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321, Addition of garage space to ex, Studies & Reports• • ENGINEERING GEOLOGY GROUP (213) 738-2828 GEOLOGIC REVIEW SHEET COUNTY OF LOS ANGELES DEPARTMENT OF PUBLIC WORKS 550 50. VERMONT AVE., LOS ANGELES, CA 90020 Tract/9 K a 6 3 9.3 Luck- , 5 Parent Tract / Site Address 3 • h _ r c /�l 1 Location l�.v//l yy hi;ifs Geologist ��' /Icx�7 �� A'Sd ,,f� 'eveloperfowner /yin c1"/!Y r /Qn �-4r9 Soils Engineer /►1 ticc,1 / a,44 T ibim���Engineer r a 1/'/ s Review of: O Grading P.C. No. • I ding P.C. No. PLAN CHECK NO. OR DATE OF REPORT(S) zz g /1 0 Geologic Site Inspection Only P.C. No. ❑ Geologic Report Dated ❑ Soils Report Dated eology & Soils Report Dated 312 /% / S as Action: O Plan is geologically approved • 0 Plan approved geologically subject to conditions below \ ❑ Sec. 309 Code requirements met Remarks: 1. A consult' g 'i engineerin map%'sCGtohsl /A cii geology, OC,Y J o v a h e� sal s �5 .7t'-#'r,fy, 2. II recomm dations o th consulting ✓ eotogist, design or shown as notes on the plans. Dist. Office, F ✓( N F '- SHEET j OF J DISTR IBUTION: 2 Dist. Engineer Geologist _ Soils Engineer ,_ / Geol. Group File ✓ — Grading Section 1I44/a, 77 rietoo/1/;5L ,,^g�,' n�D4r �e // 44 ✓ is not approved for reasons below ubmit plans for recheck soils gine-ring, T ' evert Scaft ef..SLA Lre,.; • co ° it ca r I ,jf report(s) is required r %1 USf1`t //4 /nits.• / eSo/vc.: 9 soils engineer must be incorporated in the 3. 9 ie plan must be specifically approved by the onsultant geologist, tint soils engineer by etter-report and/or anual, original signature(s) with date(s) prior to approval by the Geology Group. 4. 0 In -grading inspections must be made by the consulting ❑geologist, ' ❑soils engineer. ❑ Inspection reports must be submitted to the Geology Group for review monthly. Notify Geology Group upon start of grading. 5. 0 Rough grading must be approved by a 0 final geology report, ❑ final soils engineering report prior to approval by the Geology Group. 0 An As -Built Geologic Map must be included in the final geology report. 6. 0 Foundation and/or wall excavations must be inspected and approved by the consulting ❑ geol gist, ❑ soil engineer, prior to the placing of steel or concrete. Y eXLavt�idq {or p11evac%Sewlr/ayis a zJ¢/ c7 P ,lie 7. 0 The County Engineer Soils Engineering Section's ❑ appr6vaFis req rew et p�'e0pe`' ❑ require nts til tac fec�t.S�4LSVVS Pit / ❑ conditions of approval0 '74 are attached 0 approval is required (dated 8. all proposed tentative corrective devices (e.g. buttress, stability fills, subdrains, etc) on the plan. 9. Et1Acjg..iterne (.Add above, as notes to the plan. 10. 9-i-he geologist and) the soils engineer 3 must make a finding in accordance with Section 309, L.A. County Building Code. ,i 09 cEi)/Tr LEWI, emy, t Q0/v/S/ / eels -k sfh the_4AoPE—re-I/li 1e/rt,fn"�C/ 3/2o/ 6 S't,Ifry 1 rE ot'f lad/cjaley "-deco/et) tlyie,„*7.S0til7 g Pig v,`c 1 i ef illI/t0 4,e/ot-y le& IVO Cece1kE' , ,/ease 5ti! /(eid,f,e/ei. 0 074 rye 41w7; C) S;I; ce17r./i7L/e,75 av 4f *-o 'lent/i"7 C1171 s v.fpet/rotes Lq cote -e cAlifca� Cons G%fa `!� B r it-ec O,,r� I?ee,Yez4ti/ca,/ Ce/isu i/ j/S inc.' 4-��1 r/It I'�o �i,jj/ eye) L, o4 w o o /) /7 l �� at 7 , ! f •f-&4p€tt '�r� gyp. SE•oJ cego//off aldwi tvii Illustr !9 Qnjanc//� it4e pf/rsQ eckedrvre (0 h I1oys o f the 4I€ /400 Prepared by 76G30 - PS 7-85 Reviewed by Date 2./2//5 • • American Earth Technologies A CALIFORNIA CORPORATION March 20, 1985 File No. 1442.01 • Mr. John Rawl jn4 #13 Cinchring Road Rolling Hills, California 90274 SUBJECT: LIMITED GEOTECHNICAL REVIEW #13 Cinchring Road City of Rolling Hills, CA • Dear Mr. Rawlins: At your request the site was visited for a visual review of geotechnical con- ditions. Per our agreement, no subsurface exploration has been conducted. We were not authorized to crawl under the house or to remove carpets, linoleum, or any other floor covering. 0ur comments are based upon our observations at the site, limited research, experience and professional judgment. Some areas of Southern California have developed reputations for geotechnical problems. The reputations stem from highly publicized problems in a rela- tively few areas. The level of publicity given these problems has served to raise the public's awareness of the potential for geotechnical problems. This awareness has, in turn, served to increase substantially the number of requests for limited geotechnical reviews, which is the subject of this report. The accompanying report presents some general information about problems in the area and specific comments on items observed at the site residence. As an aid to understanding some common geotechnical phenomenon of possible influ- ence, areas of this report provide some general discussion. A brief summary, which is intended to put findings in perspective, is included at the end of this report. Respectfully submitted, AMERICAN EARTH TECHNOLOGI L7 :V, egory J4. M,ten President R.C.E. 26098 • 316 TeJon Place • Palos Verdes Estates, CA 902?4 • (;13) 375;0010 t ou vi suatttxri birth • rod bah r eso i 4 : 104 i WN 9 Ss t R File No. 1442.01 March 20, 1985 Page 1 REFERENCES The following reports and maps were reviewed during this investigation: o Geology and Paleontology of the Palos Verdes Hills, California, by W. P. Woodring, M. N. Bramle:tte, and W. S. W. Kew, 1946, U.S.G.S. Professional Paper 207. o Geology of Southern California, Bulletin 170, by California Division of Mines and Geology, 1954. o Space -Time Relationships of Landsliding on the Southerly Side of the Palos Verdes Hills, California, by Richard H. Jahns and Karl Vonder Linden, in Geology, Seismicity and Environmental Impact, Special Publication by Association of Lng n1 eering Geologists, 19/3. o Portuguese Bend Landslide, Palos Verdes Hills, California, by Richard Merriam, The Journal of Geology, Vol. 68, No. 2, March,.1960. o Landslides and Landslide Abatement, Palos Verdes Peninsula, Southern California, compiled by John D. Cooper for Association of Engineering Geologists Southern California Section, 1982. We also reviewed aerial photographs of the site area. INTRODUCTION This report presents some general background information about geotechnical conditions in the area and provides specific comments on conditions observed at the residence. Two of the most common geotechnical problems that are known to occur in the site area are expansive soils and landslides. Although expansive soils com- monly do not affect the overall gross stability of a site, they can cause sub- stantial cracking and damage to foundations and walls plus contribute to slope creep and surficial instability. Landslides, in addition to causing founda- tion and wall distress, sometimes have resulted in total loss of some residences. We are not aware of any maps that show the site to be located in a landslide. A sketch map included with the referenced report by Jahns and Vonder .Linden indicates an old landslide is located northerly of the site. This report pre- sents a substantial amount of background information pertaining to landsliding in the Palos Verdes Peninsula area. This background information is important in helping the reader understand why the landslides have occurred and should File No. 1442.01 March 20, 1985 ' Page 2 aid in understanding how the overall gross stability of the Palos Verdes Pen- insula area can be affected. SITE DESCRIPTION The site is located at #13 Cinchring •Road and consists of a single-family dwelling built on what appears to be a;cut-fill pad. A'guest house is located westerly of the main house. A fairly steep cut slope on the order of 20-feet high occurs along the easterly side of the pad area (behind the house). What appear to be fill -over -natural slopes descend from the westerly and north- westerly portions of the pad area. The westerly descending slope is on the order of 20 to 25-feet high. It descends at ratios that vary from on the order of 1.5:1 to 2:1 to what appears to be a relatively small cut -fill pad containing a guest house. The northwesterly descending slope is' on the order of 50-feet high and appears to descend at an overall ratio of 1.5:1, with some portions of the slope being locally steeper. A swimming pool with decking is located at the northerly end of the pad. The northwesternmost portion of the pad area is planted with lawn. A tile patio area is located along the westerly side of the house (in front). The area along the easterly side of the house (between the previously mentioned cut slope and house) is covered with asphalt and concrete walkways. A low height wall occurs along portions of the base of the cut slope. Most of, the interior walls of the house are covered with wallpaper or have painted surfaces. The floors are covered with tile or carpet. Some of the ceilings are of the open -beam type; others are covered with a spray -on type . acoustic material or have painted surfaces. Most of the exterior walls of the house are covered with stucco. An asphalt driveway leads from the street to the pad area. PHYSIOGRAPHIC AND GEOLOGIC SETTING The site is located on the southerly flank of the Palos Verdes Hills. These hills are underlain by the Miocene (± 15 million years old) marine Monterey formation and associated volcanic rocks. The rocks have been arched upward to form a broad domal structure with a northwest trending axis. The shape and configuration of the hills is a reflection of this structure. The domal structure is modified by small folds; however, strata within the Monterey for- mation is most commonly inclined away from the crest of the hill. The domal uplift of the Palos Verdes Hills occurred while the hills were still below sea level. During the early to middle Pleistocene (about a million years ago) the hills began to emerge above sea level as a result of regional uplift. .Simul- taneous with emergence, wave erosion cut away the strata along the shore cre- ating gently inclined terraces. The terraces were terminated at steeply sloping wave -cut cliffs. Emergence has continued to the present, probably as the result of a fairly uniform rate of regional uplift. • • . File No. 1442.01 March 20, 1985 Page 3 Potentially unstable conditions are created by wave erosion in areas where beds of the Monterey formation are inclined seaward. In such areas, erosion has removed support from the strata leaving beds dipping out of the sea cliff. This unsupported condition has led to the creation of large landslides on the south flank of the Palos Verdes Hills, such as the one which has been mapped northerly of the site. The situation can be compared to a deck of cards. Each card represents a bed of sedimentary rock. If the deck of cards are tilted with no support given to the low .end, the cards slide off. The same thing can happen to inclined strata. If support is removed from the lower end by wave erosion, the rock slides. LOCAL GEOLOGY Information obtained from the referenced reports and recent work performed by our office in the Palos Verdes area indicates that the site is located within the proximity of ancient, presently inactive and active landslides (refer to Figure 1). The active landslides include the Flying Triangle landslide and portions of the Portuguese Bend landslide. Information contained in the referenced report by Merriam indicates that the Ancient'Portuguese Bend Landslide complex may extend further north (upslope) than has been shown on more recent published maps. Information obtained from a recent investigation performed by our firm, which included the drilling of fairly deep exploratory borings, tends to confirm this viewpoint. Other information we have obtained verbally from other consultants working in the area tends to suggest that this northernmost boundary may extend eastward, toward the site. If the boundary does. continue eastward, it is possible that the site could be located within a portion of an ancient, presently inactive, landslide complex. . Although extensive subsurface investigations would have to be performed to determine whether the site is located within an ancient land- slide, the possibility cannot be ruled out at this time. SITE CONDITIONS Our review of the residence included a visual review of the interior and exte- rior of the house and yard, garage, and other appurtenant structures. The purpose of this review was to determine if evidence exists which suggests that the residence area is presently undergoing any kind of significant distress. Evidence of "abnormal or unusual distress" can sometimes be found as signifi- cant cracks in walls, ceilings, slab walkways and patios, driveways, etc. In many cases the doors in a house undergoing distress may be racked or not close properly. estimated location of site Portuguese Bend landslide complex ♦ as. e /'s.// J C /Point irrctnte l o`— Long Point FILE No. 1442.01 active Flying Triangle landslide \ tw9"e'e gory.067"1 _____ _ .... "N.1 \ \ --41;:p. .577-o,. ' / R Insprra/ron Point pbrtuyvese Point SCAL E Az / Alit s I Lrrse of .sfr-..rc/✓r'e aec%on C9 s 40 CD e Whrtes Fictive Thrc/r a//ay.a/ defsos./s de..reed flow /ands hoe m end headserrrps Yovn9es1 /endslde ',sasses,- C/der /arsds/ide ^'asses 0/des,' /ands/rde mosses Afargirs of ac/rve Por•fuyuesc Bend comp/ex Alaryrn of So&fh Shores comp/ex h'.vss of /itad5car'p, oldest hrno's/.de crisp/ex FIGURE 1. Sketch map showing distribution of principal. landslides and landslide complexes on southerly side of Palos Verdes Hills between Point Vicente and Whites Point. Modified from map included with referenced' report by Jahns and Vonder Linden. 1973. zts�zuiw�:�a�•Fur,o:ire*:+E�:.,ut,x-�tuix'+e,.e,.xr.Karra�t::aw.y�ie��ua_�suu:,;�r��art��r:::, J ! • File No. 1442.01 March 20, 1985 Page 5 Only a few very minor cracks were observed at some locations on the interior walls of the house. Most of these cracks were near the corners of doors and windows, where ordinary shrinkage cracks might be expected to occur (see dis- cussion of shrinkage below). No cracks were observed in the acoustic materials covering the -ceiling or in ceilings with painted surfaces. No cracks were observed in the kitchen or•bathroom tiles. Doors were checked and found to be operating properly (i.e. not sticking shut or difficult to close due to distorted frames). The floors did not appear to be tilted or distorted. A few minor cracks were observed on the exterior walls of the house in the stucco. Most of these cracks were located at the corners of doors and windows, where ordinary shrinkage cracks might be expected to occur. Only a few minor cracks were observed in the concrete walkway and pool deck area. No cracks were observed in the pool shell. A fairly moderate, very linear crack was observed in the patio tile along the westerly (front) side of the house. No significant cracks were observed on the interior or exterior walls of the guest house. Bedding within bedrock exposed in the cut along the easterly side of the pad (behind the house) is striking about N25°W and dipping about 20° west. A chain -link fence located on the northwesterly descending slope was leaning somewhat downslope at some locations. It also appeared the yard area adjacent to the slope was somewhat tilted toward the slope. No features were observed on the slopes within the site that indicate the slopes have undergone, or are undergoing, any major distress due to geotechnical phenomena. DISCUSSION The house appears to be in good condition when compared to other residences reviewed by this consultant in the Palos Verdes area. Most of the cracks observed in the walls of the house are probably the result of normal shrinkage processes. The apparent good condition of the house may be becapse the house appears to be built mostly or all on cut (bedrock) as opposed to being on fill. Our observations suggest that fill materials occur along the outer margins of the pad area and not underneath the house itself. A higher degree of risk is associated with what appears to be the fill -over - natural slope in the northwesterly corner of the site than for slopes of lower height and less steepness. The portions of the chain -link fence which are leaning somewhat downslope indicate the possibility that near -surface soils in' the vicinity of the slope rave tended to move somewhat downslope as a'result of creep processes (see discussion of creep below). The slopeward tilt of the outer portion of the yard covered by lawn may also be an indication that slope yielding or creep have affected the slope. It is also possible that the yard was originally constructed that way for drainage purposes. Although no • Fi l e' No. 1442.01 ,March 20, 1985 Page 6. features were observed that indicate the slopes on the site are undergoing or have undergone any significant distress, the possibility of failures occurring on the slopes in the site area cannot be ruled out, especially with regard to the relatively high and steep, what appears to be fill -over -natural slope descending from the northwesterly corner of the pad. Because of its orientation (N25°W 20°W),'bedding within the bedrock exposed in the cut along the easterly side of the pad (behind the house) is "unsupported" in the cut. This situation is not favorable with regard to gross stability of the cut. 'As previously discussed, the situation can be compared to a deck of cards. If the deck of cards are tilted with no support given to the lower end, the cards slide off. The same thing can happen to inclined strata. If support is removed from the lower end, such as resulting from the cut, the rocks can slide. Although no features were observed in the cut that indicates it has or is undergoing any major instabilities,•the possibility of failures occurring on the cut slope cannot be ruled out. The degree of risk associated with the cut slope is greater than if the slope were not so steep and had bed- ding that was favorably oriented. To aid in further understanding of these phenomena, further general discussion is presented below. Shrinkage: Shrinkage is a normal process which occurs in most cement and plaster materials. Shrinkage generally occurs during the original curing and is a function of the original water content. Shrinkage cracks generally develop at the corners of window and door openings where stress concentrations occur, and at other predictable locations such as across the central portions of long continuous areas like walkways.: It is often attempted to limit and distribute shrinkage cracking in slab areas by providing steel reinforcement. Some level.of shrinkage cracking can be found in most homes. Although it is seldom considered a significant problem, shrinkage problems can be aggravated by other phenomena such as expansive soil or settlement. Expansive Soils: Soil with a significant clay fraction tends to possess expan- sive characteristics. Expansive soil heaves when water is introduced and shrinks as it dries. Pressures produced by heaving soil can be large enough to lift most buildings. Slabs over expansive soils are often said to "walk" as a result of expansive soil movement. This process generally tends to increase separation of slab joints and/or cause exterior improvements such as patios, originally abutting structures, to separate. Expansive soils can also cause cracking of slabs and foundations. Expansive soil tends to be active near the ground surface. The actual depth varies with specific material type and environmental' differences. To reduce the effect of expansive soil on surface structures, foundation systems are • usually deepened. Slabs and foundations are usually reinforced to increase file No. 1442.01 March 20, 1985 Page 7. their resistance to differential movement. It is usually suggested in plan- ning yard improvements and a landscape theme, that maintaining uniform mois- ture conditions around isolated individual structures is desirable. Pref- erably, soil should be kept on the moist side without allowing ponding.. Since water tends to migrate upder slab areas, saturation of the slab subgrade is usually recommended prior to placement of slab concrete. Placing trees within about 10-feet of the structures is not desirable because they tend to extract water. Settlement: To some degree all materials are compressible. Settlement occurs as a result of the stresses imposed, and most significant stresses usually result from the weight of the structure, as well as the weight of the earth materials. Settlement can in some cases.be aggravated by the introduction of water to the subsoils. Fill material and natural soil tend to be more com- pressible than bedrock materials (e.g., many "cut" areas). Accordingly, set- tlement potential usually increases with increases in the depth of fill and natural soils. Where the depth of fill and natural soil vary, the potential for differential settlement increases. The amount of differential settlement is of most concern since differential movements can result in distress. Slope Softening: This process tends to be of most concern in compacted fill areas. Fill in slope areas is generally placed and compacted near optimum moisture,'well below saturation. After construction, when additional moisture is introduced to the fill through irrigation, rainfall, groundwater and/or other sources, the fill mass increases in weight. Slight strain (i.e. move- ment) occurs in response to the additional stresses imposed. Soil shear strength characteristics are commonly reduced as moisture content increases. As this lowering occurs, strain must also occur in order to mobilize the needed shear strength to maintain stability. Practically speaking, little can be done to improve the long-term slope softening process. Although moisture content below the zone of seasonally active moisture variations will inevitably increase through natural processes, certainly attempting to limit sources of moisture introduction is desirable. This can be accomplished through maintaining good surface drainage away from structures and slope areas and by constructing slope surface drain systems. Where structures are proposed in areas which may be impacted by slope soften- ing, special foundation designs and/or special structural connections can be considered. Special foundation systems generally are more rigid systems simi- lar to the conventional reinforced systems or post -tensioned slab foundation systems utilized for resisting the potentially adverse effects of highly expansive soils, or are deep in foundation systems which penetrate material • impacted by the softening process. Structural designs must consider the lateral forces imposed on the foundation systems and must provide special con- nections for adjoining improvements. Proper planning in advance of construc- tion can do much to limit the manifestations of the slope -softening process. File No. 1442.01 March 20, 1985 Page 8 Creep: As a result of weathering of the faces of .slopes, gravitational forces, and seasonal moisture variations, the near surface soils on a slope tend to gradually move downslope. This process is usually most apparent in the top- soil profile of a natural slope. The underlying formational materials can also be affected to a. more limited extent. Compacted fill slopes, particularly those composed of expansive clayey soil, can be impacted by creep. Cut slopes exposing firm, relatively fresh formational materials tend to be least affected. Although the creep process could be diminished by flattening of slopes, specific recommendations for slope flattening to mitigate creep are not generally made. The process is commonly ignored or dealt with in areas of structures by special foundation recommendations. Recommendations generally include deepening of foundations to below creep -affected materials and designing foundations for earth pressures induced by the materials retained. Surficial Slumping: A surficial slump is a form of slope instability in which a zone of soil which generally parallels the slope face slides down the slope. The shape of the failure area generally takes the form of an oval. The depth of the affected zone is usually less than about 4-feet. The slump debris generally winds up relatively few feet below its original location, leaving a near vertical escarpment above. In natural slopes this form of instability is generally limited to topsoil profiles and occasionally a weathered portion of the underlying formational material. In manufactured slopes the problem is typically manifested in the weathered zone near the surface. Accordingly, the problem in manufactured slopes is most often manifested in compacted fill slopes composed of expansive clayey soils. Only occasionally are granular fill slopes or bedrock slopes impacted by a surficial slump type instability. The failure mechanism is con- trolled by the steepness of a slope, permeability differences, and shear strength characteristics. In order to initiate a failure, sufficient water is required to saturate the soil and cause seepage forces to develop. Surficial slumping can be triggered by periods of prolonged heavy rainfall and/or exces- sive irrigation of slopes. The potential for surficial slumping in manufactured slopes can be reduced by utilizing select materials to face slopes, by flattening the slopes, and/or by utilizing a landscape .scheme with deep -rooting plant varieties requiring lit- tle watering. Such a landscape scheme provides for limited root reinforce- ment, but -more importantly, generally results in a slope which maintains a moisture content well below saturation. For most slopes with a year-round lush green surface appearance, a near -saturated condition is maintained. Dur- ing the rainy season only relatively short periods of heavy rainfall or longer periods of light to moderate rainfall are necessary to develop the saturated soil and seepage forces required to induce failure. By maintaining plant varieties without the need for heavy watering, a margin of safety against r . File No. 144241 . `• . . March 2O, 198 ,:. , Page 9 .., ,� . ` .1 .• • Y. . 4 . • slope saturation is 4chteved and, accordingly, the likelihood of surficial slumping is reduced..' SUMMARY . The house appears to be 'in better condition than most residences reviewed by this consultant in the Ralos Verdes area. Most of the cracking observed is likely the result of normal shrinkage processes. The most significant geotechnical aspects of the site appear to be the appar- ent soil creep and slope yielding on and near the slopes in the site area, the presence of unsupported bedding in the cut slope along the easterly side of the pad, and the possibility that the site could be located within an ancient landslide complex. .It,should be realized that data in hand are•not sufficient to conclusively determine whether the site is located within an ancient land- slide complex, but the•pbs'sibility cannot be ruled out. It should be realized that a substantially .higher degree of risk is usually associated with a site located within or near a.landslide as opposed to one which is not. A risk common to all southern California areas which should not be overlooked is the potential for damage resulting from seismic events (earthquakes). Although we are not aware of any active or potentially active faults within the immediate vicinity •of the site, earthquakes generated on large regional faults (Newport -Inglewood, Palos Verdes, San Andreas, etc.) could significant- ly affect the site and possibly damage any improvements (foundations, walls, etc.) on the site. • CLOSURE . . To gather more detailed information about site conditions, subsurface explora- tion and laboratory testing could be conducted. Subsurface exploration is outside the scope .of this consulting agreement. The conclusions herein are based upon limited observations and review. No warranty of future site per- formance is expressed or implied. In the event that any signs, of distress appear in the future, this office should be contacted for review. ENGINEERING GEOLOGY GROUP (213) 738-2828 Tract/PM 75 2?4.1 Parent Tract Site Address Geologist Soils Engineer Review of: /NcN,e/-i.v6. /�1 Y✓1. �O n7 ,I ❑ Grading P.C. No. • Building'P.C. No. 2 9 � f� �a.-a �C =�� 'o ❑ Geologic Site Inspection Only P.C. No. ®'Geologic Report Dated tic) `rG'vlCc{J .�, ';��/<s R .��o-71„•,4 ,;<,/.Zi.c 'p,/R-7/6.r-I ❑ Soils Report Dated ' - - _' - - - P - 9, 1 18 7 . - • • Geology & Soils Report Dated : S ///85 6 /4/8 u '• • _S /2 '/x Q. ( AI /94 a,o 1) • ❑ Plan is geologically approved gPlan approved geologically subject to conditions below ❑ Sec 309 Code requirements met': Remarks: 1. 0 A consulting GEOLOGIC REVIEW SHEET COUNTY OF LOS ANGELES DEPARTMENT OF PUBLIC WORKS 550 SO. VERMONT AVE., LOS ANGELES, CA 90020 Lot(s) w 7 /J Location RDtd--iNg ///41—r Developer/owner ' T. R o Engineer /�. na viS PLAN CHECK NO.'OR DATE OF REPORT(S) Dist. Office • I 2• F L— NF SHEET / OF DISTRIBUTION: 'Dist. Engineer Geologist • Soils Engineer 1. Geol. Group File _ Grading Section 0 engineering geology, 0 Plan is not approved for reasons below ❑ Submit plans for recheck 2. FAH recommendations of the consulting •.• . V( geologist,."; " _ .'i soils engineer design or shown as notes on the plans. 0 3. The plan must be specifically approved by the a consultant geologist, Z'consultant soils engineer by 0 letter -report and/or manual, original signature(s) with date(s) :'; prior to approval by the Geology Group. 4. p. In -grading inspections must be made by the consulting • geologist: j8'soils engineer. .)nspection reports must be submitted to the Geology Group for review monthly. Notify Geology Group upon start of grading. 5. cp Rough grading must be approved by a • - final geology report, .: :' 0 final soils engineering report . prior to approval by the Geology Group. J An As -Built Geologic Map must be included in the final geology report. 6. Foundation and/or wall excavations must be inspected and approved by the consulting - J$ geologist, J soils engineer, prior to the placing of steel or concrete. 7 0 The County Soils Engineering Section's = 0 approval is attached 0 requirements attached 0 conditions of approval are attached 0 approval is required -- (dated 8 0 Show all proposed tentatjve corrective devices (e.g buttre ss, stability fills, subdrains, etc) on the plan. 9. Pi Add items and , above, as notes to the plan. 10. J21. The geologist (and) the soils engineer must make a finding in accordance with Section 309, L.A. County Building Code. C o •,-,17 w ; % ' i./ .-. _ / 0 `a 6 0 ,, report(s) is required must be incorporated in the /° e C a .,.., ch olb / a /� r , p f %� c G o n a�74 �, i» v ,r• % ,�[,. / / fvn,G 6 ) Cl�). 1���G nap/7 7 r G' 9 �7 /a, C ®/G✓ . L7G r!/ no � arlO•�J a.1UYs . 8 it O!` �J �7�c� d� G�'/i�rs �.• CaN+dp Ar]� �i // b. ar. ch�G' /4 T� ,..1 . e�rac... Prepared by 48-0032 DPW 4/87 `/ /,/, —��� Reviewed by Date //44/A8 COUNTY OF LOS ANGELES DEPARTMENT OF PUBLIC WORKS 1540 ALCAZAR STREET LOS ANGELES, CALIFORNIA 90033 Telephone : (213) 226-8111 THOMAS A. TIDEMANSON, Director November 9, 1987 Mr. Terrence L. Belanger City Manager 2 Portuguese Bend Road Rolling Hills, California 90274 Dear Mr. Belanger: REFERENCE: PROPOSED GARAGE ADDITION, 13 CINCHRING ROAD, ROLLING HILLS, CALIFORNIA ADDRESS ALL CORRESPONDENCE TO: P.O. BOX 4089 LOS ANGELES, CALIFORNIA 90051 IN REPLY PLEASE REFER TO FILE: As you requested in a telephone conversation with Mr. David Saltzman on November 4, 1987, enclosed are two copies of each Geologic Review Sheet written for the proposed garage addition at 13 Cinchring Road, Rolling Hills, California. Very truly yours, T.A. TIDEMANSON Director of Public Works A ,A0„. Arthur G. Keene Supervising Engineering Geologist III AGK/DS:amc Enc. Tract/ Parent Tract Site Address Geologist Soils Engineer ENGINEERINE�C� etV £ D (213) 738-2828 FEB 121981 GINEIN G 0LOGY GEOLOGIC REVIEW SHEET COUNTY OF LOS ANGELES DEPARTMENT OF PUBLIC WORKS 550 SO. VERMONT AVE., LOS ANGELES, CA 90020 Loukr 1 ? C / 11( r j' pjr A i Location lqo�/Jfl Yr ' M /!ci /7 CuIt/ 1/ . e r nc7r id)eveloper/owner Nt- r /r rriv 31./ • / it' tI r u.,i i/ " f lj T f )/r,? y‘ingineer I IT 115 PLAN CHECK NO. OR DATE OF REPORT(S) Review of: ' ❑ Grading P.C. No. /" / Z-BOilding P.C. No. z 9 0" /q /�i///i 7i, zi / ❑ Geologic Site Inspection Only P.C. No. ❑ Geologic Report Dated ❑ Soils Report Dated / eology &Soils Report Dated ) �2 /7 8 S"'' T/ 2 , (3/ / I/r/ITN//>/->r r J1 �r,� / /�,,• 1' Action: Dist. Office�.i�4 F 1%( N F SHEET 1 OF DISTRIBUTION: Dist. Engineer +� 4. Geologist Soils Engineer Geol. Group File _ Grading Section ❑ Plan is geologically approved ❑ Plan approved geologically subject to conditions below ❑ Sec. 309 Code requirements met Remarks: 1. A consulting .} 11 en ineerin geology, oilsengineering, ti y g 75) lr1[ g < / i g/� ,1/ r / rla/ <ilill Srr.jtC/ /5CV5 P/ af/i r�hnr/ q ,��- ErSfii Y� /{dy v ^ / _ � %.�: rJ �'..°d°S ,/; ` i o �/ _ t 2. II recommendations of the consulting / eologist, soils engineer (] must be incorporated in the , design or shown as notes on the plans. 3. ID -The plan must be specifically ap proved by the onsuitant geologist, . . (a.eonttlt`ant soils engineer by B, ter -report and/or anual, original signature(s) with date(s) prior to approval by the Geology Group. 4. 0 In -grading inspections must be, made by the consulting ❑geologist, (lolls engineer. 0 Inspection reports must be submitted to the Geology Group for review monthly. Notify Geology Group upon start of grading. 5. 0 Rough grading must be approved by a ❑ final geology report, ❑ final soils engineering report prior to approval by the Geology Group. 0 An As -Built Geologic Map must be included in the final geology report. 6. ❑ Foundation and/or wall excavations must be inspected and approved by the consulting_, 0 geologist, 0 soils : engineer, prior to the placing of steel or concrete. 9'f E'Xr'* t1tt /r''/ ("4//`J f'/tC .— etwit /// a� �4I:;,- ,' ipl 7. 0 The CountyEngineer Soils Engineering Section's 0 appr Sire is equi �cr�,rr�//T r require ents' �/ J- . 7^ , ;:% g g gppr va is requir❑require ents attached ; r:rl,/ /, 1,conditions of approval are attached 0 approval is required (dated ) 8. El -Show all proposed tentative corrective devices (e.g. buttress, stability fills, subdrains, etc) on the plan. 9. ❑ Add items Cam` above, as notes to the plan. 10. a geologist Er(and) the soils engineer L� must make a finding in accordance with Section 309, L.A. County Building Code. / I j �/ / I -is �� /!i C rli,/ GEi^�� 1 }Ir' (JCr _;7/., /jF FNS �' sly 1) /�7L /%[iIYF-%C1'1(r(J/�1`fJ'.'r.' '%..%':' p / ' r / ./ / r 3/2CA ;�5(/rh,ill-C/ t•-/� ,.1- li- ii%/�> te7rf.0,,,i'r; /.. �:;,'T(�,�,� 4;%/ /, • / SGC I2(P is not approved for reasons below ubmit plans for recheck I _) .Jr report(s) is required c I/'' = ' %'` • �1. j/ v,, r aI , f 1_5 e�{ s'/ r�l 1 /o flie 09114lfb,r��/r1rSc.rr6r.1 ever: (cite///'ar�y� A)ri<. cl14rr!^c�i! cT�</ Srl/S e%Jy/rrEG.K // ever:jet « RKS F j c: /, e l / l , /l:%, / t f 4',.'7/%! ( I / / �J' w `I J / e e'e; e , �� r 7 J �� (i �/ii / 'r ,c/ ,/ . ' J , 1 �rt / n //r tic 1G' 1"/i�lll /� /7 C/'%c/1// p f 7 1 ir1'; c u', � G '� �� r`-E: /`r�; �� S IT. Cc. t�difirr/ 5 � 1if � �, Cl c (f'Ef11aIre/ te;0,5CfI/t /./ t..,1` ry;cG/y/ 6' t !F/!//1!r.c/ 6`/75L_ //"c/. ie // , •- ' .,, /// // % +; , �', %iJOI'/E ` �OGJ�'G1/ 0o/ P%'/i /d J" Pl � ��/:7- Rai% f!° `j r��'�;: r-�,',T -t Cf /'/2, cf 11'h r ill l j1/ /1/U5ft te_T/ 44i) ii A,i 0. / /4 `J/r 'rS,, (0n 111/c(;,5- 01 t fir QU</11/(/7 • \Pared by 30 — PS 7-85 Reviewed by 0 / Date'.;j%(ih TFrj ENGINEERINREECC ETV £ D .' (213) .738.282EB - FEB 1.21987 Tract/AK. Parent Tract, Site Address rs < Location _ l�r Ai/Geologist'' ee /t -n ` t/1^ r � i»e/eDeveloper/owner -He'. r n Soils Engineer u� T�/7„Engineer Ver :/ % PLAN CHECK NO. OR DATE OF REPORT(S) GEOLOGIC REVIEW SHEET COUNTY OF LOS ANGELES DEPARTMENT OF PUBLIC WORKS 550 SO. VERMONT AVE., LOS ANGELES, CA 90020 Review of: ❑ Grading P.C. No. I ding P.C. No. 2 9 ❑ Geologic Site Inspection Only P.C. No. ❑ Geologic Report Dated ❑ Soils Report Dated D-Giology & Soils Report Dated Action: ❑ Plan is geologically approved ❑ Plan approved geologically subject .0 Sec. 309 Code requirements met Remarks: 1. Love .3 3/2 to conditions below /,?, vk Dist.Office F NF SHEET f OF DISTRIBUTION: / Dist. Engineer +� Geologist Soils Engineer L Geol. Group File Grading Section )• /L1'72, r/ / I/',(4411/'t r D(It yl(, Sl,.,l:,lei / / / ✓ Sr 11 «Q b fir3jan is not approved for reasons below lr"tubmit plans for recheck 1/ A consulting r r ) e" naineerina aenlnnv F7 coils engineering . r7f report(s) it required Ili i.t7r %� 1 %1,i) design or shown as notes on the plans. 3. 0-The plan must be specifically approved by the a onsultant geologist, ❑-eoostiliant soils engineer by Q:ter-report and/or anual, original signature(s) with date(s) prior to approval by the Geology Group. 4. 0 In -grading inspections must be, made by the consulting ❑geologist, ❑soils engineer. 0 Inspection reports must be submitted to the Geology Group for review monthly. Notify Geology Group upon start of grading. 5. 0 Rough grading must be approved by a 0 final geology report, 0 final soils engineering report prior to approval by the Geology Group. 0 An As -Built Geologic Map must be included in the final geology report. 6. 0 Foundation and/or wall excavations must be inspected and approved by the consulting_ 0 geol gist, 0 soils , engineer, prior to the placing of steel or concrete. /'r EY` a rrr / �". ,, ; f.;,' 11'.•/c f;•� '1, ,:- 4 v4yr /Ior 'r,:j .e la ,. •``, 'ir r,( L0�1 °✓�r r r ?/J%l , 7. 0 The County Engineer Soils Engineering Section's 0 approval Is required / ❑ requirrement's' attached S ;; : r, onditions of approval are attached 0 approval is required (dated 8. 9. 10. // ❑ SJow all proposed tentative corrective devices (e.g. buttress, stability fills, subdrains, etc) on the plan. -items Ad , above, as notes to the plan. he geologist 0---(and) the soils engineer 19 must make a finding in accordance with Section 309, L.A. County Building Code. V37/1 (.0 G�rl.l, r�, i(c/r%/ 51 /)r-rill; 5, : !:L 4/,r9..1r;?1 ,/,..7;! / .V l i m `, �` f ) /:/ // / t/c t' r -): /' ( ' i' ( / 11 / a' /'5 �1,.�. •, it I t %I �r�l' ..b) (-i,, - 1 (l1 l �/'f. '//i! ;/ /cam(/ll` IS/q'.5 j e,-- (: /J//. =iLJ%1ii/ [ //%cn -C Ci/73 {• it( c c, - =-. r r 7ri / /1/i<c e..'/' S : / ' /.`-!'i ;.% A), /"11n/' Ev 4_oC4,,o // e/7 /`(/)o.-i; •,.:olr, 1 •'4� „ �.. arc%%. //2/,- r,l�z-�; li!/fl � /�>� i<y,.: i� r�rr l (% 11 1 / 1011 5 O 1 t 19 C/ l /e/ / 1 r `.) r \Pared by 30 — PS 7-85 Reviewed by 1-� / r / JP(?iC I/•!/ r7, r Date 2; 4/(56 � r this t/.iZ• ENGINEERING GEOLOGY GROUP (213) 738-2828 Tract/PM Parent Tract oC . 4 Site Address lie l .� �/ n etc?. ? / Y Geologist # //O •% Ca 6r !! it GEOLOGIC REVIEW SHEET COUNTY OF LOS ANGELES DEPARTMENT OF PUBLIC WORKS 550 SO. VERMONT AVE., LOS ANGELES, CA 90020 ,,1 /tr �, 6t Weer it C;t+%/ai7 �l�/4f %j / e/ hi Engineer . 1Z i V C Soils Engineer Action: t T ❑Grading P.C. No. ❑Building P.C. No Lo" /r �f Location ar 17, Developer/owner ,.j PLAN CHECK NO. OR DATE OF REPORT(S) ❑Geologic Site Inspection Only P.C. No. ®Geologic Report Dated ❑Soi eport Dated • • eology & Soils Report Dated P lr Dist. Offic lZ �. ! * F NF SHEET / OF DISTRIBUTION: Dist. Engineer Geologist Soils Engineer j_ Geol. Group File _ Grading Section - }-< A/• /9df2, &1/- r ❑Plan is geologically approved Ian ' of approved for reasons below ❑Plan approved geologically subject to conditions below mit plans for recheck ❑Sec. 309 Code requirements met (not met) 41- ti; e, o'f- ha" hi I) la fkl-hAYPekri • , r 14 jefi1 fa ���E' /to v/eef �, he «- o Ik e 105y 6 i$ ..t.9o4hcpia4 ;/19 /tri,1611/ .repo/.715 ('r 1 (/ 4c-,1 t/ic loos bike /eel/ s / ee4I I �i/ %r , er CCP Mpet-MIIV h I /1 eirt/ 4 re en (.2 fe /gal ( f5/der, /C Ff/i /G cu Prepared by _ 76G30A Reviewed by Date 2. 3—/ 7 T)�r✓ L'114v4//aI/E'_4t -tips rill( ENGINEERING GEOLOGY GROUP ✓✓✓✓ (213) 738.2828 Tract/PM Parent Tract �43 GEOLOGIC REVIEW SHEET COUNTY OF LOS ANGELES DEPARTMENT OF PUBLIC WORKS 550 SO. VERMONT AVE., LOS ANGELES, CA 90020 Loor Site Address 1(% x? (/ YI chi', 19 /./,, Location Geologist n 1/F t� d! .kC h, Developer/owner Soils Action: Engin eer IG;yjreri7 �qr�t%j lee �j j Engineer . %�1�ts t �J�///� PLAN CHECK NO. OR DATE OF REPORT(S) -V , ❑ Grading P.C. No. ❑Building P.C. No. ;4¶ 5 / 114,1/7i,;/4.7 ❑Geologic Site Inspection Only P.C. No. DGeologic Report Dated ❑S2j eport Dated eology & Soils Report Dated Dist. Offic 12/ F NF SHEET / OF DISTRIBUTION: 2 Dist. Engineer Geologist Soils Engineer Geol. Group File — Grading Section // /Er= Pi A/ /9I ❑Plan is geologically approved ❑Plan approved geologically subject to conditions below ❑ Sec. 309 Code requirements met (not met) Ian ' of approved for reasons below bmit plans for recheck e. 1/Ve. 0f /h f (1/1111/914e " %S ie /(; !di) 6.? 74-/7 it t/1-6..' Vet; )7) c //ey lc 6'/1t' .1,11 $ ; - O12/' iia41 /ir) t t'i ,v .re p o/r4 «T)) wv 4(.4 thc la. ,/s hn Pt- f,E e /1 SAPI/ //�'/,/4 / ,5 a CC m "col') czht P/ /15' etic 2 fe 4;1 /2 0 I Cc '/5 /6 pier /C ,1 F JIB //5 4 tie (:-.--pc/9/ c >1 Prepared by 4); 76G30A - Reviewed by Avii/L 21 4 Moc Date ENGINEERING GEOLOGY GROUP .C) (213) 738-2828 Tract/PM Parent Tract Site Address Geologist Soils Engineer Review of: Action: 343 r1-1/7 GEOLOGIC REVIEW SHEET COUNTY OF LOS ANGELES DEPARTMENT OF PUBLIC WORKS 550 SO. VERMONT AVE., LOS ANGELES, CA 90020 Lot(s) 141 jf rL dr Engineer /f .Developer/owner PLAN CHECK NO. OR DATE OF REPORT(S) 4Grad' . No. / A /_' uilding P.C. No. 7 56`r_d_ope. _/ 10 J/ ❑Geologic Site Inspection Only P.C. No. ❑Geologic Report Dated ❑Soils Dated _ eology & Soils Report Dated 6'' �Lycc�--Ir ° V•. 54 7 ,/' )/ Dist. Offige Z, F L NF SHEET / OF / DISTRIBUTION: 2Dist. Engineer 4_ Geologist Soils Engineer T Geol. Group File Grading Section ❑Plan is geologically approved Plan is not approved for reasons below ❑Plan approved geologically subject to conditions below ubmit plans for recheck ❑Sec. 309 Code requirements met (not met) k g/. Cry W f q pv e-- iteV'ftv/ rerP/4'R/di��trsr2 t ilePiel yl .,g Ai Ocargie. i$ D rj l YlIE / / Ile P tip__ TO,4 4yye'"c i,r i/.1- fites6,-/S-S 4beyg-rE 1.>>e ems/ "top2 _ / < , SAtd. Jfc/2/zJ/9q et� tfe.�/e �,fC�,�S��n�E �� I yl� CFC C��G E� iE�,v �,1 lh;5 /`�? .1/¢iv ci 9 ,, �6 h, I s�j' j j to l e-rla 0k i £ f r.te r�;po / tt; 174 r 111 4/ IC Ce:Te et tepiaftb 146 j .4 //-slf/i/ re/A,�4 ill r."numtyc,1y, 3 f. 7/er,recrilcii Viol 0 of 11,e_ tyr it f na 1; y 3 tvet6 Efr6t;cci. A; 04; .,3 loclue h y olefin',%1.S, ra1): 74e vlf 9eo ey Atl'/9 4Ye' [• - S,-<1i1 1 )'-',7 Con,9lchile r/ eri,t-p-// i7t et- 1ha,, 4,ceson/4y , ,>, , C.1l h e� 3 CC�%�1 t 5 of et For/ .slice= t'f�/ ve loci/the ... / [' . e Lj/161 Qi'' a 572�,f�,/l y an�J/L is %Ill 4i' ref UjjtW i 1 ik7 o >• 4 fki dc r` 1, i 5 it 714 erf 4)--- kt /,s5- or 1, ' • I'%, 3_1 /1 - 1 Prepared by 76G30A - 41412. a Reviewed by Date 7 ENGINEERING GEOLOGY GROUP (213) 738-2828 -/ Tract/PM Parent Tract Site Address Geologist Soils Engineer 63 Review of: ❑Gradi . No. uilding P.C. No. Action: GEOLOGIC REVIEW SHEET COUNTY OF LOS ANGELES DEPARTMENT OF PUBLIC WORKS 550 SO. VERMONT AVE., LOS ANGELES, CA 90020 Lot(s) s7� Location, d Developer/owner ✓ , rt C / Engineer fir lOct V i C PLAN CHECK NO. OR DATE OF REPORT(S) ❑Geologic Site Inspection Only P.C. No. ❑Geologic Report Dated ❑Soils Dated eology & Soils Report Dated c_ifiv/ / • y / /El /7 / Dist. OHO 2, 2- F L/ NF SHEET / OF DISTRIBUTION: - Dist. Engineer 4- Geologist Soils Engineer Geol. Group File — Grading Section ❑Plan is geologically approved ifPlan is not approved for reasons below ❑Plan approved geologically subject to conditions below Smit plans for recheck ❑Sec. 309 Code requirements met (not met) i 1. Ce cif vt—tQvitivtte o p,'t1TpPe1/rs f) k Lowill'Ate //,exanv�� a. 2 �Cl Drl . %iiE ti tle. Q E f ,t /l E=hc11�- ia/d.i filteSe7-1771 7/E 1 /e f e �c ///1 `= tr vit.) �, AaJe• -sv1,',a 4 trfryekte erry nT r44. 4bOltc6'E�--r41.-ici 4 ; V f re./1/ 2, ficsi/ p/$ 6 711 t h e C Fr/C ;fI(E v;ems' SA f 7/ 2/.//9 ie zL l- 11i is r Oil Q Gt/ c� /,tc,,»v1k5 ,t 5 76 ) I i i�1 i l >I. to & m2 e k r rf. �l i6 re ipt''1 e/ tb tie In aicz-7��4 Ks/4 t€/ 7 fs Iltyc So), .7 i / f/cam rec hC//d c,1 ©f t (LE or� J /n�/11? .S hit 1 , i./c i3 A 1,9:i 10 1 J .,t ..y �R 1'i1,� l ve1 P G � (// 1/ �E' n'I l� 1i.s ,/ y`Gl / J�J f t <S I t , e C�y j tit 41 1 �G C 0 /7,51e/ f& /Jul t P'-e y lt/e)/` ih rtii ,/�� e5�''�7� �� tom,/�".l C.t ��eet 3 CCU 1�'S of a For ..�/kit, tvio�'e/t- lei% ll E G:`/d4i It 672t!l/fit, 4 I/GL/tp%s 1401 ,k, te I tij ts 170 5A 0 1.11 4 fii tic,- t'f 5tifS 4 /eq. .5t/t5— 0r titeds --- r, r0,),-4. , ✓ �}/_�1 '- ( / . ` i►. Prepared by 76G30A - 1 i.a..; Reviewed by Date ! /-5? ZEISER GEOTECHNICAL, INC. September 29, 1987 PN 87163-1 Mr. Terrence L. Belanger City Manager City of Rolling Hills 2 Portuguese Bend Road Rolling Hills, CA 90274 Subject: Third -Party Review, Reports and Published Literature Related to Proposed Garage Area Addition, No. 13 Cinchring Road, City of Rolling Hills, Los Angeles County, California Dear Mr. Belanger: In accordance with your request, we have reviewed three geotechnical reports and published literature related to the proposed garage area addition at No. 13 Cinchring Road, City of Rolling Hills. The first two geotechnical reports entitled, "Limited Geotechnical Review, #13 Cinchring Road, City of Rolling Hills, CA", dated March 20, 1985 and "Geotechnical Engineering Report, Proposed Addition, No. 13 Cinchring Road, Rolling Hills, CA", dated June 1, 1986, were prepared by American Geotechnical, Inc. for the property owner, Mr. John Rawlins. The third geotechnical report (with accompanying review response letters) was entitled, "Geotechnical Investigation, Tentative Tract No. 26343, City of Rolling Hills, County of Los Angeles, California, For Messrs. Adams, Rustad and Shaver", dated May 28, 1969, and prepared by Geotechnical Consultants, Inc. The purpose of our third -party review was to determine if the geotechnical data from the two subject reports for the proposed addition as well as from related published literature had been competently analyzed in terms of constraints and opportunities affecting the proposed addition. During the course of this review, we reviewed the following published literature: Woodring, W.P., et al, 1946, Geology and Paleontology of the Palos Verdes Hills, California, U.S.G.S.Professional Paper 207. Merriam, Richard, 1960, Portuguese Bend Landslide, Palos Verdes Hills, California, The Journal of Geology, Vol. 68, No. 2. Johns, R.H. and Vonder Linden, K., 1973, Space -Time Relationships of Landsliding on the Southerly Side of the Palos Verdes Hills, California, in Geology, Seismicity and Environmental Impact, Special Publication, Association of Engineering Geologists. 2900 S. Bristol Street Suite B-205 Costa Mesa, CA 92626 (714) 754-1127 Mr. Terrence L. Belanger City of Rolling Hills September 29, 1987 Page two PN 87163-1 In addition, a site reconnaissance of the subject property and surrounding areas was conducted by us while in your company on September 2, 1987. DISCUSSION The following discussion is a review of the available literature and reports. A review of the published literature by Merriam confirms his stated contention that an ancient landslide area with amphitheater -like scarps exists northerly of the Portuguese Bend landslide complex just south of Crest Road in the vicinity of the abandoned Crenshaw Boulevard. Jahns and Vonder Linden later extrapolated the ancient landscape scarp toward the northeast in the vicinity of the head of Klondike Canyon, in the process identifying the now -reactivated ancient Flying Triangle landslide. However, a noticeable break in the theorized scarp trace can be observed in the approximate vicinity of No. 13 Cinchring Road. This feature is a southwest -trending crestline currently referred to as Flattop Ridge. The crestline has a geomorphic pattern which suggests present stability, while bordered by areas of instability. The crestline, which is orthogonal to the scarp, is a continuous landform with no apparent scarp trace. In other words, the subject crestline area appears as an island in the surrounding areas of exhibited instability. The underlying bedrock materials are inclined in the same direction and in similar inclinations to the adjacent slide complexes. The geotechnical consultant of record has correctly identified the parameters as they affect the property and proposed addition. These criteria are: (1) the existing structures and fill pad are underlain by Monterey Formation hale that is generally adversely oriented where measured, with trends from N10 W to N45°W and shallow inclinations from 15 to 20 degrees to the southwest; (2) substantial improvement to the site geologic conditions does not appear feasible within the confines of the subject lot due to the deep-seated and large areal nature of the potential instability; (3) the house exists and appears to be performing well; (4) the proposed addition would be a non- critical structure that would not affect the present level of site stability; and (5) a Code Section 308 waiver appears to be a viable opportunity to secure the needed building permit in view of the property owner's knowledge of site conditions through the commissioned geotechnical reports. CLOSING The geotechnical consultant of record for the proposed addition, in our opinion, appears to have performed a geotechnically competent investigation. The report has identified potential constraints and opportunities affecting the proposed addition. The potential possibility of active instability involving the site has been discussed, analyzed, and explored to the degree possible for a single lot investigation, in light of the area conditions. Mr. Terrence L. Belanger City of Rolling Hills September 29, 1987 Page three PN 87163-1 In summation, our review of site conditions has lead us to conclude that the proposed addition is justified, provided the Code Section 308 waiver is properly filed. If you have any questions do not hesitate to call. Respectfully submitted, ZEISER GEOTECHNICAL, INC. Frederick L. Zeiser Principal Geologist C.E.G. 1131 Expires 07/31/88 FLZ:RCK:jr regarding the content of this review letter, please c. Roy C. kroll Senior Project Geologist C.E.G. 1328 Expires 06/30/88 a