HomeMy WebLinkAboutPD 2019-0037; CANHAM RESIDENCE; GEOTECHNICAL PLAN REVIEW; 2020-02-03Geotechnical C Geologic C Coastal C Environmental
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T E C H N I C A L M E M O R A N D U M
Date: February 3, 2020 W.O. 7705-A-SC
To:Florence Architects
531 Encinitas Boulevard, Suite 203
Encintas, California 92024
Attention: Mr. Jason Florence
From: Robert G. Crisman, CEG 1934
David W. Skelly, RCE 47857
Exp. 3-31-20
Subject: Geotechnical Plan Review and Response to City Plan Check, Residential
Improvements at 7146 Aviara Drive (Lot 252), San Diego County, California
92054
References: 1. “Third Party Geotechnical Review (First), Proposed single Family Residence,
7146 Aviara Drive (Lot 252), APN 215-610-20-00,” Project ID PD2019-0037/GR2019-
0042, dated November 19, 2019, by Hetherington Engineering, Inc.
2. “Grading Plans for: Canham Residence, 7146 Aviara Drive,” 5 Sheets, DWG 521-6A,
Project No. PD2019-0037, undated, by dk Greene Consulting.
3. “Structural Notes, Plans, and Details, Canham Residence, Aviara Drive, Lot 252,
Carlsbad, Ca., 8 Sheets, Job No. 19230, dated December 16, 2019, by Qualls
Engineering.
4. “Geotechnical Evaluation for Proposed Construction at Lot 252, Aviara Drive,
Carlsbad, San Diego County, California, 92011, APN 215-610-20-00,” W.O. 7705-A-SC,
dated October 30, 2019, by GeoSoils, Inc.
In accordance with your request, and in response to the City’s third party reviewer
(Reference No. 1), GeoSoils, Inc. (GSI), has reviewed the grading plans (Reference No. 2) and the
structural plans (Reference No. 3) with respect to the intent of the geotechnical report
(see Reference No. 4) for this project. GSI has also reviewed the third party reviewers comments
and have provided the appropriate responses and exhibits as follows.
Grading Plan Review
Per Comment No. 1 of Reference No. 1, the site grading plan was reviewed with respect to the
intent of the geotechnical report (Reference No. 4). Based on our review, the grading plans
(Reference No. 2) reviewed are in general accordance with the intent of the geotechnical report
•
GeoSoils, Inc.
Florence Architects W.O. 7705-A-SC
7164 Aviara Drive, Carlsbad February 3, 2020
File:e:\wp12\7700\7706a.gpr Page 2
(Reference No. 4), from a geotechnical viewpoint, with the following additional
comments/recommendations:
•Sheet 2 of Reference No. 2 indicates a potential conflict between the southwest corner of
the "green roof" portion of the building foot print and the pool. A deepened footing and/or
moving the pool slightly eastward, should be anticipated so that the building does not sit
on the pool and/or surcharge the pool wall.
Foundation Plan Review
Per Comment No. 1 of Reference No. 1, the site foundation plan was reviewed with respect to the
intent of the geotechnical report (Reference No. 4). Based on our review, the foundation plans
(Reference No. 3) reviewed are in general accordance with the intent of the geotechnical report
(Reference No. 4), from a geotechnical viewpoint, with the following additional
comments/recommendations:
• Concrete Note No. 1, shown on Sheet S1.0 of Reference No. 3, indicates a minimum
compressive strength of 2,500 psi. Per Reference No. 4, concrete should also have a
maximum water/cement ratio of 0.5 for concrete, for the mitigation of water vapor
transmission through floor slabs, in order to comply with Section 895 et seq., of the
California Civil Code (current edition).
Updated Geotechnical Map
In accordance with Comment No. 2 of Reference No. 1, an updated geotechnical map is attached.
Proposed Construction
In accordance with Comment No. 3 of Reference No. 1, and based on a review of Reference No. 2,
construction is anticipated to consist of site preparation for the construction of a single-family
residential structure with associated with associated underground and surface improvements,
including landscaping, artificial turf, pavers, and concrete flatwork. An approximately 4-foot high,
CMU retaining wall is also planned near the northern property line. GSI anticipates that the
construction would consist of wood frames with typical “conventional” foundations and
slab-on-grade floors. Building loads are assumed to be typical for this type of relatively light
construction. Sewage disposal is anticipated to be connected into the regional, municipal system.
Storm water may be treated onsite prior to its delivery into the municipal system.
Impact of Proposed Grading
In accordance with Comment No. 4 of Reference No. 1, and based on a review of Reference No. 2,
site grading should not adversely affect existing improvements on adjacent properties, provided
that the recommendations presented in Reference No. 4 are properly incorporated into the design
and construction of the project. Plans (Reference No. 2) indicate a Regional Standard
Drawing C-06 retaining wall, to be located along the northern property line. Excavation for this wall
is anticipated to expose dense, formational sandstone. Back cuts for this wall may be completed
vertically to a maximum height of 4 feet, then laid back at a gradient of ½:1 (h:v). All backcuts shall
be observed by the geotechnical consultant prior to site work in the vicinity of the backcut.
GeoSoils, Inc.
Florence Architects W.O. 7705-A-SC
7164 Aviara Drive, Carlsbad February 3, 2020
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Settlement Potential
In accordance with Comment No. 5 of Reference No. 1, the following excerpt from Reference No. 4
is presented below.
“Provided that the earthwork and foundation recommendations in this reported are adhered
foundations bearing on engineered fill should be minimally designed to accommodate a differential
settlement of ¾-inch over a 40-foot horizontal span (angular distortion = 1/640).”
Gross and Surficial Slope Stability
In accordance with Comment No. 6 of Reference No. 1, the following excerpt from
Reference No. 4 is presented below.
“Based on site conditions and planned improvements, significant cut and/or fill slopes are not
anticipated. Therefore, no recommendations are deemed necessary. Temporary slopes for
construction (i.e., trenching, etc.) are discussed in subsequent sections of our report.”
Existing site slopes, including side yard slopes and the rear yard slope that descends eastward
from the existing building pad, are formed/constructed in dense, formational sandstone, and are
considered both surficially and grossly stable, provided that these slopes are properly maintained
over the life of the project. The planned pool, to be located along the top of the rear yard slope,
is anticipated to be founded into dense, formational sandstone. Code setbacks for pools shall
apply. Should pool depths not provide for an adequate setback, a thickened edge/deepened
footing for the pool may be constructed. The need for a thickened edge/deepened footing should
be evaluated by the designer once final pool plans are prepared.
Closure
Unless specifically superceded herein, the conclusions and recommendations presented in
Reference No. 4 remain valid and applicable. The conclusions and recommendations presented
herein are professional opinions, which 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.
Attachments: Plate 1 - Geotechnical Map