HomeMy WebLinkAboutCT 15-11; YADA FAMILY FARM SUBDIVISION; SUPPLEMENTAL GEOTECHNICAL RECOMMENDATIONS; 2017-11-08Geotechnical • Geologic • Coastal • Environmental
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MEMORANDUM w.o . 6927-A1 -SC
Date: November 8, 2017
To:
Attention:
From:
Subject:
References:
California West Construction, Inc.
927 Priestly Drive, Suite 11 O
Carlsbad, California 92008
Mr. Matt Howe
GeoSoils, Inc.
RECORD COPY
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Supplemental Geotechnical Recommendations, Walls and Bioretention Basins, Carlsbad12,
1835 Buena Vista Way, APN 156-220-01-
1. "Grading Plans For: Vada Family Farm Subdivision," sheets 1 through 6, 20-scale plans, project no. 1289,
latest revision/print dated November 6, 2011 , by bHA, Inc.
2. "Preliminary Geotechnical Investigation, Proposed 14-Lot Subdivision, 4.14 Acres, 1835 Buena Vista Way,
APN 156-220-01 , Carlsbad, San Diego County, California," W.O. 6927-A-SC, dated August 3, 2015, by GeoSoils,
Inc.
Based on our review of Reference No. 1, we present the following supplemental recommendations
regarding the retaining walls shown on "Vada Place Inlet Detail (North/south}," "Bioretention Basin No. 1
Cross Section," sheet 4, and "Bioretention Basin No. 2 Cross Section," and "Detail "A,"' sheet 5.
Our review indicates that the retaining walls are undrained, and are located in an area where they may
become wet, but not fully saturated (owing to the previously recommended liner on the bottom and sides
of the bioretention basins). Accordingly, a reduced bearing value of 1,500 psf appears warranted in the
retaining wall design; and, the unit weight of water, 62.4 pcf, should be added to the equivalent fluid
pressures shown on page 26 (horizontal pressures table), since the retaining walls are undrained. An
increase in maximum allowable bearing value for retaining wall footing width may also be used. The
increase should be limited to 100 psf for each additional foot of width to a maximum allowable bearing of
2,500 psf. Passive earth pressure may be computed as an equivalent fluid having a density of 200 pcf,
with a maximum earth pressure of 2,000 psf for footings founded into properly engineered fill or approved
bedrock. The designer should specify if import or native soils will be used for backfill.
In addition, a lined , but structurally unsupported vertical cut of ± 1 ½-2½ feet is indicated on the edge of
the bioretention basins fronting on Valley Street and McCauley Lane. The vertical will progressively
degrade over time, and migrate toward the right-of-way, affecting improvements (onsite and offsite), and
liner integrity. Accordingly, a retaining wall is also warranted on unsupported sides of the bioretention
basins. All other recommendations contained in Reference No. 2 remain pertinent and applicable.