Formatiom. View
looking northeast in road cut located along Glenshire Drive approximately one
mile east of the intersection with Highway 89. Overlying volcanic flow of Polaris
GH Olivine Latite (Berkeland, 1963) on right side of photo. Underlying sedimentary
=° beds of eroded volcanic material (see Figure 3)dipping southeasterly.
^^^ Seismic Investigation for TD9UD 10
Conhu|ey Geophysics, Inc.
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Figure 3. Detailed photos of same road cut
as in Figure 2. Upper photo: coarse sand beds
with clasts of scoria. Lower photo: clay-rich beds
containing pebbles and cobbles of volcanics.
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' Seismic Investigation for TDPUD 11
Cooksley Geophysics, Inc.
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Figure 4. Views looking northeast(upper photo)and north
(lower photo) at wall of gravel pit located along Glenshire Drive
approximately one-quarter mile east of intersection with Highway 89.
Alluvium (thin layer at top) overlying the Prosser Creek alluvium
member of the Lousetown Formation (Birkeland, 1963).
5
€<! Seismic Investigation for TDPUD 12
Cooksley Geophysics, Inc.
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INTERPRETATION
General
Three main types of seismic events dominate the two seismic sections derived in this project. Each
wave type acquires its signature(properties such as amplitude, frequency, continuity of events and
wave shape)from certain characteristics of the rock or soil through which the wave is advancing.
These characteristics include density and moduli (the ratio of deformation to the quantity of stress
applied to a given material)of the rock, the amount of fracturing and shearing in the rock mass, the
presence of"marker beds"(beds which are good reflectors of seismic waves), and the presence of
ground water. Thus, with some prior knowledge of the formations to be encountered, the
geophysicist can more fully interpret the type of formation and structural conditions from careful
inspection of the seismic events.
The uppermost wave type is mainly of moderate amplitude and has a frequency ranging from 80 to
120 hertz. Much of this wave type was purged from the sections by use of the FK filter, resulting in a
lesser density of seismic data in the region of zero to 150 milliseconds(ms). Several short lengths of
flat events are scattered throughout the upper 200 ms of the section, but major reflection markers are
absent. Such aspects as these suggest a poorly bedded sedimentary unit that may locally contain
thin beds of sand or silt that might contain some ground water. Such a unit equates with the
unconsolidated soil and detritus derived from glacial moraine and outwash, stream deposits and
slope wash.
The middle wave type is of strong amplitude and possesses frequencies ranging from 50 to 150
hertz. Although the reflections are strong and more continuous than the upper wave type, they do not
it form solid, ongoing events extending from one end of the section to the other. These reflections
generally occupy the time increment between 200 and 300 ms on the sections. The reflections in the
upper 20 to 30 ms are of stronger amplitude and higher frequency and are interpreted to correlate
with lava flows of the Lousetown Formation. Events with somewhat less amplitude and frequency
denote a sedimentary section interbedded with and underlying the lava flows. This sedimentary unit
is known to form an aquifer encountered in several of the wells in the basin and is designated as Ps
and the upper portion of the Truckee (?) Formation (Tsv)on the profiles.
The lower wave type is of weak to moderate amplitude, and in the frequency range from 50 to 80
hertz. Locally, some higher frequency noise is present. These events are tilted and mildly folded
>, except in backfilied gorges and valleys. This wave type tends to be somewhat more continuous
` relative to the other two wave types. From inference, this wave type is thought to originate in an older
section of sedimentary and volcanic strata, probably of middle Pliocene age or older. The base of the
r backfiiled areas as well as gravel units within these areas might constitute aquifers.
Line A
Y'
This traverse is the northern-most of the two west-to-east trending lines along which high resolution
z seismic data was obtained. Data was acquired over a length of 1.28 miles. The beginning of the line
at the west end is at an elevation of 5910 feet and the east end is 5825 feet. A fault is interpreted at
the west end of the section. This is a north-striking structure, dipping east, with the east block
downthrown.
Y The uppermost unit encountered is undifferentiated alluvium (Qai). These deposits extend from the
ground surface down to an uneven contact at a depth of 500 to 700 feet. The alluvial unit is
interpreted to rest on the top of volcanic flows and sediments of the Lousetown Formation.
The middle wave type, being of rather strong amplitude and high frequency, correlates with 100 to
200 feet of lava flows of the Lousetown Formation and a gravelly unit which may belong to the
Lousetown Formation or might be a slightly older unit. These flows occur at depths ranging from 550
to approximately 800 feet. The upper section of the Lousetown includes at least a 300-foot section
of alluvial deposits and the volcanic flow units are normally in excess of 100 feet in thickness.
Seismic Investigation for TDPUD 13
Cooksley Geophysics, Inc.
The lower wave type of moderate amplitude and lower frequency correlates with stratified units that
have been eroded, faulted, tilted, and perhaps folded. These units are likely to occur near the surface
west of the main fault at the west end of the line, but are generally in excess of 1,000 feet in depth
throughout the remainder of the line. On the basis of the above, it is concluded that this unit is
substantially older than those overlying it. A mid-Pliocene age, or perhaps slightly older seems likely.
These strata may be correlative with the Truckee Formation.
One interesting feature of this unit is the appearance of rather well defined scallops eroded into the
surface of the unit in which mildly dipping strata are apparent. These valleys and gorges appear to
be filled with horizontal or near-horizontal strata. These features may contain significant aquifers.
# The table below lists favorable exploration targets as indicated on the Line A seismic section.
Potential Targets for Groundwater Accumulation
Line A(Northern line)
r:•
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Distance from station 0 Estimated Depth
800-1000 ft 700 ft
4100-4450 ft 1000 ft
5000-5400 ft 1000 ft
5400-6000 ft 1100 ft
1300-1960 ft 1500 ft
Line B
y
Like Line A, Line B trends west-to-east and is approximately 1.0 mile long. The elevation at the west
end is 5976 feet and at the east end is 5949 feet. A north-striking, east-dipping, normal fault with at
least 100 feet of displacement, east block down, emerges at the surface near station 20, six hundred
(600)feet east of the beginning of the line.
a
The uppermost unit on Line B is a poorly bedded alluvium that appears to be eroded at the west end
f> of the line. The uppermost unit at the east end appears to be eroded and replaced by a fairly well
bedded alluvial unit. This unit appears to extend to a depth of 150 to approximately 300 feet over
most of the line. Generally, the alluvium appears to be in contact with the underlying volcanic units(s)
r y of the Lousetown Formation.
aai The middle wave type is either exposed or nearly exposed on the ground surface at the west end of
the line. Being on the west, up-thrown side of the normal fault accounts for the position of this unit.
Throughout most of the line, the top of this unit is at a depth of about 200 to 300 feet.
Potential Targets for Groundwater Accumulation
Line B(Southern line)
Distance from station 0 Estimated Depth
800-1400 ft 450 ft
2500-2900 ft 450 ft
3250-3600 ft 400 ft
Seismic Investigation for TDPUD 14
Cooksley Geophysics, Inc.
1'
pn
REFERENCES
r„s
Bateman, P.C., 1962; Granitic Formations of the East-Central Sierra Nevada near Bishop, Califomia;
Geological Society of America Bulletin, v. 72, p. 1521 — 1538,
Birkeland, P.W., 1963; Pleistocene Volcanism and Deformation of the Truckee Area, North of Lake
Tahoe, California; Geological Society of America Bulletin, v. 74, p. 1453—1464.
n,f Bonham, H.F. and Papke, K.G., 1969; Geology and Mineral Deposits of Washoe and Storey
Counties, Nevada; Nevada Bureau of Mines and Geology Bulletin 70; 140 p.
Gianella, V.P., 1936; Geology of the Silver City District and the Southern Portion of the Comstock
Lode; University of Nevada Bulletin, v. 30, no. 9, 105 p.
Hudson, F.S., 1951; Mount Lincoln—Castle Peak Area, Sierra Nevada, California; Geological Society
>' of America Bulletin, v. 62, p. 931 —952.
Saucedo, G.J. and Wagner, D.L., 1992; Geologic Map of the Chico Quadrangle; California
Department of Conservation, Division of Mines and Geology Map No. 7A(1:250,000)
it Thayer, T.P., 1937; Petrology of Later Tertiary and Quaternary Rocks of the North-Central Cascade
Mountains of Oregon, With Notes on Similar Rocks in Western Nevada; Geological Society of
" America Bulletin, v. 48, p. 1611 — 1652,
Thompson, G.A., 1956; Geology of the Virginia City Quadrangle, Nevada; U.S. Geological Survey
[ Bulletin 1042—C, p. 45—77.
L'{
E'
Seismic Investigation for TDPUD 15
f Cooksley Geophysics, Inc.
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Y-:
APPENDIX A
Alder Drive Lithologic Log
Logged by Peter Olander, Project Manager, Cooksley Geophysics, Inc.
0'—170' Alluvium and sediments: Clay and sub-rounded coarse sand-sized grains of mixed
lithologies, weak to moderate FeOx throughout section;100'-130'-strong dark brown
clay.
170'—250' Mixed section of volcanics and interbedded sediments; possible zone consisting of
sections of massive cobbles and boulders of volcanics(giving appearance of flows)
interbedded with sediments; 190'-200'-sub-rounded coarse sand-sized grains of
mixed volcanic lithologies; locally weak FeOx.
250 —270' Contact: scoria indicating top of underlying flow; brick red scoria mixed with weak
FeOx-stained clay.
270' —420' Massive volcanic flow, appears to be"Polaris olivine latite"of Birkeland (1963, Figure
5); gray, no FeOx; dense rock yielding small (<118") highly angular fragments of drill
cuttings.
430' Transition from massive flow above to angular fragments of vesicular basalt below;
weakly oxidized rocks but no FeOx stain.
440'—450' Clay zone; limonite stained; sub-rounded sand-sized grains of mixed volcanic
lithologies.
460' Clay zone; reddish clay containing sub-rounded sand-sized grains of scoria.
470' Transition zone; partially oxidized; weak brick red color.
480'—590' Massive flow(s) of gray basaltic andesite(?); uniform throughout section; no FeOx or
clay.
600'—620' Transition from massive volcanics above to sedimentary section below.
630'—710' Sedimentary section; mixed zones of clay and sand; 640'-section of strong dark
._. brown clay; 660'-670'-possible zone of massive cobbles and boulders of volcanic
f; flow rock, weak FeOx; 690'-710'-zone of strong clay with trace limonite stain
(possible fault gouge).
720'—790' Massive basaltic andesite flow, not oxidized.
790' —880' Porphyrytic dacite(?)flow; gray; massive; no FeOx; varying amounts of phenocrysts
s
of plagioclase, homblende and trace quartz.
890'—950' Increasing clay content with sub-sounded sand-sized grains of mixed volcanics; 910'-
strong clay, brick red; 920'-abundant sub-rounded coarse sand-sized grains; 930'-
940'-strong brick red clay, same color as scoria but no scoria seen in chips, red clay
s might be deeply weathered scoria; 950'-coarse sand bed, well-rounded grains, all
WW volcanic.
960, Contact with massive basaltic andesite.
970'— 1030' Massive volcanic flow(s) of basaltic andesite; no FeOx.
Seismic Investigation for TDPUD 16
Cooksley Geophysics, Inc.
f
APPENDIX A - Continued
Alder Drive Lithologic Log
'I
1040'— 1090' Sedimentary section: 1040'-1060'-sub-rounded coarse sand-sized grains of mixed
volcanic lithologies, weak FeOx; 1070'-1090'-strong clay with sub-rounded coarse
sand-sized grains of mixed volcanic lithologies(including pre-Tertiary(?)).
1100'— 1132' Transition zone grading into basalt flow, aphanitic; weak zone at top with red scoria
W
a
P sa
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it
Seismic Investigation for TDPUD 17
Cooksley Geophysics, Inc.
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M SIM
rruckee Donner Public Utilities Di
15tIrICt Appendix B
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......................
Drilling shot holes
Seismic line through timber
15-
A
...........
Laying cable on line B Seismic recording area
Seismic investigation for TDPLID 18
Cookslev Geonhv,;ir..q Inn
I ruckee Donner Public Utditle s D J"S t tiC t, Appendix B—Cont.
Looking east on Line A
Volcanics on line A
X,
Seismic recording system
Seismic Investigation for TDPUD 19
Cooksley Geophysics, Inc.