HomeMy WebLinkAboutCT 2017-0002; TYLER STREET RESIDENCES; GEOTECHNICAL REVIEW OF TENTATIVE MAP AND PRELIMINARY GRADING PLAN FOR PROPOSED 8 UNIT CONDOMINIUM DEVELOPMENT; 2017-01-22. '
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Helensch1nidt Geotechnical, Inc.
Mr. Paul W. Chandler
Tyler Street Development, LLC
4459 Hackett A venue
Lakewood, CA 90713
January 22, 2017
SUBJECT: Geotechnical Review of Tentative Map and Preliminary Grading Plan
for Proposed 8-Unit Condominium Development
RE: 3337 Tyler Street, Carlsbad, California
Dear Mr. Chandler:
Based upon your authorizati·on and our proposal dated January 17, 2017, Helenschmidt
Geotechnical Inc. (HGI) has performed a geotechnical review of a tentative map/preliminary grading
plan at the at the subject site. Our review was performed using:
Tentative Map and Preliminary Grading Plan, 3337 Tyler Street Comlominiums (one
sheet) by Sampo Engineering, Inc . (uns igned, dated January 5, 2017).
The following recommendations are provided based upon our review of the Tentative Map/
Preliminary Grading Plan . Review of design grading plans and foundation plans should be performed by
HGI prior to construction.
1. The current plan calls for installation of a detention basin/planter adjoining the
condominium building. Closed planters next to buildings are generall y not advised.
We recommend that the basin/planter be separated from the building to prevent
moisture and water vapor migration into the building. If separation and unimpeded
air flow between the building and the basin is not possible, the project architect
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should provide details on architectural drawings) for water proofing between the
building and basin. Consideration may be given to installation of a masonry stem
wall with waterproofing along thi s side of the residence to reduce potential moisture
effects on wood and drywall.
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2. To reduce potential horizontal migration of moisture from the basin/planter to
beneath the building, a vertical moisture barrier consisting of 80-mil HOPE root
barrier should be installed along the edge of the bu ilding footing adjacent to the
basin/planter box. The moisture barrier should extend from the ground surface to the
3 feet below grade and extend long the building perimeter for at least 8 feet beyond
each end of the basin/planter box.
3. To prevent tines migration and reduction in performance of the permeable
paver/infiltration system along the driveway and parking areas, filter fabric is
recommended. Filter fabric may consist of Tencate Mirafi HP370 placed along the
interface between the 3/4 -inch crushed rock base and the subgrade.
4. During high flow conditions by storm activity, temporary upward flow of water may
occur, transporting bedding course sands upward through joints 111 the pavement.
593 1 ca Lion Place, Suite I 02
Carlsbad, no IO www.hgiengi neering.com Telephone 760-579-0JD
Fa 760-9-0230
I
Mr. Chandler
Page 2
January 22, 2017
This would be of particular concern at the downstream end of the system where
through drainage will be impeded by adjacent in place soils. Loss of sand through the
pavement is likely to cause rolling of the pavement surface. To help reduce potential
loss of fines, we recommend that the bedding course throughout the drive and
parking areas be overlain with Tencate Mirafi HP370 filter fabric. The recommended
fabric is designed for high flow rate (40 gallons per minute per square foot) and will
help reinforce the pavement system. Note that installation of filter fabric beneath the
base will not preclude transport of sand out of the pavement joints in the case of
upward flow but will help reduce maintenance of pavement areas. Occasional
refilling of the pavement joints should be anticipated as part of site maintenance.
LIMITATIONS
Our services consist of professional opinions and recommendations made in accordance with
generally accepted geotechnical engineering principles and practices. No warranty, express or implied, or
merchantability of fitness, is made or intended in connection with our work, by the proposal for
consulting or other services, or by the furnishing of oral or written reports or findings. Evaluation of
waste or other environmental contaminants was not included in our scope of services.
We appreciate the opportunity to be of service. If you have any questions regarding our review,
please call at your earliest convenience.
Respectfully,
Helenschmidt Geotechnical, Inc.
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Stanley Helenschmidt
Principal Geotechnical Engineer
GE 2064