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ITEM 3.1 TOWN OF LOS ALTOS HILLS May 7, 2015 Staff Report to the Planning Commission SUBJECT: CERTIFICATE OF CORRECTION TO TRACT MAP 8331 FOR A HUMAN HABITATION SETBACK; FILE#36-15-MISC FROM: Suzanne Avila,AICP, Planning Director SPft RECOMMENDATION That the Planning Commission: Forward a recommendation to the City Council to approve the Certificate of Correction to Tract Map 8331,modifying a Human Habitation Setback on Lot 1. BACKGROUND The subject property was created as part of a 28 lot subdivision recorded in 1990. Based on available geologic information at that time, Human Habituation setbacks (HHS)were established for some of the lots,including lot 1 which is owned by the applicant. The setbacks wereestablished due to the presence of fault traces of the Berrocal Fault system. Lot 1 has two HHS lines that bisect the property (see Attachment 2). The existing residence on the property was constructed outside, the HHS zone. The applicant would like.to add a second unit on the property and conducted a geologic investigation to more accurately locate the fault trace. Based on the fault investigation, it was determined that the southern HHS could be shifted further north-as shown on Attachments,3 and ,6. Following approval and recordation of the Certificate of Correction (Attachment 3) the applicant may file an application for a second unit. Attachment 6 is a conceptual site plan that shows the proposed location of the second unit along with the location of the exploratory trench and fault scarp. DISCUSSION The geologic investigation and revision to the HHS was reviewed by the Town's Geotechnical Consultant, Cotton Shires and Associates (CSA). As part of the fault investigation, a fault exploration trench was excavated through the site in December 2014. CSA observed the trenching and reviewed the Engineering Geologic Investigation prepared by Certified Engineering Geologist Steven Connelly .(Attachment:4). "CSA concurred with the project geologist's findings and conclusion that there should be a 35 foot setback from the scarp associated withthe fault trace(see Attachment 5). This allows the HHS to be shifted as shown on Attachment 2. Since only the southern HHS was evaluated,no change is proposed to the northern HHS. Section 9-1.1210 of the Municipal Code includes findings for approval of an amendment to a Final (recorded)Map. The Planning Commission should review the findings in Attachment 1 and make a recommendation to the City Council. Staff Report to the Planning Commission Certificate of Correction to Tract 8331 May 7,2015 Page 2 of 3 Committee Review None ENVIRONMENTAL CLEARANCE (CEQA) The proposed Tract Map correction is categorically exempt from the provisions of the California Environmental Quality Act pursuant to Section 15303(a) which allows construction of a second dwelling unit in a residential zone and 15303(f) which allows trenching and backfilling when the surface is restored. ATTACHMENTS 1. Required findings(one page) 2. Except from Tract Map 8331 (one page) 3. Certificate of Correction(two pages) 4. Engineering Geologic Investigation(30 pages) 5. Report from Cotton, Shires &Associates (two pages) 6. Proposed site plan(one sheet) Staff Report to the Planning Commission ATTACHMENT 1 Certificate of Correction to Tract 8331 May.7,2015 Page 3 of 3 ATTACHMENT 1 FINDINGS FOR APPROVAL OF A CERTIFICATE OF CORRECTION TO TRACT MAP 8331,LOT 1. There are changes in circumstances which make the southern Human Habitation Setback (HHS) line shown on lot 1 of Tract 8331 no longer appropriate. An Engineering Geologic Investigation was completed by a Certified Engineering Geologist, Steven F. Connelly, and was reviewed by the Town's Geotechnical Consultant, Cotton, Shires and Associates. CSA concurred with the project geologist's findings. The revised HHS will be in compliance with the recommended 35-foot building setback from the scarp associated with the fault trace. 2. The modifications do not impose any additional burden on the present fee owner of the property. There is no effect on the lot size, location or extent of streets, or the maximum floor and development area for the property. Any future development will be required to comply with applicable Town codes and policies inclusive of MDA and MFA,and required setbacks and height. 3. The modifications do not alter any right, title, or interest in the real property reflected on the recorded map. While the correction will allow development to occur on an area of the property where it would previously not have been permitted, the restriction was based on geologic information available at the time the map was recorded in 1990. New information has been provided demonstrating that it is appropriate to revise the Human Habitation setback. 4. The map, as modified, conforms to the provisions of State Subdivision Map Act Section 66474. None of the findings for denial of a tentative map specified in this government _ code section can be made. TA4. _ SEE SHEET 4 td }' /I T • / SEE SHEET 1 BASIS OF BEARINGS - *--.-7 _ • mry / A-1n4ar Ta` . NE BEARING OF N. 22'06' E. FOR NE NORTHWESTERLY s • I {R-3260U A-'155731• " 1 FRAM HARrtA110H BOUNDARY OF LOT 45 AS SHOWN ON NE MAP OF NE (L-8134' R-3o6ae $2 `-- 3EIBAC(laaoax}•SUBDMSION OF THE HALE RANCH. RECORDED IN BOOK L : L -�� 1' _ `. (D`iOiszpis r01HD CM OF NAPS AT PACES 48 AND 49. SANTA CLARA COUNTY ,0.nut Arm acpc eAV.1 , :•$_\ 3.u a 14) • — RECORDS WAS TAKEN AS THE BASS OF BEARING FOR . I ,_,R,srm) k _ THIS NAP. R_73100 r 11 7 -- 11.1110IRARRA1f01 I.-SLOB' 1 - Cil 1 91TLr(DUD12a14) -- ---- � _ I $ _ r43•10,--------- N NOLL C1 __ I R ssov� i=,6:: 1 v I `_X01 �•1 �_• `Ila,. CPC/..r. N L-32.43' _� /31?ft, yr --- —1 -....M...._° I___ ---- _ w CP : I A-317Y24j- ��r a•ao�ogr .room 3N•v.7ALOm RO ..1.; \ R-txioC 1 i/ A.30tn71. /` �� _ i.! ~KrulcED 1mlr �iulaA+m AD u 00* LLL \ \ a -as(Cr1.16 ACRES/ . �=0� / �-12>Rd ! 1SLO cru 1.T ////���.- W•I Q' mos IIONlRlr1?T ,� I. 11°--14- �4 \ iR-740d / O / R• 4 1'2 / / �� s 74 c ....14z 1 L-DAV/ / • S - S J�' 1—((A_-071401. I C] .4-4,4 /f- Q. l• S R 33600' , + u c:�p��\`/ o• o �/ 23 ?^ 24 25 0�;_ ``L-313er I 420 i gag 1 " (� �/ , j, / / 1.25 ACRES 1.11 ACRES S9 1.10 ACRES =, =- I \ • RC d d �f " 13 A_.,y31•N. 41 a �_1d rut AHO • I R_maw $• / SLOPE[A>0M raRlol a STANDARD STREET t-w1. d • CIowa olls 1.0 Hutt. A_onR3s' if j � a 3o rlal[xi[aeTss• room 3p•RCN • t peO6•a-r-I�2a NOT R_yax , a u"CM wanrt. QAC FOAM Yr STAHOARO € R I •e un 6rt.n3 aResol AND IIOA IENT5 FT 1�. _4zx • •I.nn o�m sAwl s RttcY• oo x1. / R-MDT S I I R-tnn0c R4 rdo0INC L-1S31r 's `_ 2 MRc31r4t c ILI \ • 1 :\.k I �s d ,••`; 1.rn..'aam '•SIC • LY. / 10'PALL A� '+d NOT A PART TJ080THP 6866DIVISION ,� `T �� CORK � �g�r WI" c / SLI'[47dO1T--1 \� w • �f YTr. !V _ ...t. i c2 'fill'::"'mvri4• KV :- i ` Z \ x 1."+,=e.,._ ` C-3 210diu�2'34•-'-sard.- L.).. A.It rut AW D .s z. 27 a�TOod"-ie1aSO• tO.2e itGl / 1.23 ACRES •\ + • ti td PAUL \•^ \ 1'4 /_ 1 RK�.7.e 214.11• ; , ,0 • •3,/ TRACT N0. 8331 / :c"�1E�1 BEING A RE-SUBDIVISION OF LOTS 1 THROUGH 15. VIA MARIA / LEGEND 5�� 5 1�4•`F�:1 AND MARIA LANE AS PER THE MAP OF TRACT NO. 8200. I ofata t101ROARr BOOK 604 OF NAPS. PAGES 19 THROUGH 24. SANTA CLARA COUNTY ��r - SWEET R/1.LOT UNE 7 4 (.-,---1 RECORDS H \\11,:i!!"; 21 RAP�,R.Rn MI TOWN OF LOS ALTOS HELLS _ SANTA CLARA COUNTY. CALIFORNIA ,'q /I • 3 i I OW Rrt rnn(TO a gr R1.WON) SCALE 1' 50' SEPT.. 1990 ‘11i4 wino RTAA•ARO seer 1A9RL012 . b,' / - ® M s:R RY D-"1) BAY AREA CONSULTANTS x I ,w-• • rmo 3/4•MON r*e SASSED 11-C.E.»tn OR As--- 940 SARATOCA AVENUE. SURE 240 SAN JOSE GLL6CRNIA \\\\\\\\\\\\\\\\4 1021-Ae��'w • vK ENGINEERS- LAND SURVEYORS - ET 3 OF PLANNERS . • P.O.E. roue MDT EASISIENT • • •f2; .4 44er IMPORTANT: THIS PLAT IS NOT A SURVEY. IT IS y • MERELY FURNISHED AS A CONVENIENCE TO IN 1' LOCATE THE LAND IN RELATION TO ADJOINING • STREETS AND OTHER LANDS AND NOT TO GUARANTEE ANY DIMENSIONS. DISTANCES. ORA.f`, • BEARINGS, 1 ^t_A1:jF.. ATTACHMENT 3 Recording requested by: When recorded, return to: Space above this for recorders use CERTIFICATE OF CORRECTION NOTICE IS HEREBY GIVEN that the certain map filed for record on October 24,1990 in Volume 620 of Maps.at Pages.26--39 in the office of the County Recorder of the County of Santa Clara, California is Hereby corrected in accordance with the provisions of Section 66469 of the Subdivision Map Act as follows: Southerly limits of the Human Habitation Setback line is moved in the northerly direction. These corrections are shown on Exhibit A attached hereto and by this reference incorporated herein. The.feeowners,at the time of original recordation, of property affected by this certificate are as follows: Macar Land Company Inc., a California Corporation CERTIFICATE OF SURVEYOR THIS IS TO CERTIFY that the above Certificate of Correction was prepared by or under the direction and control of the undersigned. �‘..1,ND SVR. :(.0 ;SA8V4 . !. : . , : ! By Z'140:4953 :. ,_ . .-��.., : _ . . _ . � arty Ba ka ..,. . * L.S.495 . En).12-314015 Expires 12/31/2015 CERTIFICATE.OF THE CITY ENGINEER I-HEREBY CERTIFY that the above Certificate of Correction.has been examined this ifiN1111111111111111111iiilday of 'iil(licl ry iEF;2015 for conformance with the requirements of Section 66469 and 66470 of the Subdivision Map Act. By: Richard Chiu, City Engineer RCE 55414 Expires 12/31/2016 EXHIBIT "A" 016. CERTIFICATE OF CORRECTION Q S13'?4'56' "m• "m• ••••• S84'S4'S2"� 4.53 •� 225.20' _ '- •-� „ ` 7311-- 1"=40' tiwti t� LOT 1, TRACT NO. 8331 o cn BOOK 620 MAPS PG\0, b 4. .26-39 Ei 1 sar2f?"E� --r L- S89'00'08"E r .• f 129.10 84.85' z -----1 0. r----- 0 \ :dr ORIGINAL HUMAN HABITATION ac I SETBACK LIN SCARP LINE It (PER CONNELLY JAN,20i5) 1 ca ff v o ' cn .S: •••-•. --. ...12j, ISETB�KtiD_ 0 Hg81 N8*04'29"E tr o I I PROP S$3 2i 54.,E i ."82T`TJO UNE --- 4 co 0 S '22'22"E yOvSEG N86.34'1 �� N84'04'29"E 121.81'j _� N- 77.87 1 I Il N 18.59' �� I 't ct N720 vp ) 16-30,3..w NN , ,_____.,,,, ze,\AND So 74'‘' 4 BAB/ '1.1<•\ siN \ 2 53 9 �\ R�v'30�c '♦ �,`-.,/ No.4953 00 o * Exp.12-312015 * v. (Nr Po F F 1`SO . 3 IN 11 0 00 L=35�0� LEGEND RAZ BOUNDARY — — (E)HABITATION STBK (N)HABITATION STBK • BLDG SETBACK — — A PLAT TO ACCOMPANY A DESCRIPTION WESTFALL ENGINEERS, INC. SARATOGA, CALIFORNIA ATTACHMENT 4 RECEIVED F13 32Q15 TOWN OF LOS ALTOS HILLS ENGINEERING GEOLOGIC INVESTIGATION APN 336-25-019 24000 OAK KNOLL CIRCLE LOS ALTOS HILLS, CALIFORNIA Prepared for Mr. and Mrs.Ferdinand and Anne Fung ., 24000 tOak Knoll Circle . Los Aitos'ILills,California .I. $ ! • • •• . , • .° •• January 2015 • STEVEN F CONNELLY, C.E.G. • logy VCV. .. • t . • • j :. j I STEVEN F. CONNELLY, C.E.G. � . January 14, 2015 Project#1501 Mr. and Mrs. Ferdinand and Anne Fung 24000 Oak Knoll Circle Los Altos Hills, CA 94022 Subject: ENGINEERING GEOLOGIC INVESTIGATION APN 336-25-019 24000 Oak Knoll Circle Los Altos Hills, California Dear Mr. and Mrs. Fung, At your request, I have prepared this Engineering Geologic Investigation for the proposed guest house to be constructed on your property, APN 336-25-019, located at 24000 Oak Knoll Circle in Los Altos Hills, California. The property is located within a Town Geologic Hazard Zone for the Berrocal fault. I understand that you intend to construct a guest house on the southwest corner of the property. The accompanying report presents my findings regarding the geologic conditions and potential fault and landslide hazardsinfluencing the proposed development. I am pleased to have been of service to you on this project. Please contact me if you have any questions regarding this report. Very truly yours, C4111171711.1--7-41144r Steven F. Connelly_ Certified Engineering Geologist 1607 Copies: 7-Addressee 1 -Redwood Geotechnical, Inc. 1169 Avenida Benito, San Jose, CA 95131 www.stevenfconnelly,cotn Phone (408) 392-9999 Cell (408) 398-9339 ENGINEERING GEOLOGIC.INVESTIGATION APN 336-25-0.19 24000 OAK KNOLL CIRCLE LOS ALTOS HILLS, CALIFORNIA This report presents the results of an Engineering Geologic Investigation for the property, APN 336-25-019, located at 24000 Oak Knoll Circle in Los Altos Hills, California (see Figure 1, Site Location Map). A proposed guest house is planned at the southwest corner of the property, as shown on Figure 7, Site Geologic Map. The Berrocal fault has been mapped through the property, as shown on Figure 4, Town Geologic Map. The;property is situated within a Town Fault Rupture Hazard Zone:for the Berrocal fault, as shown on Figure 5, Town Seismic Hazard Zone Map. The Town of Los Altos Hills consequently requires a geologic investigation to assess geologic conditions and potential fault hazards to the proposed new living space. The purpose of thisEngineering Geologic Investigation is to identify existing geologic conditions and potential geologic or seismic hazards on the subject site, and to provide appropriate recommendations for the proposed new construction. The scope of this investigation included review of geologic maps and literature, review of historical air photos, review of previous reports in the site vicinity, site reconnaissance and mapping, excavation and logging of a.fault exploration trench, consultation with Mr. Ted Sayre of Cotton Shires and Associates, Inc., the Town's Reviewing Geologist, consultation with Mr. Joe Rafferty of Redwood Geotechnical, Inc., consultation with your design professionals, drafting, and report preparation. This report has been prepared for the exclusive use of Mr. and Mrs. Ferdinand and Anne Fung, new property owners, and project architects and engineers for proposed new construction. This investigation has been conducted in accordance with generally accepted engineering geology principles and practices. No other warranty, either expressed or implied,is made. In the event that any changes'in the nature or location of the improvements are planned, the conclusions_and recommendations of this report shall not be considered valid unless such changes are reviewed, and the conclusions and recommendations of this report are. modified or verified in writing by Certified Engineering Geologist 1607. STEVEN F. CONNELLY, C.E.G Page 1 APN 336-25-019 January 14, 2015 24000 Oak Knoll Circle Project#1501 Los Altos Hills, California •./4,... • 4,1:.•••••..7........2 7......7111111-•-•:........ — a �S _ `' 1'— - ,� rte- - �- • .a y •'r-._. 4- ," (I,-, . 1., • 41. ' ''r. \r ' ��f , . '�\�v• 6.-_,.. .,..:„..,•.L: �t ‘T:,. , ..may "? !A`3,, 1!.i .y • v «r-4ti'j- + . fi . �••.. 1. r ; r - '..j4. e �,. Y .-'•:::1-, • ,1- a L1 ' \_1 11 y^. .,.. , • illi, 4., _ ......,., , ,,,,,,_ „.,,,. .i.,,., 0„,N.. t,,, 1 ...—,--..Of- '---. s.''. .;. '. *.4ki.."31''' ' f4—pj• ''•' '7 :- vit,......j.•.. - ii;7. . 'T'-. i.(.. :..%- t.. • See s~ T.. ` . .;4)• - ? 12Pr n ': 1k -. i 4•. T1; Wit% . • 11,f 64:::,,,t.:::i .."." -; ; , f .le-eara . � • Photo 1: Aerial photograph from 2007 showing the subject property. Site Conditions The subject property is located along the northeast flank of the northwest-trending Santa Cruz Mountains, as shown on Figure 1. The irregularly-shaped parcel is situated along the crest and northern flank of a broad hilltop area within Los Altos Hills, as shown on Figure 2, Regional Topographic Map. The property is bordered on three sides by Oak Knoll Circle and Stonebrook Drive (see Photo 1 above). A neighboring single family home is located downslope and to the north. An existing home site is situated on the southeast corner of the property, as shown on Figure 7, Site Geologic Map. The property is vegetated by a lawn area, landscaping, and miscellaneous trees and mature oaks. The existing home and the area for the proposed guest house are located on relatively level terrain. The property slopes gently to moderately towards the north, as shown on Figure 10, Geologic Cross-Section A-A'. STEVEN F CONVNELLY,, C.E.G Page 2 APN 336-25-019 January 14, 2015 24000 Oak Knoll Circle Project #1501 Los Altos Hills, California Geology Regional geologic mapping by Brabb, Graymer, and Jones (1998) indicates that the subject property is located within an area of complexly faulted rocks. The Berrocal fault is mapped through the property, as shown on Figure 3, Regional Geologic Map. The Berrocal fault is a south-dipping thrust fault within the Range Front Fault System, generally separating older Franciscan rocks to the south from younger Monterey Formation rocks to the north. Geologic mapping by Cotton, Shires & Associates, Inc. (2004) mapped an east-west trending trace of the Berrocal fault through the subject site, as depicted on Figure 4, Town Geologic Map. The mapping is, in part, based upon previous studies by Hay (1988) that were performed for the Stonebrook Hills Development. Hay identified a south-dipping thrust fault contact contained entirely within the Monterey Formation across the subject site. Franciscan greenstone is mapped by Cotton, Shires & Associates, Inc. (2004) just to the southwest of the property. A landslide deposit is mapped about 500 feet to the northwest of the property. The California Geological Survey (2005) identifies landslide deposits and steep hillside terrain in the site vicinity as ground susceptible to potential earthquake-induced landsliding, as shown on Figure 6, State Seismic Hazard Zone Map. A potential earthquake-induced landslide hazard zone is located on the steeper northern portion of the property. The southern upper portion of the property and the proposed building site, however, are located outside of the State Seismic Hazard Zone. Seismicity The greater San Francisco Bay Area is recognized by Geologists and Seismologists as one of the most active seismic regions in the United States. Several major fault zones pass through the Bay Area in a northwest direction (see Figure 1) which have produced approximately 12 earthquakes per century strong enough to cause structural damage. The faults causing such earthquakes are part of the San Andreas Fault System, a major rift in the earth's crust that extends for at least 700 miles along western California. The San Andreas Fault System includes the San Andreas, Hayward, Calaveras, Greenville, and San Gregorio Fault Zones. According to Blake (2000), the San Andreas fault is located 3.5 miles to the southwest (see Figure 1). The Hayward and Calaveras faults are located about 16 miles and 18 miles northeast of the site, respectively. The Greenville fault is located about 33 miles to the STEVEN F CONNELLY, C.E.G Page 3 APN 336-25-019 January 14, 2015 24000 Oak Knoll Circle Project #1501 Los Altos Hills, California northeast. The San Gregorio fault is situated about 35 miles to the west. These faults are considered to be active (Hart and Bryant, 1997), having had surface displacement within the Holocene (last 10,000 years). Regional geologic mapping by Brabb, Graymer, and Jones (1998) maps a trace of the Berrocal fault through the subject property (see Figure 3). According to Brabb, Graymer, and Jones, the Berrocal fault separates rocks of the Jurassic to Cretaceous age (66 to 208 million years old) Franciscan Complex to the southwest from middle Miocene age (11 to 16 million years old) Monterey Formation to the northeast. Brabb, Graymer, and Jones (1998) map the Altamont and Monta Vista faults about 800 feet and 2000 feet to the northeast of the property, respectively. Local geologic mapping for the Town of Los Altos Hills (see Figure 4) by Cotton, Shires & Associates, Inc. (2005) show the Berrocal fault through the middle of the site. The State of California does not include the Berrocal fault within a State Earthquake Fault Zone. The Town of Los Altos Hills, however, considers the Berrocal fault to be potentially active. Hitchcock and others (1994) and Terratech, Inc. (1990) indicate that deformation occurred along the Berrocal Fault Zone during the 1989 Loma Prieta Earthquake. The deformation was considered to be secondary or induced by movement along the San Andreas fault which is likely connected to the Berrocal fault at depth. Hitchcock and others (1994) indicate that a M6.5 earthquake in 1865 may have occurred along the Berrocal fault. Kovach and Beroza (1993) indicate that a M7.1 earthquake could potentially be generated by rupture along the entire length of the Berrocal Fault Zone. Recent investigations by Steven F. Connelly, C.E.G. (2004) indicate that Holocene movement has occurred along the Berrocal fault and that it should be considered active. Air Photo Review As part of the air photo review, several Google Earth air photo images from 1948 to present were observed. The following stereographic pairs of black & white aerial photographs were also examined to observe site conditions and to aid in identifying potential geologic hazards: Date Photo Identification Type Scale 7-2-56 CIV-9R-63 & 64 B&W 1:20,000 5-12-65 SCL-4-145 & 146 B&W 1:12,000 4-12-85 WAC-85CA-13-89 &90 B&W 1:31,680 STEVEN F. CONNELLY,, C.E.G Page 4 APN 336-25-019 January 14, 2015 24000 Oak Knoll Circle Project #1501 Los Altos Hills, California The subject property is clearly visible in each set of air photos on gently-inclined hilltop terrain within Los Altos Hills The property was grass-covered grazing land with scattered oak trees, as shown on Photo 2 below. Stonebrook Drive and Oak Knoll Circle had been constructed by 1948. The existing residence was constructed on the southeast corner of the property sometime between 1993 and 2002. Evidence of landslide activity is not apparent on or projecting towards the subject property in the photos examined. A subtle break-in-slope is evident in the air photos, crossing the central portion of the property from east to west. The break-in-slope could be evidence of fault activity. The existing home site and the proposed building site, however, are located on relatively level terrain upslope of the break-in-slope. The existing home site and the proposed building site are located along a resistant broad ridge line removed from the path of potential debris flow landslides. Evidence of debris flow landsliding or source terrains for debris flows were not observed on or upslope of the property. • F ` 'X`�l,' :t. • - + 4 A A • ( { N I ,--- qi %. . • ,Iti , ► , . t 4 �, •,, . 51 . • ; 4: y ,3� vr :.; e Alt It ' is,.y j —t: • 40 40 a A r) . t et, . • . I 49 •, . -':- 41 • .. „, ,. !, ,,,. , : - ., , .,,,, , • T .:6,1". `•e / P _ , ... j+p" ~ s - 'i{+y `}__— .L --.44t 44 ms . �:. ' I Photo 2: Aerial photograph from 1965 showing the subject property. STEVEN E CONNELL 1•; C.E.G Page 5 APN 336-25-019 January 14, 2015 24000 Oak Knoll Circle Project #1501 Los Altos Hills, California FIELD INVESTIGATION Site Reconnaissance Several site reconnaissances of the subject property were completed during the course of the field investigation in December of 2014. The property is vegetated by grass, landscaping, and a few mature oak trees. The property is located along the crest of a broad resistant ridge line. An apparently natural east-west-trending break-in-slope is located across the central portion of the property, as shown on Photo 3 below and as depicted on Figure 10, Geologic Cross-Section A-A'. Evidence of recent faulting in the form of ground cracks, scarps, or fissures, however, was not observed on or projecting towards the proposed guest house. •• 1 •- . : k• .� -{ �,�. Photo 3: y FJ . i • View towards the southeast, V, F .,,..;.:.-.-•;.- ,•,.,,-7.Z.,.. y r. �4'' <i . - ;Tf . showing the •existing home site -y `- ,,,.. " -,-../..;:--:-'T "" and a break-in-slope to the .�,,. , • S -� u .•� right of the ladder. T .,C rt • s ,. Ic ~ ."• tYj. +r t _ ,. • ' fim,; . . •_V. .1 !:,i"." '=: ,-- Subsurface Investigation As part of this investigation, a fault exploration trench, about 127 feet in total length (see Photo 4 below) was excavated across the property and the proposed building site, in the approximate location shown on Figure 7, Site Geologic Map. A side wall of the trench was thoroughly cleaned, carefully examined for evidence of faulting or landsliding and logged, as shown on Figures 8 and 9, Log of Trench 1. Please refer to the trench log for detailed descriptions of soil and rock units. STEVEN F CONNELL 1'; C.E.G Page 6 APN 336-25-019 January 14, 2015 24000 Oak Knoll Circle Project #1501 Los Altos Hills, California A layer of fill (Unit 1), one to two feet in thickness, was observed at the top of the southern end of Trench 1. The fill is underlain by two to three feet of residual soil (Unit 2) composed of dark brown, firm to stiff, silty clay. The residual soil is underlain by weathered bedrock of the Franciscan Complex (Unit 3) composed of light olive brown, sheared serpentinite, inter-layered with very pale brown, carbonate. An irregular contact was observed along the base of the serpentinite with underlying Franciscan Limestone (Unit 4). The pale brown limestone is very hard, indurated, and well-cemented with blocky fracturing (see Photo 4 below). Redwood Geotechnical, Inc. drilled a 20.5-foot-deep test boring, as approximately depicted on Figure 7, Site Geologic Map. According to Mr. Joe Rafferty of Redwood Geotechnical, Inc., the boring penetrated the very hard limestone at a depth of 13 feet and encountered serpentinite to the bottom of the boring at 20.5 feet, as approximately depicted on Figure 8, Log of Trench 1. ,,y ate. . , +•.. ..* - '' .•4 ' -4 , i`, ". :. , .. y�;� ,til: �tiJ}`'j1� . '� .. �: �.� ��' � •� rid:`*�� ..�' .'. `J .. ; `.1, .• ,+fix . '- St x '',11 �! 'v,. < _ r.M4' t'• f..44 '� r �l/Y f .Zt _ht'•— . i ;, '''fir,• .! +... . • viz • •' � a1w}� ---' -ty �z ,1W.-� yam. "1,— 4t y rs v♦ .4•:.,y.- w •` ;.�' rt-Y_+ - _'ti , a� • // .:; x T � : •fir` _ �"�� '' 1'+ flit: 4.:---‘ ♦.. _ .——' • ' f:l• . ....cr,„. rote Photo 4: View of the upper end of Trench 1, with spoils of very hard limestone fragments. STEVEN F. CONNELLY, C.E.G Page 7 APN 336-25-019 January 14, 2015 24000 Oak Knoll Circle Project #1501 Los Altos Hills, California k-17-1.-,—:,- 1 • /f r • j,• " \ ..- ✓. •'{ �' 1- �'• '!,Y= ‘6 � .i ' �� Rr4' •rI ` Iy> {+rl � eit •, .-; aY ..4.45 er....*.•' a 1•.-,..„.7_._, iIy• .Cya:i+_lZig . - tir...,;;.:,,, ;_,_...,,.,,.. •.t.,',- ,.„'#1•-:.;# . .,1....:. ., -5:7,NR: i : ' ' ,s'.il',V," ' - )'041 ,t, Ak4 +=4� Yl.\t ,:%:i-•'-�!-i*qty!'. _ •'!.•. 1 1.\r it: - _ ir _� . . 1:- { • J t! • •4'... 2 h . ;{'4. 1•.' . i A i.t S�� i"• •+�• ,. •"r.9• �L 3 r 41:7-4---'•..-> • '''•-- �. ;_ r ' _ • ''�. •Y3.:'.•.t•- . /^-t•N-J+' 7`7t ' ' Y.�•.1- -r • -.1 t las\ .7:'ice a--.. - ' • I r s"_ :444"•-•,:27. }. r �' 'i' ,----°,',. •i r. �. C. Itt`,! 'i`a-!7,+ • .F•_'Dk- r - ' '1-"t'-'-i'^ cY..c ! _ . ♦ Itt`,.!-.4: /-- f - ;.„:13...,.......?; r Lao Pt tI. YJr"r .. .` L 0.�S •S 1 r«+' i�y ti ,;,..1.-1:';',41;. ,[� Ott ys''',''''''."--- .':-::----,,•11#4 •l i.- fN�-' .rl.'LY2« '-Nv'i x .1r { r - toc-r--,...._,X: ..,ty:vi,- . �:w; �r` kti` .r, _,- ?i .; N.`a Ya 1'r-i •n•ti .-14.; �±r �� ` Z.44.f. ...7.".;4"•4`.•fa - r T 0.- 7 j, .Y`._." .Yx`•`v it,s- ,_:•- Y•yl�?. ;•;.,-,,,-.:4,„,,,,, •1•G,I ;LwecVM 1` „ .` I/ r�.[',., G .t, y�10,:, - r :1iG fii„' , .•�� a it %� ,C. yt ' •1. .`l.n i'Z:>•L .L y,\---;.,---;e`atf,,j•-c `_ ” r,' ... t'a' i . ' 'I( rt .1•T•,,,,....., •-..,(;;.- �,� -W' 'I .✓� t • , 1 f Y L 176 y r • :� ' ACL -. j� k c. F. . :raw.'i ""4-.; r•, •, j� , , ..•i [1;:.-.‘.. .—'t �J_�.- Y'i. 'a�•�.• �j j , J' ,• �%... - .L r -r� r. ., C • � 1A".':es:).., y.,t' 7. Photo 5: View of colluvial soil wedge marked by white nails at Station 90 of Trench 1. Weathered limestone composed of silty clay (Unit 5) with abundant limestone rock fragments was encountered from about Station 45 to Station 50 of Trench 1. Olive brown and black, pervasively sheared, serpentinite with abundant white carbonate veins (Unit 6) was encountered at about Station 50 of Trench 1. The dominant shearing orientation within the serpentinite strikes towards the northwest and plunges towards the southwest. A section of thickened soil, about 3 feet wide and 3 feet deep, was encountered at about Station 78 of Trench 1. This soil appears to be an infilled fissure, possibly associated with the roots of an oak tree that was previously removed from the property. Colluvial soil (Unit 8) composed of several wedges of yellowish brown silty clay, topped with thin layers STEVEN F. CONNELLY, C.E.G Page 8 APN 336-25-019 January 14, 2015 24000 Oak Knoll Circle Project #1501 Los Altos Hills, California ',i'-\tet .� _ ?•,, "ti._ •.• - �.. • ' •C'r 4�, rtes '‘,..:,:• � t :1,..., ., !71''''-ti', �i J•?d + t -• i & .ti'. tilt r �.+��•.�� �r �q�� .%44; T' ,L• .r1.•��`:•' ". F\•.; ��..' _'r fir••.' ..!"S 76, . a S E K ' ^ t ;r,• . s . --kr.,t0-: ' "yy�' e.--i ,S4.4r.•'41, • � .A`_.r:tAt --a-. •Ti.a.r.•;7,f'" -,,"r.y, `+w„ • 'i re. ..7-../".:;?i: ... .^ •r • • ,p ` F',(: -.�. :.1.I, ..#moi ' i' ,7 ^.cam : .f- t .�.-,. .•,off..,-r,_ r�.:� • �r "of. -- • p} '! ,-i '. 1:::-,,.:::::,-.,.-.-r,„ ":7.:.;. \- .4.--•—.- -vr!-` ~' �..,o..7 .. .'":..-1-.,- .:s �1<}t✓' .'., i t • a. ,J .••.A►. •— sss` , .- •i l `r J . `fin-• may • •. y _', 4 ,. "4. , + Y • • i . '.•}.yee(� .� '..„., ,,o....:.;-,7,„ .,,t•. .`,3,.,‘7,14.42r ,'(t .„ y'�,T, J'`'• 1 ` !-1 ?i•' ry,.777..,`" ul'i�i` '..•.ticCilr,. tl:�i1' ' _ i ` c '.�'• 1- st '� Wil• err='; '`e '•� '����.,`.JV-`.•M1 1 'ZtiJ _\ j ' 1.' '^ - ..4...r.", -y•r ry : , i�)�. `-(•: 'i` • r .'b` i , af;-%"--;1/4 \ ;• , .T , �� , V•:C^: , �'cS x . .+ .a t }�) ` rr ,-- 'i Tt -fes• I- 1j �' •�1 j•. \.•".` + ��p! z �r, 'f i �,,.t at" '. ",e..: Y ,.r- .(9":, '^a.�T�r%°R_� ,tl k.t?t, r -14?24,, ,'' c. ._J'' ' `f-11.1 r, ►'..-_'� ±1.--- C Photo 6: View of fault contact marked by red-tipped nails, between Franciscan Serpentinite and Monterey Siltstone at Station 94 of Trench 1. The bottom of the overlying colluvial soil wedge is marked by the white-tipped nails. of black organic-rich clay was encountered at about Station 89 of Trench 1 (see Photo 5 above). The colluvial soil is associated with the east-west-trending break-in-slope across the property (see Photo 3 above). Yellowish brown and inter-layered gray siltstone of the Monterey Formation (Unit 7) was encountered at about Station 94 of Station 1 (see Photo 6 above). A sharp fault contact between the Franciscan serpentinite and the Monterey Formation siltstone is defined by a l to 4 inch thick layer of calcium carbonate. The fault has thrust older Franciscan rocks over younger Monterey siltstone. The thrust fault trends towards the northwest and plunges moderately towards the southwest. Bedding within the Monterey siltstone is oriented roughly parallel to the fault contact. STEVEN F. CONNELLY, C.E.G Page 9 APN 336-25-019 January 14, 2015 24000 Oak Knoll Circle Project#1501 Los Altos Hills, California Based upon the geomorphologic evidence of a break-in-slope, associated with several layers of young (less than 10,000 years old) colluvial soil overlying the fault contact, the fault observed in Trench 1 should be considered active. In my opinion, the fault and associated fault scarp are potential ground rupture hazards and appropriate building setbacks are warranted. FINDINGS Based..upon the results of this Engineering Geologic Investigation, an active trace of the Berrocal fault was encountered in Trench 1 on the subject :property, as approximately shown on Figure 7, Site Geologic Map. A fault scarp associated the Berrocal fault coincideswith an east-west-trending break-in-slope across the central portion of the property. A 35-foot building setback is recommended from the fault scarp. A similar- building setback was recommended by Hay (1988) in the original investigation for the Stonebrook Hills Development. In my opinion, from an engineering geologic viewpoint, construction of the proposed guest house is feasible on the subject property, provided it is built conforming to my recommended building setback. In my opinion, it is unlikely that primary ground rupture due to faulting will impact the proposed guest house, provided it is constructed as approximately shown on Figure 7, Site Geologic Map. Very hard weathered bedrock materials of Franciscan limestone underlie the proposed building site at relatively shallow depth, as approximately depicted on Figure 8, Log of Trench 1. In my.opinion, the weathered limestone bedrock should provide goodsupport for proposed guest house. In my opinion, the potential hazard from deep-seated landsliding, debris flow landsliding, earthquake-induced landsliding, liquefaction, ground subsidence, lateral spreading, tsunamis, seiches, or flooding to the proposed guest house is very low. Seismic Hazards Based upon the results of this investigation, an active trace of the Berrocal fault passes through the subject property. A 35-foot building setback is recommended from a scarp associated with the fault, as shown on.Figure 7, Site Geologic Map, Figure 8, Log of Trench 1, and Figure 10, Geologic Cross-Section A-A'. In my opinion, it is unlikely that primary ground rupture due to faulting will impact the proposed guest house, provided it is constructed in conformance to my recommended building setback. STEVEN E CONNELLY,, C.E.G Page 10 APN 336-25-019 January 14, 2015 24000 Oak Knoll Circle' Project#1501 Los Altos Hills, California It is reasonable to assume that the property and proposed guest house will be subjected to strong ground shaking from a major earthquake on the Berrocal fault, or one of the other active or potentially active faults in the Bay Area during the design life of the structure. Based on a deterministic analysis of.preliminary data for selected California faults by Blake (2000), the Berrocal fault presents the most significant seismic shaking hazard to the site. Using a fault attenuation relationship by Idriss (1994), a peak site acceleration of 0.72 g.and a Modified Mercalli shaking intensity of X1 are predicted for the site from a 6.7 Mw earthquake on the Berrocal fault. Historically, Blake (2000) indicates that the subject property experienced a site acceleration of 0.22 g and a Modified Mercalli shaking intensity of VIII during the 8.25 Mw 1906 Earthquake centered about 32 miles to the north of the site. The subject property experienced a site acceleration of 0.13 g and a Modified Mercalli shaking intensity of VIII during the 7.0 Mw 1989 Loma Prieta Earthquake centered about 26 miles to the southwest. Properly designed buildings using the California Building.Code (CBSC, 2007) and sound engineering practices should mitigate the damaging effects of ground shaking. As a minimum, the proposed guest house should be designed to building code requirements. It is possible that secondary fissures or ground cracks may damage the subject property during an earthquake on the nearby Berrocal fault. Extensive secondary ground cracks unrelated to primary fault offset occurred during the 1989 Loma Prieta Earthquake in the Santa Cruz Mountains. Evidence of cracking, however, was not observed to the hard surfaces on the property or surrounding roadways during my site reconnaissance. Evidence of secondary ground cracking also was not observed within the very hard limestone materials in Trench.1 underlying the proposed building site. Minor to severe damage occurred to several residences in the Los Altos hills area (Hitchcock and others, 1994,-and Terratech, Inc., 1990), in the Los Gatos area (Schmidt and others, 1995) and in the Summit Road area near Los Gatos as a result of secondary fault movement., These fissures or ground cracks were commonly focused on ridge top locations and were associated with weaker shale interbeds (Cotton and others, 1990), preexisting landslides, or intense ground shaking (Hart and others, 1990). The U.S. Geological Survey (2008) recently cited a 63 percent probability that a.Richter magnitude 6.7 or greater earthquake, similar to the 1989 Loma Prieta Earthquake, will occur on one of the active faults in the San Francisco Bay Region by the year 2036. A 21 STEVEN E CONNELLY,, C.E.G Page 11 APN 336-25-019 January 14, 2015 24000 Oak Knoll Circle Project#1501 Los Altos Hills, California percent probability was attributed specifically to the San Andreas fault that a large earthquake will occur along its trace by the year 2036 (see Figure 11, Earthquake Probability Map). In addition, Dr. David Schwartz of the United States Geological Survey cited a 9 percent probability for an earthquake on one of the range-front faults, such as the Berrocal fault, in the next 30 years in a recent lecture (oral communication). Landsliding In my opinion, resistant weathered bedrock materials encountered in the subsurface investigation on the property should provide adequate support for a proposed guest house. In my opinion, the potential for deep-seated landsliding on the property is very low. Evidence of recent active landsliding was not observed on or adjacent to the property. The California Geological Survey (2005) does not map the proposed building site within an earthquake-induced landslide hazard zone (see Figure 6). Based upon my review of air photos, site reconnaissance, and subsurface investigation,the proposed building site is underlain by resistant weathered limestone bedrock at shallow depth. Springs or seeps.were not observed on the property during my review of air photos, site reconnaissance, or subsurface investigation. These groundwater sources, commonly . associated with landslides or contributing to potential landsliding were not observed. I did not observe evidence of debris flow landsliding on or upslope of the property during my review of air photos or site reconnaissance. Source terrains for potential debris flow landslides are not located upslope of the property. Consequently, in my opinion, the potential hazard to.the proposed guesthouse from debris flow landsliding is negligible. Liquefaction . Liquefaction most commonly occurs..during earthquake shaking in loose fine sands and silty sands associated with a high ground water table. 'Based upon my subsurface. investigation, the building site underlain by stiffsoils and resistant weathered bedrock at relatively shallow depths. Since stiff soils and weathered bedrock underlie the proposed building site at relatively shallow depth, liquefaction is very unlikely to occur. The Association of Bay Area Governments (1980a) indicates that the subject property is located in an area with a very low susceptibility to liquefaction. STEVEN F. CONNELLY,, C.E.G Page 12 APN 336-25-019 January 14, 2015 24000 Oak Knoll Circle Project#1501 Los Altos Hills, California Ground Subsidence Ground subsidence may occur when poorly-consolidated soils densify as a result of earthquake shaking. Since the property is underlain by stiff soils and resistant weathered bedrock at relatively shallow depth, 'the hazard due to ground subsidence is; in my opinion, considered negligible. . Lateral Spreading Lateral spreading may occur when a weak layer of material, such as a sensitive silt or clay, loses its shear strength as a result of earthquake shaking. Overlying blocks of competent material may be translated laterally towards a free face. Since the property is underlain by stiff soils and resistant weathered bedrock at shallow depth, the hazard due to lateral spreading is, in my opinion, considered negligible. Tsunamis, Seiches, and Flooding The subject property is located in an inland area removed from the hazard of inundation by tsunamis (Ritter. and Dupre, 1972). The Association of Bay Area Governments (1980b) indicates that the subject property is located in an area free from the hazard of seiches and flooding caused by dam failure. * * * * * * * * * * * * * A list of References, Table, and Figures are attached and complete this report: Table Modified.Mercalli Intensity Scale Figure Site Location Map 1 Regional Topographic Map 2 Regional Geologic Map 3 Town Geologic Map 4 Town Seismic Hazard Zone Map 5 State Seismic Hazard Zone Map 6 Site Geologic Map . 7 Log of Trench 1 8-9 Geologic Cross-Section A A 10 Earthquake Probability Map 11 STEVEN E. CONNELLY, C.E.G Page 13 • APN 336-25-019 January 14, 2015 24000 Oak Knoll Circle Project#1501 Los Altos Hills, California REFERENCES Association of Bay_Area Governments, 1980a, Map of Liquefaction Susceptibility, San Francisco Bay Region,Map Scale 1:250,000. Association of Bay y Area Governments, 1980b, Dam Failure Inundation Areas, San Francisco Bay Region, Map Scale 1:250,000. Blake, Thomas, F., 2000, EQFAULT, Version 3.00,A Computer Program for the Estimation of Peak Horizontal Acceleration from 3-D Fault Sources,Windows 95/98 Version. Blake,'Thomas, F., 2000, EQSEARCH, Version 3.00,A Computer Program for the Estimation of Peak Horizontal Acceleration from California Historical Earthquake Catalog, Windows 95/98 Version. Brabb, E:E., Graymer, R.W., and Jones, D.L., 1998, Geology of the Palo Alto 30 X 60 Minute Quadrangle, California:A digital database, Open-File Report 98-348, Map Scale 1:100,000. California Building and Standards Commission, June 2007, 2007 California Building Code, California. Code of Regulations, Title 24, Part 2, Volume 2 of 2, Based on 2006 International Building Code. California Division of Mines and Geology, 1974, State of California Special Studies Zones, Mindego Hill.Quadrangle, Map Scale 1:24,000. California Division of Mines and Geology, 1997, Guidelines for Evaluating and Mitigating Seismic Hazards in California, Special Publication 117. California'Geological Survey, 2005, State of California Seismic Hazard Zones, Mindego Hill Quadrangle, Map Scale 1:24,000. Cotton, Shires and Associates, Inc., December 2004, Geotechnical and Seismic Hazard Zones, Los Altos Hills, California. • Cotton, Shires and.Associates, Inc., December 2005, Geologic Map of Los Altos Hills, Los Altos Hills, California: STEVEN F CONNELLY,, C.E.G Page 14 APN 336-25-019 January 14, 2015 24000 Oak Knoll Circle Project#1501 Los Altos Hills, California Cotton, WR., Fowler, W.L., and Van Velsor, J.E., 1990, Coseismic Bedding Plane Faults and Ground Fissures Associated with the Loma Prieta Earthquake of 17 October 1989, in "The Loma Prieta (Santa Cruz Mountains), California, Earthquake of 17 October 1989", California Division of Mines and Geology, Special Publication 104. Hart, EW, Bryant, WA., Wills, C.J., and Treiman, J.A., 1990, The Search for Fault Rupture and Significance of Ridgetop Fissures, Santa Cruz Mountains, in "The Loma Prieta (Santa Cruz Mountains),California, Earthquake of 17 October 1989", California, California Division of Mines and Geology,Special Publication 104.. Hart, E.W. and Bryant,W.A., revised 1997, Fault-Rupture Hazard Zones in California, Alquist-Priolo Earthquake Fault Zoning Act with Index to Earthquake Fault Zones Maps, California Division of Mines and Geology Special Publication 42. Hay, Edward, A.,June 16, 1988,Geotechnical Investigation of Lands of McCulloch, Los Altos Hills, California. Hitchcock, Christopher S., Kelson, Keith I., and Thompson, Stephen C., 1994, Geomorphic Investigations of Deformation Along the Northeastern Margin of the Santa Cruz Mountains, USGS Open File Report 94-187. ICBO, 1997, Uniform Building Code: International Conference of Building Officials, Whittier, California,volumes 1 and 2. Idriss, I.M., 1994,Attenuation Coefficients for Deep and Soft Soil Conditions, personal communication to T.F. Blake. Kovach, :R.L., and Beroza, G.C., 1993, Seismic potential from reverse faulting on the San Francisco Peninsula: Bulletin of Seismological Society of America,v. 83, p. 597-602. Richter, C.F., 1957, Elementary Seismology, San Francisco, CA: W.H. Freeman Co. Ritter, J.R. and Dupre, W.R., 1972, Map Showing Areas of Potential Inundation by Tsunamis in the San Francisco Bay Region, California, U.S. Geological Survey Map MF-480 Schmidt, K.M., Ellen, S.D., Haugerud, R.A., Peterson, D.M., and Phelps, G.A., 1995, Breaks in pavement.and pipes as indicators of range-front faulting resulting from the 1989 Loma Prieta earthquake near the southwest margin of the Santa Clara Valley, California: U.S. Geological Survey Open-File Report 95-820. STEVEN F. CONNELLY,, C.E.G Page 15.. • APN 336-25-019 January 14, 2015 24000 Oak Knoll Circle Project#1501 Los Altos Hills, California Southern California Earthquake Center,June 2002, Recommended Procedures for Implementation of DMG Special Publication 117 Guidelines for Analyzing and Mitigating Landslide Hazards in California. Steven F. Connelly, C.E.G., September 3, 2004, Fault Investigation, Shah Property, 25274 La Loma Drive, Santa Clara County, California. Steven F. Connelly,C.E.G., March 19, 2004, Fault Investigation, Pedersen Property, 26910 Dezahara Way, Los Altos Hills, California. Steven F. Connelly, C.E.G., February 18, 2005, Fault Investigation, Davila Property, 24405 Oak Knoll Circle, Los Altos Hills, California. Steven F. Connelly, C.E.G., December 18, 2009, Fault Investigation, APN 336-38-029, 23445 Toyonita Road, Los Altos Hills, California. Terrasearch, Inc., 1978, Geotechnical Investigation, Stonebrook Hills Development, Stonebrook Drive at Prospect Avenue, Los Altos Hills, California. Terratech, Inc., 1990, Concentrated Damage from the Loma Prieta Earthquake in the Monta Vista Fault Study Area,Santa Clara County, California. U.S. Geological Survey, 2008, 2008 Bay Area Earthquake Probabilities, http:// earthquake.usgs.gov/regional/nca/ucerf/ William Cotton and Associates, 1978, Geotechnical Map Folio.of Los Altos Hills, Map Scale: 1 Inch = 400 Feet. STEVEN F. CONNELLY, C.E.G Page 16 APN 336-25-019 January 14, 2015 24000 Oak Knoll Circle Project#1501 Los Altos Hills, California TABLE I-MODIFIED MERCALLI INTENSITY SCALE I Not felt.Marginal and long-period affects of large earthquakes. II Felt by persons at rest,on upper floors,or favorably placed. HI Felt indoors. Hanging objects swing. Vibration like passing of light trucks. Duration estimated. May not be recognized as an earthquake. IV Hanging objects swing. Vibration like passing of heavy trucks; or sensation of a jolt like a ball striking walls. Standing motor cars rock. Windows,dishes,doors rattle. Glasses clink. Crockery clashes. In theupper range of IV wooden walls and frames creak. V Felt outdoors;direction estimated. Sleepers wakened. Liquids disturbed,some spilled. Small unstable objects displaced or upset. Doors swing,close,open. Shutters,pictures move. VI Felt by all. May frightened and run outdoors. Persons walk unsteadily. Windows, dishes, glassware broken, knickknacks,books, etc., off shelves. Pictures off walls. Furniture moved or overturned. Weak plaster and masonry D cracked. Small bells ring(church,school). Trees,bushes shaken(visible,or heard to rustle). VII Difficult to stand. Noticed by drivers of motor cars. Hanging objects quiver. Furniture broken. Damage to masonry D, including cracks. Weak chimneys broken at roof line. Fall of plaster, loose bricks, stones, tiles, cornices(also unbraced parapets and architectural ornaments). Some cracks in masonry C. Waves on ponds; water turbid with mud. Small slides and caving along sand and gravel banks. Large bells ring. Concrete irrigation ditches damaged.. VIII Steering of motor cars affected. Damage to masonry C;partial collapse. Some damage to masonry B;none to masonry A. Fall of stucco and some masonry walls. Twisting, fall of chimneys, factory stacks,monuments, towers,elevated tanks. Frame houses moved on foundation if not bolted down;loose panel walls thrown out. Decayed piling broken off. Branches broken from trees. Changes in flow or temperature of springs and wells. Cracks in wet ground and on steep slopes. IX General panic. Masonry destroyed or seriously damaged. (Damage to foundations.) Frame structures, if not bolted,shifted off foundations. Frames racked. Serious damage to reservoirs. Buried pipes broken. Conspicuous ground cracks. In alluviated areas sand and mud ejected,earthquake fountains,sand craters. X Most masonry and frame structures destroyed with their foundations. Some well-built wooden structures and bridges destroyed. Serious damage to dams,dikes,embankments. Large landslides. Water thrown on banks to canals,rivers,lakes,etc. Sand and mud shifted horizontally on beaches and flat land. Rails bent slightly. XI Rails bent greatly. Underground pipelines completely out of service. XII Damage nearly total. Large rock masses displaced. Lines of sight and level distorted. Objects thrown into air. Source: Richter,C.F.,Elementary Seismology,San Francisco,CA: W.H.Freeman Co., 1957. Note: To avoid ambiguity,the quality of masonry,brick,or other material is specified by the following lettering system. (This has no connection with the conventional classes A,B,and C construction.) Masonry A. Good workmanship,mortar,and design;reinforced,especiallylaterally,and bound together by using steel,concrete, etc.;designed to resist lateral forces. Masonry B. Good workmanship and mortar;reinforced,but not designed,. to resist lateral forces. Masonry C. Ordinary workmanship and mortar;no extreme weaknesses,like failing to tie in at corners, but neither reinforced nor designed to resist horizontal forces. Masonry D. Weak materials, such as adobe;poor mortar;low standards of workmanship;weak horizontally. STEVEN F CONNELLY, C.E.G Page 17 �., , n ., 4. '. r . ;' :`ti r: Xr —, �f;: • " • :••''t ; ,9,�l,,f ., \• ; ,. ., . t . • • � i* 'Lam,4.1` } �,�; `� is r .. / : % ? r .4 >'p ift. --1,1,3',77;%,„•,'• ,.r-'• -•. . r�,A''. j •.7 • . , .-ay�e." r� - a _ ,•• .r,,. I A '4.'''•:- . ! • ! ,, -'- cis 1' • vc - ^'r-. *•• .. •r c x a ��r -_' .'�{y�i • 441, O.!).• r 'y•. -:t. rl• 7.. 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A ... .,,fier'qe4,-•- -•.,.--,--,4,....:- ,r. ,g,r4F.4. i„ ..--,, I, ••••i.,q,44,1,..,,,- , • i .-2. .10*7•41.-f �C. 01(')/4 • '� ••.'' g.. ,- t S.E ,4 • 2�`�T`, �., 7. r. -i ! -.1� :.t`< �� psi' • • J J . ' 4.17; '11, di t., �,;�`, i 4.. ' � '.>"-::.:-- • .•'0 , '-r __/1 Z ,i,=6'11.2! N r• . •% -./...;•„•• ,• • r ,. :✓ 1. ,,, � • 1 i •3{!'..,''.'7 r.i" ••i 7t- 11 r -' ' ••••% ~ r \tV .-Y' 'Tr• _ • .�j �• •fir,n •P- •••../°,,..n. .-f�- 4 ^ `V• -' • ,, 'S i s i (':a ! , .. ' -t , <, 1fE1, ' ot. • Source: U.S.G.S. and PGCE. 2001) c JE ]I •• 4 ,.t v` ': ' �',,: .,. .,: ..-:.,„). Site Location Map APN 336-25-019 STEVEN F. CONVNELLY, C.E.G. 24000 Oak Knoll Circle Los Altos Hills, California •O1fuIe In Geol.: Project # Approximate Scale Date Figure . 4 _Awe sit(I _ • 1501 1 Inch = 10 Miles 1/14/15 1 0 R.., 1 -v u��� CUESTA OR .t •-______,- uL ___A 1 ./ J, ' ` a��4\ if C 19 E I AR80LEOA DR BIOSSOr'1J� I _,,,....T___ _______ __________). 0J \ ,-...,NI__. ? � , a r Valley �1 J ¢ �I 1 9LFli .� I I I I�oi?_ L d I�RDSEAVE� • ',LOS --- = W s �• \lo �' '¢ M ,I 'i `.W I I..� - I'; - EUNIC: ,S :1'44=7'1 ��� cii �) jliv �h ~ALTO �P� �N/`j n �i^3'4. o q WI ., ` �_D A.1 '• _ I. ,� ' \ s ".� `Y �/ ''',;- -2,-(4X.1,0 s�rY �\� ¢ �' 3I.e f��r- \t 11 \\ 1 0_.` I�� Ora�R D e;�\ oar �c¢ i � 3 U I '� �iF�? — - L="1..---s—°R' moo)/'\' OItEFsf1 • P F l'.1-,..j tee, 2 y� �_ ... \ _- e..•;.'. `, i �i \\• v POS �--- / �. ivy 1�1 ......•j,- - .QO., '�"\ .: � ..��,\�, •P' fn•� T• 'Ir --FLTfliill ry �� ,, h:--, �� ,� LEV�INF%� E/' s .'i �N•�. .a „ / ` '90 I. �I `n �'L.J ���--7 'r\1 J I� ft r /`�1`. •. : •,9 • \ OJ` ' sem, ` ``V ` Flt ! ii I I.‘-'T'''' ¢� n �I p A E s J �' L R.I EDDELN, \ Lo ''� 11 wJ 1 \ L m 2 ,� ALTAM �• .y6. O' 1 ,F ---.•(--•'-'4_'41--°'-'�tE \ ' \, .o j �l BERRY AVE, ¢ is ------1'.1---__- • /►� •(; q9!•. �.�� JPS• ,�, o cclrFp�LT0SOAKSDR's 1� W LORTLANDAVE jr Li ^ c) ,sem'• HILLT .�'�\9✓�� \z,-• ..._ .• \i II \ `CfINTON RD 'I ` ` �'� c.o :'6.- � y/ Oq, '!l, XPi T .C. v ,:1,,,. -' I',. IEUREKA`Vf i�— \ y%!r�9•- Li '''•.\ S---'-it,/ 1�/ e• .i MANOR WAY I InJ ;o - --=OAWNRj°C ___41.., • /� >kE ,c:, kyr 1 I� �Q�l \ - ` ., =;\ �� y\• 9 �- �`\d '9L -1E1Ei �L ISA IN AA'H. `,.1– .-,�. � a Loyola -- �� --iil"=- ---- ‘//5"\CC ,'„ \'' Ad '----[ II ;�',-�_.�-' y rq�E�� � i%t D i ' :QP P . . Loyola 1 C\O�rngers-,;11 'A_1—_�� ' C Ii 0 L'ENA NO /t �^ �0 E,l y '-, \\W' y' )\�c �' 1 ;'t.:\` '�'' , .. ', \�y.dam.. \• � = ; N:. y •-• •`'• --a �`' J jJ. 1 •;� )OSEP \WOOdlall�d�y� yi \ ^. ^�� o' PK. ,Oq /'`: / S4�- AGreSl 'g 990 r ��,.-��,r _ _.� i — The. �/�, 90 ` ��/�\-a�o'��-�\�. � `''�oroLa DP�• � / , .� v/ . � `High��lapnds,, flop w�', --:-----------,'----------7-.--......--------s...._,� ,� -.•----‘11111: `.• �L,\!,-4. \�' i Y:\ �• f., ` i �� ,` v- Dei. 1' _4tr..' '\,\. t f soo J� I �I �� -- iy `ls_.,-....--., 9 1,Ga---Aof: �C -- �� -„,...,11:....1:..>j i, \' ;, r� V- Heaven Gem' '" ` '. � =ti"• JZZ���`'� / ,, :. ~ it �, %J'�� .111 �--_/=_ -.„---"-'2'- �_ - .•. - y \ , 'A• .rte ^`. - Regional Topographic Map APN 336-25-019 STEVEN F. CONNELLY, C.E.G. 24000 Oak Knoll Circle Los Altos Hills, California j —CrirmiltIng in _ Ge Project# Scale Date Figure 1 9 'dAir...," 1 "r �=' �� 1501 1 Inch = 2000 Feet 1/14/15 2 1 II, .41111 ,......_:"-,/',. -.- ----. " ' r f k\"--,s, -y---..,1 / .•,`-,1.,.,-\ - 1 ,_ 'i* 1 i Li' ---.---- :arY thaOrf d° *lir i ) if if ''''''(‘Z-.Z.•/---:-`•::: -st-----1... (i.1 ':. ) • ____. RI,- -xqie ---,..., : , / k 1--,..„--..., ' -7 - Pr , ____ . . , L ._ 0A10, -/-/ - s... 0 (''•• %OK 4 ' - ' .1-' - '. 4.. 1 `,73:171, • . t:. f ' - - ,-(-4 . ' ...., ft -.,;--, • 4 7-A I... - : ''' . ' )-,---- --77-.....--7-• t,:.``'. - ' 16-'1- Ir. a -- ..__....% • it- . . - , ----_ ' 4 .- - •l1. - • it ... 4 .. Al . .' -• - -- . 11 . --='---- - '-...:N...._ik;•.' 1 - lin _ . , - — - • 'a„ --„,v issi,.., .__. - .::-. -- i''' lik - it_. —"'" -, . -`', „ ,z_ — . . - Arp.:.._ . "'to - • 4 r!„..,...::., atilt / . . . 4 . ......„. : t , ,..,, 7-7:A5\7-k kiinir - -.? , =.- . ,... ,--'41.1)-&-: \ , '--a-4-- '. •• .,:c- ) _, , fi Li,...-... is-- ' -..... ei •Nit..... ' '. CC T's -....) k ‘ii:i, '• ) - , ‘ .- -- . ' r, ltr") _ _ ) z„-..•• \\._ \\ 11,17 , • .• .411, _ ,. , ,-- , ,t- - ---. -, - - -,.., 4.•1'.,- . ( _ 4E. _ ,./ ,I\ :V vs •,.. ''' •, -, , --../,. ‘: - ,-----rr ,, i - .. • .. ... - • ...,..- - _ . . -) 1.-f--. , ... - - .... _ ._. ., .. ,_ ( -, --,• . s /7144i --- ' 1 -,1110- - k t ,., • '•••-• "'...'‘Iii_ _,.-. IAL,..-.-• . .,,i.. 4 Alta Al& EXPLANATION Geologic Contact, dashed where opai Alluvial Fan Deposits approx., dotted where concealed Fault Trace, dashed where approx., ma Santa Clara Formation ........ ? dotted where concealed, queried where uncertain Timi Ladera Sandstone r r Thrust or Reverse Fault Isi Monterey Formation a5 _ L__ Strike and Dip of Bedding ft Franciscan Sandstone .26 __A__ Strike and Dip of Foliation Franciscan Greenstone far Franciscan Sheared Rock la. Source: Brabb, Graymer, and Jones, 1998 Serpentinite Regional Geologic Map APN 336-25-019 STEVEN F CONNELLY, C.E.G. 24000 Oak Knoll Circle Los Altos Hills, California Consulting in f.• Project# Scale Date Figure 0p...aeriiiyec ....., --- 1501 1 Inch = 2000 Feet 1/14/15 3 N i lit a ♦ t \till l41* tV; it ,K' a jihit\. • '' ,. - � 41;4f..,T,,ff � --1\ *At ' Tom, _ , Tim ro , -........, . , st,,,,, Ardi . 3i Z ' - 4l so !-.11 , --- Vior . 0-4 IBJ fL y j, 44e'4"- 1r' ''.*,k.,‘,. - - ...-- ., ':. 4 / ' . • . '''' - ..,......, Ni, :--- ., ).' EXPLANATION �` _ Geologic Contact Qls Landslide Deposits •.740 , Qal Young Alluvial Deposits � Fault Trace Qoal Older Alluvial Deposits QTsc Santa Clara Formation 60 Strike and Dip of Bedding Tme Merced Formation Tus Unnamed Sandstone \: T1s Ladera Sandstone"T-C--- ) Landslide Deposit Tm Monterey Formation KJfg Franciscan Greenstone KJfs Franciscan Sandstone Jsp Serpentinite Base: Cotton, Shires &Associates, Inc., 2004 Town Geologic Map APN 336-25-019 STEVEN F. CONNELLY, C.E.G. 24000 Oak Knoll Circle ... _ Los Altos Hills, California C°T"ulIng In ceoi Project # I Scale Date Figure .4 ...iuii ' ,..„,oi6H:'' :i re„ • 1501 1 Inch = 300 Feet I 1/14/15 I 4 \ i/1It --ill".riiiiii, ... 4\ t i. , \yl 1 pd 1 , .. i „,. \\;t ,1 \ • ,c,..„ .).,„ if ow ,.... . .,,,, - 0A.k. ilk MI V NINI LL CIkCL . 11 _ E J 1 i 4111 .... ill Abp. 14 • Li: 2. :J , r b .,,....-- "‘•••....„ —.... \ k\s, EXPLANATION SLOPE INSTABILITY: Zone encompasses mapped landslide deposits. FAULT RUPTURE: FZone encompasses at land located within 200 feet of a recognized trace of a potentially active fault(includes State designated active'Type B"faults). GROUND DEFORMAT1ON/FAULT RUPTURE: Zone encompasses all land located within 660 feet cf a recognized trace of a potentially active fault(includes State designated active"Type B"faults). The 660 foot distance has been selected from the dimensions prescribed by the State of California In compliance with the requirements of the Alqulst-Priolo Spedal Studies Zones Act of 1972(Chapter 7,5,Division 2, Callfomla Public Resources Code). STANDARD CONSTRAINTS: A Zone encompasses all hillside terrain and flatland regions that are not included In the areas described above(S.F.and D). Base: Cotton, Shires &Associates, Inc., 2004 Town Seismic Hazard Zone Map APN 336-25-019 STEVEN F. CONNELLY, C.E.G. 24000 Oak Knoll Circle Los Altos Hills, California Corsultirg!r. �,.. / y Project # Scale Date Figure / /-;•.- 1501 1 Inch = 300 Feet 1/14/15 5 ',./.-41 i.. -.:IF _ -)' / _<'..- ... I, ''-'i,,11`i`` _ _ ;....\ P 111 -\\ r -..iitilk theiott__, - - •. —..� �? ilt ‘40tri.J..ci - , -,,,,,,.. _ \ At. — ....1.' . \ / \ 1, Airi' oriolok ---- -'-'s.7 , ,,,4 \ ,,„,,4 ,_ ,..,, ti. 04, _ ,ff 1-,,,, ft Di ii., .. 1 --" -'7%%- . t ' —•-...... 11. ,,..'s,4,, .!..:;•# °; " .,c ,e„,... \ . / , Ill 0 , .,,II.) ( ..,_...411#. 1 iffi, of"\li 41111QZ -,,,410 "ilk v.s0 \ \ t� Eat ( y '' ,• if � . oftinkt,k,.. ;.,....\_!---.„ --:zi=liii6.-. ,t c".". 7" ...._44#1,-L, ,_ Xi -; ... .-- --... cc/ct r % EXPLANATION Liquefaction Areas where historic occurrence of liquefaction,or local geological,geotechnical and groundwater conditions indicate a potential for permanent ground displacements such that mitigation would be required Earthquake-Induced Landslides 0 Areas where previous occurrence of landslide movement, or local topographic,geological,geotechnical and subsurface water conditions indicate a potential for permanent ground displacements such that mitigation would be required. Base: California Geological Survey, 2005 State Seismic Hazard Zone Map APN 336-25-019 STEVEN F. CONNELLY, C.E.G. 24000 Oak Knoll Circle Los Altos Hills, California • Consulting Geol.„ Project # Scale Date Figure w .-• 1501 I 1 Inch = 1000 Feet 1 1/14/15 I 6 • :� �. —';� X3-1' %ji==t•'� _..�.: :_ : �• is -T =r,_ i ,` 1`` l'``' `f."� - - _$_--_-----_- _ _---_" - ^I I---1 ps= ,1 _ ^} R?l I `,• � ;. �_ 1,ag� EXPLANATION -- , 1 1 Is., __-------- _1__-_L_ts- 1.111 Monterey Formation 1`. 1 - -Trii ch _ - ' `J 1 I -._ --- --_ _ _____________'-.1-1.--_-_71:.-t 1 KJfs Franciscan Complex,Sheared Serpentinite WI ', !', I ` 1__ ill` -----— ------------------ 1 1 'A i 1' >' i,, `,i 'I-._ I B } ` ,..y. Franciscan Complex,Limestone °C' = t`,1�r"' I --- - 1.• 1 I , ' , Fault Exploration Trench Y; i, I I-_ 1_-__ :s f-F9a1 ir �, 1' { , • .4 el® Test Boring,Redwood Geotechnical,Inc. c , 1 I • nti KJfs g l 1 : > v'a i ti.. i I.- i- _° i�l` ,1 .i 1 m Geologic Contact m (1.``•§I I ` _ �:+•'_ t.; -,-- . �•- Active Thrust Fault o I t t. _, • c Active Fault Scarp •\ ft /,� , i , ' Y AGeologic Cross-Section p r Ai I. ��' -•mow; f,-,./-/, ` brt` "`rro9e�r',. d"r ' i )0 :-,....:4„,, .r,:jr.c.4‘.0, Site Geologic Map APN 336 25p1g STEVEN F.CONNELLY,C.E.G. 24000 Oak Knoll Circle ro - . -._ - � Los Altos Hills,California Project# Scale Date Figure J Base: Proposed Site Plan by Metro Design Group,1/6/15 / ^'T� 1501 1 Inch=40 Feet 1/14/15 7 N20E, Approved 35-Foot Setback 0 Situ ----- ®____ Bend -------------------- O ...1-- in m ---- --- Trench — m -5— -- ® _ — — _ _. ._ m _— — � ._j ,N-...,._ / v4 m/ KJh .. -- . • / `' Depth ® \\ If '- .-%�// (Feet) /' KJfs 1/ 15— ?----------- ? ? ' white carbonate veins O KJfs 20— Test Boring, _Redwood Geotechnical,Inc. 25— 0 5 110 I5 20 530 255 40 45 50 55 60 65 Station(Feet) ® grayish brown,2.5Y5/2,silty clay,with ® light olive brown,2.5Y5/4,serpentinite,sheared, tai dark yellowish brown,10YR3/4,silty clay,with some sandy layers and rock fragments, interlayered with very pale brown, 10YR8/3, abundant subrounded to subangular limestone moist,some roots and rootlets,soft to carbonate,abundant subangular clasts and rock fragments,moist,dense(Weathered Bedrock, firm(Fill) grains of serpentinite(Weathered Bedrock, Franciscan Limestone) -t :.+ Franciscan Serpentinite) KJfs © dark brown, 10YR3/3,silty clay,firm to stiff, ® pale brown,2.5Y7/3,limestone,very hard, O olive brown,2.5Y4/4,and black,5Y2.5/l,serpentinite, moderately plastic,mottled,trace roots and indurated,well-cemented,blocky,moderately pervasively sheared,granulated,with abundant white rootlets,moist(Residual Soil) fractured(Weathered Bedrock,Franciscan carbonate veins,moderately hard(Weathered Limestone) Bedrock,Franciscan Serpentinite) KJfs Log of Trench I ApN 336-25-019 STEVEN F CONNELLY,C.E.G. 24000 Oak Knoll Circle Los Altos Hills,California gradational contactJaw-- - Project# Scale Date Figure Logged by Steven F.Connelly,C.E.G.,12/8/14 ----- relatively sharp contact �"'°"�`— "`-r 1 1501 1 Inch=5 Feet 1/14/15 8 NIE —0.- 35-Foot 0 Setback Fault — Scarp/ --�•••••....__. .�` ..................... Break-In-slope Active KJfs Fault 5— ;�, —''".•,infilled — fault contact defined O - ,• . •'\fissure �' by 1 to 4 inch thick �F et) layer of calcium carbonate 5111 KJfs \,,,....` + white carbonate veins 5 KJ's ~ ` ` 0 ` --- 15— ♦ 7m.-'' '> i i -.... _ `--. N77W 56SW ♦ '/ / J �...._....- along fault / Tm /� ....._.._._ ii ._........._. -7'1m O contact ♦N74W 44SW // j O j measured along fault / / 20— wall to wall I I I I 90 95 1 1 1 1 I T I I I 65 70 75 80 85 100 l05 110 115 120 125 130 Station(Feet) .D grayish brown,2.5~5/2,silty clay,with p olive brown,2.5Y4/4,and black,5Y2.5/1,serpentinite, 0 yellowish brown,10YR5/4,silty clay,moist,firm to stiff, some sandy layers and rock fragments, pervasively sheared,granulated,with abundant white highly plastic,some subrounded to subangular rock moist,some roots and rootlets,soft to carbonate veins,moderately hard(Weathered fragments of Franciscan debris,several wedges or packets firm(Fill) Bedrock,Franciscan Serpentinite) KJfs of soil topped by thin black organic layers(Colluvial Soil) ® dark brown, 10YR3/3,silty clay,firm to stiff, 0 yellowish brown, 10YR5/6 interlayered with gray, moderately plastic,mottled,trace roots and 10YR6/1,siltstone,friable,moderately hard rootlets,moist(Residual Soil) (Weathered Bedrock,Monterey Formation) I ire Log of Trench 1 APN 336-25-019 STEVEN F CONNELLY,C.E.C. 24000 Oak Knoll Circle Los Altos Hills,California gradational contact .- Project# Scale Date Figure Logged by Steven F.Connelly,C.EG., 12/8/14 ----- relatively sharp contact �w `��.......�..ra 1501 1 Inch=5 Feet 1/14/15 9 A N11E A' Fault Scarp/ Break-in-slope fill residual ., a1 soil t Guest 1, 35-Foot Trench _,i°u" I' Setback colluvial soil KJfs :11*11,111 460— KJfs B1 Trn o Franciscan Complex �' > Monterey w /�toGa\ Formation e� �k 420— 6 Fay 380— Slope Profile based on Proposed Site Plan by Metro Design Group, 1/6/15 Geologic Cross-Section A-A' APN 336-25-019 STEVEN F. CONNELLY, C.E.G. 24000 Oak Knoll Circle Los Altos Hills, California Con't'iu" et; Project # Scale Date Figure ., -di. ---'-‘1111111111iiiiIIIIIII—Iiiiii Airdil.* 1501 1 Inch = 40 Feet 1/14/15 10 4 1.:..,..*-1/5•:,*.i',.'''k‘2'.•,..k... . -A9- 0.- ..-rtf.' fliar1(;..i,", -.._... , 4......... .._ , , .._... tv :5;•,,_ Ar. ,,s 1.: •.4p i .,- f• ',-,...::'-•.:%- i,! ,,,\.7,s.k6..'-‘--..:t4>'.N4%.' .1.1;•1-gii.. ; f ,A111241)1,i).•'t t. . '41,7,- , ,..,- -'''''4;k0 :. -,, •-C".:;,.‘.2',.'.',`,k, -8,,‘!t.x!,. 1 :: 'c,..-.i.‘1/4.•., 14". • ; . \.' '‘‘ .S2,1 , ', .s,-':-. ;i..,. .,‘.. , 1 ' ' . 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''''...•'..„'-.. •1•-• ; r '`.gi*:::, vi- •-.. -A111$.4; , F'i.-• ' - .,,*'.1". .t.-...'.'• ••••': - - - - - - --- - -- -- -- • 2 •-_,, \.) . •• 17 .‘ •46,„ -:, b%`•,. ,..... , • ; •••%\i`r.-4..v._ •-a •T.',.......,..4• ,..•-. `,..,•-•••% : .'..:i*:..,'-' 1• INI ••••;!{; roy 6.7 or greater quakes ,' 'V • ••,, --C•il • ,z,t`'...„--Z,N\/‘,'.,=K Probability of magnitude ; 633 •,.,.‘C.,.• s., .t) ••,,,tide...... ••• , A...,%. •,:,,N, 0 .6„. , - 4, . 1.0-- .lib OA, N. • . .. --. -,,,.., • before 2036 on the , 0, Santa Cruz .o .-- op/A.64,• .9.s • -...:••• Watsonville -'14 indicated fault ,71••\ ;L- ... .. 'II liontere.. 'Fr :- c Increasing probability =mm4. r -A Bay , along fault segments - •N‘,?,:,,,,.. 1,...x 1 . ,• " Malinai;'..4•- k .-.1 ''t,. Expanding urban areas Monterey '.• , •••vo-N-.,,,..!,,,, ..,••‘,7-, ,i URL http://earthquake;u(gs.goiii,Mich‘ lincaW :.. _. Earthquake Probability Map APN 336-25-019 STEVEN E CONNELLY, C.E.G. 24000 Oak Knoll Circle , . . Los Altos Hills, California Consulting In Project. , ee : Geol.:a # Scale Date Figure ---- 1501 As Shown 1/14/15 11 reo. COTTON, SHIRES AND ASSOCIATES, INC. ATTACHMENT 5 CONSULTING ENGINEERS AND GEOLOGISTS February 12, 2015 L5234 RECEIVED TO: Suzanne Avila Planning Director FEB 1 2015 TOWN OF LOS ALTOS HILLS 26379 Fremont Road Los Altos Hills, California 94022 TOWN OF LOS ALTOS HILLS SUBJECT: Geologic Peer Review RE: Fung Map Amendment, Secondary Dwelling 36-15-MISC 24000 Oak Knoll Circle We have completed a geologic peer review of the proposed site map amendment using: • Engineering Geologic Investigation (report) prepared by Steven F. Connelly, dated January 14, 2015; and • Proposed Site Plan — Secondary Dwelling (Sheet A-1) prepared by Metro Design Group, dated January 28, 2015. In addition, we have reviewed pertinent maps and reports from our office files and inspected site exploratory,excavations. DISCUSSION The applicant is seeking approval of a revised Human Habitation Setback Line (associated with a fault trace) that was initially established during the local subdivision processes. As part of a geologic investigation for the currently desired guest house/secondary dwelling, the Project Geologist has identified the location of a fault trace (part of the Berrocal and Altamont Fault systems) that is different than that identified during subdivision-level geologic investigation (Investigation by Edward Hay for Lands of McCulloch,June 1988). The net result of the new findings is to shift the Human Habitation Line approximately 8 to 24 feet north of the existing residence (as illustrated on the referenced Proposed Site Plan). The north arrow on the Metro Design Group plan is not correct, and north is actually approximately coincident with the local alignment of Stonebrook Drive. The other side of the existing Human Habitation Setback Zone was not evaluated as part of the geologic study for the secondary dwelling and is to remain unchanged. Northern California Office Central California Office Southern California Office 330 Village Lane 6417 Dogtown Road 550 St.Charles Drive,Suite 108 Los Gatos,CA 95030-7218 San Andreas,CA 95249-9640 Thousand Oaks,CA 91360-3995 (408)354-5542•Fax(408)354-1852 (209)736-4252•Fax(209)736-1212 (805)497-7999•Fax(805)497-7933 www_rnttnnchirpc rnm Suzanne Avila February 12, 2015 Page 2 L5234 RECENT GEOLOGIC EVALAUTIONS An exploratory trench of approximately 10 feet in depth and 127 feet in length was excavated by the Project Geologist to evaluate potential fault rupture hazards in the vicinity of the desired secondary dwelling. A trace of the Berrocal Fault was identified in the trench, and soil and geomorphic evidence was identified that suggests displacement from an active fault. The Project Geologist has recommended a 35-foot building setback from the scarp associated with the fault trace. CONCLUSIONS AND RECOMMENDED ACTION The Project Geologist has completed a fault investigation in conformance with prevailing professional standards. We recommend geologic approval of the proposed Human Habitation Setback Line change depicted on the referenced Site Plan prepared by Metro Design Group. We also do not have geotechnical objections to the future secondary dwelling location indicated on the Proposed Site Plan. Prior to approval of permits associated with construction of a secondary dwelling, a geotechnical foundation investigation should be submitted for the proposed structure. The Project Geotechnical Engineer and Project Geologist should review final proposed construction plans to verify that drawings have been completed in conformance with their recommendations. LIMITATIONS This geologic peer review has been performed to provide technical advice to assist the Town with its discretionary permit decisions. Our services have been limited to review of the documents previously identified, and a visual review of the property. Our opinions and conclusions are made in accordance with generally accepted principles and practices of the geotechnical profession. This warranty is in lieu of all other warranties, either expressed or implied. Respectfully submitted, COTTON, SHIRES AND ASSOCIATES,INC. TOWN GEOTECHNICAL CONSULTANT Ted Sayre Principal Engineering Geologist F.kG 1795 VIO, T, David T. Schrier Principal Geotechnical Engineer GE 2334 TS:DTS:kc COTTON,SHIRES AND ASSOCIATFS INC