HomeMy WebLinkAboutCT 2017-0003; LA COSTA TOWN SQUARE PARCEL 3 RESIDENTIAL; GEOTECHNICAL UPDATE AND ADDENDUM TO GEOTECHNICAL DUE DILIGENCE REPORT AND ATTACHMENTS; 2023-06-20Geotechnical C Geologic C Coastal C Environmental
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M E M O R A N D U M
DATE: June 20, 2023 W.O. 8144-A-SC
Woodside 05S, LP
1250 Corona Pointe Court, Suite 500
Corona, California 92879
Attention: Mr. Craig Moreas
From: John P. Franklin, CEG 1340
Stephen J. Coover, GE 2057
SUBJECT: Geotechnical Update and Addendum to “Geotechnical Due Diligence Report
and Attachments, La Costa Town Square Project, City of Carlsbad, California
APN 223-050-73-00" W.O. 8144-A-SC, dated February 9, 2023
References: 1. ”Third- Party Geotechnical Review (First), La Costa Town Square Parcel 3, La Costa
Avenue, Carlsbad, California, GR2022-0001/CT2017-003, Project No. 9604.1, Log No. 21774,
dated February 9, 2022, by Hetherington Engineering, Inc.
2. “Review and Response to Third Party Geotechnical Review Comments, La Costa Town
Square Townhome Site, APN 223-050-73-00, La Costa Avenue, City of Carlsbad, San Diego
County, California,” W.O. 8144-A-SC, dated March 24, 2022, by GeoSoils, Inc.
3. “Geotechnical Due Diligence Evaluation of the La Costa Town Square Townhome Site,
APN 223-050-73-00, La Costa Avenue, City of Carlsbad, San Diego County, California
92011,” W.O. 8144-A-SC, dated June 17, 2021, by GeoSoils, Inc.
Pursuant to your request from the City, GeoSoils, Inc. (GSI), has prepared this update and addendum to the
subject documents with respect to the 2022 CBC. The scope of our services has included a review of the
referenced documents, analysis and date, and preparation of the geotechnical update and addendum.
Unless specifically superceded herein, the conclusions and recommendations in the referenced reports
remain pertinent and applicable, and should be appropriately implemented during planning, design, and
construction.
Based on our review, updated seismic design parameters are provided, below.
Seismic Shaking Parameters
Based on the site conditions, the following table summarizes the updated site-specific design criteria obtained
from the 2022 CBC (CBSC, 2022a), Chapter 16 Structural Design, Section 1613, Earthquake Loads. The
computer program “U.S. Seismic Design Maps, (https://seismicmaps.org/) provided by the Structural
Engineer’s Association of California and California Office of Statewide Health Planning (2023) was used for
design parameters. The short spectral response uses a period of 0.2 seconds.
•
GeoSoils, Inc.
2022 CBC SEISMIC DESIGN PARAMETERS
PARAMETER
SITE SPECIFIC
VALUE PER
ASCE 7-16
2022 CBC OR
REFERENCE
Risk Category I, II, or III Table 1604.5
Site Class C
Section 1613.2.2,
Chap. 20
ASCE 7-16
(p. 203-204)
Spectral Response - (0.2 sec), Ss 0.955g Section 1613.2.1
Figure 1613.2.1(1)
Spectral Response - (1 sec), S1 0.348 g Section 1613.2.1
Figure 1613.2.1(2)
Site Coefficient, Fa 1.2 Table 1613.2.3(1)
Site Coefficient, Fv
1.5
(Table11.4.2)ASCE 7-16)
Maximum Considered Earthquake Spectral
Response Acceleration
(0.2 sec), SMS
1.146 g Section 1613.2.3
(Eqn 16-36)
Maximum Considered Earthquake Spectral
Response Acceleration (1 sec), SM1
0.522 g
(Section 21.4)
Section 1613.2.3
(Eqn 16-37)
5% Damped Design Spectral Response
Acceleration (0.2 sec), SDS
0.764 g Section 1613.2.4
(Eqn 16-38)
5% Damped Design Spectral
Response Acceleration (1 sec), SD1
0.341 g
(Section 21.4)
Section 1613.2.4
(Eqn 16-39)
PGAM - Probabilistic Vertical Ground Acceleration
may be assumed as about 50% of these values. 0.5 g ASCE 7-16
(Eqn 11.8.1)
Seismic Design Category D
(Section 11.6)
Section 1613.2.5/
ASCE 7-16
(p. 85: Table 11.6-1
or 11.6-2)
GENERAL DESIGN PARAMETERS
PARAMETER VALUE
Distance to Seismic Source (Rose
Canyon)
±7.1 mi (11.4
km))*
Upper Bound Earthquake (Rose
Canyon)MW 7.2**
* Blake (2000a), **Cao, et al. (2003)
Woodside 05S, LP W.O. 8144-A-SC
La Costa Town Square, Carlsbad June 20, 2023
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GeoSoils, Inc.
Conformance to the criteria above for seismic design does not constitute any kind of guarantee or assurance
that significant structural damage or ground failure will not occur in the event of a large earthquake. The
primary goal of seismic design is to protect life, not to eliminate all damage, since such design may be
economically prohibitive. Cumulative effects of seismic events are not addressed in the 2022 CBC (CBSC,
2022a) and regular maintenance and repair following locally significant seismic events (i.e., Mw5.5) will likely
be necessary, as is the case in all of southern California.
Distribution:(1) Addressee (PDF via email)
Woodside 05S, LP W.O. 8144-A-SC
La Costa Town Square, Carlsbad June 20, 2023
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