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Rancho Palos Verdes has the distinction of having one of the largest, if not the largest, landslides in the contiguous 48 states. The total area of what is commonly referred to as the ancient landslide is approximately 870 acres in size. Today the area is made up of a series of smaller landslides, which have shown varying degrees of movement during the last 50 years. It is not unusual for this entire area to sometimes be referred to as either the Abalone Cove Landslide or the Portuguese Bend Landslide but these are actually distinct slide areas. In addition there are two other identified slides which are known as the Klondike Canyon landslide and the Flying Triangle landslide.
The Portuguese Bend Landslide.
The first area to move in recent history was the Portuguese Bend slide. This landslide area is about 270 acres and began moving in 1956. County engineers had apparently allowed the storage of over 300,000 cubic yards of soil from construction of the Crenshaw right-of-way extension in exactly the wrong location, on a scarp of the ancient landslide.
Since that time several projects, including installation of de-watering wells, construction of gabions to prevent wave erosion, insertion of caissons, establishment of “half-round” metal pipe drainage systems and remedial grading, have been undertaken to control the landslide movement, with different levels of very modest short-term success. The de-watering wells in the most active portion of the Portuguese Bend Landslide have been low producers (contrary to the wells in the Abalone Cove and Klondike Canyon Landslides) and the caissons have long since migrated toward the ocean where some of their remains can still be seen. The metal pipes utilized to collect storm water runoff have been difficult to maintain and are currently in poor condition. Likewise, the gabions eventually were destroyed by the ocean.
Through the years the City has loaned over $10 million to the Rancho Palos Verdes Redevelopment Agency for studies and capital improvements in an attempt to control the movement of the Portuguese Bend landslide. With the death of Dr. Perry Ehlig in December, 1999, there has been little activity in developing new ideas and techniques for stabilizing the Portuguese Bend Landslide.
The Abalone Cove Landslide.
The Portuguese Bend slide was followed in 1974 by movement of the Abalone Cove Landslide below Palos Verdes Drive South. By 1978, that Landslide had migrated above Palos Verdes Drive South. The total Abalone Cove landslide area is about 80 acres in area. In September 1978, the City Council responded to the landslide movement and adopted Urgency Ordinance No. 108U, which established the Landslide Moratorium Area in and around the Portuguese Bend landslide (described as the area outlined in red in the ordinance) (the “Red Area”).
The Moratorium Ordinance was amended on several occasions to permit certain activities within the Moratorium area, including: repairs and renovations to existing structures (Ordinance No. 118U); remedial landslide grading (Ordinances No. 120U; 130U and 208U) and other minor changes to existing structures (Ordinances 123U, 128U). The Council also amended the Moratorium to allow minor projects and non-residential structures to be constructed in the Moratorium Area (Ordinances No. 130U, 131U, 140U). In 1989, the Code was amended to allow the construction of small additions and detached garages to developed properties within the Moratorium Area (Ordinance No. 208).
The Abalone Cove Landslide Abatement District (ACLAD).
The Abalone Cove Landslide Abatement District (ACLAD) was formed by the City in 1981. ACLAD is a “geologic hazard abatement district" created by the City of Rancho Palos Verdes for the “purposes of prevention, mitigation, abatement or control” of the Abalone Cove landslide, pursuant to special legislation passed by the California Legislature in l980. It was the first geohazard abatement district created in the state.
The District is governed by five elected Directors, which serve for a term of four years. Under the California Improvement Act of l911, the District may assess properties benefiting from the mitigation or abatement efforts for the cost of the improvements. ACLAD is broadly responsible for abatement efforts to prevent movement of the Abalone Cove landslide. To do this, the district operates and maintains dewatering wells and associated discharge lines, easements to assure access to the dewatering facilities, monitors the groundwater elevations in the greater Abalone Cove area, reviews biannual measurements of the Global Positioning System (GPS) stations for evidence of slide movement and works with the City of RPV to maintain certain storm drain culverts and other improvements related to abatement of that Landslide. The majority of the board’s time, effort and annual expenditures are directed at maintaining the dewatering wells and discharge lines.
Possibly due to dewatering wells installed by ACLAD and the RDA, landslide movement decreased until the unusual winter rains in the winter of 2004-2005. In June 2002, the installation of the Abalone Cove Sewer system was completed by the Redevelopment Agency at a total cost of over $5 million. This project exhausted the capital project funds that originated from the settlement of a Lawsuit that was filed against the County and the City by several property owners within the Abalone Cove area (often referred to as the Horan Settlement Agreement).
The Rancho Palos Verdes Redevelopment Agency (RDA) and the Joint Powers Improvement Authority----------------------------------- -
In 1984, the Rancho Palos Verdes Redevelopment Agency (RDA) and the Joint Powers Improvement Authority (JPIA) were created. The RDA was created by the City of Rancho Palos Verdes under the Community Redevelopment Law to address the physical and economic blight and damage that the landslides were causing and to provide a financing mechanism for construction and maintenance of landslide abatement projects. The Redevelopment Project Area includes the Abalone Cove, Portuguese Bend and Klondike Canyon landslides and adjoining areas and generally corresponds to the boundaries of the ancient landslide complex and the City’s landslide moratorium area. The Agency’s Project Area No. 1 was divided into two geographical areas: Abalone Cove and Portuguese Bend. The geographical areas are accounted for in separate funds of the Agency.
The Klondike Canyon Landslide.
In 1980, movement was also noticed in both the Klondike Canyon area as well as the Flying Triangle, the majority of which is in the City of Rolling Hills. As originally drawn, in September 1978, the Landslide Moratorium Area did not include any portion of the Seaview Tract, which is located in an area that currently is referred to as the area outlined in blue on the City’s Moratorium Map (the “Blue Area”).
In July, 1980, Dr. Perry Ehlig, who at that time was a consulting geologist working with Robert Stone and Associates (“RSA”) brought to the City’s attention cracking within the western end of the Seaview Tract. Dr. Ehlig recommended that the City conduct studies to determine if a landslide was causing the cracks. The Council authorized RSA to perform the studies, which included trenching and borings, and to report back to the Council.
In July, 1981, concerned homeowners in the Klondike Canyon landslide area formed the Klondike Canyon Residents Protective Association to address the control of surface and subsurface water that were identified by RSA as landslide mitigation measures that should be addressed. On September 15, 1980, RSA submitted its report to the City. The report discussed the results of the investigations and stated that a landslide was the cause of the cracks. The RSA report stated that the landslide probably was caused by increased accumulation of ground water, and that the limits of the landslide were not known. The RSA report recommended certain actions to reduce the amount of water that enters the landslide by sealing cracks, installing certain drainage devices, and performing additional studies to determine the boundaries of the landslide.
RSA produced an additional report dated December 10, 1980, which identified the extent of the headscarp of the landslide and recommended subsurface investigations be performed. In response to the RSA reports, on February 3, 1981, the City Council adopted Ordinance No. 139U, which added the entire Seaview area to the Landslide Moratorium as part of the Red Area. The City Council also authorized additional investigations be performed to gain a further understanding of the Klondike Canyon Landslide and its boundaries.
During 1981, subsurface geologic studies were performed in an attempt to ascertain the eastern limits of the Klondike Canyon Landslide. On January 21, 1982, RSA presented another report to the City Council describing the geologic investigations that had been performed (borings and trenching) and RSA’s findings and recommendations. The RSA report stated that the Landslide only included 36 lots of the Seaview Tract and that it was “unlikely that the Klondike Canyon landslide will extend further east than its present boundary. “ The RSA report stated that the most likely causes of the movement of the Klondike Canyon Landslide were ground water and “frictional dragging force” from the Portuguese Bend Landslide.
Subsequently, on March 2, 1982, the City Council adopted Ordinance No. 148U. That Ordinance amended the Moratorium to reduce the boundaries of the Klondike Canyon Landslide to exclude the eastern portion of the Seaview Tract so that only the 36 lots on the western end that were within the boundaries of the Klondike Canyon Landslide remained within the Moratorium. This is the same area that currently is described as the Blue Area; however, at that time it still was included as part of the Red Area.
In September 1989, the City Council also amended the Code to change the description of the thirty-six lots that are within the Seaview Tract and a portion of 2 Yacht Harbor Drive as the area outlined in blue on the Moratorium Map (“the Blue Area”) and to adopt more flexible development criteria for development within the Blue Area (Ordinance No. 247). The Council’s action was based on the fact that this area had been subdivided previously and was almost completely developed (only one or two lots were not developed at the time) and included a sewer system, along with a lack of indicators of recent movement in the Blue Area, all of which was believed to distinguish this Area from other portions of the Landslide Moratorium Area.
As a result of these actions, the City’s current Landslide Moratorium Ordinance (see Municipal Code Chapter 15.20) recognized two separate areas within the overall landslide moratorium area that were subject to differing development criteria. Unlike properties located in the Red Area, owners of properties in the Blue Area were entitled, subject to certain conditions, to seek approval of a landside moratorium exception permit for “[t]he construction of residential buildings, accessory structures, pools/spas, and grading….” (Municipal Code Section 15.20.040 K.) The Code also required applicants to submit geological studies reasonably required to demonstrate to the satisfaction of the city geotechnical staff that the proposed project would not aggravate the existing situation.
In May 2005, following the unusually heavy rains during the winter of 2004-2005, City Staff first witnessed indications that the Blue Area may be experiencing new landslide movement. The movement was brought to the attention of the City’s geologist, who documented the movement and recommended that the City continue to monitor the area. In October 2005, Staff received a report from the City Geologist in response to a geology report prepared by an applicant seeking to build additions to an existing residence at 4380 Dauntless in the Blue Area. The City geologist alerted Staff that observed cracks in the area were indicative of land movement and that Staff should be aware of this before issuing the development permits to the applicant.
Based on this alert from the City geologist, Staff placed an item on the City Council’s November 15, 2005 agenda to consider whether the more lenient development standards that have been allowed in the Blue Area since 1989 should be repealed so that the Blue Area will be subject to the same development restrictions as the remainder of the Landslide Moratorium Area, as was the case from February 1981 through September 1989. Based on public testimony, the City Council adopted Urgency Ordinance No. 427U establishing a temporary 60-day moratorium on the processing and issuance of building, grading or other permits, in the Blue Area, unless otherwise exempted from the moratorium. The 60-day moratorium was to allow the City’s Geologist time to acquire additional land movement data, analyze the data and report his findings to the City Council.
Ordinance No. 427 U has been extended four times, once in order for additional time to collect more GPS data and for the City’s Geologist to be able to review and evaluate that data and prepare a report to the City Council; a second time so that the City Council and the public would have adequate time to review the report from the City’s Geologist, and a third time so that the City’s geologic experts could prepare reports for a study session that the City Council would like to conduct regarding construction within the entire Moratorium Area, and a fourth time to accommodate this Workshop on the Landslide Moratorium. The fourth extension of Ordinance No. 427 U will expire on October 25, 2006.
The Klondike Canyon Landslide Abatement District.
By 1982 the Klondike Canyon Landslide Abatement District had been formed by the City. The District installed a dewatering well seaward of PVDS and drainage facilities upstream of PVDS including horizontal dewatering wells. (Currently, the primary focus of the District is to operate and maintain these facilities.)