C-631- .. KNOX, RlCKSEN, SNOOK, ANTHONY & ROBBINS w_ SAYER SNOOK, JR . .JOHN C. RICKSE:N RUPERT H. RtCKSEN STEVEN R. ANTHONY WILLIAM C. ROBBINS m STE PH EN S. HARPER ROBERT G. ALLEN THOMAS A. PALMER RICH .... RO G. LOGAN, .JR. JEFFREY A. HARPER THOMAS £. F"RAYSSE: M. PAYNE Mrs. Deborah Herrmann ATTORNEYS AT LAW ORDWAY BUILOING-KA1SER CENTER ONE KAISER PLAZA, SUITE 850 OAKLAND, CALIFORNIA 94612-3699 {415) 893-tOOO February 26, 1986 The Resources Agency of California Department of Conservation State Mining and Geology Board 1416 9th Street, Room 1326-2 Sacramento, CA 95814 RE: Syar Industries, Inc. Lake Herman Quarry WALLACE W KNOX (1905·1982) SOLANO COUNTY OFFICE 1530 WEBSTE:R STRE:ET, SUITE 0 FAIRF'IELO, CALIFORNIA 94'533 (707) 422·2:730 PLEASE DIRECT REPLY TO: Received by Deportment of \_ .'· FEB 2 7 1986 North San Francisco Bay Production-Consumption Region Sector G Dear Deborah: As we discussed on the telephone and as requested by the Board at its hearing on January 31, we are enclosing two reports done by Harding Lawson Associates entitled "Geochemical Evaluation, Old Mercury Mine Tailings Planned, Sky Valley Country Club, Benicia, and "Report Geotechnical Investigation, Sky Valley Country Club Proposed Development, Benicia, California. As indicated in the introduction of the latter study at page 1, the object of the work was "to evaluate the geology and the geologic hazards and to provide Harding Lawson's opinions on the feasibility of the residential project and the measures to mitigate the geologic hazards". The study was not done with the objective of locating aggregate deposits. As stated in the report (pages 7 through 9) and on Plate 1, the deposits of basalt are located throughout the western portion of the property. These deposits are part of those which are being quarried by Syar on its adjacent property. The findings of the Harding Lawson report are further substantiated by the State's Special Report 146 (at pages 6, 33- 36) and by Bulletin 149 by C. E. Weaver. Again, we request that the State Geologist classify (solely on the basis of geologic factors) the entire Sector G as containing significant mineral deposits and that it be designated by the Board as having regional significance.
41
Embed
KNOX, RlCKSEN, SNOOK, ANTHONY ROBBINSgmw.consrv.ca.gov/SHP/APSI_SiteInvestigation... · 4/11/1985 · .o:ttNOX, , RICR..SEN, SNOOK, ANTHONY & ROBBINS • February 26, 1986 Deborah
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
C-631-~. ..
KNOX, RlCKSEN, SNOOK, ANTHONY & ROBBINS
w_ SAYER SNOOK, JR .
.JOHN C. RICKSE:N RUPERT H. RtCKSEN STEVEN R. ANTHONY
WILLIAM C. ROBBINS m STE PH EN S. HARPER ROBERT G. ALLEN THOMAS A. PALMER RICH .... RO G. LOGAN, .JR.
JEFFREY A. HARPER
THOMAS £. F"RAYSSE: ~NNE M. PAYNE
Mrs. Deborah Herrmann
ATTORNEYS AT LAW
ORDWAY BUILOING-KA1SER CENTER
ONE KAISER PLAZA, SUITE 850
OAKLAND, CALIFORNIA 94612-3699
{415) 893-tOOO
February 26, 1986
The Resources Agency of California Department of Conservation State Mining and Geology Board 1416 9th Street, Room 1326-2 Sacramento, CA 95814
RE: Syar Industries, Inc. Lake Herman Quarry
WALLACE W KNOX (1905·1982)
SOLANO COUNTY OFFICE 1530 WEBSTE:R STRE:ET, SUITE 0
FAIRF'IELO, CALIFORNIA 94'533 (707) 422·2:730
PLEASE DIRECT REPLY TO:
Received by Deportment of Cgn~.ervafion \_ .'·
FEB 2 7 1986
North San Francisco Bay Production-Consumption Region Sector G
Dear Deborah:
As we discussed on the telephone and as requested by the Board at its hearing on January 31, we are enclosing two reports done by Harding Lawson Associates entitled "Geochemical Evaluation, Old Mercury Mine Tailings Planned, Sky Valley Country Club, Benicia, Califor~ia" and "Report Geotechnical Investigation, Sky Valley Country Club Proposed Development, Benicia, California.
As indicated in the introduction of the latter study at page 1, the object of the work was "to evaluate the geology and the geologic hazards and to provide Harding Lawson's opinions on the feasibility of the residential project and the measures to mitigate the geologic hazards". The study was not done with the objective of locating aggregate deposits.
As stated in the report (pages 7 through 9) and on Plate 1, the deposits of basalt are located throughout the western portion of the property. These deposits are part of those which are being quarried by Syar on its adjacent property.
The findings of the Harding Lawson report are further substantiated by the State's Special Report 146 (at pages 6, 33-36) and by Bulletin 149 by C. E. Weaver.
Again, we request that the State Geologist classify (solely on the basis of geologic factors) the entire Sector G as containing significant mineral deposits and that it be designated by the Board as having regional significance.
_., .o:ttNOX, RICR..SEN, SNOOK, ANTHONY & ROBBINS ,
• February 26, 1986 Deborah Herrmann Page 2
As I mentioned to you on the phone, Jim Syar would like to conduct a field trip or tour of the Quarry and Sector G deposit for your staff, the State Geologist, and any members of the Board. Please contact Jim Syar directly at 707-643-2781 to arrange the tour if desired.
WCR:kas Enclosures cc: Jim Syar
Sincerely,
KNOX, RICKSEN, SNOOK, ANTHONY & ROBBINS
WILLIAM C. ROBBINS III
0
0
0
8 copies:
4 copies:
l copy: l copy: l copy:
MSM/ECW/jd
DISTRIBUTION
REPORT GEOTECHNICAL INVESTIGATION
SKY VALLEY COUNTRY Clt13 PROPOSED DEVELOPMENT BENICIA, CALIFORNIA
The geology of the area was determined through a review of the geologic
literature concerning previous work in the area and mapping of the site
using aerial photographs viewed stereoscopically. Because of extensive soil
cover over most of the site, outcrop exposures of the bedrock were supple
mented by 21 backhoe pits in the range of 5 to 17 feet deep which usually
penetrated the soils to rock and also provided indications of soil types,
including landslide debris. The geologic reference material reviewed and
aerial photos used are listed at the rear of this report. The Geologic Map
prepared from this work is attached as Plate 1.
0 2
0
0
0
..
H•rdlng L•wson Associates
III REGIONAL SETTING
A. Ge()'llorphic Setting
The Sky Valley area is located in the central Coast Range geomorphic
province. This region is characterized by northwest trending ridges and
valleys of the Coast Ranges with drainages generally parallel to this trend
and emptying into San Pablo and San Francisco Bays.
B. Regional Geology
The geology of the region is characterized by f.'esozoic age rocks of the
Great Valley Sequence faulted and folded over the underlying rocks of the
Franciscan Assemblage. Tertiary rocks occur northeast and stratigraphically
above the Great Valley Sequence. The geologic structure is dominated by a
80rthwest trend related to the active strike-slip San Andreas fault system.
Folding in the Tertiary and Great Valley rocks is approximately parallel to ·
this trend, including a broad northwest trending syncline in the project
area.
3
0
0
Harding Lawson Associate&
IV SEISMICITY
A. Tectonics
The site lies within a seismically active region at the continental
margin represented by several major fault zones including the San Pndreas,
Hayward, and Green Valley-Concord fault systems which lie west and east of
the site, as indicated on the attached Regional Fault and Epicenter Map,
Figure 2. These faults have experienced repeated offsets during recent geo-
logic time and some have experienced one or more historical earthquakes of
significant magnitude. Geologic mapping in the vicinity of the site as a
part of a Bay Region study by the U.S. Geological Survey revealed no indica-
tions for an active fault within the site. However; recent findings as a j ~rl cl v1e - I .S,,.,
result of continuing study indicate that the West Napa fault zone lying t,.o c '~ ____,/ 5fe ,.vi b
northwest of the site is active (Herd and Helley, 1977). n.. t d" l p vur own s u ies bj
indicate that the Southampton fault lying southeast of the site may have
experienced surface displacement during relatively recent geologic time and
thereby might be classified as potentially active. As indicated by the
attached Fault Map, Figure 2, a prolongation to connect these two faults
along the dominant northwest strike of active faults in the region is
possible, but it has not been demonstrated and they may not connect.
OJr investigation of the site and.previous work (Sims, 1973) indicate a
fault contact between the rocks of the Franciscan Assemblage and those of
the Great Valley Sequence as indicated on the Project Area Geologic Map,
Plate 1. Several northeast trending tear faults are present in the folded
0 4
----- ----~~-
..
•••
•
I
)
J7•
)
l-. • \
', \ .,. . r.-'~,. :/) :
• I, ( .
\
·-·. ........ '·
_· ... ..:...... -;? • /\·~··
· ·S~ento \f .
~· \ . :·
• ;
( 1 ..
I ,... . ·---f\ / _,,. ..
• I .. ' . ,r-
... l -·
...- I : . _... .. \
. \ ... _ .. f -~-
\
_..J'.._ ••
0
r' •
,, I
\
EARTHQUAKE I· A G N I T u D E
·--- .. 11..-
C)---~- s.o
~---=- 6.~
C)---- 7.0
,e--- 8.0
TO TO
TO
4.9 I ~-9 i 6.9 '
I TO 7. 9
OR GREATER
INTEGER - MAXIMUM REPORTED INTENSITY (ONLY FOR EARTHQUAKES OF UNKNOWN MAGNITUDE)
.... ---
'
FA U LT SYMBOL
~ UNDIFFERENTIATED FAULT (Dotted where concealed, dashed where inferred~ solid where definitely located, barbs on the upper thrust bloc.kl --------- ACT IVE! FAULT (All dashed offshore faults are based on acoustic reflection profile records)
i 30 20 10 o I
30 20 10 0
' SCALE r 1:1,000,000
30 MILES
40 KILOMETERS
REFERENCES: 1. I Faults with Quaternary Displacement, Northeastern
2.
3.
San Francisco Bay Regio~. California, 1977, Helley and Herd, I S I J U.S. Geologica urvey Map MF-881
Preliminary Geologic Maplof Solano County and Parts of Napa, Contra Costa, Marin and Yolo Counties, Califo1·nia, 1973, Sims et al, Basic Data Contribution No. 54
I Earthquake Epicenter Mai? of California, 1978, Map Sheet 39, California Division of Mines and Geology
I
' 4. Fault Map of California,
0
1975, Map No. 1, California Geologic Data Map Series, California Division of Mines and Geology
Harding Lawson Aasoclates
Engineers. Geologists
Regi0~al Fault and Epicenter Map for Ealthquakes, 1900 to 1974
FIGURE
Sky ·J111cy Country Club 2 Sola1•J: County, Ca:, forn1<1
~o~,,-w~,~~~~~~~--;;,o~.~N~UV~B"'""~~~~~~--..~,""5:'°"=~doo:-~~~~~,OA~r~E~~~~~,,~V~'5~E00--~~-"~.~,.~~~~-1 7450,001 01 cc"<!( 4(85 JAS
& Geophys1c1sts
•
Harding L•w•on Ass.oclates.
0
0
Tertiary rocks northeast of the project area. None of these on-site faults
are known to have experienced geologically recent or historical seismic
activity, and there are no visible conditions on the site to indicate that
they are active. Based on the known tectonic history of the region, the
on-site fault was formed millions of years ago and, therefore, it is
inactive.
B. Earthquake History
The earthquake history includes nine major earthquakes that produced
significant ground motion in the Vallejo/Benicia area·with epicenters within
a 40-mile radius. These earthquakes extend from 1868 through 1915. Because
they largely precede the establishment of a seismograph network, both the
locations and magnitudes of the earlier events can only be established based
upon reported intensities. The largest event by far was that of April 18,
1906, with an estimated Richter magnitude of 8.3 caused by major displace
ment on the San Andreas fault which lies about 25 miles west. Other major
events include the 1836 and 1868 earthquakes on the Hayward fault about 12
miles southwest and with magnitudes of about 7 on the Richter scale. On
March 31, 1898, a strong earthquake occurred near Mare Island which caused
significant damage to the Naval Base as well as damage in Benicia and
Vallejo. The source of this earthquake is unknown, although it might have
been due to.a northerly prolongation of the Hayward fault beneath San Pablo
Bay. t'b surface rupture is reported for this event. However, it might have
been due to a displacement on the Southampton fault in which the rupture did
~ not reach the surface. Some of the early investigators in the area includ
ing Tolman (1931) believed the Southampton fault to be active. Although the
5
0
0
0
~·; . /
Harding Lewson Associates
conclusions reached by the earlier investigators must be regarded with
caution, Tolman states that "Prior to the San Francisco earthquake in 1906,
the Carquinez Straits and Suisun Bay area probably exhibited the highest
average seismic activity of any region in central California. This state-
ment is believed to be justified even in view of the incompleteness of the
older records and the fact that much of central California was partially
inhabited. Since that time, the activity has been very slight. The earth
stresses relieved along the Hayward fault south of Berkeley are expended c~tvL-;A_f
farther north along the Sunol-Southampton fault and possibly other faults to~ ,c,..,,£.f
the east." Other investigators beside Tolman have pointed out the obvious
northward bend of Carquinez Strait where it crosses the Southampton fault
near Port Costa. If it is a deflection of tectonic origin, it would be
consistent with the right lateral placement of an ·active fault in the San
Andreas system.
Other nearby active faults, including the Green Valley-Concord fault
system to the east, have experienced historical earthquakes ranging up to
about magnitude 6 based on instrt..rnental and intensity estimates for the
older events. The maximum magnitude capability of these faults is believed
to be in the range of 6 to 6.5.
6
0 H•rdlng Lawson Associates
V PROJECT AREA CONDITIONS
A. Topography
The Sky Valley Country Club project occupies approximately 350 acres
located approximately 3 miles east of the City of Vallejo. See Project
Location Map, Figure 1. Sulphur Springs Creek drains the valley flowing
through the project area from north to south. The elevation of the valley
floor is about 150 feet above sea level.
Sulphur Springs Mountain forms a high ridge rising west of the valley to
an elevation of just over 900 feet. The flanks of this mountain are deeply
dissected by short drainages with slopes varying from very steep to approx-
imately 5:1. East of the valley, the terrain is somewhat less severe with
~rounded hills to approximately 500 feet elevation with slopes varying from
approximately 3:1 to 5:1 (horizontal to vertical).
B. Geology
1. Bedrock
The bedrock is Jurassic to Cretaceous in geologic age, and composed
of the Franciscan Assemblage or an Ulnamed Formation of the Great Valley
Sequence (Sims et al., 1973). The Franciscan Assemblage is a tectonically
formed mixture of a variety of rock types commonly exhibiting peryasive
shearing and localized metamorphism. The Franciscan rocks in the project
area consist irainly of greenstone (metamorphosed basaltic volcanic rock -
map symbol KJfg), altered rocks (KJfa), and minor diabase (KJfd). The
Ulnamed Formation has two distinct rock units in the project area. First,
0 7
0
0
0
•
H•rdlng L•wson Associates
the lllJdstone unit (KJgvm) containing minor limestone and sandstone, and the
sandstone unit (Kgvs) containing limestone and lllJdstone. The._~Q£k classi--------.
fications and physical properties were based on field examination only; no
laboratory tests were performed.
Where exposed at the surface or in test pits, the greenstone is
red-brown to black, intensely fractured, moderately hard, moderately strong,
and moderately to deeply weathered. As indicated on the Geologic Map,
Plate 1, this rock occurs at the middle to higher elevations of Sulphur
Springs Mountain. The irregular occurrence of this rock and its close
association with the diabase and altered rocks indicates a complex mixing of
these rock types.
The altered rocks appear to have been produced by the hydrothermal
alteration of greenstone along· shear and fracture zones. These rocks are
commonly altered to clay, silica, and iron oxides. Typically, they are
mottled brown and white, closely fractured, moderately hard to hard, moder
ately strong, and moderately weathered. Like the greenstone, these rocks
occur throughout the middle and higher elevations of Sulphur Springs
Mountain in close association with the greenstone.
The diabase is an ultrabasic rock intrusive into the greenstone. It
was observed at the highest ridge elevations on Sulphur Springs Mountain and
in a few small outcrops just downslope from the ridge. The diabase is
generally gray, moderately fractured, hard, strong, with little to moderate
weathering.
8
0
0
0
The mudstones are brown to gray, thin bedded, closely fractured,
moderately hard, moderately strong, and deeply to moderately weathered.
Thin beds of sandstone and limestone occur within these rocks. The mud
stones were not observed in outcrop, but were encountered in test pits in
the middle to lower elevations of Sulphur Springs Mountain, the lower eleva
tions east of Sky Valley, and in the easternmost portions of the project
area.
The sandstone crops· out locally on the top and west slopes of the
ridge immediately east of Sky Valley. In outcrop, these rocks appear light
brown, blocky, moderately fractured, moderately hard and strong with deep to
moderate weathering.
2. Structure
Based on Sims' 1973 map, the rocks of Ll'Ylamed Formation dip eastward
formi~g the west lirrtJ of an asymmetric northwest trending syncline, whose
axis is located northeast of the project site.
On the west side of the project area, the lllJdstones are faulted
against the Franciscan rocks. Several northeast trending Tertiary faults
are located northeast of the project area and these may extend into the rrud
stones and sandstones of the Sky Valley area. Local folding within the
rocks of the Unnamed Formation may exist throughout the. project area.
3. Surficial Deposits
Much of the project site is blanketed by colluvial and residual
soils. These soils are generally clayey and/or silty with variable amounts
of sand and gravel. As with the bedrock types, soil classification and
9
0
0
0
.• '
Harding L..wson Associates
physical properties are based only on field examination. t-0 laboratory
tests were performed.
The deepest soils are those developed on greenstone and altered
rock. These soils reach a thickness of 17 feet or more near the base of
some slopes. I-ear hilltops the soils thin to several feet.
Test pits were not excavated in alluvial soils. These soils occur
in the streambed along Sulphur Springs Creek and probably on the adjacent
stream terraces.
4. Landslides
~merous debris and mudflow type landslides (Qls) were observed
typically within the ravines and small tributary drainages to Sulphur
Springs Creek. This type of landslide is shallow involving only the soil
zone and occurs in seasonally saturated ground conditions on the steeper
slopes. Slide movement is relatively rapid. l'ost of these landslides
contain surface indications of recent activity.
Soil creep probably occurs in much of the colluvial and residual
soils on steep slopes. This type of soil movement is typically a slow down-
slope movement of surficial soils.
The presence of older landslides (Qols) was indicated by test pits
and by topographic irregularities characteristic of landslides. Test Pits
18 through 21 indicate_ the presence of an old landslide in mudstone east of
Sulphur Springs Creek (see Plate 1). This slide was probably active at the
time of stream terrace development and is now dormant. In the western
project area, the uppermost slopes of Sulphur Springs l'ountain may contain
10
0
0
0
H•rdlng Lawson Associates
an old deep-seated landslide in the approximate area indicated on P.late 1.
The general configuration of the terrain and steep slopes are suggestive of
a large landslide extending into bedrock, although the topography could
result from differential erosion of hard and soft bedrock without landslide
movement.
C. Ground Water
t-.\.Jmerous springs and seeps occur in the project area. The more signif
icant and probably perennial are those located below.the old mine workings.
1-'eavy flows are reported to have been encountered in mine workings and the
flows influenced the flow in springs at Blue Rock Springs resort located
approximately a mile to the northwest (Gomez, personal communication, 1985).
Water seepage was observed in Test Pit SV-12 where relatively pervious top-
soil was underlain by impervious clay.
11
0
0
0
Harding Lawson Ass.oclat•s
VI CONCLUSIONS
Large areas of the site are underlain by bedrock at relatively shallow
depth. These areas are suitable for construction of rnJltiple and single
family residences, access roadways, utilities, etc. as is generally
prooosed. 1-'owever, the conditions at the site vary appreciably, both
topographically and geologically. These conditions, which represent geo
logic hazards, include steep slopes in weak soils and bedrock, active
landslides, old landslides, old mine workings, and areas of persistent
springs and ground-water seepage.
The occurrence of landslides is significant to the development, but the
total aggregate area is relatively small compared to the total area of the
property. All of the active slides are localized and relatively super
ficial. In addition to careful grading and surface drainage precautions,
mitigation measures for these slides inciude partial or complete removal of
the landslide debris, and reconstruction of the slope to the desired grades
using the excavated materials in well compacted buttress fills. Mitigation
measures for the older, inactive slides will depend upon several factors
including location relative to the develop:nent, planned grading, and the
potential for reactivation. Treatment of the old deep-seated slides, if
they exist, by the methods outlined above is technically possible although
their large size may make such measures economically unfeasible. It is
suggested that these areas be considered for use such as open space. The
existence of these slides should receive further investigation and if they
12
0 Ha..-dlng Lawson Assoclutes
are confirmed, special care should be taken in the grading plans so that any
grading in the area tends to improve slope stability.
Soil creep on the steeper slopes could damage structures located on
these slow-moving soils. To reduce the risk of damage, building foundations
should gain their support frcxn the stable rock or soil materials below the
zone of creep. Deepened foundations, drilled or cast-in-place concrete
piers penetrating to competent materials, and careful grading may provide
such support.
The mine workings include several deep vertical shafts and areas of
ground subsidence. Treatment of these workings may include backfilling and
possibly some grouting to ensure closure of them. The small areas of these
(:> workings should be avoided when siting permanent structures. Several tail
ings piles·exist near the mine workings. These piles are generally small,
but may be Ulstable. Pei investigation to evaluate these tailings with
respect to potential toxicity will be conducted shortly and those materials
found to be toxic should be removed from the site. l'bntoxic tailings should
be stabilized using measures similar to those recomnended for mitigation of
0
active landslides.
Depending on the development plans, areas of persistent springs and
ground-water seepage may require subsurface drainage to intercept and divert
the seepage away frcxn development areas. The heavily saturated areas should
be considered for ponds, wetlands, or similar recreational usage. Care
should be taken to avoid placement of intercepted water onto areas
susceptible to erosion or slope instability.
13
0 .Harding Lawson Ass.oclate-a
Where areas of steep slopes in weak soils and bedrock exist, hillside
grading to prepare level building and roadway sites involves an inherent
risk of slope stability problems, regardless of whether or not a landslide
presently exists. Where weak soils and bedrock are present, ground-water
seepage and erosion from concentrated surface runoff can often lead to new
slope instability. Careful site selection to reduce the amount of grading,
installation of adequate surface and subsurface drainage facilities, con-
struction of relatively flat cut and fill slopes of minimum depth, erosion
control, and corrective slope measures as for landslides should be applied
where development may exacerbate present slope stability problems or
adversely impact existing slopes.
~ The proximity of the project area to several major faults makes the site
susceptible to earthquake-induced geologic hazards such as landsliding and
settlement. To mitigate these hazards, the slope corrective and foundation
measures applied to the previously discussed geologic hazards should be
designed to include the applicable seismic forces. The presence of large
rock boulders below steep slopes indicates a potential hazard from falling
rock. This hazard can be minimized by careful siting of structures and
grading measures to remove the rock or provide barriers.
The seismic hazard is limited to these secondary effects of earth-
quakes. The on-site fault is not active and represents no restraint upon
the siting of structures.
Detailed geotechnical engineering studies including test borings and
laboratory testing should be performed to provide subsurface data for design
()before construction.
14
0
0
0
Harding L•wson Associ•tes
VII REFERENCES
1. Bolt, G. A., and Miller, R. D., 1970, Seismicity of Northern and Central California, 1965-1969.
2. Brown, R. D., Jr., 1970, Faults That Are Historically Active or That Show Evidence of Geologically Young Surface Displacement, San Francisco Bay Region, U.S. Geological Survey (Basic Data Contribution).
3. california Division of Mines and Geology, Special Studies Zones, Cordelia Quadrangle, July 1, 1983.
4. Harding, C.R., 1929, Location and Design of Southern Pacific Canpany's Suisu.n Bay Bridge as Affected by Consideration of Earthquakes: Bulletin of the Seismological Society of America, Vol. 19, No. 3.
6. Herd, D. G., and 1-'elley, E. J., 1977, Faults with Quaternary Displacement, Northeastern San Francisco Bay Region, California, U.S. Geological Survey Map MF-881.
7. Lawson, A. C., 1908, The California Earthquake of April 18, 1906: Carnegie Institution of Washington, Publication 87, (reprinted 1969).
8. Lawson, A. C., 1914, Geologic Atlas of the l.Klited States, San Francisco Folio: U.S. Geological Survey.
9. Louderback, G.D., 1947, Central California Earthquakes of the 1830s: Bulletin of the Seismological Society of America, Vol. 37, No. 1.
10. Pampeyan, Earl H., 1979, Preliminary Map Showing Recency of Faulting in .Qagstal North-Central California, U.S. Geological Survey, Miscellaneous Field Studies Map MF-1070.
11. Ryall, A., Slemmons, D. B., and Gedney, L. O., 1966, Seismicity, Tectonism, and Surface Faulting in the Western Ulited States During Historic Time: Bulletin of the Seismological Society of America, Vol. 56, No. 5.
12. Sharp, R. B., 1973, Map Showing Recent Tectonic Movement on the Concord Fault, Contra Costa and Solano Counties, California, U.S. Geological Survey, Miscellaneous Field Studies Map MF-505.
15
0
0
0
13.
14.
15.
16.
Harding Lawson Associ•t•s
Sims, J. D., Fox, K. F., Bartow, J. A., and Helley, E. J., 1973, Preliminary Geologic Map of Solano County and Parts of Napa, Contra Costa, Marin and Yolo Counties, California, U.S. Geological Survey, Miscellaneous Field Studies Map MF-484.
Sonneman, H. D., and Switzer, J. R., Jr., Lllpt..blished Geologic Map of Benicia, Port Chicago, Honker Bay, Denverton, Fairfield, South Cordelia, and parts of adjacent quadrangles, California, 1961-1962.
Tolman, C. F., 1931, Geology of Upper San Francisco Bay Region: in Economic Aspects of a Salt Water Barrier Below Confluence of Sacramento and San Joaquin Rivers, California Division of Water Resources, Bulletin 28.
Townley, S. D., and All, Maxwell W., 1939, Descriptive Earthquakes of the Pacific Coast of the United States, Seismological Society of America, Vol. 29, l'b. 1.
Catalog of Bulletin of the
y--17. Weaver, C. E., 1949, Geology and Mineral Deposits of anl&neric~ Area
North of San Francisco ~California Diyision of Mines, Bulletin 149.
Aerial Photos Examined Le J{,-N_:~:
Date
3/6/85 3/6/85
Code
842518 842518
Flight Line Exposures.
1 2.
121, 122, 124 135 - 138
16
)
)
C" ..,. c
) I
EXPLANATION -
AGE SYMBOL FORMATION
T af Mine Tailings
Qls Active Ll.ndslide Quaternary
....
+ Qols? Pouible Old Landslide Deposit ~ GREAT VALLEY SC GU ENCE ~
Kg vs Unc:rned Formation. largely s.andstan., Cretaceous with mudstone. ~le, lim~tone
t KJvgm Unamed Formation, largely mudstone, with shale, sandstone, limestone
Low hardness - can be gouged deeply or carved easily w1tn a '-ln1fe blade Moderately hard - can be readily scratched by a kn1te 01aae scratch leaves a neavy :ra:::e ~· -:"L:s: an::: ·s readily visible alter the powder has oeen blown away Hard - can be scratched with d1tl1cu11y. scratch produces little oowaer and rs ol!er. !ain!ly v1s.01e Very hard - cannot oe scratcned wtth knife blade. leaves a r:ietall1c streak
V STRENGTH
1. Plastic or very low strength 2. Friable - crumoies easily by rub01ng w1tn fingers 3. Weak - An unfrac1urea specimen ol such material will crumo1e unaer i1gn1 ~ammer oiows 4. Moderately strong - Soec1men will w1lhs1and a !ew heavy ~a:n:net olows oe!ore o•eak1n;; 5. Strong - Soec1men win withstand a few heavy nng1ng nammer c1ows ana will yield win··, a1!hcu::y omy
dust and small flying !ragmenls 6. Very strong - Specimen will res1s1 heavy ringing hammer blows and will y1e!d w1i'l a1lf1cu11y on:y di.;s: ar.c
small flying fragmen1s
VI WEATHERING - The physical and chemical d1sint1grat1on ana aecomoos1!1or. ol rocl.:s ana m1~e~a:s o~ nalural processes such as o:i.1dation. reduction. hydra11on. solution. caroona11on and 1reez1ng anc !:iaw1ri;;
0. Deep - MOderate to comp!e!e mineral decomposrt1on. e:i.tensive d1s1ntegra11on deep ana l'lGroug:-> ::l"~ coloration: many lraclures. all exlens1vely coated or filled with oudes caroona:es and!Or c!ay o• s1J:
M. Moderate -- Sligh! change or oan1a1 decomoos1t1on ot m1nerats ht Ile d1s1n:e<;ra11on cement.a11ori l'l::J? ~.c. unaffected Moderate to occasionally intense d1sco1orat1on Moaerately coa;ec trac1 ..... res
L. Little - No megascooic decompos111on of minerals. little or no ellect on norm.al cernen1at1on 511cn~ ano interm111ent. or iocallzea discoloration Few stains on fracture surfaces -
F. Fresh - Unallected by weathering agents No d1s1ntegrat1on or d1sco101a11on Frac1ures usuatfy 1ess. numerous than 1oints