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none, SFR relocation, Studies & Reports, • 0 KEITH W. EHLERT Consulting Engineering Geologist February 3, 1999 Project No. 2250-99 Ms. Marion Busia Remax Palos Verdes 65 Peninsula Center Rolling Hills Estates, CA 90274 SUBJECT: GEOLOGIC REVIEW Relocation of Existing Structure #6 Running Brand Road Rolling Hills, CA Pursuant to your verbal request, this report of a geologic review regarding relocation of an existing house at #6 Running Brand Road in the City of Rolling Hills, Los Angeles County, has been prepared. If you have any questions regarding the information presented in this report, please contact my office. Re-pectfully submitted, it alifo Califo gineering Geologist 1242 ologist 3982 27520 Hawthorne Boulevard, #220 • Rolling Hills Estates, CA 90274 (310) 544-7686 • Fax (310) 544-9332 • • P. N. 2250-99 Page 1 INTRODUCTION PURPOSE The purpose of this report is to present information pertaining to the geology at #6 Running Brand Road relative to relocation of an existing house. The site is located within the active Flying Triangle landslide. The existing house is presently on steel beams. The southerly portion of the house is presently "overhanging" a near -vertical landslide scarp that is an estimated 15 feet high. It is understood that it is proposed to move the house about 20 feet northerly (so that the southerly portion of the house does not overhang the scarp). SCOPE OF WORK The scope of work performed during this review included the following: • Two site visits to review site geologic conditions and perform reconnaissance geologic mapping. • Review of geologic maps of the Flying Triangle landslide and review of reports pertaining to the landslide. • Evaluation of data gathered. • Preparation of this report with map to present the findings. • • P. N. 2250-99 Page 2 GEOLOGIC OVERVIEW AND SITE CONDITIONS, The site is located within the active Flying Triangle landslide. The Flying Triangle landslide is a slow -moving massive landslide that has been active since about 1980, and possibly before that time. The portion of the landslide encompassing #6 Running Brand has been named the "Main Mass" portion by Los Angeles County. The southerly portion of the house is presently "overhanging" a near -vertical local landslide scarp. Reconnaissance mapping indicates that the scarp is a result of secondary movement into Paintbrush Canyon to the southwesterly. I reviewed the site in 1990. At that time, the house was on steel girders and was in relatively good condition. Cracks were present on the slope that descends southerly and southwesterly from the area of the house. These cracks were approximately coincident with cracks shown on a 1987 map of the Flying Triangle landslide obtained from Los Angeles County. Since my 1990 site visit, a scarp has formed under the rear of the house and at the present time the rear of the house is partially overhanging the scarp. Some of the steel beams are being supported by wood cribbing resting near the base of the scarp. Figure 1 is an enlarged copy of a portion of a map of the Flying Triangle landslide obtained from Los Angeles County. The map was prepared in 1987. The hachured lines represent scarps/fissures that were present at that time. Based on my recent reconnaissance mapping, the present scarp that the southerly portion of the building is presently "overhanging" is in approximately that same location as the scarps/fissures shown on the 1987 map. Based on my reconnaissance mapping, the easterly portion of the scarp is a few feet further north than shown on the 1987 map. This is attributed to local sloughing along the scarp. • • P. N. 2250-99 Page 3 I did not observe any features (i.e., fissures, ground cracks, etc.) that in my opinion indicate the scarp has significantly progressed northerly. I did not observe any fissures or other features northerly of the house that indicate the scarp is "migrating" northerly. As previously indicated, the scarp is approximately in the same position as indicated on the 1987 maps (Figure 1). • • P. N. 2250-99 Page 5 DISCUSSION There is little doubt the Flying Triangle landslide will continue to move. It is a relatively slow moving landslide. If the head of the local landslide (at the base of the scarp) moves further downward, it is likely that the wood cribbing will no longer support the steel beams at the rear of the house and the house will likely suddenly fail. It is my opinion that the house should be moved a minimum of 20 feet northerly of its present location. If this is not done, there is a significant risk of the house suddenly "falling" downslope. It is my opinion the risk of the scarp progressing northerly is very low. Based on the 1987 map, the scarp has not moved northerly except for local sloughing. It is my opinion that moving the house northerly will not have an adverse impact on the Flying Triangle landslide and will not have an adverse impact on neighboring properties. The house should be moved immediately. If heavy rains occur within the next few weeks, the house could suddenly fail. The purpose of this review is to provide recommendations with regard to preventing sudden failure of the house. No warranty of future site performance is expressed or implied. The possibility of the scarp eventually progressing northerly or fissures occurring at other locations on the site cannot be completely ruled out. However, based on the data in hand, it is my opinion that the risk of this occurring is very low. If any information presented in this report is not clearly understood or questions arise with respect to the information presented, this consultant should be contacted. • • I IZI vim PALOS VERDES MuSE8 Engineering RE/MAX Palos Verdes/2-98-729 February 5, 1999 Page 2 DISCUSSION AND RECOMMENDATIONS At the time of our inspection on January 13, 1999, several photographs were taken at the site. These •photos are retained in our office file, but may be made available at your request. You were present during our inspection as was Mr. Keith Ehlert. After reviewing the history of this property and observing the present condition, we believe that the immediate relocation of the house and its steel girders supports twenty feet northward is essential. The present location of the house close to the descending scarp is unstable, and likely will cause collapse or failure of the house if the house is not moved immediately. The recommendations of Keith Ehlert in his report dated February 3, 1999 concur with this opinion and should be used in conjunction with this structural engineering report as part of any review by government agencies. This report is based solely on a visual inspection and is limited to the stated areas of concern. Other conditions affecting this or other properties that were not inspected, accessible or anticipated are beyond the scope of this report. Services performed by this firm, at the subject site, were conducted in a manner consistent with that level of care and skill ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions. No other warranties are expressed or implied. Please do not hesitate to call if you have any questions or require further information. Very truly yours, PALOS VERDES ENGINEERING CORPORATION John O. Schuricht, Presiden Structural Engineer 2391 JOS:sh • • ®®® PALOS VERDES Engineering RE/MAX Palos Verdes/2-98-729 February 5, 1999 Page 2 DISCUSSION AND RECOMMENDATIONS At the time of our inspection on January 13, 1999, several photographs were taken at the site. These photos are retained in our office file, but may be made available at your request. You were present during our inspection as was Mr. Keith Ehlert. After reviewing the history of this property and observing the present condition, we believe that the immediate relocation of the house and its steel girders supports twenty feet northward is essential. The present location of the house close to the descending scarp is unstable, and likely will cause collapse or failure of the house if the house is not moved immediately. The recommendations of Keith Ehlert in his report dated February 3, 1999 concur with this opinion and should be used in conjunction with this structural engineering report as part of any review by government agencies. This report is based solely on a visual inspection and is limited to the stated areas of concern. Other conditions affecting this or other properties that were not inspected, accessible or anticipated are beyond the scope of this report. Services performed by this firm, at the subject site, were conducted in a manner consistent with that level of care and skill ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions. No other warranties are expressed or implied. Please do not hesitate to call if you have any questions or require further information. Very truly yours, PALOS VERDES ENGINEERING CORPORATION John O. Schuricht, Preside Structural Engineer 2391 JOS:sh 02-11-1999 02:19PM FROM MATERIALS ENGINEERING TO 913105305482 P.01 I4ngeles County Department of Public?Work- Dist, Office 12.0z SheeLt lot Z MATERIALS ENGINEERING DIVIS(UT F /. NF ____ L GEOLOGIC REVIEW SHEET ' .! REVIEWERS CALLING HOURS: 900 S. Fremont Ave., Alhambra, CA 91803 8:00-9:04M & 3:00-4:0OPM MON-THURS • TEL. 1626) 459-4925 FAX. (626)458-4913 • Tract/MI Lot(s) Parent Tract • ' Location Rolling Hills Ste.Addrpss . #6Runninabrand Rae Geologist' Keith•EhIert: Developer/owner.(darinn EMIR, Geotechhical Engineer NA Engineer/Arch. :NA; Review of: For: Relocation of Eicistino Structure Geologic Report(s) Dated _2/3/99 Action: • • DISTRIBUTION District Office Geologist Geotechnical Eng. 1.,_ Section File Grading Section _ Process Center Our staff has reviewed the submitted engineering geology report by Keith Ehlert dated 2/3/99 and other supporting documents.. The consultin engineering geologist has not indicated that the relocated structure will be free from Iandsliding, settlement and slippage (required by Section 111 of the LA County Building Code). The consulting engineering geologist indicates, in his report, that the possibility of the:scarp eventually progressing northerly (towards the relocated struciture) can not be completely ruled out. Our recent site visit land the District Engineer's (Ms. Lata Thakar) letter dated 10/26/98 indicated that the proposed location of the structure is currentlyII undergoing substantial movement. • It must de noted that the entire area is underlain by a very large global landslide. The subject area is also underlain by a smaller local more active landslide that is failing into the canyon west of the subject property. Failure of the high scarp, underneath the existing structure, should be anticipated. This failure will result in a new scarp north of the existing one. This new scarp could be located in the area lof'the proposed relocated structure. • • • red Revie d by Date February 11. 1959 'NOTICE; Public safety, relative to ge'atechnical eub'surfa exploration, shall be provided In accordance with current codes for excavations, inclusive :of the Les Angeles County Code, Chapter 11.48, and The State of California, Title 8, Construction Safety Orders. 48.005'2 6/22/98 F-RS:Form.6 TOTAL P.01