HomeMy WebLinkAboutCDP 2020-0007; TERRA BELLA DEVELOPMENT; RESPONSE TO THIRD-PARTY GEOTECHNICAL REVIEW; 2021-03-22
March 22, 2021
Project No.: 3630-SD
Terra Bella Development, LLC.
P.O. Box 232458
Encinitas, California 920243
Attention: Ms. Meng Xu
Subject: Response to Third-Party Geotechnical Review
6479 Surfside Lane
Carlsbad, California
Dear Ms. Xu:
This letter has been prepared to respond to “Third-Party Geotechnical Review (First)” comments
by Hetherington Engineering, Inc. The following issue numbers correspond with numbers
presented on the geotechnical review comment sheet. A copy of the comment sheet is included
in Appendix A.
Issue No. 1
The Consultant should review the project grading, shoring, and foundation plans, provide any additional
geotechnical recommendations considered necessary, and confirm that the plans have been prepared in
accordance with the geotechnical recommendations provided in the referenced reports.
GeoTek Response
As requested, GeoTek, Inc. (GeoTek) has received and completed a geotechnical review of the
temporary shoring and structural foundation plans prepared by Mercado Associates, Inc. (2021).
Reviewed plans included S-1.1, S-1.2, S-2.0, S-3.2, S-3.3, SP-1.1, SP-1.2, SP-1.3, SP-2.1, SP-3.2, SP-
3.3, SR-1.0, and SR-2.0. The plans indicated a most recent revision date of February 26, 2021.
The purpose of this review was to present our opinion whether the reviewed plans incorporated
the geotechnical recommendations presented within the referenced reports (GeoTek, 2020,
2021a & 2021b).
Based on our review, it is our opinion that the reviewed plans have been prepared in conformance
with the recommendations contained in the referenced reports and are considered to be
geotechnically suitable.
GeoTek, Inc.
1384 Poinsettia Avenue, Suite A Vista, CA 92081-8S05
(760) 599-0509 0 ice (760) 599-0593 F~ www.geotekusa.com
GEOTEK
Terra Bella Development, LLC March 22, 2021
Response to Third-Party Review Comments Project No.: 3630-SD
6579 Surfside Lane, Carlsbad, California Page 2
Issue No. 2
The Consultant should provide an updated geotechnical map/plot plan utilizing the latest grading plan
for the project to clearly show (at a minimum), a) existing site topography, b) proposed
structures/improvements, c) proposed finished grades, d) locations of the subsurface exploration, e)
geologic contacts, and f) remedial grading limits, etc.
GeoTek Response
See Appendix B, Figure 1 for an updated geotechnical map.
Issue No. 3
The Consultant should provide geologic cross-sections utilizing the current grading plan to clearly show
(at a minimum), a) existing site topography, b) proposed structures/improvements, c) proposed finished
grades, d) geologic contacts, e) geologic structure, f) locations of the subsurface exploration, g) temporary
shoring/construction slopes, and h) remedial grading, etc.
GeoTek Response
See Appendix B, Figures 2 & 3 for geologic cross-sections. The subsurface geologic structure
within the old paralic deposits is anticipated to be neutral (if present) based on a review of
geologic maps and our experience with excavations in old paralic deposits. Therefore, geologic
bedding structure is not shown in Figures 2 & 3. The proposed outline of the basement
excavation has also been shown, however the vertical improvements have been excluded.
Issue No. 4
The Consultant should provide the site seismic design category and risk category.
GeoTek Response
The seismic design category and risk category are determined by the 2019 California Building
Code’s adoption of specifications within ASCE 7-16. Seismic Design Category is determined
from ASCE 7-16 Table 11.6-1, based on design spectral response acceleration parameter at short
periods (SDS) and designated Risk Category. For Risk Category 1 to III and SDS above 0.50, the
corresponding Seismic Design Category is “D.” For this site, Risk Category II has been
determined through ASCE 7-16 Table 1.5-1, for a residential home.
Issue No. 5
The Consultant should provide a statement regarding the impact of the proposed grading and construction
on adjacent properties and improvements.
GEOTEK
Terra Bella Development, LLC March 22, 2021
Response to Third-Party Review Comments Project No.: 3630-SD
6579 Surfside Lane, Carlsbad, California Page 3
GeoTek Response
Based on our review of the temporary shoring plans (Mercado Associates, 2021b), and provided
the construction is performed as approved, the adjacent property should not be adversely
affected by proposed site grading and construction.
Issue No. 6
The Consultant should provide swimming pool recommendations.
GeoTek Response
Swimming pools may utilize retaining wall recommendations proposed in our 2020 & 2021a
referenced reports. As discussed in our response to Issue No.1, geotechnical design parameters
for retaining walls have been incorporated into the swimming pool plans (Mercado Associates,
2021b).
Issue No. 7
The Consultant should provide hardscape recommendations (thickness, reinforcement, joints, etc.).
GeoTek Response
Exterior concrete flatwork may be poured directly on compacted fills. Flatwork should be a
minimum of 4 inches thick and maybe be reinforced with 6x6 No 6 WWM or No. 3 reinforcing
bars place 24 inches on center in two directions. Control joints should be incorporated into the
construction of the slab.
Control joints are more effective the more closely spaced. We would suggest that control joints
be placed in two directions spaced the numeric equivalent of two times the thickness of the slab
in inches changed to feet (e.g., a 4-inch slab would have control joints at 8 feet centers).
Other methods to control cracking in the slab include careful control of water/cement ratios in
the concrete, along with taking appropriate curing precautions during the placement of concrete
in hot or windy weather.
LIMITATIONS
GeoTek has prepared this report in a manner consistent with that level of care and skill ordinarily
exercised by members of the engineering and science professions currently practicing under
similar conditions in the jurisdiction in which the services are provided, subject to the time limits
and physical constraints applicable to this report.
GEOTEK
Terra Bella Development, LLC March 22, 2021
Response to Third-Party Review Comments Project No.: 3630-SD
6579 Surfside Lane, Carlsbad, California Page 4
Since our recommendations are based on the site conditions observed and encountered, and
laboratory testing, our conclusions and recommendations are professional opinions that are
limited to the extent of the available data. Observations during construction are important to
allow for any change in recommendations found to be warranted. These opinions have been
derived in accordance with current standards of practice and no warranty of any kind is expressed
or implied. Standards of care/practice are subject to change with time.
The opportunity to be of service is sincerely appreciated. If you should have any questions,
please do not hesitate to contact our office.
Respectfully submitted,
GeoTek, Inc.
Christopher D. Livesey Edward H LaMont Gaby M. Bogdanoff
CEG 2733, Exp. 05/31/21 CEG 1892, Exp. 07/31/22 GE 3133, Exp. 06/30/22
Project Geologist Principal Geologist Project Engineer
Distribution: (1) Addressee via email
Attachments: Appendix A – City Geotechnical Review Comments
Appendix B – Geologic Figures and Cross Sections
GEOTEK
Terra Bella Development, LLC March 22, 2021
Response to Third-Party Review Comments Project No.: 3630-SD
6579 Surfside Lane, Carlsbad, California Page 5
REFERENCES
GeoTek, Inc., 2020, “Preliminary Geotechnical Evaluation, 6479 Surfside Lane, Carlsbad,
California,” Project No. 3630-SD, dated March 9.
____, 2021a, “Seismic Retaining Wall Pressure Recommendations, 6479 Surfside Lane, Carlsbad,
California,” Project No. 3630-SD, dated February 8.
____, 2021b, “Supplemental Temporary Shoring Recommendations, 6479 Surfside Lane,
Carlsbad, California,” Project No. 3630-SD, dated February 17.
Mercado Associates, Inc., 2021a, “Structural Calculations for 6479 Surfside Lane, Pool Design,”
Job Number 20058, dated February 24.
____, 2021b, 6479 Surfside Lane, 6479 Surfside Lane, Carlsbad, California, Sheets S-1.1, S-1.2,
S-2.0, S-3.2, S-3.3, SP-1.1, SP-1.2, SP-1.3, SP-2.1, SP-3.2, SP-3.3, SR-1.0, SR-2.0, Job Number
20058 dated February 26.
GEOTEK
APPENDIX A
City of San Diego Review Comments
GEOTEK
HETHERINGTON ENGIN EERING, ~NC.
SOIL & FOUNDATION ENGINEERING O ENGINEERING GEOLOGY II HYDROGEOLOGY
City of Carlsbad
Land Development Engineering
1635 Faraday A venue
Carlsbad, California 92008-73 14
Attenlion:
Su~ject:
Ms. Kyrenne Chua
THIRD-PARTY GEOTECHNICAL REVIEW (FIRST)
Proposed Residential Development
6479 Surfside Lane
Carlsbad, California
Project ID: CDP2020-0007
January 7, 202.l
Project No. 9278.1
Log No. 2 1260
References: I. "Preliminary Geotechnical Evaluation, 6479 Surfside Lane, Carlsbad,
California", by GeoTek, Inc., dated March 9, 2019.
2. ·'Grading Plans For: 6479 Surfside Lane", by HWL Planning and
Engineering, elated December 14, 2020 (Sheets 1 through 5).
Dear Ms. Chua:
ln accordance with your request, Hetherington Engineering, Inc. has provided third-party
geotechnical review of Reference I. The following comments are provided for analyses
and/or response by the Geotechnical Consultant.
I. The Consultant should review the project grading, shoring, and foundation plans,
provide any additional geotechnical recommendations considered necessary, and
confirm that the plans have been prepared in accordance with the geotechnical
recommendations provided in the referenced reports.
2. The Consultant should provide an updated geotechnical map/plot plan utilizing the
latest grading plan for the project to clearly show (at a minimum), a) existing site
topography, b) proposed structures/improvements, c) proposed finished grades, d)
locations of the subsurface exploration, e) geologic contacts, and f) remedial grading
limits, etc.
3. The Consultant should provide geologic cross-sections utilizing the current grading
plan to clearly show (at a minimum), a) existing site topography, b) proposed
structures/improvements, c) proposed finished grades, d) geologic contacts, e)
geologic structure, f) locations of the subsurface exploration, g) temporary
shoring/construction slopes, and h) remedial grading, etc.
5365 Avenida Encinas, Suite A• Carlsbad, CA 92008-4369 • (760) 931-1917 • Fax (760) 931-0545
333 Third Stree • Laguna Beach, CA 9265 • (949) 715-5440 • Fax (949) 715-5442
www.hetheringtonengineering.com
THIRD-PARTY GEOTECHNlCAL REVIEW (PIRST)
Project No. 9278.1
Log No. 21260
January 7, 202 I
Page 2
4. The Consul tan! should provide the site seismi c design category and risk calcgory.
5. The Consultanl should provide a statement regarding the impact of the proposed
grading and constru ction on adjacent properti es and improvements.
6. The Consultant should provide swimming pool recommendations.
7. The Consultant should provide hardscape recommendations (thickness,
reinforcement, joints, etc.).
The opportunity to be of service is sincerely appreciated. If you have any questions
regarding thi s review, please contact this office at your convenience.
Sincerely,
HETHERrNGTON ENGINEERING, INC.
r
Civi l Engineer 3048
Geotechnical .Engin
(expires 3/3 l/22)
~
aul A. Bogseth
rofossional Geologist 3772
·tified Engineering Geologist 11
·tified Hydrogeologist 591
pires 3/31/22)
Distribution: I-via e-mail (Kyrenne.Chua@carlsbadca.gov)
I-via e-mail (Elissa.Tovar@carlsbadca.gov)
HETHERINGTON ENGINEERING, INC.
APPENDIX B
Geologic Figure and Cross Sections
GEOTEK
B-2AfQopB-1AfQopQopAfB-2Quaternary Old Paralic Deposits,Circled where BuriedArtifical FillApproximate Location of BoringLEGENDApproximate Limits of Study1384 Poinsettia Avenue, Suite AVista, California 92081Terra Bella Development LLC6479 Surfside LaneCarlsbad, CaliforniaFigure 1Geologic MapPN: 3630-SD DATE: March 2021NPlan adapted from "Grading and Utility Plan"by HWL Planning & Engineering0 5 1020Scale: 1" =5'j ~ W\ 51 62.4011: 8AOfl,lfNU~ SUNl{E,N'f'ATtO 81;LOWl"EA SAP.ARA.TE I I I I ~ PERMIT -!-.~ I I I E:X19l1NG 4' HIGH /. UASONRV WALL I I ,., ! APN: 214-021-04 (EI.IPT'I' ORAOE0 OIRiLOT) :n•G•: ,.rn, """)?Ml®;,:~:\ _, ~ D~ • --~~ " 0 \ \ \ ARST LEVEL 1-"J=rHi □AS EM ENT LEV CL Ff•62.0 P'ACJ=f.i111 ♦ FlRSTLEVEL "'""" BASQIENT LEVEL FF'112..0 PAD=(.;117 ♦ I I --J < 2 ---, LU z <l'.: _J LU 0 (J) LL Ct'.'.'. ::> (J) GEOTEK
1384 Poinsettia Avenue, Suite A Vista, California 92081Terra Bella Development, LLC. 6479 Surfside LaneCarlsbad, California PN: 3630-SDMarch 2021Figure LEGEND Geologic Cross Section A-A’QopQopProposed GradeExisting GradeAA’AfuAPN 214-021-04AfuOld Paralic DepositsArtificial Fill Undocumented2PLB-2Approximate Boring LocationQopAfuPLAPN 214-021-12Elevation in Feet60657075Approximate Scale 1”=10’NorthB-1B-2TemporaryShoringTemporaryShoringApproximate limit of remedial gradingI ~ ~~ j 1:1 -1 l -' I i1 / \ -------------7 -----------/ -
1384 Poinsettia Avenue, Suite A Vista, California 92081Terra Bella Development, LLC. 6479 Surfside LaneCarlsbad, California PN: 3630-SDMarch 2021Figure LEGEND Geologic Cross Section B-B’QopQopProposed GradeExisting GradeBB’AfuAfuOld Paralic DepositsArtificial Fill Undocumented3PLB-2Approximate Boring LocationQopAfuPLElevation in Feet60657075Approximate Scale 1”=10’WestB-1B-2Anticipated Temporary Backcut (1.5:1)??Surfside LaneTemporaryShoringAfuApproximate limit of remedial gradingj .---------------------------------------------------------------_ J ____ ---------