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RPVCCA_CC_SR_2015_03_03_03_Code_Amend_Initiation_Landslide_MoratoriumCITY OF RANCHO PALOSVERDES COMMUNITY DEVELOPMENT DEPARTMENT LU4IT,Eel:Z1 kC111IT, TO: HONORABLE MAYOWMEMB RS OF THE CITY COUNCIL FROM: JOEL ROJAS, COMMELOPMENT DIRECTOR DATE: MARCH 3, 2015 SUBJECT: CODE AMENDMENT INITIATION REQUEST TO AMEND THE CITY'S LANDSLIDE MORATORIUM ORDINANCE (CHAPTER 15.20) TO CREATE A NEW MORATORIUM EXCEPTION CATEGORY THAT WOULD ALLOW VACANT UNDEVELOPED PARCELS IN ZONE 1 TO BE DEVELOPED WITH SINGLE FAMILY RESIDENCES REVIEWED: CAROLYN PETRU, DEPUTY CITY MANAGER RECOMMENDATION Direct Staff to initiate the proposed code amendment so that notification of the proposal can be provided to the surrounding property owners and the issues associated with the proposal can be vetted by the City Council through duly noticed public Council meetings. BACKGROUND In 2009, the City acquired 160 acres of open space from York Long Point Associates (the Upper Filiorum property) for inclusion into the City's Palos Verdes Nature Preserve. Excluded from the acquisition was approximately 29 acres of open space, referred to by York Long Point Associates as the Plumtree Parcel, lying between the Upper Filiorum property and the developed Portuguese Bend community (see attached aerial). The 29 - acre Plumtree parcel was carved out from the greater Upper Filiorum property by Mr. York because he felt it had a higher development potential and conversely a higher land value. Ultimately, it was excluded from the City's acquisition because the City and PVPLC did not have the funds to also purchase this property. Sometime in 2010, the partners of York Long Point Associates divided their respective interests resulting in the ownership of the Plumtree property by Plum Tree PV Associates, headed by former City of L.A. Mayor Richard Riordan. At around that time, the property owner filed a Moratorium Exclusion application with the City to exclude the Plumtree property from the City's Moratorium Ordinance so that the property could 30940 1 IAWTFIORNF BLVD. / RANCHO PA10S VERDES, cA 90275-5391 PLANNING & CODE ENFORCEMENT DIVISION (310) 544-5228 / BUILDING & SAFETY DIVISION (310) 265-71300 / DEPT. FAX (310) E-MAIL: PLANNINGORPVCOM / WWWPALOSVERDES.COM/RPV 3-1 possibly be developed with a 21 -lot residential subdivision. As a result, geotechnical reports were prepared on behalf of the owner and submitted to the City's Geologist (Jim Lancaster) for review and approval. In June 2012, the City was notified by the Plum Tree PV Associates that they intended to pursue a 12 -lot subdivision instead of a 21 -lot subdivision. In January 2013, the property owner notified the City that they had decided to pursue development of only one residence on the property. Given that approval of a Moratorium Exclusion was still necessary to develop even one home on the 29 -acre property, the property owner continued to pursue approval of the geology reports that they had submitted previously to the City. In November 2014, the City Geologist conceptually approved the property owner's submitted geology reports in support of their Moratorium Exclusion request. According to the City Geologist, the submitted geology reports demonstrate that a portion of the property measuring approximately 2,500 square feet in area (.06 acres) could be excluded from the landslide moratorium area, since the area could be stabilized to a Factor of Safety of at least 1.5, provided approximately 140,000 cubic yards of remedial grading is performed. The remedial grading would involve excavating down to the lower limit of the landslide, which is approximately 150 feet below the surface at that location, and then rebuilding the area with compacted fill. On December 11, 2014, Staff received the attached letter from Mr. Riordin, Manager of Plum Tree PV Associates, requesting that the City Council consider amending the City's Landslide Moratorium Ordinance to allow them to build one single family residence on their 29 -acre parcel without having to perform the 140,000 cubic yards of remedial grading that would be required to build the same residence under the Moratorium Exclusion process. The requested Code Amendment initiation request is being presented to the City Council for consideration this evening. DISCUSSION The City's Moratorium Exclusion Process Under the current Landslide Moratorium Ordinance, the only way a non -Monks -lot property owner can develop a new single family residence on a vacant legal lot within the Landslide Moratorium Area is to successfully "exclude" said lot from the moratorium with City Council approval of a Moratorium Exclusion request. Pursuant to Municipal Code Section 15.20.100, the 3 findings that the City Council must successfully make to approve an exclusion request are summarized as follows: 1) The exclusion is consistent with the general plan and any other applicable specific plan of the City; 2) The exclusion promotes the health, safety and welfare of the community; and 3) The exclusion shall not aggravate any existing geologic conditions in the area. The City Geologist has found the applicant's geotechnical reports to be acceptable from a geologic and geotechnical perspective to exclude a 2,500 square foot portion of the 3-2 29 -acre Plumtree Property from the City's Moratorium, thus agreeing that the proposed Exclusion would not aggravate any existing geologic conditions in the area (finding No. 3 above). The City Geologist's approval is attached. While the City Council must affirm this finding and make the additional two findings, this in -concept geologic approval is a major step for the applicant in successfully obtaining approval of the sought after exclusion request. As stated above, the conceptually approved geology reports demonstrate that a 2,500 square foot portion of the 29 -acre Plumtree property could be stabilized to a Factor of Safety of at least 1.5 provided approximately 140,000 cubic yards of remedial grading is performed. The remedial grading would involve excavating down to the lower limit of the landslide, which is approximately 150 feet below the surface at that location, and then rebuilding the area with compacted fill. Given the potential environmental impacts to surrounding residences that could result from such grading work, Staff believes that an EIR needs to be prepared prior to presenting the Plumtree Property Moratorium Exclusion Request to the City Council for consideration. The Applicant's Proposal Concerned with the prospect of having to perform 140,000 cubic yards of remedial grading work simply to build one residence, the applicant is petitioning the City Council to consider amending the City's Moratorium Ordinance so that they can apply for a Moratorium Exception Permit to build one residence on their property (located within Zone 1) under the same exact restrictions that the Monks plaintiffs are held to for developing their vacant lots in Zone 2. As noted in the attached letter, the main rationale for their request is that they would end up with the same result (one new residence) while avoiding having to perform 140,000 cubic yards of grading and thus greatly reducing the construction impacts upon the Portuguese Bend community. Applicability of Proposal to Zone 1 Based on Dr. Perry Ehlig's May 26, 1993 memo (attached), where he divided the Moratorium Area into 8 zones, the entirety of the 29 -acre Plumtree Property is located in Zone 1. In his memo, Dr. Ehlig describes Zone 1 as "unsubdivided land unaffected by large historic landslides and located uphill or to the west of subdivided areas." Since the majority of Zone 1 is now City owned Preserve land, Staff believes that there are only two privately owned undeveloped legal lots in Zone 1 that could be developed with a single family residence. These two properties are the 29 -acre Plumtree property and the approximate 60 acres of the 95 -acre Point View property that lie within the Landslide Moratorium Area. Thus, if the City Council is inclined to initiate the proposed code amendment, Staff believes that rather than applying the code amendment to a specific lot, that it be applied to all undeveloped legal lots that are located entirely within Zone 1. In addition, given the topography and geology of the area, it may be beneficial to establish a minimum lot size for such a proposal to be considered, such as 25 acres, as an example. Furthermore, a prohibition of any future subdivision of a parcel that takes advantage of the proposed Moratorium Exemption category can also be imposed. 3-3 It should be noted that according to the L.A. County Assessor's maps, the 95 -acre Point View property is made of four parcels (two of which exceed 25 acres) and the 7 -acre Vanderlip Estate property (which is also in Zone 1) is made up of two parcels that total approximately 7 acres. As a result, Staff will need to confirm that these parcels are simply tax parcels as opposed to individual legal lots, so that the Council and the surrounding community will understand the maximum number of undeveloped properties that could be developed if this proposal were approved by the City Council. Basis for Staff's Recommendation Staff believes that the City Council should initiate the proposed code amendment for the following reasons: 1) While the request would clearly benefit the Plum Tree Property owner, as they would avoid having to perform 140,000 cubic yards of remedial grading that would be very expensive and could make the project infeasible, the request also would have public benefit, because it would avoid months of noise, dust, vibration and truck impacts to the Portuguese Bend community. 2) Given that the applicant has secured in -concept approval from the City Geologist for the proposed remedial grading associated with their Moratorium Exclusion request, it is possible that the property may be sold do a different property owner who may be interested in pursuing a larger Exclusion area to accommodate a possible subdivision of the property. However, it should be pointed out that under the City's existing Code, the Moratorium does not allow for the processing of subdivision requests. 3) The City Geologist has verbally informed Staff that adding two (or three if Staff confirms that there are two legal lots greater than 25 acres as part of the Point View property) new residences to Zone 1 with no remedial grading whatsoever would not have a detrimental impact on the stability of the area provided the same restrictions that are currently applied to development of the Monks lots are also imposed. 4) A new residence on both the Plumtree Property and the Point View property could be connected to the existing sewer system, and it appears possible to direct all new runoff from both properties away from Portuguese Bend community streets. 5) It will allow Staff and the City Council to fully vet the proposal with the public at duly noticed public City Council meetings. If initiated, Staff would provide notice of the proposal to all property owners within Zone 1, all property owners within 500 feet of Zone 1, the Portuguese Bend Community Association and any other interested parties so that they will have the opportunity to provide feedback on the proposal to the City Council during the public meetings. In addition, if initiated, Staff will consult with the City Attorney and identify the appropriate CEQA review for the proposal. 3-4 CONCLUSION For the reasons described in this Staff Report, Staff recommends that the City Council initiate a proposed code amendment that could result in an amendment to the City's landslide Moratorium Ordinance to create a new Moratorium Exception Category that would allow vacant parcels in Zone 1 to be developed with single family residences. FISCAL IMPACT Initiating the proposed Moratorium Ordinance amendment will have no fiscal impact as the Staff time associated with assessing the proposal is covered by the City's current budget. ALTERNATIVES In addition to Staffs recommendation, the following alternatives are available for consideration by the City Council: 1) Identify issues with the proposal and continue discussion of the Code Amendment Initiation Request to a future City Council meeting; 2) Determine not to initiate the proposed code amendment. Attachments • Aerial of Plumtree Property • Letter from Mr. Richard Riordin • City Geologist approval letter • Dr. Perry Ehlig's May 26, 1993 memo 3-5 A - . 40 41 '� _ o } i dr ' I .p M - I. 9 r ♦ /'s 0: Plum 'Free PV Associates, LLC &"�ECEJVED 141 N. Bristol Avenue, Los Angeles, California 90049 (310) 472-5070 (3) 10) 471-7846 - Fax ',.)EC, December 8, 2011 Mr. Joel Rojas Director of Community Development Citv of Rancho Palos Verdes 30940 Hawthorne Blvd. Rancho Palos Verdes, CA 94275 COMMUNITY DEVELOPMENT DEPARTMENT RE: Request to City Council to Amend the Moratorium on Land Use Permits Dear Mr. Rojas: This letter is to make a request to the City Council of the City of Rancho Palos Verdes ("City Council") to amend the Moratorium on Land Use Permits, Chapter 15.20 of the City of Rancho Palos Verdes Municipal Code, to create a new moratorium exception category that would allow Plum Tree PV Associates, LLC ("Plum Tree") to apply for an exception permit and build one residence on a 29 -acre lot. We believe the amendment requested would be appropriate for the reasons discussed below. Plum Tree is the owner of 29 acres in the Palos Verdes Peninsula. After several amendments to its plans due to the development restrictions, Plum Tree's current plan is to build one single residence on 2.2 acres of the entire 29 -acre parcel. This plan is consistent with the surrounding residents' goal of maintaining the natural character of the area. The amendment of the Code to allow Plum Tree to apply for an exception permit will also avoid potential negative impacts to the neighborhood. If Plum 'free seeks an exclusion under Section 15.20.100 of the Code, Plum Tree may be required to ;rade in excess of 100,000 cubic yards to demonstrate that the land is stable. However, if a new exception category is created with the same restrictions contained in exception category P (The Monks' Plaintiffs Category), the grading for development of one residence on our 29 -acre lot would be limited to a maximum of 1,000 cubic yards. The limited grading will greatly reduce the temporary construction impacts of noise, vibration, and dust emitted to the neighborhood and the unsettlement of the Peninsula residents. 3-7 Mr. Joel Rojas December 8, 2014 Page Two If the City Council agrees to amend the Municipal Code to grant Plum Tree the right to apply for an exception permit similar to the right granted to the plaintiffs of the case Monks v. City of Rancho Palos Verdes; 167 Cal. App. 411' 263, 84 Cal. Rptr, 3d 75 (Cal. App. 2 Dist., 2008), consistent with Section 15.20.040 P, if and when said exception permit is granted, Plum Tree will timely comply with the permit application requirements under Section 15.20.050 (Landslide Mitigation Measures Required) that are intended to minimize impacts to the landslide. Furthennore, once the moratorium exception permit is granted, Plum Tree will abide by all of the City's applicable plan requirements such as neighborhood compatibility review, drainage review, and building code review. Please let us .know if you have any questions regarding our request or if you need additional information to provide us a positive response. Sincerely, ,F fmss....... " Richard J. l n, Manager We Category 5 P.N. 97082-1.837 crry OF RANCHO PALOS VERDES GEOTECHNICAL INVESTIGATION RESPONSE REVIEW CHECKLIST Date Received: November 20, 2014 Date Completed: November 26, 14014 Date of Response: November 14, 2014 Consultant: Ginter & Associates, Inc. Their Job No.: 111-06 Date of Response-. September 26, 2014 Prior Review: October 16, 2014 Date of Update Report: June 2014 July 7, 2014 Date of Response: January 25, 2013 February 2 5., 2013 Date of Report: May 25, 2012 July 17, 2012 Applicant Name: Plum Tree P.V. Associates, IAX Legend: N =No Site Address: Plum Tree Development y — Yes Rancho Palos Verdes, California Lot/Tract No.: A.P.N.: 7581-023-037 Proposed Project: Project has change to the development of one estate lot, report provided is to determine if the proposed project is acceptable from a geologic and geotechnical perspective to exclude the project from the RPV Landslide Moratorium by grading. Comments: The review provided is to help determine if the proposed project is feasible and that geologic hazards can be eliminated so that the project can be excluded/removed from the RP'V Landslide Moratorium (15.20.100 Exclusion). As such question and review comments were presented to determine feasibility. Sonic items not related to feasibility will be allowed to be deferred - * on July 17, 2012 review. • Geotechnical Response.- /N Responsive to checklist comments Y/N Grading/foundation plans changed as a result of response Recommended Actions: X In Concept Approval for Planning Purposes Additional Input Required Items requiring response/further evaluation: 1. None Additional Comments/Conditions of Approval (no response required): 2. The consultant's report is acceptable fi-orn a geologic and geotechnical perspective to exclude the proposed as-builtprojcct from the RPV Landslide Moratorium as set forth under Section 15.20. 100 of the RPV Municipal Code. Geotechnically for all exclusion to be processed it must be demonstrated that the exclusion shall not aggravate any existing geologic condition in the area-, however, if excluded the final mitigated site configuration must have a factor of safety of 1.5 as required by 15,18. 100 Section 111A,2 and the consultant shall provide a Safety Hazard statement as required by 15.18.090 Section 107A,3 of the Rancho Palos Verdes Municipal Code. Prior to permit issuance the following should be completed: 3. The applicant shall complete all conditions as set forth in Section 15.20. 100 of the RPV Municipal Code. 4. Please provide a complete geotechnical 40 scale grading plan review report based on all engineeredgradingplan, when available. The results of subsurface investigation and laboratory testing should be included, along with detailed geologic cross sections depicting sequence of grading, temporary cuts, recommended setbacks, property lines., and adjacent structures. 5. A foundation plan review shall be provided prior to the issuance of building permits. Recommendations for erosion/drainage, expansive soils, soil.,"rock creep, sulfate soils, retaining walls, slabs, flatwork, seismic design parameters, drivewayand pools and spas shall be provided if appropriate. 6. Note to City Staff: Staff should confirm that the Consultants (C.E.G. and R.C,E,/G.E.) have signed the filial dated grading/foundation plans, thereby verifying the plans' geotechnical conformance with tile Consultant's original report and associated addenda, 5:Aprk�icct3\1997\97082',.97082-18-')7 5th Review 11-14.doc Hurn Tree Development 3-9 Category 5 P.N. 97082-1.837 cury OF RANCHO PALOS VERDES GEOTECHNICAL INVESTIGATION RESPONSE REVIEW CHECKLIST T An as built geotechnical report should be prepared by the project geotechnical Consultant following remedial grading of the subject site. The report should include the results of all field density testing, depth of reprocessing and recompaction, as well as a map depicting the limits of grading, locations of all density testing, and geologic conditions exposed during grading/excavation. 1� _g/excavation. The report should include conclusions and recommendations regarding applicable setbacks, foundation recommendations, slope stability, erosion control and any other relevant geotechnical aspects of the site. Limitations: Our review is intended to determine if the submitted report(s) comply with City of Rancho Palos Verdes Codes and generally accepted geotechnical practices, within the local area. The scope of our services for this third party review has been limited to a brief site visit and a review of the above referenced report and associated documents, as supplied by the City of Rancho Palos Verdes. Re -analysis of reported data and/or calculations and preparation of amended construction or design recommendations are specifically not included within our scope of services. Our review should not be considered as a certification, approval or acceptance of the consultant"s work, nor is it meant as aji_acceptance of lia "" il^,,, for final design or construction recommendations made by the geotechnical consultant of rec(ird or f4p project sig -s or engineers. BY:— B3 U.' J lines NT/ I Lancaster, Jr., C.E.G _ Of! Expires 6/30/16 Henry F. Kling, G.E. 2205, Expires 3/31/16 KLIN, CONSULTING GP'&il INC. KLING CONSULTING GROUP. INC. S:\Pro'icct,s11 997\97082W7082-1837 5th RcvioI I - I 4.doc Plum TrS)e I t — fbillell TO- Trent Pulliam, Director of Public Works May 26,, 1993 City of Rancho Palos Verdes FROMz Perry L,, Ehlig, City Geologist SUBJECT: Suggested Guidelines for Permitting Development in the Moratorium Area EST.ABLISFMNT OF MORATORIUM ZONES For the purpose of these guidelines, the Moratorium area is divided into the eight zones listed below and shown on the Moratorium Map, Zone I - Unsubdivided land unaffected by large historic landslides and located uphill or to the west of subdivided areas. (about 550 acres) Zone 2 - Subdivided land unaffected by large historic landslides. (about 130 acres) Zone 3 Unsubdivided land unaffected by large historic landslides and located seaward of Sweetbay Road. (about 15 acres) Zone 4 Land affected by the Klondike Canyon landslide and adjacent land included in the Klondike Canyon Geologic Hazard Abatement District. (about 100 acres) Zone 5 - Land affected by the Abalone Cove landslide and adjacent land where minor movement has occurred due to loss of lateral support. (about 90 acres) Zone 6 - The uphill, westerly and central parts of the Portuguese Bend landslide, where movement can be stopped through mitigation without requiring shoreline protection. (about 210 acres) Zone 7 - The seaward part of the Portuguese Bend landslide where control of movement requires shoreline protection. (about 75 acres) Zone 8 - Land affected by the Flying Triangle landslide including immediately adjacent land. (about 25 acres) DESCRIPTIONs Op ZONES AND SUGGESTED GUIDELINES FOR PET�4MING DEVELOPMENT ZONE I 2�tcksdroynd Zone I includes about 550 acres of undeveloped land, Most is within the uphill Part Of a large ancient landslide that was last active about 100,000 years ago° Landslide topography is modified by erosion of canyons, filling of slide dePressions and smoothing and flattening of slide scarps. Zone I contains some broad areas where slopes are less than 5:1 (horizontal to vertical) but the majority of the area has slopes ranging between 5:1 and 2:1® Slopes steeper than 2:1 Occur locally along the sides of canyons. 3-11 memo of 5/26/93 from P. Ehlig to T. Pulliam, page 2. The large ancient landslide does not underlie all of Zone 1. Land adjoining Palos Verdes Drive South in the southwest part of the zone is unaffected by sliding and probably has a factor of safety in excess of 1.50. Land in the eastern part of the zone is also outside of the large landslide but it contains local landslides. Extensive geotechnical studies have been conducted throughout Zone 1. Major goals of the studies include (1) locating and determining the configuration of the deepest slide plane, (2) determining ground water conditions beneath the area, and (3) analyzing the stability of the ancient landslide, and (4) evaluating methods of improving the areas stability. Geotechnical studies are essentially complete in the eastern half of Zone I but more are needed in the western half. Suggested Guidelines 1m Any land in Zone I which can be shown to have a safety factor of 1.5 or greater in regard to landsliding, or is correctable to a factor of safety of 1.5 through remedial grading, and will upon development have no adverse impact on the stability of adjacent land, shall be granted an exception for habitable development upon completion of all necessary remedial work. (This is consistent with existing City code.) 2,, Any land in Zone I which can be shown to have a safety factor between 1.30 and 1.50 in regard to the large ancient landslide and has a factor of safety of 1.50 or greater in regard to local slope stability shall be granted an exception for habitable development providing it meats all other requirements in guideline I (above) and the following stipulations: a. A network of monitoring and producing wells must be installed in accordance with a plan approved by the Rancho Palos Verdes Redevelopment Agency (RDA). bn A covenant must be attached to each deed agreeing to participate in the Abalone Cove Geologic Hazard Abatement District (ACLAD) and any other district established for the purpose of maintaining the land in a geologically stable condition.. c. Surface drainage improvements must be Installed in accordance with a plan approved by the RDA.. d. A sewer system must be installed to serve all habitable structures. e. All other RDA and City requirements must be mety 3. Any land in Zone I which is to be used for purposes other than habitable structures way be granted an exception for nonhabitable development providing it has a safety factor of 1.15 or greater in regard to the large ancient landslide and it meets the following stipulations a� No land modification may be made which will adversely affect the local or regional stability of the land bo A network of monitoring and production wells must be installed in accordance with a plan approved by the RD -Am c. A covenant must be signed agreeing to support and participate in ACLAD and any other district established for the purpose of maintaining the land An a geologically stable condition. Surface drainage improvements must be installed in accordance with a plan approved by the RDA All Other RDA and City requirements must be met. 3-12 Memo of 5/26/93 from P.. Ehlig to T. Pulliam, page 3. ZONE 2 Background Zone 2 includes about 130 acres Within existing Tract 14195 and Tract 14500 (except lots 1, 2, 3 and 4 which are in the Portuguese Bend landslide), and the subdivided land served by Vanderlip Drive. It is an area of subdued topography within the central part of the large ancient landslide. Slopes of 501 and less prevail over most of the central and downhill parts of Zone 2. Slopes generally range between 5:1 and 3:1 in the uphill part. The flattest parts of Zone 2 overlie a gentle trough in the bedrock structure beneath the slide. The slide base followed the bedrock structure as the slide mass translated across this area. This caused a surface hollow to develop in an east -west direction across this area while the slide was active. The hollow was subsequently filled by stream and slope wash deposits. This created the gentle slopes which drain toward the channels of Altamira Canyon, Available geologic data indicate the base of the ancient landslide is at depths ranging from Igo to 260 feet below the ground surface in most parts of Zone 2. Four to six deep core holes would be desirable to more precisely establish the location of the slide base beneath parts of this area but new findings are unlikely to have a significant impact on existing interpretations. The slide bass is sufficiently flat in the area seaward of upper Narcissa Drive that the overlying slide mass resists movement providing the water table does not rise above its historic levels. Based on well data, the water table was at a depth of 50 to 60 feet beneath most of this area prior to the start of pumping in 1960. The water table is currently at an average depth of about 70 feet. The 25 undeveloped lots in Tract 14195 and 15 in Tract 14500, and an undetermined number in parcels served by Vanderlip Drive, could be developed without adversely affecting the stability of the large ancient landslide. In fact, if development were combined with installation of additional wells, stability would be improved. Most lots can be developed with minimal grading and without a net import or export of earth. Such grading would have no impact on the stability of the deep-seated slime r Ground water is the only variable within Zone 2 which affects its stability. Zone 2 currently contains one monitoring well and four producing -yells. Eight to ten more monitoring wells are needed to provide a detailed picture of ground water conditions within Zone 2, Four to six more producing wells are needed to better control ground water conditions. If the cost of the needed wells were funded from fees paid for permission to develop vacant lots, development would improve the stability of the large ancient landslide. 12gc g:e_Sted Guidelines Development of undeveloped lots shall be permitted in existing Tract 14195 and Tract 14500 (except lots 1, 2, 3 and 4 which are in the Portuguese Bend landslide), and the subdivided land served by Vanderlip Drive subject to the following stip-ulationsv a, The lot owner must sign a covenant agreeing to participate in ACLU and any Other district whose purpose is to maintain the land in a geologically stable condition, 3-13 Memo of 5/26/93 from P„ Ehlig to T. Pulliam, page 4. b The lot owner must pay a fee to help defray the cost of installing additional monitoring and producing wells9 Said fee shall not exceed the differential between the sum of AcLAD fees previously assessed to an equivalent sized developed lot and the sum previously assessed to the undeveloped lot. (The annual tax difference between a developed lot and an undeveloped of equal size is determined by the square footage of improvements.) c, Prior to issuance of a building permit, a geotechnical report must be submitted to and approved by the City's geotechnical reviewers indicating what, if any, local geologic hazards must be corrected prior to construction, and shall specify foundation designs based on field and laboratory studies. Grading exceeding 250 cubic yards shall require special approval by the City staff. d. If building occurs prior to installation of a sewer system, a covenant must be signed agreeing to a sewer system and providing necessary easements for one. e. All lot drainage deficiencies, if any, identified by the City staff must be corrected f. Runoff from all buildings and paved areas must be contained and directed to the street or to an approved drainage course. 90 All other relevant building code requirements must be met. ZOM 3 Background About 15 acres of undevelop land is present within the area bounded by the main channel of Altamira Canyon on the west, Sweethay Road on the north, and the edge of the Portuguese Bend landslide on the east and southeast. Most of this land has gentle rolling topography and could be developed into residential lots with only minor grading. Available data indicates the base of the large ancient landslide is nearly horizontal beneath this area and is at a depth of 200 to 250 feet below the ground surface. Three to five deep core holes are needed to confirm this. Ground -water conditions are the main variable affecting the stability of the large ancient landslide beneath this area. The area should remain stable as long as the water table rises no higher than its historic high level, The area contains two producing wells but no monitoring wells. Data from the two wells and Projections from wells in the adjoining area indicates the water table is 10 to 15 feet lower than it was in 1983. At present, the water table ranges from about 60 to as much as 130 feet below the ground surface. Three to five monitoring wells and one or two additional producing wells should be installed during development of thia area. Suggested Guidelines Additional geologic studies are needed to accurately locate the base of the large ancient 10-ndslide beneath this area« If the results of such studies are favorable, devel4agment, could be permitted contingent upon meeting all City requirements pertaining to development of residential 'tracts and subject to the following stipulationS2 a. Ground water monitoring and production wells must be installed in accordance with a plan approved by the RDA. b, Surface drainage channels must be paved in accordance with a plan approved by the RDA, 3-14 Memo of 5/26/93 from P. Ehlig to T. Pulliam, page 5� c,, A sewer system must be installed,, dA A covenant must be attached to each deed requiring the owner to participate in AC LAD and any other district whose purpose is to maintain the land in a geologically stable condition. e. All other RDA and City requirements must be met. Background The Klondike Canyon Geologic Hazard Abatement District has controlled the Klondike Canyon landslide. The maximum measured horizontal displacement is only 2.5 feet, all of which occurred prior to 1987. The primary cause of instability was the buildup of artesian water pressure beneath the downhill part of the landmlide. COntrol was obtained by pumping water from a well at the beach. Infiltration was reduced by installing a culvert in Klondike Canyon from Palos Verdes Drive South to the beach. Infiltration can be further reduced by lining Klondike Canyon at least as far upstream as the head of the Klondike Canyon landslide. This would would reduce the likelihood of renewed movement in the uphill part of the slide during periods of high rainfall. the factor of safety is not an issue in the Klondike Canyon landslide, The slide is UnCOnventional in that the downhill edge of the slide's base terminates more than 100 feet below the ground surface. This was made possible by upward bending of the downhill part of the slide. Artesian ground water pressure facilitated the uplift. The factor of safety has not been calculated because of the slide's unconventional nature, Calculations would almost certainly yield a factor of safety well above 1.5 providing there is no artesian uplift pressure. Zone 4 contains part of the Seaview tract (Tract 22835) and the Portuguese Bend Club. Most lots are already developed within these tracts. About half of Zone 4 consists of undeveloped land located on the ridge between Klondike Canyon and the Portuguese Bend landslide. Suggested Guidelines I. Lot owners in the Seaview tract and Portuguese Bend Club may rebuild or make additions to existing buildings subject to the following stipulationsr a. The owner must sign a covenant agreeing to support and participate in the Klondike Canyon Geologic 'Hazard Abatement District and any other district whose purpose is to maintain the land in a geologically stable condition. h. The building must connect to the Los Angeles County sewer system or to an approved holding tank. There shall be no on-site disposal of waste water. c. Prior to issuance of a building permit, a geotechnical report must be submitted to and approved by the City's geotechnical reviewers indicating what, if any, local geologic hazards must be corrected prior to construction, and specifying foundation designs based on field and laboratory studies. d. Roof runoff from all buildings and paved areas on the site must be contained and directed to the street or an approved drainage course. e� All lot drainage deficiencies, if any, identified by the City staff must be corrected, f. All other relevant building code requirements must be met, 3-15 Memo of 5/26/93 from P. Ehlig to T. Pulli.am, page 6. 2. Undeveloped land within the Klondike Canyon Geologic Hazard Abatement District is mainly west of Klondike Canyon and north of Palos Verdes Drive South and is accessed from the east edge of the active Portuguese Bend landslide. Development of this land shall be held in obeyance until the adjacent part of the Portuguese Bend landslide is stabilized. zone 5 Background The Abalone Cove landslide has been stabilized by lowering the water table. Most movement occurred prior to 1985. only creep at rates of less than an inch per year and local readjustments have occurred since 1935® Existing abatement activities appear adequate to prevent renewed slide movement during rainy periods, Nonetheless, it would be prudent to limit building to that permitted by the current City guidelines for this area until slide creep has stopped and planned abatement measures, such as drainage improvements, sewers and shoreline protection are completedm .Suggested Guidelines 1. Development shall be limited to that currently permitted by City guidelines, for this area until after planned remediation is completed and slide creep has stopped. 2. After the above condition are met, building shall be permitted subject to all conditions imposed in Zone 2, andT ao a sewer system must either he in operation or a holding tank must be utilized, Wo on site sewage disposal will be permitted, b, A geotechnical study must be made to determine the suitability of the site for all proposed improvements and to provide foundation design specifications for proposed buildings. in addition, foundations must be inspected and approved by a geotechnical consultant during construction. C. A covenant must be signed by the owner specifying that the City shall be held harmless in the event that ground settlement or other forms of ground movement damage improvements. Zone 6 Background The Portuguese Bend landslide can be divided into a landward zone (Zone 69 which can be stabilized without shoreline protection, and a seaward zone (Zone 73 which -requires shoreline protection for stabilization. Palos Verdes Drive South forms the approximate boundary between the two zones. Zone 6 includes about 210 acres in and adjacent to the landward and central parts of the Portuguese Bend landslide. As a result of remediation, movement has stopped or nearly stopped in the northern and western parts of Zone 6. Movement continues at a rate of one to three feet per year in the central and southeastern part of Zone 6 but is less than one-tenth the rate of movement prior to remedial grading in 1986. 3-16 Memo of 5/26/93 from P� Ehlig to T. Pulliam, page 7. Remediation to date includes (1) removal of water from 17 wells distributed throughout the area, (2) the moving of about one million cubic yards of earth so as to restore drainage and reduce driving force in the northern and eastern parts of the area, and (3) installation of a temporary culvert to conduct runoff to the oceane Movement can be stopped throughout Zone 6 by additional improvements in surface drainage and additional remedial grading. In the area west of Portuguese Canyon most of Zone 6 is subdivided into lots, part of which have houses on them. This and the subsurface structure of the landslide limit slide abatement to installation of wells, improvements In surface drainage and installation of a sewer system in most parts of the subdivided area, Lot boundaries should be reestablished before major surface modifications are permitted. The slide has displaced lot improvements, streets and utilities from their original locations. As a result, lots are no longer in their legally described locationsa The amount of displacement varies from one part of the slide to another, Xn places, the original lot boundaries have been distorted and fragmented by abrupt changes in displacement across slide ruptures. The only viable solution is to void the original descriptions of lot locations and establish new ones. East of Portuguese Canyon, Zone 6 is undeveloped. As a result, remedial grading can be performed without interference from existing improvements. The slide base is relatively shallow in the northeast part of this area� it may be feasible to remove the northeast part of slide and replace it with compacted fill founded on firm bedrock, This would create a slide -free area with a factor of safety in excess of 1.50, Suggested Guidelines 1. As long as this part of the slide continues to move, improvements shall be limited to landslide abatement and other improvements permitted by current City guidelines for this areae 2. After the landslide has stopped moving and there is reasonable assurance that movement will not resume at a future time, land ownership boundaries shall be reestablished. This may be done under the auspices of the Redevelopment Agency but the costs must be paid by land owners. 3. Following reestablishment of legal lot boundaries, building shall be permitted in the subdivided part of Zone 6 subject to the same conditions imposed in Zone 5 under suggested guideline 2. C After reestablishment of legal land ownership boundaries, the unsubdivided parts of Zone 6 shall be subject to the same suggested guidelines as Zone 10 ZONE 7 The 75 acres of the Portuguese Bend landslide located seaward of Palos Verdes Drive South is poorly controlled by existing abatement activities. Permanent control will require shoreline protection. No development should be permitted in this area until after enactment of a plan of control which includes shoreline protection, 3-17 Memo of 5/26/93 from P. Ehlig to T. Pulliam, page 8. zone 8 The Flying Triangle is currently uncontrolled. No development should be permitted within it or land affected by it until the Flying Triangle landslide has stopped moving and is under the control of an abatement district, 015• Al 7d fi^ 'w r ' A-i" �- yr.�.,s� o 1. w r •ems.