HomeMy WebLinkAboutCT 00-06; Bressi Ranch; Geotechnical Completion Letter of Mass Grading; 2005-04-29o:
Attention:
SuHject:
Reference:
pril 29, 2005
Lennar Communities
1525 Faraday Avenue, Suite 300
Carlsbad, California 92008
Mr. Rob Demaro
\·1 '0,//
. \' I
1-·--·-·---,·-··' ;
..
i I hf; /i.Y
'
t' Ii
Project No. 4971009-014
Geotechnical Completion Letter of Mass Grading, Bressi Ranch, Carlsbad,
California
Project Design Consultants, 2003, Mass Grading and Erosion Control Plans for:
Bressi Ranch, Carlsbad, California, Carlsbad Tract No. 00-06, Drawing No. 400-
-8A; dated January 7, 2003, revised November 22, 2004
In accordance with the request and authorization of representatives of Lennar Communities, we
have performed geotechnical observation and testing services during the mass grading operations
for the Bressi Ranch project (Carlsbad Tract No. 00-06), located in Carlsbad, California. As of
the date of this letter, the mass grading operations are complete for the project. The geotechnical
conditions encountered during the grading operations were generally as anticipated.
The mass grading operations included: 1) cuts and fills to achieve the design sheet-graded pads and
adjacent slopes and streets; 2) removal of potentially compressible surficial materials (including
undocumented fill, topsoil, colluvium, alluvium, landslide deposits, and weathered formational
material) to competent formational material; 3) construction of fill slope keys; 4) construction of
landslide stabilization buttresses; and 5) installation of canyon subdrains and buttress key and
backcut subdrains.
After the removals of potentially compressible soils were made in the canyons of the site,
subdrains were installed and outletted at the toe-of-slope of the canyon fills. Fill slopes constructed
above cut and natural open space areas were constructed with fill slope keys prior to the placement
of compacted fill. In accordance with the project geotechnical recommendations and
recommendations made during the grading operations, the potentially compressible portions of the
on-site landslides were removed to competent material. In addition, buttresses were excavated to
3934 Murphy Canyon Road, Suite 8205 • San Diego, CA 92123-4425
858.292.8030 • Fax 858.292.0771 • www.leightongeo.com
971009-014
stabilize the landslides and areas of potential instability (due to out-of-slope clayseams or other
adverse geologic conditions) and buttress key and backcut subdrains installed and outletted.
The placement and compaction of the fill soils were geotechnically observed and documented.
Field density testing indicated that the fill soils were placed and compacted to at least 90 percent
relative compaction (based on American Standard of Testing and Materials [ASTM] Test Method
D1557) and near-optimum moisture content in accordance with the recommendations of Leighton
and Associates and the requirements of the City of Carlsbad. To mitigate post-construction
settlement, deep fills (i.e. areas where the fill soils were generally deeper than approximately 40
feet below the finish grade elevations of the site) were placed at a minimum 95 percent relative
compaction.
The mass grading operations of the Bressi Ranch project, which occurred prior to the fine or
precise grading of the residential portions of the site and resulted in the design of the project as
shown on the mass grading plans (Project Design Consultants, 2004), were performed in general
accordance with the project geotechnical reports, geotechnical recommendations made during
grading, and the City of Carlsbad requirements. It is our professional opinion that the site is
suitable for the intended residential and commercial use provided the recommendations included in
the project as-graded geotechnical reports of rough and fine grading are incorporated into the
design and construction of the proposed development and associated improvements.
If you have any questions regarding this letter, please contact this office. We appreciate this
opportunity to be of service.
Distribution: ( 4) Addresses
(2) City of Carlsbad,
Attention: Mr. Casey Arndt
-2 -
Respectfully submitted,
LEIGHTON AND ASSOCIATES, INC.
William D. Olson, RCE 45283
Senior Project Engineer
~-kW~
Randall K. Wagner, CEG 1612
Senior Associate
Leighton