HomeMy WebLinkAboutGeoSolutions - Soils Eng Report Addendum - CSL Channel BridgeGE0_._____
80L—LJTIONS
March 10, 2020
SL08639-14
Client:
MI San Luis Ranch LLC
PO Box 3460
San Luis Obispo
California
Project name:
Cerro San Luis (CSL)
Channel Bridge
San Luis Ranch On -Site
San Luis Obispo
California
220 High Street
San Luis Obispo CA 93401
B05.543.8539
1021 Tama Lane, Suite 105
Santa Marla, CA 93455
805.614.6333
PO Box 30159
Santa Barbara, CA 93105
805.965.2200
info@geosoiutions.net
SOILS ENGINEERING REPORT ADDENDUM —
CERRO SAN LUIS (CSL) CHANNEL BRIDGE
Dear MI San Luis Ranch LLC:
This letter serves as an addendum to the Soils Engineering Report Update
(GeoSolutions, Inc. May 2015) for the proposed Cerro San Luis (CSL) Channel Bridge
associated with the San Luis Ranch development located east of Madonna Road, west
of the 101 freeway, and south of Dalidio Drive, in the city of San Luis Obispo, California.
Geotechnically, the site is suitable for the proposed development provided the
recommendations in the above referenced report for site preparation, earthwork, and
foundations are incorporated into the design, with the inclusion of the additional
information presented below.
This addendum summarizes our geotechnical recommendations for the proposed
bridge with regards to the following:
• Bridge Abutment Foundation Design Criteria
• Site Preparation — Bridge Abutments
BRIDGE ABUTMENT FOUNDATION DESIGN CRITERIA
The proposed bridge is to be constructed with shallow foundations supported by
engineered fill material comprised of imported Class II aggregate base and biaxial
geotextile reinforcing fabric. Foundation bearing values for the shallow foundation
system are presented below:
Ultimate bearing - 12,000 psf
Bearing at Service Limit State - 4,000 psf
Bearing at Strength Limit State - 6,000 psf
SITE PREPARATION
Soils within the bridge abutment foundation areas should be over -excavated to a depth
of 24 inches below bottom of proposed foundation, or to competent (stiff/dense) soil;
whichever is deeper. The exposed surfaces should then be scarified; moisture
conditioned or allowed to dry back to approximately 3% above optimum value and
compacted to a minimum relative density of 95 percent, based on the ASTM D1557 test
method. The horizontal limits of the excavation may be limited to the dimensions of the
foundation. Following compaction of the bottom of the over -excavation, a layer of Type
2 biaxial geotextile reinforcing grid, such as Tenser BX1200, Syntec SBX12, ADS
BX124GG, or equivalent should be installed on the prepared surface, in accordance
with manufacturer's specifications. A 12-inch thick layer of Class II aggregate base
material should then be placed over the geogrid and compacted to a minimum relative
density of 95 percent, followed by another layer of geogrid and a final 12-Inch thick layer
of Class II aggregate base, all compacted to a minimum relative density of 95 percent.
For additional long-term protection of the foundation supporting soils, we recommend
installation of a non -woven geotextile fabric such as Mirafi 180N or equal over the
aggregate base fill materials along the creek -facing side of the abutment. The fabric
should be installed during the placement of the geotextile grid and aggregate base
sbinfo@geosolutlons.net
Cerro San Luis (CSL) Channel Bridge
March 10. 2020
Proiect SLOB839-14
material. The fabric should be placed beneath the geogrid layers and extend approximately 3 feet into the
aggregate base material, so that the interior (creek) side of both 12-inch layers of aggregate base are
covered with the fabric, and the fabric is 'wrapped' over the upper layer of compacted aggregate base
material.
CLOSURE
This addendum is issued with the understanding that it is the responsibility of the owner or his/her
representative to ensure that the information and recommendations contained herein are brought to the
attention of the architect and engineer for the project, and incorporated into the project plans and
specifications. The owner or his/her representative is responsible to ensure that the necessary steps are
taken to see that the contractor and subcontractors carry out such recommendations in the field.
As of the present date, the findings of this letter are valid for the property studied. With the passage of
time, changes in the conditions of a property can occur whether they are due to natural processes or to
the works of man on this or adjacent properties. Therefore, this letter should not be relied upon after a
period of three years without our review nor should it be used or is it applicable for any properties other
than those studied. However, many events such as floods, earthquakes, grading of the adjacent
properties and building and municipal code changes could render sections of this report invalid in less
than three years.
Thank you for the opportunity to have been of service in preparing this report. If you have any questions or
require additional assistance, please feel free to contact the undersigned at (805) 543-8539.
Sincerely,
GeoSol
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References:
eering Report, San Luis Ranch — Dalidio, Madonna Road, San Luis Obispo,
California, by GeoSolutlons, Inc., project number SL08639-6, dated May 29, 2015.
Soils Engineering Report Update Letter — 2016 CBC, Tract 3096, San Luis Ranch, San
Luis Obispo, California, by GeoSolutions. Inc., project number SL08639-12, dated June
12, 2018.
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