Sl..a.Tf: OF ~ALIFORNl..a.-fHf RESOURCES AGf:NCY

DEPARTMENT OF CONSERVATION

DIVISION OF MINES AND GEOLOGY BAY AREA REGIONAL OFFICE

380 CIVIC DRIVE. SUITE 100 Pl£A.S.A.NT HILL. CA 945l3-1997 PHONE, (415) 646-S920

A TSS 599·5920

Town of woodside P, o. Box 620005 Woodside, California 94062

Attn: Planning Director

• AP J 112· ~-· · ' GEORGE DE:UKMEJIAN, Govemot"

•.

August 29, 1988

We are placing on open file the following reports, reviewed and approved by the City of woodside in compliance with the Alquist-Priolo Special Studies Zones Act:

Fault location study, addition to residence, Lands of Alexander, 3555 Woodside Road, Woodside, California1 by Upp Geotechnology; August 11, 1987,

Geologic fault investigation, Lot 2 (Land Division No. 265), 4175 woodside Road, Woodside, California; by PSC Associates 1 August 26, 1986.

Geological investigation, The Family Farm, 1400 Portola Road, Woodside, California; by Fowler & Associates; February 9, 1987.

Please note that these reports were sent to our Sacramento office and forwarded to me. Because our file of consulting reports are kept in Pleasant Hill, I would appreciate it if reports were sent dircetly to me in the future,

EWH: slf

cc: A-P file (3) ~

Sincerely,

Eail w. Hart, CEG 935 senior Geologist &

Program Manager

GEOTECHNlf.AL CONSULTANTS William Cotton and Associates

318'8 No1ttr'Santa·i~~ru7 Av1-~nue l.o;; Ga\(ts. CC!liforni<l 95030

(405) J~·i4·~)542 FILE COPY

TO: Ciddy Wordell, Assistant Planning nirector TOWN OF WOODSIDE P.O. Box 620005 Woodside, California 911062

SUBJECT: Preliminary Geologic and Geotechnical Review RE: Family Farm Fault Trenching, Use Pcrrni l 80-96

family Farm Drive

March 5, l 37 w: 07

At your request, we have completed a preliminary geologic and geotcchni cal review of the subject application using:

o Geotechnical Investigation (report) prepared by Fowler and Associat< ; dated February 9, 1987;

o Site Plan (l sheet, 100-scale) prepared by Martin-Carpenter Associa: s, dated January 22, 1987; ;:ind

o Family Farm Master Plan (exhibits) prepared by Martin-Carpe 1er Associates, dated January 22, 1987.

In ad di ti on, we have reviewed pertinent technical maps and reports om our office files.

DISCUSSION

The referenced documents indicate that the applicant proposes t> con· struct various habitable and non-habitable structures on the subject pr(>perty Four fault trenches have been excavated and logged by the applicant's geotechni cal consultant in order to free proposed structures from the potential hazard ( surface fault rupture. It is our understanding that currently proposed in1prove ments include: expansion of the existing artist's studio, construction of ne campsites (sleeping quarters) to the east and west of the existing So· :g Bin building, expansion of a campsite area and open-theater in the northeast portic of the property near fault trench 113, and construction of a cabin and stora building southeast of the Mathieu Playwood open-theater. Additional improv ments include relocating portions of the existing access road and expansion - ' storage facilities in the northwest portion of the property. We also understl 1d that the family Farm Master Plan calls for future construction of a recrea· :in facility in the southern corner of the property.

The referenced Master Plan indicates that the intensity of property u : is very low and that primary use by club members occurs about l 5 days per yea

---- ---------ENGINEERIN(;; CEOLOC~Y • ENVll-mNMDHf\I EARTH ~3Cl[NCl-_S • FOUNDf\TI'. N E~J:JINEEFllN(;

Ciddy Wordell - 2 - Marci> 5, I 9l w 10[ Assistant Planning Director

SITE FAUL TING

The Town Geology and Geologic Hazards Map shows three inferred fe ! .t traces traversing the subject property. The Trancos trace of the active •n Andreas fault has been mapped in the easternmost portion of the property. 'he Woodside trace crosses the central portion of the property in the vicinit. of Sausal Creek. A low confidence, unnamed fault trace is also indicated in the western portion of the property.

The Town does not permit construction of any habitable structure v thin 125 feet of an inferred active fault trace unless I) a detailed fault investi, tion demonstrates that an active fault trace does not exist at the mapped locati 1, or 2) fault trenching demonstrates that the proposed building site and an add ;anal 50-foot wide zone toward the mapped trace docs not contain an active Iau

Based on a program of fault trenching, surface reconnaissance, air photo interpretation and engineering geology analyses, the applicant's gcotcdrnical consultant has concluded that the proposed improvements may be constructed "'·' planned from a geological standpoint. The consultant is also of the opinion th'.'' an active fault does not exist along the mapped alignment of the westernrnc inferred trace.

CONCLUSIONS AND RECOMMENDED ACTION

Based on our review of the referenced report, we are in substanr J agreement with the consultant•, conclusions concerning the existence . d locations of active fault traces on the subject property. The applicant should .e aware that seismically induced landsliding could occur along the banks of Sa' ' 11 Creek. It is our understanding that fault trenches t!J and fllf shadow .. e proposed cabin site and extend an additional 50 feet toward the Woodside t ;ice of the San Andreas fault. We recommend approval of the currently prop scd improvements from a geological standpoint. However, prior to issuanc . of building permits, we recommend that the following conditions be satis[ac ··rily completed:

l. Detailed Soils Investigation -- The applicant's geotechnica! cons should conduct a site-specific, detailed soils investigation to F design parameters for foundations. This investigation shoul address, but not necessarily be limited to: site preparatic i

grading, site surface and subsurface drainage improvement.,, design parameters for retaining walls and roadways.

tant vi de also and and

The results of the soils investigation shall be submitted to the ':"own L be reviewed and approved by the Town Engineer and Geologist prior the issuance of site development and building permits.

2. Geotechnlc:al Plan Review -- The applicant's geotechnlcal cCJnsult~ t shall review and approve all geotechnical aspects of the devc~lopmt t plans (i.e., site preparation and grading, site drainage improvemen .,

Ciddy Wordell Assistant Planning Director

- 3 - March 5, l' 37 w l 07

and design parameters for foundatio11s, retaining walls and road' ys) to ensure that his recommendations have been properly incorporat J.

Th" results of the plan review should be summarized by the geotio ~hni­cal consultant in a letter and submitted to the Town Engine"'r for review and approval prior to issuance of site development and building permits.

3. Geotechnical Field Ins ction -- The geotechnical consultant sha inspect, test as needed , and approve all geotechnical aspects of t~ project construction. The inspections should include, but not nece' sarily be limited to: site preparation and grading, site surface ar subsurface drainage improvements, and excavations for fou,1datirn and retaining walls prior to the placement of concrete and steel.

. > The results of these inspections and the as-bullt conditions of the proj< 't

shall be described by the geotechnical consultant in a lett"r and submitted to Town Engineer for review prior to final project approval.

WRC:TS:la

Respectfully submitted,

WILLIAM COTTON AND ASSOClA TES, II ,...

w\~t_~V\ William R. Cotton Town Geologist CEG 882

;):::· ,• .. '

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= :"-=.

~ Fowler & Associates Geological and Geotechnical Engineering 444 30th Stroot, San Franc;sco. CA 94131 • (415) 285-1345

GEOLOGICAL INVESTIGATION THE FAMILY FARM

1400 PORTOLA ROAD WOODSIDE, CALIFORNIA

PROJECT 218-1

For

THE FAMILY FAR~! MR. MARK NOVAK

GENERAL MANAGER OF THE FAMILY 545 POWELL STREET

SAN FRANCISCO, CALIFORNIA 94108

By

FOWLRR & ASSOCIATES

February 9, 1987

'i

General

GEOLOGICAL INVESTIGATION THE FAMILY FARM

1400 PORTOLA ROAD WOODSIDE, CALIFORNIA

INTRODUCTION

This report present~ the results of the geological invest­igation for the proposed improvements at the Family Farm on Portola Road in Woodside, Colifornia. The site is located within a Special Studies Zone as defined by the California State Geol.ogist in accordance with the Alquist-Priolo Act of 1974. Tho location of the si.te relati.ve to the existing road and site topography along with the areas of proposed improvements are shown on Plate 1, Site Plan and Geologic Map.

For the preparatjon of our report, we have received a Site Plan of the Family Faru1 by Marti11-Carpenter AssociatesJ dated January 22, 1987. In addition we have discussed the requirements of the geologic stu1ly with Mr. Ted Sayre of William Cotton and Associates, Town Geologist of Woodside on Jant1'Hy 7, 1987.

Proposed I1nprovcments

We understond the present Master Plan calls for construction of one-story, wood-frame cabinsJ a recreation ccntert expansion of the Artist's studio, op~n-theater stage and seatingJ and ex1lansion of storage facilitiest as shown on Master Plan, Figure 1.

Purpose and Scope of Services

The purpose of t iJ c geolog j ni 1 investigation ~~~-~,?_.~J.ua te whcther: .. _th.e ...... \:1',ac.cs. __ of .... ,the S.:.'n , ...... Andreas Fault .and required se·~:i;:~c l( __ z_?n es . enc r.o.'0 c:.h.~.,d ... into th c proposed . building areas, anrl t·a· satTsfy ... , the requirements of the Alquist-Prioio Special Studies Zone.

The scope of our ir1vestigatior1 wos -in accordance witt1 our proposal of consisted of the following:

performed substantially November 14, 1986 and

1. Review nn<l evaluate ovaileble geologic reports and m<:ips for Lhe urea of Lhr!: site J and air photo incerpretnt.ion of selected air photos.

Fowler &. Associates

218-1 -2-

2. Perform o geologic reconnaissane of the site.

3. Explore the subsurface ge'ology by trenching the inferred traces of the San Andreas Fault . .........._.....,,.-- ""

4. Perform laboratory tests to measure the pertinent index properties of selected soil samples from the trenchefJ.

5. Perforo1 geological annlyses of the inferred traces and present the results of our investigation in a compreheI1Sive report containing our findings and conclusions.

INVESTIGATION

Field Exploration

A geologic reconnaissance geomorphology of the site sets of stereographic ai,r evidence of faulting.

wos performed to evaluate the for evidence of faulting. Three phol:os were also evaluated for

The subsurface conditionu were explored by excavating four test trenchec>, £or a total length o £ 6 70 feet and ~p_Lo.x.- _ -· itr1a_tely_J0 •. -5 .. ___ t.ri._12_Jeet .. <:l_eejl., at the locations shown on the ~-----;.;;;;z;:._ Site Plan and Geologic Map, PL1te 1. Trenches 1 and 2 we e ..... ~ located to investigate the unnamed trace along the ent nee road. Trenches 3 and 4 were located to determine · there was any surface foul ting under a pro.ro.f!ed._.cJ1bii:i_ :>it and the re_ql)J_i;e_d __ 5Q __ fo()~ _,,;;ethac_k. The field exploration was performed under t.he te .. chnical direction of our certified engineeririg geologist who exomincd and visually classified the soils encountered, maintained a continuous log of the trenches, and obtained disturbed samples of soils for laboratory examination and testing. Graphical represent-ations cf the soils encountered are presented in the Log of Trenches 1 - 4, FiBures 2 4. The soils have been classified according to the Unified Soil Classification System, explained in Figure 5. The trench logs show subsurface conditionA on the dote end at the locations indicated, ancl it is riot warranted that they are represe11talivc of sub-surface cox1ditions al: ott1er times or locations.

Laboratory Testing

In our laboratory, the soil samples confirm tl1eir field classification. includ<"<i:

were re-examined to The testing program

Fowler & Associates

f, 218-1 -4-

Terrace deposits lie on both sides of Sausal Creek consistinB of unconsolidated deposits of gravel, sand, silt and clay. Bedrock on the so11thwest side of the valley is the Butano Sandstone of Eocene age consisting of tan coarse grained sandstone and claystonc. Bedrock exposed to the northeast is the Santa Clara Formation of Pleistocene age and consisting of sandstone, claystonc and conglomerate.

The active San Andreas Fault cuts through Portola Valley where Dickinson (1973) mapped two relatively prominent, and one minor, subparollel lineaments which coincided in several locations with surface faulting known to have occurred in 1906 (J,awsan and others, 1908), as shown on the Town of Woodside Geologic and Geologic Ha~ards Map, Figure 7, Dickinson referred to Che central lineament as the Woodside fault trace and to the easternmost lineament as the Tr~rico~ fault trace. The westernmost minor trace was !J..QJ:--1\_"-IJ!§d.·--···-,,·-

In 1906, surface faulting extended southeastward into Portola Vallay along the }'/_o_;;i_.rJ.st}_?-_ J:.r .. ?-.C!"' at least to the area of the Portola Valley Town Hall south of Portola Road. In the area of Town Hall, surface rupture was transferred in a left-steppl.ng, en echelon mode to the Trances trace, along which rupturing continued southeastward to Alpine Road and beyond (Taylor, Cummings and Ridley, 1980).

The Woodside trace passes tl1rougl1 Che site in the area of Sausal Creek. The Trances trace passes through the site along the, northeastern border of the property, The minor, unnamed und inferred trace lies about half way between the Woodside trace und Portola Rood to the southwest. Pampeyan (1970) also mapped a concealed fault at the edge of the valley along Portola Road, as shown on the Palo Alto Quadrangle A-P Special Studies Map, Figure 8,

The unn~med trace mapped by Dickinson (1973) across the . ,. ',. •... parking are:J. south11est of the cab:ins was Dickinson's '.(yp~_ .. D which are "trace segments marked only by gouge shadows, vegetal linears, or forost scars that ..lllli.¥--·. ~c-~.te the position of an i,J:@f...!~.J~_YG truce rather than a.n active one 11

•

In our review of three sets of air photos, no lineaments sugges!:ive of surface faulting were observed. In addi~ion; a surface reconnaissance of the area did not reveal any topographic faatures suggestive of faulting.

The Woodside trace generally follows the course of Sausal Creek. Dickinson (1973) reported small scarplets along the northeasterly edge of the creek bottom near Wyndham Circle. Downstream in the Family Farm area, the combination of heavy

Fowler & Associates

218-1 -5-

tree cover and extensive landscaping and constructionrfilasB the course of tho Woodside trace in detail. No strong lineaments were observed in the air pl1otos because of heavy

Ctree coveij along Snusal Cre<,k. A reconnaissance of the stream course and banks did !!_9_)' ___ ..:r_e:y~e~aI~:~~-n:Y~= t-o-pographic features suggestive of faulting. The slopes are )tovereW with thick layers of forest litter and vines in more open areas. Several old, bowl-shaped landslide scars were noted along the creek, generally on the outside of meander curves.

The Trancos trace follows a shallow topographic depression along the southwest flunk of a rtd3e of Santa Clara Formation and Ilutano (?) Sandstone he<h·ock. The 01.il---"lain t!aces .. of. the San Andreas are separated by a ridge of bedrock in the"'i;l;,:,:·;J;~;~,-s·t;;~-n p'1rt of the Family Farm. The linear depression is pro!inent in the air photos reviewed f 6-r th Ls fl t 11 d y •

Subsurface Conditions

The trenches indicate the sites of proposed construction to be underlain by alluvial and colluvial doposits. No evidence of faull rupture or disruption of bedding by fau-rting'""was ob.served in the four trenches; The so-di.mentary structures·-·;;5·~crved in the trenches are characteristic of stream channel, flood plain deposits and alluvial fan deposits. (± c,~ "-"'··~ ,,..l..-z>)

Groundwater was encountered in Trench 2 at a depth of about 12 feet (approximately Elevation 380 feet) during our exploration. Tho clcv'1tion of groundwater was consistent throughout the length of the trench and there is no suggestion of a groundwater barrier, The areas without seepage were not deep enough to intersect the water table. The water t'1ble may not have had enough time to stabilize before the trench was backfilled, and groundwater depths could fluctuate at other times of the year.

Seismologic Conditions

The San Francsico Bay Area is recognized by geologists and seis1i1ologists as one of tl1e most sei~micall.y active regions in the United States. The significant earthquakes that oc~~1r in the Bay Area are associated with crustal movement generally along well-defined, active fault zones that include the Snn Andreas, Hayward and Calaveras Fault zones, The SDn AndrenH is located in the central portion of the Family Farm. Tho Hayward and Calaveras Fault zones are located approx.i.matcly 18 and 21, miles northeast of the site,

Fowler & Associates

---~----

218-1 ~6-

respectively. The Woodside trace of the Sen Andreas is located approximately in Snusal Creek. No evidence of fault rupturing wns observed in the test trenches. The likelihoo.d o_! __ !.l.urface ·-ruptul'e ·aff.<>ctini; __ t.h_<;> proposed improvements and tho require<! .. SO feet .setback is .. co_nsidered to be r·cinoteL ·

The moximum credible eorthquake which could affect the study area would be 8.3 Richter Magnitude on the San Andreas Fault (Greensfelder, 1974). In 1906, the area was subjected to earthquake intensities of X on the Rossi-Forel Ground Shaking Intensity Scale which is based on observed earth­quake damage. Intensity of groundshaking is controlled by a number of factors including mognitude of earthquake, distance from earthquake epicenter and fault, and rock and soil types and distribution. Dorcherdt, Gibbs and Lajoie (1975) have compared intensities for the 1906 earthquake with different geologic units and developed a map of predicted maximum earthquake intensity in the San Francisco Bay Region. According to their work, the atudy area would be subjected to very violer1t groundshaking intensiti~s.

Liquefaction is def incd as the transformation of a granular material from a solid state to a liquefied state as a conse­quence of increased pore-water pressure developed during shaking. Seismic ·groundshaking tends to compact granular sediments, which causes a transfer uf load from inter­granular contacts to the interstitial pore-water, thereby increasing the pore-water pressure~ Liquefaction is most likely to occur in beds of louse, water-saturated, well­sorted silt and sand within 100 feet of the ground surface (Lajoie and Delley, 1975). Altl1ough the groundwater is relatively shallow at this site, the shallow sediments were dense encl had clay binder. Because of these factors, liquefaction of the sands encountered at this site is unlikely. Smnll lenses of saturated sand were observed at the surface along the bottom of Sausal Creek. Theae sands would probably liquefy <luring an earthquake, but are probably of small areas which w~uld not affect the proposed improven1ent.~3.

Other types of ground failure such as latera·l spreading and seismically induced landslides are related to liquefation. Lateral spreading failures occur on gentle to nearly horizontal slopes underlain by saturated, loose granular layurs, and would flow towards o free surface such as an open channel. Flow landslides are failures that generally occur on moderate to steep slopes underlain by saturated, loose granular deposits. Once liquefaction has occurred, flow deformation continues until the driving shear forces

Fowler & Associates

218-1 -7-

are reduced by slope reduction to a value less than the viscous shear resistance of the liquefied soil. When this happens, the. soil stops flowing and solidifies. The potential for these types of failures at the site is similar to that for liquefation. Tl1e presence of old landslide scars a~sal Creek indicate that yiolen);_R!'._2_.!!.!J .. ds_haking especially when the slopes are saturated c~~;"tglj: __ -::n1~. landsliding such as was observed in 1906 along portions of the San Andreas fault in Snn Mateo County.

Studies by area found between the area, the horizontal subsidence occur, but unit.

Woodward-Clyde of the Portola Valley Town Hall some evidence of incremental ground warping

two traces of the San Andreas. In our study alluvial floodplain deposits are relatively

or gently sloping towards Sausal Creek. Tectonic or uplift between the two traces is not likely to if it did, the sice would probably react as a

CONCLUSIONS

Based on the field exploration program of trenching, surface reconnaissance, literoture and map review, air photo interp­retation and engineering geology analyses, i~ •. ~s our opinion that the proposed improvements m.<lY .• ~.'C .~~.:'~l.opc_d _as ,planned from a geological standpoint. ~_.Jl.'?J.!".!!Jo.!EJ ___ ~_or _J~-"°·9J,g_gic hai:;a_rds ___ af :E ec ting .. ,.the new ... _buJJ4i.i:igs _is ... ~o"., __ or . prac tic1:1lly n.o_n!"J!'!stent;. While the site is within an Aiq-uist-Priolo Special"SEudies Zone, the Woodside trace of the San Andreas appears to be located in or adjacent to Sausal Creek and there is lit-tle .. _likeJ.ihood. of. ;;urf"1ce faulting affect~ng tho P]'."~J??.s\'AJl\tildings. ..~·-----·------- -- ·• · - -· ·-·---···· - · -·------- -- ·

No evidence of faulting was observed in the area of the unnamed trace which roughly parallels the entrance road to the far~. This trace was crossed by two long trenches, and no evidence of faulting er shearing was observed. Q.l}_r i!';_;'.3.§1.:\..Ka_t.:i.Qn .-s.ugge;;;.t_s that this unnamed trace as mapped by Dickinson .is ei.thcr, not present &L so old t:hHt it has been buried by over 12 feet of Quaternary terrace and alluvial deposits. It is our opinion ~hat t Qi.~-!'.E:.i\.C,I,! .. ~ 2."' s.-"l'?.~,.<;;:x;_is t.

Fowler & Associates

218-1 -8-

LIMITATIONS

The above services consisted of professional opinions and conclusions made in accordance with generally accepted engineering geology principles and practices, Our conclusions have been based on data obtained from field explorations made at the locatio11s indicated on the Site Plan.

Report prepared by FOWLER & ASSOCIATES

V07-Z-ct Lei,£ 7 ow-.e:~_, ~~ -

Donald R, Fowler C.E.G. 1022

DRF/ma 10 copies submitted

Fowler & Associates

Exoansion of Storage Facilities

Scale 1" = 200'

--- ----~- --- ------ -- - --- _J

Open-Theater Stage and Seatinq

Camosites

A.rti st' s

New Camp Site Area

Master Plan by Martin-Carpenter Associates dated 1-22-87

Fowler & Associates Geo10g1ca~ .and Gi2(l:e"Cn.r11c.al Eng1ne-er1n9 J.4 ~ 30th S!n:!et San Francisco_ c.:.. 94~J1 41 5-285- i 3-~S

New Ca mo Site Area

- - . -:.

~"Un -_- -.___ . 1-,~ ~-

Recreation Center

MASTER PLAN

THE FAMILY FARM Woodside, California

PROJECT NO. DATE Figure 1

218-1 2-6-87

240 250 260 270 280 290

--------- --------- --- -- --------- ---------------- - ---- - ---- -- --- - - -- -=--u-:.. -_ -_-=-= =--= =-:_ = =-= -_-:..:. ----- --- -------------- --------------- ----- -------- --- 16 - - --...::... - - --

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sandy - . --------~---

- - --- - --... __ _ - - ....... _ -----

---- ----

---------

12

-!-...... _____ _ ----------------. .... - ------------ --- -- - - --- -------------------

8

Horizontal and Vertical Scales

1 Inch "' 5 feet

F owlet & Associates

300

0

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5

10

15

20

25

LOG OF TRENCH 1

THE FAMlLV FARM Woodside, California . . ' . - .

c • 'g -::r :I

-n • • -

.. _...., (;ec"'Og1C.a .and Geo1ec.nn-ca1 t: f'l'Qlinef'r:.ng «.:_30th Stiee~. San frar:u:,sci:: ... CA~ i 3-~ "4~-5-2.B-5'-~ ~~- ..

PROJECT NO

218-l 2-5-~7 Figure

-~. ---,;;,,.·.;- -- -~ -{~ ---·.._l

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2 ..

s In Feet

15 0 160 170 180 190 200 210 220 230

1G OF TRENCH 1

N36E

----- ------------ -------- -- - - ----11 -- ---- - - --------- - -- --- --- 1 --==--- - - - -- -

c:.------~-- ---, ------ -------- - --- -- ------ ------- - _:::__ -_ - -------:.:: _-_~ -""""2: 11- - - : __ .::-:_-_-_-_-_::

----------------· 12 ::..::. ;;:ti"

---- -- --~-----' ----------- --- - - - - -- - - - - - - _ 13 -orading claYey- -:_-:.. =-=--..,__ - -

~----..:..::.. ____ _ ______ - - _ _ _ _ _ _ _ abundant cha~cocl --------- -------------

--- _,,_ --- ----- -----1..... -------------~---6 root O -------- root - - - -- - - - - - - -.,i.i- -- -- --- --- - --- --- - - ----------- - - - - - - -1- - - -- - --------- -- - - - - ...;.... - - - --

- --- - -- i 7

IT DESCRIPTIONS

dark brown SILTY CLAY, with scattered l, wet, vary stiff, occass iona 1 .

gray and brown mottled SILTY CLAY, with ·ine sand, moist, very stiff

tan SANDY SILT, with occassional oist, medium dense to dense, charcoal ·

old stream channel, brown GRAVELLY ded pebbles, moist, dense

brown SILTY CLAYEY GRAVEL, with bbl es to 3", occassiona] thin lenses sand, moist, dense

tan SANDY CLAY, ·with occassional bbles, moist, stiff, scattered

13

14

15

16

Alluvium: old stream channel, yellow brown SANDY GRAVEL, rounded pebbles, moist, dense

Alluvium; dark brown SILTY CLAY, with sea ttered rounded pebb 1 es , moist, stiff to very stiff

A 11 uv i um: ye 11 ow brown SANDY GRAVEL, rounded pebbles, with charcoa 1 , moist, dense

Alluvium: old stream channel, brown SANDY GRAVEL, with pebb 1 es to 3", moist, dense

- - - - - - - - -- - - - - _[_ - - -I 8

·i

--.,·

0 o root -- - ------- - ---root o

•.

. Stations In Feet

a'o g'o •• 10 0 ' 110 • 120 130 140 15 0

LOG OF TRENC

-- N36E - - ---- - - - 1 -- ....:::'" -- -- - --- 1.:1 -- --4 --

--- ------- -- ----=--------- - - ________ 1____ 2 --------------------....... ---- -------- ------ 1 _::::,.,,.---------~-----------

~------ 9. '-- ....... ___________ ::_-- __ ----=-;:::__-_-_-_-_-_--- ------ 4 ---- -------------- - - - - - -- - ..... - - - - -- -- - --- - - - =-,::::-.-.:::::::: =.._-:... -- - - - - -- - ---- - - ----- - - - - --~ .:::.-:.. ::.._--- __ .:_,_ 11

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--------- -- - - ---------- - - --7 ... __ _ - ---- - - - ---- ------- --- --- - ------_a

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- - - -- -- -------- - .... ---- - ""if:- - - - - - --~" -----.£.!---- --<._-

---7 ------------------- -- -- ---------- -- ------- --------------------8

1 Soil-A horizon: dark brown SILTY CLAY, with trace of sand and sma 11 seat tered pe bb 1 es, rr~ist, medium stiff, crumbly texture, roots and organics, occass i ona 1 charcoa 1

2 . Soil-B horizon: brown SI l TY CLAY, with trace ·of sand, moist, medium stiff to stiff, hack1y texture, roots

3 Co11uvium: yellow brown SANDY SILT, wet, medium stiff, scattered charcoal

4

5

6

Colluvium: broW!l SANDY SILT, with occassional .rounded pebbles, moist, abundant charcoal

Col luvium: brown and yellm; brown SANDY GRAVEL, .with pebb 1 es to 3"; occa ss i ona 1 rounded cobb 1 es, m0ist,·scattered.charcoal

Alluvium: brown SANDY SILTY CLAY, with scattered : 'pebbl.es, mofst, stiff, scattered charcoa1

PRINCIPAL UNIT DESCRIP.

7 Alluvium: dark brown SILT fine gravel, wet, vary st charcoal

8 A 11 uvi um: gray and brown trace of fine sand, moist

. 9 Coll uvi um: tan SANDY SILT pebbles, moist, medium de

·scattered charcoal

10 Alluvium: old stream char SANO, rounded pebbles, me

11 Coll uvium: brown SIL TY CL rounded pebbles to 3", oc of clayey sand, moist, de

12 . Alluvium: tan SANDY CLAY, rounded pebbles, moist, s charcoal

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0

A

0

5

10

15

10 20 30 40 50

--- - - ----- --- - --~- - -- -- ----- -~------- ----- -- -- ----- -----. -- -- --

.... __ -- -- --6

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- -- -- ------...... - .... 9 -- -- - - ___ ..__. __

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60

-- --- ----- ------- ------- -- ...... _ --

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200 210 220 230 240 250 260

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10

1 i ne

--- ---- -- - ...... -- -- - ---- - ----- - -- ---- - ------ - --- ---- ------------ ---------- ,..- ---- - -- - - --------------- ------ --- ' \ -~'"!---. -- ------------ - - - -- --------- ---- ---- - -- -~ 4 . J --------5--------- I

- - - - - - - ~ -1tl.-:.. ~- - - - - - - - - - - - - - - - - - -1 6 1

-- ~

------- - ------- ----- --- ---------- --- ---- -- -- - -- ----

- --- - -- - - ...::1.0: - ---=--- -~= ------ ---------

- - -- ---------- - - -- --- ------- ------ -\ 15 \ - ----- 7 ----- -- - ----- ----------- - - ------------- ----

---- - g---- - B -------- -----------9

20

Horizontal and Vertical Scales

1 Inch = 5 feet

F ow I er & Associates Ge::;.109..::a· and Geol-e.:r-iruca; E ng.nee~1ng «..:: 30°!"1 5treE't- Sa.., Fran::::i::s:'.::o. CA g..!• 31 "'1S.-2B-s-tJ..::5

LOG OF TRENCH 2

THE FAM IL V. FARr. lioods i de. Ca 1 i forn i a

DATE

0 CD

"D -:T

::I

-n CD CD -

PROJECT NO figure. 3

218-1 2-5-87

" ' " 1 ·1 !

"j l

- j -·~

-~

-~

Stations In Feet

12 0 13 0 . 140 15 0 160 170 18 0 19 0 200

LOG OF TRENCH 2

asphalt road ditch c tia seruct 1 4. 5

11 pipe

- ~---------------------------\---:~~~~~=-=--~--=-=-===-====:-:-::-=-=-=~=-==-=-=3362~~~--~~-=------~ -==--=--=---=--=-==-:: =-= = --==~-=-= ~~--------::~=~~~4= =-==----- -- ------ -- -- --- --- ----.: =- --=-=--- - - --- - ----- - -- -- -------- --------- ---- - --- ------ ----

----- - --- ----- -- - - -- --------- - -- --- ----- ------ ----------------- -- - - - - -- - - - - ----.? --------- --------- ----- --- --- ---- -- --- -------. - -- - - ----- -- -.-- - --- ---- --- --- 6 - - ______ "";"- _____ _

-----------7 -----

----------------- - -- -- ---- -- - - --------- ---------

- - - - -- ---------------- -------------- -- - - - -- - - - -- - - - - -- - -- - --- - - - - - -6 ------ -- --- - --- - --- --- ------ ---------------...... ________________ -2_9 ------r----_:__=--===-=-=-=-=-==-=------- -------- - - - -----

PRINCIP~L_ UNIT DESCRIPTIONS

·own SILTY CLAY, with 1al pebbles, moist, :exture, roots and

-own SILTY CLAY, with 1ist, medium stiff to , roots

with gray streaks 1d occassional pebbles,

1 black SILTY CLAY, c , more aravel towards =ry stiff

~n m6tt1ed SILTY CLAY, moist, very stiff .

6 Alluvium: yellow brown with gray streaks SILTY CLAY, trace of sand and gravel, moist, very stiff

7 Alluvium: yellow brown CLAYEY GRAVEL, with sand, rounded pebb 1 es to 3", moist, very dense

8 Alluvium: gray brown SILTY CLAY, with trace of sand, wet, very stiff

9 Alluvium: gray and brown CLAYEY SAND, with gravel, wet, very dense

· 10 Alluvium; old stream channels, red brown SANDY CLAYEY GRAVEL, rounded pebbles, \ inch to l inch, moist, dense

. ''· -·~~. -.~'. -~- . ·-~ ... . .

seepage

. ,., . ·-- ' ~·· .-z ,~.--..:,..--: ..... --~~;

. ,- . ,.

40 50 60 70

N60E

------ -- - ----- ------ -------------------- ------- ------- ---- ------- - --- ---- - --- - --

---- - --- - - --- --- --- -------- ------ -- --9 ---

80 90 10 0

7 -- --- - ----------- -8

rading more sand and gravel 9

. -~·

110 1

? 0

- - ----0--------- - - - - o_ J!llli.s - - - - - -

---------- --

1 Soil-A horizon: dark brown fine sand and occassiona1 r medium stiff, crumbly textL organics·

2 Soil-B horizon: dark brown occassional pebbles, moist stiff, crumbly texture, ro(

3 Alluvium: yell ow brown wit SILTY CLAY with sand and o moist, stiff

4 Alluvium: dark brown to bl with. scattered pebbles, mo base of unit, moist, very _

5 Alluvium: gray and brown m with scattered pebbles; mo

-Cl Cl u.. c;

r. -a. Cl 0

0

B

0

s

10

:Is

10 20 30 40 so 60

- -- -- - - - - -- - - ------- - - - ------ ---- - --- - ---------- -- - --------- --- --------- ---- ------- --- ---------- -------------------- - - -- - ---- _-..::::..=- --- - - --------- - --- ------------- ----------- --- ----- ------- --- -- --- --- - ---- - - - ---- ------------ - - ----- - --------- - -- - - - - - - - - - --- -------- - - ----- - - - - - - - - -- - ----- ...... -- ----7 ------------ ------ --...... ___ _ ----- - - -------- --8 -- ---------- - ----- -- -- - -- - - -- - - ------ - ----scattered grave1 -- --- -------- -- - -- -- - .......

9 ----- -

~·

~-·

Stations In Feet

5 10 20 30 40 50 60 70 c· 75 0

LOG OF TRENCH 3 -- --- -- - ---- 3,..- -- 5 -- --..... ;-

/ D

/ 4 • "C _.,- -:r ==-~~~~,----::-~N~5~0E~=-=~=-=-=~?:=::~-:=::=:::-=::=:::~-~::::-:=-:_ -------- ------------- ---- __ 1 ___ ---- -- - -- - --- - ------- - - - -- - --- - -10 ::s

------ --~------ 2 --- __________ ....,,.. 3 ----:;...."::::::'---3

- ,,, ___ , ------- ...--- ---- ------------- ..,.,,.- ,,,,. ________ _ -- -'--------------=...=---------------- -5 _,,.,. ,/'" ------ ---- -- ------------- / - - ..,,....- -- -- -- ------- -.... ----------- -- --- - //

6

6 --- -- .....

--- 7 _..-.....::., ______ _

PRINCIPAL UNIT DESCRIPTIONS

1 Soil-A horizon: brown SAN[)Y CLAY, moist, medium stiff to loose, roots and organics, occassional pebbles

2 Soil-C horizon: reddish brown SILTY CLAY, with sand and pebbles, roots moist, medium

3

stiff ·

Colluvium: reddish brown GRAVELLY SANDY CLAY, angular rock fragments 1 to 3 inches, damp, stiff

5

6

7

Col luvium: brown CLAYEY GRAVEL, angular rock fragments, moist, very dense, scattered cnarcoal

Co11uvium: dark brown and brown mottled .SILTY CLAY with pebbles, moist, very stiff, seat tered cha rcoa 1 _

.. Co 11 uvi um: red orange SIL TY CLAY with trace of fine sand, damp, crumbly texture

"" ID ID -

15

20

Horlzontal and Vertical Scales

.1 Inch .. 5 feet

4 . , Bedrock: tan San ta Clara Fonna ti on CONGLOMERATE, weathered, damp, dense» no obvious bedding

8 Colluvium: light tan Ct,AYEY GRA~EL with sand, ~ist, very dens, ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

LOGS DF TRENCHES 3 & 4 >

PROJECl NC.

218-l

. . .- ·~

THE FAMILY FARM Woodside,.California

2-5-87 Flgu•e 4

-CD CD u.. c

.c -Q. CD 0

0 D

5

10

.15

1

2 ---

N51E o·

road

---- --- - ----7----- -~ .......... --~-::::..-:... - .,,.---- - -- - - - - ____ .,,,.. ... 2

--- - -- ---- --- -- - - - -------------- --- 3

3 ---------------------------------------- -4 ___ ...

4 sandy gravel lens --- .. ----- ---- .:s: _ _ .....,g - ..:!:. -- -- -~==--=--;z_·- - ---------

5 5

PRINCIPAL UNIT DESCRIPTIONS.

1

2

3

Fi 11 ; .gray green CLAYEY SAND, moist, medium dense, roots and organics

Soil: dark brown SILTY CLAY with sand, crumbly texture, wet, medium stiff

Alluvium: dark brown SILTY CLAY with scattered charcoal, wet, stiff

4 Alluvium: gray greenish brown SILTY CLAY with ·scattered pebbles, moist, very stiff

5

6

7

' All~vium: gray and brown mottled SILTY CLAY wit~ occassional pebbles, moist, very stiff

Alluvium: tan SANDY GRAVEL, rounded, ~ t;ii l inch, moist, dense

Alluvium: old stream channel, brown SANDY GRAVEL, moist, mediuw. dense

5 ,... -

0 - road Cl Cl

u.. - -- --c 10 -8 _--:__--:_.:

0 .c ---Cl - 5 'ti Q. -·-- Ill --5 ~ 0

-:I 15 "TI Cl

10 Cl -20

15

•

-,··-

(/) _, 0 (/)

Cl w z ~ l!l lU z u:

PRIMARY DIVISIONS

GRAVELS

MORE THAN HALF

OF COARSE FRACTION IS LARGER THAN NO. 4 SIEVE

SANDS

MORE THAN HALF OF COARSE

FRACTION IS SMALLER THAN

NO 4 SIEVE

CLEAN GRAVELS

(LfSS THAN 5% FINESJ

GRAVEL WITH FINES

SILTS AND CLAYS

LIQUID LIMIT 15

LESS THAN 50%

SILTS AND CLAYS

GAOi.iP SYMBOL , .... GW ~.:;;•

GM

ML

CL~ 'I j I 1 1 It

01,, 0 L •I

CH

SECONDARY DIVISIONS We!_! gt<tded gravel~. Qretvel s:and mixtures. little or no

fines.

Pootty gfaded grave\$ Or gravel-sand rnil(fLires ti1tlP. or no fines.

Silty gravels, grave!-sana--s.ilt miJ;:tures. non-plas1ic fir"'les

Well gfaaed s.ands. gravelly sand~. linle or no fines

·---·-Poorly gr;ided sands or gravelly sand::;. litl!c or 1'"10 lin1:"~

Clayey s.ands. setnd-clay mi)(tures, p!as:rc fin!!'S

lnorg;:inic Silt:!> 21nd veiry fine sands. rocli:. flour. silly, 01 clayey fine sands or clayl!y silts with sligh~ plasi1cr!y

lnorg;;in1i; !;'.lays o1 low to medium plasticity. gravelly i:;lays, sandy clays. silty ct;;iys. Jean clays

Organic silts and org;;inic silty clays of low plasticity

\norqanic silts, mic~ceo.us Of diatol"n<iCeat)S. fin~ sandy or tilty soils, elastic Silts.

Inorganic clays of l'iigh pla.s~icity. fat clays UQUIO \_!MIT IS

GREATE~ Tf{AN 50% OH

%... Organic clays of rnedium to l'ligh plas1icity, organic silt5 , L-~~~~~~~~~~~~~~~~~~~~~--l

HIGHLY ORGANIC SOILS pt Peat and other highly organic soils

DEFINITION OF TEAMS

IJ.S. STANDARD SERIES SIEVE CLEAR SQUARE SIEVE OPENINGS 200 40 10 3/411 3"

SAND GRAVEL SILTS AND CLAYS 1-----------~ ,----+----.-------! COBBLES BOULDERS

FINE I MEDIUM COARSE FINE I COARS<

C1;m.:.;ol - Con5olidation

LL - l.iquid Limit {In~)

PL - Pl;istii; Limit (!r'I tl!i)

Gs - Sp~c:ihc Gr2.vily

SA - Slr,veAnal\'Si:!!.

• "1Jnd1::.h11bed" $.,.mp\e

'1 BulK Ss.1nplr.

Fowler & Associates Geological ,;:ind Geotechn1ca1 Eng1f'1eenng 444 :30!h S1reet, Si'!r. Franr.isco. CA 94 1 31 J.15-285-13A5

GRAIN SIZES

T>

TxCU

OS

FVS

UC

LVS

320 (2800) Uncol'IS.Olidilf~d Undrained Tri;ixiel

320 /2800) Consolida.led Undrained Trlaxlel

2·r50 (2000! Conso!ida.led Dr;;iinad 01ract Sheer

<70 fli!\d V:!ln~ $h11:~r

2000 Ur'ICOl'llin~d Compresslorl

700 Ui.bCJr;itory Vane Sheer

KEY TO EXPLORATORY BORING LOGS AND TEST DATA

THE FAMILY FARM Woodside, California

PROJECT NO. DATE

218-1 2-7-87 Figure 5

TABLE 1

LAB TEST RESULTS

Trench Sample

1 1 2 3 4 5 6 7 8 9

11 12

2 1 2 3 4 5 6 7 8 9

3 1 2 3 4 5 6

4 1 2 3 4 5 7

Fowler & Associates Geological ~nd Geo1echnical Engineering 444 30th 51ree1, Sari ~rantis!'.:O, CA !:M 131 4, 5-285-i :345

Moisture Content

26 25 32 21 20 26 29 25 20 23 24

24 25 26 26 25 25 26 30 28

19 21

9 10 21 21

20 36 29 20 22 19

% Passing #200 Sieve

76 74 72 82 33 75 80 81 73 26 64

78 80 78 83 86 87 41 88 43

62 63 so 60 63 85

41 73 83 95 97 39

LAB TEST RESULTS

THE FAMILY FARM Woodside, California

PROJECT NO, DATE

218-1 2-7-87 Figure 6

I I

.!

111 = 600 1

. .,,o ' .~· ' i,.~

Town of Woodside, Geologic and Geologic Hazards Map

-=-~ _ Fowler & Associates ; ; Geological and Geotechnical Engineering ~ 444 30th Street. San Francisco. CA 94131 ~ 415-285-1345

GEOLOGIC AND GEOLOGIC HAZARDS MAP

THE FAMILY FARM Woodside, California

PROJECT NO. DATE

218-1 2-6-87 Figure 7

'.j

j \

•

Fowler & Associates Geoiogical ;and Geolt>l'.;hnica1 Engineering 444 ~011"'1 S!teet, San Franci$cO, CA 94131 415-2S5-131$5

PALO ALTO QUADRANGLE A-P SPECIAL STUDIES MAP

THE FAMILY FARM Woodside, California

PROJECT NO, OATE

218-1 2-6-87 Figure 8