Attachment 10 - January 23, 2025 DRB Geotechnical Report — Laguna Beach City Council, August 12, 2025

August 22, 2024
1560 Bluebird Canyon Drive, LLC Project No: 72786-00
c/o David Dyrnaes Report No: 24-9616
668 N Coast Hwy, Unit 504
Laguna Beach, California 92651
Attention: Mr. David Parker
Subject: Update Geotechnical Investigation for New Architectural Plans Proposed Two-Lot Residential Development
1560 Bluebird Canyon Drive (Parcel 1 and Parcel 2)
Laguna Beach, California
References: 1. Geofirm, 2019, “Preliminary Geotechnical Investigation for New SingleFamily Residence, 1560 Bluebird Canyon Road, APN# 644-321-31, Parcel 4, Block F, Laguna Beach, California,” Project No. 72415-00, Report No. 19-8482, dated February 5.

2. Geofirm, 2022, “Geotechnical Update Letter Proposed Single-Family Residence, 1560 Bluebird Canyon Road, APN# 644-321-31, Parcel 4, Block F, Laguna Beach, California”; Project No. 72415-01, Report No. 22-9214, dated September 9.

3. Geofirm, 2022, “Response to City of Laguna Beach Geotechnical Report, Geotechnical Report Review Checklist, 1st Review, dated September 30, 20222, 1560 Bluebird Canyon Road, APN# 644321-31, Parcel 4, Block F, Laguna Beach, California, ZPC-2020-8070”, Project No. 72415-00, 1560 Bluebird Canyon Road, APN# 644-321-31, Parcel 4, Block F, Laguna Beach, California”; Project No. 72415-01, Report No. 22-9214, dated November 29.

Dear Mr. David Dyrnaes:

This update report presents updated analyses and recommendations pertinent to the design and construction of a proposed two-lot residential development at the subject address. The previous project design has been abandoned and the new design includes a lot split at the subject property.

A two-story single-family residence terraced into the existing hillside will be constructed on each portion of the subdivided lot.

BACKGROUND
Analyses for this report are based upon conceptual design plans for the property, “Two Residential Lots, 1560 Bluebird Canyon Road, Laguna Beach, California, 92651,” by David M.

Parker, AIA dated August 12, 2024 (Parker, 2024).

August 22, 2024 Project No: 72786-00
Report No: 24-9616
Page No: 2
Proposed Development
The project plans (Parker, 2024) depict two new two-story single-family residence buildings terraced into the existing hillside with attached garages terraced below. Associated improvements include retaining walls as great as about 15± feet in overall height, a spa at each lot, landscaping retaining walls, and a paved sloped driveway. Based on this design concept we anticipate partially to fully subterranean levels for portions of the residences. We anticipate the design will utilize wood and steel-framing supported on perimeter retaining wall and isolated pad foundations. Shoring is anticipated.

Slope stability analyses have been updated to reflect the current configuration and layout based upon the new design. Previous recommendations from the referenced reports remain appliable except as superseded herein. The previously reviewed, submitted, and approved referenced reports are attached in Appendix B.

CONCLUSIONS

1. The construction of the proposed residential development at the subject sites is considered geotechnically feasible provided the recommendations herein are integrated into design, construction, and long-term maintenance. Proposed construction should not affect or be affected by adjacent properties provided appropriate construction methods and care are utilized by the contractor.

2. The site is underlain at shallow depth by bedrock materials which are overlain by residual soil. Minor fill also occurs locally. Unweathered bedrock at relatively shallow depth is considered suitable for support of structural improvements. The weathered bedrock, residual soil and fill are not suitable in their present form for support of structural improvements but are generally suitable for use as engineered fill.

3. Based upon observations and testing performed as part of the previous investigation, the expansion potential of upper earth materials is low. Soil soluble sulfate levels are negligible, and corrosivity test results indicate a moderate potential for corrosion of buried metal.

4. The site is underlain at shallow depth by competent bedrock which is considered to have favorable gross slope stability. Surficial/local instability of the fill, residual soil and shallow weathered bedrock is possible and should be addressed in design of foundations adjacent to descending slopes.

5. No active faults are known to transect the site and therefore the site is not expected to be adversely affected by surface rupturing. It will, however, be affected by ground motions from earthquakes during the design life of the residence.

6. No groundwater was observed during our onsite investigation; however, transient groundwater conditions could seasonally develop along the shallow bedrock contact.

Subsurface water is not anticipated to be a development constraint.

August 22, 2024 Project No: 72786-00
Report No: 24-9616
Page No: 3

7. Supplemental evaluation and improvement of surface drainage by a landscape architect or civil engineer is recommended.

8. Structural foundation design can anticipate using conventional foundation elements embedded into competent bedrock. Caissons and grade beams should be anticipated for retaining walls and foundations adjacent to descending slopes.

9. Temporary shoring may be required to construct the portions of the proposed development, or wherever space limitations prevent temporary slope layback.

LIMITATIONS
This report has been prepared in accordance with generally accepted practice in the engineering geologic and soils engineering field. No further warranty is offered or implied. Conclusions and recommendations presented are based on subsurface conditions encountered and are not meant to imply a control of nature. As site geotechnical conditions may alter with time, the recommendations presented herein are considered valid for a time period of one year from the report date. The recommendations are also specific to the current proposed development.

Changes in proposed land use or development may require supplemental investigation or recommendations. Also, independent use of this report in any form cannot be approved unless specific written verification of the applicability of the recommendations is obtained from this firm.

Thank you for this opportunity to be of service. If you have any questions, please contact this office.

Respectfully submitted,

GEOFIRM
Christopher L. Tomlin, E.G. 2066 Jesse Bearfield, P.E. 84335 Senior Engineering Geologist Associate Engineer
CLT/JDB: mr
Attachments: Appendix A – Updated Slope Stability Analyses Appendix B – Referenced Reports
Plate 1 – Geotechnical Plot Plan
Plate 2 – Geotechnical Cross Section A-A’, B-B’ and C-C’ Distribution: Addressee via Email

APPENDIX A

UPDATED SLOPE STABILITY ANALYSES

APPENDIX A

UPDATED SLOPE STABILITY ANALYSES

GENERAL
Engineering stability analyses were performed to assess the minimum Factors of Safety (FS) against future movement of the slope located within the subject property. The analyses were performed with the interpreted geologic conditions.

The “SLIDE2 Version 9.0” slope stability program (developed by RocScience) was utilized for the stability analyses of the slope mass. The computer program utilizes the limit equilibrium theory for the calculation of the minimum Factory of Safety (FS).

SHEAR STRENGTH PARAMETERS
The shear strength parameters utilized in our stability analyses are presented in Table A-1, below. These values were based on local experience in similar soils and engineering judgment, and are considered reasonable and representative of the on-site materials.

TABLE A-1

SUMMARY OF STRENGTH PARAMETERS
Material Type
Bulk
Density
m (pcf)
Bulk
Density
s (pcf)
Cohesion
(psf)
Friction
Angle (deg)
Topanga Formation Bedrock
(Across Bedding)
Topanga Formation Bedrock
(Along Bedding)
Topanga Formation Bedrock
(Shear Beds)
Colluvium (Qcol)
120
120
120
120
125
125
125
120
600
150
150
100
26 20

14.5 26

ANALYSES
Slope stability analyses were performed for the slope located within the property using Cross Section B-B’ and C-C’. The grades proposed to accommodate the house construction were used in analyses. To model the loading imposed by a residential structure, a distributed load of 200 psf was incorporated in the analyses at the proposed location of the structure.

The Factor of Safety (FS) criteria adopted for verifying the adequacy of the stability of the slope for the final design are as follows:

Static Conditions – FS>1.5
Pseudostatic Conditions – FS>1.2
Assumed Lateral Force (Seismic) – 0.15g
The results of the analyses are presented in Table A-2 and Figures A-1 through A-4.

TABLE A-2

SUMMARY OF STABILITY ANALYSES
Item Description FS FS Figure
B-B’
Proposed Condition, Block Search – Static 1.5 --- A-1
Proposed Condition, Block Search – Seismic --- 1.2 A-2
C-C’
Proposed Condition, Block Search – Static 1.6 --- A-3
Proposed Condition, Block Search – Seismic --- 1.2 A-4

1.5 200.00 lbs/ft2
200.00 lbs/ft2
100.00 lbs/ft2
200.00 lbs/ft2 100.00 lbs/ft2
200.00 lbs/ft2
100.00 lbs/ft2
200.00 lbs/ft2
100.00 lbs/ft2
200.00 lbs/ft2
100.00 lbs/ft2

1.5 Ru
Value
Water
Surface
Anisotropic
Function
Phi
(°)
Cohesion
(psf) Strength Type Unit Weight (lbs/ft3) Color Material Name Qcol 120 Mohr-Coulomb 100 26 None 0
Shear 125 Mohr-Coulomb 150 14.5 None 0
Tt None 0 Anisotropic Function Tt 125
120 Mohr-Coulomb 0 36 None 0 Wall Backfill
Method Name Min FS
Spencer 1.5
Safety Factor

0.00.30.50.81.01.31.51.82.02.32.52.83.03.33.53.84.04.34.54.85.05.35.55.86.0+ 520 500 480 460 440 420 400
-40 -20 0 20 40 60 80 100 120 140 160 180
Analysis Description
Drawn By CompanyDate Project No.

CROSS SECTION B-B', PROPOSED CONDITION, BLOCK ANALYSIS, STATIC Project Two Lot Residential Development
1560 Bluebird Canyon Dr, Laguna Beach
SLIDEINTERPRET 9.034
JDB
AUGUST 2024

GEOFIRM
72786-00 Figure No. A-1

1.2 200.00 lbs/ft2
200.00 lbs/ft2
100.00 lbs/ft2
200.00 lbs/ft2 100.00 lbs/ft2
200.00 lbs/ft2
100.00 lbs/ft2
200.00 lbs/ft2
100.00 lbs/ft2
200.00 lbs/ft2
100.00 lbs/ft2

1.2 0.15
Method Name Min FS
Spencer 1.2
Ru
Value
Water
Surface
Anisotropic
Function
Phi
(°)
Cohesion
(psf) Strength Type Unit Weight (lbs/ft3) Color Material Name Safety Factor

0.00.30.50.81.01.31.51.82.02.32.52.83.03.33.53.84.04.34.54.85.05.35.55.86.0+ 560 540 520 500 480 460 440
-40 -20 0 20 40 60 80 100 120 140 160 180
Analysis Description
Drawn By CompanyDateProject
SLIDEINTERPRET 9.034
Two Lot Residential Development
1560 Bluebird Canyon Dr, Laguna Beach

CROSS SECTION B-B', PROPOSED CONDITION, BLOCK ANALYSIS, SEISMIC JDB
AUGUST 2024

GEOFIRM
Project No. 72786-00 Figure No. A-2

1.6 1.9
200.00 lbs/ft2
100.00 lbs/ft2
200.00 lbs/ft2
100.00 lbs/ft2
400.00 lbs/ft2
200.00 lbs/ft2
400.00 lbs/ft2
200.00 lbs/ft2

1.6 1.9
Ru
Value
Water
Surface
Anisotropic
Function
Phi
(°)
Cohesion
(psf)
Strength
Type
Unit
Weight
(lbs/ft3)
Color Material Name
150 14.5 None 0 Mohr- Coulomb Shear 125
Tt None 0 Anisotropic Function Tt 125
0 36 None 0 Mohr- Coulomb 120 Wall Backfill
Method Name Min FS
Spencer 1.6
Safety Factor

0.00.30.50.81.01.31.51.82.02.32.52.83.03.33.53.84.04.34.54.85.05.35.55.86.0+ 520 500 480 460 440 420 400
140 160 180 200 220 240 260 280 300 320 340 360
Analysis Description
Drawn By CompanyDateProject
SLIDEINTERPRET 9.034
Two Lot Residential Development
1560 Bluebird Canyon Dr, Laguna Beach

CROSS SECTION C-C', PROPOSED CONDITION, BLOCK ANALYSIS, STATIC JDB
AUGUST 2024

GEOFIRM
Project No. 72786-00 Figure No. A-3

1.2 200.00 lbs/ft2
100.00 lbs/ft2
200.00 lbs/ft2
100.00 lbs/ft2
400.00 lbs/ft2
200.00 lbs/ft2
400.00 lbs/ft2
200.00 lbs/ft2

1.2 0.15
Method Name Min FS
Spencer 1.2
Ru
Value
Water
Surface
Anisotropic
Function
Phi
(°)
Cohesion
(psf)
Strength
Type
Unit
Weight
(lbs/ft3)
Color Material Name
150 14.5 None 0 Mohr- Coulomb Shear 125
Tt None 0 Anisotropic Function Tt 125
0 36 None 0 Mohr- Coulomb 120 Wall Backfill
Safety Factor

CROSS SECTION C-C'', PROPOSED CONDITION, BLOCK ANALYSIS, SEISMIC JDB
AUGUST 2024

GEOFIRM
Project No. 72786-00 Figure No. A-4
Slide2 Analysis Information
B-B' Proposed Parcel 1
Project Summary
File Name: B-B' Proposed Parcel 1.slmd
Last saved with Slide2 version: 9.034
Project Title: 1560 Bluebird Canyon Dr, Laguna Beach, CA Analysis: Proposed SFR Development - Parcel 1
Author: JDB
Company: Stoney Miller Consultants/Geofirm
Date Created: August 2024
Currently Open Scenarios
Group Name Scenario Name Compute Time
BB Existing
Condition -
Static
Master Scenario
BB Proposed -
Block S Master Scenario
BB Proposed -
Block PS Master Scenario
General Settings
Units of Measurement: Imperial Units
Time Units: days
Permeability Units: feet/second
Data Output: Standard
Failure Direction: Left to Right
Analysis Options
All Open Scenarios
Slices Type: Vertical
Analysis Methods Used
Spencer
Number of slices: 50
Tolerance: 0.005
Maximum number of iterations: 75
Check malpha < 0.2: Yes
Create Interslice boundaries at intersections with
water tables and piezos: Yes
Initial trial value of FS: 1
Steffensen Iteration: Yes
Eliminate vertical segments in non-circular search Yes
Groundwater Analysis
All Open Scenarios
Groundwater Method: Water Surfaces
Pore Fluid Unit Weight [lbs/ft3]: 62.4
Advanced Groundwater Method: None
Random Numbers
All Open Scenarios
Pseudo-random Seed: 10116
Random Number Generation Method: Park and Miller v.3
Surface Options
All Open Scenarios
Search Method: Cuckoo Search
Initial # of Surface Vertices: 8
Maximum Iterations: 500
Number of Nests: 50
Minimum Elevation: Not Defined
Minimum Depth: Not Defined
Minimum Area: Not Defined
Minimum Weight: Not Defined
Convex Surfaces Only: Enabled
Optimize Surfaces: Enabled
Seismic Loading
BB Existing Condition - Static
2/10
B-B' Proposed Parcel 1 Thursday, August 22, 2024
BB Existing Condition - Static
Advanced seismic analysis: No
Staged pseudostatic analysis: No
Seismic Load Coefficient (Horizontal): 0.15
BB Proposed - Block S
Advanced seismic analysis: No
Staged pseudostatic analysis: No
BB Proposed - Block PS
Advanced seismic analysis: No
Staged pseudostatic analysis: No
Seismic Load Coefficient (Horizontal): 0.15
Loading
BB Proposed - Block S
 
Distribution: Constant
Magnitude [psf]: 200
Orientation: Vertical
 
Distribution: Triangular
Magnitude 1 [psf]: 200
Magnitude 2 [psf]: 100
Orientation: Normal to boundary
 
Distribution: Triangular
Magnitude 1 [psf]: 200
Magnitude 2 [psf]: 100
Orientation: Normal to boundary
 
Distribution: Triangular
Magnitude 1 [psf]: 200
Magnitude 2 [psf]: 100
Orientation: Normal to boundary
 
Distribution: Triangular
Magnitude 1 [psf]: 200
Magnitude 2 [psf]: 100
Orientation: Normal to boundary
 
Distribution: Triangular
Magnitude 1 [psf]: 200
Magnitude 2 [psf]: 100
Orientation: Normal to boundary
BB Proposed - Block PS
3/10
B-B' Proposed Parcel 1 Thursday, August 22, 2024
 
Distribution: Constant
Magnitude [psf]: 200
Orientation: Vertical
 
Distribution: Triangular
Magnitude 1 [psf]: 200
Magnitude 2 [psf]: 100
Orientation: Normal to boundary
 
Distribution: Triangular
Magnitude 1 [psf]: 200
Magnitude 2 [psf]: 100
Orientation: Normal to boundary
 
Distribution: Triangular
Magnitude 1 [psf]: 200
Magnitude 2 [psf]: 100
Orientation: Normal to boundary
 
Distribution: Triangular
Magnitude 1 [psf]: 200
Magnitude 2 [psf]: 100
Orientation: Normal to boundary
 
Distribution: Triangular
Magnitude 1 [psf]: 200
Magnitude 2 [psf]: 100
Orientation: Normal to boundary
Materials
Qcol
Color
Strength Type Mohr-Coulomb
Unit Weight 120 lbs/ft3
Cohesion 100 psf
Phi 26 °
Water Surface Assigned per scenario
Ru Value 0
Shear
Color
Strength Type Mohr-Coulomb
Unit Weight 125 lbs/ft3
Cohesion 150 psf
Phi 14.5 °
Water Surface Assigned per scenario
Ru Value 0
4/10
B-B' Proposed Parcel 1 Thursday, August 22, 2024
Tt
Color
Strength Type Anisotropic Function
Unit Weight 125 lbs/ft3
Anisotropic Function Tt
Water Surface Assigned per scenario
Ru Value 0
Wall Backfill
Color
Strength Type Mohr-Coulomb
Unit Weight 120 lbs/ft3
Cohesion 0 psf
Phi 36 °
Water Surface Assigned per scenario
Ru Value 0
Anisotropic Functions
Name: Tt
Angle From Angle To c phi
-90 -13 600 26
-13 0 150 20
0 90 600 26
Materials In Use
Material BB Existing Condition
- Static BB Proposed - Block S BB Proposed - Block PS
Qcol
Shear
Tt
Wall Backfill
Entity Information
BB Existing Condition - Static
Shared Entities
5/10
B-B' Proposed Parcel 1 Thursday, August 22, 2024
Type Coordinates (x,y)
External Boundary
-0.01, 399.887
129.532, 399.887
129.532, 447.014
129.532, 448.299
129.532, 465.972
112.122, 465.972
106.274, 473.627
104.119, 476.449
100.201, 479.543

92.446, 483.09

77.384, 490.031

62.991, 496.428

54.693, 496.851

35.31, 496.851

17.963, 495.896

9.663, 494.827
-0.01, 493.951
-0.01, 478.781
-0.01, 477.783
Material Boundary 54.693, 496.851
106.274, 473.627
Material Boundary -0.01, 478.781
129.532, 448.299
Material Boundary -0.01, 477.783
129.532, 447.014
BB Proposed - Block S
Shared Entities
6/10
B-B' Proposed Parcel 1 Thursday, August 22, 2024
Type Coordinates (x,y)
External Boundary

0.114, 399.861
129.651, 399.861
129.651, 447.029
129.651, 447.928
129.651, 465.943
112.137, 465.943

98.963, 466.106

98.963, 471.935

95.131, 471.935

95.131, 478.929

95.131, 481.965

91.241, 481.965

91.241, 483.926

91.241, 487.925

88.006, 487.925

88.006, 488.946

80.574, 488.946

78.655, 488.946

78.655, 489.61

78.655, 491.915

73.3418, 491.915

66.3931, 491.915

39.035, 491.915

39.035, 497.058

35.115, 497.058

20.133, 496.051

12.762, 495.242

0.114, 494.057

0.114, 478.903

0.114, 477.791
Material Boundary 73.3418, 491.915

78.655, 489.61
Material Boundary 80.574, 488.946

91.241, 483.926
Material Boundary 66.3931, 491.915

95.131, 478.929
Material Boundary 0.114, 478.903
129.651, 447.928
Material Boundary 0.114, 477.791
129.651, 447.029
Scenario-based Entities
7/10
B-B' Proposed Parcel 1 Thursday, August 22, 2024
Type Coordinates (x,y) Master Scenario
Distributed Load

39.035, 491.915

66.3931, 491.915

73.3418, 491.915

78.655, 491.915
Constant
DistributionOrientation:

VerticalMagnitude: 200
lbs/ft2Creates Excess Pore
Pressure: No
Distributed Load

78.655, 488.946

78.655, 489.61

78.655, 491.915
Triangular
DistributionOrientation: Normal
to boundaryMagnitudes 1,2:
200 and 100 lbs/ft2Creates
Excess Pore Pressure: No
Distributed Load 88.006, 487.925

88.006, 488.946
Triangular
DistributionOrientation: Normal
to boundaryMagnitudes 1,2:
200 and 100 lbs/ft2Creates
Excess Pore Pressure: No
Distributed Load

91.241, 481.965

91.241, 483.926

91.241, 487.925
Triangular
DistributionOrientation: Normal
to boundaryMagnitudes 1,2:
200 and 100 lbs/ft2Creates
Excess Pore Pressure: No
Distributed Load

95.131, 471.935

95.131, 478.929

95.131, 481.965
Triangular
DistributionOrientation: Normal
to boundaryMagnitudes 1,2:
200 and 100 lbs/ft2Creates
Excess Pore Pressure: No
Distributed Load 98.963, 466.106

98.963, 471.935
Triangular
DistributionOrientation: Normal
to boundaryMagnitudes 1,2:
200 and 100 lbs/ft2Creates
Excess Pore Pressure: No
BB Proposed - Block PS
Shared Entities
8/10
B-B' Proposed Parcel 1 Thursday, August 22, 2024
Type Coordinates (x,y)
External Boundary

0.114, 399.861
129.651, 399.861
129.651, 447.029
129.651, 447.928
129.651, 465.943
112.137, 465.943

98.963, 466.106

98.963, 471.935

95.131, 471.935

95.131, 478.929

95.131, 481.965

91.241, 481.965

91.241, 483.926

91.241, 487.925

88.006, 487.925

88.006, 488.946

80.574, 488.946

78.655, 488.946

78.655, 489.61

78.655, 491.915

73.3418, 491.915

66.3931, 491.915

39.035, 491.915

39.035, 497.058

35.115, 497.058

20.133, 496.051

12.762, 495.242

0.114, 494.057

0.114, 478.903

0.114, 477.791
Material Boundary 73.3418, 491.915

78.655, 489.61
Material Boundary 80.574, 488.946

91.241, 483.926
Material Boundary 66.3931, 491.915

95.131, 478.929
Material Boundary 0.114, 478.903
129.651, 447.928
Material Boundary 0.114, 477.791
129.651, 447.029
Scenario-based Entities
9/10
B-B' Proposed Parcel 1 Thursday, August 22, 2024
Type Coordinates (x,y) Master Scenario
Distributed Load

39.035, 491.915

66.3931, 491.915

73.3418, 491.915

78.655, 491.915
Constant
DistributionOrientation:

VerticalMagnitude: 200
lbs/ft2Creates Excess Pore
Pressure: No
Distributed Load

78.655, 488.946

78.655, 489.61

78.655, 491.915
Triangular
DistributionOrientation: Normal
to boundaryMagnitudes 1,2:
200 and 100 lbs/ft2Creates
Excess Pore Pressure: No
Distributed Load 88.006, 487.925

88.006, 488.946
Triangular
DistributionOrientation: Normal
to boundaryMagnitudes 1,2:
200 and 100 lbs/ft2Creates
Excess Pore Pressure: No
Distributed Load

91.241, 481.965

91.241, 483.926

91.241, 487.925
Triangular
DistributionOrientation: Normal
to boundaryMagnitudes 1,2:
200 and 100 lbs/ft2Creates
Excess Pore Pressure: No
Distributed Load

95.131, 471.935

95.131, 478.929

95.131, 481.965
Triangular
DistributionOrientation: Normal
to boundaryMagnitudes 1,2:
200 and 100 lbs/ft2Creates
Excess Pore Pressure: No
Distributed Load 98.963, 466.106

98.963, 471.935
Triangular
DistributionOrientation: Normal
to boundaryMagnitudes 1,2:
200 and 100 lbs/ft2Creates
Excess Pore Pressure: No
10/10
B-B' Proposed Parcel 1 Thursday, August 22, 2024
Slide2 Analysis Information
C-C' Proposed Parcel 2
Project Summary
File Name: C-C' Proposed Parcel 2.slmd
Last saved with Slide2 version: 9.034
Project Title: 1560 Bluebird Canyon Dr, Laguna Beach, CA Analysis: Proposed SFR Development - Parcel 2
Author: JDB
Company: Stoney Miller Consultants/Geofrim
Date Created: August 2024
Currently Open Scenarios
Group Name Scenario Name Compute Time
CC Proposed -
Block S Master Scenario
CC Proposed -
Block PS Master Scenario
General Settings
Units of Measurement: Imperial Units
Time Units: days
Permeability Units: feet/second
Data Output: Standard
Failure Direction: Left to Right
Analysis Options
All Open Scenarios
Slices Type: Vertical
Analysis Methods Used
Spencer
Number of slices: 50
Tolerance: 0.005
Maximum number of iterations: 75
Check malpha < 0.2: Yes
Create Interslice boundaries at intersections with
water tables and piezos: Yes
Initial trial value of FS: 1
Steffensen Iteration: Yes
Eliminate vertical segments in non-circular search Yes
Groundwater Analysis
All Open Scenarios
Groundwater Method: Water Surfaces
Pore Fluid Unit Weight [lbs/ft3]: 62.4
Advanced Groundwater Method: None
Random Numbers
All Open Scenarios
Pseudo-random Seed: 10116
Random Number Generation Method: Park and Miller v.3
Surface Options
All Open Scenarios
Search Method: Cuckoo Search
Initial # of Surface Vertices: 8
Maximum Iterations: 500
Number of Nests: 50
Minimum Elevation: Not Defined
Minimum Depth: Not Defined
Minimum Area: Not Defined
Minimum Weight: Not Defined
Convex Surfaces Only: Enabled
Optimize Surfaces: Enabled
Seismic Loading
CC Proposed - Block S
2/8
C-C' Proposed Parcel 2 Thursday, August 22, 2024
CC Proposed - Block S
Advanced seismic analysis: No
Staged pseudostatic analysis: No
CC Proposed - Block PS
Advanced seismic analysis: No
Staged pseudostatic analysis: No
Seismic Load Coefficient (Horizontal): 0.15
Loading
All Open Scenarios
 
Distribution: Constant
Magnitude [psf]: 200
Orientation: Vertical
 
Distribution: Constant
Magnitude [psf]: 100
Orientation: Vertical
 
Distribution: Triangular
Magnitude 1 [psf]: 200
Magnitude 2 [psf]: 100
Orientation: Normal to boundary
 
Distribution: Triangular
Magnitude 1 [psf]: 400
Magnitude 2 [psf]: 200
Orientation: Normal to boundary
 
Distribution: Triangular
Magnitude 1 [psf]: 400
Magnitude 2 [psf]: 200
Orientation: Normal to boundary
Materials
Shear
Color
Strength Type Mohr-Coulomb
Unit Weight 125 lbs/ft3
Cohesion 150 psf
Phi 14.5 °
Water Surface Assigned per scenario
Ru Value 0
3/8
C-C' Proposed Parcel 2 Thursday, August 22, 2024
Tt
Color
Strength Type Anisotropic Function
Unit Weight 125 lbs/ft3
Anisotropic Function Tt
Water Surface Assigned per scenario
Ru Value 0
Wall Backfill
Color
Strength Type Mohr-Coulomb
Unit Weight 120 lbs/ft3
Cohesion 0 psf
Phi 36 °
Water Surface Assigned per scenario
Ru Value 0
Anisotropic Functions
Name: Tt
Angle From Angle To c phi
-90 -13 600 26
-13 0 150 20
0 90 600 26
Materials In Use
Material CC Proposed - Block S CC Proposed - Block PS
Shear
Tt
Wall Backfill
Entity Information
CC Proposed - Block S
Shared Entities
4/8
C-C' Proposed Parcel 2 Thursday, August 22, 2024
Type Coordinates (x,y)
External Boundary
312.524, 399.901
312.524, 444.873
312.524, 446.206
312.524, 473.372
297.044, 473.149
291.836, 476.361
276.208, 476.361
276.208, 487.999
276.208, 491.752
266.654, 491.752
252.51, 491.752
252.51, 497.484
252.51, 500.669
252.51, 504.988
241.052, 504.988
231.11, 504.988
202.476, 504.988
202.476, 512.02
188.946, 512.02
188.946, 508.787
183.969, 508.494
178.103, 506.727
173.401, 504.722
173.406, 478.475
173.406, 477.84
173.42, 399.901
Material Boundary 231.11, 504.988
252.51, 497.484
Material Boundary 266.654, 491.752
276.208, 487.999
Material Boundary 173.406, 478.475
312.524, 446.206
Material Boundary 173.406, 477.84
312.524, 444.873
Material Boundary 241.052, 504.988
252.51, 500.669
Scenario-based Entities
5/8
C-C' Proposed Parcel 2 Thursday, August 22, 2024
Type Coordinates (x,y) Master Scenario
Distributed Load
202.476, 504.988
231.11, 504.988
241.052, 504.988
252.51, 504.988
Constant
DistributionOrientation:

VerticalMagnitude: 200
lbs/ft2Creates Excess Pore
Pressure: No
Distributed Load
252.51, 491.752
266.654, 491.752
276.208, 491.752
Constant
DistributionOrientation:

VerticalMagnitude: 100
lbs/ft2Creates Excess Pore
Pressure: No
Distributed Load 202.476, 504.988
202.476, 512.02
Triangular
DistributionOrientation: Normal
to boundaryMagnitudes 1,2:
200 and 100 lbs/ft2Creates
Excess Pore Pressure: No
Distributed Load
252.51, 491.752
252.51, 497.484
252.51, 500.669
252.51, 504.988
Triangular
DistributionOrientation: Normal
to boundaryMagnitudes 1,2:
400 and 200 lbs/ft2Creates
Excess Pore Pressure: No
Distributed Load
276.208, 476.361
276.208, 487.999
276.208, 491.752
Triangular
DistributionOrientation: Normal
to boundaryMagnitudes 1,2:
400 and 200 lbs/ft2Creates
Excess Pore Pressure: No
CC Proposed - Block PS
Shared Entities
6/8
C-C' Proposed Parcel 2 Thursday, August 22, 2024
Type Coordinates (x,y)
External Boundary
312.524, 399.901
312.524, 444.873
312.524, 446.206
312.524, 473.372
297.044, 473.149
291.836, 476.361
276.208, 476.361
276.208, 487.999
276.208, 491.752
266.654, 491.752
252.51, 491.752
252.51, 497.484
252.51, 500.669
252.51, 504.988
241.052, 504.988
231.11, 504.988
202.476, 504.988
202.476, 512.02
188.946, 512.02
188.946, 508.787
183.969, 508.494
178.103, 506.727
173.401, 504.722
173.406, 478.475
173.406, 477.84
173.42, 399.901
Material Boundary 231.11, 504.988
252.51, 497.484
Material Boundary 266.654, 491.752
276.208, 487.999
Material Boundary 173.406, 478.475
312.524, 446.206
Material Boundary 173.406, 477.84
312.524, 444.873
Material Boundary 241.052, 504.988
252.51, 500.669
Scenario-based Entities
7/8
C-C' Proposed Parcel 2 Thursday, August 22, 2024
Type Coordinates (x,y) Master Scenario
Distributed Load
202.476, 504.988
231.11, 504.988
241.052, 504.988
252.51, 504.988
Constant
DistributionOrientation:

VerticalMagnitude: 200
lbs/ft2Creates Excess Pore
Pressure: No
Distributed Load
252.51, 491.752
266.654, 491.752
276.208, 491.752
Constant
DistributionOrientation:

APPENDIX B

REFERENCED REPORTS
APPENDIX B-1
REFERENCED REPORT NO. 1
GEOFIRM, 2019, “PRELIMINARY GEOTECHNICAL INVESTIGATION FOR NEW SINGLE-FAMILY RESIDENCE, 1560 BLUEBIRD CANYON ROAD, APN# 644-321-31, PARCEL 4, BLOCK F, LAGUNA BEACH, CALIFORNIA,” PROJECT NO. 72415-00, REPORT NO. 19-8482, DATED FEBRUARY 5.

February 5, 2019
Michael and Rosalie Arias Project No. 72415-00
4471 Dean Martin Drive, Unit 300 Report No. 19-8482
Las Vegas, Nevada 89103
Subject: Preliminary Geotechnical Investigation for
New Single-Family Residence
1560 Bluebird Canyon Road
APN# 644-321-31, Parcel 4, Block F
Laguna Beach, California

INTRODUCTION
This report presents the results and recommendations of a preliminary investigation undertaken to evaluate onsite and certain regional geotechnical conditions pertinent to the design and construction of a new single-family residence at the subject site. Analysis for this investigation is based upon the conceptual drawings prepared by your designer and our previous work related to a proposed development of the site and adjoining lots (Appendix A, References 6 through 13).

This report is considered preliminary as it precedes the development of structural foundation plans, the formulation of which is partially dependent upon the findings presented below.

Scope of Investigation
The investigation included the following:

1. Analysis of our previous work, pertinent reports, maps, aerial photographs, and published literature pertaining to the site and nearby areas, as well as project plans, in order to relate geotechnical conditions to proposed construction.

2. Field reconnaissance and the excavation and geologic logging of two additional test pits to evaluate the character and geometrical distribution of soil materials within the proposed construction areas.

3. Analyses of data and the preparation of this geotechnical report presenting conclusions and recommendations for foundation design in accordance with the 2016 California Building Code, and for use by your design professionals, contractors, and submittal to the City of Laguna Beach.

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Accompanying Illustrations and Appendices
Figure 1 - USGS Geologic Location Map
Figure 2 - CDMG Seismic Hazards Map
Figure 3 - Typical Retaining Wall Detail
Figure 4 - Typical Subdrain for Caisson Retaining Wall
Figure 5 - Typical Slab Subdrain Detail
Figure 6 - Geotechnical Cross Section A-A’
Figure 7 - Geotechnical Cross Section B-B’
Appendix A - References
Appendix B - Test Pit Logs
Appendix C - Previous Boring Logs and Lab Test Results
Appendix D - Slope Stability Analysis
Appendix E - Standard Grading Specifications
Appendix F - Utility Trench Backfill Guidelines
Appendix G - Maintenance of Hillside Home Sites
Plate1 - Regional Geologic Map and Geotechnical Cross Section A-A’ Plate2 - Geotechnical Plot Plan
Site Description
The irregularly shaped property fronts 221± feet along Bluebird Canyon Road and extends northerly between 120 and 145± feet to the rear boundary. The site is generally comprised of a former ridgetop that had been roughly graded to create a partially flattened pad for possible historic development. Based on a topographic survey prepared by Toal Engineering, Inc., and our onsite observations, the front property boundary is located along the top of the roadcut portion of the former natural slope, 12± feet inward and roughly parallel to the edge of Bluebird Canyon Road. The roadcut slope, which ascends 12± feet from the pavement edge at ratios between ¾:1 and 1:1 (horizontal: vertical), transitions to the natural slope that continues to ascend between 15 and 30± feet at an average ratio near 2:1. The aforementioned pad, which slopes gently downward to the west and generally borders the rear property boundary, is roughly 35 to 40± feet wide and 205± feet long. Maximum elevation differential across the property is 48± feet.

The site and properties adjoining to the north and east are vacant, and the property to the west is developed with a wood-frame single-family residence. Based on our previous onsite experience for the previous owner, the subject property is one of four lots that were variably combined as part of a proposed developments that never materialize.

Proposed Development
Based on conceptual drawings submitted to our office, proposed site development generally includes the construction of a new two-story residence plus buried garage that will daylight at or slightly above street level. The residence is generally proposed atop, and partially terraced into February 5, 2019 Project No: 72415-00
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the pad portion of the lot with the southerly facing elements spanning onto the slope descending to Bluebird Canyon Drive. Proposed exterior improvements, such as a pool/spa, hardscaping and landscaping are also envisioned.

The new structure and significant exterior improvements are anticipated to be supported on foundation elements constructed in bedrock. Exterior hardscape may be locally supported on new engineered fill. On or near-slope foundations supporting the southerly edge of the pool and residence may be supported on caissons embedded below a structural setback plane as recommended herein.

It should be noted that construction of the proposed buried garage will require lateral excavation into bedrock by a specialty design-build engineering contractor.

GEOTECHNICAL CONDITIONS
Geologic Setting
The property and vicinity are located on the seaward slope of the San Joaquin Hills which are underlain in the site vicinity by Miocene Age sedimentary bedrock strata. The San Joaquin Hills were formed by uplift due to regional tectonic forces acting on this region of Southern California during the late Pliocene and Pleistocene. Numerous canyons, including Rim Rock and Bluebird Canyons, have been deeply and steeply incised into the San Joaquin Hills by natural erosional processes during this uplift. The site is located on a generally westerly trending gently inclined ridgeline which separates Rim Rock and Bluebird Canyons. The site location is depicted on the Geologic Location Map, Figure 1.

Earth Materials
The site is underlain by bedrock strata assigned on the basis of regional mapping to the Mioceneage Topanga Formation. Bedrock is well exposed onsite in the northerly and southerly road cuts and was also exposed in exploratory excavations. It consists of light greenish gray to gray and locally tan, silty to clayey, micaceous, fine to medium grained sandstone with some interbedded sandy siltstone and minor lenses of coarser grained pebbly, friable sandstone. Where weathered, the sandstone is poorly indurated; where fresh, it is well indurated and hard. The sandstone is generally massive and bedding surfaces are generally poorly developed, irregular, and typically exhibit sand on sand contacts. No shale or fissile siltstone was observed during surface mapping or subsurface exploration; however, shale is a common associated rock type nearby and its presence at depth is not precluded. Firm bedrock strata are suitable for support of fill and proposed structural improvements.

The ridge crest is mantled by residual soil which consists of gray-brown, silty sand and sandy silt. It is generally soft/loose and highly porous. The thickness of the residual soil determined on the basis of shallow excavations is 1 to 3 feet thick. The residual soil is unsuitable for supporting fill or structural improvements without recompaction.

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Soils derived from the sandstone bedrock have a low expansion potential and negligible soluble sulfate content. Electrical resistivity test indicates a moderate degree of corrosivity to buried metals.

Geologic Structure
The bedrock strata are folded to strike northeasterly and dip homoclinally 20 to 50 degrees southerly. Geologic reconnaissance of the cut slope above Bluebird Canyon Drive indicates the strata become more steeply inclined, near 55+ degrees, in this area. A steepening of dip angles near the easterly property margin is also reflected in data obtained at depth from subsurface exploration within close proximity to the site. The structural orientation is consistent with the regional trend depicted on published geologic maps (CDMG, 1976). In general, however, the strata dips subparallel to the overall slope descending into the canyon bottom and is thus considered a “dip” slope. Dip slopes are naturally prone to landsliding or other instability in cases where erosion at the toe, or canyon bottom, exposes strata and removes support. Please the Slope Stability Section below for more information.

Moderate to high angle joints are also locally common in the bedrock. Some low angle shearing, inferred to be of tectonic origin, was also observed in one exploratory excavation. No faults were observed in the field and none are depicted on geologic maps as transecting the site.

Surface Drainage
Existing surface drainage within the proposed construction areas is generally uncontrolled.

Evaluation and improvement of surface drainage by a landscape architect or civil engineer is recommended.

Groundwater
Groundwater was not encountered during our previous or recent subsurface explorations and is not anticipated to be a construction nuisance or design constraint. Perched groundwater may occur seasonally along the relatively shallow bedrock contact and may promote localized sloughing or erosion of the overlying materials. Based on the results of study, however, such sloughing is not anticipated to affect the existing or proposed site improvements designed in accordance with our recommendations.

Slope Stability
The general, slope instability may manifest as either the shallow movement of the upper few feet of earth materials in the form of creep, slump or debris flow, or deep movement in the form of catastrophic landsliding or deep creep. Both forms of slope movement are affected by slope gradient and the composition and character of the earth materials comprising the slope. The potential for slope instability increases with slope steepness, the presence of adverse groundwater conditions, and during periods of seismic shaking.

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With regard to shallow instability, the over-steepened roadcut slope descending from the southerly edge of the pad area is subject to shallow instability in the form of ongoing intermittent rock spalling and shedding of debris onto the road below. Such instability is not anticipated to affect the proposed improvements designed in accordance with the recommendations presented herein.

With regard to deep, or gross slope instability, the subject site is located upslope of an ancient landslide mapped by the USGS. Previous investigations by this office and other consultants have observed the presence of this landslide, which appears to have failed to the canyon bottom along a weak bedding planes oriented in the downslope, southerly direction. Previous analyses (Reference 11) indicate the subject site is not anticipated to be affected by gross instability associated with this ancient feature.

As the bedrock strata below the site dips in the downslope direction and daylights in the roadcut along the southerly edge of the pad area, engineering analyses have been performed to evaluate local stability, including consideration of seismic loading. These analyses include the geologic structure under the site as inferred from boring data from previous investigation. The analyses were performed on the geometry depicted on Figure 6, using SLIDE 2018 computer program.

Strength parameters utilized for the analyses were as determined from laboratory testing of onsite materials and from Geofirm’s 2005 investigation of the Bluebird Canyon landslide.

Strength parameters utilized are considered reasonable and within an appropriate range for the materials encountered.

The results indicate the strata exposed in the roadcut are potentially unstable in their present configuration. A structural setback is therefore required for near slope construction in order to provide foundation support below the zone of potential instability, as depicted on Figure 6, Cross Section A-A’.

Seismic Considerations
Published Studies
One of the principals of seismic analyses and prediction is the premise that earthquakes are more likely to occur on geologically younger faults, and less likely to occur on older faults. For many years studies have described faults with Holocene movement (within the last 11,000 years) as ”Active”, and faults with documented Pleistocene movement (within the last 1.6 million years) and with undetermined Holocene movement as ”Potentially Active”. Informally, many studies have described faults documented to have no Holocene movement as ”Inactive”. Recent geologic and seismic publications are attempting to clarify the nomenclature describing faults to more accurately represent the potential affects from earthquakes.

Reports by the California Division of Mines and Geology indicate faults with documented Holocene or Historic (within the last 200 years) movement should be considered Active.

However, Potentially Active faults are more appropriately characterized in terms of the last period of documented movement. The Fault Activity Map of California (Jennings, C.W.; 1994) February 5, 2019 Project No: 72415-00
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defines four categories for onshore Potentially Active faults. The categories are associated with the time of the last displacement evidenced on a given fault and are summarized in Table 1.

Table 1, Definitions of Fault Activity in California
It is important to note these categories embrace Pre-Holocene faults as Potentially Active, and provide no methodology to designate a given fault as ”Inactive”. Although the likelihood of an earthquake or movement to occur on a given fault significantly decreases with inactivity over geologic time, the potential for such events to occur on any fault cannot be eliminated within the current level of understanding.

Local and Regional Faults
The closest published active fault to the site is the offshore extension of the Newport-Inglewood Fault Zone, approximately 2.9 miles west, (Blake, T.F., 2000, CGS/2004). Other active faults in the vicinity of the site include the San Joaquin Hills, approximately 4.0 miles away, Palos Verdes Fault, approximately 16.3 miles to the northwest, the Coronado Bank Fault, approximately 21.1 miles to the south, and the San Andreas Fault, approximately 52.4 miles to the northeast.

The California Geological Survey updated the Fault Parameters and Earthquake Catalog for the probabilistic Seismic Hazards Maps, (Cao, T., et al., 2002). This update included the addition of the “San Joaquin Hills” blind thrust fault, modeled to exist from Newport Beach to Dana Point, and ramping up inland to the Irvine area, and essentially underlying the site. Earthquakes of significant magnitude (M6.6) are presently postulated for this structure, and with the fault’s location beneath the site, it is calculated as the most significant seismic source to affect the property.

Historic Ground Motion Analyses
Utilizing attenuation relationships (Bozorgnia, et al.; 1999, uncorrected/ Pleist. Soil), one can estimate the ground motion history of the site. The study indicates the maximum site acceleration from 1800 to 2004 was approximately 0.20g and occurred during the magnitude 6.3 Long Beach Earthquake 11.9 miles from the site on March 11, 1933.

It is noted that the estimation of historic peak ground acceleration presented above is provided for the interest of the client and is required by local (City or County) review agencies. The value derived is not directly utilized in structural design of residential structures. Seismic parameters Activity Category Recency of Movement
Active Historic Within the last 200 years
Holocene Within the last 11,000 years
Potentially
Active
Late Quaternary Within the last 700,000 years
Quaternary Within the last 1.6 million years
Late Cenozoic Possibly within the last 1.6 million years Pre-Quaternary Before the last 1.6 million years
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for use by the structural engineer in accordance with 2016 California Building Code in design of the proposed structure(s) are presented in the recommendations portion of this report.

Site Classification for Seismic Design
For the purposes of determining seismic design parameters provided in the Recommendations portion of this report for use by the structural engineer, the upper 100 feet of soil underlying the subject site has been classified in accordance with Section 1613.3.2 of the 2016 CBC. Given the results of our onsite and nearby field investigations, which indicates the existing and new foundations will be constructed in intact bedrock of the San Onofre Formation, the site classifies as B.

Bedrock classification as specified above is based on the procedures outlined in Section 1613.5.5 of the 2016 CBC, which states that shear-wave velocities may be estimated by the Geotechnical Engineer or Engineering Geologist. As such, the San Onofre formation bedrock underlying the site is estimated to have shear wave velocities between 2,500 ft/sec and 5,000 ft/sec.

Secondary Seismic Hazards
Review of the Seismic Hazards Zones Map (CDMG, 1998) for the Laguna Beach Quadrangle, Figure 2, indicates this lot is located within a “zone of required investigation” for earthquake induced landsliding. Previous analyses reported by this office indicate the site is anticipated to be adequately stable under seismic conditions – see Slope Stability section above for more information.

Other secondary seismic hazards can include deep rupture, shallow ground cracking, and settlement. With the absence of active faulting onsite, the potential for deep fault rupture is not present. The potential for shallow ground cracking to occur during an earthquake is a possibility at any site, but does not pose a significant hazard to site development. Given the site is underlain by competent natural deposits, the potential for seismically induced settlement to occur is considered remote.

CONCLUSIONS

1. The construction of the proposed residential development at the subject site is considered geotechnically feasible provided the recommendations herein are integrated into design, construction, and long-term maintenance. Proposed construction should not affect or be affected by adjacent properties provided appropriate construction methods and care are utilized by the contractor.

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6. No groundwater was observed during our onsite investigation; however, transient groundwater conditions could seasonally develop along the shallow bedrock contact.

Subsurface water is not anticipated to be a development constraint.

7. Supplemental evaluation and improvement of surface drainage by a landscape architect or civil engineer is recommended.

9. Temporary shoring may be required to construct the lower level of the proposed residence, or wherever space limitations prevent temporary slope layback.

10. The design and construction of the proposed buried garage will require additional engineering and logistical evaluation, which is deferred to a design-build specialist.

Supplemental geotechnical investigation and analyses may be required to help develop finalized plans.

RECOMMENDATIONS
Site Preparation and Grading

1. General
Grading should be performed in accordance with the Standard Grading Specifications in Appendix E. Grading will generally include removal and export of existing earth materials to construct new pad grades. Minor cut/fill grading is anticipated to construct the exterior terraced walkways and retaining wall. Remedial grading, if warranted to remove and replace unsuitable soils, may be recommended by the geologist during February 5, 2019 Project No: 72415-00
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construction. Over-excavation and recompaction should be observed and approved in writing by a representative of this firm.

2. Removal of Existing Improvements
Existing vegetation and/or construction and irrigation debris should be removed and disposed of offsite.

3. Compaction Standard
Onsite soil materials are anticipated to be suitable for re-use as compacted fill. Such materials should be placed at or above optimum moisture content and compacted under the observation and testing of the soil engineer to at least 90 percent of the maximum dry density as determined by ASTM D 1557. Compacted fills should not, in general, contain rock over 6 inches in largest dimension.

4. Temporary Construction Slopes
The grading of temporary construction slopes can create two potentially adverse conditions affecting the property and onsite personnel. These conditions include slope instability and safety. As the geotechnical consultant, we are limited to recommending temporary slope geometries considered stable such that any slope failures, should they occur, are not anticipated to adversely impact adjoining properties or structures. While our recommendations may often comply with safety guidelines concerning temporary slopes, our recommendations are not intended to create “safe” working conditions as defined by Cal/OSHA. The safety of onsite personnel per Cal/OSHA is the responsibility of the general contractor as described below.

A. Protection of Property
In order to reduce the potential risk to adjoining properties/structures from slope failures, temporary construction slopes may be excavated vertically to 5 feet, with higher slopes laid back at 1:1 (horizontal: vertical). Shoring should be constructed where space or grading limitations preclude temporary slope layback or in locations where workers may be in close proximity to vertical cuts.

B. Worker Safety
The safety of onsite personnel affected by the performance of temporary construction slopes is the responsibility of the general contractor who is recommended to implement the safety practices as defined in Section 1541, Subchapter 4, of Cal/OSHA T8 Regulations (2006).

The geometry of permissible temporary cuts varies based on soil type and may differ significantly from the geometry presented in Section A above. The earth materials February 5, 2019 Project No: 72415-00
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exposed in temporary excavations should be evaluated and classified by the contractor during construction.

5. Excavation Conditions
It is anticipated that all proposed grading can be accomplished with conventional grading equipment. Local well cemented zones in the bedrock may require heavy ripping.

Structural Design of Foundations

1. General
It is anticipated that new foundation elements for the residence addition will bear in competent bedrock. Conventional foundations should be designed in accordance with the 2016 California Building Code.

Our recommendations are considered to be generally consistent with the standards of practice. They are based on both analytical methods and empirical methods derived from experience with similar geotechnical conditions. These recommendations are considered the minimum necessary for the likely soil conditions and are not intended to supersede the design of the structural engineer or criteria of governing agencies.

2. Conventional Foundations
Footings may be designed for an allowable bearing value of 4,000 pounds per square foot for bedrock, with a minimum width of 15 inches and a minimum embedment into underlying soil of 18 inches. This value may also be increased by one-third for short-term conditions such as wind or seismic loading. Footings in bedrock are not anticipated to experience any significant settlement.

Lateral loads may be resisted by passive pressure forces and by friction acting on the bottom of footings. The allowable passive pressure forces may be computed using an equivalent fluid density of 400 pounds per cubic foot, not to exceed 4,000 pounds per square foot for bedrock. A coefficient of friction of 0.35 may be used in computing the fictional resistance.

3. Caissons
Twenty-four-inch diameter caissons with minimum 10 feet embedment into competent bedrock below the setback plane may be designed for a dead plus live load end bearing value of 8,000 pounds per square foot and skin friction of 500 pounds per square foot for competent bedrock below the setback plane only. These values may be increased by onethird for wind and seismic forces. Lateral resistance may be computed utilizing 400 pounds per cubic foot equivalent fluid pressure for bedrock below the setback zone, acting on a tributary area of twice the caisson diameter for competent bedrock. The twenty-four-inch February 5, 2019 Project No: 72415-00
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diameter is required in order to assure proper cleanout by the contractor, and to allow visual inspection and cleanout confirmation by the engineering geologist.

Caissons should be designed to resist full tributary lateral pressure loading of 45 pounds per cubic foot equivalent fluid pressure to the depth of the setback plane. Passive resistance may be taken only below the setback plane. Final caisson design and locations should be accomplished by joint consultation between the geotechnical engineer and the structural engineer.

4. Slab Subdrain or Waterproofing
Percolating irrigation and meteoric water may perch on top of less pervious layers at shallow depth beneath the site. Groundwater effects on the slab can be reduced by intercepting the groundwater with a subdrain constructed beneath the slab. If utilized, the subdrain system should be constructed in accordance with the detail presented on Figure 5, and the information provided below.

The slab subdrain system should consist of 4-inch diameter perforated pipe graded to flow at one percent in the base of 12-inch deep trench around the perimeter of the slab and spaced in a 10 feet grid pattern within the interior. The trench should be lined with non-woven filter fabric and backfilled with ½ or ¾ inch rock. The slab subdrain piping system should be outletted per the Civil Engineer.

As an alternative to the suggested slab subdrain system, the lower slab may be waterproofed. Slab waterproofing design and details should be provided by the project architect or waterproofing consultant.

Footing Reinforcements
To resist adverse effects of tension cracking due to seismic shaking effects, a minimum of two No. 5 bars should be placed at the top and bottom of continuous footings.

Structural Design of Retaining Walls

1. Lateral Loads
Active pressure forces acting on walls retaining level or 2:1 (horizontal: vertical) sloping backfill may be designed using an equivalent fluid density of 35 or 50 pounds per cubic foot, respectively, if backfilled with geotechnically approved, granular non-cohesive soils and free to rotate during backfilling (refer to Figure 3 for backcut and backfill geometry).

Possible topographic or structural surcharges should be addressed by the structural engineer. Restrained walls should be designed for 60 pounds per cubic foot equivalent fluid pressure. Limited wall deformations normally occur and should be considered in design of finished surfaces.

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A dynamic lateral force should be applied to retaining walls 6 feet or more in height. The site is classified as being in Seismic Design Category D (Type II occupancy, SDs > 0.5g, SD1 > 0.2g) with a Peak Ground Acceleration of 0.641 per ASCE 7-10. Seismic design of retaining walls may be based on the Mononobe-Okabe method, as updated by Atik and Sitar (2010), using an additional dynamic load of 24 pounds per cubic foot equivalent fluid pressure, acting at 1/3 H above the base of the wall. Final design requirements should be determined by the structural engineer.

2. Subdrains
The drainage scheme depicted on Figures 3 or 4, or an approved alternative, should be used to achieve control of seepage forces behind retaining walls. The details of subdrain systems are deferred to the wall designer, builder or waterproofing consultant. The subdrain is not a substitute for waterproofing.

Slab-On-Grade Construction
Slab-on-grade should be designed by the structural engineer in accordance with the 2016 California Building Code. The minimum recommended slab thickness is 5 inches, with No. 4 bars at a spacing of 16 inches, placed in both directions.

Slabs should be underlain by 4 inches of 1/2- and 3/4-inch open-graded gravel. Slab underlayment is deferred to the project architect; however, in accordance with the American Concrete Institute, we suggest that slabs be underlain by a 15-mil thick vapor retarder/barrier (Stego Wrap or equivalent) placed over the gravel in accordance with the requirements of ASTM E:1745 and E:1643.

Slope Setback
The bottom of foundations designed in accordance with the recommendations presented herein should be embedded a minimum of 10 feet below the setback plane. Foundations supporting lightly-loaded hardscape/landscape elements may be set back a minimum of 5 feet from the nearest slope face.

Hardscape Design and Construction
Hardscape improvements may utilize conventional foundations embedded in bedrock designed in accordance with the foundation recommendations presented below.

Concrete flatwork should be divided into as nearly square panels as possible. Joints should be provided at maximum 6 feet intervals to give articulation to the concrete panels. Landscaping and planters adjacent to concrete flatwork should be designed in such a manner as to direct drainage away from concrete areas to approved outlets. Planters located adjacent to principal foundation elements should be sealed and drained.

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Flatwork elements should be a minimum 5 inches thick (actual) and reinforced with No. 4 bars 16 inches on center both ways.

Concrete
Previous laboratory test results indicate on-site soils have negligible soluble sulfate content. It is recommended that a concrete expert be retained to design an appropriate concrete mix. In lieu of retaining a concrete expert, 2016 California Building Code, Section 1904.1 should be utilized, which refers to ACI 318, Table 4.3.1.

Seismic Structural Design
Based on the geotechnical data and site parameters, the following is provided by the USGS (ASCE 7-10) to satisfy the 2016 CBC design criteria:

Table 2, Site and Seismic Design Criteria
For 2016 CBC
Design
Parameters
Recommended
Values
Site Class
Site Longitude (degrees)
Site Latitude (degrees)
Ss (g) B
S1 (g) B
SMs (g) B
SM1 (g) B
SDs (g) B
SD1 (g) B
Fa
Fv
Seismic Design Category
PGAm (g)
B
-117.7617

33.5397

1.575

0.577

1.575

0.577

1.05 0.385

1.0 1.0
D

0.641
Finished Grade and Surface Drainage
Finished grades should be designed and constructed so that no water ponds in the vicinity of footings or the rear slope. Drainage design in accordance with the California Building Code, Section 1804.4 is recommended. Roofs should be guttered and discharge conducted away from the house in a nonerosive manner as specified by the project civil engineer or landscape architect. Proper interception and disposal of all onsite surface discharge is presumed to be a matter of civil engineering or landscape architectural design.

February 5, 2019 Project No: 72415-00
Report No: 19-8482
Page No: 14
The site is geotechnically unsuitable for the local discharge or infiltration of onsite storm water due to the potential to promote slope instability in the shallow slopewash and fill over the bedrock. Onsite discharge of storm water is not recommended.

Foundation Plan Review
In order to review the plans for conformance with the recommendations of this report and as a condition of the issue of this report, the undersigned should review final foundation plans and specifications prior to submission of such to the building official for issuance of permits. Such review is to be performed only for the limited purpose of checking for conformance with the design concept and the information provided herein. This review shall not include review of the accuracy or completeness of details, such as quantities, dimensions, weights or gauges, fabrication processes, construction means or methods, coordination of the work with other trades or construction safety precautions, all of which are the sole responsibility of the Contractor.

Geofirm’s review shall be conducted with reasonable promptness while allowing sufficient time in our judgment to permit adequate review. Review of a specific item shall not indicate that Geofirm has reviewed the entire system of which the item is a component. Geofirm shall not be responsible for any deviation from the Construction Documents not brought to our attention in writing by the Contractor. Geofirm shall not be required to review partial submissions or those for which submissions of correlated items have not been received.

Observation and Testing
The 2016 California Building Code, Section 1705.6 requires geotechnical observation and testing during construction to verify proper removal of unsuitable materials, that foundation excavations are clean and founded in competent material, to test for proper moisture content and proper degree of compaction of fill, to test and observe placement of wall and trench backfill materials, and to confirm design assumptions. It is noted that the CBC requires continuous verification and testing during placement of fill, and pier/caisson drilling.

A Geofirm representative shall visit the site at intervals appropriate to the stage of construction, as notified by the Contractor, in order to observe the progress and quality of the work completed by the Contractor. Such visits and observation are not intended to be an exhaustive check or a detailed inspection of the Contractor’s work but rather are to allow Geofirm, as an experienced professional, to become generally familiar with the work in progress and to determine, in general, if the work is proceeding in accordance with the recommendations of this report.

Geofirm shall not supervise, direct, or have control over the Contractor’s work nor have any responsibility for the construction means, methods, techniques, sequences, or procedures selected by the Contractor nor the Contractor’s safety precautions or programs in connection with the work. These rights and responsibilities are solely those of the Contractor.

Geofirm shall not be responsible for any acts or omission of the Contractor, subcontractor, any entity performing any portion of the work, or any agents or employees of any of them. Geofirm does not guarantee the performance of the Contractor and shall not be responsible for the February 5, 2019 Project No: 72415-00
Report No: 19-8482
Page No: 15
Contractor’s failure to perform its work in accordance with the Contractor documents or any applicable law, codes, rules or regulations.

These observations are beyond the scope of this investigation and budget and are conducted on a time and material basis. The responsibility for timely notification of the start of construction and ongoing geotechnically involved phases of construction is that of the owner and his contractor.

Typically, at least 24 hours’ notice is required.

Jobsite Safety
Neither the professional activities of Geofirm, nor the presence of Geofirm’s employees and subconsultants at a construction/project site, shall relieve the General Contractor of its obligations, duties and responsibilities including, but not limited to, construction means, methods, sequence, techniques or procedures necessary for performing, superintending and coordination the work in accordance with the contract documents and any health or safety precautions required by any regulatory agencies. Geofirm and its personnel have no authority to exercise any control over any construction contractor or its employees in connection with their work or any health or safety programs or procedures. The General Contractor shall be solely responsible for jobsite safety.

LIMITATIONS
This investigation has been conducted in accordance with generally accepted practice in the engineering geologic and soils engineering field. No further warranty is offered or implied.

Conclusions and recommendations presented are based on subsurface conditions encountered, and are not meant to imply a control of nature. As site geotechnical conditions may alter with time, the recommendations presented herein are considered valid for a time period of one year from the report date. The recommendations are also specific to the current proposed development. Changes in proposed land use or development may require supplemental investigation or recommendations. Also, independent use of this report in any form cannot be approved unless specific written verification of the applicability of the recommendations is obtained from this firm.

February 5, 2019 Project No: 72415-00
Report No: 19-8482
Page No: 16
Thank you for this opportunity to be of service. If you have any questions, please contact this office.

Respectfully submitted,

GEOFIRM
Erik Hilde, P.G. 2303 Zi Wang, R.C.E. 80199
Associate Engineering Geologist Senior Geotechnical Engineer Registration Expires 10-31-19 Registration Expires 9-30-20 EH/ZW: np
Distribution: Addressee Via Email
JOB NO.: DATE: FIGURE:

USGS Geologic Location Map, Santa Ana 30' x 60' Quadrangle 72415-00 January 2019 1
SITE
1560 Bluebird Canyon Drive
Laguna Beach
JOB NO.: DATE: FIGURE:

CDMG Seismic Hazards Map, San Juan Capistrano and Laguna Beach Quadrangles 72415-00 January 2019 2
SITE
1560 Bluebird Canyon Drive
Laguna Beach
Onsite Native Soil Cap for
exterior ; (1.5'-2.0' thick)
Select Noncohesive
Granular Backfill
(SE > 30)
Retaining Wall Footing
Geotextile Filter Fabric
4" Perforated Plastic Collector Pipe
(Below Adjacent Finish Grade)
Single-sized 1/2"- 3/4" Drain Rock
(1 cubic foot per lineal foot)
Limit of Wall Excavation -
See Report for
Recommended Geometery
Typical
Retaining
Wall
Notes: This system consists of a geotextile fabric-wrapped gravel envelope. Collection is with a 4-inch diameter perforated plastic pipe embedded in the gravel envelope and tied to a 4-inch 12"-18"
Finish Grade - Design May
Vary per Architect or Civil
Engineer
Alternative Weep Hole(s)
for Exterior Applications,
Design per Architect or
Civil Engineer
JOB NO.: DATE: FIGURE:

Typical Retaining Wall Subdrain Detail
72415-00 January 2019 3
4 inch diameter perforated plastic pipe embedded in the gravel envelope and tied to a 4 inch diameter non-perforated plastic pipe which discharges at convenient locations. The outlet pipe should be placed such that the flow gradient is not less than 2.0 percent. The geotextile fabricwrapped gravel envelope should be placed at a similar gradient All drain pipes should be Schedule 40 PVC or ABS SDR-35. Perforations may be either bored 1/4-inch diameter holes or 3/16-inch slots placed on the bottom one-third of the pipe perimeter. If the pipe is to be bored, a minimum of 10 holes should be uniformly placed per foot of length. If slots are made, they should not exceed 2-1/2 inches in length and should not be closer than 2 inches. Total length of slots should not be less than 50 percent of the pipe length and should be uniformly spaced.

The fabric pore spaces should not exceed equivalent 30 mesh openings or be less than equivalent 100 mesh openings. The fabric should be placed such that a minimum lap of 8-inches exists at all splices.

JOB NO.: DATE: FIGURE:

Typical Subdrain for Caisson Retaining Wall
72415-00 January 2019 4
Caisson
Waterproofing per
Architectural Plan
Finished Reinforced
Retaining Wall and/or
Shotcrete Wall between
Caissons
Native Soil
Shoring Lagging
Mirafi Quickdrain, or
approved equivalent,
outletted to suuitable
location or through wall
face for exterior
applications
Miradrain or
approved
equivalent
Retained Earth
Material
Embedded Reinforcement
per Structural
JOB NO.: DATE: FIGURE:

Typical Slab Subdrain Detail
72415-00 January 2019 5
Concrete Slab
4" Gravel Layer
Single Sized 1/2 to 3/4-inch
Drain Rock
15-mil visqueen membrane
overlaying gravel
Native Soil
Geotextile Filter
Fabric
Perforated 4" PVC
Schedule 40 Drain
Pipe
12" min
12" min
ɓ
ɓ GEOTECHNICAL CROSS SECTION A-A' ARIAS RESIDENCE 1516 BLUEBIRD CANYON DRIVE LAGUNA BEACH, CALIFORNIA TYPICAL BEDDING 72415-00 18-8416 FEBRUARY 2019 6 JOB NO.: REPORT NO.: DATE: FIGURE: 530 510 500 490 480 470 460 450

ELEVATION (FEET, PER PLAN)
A A' SLOPE STABILITY STRUCTURAL SETBACK PLANE Tt 520 PROPOSED RESIDENCE EXISTING GRADE Qrs RECOMMENDED CAISSON; 10' MIN. BELOW STRUCTURAL SETBACK PLANE POSSIBLE SHEAR PROJECTED FROM B-2 5' MIN. SETBACK BLUEBIRD CANYON DRIVE GEOTECHNICAL CROSS SECTION B-B' ARIAS RESIDENCE 1516 BLUEBIRD CANYON DRIVE LAGUNA BEACH, CALIFORNIA ɓ TYPICAL BEDDING, APPARENT DIP 72415-00 18-8416 FEBRUARY 2019 7 JOB NO.: REPORT NO.: DATE: FIGURE: 520 510 500 490 480 470 460 450

ELEVATION (FEET, PER PLAN)
B 520 510 500 490 480 470 460 450 B' PROPOSED GARAGE; DESIGN AND CONSTRUCTION PER SPECIALTY ENGINEERING CONTRACTOR Tt Qrs

APPENDIX A

REFERENCES

APPENDIX A

REFERENCES

1. Al Atik, Linda, M. ASCE, and Sitar, Nicholas, M.ASCE, 2010, Seismic Earth Pressures on Cantilever Retaining Structures, ASCE Journal of Geotechnical and Geoenvironmental Engineering, dated October.

2. Bozorgnia, Y., Campbell, K.W., and Niazi, M. M., 1999, “Vertical Ground Motion:

Characteristics, Relationship with Horizontal Component, and Building Code Implications”, Proceedings of the SMIP99 Seminar on Utilization of Strong-Motion Data, pp. 23-49, dated September 15.

3. California Building Code, 2016 Edition.

4. California Division of Mines and Geology, 1998, “Seismic Hazards Zones Map, Laguna Beach Quadrangle.

5. California Division of Mines and Geology, 2008, “Guidelines for Evaluating and Mitigating Seismic Hazards in California,” Special Publication 117A.

6. Geofirm, 1992, “Geotechnical Reviewed Cut Slopes for Driveway Access Proposed Development of Four Parcels Between Morningside Drive and Bluebird Canyon Drive, Laguna Beach, California”, Project No. 70164-00, dated September 2, 1992.

7. Geofirm, 1999, “Preliminary Geotechnical Review, Feasibility for Site Grading and Driveway Construction, Bluebird Canyon Road and Morningside Drive, Laguna Beach, California,” prepared by Geofirm, dated May 24, 1999, Project No: 9-3141.

8. Geofirm, 2001, “Preliminary Geotechnical Investigation for Proposed Residential Development, Property Between Bluebird Canyon Drive and Morningside Drive, Laguna Beach, California”, Project No. 70942-02, Report No. 01-3707, dated May 23, 2001

9. Geofirm, 2006, “Preliminary Geotechnical Investigation for Proposed Residential Development, Property Between Bluebird Canyon Drive and Morningside Drive, Laguna Beach, California”, Project No. 70942-04, Report No. 06-5747

10. Geofirm 2006, Preliminary Geotechnical Investigation for Proposed Residential Development, 1546 Morningside Drive, Laguna Beach, California, Project No. 70492-03, Report No. 06-5748, dated April 21, 2006.

11. Geofirm, 2007, “Preliminary Geotechnical Investigation for Site Development, 1260 Bluebird Canyon Drive (6 lots), Laguna Beach, California”; Project No. 71746-00, Report No. 07-6183, dated December 10,

12. Geofirm, 2010, “Grading Plan Review Report, New Single-Family Residence, Parcel 1, L.L.A. 04-01, 1526 Morningside Drive, Laguna Beach, California”, Project No. 70942- 06, Report No. 10-6809, dated November 5.

13. Geofirm, 2015, “Preliminary Geotechnical Investigation, Proposed New-Single-Family Residence, 1526 Morningside Drive, Northwesterly Lot, Laguna Beach, California”; Project No. 72200-01, Report No. 15-7745, dated September 2.

14. Grant et al, 1999, “Late Quaternary Uplift and Earthquake Potential of the San Joaquin Hills, South Los Angeles Basin, California,” Geology, November 1999, V. 27, No. 11, P1031-1034.

15. Jennings, Charles W., et al, 1994, “Fault Activity Map of California and Adjacent Areas,” California Division of Mines and Geology, Geologic Data Map No. 6.

16. Tan, Siang, S., and Edgington, William J., 1976, "Geology and Engineering Geology of the Laguna Beach Quadrangle, Orange County, California," California Division of Mines and Geology, Special Report 127.

17. United States Geological Survey, 2003, “Preliminary Digital Geologic Map of the Santa Ana 30’x 60’ Quadrangle, Southern California”, Version 1, compiled by D.M. Morton.

APPENDIX B

TEST PIT LOGS

APPENDIX C

PREVIOUS BORING LOGS AND LAB TEST RESULTS

APPENDIX D

SLOPE STABILITY ANALYSIS

APPENDIX D

ENGINEERING STABILITY ANALYSES

GENERAL
Engineering stability analyses were performed to define the 1.5 and 1.1 Factors of Safety (FS) line of the slope located within the subject property. The analyses were performed with the actual geologic conditions.

The “Slide 7.0”, 2D slope stability program utilized the stability analyses. The computer program utilizes the limit equilibrium theory for the calculation of the minimum Factory of Safety (FS).

SHEAR STRENGTH PARAMETERS
The shear strength parameters utilized in our stability analyses are presented in Table D-1, below. These values were based on laboratory testing and local experience in similar soils, and engineering judgment, and are considered reasonable and representative of the on-site materials.

TABLE D-1

SUMMARY OF STRENGTH PARAMETERS
Material Type
Bulk
Density
m (pcf)
Bulk
Density
s (pcf)
Cohesion
C (psf)
Friction
Angle (deg)
Topanga Formation Bedrock
(Across Bedding)
Topanga Formation Bedrock
(Along Bedding)
Topanga Formation Bedrock
(Shear Beds)
Colluvium (Qcol)
120
120
120
120
125
125
125
120
600
150
150
100
26 20

14.5 26

ANALYSES
Slope stability analyses were performed for the slope located within the property using Cross Section A-A’. The grades proposed to accommodate the house construction were used in analyses. To model the loading imposed by a residential structure, a boundary load of 200 psf was incorporated in the analyses at the proposed location of the structure.

The Factor of Safety (FS) criteria adopted for verifying the adequacy of the stability of the slope for the final design are as follows:

Static Conditions – FS>1.5
Pseudostatic Conditions – FS>1.1
Assumed Lateral Force (Seismic) – 0.15g
The results of the analyses are presented in Table D-2 and Figures D-1 and D-2.

TABLE D-2

SUMMARY OF STABILITY ANALYSES
Section
Min.

Static
FOS
Min.

Seismic
FOS
Figure
No. Comments
A-A’

1.54 1.21
D-1
D-2
Block mode along bedding to define structural
setback plane

1.54 200.00 lbs/ft2
Material Name Color Unit Weight (lbs/Ō3) Strength Type Cohesion (psf) Phi (deg) Anisotropic FuncƟon Qcol 120 Mohr‐Coulomb 100 26
Tt 125 Anisotropic funcƟon Bedding
Shear 125 Mohr‐Coulomb 150 14.5
Safety Factor

0.000.250.500.751.001.251.501.752.002.252.502.753.003.253.503.754.004.254.504.755.005.255.505.756.00+ 540 520 500 480 460
0 20 40 60 80 100 120 140 160
Analysis Description Static - Setback Plane
Project Number 72415-00 Drawn By ZWFigure # D-1 Date 1/15/2019 Project Arias Residence
1560 Bluebird Canyon Drive, Laguna Beach, CA
SLIDEINTERPRET 8.021

1.21 200.00 lbs/ft2

0.15 Material Name Color Unit Weight (lbs/Ō3) Strength Type Cohesion (psf) Phi (deg) Anisotropic FuncƟon Qcol 120 Mohr‐Coulomb 100 26
Tt 125 Anisotropic funcƟon Bedding
Shear 125 Mohr‐Coulomb 150 14.5
Safety Factor

0.000.250.500.751.001.251.501.752.002.252.502.753.003.253.503.754.004.254.504.755.005.255.505.756.00+ 540 520 500 480 460
0 20 40 60 80 100 120 140 160
Analysis Description Seismic - Setback Plane
Project Number 72415-00 Drawn By ZWFigure # D-2 Date 1/15/2019 Project Arias Residence
1560 Bluebird Canyon Drive, Laguna Beach, CA
SLIDEINTERPRET 8.021

APPENDIX E

STANDARD GRADING SPECIFICATIONS

APPENDIX E

STANDARD GRADING SPECIFICATIONS

GENERAL
These specifications present the usual and minimum requirements for grading operations observed by Geofirm or its designated representative. No deviation from these specifications will be allowed, except where specifically superseded in the geotechnical report signed by a registered geotechnical engineer.

The placement, spreading, mixing, watering and compaction of the fills in strict accordance with these guidelines shall be the sole responsibility of the contractor. The construction, excavation, and placement of fill shall be under the direct observation of the soils engineer signing the soils report. If unsatisfactory soil-related conditions exist, the soils engineer shall have the authority to reject the compacted fill ground and, if necessary, excavation equipment will be shut down to permit completion of compaction. Conformance with these specifications will be discussed in the final report issued by the soils engineer.

SITE PREPARATION
All brush, vegetation and other deleterious material such as rubbish shall be collected, piled and removed from the site prior to placing fill, leaving the site clear and free from objectionable material.

Soil, alluvium, or rock materials determined by the soils engineer as being unsuitable for placement in compacted fills shall be removed from the site. Any material incorporated as part of a compacted fill must be approved by the soils engineer.

The surface shall then be plowed or scarified to a minimum depth of 6 inches until the surface is free from uneven features that would tend to prevent uniform compaction by the equipment used.

After the area to receive fill has been cleared and scarified, it shall be diced or bladed by the contractor until it is uniform and free from large clods, brought to the proper moisture content and compacted to minimum requirements. If the scarified zone is greater than 12 inches in depth, the excess shall be removed and placed in lifts restricted to 6 inches.

Any underground structures such as cesspools, cisterns, mining shafts, tunnels, septic tanks, wells, pipe lines or others not located prior to grading are to be removed or treated in a manner prescribed by the soils engineer.

MATERIALS
Materials for compacted fill shall consist of materials approved by the soils engineer. These materials may be excavated from the cut area or imported from other approved sources, and soils from one or more sources may be blended. Fill soils shall be free from organic vegetable matter and other unsuitable substances. Normally, the material shall contain no rocks or hard lumps greater than 6 inches in size and shall contain at least 50 percent of material smaller than 1/4- inch in size. Materials greater than 4 inches in size shall be placed so that they are completely surrounded by compacted fines; no nesting of rocks shall be permitted. No material of a perishable, spongy, or otherwise of an unsuitable nature shall be used in the fill soils.

Representative samples of materials to be utilized as compacted fill shall be analyzed in the laboratory by the soils engineer to determine their physical properties. If any material other than that previously tested is encountered during grading, the appropriate analysis of this material shall be conducted by the geotechnical engineer as soon as possible.

PLACING, SPREADING, AND COMPACTING FILL MATERIAL
The material used in the compacting process shall be evenly spread, watered, processed and compacted in thin lifts not to exceed 6 inches in thickness to obtain a uniformly dense layer.

When the moisture content of the fill material is below that specified by the soils engineer, water shall be added by the contractor until the moisture content is near optimum as specified.

When the moisture content of the fill material is above that specified by the geotechnical engineer, the fill material shall be aerated by the contractor by blading, mixing, or other satisfactory methods until the moisture content is near optimum as specified.

After each layer has been placed, mixed, and spread evenly, it shall be thoroughly compacted to 90 percent of the maximum laboratory density in compliance with ASTM D: 1557-70 (five layers). Compaction shall be accomplished by sheepsfoot rollers, vibratory rollers, multiplewheel pneumatic-tired rollers, or other types of acceptable compacting equipment. Equipment shall be of such design that it will be able to compact the fill to the specified density.

Compaction shall be continuous over the entire area and the equipment shall make sufficient passes to obtain the desired density uniformly.

A minimum relative compaction of 90 percent out to the finished slope face of all fill slopes will be required. Compacting of the slopes shall be accomplished by backrolling the slopes in increments of 2 to 5 feet in elevation gain or by overbuilding and cutting back to the compacted inner core, or by any other procedure which produces the required compaction.

OBSERVATIONS AND TESTING
The geotechnical engineer shall observe the placement of fill during the grading process and will file a written report upon completion of grading stating his observations as to compliance with these specifications.

One density test shall be required for each 2 vertical feet of fill placed, or one for each 1,000 cubic yards of fill, whichever requires the greater number of tests.

Any cleanouts and processed ground to receive fill must be observed by the soils engineer and/or engineering geologist prior to any fill placement. The contractor shall notify the geotechnical engineer when these areas are ready for observation.

PROTECTION OF WORK
During the grading process and prior to the complete construction of permanent drainage controls, it shall be the responsibility of the contractor to provide good drainage and prevent ponding of water and damage to adjoining properties or to finished work on the site.

After the geotechnical engineer has terminated his observations of the completed grading, no further excavations and/or filling shall be performed without the approval of the soils engineer, if it is to be subject to the recommendations of this report.

APPENDIX F

UTILITY TRENCH BACKFILL GUIDELINES

APPENDIX F

UTILITY TRENCH BACKFILL GUIDELINES
The following guidelines pertinent to utility trench backfills have been adopted by the County of Orange, Environmental Management Agency Grading Section, effective March 31, 1986. The application of the guidelines is strictly enforced by the County reviewers and inspectors.

1. Each utility subcontractor (gas, electric, water, sewer, telephone, cable TV, irrigation, drainage, etc.) shall submit to the developer for dissemination to his consultants (civil engineer, geotechnical engineer, and utility contractor) a plot plan of utility lines installed under his purview which identifies line type, material, size, depth, and approximate location.

2. The developer or his agent shall provide a composite plot plan of all utilities or a copy of all individual utility plot plans to his geotechnical engineer for use in evaluating whether all utility trench backfills are suitable for the intended use.

3. The geotechnical engineer shall provide the County with a report which includes a plot plan showing the location of all utility trenches which:

A. Are located within the load influence zone of a structure (1:1 projection) B. Are located beneath any hardscape
C. Are parallel and in close proximity to the top or toe of a slope and may adversely impact slope stability if improperly backfilled
D. Are located on the face of a slope in a trench 18 or more inches in depth.

Typically, trenches that are less than 18 inches in depth will not be within the load influence zone if located next to a structure, and will not have a significant effect on slope stability if constructed near the top or toe of a slope and need not be shown on the plot plan unless determined to be significant by the geotechnical engineer. This plot plan may be prepared by someone other than the soil engineer, but must meet his approval.

4. Backfill compaction test locations must be shown on the plot plan described in No. 3 above, and a table of test data provided in the geotechnical report.

5. The geotechnical report (utility trench backfill) must state that all utility trenches within the subject lots have been backfilled in a manner suitable for the intended use. This includes the backfill of all trenches shown on the plot plan described in No. 3 and the backfill of those trenches which did not need to be plotted on this plan.

APPENDIX G

MAINTENANCE OF HILLSIDE HOMESITES

APPENDIX G

MAINTENANCE OF HILLSIDE HOME SITES

SLOPE STABILITY AND EROSION
During the wet weather season, homeowners become concerned about the stability of their building site. In general, modern design and construction practice minimizes the probability of serious slope failure. The grading codes of the local jurisdiction (cities and counties) in California concerning filled land, excavation, terracing and slope construction are among the most stringent in the country and, if followed, are adequate to meet most natural occurrences.

Therefore, the concern of the homeowner should be directed toward maintaining slopes, drainage provisions, and facilities so that they will perform as designed.

The following discussion, general recommendations, and simple precautions are presented herein to help the homeowner maintain their hillside building site.

The general public often regards the natural terrain as stable- "terra firma". This, of course, is an erroneous concept. Nature is always at work altering the landscape. Hills and mountains are worn down by mass wasting (erosion, sliding, creeping) and the valleys and lowlands collect these products. Thus, the natural process is toward leveling the terrain. In some areas these processes are very slow and in others they are more rapid.

Development of hillsides for residential use is carried out, as far as possible, to enhance the natural stability of the site and to minimize the probability of instability resulting from the grading necessary to provide homesites, streets, and yards. This has been done by the developer and designers on the basis of geologic and soil mechanics investigations. In order to be successful, the slope and drainage provisions and facilities must be maintained by the homeowner.

Homeowners are accustomed to maintaining their homes; they expect to paint their house periodically, replace wiring, clean out clogged plumbing, repair roofs, et cetera. Maintenance of the homesite, particularly on hillsides, should be considered on an even more serious basis. In most cases, lot and site maintenance can be taken care of along with landscaping and can be carried out cheaper to the homeowner than repair after neglect.

Most slope and hillside lot problems are associated with water. Uncontrolled water from a broken pipe, cesspool, or wet weather, causes most damage. Wet weather is the largest cause of slope problems, particularly in California where rain is intermittent but may be torrential.

Therefore, drainage and erosion control are the most important aspects of homesite stability.

These provisions must not be altered without competent professional advice and maintenance must be carried out to assure their continued operations. We offer these procedures as a checklist to homeowners:

1. Check roof drains and gutters and downspouts to be sure they are clear. Depending on your location, if you do not have roof gutters and downspouts, you may wish to install them. Without gutters or other adequate drainage, water falls from the roof eaves, undesirably collecting against foundation and basement walls.

2. Clear surface and terrace drainage ditches and check them frequently during the rainy season, with a shovel, if necessary. Ask your neighbors to do likewise.

3. Be sure that all drainage ditches have outlet drains that are open. This should be tested during dry weather. Usually this can be done simply with a hose. If blockage is evident, you may have to clear the drain mechanically.

4. Check all drains at the top of slopes to be sure that they are clear and that water will not overflow the slope itself, causing erosion.

5. Keep subsurface drain openings (weep-holes) clear of debris and other materials which could block them in a storm.

6. Check for loose fill above and below your property if you live on a slope or terrace.

7. Watch hoses and sprinklers. During the rainy season, little, if any, irrigation is required.

Over-saturation of the ground is not only unnecessary and expensive on the water bill, but can cause subsurface damage.

8. Watch for water backup of drains inside the house and toilets during a rainy season since this may indicate drain or sewer blockage.

9. Exercise ordinary precaution. Your house and building site were constructed to meet certain standards which should protect against any natural occurrence, if you do your part in maintaining them.

10. Care and maintenance of hillside homes includes being sure that terrace drains and brow ditches on slopes or at the tops of cut or fill slopes are not blocked. They are designed to carry away runoff to a place where it can be safely distributed. Generally, a little shovel work will remove any accumulation of dirt and other debris which may clog the drain. If several homes are located on the same terrace, it is a good idea to check with your neighbors.

Water backed up on their property may eventually reach you. Water backed up in surface drains will tend to overflow and seep into the terraces, creating less stable slopes.

11. Water should not be permitted to collect or pond on your homesite. Water gathering here will tend to either seep into the ground loosening fill or natural ground, or will overflow onto the slope and begin the erosion. Once erosion is started, it is difficult to control and severe damage may result rather quickly.

12. Roof drains and gutters or downspouts should not be connected to subsurface drains.

Rather, arrange them so that water either flows off your property in a specially designed pipe or it flows out onto a paved driveway or the street. The water then may be dissipated over a wide surface, or preferably be carried away in a paved gutter or stormdrain. Subdrains are constructed to take care of ordinary subsurface water and cannot handle the overload from roofs during a heavy rain.

13. Water should not be allowed to spill over slopes, even where this may seem to be a good way to prevent ponding. This tends to cause erosion and, in the case of fill slopes, can cut away carefully designed and constructed sites.

14. Loose soil or debris should not be left on or tossed over slopes. Loose soil soaks up water more readily than compacted fill. It is not compacted to the same strength as the slope itself and will tend to slide when laden with water and may even affect the soil beneath it. The sliding may clog terrace drains below or may cause additional damage in weakening the slope. If you live below a slope try to be sure that loose fill is not dumped above your property.

15. Water should not be discharged into subsurface blanket drains close to slopes. French drains are sometimes used to get rid of excess water when other ways of disposing of water are not readily available. Overloading these drains saturates the ground and, if located close to slopes, may cause slope failure in their vicinity.

16. Surface water should not be discharged into septic tanks or leaching fields. Not only are septic tanks constructed for a different purpose, but they will tend, because of their construction, to accumulate additional water naturally from the ground during a heavy rain. Overloading them artificially during the rainy season is bad for the same reason as subsurface subdrains, and is doubly dangerous since their overflow can pose a serious health hazard. In many areas the use of septic tanks should be discontinued as soon as sewers can be made available.

17. Slopes should not be over-irrigated. Naturally, ground cover of ice plant and other vegetation will require some moisture during the hot summer months, but during the wet season, irrigation can cause ice plant and other heavy ground cover to pull loose which not only destroys the cover, but also starts serious erosion. In some areas ice plant and other heavy cover can cause surface sloughing when saturated due to the increase in weight and weakening of the near surface soil. Planted slopes should be located, where possible, in areas where they will be adequately irrigated by rainfall.

18. Water should not be allowed to gather against foundations, retaining walls and basement walls. These walls are built to withstand the ordinary moisture in the ground and are, where necessary, accompanied by subdrains to carry off the excess moisture. If water is permitted to pond against them, it may seep through the wall causing dampness and leakage inside the basement. The water may also cause the foundation to swell or the water pressure may cause structural damage to walls.

19. New fill placed behind walls or in trenches should not be compacted by flooding with water. Not only is flooding the least efficient way of compacting fine-grained soil, but could damage the wall foundation.

20. Hoses and sprinklers should not be left running on or near a slope, particularly during the rainy season. This will enhance ground saturation which may cause damage.

21. Ditches which have been graded around your house or the lot pad should not be blocked.

These shallow ditches have been put there for the purpose of quickly removing water toward the driveway, street, or other positive outlet. By all means, do not allow water to become ponded above slopes because of blocked ditches.

T.D. 124' T.D. 91' T.D. 85' T.D. 48' T.D. 70' T.D. 51' T.D. 71' T.D. 22' GB-1 GB-2 BA-5 DH-1 GB-1 BA-2 BA-3 BA-4 BA-1 TGR T.D. 80' ?
?
?
?

TYPICAL BEDDING
S
S
S
S
S
S
S
S
S
S
S
S

S BLUEBIRD CANYON DRIVE JEFFERSON WAY BLUEBIRD CANYON WYKOFF DRIVE DRIVE BLUEBIRD CANYON DRIVE BLUEBIRD CANYON DRIVE BLUEBIRD CANYON DRIVE PL
?
? Tt Tt Tt Tt Qal Qls Qcol Qlso Af APPROX LIMITS OF 1560 BH-1 BA-1 BA-4 GB-1 BA-3 BA-2 BA-5 GB-1 GB-2 GB-1 TGR ?
?
?
?
?
?
?

BLUEBIRD CANYON DRIVE

WYKOFF WAY

DYER PLACE

BLUEBIRD CANYON DRIVE

JEFFERSON WAY

BLUEBIRD CANYON DRIVE
MORNINGSIDE DRIVE Qal Qls Tt Qlso Tt Tt Qlso Tt Tt T.D. 85' T.D. 80' T.D. 22' T.D. 91' T.D. 124' T.D. 70' T.D. 72' T.D. 71' T.D. 51' T.D. 48' ? Tt SITE
?
? REGIONAL GEOLOGIC MAP & GEOTECHNICAL CROSS SECTION A-A' 1560 BLUEBIRD CANYON DRIVE LAGUNA BEACH, CALIFORNIA 72415-00 FEBRUARY 2019 1 JOB NO.: REPORT NO.: DATE: PLATE: 180 220 260 300 340 380 420 460 500 540 140 100 ELEVATION (FEET) SCALE: 1"=40'
A A' SCALE: 1"=40'
A A'180 220 260 300 340 380 420 460 500 540 140 100 2730 60 86 38 80 68 67 48 44 37 3830 36 56 40 69 3886 80 77 19 78 718076 66 64 20 1618 2434 303033- 3828 5232 13Qal Tt 40' 47' 1313 20' 32' 1331 34' 39' 24 19' 69' 13 85' 34 27' 48 21' 21' 50 10.5' 30 68' 55' 53' 51' Qls Qal Tt 24 21' Qls Qal Tt 10.5' 75' 71' 33' 30' 21' 28' 281820 2323 6657 78 29 47 12 24 6612 29 64 2321 22 17 283515 2434 69 121' 118' 117'' 117'' 112'' 110'' 85'' 81'' 64'' 18' 39' 35' 34' 29' 27' 25' 23'' 23' 22' 41' 50' 17 8738 83 15 26 67 75 262744 13 54 24 70 27 78 62 7 80 67 6046 Af Tt 7.5' 373639 19' 56 27' 7.5' 8.5' 12' 14' 15' 16' 16' 18' 18' 19' 19.5' 22' 24' 25' 27.5' 29' 29' 29' 323435' 45' 45' 54' 56' 66' 67' 74' Qls Tt 18' 72' 13' 64' Qls Qal Tt 23' 43' 33' 23' 21' 18' 16' 14' 14' 14' 267060 11 20 23 31 63 Qls UNDIFFERENTIATED LANDSLIDE DEPOSITS Qlso OLDER LANDSLIDE DEPOSITS Tt BEDROCK, TOPANGA FORMATION, LOCATION OF GEOFIRM BORING, 2007 STUDY LOCATION OF BORING BY OTHERS APPROXIMATE LITHOLOGIC CONTACT; DOTTED WHERE BURIED; QUERIED WHERE INFERRED MEASURED STRIKE AND DIP OF BEDDING MEASURED STRIKE AND DIP OF JOINTING MEASURED STRIKE AND DIP OF JOINT SETS MEASURED STRIKE AND DIP OF SHEARED BEDDING MEASURED STRIKE AND DIP OF RUPTURE SURFACE OBSERVED SEEPAGE GROUNDWATER (ASSUMMED) LOCATION OF GEOTECHNICAL CROSS-SECTION ? 27 48 61 27 32 BA-5 TGR 86 32 MEASURED STRIKE AND DIP OF SHEAR A A' BH-1Qal ALLUVIAL DEPOSITS GEOTECHNICAL SYMBOLS GEOLOGIC UNITS EXPLANATION GB-1 GB-2 GB-1 LOCATION OF GEOFIRM BORINGS, PREVIOUS STUDIES 18-8416 LIMITS OF SUBJECT PROPERTY Qcol COLLUVIAL DEPOSITS Af ARTIFICIAL FILL B-2
56 40
69 38
86 80
77 19
78 71
80 76
66 64
7'
8' 13'
20'
24'
30' 42'
45'
58' GEOTECHNICAL PLOT PLAN 1516 BLUEBIRD CANYON DRIVE LAGUNA BEACH, CALIFORNIA 72415-00 FEBRUARY 2019 2 JOB NO.: REPORT NO.: DATE: PLATE: TP-2 SCALE: 1"=10' 18-8416 TP-1 ?
?
B
B'
A
A' 460465 470475 480 485 490 495 Tt Tt Qlso B-2 Qlso ANCIENT LANDSLIDE DEPOSITS BEDROCK: TOPANGA FORMATION APPROXIMATE BUCKET AUGER BORING LOCATION, 2005 INVESTIGATION EXPLANATION Tt APPROXIMATE TEST PIT LOCATION, THIS INVESTIGATION SLOPE STABILITY SETBACK PLANE; CAISSONS AT MIN. 10' EMBEDMENT BELOW SETBACK PLANE TP-271 MEASURED STRIKE AND DIP OF SHEAR 86 77 MEASURED STRIKE AND DIP OF JOINT SET
64 MEASURED STRIKE AND DIP OF JOINT Qrs RESIDUAL SOIL, UNMAPPED APPENDIX B-2
REFERENCED REPORT NO. 2
GEOFIRM, 2022, “GEOTECHNICAL UPDATE LETTER PROPOSED SINGLEFAMILY RESIDENCE, 1560 BLUEBIRD CANYON ROAD, APN# 644-321-31, PARCEL 4, BLOCK F, LAGUNA BEACH, CALIFORNIA”; PROJECT NO. 72415-01, REPORT NO. 22-9214, DATED SEPTEMBER 19.

September 19, 2022
Michael and Rosalie Arias Project No. 72415-01
4471 Dean Martin Drive, Unit 300 Report No. 22-9214
Las Vegas, Nevada 89103
Subject: Geotechnical Update Letter
Proposed Single-Family Residence
1560 Bluebird Canyon Road
APN# 644-321-31, Parcel 4, Block F
Laguna Beach, California
Reference: Geofirm, 2019, “Preliminary Geotechnical Investigation for New Single-Family Residence, 1560 Bluebird Canyon Road, APN# 644-321-31, Parcel 4, Block F, Laguna Beach, California”, Project No. 72415-00, Report No. 19-8482, dated February 5.

Michael and Rosalie Arias:

This letter presents our updated geotechnical recommendations pertinent to the design and construction of a new single-family residence on the subject property. Based on our discussions, the current design plans for the development generally remain unchanged. Therefore, the recommendations presented in the referenced report remain applicable under the 2016 CBC. If necessary, the updated seismic design criteria are provided to conform to the 2019 CBC.

Updated Seismic Structural Design
Based on the geotechnical data and site parameters, the following is provided by the USGS (ASCE 7-16) to satisfy the 2019 CBC design criteria:

Site and Seismic Design Criteria for 2019 CBC
Design
Parameters
Recommended
Values
Site Class
Ss (g)
S1 (g)
SMs (g)
SM1 (g)
SDs (g)
SD1 (g)
Fa
Fv
B (Rock)

1.304

0.463

1.174

0.370

0.782

0.247

0.9 0.8
September 19, 2022 Project No: 72415-01
Report No: 22-9214
Page No: 2
Design
Parameters
Recommended
Values
Seismic Design Category
PGAM (g)
D

0.512
Thank you for this opportunity to be of continued service. If you have any questions, please contact this office.

Respectfully submitted,

GEOFIRM
Erik R. Hilde, E.G. Jesse D. Bearfield, P.E. 84335
Associate Engineering Geologist, C.E.G. 2303 Associate Engineer Date Signed: 9 / 9 / 2022
EH/JB: mr
Distribution: Addressee via email
APPENDIX B-3
REFERENCED REPORT NO. 3
GEOFIRM, 2022, “RESPONSE TO CITY OF LAGUNA BEACH GEOTECHNICAL REPORT, GEOTECHNICAL REPORT REVIEW CHECKLIST, 1ST REVIEW, DATED SEPTEMBER 30, 20222, 1560 BLUEBIRD CANYON ROAD, APN# 644-321-31, PARCEL 4, BLOCK F, LAGUNA BEACH, CALIFORNIA, ZPC-2020-8070”, PROJECT NO. 72415- 01, REPORT NO. 22-9242, DATED NOVEMBER 29.

November 29, 2022
Michael and Rosalie Arias Project No: 72415-01
4471 Dean Martin Drive, Unit 300 Report No: 22-9242
Las Vegas, Nevada 89103
Subject: Response to City of Laguna Beach Geotechnical Report Geotechnical Report Review Checklist, 1
st Review, dated September 30, 2022
1560 Bluebird Canyon Road
APN# 644-321-31, Parcel 4, Block F
Laguna Beach, California
ZPC-2020-8070
References: 1. Geofirm, 2019, “Preliminary Geotechnical Investigation for New SingleFamily Residence, 1560 Bluebird Canyon Road, APN# 644-321-31, Parcel 4, Block F, Laguna Beach, California”, Project No. 72415-00, Report No. 19-8482, dated February 5.

Dear Mr. and Mrs. Arias:

This letter is in response to the City of Laguna Beach Geotechnical Review Checklist dated September 30, 2022. The review requested additional information on six items associated with the referenced report. A copy of the review sheet is provided in Appendix A. Our responses are presented following each comment.

Item 1: Please provide the maximum anticipated height of temporary excavations and the recommended maximum duration of open excavations. Recommendations should take seasonal variations into account.

Response: The estimated maximum height of unshored temporary excavations is less than 10 feet. Such cuts may remain open for a duration of 30 days pending field review by the geologist and provided they are adequately protected by the contractor in accordance with appropriate BMPs.

Item 2: Updated cross sections should be provided depicting existing and proposed improvements, proposed excavations, temporary excavations, shoring, and applicable remedial earthwork.

November 29, 2022 Project No: 72415-01
Report No: 22-9242
Page No: 2
Response: See the attached updated geotechnical cross sections for the requested information.

Please note that the depth of remedial grading below exterior hardscape areas is not depicted in the graphics due to their location but is anticipated to range between 1½ and 5± feet depending on the material exposed.

Item 3: The update letter/report dated September 19, 2022 provides seismic design criteria based on the 2019 California Building Code (CBC). The update also indicates that the recommendations provided in the referenced 2019 geotechnical report remain applicable under the 2016 CBC. Please provide updated project geotechnical design recommendations for the current 2019 CBC as applicable..

Response: With the exception of the updated seismic design parameters resented in the Update Letter (reference 2), the design parameters presented in the 2019 report (reference 1), may be used for the design of the development per the 2019 CBC without revision. It was our understanding that the plans had been submitted to the City in late 2019 prior to the code change, and thus the client was unsure if the project was going to be subject to the 2016 or 2019 CBC.

Item 4: The recommended Seismic Design Criteria is based on a Site Class B (rock). In the referenced 2019 geotechnical report by the consultant on page 7, under Section:

Site Classification for Seismic Design the consultant indicates that the Site Class is based on estimated shear wave velocities for San Onofre Formation bedrock underlying the site. However, the consultant identifies under Earth Materials on page 3 of the 2019 report that the bedrock underlying the site is the Miocene aged Topanga Formation. Please provide clarification and update the Site Class and seismic design criteria.

Response: The site classification of Class B and the associated parameters are correct. The bedrock underlying the site is Topanga Formation as described in the earth materials section. We apologize for the discrepancy between sections.

Item 5: It appears that shoring.is likely necessary. Consultant should provide geotechnical design parameters for shoring.

Response: Shoring should be designed for areas where slope layback is unfeasible. Shoring should consider topographic and structural surcharges from the adjacent properties.

Piles utilized for shoring should have a minimum embedment of 10 feet into competent bedrock materials. Temporary shoring should be designed utilizing an active pressure of 45 pounds per cubic foot equivalent fluid pressure.

Vibratory techniques for placement of piles or steel sheet lagging should not be utilized, as damage to adjoining property improvements may otherwise occur. It is the contractor’s responsibility to develop appropriate means and methods of construction to avoid damage to adjacent properties. We also suggest that ground vibration monitoring be performed during construction due to the close proximity November 29, 2022 Project No: 72415-01
Report No: 22-9242
Page No: 3
of adjacent improvements and the relatively high cost of real estate in the area.

If temporary shoring elements are to be removed, the builder and homeowner must be aware that such removal could result in settlement and possible damage to improvements on the adjacent property. The adjacent property owners must be advised of the risks and the builder should provide arrangements to repair any possible damages. The contractor should also recognize the risk of leaving voids during removal of shoring elements. Lagging plates and piles should therefore be removed slowly and the voids created should be filled immediately. Consideration should be given to continuously injecting grout at the base of the piles and plates as they are being removed to fill the resultant voids.

Proper installation of shoring is the responsibility of the contractor. The adjacent property owners must be advised of the risks and the owner and builder should provide arrangements to repair any possible damages.

Item 6: A pool/spa appears to be proposed. Please provide geotechnical recommendations for the pool/spa.

Response: It is recommended that the pool/spa be supported on caisson foundations in accordance with the recommendations for residence. Recommendations for the design of caissons are presented below.

Earth pressure forces acting on the pool/spa walls should be designed using an equivalent fluid density of 60 pounds per cubic foot for onsite materials. An equivalent fluid density of 35 pounds per cubic foot may be utilized, if grading is performed to replace onsite surficial earth materials with approved granular import fill material. These recommendations may be modified pending verification of soil conditions during construction. Surcharge loads, both topographic and structural, should be considered by the pool engineer.

Minimum 24-inch diameter caissons embedded a minimum of 10 feet into competent bedrock may be designed for a dead plus live load end bearing value of 4,000 pounds per square foot and skin friction of 500 pounds per square foot.

These values may be increased by one-third for wind and seismic forces. Lateral resistance may be computed utilizing 400 pounds per square foot per foot of depth for bedrock below the setback zone, acting on a tributary area of twice the caisson diameter.

Caissons should be designed to resist full tributary lateral pressure loading of 45 pounds per cubic foot equivalent fluid pressure to the depth of the setback plane.

Passive resistance may be taken only below the setback plane. Final caisson design and locations should be accomplished by joint consultation between the geotechnical engineer and the structural engineer.

November 29, 2022 Project No: 72415-01
Report No: 22-9242
Page No: 4
This opportunity to be of continued service is appreciated. If you have any questions, please don’t hesitate to call our office.

Respectfully submitted,

GEOFIRM
Erik R. Hilde, PG Jesse D. Bearfield
Associate Engineering Geologist, EG 2303 Associate Engineer, P.E. 84335 EH/JDB : mr
Distribution: Addressee via email
Attachments: Figure 1 – Updated Geotechnical Cross Section A-A’ Figure 2 – Updated Geotechnical Cross Section B-B’
Appendix A – City of Laguna Beach Geotechnical Review Checklist dated September 30, 2022
⅊
⅊ UPDATED GEOTECHNICAL CROSS SECTION A-A'

ARIAS RESIDENCE
1560 BLUEBIRD CANYON DRIVE
LAGUNA BEACH, CALIFORNIA TYPICAL BEDDING 72415-01 22-9242 NOVEMBER 2022 1 JOB NO.: REPORT NO.: DATE: FIGURE: 530 510 500 490 480 470 460 450

ELEVATION (FEET, PER PLAN)
A A' SLOPE STABILITY STRUCTURAL SETBACK PLANE Tt 520 PROPOSED RESIDENCE EXISTING GRADE Qrs RECOMMENDED CAISSON; 10' MIN. BELOW STRUCTURAL SETBACK PLANE POSSIBLE SHEAR PROJECTED FROM B-2 5' MIN. SETBACK BLUEBIRD CANYON DRIVE TYP. SLAB SUBDRAIN (OR WATERPROOFING) PER REPORT 19-8482 TYP. TEMP CUT PER REPORT 19-8482; 5' MAX VERT TO 1:1 (HORIZ:VERT) LAYBACK

UPDATED GEOTECHNICAL CROSS SECTION B-B'

ARIAS RESIDENCE
1560 BLUEBIRD CANYON DRIVE

LAGUNA BEACH, CALIFORNIA
⅊ TYPICAL BEDDING, APPARENT DIP 72415-01 22-9242 NOVEMBER 2022 2 JOB NO.: REPORT NO.: DATE: FIGURE: 520 510 500 490 480 470 460 450

ELEVATION (FEET, PER PLAN)
B 520 510 500 490 480 470 460 450 B' PROPOSED GARAGE; DESIGN AND CONSTRUCTION PER SPECIALTY ENGINEERING CONTRACTOR Tt Qrs CONCEPTUAL CAISSON-SUPPORTED SHORING/RETAINING WALLS IF NECESSARY TYP. SLAB SUBDRAIN (OR WATERPROOFING) PER REPORT 19-8482

APPENDIX A

CITY OF LAGUNA BEACH GEOTECHNICAL REVIEW CHECKLIST DATED SEPTEMBER 30, 2022
PN 96044-993 CLB ZPC#-2021-8070

CITY OF LAGUNA BEACH

GEOTECHNICAL REPORT REVIEW CHECKLIST
1st Review
S:\Projects\KCG\1996\96044\501-1000\96044-993\96044-993 1st Review 1560 Bluebird Cyn 9-22.doc Date Received: September 29, 2022 Date Completed: September 30, 2022 Date of Report(s): Update letter/report September 19, 2022 of February 5, 2019 report.

PC #: ZPC-2020-8070
Consultant: Stony Miller Consultants, Inc./GeoFirm Their Job No.: 72415-00/01 Signed By: Erik R. Hilde License No.: CEG 2303
Zi Wang
Jesse D, Bearfield
RCE 80199
RCE 84335
Applicant Name: Michael and Rosalie Arias Legend: N = No Site Address: 1560 Bluebird Canyon Road Y = Yes
Laguna Beach, Ca NA = Not Applicable
Lot/Tract No.: Parcel 4, Block F A.P.N.:644-321-31
Proposed Project: New two story single family residence, subterranean garage that will daylight near or at street level. Pool/spa, exterior hardscape and improvements, foundations supported on caissons founded into competent bedrock.
• Project Information /Background:

Y/N Review of existing City files Y/N Reference to grading/foundation plans by date Y/N Reference to site(s) by street address Y/N Subsurface investigation Y/N Grading or Remedial Grading
• Lateral Stability Plan: • Summary of Consultant Recommendations:

Y/N/NA Illustration on Cross Sections Y/N/NA Recommended Maximum Duration of Open Excavations: --- Y/N/NA Stability Analysis Y/N/NA Anticipated Maximum Height of Temporary Excavations: --- Y/N/NA Shoring Anticipated Y/N/NA Maximum Gradient of Temporary Excavations: Maximum 5-foot vertical, excavations laid back to maximum 1:1 (H:V) above.

Y/N/NA Shoring Parameters Provided
• Bluff Top Edge Determination:

Y/N/NA
• Geologic Hazards:

Hazard
Discussion of
Hazard
Mitigation
Required
Recommendations
for Mitigation
Adverse geologic structure Y/N/NA Y/N/NA Y/N/NA
Bluff retreat Y/N/NA Y/N/NA Y/N/NA
Collapsible soils Y/N/NA Y/N/NA Y/N/NA
Debris/mud flow Y/N/NA Y/N/NA Y/N/NA
Differential settlement Y/N/NA Y/N/NA Y/N/NA
Erosion/Drainage Y/N/NA Y/N/NA Y/N/NA
Expansive soils Y/N/NA Y/N/NA Y/N/NA
Faulting Y/N/NA Y/N/NA Y/N/NA
Fractured bedrock Y/N/NA Y/N/NA Y/N/NA
Groundwater Y/N/NA Y/N/NA Y/N/NA
Landslide Y/N/NA Y/N/NA Y/N/NA
Liquefaction Y/N/NA Y/N/NA Y/N/NA
Seismic Loading Y/N/NA Y/N/NA Y/N/NA
Settlement Y/N/NA Y/N/NA Y/N/NA
Slump Y/N/NA Y/N/NA Y/N/NA
Soil/rock creep Y/N/NA Y/N/NA Y/N/NA
Sulfate rich soils Y/N/NA Y/N/NA Y/N/NA
PN 96044-993 CLB ZPC#-2021-8070

CITY OF LAGUNA BEACH

GEOTECHNICAL REPORT REVIEW CHECKLIST
1st Review
S:\Projects\KCG\1996\96044\501-1000\96044-993\96044-993 1st Review 1560 Bluebird Cyn 9-22.doc • Supporting Analysis/Data: • Recommendations For:

Y/N/NA Slope stability calculations Y/N/NA Foundations
Y/N/NA Shear strength values Y/N/NA Retaining walls
Y/N/NA Other laboratory data Y/N/NA Foundation setbacks Y/N/NA Seismic coefficients/parameters Y/N/NA Slabs
Y/N/NA Seismic loading Y/N/NA Flatwork
Y/N/NA Boring/trench logs Y/N/NA Grading
Y/N/NA Liquefaction study Y/N/NA Pools/spas
Y/N/NA Calculations supporting recommendations Y/N/NA Slope/bluff setbacks Y/N/NA Reference list Y/N/NA Temporary excavations
• Geologic Map/Cross-Sections:

Y/N Accurate topographic base extending sufficiently offsite Y/N Proposed topography Y/N Surficial drainage Y/N Slope gradients
Y/N Existing structures Y/N Proposed structures
Y/N Boring/trenches plotted Y/N Legend, scale, north arrow Y/N Geologic contacts/data illustrated Y/N Location of cross-section(s) shown Y/N Consistency with adjoining data/maps Y/N Illustrate setbacks, if any Y/N Cross-sections sufficient in number, location, and detail Y/N Proposed excavations • Report Closure:

Y/N Statement as to the adequacy of the site for the intended use Y/N Statement that proposed development will not adversely impact adjoining sites Y/N Signature of C.E.G.

Y/N Signature of R.C.E. or G.E.
• Recommended Actions:

Report Approved X Additional Input Required
Items Requiring Response/Further Evaluation:

1. Please provide the maximum anticipated height of temporary excavations and the recommended maximum duration of open excavations. Recommendations should take seasonal variations into account.

2. Updated cross sections should be provided depicting existing and proposed improvements, proposed excavations, temporary excavations, shoring, and applicable remedial earthwork.

3. The update letter/report dated September 19, 2022 provides seismic design criteria based on the 2019 California Building Code (CBC). The update also indicates that the recommendations provided in the referenced 2019 geotechnical report remain applicable under the 2016 CBC. Please provide updated project geotechnical design recommendations for the current 2019 CBC as applicable.

4. The recommended Seismic Design Criteria is based on a Site Class B (rock). In the referenced 2019 geotechnical report by the consultant on page 7, under Section: Site Classification for Seismic Design the consultant indicates that the Site Class is based on estimated shear wave velocities for San Onofre Formation bedrock underlying the site. However, the consultant identifies under Earth Materials on page 3 of the 2019 report that the bedrock underlying the site is the Miocene aged Topanga Formation. Please provide clarification and update the Site Class and seismic design criteria.

5. It appears that shoring.is likely necessary. Consultant should provide geotechnical design parameters for shoring.

6. A pool/spa appears to be proposed. Please provide geotechnical recommendations for the pool/spa.

PN 96044-993 CLB ZPC#-2021-8070

CITY OF LAGUNA BEACH

GEOTECHNICAL REPORT REVIEW CHECKLIST
1st Review
S:\Projects\KCG\1996\96044\501-1000\96044-993\96044-993 1st Review 1560 Bluebird Cyn 9-22.doc Additional Comments (no response required):

1. Note to City Staff: Consultant indicates the site is geotechnically unsuitable for the local discharge or direct infiltration of onsite stormwater and therefore onsite discharge of stormwater is not recommended.

2. Note to City Staff: Staff should confirm that the Consultants (C.E.G. and R.C.E./G.E.) have signed the final dated grading, foundation/construction, and landscaping plans, per City Code, thereby verifying the plans' geotechnical conformance with the Consultant's original report and associated addenda.

3. Note to City Staff: Consultant indicates the site is geotechnically unsuitable for the local discharge or direct infiltration of onsite stormwater and therefore onsite discharge of stormwater is not recommended.

4. Note to City Staff: It appears that a separate excavation and shoring permit is required prior to or in conjunction with the permit, City staff should confirm that the Consultants (C.E.G. and R.C.E.) have signed the final dated shoring plans, thereby verifying the plans' geotechnical conformance with the Consultant's original report and associated addenda.

5. An as built geotechnical report should be prepared by the project geotechnical consultant following grading/construction of the subject site improvements. The report should include the results of all field density testing, depth of reprocessing and recompaction, as well as a map depicting the limits of grading, locations of all density testing, and geologic conditions exposed during grading/excavation. The report should include conclusions and recommendations regarding applicable setbacks, foundation recommendations, slope stability, erosion control and any other relevant geotechnical aspects of the

6. site.

Limitations:

Our review is intended to determine if the submitted report(s) comply with City of Laguna Beach Codes and generally accepted geotechnical practices within the local area. The scope of our services for this third party review has been limited to a brief site visit and a review of the above referenced report and associated documents, as supplied by the City of Laguna Beach. Reanalysis of reported data and/or calculations and preparation of amended construction or design recommendations are specifically not included within our scope of services. Our review should not be considered as a certification, approval or acceptance of the consultant’s work, nor is it meant as an acceptance of liability for final design or construction recommendations made by the geotechnical consultant of record or the project designers or engineers.

BY:_________________________________________ BY:_______________________________________ Jeffrey P. Blake C.E.G. 2248 Dante P. Domingo, R.C.E. 57939

KLING CONSULTING GROUP KLING CONSULTING GROUP
TP-2 (2019)
TP-1 (2019)
B-2 (2005)
66 64
76 80
19 69
56 7'
8'
13'
20'
24'
30'
42'
45'
58'
77 86
A
A'
B
B'
C
C'
Tt
Tt
PROJECT: DATE: PLATE: 33 JOURNEY, SUITE 200 ALISO VIEJO, CA 92656 949-380-4886 nlee 22-Aug-24 72786-00 v3jdb.dwg

GEOTECHNICAL PLOT PLAN

PROPOSED TWO-LOT RESIDENTIAL DEVELOPMENT
1560 BLUEBIRD CANYON DRIVE

LAGUNA BEACH, CA
72786-00 AUGUST 2024 1
45 48
61 45
Tt
TP-1
B-2 (2005)

EXPLANATION

TOPANGA FORMATION BEDROCK
APPROXIMATE LOCATION OF PREVIOUS BORING; NUMBER AND DATE

INDICATED
APPROXIMATE LOCATION OF TEST PIT/TRENCH; NUMBER INDICATED APPROXIMATE LOCATION OF GEOLOGIC CONTACT; DOTTED WHERE

BURIED, QUERIED WHERE UNCERTAIN (NOT SURVEYED)

MEASURED STRIKE OF JOINT OR FRACTURE

MEASURED STRIKE AND DIP OF JOINT SETS
MEASURED STRIKE AND DIP OF BEDDING PLANE SHEAR; ARROW

INDICATES STRIA DIRECTION

LOCATION OF GEOTECHNICAL CROSS-SECTION
45 MEASURED STRIKE AND DIP OF BEDDING; DASHED WHERE BURIED

DURING PREVIOUS GRADING
C C'
?
0 10' 20'
SCALE: 1" = 10'

X X APPARENT DIP OF BEDDING PLANE SHEAR IN CROSS-SECTION

J APPARENT DIP OF JOINT OR FRACTURE IN CROSS-SECTION
⅊
⅊ B-2 PROJ. (41' W) T.D. =71' N24W TP-1 PROJ. (15'E) T.D. = 1.5' FF 492.0 BLUEBIRD CANYON ROAD J
J
J
J 410 400 420 430 440 450 460 470 480 490 500 410 400 420 430 440 450 460 470 480 490 500

ELEVATION (FEET, PER PLAN)
B B' 510 520 530 410 400 420 430 440 450 460 470 480 490 500 410 400 420 430 440 450 460 470 480 490 500

ELEVATION (FEET, PER PLAN)
C C'
⅊
⅊ ROW IMPROVEMENTS N24W FF 505.0 GARAGE FF 492.0
J
J
J
J
J FF 492.0
⅊ FF 505.0
⅊ 410 400 420 430 440 450 460 470 480 490 500

ELEVATION (FEET, PER PLAN)

ELEVATION (FEET, PER PLAN)
A A' 510 520 530 540 410 400 420 430 440 450 460 470 480 490 500 510 520 530 540 B-2 PROJ. (45' S) T.D. =71' LOT A LOT B ⅊ 66E 510 520 530 510 520 530 510 520 530
X
X
X
X
X
X
X
X B-B' C-C' TP-2 T.D. = 2.5' TP-1 PROJ. (21'S) T.D. = 1.5'

TYPICAL BEDDING
(APPARENT DIP) A-A' (13°)

TYPICAL BEDDING
(APPARENT DIP)

TYPICAL BEDDING
(APPARENT DIP) TP-2 T.D. = 2.5' A-A'
J
J
J
J
J X
X
X
X
J Tt Tt Tt Tt (13°) PROPOSED RESIDENCE PROPOSED RESIDENCE LOT A PROPOSED RESIDENCE PROPOSED RESIDENCE BLUEBIRD CANYON ROAD ROW IMPROVEMENTS LOT B B-2 PROJ. (52' E) T.D. =71' PROPOSED GARAGE PROPOSED SPA

TYPICAL BEDDING
(APPARENT DIP)
Qrs
Qrs
PROPOSED CAISSON; 10' MIN.

BEDROCK EMBED, DESIGN PER
STRUCTURAL ENGINEER (TYP.)
SLAB SUBDRAIN (TYP.) SEE FIGURE 5 STRUCTURALLY SUPPORTED SLAB REMOVE AND RECOMPACT TO COMPETENT BEDROCK BENCHING PER HILLSIDE GRADING RECOMMENDATIONS (SEE REFERENCE 1 REPORT)
SLAB SUBDRAIN (TYP.) SEE FIGURE 5 FOUNDATIONS PER THE GEOTECHNICAL RECOMMENDATIONS, DESIGN PER STRUCTURAL ENGINEER (TYP.) PROPOSED CAISSON; 10' MIN.

BEDROCK EMBED, DESIGN PER
STRUCTURAL ENGINEER (TYP.) FOUNDATIONS PER THE GEOTECHNICAL RECOMMENDATIONS, DESIGN PER STRUCTURAL ENGINEER (TYP.) FOUNDATIONS PER THE GEOTECHNICAL RECOMMENDATIONS, DESIGN PER STRUCTURAL ENGINEER (TYP.) REMOVE AND RECOMPACT TO COMPETENT BEDROCK BENCHING PER HILLSIDE GRADING RECOMMENDATIONS (SEE REFERENCE 1 REPORT) EXISTING GRADE EXISTING GRADE EXISTING GRADE EXISTING GRADE EXISTING GRADE EXISTING GRADE PROPOSED GRADE PROPOSED GRADE PROPOSED GRADE PROPOSED GRADE PROPOSED GRADE nlee
22-Aug-24 72786-00 v3jdb.dwg PROJECT: DATE: PLATE: GEOTECHNICAL CROSS SECTION A-A', B-B' & C-C' DYRNAES RESIDENCE 1560 BLUEBIRD CANYON DRIVE (PARCELS 1 & 2) LAGUNA BEACH, CALIFORNIA 72786-00 AUGUST 2024 2 0 10' 20' SCALE: 1" = 10' EXPLANATION PLEASE SEE PLATE 1

Laguna Beach City CouncilAugust 12, 2025

Laguna Beach City Council
August 12, 2025