HomeMy WebLinkAboutCT 00-06; BRESSI RANCH MASTER PACIFIC RIDGE; GEOTECH RESPONSE FOR PROPOSED PACIFIC RIDGE; 2006-11-03I
i
GEOT
OF BRESSI RANCH PLANNING AREA PA-13,
CARLSBAD, CALIFORNIA
RECEIVED
IHQV 1 6 2005
Bureau Veritas
San Dtego
Prepared for:
PACIFIC RIDGE SCHOOL
12750 High Bluff Drive, Suite 200
San Diego, California 92130
Project No. 971009-044
November 3, 2006
Leighton and Associates, Inc.
A LEIGHTON GROUP COMPANY
4
Leighton and Associates, Inc.
A LEIGHTON GROUP COMPANY
To:
Attention:
Subject:
References:
November 3,2006
ProjectNo. 971009-044
Pacific Ridge School
12750 High Bluff Drive, Suite 200
San Diego, Califomia 92130
Mr. Phil Hitch
Geotechnical Response to City of Carlsbad Review Comments and Addendum
Recommendations for the Proposed Development of the Pacific Ridge Private
School, Parcels 2 tiirough 4 of Bressi Ranch Planning Area PA-13, Carlsbad,
Califomia
Leighton and Associates, 2004, As-graded Report of Mass Grading, Planning Areas
PA-13, PA-14, and a Portion of PA-15, Bressi Ranch, Carlsbad, California, Project
No. 971009-014, dated September 17,2004
, 2006, Geotechnical Update Study, Parcels 2 through 4 of Planning
Area PA-13, Bressi Ranch, Carlsbad, California, Project No. 971009-044, dated
August 4,2006
Project Design Consultant (PDC), 2006,-Grading and Erosion Conttol Plans for
Bressi Ranch Planning Area 13, Job No. 3336.00, 9 Sheets, dated September 11,
2006
Introduction
This report has been prepared to address the City of Carlsbad review comments of the project
geotechnical documents conceming tiie proposed development of the proposed Pacific Ridge
School witiiin Parcels 2, through 4 of Bressi Ranch Planning Area PA-13, located in Carlsbad,
Califomia. Our response to the review comments by the City of Carlsbad that were hand written in
a copy oftiie Geotechnical Update Study (Leighton, 2006a) are provided below. Please note that
comments within parenthesis ( ) were added by us to clarify the City of Carlsbad's review
comments.
3934 Murphy Canyon Road, Suite B205 • San Diego, CA 92123-4425
858.292.8030 • Fax 858.292.0771 •www.leightongeo.com
971009-044
Response to Comments;
Comment No. 1:
Why isn't the undocumented fill import stockpile soil location shown on the map? Where is this
on the grading plan? (comments on Page 4 of the Update Stiidy) (The existing on-site stockpiled
soils) should be shown on the plans (comment on the back side of page 8).
Based on our review of the project grading plans (PDC, 2006), approximately 68,000-
cubic yards of import soil are needed to grade the site to the proposed elevations. At the
time of our update stiidy (Leighton, 2006), only a portion of the import soils had been
placed on the site. Since the extent of the import soils (i.e., undocumented fill) was
assumed to vary as additional import soil was brought onto the site, the location of the
undocumented fill was not shown on the Update Geotechnical Map (Plate 1 of our report
dated August 4, 2006).
Based on a site reconnaissance performed on October 30, 2006, we mapped the
approximate location of the import soil/undocumented fill. The approximate location of
these soils is presented on the revised Geotechnical Map (Plate 1) included in this report.
The location of the undocumented fill should also be presented on the project grading
plans.
As indicated on Paragraph 1 of Page 5 of our Update Study (Leighton, 2006), tiie
undocumented filL/import soil will need to be removed and replaced as compacted fill.
Depending upon tiie moisture content of these soils, the soils will either need to be
moisture conditioned or dried back in order to meet the recommended parameters
presented in Section 5.1 of tiie Update Study (Leighton, 2006). Additional
recommendations presented in Section 5.1 should also be followed during the site
remedial, rough, and fine grading operations.
Comment No. 2:
(In order to reduce the potential for differential settlement of the proposed buildings in areas of
cut/fill ti^sitions, we recommend tiie entire cut portion of tiie building pad be overexcavated and
replaced witii properly compacted fill. This...) should be evaluated and included as remedial
grading work (Comment on the back of Page 12).
Based on our review of tiie referenced grading plans (PDC, 2006) and tiie existing as-graded
conditions (Leighton, 2004), it appears tiiat there will be no cut/fill ttansition conditions
witiiin tiie proposed building pads. However, potential cut/fill ttansitions should be
evaluated during the site remedial and/or rough grading operations. • 4 -2-
Leighton
971009-044
Due to the lengtii of time since the site was mass graded and since the site has been used as
an area to stockpile excess soil fi-om the other parts of tiie Bressi Ranch project, we
recommend that at a minimum, the upper 2 feet of the existing finish grade surface be
removed, reprocessed, and recompacted. This 2-foot reprocessing should be done after tiie
undocumented fill/import soils have been removed. The actual depth of this reprocessing
should also be evaluated during tiie remedial grading operations by the project geotechnical
consultant.
Limitations
The conclusions presented in this review are based in part upon data that were obtained from a
limited number of observations, site visits, excavations, samples, and tests. Such information is by
necessity incomplete. The nature of many sites is such tiiat differing geotechnical or geological
subsurface conditions can and do occur. Therefore, the findings, conclusions and recommendations
presented in tiiis review and previous report can be relied upon only if Leighton has the opportunity
to observe tiie subsurface conditions during constmction of tiiis project. Only witii these
observations are we able to confirm tiiat our preliminary findings are representative for the site. In
addition, tiiis office should review any revised plans tiiat incorporate tiie design changes.
If you have any questions regarding this report, please contact tiiis office. We appreciate this
opportunity to be of service.
Respectfully submitted,
LEIGHTON AND ASSOCL\TES, INC.
Randall K. Wagrfer, CEG 16^
Principal Geologist
Attachment: Plate 1 - Geotechnical Map - In Pocket
Distribution: (4) Addressee
(4) Project Design Consultants, Attention: Ms. Marina Wurst
-3-4
Leighton
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