HomeMy WebLinkAboutCT 07-04; BRESSI RANCH MEDICAL PLAZA; ROUGH GRADE COMPACTION REPORT; 2008-09-18ROUGH GRADE COMPACTION REPORT
BRESSI RANCH MEDICAL PLAZA
Bressi Ranch Lot 1, Planning Area 1
Carlsbad, California
for
Urban West
September 18, 2008
Urban West
1280 Bison Ave, B9-609
Newport Beach, California 92660
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SOUTHERN
CALIFORNIA
GEOTECHNICAL
A California Corporation
Attention: Ms. Kimberly Hutchings
Vice President-Development
Project No.: 08M141-1
Subject: Rough Grade Compaction Report
Bressi Ranch Medical Plaza
Bressi Ranch Lot 1, Planning Area 1
Carlsbad, California
References: 1) Geotechnical Investigation, Proposed Industrial Building, Bressi Ranch Lot 1,
Planning Area 1, SEC of Garden Road and El Camino Real, Carlsbad, California;
Prepared by Southern California Geotechnical, Inc., dated January 23, 2006, Project
No. 05G301-1.
2) Update of Geotechnical Report and Plan Review, Proposed Bressi Ranch Medical
Plaza, Bressi Ranch Lot 1, Planning Area 1, Carlsbad, California; Prepared by
Southern California Geotechnical, Inc., dated may 10, 2007, Project No. 07G158-1.
Ms. Hutchings:
In accordance with your request, Southern California Geotechnical, Inc. (SCG) presents this Rough
Grade Compaction Report which serves as a summary of the grading observation and testing
performed by our personnel during remedial/rough grading operations at the subject site.
SITE DESCRIPTION
The subject site is located within the previously mass graded Bressi Ranch Industrial Park which is
located south of Palomar Airport Road in the city of Carlsbad, California. The specific site is a portion
of Planning Area 1 or Lot 1 and consists of 2± acres located southeast of the intersection of Town
Garden Road and El Camino Real. The site is bordered to the north by Town Garden Road, to the
west by El Camino Real, to the south by a commercial development that is currently under
construction, and to the east by Metropolitan Street.
The subject site is an irregularly-shaped parcel, approximately 2± acres in size. Graded ascending
slopes ranging in height from 6 to 9± feet border the site to the south and west. Graded descending
slopes up to 10± feet in height border the site to the east and northeast. One desilting basin was
located in the eastern portion of the site. The desilting basih was approximately 4 to 6± feet deep.
Ground surface cover consisted of exposed soil with negligible to sparse grass and weed growth.
Visually, with the exception of the aforementioned slopes and basin, the remainder of the site
consisted of gently sloping terrain dipping downward to the northeast.
PROPOSED DEVELOPMENT
The new development will consist of a 19,760± ft2 two-story medical office building. The building
22885 East Savi Ranch Parkway v Suite E v Yorba Linda, CA 92887-4624
voice: (714) 685-1115 v fax: (714) 685-1118 v www.socalgeo.com
will be located in the western portion of the property. The remainder of the site will be developed
with asphaltic and Portland cement concrete pavements, concrete flatwork, and new landscaping. A
retaining wall will be constructed along the southern property boundary.
The project precise grading plan indicates that cuts and fills of up to 1± foot were required to
establish the planned pad grade within the proposed building pad area. It should be noted that this
estimate is exclusive of any overexcavation and subsequent fill placement necessary for the
recommended remedial grading activities.
PREVIOUS STUDIES
SCG previously performed a geotechnical investigation of this site, the results of which were
presented in the above referenced report Reference 1). The subsurface exploration conducted for
this project consisted of six (6) borings advanced to depths of 15 to 191/2 ± feet below the existing
site grades.
Artificial fill soils were encountered at the ground surface at boring B-6, which was located in the
southeastern portion of the site. These fill soils extended to a maximum depth of 12± feet below
existing grade. The fill soils generally consisted of medium dense to very dense fine sands, clayey
fine sands and hard fine sandy clays. The fill soils possessed moderately high strengths, moisture
contents near or above optimum and based on their color mottling and composition, appeared to be
well mixed.
Bedrock was encountered at or near ground surface at the remaining boring locations and beneath
the fill soils at boring B-6. The bedrock encountered at this site consisted of Tertiary age Santiago
formation, which is comprised of dense to very dense sandstone with some zones of claystone and
siltstone. Bedding within the Santiago formation on site is generally massive with no significant
planes of weakness or discontinuities. The sandstone unit is typically light gray in color, contains
moderate iron oxide staining, and is comprised of weakly cemented silty fine sand. The siltstone unit
is typically light gray to gray in color, contains moderate iron oxide staining, and is comprised of fine
sandy silt. The claystone unit is typically dark gray to gray green in color, contains some shell
fragments, gypsum veins, and is comprised of silts and clays.
Based on the conditions encountered at the boring locations, it was recommended that remedial
grading be performed within the building pad area. The building pad area was recommended to be
overexcavated to a depth of at least 3 feet below existing grade and to a depth of at least 3 feet
below the proposed pad grade. The depth of overexcavation should be sufficient to provide at least
3 feet of new structural fill beneath the bearing grade of all foundations. The overexcavation was
recommended to extend laterally at least 5 feet beyond the perimeter building and foundation lines.
The foundations were recommended to be designed for a maximum allowable soil bearing pressure
of 2,500 lbs/ft2.
SUMMARY OF EARTHWORK OPERATIONS AND TESTING
The rough grading operations documented in this report were initiated on September 13, 2008 and
were completed on September 17, 2008. The building pad area was overexcavated in accordance
with the recommendations presented in the referenced geotechnical report. This resulted in the
entire building pad area being overexcavated to a depth of approximately 51/2 to 6± feet below the
proposed pad grade. The lateral limits of the overexcavation were extended at least 5± feet beyond
the building and foundation perimeters.
SOUTHERN Bressi Ranch Medical Plaza - Carlsbad, CA
CALIFORNIA Project No. 08M141-1
v GEOTECHNICAL Page 2
The exposed native formational materials exposed at the base of the overexcavation were scarified
to a depth of 12± inches, moisture conditioned, and recompacted. The prepared subgrade was
noted to be firm and unyielding beneath the weight of the grading equipment and was approved for
filling by an SCG field representative. The excavation was then backfilled with compacted structural
fill to reach the planned finished grade. Fill materials consisted of on-site soils that were moisture
treated and compacted in 6± inch thick lifts with a Caterpillar D-8 dozer and a vibratory pad-foot
roller. The results of compaction testing performed at discrete, randomly selected locations indicated
that at least 90 percent of the ASTM D-1557 maximum dry density was achieved at the test
locations.
Structural fill compaction was tested by the Nuclear Method (ASTM D-2922) and referenced to
maximum dry density values obtained by the Modified Proctor method (ASTM D-1557). Where
density tests indicated less than the minimum specified compaction, the areas were moisture treated
as necessary and recompacted until 90 percent of the ASTM D-1557 maximum dry density was
achieved, as indicated by retests. The locations of the density tests are indicated on the enclosed
Density Test Location Plan, Plate 1. Moisture-density test results are presented on Table 1, enclosed
in this report. In addition, data regarding the soil types used as structural fill are presented on Table
2.
LABORATORY TESTING
Expansion Index
Expansion index testing was performed on a representative sample of the soils used for fill in the
building pad area. This testing was performed in accordance with Uniform Building Code (UBC)
Standard 18-2. The results of the El testing are as follows:
Sample Identification Expansion Index Expansive Potential
Finished Pad 16 Low
Design recommendations provided in the project geotechnical engineering report where based on a
medium expansion potential, therefore, no additional recommendations with regard to expansive
soils are considered warranted at this time.
Soluble Sulfates
A representative sample of the on-site soils collected during the geotechnical investigation was
tested for soluble sulfate content. Results of this testing indicated a sulfate concentration of 0.014
percent, which represents a negligible level of soluble sulfates. Additional samples of the soils used
for fill were obtained from the completed building pad and were submitted for sulfate testing. The
results of the additional testing will be documented in an addendum letter when they become
available. Since only on-site soils were used for fill, it is anticipated that the forthcoming laboratory
results will also reflect negligible sulfate content.
CONCLUSIONS AND RECOMMENDATIONS
Geotechnical observation and testing of the rough grading activities indicate that the building pad
has been suitably prepared, with grading activities conducted in accordance with recommendations
SOUTHERN Bressi Ranch Medical Plaza - Carlsbad, CA
CALIFORNIA Project No. 0811141-1
.. GEOTEçHNICAL Page 3
presented in the original geotechnical engineering report and the local building codes. The building
pad is expected to provide adequate support for the intended structure which utilizes a foundation
designed for a maximum allowable soil bearing pressure of 2,500 lbs/ft2.
The foundations, floor slab, and other improvements should be designed in accordance with the
recommendations contained in the original geotechnical report referenced above. It is recommended
that SCG be contacted to perform additional earthwork observation and testing during the following
phases of the project:
Foundation Excavation
Utility Trench Backfill
Retaining Wall Construction and/or Backfill
Subgrade Preparation in New Pavement Areas
Aggregate Base Placement in New Pavement Areas
Closure
This opportunity to be of continued professional service is sincerely appreciated. Should you have
any questions regarding this project, please contact us at your earliest convenience.
Respectfully Submitted,
SOUTHERN CALIFORNIA GEOTECHNICAL, INC.
. bd--, (A
Gary Conraçis
Fiek/0pev4ions Manager
/
GE 2294
PriVpalAgineqr
Enclosures.i —....D€nsity Test Location Plan, Plate 1
\. Summary of Field Density Tests, Table 1
Summary of Moisture-Density Relationships, Table 2
Distribution: (1) Addressee
(3) Pacific Building Group, Attn: Paul Montanez
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No. 2294
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SOUTHERN Bressi Ranch Medical Plaza - Carlsbad, CA
CALIFORNIA Project No. 08M141-1
GEOTECHNICAL Page 4
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GEOTECHNICAL LEGEND
S 10 APPROXIMATE LOCATION OF IN-PLACE DENSITY TEST
F2 9-2 701 APPROXIMATE ELEVATION OF BOTTOM OF OVEREXCAVATION
- — — — — - APPROXIMATE LIMITS OF OVEREXCAVATION
-
NOTE: BASE MAP PREPARED BY FUSCOE ENGINEERING
DENSITY TEST LOCATION PLAN
BRESSI RANCH MEDICAL PLAZA
CARLSBAD, CALIFORNIA
SCALE: 1= 3E
DRAWN: GRC
SCG PROJECT W
SOUTHERN
CHKD: RGT CALIFORNIA
08M141-1 GEOTECHNICAL
PLATE I
TABLE 1
SUMMARY OF FIELD DENSITY TESTS
Test No. Date Elev. Test Soil Moisture Dry Density Relative Comments
(ft) Location Type Content (pcf) Compaction
(%) (%)
1 13-Sep-08 292.0 Building Pad A 10.1 100.3 88 BOX/Fail: 90% Required
2 13-Sep-08 292.0 Building Pad A 10.5 100.6 88 BOX/Fail: 90% Required
3 13-Sep-08 292.0 Building Pad A 15.6 102.9 90 Retest #1
4 13-Sep-08 292.0 Building Pad A 16.1 102.6 90 Retest #2
5 13-Sep-08 292.0 Building Pad A 15.8 103.1 90 BOX
6 13-Sep-08 293.5 Building Pad B 17.6 101.5 86 Fail: 90% Required
7 13-Sep-08 293.5 Building Pad B 10.0 103.8 88 Fail: 90% Required
8 13-Sep-08 293.5 Building Pad B 15.8 106.7 90 Retest #6
9 13-Sep-08 293.5 Building Pad B 15.5 106.8 91 Retest #7
10 13-Sep-08 293.5 Building Pad B 15.6 107.4 91
11 13-Sep-08 293.5 Building Pad B 15.8 106.4 90
12 13-Sep-08 293.5 Building Pad A 15.6 104.5 92
13 13-Sep-08 293.5 Building Pad A 15.7 103.9 91
14 15-Sep-08 294.5 Building Pad A 15.6 102.9 90
15 15-Sep-08 294.5 Building Pad A 15.9 103.2 91
16 15-Sep-08 295.0 Building Pad A 15.7 102.7 90
17 15-Sep-08 296.0 Building Pad B 15.5 106.4 90
18 15-Sep-08 296.0 Building Pad B 15.9 106.6 90
19 15-Sep-08 292.0 Building Pad A 15.6 103.1 90 BOX
20 15-Sep-08 292.0 Building Pad A 10.0 100.4 88 BOX/Fail: 90% Required
21 15-Sep-08 297.5 Building Pad B 15.5 106.2 90
22 15-Sep-08 297.5 Building Pad B 15.8 106.8 91
23 15-Sep-08 292.0 Building Pad A 15.6 103.2 91 Retest #20
24 15-Sep-08 297.0 Building Pad A 15.9 102.9 90
25 16-Sep-08 293.5 Building Pad A 9.6 100.7 88 Fail: 90% Required
26 16-Sep-08 293.5 Building Pad A 15.9 100.4 88 Fail: 90% Required
27 16-Sep-08 293.5 Building Pad A 15.6 103.2 91 Retest #25
28 16-Sep-08 293.5 Building Pad A 16.0 102.6 90 Retest #26
29 16-Sep-08 294.5 Building Pad A 15.6 103.9 91
30 16-Sep-08 295.0 Building Pad A. 15.9 104.0 91
31 16-Sep-08 295.0 Building Pad A 15.7 102.7 90
32 16-Sep-08 296.5 Building Pad A 115.6 102.9 90
33 16-Sep-08 296.5 Building Pad A 16.2 103.9 91
34 16-Sep-08 297.5 Building Pad A 16.1 105.0 92
35 16-Sep-08 297.5 Building Pad A 15.5 103.8 91
36 16-Sep-08 297.5 Building Pad A 15.6 103.4 9
37 16-Sep-08 292.0 Building Pad A 15.7 103.2 91 BOX
38 16-Sep-08 1 292.0 Building Pad A 15.8 103.4 91 BOX
08M141-1 Bressi Ranch Medical Plaza -- Carlsbad, California Page 1
TABLE I
SUMMARY OF FIELD DENSITY TESTS
Test No. Date Elev. Test Soil Moisture Dry Density Relative Comments
(ft) Location Type Content (pcf) Compaction
39 16-Sep-08 293.5 Building Pad A 16.8 103.0 90
40 16-Sep-08 293.5 Building Pad A 15.7 103.1 90
41 17-Sep-08 295.0 Building Pad A 15.9 104.0 91
42 17-Sep-08 295.0 Building Pad A 16.7 104.9 92
43 17-Sep-08 296.5 Building Pad A 16.0 103.8 91
44 17-Sep-08 296.5 Building Pad A 15.8 103.9 91
45 17-Sep-08 297.5 Building Pad A 15.7 104.2 91
46 17-Sep-08 297.5 Building Pad A 15.9 106.7 94
47 17-Sep-08 FP Building Pad A 15.6 107.2 94
48 17-Sep-08 FP Building Pad A 15.5 108.4 95
49 17-Sep-08 FP Building Pad A 15.8 108.6 95
50 17-Sep-08 FP Building Pad A 15.6 108.3 95
51 17-Sep-08 FP Building Pad A 15.9 108.9 96
52 17-Sep-08 FP Building Pad A 15.7 108.5 95
NOTES: B.O.X.= Bottom of Overexcavation
FP = Finished Pad Grade
Elevations Referenced To Grade Stakes Set In Field By Others
Retests Performed After Recompaction
All Tests Performed By Nuclear Test Method (ASTM D-2922)
08M141-1 Bressi Ranch Medical Plaza -- Carlsbad, California Page 2
TABLE 2
SUMMARY OF MOISTURE-DENSITY RELATIONSHIPS
Soil Type Soil Description Maximum Dry Optimum Density (pcf) Moisture (%)
A Light Gray to Gray Brown Silty fine Sand 114 13.5
B Light Brown to Yellow Brown fine Sandy Silt, trace Clay 118 13.5
Note: All Moisture-Density Relationships determined per ASTM D-1 557 (Modified Proctor)
08M141-1 Bressi Ranch Medical Plaza -- Carlsbad, California Page 1