HomeMy WebLinkAboutCT 14-01; STATE MIXED USE 30; DISCUSSION OF PERMANENT SITE DESIGN, STORM WATER TREATMENT AND HYDROMODIFICATION MANAGEMENT; 2016-10-21·~F ( · · )PY I _ ( ;i t·~·-; l t ,.
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Geotechnical • Geologic • Coastal • Environmental
5741 Pa lmer Way • Carlsbad, California 92010 • (760) 438·3155 • FAX (760) 931-09 15 • www.geosoilsinc.com
MEMORANDUM
DATE: October 21, 2016 W.O. 6636-A-SC
TO: State and Oak, LLP
c/o MAA Architects
2173 Salk Avenue, Suite 250
Carlsbad, California 92008
Attn: Mr. Kirk Moeller
From: Robert G. Crisman, CEG 1934
SUBJECT: Discussion of Permanent Site Design, Storm Water Treatment and
Hydromodification Management, 3068 State Street, Carlsbad, California
References: 1. "Geotechnical Update, 3068 State Street, City of Carlsbad, San Diego County, California,
dated March 23, 201 5
2. "Preliminary Geotechnical Evaluation, 3068 State Street, Carlsbad , San Diego County,
California," W.O. 6636-A -SC, dated December 24, 2013, by GeoSoils, Inc.
3. "Engineering Design Manual, Volume 5, Carlsbad BMP Design Manual, dated February
16, 2016, by the City of Carlsbad.
4. "Grading and Improvement Plans for: State Mixed Use 30, CT 14-01, Sheet 1-3, Job No.
13-038, Plot dated July 10, 2015, by K&S Engineering, In c.
In accordance with your request, and authorization, GSI has reviewed the geotechnical reports
(Reference Nos. 1 and 2), and the grading plan (Reference No.2) for the purpose of preparing City
Form 1-8 included in the City's BM P Design Manual (Reference No. 3), with respect to site
preparation and the construction of the planned mL.lti-unit residential building, with ground floor
parking (Reference No. 4). Per Form 1-8, the site is classified as "No Infiltration."
Unless specifically superceded herein, the conclusions and recommendations presented in
Reference No. 1 remain valid and applicable. The conclusions and recommendatiohs presented
herein are professional opinions. These opinions have been derived in accordance wHh current
standards of practice, and no warranty is express or implied. Standards of practice are subject to
change with time. GSI assumes no responsibility or liability for work or testing performed by
others, or their inaction, or work performed when GSI is not requested to be onsite, to evaluate if
our recommendations have been properly implemented. Use of th is report constitutes an
agreement and consent by the user to all the limitations outlined above, notwithstanding any other
agreements that may be in place. In addition, this report may be subject to review by the
controlling authorities.
Attachment: BMP Form 1-8
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Appendix I: Forms and Checklists
Categorization of Infiltration Condition Form 1-8
Part 1 -Full Infiltration Feasibility Screening Criteria
Would infiltration of the full design volume be feasible from a physical perspective without any undesirable consequences
that cannot be reasonably mitigated?
Criteria Screening Question
Is the estimated reliable infiltration rate below proposed facility locations greater
than 0.5 inches per hour? The response to this Screening Question shall be based on
a comprehensive evaluation of the factors presented in Appendix C.2 and Appendix D.
Provide basis:
Yes No
X
Yes. The United States Department of Agriculture (USDA) has evaluated the infiltration rate of natural
surface soils as on the order of 0.57 to 1.98 in/hr (Hydrologic Soil Group B), based on soil taxonomy, which
characterized site soil as belonging to the "Marina Loamy Coarse Sand." However, the USDA's description
of the Marina Sand indicates that it is developed with in eolian sand derived from mixed sources. Based
on our site exploration and review of regional geologic mapping, site soils are mapped as marine and
terrestrial "paralic" deposits derived from many regional formations, and typically contain local areas of fine
grained soils. Our experience with similar site soils in the vicinity, including the geologic units observed
and/or encountered during our subsurface investigation (Reference No. 1 ), indicate that these soils
typically become denser, and less permeable with depth, below more permeable surficial layers of topsoil
and colluvium. As such, the resultant infiltration rates for these much denser formational materials would
be expected to be well below the rate evaluated by th e USDA. Furthermore, artificial fill created by the
recommended removal/recompaction of onsite soils would also be considered to be of a very low
permeability.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion
of study/data source applicability.
2
Can infiltration greater than 0.5 inches per hour be allowed without increasing
risk of geotechnical hazards (slope stability, groundwater mounding, utilities, or
other factors) that cannot be mitigated to an acceptable level? The response to this
Screening Question shall be based on a comprehensive evaluation of the factors
presented in Appendix C.2.
Provide basis:
X
No. Th e reduced permeability of formation at depth will tend to result in the lateral migration of water and
saturated conditions at, or near the surface, increasing th e potential for distress to foundations, floor slabs,
etc., due to either soil saturation and settlement, or increased water vapor transmission through
slabs/foundations, with resultant distress. There is an increased potential for the creation of perched
g ro undwater (mounding) conditions along zones of contrasting permeabilities, including shallow cut/fill
contacts, and transitions between potentially clayey and sandy formational materials within the formation.
Utility trenches can potentially act as trench drains anrl provide conduits for the movement of excessive
moisture beneath the structure(s). Further such utility trenches would be subject to piping and/or
settlement in distress to overlying improvements, both onsite and offsite.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide n~rrative discussion
of study/data source applicability.
I-3 Februar y 2016
Appendix I: Forms and Checklists
Criteria
3
Form 1-8 Page 2 of 4
Screening Question
Can infiltration greater than 0.5 inches per hour be allowed without increasing
rlsk of groundwater contamination (shallow water table, storm water pollutants
or other factors) that cannot be mitigated to an acceptable level? The response to
this Screening Question shall be based on a comprehensible evaluation of the factors
presented in Appendix C.3.
Provide basis:
Yes No
X
No. While this study did not include an environmental assessment, visual observation did not indicate the
presence of potential contaminants. The regional groundwater table is not considered a factor in the
development of this site, the creation of a shallow "perched" water table can occur through infiltration.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion
of study/data source applicability.
4
Can infiltration greater than 0.5 inches per hour be allowed without causing
potential water balance issues such as a change of seasonality of ephemeral streams
or increased discharge of contaminated groundwater to surface waters? The
response to this Screening Question shall be based on a comprehensive evaluation of
the factors presented in Appendix C.3.
Provide basis:
X
Yes. The site currently drains offsite and no runoff appears to be retained onsite. A full infiltration BMP
would reduce run off into the adjacent lagoon. The regional groundwater table is not considered a factor
in the development of this site.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion
of study/data source applicability.
Part 1 Tn the answers to rows 1-4 are "Yes" a full infiltration design is potentially feasible. The feasibility
Result* screening category is Full Infiltration
If any answer from row l-4 is "No", infiltration may be possible to some extent but would not generally
be feasible or desirable to achieve a "full infiltration" design.
Proceed to Part 2
No
*Tobe completed using gathered site information and best professional judgement considering the definition ofMEP in the MS4
Permit. Additional testing and/or studies may be required by [City Engineer] to substantiate findings.
1-4 February 2016
Appendix I: Forms and Checklists
Criteria
7
Form 1-8 Page 4 of 4
Screening Question
Can Infiltration in any appreciable quantity be allowed without posing
significant risk for groundwater related concerns (shallow water table,
storm water pollutants or other factors)? The response to this Screening
Question shall be based on a comprehensive evaluation of the factors
presented in Appendix C.3.
Provide basis:
Yes No
X
No. The regional groundwater table is not considered a factor in the development of this site, the creation
of a shallow "perched" water table can occur and increase the potential for distress to the structure(s) due
to water vapor transmission through foundations, slabs, and any resultant corrosive effects on metal
conduit in trenches.
Summarize find ings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
8
Can infiltration be allowed without violating downstream water rights?
The response to th is Screening Question shall be based on a comprehensive
evaluation of the factors presented in Appendix C.3.
Provide basis:
X
Th e site currently drains offsite and no runoff appears to be retained onsite. The regional groundwater table
is not considered a factor in the development of this site.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
Part 2 Jfall answers from row 5-8 are yes then partial infiltration design is potentially feasible. The
Result* feas ibility screening category is Partial Infiltration .
If any answer from row 5-8 is no, then infiltration of any vo lume is considered to be
infeasible within the drainage area. The feasibility screening category is No Infiltration.
No
Infiltration
* To be completed using gathered site information and best professional judgement considering the definition ofMEP in the MS4
Permit. Additional testing and/or studies may be required by Agency/Jurisdictions to substantiate findings.
1-6 February 2016
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Geotechnical • Geologic • Coastal • Environmental
5741 Palmer Way • Carlsbad, California 92010 • (760) 438-3155 • FAX (760) 931-0915 • www.geosoilsinc.com
State and Oak, LLP
c/o MAA Architects
2173 Salk Avenue, Suite 250
Carlsbad, California 92008
Attention: Mr. Kirk Moeller
March 23, 2015
W.O. 6636-A-SC
,..., .., -.,/
NOV 2 2 2016
LA NT
Subject: Geotechnical Update, 3068 State Street, City of Carlsbad, San Diego County,
California
Dear Mr. Moeller:
In accordance with your request and authorization, GeoSoils, Inc. (GSI) has prepared the
following update of our geotechnical update report (see the Appendix), with respect to the
governing building code (2013 edition of the California Building Code) for this project.
GSl's scope of services included a review of the referenced report (GSI , 2013), engineering
and geologic analysis, and preparation of this report.
Unless specifically superceded in the text of this report, the conclusions and
recommendations presented in GSI (2013) are considered valid and applicable with
respect to the subject site, and should be properly incorporated into the design and
construction phases of site development.
SEISMIC DESIGN
General
It is important to keep in perspective that in the event of an upper bound (maximum
probable) or credible earthquake occurring on any of the nearby major faults, strong
ground shaking would occur in the subject site's general area. Potential damage to any
structure(s) would likely be greatest from the vibrations and impelling force caused by the
inertia of a structure's mass than from those induced by the hazards listed above. This
potential would be no greater than that for other existing structures and improvements in
the immediate vicinity.
Seismic Shaking Parameters
Based on the site conditions, the following table summarizes the updated site-specific
design criteria obtained from the 2013 CBC (CBSC, 2013), Chapter 16 Structural Design ,
Section 1613, Earthquake Loads. Th e computer program "U.S. Seismic Design Maps,
provided by the United States Geologic Survey (USGS, 2014) was utilized for design
(http://geohazards.usgs.gov/designmaps/us/application. php). The short spectral response
utilizes a period of 0.2 seconds.
2013 CBC SEISMIC DESIGN PARAMETERS
PARAMETER VALUE 2013 CBC/ASCE
REFERENCE
Risk Category 1/11/111 Table 1604.5
Site Class D Section 161 3.3.2/ASCE 7-10
(p. 203-205)
Spectral Response -(0.2 sec), S, 1.153 Section 1613.3.1
Figure 1613.3.1 (1)
Spectral Response -(1 sec), S, 0.442 Section 1613.3.1
Figure 1613.3.1 (2)
Site Coefficient, F. 1.038 Table 1613.3.3(1)
Site Coefficient, Fv 1.558 Table 1613.3.3(2)
Maximum Considered Earthquake Spectral 1.198 Section 1613.3.3
Response Acceleration (0.2 sec), S,..5 (Eqn 16-37)
Maximum Considered Earthquake Spectral 0.689 Section 1613.3.3
Response Acceleration (1 sec), S,.., (Eqn 16-38)
5% Damped Design Spectral Response 0.798 Section 1613.3.4
Acceleration (0.2 sec), S05 (Eqn 16-39)
5% Damped Design Spectral Response 0.459 Section 1613.3.4
Acceleration (1 sec), S0, (Eqn 16-40)
Seismic Design Category D Section 1613.3.5/ASCE 7-10
(Table 11.6-1 or 11 .6-2)
PGA., 0.477 Q ASCE 7-10 (Eon 11 .8.1)
GENERAL SEISMIC DESIGN PARAMETERS
PARAMETER
Distance to Seismic Source (Newport-Inglewood Offshore)
Upper Bound Earthquake (Newport-Inglewood Offshore)
,,, -From Blake (2000a)
,21 -Cao, et al. (2003).
State and Oak, LLP
3068 State Street, Carlsbad
File:e:\wp12\6600\6636a.gur GeoSoils, Inc.
VALUE
5.0 mi (8.1 km)"1
Mw = 7.1121
W .0 . 6636-A-SC
March 23, 2015
Page 2
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 2013 CBC (CBSC, 2013) 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.
FOUNDATION DESIGN
General
1. The foundation systems should be designed and constructed in accordance with
guidelines presented in the 2013 CBC.
2. Based on the anticipated foundation loads and preliminary design information
provided us, it is our opinion that the proposed structure can favorably be
supported on engineered fill, or dense paralic (terrace) deposits. Building loads
may be supported on continuous or isolated spread footings designed in
accordance with the following recommendations.
3. Settlements for these allowable bearing values have been evaluated to be about
1112 inches, or less. A review of the foundation layout and bearing pressure is
recommended in order to evaluate the differential settlement between the heaviest
and lightest footings, once plans are available.
For Isolated Spread Footings Bearing on Suitable Approved Formation (i.e., cut):
ALLOWABLE BEARING VALUES FOR ISOLATED SPREAD FOOTINGS
DEPTH BELOW LOWEST ALLOWABLE BEARING ALLOWABLE BEARING
ADJACENT FINISHED CAPACITY FOR CAPACITY FOR
GRADE (INCHES)l1' <2> SPREAD FOOTINGS SPREAD FOOTINGS
(MINIMUM WIDTH = 4 FEET) (MINIMUM WIDTH = 6 FEET)
24 3.5 ksf 4.0 ksf
36 4.0 kst 4.5 kst
48 4.5 ksf 5.5 ksf
(ll Assumes slab cover of 6 in ches plus underslab gravel/sand.
(2l Values are for net bearing at wall perimeter columns inside building.
State and Oak, LLP
3068 State Street, Carlsbad
File:e:\wp1 2\6600\6636a.gur GeoSoils, Inc.
W.O . 6636-A-SC
March 23, 2015
Page 3
For Continuous Wall Footings Bearing on Ssuitable Approved Formation (i.e ., cut):
ALLOWABLE BEARING VALUES FOR CONTINUOUS WALL FOOTINGS
DEPTH BELOW LOWEST ALLOWABLE BEARING ALLOWABLE BEARING
ADJACENT FINISHED CAPACITY FOR CONTINUOUS CAPACITY FOR CONTINUOUS
GRADE (INCHES)<'> (2>
WALL FOOTINGS WALL FOOTINGS
(MINIMUM WIDTH = 2 FEET) (MINIMUM WIDTH = 4 FEET)
30 3.0 ksf 3.5 ksf
36 3.5 ksf 4.0 ksf
48 4.0 ksf 4.5 ksf
(1l Assumes slab cover of 6 in ches plus underslab gravel/sand.
(2l Values are for net bearing at wall perimeter columns inside building.
The above values are for dead plus live loads and may be increased by one-third
for short-term wind or seismic loads. The above values are for dead plus live loads
and may be increased by one-third for short-term wind or seismic loads. Where
column or wall spacings are less than twice the width of the footing, some reduction
in bearing capacity may be necessary to compensate for the effects of group action.
GSI should review the foundation plans and overlying building load patterns and
evaluate this potential with the structural consultant. Reinforcement should be
designed in accordance with local codes and structural considerations.
4. For bearing on suitable terrace deposits, differential settlement or deflection of
shallow foundations that are differentially loaded will limit the maximum bearing
used. GSI may provide a bearing vs settlement plot upon request.
5. Isolated pad footings should have a minimum dimension of at least 36 inches
square and a minimum embedment of 24 inches below the lowest adjacent grade
into properly engineered fill. Foundation embedment depth excludes concrete
slabs-on-grade, and/or slab underlayment. Foundations should not simultaneously
bear on unweathered paralic (terrace) deposits and engineered fill.
6. For foundations deriving passive resistance from engineered fill (i.e., adjoining
mitigated existing utilities [95 percent relative compaction]), a passive earth
pressure may be computed as an equivalent fluid having a density of 300 pcf, with
a maximum earth pressure of 2,500 psf. For embedment in unweathered paralic
(terrace) deposits, a pressure of 400 pcf may be used if the footing face is
embedded entirely in formation, and the embedment is greater than 30 inches.
7. The upper 6 inches of passive pressure should be neglected if not confined by
slabs or pavement.
8. For lateral sliding resistance, a 0.30 coefficient of friction may be utilized for a
concrete to soil contact when multiplied by the dead load.
State and Oak, LLP
3068 State Street, Carlsbad
File:e:\wp12\6600\6636a.gur GeoSoils, Inc.
W.0 . 6636-A-SC
March 23, 2015
Page 4
9. When combining passive pressure and frictional resistance, the passive pressure
component should be reduced by one-third.
1 O. All footing setbacks from slopes should comply with Figure 1808.7.1 of the
2013 CBC. GSI recommends a minimum horizontal setback distance of 7 feet as
measured from the bottom, outboard edge of the footing to the slope face, if
applicable.
11 . Footings for structures adjacent to retaining/privacy walls should be deepened so
as to extend below a 1 :1 projection from the heel of the wall. Alternatively, walls
may be designed to accommodate structural loads from buildings or appurtenances
as described in the "Retaining Wall" section of this report.
Foundation Settlement Due to Structural Loads
The settlement of the structures supported on strip and/or spread footings founded on
compacted fill will depend on the actual footing dimensions, the thickness and
compressibility of fill below the bottom of the footing, and the imposed structural loads.
Provided the bottom of the footing is bearing on cut for the heaviest foundations, or at least
24 inches of compacted fill for lightly loaded footings, the bearing values presented above,
and conversations with the project structural engineer regarding foundation loading, post
construction differential settlement between the lightest and heaviest loaded footings, due
to applied loads, may occur if the foundation is of the conventional type, and is anticipated
to minimally be on the order of 112 inch, on a preliminary basis, and may be 112 to 1 inch of
deflection between foundations with bearing values that vary from 2,500 psf to 5,500 psf.
LIMITATIONS
The conclusions and recommendations presented herein are professional opinions. These
opinions have been derived in accordance with current standards of practice, and no
warranty is express or implied. Standards of practice are subject to change with time. GSI
assumes no responsibility or liability for work or testing performed by others, or their
inaction; or work performed when GSI is not requested to be onsite, to evaluate if our
recommendations have been properly implemented. Use of this report constitutes an
agreement and consent by the user to all the limitations outlined above, notwithstanding
any other agreements that may be in place. In addition, this report may be subject to
review by the controlling authorities. Thus, this report brings to completion our scope of
services for this portion of the project.
State and Oak, LLP
3068 State Street, Carlsbad
File:e:\wp12\6600\6636a.gur GeoSoils, Inc.
W.O. 6636-A-SC
March 23, 201 5
Page 5
The opportunity to be of service is greatly appreciated. If you have any questions
concerning this report, or if we may be of further assistance, please do not hesitate to
contact any of the undersigned.
Respectfully submi
GeoSoils, Inc.
Robert G. Crisman rew T. Guatelli
Engineering Geologist, CEG 1934 Geotechnical Engineer, GE 2320
RGC/ATG/JPF/jh
Attachment: Appendix -References
Distribution: (2) Addressee
(1) R2H Engineering, Attention: Mr. Brett Brady (email only)
State and Oak, LLP
3068 State Street, Carlsbad
File:e:\wp12\6600\6636a.gur GeoSoils, Inc.
W.O. 6636-A-SC
March 23, 201 5
Page 6
APPENDIX
REFERENCES
American Society of Civil Engineers, 2010, Minimum design loads for buildings and other
structures, ASCE Standard ASCE/SEI 7-10.
Blake, Thomas F., 2000, EQFAULT, A computer program for the estimation of peak
horizontal acceleration from 3-D fault sources; Windows 95/98 version.
Building News, 1995, CAL-OSHA, State of California, Construction Safety Orders, Title 8,
Chapter 4, Subchapter 4, amended October 1.
California Building Standards Commission, 2013, California Building Code, California Code
of Regulations, Title 24, Part 2, Volume 2 of 2, Based on the 2012 International
Building Code, 2013 California Historical Building Code, Title 24, Part 8; 2013
California Existing Building Code, Title 24, Part 10.
Cao, T., Bryant, W.A., Rowshandel, 8., Branum, D., and Willis, C.J., 2003, The revised 2002
California probalistic seismic hazard maps, dated June,
http://www.conversation.ca.gov/cgs/rghm/psha/fault_parameters/pdf/documents
/2002 _ca_ hazard maps. pdf
GeoSoils, Inc., 2013, Preliminary geotechnical evaluation, 3068 State Street, Carlsbad,
San Diego County, California, W.O. 6636-A-SC, dated December 24.
United States Geological Survey, 2014, U.S. Seismic design maps, earthquake hazards
program , http://geohazards.usgs.gov/designmaps/us/application. ph p.
Version 3.1.0, revisions dated October.
GeoSoils, Inc.