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TO: HONORABLE MAYOR AND MEMBERS OF THE CITY COUNCIL
FROM: DIRECTOR OF PUBLIC WORKS
DATE: APRIL 15, 2003
SUBJECT: INVESTIGATION INTO THE TARAPACA LANDSLIDE
The eastern slope of the San Ramon Canyon immediately to the east of the Palos Verdes Drive East switchbacks shows signs of failure. Cracks and other areas of distress have been clearly visible for some time. In late 2002, the City Council awarded a contract to GeoSyntec Consultants, Inc. (GeoSyntec) to investigate conditions, identify risks, and recommend solutions. This report presents that investigation.
Geologic Setting and Conditions:
The GeoSyntec investigation concluded that a landslide exists along the eastern side of the San Ramon canyon just east of the PVDrive East switchbacks. The landslide, named the Tarapaca Landslide, is an active landslide that borders the eastern edge of the larger and inactive South Shores Landslide. The Tarapaca Landslide is presently sliding westerly into the San Ramon canyon, partially blocking stream flow, and contributing sediment for transport to downstream areas of the canyon.
A landslide exists at this location due to a combination of the following factors:
These three factors have set up a cycle of
Left unchecked this cycle will occur indefinitely, the landslide will grow in size, and a solution will grow in cost.
At the outset of this report it is important to note clearly that:
Risks / Adverse Effects
The cycle described above has the following adverse effects:
The length of San Ramon canyon from the upper reaches of the landslide to 25th Street is approximately 1500 lineal feet. This project area involves two cities, and a County of Los Angeles parcel (Friendship Park), within the City of Rancho Palos Verdes. Approximately 450 lineal feet of the canyon is on property owned by the City of Rancho Palos Verdes, approximately 250 lineal feet is within the County of Los Angeles parcel, and 800 lineal feet is with a parcel within the City of Los Angeles.
The active part of theTarapaca Landslide is principally within the City of Rancho Palos Verdes on Lot 8 of Tract 20856. Part of the landslide, however, is within the County of Los Angeles parcel.
Most of the toe of the landslide is within the City of Rancho Palos Verdes.
Surface run off entering fissures of the landslide originates from private property within the City of Rancho Palos Verdes, Lots 7, 8, 9, and 10 of Tract No. 20856, and from the County parcel. The City of Los Angeles is a receiver of drainage in the San Ramon canyon.
The sediment that erodes into the canyon comes principally from within the City of Rancho Palos Verdes
The sediment plugs a storm drain, and washes onto a roadway owned by the City of Los Angeles.
In preparation of this report staff contacted both the County of Los Angeles, and the City of Los Angeles.
There have been only brief discussions with the County, however, given that a portion of the landslide is on County property, and because a significant amount of surface flow that enters the head of the landslide originates on County property, there is role for the County of Los Angeles regarding the needed improvements within the City of Rancho Palos Verdes. One of the recommendations of this report is to make additional contact with representatives of the County of Los Angeles.
There have been several in depth meetings with the City of Los Angeles regarding this project. Because the landslide impacts their roadway and storm drain the City is desirous of a solution. At one point in time the City of Los Angeles contemplated construction of a debris basis just upstream of 25th Street, however, in more recent discussion there is thought that if the City of Rancho Palos Verdes were to construct a canyon storm drain, the City of Los Angeles would consider extending that improvement downstream to 25th Street. Irrespective of their actions, staff does not see a role for the City of Los Angeles regarding the needed improvements within the City of Rancho Palos Verdes.
Three solutions have been identified
These costs include design and construction. However, the cost of permits, environmental documentation and approvals, re-vegetation of slope, and the management of the re-vegetation are all additional.
Staff recommends that the City pursue Option Two, construction of a storm drain system to control erosion. The reason is that the storm drain will control erosion at the toe of the landslide and bypass the source of erosion, thus removing one of steps in the current cycle of degradation that currently exists along the canyon. This approach will reduce the potential for enlargement of the landslide enlargement, and provide control of water retention to prevent infiltration of water into the South Shores Landslide. In addition, this solution together with a companion storm drain project in the City of Los Angeles will solve the problem of flooding and debris deposition at 25th Street.
Adopting the staff recommendations will begin the process to mitigate the Tarapaca Landslide. Staff will solicit proposals for engineering services to design the needed canyon improvements, and contact the County of Los Angeles for their financial participation. Staff will return to the City Council with a recommendation for award of contract for engineering services, and a progress report on discussions with the County.
This project faces many challenges, and processes to construct the needed and the improvements will be lengthy. Some of the challenges facing this project are:
The recommended actions include the expenditure of an additional $5,000 for engineering services. Staff anticipates this expenditure for engineering services to meet with impacted property owners, and agencies in an effort to assemble a funding program.
Staff could identify no immediate funding sources for this project other than General Fund reserves. The cost estimates provided in this staff report are preliminary and should be considered as an indicator of significant future costs rather than a precise budget. For example the first estimate of costs for the San Ramon Drainage project was $700,000.
The FY2002-2003 estimated General fund revenues in excess of adopted expenditures are only $827. Therefore, the additional appropriation for this project cannot be funded within this year’s anticipated revenues and will have to be drawn from the General fund reserve. The calculation of the projected General fund reserve available for appropriation, which is below the reserve policy level, is summarized below.
Resolution 2003 -
Photographs of the Canyon
RESOLUTION NO. 2003-
A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF RANCHO PALOS
VERDES, AMENDING RESOLUTION 2002-45, THE BUDGET APPROPRIATION
FOR FISCAL YEAR 2002-03, FOR A BUDGET ADJUSTMENT TO THE CITY’S CAPITAL PROJECTS FUND
WHEREAS, Section 3.32 of the Rancho Palos Verdes Municipal Code provides that all expenditures in excess of budgeted allocations must be by supplemental appropriation of the City Council; and
WHEREAS, on June 12, 2002, the City Council of the City of Rancho Palos Verdes adopted Resolution 2002-45, approving a spending plan and authorizing a budget appropriation for the 2002-03 fiscal year; and
WHEREAS, it is necessary for the City to allocate additional funds to conduct additional engineering investigations into the Tarapaca Landslide; and
WHEREAS, a budget increase in the Capital Improvement Projects Fund is necessary to authorize the expenditure of additional funds for the project.
BE IT, THEREFORE, RESOLVED BY THE CITY COUNCIL OF THE CITY OF RANCHO PALOS VERDES:
The following adjustment be made to the Capital Improvement Projects Fund budget::
CIP Fund 330-930-35 Professonal/Technical Services $ 5,000
PASSED, APPROVED, AND ADOPTED THE 15th DAY OF APRIL, 2003.
Resolution No. 2003-
State of California )
I, JO PURCELL, City Clerk of The City of Rancho Palos Verdes, hereby certify that the above Resolution No. 2003- was duly and regularly passed and adopted by the said City Council at regular meeting thereof held on April 15, 2003.