CITY OF LOS ANGELES DEPARTMENT OF PUBLIC WORKS BUREAU OF ENGINEERING GEOTECHNICAL ENGINEERING GROUP (GEO)

Transcription

1 CITY OF LOS ANGELES DEPARTMENT OF PUBLIC WORKS BUREAU OF ENGINEERING GEOTECHNICAL ENGINEERING GROUP (GEO) GEOTECHNICAL REAL ESTATE DISCLOSURE REPORT MASTER REPORT FOR CITY OWNED LOTS 15205, 15209, 15213, 15217, 15221, 15225, DE PAUW STREET, PACIFIC PALISADES, CA W.O. E170213F GEO FILE # NOVEMBER 4, 2009

2 TABLE OF CONTENTS GEOTECHNICAL REAL ESTATE DISCLOSURE REPORT CITY PROPERTIES DE PAUW STREET 1.0 INTRODUCTION PURPOSE SCOPE OF REPORT GENERAL SITE LOCATION AND DESCRIPTION OF PROPERTIES HISTORY AND BACKGROUND PHYSIOGRAPHY POTRERO CANYON HISTORY REVIEW OF RELEVANT RAP RECORDS RELATING TO POTRERO CANYON GRADING IN THE AREA OF THE DE PAUW STREET PROPERTIES HISTORY OF DEVELOPMENT AND GEOTECHNICAL EXPLORATION OF DE PAUW STREET GEOLOGY GEOLOGIC SETTING EARTH UNITS GEOLOGIC STRUCTURE GROUNDWATER SEISMIC HAZARDS PROPERTY WALK-THROUGHS REAL ESTATE DISCLOSURES REQUIREMENTS FOR GEOTECHNICAL INVESTIGATIONS WITHIN CITY OWNED PROPERTIES LIMITATIONS REFERENCES Appendix A: Figures 1-20 Appendix B: De Pauw Street Photos 1-22

3 GEO File No W.O. E170213F Page 1 of INTRODUCTION The City of Los Angeles provides this report of geotechnical real estate disclosure in response to a request from the Department of General Services Asset Management Division. This geotechnical disclosure report is based in part on review of readily available geotechnical records and reported data from past geologic subsurface exploration and geologic mapping by others in the immediate vicinity of the seven City owned properties covered by this report, 15205, 15209, 15213, 15217, 15221, 15225, De Pauw Street, Los Angeles, CA also know as lots 5 through 10 and B respectively. 2.0 PURPOSE The purpose of this report is to provide geotechnical information compiled for the subject properties and to make the buyer aware of the overall geotechnical condition of the properties. This disclosure is not a guarantee of any kind nor does it take the place of a thorough geotechnical investigation or warranty the buyer may wish to obtain. This disclosure report is a summary of readily available geotechnical information concerning the subject properties for the purpose of disclosing such information for the real estate transaction. 3.0 SCOPE OF REPORT This report is based on document review, visual site observation, review of readily available documented subsurface investigations and past grading work on or adjacent to the properties. Tasks completed in the preparation of this report included: Review of readily available aerial photographs, past and current; Review of published geologic maps and reports of the site area contained within Geotechnical Engineering Division (GEO) files; Review of readily available relevant documents on file at the City of Los Angeles Department of Recreation and Parks (RAP); Review of geotechnical reports specific to the individual lots obtained from the City of Los Angeles Department of Building and Safety (LADBS) files; Site observation and reconnaissance of adjacent areas. This disclosure is based on what the City of Los Angeles is aware of and available to the City at the time of the preparation of this report. It is recommended that prospective purchaser(s) of the properties obtain consultation from a qualified California State licensed engineering geologist regarding potential geotechnical hazards that may affect the properties.

4 GEO File No W.O. E170213F Page 2 of GENERAL SITE LOCATION AND DESCRIPTION OF PROPERTIES The seven properties covered by this report are located on the northeastern side of De Pauw Street approximately 400 feet east of the intersection of Lombard Avenue and Earlham Street in the Pacific Palisades community of Los Angeles. All of the lots are currently vacant. The back of all the lots face northeast to southeast into the north central portion of Potrero Canyon, the bottom of which is 54 to 60 feet below street grade in the area. The lot dimensions for all the properties are approximately 50 feet wide at the street and wider on the canyon side, and 150 feet deep with an area exceeding 7,500 square feet. The lots are relatively flat for approximately 25 feet from the street then descend a roughly 2:1 (horizontal:vertical) slope to approximately 8 feet below street grade to a level pad for the remainder of the lot. The lower pad of the lots contains numerous small stockpiles of soil. Past the property line at the rear of the lots there is an approximately 2:1 (horizontal:vertical) slope that descends approximately 50 feet vertically towards the floor of Potrero Canyon. The western property line of the properties is setback approximately 20 feet from the street. The eastern property line of the properties is directly above or adjacent to an unpaved access road above the canyon. Past grading in the area of the lots consisted of placing fill to create a level pad in the 1920s tract development, and the construction of a buttress fill at the rear of the lots in the 1990s as a part of a slope reconstruction during canyon grading for park development. The existing conditions from an aerial view (as of 2006) of the lots along the relevant section of De Pauw Street with addresses, lot numbers, and topography are shown in Figure 1. More detailed descriptions of the individual City owned properties are included in Section 7.0 of this report. 5.0 HISTORY AND BACKGROUND 5.1 Physiography The properties rest on a relatively flat marine and non-marine terrace that was dissected by fluvial processes that formed Potrero Canyon downslope at the rear of the properties. Potrero Canyon is a southwest draining canyon which trends across the Pacific Palisades area immediately north of Pacific Coast Highway (PCH). In this area, PCH trends northwest. Immediately south of the highway is Will Rogers State Beach. The relatively flat marine terraces bounded by the steep cliffs or palisades above the canyon have been developed as residential areas. Backyards of the residential areas are open to the relatively steep canyon slopes or, in the case of much of Potrero Canyon, graded 2:1 slopes. Unlike the neighborhoods above, there are no housing developments or public streets in the bottom of Potrero Canyon. The canyon walls of Potrero Canyon became over steepened in the past due to undercutting by the preexisting blue line stream at the canyon bottom, which led to surficial failures and landslides in the canyon in recent geologic history. The major landslides within the canyon were numbered as part of a canyon wide geotechnical exploration in For the purposes of this report the numbering system has been retained and included as

5 GEO File No W.O. E170213F Page 3 of 31 Figure 2 for reference. As indicated on Figure 2, Slide 2 was a mapped landslide adjacent to the lots covered in this report. 5.2 Potrero Canyon History In 1922 development of the eastern Pacific Palisades started with installation of water lines and construction of roads (Moran et al, 1959). Road grading on the mesas above the canyon began in the early 1920 s (Buckley, 1987). Based on a review of available airphotos, the grading of the tract surrounding and including the properties was complete by The airphoto from 1929, Figure 3, shows approximately 10 houses on the west mesa above the rim of Potrero Canyon. The 1929 canyon itself appears in its natural state. In the area east of the properties, the airphoto shows what appears to be the remnant of a ravine with the upper portion of the ravine approximately 60 feet from the road. At the time, the canyon bottom was approximately 170 feet below the level of De Pauw Street. In 1939, sanitary sewers were installed on the bluff (Moran, et al, 1959). Moran et al, 1959, mentions slope stability problems in Potrero Canyon, citing that filling of the canyon had been considered by the City of Los Angeles and private interests in order to stabilize slopes and provide a recreation area. At that time, the City was interested in possibly using the canyon for a disposal area for solid refuse, street sweepings and excess soil. The west rim of Potrero Canyon became densely developed in the early 1950 s. During this time Slide 3 (refer to Figure 1) reactivated and reportedly damaged a residence on De Pauw Street (KBA, 1986). In 1959 an extensive geotechnical exploration of a wide area of Pacific Palisades was conducted by Moran, et al that studied the landslides of the area (Moran et al, 1959). The report studied the slides within Potrero Canyon with piezometers and slope indicators. The study determined that the slides were caused by the groundwater flow regime, weak earth materials, and over-steepening of the canyon walls by stream erosion. It was recommended that the canyon be filled with 40 feet of fill and a storm drain installed. The slides were recommended to be allowed to erode to point of selfstabilization. The canyon was purchased by the City of Los Angeles in the 1960 s with the intention to utilize the canyon as a southern extension of the existing Palisades Park (Buckley, 1987). The City then initiated several studies to determine best course of action to create useable parkland and improve the stability of the slopes within the canyon. In 1979, several pre-existing ancient landslides became active and threatened upslope residences (KBA, 1990); among them was Slide 2 which occurred downslope of the subject properties. Figure 4 shows Potrero Canyon in the area of Slide 2 from the air shortly after the slide damaged several homes. Slides 2 and 3 reactivated and created

6 GEO File No W.O. E170213F Page 4 of 31 an earth dam at the floor of the canyon. Subsequently, a small lake, shown in the photos in Figure 5 near Slides 2 and 3, formed that accelerated movement of the slides causing headward retreat of the slide scarps. This headward retreat endangered three residences on De Pauw Street (KBA, 1986). Grading to the present day configuration is described in the section below. 5.3 Review of Relevant RAP Records Relating to Potrero Canyon Grading in the area of the De Pauw Street Properties The following is a synopsis of information from relevant, readily available documents regarding the grading of Potrero Canyon in the area of the subject properties subsequent to the 1979 slides described above. A June 3, 1986 report by Kovacs-Byer and Associates Inc. (KBA) summarizes the results of a study done for the RAP that addressed stabilization of existing landslides in Potrero Canyon to develop a recreational area. Kovacs-Byer, under the direction of the RAP, was selected to oversee the landslide mitigation and filling of the canyon. During the course of researching the grading work within Potrero Canyon, GEO has located and reviewed several interim compaction reports, memorandums, and letters, however, no records of in-grading geologic mapping have been found. The canyon stabilization project was proposed to be conducted over several phases. The first phase primarily consisted of controlling the flow of groundwater by the installation of a storm drain and subdrain system in conjunction with horizontally drilled drains, or hydraugers. The canyon bottom was proposed to be filled to a depth of 75 feet with stabilization slopes constructed in the areas of sliding. The storm drain, subdrain, and planned fill detailed in the 1986 report have all been essentially completed in the area of the subject lots at this time. The 1986 exploration study conducted slope stability calculations that Byer concluded made it, reasonable to assume that the proposed canyon fill, remedial grading, and subsurface drainage system will provide engineered fill slopes on the west side of the Potrero Canyon with a factor of safety in excess of 1.5. Stabilization of the landslides will be achieved. (KBA, 1986). It was recommended that the upper 5 to 10 feet of the slide debris be removed during grading to limit future infiltration of water into the slide masses left in place. Based on consolidation testing of the slide debris samples, Byer concluded that the debris is, not subject to excessive consolidation. (KBA, 1986). Byer determined that, deeper removals will not be necessary due to the well consolidated nature of the slide debris. As part of the 1986 exploration study, KBA drilled five borings within and adjacent to Slide 2. The locations of the borings are shown here on the geologic map in Figure 6 and the relevant cross sections are shown as Figures 7 and 8. Three bucket auger borings were drilled, B-10, B-11, and B-13. Boring B-10, drilled on the south side of Slide 2, encountered slide debris to 35 feet below the existing ground surface and Pico Formation siltstone bedrock below the debris. Heavy seepage was noted at several

7 GEO File No W.O. E170213F Page 5 of 31 depths within the debris encountered in B-10 and was only surface logged due caving hazards. Seepage was also noted to emanating from the terrace bedrock contact within the scarp during the excavation of B-10. Boring B-11, drilled on the north side of Slide 2, encountered terrace deposits to 18 feet, slide debris to 50 feet below the existing ground surface and Modelo Formation interbedded siltstone and sandstone bedrock below the debris. A well defined clay gouge zone was noted from 48 to 50 feet below the existing ground surface. Boring B-13, drilled at the toe of Slide 2, encountered slide debris to 20 feet below the existing ground surface and Modelo Formation interbedded siltstone and sandstone bedrock below the debris. Groundwater was not encountered below the zone of sliding. Two hollow stem borings were drilled, B-15 and B-16. Boring B-15, drilled at the head of the slide on the south side, encountered alluvial terrace deposits to 15 feet, marine terrace deposits to 34 feet below the existing ground surface and Pico Formation siltstone bedrock underlying the terrace deposits. Boring B-16, drilled at the head of the slide on the south side, encountered alluvial terrace deposits to 12 feet, marine terrace deposits to 28 feet below the existing ground surface and Modelo Formation siltstone and sandstone bedrock underlying the terrace deposits. It was noted in the 1986 report, five homes adjacent to Slide 2 were either undermined or destroyed by the headward advance of the slide. KBA estimated that at the time of the investigation, the volume of the slide was approximately 18,000 cubic yards of ancient and recent debris. It was postulated that the geologic structure of the canyon had not directly influenced the location of the landslides, but that it had influenced the movement and occurrence of groundwater in the area. It was concluded that the groundwater flow regime, exerted a strong influence on the development of landsliding in the canyon. (KBA, 1986) The 1986 KBA report mentioned previous work by others that was done in the vicinity of the subject properties. A 1978 Ralph Stone & Company report regarding a slope failure at and De Pauw Street was reviewed by KBA, 1986, but was not encountered in the scope of this report (RSC, 1978). As indicated on Byer s geologic map in Figure 6, there are two additional borings adjacent to Slide 2, LS-1 and LS-3 that were advanced by Lockwood-Singh and Associates (LSA). Reports from LSA were not reviewed by KBA, 1986, nor were they encountered within the scope of this report. Kovacs-Byer and Associates, Inc. issued a progress report letter in January of 1990 which detailed the requirements of subdrains and hydraugers (horizontal drains) at the scarps of Slides 1, 2, 3, and 6 (KBA, 1990a). The subdrains were deemed necessary to dewater springs encountered at the existing 25 foot fill elevation and consisted of six inch perforated pipe placed in a three foot by three foot trench packed with ¾ inch gravel. The hydraugers were specified to be 100 feet long and placed 50 feet on center and were intended to drain groundwater from the terrace/bedrock contact. In an Engineering Geologic Memorandum issued in July of 1990 Kovacs-Byer and Associates, Inc. stated that during Phase I grading, the installation of the storm drain and main canyon drain, it was found that the side slopes of Potrero Canyon were

8 GEO File No W.O. E170213F Page 6 of 31 potentially unstable above the 75 foot line. It was then proposed to raise the canyon fill to 100 feet above the original flowline of Potrero Canyon and construct 2:1 (horizontal:vertical) slope buttresses from that elevation to the rim of the canyon. (KBA, 1990b.) In a Project Status report issued in July of 1990 Kovacs-Byer and Associates, Inc. stated that the canyon bottom subdrain had been installed in bedrock 10 to 20 feet below the flowline of the canyon (KBA, 1990c). It was also noted that the hydraugers were placed laterally into the slopes to a depth of 300 to 500 feet in the most active seep areas on the slopes of the canyon. Several bores were usually drilled in a fan pattern from one location and then connected into a manifold to form and an array of hydraugers that were then connected to the subdrain. Approximately two miles of hydraugers were placed within the whole of Potrero Canyon. Initial flow rates from the hydrauger bores were commonly 100 gallons per day apiece, though typically the rates declined rapidly. Unusual flow patterns were exhibited in Array G, which sustained a total flow rate of approximately 1,000 gallons per day, and Array E, where initial flow rates were on the order of 40,000 gallons per day. Array G is located below the southern portion of Slide 2. The schematic origin point locations of these installed arrays are shown in Figure 9. The only As Built map of the hydraugers located, shown as Figure 10, details a more precise location of the arrays (KBA, Unknown Date). A Grading Memorandum was issued by Kovacs-Byer and Associates, Inc., in July of 1991 which indicated that grading had progressed to the point, where the removal of the upper 10 feet of adjacent slide material should commence in the middle portion of Slide 2 (KBA, 1991a). These removals were directed to be performed under the observation of the project geologist to ensure that, sufficient material is removed and to ensure the grading in the vicinity of the landslide does not pose a threat to the stability of offsite properties. An As-Built Geologic Conditions report was issued by Kovacs-Byer and Associates, Inc., in September of 1991 which indicated that grading had progressed to the point where the wetter portion of the debris in the southern part Slide 2 was trimmed to a 2:1 gradient (KBA, 1991b). A Progress Report was issued by Kovacs-Byer and Associates, Inc., in November of 1991 which indicated that a gravel blanket drain had been continuously placed against the southern half of Slide 2. (KBA, 1991c) The report noted that the blanket drain placement was terminated at the then current location and that the slide material above the blanket drains was observed to be dry with the seepage in the area completely stopped. A Progress Report was issued by Kovacs-Byer and Associates, Inc., in May of 1992 which indicated that grading had placed fill in the toe area of Slide 2 (KBA, 1992). It was noted that this area had been trimmed and benched as part of the Phase I grading. It was also noted that the fill placement could continue at the north end of Slide 2 for another six feet to the point where, removal of the exposed slide material will be

9 GEO File No W.O. E170213F Page 7 of 31 required prior to continuing filling. The limits of fill at the time of this report are shown in Figure 11. The Byer Group in March of 1994 prepared a report regarding the slope stability of temporary cuts to Slides 2 and 3 in response to a Building and Safety request (BG, 1994a). At the time, the fill pad had progressed to the point where benching of Slide 2 had exposed soft earth materials not suitable for the support of additional fill. It was recommended that, the northern half of Landslide #2 be removed from the base of the scarp. It was noted that the upper portion of the slide in that area exposed undisturbed terrace material and bedrock of the Pico Formation. The southern half of Slide 2 was observed to consist of saturated slide material. In order to remove the saturated material it was proposed to trim the slope to 1:1 extending into the lot pad area above the landslide. A subdrain at the toe of the trim slope to be connected to the storm drain system was also recommended. Byer also included slope stability calculations in the report that show a factor of safety in excess of 1.25 for the temporary slopes. The mapped location of the proposed trims is shown in Figure 12. The cross section line, 2-2, is shown in Figure 13. A memorandum was issued by the Byer Group in June of 1994 as an update on the grading progress (BG, 1994b.) It was noted that the grading contractor was not allowed to fill against Slide 2 until remedial grading was performed. The remedial grading was to consist of removing the upper 5 to 10 feet of the slide and removing the talus that had accumulated against the slide scarp as well as the 1:1 trim mentioned earlier. The memorandum referenced a letter from LADBS (dated April 19, 1994) that required the construction of a soldier pile system adjacent to private property south of Slide 2. The memorandum stated that the Byer Group planned subsurface exploration of the proposed pile area. The Byer Group issued an addendum report on the new subsurface exploration in July of 1994 (BG, 1994c.) Boring S2-1 was drilled to a depth of 61 feet on the flat portion of De Pauw Street approximately 70 feet from the street. The boring encountered alluvial terrace from the surface to 17 feet below ground surface (bgs), followed by marine terrace deposits to 34½ feet bgs and massive siltstone bedrock of the Pico Formation to the final depth. The report stated that slope trimming and benching had reached the point, where the remaining portions of exposed landslide debris should be removed. Using samples obtained from boring S2-1, testing was conducted for stability analysis of the proposed trim slope. The analysis indicated that the trim slope would have a factor of safety of 1.5. Therefore, the Byer Group concluded that the trim slope was stable without the need for a soldier pile system. The Byer Group recommended that, for the southern slide section, the scarp area exposing terrace be trimmed back to 1½:1 and a 1:1 slope trim in bedrock. They determined that the northern portion of the Slide 2 was more stable and removal of talus and slide debris was recommended at the toe of the scarp. The northern portion of the slide was recommended to be removed to a depth of 10 feet to expose firm in place slide debris under observation of the geologist would who give approval prior to placement of fill. Subdrains were recommended at the toe of the trim slope and at the terrace bedrock contact and as necessary as determined by the geologist. The mapped location of the

10 GEO File No W.O. E170213F Page 8 of 31 proposed trims and boring S2-1 are shown in Figure 14. The cross section line, 4-4, is shown in Figure 15. Subsequent to this report, a Request for Modification was filed to delete the requirement for soldier piles which was granted. A geologic memorandum regarding Slide 2 was issued by the Byer Group in October of 1994 that detailed the current conditions and recommendations for the area (BG, 1994d). The memo stated that the unsuitable portions of the north half of Slide 2 had been removed and the area prepared for the placement of compacted fill. The bottom for this area was approved by John Byer on October 28, The southern half of Slide 2 had not been removed at that time as the grading permit was still pending. Another geologic memorandum regarding Slide 2 was issued by the Byer Group in December of 1994 that detailed the current conditions and recommendations for the area (BG, 1994e). The memo stated that the temporary slope could not be excavated, back beyond the slide plane, and a portion of the slope moved as a result. It was recommended that the, temporary slope be trimmed from the top to remove the remaining slide debris to provide a safe and stable work area. In early January of 1995 there was approximately one week of heavier than normal rainfall which caused damage in area in and around Potrero Canyon (BG, 1995a). No damage was noted at Slide 2, but the report mentioned that LADBS had approved plans for the removal of the remaining portions of Landslide 2. It was noted that the removal was to consist of a combination of a 1½:1 and 1:1 (horizontal:vertical) temporary slope. An Interim Compaction Report was filed in June of 1995 for a portion of the grading work in the area of Slide 2 (BG, 1995b). The report stated that the bottom at Slide 2, approximately 275 by 65 by 90 feet, was identified as firm slide debris by a geologist and approved on October 28, The bottom was noted to be included on the Compaction Map enclosed with the report; however no map was attached to the report available to GEO from the RAP records. In August of 1995 a City of Los Angeles review letter (CLA, 1995a) was issued regarding the 1995 Interim Compaction Report (BG, 1995b.) This letter withheld approval for the fill covered by the 1995 compaction report. The review of the BG report was to continue upon submittal of an addendum report including a cross section through Slide 2 and a map including the subdrains. A report from the BG responding to this letter was not encountered during a review of the RAP records. In August of 1995 a City of Los Angeles review letter (CLA, 1995b) was issued regarding the 1995 Interim Compaction Report (BG, 1995b.) This letter granted approval for the fill covered by the 1995 compaction report as a non-structural fill which was not to be used for support of structures. In a Plan Review and Update report from December of 1997 the Byer Group stated that Slide 2 remained in place and had yet to be excavated and buttressed (BG, 1997a). It was noted that grading permits for the repair of Slide had been obtained and that

11 GEO File No W.O. E170213F Page 9 of 31 Slide 2 would be removed to, firm stable material and replaced as certified compacted fill. It was further noted that, for slide #2 compacted fill will be placed directly on bedrock and terrace material. Additional subdrains were recommended for Slide 2 at the terrace bedrock contact. In late December of 1997 the Byer Group issued an Engineering Geologic Consultation report that detailed the current conditions and recommendations for the Slide 2 area (BG, 1997b). It was stated that Slide 2 area was still not ready for compacted fill and that temporary 1:1 cut from the rim of the canyon down to the base of the landslide had not been made. The base of the excavation should expose bedrock adjacent to Phase I certified compacted fill. Once again, a subdrain was recommended at the terrace bedrock contact which was noted to be 40 feet below the top of the canyon. A geologic memorandum regarding Slide 2 was issued by the Byer Group in June of 1998 that detailed the current conditions and recommendations for the area (BG, 1998a). Removal of the remaining portions of Slide 2 and the excavation of the temporary cut were being performed at the time of this report. It was noted that John Byer was requested to observe the removal of the debris. It was determined that the planned temporary cut would not remove all of the remaining debris. As a result of that determination, John Byer, the project geologist, directed the grading contractor to move the top of the cut west toward the street approximately 10 feet. The Byer Group requested that the temporary back cut be surveyed for future as-built reports. Portions of the Slide 2 temporary slope were seen to be failing due to springs emanating from the face of the cut well below the terrace-bedrock contact. Additional drains were recommended to be installed to convey this water to the storm drain system under the direction of John Byer. An Interim Compaction Report was filed in December of 1998 that covered the continuing grading work in the area of Slides 2 (BG, 1998b). The report stated that the, remaining portions of Slide 2 were excavated to firm bedrock with the bottom approved by the geologist, a subdrain installed, and compacted fill placed. A subdrain was installed at the base of the Slide 2 removal per the approved grading plan. It was noted that oversized rocks and concrete rubble were placed in windrows in the area of Slide 2. The windrows were reported to be three feet by three feet and spaced every 15 feet horizontally with fill placed around the material and sand jetted into the voids. The limits of fill adjacent to the northern and southern limits of Slide 2 covered by this report is shown in the compaction maps are included here as Figures 16 and 17. On January 22, 1999, a City of Los Angeles review letter (CLA, 1999) was issued regarding the 1998 Interim Compaction Report (BG, 1998b.) This letter granted approval for the fill covered by the 1998 compaction report as a primary structural fill. An Interim Compaction Report was filed in January of 2000 that covered the continuing grading work in the area of Slides 2 (BG, 2000). Slide 2 was still in the process of being buttressed at the time of this report. It was stated that, the contractor has reached Phase III finish grade at the portion of the canyon north of station with all the

12 GEO File No W.O. E170213F Page 10 of 31 stockpiled soils used as compacted fills. Station is the south to north referencing the storm drain within the central canyon fill and is located approximately midpoint within the lot at De Pauw Street, or the northern section of Slide 2. The BG reported that the fill placed was compacted to a minimum of 90 percent of the maximum dry density as determined by ASTM D1557. The maximum fill depth covered in the report was 60 feet at the Slide 2 buttress. The last density test of fill included in this report located in the area of Slide 2 was at elevation 218 msl, or approximately 42 feet below current grade. The limits of fill adjacent to the scarp of Slide 2 covered by this report is shown in the compaction map included here as Figure 18. It was noted that rocks and rubble were placed in windrows with the same procedures described in the 1998 compaction report. The BG indicated that the foundation design values, provided in the December 1998 report, were intended for the sound barrier walls and not residential structures on the rim of the canyon. The remaining grading details contained in the report conform to standard practice for compaction reports certifying artificial fill and the slope buttresses were, graded in accordance with the plans and permits approved by the City of Los Angeles Department of Building and Safety, Grading Section. The fill covered by this report was approved as primary structural fill by the City of Los Angeles on February 4, 2000 (CLA, 2000). The BG report noted that the lots along the rim of the canyon that had been stabilized by compacted fill and stabilization fills were expected to support future residential development. The Byer Group recommended that each lot be investigated, by an independent soil testing agency to provide project specific foundation recommendations. In light of any future development, the report stated that, a complete file of geotechnical reports for the project will be maintained at the office of The J. Byer Group for outside consultants to review. A geologic memorandum regarding Slide 2 and other issues was issued by the Byer Group in April of 2000 that detailed the current conditions and recommendations for the area (BG, 1994d). Slide 2 was noted as a area of concern at the time of the report. At the time of the report, the Slide 2 area consisted, of a 1:1 temporary backcut and a false fill slope approximately 15 feet away from the cut. Groundwater was noted to be flowing from the terrace deposits down the face of the cut and saturating the compacted fill along the toe of slope complicating grading. It was proposed by the contractor to reestablish the temporary drain on the slope and begin filling with the water diverted. Saturated soils were recommended to be removed to firm subgrade prior to continuing the fill operation. This memorandum is the last grading document within the available Recreation and Parks records that specifically references the areas in and around the subject properties on De Pauw Street. 5.4 History of Development and Geotechnical Exploration of De Pauw Street In this section, a brief synopsis of past geotechnical explorations and development on or adjacent to the City owned properties on De Pauw Street within the area of Slide 2 that were encountered within the scope of this report. To that end, a review of the LADBS

13 GEO File No W.O. E170213F Page 11 of 31 documents encountered for each property in this section of De Pauw Street will be presented from south to north. A bibliographic list of documents reviewed for each property is included in this section for ease of reference. The list of documents presented in this report may not represent all available records for the individual properties due in part to inconsistencies in City document filing procedures, changes in grading code document requirements, degradation of reproductions, etc. The review of documents was limited to those relevant to a geotechnical review, i.e., plumbing and electrical permits have not been obtained or reviewed for this report. This report does not evaluate conformance issues with building codes or whether proper permits were obtained for construction at the individual properties De Pauw Street City of Los Angeles (CLA), Application for the Erection of Frame Building Class D for De Pauw St., Permit No.: 1928LA13064, dated May 7, City of Los Angeles (CLA), Application to Alter, Repair or Demolish, for De Pauw St., Permit No.: 1957LA61789, dated January 14, City of Los Angeles (CLA), Application to Alter, Repair, Demolish and for Certificate of Occupancy, for De Pauw St., Permit No.: 1957LA61789, dated January 14, The earliest record found for De Pauw Street is an application for a building permit in The application proposed constructing a single family, 2 story residence at the site. An application for a building permit to demolish the residence was filed in 1957 by the private property owner at the time. A second application for a building permit to demolish the residence was filed in 1958 that listed the City of Los Angeles as the owner De Pauw Street City of Los Angeles (CLA), Application to Erect a New Building, for De Pauw St., Permit No.: , dated April 18, City of Los Angeles (CLA), Application to Erect a New Building, for De Pauw St., Permit No.: , dated April 18, City of Los Angeles (CLA), Application to Alter, Repair, Demolish and for Certificate of Occupancy, for De Pauw St., Permit No.: 1954WL10994, dated March 19, City of Los Angeles (CLA), Certificate of Occupancy for De Pauw St. Permit No.: 1954WL10994, dated April 10, 1955.

14 GEO File No W.O. E170213F Page 12 of 31 City of Los Angeles (CLA), Certificate of Occupancy for De Pauw St. Permit No.: 1954WL10994, dated April 19, City of Los Angeles (CLA), Certificate of Occupancy for De Pauw St. Permit No.: 1956WL19634, dated August 26, City of Los Angeles (CLA), Application to Alter, Repair, Demolish and for Certificate of Occupancy, for De Pauw St., Permit No.: 1969WL75746, dated February 10, City of Los Angeles (CLA), Order to Comply, for De Pauw Street. Issued February 15, City of Los Angeles (CLA), Application to Alter, Repair, Demolish and for Certificate of Occupancy, for De Pauw St., Permit No.: 1986LA51122, dated November 19, City of Los Angeles (CLA), Range File (various City records regarding demolition of property), for De Pauw St., dated December 10, The earliest record found for De Pauw Street is an application for a new construction building permit in The application proposed constructing a single family, single story residence at the site. An application for a building permit to construct a garage on the property was also filed in An application for a building permit to construct a den at the rear of the property was filed in The Certificate of Occupancy for the den was issued the next year. A Certificate of Occupancy for the addition of a carport was issued in An application for a building permit to demolish part of one wing and close in was filed in An Order to Comply to repair the property was issued in 1969 after a major slope failure at the rear of the property due to severe January-February rainstorms. According to City records, the title to the property was acquired by the City February of An application for a building permit to demolish the residence was filed in 1986 that listed the City of Los Angeles as the owner. City records indicate that the residence was demolished in August of De Pauw Street City of Los Angeles (CLA), Certificate of Occupancy for De Pauw St. Permit No.: 1950XX00446, dated May 9, City of Los Angeles (CLA), Certificate of Occupancy for De Pauw St. Permit No.: 1963WL47194, dated October 25, City of Los Angeles (CLA), Department of Building and Safety Grading Preinspection Report, for De Pauw St., dated June 26, 1968.

15 GEO File No W.O. E170213F Page 13 of 31 City of Los Angeles (CLA), Abate Order, for De Pauw Street. Dated April 21, City of Los Angeles (CLA), Notice of Building, Structure or Premises Classified as Either Hazardous, Substandard or a Nuisance, for De Pauw Street Dated May 21, City of Los Angeles (CLA), Application to Alter, Repair, Demolish and for Certificate of Occupancy, for De Pauw St., Permit No.: 1986LA51123, dated November 19, City of Los Angeles (CLA), Termination of Notice of Building, Structure or Premises Classified as Either Hazardous, Substandard or a Nuisance, De Pauw St., Dated March 6, City of Los Angeles (CLA), Range File (various City records regarding demolition of property), for De Pauw St., dated March 6, A Certificate of Occupancy for a one story single family dwelling and garage was issued in A Certificate of Occupancy for the enclosing a portion of the existing porch and conversion to ¾ bath was issued in A grading pre-inspection report was filed in 1986 the City of Los Angeles Department of Building and Safety (LADBS) that stated that there was a recent slide at the rear of the property at the time and the existing dwelling and garage exhibited cracking. An Abate Order was issued in April of 1986 that noted the residence was vacant and vandalized and ordered that the residence be brought to a habitable condition. According to City records, the title to the property was acquired by the City February of A Notice of building, structure or premises classified as either hazardous, substandard or a nuisance was filed by the LADBS in May of 1986 with the Los Angeles County Recorder that required that the property be repaired or demolished. An application for a building permit to demolish the residence was filed in 1986 that listed the City of Los Angeles as the owner. A Termination of Notice of building, structure or premises classified as either hazardous, substandard or a nuisance was filed by the LADBS in March of 1987 with the Los Angeles County Recorder indicating that the earlier notice was no longer in force. City records indicate that the residence was demolished in December of De Pauw Street City of Los Angeles (CLA), Application to Erect a New Building, for De Pauw St., Permit No.: 1949WL01640, dated August 2, City of Los Angeles (CLA), Certificate of Occupancy for De Pauw St. Permit No.: 1949WL01640, dated December 14, 1949.

16 GEO File No W.O. E170213F Page 14 of 31 City of Los Angeles (CLA), Application to Alter, Repair, Demolish and for Certificate of Occupancy, for De Pauw St., Permit No.: 1958LA11002, dated August 22, City of Los Angeles (CLA), Geology/Soil Report Denial Letter for De Pauw St., Los Angeles Department of Building and Safety, Grading Division, dated March 20, Nigra, John O., 1974a. Project , Geological Engineering Investigation of Known Slide Area and Effect on Safe Occupancy at De Pauw St., being Lot 8, Block 19, Tract 9300, in the Pacific Palisades, City of Los Angeles, dated February 19, City of Los Angeles (CLA), Department of Building and Safety Grading Denial Letter, for De Pauw St., dated March 20, Nigra, John O., 1974b. Project (B), Supplementary Geological Report, De Paux St., Pacific Palisades, City of Los Angeles, (Lot 8, Tract 9300). Dated April 26, Merrill, John D., CPG., Engineering Geologic Report, Lot 8, Block 19, Tract 9300, De Pauw St, Pacific Palisades, California. Dated May 3, Advanced Foundation Engineering, Inc. (AFE), Soils Report for Lot 8, Block 19, Tract 9300, De Pauw St, dated May 8, City of Los Angeles (CLA), Department of Building and Safety Grading Approval Letter, for De Pauw St., dated May 30, County of Los Angeles (CoLA), Notice Regarding Erection and Maintenance of Building in Areas Subject to Inundation or Physical Hazards of a Geological Nature, De Pauw Street, Pacific Palisades CA Filed on May 30, City of Los Angeles (CLA), Application to Alter, Repair, Demolish and for Certificate of Occupancy, for De Pauw St., Permit No.: 1974WL00567, dated July 30, City of Los Angeles (CLA), Application for Grading, for De Pauw St., Permit No.: 1974WL00568, dated July 30, City of Los Angeles (CLA), Application to Alter, Repair, Demolish and for Certificate of Occupancy, for De Pauw St., Permit No.: 1976WL09273, dated August 10, City of Los Angeles (CLA), Application to Alter, Repair, Demolish and for Certificate of Occupancy, for De Pauw St., Permit No.: 1976WL09273, dated August 10, 1976.

17 GEO File No W.O. E170213F Page 15 of 31 City of Los Angeles (CLA), Certificate of Occupancy for De Pauw St. Permit No.: 1976WL09273, dated November 23, City of Los Angeles (CLA), Certificate of Substandard Property, for De Pauw St., Dated June 23, City of Los Angeles (CLA), Notice to Abate Damaged or Vandalized Buildings, for De Pauw Street. Dated June 29, City of Los Angeles (CLA), Notice of Building Classified as a Nuisance or Hazard to Life or Property, Demolition Abatement Proceedings, for De Pauw St., Dated July 11, City of Los Angeles (CLA), Application to Alter, Repair, Demolish and for Certificate of Occupancy, for De Pauw St., Permit No.: 1985LA11787, dated May 10, City of Los Angeles (CLA), Termination of Notice of Building, Structure or Premises Classified as Either Hazardous, Substandard or a Nuisance, for De Pauw St., Dated August 7, The earliest record found for De Pauw Street is an application for a new construction building permit and Certificate of Occupancy issued in The application proposed constructing a single family, single story residence and garage at the site. An application for a building permit to extend the front of the garage approximately four (4) feet towards the street was filed in In February of 1974, a geologic engineering investigation was conducted on the property by John O. Nigra regarding the landslide at the rear of the lot and corrective measures (Nigra, 1974a). It was noted that the concrete slab and block wall in the rear yard of the property, resting on undisturbed clay soil and terrace gravel, had failed. A vertical drop off of feet was noted at the base of the exposed footings in this area. Indications of creep were seen in the slope below the southeast corner of the rear yard, but these features were not seen to be related to the landslide. Unlawfully placed drainage conduits were seen to be installed in the rear yards of neighboring properties to the north and south that, combined with poor drainage on the subject property, likely produce the recent sliding. It was noted that there was, no unfavorable dip components in the supporting rocks to warrant fear of bedding plane slides. Gradual pop-outs and vertical slabbing seem to be more the case, and only where concentrated water run-off saturates the underlying rocks. As part of the investigation a six (6) foot deep test was dug that showed terrace deposits at the location shown on the map included with the report, provided here as Figure 19. Vertical cracking of the foundation was observed extending into the footing only at the location of the test pit. It was determined by the consultant that the foundation distress was not caused by the landslide. Removal of the area of the structure and concrete slabs directly adjacent to

18 GEO File No W.O. E170213F Page 16 of 31 the landslide was recommended as well as correcting the drainage for the entire property as well as the neighbors. LADBS issued a letter in March of 1974 with-holding approval of the John O. Nigra February, 1974 report due to its lack of, a detailed soil engineering analysis of the proximal landslide mass, and insufficient corrective measures. A supplementary report was prepared on the property by John O. Nigra in April of 1974 (Nigra, 1974b). This report clarified that the building structures were, not damaged and that there were no signs of encroachment of the head scarp under the structure. The report restated the need for the recommended corrective measures to limit the potential for future damage to the property. John Merrill Engineering Geologists completed a geologic report on the property in May of The scarp at that time was noted to be about 22 feet high and within terrace deposits. The movement of the landslide was attributed to poor drainage and unusually heavy and prolonged rainfall. The terrace bedrock contact was noted at approximate elevation 236 and was seen to contain a zone of cobbles and boulders up to a foot in diameter. The bedrock was identified as the Monterey Formation with the bedding having a general west strike and a north dip of about 40 degrees. The report concluded that a slope trim at the rear of the property and drainage correction for the site and the neighboring properties would, restore the property. A Notice Regarding Erection and Maintenance of Building in Areas Subject to Inundation or Physical Hazards of a Geological Nature was filed with the Los Angeles County Registrar-Recorder in May of Advanced Foundation Engineering, Inc. also completed an inspection of the site in May of As a part of the inspection the consultant focused on the soils of the east facing slope at the rear of the house and what was encountered in two test pits, one adjacent to the foundation on the south side of the house and the other at the northeast corner of the structure. The report noted a near vertical slope at the rear of the lot which was undercutting the slab at its northeast corner. The erosion was thought to be caused by faulty roof and surface drainage that concentrated runoff at the location. Some settlement was noted in the northeast corner of the foundation. The report recommended the removal of the hardscape and wall in the rear yard as well as the east end of the kitchen. Proper drainage towards the street was recommended for the entire property. Construction of a new foundation in the northeast and southern sections of the structure and a 1:1 slope trim at the rear of the lot was also recommended. With the recommended corrective measures taken, it was thought that the structure should have an estimated life of 15 to 20 years and the house would once again be considered safe for occupancy. An approval letter was issued in May of 1974 from LADBS granting permission to reoccupy the residence on the property. The approval was based on favorable reports prepared by AFE, dated May 8, 1974 and John Merrill dated May 3, The letter required that the recommendations of the consultants be followed. One of the

19 GEO File No W.O. E170213F Page 17 of 31 requirements of the approval letter was a sworn affidavit filed with the County Recorder stating that, the owner is fully aware that the site is in an area subject to slides or unstable soil. An application for a building permit to trim the slope at the rear of the property to 1:1 (horizontal:vertical) was filed in July of An application for a building permit to construct a deck at the rear of the property and to remove a portion of the kitchen was filed in An application for a building permit to remodel the kitchen and move a wall 2.5 feet into the garage was filed in 1976 with the Certificate of Occupancy issued in A Certificate of Substandard Property was filed by LADBS in June of 1981 with the Los Angeles County Recorder because of a landslide affecting the property. An Abate Order was issued in June of 1984 that noted the residence was damaged and that there was a slope failure and the rear foundation was gone and ordered that the residence be brought to a habitable condition or demolished. A Notice of Building Classified as a Nuisance or Hazard to Life or Property was filed by the LADBS in July of 1984 with the Los Angeles County Recorder that required that the property be repaired or demolished. An application for a building permit to demolish the residence was filed in 1985 that listed the City of Los Angeles as the owner. City records indicate that the residence was demolished in May of A Termination of Notice of building, structure or premises classified as either hazardous, substandard or a nuisance was filed by the LADBS in August of 1985 with the Los Angeles County Recorder indicating that the earlier notice was no longer in force De Pauw Street City of Los Angeles (CLA), Certificate of Occupancy for De Pauw St. Permit No.: 1949XX00127, dated May 12, City of Los Angeles (CLA), Order to Comply, for De Pauw Street. Issued May 1, City of Los Angeles (CLA), Certificate of Substandard Property, for De Pauw St., Dated August 25, City of Los Angeles (CLA), Notice to Abate Damaged or Vandalized Buildings, for De Pauw Street. Dated June 29, City of Los Angeles (CLA), Notice of Building Classified as a Nuisance or Hazard to Life or Property, Demolition Abatement Proceedings, for De Pauw St., Dated July 11, City of Los Angeles (CLA), Application to Alter, Repair, Demolish and for Certificate of Occupancy, for De Pauw St., Permit No.: 1985LA11786, dated May 10, 1985.