HomeMy WebLinkAbout; Broccato by Batiquitos Shores; Interim As-Graded Letter for Model Lots; 1996-09-11Geotechnics
Incorporated
September 11, 1996
Principals:
Anthony F. Belfast
Michael P. Imbriglio
W. Lee Vanderhurst
Brookfield Davidson Homes
12865 Pointe Del Mar, Suite 200
San Diego, California 92014
Project No. 0002-008-03
Document No. 6-0589
Attention: Mr. Luis Nunez
SUBJECT: INTERIM AS-GRADED LETTER FOR MODEL LOTS
Lots 10 Through 15
Broccato by Batiquitos Shores
Carlsbad, California
References: Foundation Design Recommendations, Lots 11, 12,13, 47, 48, and 53 through 60,
Broccato by Batiquitos Shores, Carisbad, California, by Geotechnics Incorporated,
dated August 13, 1996, Project No. 0002-008-03.
Interim Compaction Report, Broccato Development, Carlsbad , California, by
Geotechnics incorporated, dated March 13, 1995, Project No. 0002-008-00.
Dear Mr. Nunez:
In accordance with your request, we have prepared this letter presenting our conclusions and
recommendations regarding the as-graded conditions of Lots 10 through 15 in the Broccato
development. The following conclusions and recommendations are based on the observation and
testing services provided by Geotechnics Incorporated during the earthwork construction of the
subject lots. Our services did not include supervision nor direction of the actual work of the
contractor, his employees, or agents.
The earthwork conducted for Lots 10 through 15 consisted primarily of the excavation of the
stockpiled material to expose previously compacted fill materials. Up to approximately 20 feet
of additional compacted fill was then placed to achieve design grades. The exposed previously
compacted fill materials were observed and tested by our firm. The results of our observations
and tests of those fill materials are presented in our referenced March 13, 1995 report.
Accordingly, the subject mode! lots are underiain by approximately 30 to 40 feet of compacted
fill soils.
9951 Business Park Ave., Ste. 6 > San Diego Caiifornia • 92131
Piione (619) 536-1000 • Fax (619) 536-8311
Brookfield Davidson Homes Project No, 0002-008-03
September 11, 1996 Document No, 6-0589
Page No, 2
The fill materials are underiain by alluvium that was not removed due to groundwater constraints.
As indicated in the referenced March 13, 1995 report, settlement monuments were placed above
the alluvium to monitor consolidation during fill placement. Settlement on the order of
approximately 5 inches was measured during the monitoring period. Based on the settlement
monitoring, the primary settlement of the underiying alluvium appears to have been completed.
In our opinion, grading and compaction of the fill soils within the subject lots was performed in
genera! accordance with the intent of the project geotechnical recommendations and with the
requirements of the City of Carlsbad. Based upon our observations and testing, it is our
professional opinion that the fill soils were placed in accordance with the compaction criteria of
90 percent of the maximum density as evaluated by ASTM D1557-91. The conclusions contained
herein are based on the observations and testing performed through September 6, 1996. No
representations are made as to the quality and extent of materials not observed.
The following recommendations are provided for one- or two-story residential structures with post-
tension slabs, and are consistent with the recommendations provided in the referenced letter.
Based on the results of our expansion index tests and our field observations, the subject lots are
underiain by materials exhibiting a low potential for expansion. We recommend the building pad
be thoroughly moistened prior to placement of the slab.
Allowable Bearing Capacity: 2,000 pounds per square-foot
Footing Embedment: 12 inches minimum below the lowest adjacent grade
Differential Settlement: l-l^ inches
Capillary Break: 4 inches of crushed rock or clean sand with a Sand
Equivalent of at least 50, and 10-mil visqueen vapor barrier
with 2 inches of clean sand above the moisture barrier.
Lateral loads against structures may be resisted by friction between the bottoms of footings or
slabs and the supporting soil. For each of the subject lots, a coefficient of friction of 0.3 is
recommended. Alternatively, a passive pressure of 300 pounds per cubic-foot is recommended
Geotechnics Incorporated
Brookfield Davidson Homes Project No. 0002-008-03
September 11, 1996 Document No, 6-0589
Page No. 3
for the portion of vertical foundation members embedded into compacted fill. If friction and
passive pressure are combined, the passive pressure value should be reduced by one-third.
The recommendations presented herein are considered generally consistent with methods
typically used in southern California, and have been developed using the degree and skill
ordinarily exercised, under similar circumstances, by reputable geotechnical consultants practicing
in this or similar localities. No other warranty, expressed or implied, is made as to the
conclusions and professional opinions included in this letter. Other alternatives may be available.
The foundation recommendations herein should not be considered to preclude more restrictive
criteria of governing agencies or by the structural engineer. The design of the foundation system
should be performed by the project structural engineer, incorporating the geotechnical parameters
described in this letter.
A final report presenting the results of our observations and tests of the overall site grading will
be prepared after completion of the grading. Please call If you have any questions or if we can
be of further service. We appreciate this opportunity to provide continued services on this project.
GEOTECHNICS INCORPORATED
Dick Roberts Robert A. Torres, P.E. 43077
Project Geologist Senior Engineer
DR/RAT/39
Distribution: (5) Addressee
Geotechnics Incorporated