COUNTY OF SAN MATEO

Inter-Departmental Correspondence

Department of Public Works

DATE:

October 18, 2007

BOARD MEETING DATE:

October 30, 2007

SPECIAL NOTICE/HEARING:

None

VOTE REQUIRED:

4/5ths Vote

TO:

Honorable Board of Supervisors

FROM:

James C. Porter, Director of Public Works

SUBJECT:

La Honda Slides, Executive Summary

Recommendation

A) Adopt a resolution:

1)

Authorizing a County contribution equivalent to funds that are made available from non-County sources, up to a maximum of $3,000,000 for the implementation of slope stabilization activities in the La Honda area and directing the Department of Public Works to facilitate slope stabilization projects utilizing these funds, if equivalent funds are received;

2)

Appropriating funds not to exceed $400,000 from the Department of Public Works Road Fund to construct a french drain system to help dewater the failed slope areas;

3)

Authorizing the Department of Public Works to continue to winterize previously failed slope areas by re-grading and reseeding them annually.

B) Adopt a resolution:

1)

Authorizing an Appropriation Transfer Request in the amount of $250,000 from the General Fund, Departmental Reserves to the Road Fund for the cost of the improvements to Escondido Drive as per recommendation 2).

Vision Alignment

Commitment: Ensure basic health and safety for all.

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

Background

History

Heavy winter rains in 2005 reinitiated landslide movement in the immediate vicinity of lower Scenic Drive.

Subsequent to the land movement in 2005, San Mateo County contracted with
UPP Geotechnical, Parikh Consultants and with Soil Engineering Construction (SEC) in order to develop and evaluate possible remedial measures for mitigating the slope failures.

Discussion

San Mateo County met with property owners in August, 2007 and presented the property owners with a series of mitigation options, which were developed by the County’s geotechnical team.

These measures would reduce, but not eliminate the risk of future earth movement.

The most extensive mitigation plan presented is estimated to cost $6,355,500.

Recommendation Benefits:

Staff believes that an improved, all weather Escondido Drive can serve as an alternate access point to portions of the community and that dewatering the slope, through the installation of a french drain, can effectively reduce the risk of future ground movement. Re-grading the hillside to eliminate ponding will also promote drainage off the site.

Fiscal Impact

The cost for improving Escondido Drive is estimated to be $250,000. The cost for installing the french drain system is estimated to be $400,000, with annual winterization costs estimated to be $50,000.

Sufficient funds for the construction of the french drain improvements and for winterization work are available in Public Work’s Road Fund budget, although the funds have not been specifically budgeted. It is recommended that County General Fund reserves be used for the improvements to Escondido Drive and to match any non-County funding to pay for any additional construction activities. The Road Fund does not have an adequate balance to absorb implementation of all of the recommended mitigation measures without the elimination of a significant portion of the road construction projects which have previously been budgeted.