HomeMy WebLinkAboutMS 16-06; CARLSBAD VILLAGE LOFTS; UPDATED PRELIMINARY GEOTECHNICAL RECOMMENDATIONS - ADDENDUM 01; 2019-03-31'5~ CTE I~,,,
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Construction Testing & Engineering, Inc.
Inspection I Testing I Geotechnical I Environmental & Construction Engineering I Civil Engineering I Surveying
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March 31, 2019 JUN 24 2019 CTE Job No. 10-14798G
Wermers Properties LAND DEVELOPMENT Attn: Austin Wermers ENGINEERING 5080 Shoreham Place, Suite 105
San Diego California 92122
(858) 623-4958 Via Email: AustinW@wermerscompanies.com
Subject: Updated Preliminary Geotechnical Recommendations - Addendum 01
Proposed Carlsbad Village Lofts
1044 Carlsbad Village Drive (APNs: 203-320-3200, -3900, & -4700)
Carlsbad, California
References: Updated Preliminary Geotechnical Recommendations and Grading Plan Review
Proposed Carlsbad Village Lofts
1044 Carlsbad Village Drive (APNs: 203-320-3200, -3900, & -4700)
Carlsbad, California
CTE Job No. 10-14798G, dated February 28, 2019
Geotechnical Investigation
Proposed Carlsbad Village Drive Apartments
1044 Carlsbad Village Dive
Carlsbad, California
CTE Job No. 10-12371G. dated January 27, 2016
Mr. Wermers:
As requested, Construction Testing and Engineering, Inc. (CTE) provides the updated
geotechnical recommendations herein as an addendum to the referenced geotechnical report.
These recommendations are provided in response to an email request from the structural
engineer (VCA Structural), which is provided herewith. Updated and/or additional geotechnical
recommendations are provided below and are numbered per the information requests in the
aforementioned email, and supersede any conflicts with previously provided recommendations.
4.3 Groundwater Conditions
Based on review of the boring logs from CTE's referenced 2016 report, groundwater was not
encountered at the site to the maximum explored depth of 18.5 feet below existing ground
surface (bgs). However, based on review of available documents on the State Water Resources
Control Board's (SWRCB's) Geotracker database for the subject site and nearby sites,
groundwater has been encountered at approximately ten feet bgs. Additionally, groundwater
1441 Montiel Road, Suite 115 1 Escondido, CA 92026 1 Ph (760) 746-4955 1 Fax (760) 746-9806 1 www.cte-inc.net
Updated Preliminary Geotechnical Recommendations - Addendum 1 Page 2
Proposed Carlsbad Village Lofts
1044 Carlsbad Village Drive (APNs: 203-320-3200, -3900, & -4700), Carlsbad, California
March 31, 2019 CTE Job No. 10-14798G
elevations may fluctuate due to precipitation and other causes. Therefore, we believe a
conservative design groundwater elevation of ten feet bgs is appropriate.
5.5 Fifi Materials
A conceptual retaining wall backdrain detail was provided as Figure 4 to CTE's 2016
geotechnical report. This conceptual detail may or may not be used by the appropriate
professional, at their discretion, to detail specific retaining wall backdrains and waterproofing, as
appropriate, for the project.
5.8.1 Foundations
Based on review of the boring logs from CTE' s referenced 2016 report, Paralic Deposits are
anticipated to be encountered at approximately 1.5 feet bgs across the site. For foundations near
grade (i.e., foundations not at depth for the subterranean parking structure), foundation
dimensions and reinforcement should be based on an allowable bearing value of 2,500 psf for
footings embedded a minimum of 24 inches below nearest adjacent subgrade elevation and into
competent formational materials. An allowable increase of 250 psf may be applied for each
additional six inches of embedment up to a maximum allowable bearing value of 4,500 psf.
Continuous footings should be at least 24 inches wide; isolated footings should be at least 36
inches in least dimension. The above bearing values may also be increased by one third for short
duration loading which includes the effects of wind or seismic forces.
Maximum total and differential static settlement estimates for near-grade foundations should be
considered to be the same as the previously provided total and differential static settlement for
at-depth foundations. However, it is anticipated that shallow structure footing will be stepped
down gradually to remain embedded in native materials and transition down to the deeper level
basement foundations. Additional deepening of all foundations could be required based on the
actual conditions encountered during construction.
A 140 pci uncorrected subgrade modulus of reaction is also considered appropriate for near-
grade foundations in competent native materials.
The following equation can be used to calculate the corrected subgrade modulus of reaction, k,
based on footing size:
k=k1 *((B+ 1)/2B)2
where k1 is the uncorrected subgrade modulus of reaction and B is the footing width.
Please note that, depending on the methods used for constructing the subterranean portion of the
structure (e.g., typical excavation with laid back temporary slopes, temporary shoring, etc.), it
may be necessary to deepen or step-down near-grade footings as they approach the subterranean
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Updated Preliminary Geo chnical Recommendations - Addendum 1 Page 3
Proposed Carlsbad Village Lofts
1044 Carlsbad Village Drive (APNs: 203-320-3200, -3900, & -4700), Carlsbad, California
March 31, 2019 CTE Job No. 10-14798G
portion of the structure to ensure that they continuously bear on undisturbed, dense, competent
native materials, and that they extend through any fill placed during construction.
5.8.2 Foundation Settlement
As it is anticipated that all foundations will be embedded into competent formational materials,
the previously provided estimates for total and differential static and dynamic settlement remain
unchanged.
5.8.4 Interior Concrete Slabs
Based on review of the boring logs from CTE's referenced 2016 report, groundwater was not
encountered at the site to the maximum explored depth of 18.5 feet below existing ground
surface (bgs). However, based on review of available documents on the State Water Resources
Control Board's (SWRCB's) Geotracker database for the subject site and nearby sites,
groundwater has been encountered at approximately ten feet bgs. Additionally, groundwater
elevations may fluctuate due to precipitation and other causes. Therefore, we believe a
conservative design groundwater elevation often feet bgs is appropriate.
5.10 Lateral Resistance and Earth Pressures
For typical street or other traffic that remains more than 10 feet away from retaining structures,
surcharge loading may be neglected. Retaining structures up to 15 feet in height that may receive
traffic surcharging within 10 feet of the back of the retaining structure should be designed to
resist a uniform lateral pressure of 100 pounds per square foot (psf) that results from an assumed
300-psf surcharge behind the shoring due to typical street or other traffic.
The following equations may be used to calculate lateral pressures on cantilevered retaining
walls (yielding walls) over six feet in height (based on the work by Seed & Whitman, 1970) and
restrained (non-yielding) over six feet in height (based on the work by Wood, 1973):
YIELDING CASE
PAE = PA + APAE
PA/b = Static Active Earth Pressure = GhH2/2
zPIb = Dynamic Active Earth Pressure Increment = (3/8) kh 7H2/2
NON YIELDING CASE
PKE = PK + APKE
PK/b = Static Restrained Wall Earth Pressure = GhH2/2
APKEIb = Dynamic Restrained Earth Pressure Increment = kh'yH2/2
where:
b = unit length of wall (usually 1 foot)
kh = '/2k PGA,,, (PGAm given previously Table 5.9)
\\ESC_SERVER\Projects\10-14798G'Ltr_Geo Adendum 01 & Response to Structural .doc
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Dan T. Math, GE# 2665
Vice President, Principal
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Co . Kenny, RCE #84406
Senior Engineer
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Updated Preliminary GeoVnical Recommendations - Addendum 1 Page 4
Proposed Carlsbad Village Lofts
1044 Carlsbad Village Drive (APNs: 203-320-3200, -3900, & -4700), Carlsbad, California
March 31, 2019 CTE Job No. 10-14798G
Gh = Equivalent Fluid Unit Weight (given previously Table 5.10)
H = Total Height of the retained soil
y = Total Unit Weight of Soil z 135 pounds per cubic foot
*A 1/2 reduction factor is anticipated to be acceptable based on the assumption that the walls are
not overly sensitive to some movement during the design seismic event, but this should be
confirmed or determined by the project structural engineer (see SEAOC, 2013). If the walls are
considered to be overly sensitive to some movement during a seismic event, a 2/3 reduction
factor may be feasible at the discretion of the project structural engineer and governing authority.
The increment of dynamic thrust in both cases should be distributed triangularly with a line of
action located at H/3 above the bottom of the wall (SEAOC, 2013).
The opportunity to be of service on this project is appreciated. If you have any questions
regarding this report, please do not hesitate to contact the undersigned.
Respectfully submitted,
CONSTRUCTION TESTING & ENGINEERING, INC.
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Natasha Indegno
From: Austin Wermers <austinw@wermerscompanies.com >
Sent: Thursday, March 28, 2019 3:30 PM
To: Dan Math
Cc: Phuong Do (Structural); Eugene Kuehl; Tam Nguyen (Structural); Kia Assadzadeh; Ed
Wu
Subject: RE: Carlsbad Village Lofts - Soils Report Review
Dan, please see the below email
From: Tam Nguyen (Structural) [mailto:Tam . Nguyen @vcastructural.com]
Sent: Thursday, March 28, 2019 3:25 PM
To: Austin Wermers <austinw@wermerscompanies.com>; Kia Assadzadeh (kiaa@architectsorange.com)
<kiaa@architectsorange.com>; Ed Wu (edwardw@architectsorange.com) <edwardwarchitectsorange.com>
Cc: Phuong Do (Structural) <Phuong.Docvcastructural.com>; Eugene Kuehl <Eugene.Kuehl@vcastructural.com>
Subject: Carlsbad Village Lofts - Soils Report Review
All—
We have reviewed the soils report for Carlsbad Village Lofts and have the following comments for the soils
engineer. Please forward these on to him to so that he can provide responses. Thanks.
4.3 Groundwater Conditions
1) Provide design groundwater elevation.
5.5 Fill Materials
1) Detailing wall backdrains is not in structural
percent passing the Na. 200 sieve. The upper 12 to 18 inches ofwalt bickfihI couldconsistoflowcr
peniieabftit' soils, in order to rchioe surface water intiiimtioit behind walls. Th ti uiu (LI
b"
r1it1 r1,11. IJuu qn.* liowcvcr, a conceptual wall backdram de-tai L which may or
may not he suitable for use at the site, is pmvidcd as Fiurc 4.
5.8.1 Foundations
1) Not all foundations @ subterranean; Retail is on grade.
indicated, it is anticipated that the proposed structure footings will be fH1I dtidé
to the proposed le ci ofsubtenaneanparkiiig As such, proposed foundations are anticipated
Provide foundation recommendations for on grade condition. Also, address potential differential settlement.
Provide subgrade modulus reduction equation for size of footing.
Provide subgrade modulus for on grade conditions.
5.8.2 Foundation Settlement
1) Update for actual foundation conditions.
maximum differential static settlement is expected to be on the order of!72. inch over
istáncofappróximaiely 40f6cfl Due to the absence of a shallow groundwater table and
2) Doe this conflict with design water elevation?
maximum differential static settlement is expected to be on the order of Va inch over a
distance of approximately 40 feet, Due to the absence of a shallow groundwatcrjabié and
5.8.4 Interior Concrete Slabs
1) Provide groundwatei elevation.
It is our experience that the subterranean parking level slab on grade would not be
considered a moisture-sensitive application. :}iowcvcr, due to the potential for groundwater,
this slab on grade could be considered a moisture-sensitive application,. Therefore., the
5.10 Lateral Resistance and Earth Pressures
Provide traffic surcharge design value.
Provide dynamic thrust increment value as a function of H.
PAE ~ PA
0
Tam Nguyen Jr., P.E. I Senior Project Engineer
VCA Structural I Orange + Oakland
714.978.9780 ext. 217 I vcastructural.com I !L.YiI 1845 W. Orangewood Ave., Ste. 200
Orange, CA 92868
2