HomeMy WebLinkAboutCDP 2022-0067; LABOUNTY RESIDENCE - 3950; GEOTECHNICAL REPORT REIVIEW OF RESPONSE TO CITY REVIEW; 2024-03-11 GEOTECHNICAL REPORT REVIEW
__________________________________________________________
DATE: March 11, 2024
TO: City of Carlsbad
Land Development Engineering
1635 Faraday Avenue
Carlsbad, CA 92008
Attention: David Rick
PROJECT ID: CPD2022-0067
GRADING PERMIT NO.: GR2023-0040
SUBJECT: LaBounty Residence, 3950 Garfield Street (2nd review)
Items Submitted by Applicant Items Being Returned to Applicant
“Report of Preliminary Geotechnical
Investigation, LaBounty Residences, 3940 and
3950 Garfield Street, Carlsbad, California,” by
Geotechnical Exploration, Inc., dated April 21,
2023.
.
“Response to City Review, LaBounty
Residences, 3950 Garfield Street, Carlsbad,
California,” by Geotechnical Exploration, Inc.,
dated February 22, 2024.
Written report review comments.
Based on our review of the submitted geotechnical reports, we are providing the following
comments that should be addressed prior to the next submittal. Please provide complete and
thorough written responses to all comments.
GEOTECHNICAL COMMENTS:
1. Strength (direct shear) testing of the on-site soils is not provided in the reviewed report.
Please provide the appropriate laboratory testing to substantiate the values for bearing
capacity, passive earth pressure, and coefficient of friction that are presented in the report
(and the active/at-rest earth pressures for retaining wall design that are requested in this
review). If presumptive values from the code are being recommended by the consultant,
please indicate the soil class and use values consistent with the appropriate soil type
(Class) in Tables 1806.2 and 1610.1 of the 2022 California Building Code. If soil
parameters other than soil class 5 in Tables 1806.2 and 1610.1 are provided, please justify
the soil type by site specific laboratory testing. The reviewer notes that the values provided
in the report exceed the respective values for Class 5 and Class 4 soils in Table 1806.2.
Please provide site specific laboratory test results to justify the use of any assumed values
of C and Φ for the calculation of the parameters requested above. (repeat comment –
GR2023-0040
March 11, 2024
Page 2 of 2
with the response provided in the “Response to City Review…” in mind and as the
Old Paralic Deposits underlying the site consist of relatively young approximate
80,000 to 120,000 year old ancient beach/dune/alluvium sediments and not
approximate 40 million year old Eocene (Santiago formation) bedrock, please
provide supporting documentation (published reports, laboratory testing, etc.) to
justify that the Old Paralic Deposits (and compacted fill composed of these
deposits) are comparable to “Sedimentary and Foliated Rock” with respect to the
engineering characteristics of the sediments and providing presumptive
parameters for foundation design per Section 1806.2 and Table 1806.2 of the 2022
California Building Code. The use of presumptive values from a Class of Materials
greater than those provided in Class 4 of Table 1806.2 (2000 psf, 150 psf/ft, 0.25)
would require justification through laboratory testing (strength testing – direct
shear) if the assertion by the geotechnical consultant is that the Old Paralic
Deposits (Pleistocene terrace deposits), and fill composed of the Old Paralic
Deposits, are comparable to the “Sedimentary and Foliated Rock” (Class of
Materials 2 – 4000 psf, 400 psf/ft, 0.35) in Table 1806.2. Please provide calculations
to justify values if necessary.
2. Expansion testing of the on-site soils is not provided in the submitted geotechnical report.
Please provide laboratory testing of the on-site soils to determine the Expansion Index
and provide recommendations as necessary to address Sections 1803.5.3 and 1808.6 of
the 2022 California Building Code. If soils with an Expansion Index between 20 and 50
are used, please indicate the method of Section 1808.6 (1808.6.1 through 1808.6.4) that
is being recommended to satisfy the requirement for expansive soils, and provide the
Effective Plasticity Index and any other parameters for slab-on-ground design in
accordance with 1808.6.2 and WRI/CRSI Design of Slab-on-Ground floors or a post-
tensioned design in accordance with PTI DC 10.5 and provide a statement that the
foundation/slab system for the proposed residential structures will meet the requirements
of Section 1808.6 of the 2022 California Building Code. (repeat comment – if soils with
an expansion index between 20 and 50 are considered acceptable for use as
appears to be indicated in the response to this comment in the “Response to City
Review…” report, please provide recommendations as necessary and a statement
that the proposed foundation system/slabs-on-ground will meet the requirements
of Section 1808.6 of the 2022 California Building Code. Please indicate the method
of Section 1808.6 (1808.6.1 through 1808.6.4) that is being recommended to satisfy
the requirement for expansive soils, and provide the Effective Plasticity Index and
any other parameters for slab-on-ground design in accordance with 1808.6.2 and
WRI/CRSI Design of Slab-on-Ground floors.)