HomeMy WebLinkAboutX2021-3462 - SoilsENGINEERS + GEOLOGISTS + ENVIRONMENTAL SCIENTISTS
June 18, 2024
J.N. 21-422
NICHOLSON CONSTRUCTION
1 Corporate Plaza, Suite 110
Newport Beach, California 92660
Attention: Ms. Nanci Glass
Subject: Final Soils Report, Geotechnical Observations and Testing, Foundation Excavations,
Slab Subgrades and Utility Trench Backfill, 225 Jasmine Avenue, Corona Del Mar
Area, City of Newport Beach, California
References: 1) Geotechnical Investigation, Proposed Single Family Residence, 225 Jasmine Avenue,
Corona Del Mar Area, City of Newport Beach, California; report by Petra Geosciences,
Inc., J.N. 21-422, dated November 10, 2021.
2) Geotechnical Report of Rough Grading, Proposed Single -Family Residence,
225 Jasmine Avenue, Corona Del Mar Area, City of Newport Beach, California; report by
Petra Geosciences, Inc., J.N. 21-422, dated December 5, 2022.
3) Geotechnical Commentary on Construction of Northerly Property Line Retaining Wall,
225 Jasmine Avenue, Corona Del Mar Area, City of Newport Beach, California; report by
Petra Geosciences, Inc., J.N. 21-422, dated March 15, 2024.
Dear Ms. Glass:
Petra Geosciences, Inc. (Petra) is submitting herewith a summary of our observations of foundation
excavations for the site structures, and our observations and test results pertaining to slab subgrade soils,
and placement and compaction of backfill within utility trenches located in landscape areas, and under
proposed slabs within the subject site.
Representatives from our firm performed on -call field density testing and field observations at the request
of the project superintendent during post -grade operations. It should be noted that Petra was not contacted
and therefore did not perform geotechnical observation of the foundation excavation for the wall along the
northerly property line and as such, this item is not under the purview of this report.
SUMMARY
Foundation Excavation Observations
Excavations of footing trenches for the residence and site structures were probed and observed to be
excavated into engineered fill per the foundation plans and the recommendations presented in our reference
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NICHOLSON CONSTRUCTION June 18, 2024
225 Jasmine Avenue / Corona Del Mar J.N. 21-422
Page 2
reports. As noted earlier, Petra was not contacted and therefore did not perform geotechnical observation
of the foundation excavation for the northerly property line wall and as such, this item is not under the
purview of this report.
Utility Trench Backfill
1. Backfill of interior and exterior trenches consisted of onsite soils placed above select sand bedding.
The sand bedding placed above utility lines was jetted and varied from approximately 6 inches to 2 feet
in depth. Backfill materials were moisture conditioned, as necessary, to achieve optimum or above
optimum moisture conditions prior to and/or during placement, and then compacted in 6- to 8-inch lifts
with a pneumatic tamper to a minimum relative compaction of 90 percent (based on ASTM D 1557).
2. Exterior trench backfill consisted of sewer, water, area drain, and a common (joint) trench containing
electric, gas, telephone and data lines. The approximate maximum depth of soil backfill placed over
bedding sand for the various trenches was approximately 3 feet in the sewer trench excavation.
3. Utility trench backfills, where probed and/or tested, are considered to have been placed in accordance
with the recommendations presented in the referenced reports.
Slab Subgrades
Due to the amount of time that had elapsed since the completion of rough grading, and due to disturbance
during construction activities, the surficial subgrade soils of the slabs were moisture conditioned to achieve
optimum or above optimum moisture content and then compacted in -place to a minimum relative
compaction of 90 percent of the applicable laboratory maximum dry density in general accordance with
ASTM Test Method D 1557. These subgrade soils were tested prior to concrete placement and are
considered acceptable from a geotechnical point of view. The subgrade soils were also pre -watered as per
our recommendations (References).
Field and Laboratory Testing
1. Field density tests results for trench backfills and slab subgrades are summarized in Table I, and
approximate test locations are shown on the accompanying Density Test Location Map (Figure 1). Field
density tests were taken with a Nuclear Gauge (ASTM D 6938).
2. Field density tests were taken at vertical intervals of 1 to 2 feet.
3. The laboratory maximum dry density and optimum moisture values for the most prominent onsite soils
(Soil Type A) were determined according to Test Method ASTM D 1557 and are listed in Table II.
CONCLUSIONS
Footing trench excavations for the residence and site structures were observed to have been founded into
engineered fill. In addition, where observed and tested, utility trench backfill and slab subgrade soils as
discussed in this report were found to be in general compliance with our recommendations and the grading
PETRA - SOLID ASA ROCK
GEOSCIENCES"°
NICHOLSON CONSTRUCTION June 18, 2024
225 Jasmine Avenue / Corona Del Mar J.N. 21-422
Page 3
codes of the City of Newport Beach, California. The completed work within this firm's purview to the
extent observed, as discussed herein, has been reviewed and is considered adequate from a geotechnical
perspective. As mentioned earlier herein, Petra was not contacted and therefore did not perform
geotechnical observation of the foundation excavation for the northerly property line wall and as such, this
item is not under the purview of this report.
REPORT LIMITATIONS
Representatives of Petra were present on -site on an on -call basis during post -grading operations for the
purpose of providing the owner's representative with professional opinions and recommendations. These
opinions and recommendations were developed based on field observation and selective testing of the
contractor's work. Our scope of services during this project did not include supervision or direction of the
contractor, his personnel or his subcontractors.
As documented in this report, our observations and testing did not reveal any obvious deviations from the
recommendations provided in the referenced geotechnical reports; however, Petra does not in any way
guarantee the contractor's work, nor do our services relieve the contractor (or any subcontractors) of their
liability should any defects subsequently be discovered in their work product.
Based on our findings, this report was prepared in conformance with generally accepted professional
engineering practices, and no warranty is implied nor made.
This report is subject to review by the controlling authorities for the project. Please call if you have any
questions pertaining to this report.
Respectfully submitted,
PET E CIENCES, INC.
Don Obert
Associate Engineer
RGE 2872
SM/DO/Iv
Attachments: Table I — Field Density Test Summary
Table H — Laboratory Optimum Moisture and Maximum Dry Density Test Data
Figure 1 — Density Test Location Map
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NICHOLSON CONSTRUCTION
225 Jasmine Avenue / Corona Del Mar
TABLE
FIELD DENSITY TEST SUMMARY
June 18,2024
J.N. 21-422
Date of
Test
Test No.
Location
Depth*
ft.
Moist.
%
Unit Wt.
bs./cu.ft.)
% Rel.
Comp.
Soil
Type
12/7/2022
1-IT
Interior
0.5
12.9
110.1
92
A
12/7/2022
I -SG
Building Pad
0.0
12.8
111.0
93
A
12/9/2022
1-S
Exterior
1.5
11.6
108.6
91
A
12/9/2022
2-S
Exterior
0.0
11.4
109.2
91
A
12/9/2022
1-W
Exterior
0.5
12.6
109.9
92
A
12/9/2022
1-1
Exterior
1.0
12.2
110.2
92
A
3/20/2024
2-SG
Drive Approach
0.0
11.7
111.4
93
A
3/20/2024
3-SG
Side Patio
0.0
11.9
109.5
92
A
3/20/2024
4-SG
Entry
0.0
10.8
111.2
93
A
3/20/2024
1-AD
Side Yard
0.0
10.1
108.8
91
A
SC - SUBGRADE
IT - INTERIOR TRENCH
S - SEWER
W - WATER
J - JOINT (ELECTRIC, TELEPHONE, TV, GAS)
AD - AREA DRAIN
* - DEPTH BELOW FINISH GRADE
PETRA SOLID AS A ROCK
NICHOLSON CONSTRUCTION June 18, 2024
225 Jasmine Avenue / Corona Del Mar J.N. 21-422
TABLE II
LABORATORY OPTIMUM MOISTURE AND MAXIMUM DRY DENSITY TEST DATA
Soil Type
Optimum Moisture
Maximum Dry Density
( /o)
(PC,)
A —Silty Sand (SM)
9.5
119.5
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