COUNTY OF SAN MATEO

Inter-Departmental Correspondence

Department of Public Works

DATE:

December 24, 2007

BOARD MEETING DATE:

January 8, 2008

SPECIAL NOTICE/HEARING:

None

VOTE REQUIRED:

Majority

TO:

Honorable Board of Supervisors

FROM:

James C. Porter, Department of Public Works

SUBJECT:

La Honda Area Landslide

RECOMMENDATION:

Adopt a resolution:

1.

Authorizing execution of an agreement with Soil Engineering Construction, Inc. (SEC) for design services for work within the landslide on Scenic Drive in the La Honda area for an amount not to exceed $100,000, and

2.

Waiving the Request for Proposals process.

VISION ALIGNMENT:

Commitment: Ensure basic health and safety for all.

Goal 7: Maintain and enhance the public safety of all residents and visitors.

This action furthers the above-mentioned commitment and goal by initiating the process to implement mitigation efforts and improve the stability of a landslide in the community of La Honda, subject to previous direction by your Board.

BACKGROUND:

PREVIOUS BOARD ACTION

Adopted Resolution No. 069071, on October 30, 2007, authorizing among other things, that the Department of Public Works proceed with preparations for the construction of recommended slope stabilization improvements such that the work could begin at the earliest opportunity during the next construction season, and continue to communicate and work with the La Honda community in the consideration of cooperative funding arrangements and other potential third party funding sources. The Board considered the notion of a County matching contribution of up to $3,000,000, but took no action regarding that consideration.

HISTORY

Two separate landslides occurred in the La Honda Area in 1998, one between the closed portion of Recreation Drive (lower Recreation) and a portion of Scenic Drive (lower Scenic) and the other on the hillside immediately above and below (including) lower Scenic Drive. Lower Recreation Drive, which was previously damaged in Winter 1995/1996 and repaired by County forces, was damaged again during the 1998 slide and has not been accessible since that time.

Heavy winter rains in 2005 reinitiated landslide movement in the immediate vicinity of lower Scenic Drive. Lower Scenic Drive was once again displaced by landslide movement and, over the course of the following two years, significant movement resulted in a much larger landslide mass that currently encompasses the entire 1998 landslides and significantly larger areas both above and below these landslides. The segment of Scenic Drive located above the failure (upper Scenic) is now located very near the uppermost limits of the visible slide and tension cracks have developed in the road, indicating that additional expansion of the slide could have a direct impact on this segment of road.

San Mateo County contracted with UPP Geotechnology to re-evaluate the lower Scenic Drive segment of the landslide and with Parikh Consultants to geotechnically evaluate the upper segments of the slide, and to provide recommendations to stabilize the slope failures. Public Works also contracted with Soil Engineering Construction, Inc., a geotechnical engineering and construction firm (“SEC”), to develop further strategies for addressing the large-scale slope failures and to protect and restore threatened or damaged segments of the road.

As part of winterization efforts, the Department of Public Works has re-graded and reseeded the failed slopes, and County forces have installed a portion of a french drain system to help dewater failed slope areas. Construction of the french drain system has been suspended due to inclement weather conditions.

DISCUSSION:

SEC has presented to the County a repair scheme that involves construction of various elements throughout the slide mass that is based on data provided by UPP Geotechnology and Parikh Consultants. The repairs would be implemented using a design/build contracting approach, rather than the typical design, bid award, construct approach. SEC is being recommended to perform this project because of their successful completion of slope failure repairs on Polhemus Road near Highway 92 using a similar design/build approach and their significant expertise in geotechnical engineering and landslide repair. Restoration of Lower Scenic Drive is not included in the proposed Agreement with SEC, but will be designed by staff and separately constructed through another contract.

SEC is prepared to begin development of design plans in order to begin construction in the Spring of 2008, based on a design-build approach. This proposed development and planning agreement with SEC (“Plan Development Agreement”) is the first step in the formal process of contracting for the construction of the entire slide mitigation project and is a precursor to an agreement regarding the actual construction of the slope stabilization improvements. The Plan Development Agreement, allows the preparations for construction to continue, while the full funding is still being explored and discussed with the La Honda community.

FISCAL IMPACT:

The design of the repairs recommended by SEC for remediating the slide mass, restoring the damaged lower Scenic Drive, and constructing subsurface drainage systems are estimated to cost $100,000. The Department will return with future contracts for constructing the mitigation measures, subject to the availability of funding. It is currently anticipated that the County’s total cost for the planning, design and construction of the slope stabilization improvements would not exceed $3,000,000 with an additional $3,100,000 being provided by the La Honda community through an assessment district that is yet to be formed.