HomeMy WebLinkAboutCT 14-09; UPTOWN BRESSI RANCH; UPDATED GRADING RECOMMENDATIONS; 2017-10-25GEOCON -
INCORPORATED
GEOTECHNICAL ■ENVIRONMENTAL ■ MATERIALS
Project No. 02108-32-02
October 25, 2017
Shea Homes
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NOV O 9 2017 9990 Mesa Rim Road
San Diego, California 92121 LAND DEVELOPMENT
ENGINEERING Attention: Mr. Greg Ponce
Subject: UPDATED GRADING RECOMMENDATIONS
UPTOWN BRESSI RANCH
CARLSBAD, CALIFORNIA
References: 1. Update Report and Change of Geotechnical Engineer of Record, Bressi Ranch,
Lots 29 through 32, _Carlsbad, California, prepared by Geocon Incorporated, dated
April 24, 2017.
2. Addendum to Update Report, Uptown Bressi Ranch, Carlsbad, California, prepared
by Geocon Incorporated, dated August 2, 2017.
3. Geotechnical Engineering Investigation, Proposed CVS Pharmacy, Southwest
Corner of Palomar Airport Road and El Fuerte Street, Carlsbad, California,
prepared by Moore Twining Associates, Inc., dated January 21, 2017.
Dear Mr. Ponce:
In accordance with your request, we have prepared this letter to memorialize our recent discussions
regarding the grading recommendations at the subject site. It should be noted that the
recommendations provided in Reference No. 2 to chemically stabilize the highly expansive soils are
no longer being considered. As such, the recommendations presented in Reference No. 1 are being
utilized, except as superseded herein.
We understand that the following recommendations are proposed:
• Due to the presence of highly expansive soils observed in recent exploratory excavations,
remedial grading of the CVS building pad will consist of removing the upper 5 feet of existing
soil and replacement with soils exhibiting a ''very low'' to "low" expansion potential
(Expansion Index less than 50). The lateral limits of remedial grading should extend at least
2 feet outside the perimeter walkway areas, or at least 5 feet outside the building footprint,
whichever is greater. The upper 1 foot of fill beneath the CVS building pad and walkways
should consist of Class II aggregate base compacted to at least 95 percent relative compaction.
These recommendations are presented per our discussion today with Mr. Read Andersen of
Moore Twining Associates, Inc. The Moore Twining report (Reference No. 3) indicates a
maximum EI of 90, however, this recommendation is superseded by today's discussion.
6960 Flanders Drive ■ San Diego, California 92121 ■ Telephone (858) 558-6900 ■ Fax (858) 558-6159
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' ..,,/ • In order to provide l.mi'form soil support characteristics, the adjacent Sprouts building pad will
be grading similar to the CVS building pad. As such, the upper 5 feet of existing soil beneath
the building pad should be replaced with soils exhibiting a "low" to "medium" expansion
potential (Expansion Index less than 90). The lateral limits should extend at least 5 feet
outside the building footprint. In the depressed loading dock area, the removals should extend
horizontally at least 5 feet beyond the loading dock and at least 2 feet below the ramp
structure.
• Retaining wall backfill should consist of soils exhibiting a ''very low" to "low" expansion
potential (Expansion Index less than 50) per the recent design provided by the structural peer
review engineer K.PFF, and now utilized by R2H Engineering, Inc., the project Structural
Engineer. It is our understanding that the new wall design utilizes the parameters for EI less
than 50 soil (K.PFF design). However, retaining walls may be designed considering
moderately expansive backfill {El less than 90) in accordance with the design parameters
provided in Reference No. 1.
• If practical, the granular, "low" to "medium" expansive slope zone soils being removed to
facilitate retaining wall construction along north side of the residential portion should be
placed on the commercial building pads (Pads C, D, E, F, G, and H).
• If practical, the granular, low expansive slope zone soils being removed for retaining walls on
the commercial portion should be stockpiled and utilized as wall backfill.
If you have any questions regarding this correspondence, or if we may be of further service, please
contact the undersigned at your convenience.
Very truly yours,
GEOCON INCORPORATED
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(e-mail)
(e-mail)
Addressee
Shea Properties
Attention: Mr. Min Kang and Mr. Robert Senour
Project No. 02108-32-02 -2-October 25, 2017