Appendix D-3 Supplemental Fault Ground Rupture
Appendix D-3
Supplemental Fault Ground Rupture
SOIL ENGINEERS ENGINEERING GEOLOGISTS 5587 SUNOL BOULEVARD PLEASANTON, CA 94566 (925) 484-0220 FAX: (925) 846-964
Via E-Mail
January 6, 2017
BSA Job No. 3823.100
Mr. Kyle Masters
The Grupe Company
3255 West March Lane
Stockton, California 95219
Subject: Supplemental Fault Ground-Rupture Investigation
Ersted Property
APN: 078C-0461-001-13
Hayward, California
Dear Mr. Masters:
Berlogar Stevens & Associates (BSA) is pleased to present this Supplemental Fault Ground-
Rupture Investigation report for a portion of the Ersted property in Hayward, California. The
scope of services conducted during the course of this investigation, our findings and our
recommendations for modification of the previously identified “Development Zone” in the lower
portion of the site are presented below.
Several previous site investigations identified faults considered to be active crossing the Ersted
property, as shown on Plate 2. The presence of these faults reduced the area of potential
property development. Engeo (Engeo 2005 and 2007) identified two “Tentative Residential
Structure Development Zones.” The upper or more northeasterly of the two zones was modified
by Makdissy in 2013. Makdissy adopted the lower or more southwesterly zone as mapped by
Engeo. The lower zone, which covers an area of about 4 acres, has not been shown to be crossed
by active faults and is the subject of this report. It is our understanding that The Grupe
Company’s interest in development of the site is limited to the previously identified lower
development zone; there are no plans for development the upper portion of the site at this time.
Thus, our investigation for potential fault ground rupture was limited to the area southwest of
Fault 2 as mapped by Engeo and shown on the Site Plan, Plate 3. This area will be referred to in
this report as the “Study Area.” The USGS quadrangle shows the coordinates of a point near its
approximate center of the Study Area are latitude: 37.6355 N and longitude: 122.0500 W.
SITE DESCRIPTION
The southwest sloping Ersted property lies on the west flank of the East Bay Hills about six
miles northeast of the San Francisco Bay. The approximately 15½-acre, roughly triangular-
shaped property (Assessor’s Parcel Number 078C-0461-001-13) is located about 450 feet east of
Mission Boulevard and south of the La Vista Quarry in Hayward (Vicinity Map, Plate 1). The
parcel is about 1,500 feet deep and is elongated in a northeastern direction, narrowing toward the
BERLOGAR
STEVENS &
ASSOCIATES
January 6, 2017
BSA Job No. 3823.100
Page 2
BERLOGAR STEVENS & ASSOCIATES
northeast. The United States Geologic Survey 7½-minute Hayward quadrangle topographic map
(USGS, 1980) indicates that the property ranges from an elevation of about 50 feet above mean-
sea-level (msl) in its southern corner to about 265 feet in its northwestern corner. Existing
vegetation is predominantly seasonal grasses with a few scattered palm and willow trees. A
linear stand of eucalyptus trees is located along the southwestern property line.
PURPOSE AND SCOPE
The purpose of this investigation is to further characterize the geologic conditions of the lower,
southwestern part of the Ersted property, specifically with respect to potential ground rupture
from active fault displacement. Evaluation of seismic shaking, discussion of other geologic
hazards, and geotechnical design considerations and parameters will need to be addressed in a
subsequent geotechnical investigation of the site.
Our investigation included the following:
Review of readily available published and unpublished geologic maps and documents
relating to the site and vicinity.
Examination of historical topographic maps, aerial photographs; and LiDAR images of
the site and vicinity.
Reconnaissance of the site and surrounding area to observe surface geologic conditions.
Contacting the City of Hayward’s consulting geologist, Mr. Lou Richardson, to briefly
discuss the site and our proposed study, and to schedule the consulting geologist for
observation of our trenches along with periodic review of our trench logging.
Mark the field exploration locations and contacting USA.
Exploration of subsurface conditions by excavating and logging six exploratory trenches.
The trenches were excavated in two phases with Trenches T-1 through T-5 excavated
during our initial phase of field exploration and an additional trench, T-6, excavated after
review of the first phase data and additional data received for a study conducted on an
adjoining site.
Preparation and submittal of a Work Plan to the City of Hayward for approval prior to
conducting the second phase of our field exploration program.
Backfilling of the trenches with the trench spoils. The backfill was placed as
uncontrolled fill and will need to be re-excavated and then replaced as engineered fill
during future grading activities.
Consultation with The Grupe Company (Grupe) during the field exploration and report
preparation phases.
Review and discussion of our findings with Mr. Lou Richardson, C.E.G., acting as peer
reviewer for the City of Hayward.
January 6, 2017
BSA Job No. 3823.100
Page 3
BERLOGAR STEVENS & ASSOCIATES
Analysis of geologic data from researched documents and collected field data to develop
conclusions and recommendations for the Study Area regarding potential earthquake
ground rupture.
Preparation of this report presenting our findings and recommendations.
REGIONAL GEOLOGY
The City of Hayward and the Ersted property are located within the Coast Ranges Geomorphic
Provinces. The province consists of a series of discontinuous northwest trending mountain
ranges, ridges, and intervening valleys characterized by complex folding and faulting. The
general geologic framework of the area is illustrated in studies by Schlocker (1970), Dibblee
(1980), Wagner and others (1991), Chin and others (1993), Ellen and Wentworth (1995), and
Helley and Graymer (1997), Graymer (1995), the California Geological Survey (CGS, 2002),
among others. A summary of compiled regional geologic mapping is presented on Plate 4,
Regional Geologic Map.
Geologic and geomorphic structures within the San Francisco Bay Area are dominated by the
San Andreas fault system, a right-lateral strike-slip transform boundary that extends from the
Gulf of California in Mexico, to Cape Mendocino in Humboldt County, California. It forms a
portion of the boundary between two independent tectonic plates. To the west of the San
Andreas fault system is the Pacific plate, which moves north relative to the North American
plate, located east of the fault system. In northern California, movement across this plate
boundary is concentrated on the San Andreas fault. However, a portion of the movement is also
distributed across a number of faults including the Calaveras, Hayward, San Gregorio, Paicines,
Zayante-Vergeles, and Quien Sabe among others. Together, these faults are referred to as the
San Andreas fault system. Movement along this fault system has been ongoing for about the last
25 million years. The northwest trend of the faults within this system is largely responsible for
the strong northwest/southeast structural grain of geologic and geomorphic features along coastal
California and the San Francisco Bay Area.
Basement rocks east of the San Andreas fault system consist of a chaotic mixture of highly
deformed marine sedimentary, submarine volcanic and metamorphic rocks of the Franciscan
Complex of Jurassic to Cretaceous age (205-65 million years old). West of the San Andreas
fault system the basement rocks consist of successive slivers of granite once associated with the
Sierra Nevada - Peninsular intrusive complex (batholith) but which have been sliced by the San
Andreas fault and "stretched out" to the northwest to their current position.
FAULTING
The project site is located in an area characterized by moderate to high seismic activity. Plate 6,
Fault Activity Map, shows faults and their inferred activity in the vicinity of the project site. An
January 6, 2017
BSA Job No. 3823.100
Page 4
BERLOGAR STEVENS & ASSOCIATES
active fault is a fault that has experienced seismic activity during historic time (since roughly
1800 A.D.) or exhibits evidence of surface displacement during Holocene time (latest 11,700
years) (Hart and Bryant, 2007) and is therefore considered more likely than older faults to cause
ground rupture. Two significant aspects of fault activity that can damage buildings and
infrastructure are ground rupture along active earthquake-fault traces and seismic shaking. This
present study is limited to evaluation of ground rupture only. Seismic shaking will be addressed
in a later design-level geotechnical investigation report.
AREA AND SITE GEOLOGY
Approximately two-thirds of the northeast part of the Ersted property is located within a State of
California Earthquake Fault Hazard Zone (CGS, 1982) for the Hayward fault as shown on the
Earthquake Fault Hazard Zone Map (Plate 7). The main trace of the Hayward fault is mapped to
cross the Ersted parcel near the property’s eastern property line (California Geological Survey,
CGS, 1982; Graymer, 1995; Crane, 1988; Dibblee, 1980; Radbruch-Hall, 1974; Herd, 1978;
Lienkaemper, 2006) about 750 feet northeast of the Study Area. The current Study Area is not
within and is southwest of the state designated Fault Hazard Zone. However, previous geologic
investigations indicate the presence of several fault traces south of the hazard zone (Site Plan).
The presence of active faults south of the state’s Fault Hazard Zone gives reason for a subsurface
investigation in the southwest portion of the Ersted property prior to site development.
The Ersted Study Area is underlain by basement rock consisting of a complicated mixture of
metamorphosed rocks of the Franciscan Complex derived from deformed and accreted seafloor
rocks. Structurally adjacent to or unconformably overlying the Franciscan are marine
sedimentary rocks of the Great Valley Group deposited during Jurassic and Cretaceous time.
The Great Valley Group in the Study Area is mantled by alluvial fan and colluvial materials shed
from the hills to the east. Mapping by Graymer and others (1995) of the USGS indicates that the
Study Area is underlain by the Jurassic Age Knoxville Formation of the Great Valley Group
(JKkc on the Vicinity Geologic Map, Plate 5). Graymer and others describe the Knoxville
Formation as mainly dark, greenish-gray silt or clay shale with thin sandstone interbeds. Locally
the formation includes thick pebble to cobble conglomerate beds in its lower part (JKkc) and
beds of angular, volcanoclastic breccia derived from underlying ophiolite and silicic volcanic
rocks.
PREVIOUS EXPLORATORY TRENCHING
The general northeast and southwest boundaries of the current Study Area within the Ersted
property were established based on the presence of faults found in trenches excavated by Engeo
(2005). In the north, Engeo’s trenches ET-1, and ET-2 exposed a series of faults in a fault zone
about 50 feet wide striking about N85°E to N65°W and shown on trench log of ET-1 to dip
about 29°N to 60°N. This fault zone is labeled Fault 2 on Engeo’s Site Plan, included as Plate 2,
and on our Site Plan, Plate 3. To the south, Engeo’s trenches ET-1, and ET-3 exposed two
January 6, 2017
BSA Job No. 3823.100
Page 5
BERLOGAR STEVENS & ASSOCIATES
additional faults with strikes about N40°W (Faults 3 and 4, Plate 2). Engeo’s site plan shows the
dips of these faults to vary between 21°N and 36°N. However, these dips correlate in the trench
log with the faults’ attitudes near the ground surface where they appear to be distorted or bent
over by near surface soil creep. The log of trench ET-3 shows the dip of Fault 3 near the bottom
of the trench to be about 75°N. This difference in dip suggests that the faults’ ground-surface
intercept in the southeast part of the Study Area would be further downslope to the southwest
than the uncertain fault locations shown on Engeo’s site plan (dashed and queried lines, Engeo
Site Plan, Plate 2). Furthermore, the strikes recorded by Engeo indicate the faults should trend in
an east-southeast to southeasterly direction, not easterly as shown by Engeo. The queried
locations of Faults 3 and 4 are not supported by the strikes and dips of the faults as logged by
Engeo. Engeo’s Faults 2, 3 and 4 are interpreted to be splays off of the Hayward fault and
probably merge with the main trace laterally and at depth. In addition to the faults discussed
above, Engeo’s logs of ET-1 ET-3 show the presence of shears in material below the upper soil
layers. Numerous shears within the Franciscan Complex were mapped with strikes ranging from
N15ºW to N60ºW with dips between 23ºNE to 54ºNE.
The California Department of Mines and Geology1 1981 Fault Evaluation Report (FER) No. 103
states that south of the mapped trace of the Hayward fault the “consulting reports in the Hayward
quadrangle tend to present a confusing picture.” The FER describes a Judd Hull & Associates
(JHA, Alquist-Priolo number AP No. 200, 1975) trench on property adjacent to and southeast of
the Study Area (Site Plan) where a fault gouge zone was detected in one trench but not in another
nearby trench. The FER reports that JHA did, however, establish a setback from the fault gouge.
The fault identified by JHA southeast of the Study Area approximately correlates with Engeo’s
Fault 4 when the fault outcrop pattern is corrected to the fault’s dip at the bottom of the trench.
HISTORICAL TOPOGRAPHIC MAP AND AERIAL PHOTOGRAPHIC REVIEW
We reviewed readily available topographic maps and aerial photographs of the area to evaluate
historical surface features that may relate to fault locations and areas of past fault deformation.
The years covered by the topographic maps and aerial photographs reviewed for this study are
listed in the tables included as an attachment.
The 1899 and subsequent 15- and 7½-minute topographic quadrangles show a roadway leading
from Mission Boulevard upslope to the current Ersted property. Several structures are shown on
the 1899 and 1915 maps scattered around the slope, but none on the Ersted property. Most of the
structures do not have roads to them and therefore may be barns or other outbuildings. The 1941
and later topographic maps do not show the structures. The 1959 7½-minute Hayward
quadrangle is the first to show symbols of a quarry north of the current Ersted property and to
show an elevation benchmark near the property’s west property line. The 1968 quadrangle
1 California Geological Survey, CGS, was formerly known as the California Department of Mines and Geology until its name
change in 2006.
January 6, 2017
BSA Job No. 3823.100
Page 6
BERLOGAR STEVENS & ASSOCIATES
shows a large excavated pit in the upper, narrow part of the Ersted property that is not shown on
the 1959 or earlier maps. No local lineations or other features suggestive of faulting were
observed on the topographic maps.
The series of aerial photographs reviewed show seasonal vegetation changes and variation of
trails and show that cultural changes such as permanent roads or structures have not been made
on the property during this period. The photographs were studied for the presence of features
characteristic of fault traces such as linear discontinuities in rock or soil, offset watercourses,
linear scarps, topographic lows, vegetation patterns or breaks in slope. The photographs show
that Engeo’s Trenches ET-1 and ET-3 were excavated between December 21, 2004 and June 11,
2005. No tonal changes within the Study Area possibly resulting from fault deformation are
observed in the aerial photographs.
LiDAR images of one-meter resolution, bare earth hill-shades topography dataset provided by
Northern California GeoEarthScope (KMZ Google Earth file) were examined for shadow
features that may be associated with ground deformation related to faulting. The hillshades 45°
sun-angle image that covers the Study Area suggests a topographic shadow lineation along a
similar local trend of the Hayward fault, which is located northeast of the Study Area. The
lineation, expressed as southwest-facing topographic shadows, is observed about 450 feet south
of the Study Area trending about N35°W through the headscarp of a landslide adjacent to the
property’s southeast property line. The feature is not observed on the ground surface in the
LiDAR image within the Study Area possibly due to ground modification caused by downslope
soil creep. The shadow feature is observed as far as about 800 feet northwest of the Study Area
along approximately the same trend observed southeast of the Study Area. Other strong
lineation features are observed north of the Study Area in the vicinity of the mapped trace of the
Hayward fault.
SITE RECONNAISSANCE
A Certified Engineering Geologist (C.E.G.) representing BSA performed reconnaissance of the
site and surrounding vicinity on several occasions between November 2 and December 19, 2016
to observe surface conditions that may relate to fault ground rupture. The Study Area and parts
of adjacent properties were walked to observe possible evidence of surface disturbance from
faulting. The property north of the Study Area has recently been graded to construct a roadway
accessing a new subdivision east of the Ersted property. The earthwork for the roadway has
obscured possible evidence of faulting. The landslide scarp south of the Study Area noted in the
LiDAR discussion above was observed in the field to align generally parallel with the local strike
of the Hayward fault. No ground-surface evidence of fault activity affecting the Study Area was
observed during our site reconnaissance.
January 6, 2017
BSA Job No. 3823.100
Page 7
BERLOGAR STEVENS & ASSOCIATES
BSA EXPLORATORY TRENCHES
Six exploratory trenches were excavated and logged in the Ersted Study Area to explore for the
possible presence or absence of potentially ground-rupturing faults, possibly associated with
shears logged by Engeo in their trench ET-1, between Engeo’s Faults 2 and 4, as well as to
investigate the queried Faults 3 and 4, projected eastward from the faults logged by Engeo in
their trench ET-1, in the vicinity of the southeast property line. During excavation and logging
of the exploratory trenches, Mr. Lou Richardson, C.E.G., representing the City of Hayward as
the peer reviewer, was present periodically to review our findings in the trenches as they were
logged. At completion of logging, the ends of the trenches and fault traces encountered in the
trenches were staked and surveyed for plotting as shown on the Site Plan, Plate 3. The trenches
were backfilled and nominally compacted with the excavator bucket. Trench T-6 was covered
with straw blankets to reduce erosion potential.
TRENCH T-1
Exploratory Trench T-1 (Log of Trench T-1, Plate 8) was located northeast of Engeo’s Trench
ET-1 to further explore for the possible presence of fault displacement within the Study Area and
to evaluate the character of the shears previously encountered in the area. The 380-foot long
trench was laid out along a trend of N62°E and cut through the fill berm near the north part of the
Study Area. Beneath the black clayey colluvial soil of up to about 2½ feet thick, bedrock of the
Knoxville Formation was encountered. The Knoxville Formation represented in the trench
consists of discontinuous and deformed beds of shale, claystone containing completely
weathered sandstone cobbles, serpentinized lithic fragments, and volcanic breccia. According to
published reports by the USGS (Graymer, 1995), this material is associated with the lower
section of the Knoxville Formation and is derived in part from the underlying ophiolite deposits.
Between about Station 0+50 and 0+56, a 6- to 12-inch thick white calcareous fault-gouge vein
(attitude of N50°W52°N) was encountered near the bottom of the trench. Bedrock materials
north and south of the fault are distinctly different (Log of Trench T-1). The fault extends
upward into the overlying colluvial soil where soil creep has bent and stretched the fault material
downslope.
Six prominent shear planes were mapped in Trench T-1. The shears deform, and are entirely
within, the Knoxville Formation beds (described as Franciscan mélange in the Engeo trench) and
do not extend into or affect overlying soils. As opposed to the fault in Trench T-1 near Station
0+50 that dips to the north, the shears dip to the south with attitudes of N20°-25°W50°-59°S.
The shears encountered in Trench T-1 do not align along strike with or project to the shears
mapped in Engeo’s Trench ET-1, which differ in dip direction from those in T-1. The shears
observed in Trench T-1 and Engeo’s ET-1 are therefore interpreted to be discontinuous, localized
features. In addition, because of their non-congruous attitudes with local fault traces, the shears
appear to be related to compressional history not associated with Hayward fault displacement.
January 6, 2017
BSA Job No. 3823.100
Page 8
BERLOGAR STEVENS & ASSOCIATES
TRENCH T-2
Trench T-2 was positioned near the northwest corner of the Study Area to explore for the
possible presence of faulting west of the projected north alignment of Engeo’s Fault 2 (Site
Plan). The 197-foot long trench, laid out along a trend of N68°E, was excavated to a depth of
about 6 feet. Beneath the dark gray gravelly, clayey colluvial soil up to about 2 feet thick,
bedrock of Knoxville Formation conglomerate was encountered. The bedrock consists of well-
rounded fine-grained sandstone in a hard clay matrix. A depositional channel consisting of loose
to dense, clast supported sandy gravel was located between Stations 0+30 and 0+40. Well
indurated but closely to widely fractured siltstone beds were exposed northwest of Station 0+70.
Depositional contacts observed in the trench range from sharp to gradational. No evidence of
fault displacement was found in the trench.
TRENCH T-3
A third exploratory trench (Trench T-3) was positioned near the Ersted property line in the
southeast portion of the Study Area to investigate the possible continuation of Engeo’s uncertain
(dashed and queried) Faults 3 and 4, and possible presence of shears. The 155-foot long trench,
laid out along a trend of N3°E, was excavated to a depth of about 11 feet. Beneath the black silty
clay colluvial soil (up to about 6 feet thick near the trench’s north end), claystone of the
Knoxville Formation was encountered. Contacts observed in the trench range from sharp to
gradational deposition. Deformation of the Knoxville Formation by shearing was not observed
in the trench. No evidence of fault displacement was found in the trench.
TRENCHES T-4 and T-5
Two short offset Trenches T-4 and T-5 were located about 35 feet north and south, respectively,
of Trench T-1 in order to measure the trend of the fault observed in T-1. The trenches were
about 35 feet long and up to about 5½ to 6 feet deep. Approximately the same fault
configuration was found in these two trenches as was seen in Trench T-1 (Log of Trenches, Plate
8). The fault near the base of the trenches is about 6- to 12-inches thick consisting of white
calcareous gouge. As the fault nears the overlying colluvial soil, it is bent, stretched and pinches
out downslope.
TRENCH T-6
Because the dashed and queried Engeo Faults 3 and 4 were found not to be present in Trench T-
3, Trench T-6 was positioned to evaluate if the fault found in Trenches T-1, T-4 and T-5 passes
south of Trench T-3. The north end of Trench T-6 was located about 150 feet west of T-3 and
was excavated in a southerly direction for about 145 feet in an attempt to define the most
northern extent of the fault. Between trench Stations 0+40 and 0+48, a 6- to 12-inch thick
calcareous fault vein with an attitude of N65°W60°N was encountered (Log of Trench T-6, Plate
January 6, 2017
BSA Job No. 3823.100
Page 9
BERLOGAR STEVENS & ASSOCIATES
8). Bedrock materials north and south of the fault are distinctly different (Log of Trench T-6).
The structural pattern of the fault in Trench T-6 matches the configuration of the fault observed
in Trenches T-1, T-4, and T-5. As the fault approaches the overlying colluvial soil, it is bent,
stretched and pinches out downslope. A subtle change in ground-surface slope with the
northeast side up is present above an apparent vertical fault offset of the colluvial soil/bedrock
contact about 4 feet below the surface (Log of Trench T-6).
About 50 feet southeast of the south end of Trench T-6, there is a landslide in the over-steepened
cut slope on adjacent property. The landslide was observed in the field and on LiDAR images.
The headscarp of the landslide is approximately along strike of the fault mapped in Trench T-6.
The landslide may have failed along the weak fault plane, although no surface features indicative
of a fault were observed in the area.
APPLICABLE FAULT-SPLAY MECHANICS
Because the faults found near and within the Ersted Study Area trend sub-parallel to the
Hayward fault and dip back into the hillside toward the Hayward, they are considered splays
from the main trace and are, therefore, not primary areas of ground rupture. Splay faults form
when the primary fault becomes critically misaligned with the principal stresses such that splay
fault formation, on the optimum plane of faulting, is favored (Scholz and others, 2009). Splay
faults form sequentially away from the principal fault trace so that subsequent and further away
traces exhibit successively reduced slip. Splay faults do not always rupture during an earthquake
on the primary fault (USGS, Wald, https://earthquake.usgs.gov/research/splays/splays.php) and
when they do it is only in response to, and with lesser slip displacement than, movement on the
principal fault plane.
CONCLUSIONS AND RECOMMENDATIONS
The following observations and conclusions are derived from our research and field exploration
for the specified Study Area of the Ersted property. Our study area was limited to the previously
identified Development Zone southwest of Engeo’s Fault 2, and includes portions of the site
crossed by the uncertain (queried) locations of Engeo’s Faults 3 and 4.
BSA Trench T-1 was excavated across the Study Area to explore the possibility that shears
logged by Engeo in their trenches ET-1 and ET-3 may or may not be active faults. Because the
shears are structurally different in both strike and dip from the splay fault encountered in Trench
T-1 and do not correlate from one trench to another, they appear to be unrelated to active faulting
but appear to be related to deformation history not associated with Hayward fault displacement.
Consequently, in our opinion these features are not active faults and do not require setbacks for
structures. As mentioned above, we encountered a fault in Trench T-1. The continuation of fault
trace was verified and the fault orientation (strike and dip) were confirmed with the excavation
of Trenches T-4 and T-5.
January 6, 2017
BSA Job No. 3823.100
Page 10
BERLOGAR STEVENS & ASSOCIATES
Given Engeo’s uncertain (queried and dashed) projection of Fault 2 in the northwest portion of
the Development Zone, BSA’s Trench T-2 was excavated southwest of queried Fault 2 to check
for the presence or absence of faulting. There was no evidence of faulting exposed in Trench T-
2.
BSA Trench T-3 was excavated across Engeo’s uncertain (queried and dashed) Faults 3 and 4.
No evidence of fault displacement was found in the trench. Furthermore, there was no evidence
of deformation of the Knoxville Formation by shearing in the trench, which is further evidence
that shears in Trenches T-1 are not continuous across the site and are not associated with active
faulting.
To resolve the issue of the unsupported and questioned fault projections by Engeo through the
area of BSA Trench T-3 (fault traces which are not present in T-3) and to investigate where the
fault identified in Trenches T-1, T-4 and T-5 extends to, BSA Trench T-6 was excavated
between Engeo Trench ET-1 and BSA Trench T-3. A fault interpreted to be the continuation of
the fault observed in Trenches T-1, T-4, T-5, and ET-1 was exposed in Trench T-6. This fault
aligns with the strikes and dips of the three BSA trench (T-1, T-4 and T-5) exposures and with
corrected projections of fault trends based on the strike and dips in Engeo’s Trench ET-1.
Trench exploration carried out in this current BSA investigation revealed a fault within the Study
Area. The fault passes through Trench T-1 near Station 0+50, and through Trench T-6 near
Station 0+48 following a general trend of N60°W with a dip of about 60°N. This trend is
consistent with the strikes shown by Engeo for faults logged at their trenches ET-1 and ET-3 and
consistent with the fault dips near the bottom of Engeo’s Trenches. Given: 1) the similarity in
fault’s strike in Trenches T-1, ET-1 and T-3, and 2) the absence of faulting in Trench T-3, it is
our opinion that the queried Faults 3 and 4 are not present at the locations shown by Engeo east
of their trench ET-1. It is our opinion, based on fault exposures in the trenches, that the fault we
encountered corresponds to Engeo’s Fault 3 in Trench ET-1. Instead of projecting toward
Trench T-3 as shown by Engeo, the fault continues along strike downslope to the southeast as
depicted on the Site Plan.
The fault identified in this study and Fault 2 in the Engeo report are steeply dipping splays from
the Hayward. Because of the steep dip exhibited by the faults (greater than 45°), they are not
thrusts as suggested by the fault symbols displayed on the Engeo Site Plan. These splay faults
are not independent sources of ground deformation but they may exhibit displacement in the
event of fault rupture on the Hayward. However, because the traces are splays, they would be
expected to produce less movement than on the primary fault trace located about 750 feet to the
northeast. Considering the above discussion, we recommend a setback of 25 feet for future
structures intended for human occupancy from the mapped splay trace observed in BSA
Trenches T-1, T-4, T-5 and T-6 as shown on the Site Plan.
January 6, 2017
BSA Job No. 3823.100
Page 11
BERLOGAR STEVENS & ASSOCIATES
The shears described in the Engeo trench logs and encountered in Trenches T-1 and T-6 of this
investigation are found not to be continuous across the Study Area and therefore are interpreted
not to be active faults. Although no setbacks from the shears are needed, it is recommended that
that foundations within the Study Area be designed to accommodate expected earth deformation
caused by an earthquake on the Hayward or other nearby Bay Area faults. The design-level
geotechnical report should include design recommendation for structural foundations in
accordance with the expected fault-related deformation.
With consideration of the work by others as discussed above, and the data collected by BSA
though the course of this investigation, we have delineated a revised Development Zone for the
southwest portion of the site. The revised zone is based on the previously established 50-foot
setback from Fault 2 as identified by Engeo and the recommended 25-foot setback from the fault
trace identified in our trenches. The modified Development Zone is shown on the Site Plan,
Plate 3.
LIMITATIONS
This study was conducted for due diligence purposes for faulting and does not constitute a
comprehensive geologic and geotechnical investigation of the site. Prior to development of the
Study Area, a geologic hazard evaluation addressing slope stability, other geologic site
conditions and a design-level geotechnical investigation should be completed.
The conclusions and recommendations presented in this report are based upon the information
provided to us regarding the proposed project, review of readily available published maps and
reports, review of unpublished consultant’s reports, subsurface conditions encountered in the
exploratory trenches, and professional judgment. This study has been conducted in accordance
with professional geologic and engineering geologic standards current at the time this study was
performed and in the geographic area of the study site; no other warranty is expressed or implied.
Site conditions described in the text are those existing at the time of our field exploration, and are
not necessarily representative of such conditions at other locations and times. In the event that
changes in nature, design or location of the proposed project are planned, or if it is found during
construction that subsurface conditions differ from those described herein, then the conclusions
and recommendations in this report shall be considered invalid, unless the changes are reviewed,
and the conclusions and recommendations are modified or approved in writing.
January 6, 2017
BSA Job No. 3823.100
Page 12
BERLOGAR STEVENS & ASSOCIATES
We trust this report provides the necessary information you need for your due diligence
evaluation of the site. If you have any questions, please contact the undersigned at (925) 484-
0220. Thank you for the opportunity of providing our professional services.
Respectfully submitted,
BERLOGAR STEVENS & ASSOCIATES
Michael Clark
Consulting Principal Geologist
CEG 1264
Gregory J. Ruf
Principal Engineer
GE 2940
Frank Berlogar
Principal Engineer
RCE 20383
MC/GJR/FB:aw
Attachments:
References
Tables – Topographic Maps and Aerial Photographs
Plate 1 – Vicinity Map
Plate 2 – Engeo Site Plan
Plate 3 – Site Plan
Plate 4 –Regional Geologic Map
Plate 5 – Vicinity Geologic Map
Plate 6 – Fault Activity Map
Plate 7 – Earthquake Fault Hazard Zone Map
Plate 8 – Logs of Trenches T-1 through T-6
U:\@@@Public\1-Pleasanton\3823 Grupe - Ersted Hayward\100\Supp Fault Study - 29118.docx
January 6, 2017
BSA Job No. 3823.100
BERLOGAR STEVENS & ASSOCIATES
REFERENCES
California Division Of Mines And Geology, January 19, 1981, Fault Evaluation Report Fer-103
California Geological Survey, 1982, California Earthquake Fault Hazard Zone, Earthquake Fault
Zones Map, Hayward-7.5' Quadrangle.
California Geological Survey, California Department of Conservation, Division of Mines
and Geology (2000), Digital Images of Official Maps of Alquist-Priolo Earthquake
Fault Zones of California, Central Coast Region.
Chin, J.L., Morrow, J.R., Ross, C.R., and Clifton, H.E. (1993), Geologic Maps of Upper
Cenozoic deposits in Central California, U.S.G.S., Miscellaneous Investigation Series Map I-
1943.
Crane, R. C., 1988, NCGS Field Trip Guide to the Geology of the San Ramon Valley and
Environs.
Dibblee, T.W., Jr., 1980, Preliminary Geologic Map of the Hayward Quadrangle, Alameda
County, California, U.S. Geological Survey Open-File Report.
Ellen, D.S. and Wentworth, C.M. (1995), Hillside Materials and Slopes of the San Francisco Bay
Region, California: U.S. Geological Survey Professional Paper 1357.
ENGEO Incorporated, July 26, 2005, Fault Exploration, Ersted et al Property, Hayward,
California, Project No. 6799.1.001.01.
ENGEO Incorporated, July 13, 2007, Supplemental Fault Exploration, Ersted et al Property,
Hayward, California, Project No. 6799.1.002.01.
Graymer, R.W., 1995, Geologic Map of the Hayward Fault Zone, U.S. Geological Survey, Open-
File Report 95-597.
Hart, E.W. and Bryant, William A., revised 1997 (Supplements 1 and 2 added 1999), Fault-
Rupture Hazard Zones in California, California Department of Conservation, Division of
Mines and Geology, Special Publication 42.
Helley, E. J. and Graymer, R. W. (1997), Quaternary Geology of Contra Costa County and
Surrounding Areas: United States Geological Survey Digital Database Open-File 97-98.
Herd, Darrell, 1978, Map of Quaternary faulting along the northern Hayward fault zone: U.S.
Geological Survey, Open-File Report OF-78-308, scale 1:24,000.;
Hull, Judd, and Associates, and Rose, R.B., 1975c, soil and geologic investigation for proposed
44-unit apartment development at 29298 Mission Boulevard, Unpublished consulting report
filed with the City of Hayward (AP# 200).
Jennings, C. W., 1994, Fault Activity Map of California and Adjacent Areas, California Division
of Mines and Geology, California Geologic Data Map series, Map No. 6.
Lienkaemper, J.J., 1992, Map of recently active traces of the Hayward fault, Alameda and Contra
Costa Counties, California: U.S. Geological Survey, Miscellaneous Field Studies Map MF-
2196, scale 1:24,000.
Liekaemper, J.J., 2006, Digital database of recently active traces of the Hayward fault,
California: U.S. Geological Survey, Data Series DS-177, scale 1:12,000.
January 6, 2017
BSA Job No. 3823.100
BERLOGAR STEVENS & ASSOCIATES
Radbruch-Hall, D.H., 1974, Map showing recently active breaks along the Hayward fault zone
and the southern part of the Calaveras fault zone, California: U.S. Geological Survey,
Miscellaneous Investigations Series Map I-813, scale 1:24,000.
Schlocker, J. (1970), Generalized Geologic Map of the San Francisco Bay Region, California:
United States Geological Survey Open-File Report 71-246, scale 1:500000.
Scholz, Ando, Shaw, 2009, The Mechanics of First Order Splay Faulting: The Strike Slip Case,
Journal of Structural Geology, 32 118-126
USGS, 1980, Hayward Quadrangle, 7½-minute topographic map
Wagner, D.L., Bortugno, E. J. and Mc Junkin, R. D. (1991), Geologic Map of the San Francisco-
San Jose Quadrangle: California Division of Mines and Geology Regional Geologic Map
Series 5A, scale 1:250,000.
January 6, 2017
BSA Job No. 3823.100
BERLOGAR STEVENS & ASSOCIATES
TABLES
Topographic Maps
Year Scale
(Minutes)
1899 15
1915 15
1947 7.5
1950 7.5
1968 7.5
Aerial Photographs
Year Source
10/14/1974 Pacific Aerial
07/08/1993 US Geological Survey
07/27/2002 Digital Global
12/21/2004 Digital Global
06/11/2005 USDA Farm Service
08/31/2009 US Geological Survey
05/19/2012 Google Earth
10/30/2015 Google Earth
JO
B N
UM
BE
R: 3823.100 D
AT
E: 1-4-17 B
Y: C
C
BASE: PORTION OF U.S.G.S. 7.5 MINUTE TOPOGRAPHIC QUADRANGLE,
HAYWARD, CALIFORNIA
PLATE 1
SITE
0 2000
1"=2000'
VICINITY MAP
ERSTED PROPERTY
HAYWARD, CALIFORNIA
FOR
THE GRUPE COMPANY
JO
B N
UM
BE
R: 3
82
3.10
0 D
AT
E: 1
-5
-1
7 D
RA
WN
B
Y: C
C
PLATE 2
ENGEO
SITE PLAN
ERSTED PROPERTY
MISSION BOULEVARD SOUTH
OF TENNYSON
HAYWARD, CALIFORNIA
FOR
THE GRUPE COMPANY
Berlogar Stevens & Associates
SOIL ENGINEERS * ENGINEERING GEOLOGISTS
FAULT "A"
FAULT "B"
FAULT "C"
FAULT "D"
SUSPECTED
FAULT "E"
??
??
?
?
?
?
T
-
4
B
T
-
4
T
-
9
T
-3
T
-
1
3
T
-
1
4
T
-
1
5
T
-
1
6
T
-2B
T
-2
B
T
-2
A
T
-2
C
T
-
1
0
T
-
5T
-
5
A
T
-
1
T
-
3
T
-
2
T
-
4
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
F
A
U
L
T
1
F
A
U
L
T
2
E
T
-
1
ET
-2
E
T
-
3
37
TR
7
T
R
8
T
3
(1
9
7
5
)
T
1
(
2
0
1
2
)
T
4
(
1
9
7
5
)
L
2
(
2
0
1
2
)
T
1
(
1
9
7
5
)
T
-
1
T
-
5
T
-
4
T
-
2
T-3
HAYWARD FAULT
ZONE
62
32
29
21
29
21
36
66
40
SITE PLAN
ERSTED PROPERTY
MISSION BOULEVARD SOUTH
OF TENNYSON
HAYWARD, CALIFORNIA
FOR
THE GRUPE COMPANY
Berlogar Stevens & Associates
SOIL ENGINEERS * ENGINEERING GEOLOGISTS
EXPLANATION
PROPERTY LINE
DEVELOPMENT AREA
TRENCH LOCATION (THIS STUDY)
APPROXIMATE TRENCH LOCATION
(C&A 2012)
APPROXIMATE TRENCH LOCATION
(ENGEO, 2005)
APPROXIMATE TRENCH LOCATION
(BERLOGAR GEOTECHNICAL CONSULTANTS, 2001)
APPROXIMATE TRENCH LOCATION
(EARTH SYSTEMS CONSULTANTS, 1980)
APPROXIMATE TRENCH LOCATION
(JUDD HULL & ASSOCIATES, 1975)
APPROXIMATE TRENCH LOCATION
(SOIL ENGINEERING CONSULTANTS, 1973)
SOUTHWESTERN LIMIT OF EARTHQUAKE FAULT
HAZARD ZONE (STATE OF CALIFORNIA, 1982)
APPROXIMATE THRUST FAULT LOCATION
(ENGEO, 2005)
APPROXIMATE THRUST FAULT LOCATION
(CRANE, 1988)
APPROXIMATE FAULT LOCATION
(BERLOGAR STEVENS & ASSOCIATES (THIS STUDY)
APPROXIMATE FAULT LOCATION
(BERLOGAR GEOTECHNICAL CONSULTANTS, 2001)
APPROXIMATE FAULT LOCATION
(SOIL ENGINEERING CONSULTANTS, 1973)
STRIKE AND DIP OF SHEAR (ENGEO, 2005)
STRIKE AND DIP OF SHEAR
(SOIL ENGINEERING CONSULTANTS, 1973)
APPROXIMATE LOCATION OF PHOTO LINEAMENT
(ENGEO, 2005)
JO
B N
UM
BE
R: 3
82
3.10
0 D
AT
E: 1
-4
-1
7 D
RA
WN
B
Y: C
C
PLATE 3
0 100
1"=100'
WORKING DRAWING
IN PROGRESS
ET-3
T-16
T-4
T4 (1975)
TR8
L2 (2012)
JO
B N
UM
BE
R: 3823.100 D
AT
E: 1-4-17 B
Y: C
C
BASE: CGS, 2002, GEOLOGIC MAP OF CALIFORNIA
PLATE 4
0 20 MILES
1"=20 MILES
SITE
REGIONAL GEOLOGIC MAP
ERSTED PROPERTY
HAYWARD, CALIFORNIA
FOR
THE GRUPE COMPANY
JO
B N
UM
BE
R: 3823.100 D
AT
E: 1-4-17 B
Y: C
C
BASE: GEOLOGIC MAP OF THE HAYWARD FAULT ZONE, CONTRA COSTA,
ALAMEDA, AND SANTA CLARA COUNTIES, CALIFORNIA: A DIGITAL DATABASE BY:
R.W. GRAYMER, D.L. JONES, AND E.E. BRABB
PLATE 5
0 4000
1"=4000'
EXPLANATION OF SYMBOLS
UNDIVIDED QUATERNARY DEPOSITS
MELANGE
KNOXVILLE CONGLOMERATE BEDS
KERATOPHYRE
VICINITY GEOLOGIC MAP
ERSTED PROPERTY
HAYWARD, CALIFORNIA
FOR
THE GRUPE COMPANY
SITE
Jsv
Qu
JKfm
JKkc
Jsv
JO
B N
UM
BE
R: 3823.100 D
AT
E: 1-4-17 B
Y: C
C
BASE: CGS, 2010, FAULT ACTIVITY MAP
PLATE 6
0 5 MILES
1"=5 MILES
SITE
FAULT ACTIVITY MAP
ERSTED PROPERTY
HAYWARD, CALIFORNIA
FOR
THE GRUPE COMPANY
JO
B N
UM
BE
R: 3823.100 D
AT
E: 1-4-17 B
Y: C
C
PLATE 7
0 2000
1"=2000'
BASE: PORTION OF CGS, 2012, EARTHQUAKE ZONES OF REQUIRED INVESTIGATION,
HAYWARD QUADRANGLE
EARTHQUAKE FAULT HAZARD ZONE MAP
ERSTED PROPERTY HAYWARD, CALIFORNIA FOR
THE GRUPE COMPANY
SITE
A
A
G
F
D
D
D
C
B
E
E
C
WEST END
0+00 0+10 0+20 0+30 0+40
0+50 0+60 0+70 0+80 0+90
EAST END
SOUTHEAST END
0+00 0+10 0+20 0+30 0+40 0+50 0+60
0+70 0+80 0+90 1+00 1+10
1+20 1+30 0+40 1+50
1+60 1+70 1+80 1+90 2+00
A
?
?
?
A
A
A
T
U
V
PS
R
R
Q
M
P
M
J
O
N
F
L
J
K
J
H
G
I
H
G
F
F
B
F
D
B
B
D
F
C
CHLORITE COBBLE
WITH WEATHERING
RIND APPROXIMATELY
2 INCHES THICK
IMBRICATED
STRETCHED
CALCIUM
CARBONATE STRINGERS
N80°W 48°N
MIXED AND CONVOLUTED
FOLDING OF WHITE
AND BROWN TO BLACK CLAY
FAULT
N60°W52°N WHITE TO
LIGHT GRAY CLAY
GOUGE CALCIUM
CARBONATE RICH AT
BOTTOM OF TRENCH
GOUGE
STRIKE 42°W
FINE-GRAINED
SANDSTONE, RED
N52°W60°N
FRAGMENTS OF
SCHIST, SHALE AND
QUARTZ
CALCIUM
CARBONATE
ANGULAR ROCK
VOLCANIC?
MA
TC
H LIN
E
2+00 2+10
2+20 2+30 2+40 2+50 2+60 2+70 2+80
2+90 3+00 3+10 3+20 3+30 3+40 3+50
3+60 3+70 3+80 3+90
NORTHEAST END
A
A
A
X
C
X
X
W
L
W
T
T
V
SHALE
SAND LENS
FILL
FILL
FILL
FILL
FILL
Y
Y
MA
TC
H LIN
E
?
A
A
A
A
B
G
F
B
B
B
B
C
D
E
E
D
E
F
D
F
FAULT
HARD CALCIUM
CARBONATE
CONCRETION
CALCIUM CARBONATE
SHEAR N60W 55N
BASALT, HIGHLY
STRETCHED,
COMPLETELY
WEATHERED
SHEAR N40W 47N
CALCIUM CARBONATE SEAM
SHEAR N75W 50N
VOLCANIC INCLUSIONS, COMPLETELY
WEATHERED, CALCIUM CARBONATE RICH
CALCIUM
CARBONATE
GOUGE
N65W 60N AT
BOTTOM OF
TRENCH
SOUTH END
0+00 0+10 0+20 0+30 0+40 0+50 0+60 0+70 0+80 0+90 1+00 1+10 1+20 1+30 1+40 1+50
NORTH END
D
A
A
A
A
E
D
C
C
B
C
D
D
D
SOUTH END
0+00 0+10 0+20 0+30
0+40 0+50 0+60 0+70 0+80 0+90
1+00 1+10 1+20 1+30 1+40 1+50
NORTH END
CALCIUM CARBONATE
VEIN ALONG CONTACT
C
A
B
C
D
FAULT
N73W 90 AT BOTTOM
OF TRENCH
SOUTHWEST END
0+00 0+10 0+20 0+30
NORTHEAST END
A
B
C
D
D
B
SILTSTONE COBBLES
FAULT
N52W 80N AT BOTTOM OF TRENCH
SOUTHWEST END
0+00 0+10 0+20 0+30
NORTHEAST END
TRENCH LOGS
TRENCH T-1 THROUGH T-6
ERSTED PROPERTY
HAYWARD, CALIFORNIA
FOR
THE GRUPE COMPANY
Berlogar Stevens & Associates
SOIL ENGINEERS * ENGINEERING GEOLOGISTS
JO
B N
UM
BE
R: 3
823
.1
00
D
AT
E: 1
-4
-1
7 D
RA
WN
B
Y: C
C
PLATE 8
0 5
1"=5'
TRENCH T-1
LOG OF NORTH WALL
TREND N62°E
TRENCH T-1
LOG OF NORTH WALL (CONTINUED)
TREND N62°E
130
EL
EV
AT
IO
N IN
F
EE
T
135
140
145
125
GROUND SURFACE AND BOTTOM OF TRENCH
GEOLOGIC CONTACT, SOLID WHERE SHARP, DASHED WHERE APPROXIMATE
CLAY, DARK GRAY TO BLACK, WET, SOFT TO MEDIUM STIFF
CLAY, BLACK, DRY, VERY STIFF TO HARD, CONTAINS CALCIUM CARBONATE
NODULES ( UP TO 1 INCH DIAMETER) AND STRINGERS (UP TO 3 INCH DIAMETER)
BRECCIA, LIGHT GRAY-BROWN, DRY, CONTAINS ANGULAR ROCK CLASTS FROM
APPROXIMATELY 1/2 TO 6 INCH DIAMETER, SERPENTINIZED ROCK, HIGHLY
WEATHERED
CLAYSTONE, DARK BROWN, SLIGHTLY MOIST, STIFF TO VERY STIFF,
COMPLETELY WEATHERED
CLAYSTONE, DARK ORANGE-BROWN, SLIGHTLY MOIST, STIFF, COMPLETELY
WEATHERED
BRECCIA, MEDIUM ORANGE-BROWN, SLIGHTLY MOIST, STIFF, COMPLETELY
WEATHERED
BRECCIA, MEDIUM BROWN, SLIGHTLY MOIST, STIFF MATRIX, COMPLETELY
WEATHERED
CLAYSTONE, STREAKS OF BLUE, GRAY, BLACK AND LIGHT GRAY, SLIGHTLY
MOIST, STIFF, COMPLETELY WEATHERED
CLAY, MEDIUM RED-BROWN, SLIGHTLY MOIST, STIFF TO VERY STIFF
CLAY, LIGHT TAN TO WHITE, CALCIUM CARBONATE RICH
CLAY, MOTTLED BROWN AND BLUE, SLIGHTLY MOIST, VERY STIFF
SHALE, SHATTERED, DARK BROWN, HIGHLY WEATHERED, NO APPARENT
BEDDING
CLAY, VERY LIGHT BLUE, SLIGHTLY MOIST, VERY STIFF
BRECCIA, CLAST SUPPORTED, GRAVEL TO COBBLES
CLAY WITH ANGULAR GRAVEL SIZE ROCK FRAGMENTS, DARK BROWN, STIFF TO
HARD
CLAY WITH ROUNDED GRAVEL SIZE ROCK FRAGMENTS, LIGHT TAN TO LIGHT
GRAY, WITH STREAKS OF UNIT "A" IN UPPER PART
BRECCIA, DARK GREENISH GRAY, CLAST SUPPORTED
BRECCIA, LIGHT GRAY, HIGH CALCIUM CARBONATE CONTENT
SHALE, SHATTERED, VERY DARK BROWN, NO STRUCTURE, FRACTURES
APPROXIMATELY 1 TO 3 INCHES
SHALE/SLATE, LIGHT GRAY, STRONG TO VERY STRONG, MODERATELY
WEATHERED
CLAY, BLACK, HARD, CONCODIAL FRACTURES, CONTAINS SLATE, SCHIST AND
QUARTZ ROCK
SCHIST, SHATTERED
CLAY, LIGHT BLUE WITH ORANGE BROWN DECOMPOSED ROCKS, SLIGHTLY
MOIST, VERY STIFF
CLAYEY SHALE (GRAVEL SIZE ANGULAR FRAGMENTS OF SHALE) DARK BROWN
WITH WHITE CALCIUM CARBONATE STRINGERS
CLAY WITH SCATTERED ANGULAR ROCK FRAGMENTS, MEDIUM BROWN WITH
ABUNDANT CALCIUM CARBONATE STRINGERS AND NODULES
SANDY GRAVELLY CLAY WITH WOOD FRAGMENTS AND ROTTED GRASS,
MOTTLED BROWN AND BLACK, SLIGHTLY MOIST, SOFT
T-1 EXPLANATION
A
B
C
E
D
F
G
H
I
J
K
TRENCH T-2
LOG OF NORTH WALL
TREND N68°E
TRENCH T-3
LOG OF WEST WALL
TREND N4°E
TRENCH T-6
LOG OF WEST WALL
TREND N-S
TRENCH T-4
LOG OF NORTH WALL
TREND N35°E
TRENCH T-5
LOG OF NORTH WALL
TREND N47°E
110
EL
EV
AT
IO
N IN
F
EE
T
115
120
125
105
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
FILL
GROUND SURFACE AND BOTTOM OF TRENCH
GEOLOGIC CONTACT, SOLID WHERE SHARP, DASHED WHERE APPROXIMATE
SANDY GRAVELLY CLAY, DARK GRAY, WET AT SURFACE, SLIGHTLY MOIST AT
BASE, SOFT
GRAVELLY SANDY CLAY TO CLAYEY SAND, DARK GRAY, SLIGHTLY MOIST,
MEDIUM STIFF TO STIFF
SILTY GRAVELLY CLAY, BLACK WITH ABUNDANT WHITE CALCIUM CARBONATE
NODULES UP TO APPROXIMATELY 1 INCH DIAMETER, HARD
SILTY GRAVELLY CLAY, LIGHT BROWN, DRY, HARD, GRAVEL IS BLACK ROCK
FRAGMENTS
SANDY GRAVEL, LIGHT BROWN, DRY, LOOSE TO DENSE, CLAST SUPPORTED,
GRAVEL IS ROUNDED UP TO 2 INCH DIAMETER
SANDSTONE AND SILTSTONE COBBLES AND BOULDERS IN CLAY MATRIX
(CONGLOMERATE), DARK GRAY WHERE WEATHERED
SILTSTONE, LIGHT BROWN NO APPARENT BEDDING, JOINTS AT ABOUT 1/2 INCH
N60W>8N
T-2 EXPLANATION
A
B
C
E
D
F
G
GROUND SURFACE AND BOTTOM OF TRENCH
GEOLOGIC CONTACT, SOLID WHERE SHARP, DASHED WHERE APPROXIMATE
SILTY CLAY, BLACK, DRY, SOFT TO STIFF
CLAY, BLACK WITH OCCASIONAL CALCIUM CARBONATE NODULES
APPROXIMATELY 1/2 INCH DIAMETER
CLAY, BLACK WITH COMMON TO ABUNDANT WHITE CALCIUM CARBONATE
STRINGERS IMBRICATED TO UPPER AND LOWER CONTACTS
CLAY, LIGHT TAN TO LIGHT BROWN, DRY, HARD, WITH ABUNDANT CALCIUM
CARBONATE VEINS
CLAY, MEDIUM BROWN, DRY, HARD
T-3 EXPLANATION
A
B
C
D
GROUND SURFACE AND BOTTOM OF TRENCH
GEOLOGIC CONTACT, SOLID WHERE SHARP, DASHED WHERE APPROXIMATE
SILTY CLAY, BLACK, MOIST TO SLIGHTLY MOIST, SOFT TO STIFF
CLAY, BLACK WITH ABUNDANT CALCIUM CARBONATE NODULES AND
STRINGERS, DRY TO SLIGHTLY MOIST, HARD
CLAY, MEDIUM BROWN, SLIGHTLY MOIST TO DRY, HARD, CONTAINS SOME
CALCIUM CARBONATE IN-FILL VEINS
CLAY, LIGHT BROWN TO LIGHT TAN, SLIGHT GREEN TINT, DRY, HARD
T-4 EXPLANATION
A
B
C
D
GROUND SURFACE AND BOTTOM OF TRENCH
GEOLOGIC CONTACT, SOLID WHERE SHARP, DASHED WHERE APPROXIMATE
SILTY CLAY, BLACK, MOIST TO SLIGHTLY MOIST, SOFT TO STIFF
CLAY, LIGHT TAN, DRY, STIFF TO VERY STIFF
CLAY, MEDIUM GREEN BROWN, DRY, STIFF TO HARD, CONTAINS HIGHLY
WEATHERED SILTSTONE COBBLES
CLAY, LIGHT BROWN TO MEDIUM BROWN WITH GREEN TINT, DRY, HARD
T-5 EXPLANATION
A
B
C
D
GROUND SURFACE AND BOTTOM OF TRENCH
GEOLOGIC CONTACT, SOLID WHERE SHARP, DASHED WHERE APPROXIMATE
SILTY CLAY, BLACK, SLIGHTLY MOIST, STIFF TO VERY STIFF
CLAYSTONE WITH ABUNDANT CALCIUM CARBONATE NEAR BASE OF UNIT, DARK
BROWN TO BLACK WITH WHITE STRINGERS AND LOOSE NODULES
CLAYSTONE WITH SOME CALCIUM CARBONATE NEAR TOP OF UNIT, DRY, DARK
TO LIGHT ORANGE-BROWN, CONTAINS FINE-GRAINED ROCK FRAGMENTS
(VOLCANIC) WITH FEW GRAVEL, SANDSTONE, WELL ROUNDED WITH
WEATHERING RIND
CLAYSTONE, LIGHT GRAY TO WHITE, DRY, VERY STIFF, CALCIUM CARBONATE
RICH
CLAYSTONE, MEDIUM TO DARK BROWN, DRY, VERY STIFF TO HARD, CONTAINS
GRAVEL WELL ROUNDED TO ABOUT 2 INCH DIAMETER OF SERPENTINITE AND
VOLCANIC ROCK
CLAYSTONE, SIMILAR TO UNIT "E" BUT LIGHT YELLOW-BROWN, CONTAINS
GRAVEL OF SERPENTINITE AND VOLCANIC ROCK
CARBONATE ROCK WITH MINOR CLAY CONTENT
T-6 EXPLANATION
A
B
C
E
D
F
G
110
EL
EV
AT
IO
N IN
F
EE
T
115
120
125
105
120
EL
EV
AT
IO
N IN
F
EE
T
125
130
115
110
EL
EV
AT
IO
N IN
F
EE
T
115
120
125
105
130
EL
EV
AT
IO
N IN
F
EE
T
135
140
125
EL
EV
AT
IO
N IN
F
EE
T
115
120
125
EL
EV
AT
IO
N IN
F
EE
T
120
125
130
EL
EV
AT
IO
N IN
F
EE
T
105
110
115
EL
EV
AT
IO
N IN
F
EE
T
110
115
120
115
EL
EV
AT
IO
N IN
F
EE
T
120
125
130
110
125
EL
EV
AT
IO
N IN
F
EE
T
130
135
140
120
130
EL
EV
AT
IO
N IN
F
EE
T
135
140
145
140
EL
EV
AT
IO
N IN
F
EE
T
145
150
155
E