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SMITH -EMERY SAN FRANCISCO
An Independent Commercial Testing Laboratory
1940 Oakdale Avenue
San Francisco, CA 94124
(415) 642-7326
Fax (415) 642-7055
SEP 16 2019
City of Rolling Hills
B7,31 East Washington Blvd.
L sAngeles, California90021
(213) 749-3411
Fax (213) 746-7228
September 13, 2019 SESF File No. 7141-1
SESF Report No. 19-176
Rolling Hills Building Department
2 Portuguese Bend Road
Rolling Hills, California 90274
RE: Proposed House Addition
67 Portuguese Bend Road
Rolling Hills, California
SUBJECT: Geotechnical Consultation
Foundation Recommendations
Introduction
A Smith -Emery staff member visited the subject property on August 24, 2019 and observed the soil
and rock conditions at the site as related to the proposed approximately 725 square foot addition to
the existing residence. The site is located within the Flying Triangle Landslide Area in Rolling Hills,
California. No evidence of ground cracking or heaving was observed at the site during our
reconnaissance.
Proposed Construction
We understand an addition is planned for the existing wood framed structure and will consist of
similar construction materials and building loads. We also understand steel stem walls with cribbing
are planned for the addition to match the existing structure.
Purpose
The purpose of our consultations is to examine the site conditions and develop conclusions and
recommendations for design and construction of the proposed foundation support.
67 Portuguese Bend Road SESF File No. 72141-1
Rolling Hills, California SESF Report No. 19-176
SMITH -EMERY SAN FRANCISCO
Site Conditions
The subject site is a relatively level parcel on the west side of Portuguese Bend Road and north of
Running Brand Road. The overall topography of the area slopes downward to the west-southwest.
There is an approximately 140 foot high escarpment about 550 feet northwest of the property. The
original grading of the parcel consisted of an approximately 3 to 4 foot cut into underlying bedrock
block. The site elevation is 860 feet above Mean Sea Level (MSL). Subsurface conditions consist of a
gray to tan shale known as the Altamira Shale of the Monterey Formation that is moderately
weathered, moderately fractured, hard, and thinly bedded. The shale unit exposed at the site is
horizontally bedded.
Conclusions and Recommendations
The Flying Triangle slide in the area of the subject project at 67 Portuguese Bend Road, Rolling Hills
is slow moving. We have monitored the home next door at 69 Portuguese Bend Road for over 25
years. Our responsibilities have been to monitor ground movement for the purpose of leveling steel
supporting framework upon which the house structure is founded. The movement has been minimal.
It is our opinion that the house structure at 67 Portuguese and its proposed addition of 25% increased
area will have no effect on the landslide activity whatsoever.
The proposed shallow spread footing foundation, bearing on undisturbed shale may be supported on
spread footings bearing on the existing subgrade.
Spread footings should have a minimum embedment of 18 inches below the lowest adjacent finished
grade and be a minimum width of 12 inches. For this condition we recommend an allowable bearing
value of 2,000 pounds per square foot (psf) for dead plus real live loads. The bearing pressures may
be increased by one-third for total design loads, including wind or seismic.
We estimate that settlement of the new foundation relative to the existing foundation when designed
and constructed as recommended herein will be less than about one-half of an inch.
67 Portuguese Bend Road SESF File No. 72141-1
Rolling Hills, California SESF Report No. 19-176
SMITH -EMERY SAN FRANCISCO
Limits of Investigation
The analyses, conclusions, and recommendations contained in this report are based on site conditions
as they existed at the time of our reconnaissance and further assume the observations to be
representative of the subsurface conditions throughout the site. No warranty is made nor should any
be construed that unforeseen geotechnical weakness may not exist between exploratory points or
below the depths explored. If different subsurface conditions are observed during construction, we
should be promptly notified for review and reconsideration of our recommendations.
The services as described in this report include professional opinions and judgments based on the
data collected. Our investigation was performed using the standard of care and level of skill
ordinarily exercised under similar circumstances by reputable soil engineers and geologists currently
practicing in this or similar localities. No other warranty, express or implied, is made as to the
conclusions and professional advice included in this report.
We would be pleased to provide you with additional consultation services through the design and
construction phases of this challenging project. If you have any questions concerning this project or
desire any additional information, please contact us.
Respectfully Submitted,
SMITH -EMERY SAN FRANCISCO
JAMES E. PARTRIDGE, RCE # 25270
Reg stered Civil Engineer ko.we,W 6ff21
PATRICK MORRISON, PG #7174, CEG #2643
Professional Geologist
Certified Engineering Geologist