HomeMy WebLinkAboutPD 2020-0034; HARBOR POINTE SLOPE REPAIR; GEOTECHNICAL INVESTIGATION, HARBOR POINTE HOA SURFICIAL SLOPE FAILURE, SLOPE BELOW 6887 AND 6899 WATERCOURSE DRIVE, CARLSBAD, CALIFORNIA; 2020-05-29
GEOTECHNICAL INVESTIGATION
Harbor Pointe HOA
Surficial Slope Failure
Slope below 6887 and 6899 Watercourse Drive
Carlsbad, California
prepared for:
Harbor Pointe HOA
c/o Ms. Joanne Diaz
Curtis Management Company
5050 Avenida Encinas, Suite 160
Carlsbad, CA 92008
by:
TerraPacific Consultants, Inc.
4010 Morena Boulevard, Suite 108
San Diego, CA 92117
May 29, 2020
File No. 20-065
•
Harbor Pointe HOA
c/o Ms. Joanne Diaz
Curtis Management Company
5050 Avenida Encinas, Suite 160
Carlsbad, CA 92008
Subject: Geotechnical Investigation
Harbor Pointe HOA
Surficial Slope Failure
May 29, 2020
File No. 20-065
Slope below 6887 and 6899 Watercourse Drive
Carlsbad, California
Dear Ms. Diaz:
In accordance with our proposa l dated April 16, 2020, TerraPacific Consultants, Inc. (TCI)
has prepared this report providing the findings and recommendations from our
geotechnical investigation of the referenced slope failure located below 6887 and 6899
Watercourse Drive within the Harbor Pointe Homeowners Association (HOA) in Carlsbad,
California. The purpose of our investigation was to define the limits of the surficial
failure, opine on a potential cause, and provide geotechnical recommendations for
restoring the slope. The recommendations are based on visual reconnaissance of the
slope area, subsurface investigation, laboratory testing, and engineering/geologic
analysis.
We appreciate the opportunity to be of service. If you should have any questions, please
do not hesitate to contact the undersigned.
Sincerely, T71:_i?I;:-nts, Inc.
Dylan Thomas
Associate Geologist
DT/MHM:gg
Matthew H. Marquez, PE 70072
Senior Engineer
4010 Morena Boulevard, Suite 108 • San Diego, CA 92117 • (858) 521 -1190 • (858) 521 -1199 fax • terropac.net
TABLE OF CONTENTS
1.0 INTRODUCTION .............................................................................................................1
1.1 General ...............................................................................................................1
1.2 Scope of Services ...............................................................................................1
2.0 PROJECT BACKGROUND ..............................................................................................2
2.1 Site Description and Background ......................................................................2
3.0 SITE GEOLOGY ..............................................................................................................3
4.0 SITE INVESTIGATION ....................................................................................................3
4.1 Visual Review .....................................................................................................3
4.2 Subsurface Exploration .....................................................................................4
4.3 Laboratory Testing .............................................................................................4
5.0 CONCLUSIONS AND RESTORATION RECOMMENDATIONS .....................................5
6.0 Restoration Concept...........................................................................................5
6.1 Design Calculations and Stability Analysis ......................................................6
6.2 Plan Review, Bid Review, and Geotechnical Observation ...............................7
7.0 CLOSURE .......................................................................................................................7
7.1 Limits of Investigation .......................................................................................7
7.2 Additional Services ............................................................................................8
APPENDICES
Appendix A: Figures
Appendix B: References
Appendix C: Test Pit Logs
Appendix D: Laboratory Data
Appendix E: Surficial Stability and Restoration Analysis
•
Harbor Pointe HOA • Watercourse Drive, Carlsbad, California • F.N. 20-065 • May 29, 2020
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1.0 INTRODUCTION
1.1 General
The following report presents the findings and recommendations from a geotechnical
investigation of a surficial failure that occurred on the west-facing descending slope
located behind 6887 (Lot 50) and 6899 (Lot 53) Watercourse Drive within the Harbor
Pointe HOA in Carlsbad, California (see Figure 1 in Appendix A). The information
presented herein may be utilized by experienced slope restoration contractors to prepare
a cost estimate for construction. Ultimately, the contractor and owner will need to
determine what permits may be required from the local building jurisdiction and/or if a
design civil engineer/surveyor will be needed to survey the restoration area and develop
formal plans and details for submittal to the City of Carlsbad for approval. It should be
stated that the recommendations presented herein are intended to address the existing
surficial failure area and not slope areas within the HOA beyond the existing failure limits.
In addition, the gross or deep-seated stability has not been evaluated and is not
addressed by this report or the recommendations presented herein.
1.2 Scope of Services
The scope of the investigation performed consisted of the following:
- Site reconnaissance of the failure area, including photo-documentation of
observed conditions.
- Subsurface exploration consisting of the excavation, logging, and sampling of
four test pit excavations. The approximate locations of the test pits are depicted
on the Existing Conditions Plan, Sheet 1 in Appendix A.
- Research of original grading plans and soils reports with the City of Carlsbad. A
list of references is provided in Appendix B.
- Laboratory testing of selected soil samples.
- Engineering and geologic analysis of data acquired.
- Preparation of this report presenting our findings and recommendations.
Harbor Pointe HOA • Watercourse Drive, Carlsbad, California • F.N. 20-065 • May 29, 2020
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2.0 PROJECT BACKGROUND
2.1 Site Description and Background
The subject surficial failure area is located behind 6887 to 6899 Watercourse Drive on the
west-facing, descending slope situated to the north of Harbor Pointe Road. From the top
of the subject slope, which is roughly defined by the rear property line for the homes
(Lots 50 through 53), it descends approximately 35 feet at approximately a 2:1 (horizontal:
vertical) inclination to the rear property lines of the homes at the bottom on Shearwater
Drive (Lots 54 through 56). The slope is landscaped with a combination of non-native,
irrigated ground cover and shrubs.
Based on the grading plans, the subject slope is composed of engineered fill and was
constructed in the mid-1980s. The originally planned grading configuration of the slope
was to be fill over cut/native soil; however, due to seepage conditions reportedly
occurring at the bedrock contact, the lower portion of the slope was over-excavated and
replaced as a stability fill equipped with an internal subdrain system. A retaining wall
ranging from approximately 1.3 to 4.0 feet tall is indicated on the grading plans at the toe
of the slope along the rear property lines; however, the wall had been replaced with
timber beams at 6896 Shearwaters Drive (Lot 54).
The surficial failure is located approximately between the midpoint and top of the slope
and consists of two defined scarps with associated debris and tension cracks. The larger
of the two scarps is located below Lot 52 (6895 Watercourse Drive) and is approximately
30 feet wide by 16 long by 1.5-2.5 feet deep. The smaller scarp is located to the south
below Lot 53 (6899 Watercourse Drive) and is approximately 10 feet wide by 6 feet wide
by 1.5 feet deep. The failure debris from these two features encroached into the
backyards of Lots 54 and 55 (6896 and 6892 Shearwater Drive). There are also tension
cracks that developed on the slope, indicating imminent surficial failure below the
southern portion of Lot 50 (6887 Watercourse Drive) and below the majority of Lot 51
(6891 Watercourse Drive). The tension cracks are generally aligned with the head scarp
of the scarps to the south and should be addressed with the slope restoration effort. The
existing conditions mapped on the slope are presented on Sheet 1 on Appendix A.
The Carlsbad area experienced relatively heavy rainfall the week of April 5, 2020, with a
nearby NOAA weather station (Carlsbad McClellan Palomar Airport, CA US
USW00003177) reporting 2.88 inches of rain on April 10 alone, the day the slope failure
reportedly occurred. Additionally, TCI was provided photographic evidence of a drain
outlet discharging onto the slope face below Lot 51 taken during the week of rain;
however, during the time of our review, the outlet had been removed.
Harbor Pointe HOA • Watercourse Drive, Carlsbad, California • F.N. 20-065 • May 29, 2020
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3.0 SITE GEOLOGY
The site is located within the coastal portion of the Peninsular Ranges Geomorphic
Province of California. This province, which extends 900 miles from Southern California
to the southern tip of Baja California, is characterized by northwest-trending structural
blocks. The coastal portion of the province in San Diego County is typically comprised of
upper Cretaceous-aged to Tertiary-aged (1.8 million to 65 million years) marine and non-
marine sedimentary formational units that have been deposited within a northwest-
trending basin known as the San Diego Embayment (Norris & Webb, 1976). Recent
geologic uplift along the San Diego Coastal margin, combined with sea-level changes, have
created marine terraces with associated deposits consisting of near-shore marine, beach
estuarine, lagoonal, and continental dune facies. The site location is identified on the
Geologic Map presented in Figure 2 in Appendix A.
According to the geologic literature (Kennedy and Tan, 2005), the site is underlain by
Quaternary-aged Old Paralic Deposits (Unit 2-4), formerly identified as Terrace Deposits.
This material is described as mostly poorly sorted, moderately permeable, reddish-
brown, interfingered strandline, beach, estuarine and colluvial deposits consisting of
siltstone, sandstone, and conglomerate. It should be noted that our subsurface
exploration and the as-built/grading plans from the time of original construction identified
the site to be underlain by Quaternary-aged Paralic Deposits and Tertiary-aged Delmar
Formation. Additional descriptions of the earth materials encountered on-site are
presented in Section 4.2 below.
4.0 SITE INVESTIGATION
4.1 Visual Review
Visual reconnaissance and mapping of the slope below Lots 50 - 53 was performed on May
1, 2020, during the subsurface exploration. The following provides a general description of
the conditions observed. Please refer to the Existing Conditions Plan, Sheet 1, in Appendix
A for the approximate locations of the features described below.
The larger of the two scarps is located below lot 52 in the mid to upper portion of the
slope. The head scarp along the top is a maximum of approximately 1.5 feet high.
The failure is estimated to be approximately 1.5 to 2.5 feet deep, 16 feet long, and 30
feet wide.
The smaller of the two scarps is located further to the south below lot 53. The head
scarp at the top is approximately 1.5 feet high. The failure is approximately 1.5 feet
deep, 10 feet wide, and 6 feet long.
Harbor Pointe HOA • Watercourse Drive, Carlsbad, California • F.N. 20-065 • May 29, 2020
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Longitudinal tension cracks to the north of the larger scarp are located below the
southern portion of Lot 50 and the majority of Lot 51. The tension cracks were
approximately 1 foot deep, trend approximately north-south, and roughly line up
with the head scarp of the adjacent feature.
4.2 Subsurface Exploration
The subsurface exploration was also conducted on May 1, 2020, consisting of four hand
excavated test pits (T-1 through T-4) within/near the failure area. The purpose of the
exploration was to expose the subsurface conditions in the vicinity of the failure and to
collect samples for laboratory testing. The test pits were excavated to depths of up to
14.2 feet below the existing ground surface (bgs), and are located on Sheet 1 in Appendix
A. Each test pit was logged in the field by a geologist from our office, and representative
soil samples were collected from the excavations. The logs of each excavation are
presented in Appendix C.
In general, the excavations exposed both man-placed fill and native soils identified as
Quaternary-aged Old Paralic Deposits and Tertiary-aged Delmar Formation. The fill soils
were encountered in all test pits T-1 through T-4, to depths of 8.6, 6.5, 6.7, and 5.4 feet
below the ground surface (bgs), respectively. The fill soils consisted of silty sand that
was generally described as medium to reddish-brown, moist to wet, medium dense in
consistency. Directly below the fill soils, Old Paralic Deposits and sedimentary bedrock of
the Del Mar Formation were encountered. The Old Paralic Deposits were encountered in
test pit T-1 and T-2 at 8.6 and 6.5 feet bgs, respectively. The Old Paralic Deposits were
described as a poorly cemented reddish-brown silty sandstone that was dense to very
dense in consistency. The Del Mar Formation was encountered in test pits T-3 and T-4 at
6.7 and 5.4 feet bgs, respectively. The Del Mar Formation was generally described as
sandy siltstone that was light gray to greenish-gray, moist, and very stiff in consistency.
Minor groundwater seepage was encountered in test pit T-3 and T-4 at 4.8 and 5.3 feet
bgs, respectively.
4.3 Laboratory Testing
Soil samples collected during the field exploration were transported to our laboratory for
testing. The purpose of the testing was to characterize the soil types and evaluate the
engineering properties of the soil for design of the restoration. The laboratory testing
included: field density and moisture content, maximum dry density/optimum moisture
content, and direct shear. Each of the laboratory tests was performed in accordance with
ASTM specifications or other accepted testing procedures. The results of the laboratory
tests are presented in Appendix D.
Harbor Pointe HOA • Watercourse Drive, Carlsbad, California • F.N. 20-065 • May 29, 2020
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5.0 CONCLUSIONS AND RESTORATION RECOMMENDATIONS
Based on our investigation, it has been determined that the slope failure is limited to the
near surface and can be directly related to saturated soil conditions at the time of failure.
The surficial failure is located within the outer approximately 2 to 3 feet of the slope face.
As in this case, surficial failures typically affect the outer 2 to 4 feet of the slope face and
are usually triggered by infiltration of water, which causes erosion and the development
of seepage forces in the soil, reducing the surficial slope stability. It is our opinion that
saturation was primarily due to prolonged rainfall; however, the concentration of
drainage from the aforementioned drain outlet that was removed at Lot 51 prior to our
inspection may have also contributed. Additionally, the failure area was primarily
vegetated with ground cover and void of established trees and/or shrubs, which tend to
have deeper root systems that help reinforce the hillside.
The following recommendations are provided to restore the failed portion of the slope.
The findings and recommendations do not apply to other slope locations within the HOA
and are specific to the location behind Lots 50 to 53 only. It should be mentioned that the
restoration concept presented below should provide sufficient information/detail for
construction. However, if permits are required by the local jurisdiction, our concept plan
may need to be incorporated into a set of formal plans and details prepared by a design
civil engineer/surveyor.
6.0 Restoration Concept
The restoration concept consists of rebuilding the surficial failure area with properly
compacted fill that incorporates geogrid reinforcement and additional subsurface
drainage facilities. The approximate extent of the restoration and concept details are
provided on the Geotechnical Plan, Sheet 2 in Appendix A. However, the actual extent
will ultimately need to be verified in the field prior to construction. A general description
of the restoration is provided below. It should be stated that the restoration concept is
provided with the intent of rebuilding the slope to essentially the pre-failure topography.
Initially, a keyway should be constructed at the base of the surficial failure area.
The keyway should be at least 8 feet wide and established substantially into
properly compacted fill soil. As part of the keyway, a gravel back drain system
with a 4-inch diameter, Schedule 40, or SDR 35, perforated PVC pipe shall be
placed along the keyway heel. The keyway drain should be connected to a solid
Schedule 40 or SDR 35 PVC outlet pipe to suitable disposal, e.g., rip-rap energy
dissipator on the slope.
Harbor Pointe HOA • Watercourse Drive, Carlsbad, California • F.N. 20-065 • May 29, 2020
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Restoration continues up the slope by benching into competent fill to provide an
adequate bond between the new fill and existing fill soil. The fill should be
reinforced with 8-foot long geogrid layers (Tencate Miragrid 3XT or equivalent) at
2-foot vertical intervals, which can be rolled back at the top. Geo-composite
chimney drains or gravel sandbag chimney drains should be installed vertically up
the back cut of the restoration at 30 feet on center to help intercept water above
the key.
The approved fill soil may be placed in thin lifts (i.e., approximately 6-inch loose
thickness), moisture conditioned, and compacted to a minimum 90 percent relative
compaction. This process should continue until the slope is reconstructed to finish
grade. The fill compaction and geogrid placement should be checked by the
geotechnical consultant.
The fill soil used for construction may consist of the existing on-site soil. Soils
recovered from the failure area used for construction should be free of vegetative
matter, construction debris, and oversized material. If import soils are required,
they should consist of a relatively granular free-draining soil, such as silty sand or
clayey sand. Import fill soils should be approved by the soil engineer prior to
transporting to the site.
Once the slope is reconstructed, the slope face should be covered with a soil
erosion control mat. In addition, the slope should be planted as soon as practical
to help provide ground cover and root reinforcement. Drought-tolerant vegetation
should be used. Ice plant, red apple, and fescue should be avoided. Consult with
a landscape architect for specific plant palette.
6.1 Design Calculations and Stability Analysis
A slope stability analysis was performed to evaluate the suitability of the proposed
restoration concept. The surficial slope stability analysis was performed with soil strength
parameters obtained from the original soils report and our investigation (i.e., peak shear
strength values of 32 degrees and 80 psf). Based on the results of the surficial stability
analysis, we confirmed an adequate factor of safety for surficial stability, i.e., a factor
greater than 1.5, for the existing slope using appropriately compacted, geogrid reinforced
fill soils (minimum of 90 percent relative compaction) with an assumed depth to seepage
of 3.5 feet below the slope face. The design calculations and stability analysis are
presented in Appendix E.
Harbor Pointe HOA • Watercourse Drive, Carlsbad, California • F.N. 20-065 • May 29, 2020
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6.2 Plan Review, Bid Review, and Geotechnical Observation
As noted previously, formal plans and details, which would require surveying and
preparation by a design civil engineer/surveyor, may be required by the local building
jurisdiction. If required, the plans and details should be forwarded to TCI to review
general conformance with our recommendations. Observation by TCI’s geotechnical
representative is essential during grading to confirm conditions anticipated by this
investigation, to adjust designs to actual field conditions, and to determine that grading
proceeds in general accordance with the recommendations. A pre-construction meeting
is recommended to establish the restoration limits and schedules for geotechnical
observation and testing. It is also recommended that the restoration estimates be
forwarded to this office for review to verify that the bids contain the required elements of
the restoration. If necessary, we can meet with the contractor to discuss the details of the
restoration concept.
7.0 CLOSURE
7.1 Limits of Investigation
Our investigation was performed using the skill and degree of care ordinarily exercised,
under similar circumstances, by reputable soils engineers and geologists practicing in
this or similar localities. No warranty, expressed or implied, is made as to the conclusions
and professional advice in this report. This report is prepared for the sole use of our
client and may not be assigned to others without the written consent of the client and TCI.
As in most projects, conditions revealed by construction excavations may vary with the
preliminary findings. If this occurs, the geotechnical consultant should evaluate the
changed conditions and designs adjusted as required.
The findings of this report are valid as of the present date. However, the conditions can
change with the passage of time, whether they are due to natural processes or the works
of man. In addition, changes in applicable or appropriate standards may occur from
legislation or the broadening of knowledge. Accordingly, the findings of this report may
be invalidated wholly or partially by changes outside of our control. This report is subject
to review and should be updated after a period of 2 years.
Harbor Pointe HOA • Watercourse Drive, Carlsbad, California • F.N. 20-065 • May 29, 2020
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7.2 Additional Services
The review of plans and specifications, field observations, and testing under our direction
is an integral part of the recommendations made in this report. If TCI is not retained for
these services, the client agrees to assume our responsibility for any potential claims that
may arise during construction. Consultation and testing include, but are not limited to:
observations and testing during site preparation, grading and placement of engineered
fill, and consultation as required or requested. Observation, testing and engineering
consulting services are provided by our firm and should be budgeted within the cost of
development.
* * * TerraPacific Consultants, Inc. * * *
APPENDIX A
Figures
PA SE O DEL NORTE
WATERCOURSE
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SHEARWATERS
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V E HABOR POINT ROADT-3T-4T-1T-2P-104.2P-104.0P-136.2P-137.8P-139.0P-104.51301201106899(LOT 53)6895(LOT 52)6891(LOT 51)6887(LOT 50)6896(LOT 54)6892(LOT 55)6888(LOT 56)AA'Approximate location ofremoved drain outletLEGENDExisting grading contoursApproximate location of surficial slope failure/tension crackApproximate location of failure debrisApproximate location of test pit by TerraPacificExisting finish grade elevationCross section A-A'130T-4P-104.5A A'File No. 20-065May 2020Harbor PointeEXISTING CONDITIONSPLANTITLESHEET14010 Morena BoulevardSuite 108San Diego CA 92117858-521-1190Harbor Pointe6887-6899 Watercourse DriveCarlsbad, California 04020APPROX. SCALE IN FEETNREFERENCES:Grading Plan for Carlsbad Tract No. 83-29 Harbor PointeAerial image from Google Earth\r--= .~, / \ ' ' ,,, I : : I • .. I 'A I ~I I ;;; :,: I I ii I ~ '• ...... _ ----.. .. .... 1 ,,;?,; t I •• 1~--••0,1/) , .j:_L//' ;,,,,,,,"77; / / /, I .· ... ,·· / .. / ./ I .·· ./ .. ........ l' ...---, I I -t
T-1T-3(projected)8' NT-4(projected)21' ST-2(projected)53' SQcfQlsQcfQopTdTdPLPLSUB-DRAINKEYWAY PERGRADING PLANPRE-EXISTING GRADEAS-BUILT GRADE 1985WATERCOURSE DRIVELOT 52SHEARWATER DRIVELOT 54APPROXIMATE LIMITSOF FAILUREElevation in Feet (MSL)1501301401201101009080A1501301401201101009080A'EASTWESTQuaternary-aged landslide depositsGeologic contact (dashed where queried)LEGENDQlsQuaternary-aged compacted fillQcfQuaternary-aged Paralic deposits, units 2-4QopTertiary-aged Del Mar formationTd??????????QcfQcfQlsQcfTdTdPLPLSUB-DRAINKEYWAY PERGRADING PLANWATERCOURSE DRIVELOT 52SHEARWATER DRIVELOT 54Rebuild slope with engineered fillcompacted to a minimum 90% ofmax. dry density per ASTM D-1557Install erosion control mat overrebuilt slope. Refer to landscaper’srecommendation for re-vegetation.Lot drainage not to be directed over slope.Chimney drain constructed withwoven gravel bags or drain board(Mirafi G200N or similar) spaced 30-feet on center.Bench new fill into competent existing fill.Install 8' long geogrid reinforcement(Tencate Miragrid 3XT or equivalent)at 24" vertical spacing.Install subdrain at heel of keyway.Use 4" diameter SDR-35 orsimilar PVC perforated pipe.Surround with min. 2 ft³/linear ft.of ¾" drain rock wrapped withMirafi 140N filter fabric. Outletsubdrain to rip-rap dissipator.QopElevation in Feet (MSL)1501301401201101009080A1501301401201101009080A'EASTWESTQuaternary-aged landslide depositsGeologic contact (dashed where queried)LEGENDQlsQuaternary-aged compacted fillQcfQuaternary-aged compacted restoration fillQcfTertiary-aged Del Mar formationTdQuaternary-aged Paralic deposits, units 2-4Qop0105APPROX. SCALE IN FEET0105APPROX. SCALE IN FEETGEOLOGIC CROSS SECTION A-A'RESTORATION CROSS SECTION A-A'WATERCOURSE
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V E HABOR POINT ROADT-3T-4T-1T-2P-104.2P-104.0P-136.2P-137.8P-139.0P-104.51301201106899(LOT 53)6895(LOT 52)6891(LOT 51)6887(LOT 50)6896(LOT 54)6892(LOT 55)6888(LOT 56)AA'LEGENDExisting grading contoursApproximate location of surficial slope failure/tension crackApproximate location of failure debrisApproximate location of test pit by TerraPacificExisting finish grade elevationCross section A-A'130T-4P-104.5A A'Contractor should employ methods necessary to maintain a safework site in accordance with CAL/OSHA.NOTES:1)Contractor to determine the locations and take measuresto protect any existing underground utilities or other improvementsin restoration area.2)Elevations presented on these plans are based on the originalgrading plans for the project on file with the City of Carlsbadreferenced on this plan.3)All on-site work is for reference only and any required permits arethe responsibility of the owner and/or contractor.4)Geotechnical Consultant should be contacted to field inspect thelimits of restoration area, keyway excavation and subdrain placementprior to backfilling.5)Fill compaction should be observed and tested by the Geotech-nical Consultant.6)Soil used for surficial re-grading and slope recompaction mayconsist of on-site soil provided it is properly moisture conditionedand free of vegetative mater or deleterious material. Import soilshould be pre-approved by the Geotechnical Consultant.7)Refer to TerraPacific Consultants, Inc. report dated May 28,2020 for additional information and details.8)Approximate location of recommended surficial slope restoration.Actual limits to be verified by geotechnical representative at time ofconstruction. See Repair Cross Section for additional details.Tightline subdrain to rip-rap energy dissipatorApproximate location of recommended subdrain system for surficialgrading/slope re-compaction. Actual location to be verified bygeotechnical representative at time of construction. See Repair CrossSection for additional details.Chimney drainREPAIR LEGENDFile No. 20-065May 2020Harbor PointeGEOTECHNICALPLANTITLESHEET24010 Morena BoulevardSuite 108San Diego CA 92117858-521-1190Harbor Pointe6887-6899 Watercourse DriveCarlsbad, California 04020APPROX. SCALE IN FEETNREFERENCES:Grading Plan for Carlsbad Tract No. 83-29 Harbor PointeAerial image from Google EarthI ----------------_ _./ t • .--·----: i._ _ _J !■■■■■■■■■■■■■ 1111111 -----------------------------------------------------------------------------------;-/---......---_/-------~ r _ __/ ~/ I /-__ _J--_____ __r, ________ __n__ ___ _ L_ --1\ ----o __/; -u-_J-------~-1-I I '-'~ /-· __ _J--------L __ -1\
SITE LOCATION
SITE LOCATION
5
5
5
78
Paseo Del NortePaseo Del NorteCarlsbard B
lvd
Poinsettia L
a
n
e
Carlsbad
REFERENCE: Google Maps
NSite Location Plan Figure 1
LOCATION:
6887-6899 Watercourse Drive
Carlsbad, CA
4010 Morena Boulevard
Suite 108
San Diego CA 92117
858-521-1190
Harbor Pointe
File No. 20-065
May 2020
t
250250250250 25025025025025025050 20050 2005020020050200505015050200502005050505050200150
200350450200450400300200 350 35045040 0 3 00300
150400350400 350300 150300300200
150200200400200400350 300150150300200
50200202003501505030020 0200 350300200150200 20050150 50150200 500 50050
250 250
25 0
650 600 550 450 450 450
400 400 40 0
350 350 350 300 300 300 30 0 2 00 200
200 200
150 150 150 150
100 100 100 100
50 50 5 0 50 550Description of Map UnitsOld paralic deposits undivided (late to middle Pleistocene)—Mostly poorly sorted, moderately permeable, reddish-brown, interfingered strandline, beach, estuarine and colluvial deposits composed of siltstone, sandstone and conglomerate. These deposits rest on the now emergent wave cut abrasion platforms preserved by regional uplift. Where more than one number is shown (e.g., Qop2-4) those deposits are undivided (Fig. 3). Includes:QopDelmar Formation (middle Eocene)—Dusky yellowish-green, sandy claystone interbedded with medium-gray, coarse-grained sandstone. This unit is the Delmar Sand Member of Hanna (1926) and was named for exposures in the sea cliffs at Del Mar. It is now considered a formation of the La Jolla Group (Kennedy and Moore, 1971)TdGeologic MapSITE LOCATION1.0 mile0Oceanside QuadrangleCompiled byMichael P. Kennedy and Siang S. Tan20051. U.S. Geological Survey, Department of Earth Sciences, University of California, Riverside4010 Morena BoulevardSuite 108San Diego CA 92117858-521-1190Figure 2Harbor PointeFile No. 20-065May 2020ff-r/Y;~ "; ~'c:::, (..___,I.. • D / -~-~~, ~~~-/. "' \ I L
APPENDIX B
References
REFERENCES
1. Earth Research Associates, Inc., “Final Soils Engineering Report of Regrading, Lots 1,
2, 4, 5, 6, and 52, Tract No. 83-29, City of Carlsbad, California,” dated February 19,
1988.
2. Earth Research Associates, Inc., “Interim Final Soils Engineering and Engineering
Geologic Report No. 2, Lots 5 through 48, 54 through 143, 148 through 161, 198
through 207, 217 through 221, 226, 229 through 241, 243 through 262, 267 through
293, 301 through 339, 343 through 347, and 352 through 380, Tract No. 83-29, City of
Carlsbad, California,” dated March 27, 1985.
3. Earth Research Associates, Inc., “Preliminary Soils Engineering and Engineering
Geologic Investigation, Tentative Tract No. 83-29, City of Carlsbad-, California,” dated
May 1, 1984.
4. Google Maps, Aerial Images obtained online, 2014.
5. Hunsaker & Associates, Inc., “Grading Plans for Carlsbad Tract No. 83-29, Harbor
Pointe, Project No. PE 2.84.53, Drawing No. 245-1A,” latest revision date July 26, 1989.
6. Kennedy, M.P. and Tan, S.S., 2005, Geologic Map of the Oceanside 30’ by 60’
Quadrangle, California, California Geological Survey, Regional Geologic Map Series,
1:100,000 Scale, Map No. 2.
7. Norris, R.M. and Webb, R.W., Geology of California, New York, John Wiley and Sons,
pp. 169-190, 1976.
APPENDIX C
Test Pit Logs
a
DESCRIPTION & REMARKSLithology
Depth(ft)Project No:Project Name:Location:Sample Method:Date:Logged By:Instrumentation:Test Pit No:Test Pit LogElevation:Hammer Wt. & Drop:Excavation Method:Excavator:(%)Moisture(pcf)Dry DensityCountsBlowTypeSampleUSCSExcavating Company:
Total Depth:Test Pit
Page 1 of 1
Water:
Caving:
Footing Dimensions:
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
20-065Harbor PointeHillside Behind 6887 and 6899 Watercourse Drive (Head Scarp)Modified California Sampler 5/1/20E. PerezNone installed T-1~124.0'35 lbs. for 30"Hand laborHarry / Geroge Jr.Mansolf Excavation
14.2'
No
No
N/A
T-1
@ 2.3', Medium brown to gray-brown, wet, some light gray and beige mottling
@ 5.0', Hand auger
@ 6.8', Refusal, rock
@ 7.5', Loose to medium dense, some red-brown mottling, wet
FILL: From 0.0', Silty sand, medium brown, mosit to wet, medium dense to dense, fine to
medium grained sand, friable
NATIVE (Qop 2-4, Old Paralic Deposits): From 8.6', Silty sand, medium brown to red
brown, dense to very dense, moist, some carbon flecks, fine to meduim grained snad,
poorly cemented
From 10.5', Sand, beige to red brown, moist, hard, poorly cemented, highly oxidized
Bulk
Ring
Ring
Bulk
Builk
Ring
Bulk
Ring
--
118.3
116
--
--
120.6
--
109
--
8.4
15
--
--
8.9
--
9.9
--
17/38
23/30
--
50 for 3"
50 for 4"
--
50 for 3"uu •-z '-I--·-u: Cz c...~ c~ L.. ... L..z Q)o t-=,u fl ............ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I
DESCRIPTION & REMARKSLithology
Depth(ft)Project No:Project Name:Location:Sample Method:Date:Logged By:Instrumentation:Test Pit No:Test Pit LogElevation:Hammer Wt. & Drop:Excavation Method:Excavator:(%)Moisture(pcf)Dry DensityCountsBlowTypeSampleUSCSExcavating Company:
Total Depth:Test Pit
Page 1 of 1
Water:
Caving:
Footing Dimensions:
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
20-065Harbor PointeHillside Behind 6887 and 6889 Watercourse Drive (Tension Crack)Modified California Sampler 5/1/20E. PerezNone installed T-2~129.0'35 lbs. for 30"Hand laborHarry / George Jr.Mansolf Excavation
7.3'
No
No
N/A
T-2
@ 2.2', Medium dense to dense
@ 3.7', Hand auger
FILL: From 0.0', Silty sand, meidum rbown to gray brown, mosit to wet, loose, with roots
NATIVE (Qop 2-4, Old Paralic Deposits): From 6.5', Sitly sandstone, red brown, fine to
medium grained, moist, hard, some carbon flecks, dark red iron oxide nodules, refusal
with hand auger
Bulk
Ring
Ring
BulkRing
--
123.8
121
----
--
8.6
11.5
----
--
27/38
22/34
--50 for 2"uu •-z '-I--·-u: Cz c...~ c~ L.. ... L..z Q)o t-=,u fl I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I
DESCRIPTION & REMARKSLithology
Depth(ft)Project No:Project Name:Location:Sample Method:Date:Logged By:Instrumentation:Test Pit No:Test Pit LogElevation:Hammer Wt. & Drop:Excavation Method:Excavator:(%)Moisture(pcf)Dry DensityCountsBlowTypeSampleUSCSExcavating Company:
Total Depth:Test Pit
Page 1 of 1
Water:
Caving:
Footing Dimensions:
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
20-065Harbor PointeHillside Behind 6887 and 6899 Watercourse Drive (Toe of Landslide)Modified California Sampler 5/1/20E. PerezNone installed T-3~ 108.0'35 lbs. for 30"Hand laborGeorge Jr.Mansolf Excavation
7.5'
Seepage @ 4.8'
No
N/A
T-3
@ 4.8', Seepage observed at ascending slope side
From 0.0', Silty sand, medium brown, mosit to wet, loose, some plastic, roots mixed in,
surface vegetation at lower contact
FILL: From 0.5', Silty sand, dark brown, loose, moist, with clay, with roots
From 0.7', Silty sand, medium brown to beige, loose to medium dense, moist to wet, fine
to medium rgained sand, some gravel size rock, pockets of clay
@ 1.0', 1" PVC line
From 5.7', Silty sand, red brown, moist to wet, dense to very dense, micaceous, fine to
medium grained sand, friable, some clay, some gravel to cobble size rock (well rounded)
NATIVE (Del Mar Formation): From 6.7', Sandy siltstone, light gray to greenish gray,
moist, very stiff
Bulk
Ring
Ring
Ring
--
108.9
110.8
--
--
14.1
16.8
--
--
8/17
30/50 for 4"
50 for 5"uu •-z '-I--·-u: Cz c...~ c~ L.. ... L..z Q)o t-=,u fl t.., t.., t.., I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I
DESCRIPTION & REMARKSLithology
Depth(ft)Project No:
Project Name:
Location:
Sample Method:
Date:
Logged By:
Instrumentation:
Test Pit No:
Test Pit Log
Elevation:Hammer Wt. & Drop:
Excavation Method:
Excavator:(%)Moisture(pcf)Dry DensityCountsBlowTypeSampleUSCSExcavating Company:
Total Depth:Test Pit
Page 1 of 1
Water:
Caving:
Footing Dimensions:
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
20-065
Harbor Pointe
Hillside Behind 6887 and 6899 Watercourse Drive (Toe of Slope)
Modified California Sampler
5/1/20
E. Perez
None installed
T-4
~ 107.5'35 lbs. for 30"
Hand labor
George Jr.
Mansolf Excavation
8.2'
Seepage @ 5.3'
No
N/A
T-4
@ 1.6', 3/4" PVC line
@ 5.3', Seepage
FILL: From 0.0', Silty sand, gray to gray brown, moist to wet, loose to medium dense,
some mottling, some roots
From 4.1', Stily sand, red brown, moist, medium dense, with gray siltstone mottling
NATIVE (Del Mar Formation): From 5.4', Sandy siltstone, light gray to greenish gray,
moist, very stiff to hard
Ring
Bulk
Ring
--
--
--
--
--
--
28/38
--
50 for 5"
...r ...r ...r
...r ...r ...r
...r ...r ...r
...r ...r ...r
...r ...r ...r
APPENDIX D
Laboratory Data
Sample Sample Maximum Opt. Moist Dry Moisture Peak Peak
Location Depth Type Dry Density Content Density Content φ c
(ft)(pcf)(%)(pcf)(degrees)(psf)
T-1 0-2'L Bulk ----127.8 9.5 ----
T-1 1.7'Ring 118.3 8.4 --------
T-1 4.0'Ring 116 15 --------
T-1 8.6'Ring 120.6 8.9 ----37.0 550.0
T-1 13.1 Ring 109 9.9 --------
T-2 2.0'Ring 123.8 8.6 --------
T-2 4.0'Ring 121 11.5 --------
T-3 2.0'Ring 108.9 14.1 --------
T-3 5.0'Ring 110.8 16.8 --------
T-4 6.5'Ring --------36.0 80.0
FN: 20-065
ASTM D 2937
Harbor Pointe
Summary of Laboratory Test Results
ASTM D 3080 ASTM D 1557Sample Location
File Name:
DIRECT SHEAR TEST File No.:
Laboratory Report Date:
Technician:
Peak Ultimate
37 36
550 200
TerraPacific Consultants Inc. 4010 Morena Boulevard, Suite 108, San Diego, CA 92117 / Phone: (858) 521-1190 Fax: (858) 521-1199
Harbor Pointe
Friction Angle Φ' (deg)
Cohesion C' (psf)
20-065
5/7/2020
JMS
Sample No.&
Location: T-1 @ 8.6'
Specimen
Preparation:Inundated
Sample Type:
Soil Description:Brown Silty Sand
Intact
0 500 1000 1500 2000 2500 3000 3500 4000
0
500
1000
1500
2000
2500
3000
3500
4000
Peak Strength Test
Results
Ultimate Strength Test
Results
0
500
1000
1500
2000
2500
3000
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30Shear Stress (PSF)Strain (%)
500 PSF
1000 PSF
2000 PSF
Shear Stress (PSF)Normal Stress (PSF)
----------~ .,_.. -,__
~
---V
J 1,
'
I I
I I
~~ ~~ □ ~~ -~ .... .....
~~ -~ I:,. ~~ ~~
f-+-!-+-
I
I
I
I
I I I I
■ T~rr~P.9~i~i.<t
File Name:
DIRECT SHEAR TEST File No.:
Laboratory Report Date:
Technician:
Peak Ultimate
36 36
80 50
TerraPacific Consultants Inc. 4010 Morena Boulevard, Suite 108, San Diego, CA 92117 / Phone: (858) 521-1190 Fax: (858) 521-1199
Harbor Pointe
Friction Angle Φ' (deg)
Cohesion C' (psf)
20-065
5/7/2020
JMS
Sample No.&
Location:T-4 @ 6.5'
Specimen
Preparation:Inundated
Sample Type:
Soil Description:Light Grey Clayey Sand
Intact
0 500 1000 1500 2000 2500 3000 3500 4000
0
500
1000
1500
2000
2500
3000
3500
4000
Peak Strength Test
Results
Ultimate Strength Test
Results
0
500
1000
1500
2000
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30Shear Stress (PSF)Strain (%)
500 PSF
1000 PSF
2000 PSF
Shear Stress (PSF)Normal Stress (PSF)
-·------
~ --i-----~
j _ ~ ""'"" lit ~ ...--
'
I I
I I
~~ ~~ □ ~~ -~ .... .....
~~ -~ I:,. ~~ ~~
f-+-!-+-
I
I I I I
■ T~rr~P.9~i~i.<t
Project Name:Harbor Pointe
Project No. :20-065
Boring No.:T-1 @ 0-2'
Technician:JS
Date:5/7/20
Visual Sample Description: Light Brown Silty Sand
X Manual Ram
Ram Weight 10 LBS Drop 18 inches
TEST NO.1 2 3 4 5 6
A Wt. Comp. Soil + Mold (gm.)3659.00 3783.00 3902.00 3928.00
B Wt. of Mold (gm.)1794.00 1794.00 1794.00 1794.00
C Net Wt. of Soil (gm.)A - B 1865.00 1989.00 2108.00 2134.00
D Wet Wt. of Soil + Cont. (gm.)1486.8 1733.9 1649.3 906.5
E Dry Wt. of Soil + Cont. (gm.)1425.1 1636.7 1543.1 835.1
F Wt. of Container (gm.)193.1 187.6 302.3 187.7
G Moisture Content (%)[(D-F)-(E-F)]/(E-
F)5.0 6.7 8.6 11.0
H Wet Density (pcf)C*29.76
/453.6 122.4 130.5 138.3 140.0
I Dry Density (pcf)H/(1+G/100)116.5 122.3 127.4 126.1
Maximum Dry Density (pcf)127.8 9.5
PROCEDURE USED
Procedure
COMPACTION TEST
ASTM D 1557
Modified Proctor
TerraPacific Consultants, Inc. 4010 Morena Boulevard, Suite 108, San Diego, CA 92117 / Phone: (858) 521-1190 Fax: (858) 521-1199
95.0
100.0
105.0
110.0
115.0
120.0
125.0
130.0
135.0
140.0
145.0
150.0
0.0 5.0 10.0 15.0 20.0Dry Density (pcf)Moisture Content (%)
SP. GR. = 2.65
SP. GR. = 2.70
SP. GR. = 2.75
I I I I ' ' ' ' ' ' ' .,., ' ~
' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' '
' ' " -' ' ' ' ' ' ' ' " -' ' ' ' ' " ' ' " " ' ' " ' '
I"-" ' ' " " ' "
"
APPENDIX E
Surficial Stability Analysis
Project:
Location:
File No.:
Date:
Given:
γT =125 pcf
Φ' = 32 °
C' = 80 psf
α = 26.6 °
D = 3.5 feet
FR =Force required to resist failure
(1) Σx = 0
(EQ-1)
(2) Σy = 0
where
(EQ-2)
(3) Put EQ-2 into EQ-1
(EQ-3)
(EQ-4)
(EQ-5)
20-065
5/28/2020
Harbor Pointe
Watercourse Drive, Carlsbad CA
Slope Repair.xls, 11/08
-F R cos a -_S_ + W sin a = 0 FOS
. C'L + N'Tan ¢' F R cos a = W sin a --------FOS
N -W cos a -FR sin a = 0
N = N '+U U = {rw D cos 2 a )x L
N' = W cos a + FR sin a -rwDL cos 2 a
W sin _ C"L + Woos a ..... P11.sln a-'!NOL. oos ' a )teirn ,
FOS
F rt COS ct F P Slll'I a tan e w sin a· -C"l. + (w ,co . a-Fo~-·SL COS J a}tan f
FOS
W I C'L -w.D.L co: ·1 a tan 1' sn ~---_._-----'-----~------'~-FOS __________ _._ ________ x _
----') FOS oo:e a ~
FOS ,W
Lsina = 1 ⇒ L = -.-1-sma
FOS
cosa y,D W = y,DL cos a ⇒ W = yrD-. -= --sma tan a
( Q..3)
Project:2/3
(4) Substitute EQ-4 and EQ-5 into EQ-3
(5) For FOS =1.5
FR =101 psf
Using Miragrid 3XT geogrid therefore long term strength = 2104 plf (based on soil type)
20.8 feet
= 250.1 inches
Recommended spacing = 24 inches
(6) Check Anchor Length:
2.4 meter grid 7.87 feet
D = 3.5
LB =Bond Length
LA =Anchorage Length
LB =7.0 feet
LA = Grid - LB LA =0.88 feet
WL =465 psf (Average Stress)
soil resistance to pullout
Ci =0.8 465 plf
T = 411 pounds
Actual pullout = spacing x FR = 202 pounds
FOS = 2.0 >1.5 (OK)
Required Spacing =
Harbor Pointe
Slope Repair.xls, 11/08
C' ( \n cos2 a , FOS • y,Dcos a --.--yr -JW JJ . tan ¢
F _ Sin a Sin a R -FQS • cos a+ sin a tan ¢'
tan a D D =-⇒L a=---L a tan a
D+H lM. =--·yr 2
r
r 2 C ; W L tan <jJ '
T = r L A
r
Project:3/3
(7) Check Bond Length
= 87.3 psf
= 219 psf
131 psf
= 131
= 919
FOS Bond = 4.5 >1.5 (OK)
Harbor Pointe
Slope Repair.xls, 11/08
AverageW 0 + yw O cos 2 a
B = 2
Average W a 0 + yrOL a a = ---L a 2L a
Average a'=a -W a
, = a'tan ¢'= 2c;(Average a')tan ¢'
T = ,L B