HomeMy WebLinkAboutCT 13-04; Golden Surf; Tentative Map (CT)Geotechnical • Geologic • Coastal • Environmental
5741 Pal,,.„, .".ay • Carlsbad, California 92010 • (760)438-3155 • FAX (760) 931-0915 • www.geosoilsinc.com
Revised December 10, 2014
W.O. 6309-A5-SC
Golden Surf Holdings, Ltd
6798 Paseo Del Norte
Carlsbad, California 92009
Attention: Mr. Farzan Demoubed
Subject: Addendum and Geotechnical Response to City of Carlsbad Engineering
Department Plan Check Comments, Parcel 1, Parcel Map 6136,
1000 Camino De Las Ondas, Carlsbad, San Diego County, California,
CT 13-04, PUD 13-10, and CDP 13-33
Dear Mr. Demoubed:
In accordance with your request and authorization, GeoSoils, Inc. (GSI) is providing this
addendum and geotechnical response to October 27, 2014 plan check comments
prepared by the City of Carlsbad Engineering Department (City of Carlsbad, 2014 [see the
Appendix]). The sen/ices GSI performed for this study included a review of the referenced
documents (Appendix), analysis of data, and the preparation of this addendum and
response letter. Unless specifically superseded herein, the conclusions and
recommendations contained in the project geotechnical reports listed in the Appendix, are
still considered valid and applicable, and should be appropriately implemented during
project design and construction.
RESPONSE TO CITY OF CARLSBAD (2014)
Based on our review of City of Carlsbad (2014), GSI understands that we are required to
respond to the geotechnical aspects of Engineering Department Comment No. 3. This
plan check comment is repeated below in /fa//c font, followed by GSI's response.
Citv of Carlsbad Eng/neer/nq Department Plan Check Commenf No. 3
Based on GSI's response to first review comment #6, provide an addendum from the
geotechnical consultant indicating the project's technical ability to be constructed as
proposed.
GSI Response to City of Carisbad Engineering Department Plan Check Comment
No. 3
Based on our review of Spear and Associates (2014) and GSI (2011 and 2014), it is our
opinion that the project is feasible from a geotechnical perspective. The most significant
geotechnical issues with the proposed residential development shown on Spear and
Associates (2014) are: 1) the potentially compressible nature of the near-surface soils (i.e.,
overburden soils); 2) expansive near-surface soil conditions within the northerly quadrant
ofthe project; 3) the potential for corrosion to exposed buried metals if left in direct contact
with the onsite soils; 4) limitations to remedial grading and support of planned
improvements near property lines due to boundary/perimeter conditions; and 5) retaining
wall construction along portions ofthe westerly and southwesterly project boundaries. GSI
points out that remedial earthwork recommendations for the treatment of the potentially
compressible soils were previously provided in GSI (2011). In addition, in GSI (2011), we
provided recommendations for the design and construction of post-tension and mat
foundation systems to mitigate the expansive onsite soils. As an alternative to the use of
structural mitigation for expansive soils, the developer may elect to remove expansive soils
from the site, and replace those soils with non-detrimental ly expansive soils (i.e., soils with
an expansion index less than 21 and a plasticity index less than 15), or place them outside
the influence of the residential structures. However, the latter could affect the long-term
performance of any ancillary site improvement (i.e., walls, hardscape, pavements, etc.)
constructed above or near expansive soils. We note that recommendations for walls and
flatwork in consideration of expansive soils, are provided in GSI (2011). Recommendations
to mitigate the corrosive effects ofthe onsite soils are also provided in GSI (2011).
The project is bounded by private property on its westerly, easterly, and northerly sides,
and by City of Carlsbad property (i.e., Camino De Las Ondas) on its southerly side. On
page 17 of GSI (2011), we recommended that the removal and recompaction of potentially
compressible soils be completed below a 1:1 (hohzontakvertical [h:v])projection down
from the bottom outboard edge of any planned settlement-sensitive improvement and/or
limits of new planned fills. Given the boundary conditions, it appears that remedial grading
will be limited at the property lines. Thus, the developer should consider the use of
deepened foundations for the support of the planned perimeter retaining walls. Geogrid,
soil cement, and/or structural mitigation may be used for other settlement-sensitive
improvements (i.e, hardscape and pavements) constructed abovea 1:1 (h:v) plane upfrom
the bottom outboard edge ofthe remedial grading excavation. Alternatively, the developer
may elect to not perform any mitigation within this zone. Should this be the case, the
potential for settlement and associated distress, and a reduced serviceable life of
improvements constructed within this zone cannot be precluded.
Planned retaining wall construction along the westerly and southwesterly property lines
appears to require temporary slopes that will exceed the recommendations provided on
page 18 of GSI (2011), without the implementation of offsite grading. General
recommendations, including the use of shoring structures, constructing the walls in
Golden Surf Holdings, Ltd. W.O. 630g-A5-SC
Parcel 1 of Parcel Map 6136, Carlsbad , Revised December 10, 2014
File: e\wp12\6300\6309a5.rgrt GCOSoilS, IlIC. Page 2
alternating slot excavations, or relocating these walls were provided in GSI (2014). The
developer may perform a value engineering study centered on quality, speed of
construction, and cost, prior to the selection ofthe engineered solution. Based on limited
space, gravel backfill wrapped in filter fabric may be necessary behind these particular
walls.
In summary, recommendations have been provided by GSI for the project to be
constructed as proposed, from a geotechnical viewpoint.
If you have any questions or comments regarding this letter, please do not hesitate to
contact the undersigned.
Respectfully submitted,
GeoSoils, Inc.
'John P. Franklin
Engineering Geologist, CEG 1340
nowiH \A/ i David W
Civil Engineer,
yan B. Boehmer
Project Geologist
RBB/JPF/DWS/jh
Attachment: Appendix - References
Distribution: (2) Addressee (via email and US mail)
(1) Spear and Associates, Inc., Attention: Mr. Josh Ziegler (via email)
(1) Karnak Planning and Design, Attention: Mr. Robert Richardson (viaemail)
Golden Surf Holdings, Ltd.
Parcel 1 of Parcel Map 6136, Carlsbad
File: e\wp12\6300\6309a5.rgrt GeoSoils, Inc.
W.O. 6309-A5-SC
Revised December 10, 2014
Page 3
APPENDIX
REFERENCES
City of Carlsbad Community and Economic Development, 2014, 2"" review for
CT 13-04/PUD 13-10/CDP 13-33 - Golden Surf, dated October 27.
GeoSoils, Inc., 2014, Geotechnical response to City of Carlsbad Engineering Department
plan check comments. Parcel 1, Parcel Map 6136, 1000 Camino De Las Ondas,
Carlsbad, San Diego County, California, CT 13-04, PUD 13-10, and CDP 13-33,
W.O. 6309-A4-SC, dated July 25.
, 2011, Preliminary geotechnical evaluation, Paseo Point Minor Subdivision,
6798 Paseo Del Norte, City of Carlsbad, San Diego County, California,
W.O. 6309-A-SC, dated November 30.
Spear and Associates, Inc., 2014, Conceptual grading plans for: Parcel 1, P.M. 6136,
1000 Camino De Las Ondas, Sheets 2 and 3 of 3, Drawing Nos, C-2 and C-3,
20-scale, dated July 10.
GeoSoils, Inc.