HomeMy WebLinkAbout3811; El Camino Real Widening Project Geotechnical; El Camino Real Widening Project Geotechnical; 2008-05-09o
Geotechnical and Environmental Sciences Consultants
^CEIVED
MA)' I u May 9, 2008
Project No. 106345001
Mr. Jacob Moeder, P.E.
Public Works Engineering
1635 Faraday Avenue
Carlsbad, Califomia 92008
Subject: Third Party Review
Palomar Airport Road Widening Signage
Carlsbad, Califomia
On-Call Contract No. PWENG 562
Reference: Leighton and Associates, 1994, Preliminary Geotechnical Evaluation for Tentative
Map Purposes, Carlsbad Ranch, Carlsbad, Califomia: dated July 5.
Dear Mr. Moeder:
In accordance with your request and the authorization of the City of Carlsbad, we have performed a
third party review of the pertinent portions of the 60 percent-level grading and storm drain plans for the
widening of Palomar Airport Road from Paseo del Norte, east to Armada Drive, We have also re-
viewed the above-referenced geotechnical report for a tract of land north of, and adjacent to, Palomar
Airport Road, and east of Paseo del Norte. We understand that the road widening project will include
the installation of a new Caltrans tubular sign structure across Palomar Airport Road at approximate
Station 31+50. The foundation for the sign will be in accordance with Caltrans Standard Plan S37,
Type II. Accordingly, the sign supports will consist of 5-foot diameter cast-in-drilled-hole (CIDH) piles
with an embedment of approximately 25 feet. The purpose of our third-party review was to evaluate
whether the soil conditions extrapolated from the above-referenced report will meet the soil properties
(friction angle of 30 degrees, unit weight of 120 pounds per cubic foot) used for foundation design as
indicated on the Caltrans Standard Plan.
Based on our review of a geologic map from the above-referenced report, the subject sign site is
anticipated to be underlain by sedimentary materials of the Tertiary-aged Santiago Formation. Re-
portedly, this unh generally consists of massive to poorly bedded sandstone with interbedded
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Palomar Airport Road Wi
Carlsbad, Califomia
mg Signage O May 9, 2008
Project No. 106345001
clayey siltstone and silty claystone. Based on the geotechnical report and our local experience, in-
tact materials of the Santiago Formation should meet or exceed the soil property assumptions used
by Caltrans for design of the subject sign foundation.
We note that the above-referenced report discusses the presence of perched groundwater conditions
in the site area. Accordingly, groundwater may be encountered during the drilling operations for the
sign foundations and the drilling contractor should be prepared for this possible occurrence. Also, we
recommend that during excavation ofthe sign foundations, a representative from our firm be on site
to observe encountered soil conditions to substantiate the validity of the assumed soil properties. If
we can be of frirther assistance regarding this matter, please let us know at your convenience.
We appreciate the opportunity to be of service on this project.
Sincerely,
NINYO & MOORE
Andres Bemal, GE.
Senior Project Engineer
RI/ABS/kh
Distribution: (1) Addressee
Landal L. Irwin, C.E.C
Chief Engineering Geologist
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