HomeMy WebLinkAboutSDP 02-16; COASTLINE COMMUNITY CHURCH; RESPONSE TO CITY REVIEW COMMENTS; 2020-02-04GEOCON
INCORPORATED
GEOTECHNICAL e ENVIRONMENTAL U MATERIALS
Project No. G1968-1 1-02
February 4, 2020
Coastline Church
% Grant General Contractors
5051 Avenida Encinitas
Carlsbad, California 92008
Attention: Mr. Jim Grant
Subject: RESPONSE-TO CIT-Y-REVTEWCOMMENTS
COASTLINE-COMMUNITY EX t PANSION
2215 CALLE BARCELONA
CARLSBAD, CALIFORNIA
References: 1. Update Geotechnical Report, Coastline Community Church Expansion, 2215 Calle
Barcelona, Carlsbad, California, prepared by Geocon Incorporated, dated October 12,
2018 (Project No. G1968-1 1-02).
MSE Retaining Wall Design Recommendations, Coastline Community Church
Expansion, 2215 Call Barcelona, Carlsbad, California, prepared by Geocon
Incorporated, dated June 12,2019 (Project No. G1968-11-02).
Anchor Retaining Wall Plans for: Coastline Community Church, Lot 482, Tract
No. 88-03-2, City of Carlsbad, California, prepared by Geogrid Retaining Wall
Systems Incorporated, dated January 24, 2020 (Project No. SDP02-16).
Anchor Retaining Wall Structural Calculations for: SDP02-16/GR 2019-0006,
Coastline Church/DWG 423-IC, City of Carlsbad, California, prepared by Geogrid
Retaining Wall Systems Incorporated, dated December 5, 2019.
Coastline Community Church, SDP 02-16, Segmental Retaining Walls - First Review, Carlsbad, California, prepared by NV5, dated December 13, 2019.
Dear Mr. Grant:
We prepared this letter to address the referenced review comment in the letter provided by NVS for the
City of Carlsbad regarding development of the subject site. The comment is listed herein with the
Geocon response immediately following.
Comment 1: The calculations assumed a soil unit weight of 130 lb/ft3 and a friction angle of
30 degrees. It is not clear whether the soil parameters accurately reflect the onsite
soil conditions. The retaining wall calculations package includes the statement:
6960 Flanders Drive I Son Diego, California 92121-2974 U Telephone 858.558.6900 • Fax 858.558.6159
"The retaining walls have been designed for internal and external wall stability
only. The Geotechnical Engineer of Record shall confirm site global stability.
Soil design parameters are based upon the MSE Retaining Wall Design
Recommendations by Geocon, Inc. dated June 12, 2019. All soil design
parameters shall be confirmed by the geotechnical engineer prior to the
commencement of construction."
The applicant should submit a copy of the June 12, 2019 letter from Geocon. The
retaining wall plans and calculations should be reviewed and approved by the
geotechnical consultant (Geocon). The approval should be provided in a formal
letter, and include a statement indicating that they agree with the soil parameters
used in the design.
Response: We reviewed the referenced MSE wall plans for the Coastline Community Church
expansion project located in the City of Carlsbad, California. Based on our
review, we opine the plans and details have been prepared in substantial
conformance with the recommendations presented in the referenced geotechnical
report and letter. We opine the soil parameters used for design are in accordance
with the recommendations provided in the referenced geotechnical report and
letter.
In addition, we performed a global slope stability analysis using the two-
dimensional computer software GeoStudio 2018 developed by Geo-Slope
International Ltd. We analyzed the critical mode of potential slip surfaces using
rotational-mode based on Spencer's method.
We estimated the shear strength characteristics of the existing geologic units
based on laboratory direct shear tests on samples obtained during previous
grading operations performed at the site in accordance with ASTM D 3080, and
our experience with similar materials. Table 1 presents the soil parameters used
for the stability analysis.
TABLE I
SUMMARY OF SOIL PROPERTIES USED FOR SLOPE STABILITY
ANALYSES
The case condition and the calculated factor of safety are presented herein. The
plots of analysis results, including the soil stratigraphy, potential failure surfaces,
and calculated factors of safety, are attached herein.
We selected Cross Section 1-1', as shown on the Site Plan, Figure 1, to perform
the slope stability analysis. The cross section intersects Station 3+50 of the
proposed MSE wall and an ascending 2:1 (horizontal to vertical) buttressed fill
slope with a height of approximately 25 feet. We opine this is the most critical
Geocon Project No. G1968-I 1-02 -2 - February 4, 2020
geologic cross-section for use in the slope stability analysis. Table 2 provides a
summary of the case analyzed, the case condition, and the calculated factor of
safety. A minimum factor of safety of 1.5 under static condition is currently
required by the City of Carlsbad for slope stability. Results of the slope stability
analysis, surficial slope stability calculations and selected shear strength
parameters of soil based on the laboratory test results is presented in Figure 2
herein.
TABLE 2
SUMMARY OF SLOPE STABILITY ANALYSES
Our calculations indicate the proposed conditions for the proposed MSE wall and
2:1 (horizontal to vertical) slope to the south of the proposed ministry building
possesses a calculated factor of safety (FOS) of at least 1.5 under static deep-
seated failure when the recommendations of the referenced geotechnical report
and letter are followed.
If you have any questions regarding this response, or if we may be of further service, please contact
the undersigned at your convenience.
Very truly yours,
GEOCON INCORPORATED
Lilian E. Rodriguez
RICE 83227
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Shawn Foy Weedon
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Attachments: Figure 1, Site Plan
Slope Stability Analysis
(e-mail) Addressee
Geoon Project No. G1968-1 1-02 - 3 - February 4, 2020
L GENERAL CONTRACTOR/DEVELOPER AND jtURIU, INC. SHALL COORDINATE THE INSTALLATION
OF ALL SUBTERRANEAN CONSTRUCTION WITHIN THE REINFORCED ZONE. RED ONE ENGINEERING, INC.
SHALL BE CONSULTED PRIOR TO ANY EXCAVATION WITHIN THE REINFORCED ZONE. ALL EFFORTS
SHALL BE MADE TO COORDINATE INSTALLATION OF SUBTERRANEAN FEATURES DURING WALL
CONSTRUCTION.
DURING CONSTRUCTION AND AFTER WALL COMPLETION COMPLETION THE FINISHED GRADE SHALL BE GRADED I I by PREPARED FOR THE EXCLUSIVE USE OF
TO DRAIN AWAY FROM THE ANCHOR RETAINING WALL UNTIL FINAL DRAINAGE SYSTEM IS COMPLETE. NO STANDING WATER SHALL BE ALLOWED TO POND ABOVE THE ANCHOR RETAINING WALL d l29sclsttlbulionway
1295 flSTNBU11ON Viny vista cv R2(I TEL 7eO5O9a .00 GEOGRID. INC. TO PROVIDE SUBORAIN STUB OUT AS SHOWN ON THE WALL PROFILES. THE II( viola. Ca 92081 phone 760.410.1665
FAX 7605(51191W
GENERAL CONTRACTOR/DEVELOPER IS RESPONSIBLE FOR PROVIDING CONNECTIONS AND/OR
OUTLETS AS SHOWN ON THE WALL PROFILES AND IN ACCORDANCE WITH THEIR CIVIL ENGINEER.
YIJ "° 95609 JIIII)
",,\ J'/J tacstmk 760.509.0078
REViSION DESCRIPTION
SHEET CITY OF CARLSBAD 8 I ENGINEERING DEPARTMENT L1.0
ANCHOR RETAINING WAIL PLANS 9'ORi
COASTUNE COMMUNITY CHURCH LOT 492, TRACT NO. 85-03-2
WALL PLAN VIEW
OR 2018-0006
APPROVED: JASON S. GELDERT
OTT ENGINEER RCE 63912 EXPIRES 9/30/20 DATE
OWN BY: PROJECT NO. -IfDRAWING NO. CHKD BY: RYWD BY: .................... - -
—
Figure 1 Site Plan ANCHOR RETAINING WALL PLSAN VIEW S: io
- "AS BUILT"
Geocon Legend RETAINING WALL DATA TABLE
CONSTRUCTION NOTES WALL A TYPE LENCTM
RCE EXP. DATE
GRADING1. . AND ELEVATIONS ARE SHOWN FOR REFERENCE ONLY. PLEASE ... Approx. Location of Geologic Cross Section 345 FT REVIEWED BY.
SEE PROJECT GRADING PLAN FOR SITE INFORMATION.
-- - INSPECTOR DATE
1.67
Material Properties:
('.nstlinA Cnmmiinity Chijrch\c
Project No. G1968-11-01
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Section 1-1'
Name: 1-1_Case 1.gsz
Date: 01/31/2020 Time: 01:39:52 PM
140
Color Name Unit Cohesion' Phi'
Weight (psf) (°)
(pcf)
Qpf 130 200 30
• Td 130 500 26 1L
130
120
I-
() 110 U-
70
130
120
110
0
100 CO > 0)
90
70
we 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
60
Distance, Feet
Directory: X:\Engineenng and Geology\ENGINEER PROGRAMS, GUIDES, ETC\EngrgPrg\GEO-SLOPE20I8\G1968-11-02 ChurchFiIe Name: 1-1—Case 1.gszDate: 01/31/2020